- Department of Chemistry
College of Arts and Sciences
University of the Philippines Visayas
Miag-ao, Ilolio 5023
Philippines
- I am a retired geologist with more than 30 years experience in mineralogy, especially clay science and mineral spectr... moreI am a retired geologist with more than 30 years experience in mineralogy, especially clay science and mineral spectroscopy (infrared and Raman spectroscopy, MAS-NMR and XPS) as well as other characterisation techniques (e.g. XRD, TGA/DTA, SEM/TEM, ICP-AES, ICP-MS, AAS, etc.). I worked most of my career in Australia at the Queensland University of Technology where I taught analytical chemistry, inorganic chemistry, mineralogy and crystallography. After my retirement I am still active as an Honorary Senior Fellow at the University of Queensland (School of Earth and Environmental Sciences) and as an Adjunct Professor at the University of the Philippines Visayas (Dept. Chemistry).edit
Brings together and expands information available on the Mid-infrared spectroscopy of the major rock-forming and ore minerals in one handbook The second in a four-volume set, Handbook of Mineral Spectroscopy, Volume 2: Infrared Spectra,... more
Brings together and expands information available on the Mid-infrared spectroscopy of the major rock-forming and ore minerals in one handbook
The second in a four-volume set, Handbook of Mineral Spectroscopy, Volume 2: Infrared Spectra, presents a database of Infrared spectra, showing both full spectra and high resolutiondetailed spectral regions with band component analyses of the rock-forming and major ore minerals. IR of minerals is a very powerful technique for analyzing the different vibrational modes of minerals (in particular functional groups) but also the local environment of atoms in a crystal structure. The book includes a section on silicates and one on non-silicates, subdivided according to the normal mineral classes.
The Handbook of Mineral Spectroscopy, Volume 2: Infrared Spectra is a go-to guide for anyone working with minerals and can be used for research and writing or as a handbook in the laboratory while running analyses of minerals.
Key Features
• Features over 200 full color full range Mid-infrared Spectra, for use by researchers in the lab and as a reference
• Includes band component analyses of the spectral regions of interest for each mineral
• Written by an expert with more than 25 years of mineral spectroscopy experience
The second in a four-volume set, Handbook of Mineral Spectroscopy, Volume 2: Infrared Spectra, presents a database of Infrared spectra, showing both full spectra and high resolutiondetailed spectral regions with band component analyses of the rock-forming and major ore minerals. IR of minerals is a very powerful technique for analyzing the different vibrational modes of minerals (in particular functional groups) but also the local environment of atoms in a crystal structure. The book includes a section on silicates and one on non-silicates, subdivided according to the normal mineral classes.
The Handbook of Mineral Spectroscopy, Volume 2: Infrared Spectra is a go-to guide for anyone working with minerals and can be used for research and writing or as a handbook in the laboratory while running analyses of minerals.
Key Features
• Features over 200 full color full range Mid-infrared Spectra, for use by researchers in the lab and as a reference
• Includes band component analyses of the spectral regions of interest for each mineral
• Written by an expert with more than 25 years of mineral spectroscopy experience
Research Interests:
Brings together and expands the limited information available on the X-ray Photoelectron Spectroscopy of the major rock-forming and ore minerals into one handbook The first in a four-volume set, Handbook of Mineral Spectroscopy, Volume 1:... more
Brings together and expands the limited information available on the X-ray Photoelectron Spectroscopy of the major rock-forming and ore minerals
into one handbook
The first in a four-volume set, Handbook of Mineral Spectroscopy, Volume 1: X-ray Photoelectron Spectra, presents a database of X-ray
Photoelectron spectra showing both survey (with chemical analysis) and high-resolution spectra of more than 200 rock-forming and
major ore minerals. XPS of minerals is a very powerful technique for analyzing not only the chemical composition of minerals, including,
for other techniques, difficult elements such as F and Cl, but also the local environment of atoms in a crystal structure. The book is divided
into a section on silicates as well as a section on non-silicates, further subdivided according to the normal mineral classes.
The Handbook of Mineral Spectroscopy, Volume 1: X-ray Photoelectron Spectra is a go-to guide for anyone working with minerals and can be
used for research and writing or as a handbook in the laboratory while running analyses of minerals.
Key Features
• Brings together and expands the limited information available on the XPS of minerals into one handbook
• Features over 1000 full color, X-ray photoelectron survey and high-resolution spectra of more than 200 minerals
• Includes chemical information of each mineral
• Written by experts with more than 50 years of combined mineral spectroscopy experience
into one handbook
The first in a four-volume set, Handbook of Mineral Spectroscopy, Volume 1: X-ray Photoelectron Spectra, presents a database of X-ray
Photoelectron spectra showing both survey (with chemical analysis) and high-resolution spectra of more than 200 rock-forming and
major ore minerals. XPS of minerals is a very powerful technique for analyzing not only the chemical composition of minerals, including,
for other techniques, difficult elements such as F and Cl, but also the local environment of atoms in a crystal structure. The book is divided
into a section on silicates as well as a section on non-silicates, further subdivided according to the normal mineral classes.
The Handbook of Mineral Spectroscopy, Volume 1: X-ray Photoelectron Spectra is a go-to guide for anyone working with minerals and can be
used for research and writing or as a handbook in the laboratory while running analyses of minerals.
Key Features
• Brings together and expands the limited information available on the XPS of minerals into one handbook
• Features over 1000 full color, X-ray photoelectron survey and high-resolution spectra of more than 200 minerals
• Includes chemical information of each mineral
• Written by experts with more than 50 years of combined mineral spectroscopy experience
Research Interests:
This book systematically provides an overview of the use of a wide range of spectroscopic methods (Mid- and Near-Infrared, Infrared Emission, Raman, Solid-State Magic Angle Spinning Nuclear Magnetic Resonance, X-ray Photoelectron,... more
This book systematically provides an overview of the use of a wide range of spectroscopic methods (Mid- and Near-Infrared, Infrared Emission, Raman, Solid-State Magic Angle Spinning Nuclear Magnetic Resonance, X-ray Photoelectron, Extended X-ray Absorption Fine Structure, X-ray Absorption Near Edge, Electron Spin and Mössbauer spectroscopy) to investigate kaolin minerals (kaolinite, dickite, nacrite and halloysite) and their modifications (intercalation compounds, nanocomposites and other modifications).
Research Interests:
Research Interests:
Volume 13, 2005, The Application of Vibrational Spectroscopy to Clay Minerals and Layered Double Hydroxides J. Theo Kloprogge, Editor Short introduction to infrared and Raman spectroscopy………..J. Theo Kloprogge INTRODUCTION What is... more
Volume 13, 2005, The Application of Vibrational Spectroscopy to Clay Minerals and Layered Double Hydroxides
J. Theo Kloprogge, Editor
Short introduction to infrared and Raman spectroscopy………..J. Theo Kloprogge
INTRODUCTION
What is vibrational spectroscopy?
INFRARED AND NEAR-INFRARED SPECTROSCOPY
Mid-infrared spectroscopy
Near-infrared spectroscopy
RAMAN SPECTROSCOPY
Introduction
Principles of the Raman effect
Polarizability
Absorption and fluorescence
CONCLUSIONS
REFERENCES
Raman spectroscopy of kaolinite and selected
Intercalates…………………………………...Ray L. Frost and Wayde N. Martens
INTRODUCTION
INTERCALATION OF KAOLINITE
The technique of intercalation
Intercalation with formamide
Intercalation with hydrazine
Intercalation with dimethylsulfoxide
Intercalation with potassium acetate
Intercalation with cesium acetate
EXPERIMENTAL TECHNIQUE OF RAMAN MICROSCOPY OF KAOLINITE
The Raman microscopic technique
SUMMARY
ACKNOWLEDGMENTS
REFERENCES
Crystal-chemistry of talcs: a NIR and MIR spectroscopic approach….Sabine Petit
INTRODUCTION
THE HYDROXYL GROUP: A GOOD PROBE OF THE CLAY CRYSTAL-CHEMISTRY
The hydroxyl group vibrations
Effect of the octahedral environment
Effect of the surrounding tetrahedral environment:
Example of the synthetic Ge-tales
Ordered-disordered cationic distribution
Example of Ni-Mg tales
Example of Ni-Co kerolites
APPLICATION TO NATURAL TALCS: POTENTIAL OF THE NIR REGION
Materials
Comparison between MIR and NIR
Chemical composition calculation
Cation distribution
Proposal of structural formulae
SUMMARY AND CONCLUSIONS
ACKNOWLEDGMENTS
REFERENCES
Information available from infrared spectra of the fine
fractions of bentonites…………………………Jana Madejová and Peter Komadel
INTRODUCTION
CHARACTERIZATION OF BENTONITES
Identification of silica admixtures
Identification of layer silicate admixtures
Identification of kaolinite in smectite rich samples
Identification of mixed-layer illite-smectite
Identification of other admixtures
CHARACTERIZATION OF SMECTITES
Identification of smectites
Distribution of the central atoms in the octahedral sheets of smectites
SUMMARY
ACKNOWLEDGMENTS
REFERENCES
Infrared emission spectroscopy of
clay minerals…………………………………J. Theo Kloprogge and Ray L. Frost
INTRODUCTION
THE THEORY OF INFRARED EMISSION SPECTROSCOPY (IES)
EXPERIMENTAL METHODS
THE EXAMPLE OF CALCIUM OXALATE DIHYDRATE
IES OF CLAY MINERALS
Kaolinite group
Smectite group
Interstratified clay minerals
Chlorite group
Modulated clay minerals
ACKNOWLEDGMENTS
REFERENCES
Infrared spectroscopy and the chemistry of dioctahedral smectites……W.P. Gates
INTRODUCTION
BACKGROUND AND THEORY
Structural considerations of isomorphic substitution Affects of isomorphic substitutions on bond strength
and H-bonding
Mass and valence of OH - sharing cations
SAMPLES STUDIED
Chemistry of samples
Infrared spectroscopy
OCTAHEDRAL SITE OCCUPANCIES
Octahedral cation-OH bend and lattice deformations (1100- 550 cm-1)
Octahedral cation - OH stretching (3700 - 3500 cm-1) Octahedral cation - OH combination (4800 - 3800 cm-1)
OCTAHEDRAL CATION COMPOSITION
NEIGHBORING OCTAHEDRAL AND TETRAHEDRAL SITES
Influence of layer charge location
Influence of Fe3+
SUMMARY AND CONCLUSIONS
ACKNOWLEDGEMENTS
REFERENCES
Studies of Reduced-Charge Smectites by Near Infrared
Spectroscopy J Madejová
INTRODUCTION
MATERIALS AND METHODS
FIXATION OF SMALL EXCHANGEABLE CATIONS IN SMECTITES
Fixation of Li+ in SAz-1 montmorillonite
Layer charge characterization of NH4-saturated smectites
NIR spectra of dioctahedral smectites
NIR spectra of reduced-charge Li-Saz
The effect of chemical composition on the infrared spectra of Li-saturated dioctahedral smectites
The effect of ion size and charge of exchangeable cations on the extent of their fixation in montmorillonites
ACID DISSOLUTION OF REDUCED-CHARGE SMECTITES
NIR study of structural modifications of Li- and
Ni-montmorillonites upon acid treatment
SUMMARY
ACKNOWLEDGEMENT
REFERENCES
Infrared and Raman Spectroscopy of Naturally Occurring
Hydrotalcites and Their Synthetic Equivalents J. Theo Kloprogge
INTRODUCTION
FACTOR GROUP ANALYSIS
THE HYDROXIDE LAYERS
WATER
SIMPLE INTERLAYER ANIONS
C032-
NO3-
SO42-
ClO4-
THERMAL BEHAVIOR
ACKNOWLEDGEMENTS
REFERENCES
Molecular Modeling of the Vibrational Spectra of Interlayer
and Surface Species of Layered Double Hydroxides…………R. James Kirkpatrick, Andrey G. Kalinichev, Jianwei Wang, Xiaoqiang Hou and James E. Amonette
INTRODUCTION
MOLECULAR DYNAMICS MODELING
INTERATOMIC POTENTIALS
ANALYSIS OF ATOMIC VIBRATIONAL DYNAMICS FROM MD SIMULATIONS
EXPERIMENTAL FAR INFRARED SPECTRA OF LDH PHASES COMPARISON OF CALCULATED AND OBSERVED DATA
Ca2Al-Cl LDH
LiAl2-Cl LDH
LiAl2-SO4 LDH
Mg3Al-Cl LDH
POWER SPECTRA OF AQUEOUS SPECIES ASSOCIATED WITH LDH SURFACES
CONCLUSIONS
ACKNOWLEDGEMENTS
REFERENCES
J. Theo Kloprogge, Editor
Short introduction to infrared and Raman spectroscopy………..J. Theo Kloprogge
INTRODUCTION
What is vibrational spectroscopy?
INFRARED AND NEAR-INFRARED SPECTROSCOPY
Mid-infrared spectroscopy
Near-infrared spectroscopy
RAMAN SPECTROSCOPY
Introduction
Principles of the Raman effect
Polarizability
Absorption and fluorescence
CONCLUSIONS
REFERENCES
Raman spectroscopy of kaolinite and selected
Intercalates…………………………………...Ray L. Frost and Wayde N. Martens
INTRODUCTION
INTERCALATION OF KAOLINITE
The technique of intercalation
Intercalation with formamide
Intercalation with hydrazine
Intercalation with dimethylsulfoxide
Intercalation with potassium acetate
Intercalation with cesium acetate
EXPERIMENTAL TECHNIQUE OF RAMAN MICROSCOPY OF KAOLINITE
The Raman microscopic technique
SUMMARY
ACKNOWLEDGMENTS
REFERENCES
Crystal-chemistry of talcs: a NIR and MIR spectroscopic approach….Sabine Petit
INTRODUCTION
THE HYDROXYL GROUP: A GOOD PROBE OF THE CLAY CRYSTAL-CHEMISTRY
The hydroxyl group vibrations
Effect of the octahedral environment
Effect of the surrounding tetrahedral environment:
Example of the synthetic Ge-tales
Ordered-disordered cationic distribution
Example of Ni-Mg tales
Example of Ni-Co kerolites
APPLICATION TO NATURAL TALCS: POTENTIAL OF THE NIR REGION
Materials
Comparison between MIR and NIR
Chemical composition calculation
Cation distribution
Proposal of structural formulae
SUMMARY AND CONCLUSIONS
ACKNOWLEDGMENTS
REFERENCES
Information available from infrared spectra of the fine
fractions of bentonites…………………………Jana Madejová and Peter Komadel
INTRODUCTION
CHARACTERIZATION OF BENTONITES
Identification of silica admixtures
Identification of layer silicate admixtures
Identification of kaolinite in smectite rich samples
Identification of mixed-layer illite-smectite
Identification of other admixtures
CHARACTERIZATION OF SMECTITES
Identification of smectites
Distribution of the central atoms in the octahedral sheets of smectites
SUMMARY
ACKNOWLEDGMENTS
REFERENCES
Infrared emission spectroscopy of
clay minerals…………………………………J. Theo Kloprogge and Ray L. Frost
INTRODUCTION
THE THEORY OF INFRARED EMISSION SPECTROSCOPY (IES)
EXPERIMENTAL METHODS
THE EXAMPLE OF CALCIUM OXALATE DIHYDRATE
IES OF CLAY MINERALS
Kaolinite group
Smectite group
Interstratified clay minerals
Chlorite group
Modulated clay minerals
ACKNOWLEDGMENTS
REFERENCES
Infrared spectroscopy and the chemistry of dioctahedral smectites……W.P. Gates
INTRODUCTION
BACKGROUND AND THEORY
Structural considerations of isomorphic substitution Affects of isomorphic substitutions on bond strength
and H-bonding
Mass and valence of OH - sharing cations
SAMPLES STUDIED
Chemistry of samples
Infrared spectroscopy
OCTAHEDRAL SITE OCCUPANCIES
Octahedral cation-OH bend and lattice deformations (1100- 550 cm-1)
Octahedral cation - OH stretching (3700 - 3500 cm-1) Octahedral cation - OH combination (4800 - 3800 cm-1)
OCTAHEDRAL CATION COMPOSITION
NEIGHBORING OCTAHEDRAL AND TETRAHEDRAL SITES
Influence of layer charge location
Influence of Fe3+
SUMMARY AND CONCLUSIONS
ACKNOWLEDGEMENTS
REFERENCES
Studies of Reduced-Charge Smectites by Near Infrared
Spectroscopy J Madejová
INTRODUCTION
MATERIALS AND METHODS
FIXATION OF SMALL EXCHANGEABLE CATIONS IN SMECTITES
Fixation of Li+ in SAz-1 montmorillonite
Layer charge characterization of NH4-saturated smectites
NIR spectra of dioctahedral smectites
NIR spectra of reduced-charge Li-Saz
The effect of chemical composition on the infrared spectra of Li-saturated dioctahedral smectites
The effect of ion size and charge of exchangeable cations on the extent of their fixation in montmorillonites
ACID DISSOLUTION OF REDUCED-CHARGE SMECTITES
NIR study of structural modifications of Li- and
Ni-montmorillonites upon acid treatment
SUMMARY
ACKNOWLEDGEMENT
REFERENCES
Infrared and Raman Spectroscopy of Naturally Occurring
Hydrotalcites and Their Synthetic Equivalents J. Theo Kloprogge
INTRODUCTION
FACTOR GROUP ANALYSIS
THE HYDROXIDE LAYERS
WATER
SIMPLE INTERLAYER ANIONS
C032-
NO3-
SO42-
ClO4-
THERMAL BEHAVIOR
ACKNOWLEDGEMENTS
REFERENCES
Molecular Modeling of the Vibrational Spectra of Interlayer
and Surface Species of Layered Double Hydroxides…………R. James Kirkpatrick, Andrey G. Kalinichev, Jianwei Wang, Xiaoqiang Hou and James E. Amonette
INTRODUCTION
MOLECULAR DYNAMICS MODELING
INTERATOMIC POTENTIALS
ANALYSIS OF ATOMIC VIBRATIONAL DYNAMICS FROM MD SIMULATIONS
EXPERIMENTAL FAR INFRARED SPECTRA OF LDH PHASES COMPARISON OF CALCULATED AND OBSERVED DATA
Ca2Al-Cl LDH
LiAl2-Cl LDH
LiAl2-SO4 LDH
Mg3Al-Cl LDH
POWER SPECTRA OF AQUEOUS SPECIES ASSOCIATED WITH LDH SURFACES
CONCLUSIONS
ACKNOWLEDGEMENTS
REFERENCES
Research Interests:
Infrared and Raman spectroscopy have become mainstream techniques in mineralogy and inorganic chemistry. These vibrational spectroscopic techniques allow the identification of different materials based on band positions in the low... more
Infrared and Raman spectroscopy have become mainstream techniques in mineralogy and inorganic chemistry. These vibrational spectroscopic techniques allow the identification of different materials based on band positions in the low wavenumber region, but also the anionic groups. Recently these methods have entered the field of gemology, where it is not only used to identify gemstones, but also to obtain information about e.g. synthetic vs. natural minerals (e.g. diamond - cubic zirconia, synthetic/natural turquoise), origin, etc. Mineral pigments in paintings and old manuscripts can also be non-destructively identified by IR and Raman microscopy, fiber-optics and Attenuated Total Reflection (ATR) IR spectroscopy.
Research Interests:
This chapter provides an overview of results obtained by a variety of spectroscopic techniques. The most common techniques employed are infrared and Raman spectroscopy, which enable detailed observation of in particular the behaviour of... more
This chapter provides an overview of results obtained by a variety of spectroscopic techniques. The most common techniques employed are infrared and Raman spectroscopy, which enable detailed observation of in particular the behaviour of water and OH-groups and the type of H-bonds formed. The inner-surface OH-groups that normally form H-bonds with adjacent layers in the kaolins, form H-bonds with water in the interlayer in halloysite. IES showed that the four inner and inner-surface OH-groups were removed at different temperatures and/or at different rates. A slight increase in the Al 2p binding energy observed in the XPS spectra from kaolinite to halloysite reflects a change in the stacking order due to the interlayer water. The overall shape of the O 1s is indicative of two peaks associated with the oxygen atoms and with the OH-groups. A third, very weak peak was observed associated with interlayer water still present despite the ultrahigh vacuum.
Research Interests:
Research Interests:
The dehydration, dehydroxylation, decarbonization behavior and other phase changes of minerals have only been studied to a limited extend by in situ spectroscopic methods. Normally. minerals are heated to a certain temperature, then... more
The dehydration, dehydroxylation, decarbonization behavior and other phase changes of minerals have only been studied to a limited extend by in situ spectroscopic methods. Normally. minerals are heated to a certain temperature, then rapidly cooled down (quenched), followed by spectroscopic analysis at room temperature. Although in many cases this provides useful information, there is no certainty that the mineral structure does not change upon cooling. Therefore, it would be useful to have a technique that can be applied in situ during the heat treatment. Such a technique is infrared emissiqn spectroscopy (IES). The technique of measurement of discrete vibrational frequencies emitted by thermally excited molecules, known as Fourier Transform Infrared Emission Spectroscopy (FTIR ES or. !ES for short), has not been widely used for the study of mineral structures. The major advantages of IES are that the samples are measured in situ at elevated temperatures and no sample treatment other than making the sample of sub micron particle· size is required. Further. the technique removes the difficulties of heating the sample to temperatures where reactions take place and subsequent
quenching prior to the measurement. as IES measures the process as it is actually taking place.
quenching prior to the measurement. as IES measures the process as it is actually taking place.
Research Interests:
The near-infrared spectra of hydrothermally synthesized beidellites with increasing layer charge, pyrophyllite and paragonite have been compared and interpreted based on their associated mid-infrared spectra. The 6000-7500 cm·1 region for... more
The near-infrared spectra of hydrothermally synthesized beidellites with increasing layer charge, pyrophyllite and paragonite have been compared and interpreted based on their associated mid-infrared spectra. The 6000-7500 cm·1 region for beidellite is dominated by the first overtone of the adsorbed H20 stretching mode around 6900 cm·1, while the 7100 and 7150 cm·1 bands are the first overtones of the two Al-OH stretching
modes. Pyrophyllite is characterised by a sharp band at 7172 cm·1 while paragonite shows a weaker and broader band at 7 147 cm·1. The 5000-6000 cm·1 region is characterised by combination bands of interlayer H20 stretching modes with the adsorbed H20 bending mode around 5240 and 5140 cm· 1. Furthemore, the combination modes are broad as
expected based on the broad nature of the H20 bands in the mid-infrared region. Minor bands in the pyrophyllite spectrum are due to the presence of a small amount of beidellite. Bands in the 4000-5500 cm·1 region at 4545 and 4595 cm·1 are attributed to the combination bands of the stretching and libration modes of the Al2QH units in the beidellite structure. Pyrophyllite exhibits a single sharp band around 4615 cm·'. A similar but broader band is observed for paragonite at 4575 cm· 1.
modes. Pyrophyllite is characterised by a sharp band at 7172 cm·1 while paragonite shows a weaker and broader band at 7 147 cm·1. The 5000-6000 cm·1 region is characterised by combination bands of interlayer H20 stretching modes with the adsorbed H20 bending mode around 5240 and 5140 cm· 1. Furthemore, the combination modes are broad as
expected based on the broad nature of the H20 bands in the mid-infrared region. Minor bands in the pyrophyllite spectrum are due to the presence of a small amount of beidellite. Bands in the 4000-5500 cm·1 region at 4545 and 4595 cm·1 are attributed to the combination bands of the stretching and libration modes of the Al2QH units in the beidellite structure. Pyrophyllite exhibits a single sharp band around 4615 cm·'. A similar but broader band is observed for paragonite at 4575 cm· 1.
Research Interests:
In this chapter, the iniercalation of a number of organic molecules in kaolinite, a 1: 1 clay mineral which is generally assumed not to swell, is described along with the influence of these molecules on the clay internal and external... more
In this chapter, the iniercalation of a number of organic molecules in kaolinite, a 1: 1 clay mineral which is generally assumed not to swell, is described along with the influence of these molecules on the clay internal and external surfaces. The reactive molecules are inserted between the successive kaolinite layers, thereby disrupting the hydrogen bonds between the hydroxyl groups on one side and the oxygen atoms of the siloxane layer on the other side. The organic molecules will form new bonds with either the more hydrophobic siloxane layer or with the more hydrophilic hydroxyl groups. In this article, the intercalation
of molecules such as hydrazine, urea, formamide, acetamide, DMSO and acetate are discussed. Extensive infrared and Raman spectroscopic research has resulted in a much more detailed picture of how these organic molecules are incorporated in the kaolinite structure.
of molecules such as hydrazine, urea, formamide, acetamide, DMSO and acetate are discussed. Extensive infrared and Raman spectroscopic research has resulted in a much more detailed picture of how these organic molecules are incorporated in the kaolinite structure.
Research Interests:
New phases of kaolinite expanded with potassium acetate have been studied over the ambient to predehydroxylation temperature range using a combination of X-ray diffraction and Raman spectroscopy. Upon intercalation, the kaolinite expanded... more
New phases of kaolinite expanded with potassium acetate have been studied over the ambient to predehydroxylation temperature range using a combination of X-ray diffraction and Raman spectroscopy. Upon intercalation, the kaolinite expanded along the c-axis direction to 13.88A. Upon heating the intercalation complex over the 50 to 300°C range, three additional intercalation phases with d-spacings of 9.09, 9.60, and 11. 4 7 A were observed. The amount of each phase is temperature dependent. These expansions are reversible and upon cooling the intercalation complex returns to its original ct-spacing. The 13.88A phase only existed in the presence of water. It is proposed that the expanded kaolinite
intercalation phases result from the orientation of the acetate within the intercalation complex. Similar results are obtained when halloysite is expanded. X-ray diffraction shows that the halloysite upon intercalation with potassium acetate is completely expanded to 13.80A. Upon heating the intercalation complex to 50°C under nitrogen, two expanded phases are observed with d-spacings of 11.47 and 8.95A. Upon thermal treatment, the 11.4 7 A phase is stable in both the heating and cooling cycles. The -9.0A phase undergoes an expansion at 100°C to 9.2A. Upon exposure to air, the intercalated kaolinite returns to a 13.80A phase. The completely intercalated kaolinite showed a single band at 3607 cm·1 attributed to the inner surface hydroxyl hydrogen bonded to the acetate ion. This band corresponds to the 13.88A phase. Mild heating of the intercalated complex to 50°C caused a rearrangement of the surface
structure with Raman hydroxyl-stretching bands being observed at 3594, 3604 and 3624 cm·1 . Further thermal treatment at I 00°C caused these bands to shift to 3599, 3605 and 3624 cm·1. At the predehydroxylation temperature for potassium acetate intercalated kaolinite (250°C) two bands were observed at 360 I and 3633 cm·1. At this temperature, only the 11 .62A phase existed, suggesting the 360 I cm·1 band is related to the 11.62A phase. Above this temperature no hydroxyls are spectroscopically evident. Upon cooling to room temperature, the Raman spectra of the hydroxyl surfaces are identical to that of the initial intercalation complex, showing that the thermal modification of the
kaolinite surfaces is reversible.
intercalation phases result from the orientation of the acetate within the intercalation complex. Similar results are obtained when halloysite is expanded. X-ray diffraction shows that the halloysite upon intercalation with potassium acetate is completely expanded to 13.80A. Upon heating the intercalation complex to 50°C under nitrogen, two expanded phases are observed with d-spacings of 11.47 and 8.95A. Upon thermal treatment, the 11.4 7 A phase is stable in both the heating and cooling cycles. The -9.0A phase undergoes an expansion at 100°C to 9.2A. Upon exposure to air, the intercalated kaolinite returns to a 13.80A phase. The completely intercalated kaolinite showed a single band at 3607 cm·1 attributed to the inner surface hydroxyl hydrogen bonded to the acetate ion. This band corresponds to the 13.88A phase. Mild heating of the intercalated complex to 50°C caused a rearrangement of the surface
structure with Raman hydroxyl-stretching bands being observed at 3594, 3604 and 3624 cm·1 . Further thermal treatment at I 00°C caused these bands to shift to 3599, 3605 and 3624 cm·1. At the predehydroxylation temperature for potassium acetate intercalated kaolinite (250°C) two bands were observed at 360 I and 3633 cm·1. At this temperature, only the 11 .62A phase existed, suggesting the 360 I cm·1 band is related to the 11.62A phase. Above this temperature no hydroxyls are spectroscopically evident. Upon cooling to room temperature, the Raman spectra of the hydroxyl surfaces are identical to that of the initial intercalation complex, showing that the thermal modification of the
kaolinite surfaces is reversible.
Research Interests:
There are three groups of scientists dominating the search for the origin of life: the organic chemists (the Soup), the molecular biologists (RNA world), and the inorganic chemists (metabolism and transient-state metal ions), all of which... more
There are three groups of scientists dominating the search for the origin of life: the organic chemists (the Soup), the molecular biologists (RNA world), and the inorganic chemists (metabolism and transient-state metal ions), all of which have experimental adjuncts. It is time for Clays and the
Origin of Life to have its experimental adjunct. The clay data coming from Mars and carbonaceous chondrites have necessitated a review of the role that clays played in the origin of life on Earth. The data from Mars have suggested that Fe-clays such as nontronite, ferrous saponites, and several other clays were formed on early Mars when it had sufficient water. This raised the question of the possible role that these clays may have played in the origin of life on Mars. This has put clays front and center in the studies on the origin of life not only on Mars but also here on Earth. One of the major questions is: What was the catalytic role of Fe-clays in the origin and development of metabolism here on Earth? First, there is the recent finding of a chiral amino acid (isovaline) that formed on the surface of a clay mineral on several carbonaceous chondrites. This points to the formation of amino acids on the surface of clay minerals on carbonaceous chondrites from simpler molecules, e.g., CO2, NH3, and HCN. Additionally, there is the catalytic role of small organic molecules, such as dicarboxylic acids and amino acids found on carbonaceous chondrites, in the formation of Fe-clays themselves. Amino acids and nucleotides adsorb on clay surfaces on Earth and subsequently polymerize. All of these observations and more must be subjected to strict experimental analysis. This review provides an overview of what has happened and is now happening in the experimental clay world related to the origin of life. The emphasis is on smectite-group clay minerals, such as montmorillonite and nontronite.
Origin of Life to have its experimental adjunct. The clay data coming from Mars and carbonaceous chondrites have necessitated a review of the role that clays played in the origin of life on Earth. The data from Mars have suggested that Fe-clays such as nontronite, ferrous saponites, and several other clays were formed on early Mars when it had sufficient water. This raised the question of the possible role that these clays may have played in the origin of life on Mars. This has put clays front and center in the studies on the origin of life not only on Mars but also here on Earth. One of the major questions is: What was the catalytic role of Fe-clays in the origin and development of metabolism here on Earth? First, there is the recent finding of a chiral amino acid (isovaline) that formed on the surface of a clay mineral on several carbonaceous chondrites. This points to the formation of amino acids on the surface of clay minerals on carbonaceous chondrites from simpler molecules, e.g., CO2, NH3, and HCN. Additionally, there is the catalytic role of small organic molecules, such as dicarboxylic acids and amino acids found on carbonaceous chondrites, in the formation of Fe-clays themselves. Amino acids and nucleotides adsorb on clay surfaces on Earth and subsequently polymerize. All of these observations and more must be subjected to strict experimental analysis. This review provides an overview of what has happened and is now happening in the experimental clay world related to the origin of life. The emphasis is on smectite-group clay minerals, such as montmorillonite and nontronite.
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Layered clay systems intercalated with inorganic and organic compounds were analyzed to highlight how XPS can provide information on the different environments surrounding a particular atom as well as provide discernments on the size,... more
Layered clay systems intercalated with inorganic and organic compounds were analyzed
to highlight how XPS can provide information on the different environments surrounding a particular
atom as well as provide discernments on the size, coordination, and structural and oxidative
transformations of the intercalating/pillaring compounds. XPS data on the intercalation of urea and
K-acetate in low- and high-defect kaolinite revealed the interaction of the intercalating group NH2
with the siloxane functional groups in the interlayer surface. The intercalation of HDTMA in Mt
demonstrated the use of XPS in monitoring the change in conformation assumed by alkylammonium
intercalating compounds in Mt with increasing CEC. Studies on the pillaring of Mt by Al13 and
Ga13 by XPS allowed determination of the coordination of the pillaring compound within the Mt
layer. Lastly, the intercalation of hexacyanoferrate in hydrotalcite demonstrated the capability of
XPS in following changes in the oxidation state of the iron compound. These were gleaned from
interpretation of the shifts in binding energies and presence of multiplet splitting in the XPS of the
component elements of the minerals or the intercalating compounds.
to highlight how XPS can provide information on the different environments surrounding a particular
atom as well as provide discernments on the size, coordination, and structural and oxidative
transformations of the intercalating/pillaring compounds. XPS data on the intercalation of urea and
K-acetate in low- and high-defect kaolinite revealed the interaction of the intercalating group NH2
with the siloxane functional groups in the interlayer surface. The intercalation of HDTMA in Mt
demonstrated the use of XPS in monitoring the change in conformation assumed by alkylammonium
intercalating compounds in Mt with increasing CEC. Studies on the pillaring of Mt by Al13 and
Ga13 by XPS allowed determination of the coordination of the pillaring compound within the Mt
layer. Lastly, the intercalation of hexacyanoferrate in hydrotalcite demonstrated the capability of
XPS in following changes in the oxidation state of the iron compound. These were gleaned from
interpretation of the shifts in binding energies and presence of multiplet splitting in the XPS of the
component elements of the minerals or the intercalating compounds.
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In nature numerous minerals are known with the general formula X2M(TO4)2•2(H2O) and an important group is formed by minerals with T = As. Most of these occur as minor or trace minerals in environments such as hydrothermal alterations of... more
In nature numerous minerals are known with the general formula X2M(TO4)2•2(H2O) and an important group is formed by minerals with T = As. Most of these occur as minor or trace minerals in environments such as hydrothermal alterations of primary sulfides and arsenides. Xray Photoelectron Spectroscopy and Raman spectroscopy have been utilized to study the chemistry and crystal structure of the roselite subgroup minerals, Ca2M(AsO4)2•2H2O (with M = Co, Mg, Mn, Zn, and Cu). The AsO4 stretching region exhibited minor differences between the roselite subgroup minerals, which can be explained by the ionic radius of the cation substituting on the M position in the structure. Multiple AsO4 antisymmetric stretching and bending modes were found, pointing to a tetrahedral symmetry reduction. Bands around 450 cm-1 were attributed to ν4 bending modes. Several bands in the 300-350cm-1 region attributed to ν2 bending modes also provide evidence of symmetry reduction of the AsO4 anion. Two broad bands for roselite were found around 3330 and 3120 cm-1 and were attributed to the OH stretching bands of crystal water. These bands are accompanied by two bands around 1700 and 1610 cm-1 attributed to the corresponding OH-bending modes. In conclusion, both XPS and Raman spectroscopy are valuable non-destructive analytical tools to characterize these secondary arsenate minerals. X-ray Photoelectron Spectroscopy and Raman microspectroscopy allow the chemistry and molecular structure of the roselite group minerals to be studied in a non-destructive way. The minerals in the roselite subgroup are easily distinguished based on their chemical composition as determined by XPS. As expected for minerals with the same crystal structure, similarities exist in the Raman spectra, sufficient differences exist to be able to identify these minerals.
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Roselite from the Aghbar Mine, Morocco, [Ca2(Co2+,Mg)(AsO4)2 2H2O], was investigated by X-ray Photoelectron and Raman spectroscopy. X-ray Photoelectron Spectroscopy revealed a cobalt to magnesium ratio of 3:1. Magnesium, cobalt and... more
Roselite from the Aghbar Mine, Morocco, [Ca2(Co2+,Mg)(AsO4)2 2H2O], was investigated by X-ray Photoelectron and Raman spectroscopy. X-ray Photoelectron Spectroscopy revealed a cobalt to magnesium ratio of 3:1. Magnesium, cobalt and calcium showed single bands associated with unique crystallographic positions. The oxygen 1s spectrum displayed two bands associated with the arsenate group and crystal water. Arsenic 3d exhibited bands with a ratio close to that of the cobalt
to magnesium ratio, indicative of the local arsenic environment being sensitive to the substitution of magnesium for cobalt. The Raman arsenate symmetric and antisymmetric modes were all split with the antisymmetric modes observed around 865 and 818 cm-1, while the symmetric modes were found around 980 and 709 cm-1. An overlapping water-libration mode was observed at 709 cm-1. The region at 400–500 cm-1 showed splitting of the arsenate antisymmetric mode with bands at 499, 475, 450 and 425 cm-1. The 300–400 cm-1 region showed the corresponding symmetric bending modes at 377, 353, 336 and 304 cm-1. The bands below 300 cm-1 were assigned to lattice modes.
to magnesium ratio, indicative of the local arsenic environment being sensitive to the substitution of magnesium for cobalt. The Raman arsenate symmetric and antisymmetric modes were all split with the antisymmetric modes observed around 865 and 818 cm-1, while the symmetric modes were found around 980 and 709 cm-1. An overlapping water-libration mode was observed at 709 cm-1. The region at 400–500 cm-1 showed splitting of the arsenate antisymmetric mode with bands at 499, 475, 450 and 425 cm-1. The 300–400 cm-1 region showed the corresponding symmetric bending modes at 377, 353, 336 and 304 cm-1. The bands below 300 cm-1 were assigned to lattice modes.
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This paper describes the formation of "sandwich" wulfenite. Banded wulfenite from the Ojuela Mine, Mapimí, Durango, Mexico, have been found since 2017, but an explanation for the band formation has not been provided. X-ray diffraction... more
This paper describes the formation of "sandwich" wulfenite. Banded wulfenite from the Ojuela Mine, Mapimí, Durango, Mexico, have been found since 2017, but an explanation for the band formation has not been provided. X-ray diffraction (XRD) showed the wulfenite to have a tetragonal unit cell of a = 5.4374(1), c = 12.1123(7) Å. The Raman spectrum was dominated by ν 1 (A g) around 870 cm-1 , while the weak shoulder at 859 cm-1 represents the strain activated ν 1 (B u) infrared (IR) band. Two ν 2 modes were observed at 318 cm-1 (A g) and 351 cm-1 (B g). For the ν 3 (E g), the band at 768 cm-1 was assigned to the B g symmetric mode and the 745 cm-1 band to the E g vibration. The IR spectrum showed two strong bands at 835 and 779 cm-1 corresponding to v 3 modes and a very weak one at 496 cm-1. SEM-EDX (scanning electron microscopy-energy dispersive X-ray analysis) showed that the band does not extend into the main crystal but is limited to the surface as secondary growth. The main thick tabular crystal was dominated by {001}, {110}, and {111}. The {001} surfaces of the wulfenite crystals showed evidence of later dissolution, which may have been part of the source material for this secondary crystallization. The chemical composition of the main wulfenite crystal proved only minor substitution of W for Mo. Contrastingly, a much higher number of substitutions by V, As, and W for Mo-as well as Ca, Fe, Zn, Cu, and Al for Pb-was observed in the secondary band, indicating a change in the fluid composition from which the band crystallized compared to the original wulfenite. Changes in lattice parameters of the secondary wulfenite crystals and the energy involved in nucleation on the surface of the original wulfenite as well as the different bonds exposed on different faces favored the formation of the band on only {110}.
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Saponite is a trioctahedral 2:1 smectite with the ideal composition MxMg3AlxSi4xO10(OH,F)2.nH2O (M= interlayer cation). Both the success of the saponite synthesis and the determination of its applications depends on robust knowledge of... more
Saponite is a trioctahedral 2:1 smectite with the ideal composition MxMg3AlxSi4xO10(OH,F)2.nH2O (M= interlayer cation). Both the success of the saponite synthesis and the determination of its
applications depends on robust knowledge of the structure and composition of saponite. Among the routine characterization techniques, spectroscopic methods are the most common. This review, thus, provides an overview of various spectroscopic methods to characterize natural and synthetic saponites with focus on the extensive work by one of the authors (JTK). The Infrared (IR) and Raman spectra of natural and synthetic saponites are discussed in detail including the assignment of the observed bands. The crystallization of saponite is discussed based on the changes in the IR and Raman spectra and a
possible crystallization model is provided. Infrared emission spectroscopy has been used to study the
thermal changes of saponite in situ including the dehydration and (partial) dehydroxylation up to 750 C. 27Al and 29Si magic-angle-spinning nuclear magnetic resonance spectroscopy is discussed (as
well as 11B and 71Ga for B- and Ga-Si substitution) with respect to, in particular, Al(IV)/Al(VI) and Si/Al(IV) ratios. X-ray photoelectron spectroscopy provides chemical information as well as some
information related to the local environments of the different elements in the saponite structure as reflected by their binding energies.
applications depends on robust knowledge of the structure and composition of saponite. Among the routine characterization techniques, spectroscopic methods are the most common. This review, thus, provides an overview of various spectroscopic methods to characterize natural and synthetic saponites with focus on the extensive work by one of the authors (JTK). The Infrared (IR) and Raman spectra of natural and synthetic saponites are discussed in detail including the assignment of the observed bands. The crystallization of saponite is discussed based on the changes in the IR and Raman spectra and a
possible crystallization model is provided. Infrared emission spectroscopy has been used to study the
thermal changes of saponite in situ including the dehydration and (partial) dehydroxylation up to 750 C. 27Al and 29Si magic-angle-spinning nuclear magnetic resonance spectroscopy is discussed (as
well as 11B and 71Ga for B- and Ga-Si substitution) with respect to, in particular, Al(IV)/Al(VI) and Si/Al(IV) ratios. X-ray photoelectron spectroscopy provides chemical information as well as some
information related to the local environments of the different elements in the saponite structure as reflected by their binding energies.
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Clay minerals surfaces potentially play a role in prebiotic synthesis through adsorption of organic monomers that give rise to highly concentrated systems; facilitate condensation and polymerization reactions, protection of early... more
Clay minerals surfaces potentially play a role in prebiotic synthesis through adsorption of organic monomers that give rise to highly concentrated systems; facilitate condensation and polymerization reactions, protection of early biomolecules from hydrolysis and photolysis, and surface-templating for specific adsorption and synthesis of organic molecules. This review presents processes of clay formation using saponite as a model clay mineral, since it has been shown to catalyze organic reactions, is easy to synthesize in large and pure form, and has tunable properties. In particular, a method involving urea is presented as a reasonable analog of natural processes. The method involves a two-step process: (1) formation of the precursor aluminosilicate gel and (2) hydrolysis of a divalent metal (Mg, Ni, Co, and Zn) by the slow release of ammonia from urea decomposition. The aluminosilicate gels in the first step forms a 4-fold-coordinated Al 3+ similar to what is found in nature such as in volcanic glass. The use of urea, a compound figuring in many prebiotic model reactions, circumvents the formation of undesirable brucite, Mg(OH)2, in the final product, by slowly releasing ammonia thereby controlling the hydrolysis of magnesium. In addition, the substitution of B and Ga for Si and Al in saponite is also described. The saponite products from this urea-assisted synthesis were tested as catalysts for several organic reactions, including Friedel-Crafts alkylation, cracking, and isomerization reactions.
Research Interests: Materials Science, Chemistry, Inorganic Chemistry, Physical Chemistry, Transmission Electron Microscopy, and 7 moreClay Minerals, Heterogeneous Catalysis, Synthesis and Characterization of nanomaterials, Infrared spectroscopy, Thermal Analysis, X ray diffraction, and Magic-angle Spinning Nuclear Magnetic Resonance
This paper presents an overview of the chemical analyses of the Clay Mineral Society Source Clays based on X-ray Photoelectron Spectroscopy. This technique does not require any detailed sample preparation and is therefore easy to perform.... more
This paper presents an overview of the chemical analyses of the Clay Mineral Society Source Clays based on X-ray Photoelectron Spectroscopy. This technique does not require any detailed sample preparation and is therefore easy to perform. In contrast to other common chemical analytical techniques fluorine and chlorine can be analysed together with all the major elements. In addition, the high resolution spectra reveal some details about the local environment of different cations in the clay structure, such as the presence of water, distinction between octahedral and tetrahedral aluminium and the presence of two types of Mg in the octahedral sheets.
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X-ray Photoelectron Spectroscopy was used to study a ferroan platinum crystal from the Kondyor Massif, Russian Far East. Prior to the X-ray Photoelectron Spectroscopic analyses, the nature of the crystal was confirmed by X-ray... more
X-ray Photoelectron Spectroscopy was used to study a ferroan platinum crystal from the Kondyor Massif, Russian Far East. Prior to the X-ray Photoelectron Spectroscopic analyses, the nature of the crystal was confirmed by X-ray diffraction. The survey scan showed mainly the presence of Pt and Fe, with smaller amounts of O and Si. The high resolutions spectra of the Pt 4f and Fe 2p showed 18.3 atom% Fe in the crystal, which puts the composition on the lower boundary for ferroan platinum and confirms earlier analyses using other methods such as Scanning Electron Microscopy-Energy Dispersive X-ray analysis/microprobe. The binding energy of the Pt 4f5/2 was 74.0 eV and Pt 4f7/2 70.5 eV, while the Fe 2p3/2 for metallic Fe was observed at 707.2 eV. The Fe 2p3/2 for metallic Fe was significantly sharper than that of Fe 2p3/2 at 710.7 eV associated with surface material. The Raman spectrum was dominated by the Pt–Pt stretching mode at 253 cm−1. Changed orientation resulted in the observation of two bands at 127 and 139 cm−1, interpreted as being due to stretching modes of two Pt–Pt bonds with the third bond to Fe and Pt fixed. The presence of Ca-Fe-Al-Mg-Si-O on the surface was probably associated with the presence of a clinopyroxene. These minerals can be expected since the crystal came originally from a clinopyroxenite-dunite matrix. The spectra showed a variety of interferences, e.g. Al 2p with Pt 4f, Mg 2p with Fe 3p, and Ca 2p1/2 with Mg Auger, making exact determinations of the ratios of these elements difficult.
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This paper aims at a full description of the Raman and Infrared spectra of the arsenate mineral tilasite, CaMg(AsO4)F, from Långban, Värmland, Sweden. X-ray diffraction showed the two samples to be phase pure with a monoclinic unit cell... more
This paper aims at a full description of the Raman and Infrared spectra of the arsenate mineral tilasite, CaMg(AsO4)F, from Långban, Värmland, Sweden. X-ray diffraction showed the two samples to be phase pure with a monoclinic unit cell of a = 6.683(3) Å, b = 8.950(5) Å, c = 7.572(4) Å, and β = 121.09(2)°. The infrared and Raman spectra were dominated by the arsenate modes. The two highest intensity bands were observed at 850 cm–1 and 831 cm–1 and were assigned to the Raman active ν1 symmetric stretching vibration (A1) and the Raman active triply degenerate ν3 antisymmetric stretching vibration (F2). The Raman and infrared active triply degenerate ν3 antisymmetric stretching vibration (F2) was observed in the infrared spectrum at 822 cm–1, 792 cm–1, and 761 cm–1. The intense Raman band at 465 cm–1 was assigned to the Raman active triply degenerate ν4 bending vibration (F2). The corresponding infrared bands were observed at 523 cm–1, 449 cm–1, and 414 cm–1. The intense Raman band at 329 cm–1 was attributed to the Raman active doubly degenerate ν2 symmetric bending vibration (E). Lowering of the symmetry of the tetrahedral arsenate group led to significant splitting of these modes. The low wavenumber region below 320 cm–1 was assigned to metal-oxygen stretching and lattice vibrations. In the range of 1000–1100 cm–1, four very weak bands were observed. These bands were probably due to the ν3(F2) of a very small amount of phosphate substituted for arsenate in the crystal structure of tilasite.
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A detailed analysis was undertaken of the X-ray photoelectron spectra of the three polymorphs of Al 2 Si 2 O 5 (OH) 4 ; kaolinite, dickite, nacrite plus the related mineral halloysite. Comparison of the spectra was made based on the... more
A detailed analysis was undertaken of the X-ray photoelectron spectra of the three polymorphs of Al 2 Si 2 O 5 (OH) 4 ; kaolinite, dickite, nacrite plus the related mineral halloysite. Comparison of the spectra was made based on the chemical bonding and structural differences in the Al-and Si-coordination within each polymorph. The spectra for Si(2p) for all four polymorphs are nearly identical, consistent with the fact that all the Si atoms are in 4-fold (tetrahedral) coordination, whereas the binding energies for Al(2p) vary slightly depending on the type of polymorph and the corresponding change in the stacking order of the layers. The overall shapes of the O 1s peaks observed in the four polymorphs are similar. Theoretically the ratio of oxygen atoms versus oxygen in hydroxyl groups is 5:4 (55% vs 45%). For all four polymorphs the observed values are between 53 and 58% for the oxygen atoms and 38 to 45% for the oxygen atom in the hydroxyl groups. The lower-VB spectra for the kaolin polymorphs are similar to those of α-SiO 2 in terms of binding energies, but appear ~2 eV higher than that for α-Al 2 O 3. Compared with O 1s peaks, the lower VB peaks are considerably broader (~3-4 eV FWHM), and therefore, detailed structures cannot be resolved. Nevertheless, this difference implies that the bonding character for the kaolin polymorphs is more covalent than that of α-Al 2 O 3 , but similar to that of α-SiO 2 .
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In two papers Cheng et al. (2010) reported in this journal on the mid-infrared, near-infrared and infrared emission spectroscopy of a halloysite from Hunan Xianrenwan, China. This halloysite contains around 8% of quartz (SiO2) and nearly... more
In two papers Cheng et al. (2010) reported in this journal on the mid-infrared, near-infrared and infrared emission spectroscopy of a halloysite from Hunan Xianrenwan, China. This halloysite contains around 8% of quartz (SiO2) and nearly 9% gibbsite (Al(OH)3). In their interpretation of the spectra these impurities were completely ignored. Careful comparison with a phase pure halloysite from Southern Belgium, synthetic gibbsite, gibbsite from Minas Gerais, and quartz show that these impurities do have a marked influence on the mid-infrared and infrared emission spectra. In the near-infrared, the effect is much less pronounced. Quartz does not show bands in this region and the gibbsite bands will be very weak. Comparison still show that the presence of gibbsite does contribute to the overall spectrum and bands that were ascribed to the halloysite alone do coincide with those of gibbsite.
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A detailed analysis was undertaken of the X-ray photoelectron spectra obtained from microcline, orthoclase and several samples of plagioclase with varying Na/Ca ratio. Comparison of the spectra was made based on the chemical bonding and... more
A detailed analysis was undertaken of the X-ray photoelectron spectra obtained from microcline, orthoclase and several samples of plagioclase with varying Na/Ca ratio. Comparison of the spectra was made based on the chemical bonding and structural differences in the Al- and Si-coordination within each specimen. The spectra for Si 2p and Al 2p vary with the change in symmetry between microcline and orthoclase, while in plagioclase an increase in Al-O-Si linkages results in a small but observable decrease in binding energy. The overall shapes of the O 1s peaks observed in all spectra are similar and show shifts similar to those observed for Si 2p and Al 2p. The lower-VB spectra for microcline and orthoclase are similar intermediate between α-SiO2 and α-Al2O3 in terms of binding energies. In the plagioclase series increasing coupled substitution of Na and Si for Ca and Al results in a change of the overall shape of the spectra, showing a distinct broadening associated with the presence...
Research Interests: Analytical Chemistry, Carbon, Minerals, Calcium, Silicon, and 13 morePotassium, Oxygen, Sodium, X ray diffraction, Spectrum analysis, Molecular Conformation, Aluminum oxide, X Ray Photoelectron Spectroscopy, Semiconducting Aluminum Compounds, Silicates, Cations, Silicon Dioxide, and Potassium Compounds
A detailed analysis was undertaken of the X-ray photoelectron spectra of the blue variety of pectolite known by the trade name Larimar from the Dominican Republic in an attempt to elucidate the origin of the blue colour. The survey scan... more
A detailed analysis was undertaken of the X-ray photoelectron spectra of the blue variety of pectolite known by the trade name Larimar from the Dominican Republic in an attempt to elucidate the origin of the blue colour. The survey scan confirmed the chemical composition of pectolite. The O 1s showed a complex set of bands associated with Si-O-Si, Si-O-(Na,Ca) and OH in the crystal structure of pectolite. From the possible elements suspected to cause the colour, such as Cu, Fe, Mn, and V, only Cu and Fe were observed above the detection limit of the XPS instrument. For the first time about 0.02 atom% of Pb was observed in one sample, while another sample from the same block showed the presence of 1.05 atom% Sb. The possible presence of [Pb-Pb] 3+ pairs can act as a chromophore analogous to that observed in the blue-green feldspar variety amazonite. This would explain the till now unexplained optical band at 630 nm as well as part of the high hydroxyl concentration. Though other chromophores cannot be excluded, the observation of Pb adds a new possible explanation for the blue colour of Larimar.
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Ga-substituted boehmites were synthesized using a soft-chemistry route in the presence of poly(ethylene oxide) surfactant under hydrothermal conditions. The effect of Ga-substitution was studied by X-ray diffraction and X-ray... more
Ga-substituted boehmites were synthesized using a soft-chemistry route in the presence of poly(ethylene oxide) surfactant under hydrothermal conditions. The effect of Ga-substitution was studied by X-ray diffraction and X-ray Photoelectron Spectroscopy. Initial precipitates were amorphous (minor bayerite). After hydrothermal treatment XRD showed broad reflections at low Ga-substation indicating low crystallinity and formation of pseudoboehmite. This was confirmed by high resolution XPS of Al 2p, Ga 2p and O 1s. The Al 2p binding energy of 74.03 eV was closer to boehmite than pseudoboehmite, probably caused by the Ga-substitution in the structure. The O 1s showed the presence of O, OH and H2O. The ratio of (total O)/(Al+Ga) showed an excess of O as expected for pseudoboehmite. The ratio of (O+OH)/Al+Ga) was also slightly larger than the theoretical value of 2 for boehmite. High concentrations of added Ga (10%, 20%) resulted in amorphous material after hydrothermal treatment.
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Bayldonite [Cu3Pb(AsO4)2(OH)2], Wheal Carpenter (Cornwall, UK) was studied by X-ray Photoelectron Spectroscopy and Raman Microscopy. X-ray Photoelelectron Spectroscopy revealed single copper, lead and arsenic positions in the crystal... more
Bayldonite [Cu3Pb(AsO4)2(OH)2], Wheal Carpenter (Cornwall, UK) was studied by X-ray Photoelectron Spectroscopy and Raman Microscopy. X-ray Photoelelectron Spectroscopy revealed single copper, lead and arsenic positions in the crystal structure. Two oxygen bands with a 1:4 ratio were associated oxygen positions in arsenate- and hydroxyl-groups, excluding the presence of acidic arsenate groups. The relatively large difference in binding energy for the two oxygen bands was interpreted as being due to the dynamic Jahn-Teller distortion of the copper octahedral in the bayldonite crystal structure. Raman microscopy showed bands at 804 and 837 cm-1 assigned to arsenate antisymmetric stretching mode and the symmetric stretching mode. Supported by the X-ray Photoelectron Spectroscopic results the bands at 726, 761, 822 and 886 cm-1 were assigned to copper-hydroxyl modes. Bands around 497 cm-1 were assigned to the arsenate antisymmetric bending modes and around 427 cm-1 to the symmetric bending modes. The 539 cm-1 band was associated with a copper-hydroxyl stretching mode or another υ4. The region 250-400 cm-1 showed sharp bands at 313 and 328 cm-1 with weaker bands at 298 and 342 cm-1 assigned to copper-oxygen and/or lead-oxygen stretching modes.
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Several structurally related AsO4 and PO4 minerals, were studied with Raman microscopy and X-ray Photoelectron Spectroscopy (XPS). XPS revealed only Fe, As and O for scorodite. The Fe 2p, As 3d, and O 1s indicated one position for Fe2+,... more
Several structurally related AsO4 and PO4 minerals, were studied with Raman microscopy and X-ray Photoelectron Spectroscopy (XPS). XPS revealed only Fe, As and O for scorodite. The Fe 2p, As 3d, and O 1s indicated one position for Fe2+, while 2 different environments for O and As were observed. The O 1s at 530.3 eV and the As 3d 5/2 at 43.7 eV belonged to AsO4, while minor bands for O 1s at 531.3 eV and As 3d 5/2 at 44.8 eV were due to AsO4 groups exposed on the surface possibly forming OH-groups. Mansfieldite showed, besides Al, As and O, a trace of Co. The PO4 equivalent of mansfieldite is variscite. The change in crystal structure replacing As with P resulted in an increase in the binding energy (BE) of the Al 2p by 2.9 eV. The substitution of Fe3+ for Al3+ in the structure of strengite resulted in a Fe 2p at 710.8 eV. An increase in the Fe 2p BE of 4.8 eV was found between mansfieldite and strengite. The scorodite Raman OH-stretching region showed a sharp band at 3513 cm-1 and a broad band around 3082 cm-1. The spectrum of mansfieldite was like that of scorodite with a sharp band at 3536 cm-1 and broader maxima at 3100 cm-1 and 2888 cm-1. Substituting Al in the arsenate structure instead of Fe resulted in a shift of the metal-OH-stretching mode by 23 cm-1 towards higher wavenumbers due to a slightly longer H-bonding in mansfieldite compared to scorodite. The intense band for scorodite at 805 cm-1 was ascribed to the symmetric stretching mode of the AsO4. The medium intensity bands at 890, 869, and 830 cm-1 were ascribed to the internal modes. A significant shift towards higher wavenumbers was observed for mansfieldite. The strengite Raman spectrum in the 900-1150 cm-1 shows a strong band at 981 cm-1 accompanied by a series of less intense bands. The 981 cm-1 band was assigned to the PO4 symmetric stretching mode, while the weak band at 1116 cm-1 was the corresponding antisymmetric stretching mode. The remaining bands at 1009, 1023 and 1035 cm-1 were assigned to υ1(A1) internal modes in analogy to the interpretation of the AsO4 bands for scorodite and mansfieldite. The variscite spectrum showed a shift towards higher wavenumbers in comparison to the strengite spectrum with the strongest band observed at 1030 cm-1 and was assigned to the symmetric stretching mode of the PO4, while the corresponding antisymmetric stretching mode was observed at 1080 cm-1. Due to the band splitting component bands were observed at 1059, 1046, 1013 and 940 cm-1. The AsO4 symmetric bending modes for scorodite were observed at 381 and 337 cm-1, while corresponding antisymmetric bending modes occurred at 424, 449 and 484 cm-1. Comparison with other arsenate and phosphate minerals showed that both XPS and Raman spectroscopy are fast and non-destructive techniques to identify these minerals based on their differences in chemistry and the arsenate/phosphate vibrational modes due to changes in the symmetry and the unique fingerprint region of the lattice modes.
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The changes in the structure of sabugalite have been undertaken using thermo-Raman and infrared spectroscopy based upon the results of thermogravimetric analysis. Two Raman bands are observed at 835 and 830 cm-1 assigned to the (UO 2) 2+... more
The changes in the structure of sabugalite have been undertaken using thermo-Raman and infrared spectroscopy based upon the results of thermogravimetric analysis. Two Raman bands are observed at 835 and 830 cm-1 assigned to the (UO 2) 2+ stretching vibrations resulting from the non-equivalence of the uranyl bonds (UO 2) 2+. These bands give calculated U-O bond lengths of 1.773 and 1.7808 Å. A low intensity band is observed at 895 cm-1 assigned to the ν 3 antisymmetric stretching vibration of (UO 2) 2+ units. Five bands are observed in the 950 to 1050 cm-1 region in the Raman spectrum of sabugalite and are assigned to the ν 3 antisymmetric stretching vibration of (PO 4) 3-units. Changes in the Raman spectra reflect changes in the structure of sabugalite as dehydration occurs. No (PO 4) 3-symmetric stretching mode is observed. This result is attributed to the non-equivalence of the PO bonds in the PO 4 units. The PO 4 vibrations were not affected by dehydration. Thermo-Raman spectroscopy proved to be a very powerful technique for the study of the changes in the structure of sabugalite during dehydration.
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The study of kaolinite surfaces is of industrial importance. In this work we report the application of chemometrics to the study of modified kaolinite surfaces. DRIFT spectra of mechanochemically activated kaolinites (Kiralhegy, Zettlitz,... more
The study of kaolinite surfaces is of industrial importance. In this work we report the application of chemometrics to the study of modified kaolinite surfaces. DRIFT spectra of mechanochemically activated kaolinites (Kiralhegy, Zettlitz, Szegi and Birdwood) were analysed using, Principal Component Analysis (PCA), and multi-criteria decision making (MCDM) methods, PROMETHEE and GAIA. The clear discrimination of the Kiralhegy spectral objects on the two PC scores plots (400-800 and 800-2030 cm-1) indicated the dominance of quartz. Importantly, no ordering of any spectral objects appeared to be related to grinding time in the PC plots of these spectral regions. Thus, neither the kaolinite nor the quartz, are systematically responsive to grinding time according to the spectral criteria investigated. The third spectral region (2600-3800 cm-1 – OH vibrations), showed apparent systematic ordering of the Kiralhegy and, to a lesser extent, Zettlitz spectral objects with grinding time. This was attributed to the effect of the natural quartz on the delamination of kaolinite and the accompanying phenomena (i.e. formation of kaolinite spheres and water). With the MCDM methods, it was shown that useful information on the basis of chemical composition, physical properties and grinding time can be obtained. For example, the effects of the minor chemical components (e.g. MgO, K 2 O etc) indicated that the Birdwood kaolinite is arguably the most pure one analysed. In another MCDM experiment, some support was obtained for the apparent trend with grinding time noted in the PC plot of the OH spectral region.
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Synthetic saponites prepared at atmospheric pressure and at 90°C within 20 hours with Mg2+, Zn2+, Ni2+, Cu2+, and/or Co2+ in the octahedral sheets have been thermally treated under reducing and non-reducing conditions with or without the... more
Synthetic saponites prepared at atmospheric pressure and at 90°C within 20 hours with Mg2+, Zn2+, Ni2+, Cu2+, and/or Co2+ in the octahedral sheets have been thermally treated under reducing and non-reducing conditions with or without the presence of steam. The thermal stability of saponite in air is investigated at temperatures up to 900 degrees Celsius. The nature of the octahedral cation largely determines the thermal stability of the saponite, which increases in the order Zn2+, Co2+, Mg2+, to Ni2+ from 450 to 800 degrees Celsius. The stability against reduction of the octahedral cations increases in the order Cu2+, Ni2+, to Co2+ from 150 to 600 degrees Celsius. The recrystallization of saponite at high temperatures is usually topotactic resulting in the formation of either pyroxene or olivine types of minerals. The reduction of saponites depends also on the nature of the octahedral cation. Cu2+ containing saponites are most easily reduced, followed by Ni2+ containing saponites. The difficult reduction of Co-saponites is possibly related to the thermal breakdown of the saponite structure. Mg- and Zn-saponites do not show any reduction up to 800 degrees Celsius. Incorporation of Mg2+ in Co2+ or Ni2+ containing saponites enhances the resistance against reduction. A fully reduced Ni-saponite shows a high dispersion of small Ni particles (10 nm) throughout the sample, whereas a fully reduced NiMg-saponite consists of large Ni particles (up to 60 nm), clustered together. The influence of steam on Mg-saponite is small, though incorporation of Zn2+ corresponding to an Mg/Zn ratio of 2 into the octahedral sheets results in a decrease of the hydrothermal stability. The drop in the stability is evidenced by a decrease in crystallinity and in a movement of aluminium from sites within the saponite structure to non-framework positions
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A new procedure has been developed for a fast preparation of saponite clays under the non-hydrothermal synthesis conditions of 90 degrees Celsius and 1 atmosphere. Saponites were synthesised from a stoichiometric mixture containing... more
A new procedure has been developed for a fast preparation of saponite clays under the non-hydrothermal synthesis conditions of 90 degrees Celsius and 1 atmosphere. Saponites were synthesised from a stoichiometric mixture containing Si/Al3+ gel, M2+-nitrate (M2+ = Mg, Zn, Ni, Co, or Cu), urea and water within a few hours. The synthesis products were characterised with XRD, IR, TEM, XRF, N2-physisorption, Al-EXAFS, and 27Al- and 29Si-MASNMR Incorporation of Mg, Zn, Co, Ni, or a combination of these cations in the octahedral sheet, as well as controlling the Si/Al ratio in the tetrahedral sheet in the range between 5.67 and 39.0 could easily be established. Pure Cu-saponite could not be synthesised due to the preferred formation of chrysocolla, but a combination of Mg2+ and Cu2+ resulted in saponite formation. The chemical composition strongly influences the textural properties of the saponites. It is possible to prepare saponite samples of a specific surface area and pore volume of 100 to 750 m2/g and 0.15 to 1.05 ml/g, respectively. The lateral size and the amount of stacking of the saponite platelets could be influenced by the composition, synthesis duration and amount of urea. The new synthesis procedure provides an easy way to prepare high quantities of saponites with far-reaching control on the texture as well as the composition.
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Catalytic activity of synthetic saponite clays: effects of tetrahedral and octahedral composition. Journal of Catalysis, 231(2), 443-452. ABSTRACT This paper describes the catalytic characteristics of synthetic saponites with well-known... more
Catalytic activity of synthetic saponite clays: effects of tetrahedral and octahedral composition. Journal of Catalysis, 231(2), 443-452. ABSTRACT This paper describes the catalytic characteristics of synthetic saponites with well-known chemical composition, thermal stability and acidity in three catalytic reactions: 1) catalytic cracking of n-dodecane, 2) hydro-isomerization of n-heptane and 3) Friedel-Crafts alkylation of benzene. Saponites with Mg in the octahedral position was by far the best catalyst for the catalytic cracking of n-dodecane, which can be explained by the higher surface area of these saponites compared to saponites with other compositions. All saponites performed better in the hydro-isomerization reaction of n-heptane and Friedel-Crafts alkylation compared to commercially available catalysts such as HZSM-5 and ASA. The shape selectivity in the Friedel-Crafts alkylation of benzene towards p-and o-DIOPB was remarkably high for the synthetic saponites.
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Homogeneous hydrolysis of aluminium by decomposition of urea in solution was achieved because the urea coordinates to the Al 3+ in solution forming [Al(H 2 O) 5 (urea)] 3+ and to a lesser extend [Al(H 2 O) 4 (urea) 2 ] 3+. Upon hydrolysis... more
Homogeneous hydrolysis of aluminium by decomposition of urea in solution was achieved because the urea coordinates to the Al 3+ in solution forming [Al(H 2 O) 5 (urea)] 3+ and to a lesser extend [Al(H 2 O) 4 (urea) 2 ] 3+. Upon hydrolysis more hydrolysed monomeric species [Al(H 2 O) 5 (OH)] 2+ , [Al(H 2 O) 4 (OH) 2 ] + , [Al(H 2 O) 4 (urea)(OH)] 2+ , and [Al(H 2 O) 3 (urea)(OH) 2 ] + were formed, followed by trimeric species and the Al 13 Keggin complex [AlO 4 Al 12 (OH) 24 (H 2 O) 12 ] 7+. The 27 Al NMR spectra indicated the formation of other complexes in addition to the Al 13 at the end of the hydrolysis reaction.
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Brucite [Mg(OH)2] microbialites occur in vacated interseptal spaces of living scleractinian coral colonies (Acropora, Pocillopora, Porites) from subtidal and intertidal settings in the Great Barrier Reef, Australia, and subtidal... more
Brucite [Mg(OH)2] microbialites occur in vacated interseptal spaces of living scleractinian coral colonies (Acropora, Pocillopora, Porites) from subtidal and intertidal settings in the Great Barrier Reef, Australia, and subtidal Montastraea from the Florida Keys, United States. Brucite encrusts microbial filaments of endobionts (i.e., fungi, green algae, cyanobacteria) growing under organic biofilms; the brucite distribution is patchy both within interseptal spaces and within coralla. Although brucite is undersaturated in seawater, its precipitation was apparently induced in the corals by lowered pCO2 and increased pH within microenvironments protected by microbial biofilms. The occurrence of brucite in shallow-marine settings highlights the importance of microenvironments in the formation and early diagenesis of marine carbonates. Significantly, the brucite precipitates discovered in microenvironments in these corals show that early diagenetic products do not necessarily reflect ambient seawater chemistry. Errors in environmental interpretation may arise where unidentified precipitates occur in microenvironments in skeletal carbonates that are subsequently utilized as geochemical seawater proxies.
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Synthesis and characterisation of boron and gallium substituted saponite clays below 100°C and 1 atmosphere. Microporous and Mesoporous Materials, 77, 159-165. ABSTRACT This paper describes a simple procedure for the synthesis of... more
Synthesis and characterisation of boron and gallium substituted saponite clays below 100°C and 1 atmosphere. Microporous and Mesoporous Materials, 77, 159-165. ABSTRACT This paper describes a simple procedure for the synthesis of saponites with isomorphous substitution of Si 4+ by B 3+ and Ga 3+ below 100°C and at 1 atmosphere. The XRD patterns of the Ga-and B-substituted saponites are similar to Al-substituted saponites. The 71 Ga MAS-NMR spectra of Ga 3+ containing Mg-and Zn-saponite show two broad peaks at approximately 25 and 180-195 ppm, attributed to Ga 6 and Ga 4 , respectively. the dimensions of Mg-saponite particles are considerably smaller than those of Zn-saponites. The lateral dimensions of the platelets of B 3+ containing Mg-saponites range between 40 and l00 nm, exhibiting hardly any stacking after 20 hours of synthesis, while the platelets of the Zn-saponites are 200 to 350 nm in length with some degree of stacking. B 3+ containing Mg-saponite exhibits a broad double signal at 12.6 and 9.0 ppm of a low intensity together with a sharp peak at-0.8 ppm, presumably corresponding to BO 3 and BO 4 , respectively. 29 Si MAS-NMR on the B 3+ containing saponites reveals two signals at approximately-85 due to Q 2 Si(OB)and-96 ppm corresponding to Q 3 Si(OB).
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Raman spectroscopy complimented with infrared ATR spectroscopy has been used to characterise a halotrichite FeSO(4) x Al(2)(SO(4))(3) x 22 H(2)O from The Jaroso Ravine, Aquilas, Spain. Halotrichites form a continuous solid solution series... more
Raman spectroscopy complimented with infrared ATR spectroscopy has been used to characterise a halotrichite FeSO(4) x Al(2)(SO(4))(3) x 22 H(2)O from The Jaroso Ravine, Aquilas, Spain. Halotrichites form a continuous solid solution series with pickingerite and chemical analysis shows that the jarosite contains 6% Mg(2+). Halotrichite is characterised by four infrared bands at 3569.5, 3485.7, 3371.4 and 3239.0 cm(-1). Using Libowitsky type relationships, hydrogen bond distances of 3.08, 2.876, 2.780 and 2.718 Angstrom were determined. Two intense Raman bands are observed at 987.7 and 984.4 cm(-1) and are assigned to the nu(1) symmetric stretching vibrations of the sulphate bonded to the Fe(2+) and the water units in the structure. Three sulphate bands are observed at 77K at 1000.0, 991.3 and 985.0 cm(-1) suggesting further differentiation of the sulphate units. Raman spectrum of the nu(2) and nu(4) region of halotrichite at 298 K shows two bands at 445.1 and 466.9 cm(-1), and 624.2 and 605.5 cm(-1), respectively, confirming the reduction of symmetry of the sulphate in halotrichite.
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The mineral rhodonite an orthosilicate has been characterised by Raman spectroscopy. The Raman spectra of three rhodonites from Broken Hill, Pachapaqui and Franklin were compared and found to be similar. The spectra are characterised by... more
The mineral rhodonite an orthosilicate has been characterised by Raman spectroscopy. The Raman spectra of three rhodonites from Broken Hill, Pachapaqui and Franklin were compared and found to be similar. The spectra are characterised by an intense band at around 1000 cm(-1) assigned to the nu(1) symmetric stretching mode and three bands at 989, 974 and 936 cm(-1) assigned to the nu(3) antisymmetric stretching modes of the SiO(4) units. An intense band at around 667 cm(-1) was assigned to the nu(4) bending mode and showed additional bands exhibiting loss of degeneracy of the SiO(4) units. The low wave number region of rhodonite is complex. A strong band at 421.9 cm(-1) is attributed to the nu(2) bending mode. The spectra of the three rhodonite mineral samples are similar but subtle differences are observed. It is proposed that these differences depend upon the cationic substitution of Mn by Ca and/or Fe(2+) and Mg.
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Raman spectroscopy has been used to study the nitrate hydrotalcite mbobomkulite NiAl2(OH)16(NO3).4H2O. Mbobomkulite along with hydrombobomkulite and sveite are known as ‘cave’ minerals as these hydrotalcites are only found in caves. Two... more
Raman spectroscopy has been used to study the nitrate hydrotalcite mbobomkulite
NiAl2(OH)16(NO3).4H2O. Mbobomkulite along with hydrombobomkulite and sveite are known as ‘cave’ minerals as these hydrotalcites are only found in caves. Two types of nitrate anion are observed using Raman spectroscopy namely free or non-hydrogen bonded nitrate and nitrate hydrogen bonded to the interlayer water and to the ‘brucite-like’ hydroxyl surface. Two bands are observed in the Raman spectrum of Ni-Mbobomkulite at 3576 and 3647 cm-1 with an intensity ratio of 3.36/7.37 and are attributed to the Ni3OH and Al3OH stretching vibrations. The observation of multiple water stretching vibrations implies that there are different types of water present in the hydrotalcite structure. Such types of water would result from different hydrogen bond structures.
NiAl2(OH)16(NO3).4H2O. Mbobomkulite along with hydrombobomkulite and sveite are known as ‘cave’ minerals as these hydrotalcites are only found in caves. Two types of nitrate anion are observed using Raman spectroscopy namely free or non-hydrogen bonded nitrate and nitrate hydrogen bonded to the interlayer water and to the ‘brucite-like’ hydroxyl surface. Two bands are observed in the Raman spectrum of Ni-Mbobomkulite at 3576 and 3647 cm-1 with an intensity ratio of 3.36/7.37 and are attributed to the Ni3OH and Al3OH stretching vibrations. The observation of multiple water stretching vibrations implies that there are different types of water present in the hydrotalcite structure. Such types of water would result from different hydrogen bond structures.
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Surfaces of Wyoming SWy-2-Na-montmorillonite were modified using ultrasonic and hydrothermal methods through the intercalation and adsorption of the cationic surfactant octadecyltrimethylammonium bromide (ODTMA). Changes in the surfaces... more
Surfaces of Wyoming SWy-2-Na-montmorillonite were modified using ultrasonic and hydrothermal methods through the intercalation and adsorption of the cationic surfactant octadecyltrimethylammonium bromide (ODTMA). Changes in the surfaces and structure were characterized using X-ray diffraction (XRD), thermal analysis (TG), and electron microscopy. The ultrasonic preparation method results in a higher surfactant concentration within the montmorillonite interlayer when compared with that from the hydrothermal method. Three different molecular environments for surfactants within the surface-modified montmorillonite are proposed upon the basis of their different decomposition temperatures. Both XRD patterns and TEM images demonstrate that SWy-2-Na-montmorillonite contains superlayers. TEM images of organoclays prepared at high surfactant concentrations show alternate basal spacings between neighboring layers. SEM images show that modification with surfactant reduces the clay particle size and aggregation. Organoclays prepared at low surfactant concentration display curved flakes, whereas they become flat with increasing intercalated surfactant. Novel surfactant-modified montmorillonite results in the formation of new nanophases with the potential for the removal of organic impurities from aqueous media.
Research Interests: Electron Microscopy, Scanning Electron Microscopy, Transmission Electron Microscopy, Nanochemistry, Multidisciplinary, and 13 moreAdsorption, Temperature, Bentonite, Thermogravimetry, X ray diffraction, Particle Size, Surface Properties, Surface Active Agents, Langmuir, Sensitivity and Specificity, Quaternary Ammonium Compounds, Cations, and Alkanes
We have explored the possibilities offered by the Environmental SEM to study minerals under a variety of conditions. Low voltage SEM can be used to study minerals without coating with gold or carbon, thereby allowing the researcher to use... more
We have explored the possibilities offered by the Environmental SEM to study minerals under a variety of conditions. Low voltage SEM can be used to study minerals without coating with gold or carbon, thereby allowing the researcher to use other analytical techniques on the same sample. Changes in pressure and temperature can be used to study mineral reactions such as wetting and drying but also the thermal behaviour such dehydration, dehydroxation or decarbonation. The general principles shown are not limited to the study of minerals but can be applied to a range of materials.
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Members of the solid-solutions series between erythrite [Co3(AsO4)2.8H2O] and annabergite [Ni3(AsO4)2.8H2O] were synthesized and studied by a combination of X-ray diffraction, scanning electron microscopy, and Raman and infrared... more
Members of the solid-solutions series between erythrite [Co3(AsO4)2.8H2O] and annabergite [Ni3(AsO4)2.8H2O] were synthesized and studied by a combination of X-ray diffraction, scanning electron microscopy, and Raman and infrared spectroscopy. The solid solution is complete, with the monoclinic C2/m space group being retained throughout. The unit-cell parameters decrease in size along all crystallographic directions as the amount of Ni increases. The β angle in the unit cell also decreases from 105.05(1) ° (erythrite) to 104.90(1) ° (annabergite). Crystals of annabergite and samples with high Ni content elongate along the a axis, contrasting with crystals of erythrite and Co-rich samples, which elongate along c. In the Raman and infrared spectra of the synthetic minerals, the band positions shift in accordance with the increase in bond strength associated with the decrease in the unit-cell parameters. Trends in Raman band positions of the antisymmetric arsenate stretching vibrations are sensitive to the site occupancy of metal ions in the crystal structure. Changes in the crystal morphology, unit-cell parameters and vibrational spectra have been rationalized in terms of the site occupancy of Co and Ni in the crystal structure. Substitution of Ni is directed to metal site 1 (C2h site symmetry) whereas Co is directed to metal site 2 (C2 site symmetry). Raman spectroscopy has proved to be useful for the determination of site occupancy of metal ions in solid solutions of minerals.
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High resolution thermogravimetric analysis (HRTG) coupled to a gas evolution mass spectrometer has been used to study the thermal decomposition of zinc-modified hydrotalcites of takovite formulation (NixZn6-xAl2(CO3)(OH)16.4H2O) where x... more
High resolution thermogravimetric analysis (HRTG) coupled to a gas evolution mass
spectrometer has been used to study the thermal decomposition of zinc-modified
hydrotalcites of takovite formulation (NixZn6-xAl2(CO3)(OH)16.4H2O) where x varies from 0 to 6. X-ray diffraction data indicate an increase in the crystallinity and decrease in the interlayer spacing of the materials with increase in the zinc composition. The results of HRTG and mass spectrometry (MS) indicate that water is lost in two major steps at 90-150 and 160-300 °C, with carbon dioxide coming off simultaneously at the second step at 200-300 °C. Further loss of CO2 was also observed at about 550-560 °C and 735-765 °C due to decomposition of carbonate chemically bound to layer Zn2+ and Al3+ cations, respectively. These two steps are attributed to dehydration and dehydroxylation/decarbonation, respectively. The temperature of dehydration was found to increase linearly with increase in the moles of zinc in the takovite formula. In contrast, the temperature of dehydroxylation/decarbonation decreases almost linearly with increase in zinc composition from Ni5Zn1 hydrotalcite. These observations are discussed in terms of the effects of stabilisation of the layer structure, the electronegativity of the layer metals, the charge-to-size ratio of the layer cations and the layer-interlayer hydrogen bonding interactions. Chemical reactions are proposed for the decomposition of the synthesised takovite and zinc-substituted hydrotalcites.
spectrometer has been used to study the thermal decomposition of zinc-modified
hydrotalcites of takovite formulation (NixZn6-xAl2(CO3)(OH)16.4H2O) where x varies from 0 to 6. X-ray diffraction data indicate an increase in the crystallinity and decrease in the interlayer spacing of the materials with increase in the zinc composition. The results of HRTG and mass spectrometry (MS) indicate that water is lost in two major steps at 90-150 and 160-300 °C, with carbon dioxide coming off simultaneously at the second step at 200-300 °C. Further loss of CO2 was also observed at about 550-560 °C and 735-765 °C due to decomposition of carbonate chemically bound to layer Zn2+ and Al3+ cations, respectively. These two steps are attributed to dehydration and dehydroxylation/decarbonation, respectively. The temperature of dehydration was found to increase linearly with increase in the moles of zinc in the takovite formula. In contrast, the temperature of dehydroxylation/decarbonation decreases almost linearly with increase in zinc composition from Ni5Zn1 hydrotalcite. These observations are discussed in terms of the effects of stabilisation of the layer structure, the electronegativity of the layer metals, the charge-to-size ratio of the layer cations and the layer-interlayer hydrogen bonding interactions. Chemical reactions are proposed for the decomposition of the synthesised takovite and zinc-substituted hydrotalcites.
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The distribution of Ga in the interlayer of montmorillonite pillared with a Ga13 polyoxocation complex has been studied by transmission electron microscopy, energy-dispersive X-ray microanalysis (EDX), X-ray mapping and powder X-ray... more
The distribution of Ga in the interlayer of montmorillonite pillared with a Ga13 polyoxocation complex has been studied by transmission electron microscopy, energy-dispersive X-ray microanalysis (EDX), X-ray mapping and powder X-ray diffraction in combination with N2 adsorption–desorption. To view the clay layers by TEM, the pillared clay was embedded in Spurrs resin in a preferred orientation, and sectioned with an ultramicrotome perpendicular to the layers. Montmorillonites pillared with Al13 and Al12Ga complexes were also prepared for microanalysis in the TEM. The Ga X-ray peaks could be easily distinguished in the EDX spectra, allowing concentrations relative to other elements to be determined. Elemental X-ray maps for Ga, Si and Al in the Ga13-pillared clay cross-sections demonstrated that the Ga was homogeneously distributed throughout the crystal thickness. Comparison of the analytical data with that from the Al13 and Al12Ga-pillared clays and the starting material suggested that an approximately constant amount of the intercalated species per amount of Si in the clay became incorporated into the structure in each case. Calculation of the formula for the Ga-pillared montmorillonite showed that 0.89 Ga is present per formula unit containing 8 (Si + Al), which is equivalent to 20 silicate rings, each consisting of 6 tetrahedra, for every Ga13 pillar. The actual dimension of the pillar, based results from the elemental analyses and XRD is 8.7 Å and the mean distance between the pillars is 44.3 Å, which is in good agreement with the average pore size of 39 Å obtained by N2 adsorption–desorption measurements. This study shows a new approach for obtaining more detailed information on the pillars in pillared clay by combining analytical data from X-ray microanalysis with measurements by XRD and N2 adsorption–desorption.
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Raman spectroscopy using a hot stage indicates that the intercalation of hexacyanoferrate(II) and (III) in the interlayer space of a Mg, Al hydrotalcites leads to layered solids where the intercalated species is both hexacyanoferrate(II)... more
Raman spectroscopy using a hot stage indicates that the intercalation of hexacyanoferrate(II) and (III) in the interlayer space of a Mg, Al hydrotalcites leads to layered solids where the intercalated species is both hexacyanoferrate(II) and (III). Raman spectroscopy shows that depending on the oxidation state of the initial hexacyanoferrate partial oxidation and reduction takes place upon intercalation. For the hexacyanoferrate(III) some partial reduction occurs during synthesis. The symmetry of the hexacyanoferrate decreases from Oh existing for the free anions to D3d in the hexacyanoferrate interlayered hydrotalcite complexes. Hot stage Raman spectroscopy reveals the oxidation of the hexacyanoferrate(II) to hexacyanoferrate(III) in the hydrotalcite interlayer with the removal of the cyanide anions above 250 °C. Thermal treatment causes the loss of CN ions through the observation of a band at 2080 cm -1. The hexacyanoferrate (III) interlayered Mg, Al hydrotalcites decomposes above 150 °C.
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Basic aluminium sulphate and nitrate crystals were prepared by forced hydrolysis of aluminium salt solution followed by precipitation with a sulphate solution or by evaporation for the basic aluminium nitrate. X-ray Photoelectron... more
Basic aluminium sulphate and nitrate crystals were prepared by forced hydrolysis of aluminium salt solution followed by precipitation with a sulphate solution or by evaporation for the basic aluminium nitrate. X-ray Photoelectron Spectroscopy (XPS) confirms the chemical composition determined by ICP-AES in earlier work. High resolution XPS scans of the individual elements allow the identification of both the central IVAlO4 group and the 12 aluminium octahedra in the [IVAlO4AlVI(OH)24(H2O)12] building unit by two Al 2p transitions with binding energies of 73.7 and 74.2 eV in both the basic aluminium sulphate and nitrate. Four different types of oxygen atoms were identified in the basic aluminium sulphate associated with the central AlO4, OH, H2O and SO4 groups in the crystal structure with transitions at 529.4, 530.1, 530.7 and 531.8 eV, respectively.
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This paper presents an overview of the modification of clay minerals by propping apart the clay layers with an inorganic complex. This expanded material is converted into a permanent two-dimensional structure, known as pillared clay or... more
This paper presents an overview of the modification of clay minerals by propping apart the clay layers with an inorganic complex. This expanded material is converted into a permanent two-dimensional structure, known as pillared clay or shortly PILC, by thermal treatment. The resulting material exhibits a two-dimensional porous structure with acidic properties comparable to that of zeolites. Synthetic as well as natural smectites serve as precursors for the synthesis of Al, Zr, Ti, Fe, Cr, Ga, V, Si and other pillared clays as well as mixed Fe/Al, Ga/Al, Si/Al, Zr/Al and other mixed metal pillared clays. Biofuels form an interesting renewable energy source, where these porous catalytically active materials can play an important role in the conversion of vegetable oils, such as canola oil, into biodiesel. Transesterification of vegetable oil is currently the method of choice for conversion to biofuel. The second part of this review focuses on the catalysts and cracking reaction conditions used for the production of biofuel. A distinction has been made in three different vegetable oils as starting materials: canola oil, palm oil and sunflower oil.
Research Interests: Civil Engineering, Environmental Geology, Clay Minerals, Earth and Environmental Sciences, renewable Energy sources, and 11 morePorous Media, Vegetation, Palm Oil, Canola Oil, Vegetable oil, Thermal Treatment, Smectite, Porous Material, Interdisciplinary Engineering, Sunflower Oil, and Catalytic Activity
Zn/Cr hydrotalcites were synthesised by coprecipitation, with varying pH values and divalent/trivalent metal ion ratio. Depending on the pH conditions, two 3R rhombohedral varieties were synthesised with different layer spacings of 7.8... more
Zn/Cr hydrotalcites were synthesised by coprecipitation, with varying pH values and divalent/trivalent metal ion ratio. Depending on the pH conditions, two 3R rhombohedral varieties were synthesised with different layer spacings of 7.8 and 8.9 Å, at room temperature. More carbonate was incorporated in the interlayer of samples prepared at low pH values, increasing the interlayer distance and the unit cell. Preparation under acidic conditions lead to a more crystalline, pure and thermally stable compound. Spectroscopy was used to determine the effect of varying the ratio of divalent/trivalent metal ion ratio. It was shown that although ratios >2 yield crystalline compounds a ratio of 3 was preferred for both phases.
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Thermogravimetry combined with mass spectrometry has been used to study the thermal decomposition of a synthetic hydronium jarosite. Five mass loss steps are observed at 262 294, 385, 557 and 619°C. The mass loss step at 557 °C is sharp... more
Thermogravimetry combined with mass spectrometry has been used to study the thermal decomposition of a synthetic hydronium jarosite. Five mass loss steps are observed at 262 294, 385, 557 and 619°C. The mass loss step at 557 °C is sharp and marks a sharp loss of sulphate as SO3 from the hydronium jarosite. Mass spectrometry through evolved gases confirms the first three mass loss steps to dehydroxylation, the fourth to a mass loss of the hydrated proton and a sulphate and
the final step to the loss of the remaining sulphate. Changes in the molecular structure of the hydronium jarosite were followed by infrared emission spectroscopy. This technique allows the infrared spectrum at the elevated temperatures to be obtained. Infrared emission spectroscopy confirms the dehydroxylation has taken place by 400 °C and the sulphate loss by 650 °C. Jarosites are a group of minerals formed in evaporite deposits and form a component of the efflorescence. The minerals can function as cation and heavy metal collectors. Hydronium jarosite has the potential to act as a cation collector by the replacement of the proton with a heavy metal cation.
the final step to the loss of the remaining sulphate. Changes in the molecular structure of the hydronium jarosite were followed by infrared emission spectroscopy. This technique allows the infrared spectrum at the elevated temperatures to be obtained. Infrared emission spectroscopy confirms the dehydroxylation has taken place by 400 °C and the sulphate loss by 650 °C. Jarosites are a group of minerals formed in evaporite deposits and form a component of the efflorescence. The minerals can function as cation and heavy metal collectors. Hydronium jarosite has the potential to act as a cation collector by the replacement of the proton with a heavy metal cation.
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A series of organoclays with monolayers, bilayers, pseudotrilayers, paraffin monolayers and paraffin bilayers were prepared from montmorillonite by ion exchange with hexadecyltrimethylammonium bromide (HDTMAB). The HDTMAB concentrations... more
A series of organoclays with monolayers, bilayers, pseudotrilayers, paraffin monolayers and paraffin bilayers were prepared from montmorillonite by ion exchange with hexadecyltrimethylammonium bromide (HDTMAB). The HDTMAB concentrations used for preparing the organoclays were 0.5, 0.7, 1.0, 1.5, 2.0 and 2.5 times the montmorillonite cation exchange capacity (CEC). The microstructural parameters, including the BET-N2 surface area, pore volume, pore size, and surfactant loading and distribution, were determined by X-ray diffraction, N2 adsorption-desorption and high-resolution thermogravimetric analysis (HRTG). The BET-N2 surface area decreased from 55 to 1 m2/g and the pore volume decreased from 0.11 to 0.01 cm3/g as surfactant loading was increased from Na-Mt to 2.5CEC-Mt. The average pore diameter increased from 6.8 to 16.3 nm as surfactant loading was increased. After modifying montmorillonite with HDTMAB, two basic organoclay models were proposed on the basis of HRTG results: (1) the surfactant mainly occupied the clay interlayer space (0.5CEC-Mt, 0.7CEC-Mt, 1.0CEC-Mt); and (2) both the clay interlayer space and external surface (1.5CEC-Mt, 2.0CEC-Mt, 2.5CEC-Mt) were modified by surfactant. In model 1, the sorption mechanism of p-nitrophenol to the organoclay at a relatively low concentration involved both surface adsorption and partitioning, whereas, in model 2 it mainly involved only partitioning. This study demonstrates that the distribution of adsorbed surfactant and the arrangement of adsorbed HDTMA+ within the clay interlayer space control the efficiency and mechanism of sorption by the organoclay rather than BET-N2 surface area, pore volume, and pore diameter.
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The thermal stability and thermal decomposition pathways for synthetic iowaite have been determined using thermogravimetry in conjunction with evolved gas mass spectrometry. Chemical analysis showed the formula of the synthesised iowaite... more
The thermal stability and thermal decomposition pathways for synthetic iowaite have been determined using thermogravimetry in conjunction with evolved gas mass spectrometry. Chemical analysis showed the formula of the synthesised iowaite to be Mg6.27Fe1.73(Cl)1.07(OH)16(CO3)0.33.6.1H2O and X-ray diffraction confirms the layered structure. Dehydration of the iowaite occurred at 35 and 79 °C. Dehydroxylation occurred at 254 and 291 °C. Both steps were associated with the loss of CO2. Hydrogen chloride gas was evolved in two steps at 368 and 434 °C. The products of the thermal decomposition were MgO and a spinel MgFe2O4. Experimentally it was
found to be difficult to eliminate CO2 from inclusion in the interlayer during the synthesis of the iowaite compound and in this way the synthesised iowaite resembled the natural mineral.
found to be difficult to eliminate CO2 from inclusion in the interlayer during the synthesis of the iowaite compound and in this way the synthesised iowaite resembled the natural mineral.
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A Ni-Co-As ore sample from Cobalt City, Ontario, Canada was examined with Scanning electron microscopy and Energy Dispersive X-ray analysis. In addition to cobaltian (para)rammelsbergite with variable cobalt content, for which Cobalt City... more
A Ni-Co-As ore sample from Cobalt City, Ontario, Canada was examined with Scanning electron microscopy and Energy Dispersive X-ray analysis. In addition to cobaltian (para)rammelsbergite with variable cobalt content, for which Cobalt City is the type locality, and erythrite one new minerals was observed for this locality. Well formed crystals of arsenolite, As2O3, were found embedded in what appears to be
fibrous spherocobaltite, CoCO3. Additional information was obtained by Raman microscopy confirming the identification of the arsenolite. Both are considered to be secondary minerals formed by exposure to air resulting in oxidation and the formation of secondary carbonates.
fibrous spherocobaltite, CoCO3. Additional information was obtained by Raman microscopy confirming the identification of the arsenolite. Both are considered to be secondary minerals formed by exposure to air resulting in oxidation and the formation of secondary carbonates.
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Hydrotalcite-like compounds of the formula NixZn6−xAl2(OH)16(SO4)·4H2O where x varies from 0 to 6, equivalent to a zinc-substituted carrboydite have been synthesised and characterised by X-ray diffraction, electron microscopy and... more
Hydrotalcite-like compounds of the formula NixZn6−xAl2(OH)16(SO4)·4H2O where x varies from 0 to 6, equivalent to a zinc-substituted carrboydite have been synthesised and characterised by X-ray diffraction, electron microscopy and vibrational spectroscopy. Both the d (0 0 3) spacing and the crystallite size are a function of the amount of zinc replacement for nickel in the carrboydite-like compounds. Transmission electron microscopy (TEM) shows the clay-like crystal structure for these hydrotalcite compounds. These compounds were characterised by vibrational spectroscopic techniques and a comparison made with the naturally occurring minerals. Additional bands in the sulphate antisymmetric stretching and bending region leads to the conclusion that the symmetry of the sulphate anion is reduced inferring the bonding of the sulphate anion to the hydrotalcite hydroxyl surface.
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Studies of kaolinite surfaces are of industrial importance. One useful method for studying the changes in kaolinite surface properties is to apply chemometric analyses to the kaolinite surface infrared spectra. A comparison is made... more
Studies of kaolinite surfaces are of industrial importance. One useful method for studying the changes in kaolinite surface properties is to apply chemometric analyses to the kaolinite surface infrared spectra. A comparison is made between the mechanochemical activation of Kiralyhegy kaolinites with significant amounts of natural quartz and the mechanochemical activation of Zettlitz kaolinite with added quartz. Diffuse reflectance infrared Fourier transform (DRIFT) spectra were analyzed using principal component analysis (PCA) and multi-criteria decision making (MCDM) methods, the preference ranking organization method for enrichment evaluations (PROMETHEE) and geometrical analysis for interactive assistance (GAIA). The clear discrimination of the Kiralyhegy spectral objects on the two PC scores plots (400–800 and 800–2030 cm−1) indicated the dominance of quartz. Importantly, no ordering of any spectral objects appeared to be related to grinding time in the PC plots of these spectral regions. Thus, neither the kaolinite nor the quartz are systematically responsive to grinding time according to the spectral criteria investigated. The third spectral region (2600–3800 cm−1, OH vibrations), showed apparent systematic ordering of the Kiralyhegy and, to a lesser extent, Zettlitz spectral objects with grinding time. This was attributed to the effect of the natural quartz on the delamination of kaolinite and the accompanying phenomena (i.e., formation of kaolinite spheres and water). The mechanochemical activation of kaolinite and quartz, through dry grinding, results in changes to the surface structure. Different grinding times were adopted to study the rate of destruction of the kaolinite and quartz structures. This relationship (i.e., grinding time) was classified using PROMETHEE and GAIA methodology.
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The thermal decompositions of hydrotalcites with hexacyanoferrate(II) and hexacyanoferrate(III) in the interlayer have been studied using thermogravimetry combined with mass spectrometery. X-ray diffraction shows the hydrotalcites have a... more
The thermal decompositions of hydrotalcites with hexacyanoferrate(II) and
hexacyanoferrate(III) in the interlayer have been studied using thermogravimetry
combined with mass spectrometery. X-ray diffraction shows the hydrotalcites have a
d(003) spacing of 11.1 and 10.9 Å which compares with a d-spacing of 7.9 and 7.98 Å
for the hydrotalcite with carbonate or sulphate in the interlayer. XRD was also used to
determine the products of the thermal decomposition. For the hydrotalcite
decomposition the products were MgO, Fe2O3 and a spinel MgAl2O4. Dehydration
and dehydroxylation take place in three steps each and the loss of cyanide ions in two
steps.
hexacyanoferrate(III) in the interlayer have been studied using thermogravimetry
combined with mass spectrometery. X-ray diffraction shows the hydrotalcites have a
d(003) spacing of 11.1 and 10.9 Å which compares with a d-spacing of 7.9 and 7.98 Å
for the hydrotalcite with carbonate or sulphate in the interlayer. XRD was also used to
determine the products of the thermal decomposition. For the hydrotalcite
decomposition the products were MgO, Fe2O3 and a spinel MgAl2O4. Dehydration
and dehydroxylation take place in three steps each and the loss of cyanide ions in two
steps.
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Hydrotalcites with phosphate in the interlayer were prepared at different pH. At pH >11.0 (PO4)3- was the intercalated ionic species whereas at pH < 11.0 a mixture of (PO4)3- and (HPO4)2- ions was intercalated. Powder X-ray diffraction... more
Hydrotalcites with phosphate in the interlayer were prepared at different pH. At pH >11.0 (PO4)3- was the intercalated ionic species whereas at pH < 11.0 a mixture of (PO4)3- and (HPO4)2- ions was intercalated. Powder X-ray diffraction shows the hydrotalcite formed at pH 9.5 is poorly diffracting with a d-spacing of 11.9; whereas the d(003) spacing for the phosphate interlayered hydrotalcite formed at pH 11.9 and 12.5 were 8.0 and 7.9 Å. The addition of a thermally activated ZnAl-HT to a phosphate solution resulted in the uptake of the phosphate and the reformation of the hydrotalcite. Raman spectroscopy of the phosphate interlayered hydrotalcites shows the interlayered anion is pH dependent and only above pH 11.9 is the orthophosphate anion intercalated. At lower pH the monohydrogen phosphate anion is intercalated. Raman spectroscopy shows that upon addition of the thermally activated hydrotalcite to an aqueous phosphate solution results in the uptake of phosphate anion from the solution.
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ABSTRACT The mid- and near-infrared spectra of holmquistite, a lithium-containing orthorhombic amphibole, from Barraute (Quebec, Canada) has been measured The OH-stretching region is characterised by bands around 3660, 3645, 3629 and 3613... more
ABSTRACT The mid- and near-infrared spectra of holmquistite, a lithium-containing orthorhombic amphibole, from Barraute (Quebec, Canada) has been measured The OH-stretching region is characterised by bands around 3660, 3645, 3629 and 3613 cm-1 assigned to (3Mg)-OH, (2Mg + Fe2+)-OH, (Mg + 2Fe2+)-OH and (3Fe2+)-OH, respectively. Based on the ratio between the 3645 and 3660 cm-1 bands Fe2+/(Fe2+ + Mg2+) ratios in the M1 and M3 sites were determined to be in the range between 0.35 and 0.45. In the near-infrared region two times four bands were observed associated with the four possible combination modes of the four M-OH stretching and bending modes around 4029, 4193, 4323 and 4400 cm-1 and with the four overtones of M-OH stretching modes around 7055, 7091, 7123 and 7155 cm-1.
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Raman spectra of walpurgite, (UO2)Bi4O4(AsO4)2. 2H2O, recorded at 298 K and 77 K are presented and compared with infrared spectra of walpurgite and phosphowalpurgite. Bands connected with (UO2)2+ , (AsO4)3-and H2O stretch and bend, and... more
Raman spectra of walpurgite, (UO2)Bi4O4(AsO4)2. 2H2O, recorded at 298 K and 77 K are presented and compared with infrared spectra of walpurgite and phosphowalpurgite. Bands connected with (UO2)2+ , (AsO4)3-and H2O stretch and bend, and Bi-O stretch are tentatively assigned. Hydrogen bond lengths are calculated from the wavenumbers of the H2O stretching vibrations and compared with those from crystal structure analysis of walpurgite.
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Raman spectroscopy at 298 and 77 K has been used to characterise alunites [M2(Al 3+)6(SO4)4(OH)12] where M is the monovalent cations K+, Na+, NH4+. The minerals are characterised by well-defined hydroxyl stretching patterns, which give... more
Raman spectroscopy at 298 and 77 K has been used to characterise alunites [M2(Al 3+)6(SO4)4(OH)12] where M is the monovalent cations K+, Na+, NH4+. The minerals are characterised by well-defined hydroxyl stretching patterns, which give two groups of hydrogen bonds with calculated hydrogen bond distances of 2.90 and 2.84–7 Å. The Raman spectrum of alunites shows an intense sharp band at 1026 cm−1 which is cation dependent. Multiple bands attributed to the ν4-bending mode are observed around 655 cm−1 showing a reduction in sulphate symmetry from D53d to C3v. This symmetry reduction is confirmed by the observation of multiple bands in the 480–508 cm−1 region ascribed to ν2 bending modes. Intense bands are observed at 563 cm−1 (K-alunite) 576 cm−1 (Na-alunite) and 564 cm−1 (H3O+alunite) assigned to an OH deformation vibrations. Intense bands are observed at 235 cm−1 (K-al), 238 cm−1 (Na-al) and 235 cm−1 (NH4-al) attributed is to OH⋯O hydrogen bond stretching. Raman spectroscopy enables the differentiation between the alunites synthesised with different cations.
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Thermogravimetry combined with mass spectrometry has been used to study the thermal decomposition of a synthetic ammonium jarosite. Five mass loss steps are observed at 120, 260, 389, 510 and 541 °C. Mass spectrometry through evolved... more
Thermogravimetry combined with mass spectrometry has been used to study the
thermal decomposition of a synthetic ammonium jarosite. Five mass loss steps are
observed at 120, 260, 389, 510 and 541 °C. Mass spectrometry through evolved
gases confirms these steps as loss of water, dehydroxylation, loss of ammonia and
loss of sulphate in two steps. Changes in the molecular structure of the ammonium
jarosite were followed by infrared emission spectroscopy (IES). This technique allows
the infrared spectrum at the elevated temperatures to be obtained. IES confirms the
dehydroxylation to have taken place by 300 °C and the ammonia loss by 450 °C. Loss
of the sulphate is observed by changes in band position and intensity after 500 °C.
thermal decomposition of a synthetic ammonium jarosite. Five mass loss steps are
observed at 120, 260, 389, 510 and 541 °C. Mass spectrometry through evolved
gases confirms these steps as loss of water, dehydroxylation, loss of ammonia and
loss of sulphate in two steps. Changes in the molecular structure of the ammonium
jarosite were followed by infrared emission spectroscopy (IES). This technique allows
the infrared spectrum at the elevated temperatures to be obtained. IES confirms the
dehydroxylation to have taken place by 300 °C and the ammonia loss by 450 °C. Loss
of the sulphate is observed by changes in band position and intensity after 500 °C.
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Raman spectroscopy has been used to study the molecular structure of a series of selected uranyl silicate minerals, including weeksite K2[(UO2)2(Si5O13)].H2O, soddyite [(UO2)2SiO4.2H2O] and haiweeite Ca[(UO2)2(Si5O12(OH)2](H2O)3 with... more
Raman spectroscopy has been used to study the molecular structure of a series of selected uranyl silicate minerals, including weeksite K2[(UO2)2(Si5O13)].H2O, soddyite [(UO2)2SiO4.2H2O] and haiweeite Ca[(UO2)2(Si5O12(OH)2](H2O)3 with UO2(2+)/SiO2 molar ratio 2:1 or 2:5. Raman spectra clearly show well resolved bands in the 750-800 cm-1 region and in the 950-1000 cm-1 region assigned to the nu1 modes of the (UO2)2+ units and to the (SiO4)4- tetrahedra. For example, soddyite is characterized by Raman bands at 828.0, 808.6 and 801.8 cm-1 (UO2)2+ (nu1), 909.6 and 898.0 cm-1 (UO2)2+ (nu3), 268.2, 257.8 and 246.9 cm-1 are assigned to the nu2 (delta) (UO2)2+. Coincidences of the nu1 (UO2)2+ and the nu1 (SiO4)4- is expected. Bands at 1082.2, 1071.2, 1036.3, 995.1 and 966.3 cm-1 are attributed to the nu3 (SiO4)4-. Sets of Raman bands in the 200-300 cm-1 region are assigned to nu2 (delta) (UO2)2+ and UO ligand vibrations. Multiple bands indicate the non-equivalence of the UO bonds and the lifting of the degeneracy of nu2 (delta) (UO2)2+ vibrations. The (SiO4)4- tetrahedral are characterized by bands in the 470-550 cm-1 and in the 390-420 cm-1 region. These bands are attributed to the nu4 and nu2 (SiO4)4- bending modes. The minerals show characteristic OH stretching bands in the 2900-3500 cm-1 and 3600-3700 cm-1.
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Layered double hydroxides containing Ni2+ and Al3+ have been synthesized by homogeneous precipitation through urea hydrolysis. The nature of the interlayer species changes according to the treatment of the samples, formation of interlayer... more
Layered double hydroxides containing Ni2+ and Al3+ have been synthesized by homogeneous precipitation through urea hydrolysis. The nature of the interlayer species changes according to the treatment of the samples, formation of interlayer (NH2)COO- species being observed immediately after precipitation, which undergo transformation to carbonate after hydrothermal treatment. Simultaneously, liberation of ammonia during decomposition under hydrothermal conditions gives rise to formation of [Ni(NH3)6]2+ species in solution.
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The detailed understanding of the interlayer structure of organoclays is of importance in the design of organoclay based materials and their industrial applications. In this study, transmission electron microscopy (TEM), scanning electron... more
The detailed understanding of the interlayer structure of organoclays is of importance in the design of organoclay based materials and their industrial applications. In this study, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD) have been used to provide new insights into the interlayer structure and morphology of HDTMA+/montmorillonite organoclays. XRD patterns show that thermal treatment
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ABSTRACT This paper represents an overview of the spectroscopic studies of both synthetic and naturally occurring beidellites performed as part of my research over the past 16 years. It shows that detailed information on the local... more
ABSTRACT This paper represents an overview of the spectroscopic studies of both synthetic and naturally occurring beidellites performed as part of my research over the past 16 years. It shows that detailed information on the local structure of beidellite and changes in this local structure upon heating can be obtained by combining a range of spectroscopic techniques such as mid-infrared, near-infrared, infrared emission, Raman, nuclear magnetic resonance and X-ray photoelectron spectroscopy. (c) 2005 Elsevier B.V. All rights reserved.
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Middle Infrared Spectroscopy (Mid-IR) and Infrared Emission Spectroscopy (IES) were employed to characterise Cu-exchanged montmorillonites, which were derived from two different types of montmorillonite clays, Ca-exchanged montmorillonite... more
Middle Infrared Spectroscopy (Mid-IR) and Infrared Emission Spectroscopy (IES) were employed to characterise Cu-exchanged montmorillonites, which were derived from two different types of montmorillonite clays, Ca-exchanged montmorillonite (Cheto clay) and
Na-exchanged montmorillonite (Miles clay). Copper was exchanged under both acidic and basic conditions at different Cu / clay ratios. All Cu-exchanged montmorillonites experienced a shift in most of non-lattice bands, with hydroxyl bands playing a major role in the
characterisation of the clays. Furthermore, a relationship between the ratio of bands at 3630 and 3500 cm-1 and the Cu-concentration of the starting solutions was indicated and used to compare the degree of cation exchange between two preparation methods. Two dehydration
stages were observed in the IES experiments. Additional bands were observed in all Cu exchanged montmorillonites prepared with the ‘basic conditions method’, and these bands were assigned to ammonia molecules trapped within the clay structure or absorbed on the surface of the clay.
Na-exchanged montmorillonite (Miles clay). Copper was exchanged under both acidic and basic conditions at different Cu / clay ratios. All Cu-exchanged montmorillonites experienced a shift in most of non-lattice bands, with hydroxyl bands playing a major role in the
characterisation of the clays. Furthermore, a relationship between the ratio of bands at 3630 and 3500 cm-1 and the Cu-concentration of the starting solutions was indicated and used to compare the degree of cation exchange between two preparation methods. Two dehydration
stages were observed in the IES experiments. Additional bands were observed in all Cu exchanged montmorillonites prepared with the ‘basic conditions method’, and these bands were assigned to ammonia molecules trapped within the clay structure or absorbed on the surface of the clay.
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Synthetic corundum (Al2O3), gibbsite (Al(OH)3), bayerite (Al(OH)3), boehmite (AlO(OH)) and pseudoboehmite (AlO(OH)) have been studied by high resolution XPS. The chemical compositions based on the XPS survey scans were in good agreement... more
Synthetic corundum (Al2O3), gibbsite (Al(OH)3), bayerite (Al(OH)3), boehmite (AlO(OH)) and pseudoboehmite (AlO(OH)) have been studied by high resolution XPS. The chemical compositions based on the XPS survey scans were in good agreement with the expected composition. High resolution Al2p scans showed no significant changes in binding energy, with all values between 73.9 and 74.4 eV. Only bayerite showed two transitions, associated with the presence of amorphous material in the sample. More information about the chemical and crystallographic environment was obtained from the O1s high resolution spectra. Here a clear distinction could be made between oxygen in the crystal structure, hydroxyl groups and adsorbed water. Oxygen in the crystal structure was characterised by a binding energy of about 530.6 eV in all minerals. Hydroxyl groups, present either in the crystal structure or on the surface, exhibited binding energies around 531.9 eV, while water on the surface showed binding energies around 533.0 eV. A distinction could be made between boehmite and pseudoboehmite based on the slightly lower ratio of oxygen to hydroxyl groups and water in pseudoboehmite.
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Raman spectroscopy has been used to investigate raw cotton acetylation using acetic anhydride/4-dimethylaminopyridine (DMAP) catalyst blend without solvent. The Raman data further confirm successful acetylation as shown by FTIR that was... more
Raman spectroscopy has been used to investigate raw cotton acetylation using acetic anhydride/4-dimethylaminopyridine (DMAP) catalyst blend without solvent. The Raman data further confirm successful acetylation as shown by FTIR that was demonstrated previously to be highly sensitive for determining the level of acetylation. However, the Raman peaks are much weaker than the FTIR bands. Nevertheless, the variations of the extent of acetylation estimated from both Raman and FTIR spectra with weight percent gain due to acetylation (WPG) were observed to follow the same pattern. The degrees of acetylation calculated from Raman data were also found to increase linearly with that calculated from the more sensitive FTIR technique. Raman technique is thus suitable for further development as an analytical tool for determining the acetylation level of natural cellulose fibres. Raman data have also shown that the acetylation reaction reduces the crystallinity of cotton.
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Raman and infrared spectroscopy has enabled insights into the molecular structure of the sampleite group of minerals. These minerals are based upon the incorporation of either phosphate or arsenate with chloride anion into the structure... more
Raman and infrared spectroscopy has enabled insights into the molecular
structure of the sampleite group of minerals. These minerals are based upon the
incorporation of either phosphate or arsenate with chloride anion into the structure
and as a consequence the spectra refect the bands attributable to these anions, namely
phosphate or arsenate with chloride. The sampleite vibrational spectrum reflects the
spectrum of the phosphate anion and consists of ν1 at 964, ν2 at 451 cm-1, ν3 at 1016
and 1088 and ν4 at 643, 604, 591 and 557 cm-1. The lavendulan spectrum consists of
ν1 at 854, ν2 at 345 cm-1, ν3 at 878 cm-1 and ν4 at 545 cm-1. The Raman spectrum of
lemanskiite is different from that of lavendulan consistent with a different structure.
Low wavenumber bands at 227 and 210 cm-1 may be assigned to CuCl TO/LO optic
vibrations. Raman spectroscopy identified the substitution of arsenate by phosphate in
zdenekite and lavendulan.
structure of the sampleite group of minerals. These minerals are based upon the
incorporation of either phosphate or arsenate with chloride anion into the structure
and as a consequence the spectra refect the bands attributable to these anions, namely
phosphate or arsenate with chloride. The sampleite vibrational spectrum reflects the
spectrum of the phosphate anion and consists of ν1 at 964, ν2 at 451 cm-1, ν3 at 1016
and 1088 and ν4 at 643, 604, 591 and 557 cm-1. The lavendulan spectrum consists of
ν1 at 854, ν2 at 345 cm-1, ν3 at 878 cm-1 and ν4 at 545 cm-1. The Raman spectrum of
lemanskiite is different from that of lavendulan consistent with a different structure.
Low wavenumber bands at 227 and 210 cm-1 may be assigned to CuCl TO/LO optic
vibrations. Raman spectroscopy identified the substitution of arsenate by phosphate in
zdenekite and lavendulan.
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The distribution of Al13 pillars and the process of intercalation in montmorillonite can be enhanced through the application of an ultrasonic treatment. This paper describes the results of ultrasonic treatment in the preparation of... more
The distribution of Al13 pillars and the process of intercalation in montmorillonite can be enhanced through the application of an ultrasonic treatment. This paper describes the results of ultrasonic treatment in the preparation of Al-pillared montmorillonite with and without prior exchange with Na+. The resulting materials have been characterised
by X-ray diffraction (XRD), N2 adsorption/desorption, Scanning Electron Microscopy and Atomic Force Microscopy (AFM). The catalytic activity was tested with the n-heptane hydroconversion test. Optimum results were obtained after ultrasonic treatment up to 20 min without prior Na-exchange before the Al13 intercalation. Longer ultrasonic treatment resulted in partial destruction of the pillared structure. The pore size diameter also increased with increasing ultrasonic treatment up to 20 min with values in the range of 4 nm. This behaviour can be explained by the loss of
the typical house of cards structure after prolonged ultrasonic treatment. AFM showed that the pillars in the interlayer of the montmorillonite resulted in a distortion of the tetrahedral sheets of the clay. At atomic scale resolution it was clear that the pillar distribution is not homogenous, confirming earlier results using high resolution TEM. The effects of ultrasonic treatment on the catalytic activity is rather limited, although the pillared clays prepared with short ultrasonic treatments of 5 and 10 min performed slightly better.
by X-ray diffraction (XRD), N2 adsorption/desorption, Scanning Electron Microscopy and Atomic Force Microscopy (AFM). The catalytic activity was tested with the n-heptane hydroconversion test. Optimum results were obtained after ultrasonic treatment up to 20 min without prior Na-exchange before the Al13 intercalation. Longer ultrasonic treatment resulted in partial destruction of the pillared structure. The pore size diameter also increased with increasing ultrasonic treatment up to 20 min with values in the range of 4 nm. This behaviour can be explained by the loss of
the typical house of cards structure after prolonged ultrasonic treatment. AFM showed that the pillars in the interlayer of the montmorillonite resulted in a distortion of the tetrahedral sheets of the clay. At atomic scale resolution it was clear that the pillar distribution is not homogenous, confirming earlier results using high resolution TEM. The effects of ultrasonic treatment on the catalytic activity is rather limited, although the pillared clays prepared with short ultrasonic treatments of 5 and 10 min performed slightly better.
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Electronic and vibrational spectra of two different tourmalines: green and pink coloured minerals from Minas Gerais, Brazil, have been investigated by UV–vis, NIR, IR and Raman spectroscopies. The behaviour of transition metal ions in... more
Electronic and vibrational spectra of two different tourmalines: green and pink coloured minerals from Minas Gerais, Brazil, have been investigated by UV–vis, NIR, IR and Raman spectroscopies. The behaviour of transition metal ions in their electronic spectra is presented. Both minerals show a strong broad band at 300 nm (33,300 cm-1) due to Mn(II) ion. In pink tourmaline three sharp bands at 365, 345, and 295 nm
(27,400, 28,990 and 33,900 cm-1) are assigned to 6A1g (S)1 4T2g (D), 6A1g (S) 4Eg (D) and 6A1g (S) 4T1g (F) transitions of Mn(II) ion. The pink colour arises from the Mn(II) ion while the band at 520 nm comes from Mn(III) ion which acts as an aid to the transmission window from 700 to 900 nm in pink tourmaline. NIR spectroscopy provides evidence for Fe(II) through the observation of two bands at 10,240 and 8000 cm-1. The observation of four OH stretching bands in the hydroxyl stretching region 3800–3200 cm-1 near 3650, 3600 and 3555 and 3460 cm-1 shows mixed occupancy of octahedral sites in the minerals studied. The band positions in the spectra of green and pink tourmalines differ slightly due to compositional variations. Experimentally, a number of cation–oxygen vibrational modes in the Raman spectra could be observed in the low wavenumber region 1200–200 cm-1.
(27,400, 28,990 and 33,900 cm-1) are assigned to 6A1g (S)1 4T2g (D), 6A1g (S) 4Eg (D) and 6A1g (S) 4T1g (F) transitions of Mn(II) ion. The pink colour arises from the Mn(II) ion while the band at 520 nm comes from Mn(III) ion which acts as an aid to the transmission window from 700 to 900 nm in pink tourmaline. NIR spectroscopy provides evidence for Fe(II) through the observation of two bands at 10,240 and 8000 cm-1. The observation of four OH stretching bands in the hydroxyl stretching region 3800–3200 cm-1 near 3650, 3600 and 3555 and 3460 cm-1 shows mixed occupancy of octahedral sites in the minerals studied. The band positions in the spectra of green and pink tourmalines differ slightly due to compositional variations. Experimentally, a number of cation–oxygen vibrational modes in the Raman spectra could be observed in the low wavenumber region 1200–200 cm-1.
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X-ray photoelectron spectroscopy (XPS) in combination with X-ray diffraction (XRD) and high-resolution thermogravimetric analysis (HRTG) has been used to investigate the surfactant distribution within the organoclays prepared at different... more
X-ray photoelectron spectroscopy (XPS) in combination with X-ray diffraction (XRD) and high-resolution thermogravimetric analysis (HRTG) has been used to investigate the surfactant distribution within the organoclays prepared at different surfactant concentrations. This study demonstrates that the surfactant distribution within the organoclays depends strongly on the surfactant loadings. In the organoclays prepared at relative low surfactant concentrations, the surfactant cations mainly locate in the clay interlayer, whereas the surfactants occupy both the clay interlayer space and the interparticle pores in the organoclays prepared at high surfactant concentrations. This is in accordance with the dramatic pore volume decrease of organoclays compared to those of starting clays. XPS survey scans show that, at low surfactant concentration (<1.0 CEC), the ion exchange between Na+ and HDTMA+ is dominant, whereas both cations and ion pairs occur in the organoclays prepared at high concentrations (>1.0 CEC). High-resolution XPS spectra show that the modification of clay with surfactants has prominent influences on the binding energies of the atoms in both clays and surfactants, and nitrogen is the most sensitive to the surfactant distribution within the organoclays.
Research Interests: Chemistry, Analytical Chemistry, Spectroscopy, Nanocomposites, Clay Minerals, and 15 moreNanochemistry, Surface Chemistry, Colloids, Nitrogen, Bentonite, Thermogravimetry, High Resolution, XPS, X ray diffraction, Thermogravimetric Analysis, Spectrum analysis, Smectite, Binding Energy, Surface Active Agents, and Ion Exchange
Abstract Rare earth element geochemistry in carbonate rocks is utilized increasingly for studying both modern oceans and palaeoceanography, with additional applications for investigating water–rock interactions in groundwater and... more
Abstract Rare earth element geochemistry in carbonate rocks is utilized increasingly for studying both modern oceans and palaeoceanography, with additional applications for investigating water–rock interactions in groundwater and carbonate diagenesis. However, the study of rare earth element geochemistry in ancient rocks requires the preservation of their distribution patterns through subsequent diagenesis. The subjects of this study, Pleistocene scleractinian coral skeletons from Windley Key, Florida, have undergone ...
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Metal oxide pillared clay (PILC) possesses several interesting properties, such as large surface area, high pore volume and tunable pore size (from micropore to mesopore), high thermal stability, strong surface acidity and catalytic... more
Metal oxide pillared clay (PILC) possesses several interesting properties, such as large surface area, high pore volume and tunable pore size (from micropore to mesopore), high thermal stability, strong surface acidity and catalytic active substrates/metal oxide pillars. These unique characteristics make PILC an attractive material in catalytic reactions. It can be made either as catalyst support or directly used as catalyst. This paper is a continuous work from Kloprogge's review (J.T. Kloprogge, J. Porous Mater. 5, 5 1998) on the synthesis and properties of smectites and related PILCs and will focus on the diverse applications of clay pillared with different types of metal oxides in the heterogeneous catalysis area and adsorption area. The relation between the performance of the PILC and its physico-chemical features will be addressed.
Research Interests:
The Raman spectrum of holmquistite, a Li-containing orthorhombic amphibole from Bessemer City, USA has been measured. The OH-stretching region is characterized by bands at 3661, 3646, 3634 and 3614 cm–1 assigned to 3 Mg–OH, 2 Mg +... more
The Raman spectrum of holmquistite, a Li-containing orthorhombic amphibole from Bessemer City, USA has been measured. The OH-stretching region is characterized by bands at 3661, 3646, 3634 and 3614 cm–1 assigned to 3 Mg–OH, 2 Mg + Fe2+–OH, Mg + 2Fe2+–OH and 3 Fe2+–OH, respectively. These Mg and Fe2+ cations are located at the M1 and M3 sites and have a Fe2+/(Fe2+ + Mg) ratio of 0.35. The 960–1110 cm–1 region represents the antisymmetric Si–O–Si and O–Si–O stretching vibrations. For holmquistite, strong bands are observed around 1022 and 1085 cm–1 with a shoulder at 1127 cm–1 and minor bands at 1045 and 1102 cm–1. In the region 650–800 cm–1 bands are observed at 679, 753 and 791 cm–1 with a minor band around 694 cm–1 attributed to the symmetrical Si–O–Si and Si–O vibrations. The region below 625 cm–1 is characterized by 14 vibrations related to the deformation modes of the silicate double chain and vibrations involving Mg, Fe, Al and Li in the various M sites. The 502 cm–1 band is a Li–O deformation mode while the 456, 551 and 565 cm–1 bands are Al–O deformation modes.
Research Interests:
X-ray powder diffraction studies have shown that solid solution in the orthorhombic lead(ll) chromate-orthorhombic lead(IT) sulfate system, space group Pnma, is lacunar at 25 °C, with the miscibility gap bounded by Pb(CrO4)0.8(SO4)0.2 and... more
X-ray powder diffraction studies have shown that solid solution in the
orthorhombic lead(ll) chromate-orthorhombic lead(IT) sulfate system, space group Pnma, is lacunar at 25 °C, with the miscibility gap bounded by Pb(CrO4)0.8(SO4)0.2 and Pb(CrO4)0.1(SO4)0.9 - All Cr-rich compositions are metastable with respect to the monoclinic polymorph, corresponding to crocoite, space group P21/n. The extent of solid solution of sulfate in crocoite at 25 °C is Pb(CrO4) 0.6(SO4)0.4· The transformation of orthorhombic Pb(CrO4)x(SO4) 1-x to the monoclinic phase is slow in the solid state, as compared to when solid samples are allowed to remain in contact with the solution from which they crystallized. Recrystallization at ambient temperatures is acid-catalyzed and these effects explain a number of disparate reports concerning
the stabilities of the various series in the literature. A value for the solubility product of orthorhombic lead (II) chromate has been determined using solution methods as logKsp(PbCrO4 ,s,orthorhombic, 298.2 K) = - 10.71 (12) and this has been used in turn to assess the nature of solid solution in Pb(CrO4)x(S)4)1-x(0< x<0.1). Results
of the study have been applied to an assessment of the extent of solid solution in naturally occurring sulfatian crocoite and chromian anglesite. Microprobe analyses of specimens of the latter mineral from the Red Lead mine, Dundas, Tasmania, shows significant chromate substitution, which can conveniently be detected at very low levels by laser Raman microprobe spectroscopy at room temperature.
orthorhombic lead(ll) chromate-orthorhombic lead(IT) sulfate system, space group Pnma, is lacunar at 25 °C, with the miscibility gap bounded by Pb(CrO4)0.8(SO4)0.2 and Pb(CrO4)0.1(SO4)0.9 - All Cr-rich compositions are metastable with respect to the monoclinic polymorph, corresponding to crocoite, space group P21/n. The extent of solid solution of sulfate in crocoite at 25 °C is Pb(CrO4) 0.6(SO4)0.4· The transformation of orthorhombic Pb(CrO4)x(SO4) 1-x to the monoclinic phase is slow in the solid state, as compared to when solid samples are allowed to remain in contact with the solution from which they crystallized. Recrystallization at ambient temperatures is acid-catalyzed and these effects explain a number of disparate reports concerning
the stabilities of the various series in the literature. A value for the solubility product of orthorhombic lead (II) chromate has been determined using solution methods as logKsp(PbCrO4 ,s,orthorhombic, 298.2 K) = - 10.71 (12) and this has been used in turn to assess the nature of solid solution in Pb(CrO4)x(S)4)1-x(0< x<0.1). Results
of the study have been applied to an assessment of the extent of solid solution in naturally occurring sulfatian crocoite and chromian anglesite. Microprobe analyses of specimens of the latter mineral from the Red Lead mine, Dundas, Tasmania, shows significant chromate substitution, which can conveniently be detected at very low levels by laser Raman microprobe spectroscopy at room temperature.
Research Interests:
The Raman spectra of the isomorphous series descloizite [PbZn(VO4)(OH)] and mottramite [PbCu(VO4) (OH)] were obtained at 298 and 77 K. The Raman band at 844 cm-1, assigned to the 1 symmetric (VO4-) stretching mode for descloizite, is... more
The Raman spectra of the isomorphous series descloizite [PbZn(VO4)(OH)] and mottramite [PbCu(VO4) (OH)] were obtained at 298 and 77 K. The Raman band at 844 cm-1, assigned to the 1 symmetric (VO4-) stretching mode for descloizite, is shifted to 814 cm-1 for mottramite. The 3 mode of descloizite is observed as a single band at 777 cm-1 but this mode is more complex for mottramite with three bands observed in the 77 K spectrum at 811, 785 and 767 cm-1. The bending mode (2) is observed at 437 cm-1 for descloizite and at 426 cm-1 for mottramite. The 3 region is complex for both minerals and this is attributed to symmetry reduction of the vanadate unit from Td to Cs. Collecting Raman spectra at 77 K allowed better band separation with observation of additional bands ascribed to the removal of degeneracy.
Research Interests:
The infrared emission spectra of hydrothermally synthesized saponites have been compared to those of naturally occurring saponites. The spectra are very similar and only very minor differences are observed in the band positions and... more
The infrared emission spectra of hydrothermally synthesized saponites
have been compared to those of naturally occurring saponites. The spectra are very
similar and only very minor differences are observed in the band positions and intensities. The OH-stretching region reveals for only the synthetic saponite a small
band around 3040 -3120 cm-1 ascribed to ammonium in the interlayer position. OH stretching bands associated with adsorbed and interlayer water are observed around 3250 and 3425 cm-1. The strong band around 3600- 3630 cm-1 is ascribed to the Mg2(Al, vac)-OH stretching mode whereas the band around 3670 cm-1 is ascribed
to the Mg3-OH stretching mode. Upon heating the OH-stretching region shows
firstly the disappearance of the interlayer water and secondly a decrease in intensity
of the Mg2(Al, vac)-OH hydroxyl-band. In contrast the Mg3-(OH) hydroxyl-band
decreases far less in intensity. A silanol band at 3778 cm-1 is observed over the
whole temperature range from room temperature to 750 °C in the spectra of all saponites. The Mg2Al-OH translation mode around 450 cm-1 and deformation mode
around 750 cm-1 decrease in intensity and are no longer observed in the 700 °C spectrum. Instead, a new band is observed around 730-740 cm-1 ascribed to the restructuring of the octahedral layer and the formation of a new Al-0 bond after the dehydroxylation. Because the dehydroxylation is not complete at 700-750 °C no new
bands due to the formation of new Mg-O- Mg, Mg-0- AI or Mg-O- Si bonds are observed. Only a minor decrease in the Mg3-0H bands is observed.
have been compared to those of naturally occurring saponites. The spectra are very
similar and only very minor differences are observed in the band positions and intensities. The OH-stretching region reveals for only the synthetic saponite a small
band around 3040 -3120 cm-1 ascribed to ammonium in the interlayer position. OH stretching bands associated with adsorbed and interlayer water are observed around 3250 and 3425 cm-1. The strong band around 3600- 3630 cm-1 is ascribed to the Mg2(Al, vac)-OH stretching mode whereas the band around 3670 cm-1 is ascribed
to the Mg3-OH stretching mode. Upon heating the OH-stretching region shows
firstly the disappearance of the interlayer water and secondly a decrease in intensity
of the Mg2(Al, vac)-OH hydroxyl-band. In contrast the Mg3-(OH) hydroxyl-band
decreases far less in intensity. A silanol band at 3778 cm-1 is observed over the
whole temperature range from room temperature to 750 °C in the spectra of all saponites. The Mg2Al-OH translation mode around 450 cm-1 and deformation mode
around 750 cm-1 decrease in intensity and are no longer observed in the 700 °C spectrum. Instead, a new band is observed around 730-740 cm-1 ascribed to the restructuring of the octahedral layer and the formation of a new Al-0 bond after the dehydroxylation. Because the dehydroxylation is not complete at 700-750 °C no new
bands due to the formation of new Mg-O- Mg, Mg-0- AI or Mg-O- Si bonds are observed. Only a minor decrease in the Mg3-0H bands is observed.
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The behavior of the hydroxyl units of synthetic goethite and its dehydroxylated product hematite was characterized using a combination of Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) during the thermal... more
The behavior of the hydroxyl units of synthetic goethite and its dehydroxylated product hematite was characterized using a combination of Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) during the thermal transformation over a temperature range of 180-270 degrees C. Hematite was detected at temperatures above 200 degrees C by XRD while goethite was not observed above 230 degrees C. Five intense OH vibrations at 3212-3194, 1687-1674, 1643-1640, 888-884 and 800-798 cm(-1), and a H2O vibration at 3450-3445 cm(-1) were observed for goethite. The intensity of hydroxyl stretching and bending vibrations decreased with the extent of dehydroxylation of goethite. Infrared absorption bands clearly show the phase transformation between goethite and hematite: in particular. the migration of excess hydroxyl units from goethite to hematite. Two bands at 536-533 and 454-452 cm(-1) are the low wavenumber vibrations of Fe-O in the hematite structure. Band component analysis data of FTIR spectra support the fact that the hydroxyl units mainly affect the a plane in goethite and the equivalent c plane in hematite.
Research Interests: Analytical Chemistry, FTIR spectroscopy, Minerals, Macromolecular X-Ray Crystallography, Infrared spectroscopy, and 10 moreGoethite, Hematite, Phase Transformation, X ray diffraction, Component Analysis, Fourier transform infrared spectroscopy, Ferric Compounds, Iron Compounds, Fourier transform infrared, and hydroxide minerals
Near-IR spectroscopy has been used to distinguish between palygorskites and sepiolites. Three near-IR spectral regions contain bands due to (a) the high frequency region between 6400 and 7400 cm−1 attributed to the first overtone of the... more
Near-IR spectroscopy has been used to distinguish between palygorskites and sepiolites. Three near-IR spectral regions contain bands due to (a) the high frequency region between 6400 and 7400 cm−1 attributed to the first overtone of the hydroxyl stretching mode, (b) the 4800–5400 cm−1 region attributed to water combination modes and (c) the 4000–4800 cm−1 region attributed to the combination of the stretching and deformation modes of the M–MgOH units of palygorskites and sepiolites. Near-IR bands are observed in the first region and are assigned to the first overtone of the hydroxyl stretching frequency observed at 3620 and 3410 cm−1 in the mid-IR spectra. The near-IR bands observed in the second region are assigned to the combination of the water OH stretching and deformation vibrational modes. A complex set of low intensity bands are observed in the 4100–4600 cm−1 region and are attributed to the combination of the cation hydroxyl stretching, deformation and translation modes. The difference between the near-IR spectra of palygorskites and sepiolites depends on the dioctahedral nature of the palygorskites and the trioctahedral structure of the sepiolites. Changes in the near-IR spectra are therefore related to the Mg3(OH) and Mg2(OH) units in the palygorskites.
Research Interests:
Raman spectroscopy of formamide-intercalated kaolinites treated using controlled-rate thermal analysis technology (CRTA), allowing the separation of adsorbed formamide from intercalated formamide in formamide-intercalated kaolinites, is... more
Raman spectroscopy of formamide-intercalated kaolinites treated using controlled-rate thermal analysis technology (CRTA), allowing the separation of adsorbed formamide from intercalated formamide in formamide-intercalated kaolinites, is reported. The Raman spectra of the CRTA-treated formamide-intercalated kaolinites are significantly different from those of the intercalated kaolinites, which display a combination of both intercalated and adsorbed formamide. An intense band is observed at 3629 cm-1, attributed to the inner surface hydroxyls hydrogen bonded to the formamide. Broad bands are observed at 3600 and 3639 cm-1, assigned to the inner surface hydroxyls, which are hydrogen bonded to the adsorbed water molecules. The hydroxyl-stretching band of the inner hydroxyl is observed at 3621 cm-1 in the Raman spectra of the CRTA-treated formamide-intercalated kaolinites. The results of thermal analysis show that the amount of intercalated formamide between the kaolinite layers is independent of the presence of water. Significant differences are observed in the CO stretching region between the adsorbed and intercalated formamide.
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The thermal behaviour of fully and partially expanded kaolinites intercalated with formamide has been investigated in nitrogen atmosphere under quasi-isothermal heating conditions at a constant, pre-set decomposition rate of 0.20 mg min–1... more
The thermal behaviour of fully and partially expanded kaolinites intercalated with formamide has been investigated in nitrogen atmosphere under quasi-isothermal heating conditions at a constant, pre-set decomposition rate of 0.20 mg min–1 . With this technique it is possible to distinguish between loosely bonded (surface bonded) and strongly bonded (intercalated) formamide. Loosely bonded formamide is liberated in an equilibrium reaction under quasi-isothermal conditions at 118°C, while the strongly bonded (intercalated) portion is lost in an equilibrium, but non-isothermal process between 130 and 200°C. The presence of water in the intercalation solution can influence the amount of adsorbed formamide, but has no effect on the amount of the intercalated reagent. When the kaolinite is fully expanded, the amount of formamide hydrogen bonded to the inner surface of the mineral is 0.25 mol formamide/mol inner surface OH group. While the amount of surface bonded formamide is decreasing with time, no change can be observed in the amount of the intercalated reagent. With this technique the mass loss stages belonging to adsorbed and intercalated formamide can be resolved thereby providing a complex containing only one type of bonded (intercalated) formamide.
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Holmquistite is a lithium-bearing orthorhombic amphibole , named after the Swedish petrologist Per Holmquist. It typically occurs at the contact of lithium rich pegmatites with surrounding rocks and is associated with metasomatic... more
Holmquistite is a lithium-bearing orthorhombic amphibole , named after the Swedish petrologist Per Holmquist. It typically occurs at the contact of lithium rich pegmatites with surrounding rocks and is associated with metasomatic processes. The bands around 3660, 3645, 3635 and 3615 cm- 1 have been assigned to (3Mg)-OH, (2Mg + Fe2+)-0H, (Mg + 2Fe2+)-0H and (3Fe2+)-0H, respectively. Based on the ratio between
the 3645 and 3660 cm- 1 bands in the Raman spectrum the Fe2+ /(Fe2+ + Mg2+) ratio in the M1 and M3 sites has been determined to be 0.4 [14]. A similar calculation on the infrared OH-stretching bands indicate a slightly lower ratio around 0.3, but this value is less precise due to the presence of a broad background signal of adsorbed water.A limited number of vibrations are only infrared active, such as the bands
at 649, 737, 873, 923, and 1011 cm-1, while bands at 751 , 998, 1041 and 11 27 cm- 1 are only Raman active. All other bands are both infrared and Raman active. From the theoretically 86 possible vibrations in the infrared and Raman spectra in this region below 1200 cm-1 fo rty-four bands are observed. The 950--11 30 cm- 1 region represents the antisymmetric Si-0-Si and 0 - Si-O stretching vibrations. In the region
between 650 and 800 cm-1 bands are observed attributed to the symmetrical Si-0-Si and Si-0 vibrations. The region below 625 cm-1 is characterized by vibrations related to the deformation modes of the silicate chain and vibrations involving Mg, Fe, Al and Li in the various M sites. The 499 cm- 1 band is a Li-0 deformation mode while the bands at 448-454 and 557- 558 cm- 1 are Al-0 deformation modes. OH-libration and translation modes are observed around 302, 534, 587 and 6 12 cm-1.
the 3645 and 3660 cm- 1 bands in the Raman spectrum the Fe2+ /(Fe2+ + Mg2+) ratio in the M1 and M3 sites has been determined to be 0.4 [14]. A similar calculation on the infrared OH-stretching bands indicate a slightly lower ratio around 0.3, but this value is less precise due to the presence of a broad background signal of adsorbed water.A limited number of vibrations are only infrared active, such as the bands
at 649, 737, 873, 923, and 1011 cm-1, while bands at 751 , 998, 1041 and 11 27 cm- 1 are only Raman active. All other bands are both infrared and Raman active. From the theoretically 86 possible vibrations in the infrared and Raman spectra in this region below 1200 cm-1 fo rty-four bands are observed. The 950--11 30 cm- 1 region represents the antisymmetric Si-0-Si and 0 - Si-O stretching vibrations. In the region
between 650 and 800 cm-1 bands are observed attributed to the symmetrical Si-0-Si and Si-0 vibrations. The region below 625 cm-1 is characterized by vibrations related to the deformation modes of the silicate chain and vibrations involving Mg, Fe, Al and Li in the various M sites. The 499 cm- 1 band is a Li-0 deformation mode while the bands at 448-454 and 557- 558 cm- 1 are Al-0 deformation modes. OH-libration and translation modes are observed around 302, 534, 587 and 6 12 cm-1.
Research Interests:
This paper describes the Raman and infrared spectroscopy of SrSO4 or celestine from the Muschelkalk of Winterswijk, The Netherlands. The infrared absorption spectrum is characterised by the SO4 2-modes V1 at 991 cm-1, v3 at 1201, 1138 and... more
This paper describes the Raman and infrared spectroscopy of SrSO4 or celestine from the Muschelkalk of Winterswijk, The Netherlands. The infrared absorption spectrum is characterised by the SO4 2-modes V1 at 991 cm-1, v3 at 1201, 1138 and 1091 cm-1, and v4 at 643 and 611 cm-1. An unidentified band is observed at 1248 cm-1. In the Raman spectrum at 293 K the V1 mode is found at 1000 cm-1 and is split in two bands at 1001 and 1003 cm-1 upon cooling to 77 K.The v2 mode, not observed in the infrared spectrum, is observed as a doublet at 460 and 453 cm-1. The v3 mode is represented by four bands in the Raman spectrum at 1187, 1158, 1110 and 1093 cm-1 and the v4 mode as three bands at 656, 638 and 620 cm-1. Cooling to 77 K results in a general decrease in bandwidth and a minor shift in frequencies. A decrease in intensities is observed upon cooling to 77 K due to movement of the Sr atom towards one or more of the oxygen atoms in the sulfate group.
Research Interests:
High‐quality Raman spectra were used for the characterization of alumina phases of gibbsite, bayerite, diaspore and boehmite. The Raman spectrum of gibbsite shows four strong, sharp bands at 3617, 3522, 3433 and 3364 cm−1 in the hydroxyl... more
High‐quality Raman spectra were used for the characterization of alumina phases of gibbsite, bayerite, diaspore and boehmite. The Raman spectrum of gibbsite shows four strong, sharp bands at 3617, 3522, 3433 and 3364 cm−1 in the hydroxyl stretching region. The spectrum of bayerite shows seven bands at 3664, 3652, 3552, 3542, 3450, 3438 and 3420 cm−1. Five broad bands at 3445, 3363, 3226, 3119 and 2936 cm−1 and four broad and weak bands at 3371, 3220, 3085 and 2989 cm−1 are present in the Raman spectrum of the hydroxyl stretching region of diaspore and boehmite. The hydroxyl stretching bands are related to the surface structure of the minerals. The Raman spectra of bayerite, gibbsite and diaspore are complex whereas the Raman spectrum of boehmite shows only four bands in the low‐wavenumber region. These bands are assigned to deformation and translational modes of the alumina phases. A comparison of the Raman spectrum of bauxite with those of boehmite and gibbsite showed the possibility of using Raman spectroscopy for on‐line processing of bauxites that contain a mixture of alumina phases.
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The Raman spectra of both low- and high-defect kaolinites in the hydroxyl stretching and low-wavenumber region were obtained with excitation at three visible wavelengths of 633, 514 and 442 nm and a UV wavelength of 325 nm. The UV-excited... more
The Raman spectra of both low- and high-defect kaolinites in the hydroxyl stretching and low-wavenumber region were obtained with excitation at three visible wavelengths of 633, 514 and 442 nm and a UV wavelength of 325 nm. The UV-excited spectra were comparable to those excited by the visible wavelengths. The Raman spectra show hydroxyl stretching bands at 3621 cm-1 attributed to the inner hydroxyl, at 3692 and 3684 cm-1 attributed to the longitudinal and transverse optic modes of the inner surface hydroxyls and at 3668 and 3653 cm-1 assigned to the out-of phase vibrations of the inner surface hydroxyls. Two bands were observed in the spectral profile at 3695 cm-1 for the high-defect kaolinite at 3698 and 3691 cm-1 and were assigned to TO/LO splitting. An increase in relative intensity of the transverse optic mode is observed with decrease in laser wavelength. The intensity of the out-of-phase vibrations at 3668 and 3653 cm-1 of the inner surface hydroxyls shows a linear relationship with the longitudinal and transverse optic modes. In the low-wavenumber region excellent correlation was found between the experimentally determined and the calculated band positions.
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Kaolinite surfaces were modified by mechanochemical treatment for periods of time up to 10 h. X-ray diffraction shows a steady decrease in intensity of the d(001) spacing with mechanochemical treatment, resulting in the delamination of... more
Kaolinite surfaces were modified by mechanochemical treatment for periods of time up to 10 h. X-ray diffraction shows a steady decrease in intensity of the d(001) spacing with mechanochemical treatment, resulting in the delamination of the kaolinite and a subsequent decrease in crystallite size with grinding time. Thermogravimetric analyses show the dehydroxylation patterns of kaolinite are significantly modified. Changes in the molecular structure of the kaolinite surface hydroxyls were followed by infrared spectroscopy. Hydroxyls were lost after 10 h of grinding as evidenced by a decrease in intensity of the OH stretching vibrations at 3695 and 3619 cm−1 and the deformation modes at 937 and 915 cm−1. Concomitantly an increase in the hydroxyl stretching vibrations of water is found. The water-bending mode was observed at 1650 cm−1, indicating that water is coordinating to the modified kaolinite surface. Changes in the surface structure of the OSiO units were reflected in the SiO stretching and OSiO bending vibrations. The decrease in intensity of the 1056 and 1034 cm−1 bands attributed to kaolinite SiO stretching vibrations were concomitantly matched by the increase in intensity of additional bands at 1113 and 520 cm−1 ascribed to the new mechanically synthesized kaolinite surface. Mechanochemical treatment of the kaolinite results in a new surface structure.
Research Interests: Vibrational Spectroscopy, Clay Minerals, X-ray Diffraction, Infrared spectroscopy, Physical sciences, and 14 moreAluminosilicate, Thermogravimetry, CHEMICAL SCIENCES, Kaolinite Clay, Thermal Analysis, Surface Structure, Crystallite Size, X ray diffraction, Thermogravimetric Analysis, Colloid, Kaolinite, Aluminosilicates, Molecular Structure, and MECHANOCHEMICAL ACTIVATION
Kaolinite surfaces were modified by grinding kaolinite/quartz mixtures with mole fractions of 0.25 kaolinite and 0.75 quartz for periods of time up to 4 h. X-ray diffraction shows the loss of intensity of the d(001) spacing with... more
Kaolinite surfaces were modified by grinding kaolinite/quartz mixtures with mole fractions of 0.25 kaolinite and 0.75 quartz for periods of time up to 4 h. X-ray diffraction shows the loss of intensity of the d(001) spacing with mechanical treatment resulting in the delamination of the kaolinite. Thermogravimetric analyses show the kaolinite surface is significantly modified and surface hydroxyls are replaced with water molecules. Changes in the molecular structure of the surface hydroxyls of the kaolinite/quartz mixtures were followed by infrared spectroscopy. Kaolinite hydroxyls were lost after 2 h of grinding as evidenced by the decrease in intensity of the OH stretching vibrations at 3695 and 3619 cm-1 and the deformation modes at 937 and 915 cm-1. Changes in the surface structure of the OSiO units were reflected in the SiO stretching and OSiO bending vibrations. The decrease in intensity of the 1056 and 1034 cm-1 bands attributed to kaolinite SiO stretching vibrations were concomitantly matched by the increase in intensity of additional bands at 1113 and 520 cm-1 ascribed to the new mechanically synthesized kaolinite surface. Mechanochemical treatment of the kaolinite results in a new surface structure.
Research Interests:
Raman microscopy has been used to study low and high defect kaolinites and their potassium acetate intercalated complexes at 298 and 77 K. Raman spectroscopy shows significant differences in the spectra of the hydroxyl-stretching region... more
Raman microscopy has been used to study low and high defect kaolinites and their potassium acetate intercalated complexes at 298 and 77 K. Raman spectroscopy shows significant differences in the spectra of the hydroxyl-stretching region of the two types of kaolinites, which is also reflected in the spectroscopy of the hydroxyl-stretching region of the intercalation complexes. Additional bands to the normally observed kaolinite hydroxyl stretching frequencies are observed for the low and high defect kaolinites at 3605 and 3602 cm(-1) at 298 K. Upon cooling to liquid nitrogen temperature, these bands are observed at 3607 and 3604 cm(-1), thus indicating a weakening of the hydrogen bond formed between the inner surface hydroxyls and the acetate ion. Upon cooling to liquid nitrogen temperature, the frequency of the inner hydroxyls shifted to lower frequencies. Collection of Raman spectra at liquid nitrogen temperature did not give better band separation compared to the room temperature spectra as the bands increased in width and shifted closer together.
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A low temperature synthesis method based on the decomposition of urea at 90°C in water has been developed to synthesise fraipontite. This material is characterised by a basal reflection 001 at 7.44 Å. The trioctahedral nature of the... more
A low temperature synthesis method based on the decomposition of urea at 90°C in water has been developed to synthesise fraipontite. This material is characterised by a basal reflection 001 at 7.44 Å. The trioctahedral nature of the fraipontite is shown by the presence of a 06l band around 1.54 Å, while a minor band around 1.51 Å indicates some cation ordering between Zn and Al resulting in Al-rich areas with a more dioctahedral nature. TEM and IR indicate that no separate kaolinite phase is present. An increase in the Al content however, did result in the formation of some SiO2 in the form of quartz. Minor impurities of carbonate salts were observed during the synthesis caused by to the formation of CO32- during the decomposition of urea.
Research Interests:
Near-IR spectroscopy has been used to elucidate the structure of potassium and cesium acetate-intercalated kaolinites. Three near-IR spectral regions are identified: (a) the high frequency region between 6400 and 7400 cm−1 attributed to... more
Near-IR spectroscopy has been used to elucidate the structure of potassium and cesium acetate-intercalated kaolinites. Three near-IR spectral regions are identified: (a) the high frequency region between 6400 and 7400 cm−1 attributed to the first overtone of the hydroxyl stretching mode, (b) the 4800–5400 cm−1 region attributed to water combination modes and (c) the 4000–4800 cm−1 region attributed to the combination of the stretching and deformation modes of the AlOH units of kaolinite. The technique of near-IR spectroscopy for the study of intercalated kaolinites shows great potential for the understanding of the interactions between the surface hydroxyls of kaolinite and the inserting potassium and acetate ions. In particular, whereas the overlap of the hydroxyl stretching frequencies of water and the kaolinite overlap in the mid-IR, such overlap does not occur in the near-IR. In the first overtone region, a single sharp band is observed at 7045 cm−1 which is assigned to the combination of the hydroxyl stretching frequencies of the inner surface hydroxyls and water. Such an observation supports the concept of an interaction between the water and the inner surface hydroxyls of the intercalated kaolinite. It is suggested that the bonding of the acetate to the kaolinite hydroxyls is through the water molecule.
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Controlled rate thermal analysis (CRTA) technology made possible the separation of adsorbed formamide from intercalated formamide in formamide-intercalated kaolinites. X-ray diffraction shows that the CRTA-treated formamide-intercalated... more
Controlled rate thermal analysis (CRTA) technology made possible the separation of adsorbed formamide from intercalated formamide in formamide-intercalated kaolinites. X-ray diffraction shows that the CRTA-treated formamide-intercalated kaolinites remain expanded after CRTA treatment. The Raman spectra of the CRTA-treated formamide-intercalated kaolinites are significantly different from those of the intercalated kaolinites with both intercalated and adsorbed formamide. An intense band is observed at 3629 cm−1, attributed to the inner surface hydroxyls hydrogen bonded to the formamide. Broad bands are observed at 3600 and 3639 cm−1 and are attributed to the inner surface hydroxyls, which are hydrogen bonded to the adsorbed water molecules. The hydroxyl stretching band of the inner hydroxyl is readily observed at 3621 cm−1 in the Raman spectra of the CRTA-treated formamide-intercalated kaolinites. The results of thermal analysis show that the amount of intercalated formamide between the kaolinite layers is independent of the presence of water. The Raman bands of the formamide in the CRTA-treated intercalated kaolinites are readily observed.
Research Interests:
Controlled rate thermal analysis (CRTA) has been used to separate adsorbed formamide from intercalated formamide in formamide-intercalated kaolinites. This separation is achieved by removal of the sample at the end of the controlled... more
Controlled rate thermal analysis (CRTA) has been used to separate adsorbed formamide from intercalated formamide in formamide-intercalated kaolinites. This separation is achieved by removal of the sample at the end of the controlled isothermal desorption step. The temperature of this isothermal desorption is dependent on the use of open or closed crucibles in the thermal analysis unit but is independent of the formamide/water ratio. X-ray diffraction shows that the formamide-intercalated kaolinite remains expanded after formamide desorption with a d(001) spacing of 10.09 Å. Further heating to 300 °C results in the deintercalation of the formamide-intercalated kaolinite. DRIFT spectroscopy shows differences between the infrared spectra of the adsorbed and formamide-intercalated kaolinites. An intense band observed at 3629 cm-1 is attributed to the inner surface hydroxyls hydrogen bonded to the formamide. The adsorbed formamide-intercalated kaolinites contain adsorbed water and show intensity in the 1705 cm-1 band, which is absent in the CRTA-treated formamide-intercalated kaolinites.
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A combination of X-ray diffraction and thermal analysis was employed to characterise alumina hydrolysates synthesised from the hydrolysis of anhydrous trisecbutoxyaluminium (III). X-ray diffraction showed that the alumino-oxy(hydroxy)... more
A combination of X-ray diffraction and thermal analysis was employed to characterise alumina hydrolysates synthesised from the hydrolysis of anhydrous trisecbutoxyaluminium (III). X-ray diffraction showed that the alumino-oxy(hydroxy) hydrolysates were boehmite. For boehmite the lamellar spacings are in the b direction and multiple d(0 2 0) peaks are observed for the unaged hydrolysate. After 4 h of ageing, a single d(0 2 0) peak is observed at 6.53 Å. Thermal analysis showed five endotherms at 70, 140, 238, 351 and 445°C. These endotherms are attributed to the dehydration and dehydroxylation of the hydrolysate. Alumina oxy(hydroxy) gels were formed from the hydrolysates of anhydrous aliphatic acid modified trisecbutoxyaluminium(III). X-ray diffraction shows the gels were expanded above the (0 2 0) spacing of boehmite due to the incorporation of acid in the interlamellar space. The thermal analysis patterns of the acid modified gels were significantly different from that of the unmodified gel.
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Changes in the hydroxyl surfaces of cesium acetate intercalated kaolinite have been studied over the ambient to predehydroxylation temperature range using a combination of FTIR and Raman spectroscopy, combined with X-ray diffraction. Upon... more
Changes in the hydroxyl surfaces of cesium acetate intercalated kaolinite have been studied over the ambient to predehydroxylation temperature range using a combination of FTIR and Raman spectroscopy, combined with X-ray diffraction. Upon intercalation of a low-defect kaolinite with cesium acetate, the kaolinite layers expanded to 14.0 Å. Upon heating the intercalate to 50 C, the kaolinite expands to 17.0 Å. Over the temperature range 100-200 C, a third phase with a d(001) spacing of 12.80 Å was observed. These expansions are reversible, and upon cooling the intercalation complex and upon exposure to air for sufficient lengths of time, the d(001) spacing returned to 14.0 Å. These expansions are in harmony with thermal decomposition measurements. Diffuse reflectance spectroscopy shows that the cesium acetate intercalated kaolinite is almost completely intercalated and that the thermal treatment of the intercalate is reversible. The Raman spectrum of the hydroxyl stretching region of the intercalated kaolinite showed a new band at 3606 cm-1, which was attributed to the inner surface hydroxyl hydrogen bonded to the acetate ion. Mild heating of the intercalated complex to 50 C caused a rearrangement of the surface structure with a Raman band being observed at 3610 cm-1. It is proposed that the 3610 cm-1 band is associated with the 17.0 Å phase and that the 3606 cm-1 band is associated with the 14.0 Å phase. Further thermal treatment over the 100-200 C temperature ranges resulted in two hydroxyl bands at 3618 and 3609 cm-1. The 3618 cm-1 band is attributed to the inner hydroxyl. At the predehydroxylation temperature for cesium acetate intercalated kaolinite (~300 C), two bands were observed at 3609 and 3619 cm-1. Above this temperature, no hydroxyls are spectroscopically evident. Upon cooling to room temperature, the Raman spectra of the hydroxyl surfaces are identical to that of the initial intercalation complex, showing that the thermal modification of the kaolinite surfaces is reversible. The thermal treatment results in some minor deintercalation.
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Chrysotile and its dimethylsilyl (DMS) and dimethylphenylsilyl (DMPS) derivatives were studied by Fourier transform infrared–photoacoustic spectroscopy. In the Si–O stretching region of chrysotile a new band was revealed at 985 cm−1,... more
Chrysotile and its dimethylsilyl (DMS) and dimethylphenylsilyl (DMPS) derivatives were studied by Fourier transform infrared–photoacoustic spectroscopy. In the Si–O stretching region of chrysotile a new band was revealed at 985 cm−1, besides absorptions at 1083, 1028, and 947 cm−1. The Si–O stretching frequencies did not undergo major changes in the DMS derivative, but the 985- and 1028-cm−1 peaks were undetected in DMPS due to the HCl attack on chrysotile tetrahedral sheets. Similar effects were observed in the region 900–400 cm−1, by a decrease in intensities of the 600- and 642-cm−1 Mg-OH libration modes in the DMPS spectrum, indicating also a HCl attack on the octahedral sheet. The Si–C band at 800 cm−1 in the spectra of both DMS and DMPS was accompanied by minor components. DMPS showed a strong peak at 813 cm−1 assigned to a Si–phenyl vibration. A sharp peak at 1263 cm−1 in the DMS spectrum was ascribed to a diagnostic C–H bending mode of the dimethylsilyl groups in DMS. The complex bands around 1413 cm−1 in DMS were attributed to CH3 deformation vibrations and that at 1466 cm−1 in DMPS to phenyl groups. In DMPS a distinct peak at 1593 cm−1 was attributed to a Si–phenyl vibration. In the region 3700–2500 cm−1 absorptions at 2964, 2931, and 2907 cm−1 in DMS were ascribed to C–H-stretching vibrations of dimethylsilyl groups, while a strong peak at 2919 cm−1 in the DMPS spectrum was attributed to a Si–C6H5 mode.
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A combination of X-ray diffraction, thermal analysis and Raman spectroscopy was employed to characterise the ageing of alumina hydrolysates synthesised from the hydrolysis of anhydrous tri-sec-butoxyaluminium(III). X-Ray diffraction... more
A combination of X-ray diffraction, thermal analysis and Raman spectroscopy was employed to characterise the ageing of alumina hydrolysates synthesised from the hydrolysis of anhydrous tri-sec-butoxyaluminium(III). X-Ray diffraction showed that the alumino-oxy(hydroxy) hydrolysates were pseudoboehmite. For boehmite the lamellar spacings are in the b direction and multiple d(020) peaks are observed for the un-aged hydrolysate. After 4 h of ageing, a single d(020) peak is observed at 6.53 Å. Thermal analysis showed five endotherms at 70, 140, 238, 351 and 445°C. These endotherms are attributed to the dehydration and dehydroxylation of the boehmite-like hydrolysate. Raman spectroscopy shows the presence of bands for the washed hydrolysates at 333, 355, 414, 455, 475, 495, 530 and 675 cm–1. These bands are attributed to pseudoboehmite. Ageing of the hydrolysates results in an increase in the crystallite size of the pseudoboehmite.
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Valverde et al. (2000) recently reported on the preparation and characterization of Al-pillared smectites modified with Ce and La. Pillaring of clays with Al polyoxocations (Keggin type Al13 ) and a large variety of other complexing... more
Valverde et al. (2000) recently reported on the preparation and characterization of Al-pillared smectites modified with Ce and La. Pillaring of clays with Al polyoxocations (Keggin type Al13 ) and a large variety of other complexing cations has been reported many times since the seventies. McCauley (1988) described in a patent the preparation of thermally stable pillared clays with large basal spacings of -28 A, followed by publications by Sterte (1991a, 1991b) and Booij and coworkers (Booij et al., 1996a, 1996b). These authors used hydrothermally treated or refluxed solutions containing the Al polyoxocation and the rare earth elements in the form of their chloride salts. The presence of cerium or lanthanum seems to promote polymerization of the Al polyoxocation. Until now however, nobody has been able to assess the structure of the newly formed pillaring molecules. Although the interlayer
spacing is about twice that of the normal Al-pillared clay, chemical analyses indicate smaller amounts of Ce and La than expected from polymerization of the Al polymer alone. Several other studies on the combination of Al pillars with Ce or La resulted
in the formation of pillared clays with basal spacings characteristic of Al-pillared clays. However, catalytic activity is enhanced owing to Ce or La (e.g., Gonzalez et al., 1992; Mendioroz et aL, 1993; Trillo et al., 1993).
spacing is about twice that of the normal Al-pillared clay, chemical analyses indicate smaller amounts of Ce and La than expected from polymerization of the Al polymer alone. Several other studies on the combination of Al pillars with Ce or La resulted
in the formation of pillared clays with basal spacings characteristic of Al-pillared clays. However, catalytic activity is enhanced owing to Ce or La (e.g., Gonzalez et al., 1992; Mendioroz et aL, 1993; Trillo et al., 1993).
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Brucite and hydrotalcite molecular structures have been studied using near-IR reflectance spectroscopy.Three Near-IR spectral regions are identified: (a) the high frequency region between 6400 and 7400cm·1 attributed to the first overtone... more
Brucite and hydrotalcite molecular structures have been studied using near-IR reflectance spectroscopy.Three Near-IR spectral regions are identified: (a) the high frequency region between 6400 and 7400cm·1 attributed to the first overtone of the fundamental hydroxyl stretching mode, (b) the 4800-5400 cm·1 region attributed to water combination modes of the hydroxyl fundamentals of water, and (c) the 4000-4800 cm·1 region attributed to the combination of the stretching ·and deformation modes of the MOH units of hydrotalcite. Brucites are characterized by intense bands at 7154 and 4298 cm·1• NIR spectroscopy enables the separation of the hydroxyl bands of the water and M-OH units for the hydrotalcites. Compared with the NIR spectroscopy of the structural units of the hydrotalcites namely gibbsite and brucite, the bands are broad. Fiue bands are identified in the hydroxyl stretching ouertone region centred around 7650 7215
7078, 6918 and 6600 cm·1. Water combination' band; were found at -5200, 5130, 4980 and 4800cm·1. Two types of water were identified: water coordinated to the hydroxyl surface and water coordinated to the
interlayer anion. Combination bands of the hydroxyl fundamentals were identified at -4430, 4295, 4090 and 4010cm·1.
7078, 6918 and 6600 cm·1. Water combination' band; were found at -5200, 5130, 4980 and 4800cm·1. Two types of water were identified: water coordinated to the hydroxyl surface and water coordinated to the
interlayer anion. Combination bands of the hydroxyl fundamentals were identified at -4430, 4295, 4090 and 4010cm·1.
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Raman microscopy has been used to study low and high defect kaolinites and their potassium acetate intercalated complexes at 298 and 77 K. Raman spectroscopy shows significant differences in the spectra of the hydroxyl-stretching region... more
Raman microscopy has been used to study low and high defect kaolinites and their potassium acetate intercalated complexes at 298 and 77 K. Raman spectroscopy shows significant differences in the spectra of the hydroxyl-stretching region of the two types of kaolinites, which is also reflected in the spectroscopy of the hydroxyl-stretching region of the intercalation complexes. Additional bands to the normally observed kaolinite hydroxyl stretching frequencies are observed for the low and high defect kaolinites at 3605 and 3602 cm−1 at 298 K. Upon cooling to liquid nitrogen temperature, these bands are observed at 3607 and 3604 cm−1, thus indicating a weakening of the hydrogen bond formed between the inner surface hydroxyls and the acetate ion. Upon cooling to liquid nitrogen temperature, the frequency of the inner hydroxyls shifted to lower frequencies. Collection of Raman spectra at liquid nitrogen temperature did not give better band separation compared to the room temperature spectra as the bands increased in width and shifted closer together.
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Near-infrared (IR) spectroscopy has been used to distinguish between alumina oxo and hydroxy phases. Two near-IR spectral regions are identified for this function: (1) the high-frequency region between 6400 and 7400 cm−1, attributed to... more
Near-infrared (IR) spectroscopy has been used to distinguish between alumina oxo and hydroxy phases. Two near-IR spectral regions are identified for this function: (1) the high-frequency region between 6400 and 7400 cm−1, attributed to the first overtone of the hydroxyl stretching mode, and (2) the 4000–4800 cm−1 region attributed to the combination of the stretching and deformation modes of the AlOH units. Near-IR spectroscopy allows the study and differentiation of the hydroxy and oxo(hydroxy) alumina phases, since each phase has its own characteristic spectrum. The spectrum of bayerite resembles that of gibbsite, whereas the spectrum of boehmite is similar to that of diaspore. Bayerite has four characteristic near-IR bands at 7218, 7128, 6996, and 6895 cm−1. Gibbsite shows five major bands at 7151, 7052, 6958, 6898, and 6845 cm−1. Boehmite displays three near-IR bands at 7152, 7065, and 6960 cm−1. Diaspore shows a prominent band at around 7176 cm−1. The use of near-IR reflectance spectroscopy to study alumina surfaces has a wide application, particularly with thin films and surfaces. The technique is rapid and accurate. Near-IR, because of its sensitivity, can be used in reflectance mode for the on-line processing of bauxitic minerals.
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The Raman spectra of three samples of holmquistite, a lithium-containing orthorhombic amphibole, from Bessemer City (NC, USA), Banaute (Quebec, Canada) and Brandgraben (Austria), have been measured by Raman microscopy. The OH-stretching... more
The Raman spectra of three samples of holmquistite, a lithium-containing orthorhombic amphibole, from Bessemer City (NC, USA), Banaute (Quebec, Canada) and Brandgraben (Austria), have been measured by Raman microscopy. The OH-stretching region is characterised by bands around 3660, 3645, 3635 and 3615 cm- 1 assigned to (3 Mg)-OH, (2Mg + Fe2+)-OH, (Mg + 2Fe2+)-OH and (3Fe2 +)-OH, respectively. Based on the ratio between the 3645 and 3660 cm-1
bands Fe2+/(Fe2+ + Mg2+) ratios in the M 1 and M3 sites were determined to be in the range between 0.35 and 0.45. The 950-1130cm- 1 region represents the antisymmetric Si-O-Si and O-Si-O stretching vibrations. For holmquistite from Bessemer City, U.S.A, strong bands are observed around 1022 and 1085cm-1 with a shoulder at 1127 cm- 1 and minor bands at 1045 and 1102 cm- 1. In the spectra of the other samples these two bands are very weak and accompanied by bands around 965, 998 and 1061 cm- 1. In the region between 650 and 800cm- 1 bands are observed at 679, ~ 753 and 791 cm- 1 with a minor band around 694 cm-1 attributed to the symmetrical Si-O-Si and Si-O vibrations. The region below 625 cm-1 is characterised by vibrations
related to the deformation modes of the silicate chain and vibrations involving Mg, Fe, Al and Li in the various M sites. The 502cm-1 band is a Li-O deformation mode while the bands at 456, 551 and 565 cm- 1 are Al-O deformation modes. OH-libration and translation modes are observed around 300, 530, 582 and 613cm- 1.
bands Fe2+/(Fe2+ + Mg2+) ratios in the M 1 and M3 sites were determined to be in the range between 0.35 and 0.45. The 950-1130cm- 1 region represents the antisymmetric Si-O-Si and O-Si-O stretching vibrations. For holmquistite from Bessemer City, U.S.A, strong bands are observed around 1022 and 1085cm-1 with a shoulder at 1127 cm- 1 and minor bands at 1045 and 1102 cm- 1. In the spectra of the other samples these two bands are very weak and accompanied by bands around 965, 998 and 1061 cm- 1. In the region between 650 and 800cm- 1 bands are observed at 679, ~ 753 and 791 cm- 1 with a minor band around 694 cm-1 attributed to the symmetrical Si-O-Si and Si-O vibrations. The region below 625 cm-1 is characterised by vibrations
related to the deformation modes of the silicate chain and vibrations involving Mg, Fe, Al and Li in the various M sites. The 502cm-1 band is a Li-O deformation mode while the bands at 456, 551 and 565 cm- 1 are Al-O deformation modes. OH-libration and translation modes are observed around 300, 530, 582 and 613cm- 1.
Research Interests:
The Raman spectra of some common naturally occurring alums, kalinite (K2SO4 · Al2(SO4h · 22H2O) and tschermigite ((NH4)2SO4 · Al2(SO4h · 24H2O) have been obtained at 298 and 77K. A comparison is made with lonecreekite ((NH4)iSO4 · -... more
The Raman spectra of some common naturally occurring alums, kalinite
(K2SO4 · Al2(SO4h · 22H2O) and tschermigite ((NH4)2SO4 · Al2(SO4h · 24H2O) have
been obtained at 298 and 77K. A comparison is made with lonecreekite ((NH4)iSO4 · -
Fe2(SO4h · 24H2O), the ammonium ferric alum. Two bands are observed at 990 and
972cm-1 and are assigned to the v 1(AR) SO4 vibration. Two bands are also observed
at 1130 and 1104 cm- 1 and are attributed to the antisymmetric stretching vibration
v3(Bg) SO4 . A single band at 454cm-1 attributed to the v2(A8 ) SO4 mode splits into
three bands at 476, 457 and 442cm-1 in the 77K spectrum. The band at 618cm- 1 assigned to the v4(B,) SO4 mode resolves into three bands at 632, 612 and 596cm- 1 at
77K. The splitting of the v2, v3 and v4 modes is attributed to the reduction of symmetry
of the SO4 and it is proposed that the sulphate coordinates to water in the hydrated
aluminium in bidentate chelation.
(K2SO4 · Al2(SO4h · 22H2O) and tschermigite ((NH4)2SO4 · Al2(SO4h · 24H2O) have
been obtained at 298 and 77K. A comparison is made with lonecreekite ((NH4)iSO4 · -
Fe2(SO4h · 24H2O), the ammonium ferric alum. Two bands are observed at 990 and
972cm-1 and are assigned to the v 1(AR) SO4 vibration. Two bands are also observed
at 1130 and 1104 cm- 1 and are attributed to the antisymmetric stretching vibration
v3(Bg) SO4 . A single band at 454cm-1 attributed to the v2(A8 ) SO4 mode splits into
three bands at 476, 457 and 442cm-1 in the 77K spectrum. The band at 618cm- 1 assigned to the v4(B,) SO4 mode resolves into three bands at 632, 612 and 596cm- 1 at
77K. The splitting of the v2, v3 and v4 modes is attributed to the reduction of symmetry
of the SO4 and it is proposed that the sulphate coordinates to water in the hydrated
aluminium in bidentate chelation.
Research Interests:
The Raman spectra at 77 K of the hydroxyl stretching of kaolinite were obtained along the three axes perpendicular to the crystal faces. Raman bands were observed at 3616, 3658 and 3677 cm -1 together with a distinct band observed at 3691... more
The Raman spectra at 77 K of the hydroxyl stretching of kaolinite were obtained along the three axes perpendicular to the crystal faces. Raman bands were observed at 3616, 3658 and 3677 cm -1 together with a distinct band observed at 3691 cm -1 and a broad profile between 3695 and 3715 cm -1. The band at 3616 cm -1 is assigned to the inner hydroxyl. The bands at 3658 and 3677 cm -1 are attributed to the out-of-phase vibrations of the inner surface hydroxyls. The Raman spectra of the in-phase vibrations of the inner-surface hydroxyl-stretching region are described in terms of transverse and longitudinal optic splitting. The band at 3691 cm -1 is assigned to the transverse optic and the broad profile to the longitudinal optic mode. This splitting remained even at liquid nitrogen temperature. The transverse optic vibration may be curve resolved into two or three bands, which are attributed to different types of hydroxyl groups in the kaolinite.
Research Interests:
The thermal behaviour of synthetic hydrotalcite, Mg5.6Al2.4(OH)16(CO3,NO3)·nH2O, has been studied by Infrared Emission Spectroscopy (IES) and heating stage Raman microscopy. Heating stage Raman microscopy reveals that upon heating and... more
The thermal behaviour of synthetic hydrotalcite, Mg5.6Al2.4(OH)16(CO3,NO3)·nH2O, has been studied by Infrared Emission Spectroscopy (IES) and heating stage Raman microscopy. Heating stage Raman microscopy reveals that upon heating and subsequent dehydration the bands at 553, 1052, 3503, 3603 and 3689 cm−1 associated with the (Mg,Al)3–OH translation, deformation and stretching vibrations decrease in intensity due to changes in the stacking order of the hydroxide layers. During this rearrangement around 150–175°C the free interlayer nitrate forms a type of bridging nitrato complex with the metals in the hydroxide layers as evidenced by the disappearance of the normal free nitrate vibrations at 716, 1067 and 1386 cm−1 and the formation of a new band at 1039 cm−1. Further heating to 300°C results in the dehydroxylation and decarbonisation of the hydrotalcite, which is only partially reversed upon cooling in air over a period of more than 12 h. The Mg-hydrotalcite IES spectra show major changes around 350–400°C indicating the end of the dehydroxylation. In this temperature range, “Al”–OH bands at 772, 923 and 1029 cm−1 disappear. New bands are observed around 713, 797 and 1075 cm−1. The first and the last bands plus the 545 cm−1 band indicate the formation of spinel (MgAl2O4). The 713 cm−1 band is also close to the νLO position of MgO at 717 cm−1, which is another product formed after dehydroxylation. However, decarbonisation is not complete at this stage as evidenced by both a continuing weight loss in the TGA up to at least 625°C and a decreasing carbonate signal in the IES up to 800°C.
Research Interests: Earth Sciences, Raman Spectroscopy, Vibrational Spectroscopy, Layered Inorganic Materials, Layered Double Hydroxide (LDH), and 9 moreInfrared spectroscopy, Infrared, Dehydration, Dehydroxylation, Thermal Decomposition, MATERIALS RESEARCH ( HYDROTALCITE LIKE COMPOUNDS), Applied Clay science, Infrared Emission Spectroscopy, and Heating stage Raman spectroscopy
The tridecameric Al-polymer [AlO4Al12(OH)24(H2O)12]7+ was prepared by forced hydrolysis of Al3+ up to an OH/Al molar ratio of 2.2. Under slow evaporation crystals were formed of Al13-nitrate. Upon addition of sulfate the tridecamer... more
The tridecameric Al-polymer [AlO4Al12(OH)24(H2O)12]7+ was prepared by forced hydrolysis of Al3+ up to an OH/Al molar ratio of 2.2. Under slow evaporation crystals were formed of Al13-nitrate. Upon addition of sulfate the tridecamer crystallised as the monoclinic Al13-sulfate. These crystals have been studied using near-infrared spectroscopy and compared to Al2(SO4)3.16H2O. Although the near-infrared spectra of the Al13-sulfate and nitrate are very similar indicating similar crystal structures, there are minor differences related to the strength with which the crystal water molecules are bonded to the salt groups. The interaction between crystal water and nitrate is stronger than with the sulfate as reflected by the shift of the crystal water band positions from 6213, 4874 and 4553 cm–1 for the Al13 sulfate towards 5925, 4848 and 4532 cm–1 for the nitrate. A reversed shift from 5079 and 5037 cm–1 for the sulfate towards 5238 and 5040 cm–1 for the nitrate for the water molecules in the Al13 indicate that the nitrate-Al13 bond is weakened due to the influence of the crystal water on the nitrate. The Al-OH bond in the Al13 complex is not influenced by changing the salt group due to the shielding by the water molecules of the Al13 complex.
Research Interests:
The molecular structure of the three vivianite-structure, compositionally related phosphate minerals vivianite, baricite and bobierrite of formula M32+(PO4)2.8H2O where M is Fe or Mg, has been assessed using a combination of Raman and... more
The molecular structure of the three vivianite-structure, compositionally related phosphate minerals vivianite, baricite and bobierrite of formula M32+(PO4)2.8H2O where M is Fe or Mg, has been assessed using a combination of Raman and infrared (IR) spectroscopy. The Raman spectra of the hydroxyl-stretching region are complex with overlapping broad bands. Hydroxyl stretching vibrations are identified at 3460, 3281, 3104 and 3012 cm–1 for vivianite. The high wavenumber band is attributed to the presence of FeOH groups. This complexity is reflected in the water HOH-bending modes where a strong IR band centred around 1660 cm–1 is found. Such a band reflects the strong hydrogen bonding of the water molecules to the phosphate anions in adjacent layers. Spectra show three distinct OH-bending bands from strongly hydrogen-bonded, weakly hydrogen bonded water and non-hydrogen bonded water. The Raman phosphate PO-stretching region shows strong similarity between the three minerals. In the IR spectra, complexity exists with multiple antisymmetric stretching vibrations observed, due to the reduced tetrahedral symmetry. This loss of degeneracy is also reflected in the bending modes. Strong IR bands around 800 cm–1 are attributed to water librational modes. The spectra of the three minerals display similarities due to their compositions and crystal structures, but sufficient subtle differences exist for the spectra to be useful in distinguishing the species.
Research Interests:
The use of a Raman microscope combined with a thermal stage enabled the Raman spectra of the three minerals cinnabar, realgar and orpiment. Each of these minerals is of archaeological and medieval interest because of their use as... more
The use of a Raman microscope combined with a thermal stage enabled the Raman spectra of the three minerals cinnabar, realgar and orpiment. Each of these minerals is of archaeological and medieval interest because of their use as colouring agents. The spectra of these sulphides of Hg and As may be conveniently divided into three sections namely (a) the region centred upon 355 cm-1 where the stretching vibrations are observed (b) the region centred upon 250 cm-1 ascribed to the bending vibrations and (c) the region below 100 cm-1 assigned to the lattice modes. Cinnabar Raman spectra displayed prominent bands 353, 342, 290, 277 and 253cm-1. These bands are assigned to HgS stretching modes and are orientation dependent. The Raman spectrum of realgar shows AsS stretching vibrations at 374, 367, 353, 340 and 327cm-1 and bending modes at 219, 210, 191 and 181cm-1. Orpiment also displays five Raman bands at 382, 355, 325, 310 and 294 cm-1 with bending modes at 202 and 180 cm-1. Differences in the results between this work and published data are accounted for by the sample preparation and the advances in technology with improved signal to noise.
Research Interests:
The vibrational spectra of pseudomalachite, reichenbachite and ludjibaite have been obtained at 298 K using a combination of FTIR and Raman microscopy. The vibrational spectra of the minerals are different, in line with differences in... more
The vibrational spectra of pseudomalachite, reichenbachite and ludjibaite have been obtained at 298 K using a combination of FTIR and Raman microscopy. The vibrational spectra of the minerals are different, in line with differences in crystal structure and composition. Some similarity in the Raman spectra of the three polymorphs pseudomalachite, reichenbachite and ludjibaite exists, particularly in the OH stretching region, but characteristic differences in the OH deformation regions are observed. Differences are also observed in the phosphate stretching and deformation regions.
Research Interests:
The modification of kaolinite surfaces through mechanochemical treatment has been studied using a combination of mid-IR and near-IR spectroscopy. Kaolinite hydroxyls were lost after 10 h of grinding as evidenced by the decrease in... more
The modification of kaolinite surfaces through mechanochemical treatment has been studied using a combination of mid-IR and near-IR spectroscopy. Kaolinite hydroxyls were lost after 10 h of grinding as evidenced by the decrease in intensity of the OH stretching vibrations at 3695 and 3619 cm−1 and the deformation modes at 937 and 915 cm−1. Concomitantly an increase in the hydroxyl-stretching vibrations of water is observed. The mechanochemical activation (dry grinding) causes destruction in the crystal structure of kaolinite by the rupture of the OH, AlOH, AlOSi and SiO bonds. Evidence of this destruction may be followed using near-IR spectroscopy. Two intense bands are observed in the spectral region of the first overtone of the hydroxyl-stretching vibration at 7065 and 7163 cm−1. These two bands decrease in intensity with mechanochemical treatment and two new bands are observed at 6842 and 6978 cm−1 assigned to the first overtone of the hydroxyl-stretching band of water. Concomitantly the water combination bands observed at 5238 and 5161 cm−1 increase in intensity with mechanochemical treatment. The destruction of the kaolinite surface may be also followed by the loss of intensity of the two hydroxyl combination bands at 4526 and 4623 cm−1. Infrared spectroscopy shows that the kaolinite surface has been modified by the removal of the kaolinite hydroxyls and their replacement with water adsorbed on the kaolinite surface. NIR spectroscopy enables the determination of the optimum time for grinding of the kaolinite. Further NIR allows the possibility of continual on-line analysis of the mechanochemical treatment of kaolinite.
Research Interests:
Raman spectra of the basic copper chloride minerals atacamite and paratacamite have been obtained at 298 and 77K using a Raman microprobe in combination with a thermal stage. Four distinct regions involved with hydroxyl stretching,... more
Raman spectra of the basic copper chloride minerals atacamite and paratacamite have been obtained at 298 and 77K using a Raman microprobe in combination with a thermal stage. Four distinct regions involved with hydroxyl stretching, hydroxyl deformation, CuO stretching and CuCl stretching and bending have been identified. The implication from the study is that Raman spectroscopy can be a useful tool for identifying corrosion products of copper, brass and bronze objects of archaeological or antiquarian significance. In addition, the technique may be a useful aid in the restoration degraded pigment products from old paintings.
Research Interests:
The Raman spectra of strunzite, ferristrunzite and ferrostrunzite have been obtained at 298 and 77K using a combination of a thermal stage and Raman microscopy. These spectra are compared with their infrared spectra. The vibrational... more
The Raman spectra of strunzite, ferristrunzite and ferrostrunzite have been
obtained at 298 and 77K using a combination of a thermal stage and Raman
microscopy. These spectra are compared with their infrared spectra. The
vibrational spectra of the two minerals are different, in line with differences in
crystal structure and composition. Some similarity in the Raman spectra of the
hydroxyl-stretching region exists, particularly at 298K, but characteristic
differences in the OH deformation regions are observed. Significant shifts in the
position of the Raman bands are observed by obtaining the spectra at 77K.
Differences are also observed in the phosphate stretching and deformation
regions.
obtained at 298 and 77K using a combination of a thermal stage and Raman
microscopy. These spectra are compared with their infrared spectra. The
vibrational spectra of the two minerals are different, in line with differences in
crystal structure and composition. Some similarity in the Raman spectra of the
hydroxyl-stretching region exists, particularly at 298K, but characteristic
differences in the OH deformation regions are observed. Significant shifts in the
position of the Raman bands are observed by obtaining the spectra at 77K.
Differences are also observed in the phosphate stretching and deformation
regions.
Research Interests:
The minerals connellite and buttgenbachite, complex hydroxy sulfate and nitrate, respectively, of Cu(II), are rare products formed during the corrosion of bronze and brass objects. Infrared and Raman spectra of buttgenbachite and... more
The minerals connellite and buttgenbachite, complex hydroxy sulfate and nitrate, respectively, of Cu(II), are rare products formed during the corrosion of bronze and brass objects. Infrared and Raman spectra of buttgenbachite and connellite were obtained at 298 and 77 K using a Raman microprobe in combination with a thermal stage. The Raman spectra show the presence of nitrate, sulfate and chloride in the mineral. Spectra of the hydroxyl‐stretching region are complex with multiple bands being observed. These observations are in agreement with the structure of the minerals in that the nitrate ion occupies two different sites and that six hydroxyl groups are crystallographically independent. Various OH stretching bands are attributed to independent hydroxyl units in the crystal structure and zeolitic water OH stretching modes. Raman spectroscopy is an excellent technique for the identification of these complex minerals and for the determination of the distribution of anions in their structure.
Research Interests:
The thermal behaviour of mechanochemically treated kaolinite has been investigated under dynamic and controlled rate thermal analysis (CRTA) conditions. Ten hours of grinding of kaolinite results in the loss of the d(001) spacing and the... more
The thermal behaviour of mechanochemically treated kaolinite has been investigated under dynamic and controlled rate thermal analysis (CRTA) conditions. Ten hours of grinding of kaolinite results in the loss of the d(001) spacing and the replacement of some 60% of the kaolinite hydroxyls with water. Kaolinite normally dehydroxylates in a single mass loss stage between 400 and 600°C. CRTA technology enables the dehydroxylation of the ground mineral to be observed in four overlapping stages at 385, 404, 420 and 433°C under quasi-isobaric condition in a self-generated atmosphere. It is proposed that mechanochemical treatment of the kaolinite causes the localization of the protons when the long range ordering is lost.
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Insight into the unique structure of hydrotalcites has been obtained using a infrared spectroscopy. The hydroxyl-stretching units of CuOH, ZnOH and AlOH, are identified by unique band positions. The identification of these positions or... more
Insight into the unique structure of hydrotalcites has been obtained using a infrared spectroscopy. The hydroxyl-stretching units of CuOH, ZnOH and AlOH, are identified by unique band positions. The identification of these positions or lack thereof for these units makes it possible to assess whether there is a unique and regular arrangement of cations in the hydrotalcite structure. It is proposed that for CuxZn6−xAl2-
(OH)16(CO3) · 4H2O hydrotalcites when x is less than or equal to two, that the cations are randomly assembled. However when x =3, separate bands for each of the cationic hydroxyls can be identified. This means that “lakes” or “islands” of the cations are formed in the hydrotalcite structures. If separate bands are observed in the spectral profile then this is evidence for cationic segregation. If a continuum of states is observed such that separate bands cannot be identified then it is proposed that the cations are arranged in a molecular assembly.
(OH)16(CO3) · 4H2O hydrotalcites when x is less than or equal to two, that the cations are randomly assembled. However when x =3, separate bands for each of the cationic hydroxyls can be identified. This means that “lakes” or “islands” of the cations are formed in the hydrotalcite structures. If separate bands are observed in the spectral profile then this is evidence for cationic segregation. If a continuum of states is observed such that separate bands cannot be identified then it is proposed that the cations are arranged in a molecular assembly.
Research Interests:
Raman microscopy was used to characterize synthesized hydrotalcites of formula MgxZn6−xAl2(OH)16 (CO3)·4H2O. The Raman spectra are conveniently subdivided into spectral features based on (a) the carbonate anion, (b) the hydroxyl units and... more
Raman microscopy was used to characterize synthesized hydrotalcites of formula MgxZn6−xAl2(OH)16 (CO3)·4H2O. The Raman spectra are conveniently subdivided into spectral features based on (a) the carbonate anion, (b) the hydroxyl units and (c) metal–oxygen units. A model is proposed based on a tripod of M3OH units in the hydrotalcite structure. In a simplified model, Raman spectra of the hydroxyl‐stretching region enable bands to be assigned to the Mg3OH, Zn3OH and Al3OH units. Bands are also assigned to the hydroxyl stretching vibrations of water. Three types of water are identified: (a) water hydrogen bonded to the interlayer carbonate ion, (b) water hydrogen bonded to the hydrotalcite hydroxyl surface and (c) interlamellar water. A model of water in the hydrotalcite structure is proposed in which water is in a highly ordered structure as it is hydrogen bonded to both the carbonate anion and the hydroxyl surface and also forms bridges between the MOH surface and the carbonate anion.
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Controlled rate thermal analysis (CRTA) allows the separation of adsorbed and intercalated hydrazine. CRTA displays the presence of three different types of hydrogen-bonded hydrazine in the intercalation complex (a) adsorbed loosely... more
Controlled rate thermal analysis (CRTA) allows the separation of adsorbed and intercalated hydrazine. CRTA displays the presence of three different types of hydrogen-bonded hydrazine in the intercalation complex (a) adsorbed loosely bonded on the kaolinite structure fully expanded by hydrazine-hydrate and liberated between approx. 50 and 70°C (b) The second intercalated-hydrazine is lost between approx. 70 and 85°C, (c) The third type of intercalated-hydrazine molecule is lost in the 85-130°C range. CRTA at 70 °C enables the removal of hydrazine-water and results in the partial collapse of the hydrazine-intercalated kaolinite structure to form a hydrazine-intercalated kaolinite. Removal of the adsorbed hydrazine enables the DRIFT spectra of the hydrazine-intercalation complex. A band at 3626 cm-1
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Much interest focuses on the use of nano-scale copper and copper oxide for catalyst use. The copper oxide may be used as a solid solution or as a mixture of mixed oxides. The application of these mixed oxides is in environmental... more
Much interest focuses on the use of nano-scale copper and copper oxide for
catalyst use. The copper oxide may be used as a solid solution or as a mixture of
mixed oxides. The application of these mixed oxides is in environmental
applications such as the catalytic oxidation of carbon monoxide and the wet oxidation
of organics in aqueous systems. These nano-scale chemicals are produced
through the thermal decomposition of copper salts such as copper carbonate, copper
hydroxy-carbonate either synthetic or natural (malachite).
catalyst use. The copper oxide may be used as a solid solution or as a mixture of
mixed oxides. The application of these mixed oxides is in environmental
applications such as the catalytic oxidation of carbon monoxide and the wet oxidation
of organics in aqueous systems. These nano-scale chemicals are produced
through the thermal decomposition of copper salts such as copper carbonate, copper
hydroxy-carbonate either synthetic or natural (malachite).
Research Interests:
Azurite and malachite have been extensively used as pigments in ancient and medieval manuscripts, glasses and glazes. The thermal stability of naturally occurring azurite and malachite was determined using a combination of controlled rate... more
Azurite and malachite have been extensively used as pigments in ancient and medieval manuscripts, glasses and glazes. The thermal stability of naturally occurring azurite and malachite was determined using a combination of controlled rate thermal analysis (CRTA) combined with mass spectrometry and infrared emission spectroscopy. Both azurite and malachite thermally decompose in six overlapping stages but the behavior is different
Research Interests:
Research Interests:
Research Interests:
Ammonium-saponite is hydrothermally grown at temperatures below 300oC from a gel with an overall composition corresponding to (NH4)0.6Mg3Si3.4Al0.6O10(OH)2 . The synthetic saponite and coexisting fluid have been characterized by means of... more
Ammonium-saponite is hydrothermally grown at temperatures below 300oC from a gel with an overall composition corresponding to (NH4)0.6Mg3Si3.4Al0.6O10(OH)2 . The synthetic saponite and coexisting fluid have been characterized by means of X-ray powder diffraction, X-ray fluorescence, Induced Coupled Plasma-Atomic Emission Spectroscopy, thermogravimetric analysis, transmission electron microscopy,
CEC determination using an ammonia selective electrode, and pH measurement. In the crystallization model developed, crystallization started with the growth of individual tetrahedral layers with an aluminum substitution not controlled by the AlIV/AlVI ratio in the gel and hydrothermal fluid, on which the octahedral Mg layers can grow. During the synthesis, individual sheets stacked to form thicker flakes while lateral growth also took place. The remaining AlVI partly replaced ammonium as the interlayer cation.
CEC determination using an ammonia selective electrode, and pH measurement. In the crystallization model developed, crystallization started with the growth of individual tetrahedral layers with an aluminum substitution not controlled by the AlIV/AlVI ratio in the gel and hydrothermal fluid, on which the octahedral Mg layers can grow. During the synthesis, individual sheets stacked to form thicker flakes while lateral growth also took place. The remaining AlVI partly replaced ammonium as the interlayer cation.
Research Interests: Minerals, Transmission Electron Microscopy, Vibrational Spectroscopy, Clay Minerals, Inorganic synthesis, and 12 moreLayered Inorganic Materials, X-ray Diffraction, Infrared spectroscopy, Thermogravimetry, Thermal Analysis, Differential Thermal Analysis, Fourier transform infrared spectroscopy, Thermogravimetric Analysis, Hydrothermal Synthesis, Smectite, Cation Exchange Capacity, and saponite
An optical and electron microscope study has been made of inverted pigeonite from the Sjelset Igneous Complex, Rogaland, SW Norway. The inverted pigeonites reveal a Stillwater-type of microstructure: the pigeonite to orthopyroxene... more
An optical and electron microscope study has been made of inverted pigeonite from the Sjelset Igneous Complex, Rogaland, SW Norway. The inverted pigeonites reveal a Stillwater-type of microstructure: the pigeonite to orthopyroxene transformation has been pre-and postdated by two stages of augite exsolution (parallel to (001)pig and (100)opx respectively). In addition. two distinct microstructural domains have been recognized: (1) single and (2) clusters of inverted pigeonite crystals. Most clusters of pigeonite crystals have been replaced by single orthopyroxene crystals which exhibit domains of differently oriented (001)opx exsolution lamellae. The mechanism of exsolution is interpreted to be heterogeneous nucleation and growth, while the transformation of pigeonite to orthopyroxene is regarded as massive.
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Na-beidellite was hydrothermally synthesized using various starting materials at a range of P-T conditions. The best crystallized Na-beidellite was carefully investigated with XRD, SEM, TGA, MAS-NMR and IR-spectroscopy. Cell parameters... more
Na-beidellite was hydrothermally synthesized using various starting materials at a range of P-T conditions. The best crystallized Na-beidellite was carefully investigated with XRD, SEM, TGA, MAS-NMR and IR-spectroscopy. Cell parameters are: a= 5.18 ± 0.005 A; b = 8.96 ± 0.008 A; c = 12.54 ± 0.011 A; V = 581.9 ± 0.5 A3. Indexing is based on an orthorhombic cell. 29Si MAS-NMR reveal three peak positions: - 92.7 ppm (Si-0AI); - 88.4 ppm (Si-1Al) ; - 82.3 ppm (Si-2Al), indicating an AlIV/Si ratio of 0.106 per unit cell. The presence of small amounts of F in the hydrothermal fluid causes a significant increase in crystallinity.
Na-beidellite is the only crystalline product applying a starting gel of composition Nao 7Al47Si730 22 . A Na10Al50Si70 22 gel results in Na-beidellite + paragonite and gels with higher Na content produce only
paragonite.
Na-beidellite is the only crystalline product applying a starting gel of composition Nao 7Al47Si730 22 . A Na10Al50Si70 22 gel results in Na-beidellite + paragonite and gels with higher Na content produce only
paragonite.
Research Interests: Minerals, Scanning Electron Microscopy, Vibrational Spectroscopy, Clay Minerals, Solid State NMR, and 12 moreInorganic synthesis, X-ray Diffraction, Infrared spectroscopy, Thermogravimetry, Thermal Analysis, Thermogravimetric Analysis, Hydrothermal Synthesis, Smectite, Magic-angle Spinning Nuclear Magnetic Resonance, Solid-State 27Al NMR, beidellite, and solid-state 29Si NMR
Ahstract-Na-beidellite, a member of the smectite group, was grown hydrothermally from a gel of composition 0.35Na2O.2.35Al2O3.7.3SiO2 in NaOH solutions at a pH between 7.5 and 13.5, a pressure of 1 kbar, and a temperature of 350"C. The... more
Ahstract-Na-beidellite, a member of the smectite group, was grown hydrothermally from a gel of composition 0.35Na2O.2.35Al2O3.7.3SiO2 in NaOH solutions at a pH between 7.5 and 13.5, a pressure of 1 kbar, and a temperature of 350"C. The synthetic Na-beidellite was characterized by means of scanning electron microscopy, X-ray powder diffraction, infrared spectroscopy, electron microprobe, inductively coupled plasma-atomic emission spectroscopy, and thermogravimetric analysis. The unit-cell parameters of the orthorhombic cell are: a = 5.18, b = 8.96, and c = 12.54/~. The cation-exchange capacity was determined to be 70 meq/100 g. A maximum of 40 wt. % water was present and reversibly lost by heating to about 55"C. The loss of water caused a decrease of the basal spacing to 9.98/~. At temperatures >600"C, the Na-beidellite started to dehydroxylate, reaching its maximum in the range 600"-630"C. At 1100"C the remaining solid recrystallized to Alhy6Si2013 (mullite) and SiO2 (cristobalite).
Research Interests: Minerals, Scanning Electron Microscopy, ICP-AES, Vibrational Spectroscopy, Clay Minerals, and 15 moreInorganic synthesis, Layered Inorganic Materials, X-ray Diffraction, Infrared spectroscopy, Thermogravimetry, Thermal Analysis, Dehydration, Thermogravimetric Analysis, Dehydroxylation, Hydrothermal Synthesis, Smectite, Cation Exchange Capacity, Mullite, beidellite, and cristobalite
The tridecameric aluminum polymer [AlO4Al12(OH)24(H2O)12]7+ is prepared by forced hydrolysis of an Al(NO3)3 solution by NaOH up to an OH:Al mol ratio of 2.2. Upon addition of sulfate the tridecamer crystallizes into macroscopic... more
The tridecameric aluminum polymer [AlO4Al12(OH)24(H2O)12]7+ is prepared by forced hydrolysis of an Al(NO3)3 solution by NaOH up to an OH:Al mol ratio of 2.2. Upon addition of sulfate the tridecamer crystallizes into macroscopic crystallites of the basic aluminum sulfate Na0.1[Al13O4(OH)24(H2O)12](SO4)3.55, which is characterized structurally by means of X-ray diffraction, 27Al solid-state magic angle spinning NMR, IR and chemically by inductively coupled plasma atomic emission Spectroscopy. The basic aluminum sulfate has a monoclinic unit cell with a = 20.188±0.045 Å, b = 11.489±0.026Å, c = 24.980±0.056 Å, and β= 102.957±0.022°. With TG analysis, DTA and heating stage X-ray diffraction the thermal decomposition is studied. The tridecamer persists as a stable unit in the sulfate structure to temperatures of 80°C. Approximately 9 mol H2O are adsorbed in excess per one mol basic aluminum sulfate; these are easily lost by heating to 80°C. From 80 to 360°C the tridecamer unit will gradually decompose losing its 12 water and 24 hydroxyl groups, to finally become X-ray amorphous. From 360 to 950°C, with a maximum between 880 and 950°C, SO3 is removed, leaving behind primary aluminum oxide.
Research Interests: Nuclear Magnetic Resonance, Solid State NMR, X-ray Diffraction, Thermogravimetry, Thermal Analysis, and 11 moreDehydration, Thermal Stability, Differential Thermal Analysis, Thermogravimetric Analysis, Magic-angle Spinning Nuclear Magnetic Resonance, Keggin, Solid-State 27Al NMR, Basic aluminum sulphate, forced hydrolysis, tridecamer, and heating stage X-ray diffraction
Synthesis conditions strongly influence the yield of the tridecameric polymer Al13 ([AlO4Al12(OH)24(H2O)12]7+). An amount of 68% tridecamer was achieved by injection of alkali through a capillary tube into a 5 × 10−2 M Al solution at a... more
Synthesis conditions strongly influence the yield of the tridecameric polymer Al13 ([AlO4Al12(OH)24(H2O)12]7+). An amount of 68% tridecamer was achieved by injection of alkali through a capillary tube into a 5 × 10−2 M Al solution at a rate of 0.015 ml/s up to an OH/Al ratio of 2.2. Dropwise addition of alkali yielded significantly less tridecameric polymer. During progressive hydrolysis the monomeric Al NMR resonance moved from 0.1 to 0.9 ppm and the linewidth increased from 37 to 112 Hz. Simultaneously the resonance at 63.3 ppm due to tridecameric fourfold coordinated Al changed by 0.02 ppm. During aging the tridecamer rearranged to polymers undetectable by NMR, due to loss of the tetrahedral symmetry of the central Al, which was deduced from the decrease in intensity and the broadening of the 63.3 ppm resonance. The formation of tetrahedral Al(OH)4−, due to the inhomogeneous conditions at the point of base introduction, is essential for the synthesis of Al13. Aging over a period of 1 year caused a strong decrease in Al13 concentration, which showed that Al13 is a metastable polymer.
Research Interests:
Stepwise heating to 85°C in the NMR apparatus does not notably change the monomer and tridecamer (Al13) concentrations in a 0.2M Al(NO3)3 solution neutralized with 0.2M NaOH up to an OH/Al molar ratio of 2.4. Upon heating the fourfold... more
Stepwise heating to 85°C in the NMR apparatus does not notably change the monomer and tridecamer (Al13) concentrations in a 0.2M Al(NO3)3 solution neutralized with 0.2M NaOH up to an OH/Al molar ratio of 2.4. Upon heating the fourfold coordinated 27Al NMR signal of Al13 at 63.3 ppm and the very broad sixfold coordinated 27Al NMR signal of Al13 at 12 ppm exhibit an increasing intensity and decreasing linewidth, due to diminishing ‘missing intensity’ and ‘quadrupole relaxation’, respectively. An analogous effect for a Na2CO3 neutralized 0.2M AlCl3 solution confirmed that the 12 ppm signal must be assigned to the sixfold coordinated Al of the Al13 complex. The surface ratio of fourfold coordinated Al to sixfold coordinated Al of the Al13 complex experimentally established is smaller than the theoretical 1 : 12 ratio. During heating, a more intensive exchange interaction between monomer and other Al-species is proposed without any effect on the actual concentrations. High symmetry in the Al13 complex is determined at elevated preparation temperatures from the decreasing linewidth of the 63.3 ppm resonance. Above 85°C the tridecamer transforms to other species, which cannot be observed with NMR.
Research Interests:
The dehydration and migration of the interlayer cation of the synthetic beidellite Na0.7Al4.7Si7.3O20(OH)4.nH2O, were studied with solid-state 23Na and 27Al MAS-NMR, heating stage XRD, and thermogravimetric analyses (TGA, DTA). The 23Na... more
The dehydration and migration of the interlayer cation of the synthetic beidellite Na0.7Al4.7Si7.3O20(OH)4.nH2O, were studied with solid-state 23Na and 27Al MAS-NMR, heating stage XRD, and thermogravimetric analyses (TGA, DTA). The 23Na MAS-NMR of Na-beidellite at 25oC displays a chemical shift of 0.2 ppm, which indicates a configuration comparable with that of Na+ in solution. Total dehydration proceeds reversibly in two temperature ranges. Four water molecules per Na+ are gradually
removed from 25 to 85"C. As a result, the basal spacing decreases from 12.54 A to 9.98 A and the Na+ surrounded by the two remaining water molecules is relocated in the hexagonal cavities of the tetrahedral sheet. The chemical shift of 1.5 ppm exhibited after the first dehydration stage illustrates the increased influence of the tetrahedral sheet. The high local symmetry is maintained throughout the entire first dehydration stage. During the second dehydration, which proceeds in a narrow temperature range around
400oC the remaining two water molecules are removed reversibly without any change of the basal spacing.
removed from 25 to 85"C. As a result, the basal spacing decreases from 12.54 A to 9.98 A and the Na+ surrounded by the two remaining water molecules is relocated in the hexagonal cavities of the tetrahedral sheet. The chemical shift of 1.5 ppm exhibited after the first dehydration stage illustrates the increased influence of the tetrahedral sheet. The high local symmetry is maintained throughout the entire first dehydration stage. During the second dehydration, which proceeds in a narrow temperature range around
400oC the remaining two water molecules are removed reversibly without any change of the basal spacing.
Research Interests: Minerals, Clay Minerals, Solid State NMR, X-ray Diffraction, Thermal Analysis, and 12 moreDehydration, Differential Thermal Analysis, Thermogravimetric Analysis, Hydrothermal Synthesis, Smectite, Chemical Shift, Solid-State 27Al NMR, Magic Angle Spinning, thermal behaviour, beidellite, heating stage X-ray diffraction, and Solid-State 23Na NMR
Al-pillared clays, prepared by exchange with partly hydrolyzed aluminium nitrate solutions, dried in air or freeze-dried, and calcined, were used as supports for nickel sulfide catalysts. The catalysts were tested on their... more
Al-pillared clays, prepared by exchange with partly hydrolyzed aluminium nitrate solutions, dried in air or freeze-dried, and calcined, were used as supports for nickel sulfide catalysts. The catalysts were tested on their hydrodesulfurization (HDS) activity for thiophene. The catalysts show a high thiophene HDS activity. It appears that details in the preparation and calcination of the pillared clays have a strong influence on the catalytic activity.
Research Interests:
The Al concentration and forced hydrolysis influence the polymerization of aqueous Al(III) and thus the 27Al NMR spectra. An increase of the Al concentration results in an increase of the fraction present as monomer, in the formation of... more
The Al concentration and forced hydrolysis influence the polymerization of aqueous Al(III) and thus the 27Al NMR spectra. An increase of the Al concentration results in an increase of the fraction present as monomer, in the formation of an oligomer of an OH/Al molar ratio of 2.4, and in the disappearance of the tridecamer above an Al concentration of 0.15M. Increasing the OH/Al molar ratio at a constant Al concentration leads to a linear drop of the fraction present as monomer over the entire range between 1 and 2.5 and a maximum in oligomer fraction between 1.5 and 2.5. At low Al concentrations, the fraction of tridecamer exhibits an optimum yield between OH/Al ratios of 2.2 and 2.4. At ratios higher than 2.4, NMR unobservable polymers are formed. The chemical shift and the linewidth of the monomer resonance are lowered by increasing spin-spin relaxation, T2, and a consequently decreasing quadrupole coupling constant upon increasing Al concentration. With increasing OH/Al molar ratio, [Al(H2O)6]3+ is mainly replaced by [Al(H2O)5(OH)]2+ and [Al(H2O)4(OH)2]+ and subsequently the chemical shift and linewidth of the monomer resonance increase. The Al concentration or OH/Al molar ratio hardly affect the resonance of the central fourfold coordinated Al of the tridecamer, due to its very strong shielding.
Research Interests:
In the chemical system Na2O-AI2O3-SiO2-H2O, the stability field of Na-beidellite is presented as a function of pressure, temperature, and Na- and Si-activity. Na0.7-beidellite was hydrothermally synthesized using a stoichiometric gel... more
In the chemical system Na2O-AI2O3-SiO2-H2O, the stability field of Na-beidellite is presented as a function of pressure, temperature, and Na- and Si-activity. Na0.7-beidellite was hydrothermally synthesized using a stoichiometric gel composition in the temperature range from 275 to 475oC and at pressures from 0.2 to 5 kbar. Below 275oC kaolinite was the only crystalline phase, and above about 500oC paragonite and quartz developed instead of beidellite. An optimum yield of 95% of the Na0.7-
beidellite was obtained at 400~ and 1 kbar after 20 days. Gels with a Na-content equivalent to a layer charge lower than 0.3 per O20(OH)4 did not produce beidellite. They yielded kaolinite below 325oC and pyrophyllite above 325oC. With gels of a Na-content equivalent to a layer charge of 1.5, the Na-beidellite field shifted to a minimum between temperatures of 275oC and 200oC. This procedure offers the potential to synthesize beidellite at low temperatures. Beidellite synthesized from Na1.0-gel approach a Na1.35
composition and those from Na1.5- and Na2.0-gels a Na1.8 composition.
beidellite was obtained at 400~ and 1 kbar after 20 days. Gels with a Na-content equivalent to a layer charge lower than 0.3 per O20(OH)4 did not produce beidellite. They yielded kaolinite below 325oC and pyrophyllite above 325oC. With gels of a Na-content equivalent to a layer charge of 1.5, the Na-beidellite field shifted to a minimum between temperatures of 275oC and 200oC. This procedure offers the potential to synthesize beidellite at low temperatures. Beidellite synthesized from Na1.0-gel approach a Na1.35
composition and those from Na1.5- and Na2.0-gels a Na1.8 composition.
Research Interests: Geology, Minerals, Scanning Electron Microscopy, Vibrational Spectroscopy, Clay Minerals, and 13 moreInorganic synthesis, Layered Inorganic Materials, X-ray Diffraction, Quartz, X ray diffraction, Fourier transform infrared spectroscopy, Hydrothermal Synthesis, Low Temperature, Pyrophyllite, Phyllosilicates, Kaolinite, beidellite, and Paragonite
The Al concentration and forced hydrolysis influence the polymerization of aqueous Al(III) and thus the 27Al NMR spectra. An increase of the Al concentration results in an increase of the fraction present as monomer, in the formation of... more
The Al concentration and forced hydrolysis influence the polymerization of aqueous Al(III) and thus the 27Al NMR spectra. An increase of the Al concentration results in an increase of the fraction present as monomer, in the formation of an oligomer of an OH/Al molar ratio of 2.4, and in the disappearance of the tridecamer above an Al concentration of 0.15M. Increasing the OH/Al molar ratio at a constant Al concentration leads to a linear drop of the fraction present as monomer over the entire range between 1 and 2.5 and a maximum in oligomer fraction between 1.5 and 2.5. At low Al concentrations, the fraction of tridecamer exhibits an optimum yield between OH/Al ratios of 2.2 and 2.4. At ratios higher than 2.4, NMR unobservable polymers are formed. The chemical shift and the linewidth of the monomer resonance are lowered by increasing spin-spin relaxation, T2, and a consequently decreasing quadrupole coupling constant upon increasing Al concentration. With increasing OH/Al molar ratio, [Al(H2O)6]3+ is mainly replaced by [Al(H2O)5(OH)]2+ and [Al(H2O)4(OH)2]+ and subsequently the chemical shift and linewidth of the monomer resonance increase. The Al concentration or OH/Al molar ratio hardly affect the resonance of the central fourfold coordinated Al of the tridecamer, due to its very strong shielding.
Research Interests:
Aluminum-pillared clays based on synthetic beidellite have been prepared by exchanging hydrothermally synthesized beidellite with partly hydrolyzed aluminum nitrate solution followed by calcination. It is shown that a catalyst containing... more
Aluminum-pillared clays based on synthetic beidellite have been prepared by exchanging hydrothermally synthesized beidellite with partly hydrolyzed aluminum nitrate solution followed by calcination. It is shown that a catalyst containing 50 wt% amorphous silica and 50 wt% pillared beidellite loaded with 0.8 wt% Pt has an n-heptane hydroconversion comparable to a commercially available silica-alumina and does not significantly deactivate with increasing time on stream (within 14 h).
Research Interests:
Ammonium-saponite is hydrothermally grown at temperatures below 300~ from a gel with an overall composition corresponding to (NH4)0.6Mg3Al0.6Si3.4O10(OH)2. Using 27Al and 29Si solid-state Magic Angle Spinning NMR techniques it is... more
Ammonium-saponite is hydrothermally grown at temperatures below 300~ from a gel with an overall composition corresponding to (NH4)0.6Mg3Al0.6Si3.4O10(OH)2. Using 27Al and 29Si solid-state Magic Angle Spinning NMR techniques it is demonstrated that synthetic ammonium-saponites have a rather constant Si/AlIV ratio (~5.5) and an AlIV/AlVl ratio that varies between 1.5 and 3.8. The above ratios are independent of the synthesis temperature, although an increasing amount of Si, N, and, to a lesser extent, Al are incorporated in an amorphous phase with increasing temperature. 27Al MAS-NMR is unable to differentiate between AI at octahedral and Al3+ at interlayer sites. CEC, XRD, and the inability to swell prove the AlVI to be mainly on the interlayer sites. Based on the NH4-exchange capacity, X-ray fluorescence, 27Al and 29Si MAS-NMR, it is possible to calculate a relatively accurate structural formula.
Research Interests:
This paper is a summary of the contents of a Ph-D-thesis, which was defended on october 15, 1992 at the University of Utrecht. The research concentrated on the synthesis of beidellite, a clay mineral from the smectite group and the... more
This paper is a summary of the contents of a Ph-D-thesis, which was defended on october 15, 1992 at the University of Utrecht. The research
concentrated on the synthesis of beidellite, a clay mineral from the smectite group and the formation of the aluminum tridecamer (Al13) complex during forced hydrolysis of aluminum nitrate. This aluminum complex can be used to expand (to pillar) clay minerals. The synthetic clay mineral is briefly compared with pillared natural montmorillonite.
concentrated on the synthesis of beidellite, a clay mineral from the smectite group and the formation of the aluminum tridecamer (Al13) complex during forced hydrolysis of aluminum nitrate. This aluminum complex can be used to expand (to pillar) clay minerals. The synthetic clay mineral is briefly compared with pillared natural montmorillonite.
Research Interests: Nuclear Magnetic Resonance, Minerals, Transmission Electron Microscopy, Clay Minerals, Inorganic synthesis, and 14 moreLayered Inorganic Materials, X-ray Diffraction, Solid-state NMR, Porous Materials, Pillared Clay, Montmorillonite, Hydrothermal Synthesis, Smectite, Magic-angle Spinning Nuclear Magnetic Resonance, Keggin, PILC, beidellite, forced hydrolysis, and tridecamer
The pillaring process of montmorillonite and beidellite with Al and Ga polymers has been studied using XRD, IR, 27Al, 71Ga, and 29Si MAS NMR, TGA, TEM, N2 adsorption and chemical analyses. The Al adsorption maximum for montmorillonite is... more
The pillaring process of montmorillonite and beidellite with Al and Ga polymers has been studied using XRD, IR, 27Al, 71Ga, and 29Si MAS NMR, TGA, TEM, N2 adsorption and chemical analyses. The Al adsorption maximum for montmorillonite is close to 5.5 mEq Al/g clay, whereas the maximum for Ga is higher. Basal spacings of both Ga-and Al-pillared clays vary between 16.7 and 18.8 A. Freeze-drying of pillared products followed by calcination yielded more regular pillared structures. Pillaring montmorillonite increased the BET surface area from 35 m2/g to 350 m2/g mainly by the creation of micropores <20 A. in diameter. The Al-pillared clays are thermally stable to ~700oC. Calcination of pillared montmorillonite liberates protons from the pillar, which diffuse into the clay sheet, lowering the thermal stability. In pillared beidellite, mainly silanol groups are formed by breaking Si-O-AI bonds. No reaction is observed between pillars and montmorillonite upon calcination, whereas in pillared beidellite a structural transformation links the pillar to inverted tetrahedra of the tetrahedral sheet. The basal spacing of Ga-pillared montmorillonite collapses to 9.5 A at 350oC due to the Ga polymer decomposing to Ga3+ cations.
Research Interests: Nuclear Magnetic Resonance, Transmission Electron Microscopy, ICP-AES, Vibrational Spectroscopy, Clay Minerals, and 15 moreSolid State NMR, X-ray Diffraction, Thermal Analysis, Pillared Clay, Montmorillonite, Surface Area, Thermal Stability, BET surface area, Differential Thermal Analysis, Fourier transform infrared spectroscopy, Thermogravimetric Analysis, Cation Exchange Capacity, Magic-angle Spinning Nuclear Magnetic Resonance, PILC, and beidellite
Saponites were hydrothermally grown in the presence of amounts of NH4+ , Na+, K+, Rb+, Ca2+, Ba2+, and Ce4+ equivalent with the CEC of the saponite (155 meq/100 g), with or without F , at a temperature of 200oC for 72 hr. XRD and CEC data... more
Saponites were hydrothermally grown in the presence of amounts of NH4+ , Na+, K+, Rb+, Ca2+, Ba2+, and Ce4+ equivalent with the CEC of the saponite (155 meq/100 g), with or without F , at a temperature of 200oC for 72 hr. XRD and CEC data revealed the formation of a two-water-layer saponite with mainly Mg2+ as interlayer cation. Dehydration occurred between 25* and 450oC and dehydroxylation occurred in two steps between 450 ~ and 790oC and between 790 and 890oC. The relatively small length of the b-axis between 9.151 and 9.180 A is explained by considerable octahedral AI substitution (between 0.28 and 0.70 per three sites) and minor tetrahedral AI substitution (between 0.28 and 0.58 per four sites). Under the synthesis conditions applied in this study, less than 13% of the interlayer sites are occupied
by Na+, K+, and Rb+; between 13.3% and 21% by Ca2+ and Ba2+; while NH4+ gives the highest value at 34%. The remaining sites are mainly filled by Mg2+ . Ce4+ is not found in the saponite structure due to the formation of cerianite, CeO2. The presence of F- had little influence on the saponite composition. The formation of Mg-saponites is explained by a model in which an increased bayerite formation resulting in a higher octahedral Al3+ substitution and more Mg2+ in solution. Mg2+ is preferentially incorporated compared with the other interlayer cations due to its smallest ionic radius in combination with its 2+ charge.
by Na+, K+, and Rb+; between 13.3% and 21% by Ca2+ and Ba2+; while NH4+ gives the highest value at 34%. The remaining sites are mainly filled by Mg2+ . Ce4+ is not found in the saponite structure due to the formation of cerianite, CeO2. The presence of F- had little influence on the saponite composition. The formation of Mg-saponites is explained by a model in which an increased bayerite formation resulting in a higher octahedral Al3+ substitution and more Mg2+ in solution. Mg2+ is preferentially incorporated compared with the other interlayer cations due to its smallest ionic radius in combination with its 2+ charge.
Research Interests: Geology, Minerals, ICP-AES, X-Ray Fluorescence (XRF) Spectroscopy, Clay Minerals, and 13 moreInorganic synthesis, X-ray Diffraction, Soil sciences, Thermogravimetry, Thermal Analysis, Dehydration, Thermogravimetric Analysis, Dehydroxylation, Hydrothermal Synthesis, Smectite, Thermal Decomposition, Cation Exchange Capacity, and saponite
Infrared absorption spectra and light element contents of several natural cordierites across the Arendal amphibolite-granulite facies transition, Bamble Sector, south Norway are presented. The infrared spectra record H2O (both type-I and... more
Infrared absorption spectra and light element contents of several natural cordierites across the Arendal amphibolite-granulite facies transition, Bamble Sector, south Norway are presented. The infrared spectra record H2O (both type-I and type-II) and CO2 as fluid constituents in the channels, CO and hydrocarbons were not detected. Type-II water and (Ca+Na+K) are correlated and show a 2:1 molar ratio. The infrared and light element data indicate a decrease of Na, type-II H2O, CO2 and Li with metamorphic grade, while type-I H2O and Be are variable. The decrease of these volatiles and alkalies and the low total volatile contents of the granulite facies cordierites are best explained by progressive dehydration and decarbonation processes, possibly related to partial melting. A progressive change of the ratio in the cordierites across the transition, as suggested by previous studies, is not observed. Greenschist to low-amphibolite facies re-equilibrated cordierites show a significant increase in either CO2, or H2O+CO2. Na is introduced at some localities. The retrograde fluid phase is calculated to be CO2-rich.
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Hydrothermally synthesized smectites like beidellite and saponite are receiving increasing interest because of their high purity and their possible application as catalysts and molecular sieves. Beidellite with only tetrahedral Al-Si... more
Hydrothermally synthesized smectites like beidellite and saponite are receiving increasing interest because of their high purity and their possible application as catalysts and molecular sieves. Beidellite with only tetrahedral Al-Si substitution and its corresponding acidity is therefore an interesting candidate to be synthesized in the ammonium-form. This note briefly describes the first laboratory experiments to synthesize ammonium-beidellite using urea (H2NCONH2), glycine (H2NCH2CO2H), ammoniumhydroxide (NH4OH), ammonium-chloride (NH4C1), and ammonium-aluminum-fluoride ([NHa]3AIF6) as ammonium sources. Hydrothermal treatment at 250 oC does only succeed in the crystallization of H+ beidellite when using urea
or [NH4]3AIF6. Increasing the temperature to 350 oC results first in the formation of ammonium-analcime followed by H+-beidellite. The high crystallinity of the beidellite in the [NH4]3AIF6 experiments can be explained by the incorporation of fluor at hydroxyl sites, the formation of NH4-beidellite in the glycine experiment is explained by the slightly acidic fluid prohibiting analcime formation.
or [NH4]3AIF6. Increasing the temperature to 350 oC results first in the formation of ammonium-analcime followed by H+-beidellite. The high crystallinity of the beidellite in the [NH4]3AIF6 experiments can be explained by the incorporation of fluor at hydroxyl sites, the formation of NH4-beidellite in the glycine experiment is explained by the slightly acidic fluid prohibiting analcime formation.
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The quadrupole coupling constants (QCC) and asymmetry parameters (η) of the fourfold and sixfold coordinated Al sites in basic aluminum sulfate have been determined by using the field dependent second order quadrupole shift, 2-dimensional... more
The quadrupole coupling constants (QCC) and asymmetry parameters (η) of the fourfold and sixfold coordinated Al sites in basic aluminum sulfate have been determined by using the field dependent second order quadrupole shift, 2-dimensional nutation nuclear magnetic resonance and computer simulation. The quadrupole data from these three methods are consistent. The fourfold coordinated Al site has a QCC of 1.6 MHz and 0 ≤ η ≤ 0.22, while the 12 sixfold coordinated Al sites have an average QCC of 5.5 MHz and an 0 ≤ η ≤ 0.2.
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The aging of the aluminum tridecamer in acidified aluminum sec-butoxide is studied with 27Al nuclear magnetic resonance. At 20°C the tridecamer content passes through a maximum of 19.7% after 133 h of aging to decline subsequently to a... more
The aging of the aluminum tridecamer in acidified aluminum sec-butoxide is studied with 27Al nuclear magnetic resonance. At 20°C the tridecamer content passes through a maximum of 19.7% after 133 h of aging to decline subsequently to a final content of approximately 12%. At 90°C the tridecamer disappears within 21 h of aging due to clustering. After 91 h colloidal gibbsite forms, while the pH drops continuously from 4.3 to 3.5. Simultaneously the monomer concentration increases to approximately 6.6%. The increase is possibly due to liberation of the central fourfold-coordinated Al from the tridecamer that rearranges to hexameric rings, and to dissolution of some gibbsite in the acid solution. The hexameric rings are considered to be the precursor for the crystallization of gibbsite and boehmite. Increase of the preparation temperature from 20°C to 80°C has no effect on the amount of tridecamer, although at 90°C the amount increases from approximately 9% to 14.1%. An increase of the preparation temperature leads to changes in the second-order quadrupole effects, which results in a line sharpening from 19.5 to 9.8 Hz for the central fourfold-coordinated Al signal of the tridecamer at 63.3 ppm.
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Ce/Al-and La/Al-pillared smectites were prepared by cation exchange of bentonite, saponite and laponite with hydrothermally treated (130-160 ~ for 16-136 h) solutions containing mixtures of aluminumchlorohydrate (ACH) and Ce3+-/and... more
Ce/Al-and La/Al-pillared smectites were prepared by cation exchange of bentonite, saponite and laponite with hydrothermally treated (130-160 ~ for 16-136 h) solutions containing mixtures of aluminumchlorohydrate (ACH) and Ce3+-/and La3+-salts. After calcination at 500 ~ the pillared products are characterized by basal spacings between 24.8 and 25.7 ,~ and surface areas of approximately 430 m 2 g 1. The products are hydrothermally stable at 500 ~ after 2 h in steam. The large basal spacings are due to the formation of a large Ce/La-bearing Al-polyoxocation, whose formation is favored by initially high Al concentrations ~3.7 M and an OH/Al molar ratio of approximately 2.5. The Ce/Al or La/Al molar ratios can be as low as 1/30. 27Al nuclear magnetic resonance (NMR) spectroscopy has shown that the polyoxocation has a higher Altetrahedral/Aloctahedral ratio than the Keggin structure Al13, which may partly explain the higher stability compared to normal Al-pillared clays. Hydroconversion of n-heptane indicated that the activity of the Pt-loaded pillared products is higher than that of a conventional Pt-loaded amorphous silica-alumina catalyst. Selectivity is strongly dependent on the type of starting clay and its acidity. In industrial hydrocracking of normal feedstock, a Ni/W-loaded Ce/Al-pillared bentonite catalyst showed rapid deactivation due to coke-formation reducing the surface area and the pore volume. Additionally, coke-formation is facilitated by the relatively high iron content of the pillared bentonite (3.43 wt% Fe203).
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Pyrophyllite, kaolinite + quartz and beidellite were synthesized at 300 and 350 °C at 1 kbar within a period of 10 days. For the crystallization silica-alumina gels in salt solutions were used as starting materials. In all cases lowering... more
Pyrophyllite, kaolinite + quartz and beidellite were synthesized at 300 and 350 °C at 1 kbar within a period of 10 days. For the crystallization silica-alumina gels in salt solutions were used as starting materials. In all cases lowering the temperature from 350 to 300 °C results in the formation of only kaolinite and quartz instead of pyrophyllite and sometimes kaolinite. In NaOH and NaF solutions beidellite is formed
accompanying pyrophyllite. Some additional experiments with gels containing the cations Na+, K +, Li+, or Ca2+ resulted in the formation of beidellite with sometimes kaolinite. The anions present in the solution and the state and quantity of the interlayer cation and especially the counter anion in solution are important factors determining the phyllosilicate formed under relatively low grade metamorphic conditions and hydrothermal alteration.
accompanying pyrophyllite. Some additional experiments with gels containing the cations Na+, K +, Li+, or Ca2+ resulted in the formation of beidellite with sometimes kaolinite. The anions present in the solution and the state and quantity of the interlayer cation and especially the counter anion in solution are important factors determining the phyllosilicate formed under relatively low grade metamorphic conditions and hydrothermal alteration.
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Ce/Al and La/Al pillared bentonites were prepared by cation-exchange of different bentonites with hydrothermally treated (130–160°C for 16–136 h) solutions containing mixtures of aluminiumchlorohydrate (ACH) and REE (Ce and La)-salts.... more
Ce/Al and La/Al pillared bentonites were prepared by cation-exchange of different bentonites with hydrothermally treated (130–160°C for 16–136 h) solutions containing mixtures of aluminiumchlorohydrate (ACH) and REE (Ce and La)-salts. After calcination at 500°C the pillared clays are characterised by basal spacings of 24.8–25.7 Å, and have BET surface areas of approximately 430 m2/g. The pillared products are hydrothermally stable to at least 500°C. The large basal spacings and surface areas are due to the formation of large REE/Al containing polyoxycations. The formation of this cation is favoured by high initial Al concentrations (≥3.7 M) and an OH/Al molar ratio of approximately 2.5. Ce/Al or La/Al ratios can be as low as 130. Hydroconversion of n-heptane indicated that the activity of these materials is higher than that of a conventional Pt loaded amorphous silica alumina (ASA) reference catalyst. The selectivity is strongly dependant on the type of starting clay. In industrial hydrocracking of normal feedstock, a Ni/W loaded REE/Al pillared clay catalyst showed slightly higher initial activity than the ASA reference catalyst. However, the pillared clay catalyst showed rapid deactivation due to coke-formation, which reduced the surface area and pore volume. Additionally coke formation may be facilitated by the relatively high iron content of the pillared bentonite (3.43 wt%).
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The results from the adsorption of chlorobenzene on cation exchanged, Al-pillared and organically modified montmorillonite have shown that head-space gaschromatography is a very simple and powerful tool to screen a large number of porous... more
The results from the adsorption of chlorobenzene on cation exchanged, Al-pillared and organically modified montmorillonite have shown that head-space gaschromatography is a very simple and powerful tool to screen a large number of porous materials for their usefulness as possible adsorbents. This method allows the analysis of the adsorption capability directly from suspension without separating the fluid from the solid adsorbent.
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The effects of reaction time (2 to 72 h) and NH4+/Al3+ molar ratio (1.6, 2.4 and 3.2) on the hydrothermal synthesis of ammonium-saponites are investigated. The gels are obtained by mixing powders , resulting in a stoichiometric... more
The effects of reaction time (2 to 72 h) and NH4+/Al3+ molar ratio (1.6, 2.4 and 3.2) on the hydrothermal synthesis of ammonium-saponites are investigated. The gels are obtained by mixing powders , resulting in a stoichiometric composition, Mg3Si3.4Al0.6O10(OH)2, with aqueous ammonium solutions, with and without F to result in initial NH4+/Al3+ molar ratios of 1.6, 2.4 and 3.2. The solid bulk products are characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF) and scanning electron microscopy (SEM) combined with energy-dispersive X-ray (EDX) analysis. The cation exchange capacity (CEC) is determined with an ammonia selective electrode and the pH of the water from the first washing is measured. Ammonium-saponite is formed rapidly within 16 h. A higher NH4+/Al3+molar ratio and the presence of F facilitate the crystallization of saponite. Small metastable amounts of bayerite, AI(OH)3, are present at low NH4+/Al3+ molar ratios; after short reaction times, they disappear. During the first 4 h, the pH decreases rapidly, then drops slowly to a constant level of approximately 4.6 after 60 h. With increasing reaction time, saponite crystallites grow in the ab directions of the individual sheets with almost no stacking to thicker flakes. The NH4+ CEC of the solid products increases strongly within the first 24 h. A maximum of 53.3 meq/100 g is observed. The saponite yield increases from approximately 25% after 2 h to almost 100% after 72 h.
Research Interests: Nanomaterials Characterization, Minerals, Materials Characterisation, Scanning Electron Microscopy, X-Ray Fluorescence (XRF) Spectroscopy, and 7 moreClay Minerals, Inorganic synthesis, X-ray Diffraction, Energy Dispersive X-Ray Analysis, Hydrothermal Synthesis, Cation Exchange Capacity, and saponite
Upon the intercalation of kaolinite with DMSO, new Raman bands at 3660, 3536, and 3501 cm-1 are observed for the low-defect kaolinite and at 3664, 3543, and 3509 cm-1 for the high-defect kaolinite. An additional band at 3598 cm-1 was... more
Upon the intercalation of kaolinite with DMSO, new Raman bands at 3660, 3536, and 3501 cm-1 are observed for the low-defect kaolinite and at 3664, 3543, and 3509 cm-1 for the high-defect kaolinite. An additional band at 3598 cm-1 was observed for the high-defect kaolinite. The band at 3660 cm-1 was assigned to the inner-surface hydroxyls hydrogen bonded to the SO group. The other three bands are attributed to the hydroxyl stretching frequencies of water in the intercalation complex. The hydroxyl deformation region is characterized by one intense band in both the FTIR and Raman spectra at 905 cm-1. Significant changes in the Raman spectra of the intercalating molecule are observed. Splitting of the C−H symmetric and antisymmetric stretching vibrations occurs. Two Raman bands at 2917 and 2935 cm-1 and four bands at 2999, 3015, 3021, and 3029 cm-1 are observed. The in-plane methyl bending region shows two Raman bands at 1411 and 1430 cm-1. The DRIFT spectra show complexity in these regions. The SO stretching region shows bands at 1066, 1023, and 1010 cm-1 upon intercalation with DMSO for the low-defect kaolinite and 1058, 1028, and 1004 cm-1 for the high-defect kaolinite. The 1058 cm-1 band is assigned to the free monomeric SO group and the 1023 and 1010 cm-1 bands to two different polymeric SO groups. Bands attributed to the C−S stretching vibrations, the in-plane and out-of-plane SO bending and the CSC symmetric bends all move to higher frequencies upon intercalation. It is proposed that intercalation with DMSO depends on the presence of water and that the additional bands at 3536 and 3501 cm-1 are due to the presence of water in the intercalate.
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The dehydration and dehydroxylation of the clay minerals attapulgite, sepiolite and `Rocky Mountain leather' have been analysed by infrared emission spectroscopy. The `Rocky Mountain leather' and attapulgite are shown to be identical.... more
The dehydration and dehydroxylation of the clay minerals attapulgite, sepiolite and `Rocky Mountain leather' have been analysed by infrared emission spectroscopy. The `Rocky Mountain leather' and attapulgite are shown to be identical. Infrared emission spectroscopy of the thermal degradation over the temperature range of 100 to 700°C has been used to characterise the thermal decomposition of both sepiolite and attapulgite. Attapulgite is characterised by two bands in the water bending region at 1595 and 1635 cm−1, attributed to coordinated zeolitic and adsorbed water, respectively. A band was also observed in this region at 1425 cm−1. The hydroxyl stretching region of attapulgite is complex with bands observed at 3731, 3710, 3670, 3645, 3610, 3590, and 3532 cm−1. Bands in this region are assigned to either hydroxyl stretching vibrations of water, occurring below 3600 cm−1 or to hydroxyl bands associated with coordinated hydroxyl groups, occurring above 3600 cm−1. The first two bands at 3731 and 3710 cm−1 are attributed to SiOH stretching vibrations. The next five bands are attributed to hydroxyls associated with the magnesium. Another two hydroxyl stretching bands at ∼3385 and 3315 cm−1 are attributed to the two types of water molecules, the zeolitic water and coordinated water. The infrared emission spectra of sepiolite were found to be considerably different. Four hydroxyl-stretching frequencies were observed at 3735, 3722, 3688, and 3670 cm−1. This difference is attributed to the basic difference in the two minerals. The dehydration of attapulgite and sepiolite is followed by the loss of intensity of the water hydroxyl bands. Dehydroxylation is followed by the decrease in intensity in the bands between 3731 and 3532 cm−1. Dehydration was complete by 300°C and partial dehydroxylation by 700°C. The Si–OH hydroxyl groups remained until ∼970°C.
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Water in intercalated kaolinites is observed first as bands in the hydroxyl-stretching region at 3300 to 3550 cm−1 and by the water H–O–H bending vibrations in the 1560 to 1680-cm−1 region. For potassium-acetate-intercalated kaolinite,... more
Water in intercalated kaolinites is observed first as bands in the hydroxyl-stretching region at 3300 to 3550 cm−1 and by the water H–O–H bending vibrations in the 1560 to 1680-cm−1 region. For potassium-acetate-intercalated kaolinite, hydroxyl-stretching bands attributed to water are observed at ∼3540,∼3475, ∼3430, and ∼3380 cm−1. Water bending modes are observed at 1560, 1586, 1610, and 1679 cm−1. These bands are attributed to (a) water molecules adsorbed on the kaolinite surface, (b) zeolitic water, (c) molecular first layer water, and (d) ordered water on the hydroxyl surface, respectively. The intensities of the bands are a function of the method of preparation of the intercalated kaolinite. As the kaolinite was washed for varying time intervals, the 1560 cm−1 band decreased in intensity more rapidly than the 1610 cm−1 band. Even after washing for 24 h significant concentrations of water remained on the kaolinite and only heating removed the water. The 1560, 1586, and 1610 cm−1 bands are attributed (a) to free or non-hydrogen-bonded water held in the interlayer spaces of the kaolinite, (b) to water in the hydration sphere of the potassium ion, and (c) to surface-adsorbed water on the kaolinite layers. In kaolinites intercalated under pressure, an additional band was observed at 1679 cm−1. It is proposed that this band is due to water coordinated to the kaolinite surface.
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In this pape r a new spectroscopic technique is described for in-situ measurement at elevated temperatures. This technique is known as Infrared Emission Spectroscopy or IES. This technique comprises the measurement of discrete vibrational... more
In this pape r a new spectroscopic technique is described for in-situ measurement at elevated temperatures. This technique is known as Infrared Emission Spectroscopy or IES. This technique comprises the measurement of discrete vibrational frequencies emitted by the thermally excited molecules. Infra red Emission Spectroscopy appears
to be very suitable for the study of phase transitions in both organic and inorganic materials. Good examples of these are the dehydroxylation of clay minerals and hydroxides. Other applications of this technique within the CIDC comprise the study of in-situ calcination of sol-gel materials and the thermal degradation of plastics.
to be very suitable for the study of phase transitions in both organic and inorganic materials. Good examples of these are the dehydroxylation of clay minerals and hydroxides. Other applications of this technique within the CIDC comprise the study of in-situ calcination of sol-gel materials and the thermal degradation of plastics.
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In this article, after a short explanation o f the basic principles of Raman spectroscopy, some examples are given of the possibilities t his technique offers in the spectroscopic investigation of clay minerals. Successively the... more
In this article, after a short explanation o f the basic principles of Raman spectroscopy, some examples are given of the possibilities t his technique offers in the spectroscopic investigation of clay minerals. Successively the differences are shown between various kaolinite polymorphs, between kaolinites with various degrees of crystallinity (defect structures), and the adsorption of organic compounds on various clayminerals. It becomes clear that Raman microscopy is a simple and easily used technique to obtain rapid and accurate spectral information about clay minerals.
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Beide llite is a dioctahedral clay mineral be longing to the smectite group . Beidellite is defined as the Al-endmember of the dioctahedral smectites, with a general unit cell formula of (0.5Ca,Na, K)pA14+pSi8-p(OH)4. nH2O, in which the... more
Beide llite is a dioctahedral clay mineral be longing to the smectite group . Beidellite is defined as the Al-endmember of the dioctahedral smectites, with a general unit cell formula of (0.5Ca,Na, K)pA14+pSi8-p(OH)4. nH2O, in which the interlayer cations are compensated by Al3+ for Si4+ substitution in the tetrahedral sheet. A complete characterization of natural beidellitic clays is often difficult because of its heterogeneous composition. Because of its simplicity in chemistry and its
associated acidity, synthetic beidellite has received a lot of attention for use as a starting material for the preparation of pillared clay catalysts. There is a large resemblance in band positions of the major bands in the complete IR spectra of the natural beidellite, in comparison with the two synthetic beidellites. StiII, there are minor differences in the exact position and relative intensities. Preliminary results of the band-component analysis of the broad band around 1020-1050 cm- 1 of all three samples indicate that this band consists of a major band at 1025- 1032 cm-1 and a very broad band around 111 5-1 130 cm-1. Both of the synthetic beidellites contain an extra very small band at approximately I 050 cm-1 , which is interpreted to
belong to some silica-containing amorphous material. Synthetic beidellites are characterized by Si-O bending vibrations, shifted by approximately 5 to 10 cm-1 toward higher wavenumbers compared to the natural beidellite. The clearly developed bands at 695, 779, and 799 cm-1 of the natural beidellite are absent in the synthetic ones. In this case, only one broad band, around 810- 8 17 cm-1 can be distinguished.
The bands at 416, 432, 884, and 926 cm-1 are far more clearly developed for the synthetic beidellite prepared from the TEOS calcined gel, compared to the beidellite prepared from the coprecipitated gel, indicating that the crystallinity of the former material is better.
associated acidity, synthetic beidellite has received a lot of attention for use as a starting material for the preparation of pillared clay catalysts. There is a large resemblance in band positions of the major bands in the complete IR spectra of the natural beidellite, in comparison with the two synthetic beidellites. StiII, there are minor differences in the exact position and relative intensities. Preliminary results of the band-component analysis of the broad band around 1020-1050 cm- 1 of all three samples indicate that this band consists of a major band at 1025- 1032 cm-1 and a very broad band around 111 5-1 130 cm-1. Both of the synthetic beidellites contain an extra very small band at approximately I 050 cm-1 , which is interpreted to
belong to some silica-containing amorphous material. Synthetic beidellites are characterized by Si-O bending vibrations, shifted by approximately 5 to 10 cm-1 toward higher wavenumbers compared to the natural beidellite. The clearly developed bands at 695, 779, and 799 cm-1 of the natural beidellite are absent in the synthetic ones. In this case, only one broad band, around 810- 8 17 cm-1 can be distinguished.
The bands at 416, 432, 884, and 926 cm-1 are far more clearly developed for the synthetic beidellite prepared from the TEOS calcined gel, compared to the beidellite prepared from the coprecipitated gel, indicating that the crystallinity of the former material is better.
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Raman spectra of kaolinite and of the formamide‐intercalated kaolinite were obtained at both 298 and 77 K using a Raman microprobe equipped with a thermal stage. Upon cooling to 77 K, the band attributed to the inner hydroxyl shifts by 5... more
Raman spectra of kaolinite and of the formamide‐intercalated kaolinite were obtained at both 298 and 77 K using a Raman microprobe equipped with a thermal stage. Upon cooling to 77 K, the band attributed to the inner hydroxyl shifts by 5 cm‐1 to lower wavenumbers and the bands assigned to the inner surface hydroxyls move to higher wavenumbers. Upon intercalation of the kaolinite with formamide, an additional Raman band attributed to the formation of a hydrogen‐bonded complex between the inner surface hydroxyls and the carbonyl group of the formamide is observed at 3627 cm‐1 at 298 K and at 3631 cm‐1 at 77 K. Raman spectra of the deintercalation of the formamide‐intercalated kaolinite are obtained by using the thermal stage to heat the intercalated kaolinite in situ. A decrease in intensity of the bands formed through intercalation and at the same time an increase in intensity of the inner surface hydroxyl bands are observed. A loss of intensity of the low‐wavenumber region of the formamide‐intercalated kaolinite is also observed.
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Kaolinite hydroxyl surfaces have been modified upon intercalation with potassium acetate under a range of conditions. Modification is observed by changes in the hydroxyl stretching region using Raman and infrared spectroscopy. Upon the... more
Kaolinite hydroxyl surfaces have been modified upon intercalation with potassium acetate under a range of conditions. Modification is observed by changes in the hydroxyl stretching region using Raman and infrared spectroscopy. Upon the intercalation of low defect kaolinite with potassium acetate under a pressure of 20 bars and 220°C, the Raman spectra showed additional bands at 3590, 3603, and 3609 cm−1. The DRIFT spectra of this intercalate showed new bands at 3595 and 3605 cm−1. These bands are attributed to the inner surface hydroxyls hydrogen bonded to the acetate anion. Intercalation under 20 bars pressure at 220°C caused the differentiation of the inner surface hydroxyl groups, resulting in these additional bands. By using milder conditions of 2 bars and at 120°C, additional Raman bands were found at 3592, 3600, and 3606 cm−1. If the kaolinite was intercalated at 1 bar and 100°C, a new broad Raman band was found at 3605 cm−1. It is proposed that the effect of intercalation of the low defect kaolinite under pressure caused the kaolinite to become disordered and this disordering was dependent upon the temperature of intercalation.
Research Interests: High Pressure, Raman Spectroscopy, Minerals, Vibrational Spectroscopy, Clay Minerals, and 15 moreInfrared spectroscopy, Physical sciences, Intercalation Chemistry, Hydrogen Bond, CHEMICAL SCIENCES, Kaolinite Clay, Hydroxyl, Raman microscopy, Fourier transform infrared spectroscopy, Kaolin, Raman Spectra, Kaolinite, Intercalation, Diffuse Reflectance Spectroscopy, and Potassium acetate
A low-defect kaolinite of 7.18-Å basal spacing was expanded upon intercalation with hydrazine. The 001d-spacing was broad and the peak resolved into components at 10.28, 9.48, and 8.80 Å. It was found that the ordered kaolinite... more
A low-defect kaolinite of 7.18-Å basal spacing was expanded upon intercalation with hydrazine. The 001d-spacing was broad and the peak resolved into components at 10.28, 9.48, and 8.80 Å. It was found that the ordered kaolinite predominantly expanded to 9.48 Å with 31.2% and 10.28 Å with 38.0% of the total peak area. A high-defect kaolinite showed expansion by hydrazine in identical steps withd-spacings of 10.27, 9.53, and 8.75 Å. It is proposed that the intercalation of the kaolinite by hydrazine occurs according to the orientation of the hydrazine molecule and that water plays an integral part in the process of kaolinite expansion. For the hydrazine-intercalated kaolinite, hydroxyl stretching bands attributed to water are observed at 3413, 3469, and 3599 cm−1for the low-defect kaolinite and at 3600 and 3555 cm−1 for the high-defect kaolinite. Upon the exposure of the low-defect hydrazine-intercalated kaolinite to air, an additional water band is observed at 3555 cm−1. Water bending modes are observed at 1578, 1598, 1612, 1627, 1650, and 1679 cm−1for the hydrazine-intercalated low-defect kaolinite and at 1578, 1598, 1613, 1627, 1652, and 1678 cm−1 for the hydrazine-intercalated high-defect kaolinite. The intensities of these bands are a function of the exposure to air and measurement time. The 1650- and 1679 cm−1 bands increased in intensity as the intensity of the 1612 cm−1band decreased. Even after exposure to air for 24 h, water remained in the kaolinite interlayer space and only after heating was the water removed. The 1578, 1598, and 1612 cm−1 bands as well as the 1627 cm−1 band are attributed to (a) free or non-hydrogen-bonded water held in the interlayer spaces of the kaolinite, (b) water in the hydration spheres of the hydrazine, and (c) adsorbed water on the kaolinite surface. In kaolinites additional bands at 1650 and 1679 cm−1are attributed to water coordinated to the siloxane surface.
Research Interests: Water, Minerals, Vibrational Spectroscopy, Clay Minerals, X-ray Diffraction, and 14 moreInfrared spectroscopy, Physical sciences, Intercalation Chemistry, Hydrogen Bond, CHEMICAL SCIENCES, Kaolinite Clay, Diffuse reflectance, Kaolin, Colloid, Hydrazine, Kaolinite, Intercalation, Diffuse Reflectance Spectroscopy, and Fourier transform infrared
Intercalation of an ordered kaolinite with potassium acetate (KCH 3 COO) under a pressure of 20 bars and 220 degrees C, induced new Raman bands at 3590, 3603, and 3609 cm (super -1) in addition to the normal kaolinite bands. These bands... more
Intercalation of an ordered kaolinite with potassium acetate (KCH 3 COO) under a pressure of 20 bars and 220 degrees C, induced new Raman bands at 3590, 3603, and 3609 cm (super -1) in addition to the normal kaolinite bands. These bands are attributed to the inner surface hydroxyls hydrogen bonded to the acetate. It is proposed that the intercalation under 20 bars pressure at 220 degrees C caused the differentiation of the inner surface hydroxyl groups, resulting in the appearance of these additional bands. Diffuse reflectance infrared spectra of the potassium acetate intercalated kaolinite that was formed at 20 bars and at 220 degrees C showed new bands at 3595 and 3605 cm (super -1) . Upon formation of the intercalate at 2 bars and at 120 degrees C additional infrared (IR) bands were found at 3592, 3600, and 3606 cm (super -1) . These IR bands correspond well with the observed Raman spectra. It is proposed that the effect of intercalation of the highly ordered kaolinite under pressure caused the kaolinite to become disordered and this disordering was dependent on the temperature of intercalation. It is suggested that when pressure is applied to the kaolinite crystal in the presence of an intercalating agent, the hydrogen bonds between adjacent layers are broken to create space for the intercalating agent between the layers. A direct result is that the order of the kaolinite crystals shows a decrease resulting in more defect structures. This is evidenced by the additional spectroscopic bands in both the Raman and IR spectra.
Research Interests: Geology, Geochemistry, High Pressure, Minerals, Vibrational Spectroscopy, and 13 moreClay Minerals, Temperature, Intercalation Chemistry, Hydrogen Bond, Kaolinite Clay, Infrared, Infrared spectra, Kaolin, Raman Spectra, Kaolinite, Intercalation, Diffuse Reflectance Spectroscopy, and Potassium acetate
The tridecameric aluminum polymer [AlO4Al12(OH)24(H2O)12]7+ was prepared by forced hydrolysis of Al3+ up to an OH/Al molar ratio of 2.2. Upon addition of sulfate, the tridecamer crystallized as the monoclinic basic aluminum sulfate... more
The tridecameric aluminum polymer [AlO4Al12(OH)24(H2O)12]7+ was prepared by forced hydrolysis of Al3+ up to an OH/Al molar ratio of 2.2. Upon addition of sulfate, the tridecamer crystallized as the monoclinic basic aluminum sulfate Na0.1[AlO4Al12(OH)24(H2O)12](SO4)3.55. The dehydroxylation of the basic aluminum sulfate has been studied by Fourier transform in-situ infrared emission spectroscopy over a temperature range of 200° to 750°C at 50°C intervals. The spectrum is characterized by the sulfate ν1 (1024 cm−1), ν3 doublet (1117 and 1168 cm−1) and the ν4 doublet (568 and 611 cm−1) modes. Furthermore, minor bands assigned to nitrate are observed. Upon heating from ≈350° to 400°C major changes are observed, especially in the bandwidth and band intensities. The bands in the hydroxyl stretching region due to the Al13 group disappear, whereas the bands around 1050 cm−1 display various changes in bandwidths, intensities and positions associated with the dehydration and dehydroxylation of the basic sulfate and the changing of the structure into an aluminum oxosulfate. The nitrate bands diminish upon heating.
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Raman spectroscopy of two types of kaolinites has been obtained at liquid nitrogen temperature (77 K) with the use of a Raman microprobe and a thermal stage. The Raman spectrum is characterized by the combination of the frequencies of the... more
Raman spectroscopy of two types of kaolinites has been obtained at liquid nitrogen temperature (77 K) with the use of a Raman microprobe and a thermal stage. The Raman spectrum is characterized by the combination of the frequencies of the inner hydroxyl and the inner surface hydroxyl groups. The inner hydroxyl frequency is reduced, and the outer hydroxyl frequencies move to higher frequencies upon cooling to 77 K. The inner hydroxyl frequency shifts from 3620 cm−1 at 298 K to 3615 cm−1 at 77 K. The two in-phase inner surface hydroxyl frequencies move from 3684 and 3689 cm−1 at 298 K to 3690 and 3699 cm−1 at 77 K. The two out-of-phase vibrations shift from 3650 and 3668 cm−1 to 3656 and 3675 cm−1. The bandwidth of the inner hydroxyl frequency decreases from 3.7 to 2.1 cm−1 at 77 K. The bandwidth of the inner surface hydroxyl frequency (v1) increases upon cooling from 17.4 to 19.2 cm−1. It is proposed that the increased resolution at low temperature enabled an additional inner surface hydroxyl frequency to be observed.
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This paper reviews the synthesis of smectites and porous pillared clay catalysts. Synthetic as well as natural smectites serve as precursors for the synthesis of Al, Zr, Ti, Fe, Cr, Ga, V, Si, and other pillared clays as well as mixed... more
This paper reviews the synthesis of smectites and porous pillared clay catalysts. Synthetic as well as natural smectites serve as precursors for the synthesis of Al, Zr, Ti, Fe, Cr, Ga, V, Si, and other pillared clays as well as mixed Fe/Al, Ga/Al, Si/Al, Zr/Al and other mixed metal/Al pillared clays. The use of these pillared clays in some catalytic reactions is also briefly reviewed.
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In this article we describe the intercalation of potassium and caesium acetate in kaolinite, a 1 :1 clay mineral which is generally assumed not to swell. The reactive molecule will insert between the successive kaolinite layers, thereby... more
In this article we describe the intercalation of potassium and caesium acetate in kaolinite, a 1 :1 clay mineral which is generally assumed not to swell. The reactive molecule will insert between the successive kaolinite layers, thereby disrupting the hydrogen-bonds between the hydroxyl groups on one side and the oxygen atoms of the siloxane layer on the other side. The organic molecule will form new bonds with either the more hydrophobic siloxane layer or with the more hydrophilic hydroxyl groups. Extensive infrared and Raman spectroscopic research has resulted in a much more detailed picture how these organic molecules
are incorporated in the kaolinite structure.
are incorporated in the kaolinite structure.
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Both Raman microscopy and Fourier transform (FT)-Raman spectroscopy have been used to determine the low-frequency vibrations of kaolinite at both 298 and 77 K. The low-frequency region is characterized by bands attributed to the hydroxyl... more
Both Raman microscopy and Fourier transform (FT)-Raman spectroscopy have been used to determine the low-frequency vibrations of kaolinite at both 298 and 77 K. The low-frequency region is characterized by bands attributed to the hydroxyl deformation, hydroxyl translation, silicon oxygen bending, and OHO vibrations. The inner hydroxyl stretching frequency shifts from 3620 to 3615 cm−1 upon cooling to liquid nitrogen temperature, and the inner surface hydroxyl bands show increased complexity with a number of overlapping bands in the 3685 to 3710 cm−1 region at 77 K, which are not observed in the 298 K spectrum. The hydroxyl deformation modes shift by 3 cm−1 to higher frequency upon cooling to liquid nitrogen temperature. The hydroxyl translation and other spectral regions show less sensitivity to the thermal treatment. Upon cooling to liquid nitrogen temperature, additional bands are observed in the low-frequency region: in the hydroxyl deformation region a new band is observed at 943 cm−1, in the OSiO bending region at 448 and 411 cm−1, and in the low-frequency region at 370 and 330 cm−1.
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The Raman spectrum of single‐crystal tubular hydrated 10 Å halloysite obtained by Raman microscopy clearly shows differences from dehydrated or metahalloysite. The hydroxyl stretching region shows two relatively strong asymmetric bands... more
The Raman spectrum of single‐crystal tubular hydrated 10 Å halloysite obtained by Raman microscopy clearly shows differences from dehydrated or metahalloysite. The hydroxyl stretching region shows two relatively strong asymmetric bands representing multiple bands ν1 and ν2 ascribed to the outer hydroxyl groups and ν3 and ν4 ascribed to the inner hydroxyl groups of the halloysite with two additional broad, low‐intensity bands at 3556 and 3598 cm−1. These bands are absent in dehydrated halloysite and are assigned to OH stretching modes of the adsorbed surface and interlayer water. Comparison between the 10 Å halloysite and metahalloysite shows that almost all bands observed for the hydrated halloysite are also observed for the metahalloysite, but with small differences in the band positions. These differences may indicate differences in crystal structure (interlayer water) or folding of the layers. New bands observed for the 10 Å halloysite are at 359 and 332 cm−1, which are absent in all other kaolin minerals. Therefore, these vibrations are assigned to hydrogen‐bonded water modes of adsorbed and interlayer water corresponding to the two hydroxyl stretching modes around 3556 and 3598 cm−1.
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The identification of minerals is, in many cases, based on techniques like X-ray diffraction, optical microscopy and electron microprobe analysis. A major disadvantage of these techniques is that the mineral crystals have to be destroyed... more
The identification of minerals is, in many cases, based on techniques like X-ray diffraction, optical microscopy and electron microprobe analysis. A major disadvantage of these techniques is that the mineral crystals have to be destroyed either to a powder or a thin section. Raman spectroscopy has been used for the identification of minerals. This paper describes the application of Raman microscopy as a non-destructive technique for the identification of minerals, suitable also for single crystals as small as a few hundred micrometers.
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Synthetic Mg-, Ni- (takovite), and Co-hydrotalcite are characterized by FT-IR and FT-Raman spectroscopy. Changes in the composition brought about by changing the divalent metal result in small but significant changes in band positions of... more
Synthetic Mg-, Ni- (takovite), and Co-hydrotalcite are characterized
by FT-IR and FT-Raman spectroscopy. Changes in the composition brought about by changing the divalent metal result in small but significant changes in band positions of the modes related to the hydroxyl groups, as each hydroxyl group in the hydrotalcite structure is coordinated to three metal cations. It has also a similar effect on the interlayer water and carbonate band positions as evidenced by small shifts in band positions and the occurrence of doublets, especially for the interlayer carbonate ions. The carbonate doublets are due to site symmetry lowering.
by FT-IR and FT-Raman spectroscopy. Changes in the composition brought about by changing the divalent metal result in small but significant changes in band positions of the modes related to the hydroxyl groups, as each hydroxyl group in the hydrotalcite structure is coordinated to three metal cations. It has also a similar effect on the interlayer water and carbonate band positions as evidenced by small shifts in band positions and the occurrence of doublets, especially for the interlayer carbonate ions. The carbonate doublets are due to site symmetry lowering.
Research Interests: Raman Spectroscopy, Vibrational Spectroscopy, Layered Inorganic Materials, Carbonates, Layered Double Hydroxide (LDH), and 7 moreInfrared spectroscopy, Hydroxyl, Fourier transform infrared spectroscopy, MATERIALS RESEARCH ( HYDROTALCITE LIKE COMPOUNDS), Layered Double Hydroxides, Fourier Transform Raman Spectroscopy, and takovite
In this article we describe the intercalation of a number of organic molecules in kaolinite, a 1 :1 clay mineral which is generally assumed not to swell. The reactive molecule will insert between the successive kaolinite layers, thereby... more
In this article we describe the intercalation of a number of organic molecules in kaolinite, a 1 :1 clay mineral which is generally assumed not to swell. The reactive molecule will insert between the successive kaolinite layers, thereby disrupting the hydrogen-bonds between the hydroxyl groups on one side and the oxygen atoms of the siloxane layer on the other side. The organic molecule will form new bonds with either the more hydrophobic siloxane layer or with the more hydrophilic hydroxyl groups. In this article we will discuss the intercalation of molecules, such as hydrazine, urea, formamide, acetamide and DMSO. Extensive infrared and Raman spectroscopic research has resulted in a
much more detailed picture how these organic molecules are incorporated in the kaolinite structure.
much more detailed picture how these organic molecules are incorporated in the kaolinite structure.
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In this paper the Raman spectra of scheelite, wolframite and wulfenite are described. Calculations for the scheelite and wulfenite structure indicate the following Raman bands v1: Ag+ Bu (inactive, but activated due to strain), v2: Ag +... more
In this paper the Raman spectra of scheelite, wolframite and wulfenite
are described. Calculations for the scheelite and wulfenite structure indicate the following Raman bands v1: Ag+ Bu (inactive, but activated due to strain), v2: Ag + Bg + Bu, v3, v4: Bg + Eg, most of which are easily observed for scheelite and wulfenite. The v4(Eg) band, however, was absent for scheelite. Additional bands were observed at 193, 208 and 271 cm-1, assigned as translational modes of Ca-O and WO4• Similarly, bands at 190 and 166 cm-1 are assigned as translational modes of
Pb-O and MoO4 for wulfenite. Wolframite shows (Fe.Mn)-O lattice modes at 199, 205 and 236 cm-1. The band at 260 cm-1 is assigned as vdef(Ag) of the cationic sublattices. The bands at 353 and 401 cm-1 are assigned as either deformation modes or as r(Bg) and o(Ag) modes of terminal WO2• The band at 462 cm-1 has an equivalent band in the infrared at 455 cm-1 assigned as oas(Au) of the (W2O4)n chain. The band at 508 cm-1 is assigned as Vsym(Bg) of the (W2O4)n chain. The band at 695 cm-1 is interpreted as an antisymmetric bridging mode associated with the tungstate chain. The bands at 790 and 881 cm-1 are associated with the antisymmetric and symmetric Au modes of terminal WO2 whereas the origin of the 806 cm-1 band remains unclear.
The region 950- 1,750 cm-1 for wulfenite and wolframite is characterised by combination. overtone and fluorescence bands. The region 3,200- 3,600 cm-1 shows for scheelite and wulfenite three different intervals with bands assigned to adsorbed water around 3.550 cm-1, surface hydroxyls formed by protonation of the oxygens of the WO4 or MoO4 group between 3,250 and 3,300 cm-1 and chemically bonded or coordinated water between 3,325 and 3,450cm-1.
are described. Calculations for the scheelite and wulfenite structure indicate the following Raman bands v1: Ag+ Bu (inactive, but activated due to strain), v2: Ag + Bg + Bu, v3, v4: Bg + Eg, most of which are easily observed for scheelite and wulfenite. The v4(Eg) band, however, was absent for scheelite. Additional bands were observed at 193, 208 and 271 cm-1, assigned as translational modes of Ca-O and WO4• Similarly, bands at 190 and 166 cm-1 are assigned as translational modes of
Pb-O and MoO4 for wulfenite. Wolframite shows (Fe.Mn)-O lattice modes at 199, 205 and 236 cm-1. The band at 260 cm-1 is assigned as vdef(Ag) of the cationic sublattices. The bands at 353 and 401 cm-1 are assigned as either deformation modes or as r(Bg) and o(Ag) modes of terminal WO2• The band at 462 cm-1 has an equivalent band in the infrared at 455 cm-1 assigned as oas(Au) of the (W2O4)n chain. The band at 508 cm-1 is assigned as Vsym(Bg) of the (W2O4)n chain. The band at 695 cm-1 is interpreted as an antisymmetric bridging mode associated with the tungstate chain. The bands at 790 and 881 cm-1 are associated with the antisymmetric and symmetric Au modes of terminal WO2 whereas the origin of the 806 cm-1 band remains unclear.
The region 950- 1,750 cm-1 for wulfenite and wolframite is characterised by combination. overtone and fluorescence bands. The region 3,200- 3,600 cm-1 shows for scheelite and wulfenite three different intervals with bands assigned to adsorbed water around 3.550 cm-1, surface hydroxyls formed by protonation of the oxygens of the WO4 or MoO4 group between 3,250 and 3,300 cm-1 and chemically bonded or coordinated water between 3,325 and 3,450cm-1.
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The tridecameric aluminium polymer [AlO4Al12(OH)23(H2O)12]7+-O-Si(OH)3 was prepared by forced hydrolysis of Al3+ up to an OH/Al molar ratio of 2.0 in the presence of monomeric orthosilicic acid with increasing Si/Al ratio up to 1.00.... more
The tridecameric aluminium polymer [AlO4Al12(OH)23(H2O)12]7+-O-Si(OH)3 was prepared by forced hydrolysis of Al3+ up to an OH/Al molar ratio of 2.0 in the presence of monomeric orthosilicic acid with increasing Si/Al ratio up to 1.00. Crystalline material was obtained by slow evaporation. The Raman spectra are characterised by the similar bands as the Al13 nitrate. The Fourier transform-IR spectrum of the Al13 crystals without any SiO(OH)3 added indicates that previous assignments of the bands between 450 and 800 cm−1 to the sulphate in the crystal structure of basic aluminium sulphate are not correct for the Al13 in this study. These bands are more likely to correspond with deformation bands within the Al octahedra of the Al13 complex. Upon increasing the Si/Al ratio, a part of the nitrate is replaced as evidenced by the decrease in intensity of one of each set of double nitrate bands in both the Raman and Fourier transform-IR spectra. The incorporation of SiO(OH)3 in the crystal structure results in the formation of new Fourier transform-IR bands at 3740 cm−1 assigned to silanol groups, 1106 cm−1 assigned to Si–O stretching mode and a band at 724 cm−1 assigned to Si–O–Al deformation mode. The formation of the [AlO4Al12(OH)23(H2O)12]7+-O-Si(OH)3 therefore is thought to proceed via the replacement of incorporated nitrate groups in the Al13 structure instead of via the hydroxyl groups.
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Two series of copper-loaded titania pillared clays (Cu/Ti-PILCs) with various copper amounts were synthesized using an ion-exchange method. The starting materials were titania pillared clay prepared from normal sol-gel method (Ti-PILC)... more
Two series of copper-loaded titania pillared clays (Cu/Ti-PILCs) with various copper amounts were synthesized using an ion-exchange method. The starting materials were titania pillared clay prepared from normal sol-gel method (Ti-PILC) and from hydrothermal treatment method (Ti-PILC-H), respectively. Copper was loaded on these two samples (TiPILC and Ti-PILC-H) by suspending them in copper (II) nitrate solutions at pH of 6. It was found that for both supporting materials; the amounts of loaded copper were proportional to the starting concentrations of the copper (II) nitrate solutions. XRD results showed that for samples freshly prepared from the highest copper nitrate concentration, the loaded copper was mainly in gerhardtite phase, which transformed to copper (II) oxide phase upon calcination. In addition, Ti-PILC-H showed better-crystallized anatase phase but lower surface area than TiPILC and the copper-loading amount was more related to the surface area. More importantly, it was found that these loaded copper phases were stable against mild acid washing and even after being treated by concentrated nitric acid solution, there was still certain amount of copper remained in the samples.
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Fourier transform infrared photoacoustic spectroscopy (FTIR.-PAS) has advantages in distinguishing hydroxyl surface spectra as a function of depth. FTIR-PAS spectra of kaolinite were recorded at mirror velocities of 0.05, 0.1, and 0.2 cm... more
Fourier transform infrared photoacoustic spectroscopy (FTIR.-PAS) has advantages in distinguishing hydroxyl surface spectra as a function of depth. FTIR-PAS spectra of kaolinite were recorded at mirror velocities of 0.05, 0.1, and 0.2 cm s·1 , and compared to gibbsite spectra recorded at mirror velocity of 0.2 cm s·1 • Four strong bands at 3694, 3670, 3654 and 3621 cm·1, and a weak band at 3435 cm·1 in the hydroxyl stretching region were observed for kaolinite. The intensity of these bands increased as mirror velocity increased. Because an increase in mirror velocity means a shallower depth of the surface is measured, the increasing intensity of the hydroxyl stretching and bending vibrations is a consequence of more hydroxyl units on the outer surface than on the inner surface. The intensity of the kaolinite band at 103 7 cm·1 was
greater than that at 1010 cm·1 at 0.2 cm s-1 velocity but this order changed when mirror velocity was reduced to 0.05 cm s·1 in the hydroxyl deformation and water bending region. For the Si-0-Al modes of kaolinite in the low frequency region, one band at 473 cm·1 is observed at 0.2
cm s·1 velocity, while this band is split into two at 477 and 467 cm·1 at 0.05 cm s·1 velocity. Some vibrations of gibbsite resemble those of kaolinite.
greater than that at 1010 cm·1 at 0.2 cm s-1 velocity but this order changed when mirror velocity was reduced to 0.05 cm s·1 in the hydroxyl deformation and water bending region. For the Si-0-Al modes of kaolinite in the low frequency region, one band at 473 cm·1 is observed at 0.2
cm s·1 velocity, while this band is split into two at 477 and 467 cm·1 at 0.05 cm s·1 velocity. Some vibrations of gibbsite resemble those of kaolinite.
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Gibbsite, bayerite, boehmite and diaspore were investigated using FT-Raman spectroscopy in conjunction with scanning electron microscopy (SEM) in order to provide information for the characterization of bauxite. The Raman spectrum of... more
Gibbsite, bayerite, boehmite and diaspore were investigated using FT-Raman spectroscopy in conjunction with scanning electron microscopy (SEM) in order to provide information for the characterization of bauxite. The Raman spectrum of gibbsite shows four strong, sharp bands at 3617, 3522, 3433 and 3364 cm-1 and the spectrum of bayerite shows
seven bands at 3664, 3652, 3552, 3542, 3450, 3438, and 3420 cm-1 in the hydroxyl stretching region. Four broad and weak bands are observed at 3371, 3220, 3085 and 2989 cm-1 for boehrnite, and five broad bands are observed at 3445, 3363, 3226, 3119 and 2936 cm-1 for diaspore in the hydroxyl stretching region. The hydroxyl stretching bands are related to the surface structure of these minerals. The Raman spectra of bayerite, gibbsite and diaspore are complex while the Raman spectrum of boehmite only shows three major bands in the hydroxyl deformation and water bending, and low frequency regions. These bands are
assigned to hydroxyl deformation and translational, and Al-0 modes of the alumina phases. The present results in relation to the characterization of bauxite are interpreted.
seven bands at 3664, 3652, 3552, 3542, 3450, 3438, and 3420 cm-1 in the hydroxyl stretching region. Four broad and weak bands are observed at 3371, 3220, 3085 and 2989 cm-1 for boehrnite, and five broad bands are observed at 3445, 3363, 3226, 3119 and 2936 cm-1 for diaspore in the hydroxyl stretching region. The hydroxyl stretching bands are related to the surface structure of these minerals. The Raman spectra of bayerite, gibbsite and diaspore are complex while the Raman spectrum of boehmite only shows three major bands in the hydroxyl deformation and water bending, and low frequency regions. These bands are
assigned to hydroxyl deformation and translational, and Al-0 modes of the alumina phases. The present results in relation to the characterization of bauxite are interpreted.
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Kaolinite surfaces were modified by grinding kaolinite/quartz mixtures for periods of time up to 10 hours. X-ray diffraction shows the loss of intensity of the d(OOl) spacing with mechanical treatment resulting in the delamination of the... more
Kaolinite surfaces were modified by grinding kaolinite/quartz mixtures for periods of time up to 10 hours. X-ray diffraction shows the loss of intensity of the d(OOl) spacing with mechanical treatment resulting in the delamination of the kaolinite. Thermogravimetric analyses show the kaolinite surface is signifi~antly modified and surface hydroxyls are replaced with both coordinated and adsorbed water molecules. Changes in the molecular structure of the surface hydroxyls of the kaolinite/quartz mixtures were followed by DRIFT spectroscopy. Kaolinite hydroxyls were lost after two hours of grinding as evidenced by the decrease in intensity of the OH stretching vibrations at 3695 and 3619 cm-1 and the deformation modes at 937 and 915 cm-1. Changes in the surface structure of the OSiO units were reflected in the SiO stretching and OSiO bending vibrations. The decrease in intensity of the 1056 and 1034 cm-1 bands attributed to kaolinite SiO stretching vibrations were concomitantly match.ed by the increase in intensity of additional bands at 1113 and 520 cm-1 ascribed to the new mechanically synthesized kaolinite surface.
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This paper describes an X-ray diffraction and spectroscopic study, including infrared, near-infrared and Raman spectroscopy of some selected zinnwaldites. In general, zinnwaldite forms a member of the trioctahedral true micas with... more
This paper describes an X-ray diffraction and spectroscopic study, including infrared, near-infrared and Raman spectroscopy of some selected zinnwaldites. In general, zinnwaldite forms a member of the trioctahedral true micas with characteristically Li in the octahedral positions and low iron contents. Although the infrared spectrum of zinnwaldite has been described before, near infrared and Raman spectroscopy have not been used so far to study this mineral. X-ray diffraction showed that all the samples reported in this study have the 1M structure. The Raman spectra are characterised by a strong band at 700-705 cm-1 plus a broad band associated with the SiO modes around 1100 cm-1. Less intense bands are observed around 560, 475, 403 and 305 cm-1. The corresponding IR spectra show strong overlapping SiO modes around 1020 cm-1 plus less intense bands around 790, 745, 530, 470-475 and 440 cm-1. Two overlapping OH-stretching modes can be observed around 3550-3650 cm-1, in agreement with a broad band in the IR around 3450 cm-1 and a complex band around 3630 cm-1. The near-IR spectra basically reflect combination and overtone bands associated with protons in the zinnwaldite structure. A very broad band observed around 5230 cm-1 is characteristic for adsorbed water while bands around 4530, 4435 and 4260 cm-1 can be ascribed to metal-hydroxyl groups.
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Mg/Al-hydrotalcites containing NO3-, Cl-, SO42- or ClO4- were synthesised under N2 to prevent incorporation of CO32-. The presence of the anions in the hydrotalcite structure was confirmed by infrared and Raman spectroscopy. The CO32- and... more
Mg/Al-hydrotalcites containing NO3-, Cl-, SO42- or ClO4- were synthesised under N2 to prevent incorporation of CO32-. The presence of the anions in the hydrotalcite structure was confirmed by infrared and Raman spectroscopy. The CO32- and the NO3- hydrotalcites contained both NO3- and CO32-, while the Cl-hydrotalcite also contained some CO32-. It is known that during thermal treatment of hydrotalcites
dehydroxylation and decarbonisation strongly overlap. Mass spectrometry following TGA enables one to identify both reactions. For CO3-hydrotalcite CO2 is released simultaneously with water (dehydroxylation) around 335°C followed by NO around 365 and 500°C. The stability of the NO3-hydrotalcite is different showing a major loss
of CO2 and H2O (dehydroxylation) around 410°C with losses of NO around 345 and 450°C. The Cl-hydrotalcite shows a similar behaviour for the H2O loss (dehydroxylation), but Cl is lost over a range from 400 to 900°C and CO2 comes off in steps around 360 and 500°C. Completely different is the thermal behaviour of SO4- and ClO4-hydrotalcites. SO4-hydrotalcite shows a gradual weight-loss due to dehydroxylation with two minor water peaks around 260 and 375°C, while the sulphate remains in the structure. The sulphate is not lost until heated to 900°C. The ClO4-hydrotalcite shows a complex thermal behaviour with 2 steps of water loss around 375 and 440°C, where the second step is accompanied by the loss of O2. A possible explanation is a redox reaction between perchlorate and the cations giving metal-chlorides and O2.
dehydroxylation and decarbonisation strongly overlap. Mass spectrometry following TGA enables one to identify both reactions. For CO3-hydrotalcite CO2 is released simultaneously with water (dehydroxylation) around 335°C followed by NO around 365 and 500°C. The stability of the NO3-hydrotalcite is different showing a major loss
of CO2 and H2O (dehydroxylation) around 410°C with losses of NO around 345 and 450°C. The Cl-hydrotalcite shows a similar behaviour for the H2O loss (dehydroxylation), but Cl is lost over a range from 400 to 900°C and CO2 comes off in steps around 360 and 500°C. Completely different is the thermal behaviour of SO4- and ClO4-hydrotalcites. SO4-hydrotalcite shows a gradual weight-loss due to dehydroxylation with two minor water peaks around 260 and 375°C, while the sulphate remains in the structure. The sulphate is not lost until heated to 900°C. The ClO4-hydrotalcite shows a complex thermal behaviour with 2 steps of water loss around 375 and 440°C, where the second step is accompanied by the loss of O2. A possible explanation is a redox reaction between perchlorate and the cations giving metal-chlorides and O2.
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In present-day chemistry a whole range of layered materials exists but only a few of them are as widely used as those described in this book. As the authors suggest, this book is intended to give a general background and does not imply an... more
In present-day chemistry a whole range of layered materials exists but only a few of them are as widely used as those described in this book. As the authors suggest, this book is intended to give a general background and does not imply an up-to-date review of the existing literature. Having bought Handbook of Zeolite Science and Technology by the same editors (Auerbach et al., 2003), I had high expectations of this accompanying volume on layered materials, and in general I was not disappointed.
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Microporous and Mesoporous Mineral Phases edited by G. Ferraris and S. Merlino. Mineralogical Society of America and the Geochemical Society, in partnership with Accademia Nazionale dei Lincei – Reviews in Mineralogy and Geochemistry, 57, 2005, 448 pp. [ISBN 093995069-3]. Price $40 (25% discount ...more
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Upon the intercalation of kaolinite with DMSO, new Raman bands at 3660, 3536, and 3501 cm-1 are observed for the low-defect kaolinite and at 3664, 3543, and 3509 cm-1 for the high-defect kaolinite. An additional band at 3598 cm-1 was... more
Upon the intercalation of kaolinite with DMSO, new Raman bands at 3660, 3536, and 3501 cm-1 are observed for the low-defect kaolinite and at 3664, 3543, and 3509 cm-1 for the high-defect kaolinite. An additional band at 3598 cm-1 was observed for the high-defect kaolinite. The band at 3660 cm-1 was assigned to the inner-surface hydroxyls hydrogen bonded to the SO group. The other three bands are attributed to the hydroxyl stretching frequencies of water in the intercalation complex. The hydroxyl deformation region is characterized by one intense band in both the FTIR and Raman spectra at 905 cm-1. Significant changes in the Raman spectra of the intercalating molecule are observed. Splitting of the C−H symmetric and antisymmetric stretching vibrations occurs. Two Raman bands at 2917 and 2935 cm-1 and four bands at 2999, 3015, 3021, and 3029 cm-1 are observed. The in-plane methyl bending region shows two Raman bands at 1411 and 1430 cm-1. The DRIFT spectra show complexity in these regions. The SO stretching region shows bands at 1066, 1023, and 1010 cm-1 upon intercalation with DMSO for the low-defect kaolinite and 1058, 1028, and 1004 cm-1 for the high-defect kaolinite. The 1058 cm-1 band is assigned to the free monomeric SO group and the 1023 and 1010 cm-1 bands to two different polymeric SO groups. Bands attributed to the C−S stretching vibrations, the in-plane and out-of-plane SO bending and the CSC symmetric bends all move to higher frequencies upon intercalation. It is proposed that intercalation with DMSO depends on the presence of water and that the additional bands at 3536 and 3501 cm-1 are due to the presence of water in the intercalate.
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Research Interests: Chemistry, Raman Spectroscopy, Vibrational Spectroscopy, Clay Minerals, Dimethylsulfoxide, and 12 moreIntercalation Chemistry, Sulfoxide, Kaolinite Clay, Micro-Raman and FTIR spectroscopy, THEORETICAL AND COMPUTATIONAL CHEMISTRY, DMSO, Kaolin, Liquid Nitrogen, Kaolinite, Intercalation, Molecular Structure, and Heating stage Raman spectroscopy
Research Interests: Condensed Matter Physics, Materials Science, Chemistry, Surfaces and Interfaces, Electrochemistry, and 15 moreSpectroscopy, Clay Minerals, Multidisciplinary, Adsorption, Infrared spectroscopy, Intercalation Chemistry, Desorption, Kaolinite Clay, Thermal Analysis, Thermogravimetric Analysis, Langmuir, Kaolinite, Intercalation, Thermal desorption, and formamide
Research Interests: Engineering, Chemistry, Inorganic Chemistry, Clay Minerals, Medicine, and 15 moreLayered Inorganic Materials, Adsorption, Infrared spectroscopy, Physical sciences, Intercalation Chemistry, Hydrogen Bond, Thermogravimetry, CHEMICAL SCIENCES, Kaolinite Clay, Thermal Analysis, Thermogravimetric Analysis, Organoclay, Hydrate, Hydrazine, and Kaolinite
Research Interests: Engineering, Chemistry, Biomaterials, Clay Minerals, Medicine, and 15 moreAdsorption, FTIR, Infrared spectroscopy, Intercalation Chemistry, Hydrogen Bond, CHEMICAL SCIENCES, Kaolinite Clay, Fourier transform infrared spectroscopy, Drift, Colloid and Surface Chemistry, Kaolin, Colloid, Kaolinite, Intercalation, and Diffuse Reflectance Infrared Fourier Transform Spectroscopy
Research Interests: Geology, Geochemistry, Soil Science, Thermodynamics, Chemistry, and 15 moreFluoride, Clay Minerals, Biogeosciences, Soil sciences, Montmorillonite, Water Science and Technology, Surface Properties, Hectorite, Low Temperature, Thermodynamic Stability, Hydrothermal, Transition metal oxides, nontronite, saponite, and beidellite
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The minerals connellite and buttgenbachite, complex hydroxy sulfate and nitrate, respectively, of Cu(II), are rare products formed during the corrosion of bronze and brass objects. Infrared and Raman spectra of buttgenbachite and... more
The minerals connellite and buttgenbachite, complex hydroxy sulfate and nitrate, respectively, of Cu(II), are rare products formed during the corrosion of bronze and brass objects. Infrared and Raman spectra of buttgenbachite and connellite were obtained at 298 and 77 K using a Raman microprobe in combination with a thermal stage. The Raman spectra show the presence of nitrate, sulfate and chloride in the mineral. Spectra of the hydroxyl‐stretching region are complex with multiple bands being observed. These observations are in agreement with the structure of the minerals in that the nitrate ion occupies two different sites and that six hydroxyl groups are crystallographically independent. Various OH stretching bands are attributed to independent hydroxyl units in the crystal structure and zeolitic water OH stretching modes. Raman spectroscopy is an excellent technique for the identification of these complex minerals and for the determination of the distribution of anions in their s...
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Research Interests: Geology, Soil Science, Chemistry, Minerals, Crystallization, and 15 moreClay Minerals, Inorganic synthesis, Layered Inorganic Materials, Synthesis, Infrared spectroscopy, Biogeosciences, Soil sciences, Differential Thermal Analysis, Fourier transform infrared spectroscopy, Ammonium, Hydrothermal Synthesis, Smectite, Low Temperature, Cation Exchange Capacity, and saponite
Research Interests: Geology, Soil Science, Materials Science, Minerals, Scanning Electron Microscopy, and 15 moreClay Minerals, Inorganic synthesis, Layered Inorganic Materials, Synthesis, Infrared spectroscopy, Soil sciences, Dehydration, Scanning Electron Microscope, Dehydroxylation, Hydrothermal Synthesis, Smectite, Cation Exchange Capacity, Mullite, beidellite, and cristobalite
The pillaring process of montmorillonite and beidellite with Al and Ga polymers has been studied using XRD, IR,27Al,71Ga, and29Si MAS NMR, TGA, TEM, N2adsorption and chemical analyses. The Al adsorption maximum for montmorillonite is... more
The pillaring process of montmorillonite and beidellite with Al and Ga polymers has been studied using XRD, IR,27Al,71Ga, and29Si MAS NMR, TGA, TEM, N2adsorption and chemical analyses. The Al adsorption maximum for montmorillonite is close to 5.5 mEq Al/g clay, whereas the maximum for Ga is higher. Basal spacings of both Ga- and Al-pillared clays vary between 16.7 and 18.8 Å. Freeze-drying of pillared products followed by calcination yielded more regular pillared structures. Pillaring montmorillonite increased the BET surface area from 35 m2/g to 350 m2/g mainly by the creation of micropores <20 Å in diameter. The Al-pillared clays are thermally stable to ∼700°C. Calcination of pillared montmorillonite liberates protons from the pillar, which diffuse into the clay sheet, lowering the thermal stability. In pillared beidellite, mainly silanol groups are formed by breaking Si-O-Al bonds. No reaction is observed between pillars and montmorillonite upon calcination, whereas in pillare...
Research Interests: Geology, Materials Science, Chemistry, Nuclear Magnetic Resonance, Clay Minerals, and 15 moreSolid State NMR, Adsorption, Silanol, Thermal Analysis, Pillared Clay, Montmorillonite, Surface Area, Thermal Stability, Calcination, BET surface area, Differential Thermal Analysis, Fourier transform infrared spectroscopy, Cation Exchange Capacity, PILC, and beidellite
In this chapter, the iniercalation of a number of organic molecules in kaolinite, a 1: 1 clay mineral which is generally assumed not to swell, is described along with the influence of these molecules on the clay internal and external... more
In this chapter, the iniercalation of a number of organic molecules in kaolinite, a 1: 1 clay mineral which is generally assumed not to swell, is described along with the influence of these molecules on the clay internal and external surfaces. The reactive molecules are inserted between the successive kaolinite layers, thereby disrupting the hydrogen bonds between the hydroxyl groups on one side and the oxygen atoms of the siloxane layer on the other side. The organic molecules will form new bonds with either the more hydrophobic siloxane layer or with the more hydrophilic hydroxyl groups. In this article, the intercalation of molecules such as hydrazine, urea, formamide, acetamide, DMSO and acetate are discussed. Extensive infrared and Raman spectroscopic research has resulted in a much more detailed picture of how these organic molecules are incorporated in the kaolinite structure.
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Raman microscopy has been used to study low and high defect kaolinites and their potassium acetate intercalated complexes at 298 and 77 K. Raman spectroscopy shows significant differences in the spectra of the hydroxyl-stretching region... more
Raman microscopy has been used to study low and high defect kaolinites and their potassium acetate intercalated complexes at 298 and 77 K. Raman spectroscopy shows significant differences in the spectra of the hydroxyl-stretching region of the two types of kaolinites, which is also reflected in the spectroscopy of the hydroxyl-stretching region of the intercalation complexes. Additional bands to the normally observed kaolinite hydroxyl stretching frequencies are observed for the low and high defect kaolinites at 3605 and 3602 cm(-1) at 298 K. Upon cooling to liquid nitrogen temperature, these bands are observed at 3607 and 3604 cm(-1), thus indicating a weakening of the hydrogen bond formed between the inner surface hydroxyls and the acetate ion. Upon cooling to liquid nitrogen temperature, the frequency of the inner hydroxyls shifted to lower frequencies. Collection of Raman spectra at liquid nitrogen temperature did not give better band separation compared to the room temperature spectra as the bands increased in width and shifted closer together.
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Raman spectroscopy of formamide‐intercalated kaolinites treated using controlled‐rate thermal analysis technology (CRTA), allowing the separation of adsorbed formamide from intercalated formamide in formamide‐intercalated kaolinites, is... more
Raman spectroscopy of formamide‐intercalated kaolinites treated using controlled‐rate thermal analysis technology (CRTA), allowing the separation of adsorbed formamide from intercalated formamide in formamide‐intercalated kaolinites, is reported. The Raman spectra of the CRTA‐treated formamide‐intercalated kaolinites are significantly different from those of the intercalated kaolinites, which display a combination of both intercalated and adsorbed formamide. An intense band is observed at 3629 cm−1, attributed to the inner surface hydroxyls hydrogen bonded to the formamide. Broad bands are observed at 3600 and 3639 cm−1, assigned to the inner surface hydroxyls, which are hydrogen bonded to the adsorbed water molecules. The hydroxyl‐stretching band of the inner hydroxyl is observed at 3621 cm−1 in the Raman spectra of the CRTA‐treated formamide‐intercalated kaolinites. The results of thermal analysis show that the amount of intercalated formamide between the kaolinite layers is independent of the presence of water. Significant differences are observed in the CO stretching region between the adsorbed and intercalated formamide. Copyright © 2001 John Wiley &amp; Sons, Ltd.
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Research Interests: Materials Science, Chemistry, Analytical Chemistry, Spectroscopy, Vibrational Spectroscopy, and 15 moreClay Minerals, Medicine, Instrumentation, Crystal structure, Infrared spectroscopy, NIR spectroscopy, Kaolinite Clay, Infrared, Mechanical Stress, IR Spectroscopy, Overtone, Kaolin, Kaolinite, Modification of Surfaces, and MECHANOCHEMICAL ACTIVATION
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Kaolinite surfaces were modified by mechanochemical treatment for periods of time up to 10 h. X-ray diffraction shows a steady decrease in intensity of the d(001) spacing with mechanochemical treatment, resulting in the delamination of... more
Kaolinite surfaces were modified by mechanochemical treatment for periods of time up to 10 h. X-ray diffraction shows a steady decrease in intensity of the d(001) spacing with mechanochemical treatment, resulting in the delamination of the kaolinite and a subsequent decrease in crystallite size with grinding time. Thermogravimetric analyses show the dehydroxylation patterns of kaolinite are significantly modified. Changes in the molecular structure of the kaolinite surface hydroxyls were followed by infrared spectroscopy. Hydroxyls were lost after 10 h of grinding as evidenced by a decrease in intensity of the OH stretching vibrations at 3695 and 3619 cm(-1) and the deformation modes at 937 and 915 cm(-1). Concomitantly an increase in the hydroxyl stretching vibrations of water is found. The water-bending mode was observed at 1650 cm(-1), indicating that water is coordinating to the modified kaolinite surface. Changes in the surface structure of the OSiO units were reflected in the SiO stretching and OSiO bending vibrations. The decrease in intensity of the 1056 and 1034 cm(-1) bands attributed to kaolinite SiO stretching vibrations were concomitantly matched by the increase in intensity of additional bands at 1113 and 520 cm(-1) ascribed to the new mechanically synthesized kaolinite surface. Mechanochemical treatment of the kaolinite results in a new surface structure. Copyright 2001 Academic Press.
Research Interests: Engineering, Materials Science, Chemistry, Biomaterials, Clay Minerals, and 15 moreMedicine, Infrared spectroscopy, Physical sciences, Aluminosilicate, CHEMICAL SCIENCES, Kaolinite Clay, Surface Structure, Crystallite Size, Colloid and Surface Chemistry, Colloid, Crystallite, Kaolinite, Aluminosilicates, Molecular Structure, and MECHANOCHEMICAL ACTIVATION
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ABSTRACT
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A detailed analysis was undertaken of the X-ray photoelectron spectra obtained from microcline, orthoclase and several samples of plagioclase with varying Na/Ca ratio. Comparison of the spectra was made based on the chemical bonding and... more
A detailed analysis was undertaken of the X-ray photoelectron spectra obtained from microcline, orthoclase and several samples of plagioclase with varying Na/Ca ratio. Comparison of the spectra was made based on the chemical bonding and structural differences in the Al- and Si-coordination within each specimen. The spectra for Si 2p and Al 2p vary with the change in symmetry between microcline and orthoclase, while in plagioclase an increase in Al-O-Si linkages results in a small but observable decrease in binding energy. The overall shapes of the O 1s peaks observed in all spectra are similar and show shifts similar to those observed for Si 2p and Al 2p. The lower-VB spectra for microcline and orthoclase are similar intermediate between α-SiO2 and α-Al2O3 in terms of binding energies. In the plagioclase series increasing coupled substitution of Na and Si for Ca and Al results in a change of the overall shape of the spectra, showing a distinct broadening associated with the presence of two separate but overlapping bands similar to the 21 eV band observed for quartz and the 23 eV band observed for corundum. The bonding character for microcline and orthoclase is more covalent than that of α-Al2O3, but less than that of α-SiO2. In contrast, the plagioclase samples show two distinct bonding characters that are comparable with those of α-SiO2 and α-Al2O3.
Research Interests: Materials Science, Chemistry, Analytical Chemistry, Crystallography, Carbon, and 15 moreMinerals, Calcium, Medicine, Instrumentation, Potassium, Oxygen, Plagioclase, Molecular Conformation, Aluminum oxide, Semiconducting Aluminum Compounds, Silicates, Cations, Potassium Compounds, albite, and Microcline
Research Interests: Condensed Matter Physics, Materials Science, Chemistry, Inorganic Chemistry, Surfaces and Interfaces, and 15 moreElectrochemistry, Spectroscopy, Raman Spectroscopy, Clay Minerals, Multidisciplinary, Layered Inorganic Materials, Intercalation Chemistry, Potassium, Kaolinite Clay, Langmuir, Colloid and Surface Chemistry, Kaolinite, Intercalation, Rehydration, and Potassium acetate
Research Interests: Engineering, Materials Science, Chemometrics, Multi Criteria Decision Making, Clay Minerals, and 15 moreNanochemistry, Medicine, Infrared spectroscopy, Multicriteria decision making, Nanoscience, Grinding, Pca, CHEMICAL SCIENCES, Kaolinite Clay, Drift, Chemical Composition, Colloid, Physical Properties, Mechanical Activation, and Kaolinite
Abstract This chapter provides the survey scans and high resolution scans of the minerals belonging to the chemical class of the oxides and hydroxides together with tables of the peak positions and atomic ratios. Minerals covered in this... more
Abstract This chapter provides the survey scans and high resolution scans of the minerals belonging to the chemical class of the oxides and hydroxides together with tables of the peak positions and atomic ratios. Minerals covered in this chapter are: cuprite, periclase, corundum, hematite, perovskite, ilmenite, rutile, pyrolusite, cassiterite, anatase, brookite, thorianite, gahnite, magnetite, franklinite, chromite, minium, chrysoberyl. tantalite/columbite-(Fe,Mg,Mn), goethite, bohmite, manganite, brucite, gibbsite, bayerite, and romanechite.
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Research Interests: Condensed Matter Physics, Materials Science, Chemistry, Surfaces and Interfaces, Electrochemistry, and 15 moreSpectroscopy, Raman Spectroscopy, Vibrational Spectroscopy, Clay Minerals, Multidisciplinary, Infrared spectroscopy, Intercalation Chemistry, Kaolinite Clay, Fourier transform infrared spectroscopy, Thermal Decomposition, Langmuir, Kaolinite, Intercalation, Caesium, and cesium acetate
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Research Interests: Geology, Soil Science, Chemistry, Raman Spectroscopy, Vibrational Spectroscopy, and 15 moreClay Minerals, Infrared spectroscopy, Intercalation Chemistry, Soil sciences, Hydrogen Bond, Kaolinite Clay, Hydrogen Bonding, Raman microscopy, Kaolin, Raman Spectra, Hydrazine, Kaolinite, Hydroxyl Groups, Intercalation, and deintercalation
The vibrational spectroscopy of low and high defect kaolinites fully and partially intercalated with formamide have been determined using a combination of X-ray diffraction, DRIFT and Raman spectroscopy. Expansion of the high defect... more
The vibrational spectroscopy of low and high defect kaolinites fully and partially intercalated with formamide have been determined using a combination of X-ray diffraction, DRIFT and Raman spectroscopy. Expansion of the high defect kaolinite to 10.09 A resulted in a decrease in the peak width of the d(001) peak attributed to a decrease in defect structures upon intercalation. Changes in the defect structures of the low defect kaolinite were observed. Additional infrared bands were observed for the formamide intercalated kaolinites at 3629 and 3606 cm(-1). The 3629 cm(-1) band is attributed to the hydroxyl stretching frequency of the inner surface hydroxyl group hydrogen bonded to the carboxyl group of the formamide. The 3606 cm(-1) band is ascribed to water in the interlayer. Concomitant changes are observed in both the hydroxyl deformation modes and in the carboxyl bands.