Layer charge is an important property of 2:1 phyllosilicates originating from isomorphic substitu... more Layer charge is an important property of 2:1 phyllosilicates originating from isomorphic substitutions in the structure, from vacancies in the octahedral sheet and from unsatisfied bonds at the edges of the crystals. It is of particular interest in the case of smectites because it affects important properties of this mineral. Several methods have been proposed for determining the layer charge of smectites, namely the structural formula method (SFM), the alkylammonium method (AAM), the NH 4-method, the K-saturation method, and the O-D method. Most of these methods have been used extensively in the past and they all have advantages and shortcomings. The SFM and the AAM are based on different principles and are considered as primary methods. They have been used for a long time but they are time consuming and they provide contrasting layer charge values, with the AAM yielding consistently lower layer charge values than the SFM, especially for low-charge smectites. The remaining methods have been developed more recently and have been calibrated over their primary counterparts. They are applied easily and are capable of producing a large amount of data within a short time. In this sense they can be used both for geological interpretations and for assessment of bentonite deposits at an industrial scale.
Chitosan-clay bionanocomposites were prepared from chitosan biopolymer solutions and four differe... more Chitosan-clay bionanocomposites were prepared from chitosan biopolymer solutions and four different smectites (SAz-1 and SWy-2 montmorillonites, SBId-1 beidellite and NAu-1 nontronite), and the effect of layer charge and charge distribution on the formation of bionanocomposites was examined. The intercalation of the chitosan in the homoionic Na +-smectite samples showed that all samples produced chitosan-smectite nanocomposites even at the lowest chitosan-clay ratios. The adsorption isotherms of chitosan by the smectites were classified as L-type isotherms. The equilibrium data were fitted to Langmuir and Freundlich isotherms and the equilibrium adsorption was best described by the Langmuir isotherm model for SWy-2 and SBId-1 while the Freundlich model achieved a better description for SAz-1 and NAu-1 for the higher chitosan concentrations. The adsorption of chitosan exceeded the CEC in the montmorillonites (SWy-2 and SAz-1) whereas in SBId-1 and NAu-1 with tetrahedral charge it either reached or it was lower than the CEC showing that layer charge and charge localization may hinder chitosan adsorption.
Link to publication on Research at Birmingham portal General rights Unless a licence is specified... more Link to publication on Research at Birmingham portal General rights Unless a licence is specified above, all rights (including copyright and moral rights) in this document are retained by the authors and/or the copyright holders. The express permission of the copyright holder must be obtained for any use of this material other than for purposes permitted by law. • Users may freely distribute the URL that is used to identify this publication. • Users may download and/or print one copy of the publication from the University of Birmingham research portal for the purpose of private study or non-commercial research. • User may use extracts from the document in line with the concept of 'fair dealing' under the Copyright, Designs and Patents Act 1988 (?) • Users may not further distribute the material nor use it for the purposes of commercial gain. Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document. When citing, please reference the published version. Take down policy While the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.
Bulletin of the Geological Society of Greece, 2001
Mean thickness and thickness distribution of kaolinite and halloysite clay fractions was obtained... more Mean thickness and thickness distribution of kaolinite and halloysite clay fractions was obtained by X-ray diffraction, using the Bertaut-Warren-Averbach (BWA) technique, which determines the coherent scattering domain (CSD). Mean thickness of kaolinite and halloysite was 11.8 nm and 10.6 nm respectively and both minerals are characterized by lognormal thickness distribution. Laser scattering, which is often used by the industry, yielded considerably greater mean grain size and bimodal size distribution for both materials due to particle agglomeration. Agglomeration affects optical properties of mineral powders such as brightness adversely, because of light diffusion. A greater discrepancy in particle size determined by the two techniques might explain lower brightness observed in white powders.
The widespread Balıkesir bentonite deposits within the Miocene volcano-sedimentary units in weste... more The widespread Balıkesir bentonite deposits within the Miocene volcano-sedimentary units in western Anatolia have economic potential; they are important raw materials for the paper and bleaching industries in Turkey. No detailed geological, mineralogical, geochemical, or genesis characterizations of these bentonite deposits have been carried out to date. The present study was undertaken to close this gap. The mineralogical characteristics of the bentonites and their parent rocks were examined using polarized-light microscopy, X-ray powder diffractometry (XRD), scanning-and transmission-electron microscopies (SEM-EDX and TEM), and chemical (ICP-AES and-MS) methods. In the bentonite deposits, smectite is associated with smaller amounts of illite, chlorite, quartz, feldspar, dolomite, calcite, opal-CT, and amphibole. The smectite was identified by sharp basal reflections at 14.42-14.93 Å. Plagioclase and sanidine crystals in volcanic units are altered and sericitized. Biotite and hornblende are partly to completely Fe-(oxyhydr)oxidized and chloritized. Smectite flakes occur on altered feldspar and mica grains and devitrified volcanic glass fragments in association with or without calcite ± dolomite crystals. Increasing Al+ Fe+Mg/Si ratios with increasing degree of alteration reveal that hydration of volcanogenic grains (feldspar, mica, hornblende, glass shard) favored precipitation of smectite with montmorillonite composition, with an average structural formula: (Ca 0.31 Na 0.05 K 0.08)(Al 2.72 Fe 0.17 Mg 1.27 Ti 0.011 Mn 0.01)(Si 7.94 Al 0.06)O 20 (OH) 4. The concentration of Al 2 O 3 and MgO and increase of LREE/HREE ratio, and a distinct, negative Eu anomaly show that smectite was probably formed as a result of the decomposition of volcanic feldspar, mica, amphibole, and volcanic glass. Association of carbonate rocks within the smectite-rich material and the absence of chlorite and detrital materials such as rock fragments in the bentonites suggest that the bentonite deposits formed authigenetically as 'primary bentonites' from volcanoclastic materials deposited in a calm lacustrine-palustrine environment during an early diagenetic process.
Surface plasmon resonance was employed for the in-situ investigation of film formation from aqueo... more Surface plasmon resonance was employed for the in-situ investigation of film formation from aqueous dispersions of clay minerals on gold/water interface. High charge (SAz-1) and intermediate charge smectite (STx-1b) were studied for their ability to form stable clay films on gold surfaces and their adhesion kinetics at different concentrations was investigated. Layer charge and charge distribution seems to affect not only the kinetics of film formation but also the overall amount of clay mineral on the gold substrate. Subsequently to stable clay mineral film formation, the in-situ preparation of hybrid organo-clay films with the introduction of alkylammonium chains and their adsorption kinetics was examined. Alkylammonium adsorption via ion exchange in the interlayer of the clay minerals is controlled by the density of the clay mineral film in full accordance with layer charge and charge localization. Hence, a simple self-assembly procedure for the in-situ preparation of hybrid organo-clay films for novel applications is proposed.
Greece is a major bentonite producer, with Milos Island being one of the largest bentonite mining... more Greece is a major bentonite producer, with Milos Island being one of the largest bentonite mining centres in the world. In addition to the bentonite deposits which are well known, various other occurrences exist in the islands of Chios and Samos, Eastern Aegean and in some areas of Thrace, in NE Greece. These bentonites are associated with volcanic activity and their age ranges from Lower Oligocene in Thrace, to Lower–Middle Miocene in Chios and to Upper Miocene in Samos. Although some of these materials have been utilized since ancient times (e.g.the Samian Earth), these bentonites have been mined only at a local scale. In this study the first data on the mineralogical and geochemical characteristics of these bentonites are presented.The Samos bentonites of UpperMiocene age are medium–lowgrade (40–70% smectite) and crop out in the SE margin of the Karlovasi Basin formed at the expense of acidic pyroclastic flows mainly in a subaeriallacustrine environment. They consist mainly of Ca...
Sediments from two deep-sea bottom cores from the Myrtoon basin in the SW Aegean Sea and Eastern ... more Sediments from two deep-sea bottom cores from the Myrtoon basin in the SW Aegean Sea and Eastern Cretan Sea were examined by quantitative mineralogical and geochemical analysis to infer sediment provenance and climatic conditions and palaeo-environmental control on sediment deposition. Both cores contain calcareous muds and silts with dark olive-grey organic rich intervals corresponding to the regional sapropel S1 horizon. The presence of a few tephra layers documents volcanic activity in the southern part of the Aegean Sea. The bulk sediments contain abundant carbonate minerals (mainly calcite and Mg-calcite) and clay minerals (mainly illite and smectite) and accessory serpentine, talc and hornblende, which attest to contributions from ultrabasic sources. There is a sharp decrease of the Mg-calcite content and the Mg/Ca ratio of the carbonate fraction in sapropelic sediments followed by an increase of the average grain size. A well expressed negative relationship between illite and smectite was observed in the clay fraction in full accordance with previous studies. However, this trend is absent from the bulk sediments, because smectite is significantly overestimated in the oriented clay fractions. Clay mineral distribution is controlled mainly by sediment sorting, with deposition in the sapropelic sediments being also affected by climatic changes. The different types of smectite in the cores and the presence of smectite with high dehydroxylation temperature in the SE Aegean, suggests that the sediment supply from SE Mediterranean sources should be limited.
Proceedings of the Society of Antiquaries of Scotland, 2018
This project seeks to recover and record the archaeological evidence associated with the extracti... more This project seeks to recover and record the archaeological evidence associated with the extraction of sulfur (and perhaps other minerals as well) by James Stevenson, a Glasgow industrialist, from the volcanic island of Vulcano, Aeolian Islands, Italy, in the second half of the 19th century. This short preliminary report sets the scene by linking archival material with present conditions and by carrying out select mineralogical analyses of the type of the mineral resource Stevenson may have explored. New 3D digital recording tools (structure-from-Motion photogrammetry) have been introduced to aid future multidisciplinary research. This is a long-term project which aims to examine a 19th-century Scottish mining venture in a southern European context and its legacy on the communities involved. It also aims to view Stevenson’s activities in a diachronic framework, namely as an integral part of a tradition of minerals exploration in southern Italy from the Roman period or earlier.
This paper introduces a holistic approach to the study of Greco-Roman (G-R) lithotherapeutics. Th... more This paper introduces a holistic approach to the study of Greco-Roman (G-R) lithotherapeutics. These are the minerals or mineral combinations that appear in the medical and scientific literature of the G-R world. It argues that they can best be described not simply in terms of their bulk chemistry/mineralogy but also their ecological microbiology and nanofraction component. It suggests that each individual attribute may have underpinned the bioactivity of the lithotherapeutic as an antibacterial, antifungal or other. We focus on miltos, the highly prized, naturally fine, red iron oxide-based mineral used as a pigment, in boat maintenance, agriculture and medicine. Five samples (four geological (from Kea, N. Cyclades) and one archaeological (from Lemnos, NE Aegean)) of miltos were analyzed with physical and biological science techniques. We show that: a. Kean miltos and Lemnian earth/miltos must have been chemically and mineralogically different; b. Lemnian miltos must have been more effective as an antibacterial against specific pathogens (Gram + and Gram − bacteria) than its Kean counterpart; c. two samples of Kean miltos, although similar, chemically, mineralogically and eco-microbiologically (phylum/class level), nevertheless, displayed different antibacterial action. We suggest that this may constitute proof of microbial ecology playing an important role in effecting bioactivity and, interestingly, at the more specific genus/species level. From the perspective of the historian of G-R science, we suggest that it may have been on account of its bioactivity, rather than simply its 'red-staining' effect, that miltos gained prominent entry into the scientific and medical literature of the G-R world.
This paper examines the ion-exchange properties of synthetic zeolite Na-P0, which was produced fr... more This paper examines the ion-exchange properties of synthetic zeolite Na-P0, which was produced from perlite-waste fines and has a SiO2:A1203 ratio of 4.45:1 and a cation-exchange capacity (CEC) of 3.95 meq g ~. Although equilibrium is attained rapidly for all three metals, exchange is incomplete, with At(max) (maximum equilibrium fraction of the metal in the zeolite) being 0.95 for Pb, 0.76 for Zn, and 0.27 for Ni. In both Na ~ 89 and Na-* 89 exchange, the normalized selectivity coefficient is virtually constant for :~A~ (normalized equilibrium fraction of the metal in the zeolite) values of-<0.6, suggesting a pronounced homogeneity of the available exchange sites. The Gibbs standard free energy, AG ~ of the Na-) 89 exchange calculated from the normalized selectivity coefficient is-3.11 kJ eq and, for the Na ~ 1/2Zn exchange, it is 2.75 kJ eq ~. Examination of the solid exchange products with X-ray diffraction (XRD) revealed a possible decrease in crystallinity of zeolite Pb-Pc as suggested by the significant broadening and disappearance of diffraction lines. This decrease is associated with a reduction of pore opening, as indicated from Fourier-transform infrared analysis (FTIR), which in turn results in a decrease of the amount of zeolitic water. Thermogravimetric-differential thermogravimetric (TG-DTG) analysis showed that water loss occurs in three steps, the relative significance of which depends on the type of exchangeable cation and subsequently on the type of complex formed with the cation and/or the zeolite channels. Zeolite NaP c might be utilized in environmental applications, such as the treatment of acid-mine drainage and electroplating effluents.
The Tertiary basin of Feres consists of sedimentary rocks, andesitic-rhyolitic volcanic rocks of ... more The Tertiary basin of Feres consists of sedimentary rocks, andesitic-rhyolitic volcanic rocks of K-rich calc-alkaline affinities, rocks with calc-alkaline and shoshonitic affinities and volcaniclastic fall and flow deposits. Volcanic and volcaniclastic rocks have variable concentrations of LIL elements (Ba, Sr, Rb, Th) and HFS elements (Zr, V) due to their mode of origin. The pyroclastic flows frequently show more or less intense devitrification, vapour-phase crystallization and, in some cases, evidence of fumarolic activity, as is indicated by the presence of scapolite. The volcanic and volcaniclastic rocks display various types of alteration including formation of zeolites (clinoptilolite, heulandite, mordenite, and laumontite) and smectite, as well as hydrothermal alteration (development of silicic, argillic, sericitic and propylitic zones) associated with polymetallic mineralization. The behaviour of chemical elements during alteration varies. Some are immobile and their distrib...
This study examines the synthetic zeolites produced from perlite waste. Zeolitisation was carried... more This study examines the synthetic zeolites produced from perlite waste. Zeolitisation was carried out in autoclaves with NaOH solutions at 1008-1408C. The volcanic glass was converted to zeolite-P , zeolite-V and hydroxysodalite. The rate of conversion of the glass and the c transformation of zeolites depended on temperature, time and NaOH concentration. The principal chemical changes observed between the initial glass and the end product involved the removal of Si and K and the uptake of Na. The amount of Si and K released increased with increasing alkalinity, reaching a steady state in the whole temperature range. The amount of Si at the steady state decreased with increasing temperature, while that of K followed an opposite trend. Therefore, the SiO :Al O ratio of the solid phase at steady state increased with increasing 2 2 3 temperature. The amount of Na taken up increased with increasing alkalinity, increasing the Na O:Al O ratio and decreasing the SiO :Na O ratio of the solid phase, as reaction progresses. 2 2 3 2 2 The crystallinity of zeolite-P increased with the amount of Na O present in solution up to a c 2 maximum value, then decreased rapidly. The zeolite-P initially formed had a high SiO :Al O c 2 2 3 ratio, which then decreased gradually until zeolite-V was formed. Both zeolites were replaced by hydroxysodalite at higher alkalinity. Zeolite-V was metastable and converted to zeolite-P after c Ž. prolonged exposure to the atmosphere. The average cation exchange capacity CEC of the zeolite products is 3.0 meqrg and equilibrium was attained very fast, suggesting that the products can be
Bulletin of the Geological Society of Greece, 2001
Calcination of an Upper Cretaceous limestone from the Ionian Unit at 700-1100°C for 1-4 hours yie... more Calcination of an Upper Cretaceous limestone from the Ionian Unit at 700-1100°C for 1-4 hours yielded very reactive lime end products. Lime formation was monitored by means of kinetic curves and TTT diagrams. Particle size seems to control the onset of lime crystallization at low temperatures, but is of minor importance at higher temperatures. With the experimental setting used, lime formation was completed at 900 °C. The specific surface area of the end products increases with firing temperature up to 800 °C, decreasing thereafter. Decrepitation of lime increases gradually with firing temperature. Hydration temperature during slaking increases rapidly up to 900 °C being relatively constant thereafter. Sintering and production of fines during firing control the physical properties of lime.
SWy-1 and SAz-1 smectites and an Italian bentonite from Sardinia were mechanically deformed via h... more SWy-1 and SAz-1 smectites and an Italian bentonite from Sardinia were mechanically deformed via high-energy ball milling for 20 h, in a controlled thermodynamic environment at constant temperature (25°C) under vacuum. The deformed smectites have a lower cation exchange capacity (CEC) and form thicker particles than the original ones, due to agglomeration of smectite crystallites. The 001 diffraction maximum shifted to lower d spacings, the intensity of the 060 reflection decreased and the background at 20-30°2θ increased, suggesting partial amorphization of the smectite. Moreover, the layer charge of the smectites decreased. The intensity of the complex stretching band at 3625 cm-1, and the AlAlOH, and AlFe3+OH bending bands at 916 cm-1 and 886 cm-1, respectively, decreased, while the band at AlMgOH bending at 849 cm-1, disappeared. Deformation mainly disrupted the octahedral sheet and preferentially destroyed those sites occupied by Mg cations, thus explaining the observed decrease...
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
International Conference on Raw Materials and Circular Economy
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
This study evaluates the rare earth element (REE) geochemistry in altered trachyandesitic ignimbr... more This study evaluates the rare earth element (REE) geochemistry in altered trachyandesitic ignimbrites, tuff and lava flows in the Hashtjin area by assessing chondrite-normalized REE patterns and Y/Ho geochemical ratios. Modifications in the REE patterns took place along altered fault zones that were affected by hypogene and supergene alterations. The precursor volcanic and pyroclastic rocks contain phenocrysts of plagioclase accompanied by augite, zircon, apatite and pyrite. Based on X-ray diffraction analysis, the main mineral assemblages of the altered units consist of kaolinite as the main clay mineral, SiO2 polymorphs (quartz and cristobalite) and anatase as a minor constituent. The chondrite-normalized REE patterns of argillic samples reveal fractionation of light REEs (LREEs) compared to heavy REEs (HREEs), together with a marked Eu anomaly and a weak W-type tetrad effect related to the weak non-charge radius control (CHARAC) behaviour of REEs and slightly higher Y/Ho and Zr/H...
Layer charge is an important property of 2:1 phyllosilicates originating from isomorphic substitu... more Layer charge is an important property of 2:1 phyllosilicates originating from isomorphic substitutions in the structure, from vacancies in the octahedral sheet and from unsatisfied bonds at the edges of the crystals. It is of particular interest in the case of smectites because it affects important properties of this mineral. Several methods have been proposed for determining the layer charge of smectites, namely the structural formula method (SFM), the alkylammonium method (AAM), the NH 4-method, the K-saturation method, and the O-D method. Most of these methods have been used extensively in the past and they all have advantages and shortcomings. The SFM and the AAM are based on different principles and are considered as primary methods. They have been used for a long time but they are time consuming and they provide contrasting layer charge values, with the AAM yielding consistently lower layer charge values than the SFM, especially for low-charge smectites. The remaining methods have been developed more recently and have been calibrated over their primary counterparts. They are applied easily and are capable of producing a large amount of data within a short time. In this sense they can be used both for geological interpretations and for assessment of bentonite deposits at an industrial scale.
Chitosan-clay bionanocomposites were prepared from chitosan biopolymer solutions and four differe... more Chitosan-clay bionanocomposites were prepared from chitosan biopolymer solutions and four different smectites (SAz-1 and SWy-2 montmorillonites, SBId-1 beidellite and NAu-1 nontronite), and the effect of layer charge and charge distribution on the formation of bionanocomposites was examined. The intercalation of the chitosan in the homoionic Na +-smectite samples showed that all samples produced chitosan-smectite nanocomposites even at the lowest chitosan-clay ratios. The adsorption isotherms of chitosan by the smectites were classified as L-type isotherms. The equilibrium data were fitted to Langmuir and Freundlich isotherms and the equilibrium adsorption was best described by the Langmuir isotherm model for SWy-2 and SBId-1 while the Freundlich model achieved a better description for SAz-1 and NAu-1 for the higher chitosan concentrations. The adsorption of chitosan exceeded the CEC in the montmorillonites (SWy-2 and SAz-1) whereas in SBId-1 and NAu-1 with tetrahedral charge it either reached or it was lower than the CEC showing that layer charge and charge localization may hinder chitosan adsorption.
Link to publication on Research at Birmingham portal General rights Unless a licence is specified... more Link to publication on Research at Birmingham portal General rights Unless a licence is specified above, all rights (including copyright and moral rights) in this document are retained by the authors and/or the copyright holders. The express permission of the copyright holder must be obtained for any use of this material other than for purposes permitted by law. • Users may freely distribute the URL that is used to identify this publication. • Users may download and/or print one copy of the publication from the University of Birmingham research portal for the purpose of private study or non-commercial research. • User may use extracts from the document in line with the concept of 'fair dealing' under the Copyright, Designs and Patents Act 1988 (?) • Users may not further distribute the material nor use it for the purposes of commercial gain. Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document. When citing, please reference the published version. Take down policy While the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.
Bulletin of the Geological Society of Greece, 2001
Mean thickness and thickness distribution of kaolinite and halloysite clay fractions was obtained... more Mean thickness and thickness distribution of kaolinite and halloysite clay fractions was obtained by X-ray diffraction, using the Bertaut-Warren-Averbach (BWA) technique, which determines the coherent scattering domain (CSD). Mean thickness of kaolinite and halloysite was 11.8 nm and 10.6 nm respectively and both minerals are characterized by lognormal thickness distribution. Laser scattering, which is often used by the industry, yielded considerably greater mean grain size and bimodal size distribution for both materials due to particle agglomeration. Agglomeration affects optical properties of mineral powders such as brightness adversely, because of light diffusion. A greater discrepancy in particle size determined by the two techniques might explain lower brightness observed in white powders.
The widespread Balıkesir bentonite deposits within the Miocene volcano-sedimentary units in weste... more The widespread Balıkesir bentonite deposits within the Miocene volcano-sedimentary units in western Anatolia have economic potential; they are important raw materials for the paper and bleaching industries in Turkey. No detailed geological, mineralogical, geochemical, or genesis characterizations of these bentonite deposits have been carried out to date. The present study was undertaken to close this gap. The mineralogical characteristics of the bentonites and their parent rocks were examined using polarized-light microscopy, X-ray powder diffractometry (XRD), scanning-and transmission-electron microscopies (SEM-EDX and TEM), and chemical (ICP-AES and-MS) methods. In the bentonite deposits, smectite is associated with smaller amounts of illite, chlorite, quartz, feldspar, dolomite, calcite, opal-CT, and amphibole. The smectite was identified by sharp basal reflections at 14.42-14.93 Å. Plagioclase and sanidine crystals in volcanic units are altered and sericitized. Biotite and hornblende are partly to completely Fe-(oxyhydr)oxidized and chloritized. Smectite flakes occur on altered feldspar and mica grains and devitrified volcanic glass fragments in association with or without calcite ± dolomite crystals. Increasing Al+ Fe+Mg/Si ratios with increasing degree of alteration reveal that hydration of volcanogenic grains (feldspar, mica, hornblende, glass shard) favored precipitation of smectite with montmorillonite composition, with an average structural formula: (Ca 0.31 Na 0.05 K 0.08)(Al 2.72 Fe 0.17 Mg 1.27 Ti 0.011 Mn 0.01)(Si 7.94 Al 0.06)O 20 (OH) 4. The concentration of Al 2 O 3 and MgO and increase of LREE/HREE ratio, and a distinct, negative Eu anomaly show that smectite was probably formed as a result of the decomposition of volcanic feldspar, mica, amphibole, and volcanic glass. Association of carbonate rocks within the smectite-rich material and the absence of chlorite and detrital materials such as rock fragments in the bentonites suggest that the bentonite deposits formed authigenetically as 'primary bentonites' from volcanoclastic materials deposited in a calm lacustrine-palustrine environment during an early diagenetic process.
Surface plasmon resonance was employed for the in-situ investigation of film formation from aqueo... more Surface plasmon resonance was employed for the in-situ investigation of film formation from aqueous dispersions of clay minerals on gold/water interface. High charge (SAz-1) and intermediate charge smectite (STx-1b) were studied for their ability to form stable clay films on gold surfaces and their adhesion kinetics at different concentrations was investigated. Layer charge and charge distribution seems to affect not only the kinetics of film formation but also the overall amount of clay mineral on the gold substrate. Subsequently to stable clay mineral film formation, the in-situ preparation of hybrid organo-clay films with the introduction of alkylammonium chains and their adsorption kinetics was examined. Alkylammonium adsorption via ion exchange in the interlayer of the clay minerals is controlled by the density of the clay mineral film in full accordance with layer charge and charge localization. Hence, a simple self-assembly procedure for the in-situ preparation of hybrid organo-clay films for novel applications is proposed.
Greece is a major bentonite producer, with Milos Island being one of the largest bentonite mining... more Greece is a major bentonite producer, with Milos Island being one of the largest bentonite mining centres in the world. In addition to the bentonite deposits which are well known, various other occurrences exist in the islands of Chios and Samos, Eastern Aegean and in some areas of Thrace, in NE Greece. These bentonites are associated with volcanic activity and their age ranges from Lower Oligocene in Thrace, to Lower–Middle Miocene in Chios and to Upper Miocene in Samos. Although some of these materials have been utilized since ancient times (e.g.the Samian Earth), these bentonites have been mined only at a local scale. In this study the first data on the mineralogical and geochemical characteristics of these bentonites are presented.The Samos bentonites of UpperMiocene age are medium–lowgrade (40–70% smectite) and crop out in the SE margin of the Karlovasi Basin formed at the expense of acidic pyroclastic flows mainly in a subaeriallacustrine environment. They consist mainly of Ca...
Sediments from two deep-sea bottom cores from the Myrtoon basin in the SW Aegean Sea and Eastern ... more Sediments from two deep-sea bottom cores from the Myrtoon basin in the SW Aegean Sea and Eastern Cretan Sea were examined by quantitative mineralogical and geochemical analysis to infer sediment provenance and climatic conditions and palaeo-environmental control on sediment deposition. Both cores contain calcareous muds and silts with dark olive-grey organic rich intervals corresponding to the regional sapropel S1 horizon. The presence of a few tephra layers documents volcanic activity in the southern part of the Aegean Sea. The bulk sediments contain abundant carbonate minerals (mainly calcite and Mg-calcite) and clay minerals (mainly illite and smectite) and accessory serpentine, talc and hornblende, which attest to contributions from ultrabasic sources. There is a sharp decrease of the Mg-calcite content and the Mg/Ca ratio of the carbonate fraction in sapropelic sediments followed by an increase of the average grain size. A well expressed negative relationship between illite and smectite was observed in the clay fraction in full accordance with previous studies. However, this trend is absent from the bulk sediments, because smectite is significantly overestimated in the oriented clay fractions. Clay mineral distribution is controlled mainly by sediment sorting, with deposition in the sapropelic sediments being also affected by climatic changes. The different types of smectite in the cores and the presence of smectite with high dehydroxylation temperature in the SE Aegean, suggests that the sediment supply from SE Mediterranean sources should be limited.
Proceedings of the Society of Antiquaries of Scotland, 2018
This project seeks to recover and record the archaeological evidence associated with the extracti... more This project seeks to recover and record the archaeological evidence associated with the extraction of sulfur (and perhaps other minerals as well) by James Stevenson, a Glasgow industrialist, from the volcanic island of Vulcano, Aeolian Islands, Italy, in the second half of the 19th century. This short preliminary report sets the scene by linking archival material with present conditions and by carrying out select mineralogical analyses of the type of the mineral resource Stevenson may have explored. New 3D digital recording tools (structure-from-Motion photogrammetry) have been introduced to aid future multidisciplinary research. This is a long-term project which aims to examine a 19th-century Scottish mining venture in a southern European context and its legacy on the communities involved. It also aims to view Stevenson’s activities in a diachronic framework, namely as an integral part of a tradition of minerals exploration in southern Italy from the Roman period or earlier.
This paper introduces a holistic approach to the study of Greco-Roman (G-R) lithotherapeutics. Th... more This paper introduces a holistic approach to the study of Greco-Roman (G-R) lithotherapeutics. These are the minerals or mineral combinations that appear in the medical and scientific literature of the G-R world. It argues that they can best be described not simply in terms of their bulk chemistry/mineralogy but also their ecological microbiology and nanofraction component. It suggests that each individual attribute may have underpinned the bioactivity of the lithotherapeutic as an antibacterial, antifungal or other. We focus on miltos, the highly prized, naturally fine, red iron oxide-based mineral used as a pigment, in boat maintenance, agriculture and medicine. Five samples (four geological (from Kea, N. Cyclades) and one archaeological (from Lemnos, NE Aegean)) of miltos were analyzed with physical and biological science techniques. We show that: a. Kean miltos and Lemnian earth/miltos must have been chemically and mineralogically different; b. Lemnian miltos must have been more effective as an antibacterial against specific pathogens (Gram + and Gram − bacteria) than its Kean counterpart; c. two samples of Kean miltos, although similar, chemically, mineralogically and eco-microbiologically (phylum/class level), nevertheless, displayed different antibacterial action. We suggest that this may constitute proof of microbial ecology playing an important role in effecting bioactivity and, interestingly, at the more specific genus/species level. From the perspective of the historian of G-R science, we suggest that it may have been on account of its bioactivity, rather than simply its 'red-staining' effect, that miltos gained prominent entry into the scientific and medical literature of the G-R world.
This paper examines the ion-exchange properties of synthetic zeolite Na-P0, which was produced fr... more This paper examines the ion-exchange properties of synthetic zeolite Na-P0, which was produced from perlite-waste fines and has a SiO2:A1203 ratio of 4.45:1 and a cation-exchange capacity (CEC) of 3.95 meq g ~. Although equilibrium is attained rapidly for all three metals, exchange is incomplete, with At(max) (maximum equilibrium fraction of the metal in the zeolite) being 0.95 for Pb, 0.76 for Zn, and 0.27 for Ni. In both Na ~ 89 and Na-* 89 exchange, the normalized selectivity coefficient is virtually constant for :~A~ (normalized equilibrium fraction of the metal in the zeolite) values of-<0.6, suggesting a pronounced homogeneity of the available exchange sites. The Gibbs standard free energy, AG ~ of the Na-) 89 exchange calculated from the normalized selectivity coefficient is-3.11 kJ eq and, for the Na ~ 1/2Zn exchange, it is 2.75 kJ eq ~. Examination of the solid exchange products with X-ray diffraction (XRD) revealed a possible decrease in crystallinity of zeolite Pb-Pc as suggested by the significant broadening and disappearance of diffraction lines. This decrease is associated with a reduction of pore opening, as indicated from Fourier-transform infrared analysis (FTIR), which in turn results in a decrease of the amount of zeolitic water. Thermogravimetric-differential thermogravimetric (TG-DTG) analysis showed that water loss occurs in three steps, the relative significance of which depends on the type of exchangeable cation and subsequently on the type of complex formed with the cation and/or the zeolite channels. Zeolite NaP c might be utilized in environmental applications, such as the treatment of acid-mine drainage and electroplating effluents.
The Tertiary basin of Feres consists of sedimentary rocks, andesitic-rhyolitic volcanic rocks of ... more The Tertiary basin of Feres consists of sedimentary rocks, andesitic-rhyolitic volcanic rocks of K-rich calc-alkaline affinities, rocks with calc-alkaline and shoshonitic affinities and volcaniclastic fall and flow deposits. Volcanic and volcaniclastic rocks have variable concentrations of LIL elements (Ba, Sr, Rb, Th) and HFS elements (Zr, V) due to their mode of origin. The pyroclastic flows frequently show more or less intense devitrification, vapour-phase crystallization and, in some cases, evidence of fumarolic activity, as is indicated by the presence of scapolite. The volcanic and volcaniclastic rocks display various types of alteration including formation of zeolites (clinoptilolite, heulandite, mordenite, and laumontite) and smectite, as well as hydrothermal alteration (development of silicic, argillic, sericitic and propylitic zones) associated with polymetallic mineralization. The behaviour of chemical elements during alteration varies. Some are immobile and their distrib...
This study examines the synthetic zeolites produced from perlite waste. Zeolitisation was carried... more This study examines the synthetic zeolites produced from perlite waste. Zeolitisation was carried out in autoclaves with NaOH solutions at 1008-1408C. The volcanic glass was converted to zeolite-P , zeolite-V and hydroxysodalite. The rate of conversion of the glass and the c transformation of zeolites depended on temperature, time and NaOH concentration. The principal chemical changes observed between the initial glass and the end product involved the removal of Si and K and the uptake of Na. The amount of Si and K released increased with increasing alkalinity, reaching a steady state in the whole temperature range. The amount of Si at the steady state decreased with increasing temperature, while that of K followed an opposite trend. Therefore, the SiO :Al O ratio of the solid phase at steady state increased with increasing 2 2 3 temperature. The amount of Na taken up increased with increasing alkalinity, increasing the Na O:Al O ratio and decreasing the SiO :Na O ratio of the solid phase, as reaction progresses. 2 2 3 2 2 The crystallinity of zeolite-P increased with the amount of Na O present in solution up to a c 2 maximum value, then decreased rapidly. The zeolite-P initially formed had a high SiO :Al O c 2 2 3 ratio, which then decreased gradually until zeolite-V was formed. Both zeolites were replaced by hydroxysodalite at higher alkalinity. Zeolite-V was metastable and converted to zeolite-P after c Ž. prolonged exposure to the atmosphere. The average cation exchange capacity CEC of the zeolite products is 3.0 meqrg and equilibrium was attained very fast, suggesting that the products can be
Bulletin of the Geological Society of Greece, 2001
Calcination of an Upper Cretaceous limestone from the Ionian Unit at 700-1100°C for 1-4 hours yie... more Calcination of an Upper Cretaceous limestone from the Ionian Unit at 700-1100°C for 1-4 hours yielded very reactive lime end products. Lime formation was monitored by means of kinetic curves and TTT diagrams. Particle size seems to control the onset of lime crystallization at low temperatures, but is of minor importance at higher temperatures. With the experimental setting used, lime formation was completed at 900 °C. The specific surface area of the end products increases with firing temperature up to 800 °C, decreasing thereafter. Decrepitation of lime increases gradually with firing temperature. Hydration temperature during slaking increases rapidly up to 900 °C being relatively constant thereafter. Sintering and production of fines during firing control the physical properties of lime.
SWy-1 and SAz-1 smectites and an Italian bentonite from Sardinia were mechanically deformed via h... more SWy-1 and SAz-1 smectites and an Italian bentonite from Sardinia were mechanically deformed via high-energy ball milling for 20 h, in a controlled thermodynamic environment at constant temperature (25°C) under vacuum. The deformed smectites have a lower cation exchange capacity (CEC) and form thicker particles than the original ones, due to agglomeration of smectite crystallites. The 001 diffraction maximum shifted to lower d spacings, the intensity of the 060 reflection decreased and the background at 20-30°2θ increased, suggesting partial amorphization of the smectite. Moreover, the layer charge of the smectites decreased. The intensity of the complex stretching band at 3625 cm-1, and the AlAlOH, and AlFe3+OH bending bands at 916 cm-1 and 886 cm-1, respectively, decreased, while the band at AlMgOH bending at 849 cm-1, disappeared. Deformation mainly disrupted the octahedral sheet and preferentially destroyed those sites occupied by Mg cations, thus explaining the observed decrease...
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
International Conference on Raw Materials and Circular Economy
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
This study evaluates the rare earth element (REE) geochemistry in altered trachyandesitic ignimbr... more This study evaluates the rare earth element (REE) geochemistry in altered trachyandesitic ignimbrites, tuff and lava flows in the Hashtjin area by assessing chondrite-normalized REE patterns and Y/Ho geochemical ratios. Modifications in the REE patterns took place along altered fault zones that were affected by hypogene and supergene alterations. The precursor volcanic and pyroclastic rocks contain phenocrysts of plagioclase accompanied by augite, zircon, apatite and pyrite. Based on X-ray diffraction analysis, the main mineral assemblages of the altered units consist of kaolinite as the main clay mineral, SiO2 polymorphs (quartz and cristobalite) and anatase as a minor constituent. The chondrite-normalized REE patterns of argillic samples reveal fractionation of light REEs (LREEs) compared to heavy REEs (HREEs), together with a marked Eu anomaly and a weak W-type tetrad effect related to the weak non-charge radius control (CHARAC) behaviour of REEs and slightly higher Y/Ho and Zr/H...
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Papers by George Christidis