Kinetics of the amorphous–anatase phase transition in single immobilized 5-nm TiO2 nanoparticles has been studied at temperatures between 400 and 1000 C at the DORIS-III synchrotron source of Hasylab. The measurements indicate the... more
Kinetics of the amorphous–anatase phase transition in single immobilized 5-nm TiO2 nanoparticles has
been studied at temperatures between 400 and 1000 C at the DORIS-III synchrotron source of Hasylab.
The measurements indicate the anatase phase appearance at temperatures above 500 C. No formation of
rutile phase was observed. The transformation kinetics for each fixed temperature is rapid and completes
within 5 min. The crystalline mass progressively increases with temperature and the full transformation
into anatase polymorph is achieved above 800 C. The results suggest higher surface energy of the anatase
phase compared to amorphous one, which delays the crystallization process.
been studied at temperatures between 400 and 1000 C at the DORIS-III synchrotron source of Hasylab.
The measurements indicate the anatase phase appearance at temperatures above 500 C. No formation of
rutile phase was observed. The transformation kinetics for each fixed temperature is rapid and completes
within 5 min. The crystalline mass progressively increases with temperature and the full transformation
into anatase polymorph is achieved above 800 C. The results suggest higher surface energy of the anatase
phase compared to amorphous one, which delays the crystallization process.
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Over the past few decades, enzyme-based green and sustainable chemistry has attracted extensive research attention, which provides a promising alternative to the conventional treatment methods of recalcitrant micropollutants. However,... more
Over the past few decades, enzyme-based green and sustainable chemistry has attracted extensive research attention, which provides a promising alternative to the conventional treatment methods of recalcitrant micropollutants. However, enzyme denaturation and stability loss remain critical challenges for its potential applications in industrial wastewater treatment. In this study, laccase from Trametes versicolor (laccase T.) was cross-linked immobilized by ultraporous alumina (UPA) for the sustainable biodegradation of Remazol Brilliant Blue R (RBBR). Through sequential use of an aminosilane coupling agent (3-aminopropyl)triethoxysilane (APTES) and bifunctional cross-linker glutaraldehyde (GA), the synthesized biocatalysts showed better immobilization performances (about 4-fold to physical adsorption). The GA concentration considerably affected the laccase T. cross-linking degree, while the GA post-treatment protocol showed the highest laccase T. immobilization yield with lower acti...
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We describe the preparation of mixed metal oxide nanoparticles of a desirable composition and their transformation to the crystalline solids ZrxTi1−xO2 (0.0 ≤ x ≤ 1.0) after heat treatment.
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Effects of some characteristics of alumina as material adsorbent on arsenic removal from water are presented. In particular, the effect of the alumina particle size has been firstly experimentally observed, then studied by means of a... more
Effects of some characteristics of alumina as material adsorbent on arsenic removal from water are presented. In particular, the effect of the alumina particle size has been firstly experimentally observed, then studied by means of a diffusive model. The effects of pH and other contaminants in the aqueous solution have been also measured. Finally, an improvement of the arsenic adsorption performances has been attempted by using a TiO2 coating of commercial alumina. The characterization of alumina in the different forms has been done by X‐ray diffraction, Brunauer–Emmett–Teller specific area measurement and scanning electron microscopy. The kinetics and equilibrium experiments of arsenic(V) removal by the adsorbent materials were studied in a batch mode. The alumina particulate size showed to play a key role in the adsorption process. In fact, among the tested adsorbent types, that material with the lowest particle size (i.e., 20 μm) showed the maximum arsenic(V) uptake capacity, whi...
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The photocatalysis activity of mixed nanocomposite ZrxTi1-xO2 catalyst was studied. The catalysts with x=0, 0.1 and 0.2 were prepared via sol-gel method in a reactor with rapid micromixing using titanium tetra-isopropoxide and zirconium... more
The photocatalysis activity of mixed nanocomposite ZrxTi1-xO2 catalyst was studied. The catalysts with x=0, 0.1 and 0.2 were prepared via sol-gel method in a reactor with rapid micromixing using titanium tetra-isopropoxide and zirconium tetra-propoxide precursors and n-propanol solvent. The colloids were coated on cleaned borosilicate beads and treated at temperatures in the range between 400 and 600 °C to achieve crystalline anatase phase. The prepared materials were characterized by ICP-OES, BET, TDA and optical absorption measurements. The photocatalytic experiments were carried out in a continuous-flow fixed bed reactor on the gaseous ethylene decomposing. The photocatalytic activity of the prepared material was depended on the elemental compositions and calcination temperature. The enhanced activity, 50% higher compared to pure anatase TiO2, was obtained in the material containing 10 mol% Zr and thermally treated at 500 °C.
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The purpose of this work is development of the solid-state materials possessing a small absorption combined with sufficient refraction index in the THz range. The main criteria, which were used for the material selection, were quite... more
The purpose of this work is development of the solid-state materials possessing a small absorption combined with sufficient refraction index in the THz range. The main criteria, which were used for the material selection, were quite simple: inorganic compound with strong chemical bonds, stoichiometric composition, small concentration of delocalized charge carriers and sufficient polarizability over THz frequency range. It is obvious, that inorganic materials match these criteria in the greatest degree and, first of all, stable oxides with a high fusion temperature: Al2O3 , SiO2. In this work we studied monolithic nanofibrous alumina for the THz frequency range, which synthesis process was previously developed.
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The purpose of this work is development of the solid-state materials possessing a small absorption combined with sufficient refraction index in the THz range. The main criteria, which were used for the material selection, were quite... more
The purpose of this work is development of the solid-state materials possessing a small absorption combined with sufficient refraction index in the THz range. The main criteria, which were used for the material selection, were quite simple: inorganic compound with strong chemical bonds, stoichiometric composition, small concentration of delocalized charge carriers and sufficient polarizability over THz frequency range. It is obvious, that inorganic materials match these criteria in the greatest degree and, first of all, stable oxides with a high fusion temperature: Al2O3 , SiO2. In this work we studied monolithic nanofibrous alumina for the THz frequency range, which synthesis process was previously developed.
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Vanadium oxo-alkoxy nanoparticles were prepared via sol-gel method, manually and in a chemical reactor with ultra-rapid micromixing. The materials were characterized by DLS, ATG-ATD, XRD and SEM methods. The influence of micromixing... more
Vanadium oxo-alkoxy nanoparticles were prepared via sol-gel method, manually and in a chemical reactor with ultra-rapid micromixing. The materials were characterized by DLS, ATG-ATD, XRD and SEM methods. The influence of micromixing conditions on the particle size and growth kinetics was evaluated. Complementary, the preparation of mixed-oxide nanoparticles in presence of vanadium and titanium precursors was performed, showing a strong interaction between the two systems, promising for the fabrication of size- and compositional selective Ti-V oxide nanoparticles for photocatalysis.
Effect of the femtosecond and nanosecond UV laser irradiation (below the ablation threshold) of graphite-like hexagonal boron nitride (hBN) has been studied. Experiments were carried out with the compacted powder under high vacuum at room... more
Effect of the femtosecond and nanosecond UV laser irradiation (below the ablation threshold) of graphite-like hexagonal boron nitride (hBN) has been studied. Experiments were carried out with the compacted powder under high vacuum at room temperature using excimer KrF laser (248 nm). In the nanosecond operation mode, the laser-induced fluorescence spectra are found strongly modified depending on the integrated doze, which is attributed to a progressive enrichment of the surface layer by elemental boron. A slow sample recovery after the laser irradiation has been observed. On the other hand, in the femtosecond mode the fluorescence spectra depend on the laser fluence, and the changes are reversible: low energy fluorescence spectra are restored immediately when the laser energy decreases. This effect can be explained by a material bleaching, which favors a bulk centers emission. The ablation threshold has been determined as 78 mJ/cm2 in the femtosecond laser operational mode.
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The adsorption process is widely used for the treatment of drinking water sources containing high levels of arsenic. The choice of the adsorbent is crucial for the efficiency of the process. Very good performances were obtained in the... more
The adsorption process is widely used for the treatment of drinking water sources containing high levels of arsenic. The choice of the adsorbent is crucial for the efficiency of the process. Very good performances were obtained in the past by activated alumina, while more recent studies have shown that also other media such as titanium oxide can provide high removal rates. In the present work, four types of adsorbents were tested for their removal capability of pentavalent arsenic from liquid solutions. Specifically, it was investigated if modifications of activated alumina by coating with titanium oxide nanoparticles or by reducing particle size might improve their performance. The adsorbents were firstly characterized by X-ray diffraction, BET specific area measurement and SEM analysis. Then, kinetics, equilibrium isotherm experiments were conducted in batch mode at fixed pH. All the tested adsorbents showed satisfactory arsenic removal, with the best performance obtained by the m...
In a previous work in our team (Oualha et al., Chem Eng Trans, vol 73, 67-72 (2019)) it was shown that at large Reynold numbers (Re > 8000) a vapor phase appears by cavitation in T-mixer reactors used for chemical precipitation of... more
In a previous work in our team (Oualha et al., Chem Eng Trans, vol 73, 67-72 (2019)) it was shown that at large Reynold numbers (Re > 8000) a vapor phase appears by cavitation in T-mixer reactors used for chemical precipitation of nanoparticles. This phenomenon can affect dramatically the properties of the obtained nanoparticles. In the work of Oualha et al (2019), the apparent size (more precisely the hydrodynamic diameters) of vapor bubbles due to the cavitation, was in situ monitored in the reactor by using SLS (Static Light Scattering) and DLS (Dynamic Light Scattering) methods. A modeling was also given using Fluent software: calculated size population of bubble was provided. Unfortunately this population could not be directly compared to experimental data since the relationship between apparent and real size was unknown. In the present work, new DLS measurements using particles of calibrated sizes are presented to help us to interpret and comment our previous results on bub...
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We report on our recent progress in preparation of pure and N-doped TiO2 nanocoatings for reactive gas cleaning. The oxo-particles are generated in the sol-gel reactor with rapid reagent mixing, temperature and atmosphere control. Their... more
We report on our recent progress in preparation of pure and N-doped TiO2 nanocoatings for reactive gas cleaning. The oxo-particles are generated in the sol-gel reactor with rapid reagent mixing, temperature and atmosphere control. Their size is monitored in situ by light scattering method using optical-fibre probe. The N-doping is achieved during the particle nucleation stage. An ultra-thin surface coverage is achieved during a short contact time between the chemically active sols and a support. The coatings are then treated at 450°C during 4h. They are mechanically stable and exhibit high photocatalytic activity in both UV and visible spectral ranges.
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In this study, ultraporous aluminas (UPA) were synthesized as new effective adsorbents for Remazol Brilliant Blue R (RBBR) removal from aqueous solutions. The UPA monoliths were grown via facile oxidation process, followed by isochronous... more
In this study, ultraporous aluminas (UPA) were synthesized as new effective adsorbents for Remazol Brilliant Blue R (RBBR) removal from aqueous solutions. The UPA monoliths were grown via facile oxidation process, followed by isochronous annealing treatment in air at different temperatures, through which γ, θ, and α phase polycrystalline fibrous grains of UPA can be accordingly obtained. The experimental factors that affect the material adsorption performances including initial pH, contact time, and temperature were comprehensively studied by batch experiments. The RBBR adsorption isotherms of UPA(γ) and UPA(θ) powders were found almost identical, while UPA(α) powders showed low effectiveness. To obtain the desirable mechanical stability of the UPA monolith with considerable RBBR adsorption capacity, UPA(θ) powders were further studied. The UPA(θ) powders exhibited maximum RBBR adsorption at pH 2 due to the positively charged surface under acidic conditions. Compared with the Lagerg...
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In emergency, to produce safe water, that is “potable water free from harmful microorganisms and substances even if it may have colour, odour or taste problem due to dissolved minerals”, applied methods should be immediately available to... more
In emergency, to produce safe water, that is “potable water free from harmful microorganisms and substances even if it may have colour, odour or taste problem due to dissolved minerals”, applied methods should be immediately available to treat contaminated water, to reach at least a microbiological pollution in terms of bacteria concentration is maximum 108 UFC/mL and a maximum concentration of As and COD are 0.1 mg/L and 20 mg/L, respectively. In this work, the treatment of contaminated water to use in environmental and sanitary emergency is performed by the production and employment of proper nanomaterials produced locally. The development of a novel equipment capable to produce quickly and continuously these specific nanomaterials is necessary. Therefore, it was suggested to perform continuous production of the materials by means of process intensification techniques such as the spinning disk reactor (SDR) or the T-mixer reactor (TMR), respectively.Both equipment performed well i...
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The photocatalysis activity of mixed nanocomposite ZrxTi1-xO2 catalyst was studied. The catalysts with x=0, 0.1 and 0.2 were prepared via sol-gel method in a reactor with rapid micromixing using titanium tetra- isopropoxide and zirconium... more
The photocatalysis activity of mixed nanocomposite ZrxTi1-xO2 catalyst was studied. The catalysts with x=0, 0.1 and 0.2 were prepared via sol-gel method in a reactor with rapid micromixing using titanium tetra- isopropoxide and zirconium tetra-propoxide precursors and n-propanol solvent. The colloids were coated on cleaned borosilicate beads and treated at temperatures in the range between 400 and 600 °C to achieve crystalline anatase phase. The prepared materials were characterized by ICP-OES, BET, TDA and optical absorption measurements. The photocatalytic experiments were carried out in a continuous-flow fixed bed reactor on the gaseous ethylene decomposing. The photocatalytic activity of the prepared material was depended on the elemental compositions and calcination temperature. The enhanced activity, 50% higher compared to pure anatase TiO2, was obtained in the material containing 10 mol% Zr and thermally treated at 500 °C.
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V-TiO2 photocatalyst with 0 ≤ V ≤ 20 mol% was prepared via the sol–gel method based on mixed oxide titanium–vanadium nanoparticles with size and composition control. The mixed oxide vanadium–titanium oxo-alkoxy nanonoparticles were... more
V-TiO2 photocatalyst with 0 ≤ V ≤ 20 mol% was prepared via the sol–gel method based on mixed oxide titanium–vanadium nanoparticles with size and composition control. The mixed oxide vanadium–titanium oxo-alkoxy nanonoparticles were generated in a chemical micromixing reactor, coated on glass beads via liquid colloid deposition method and underwent to an appropriate thermal treatment forming crystallized nanocoatings. X-ray diffraction, Raman, thermogravimetric and differential thermal analyses confirmed anatase crystalline structure at vanadium content ≤ 10 mol%, with the cell parameters identical to those of pure TiO2. At a higher vanadium content of ~20 mol%, the material segregation began and orthorhombic phase of V2O5 appeared. The crystallization onset temperature of V-TiO2 smoothly changed with an increase in vanadium content. The best photocatalytic performance towards methylene blue decomposition in aqueous solutions under UVA and visible light illuminations was observed in ...
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The apparition of the cavitation phenomenon in chemical precipitation reactors with rapid micromixing can significantly affect the elaboration process. The bubbles appear in the reactive fluid flow when the local hydrostatic pressure... more
The apparition of the cavitation phenomenon in chemical precipitation reactors with rapid micromixing can significantly affect the elaboration process. The bubbles appear in the reactive fluid flow when the local hydrostatic pressure decreases down to the liquid vapour pressure, which also corresponds to the maximum energy input producing the micromixing. In this paper, we study the bubbles kinetics (trajectory, size and number density evolution along the outlet leg of our exocentric T-mixer) in water experimentally by light scattering SLS/DLS measurements and numerically via FLUENT software using the cavitation and population balance models. We conclude about the generation and oscillatory movement of cavitation bubbles with the most abundant sizes between 0.1 and 1 (m, which control allows exploring the cavitation regime of the reactors.Keywords: T-mixer, Cavitation, Light scattering (DLS/SLS), FLUENT modelling.
Synthesis and Characterization of Nanometric Titania Coated on Granular Alumina for Arsenic Removal Agostina Chiavola*, Viktor K. Tchieda, Emilio D’Amato, Angelo Chianese, Andrei Kanaev Sapienza University of Rome, Department of Civil,... more
Synthesis and Characterization of Nanometric Titania Coated on Granular Alumina for Arsenic Removal Agostina Chiavola*, Viktor K. Tchieda, Emilio D’Amato, Angelo Chianese, Andrei Kanaev Sapienza University of Rome, Department of Civil, Building and Environmental Engineering, Via Eudossiana, 18, Rome 00184, Italy University of Yaoundé 1, Laboratory of Analytical Chemistry, P.O Box 812 Yaoundé, Cameroon Sapienza University of Rome, Department of Chemical Engineering Materials Environment Via Eudossiana, 18, Rome 00184, Italy Université Paris 13, Laboratoire des Sciences des Procédés et des Matériaux, CNRS, 99, Avenue J.-B. Clément, 93430 Villataneuse, France agostina.chiavola@uniroma1.it
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A theoretical investigation of the underlying ultrafast processes upon irradiation of rutile TiO2 of (001) and (100) surface orientation with femtosecond (fs) double pulsed lasers was performed in ablation conditions, for which, apart... more
A theoretical investigation of the underlying ultrafast processes upon irradiation of rutile TiO2 of (001) and (100) surface orientation with femtosecond (fs) double pulsed lasers was performed in ablation conditions, for which, apart from mass removal, phase transformation and surface modification of the heated solid were induced. A parametric study was followed to correlate the transient carrier density and the produced lattice temperature with the laser fluence, pulse separation and the induced damage. The simulations showed that both temporal separation and crystal orientation influence the surface pattern, while both the carrier density and temperature drop gradually to a minimum value at temporal separation equal to twice the pulse separation that remain constant at long delays. Carrier dynamics, interference of the laser beam with the excited surface waves, thermal response and fluid transport at various pulse delays explained the formation of either subwavelength or suprawav...