The Experts below are selected from a list of 240 Experts worldwide ranked by ideXlab platform
Quanxing Zhang - One of the best experts on this subject based on the ideXlab platform.
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heavy metal removal from water wastewater by nanosized metal Oxides a review
Journal of Hazardous Materials, 2012Co-Authors: Ming Hua, Bingcai Pan, Lu Lv, Shujuan Zhang, Weiming Zhang, Quanxing ZhangAbstract:Abstract Nanosized metal Oxides (NMOs), including nanosized ferric Oxides, manganese Oxides, aluminum Oxides, titanium Oxides, magnesium Oxides and Cerium Oxides, provide high surface area and specific affinity for heavy metal adsorption from aqueous systems. To date, it has become a hot topic to develop new technologies to synthesize NMOs, to evaluate their removal of heavy metals under varying experimental conditions, to reveal the underlying mechanism responsible for metal removal based on modern analytical techniques (XAS, ATR-FT-IR, NMR, etc.) or mathematical models, and to develop metal oxide-based materials of better applicability for practical use (such as granular Oxides or composite materials). The present review mainly focuses on NMOs’ preparation, their physicochemical properties, adsorption characteristics and mechanism, as well as their application in heavy metal removal. In addition, porous host supported NMOs are particularly concerned because of their great advantages for practical application as compared to the original NMOs. Also, some magnetic NMOs were included due to their unique separation performance.
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Heavy metal removal from water/wastewater by nanosized metal Oxides: A review
Journal of Hazardous Materials, 2012Co-Authors: Ming Hua, Bingcai Pan, Lu Lv, Shujuan Zhang, Weiming Zhang, Quanxing ZhangAbstract:Nanosized metal Oxides (NMOs), including nanosized ferric Oxides, manganese Oxides, aluminum Oxides, titanium Oxides, magnesium Oxides and Cerium Oxides, provide high surface area and specific affinity for heavy metal adsorption from aqueous systems. To date, it has become a hot topic to develop new technologies to synthesize NMOs, to evaluate their removal of heavy metals under varying experimental conditions, to reveal the underlying mechanism responsible for metal removal based on modern analytical techniques (XAS, ATR-FT-IR, NMR, etc.) or mathematical models, and to develop metal oxide-based materials of better applicability for practical use (such as granular Oxides or composite materials). The present review mainly focuses on NMOs' preparation, their physicochemical properties, adsorption characteristics and mechanism, as well as their application in heavy metal removal. In addition, porous host supported NMOs are particularly concerned because of their great advantages for practical application as compared to the original NMOs. Also, some magnetic NMOs were included due to their unique separation performance. © 2011 Elsevier B.V.
Gilles Flamant - One of the best experts on this subject based on the ideXlab platform.
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investigation of reactive Cerium based Oxides for h2 production by thermochemical two step water splitting
Journal of Materials Science, 2010Co-Authors: Stephane Abanades, Gilles Flamant, Anne Cordier, Gilles Peraudeau, Anne JulbeAbstract:This study focuses on the use of Cerium-based mixed Oxides for hydrogen production by solar-driven thermochemical two-step water-splitting. Mixed Cerium Oxides are proposed in order to decrease the reduction temperature of ceria and to avoid material sublimation occurring above 2,000 °C during the high-temperature solar step. Ceria-based nanopowders were synthesized by soft chemistry methods including the modified Pechini method. The influence of the synthesis method, the type of cationic element mixed with Cerium, and the content of this added element was investigated by comparing the reduction temperatures of the derived materials. The synthesized powders were characterized by X-ray diffraction, thermogravimetric analysis, SEM, and Raman spectroscopy. Results showed that the synthesized pure Cerium oxide is more reactive toward reduction than a commercial powder. Among the different elements added to ceria that were screened, the addition of zirconium significantly improved the reduction of ceria at temperatures below 1,500 °C. Increasing zirconium content further favored Cerium reduction yield up to 70%. Water-splitting tests were performed to demonstrate the reactivity of the developed materials for H2 production. The amount of H2 evolved was enhanced with a temperature increase, the maximum H2 production from Ce0.75Zr0.25O2−δ was 0.24 mmol/g at 1,045 °C, and the powder reactivity upon cycling was demonstrated via thermogravimetry through two successive reduction–hydrolysis reactions.
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hydrogen production from mixed Cerium Oxides via three step water splitting cycles
Solid State Ionics, 2009Co-Authors: Patrice Charvin, Eric Beche, Stephane Abanades, Florent Lemont, Gilles FlamantAbstract:This study deals with the production of hydrogen from water-splitting thermochemical cycles based on mixed metal Oxides. The solar synthesis of mixed Oxides based on ceria was achieved by melting mixed powders of component Oxides at high temperature. The reduced Oxides (Ce2Ti2O7, Ce2Si2O7, CeFeO3, CeVO4, and CeNbO4) produced hydrogen in a three-step thermochemical cycle except CeVO4. The three-step cycle uses an alkali hydroxide (NaOH or KOH) in an activation reaction to improve oxidation and to facilitate water-splitting during the third step. Experimental investigations were performed to demonstrate the concept and to quantify the reactions performance for hydrogen production. The high temperature synthesis of reduced Cerium-based mixed Oxides was performed in a laboratory-scale solar reactor. The mixed Oxides were analysed by X-ray diffraction and characterized by XPS, which identified Ce(III) species in the structure. The activation reaction with NaOH or KOH producing hydrogen was studied to determine the effect of temperature and particle diameter, and to quantify the chemical conversion for each Cerium-based mixed oxide.
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ce 3d xps investigation of Cerium Oxides and mixed Cerium oxide cextiyoz
Surface and Interface Analysis, 2008Co-Authors: Eric Beche, Patrice Charvin, Danielle Perarnau, Stephane Abanades, Gilles FlamantAbstract:This article presents an XPS study of Ce 3d emission spectra dominated by atomic multiplet effects in core level spectroscopy of rare earth compounds (Ce Oxides). Core level spectroscopy has been used to study the electronic states of Ce 3d5/2 and Ce 3d3/2 levels in Ce4+ and Ce3+ states. The well-resolved components of Ce 3d5/2 and Ce 3d3/2 spin-orbit components, due to various final states (4f0, 4f1, 4f2 configurations), were determined on 3d XPS spectra from commercial powders (CeO2, CePO4). These results were used to study the 3d spin-orbit component of mixed Cerium-titanium oxide. This compound was prepared by co-melting commercial powders of CeO2 and TiO2 at 1800 K under air using a solar furnace with a flux density of 16 MW.m−2 at the focal point of the parabolic concentrator. The mixed oxide Ce2Ti2O7 was produced and contained Ce(III) species which may be reactive with water to give back the initial metal Oxides and generate hydrogen, a valuable product considered as a promising energy carrier in the future in replacement of oil. The 3d photoemission spectra revealed the presence of mixed components attributed to mainly Ce(III) and Ce(IV) species. Copyright © 2008 John Wiley & Sons, Ltd.
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thermochemical hydrogen production from a two step solar driven water splitting cycle based on Cerium Oxides
Solar Energy, 2006Co-Authors: Stephane Abanades, Gilles FlamantAbstract:Abstract A new thermochemical cycle for H2 production based on CeO2/Ce2O3 Oxides has been successfully demonstrated. It consists of two chemical steps: (1) reduction, 2CeO2 → Ce2O3 + 0.5O2; (2) hydrolysis, Ce2O3 + H2O → 2CeO2 + H2. The thermal reduction of Ce(IV) to Ce(III) (endothermic step) is performed in a solar reactor featuring a controlled inert atmosphere. The feasibility of this first step has been demonstrated and the operating conditions have been defined (T = 2000 °C, P = 100–200 mbar). The hydrogen generation step (water-splitting with Ce(III) oxide) is studied in a fixed bed reactor and the reaction is complete with a fast kinetic in the studied temperature range 400–600 °C. The recovered Ce(IV) oxide is then recycled in first step. In this process, water is the only material input and heat is the only energy input. The only outputs are hydrogen and oxygen, and these two gases are obtained in different steps avoiding a high temperature energy consuming gas-phase separation. Furthermore, pure hydrogen is produced (it is not contaminated by carbon products like CO, CO2), thus it can be used directly in fuel cells. The results have shown that the Cerium oxide two-step thermochemical cycle is a promising process for hydrogen production.
Ming Hua - One of the best experts on this subject based on the ideXlab platform.
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heavy metal removal from water wastewater by nanosized metal Oxides a review
Journal of Hazardous Materials, 2012Co-Authors: Ming Hua, Bingcai Pan, Lu Lv, Shujuan Zhang, Weiming Zhang, Quanxing ZhangAbstract:Abstract Nanosized metal Oxides (NMOs), including nanosized ferric Oxides, manganese Oxides, aluminum Oxides, titanium Oxides, magnesium Oxides and Cerium Oxides, provide high surface area and specific affinity for heavy metal adsorption from aqueous systems. To date, it has become a hot topic to develop new technologies to synthesize NMOs, to evaluate their removal of heavy metals under varying experimental conditions, to reveal the underlying mechanism responsible for metal removal based on modern analytical techniques (XAS, ATR-FT-IR, NMR, etc.) or mathematical models, and to develop metal oxide-based materials of better applicability for practical use (such as granular Oxides or composite materials). The present review mainly focuses on NMOs’ preparation, their physicochemical properties, adsorption characteristics and mechanism, as well as their application in heavy metal removal. In addition, porous host supported NMOs are particularly concerned because of their great advantages for practical application as compared to the original NMOs. Also, some magnetic NMOs were included due to their unique separation performance.
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Heavy metal removal from water/wastewater by nanosized metal Oxides: A review
Journal of Hazardous Materials, 2012Co-Authors: Ming Hua, Bingcai Pan, Lu Lv, Shujuan Zhang, Weiming Zhang, Quanxing ZhangAbstract:Nanosized metal Oxides (NMOs), including nanosized ferric Oxides, manganese Oxides, aluminum Oxides, titanium Oxides, magnesium Oxides and Cerium Oxides, provide high surface area and specific affinity for heavy metal adsorption from aqueous systems. To date, it has become a hot topic to develop new technologies to synthesize NMOs, to evaluate their removal of heavy metals under varying experimental conditions, to reveal the underlying mechanism responsible for metal removal based on modern analytical techniques (XAS, ATR-FT-IR, NMR, etc.) or mathematical models, and to develop metal oxide-based materials of better applicability for practical use (such as granular Oxides or composite materials). The present review mainly focuses on NMOs' preparation, their physicochemical properties, adsorption characteristics and mechanism, as well as their application in heavy metal removal. In addition, porous host supported NMOs are particularly concerned because of their great advantages for practical application as compared to the original NMOs. Also, some magnetic NMOs were included due to their unique separation performance. © 2011 Elsevier B.V.
Stephane Abanades - One of the best experts on this subject based on the ideXlab platform.
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investigation of reactive Cerium based Oxides for h2 production by thermochemical two step water splitting
Journal of Materials Science, 2010Co-Authors: Stephane Abanades, Gilles Flamant, Anne Cordier, Gilles Peraudeau, Anne JulbeAbstract:This study focuses on the use of Cerium-based mixed Oxides for hydrogen production by solar-driven thermochemical two-step water-splitting. Mixed Cerium Oxides are proposed in order to decrease the reduction temperature of ceria and to avoid material sublimation occurring above 2,000 °C during the high-temperature solar step. Ceria-based nanopowders were synthesized by soft chemistry methods including the modified Pechini method. The influence of the synthesis method, the type of cationic element mixed with Cerium, and the content of this added element was investigated by comparing the reduction temperatures of the derived materials. The synthesized powders were characterized by X-ray diffraction, thermogravimetric analysis, SEM, and Raman spectroscopy. Results showed that the synthesized pure Cerium oxide is more reactive toward reduction than a commercial powder. Among the different elements added to ceria that were screened, the addition of zirconium significantly improved the reduction of ceria at temperatures below 1,500 °C. Increasing zirconium content further favored Cerium reduction yield up to 70%. Water-splitting tests were performed to demonstrate the reactivity of the developed materials for H2 production. The amount of H2 evolved was enhanced with a temperature increase, the maximum H2 production from Ce0.75Zr0.25O2−δ was 0.24 mmol/g at 1,045 °C, and the powder reactivity upon cycling was demonstrated via thermogravimetry through two successive reduction–hydrolysis reactions.
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hydrogen production from mixed Cerium Oxides via three step water splitting cycles
Solid State Ionics, 2009Co-Authors: Patrice Charvin, Eric Beche, Stephane Abanades, Florent Lemont, Gilles FlamantAbstract:This study deals with the production of hydrogen from water-splitting thermochemical cycles based on mixed metal Oxides. The solar synthesis of mixed Oxides based on ceria was achieved by melting mixed powders of component Oxides at high temperature. The reduced Oxides (Ce2Ti2O7, Ce2Si2O7, CeFeO3, CeVO4, and CeNbO4) produced hydrogen in a three-step thermochemical cycle except CeVO4. The three-step cycle uses an alkali hydroxide (NaOH or KOH) in an activation reaction to improve oxidation and to facilitate water-splitting during the third step. Experimental investigations were performed to demonstrate the concept and to quantify the reactions performance for hydrogen production. The high temperature synthesis of reduced Cerium-based mixed Oxides was performed in a laboratory-scale solar reactor. The mixed Oxides were analysed by X-ray diffraction and characterized by XPS, which identified Ce(III) species in the structure. The activation reaction with NaOH or KOH producing hydrogen was studied to determine the effect of temperature and particle diameter, and to quantify the chemical conversion for each Cerium-based mixed oxide.
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ce 3d xps investigation of Cerium Oxides and mixed Cerium oxide cextiyoz
Surface and Interface Analysis, 2008Co-Authors: Eric Beche, Patrice Charvin, Danielle Perarnau, Stephane Abanades, Gilles FlamantAbstract:This article presents an XPS study of Ce 3d emission spectra dominated by atomic multiplet effects in core level spectroscopy of rare earth compounds (Ce Oxides). Core level spectroscopy has been used to study the electronic states of Ce 3d5/2 and Ce 3d3/2 levels in Ce4+ and Ce3+ states. The well-resolved components of Ce 3d5/2 and Ce 3d3/2 spin-orbit components, due to various final states (4f0, 4f1, 4f2 configurations), were determined on 3d XPS spectra from commercial powders (CeO2, CePO4). These results were used to study the 3d spin-orbit component of mixed Cerium-titanium oxide. This compound was prepared by co-melting commercial powders of CeO2 and TiO2 at 1800 K under air using a solar furnace with a flux density of 16 MW.m−2 at the focal point of the parabolic concentrator. The mixed oxide Ce2Ti2O7 was produced and contained Ce(III) species which may be reactive with water to give back the initial metal Oxides and generate hydrogen, a valuable product considered as a promising energy carrier in the future in replacement of oil. The 3d photoemission spectra revealed the presence of mixed components attributed to mainly Ce(III) and Ce(IV) species. Copyright © 2008 John Wiley & Sons, Ltd.
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thermochemical hydrogen production from a two step solar driven water splitting cycle based on Cerium Oxides
Solar Energy, 2006Co-Authors: Stephane Abanades, Gilles FlamantAbstract:Abstract A new thermochemical cycle for H2 production based on CeO2/Ce2O3 Oxides has been successfully demonstrated. It consists of two chemical steps: (1) reduction, 2CeO2 → Ce2O3 + 0.5O2; (2) hydrolysis, Ce2O3 + H2O → 2CeO2 + H2. The thermal reduction of Ce(IV) to Ce(III) (endothermic step) is performed in a solar reactor featuring a controlled inert atmosphere. The feasibility of this first step has been demonstrated and the operating conditions have been defined (T = 2000 °C, P = 100–200 mbar). The hydrogen generation step (water-splitting with Ce(III) oxide) is studied in a fixed bed reactor and the reaction is complete with a fast kinetic in the studied temperature range 400–600 °C. The recovered Ce(IV) oxide is then recycled in first step. In this process, water is the only material input and heat is the only energy input. The only outputs are hydrogen and oxygen, and these two gases are obtained in different steps avoiding a high temperature energy consuming gas-phase separation. Furthermore, pure hydrogen is produced (it is not contaminated by carbon products like CO, CO2), thus it can be used directly in fuel cells. The results have shown that the Cerium oxide two-step thermochemical cycle is a promising process for hydrogen production.
Mamoun Muhammed - One of the best experts on this subject based on the ideXlab platform.
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total oxidation of methane over doped nanophase Cerium Oxides
Catalysis Letters, 1998Co-Authors: Anders Palmqvist, E M Johansson, S G Jaras, Mamoun MuhammedAbstract:The formation of solid solutions of Cerium oxide with the Oxides of calcium, manganese, or neodymium enhances the catalytic activity of Cerium oxide for the total oxidation of methane, whereas solid solutions with lead oxide showed an opposite effect. Reasons for this are discussed in terms of oxygen vacancy concentrations and mobilities, local structure configurations, number of oxidation states of dopant, and electron transfer properties. The effects of increased oxygen ion mobility and a more beneficial local structure support the increased catalytic activity for the calcium- and neodymium-doped Cerium oxide samples. In addition, a reduced energy for charge transfer from oxygen to Cerium supports a higher activity for the calcium-doped sample. The activity data were fitted to an Arrhenius equation, and the apparent activation energies were found to be between 110 and 130 kJ/mol. The particle sizes and the BET areas of the samples were only little affected by the reactor runs, and none of the samples were subjected to phase changes.
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nanophase catalytic Oxides i synthesis of doped Cerium Oxides as oxygen storage promoters
Applied Catalysis B-environmental, 1995Co-Authors: Yu Zhang, Sara Andersson, Mamoun MuhammedAbstract:Abstract Doped CeO2 materials were synthesized with the aim to improve the performance of CeO2 as oxygen storage promoter in gas catalytic reactions. The coprecipitation method was used for the synthesis of fine oxalate precursors of high homogeneity and well defined composition. The chemical and morphological properties of both the coprecipitated oxalates and the calcined Oxides were examined. The influence of doping of different metal cations into the CeO2 structure on the oxygen storage capacity in particular was investigated. Some of the doped Oxides Ce0.9M0.1 O2 − δ (M = Ca, Nd, Pb, etc.) give an increased oxygen storage capacity, 20–40% higher than the undoped. Their redox activity also remarkably increased.