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Siddhartha Mukherjee - One of the best experts on this subject based on the ideXlab platform.
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Isothermal in situ Reduction Kinetics of CoCl2-SiO2 gels to Co-SiO2 nanocomposites
Thermochimica Acta, 1999Co-Authors: A. Basumallick, G. C. Das, Siddhartha MukherjeeAbstract:Abstract In situ Reduction Kinetics of CoCl 2 –SiO 2 gel to Co–SiO 2 nanocomposite in the 800–950°C range has been studied. The presence of nanosized metallic Co in the host matrix has been established from the X-ray diffraction patterns of the reduced gels. The metallic particle size has been found to be 17 and 23 nm when reduced at 850° and 950°C, respectively. Nucleation and growth type of mechanism remain operative during the course of the Reduction. The activation energy is found to be in the range of 55–61 kJ/mol.
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IN SITU Reduction Kinetics OF NICL2 IN SIO2 GEL MATRIX
Journal of Materials Research, 1995Co-Authors: Amitava Basumallick, K. Biswas, G. C. Das, Siddhartha MukherjeeAbstract:Silica gcls containing NiCl2 and dextrose have been reduced by heat-treating the gels under N2 atmosphere at 800 °C, 850 °C, 900 °C, and 950 °C, respectively. The influence of the volume ratio of ethyl alcohol to tetraethylorthosilicate and the amount of dextrose on the in situ Reduction Kinetics of NiCl2 in gel matrix have been investigated. The kinetic data on in situ Reduction have been analyzed by a reduced time method which indicates that mixed mechanisms are operative. The predominant mechanism of Reduction of NiCl2 in SiO2 gel matrix is of nucleation and growth type. The activation energies over different temperatures and fraction converted have been computed by the integration method.
Céline Pallud - One of the best experts on this subject based on the ideXlab platform.
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Temperature sensitivity of microbial Fe(III) Reduction Kinetics in subalpine wetland soils
Biogeochemistry, 2019Co-Authors: Kathrin Schilling, Thomas Borch, Charles C. Rhoades, Céline PalludAbstract:Microbially-mediated iron (Fe) cycling controls the fate of organic matter, contaminants, and nutrients in terrestrial ecosystems including wetland soils. However, the effects of temperature variations due to seasonal differences on Fe(III) Reduction rates and Kinetics in such ecosystems remains poorly understood. To evaluate the potential temperature impact on dissimilatory microbial Fe(III) Reduction it is crucial to determine environmentally-relevant reaction rates and kinetic parameters. Here, we investigate the relationship between soil temperature and microbial Fe(III) Reduction Kinetics in mineral soils from two subalpine wetlands with distinct hydrologic and edaphic conditions. We conducted flow-through experiments (FTR) at three temperatures (6, 12, and 18 °C) using intact soil cores collected from 30 cm [(higher organic carbon (C_org) and total nitrogen (TN)] and 70 cm (lower C_org and TN) soil depths in order to determine the apparent Fe(III) affinity constant (K_m), apparent maximum Fe(III) Reduction rates (V_max) and temperature sensitivity (Q_10 and E_a) of Fe(III) Reduction. We used Fe(III)-NTA, a model compound for aqueous labile and complexed Fe present in natural organic matter. Our results show that changes in apparent V_max and K_m are driven primarily by temperature. Significant differences in apparent V_max at 18 °C relative to 6 and 12 °C ( P
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Temperature sensitivity of microbial Fe(III) Reduction Kinetics in subalpine wetland soils
Biogeochemistry, 2018Co-Authors: Kathrin Schilling, Thomas Borch, Charles C. Rhoades, Céline PalludAbstract:Microbially-mediated iron (Fe) cycling controls the fate of organic matter, contaminants, and nutrients in terrestrial ecosystems including wetland soils. However, the effects of temperature variations due to seasonal differences on Fe(III) Reduction rates and Kinetics in such ecosystems remains poorly understood. To evaluate the potential temperature impact on dissimilatory microbial Fe(III) Reduction it is crucial to determine environmentally-relevant reaction rates and kinetic parameters. Here, we investigate the relationship between soil temperature and microbial Fe(III) Reduction Kinetics in mineral soils from two subalpine wetlands with distinct hydrologic and edaphic conditions. We conducted flow-through experiments (FTR) at three temperatures (6, 12, and 18 °C) using intact soil cores collected from 30 cm [(higher organic carbon (Corg) and total nitrogen (TN)] and 70 cm (lower Corg and TN) soil depths in order to determine the apparent Fe(III) affinity constant (Km), apparent maximum Fe(III) Reduction rates (Vmax) and temperature sensitivity (Q10 and Ea) of Fe(III) Reduction. We used Fe(III)-NTA, a model compound for aqueous labile and complexed Fe present in natural organic matter. Our results show that changes in apparent Vmax and Km are driven primarily by temperature. Significant differences in apparent Vmax at 18 °C relative to 6 and 12 °C (P < 0.05) suggest that dissimilatory microbial Fe(III) Reduction in wetland soils accelerates during warmer summer days. However, temperature alone fails to explain the large variability of the apparent parameters Q10 (1.5–8.9) and Ea (26–148 kJ mol−1) for the two wetland types and depths (30 and 70 cm). Strong relationship between both parameters of temperature sensitivity (Q10 and Ea) and reactive soil Fe content at 30 cm and Corg/TN at 70 cm depth demonstrate the notable impact of soil properties on the temperature sensitivity for mirobial Fe(III) Reduction in these wetland soils. Our results emphasize the importance of soil temperature on Fe(III) Reduction Kinetics and must be considered when predicting dissimilatory Fe(III) Reduction under different seasonal temperatures or in wetlands located at different temperature regimes.
Khalil Hanna - One of the best experts on this subject based on the ideXlab platform.
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Reduction Kinetics of Nitroaromatic Compounds by Titanium-Substituted Magnetite
The Journal of Physical Chemistry C, 2017Co-Authors: Rémi Marsac, Mathieu Pasturel, Khalil HannaAbstract:Although there is a growing interest in environmentally friendly catalytic processes based on magnetic solids, the reactivity of titanomagnetite (Fe3–xTixO4) having a “tunable” solid-state Fe(II)/Fe(III) ratio for reductive transformation of nitroaromatic compounds has been never investigated. This study, for the first time, comprehensively examines the Reduction Kinetics of nitroaromatic compounds by titanium-substituted magnetite and compares with that of Fe(II) amended-unsubstituted magnetite at equal amounts of total Fe(II). First, we demonstrated that Ti substitution in magnetite increased considerably the ability of magnetite to reduce 4-nitrophenol (4-NP) as well as nitrobenzene (NB) in a surface-mediated electron transfer pathway. However, Fe(II) amendment of magnetite (x = 0) to have an equivalent amount of total Fe(II) as in the corresponding titanomagnetite (0.25 ≤ x ≤ 0.75) resulted in higher Reduction rate constants for both substrates (4-NP and NB). Initial kobs was shown to increase exponen...
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Reduction Kinetics of Nitroaromatic Compounds by Titanium Substituted Magnetite
Journal of Physical Chemistry C, 2017Co-Authors: Rémi Marsac, Mathieu Pasturel, Khalil HannaAbstract:Although there is a growing interest in environmentally friendly catalytic processes based on magnetic solids, the reactivity of titanomagnetite (Fe-3,TixO4) having a "tunable" solid-state Fe(II)/Fe(III) ratio for reductive transformation of nitroaromatic compounds has been never investigated. This study, for the first time, comprehensively examines the Reduction Kinetics of nitroaromatic compounds by titanium-substituted magnetite and compares with that of Fe(II) amended-unsubstituted magnetite at equal amounts of total Fe(ll). First, we demonstrated that Ti substitution in magnetite increased considerably the ability of magnetite to reduce 4-nitrophenol (4-NP) as well as nitrobenzene (NB) in a surface-mediated electron transfer pathway. However, Fe(II) amendment of magnetite (x = 0) to have an equivalent amount of total Fe(II) as in the corresponding titanomagnetite (0.25
Kathrin Schilling - One of the best experts on this subject based on the ideXlab platform.
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Temperature sensitivity of microbial Fe(III) Reduction Kinetics in subalpine wetland soils
Biogeochemistry, 2019Co-Authors: Kathrin Schilling, Thomas Borch, Charles C. Rhoades, Céline PalludAbstract:Microbially-mediated iron (Fe) cycling controls the fate of organic matter, contaminants, and nutrients in terrestrial ecosystems including wetland soils. However, the effects of temperature variations due to seasonal differences on Fe(III) Reduction rates and Kinetics in such ecosystems remains poorly understood. To evaluate the potential temperature impact on dissimilatory microbial Fe(III) Reduction it is crucial to determine environmentally-relevant reaction rates and kinetic parameters. Here, we investigate the relationship between soil temperature and microbial Fe(III) Reduction Kinetics in mineral soils from two subalpine wetlands with distinct hydrologic and edaphic conditions. We conducted flow-through experiments (FTR) at three temperatures (6, 12, and 18 °C) using intact soil cores collected from 30 cm [(higher organic carbon (C_org) and total nitrogen (TN)] and 70 cm (lower C_org and TN) soil depths in order to determine the apparent Fe(III) affinity constant (K_m), apparent maximum Fe(III) Reduction rates (V_max) and temperature sensitivity (Q_10 and E_a) of Fe(III) Reduction. We used Fe(III)-NTA, a model compound for aqueous labile and complexed Fe present in natural organic matter. Our results show that changes in apparent V_max and K_m are driven primarily by temperature. Significant differences in apparent V_max at 18 °C relative to 6 and 12 °C ( P
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Temperature sensitivity of microbial Fe(III) Reduction Kinetics in subalpine wetland soils
Biogeochemistry, 2018Co-Authors: Kathrin Schilling, Thomas Borch, Charles C. Rhoades, Céline PalludAbstract:Microbially-mediated iron (Fe) cycling controls the fate of organic matter, contaminants, and nutrients in terrestrial ecosystems including wetland soils. However, the effects of temperature variations due to seasonal differences on Fe(III) Reduction rates and Kinetics in such ecosystems remains poorly understood. To evaluate the potential temperature impact on dissimilatory microbial Fe(III) Reduction it is crucial to determine environmentally-relevant reaction rates and kinetic parameters. Here, we investigate the relationship between soil temperature and microbial Fe(III) Reduction Kinetics in mineral soils from two subalpine wetlands with distinct hydrologic and edaphic conditions. We conducted flow-through experiments (FTR) at three temperatures (6, 12, and 18 °C) using intact soil cores collected from 30 cm [(higher organic carbon (Corg) and total nitrogen (TN)] and 70 cm (lower Corg and TN) soil depths in order to determine the apparent Fe(III) affinity constant (Km), apparent maximum Fe(III) Reduction rates (Vmax) and temperature sensitivity (Q10 and Ea) of Fe(III) Reduction. We used Fe(III)-NTA, a model compound for aqueous labile and complexed Fe present in natural organic matter. Our results show that changes in apparent Vmax and Km are driven primarily by temperature. Significant differences in apparent Vmax at 18 °C relative to 6 and 12 °C (P < 0.05) suggest that dissimilatory microbial Fe(III) Reduction in wetland soils accelerates during warmer summer days. However, temperature alone fails to explain the large variability of the apparent parameters Q10 (1.5–8.9) and Ea (26–148 kJ mol−1) for the two wetland types and depths (30 and 70 cm). Strong relationship between both parameters of temperature sensitivity (Q10 and Ea) and reactive soil Fe content at 30 cm and Corg/TN at 70 cm depth demonstrate the notable impact of soil properties on the temperature sensitivity for mirobial Fe(III) Reduction in these wetland soils. Our results emphasize the importance of soil temperature on Fe(III) Reduction Kinetics and must be considered when predicting dissimilatory Fe(III) Reduction under different seasonal temperatures or in wetlands located at different temperature regimes.
Rémi Marsac - One of the best experts on this subject based on the ideXlab platform.
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Reduction Kinetics of Nitroaromatic Compounds by Titanium-Substituted Magnetite
The Journal of Physical Chemistry C, 2017Co-Authors: Rémi Marsac, Mathieu Pasturel, Khalil HannaAbstract:Although there is a growing interest in environmentally friendly catalytic processes based on magnetic solids, the reactivity of titanomagnetite (Fe3–xTixO4) having a “tunable” solid-state Fe(II)/Fe(III) ratio for reductive transformation of nitroaromatic compounds has been never investigated. This study, for the first time, comprehensively examines the Reduction Kinetics of nitroaromatic compounds by titanium-substituted magnetite and compares with that of Fe(II) amended-unsubstituted magnetite at equal amounts of total Fe(II). First, we demonstrated that Ti substitution in magnetite increased considerably the ability of magnetite to reduce 4-nitrophenol (4-NP) as well as nitrobenzene (NB) in a surface-mediated electron transfer pathway. However, Fe(II) amendment of magnetite (x = 0) to have an equivalent amount of total Fe(II) as in the corresponding titanomagnetite (0.25 ≤ x ≤ 0.75) resulted in higher Reduction rate constants for both substrates (4-NP and NB). Initial kobs was shown to increase exponen...
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Reduction Kinetics of Nitroaromatic Compounds by Titanium Substituted Magnetite
Journal of Physical Chemistry C, 2017Co-Authors: Rémi Marsac, Mathieu Pasturel, Khalil HannaAbstract:Although there is a growing interest in environmentally friendly catalytic processes based on magnetic solids, the reactivity of titanomagnetite (Fe-3,TixO4) having a "tunable" solid-state Fe(II)/Fe(III) ratio for reductive transformation of nitroaromatic compounds has been never investigated. This study, for the first time, comprehensively examines the Reduction Kinetics of nitroaromatic compounds by titanium-substituted magnetite and compares with that of Fe(II) amended-unsubstituted magnetite at equal amounts of total Fe(ll). First, we demonstrated that Ti substitution in magnetite increased considerably the ability of magnetite to reduce 4-nitrophenol (4-NP) as well as nitrobenzene (NB) in a surface-mediated electron transfer pathway. However, Fe(II) amendment of magnetite (x = 0) to have an equivalent amount of total Fe(II) as in the corresponding titanomagnetite (0.25
