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Mesoporous SBA-15 Supported Iron Oxide: A Potent Catalyst for Hydrogen Sulfide Removal
2008
Wang, Xiaohui | Jia, Jinping | Zhao, Ling | Sun, Tonghua
A novel silicate mesoporous material, SBA-15 supported Fe₂O₃, was synthesized by post-synthesis method via ultrasonic-assisted route. The desulfurization test from a gas mixture containing 0.1 vol% H₂S was carried out over SBA-15 supported Fe₂O₃ in a fixed-bed system at atmospheric pressure and room temperature. The effects of the chemical nature of Fe₂O₃ and the textural properties of the material on desulfurization capacity were studied. Materials before and after the desulfurization test were characterized using nitrogen adsorption, XRD, TEM, FTIR, XPS, ICP and other standard methods. The characterization results suggest that modification process does not change the two-dimensional hexagonal mesostructure of SBA-15. Iron species disperses inside channels and the outside surface in the crystalline phase of iron oxide. The material with iron content of 31.3 wt% presented highest H₂S uptake capacity. Structural properties of the material also play important roles in desulfurization performance besides the catalytic effects of iron oxide. The basic feature of material and enough oxygen supply are benefit for the reaction. SBA-15 supported Fe₂O₃ can be an effective alternative to capture H₂S from gas streams.
اظهر المزيد [+] اقل [-]Benzene Biodegradation under Anaerobic Conditions Coupled with Metal Oxides Reduction
2008
Villatoro-Monzón, Wilverth R. | Morales-Ibarria, Marcia G. | Velázquez, Elia K. | Ramírez-Saad, Hugo | Razo-Flores, Elías
Anaerobic benzene biodegradation was performed in batch experiments using Rhine River sediment as inoculum and amorphous Mn(IV) or Fe(III) as independent final electron acceptors. Benzene (4.5 μmol) was degraded in 80 and 710 days in batch experiments under Mn(IV) and Fe(III) reducing conditions, respectively. Highest benzene degradation rate, 0.07 μmol/day, was obtained under Mn (IV) reducing conditions, with soluble Mn(II) and CO₂ recoveries of 71.5% and 93% regarding to the stoichiometric values, respectively. Likewise, benzene biodegradation was performed in a continuous column coupled to the reduction of Mn(IV). Efficiency of benzene biodegradation was up to 97% under steady state operation in a sediment column operated continuously for more than 160 days. The carbon dioxide and Mn(II) recoveries were 88% and 77%, respectively, of the theoretical ratio according to the stoichiometry for benzene biodegradation.
اظهر المزيد [+] اقل [-]Stability of Arsenic Species in Soils Contaminated Naturally and in an Anthropogenic Manner
2008
Doušová, Barbora | Martaus, Alexandr | Filippi, Michal | Koloušek, David
Stability and transport of As species in soils were investigated in three contaminated Central European regions in the Czech Republic; one of them represents naturally contaminated area, the others are results of a former mining activity. Total As content varied from 60 to <18,000 ppm depending on locality and sampling layer. Sequential extraction procedure (SEP) enabled to distinguish five main fractions of As in soils based on different chemical and binding properties. Non-specifically and weakly sorbed As, as well as As remained in solid rests of samples did not exceed 10% of total As; specifically bounded As varied from 5 to 15%. The substantial portion of As was bound to hydrated Fe oxides (HFO) in amorphous and poorly-crystalline forms (10-30% of the total As) and/or to a well-crystallized forms of the same phases (50-80%). As sorption on HFO surface, particularly on well-crystallized phases represented the most significant and stable As bond in soils. Model leaching experiments illustrated the increased mobility of As species at pH [almost equal to] 7.0 in the soil-groundwater-surface water systems.
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