![]() Google Patents US4598062A - Iron oxide-chromium oxide catalyst and process for high temperature water-gas shift reaction We thank the anonymous reviewers for careful review and insightful comments.US4598062A - Iron oxide-chromium oxide catalyst and process for high temperature water-gas shift reaction Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the Office of Basic Energy Sciences within the DOE Office of Science under Contract No. Part of this research was conducted at the Stanford Synchrotron Radiation Lightsource. vulgaris strain RCH1 Jingling Hu and Preston Larson at the University of Oklahoma for help with laboratory and SEM measurements, respectively and Yuanzhi Tang at Harvard University for preparing the Al-goethite. Romy Chakraborty at Lawrence Berkeley National Laboratory for providing the culture of D. Department of Energy (DOE) Office of Science. Department of Energy, Biological and Environmental Research (SC-33)įunding for this work was provided by the Subsurface Biogeochemical Research Program (grant DE-SC0006902) of the Office of Biological and Environmental Research, within the U.S. If exposed to environmentally common Mn oxides such as birnessite in the absence of microbial activity, there is the potential for rapid (re)formation of dissolved Cr(VI) above regulatory levels. The results of this study suggest that Fe-Cr precipitates formed in groundwater remediation may remain stable only in the presence of active anaerobic microbial reduction. This pattern was not observed in the solids generated by microbial Cr(VI) reduction, and could be due to re-reduction of any Cr(VI) generated upon oxidation by birnessite via active bacteria or microbial enzymes. Reaction between birnessite and the abiotically formed Cr(III) solids led to production of significant dissolved Cr(VI) compared to the no-birnessite controls. ![]() The solid formed when Cr(VI) was reduced by FeS contained a high proportion of Cr(III) and was poorly crystalline. In microcosms where Cr(VI) was reduced by Desulfovibrio vulgaris strain RCH1, and where hematite or Al-goethite were present as iron sources, there was significant initial loss of Cr(VI) in a pattern consistent with adsorption, and significant Cr(VI) was found in the resulting solids. The properties of the resulting Fe-Cr solids and their behavior upon exposure to birnessite differed significantly. This study provided a systematic investigation of the rates of Cr(VI) reduction by both abiotic minerals and a chromium-reducing bacterium, the properties of the resulting Fe-Cr precipitates, and the susceptibility for reoxidation and remobilization of Cr(VI) upon precipitate exposure to the manganese oxide birnessite. ![]() Reductive immobilization of hexavalent chromium (Cr(VI)), often forming iron-chromium (Fe-Cr) precipitates, is a frequent remediation alternative, yet the relationship between the conditions of precipitate formation, the structural and chemical properties of the precipitates, and the rate and extent of precipitate oxidation by Mn oxides is needed. Potential for Reoxidation of Iron-Chromium Precipitates by Manganese Oxideįe-Cr precipitates formed in groundwater remediation may remain stable only in the presence of active anaerobic microbial reduction. ![]()
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