XAFS Investigation of the Interactions of UVI with Secondary Mineralization Products from the Bioreduction of FeIII Oxides

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• 作者：Edward J. O’ ; Loughlin ; Shelly D. Kelly ; Kenneth M. Kemner
• 刊名：Environmental Science & Technology
• 出版年：2010
• 出版时间：March 1, 2010
• 年：2010
• 卷：44
• 期：5
• 页码：1656-1661
• 全文大小：285K
• 年卷期：v.44,no.5(March 1, 2010)
• ISSN：1520-5851

文摘

Biogenic Fe^II phases (magnetite, green rust, siderite, vivianite, etc.) provide a reservoir of reducing capacity in many subsurface environments that may contribute to the reduction of contaminants such as U^VI. We have examined the uptake and reduction of U^VI in the presence of biogenic green rust (BioGR), magnetite (BioMAG), and siderite (BioSID) formed during the reduction of Fe^III oxides by Shewanella putrefaciens CN32. Within 48 h, total solution-phase U^VI concentrations decreased from 500μM to 1.5μM, 392μM, and 472μM in the U-BioGR, U-BioMAG, and U-BioSID systems, respectively. Analysis of the samples by U L_III extended X-ray absorption fine structure spectroscopy (EXAFS) indicated that despite a stoichiometric excess of Fe^II, no more than 6% of U^VI was reduced to U^IV in the U-BioSID system, and no more than 22% of U^VI was reduced in the U-BioMAG system. For comparison, in the U-BioGR system, >99% of U^VI was reduced to U^IV. Uptake of U^VI by BioGR and BioMAG was accompanied by formation of nanoparticulate uraninite. The U EXAFS data for the U-BioSID system were consistent with partial U^VI/U^IV substitution for Fe^II in the surface layer of siderite particles and adsorption of U^IV.