Non-Uraninite Products for Microbial U(VI) Reduction

Bernier-Latmani, R. et al. (2010) Non-Uraninite Products for Microbial U(VI) Reduction. In: Goldschmidt 2010, Knoxville, TN USA, 13-18 June 2010,

Abstract

The microbially-mediated reduction of U (VI) is a potential in situ strategy for the remediation of uraniumcontaminated sites. The product of this reduction is often thought to be the highly insoluble mineral uraninite (UO2). While this product is dominant under certain conditions, recent work has shown that other species of U (IV) are likely to be involved in uranium immobilization. Here, we present work investigating the product of U (VI) reduction by three bacteria – Shewanella oneidensis MR-1, Desulfotomaculum reducens and Clostridium acetobutylicum- under various geochemical conditions using X-ray absorption spectroscopy (XAS) and high-resolution transmission electron microscopy (HRTEM). Results for these three organisms show that at higher ionic strength, the product of microbial U (VI) reduction is primarily a U (IV) species sorbed to the bacterial biomass. In contrast, in incubations for which reduction occurs at low ionic strength, the same bacterium yields uraninite. The structure of the sorbed U (IV) species is unknown but Energy Dispersive X-ray (EDS) analysis reveals consistent association of U (IV) with phosphorus, suggesting that phosphato groups may be the associated with U (IV). Additionally, HRTEM suggests the presence of other mineral phases such as a ningyoite-like mineral (CaU (PO4)2) and a U (IV) phosphate phase U2O (PO4)2. These two minerals were not detected by XAS, suggesting their presence at lower ratios of total species (<20%). Our study suggests that the products of microbial U (VI) reduction can vary considerably as a function of in situ geochemical conditions. The stability of these products with respect to oxidation may also deviate significantly from that expected for uraninite.

• Item Type: Conference Proceedings
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Veeramani, Dr Harish
• Authors: Bernier-Latmani, R., Vecchia, E. D., Junier, P., Lezama, J., Veeramani, H., Suvorova, E. I., Bargar, J. R., Alessi, D. A., Sharp, J. O., Wiggington, N. S., and Stubbs, J. E.
• College/School: College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering

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