Structural Chemistry of Cation-doped Bacteriogenic UO2

Schofield, E., Bernier-Latmani, R., Veeramani, H., Sharp, J.O., Clark, D.L., Conradson, S.D. and Bargar, J.R. (2007) Structural Chemistry of Cation-doped Bacteriogenic UO2. In: Goldschmidt 2007, Cologne, Germany, 19-24 Aug 2007,

Abstract

The chemical stability of bacteriogenic uraninite, “UO2”, is one of the seminal issues governing its success as an in situ immobilization strategy in remediated subsurface locations. Little detail is known about the structure and reactivity of this material, but based on comparison to its closest abiotic analog, UO2+x (0 < x < 0.25), we expect that it is complex and disordered, likely to exhibit non-stoichiometry, and capable of structurally incorporating common ground water cations and U(VI). These subtle changes in mineralogy are expected to substantially impact its stability in ground water. In this study, the product of microbial U(VI) reduction under varying conditions of pH, carbonate and divalent cation concentration (Mg2+, Mn2+, and Ca2+) was investigated. To facilitate x-ray scattering measurements, a gentle aqueous cleaning method was developed to separate the biooxide and organic components without altering the biooxides. The local and long-range atomic structures and nano-scale structures of the wet oxides have been measured using EXAFS, WAXS, SAXS and TEM. The material exhibits a range of particle sizes with a mean around 4 nm. The first oxygen shell is distorted, consistent with a nonstoichiometric composition. Mn2+ and Mg2+ were found to attenuate the particle size of bacteriogenic UO2+x and to be structurally incorporated. These findings suggest that ground water composition can have a pronounced impact on the structure and properties of bacteriogenic uraninte.

• Item Type: Conference Proceedings
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Veeramani, Dr Harish
• Authors: Schofield, E., Bernier-Latmani, R., Veeramani, H., Sharp, J.O., Clark, D.L., Conradson, S.D., and Bargar, J.R.
• College/School: College of Science and Engineering > School of Engineering > Infrastructure and Environment

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