Structure, Composition, Size and Reactivity of Biogenic Nano-Uraninite

Bargar, J. R., Bernier-Latmani, R., Giammar, D. E., Mehta, A., Schofield, E., Sharp, J. O., Suvorova, E. I., Ulrich, K.-U. and Veeramani, H. (2009) Structure, Composition, Size and Reactivity of Biogenic Nano-Uraninite. In: Goldschmidt 2009, Davos, Switzerland, 21-26 June 2009, A87.

Abstract

Nanoparticulate biogenic uraninite is formed from the bacterial reduction of uranium(VI) and is of great importance to planned bioremediation strategies at uranium-contaminated sites in the U.S. The primary barrier to uranium release from this material in the subsurface is the material itself. A better understanding the chemical and physical properties of the material is therefore critical. Biogenic uraninite is fascinating from the standpoint that particle size (typically 2 to 5 nm), molecular-scale structure, and unit cell composition all have been posited to strongly moderate its stability in the subsurface. In particular, there has been concern that the nanosize of this material induces strain that destabilizes the material. We have used EXAFS, in situ synchrotron powder diffraction, TEM, XPS, and continuous-flow dissolution measurements to assess the impacts of size, structure, and composition on the stability of biogenic uraninite. In the absence of cation dopants, biogenic uraninite was found to be unstrained and structurally homologous to stoichiometric UO2, and this similarity persists in the solubility and kinetics of this material. These results suggest that size does not intrinsically impact reactivity. In contrast, unit cell composition, and in particular the presence of structural impurity cations, was found to have a pronounced impact on stability (as predicted from sedimentary uraninites), as well as on structure and particle size. These findings indicate that ground water solute chemistry is an important moderator of biogenic uraninite stability and raise intriguing questions about the role of size in the reactivity of nanoparticles in aquatic environments.

• Item Type: Conference Proceedings
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Veeramani, Dr Harish
• Authors: Bargar, J. R., Bernier-Latmani, R., Giammar, D. E., Mehta, A., Schofield, E., Sharp, J. O., Suvorova, E. I., Ulrich, K.-U., and Veeramani, H.
• College/School: College of Science and Engineering > School of Engineering > Infrastructure and Environment

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