Does the Electron Transfer Process Determine the Product of U(VI) Reduction?

Bernier-Latmani, R., Alessi, D., Veeramani, H., Sharp, J. O., Dalla Vecchia, E., Suvorova, E. I., Stubbs, J. E., Lezama- Pacheco, J. S. and Bargar, J. R. (2011) Does the Electron Transfer Process Determine the Product of U(VI) Reduction? In: Goldschmidt 2011, Prague, Czech Republic, 14-19 Aug 2011,

Abstract

The bioremediation of uranium-contaminated sites is based on the amendment of an electron donor to stimulate microbial activity. Typically, Fe(III) and U(VI) serve as electron acceptors for microorganisms with the former supporting microbial growth. However, this biostimulation process may generate competing mechanisms of uranium bioreduction. While direct enzymatic reduction of U(VI) by microbes is a possible route of immobilization of U(IV), Fe(II) produced by the reduction of Fe(III) also is thermodynamically capable of abiotically reducing U(VI). Here we investigate the question of whether different U(IV) products are expected from these various U(VI) reduction processes. Specifically, we consider the reduction of U(VI) via direct enzymatic reduction by both Gram-positive and Gram-negative bacteria, via abiotic reduction by Fe(II)- bearing minerals as well as through a potential combination of these direct and indirect processes in sediment columns. The results indicate that geochemical conditions dictate the product of U(VI) reduction. For example, the same microorganism produced a monomeric sorbed U(IV) complex in the presence of particular solutes but nanoparticles of the mineral uraninite in their absence. A phosphate-reacted magnetite (Fe3O4) suspension produced a similar monomeric U(IV) product while unreacted magnetite produced uraninite. Finally, in studying U(VI) reduction in sediments, both laboratory and field-run columns yielded non-uraninite U(IV), suggesting that in situ geochemical conditions favor monomeric U(IV) formation. This work shows that, while the kinetics of U(VI) reduction have been shown to depend on the reduction mechanism, the end-product of the reduction is largely determined by the geochemical conditions under which the reduction–biotic or abiotic- takes place

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

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