Biological U(VI) reduction to U(IV) has been touted as a bioremediation strategy to address U(VI) contamination at U.S. DOE sites. A product of the reduction is monomeric U(IV), a biomass-associated U(IV) species lacking intermediate range structure. Besides this characteristic, little is known about the structure of monomeric U(IV). Its importance lies in the observation that it is produced, at least initially, during in situ U(VI) bioremediation. Solute composition was found to control its formation but the mechanism by which solutes impact the product of U(VI) reduction is unknown. In order to better understand the structure, stability and formation process of monomeric U(IV), we have undertaken its extensive characterization using Fourier transform infrared (FTIR) spectroscopy, cryo-electron microscopy, scanning transmission X-ray microscopy, X-ray absorption spectroscopy (XAS) and a chemical extraction method. Results indicate that monomeric U(IV) presents a clear signature for U(IV) associated with phosphate and we propose that it forms in association with phosphate-rich biomolecules at the cell surface.

Formation, structure and stability of monomeric U(IV), a product of microbial U(VI) reduction

243rd National Meeting (2012)

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