Uranyl uptake on the magnetite (111) surface results in both adsorption of U(VI) and reduction to nanoparticulate UO2 at areas of heterogeneous reactivity.  Reduction to U(IV) is inhibited by the presence of Ca, and the formation of U(VI)-CO3-Ca surface species has been identified by U LIII-edge GI-XAS.  The rate of U sorption and reduction has been determined by batch-flow sorption experiments in combinations with batch-flow GI-XAS and AFM experiments.  The total U sorption loading and Fe released is greater in the absence of Ca.  The trend in Fe release during U sorption was tracked by the AFM experiments and determined by measuring the increase in depth of surface features as the crystal was exposed to the U(VI)-bearing solution, which matched well to the batch-sorption trends.  These results are consistent with the coupling of U(VI) and Fe(II) at the magnetite surface, and the release of Fe(III) upon U reduction.

Reaction products and kinetics of U(VI) sorption and reduction on the magnetite (111) surface

243rd National Meeting (2012)

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