THE INFLUENCE OF REDUCTIVE DISSOLUTION OF IRON OXIDES BY S(-II) ON URANIUM MOBILITY


Published: Jan 1, 2010
Keywords:
uranium mobilization reductive dissolution iron mineral transformation redox transitions iron sulfides X-ray absorption spectroscopy
V. G. Alexandratos
T. Behrends
P. Van Cappellen
Abstract

This study investigates possible redox transformations of uranium under Ntransient redox conditions. NSpecific focus lies on the fate of U as reductive dissolution of iron oxyhydroxides by S(-II) is initiated. In batch experiments sulfide was incrementally added to a lepidocrocite suspension containing adsorbed U(VI). The partitioning of uranium was monitored during the progressing transformation of lepidocrocite into FeS. Synchrotron-based X-ray absorption spectroscopy was used to resolve the oxidation state of uranium.Upon addition of sulfide intermediate release of U from the solid to the solution was observed. The mobilization of U was followed by immobilization in later stages. XAS reveals that this immobilization coincides with reduction of NU(VI) to U(IV). Consequently, reduction of U(VI) and precipitation of U(IV) solids, due to a shift from oxic to sulfate reducing conditions is possible. NHowever, kinetic effects might lead to an intermediate mobilization of U that should be considered for the risk assessment of nuclear waste repositories and the remediation of sites, contaminated with radionuclides.

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  • Geochemistry and Ore Deposit Geology
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