title: Reduction of U(VI) by Fe(II) during the Fe(II)-accelerated transformation of ferrihydrite.
abstract: X-ray absorption spectroscopy has been used to study the reduction of adsorbed U(VI) during the Fe(II)-accelerated transformation of ferrihydrite to goethite. The fate of U(VI) was examined across a variety of pH values and Fe(II) concentrations, with results suggesting that, in all cases, it was reduced over the course of the Fe(III) phase transformation to a U(V) species incorporated in goethite. A positive correlation between U(VI) reduction and ferrihydrite transformation rate constants implies that U(VI) reduction was driven by the production of goethite under the conditions used in these studies. This interpretation was supported by additional experimental evidence that demonstrated the (fast) reduction of U(VI) to U(V) by Fe(II) in the presence of goethite only. Theoretical redox potential calculations clearly indicate that the reduction of U(VI) by Fe(II) in the presence of goethite is thermodynamically favorable. In contrast, reduction of U(VI) by Fe(II) in the presence of ferrihydrite is largely thermodynamically unfavorable within the range of conditions examined in this study.
authors.affiliation: School of Civil and Environmental Engineering, University of New South Wales , Sydney, NSW 2052, Australia.
authors.forename: Daniel D
authors.initials: DD
authors.lastname: Boland
authors.forename: Richard N
authors.initials: RN
authors.lastname: Collins
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Glover
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Payne
authors.forename: T David
authors.initials: TD
authors.lastname: Waite
mesh_terms: D000327:Adsorption; D005290:Ferric Compounds / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D058085:Iron Compounds / Q000737:chemistry*; D008903:Minerals / Q000737:chemistry*; D010084:Oxidation-Reduction; D013816:Thermodynamics; D014501:Uranium / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D005290:Ferric Compounds; D058085:Iron Compounds; D008903:Minerals; C094886:goethite; D014501:Uranium; C092844:ferric oxyhydroxide; D007501:Iron