title: Reduced Uranium Phases Produced from Anaerobic Reaction with Nanoscale Zerovalent Iron.
abstract: Nanoscale zerovalent iron (nZVI) has shown potential to be an effective remediation agent for uranium-contaminated subsurface environments, however, the nature of the reaction products and their formation kinetics have not been fully elucidated over a range of environmentally relevant conditions. In this study, the oxygen-free reaction of U(VI) with varying quantities of nZVI was examined at pH 7 in the presence of both calcium and carbonate using a combination of X-ray absorption spectroscopy, X-ray diffraction and transmission electron microscopy. It was observed that the structure of the reduced U solid phases was time dependent and largely influenced by the ratio of nZVI to U in the system. At the highest U:Fe molar ratio examined (1:4), nanoscale uraninite (UO2) was predominantly formed within 1 day of reaction. At lower U:Fe molar ratios (1:21), evidence was obtained for the formation of sorbed U(IV) and U(V) surface complexes which slowly transformed to UO2 nanoparticles that were stable for up to 1 year of anaerobic incubation. After 8 days of reaction at the lowest U:Fe molar ratio examined (1:110), sorbed U(IV) was still the major form of U associated with the solid phase. Regardless of the U:Fe molar ratio, the anaerobic corrosion of nZVI resulted in the slow formation of micron-sized fibrous chukanovite (Fe2(OH)2CO3) particles.
authors: UNSW Water Research Centre, School of Civil and Environmental Engineering, UNSW Australia , Sydney, New South Wales 2052, Australia.
authors: Sergey
authors: S
authors: Tsarev
authors: UNSW Water Research Centre, School of Civil and Environmental Engineering, UNSW Australia , Sydney, New South Wales 2052, Australia.
authors: Richard N
authors: RN
authors: Collins
authors: Centre for Organic Electronics, University of Newcastle , Callaghan, New South Wales 2038, Australia.
authors: Adam
authors: A
authors: Fahy
authors: UNSW Water Research Centre, School of Civil and Environmental Engineering, UNSW Australia , Sydney, New South Wales 2052, Australia.
authors: T David
authors: TD
authors: Waite
mesh_terms: D000693:Anaerobiosis; D002254:Carbonates / Q000737:chemistry; D018360:Crystallography, X-Ray; D004777:Environment; D007501:Iron / Q000737:chemistry*; D016018:Least-Squares Analysis; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D017711:Nonlinear Dynamics; D010084:Oxidation-Reduction; D014501:Uranium / Q000737:chemistry* / Q000302:isolation & purification; D056928:X-Ray Absorption Spectroscopy
chemical_list: D002254:Carbonates; D014501:Uranium; D007501:Iron