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Uranium(V) incorporation mechanisms and stability in Fe(II)/Fe(III) (oxyhydr)oxides

DOI: 10.1021/acs.estlett.7b00348 DOI Help

Authors: Hannah Roberts (The University of Manchester) , Katherine Morris (The University of Manchester) , Gareth Law (The University of Manchester) , J. Frederick W. Mosselmans (Diamond Light Source) , Kristina Kvashnina (The Rossendorf Beamline at ESRF – The European Synchrotron; Helmholtz Zentrum Dresden-Rossendorf (HZDR), Institute of Resource Ecology) , Pieter Bots (The University of Manchester) , Samuel Shaw (The University of Manchester)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Environmental Science & Technology Letters

State: Published (Approved)
Published: September 2017
Diamond Proposal Number(s): 9621 , 10163 , 12767

Open Access Open Access

Abstract: Understanding interactions between radionuclides and mineral phases underpins site environmental clean-up and waste management in the nuclear industry. Transport and fate of radionuclides in many subsurface environments are controlled by adsorption, redox and mineral incorporation processes. Interactions of iron (oxyhydr)oxides with uranium have been extensively studied due to the abundance of uranium as an environmental contaminant and ubiquity of iron (oxyhydr)oxides in engineered and natural environments. Despite this, detailed mechanistic information regarding the incorporation of uranium into Fe(II) bearing magnetite and green rust is sparse. Here, we present a co-precipitation study where U(VI) was reacted with environmentally relevant iron(II/III) (oxyhydr)oxide mineral phases. Based on diffraction, microscopic, dissolution and spectroscopic evidence, we show the reduction of U(VI) to U(V) and stabilisation of the U(V) by incorporation within the near-surface and bulk of the particles during co-precipitation with iron (oxyhydr)oxides. U(V) was stable in both magnetite and green rust structures and incorporated via substitution for octahedrally coordinated Fe in a uranate-like coordination environment. As the Fe(II)/Fe(III) ratio increased, a proportion of U(IV) was also precipitated as surface associated UO2. These novel observations have significant implications for the behaviour of uranium within engineered and natural environments.

Journal Keywords: Uranium; Magnetite; Green Rus; Incorporation; Environmental fate

Subject Areas: Environment, Chemistry, Earth Science
Collaborations: Diamond Manchester

Instruments: B18-Core EXAFS

Other Facilities: ESRF