U(V) in metal uranates: a combined experimental and theoretical study of MgUO4, CrUO4, and FeUO4

Xiaofeng Guo; Eitan Tiferet; Liang Qi; Jonathan M. Solomon; Antonio Lanzirotti; Matthew Newville; Mark H. Engelhard; Ravi K. Kukkadapu; Di Wu; Eugene S. Ilton; Mark Asta; Stephen R. Sutton; Hongwu Xu; Alexandra Navrotsky

doi:10.1039/C6DT00066E

U(v) in metal uranates: a combined experimental and theoretical study of MgUO₄, CrUO₄, and FeUO₄†

Xiaofeng Guo,

^ab Eitan Tiferet,^bc Liang Qi,^de Jonathan M. Solomon,^d Antonio Lanzirotti,^f Matthew Newville,^f Mark H. Engelhard,^g Ravi K. Kukkadapu,^g Di Wu,^b Eugene S. Ilton,^h Mark Asta,^d Stephen R. Sutton,^fi Hongwu Xu^a and Alexandra Navrotsky*^b

Author affiliations

* Corresponding authors

^a Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
E-mail: anavrotsky@ucdavis.edu

^b Peter A. Rock Thermochemistry Laboratory and Nanomaterials in the Environment, Agriculture and Technology Organized Research Unit, University of California, Davis, CA 95616, USA

^c Nuclear Research Center – Negev Be'er-Sheva 84190, Israel Institution, Israel

^d Department of Materials Science and Engineering, University of California, Berkeley, CA 94720, USA

^e Department of Materials Science and Engineering, University of Michigan, MI 48109, USA

^f Center for Advanced Radiation Sources, University of Chicago, Chicago, Illinois 60637, USA

^g Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99354, USA

^h Pacific Northwest National Laboratory, Richland, WA 99352, USA

ⁱ Department of Geophysical Sciences, University of Chicago, Chicago, Illinois 60637, USA

Abstract

Although pentavalent uranium can exist in aqueous solution, its presence in the solid state is uncommon. Metal monouranates, MgUO₄, CrUO₄ and FeUO₄ were synthesized for detailed structural and energetic investigations. Structural characteristics of these uranates used powder X-ray diffraction, synchrotron X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, and ⁵⁷Fe-Mössbauer spectroscopy. Enthalpies of formation were measured by high temperature oxide melt solution calorimetry. Density functional theory (DFT) calculations provided both structural and energetic information. The measured structural and thermodynamic properties show good consistency with those predicted from DFT. The presence of U⁵⁺ has been solidly confirmed in CrUO₄ and FeUO₄, which are thermodynamically stable compounds, and the origin and stability of U⁵⁺ in the system was elaborated by DFT. The structural and thermodynamic behaviour of U⁵⁺ elucidated in this work is relevant to fundamental actinide redox chemistry and to applications in the nuclear industry and radioactive waste disposal.

Dalton Transactions

U(v) in metal uranates: a combined experimental and theoretical study of MgUO₄, CrUO₄, and FeUO₄†

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U(V) in metal uranates: a combined experimental and theoretical study of MgUO₄, CrUO₄, and FeUO₄

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