Dalton Transactions
Dalton Transactions View Article Online PAPER View Journal | View Issue U(V) in metal uranates: a combined experimental and theoretical study of MgUO4, CrUO4, and Cite this: Dalton Trans., 2016, 45, 4622 FeUO4† Xiaofeng Guo,a,b Eitan Tiferet,b,c Liang Qi,d,e 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,f,i Hongwu Xua and Alexandra Navrotsky*b 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 5+ Received 6th January 2016, presence of U has been solidly confirmed in CrUO4 and FeUO4, which are thermodynamically stable Accepted 2nd February 2016 compounds, and the origin and stability of U5+ in the system was elaborated by DFT. The structural and DOI: 10.1039/c6dt00066e thermodynamic behaviour of U5+ elucidated in this work is relevant to fundamental actinide redox chem- www.rsc.org/dalton istry and to applications in the nuclear industry and radioactive waste disposal. Introduction chemistry associated with geologic, environmental and techno- logical applications is dominated by U6+ because of the greater 2+ Metal monouranates, MUO4, are of considerable interest due solubility of its related uranyl (UO2 ) ion.
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