Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

2 Publications
A Comparative Study of U(V)O2+- and U(VI)O22+-Carbonato Complexes in Aqueous Solution
Ikeda, A.; Hennig, C.; Rossberg, A.; Scheinost, A.; Bernhard, G.; Mizuoka, K.; Ikeda, Y.;
The properties of pentavalent uranium have not been well understood yet, although a large number of studies have been performed and reported concerning the uranium chemistry up to now, because it is very unstable due to its disproportionation reaction to U(IV) and U(VI). At the moment, the uranyl tricarbonate complex, [UO2(CO3)3]n-, is the only known species that can be stabilized as U(V) in aqueous solution. In order to elucidate the properties of this complex in detail, we performed electrochemical (cyclic voltammetry) and spectroscopic (UV-visible absorption and XAFS) measurement.
From the electrochemical study, it was found that the UVO2+-carbonate complex was stable only in the limited concentration range of 0.8 M < [Na2CO3] < 1.4 M, and a Pt- or Au working electrode is more efficient to reduce UVIO22+ to UVO2+ than a glassy carbon electrode. Therefore, the UVO2+ samples for XAFS measurements were prepared in 1.4 M-Na2CO3 solution by using a Pt-mesh working electrode. The UVO2+ solution was transferred to a glass cuvette that was completely sealed by hot melting to avoid the possibility of any O2-penetration in the cuvette during sample transportation and measurement. The results of XAFS measurement indicated that both uranyl(V) and uranyl(VI) ions form the tricarbonate complex, [UO2(CO3)3]n- (n = 5 for uranyl(V) and 4 for uranyl(VI)). The coordination occurs in a bidentate manner and, in general, all bond lengths for the uranyl(V) complex were longer than those for the uranyl(VI) complex. Additionally, a chemical shift was also observed in the U LI- and LIII-XANES spectra.
  • Poster
    Actinide XAS 2006, 18.-20.09.2006, Karlsruhe, Germany
  • Contribution to proceedings
    Actinide XAS 2006, 18.-20.09.2006, Karlsruhe, Germany
    Speciation Techniques and Facilities for Radioactive Materials at Synchrotron Light Sources: OECD, ISBN 978-92-64-99006-7, 225-231

Publ.-Id: 8792 - Permalink