Uranyl(VI) complexes with alpha-substituted carboxylic acids in aqueous solution


Uranyl(VI) complexes with alpha-substituted carboxylic acids in aqueous solution

Moll, H.; Geipel, G.; Reich, T.; Bernhard, G.; Fanghänel, T.; Grenthe, I.

Alpha substituted carboxylic acids are present as degradation products of wood in nature and in repositories for low-level radioactive waste. Such substances find extensive application in separation processes of various types, i.e., group separations of 4f and 5f elements. Their interaction with radionuclides was investigated in the pH range 3 to 5 mainly by potentiometry and NMR techniques. Whereas information on their structural and spectroscopic properties are rare.

The complex formation in the binary uranium(VI)-glycolate, -alpha-hydoxyisobutyrate, -alpha-aminoisobutyrate systems in 1.0 M NaClO4 medium was investigated by means of UV-vis and TRLFS. From spectroscopic investigations by UV-vis, single component absorption spectra are suggested and extinction coefficients calculated. An increase in absorption and a red shift of the spectra, 5 nm compared to the free UO22+, are indicating the interaction of UO22+ and a-substituted carboxylic acids already at pH 2. 1:1 complexes are dominating the uranyl speciation in the glycolate, alpha-hydoxyisobutyrate, and alpha-aminoisobutyrate system at pH 2 and 3, respectively. The formation constant of the 1:2 complex of uranyl with alpha-aminoisobutyric acid is reported for the first time at pH 4. A variety of techniques, such as XRD, XAS, TRLFS, and IR, were applied to explore the structure of the main species in solution and in solid state.

This work was supported by the European Union under contract number: HPMF-CT-1999-00342.

Keywords: Uranium(VI); Complex formation; Alpha-substituted carboxylic acids

  • Lecture (Conference)
    MIGRATION '01, 8th International Conference on Chemistry and Migration Behavior of Actinides and Fission Products in the Geosphere Bregenz, Austria September 16 - 21, 2001
  • Radiochimica Acta 91, 11-20 (2003)

Permalink: https://www.hzdr.de/publications/Publ-3763
Publ.-Id: 3763