Structure analysis of actinide compounds in solution by X-ray absorption spectroscopy

Actinides with their large number of oxidation states are susceptible to redox conditions, forming different complexes in aqueous solution which may greatly differ by solubility and mobility. These complexes are often difficult to investigate due to their complex species distribution and thermodynamic metastability. Thermodynamic estimation of species distribution may fail for higher actinide concentrations. In such cases X-ray absorption spectroscopy is able to reveal structural parameters that provide information on the solution species. A spectroelectrochemical cell was developed for the study of structure and speciation of actinide complexes in situ by X-ray absorption spectroscopy, while applying and maintaining a constant potential. This equipment allows the investigation of actinide complexes under different redox conditions. An overview about the actual knowledge of actinides coordination in valence states III, IV, V, VI and VII in aqueous solution will be given.