Molecular approach of the uranyl/mineral interfacial phenomena

Abstract

In order to understand, at a molecular level, the mechanisms involved in the interactions between radionuclides and minerals, both thermodynamic and structural investigations, using spectroscopic techniques, are presented. However, the natural clays are rather complex minerals. Therefore, it is first necessary to perform these studies on simple substrates such as single crystal and oxides, and then extrapolate the obtained results on the natural minerals. We examine in this review the sorption processes of the hexavalent uranium onto montmorillonite, TiO 2 (powder and single crystal), silica and alumina as well. The corresponding sorption constants are determined using the results obtained with the following techniques: laser-induced spectrofluorimetry, X-ray photoelectron spectroscopy, second-harmonic generation and X-ray absorption spectroscopy. In addition, for TiO 2 , these results are compared with theoretical calculations using periodic density functional theory, which gives the atom distribution at the interface and the relative energy stabilities of the different surface complexes.