vendredi 8 mars 2013 à 11:00
Amphi G. Besse
The chemistry of actinides in the environment is largely determined by their interactions in natural waters and with mineral surfaces. In my research I study both problems by performing quantum mechanical calculations on suitable models.
To describe uranyl complexation by humic substances, all-electron relativistic density functional calculations were carried out on various solvated uranyl complexes with small ligands representing various functional groups. Aliphatic and phenolic alcohols and alcoholates, N-, sulfo-containing ligands were examined. The results support experiments that suggest a contribution of OH groups to uranyl complexation by humic acids, however only minor (or no at all) contribution from sulfo- or N- functional groups.
Uranyl adsorption on bare and solvated surfaces of the clay minerals kaolinite and pyrophyllite-type (beidellite, montmorillonite models) were examined by plane-wave based density functional calculations on periodic supercell models. Surface solvation was approximated by a monolayer of water. The following questions were addressed in my study: (i) what type of surfaces, basal or edge, are preferred for uranyl adsorption, (ii) what type of adsorption sites and which surface groups are mainly involved in adsorption, (iii) how the substitutions in clays structures affect the adsorption?