Sorption of Am(III) onto 6-Line-Ferrihydrite and its alteration products: Investigation by EXAFS

For the long-term performance assessment of nuclear waste repositories, knowledge concerning the interactions of actinide ions with mineral surfaces is imperative. The mobility of released radionuclides is strongly dependent on the sorption/desorption processes at mineral surfaces and their incorporation into the mineral frame. Hydrous iron oxides (ferrihydrite) are globally of great importance in the environment. Upon heating pure ferrihydrite converts to crystalline goethite and hematite. In the presence of di- or trivalent metal ions the transformation is affected leading to the promotion of one crystal formation over the other and incorporation of these ions. This Study deals with the question if released Am(III) can be immobilized by sorption onto 6-line-ferrihydrite. Moreover it is studied what happens if ferrihydrite transforms to a more crystalline phase.