Study of Pu(IV) and Am(III) sorption to clay minerals: laboratory experiments and modeling

Abstract

Sorption of Pu(IV) and Am(III) to natural clay from a mixture of synthetic rainwater — cement water was studied by batch and sequential extraction experiments as a function of pH and ionic strength These experiments were intended to simulate the effect of cement dissolution, causing the release of K + , Ca 2+ and other cations from solidified radioactive waste into the aqueous phass. The results indicated a complex sorption behavior of the elements studied. It was found that iron oxides play an important role in the uptake of Pu(IV), whereas ion exchange and CaCO 3 are mainly responsible for the binding of Am(III) on the clay. Simplified sorption experiments were conducted with clay minerals and iron oxides, using 0.01 and 0.1 mol/L NaNO 3 as background electrolyte under an Ar atmosphere, for a better understanding of the sorption mechanisms. The experimental data were interpreted using the combination of surface complexation and ion-exchange models.