Eu(III) Sorption on Kaolinite: Experiments and Modeling

The present study was focused on the sorption of Eu(III) onto kaolinite. Two kaolinite samples with different origins and compositions were studied. A high-purity natural sample of kaolinite was used to obtain the sorption behavior: dependence of sorption on the ionic strength, pH, and radionuclide concentrations. It was compared with the data for another kaolinite sample containing admixtures of other clay minerals (illite and smectite). In addition, the effect of cations leaching from clay on the sorption was observed. Collected experimental results allowed to develop of a thermodynamic sorption model of Eu(III) sorption onto kaolinite accounting ion-exchange and surface complexation reaction as well competition with the sorption of Al3+. The model was also successfully tested on the available literature data for other kaolinite samples.