Ca and Sr sorption on Ca-illite experimental study and modelling

Abstract : To ensure the environmental monitoring of nuclear sites, sorption models enabling the prediction of contaminant migration (such as $^{90}$Sr) in soils, sediments and aquifers need to be developed. Recently, a multi-site ion exchanger model has successfully been applied to the sorption of a contaminant on a natural soil under static and dynamic conditions. To use this sorption model for natural environments, sorption data concerning Sr and Ca on the natural clay mineral illite are necessary. Batch experiments performed in this study enabled to collect sorption data of Ca and Sr on Ca-illite. These sorption data were modeled successfully with a multi-site ion exchanger formalism by using four sorption site types and concentrations. The obtained selectivity coefficients were thereafter introduced in the multi-site ion exchanger model to describe the Sr sorption in natural environments.