Zn sorption on Ca-illite and Ca-smectite: experiment and modelling

Abstract : To predict Zn behaviour in soil, the retention properties of clay minerals plays a relevant role. In a continental environment Ca is the main cation in solution. Soil reactivity may be reduced to sorption properties of illite and smectite towards Zn and Ca, major clay minerals in soil components. With this assumption, a multi-site ion exchanger model has successfully been applied to the Zn sorption on Ca-illite and Ca-smectite. New batch experiments performed in this study enabled to collect sorption data for Zn on Ca-illite by concentration and pH isotherms. Zn sorption reversibility was then verified. These sorption data were modelled successfully with a multi-site ion exchanger formalism by using four sorption site types. Zn sorption isotherm on smectite were retrieved from literature and interpreted following the MSIE formalism The obtained selectivity coefficients may be thereafter put into ion exchange models to describe the Zn sorption in natural environments.