Adsorption characteristics of cesium on the clay minerals: Structural change under wetting and drying condition

The fate and transport of cesium (Cs ⁺ ) is strongly related to the presence of clay minerals in soils, and their weathering due to natural cycles of wetting and drying. In this study, the adsorption characteristics of Cs ⁺ under repeated wetting and drying conditions were investigated using the 1:1 lattice clay mineral, kaolinite, the non-expanding 2:1 lattice clay mineral, illite, and the expanding 2:1 lattice clay minerals, hydrobiotite and montmorillonite. Unlike the cation exchange capacity of clay minerals (montmorillonite > hydrobiotite > illite > kaolinite), the amount of Cs ⁺ adsorbed followed the order of hydrobiotite > montmorillonite > illite > kaolinite. The expanding 2:1 lattice clay minerals (hydrobiotite and montmorillonite) displayed a fixed d-spacing when Cs ⁺ was adsorbed and dried, after which they had a structure similar to that of illite. The desorption efficiency of Cs ⁺ in illite and montmorillonite also was lowered after drying at 80 °C. Desorption efficiencies of Cs ⁺ in clay minerals were in the order of kaolinite > illite > montmorillonite > hydrobiotite. Therefore, there are differences on desorption efficiencies of Cs according to clay minerals due to each clay mineral structure and characteristics.