Ion-exchange and sorption kinetics of cesium and strontium in soils

The characteristics of sorption kinetics of cesium and strontium were studied via the batch method for some varieties of important crude soils in Taiwan, i.e. sorption mechanism and intraparticle diffusion coefficients. Ion-exchange is the dominant reaction of Cs and Sr sorption for both soils chosen. In this study, the amount of exchanged cations was significantly affected by the mineral composition of soil. Experimental results indicated that monovalent cations were more exchangeable for Cs sorption and divalent cations were more exchangeable for Sr sorption on both soils. The rate limiting processes of Cs and Sr sorption reaction on chosen soils were film diffusion-controlled. The film diffusion coefficients of Cs+ (DFCs+) sorption on both soils were larger than those of strontium (DFsr2+), in addition, the ratio of DFCs+/DFSr2+ is approximately equal to 4. The value revealed that the influence of ion charge on film diffusion is significant, and the film diffusion coefficient increases as the nuclide charge decreases.