Selective sorption of radiocaesium by sorbents based on natural clays

Abstract

Natural clays are widely used in modern technology for the purification of water that has been contaminated by radionuclides, based on the sorption processes. Of all the components to be sorbed, the sorbents based on natural clays are most effective for radiocaesium (R-Cs), due to its selective sorption processes. The current understanding of radiocaesium selective sorption and fixation mechanisms in sorbents based on natural clays is briefly described in this paper. According to generally accepted conceptions, strong R-Cs retention in the clays is essentially controlled by illitic clay minerals. Selective radiocaesium sorption occurs on frayed edge sites (FES), located at the edges of micaceous clay particles.
This work includes a review of papers that demonstrate the development of quantitative measurement methods for R-Cs selective sorption parameters: the selective exchange sites capacity (FES) and radiocaesium interception potential (RIP). RIP is the product of the FES capacity and the selectivity coefficient of caesium in relation to the corresponding competitive ion on FES. The importance of RIP parameter is determined by the fact that you can easily predict the value of the exchangeable distribution coefficient Kd (R-Cs) based on competitive cation concentrations. The bentonite clays modification methods, aimed at increasing the number of highly selective sorption sites with respect to the R-Cs are described.
Based on uniform methodology, RIP (K) measurements allow the performance of comparative assessment of different natural materials in their ability to absorb R-Cs, the prediction of the Kd (R-Cs), as well as the evaluation of the natural clays modification methods’ effectiveness.