Study of the kinetics and mechanism of Sr²⁺ sorption by clinoptilolite

The parameters of kinetics of Sr²⁺ sorption by natural clinoptilolite were investigated. The overall rate constants were determined by application of pseudo-first and pseudo-second order kinetic models. The actual sorption mechanism was studied by application of both intraparticle and surface film diffusion models. The application of Rietveld structure refinement shows the preferable sites of strontium ion exchange in the clinoptilolite structure and their diffusion through cationic sites with time, as well as indicates the positions occupied by Sr²⁺ ions at the start of the exchange process and the positions where Sr²⁺ accumulates in subsequent ion exchange stages. (author)