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SummaryThe sorption behaviour of Ba

The adsorption characteristics of montmorillonite and zeolite minerals and their mixtures for Sr removal have been studied by means of a radiotracer technique using the 90Sr isotope. Experimentally measured distribution coefficients for both single and binary adsorbent systems are in agreement with mathematically calculated values. Adsorption capacities for Sr calculated from Dubinin−Radushkevich isotherm parameters increase with increasing zeolite fraction in binary mixtures, whereas they decrease in the presence of NaCl with respect to pure SrCl2 solutions. Thermodynamic parameters have been estimated from the temperature dependency of the adsorption equilibrium constants evaluated from the selectivity coefficients in brines. Results show that Sr adsorption is an endothermic process, but the spontaneity of adsorption increases with increasing zeolite fraction and temperature. A site distribution function has been mathematically calculated by using the Freundlich isotherm parameters, which gives valuable information about the affinity of exchange sites on the adsorbents for binary exchange between Sr and Na.

The cesium ion adsorption by Turkish clays, i.e., bentonite, zeolite, sepiolite, and kaolinite, was investigated as a function of Cs 1 concentration, pH, time, and temperature using the Cs-137 radiotracer method. The analysis of some major and minor components of clays was performed with ED-XRF. Bentonite was shown to exhibit the highest capacity and sorption affinity toward Cs. The best fits for adsorption isotherms were with Freundlich and D-R models. The second order rate constant of cesium sorption was highest for kaolinite among the clays. Cesium adsorption proceeded essentially by ion exchange and partly by specific adsorption mechanisms. The results showed that especially bentonite and zeolite can be used as effective barrier materials for sorptive hindrance of an expanding Cs radioisotope plume.

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