Ion exchange of Cs+ and Sr2+ by natural clinoptilolite from bi-cationic solutions and XRD control of their structural positioning

Clinoptilolite from Bulgaria was tested for uptake towards Cs+ and Sr2+ from bi-cationic solutions using batch technique. Contact time and cation concentrations were investigated, revealing minor difference in Cs+ sorption from single and mixed solutions but clear difference in Sr2+ uptake. Kinetic data were fit with pseudo-second-order kinetic model. The Langmuir isotherm model provided best description of equilibrium ion-exchange data [qmax (mg/g) is 122.7 for Cs+ and 21.50 for Sr2+]. Desorption experiments show that cesium and strontium ions are retained strongly by clinoptilolite. Rietveld structure refinement showed that approximately four Cs+ ions were exchanged versus one Sr2+ ion in clinoptilolite.