Uptake of cesium and strontium by crystalline silicotitanates from radioactive wastes

Crystalline silicotitanate inorganic ion exchanger, with a sitinakite structure is candidate material for remediation of aqueous nuclear waste streams. The syntheses of crystalline silicotitanate (CST) and Nb-substituted crystalline silcotitanate (Nb-CST) were carried out under hydrothermal conditions and the products were characterized using techniques viz., XRD, SEM/EDS, DTA/TGA, surface area respectively. Batch experiments were carried out to study the kinetics of uptake of Cs-137 and Sr-90, to estimate the decontamination factor (DF) values and distribution coefficients (K (d)) for the above synthesized CST and Nb-CST samples from actual radioactive waste solutions. The DF values for uptake of Cs and Sr by Nb-CST after 24 h of equilibration was 355 and 136 whereas for CST it was found to be 40 and 176 respectively. The K (d) values for uptake of Cs and Sr for Nb-CST after 24 h of equilibration was found to be 35,490 and 13,500 mL/g respectively whereas the K (d) values for uptake of Cs and Sr for CST was found to be 4,025 and 17,525 mL/g respectively. The ion exchange capacity of Nb-CST towards Sr-90 and Cs-137 was estimated to be 11.8 and 3.2 meq/g respectively whereas the ion exchange capacity of CST towards Sr-90 and Cs-137 was estimated to be 14.6 and 4.4 meq/g respectively.