Cation exchange applications of synthetic tobermorite for the immobilization and solidification of cesium and strontium in cement matrix

Abstract

Immobilization and solidification of hazardous cations like Cs137 and Sr90 are required while handling the radioactive waste of nuclear power plants. Efforts are on to find a fail proof method of safe disposal of nuclear wastes. In this context, various materials like borosilicate glass, zeolites, cements and synthetic rocks have been tried by several workers. This communication deals with the synthesis, characterization, cesium uptake capacity and leaching behaviour of synthetic alumina-substituted calcium silicate hydroxy hydrate, which are close to that obtained for the natural mineral, 11 angstrom tobermorite. The synthetic mineral show cation selectivity for Cs+ in presence of 500-1000 times concentrated solutions of Na+, K+, Mg2+, Ca2+, Ba2+ and Sr2+. Although the ordinary portland cement (OPC) which is often used in waste management operations alone holds negligible amounts of Cs+ and Sr2+, the addition of alumina-substituted tobermorite to OPC enhances the retention power of cement matrix by drastically lowering the leach rate of cations.