APPLICATION OF COMMERCIAL ZEOLITE-13X IN THE TREATMENT OF SIMULATED AND ACTUAL RADIOACTIVE EFFLUENT CONTAINING CESIUM

The removal of Cs+ ions from aqueous solution and radioactive effluent , by ion-exchange with Na ions of indigenously available synthetic zeo lite-13X, has been studied. The zeolite has been characterized with re spect to chemical composition, stability to acid, XRD and IR spectral patterns. Batch studies on the kinetics of the Cs-Na exchange process indicate that at higher Cs concentrations in solution, such as 50 mM a nd 100 mM Cs, 'particle diffusion' is the controlling factor, as infer red from the observed linearity in the Bt-t plots. The linearity is ab sent in case of lower concentrations where the process may be controll ed by 'film diffusion'. The K-d value are of the order of a few thousa nds to a few tens of ml/g, depending on the initial concentration of t he Cs ions. Agitation affected the kinetics in such a way that the tim e required for attainment of equilibrium is reduced from about 48 h in an unstirred solution to 2 h in a thoroughly stirred solution. Equili brium studies, carried out under isonormal solution conditions at two different total (Cs + Na) ionic concentrations, 0.025 N and 0.1 N, res ulted into 'adsorption isotherms' showing replacement of 35% and 50% o f the exchangeable Na+ ions for the two cases, respectively. The colum n studies, conducted with a pure solution of Cs-137 in ordinary water and a 2g ( = 3 ml) column of the zeolite,]ed to a removal of as high a s 99.9% Cs-137. When an actual radioactive waste solution, received fr om the Madras Atomic Power Station, Kalpakkam, and containing predomin antly Cs-137, is passed through a 1g( = 1.5 ml) bed of zeolite-13X, th e per cent breakthrough is found to be less than 4% (96% removal) till the passage of 1000 bed volumes.