Sorption of Zinc on Na-Bentonite

The sorption of Zn radionuclides into Na-bentonite as candidate for buffer material in the radioactive waste disposal system has been performed. Zinc was used for this study as a model for bivalence elements. Batch experiment was adopted to study sorption isotherm, influence of pH, carbonate and EDTA. In a simple media, pure water, Zn was retained with a high affinity. Freundlich sorption isotherm was shown, with high coefficient distribution and sorption capacities. It could be interpreted that the high sorption of Zn related to the contribution of Zn(OH)2(s) precipitation. This is shown on the increasing of Kd value with the increasing of pH. The presence of carbonate in solution increased distribution coefficient, that also could be contributed by the ZnCO3(s) precipitation. While the presence of EDTA, decrease the distribution coefficient value. Speciation models was presented in this paper, in order to explain better on Zn sorption in bentonite, in difference condition. (author)