Adsorption of cs-137 and am-241 ions from aqueous solutions on bentonites

Abstract

As materials used for sealing of landfills and removal of inorganic pollutants, bentonites are also potentially useful for the treatment of radionuclides from aqueous solutions. The ability of two coming from different continents bentonites (Wyoming and Karakaya) to take up the radioisotopes Cs-137 and Am-241 has been examined as a function of contact time and pH of the aqueous solutions. The sorption capacity of bentonites was determined as the decontamination factor (DF) and distribution coefficient Kd . It is demonstrated herein that the Wyoming and Karakaya bentonites seem to be effective sorbents for the removal of radionuclide ions from aqueous solutions. The bentonites are characterized by the decontamination factor equal to 50% for cesium ions (Cs(I)) and 33% for americium ions (Am(III)). Additionally, it was observed that an increase in solution pH negatively influenced the removal of ions. The calculations done by Hydra-Medusa Software were performed to create chemical equilibrium diagrams for Cs(I) and Am(III) species. The porous structure of both bentonites was characterized on the basis of determined nitrogen low-temperature adsorption-de-sorption isotherms. The surface characteristics were analyzed with the use of scanning electron microscope photographs and the chemical composition was determined by energy-dispersive X-ray spectroscopy analysis. The properties of the sorbent surfaces are important for their usefulness in radionuclide removal. The results of this study indicate the potential application of natural sorbents in treating radioactive effluents. Both used bentonites are readily available in large quantities.