Sorption of heavy metals and radionuclides on zeolites and clays

摘要

The sorptin of zinc, strontium, technetium, cadmium, caesium, mercury, lead, plutonium and americium from their queous solutions by natural zeolitic materials from Metaxades (Greece), Nizny Hrabovec (Slovakia), synthetic zeolities Nalsit and Ysit (VURUP, Slovakia) and bentonites from Melos Ishand (Greece) and Jelsovy Potok (Slovakia) was investigated using a batch-type procedure and radiotracer technqiues. The metal uptake and the distribution coefficient (K_d) values determined for the materials of different origin were ocrelated with their mineralogical composition and their gross cation exchange capacity (CEC). Theidentification of specific uptake sites was attempted on the basis of the sorption isotherms and the exchangeable cation content. The experimental results provide information on the suitability of the individual materials for the treatment of radioactive waste and their application as a backfill in ptential nuclear waste repositories. It was found, that the zeolites (natural and synthetic) are very efficient sorbents for caesium. The removal of lead from aqueous solutions by the investigated natural zeolites was almost as effective as the removal of caesium, whereas the materials were less effective for the removal of other heavy metal ions. The sorption of radionuclides (~(239)Pu, ~(241)Am, ~(90)Sr, ~(99)Tc, ~(137)Cs) on zeolities and bentonites was ccorrelated with their Gross Annual Stopping Power (GASP). The comparison of the obtained data indicated, that the Slovak synthetic zeolite NaY shows that best sorption characteristics among the studied materials.