Sorption and desorption of radioiodine on organo-clays

Distribution ratios (RD-values) for sorption and desorption of radioiodine (125I) were determined on vermiculite and cretaceous clay treated with the quaternary alkylammonium ion hexadecylpyridinium (HDPY+). Constantly high RD-values (∝ 5,000) were obtained with bidistilled water at I--ion loadings of up to about 10-1 mmol x g-1. At higher iodide concentrations the sorption decreased sharply. The chemical composition of the liquid phase influenced the sorption behaviour of radioiodine significantly. Dialysis and ion exchange tests suggest that radioiodine exhibits a limited tendency to react with the alkylammonium ions in absence of the clay minerals. The treatment with HDPY+ causes an increased expansion of the basal spacing. (orig.)