Adsorption of uranium on organo-clay complex

Adsorption of uranium from carbonate solution onto organo-clay complex allowed to react with montmorillonite and dodecylammonium chloride, has been investigated by using various amines as a collector. Comparison of primary, secondary, tertiary and quarternary amines showed that the adsorption amount of uranium was greatest for the quarternary amine and least for the primary amine. Among quarternary amines, zephyramine is the best collector. It was found that the adsorption occurs remarkably at the narrow region of pH 6-8, and the pH dependence resulted from the uranyl species such as UO22+, UO2(CO3)22-, UO2(CO3)34-, UO2(OH)3- and so on. Little adsorption occurs at pH<5 and pH>9, because less zephyramine-uranil carbonato complex was formed in both pH ranges. On the other hand in the pH 6-8, uranium is adsorbed largely through hydrophobic interaction between the alkyl-chain of zephyramine-UO2(CO3)n complex (n=2 or 3) and the organo-clay complex. Thus, hydrated alkylammonium-clay complex shows a useful absorbent for alkylamine-tricarbonate complex. (author)