Desorption of cesium from kaolinite and illite using alkylammonium salts

This study addresses Cs+ desorption from a kaolinite (KGa-1b) and an illite (Morris, IL) by quaternary ammonium ions. The Cs+ sorption capacities on the kaolinite and illite were 14 and 24 mmol/kg, respectively. Desorption of Cs+ from Cs+-preloaded kaolinite and illite at different loading levels followed different trends. In general, Cs+ was more readily removed from kaolinite than from illite. The hydrocarbon chain lengths of the alkylammonium ions had strong influences on Cs+ desorption from kaolinite. At the same alkylammonium concentration, the percentage of Cs+ removal from kaolinite increased as the chain length of the alkylammonium ions increased because of a stronger affinity for clay surfaces with a longer chain length. In contrast, initial alkylammonium concentrations bad a greater influence on Cs+ removal from illite than surfactant chain length. As the alkylammonium concentrations increased, the percentage of Cs+ desorption increased. For kaolinite, at the same alkylammonium concentration, a higher percentage of Cs+ desorption was achieved when Cs+ loading was low. As the Cs+ loading on kaolinite increased, the percentage of Cs+ desorption decreased. In contrast, a higher percentage of Cs+ desorption was obtained from illite when Cs+ loading was high. The percentage of Cs+ desorption decreased as the Cs+ loading on illite decreased. For kaolinite and illite with higher Cs+ loading, the percentage of Cs+ removal increased logarithmically with the increase in the ratio of hexadecyltrimethylammonium/Cs+. A minimum value of 30 for this ratio is required to achieve 80% Cs+ removal from kaolinite. (C) 2003 Elsevier B.V. All rights reserved.