A zirconia-pillared and an alumina-pillared montmorillonite clay were found to exhibit high K(d)S for trace levels of cesium (2.5 ppb) in the presence of high concentrations of Ca2+, Mg2+, and Na+ ions with distribution coefficients (K(d)S) for 137Cs exceeding 1 X 105 mL/g over a wide range of competing ion concentrations. An excess of K+ ions, however, caused a dramatic reduction in the Cs K(d)S for both of the materials. These results were in contrast to the parent montmorillonite which exhibited far lower K(d)S for 137Cs, particularly in the presence of high concentrations of Mg2+ and Ca2+. Batch tests in simulated groundwaters showed that both pillared clays efficiently removed 137Cs from solution, with the best K(d)S being approximately 8.5 X 105 mL/g in a potassium-free groundwater. The materials performed less well in a groundwater with a high potassium concentration, but still gave K(d)S similar to commercially available zeolites. The rate of 137Cs uptake was found to be rapid with both the alumina- and zirconia-pillared clays extracting > 90% of the 137Cs from a 0.1 M NaNO3 solution within 5 minutes.
