SORPTION OF NICKEL AND COBALT ON A SIZE-FRACTION OF UNCONSOLIDATED GLACIOFLUVIAL DEPOSITS AND ON CLAY-MINERALS

In earlier studies we investigated the sorption behaviour of cesium, b arium and strontium on size fractions of glaciofluvial materials and o n the clay minerals montmorillonite, illite and chlorite. Here, we rep ort on sorption and desorption experiments with nickel and cobalt in s ynthetic groundwater on the < 32 mu m size-fraction of a glaciofluvial deposit, on the clay minerals montimorillonite and illite, and on syn thetic SiO2 and CaCO3. In general, sorption and desorption equilibrium is not reached for nickel and cobalt, which is in striking contrast t o the behaviour observed for strontium and barium. A significant incre ase in the distribution ratios was observed for nickel and cobalt up t o sorption times of 182 and 56 days, respectively. In most cases, the sorption process was largely irreversible. The sorptive power of the < 32 mu m materials with artificially changed mineralogies is considera bly reduced as compared to that of the < 32 mu m material with the ori ginal mineralogical composition, i. e., during the removal of the carb onates a significant decrease in the sorptive power occurred. A compar ison of the sorption behaviour of nickel and cobalt with that of cesiu m, strontium and barium is also shown.