SORPTION AND DESORPTION OF COBALT BY SOILS AND SOIL COMPONENTS

The sorption-desorption of cobalt was studied on different soils of India and different components of soil at cobalt concentrations within the range 0.5 - 8 mug ml-1 with 0.01M CaCl2 as background electrolyte at pH 6.5. The maximum adsorption of Co occurs at pH 6.5 and almost complete sorption occurs within 48 h. The sorption was maximum with ferromanganese oxide followed by organic materials. The order of desorption was clay minerals > humic acids > ferro manganese oxide. The sorption isotherms for natural soils at low site coverages were linear and sorption on different soils was studied. The studies also showed that cobalt sorption in natural soil is largely controlled by ferro-manganese oxide.