Adsorption of cadmium to kaolinite in the presence of organic material

Kaolinite was equilibrated with Cd and with varying amounts of the individual compounds: EDTA, NTA, alginic acid, and humic acid. In experiments in which the Cd and kaolinite concentrations were held constant, and the ligand concentration allowed to vary, conditions under which ligand enhanced and inhibited Cd association with the solid phase were noted. Further experiments at constant Cd: ligand confirmed that, for alginic acid and humic acid, enhancement of uptake occurred, while EDTA diminished uptake. These results were compared with the adsorption of ligand by clay in the absence of organic, and it is suggested that the enhancement of uptake is due to the formation of an adsorbed organic layer on the clay serving as a solid phase ligand.