Concentration effects of EDTA and chloride on the retention of trace metals in clays

This study investigates the heavy-metal retention potential of complexing a gents in a clay soil with different constituents. The organic and inorganic effects, respectively, of EDTA and sodium chloride were considered. Kaolin ite and kaolinite mixtures [including kaolinite mixed with silica gel and c alcium carbonate (KS, KC, KSC)] were exposed to two types of trace-metal so lution, namely lead and zinc with increasing amounts of chloride and EDTA c oncentrations. The retention of each mixture was measured. It was demonstra ted that with increasing concentrations of a complexing component such as E DTA, the retention of trace metals significantly decreased in all types of soil model. The results were also verified through SEM and XRD analyses. Mo reover, increases in chloride concentration affected the trace-metal retent ion in kaolinite with a low affinity for adsorption. This retention varied with the soil constituents, cation exchange capacity (CEC), specific surfac e area (SSA) and pH of the soil solution. (C) 2000 Elsevier Science B.V. Al l rights reserved.