Contamination of a calcareous soil by battery industry wastes. II. Treatment

This study evaluated treatment of a soil that was heavily contaminated by the disposal of waste from a Pb battery industry. The site was of interest from a remediation point of view, since the soil contained substantial quantities of calcareous material. Treatment involved extraction of the metals from the soil using aqueous solutions of EDTA (ethylenediaminetetraacetic acid). The impact of pH, EDTA concentration, and reaction time on the extent of leaching of Pb was evaluated. The leaching efficiency was found to be independent of pH over a range of values from 4 to 8.2. The leaching of Pb and Ca increased with EDTA concentration with 99% of the Pb removed at an EDTA dosage of 3.2 M/kg soil. The removal efficiencies of Cu, Cr, Cd, Ni, and Zn were consistently less than that of Pb; however, with their lower initial concentrations, acceptable levels were achieved for all metals except Cd. A two-reaction model was successfully used to describe the results of a batch extraction test. The results indicated relatively rapid extraction kinetics for a substantial fraction of the Pb contamination. Treatment of the liquid effluent from the soil treatment process with nano-level filtration indicated that both the EDTA and Pb were consistently removed at efficiencies greater than 98%. The nano-filtration process was not affected by pH over a range of values from 4.8 to 7.6