Removal of trace metals from contaminated soils using EDTA incorporating resin trapping techniques

A series of experiments was conducted using two urban soils from Montreal contaminated with high levels of trace metals. The experiments were aimed at removing and recuperating trace metals from the contaminated soils using ethylene diamine tetraacetic acid (EDTA) and HCl. Acid washing with 1×10−3 M HCl was found to be ineffective in removing trace metals from the soils. In contrast, the extraction with EDTA is a promising approach; at a low concentration it removed large amounts of metals. In one soil we were able to decrease Cd concentration from 6.2 to 1.4 mg kg−1; the corresponding results for Cu were 700 to 330 mg kg−1, Pb 800 to 410 mg kg−1, and Zn 2600 to 431 mg kg−1 after 12 times 24-h extraction with 2.74×10−3 M EDTA. These represent decreases of 76% for Cd, 53% for Cu, 49% for Pb, and 84% for Zn. In a second, less contaminated soil, the Cu concentration was reduced from 130 to 85 mg kg−1 after three 24-h extractions with 2.74×10−3 M EDTA. We have also developed a procedure to remove metal–EDTA complexes from the leachates using an anion exchange resin. With this technique we were able to trap up to 99% of the Cd, Cu, and Zn, and 93% of the Pb in the soil leachates.