Use of Chelating Agents for Remediation of Heavy Metal Contaminated Soil

The efficiency of removing lead (Pb) from a contaminated soil of high clay and silt content was studied in a laboratory investigation where chelating agents were used to extract the lead from the soil. Lead concentrations in the soil ranged from 500 to 10,000 mg/kg. Ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA) were examined for their potential extractive capabilities. Concentrations of the chelating agents examined in this study ranged from 0.01 to 0.10 M. The pH of the suspensions in which the extractions were performed ranged from 4 to 12. Results showed that the removal of lead using NTA and water was pH-dependent, whereas the removal of lead using EDTA was pH-insensitive. For an initial lead concentration of 10,000 mg/kg, the maximum removals of lead using EDTA, NTA, and water (compared with nominal initial Pb concentrations) were 64.2, 19.1, and 5.8%, respectively.