Remediation of Soils Polluted by Heavy Metals using Salts of Organic Acids and Chelating Agents

Various weak organic acids and/or their salts were tested for the remediation of a loam and a sandy clay loam naturally polluted by heavy metals for over three years against two strong synthetic chelating agents (EDTA and DTPA). Among 7 weak organic acids and/or their salts, citrate, tartarate and oxalate were found to effectively remove Cd, Cu, Pb and Zn from the two soils in double extractions, at a wide range of pH. Citrate removed 80 to 99.9% of all four metals within 24 h at pH from 2.3 to 7.5. Tartarate removed 84 to 99.9% of all metals from both soils within 24 h at pH from 2.1 to 6.7. Oxalate alone is not effective in removing metals particularly Pb but with ammonium citrate (1:1 ratio) removed effectively 82, 70, 99.9, and 99.9% for Cd, Pb, Cu and Zn, respectively at pH from 2.6 to 5.8. Zinc met the Quebec A level soil clean-up criteria after two extractions whereas Cu and Pb reached the B level. Probably, two more extractions with these weak organic acids and/or their salts are required to meet ...