This research was carried out to determine the possibility of decontaminating two soil samples (sandy loam and silty clay loam), contaminated with zinc, lead, and cadmium (with concentrations as high as 500 to 1000 mg kg-1 of soil), using two chelating agents (EDTA and NTA). All experiments were carried out in 10.5 x 13.5 cm columns (leaching cells). Treatments were done at various pHs and soil densities. Results showed increased removal of metals at acidic pH for both chelating agents. Soil treatment with EDTA was effective when the initial metal concentration was less, except for Pb emoval for which an initial high concentration resulted in more removal by EDTA. When the Cd concentration was increased from 500 to 1000 mg kg-1, the removal efficiency by NTA was the same. But when the Pb and Zn concentrations were increased from 500 to 1000 mg kg-1, the removal efficiency by NTA for Pb and Zn increased.
Removal efficiencies determined for the NTA treatment for soil samples with a density of 1.9 g cm-3 were 33.8, 23.7, 19.9% for Pb, Zn, and Cd, respectively. But when the metals were mixed, the efficiency of removal from the soil reached 42.5, 23.0, and 70.0%, respectively. EDTA treatment in soils with mixed metals was better than NTA treatment, and removal efficiencies with EDTA for these metals were 88.9, 75.0, and 80.0%, respectively.