Influence of EDTA and NTA on heavy metal extraction from sandy-loam contaminated soils

In this study, Pb, Cd, and Zn as heavy metal compounds were extracted from the sandy-loam soil; the soil was prepared synthetically inside the laboratory and also taken from the field by using EDTA and NTA as the chelating agents. By using EDTA 0.1 M to extract the contaminants from the synthetically contaminated soil with single metal concentration of 500 mg/kg, the efficiency of extracting Pb, Cd, and Zn in the first pore volume (PV) were found to be respectively 43.84%, 20.6%, and 43.7%; the corresponding amounts after the third PV for the contaminants were 85.25%, 83.2%, and 69.7%, respectively. The efficiency of NTA 0.1 M in extracting Pb, Cd, and Zn in the first PV was 8.3%, 59.6%, and 14.87%, respectively; after the third PV, the corresponding efficiency reached to 21.8%, 83.56%, and 24.49%, respectively, for the contaminants. At pH 4.5, the efficiency of extracting Pb, and Zn using EDTA and NTA were higher than other levels of pH; and also, the maximum Cd extraction was achieved in pH 7. Considering the samples taken from the field, the extraction efficiency of Pb, Cd, and Zn using EDTA 0.1 M after the fifth PV were 89.42%, 64.21%, and 63.5%, respectively.