Enhancement of Heavy Metals Release from Mining Contaminated Soils

Laboratory batch experiments were conducted to study arsenic (As), lead (Pb) as well as cadmium (Cd), coper (Cu), and zinc (Zn) removal from arsenic lead mining wastes (MW) contaminated site using  phosphate and/or oxalate acid EDTA solutions . Soils used in this study were Sultan silt loam soil (Aquandic Xerochrept). The results indicate that Phosphate and/or oxalate acid EDTA solution were very significant in extracting arsenic from MW polluted soils. The percentage of As extracted ranged from 3.8 to 38.8% from the total amount in soil. The oxalate acid and EDTA extraction solution extract less As than phosphate solution in general.  Overall, the percentage of As and Pb released increased with increasing of KH₂PO₄ + EDTA and/or oxalate acid + EDTA.  A higher amount of  Pb was extracted with 10 mM of oxalate acid in EDTA solutions. Combination of EDTA and oxalate acid seemed to extract a higher amount of  3304.4 mg kg^-1 and 51.2 mg kg^-1form both As and Pb respectively. Compared to As and Pb, much smaller amounts from Cd, Cu and Zn were generally extracted,  indicating that phosphate  and oxalate are not efficient  in releasing Cd, Cu and Zn from MW polluted soils.