EXTRACTION OF HEAVY METALS BY PHOSPHATE AND OXALATE FROM A CONTAMINATED SOIL

摘要

Laboratory batch experiments were conducted to study arsenic (As), lead (Pb) as well as, cadmium (Cd),cooper (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 solutions were very significant in extracting As 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 solutions in generals. In overall, the percentages of As and Pb extracted increased with increasing of KH_2PO_4 + 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 extract the maximum amounts from both As and Pb. 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 extracting Cd, Cu and Zn from MW polluted soils.