[Research on the effect and technique of remediation for multi-metal contaminated tailing soils]

Soil samples were collected from compound polluted tailings to analyze the contents of total heavy metals and their speciation in the soil. Laboratory batch tests were conducted to examine the effects of distilled water and different concentrations of oxalic acid, citric acid, acetic acid, HNO3 and EDTA on the removal of heavy metals from the polluted soils. The suitable eluent and its optimal conditions including liquid to soil ratio, reaction time and washing number were also optimized, and the total toxicity reduction index was proposed to evaluate the effect of the eluent on the remediation of polluted soil. The results showed that Cd and Pb were the most abundant heavy metals in the soil, reaching 52.2 mg x kg(-1) and 4836.5 m x kg(-1), respectively. There was significant difference in the removal efficiency for different heavy metals. Cr had a maximum removal efficiency of 2.7%, while the maximum Cd and Pb removal efficiency was both about 60%. Distilled water had little removal efficiency for heavy metals, with less than 0.1% removal rate; the heavy metal removal efficiency of oxalic acid and acetic acid was also quite low; EDTA in 0.1 mol x L(-1) was selected as the suitable eluent for the polluted soil. Evaluation of the total toxicity reduction index and the cost suggested that EDTA should be used with a liquid to soil ratio of 6:1, a reaction time of 3 h and 2 washings.