废弃铅锌冶炼企业重金属复合污染土壤淋洗修复效果研究

采用不同浓度的EDTA溶液对废弃铅锌冶炼企业重金属复合污染的土壤进行土柱淋洗修复试验,研究在不同浓度、不同淋洗速率和不同淋洗时间条件下,EDTA淋洗剂对土壤中重金属的去除效果,并采用连续分级的方法研究淋洗前后土壤中重金属的形态变化.结果表明:(1)用EDTA溶液对表面积为350 cm2,高度为15 cm,重金属铜(Cu)、铅(Pb)、锌(Zn)含量分别为462.76、2 043、3 260 mg/kg的土壤进行淋洗修复,当淋洗剂浓度为0.01 mol/L、淋洗速率为1 mL/min、淋洗时间为24 h时,淋洗效果最佳,对Cu、Pb、Zn的去除率分别达到57.01％、47.5％、61.6％.(2)用EDTA溶液对重金属污染的土壤进行淋洗,能有效去除土壤中的可交换态、碳酸盐结合态、铁锰氧化物结合态以及有机结合态重金属,平均去除率分别为76.02％、60.9％、57.69％；而对残余态重金属的去除效果不太明显.由于以可交换态、碳酸盐结合态和铁锰氧化物结合态存在的重金属的移动能力及生物有效性都比较高,对环境危害大,EDTA淋洗可以有效去除这几种形态的重金属.因此,用EDTA溶液淋洗法修复重金属污染的土壤是切实可行的.

Remediation of heavy metals from abandoned lead and zinc smelting corporate contaminated soil by washing with EDTA

EDTA was used as eluent to wash heavy metals from abandoned lead and zinc smelting corporate contaminated soils in soil columns and studied the removal of heavy metals in the soil under the three conditions of different concentrations, different flow rates and different washing time. The redistributions of heavy metals were determined using the sequential extraction procedure before and after treatment. The results were as followsing:(1) When the concentration of EDTA was 0.01 mol/L, the flow rate was 1 mL/min, the washing time was 24 h, the removal rate of Cu, Pb, Zn were 57.01%, 47.5% and 61.6% respectively. (2) EDTA was very effective in removing the exchangeable, carbonate, Fe-Mn oxide bound and organic-bound states of heavy metals from the contaminated soils. The average removal rates were 76.02%, 60.9%, 57.69%, respectively. The removal of residual heavy metals was not very good. Exchangeable, carbonate and Fe-Mn oxide bound states of heavy metals were with relatively high mobile capabilities and bioavailability, they were more harmful to the environmental. EDTA could effectively remove the forms of heavy metal. So remediation of heavy metals from contaminated soil by washing with EDTA was feasible.