工业废弃地多金属污染土壤组合淋洗修复技术研究

SEQUENTIAL ELUTION TECHNIQUE FOR REMEDIATION OF MULTI-METAL CONTAMINATED BROWNFIELD SOILS

采用批量淋洗实验方法,对比了采用人工螯合剂乙二胺四乙酸二钠盐(EDTA-Na2)和天然有机酸草酸(oxalic acid,OX)对工业废弃地污染土壤中重金属的去除效果,并采用不同浓度草酸和EDTA组合的两步淋洗法研究多金属污染土壤的最佳淋洗方式。结果表明,EDTA淋洗剂对土壤中Zn、Pb、Cu、Ni去除效果较好,而对Cr去除效果较差,实验条件下,EDTA对金属的去除率并未随着浓度增加而增加;相反,草酸对Cr去除效果较好,且去除率随着淋洗剂浓度的增加而增加,而对Zn、Cu、Ni的去除效果随着淋洗剂浓度增加而降低,对Pb的去除率非常低;采用先以0.20 mol L-1草酸提取2 h,再以0.01 mol L-1EDTA提取2 h的两步淋洗法可以达到对多金属同时去除,且对Zn、Cu、Cr、Ni的去除率明显高于单用草酸和EDTA,总去除率分别为Zn 75.21%、Pb 21.30%、Cu 59.81%、Cr 60.72%和Ni 62.10%,更为有意义的是两步淋洗法对非残渣态金属去除效果分别高达Zn 91.93%、Pb 57.75%、Cu 75.33%、Cr 73.94%、Ni 77.99%。利用不同化学淋洗剂对金属去除能力的差异进行组合的多步淋洗法是一种较为高效的去除工业废弃地污染土壤中重金属的化学淋洗修复方法。

A batch leaching experiment was conducted to compare the use of EDTA-Na2 with the use of oxalic acid（OX） in effect of removing heavy metal pollutants from brownfield soils.Also,a two-step eluting method with EDTA-Na2 and OX was tested in an attempt to find out optimal combination of OX and EDTA.It was found that EDTA-Na2 was quite effective in removing zinc（Zn）,lead（Pb）,copper（Cu） and nickel（Ni） from the contaminated soil,but not chromium（Cr）.In the experiment,the effect of EDTA did not increase with its concentration,however,OX was effective in removing Cr and the effect increased with the concentration OX used,but its effect of removing Zn,Cu and Ni decreased with its rising concentration.Moreover its effect was particularly low on Pb.The two-step eluting technique using OX（0.20 mol L-1 for 2 h） and EDTA-Na2（0.01 mol L-1 for 2 h） sequentially could remove the heavy metal pollutants simultaneously and was better than the use of EDTA-Na2 or OX individually in removing Zn,Cu,Cr and Ni.Its total removal rate of Zn was 75.21%,of Pb 21.30%,of Cu 59.81%,of Cr 60.72% and of Ni 62.10%.It is more noteworthy that the two-step eluting technique was very effective in removing metals of non-residual form,with removing rate reaching 91.93% for Zn,57.75% for Pb,75.33% for Cu,73.94% for Cr,and 77.99% for Ni.The findings of the study indicate that the sequential elution technique using different combinations of chemical eluents different in capability of removing heavy metals is a high-efficiency method to remedy heavy metal pollutant contaminated brownfield soils.