重金属污染土壤的草酸和EDTA混合淋洗研究

采用不同浓度的草酸(oxalic acid,OX)和乙二胺四乙酸(EDTA)混合的淋洗方法研究重金属污染土壤的最佳混合淋洗方式,探讨了液固比、淋洗时间及pH对淋洗效果的影响,并分析了0.2 mol/L OX+0.2 mol/L EDTA处理前后土壤中重金属形态的变化。结果表明,采用0.2 mol/L OX+0.2 mol/L EDTA混合的淋洗法可同时去除多种重金属,且对Cu、Zn、Ni和Cr的去除率明显高于单用OX和EDTA,去除率分别为Cu 41.29%、Zn 84.73%、Ni 54.2%和Cr 66.01%。0.2mol/L OX+0.2 mol/L EDTA在液固比为5∶1、淋洗时间为4 h、pH为6时可分别达到最佳淋洗效果,且分别为Cu 62.59%、Zn 93.48%、Ni 55.95%和Cr 71.57%;Cu 50.47%、Zn 86.67%、Ni 61.53%和Cr 72.68%;Cu 44.40%、Zn 81.82%、Ni68.76%和Cr 74.93%。形态分析结果表明,0.2 mol/L OX+0.2 mol/L EDTA能较好地改变土壤中重金属形态的分布。

Study on mixture of OX and EDTA leaching heavy metals contaminated soil

Different concentrations of OX and EDTA were mixed to determine the optimal mixing concentration on leaching heavy metals contaminated soil. Also, the effects of liquid-solid ratio, leaching time, and pH on leaching efficiency were investigated, and the morphology was analyzed before and after tested heavy metals were leached by the mixture of 0.2 mol/L OX+0.2 mol/L EDTA. The results showed that the mixture of 0.2 mol/L OX+0.2 mol/L EDTA could not only remove various heavy metals simultaneously but also be better than single OX or EDTA, with removal rates of Cu, Zn, Ni and Cr 41.29%, 84.73%, 54.2% and 66.01%, respectively. The mixture of 0.2 mol/L OX+0.2 mol/L EDTA could obtain the highest leaching efficiencies when liquid-solid ratio was 5:1, leaching time was 4 hours, or pH was 6. Accordingly, the removal rates were Cu 62.59%, Zn 93.48%, Ni 55.95% and Cr 71.57%; Cu 50.47%, Zn 86.67%, Ni 61.53% and Cr 72.68%; Cu 44.40%, Zn 81.82%, Ni 68.76% and Cr 74.93%. Furthermore, the mixture of 0.2 mol/L OX+0.2 mol/L EDTA could well change the distributions of morphology of heavy metals in soil.