利用乙二胺四乙酸淋洗修复重金属污染的土壤及其动力学

通过室内模拟试验，采用振荡淋洗的方法研究了乙二胺四乙酸(EDTA)浓度、pH、淋洗时间对重金属去除效果的影响.利用一级反应动力学模型对试验数据进行拟合，并测定了EDTA处理前后土壤中重金属形态的变化.结果表明，EDTA溶液在浓度为0.1 mol·L^-1、pH 7、淋洗时间1 d的条件下能达到对污染土壤重金属的最大去除率，去除率分别为Cd 89.14%、Pb 34.78%、Cu 14.96%、Zn 45.14%.模型拟合结果表明，Cd的质量转移系数最大，其次是Zn、Pb和Cu.说明在土壤淋洗过程中，Cd和Zn最先达到质量转移的平衡状态，然后是Pb和Cu.形态分级结果表明，EDTA能有效地去除交换态、碳酸盐结合态和氧化物结合态重金属，而对有机态和残余态部分重金属作用效果不明显.

Heavy metals removal and its kinetics in contaminated soil under effects of EDTA washing

In this paper, batch experiments were made to examine the effects of different EDTA concentrations, pH, and washing duration of EDTA on the removal of heavy metals from contaminated soil. An empirical model was employed to describe the kinetics of heavy metals dissolution and desorption, and the form changes of test heavy metals were determined before and after EDTA washing. The results showed that EDTA was effective to the removal of heavy-metals from contaminated soil. At 0.1 mol x L(-1) and pH 7 of EDTA and within 24 h, the removal rate of test heavy metals was the maximum, being 89.14% for Cd, 34.78% for Pb, 14.96% for Cu, and 45.14% for Zn. The mass transfer coefficient was in the order of Cd > Zn > Pb > Cu. Sequential fractionations of treated and untreated soil samples showed that EDTA was effective in removing the exchangeable, carbonate and oxide forms of Cd, Pb, Zn and Cu, but ineffective for the organic and residual forms of test heavy metals.