3种萃取剂对土壤重金属的去除及其对重金属有效性的影响

通过重金属污染土壤的浸泡试验,比较了HCl、柠檬酸、EDTA3种萃取剂对污染土壤中3种重金属Pb、Cd、Zn的去除能力,并研究了这3种萃取剂的萃取对土壤重金属有效性的影响。结果表明,随着浓度的提高,3种萃取剂对Pb、Cd、Zn的去除作用增强。EDTA去除3种重金属的能力远远大于其他2种萃取剂。HCl和柠檬酸对3种重金属去除率的顺序均为Cd>Zn>Pb,EDTA溶液对3种重金属去除率的顺序为Pb>Cd>Zn。HCl和柠檬酸萃取提高了土壤Pb的有效性,降低了Cd、Zn的有效性。EDTA萃取降低了土壤Pb、Cd、Zn的有效性,并且这3种重金属的有效性低于HCl和柠檬酸的处理。可见,EDTA作为治理重金属污染土壤的萃取剂比HCl和柠檬酸更合适,HCl和柠檬酸虽然也能明显地去除土壤中的重金属,但它提高土壤Pb的有效性的效应值得注意。

Effects of Three Extractants on Removal and Availabilities of Heavy Metals in the Contaminated Soil

A batch experiment was conducted to investigate the removal efficiency of Pb,Cd and Zn by HCl,citric acid and EDTA and the effects of these 3 extractants on availabilities of heavy metals in contaminated soil.The results showed that,with increasing in HCl,citric acid and EDTA concentrations,removals of Pb,Cd and Zn significantly increased.The removal ability of EDTA on heavy metals was much higher than those of the other 2 extractants.Removal percentages of heavy metals due to extracting of both HCl and citric acid were in a sequence of Cd > Zn > Pb,while removal percentages of heavy metals due to extracting of EDTA were in a sequence of Pb > Cd > Zn.HCl and citric acid decreased availabilities of Cd and Zn but increased availability of Pb in the soil.Extracting of EDTA decreased availabilities of all 3 heavy metals,and availabilities of heavy metals in the soil were lower than those after extracting of HCl and citric acid.Therefore,compared with HCl and citric acid,EDTA was more suitable as an extractant for remediation of heavy metal contaminated soil.HCl and citric acid could effectively remove heavy metals,but the availability of Pb increased due to the extracting of these 2 extractants,which should be concerned with.