表面活性剂强化EDTA络合洗脱污灌土壤中重金属的试验研究

在实验室条件下研究了表面活性剂十二烷基硫酸钠(SDS)、聚氧乙烯月桂醚(Brij35)和重金属洗脱螯合剂EDTA对土壤中Cd、Pb的解吸去除作用,同时研究了加入SDS和Brij35后对EDTA解吸污染土壤中Cd、Pb作用的影响,并对解吸前后重金属在土壤介质中形态变化进行了测定。结果表明,加入表面活性剂SDS可使EDTA对Cd的解吸量由61.67%增加到79.68%、对Pb的解吸量由57.25%增加到89.65%。在EDTA浓度较小时,加入SDS对Cd、Pb的解吸产生拮抗作用,抑制了EDTA对污染土样中Cd、Pb的解吸;随着EDTA浓度的不断增加,加入SDS与EDTA产生明显的协同增溶作用;表面活性剂Brij35具有相同的增溶作用,但增溶效果不如SDS。比较复配解吸前后重金属形态变化,可溶态、碳酸盐结合态较解吸前减少60%￣90%,大大降低了污灌土壤中重金属的毒性和生物可利用性。试验结果可为利用表面活性剂与EDTA复配提高重金属在土壤介质中的解吸率提供理论依据,并可应用于污灌土壤中重金属的冲洗治理。

Washing Efficiency of Heavy Metals in Soils with EDTA Enhanced by Surfactants

The effects of sodium dodecyl sulfate (SDS), laural polooxyethylene ether (Brij35) and Ethylenediaminetetraacetic acid(EDTA) on desorption of Cd and Pb from the soil contaminated by the wastewater irrigation are studied in laboratory, also the influence of adding SDS and Brij35 on EDTA desorption capacity is certified. The species changes of the heavy metals before and after desorption in the soil matrix are determined too. The results show that the removal of Cd from the soil increases from 61.67% by using EDTA alone to 79.68% when adding SDS, while, the removal of Pb increases from 57.25% to 79.68%. However, adding the surfactants could restrain the desorption capacity of EDTA at low concentrations. SDS can significantly enhance the synergetic solubilization of Cd and Pb with the increase of EDTA concentrations. Brij35 has the same effect on the enhanced solubilization of Cd and Pb, but its efficiency shows little weaker than SDS. The contents of soluble and carbonate species of the heavy metals are decreased by 60%~90% in the desorption processes, compared to that before desorption, which indicates that bioavailability and toxicity of heavy metals in sewage farmland have been decreased. These results not only could theoretically provide the approach to use surfactants to enhance the capacity of EDTA for desorption of heavy metals from soil media, but also could extensively be used in the in-situ flushing technique for heavy metal contaminated soils.