洗涤剂组合两步洗涤修复重金属污染土壤研究

本文以某化工厂受As、Cd、Cu和Pb污染场地土壤为研究对象,将EDTA分别与柠檬酸、鼠李糖脂和草酸组合进行2轮搅拌洗涤修复,考察实验室条件下不同洗涤剂组合对重金属提取能力差异和形态分布的影响,研究多金属污染土壤的最佳洗涤方式.结果表明,与单轮洗涤相比,两轮洗涤处理明显提高了As、Cd、Cu和Pb的去除率,增幅范围在8.45%~36.81%.经过EDTA+草酸组合的洗涤,As和Cu的去除率分别可达24.04%和29.25%;EDTA+鼠李糖脂和鼠李糖脂+EDTA组合对Cd和Pb的去除效果显著,洗脱率分别为47.83%和30.59%.柠檬酸和EDTA组合能有效削减4种重金属有效态比例,使As、Cd、Cu和Pb的有效态分别降低了8.61%、9.37%、14.12%和25.16%.实际工程应用中对多种洗涤剂进行选配,并对多重金属污染土壤进行多轮洗涤修复,应充分考虑重金属去除量以及有效态削减情况,确定洗涤剂最优组合,确保治理修复后土样残留重金属的稳定性以减少对环境后续影响.

Remediation of heavy metal contaminated soil by using two-step sequential washing with different reagents

Washing performance of soil polluted by As, Cd, Cu, and Pb was studied to reveal the optimal parameters for remediation of heavy metal contaminated soil. Three reagents, namely citric acid, rhamnolipid, and oxalic acid, were selected and combined with EDTA, respectively. Compared with one-step washing, the two-step sequential washing with different reagents increased the removal efficiencies of As, Cd, Cu, and Pb by 8.45%~36.81%. The removal of As and Cu could reach 24.85% and 29.25%, respectively, when applying the two-step sequential washing with the combination of EDTA and oxalic acid, 47.83% of Cd and 30.59% of Pb in the soil could be eluted by washing with the combination of EDTA and rhamnolipid. After washing with the combination of EDTA and citric acid, the available contents of As, Cd, Cu and Pb in the soil decreased by 8.61%, 9.37%, 14.12%, and 25.16%, respectively. From practical perspective, the application of combining different reagents and adopting multi-step sequential washing require further process optimization, with special attention to the removal of both total metal amount and the available contents. The stability of heavy metal residues after remediation can thus be ensured, and subsequent impacts to the environment can be mitigated.