基于重复分凝成冰作用提高季冻区重金属污染黏性土淋洗效率的研究

Improving washing efficiency of heavy metal-contaminated clayey soils based on repeated ice-segregation in seasonal frozen areas

基于程国栋院士的“厚层地下冰的重复分凝机制”理论,提出利用重复分凝成冰作用以提高重金属污染黏性土的淋洗效率。以Cd、Pb污染黏性土为研究对象,选用EDTA、酒石酸为淋洗液,通过室内振荡淋洗试验和冻融–淋洗土柱试验,比较分析了不同工况下重金属的去除效果。结果表明,通过融化速率控制为正融土中水分迁移和重复分凝成冰提供有利条件,较单一冻结–吸水模式淋洗液的摄入量约增加20%,而且冻–融界面的反复波动,有助于淋洗液与土壤中重金属充分接触,两者的协同作用能够显著提高重金属去除率,Cd、Pb的去除率分别提高了43.95%和171.74%。该方法在实际工程应用上具有一定的现实性和普适性,对季冻区重金属污染黏性土修复提供了一个新的思路。

The scheme to improve the washing efficiency of heavy metal-contaminated clayey soil is proposed by using the repeated ice-segregation based on the theory of "repeated segregation mechanism of thick ground ice". The laboratory batch washing tests and freezing-thawing and washing tests are performed on Cd-and Pb-contaminated clayey soils with EDTA,tartaric acid as eluents. Subsequently, the removal effects of heavy metals under different working conditions are analyzed. The results show that it provides advantages for water migration in thawing soils and repeated ice-segregation by controlling the thawing rate. Compared with that of the single freezing-water intaking mode, the eluent intaking amount of the freezing-thawing and washing tests with repeated ice-segregation increases by about 20%. The repeated fluctuations of the freezing-thawing interface will promote the eluent to fully contact with the heavy metal in the soils. Their synergistic effects can effectively increase the removal effeciency of heavy metals. The removal efficiency of Cd and Pb increases by 43.95% and 171.74%, respectively. It is of certain reality and universality in practical engineering application and provides a new idea for the remediation of heavy metal-contaminated clayey soils in seasonal frozen areas.