复合冻融与淋洗方法修复重金属污染黏性土的研究

Remediation of heavily metal-contaminated clayey soils by composite freeze-thaw and soil washing method

土壤淋洗被认为是一种高效、可广泛应用和彻底治理重金属土壤污染的方法,但因黏质土壤的低渗透性、较大颗粒比表面积对重金属离子所具有的强烈吸附作用,影响水或淋洗剂在土壤中的混合传质,导致淋洗效果不佳。利用人工冻结方法,通过未冻土侧水分向冻结锋面迁移和冻融循环重构土粒结构提高渗透性的原理,再结合化学淋洗方法,对铅、镉污染的黏性土壤进行了修复试验。结果表明,土体经反复冻融后会破坏土体颗粒原有结构,从而有助于淋洗液与污染物充分接触,因而提高了淋洗效率,为利用自然冷能对季冻区重金属污染土壤修复提供了思路。

Soil washing is considered as an efficient and widely applicable technology for the thorough treatment of heavy metal pollution in soils.However,due to the low permeability of clayey soils,the large particle specific surface area strongly adsorbs ions,affecting the mixing and mass transfer of water or washing agent in the soils,thus reducing the washing efficiency.Using the artificial freezing method,and adopting the principles of the unfrozen soil moisture migrating to freezing front side and the freeze-thaw cycle for improving permeability combined with the chemical leaching method,remediation experiments on clayey soils contaminated with lead and cadmium are carried out.The results show that the soils after repeated freeze-thaw will destroy the original structure of soil particles,which will help the full contact with the washing agent and contaminants,thus improving the efficiency of the washing,which provides a good idea for using natural cool energy to repair heavily metal-contaminated seasonal frozen soils.