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

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.