Study of polluted soil remediation based on freezingand thawing cycles

It is generally known that soil pollution poses a terrible hazard to the environment, but the present techniques of contaminatedsoil remediation cannot control this growing threat. This paper compares the pollutant extraction efficiency oftraditional pumping and treating, which is a typical washing technology for the remediation of contaminated soils, withmethods that utilize freeze-thaw cycles. In the soil freezing process, water shifts from unfrozen soils to the freezing front,and the permeability of soil will be enhanced under certain temperature gradients and water conditions. Therefore, thispaper discusses the purification of contaminated soil through freeze-thaw action. We conducted a cleansing experiment onclay and silica sand infused with NaCl (simulation of heavy metals) and found that the efficiency of purification was enhancedremarkably in the latter by the freeze-thaw action. To assess the effective extraction of DNAPLs in soil, we conductedan experiment on suction by freezing, predicated on the different freezing points of moisture and pollutants. Wefound that the permeability coefficient was significantly increased by the freezing-thawing action, enabling the DNAPLcontaminants to be extracted selectively and effectively.