Experiments and mechanisms for bottom vacuum leaching remediation of low permeability Cu, Zn-contaminated soil

The model box test of Cu and Zn composite contaminated clay was conducted to perfect the treatment technique for low permeability contaminated soil—bottom vacuum leaching technology. In order to evaluate the effect of vacuum pressure on the efficiency of contaminated soil remediation, model box tests with four distinct vacuum pressures were designed. The mechanism of the varying vacuum pressures on the difference in contaminated soil remediation efficiency was analyzed from a microscopic perspective by particle analysis and mercury intrusion porosimetry (MIP) tests. The findings of the experiments showed that the volume of solution leached from contaminated soil varied significantly depending on the vacuum pressure used. The distinction in removal efficiency was self-evident. The maximum heavy metal removal efficiency, with 88.16% (Cu) and 82.79% (Zn), respectively, and the largest volume of leaching liquid, were found at 60 kPa. Microscopical examinations revealed that particle movement was significantly affected by vacuum pressure and that significant influence was exerted by micropores on the leaching status of contaminated soil. The research findings can be used to provide technical guidance for the application of the bottom vacuum leaching technology and serve as a valuable reference for the treatment of contaminated soil with low permeability.