[Effectiveness and Mechanisms of Chemical Leaching Combined with Electrokinetic Technology on the Remediation of...

In this study, chemical leaching and electrokinetic technology were used to remediate heavy metal contaminated soil to elucidate its effectiveness and mechanisms. Chemical leaching agents of FeCl₃, Fe(NO₃)₃, KCl, KNO₃, and HCl solutions were selected, and the effects of Fe³⁺, K⁺, H⁺, and Cl^- on four heavy metal (Cd, Pb, Cu, and Zn) removals were compared and analyzed. Then, the influence of the speciation of heavy metals in soil after chemical leaching on the electrokinetic remediation efficiency was studied. The results showed that Fe³⁺, K⁺, H⁺, and Cl^- had different effects on the four heavy metal removals; for Cd and Zn, the removal effect of H⁺was the most effective, but for Pb and Cu, the effect of Fe³⁺ was the most obvious. On the whole, FeCl₃ and Fe(NO₃)₃ showed the best removal effect for Cd, Pb, and Cu. For the removal of Zn from the soil, the difference in the removal effect of the five leaching agents was not obvious. In comparison with that of FeCl₃ and Fe(NO₃)₃, the HCl solution had a moderate removal effect on the four heavy metals in the soil, and the neutral salts KCl and KNO₃ had little removal effect on the four heavy metals. Especially for Cd and Cu, KCl and KNO₃ addition significantly increased the removal of heavy metals through the subsequent electrokinetic remediation. After the chemical leaching, electrokinetic remediation could make heavy metals in the topsoil (0-10 cm) migrate downward and enrich the 10-20 cm and 20-30 cm soil layers, which requires further studies to resolve.