A Review of the Electrochemical Coupled Leaching Technique: An Effective Solution for Remediation of Heavy Metal Contaminated Soils

Electrochemical technology is a widely employed technique for remediating soil contaminated with heavy metals. This technology can be utilized alone or in conjunction with other remediation techniques to improve the efficacy of heavy metals removal. The principle of electrochemical remediation technology involves utilization of electromigration, electroosmosis, and electrodialysis effects generated by an external electric field to transfer heavy metals from the soil to electrodes’ vicinity. However, this technology has not without limitations and challenges, including low permeability, pH gradient, soil composition, and heavy metal form, among other influencing factors. To overcome these obstacles, novel electrochemical coupling techniques have been proposed and developed, such as incorporating leaching agents, altering electrode materials or structures, employing pulse or alternating current sources. These technologies aim to increase the migration rate of heavy metals, decrease energy consumption, minimize by-products, and enhance the remediation effects. Among these, chemical leaching agents have garnered attention due to their outstanding treatment effects, simple technology, and ease of operation. Consequently, this paper first delineates the advantages of electrochemical technology and leaching technology over traditional adsorption passivation technology from the perspective of the removal mechanism. Secondly, the emphasis was placed on elucidating the technical principles of electrochemical technology and leaching techniques, as well as highlighting the drawbacks and limitations associated with their standalone application. Lastly, a remediation scheme for heavy metal-contaminated soil utilizing electrochemical coupling leaching technology is proposed. The practical significance of this work lies in the fact that electrochemical coupling leaching technology, compared to traditional adsorption passivation techniques, can greatly enhance the efficiency and effectiveness of heavy metal-contaminated soil remediation. It achieves the efficient, rapid, and thorough removal of heavy metal ions from the soil. Electrochemical coupling leaching technology speeds up the chemical leaching process that removes heavy metals from the soil, taking advantage of the best parts of both methods. The electric field then directs, aggregates, and deposits the released heavy metal ions onto electrodes, effectively separating them from the soil. This technology represents a thoroughly effective removal method, capable of avoiding the problem of secondary pollution caused by the re-release of heavy metal ions into the soil due to the changes in external environmental conditions. Therefore, research and application of electrochemical coupling leaching technology hold significant practical and scientific value.