Influence of Chelator Type on the Efficiency and Mechanisms of Electrokinetic Remediation of Copper- and Lead-Contaminated Loess

With the continued advancement of industrialization and urbanization in northwestern China, heavy metal contamination of loess sites has become an increasingly serious environmental issue. Heavy metals such as copper (Cu) and lead (Pb) are toxic, persistent, and readily retained by the mineral-pore framework of loess, which makes remediation difficult and threatens regional ecological security and human health. This study investigated electrokinetic (EK) remediation of artificially prepared loess co-contaminated with Cu and Pb using tartaric acid (TA), citric acid (CA), and disodium ethylenediaminetetraacetate (EDTA) as catholytes. Cu was generally removed more effectively than Pb because Pb was less adsorbed and immobilized more strongly. All three chelators enhanced metal desorption and migration through complexation, particularly in the cathode-side section. EDTA produced the greatest enhancement because it formed stable, negatively charged complexes with Cu and Pb over a broad pH range. Relative to the deionized-water control, EDTA increased the overall removal efficiencies of Cu and Pb to 55.4% and 27.2%, respectively, and promoted their transfer from the soil to the anolyte. These findings demonstrate that chelator-assisted EK treatment, particularly with EDTA, can effectively improve Cu and Pb removal from loess, while field application requires control of energy use, residual chelator, and post-treatment metal mobility.