Experimental study and mechanism analysis of chelating agent enhanced on electrokinetic removal of copper and lead from loess

The rapid development in the western areas of China has resulted in a growing problem of heavy metal pollution in the loess land. The electrokinetic remediation has gained attention due to its great maneuverability. However, certain factors such as polarization phenomena and precipitation of heavy metals near the cathode have lead to a decrease in the efficiency of the electrokinetic remediation. Therefore, focusing on studying the copper and lead-contaminated loess as the research subject, by combining the technology of chelating agent coupling electric remediation with the addition of catholyte, the effects of tartaric acid, citric acid and EDTA as the cathode electrode liquid on the removal efficiency of copper and lead metals in loess as well as the removal mechanism are investigated. The results indicate that the tartaric acid, citric acid and EDTA can enhance the migration capability of copper and lead through complexation, thereby improving the removal efficiency of these metals to varying estents. The improvement in the removal efficiency of copper and lead metals is particularly noticeable in the vicinity of the cathode. Among the three chelating agents, the EDTA exhibits strong chelating capability and can react with copper and lead metals across different pH ranges, resulting in the formation of a more stable complex and enhancing the removal efficiency. Compared with the control group, the EDTA forms a stable complex by coordinating with heavy metals through six atoms, converting them into exchangeable states with enhanced migration capabilities, and making them easier to remove. As a result, the overall removal efficiencies of copper and lead increase to 55.4% and 27.2%, respectively.