Insight into the electrochemical process of EDTA-assisted soil washing effluent under alternating current

EDTA has been widely utilized as a chelating agent in soil heavy metal remediation, due to its strong coordination capability. Electrochemical deposition is a promising avenue to treat soil washing effluent. However, the impact of advanced electrochemical techniques on EDTA remains incompletely understood. Herein, we present a pioneering approach, utilizing a dual-chamber electrolytic cell and alternating current (AC) power supply. This approach achieves concurrent removal of M-EDTA while efficiently recovering heavy metal and recycling EDTA. Results demonstrate AC displays superior heavy metal removal capability for Cu, Pb, and Cd compare to direct current (DC), with EDTA decomposition mainly occurring in the anolyte. Substituting DC with AC and employing the dual-chamber electrolytic cell significantly enhances EDTA recovery efficiency from 47% to an impressive 96.8%. XPS and Raman spectra reveal an enhanced oxidative surface of the graphite anode under AC, which diminishes the decomposition of EDTA. Long-term experiments validate that this strategy boosts EDTA cyclability to 20 cycles with an outstanding 84% recovery efficiency and negligible electrode corrosion, surpassing the 8 cycles under the traditional strategy. This study innovatively combines cell design and electrochemical techniques, remarkably improving the reusability of EDTA and anode, offering valuable insights for chelate-related applications. Statement of Environmental Implication The global escalation of anthropogenic activities has triggered severe heavy metal pollution, posing significant threats to human health. The utilization of chelate such as ethylenediaminetetraacetic acid (EDTA) for soil remediation, coupled with the electrochemical treatment of effluent, not only facilitates the comprehensive removal of heavy metals from the soil but also enables metal recovery through electro-deposition methods. However, the economic recovery of EDTA during the wastewater treatment process, while simultaneously ensuring the effective removal of heavy metal pollutants, remains a challenging task. Alternating Current (AC) emerges as a promising electrochemical-assisted technology, particularly in the electrodeposition of heavy metals. Recent study by Chen et al. reported that AC induces enhanced dehydration and faster electron transport near the electrode, leading to higher M(II) removal and faster kinetics. The application of AC can address the challenge of coulomb repulsion in soil washing effluent. However, existing electrochemical systems using AC for M-EDTA primarily focus on heavy metal recovery, neglecting EDTA recovery efficiency and counter electrode duration, especially in comparison with Direct Current (DC).