A novel electrokinetic flushing coupled with dual-anode system for enhanced PAHs removal from soil

Conventional electrokinetic in-situ chemical oxidation (EK-ISCO) suffers from inefficient oxidant utilization and secondary contamination due to external oxidant dependency. To address these limitations, this study developed a dual-anode electrokinetic (EK-DAO) system integrating electroosmotic transport and in-situ electrochemical oxidation for remediating polycyclic aromatic hydrocarbons (PAHs)-contaminated soil without external oxidants. The dual-anode configuration integrated a graphite electrode serving as both the anode and cathode for electrokinetic transport, in series with a boron-doped diamond (BDD) anode for the generation of radicals. By optimizing surfactant selection and maintaining the electrolyte pH at 8.0, the system achieved effective and sustained electroosmotic transport of PAHs to the BDD anode, resulting in a 79.6 % enhancement in electroosmotic flow compared to the system without pH control. The BDD anode demonstrated superior •OH production (87 μM at 20 mA cm^-2), enabling efficient degradation of PAHs transported to the electrode chamber. Mechanistic analysis revealed •OH, SO₄•^-, and direct electron transfer as primary contributors for PAHs degradation, with degradation kinetics influenced by the structure of PAHs and coexisting anions. With slight variations in soil properties and soil enzyme activities, EK-DAO exhibited environmental sustainability. This work successfully achieved in-situ removal of PAHs from soils and their subsequent anode oxidation, establishing EK-DAO as a sustainable and high-efficiency strategy for soil remediation that eliminates the need for external oxidants.