Cathodic enhanced electrokinetic remediation of PFOA contaminated soil: Auxiliary agents-enhanced desorption and migration

Abstract

Electrokinetic (EK) remediation is a promising in-situ technique for remediating soils contaminated with persistent pollutants, but its efficiency is often limited by poor pollutant desorption and migration. This study explores the use of cathodic auxiliary agents to enhance the EK remediation of PFOA-contaminated soil. Among the desorption tests, SDS (50.93 %) and NaC (43.62 %) were most effective in desorbing PFOA through electrostatic, hydrophobic interactions, and micelle formation, outperforming DTAB (15.29 %) and CA (37.76 %). Continuous desorption tests validated the effectiveness of employing auxiliary agents as electrolytes. EK remediation experiments revealed that these agents facilitated PFOA desorption and migration, achieving higher removal efficiencies. After 7 d, NaC achieved a greater enhancement effect than SDS, with PFOA removal rates of 58.04 % (2 V/cm) and 63.70 % (2 V/cm), respectively. PFOA accumulation in the middle soil area was observed, due to opposing electroosmotic and electrokinetic forces, with electromigration being the dominant factor. Extending remediation time alleviated this accumulation. Kinetic analysis revealed that PFOA migration in most areas followed pseudo-second-order kinetics, while the middle area exhibited first-order kinetics due to PFOA accumulation. The auxiliary agents primarily enhanced PFOA removal efficiency indirectly by influencing electromigration, electroosmosis, and desorption processes, while changes in soil physicochemical properties served as limiting factors. This study provides valuable insights into the combined effects of cathodic-enhanced EK and auxiliary agents on PFOA remediation, offering theoretical and practical guidance for the development of efficient and sustainable remediation technologies.