Electrokinetic mobilization of PFAS in soils: Linking head group and chain length to remediation efficiency

PFAS pose significant remediation challenges due to their chemical stability, structural diversity, and strong affinity for soil components. These properties complicate their mobilization from contaminated soils and necessitate compound-specific treatment approaches. Five PFAS compounds (PFBA, PFOA, PFDA, PFOS, and FOSA) were selected to investigate the influence of molecular structure, representing variations in chain length and head group. Electrokinetic (EK) remediation and hydraulic gradient (HG) treatments were applied to soils with organic matter (OM) contents of 5 %, 30 %, and 50 %. Results showed that PFAS removal was highly influenced by the molecular structure of the species. Both EK and HG were effective at mobilizing short-chain PFAS, which are more mobile in porewater. However, moving longer-chain or more strongly sorbing PFAS was more challenging. These compounds responded better to HG due to the stronger advective forces and may require a combination of HG and EK to achieve significant mobilization. Overall, PFOS, FOSA, and PFDA showed limited mobilization under either treatment due to their stronger sorption to soil organic matter, which restricts both electrokinetic and hydraulic transport. These findings highlight the need to align remediation strategies with PFAS physicochemical properties and soil composition to improve field-scale treatment efficiency.