Laboratory‑scale leaching behavior and partitioning mechanism of PFAS during organic solvent-assisted site soil...

Remediation of globally concerning Per- and polyfluoroalkyl substances (PFAS) is imperative yet challenging. This study employs soil washing to remediate PFAS contaminated brown loam soil, focusing on evaluating the effectiveness of methanol (MeOH), ethanol (EtOH), and acetonitrile (ACN), and co-solvent systems. Results revealed EtOH and ACN reached maximum elution efficiency at 25%, while MeOH at 50%. MeOH outperformed EtOH and ACN in removing PFOS, PFOA, and PFBS under their respective optimal concentrations. The role of the co-solvent systems was investigated, revealing higher PFAS removal efficiencies compared to those achieved with a single solvent system. The 15% EtOH + 200 mM NaOH co-solvent system markedly promoted PFAS leaching from contaminated soil, with efficiencies of 86.45% for PFHpA, 89.74% for PFPeA, 84.34% for PFOA, 75.32% for PFOS, 80.59% for PFBS, and 73.59% for PFHxS, with perfluoroalkyl carboxylates (PFCAs) notably achieving a higher removal rate than perfluoroalkane sulfonates (PFSAs). The partitioning coefficient (K_d) of PFAS was investigated in three solvent systems: pure water, EtOH, and EtOH + NaOH. The lower log K_d values correlated with higher PFAS leaching rates, reflecting high mobility in corresponding solutions. A strong positive linear relationship was observed between PFAS' molecular weights and average log K_d values (R²=0.986, p < 0.05). In brown loam soil, short-chain PFAS (C<7) have higher adsorption capacity in organic matter-free soils than untreated soils, while long-chain PFAS (C≥7) exhibit the opposite trend. Overall, this study provides suitable washing agents to improve laboratory-scale remediation of PFAS-contaminated soil.