Modified clays reduce leaching of per‐ and polyfluoroalkyl substances from AFFF‐contaminated soils

Abstract

AbstractTechnologies applicable at a field scale to mitigate soil and groundwater pollution by per‐ and polyfluoroalkyl substances (PFAS) due to the release of aqueous film‐forming foams are urgently needed. We demonstrate that modified bentonite clays as soil amendments can effectively reduce the leaching of PFAS from impacted soils. In batch experiments, the significant decrease (95%–99%) of leachable anionic PFAS, including perfluorooctane sulfonate, perfluorohexane sulfonate, and perfluorooctane carboxylate, was achieved in 1–4 days at a clay dosage as low as 0.5% w/w. A significant decline of leachable cationic and zwitterionic PFAS (70%–99%) was also observed. The clays performed the best in immobilizing PFAS anions, while granular activated carbon was effective in preventing PFAS cation leaching. Hardwood biochar had minor or negligible effects on any PFAS. The study provides strong evidence to support using modified clays as part of mitigation or remediation strategies to prevent PFAS from mobilizing on a field scale.Article Impact StatementThe study demonstrated that modified bentonite clays effectively immobilize various PFAS in AFFF‐contaminated soils to prevent leaching.