Removal of Per- and Polyfluoroalkyl Substances (PFASs) in Aqueous Film-Forming Foam (AFFF) Using Ion-Exchange and Nonionic Resins

Despite benefits to the firefighting industry, the release of per- and polyfluoroalkyl substances (PFASs) from aqueous film-forming foam (AFFF) into aquatic systems poses significant risks to human health and other organisms. While anion-exchange technologies have proven to be effective for removing perfluoroalkyl acids (PFAAs) from water, their effectiveness for removing the diverse PFAS structures discovered in AFFF remains unknown. Here, we report on the adsorption of 75 PFASs, including 63 polyfluorinated substances, in a diluted AFFF mixture using 14 commercially available ion-exchange (IX)/nonionic resins and granular activated carbon (GAC). Results showed that anion-exchange resins (AERs) exhibited significant adsorption of PFASs compared to cation-exchange resins (CERs), nonionic resins (NIRs), and GAC regardless of the PFAS's predicted charge. Isotherm data showed that macroporous AERs have a higher PFAS adsorption capacity compared to gel-type AERs. Cross-correlation comparison of PFAS/Cl- selectivity coefficients (K-ex) for each PFAS-AER combination showed that the hydrophobicity of the AER functional group, and polymer matrix played a dominant role in determining resin affinity for PFASs. PFAS structural characteristics also significantly affected adsorption, with increasing chain length and a net negative charge increasing the extent of adsorption. Results from this study provide guidelines for the selection of resins to adsorb a wider range of PFASs and meaningful insights for the development of quantitative models for IX treatment of AFFF-impacted water.