Comparing the removal and fate of long and short chain per- and polyfluoroalkyl substances (PFAS) during surface water treatment via specialty adsorbents

The oleophobic and hydrophobic properties of per- and polyfluoroalkyl substances (PFAS) favoring their industrial applications have resulted in the persistence, transport, transformation, and accumulation of PFAS in environmental matrices around the globe. Specialty adsorbents comprise specialty ingredients that have wide availability tailored for scalable applications in any landscape. This study investigated 2 specialty adsorbents, Zero-Valent-Iron and Perlite-based Green Environmental Media (ZIPGEM) and Clay-Perlite and Sand sorption media (CPS) in removing long-chain and short-chain PFAS via a fixed-bed column study. The adsorption of perfluorooctane sulfonic acid (PFOS) by ZIPGEM was best explained by pseudo-second-order kinetics. The intraparticle diffusion model was a better fit for adsorption of perfluorooctanoic acid (PFOA) by both CPS and ZIPGEM. CPS exhibited a higher initial removal of PFOA (approximately 91 %) compared to that by ZIPGEM (approximately 84 %). During the initial 2-h run, the removals of perfluoropentanoic acid (PFPeA), perfluorobutanesulfonic acid (PFBS), and perfluorobutanoic acid (PFBA) by CPS were approximately 82 %, 72 %, and 54 %, respectively. The removals of PFPeA, PFBS, and PFBA by ZIPGEM were approximately 42 %, 90 %, and 36 %, respectively. In general, the order of adsorption by CPS and ZIPGEM was PFOS > PFOA > PFHxS > PFHpA > PFHxA > PFPeA > PFBS > PFBA. The preference of adsorption generally follows the media affinity initially by adsorbing larger molecules with higher molecular weights, followed by short-chain perfluorocarboxylic acids and perfluorosulfonic acids. Overall, adsorption was the dominant PFAS removal mechanism with some possible transformation of long-chain PFAS to short-chain PFAS when using CPS and ZIPGEM.