Zeolites for Sorption of PFAS from Water

Abstract

Per- and polyfluoroalkyl substances (PFAS) are persistent organic pollutants that are widespread throughout the environment. While traditional adsorbents such as activated carbon and ion exchange resins have been used to adsorb PFAS from water, the technologies may be limited to certain classes of PFAS compounds. As such, technologies that can address a range of PFAS compounds are needed. In this study, 70 zeolites and molecular sieves with 15 different frameworks and varying pore sizes, framework compositions, and silica–alumina ratios, were tested with 24 PFAS compounds, including perfluoroalkyl carboxylic acids (C4–C14), perfluoroalkanesulfonates (C4–C10), three fluorotelomer sulfonates, NMeFOSAA, FOSA, and NEtFOSAA. PFAS adsorption generally increased with increasing compound hydrophobicity and with molecular sieve ring size. Most β and Faujasite frameworks adsorbed >85% of C8 and larger PFAS compounds. However, β zeolites outperformed all other structures for the sorption of C4–C7 compounds. In addition to the molecular sieves, two calcined hydrotalcites, an aluminum oxide, a magnesium oxide, and an activated carbon were also tested for comparison. The hydrotalcites and activated carbon performed well, adsorbing >74 and >94% of all analytes, while the Al₂O₃ and MgO adsorbed 43 and 34% on average.