Adsorption of PFAS by All-Silica Zeolite β: Insights into the Effect of the Water Matrix, Regeneration of the Material, and Continuous PFAS Adsorption

Abstract

Per- and polyfluoroalkyl substances (PFAS) are man-made organic compounds ubiquitously present in the environment. Due to their persistency and bioaccumulative nature, and because of increasingly stringent regulations of PFAS, their removal from the environment is necessary. Our initial study identified all-silica zeolite β as an alternative adsorbent with a high selectivity, affinity, and capacity for perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) removal. Here, we study the influence of the PFAS chain length on the affinity and capacity of a novel material, all-silica zeolite β, showing that the *BEA zeolite is an ideal sorbent for the removal of PFAS with 8 carbons. The solution pH and the addition of cations or natural organic substances to the water matrix have minimal influence on PFOA/PFOS removal with the zeolite. Next, regeneration of a PFOS-loaded zeolite was assessed; besides thermal, solvent-driven regeneration of the zeolite is also possible, using well-selected combinations of non-noxious solvents. Lastly, continuous adsorption experiments show that zeolite can be used for larger-scale applications.

Zeolites for Sorption of PFAS from Water

“…The BEA and FAU 12-ring zeolites had the best removal of long-chain zeolite compounds of all frameworks tested, while only MFI had comparable removal for short-chain compounds (Figure ). This is consistent with the existing literature, where these compounds are the most-studied for PFAS adsorption. ,− ,− The BEA zeolite framework had the overall highest adsorption, which is consistent with the literature. , BEA zeolites also had the most consistently high removal levels across different PFAS structures (Figure ). However, the exact adsorption mechanism is not yet determined.…”

“…Zeolites are crystalline aluminosilicates, and are typically utilized in gas-phase applications, but can also operate successfully in aqueous systems (e.g., commercial laundry detergents) . Previous studies have shown the effectiveness of zeolites for removing PFAS in aqueous solution, ,− and surface modifications can further enhance electrostatic and hydrophobic interaction . Compared to activated carbon and mesoporous silicas, zeolites have the benefit of a more targeted removal of specific compounds through molecular sieving effects; however, a limited number of experimental studies focused on zeolites have been reported.…”

Exploring the Potential of Biochar Derived from Chinese Herbal Medicine Residue for Efficient Removal of Norfloxacin

“…However, it is crucial to recognize that the adsorption efficiency is contingent upon the specific adsorbent type and its inherent characteristics [13][14][15]. To date, various adsorbents, including activated carbon [16], nanotube [17], metal-organic frameworks (MOFs) [18], osmotic membrane bioreactors [19], clay [20], and silica [21], have been extensively utilized for the removal of antibiotics. Specifically, biochar has attracted significant attention in the removal process of antibiotics owing to its easy availability, large surface area, abundance of surface functional groups, and developed pores [22,23].…”