Comparing activated carbons, ion exchange resins and alternative adsorbents for the removal of perfluoroalkyl and other persistent and mobile substances

• surface modified clays selectively remove PFAS from water with high content of DOM. • PFAS-specific anion exchange resins achieve highest PFAS removals. • Many organic micropollutants (non-PFAS) could only be removed by activated carbon. • TGA-FTIR supports selection of activated carbon for organic micropollutant removal. • Acesulfame could serve as well-studied indicator substance for PFAS removal. Per- and polyfluoroalkyl substances (PFAS) are highly persistent and potentially toxic chemicals that have been found in many drinking water resources worldwide. Increasingly stringent limits for these substances require advanced treatment concepts to remove these substances during drinking water treatment. Today, the majority of treatment systems for PFAS removal rely on granular activated carbon (AC) or ion exchange resins (IX), whose capacities are often limited by competitive adsorption of dissolved organic matter. In this study, a screening of six AC, five PFAS-specific IX, and seven alternative adsorbents was performed using equilibrium jar tests. The removal of 12 selected PFAS was compared to the removal of 16 other non-PFAS organic micropollutants. Dissolved organic matter competition was investigated using size exclusion chromatography with online organic carbon and UV 254 detection. In addition, AC were characterized by determination of the pH at the point of zero charge, cation and anion exchange capacity, and surface oxygen groups. While IX appear to be the best choice for short-chain PFAS removal, AC allows for broader removal of organic micropollutants, and bentonite-based surface modified clays allow for highly selective PFAS removal with very low DOM competition. The data also show that the removal of acesulfame might be used as an indicator for removal of some PFAS, allowing an initial selection of activated carbon or ion exchange resin in the absence of PFAS data. Carbonyl surface oxygen groups determined with thermogravimetric analysis coupled to Fourier-transform infrared spectroscopy served as best predictor for organic micropollutant removal by AC.