Enhanced Adsorption of Mixtures of Per- and Polyfluoroalkyl Substances in Water by Chemically Modified Activated Carbon

Chemical modifications of granular activated carbon (GAC) and powdered activated carbon (PAC) are necessary for enhanced removal of perfluoroalkyl and polyfluoroalkyl substances (PFAS) in water. Herein, we synthesized and tested goethite (α-FeOOH)-coated GAC and PAC for the adsorption of mixtures of 13 PFAS (9 short- and long-chain PFAAs, GenX, and 3 precursors) from water at an initial concentration of 10 μg/L for each. Among the sorbents tested, modified PAC (MPAC) had excellent adsorption compared to pristine PAC and GAC and modified GAC (MGAC). Based on the isotherms, the maximum adsorption capacity of MPAC toward total PFAS removal was 234 mg/g. Detailed characterizations revealed that the adsorption performance of MPAC was due to its powdered nature, which enabled a shorter diffusion path and rapid mass transfer in the internal pores of this sorbent in addition to the electrostatic and hydrophobic interactions. Results obtained from this study provide valuable insights and knowledge for properly modifying GAC and PAC to address the critical challenges associated with PFAS, especially those associated with short-chain compounds.