Hydrated Electron Degradation of PFOA Laden on Ion-Exchange Resins in the Presence of Natural Organic Matter

This study aimed to probe the interactions of hydrated electrons (e_aq^-) and perfluorooctanoic acid (PFOA)-laden ion-exchange (IX) resins in the presence of natural organic matter (NOM). PFOA and Suwannee River NOM-loaded resins were prepared through the removal of PFOA in simulated natural water with weak-base anion (WBA) resins (IRA67). Adsorption tests reveal that sorbed NOM was much more abundant than cosorbed PFOA, highlighting the role of NOM in resin saturation. Ensuing UV/SO₃^2- treatment of PFOA/NOM-laden resins (pH 10.0) under a dissolved oxygen-free condition indicates that e_aq^- generated could effectively degrade sorbed and aqueous PFOA, the latter of which derived from desorption of PFOA due to pH increase. Finally, cyclic adsorption-UV/SO₃^2- treatment tests demonstrate that the PFOA sorbed on the WBA resins could be mostly degraded over six cycles. However, e_aq^- could not effectively decompose cosorbed NOM, resulting in a gradual decrease in the recovered PFOA adsorption capability with the cycle number. This study spotlights that e_aq^- can decompose PFOA sorbed on the WBA resins in the presence of NOM. The UV/SO₃^2- process, when jointly used with appropriate strategies for mitigating cosorbed NOM, can enable a promising on-site resin regeneration process with PFOA degradation while producing a relatively small volume of regenerant waste.