Regeneration efficiency of strong-base anion exchange resin for perfluoroalkyl and polyfluoroalkyl substances

The objectives of this research were to evaluate the regeneration efficiency of strong-base anion exchange resin (AER) considering (i) total perfluoroalkyl and polyfluoroalkyl substances (PFAS) concentration, (ii) AER polymer composition, and (iii) regeneration solution composition. Laboratory column experiments were conducted over multiple treatment and regeneration cycles using groundwater spiked with six perfluoroalkyl acids (PFAAs): perfluorobutanoic acid, perfluorohexanoic acid perfluorooctanoic acid, perfluorobutane sulfonic acid, perfluorohexane sulfonic acid, and perfluorooctane sulfonic acid. Regeneration efficiency was calculated as the mass of PFAAs desorbed from the resin during regeneration divided by the mass of PFAAs adsorbed to the resin during treatment. Higher PFAS concentration in the influent resulted in higher PFAS loading on the resin and higher regeneration efficiency. This was especially true for polystyrene AER, which exhibited greater removals of perfluoroalkyl sulfonic acids than perfluoroalkyl carboxylic acids, and greater removal of long-chain PFAAs than short-chain analogs. The most important result was the higher regeneration efficiency for solution composed of salt + organic cosolvent than the aqueous-only solution.