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Abstract
Ion-exchange (IX) is an effective method for PFAS removal from water and wastewater, but the treatment of concentrated PFAS from IX resin regeneration remains a major technical barrier. This study investigates the challenges and solutions associated with photochemical treatment of waste brines from resin regeneration. We first tested the defluorination of perfluorooctanoic acid (PFOA) by UV/sulfite/iodide in synthetic solutions containing individual inorganic and organic species. We identified NO3−, NO2−, and natural organic matter (NOM) as the major inhibitors. NO3− and NO2− quenched hydrated electron (eaq−), but they could be readily removed by increasing the sulfite dose. We used humic acid as a representative NOM. It significantly slowed down defluorination but can be readily removed by ferric flocculation without removing PFOA. The integration of flocculation and UV/S/I treatment successfully treated two waste brines, which primarily contained short-chain PFAS. PFAS removal achieved >99% within 20 hours. The maximum defluorination reached 85% and 70% for the two waste brines, respectively. This study advances UV technologies for PFAS destruction and enhances the sustainability of ion-exchange resin for PFAS removal.
