Sorption/desorption and degradation of long- and short-chain PFAS by anion exchange resin and UV/sulfite system
Zhongfei Ren, Ruichi Zhang, Xing Xu, Yanwei Li, Ningru Wang, Tiina Leiviskä
Abstract
A combined sorption/desorption and UV/sulfite degradation process was investigated for achieving efficient elimination of PFAS from water. Two gel-type resins, Purolite A532E and A600, and one macroporous resin, Purolite A860, were firstly tested for the sorption of individual PFPrA, PFHxA, PFOA, PFOS, and GenX at different concentrations. Sorption data and density functional theory (DFT) calculations revealed that electrostatic interactions predominated for short-chain PFAS sorption and hydrophobic interactions played a more significant role for long-chain PFAS than for short-chain PFAS. A600 and A860 were selected for desorption tests with 0.025% NaOH, 5% NaCl, and 5% NH 4 Cl solution with or without 20% ethanol (EtOH) due to their high sorption capacity for all target PFAS. The mixture of 5% NH 4 Cl and 20% EtOH as the desorption solution typically showed the highest desorption efficiency. PFOS was the most resistant for desorption but its desorption could be enhanced by stronger mixing conditions (in 5% NaCl + 20% EtOH). Direct degradation of studied PFAS in the desorption solution (0.025% NaOH, 5% NaCl, and 5% NH 4 Cl) by UV/sulfite achieved 97.6–100% degradation and 46.6–86.1% defluorination. EtOH hindered degradation and thus should be separated from the water before UV/sulfite degradation. • Sorption/desorption performance of various PFAS on AERs investigated. • Long-chain PFAS may bind multiple quaternary ammonium groups on their fluorine side. • Addition of EtOH in desorption solution increases PFAS desorption. • UV/sulfite system efficiently degrades PFPrA, PFHxA, PFOA and GenX in brines. • Degradation of PFAS in brine is greatly inhibited by the presence of EtOH.