Managing PFAS exhausted Ion-exchange resins through effective regeneration/electrochemical process

Water Res. 2024 May 15:255:121529. doi: 10.1016/j.watres.2024.121529. Epub 2024 Mar 26.


This study proposes an integrated approach that combines ion-exchange (IX) and electrochemical technologies to tackle problems associated with PFAS contamination. Our investigation centers on evaluating the recovery and efficiency of IX/electrochemical systems in the presence of five different salts, spanning dosages from 0.1 % to 8 %. The outcomes reveal a slight superiority for NaCl within the regeneration system, with sulfate and bicarbonate also showing comparable efficacy. Notably, the introduction of chloride ion (Cl-) into the electrochemical system results in substantial generation of undesirable chlorate (ClO3-) and perchlorate (ClO4-) by-products, accounting for ∼18 % and ∼81 % of the consumed Cl-, respectively. Several agents, including H2O2, KI, and Na2S2O3, exhibited effective mitigation of ClO3- and ClO4- formation. However, only H2O2 demonstrated a favorable influence on the degradation and defluorination of PFOA. The addition of 0.8 M H2O2 resulted in the near-complete removal of ClO3- and ClO4-, accompanied by 1.3 and 2.2-fold enhancements in the degradation and defluorination of PFOA, respectively. Furthermore, a comparative analysis of different salts in the electrochemical system reveals that Cl- and OH- ions exhibit slower performance, possibly due to competitive interactions with PFOA on the anode's reactive sites. In contrast, sulfate and bicarbonate salts consistently demonstrate robust decomposition efficiencies. Despite the notable enhancement in IX regeneration efficacy facilitated by the presence of methanol, particularly for PFAS-specific resins, this enhancement comes at the cost of reduced electrochemical decomposition of all PFAS. The average decay rate ratio of all PFAS in the presence of 50 % methanol, compared to its absence, falls within the range of 0.11-0.39. In conclusion, the use of 1 % Na2SO4 salt stands out as a favorable option for the integrated IX/electrochemical process. This choice not only eliminates the need to introduce an additional chemical (e.g., H2O2) into the wastewater stream, but also ensures both satisfactory regeneration recovery and efficiency in the decomposition process through electrochemical treatment.

Keywords: GenX; Hydrogen peroxide; Organic solvent; PFAS-specific resin; Perchlorate; Regeneration recovery.