Pre Treatment of PFOA Laden Synthetic Wastewater Via UV/Peroxydisulfate, UV/Peroxymonosulfate, and UV/Sulfite Processes: A Comparative Evaluation

Introduction: Perfluorooctanoic acid (PFOA) is a persistent and toxic contaminant that requires effective degradation and defluorination strategies. Although several UV-based advanced oxidation and reduction processes have been investigated, direct comparisons under identical conditions are limited. In this study, we compared the degradation efficiency, mechanisms, and defluorination potential of three UV-based systems: UV/persulfate (UV/PDS), UV/peroxymonosulfate (UV/PMS), and UV/sulfite (UV/SS). Materials and Methods: PFOA degradation experiments were conducted under ۲۵۴ nm UV irradiation with an initial PFOA concentration of ۰.۲۴ mM and oxidant/reductant dosages of ۱.۰ mM. Reaction kinetics, transformation products, and fluoride generation were analyzed using LC‑MS/MS and ion chromatography over a ۶‑hour treatment period. Results: Direct UV photolysis was ineffective, achieving only ۴% removal. Among the tested systems, UV/SS exhibited the highest performance, achieving ۴۷% PFOA removal, compared with ۲۴% and ۳۱% for UV/PDS and UV/PMS, respectively. UV/PDS and UV/PMS primarily proceeded through oxidative radical pathways (sulfate and hydroxyl radicals), resulting in chain shortening and accumulation of shorter-chain perfluorinated carboxylic acids (PFHpA, PFHxA, PFPeA, PFBA, and TFA). In contrast, UV/SS operated through reductive pathways mediated by hydrated electrons, promoting sequential C–F bond cleavage and enhanced defluorination. Conclusion: The UV/SS process demonstrated the greatest potential for PFOA pretreatment due to its ability to achieve true defluorination, whereas oxidative systems mainly transformed PFOA into persistent short-chain intermediates.

کلیدواژه ها:

PFOA ، Advanced oxidation processes (AOPs) ، Ultraviolet/Sulfite ، Defluorination ، Water remediation ، Perfluorinated compounds.