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

Ali  Behnami; Mojtaba  Pourakbar; Khaled  Zoroufchi Benis; Mahdi  Farzadkia; Roshanak Rezaei  Kalantari; Mojtaba  Yeganeh; Ali  Esrafili; Mitra  Gholami

doi:10.18502/jehsd.v11i2.21959

Ali Behnami Department of Environmental Health Engineering, Iran University of Medical Sciences, Tehran, Iran.
Mojtaba Pourakbar Department of Environmental Health Engineering, Maragheh University of Medical Sciences, Maragheh, Iran
Khaled Zoroufchi Benis Department of Process Engineering and Applied Science, Dalhousie University, Halifax, NS, Canada.
Mahdi Farzadkia Department of Environmental Health Engineering, Iran University of Medical Sciences, Tehran, Iran.
Roshanak Rezaei Kalantari Department of Environmental Health Engineering, Iran University of Medical Sciences, Tehran, Iran.
Mojtaba Yeganeh Department of Environmental Health Engineering, Iran University of Medical Sciences, Tehran, Iran.
Ali Esrafili Department of Environmental Health Engineering, Iran University of Medical Sciences, Tehran, Iran.
Mitra Gholami Department of Environmental Health Engineering, Iran University of Medical Sciences, Tehran, Iran.

DOI: https://doi.org/10.18502/jehsd.v11i2.21959

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

Abstract

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 254 nm UV irradiation with an initial PFOA concentration of 0.24 mM and oxidant/reductant dosages of 1.0 mM. Reaction kinetics, transformation products, and fluoride generation were analyzed using LC‑MS/MS and ion chromatography over a 6‑hour treatment period.

Results: Direct UV photolysis was ineffective, achieving only 4% removal. Among the tested systems, UV/SS exhibited the highest performance, achieving 47% PFOA removal, compared with 24% and 31% 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.