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Abstract
This study explored different pretreatment methods to enhance photochemical degradation of PFAS in still-bottom (SB) brine. The brine contained concentrated natural organic matter and inorganic salts, which severely inhibited PFAS destruction by prevailing technologies. Pretreatment methods evaluated included flocculation, Fenton oxidation, and Soxhlet extraction. Soxhlet extraction works by repeatedly passing a small volume of solvent through the solid from drying the SB, resulting in efficient extraction of most PFAS. The extract reduced 73% of organic content and 84-98% of inorganic salts in the original SB. The redissolved extract in water (equivalent to 10x dilution of the original SB) yielded 100% PFAS removal and 80% defluorination within 24 hours by UV/sulfite/iodide treatment. In comparison, only 20% defluorination was achieved in 10x diluted SB without pretreatment, 56% with Fenton pretreatment, and 24% with flocculation pretreatment. These findings underscore the importance of removing co-existing components in challenging water matrices to enable efficient PFAS destruction.
