Photochemical degradation of PFOA was greatly accelerated by soluble Fe^3＋under irradiation of 254 nm UV light. When the concentration of Fe^3＋ was kept at 30 μmol•L^－1, Fe₂(SO₄)₃, FeCl₃ and Fe (NO₃)₃ had no obvious difference in accelerating the degradation and defluorination of PFOA. Sulphate ion () exhibits stronger potential than chloride (Cl^－) to coordinate with Fe^3＋. According to the calculation results with Visual MINTEQ 2.52, when excessive was added ([]_total/[Fe^3＋]_total＝50∶1, pH＝3.69), about 16.32% of total ferric ion existed in the form of Fe(SO₄)^＋and Fe(SO₄), which reduced the probability of Fe^3＋ coordination with PFOA and correspondingly inhibited the photochemical degradation of PFOA. While only 0.12% of total Fe^3＋ complexed with Cl^－ when excessive Cl^－ was added, which had little impact on the degradation of PFOA. Theoretical calculations were consistent with the experimental results. The addition of hydroxyl radical scavenger (isopropanol) did not substantially decrease the degradation of PFOA and the presence of TiO₂ did not increase the degradation of PFOA, which further indicated that the photochemical degradation of PFOA induced by Fe^3＋ did not abide by oxidation mechanism of hydroxyl radical.

Key words: photochemical degradation, perfluorooctanoic acid, ferric ion, inorganic anion, hydroxyl radical