Efficient Reductive Decomposition of Perfluorooctanesulfonate in a High Photon Flux UV/Sulfite System

Hydrated electron (eaq–) induced reduction techniques are promising for decomposing recalcitrant organic pollutants. However, its vigorous reactivity with copresent scavenging species and the difficulty in minimizing the competitive reactions make the proportion of eaq– participating in pollutant decomposition low, reflecting by slow decomposition kinetics. In this study, a high photon flux UV/sulfite system was employed to promote eaq– production. Its feasibility in enhancing a notorious recalcitrant pollutant, PFOS, decomposition was investigated. The effective photon flux utilized for producing eaq– was 9.93 × 10–8 einstein/cm2·s. At initial solution pH 9.2, with DO about 5 mg/L, and at around 25 °C, 98% PFOS was decomposed within 30 min from its initial concentration of 32 μM. The kobs of PFOS decomposition was 0.118 min–1 (7.08 h–1), and about 8–400 folds faster than those obtained in other reductive approaches. In this system, PFOS decomposition showed can tolerate copresent 7 mg N/L of NO3–. Suggested by molecular orbitals and thermodynamic analyses, the mechanisms responsible for PFOS decomposition involve defluorination, desulfonation, and centermost C–C bond scission. By demonstrating a more practical relevant treatment process, the outcomes of this study would be helpful for facilitating future applications of eaq– induced reduction techniques for efficient recalcitrant pollutants decomposition.