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

Hydrated electron (e aq – ) 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 e aq – participating in pollutant decomposition low, reflecting by slow decomposition kinetics. In this study, a high photon flux UV/sulfite system was employed to promote e aq – production. Its feasibility in enhancing a notorious recalcitrant pollutant, PFOS, decomposition was investigated. The effective photon flux utilized for producing e aq – was 9.93 × 10 –8 einstein/cm 2 ·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 k obs 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 NO 3 – . 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 e aq – induced reduction techniques for efficient recalcitrant pollutants decomposition.