Nitrogen dioxide radicals mediated mineralization of perfluorooctanoic acid in aqueous nitrate solution with UV irradiation

- An attractive strategy ofNO2-mediated complete mineralization of PFOA developed.
- NO2 generated by the photolysis of nitrate aqueous solution (UV/Nitrate).
- The feasibility of PFOA removal with NO2 confirmed by DFT calculations.
- Prompted roles of hydroxyl radical scavengers explored for the degradation of PFOA.
- Near-stoichiometry of fluorides release and high TOC removal efficiencies realized.

Effective decomposition of perfluorooctanoic acid (PFOA) has received increasing attention in recent years because of its global occurrence and resistance to most conventional treatment processes. In this study, the complete mineralization of PFOA was achieved by the UV-photolysis of nitrate aqueous solution (UV/Nitrate), where the in-situ generated nitrogen dioxide radicals (NO2) efficiently mediated the degradation of PFOA. In particular, when the twinborn hydroxyl radicals were scavenged, the production of more NO2 radicals realized the complete mineralization of PFOA. DFT calculations further confirm the feasibility of PFOA removal with NO2. Near-stoichiometric equivalents of fluoride released rather than the related intermediates were detected in solution after decomposition of PEOA, further demonstrating the complete degradation of PFOA. Possible PFOA degradation pathways were proposed on the basis of experimental results. This work offers an efficient strategy for the complete mineralization of perfluorinated chemicals, and also sheds light on the indispensable roles of nitrogen dioxide radicals for environmental pollutants removal.

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