Degradation differences in N -ethylperfluorooctane sulfonamidoacetic acid by vacuum ultraviolet (VUV)/peroxydisulfate and VUV/sulfite: Kinetics, products, and mechanism

N -ethylperfluorooctane sulfonamidoacetic acid (N-EtFOSAA) is a precursor of perfluorooctane sulfonate and has seen increased production and usage in numerous developing and emerging industrialized countries. However, it has been proven toxic. This study presents the first investigation into the treatability of N-EtFOSAA utilizing the vacuum ultraviolet (VUV)/peroxydisulfate (PDS) and VUV/sulfite (SF) redox processes. The results demonstrate that a relatively high reaction rate constant of 0.0364 min −1, but a low defluorination rate of 43.7 % and a total organic carbon (TOC) removal extent of 30.5 % were obtained in the VUV/PDS process. By contrast, a higher defluorination rate of 77.1 % and a TOC removal extent of 45.1 %, along with the generation of a series of fluorinated intermediates, were obtained in VUV/SF. Combined with theoretical calculations and the identification of intermediates, distinctive removal pathways in the oxidation and reduction processes were speculated. We observed that the VUV/PDS process led to an increase in the aquatic toxicity of N-EtFOSAA, whereas the VUV/SF process resulted in a decrease. The findings illustrate that the reductive degradation of N-EtFOSAA is more feasible through the synergistic interaction between hydrated electrons and hydroxyl radicals.