Abstract
Perfluorooctanoic acid (PFOA), as an anthropogenic persistent contaminant, is widely distributed in the natural aquatic environment and has been a considerable threat to ecological security and human health. In this work, we propose and evaluate the vacuum ultraviolet (VUV)/sulfite-iodide system under N2 saturated condition for the decomposition of PFOA. The in situ generated hydrated electrons (eaq−) were demonstrated to be the main active species responsible for the PFOA degradation. With observation of the intermediate products, two major degradation pathways of PFOA in VUV/sulfite-iodide system were proposed: H/F exchange and chains shortening. A significant enhancement of PFOA defluorination was observed with increasing pH values from 9.0 to 12.0, which can be explained by the decreasing quenching effect of eaq− and accelerated disproportionation of I2 to I− and IO3−. Meanwhile, VUV/sulfite-iodide system also exhibited satisfactory performance in degrading high concentration of PFOA (200 μM). However, the presence of Cl−, NO3−, and humic acid inhibited the removal of PFOA via various reaction mechanism. The VUV/sulfite-iodide system was effective toward the chosen PFCAs (trifluoroacetic acid (TFA) and perfluorobutyric acid (PFBA)), demonstrating a chain length independence on the degradation of PFCAs, supporting its broad applicability.
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