Differences between Reductive Defluorination of Perfluorooctanoic Acid by Chlorinated, Brominated, and Iodinated in the Vacuum-Ultraviolet/Sulfite Process

Abstract

The introduction of iodide (I−) has broad perspectives on the decomposition of perfluorocarboxylates (PFCAs, CnF2n+1COO-). However, the iodinated substances produced are highly toxic synthetic chemicals, it is urgent to find a similar alternative with less toxicity. In this work, the defluorination of perfluorooctanoic acid (PFOA) by I-, bromide (Br-) and chlorine (Cl-) was systematically compared in the VUV/sulfite process. Results indicated that the PFOA defluorination rates increased with increasing nucleophilicity of halogens (I > Br > Cl). Meanwhile, the introduction of I-, Br- and Cl- reduced the interference of the coexisting water matrix on the degrading influence of PFOA. The in situ produced eaq-, SO3•-, H• and HO• were recognized, among the addition of I- maximized the relative contribution of eaq- while Br- and Cl- decreased that of H• and other radicals. Additionally, HPLC/MS analysis revealed the presence of I-, Br- and Cl- had a vital impact on the difference in product concentrations, while they had a negligible effect on the change in pathway of reaction degradation. Overall, this study demonstrated the similarities and differences between I-, Br- and Cl-, which has significant implications for further understanding VUV/sulfite degradation.

Keywords: micropollutants, ARPs, Halogen, Hydrated electron, Water treatment