The F and Sb co-doped Ti/SnO 2 electrode containing Sn-Sb interlayer was innovatively synthesized for electro-oxidation (EO) removal of perfluorooctane sulfonate (PFOS) in water. Stronger oxidation capability and remarkably longer lifetime were performed for Ti/Sn-Sb/SnO 2 -F-Sb electrode than these similar electrodes in this study without Sn-Sb interlayer and F/Sb doping, which could removed more than 99% of PFOS ( C 0 = 100 mg L −1 ) after 120-min electrolysis. The attribute of Ti/Sn-Sb/SnO 2 -F-Sb anode and its EO mechanism were surveyed by XRD, XPS, SEM, and LSV. F and Sb co-doping could improve the stability and EO capability of the electrode, which resulted from that the smooth surface was formed conveniently to produce physically adsorbed hydroxyl radical and lead to relatively high OEP. The operating parameters of EO process were also investigated including current density, pH value, and stirring speed, which revealed the effect of these parameters on PFOS decomposition. Additionally, the mineralization parameters, TOC and F − concentration, as well as short-chain perfluorocarboxylic acids were analyzed in solution during the electrolysis. Consequently, the EO pathway of PFOS was proposed through the detection of intermediates. These results manifest that Ti/Sn-Sb/SnO 2 -F-Sb anode is prospective to effectively decompose PFOS in wastewater.
Pengtao Cai,Tong Chen,Mingxiu Zhan,Xiaojun Ma,Masaki Takaoka,Chen Sun,Xiaodong Li
Global concern over per- and polyfluoroalkyl substances (PFASs), especially perfluorooctane sulfonate (PFOS), disposal prompts the search for effective degradation methods. Subcritical water hydrothermal treatment shows promise but suffers from unclear degradation pathways, hindering engineering application design due to unknown intermediate products. This study introduces Fe-based amorphous alloy to enhance the subcritical water hydrothermal degradation of PFOS, achieving a degradation rate of approximately 85 % under optimized conditions of 325 °C and 1 M sodium bicarbonate (NaHCO₃), compared to 56 % without the alloy. Analysis of liquid and gas-phase products, along with identification of potential intermediate products, led to proposing a reaction pathway for Fe-based amorphous alloy-enhanced subcritical water hydrothermal PFOS degradation. Additionally, the distribution of fluorine in PFOS was determined by fluorine-19 nuclear magnetic resonance ( 19 F NMR), and the energy changes of key degradation steps were calculated based on DFT, which provided concrete evidence for the degradation process and verified the mechanism of subcritical hydrothermal degradation of PFOS enhanced by Fe-based amorphous alloys. Most importantly, the Fe-based amorphous alloy demonstrated effectiveness upon repeated use after water washing. These results endorse its potential as a PFOS degradation catalyst.
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