Electrochemical degradation of perfluorinated compounds by Ag coated Ti (Ti/Ag) anode: electrode preparation, characterization and application

Abstract

Perfluorinated compounds (PFCs) are environmentally persistent, bioaccumulative, and globally distributed pollutants, which exhibit potential toxicity to both humans and ecosystems. In this study, the electrochemical degradation of PFCs in the effluent of a municipal wastewater treatment plant (MWWTP) was conducted using an Ag coated titanium (Ti/Ag) anode. Results from the Tafel polarization analysis showed that the Ag film was uniformly coated on the surface of a Ti plate, and a higher corrosion potential (−0.3086 V) was obtained when compared with that of the original Ti electrode (−0.9707 V). To optimize the degradation process, response surface methodology (RSM) combined with a Box–Behnken design (BBD) was applied to optimize the factors that could affect the degradation of the PFCs. Results indicated that the maximum removal efficiencies of short chain PFCs (C–F < 7), long chain PFCs (C–F ≥ 7), and chemical oxygen demand (COD) were about 70.8%, 91.5%, and 92.0%, respectively, under optimum conditions, at which the current density was 20.0 mA cm⁻², the pH was 6, the electrode distance was 1.6 cm within 100 min of electrolysis time. Moreover, triplicate tests were carried out and demonstrated that the relative standard deviation (RSD%) was lower than 5.0% which meant that the experimental design and the optimized factors were significant. The degradation kinetic analysis suggested that the degradation of COD and PFCs was in agreement with the pseudo-first-order kinetic reaction, and the COD degradation occurred prior to the long-chain PFCs and short-chain PFCs degradation.