title: Electrochemical oxidation of 1H,1H,2H,2H-perfluorooctane sulfonic acid (6:2 FTS) on DSA electrode: operating parameters and mechanism.
abstract: The 6:2 FTS was the substitute for perfluorooctane sulfonate (PFOS) in the chrome plating industry in Japan. Electrochemical oxidation of 6:2 FTS was investigated in this study. The degradabilities of PFOS and 6:2 FTS were tested on the Ti/SnO₂-Sb₂O₅-Bi₂O₃ anode. The effects of current density, potential, and supporting electrolyte on the degradation of 6:2 FTS were evaluated. Experimental results showed that 6:2 FTS was more easily degraded than PFOS on the Ti/SnO₂-Sb₂O₅-Bi₂O₃ anode. At a low current density of 1.42 mA/cm², 6:2 FTS was not degraded on Ti/SnO₂-Sb₂O₅-Bi₂O₃, while the degradation ratio increased when the current density ranged from 4.25 to 6.80 mA/cm². The degradation of 6:2 FTS at current density of 6.80 mA/cm² followed pseudo first-order kinetics with the rate constant of 0.074 hr⁻¹. The anodic potential played an important role in the degradation of 6:2 FTS, and the pseudo first-order rate constants increased with the potential. The surface of Ti/SnO₂-Sb₂O₅-Bi₂O₃ was contaminated after electrolysis at constant potential of 3V, while the fouling phenomenon was not observed at 5V. The fouled anode could be regenerated by incinerating at 600°C. The intermediates detected by ultra-performance liquid chromatography coupled with a triple-stage quadrupole mass spectrometer (UPLC-MS/MS) were shorter chain perfluorocarboxylic acids. The 6:2 FTS was first attacked by hydroxyl radical, and then formed perfluorinated carboxylates, which decarboxylated and removed CF2 units to yield shorter-chain perfluorocarboxylic acids.
authors.affiliation: POPs Research Center, School of Environment, Tsinghua University, Beijing 100084, China; South China Institute of Environmental Sciences, the Ministry of Environment Protection, Guangzhou 510655, China. Electronic address: zhuoqiongfang@scies.org.
authors.forename: Qiongfang
authors.initials: Q
authors.lastname: Zhuo
authors.affiliation: POPs Research Center, School of Environment, Tsinghua University, Beijing 100084, China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Li
authors.affiliation: POPs Research Center, School of Environment, Tsinghua University, Beijing 100084, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Yan
authors.affiliation: College of Chemistry and Chemical Engineering, Shenzhen University, Shenzhen 518060, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Yang
authors.affiliation: POPs Research Center, School of Environment, Tsinghua University, Beijing 100084, China.
authors.forename: Shubo
authors.initials: S
authors.lastname: Deng
authors.affiliation: POPs Research Center, School of Environment, Tsinghua University, Beijing 100084, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Huang
authors.affiliation: POPs Research Center, School of Environment, Tsinghua University, Beijing 100084, China. Electronic address: yg-den@tsinghua.edu.cn.
authors.forename: Gang
authors.initials: G
authors.lastname: Yu
mesh_terms: D017738:Alkanesulfonic Acids / Q000737:chemistry*; D002241:Carbohydrates / Q000737:chemistry; D055664:Electrochemical Techniques / Q000379:methods*; D005466:Fluorocarbons / Q000737:chemistry*; D010084:Oxidation-Reduction; D052980:Phycobilins / Q000737:chemistry; D011506:Proteins / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D014874:Water Pollutants, Chemical / Q000737:chemistry
chemical_list: D017738:Alkanesulfonic Acids; D002241:Carbohydrates; D005466:Fluorocarbons; D052980:Phycobilins; D011506:Proteins; D014874:Water Pollutants, Chemical; C076994:perfluorooctane sulfonic acid
keywords: 6:2 FTS; Electrochemical oxidation; Intermediates; Mechanism