title: Electro-oxidation of perfluorooctanoic acid by carbon nanotube sponge anode and the mechanism.
abstract: As an emerging persistent organic pollutant (POPs), perfluorooctanoic acid (PFOA) exists widely in natural environment. It is of particular significance to develop efficient techniques to remove low-concentration PFOA from the contaminated waters. In this work, we adopted a new material, carbon nanotube (CNT) sponge, as electrode to enhance electro-oxidation and achieve high removal efficiency of low-concentration (100μgL(-1)) PFOA from water. CNT sponge was pretreated by mixed acids to improve the surface morphology, hydrophilicity and the content of carbonyl groups on the surface. The highest removal efficiencies for low-concentration PFOA electrolyzed by acid-treated CNT sponge anode proved higher than 90%. The electro-oxidation mechanism of PFOA on CNT sponge anode was also discussed. PFOA is adsorbed on the CNT sponge rapidly increasing the concentration of PFOA on anode surface. When the potential on the anode is adjusted to more than 3.5V, the adsorbed PFOA undergoes electrochemically oxidation and hydrolysis to produce shorter-chain perfluorocarboxylic acids with less CF2 unit. The efficient electro-oxidation of PFOA by CNT sponge anode is due to the combined effect of adsorption and electrochemical oxidation. These findings provide an efficient method to remove actual concentration PFOA from water.
authors.affiliation: Department of Environmental Engineering, Peking University, Beijing 100871, People's Republic of China; The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing 100871, People's Republic of China.
authors.forename: An
authors.initials: A
authors.lastname: Xue
authors.affiliation: Department of Environmental Engineering, Peking University, Beijing 100871, People's Republic of China; The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing 100871, People's Republic of China.
authors.forename: Zi-Wen
authors.initials: ZW
authors.lastname: Yuan
authors.affiliation: Department of Environmental Engineering, Peking University, Beijing 100871, People's Republic of China; The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing 100871, People's Republic of China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, People's Republic of China.
authors.forename: An-Yuan
authors.initials: AY
authors.lastname: Cao
authors.affiliation: Department of Environmental Engineering, Peking University, Beijing 100871, People's Republic of China; The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing 100871, People's Republic of China. Electronic address: zhaohuazhang@pku.edu.cn.
authors.forename: Hua-Zhang
authors.initials: HZ
authors.lastname: Zhao
mesh_terms: D000327:Adsorption; D002210:Caprylates / Q000032:analysis* / Q000737:chemistry; D004566:Electrodes; D004572:Electrolysis; D005466:Fluorocarbons / Q000032:analysis* / Q000737:chemistry; D037742:Nanotubes, Carbon / Q000737:chemistry*; D010084:Oxidation-Reduction; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000737:chemistry; D018508:Water Purification / Q000379:methods*
chemical_list: D002210:Caprylates; D005466:Fluorocarbons; D037742:Nanotubes, Carbon; D014874:Water Pollutants, Chemical; C023036:perfluorooctanoic acid
keywords: Adsorption; Carbon nanotube sponge; Electro-oxidation; Perfluorooctanoic acid (PFOA)