title: Enhanced photochemical decomposition of environmentally persistent perfluorooctanoate by coexisting ferric ion and oxalate.
abstract: Perfluorooctanoic acid (PFOA), an environmentally persistent pollutant, was found to be quickly decomposed under 254 nm UV irradiation in the presence of ferric ion and oxalic acid. To understand the PFOA decomposition mechanism by this process, the effects of reaction atmosphere and concentrations of ferric ions and oxalic acids on PFOA decomposition were investigated, as well as decomposition intermediates. PFOA mainly decomposes via two pathways: (i) photochemical oxidation via Fe(III)-PFOA complexes and (ii) one-electron reduction caused by carboxylate anion radical (CO2 (•-)), which was generated by photolysis of ferrioxalate complexes. Under excess oxalic acid, PFOA decomposition was accelerated, and its corresponding half-life was shortened from 114 to 34 min as ferric concentration increased from 7 to 80 μM. Besides fluoride ions, six shorter chain perfluorinated carboxylic acids (PFCAs) bearing C2-C7 were identified as main intermediates. The presence of O2 promoted the redox recycling of Fe(3+)/Fe(2+) and thus avoided the exhaustion of the Fe(III).
authors: College of Resource and Environmental Engineering, Guizhou University, Guiyang, Guizhou Province, 550025, People's Republic of China.
authors: Yuan
authors: Y
authors: Wang
authors: State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, 100084, People's Republic of China. zpy@tsinghua.edu.cn.
authors: Pengyi
authors: P
authors: Zhang
mesh_terms: D002210:Caprylates / Q000032:analysis / Q000737:chemistry; D004785:Environmental Pollutants / Q000032:analysis / Q000737:chemistry; D052918:Environmental Restoration and Remediation / Q000379:methods*; D005290:Ferric Compounds; D005466:Fluorocarbons / Q000032:analysis / Q000737:chemistry; D019815:Oxalic Acid; D010782:Photolysis; D014466:Ultraviolet Rays
chemical_list: D002210:Caprylates; D004785:Environmental Pollutants; D005290:Ferric Compounds; D005466:Fluorocarbons; C023036:perfluorooctanoic acid; D019815:Oxalic Acid
keywords: Carboxylate radical; Ferrioxalate; One-electron reduction; Perfluorinated carboxylic acids (PFCAs); Photolytic oxidation