title: Effects of pH on photochemical decomposition of perfluorooctanoic acid in different atmospheres by 185nm vacuum ultraviolet.
abstract: Perfluorooctanoic acid (PFOA), a persistent organic pollutant, receives increasing concerns due to its worldwide occurrence and resistance to most conventional treatment processes. The photochemical decomposition by 185nm vacuum ultraviolet (VUV) is one of the efficient methods for PFOA decomposition. The effects of pH on PFOA decomposition in nitrogen atmosphere or oxygen atmosphere were investigated. At its original pH (4.5) of PFOA aqueous solution, PFOA decomposed efficiently both in nitrogen and in oxygen atmosphere. However, when the pH increased to 12.0, PFOA decomposition was greatly inhibited in oxygen atmosphere, while it was greatly accelerated in nitrogen atmosphere with a very short half-life time (9min). Furthermore, fluorine atoms originally contained in PFOA molecules were almost completely transformed into fluoride ions. Two decomposition pathways have been proposed to explain the PFOA decomposition under different conditions. In acidic and neutral solutions, PFOA predominantly decomposes via the direct photolysis in both atmospheres; while in the alkaline solution and in the absence of oxygen, the decomposition of PFOA is mainly induced by hydrated electrons.
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China; School of Chemistry and Chemical Engineering, Guizhou University, Guiyang, Guizhou 550025, China. Electronic address: wang_yuan@tsinghua.edu.cn.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China. Electronic address: zpy@tsinghua.edu.cn.
authors.forename: Pengyi
authors.initials: P
authors.lastname: Zhang
mesh_terms: D000393:Air Pollutants / Q000737:chemistry*; D001272:Atmosphere; D002210:Caprylates / Q000737:chemistry*; D005466:Fluorocarbons / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D014466:Ultraviolet Rays
chemical_list: D000393:Air Pollutants; D002210:Caprylates; D005466:Fluorocarbons; C023036:perfluorooctanoic acid
keywords: 185nm vacuum ultraviolet; Perfluorinated compounds; Perfluorocarboxylic acids (PFCAs); Persistent organic pollutants; Photochemical