title: Ferric ion mediated photochemical decomposition of perfluorooctanoic acid (PFOA) by 254nm UV light.
abstract: The great enhancement of ferric ion on the photochemical decomposition of environmentally persistent perfluorooctanoic acid (PFOA) under 254nm UV light was reported. In the presence of 10microM ferric ion, 47.3% of initial PFOA (48microM) was decomposed and the defluorination ratio reached 15.4% within 4h reaction time. While the degradation and defluorination ratio greatly increased to 80.2% and 47.8%, respectively, when ferric ion concentration increased to 80microM, and the corresponding half-life was shortened to 103min. Though the decomposition rate was significantly lowered under nitrogen atmosphere, PFOA was efficiently decomposed too. Other metal ions like Cu(2+) and Zn(2+) also slightly improved the photochemical decomposition of PFOA under irradiation of 254nm UV light. Besides fluoride ion, other intermediates during PFOA decomposition including formic acid and five shorter-chain perfluorinated carboxylic acids (PFCAs) with C7, C6, C5, C4 and C3, respectively, were identified and quantified by IC or LC/MS. The mixture of PFOA and ferric ion had strong absorption around 280nm. It is proposed that PFOA coordinates with ferric ion to form a complex, and its excitation by 254nm UV light leads to the decomposition of PFOA in a stepwise way.
authors.affiliation: State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Science, Chinese Academy of Science, Beijing, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Wang
authors.forename: Pengyi
authors.initials: P
authors.lastname: Zhang
authors.forename: Gang
authors.initials: G
authors.lastname: Pan
authors.forename: Hao
authors.initials: H
authors.lastname: Chen
mesh_terms: D002210:Caprylates / Q000737:chemistry* / Q000528:radiation effects*; D002264:Carboxylic Acids / Q000737:chemistry; D005290:Ferric Compounds / Q000737:chemistry*; D005459:Fluorides / Q000737:chemistry; D005466:Fluorocarbons / Q000737:chemistry* / Q000528:radiation effects*; D006207:Half-Life; D008670:Metals / Q000737:chemistry; D010777:Photochemistry; D014466:Ultraviolet Rays
chemical_list: D002210:Caprylates; D002264:Carboxylic Acids; D005290:Ferric Compounds; D005466:Fluorocarbons; D008670:Metals; C023036:perfluorooctanoic acid; D005459:Fluorides