title: Efficient decomposition of environmentally persistent perfluorooctanesulfonate and related fluorochemicals using zerovalent iron in subcritical water.
abstract: Decomposition of perfluorooctanesulfonate (PFOS) and related chemicals in subcritical water was investigated. Although PFOS demonstrated little reactivity in pure subcritical water, addition of zerovalent metals to the reaction system enhanced the PFOS decomposition to form F-ions, with an increasing order of activity of no metal approximately equal Al < Cu < Zn << Fe. Use of iron led to the most efficient PFOS decomposition: When iron powder was added to an aqueous solution of PFOS (93-372 microM) and the mixture was heated at 350 degrees C for 6 h, PFOS concentration in the reaction solution fell below 2.2 microM (detection limit of HPLC with conductometric detection), with formation of F-ions with yields [i.e., (moles of F- formed)/(moles of fluorine content in initial PFOS) x 100] of 46.2-51.4% and without any formation of perfluorocarboxylic acids. A small amount of CHF3 was detected in the gas phase with a yield [i.e., (moles of CHF3)/(moles of carbon content in initial PFOS) x 100] of 0.7%, after the reaction of PFOS (372 microM) with iron at 350 degree C for 6 h. Spectroscopic measurements indicated that PFOS in water markedly adsorbed on the iron surface even at room temperature, and the adsorbed fluorinated species on the iron surface decomposed with rising temperature, with prominent release of F- ions to the solution phase above 250 degrees C. This method was also effective in decomposing other perfluoroalkylsulfonates bearing shorter chain (C2-C6) perfluoroalkyl groups and was successfully applied to the decomposition of PFOS contained in an antireflective coating agent used in semiconductor manufacturing.
authors.affiliation: National Institute of Advanced Industrial Science and Technology, AIST Tsukuba West, 16-1 Onogawa, Tsukuba 305-8569, Japan. h-hori@aist.go.jp
authors.forename: Hisao
authors.initials: H
authors.lastname: Hori
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Nagaoka
authors.forename: Ari
authors.initials: A
authors.lastname: Yamamoto
authors.forename: Taizo
authors.initials: T
authors.lastname: Sano
authors.forename: Nobuyoshi
authors.initials: N
authors.lastname: Yamashita
authors.forename: Sachi
authors.initials: S
authors.lastname: Taniyasu
authors.forename: Shuzo
authors.initials: S
authors.lastname: Kutsuna
authors.forename: Issey
authors.initials: I
authors.lastname: Osaka
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Arakawa
mesh_terms: D017738:Alkanesulfonic Acids / Q000737:chemistry*; D004785:Environmental Pollutants; D005466:Fluorocarbons / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D010084:Oxidation-Reduction; D012666:Semiconductors; D014867:Water / Q000737:chemistry
chemical_list: D017738:Alkanesulfonic Acids; D004785:Environmental Pollutants; D005466:Fluorocarbons; D014867:Water; C076994:perfluorooctane sulfonic acid; D007501:Iron