title: Rate laws and kinetic modeling of N-ethyl perfluorooctane sulfonamidoethanol (N-EtFOSE) transformation by hydroxyl radical in aqueous solution.
abstract: The degradation of perfluorochemicals (PFCs) by hydroxyl radical ((·)OH) follows complex pathways resulting in stable products. Kinetic models are needed to predict the product distribution of (·)OH-initiated PFC degradation under environmental and treatment conditions. The bimolecular rate constants were measured in water for the reaction of (·)OH and N-ethyl perfluorooctane sulfonamidoethanol (N-EtFOSE), and intermediates, N-ethyl perfluorooctane sulfonamidoacetate (N-EtFOSAA), N-ethyl perfluorooctane sulfonamide (N-EtFOSA) and perfluorooctane sulfonamidoacetate (FOSAA). Under standard conditions (pH = 6, 25 ± 2 °C, Co PFC = 5-10 μg L(-1), Co H2O2 = 10 mM, irradiation intensity = 765 W m(-2)), the measured constants for N-EtFOSE, N-EtFOSAA, N-EtFOSA and FOSAA were (1.05 ± 0.12) × 10(9) M(-1) s(-1), (0.68 ± 0.05) × 10(9) M(-1) s(-1), (0.68 ± 0.05) × 10(9) M(-1) s(-1) and (0.53 ± 0.05) × 10(9) M(-1) s(-1), respectively. Constants in the pH range from 1 to 10 varied within a factor of 2-4 for most compounds. Over a period of 2-days, N-EtFOSE reacted directly (without forming long-lived intermediates) to perfluorooctane sulfonamide (FOSA) (18.8%) and perfluorooctanoic acid (PFOA) (39.1%). N-EtFOSE reacted via oxidation of the ethanolic hydroxyl group to N-EtFOSAA (12.4%) and N-dealkylation to N-EtFOSA (13.3%) and FOSAA (0.2%) and unknown intermediates. In sunlit surface waters, the (·)OH-induced transformation of N-substituted sulfonamide compounds to photostable products occurs on a time scale of days to weeks by model prediction.
authors: Department of Civil and Environmental Engineering, Faculty of Engineering, National University of Singapore, 1 Engineering Drive 2, E1A-07-03, Singapore 117576, Singapore. ceenvt@nus.edu.sg
authors: Tung Viet
authors: TV
authors: Nguyen
authors: Martin
authors: M
authors: Reinhard
authors: Karina Yew-Hoong
authors: KY
authors: Gin
mesh_terms: D004777:Environment; D005466:Fluorocarbons / Q000737:chemistry; D006845:Hydrocarbons, Fluorinated / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical / Q000737:chemistry*; D007700:Kinetics; D008962:Models, Theoretical; D012996:Solutions; D013449:Sulfonamides / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: C435127:2-(N-ethylperfluorooctanesulfonamido)ethyl alcohol; D005466:Fluorocarbons; D006845:Hydrocarbons, Fluorinated; C542083:N-ethyl perfluorooctane sulfonamido acetate; D012996:Solutions; D013449:Sulfonamides; D014874:Water Pollutants, Chemical; D017665:Hydroxyl Radical