title: Oxidation of triclosan by ferrate: reaction kinetics, products identification and toxicity evaluation.
abstract: The oxidation of triclosan by commercial grade aqueous ferrate (Fe(VI)) was investigated and the reaction kinetics as a function of pH (7.0-10.0) were experimentally determined. Intermediate products of the oxidation process were characterized using both GC-MS and RRLC-MS/MS techniques. Changes in toxicity during the oxidation process of triclosan using Fe(VI) were investigated using Pseudokirchneriella subcapitata growth inhibition tests. The results show that triclosan reacted rapidly with Fe(VI), with the apparent second-order rate constant, k(app), being 754.7 M(-1) s(-1) at pH 7. At a stoichiometric ratio of 10:1 (Fe(VI):triclosan), complete removal of triclosan was achieved. Species-specific rate constants, k, were determined for reaction of Fe(VI) with both the protonated and deprotonated triclosan species. The value of k determined for neutral triclosan was 6.7(±1.9)×10(2) M(-1) s(-1), while that measured for anionic triclosan was 7.6(±0.6)×10(3) M(-1) s(-1). The proposed mechanism for the oxidation of triclosan by the Fe(VI) involves the scission of ether bond and phenoxy radical addition reaction. Coupling reaction may also occur during Fe(VI) degradation of triclosan. Overall, the degradation processes of triclosan resulted in a significant decrease in algal toxicity. The toxicity tests showed that Fe(VI) itself dosed in the reaction did not inhibit green algae growth.
authors.affiliation: State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Yang
authors.forename: Guang-Guo
authors.initials: GG
authors.lastname: Ying
authors.forename: Jian-Liang
authors.initials: JL
authors.lastname: Zhao
authors.forename: Li-Juan
authors.initials: LJ
authors.lastname: Zhang
authors.forename: Yi-Xiang
authors.initials: YX
authors.lastname: Fang
authors.forename: Long Duc
authors.initials: LD
authors.lastname: Nghiem
mesh_terms: D000890:Anti-Infective Agents / Q000737:chemistry* / Q000633:toxicity; D008401:Gas Chromatography-Mass Spectrometry; D006863:Hydrogen-Ion Concentration; D007202:Indicators and Reagents; D007501:Iron / Q000737:chemistry*; D007700:Kinetics; D010084:Oxidation-Reduction; D012015:Reference Standards; D014260:Triclosan / Q000737:chemistry* / Q000633:toxicity
chemical_list: D000890:Anti-Infective Agents; D007202:Indicators and Reagents; C017311:ferrate ion; D014260:Triclosan; D007501:Iron