title: Oxidation of microcystin-LR by ferrous-tetrapolyphosphate in the presence of oxygen and hydrogen peroxide.
abstract: Ferrous-tetrapolyphosphate complexes (Fe(II)-TPP) activate oxygen and hydrogen peroxide to produce reactive oxidants capable of degrading organic compounds. In this study, the Fe(II)-TPP/O2and Fe(II)-TPP/H2O2systems were assessed for oxidative degradation of microcystin-LR (MC-LR), the most toxic and abundant cyanotoxin. The degradation of MC-LR was optimized for both the Fe(II)-TPP/O2and Fe(II)-TPP/H2O2systems when the molar ratio of TPP:Fe(II) was approximately 5.7-5.9. The optimal H2O2dose for MC-LR degradation by Fe(II)-TPP/H2O2was found to be 320 μM. The Fe(II)-TPP/O2and Fe(II)-TPP/H2O2systems exhibited two pH optima for MC-LR degradation i.e., ∼7 and 9, which can be attributed to pH-dependent reactivity changes of the resultant oxidants (most likely the ferryl-tetrapolyphostate complex, Fe(IV)-TPP). Liquid chromatography-mass spectrometry identified 22 compounds produced by the oxidation of MC-LR, including four primary oxidation products. One of the primary products, in particular, was formed via oxidative cleavage of the alkene group in the Mdha moiety of MC-LR. This compound and its secondary oxidation products are rarely found when MC-LR is transformed by other oxidants and is believed to reflect a unique reaction pathway involving Fe(IV)-TPP. Meanwhile, the hepatotoxicity of the reaction solution decreased concurrently with a decrease on MC-LR concentration.
authors.affiliation: School of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulju-gun, Ulsan, 44919, Republic of Korea.
authors.forename: Min Sik
authors.initials: MS
authors.lastname: Kim
authors.affiliation: School of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulju-gun, Ulsan, 44919, Republic of Korea.
authors.forename: Hak-Hyeon
authors.initials: HH
authors.lastname: Kim
authors.affiliation: School of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulju-gun, Ulsan, 44919, Republic of Korea.
authors.forename: Ki-Myeong
authors.initials: KM
authors.lastname: Lee
authors.affiliation: School of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulju-gun, Ulsan, 44919, Republic of Korea.
authors.forename: Hye-Jin
authors.initials: HJ
authors.lastname: Lee
authors.affiliation: School of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulju-gun, Ulsan, 44919, Republic of Korea. Electronic address: clee@unist.ac.kr.
authors.forename: Changha
authors.initials: C
authors.lastname: Lee
mesh_terms: D002853:Chromatography, Liquid; D006861:Hydrogen Peroxide / Q000737:chemistry*; D016877:Oxidants / Q000737:chemistry; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*
chemical_list: D016877:Oxidants; D006861:Hydrogen Peroxide; D010100:Oxygen
keywords: Fenton reaction; Ferryl ion; Microcystin-LR; Oxidation; Oxidation product; Tetrapolyphosphate