title: Singlet-Oxygen Generation in Alkaline Periodate Solution.
abstract: A nonphotochemical generation of singlet oxygen ((1)O2) using potassium periodate (KIO4) in alkaline condition (pH > 8) was investigated for selective oxidation of aqueous organic pollutants. The generation of (1)O2 was initiated by the spontaneous reaction between IO4(-) and hydroxyl ions, along with a stoichiometric conversion of IO4(-) to iodate (IO3(-)). The reactivity of in-situ-generated (1)O2 was monitored by using furfuryl alcohol (FFA) as a model substrate. The formation of (1)O2 in the KIO4/KOH system was experimentally confirmed using electron spin resonance (ESR) measurements in corroboration with quenching studies using azide as a selective (1)O2 scavenger. The reaction in the KIO4/KOH solution in both oxic and anoxic conditions initiated the generation of superoxide ion as a precursor of the singlet oxygen (confirmed by using superoxide scavengers), and the presence of molecular oxygen was not required as a precursor of (1)O2. Although hydrogen peroxide had no direct influence on the FFA oxidation process, the presence of natural organic matter, such as humic and fulvic acids, enhanced the oxidation efficiency. Using the oxidation of simple organic diols as model compounds, the enhanced (1)O2 formation is attributed to periodate-mediated oxidation of vicinal hydroxyl groups present in humic and fulvic constituent moieties. The efficient and simple generation of (1)O2 using the KIO4/KOH system without any light irradiation can be employed for the selective oxidation of aqueous organic compounds under neutral and near-alkaline conditions.
authors.affiliation: School of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH) , Pohang 790-784, Korea.
authors.forename: Alok D
authors.initials: AD
authors.lastname: Bokare
authors.affiliation: School of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH) , Pohang 790-784, Korea.
authors.forename: Wonyong
authors.initials: W
authors.lastname: Choi
mesh_terms: D000468:Alkalies / Q000737:chemistry*; D001386:Azides; D004578:Electron Spin Resonance Spectroscopy; D005663:Furans / Q000737:chemistry; D006861:Hydrogen Peroxide; D006878:Hydroxides / Q000737:chemistry; D017665:Hydroxyl Radical / Q000737:chemistry; D007700:Kinetics; D008027:Light; D009930:Organic Chemicals / Q000737:chemistry; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D010504:Periodic Acid / Q000737:chemistry*; D017680:Potassium Compounds / Q000737:chemistry*; D026082:Singlet Oxygen / Q000737:chemistry*; D012996:Solutions; D013481:Superoxides; D014867:Water
chemical_list: D000468:Alkalies; D001386:Azides; D005663:Furans; D006878:Hydroxides; D009930:Organic Chemicals; D017680:Potassium Compounds; D012996:Solutions; D014867:Water; D010504:Periodic Acid; D013481:Superoxides; D026082:Singlet Oxygen; D017665:Hydroxyl Radical; C009288:metaperiodate; D006861:Hydrogen Peroxide; C012986:furfuryl alcohol; C037192:potassium periodate; D010100:Oxygen; C029943:potassium hydroxide