title: A novel use of TiO2 fiber for photocatalytic ozonation of 2,4-dichlorophenoxyacetic acid in aqueous solution.
abstract: More efficient oxidation methods are needed to degrade especially newly emerging recalcitrant organic contaminants at low concentrations in the water environment. Reduced photonic efficiency of immobilized TiO2 is a major challenge in TiO2-assisted advanced oxidation processes (AOP). Mineralization of 2,4-dichllorophenoxyacetic acid (2,4-D) in low aqueous solution by O3/UV/TiO2 using the world's first high-strength TiO2 fiber was investigated and compared with O3, UV/TiO2, and O3/TiO2 in laboratory batch experiments. The 2,4-D degradation and total organic carbon (TOC) removal followed pseudo first-order reaction kinetic, while their rates in O3/UV/TiO2 were respectively about 1.5 and 2.4 times larger than the summation of the values in 03 and UV/TiO2. The O3/UV/TiO2 was characterized by few aromatics with very low abundance, fast disappearance of aliphatics and more than 95% dechlorination. The discrepancies in organic carbon mass balance among the intermediates and 2,4-D were attributed mainly to few apparently major unidentified intermediates. The significantly enhanced 2,4-D mineralization in O3/UV/TiO2 was attributed to increased ozone dissolution followed by its decomposition, and reduced electron-hole recombination in presence of dissolved ozone resulting in a large number of hydroxyl radical (*OH) generation from more than one parallel path. The removal efficiencies of the systems can further be enhanced by optimizing design parameters, and O3/UV/TiO2 with the TiO2 fiber is promising to mineralize recalcitrant organic contaminants in water at low concentrations.
authors.affiliation: New Industrial R & D Center Osaka Sangyo University, 3-1-1 Nakagaito, Daito City, 574-8530 Osaka, Japan. rabindra@cnt.osaka-sandai.ac.jp
authors.forename: Raj Rabindra
authors.initials: RR
authors.lastname: Giri
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Ozaki
authors.forename: Ryohei
authors.initials: R
authors.lastname: Takanami
authors.forename: Shogo
authors.initials: S
authors.lastname: Taniguchi
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000737:chemistry*; D002384:Catalysis; D007700:Kinetics; D010084:Oxidation-Reduction; D010126:Ozone; D010777:Photochemistry; D012996:Solutions; D014025:Titanium / Q000737:chemistry*; D014865:Waste Disposal, Fluid / Q000379:methods; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000302:isolation & purification; D018508:Water Purification / Q000379:methods
chemical_list: D012996:Solutions; D014874:Water Pollutants, Chemical; D014867:Water; C009495:titanium dioxide; D015084:2,4-Dichlorophenoxyacetic Acid; D010126:Ozone; D014025:Titanium