title: Photocatalytic oxidation of low concentration 2,4-D solution with new TiO2 fiber catalyst in a continuous flow reactor.
abstract: Environmental pollution by low concentrations of 2,4-Dichlorophenoxyacetic acid (2,4-D) is a concern these days due to ever increasingly stringent regulations. Photocatalysis with immobilized TiO2 fiber is a promising oxidation method. Laboratory experiments on photocatalytic degradation of 0.045 mmol l(-1) 2,4-D with the world's first high-strength TiO2 fiber catalyst were carried out in a continuous flow reactor in which the degradations were, in general, similar to those with high 2,4-D concentrations investigated elsewhere. Degradation and mineralization of 2,4-D were significantly enhanced with no initial pH adjustments. The rate constants for total organic carbon (TOC) without pH adjustment were about two-fold bigger than the pH adjustment cases. CO2 gas measurement and carbon mass-balance were carried out for the first time, where about 34% organic carbon converted into CO2 gas during four-hour oxidation. 2,4-Dichlorophenol (2,4-DCP), phenol, benzyl alcohol and two unknowns (RT = 2.65 and 3.78 min.) were detected as aromatic intermediates while Phenol was the new aromatic in HPLC analysis. Dechlorination efficiencies were high (> 70%) in all the cases, and more than 90% efficiencies were observed in chloride mass balance. Bigger flow rates and solution temperature fixed at 20 degrees C without pH adjustment greatly enhanced 2,4-D mineralization. These results can be an important basis in applying the treatment method for dioxin-contaminated water and wastewater.
authors.affiliation: Dept. of Human Environment, Osaka Sangyo University, 3-1-1 Nakataito, Daito City, 574-8530 Osaka, Japan. terashima@due.osaka-sandai.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Terashima
authors.forename: H
authors.initials: H
authors.lastname: Ozaki
authors.forename: R R
authors.initials: RR
authors.lastname: Giri
authors.forename: T
authors.initials: T
authors.lastname: Tano
authors.forename: S
authors.initials: S
authors.lastname: Nakatsuji
authors.forename: R
authors.initials: R
authors.lastname: Takanami
authors.forename: S
authors.initials: S
authors.lastname: Taniguchi
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000737:chemistry* / Q000378:metabolism; D002384:Catalysis; D006540:Herbicides / Q000737:chemistry* / Q000378:metabolism; D006573:Heterocyclic Compounds, 1-Ring / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D010777:Photochemistry; D014025:Titanium / Q000737:chemistry*; D014466:Ultraviolet Rays; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000737:chemistry* / Q000378:metabolism; D018508:Water Purification / Q000295:instrumentation / Q000379:methods*
chemical_list: D006540:Herbicides; D006573:Heterocyclic Compounds, 1-Ring; D014874:Water Pollutants, Chemical; C009495:titanium dioxide; D015084:2,4-Dichlorophenoxyacetic Acid; D014025:Titanium