Titanium dioxide irradiation

Augugliaro V, Bianco Prevot A, Caceres Vazquez J, Garcia-L6pez E, Loddo V, Malato-Rodriguez S, Mard G, Palmisano L and Pramauro E (2004b), Photocatalytic oxidation of acetonitrile in aqueous suspension of titanium dioxide irradiated by sunlight , Adv Environ Res, 8,329-335. 

Heterogeneous Photocatalysis. Heterogeneous photocatalysis is a technology based on the irradiation of a semiconductor (SC) photocatalyst, for example, titanium dioxide [13463-67-7] Ti02, zinc oxide [1314-13-2] ZnO, or cadmium sulfide [1306-23-6] CdS. Semiconductor materials have electrical conductivity properties between those of metals and insulators, and have narrow energy gaps (band gap) between the filled valence band and the conduction band (see Electronic materials Semiconductors). 

Spin trapping by PBN has also been employed to detect radical formation in a photo-Kolbe reaction in which acetic acid is irradiated (A > 360 nm) in the presence of platinized titanium dioxide powder (Kraeutler et al, 1978). The nitroxide observed was considered to be (PBN—Me ), but the published spectrum clearly shows the presence of a second species spectral overlap might therefore be an alternative to solvent polarity as an explanation of the discrepancy between the observed splitting parameters and those previously reported for this species. Where poor resolution obtains, it is important that... 

Fujishima and Honda reported the splitting of water by the use of a semiconductor electrode of titanium dioxide (rutile) connected through an electrical load to a platinum black counter-electrode. Irradiation of the Ti02 electrode with near-UV light caused electrons to flow from it to the platinum counter-electrode via the external circuit. 

Titanium dioxide suspended in an aqueous solution and irradiated with UV light X = 365 nm) converted benzene to carbon dioxide at a significant rate (Matthews, 1986). Irradiation of benzene in an aqueous solution yields mucondialdehyde. Photolysis of benzene vapor at 1849-2000 A yields ethylene, hydrogen, methane, ethane, toluene, and a polymer resembling cuprene. Other photolysis products reported under different conditions include fulvene, acetylene, substituted trienes (Howard, 1990), phenol, 2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol, 2,6-dinitro-phenol, nitrobenzene, formic acid, and peroxyacetyl nitrate (Calvert and Pitts, 1966). Under atmospheric conditions, the gas-phase reaction with OH radicals and nitrogen oxides resulted in the formation of phenol and nitrobenzene (Atkinson, 1990). Schwarz and Wasik (1976) reported a fluorescence quantum yield of 5.3 x 10" for benzene in water. 

Titanium dioxide suspended in an aqueous solution and irradiated with UV light (A. = 365 nm) converted chlorobenzene to carbon dioxide at a significant rate (Matthews, 1986). Products identified as intermediates in this reaction include three monochlorophenols, chlorohydroquinone, and hydroxyhydroquinone (Kawaguchi and Furuya, 1990). 

Photolytic. Complete mineralization was reported when distilled deionized water containing chloroform (118 ppm) and 0.1 wt % titanium dioxide as a catalyst was irradiated with UV light. Mineralization products included carbon dioxide and HCl (Pruden and Ollis, 1983). Photocatalyzed mineralization of chloroform in the presence of titanium dioxide as catalyst... 

Photolytic. An aqueous solution containing p-chloronitrobenzene and a titanium dioxide (catalyst) suspension was irradiated with UV light ilk >290 nm). 2-Chloro-5-nitrophenol was the only compound identified as a minor degradation product. Continued irradiation caused additional degradation yielding carbon dioxide, water, hydrochloric and nitric acids (Hustert et al., 1987). 

When an aqueous solution containing pentachlorophenol (45 pM) and a suspension of titanium dioxide (2 g/L) was irradiated with UV light, carbon dioxide and HCl formed in quantitative amounts. The half-life for this reaction at 45-50 °C is 8 min (Barbeni et al, 1985). When an aqueous solution containing pentachlorophenol was photooxidized by UV light at 90-95 °C, 25, 50, and 75% degraded to carbon dioxide after 31.7, 66.0, and 180.7 h, respectively (Knoevenagel and Himmelreich, 1976). The photolysis half-lives of pentachlorophenol under sunlight irradiation in distilled water and river water were 27 and 53 h, respectively (Mansour et al., 1989). 

Photolytic. When 2,4,5-T (100 pM), in oxygenated water containing titanium dioxide (2 g/L) suspension, was irradiated by sunlight (L >340 nm), 2,4,5-trichlorophenol, 2,4,5-trichlorophenyl formate, and nine chlorinated aromatic hydrocarbons formed as major intermediates. Complete... 

Irradiation of toluene (80 ppm) by UV light (A, = 200-300 nm) on titanium dioxide in the presence of oxygen (20%) and moisture resulted in the formation of benzaldehyde and carbon dioxide. Carbon dioxide concentrations increased linearly with the increase in relative humidity. However, the concentration of benzaldehyde decreased with an increase in relative humidity. An identical experiment, but without moisture, resulted in the formation of benzaldehyde, carbon dioxide, hydrogen cyanide, and nitrotoluenes. In an atmosphere containing moisture and nitrogen dioxide (80 ppm), cresols, benzaldehyde, carbon dioxide, and nitrotoluenes were the photoirradiation products (Ibusuki and Takeuchi, 1986). 

Jacoby et al. (1994) studied the photocatalytic reaction of gaseous trichloroethylene in air in contact with UV-irradiated titanium dioxide catalyst. The UV radiation was kept less than the maximum wavelength so that the catalyst could be excited by photons, i.e., X <356 nm. Two reaction pathways were proposed. The first pathway includes the formation of the intermediate dichloroacetyl chloride. This compound has a very short residence time and is quickly converted to the following compounds phosgene, carbon dioxide, carbon monoxide, carbon dioxide, and hydrogen chloride. The second pathway involves the formation of the final products without the formation of the intermediate. 

CASRN 108-43-0 molecular formula CeHsClO FW 128.56 Photolytic. Irradiation of an aqueous solution containing 3-chlorophenol and titanium dioxide with UV light (X >340 nm) resulted in the formation of chlorohydroquinone then to hydroxyhydroquinone. Identification of compounds from the oxidation of hydroxyhydroquinone to carbon dioxide were not identified because of the low concentrations (D Oliveira et al, 1990). 

Ibusuki, T. and Takeuchi, K. Toluene oxidation on U.V.-irradiated titanium dioxide with and without O2. NO2 or H2O at ambient temperature, Atmos. Environ., 29(9) 1711-1715, 1986. 

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