TiO 2-photocatalyzed oxidative degradation of binary mixtures of vaporized organic compounds

Abstract

Rates of photocatalytic removal of the components for 14 binary mixtures of vaporized organic components over Degussa P-25 TiO 2 at 360 nm in the presence of air were measured. In some cases, intermediate products were identified and their rates of removal measured. Seven binary mixtures were reacted in a static reactor: CH 3OH strongly inhibited removal of CH 2Cl 2 while CH 2Cl 2 somewhat inhibited removal of CH 3OH. CH 3OH and trichloroethylene (TCE) strongly inhibited each other's removal. Strong memory effects were observed in inhibition of removal of CH 2Cl 2 from its mixture with CH 3OH and of CH 3OH from its mixture with TCE. CCl 4 significantly promoted removal of CH 3OH while CH 3OH had little effect on the rate of removal of CCl 4. Either 2-propanol or t-butanol and CCl 4 had little effect on each other's rates of removal. CH 2Cl 2 somewhat diminished only the initial rate of removal of C 2Cl 3F 3 (Freon 113). The Freon somewhat inhibited the much faster removal of CH 2Cl 2. Methanol somewhat inhibited removal of acetone while acetone had a negligible effect on the removal of methanol. Seven binary mixtures were reacted in flow reactors: TCE and perchloroethylene (PCE) somewhat promoted each other's removal. TCE strongly promoted removal of iso-octane, CH 2Cl 2 and CHCl 3. A strong memory effect occurred with iso-octane and probably with methylene chloride and chloroform. TCE substantially inhibited removal of acetone. The onset of inhibition of removal of acetonitrile by TCE was gradual and a memory effect occurred. Iso-octane somewhat reduced the rate of removal of benzene. Benzene had no effect on the rate of removal of iso-octane but greatly diminished the yield of acetone produced as an intermediate. Rationalizations of some of the data in terms of adsorption effects and chemical mechanism are presented.