TiO2-photocatalyzed oxidative degradation of binary mixtures of vaporized organic compounds

Rates of photocatalytic removal of the components for 14 binary mixtures of vaporized organic components over Degussa P-25 TiO2 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: CH3OH strongly inhibited removal of CH2Cl2 while CH2Cl2 somewhat inhibited removal of CH3OH. CH3OH and trichloroethylene (TCE) strongly inhibited each other's removal. Strong memory effects were observed in inhibition of removal of CH2Cl2 from its mixture with CH3OH and of CH3OH from its mixture with TCE CCl4 significantly promoted removal of CH3OH while CH3OH had little effect on the rate of removal of CCl4. Either 2-propanol or t-butanol and CCl4 had little effect on each other's rates of removal. CH2Cl2 somewhat diminished only the initial rate of removal of C2Cl3F3 (Freon 113). The Freon somewhat inhibited the much faster removal of CH2Cl2. 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, CH2Cl2 and CHCl3. 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. Copyright (C) 1996 Elsevier Science Ltd.