TIO2-PHOTOCATALYZED OXIDATIVE-DEGRADATION OF BINARY-MIXTURES OF VAPORIZED ORGANIC-COMPOUNDS

Rates of photocatalytic removal of the components for 14 binary mixtur es of vaporized organic components over Degussa P-25 TiO2 at 360 nm in the presence of air were measured. In some cases, intermediate produc ts were identified and their rates of removal measured. Seven binary m ixtures were reacted in a static reactor: CH3OH strongly inhibited rem oval 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 CC l4 significantly promoted removal of CH3OH while CH3OH had little effe ct 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 somewh at diminished only the initial rate of removal of C2Cl3F3 (Freon 113). The Freon somewhat inhibited the much faster removal of CH2Cl2. Metha nol somewhat inhibited removal of acetone while acetone had a negligib le effect on the removal of methanol. Seven binary mixtures were react ed in flow reactors: TCE and perchloroethylene (PCE) somewhat promoted each other's removal. TCE strongly promoted removal of iso-octane, CH 2Cl2 and CHCl3. A strong memory effect occurred with iso-octane and pr obably with methylene chloride and chloroform. TCE substantially inhib ited removal of acetone. The onset of inhibition of removal of acetoni trile by TCE was gradual and a memory effect occurred. Iso-octane some what 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 d ata in terms of adsorption effects and chemical mechanism are presente d. Copyright (C) 1996 Elsevier Science Ltd.