Photochemical and photocatalytic degradation of gaseous toluene using short-wavelength UV irradiation with TiO 2 catalyst: comparison of three UV sources

Abstract

The feasibility of the use of short-wavelength UV (254 + 185 nm) irradiation and TiO 2 catalyst for photodegradation of gaseous toluene was evaluated. It was clear that the use of TiO 2 under 254 + 185 nm light irradiation significantly enhanced the photodegradation of toluene relative to UV alone, owed to the combined effect of photochemical oxidation in the gas phase and photocatalytic oxidation on TiO 2. The photodegradation with 254 + 185 nm light irradiation was compared with other UV wavelengths (365 nm (black light blue lamp) and 254 nm (germicidal UV lamp)). The highest conversion and mineralization were obtained with the 254 + 185 nm light. Moreover, high conversions were achieved even at high initial concentrations of toluene. Catalyst deactivation was also prevented with the 254 + 185 nm light. Regeneration experiments with the deactivated catalyst under different conditions revealed that reactive oxygen species played an important role in preventing catalyst deactivation by decomposing effectively the less reactive carbon deposits on the TiO 2 catalyst. Simultaneous elimination of photogenerated excess ozone and residual organic compounds was accomplished by using a MnO 2 ozone-decomposition catalyst to form reactive species for destruction of the organic compounds.