Photooxidation of a model pollutant in an oscillatory flow reactor with baffles

The degradation of an organic model pollutant, salicylic acid, by means of heterogeneous photocatalytic oxidation in a pulsed baffled tubular photochemical reactor (PBTPR), has been studied. Our studies show that oscillatory flow in the PBTPR can efficiently produce uniform dispersion of catalysts of a wide range of catalyst particle sizes, ranging from 20–150 (mu)m, and completely mineralize organic compounds. An interesting observation is that using the PBTPR with excess hydrogen peroxide, a nearly 100% rutile titania (Aldrich) is more efficient in mineralizing organics than the anatase-rich Degussa P25. We attribute this to the enhanced mass transfer for the Aldrich catalyst due to chaotic mixing, which renders the hydrogen peroxide a more efficient electron acceptor and facilitates the rapid conversion of hydrogen peroxide to hydroxyl radicals. This simultaneously lowers the electron–hole recombination rate, which has been considered to be a major factor for the low oxidation efficiency of rutile titania catalysts.