A “deactivation” kinetic model for predicting the performance of photocatalytic degradation of indoor toluene, o-xylene, and benzene

A glass-plate reactor coated with a commercial titanium dioxide was used to investigate the performance of ultraviolet photocatalytic oxidation (UV-PCO) of toluene, o-xylene and benzene contained in air. The concentration of each compound at reactor inlet ranged from 0 to 3.5 ppm. Under indoor air conditions, the degradation rate of toluene and o-xylene rose to a maximum value with the concentration increase, and then began to decrease. This could not be interpreted by the classic L–H model. Considering the possibility of the photoactivity decay, a “deactivation model” fitted for the concentration levels tested. Studies found that the degradation performance of benzene also worked well with this model. Besides, the concepts of active region, deactivation region, inhibiting concentration, maximum reaction rate, and maximum required light intensity were applied to explain the phenomena. The results would be useful for better understanding the reaction kinetics of PCO in deactivating common indoor air contaminants.