Degradation of toluene gas at the surface of ZnO/SnO2 photocatalysts in a baffled bed reactor

Abstract

To eliminate volatile organic compounds (VOCs) from contaminated air, a novel medium-scale baffled photocatalytic reactor was designed and fabricated, using immobilized ZnO/SnO2 coupled oxide photocatalysts. Toluene was chosen as a representative pollutant of VOCs to investigate the degradation mechanism and the parameters affecting photocatalytic degradation efficiency. The preliminary experimental results indicate that the degradation efficiency of toluene increased with the increase of the light irradiation dosage, while it decreased with the increase of concentrations of toluene. The degradation efficiency increased rapidly with the increase of the relative humidity in a low humidity range from 0 to 35%, but decreased gradually in a high relative humidity (i.e., >35%). The optimum experimental conditions for toluene degradation is a toluene concentration of 106 mg m−3, a relative humidity of 35%, and an illumination intensity of ca. 6 mW cm−2 at the surface of ZnO/SnO2 photocatalysts. The intermediates produced during the gaseous photocatalytic degradation process were identified using the GC–MS technique. Based on these identified intermediates, the photocatalytic mechanism of toluene into ZnO/SnO2 coupled oxide catalyst was also deduced.