Bed flow photoreactor experiments to assess the photocatalytic nitrogen oxides abatement under simulated atmospheric conditions

Abstract

Small scale bed flow photoreactor experiments were performed to assess the photocatalytic performance of cement-based TiO2-containing materials for NOx reduction through the determination of kinetic parameters under variation of the experimental conditions (relative humidity, flow rate, mixing ratio and light intensity) and monitoring of potential reaction products in the gas phase and the aqueous extract of the surface. The results clearly demonstrated the general potential of the tested material to photocatalytically remediate gas phase NOx by conversion into nitrite and nitrate as identified reaction products at the surface. The measured uptake coefficients for NO and NO2 under atmospheric relevant conditions were in the range of 5 × 10−5 with a corresponding surface deposition velocity of about 0.5 cm s−1. However, it became also clear that the photocatalytic activity is in part significantly dependent on the experimental conditions. The relative humidity and the mixing ratio of the air pollutant were identified as the most important parameters. In addition, under certain conditions, a renoxification process can occur. The comprehensive results of the present study are discussed in detail to develop recommendations for a possible future application of this technique to improve urban air quality.