Impact of Mixed Nitrogen Dioxide (NO/d2) and Nitrogen Oxide (NO) Gases on Titanium Dioxide Photodegradation of NO/dx

Nitrogen oxides (NO_x) emitted from vehicle exhausts are associated with adverse health effects on the public. Self-cleaning, air-purifying concrete pavement is a rapidly emerging technology that can be constructed using photocatalyst such as titanium dioxide (TiO₂). The main objective of this study was to evaluate the environmental effectiveness of TiO₂ coating in photodegrading mixed NO₂ and NO gases from the atmosphere. Results of the experimental program determined that increasing the flow rate and NO₂/NO_x ratio negatively affect the effectiveness of the photocatalytic process. However, within the evaluated range, the titanium content and aggregate gradation had little impact on NO_x removal efficiency. The highest photodegradation rate was observed at 25% relative humidity, which balances the availability of hydroxyl radicals at the surface with NO_x contact with the photocatalytic surface.