Elsevier

Applied Catalysis B: Environmental

Volume 231, 5 September 2018, Pages 161-172
Applied Catalysis B: Environmental

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

https://doi.org/10.1016/j.apcatb.2018.03.010Get rights and content
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Highlights

  • Photocatalytic cementbased materials were tested for reaction with NO, NO2, HONO.

  • Fast uptake was observed under simulated atmospheric conditions for all NOy species.

  • Strong dependence of the uptake of NO and NO2 on humidity and concentration.

  • A consecutive mechanism was proposed: NO → NO2 → HNO3.

  • NOx-abatement of only a few % estimated for typical urban street canyon 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.

Keywords

Heterogeneous photocatalysis
Titanium dioxide
Cement-based material
NOx
Bed flow reactor

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