Investigation Of The Photochemical Conversion Of NO₂on The Surface Of SiO₂, Al₂O₃and Fe₂O₃

The mechanism of the reaction of photolysis of NO2and photochemical reaction ofNO2on the surface of SiO2, Al2O3and Fe2O3at308nm UV light,365nm UV light andin the dark were investigated, using Fourier transform infrared spectroscopy (FTIR) andion chromatogram (IC). In addition, the effect of different factors (time, concentration,humidity) on the reactions was also studied in this paper. The results are as follows：NO2gas phase photodissociation experiments suggested that the concentration andyield of NO production increased with the increase of illumination time，NO2initialconcentration and relative humidity. In addition, NO concentration was higher at308nmUV light.When NO2initial concentration of was300Pa, reaction temperature was25℃and exposured to80min at308nm UV light, NO concentration could reach2.05Pa. Inthe presence of UV light and water vapor, HONO concentration and yield increasedwith the increase of relative humidity. With NO2initial concentration of300Pa,reaction temperature of25℃，relative humidity of60%and illumination time of40minat308nm UV light, HONO concentration and yield could be1.71and0.17, respectively.The photochemical reaction of NO2on the surface of SiO2at308nm and365nm UVlight showed that the main gas-phase product NO concentration and yield and NO3-,NO2-production showed an increase with the increase of irradiation time and initialconcentration of NO2. Gas phase products NO and HONO concentration increased withincreasing humidity while NO3-and NO2-yield decreased with the increase of humidity.With NO2initial concentration of300Pa, reaction temperature of25℃，relativehumidity of60%and illumination time of40min at308nm UV light, HONOconcentration could be5.11Pa and H yiele was0.28. NO3-and NO2-yield on SiO2surface were0.009and0.0001，respectively.The photochemical reaction of NO2on the surface of Al2O3at308nm and365nmUV light suggested that the main product NO concentration and yield and NO3-, NO2-production increased as irradiation time and NO2initial concentration increased.Withincreasing humidity, gas phase products NO and HONO emissions showed a risingtrend, and NO2-, NO3-content on particle surfaces showed a decrease. When NO2initialconcentration was300Pa, reaction temperature was25℃，relative humidity was60%and illumination time was40min at308nm UV light, HONO yield was0.25. NO3-andNO2-yield on Al2O3surface were0.30and0.09，respectively. The photochemical reaction of NO2on Fe2O3surface at308nm and365nm UVlight suggested that with increasing illumination time and the initial concentration ofNO2, NO concentration, NO yield and NO3-, NO2-content on Fe2O3surface increased.As the humidity increases, NO and HONO concentration increased, while the NO3-,NO2-adsorption amount decreased. With NO2initial concentration of300Pa, reactiontemperature of25℃，relative humidity of60%and illumination time of40min at308nm UV light, HONO concentration could be6.03Pa and HONO yield was0.27.NO3-and NO2-yield were0.32and0.07，respectively.