The Comparison of Toluene Removal Rate in Two Photocatalytic Oxidation Systems of ZnO and TiO2 Nanoparticles on SiO2 bed

Volatile organic compounds (VOCs) are one of the main group of air pollutants. Photocatalytic oxidation is one of the destructive methods for gaseous pollutants and has been received more attention in the past years. In this study investigated the comparison of the toluene removal efficiency by Photocatalytic Oxidation of Toluene by ZnO/SiO2 and TiO2/SiO2. In this study, the effect of parameters such as the amount of relative humidity, initial concentration of pollutant, the apparent speed of gas and the minimum speed of fluidizing of bed on the process of photocatalytic oxidation of Toluene is examined by comparison between TiO2/SiO2 and ZnO/SiO2 catalysts in a fluidized bed reactor. as it was explained, by absorption of water molecules on the surface of the catalyst and converting them to hydroxyl active radicals, these radicals act as a pushing factor in the reaction. The study also showed that an increase in the relative humidity in the 15–45% range would increase the efficacy of toluene oxidation. Conversion percentages between TiO2/SiO2 and ZnO/SiO2 catalysts were not significantly different (pv> 0.05), while the reaction rate of ZnO/SiO2 catalyst was higher than TiO2/ SiO2 catalyst (pv<0.05). In the study of the interaction between the apparent velocity variables, initial concentration of toluene and loading of zinc oxide and titanium dioxide, only the interaction between two gas velocity variables and initial concentration of toluene was significant. The results showed that ZnO/SiO2 catalysts generally have a larger efficacy than TiO2/SiO2, presumably because ZnO/SiO2 has more active sites. Additionally, the ZnO/SiO2 catalysts offer better fluidity than TiO2/SiO2. The photo catalytic transformation rate of the pollutant is relatively low, as the optimum humidity level for appears to be 45%.

Keywords:

Photocatalysis , Toluene , ZnO/ TiO2 , TiO2/SiO2 , Fluidized bed Reactor