Effect of catalyst and irradiation characteristics on volatile organic compounds degradation in aqueous phase using TiO2 photocatalyst.

Titanium dioxide (TiO₂) has been regarded as the most suitable photocatalyst due to its cost-effectiveness, high stability, and great potential to degrade various volatile organic compounds (VOCs). However, there is a knowledge limitation through the characteristics of TiO₂-based photocatalysts for practical application in the aqueous phase as well as its suitable irradiation source. Therefore, the present work aims to investigate the relative effect of various irradiation sources and TiO₂ catalysts types for VOCs degradation in an aqueous solution for optimization purposes. The experiment was conducted in a cylindrical photocatalytic oxidation column (PCO) with a 6-cm diameter to carry a 650 mL volume of VOC (benzene) solution. For irradiation investigation, lamp types (visible, UVA, VUV, and UVC) and lamp power (6 – 15 W) were investigated, under 1 g of TiO₂ commercial powder. Moreover, types of TiO₂ catalyst (commercial powder, coating on ring-shaped plastic media at different TiO₂ percentage by mass: 1% (1TPcB), 3% (3TPcB), and 5% (5TPcB), and coating 5% by mass on alumina ball) were studied at the identical mass usage of TiO₂. To identify the optimum dose, the different volume loading (5% – 20% v/v) of selective catalyst type was examined. The result indicated that the UVC lamp showed a significant degradation efficiency among other types of lamps. Additionally, when using the UVC at different powers, the degradation efficiencies at 100 minutes were at 30%, 40%, and 31% for 6, 12, and 15 W, respectively. This indicates that the UVC lamp at 12 W was the suitable wavelength and power for the degradation of benzene. Further investigation showed that coating TiO₂ on ring-shaped plastic media provided the highest degradation efficiency over the spherical and powder forms. It was because the light from the lamp had a better transmission through the hollow of the ring-shaped catalyst and, therefore, provided a better reaction rate than other types of catalysts. At the same condition and 100 min of operation time, the degradation efficiency of each catalyst is orderly: 5TPcB (56%)>3TPcB (49%)>1TPcB (43%)>alumina ball (32%)>powder (20%). In addition, it was also found that the optimum volume loading of ring-shaped 5TPcB catalyst in the column was 15% v/v. It provided the best degradation efficiency about 58% which was significantly higher among other conditions. This finding has proven the suitability of photocatalysis as an alternative polishing VOCs degradation in aqueous phase for further absorbent regeneration. [ABSTRACT FROM AUTHOR]