Korean Society of Environmental Engineers Photocatalysis of Low Concentration of Gaseous-Phase Benzene Using Visible-Light Irradiated N-doped and S-doped Titanium Dioxide

Studies on visible-light-driven photocatalysis of air pollutants at indoor air quality (IAQ) levels have been limited. Current study investigated visible-light derived photocatalysis with N-doped and S-doped titanium dioxide (TiO2) for the control of benzene at indoor levels. Two preparation processes were employed for each of the two types of photocatalyst: urea-Degussa P-25 TiO2 and titania-colloid methods for the N-doped TiO2; and titanium isopropoxid- and tetraisopropoxide-thiourea methods for the S-doped TiO2. Furthermore, two coating methods (EDTA- and acetylacetone-dissolving methods) were tested for both the N-doped and S-doped TiO2. The two coating methods exhibited different photocatalytic degradation efficiency for the N-doped photocatalysts, whereas they did not exhibit any difference for the S-doped photocatalysts. In addition, the two doping processes showed different photocatalytic degradation efficiency for both the S-doped and N-doped photocatalysts. For both the N-doped and S-doped TiO2, the photocatalytic oxidation (PCO) efficiency increased as the hydraulic diameter (HD) decreased. The degradation efficiency deter-mined via a PCO system with visible-light induced TiO2 was lower than that with UV-light induced unmodified TiO2, which was obtained from previous studies. Nevertheless, it is noteworthy that for the photocatalytic annular reactor with the HD of 0.5 cm, PCO efficiency increased up to 52 % for the N-doped TiO2 and 60 % for the S-doped TiO2. Consequently, when combined with the advantage of visible light use over UV light use, it is suggested that with appropriate HD conditions, the visible-light-assisted photocatalytic systems can also become an important tool for improving IAQ