The Effect of Ozone on the Removal Effectiveness of Photocatalysis on Indoor Gaseous Biogenic Volatile Organic Compounds

In this study, the degradation of d-limonene by photocatalytic oxidation (PCO) (titanium dioxide [TiO2]/ultraviolet [UV]) and by the combination of PCO and ozone (O-3) (TiO2/UV/O-3) was investigated to evaluate the enhancement effect of O-3. The degradation of d-limonene by UV/O-3 was also investigated for comparison. The experiments were conducted with a quartz photoreactor under various gas flow rates (600-1600 mL d-limonene concentrations (0.5-9 parts per million [ppm]), and relative humidity (RH) (20-80%). The d-limonene removal efficiency of TiO2/UV/O-3, TiO2/UV, and UV/O-3 ranged from 62 to 99%, from 49 to 99%, and from 46 to 75%, respectively. The addition of 120-ppb O-3 can enhance the d-limonene removal efficiency of PCO up to 12%. The apparent kinetic parameters (apparent rate constants, k(apparent) and Langmuir adsorption constants, K-apparent) of TiO2/UV and TiO2/UV/O-3 reactions obtained from fitting residual intermediates yield rates of d-limonene by up to 1.46 mu mol carbon m(-2) sec(-1). These experimental results showed that O-3 can enhance the effectiveness of photocatalysis on the removal of d-limonene.