The effect of ozone on the removal effectiveness of photocatalysis on indoor gaseous biogenic volatile organic compounds

Abstract

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 (O3) (TiO2/UV/O3) was investigated to evaluate the enhancement effect of O3. The degradation of d-limonene by. UV/O3 was also investigated for comparison. The experiments were conducted with a quartz photoreactor under various gas flow rates (600-1600 mL min-1), d-limonene concentrations (0.5-9 parts per million [ppm]), and relative humidity (RH) (20-80%). The d-limonene removal efficiency of TiO2/UV/O3, TiO 2/UV, and UV/O3 ranged from 62 to 99%, from 49 to 99%, and from 46 to 75%, respectively. The addition of 120-ppb O3 can enhance the d-limonene removal efficiency of PCO up to 12%. The apparent kinetic parameters (apparent rate constants, kapparent and Langmuir adsorption constants, Kapparent) of TiO2/UV and TiO 2/UV/O3 reactions obtained from fitting Langmuir-Hinshelwood models are TiO2/UV: kapparent = 1.45 × 10-3 ppm-m sec-1, Kapparent = 0.34 ppm-1; TiO2/UV/O3: kapparent = 1.83 × 10-3 ppm-m sec-1, and Kapparent = 0.35 ppm-1. When RH was higher than 40%, the residual intermediates yield rates of d-limonene of TiO2/UV/O3, TiO2/UV, and UV/O3 reactions ranged from 0.39 to 0.51 μmol carbon m -2 sec-1, 0.56 to 1.96 μmol carbon m-2 sec-1, and 157 to 177 μmol carbon m-3 sec-1, respectively. In the photocatalytic reaction experiments, the addition of 120-parts per billion (ppb) O3 can reduce the residual intermediates yield rates of d-limonene by up to 1.46 μmol carbon m-2 sec -1. These experimental results showed that O3 can enhance the effectiveness of photocatalysis on the removal of d-limonene. Copyright 2010 Air & Waste Management Association.