A plug-flow reactor coated with carbon-doped TiO2 (C-TiO2) powder was investigated for the control of vaporous aromatics (benzene, toluene, ethylbenzene, and o-xylene (BTEX)) under a range of experimental conditions. The characteristics of the as-prepared C-TiO2 and a reference Degussa P25 TiO2 powder were examined using X-ray diffraction, scanning electron microscopy, diffuse-reflectance ultraviolet-visible-near infrared spectroscopy, and Fourier transform infrared spectroscopy. The experimental conditions for the photocatalytic performance of the as-prepared C-TiO2 photocatalyst were controlled using three operational parameters, relative humidity, flow rate, and input concentration. Unlike other target compounds, very little benzene was removed by the C-TiO2 photocatalyst under visible-light irradiation. In contrast, the C-TiO2 exhibited higher removal efficiencies for the other three target compounds (toluene, ethylbenzene, and xylene) compared with those achieved using unmodified TiO2 under visible-light irradiation. The highest removal efficiency was obtained at a relative humidity value of 45%. Specifically, the toluene removal efficiency determined at a relative humidity of 45% was 78%, whereas it was close to 0%, 7.2%, and 5.5% for relative humidity values of 20%, 70%, and 95%, respectively. In addition, the removal efficiencies for the three target compounds decreased as the flow rate or input concentration increased. These findings indicate that the as-prepared C-TiO2 photocatalyst could be used for the removal of toxic vaporous aromatics under optimized operating conditions.
