Photodegradation of benzene by TiO2 nanoparticles prepared by flame CVD process

Photodegradation of benzene at ppb levels by mixed-phase TiO2 nanoparticles, synthesized by the oxidation of TiCl4 in propane/air turbulent flame chemical vapor deposition (CVD) process, is investigated experimentally by using a tubular photoreactor with thin TiO2 films coated on the reactor wall by sedimentation. Effects of inlet benzene concentration from 10 to 300 mu g/m(3), rutile mass fraction from about 20 to 50% and photoluminescence (PL) intensity of TiO2 nanoparticles on degradation degree are examined under the conditions of 70% relative humidity, 38 mu g/cm(2) catalyst loading, 24 mW/cm(2) UV irradiation of 254 nm and 5.7 s residence time in the reactor. Based on experimental results, separation of photoinduced electron (e(-)) and hole (h(+)) pairs by rutile phase is discussed as photo-induced electron (e-) in anatase phase will migrate to ruffle surface due to that the potential of conductive band of ruffle is lower than that of anatase, leading to more holes ready on anatase surface for oxidation reactions. (C) 2010 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.