Efficient photocatalytic oxidation of gaseous toluene over F-doped TiO2 in a wet scrubbing process

The application of photocatalytic oxidation (PCO) of volatile organic compounds (VOCs) is strongly limited by catalyst deactivation, low mineralization ability and mass-transfer in gas-solid phase. Wet-scrubbing coupled with PCO (WPCO) provides a novel and efficient method for VOCs degradation. Fluorine-doped TiO2 (F-TiO2) photocatalyst was prepared and applied in this coupled process for toluene degradation. Toluene removal efficiency reached 80% over F-TiO2, while it was only 25% over TiO2 in the WPCO process. As for gas-solid PCO process, F-TiO2 had a low toluene removal efficiency of 10%. Furthermore, the mineralization capability of WPCO process over F-TiO2 also remarkably increased, achieving about 92 ppmv CO2 generated from toluene oxidation. Compared with TiO2, the surface fluorinated TiO2 significantly enhanced toluene degradation since it generated mobile hydroxyl radical (OH) in the WPCO process. The F/Ti molar ratio (RF) greatly affected photocatalytic activity towards toluene degradation, and the F-TiO2 with RF at 1 obtained the best performance. The photocatalytic activity of F-TiO2 had good stability and remained highly efficient after four runs.