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 (R-F) greatly affected photocatalytic activity towards toluene degradation, and the F-TiO2 with R-F at 1 obtained the best performance. The photocatalytic activity of F-TiO2 had good stability and remained highly efficient after four runs.