**Acknowledgement**

This work was supported by National high technology research and development program of China (2011AA03A406) and Project of Beijing Municipal Education Commission (KM201110005011).

## **5. References**


best photo-catalytic abilities among the catalysts.

*College of Environmental and Energy Engineering, Beijing University of Technology, Beijing, China* 

Wenjun Liang, Jian Li and Hong He

**Author details** 

**Acknowledgement** 

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(KM201110005011).

**5. References** 

while p-xylene was difficult to remove from gas flow. (5) The degradation efficiency gradually increased with gas temperature and 45 °C had the best removal efficiency. (6) 35% was the optimal humidity for photo-catalyst process under the experimental conditions. (7) Higher concentration of oxygen was better for HCHO removal. (8) The flow rate greatly influenced the degradation rate. For acetone and toluene, the degradation rate was highest with a flow rate of 3 L/min. For p-xylene, the degradation rate was highest when the flow rate was 7 L/min. The highest degradation rates for acetone, toluene and p-xylene were 77.7 %, 61.9 % and 55 %, respectively. (9) Illumination using a 254 nm light source was better than 365 nm. (10) The photo-catalytic degradation efficiency increased with increasing the amount of TiO2 when TiO2 amount was lower than 70mg. (11) In the gas mixture, acetone and p-xylene had much lower degradation rates than for their pure counterparts. The opposite trend was observed for toluene. Among acetone, toluene and p-xylene, the removal efficiency of acetone was highest both when pure and as a part of the gas mixture. (12) The photo-catalytic process used in pollutant degradation involved the adsorption of pollutants on the surface sites, and chemical reactions of converting pollutant into CO2 and H2O at the end. By-products of toluene or p-xylene were detected by GC-MS analysis, and involved phenol, benzaldehyde, aldehydes, alcohols, etc. The reaction rate constant (k) of ATP was sequenced kAcetone>kToluene>kP-xylene, meaning that the decomposition capability of acetone was the best, probably due to molecular structure and molecular weight. Formic acid was the main byproduct during the decomposition of HCHO. The reaction rate constant (k) of TiO2、Ag/TiO2、Ce/TiO2 was sequenced kCe/TiO2>kAg/TiO2>kTiO2, meaning that Ce/TiO2 had the

This work was supported by National high technology research and development program of China (2011AA03A406) and Project of Beijing Municipal Education Commission

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