| Titania pillared bentonite was prepared by the sol method. The results of N2 adsorption-desorption showed that the specific surface areas of the catalysts calcined at 573, 673 and 773K were 140.15, 110.13 and 88.38m2/g, respectively. Their catalytic activities were evaluated for the gas phase degradation of toluene. The effects of humidity on the activity were studied in a continuous system. Results indicated that competitive adsorption between toluene and water molecules occurred on the catalyst surface, thus the photoactivities decreased with the increasing humidity. The photodegradation matched well with the Langmuir-Hinshelwood (L-H) kinetic mode1, and the adsorption constants of water for the catalysts calcined at 573, 673, and 773K were 2.8×10-5, 4.1×10-5 and 1.8×10-4 m3·mg-1, respectively. The photoactivity of the catalyst calcined at 573K was worst under low humidity but was best under high humidity compared with those of the catalysts calcined at 673K and 773K, suggesting it was most capable of resisting the impact of humidity. The thermal desorption was adopted to analyse the adsorption capability of toluene on catalysts. As the relative humidity increased from 25% to 75%, the adsorption amount of toluene for the catalysts calcined at 573, 673, and 773K decreased from 184.8 to 3.25 μg/g, 130.5 to 1.92 μg/g, 77.6 to 1.65 μg/g, respectively. Adsorption capability of catalysts increased with the specific surface area, thus the apparent adsorption constant of water was reduced and the ability to resist the effect of humidity was enhanced. Experimental results indicate that during practical application of titania pillared bentonite for gaseous pollutants degradation, the environmental humidity and catalyst structure should be considered to screen out the catalyst with best activity. |
