| Titanium dioxide (TiO2) has been widely used as photocatalyst for the photocatalytic reaction, because of good chemical stability, wear resistance, low cost, non-toxic to human body, and higher photocatalytic activity to the majority of pollutants, But there is the problem of small response range to the light, and the catalytic efficiency is low. Meanwhile, the direct application of the TiO2 powder as photocatalyst is apt to deactivation, and difficult to be separated from the reaction system.The photocatalysts TiO2 supported by actived carbon (AC) and actived carbon fiber (ACF) were prepared with the hydrolysis of tetrabutyl titanate (Ti(OR)4) by a sol-gel method, using iron (Fe) and nitrogen (N) co-doped to improve the photocatalytic activity of TiO2. Based on this, photocatalytic degradation experiments were carried out to evaluate the photocatalytic activity of the prepared photocatalysts, in which toluene was selected as a typical volatile organic compounds (VOCs). Many affecting factors (such as ion co-doping content, inhibitor types, calcination temperature, TiO2 loading amount, support type, initial concentrations of pollutant, recycling time of photocatalysts and using amount) have been investigated to obtain the optimal technology condition and application condition for the prepared composite photocatalysts. Meanwhile, the photocatalytic activities for different kinds of VOCs—acetone and formaldehyde were also evaluated. And the following results are obtained.The prepared composite photocatalyst TiO2/AC showed the highest activity when the ion co-doping content were N 8% and Fe 8%, acetic acid was used as inhibitor, and photocatalyst samples were calcined in 500℃for 2 h, comparing with other photocatalysts supported by AC. And the photocatalytic activity of TiO2/ACF was higher than that of TiO2/ACF. More importantly, the photocatalytic degradation efficiency of the prepared photocatalysts were improved with an increasing of the initial concentrations of pollutant (i.e. toluene), without the phenomenon of photocatalyst deactivation.On recycling using performance, the photocatalytic activity of TiO2/AC was decreased with an increase of recycling time, but their photocatalytic activities were still higher than P-25 after 6 time recycling. And the composite photocatalysts TiO2/ACF still maintain high photocatalytic activities after 6 time recycling, and almost the same every time. The photocatalytic degradation rate of toluene were increased with an increasing of the amount of catalyst when the amount of binder (i. e., water glass) was constant.In the process of different kinds of VOCs degradation, the prepared photocatalysts exhibited higher ptotocatalytic activities for toluene and acetone, but less for formaldehyde. The photocatalysts were characterized with scanning electron microscope (SEM), X-ray diffraction (XRD) and UV-visible spectrophotometer (UV-Vis). And the SEM observation results showed that the majority of TiO2 particles embedded in the pore of AC, but coating on the surface of ACF as membranous. XRD analysis results indicated that all the prepared photocatalysts were existed in anatase phase, and the effects of calcination temperature and carrier types on the anatase content were obvious. UV-Vis analysis revealed that the photocatalysts co-doping with Fe ion and N ion achieved the response to visible light, and the photocatalysts achieved dual-enhancement in the visible and UV region absorption when photocatalysts were supported on AC.The reaction kinetics of photocatalytic degradation of different VOCs were investigated with the irradiation of high-pressure mercury lamp (300 W) using the prepared TiO2/AC photocatalyst samples. The results showed that the photocatalytic degradation of toluene,acetone and formaldehyde obeyed the first-order reaction kinetic equation, i.e., ln[1/(1-X)] = kt. There were a little influence of contamination concentrations and the using amount of composite photocatalysts on the photocatalytic degradation kinetics.
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