Composite-modified nano-TiO2 for the degradation of automobile exhaust in tunnels

Abstract

To improve the degradation efficiency of automobile exhaust in highway tunnels, which have the special lighting conditions, nano-TiO2 based on the composite modification of metal ions (Fe), nonmetal ions (N), and semiconductors (WO3) was developed. Composite-modified nano-TiO2 was prepared via the sol–gel method, and its properties were characterized by X-ray diffraction, UV–Vis spectrophotometry, IR-spectroscopy, fluorescence spectra, and electron paramagnetic resonance. X-ray diffraction analysis showed that composite modification reduced the size of nano-TiO2 grains, which is conducive to the surface scale effect of nano-TiO2. UV–visible diffuse reflection showed that composite modification made the absorption band of nano-TiO2 red shift, and the absorption of visible light increased. Infrared spectrum analysis and electron paramagnetic resonance showed that the composite-modified nano-TiO2 was conducive to the formation of OH free radicals under the action of visible light, and the photocatalytic activity was enhanced. An orthogonal test scheme with three factors and three levels was designed, and the automobile exhaust degradation test was conducted by using homemade automobile exhaust degradation test device. Results showed that the composite modification improved the catalytic efficiency of nano-TiO2, and the addition of Fe3+ had the most considerable effect on the degradation of automobile exhaust. When the Fe3+ content was 1.69 %, the N content was 1.5 % the WO3 content was 6.12 %, the automobile exhaust degradation efficiency was the highest. Within 120 min, the maximum degradation efficiencies of CO and NO by composite-modified nano-TiO2 were 13.08 % and 69.18 % respectively.