Purification of automobile exhaust gas by activated carbon supported Fe³⁺ modified nano-TiO₂ and its application on asphalt pavement

Automobile exhaust gas discharged into the air not only pollutes the environment but also seriously harms human health. Although pure nano-TiO2 has a purified effect on exhaust gas, it has a wide band-gap, a narrow response range of visible light, and is prone to agglomerate, leading to the lower catalytic efficiency. In this study, Fe3+ doping and activated carbon loading were used to compositely modify TiO2 to extend the spectral response range and dispersion performance of TiO2. Firstly, activated carbon supported Fe3+ modified nano-TiO2 (Fe-TiO2/AC) composite catalysts were prepared by sol–gel method. Then the specimens were characterised by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and ultraviolet–visible spectrophotometer (UV-Vis). The micro-structures were observed by scanning electron microscopy (SEM). Based on the self-developed exhaust gas test system, the effects of the activated carbon dosage, light source, temperature, catalyst dosage and other factors on the catalytic performance were investigated. Finally, the application method and effect of the catalyst in the asphalt pavement was explored. The results showed that with the increase of Fe3+ content, the grain size of nano-TiO2 decreases gradually, the band-gap narrows gradually, and the response range to visible light broadens gradually. The activated carbon loading not only increases the dispersibility of the nano-TiO2 but also increases the absorption of the exhaust gas. The Fe-TiO2/AC composite catalyst has the best degradation effect on CO, NO and HC exhaust gas, which is better than pure nano-TiO2 and Fe3+ modified TiO2. By using the spraying method, the catalytic performance of Fe-TiO2/AC photocatalyst combined with OGFC asphalt mixture reaches the maximum. With the increase of wear times, the degradation effect of the test specimen on the exhaust gas was reduced, the rate of decrease was fast, then slowly, and finally the degradation performance gradually tends to be stable.