Experimental Study On Photocatalytic Degradation Of Micro-environment MACHs By Composite Nanotube Arrays

Micro-environment volatile organic compounds?VOCs? pollution has caused debilitating damage to our health, while monoaromatic hydrocarbons?MACHs? are major concerns among VOCs, the technology of effective processes to treat MACHs is of great and continuous interest. Because of the advantages of low price, non-toxic and corrosion resistance,semiconductor titanium dioxide?TiO₂? is widely used as the photocatalyst. But the technology of using TiO₂ to remove indoor MACHs still has some problems such as low visible light utilization rate and low photoctalytic degradation rate. How to solve those problems has become the most challenging subject in this domain. Using TiO₂ nanotube arrays as matrix to synthesize composite nanotube arrays used in the degradation of organic pollutants has attracted the attention of many researchers at home and abroad. Around these problems, ferric oxide/titanium dioxide?Fe₂O₃/TiO₂? nanotube arrays are successfully synthesized and optimized. The effect of process parameters on photocatalytic degradation rate and mineralization rate and the degradation process of MACHs are studied.The specific research contents and conclusions are as follows:?1?Using TiO₂ nanotube arrays as matrix material, Cu₂O/TiO₂ and Fe₂O₃/TiO₂ composite nanotubes are prepared by cathodic deposition and cathodic deposition-anodic oxidation, respectively.The influence of cathodic deposition of conditions?deposition temperature, deposition time, stirring speed? on the morphology of Cu₂O/TiO₂ composite nanotube and the influence of shape and size of titanium foil on Fe₂O₃/TiO₂ are studied, and the photocatalytic properties of the two kinds of catalysts are compared. The results show that: in this condition?mixing speed=180r/min, deposition time=3min, reaction temperature=40??,regular structure and highly ordered Cu₂O/TiO₂ nanotubes can be prepared. And using an area of 12.5cm² circular titanium foil as matrix, the nanotubes distribute neatly, and its diameter size is uniform, and Fe₂O₃ particles has been evenly doped into the TiO₂ nanotubes.Elements content analysis is carried out on the two kinds of photocatalyst, it can be found that the percentage of Cu atoms in the Cu₂O/TiO₂ is 0.07 to 0.07, while the percentage of Fe atoms in the Fe₂O₃/TiO₂ is 1.07 to 1.74. From the ultraviolet-visible spectrophotometry characterization, visible light?400-760nm? absorption effect of Fe₂O₃/TiO₂ composite nanotubes is far better than that of Cu₂O/TiO₂.?2?Using Fe₂O₃/TiO₂ composite nanotubes as photocatalytic materials, the effect of relative humidity and catalyst area addition on the photocatalytic oxidation efficiency of micro-environment MACHs on Fe₂O₃/TiO₂ semiconductor powders under visible light are investigated and the reaction mechanisms are also deduced. The results indicates that :when the optical power density is 0.9W/cm², and residence time is 10 min the photocatalytic efficiency can reach 75%-95.3%, and the degradation rate of benzene, toluene, xylene, styrene is 73%-92.2%?78.3%-95.1%?79.2%-93.9%?79.4%-96.2%?83.2%-96.9%, respectively; when the humidity is 60% and catalyst area is 50cm²-62.5cm², the degradation rate of each composition reaches the highest; when the humidity is 0-30%, and catalyst area is 25cm²-37.5cm², the degradation rate of each composition is higher; under different relative humidity, the oxidation of each component is mainly affected by the number of H2O+ and·O2-.?3? Using Fe₂O₃/TiO₂ composite nanotubes as photocatalytic materials, and three factors-three levels orthogonal experiment is designed to analyse the degradation rate and mineralization rate in photocatalytic reaction. The results show that: when the humidity is 30%-60% the degradation of benzene reaches the highest, while when the humidity is 90%, the degradation rate is reduced. In the condition of higher humidity and longer residence, the degradation rate of toluene is high, but the rangeability is not obvious when the humidity is from 60% to 90%. For mineralization rate, both benzene and toluene reach the highest when the humidity is 60%. The degradation rate of benzene is 72.82%-98.38%, and the mineralization rate is 13.03%-36.94%. While the degradation rate of toluene is 85.49%-98.69%, and the mineralization rate is 9.03%-44.32%.In short, this paper studies the preparation process parameters of composite nanotubes, and Fe₂O₃/TiO₂ composite nanotubes which have high visible light utilization rate have been preparaed. By designing level experiment, the photocatalytic reaction mechanism of MACHs is analysed. And by designing orthogonal experiment, the process parameters are optimized by analyzing the degradation rate and the mineralization rate.