| The rapid development of automobile industry in our country led to a serious air pollution situation in the semi-enclosed space such as tunnel and underground garage. For the detected pollutants, NOx gave the largest contribution to air pollution. The present air purification technology for semi-enclosed space had the typical shortcoming of high cost or poor removal performance. Whilst, the photocatalytic technology had the advantages such as low operation cost, mild reaction conditions etc. Due to the shortcoming of poor removal efficiency of photocatalytic technology in actual applications, this dissertation developed a photocatalytic & adsorption removal method for low concentration NOx in semi-closed spaces and realized the simultaneous removal of other gas pollutants.Firstly, the adsorption performance of NO2 was investigated. The honeycomb activated carbon was selected as the optimized adsorption material. The chemical modifications were progressed on honeycomb activated carbon for the improvement of adsorption capability by using KOH, KMnO4 and HNO3 etc. It was found that the activated carbon modified by 0.1% KOH and 0.1% KMnO4 solution showed the wonderful performance for NO2 adsorption. The preparation methods of the supported TiO2 photocatalysts were studied, and the influence factors such as the load process, load content, relative humidity, oxygen content, initial NO concentration and residence time were investigated. The results showed that the TiO2 nanoparticles prepared by sol-gel method had the best photocatalytic activity. The optimal load content of photocatalysts was 0.01 g/cm2. When the relative humidity was between 45-75%, the photocatalytic oxidation rate of 10 ppm NO was 100%. When the O2 concentration was higher than 20%, the photocatalytic oxidation rate of 10 ppm NO was 100%. Relative humidity and oxygen content of normal environment was well matched the requirements of photocatalytic reaction. When the initial concentration of NO was less than 100ppm, the oxidation efficiency decreased and the NO conversion rate increased as the initial concentration of NO increased.The modifications of Pt and Pd were took place on the supported photocatalysts for the improvement of photocatalytic oxidation capability. Results showed that the doping of oxidized Pt materials and Pd ions were the better modification for the improvement of photocatalytic oxidation activity for NO.0.01 wt% Pd doped P25 which supported on Al2O3 carriers revealed a 100% photocatalytic oxidation efficiency of 10ppm NO in 24 h. By using 0.01 wt% Pd doped P25 loading on Al2O3 and 0.1% KOH modified honeycomb activated carbon, the photocatalytic oxidation & adsorption method maintained a high removal efficiency among 90%-100% for the removal of 10 ppm NO in 30 days.The removal performances of NO and other gas pollutants of the photocatalytic oxidation & adsorption method were then investigated in a self-made 100 m3/h simulation device. The study found that 0.05 wt% Pd modified P25 catalyst showed the best removal performance of NO, and it also showed a good removal efficiency for CO and SO2. The increasing of Pd doping content was helpful for the photocatalytic removal of CO. In this experiment, the calcination method was the optimal regeneration method for the used photocatalysts.Finally, the economic efficiency and removal performance of the wall-hanging method and the surface-coating method were compared. The results showed that the investment and operation cost of the wall-hanging method were higher than that of surface-coating method, but the NO removal efficiency of wall-hanging method was much higher. |
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