Research Of Treatment Of Industrial Wastewater Containing Phenols Using Photocatalytic Method

With the rapid development of industry in recent years, a large amount of industrial wastewater has been discharged to environment and lead to a series of environmental issues. In addition to solving the problem of the discharges of industrial wastewater, the pollution should be treated meanwhile. Using photocatalytic method to solve the environmental problem has great significance, but how to improve the efficiency of utilizing solar energy is the greatest challenge. Photocatalysis has been a hot content since it was discovered in 1976. Titanium dioxide (TiO2) has been considered to be one of the best photocatalyst and it has been widely used in the area of photocatalysis because of its non-toxic harmless, high stability, low cost, and simple synthesis process. However, due to its large band gap and high recombination rate of photo-induced electron-holes, so TiO2 must be used under UV light, which only takes up 4% of sunlight, and it has limited the development of the use of TiO2 in photocatalysis. Thus, in order to improve visible light utilization effectively of TiO2, researchers have developed several methods such as element doping, compositing with noble metal or other semiconductors, and dye sensitization. In this thesis, we prepared noble metals supported three-dimensionally ordered macroporous TiO2 photocatalysts [3DOM M/TiO2 (M=Au/Ag)]. Due to its special morphology and improved band structure, we hope to develop their photocatalytic activity in visible light. In addition, we tested the activity of photodegradation of simulation of industrial wastewater, as a result, the as-prepared 3DOM M/TiO2 (M=Au/Ag) photocatalysts show good performance in photocatalytic reaction. The photocatalytic performance is deeply influcenced by the pore size and loading comtent of nobel metal of 3DOM M/TiO2.The first charpter is introduction. In this charpter, we introduced the research development of photocatalyst, methods to develop the photocatalytic activity of TiO2 and the applictions of TiO2 photocatalyst. Then it talked about the design and content of the thesis.In the second chapter, a series of 3DOM Au/TiO2 photocatalysts were synthesized via a colloidal crystal templating method using TBOT as titanium precursor. Then, the properties were studied by various characterization methods such as XRD, SEM, TEM, XPS, IR, DRS etc. The results show that the as-synthesized 3DOM Au/TiO2 has different pore sizes and loading capacities. But they all have macroporous-mesoporous structure and excellent response in visible light region. In addition, uniform-sized Au nanoparticles are coverd on the surface of TiO2 uniformly. Then we studied the performances of degradations of simulative industrial wastewater which is composed of phenol; phenol, quinoline; phenol, pyridine and phenol, quinoline, pyridine under UV and visible light. Under the irradiation of UV light, it takes 80min to degrade the simulative industrial wastewater which is composed of phenol and takes 11h under visible light in presence of 3DOM Au/TiO2 (1%,600nm) catalyst. Because of its enhanced response in visible light region and high electron-hole separation efficiency, the photocatalytic activity has been improved by compositing with Au. Furthermore, the effect of surface plasmon resonance of Au nanoparticles leads to higher efficiency in visible light utilization. COD tests are used to evaluate the properties, as a result, the pollutions are almost degraded in presence of as-synthesized 3DOM Au/TiO2 photocatalyst. Because of the excellent performance of degradation of simulative industrial wastewater,3DOM Au/TiO2 is considered to be a potential material in the area of waste water treatment.In the third charpter, we prepared 3DOM Ag/TiO2 with different pore sizes and Ag loading capacity using the same method as the second charpter. And we studied the performance of degradation of simulative industrial wastewater, it takes 15min to degrade phenol under UV light and takes 10h under visible light in the presence of 3DOM Ag/TiO2 (1%,600nm) catalyst. COD tests are used to evaluate the properties, as a result, the pollutions are almost degraded in presence of as-synthesized photocatalyst. Same as 3DOM Au/TiO2, compositing with Ag developed the catalytic activity of TiO2 because of the effect of surface plasmon resonance and the absorbance in visible light which are resulting from Ag nanocrystal. Because of lower cost of Ag,3DOM Ag/TiO2 is considered to have more important value in use.The fourth charpter is the summary and prospect of the thesis.