Degradation Of Organic Compounds In Wastewater Based On Titanium Dioxide Photocatalyst

With the rapid development of modern industry, environmental pollution and control and energy crises have become the major problems facing humanity. Photocatalytic oxidation technology is an important way to solve these problems. Nano-TiO2 photocatalytic technology has been widespread concerned, and is considered as the most promising environmental pollution dealing technology due to the use of new energy sources as solar, mild reaction conditions, fast catalytic reaction, a small secondary pollution, and so on. But Nano-TiO2 photocatalytic activity and visible light utilization is not high enough. Thus, the development of strong respond to visible light and high photocatalytic activity is the hot research. In addition, powdered TiO2 is difficult to recover in practice.Herein, on the one hand, the sol-gel method was used to synthesis nonmetal C, N-doped nano-TiO2 photocatalyst with narrowing band gap and visible light activity to realize the visible or effective use of sunlight and to improve the photocatalytic activity. On the other hand, hydrothermal method was used to prepare the ACF/rGO/TiO2 composite material, easier to solid-liquid separation and recycling. The photocatalytic carbonaceous material was prepared to broaden the range of photocatalysis application.Using XRD, SEM, UV-Vis absorption spectra and XPS means to characterize them, and measuring the photocatalytic activity by the degradation test of the catalyst, mainly from the following aspects:(1) Optimizing the conditions of removal of toxic organic compounds methyl hydrazine. By comparing the degradation of methyl hydrazine of carbon fiber physical adsorption, Fenton reagent chemical oxidation method with TiO2 photocatalytic, and examining the effects of initial pH, reaction time and the amount of reactants and other factors on the removal of methyl hydrazine. The results indicate that:the use of activated carbon fiber adsorption treatment of wastewater containing methyl hydrazine, the amount of activated carbon fiber 3g/L=1, the adsorption time 40 min, when the effluent pH> 8, the adsorption rate increases rapidly when the pH is neutral, removal efficiency of only 30.29%, when the pH is 10, the removal efficiency can reach 83.50%. However, using Fenton’s reagent to treat wastewater containing methyl hydrazine in neutral system, reaction temperature 60℃, time 30 min, FeSO4·7H2O and H2O2 concentrations were 1.8 mmol·L-1 and 0.65 mol·L-1, the removal efficiency of methyl hydrazine of 96.32%. Using TiO2 to treat wastewater containing methyl hydrazine, TiO2 optimal concentration of 0.6g·L-1, methyl hydrazine removal efficiency increases with increasing pH value, when the illumination time of 90 min, the wastewater removal efficiency of only 13.86%, but methyl hydrazine removal efficiency reached 95.71% with pH of 10. By comparing the three methods to remove methyl hydrazine, nano-TiO2 photocatalytic technology is an efficient, environmentally friendly pollution treatment technology.(2) On the basic research of doped TiO2 photocatalyst at home and abroad, in this paper C, N co-doped nano-TiO2 photocatalyst was prepared by a sol-gel method. X-ray diffraction, scanning electron microscopy, UV-visible absorption spectrum and X-ray photoelectron spectroscopy and other means were used to characterize the structure and physicochemical properties. The visible light catalytic activity of C, N co-doped TiO2 catalysts, and the degradation of organic compounds dye RhB colorless, poisonous methyl hydrazine and formaldehyde in wastewater were studied. The mechanism of the C, N doped TiO2 effective improvement of visible light catalytic activity was discussed. The results indicated that:the average particle size of the resulting co-doped nano-TiO2 of about 50-60 nm, its absorption wavelength red shifts to the visible region and has a better photocatalytic activity. The photocatalytic degradation process should be adsorption-photocatalytic degradation mechanism.(3) Graphene with the excellent electrical, mechanical, thermal and other properties attracts a growing attention of the number of research workers. In this paper, the hydrothermal method was used to prepare ACF/rGO/TiO2 ternary composite materials, in which TiO2 photocatalyst and rGO loaded on the surface of activated carbon fiber (ACF). XRD, SEM, XRD and other means were used to characterize the structures and properties of the obtained ternary composite material. Compared with ACF, ACF/rGO, photocatalytic degradation organic compounds of dye RhB and colorless poisonous formaldehyde solution of TiO2/graphene composite were investigated. The results demonstrate that TiO2/graphene composite material is not only able to adsorb organic dyes, but also broadens the range of the visible light response, due to the introduction of graphene. The synergistic effect of TiO2 and graphene can promote the photo-generated electron transfer to graphene, the effective separation of photo-generated electrons and holes, thus improving the photocatalytic activity of TiO2.