| Dye wastewater is recongnized as a kind of unmanageable in dustrial iffiuent, which can be ascribed to its large quantum, high concentration, complex component, dark chroma, high salinity, strong toxicity, and difficulty by biochemical degradation. Currently, more and more researchers become interested in this issue.With the rapid development of industry, energy crisis and environment pollution become more and more serious.The treatment of organic wastewater by conventional methods has drawback due to expensive and difficulties. From the viewpoint of protecting environment and saving energy, many researches focused on the Photocatalysis-oxidation which is a senior oxidation technology with high efficency. Because of its light stability, high effect, bearing the light corrosion, no two pollutions, gotting easly, and low price etc., titanium dioxide as a photocatalyzer has become a hotspot of domestic and international study at present.Because titanium dioxide can only sdsorb the ultraviolet light, the adsorption rate for visible light or sun's rays is quite low. Doped some metallic ion can effectively hinder charge recovery in the course of transferring and improve its catalyst activity, while it can expand its respondingspectrum area and make full use of sunlight.The study on using sunlight to deal with pollutants is very important for protecting enviorment, maintaining zoology banlance and achieving sustained development.In this thesis, the TiO2 were prepared with the sol-gel hyrolytic method. The process conditiongs were selected by using the orthogonal tests. The results are that n(C2H5OH):n(H2O):n(CH3COOH):n[Ti(BuO4)]=10:5:0.5:1, reaction temperature is 40℃, the pH value is 2-3.In order to get higher photocatalytic performance under visible light, the different ions(La3+,Sn4+,Ni2+,Ce3+) were added into the TiO2 sol, and the photocatalytic activity of TiO2 was studied too. The result showed that photocatalytic property can beimproved by adding suitable dosage of ions. La3+-doped TiO2 had the highest photocatalytic property, Sn4+-doped TiO2 was the second, Ni2+-doped TiO2 was the third, and Ce3+-doped TiO2 was the lowest of all. When the dopant concentration of La3+ was 0.1%, the degration rate of methyl orange is 89.9%, which is 70% higher than the pure TiO2 without doped.Methyl orange was chosen as the respresentative of dye wastewater to investigate the photocatalytic activity of the La3+-doped TiO2 with the sunlight and different conditions. The optimal conditions were 0.1% La3+,500℃calcination temperature, pH=5,1g/L La3+-doped TiO2,5mg/L methyl orange and 3 hours.Reaserch in sunlight conditions, La3+/Ti02 photocatalyst the actual dye wastewater, provide for further pratical application of the conditions.It is discussed that the influence of the actual dye wastewater degrationg impact, which is different weather, different potocatalyst concentration, and different pH. The result is that the COD degration is best when the concentration of La3+/TiO2 is 2mg/L, in the pH=3, at noon in the sunny.
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