Study On Degradation Of Organics With Modified Tio₂ Nanoparticles

The contemporary era, the serious deterioration of the Earth's environment has caused great concerns in the world's people. With the awareness of environmental protection, environmental protection and governance tends to be "green". As heterogeneous photocatalysis, photocatalytic technology is used to degrade organic pollutants in the dye wastewater to biodegradable non-toxic or low toxic small molecules readily. For its high efficiency, energy saving, no secondary pollution and so on, it is used in the control of environmental pollution and governance. How to modified titanium dioxide to obtain a higher photocatalytic efficiency has become the research hotspot.In this paper, pure titanium dioxide was prepared by sol-gel method to degrade azocarmine. The factors of dye's photocatalytic degradation were studied to obtain the optimum conditions. The results showed that: Anatase titanium dioxide prepared has small particle size; azocarmine can be degraded significantly only using photocatalyst. When the dosage of titanium dioxide is 1.5g/L, azocarmine's initial concentration is 40mg/L, pH=8.2, and 300W UV high pressure mercury lamp irradiates 60min, photocatalysis is the best. The degradation rate is 97.8% and COD removal rate is more than 68%. Titanium dioxide can degrade many dyes.The effects such as concentrated nitric acid volume, the percents of Bismuth-doped contents, the water volume, the solvent of ethanol volume, and the depressor of acetic acid volume, on performance of photocatalysis which was exhibited by the degradation rate of azocarmine solution were discussed by the orthogonalizing analysis. The best level was as follows: concentrated nitric acid was 0.2mL; the percents of Bismuth-doped contents was 0.5%; the water volume was 7.2mL; the ethanol volume was 60mL; the acetic acid volume was 7.5mL.When azocarmine was degraded by using Bismuth-doped titanium dioxide, the degradation rate of dye solution increases and then decreases with initial pH, catalyst dosage and initial dye concentration increases. The best level is that pH=8.2, the dosage of Bismuth-doped titanium dioxide is 1.0g/L, azocarmine's initial concentration is 60mg/L and 300W UV high pressure mercury lamp irradiates 60min. The degradation rate is 99.9%, and COD removal rate is more than 70%. Plus ion such as Cu²⁺, Fe³⁺ inhibited the degradation of the dye, light intensity increases to the promotion of dye degradation; Bismuth-doped titanium dioxide can degrade many dyes. The degradation reaction mechanism of azocarmine is speculated.Kinetic parameters and various factors on the chemical reaction rate was studied. Bismuth-doped titanium dioxide photocatalytic degradation of azocarmine solution of low concentration follow first order reaction kinetics equation based on Langmuir-Hinshelwood reaction mechanism. Its adsorption rate constant k1 is 2.053×10-3L/mg, and its surface reaction rate constant k2 is 20mg·(L·min)-1.Fe-doped titanium dioxide was prepared by sol-gel method.The experiments showed that the optimal iron-doped titanium dioxide was prepared on the conditions of calcination temperature of 500℃, acetic acid solvent 5mL, mixed 0.5% iron. When using these photocatalyst to degrade azocarmine, the results showed Bismuth-doped titanium dioxide is better than Fe-doped titanium dioxide and much better than titanium dioxide. XRD showed ion doped titanium dioxide can reduce the size significantly; type is gap-type doping.Modifying titanium dioxide to prepare a new photocatalyst can improve the photocatalytic efficiency and obtain better photocatalytic degradation. This conclusion is a certain significance for rich photocatalytic basic theory and practical application.