The Degradation Of Methylene Blue Over Bismuth And Cerium Based Materials

Removal pollutants from industrial process such as waste waters have driven considerable research efforts as the amount and the quality of fresh water available in the world continues to decrease.Chemical industries generate a wide variety of organic wastes. Among these,ethylene blue dye（MB）, used as organic dye, have received increased attention due to its good stability how to effectively degrade organic dye pollutants has becoming an important research topic. Semiconductor photocatalysis may be considered as one of the most promising technology because it represents an easy way to utilize the energy of either natural sunlight or artificial indoor illumination, and thus abundantly available everywhere in the world. In this thesis, Bisumth-based oxides and cerium-based oxides were prepared and used for the degration of MB in visible light. Some interesting results were obtained and listed as follow:1. Photocatalytic degradation reaction conditions were optimized, including the concentration of methylene blue, amount of catalyst, adsorption equilibrium time and the impact of self-degradation of methylene blue. The optimum conditions were used for the study, including the concentration of methylene blue solution 4 5 ug/m L, darkroom still 1 h adsorption reached equilibrium, the amount of catalyst 5 mg/mL and W lamp.2. The degradation of MB over bismuth-based photocatalysts has good prospects. Three series of bismuth-based materials were prepared, including bismuth oxide with different crystal phases prepared by methods A, B and C, Ca-Bi composite oxide and Ti-Bi composite oxide. Their catalytic performances were test by using a W lamp. The results indicated that the photocatalytic properties of bismuth oxide is related to bismuth oxide phase and composition: 1) the photocatalytic activity of bismuth oxide is related to the crystalline phase,i.e., a-Bi2O3 is superior to g- Bi2O3; 2) Ca-Bi composite oxide prepared by impregnation showed the highest photocatalytic activity for the degradation of methylene blue with methylene blue degradation rate of 99.33 % in four hours, which is related to the composition of Bi_1.8Ca_0.4O calcinated at 600 ℃; photocatalytic activity increased as function of Ti-Bi composite.3. Ceria-based materials are equally effective in the photocatalytic degradation of organic pollutants present in waste water. In present research, the ceria-based materials with different morphology and compostion were prepared and used for the degradation of MB. It was found that the degradation of MB is depended on the morphology of ceria, CeO2-short rods show thebest photocatalytic activity. Ce-Sn-O and Ce-Zn-O catalysts were prepared with different Ce/Sn or Ce/Zn ratios. The photocatalytic activity was improved due to a small amount of Sn or Zn was incorperated into ceria lattice, but the degradation rate decreased with time because of the deactivation.The degradation of MB was tested over Ce-Ti-O and Au/CexTiyO2 catalysts. It was found that a small amount of Ce improved the photocatalytic activity of Au/TiO₂ and the degradation concentration about 99% was obtained over Au/Ce0.03TiO₂. The degradation of MB over Au/CexTiyO2 showed the first order kinetics, A increased kinetic constant was obtained in the degradation of MB by Au/Ce0.08TiO₂, which is the reason for its high degradation activity.