Preparation Of Nano-CeO₂ And The Photo-catalysis Degeneration Of Methyl Blue

The serious problem now faced is the water pollution which gets worse and worse, it is hard to remove the virulent organic pollutant in the pollution water. The methyl blue is one of the virulent organic pollutant, which has created the severely harm to the human health and daily life. In view of this serious reality this article enhances the research of the preparation technology in enhancing photo-catalysis active and the ion implantation as well as to the degeneration of methyl blue based on the photo-catalysis characteristic of nanometer CeO₂ semiconductor. Then it has the vital practical significance to treatment of water pollution, improves the domestic water quality and safeguards people's health.The best conditions of preparing nanometer CeO₂ by sol-gel method are researched and optimized which raw material is the cerous nitrate and the citric acid, the pH of cerous nitrate and the ascorbic-citric solution is 1.5, reacts in 65℃the water bath, dries 1h in 100℃, heats 2h in 500℃. Under this kind of condition it can produce the CeO₂ powders which the average grain diameter is the 12.21 nm. The XRD indicated that the crystal structure of nano-CeO₂ powders obtained is the cubic system, and along with the extension of heating temperature and time, the crystallinity of sample elevates, the crystal growth is more complete and the grain size increases. The SEM analysis indicated that the CeO₂ is sphere, and along with the extension of heating temperature and time, the reunion phenomenon increases.In order to improve the reunion phenomenon of the nanometer CeO₂, the ethyl alcohol and the water, mole rate 9:1, is used as resolver, in this way the reunion phenomenon has the distinct improvement. The rubber time reduces from original 23.5h to 2h in the microwave heating, saved the energy. The dispersivity effect of preparing nanometer CeO₂ in microwave heating is better than that in heating in water bath from the SEM picture.The experiment of photo-catalysis degeneration indicates that the nanometer CeO₂ prepared has the better degeneration function to the methyl blue under the illumination of ultraviolet lamp, the degeneration rate under 6h of photochemical catalysis reaction has achieved above 70%, the nanometer CeO₂ prepared under the changed resolver (water and ethyl alcohol) and microwave heating has the good dispersivity, which both enhanced the photochemical catalysis degeneration rate, the degeneration rate of the methyl blue (reaction for 6h) respectively is 85.6% and 77.2%. The quantity of catalyst has greatly affect to the photo-catalysis activeness of methyl blue, when adding the catalyst of 0.6g/L-1.4g/L and CeO₂ of 1.0g/L it has the higher photochemical catalysis degeneration rate.The heating temperature and time affect greatly to the CeO₂ photochemical catalysis degeneration methyl blue effect, in the temperature range, the nanometer CeO₂ sample in 500℃for 2h has the relatively best to the methyl blue photochemical catalysis activeness.In order to enhance photo-catalysis activeness of nanometer CeO₂ to the methyl blue, we can modificate the nanometer CeO₂ by doping Zn²⁺, Ti⁴⁺, Si⁴⁺, V⁵⁺, Fe³⁺. The experiment indicated that the introduction of the ions can all enhance the photochemical catalysis activeness of nanometer CeO₂ to the methyl blue. In the same condition of 500℃for 2h and 6h of photochemical catalysis reaction, the best doping quantity of Zn²⁺ is 3% which has the highest photo-catalysis degeneration and the degeneration rate of methyl blue is 88.41%, the best doping quantity of Ti⁴⁺ is 3% which the degeneration rate of methyl blue is 93.8%. Then heating 2h in 500℃the nanometer CeO₂ doped 2% Si has the best photochemical catalysis activeness in the series of doped Si⁴⁺ , after 6h the degeneration rate of methyl blue is 90.16%, while the degeneration rate doped 2%Fe³⁺ is 98.6%. Then heating 2h in 450℃the nanometer CeO₂ doped 1 % V⁵⁺ has the best photochemical catalysis activeness in the series of doped V⁵⁺ , after 6h the degeneration rate of methyl blue is 88.7%.