Studies On The Morphology And Structure Control Of Nano-photocatalysts And Their Applications

With several innovational technics adapted, the paper studies the preparation methods on highly active nano-photocatalysts and their applications.Study on the preparation and application of visible-light sensitive highly active nano-photocatalytic TiO_2-xN_x. A kind of novel visible-light sensitive photocatalyst, nanosized TiO_2-xN_x, was synthesized by using titanic hydroxide as a source of material doping with nitrogen in pipe-still heater or rotary kiln. The influences of the process parameters, such as the doping temperature and time and mixed gases flow rate on the morphologies, structures and performances of TiO_2-xN_x were studied. The results showed that the doping amount of nitrogen increased with the increasing reaction temperature or the prolonging of time. When the doping temperature was at 450°C for 3 h , and the flow rate of NH3 and Ar was 1:1, the nitrogen content was approximately 0.8%, the product was anatase and the average grain size was about 20nm. The optical absorption edges of TiO₂ and TiO_2-xN_x shifted from 387nm to 500nm significantly. TiO_2-xN_x has higher photocatalytic activity than the undoped samples during the degradation of sulfur dioxide or methylene blue in visible light radiation. Furthermore, the photodegradation performance of TiO_2-xN_x obtained in 100 liter rotary kiln is well consistent with the experimental result.On the base of designing and optimizing the components, an air-purification wall coating added with TiO_2-xN_x as the key material was developed. The influences of kinds of film forming materials on the anti-UV performance were investigated, thus the components of film forming materials used for the coating were established. And PVC of 70 was proved to be the optimal quantity of the emulsion. Normal properties such as scrub resistance, stain resistance, pencil hardness and contrast ration of the coating was remarkably improved with the contents of the TiO_2-xN_x in adequate amount contrast to the coating without TiO_2-xN_x. Photocatalytic degradation rate of the coating for formaldehyde followed first order kinetics. The degradation residue of NO and SO₂ were proved to be harmless NO3" and SO42' respectively. The coating was produced in large scale and was applied in some places such as hospital and office successfully.The preparation of superhydrophilic film transparently was studied on under low temperature. Based on orthogonal experiments, the synthesis of photoactive nano-TiO₂ sol was optimized. Crystalline phase of the sample prepared in optimum condition was mixture of anatase and rutile, and the average grain size was about 11nm. Transparent nano-TiO₂ films were achieved under low temperature on normal transparent polymer-PC using the hydrolysate of 3-APS and TEOS as bond coating, mixing hydrolysate of 3-APS and TEOS and nano-TiO₂ gel as coating solution. The preparation conditions were studied in detail. The results showed that the surface of the film was smooth and well uniform without any cracks, the transmittance ratio was 84% or so, the minimum contact angle of water was 4.4°, and the photodegradation ratio of SO₂ gas was 98%. The film has high super-hydrophilicity activity and good anti-fogging ability.The preparation and application of fixed nano-photocatalystic film with mesopores was investigated. TiO₂ nano films with mesopores supported on the stainless steel mesh were successfully prepared using tetrabutylorthotitanate as the precursor via sol-gel method. The influences of the process parameters, such as the kind of PEG, the dosage of PEG, the dosage of water in sol, the coating times and different sintering temperatures, on the photocatalytic activity of the material were studied. The photocatalytic activity of the film was high when the film was composed of anatase and rutile mixing nanocrystals and the average size was about 30nm. For the utilization of the film and multi-technique, an indoor air cleaner which can get rid of harmful gases was constructed. About 84.6% NH3 and 93.3% VOC can be removed in 2 hours by using the air cleaner. Using the mesoporous film as working electrode, the photoelectrocatalytic degradation of chloroform in drinking water was investigated. The results indicated that initial chloroform concentration, applied potential, and light intensity had significant influence on the degradation of chloroform. The kinetics and mechanism of photoelectrocatalytic degradation were also studied. Devices for deep treatment of drinking water was developed. The degradation rate of chloroform was up to 76% by using this device.