Low Temperature Preparation Of Two Kinds Of Magnetic Photocatalyst And Its Photocatalytic Activity And Magnetic Recovery

Because of its non-toxic, harmless, non corrosive, large specific surface area and can bereused, titanium dioxide nanoparticle can be used for the organic pollutants. The organicmatter what is difficult to degrade will be completely mineralized formation into nontoxicinorganic ion and water. However, after the nano TiO2is used，it is very difficult to separatefrom the reaction system, and a considerable part of TiO2photocatalysis powder lost. Theactivity of recovery of catalyst is decreased. The catalyst loaded onto the glass, ceramics andother bulk materials can solve the problem of separation and recovery of photocatalyst, butthe photocatalytic efficiency is lower than the suspension system. Therefore, how to keepTiO2high catalytic activity and giving some properties of TiO2nanoparticles, which can beeasily separated from the reaction system, becomes the key of the application ofphotocatalysis in wastewater treatment. The action of the magnetic field is used to separatemagnetic photocatalyst from the reaction system.It has become a research hotspot at present.Magnetic titania photocatalyst is a composite produced by coating tiatania on magneticmaterials. The prepared magnetic photocatalyst with response characteristics, not only havehigh specific surface area and mass transfer efficiency, it also can be separate for recyclinguse from the treatment of sewage. However, in the study of magnetic photocatalyst powder,we found out that when putting the magnetic photocatalyst polishing sieved into the reactionsystem, TiO2shedding from the magnetic core material. The magnetic catalysts withoutgrinding in the system, has the disadvantage of poor dispersion. The Fe3O4nano-particles arecoated by inert isolating layer, and then coating the TiO2photocatalyst onto it by lowtemperature method. The preparated magnetic fluid will be able to overcome the powderedmagnetic photocatalyst poor dispersion and preparation process complicated.The nano ferrite is prepared by chemical co-precipitation method, and the SiO2/Fe3O4composite particles synthesis in situ. Then nano TiO2is loaded onto the surface of SiO2/Fe3O4composite particles by low temperature hydrothermal method. The magnetic photocatalystTiO2/SiO2/Fe3O4with high photocatalytic activity and good recovery performance areprepared. While in order to solve the problems of low catalytic activity caused by poordispersibility of the magnetic photocatalyst, TiO2/PANI/Fe3O4photocatalytic magnetic fluid isprepared by in-situ growth method in the liquid system. The PANI/Fe3O4magnetic fluid isprepared via in-situ synthesis, and then the titanium dioxide is loaded on them throung twooptimal hydrothermal methods in liquid system. In the synthesis process of the catalysts,many large analytical and testing instruments are helpful to characterize their physical andchemical properties, which is helpful to optimize the preparation technology. The preparationmethod of TiO2/PANI/Fe3O4photocatalytic magnetic fluid is built. The optimum synthesizetechnique of TiO2/PANI/Fe3O4photocatalytic magnetic fluid is established which will be highefficiency and energy saving. The photocatalytic magnetic fluid TiO2/PANI/Fe3O4has excellent photocatalytic activity and good magnetic recyclability, which will has goodapplication foreground.The following conclusions are obtained through the experimental study:(1) The magnetic photocatalysts TiO2/SiO2/Fe3O4(nTi:nSi:nFe=16:1:1，named TSF5)prepared has better photocatalytic activity. The phenol solution has been degraded99.7%from the initial value25mg/L in100min, which is slightly lower than that of pure TiO2of100%and P25of99.8%. Compared with TiO2, the magnetic photocatalyst TSF5has better magneticrecovery performance, whose magnetic recovery rate is as high as91.3%. After reused, thecatalyst still has high photocatalytic activity. After5times recycling, the photocatalyticdegradation rate reduced only by7.4%, from100%to92.6%.(2) Tetrabutyl titanate as raw materials, the photocatalytic magnetic fluid TPF2isprepared by lower temperature (170℃,18h) that has better photocatalytic activity. The phenolsolution has been degraded36.9%from the initial value100mg/L in120min. The magneticphotocatalyst TPF2have good magnetic recovery properties and photocatalytic life. After5times recycling, the photocatalytic degradation rate reduced only by3.3%.(3) Titanium sulfate as raw material, the photocatalytic magnetic fluid TiPF1is preparedby lower temperature (180℃,4h) that has better photocatalytic activity. The phenol solutionhas been degraded20.7%from the initial value100mg/L in120min. The magneticphotocatalyst TPF2have good magnetic recovery properties and photocatalytic life. After5times recycling, the photocatalytic degradation rate reduced only by4%.(4) In this paper, the photocatalytic effect of TF which coating the nano crystallinetitanium dioxide particles coated onto a magnetic core directly is much lower than themagnetic photocatalyst with the layers of inert isolation (SiO2, PANI). This shows thatincreasing the layers of inert isolation can successfully avoid direct contact of TiO2and Fe3O4,and the diffusion of Fe3O4to TiO2. Then the photocatalytic activity of magnetic photocatalystis improved.(5) When the same concentration of phenol and ethanol are degraded by P25, thedegradation of ethanol is faster. The degradation rate of ethanol reached100%in100min,slightly higher than phenol of97.4%. It shows that, P25preferentially degraded ethanolinstead of phenol in the same reaction system. When the reaction time was prolonged to6h,and the dosage of catalyst is1g/L, the degradation rate of ethanol and butanol mixed solutionby P25is lower than TiO2sol. The prepared TiO2sol by hydrothermal method has betterdispersion, making it has higher photocatalytic efficiency than P25.