Study On Preparation And Photocatalytic Properties Of Composite Photocatalytic Materials Based On N-TiO₂

Recently,it has drawn attention to photocatalysis.A variety of photocatalysts have been gradually synthesized from the laboratory to factory commercially.Although there are lots of photocatalysts,TiO₂ is one of the most appropriate materials now and even in the future.It is because that not only TiO₂ is an effective and stable material,but as a common white coating,it is environmentally friendly.When TiO₂ particles is illuminated by incident light exceeding its band gap energy,photoproduction electron?e-?from conduction band will reduce O₂ into peroxide hydroxyl radicals?·O₂-?and left photoproduction holes?h+?will oxide OH-and H2 O into hydroxyl radicals?·OH?on valence band.These active radicals can oxide numbers of refractory pollutants almost without selectivity.In this paper,some common methods were employed to prepare the N-TiO₂ such as sol-gel method,hydrothermal method and self-assembly method.Then based on N-TiO₂,two novel photocatalytic composite materials were successfully prepared: MIL-125/N-TiO₂ and Fe₃O₄@nSiO₂@mSiO₂/N-TiO₂.Besides,the photocatalytic performance of these materials were studied: N-TiO₂,MIL-125/N-TiO₂ and Fe₃O₄@nSiO₂@mSiO₂/N-TiO₂.The main work of performed in this dissertation is as follows:1.We used carbamide as the source of N,tetrabutyl titanate as the source of Ti.By using the method of sol-gel to prepare N-TiO₂,and it was characterized by Scanning electron microscope?SEM?,Infrared Spectroscopy?IR?,X-ray diffraction?XRD?,X-ray photoelectron spectroscopy?XPS?and Fluorescence spectra.The results show that the size of N-TiO₂ is 20 nm.Photoelectric composite ability is greatly reduced compared with the pure TiO₂.4N-TiO₂-500 as the most suitable of photocatalyst,simulated photodegradation of Rhodamine 6G.Indicated after the experiment that,has a great ability of photocatalytic degradation.After irradiated by 500 w high pressure mercury lamp,the degradation rate reach to 99.1%.2.Through the sol-gel method,N-TiO₂ was prepared with carbamide as the source of N and hydrolyzation of tetrabutyl titanate.It was characterized by Scanning electron microscope?SEM?,Infrared Spectroscopy?IR?,X-ray diffraction?XRD?,X-ray photoelectron spectroscopy?XPS?and Fluorescence spectra.It was turned outthat the particle size of N-TiO₂ was about 20 nm.Compared with TiO₂,the ability of photoelectric composite was sharply decreased.It was found that 4N-TiO₂-500 is the most effective photocatalyst to photo degrade Rhodamine 6G?R6G?,which,after120 min,99.1% of R6 G was degraded with 500 W high pressure mercury lamp,which suggested the material prepared has a wonderful ability of photocatalytic.The N-TiO₂ nanoparticles and MIL-125 MOFs were prepared by the sol-gel method and hydrothermal method respectively.Then by self-assembly method,the MIL-125/N-TiO₂ composite was synthesized and characterized by Scanning electron microscope?SEM?,Infrared Spectroscopy?IR?,X-ray diffraction?XRD?and nitrogen adsorption.It was found that the MIL-125/N-TiO₂ was synthesized successfully,and from the results of photocatalytic degradation of rhodamine 6G,the property of photocatalytic degradation has been endowed to the composite material.The degradation rate could be achieved about 98.12% when the pH value was 7 and the ratio of MIL-125 and N-TiO₂ is 1:1.While the adsorption rate is 63.7% with the ratio of 3:1.It was concluded that R6 G was adsorbed and degraded by the composite through a comparison of the materials before and after reaction.3.Controllable recycling could be achieved by combining N-TiO₂ and magnetic materials.Mesoporous Fe₃O₄@nSiO₂@mSiO₂ was prepared by sol-gel method and template method,then Fe₃O₄@nSiO₂@mSiO₂/N-TiO₂?1:30?was successfully synthesized by hydrothermal method.The crystal structure,morphology and saturation magnetic strength of the composites were characterized by XRD,TEM,SEM and hysteresis loops.It was turned out that two layers of SiO₂ shell were created around the surface of Fe₃O₄ with the of size 0.3?m and the saturation magnetic intensity of 15 emu/g.The adsorption efficiency of Fe₃O₄@ nSi O₂ @ mSiO₂ /4N-TiO₂?1: 1?could be achieved to 93.2% under the irradiation of 500 W xenon lamp.When the magnetic property of the material was taken into account,Fe₃O₄@ nSiO₂ @mSiO₂ / 4N-TiO₂?1: 30?,the efficiency of photo degradation could be up to 94.3%after 120 min.With study of the degradation conditions,the highest degradation efficiency of 98.21% could be obtained,when the amount of catalyst was 1.0 g/L,the concentration of R6 G was 5 mg / L and the value of pH was 8.