Preparation Of Carbonaceous Photocatalytic Composite Materials And Their Liquid Organic Removal Performance

In the environmental protection field, the reactions of photocatalytic materials degradation organic molecule in solutions have been researched for decades, but pure semiconductor metal oxide powders have some disadvantages such as hardly to be recovered, low stability, weak visible light responsiveness, low reaction efficiency and so on, which always restrict the promotion of this technology to civil industry. Carbon materials exhibt good stability, strong adsorption performance, and a wide range of applications as catalyst supports, thus combining the novel carbon materials and traditional semiconductor metal oxide, can avoid various problems of pure powder catalysts, and provide a new way for photocatalytic materials in the field of environmental protection. Therefore, this thesis was aimed to use a variety of preparation method to construct a series of new type of carbonaceous photocatalytic composite materials, and to investigate the removing performance for organics in liquid solution.1. The TiO2/PSAC composites were prepared through sol-gel method and impregnation-calcination method, respectively, with tetrabuty tinanate as titanium source and pitch-based spherical activated carbon (PSAC) as support. The photocatalytic degradation activity and cyclic reaction of samples were studied using organic solution as a probe. The results indicated that the samples synthesized from the two methods exhibit microporous structure and show high photocatalytic activity. The composite prepared by sol-gel method sintered at450℃dunder N2atmosphere has an anatase crystal model coating on the surface of carrier, and its photocatalytic activities for probe organic can reach96.7%after the first cycle reaction, and84.0%after the third cycle, while the activities of composite sample prepared by impregnation-calcination method can just reach90.1%and69.1%, respectively, superior to pure PSAC just about55.0%.2. Mesopous carbons (MC) from colloid silica templates were employed as supports to prepare TiO2/MC nanocomposites through a sol-gel process. TiO2content and crystalline structure of photocatalysts were turned by changing the precursor composition and calcination temperature, respectively. The experiment results showed that anatase TiO2nanoparticles could be highly dispersed on the surface of carbon framework, leading to the formation of high performance photocatalysts for degradation of probe organic under UV irradiation. The MC promoted the dispersion of TiO2in composite system and induced synergistic effects of adsorption and phtocatalytic degradation on the removal of probe organic. The organic removing rate could reach as high as89%in75min and93%at last under UV irradiation. The kinetics of organic degradation fitted well the first-order reaction kinetic and the largest rate constant was about0.015min-1.3. Different pore structure mesoporous carbon were prepared with7nm and12nm SiO2particle as templates, then nitrogen element doped titanium dioxide mesoporous composites were prepared through hydrothermal process, results of nitrogen adsorption and electron microscope showed that pore structure parameters of MCs changed a lot after TiO2loading, and nitrogen doped did not change the crystal structure of TiO2loading on support, nitrogen doping prompted sample visible light excitation response and MC-7was more suitable than MC-12as a composite suppot, the removing rate of30%N-TiO2/MC-7for orgnic could reach68%in75min reaction.4. Three kinds of carbon nanofibers (CNFs) pretreated by acidity oxidation treatment were employed as supports to prepare TiO2/CNFs nanocomposites by a hydrothermal process with titanium (IV) isopropoxide as the precursor, their photocatalysis activity and recycle property were investigated. The TiO2content of photocatalysts was turned by changing the precursor composition. Anatase TiO2nanoparticles could be highly dispersed on the surface of fibers, leading to the formation of high performance photocatalysts for degradation of probe organic under UV irradiation. The CNFs promoted the dispersion of TiO2in composite system and induced synergistic effects of adsorption and phtocatalytic degradation on the removal of organic. The TiO2/PCNF showed better performance than other composite, and the highest organic removing rate of TiO2/PCNF could reach as high as80.1%in120min for different TiO2content samples and79.2%for different temperature under UV irradiation. After three cycle reaction, the organic removing rate of TiO2/PCNF could still reach80%.5. Block copolymers F127as template agent, titanium acid butyl acetate as titanium source, using solvent evaporation induced self-assembly process to prepare nonmetallic element doped mesopore TiO2system. The effect on removing properties for organic compound of sample preparation process conditions like heat treatment temperature, ratio of precursors, and oxygen post-treatment were investigated. The results showed that the liquid adsorption performance of samples was determined by its pore structure and the photocatalytic degradation performance was determined by the crystal structure, element doping content and so on. When precursor ratio1/1, calcining temperature700℃, the sample had strongest ultraviolet excitation catalytic activity, when the ratio of precursor were3/1,4/1and after oxygen post-processing, the samples showed visible light excitation response, at the same time ultraviolet excitation response also have greatly improved, and total removing rate for probe organic can reach up to89.6%and89.5%, respectively. The removing rate under dark reaction, ultraviolet and visible light excitation response to probe organic can remain stable for multiple cycle reaction that proved the high stability of the samples.