Preparation And Properties Of Fiber Supported Photocatalytic Composites

Environmental pollution and energy crisis have become the critical issues for the sustainable development of the world.Semiconductor-based photocatalysis oxygenation is an advanced technique for chemical reacitons under the light irradiation.The photocatalysis technology has been regarded as a green and the most promising effective way to solve the critical issues because the method can degrade environmental pollutant and directly use of solar energy as fuels.However,there are some problems in the application of photocatalytic technology.On the one hand,the nano powder photocatalysts are easy to blow in the air and to agglomerate in water and difficult to recycle.On the other hand,most the semiconductor photocatalysts can only absorb ultraviolet light,and have no active under visible-light which accounts for more than 40%of the solar energy.In the present study,fiber was used as catalyst carrier and titanium dioxide and tantalum acid sodium with higher catalytic activity were selected as photocatalysts.The photocatalyst composites were prepared through sol-gel method,and the morphology structure.The load fastness and photocatalytic properties of the composites were studied.On the basis of the experimental results,the visible light response performance of the fiber supported photocatalyst composites and the removing kinetic model of printing and dyeing waste water?rhodamine B?were explored.The main research contents are as follows:?1?The ultrafine polyester island fiber with microporous structure,large specific surface area,strong adsorption,and excellent moisture conductivity was used as carrier for the photocatalyst.Basis on the study of the dispersion mechanism of nano powder,the TiO₂/ultrafine polyester island fiber composites were prepared through dip-padding technique.The microstructure and photocatalytic properties of the composites were investigated.The results indicated that the TiO₂/ultrafine polyester island fiber composites possessed excellent photocatalytic activity owing to the polyester island fiber.The polyester island fiber can rapidly concentrate pollutants,capture intermediate byproducts,and timely transmit the final products of the photocatalytic degradation.?2?However,the polyester island fiber can be oxidized and decomposed under light irradiation due to the characteristic of organic.In this chapter,the inorganic polyacrylonitrile-based carbon fiber?CF?with high mechanical strength,strong oxidation resistance and good corrosion resistance was used as photocatalytic carrier.The TiO₂/CF composites were prepared through sol-gel method,dip-coating and superheated steam annealing techniques.In addition,the microstructure and photocatalytic performance of the composites were investigated.The results showed that the micromorphology,load fastness and phase structure of the TiO₂/CF composites were significantly effect by the sol concentration and annealing temperature..The TiO₂/CF composites exhibited excellent photocatalytic properties due to the synergistic effect of the TiO₂catalyst and the CF carrier.However,TiO₂ has the defect of low efficiency in photo-generated carrier separation,resulting in a low quantum efficiency for photocatalysis.?3?In order to improve the photocatalytic activity of carbon fiber supported photocatalyst,the carbon-coated NaTaO₃/CF composites were prepared through sol-gel method combined with dip-coating technique.Here,the cetyl trimethyl ammonium bromide?CTAB?was used as surfactant for NaTaO₃.The results showed that CTAB and polyvinylpyrrolidone?PVP?were conductive to the dispersion performance of NaTaO₃ colloidal particles due to their formed dual stability mechanism of electrostatic and steric hindrance.In addition,the NaTaO₃ nanoparticles around porous carbon film were formed.The surface morphology,load fastness,decentralized state,crystallization temperature and adsorption performance of the composites were improved owing to CTAB.The carbon-coated NaTaO₃/CF composites exhibit excellent photocatalytic stability and activity under ultraviolet light irradiation,.?4?To obtain visible-light-driven photocatalyst,the nitrogen doped NaTaO₃/CF composites with visible light catalysis activity were prepared using melamine as the nitrogen source.Based on the theory of the energy band structure and experimental research,the results showed that when the molar ratio of melamine and tantalum pentachloride were more than or equal to 1:1,the nitrogen elements successfully doped in NaTaO₃ and the part of O^2-replaced by N^3-.The band gap and the recombination rate of the photo-generated electron were narrowed and reduced,respectively.?5?Based on the studying of adsorption and degradation kinetics of the composites to rhodamine B solution,it was found that the adsorption processes of both carbon coated NaTaO₃/CF and nitrogen doped NaTaO₃/CF composites were in line with the quasi-first-order adsorption kinetic model,and the photocatalytic degradation processes were in accordance with the Langmuir-Hinshelwood pseudo-first-order reaction kinetic model.The degradation mechanism of rhodamine B under the NaTaO₃/CF composites showed that superoxide anion free radical(O₂^�-)was the main active substance in the photocatalytic reaction.The photo-generated e^-reached the surface of the catalyst and generated amount of strong oxidation O₂^�-which can break the bond of rhodamine B.