Preparation Of Electrospun Nano-fiber Mats And Its Application Of Titanium Dioxide Photocatalyst Immobilzation

With the development of society, people pay more and more attention to the water pollution problems. Photocatalytic technology is one of the most potential methods to deal with those problems in many water treatment methods. Powder TiO₂, which is superior in photocatalytic performance, becomes one of the suitable materials for degradation of toxic organic compound. Titanium dioxide (TiO₂) is a kind of the environment-friendly photocatalytic material, which have been applied in many fields. Because its no poison to creature, stability in chemical properties, no side-effect, no secondary pollution, and can effectively degrade many kinds of organic pollutants. For powder TiO₂, it is difficult to reuse and disperse as well as the aggregation tendency of the suspended particles would greatly limit its application in actual wastewater treatment. Therefore, TiO₂ photocatalyst immobilization becomes the main trend in the future. In this paper, PAN-based nano fiber mats were preparation by electrospinning method. And composite photocatalyst were prepared by means of TiO₂ loaded onto nano-fiber mats. Composite photocatalyst have application in photocatalytic degradation of phenol in simulation wastewater.The following researches have been done in this thesis:Effects of process parameters (solution concentration, voltage and collector distance) on the diameter of electrospun polyacrylonitrile fibers were experimentally investigated by single factor analysis and orthogonal experiment analysis. The results show that solution concentration which range from 3% to 20% was positively correlated with diameter of nano-fiber. The other process parameters (voltage and collector distance) had a little impact on diameter, while have great impacts on the scattered ability of jet flows.Micro-structrue and properties of PAN nano-fiber mats were characterized by Thermo-Gravimetry Analysis (TGA), X-ray diffraction (XRD) and FTIR method during stabilization process and carbonization process. Structure of PAN nanofibers have been formed ladder structure in the period of stabilization process at 280℃, oxidation degree of fibers is suitable when Aromatization Index (AI) is 0.807. Internal microstructure of stabilization nanofiber mats has changed hexatomic ring-like and graphite-like structure in the process of carbonization at 700℃. It is show that PAN nanofiber mats change into Carbon Nano-Fibers (CNF) completely.CNF were used as supporters, TiCVCNF composite photocatalysts were prepared through sol-gel method. Meanwhile, TiO₂ nano-particles were mixed with solution of polyacrylonitrile (PAN) / N, N-dimethyl-formamide (DMF) and then TiO₂/PAN nanofiber mats were frabricated by electrospinning method. TiO₂/CNF and TiO₂/PAN nano-fiber mats were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) SEM showed that crystal type of TiO₂ was anatase phase, and morphologies of TiO₂ nano-particles supported on fibers were relatively evenly distributed.TiO₂/CNF and TiO₂/PAN nanofiber mats were used for photocatalytic degradation of phenol in simulation wastewater. We discussed different pH value, different phenol concentration, different light intensities as influencing factors, then draw a conclusion as follow: (1) It was found that the photocatalytic activity of TiO₂/CNF, TiO₂/PAN nanofiber mats was much higher than common TiO₂ powders. (2) The photocatalysis reaction of phenol could be expressed as first-order kinetics, and phenol photodegradation ratio decreased with the increased of initial concentration of phenol. (3) The pH value of solution had obvious effects on the photodegradation reaction. Reactions were favored under acidic and neutral pH condition. (4) Increasing light intensity help to improve degradation rate, but only 7% degradation rate increase.Photocatalytic stability of TiCVCNF and TiO₂/PAN nanofibers were also investigated in my work. The results indicated that the photocatalytic activity of TiO₂/CNF and TiO₂/PAN nanofiber presented the downward trend. The main reason probably was that intermediate accumulates on the surface of TiO₂ particles at the process of photodegradation. The other reason could be TiO₂ particles desquamate from nanofibers after recycling use of the catalyst for 5 times.Chen Chao (Environmental Science) Supervised by Zhou mei-hua...