Study On The Preparation And Property Of ZnO-PANI Nanocomposites

With the increasing serious extension of environmental pollution, more and more people are attracted to devote into themselves to environmental propection. Semiconductor nanomaterial used as efficient photocatalyst plays a important role in the decomposition of organic contamination. Nano-ZnO has the advantages of low cost, easy preparation, stability under illumination, nontoxic and recycle. However, its light absorption is limited to the ultraviolet region. The dispersibility in organic solvents and acid-resistance of nano-ZnO are poor. Therefore, how to process ZnO nanomaterials to improve the performance for actual application becomes the key point which the researchers study.In the thesis, ZnO nanomaterials with different morphologies were successfully prepared through hydrothermal and liquid-phase precipitation methods. The influence of organic solvents, reaction temperature and time on the morphologies of nanometer ZnO was investigated. The formation mechanism was discussed. Nanometer ZnO was chemical modified by reflux and hydrothermal method respectively. ZnO-PANI nanocomposite was prepared by the solution and emulsion in-situ polymerization methods. The influence of the reaction time, the preparation method and reactants proportion on the structure and performance of the prepared samples was studied. The photodegradation performance of nano-ZnO and ZnO-PANI nanocomposites for MB was carried out. There are three sections of our researching work as follows:First, ZnO nanocrystals with different morphologies of rod, particle and sphere were successfully prepared by liquid-phase precipitation and hydrothermal methods. Different morphologies ZnO nanocrystals were prepared by liquid-phase precipitation method using zinc acetate and sodium hydroxide in various alcoholic solution. The morphologies of ZnO naocrystallites are influenced by reaction conditions such as type of alcohol, temperature and time, in which the reaction temperature and time are more important. Uniform ZnO nanoparticles or nanorods could be obtained in ethanol by varying reaction temperature、time. Microstructural ZnO spheres consisted of nanometer flakes was prepared by hydrothermal method. The influence of reaction temperature and zinc source reactants on the samples was studied. The results show that zinc salts and reaction temperature strongly influenced the morphology of microsphere.Second, ZnO-PANI nanocomposite was prepared by the solution and emulsion polymerization methods. Chemical modification of ZnO was done by reflux and hydrothermal methods using coupling agent KH-42. Hydrothermal method is more effective. ZnO-PANI nanocomposites were prepared at room temperature by solution and emulsion polymerization methods using APS as oxidant. The experiment results show that all the nanocomposites extend their absorption band to visible wavelength range of400-700nm.Third, the photocatalytic degradation of MB was carried out using ZnO nanomaterials and ZnO-PANI nanocomposites as photocatalysts. The effects of photocatalyst dosage and morphology on photodegradation performance were studied. The results show that ano-ZnO with different morphology has good UV photocatalytic efficiency, in which rodlike and spheroidal ZnO have higher decolorization ratio more than98.9%. ZnO-PANI nanocomposites could photodegrade MB under visible light irradiation, while the ZnO-PANI nanocomposite of modified ZnO nanorod decolorization ratio is more than97%. The crystal structure and ultraviolet visible absorption of photocatalyst after photodegradation have no change. The decolorization ratio of recycled sphere nano-ZnO is more than96%.In conclusion, high photocatalytic activity uniform ZnO with different morphologies such as rod, particle and sphere could be prepared with liquid-phase precipitation and hydrothermal methods; ZnO-PANI nanocomposites prepared by in-situ polymerization which extend their absorption band to visible wavelength region have good visible photodegradation performance. The researching work will promote ZnO nanomaterials used as photocatalyst in practical application.