Preparation And Photocatalytic Properties Of Supported Heteropoly Acid Magnetic Nanoparticles And TiO₂ Modified Nanofibers

Environmental pollution and energy crisis have become the two major problems that threaten human society and the life of the earth in twenty-first Century.Development and utilization of clean energy and effective management and control of environmental pollution has become a big challenge for scientists all over the world.Photocatalytic reaction is simple,efficient and fast,and has become an effective way to produce clean energy and environmental trement.Photo catalyst can not only use the solar energy to directly decompose water to produce hydrogen,realize the conversion of solar energy to high efficiency chemical energy,but also can decompose organic pollutants through the photocatalytic reaction.In recent decades,there have been a lot of photocatalytic activity reports about TiO₂ and heteropoly acid.However,the catalysts that has been reported has several shortcoming,such as low utilization rate of light energy,difficulty in separation,low photocatalytic efficiency and so on.Therefore,modification of titanium dioxide and heteropoly acid,is of great significance to improve its photocatalytic activity.In this paper,we prepared the magnetic nanoparticles and tungsten doped titania nanofibers with multi acid doped,and studied their structure,morphology and photocatalytic properties.The main work of this paper is as follows:1.The?Fe₃O₄@SiO₂@HPW?3a,3b and the 3c were prepared by impregnation method and sol gel method respectively.The structure of the product was characterized by XRD and FT-IR method,and the content of HPW?3a:5.83%;3b:13.25%?was determined by ICP-AES method.The results of SEM and TEM show that they have a spherical core shell structure with uniform size distribution.The analysis of their magnetic properties show that they are all superparamagnetic with typical S-shap curves.Finally,we studied the photocatalytic reaction of RB by UV irradiation.The results show that the prepared nanoparticles have very good catalytic activity and stability,and the degradation rate is more than 90%.The results of kinetic behavior analysis of the catalytic reaction show that the linear relationship between In?Ct/C0?vs time shows that they follow the first order reaction kinetics.2.In this experiment,we prepared core-shell magnetic nanoparticles photocatalysts by the impregnation method which were loaded with different amount of H₄SiW₁₂O₄₀ and H₃PMo₁₂O₄₀,respectively.They are Fe₃O₄@SiO₂@HSiW?S4?,Fe₃O₄@SiO₂@HSiW?S3?,Fe₃O₄@SiO₂@HSiW?S2?,Fe₃O₄@SiO₂@HSiW?S1?,Fe₃O₄@SiO₂@HPMo?P4?,Fe₃O₄@SiO₂@HPMo?P3?,Fe₃O₄@SiO₂@HPMo?P2?and Fe₃O₄@SiO₂@HPMo?P1?.The XRD and FT-IR methods were used to characterize the structure of the photocatalyst,and the photocatalytic reaction of RB was studied.The results show that the prepared supported heteropoly acid core-shell magnetic nanoparticles have good photocatalytic activity under ultraviolet light at about 60min degradation rate were higher than or close to 90%.3.W doped TiO₂ nanofibers were prepared by electrospinning,and 12 nanofibers were obtained by changing the calcination temperature and W/Ti ratio.In order to compare the effects of W doping on the structure and photocatalytic activity of TiO₂ nanofibers,TiO₂ nanofibers and WO3 nanofibers were prepared by the same method.All the prepared nanofibers were characterized by XRD and Raman,and the results showed that the calcination temperature had a great influence on the structure.When the calcination temperature is 520? or 620? only the W doped TiO₂ nanofibers was,which the W atoms exists in the TiO₂ lattice with the anatase structure.When the calcination temperature is 720?,a small amount of WO3 was observed.Calcination temperature to 720?,is in addition to,the other W still exists in the TiO₂ lattice to form doped,and to maintain the anatase structure temperature to 820 ?.Calcination,the formation of WO3 increased significantly,and there is a small amount of TiO₂ into rutile structure.SEM photo shows that the product is composed of the orientation disorder of the nanofiber,and with the increase of the calcination temperature,the surface roughness increases gradually.The results of EDX spectra showed that the prepared nanofibers were mainly composed of W,O and Ti,indicating that W was successfully doped into the lattice of TiO₂.By the photocatalytic degradation of RB under UV irradiation,the W doped TiO₂ nanofiber has excellent photocatalytic activity,and the degradation rate of RB is close to 100%.The log curves of RB were linear,and the linear correlation coefficients were all close to 1,indicating that the RB degradation reaction followed the first order reaction kinetics.