Study On The Construction Of Bismuth Vanadate?BiVO₄? Based Photocatalyst And Its Degradation Of Methylene Blue

Methylene blue was a kind of cationic dye,which is widely used in dyeing industry.Which contained some kinds of difficult-to-degrade organic compound.If it was not treated effectively and discharged directly to the water body,it would caused serious pollution to the water environment.The harm of Dyeing wastewater to water body included:reducing the transparency of water body,affecting the light and function of animals and plants in water body,reducing the water quality,affecting the self-purification ability of water body and endangering the production and life of human beings.Photocatalytic technology was green and environmentally friendly wastewater treatment technology,its core was the catalyst,and Bi VO₄was a kind of semiconductor photocatalyst which can respond in the visible wavelength and degrade all kinds of pollutants in the water body under the sunlight irradiation,which can degrade all kinds of pollutants in the water body under the sunlight irradiation,and it can reduce the pollution degree of the water body by oxidation and decomposition of the pollutants in the water body.Such as:dye molecule,antibiotic molecule,etc.However,the separation time of photo-generated holes and photo-generated electrons was very short,which greatly limited the photocatalytic efficiency of Bi VO₄.Therefore,The research of Bi VO₄at home and abroad mainly focused on improving the photocatalytic degradation performance of Bi VO₄through the construction of heterostructure,doping and morphology.The effects of hydrothermal time,hydrothermal temperature and p H value of precursor solution on the physical and chemical properties of Bi VO₄were studied in detail.The photocatalytic activity of Bi VO₄was improved by the doping of P25,Ag and P25+Ag.The photocatalytic degradation rate of methylene blue dye was used as probe reaction,and the X-ray diffraction?XRD?,X-ray photoelectron spectroscopy?XPS?,Raman Spectra?Raman?,Fourier transform Infrared Spectroscopy?FT-IR?,Ultraviolet visible diffuse Reflectance Spectroscopy?UV-Vis?,scanning Electron microscope?SEM?,Transmission electron microscope?TEM?and high power transmission electron microscope?HRTEM?were used to analyze the mechanism of P25,Ag and P25+Ag loading to improve the photocatalytic activity of Bi VO₄.The details of the work are as follows:?1?In the process of hydrothermal synthesis of Bi VO₄,the hydrothermal time,hydrothermal temperature and the p H value of the precursor solution were controlled to explore in detail the crystal form of Bi VO₄during the process,such as hydrothermal time,hydrothermal temperature and the p H value of the precursor solution,and the effect of the hydrothermal time,the hydrothermal temperature and the p H value of the precursor solution on the crystallinity of Bi VO₄was investigated in detail.Effect of shape and photocatalytic properties.The experimental results showed that the influence of hydrothermal time,hydrothermal temperature and p H value on the crystal structure of Bi VO₄was as follows:hydrothermal time>p H value>hydrothermal temperature.By analyzing the morphology of Bi VO₄in different hydrothermal time,it was concluded that the formation mechanism of Bi VO₄in hydrothermal process may be as follows:First of all,a smooth sphere was formed.With the increase of hydrothermal time,a lot of polyhedron was gradually formed on the surface of the smooth sphere,and when the hydrothermal time was 14 h,the polyhedron formed on the spherical surface falls off from its parent body.With the increase of hydrothermal time,the particle size of the crystal increases and agglomeration occurs.?2?Bi VO₄/P25 heterostructure catalyst was prepared by one-step hydrothermal method.Compared with pure the Bi VO₄,the Bi VO₄/P25 samples have a better photocatalytic activity and adsorption ability to methylene blue.Under the irradiation of visible light?550W Xenon lamp,?>420 nm?,the degradation rate of methylene blue solution can reach 85%within 60 min.The Bi VO₄/P25 nanocomposites were characterized by X-ray photoelectron spectroscopy?XPS?,Raman spectrum?Raman?,Fourier transform infrared spectroscopy?FT-IR?and so on.High power transmission electron microscopy?HRTEM?showed that the structure of Bi VO₄was a flower-like structure composed of polyhedron.Compared with pure Bi VO₄,Bi VO₄/P25nanocomposites have rougher surface and larger specific surface area,which can effectively improve the photocatalytic activity of Bi VO₄and the adsorption performance of methylene blue.?3?Bi VO₄/Ag heterostructure was synthesized by hydrothermal method and photoreduction method.Under the irradiation of visible light?550 W Xenon lamp,?>420 nm?,the degradation rate of methylene blue was 95%within 150 min,and the photocatalytic efficiency of the composite catalyst was increased by about 50%compared with pure Bi VO₄.It can be seen from the scanning electron microscope?SEM?and X-ray diffraction?XRD?that the doping of Ag has no effect on the growth of Bi VO₄crystal structure and crystal plane.The doping of Ag⁺increases the specific surface area of Bi VO₄/Ag heterostructure compared with pure Bi VO₄,and the surface morphology of Bi VO₄/Ag heterostructure was rougher than that of pure Bi VO₄,which was beneficial to the adsorption of organic pollutants such as methylene blue.The UV-vis diffuse reflectance?UV-Vis?analysis showed that the light absorption of Bi VO₄/Ag heterostructure was red-shifted than that of pure Bi VO₄,which proved that the photocatalytic activity of Bi VO₄/Ag heterostructure was higher than that of pure Bi VO₄,which indicated that the photocatalysis activity of Bi VO₄/Ag heterostructure was higher than that of pure Bi VO₄.?4?The ternary composite structure of Bi VO₄/P25/Ag was synthesized by photoreduction method and hydrothermal method.The photocatalytic degradation effect of Bi VO₄/P25/Ag was tested by using methylene blue solution as probe.The experimental results show that the degradation ability of Bi VO₄/P25/Ag to methylene blue solution was worse than that of Bi VO₄/P25 and Bi VO₄/Ag.