Preparation Of Fe³⁺ Doped Bi₃NbO₇ Catalyst And Study On Its Photocatalytic Performance

Nowadays,the dye manufacturing industry and textile industry are in the period of vigorous development.While bringing the dazzling world to human beings,a large amount of organic waste water is produced,which has a serious impact on the living environment.The disposal of these wastewater has become the focus of environmental concern.Photocatalytic degradation technology is a new catalytic technology and has become a research hotspot in the field of dye wastewater degradation.Among them,the development and research of photocatalyst is the core and key of photocatalytic degradation of dye wastewater technology.As a common photocatalyst,TiO₂has a wide band gap,low solar energy utilization rate and low photocatalytic degradation efficiency,so its application is limited.Bismuth（Bi）catalyst is a kind of semiconductor photocatalyst with better performance than TiO₂.Its band gap is smaller and its performance is good under visible light condition.Bi₃NbO₇is a semiconductor photocatalyst with oxygen defect fluorite structure.It has stable chemical properties and a band gap of 2.5-2.75e V.The photocatalytic performance can be stimulated under visible light conditions.However,Bi₃NbO₇photocatalyst has a high recombination rate of photogenerated electron and hole pairs,and its photocatalytic performance needs to be further improved.In this paper,Fe³⁺doping was used to improve the photocatalytic performance of Bi₃NbO₇catalyst.Adopt the method of coprecipitation preparation for Bi₃NbO₇and Fe³⁺doped Bi₃NbO₇catalyst,XRD,BET,XPS,UV-vis DRS,characterized by SEM,TEM and other technical preparation of catalyst,this paper discusses the solution pH,roasting temperature and Fe³⁺doping amount on Bi₃NbO₇catalyst structure and catalytic activity,the influence of fitting analysis,dynamics of degradation data for the preliminary discussion on the degradation mechanism,the conclusions are as follows.1.The effects of calcination temperature and pH value on the structure and properties of the catalyst were investigated by controlling a single variable.The experimental results show that the pH value of the solution during preparation has a great influence on the structure of the final catalyst,and the strong alkalinity（pH≥13）is conducive to the preparation of single crystal phase catalyst.In selected roasting temperature range,the higher the calcination temperature,catalyst for the preparation of crystal type,the more complete,under 500℃calcination can be single phase,complete crystal shape of the catalyst,while the temperature for the preparation of the catalyst photocatalytic performance slightly inferior at 300℃and 400℃calcination of catalyst,but the light time after 300 min,fuchsine dye degradation rate can reach about 91%.2.Based on the necessary characterization of different Fe³⁺doped Bi₃NbO₇catalysts and the analysis and test of the photocatalytic degradation of basic fuchsin,the effects of Fe³⁺doping on the structure and photocatalytic activity of Bi₃NbO₇were discussed.The XRD results show that the doped Fe³⁺enters the crystal lattice of Bi₃NbO₇,forming a single Bi₃NbO₇crystal phase,and no other phase is formed.The results of specific surface area and pore size analysis show that the catalyst is mainly mesoporous,but there are also large pores.The results of UV-Vis DRS analysis show that with the increase of Fe³⁺doping amount,the band gap decreases and the optical response performance increases.The morphology analysis of SEM and TEM shows that the catalyst particles pile up with each other,presenting a loose cluster state.XPS test results show that oxygen vacancy is formed with Fe³⁺entering Bi₃NbO₇lattice,but the concentration of oxygen vacancy is related to the doping amount of Fe³⁺.The results of photocatalytic activity test showed that the Fe³⁺doped Bi₃NbO₇catalyst prepared with the Fe³⁺doping amount of 1%had the best degradation effect of basic fuchsin.Under the conditions of the initial concentration of basic fuchsine of 5 mg/L and the dosage of catalyst of 1 g/L,the degradation rate of basic fuchsine could reach100%after the irradiation time of 180 min.3.Through the discussion of the photocatalytic reaction conditions,such as the amount of catalyst and the initial concentration of basic fuchsine,it is concluded that the degradation efficiency of basic fuchsine is higher when the addition of catalyst is1 g/L and the dye concentration is less than 5 mg/L.The prepared Fe³⁺doped Bi₃NbO₇showed different degradation properties for different dyes,among which the degradation rate of basic fuchsin was the highest.4.The analysis of photocatalytic mechanism shows that both the active groups·OH and·O₂（?）play a role in the degradation of basic fuchsine molecules.In the photocatalytic degradation process,the conjugatedπbond and benzene ring in the structure of basic fuchsine molecules are broken to form CO₂and H₂O.