Preparation Of Porous Bismuth Composite Material And Study On Its Photocatalytic Degradation Performance

At present,human beings are facing severe water pollution problems.The traditional treatment methods are time-consuming and labor-intensive.As a new method of green,environmental protection and high efficiency,photocatalytic degradation technology can effectively solve the water pollution problem.However,most of the reported photocatalytic materials,such as titanium dioxide,have a wide band gap,which results in their catalytic performance only in the higher energy ultraviolet region.However,elements such as lanthanides as photocatalysts are not only expensive,but also difficult to extract and make into photocatalysts.In response to the above problems,this thesis uses bismuth metal oxide bismuth oxide(Bi₂O₃)as the photocatalytic material matrix.Bismuth is not only low in cost,but also has the excellent properties of lanthanide metals and has an appropriate forbidden band width,and has photocatalytic properties in the visible light region.However,bismuth oxide has a variety of crystal structures,and its multiple crystal structures are easy to change in the external environment,and there is a certain degree of instability.In this thesis,UiO-66 metal organic framework material with high stability and high specific surface area is used to composite bismuth oxide,which effectively improves the efficiency of electron-hole separation,enhances the adsorption effect of the material on pollutants,and reduces the unstable form of bismuth oxide.The bismuth oxide is modified with bismuth oxide iodide(BiOI),which is enriched in anions and has a lower band gap,reduces the band gap of bismuth oxide to improve the photocatalytic activity of the material,and is compounded with UiO-66 to enhance the catalytic activity of the material.Stability and adsorption effect.The specific work is as follows:First,UiO-66 is loaded onto Bi₂O₃ to make composite materials by solvothermal method.Through a series of different ratios of Bi₂O₃@UiO-66 under visible light to carry out the photocatalytic degradation test of tetracycline,the results show that when Bi₂O₃:UiO-66 is 1:1,it exhibits the best degradation effect and the degradation rate reaches k=0.0492 min^-1.At the same time,repeated degradation experiments were performed on the samples of this ratio,and it was found that the material has excellent stability and can be repeatedly applied to the degradation of tetracycline.Secondly,BiOI was used to modify Bi₂O₃ to prepare a series of Bi₂O₃@BiOI composite materials with different proportions.At the same time,the Bi₂O₃@UiO-66composite material loaded with UiO-66 was used for BiOI with a sheet structure to Bi₂O₃@UiO-66 To compound,prepare Bi₂O₃@BiOI@UiO-66 ternary composite material.In addition to the photodegradation test of tetracycline under photocatalysis,the photodegradation test of the organic dye Rhodamine B was carried out to evaluate the visible light degradation performance of the material.The results show that Bi₂O₃@BiOI@UiO-66 ternary material has significantly better degradation performance on tetracycline and rhodamine B than Bi₂O₃@BiOI binary material.The photodegradation rate of tetracycline is 0.01103 min^-1,and the degradation rate of Rhodamine B is 0.03546 min^-1.And after repeated photodegradation experiments,the performance of the material remained basically unchanged,while maintaining high-efficiency degradation efficiency of pollutants.This verifies the high stability performance and high catalytic efficiency of the material.Finally,by changing the environment for the photocatalytic degradation of pollutants,the impact of the environment on the two materials is explored,and the photocurrent and electron paramagnetic resonance tests are used to analyze the photocatalytic degradation mechanism and effect of the composite materials.The results showed that Bi₂O₃@UiO-66 composite material still has the ability to degrade tetracycline in different pH environments,and the best pH is 7;it can also maintain the degradation effect on tetracycline in solutions of different ions,with the least impact on yin and yang.The ions are calcium ion and bicarbonate ion.For Bi₂O₃@BiOI and Bi₂O₃@BiOI@UiO-66 materials,they also have stable degradation performance in different pH and ions,and the optimal pH is still 7.At the same time,the photocatalytic mechanism of the two materials was studied,and it was found that the two materials had a stronger current response than the monomer under visible light,and the hydroxyl radicals and ultrastructures could be detected in the degradation environment of the two materials.Oxygen free radicals prove that the two materials have high photocatalytic activity under visible light and are visible light catalytic materials with bright prospects.