Preparation Of Bismuth Vanadate-based Photocatalytic Material And Experimental Study On Formaldehyde Degradation By Visible Light

Formaldehyde is one of the typical pollutants that exist in close contact with people in the indoor environment,and it has widespread harm to the human body.The semiconductor photocatalytic material titanium dioxide（Ti O₂）is widely used in the degradation of formaldehyde gas.However,due to its large forbidden band width,it can only play a role under the excitation of ultraviolet light,so there are some restrictions on application conditions.At present,scholars have begun to focus on the degradation of pollutants by various photocatalytic materials with visible light response.The photocatalytic technology treatment of formaldehyde gas is no exception.As another type of semiconductor material after Ti O₂,bismuth vanadate has the advantages of non-toxicity,visible light response,and simple preparation.It is an excellent photocatalytic material.However,current bismuth vanadate materials still have the problems of insufficient photocatalytic efficiency.This research first carried out the modification of bismuth vanadateto improve its photocatalytic activity.The thesis uses reduced graphene oxide（r GO）to modify bismuth vanadate to prepare reduced graphene oxide/bismuth vanadate（r GO/Bi VO₄）composite materials.Through orthogonal experiments,the optimal combination conditions of the preparation factors for the hydrothermal preparation of the composite material are obtained,namely:the ratio of reduced graphene oxide（r GO）is 1 wt%,and the addition amount of ethylenediaminetetraacetic acid（EDTA）is 3 mmol,The p H is adjusted to 6,and the hydrothermal temperature is 170℃.The paper further used X-ray crystal diffraction,electron microscope scanning,ultraviolet-visible light diffuse reflectance spectroscopy and other characterization techniques to examine the phase structure,morphology,surface valence bond and light absorption properties of Bi VO₄ and r GO/Bi VO₄.The characterization results show that the material prepared in this paper has good crystallinity and is the monoclinic scheelite phase with the best activity.Bi VO₄ has a special structure with mesoporous morphology,and the reduced graphene oxide is tightly combined with bismuth vanadate.The developed material has a good response to visible light,especially enhanced absorption performance in the visible spectrum range from 500 nm to 760 nm.After that,the paper used a self-made reactor to simulate the indoor environment to degrade the formaldehyde in the air.The Bi VO₄ and r GO/Bi VO₄ developed in this thesis were used to carry out the experimental study on the degradation effect of indoor air formaldehyde.To examine the photocatalytic degradation of formaldehyde in indoor air.The experimental results show that the introduction of reduced graphene oxide enhances the photocatalytic activity under visible light.The composite material r GO/Bi VO₄ has a high degradation efficiency of formaldehyde in indoor air under visible light,and the degradation rate of formaldehyde in 180 minutes is 72.23%.It shows that it has good visible light response and degradation efficiency,and can be used to degrade formaldehyde.Finally,the paper uses the hydrothermal in-situ growth method to load Bi VO₄ and r GO/Bi VO₄ on glass fiber for the first time,and develops three-dimensional materials Bi VO₄@GFs and r GO/Bi VO₄@GFs.Characterization methods were used to confirm the phase,morphology,and surface valence bonds of the material.The results showed that the mesoporous bismuth vanadate was supported on glass fiber filaments with good dispersibility.The GO material in the precursor was successfully reduced to r GO,which was present between the glass fiber filaments or on the bismuth vanadate material,but it had an impact on the dispersion and growth of the Bi VO₄ photocatalytic material on the glass fiber.The thesis also examined the three major properties of the prepared materials:degradation rate,cycle stability performance and load firmness performance.The material has good degradation rate and stability,and certain firmness.It has laid a certain theoretical foundation for the application of Bi VO₄@GFs and r GO/Bi VO₄@GFs in the degradation of indoor air formaldehyde.