Study On Preparation Of Bismuth Semiconductor Photocatalyst And Visible Light Purification Of Indoor And Water Pollution

With the rapid development of the economy,people’s living standards are also improving day by day,and the living environment is becoming more and more superior.The use of indoor coatings and wooden furniture will release a large amount of formaldehyde to cause serious harm to people’s health,and studies have shown that the release cycle of formaldehyde can be as long as 3-15 years.The development of industry and agriculture has brought convenience to people’s production and life,but the use of a large number of dyes and drugs has caused water pollution problems.Photocatalysis technology is considered to be an important means of controlling environmental pollution in recent years.Photocatalytic technology has the advantages of clean and pollution-free,low price and simple preparation process.However,some semiconductors can only respond to ultraviolet light and have the disadvantage of high photogenerated electron-hole recombination,which greatly limits the photocatalytic efficiency of the catalyst.Therefore,enhancing the visible light response ability of semiconductors and solving the problem of high photoelectron recombination rate have become important ways to improve the photocatalytic degradation efficiency.Based on the above problems,BiOI was prepared with[Bi（NO₃）₃]·5H₂O and KI as the original,and Zn O,H₃PW₁₂O₄₀and diatomaceous earth（hereinafter referred to as DE）were introduced with BiOI as the base,respectively,and Zn O/BiOI p-n heterojunction composite photocatalyst,BiOI/DE composite photocatalyst and BiOI/H₃PW₁₂O₄₀(abbreviated:BiOI/PW₁₂)composite photocatalyst were designed and prepared.A series of Zn O/BiOI p-n heterojunction composite photocatalysts were prepared by co-deposition method,and Zn O nanoparticles were uniformly covered on BiOI nanoflowers by scanning electron microscopy（SME）,and the experimental data showed that the degradation rates of Rh B and HCHO by Zn O/BiOI composites doped with 0.5 g Zn O reached 96%and 60%,respectively.The photocatalytic mechanism of Zn O/BiOI p-n heterojunction was analyzed,and the free radical capture experiment proved that·O₂^-and h⁺were the main active substances in the photocatalytic reaction.After the contact between the p-type semiconductor BiOI and the Z-type semiconductor Zn O,an internal electric field will be formed,and the electrons on the BiOI conduction band will be transferred to the conduction band of Zn O,so as to achieve electric field balance and realize the effective separation of BiOI conduction band electrons and valence band holes.A series of BiOI/PW₁₂composites were prepared by using phosphotungstic acid H₃PW₁₂O₄₀modified BiOI,and a series of characterization methods such as XRD,SEM,DRS were used to characterize the catalyst,and the characterization results showed that BiOI/H₃PW₁₂O₄₀was successfully composed,the BiOI morphology was maintained well,and the composite maintained the absorption characteristics of visible light.Formaldehyde and methyl orange（MO）degradation tests were performed using BiOI/PW₁₂（0.05）modified with phosphotungstic acid,(0.05 is the mass of H₃PW₁₂O₄₀used,unit:g).The experimental data show that the degradation rate of the modified BiOI/PW₁₂（0.05）composite photocatalyst to gas formaldehyde（HCHO）and MO reaches 75%and 77%.The photocatalytic mechanism analysis showed that H₃PW₁₂O₄₀acted as an e-acceptor,and the e^-on the BiOI conduction band was transferred to the conduction band of H₃PW₁₂O₄₀,which realized the effective separation of photogenerated electron-hole pairs.BiOI/DE composites were prepared by co-deposition method,and a series of characterization methods such as XRD,SEM,DRS were used to characterize the catalysts,and the characterization results showed that BiOI nanoflowers were uniformly distributed on the molecular disc of diatomaceous earth,and BiOI/DE composites maintained good visible light absorption.Photocatalytic degradation experiments of methyl orange（MO）solution and formaldehyde（HCHO）gas were carried out on BiOI/DE composites.Experimental data show that the degradation rate of BiOI/DE composites to MO and HCHO reaches 85%and 82%.Combined with free radical capture experiments,the photocatalytic mechanism analysis was carried out,and the mechanism analysis results showed that the diatomite molecular disk acted as a photogenerated carrier transfer platform for BiOI,which inhibited the photogenerated carrier recombination.