Preparation Of Bi-based Binary Heterojunction Photocatalytic Material And Its Application In Control

With the continuous development of photocatalytic technology,traditional TiO₂ semiconductor materials have the disadvantages of low solar energy utilization and low separation efficiency of photo-generated electrons and holes,which severely limited their application in the treatment of wastewater.Therefore,the development of new photocatalyst with high efficiency of photoelectron and hole separation has become a research focus in the field of photocatalysis all over the world.Bismuth-based photocatalytic materials have attracted wide attention among researchers in recent years.Among them,bismuth oxyformate（BiOCOOH）and bismuth oxyacetate（BiOAc）have special[Bi₂O₂]²⁺structures.With only C,N,O and H elements besides Bi,it brings almost no secondary pollution to the environment.In this study,BiOCOOH and BiOAc were studied by forming heterojunctions with other semiconductors,and a series of binary composite photocatalytic materials were synthesized and combined with other advanced oxidation processes for the degradation of common pollutants in water.Simultaneously,the photocatalytic mechanism of each system was investigated by detecting the active species in the reaction process.The main contents and conclusions are as follows:（1）BiOAc/BiOCl photocatalytic materials were synthesized by ion exchange and chemical precipitation method using CH₃COOH,Bi₂O₃,and KCl as raw material with magnetic stirring at room temperature.The prepared materials were characterized by XRD,SEM,TEM,XPS,and UV-vis.The results indicated the successful synthesis of BiOAc/BiOCl heterojunction.The cationic mixed dyes（rhodamine B（Rh B）and methylene blue（MB））and anionic mixed dyes（Isatin and Titan yellow）were used as target pollutants to investigate the photocatalytic activity of BiOAc/BiOCl composites and explore the photocatalytic mechanism.（2）BiOAc/BiOBr composite photocatalytic materials were prepared by ion exchange and chemical precipitation method using CH₃COOH,Bi₂O₃and KBr as raw materials.A series of characterizations confirmed the successful combination of BiOAc and BiOBr.The photocatalytic activity of BiOAc/BiOBr composites on cationic mixed dyes（Rh B and MB）and anionic mixed dyes（Isatin and Titan yellow）were investigated,and the photocatalytic degradation mechanism was proposed.（3）BiOCOOH/g-C₃N₄heterojunction photocatalytic materials were prepared by solvothermal and high-temperature solid-phase method,and applied in pollutants degradation in water coupled with PMS technique.The BiOCOOH/g-C₃N₄composites were characterized by means of techniques,the cationic dyes,rhodamine B（Rh B）,and anionic dyes（MG）were utilized as target pollutants to investigate their degradation efficiency in a simple photocatalytic system and a photocatalytic/PMS system,respectively,under the illumination of LED.The reactive species in the two systems were detected by free radical trapping experiment,and the possible degradation mechanisms of the two systems were speculated.By examining the stability and reusability of BiOCOOH/g-C₃N₄,its application prospects in wastewater treatment were evaluated.