Preparation Of Bismuth Oxyhalide-Based Composite Photocatalyst And Its Photocatalytic Degradation Performance For Organic Pollutants

In recent years,China has developed at an extremely fast rate,but the process of development has also brought a lot of sewage discharge,making water resources shortage.In these sewage,organic dyes and antibiotics account for a large proportion.Organic dyes have color,which will affect the transparency of water after entering the water environment,resulting in the death of animals and plants in the water.On the other hand,organic dyes are also a kind of three pollutants,which can cause the deformity of animals and plants in the water environment.Antibiotics can induce pathogens after entering natural water bodies,causing pathogens to produce resistance genes,and even superbugs resistant to multiple antibiotics,threatening human life and health.Semiconductor photocatalytic technology is a sewage treatment method that can use sunlight as energy to remove various pollutants.It has simple operation,low cost,and is not suitable for strong oxidizing and reducing agents.It is environmentally friendly and can achieve efficient mineralization of organic pollutants.The focus of photocatalytic technology is on materials.Bi OX（X=F,Cl,Br,I）has a suitable valence band conduction band position and can degrade organic pollutants.However,a single material also has problems such as high photogenerated carrier recombination efficiency,low quantum utilization,and insufficient visible light activity.Therefore,in this paper,bismuth oxyhalide-based composite photocatalysts were prepared by metal doping,introducing oxygen vacancies and constructing heterojunctions to achieve efficient degradation of organic dyes and antibiotic pollution in water under visible light conditions.The reaction mechanism of the material and the ecotoxicological effects of the actual use were elucidated in detail.The main contents include the following two parts:（1）The nanoflower-like Bi/BiOCl photocatalyst was successfully prepared by introducing a weak reducing agent DMF into the traditional hydrothermal preparation method of Bi OCl and using Ni Cl₂ as a chlorine source.The presence of weak reducing agent DMF reduced Bi³⁺on the surface of Bi OCl to elemental bismuth in situ.ESR characterization proved the presence of oxygen vacancies.XRD,SEM,HR-TEM,XPS and other characterizations confirmed the successful preparation of Bi/Bi OCl composites,and realized the dual modification of metal doping and introduction of oxygen vacancies.The Bi/Bi OCl material has excellent visible light photocatalytic activity,and can remove 98.7%of rhodamine B in 200 seconds under visible light irradiation.The main active substances and intermediate products of photocatalytic degradation of rhodamine B were also elucidated.The mung bean seedling experiment proved that the final product of rhodamine B degradation had low toxicity,and it was found that the nitrogen element in rhodamine B was converted into the form of ammonia nitrogen during photocatalytic degradation.（2）Bi/BiOBr/Bi₂O₂CO₃ ternary heterojunction photocatalyst was successfully prepared by introducing organic DMF into the traditional hydrothermal preparation method of Bi OBr,which was used as a reducing agent and a carbon source of Bi₂O₂CO₃.The successful preparation of Bi/Bi OBr/Bi₂O₂CO₃ composite photocatalyst was proved by XRD,SEM,HR-TEM,XPS,ESR and other characterizations.The triple modification of Bi OBr metal doping,oxygen vacancy introduction and heterojunction construction were realized.Bi/Bi OBr/Bi₂O₂CO₃ can efficiently degrade rhodamine B,tetracycline and oxytetracycline under visible light irradiation.In this study,the mechanism of photocatalytic reaction,the degradation pathway of pollutants and the stability cycle of materials were also elucidated in detail.In the experiment of plant toxicology analysis,the effects of degradation products on various enzyme activities in rice seedlings were concerned,and it was concluded that the degradation products had lower ecotoxicological effects on plants.