Synthesis Of Visible-Light-Driven Bi-Based Nanomaterials And Study On Their Photocatalytic Activity For Antibiotic Pollutants Degradation

In recent years,the extensive use of antibiotics has brought great convenience to human beings in medical care,agriculture,etc.But due to its inherent difficulty in degrading,the continuous existence of a large amount in the water environment poses a serious burden on the environment,while the traditional sewage treatment technology is difficult to its removal,which has caused widespread concern in society.Photocatalytic technology based on semiconductor photocatalyst and renewable solar energy is an important way to solve the environmental problems caused by antibiotics.However,the traditional semiconductor photocatalytic materials have the problems of narrow light absorption range,fast photocarrier generation,low quantum efficiency of the catalyst and so on,which seriously restrict the practical application of the photocatalyst.Therefore,the development of new visible light-responsive high-efficiency photocatalysts or the construction of composite photocatalytic systems that are beneficial to the separation of photogenerated carriers is a hot topic in the field of photocatalysis.In this paper,as a goal,a new lanthanide series material was selected as the research object.Through the regulation of synthesis methods and the construction of a composite system,the catalyst solar light absorption range was successfully broadened,the photogenerated charge separation efficiency was increased,and the photoelectron electron transfer rate was promoted,thereby increasing photocatalytic performance.The properties of the photocatalytic materials and the carrier’s migration path were explored in many aspects such as morphology control and composition adjustment,which provided a theoretical basis for the development of new high-efficiency visible light catalytic materials.The specific research results obtained in this paper are as follows:（1）A new type of Bi₃O₄Cl was prepared by a simple solvothermal-calcination method.The prepared Bi₃O₄Cl has a layered structure and has a narrow band gap（2.62 eV）.Compared with the traditional BiOCl and Bi₃O₄Cl synthesized by the solid state method,the layered Bi₃O₄Cl exhibited better photocatalytic degradation of tetracycline hydrochloride（TC-HCl）.The structure and morphology of the novel Bi₃O₄Cl were characterized by XRD,SEM and TEM.In addition,after many cycles of degradation,the layered Bi₃O₄Cl can maintain a good photocatalytic activity,which proves that it has good photocatalytic stability.The photocatalytic degradation mechanism of layered Bi₃O₄Cl was further studied by photocurrent experiments.（2）The Bi₂₄O₃₁Cl₁₀0 nanosheets were synthesized by a simple solvothermal method,and the crystallinity of the Bi₂₄O₃₁Cl₁₀0 nanosheets was further improved by heat treatment.Compared with traditional Bi OCl and TiO₂（P25）,Bi₂₄O₃₁Cl₁₀0 prepared in this paper exhibits excellent photocatalytic degradation of TC-HCl.In addition,according to the XPS valance band spectrum analysis and photocatalytic active species capture experiments,possible photocatalytic mechanisms were proposed.Through cycling experiments,it was proved that nanoplatelets have excellent photochemical stability.This work provides a simple method for the development of new and efficient ruthenium-based nanomaterials that degrade antibiotic contaminants.（3）A novel core-shellβ-Bi₂O₃@g-C₃N₄ photocatalyst was prepared by a simple self-assembly method.The core-shell heterostructure not only increases the light absorption range of the composite material,but also can effectively increase the contact area of the heterojunction interface,which greatly facilitates the rapid separation and transfer of photoelectron-hole pairs.The photocatalytic activity of the composites was studied by degrading antibiotic tetracycline（TC）under visible light（λ>420 nm）irradiation.The results show that the photocatalytic performance of the developedβ-Bi₂O₃@g-C₃N₄core/shell photocatalyst is greatly improved compared with the single-phaseβ-Bi₂O₃nanoparticles and g-C₃N₄.After an experimental investigation to find the best ratio,we finally found that the core/shell sample loaded with 5 wt%g-C₃N₄ has the best photocatalytic efficiency,and its TC degradation rate constant(k=0.0311 min^-1)is much higher than otherβ-Bi₂O₃ photocatalytic materials reported in the literature.