Preparation Of Bismuth-based Semiconductor Composites And Photocatalytic Degradation Of Levofloxacin Hydrochloride

In recent years,antibiotics have played an important role in saving human lives and health,promoting livestock production and making a great contribution to social and economic development.However,with the misuse of antibiotics by human beings,it has led to an increasingly serious problem of bacterial resistance to antibiotics,therefore,how to treat antibiotics in wastewater has become an urgent problem to be solved.Bismuth-based semiconductor photocatalysts have the advantages of being environmentally friendly,abundant raw materials and good visible light response,but when a single bismuth-based semiconductor material is used for photocatalysis,the rapid compounding of photogenerated electrons-hole severely limits the photocatalytic performance of the material,therefore,how to effectively separate the photogenerated electron-hole pairs and reduce their compounding rate has become an urgent problem.In this thesis,different binary and ternary bismuth-based heterojunction photocatalyst materials were prepared to address the above problems,and the photocatalytic performance of the different materials was investigated experimentally.In addition,SEM,XRD,XPS,UV-Vis DRS,FT-IR,TEM,HRTEM and other characterisation methods were used to characterise the morphology,constituent elements and optical properties of the materials;followed by the photocatalytic degradation of a certain concentration of antibiotic solution to assess the photocatalytic performance of the materials.Finally,the possible mechanism of the prepared materials in the photocatalytic degradation of antibiotics is proposed based on the experimental data.The thesis is divided into three parts as follows:1.The flower-like nanomaterial BiOCOOH was firstly synthesized by low-temperature hydrothermal method,and then the PDIsm/BiOCOOH composite photocatalyst was prepared by self-assembling perylenimine(PDI)on the surface of BiOCOOH by atmospheric pressure reflux method.The PDIsm/BiOCOOH material with 10%PDIsm loading showed the highest photocatalytic activity,and the UV-diffuse spectra showed that the response to visible light was significantly enhanced.In this paper,the photocatalytic performance of the synthesized materials was tested under visible light irradiation to investigate their degradation of levofloxacin hydrochloride.It was shown that during the synthesis of the materials,Type-I heterojunctions were formed between the rod-like PDIsm and flower-like BiOCOOH,and such heterojunctions could effectively separate the photogenerated electron-hole pairs in BiOCOOH under visible light irradiation,and the photocatalytic performance was greatly enhanced compared with that of pure BiOCOOH.Finally,the possible degradation pathways of levofloxacin hydrochloride in the photocatalytic experiments were speculated based on the experimental data.The photocatalytic mechanism of the PDIsm/BiOCOOH heterojunction material is proposed based on radical capture experiments and ESR tests.2.Bi/Bi2O2CO3 nanosheets were prepared by a high-temperature hydrothermal method assisted by formamide,which enabled the in situ generation of Bi nanoparticles on the surface of the flake material Bi2O2CO3.The PDIsm/Bi/Bi2O2CO3 ternary heterojunction was obtained by self-assembly of PDI rods on the surface of Bi/Bi2O2CO3 nanosheets by atmospheric reflux.The photocatalytic activity of the prepared materials was investigated by degrading levofloxacin hydrochloride under visible light irradiation according to the degradation rate of the materials for levofloxacin hydrochloride.The experimental results showed that the 10%PDIsm/Bi/Bi2O2CO3 material exhibited the most excellent photocatalytic performance compared to the pure Bi/BOC and pure PDIsm.This is due to the SPR effect of metallic Bi nanoparticles and the configuration of Type-I heterojunctions.The degradation mechanism of this semiconductor photocatalyst is proposed based on radical trapping experiments and the energy band structure of the semiconductor.3.Ti3C2/Bi2O2CO3 materials were successfully synthesized by hydrothermal loading of Bo2O2CO3 onto the highly conductive Ti3C2 surface,forming a heterojunction structure between the two.the interface formed by the close contact between BOC and Ti3C2 provided a channel for charge transfer between the two.In the degradation experiments of levofloxacin hydrochloride under simulated sunlight irradiation,20%Ti3C2/BOC showed the highest photocatalytic activity,which was attributed to the large specific surface area,high light absorption capacity and high carrier separation efficiency of the composite of BOC and Ti3C2.Meanwhile,the active species of the material in the photocatalytic process were identified as superoxide radicals as well as holes based on the results of radical trapping experiments and ESR tests,and finally the photocatalytic mechanism of the photocatalyst was proposed.