Study On Design,synthesis And Properties Of BiOBr-based Photocatalysts For Degradation Of Tetracycline Hydrochloride

Since the continuing development of the social economy,tetracycline hydrochloride（TCH）has been made available as a broad-spectrum antibiotic each year,and its accumulation in the water environment as well as its effects on human health have gradually caught the attention of researchers and the public.A series of environmental problems have resulted from its inability to degrade and bioconcentration.In the emerging field of green environmental protection,the photocatalytic method has the advantages of high efficiency,no secondary pollution,and it utilizes solar energy.Among the treatment methods of tetracycline wastewater,it has been proven to be a highly efficient,low-cost,and effective method.Over the past few years,bismuth halide oxide has attracted research attention for its unique electronic structure,stable chemical properties,and efficient photodegradation ability.However,the quantum efficiency of pure BiOBr photocatalysts is too low and it exhibits blunted photocatalytic performance under visible light.This thesis focuses on exploring the ways to improve the photocatalytic performance of BiOBr.Three kinds of photocatalysts were synthesized and screened in batch by solvothermal,hydrothermal and electrostatic spinning methods,such as the BiOBr microsphere with the higher content of oxygen vacancies（OVs）,BiOBr microsphere photocatalysts with Ce³⁺/Ce⁴⁺synergistic catalysis,and flexible TiO₂@BiOBr heterojunction fiber membranes.Besides,the crystal structure,micromorphology,energy band structure and chemical state of the materials were characterized by XRD,SEM,UV-Vis diffuse reflectance and XPS.Further,the photocatalytic performance of the photocatalysts for TCH in water was also investigated respectively,and the main findings are as follows.（1）Three-dimensional BiOBr microspheres photocatalysts with the abundant concentration of OVs were constructed and screened through the strategy of"solvent-coordination induced self-assembly".Under UV-Vis light irradiation,the degradation efficiency of TCH was nearly 86.8%in the first 20min and 96.5%in 60 min.Moreover,the photodegradation efficiencies under visible light（λ>400 nm）and actual sunlight irradiation were 70.1%and 91.2%within 60 min,respectively,which greatly enhanced the treatment capacity of the polluted water body.The abundant OVs and the three-dimensional open multi-pore channel system are beneficial to improve the mass transfer efficiency,thus obtaining the excellent photocatalytic performance.（2）BiOBr microsphere photocatalysts were prepared with Ce³⁺/Ce⁴⁺synergistic catalysis.The internal Ce³⁺/Ce⁴⁺electron pair can rapidly capture photogenerated electrons,thus effectively reducing the composite rate of photogenerated carriers.The UV-vis diffuse reflectance characterization showed the smaller bandgap and good light absorption ability of Ce/BiOBr composite photocatalyst,which can improve the absorption and utilization of the visible light.Among the prepared catalysts,the photocatalyst with component Ce/BiOBr-0.2 greatly improved the photocatalytic degradation of TCH,and the degradation efficiency was as high as 97.1%at 30 min under UV-vis light irradiation.It is shown that Ce ion doping is beneficial to increase the charge transfer rate and reduce the recombination of photogenerated carriers,thus improving its photocatalytic performance.（3）Flexible TiO₂@BiOBr heterojunction fiber membranes were successfully synthesized by electrostatic spinning and solvothermal methods.BiOBr flake crystals were uniformly loaded on the surface of TiO₂ fibers,and the modified membrane structure and morphology were completely preserved,which proved the excellent chemical and thermal stability of TiO₂ fiber membranes possessed.As a result,TiO₂@BiOBr fiber membranes showed good degradation of TCH.Moreover,the 10 times recycling experiment not only proved the good stability and repeatability of the complex fiber membrane,but also solved the recycling problem of the photocatalyst,which greatly reduces the production cost and does not cause secondary pollution to the water body,with the excellent performance of"two birds with one stone".