Preparation And Photocatalytic Properties Of Composite Magnetic Photocatalyst

With the rapid development of global science and technology in recent years,people’s access to social services and healthcare has increased dramatically.However,a series of environmental pollution problems have followed,especially for water resources.The abuse of antibiotics is one of the main causes of water pollution.Among the numerous antibiotics,the tetracycline antibiotics can be used to treat some diseases in human and animal bodies,but only a very small part can be absorbed.Most of them are discharged into the environment in their original form,which will destroy the ecological balance of water bodies if there are a large amount of them in water.Therefore,it has a profound impact on human society that finding an effective method to degrade the residual tetracycline antibiotics in water.So far,there are many ways to degrade tetracycline antibiotics,such as chemical,physical,biological and photocatalytic degradation methods.The photocatalytic methods are favored by researchers because of their simple operation steps,high degradation rate and low economic cost.However,the recovery problem of the photocatalysts after use and the low utilization rate of visible light have hindered their application in production practices.In this paper,Fe₃O₄@PPy@Ti O₂ and Fe₃O₄@PPy@g-C₃N₄ composite magnetic photocatalysts were synthesized on the basis of previous research.Besides,the photocatalytic degradation of tetracycline hydrochloride and chlortetracycline hydrochloride was carried out.Meanwhile,the photocatalytic performance of the composite magnetic photocatalyst prepared under nature light was explored.The main research contents are as follows:（1）Preparation and characterization of Fe₃O₄ nanoparticles:Fe₃O₄ nanoparticles were prepared by the solvothermal method.Then,their sample sizes were characterized by transmission electron microscope（TEM）and their phase composition was analyzed by X-ray diffraction（XRD）.Besides,their characteristic groups were analyzed by Fourier Infrared Spectroscopy（FT-IR）and their room temperature magnetic intensity was characterized by vibrating sample magnetometer（VSM）.The results show that the Fe₃O₄ nanoparticles prepared by the solvothermal method are close to spherical in shape,with a particle size generally around 200 nm,good dispersion and a saturation magnetization intensity value of73.42 emu/g at room temperature.（2）Synthesis and characterization of Fe₃O₄@PPy compounds:Sodium lauryl sulfate was chosen as the surfactant and Fe Cl₃·6H₂O was used as the oxidant.And polypyrrole（PPy）was coated on the outer layer of Fe₃O₄ by chemical oxidation to produce Fe₃O₄@PPy compounds.Then,TEM,XRD,FT-IR,VSM and other means were used to characterize the properties of the samples.The results show that the synthesized Fe₃O₄@PPy compounds have a core-shell structure with a size of about 280 nm and good dispersion.The magnetization at room temperature is 28.42 emu/g.（3）Synthesis and characterization of Fe₃O₄@PPy@TiO₂ compounds:TiO₂ was coated on the surface of Fe₃O₄@PPy compounds using sol-gel method with tetra-n-butyl titanate and ethanol as raw materials under mechanical stirring.The synthesized Fe₃O₄@PPy@TiO₂compounds have a uniformly distributed core-shell structure,a particle size of about 320 nm,and a saturation magnetization of 4.94 emu/g at room temperature,which can be quickly separated and recovered under the action of an applied magnet.（4）Preparation and characterization of Fe₃O₄@PPy@g-C₃N₄ compounds:First,graphitic carbon nitride（g-C3N4）was produced by calcination at 550℃ for 4 h in a tube furnace using melamine as a precursor by thermal polycondensation synthesis method.Then,Fe₃O₄@PPy was compounded with g-C₃N₄by ultrasonic method to prepare Fe₃O₄@PPy@g-C₃N₄compounds.TEM,XRD,FT-IR,VSM and other means were used to characterize the properties of the samples.The results show that Fe₃O₄@PPy is evenly and densely dispersed on the layered surface of g-C₃N₄,and the saturation magnetization at room temperature is7.46 emu/g.（5）Photocatalytic degradation reaction:The prepared Fe₃O₄@PPy@TiO₂ compounds and Fe₃O₄@PPy@g-C₃N₄ compounds were used as magnetic photocatalysts to investigate the photocatalytic degradation effect of the two photocatalysts on tetracycline antibiotics.And the control variable method was used to explore the degradation rate of tetracycline antibiotics effect over time under different light sources,different catalyst types,different catalyst dosage and different water environment（p H value,initial concentration）.Both composite magnetic photocatalysts prepared in this paper have showed excellent photocatalytic performance.The preparation method is non-toxic,environmentally friendly and simpler than other photocatalysts’.Besides,it can be directly recycled with applied magnets.