Design Of Bi₂WO₆-based Composite Photocatalyst And Research On Its Photodegradation Performance And Mechanism Of Tetracycline

Tetracycline?TC?,one of the most widely used antibiotics,is a broad-spectrum antibiotic in the world.The application of antibiotics has contributed to the development of human medicine.However,the abuses of antibiotics pose a serious threat to the health of humans and animals,the accumulation of residual antibiotics in water also exacerbates the degree of environmental degradation.Photocatalytic technology is an environmental-friendly technology with stable performance,green pollution-free and low cost.It shows a good application prospect in the degradation of organic pollutants in water.Bi₂WO₆,the simplest Aurivillius type perovskite layered structure oxide,has received more and more attention due to its good photocatalytic performance.Whereas the visible light absorption and recycling ability of pure Bi₂WO₆ are poor,its'application is confined by easy recombination of photogenerated electrons.In the paper,firstly,when Bi₂WO₆ load on graphene oxide,separation of electrons and holes gets promoted.Secondly,biomass carbon materials introduced to Bi₂WO₆ improve the absorption performance of the system.Thirdly,constructing Z-type heterojunction between semiconductors and the introduction of biomass carbon quantum dots effectively improves the electron migration efficiency and the absorption efficiency of the catalyst for light energy.Finally,the method of carbon doping and composite magnetic materials improves the photocatalytic activity of the catalyst and facilitates the recovery and reuse of the catalyst.The specific research contents are as follows:1.The graphene oxide?GO?was synthesized by Hummers method.Then Bi₂WO₆/GO composite composed of three-dimensional flower-sphere Bi₂WO₆nanosheets on GO was prepared by hydrothermal method.The material was characterized by many detection instruments and its degradation mechanism of TC under visible light was investigated.The results showed that the prepared composite photocatalyst not only has good morphology,but also has high photocatalytic degradation ability to TC.When the content of GO is 5.0 wt%,the degradation effect is optimal.The degradation efficiency can reach 76%within 90 min.2.Biomass carbon was prepared by peach flower as biomass carbon source though high temperature calcination.Then,Bi₂WO₆ was synthesized by hydrothermal method,and Bi₂WO₆/C binary composite was prepared by ultrasonic method.The prepared Bi₂WO₆/C composite photocatalytic materials were characterized by XRD,PL,TEM,SEM and electrochemical methods.The best ratio was determined by comparing the degradation effects of TC for different carbon contents under visible light.The results show that when the mass ratio of biomass carbon to Bi₂WO₆ is 1:6,the photocatalytic effect is the best,reaching 74%within 90 min.The introduction of biomass carbon material improves the efficiency of separation of Bi₂WO₆electron-hole pairs and photocatalytic activity.3.The biomass carbon quantum dots?CQDs?were prepared by hydrothermal method.Then the obtained CQDs were added to the precursor solution of Bi₂WO₆ to prepare CQDs/Bi₂WO₆ binary composite materials.The CQDs/Bi₂WO₆/Cu₂O ternary composite photocatalyst was prepared by adding CQDs/Bi₂WO₆ into the precursor of Cu₂O by water bath heating method.The results show that the introduction of up-conversion function CQDs changes the long-wavelength light to short-wavelength one and promotes the utilization of light energy of the catalyst.At the same time,the construction of the Z-type heterojunction structure promotes the migration efficiency of electrons.The photocatalytic degradation efficiency of CQDs/Bi₂WO₆/Cu₂O ternary composite photocatalyst reaches 80%in 90 min.4.Carbon-doped Bi₂WO₆?C-BWO?was prepared by hydrothermal method using L-cysteine as carbon source.The ternary composite Fe₃O₄/C-BWO was synthesized by heating and stirring in a water bath.The results show that the ternary composite exhibits good catalytic removal ability for TC 90.2%in 90 min,which further proves that carbon doping greatly promotes the improvement of photocatalytic activity.And the introduction of magnetic Fe₃O₄ promotes the transfer of electrons and the recycling of catalysts.