Study On Degradation Of Ciprofloxacin In Water By Photocatalytic Activation Of Persulfate By Bismuth Tungstate Coupled Magnetic Biochar

The main function of antibiotics is to fight bacterial infections and cure some diseases that occur in humans.However,in recent years,the overuse of antibiotics has led to the development of resistance of pathogenic microorganisms,resulting in an increasing effective dose of antibiotics to kill bacteria,which poses a potential threat to the ecological environment and human health.Ciprofloxacin（CPFX）,a quinolone antibiotic,is widely used in the medical,agricultural,animal husbandry and aquaculture industries.It can enter the environmental water body through many channels to cause toxicity to humans and can also cause resistance to bacteria or viruses in the environment.So,its presence in the environment poses a potential threat to human health and ecosystems.In this study,magnetic biochar（Fe-N-Biochar）was obtained by calcining the mixture of corn stalk-urea-Fe（NO₃）₃,and magnetic hydrothermal carbon（Fe-Hydrochar）was prepared by solvothermal method,and they were modified with bismuth tungstate to prepare new photocatalytic materials—Bi₂WO₆/Fe-N-Biochar and Bi₂WO₆/Fe-Hydrochar.Based on its good photocatalytic activity,a persulfate heterogeneous catalytic system with good degradation performance was constructed.A series of photoelectrochemical analysis such as SEM,TEM,XRD,XPS,EIS,UV-Vis and PL were carried out on Bi₂WO₆/Fe-N-Biochar and Bi₂WO₆/Fe-Hydrochar to explore their physical and chemical properties.The degradation performance and mechanism of Bi₂WO₆/Fe-N-Biochar and Bi₂WO₆/Fe-Hydrochar photocatalytic activated sodium persulfate（Na₂S₂O₈）heterogeneous catalytic system was analyzed through the degradation of ciprofloxacin（CIP）test,free radical capture test,repeated cycle test,ESR test and M-S test,providing theoretical basis for the application of this new heterogeneous catalytic system in the purification of water antibiotic pollution.The main conclusions of this paper are as follows:（1）The properties and characterization of Bi₂WO₆/Fe-N-Biochar showed that Fe-N-Biochar containing Fe₂O₃ and C₃N₄ biochar could be combined with Bi₂WO₆ to form a composite material（BW/Fe-N-B）,which was presented as the nanoparticles made of stacked nanosheets.It has been proved that the heterojunction structure between Bi₂WO₆ and Fe-N-Biochar and the good electrical conductivity of Fe-N-Biochar can enhance the visible light response of BW/Fe-N-B,thus improving the separation efficiency of photogenerated electron-hole pairs.In addition,the enhanced photocatalytic activity and magnetic properties of BW/Fe-N-B can effectively activate persulfate to construct a heterogeneous catalytic system,and the degradation of ciprofloxacin（CIP）can reach 95.18%within 30 min.Photogenic electrons（e^-）and holes（h⁺）are the main active substances in the photocatalytic degradation of CIP and play a key role in the efficient degradation of CIP by generating OH·,O₂^-·and SO₄^-·in the activation process of persulfate.（2）The properties and characterization of Bi₂WO₆/Fe-Hydrochar showed that Fe₃O₄ and C₃N₄ biochar were generated in the process of solvothermal preparation of Fe-Hydrochar,and the added iron was also combined with the hydrothermal carbon in the form of a compound of iron,nitrogen and carbon.After coupling Fe-Hydrochar with Bi₂WO₆,a composite material Bi₂WO₆/Fe-Hydrochar with regular nano particle morphology formed by stacking nano sheets is formed.Moreover,the composite has a high specific surface area and provides abundant active sites for photocatalytic reactions.Bi₂WO₆/Fe-Hydrochar has heterostructure,Fe₃O₄ is formed in the preparation process,and has good photocatalytic activity.It can effectively activate persulfate（Na₂S₂O₈）to construct a heterogeneous catalytic system to degrade ciprofloxacin（CIP）.The CIP degradation efficiency reaches 91.83%in 30 min.Fe²⁺/Fe³⁺is the main activation factor.Photogenic electrons（e^-）,holes（h⁺）,OH·,O₂^-·and SO₄^-·are all active substances in the heterogeneous catalytic system,which play an important role in the degradation of CIP.