Study On The Performance And Mechanism Of PDI-based S-scheme Heterojunction Photocatalyst In Photodegradation Of Tetracycline Residues In Water Environment

The widespread use of tetracycline has led to more and more residues in the water environment,posing a serious threat to the environment and human health.Therefore,there is an urgent need to develop an efficient and economical method to control residual pollution of tetracycline.Green photocatalysis technology is widely used in the field of water pollution control due to its high-efficiency catalysis,stability and no secondary pollution.As a new photocatalytic material,Peryleneimide（PDI）has unique light stability,thermal stability and light trapping properties,and can achieve rapid and efficient degradation of tetracycline residues in water environments.In addition,in the current research,the construction of S-scheme heterojunction is considered to be an effective way to achieve strong redox and improve photocatalytic performance.Therefore,this paper takes PDI as the research object,and designs a series of PDI-based S-scheme heterojunction composite photocatalysts to achieve the efficient degradation of tetracycline residual pollutants in the water environment.The main research work is as follows:（1）Combining PDI and g-C₃N₄,the PDI/g-C₃N₄ S-scheme heterojunction photocatalyst is successfully prepared.The construction of the S-scheme heterojunction structure is conducive to the transfer and separation of carriers,improving the photocatalytic degradation ability of the material.After 20 minutes of visible light irradiation,the degradation rate of PDI/g-C₃N₄ to the residual pollutants of tetracycline is 69.07%,which is 4.88 times that of PDI and 10.10 times that of g-C₃N₄,and the stability is good.In addition,the experimental results of the photocatalytic mechanism show that superoxide radicals and holes are the main active species in the degradation process of PDI/g-C₃N₄,and the role of hydroxyl and singlet oxygen is weak.（2）Combining PDI and Zn Fe₂O₄,the PDI/Zn Fe₂O₄ S-scheme heterojunction magnetic photocatalyst is successfully prepared,and the morphology of the material is effectively controlled.The PDI in the composite material is a uniform rod,and Zn Fe₂O₄ is restricted to small particles and dispersed on the surface of the PDI.The S-scheme heterojunction structure formed between PDI and Zn Fe₂O₄ facilitates the separation of electron-hole pairs and retains strong redox effects to further enhance the photodegradability.Therefore,PDI/Zn Fe₂O₄ has good stability and photocatalytic degradation ability.The degradation rate of tetracycline under visible light irradiation is 66.67%,which is 9.18 times that of PDI（7.26%）and 9.73 times that of Zn Fe₂O₄（6.85%）.In addition,the experimental results of the photocatalytic mechanism show that superoxide radicals play a major role in the degradation process of PDI/Zn Fe₂O₄,while the role of holes and hydroxyl radicals is weak.（3）Using Zn Fe₂O₄ as a carrier,PDI nanofibers as functional monomers,and tetracycline as template molecules,imprinted modified PDI nanofibers/Zn Fe₂O₄S-scheme heterojunction magnetic photocatalysts are successfully prepared by imprinting modification technology and microwave synthesis.The imprinted modified PDI nanofiber/Zn Fe₂O₄ not only has excellent photodegradation ability（69.12%）for tetracycline,but also has good selective degradation ability for tetracycline.The selectivity coefficients of imprinted modified PDI nanofiber/Zn Fe₂O₄ to other contrast materials can reach 1.94,2.31 and 1.51.In addition,the experimental results of the photocatalytic mechanism show that superoxide radicals play a major role in the degradation process of the imprinted modified PDI nanofiber/Zn Fe₂O₄,while the role of holes and hydroxyl radicals is relatively weak.