Boron Doped Tubular Carbon Nitride Photocatalyst And Study On The Mechanism Of Photocatalytic Tetracycline Hydrochloride Degradation

Antibiotics are widely applied in the field of healthcare,animal husbandry and aquaculture.However,most antibiotics with stable structure cannot be completely metabolized by human or animal body and so that they are constantly discharged into water in various forms,which will pollute the environment and even threaten the safety of human.Therefore,how to remove antibiotics from wastewater efficiently and environmentally has become an important topic.In recent years,photocatalytic technology has been more and more extensively used in the treatment of environmental pollutants because of its advantages of strong redox ability,low cost and green environmental protection,which can rapidly and efficiently decompose or even completely mineralized organic pollutants in wastewater.g-C₃N₄（CN）,as a kind of nonmetallic photocatalytic material,is favored because of its simple preparation method,low cost and good performance,however,the shortcomings of small specific surface area and high electron-hole pair recombination rate limit its practical photocatalytic applications.In this study,a new tubular carbon nitride（BTCN-2）was synthesized by hydrothermal method and calcination method by adjusting the structure and properties of the original massive carbon nitride by doping non-metallic boron element and regulating the tubular morphology.A variety of characterization techniques and tetracycline hydrochloride（TCH）degradation experiment were conducted to explore the morphology,crystal chemical structure,photoelectric and chemical properties of the photocatalyst,reaction factors（different catalyst dosing quantity,concentration of initial TCH,p H,coexisting ions and water）,degradation products and path,and the active substances and degradation mechanism were also involved.It is found that the synergistic effect of boron doping and tubular structure can effectively promote light capture and accelerate charge transfer.BTCN-2 showed the best TCH degradation efficiency of 83.2%under 60 min visible-light irradiation,and the apparent rate constant of reaction was 0.0275 min^-1,twice that of CN.BTCN-2 has higher carrier separation and transfer efficiency,higher specific surface area and good light absorption capacity.The characteristics of tubular morphology shorten the migration path of photogenerated carriers,and also enhances the visible light capture ability due to the multiple reflection of incident light.The stability of the prepared samples was evaluated,and the results showed that the samples still had good degradation performance and stable structure after four consecutive experiments,moreover,it also showed good photocatalytic degradation performance in the presence of common inorganic anions,in a wide p H range,and in actual water applications,which further verifies its potential in practical applications.The photoinduced active substances superoxide radical（?O₂^-）and hole（h⁺）are the main active substances in the photocatalytic reaction,and hydroxyl（?OH）also participates in the reaction,and the three jointly participate in the gradual degradation of TCH into small molecules.This study provides a promising method for the construction of high efficiency carbon nitride based photocatalyst.The comprehensive engineering strategy of element doping co-morphology group control provides a reference for the rational design of new photocatalyst,and provides a theoretical basis for the removal of antibiotics in practical wastewater.