Preparation And Properties Of Graphitic Carbon Nitride Based On Photo-fenton Catalysts

Water pollution caused by persistent organic pollutants（POPs）has become a common concern in the world.Due to the widespread production and consumption of antibiotics,they have become an emerging pollutant,causing significant harm to the ecological environment and human health.The development of technology to completely remove antibiotics from water supplies is a hotspot of research and a social demand in the sustainable development goals.The advanced oxidation technology based on the photo-Fenton reaction has become one of the most commonly used methods for treating antibiotic wastewater owing to its wide range of applications,strong anti-interference ability,simple operation,fast degradation and mineralization.In order to optimize the performance of photo-Fenton,it is necessary to design and develop heterogeneous photo-Fenton catalysts with high catalytic activity and high stability.Graphite carbon nitride（g-C₃N₄）is an excellent photocatalytic material with high chemical stability,suitable energy band structure and unique visible light response,which has broad application prospects in the field of photo-Fenton.In this paper,tetracycline（TC）,an antibiotic widely used to treat diseases or promote the growth of organisms,is used as a simulated antibiotic wastewater treatment object.Two kinds of composite materials（α-Fe₂O₃/g-C₃N₄ and Zn Fe₂O₄/g-C₃N₄）prepared by a simple and feasible method,were used as catalysts to participate in the photo-Fenton reaction.Meanwhile,the degradation behavior and mechanism of antibiotic wastewater during the reaction were studied.The main research contents are as follows:i)The 2D/2Dα-Fe₂O₃/g-C₃N₄ composite catalyst was prepared by one-step hydrothermal method,whose crystal structure,morphology,specific surface area,optical properties were characterized by a variety of analytical and testing techniques.At the same time,the performance of the prepared catalyst was evaluated according to the degradation efficiency of TC by photo-Fenton reaction.The photo-Fenton performance of 5.26wt%α-Fe₂O₃/g-C₃N₄ composite catalyst was the best,and the removal rate of TC could reach 97%within 180 min.The electron-hole separation efficiency was further studied by photoelectrochemistry,photoluminescence（PL）spectra,and time-resolved PL spectra to explain the improvement of photo-Fenton performance.The TC degradation intermediates were analyzed by the high performance liquid chromatograohy-mass spectrometry（HPLC-MS）,and possible degradation pathways were proposed.Finally,the electron spin-resonance spectroscopy（ESR）was used to verify the direct Z-scheme heterojunction structure in the composite material,and further explain the reason for the excellent performance of the composite catalyst.ii)The Zn Fe₂O₄/g-C₃N₄ composite catalyst（named ZFO/NCN）was successfully constructed through a two-step method of solvothermal and calcination.The crystal structure,morphology,specific surface area,and optical characteristics and so on of the prepared catalyst were characterized with the help of a variety of analytical and testing techniques.At the same time,the performance of the prepared catalyst was evaluated according to the degradation efficiency of TC by photo-Fenton reaction.The photo-Fenton performance of ZFO/NCN-2 composite catalyst was the best,and the TC removal rate could reach 95%within 40 min.The electron-hole separation efficiency was further studied by photoelectrochemistry,PL spectra,and time-resolved PL spectra to explain the improvement of photo-Fenton performance.The TC degradation intermediates were analyzed by the HPLC-MS,and possible degradation pathways were proposed.Finally,the ESR was used to verify the direct Z-scheme heterojunction structure in the composite material,and further explain the reason for the excellent performance of the composite catalyst.