Preparation Of Carbon Nitride-based Composites And Photo-fenton Degradation Performance Of Tetracycline Hydrochloride

With the increasingly serious water pollution problem,Fenton technique,which is a member of Advanced Oxidation Process（AOP）,has gained considerable attention in water pollution treatment to remove organic pollutants.So far,graphitic carbon nitride（g-C₃N₄）semiconductor presents unique advantages in their photocatalytic degradation capabilities.In addition,the Fenton reaction based on g-C₃N₄ has shown great development prospects.Here,based on the Fenton reaction characteristics of g-C₃N₄,the Fenton reaction mechanism of modified materials based on g-C₃N₄ in metal oxides was studied in detail,and the main formation pathways and interactions of hydroxyl radicals and superoxide radicals were studied.The main research contents are as follows:（1）Fe₃O₄ composite deposited phosphorus-doped carbonitride（g-C₃N₄）photocatalyst（CNP/Fe₃O₄）was synthesized by one-pot thermal polymerization.The results of X-ray diffraction test（XRD）and X-ray photoelectron spectroscopy（XPS）.The characterization showed that Fe₃O₄ was immobilized on the g-C₃N₄ sheet.Fluorescence spectroscopy（PL）and transient photocurrent response indicate that Fe₃O₄ can accelerate the separation of photogenerated carriers and increase the production of active materials.Among the catalysts with various proportions,the composite 5%CNP/Fe₃O₄ catalyst has the best degradation performance for tetracycline hydrochloride（TC）under visible light irradiation.When the 5%CNP/Fe₃O₄ catalyst is irradiated with visible light for 120minutes,the degradation rate of degrading TC reaches 96%,exhibiting a good stability in the cycle test.（2）The in-situ synthesis method of introducing KCl and NH₄Cl during the polymerization of dicyandiamide has realized the grafting of hydroxyl on g-C₃N₄（CN-OH）,which is combined with Fe₃O₄ to produce CN-OH/Fe₃O₄.The characterization of fourier transform infrared spectroscopy（FT-IR）,ESR spectroscopy and X-ray photoelectron spectroscopy showed that the hydroxyl group was successfully grafted and that CN-OH was successfully combined with Fe₃O₄.The combination of Fe₃O₄ increases the specific surface area of the catalyst and promotes the separation of photogenerated carriers.The photocatalytic activity of the composite catalyst is enhanced under visible light irradiation,and the degradation rate of organic pollutants TC reaches 92.5%.The composite catalyst has good stability and recycling in the cycle test.（3）Based on the above preparation method,the g-C₃N₄/CuFe₂O₄ composite material（CN-OH/CuFe₂O₄）was successfully prepared by using visible light-responsive CuFe₂O₄instead of Fe₃O₄.A series of analytical tests such as SEM,TEM,XPS showed that the material was successfully prepared.The catalyst degrades tetracycline under visible light.After 120 minutes of light,the degradation can reach 93%.In the cycle test,the composite catalyst has excellent stability characteristics.It was verified that CuFe₂O₄ has certain magnetic properties,which facilitates the recycling and reuse of the composite catalyst.