The Degradation Of Tetracycline Based On Graphite Phase Carbon Nitride Materials By Visible Light Catalysis

With the development of the pharmaceutical industry,antibiotic pollution in pharmaceutical wastewater has become an increasingly serious environmental problem.Tetracycline is one of the most commonly used antibiotics and poses a serious threat to human health.Traditional wastewater treatment methods are difficult to effectively remove tetracycline.Metal free polymeric graphitic phase carbon nitride（g-C₃N₄）is a stable visible photocatalyst with good catalytic effect and specific band structure.However,due to its fast carrier complexation rate,a modification approach is needed to improve the catalytic activity.In this study,the preparation conditions of the catalyst were investigated,melamine was taken as a precursor to prepare g-C₃N₄,and the elemental doping modification was used to enhance its photocatalytic performance.The morphology and microstructure of the catalysts were analyzed,and the efficiency of the prepared catalysts for the removal of tetracycline from simulated wastewater was investigated.The main contents were studied as follows:（1）The g-C₃N₄ was prepared by the thermal polycondensation method using melamine as the precursor.The optimum preparation conditions for the catalysts were investigated as a heating rate of 25℃/min,a heat preservation time of 4h and a constant temperature of 550℃by changing the heating rate and heat preservation time.（2）K⁺-doped g-C₃N₄ was prepared by the polymerization of potassium nitrate and melamine.A three-factors and three-level orthogonal test was conducted to determine the optimal preparation conditions for K⁺/g-C₃N₄ with respect to the amount of metal doping,heat preservation time and temperature increase rate.The prepared catalysts were characterized and tested for analysis by SEM,EDS and XRD,and the influencing factors such as the initial p H of the solution,the initial concentration of tetracycline and the catalyst dosage for its degradation of tetracycline were also analyzed.The chemical reaction kinetics analysis of the catalytic oxidation process was carried out and it was concluded that the reaction process is in accordance with the secondary reaction kinetics.The main reactive substances in the reaction process were investigated and it was concluded that the main reactive groups in the degradation of tetracycline are?O₂^-、h⁺、?OH.（3）C-doped g-C₃N₄ was prepared by polymerization of 6-methyl-2-thiouracil with melamine,and the optimal preparation conditions of C/g-C₃N₄ were determined by changing different doping amounts.The catalysts were characterized and analyzed by XRD,SEM and EDS,and the initial p H of the solution,catalyst dosing and initial concentration of tetracycline were also analyzed for their degradation of tetracycline.For the catalytic oxidation process kinetic studies were conducted to obtain that the reaction process in consistent with secondary reaction kinetics.The reactive groups in the reaction process were also investigated,and the mechanism of photocatalytic degradation of tetracycline and the main reactive groups were?O₂^-、h⁺、?OH.