Preparation Of G-C₃N₄ Based Composite Photocatalysts And Study On Its Photocatlytic Degradation On Tetracyclines

The abuse of antibiotics showed many side effects in clinical use. Antibiotic residues was released into the environment will cause potential harm to the ecological balance and human health. It is difficult to dispose the antibiotic wastewater with the traditional biological or chemical treatment, which is characterized as high concentration, dark color,great toxicity and biorecalcitrant. Photocatalytic advanced oxidation technology has received much attention in wastewater treatment because it exhibits many compelling advantages such as chemical stability, catalytic activity and can be repeated use. g-C₃N₄ is a kind of photocatalyst with good stability and low production cost, and it has high efficient catalytic activity under visible light irradiation because of its proper band gap. However,the high rate of recombination of photogenerated electron-hole pairs and a low quantum yield limit theapplication for environment remediation.The g-C₃N₄@ZnO, g-C₃N₄@Fe₃O₄ and g-C₃N₄/HNTs composite photocatalytic materials were prepared in order to improve the photocatalytic activity of g-C₃N₄. The physical and chemical properties of the synthesized samples were characterized by X-ray diffraction, scanning electron microscopy, infrared spectrum analysis, UV-Vis diffuse reflectance spectroscopy and other characterization techniques. The g-C₃N₄@ZnO composite photocatalyst heterostructures are prepared by solvothermal method. The research results show that the crystal type and structure is almost not affected, but the response to visible light was significantly enhanced compared with the pure g-C₃N₄.g-C₃N₄@Fe₃O₄ composite photocatalyst is prepared by a simple chemical adsorption method. The SEM result shows that Fe₃O₄ nanoparticles dispersed on the g-C₃N₄ surface and lamellar. The lattice differences between Fe₃O₄ and g-C₃N₄ can improve the absorption ability of visible light. At the same time due to the characteristic with magnetic effect makes the material is recycled. The g-C₃N₄/HNTs composite photocatalyst prepared by chemical adsorption, which absorption range of visible light did not change significantly maybe due to HNTs has no absorption of visible light.In addition, the photocatalytic properties, optimum compound ratio and degradationkinetics behavior of synthetic samples was evaluated by monitoring the degradation of antibiotic tetracycline（TC） solution under 300 W xenon lamp irradiation. The result shows that the photocatalytic efficiency is the best and can remove 96.31% TC when the ZnO loading with 40 wt%. The g-C₃N₄@Fe₃O₄ can remove 92.84% TC solution and shows the best photocatalytic activity when g-C₃N₄ and Fe₃O₄ ratio is 3:1,and it can be recycled because of its strong magnetic characteristic. Because of HNTs has strong adsorption performance and can provide active adsorption sites for organic matter, g-C₃N₄/HNTs composite materials in the process of photodegradation of TC solution showed excellent catalytic activity. When the HNTs is 20wt%, the photocatalytic activity of g-C₃N₄/HNTs is best, the solution of TC removal ratio is about 94.34%. The degradation process of these composite photocatalysts conforms to the first-order reaction kinetic behavior.