Study On Preparation Of G-C₃N₄-based Photocatalysts And Their Application In Photodegradation Of Tetracycline

The harm to environment and ecology caused by tetracycline in water has become an urgent problem.Traditional processing such as adsorption and ozonation has disadvantages of low degradability and restricted by the water condition.Photocatalytic oxidation make use of highly reactive hydroxyl radical degrading the persistent and refractory biodegradation organic compound,which is one of the most promising technologies.As a novel visible-light-driven photocatalyst,g-C₃N₄ has been widely used in the field of organic pollutants degradation and hydrogen production.However,due to its high rate of recombination of photogenerated electron/hole pairs and a low quantum yield,the application of pure g-C₃N₄ is severely limited.The main work of this paper was focused on the modification of g-C₃N₄,via forming semiconductor composites,depositing noble metal.The samples were characterized by X-ray diffraction?XRD?,scanning electron microscopy?SEM?,ultraviolet and visible diffuse reflectance spectra?UV-vis?,Energy Dispersive Spectrometer?EDS?and Fourier Transform Infrared Spectroscopy?FT-IR?.The photocatalytic activity of the synthesized products was evaluated by degradation of tetracycline?TC?under a xenon lamp irradiation.There are mainly three parts in this paper:?1?The g-C₃N₄/CeO₂ nano-heterojunction photocatalysts were synthesized by chemical adsorption.The results show that the CeO₂ particles dispersed on the surface of g-C₃N₄ and the formation of the heterojunction enhanced the separation efficiency of the photogenerated electron hole and improved the photocatalytic activity of the composite.When R?CeO₂/g-C₃N₄?=2wt%,the products exhibit the highest TC degradation ratio in 90 min of 80% under visible-light illumination and the photocatalysis can be described by the first order kinetic model.The TC degradability of g-C₃N₄/CeO₂ remained above 70% after repeated five cycles.In addition,the mechanism of improving the photocatalytic activity of g-C₃N₄/CeO₂ heterojunction was also discussed.?2?The Ag/g-C₃N₄/CeO₂ photocatalysts were synthesized by photoreduction deposition method.The Ag nanoparticles were deposited on the surface of g-C₃N₄/CeO₂ composites and the surface plasma resonance promoted the separation of photogenerated electron hole,thus improving the photocatalytic activity of materials.When the deposition amount of Ag was 2wt%,the products exhibit the highest TC degradation ratio in 40 min of 80% under visible-light illumination and the photocatalysis can be described by the first order kinetic model.The TC degradability of g-C₃N₄/CeO₂ remained above 75% after repeated five cycles.?3?Ag/g-C₃N₄/ZnO photocatalyst was prepared by photoreduction deposition method.The analysis results show that silver nanoparticles deposited on the surface of the g-C₃N₄/ZnO photocatalysts.Compared with the pure ZnO?pure g-C₃N₄ and g-C₃N₄/ZnO,Ag/g-C₃N₄/ZnO exhibit the hightest TC degradation ratio in 60 min of 85% under visible-light irradiation.