Preparation Of Graphitic Carbon Nitride Based Porous Composites And Their Photocatalytic Degradation Of Antibiotics

With the rapid development of modernization,more and more attention is focus on the pollution status of antibiotics in water environment.Photocatalytic technology is a relatively advanced and green way to treat antibiotics.It uses solar energy as the main energy source to convert macromolecular antibiotics into small molecular compounds that can be turned into water and carbon dioxide.Among them,non-metallic conjugated semiconductor graphite phase carbon nitride materials（g-C₃N₄）are widely used.It possesses excellent chemical stability and unique band gap structure,but the photocatalytic activity of g-C₃N₄monomer is limited.In order to improve the photocatalytic performance of g-C₃N₄,the morphology of g-C₃N₄ was regulated and heterojunctions were constructed with other semiconductor materials to prepare new graphite phase carbon nitride based porous composites with high efficiency and environmental protection.The main contents of this paper are as follows:（1）Carbon nitride quantum dots（GCNQDs）were prepared by morphology regulation based on graphite phase carbon nitride,and porous nanoflower Ni₅P₄ was introduced.GCNQDs/Ni₅P₄ porous composite material was prepared by simple ultrasonic impregnation method,which was used for degradation of norfloxacin in wastewater under UV light.The particle size of GCNQDs is small and has obvious quantum confined effect.For Ni₅P₄,the larger specific surface area is conducive to the adhesion of GCNQDs,which makes GCNQDs/Ni₅P₄ porous composite materials have excellent photocatalytic performance.In addition,experimental and density functional theory（DFT）calculations confirmed the important role of porous nanoflower Ni₅P₄ in promoting electron hole pair separation and photocatalytic performance.Through the mass spectrum and toxicity test,the products in the degradation process were analyzed and finally could be degraded into non-toxic green environmental protection aqueous solution.（2）Compared with the recovery of composite material by centrifugal method in the previous chapter,magnetic semiconductor material is introduced in this chapter to effectively improve the separation speed and save time and cost efficiently.Based on carbon nitride quantum dots（GCNQDs）,a dual Z-Scheme GCNQDs/CoTiO₃/CoFe₂O₄（GCC）porous composite material was synthesized by introducing transition metal oxide CoFe₂O₄（CFO）and porous metal titanate oxide CoTiO₃（CTO）,which was used for the degradation of oxytetrocline in wastewater.The degradation rate can reach 88%.At the same time,GCC porous composite material shows good magnetic controllability and circulability,which makes the composite material more valuable in application.（3）Based on the low utilization rate of visible light in the previous two chapters,this chapter adopts the method of combining wideband gap semiconductor with narrowband gap semiconductor,and adopts the morphology based on reticulocarbon nitride（RCN）.A dual Z-Scheme In OOH/RCN/CoWO₄ porous composite material was prepared by in-situ growth method and ultrasonic impregnation method,and were applied to degrade norfloxacin efficiently under visible light.The degradation rate of 0.5 IRC porous composite material to norfloxacin can reach 94% within 80min under the simulated sunlight irradiation condition,which effectively improves the utilization rate of visible light and the separation and transfer rate of photogenerated electrons.In addition,the degradation path analysis showed that the composite realized the conversion of large molecule compounds to small molecule non-toxic compounds.