Preparation Of Modified Graphite Phase Carbon Nitride And Its Application In Photocatalytic Degradation Of Dyeing Wastewater

With the rapid development of modern society’s industrialization,industrial water consumption is increasing,and industrial wastewater discharged with it accounts for most of the wastewater pollution.Printing and dyeing wastewater is one of industrial wastewater discharges with huge discharge volume and difficult treatment.Its pollutants can affect human life and health through various aspects.At present,the treatment of dyeing wastewater has attracted widespread attention from the global community,and its treatment methods are required to be environmentally friendly and the materials or methods used are cheap and stable.Currently,commonly used methods include adsorption,chemical oxidation,biological treatment and photocatalytic oxidation.Photocatalysis uses light irradiation as energy,most of which use semiconductors as catalysts to degrade and mineralize pollutants.The method is green and environmentally friendly.The synthesis of semiconductor catalysts is low in cost and the photocatalytic performance is stable.Therefore,it has a very good application prospect in solving environmental pollution problems.With the development of non-metal semiconductor photocatalysts,graphite phase carbon nitride（g-C₃N₄）due to its simple and convenient production method,cheap and easy-to-obtain raw materials has attracted much attention from scholars in the field of photocatalysis.However,due to certain limitations of g-C₃N₄,the efficiency of charge separation and transfer is low,which limits its further development.In this study,the pollution of printing and dyeing wastewater and the research status of photocatalysis were briefly introduced,and the development of semiconductor photocatalysts was reviewed.In order to improve the photocatalytic performance of g-C₃N₄ and obtain an efficient and stable photocatalyst for degradation of organic dye pollutants,in this paper,the following modification studies on g-C₃N₄ materials have been completed,and the photocatalytic performance of the modified materials has significantly improved:1.A simple precursor treatment method was used to synthesize a porous g-C₃N₄photocatalyst containing nitrogen defects（CN）,and used infrared spectroscopy,X-ray powder diffraction,etc.to characterize its appearance morphology and structure characteristics.Through the degradation of rhodamine B（Rh B）combined with UV analysis and detection,the optimal processing conditions for the precursor of the photocatalyst were discussed,and its reusability and stability were discussed through cycling experiments,and the reaction in the photocatalytic degradation of Rh B system active substances were studied.Results show that the product g-C₃N₄ catalyst can basically achieve complete decolorization of Rh B photodegradation within 20minutes,and the degradation rate is 1.7 times that of the bulk g-C₃N₄in 20 minutes.2.In this experiment,g-C₃N₄ was sensitized and doped to successfully synthesize a peel-off sheet-like g-C₃N₄ photocatalyst（F-SCN）,which can effectively photocatalyze the degradation of MO.The fluorination ratio and conditions were optimized,and the best fluorination modification conditions were found.At the same time,its stability and reaction mechanism were discussed.The results show that F-SCN has good photocatalytic performance,and the degradation rate of MO can reach 62%in 1 h,which is 3.7 times and 1.4 times that of BCN and SCN,respectively.The removal rate can reach 77%in 1 h,which is 3.8 times of BCN and1.6 times of SCN.3.A simple heterojunction composite method was used to synthesize the carbon dot modified molybdenum trioxide/graphite carbon nitride（CDs-h-MoO₃/g-C₃N₄）composite material（CMOCN）.After a series of characterization,the material was used for MB photocatalytic degradation,combined with UV analysis and detection,three different h-MoO₃/g-C₃N₄ heterogeneous combination methods,composite ratios and carbon dot modification dosages were discussed.Under the optimal compounding conditions,CMOCN has better photocatalytic performance,reusability and good stability than BCN.After 1 h of simulated visible light irradiation,the degradation rate of MB by CMOCN reached 67%,which was 2.7,2.6 and 5.8 times of bulk g-C₃N₄,pure h-MoO₃ and pure CDs,respectively.