Study On The Photocatalytic Performance Of G-C₃N₄/Fe-MOF Composite

The clothing textile industry occupies an important position in the national economy,but the high-chroma,difficult-to-degrade dye wastewater produced by it has caused serious harm to the environment and is one of the environmental problems that need to be solved urgently.The use of p Hotocatalytic technology to degrade dye wastewater has become an effective method,but a single p Hotocatalytic material has a very high recombination rate of electron-hole pairs in the reaction process,which severely restricts its practical application.Among the many methods of p Hotocatalytic material modification,the combination of two or more materials to form a heterogeneous structure is a hot research topic at present.In this study,two materials,g-C₃N₄ and MOF were used for compounding.The advantages of g-C₃N₄ that are low in cost,high in chemical stability,and large specific surface area of MOF can enhance the contact between the reactants and the catalyst surface and form a heterogeneous structure.Efficient electron transport can be obtained,and the separation of electrons and holes can be accelerated,thereby enhancing the p Hotocatalytic performance.This paper studies the synthesis of two binary complexes of CN/MIL-88 and CN/MIL-100and the performance of p Hotocatalytic simulated dye wastewater(methylene blue).The main contents are as follows:(1)G-C₃N₄ is prepared by melamine high temperature calcination and pyrolysis,and then it is compounded with MIL-88 and MIL-100 respectively by hydrothermal method to prepare two heterojunction p Hotocatalysts CN/MIL-88 and CN/MIL-88 in different ratios.CN/MIL-88.The structure and p Hysicochemical properties of the catalyst were analyzed by X-ray diffraction(XRD),scanning electron microscope(SEM),ultraviolet-visible diffuse reflectance spectroscopy(UV-Vis DRS)and nitrogen adsorption and desorption isotherm.The characterization results show that g-C₃N₄ has a sheet-like shape and is successfully compounded with MIL-88B.The spindle-shaped MIL-88 tightly wraps the CN,while for CN/MIL-100,CN is mainly attached to the surface of MIL-100.Compared with pure g-C₃N₄,the two composite materials show excellent p Hotoelectric effect.The composite catalyst was used for p Hotocatalytic degradation of methylene blue,the factors affecting the p Hotocatalytic reaction were explored,and the decolorization rate was evaluated.The test showed that the obtained heterojunction composite p Hotocatalytic material has very good p Hotocatalytic degradation ability.CN/MIL-88 p Hotocatalytic degradation of methylene blue dye is twice that of pure MIL-88 and three times that of CN.The dye degradation effect of CN/MIL-100is better than CN/MIL-88.Under the optimal compound ratio,80%of methylene blue can be degraded after 80 minutes of light.(2)The p Hotocatalytic degradation of methylene blue by CN/MIL-88 is not ideal,and CN/MIL-88 is used as an iron-based metal-organic framework.The iron-oxygen complex in the material can stimulate the strong Fenton reaction of hydrogen peroxide,so CN/MIL-88was used as a heterogeneous Fenton-like catalyst,and an appropriate amount of hydrogen peroxide was added to optimize the p Hotocatalytic effect of CN/MIL-8.The experimental results show that under the same reaction conditions,the degradation efficiency of methylene blue after continuous reaction of CN/MIL-88 under light conditions for 80 minutes is less than45%,but under the condition of adding hydrogen peroxide,the degradation of methylene blue almost reaches 90%after light exposure for 80 minutes.Studies have shown that CN/MIL-88has a good heterogeneous Fenton-like catalytic performance.The excited electrons on the CB of g-C₃N₄ are transferred to the CB of MIL-88 and induce Fenton-like reactions to produce strong oxidizing Hydroxyl radicals cause a significant increase in the degradation of methylene blue light.(3)For the optimization of the p Hotocatalytic performance of composite material CN/MIL-100,based on the analysis of various optimization design methods and theories,the response surface method was used to optimize the design of its p Hotocatalytic experiment.Use Design-Expert software to analyze the experimental data,obtain the response surface map and contour map,analyze the mutual influence relationship between various factors,and obtain the optimal working condition and the optimal decolorization rate response value.The research shows that the quadratic regression model considering the three influencing factors of p H,methylene blue solution concentration and composite material ratio is significant,the importance factor F=18.90,the determination coefficient R²=0.9605,which can prove the predicted decolorization rate and the actual test decolorization rate Strong relevance.The optimal conditions predicted after simulation are as follows:p H is 13,the concentration of methylene blue solution is 9.37mg/L,and the ratio of composite material is 1.43.Under these conditions,the decolorization rate of methylene blue is 87.99%,and the actual measured degradation rate is 89.2%,with a relative error of about It is 1.21%,verifying that the actual value and the optimized predicted value are in good agreement,indicating the accuracy of the model selection.