The Preparation Of Modified Carbon Nitride And Its Photocatalytic Degradation Of Organic Pollutants

Photocatalytic technology shows great value in the treatment ofenvironmental pollution.Graphite-like carbon nitride?g-C₃N₄,hereinafter referred to as CN?is a new type of semiconductor photocatalyst,which has high photocatalytic activity and stability.Therefore,it is widely used in photocatalytic treatment of environmental pollution.However,the forbidden band width?Eg=2.7eV?of CN limits the visible light absorption range,and the separation efficiency of photo-generated carriers is low,which affects its photocatalytic activity.In order to improve the photocatalytic activity of CN,this article focuses on the following researches on CN:?1?Preparation of Bi₂S₃/g-C₃N₄ semiconductor composite materials;?2?Preparation of NaBiO₃/g-C₃N₄ semiconductor composite materials;?3?NH₄Cl assisted regulation of modified CN.XRD,FT-IR,SEM,TEM,XPS,BET,PL,UV-visDRS and other characterization methods are used to analyze the microstructure and optical properties of the modified catalyst,and liquid phase test methods are used to evaluate its photocatalytic performance.The contents are as follows:?1?Microwave synthesis of Bi₂S₃/g-C₃N₄?BS/CN?composite photocatalyst:The BS/CN composite catalyst is prepared by a simple,efficient and fast microwave synthesis method.A p-n type heterojunction is formed between two semiconductor materials.The overall energy band of Bi₂S₃?BS?rises.Eventually,the energy bands of the two are well matched to form a heterojunction structure,which enhances the efficiency of photo-generated electron-hole separation and effectively improves the photocatalytic activity of the catalyst.Using rhodamine B?RhB?as the target pollutant,the photocatalytic activity of BS/CN composites was evaluated.Compared to CN and BS monomers,the visible light catalytic activity of X-BS/CN composite photocatalysts with different mass ratios has been significantly improved.Sample 5-BS/CN shows the best photocatalytic activity,and the degradation rate of RhB can reach about 99%.The degradation efficiency of pure CN and BS monomers to RhB was 1.5 times and 5.2times,respectively.?2?Preparation of NaBiO₃/g-C₃N₄ nanocomposite:The semiconductorphotocatalyst NaBiO₃?NaB?was successfully prepared by a simple room temperature co-precipitation method,and it was simply compounded with CN to form a semiconductor composite photocatalyst NaB/CN.The energy bands between NaB and CN semiconductor materials can be well matched,so that photo-generated electrons and holes are transferred between the valence and conduction bands of the two.This process enhances the efficiency of photo-generated electron-hole separation and simultaneously generates multiple This kind of active substance mineralizes the pollutants,which is beneficial to improve the photocatalytic activity of the composite material.Antibiotic wastewater tetracycline hydrochloride?TC?was used as the target to evaluate the visible light degradation activity of NaB/CN photocatalyst.The sample1%-NaB/CN composite showed the best degradation rate,and the activity to TC under visible light was up to 95.6%,which was significantly higher than that of pure CN and NaB monomers.?3?NH₄Cl assisted regulation of carbon nitride?NCN?:Using melamine andNH₄Cl as precursors,one-step in-situ thermal polymerization successfully prepared a modified carbon nitride X-NCN system.NH₄Cl is thermally decomposed,and a large amount of NH₃ and HCl hot gas is released,which affects the original morphology of carbon nitride and forms a carbon nitride catalyst with an ordered pore structure.At the same time,the introduction of strong electron-donating amino and hydroxyl groups in the reaction process expands the visible light absorption range of the catalyst,improves the separation efficiency of photogenerated carriers,and enhances the photocatalytic activity of the catalyst.The change of microstructure has improved the efficiency of photocatalytic degradation of organic pollutant RhB.Sample 3-NCN has the best photocatalytic degradation ability.The visible light catalytic degradation rate reaches97.8%,which is much higher than the CN degradation rate?66.3%?.