Graphite carbon nitride catalytic membrane material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of composite materials, in particular to a graphite carbon nitride catalytic membrane material and a preparation method and application thereof. The preparation method comprises the following steps: mixing melamine, a halogen source and water, drying, and carrying out heat treatment to obtain the halogen intercalation carbon nitride composite material; mixing the halogen intercalation carbon nitride composite material dispersion liquid with a metal salt solution, then adjusting the pH value to be alkaline, carrying out an in-situ coprecipitation reaction to obtain a metal oxide / halogen intercalation carbon nitride heterojunction, and carrying out vacuum calcination on the metal oxide / halogen intercalation carbon nitride heterojunction to obtain metal oxide / halogen intercalation carbon nitride heterojunction composite powder; mixing the metal oxide / halogen intercalation carbon nitride heterojunction composite powder, a polymer carrier and N, N-dimethylformamide to obtain a spinning solution, and performing electrostatic spinning to obtain a nascent fiber membrane; and calcining the nascent fiber membrane to obtain the graphite carbon nitride catalytic membrane material. The preparation method is high in operability, and the prepared material has the characteristics of stable structure and high catalytic efficiency.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of composite materials, and in particular to a graphite carbon nitride catalytic membrane material and a preparation method and application thereof. BACKGROUND

[0002] With the development of modern industry, water environmental pollution is becoming increasingly serious. The organic pollutants in industrial wastewater are highly toxic, complex in structure and difficult to degrade, and are difficult to treat. Under the dual pressures of water resource shortage and pollution, how to green and efficiently purify and repair industrial polluted water bodies and improve economic benefits has become a difficult problem to be solved. At present, technologies such as flocculation sedimentation, biodegradation, selective adsorption and membrane filtration have been developed for the treatment of industrial wastewater, but traditional methods generally have the limitations of low treatment efficiency and poor reusability. Therefore, it is urgent to develop new and efficient water purification technologies.

[0003] Advanced oxidation processes (AOPs) are considered as one of the most promising emerging technologies in the field of water environmental remediation due to their strong oxidation ability, high reaction rate, small reactor volume, low secondary pollution and wide applicability to organic compounds. Some scholars observed that BOD, COD, color and dissolved organic carbon were reduced by 93%, 80%, 85% and 88% respectively when using multiple AOPs in the integration of photo-Fenton process and biological system. However, some AOPs face problems such as high power demand, high dosage of oxidizing agent, and high temperature and pressure reaction conditions in industrial water purification applications.

[0004] Photocatalysis technology is a new type of water purification technology with high efficiency and green characteristics. In the field of photocatalysis, carbon nitride is a new type of photocatalytic material with low cost, non-toxicity and high stability. The intercalation of halogen can effectively improve the photocatalytic performance of carbon nitride, and the construction of heterojunction can further improve the photocatalytic efficiency, promote the separation and transfer of photo-generated carriers, and thus improve the ability of photocatalytic degradation of organic pollutants. The development of these technologies provides new ideas and methods for the purification and repair of industrial wastewater. Among them, two-dimensional (2D) layered materials become ideal carriers due to their unique two-dimensional confined structure. Graphitic carbon nitride (g-C3N4) is a non-toxic, non-metallic and easily available layered material, which is widely used in the field of photocatalysis due to its suitable band gap width, high physical and chemical stability, simple preparation and adjustable energy band structure. However, the photocatalytic performance of g-C3N4 is limited by the low quantum efficiency caused by low charge mobility and fast carrier recombination. To solve this problem, researchers have optimized the strategies such as constructing nanostructures, surface modification, preparing heterojunctions and chemical doping.

[0005] Among the modification methods, non-metallic doping is attracting attention because it can avoid metal stability defects. Halogen (such as Cl) is a highly efficient modifier due to its high electronegativity and ionization energy. In addition, heterostructures promote charge separation and transmission, and become a key strategy to improve catalytic efficiency. Type II, type Z and type S heterojunctions have been proven to optimize carrier behavior, and type S heterojunctions can achieve low-energy carrier recombination through built-in electric fields and band bending, and retain high redox ability of electron-hole pairs, which has better separation efficiency than traditional heterojunctions.

[0006] In particular, the construction of heterojunctions with transition metal oxide semiconductors (such as oxides of Fe, Co, Cu, Mn, Ni, etc.) has become a research hotspot. Metal oxides can adsorb reactant molecules due to their complex surface composition, while providing suitable energy platforms to regulate charge transfer. In addition to the component and structural design of the catalyst itself, the carrier morphology and separation efficiency in practical applications are also crucial - traditional granular catalysts often face high loss rate and high operating cost problems in recycling and continuous processing. For example, current studies have shown that most conventional granular photocatalysts are difficult to maintain stable photocatalytic performance in a flat reactor, which indicates that granular catalysts are not conducive to practical application and promotion. In contrast, membrane materials as a new carrier provide a new way to solve these problems. Membrane materials have significant advantages over granular materials: integration of catalysis and separation, no need for additional separation steps, greatly reducing processing costs; reducing catalyst loss, making the material have superior stability and reusability; the porous structure of the membrane can enhance mass transfer, making the reaction more complete and the treatment effect better; strong anti-pollution, suitable for continuous flow operation, can reduce the risk of secondary pollution, suitable for efficient and sustainable wastewater treatment. Among them, blending spinning is considered the most effective method for producing nanofiber membranes due to its simple process, precise control of catalyst structure, strong material compatibility, and ability to construct high specific surface area and porous network.

[0007] In summary, how to develop a heterojunction catalyst based on halogen intercalated g-C3N4 supported metal oxide, combining the synergistic effect of halogen intercalation and heterojunction, to solve the bottleneck of traditional water treatment technology and provide a green and economic solution for efficient purification of industrial polluted water is a technical problem that needs to be solved by those skilled in the art. SUMMARY

[0008] The purpose of the present application is to provide a graphite carbon nitride catalytic membrane material and its preparation method and application, in order to solve the problems of difficult recycling of traditional photocatalysts, easy loss of metal active sites and low mass transfer efficiency of pollutants.

[0009] In order to achieve the above-mentioned purpose of the application, the present application provides the following technical solutions:

[0010] This invention provides a method for preparing a graphitic carbon nitride catalytic membrane material, comprising the following steps:

[0011] (1) After mixing and drying melamine, halogen source and water, heat treatment is performed to obtain halogen intercalated carbon nitride composite material.

[0012] (2) The halogen intercalated carbon nitride composite material is dispersed in a solvent to form a halogen intercalated carbon nitride composite material dispersion; the halogen intercalated carbon nitride composite material dispersion is mixed with a metal salt solution, and then the pH is adjusted to alkaline to carry out an in-situ co-precipitation reaction to obtain a metal oxide / halogen intercalated carbon nitride heterojunction.

[0013] (3) The metal oxide / halogen intercalated carbon nitride heterojunction is calcined under vacuum conditions to obtain metal oxide / halogen intercalated carbon nitride heterojunction composite powder.

[0014] (4) The metal oxide / halogen intercalated carbon nitride heterojunction composite powder, polymer carrier and N,N-dimethylformamide are mixed to obtain a spinning solution, and the spinning solution is electrospun to obtain a nascent fiber membrane.

[0015] (5) The nascent fiber membrane is calcined to obtain a graphite carbon nitride catalytic membrane material.

[0016] Optionally, the halogen source includes ammonium bromide, ammonium chloride, or ammonium iodide; the molar ratio of melamine to the halogen source is 1:5 to 30.

[0017] The heating rate of step (1) is 2℃, the temperature of the heat treatment is 520℃, and the time is 4h.

[0018] Optionally, the concentration of the halogen-intercalated carbon nitride composite material dispersion is 0.5–2.5 mg / mL; the solvent includes ethanol and water; and the volume ratio of ethanol to water is 1:1–5.

[0019] The metal salt solution includes an iron salt solution, a copper salt solution, a cobalt salt solution, or a molybdenum salt solution; the concentration of the metal salt solution is 0.01–0.05 mmol / mL; the volume ratio of the halogen intercalated carbon nitride composite material dispersion to the metal salt solution is 5:1.

[0020] Optionally, the pH is 10; the temperature of the in-situ coprecipitation reaction in step (2) is 60-140°C and the time is 30-60 min.

[0021] Optionally, the heating rate of step (3) is 5℃ / min, the calcination temperature is 500~600℃, and the holding time is 4~6h.

[0022] Optionally, the polymer carrier includes polyvinylpyrrolidone; the mass ratio of the metal oxide / halogen intercalated carbon nitride heterojunction composite powder to the polymer carrier is 1:5 to 8.

[0023] Optionally, the parameters of the electrospinning include: a spinning solution flow rate of 0.4–2 mL / h, an aluminum foil receiving plate distance of 30 cm from the needle tip, a voltage of 18–25 kV, and an ambient humidity of 30–45% RH.

[0024] Optionally, the heating rate of calcination in step (5) is 1℃ / min, the calcination temperature is 280~350℃, and the holding time is 2h.

[0025] The present invention also provides a graphite carbon nitride catalytic membrane material prepared by the above preparation method.

[0026] The present invention also provides the application of the above-mentioned graphite carbon nitride catalytic membrane material in wastewater treatment.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) This invention innovatively introduces metal salts into the spinning process of halogen intercalation g-C3N4 and combines it with an improved in-situ co-precipitation method to achieve in-situ uniform generation and embedding of metal oxide nanoparticles on the intercalation substrate. This method significantly simplifies the process, greatly shortens the heat treatment time, and eliminates the need for complex post-treatment, making it green and efficient. At the same time, by precisely controlling parameters such as metal salt concentration, the metal loading, grain size, and dispersion can be effectively controlled, fundamentally inhibiting particle agglomeration and leaching, and endowing the material with high crystallinity, excellent structural stability, and solution dispersibility;

[0029] (2) A unique composite structure with strong interactions between metal oxides and halogen-intercalated g-C3N4 was successfully constructed through spinning and in-situ composite processes. Halogen intercalation effectively expands the interlayer spacing of g-C3N4, significantly improving mass transfer efficiency; the formation of a membrane structure facilitates efficient catalyst recovery; and the strong chemical bonds generated in situ greatly enhance the mechanical strength, structural stability, cycle stability, and regeneration capacity of the composite material. This results in a catalyst with higher active site utilization, better catalytic selectivity (especially for organic pollutants), and a longer service life.

[0030] (3) The macroscopic membrane structure formed by spinning technology is a key advantage of this invention, endowing the material with high specific surface area, abundant porosity, and good dispersibility, resulting in excellent application performance. After the material is combined with the membrane, the huge specific surface area and porosity of its membrane structure provide sufficient contact interfaces and diffusion channels for the reactants, significantly improving mass transfer efficiency and catalytic reaction rate, and exhibiting excellent degradation efficiency of organic pollutants in wastewater treatment. At the same time, the material combined with the membrane makes catalyst recovery extremely simple and efficient, greatly reducing losses and the risk of secondary pollution; after the membrane is combined, the material has excellent mechanical strength and regeneration ability, ensuring that it can be recycled multiple times, effectively extending its service life and significantly reducing regeneration costs. In addition, the material is easy to prepare, low in cost, and easy to scale up, making it a promising and highly practical material for industrial wastewater treatment and other fields. Attached Figure Description

[0031] Figure 1 This is a TEM image of Cl-g-C3N4 from Example 2;

[0032] Figure 2 The XRD pattern of Cl-g-C3N4 in Example 3;

[0033] Figure 3 This is a schematic diagram of the electrospinning process of the present invention. Detailed Implementation

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0035] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0036] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0037] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0038] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0039] All raw materials used in this invention can be obtained commercially or prepared using existing technologies.

[0040] This invention provides a method for preparing a graphitic carbon nitride catalytic membrane material, comprising the following steps:

[0041] (1) After mixing and drying melamine, halogen source and water, heat treatment is performed to obtain halogen intercalated carbon nitride composite material.

[0042] (2) The halogen intercalated carbon nitride composite material is dispersed in a solvent to form a halogen intercalated carbon nitride composite material dispersion; the halogen intercalated carbon nitride composite material dispersion is mixed with a metal salt solution, and then the pH is adjusted to alkaline to carry out an in-situ co-precipitation reaction to obtain a metal oxide / halogen intercalated carbon nitride heterojunction.

[0043] (3) The metal oxide / halogen intercalated carbon nitride heterojunction is calcined under vacuum conditions to obtain metal oxide / halogen intercalated carbon nitride heterojunction composite powder.

[0044] (4) The metal oxide / halogen intercalated carbon nitride heterojunction composite powder, polymer carrier and N,N-dimethylformamide are mixed to obtain a spinning solution, and the spinning solution is electrospun to obtain a nascent fiber membrane.

[0045] (5) The nascent fiber membrane is calcined to obtain a graphite carbon nitride catalytic membrane material.

[0046] This invention utilizes halide-intercalated g-C3N4 as a substrate, leveraging halogens to expand interlayer spacing and form electron-rich surfaces, providing more anchoring sites for metal oxides and enhancing bonding strength. Through co-precipitation in-situ growth technology, metal ions are directionally nucleated on the halide-intercalated g-C3N4 surface, generating metal oxide particles <20nm in size, forming strong metal-NC bonds and inhibiting metal dissolution. This design fully utilizes the high catalytic performance of metal oxides, effectively improving the catalytic activity of the catalyst while avoiding the problems of metal active site agglomeration and dissolution. Compared to traditional heterojunction powder materials, the advantages are even more significant when prepared as a composite membrane material: the membrane material has a macroscopically continuous three-dimensional network structure, which not only solves the problems of easy agglomeration and difficult separation of powder materials in the reaction system, but also enables dynamic continuous reaction through membrane modules, greatly improving the operability of the catalytic process. Simultaneously, the porous structure of the membrane further expands the specific surface area, providing more contact sites for pollutants, and the forced convection of fluid within the membrane channels accelerates mass transfer, breaking through the bottleneck of limited mass transfer in traditional powder suspension systems.

[0047] Step (1) of the present invention is to completely mix melamine and halogen source in deionized water and keep stirring, then dry to obtain a precursor, and heat treat the precursor to obtain halogen intercalated carbon nitride composite material.

[0048] The stirring time is 24 hours, and the drying temperature is 90℃ for 12 hours.

[0049] In this invention, the halogen source includes ammonium bromide, ammonium chloride, or ammonium iodide; the molar ratio of melamine to the halogen source is 1:5 to 30, for example, it can be 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:15, 1:20, 1:25, or 1:30, etc.

[0050] The heating rate of step (1) is 2℃, the temperature of the heat treatment is 520℃, and the time is 4h.

[0051] Step (2) of this invention involves dispersing the halogen-intercalated carbon nitride composite material in a solvent to form a halogen-intercalated carbon nitride composite material dispersion; then, a metal salt solution is added dropwise to the halogen-intercalated carbon nitride composite material dispersion while vigorously stirring during the dropwise addition process; then, the pH is adjusted to alkaline, and the mixture is stirred at a constant temperature to promote the in-situ growth of metal oxide nanoparticles on the surface of the halogen-intercalated carbon nitride and the formation of heterojunctions; the mixture is then naturally cooled to room temperature and washed several times with deionized water and ethanol alternately to obtain a metal oxide / halogen-intercalated carbon nitride heterojunction.

[0052] The temperature at which the drops are added is 80°C, and the time is 10 minutes.

[0053] In this invention, the concentration of the halogen-intercalated carbon nitride composite material dispersion is 0.5–2.5 mg / mL, for example, it can be 0.5 mg / mL, 0.8 mg / mL, 1 mg / mL, 1.2 mg / mL, 1.5 mg / mL, 1.8 mg / mL, 2 mg / mL, 2.2 mg / mL, or 2.5 mg / mL, etc.; the solvent includes ethanol and water; the volume ratio of ethanol to water is 1:1–5, for example, it can be 1:1, 1:2, 1:3, 1:4, or 1:5, etc.

[0054] The metal salt solution includes an iron salt solution, a copper salt solution, a cobalt salt solution, or a molybdenum salt solution; the iron salt solution is a mixed solution of ferric sulfate and ferric chloride; the copper salt solution is a mixed solution of copper nitrate and copper chloride; the cobalt salt solution is a mixed solution of cobalt nitrate and cobalt chloride; and the molybdenum salt solution is an ammonium molybdate solution; the metal salt solution is prepared by dissolving a metal salt in deionized water.

[0055] In this invention, the use of different anions in the metal salt solution can balance the anion effect, providing trivalent and divalent iron, which is beneficial for preparing catalysts with mixed valence states and improving catalyst activity.

[0056] The concentration of the metal salt solution is 0.01–0.05 mmol / mL, 0.01 mmol / mL, 0.02 mmol / mL, 0.03 mmol / mL, 0.04 mmol / mL, or 0.05 mmol / mL, etc.; the volume ratio of the halogen intercalated carbon nitride composite material dispersion to the metal salt solution is 5:1.

[0057] In this invention, the pH is 10, and the pH is adjusted by an alkaline solution, which includes sodium hydroxide solution or ammonia solution, and the concentration of the alkaline solution is 2 mol / L; the temperature of the in-situ coprecipitation reaction in step (2) is 60-140℃, for example, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃ or 140℃, etc., and the time is 30-60 min, for example, 30 min, 40 min, 50 min or 60 min, etc.

[0058] Step (3) of the present invention is to calcine the metal oxide / halogen intercalated carbon nitride heterojunction under vacuum to obtain the metal oxide / halogen intercalated carbon nitride heterojunction composite powder.

[0059] In this invention, the heating rate of step (3) calcination is 5℃ / min, the calcination temperature is 500~600℃, for example, it can be 500℃, 510℃, 520℃, 550℃, 560℃, 580℃ or 600℃, etc., and the holding time is 4~6h, for example, it can be 4h, 5h or 6h.

[0060] Step (4) of this invention involves mixing metal oxide / halogen intercalated carbon nitride heterojunction composite powder, polymer carrier and N,N-dimethylformamide evenly to obtain a spinning solution, electrospinning the spinning solution, and depositing the spun fibers onto the receiving substrate in a low-temperature receiver containing liquid nitrogen to obtain a nascent fiber membrane.

[0061] In this invention, the polymer carrier includes polyvinylpyrrolidone; the mass ratio of the metal oxide / halogen intercalated carbon nitride heterojunction composite powder to the polymer carrier is 1:5 to 8, for example, it can be 1:5, 1:6, 1:7 or 1:8, etc.

[0062] In this invention, the parameters of the electrospinning include: the flow rate of the spinning solution is 0.4 to 2 mL / h, for example, it can be 0.4 mL / h, 0.5 mL / h, 1 mL / h, 1.5 mL / h or 2 mL / h, etc.; the distance between the aluminum foil receiving plate and the needle tip is 30 cm; the voltage is 18 to 25 kV, for example, it can be 18 kV, 20 kV, 22 kV, 24 kV or 25 kV, etc.; and the ambient humidity is 30 to 45% RH.

[0063] Step (5) of this invention involves calcining the nascent fiber membrane to remove the polymer template and obtain a graphite carbon nitride catalytic membrane material.

[0064] In this invention, the heating rate of step (5) calcination is 1℃ / min, the calcination temperature is 280~350℃, for example, it can be 280℃, 300℃, 320℃, 330℃, 340℃ or 350℃, etc., and the holding time is 2h.

[0065] In this invention, blending spinning technology plays a crucial role in the preparation process. This technology uniformly disperses the metal oxide / halogen intercalated carbon nitride composite material in the spinning solution. Through the stretching effect of the spinning process, nanoparticles are ordered along the fiber axis, forming a structurally stable fibrous membrane skeleton. The calcination treatment after spinning not only removes organic components but also promotes interfacial fusion between composite particles, enhancing the mechanical strength and chemical stability of the catalyst during use and ensuring a long catalytic lifetime during long-term cycling. Furthermore, the expanded interlayer spacing significantly improves the pollutant diffusion rate and mass transfer efficiency, demonstrating good treatment capabilities for organic pollutants. The metal oxide / halogen intercalated carbon nitride composite material of this invention exhibits excellent catalytic performance, good cycling stability, and efficient separation and recovery capabilities, possessing extremely high practical application value.

[0066] The present invention also provides a graphite carbon nitride catalytic membrane material prepared by the above preparation method.

[0067] The present invention also provides the application of the above-mentioned graphite carbon nitride catalytic membrane material in wastewater treatment.

[0068] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0069] Example 1

[0070] A method for preparing Fe3O4 / Br intercalated-g-C3N4 composite membrane material:

[0071] (1) Preparation and dispersion of Br-g-C3N4

[0072] (1-1) Take a dry and clean beaker, pour in pre-weighed melamine (0.0317 mol) and ammonium bromide (0.9508 mol) in deionized water, mix thoroughly and keep stirring for 24 hours, dry at 90℃ for 12 hours to obtain the precursor. Heat the precursor in a muffle furnace at a heating rate of 2℃ / min to reach 520℃, hold for 4 hours to obtain Br(intercalated)-g-C3N4;

[0073] (1-2) Br-g-C3N4 (200 mg) was dispersed in 200 mL of ethanol / water (volume ratio 1:1) and sonicated for 2 hours to ensure uniform dispersion of Br-g-C3N4, thus obtaining a suspension of Br-g-C3N4.

[0074] (2) Preparation of Fe3O4 / Br intercalated-g-C3N4 by in-situ coprecipitation method

[0075] (2-1) Weigh out FeSO4·7H2O (0.525 mmol) and FeCl3·6H2O (0.740 mmol), dissolve the above metal salts in 40 mL of deionized water to form a mixed metal salt solution;

[0076] (2-2) The above mixed metal salt solution was added dropwise to the Br-g-C3N4 suspension and stirred vigorously at 80°C for about 10 minutes. NaOH solution (2M) was added to the solution to adjust the pH to 10. Stirring was continued at 80°C for 30 minutes to obtain a mixture. The mixture was allowed to cool naturally to room temperature and washed several times with deionized water and ethanol alternately. The mixture was heated to 500°C at a program of 5°C / min and calcined under vacuum for 4 hours to obtain Fe3O4 / Br intercalated-g-C3N4 composite powder.

[0077] (3) Blending spinning and calcination

[0078] (3-1) Dissolve the above Fe3O4 / Br intercalated-g-C3N4 composite powder (0.2g) and PVP (1.6g) in DMF (10mL), and sonicate at 600W for 2h to obtain spinning solution;

[0079] (3-2) Electrospinning is performed on the spinning solution. The flow rate of the spinning solution is 1.0 mL / h, the aluminum foil receiving plate is 30 cm away from the needle tip, and the voltage is controlled at 20 kV. The spun fibers are deposited on the receiving substrate in the low temperature receiver containing liquid nitrogen to obtain the nascent fiber membrane.

[0080] (3-3) The nascent fiber membrane was calcined at 280℃ for 2h (heating rate 1℃ / min) to remove the polymer template and obtain Fe3O4 / Br-g-C3N4 heterojunction composite material (graphite carbon nitride catalytic membrane material).

[0081] In this embodiment, 50 mg of the Fe3O4 / Br intercalated-g-C3N4 composite membrane material was added to 100 mL of an initial concentration of 10 mg / L methylene blue aqueous solution. First, the suspension was magnetically stirred in the dark for 30 minutes to reach adsorption-desorption equilibrium. Then, a 300W xenon lamp was turned on, and the photo-reaction was carried out under continuous magnetic stirring. The results showed that after 60 minutes of visible light irradiation, the degradation rate of MB reached 96.5%. After the first degradation experiment, the membrane was removed, washed, dried at 70°C, and re-immersed in 100 mL of freshly prepared 10 mg / L MB solution. The next catalytic degradation experiment was conducted under identical conditions. The above steps were repeated for 5 cycles to fully evaluate its stability. After 5 cycles, the degradation rate of MB by the catalytic membrane remained above 90%, and the iron ion leaching concentration was extremely low, less than 0.5 mg / L each time.

[0082] Example 2

[0083] A method for preparing a CuO / Cl intercalated-g-C3N4 composite film material:

[0084] (1) Preparation and dispersion of Cl-g-C3N4

[0085] (1-1) Take a dry and clean beaker, pour in pre-weighed melamine (0.0317 mol) and ammonium chloride (0.9508 mol) in deionized water, mix thoroughly and keep stirring for 24 hours, dry at 90℃ for 12 hours to obtain the precursor. Heat the precursor in a muffle furnace at a heating rate of 2℃ / min to reach 520℃, hold for 4 hours to obtain Cl(intercalated)-g-C3N4;

[0086] (1-2) Disperse Cl-g-C3N4 (200 mg) in 200 mL of ethanol / water (volume ratio 1:1) and sonicate for 2 hours to ensure uniform dispersion of Cl-g-C3N4, thus obtaining a suspension of Cl-g-C3N4;

[0087] (2) Preparation of CuO / Cl intercalated-g-C3N4 by in-situ coprecipitation method

[0088] (2-1) Weigh out Cu(NO3)2·3H2O (0.525 mmol) and CuCl2·2H2O (0.740 mmol), dissolve the above metal salts in 40 mL of deionized water to form a mixed metal salt solution;

[0089] (2-2) The above mixed metal salt solution was added dropwise to the Cl-g-C3N4 suspension and stirred vigorously at 80°C for about 10 minutes. NaOH solution (2M) was added to the solution to adjust the pH to 10. Stirring was continued at 80°C for 30 minutes to obtain a mixture. The mixture was allowed to cool naturally to room temperature and washed several times with deionized water and ethanol alternately. The mixture was heated to 500°C at a program of 5°C / min and calcined under vacuum for 4 hours to obtain CuO / Cl intercalated-g-C3N4 composite powder.

[0090] (3) Blending spinning and calcination

[0091] (3-1) CuO / Cl intercalated-g-C3N4 composite powder (0.2g) and PVP (1.6g) were dissolved in DMF (10mL) and sonicated at 600W for 2h to obtain spinning solution;

[0092] (3-2) Electrospinning is performed on the spinning solution. The flow rate of the spinning solution is 1.0 mL / h, the aluminum foil receiving plate is 30 cm away from the needle tip, and the voltage is controlled at 20 kV. The spun fibers are deposited on the receiving substrate in the low temperature receiver containing liquid nitrogen to obtain the nascent fiber membrane.

[0093] (3-3) The nascent fiber membrane was calcined at 280℃ for 2h (heating rate 1℃ / min) to remove the polymer template and obtain CuO / Cl intercalated-g-C3N4 heterojunction composite material (graphite carbon nitride catalytic membrane material).

[0094] In this embodiment, 50 mg of the CuO / Cl intercalated-g-C3N4 composite membrane material was added to 100 mL of an initial concentration of 10 mg / L methylene blue aqueous solution. First, the suspension was magnetically stirred in the dark for 30 minutes to reach adsorption-desorption equilibrium. Then, a 300 W xenon lamp was turned on, and the photoreaction was carried out under continuous magnetic stirring. The results showed that after 60 minutes of visible light irradiation, the degradation rate of MB reached 97.2%. Cyclic experiments were conducted using the same steps as in Example 1, and the degradation rate remained above 90%, with extremely low copper ion leaching concentrations, each less than 0.40 mg / L.

[0095] Figure 1This is a TEM image of the precursor of the composite catalytic membrane. The interlayer stacking structure of g-C3N4 can be clearly observed at the 500 nm scale, and the introduction of Cl does not affect its interlayer structure, indicating good stability.

[0096] Example 3

[0097] A method for preparing a CoO / Cl intercalated-g-C3N4 composite membrane material:

[0098] (1) Preparation and dispersion of Cl-g-C3N4

[0099] (1-1) Take a dry and clean beaker, pour in pre-weighed melamine (0.0317 mol) and ammonium chloride (0.9508 mol) in deionized water, mix thoroughly and keep stirring for 24 hours, dry at 90℃ for 12 hours to obtain the precursor. Heat the precursor in a muffle furnace at a heating rate of 2℃ / min to reach 520℃, hold for 4 hours to obtain Cl(intercalated)-g-C3N4;

[0100] (1-2) Disperse Cl-g-C3N4 (200 mg) in 200 mL of ethanol / water (volume ratio 1:1) and sonicate for 2 hours to ensure uniform dispersion of Cl-g-C3N4, thus obtaining a suspension of Cl-g-C3N4;

[0101] (2) Preparation of CoO / Cl intercalated-g-C3N4 by in-situ coprecipitation method

[0102] (2-1) Weigh out Co(NO3)2·6H2O (0.525 mmol) and CoCl2·6H2O (0.740 mmol), dissolve the above metal salts in 40 mL of deionized water to form a mixed metal salt solution;

[0103] (2-2) The above mixed metal salt solution was added dropwise to the Cl-g-C3N4 suspension and stirred vigorously at 80°C for about 10 minutes. NaOH solution (2M) was added to the solution to adjust the pH to 10. Stirring was continued at 80°C for 30 minutes to obtain a mixture. The mixture was allowed to cool naturally to room temperature and washed several times with deionized water and ethanol alternately. The mixture was heated to 500°C at a program of 5°C / min and calcined under vacuum for 4 hours to obtain CoO / Cl intercalated-g-C3N4 composite powder.

[0104] (3) Blending spinning and calcination

[0105] (3-1) CoO / Cl intercalated-g-C3N4 composite powder (0.2g) and PVP (1.6g) were dissolved in DMF (10mL) and sonicated at 600W for 2h to obtain spinning solution;

[0106] (3-2 Electrospinning is performed on the spinning solution. The flow rate of the spinning solution is 1.0 mL / h. The aluminum foil receiving plate is 30 cm away from the needle tip. The voltage is controlled at 20 kV. The spun fibers are deposited on the receiving substrate in the low temperature receiver containing liquid nitrogen to obtain the nascent fiber membrane.

[0107] (3-3) The nascent fiber membrane was calcined at 280℃ for 2h (heating rate 1℃ / min) to remove the polymer template and obtain CoO / Cl intercalated-g-C3N4 heterojunction composite material (graphite carbon nitride catalytic membrane material).

[0108] In this embodiment, 50 mg of the CoO / Cl intercalated-g-C3N4 composite membrane material was added to 100 mL of an initial concentration of 10 mg / L methylene blue aqueous solution. First, the suspension was magnetically stirred in the dark for 30 minutes to reach adsorption-desorption equilibrium. Then, a 300 W xenon lamp was turned on, and the photoreaction was carried out under continuous magnetic stirring. The results showed that after 60 minutes of visible light irradiation, the degradation rate of MB reached 95.8%. Cyclic experiments were conducted using the same steps as in Example 1, and the degradation rate remained above 90%, with extremely low cobalt ion leaching concentrations, consistently less than 0.75 mg / L.

[0109] Figure 2 This is the XRD pattern of the composite catalytic membrane precursor, from... Figure 2 It can be seen that the sharp peak around 2θ = 27° corresponds to the (001) crystal plane of g-C3N4, indicating that the graphitic carbon nitride with well-stacked interlayer structure was successfully prepared, and no additional characteristic peaks were observed, indicating that the intercalation structure of Cl did not affect the crystal phase structure of g-C3N4.

[0110] Example 4

[0111] A method for preparing Fe3O4 / I intercalated-g-C3N4 composite membrane material:

[0112] (1) Preparation and dispersion of Ig-C3N4

[0113] (1-1) Take a dry and clean beaker, pour in pre-weighed melamine (0.0317 mol) and ammonium iodide (0.6340 mol) in deionized water, mix thoroughly and keep stirring for 24 hours, dry at 90℃ for 12 hours to obtain the precursor. Heat the precursor in a muffle furnace at a heating rate of 2℃ / min to reach 520℃, hold for 4 hours to obtain I(intercalated)-g-C3N4;

[0114] (1-2) Ig-C3N4 (200mg) was dispersed in 200mL of ethanol / water (volume ratio 1:1) and ultrasonically treated for 2 hours to ensure uniform dispersion of Ig-C3N4, thus obtaining a suspension of Ig-C3N4.

[0115] (2) Preparation of Fe3O4 / I intercalated-g-C3N4 by in-situ coprecipitation method

[0116] (2-1) Weigh out FeSO4·7H2O (0.525 mmol) and FeCl3·6H2O (0.740 mmol), dissolve the above metal salts in 40 mL of deionized water to form a mixed metal salt solution;

[0117] (2-2) The above mixed metal salt solution was added dropwise to the suspension of Ig-C3N4 and stirred vigorously at 80°C for about 10 minutes. Ammonia solution (2M) was added to the solution to adjust the pH to 10. The mixture was stirred at 80°C for 30 minutes to obtain a mixture. The mixture was allowed to cool naturally to room temperature and washed several times with deionized water and ethanol alternately. The mixture was heated to 500°C at a program of 5°C / min and calcined under vacuum for 4 hours to obtain Fe3O4 / I intercalated-g-C3N4 composite powder.

[0118] (3) Blending spinning and calcination

[0119] (3-1) Dissolve the above Fe3O4 / I intercalated-g-C3N4 composite powder (0.2g) and PVP (1.6g) in DMF (10mL), and sonicate at 600W for 2h to obtain spinning solution;

[0120] (3-2) Electrospinning is performed on the spinning solution. The flow rate of the spinning solution is 1.0 mL / h, the aluminum foil receiving plate is 30 cm away from the needle tip, and the voltage is controlled at 20 kV. The spun fibers are deposited on the receiving substrate in the low temperature receiver containing liquid nitrogen to obtain the nascent fiber membrane.

[0121] (3-3) The nascent fiber membrane was calcined at 280℃ for 2h (heating rate 1℃ / min) to remove the polymer template and obtain Fe3O4 / Ig-C3N4 heterojunction composite material (graphite carbon nitride catalytic membrane material).

[0122] The Fe3O4 / I intercalated-g-C3N4 composite membrane material (50 mg) prepared in this embodiment was added to 100 mL of an initial concentration of 10 mg / L methylene blue aqueous solution. First, the suspension was magnetically stirred in the dark for 30 minutes to reach adsorption-desorption equilibrium. Then, a 300W xenon lamp was turned on, and the photoreaction was carried out under continuous magnetic stirring. The results showed that after 60 minutes of visible light irradiation, the degradation rate of MB reached 94.8%. A cyclic experiment with the same steps as in Example 1 was conducted, and the degradation rate remained above 90%, with the iron ion leaching concentration below 2 mg / L each time.

[0123] Example 5

[0124] A method for preparing CuO / Br intercalated-g-C3N4 composite film material:

[0125] (1) Preparation and dispersion of Br-g-C3N4

[0126] (1-1) Take a dry and clean beaker, pour in pre-weighed melamine (0.0317 mol) and ammonium bromide (0.9508 mol) in deionized water, mix thoroughly and keep stirring for 24 hours, dry at 90℃ for 12 hours to obtain the precursor. Heat the precursor in a muffle furnace at a heating rate of 2℃ / min to reach 520℃, hold for 4 hours to obtain Br(intercalated)-g-C3N4;

[0127] (1-2) Br-g-C3N4 (200 mg) was dispersed in 200 mL of ethanol / water (volume ratio 1:2) and sonicated for 2 hours to ensure uniform dispersion of Br-g-C3N4, thus obtaining a suspension of Br-g-C3N4.

[0128] (2) Preparation of CuO / Br intercalated-g-C3N4 by in-situ coprecipitation method

[0129] (2-1) Weigh out Cu(NO3)2·3H2O (0.525 mmol) and CuCl2·2H2O (0.740 mmol), dissolve the above metal salts in 40 mL of deionized water to form a mixed metal salt solution;

[0130] (2-2) The above mixed metal salt solution was added dropwise to the Br-g-C3N4 suspension and stirred vigorously at 80°C for about 10 minutes. Ammonia solution (2M) was added to the solution to adjust the pH to 10. The mixture was stirred at 80°C for 30 minutes to obtain a mixture. The mixture was allowed to cool naturally to room temperature and washed several times with deionized water and ethanol alternately. The mixture was heated to 500°C at a program of 5°C / min and calcined under vacuum for 4 hours to obtain CuO / Br intercalated-g-C3N4 composite powder.

[0131] (3) Blending spinning and calcination

[0132] (3-1) CuO / Br intercalated-g-C3N4 composite powder (0.2g) and PVP (1.6g) were dissolved in DMF (10mL) and sonicated at 600W for 2h to obtain spinning solution;

[0133] (3-2) Electrospinning is performed on the spinning solution. The flow rate of the spinning solution is 1.0 mL / h, the aluminum foil receiving plate is 30 cm away from the needle tip, and the voltage is controlled at 20 kV. The spun fibers are deposited on the receiving substrate in the low temperature receiver containing liquid nitrogen to obtain the nascent fiber membrane.

[0134] (3-3) The nascent fiber membrane was calcined at 280℃ for 2h (heating rate 1℃ / min) to remove the polymer template and obtain CuO / Br intercalated-g-C3N4 heterojunction composite material (graphite carbon nitride catalytic membrane material).

[0135] In this embodiment, 50 mg of the CuO / Br intercalated-g-C3N4 composite membrane material was added to 100 mL of an initial concentration of 10 mg / L methylene blue aqueous solution. First, the suspension was magnetically stirred in the dark for 30 minutes to reach adsorption-desorption equilibrium. Then, a 300 W xenon lamp was turned on, and the photoreaction was carried out under continuous magnetic stirring. The results showed that after 60 minutes of visible light irradiation, the degradation rate of MB reached 96.0%. Cyclic experiments conducted using the same steps as in Example 1 maintained a degradation rate above 90%, and the copper ion leaching concentration was consistently below 1.65 mg / L.

[0136] Example 6

[0137] A method for preparing a CoO / Br intercalated-g-C3N4 composite membrane material:

[0138] (1) Preparation and dispersion of Br-g-C3N4

[0139] (1-1) Take a dry and clean beaker, pour in pre-weighed melamine (0.0317 mol) and ammonium bromide (0.9508 mol) in deionized water, mix thoroughly and keep stirring for 24 hours, dry at 90℃ for 12 hours to obtain the precursor. Heat the precursor in a muffle furnace at a heating rate of 2℃ / min to reach 520℃, hold for 4 hours to obtain Br(intercalated)-g-C3N4;

[0140] (1-2) Br-g-C3N4 (200 mg) was dispersed in 200 mL of ethanol / water (volume ratio 1:2) and sonicated for 2 hours to ensure uniform dispersion of Br-g-C3N4, thus obtaining a suspension of Br-g-C3N4.

[0141] (2) Preparation of CoO / Br intercalated-g-C3N4 by in-situ coprecipitation method

[0142] (2-1) Weigh out Co(NO3)2·6H2O (0.525 mmol) and CoCl2·6H2O (0.740 mmol), dissolve the above metal salts in 40 mL of deionized water to form a mixed metal salt solution;

[0143] (2-2) The above mixed metal salt solution was added dropwise to the Br-g-C3N4 suspension and stirred vigorously at 80°C for about 10 minutes. NaOH solution (2M) was added to the solution to adjust the pH to 10. Stirring was continued at 80°C for 30 minutes to obtain a mixture. The mixture was allowed to cool naturally to room temperature and washed several times with deionized water and ethanol alternately. The mixture was heated to 500°C at a program of 5°C / min and calcined under vacuum for 4 hours to obtain CoO / Br intercalated-g-C3N4 composite powder.

[0144] (3) Blending spinning and calcination

[0145] (3-1) CoO / Br intercalated-g-C3N4 composite powder (0.2g) and PVP (1.6g) were dissolved in DMF (10mL) and sonicated at 600W for 2h to obtain spinning solution;

[0146] (3-2 Electrospinning is performed on the spinning solution. The flow rate of the spinning solution is 1.0 mL / h. The aluminum foil receiving plate is 30 cm away from the needle tip. The voltage is controlled at 20 kV. The spun fibers are deposited on the receiving substrate in the low temperature receiver containing liquid nitrogen to obtain the nascent fiber membrane.

[0147] (3-3) The nascent fiber membrane was calcined at 280℃ for 2h (heating rate 1℃ / min) to remove the polymer template and obtain CoO / Br intercalated-g-C3N4 heterojunction composite material (graphite carbon nitride catalytic membrane material).

[0148] In this embodiment, 50 mg of the CoO / Br intercalated-g-C3N4 composite membrane material was added to 100 mL of an initial concentration of 10 mg / L methylene blue aqueous solution. First, the suspension was magnetically stirred in the dark for 30 minutes to reach adsorption-desorption equilibrium. Then, a 300 W xenon lamp was turned on, and the photoreaction was carried out under continuous magnetic stirring. The results showed that after 60 minutes of visible light irradiation, the degradation rate of MB reached as high as 95.5%, and the cobalt ion leaching concentration was 1.82 mg / L.

[0149] Example 7

[0150] A MoO 2.8 Preparation method of Cl-intercalated-g-C3N4 composite membrane material:

[0151] (1) Preparation and dispersion of Cl-g-C3N4

[0152] (1-1) Take a dry and clean beaker, pour in pre-weighed melamine (0.0317 mol) and ammonium chloride (0.6340 mol) in deionized water, mix thoroughly and keep stirring for 24 hours, dry at 90℃ for 12 hours to obtain the precursor. Heat the precursor in a muffle furnace at a heating rate of 2℃ / min to reach 520℃, hold for 4 hours to obtain Cl(intercalated)-g-C3N4;

[0153] (1-2) Disperse Cl-g-C3N4 (200 mg) in 200 mL of ethanol / water (volume ratio 1:2) and sonicate for 2 hours to ensure uniform dispersion of Cl-g-C3N4, thus obtaining a suspension of Cl-g-C3N4;

[0154] (2) Preparation of MoO by in-situ coprecipitation method 2.8 / Cl intercalation-g-C3N4

[0155] (2-1) Ammonium molybdate (0.181 mmol) was dissolved in 40 mL of deionized water to form a metal salt solution;

[0156] (2-2) The above metal salt solution was added dropwise to the Cl-g-C3N4 suspension, and the mixture was vigorously stirred at 80°C for about 10 minutes. Ammonia solution (2M) was added to the solution to adjust the pH to 10, and the mixture was stirred at 80°C for another 30 minutes to obtain a mixture. The mixture was allowed to cool naturally to room temperature and washed several times with deionized water and ethanol alternately. The mixture was then heated to 500°C at a rate of 5°C / min and calcined under vacuum for 4 hours to obtain MoO. 2.8 / Cl intercalated-g-C3N4 composite powder;

[0157] (3) Blending spinning and calcination

[0158] (3-1)MoO 2.8 / Cl intercalated-g-C3N4 composite powder (0.2g) and PVP (1.6g) were dissolved in DMF (10mL) and sonicated at 600W for 2h to obtain spinning solution;

[0159] (3-2 Electrospinning is performed on the spinning solution. The flow rate of the spinning solution is 1.0 mL / h. The aluminum foil receiving plate is 30 cm away from the needle tip. The voltage is controlled at 20 kV. The spun fibers are deposited on the receiving substrate in the low temperature receiver containing liquid nitrogen to obtain the nascent fiber membrane.

[0160] (3-3) The nascent fibrous membrane was calcined at 280℃ for 2 hours (heating rate 1℃ / min) to remove the polymer template and obtain MoO2. 2.8 / Cl intercalated-g-C3N4 heterojunction composite material (graphite carbon nitride catalytic membrane material).

[0161] The MoO prepared in this embodiment 2.8 50 mg of / Cl intercalated-g-C3N4 composite membrane material was added to 100 mL of an initial concentration of 10 mg / L methylene blue aqueous solution. First, the suspension was magnetically stirred in the dark for 30 minutes to reach adsorption-desorption equilibrium. Then, a 300 W xenon lamp was turned on, and the photoreaction was carried out under continuous magnetic stirring. The results showed that after 60 minutes of visible light irradiation, the degradation rate of MB reached 95.3%, and the molybdenum ion leaching concentration was 1.90 mg / L.

[0162] Comparative Example 1

[0163] Same as Example 2, except that 0.1585 mol of ammonium chloride is used in step (1-1).

[0164] The results showed that, compared with Example 2, the Cl intercalation of the CuO / Cl intercalated-g-C3N4 composite membrane material prepared in this comparative example was significantly reduced, resulting in decreased mass transfer efficiency, reduced utilization of active sites and catalytic selectivity of the catalyst. Compared with Example 2, the CuO / Cl intercalated-g-C3N4 composite membrane material prepared in this comparative example achieved a degradation rate of 80% in the catalytic oxidation degradation of methylene blue under the same conditions, which is low.

[0165] Comparative Example 2

[0166] Same as Example 1, except that the ratio of ethanol to water is 1:15 in steps (1-2).

[0167] The results showed that, compared with Example 1, the dispersibility of the catalyst Br-g-C3N4 prepared in this comparative example was worse, which damaged the high crystallinity, excellent structural stability and solution dispersibility of the material. The specific surface area decreased from ~118 m² in Example 1. 2 / g decreased to ~78m 2 / g, which leads to a decrease in mass transfer efficiency, thereby reducing the overall catalytic activity.

[0168] The performance of the Fe3O4 / Br intercalated-g-C3N4 catalyst prepared in this comparative example was tested in the same way as in Example 1. Compared with Example 1, the Fe3O4 / Br intercalated-g-C3N4 catalyst prepared in this comparative example achieved a degradation rate of 83% in the catalytic oxidation degradation of methylene blue under the same conditions, which is a low degradation rate.

[0169] Comparative Example 3

[0170] Same as Example 4, except that the amount of FeSO4·7H2O in step (1-1) is reduced to 0.2625 mmol.

[0171] The results showed that, compared with Example 4, the Fe3O4 / I intercalated-g-C3N4 catalyst prepared in this comparative example had less uniform pore size and lower mechanical strength, which affected the specific surface area and porosity. The specific surface area decreased from ~125 m² in Example 4. 2 / g decreased to ~85m 2 / g, thus reducing the overall catalytic activity.

[0172] The performance of the Fe3O4 / I intercalated-g-C3N4 catalyst prepared in this comparative example was tested in the same way as in Example 4. Compared with Example 4, the Fe3O4 / I intercalated-g-C3N4 catalyst prepared in this comparative example had a degradation rate of 81% and a significantly increased iron ion leaching concentration to 3.5 mg / L in the catalytic oxidation degradation of methylene blue under the same conditions.

[0173] Comparative Example 4

[0174] Same as in Example 1, except that step (3) blending and spinning and calcination are omitted.

[0175] The results showed that, compared with Experimental Example 1, the catalyst prepared in this comparative study had poor dispersibility, was prone to agglomeration, resulting in insufficient exposure of active sites; low mass transfer efficiency and limited reaction interface; difficult recovery and complex operation in practical applications; poor stability and greater leaching of metal ions.

[0176] After 60 minutes of visible light irradiation, the degradation rate of MB was 62%. In addition, the powder exhibited significant agglomeration during the reaction, making it difficult to disperse and difficult to recover after the reaction, requiring centrifugation. Furthermore, the iron ion leaching concentration was relatively high (5 mg / L).

[0177] In summary, the graphitic carbon nitride catalytic membrane material prepared by this invention leverages the synergistic advantages of both metal oxides and halide-intercalated graphitic carbon nitride through a heterojunction structure, exhibiting characteristics such as large specific surface area, high crystallinity, and structural stability. In practical water purification applications, this composite membrane material overcomes the drawbacks of low mobility, rapid recombination of photogenerated carriers, and difficulty in recovery, while also utilizing the membrane structure to improve mass transfer efficiency and reaction interface, thereby significantly enhancing catalytic efficiency and enabling it to demonstrate superior performance in the catalytic field.

[0178] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a graphite carbon nitride catalytic membrane material, characterized in that, Includes the following steps: (1) After mixing and drying melamine, halogen source and water, heat treatment is performed to obtain halogen intercalated carbon nitride composite material. (2) The halogen intercalated carbon nitride composite material is dispersed in a solvent to form a halogen intercalated carbon nitride composite material dispersion; the halogen intercalated carbon nitride composite material dispersion is mixed with a metal salt solution, and then the pH is adjusted to alkaline to carry out an in-situ co-precipitation reaction to obtain a metal oxide / halogen intercalated carbon nitride heterojunction. (3) The metal oxide / halogen intercalated carbon nitride heterojunction is calcined under vacuum conditions to obtain metal oxide / halogen intercalated carbon nitride heterojunction composite powder. (4) The metal oxide / halogen intercalated carbon nitride heterojunction composite powder, polymer carrier and N,N-dimethylformamide are mixed to obtain a spinning solution, and the spinning solution is electrospun to obtain a nascent fiber membrane. (5) The nascent fiber membrane is calcined to obtain a graphite carbon nitride catalytic membrane material.

2. The preparation method according to claim 1, characterized in that, The halogen source includes ammonium bromide, ammonium chloride, or ammonium iodide; the molar ratio of melamine to the halogen source is 1:5 to 30. The heating rate of step (1) is 2℃, the temperature of the heat treatment is 520℃, and the time is 4h.

3. The preparation method according to claim 1, characterized in that, The concentration of the halogen-intercalated carbon nitride composite material dispersion is 0.5–2.5 mg / mL; the solvent includes ethanol and water; the volume ratio of ethanol to water is 1:1–5; The metal salt solution includes an iron salt solution, a copper salt solution, a cobalt salt solution, or a molybdenum salt solution; the concentration of the metal salt solution is 0.01–0.05 mmol / mL; the volume ratio of the halogen intercalated carbon nitride composite material dispersion to the metal salt solution is 5:

1.

4. The preparation method according to claim 1, characterized in that, The pH is 10; The temperature for the in-situ coprecipitation reaction in step (2) is 60–140 °C, and the time is 30–60 min.

5. The preparation method according to claim 1, characterized in that, The heating rate of step (3) calcination is 5℃ / min, the calcination temperature is 500~600℃, and the holding time is 4~6h.

6. The preparation method according to claim 1, characterized in that, The polymer carrier includes polyvinylpyrrolidone; the mass ratio of the metal oxide / halogen intercalated carbon nitride heterojunction composite powder to the polymer carrier is 1:5 to 8.

7. The preparation method according to claim 1, characterized in that, The parameters for electrospinning include: a spinning solution flow rate of 0.4–2 mL / h, an aluminum foil receiving plate distance of 30 cm from the needle tip, a voltage of 18–25 kV, and an ambient humidity of 30–45% RH.

8. The preparation method according to claim 1, characterized in that, The heating rate of step (5) is 1℃ / min, the calcination temperature is 280~350℃, and the holding time is 2h.

9. The graphite carbon nitride catalytic membrane material prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the graphite carbon nitride catalytic membrane material according to claim 9 in wastewater treatment.

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