Separation membrane as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of membrane separation, and particularly relates to a separation membrane as well as a preparation method and application thereof. The separation membrane comprises carbon cloth, wherein the carbon cloth comprises holes; the metal organic framework is arranged on the surface of the carbon cloth or inside the carbon cloth. The separation membrane is high in water flux and separation efficiency in oil-water separation, and has the advantages of high water permeability, high interception performance and stable long-term performance.

Description

Technical Field

[0001] This application belongs to the technical field of membrane separation, and specifically relates to a separation membrane, its preparation method and application. Background Art

[0002] With the continuous acceleration of urbanization and industrialization, the pollution of oily wastewater has a particularly serious impact on the natural environment and human health. Solving the problem of oil-water separation is a major challenge. Membrane separation technology has shown many significant advantages in the application of oil-water separation. It has the advantages of low energy consumption, high separation efficiency, simple operation, etc., providing a reliable, efficient and sustainable solution for the field of oil-water separation. However, the problem of membrane fouling still needs to be solved.

[0003] Therefore, it is crucial to develop an oil-water separation membrane with both high flux and high separation efficiency. Summary of the Invention

[0004] In view of the above problems, this application provides a separation membrane, its preparation method and application. The separation membrane has high water flux and separation efficiency in oil-water separation, and has the advantages of high water permeability, high rejection performance and long-term performance stability.

[0005] In a first aspect, this application provides a separation membrane, which includes a carbon cloth, and the carbon cloth includes pores; A metal-organic framework disposed on the surface or inside of the carbon cloth; The metal-organic framework includes MOF-303.

[0006] Metal-organic framework (MOF) materials are materials with a three-dimensional spatial structure formed by connecting metal ions or ion clusters with organic ligands through chemical bonds. MOF has characteristics such as extremely high porosity, large specific surface area, highly adjustable pore size, clear molecular adsorption sites and regular geometric shapes. It can modify substrates such as stainless steel meshes, fiber cloths, and filter membranes and be applied to the treatment of oily wastewater. However, it lacks chemical stability, and the application of MOF membranes in oil-water separation is still a challenge.

[0007] In the technical solution of the embodiment of the present application, carbon cloth and metal-organic framework are used in combination. Among them, carbon cloth, as a typical carbon-based material, its porous structure endows it with excellent liquid penetration ability. Its excellent mechanical properties enable it to be flexibly folded and bent during use without damaging its structure, and it also has the common corrosion resistance characteristics of carbon-based materials. These characteristics greatly improve the efficiency of its recycling. These advantages make it an ideal substrate material for oil-water separation membranes; metal-organic frameworks exhibit remarkable characteristics such as high specific surface area, high porosity, structural diversity, and high adjustability. Its pore size and pore morphology can be precisely regulated by adjusting the length of the organic ligand and its functional groups during the synthesis process. In addition, it also exhibits excellent chemical stability and thermal stability. These characteristics further broaden its potential in the treatment of oily wastewater. Therefore, the obtained separation membrane has high water flux and separation efficiency in oil-water separation, and has the advantages of high water permeability, high rejection performance, and long-term performance stability.

[0008] In the technical solution of the embodiment of the present application, MOF-303 is selected as the metal-organic framework. Compared with other MOF materials, MOF-303 has a three-dimensional framework composed of hydrophilic one-dimensional diamond-shaped channels, showing extremely high water stability and excellent water absorption performance, which helps to form an anti-fouling hydration layer. In addition, the preparation of MOF-303 uses metal and ligand resources with lower costs and follows a simple and environmentally friendly process flow, which is more in line with the green concept. Therefore, MOF-303 is selected.

[0009] In some embodiments, based on the area of the carbon cloth being 9 cm 2 counting, the mass of the metal-organic framework is 0.01 - 0.05 g, such as 0.02 g, 0.03 g, 0.04 g, etc.

[0010] In the technical solution of the embodiment of the present application, based on the area of the carbon cloth being 9 cm 2 counting, the mass of the metal-organic framework is within the above range. The reason is that the above technical solution shows the loading amount of the metal-organic framework on the carbon cloth per unit area. Setting it within the above range can achieve a balance among porosity, loading amount, and interfacial bonding; if the mass of the metal-organic framework is too large, it will cause pore blockage, a decrease in permeability, and deterioration of mechanical strength; if the mass of the metal-organic framework is too small, it will lead to insufficient hydrophilicity and pore size regulation, resulting in low separation efficiency.

[0011] In the present application, MOF-303 is an aluminum-based metal-organic framework material, the coordinated metal is aluminum, and the organic ligand is 3,5-pyrazoledicarboxylic acid.

[0012] In the technical solution of the embodiment of the present application, aluminum is selected as the coordinated metal. Compared with other metals, when combined with carbon cloth, its advantages lie in high stability and water resistance, environmental friendliness and low cost, and it is easy to form a rigid skeleton and surface hydroxyl groups. Therefore, aluminum is selected as the coordinated metal.

[0013] The organic ligand is 3,5-pyrazoledicarboxylic acid. Compared with other organic ligands, when combined with carbon cloth, its advantages are that the dicarboxylic acid groups provide strong coordination sites and improve hydrophilicity, and the pyrazole ring enhances the stability of the MOF framework while its hydrophobic part can synergistically regulate the surface energy to achieve "hydrophilic-lipophobic" selectivity. Therefore, 3,5-pyrazoledicarboxylic acid is selected as the organic ligand.

[0014] In some embodiments, the porosity of the separation membrane is 60%-80%, such as 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, etc.

[0015] In a second aspect, the present application provides a method for preparing a separation membrane. The preparation method includes the following steps: The carbon cloth is subjected to acid treatment, and then a metal-organic framework is in-situ grown on its surface to obtain the separation membrane; The metal-organic framework includes MOF-303.

[0016] In the technical solution of the embodiment of the present application, first performing acid treatment on the carbon cloth is beneficial to form more adsorption sites and is conducive to in-situ growth of a metal-organic framework on its surface; compared with other treatment methods, the advantage of acid treatment is that it can clean the surface, remove impurities, introduce oxygen-containing functional groups, regulate the surface roughness and pore structure, and enhance the uniformity of material growth. Therefore, the preparation method obtains a separation membrane that can effectively achieve oil-water separation through a simple method.

[0017] In some embodiments, the acid used for the acid treatment includes any one or a combination of at least two of hydrochloric acid, nitric acid, or sulfuric acid.

[0018] In some embodiments, the temperature of the acid treatment is 5-45°C, optionally at room temperature, such as 5°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, etc.; and / or; The time of the acid treatment is 15-20 h, such as 16 h, 17 h, 18 h, 19 h, etc.

[0019] In some embodiments, before the acid treatment, it includes cleaning with acetone, anhydrous ethanol, and deionized water; and / or; After the acid treatment, it further includes soaking in an alcohol solvent.

[0020] As an example, the alcohol solvent includes ethanol and / or methanol.

[0021] In some embodiments, the in-situ growth includes immersing carbon in a metal-organic framework precursor solution and then performing a heat treatment to complete the in-situ growth; The metal-organic framework precursor solution includes a metal salt, an organic ligand, a base, and a solvent.

[0022] As an example, the raw materials for preparing MOF-303 include a metal salt (such as aluminum chloride hexahydrate) and an organic ligand (such as 3,5-pyrazoledicarboxylic acid monohydrate).

[0023] As an example, the mass ratio of the metal salt to the organic ligand is 1:(0.1 - 10), where 0.1 - 10 can be 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, etc.

[0024] As an example, the raw materials for preparation further include a base. For example, the base can include any one or a combination of at least two of sodium hydroxide, potassium hydroxide, or ammonia water.

[0025] As an example, the mass ratio of the metal salt to the base is 1:(0.1 - 5), where 0.1 - 5 can be 0.5, 1, 2, 3, 4, etc.

[0026] As an example, the raw materials for preparation further include a solvent. For example, the solvent can include water.

[0027] In some embodiments, the soaking time is 5 - 15 min, such as 6 min, 8 min, 10 min, 12 min, 14 min, etc.; and / or; The temperature of the heat treatment is 80 - 120 °C, such as 85 °C, 90 °C, 95 °C, 100 °C, 105 °C, 110 °C, 115 °C, etc.; and / or; The time of the heat treatment is 5 - 15 h, such as 6 h, 8 h, 10 h, 12 h, 14 h, etc.

[0028] In the technical solution of the embodiments of the present application, the temperature of the heat treatment is within the above range. The reason is that: a too high temperature will lead to the permeability, mechanical strength, and oil repellency of the sacrificial membrane, which may cause the collapse of the MOF structure; a too low temperature will result in low MOF crystallinity, insufficient loading, imbalance of hydrophilic-lipophobic properties, and low separation efficiency.

[0029] The time of the heat treatment is within the above range. The reason is that: combined with the temperature for process optimization, efficient loading of MOF-303 and preparation of a high-performance separation membrane are achieved; a too long time will lead to overgrowth of MOF, pore blockage, and structural damage, sacrificing separation efficiency and mechanical strength; a too short time will result in incomplete crystallization of MOF, insufficient loading, imbalance of hydrophilic-lipophobic properties, and low separation efficiency.

[0030] In some embodiments, the preparation method includes the following steps: (1) Prepare a metal-organic framework precursor solution: Dissolve 3,5-pyrazoledicarboxylic acid monohydrate, aluminum chloride hexahydrate, and sodium hydroxide in water and ultrasonically homogenize to obtain a uniformly mixed metal-organic framework precursor solution.

[0031] (2) Treat the carbon cloth: Place the carbon cloth in acetone, absolute ethanol, and deionized water for ultrasonic cleaning. At 5 - 45 °C (such as room temperature), soak it in an acid (such as hydrochloric acid, etc., with a concentration of 2 - 4 M) for 15 - 20 h (such as 18 h, etc.) to complete the acid treatment; then place the carbon cloth in an alcohol solvent for soaking.

[0032] (3) Prepare the separation membrane: Place the carbon cloth obtained in step (2) in the metal-organic framework precursor solution obtained in step (1), soak it for 5 - 15 min, then react at 80 - 120 °C for 5 - 15 h. After the reaction ends and cools to room temperature, wash and dry to obtain the separation membrane.

[0033] In a third aspect, the present application provides an application of the separation membrane described in the first aspect, or the separation membrane obtained by the preparation method described in the second aspect, in oil-water separation.

[0034] Compared with the prior art, the present application has at least the following advantages: (1) The separation membrane described in the present application has excellent oil-water separation performance and long-term stability; specifically, the separation membrane has significant hydrophilicity and underwater oleophobicity, a high pure water flux, high separation efficiency for different oil-water mixtures, excellent stability, and can still maintain stability after multiple cycle filtrations, that is, it has the advantages of high water permeability, high rejection performance, and long-term performance stability.

[0035] (2) The preparation method described in the present application has the advantages of simple operation and batch production. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to limit the present application. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings: Figure 1 is a schematic flow chart of the preparation method of some embodiments of the present application; wherein, 1 - raw materials of the metal-organic framework precursor solution; 2 - carbon cloth; 3 - metal-organic framework precursor solution; 4 - separation membrane; Figure 2 is a scanning electron microscope image of the carbon cloth of Comparative Example 1 at a scale of 5 μm; Figure 3 Scanning electron microscope image of the carbon cloth of Comparative Example 1 at a scale of 2 μm; Figure 4 Scanning electron microscope image of the carbon cloth of Comparative Example 1 at a scale of 1 μm; Figure 5 Scanning electron microscope image of the separation membrane of Example 1 at a scale of 5 μm; Figure 6 Scanning electron microscope image of the separation membrane of Example 1 at a scale of 2 μm; Figure 7 Scanning electron microscope image of the separation membrane of Example 1 at a scale of 1 μm; Figure 8 Element mapping diagram of the separation membrane of Example 1, the element is C; Figure 9 Element mapping diagram of the separation membrane of Example 1, the element is O; Figure 10 Element mapping diagram of the separation membrane of Example 1, the element is Al; Figure 11 Comparison diagram of the water contact angles of the carbon cloth of Comparative Example 1 and the separation membrane of Example 1; Figure 12 Comparison diagram of the underwater oil contact angles of the carbon cloth of Comparative Example 1 and the separation membrane of Example 1; Figure 13 Result diagram of the flux and rejection rate of the separation membrane of Example 1 for different oil / water mixtures (n - hexane, n - heptane, petroleum ether, gasoline and edible oil); Figure 14 Result diagram of the stability of the separation membrane of Example 1 for 50 cycles of n - hexane / water mixture. Detailed implementation manners

[0037] Hereinafter, embodiments of the technical solutions of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, so they are only examples and cannot be used to limit the protection scope of the present application.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above - mentioned accompanying drawing description are intended to cover non - exclusive inclusion.

[0039] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is more than two, unless otherwise specifically defined.

[0040] Reference to "embodiment" herein means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0041] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of the specific range. The ranges defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, ranges of 60-110 and 80-120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise specified, the numerical range "a-b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "2-10" means that all real numbers between "2-10" have been fully listed herein, and "2-10" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0042] In the description of the embodiments of the present application, the term "and / or" is merely a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: the existence of A, the simultaneous existence of A and B, and the existence of B. Additionally, the character " / " in this article generally represents an "or" relationship between the associated objects before and after.

[0043] The composite film and its preparation method in the present application will be further described below in conjunction with specific embodiments; the materials and reagents used in the following embodiments, unless otherwise specified, can all be commercially available products without limitation.

[0044] Example 1 This embodiment provides a separation membrane with a porosity of 70%. The separation membrane specifically includes a carbon cloth with holes provided thereon. A metal-organic framework (MOF-303) disposed on the surface or inside of the carbon cloth.

[0045] Taking the area of the carbon cloth as 9 cm 2 as an example, the mass of the metal-organic framework is 0.02 g.

[0046] The separation membrane is obtained by the following preparation method. The process schematic diagram of the preparation method is as Figure 1 shown and specifically includes the following steps: (1) Prepare the metal-organic framework precursor solution: The raw material 1 of the metal-organic framework precursor solution is added to a 50 mL beaker, specifically, 0.22 g of 3,5-pyrazoledicarboxylic acid monohydrate, 0.30 g of aluminum chloride hexahydrate, and 0.100 g of sodium hydroxide are added in sequence. The solid mixture is dissolved in 45.0 g of deionized water and ultrasonically homogenized. Specifically, at room temperature, the solution is placed on a magnetic stirrer with a rotation speed of 100 rpm and continuously stirred for 30 min to obtain a uniformly mixed metal-organic framework precursor solution 3.

[0047] (2) Treat the carbon cloth: Cut the carbon cloth 2 (purchased from Carbon Energy Technology Co., Ltd., Taiwan, China, with the brand number W0S1011) into a square cloth of 3 cm × 3 cm, and then place it in acetone, absolute ethanol, and deionized water in sequence for ultrasonic cleaning. The ultrasonic condition is ultrasonic cleaning for 30 min at 20 °C; then at room temperature, soak it in hydrochloric acid with a concentration of 3 M for 18 h to complete the acid treatment; then place the carbon cloth in absolute ethanol and soak it for 10 min.

[0048] (3) Prepare the separation membrane: Place the carbon cloth obtained in step (2) into the metal-organic framework precursor solution obtained in step (1), soak it for 10 min, and then transfer them together to a reaction kettle lined with polytetrafluoroethylene. Continuously react in a blast drying oven with the temperature set at 100 °C for 12 h. After the reaction ends and cools to room temperature, take out the carbon cloth covering the product, wash it three times with ultrapure water and absolute ethanol respectively to remove the loose powder on the membrane surface and the residues in the membrane channels, and dry it overnight in a blast drying oven at a temperature of 60 °C to obtain the separation membrane 4.

[0049] Comparative Example 1 This comparative example provides a carbon cloth without in-situ growth of a metal-organic framework.

[0050] Performance Test (1) Morphology and Elemental Characteristics Taking the separation membrane of Example 1 and the carbon cloth of Comparative Example 1 as examples, the morphology was observed by scanning electron microscopy. The results showed thatFigure 2 , Figure 3 and Figure 4 Under different scales, when observing the carbon cloth of Comparative Example 1, its surface is smooth, and root-like fibers are evenly distributed. Figure 5 , Figure 6 and Figure 7 Under different scales, when observing the separation membrane of Example 1, its surface is rough. After further magnification, it can be clearly seen that compared with the smoother original carbon cloth membrane, a large number of MOF-303 crystal particles with a cuboid-like structure are evenly distributed on its surface, and the successful coverage of MOF-303 particles greatly increases the roughness of the separation membrane.

[0051] Taking the separation membrane of Example 1 as an example, the element mapping (EDX) diagrams are as shown in Figure 8 , Figure 9 and Figure 10 . The uniform distribution of C, O, and Al elements in the separation membrane on the carbon cloth indicates that MOF-303 has been successfully grown in-situ on the carbon cloth and is evenly distributed.

[0052] (2) Hydrophilicity Taking the carbon cloth of Comparative Example 1 and the separation membrane of Example 1 as examples, to explore the hydrophilicity of the separation membrane, water contact angle (WCA) and underwater oil contact angle (UOCA) tests are carried out on them. The specific test method is as follows: Measured by a contact angle meter: When measuring the water contact angle, the membrane is placed horizontally on the sample stage, and ultrapure water droplets are dropped on the dry sample surface. The droplet morphology is captured by a high-speed camera, and the water contact angle is read. For the underwater oil contact angle, the membrane needs to be fixed horizontally at the bottom of the water, and dichloromethane oil droplets are injected with a syringe. The droplet morphology is captured by a high-speed camera, and the underwater oil contact angle is read.

[0053] As shown in Figure 11 , the comparative image of the water contact angles of the carbon cloth of Comparative Example 1 and the separation membrane of Example 1 is shown. When the water droplet contacts the carbon cloth surface, it bounces back, indicating that the carbon cloth has superhydrophobic properties; while when the water droplet contacts the separation membrane surface, it is instantly absorbed, indicating that the separation membrane of the present application has superhydrophilic properties.

[0054] As shown in Figure 12 , the comparative image of the underwater oil contact angles of the carbon cloth of Comparative Example 1 and the separation membrane of Example 1 is shown. When the oil droplet contacts the carbon cloth surface, it is quickly absorbed, indicating that the carbon cloth has underwater oleophilic properties; while when the oil droplet contacts the separation membrane surface, it adsorbs on it and shows an underwater oil contact angle of 155°, indicating that the separation membrane of the present application has underwater superoleophobic properties.

[0055] In summary, the potential value of the separation membrane of the present application in the field of oil-water separation.

[0056] (3) Separation performance The separation membrane was tested for separating oil-water mixtures. The specific test process was as follows: A filtration device with a customized effective filtration area of 1.78 cm 2 was used to carry out a gravity-driven filtration process. Oil Red O was used to dye different kinds of oils red, and methylene blue was used to dye deionized water blue. The same volume of the two solutions was weighed and mixed to prepare a simulated oil-water mixture. The separation performance of the membrane was determined by directly pouring the oil-water mixture onto the membrane surface.

[0057] Taking Example 1 as an example, according to Figure 13 the test results shown, due to the successful growth of MOF-303, the water flux of the separation membrane increased significantly. Specifically, the separation efficiency of the separation membrane for five different oil-water mixtures of n-hexane, n-heptane, petroleum ether, gasoline, and edible oil all exceeded 99%, and the highest flux could reach 2.66×10 5 L·m -2 ·h -1 , and the water flux of edible oil decreased slightly due to its high viscosity. The above results demonstrated the high oil-water separation performance of the separation membrane for various oil-water mixtures.

[0058] (4) Stability The stability of the separation membrane was tested. The specific test process was as follows: It was determined by the method of manual cyclic filtration, and the method for testing the membrane separation performance described above was followed.

[0059] Taking Example 1 as an example, a cyclic test of n-hexane / water oil-water mixture was carried out on it. According to Figure 14 the test results shown, the carbon cloth MOF composite membrane still maintained a high flux and separation efficiency after 50 cycles. This characteristic demonstrated that the carbon cloth MOF composite membrane had important potential in the practical application of treating oily wastewater.

[0060] Finally, it should be noted that: The above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit them; Although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: They can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; And these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be covered within the scope of the claims and the description of the present application. In particular, as long as there is no structural conflict, the technical features mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. A separation membrane, characterized in that, The separation membrane includes carbon cloth, and the carbon cloth includes pores; a metal-organic framework disposed on the surface or inside of the carbon cloth; the metal-organic framework includes MOF-303.

2. The separation membrane according to claim 1, wherein Based on the area of the carbon cloth being 9 cm 2 counting, the mass of the metal-organic framework is 0.01 - 0.05 g.

3. The separation membrane according to claim 1, wherein The porosity of the separation membrane is 60%-80%.

4. A method for preparing the separation membrane according to any one of claims 1-3, characterized in that, The preparation method includes the following steps: performing acid treatment on the carbon cloth, and then in-situ growing a metal-organic framework on its surface to obtain the separation membrane; the metal-organic framework includes MOF-303.

5. The preparation method according to claim 4, wherein The acid used for the acid treatment includes any one or a combination of at least two of hydrochloric acid, nitric acid or sulfuric acid.

6. The preparation method according to claim 4, wherein The temperature of the acid treatment is 5-45°C; and / or; The time of the acid treatment is 15-20 h.

7. The preparation method according to claim 4, characterized in that, Before the acid treatment, it includes cleaning with acetone, absolute ethanol, and deionized water; After the acid treatment, it further includes soaking in an alcohol solvent.

8. The preparation method according to claim 4, wherein The in-situ growth includes soaking the carbon cloth in a metal-organic framework precursor solution, and then performing heat treatment to complete the in-situ growth; The metal-organic framework precursor solution includes a metal salt, an organic ligand, a base, and a solvent.

9. The preparation method according to claim 8, characterized in that, The soaking time is 5-15 min; and / or; The temperature of the heat treatment is 80-120°C; and / or; The time of the heat treatment is 5-15 h.

10. Use of the separation membrane according to any one of claims 1-3, or the separation membrane obtained by the preparation method according to any one of claims 4-9, in oil-water separation.

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