Emulsion separation membrane and method of use thereof

Abstract

The application relates to an emulsion separation membrane and an application method thereof, and belongs to the technical field of chemical separation, in particular to an oil-water separation membrane. The separation membrane is woven by yarn, the yarn surface is covered with a PMMA-co-PDEAEMA polymer coating, and the PMMA-co-PDEAEMA polymer is prepared through polymerization reaction of DEAEMA monomers and MMA monomers. The separation membrane is used for separating a dispersed phase emulsion and has the function of wetting switching.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of chemical separation technology, and relates to an oil-water separation membrane, in particular to an emulsion separation membrane as well as a preparation method and an application method thereof. BACKGROUND

[0002] Membrane separation method is considered as a new technology in the field of oil-water separation at present due to its low cost, simple operation, high selectivity and other advantages. However, there are still many difficulties in separating nano-scale dispersed phase emulsion by using the membrane separation method. The dispersed phase particle size of nano-emulsion is between 0-300 nanometers, and the conventional emulsion separation membrane material has a wide distribution of pores of 0-3 microns, which is difficult to separate the emulsion of this size, especially the emulsion with a particle size below 100 nanometers is difficult to separate efficiently. Therefore, it is crucial to develop a membrane material that can realize high-efficiency separation of nano-scale dispersed phase emulsion.

[0003] And the nano-emulsion includes water-in-oil nano-emulsion and oil-in-water nano-emulsion, and the membrane material usually has a single wettability. Most of the membrane materials are either oleophilic / hydrophobic, which can be used to separate water-in-oil emulsion, or hydrophilic / hydrophobic, which can be used to separate oil-in-water emulsion. This means that most of the membrane materials can only separate a fixed type of emulsion. However, the composition of oil-water mixture in practice is often very complex, so it is crucial to realize the controllable switching of the wettability of the membrane surface to realize the on-demand oil-water separation.

[0004] The existing wettability-switchable membranes include pre-wetting membranes, Janus membranes and stimulus-responsive membranes. The pre-wetting membrane has a high affinity for both water and oil. If the membrane is wetted with water, a hydrophilic / hydrophobic membrane can be obtained, and if the membrane is wetted with oil, an oleophilic / hydrophobic membrane can be obtained. Because the pre-wetting membrane has a high affinity for oil, it inevitably has a serious membrane pollution problem. The Janus membrane has one hydrophilic side and one oleophilic side. By placing the hydrophilic side upward, a hydrophilic / hydrophobic membrane can be obtained, and by placing the oleophilic side upward, an oleophilic / hydrophobic membrane can be obtained. The Janus membrane material is usually complex to prepare, and it also has a serious oil pollution problem. The stimulus-responsive membrane material can change its physical and chemical properties according to external stimuli (such as light, electricity, PH, heat, chemicals, etc.), thereby realizing the switching of the surface wettability. However, in practice, the separation system is often turbid and opaque, and light is difficult to penetrate the emulsion to reach the membrane. PH and chemical response types will cause the accumulation of chemicals in the system, and the electric and thermal response types require a large amount of energy when the separation system is very large.

[0005] Compared with the above-mentioned wetting switching strategy, the carbon dioxide stimulus-responsive wetting switching strategy has wide application scenarios, low energy consumption, easy removal and no secondary pollution. In addition, carbon dioxide is safe, stable and easy to obtain. Therefore, the carbon dioxide stimulus-responsive separation membrane has a very broad prospect in the field of oil-water separation. However, the existing carbon dioxide-responsive separation membranes are generally prepared by conventional methods such as blending (mixing carbon dioxide-responsive polymers with other polymers physically), surface grafting (grafting carbon dioxide-responsive polymers on the surface of the membrane through chemical bonds) and the like. Therefore, there are problems of low grafting rate of responsive polymers, slow response speed, poor separation performance, uneven pore size distribution, only micron emulsion separation, even only layered oil-water mixture separation and no nanometer emulsion separation and the like.

[0006] CN 108837707 A uses a porous mesh film as a base film, constructs a multistage structure micro-nano scale coating on it through a hydrothermal and calcination process, obtains a coating separation membrane with super hydrophilic, modifies it with sodium laurate to obtain a super hydrophobic surface, and can make the surface of the separation membrane change from super hydrophobicity to super hydrophilicity and super oleophobicity under water again through a high temperature treatment process. And this integrated high temperature treatment and surface modification process can be cycled for a certain number of times, and due to the selectivity of the surface wettability, it realizes the on-demand separation of different types of oil-water mixtures. However, the wetting switching of the oil-water separation membrane involved in this patent needs to use high temperature treatment, and the treatment time is long and the treatment conditions are harsh. For example, in the hydrophilic switching process, it needs to be calcined at 500-800 degrees Celsius for 3-6 hours under nitrogen protection, and in the hydrophobic switching process, it needs to be reacted in a sodium laurate solution at 40-70 degrees Celsius for 5-9 hours and then vacuum dried for 4-8 hours. At the same time, since high temperature is needed in the wetting switching process of this patent, the selected base film is a high-temperature-resistant material such as carbon fiber cloth, glass fiber cloth, basalt fiber cloth or mullite fiber cloth, which is harsh in the selection of base film and has a wide pore size distribution.

[0007] CN 104841293 A discloses an oil-water separation nanofiber membrane with CO2 stimulus response and its preparation method and application. The nanofiber membrane prepared by electrospinning technology has CO2 stimulus response function and can selectively separate oil and water. It is low in cost, simple in operation, clean and environmentally friendly, and has high separation effect on different types of oil-water mixed systems. However, the oil-water separation membrane described in the patent is an electrospun fiber membrane. The biggest feature of the electrospun fiber membrane is that the fibers are randomly staggered, the pores formed are large and small, the pore size distribution is wide, and it is difficult to ensure that all the pore sizes are small enough to effectively screen the emulsion dispersed phase droplets. The wetting switch of the patent belongs to the switch between hydrophilic (contact angle about 30°) and hydrophobic (contact angle about 140°), not the switch between superhydrophilic (contact angle 0°) and superhydrophobic (contact angle 150°). The surface wetting performance of the super-wetting category further enhances the repulsion of the dispersed phase on the membrane surface, improving the separation capacity of the oil-water mixture. Therefore, the patent can only separate layered oil-water mixtures, but cannot separate emulsions. SUMMARY

[0008] In view of the above problems, the purpose of the present application is to provide an emulsion separation membrane, which is woven from yarns, the surface of the yarns is coated with a PMMA-co-PDEAEMA polymer coating, and the PMMA-co-PDEAEMA polymer is prepared by polymerization reaction of DEAEMA monomers and MMA monomers.

[0009] In one embodiment, the emulsion separation membrane comprises a fabric and a coating layer coated on the surface of the fabric, and the coating layer is a switchable oil-water wetting coating layer.

[0010] In one embodiment, the fabric is woven from yarns by a loom, and the coating layer is pre-coated on the surface of the yarns and completely covers the surface of the yarns.

[0011] In one embodiment, the DEAEMA monomers and MMA monomers are reacted at a ratio of 1:0.5-2.

[0012] The present application coats the polymer on the yarns first and then weaves the yarns into a membrane. First, the mechanical properties of the yarns are ensured, and the weavability is improved. Second, the polymer is uniformly coated on each yarn, thereby improving the switching ability of the surface wetting of the prepared membrane. Finally, by weaving this regular membrane preparation method, the problem of uneven polymer coating in the membrane pores can be solved, and uniform and narrow distribution of the membrane pore size can be achieved.

[0013] The second object of the present application is to provide a preparation method of an emulsion separation membrane, comprising the following steps:

[0014] S1, preparation of PMMA-co-PDEAEMA polymer: DEAEMA monomer and MMA monomer were dissolved in tetrahydrofuran at a mass ratio of 1:0.5-2, an initiator was added, and the reaction was stirred under a nitrogen atmosphere for 24 hours at a heating temperature of 65-75°C. Excess n-hexane was added to precipitate the polymer, and the precipitated polymer was dried in an oven;

[0015] S2, preparation of a polymer solution: the polymer prepared in step S1 was dissolved in tetrahydrofuran to prepare a 10wt% polymer solution;

[0016] S3, preparation of a polymer film coated yarn: the polymer solution prepared in step S2 was uniformly coated on the surface of the yarn, and the yarn was guided into a 70°C drying oven for heat treatment for 30 minutes to obtain a polymer film coated yarn;

[0017] S4, preparation of an emulsion separation membrane: the polymer film coated yarn prepared in step S3 was woven into a fabric by a weaving machine to obtain an oil-wet emulsion separation membrane.

[0018] In one embodiment, the separation wetting switching method is as follows: when needed, the emulsion separation membrane prepared in step S4 is placed in deionized water, and CO2 is bubbled for 10-20 minutes to obtain a water-wet emulsion separation membrane; when needed, the water-wet emulsion separation membrane is placed in deionized water, and nitrogen is bubbled or directly heated for 10-20 minutes, and the water-wet emulsion separation membrane is converted into an oil-wet emulsion separation membrane again.

[0019] In one embodiment, the initiator includes a peroxide initiator or an azo initiator

[0020] In one embodiment, the azo initiator is azobisisobutyronitrile or azobisisoheptyl nitrile; and the peroxide initiator is any one of dibenzoyl peroxide, dodecanoyl peroxide, tert-butyl tert-amyl peroxide, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, cumene hydroperoxide, and potassium persulfate.

[0021] A third object of the present application is to provide an application method of an emulsion separation membrane, which is used for separating a dispersed phase emulsion and has a wetting switching function.

[0022] In one embodiment, when separating an oil-in-water nanoemulsion, the gas-responsive nanoemulsion separation membrane is placed in a water environment, CO2 is introduced for 5-10 minutes to convert it into a hydrophilic / underwater oleophobic separation membrane for separation.

[0023] In one embodiment, the gas-responsive nanolamellar emulsion separation membrane is directly used for separation without CO2 treatment; or the gas-responsive nanolamellar emulsion separation membrane is placed in a water environment and N2 is introduced for 10-30 min to convert the separation membrane into a hydrophobic / oleophilic separation membrane, and then separation is performed.

[0024] Advantages:

[0025] The membrane material has an all-around equivalent flux, and the fabric has the advantages of uniform pores and adjustable voids, uniform pore size, and almost the same flux and separation efficiency at each part of the fabric membrane. Moreover, the separation of nanolamellar emulsion can be realized by adjusting the density of the fabric.

[0026] The membrane material has self-cleaning ability. Under the alternating stimulation of CO2 and N2, the gas-responsive polymer coating continuously switches between hydrophobic oleophilic and hydrophilic oleophobic, which can effectively remove oil stains and achieve self-cleaning.

[0027] The emulsion separation membrane has strong durability. Since the yarn is used as the substrate to provide mechanical strength, the coating is in the form of a closed tubular polymer wrapped around the surface of the yarn. Compared with the separation membrane modified by grafted polymer, the coating has stronger adhesion and is more stable on the yarn and is not easy to fall off. DETAILED DESCRIPTION

[0028] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0029] Example 1:

[0030] An emulsion separation membrane includes a fabric 1 and a coating 2 coated on the surface of the fabric 1. The coating 2 is a switchable oil-water wetting coating, and in this embodiment, the coating is specifically a PMMA-co-PDEAEMA polymer coating. The chemical structure of the coating 2 is

[0031]

[0032] In this embodiment, the fabric 1 is woven by yarn 101 through a weaving machine, and the coating 2 is pre-coated on the surface of the yarn 101 and completely covers the surface of the yarn 101.

[0033] In reality, the fabric 1 can also be non-woven, such as non-woven fabric, foamed plastic cloth, and cast film cloth, as long as it has pores and can be penetrated by oil or water.

[0034] In reality, the coating 2 can be directly coated on the finished fabric 1, which can be single-sided or double-sided.

[0035] Example 2:

[0036] The method for preparing the emulsion separation membrane above, characterized in that, comprising the following specific steps:

[0037] S1, preparation of PMMA-co-PDEAEMA polymer: DEAEMA monomer and MMA monomer are dissolved in tetrahydrofuran at a mass ratio of 1:0.5, an initiator is added, and heating and stirring are carried out under a nitrogen atmosphere for 24 hours, the heating temperature is 65°C, an excess of n-hexane is added to precipitate the polymer, and the precipitated polymer is dried in an oven;

[0038] S2, preparation of a polymer solution: the polymer prepared in step S1 is dissolved in tetrahydrofuran to prepare a 10wt% polymer solution;

[0039] S3, preparation of a polymer film coated yarn: the polymer solution prepared in step S2 is uniformly coated on the surface of the yarn to form a coating layer, the yarn is guided into a 70°C drying room for heat treatment for 30 minutes to obtain a polymer film coated yarn; the chemical structure of the coating layer is

[0040]

[0041] S4, preparation of an emulsion separation membrane: the polymer film coated yarn prepared in step S3 is woven into a fabric by a weaving machine to prepare an oil-wet emulsion separation membrane.

[0042] S5, wetting switching: when needed, the emulsion separation membrane prepared in step S4 is placed in deionized water, and CO2 is bubbled for 10 minutes to prepare a water-wet emulsion separation membrane; at this time, the chemical structure of the coating layer on the surface of the yarn changes to

[0043]

[0044] When needed, the water-wet emulsion separation membrane can still be placed in deionized water, and nitrogen gas is bubbled or directly heated for 10 minutes, and the water-wet emulsion separation membrane is converted into an oil-wet emulsion separation membrane again

[0045] The above emulsion separation membrane is used for separating oil and water emulsion, when the emulsion is in a water-in-oil state, an oil-wet emulsion separation membrane is used for separation, and the separation performance test data are shown in Table 1; when the emulsion is in an oil-in-water state, the oil-wet emulsion separation membrane is converted into a water-wet emulsion separation membrane by bubbling CO2 for 10 minutes, and then separation is performed, and the separation performance test data are shown in Table 1; when it is needed to separate the emulsion in a water-in-oil state again, the water-wet emulsion separation membrane is placed in deionized water, and nitrogen gas is bubbled or directly heated for 10 minutes, so that the water-wet emulsion separation membrane is converted into an oil-wet emulsion separation membrane again, and then the emulsion in a water-in-oil state is separated.

[0046] Example 3

[0047] The method for preparing the above-mentioned emulsion separation membrane is characterized by comprising the following specific steps:

[0048] S1, preparation of PMMA-co-PDEAEMA polymer: DEAEMA monomers and MMA monomers are dissolved in tetrahydrofuran at a mass ratio of 1:1, an initiator is added, and heating and stirring are carried out under a nitrogen atmosphere for 24 hours at a heating temperature of 70°C. Excess n-hexane is added to precipitate the polymer, and the precipitated polymer is dried in an oven;

[0049] S2, preparation of a polymer solution: the polymer prepared in step S1 is dissolved in tetrahydrofuran to prepare a polymer solution with a mass fraction of 10wt%;

[0050] S3, preparation of a polymer film-coated yarn: the polymer solution prepared in step S2 is uniformly coated on the surface of the yarn, and the yarn is guided into a 70°C drying room for heat treatment for 30 minutes to obtain a polymer film-coated yarn;

[0051] S4, preparation of an emulsion separation membrane: the polymer film-coated yarn prepared in step S3 is woven into a fabric by a weaving machine to obtain an oil-wet emulsion separation membrane.

[0052] S5, wetting switching: when needed, the emulsion separation membrane prepared in step S4 is placed in deionized water, and CO2 is bubbled for 10 minutes to obtain a water-wet emulsion separation membrane; when needed, the water-wet emulsion separation membrane is placed in deionized water, and nitrogen gas is bubbled or heated directly for 10 minutes, and the water-wet emulsion separation membrane is converted into an oil-wet emulsion separation membrane again.

[0053] The above-mentioned emulsion separation membrane is used to separate oil and water emulsion. When the emulsion is in a water-in-oil state, an oil-wet emulsion separation membrane is used for separation, and the separation performance test data are shown in Table 1. When the emulsion is in an oil-in-water state, the oil-wet emulsion separation membrane is converted into a water-wet emulsion separation membrane by bubbling CO2 for 10 minutes, and then the separation is performed, and the separation performance test data are shown in Table 1. When it is needed to separate the emulsion in a water-in-oil state again, the water-wet emulsion separation membrane is placed in deionized water, and nitrogen gas is bubbled or heated directly for 10 minutes, so that the water-wet emulsion separation membrane is converted into an oil-wet emulsion separation membrane again, and then the emulsion in a water-in-oil state is separated.

[0054] Example 4

[0055] The method for preparing the above-mentioned emulsion separation membrane is characterized by comprising the following specific steps:

[0056] S1, Preparation of PMMA-co-PDEAEMA polymer: DEAEMA monomer and MMA monomer were dissolved in tetrahydrofuran at a mass ratio of 1:1.5, an initiator was added, and the reaction was stirred under a nitrogen atmosphere for 24 hours at a heating temperature of 75°C. Excess n-hexane was added to precipitate the polymer, and the precipitated polymer was dried in an oven;

[0057] S2, Preparation of a polymer solution: The polymer prepared in step S1 was dissolved in tetrahydrofuran to prepare a 10wt% polymer solution;

[0058] S3, Preparation of a polymer film-coated yarn: The polymer solution prepared in step S2 was uniformly coated on the surface of the yarn, and the yarn was guided into a 70°C drying oven for heat treatment for 30 minutes to obtain a polymer film-coated yarn;

[0059] S4, Preparation of an emulsion separation membrane: The polymer film-coated yarn prepared in step S3 was woven into a fabric by a weaving machine to obtain an oil-wet emulsion separation membrane.

[0060] S5, Wetting switching: When needed, the emulsion separation membrane prepared in step S4 was placed in deionized water, and CO2 was bubbled for 20 minutes to obtain a water-wet emulsion separation membrane. When needed, the water-wet emulsion separation membrane was placed in deionized water, and nitrogen was bubbled or directly heated for 20 minutes, and the water-wet emulsion separation membrane was converted into an oil-wet emulsion separation membrane.

[0061] The above emulsion separation membrane was used to separate oil and water emulsion. When the emulsion was in a water-in-oil state, an oil-wet emulsion separation membrane was used for separation, and the separation performance test data are shown in Table 1. When the emulsion was in an oil-in-water state, the oil-wet emulsion separation membrane was converted into a water-wet emulsion separation membrane by bubbling CO2 for 20 minutes, and then the separation was performed, and the separation performance test data are shown in Table 1. When it was needed to separate the water-in-oil emulsion again, the water-wet emulsion separation membrane was placed in deionized water, and nitrogen was bubbled or directly heated for 20 minutes, so that the water-wet emulsion separation membrane was converted into an oil-wet emulsion separation membrane again, and then the water-in-oil emulsion was separated.

[0062] Example 5

[0063] A method for preparing the above emulsion separation membrane, characterized in that it comprises the following specific steps:

[0064] S1, Preparation of PMMA-co-PDEAEMA polymer: DEAEMA monomer and MMA monomer were dissolved in tetrahydrofuran at a mass ratio of 1:2, an initiator was added, and the reaction was stirred under a nitrogen atmosphere for 24 hours at a heating temperature of 68°C. Excess n-hexane was added to precipitate the polymer, and the precipitated polymer was dried in an oven;

[0065] S2, Preparation of a polymer solution: The polymer prepared in step S1 was dissolved in tetrahydrofuran to prepare a polymer solution with a mass fraction of 10wt%.

[0066] S3, Preparation of a polymer film-coated yarn: The polymer solution prepared in step S2 was uniformly coated on the surface of a yarn, and the yarn was guided into a 70°C drying oven for heat treatment for 30 minutes to obtain a polymer film-coated yarn.

[0067] S4, Preparation of an emulsion separation membrane: The polymer film-coated yarn prepared in step S3 was woven into a fabric by a weaving machine to obtain an oil-wet emulsion separation membrane.

[0068] S5, Wetting switching: When needed, the emulsion separation membrane prepared in step S4 was placed in deionized water, and CO2 was bubbled for 20 minutes to obtain a water-wet emulsion separation membrane. When needed, the water-wet emulsion separation membrane was placed in deionized water, and nitrogen was bubbled or directly heated for 20 minutes to convert the water-wet emulsion separation membrane into an oil-wet emulsion separation membrane.

[0069] The oil and water emulsion was separated by using the above-mentioned emulsion separation membrane. When the emulsion was in a water-in-oil state, the oil-wet emulsion separation membrane was used for separation, and the separation performance test data are shown in Table 1. When the emulsion was in an oil-in-water state, the oil-wet emulsion separation membrane was converted into a water-wet emulsion separation membrane by bubbling CO2 for 20 minutes, and then the separation was performed. The separation performance test data are shown in Table 1. When the oil-in-water emulsion needed to be separated again, the water-wet emulsion separation membrane was placed in deionized water, and nitrogen was bubbled or directly heated for 20 minutes to convert the water-wet emulsion separation membrane into an oil-wet emulsion separation membrane, and then the oil-in-water emulsion was separated.

[0070] In the above-mentioned examples 2-5, the initiator is a commonly used azo initiator or a peroxide initiator. The azo initiator is preferably azobisisobutyronitrile or azobisisoheptyl nitrile. The peroxide initiator is preferably any one of dibenzoyl peroxide, dodecanoyl peroxide, tert-butyl tert-amyl peroxide, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, cumene hydroperoxide, and potassium persulfate. The amount of the initiator is used according to the amount of the different initiators. In the present application, the amount of the initiator used in examples 2-5 is 1% of the total mass of the DEAEMA monomer and the MMA monomer.

[0071] Table 1

[0072]

[0073] From the experimental data of Table 1, it can be seen that the emulsion separation membrane of the present application can effectively separate water-in-oil emulsion when switched to hydrophobicity, and can effectively separate oil-in-water emulsion when switched to hydrophilicity.

[0074] The working principle of the present application is that the tertiary amine group in DEAEMA (diethylaminoethyl methacrylate) can react with carbon dioxide in water, thereby exhibiting an elongated hydrophilic chain conformation, and after heating or passing nitrogen to remove carbon dioxide in water, the DEAEMA will restore to a hydrophobic state. The present application uses DEAEMA (diethylaminoethyl methacrylate) as a responsive monomer, MMA (methyl methacrylate) as a hard monomer, and tetrahydrofuran as a solvent to configure a raw material solution, and under certain conditions, a gel is generated by free radical polymerization and coated on the surface of the yarn. The yarn with the coating is woven into a fabric by a weaving machine to obtain an emulsion separation membrane with adjustable switchable oil-water wettability.

[0075] It can be understood that the specific examples herein are only to help those skilled in the art better understand the present disclosure, and are not intended to limit the scope of the present application.

[0076] It can be understood that the various embodiments described in the present specification can be implemented alone or in combination, and the present disclosure does not limit this.

[0077] Unless otherwise defined, all technical and scientific terms used in the present disclosure have the same meaning as commonly understood by one of ordinary skill in the art to which this specification belongs. The terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the scope of the present specification. The term "and / or" used in the present specification includes any and all combinations of one or more of the listed terms. The singular forms "a", "an" and "the" used in the present disclosure and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0078] The above is only a specific embodiment of the present specification, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present specification, which should be covered within the protection scope of the present specification. Therefore, the protection scope of the present application should be limited by the protection scope of the claims.

Claims

1. An emulsion separation membrane characterized by, The separation membrane is woven by yarns, and the yarns are coated with a PMMA-co-PDEAEMA polymer coating, wherein the PMMA-co-PDEAEMA polymer is obtained by polymerization of DEAEMA monomers and MMA monomers; The preparation method of the emulsion separation membrane comprises the following steps: S1, preparation of PMMA-co-PDEAEMA polymer: DEAEMA monomers and MMA monomers are dissolved in tetrahydrofuran at a mass ratio of 1: (0.5-2), an initiator is added, and the mixture is heated and stirred for 24 hours in a nitrogen atmosphere at a heating temperature of 65-75°C. An excess of n-hexane is added to precipitate the polymer, and the precipitated polymer is dried in an oven; S2, preparation of a polymer solution: the polymer prepared in step S1 is dissolved in tetrahydrofuran to prepare a polymer solution with a mass fraction of 10wt%; S3, preparation of a polymer film-coated yarn: the polymer solution prepared in step S2 is uniformly coated on the surface of the yarn, and the yarn is guided into a drying oven at 70°C for heat treatment for 30 minutes to obtain a polymer film-coated yarn; S4, preparation of an emulsion separation membrane: the polymer film-coated yarn prepared in step S3 is woven into a fabric by a weaving machine to obtain an oil-wet emulsion separation membrane.

2. The emulsion separation membrane according to claim 1, wherein The initiator includes a peroxide initiator or an azo initiator.

3. The emulsion separation membrane according to claim 2, wherein The azo initiator is azobisisobutyronitrile or azobisisoheptyl nitrile; and the peroxide initiator is any one of dibenzoyl peroxide, dodecanoyl peroxide, tert-butyl tert-amyl peroxide, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, cumene hydroperoxide, and potassium persulfate.

4. The method of claim 1-3, wherein the emulsion separation membrane is used for separating an emulsion. The separation membrane is used for separating dispersed phase emulsions and has a wetting switching function.

5. The application method of the emulsion separation membrane according to claim 4, wherein, when separating oil-in-water nanoemulsions, the gas-responsive nanoemulsion separation membrane is placed in a deionized water environment and is converted into a hydrophilic / underwater oleophobic separation membrane by bubbling CO2 for 10-20 minutes to separate the oil-in-water nanoemulsions.

6. The application method of the emulsion separation membrane according to claim 4, wherein, when separating water-in-oil nanoemulsions, the gas-responsive nanoemulsion separation membrane that has not been treated by CO2 is directly used to separate the water-in-oil nanoemulsions; or the gas-responsive nanoemulsion separation membrane is placed in a deionized water environment, is converted into a hydrophobic / oleophilic separation membrane by bubbling N2 or direct heating for 10-20 minutes, and is then used to separate the water-in-oil nanoemulsions. ​ ​

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