Gas-responsive nanoemulsion separation membrane and method of use thereof

Abstract

A gas-responsive nano-emulsion separation membrane and its application method, the present application belongs to the field of chemical separation technology, specifically relates to oil-water separation membrane. The separation membrane is woven by polar yarn, the surface of the polar yarn is covered with a polymer coating, the polymer coating is prepared by polymerization reaction of carbon dioxide responsive monomer and hard end monomer; the carbon dioxide responsive monomer is a monomer containing end double bond and tertiary amine response group; the hard end monomer is an unsaturated carbonyl compound containing end double bond; the sum of the warp density and the weft density of the woven is between 300T-400T, the pore size distribution of more than 80-90% of the separation membrane is 0.1-0.3um; the separation membrane is used for separating nano-scale dispersed phase emulsion, the nano-scale dispersed phase emulsion is oil-in-water emulsion or water-in-oil emulsion with dispersed phase particle size of 20nm-50nm. The separation membrane has switchable surface wettability, and can realize on-demand separation of water-in-oil emulsion and oil-in-water emulsion by adjusting the surface wettability.

Description

Technical Field

[0001] The present invention belongs to the field of chemical separation technology, relates to an oil-water separation membrane, and in particular to a single-pore gas-responsive nanoemulsion separation membrane and a preparation method and a use method thereof. Background Art

[0002] With the continuous strengthening of industrialization, the purification and separation of various types of oil-water mixtures produced by the oil extraction industry, ocean shipping industry, food industry, metalworking industry, etc. is a very serious problem. Membrane separation method is considered to be an emerging technology in the field of oil-water separation at this stage due to its advantages such as low cost, simple operation and high selectivity. However, there are still many difficulties in separating emulsions with nanoscale dispersed phases using membrane separation methods. The dispersed phase particle size of nanoemulsions is between 0-300 nanometers, and conventional emulsion separation membrane materials have pores with a wide distribution of 0-3 microns, which makes it difficult to separate emulsions of this size, especially emulsions with a particle size below 100 nanometers. It is even more difficult to separate them efficiently. Therefore, it is very important to develop a membrane material that can achieve efficient separation of nanoscale dispersed phase emulsions.

[0003] Nanoemulsions include both water-in-oil and oil-in-water nanoemulsions, while membrane materials typically have a single wettability: most membrane materials are either oleophilic / hydrophobic, enabling separation of water-in-oil emulsions, or hydrophilic / submerged oleophobic, enabling separation of oil-in-water emulsions. This means that most membrane materials can only separate a single type of emulsion. However, in practice, the composition of oil-water mixtures is often complex, making it crucial to controllably switch the membrane surface wettability to achieve on-demand oil-water separation.

[0004] Existing wettability switchable membranes include pre-wetting membranes, Janus membranes, and stimuli-responsive membranes. Pre-wetted membranes have a high affinity for both water and oil. Wetting the membrane with water results in a hydrophilic / underwater oleophobic membrane, while wetting the membrane with oil results in an oleophilic / oil-underwater hydrophobic membrane. However, the high affinity of pre-wetted membranes for oil inevitably leads to serious membrane fouling. Janus membranes are hydrophilic on one side and oleophilic on the other. Turning the hydrophilic side upward results in a hydrophilic / underwater oleophobic membrane, while turning the oleophilic side upward results in an oleophilic / oil-underwater hydrophobic membrane. Janus membrane materials are generally complex to prepare and are also subject to severe oil contamination. Stimuli-responsive membrane materials can change their physical and chemical properties in response to external stimuli (such as light, electricity, pH, heat, and chemicals), thereby switching surface wettability. However, in practice, the separation system is often turbid and opaque, making it difficult for light to penetrate the emulsion and reach the membrane. pH and chemical responses can cause chemical accumulation in the system, and electrical and thermal responses require significant energy consumption when the separation system is very large.

[0005] Compared with the above-mentioned wettability switching strategy, the carbon dioxide stimulus-responsive wettability switching strategy has a wide range of applicable scenarios, low energy consumption, is easy to remove and does not cause secondary pollution, and carbon dioxide is safe, stable and easily available. Therefore, carbon dioxide stimulus-responsive separation membranes have very broad prospects in the field of oil-water separation. However, existing carbon dioxide responsive separation membranes are generally prepared by conventional means such as blending (physical mixing of carbon dioxide responsive polymers with other polymers) and surface grafting (grafting carbon dioxide responsive polymers on the membrane surface through chemical bonds), so there is a low grafting rate of responsive polymers, resulting in a slow response speed and poor separation performance. There are also problems such as uneven pore size distribution that can only achieve the separation of microemulsions or even can only achieve the separation of stratified oil-water mixtures but cannot achieve the separation of nanoemulsions.

[0006] CN114259889A The present invention relates to an emulsion separation membrane and its preparation method and use method. The emulsion separation membrane includes a fabric and a coating coated on the surface of the fabric. The preparation method includes S1, preparation of PMMA-co-PDEAEMA polymer; S2, preparation of polymer solution; S3, preparation of polymer membrane coated yarn; S4, manufacture of emulsion separation membrane. The use method is that when the emulsion is in an oil-in-water state, an oil-wettable emulsion separation membrane is used for separation; when the emulsion is in an oil-in-water state, the oil-wettable emulsion separation membrane is converted into a water-wettable emulsion separation membrane before separation. However, the adhesion problem between the polymer coating and the yarn is not considered, resulting in insufficient bonding force and uneven pore size distribution. The separation experiment can only be carried out under the action of gravity, resulting in flux attenuation. Summary of the Invention

[0007] In view of the above problems, the object of the present invention is to provide a gas-responsive nanoemulsion separation membrane, wherein the separation membrane is woven from polar yarns, the surface of the polar yarns is covered with a polymer coating, and the polymer coating is prepared by the polymerization reaction of a carbon dioxide-responsive monomer and a hard-end monomer;

[0008] The carbon dioxide responsive monomer is a monomer containing a terminal double bond and a tertiary amine responsive group; the hard end monomer is an unsaturated carbonyl compound containing a terminal double bond;

[0009] The sum of the warp density and the weft density of the weaving is between 300T and 400T, and the pore size distribution range of more than 80-90% of the separation membrane is 0.1-0.3um;

[0010] The separation membrane is used for separating nano-scale dispersed phase emulsions, and the nano-scale dispersed phase emulsions are oil-in-water emulsions or water-in-oil emulsions with dispersed phase particle sizes between 20 nm and 50 nm.

[0011] The carbonyl and ester groups in the polymer coating have high polarity, and the polarity of the carbonyl and ester bonds easily forms large hydrogen bonds with excellent adhesion to the polar yarns, thus avoiding the phenomenon of coating separation during the process of passing carbon dioxide gas into the separation membrane.

[0012] In one embodiment, the polar yarn includes any one or more of cotton yarn, polyester yarn, spandex yarn, nylon yarn, acrylic yarn, glass fiber yarn or carbon fiber yarn.

[0013] In one embodiment, the yarn has a specification of any one or more combinations of 20-150 deniers.

[0014] In one embodiment, the monomer containing a tertiary amine responsive group includes one or more of N,N-dimethylphenylene glycol, dimethylaminoethyl methacrylate, or diethylaminoethyl methacrylate;

[0015] The terminal double bond-containing unsaturated carbonyl compound includes one or more of hydroxyethyl methacrylate, 2-ethoxyethyl methacrylate, N-(2-aminoethyl)methacrylamide or alkyl methacrylate.

[0016] In one embodiment, a carbon dioxide responsive monomer and a hard-end monomer are added to a solvent in a mass ratio of 1:0.5-2, an initiator is added, and the mixture is heated and stirred in a nitrogen atmosphere for reaction. The polymer is separated and purified to obtain a polymer solution with a mass fraction of 5 to 20 wt% and uniformly coated on the surface of the polar yarn.

[0017] In one embodiment, the heating and stirring reaction time is 24 to 48 hours at a temperature of 65 to 95° C.; the separation and purification method is to add excess n-hexane to precipitate the polymer, take out the precipitated polymer and dry it in an oven.

[0018] In one embodiment, the initiator includes a peroxide initiator or an azo initiator, the azo initiator is preferably azobisisobutyronitrile or azobisisoheptanenitrile, and the peroxide initiator is preferably any one of dibenzoyl peroxide, dodecyl peroxide, tert-butyl pervalerate, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, cumene hydroperoxide, and potassium persulfate;

[0019] The solvent includes one or more of dichloromethane, tetrahydrofuran or ethanol.

[0020] In one embodiment, the specific step of uniformly coating the polymer solution on the surface of the polar yarn is to uniformly coat the polymer solution on the surface of the polar yarn through a sizing machine and then perform heat treatment.

[0021] In one embodiment, the heat treatment is placed in a drying oven at 65° C.-85° C. for 10 to 20 minutes.

[0022] The second object of the present invention is to provide a method for preparing the gas-responsive nanoemulsion separation membrane.

[0023] S1. Preparation of polymer: preparing a carbon dioxide-responsive functional polymer by free radical polymerization of a carbon dioxide-responsive monomer and a hard-end monomer in a solvent;

[0024] S2. Preparation of polymer solution: dissolving the carbon dioxide responsive functional polymer prepared in S1 in a solvent to prepare a polymer solution;

[0025] S3, preparation of polymer coated yarn: uniformly coating the polymer solution prepared in S2 on the yarn surface and heat treating to obtain polymer coated yarn;

[0026] S4. Preparation of a single-pore gas-responsive nanoemulsion separation membrane: The polymer-coated yarn prepared in S3 is woven into a fabric at a certain density using a loom to obtain a hydrophobic and lipophilic single-pore gas-responsive nanoemulsion separation membrane.

[0027] In one embodiment, the mass fraction of the polymer solution in S2 is 5 to 20 wt%.

[0028] In one embodiment, the coating is performed using a sizing machine in S3.

[0029] In one embodiment, the heat treatment method in S3 is: placing the yarn in a drying room at 70° C. for 2-10 minutes to obtain the polymer coated yarn.

[0030] The third object of the present invention is to provide an application of a gas-responsive nanoemulsion separation membrane, wherein the separation membrane is used for separating nanoscale dispersed phase emulsions.

[0031] In one embodiment, the nano-scale dispersed phase emulsion is an oil-in-water emulsion or a water-in-oil emulsion with a dispersed phase particle size between 20 nm and 50 nm.

[0032] In one embodiment, when separating oil-in-water nanoemulsions, the gas-responsive nanoemulsion separation membrane is placed in a water environment and CO2 is introduced for 5-10 minutes to convert it into a hydrophilic / underwater oleophobic separation membrane for separation.

[0033] In one embodiment, when separating the water-in-oil nanoemulsion, a gas-responsive nanoemulsion separation membrane that has not been treated with CO2 is directly used for separation; or the gas-responsive nanoemulsion separation membrane is placed in a water environment and N2 is introduced for 10-30 minutes to convert it into a hydrophobic / lipophilic separation membrane before separation.

[0034] In one embodiment, the wettability switching method is: placing a hydrophobic and oleophilic gas-responsive nanoemulsion separation membrane in a water environment and introducing CO2 for 5-10 minutes to obtain a hydrophilic underwater oleophobic gas-responsive nanoemulsion separation membrane; placing a hydrophilic underwater oleophobic single-pore gas-responsive nanoemulsion separation membrane in a water environment and introducing N2 for 10-30 minutes to obtain a hydrophobic and oleophilic single-pore gas-responsive nanoemulsion separation membrane again.

[0035] Beneficial effects:

[0036] The separation membrane produced by the weaving method used in the present invention has an extremely narrow pore size distribution. Benefiting from the regular microstructure and the properties of the polymer itself, the contact angle of the membrane can reach 0° in the hydrophilic state and can reach more than 150° in the hydrophobic state, both of which fall into the category of superwettability. Therefore, the present invention can effectively achieve the separation of nano-scale dispersed phase emulsions.

[0037] The membrane material described in the present invention has the characteristics of narrow submicron pore size distribution and omnidirectional equivalent flux. The flux and separation efficiency of each part of the fabric membrane are almost the same. By adjusting the weaving density, the submicron narrow distribution of membrane pore size and the reversible switching of membrane surface wettability can be achieved to realize the separation of nanoemulsions.

[0038] The membrane material of the present invention has switchable surface wettability, enabling on-demand separation of water-in-oil and oil-in-water emulsions by adjusting the surface wettability. The membrane material also exhibits self-cleaning capabilities. Under alternating stimulation by CO₂ and N₂, the gas-responsive polymer coating continuously switches between hydrophobic and oleophilic properties, and hydrophilic and underwater oleophobic properties, effectively removing oil stains and achieving self-cleaning. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Comparison of the nanoemulsion separation efficiency of the nanoemulsion separation membrane prepared in the example before and after tape stripping (a), ultrasonic cleaning (b), and knife scratching (c) tests.

[0040] Figure 2 Particle size distribution of n-hexane oil-in-water emulsion (a); particle size distribution of n-hexane oil-in-water emulsion (b).

[0041] Figure 3 Microstructure of gas-responsive nanoemulsion separation membrane-1, scale bars in a and b are 200 μm and 100 μm, respectively.

[0042] Figure 4 Microstructure of gas-responsive nanoemulsion separation membrane-2.

[0043] Figure 5 Microstructure of gas-responsive nanoemulsion separation membrane-3.

[0044] Figure 6 Microstructure of gas-responsive nanoemulsion separation membrane-4.

[0045] Figure 7 Microstructure of the separation membrane of Comparative Example 6. DETAILED DESCRIPTION

[0046] Permeation flux test method for water-in-oil emulsion and oil-in-water emulsion:

[0047] Use a dead-end filtration device to test the flux of water-in-oil emulsions and oil-in-water emulsions. Record the amount of permeate v in a certain filtration time t. s is the effective permeation area of ​​the filtration device. The flux F can be calculated according to the following formula:

[0048] F=v / st

[0049] Test method for separation efficiency of water-in-oil emulsion and oil-in-water emulsion:

[0050] The water content of the water-in-oil emulsion feed and filtrate is measured by a Karl Fischer moisture analyzer, and the oil content of the oil-in-water emulsion feed and filtrate is measured by a total organic carbon analyzer. The separation efficiency η can be calculated according to the following formula:

[0051] η=(1-cp / cf)×100%

[0052] Where Cf and Cp are the concentrations of feed solution and filtrate respectively.

[0053] Preparation method of water-in-oil nanoemulsion:

[0054] Water and oil were mixed in a volume ratio of 1:99, surfactant was added, ultrasonicated for more than 1 hour, and diluted several times with oil to nanoparticle size. The specific particle size of the dispersed phase droplets was measured using a nanoparticle size analyzer. The average particle size of the n-hexane oil-in-water emulsion was about 40 nm, and the particle size distribution was as follows: Figure 2 .

[0055] Preparation method of oil-in-water nanoemulsion:

[0056] Water and oil were mixed in a volume ratio of 99:1, surfactant was added, ultrasonicated for more than 1 hour, diluted several times with water to nanoparticle size, and the specific particle size of the dispersed phase droplets was measured using a nanoparticle size analyzer. The average particle size of the n-hexane water-in-oil emulsion was about 40 nm, and the particle size distribution was as follows: Figure 2 .

[0057] The present invention will be described in detail below with reference to the following examples so that those skilled in the art can better understand the present invention. However, the present invention is not limited to the following examples.

[0058] Example 1 Preparation of Gas-Responsive Nanoemulsion Separation Membrane-1

[0059] In this embodiment, the polymer is formed by free radical polymerization of two monomers, DMAEMA (a carbon dioxide responsive monomer) and HEMA (a hard monomer), in a solvent. The amount of initiator used is 1% of the total mass of the DMAEMA and HEMA monomers.

[0060] The method for preparing the above-mentioned nanoemulsion separation membrane comprises the following specific steps:

[0061] S1. Preparation of polymer: DMAEMA monomer and HEMA monomer were dissolved in tetrahydrofuran at a mass ratio of 1:0.5, and azobisisobutyronitrile (initiator) was added. The mixture was heated and stirred in a nitrogen atmosphere for 24 hours at a heating temperature of 65° C., and an excess of n-hexane was added to precipitate the polymer. The precipitated polymer was taken out and dried in an oven;

[0062] S2. Preparation of polymer solution: dissolving the carbon dioxide responsive functional polymer prepared in S1 in ethanol to prepare a polymer solution with a mass fraction of 5 wt%;

[0063] S3. Preparation of polymer coated yarn: The polymer solution prepared in S2 was uniformly coated on the surface of spandex yarn containing carbonyl groups using a sizing machine and heat treated in a drying oven at 65° C. for 10 min to obtain the polymer coated yarn;

[0064] S4. Preparation of gas-responsive nanoemulsion separation membrane: The polymer membrane-coated yarn prepared in step S3 was woven into a fabric with a sum of warp and weft densities of 300T by a loom to prepare a hydrophobic and oleophilic gas-responsive nanoemulsion separation membrane-1 with a pore size of 0.18 μm.

[0065] Example 2 Wettability switching process of gas-responsive nanoemulsion separation membrane-1

[0066] When needed, the hydrophobic / oleophilic single pore size gas-responsive nanoemulsion separation membrane-1 was placed in a water environment and CO2 was introduced for 5 minutes to obtain a hydrophilic / underwater oleophobic single pore size gas-responsive nanoemulsion separation membrane. The water contact angle of the membrane in the air at this time was measured using a contact angle meter, and the contact angle was measured to be 0°.

[0067] When needed, the hydrophilic / underwater oleophobic single-pore gas-responsive nanoemulsion separation membrane-1 was placed in a water environment and nitrogen was introduced for 10 minutes to obtain a hydrophobic / oleophilic single-pore gas-responsive nanoemulsion separation membrane again. The water contact angle of the membrane in air at this time was measured using a contact angle meter, and the contact angle was measured to be 151.2°.

[0068] Example 3 Performance Testing of Gas-Responsive Nanoemulsion Separation Membrane-1

[0069] When the gas-responsive nanoemulsion separation membrane-1 is used to separate the oil-water mixture, when the mixture type is oil-water nanoemulsion, a hydrophobic / lipophilic separation membrane is used for separation. The separation performance test data are shown in Table 1;

[0070] When the mixture type is an oil-in-water nanoemulsion, the hydrophobic / oleophilic separation membrane is placed in a water environment and CO2 is introduced for 5 minutes to convert it into a hydrophilic / underwater oleophobic separation membrane, and then separation is performed. The separation performance test data are shown in Table 1;

[0071] When the water-in-oil nanoemulsion needs to be separated again, the hydrophilic / underwater oleophobic separation membrane is placed in an aqueous environment and nitrogen is introduced for 10 minutes to convert it back into a hydrophobic / oleophilic separation membrane before separation.

[0072] After 50 cycles of separation, the separation efficiency of the prepared separation membrane for n-hexane oil-in-water nanoemulsion (40 nm) and oil-in-water nanoemulsion (40 nm) can be maintained above 99%.

[0073] Tape stripping experiment: The polymer film is adhered to the tape and then peeled off to test the effect of the number of tape stripping times on the separation efficiency of the polymer film.

[0074] Ultrasonic cleaning experiment: The polymer membrane was placed in an ultrasonic cleaning machine for cleaning to test the effect of ultrasonic cleaning time on membrane separation efficiency.

[0075] Knife scratching experiment: The polymer membrane was scratched 30 times horizontally and 30 times vertically with a knife, with each 30 scratches being considered as one cycle, to test the effect of the number of knife scratching cycles on the membrane separation performance.

[0076] The nanoemulsion separation membrane prepared by the present invention still maintains a high nanoemulsion separation efficiency after tape stripping, ultrasonic cleaning, knife scratching and other tests, proving the strong bonding force between the coating and the yarn. The specific results are shown in Figure 1 .

[0077] The microstructure of the gas-responsive nanoemulsion separation membrane-1 was obtained by scanning electron microscopy. Figure 3 shown.

[0078] Example 4 Preparation of Gas-Responsive Nanoemulsion Separation Membrane-2

[0079] In this embodiment, the polymer is formed by free radical polymerization of two monomers, DMSt (a carbon dioxide responsive monomer) and HEMA (a hard monomer), in a solvent, and the amount of initiator used is 1% of the total mass of the DMSt and HEMA monomers.

[0080] The method for preparing the above-mentioned nanoemulsion separation membrane comprises the following specific steps:

[0081] S1. Preparation of polymer: DMSt monomer and HEMA monomer were dissolved in tetrahydrofuran at a mass ratio of 1:1, and an initiator, azobisisoheptane, was added. The mixture was heated and stirred in a nitrogen atmosphere at 75°C for 36 hours. An excess of n-hexane was added to precipitate the polymer, and the precipitated polymer was removed and dried in an oven.

[0082] S2. Preparation of polymer solution: dissolving the carbon dioxide responsive functional polymer prepared in S1 in ethanol to prepare a polymer solution with a mass fraction of 10 wt%;

[0083] S3. Preparation of polymer coated yarn: The polymer solution prepared in S2 was uniformly coated on the surface of nylon yarn containing carbonyl groups using a sizing machine and heat treated in a drying room at 75°C for 15 minutes to obtain the polymer coated yarn;

[0084] S4. Preparation of gas-responsive nanoemulsion separation membrane: The polymer membrane-coated yarn prepared in step S3 was woven into a fabric with a sum of warp and weft densities of 330T by a loom to prepare a hydrophobic and oleophilic gas-responsive nanoemulsion separation membrane-2 with a pore size of 0.15 μm.

[0085] Example 5 Wettability switching process of gas-responsive nanoemulsion separation membrane-2

[0086] When needed, the hydrophobic / oleophilic single pore size gas-responsive nanoemulsion separation membrane was placed in a water environment and CO2 was introduced for 6 minutes to obtain a hydrophilic / underwater oleophobic single pore size gas-responsive nanoemulsion separation membrane. The water contact angle of the membrane in air at this time was measured using a contact angle meter, and the contact angle was measured to be 0°.

[0087] When needed, the hydrophilic / underwater oleophobic single-pore gas-responsive nanoemulsion separation membrane was placed in an aqueous environment and nitrogen was introduced for 20 minutes to obtain a hydrophobic / oleophilic single-pore gas-responsive nanoemulsion separation membrane again. The water contact angle of the membrane in air at this time was measured using a contact angle meter, and the contact angle was measured to be 152.6°.

[0088] Example 6 Performance Testing of Gas-Responsive Nanoemulsion Separation Membrane-2

[0089] When the gas-responsive nanoemulsion separation membrane-2 is used to separate the oil-water mixture, when the mixture type is oil-water nanoemulsion, a hydrophobic / lipophilic separation membrane is used for separation. The separation performance test data are shown in Table 1;

[0090] When the mixture type is an oil-in-water nanoemulsion, the hydrophobic / oleophilic separation membrane is placed in a water environment and CO2 is introduced for 6 minutes to convert it into a hydrophilic / underwater oleophobic separation membrane, and then separation is performed. The separation performance test data are shown in Table 1;

[0091] When the water-in-oil nanoemulsion needs to be separated again, the hydrophilic / underwater oleophobic separation membrane is placed in an aqueous environment and nitrogen is introduced for 20 minutes to convert it back into a hydrophobic / oleophilic separation membrane before separation.

[0092] After 50 cycles of separation, the separation efficiency of the prepared separation membrane for n-hexane oil-in-water nanoemulsion (40 nm) and oil-in-water nanoemulsion (40 nm) can be maintained above 99%.

[0093] The microstructure of the gas-responsive nanoemulsion separation membrane-2 was obtained by scanning electron microscopy. Figure 4 shown.

[0094] Example 7 Preparation of Gas-Responsive Nanoemulsion Separation Membrane-3

[0095] In this embodiment, the polymer is formed by free radical polymerization of two monomers, DMSt, a carbon dioxide responsive monomer, and AEMA, a hard monomer, in a solvent. The amount of initiator used is 1% of the total mass of the DMSt monomer and the AEMA monomer.

[0096] The method for preparing the above-mentioned nanoemulsion separation membrane comprises the following specific steps:

[0097] S1. Preparation of polymer: DMAEMA monomer and HEMA monomer were dissolved in tetrahydrofuran at a mass ratio of 1:1.5, dibenzoyl peroxide (initiator) was added, and the mixture was heated and stirred in a nitrogen atmosphere for 36 hours at a heating temperature of 85°C. Excess n-hexane was added to precipitate the polymer, and the precipitated polymer was taken out and dried in an oven;

[0098] S2. Preparation of polymer solution: dissolving the carbon dioxide responsive functional polymer prepared in S1 in ethanol to prepare a polymer solution with a mass fraction of 15 wt%;

[0099] S3. Preparation of polymer coated yarn: The polymer solution prepared in S2 was uniformly coated on the surface of nylon yarn containing carbonyl groups using a sizing machine and heat treated in a drying oven at 80° C. for 15 min to obtain the polymer coated yarn;

[0100] S4. Preparation of gas-responsive nanoemulsion separation membrane: The polymer membrane-coated yarn prepared in step S3 was woven into a fabric with a sum of warp and weft densities of 360T by a loom to prepare a hydrophobic and oleophilic gas-responsive nanoemulsion separation membrane-3 with a pore size of 0.13 μm.

[0101] Example 8 Wettability switching process of gas-responsive nanoemulsion separation membrane-3

[0102] When needed, the hydrophobic / oleophilic single pore size gas-responsive nanoemulsion separation membrane was placed in a water environment and CO2 was introduced for 8 minutes to obtain a hydrophilic / underwater oleophobic single pore size gas-responsive nanoemulsion separation membrane. The water contact angle of the membrane in air at this time was measured using a contact angle meter, and the contact angle was measured to be 0°.

[0103] When needed, the hydrophilic / underwater oleophobic single-pore gas-responsive nanoemulsion separation membrane was placed in an aqueous environment and nitrogen was introduced for 20 minutes to obtain a hydrophobic / oleophilic single-pore gas-responsive nanoemulsion separation membrane again. The water contact angle of the membrane in air at this time was measured using a contact angle meter, and the contact angle was measured to be 151.7°.

[0104] Example 9 Performance Testing of Nanoemulsion Separation Membrane-3

[0105] When the gas-responsive nanoemulsion separation membrane-3 is used to separate the oil-water mixture, when the mixture type is oil-water nanoemulsion, a hydrophobic / lipophilic separation membrane is used for separation. The separation performance test data are shown in Table 1;

[0106] When the mixture type is an oil-in-water nanoemulsion, the hydrophobic / oleophilic separation membrane is placed in a water environment and CO2 is introduced for 8 minutes to convert it into a hydrophilic / underwater oleophobic separation membrane, and then separation is performed. The separation performance test data are shown in Table 1;

[0107] When the water-in-oil nanoemulsion needs to be separated again, the hydrophilic / underwater oleophobic separation membrane is placed in an aqueous environment and nitrogen is introduced for 20 minutes to convert it back into a hydrophobic / oleophilic separation membrane before separation.

[0108] After 50 cycles of separation, the separation efficiency of the prepared separation membrane for n-hexane oil-in-water nanoemulsion (40 nm) and oil-in-water nanoemulsion (40 nm) can be maintained above 99%.

[0109] The microstructure of the gas-responsive nanoemulsion separation membrane-3 was obtained by scanning electron microscopy. Figure 5 shown.

[0110] Example 10 Preparation of Gas-Responsive Nanoemulsion Separation Membrane-4

[0111] In this embodiment, the polymer is formed by free radical polymerization of two monomers, DMAEMA, a carbon dioxide-responsive monomer, and AEMA, a hard monomer, in a solvent. The amount of initiator used is 1% of the total mass of the DMAEMA and AEMA monomers.

[0112] The method for preparing the above-mentioned nanoemulsion separation membrane comprises the following specific steps:

[0113] S1. Preparation of polymer: DMAEMA monomer and AEMA monomer were dissolved in tetrahydrofuran at a mass ratio of 1:2, and an initiator, dodecyl peroxide, was added. The mixture was heated and stirred in a nitrogen atmosphere for 48 hours at a heating temperature of 95° C. An excess of n-hexane was added to precipitate the polymer, and the precipitated polymer was removed and dried in an oven;

[0114] S2. Preparation of polymer solution: dissolving the carbon dioxide responsive functional polymer prepared in S1 in ethanol to prepare a polymer solution with a mass fraction of 20 wt%;

[0115] S3. Preparation of polymer coated yarn: The polymer solution prepared in S2 was uniformly coated on the surface of polyester yarn containing carbonyl groups using a sizing machine and heat treated in a drying room at 85°C for 20 minutes to obtain the polymer coated yarn;

[0116] S4. Preparation of gas-responsive nanoemulsion separation membrane: The polymer membrane-coated yarn prepared in step S3 was woven into a fabric with a sum of warp and weft densities of 400T by a loom to prepare a hydrophobic and oleophilic gas-responsive nanoemulsion separation membrane-4 with a pore size of 0.11 μm.

[0117] Example 11 Wettability switching process of gas-responsive nanoemulsion separation membrane-4

[0118] When needed, the hydrophobic / oleophilic single pore size gas-responsive nanoemulsion separation membrane was placed in a water environment and CO2 was introduced for 10 minutes to obtain a hydrophilic / underwater oleophobic single pore size gas-responsive nanoemulsion separation membrane. The water contact angle of the membrane in air at this time was measured using a contact angle meter, and the contact angle was measured to be 0°.

[0119] When needed, the hydrophilic / underwater oleophobic single-pore gas-responsive nanoemulsion separation membrane was placed in an aqueous environment and nitrogen was introduced for 30 minutes to obtain a hydrophobic / oleophilic single-pore gas-responsive nanoemulsion separation membrane again. The water contact angle of the membrane in air at this time was measured using a contact angle meter, and the contact angle was measured to be 150.5°.

[0120] Example 12 Performance Testing of Gas-Responsive Nanoemulsion Separation Membrane-4

[0121] When the gas-responsive nanoemulsion separation membrane-4 is used to separate the oil-water mixture, when the mixture type is oil-water nanoemulsion, a hydrophobic / lipophilic separation membrane is used for separation. The separation performance test data are shown in Table 1;

[0122] When the mixture type is oil-in-water nanoemulsion, the hydrophobic / oleophilic separation membrane is placed in a water environment and CO2 is introduced for 10 minutes to convert it into a hydrophilic / underwater oleophobic separation membrane, and then separation is performed. The separation performance test data are shown in Table 1;

[0123] When the water-in-oil nanoemulsion needs to be separated again, the hydrophilic / underwater oleophobic separation membrane is placed in an aqueous environment and nitrogen is introduced for 30 minutes to convert it back into a hydrophobic / oleophilic separation membrane before separation.

[0124] After 50 cycles of separation, the separation efficiency of the prepared separation membrane for n-hexane oil-in-water nanoemulsion (40 nm) and oil-in-water nanoemulsion (40 nm) can be maintained above 99%.

[0125] The microstructure of the gas-responsive nanoemulsion separation membrane-4 was obtained by scanning electron microscopy. Figure 6 shown.

[0126] Comparative Example 1 Effect of cross-linking agent on separation efficiency

[0127] The method for preparing the above-mentioned single pore size nanoemulsion separation membrane comprises the following specific steps:

[0128] S1. Preparation of raw material solution: DMAEMA monomer and HEMA monomer are dissolved in tetrahydrofuran at a mass ratio of 1:0.5, BIS crosslinking agent is added, and then azobisisobutyronitrile initiator is added and stirred to obtain a raw material solution; the amount of initiator used is 1% of the total mass of DMAEMA monomer and HEMA monomer.

[0129] S2. Preparation of polymer coated yarn: The raw material solution prepared in S1 was evenly coated on the surface of the spandex yarn using a sizing machine and heat treated in a drying room at 70°C for 12 hours to obtain the polymer coated yarn;

[0130] S3. Preparation of single-pore-size gas-responsive nanoemulsion separation membrane: The polymer membrane-coated yarn prepared in step S2 was woven into a fabric with a sum of warp and weft densities of 300T by a loom to prepare a hydrophobic and oleophilic nanoemulsion separation membrane with a pore size of 0.14 μm.

[0131] S4. Wettability switching: When needed, the hydrophobic / oleophilic single-pore gas-responsive nanoemulsion separation membrane is placed in a water environment and CO2 is introduced for 10 minutes to obtain a hydrophilic / underwater oleophobic single-pore gas-responsive nanoemulsion separation membrane; when needed, the hydrophilic / underwater oleophobic single-pore gas-responsive nanoemulsion separation membrane is placed in a water environment and N2 is introduced for 20 minutes to obtain a hydrophobic / oleophilic single-pore gas-responsive nanoemulsion separation membrane again.

[0132] When using the above-mentioned single pore size gas-responsive nanoemulsion separation membrane to separate an oil-water mixture, when the mixture type is oil-in-water nanoemulsion, a hydrophobic / oleophilic separation membrane is used for separation, and the separation performance test data are shown in Table 1; when the mixture type is oil-in-water nanoemulsion, the hydrophobic / oleophilic separation membrane is placed in a water environment and CO2 is introduced for 10 minutes to convert it into a hydrophilic / underwater oleophobic separation membrane, and then separation is performed, and the separation performance test data are shown in Table 1; when the oil-in-water nanoemulsion needs to be separated again, the hydrophilic / underwater oleophobic separation membrane is placed in a water environment and N2 is introduced for 20 minutes to convert it again into a hydrophobic / oleophilic separation membrane, and then separation is performed. After 5 cycles of separation, the separation efficiency of the prepared separation membrane for n-hexane oil-in-water nanoemulsion (40nm) and oil-in-water nanoemulsion (40nm) dropped to below 90%.

[0133] By comparing with Comparative Example 1, it was found that the addition of a cross-linker would cause the flexible polymer coating originally formed by entanglement between polymer chains to become a rigid solid coating in which the polymer chains were connected by chemical bonds. This rigid coating is fragile during recycling and falls off from the yarn surface, resulting in a decrease in separation efficiency.

[0134] Comparative Example 2: Effect of no hardening monomer on separation efficiency

[0135] The method for preparing the above-mentioned single pore size nanoemulsion separation membrane comprises the following specific steps:

[0136] S1. Preparation of polymer: DMAEMA monomer was dissolved in tetrahydrofuran, and azobisisobutyronitrile (initiator) was added. The mixture was heated and stirred in a nitrogen atmosphere for 36 hours at a heating temperature of 75°C. An excess of n-hexane was added to precipitate the polymer. The precipitated polymer was taken out and dried in an oven. The amount of initiator used was 1% of the total mass of the DMAEMA monomer.

[0137] S2. Preparation of polymer solution: dissolving the carbon dioxide responsive functional coating polymer prepared in S1 in ethanol to prepare a polymer solution with a mass fraction of 15 wt%;

[0138] S3. Preparation of polymer coated yarn: The polymer solution prepared in S2 was evenly coated on the surface of the spandex yarn using a sizing machine and heat treated in a drying oven at 75°C for 10 min to obtain the polymer coated yarn;

[0139] S4. Preparation of single-pore gas-responsive nanoemulsion separation membrane: The polymer membrane-coated yarn prepared in step S3 was woven into a fabric with a sum of warp and weft densities of 300T by a loom to prepare a hydrophobic and oleophilic nanoemulsion separation membrane with a pore size of 0.13 μm.

[0140] Wettability switching: When needed, the hydrophobic / oleophilic single-pore gas-responsive nanoemulsion separation membrane is placed in a water environment and CO2 is introduced for 10 minutes to obtain a hydrophilic / underwater oleophobic single-pore gas-responsive nanoemulsion separation membrane; when needed, the hydrophilic / underwater oleophobic single-pore gas-responsive nanoemulsion separation membrane is placed in a water environment and N2 is introduced for 20 minutes to obtain a hydrophobic / oleophilic single-pore gas-responsive nanoemulsion separation membrane again.

[0141] When using the above-mentioned single pore size gas-responsive nanoemulsion separation membrane to separate an oil-water mixture, when the mixture type is oil-in-water nanoemulsion, a hydrophobic / oleophilic separation membrane is used for separation, and the separation performance test data are shown in Table 1; when the mixture type is oil-in-water nanoemulsion, the hydrophobic / oleophilic separation membrane is placed in a water environment and CO2 is introduced for 10 minutes to convert it into a hydrophilic / underwater oleophobic separation membrane, and then separation is performed, and the separation performance test data are shown in Table 1; when the oil-in-water nanoemulsion needs to be separated again, the hydrophilic / underwater oleophobic separation membrane is placed in a water environment and N2 is introduced for 20 minutes to convert it again into a hydrophobic / oleophilic separation membrane, and then separation is performed. After three cycles of separation, the separation efficiency of the prepared separation membrane for n-hexane oil-in-water nanoemulsion (40nm) and oil-in-water nanoemulsion (40nm) dropped to below 90%.

[0142] By comparing with Comparative Example 2, it was found that the adhesion of the pure responsive monomer polymer coating prepared without adding a hardening monomer was significantly reduced, and it was easy to fall off from the yarn surface during recycling, resulting in a decrease in separation efficiency.

[0143] Comparative Example 3 Effect of Improper Ratio of Soft and Hard Monomers on Separation Efficiency

[0144] In this embodiment, the polymer is formed by free radical polymerization of two monomers, DMAEMA (a carbon dioxide responsive monomer) and HEMA (a hard monomer), in a solvent. The amount of initiator used is 1% of the total mass of the DMAEMA and HEMA monomers.

[0145] The method for preparing the above-mentioned nanoemulsion separation membrane comprises the following specific steps:

[0146] S1. Preparation of polymer: DMAEMA monomer and HEMA monomer were dissolved in tetrahydrofuran at a mass ratio of 1:0.2, and azobisisobutyronitrile (initiator) was added. The mixture was heated and stirred in a nitrogen atmosphere for 24 hours at a heating temperature of 65° C., and an excess of n-hexane was added to precipitate the polymer. The precipitated polymer was taken out and dried in an oven;

[0147] S2. Preparation of polymer solution: dissolving the carbon dioxide responsive functional polymer prepared in S1 in ethanol to prepare a polymer solution with a mass fraction of 5 wt%;

[0148] S3. Preparation of polymer coated yarn: The polymer solution prepared in S2 was evenly coated on the surface of the spandex yarn using a sizing machine and heat treated in a drying room at 65° C. for 10 min to obtain the polymer coated yarn;

[0149] S4. Preparation of gas-responsive nanoemulsion separation membrane: The polymer membrane-coated yarn prepared in step S3 was woven into a fabric with a sum of warp and weft densities of 300T by a loom to prepare a hydrophobic and oleophilic nanoemulsion separation membrane with a pore size of 0.17 μm.

[0150] Wettability switching: When needed, the hydrophobic / oleophilic single-pore gas-responsive nanoemulsion separation membrane is placed in a water environment and CO2 is introduced for 5 minutes to obtain a hydrophilic / underwater oleophobic single-pore gas-responsive nanoemulsion separation membrane; when needed, the hydrophilic / underwater oleophobic single-pore gas-responsive nanoemulsion separation membrane is placed in a water environment and N2 is introduced for 10 minutes to obtain a hydrophobic / oleophilic single-pore gas-responsive nanoemulsion separation membrane again.

[0151] When the above-mentioned single pore size gas-responsive nanoemulsion separation membrane is used to separate the oil-water mixture, when the mixture type is oil-in-water nanoemulsion, a hydrophobic / oleophilic separation membrane is used for separation, and the separation performance test data are shown in Table 1; when the mixture type is oil-in-water nanoemulsion, the hydrophobic / oleophilic separation membrane is placed in a water environment and CO2 is introduced for 5 minutes to convert it into a hydrophilic / underwater oleophobic separation membrane, and then separation is performed, and the separation performance test data are shown in Table 1; when the oil-in-water nanoemulsion needs to be separated again, the hydrophilic / underwater oleophobic separation membrane is placed in a water environment and N2 is introduced for 10 minutes to convert it into a hydrophobic / oleophilic separation membrane again, and then separation is performed. After 6 cycles of separation, the separation efficiency of the prepared separation membrane for n-hexane oil-in-water nanoemulsion (40nm) and oil-in-water nanoemulsion (40nm) dropped to below 90%.

[0152] By comparing with Comparative Example 3, it is found that when the amount of hard monomer used is too small, the adhesion of the polymer coating is significantly reduced, and it is easy to fall off from the yarn surface during recycling, resulting in a decrease in separation efficiency.

[0153] Comparative Example 4: Effect of Improper Ratio of Soft and Hard Monomers on Separation Efficiency

[0154] In this embodiment, the polymer is formed by free radical polymerization of two monomers, DMAEMA (a carbon dioxide responsive monomer) and HEMA (a hard monomer), in a solvent. The amount of initiator used is 1% of the total mass of the DMAEMA and HEMA monomers.

[0155] The method for preparing the above-mentioned nanoemulsion separation membrane comprises the following specific steps:

[0156] S1. Preparation of polymer: DMAEMA monomer and HEMA monomer were dissolved in tetrahydrofuran at a mass ratio of 1:5, and azobisisobutyronitrile (initiator) was added. The mixture was heated and stirred in a nitrogen atmosphere at 75° C. for 36 hours. An excess of n-hexane was added to precipitate the polymer. The precipitated polymer was taken out and dried in an oven.

[0157] S2. Preparation of polymer solution: dissolving the carbon dioxide responsive functional polymer prepared in S1 in ethanol to prepare a polymer solution with a mass fraction of 10 wt%;

[0158] S3. Preparation of polymer coated yarn: The polymer solution prepared in S2 was evenly coated on the surface of the spandex yarn using a sizing machine and heat treated in a drying oven at 75°C for 15 minutes to obtain the polymer coated yarn;

[0159] S4. Preparation of gas-responsive nanoemulsion separation membrane: The polymer membrane-coated yarn prepared in step S3 was woven into a fabric with a sum of warp and weft densities of 330T by a loom to prepare a hydrophobic and oleophilic nanoemulsion separation membrane with a pore size of 0.17 μm.

[0160] Wettability switching: When needed, the hydrophobic / oleophilic single-pore gas-responsive nanoemulsion separation membrane is placed in a water environment and CO2 is introduced for 6 minutes to obtain a hydrophilic / underwater oleophobic single-pore gas-responsive nanoemulsion separation membrane; when needed, the hydrophilic / underwater oleophobic single-pore gas-responsive nanoemulsion separation membrane is placed in a water environment and N2 is introduced for 20 minutes to obtain a hydrophobic / oleophilic single-pore gas-responsive nanoemulsion separation membrane again.

[0161] When the above-mentioned single pore size gas responsive nanoemulsion separation membrane is used to separate the oil-water mixture, when the mixture type is oil-in-water nanoemulsion, a hydrophobic / oleophilic separation membrane is used for separation, and the separation performance test data are shown in Table 1; when the mixture type is water-in-oil nanoemulsion, the hydrophobic / oleophilic separation membrane is placed in a water environment and CO2 is introduced for 6 minutes to convert it into a hydrophilic / underwater oleophobic separation membrane, and then separation is performed, and the separation performance test data are shown in Table 1; when the water-in-oil nanoemulsion needs to be separated again, the hydrophilic / underwater oleophobic separation membrane is placed in a water environment and N2 is introduced for 20 minutes to convert it into a hydrophobic / oleophilic separation membrane again, and then separation is performed. After 50 cycles of separation, the separation efficiency of the prepared separation membrane for n-hexane water-in-oil nanoemulsion (40nm) is maintained at more than 99%, while the separation efficiency for water-in-oil nanoemulsion (40nm) is maintained at about 70%.

[0162] By comparing with Comparative Example 4, it is found that when the amount of hard monomer is too large, the amount of responsive monomer is relatively reduced, and there are not enough hydrophilic polymer segments when separating the oil-in-water emulsion, resulting in small flux and low separation efficiency.

[0163] Comparative Example 5 Effect of Low Weaving Density on Separation Efficiency

[0164] In this embodiment, the polymer is formed by free radical polymerization of two monomers, DMSt, a carbon dioxide responsive monomer, and AEMA, a hard monomer, in a solvent. The amount of initiator used is 1% of the total mass of the DMSt monomer and the AEMA monomer.

[0165] The method for preparing the above-mentioned nanoemulsion separation membrane comprises the following specific steps:

[0166] S1. Preparation of polymer: DMSt monomer and AEMA monomer were dissolved in tetrahydrofuran at a mass ratio of 1:1.5, dibenzoyl peroxide (initiator) was added, and the mixture was heated and stirred in a nitrogen atmosphere for 36 hours at a heating temperature of 85°C. Excess n-hexane was added to precipitate the polymer, and the precipitated polymer was taken out and dried in an oven;

[0167] S2. Preparation of polymer solution: dissolving the carbon dioxide responsive functional polymer prepared in S1 in ethanol to prepare a polymer solution with a mass fraction of 15 wt%;

[0168] S3. Preparation of polymer coated yarn: The polymer solution prepared in S2 was evenly coated on the surface of nylon yarn using a sizing machine and heat treated in a drying room at 80°C for 15 minutes to obtain the polymer coated yarn;

[0169] S4. Preparation of gas-responsive nanoemulsion separation membrane: The polymer membrane-coated yarn prepared in step S3 was woven into a fabric with a sum of warp and weft densities of 100T by a loom to prepare a hydrophobic and oleophilic nanoemulsion separation membrane with a pore size of 3.4 μm.

[0170] Wettability switching: When needed, the hydrophobic / oleophilic single-pore gas-responsive nanoemulsion separation membrane is placed in a water environment and CO2 is introduced for 8 minutes to obtain a hydrophilic / underwater oleophobic single-pore gas-responsive nanoemulsion separation membrane; when needed, the hydrophilic / underwater oleophobic single-pore gas-responsive nanoemulsion separation membrane is placed in a water environment and N2 is introduced for 20 minutes to obtain a hydrophobic / oleophilic single-pore gas-responsive nanoemulsion separation membrane again.

[0171] When the above-mentioned single pore size gas-responsive nanoemulsion separation membrane is used to separate the oil-water mixture, when the mixture type is oil-in-water nanoemulsion, a hydrophobic / oleophilic separation membrane is used for separation, and the separation performance test data are shown in Table 1; when the mixture type is water-in-oil nanoemulsion, the hydrophobic / oleophilic separation membrane is placed in a water environment and CO2 is introduced for 8 minutes to convert it into a hydrophilic / underwater oleophobic separation membrane, and then separation is performed, and the separation performance test data are shown in Table 1; when the water-in-oil nanoemulsion needs to be separated again, the hydrophilic / underwater oleophobic separation membrane is placed in a water environment and N2 is introduced for 20 minutes to convert it into a hydrophobic / oleophilic separation membrane again, and then separation is performed. After 50 cycles of separation, the separation efficiency of the prepared separation membrane for n-hexane water-in-oil nanoemulsion (40nm) and water-in-oil nanoemulsion (40nm) was maintained at above 40%.

[0172] By comparing with Comparative Example 5, it is found that when the weaving density is too low, the pore size will become significantly larger and the nanoemulsion separation efficiency will be significantly reduced.

[0173] Table 1

[0174]

[0175]

[0176] Comparative Example 6 Effect of Using Non-polar Yarn on Separation Efficiency

[0177] In this embodiment, the polymer is formed by free radical polymerization of two monomers, DEAEMA (a carbon dioxide responsive monomer) and MMA (a hard monomer), in a solvent. The amount of initiator used is 1% of the total mass of the DMAEMA and MMA monomers.

[0178] The method for preparing the above-mentioned emulsion separation membrane comprises the following specific steps:

[0179] S1. Preparation of polymer: DEAEMA monomer and MMA monomer were dissolved in tetrahydrofuran at a mass ratio of 1:0.5, and azobisisobutyronitrile (initiator) was added. The mixture was heated and stirred in a nitrogen atmosphere for 24 hours at a heating temperature of 65° C. Excess n-hexane was added to precipitate the polymer, and the precipitated polymer was taken out and dried in an oven;

[0180] S2. Preparation of polymer solution: dissolving the carbon dioxide responsive functional polymer prepared in S1 in ethanol to prepare a polymer solution with a mass fraction of 10 wt%;

[0181] S3. Preparation of polymer coated yarn: The polymer solution prepared in S2 was evenly coated on the surface of non-polar polypropylene yarn using a sizing machine and heat treated in a drying room at 70°C for 30 minutes to obtain the polymer coated yarn;

[0182] S4. Preparation of gas-responsive emulsion separation membrane: The polymer membrane-coated yarn prepared in step S3 is woven into a fabric with a sum of warp and weft densities of 300T by a loom to prepare a hydrophobic and oleophilic emulsion separation membrane with a pore size of 0.18-0.6 μm.

[0183] Wettability switching: When needed, the hydrophobic / oleophilic single-pore gas-responsive emulsion separation membrane is placed in a water environment and CO2 is introduced for 10 minutes to obtain a hydrophilic / underwater oleophobic single-pore gas-responsive emulsion separation membrane; when needed, the hydrophilic / underwater oleophobic single-pore gas-responsive emulsion separation membrane is placed in a water environment and N2 is introduced for 20 minutes to obtain a hydrophobic / oleophilic single-pore gas-responsive emulsion separation membrane again.

[0184] When using the above-mentioned single-pore gas-responsive emulsion separation membrane to separate oil-water mixtures, when the mixture type is an oil-in-water emulsion, a hydrophobic / oleophilic separation membrane is used for separation; when the mixture type is an oil-in-water emulsion, the hydrophobic / oleophilic separation membrane is placed in a water environment and CO2 is introduced for 10 minutes to convert it into a hydrophilic / underwater oleophobic separation membrane before separation; when the oil-in-water emulsion needs to be separated again, the hydrophilic / underwater oleophobic separation membrane is placed in a water environment and N2 is introduced for 20 minutes to convert it again into a hydrophobic / oleophilic separation membrane before separation.

[0185] When separating n-hexane oil-in-water microemulsion (3 μm), the separation efficiency is 99.2% and the flux is 327 L / m2·h;

[0186] When separating n-hexane oil-in-water microemulsion (5 μm), the separation efficiency is 99.4% and the flux is 150 L / m2·h;

[0187] When separating n-hexane oil-in-water nanoemulsion (40 nm), the separation efficiency was 83.4% and the flux was 387 L / m2·h;

[0188] When separating n-hexane oil-in-water nanoemulsion (40 nm), the separation efficiency was 85.9% and the flux was 173 L / m2·h.

[0189] The microstructure was obtained by scanning electron microscopy, such as Figure 7 As shown, obvious interface defects appear.

[0190] By comparing with Comparative Example 6, it was found that when non-polar yarn was used as the substrate to prepare the membrane, the bonding force between the polymer coating and the yarn was not sufficient to allow the coating to be evenly wrapped on the yarn surface, resulting in a membrane with a single pore size. It can only be used to separate microemulsions but not further separate nanoemulsions. Moreover, due to the uneven pore size distribution, separation experiments can only be carried out under the action of gravity, resulting in flux attenuation.

[0191] It should be understood that the specific examples herein are only intended to help those skilled in the art better understand the present disclosure, rather than to limit the scope of the present invention.

[0192] It can be understood that the various embodiments described in this specification can be implemented individually or in combination, and the present disclosure is not limited thereto.

[0193] Unless otherwise indicated, all technical and scientific terms used in this disclosure have the same meaning as commonly understood by those skilled in the art in the technical field of this specification. The terms used in this specification are only for the purpose of describing specific embodiments and are not intended to limit the scope of this specification. The term "and / or" used in this specification includes any and all combinations of one or more related listed items. The singular forms "a", "above", and "the" used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0194] The above description is merely a specific embodiment of this specification, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this specification should be included in the scope of protection of this specification. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A gas-responsive nanoemulsion separation membrane, characterized in that: The separation membrane is woven from polar yarns, the surface of the polar yarns is covered with a polymer coating, and the polymer coating is prepared by polymerization of a carbon dioxide responsive monomer and a hard-end monomer; The carbon dioxide responsive monomer is a monomer containing a terminal double bond and a tertiary amine responsive group; the hard end monomer is an unsaturated carbonyl compound containing a terminal double bond; The sum of the warp density and the weft density of the weaving is between 300T and 400T, and the pore size distribution range of more than 80% to 90% of the separation membrane is 0.1 to 0.3 μm; The separation membrane is used to separate nano-scale dispersed phase emulsions, wherein the nano-scale dispersed phase emulsions are oil-in-water emulsions or water-in-oil emulsions with dispersed phase particle sizes between 20 nm and 50 nm; The polar yarn includes any one or more of polyester yarn, nylon yarn or spandex yarn containing carbonyl groups; The monomer containing a double bond and a tertiary amine responsive group includes one or more of N,N-dimethylphenylene glycol, dimethylaminoethyl methacrylate or diethylaminoethyl methacrylate; The terminal double-bond unsaturated carbonyl compound includes one or more of hydroxyethyl methacrylate, 2-ethoxyethyl methacrylate, N-(2-aminoethyl) methacrylamide or alkyl methacrylate; A carbon dioxide responsive monomer and a hard-end monomer are added to a solvent in a mass ratio of 1:0.5-2, an initiator is added, and the mixture is heated and stirred in a nitrogen atmosphere for reaction. The polymer is separated and purified to obtain a polymer solution with a mass fraction of 5-20wt% and uniformly coated on the surface of the polar yarn; the initiator includes a peroxide initiator or an azo initiator.

2. A gas-responsive nanoemulsion separation membrane according to claim 1, characterized in that: The heating and stirring reaction time is 24 to 48 hours at a temperature of 65 to 95° C. The separation and purification method comprises adding excess n-hexane to precipitate the polymer, taking out the precipitated polymer and drying it in an oven.

3. A gas-responsive nanoemulsion separation membrane according to claim 1, characterized in that: The azo initiator is azobisisobutyronitrile or azobisisoheptanenitrile, and the peroxide initiator is any one of dibenzoyl peroxide, dodecyl peroxide, tert-butyl pervalerate, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, cumene hydroperoxide, and potassium persulfate; The solvent includes one or more of dichloromethane, tetrahydrofuran or ethanol.

4. A gas-responsive nanoemulsion separation membrane according to claim 1, characterized in that: The specific step of uniformly coating the polymer solution on the surface of the polar yarn is to uniformly coat the polymer solution on the surface of the polar yarn through a sizing machine and then perform heat treatment.

5. A gas-responsive nanoemulsion separation membrane according to claim 4, characterized in that: The heat treatment is carried out by placing the product in a drying room at 65° C. to 85° C. for 10 to 20 minutes.

6. The use of a gas-responsive nanoemulsion separation membrane according to any one of claims 1 to 5, characterized in that: When separating oil-in-water nanoemulsion, the gas-responsive nanoemulsion separation membrane is placed in a water environment and CO2 is introduced for 5-10 minutes to convert it into a hydrophilic / underwater oleophobic separation membrane for separation.

7. The use of a gas-responsive nanoemulsion separation membrane according to claim 6, characterized in that: When separating water-in-oil nanoemulsions, the gas-responsive nanoemulsion separation membrane that has not been treated with CO2 is directly used for separation; or the gas-responsive nanoemulsion separation membrane is placed in a water environment and N2 is introduced for 10-30 minutes to convert it into a hydrophobic / lipophilic separation membrane before separation.

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