A zwitterion-modified graphene oxide double-layer structure composite membrane and a preparation method and application thereof

Abstract

The application belongs to the technical field of separation membranes, and discloses a zwitterionic modified graphene oxide double-layer structure composite membrane and a preparation method thereof. First, a graphene oxide layer is formed on the surface of a porous supporting base membrane by a vacuum-assisted self-assembly method, and then a zwitterionic layer is constructed on the surface of the graphene oxide layer by a biomimetic co-deposition method to obtain a double-layer structure composite membrane. The zwitterionic layer on the top can improve the hydrophilicity of the membrane surface, strengthen the dissolution process of water molecules on the membrane surface, and improve the separation selectivity; the graphene oxide layer on the bottom serves as a rapid mass transfer channel for molecules, strengthens the diffusion process of molecules, and improves the permeability of the membrane; dopamine can improve the interfacial compatibility between layers, which is conducive to the stability of the membrane structure. The composite membrane prepared by the application can realize the pervaporation process of preferential dissolution and preferential diffusion of water molecules, obtain high permeation flux and high separation factor, and maintain good long-term operation stability, and has certain universality, good application prospect, and the like.

Description

Technical Field

[0001] The invention relates to a preparation method of a zwitterion-modified graphene oxide double-layer structure composite membrane, which can be used for selective and rapid water transmission in a pervaporation alcohol-water separation process. Background Art

[0002] Compared to traditional separation methods such as distillation, extraction, and adsorption, membrane separation technology saves nearly 50% of energy. Its advantages, such as high efficiency, environmental friendliness, and ease of operation, make it a promising new technology for promoting sustainable development. Membrane materials are crucial for membrane separation. Traditional dense polymer membranes suffer from a trade-off between permeability and selectivity, and the single-minded approach to membrane design has hindered the development of both highly permeable and highly selective separation membranes. Therefore, the development of new, high-performance membrane materials is crucial.

[0003] Two-dimensional materials have atomic dimensions and large specific surface areas, and are expected to become ultra-thin membrane separation materials. Among them, graphene oxide, as a typical two-dimensional material, has an ultra-thin sheet structure and is easy to stack and assemble into membranes. The abundant oxygen-containing groups on the surface facilitate post-functional modification and regulation. The confined mass transfer channels formed between the sheets give the graphene oxide membrane excellent permeability, laying the foundation for high-permeability separation membranes. The abundant oxygen-containing groups on the surface of graphene oxide can adsorb water molecules through hydrogen bonding, which is conducive to the construction of selective channels for water molecules. However, its adsorption performance is limited, and the interlayer confined mass transfer channels are difficult to achieve precise separation of systems with strong coupling effects and small molecular size differences. In addition, graphene oxide membranes are prone to swelling in polar liquid environments, resulting in poor separation stability. Therefore, it is necessary to rationally design its structure. Summary of the Invention

[0004] To address these issues, the present invention utilizes zwitterionic materials and graphene oxide to collaboratively construct a double-layer composite membrane. A graphene oxide layer is first prepared using a vacuum-assisted self-assembly method, and then a zwitterionic layer is constructed using a biomimetic co-deposition technique. Ultimately, a zwitterionic-modified graphene oxide double-layer composite membrane is obtained. The physical structure and chemical properties of the membrane are optimized by regulating the ratio of zwitterions to dopamine. The composite membrane prepared by the present invention exhibits high separation performance and stability in pervaporation dehydration of ethanol-water and butanol-water systems, and the preparation method is simple and easy.

[0005] In order to achieve the purpose of the present invention, the technical solutions adopted are as follows:

[0006] A zwitterion-modified graphene oxide double-layer structure composite membrane and a preparation method thereof, comprising the following preparation steps:

[0007] The composite membrane consists of a porous supporting base membrane and a double-layer separation layer; the polymer ultrafiltration membrane serves as the porous supporting base membrane, and the double-layer separation layer is composed of a graphene oxide layer and a zwitterionic layer; the graphene oxide layer is first formed on the surface of the porous supporting base membrane, and then the zwitterionic layer is constructed on the surface of the graphene oxide layer; the dopamine biomimetic adhesive is used between the double-layer structure to enhance the interlayer compatibility.

[0008] The specific steps for preparing the composite membrane are as follows:

[0009] Step 1: dispersing graphene oxide in deionized water to form a graphene oxide dispersion by stirring and ultrasonication, wherein the concentration of the dispersion is 3.0 to 10.0 mg / mL;

[0010] Step 2: Fix the porous support base membrane, take the graphene oxide dispersion in step 1, and use vacuum-assisted filtration to deposit graphene oxide on the surface of the support base membrane. After heat treatment, a graphene oxide composite membrane is obtained, and the graphene oxide deposition amount is 0.02-0.1 mg / cm 2 ;

[0011] Step 3: Dissolve tris(hydroxymethyl)aminomethane in deionized water, stir evenly, and adjust the pH of the solution to obtain a Tris buffer solution with a concentration of 20-60 mM;

[0012] Step 4: dissolve the zwitterionic material in the Tris buffer solution of step 3, stir evenly, add dopamine hydrochloride, and further stir to dissolve to obtain a mixed solution, wherein the mass ratio of the zwitterionic material to the dopamine hydrochloride is 0.5 to 20:1.

[0013] Step 5: placing the graphene oxide composite film prepared in step 2 in the solution prepared in step 4, with the graphene oxide film surface in contact with the solution, and performing deposition in an oscillator. After deposition, washing with deionized water and drying to obtain a double-layer composite film;

[0014] Furthermore, the zwitterionic material in step 4 is one of carboxylic acid betaine, sulfobetaine, and phosphate betaine. Preferably, sulfobetaine is prepared by adding sodium metabisulfite and ammonium persulfate to a mixed solvent of ethanol and water, then adding methacryloylethyl sulfobetaine, reacting at a certain temperature, dialyzing the product, and lyophilizing it.

[0015] Furthermore, in the preparation of sulfobetaine, the volume ratio of ethanol and water in the mixed solvent was 1:1, and the molar ratio of sodium metabisulfite, ammonium persulfate, and methacryloylethyl sulfobetaine was 1:2.2:43. The reaction temperature was 38°C, the reaction time was 1 hour, and the reaction was terminated by placing the mixture at -20 to -50°C for 20 to 60 minutes. The dialysis time was 2 to 3 days.

[0016] Furthermore, the porous supporting base membrane in step 2 is one of aminated polyacrylonitrile and hydrophilic polytetrafluoroethylene.

[0017] Furthermore, the heat treatment temperature in step 2 is 40-80° C., and the time is 20-120 min.

[0018] Furthermore, the pH in step three is adjusted to 8.0-9.0.

[0019] Furthermore, in step 4, the mass ratio of the zwitterionic material to dopamine hydrochloride is 0.5 to 10:1.

[0020] Furthermore, the concentration of dopamine hydrochloride in the mixed solution in step 4 is 2-5 mg / mL.

[0021] Furthermore, the deposition time in step five is 0.5 to 5 hours.

[0022] The composite membrane prepared by the invention is used for dehydration of pervaporation ethanol-water or / and butanol-water solution system.

[0023] Specifically, the performance of the composite membrane was evaluated in an ethanol-water solution system with a temperature of 76°C and a water content of 10 wt% in the raw material liquid. The permeation flux was 2500 to 4500 g / (m 2 h), the separation factor is 250~2000.

[0024] Specifically, the performance of the composite membrane was evaluated in a butanol-water solution system with a temperature of 80°C and a water content of 10 wt% of the raw material liquid. The permeation flux was 3000 to 5000 g / (m 2 h), the separation factor is 500-2000.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention utilizes a biomimetic co-deposition technique to load zwitterions onto a graphene oxide layer to prepare a zwitterion-modified graphene oxide double-layer composite membrane. The zwitterion layer forms a hydrophilic cross-linked network on the surface of the graphene oxide composite membrane, improving the hydrophilicity of the membrane surface. The abundant ionized hydrophilic groups can break the strong coupling between water molecules and alcohol molecules, promoting the rapid permeation of water molecules while inhibiting the transport of alcohol molecules. The interlayer channels of the graphene oxide serve as rapid mass transfer channels for molecules, enhancing the diffusion and transport process of molecules. Dopamine, as a biomimetic adhesive, can optimize interlayer interfacial interactions and inhibit excessive swelling of the graphene oxide composite membrane in a polar liquid environment, thereby resolving the problems of poor mechanical stability and separation stability of the graphene oxide composite membrane. The preparation steps of the present invention are simple and easy, with strong universality. The synergistic optimization of physical structure and chemical properties enables the prepared composite membrane to exhibit high permeation flux and separation factor in the dehydration of ethanol-water and butanol-water solution systems by pervaporation, and maintain stable separation performance during long-term operation, providing a reference for the development of two-dimensional material composite membranes and their application in the field of separation of strong coupling effect systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the structure of the composite membrane prepared in Example 4;

[0028] Figure 2 This is a scanning electron micrograph of a cross section of the composite membrane obtained in Example 4;

[0029] Figure 3 This is a graph showing the long-term operational stability of the composite membrane prepared in Example 4. DETAILED DESCRIPTION

[0030] The zwitterionic material described in the following examples is sulfobetaine, and its preparation process is as follows: sodium metabisulfite, ammonium persulfate, and methacryloylethyl sulfobetaine are added to a mixed solvent of ethanol and water in a volume ratio of 1:1 at a molar ratio of 1:2.2:43, and the mixture is reacted at 38°C for 1 hour, and then placed at -20°C for 30 minutes to terminate the reaction. The obtained product is dialyzed for 2 days and freeze-dried to obtain.

[0031] Example 1

[0032] A zwitterion-modified graphene oxide double-layer structure composite membrane is prepared, and the preparation steps are as follows:

[0033] Step 1: Disperse graphene oxide in deionized water to form a graphene oxide dispersion by stirring and ultrasonication, with a concentration of 4.5 mg / mL;

[0034] Step 2: Take 90 μL of the graphene oxide dispersion from step 1 and dilute it in 150 mL of deionized water, stir for 30 min, and ultrasonicate for 15 min. 2 ) is fixed on a vacuum filtration device, the dispersion liquid is poured in, and after the graphene oxide is deposited on the surface of the base film, a heat treatment is performed at 60° C. for 2 h to obtain a graphene oxide composite film;

[0035] Step 3: Dissolve tris(hydroxymethylaminomethane) in deionized water, stir evenly, and adjust the pH of the solution to 8.5 to obtain a Tris buffer solution with a concentration of 50 mM;

[0036] Step 4: Dissolve the zwitterionic material in the Tris buffer solution of step 3, stir evenly, add 2 mg / mL dopamine hydrochloride, and further stir to dissolve. The concentration ratio of the zwitterionic material to dopamine hydrochloride is 1:1;

[0037] Step 5: Place the graphene oxide composite film prepared in step 2 in the solution of step 4, with the graphene oxide film surface in contact with the solution, and perform co-deposition in an oscillator for 4 hours. Then, wash the molecules physically attached to the surface with deionized water, and obtain a composite film after vacuum drying at 30°C.

[0038] The separation performance of the composite membrane prepared in this example for the ethanol-water system was tested. When the temperature was 76°C and the water content in the raw liquid was 10 wt%, the membrane permeation flux was 3266 g / (m 2 h), the separation factor is 745.

[0039] Example 2

[0040] A zwitterion-modified graphene oxide double-layer structure composite membrane was prepared. The preparation steps were different from those in Example 1 only in that the aminated polyacrylonitrile ultrafiltration membrane was replaced with a hydrophilic polytetrafluoroethylene ultrafiltration membrane in step 2. The other operations were the same as in Example 1.

[0041] The separation performance of the composite membrane prepared in this example for the ethanol-water system was tested. When the temperature was 76°C and the water content in the raw liquid was 10 wt%, the membrane permeation flux was 3972 g / (m 2 h), the separation factor is 271.

[0042] Example 3

[0043] A zwitterion-modified graphene oxide double-layer structure composite membrane was prepared. The preparation steps were different from those in Example 1 only in that the concentration of the zwitterion material and dopamine hydrochloride in step 4 was changed from 1:1 to 2:1, and the other operations were the same as in Example 1.

[0044] The separation performance of the composite membrane prepared in this example for the ethanol-water system was tested. When the temperature was 76°C and the water content in the raw liquid was 10 wt%, the membrane permeation flux was 3629 g / (m 2 h), the separation factor is 951.

[0045] Example 4

[0046] A zwitterion-modified graphene oxide double-layer structure composite membrane was prepared. The preparation steps were different from those in Example 1 only in that the concentration of the zwitterion material and dopamine hydrochloride in step 4 was changed from 1:1 to 5:1, and the other operations were the same as in Example 1.

[0047] The separation performance of the composite membrane prepared in this example for the ethanol-water system was tested. When the temperature was 76°C and the water content in the raw liquid was 10 wt%, the membrane permeation flux was 3820 g / (m 2 h), the separation factor is 1086. Figure 1 and Figure 2 They are respectively a structural schematic diagram and a cross-sectional scanning electron microscope image of the composite membrane prepared in Example 4.

[0048] Example 5

[0049] A zwitterion-modified graphene oxide double-layer structure composite membrane was prepared. The preparation steps were different from those in Example 1 only in that the concentration of the zwitterion material and dopamine hydrochloride in step 4 was changed from 1:1 to 10:1, and the other operations were the same as in Example 1.

[0050] The separation performance of the composite membrane prepared in this example for the ethanol-water system was tested. When the temperature was 76°C and the water content in the raw liquid was 10 wt%, the membrane permeation flux was 3056 g / (m 2 h), the separation factor is 1525.

[0051] Example 6

[0052] A zwitterion-modified graphene oxide double-layer structure composite membrane was prepared. The preparation steps were different from those in Example 1 only in that in step 2, the polyacrylonitrile ultrafiltration membrane was changed to a hydrophilic polytetrafluoroethylene ultrafiltration membrane, and in step 4, the concentration of the zwitterion material and dopamine hydrochloride was changed from 1:1 to 2:1. The other operations were the same as in Example 1.

[0053] The separation performance of the composite membrane prepared in this example for the ethanol-water system was tested. When the temperature was 76°C and the water content in the raw liquid was 10 wt%, the membrane permeation flux was 4150 g / (m 2 h), the separation factor is 523.

[0054] Example 7

[0055] A zwitterion-modified graphene oxide double-layer structure composite membrane was prepared. The preparation steps were different from those in Example 1 only in that in step 2, the polyacrylonitrile ultrafiltration membrane was changed to a hydrophilic polytetrafluoroethylene ultrafiltration membrane, and in step 4, the concentration of the zwitterion material and dopamine hydrochloride was changed from 1:1 to 5:1. The other operations were the same as in Example 1.

[0056] The separation performance of the composite membrane prepared in this example for the ethanol-water system was tested. When the temperature was 76°C and the water content in the raw liquid was 10 wt%, the membrane permeation flux was 4313 g / (m 2 h), the separation factor is 856.

[0057] Example 8

[0058] A zwitterion-modified graphene oxide double-layer structure composite membrane was prepared. The preparation steps were different from those in Example 1 only in that in step 2, the polyacrylonitrile ultrafiltration membrane was changed to a hydrophilic polytetrafluoroethylene ultrafiltration membrane, and in step 4, the concentration of the zwitterion material and dopamine hydrochloride was changed from 1:1 to 10:1. The other operations were the same as in Example 1.

[0059] The separation performance of the composite membrane prepared in this example for the ethanol-water system was tested. When the temperature was 76°C and the water content in the raw liquid was 10 wt%, the membrane permeation flux was 4072 g / (m 2 h), the separation factor is 1131.

[0060] Example 9

[0061] A zwitterion-modified graphene oxide double-layer structure composite membrane was prepared. The preparation steps were the same as those in Example 1, except for the detection system. The separation performance of the composite membrane prepared in this example for the butanol-water system was tested. When the temperature was 80°C and the water content in the raw material solution was 10 wt%, the membrane permeation flux was 3520 g / (m 2 h), the separation factor is 932.

[0062] Example 10

[0063] A zwitterion-modified graphene oxide double-layer structure composite membrane was prepared. The preparation steps were different from those in Example 1 only in that the concentration of the zwitterion material and dopamine hydrochloride in step 4 was changed from 1:1 to 2:1, and the other operations were the same as in Example 1.

[0064] The separation performance of the composite membrane prepared in this example for butanol-water system was tested. When the temperature was 80°C and the water content in the raw liquid was 10 wt%, the membrane permeation flux was 3782 g / (m 2 h), the separation factor is 1082.

[0065] Example 11

[0066] A zwitterion-modified graphene oxide double-layer structure composite membrane was prepared. The preparation steps were different from those in Example 1 only in that the concentration of the zwitterion material and dopamine hydrochloride in step 4 was changed from 1:1 to 5:1, and the other operations were the same as in Example 1.

[0067] The separation performance of the composite membrane prepared in this example for butanol-water system was tested. When the temperature was 80°C and the water content in the raw liquid was 10 wt%, the membrane permeation flux was 4037 g / (m 2 h), the separation factor is 1245.

[0068] Example 12

[0069] A zwitterion-modified graphene oxide double-layer structure composite membrane was prepared. The preparation steps were different from those in Example 1 only in that the concentration of the zwitterion material and dopamine hydrochloride in step 4 was changed from 1:1 to 10:1, and the other operations were the same as in Example 1.

[0070] The separation performance of the composite membrane prepared in this example for butanol-water system was tested. When the temperature was 80°C and the water content in the raw liquid was 10 wt%, the membrane permeation flux was 4381 g / (m 2 h), the separation factor is 1762.

[0071] Example 13

[0072] A zwitterion-modified graphene oxide double-layer structure composite membrane was prepared. The preparation steps were different from those in Example 1 only in that in step 2, the polyacrylonitrile ultrafiltration membrane was replaced with a hydrophilic polytetrafluoroethylene ultrafiltration membrane. Other operations were the same as in Example 1.

[0073] The separation performance of the composite membrane prepared in this example for butanol-water system was tested. When the temperature was 80°C and the water content in the raw liquid was 10 wt%, the membrane permeation flux was 4283 g / (m 2 h), the separation factor is 936.

[0074] Example 14

[0075] A zwitterion-modified graphene oxide double-layer structure composite membrane was prepared. The preparation steps were different from those in Example 1 only in that in step 2, the polyacrylonitrile ultrafiltration membrane was changed to a hydrophilic polytetrafluoroethylene ultrafiltration membrane, and in step 4, the concentration of the zwitterion material and dopamine hydrochloride was changed from 1:1 to 2:1. The other operations were the same as in Example 1.

[0076] The separation performance of the composite membrane prepared in this example for butanol-water system was tested. When the temperature was 80°C and the water content in the raw liquid was 10 wt%, the membrane permeation flux was 4457 g / (m 2 h), the separation factor is 1152.

[0077] Example 15

[0078] A zwitterion-modified graphene oxide double-layer structure composite membrane was prepared. The preparation steps were different from those in Example 1 only in that in step 2, the polyacrylonitrile ultrafiltration membrane was changed to a hydrophilic polytetrafluoroethylene ultrafiltration membrane, and in step 4, the concentration of the zwitterion material and dopamine hydrochloride was changed from 1:1 to 5:1. The other operations were the same as in Example 1.

[0079] The separation performance of the composite membrane prepared in this example for butanol-water system was tested. When the temperature was 80°C and the water content in the raw liquid was 10 wt%, the membrane permeation flux was 4680 g / (m 2 h), the separation factor is 1487.

[0080] Example 16

[0081] A zwitterion-modified graphene oxide double-layer structure composite membrane was prepared. The preparation steps were different from those in Example 1 only in that in step 2, the polyacrylonitrile ultrafiltration membrane was changed to a hydrophilic polytetrafluoroethylene ultrafiltration membrane, and in step 4, the concentration of the zwitterion material and dopamine hydrochloride was changed from 1:1 to 10:1. The other operations were the same as in Example 1.

[0082] The separation performance of the composite membrane prepared in this example for butanol-water system was tested. When the temperature was 80°C and the water content in the raw liquid was 10 wt%, the membrane permeation flux was 4213 g / (m 2 h), the separation factor is 1782.

[0083] Comparative Example 1

[0084] A graphene oxide composite film is prepared, and the preparation steps are as follows:

[0085] Step 1: Disperse graphene oxide in deionized water to form a graphene oxide dispersion by stirring and ultrasonication, with a concentration of 4.5 mg / mL;

[0086] Step 2: 90 μL of the graphene oxide dispersion from step 2 was diluted in 150 mL of deionized water, stirred for 30 min, and ultrasonically treated for 15 min. An aminated polyacrylonitrile ultrafiltration membrane was fixed on a vacuum filtration device, and the dispersion was poured into the membrane. After the graphene oxide was deposited on the surface of the base membrane, the membrane was heat treated at 60° C. for 2 h to obtain a graphene oxide composite membrane.

[0087] The separation performance of the composite membrane prepared in this example for the ethanol-water system was tested. When the temperature was 76°C and the water content in the raw liquid was 10 wt%, the membrane permeation flux was 2769 g / (m 2 h), the separation factor is 368.

[0088] Comparative Example 2

[0089] A dopamine-modified graphene oxide composite film is prepared, and the preparation steps are as follows:

[0090] Step 1: Disperse graphene oxide in deionized water to form a graphene oxide dispersion by stirring and ultrasonication, with a concentration of 4.5 mg / mL;

[0091] Step 2: Take 90 μL of the graphene oxide dispersion in step 1 and dilute it in 150 mL of deionized water, stir for 30 minutes, and ultrasonically treat for 15 minutes. Fix the aminated polyacrylonitrile ultrafiltration membrane on a vacuum filtration device, pour the dispersion into it, and after the graphene oxide is deposited on the surface of the base membrane, heat treat it at 60°C for 2 hours to obtain a graphene oxide composite membrane;

[0092] Step 3: Dissolve tris(hydroxymethylaminomethane) in deionized water, stir evenly, and adjust the pH of the solution to 8.5 to obtain a Tris buffer solution with a concentration of 50 mM;

[0093] Step 4: Dissolve 2 mg / mL dopamine hydrochloride in the Tris buffer solution prepared in step 3 and stir evenly;

[0094] Step 5: Place the graphene oxide composite film prepared in step 2 in the solution of step 4, with the graphene oxide film surface in contact with the solution, and perform co-deposition in an oscillator for 4 hours. Then, wash the molecules physically attached to the surface with deionized water, and obtain a composite film after vacuum drying at 30°C.

[0095] The separation performance of the composite membrane prepared in this example for the ethanol-water system was tested. When the temperature was 76°C and the water content in the raw liquid was 10 wt%, the membrane permeation flux was 2846 g / (m 2 h), the separation factor is 516.

[0096] Comparative Example 3

[0097] A graphene oxide composite membrane was prepared. The preparation steps were the same as those in Comparative Example 1, except for the detection system. The separation performance of the composite membrane prepared in this example for a butanol-water solution system was tested. When the temperature was 80°C and the water content in the raw material solution was 10 wt%, the membrane permeation flux was 3071 g / (m 2 h), the separation factor is 523.

[0098] Comparative Example 4

[0099] A dopamine-modified graphene oxide composite membrane was prepared. The preparation steps were the same as those in Comparative Example 2, except for the detection system. The separation performance of the composite membrane prepared in this example for a butanol-water solution system was tested. When the temperature was 80°C and the water content in the raw material solution was 10 wt%, the membrane permeation flux was 3215 g / (m 2 h), the separation factor is 684.

[0100] The separation performance of the double-layer composite membrane prepared by the present invention is significantly improved compared to the unmodified graphene oxide composite membrane. This is because the zwitterionic layer in the membrane structure forms a hydrophilic cross-linked network on the membrane surface. The abundant ionized hydrophilic groups promote the dissolution process of water molecules on the membrane surface, which is beneficial to the membrane's selective permeability to water molecules. The graphene oxide layer in the membrane structure acts as a rapid mass transfer channel for molecules, which can enhance the diffusion process of molecules. The synergistic enhancement of the dissolution process and the diffusion process helps to improve the permeability and separation selectivity of the membrane. The biomimetic co-deposition technology is simple and easy to use. Dopamine, as a biomimetic adhesive, helps to improve the interfacial interaction between layers and has a positive effect on the stability of the membrane during application. The membrane separation performance remains stable after 120 hours of continuous operation ( Figure 3 In addition, the preparation method of the present invention can be applied to different types of porous support base membranes to achieve the dehydration process of different types of alcohols, and has a certain universality.

[0101] The above content merely exemplifies and describes the present invention, but the present invention is not limited to the above-mentioned specific embodiments. The above-mentioned specific embodiments are merely illustrative and not restrictive. Those skilled in the art may, under the guidance of the present invention, modify or supplement the described specific embodiments to varying degrees or replace them with similar methods. Without departing from the spirit of the present invention, these shall all fall within the scope of protection of the present invention.

Claims

1. An application of a zwitterion-modified graphene oxide double-layer structure composite membrane, characterized in that: The composite membrane is used for dehydration of pervaporation ethanol-water or / and butanol-water solution system; The composite membrane includes a porous supporting base membrane and a double-layer separation layer; wherein the double-layer separation layer is composed of a graphene oxide layer and a zwitterion layer; the graphene oxide layer is first formed on the surface of the porous supporting base membrane, and then the zwitterion layer is constructed on the surface of the graphene oxide layer; a dopamine component is also included between the double-layer structure to enhance the interfacial compatibility between the layers; The preparation steps of the double-layer composite membrane are as follows: Step 1: dispersing graphene oxide in deionized water to form a graphene oxide dispersion by stirring and ultrasonication; Step 2: Fix the porous support base membrane, take the graphene oxide dispersion in step 1, and use vacuum-assisted filtration to deposit the graphene oxide on the surface of the support base membrane. After heat treatment, obtain a graphene oxide composite membrane; Step 3: Dissolve tris(hydroxymethylaminomethane) in deionized water, stir evenly, and adjust the pH of the solution to obtain a Tris buffer solution with a concentration of 20-60 mM; Step 4: dissolving the zwitterionic material in the Tris buffer solution of step 3, stirring evenly, adding dopamine hydrochloride, and further stirring to dissolve to obtain a mixed solution; wherein the mass ratio of the zwitterionic material to dopamine hydrochloride is 5-20:1; Step 5: Place the graphene oxide composite film prepared in step 2 in the solution of step 4, with the graphene oxide film surface in contact with the solution, and deposit in an oscillator. After deposition, wash with deionized water and dry to obtain a double-layer composite film.

2. The use according to claim 1, characterized in that The zwitterionic material in step 4 is one of carboxylic acid betaine, sulfobetaine, and phosphate betaine; wherein the preparation method of sulfobetaine is as follows: sodium metabisulfite and ammonium persulfate are added to a mixed solvent of ethanol and water, and then sulfobetaine is added, reacting at a certain temperature, dialyzing the product, and freeze-drying to obtain.

3. The use according to claim 1, characterized in that The porous supporting base membrane described in step 2 is a polymer ultrafiltration membrane; specifically, it is one of aminated polyacrylonitrile and hydrophilic polytetrafluoroethylene.

4. The use according to claim 1, characterized in that The heat treatment temperature in step 2 is 40-80°C and the time is 20-120 min.

5. The use according to claim 1, characterized in that The concentration of graphene oxide dispersion is 3.0~10.0 mg / mL; the amount of graphene oxide deposited in the graphene oxide composite film is 0.02~0.1 mg / cm 2 .

6. The use according to claim 1, characterized in that The pH in step 3 is adjusted to 8.0-9.

0.

7. The use according to claim 1, characterized in that The mass ratio of the zwitterionic material to dopamine hydrochloride in step 4 is 5-10:1, and the concentration of dopamine hydrochloride in the mixed solution is 2-5 mg / mL.

8. The use according to claim 1, characterized in that The deposition time in step five is 0.5 to 5 h.

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