Modified graphene oxide film as well as preparation method and application thereof

Abstract

The invention provides a modified graphene oxide membrane as well as a preparation method and application thereof, and belongs to the technical field of pervaporation membranes. The preparation method of the modified graphene oxide film comprises the following steps: (1) uniformly mixing a graphene oxide aqueous dispersion and a covalent organic framework material powder dispersion to obtain a mixed solution; and (2) adding deionized water into the mixed solution obtained in the step (1), uniformly stirring, adjusting the pH value of the system to 7.8-8.5, carrying out ultrasonic treatment, depositing the dispersion liquid subjected to ultrasonic treatment on a PAN base membrane through positive pressure filtration, and carrying out heat treatment to obtain the modified graphene oxide membrane. The prepared modified graphene oxide membrane has good isopropanol dehydration performance and structural stability, and a new thought is provided for improving the isopropanol dehydration performance and structural stability of the GO-based separation membrane.

Description

Technical Field

[0001] This invention relates to the field of pervaporation membrane technology, and in particular to a modified graphene oxide membrane, its preparation method, and its application. Background Technology

[0002] In chemical synthesis and pharmaceutical manufacturing, organic solvents are widely used in synthetic reactions and product purification processes. To ensure process quality, high-purity solvents are typically required. However, after a single use, solvents often contain moisture or other impurities and cannot be directly reused. The resulting large amounts of wastewater containing organic matter, if discharged directly without treatment, not only waste resources but also severely pollute the environment. Therefore, developing efficient dehydration technologies to achieve solvent recycling is of great significance for promoting green manufacturing and sustainable development.

[0003] In the chemical industry, pervaporation technology has demonstrated superior separation performance for azeotropic systems or near-boiling point mixtures that are difficult to handle using conventional techniques. Pervaporation relies on the selective adsorption and permeation diffusion of components on the membrane surface to achieve separation. As a membrane separation technology, pervaporation boasts core advantages such as compact equipment, high recovery efficiency, and flexible device adaptability. When processing liquid mixtures, it also exhibits excellent economic efficiency, high safety, and environmental friendliness. Therefore, pervaporation is considered a highly promising alternative to traditional high-energy-consuming separation processes such as extractive distillation and azeotropic distillation.

[0004] Pervaporation membranes can be classified into organic membranes, inorganic membranes, two-dimensional material membranes, and organic-inorganic composite membranes based on their materials. Organic polymer membranes have good film-forming properties, high flexibility, and low cost. Their polar groups can form hydrogen bonds with water molecules, which is beneficial for selective adsorption and dehydration. However, they have poor resistance to high temperature and pressure and solvent swelling, limiting their stability. Inorganic membranes exhibit excellent thermal stability, mechanical strength, and solvent resistance, but their high manufacturing cost restricts large-scale application. Two-dimensional material membranes, such as graphene oxide membranes, are a new type of membrane material. Their atomically thin sheet structure can construct ultrathin separation layers, achieving high permeability and selectivity through sheet defects and interlayer channels. They are currently widely used in the field of organic solvent dehydration. However, the presence of oxygen-containing groups at the edges of graphene oxide sheets makes the membrane material prone to water absorption and swelling, which affects the separation performance and water flux of the membrane. Summary of the Invention

[0005] In view of this, the present invention provides a method for preparing a modified graphene oxide film, comprising the following steps:

[0006] (1) Mix the aqueous dispersion of graphene oxide and the powder dispersion of covalent organic framework material evenly to obtain a mixed solution;

[0007] (2) Add deionized water to the mixed solution in step (1), stir evenly, adjust the pH of the system to 7.8-8.5, sonicate, deposit the ultrasonically treated dispersion onto the PAN substrate through positive pressure filtration, and heat treat to obtain the modified graphene oxide membrane.

[0008] Furthermore, the mass concentration of the graphene oxide aqueous dispersion in step (1) is 0.1-0.3 mg / mL.

[0009] Furthermore, the mass concentration of the covalent organic framework material powder dispersion in step (1) is 0.5-0.8 mg / mL.

[0010] Furthermore, the mass ratio of the graphene oxide to the covalent organic framework material powder is 1:1-2.

[0011] Furthermore, the preparation method of the covalent organic framework material powder dispersion includes the following steps:

[0012] (1) 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene and mesitylene were mixed and ultrasonically treated to obtain a mixture; the mixture was placed in a reaction vessel, and then an acetic acid solution was added to the reaction vessel, the temperature was raised to 80-100℃, and the temperature was maintained for 72-120h to obtain an intermediate; the intermediate was washed until the supernatant was colorless, dried, ground, and sieved to obtain a covalent organic framework material powder;

[0013] (2) The covalent organic framework material powder is dispersed in N,N-dimethylformamide and ultrasonically treated to obtain a covalent organic framework material powder dispersion.

[0014] Furthermore, the mass ratio of the 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene, mesitylene and acetic acid solution in step (1) is 7-9:6-8:1-1.5:3-5.

[0015] Furthermore, the molar concentration of the acetic acid solution in step (1) is 1-3 mol / L.

[0016] Further, in step (2), the pH of the system is adjusted using 0.1 M NaOH.

[0017] Furthermore, the positive pressure filtration in step (2) is at a pressure of 6-8 bar.

[0018] The present invention also provides a modified graphene oxide membrane prepared according to the method, and the application of the modified graphene oxide membrane in the field of organic solvent dehydration and recycling.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] This invention utilizes covalent organic framework materials to dope and modify GO membranes, effectively suppressing the swelling of layered GO membranes in aqueous environments and improving membrane structural stability. The modified graphene oxide membrane prepared by this invention maintains a relatively constant isopropanol / water separation factor, exceeding 3000, during long-term separation performance testing exceeding 40 hours. Therefore, this invention successfully prepares a modified graphene oxide membrane with good isopropanol dehydration performance and structural stability, providing a new approach for improving the isopropanol dehydration performance and structural stability of GO-based separation membranes. Detailed Implementation

[0021] This invention provides a method for preparing a modified graphene oxide film, comprising the following steps:

[0022] (1) Mix the aqueous dispersion of graphene oxide and the powder dispersion of covalent organic framework material evenly to obtain a mixed solution;

[0023] (2) Add deionized water to the mixed solution in step (1), stir evenly, adjust the pH of the system to 7.8-8.5, sonicate, deposit the ultrasonically treated dispersion onto the PAN substrate through positive pressure filtration, and heat treat to obtain the modified graphene oxide membrane.

[0024] In some embodiments of the present invention, the mass concentration of the graphene oxide aqueous dispersion in step (1) is 0.1-0.3 mg / mL. Preferably, the mass concentration of the graphene oxide aqueous dispersion is 0.1 mg / mL.

[0025] In some embodiments of the present invention, the mass concentration of the covalent organic framework material powder dispersion in step (1) is 0.5-0.8 mg / mL. Preferably, the mass concentration of the covalent organic framework material powder dispersion is 0.6 mg / mL.

[0026] In some embodiments of the present invention, the mass ratio of graphene oxide to covalent organic framework material powder is 1:1-2. Preferably, the mass ratio of graphene oxide to covalent organic framework material powder is 1:2.

[0027] In some embodiments of the present invention, the preparation method of the covalent organic framework material powder dispersion includes the following steps:

[0028] (1) 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene and mesitylene were mixed and ultrasonically treated to obtain a mixture; the mixture was placed in a reaction vessel, and then an acetic acid solution was added to the reaction vessel, the temperature was raised to 80-100℃, and the temperature was maintained for 72-120h to obtain an intermediate; the intermediate was washed until the supernatant was colorless, dried, ground, and sieved to obtain a covalent organic framework material powder;

[0029] (2) The covalent organic framework material powder is dispersed in N,N-dimethylformamide and ultrasonically treated to obtain a covalent organic framework material powder dispersion.

[0030] In some embodiments of the present invention, the mass ratio of the 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene, mesitylene, and acetic acid solution in step (1) is 7-9:6-8:1-1.5:3-5. Preferably, the mass ratio of the 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene, mesitylene, and acetic acid solution is 9:7:1:0.3.

[0031] In some embodiments of the present invention, the molar concentration of the acetic acid solution in step (1) is 1-3 mol / L. Preferably, the molar concentration of the acetic acid solution is 1 mol / L.

[0032] In some embodiments of the present invention, the washing in step (1) specifically includes washing with N,N-dimethylacetamide, acetone and anhydrous ethanol in sequence.

[0033] In some embodiments of the present invention, the drying temperature in step (1) is 60-80°C. Preferably, the drying temperature is 65°C.

[0034] In some embodiments of the present invention, step (2) uses 0.1 M NaOH to adjust the pH of the system.

[0035] In some embodiments of the present invention, the ultrasonic treatment time in step (2) is 10-50 min. Preferably, the ultrasonic treatment time is 30 min.

[0036] In some embodiments of the present invention, the pressure of the positive pressure filtration in step (2) is 6-8 bar. Preferably, the pressure of the positive pressure filtration is 7 bar.

[0037] The present invention also provides a modified graphene oxide membrane prepared according to the method, and the application of the modified graphene oxide membrane in the field of organic solvent dehydration and recycling.

[0038] This invention utilizes covalent organic framework materials to modify GO, thereby firmly fixing GO nanosheets, preventing excessive swelling of GO nanosheets in organic solvents, and thus maintaining their stability in organic solvents.

[0039] The addition of covalent organic framework materials can provide more adsorption sites for graphene oxide membranes, which is beneficial for the purification of isopropanol-containing wastewater.

[0040] The addition of covalent organic framework materials can also increase water flow channels and improve the water flux of the membrane material, thereby achieving rapid transport of water molecules while improving the interception rate of isopropanol.

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0042] Unless otherwise specified, the test methods or experimental methods described in the following examples are all conventional methods; unless otherwise specified, the raw materials and additives are obtained from conventional commercial sources or prepared by conventional methods.

[0043] In the following examples or comparative examples, the 1,3,5-tris(4-aminophenyl)benzene (TAPB) has CAS number 118727-34-7. The 2,6-dialdehyde-1,5-dihydroxynaphthalene has CAS number 7235-47-4.

[0044] The graphene oxide aqueous dispersion was prepared according to Section 2.2.5 of Chapter 2 of the paper "Preparation and Separability of Graphene-based Composite Nanofiltration Membrane, Deng Huihui, Zhejiang Sci-Tech University".

[0045] Example 1

[0046] (1) 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene, and mesitylene were mixed and ultrasonically treated to obtain a mixture; the mixture was placed in a reaction vessel, and then acetic acid solution (1 mol / L) was added to the reaction vessel. The mass ratio of 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene, mesitylene and acetic acid solution was 9:7:1:3. The mixture was heated to 100°C and kept at that temperature for 96 h to obtain an intermediate; the intermediate was washed sequentially with N,N-dimethylacetamide, acetone and anhydrous ethanol until the supernatant was colorless, dried at 65°C to constant weight, ground and passed through a 200-mesh sieve to obtain covalent organic framework material powder; the covalent organic framework material powder was dispersed in N,N-dimethylformamide and ultrasonically treated for 30 min to obtain a covalent organic framework material powder dispersion;

[0047] (2) Mix 0.1 mg / mL graphene oxide aqueous dispersion and 0.6 mg / mL covalent organic framework material powder dispersion evenly, wherein the mass ratio of graphene oxide to covalent organic framework material powder is 1:2, to obtain a mixed solution;

[0048] (3) Add deionized water to the mixed solution in step (2) until the volume of the mixed solution is 200 mL, stir evenly, adjust the pH value of the dispersion to 8.5 with 0.1 M NaOH, then sonicate for 30 min, stir at 85 ℃ for 2 h, sonicate again for 25 min, and then deposit the ultrasonically treated dispersion on the PAN substrate by positive pressure filtration (film forming pressure 8 bar), and heat treat in an oven at 70 ℃ for 1 h to obtain the modified graphene oxide membrane.

[0049] Example 2

[0050] A method for preparing a modified graphene oxide film, comprising the following specific steps:

[0051] (1) 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene, and mesitylene were mixed and ultrasonically treated to obtain a mixture; the mixture was placed in a reaction vessel, and then acetic acid solution (2 mol / L) was added to the reaction vessel. The mass ratio of 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene, mesitylene and acetic acid solution was 8:7:1:3. The mixture was heated to 80°C and kept at that temperature for 78 h to obtain an intermediate; the intermediate was washed sequentially with N,N-dimethylacetamide, acetone and anhydrous ethanol until the supernatant was colorless, dried at 65°C to constant weight, ground and passed through a 200-mesh sieve to obtain covalent organic framework material powder; the covalent organic framework material powder was dispersed in N,N-dimethylformamide and ultrasonically treated for 30 min to obtain a covalent organic framework material powder dispersion;

[0052] (2) Mix 0.2 mg / mL graphene oxide aqueous dispersion and 0.6 mg / mL covalent organic framework material powder dispersion evenly, wherein the mass ratio of graphene oxide to covalent organic framework material powder is 1:1, to obtain a mixed solution;

[0053] (3) Add deionized water to the mixed solution in step (2) until the volume of the mixed solution is 200 mL, stir evenly, adjust the pH value of the dispersion to 8.0 with 0.1 M NaOH, then sonicate for 30 min, stir at 85 ℃ for 2 h, sonicate again for 25 min, and then deposit the ultrasonically treated dispersion on the PAN substrate by positive pressure filtration (film forming pressure 6 bar), and heat treat in an oven at 70 ℃ for 1 h to obtain the modified graphene oxide membrane.

[0054] Example 3

[0055] A method for preparing a modified graphene oxide film, comprising the following specific steps:

[0056] (1) 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene, and mesitylene were mixed and ultrasonically treated to obtain a mixture; the mixture was placed in a reaction vessel, and then acetic acid solution (1 mol / L) was added to the reaction vessel. The mass ratio of 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene, mesitylene and acetic acid solution was 7:6:1:3. The mixture was heated to 100°C and kept at that temperature for 96 h to obtain an intermediate; the intermediate was washed sequentially with N,N-dimethylacetamide, acetone and anhydrous ethanol until the supernatant was colorless, dried at 60°C to constant weight, ground and passed through a 200-mesh sieve to obtain covalent organic framework material powder; the covalent organic framework material powder was dispersed in N,N-dimethylformamide and ultrasonically treated for 30 min to obtain a covalent organic framework material powder dispersion;

[0057] (2) Mix 0.1 mg / mL graphene oxide aqueous dispersion and 0.5 mg / mL covalent organic framework material powder dispersion evenly, wherein the mass ratio of graphene oxide to covalent organic framework material powder is 1:1, to obtain a mixed solution;

[0058] (3) Add deionized water to the mixed solution in step (2) until the volume of the mixed solution is 200 mL, stir evenly, adjust the pH value of the dispersion to 7.8 using 0.1 M NaOH, then sonicate for 30 min, stir at 85 ℃ for 2 h, sonicate again for 20 min, and then deposit the ultrasonically treated dispersion onto the PAN substrate by positive pressure filtration (film forming pressure 6 bar), and heat treat in an oven at 70 ℃ for 1 h to obtain the modified graphene oxide membrane.

[0059] Example 4

[0060] (1) 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene, and mesitylene were mixed and ultrasonically treated to obtain a mixture; the mixture was placed in a reaction vessel, and then acetic acid solution (3 mol / L) was added to the reaction vessel. The mass ratio of 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene, mesitylene and acetic acid solution was 9:8:1.5:5. The mixture was heated to 100°C and kept at that temperature for 96 h to obtain an intermediate; the intermediate was washed sequentially with N,N-dimethylacetamide, acetone and anhydrous ethanol until the supernatant was colorless, dried at 70°C to constant weight, ground and passed through a 200-mesh sieve to obtain covalent organic framework material powder; the covalent organic framework material powder was dispersed in N,N-dimethylformamide and ultrasonically treated for 30 min to obtain a covalent organic framework material powder dispersion;

[0061] (2) Mix 0.3 mg / mL graphene oxide aqueous dispersion and 0.8 mg / mL covalent organic framework material powder dispersion evenly, wherein the mass ratio of graphene oxide to covalent organic framework material powder is 1:1, to obtain a mixed solution;

[0062] (3) Add deionized water to the mixed solution in step (2) until the volume of the mixed solution is 200 mL, stir evenly, adjust the pH value of the dispersion to 8.0 with 0.1 M NaOH, then sonicate for 30 min, stir at 85 ℃ for 2 h, sonicate again for 20-30 min, and then deposit the ultrasonically treated dispersion on the PAN substrate by positive pressure filtration (film forming pressure 6 bar), and heat treat in an oven at 70 ℃ for 1 h to obtain the modified graphene oxide membrane.

[0063] Example 5

[0064] (1) 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene, and mesitylene were mixed and ultrasonically treated to obtain a mixture; the mixture was placed in a reaction vessel, and then acetic acid solution (1 mol / L) was added to the reaction vessel. The mass ratio of 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene, mesitylene and acetic acid solution was 7:8:1.5:3. The mixture was heated to 100°C and kept at that temperature for 80 h to obtain an intermediate; the intermediate was washed sequentially with N,N-dimethylacetamide, acetone and anhydrous ethanol until the supernatant was colorless, dried at 60°C to constant weight, ground and passed through a 200-mesh sieve to obtain covalent organic framework material powder; the covalent organic framework material powder was dispersed in N,N-dimethylformamide and ultrasonically treated for 40 min to obtain a covalent organic framework material powder dispersion;

[0065] (2) Mix 0.2 mg / mL graphene oxide aqueous dispersion and 0.7 mg / mL covalent organic framework material powder dispersion evenly, wherein the mass ratio of graphene oxide to covalent organic framework material powder is 1:1, to obtain a mixed solution;

[0066] (3) Add deionized water to the mixed solution in step (2) until the volume of the mixed solution is 200 mL, stir evenly, adjust the pH value of the dispersion to 8.5 with 0.1 M NaOH, then sonicate for 30 min, stir at 85 ℃ for 2 h, sonicate again for 28 min, and then deposit the ultrasonically treated dispersion on the PAN substrate by positive pressure filtration (film forming pressure 6 bar), and heat treat in an oven at 70 ℃ for 1 h to obtain the modified graphene oxide membrane.

[0067] Example 6

[0068] (1) 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene, and mesitylene were mixed and ultrasonically treated to obtain a mixture; the mixture was placed in a reaction vessel, and then acetic acid solution (1 mol / L) was added to the reaction vessel. The mass ratio of 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene, mesitylene and acetic acid solution was 9:6:1:3. The mixture was heated to 100°C and kept at that temperature for 85 h to obtain an intermediate; the intermediate was washed sequentially with N,N-dimethylacetamide, acetone and anhydrous ethanol until the supernatant was colorless, dried at 80°C to constant weight, ground and passed through a 200-mesh sieve to obtain covalent organic framework material powder; the covalent organic framework material powder was dispersed in N,N-dimethylformamide and ultrasonically treated for 30 min to obtain a covalent organic framework material powder dispersion;

[0069] (2) Mix 0.3 mg / mL graphene oxide aqueous dispersion and 0.8 mg / mL covalent organic framework material powder dispersion evenly, wherein the mass ratio of graphene oxide to covalent organic framework material powder is 1:2, to obtain a mixed solution;

[0070] (3) Add deionized water to the mixed solution in step (2) until the volume of the mixed solution is 200 mL, stir evenly, adjust the pH value of the dispersion to 7.8 using 0.1 M NaOH, then sonicate for 30 min, stir at 85 ℃ for 2 h, sonicate again for 20 min, and then deposit the ultrasonically treated dispersion onto the PAN substrate by positive pressure filtration (film forming pressure 6 bar), and heat treat in an oven at 70 ℃ for 1 h to obtain the modified graphene oxide membrane.

[0071] Example 7

[0072] (1) 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene, and mesitylene were mixed and ultrasonically treated to obtain a mixture; the mixture was placed in a reaction vessel, and then acetic acid solution (1 mol / L) was added to the reaction vessel. The mass ratio of 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene, mesitylene and acetic acid solution was 9:6:1.5:3. The mixture was heated to 100°C and kept at that temperature for 72 h to obtain an intermediate; the intermediate was washed sequentially with N,N-dimethylacetamide, acetone and anhydrous ethanol until the supernatant was colorless, dried at 70°C to constant weight, ground and passed through a 200-mesh sieve to obtain covalent organic framework material powder; the covalent organic framework material powder was dispersed in N,N-dimethylformamide and ultrasonically treated for 30 min to obtain a covalent organic framework material powder dispersion;

[0073] (2) Mix 0.1 mg / mL graphene oxide aqueous dispersion and 0.6 mg / mL covalent organic framework material powder dispersion evenly, wherein the mass ratio of graphene oxide to covalent organic framework material powder is 1:1, to obtain a mixed solution;

[0074] (3) Add deionized water to the mixed solution in step (2) until the volume of the mixed solution is 200 mL, stir evenly, adjust the pH value of the dispersion to 7.8 with 0.1 M NaOH, then sonicate for 30 min, stir at 85 ℃ for 2 h, sonicate again for 28 min, and then deposit the ultrasonically treated dispersion on the PAN substrate by positive pressure filtration (film forming pressure 8 bar), and heat treat in an oven at 70 ℃ for 1 h to obtain the modified graphene oxide membrane.

[0075] Example 8

[0076] (1) 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene, and mesitylene were mixed and ultrasonically treated to obtain a mixture; the mixture was placed in a reaction vessel, and then acetic acid solution (3 mol / L) was added to the reaction vessel. The mass ratio of 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene, mesitylene and acetic acid solution was 8:7:1.5:3. The mixture was heated to 90°C and kept at that temperature for 96 h to obtain an intermediate; the intermediate was washed sequentially with N,N-dimethylacetamide, acetone and anhydrous ethanol until the supernatant was colorless, dried at 80°C to constant weight, ground and passed through a 200-mesh sieve to obtain covalent organic framework material powder; the covalent organic framework material powder was dispersed in N,N-dimethylformamide and ultrasonically treated for 30 min to obtain a covalent organic framework material powder dispersion;

[0077] (2) Mix 0.3 mg / mL graphene oxide aqueous dispersion and 0.8 mg / mL covalent organic framework material powder dispersion evenly, wherein the mass ratio of graphene oxide to covalent organic framework material powder is 1:2, to obtain a mixed solution;

[0078] (3) Add deionized water to the mixed solution in step (2) until the volume of the mixed solution is 200 mL, stir evenly, adjust the pH value of the dispersion to 8.5 with 0.1 M NaOH, then sonicate for 30 min, stir at 85 ℃ for 2 h, sonicate again for 30 min, and then deposit the ultrasonically treated dispersion on the PAN substrate by positive pressure filtration (film forming pressure 8 bar), and heat treat in an oven at 70 ℃ for 1 h to obtain the modified graphene oxide membrane.

[0079] Comparative Example 1

[0080] The difference from Example 1 is that deionized water was used to replace the covalent organic framework material powder dispersion in equal amounts to obtain a graphene oxide film; the remaining steps are the same as in Example 1.

[0081] Comparative Example 2

[0082] The difference from Example 1 is that the mass ratio of the 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene, mesitylene and acetic acid solution is 6:7:1:3, and the remaining steps are the same as in Example 1.

[0083] Comparative Example 3

[0084] The difference from Example 1 is that the mass ratio of the 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene, mesitylene and acetic acid solution is 10:7:1:3, and the remaining steps are the same as in Example 1.

[0085] Comparative Example 4

[0086] The difference from Example 1 is that the mass ratio of graphene oxide to covalent organic framework material powder is 1:0.8, and the remaining steps are the same as in Example 1.

[0087] Comparative Example 5

[0088] The difference from Example 1 is that the mass ratio of graphene oxide to covalent organic framework material powder is 1:2.2, and the remaining steps are the same as in Example 1.

[0089] Comparative Example 6

[0090] The difference from Example 1 is that the film forming pressure is 5 bar, while the rest of the steps are the same as in Example 1.

[0091] Comparative Example 7

[0092] The difference from Example 1 is that the film forming pressure is 9 bar, while the rest of the steps are the same as in Example 1.

[0093] Comparative Example 8

[0094] The difference from Example 1 is that 1,3,5-benzenetricarboxyhydrazide is used to replace 1,3,5-tris(4-aminophenyl)benzene in equal amounts, while the other steps are the same as in Example 1.

[0095] Performance testing

[0096] The permeation flux and separation performance of the modified graphene oxide membranes provided in the test examples and comparative examples for a 10wt% / 90wt% water / butanol mixture were tested at a temperature of 60℃, and the results are shown in Table 1.

[0097] Table 1

[0098] Group <![CDATA[Permeation flux / kg / m 2 h]]> Separation factor Example 1 6.89 5937 Example 2 6.53 5525 Example 3 6.86 5927 Example 4 6.75 5871 Example 5 6.69 5882 Example 6 6.32 5224 Example 7 6.71 5879 Example 8 6.17 5028 Comparative Example 1 2.61 273 Comparative Example 2 4.25 3938 Comparative Example 3 5.13 4026 Comparative Example 4 4.49 3421 Comparative Example 5 4.29 3175 Comparative Example 6 5.36 4179 Comparative Example 7 5.17 3819 Comparative Example 8 4.53 3672

[0099] As shown in Table 1, the membrane materials prepared in the various embodiments of the present invention have high permeation flux and water / isopropanol separation factor.

[0100] The experimental data from Comparative Example 1 show that the permeation flux of pure graphene oxide membrane is relatively low. This may be because the structure of pure graphene oxide membrane is relatively compact, which affects the transfer rate of water molecules inside the membrane; and pure graphene oxide membrane is prone to swelling in aqueous solution environment, which reduces the flow rate of water molecules.

[0101] The membrane materials prepared in Comparative Examples 2 and 3 had low permeation flux and water / isopropanol separation factor, indicating that the mass ratio of 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene, mesitylene, and acetic acid solution was specific. Membrane materials prepared at ratios higher or lower than those defined in this invention exhibited poor separation performance.

[0102] The experimental data from Comparative Examples 4 and 5 show that the amount of covalent organic framework material added is closely related to the separation performance of the membrane material. When the amount of covalent organic framework material added is small, it cannot inhibit the swelling of graphene oxide in water and reduce the separation performance. When the amount of covalent organic framework material added is large, on the one hand, it will aggregate disorderly in the membrane, block the water flow channels, and reduce the water flux. On the other hand, it will destroy the regular stacking structure of the membrane layer, generate a large number of defective pores, and reduce the interception effect of isopropanol.

[0103] The experimental data from Comparative Examples 6 and 7 show that changing the membrane deposition pressure can regulate the separation performance of the membrane material. Lower deposition pressure requires a longer filtration time, resulting in a looser membrane structure and reduced separation performance. Higher deposition pressure reduces filtration time, but excessively fast deposition rates also reduce the membrane material's separation performance.

[0104] The experimental data from Comparative Example 8 show that the separation performance of the membrane material deteriorates after changing the type of monomer.

[0105] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a modified graphene oxide film, characterized in that, Includes the following steps: (1) Mix the aqueous dispersion of graphene oxide and the powder dispersion of covalent organic framework material evenly to obtain a mixed solution; (2) Add deionized water to the mixed solution in step (1), stir evenly, adjust the pH of the system to 7.8-8.5, sonicate, deposit the ultrasonically treated dispersion onto the PAN substrate through positive pressure filtration, and heat treat to obtain the modified graphene oxide membrane.

2. The method for preparing the modified graphene oxide film according to claim 1, characterized in that, The mass concentration of the graphene oxide aqueous dispersion in step (1) is 0.1-0.3 mg / mL.

3. The method for preparing the modified graphene oxide film according to claim 1, characterized in that, The mass concentration of the covalent organic framework material powder dispersion in step (1) is 0.5-0.8 mg / mL.

4. The method for preparing the modified graphene oxide film according to claim 1, characterized in that, The mass ratio of the graphene oxide and covalent organic framework material powder is 1:1-2.

5. The method for preparing the modified graphene oxide film according to claim 1, characterized in that, The preparation method of the covalent organic framework material powder dispersion includes the following steps: (1) 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene and mesitylene were mixed and ultrasonically treated to obtain a mixture; the mixture was placed in a reaction vessel, and then an acetic acid solution was added to the reaction vessel, the temperature was raised to 80-100℃, and the temperature was maintained for 72-120h to obtain an intermediate; the intermediate was washed until the supernatant was colorless, dried, ground, and sieved to obtain a covalent organic framework material powder; (2) The covalent organic framework material powder is dispersed in N,N-dimethylformamide and ultrasonically treated to obtain a covalent organic framework material powder dispersion.

6. The method for preparing the modified graphene oxide film according to claim 5, characterized in that, The mass ratio of 1,3,5-tris(4-aminophenyl)benzene, 2,6-dialdehyde-1,5-dihydroxynaphthalene, mesitylene and acetic acid solution in step (1) is 7-9:6-8:1-1.5:3-5; the molar concentration of acetic acid solution in step (1) is 1-3 mol / L.

7. The method for preparing the modified graphene oxide film according to claim 1, characterized in that, Step (2) Use 0.1M NaOH to adjust the pH of the system.

8. The method for preparing the modified graphene oxide film according to claim 1, characterized in that, The pressure of the positive pressure filter in step (2) is 6-8 bar.

9. The modified graphene oxide film prepared by the method according to any one of claims 1-8.

10. The modified graphene oxide membrane prepared by the method according to any one of claims 1-8, or the application of the modified graphene oxide membrane according to claim 9 in the field of organic solvent dehydration and recycling.