Composite nanofiltration membrane, preparation method and application thereof
The method of constructing composite nanofiltration membranes by combining photoresponsive molecules with graphene oxide solves the problems of easy damage to graphene oxide membranes under harsh environments and complex preparation, and achieves improved high-efficiency permeation performance and antifouling performance, making it suitable for water purification.
Patent Information
- Application Number
- CN202310945429.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-07-28
- Publication Date
- 2026-01-23
- Estimated Expiration
- 2043-07-28
AI Technical Summary
Traditional graphene oxide membranes are easily damaged in harsh environments, resulting in decreased separation performance, and their preparation process is complex and costly.
A photoresponsive composite nanofiltration membrane was constructed by combining photoresponsive molecular aggregates with graphene oxide and using a vacuum filtration method. The composite nanofiltration membrane with uniform structure was formed by utilizing the chelation and hydrogen bonding between the photoresponsive molecules and graphene oxide.
It improves the membrane's permeability and antifouling properties, simplifies the preparation process, reduces costs, and is suitable for mass industrial production.
Smart Images
Figure CN117101430B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to the field of membrane separation technology, in particular to a composite nanofiltration membrane and a preparation method and application thereof. BACKGROUND
[0002] The biggest survival challenge faced by the global human beings at present is water resource shortage, and solving water pollution is a key to alleviating the water resource shortage. Emerging membrane separation technology has the advantages of high efficiency and energy saving in the process of treating dye wastewater, organic wastewater and oil-containing wastewater.
[0003] Although the most commonly used polymer membrane has good performance in the separation process, the polymer membrane is easily damaged in harsh environments, thereby destroying the separation performance. As a carbon-based membrane, the two-dimensional layered graphene oxide membrane has become a popular object due to its stable structure and layered water transmission channel. However, the traditional graphene oxide membrane molecular separation process is too single, and is easily polluted by pollutants, thereby reducing the service life of the membrane. SUMMARY
[0004] In view of the problems in the background art, the application provides a composite nanofiltration membrane and a preparation method and application thereof. The preparation method of the composite nanofiltration membrane is simple in operation, low in reaction condition and environmentally friendly, and the flux of the prepared composite nanofiltration membrane is significantly improved.
[0005] According to a first aspect of the application, a preparation method of a composite nanofiltration membrane is provided, comprising the following steps: preparing a light-responsive molecular aggregate; adding the light-responsive molecular aggregate into a graphene oxide solution to obtain a mixed light-responsive molecular aggregate / graphene oxide mixed solution; and performing vacuum filtration on the light-responsive molecular aggregate / graphene oxide mixed solution on the surface of a base membrane by a vacuum filtration method, so as to form a composite nanofiltration membrane with uniform structure by chelation and hydrogen bonding between the light-responsive molecular aggregate and the graphene oxide.
[0006] In some embodiments of the application, the preparation of the light-responsive molecular aggregate comprises: dissolving a light-responsive molecular material in a benign solvent to obtain a light-responsive molecular benign solvent solution; adding the light-responsive molecular benign solvent solution into a centrifuge tube, adding a poor solvent into the centrifuge tube to form the light-responsive molecular aggregate.
[0007] In some embodiments of the application, the light-responsive molecular material is N-hydroxyethyl-3,3-dimethyl-6-nitroindoline spiropyran.
[0008] In some embodiments of the application, the benign solvent is methanol, and the poor solvent is deionized water.
[0009] In some embodiments of the present application, after obtaining the benign solvent solution of the light-responsive molecules, the methanol solution of the light-responsive molecules is first subjected to dark treatment or light irradiation.
[0010] In some embodiments of the present application, after adding the light-responsive molecular aggregates into the graphene oxide solution, ultrasonic treatment is performed to obtain a uniformly dispersed light-responsive molecular aggregate / graphene oxide mixed solution; the ultrasonic treatment is performed for 1-2 min.
[0011] In some embodiments of the present application, in the light-responsive molecular aggregate / graphene oxide mixed solution, the mass ratio of the light-responsive molecular material to graphene oxide is 0.5-10:1.
[0012] In some embodiments of the present application, the substrate film is one of a cellulose acetate film, a nylon film and a polytetrafluoroethylene film.
[0013] According to a second aspect of the present application, there is provided a composite nanofiltration membrane prepared according to the above preparation method.
[0014] According to a third aspect of the present application, there is provided the use of the composite nanofiltration membrane prepared according to the above preparation method in water purification.
[0015] Compared with the prior art, the present application achieves the following technical effects:
[0016] 1. The present application constructs a light-responsive graphene oxide film by combining light-responsive molecules with graphene oxide, and for the first time introduces molecular aggregates for the construction of light-responsive films. Compared with other chemically synthesized responsive polymers, the synthesis process of the molecular aggregates is more environmentally friendly.
[0017] 2. The composite nanofiltration membrane preparation method provided by the present application can be quickly prepared by vacuum suction filtration, and the membrane preparation process is simple, does not require a large amount of organic solvent, and is low in cost, and can be applied to large-scale industrial production.
[0018] 3. The GP light-responsive film has excellent performance of active and passive synergistic antifouling. BRIEF DESCRIPTION OF DRAWINGS
[0019] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The accompanying drawings are included to provide a description of the preferred embodiments and are not intended to limit the scope of the present application. Moreover, the same reference numerals are used throughout the various drawings to designate identical parts. In the drawings:
[0020] Figure 1 is a scanning electron micrograph of the film, Figure 1 a is a scanning electron micrograph of the GO film obtained in Comparative Example 1,Figure 1 b is a scanning electron microscope image of the GP-250 film obtained in Example 1, Figure 1 c is a scanning electron microscope image of the GP-500 film obtained in Example 1;
[0021] Figure 2 is a water contact angle image of the film, Figure 2 a is a water contact angle image of the GP-250 (Vis / Dark) film obtained in Example 1, Figure 2 b is a water contact angle image of the GP-500 (Vis / Dark) film obtained in Example 1, Figure 2 c is a water contact angle histogram of the GP-250 (Vis / Dark) film, the GP-500 (Vis / Dark) film obtained in Example 1;
[0022] Figure 3 is a pure water flux image of the GO film obtained in Comparative Example 1, each GP composite film obtained in Example 1;
[0023] Figure 4 is a dye rejection performance image of the film, Figure 4 a is a dye rejection performance image of the GO film obtained in Comparative Example 2, the GP-250 composite film obtained in Example 3 against CrV, Figure 4 b is a dye rejection performance image of the GO film obtained in Comparative Example 1, the GP-250 composite film obtained in Example 2 against O-YG;
[0024] Figure 5 is an antifouling performance image of the film, Figure 5 a is an antifouling performance image of the GP-500 composite film obtained in Example 4 against the BSA solution, Figure 5 b is an antifouling performance image of the GP-500 composite film obtained in Example 5 against the HA solution. DETAILED DESCRIPTION
[0025] Exemplary embodiments of the present disclosure will be described in greater detail below with reference to the accompanying drawings. It should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure can be more thoroughly understood, and so that the scope of the present disclosure can be completely conveyed to those skilled in the art.
[0026] The two-dimensional layered graphene oxide film as a carbon-based film has become a popular object due to its stable structure and layered water transport channel. However, the conventional graphene oxide film molecular separation process is too single, and is easily contaminated by contaminants, causing the permeability to decrease, and reducing the service life of the film. Therefore, it is of great significance to develop a graphene oxide film with antifouling performance and multifunctional separation.
[0027] Inspired by the stimulable response of biological membranes in nature, intelligent responsive membranes have been developed to meet the complex separation process. These intelligent responsive membranes mainly rely on the sensing of some responsive polymers themselves to chemical / physical signals, and their own characteristics will change to adjust the structure of the membrane. These chemical / physical signals mainly include light, temperature, pH, oxidation and reduction, electric field, ion concentration, magnetic field.
[0028] Therefore, the application provides a preparation method of a light-responsive composite nanofiltration membrane constructed by a green light-responsive molecular aggregate and graphene oxide, which is simple to operate and has a low-carbon and environmentally friendly preparation process, to solve the problems of poor antifouling performance of the graphene oxide membrane and relatively complex preparation process and high cost in the current preparation method.
[0029] Meanwhile, in order to further adhere to the theme of environmental protection, the light-responsive molecular aggregate is introduced for the first time by switching between a good solvent and a poor solvent to construct a light-responsive membrane, and a series of light-responsive composite nanofiltration membranes are prepared by vacuum assisted filtration, i.e., a light-responsive composite nanofiltration membrane constructed by a light-responsive molecular aggregate and graphene oxide.
[0030] The preparation method of the composite nanofiltration membrane first prepares a light-responsive molecular aggregate, then ultrasonically mixes graphene oxide solution and the light-responsive molecular aggregate to assist the dispersion, obtains a mixed light-responsive molecular aggregate / graphene oxide mixed solution, and finally filters the light-responsive molecular aggregate / graphene oxide mixed solution to the surface of a polymer substrate membrane by vacuum filtration, to form a composite nanofiltration membrane with uniform structure by using the hydrogen bond and electrostatic interaction between the light-responsive molecular aggregate and graphene oxide.
[0031] The preparation method of the composite nanofiltration membrane specifically includes the following steps:
[0032] (1) Preparing a light-responsive molecular aggregate: first, dissolving a light-responsive molecular material in a good solvent to obtain a light-responsive molecular good solvent solution; then adding the light-responsive molecular good solvent solution into a centrifuge tube, adding a poor solvent in the centrifuge tube, and forming a light-responsive molecular aggregate.
[0033] Specifically, the light-responsive molecular material can be N-hydroxyethyl-3,3-dimethyl-6-nitroindoline spiropyran, the good solvent can be methanol, and the poor solvent can be deionized water.
[0034] Further, after obtaining the light-responsive molecular good solvent solution, first, the light-responsive molecular good solvent solution is subjected to dark treatment or light treatment, and then the light-responsive molecular good solvent solution is added into the centrifuge tube, the poor solvent is added in the centrifuge tube, and the light-responsive molecular aggregate is formed.
[0035] (2) Preparation of a light-responsive molecular aggregate / oxidized graphene mixed solution: the light-responsive molecular aggregate is added to the oxidized graphene solution to obtain a light-responsive molecular aggregate / oxidized graphene mixed solution that is uniformly mixed. It should be noted that when the poor solvent in the light-responsive molecular aggregate and the solvent in the oxidized graphene solution are both deionized water, the light-responsive molecular good solvent solution and the oxidized graphene can be directly added to the deionized water, and then uniformly mixed to obtain the light-responsive molecular aggregate / oxidized graphene mixed solution.
[0036] Further, after the light-responsive molecular aggregate is added to the oxidized graphene solution, ultrasonic treatment can be performed to obtain a uniformly dispersed light-responsive molecular aggregate / oxidized graphene mixed solution. Specifically, the ultrasonic treatment time can be 1-2 min.
[0037] Further, in the light-responsive molecular aggregate / oxidized graphene mixed solution, the mass ratio of the light-responsive molecular material to the oxidized graphene is 0.5-10:1, for example, the mass ratio of the light-responsive molecular material to the oxidized graphene is 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, etc.
[0038] (3) Filtration: the light-responsive molecular aggregate / oxidized graphene mixed solution is filtered onto the surface of a substrate film by vacuum filtration, and a composite nanofiltration membrane with uniform structure is formed by the chelation and hydrogen bonding between the light-responsive molecular aggregate and the oxidized graphene.
[0039] Specifically, the substrate film can be one of a cellulose acetate film, a nylon film, and a polytetrafluoroethylene film.
[0040] The preparation method of the composite nanofiltration membrane will be further described below in combination with specific examples; in the following examples, the materials and reagents used, unless otherwise specified, can be commercially available products and are not limited.
[0041] Example 1
[0042] (1) N-hydroxyethyl-3,3-dimethyl-6-nitroindoline spiropyran is fully dissolved in methanol to obtain a 0.5 mg / mL SP (spiropyran) methanol solution. The SP methanol solution is divided into dark treatment and light treatment, each of which is named SP-Dark (dark treatment) and SP-Vis (light treatment).
[0043] (2) Take 50 μg, 100 μg, 250 μg, 500 μg, 1000 μg of the SP methanol solution obtained in step (1) under the two conditions respectively, and 100 μg of graphene oxide, add them into 50 mL of water, and ultrasonically treat for 1 min to make them uniformly mixed, to obtain 10 kinds of light-responsive SP molecular aggregate / graphene oxide mixed solutions, namely GP-50(Vis / Dark), GP-100(Vis / Dark), GP-250(Vis / Dark), GP-500(Vis / Dark), and GP-1000(Vis / Dark).
[0044] (3) Take the 10 kinds of light-responsive SP molecular aggregate / graphene oxide mixed solutions obtained in step (2) and filter them on the surface of an organic nylon membrane with a diameter of 47 mm and a pore size of 0.22 μm, and after the filtration is completed, store the formed GP-50(Vis / Dark), GP-100(Vis / Dark), GP-250(Vis / Dark), GP-500(Vis / Dark), and GP-1000(Vis / Dark) composite nanofiltration membranes in deionized water.
[0045] After the preparation is completed, the wettability, membrane surface morphology, and other properties of each composite nanofiltration membrane constructed by the light-responsive SP molecular aggregate and graphene oxide are characterized, and the response law of the pure water flux is analyzed, and the test analysis results are as shown in Figures 1-5
[0046] As shown in Figs. b and c in Figure 1 , the surface morphology of the GP-250 and GP-500 membranes changes with the increase of the content of the SP molecular aggregate, and the SP molecular aggregate is generated on the surface of the GP-500 membrane.
[0047] As shown in Figure 2 , compared with the GP-250 membrane, the water contact angle of the GP-500 membrane changes more greatly under the Vis / Dark condition.
[0048] As shown in Figure 3 , the water flux of the GP membrane under the Vis / Dark condition has a clear response law.
[0049] As shown in Figure 4 , the GP-250 membrane separates different dye molecules through size effect and electrostatic interaction.
[0050] As shown in Figure 5 , the flux recovery rate of the GP-500 Vis membrane for BSA reaches 95.80%, and the flux recovery rate of the GP-500 Dark membrane for HA reaches 86.50%.
[0051] Example 2
[0052] (1) N-hydroxyethyl-3, 3-dimethyl-6-nitroindoline spiropyran was dissolved in methanol to obtain a 0.5 mg / mL SP methanol solution. The SP methanol solution was divided into dark treatment and light treatment, each one, and named SP-Dark and SP-Vis, respectively.
[0053] (2) 250 μg of the SP methanol solution obtained under the two conditions of step (1) was added to 50 mL of water, respectively, and 100 μg of graphene oxide was added to each to mix uniformly under ultrasonic treatment for 1 min, to obtain a mixed solution of light-responsive SP molecular aggregate / graphene oxide.
[0054] (3) The light-responsive SP molecular aggregate / graphene oxide mixed solution obtained in step (2) was filtered on the surface of an organic nylon membrane (diameter 47 mm, pore size 0.22 μm), and after filtration was completed, the GP-250 (Vis / Dark) composite nanofiltration membrane formed was stored in deionized water.
[0055] After preparation, the separation performance of the composite nanofiltration membrane constructed by the above light-responsive SP molecular aggregate and graphene oxide was tested, and it was applied to the filtration and separation of orange yellow G solution (O-YG), Figure 4 The results of Figure b in the above table show that the fluxes of the GP-250Vis membrane and the GP-250Dark membrane to the orange yellow G solution are 16.46 · m -2 ·h -1 ·bar -1 , 15.83 L·m -2 ·h -1 ·bar -1 , and the retention rates are 92.56%, 96.53%, respectively.
[0056] Example 3
[0057] (1) N-hydroxyethyl-3, 3-dimethyl-6-nitroindoline spiropyran was dissolved in methanol to obtain a 0.5 mg / mL SP methanol solution. The SP methanol solution was divided into dark treatment and light treatment, each one, and named SP-Dark and SP-Vis, respectively.
[0058] (2) 250 μg of the SP methanol solution obtained under the two conditions of step (1) was added to 50 mL of water, respectively, and 100 μg of graphene oxide was added to each to mix uniformly under ultrasonic treatment for 1 min, to obtain a mixed solution of light-responsive SP molecular aggregate / graphene oxide.
[0059] (3) The light-responsive SP molecular aggregate / oxidized graphene mixed solution obtained in step (2) was filtered on the surface of an organic nylon membrane (diameter 47 mm, pore size 0.22 μm), and after the filtration was completed, the GP-250 (Vis / Dark) composite nanofiltration membrane formed was stored in deionized water.
[0060] After the preparation was completed, the separation performance test was performed on the composite nanofiltration membrane of each light-responsive SP molecular aggregate and oxidized graphene, and the composite nanofiltration membrane was applied to the filtration and separation of crystal violet solution (CrV), Figure 4 The results in FIG. a of the above show that the fluxes of the GP-250Vis membrane and the GP-250Dark membrane to the crystal violet solution were 28.33 L·m -2 ·h -1 ·bar -1 , and the rejection rates were 66.27% and 56.06%, respectively.
[0061] Example 4
[0062] (1) N-hydroxyethyl-3,3-dimethyl-6-nitroindoline spiropyran was fully dissolved in methanol to obtain a 0.5 mg / mL SP methanol solution. The SP methanol solution was divided into dark treatment and light treatment, each of which was named SP-Dark and SP-Vis.
[0063] (2) 500 μg of the SP methanol solution obtained in step (1) under the two conditions was added to 100 μg of oxidized graphene in 50 mL of water, and ultrasonic treatment was performed for 1 min to mix them uniformly. A light-responsive SP molecular aggregate / oxidized graphene mixed solution was obtained.
[0064] (3) The light-responsive SP molecular aggregate / oxidized graphene mixed solution obtained in step (2) was filtered on the surface of an organic nylon membrane (diameter 47 mm, pore size 0.22 μm), and after the filtration was completed, the GP-500 (Vis / Dark) composite nanofiltration membrane formed was stored in deionized water.
[0065] After the preparation was completed, the anti-fouling performance test was performed on the composite nanofiltration membrane of each light-responsive SP molecular aggregate and oxidized graphene, and the anti-fouling performance test was performed on the composite nanofiltration membrane by applying it to a BSA solution, Figure 5 The results in FIG. a of the above show that the flux recovery rates of the GP-500Vis membrane and the GP-500Dark membrane to the BSA solution were 95.80% and 77.52%, respectively.
[0066] Example 5
[0067] (1) N-hydroxyethyl-3,3-dimethyl-6-nitroindoline spiropyran was fully dissolved in methanol to obtain a 0.5 mg / mL SP methanol solution. The SP methanol solution was divided into one portion for dark treatment and one portion for light treatment, named SP-Dark and SP-Vis, respectively.
[0068] (2) Take 500 μg of each of the SP methanol solutions obtained in step (1) under the two conditions and add them to 50 mL of water with 100 μg of graphene oxide. Sonicate the solution for 1 min to make it homogeneous. A homogeneous photoresponsive SP molecular aggregate / graphene oxide mixed solution is obtained.
[0069] (3) The photoresponsive SP molecular aggregate / graphene oxide mixed solution obtained in step (2) is filtered onto the surface of an organic nylon membrane (47 mm in diameter and 0.22 μm in pore size). After filtration, the GP-500 (Vis / Dark) composite nanofiltration membrane is stored in deionized water.
[0070] After preparation, the antifouling performance of each composite nanofiltration membrane constructed from the above-mentioned photoresponsive SP molecular aggregates and graphene oxide was tested, and it was applied to the antifouling performance test of HA solution. Figure 5 Figure b shows that the flux recovery rates of the GP-500Vis membrane and the GP-500Dark membrane for HA solution were 75.17% and 86.50%, respectively.
[0071] Comparative Example 1:
[0072] (1) Add 100 μg of graphene oxide to 50 mL of water and sonicate for 1 min to disperse it evenly. Divide the solution into one portion for dark treatment and one portion for light treatment.
[0073] (2) The graphene oxide dispersion obtained in step (1) was filtered onto the surface of an organic nylon membrane (47 mm in diameter and 0.22 μm in pore size). After filtration, the nanofiltration membrane was stored at room temperature.
[0074] After preparation, the nanofiltration membrane was characterized structurally and its separation performance was tested. It was then applied to the filtration and separation of orange-yellow G solution. Figure 4 Figure b shows that the water flux of the GO-Vis membrane and the GO-Dark membrane is 7.08 L·m⁻¹. -2 ·h -1 ·bar -1 and 6.25 L·m -2 ·h -1 ·bar -1 The retention rates for Orange G solution were 59.6% and 64.32%, respectively. Its surface morphology is as follows: Figure 1As shown in Fig. a of the drawings, the pure GO surface is smooth and dense, which is not conducive to the transmission of water, and thus the water flux is small.
[0075] Comparative Example 2:
[0076] (1) 100 μg of graphene oxide was added to 50 mL of water and ultrasonically treated for 1 min to disperse uniformly. The solution was divided into dark treatment and light treatment each one.
[0077] (2) The graphene oxide dispersion obtained in step (1) was filtered on the surface of an organic nylon membrane (diameter 47 mm, pore size 0.22 μm), and after the filtration was completed, the nanofiltration membrane formed was stored at room temperature.
[0078] After preparation, the above nanofiltration membrane was subjected to structural characterization, separation performance test, and was applied to the filtration and separation of crystal violet solution, Figure 4 The results of Fig. a of the drawings show that the water fluxes of GO-Vis membrane and GO-Dark membrane are 23.96 L·m -2 ·h -1 ·bar -1 and 23.91 L·m -2 ·h -1 ·bar -1 , respectively, and the rejection rates of crystal violet solution are 31% and 30.16%, respectively.
[0079] The above-described embodiments are only a preferred scheme of the present application, and are not intended to limit the present application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application. For example, the types of SP molecular aggregates, SP molecular aggregate solutions configured with different organic solvents, drying temperature and drying time of the composite nanofiltration membrane can be adjusted, but the drying temperature should not be too high to prevent the reduction of graphene oxide. Therefore, any technical scheme obtained by equivalent substitution or equivalent transformation falls within the protection scope of the present application.
Claims
1. A method for preparing a composite nanofiltration membrane, characterized in that, Includes the following steps: Preparation of photoresponsive molecular aggregates; Photoresponsive molecular aggregates were added to the graphene oxide solution to obtain a homogeneous mixed solution of photoresponsive molecular aggregates / graphene oxide. A mixed solution of photoresponsive molecular aggregates and graphene oxide was filtered onto the surface of a substrate membrane using a vacuum filtration method. The chelation and hydrogen bonding between the photoresponsive molecular aggregates and graphene oxide were then used to form a composite nanofiltration membrane with a uniform structure.
2. The method for preparing the composite nanofiltration membrane according to claim 1, characterized in that, The preparation of the photoresponsive molecular aggregates includes: The photoresponsive molecular material is dissolved in a benign solvent to obtain a photoresponsive molecular benign solvent solution; A good solvent solution for photoresponsive molecules is added to a centrifuge tube, and a bad solvent is added to the centrifuge tube to form aggregates of photoresponsive molecules.
3. The method for preparing the composite nanofiltration membrane according to claim 2, characterized in that, The photoresponsive molecular material is N-hydroxyethyl-3,3-dimethyl-6-nitroindolinespiropyran.
4. The method for preparing the composite nanofiltration membrane according to claim 2, characterized in that, The benign solvent is methanol, and the undesirable solvent is deionized water.
5. The method for preparing the composite nanofiltration membrane according to claim 2, characterized in that, After obtaining the photoresponsive molecule benign solvent solution, the photoresponsive molecule benign solvent solution is first subjected to dark treatment or light treatment.
6. The method for preparing the composite nanofiltration membrane according to claim 1, characterized in that, After adding the photoresponsive molecular aggregates to the graphene oxide solution, ultrasonic treatment was performed to obtain a uniformly dispersed photoresponsive molecular aggregates / graphene oxide mixed solution. The ultrasonic treatment time is 1-2 minutes.
7. The method for preparing the composite nanofiltration membrane according to claim 1, characterized in that, In the photoresponsive molecular aggregate / graphene oxide mixed solution, the mass ratio of the photoresponsive molecular material to the graphene oxide is 0.5-10:
1.
8. The method for preparing the composite nanofiltration membrane according to claim 1, characterized in that, The base membrane is one of cellulose acetate membrane, nylon membrane, or polytetrafluoroethylene membrane.
9. A composite nanofiltration membrane, characterized in that, The composite nanofiltration membrane is prepared by the preparation method according to any one of claims 1-8.
10. The application of the composite nanofiltration membrane prepared by the preparation method according to any one of claims 1-8 in water purification.