Composite nanofiltration membrane based on bidirectional interfacial polymerization as well as preparation method and application of composite nanofiltration membrane
By using bidirectional interfacial polymerization to carry out the polymerization reaction in the in-plane channels of two-dimensional porous graphene, the problem of balancing permeability and selectivity in nanofiltration membranes is solved, achieving highly efficient antibiotic separation.
Patent Information
- Application Number
- CN202610523939.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-04-20
- Publication Date
- 2026-05-26
AI Technical Summary
Existing nanofiltration membranes struggle to balance permeability and selectivity, and the in-plane pores of two-dimensional porous materials are difficult to precisely control and stably encapsulate, resulting in limited improvements in membrane performance.
A two-way interfacial polymerization method is adopted, in which aqueous amine monomers are introduced from the lower surface and organic monomers are introduced from the upper surface. Through interfacial polymerization reaction, in-situ polymerization is carried out in the in-plane channels of two-dimensional porous graphene to achieve precise pore shrinkage and encapsulation, forming a two-dimensional porous graphene/polymer separation layer.
A composite nanofiltration membrane with both high permeation flux and high selectivity was prepared, solving the "trade-off" effect between permeability and selectivity, and achieving efficient retention and high permeation flux for antibiotics of different molecular sizes.
Smart Images
Figure CN122076266A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of membrane separation technology, and in particular to a composite nanofiltration membrane based on bidirectional interfacial polymerization, its preparation method, and its application. Background Technology
[0002] The environmental pollution caused by antibiotic overuse is becoming increasingly serious, making the development of efficient and energy-saving antibiotic separation technologies a research hotspot. Nanofiltration membranes, due to their nanoscale pore size (0.5-2 nm) and surface charge effect, exhibit significant advantages in the removal of small-molecule organic pollutants such as antibiotics. Currently, most mainstream nanofiltration membranes are polyamide film composite membranes prepared through traditional interfacial polymerization methods. However, the traditional interfacial polymerization process is difficult to precisely control, easily forming excessively thick or dense polymer separation layers, resulting in low membrane permeation flux, high operating energy consumption, and a common "trade-off" effect between permeability and selectivity.
[0003] To overcome these limitations, researchers have attempted to introduce two-dimensional nanomaterials (such as graphene oxide and MXene) into polymer separation layers to construct thin-layer nanocomposite membranes. However, these two-dimensional materials are typically dispersed in the separation layer as fillers, lacking in-plane mass transfer channels and prone to aggregation, thus offering limited improvement to membrane performance. Recent research shows that constructing regular nanopores within the plane of two-dimensional materials can create vertical mass transfer channels, significantly reducing water molecule transport resistance. However, precisely controlling the size of these in-plane nanopores and stably encapsulating them in the composite membrane structure, while avoiding selectivity degradation due to excessively large pores, remains a key technical challenge that urgently needs to be addressed.
[0004] To address the aforementioned problems, this invention proposes a novel method for preparing composite nanofiltration membranes based on a "bidirectional interfacial polymerization" strategy. This method uses two-dimensional porous graphene with abundant in-plane pores as the intermediate functional layer. Through a bidirectional diffusion interfacial polymerization reaction, two-phase monomers are polymerized in situ within the in-plane pores of the two-dimensional porous graphene, achieving precise pore reduction and efficient encapsulation of the in-plane pores of the two-dimensional porous graphene, thereby preparing a composite nanofiltration membrane with both high permeability and high selectivity.
[0005] This invention develops a novel interfacial polymerization method that is simple, easy to operate, low in cost, pollution-free, and easy to promote, which is of great significance for the separation and application of antibiotics. Summary of the Invention
[0006] The purpose of this invention is to address the problems in the prior art where it is difficult to balance the permeability and selectivity of nanofiltration membranes and the difficulty in precisely controlling and stably encapsulating the in-plane pores of two-dimensional porous materials, and to provide a composite nanofiltration membrane based on bidirectional interfacial polymerization, its preparation method, and its application.
[0007] The technical solution adopted to achieve the purpose of this invention is: A method for preparing a composite nanofiltration membrane based on bidirectional interfacial polymerization includes the following steps: Step 1: Load two-dimensional porous graphene onto the upper surface of a porous support membrane to obtain a composite membrane of two-dimensional porous graphene layer / support layer. Step 2: Contact the lower surface of the composite membrane obtained in Step 1 with an aqueous amine monomer solution, so that the aqueous solution wets the support layer and diffuses upward to the two-dimensional porous graphene layer. Step 3: The upper surface of the two-dimensional porous graphene layer of the composite membrane treated in Step 2 is brought into contact with the organic phase monomer solution, so that the aqueous phase amine monomer and the organic phase monomer undergo an interfacial polymerization reaction in the in-plane pores of the two-dimensional porous graphene to form a porous graphene / polymer separation layer, thereby achieving in-situ pore reduction and encapsulation of the in-plane pores of the two-dimensional porous graphene, and obtaining the composite nanofiltration membrane.
[0008] Preferably, in step 1, the two-dimensional porous graphene is prepared by a top-down liquid phase etching method or a bottom-up interfacial polymerization method, and the in-plane pore size of the two-dimensional porous graphene is 0.5-20.0 nm.
[0009] Preferably, in step 1, the supporting membrane is one of polyethersulfone membrane, polysulfone membrane, polyvinylidene fluoride membrane, and polytetrafluoroethylene membrane; the two-dimensional porous graphene is loaded onto the surface of the supporting membrane by vacuum-assisted self-assembly, pressure-assisted self-assembly, or spin-coating, with a loading amount of 20-500 mg·m³. -2 By controlling the loading of two-dimensional porous graphene, precise separation of antibiotics with different molecular sizes can be achieved.
[0010] Preferably, in step 2, the aqueous amine monomer is at least one of piperazine, m-phenylenediamine, polyethyleneimine, ethylenediamine, and triethylenetetramine; and the concentration of the aqueous amine monomer in the aqueous amine monomer solution is 0.01-2 w / v.
[0011] Preferably, in step 2, the specific steps for contacting the lower surface of the composite membrane obtained in step 1 with the aqueous amine monomer solution are as follows: the two-dimensional porous graphene layer of the composite membrane is placed on top and the support layer is placed on the bottom, and the aqueous amine monomer solution is sprayed or scraped onto the lower surface of the support layer, allowing it to naturally diffuse and wet upwards.
[0012] Preferably, in step 3, the organic phase monomer is at least one selected from pyromellitic trimethylolpropionate, pyromellitic tetramethylolpropionate, isophthaloyl chloride, terephthalic diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, 4,4-diphenylmethane diisocyanate, and 1,4-phenyl diisocyanate; the solvent of the organic phase monomer solution is at least one selected from n-hexane, cyclohexane, or isoalkanes; and the concentration of the organic phase monomer in the organic phase monomer solution is 0.05-1 w / v.
[0013] Preferably, in step 3, the interfacial polymerization reaction time is 10-300 s and the reaction temperature is 20-50℃.
[0014] Preferably, in step 3, the in-situ pore shrinkage and the encapsulated composite membrane are further post-processed to obtain the composite nanofiltration membrane. The post-processing step is to perform air bath heat treatment at 40-80 ℃ for 1-30 min to improve the post-crosslinking process of the polymer crosslinking network.
[0015] Another aspect of the present invention includes a composite nanofiltration membrane obtained by the preparation method, the composite nanofiltration membrane comprising a porous support layer and a two-dimensional porous graphene / polymer separation layer; the two-dimensional porous graphene layer is encapsulated by a polymer to form a two-dimensional porous graphene / polymer separation layer, and the in-plane pores of the two-dimensional porous graphene are reduced in size after in-situ pore reduction by the polymer.
[0016] In the above technical solution, the average pore size of the two-dimensional porous graphene / polymer separation layer is less than 7 Å.
[0017] Another aspect of the present invention includes the application of the composite nanofiltration membrane in antibiotic separation.
[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. An innovative two-way interfacial polymerization strategy: By introducing aqueous amine monomers from the lower surface of the composite membrane and organic monomers from the two-dimensional porous graphene layer on the upper surface, the interfacial polymerization reaction occurs precisely within the in-plane channels of the two-dimensional porous graphene. The polymer undergoes a cross-linking reaction within the in-plane channels of the two-dimensional porous graphene, reducing the originally large in-plane pores (1.0-20.0 nm) in situ to a smaller separation pore size (~7.0 Å), achieving precise pore reduction of the two-dimensional porous graphene. This strategy overcomes the challenges of difficult pore control and structural instability in two-dimensional materials, resulting in a stable composite nanofiltration membrane that can operate stably for long periods.
[0019] 2. The two-dimensional porous graphene layer regulates the diffusion behavior of aqueous amine monomers during interfacial polymerization, resulting in a more porous polymer separation layer structure. At the same time, during the separation process, the in-plane pores of the two-dimensional porous graphene itself provide short-range vertical transport paths for water molecules, effectively overcoming the "trade-off" effect of permeability and selectivity.
[0020] 3. In traditional interfacial polymerization, the aqueous phase and organic phase are in direct contact, resulting in a rapid reaction rate and concentrated exothermic reaction. The thickness, crosslinking degree, and uniformity of the polymer separation layer are difficult to control, easily leading to excessively thick or dense separation layers. For mesolayer nanofiltration membranes, a dense polymer coating layer is typically formed on the surface of the two-dimensional material. The polymer and the two-dimensional material exhibit a simple physical superposition, making it difficult to fully utilize the in-plane mass transfer advantages of the two-dimensional material. This invention's unique "bidirectional interfacial polymerization" strategy diffuses the aqueous amine monomer upwards from the lower surface of the support layer, while the organic monomer contacts downwards from the upper surface of the graphene layer. The encounter between the two monomer phases is confined within the in-plane channels of the two-dimensional porous graphene. This spatial confinement effect significantly reduces the reaction rate, transforming the polymerization reaction from an "instantaneous burst" to a "controlled growth," facilitating the preparation of ultrathin two-dimensional porous graphene / polymer separation layers.
[0021] 4. By simply adjusting the loading amount of two-dimensional porous graphene (20-500 mg·m³), -2 By selecting different two-dimensional porous graphenes, it is possible to achieve efficient retention and high permeability of antibiotics of different molecular sizes, such as ciprofloxacin (CIP), tetracycline (TC), erythromycin (ERY), and bacitracin (BAC), demonstrating good versatility and flexibility in application. Attached Figure Description
[0022] Figure 1 The images shown are double spherical aberration electron microscope images of the two-dimensional porous graphene in-plane pore structure in Examples 1-2. Figure 2 This is a comparison of the dimensional changes of the inner pores of the two-dimensional porous graphene before and after in-situ pore reduction by the polyamide layer in Example 1; Figure 3 This is a TEM image showing the thickness of the separation layer at the cross-section of the composite nanofiltration membrane in Example 1; Figure 4 This is an FESEM image of the separation layer thickness at the cross-section of the composite nanofiltration membrane in Example 2; Figure 5 These are TEM images of the two-dimensional porous graphene in Example 3 before and after polyamide shrinkage and encapsulation. Figure 6 This is an FESEM image of the separation layer thickness at the cross-section of the composite nanofiltration membrane in Example 3; Figure 7 These are TEM images of the two-dimensional porous graphene in Example 4 before and after polyurea pore reduction and encapsulation. Figure 8 This is a TEM image showing the thickness of the separation layer at the cross-section of the composite nanofiltration membrane in Example 4. Detailed Implementation
[0023] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
[0024] Example 1 A method for preparing a composite nanofiltration membrane based on bidirectional interfacial polymerization includes the following steps: Step 1: The two-dimensional porous graphene prepared by bottom-up interfacial polymerization was ultrasonically dispersed in deionized water to prepare a solution of 0.04 g·L⁻¹. -1 A two-dimensional porous graphene dispersion was obtained. 10 mL of this dispersion was diluted to 50 mL with deionized water and vacuum filtered through a polyethersulfone microfiltration membrane (support membrane) at 0.6 bar, yielding a two-dimensional porous graphene loading of 203.8 mg·m³. -2 A composite film of two-dimensional porous graphene layer / polyethersulfone support layer. Double aberration electron microscopy image of the in-plane pore structure of the two-dimensional porous graphene is shown below. Figure 1 As shown in the figure, this two-dimensional porous graphene has abundant in-plane pore structures.
[0025] Step 2: Keeping the orientation of the composite membrane unchanged, spray 1 mL of a 0.05 w / v% aqueous solution of piperazine (aqueous amine monomer) onto the lower surface of the support layer, allowing it to naturally diffuse upwards and wet for 1 min, and then use filter paper to absorb the excess droplets.
[0026] Step 3: 2 mL of a 0.2 w / v% pyromellitic acid chloride / n-hexane solution was used to wet the upper surface of the two-dimensional porous graphene layer, and the interfacial polymerization reaction was carried out at room temperature for 20 s. The organic phase was then discarded, and the membrane was heat-treated in a 60 ℃ oven for 5 min. It was then washed sequentially with n-hexane and deionized water to obtain the composite nanofiltration membrane.
[0027] The composite nanofiltration membrane obtained in this embodiment includes a porous support layer (polyethersulfone microfiltration membrane) and a two-dimensional porous graphene / polymer separation layer; the two-dimensional porous graphene is in-situ pore-shrinking and encapsulated by a polymer (a polyamide layer formed by the polymerization of piperazine and trimesoyl chloride) (the macropores in the two-dimensional porous graphene are partially blocked and shrunk, while the polymer connects the graphene sheets to form a whole) to form the two-dimensional porous graphene / polyamide separation layer, such as... Figure 2 As shown, the in-plane pores of two-dimensional porous graphene are reduced in size from 13.70 Å to 6.98 Å after in-situ pore shrinkage by polymer.
[0028] The TEM image of the separation layer thickness at the cross-section of the composite nanofiltration membrane obtained in this embodiment is shown below. Figure 3 As shown in the figure, the two-dimensional porous graphene / polyamide layer has an ultrathin thickness of approximately 35.6 nm.
[0029] Tests showed that the composite nanofiltration membrane exhibited a 94.2% rejection rate for ERY and a permeation flux of 42.6 L·m⁻² at an operating pressure of 2 bar. -2 ·h -1 ·bar -1 The rejection rate for BAC was 99.1%, and the permeation flux was 40.8 L·m⁻¹. -2 ·h -1 ·bar -1 .
[0030] Example 2 A method for preparing a composite nanofiltration membrane based on bidirectional interfacial polymerization includes the following steps: Step 1: The two-dimensional porous graphene prepared by bottom-up interfacial polymerization was ultrasonically dispersed in deionized water to prepare a solution of 0.04 g·L⁻¹. -1 A dispersion was prepared. 5 mL of this dispersion was diluted to 50 mL with deionized water and vacuum filtered through a polyethersulfone microfiltration membrane at 0.6 bar to obtain a two-dimensional porous graphene loading of 101.9 mg·m³. -2 Two-dimensional porous graphene / polyethersulfone composite membrane; Step 2 is the same as step 2 in Example 1; Step 3 is the same as step 3 in Example 1.
[0031] The difference between this embodiment and Example 1 lies in the reduced loading of two-dimensional porous graphene. The lower loading results in a thinner two-dimensional porous graphene layer, and consequently, a thinner two-dimensional porous graphene / polyamide layer. However, the reduced loading of the two-dimensional porous graphene leads to a more dense cross-linking of the polyamide, making the two-dimensional porous graphene / polyamide layer suitable for the separation of antibiotics with smaller sizes and molecular weights (such as TC and CIP).
[0032] The FESEM image of the separation layer thickness at the cross-section of the composite nanofiltration membrane obtained in this embodiment is shown below. Figure 4 As shown in the figure, the thickness of the two-dimensional porous graphene / polyamide layer is approximately 33.1 nm.
[0033] Tests showed that the composite nanofiltration membrane achieved a TC rejection rate of 94.8% and a permeation flux of 22.4 L·m⁻² at an operating pressure of 2 bar. -2 ·h -1 ·bar -1 The rejection rate for CIP was 92.5%, and the penetration flux was 20.1 L·m⁻¹. -2 ·h-1 ·bar -1 .
[0034] Example 3 A method for preparing a composite nanofiltration membrane based on bidirectional interfacial polymerization includes the following steps: Step 1: The two-dimensional porous graphene prepared by the top-down liquid phase etching method is ultrasonically dispersed in deionized water to prepare a solution of 0.04 g·L⁻¹. -1 The dispersion was diluted with 2 mL of deionized water to 50 mL, and then vacuum filtered through a polyethersulfone microfiltration membrane at 0.6 bar to obtain a two-dimensional porous graphene loading of 50.96 mg·m³. -2 Two-dimensional porous graphene / polyethersulfone composite membrane.
[0035] Step 2: Keeping the orientation of the composite membrane unchanged, spray 1 mL of 0.05 w / v% ethylenediamine aqueous solution onto the lower surface of the support layer, allowing it to naturally diffuse upwards and wet for 1 min, and then use filter paper to absorb the excess droplets.
[0036] Step 3 is the same as step 3 in Example 1.
[0037] Compared to Example 1, this embodiment uses two-dimensional porous graphene with a large in-plane pore structure and reduces its loading. The aqueous phase amine monomer is changed from piperazine to ethylenediamine. Because this embodiment uses two-dimensional porous graphene with large in-plane pores, the vertical transport resistance of water molecules during permeation is significantly reduced. Furthermore, ethylenediamine has a smaller molecular weight and higher reactivity, making it easier to crosslink at the in-plane pores of the two-dimensional porous graphene, forming in-situ shrinkage pores.
[0038] TEM images of two-dimensional porous graphene before and after polyamide pore reduction and encapsulation are shown below. Figure 5 As shown in the figure, the in-plane pore structure of the two-dimensional porous graphene has been completely reduced and encapsulated, with no obvious defects.
[0039] The FESEM image of the separation layer thickness at the cross-section of the composite nanofiltration membrane prepared in this embodiment is shown below. Figure 6 As shown in the figure, the thickness of the two-dimensional porous graphene / polyamide layer is approximately 45.9 nm. This is because the higher reactivity of ethylenediamine and the lower loading of the two-dimensional porous graphene lead to a shorter upward diffusion path and a faster diffusion rate of the aqueous monomers. Both of these factors contribute to a significant increase in the interfacial polymerization rate, resulting in the formation of more polyamide per unit time and thus a thicker two-dimensional porous graphene / polyamide separation layer.
[0040] Tests showed that the composite nanofiltration membrane achieved a TC rejection rate of 98.5% and a permeation flux of 16.8 L·m⁻¹ at an operating pressure of 2 bar. -2 ·h-1 ·bar -1 The rejection rate for CIP was 95.1%, and the permeation flux was 14.7 L·m⁻¹. -2 ·h -1 ·bar -1 .
[0041] Example 4 A method for preparing a composite nanofiltration membrane based on bidirectional interfacial polymerization includes the following steps: Step 1: The two-dimensional porous graphene prepared by the top-down liquid phase etching method is ultrasonically dispersed in deionized water to prepare a solution of 0.04 g·L⁻¹. -1 A dispersion was prepared. 10 mL of this dispersion was diluted to 50 mL with deionized water and vacuum filtered through a polyethersulfone microfiltration membrane at 0.6 bar to obtain a two-dimensional porous graphene loading of 203.8 mg·m³. -2 Two-dimensional porous graphene / polyethersulfone composite membrane; Step 2 is the same as step 2 in Example 1; Step 3: Impregnate the upper surface of the two-dimensional porous graphene layer with 2 mL of a 0.2 w / v terephthalic diisocyanate / n-hexane solution and allow the interfacial polymerization reaction to proceed at room temperature for 30 s. Discard the organic phase, place the membrane in a 70 °C oven for heat treatment for 8 min, and then wash it sequentially with n-hexane and deionized water to obtain the composite nanofiltration membrane.
[0042] Compared with Example 1, this embodiment changes the oil phase monomer by replacing pyromellitic trimethylol chloride with terephthalic diisocyanate. The resulting polyurea has excellent chemical structural stability (urea bonds are more resistant to hydrolysis than amide bonds) and can be applied to the separation of antibiotics under acidic and alkaline conditions, such as the acidic extraction or alkaline dissolution process in antibiotic preparation.
[0043] TEM images of two-dimensional porous graphene before and after polyurea pore reduction and encapsulation are shown below. Figure 7 As shown in the figure, the porous structure within the two-dimensional porous graphene surface was successfully reduced in size and encapsulated by polyurea.
[0044] TEM image of the separation layer thickness at the cross-section of the composite nanofiltration membrane is shown below. Figure 8 As shown in the figure, the thickness of the two-dimensional porous graphene / polyurea layer is approximately 67.1 nm.
[0045] Tests showed that the membrane exhibited a 96.1% rejection rate for ERY and a permeation flux of 38.2 L·m⁻¹ at an operating pressure of 2 bar. -2 ·h -1 ·bar -1 The rejection rate for BAC was 99.3%, and the permeation flux was 36.5 L·m⁻¹. -2 ·h -1 ·bar-1 .
[0046] 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 composite nanofiltration membrane based on bidirectional interfacial polymerization, characterized in that, Includes the following steps: Step 1: Load two-dimensional porous graphene onto the upper surface of a porous support membrane to obtain a composite membrane of two-dimensional porous graphene layer / support layer. Step 2: Contact the lower surface of the composite membrane obtained in Step 1 with an aqueous amine monomer solution, so that the aqueous solution wets the support layer and diffuses upward to the two-dimensional porous graphene layer. Step 3: The upper surface of the two-dimensional porous graphene layer of the composite membrane treated in Step 2 is brought into contact with the organic phase monomer solution, so that the aqueous phase amine monomer and the organic phase monomer undergo an interfacial polymerization reaction in the in-plane pores of the two-dimensional porous graphene to form a porous graphene / polymer separation layer, thereby achieving in-situ pore reduction and encapsulation of the in-plane pores of the two-dimensional porous graphene, and obtaining the composite nanofiltration membrane.
2. The preparation method according to claim 1, characterized in that, In step 1, the two-dimensional porous graphene is prepared by a top-down liquid phase etching method or a bottom-up interfacial polymerization method; preferably, the in-plane pore size of the two-dimensional porous graphene is 0.5-20.0 nm. The supporting membrane is one of polyethersulfone membrane, polysulfone membrane, polyvinylidene fluoride membrane, and polytetrafluoroethylene membrane; The two-dimensional porous graphene is loaded onto the surface of the support film via vacuum-assisted self-assembly, pressure-assisted self-assembly, or spin-coating. Preferably, the loading amount is 20-500 mg·m³. -2 .
3. The preparation method according to claim 1, characterized in that, In step 2, the aqueous amine monomer is at least one of piperazine, m-phenylenediamine, polyethyleneimine, ethylenediamine, and triethylenetetramine; preferably, the concentration of the aqueous amine monomer in the aqueous amine monomer solution is 0.01-2 w / v.
4. The preparation method according to claim 1, characterized in that, In step 2, the specific steps for contacting the lower surface of the composite membrane obtained in step 1 with the aqueous amine monomer solution are as follows: the two-dimensional porous graphene layer of the composite membrane is placed on top and the support layer is placed on the bottom. The aqueous amine monomer solution is sprayed or scraped onto the lower surface of the support layer, allowing it to naturally diffuse and wet upwards.
5. The preparation method according to claim 1, characterized in that, In step 3, the organic phase monomer is at least one selected from pyromellitic trimethylol chloride, pyromellitic tetramethylol chloride, isophthaloyl chloride, terephthalic diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, 4,4-diphenylmethane diisocyanate, and 1,4-phenyl diisocyanate; the solvent of the organic phase monomer solution is at least one selected from n-hexane, cyclohexane, or isoalkanes; preferably, the concentration of the organic phase monomer in the organic phase monomer solution is 0.05-1 w / v.
6. The preparation method according to claim 1, characterized in that, In step 3, the interfacial polymerization reaction time is 10-300 s and the reaction temperature is 20-50 ℃.
7. The preparation method according to claim 1, characterized in that, In step 3, the composite membrane after in-situ shrinkage and encapsulation is further processed to obtain the composite nanofiltration membrane. The post-processing step is to perform air bath heat treatment at 40-80 ℃ for 1-30 min.
8. A composite nanofiltration membrane obtained by the preparation method according to any one of claims 1-7, characterized in that, The composite nanofiltration membrane includes a porous support layer and a two-dimensional porous graphene / polymer separation layer; the two-dimensional porous graphene layer is encapsulated by a polymer to form a two-dimensional porous graphene / polymer separation layer, and the in-plane pores of the two-dimensional porous graphene are reduced in size after in-situ pore reduction by the polymer.
9. The composite nanofiltration membrane as described in claim 8, characterized in that, The average pore size of the two-dimensional porous graphene / polymer separation layer is less than 7 Å.
10. The application of the composite nanofiltration membrane as described in claim 8 or 9 in antibiotic separation.