High-performance polyamide nanofiltration membrane, preparation method thereof and application thereof

Abstract

The application provides a high-performance polyamide nanofiltration membrane and a preparation method and application thereof. The high-performance polyamide nanofiltration membrane comprises an organic solution containing trimesoyl chloride, an aqueous solution containing piperazine, an aqueous solution containing a polymerizable amphiphilic molecule, and a macroporous support polyethersulfone bottom membrane; wherein the polymerizable amphiphilic molecule can form a monolayer membrane at a water / oil interface and is converted into a monolayer membrane through ultraviolet light-induced reaction; the trimesoyl chloride and the piperazine perform condensation polymerization at the interface, so that an ultrathin active separation layer with rich wrinkle morphology is formed on the surface of the macroporous support bottom membrane. The preparation method is simple, and has wide application prospects in aspects of multivalent / monovalent salt separation, water treatment, water quality softening and the like.

Description

Technical Field

[0001] This invention relates to a nanofiltration membrane, and more particularly to a high-performance polyamide nanofiltration membrane and its preparation method, belonging to the field of materials technology. Background Technology

[0002] Nanofiltration, with its separation size falling between ultrafiltration and reverse osmosis, offers superior separation precision and significantly lower energy consumption. In recent years, it has been widely applied in domestic water filtration, industrial wastewater treatment, food processing, and pharmaceuticals. Nanofiltration membranes have a pore size of approximately 2 nm and a rejection rate exceeding 90% for neutral organic molecules with a molecular weight greater than 200 Da. The surface of nanofiltration membranes is generally charged, allowing them to effectively retain multivalent ions, even those smaller than the membrane pore size. Simultaneously, nanofiltration membranes can retain monovalent inorganic ions such as sodium, potassium, and chloride, achieving precise separation of monovalent and divalent salt ions—a feat impossible with ultrafiltration and reverse osmosis. Polyamide composite nanofiltration membranes dominate the market due to their high flux, low cost, and simple manufacturing process. Interfacial polymerization remains the primary method for the industrial production of polyamide thin-film composite membranes due to its simple operation, mild reaction conditions, and ease of large-scale application. However, due to the violent reactions and uncontrollable monomer diffusion in traditional interfacial polymerization processes, the resulting nanofiltration membranes exhibit uneven pore size distribution, failing to meet market demands. Currently, most commercially available nanofiltration membranes suffer from low water permeation flux, insufficient brine separation performance, and inadequate selectivity for monovalent and divalent salts. In-situ regulation and intervention in the interfacial polymerization process, such as expanding the variety of monomers, externally intervening in the reaction, and controlling the monomer diffusion rate or process, are effective methods for preparing high-performance thin-layer composite nanofiltration membranes.

[0003] Amphiphiles are a common method for controlling the properties of water-oil interfaces. They are molecular compounds that possess both hydrophilic and oleophilic portions in their molecular structure. Amphiphiles spontaneously assemble at the water-oil interface, exhibiting an interfacial behavior where the hydrophilic head is in the aqueous phase and the hydrophobic tail is in the oil phase. Recent years have seen significant progress in the preparation of ordered nanostructures using amphiphiles. Studies have found that polymerizable surfactants can be used to prepare monolayer films at the water-air interface via UV light initiation. The interfacial behavior of amphiphiles changes dramatically before and after photopolymerization, leading to alterations in interfacial properties. UV irradiation induces the orientation of polymerizable amphiphiles at the interface. Similar to non-polymerizable amphiphiles, the adsorption of polymerizable surfactants with sufficiently long hydrophobic tails results in a transition from planar to isotropic anchoring. UV polymerization of amphiphiles with polymerizable groups located in the hydrophobic tail region causes their anchoring to shift from isotropic to planar. Polymerization in the hydrophilic head region does not produce an optical transition. By utilizing the altered interfacial behavior following photopolymerization of polymerizable amphiphilic molecules, it is hoped that the interfacial polymerization process can be controlled, thereby enabling the preparation of high-performance nanofiltration membranes with highly ordered nanostructured polyamide separation layers. Summary of the Invention

[0004] The main objective of this invention is to provide a high-performance polyamide nanofiltration membrane, its preparation method, and its applications. This control method is simple and feasible, and does not alter existing interfacial polymerization processes. It polymerizes amphiphilic molecules that are non-toxic, environmentally friendly, inexpensive, and easy to scale up. Simultaneously, it overcomes the drawbacks of traditional interfacial polymerization processes, such as violent reactions and uncontrollable monomer diffusion, thus addressing the shortcomings of existing technologies.

[0005] Another object of the present invention is to provide applications of the aforementioned high-performance polyamide nanofiltration membrane.

[0006] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0007] This invention provides a high-performance polyamide nanofiltration membrane, comprising:

[0008] An aqueous solution containing piperazine, an organic solution containing trimesoyl chloride, and an aqueous solution of a polymerizable amphiphilic molecule are provided, wherein the polymerizable amphiphilic molecule is capable of forming a monolayer film and is reacted to form a monolayer film by ultraviolet light.

[0009] The surface of a macroporous polyethersulfone substrate is used as the interface between the aqueous solution of piperazine and the organic solution, and the polymerizable amphiphilic molecule is constructed at the interface to form a monolayer film. The piperazine and trimesoyl chloride undergo a condensation polymerization reaction at the interface, thereby forming an active separation layer with rich wrinkles on the surface of the macroporous polyethersulfone substrate.

[0010] In some embodiments, a method for preparing a high-performance polyamide nanofiltration membrane is provided, specifically including:

[0011] The macroporous polyethersulfone substrate surface is fully wetted with the aqueous solution of piperazine, and then the macroporous polyethersulfone substrate surface is brought into full contact with the aqueous solution of the polymerizable amphiphilic molecule, and then into full contact with the organic solution, so that the macroporous polyethersulfone substrate surface is located at the interface of the aqueous solution and the organic solution, thereby allowing the polymerizable amphiphilic molecule to form a monolayer film at the interface, and the piperazine and trimesoyl chloride undergo a condensation polymerization reaction at the interface.

[0012] In some embodiments, the polymerizable amphiphilic molecule includes any one or a combination of two of polymerizable anionic surfactants, polymerizable cationic surfactants, and polymerizable zwitterionic surfactants.

[0013] The structural formulas of the polymerizable anionic surfactant are shown in formulas (I)-(III) below:

[0014]

[0015]

[0016] Furthermore, the pure water permeation flux of the high-performance polyamide nanofiltration membrane is 25–45 Lm. -2 h -1 bar -1 Meanwhile, the retention rate of sodium sulfate is 98.5% to 99.8%, the retention rate of various polyvalent cations and polyvalent anions is greater than 95%, and the retention rate of various monovalent cations and monovalent anions is less than 25%.

[0017] This invention also provides applications of the aforementioned high-performance polyamide nanofiltration membrane in the fields of removing polyvalent salts from water, desalination of brackish water, separation of polyvalent / monovalent salts, separation of glucose and salt, seawater desalination pretreatment, water softening, industrial wastewater treatment, food processing, pharmaceutical preparation, lithium extraction from salt lakes, or desalination of chemical wastewater.

[0018] Compared with the prior art, the advantages of the present invention include:

[0019] 1) The high-performance polyamide nanofiltration membrane provided by this invention exhibits high selectivity for monovalent and divalent salts, capable of retaining divalent or polyvalent salt ions in solution (retention rate > 95%), while having a low retention rate (< 25%) for monovalent salt ions. Simultaneously, it maintains an ultra-high permeation flux (25–45 Lm). -2 h -1 bar -1 );

[0020] 2) The high-performance polyamide nanofiltration membrane provided by this invention has a simple and feasible manufacturing process, good compatibility with traditional preparation processes, and is easy to scale up for production;

[0021] 3) The high-performance polyamide nanofiltration membrane provided by this invention can achieve rapid separation of divalent or polyvalent salt ions with monovalent salt ions with high separation efficiency. It has broad application prospects in the fields of removing polyvalent salts from water, desalination of brackish water, separation of glucose and salt, seawater desalination pretreatment, water softening, industrial wastewater treatment, food processing, pharmaceutical preparation, lithium extraction from salt lakes, and chemical wastewater desalination. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0023] Figure 1 These are scanning electron microscope images of the surfaces of the polyamide composite nanofiltration membranes prepared in the comparative examples and Examples 1-3 of this invention.

[0024] Figure 2 The nanofiltration membrane prepared by interfacial polymerization in Example 1 of this invention utilizes a polymerizable amphiphilic molecular membrane to regulate the separation performance of divalent and monovalent salt ions. Detailed Implementation

[0025] In view of the shortcomings of the prior art, the inventors of this case, through long-term research and extensive practice, unexpectedly discovered that in an interfacial condensation polymerization reaction system, by introducing a monolayer film composed of polymerizable amphiphilic molecules at the water / oil interface, and by controlling the interaction between the head groups of the polymerizable amphiphilic molecules and piperazine, the diffusion rate of piperazine from the aqueous phase to the oil phase can be effectively improved, thus promoting the interfacial polymerization condensation reaction and preparing a high-performance polyamide nanofiltration membrane. Based on this discovery, the inventors of this case proposed the technical solution of this invention, which will be further explained below, including its implementation process and principles.

[0026] As one aspect of the technical solution of the present invention, it relates to a high-performance polyamide nanofiltration membrane. The main structure of the nanofiltration membrane consists of a macroporous polyethersulfone substrate and an active separation layer with rich pleated morphology. The nanofiltration membrane has a high rejection rate (>95%) for divalent or multivalent positive ions and divalent or multivalent negative ions, and a low rejection rate (<25%) for monovalent positive ions and monovalent negative ions.

[0027] Furthermore, the high-performance polyamide nanofiltration membrane is a thin-film composite membrane structure, consisting of an ultrathin active separation layer with rich pleated morphology and a macroporous polyethersulfone substrate membrane from top to bottom. The active separation layer is formed by interfacial condensation polymerization between an aqueous solution of polyamine and an organic solution of polyacrylamide on the macroporous polyethersulfone substrate membrane.

[0028] In some embodiments, the macroporous polyethersulfone substrate membrane comprises a microfiltration membrane with an effective pore size of 0.1 to 1.2 μm, preferably 0.22 to 0.45 μm.

[0029] Furthermore, the material of the ultrafiltration membrane is polyethersulfone, polysulfone, sulfonated polysulfone, polyacrylonitrile and its derivatives, synthetic cellulose, regenerated cellulose, polyvinylidene fluoride and its derivatives, polyamide, etc., but not limited to these; it can be with a non-woven fabric substrate or without a non-woven fabric substrate.

[0030] As another aspect of the technical solution of the present invention, it also relates to a method for preparing a high-performance polyamide nanofiltration membrane, comprising:

[0031] Provided are an aqueous solution containing piperazine, an organic solution containing pyromellitic trimethylol chloride, and an aqueous solution of a polymerizable amphiphilic molecule, wherein the polymerizable amphiphilic molecule is capable of forming a monolayer film;

[0032] Using the surface of a macroporous polyethersulfone substrate as the interface between the aqueous solution of piperazine and the organic solution, and constructing a monolayer film at the interface with polymerizable amphiphilic molecules, and subjecting the piperazine and trimesoyl chloride to a condensation polymerization reaction at the interface, thereby forming an ultrathin active separation layer with rich fold morphology on the surface of the macroporous polyethersulfone substrate.

[0033] The preparation principle of the high-performance polyamide nanofiltration membrane of the present invention may be as follows: using an ultrafiltration membrane as a porous supporting base membrane, an ultrathin active separation layer with rich wrinkled morphology is formed on the surface of a macroporous polyethersulfone substrate membrane through an interfacial condensation polymerization reaction between an aqueous solution of piperazine and an organic solution of trimesoyl chloride; during the interfacial polymerization process, a monolayer membrane composed of polymerizable amphiphilic molecules is introduced at the interface between the two phases of water and organic solvent. Through the interaction between the hydrophilic head groups of the polymerizable amphiphilic molecules and the polyamine monomers, this monolayer membrane can effectively promote the diffusion of piperazine from the aqueous phase into the oil phase during the interfacial polymerization process, thereby promoting the interfacial condensation polymerization reaction between piperazine and trimesoyl chloride, making the reaction process more uniform.

[0034] In some embodiments, the preparation method specifically includes:

[0035] The macroporous polyethersulfone substrate surface is fully wetted with the aqueous solution of the piperazine, and then the macroporous polyethersulfone substrate surface is brought into full contact with the polymerizable amphiphilic molecule aqueous solution, and then into full contact with the organic solution, so that the macroporous polyethersulfone substrate surface is located at the interface of the aqueous solution and the organic solution, thereby allowing the polymerizable amphiphilic molecule to form a monolayer film at the interface, and the piperazine and trimesoyl chloride undergo a condensation polymerization reaction at room temperature at the interface.

[0036] In some more preferred embodiments, the preparation method specifically includes:

[0037] The macroporous polyethersulfone substrate surface was thoroughly wetted with the aqueous solution of the piperazine for 10-120 seconds.

[0038] The macroporous polyethersulfone substrate surface is fully wetted with the polymerizable amphiphilic aqueous solution for 10-120 seconds; and,

[0039] The surface of the macroporous polyethersulfone substrate membrane is fully wetted with the organic solution for 30-60 seconds, so that the surface of the macroporous polyethersulfone substrate membrane is located at the interface between the aqueous solution and the organic solution. Piperazine and polyacrylamide chloride undergo interfacial condensation polymerization at 25-30°C, and then heat treatment is carried out in a forced-air oven or constant-temperature hot water bath at 60-90°C to obtain the high-performance polyamide nanofiltration membrane.

[0040] In some embodiments, the preparation method includes: fully dissolving a polymerizable amphiphilic molecule in an aqueous solution to form an amphoteric molecule aqueous solution, wherein the concentration of the polymerizable amphiphilic molecule in the aqueous solution is 8-16 mM, exceeding the critical micelle concentration of the polymerizable amphiphilic molecule in water.

[0041] In some embodiments, the polymerizable amphiphilic molecule mainly includes any one or a combination of two of polymerizable anionic surfactants, polymerizable cationic surfactants, and polymerizable zwitterionic surfactants, but is not limited thereto.

[0042] Furthermore, the polymerizable anionic surfactant includes, but is not limited to, sodium 11-(methacryloyloxy)undecane-1-sulfonate (MUSS).

[0043] Furthermore, the polymerizable cationic surfactant 11-(methacryloyloxy)undecane-1-trimethylammonium bromide (MTAB) is used, but is not limited thereto.

[0044] Furthermore, the polymerizable zwitterionic surfactant includes, but is not limited to, 11-(methacryloyloxy)-3-sulfopropylundecyldimethylammonium (MAC).

[0045] In some embodiments, the concentration of the piperazine in the aqueous solution is 1 to 10 g / L.

[0046] In some embodiments, the concentration of pyromellitic acid chloride in the organic solution is 0.5–5 g / L.

[0047] Furthermore, the organic solvent is immiscible with water, preferably any one or a combination of two or more of n-hexane, Isopar G, toluene, ethyl acetate, and benzene, but not limited thereto.

[0048] In some more specific embodiments, the preparation method may specifically include the following steps:

[0049] The polymerizable amphiphilic molecule is fully dissolved in an aqueous solution at a concentration of 8-16 mM. The macroporous polyethersulfone (PES) membrane is completely wetted with the piperazine aqueous solution. After removing any residual aqueous solution from the supporting membrane surface, the PES membrane is immersed in the polymerizable amphiphilic molecule aqueous solution. After removing excess aqueous solution again, a controlled-intensity UV lamp is used to initiate the polymerization of the polymerizable amphiphilic molecule at the water-air interface. The PES membrane is then immersed in an organic solution of trimesoyl chloride, or the upper surface of the PES membrane can be brought into contact with the organic solution of trimesoyl chloride. The reaction is allowed to proceed for 10-120 seconds. After post-treatment steps such as washing and drying, a high-performance nanofiltration membrane is obtained.

[0050] Furthermore, the heat treatment temperature is 60°C and the time is 30 minutes.

[0051] Furthermore, the preparation method includes: using any one of the following methods to fully contact the aqueous solution of piperazine, the aqueous solution of polymerizable amphiphilic molecules, or the organic solution with the surface of the macroporous polyethersulfone substrate film using air spraying, low-speed spin coating, physical coating, brush coating, or impregnation.

[0052] In some embodiments, the macroporous polyethersulfone substrate membrane includes porous membranes such as microfiltration membranes, and the pore size of the macroporous polyethersulfone substrate membrane is 0.1 to 1.2 μm, preferably 0.22 to 0.45 μm.

[0053] Furthermore, the material of the macroporous polyethersulfone substrate includes, but is not limited to, polyethersulfone, polysulfone, sulfonated polysulfone, polyacrylonitrile and its derivatives, synthetic cellulose, regenerated cellulose, polyvinylidene fluoride and its derivatives, and polyamide.

[0054] Furthermore, the macroporous polyethersulfone substrate includes polyethersulfone porous membranes, polysulfone porous membranes, sulfonated polysulfone porous membranes, polyacrylonitrile porous membranes, polyacrylonitrile derivative porous membranes, synthetic cellulose porous membranes, regenerated cellulose porous membranes, polyvinylidene fluoride porous membranes, polyvinylidene fluoride derivative porous membranes, nylon porous membranes, etc. The macroporous polyethersulfone substrate may have a nonwoven fabric substrate or may not have a nonwoven fabric substrate.

[0055] As another aspect of the technical solution of the present invention, it also relates to a high-performance polyamide nanofiltration membrane prepared by the aforementioned method.

[0056] Furthermore, the pure water permeation flux of the high-performance polyamide nanofiltration membrane is 25–45 Lm. -2 h -1 bar -1 Meanwhile, the retention rate of sodium sulfate is 98.5% to 99.8%, the retention rate of various polyvalent cations and polyvalent anions is greater than 95%, and the retention rate of various monovalent cations and monovalent anions is less than 25%.

[0057] Furthermore, the high-performance polyamide nanofiltration membrane has a high degree of cross-linking and a narrow pore size distribution, specifically 0.3–0.7 nm, which can simultaneously retain divalent positive and divalent negative ions, while retaining less than 25% of monovalent salt ions, exhibiting excellent selectivity.

[0058] The technical solution of the present invention will be explained in more detail below with reference to several preferred embodiments and accompanying drawings. The specific embodiments described below are only used to further illustrate and explain the present invention, and are not intended to limit the present invention; any simple improvements based on the method of the present invention should be within the scope of protection of the claims.

[0059] Example 1

[0060] The PES porous membrane was immersed in a 2.5 g / L piperazine aqueous solution for 30 s, and then the excess aqueous solution on the surface of the PES porous membrane was dried with a rubber roller. The dried PES porous membrane was then immersed in an 8 mM MUSS aqueous solution for 30 s, and then the excess aqueous solution on the surface of the PES porous membrane was removed. After that, it was air-dried for 2 min, and then the MUSS reaction was initiated by ultraviolet light for 20 s. The photo-initiated PES porous membrane was then immersed again in a 2 g / L trimesoyl chloride (TMC) hexane solution at 25 °C for 30 s. After removing the excess hexane solution, the PES was placed in a 60 °C oven and dried for 30 min to prepare a high-performance polyamide nanofiltration membrane. The scanning electron microscope image of the surface of the polyamide composite nanofiltration membrane prepared in this embodiment is shown below. Figure 1 As shown in the figure, the separation performance of the polyamide composite nanofiltration membrane prepared in this embodiment for divalent and monovalent salt ions is illustrated in the figure below. Figure 2 As shown.

[0061] Example 2

[0062] The PES porous membrane was immersed in a 2.5 g / L piperazine aqueous solution for 30 s, and then the excess aqueous solution on the surface of the PES porous membrane was dried with a rubber roller. The dried PES porous membrane was then immersed in a 9 mM MAC aqueous solution for 30 s, and then the excess aqueous solution on the surface of the PES porous membrane was removed. After that, it was air-dried for 3 min, and then the MAC reaction was initiated by ultraviolet light for 20 s. The photo-initiated PES porous membrane was then immersed again in a 2 mg / ml trimesoyl chloride (TMC) hexane solution at 25 °C for 30 s. After removing the excess hexane solution, the PES was placed in a 60 °C oven and dried for 30 min to prepare a high-performance polyamide nanofiltration membrane. The scanning electron microscope image of the surface of the polyamide composite nanofiltration membrane prepared in this example is shown below. Figure 1 As shown.

[0063] Example 3

[0064] The PES porous membrane was immersed in a 2.5 g / L piperazine aqueous solution for 30 s, and then the excess aqueous solution on the surface of the PES porous membrane was dried with a rubber roller. The dried PES porous membrane was then immersed in a 12 mM MTAB aqueous solution for 30 s, and then the excess aqueous solution on the surface of the PES porous membrane was removed. After that, it was air-dried for 3 min, and then the MTAB reaction was initiated by ultraviolet light for 20 s. The photo-initiated PES porous membrane was then immersed again in a 2 mg / ml trimesoyl chloride (TMC) hexane solution at 25 °C for 30 s. After removing the excess hexane solution, the PES was placed in a 60 °C oven and dried for 30 min to prepare a high-performance polyamide nanofiltration membrane. The scanning electron microscope image of the surface of the polyamide composite nanofiltration membrane prepared in this example is shown below. Figure 1 As shown.

[0065] Compare with Example 1

[0066] To verify the effect of surface-active monolayer membranes on the separation performance of nanofiltration membranes, nanofiltration membranes were prepared under conditions without polymerizable amphiphilic molecules. The specific implementation method was as follows: a PES porous membrane was immersed in a 2.5 g / L PIP aqueous solution for 30 s, then excess aqueous solution was removed from the surface of the PES porous membrane, and it was air-dried for 3 min; the dried PES porous membrane was then immersed in a 2 g / L trimesoyl chloride (TMC) hexane solution for 30 s; excess hexane solution was removed, and the PES was dried in a 60 °C oven for 30 min to obtain the nanofiltration membrane.

[0067] Using raw water at concentrations of 2000 ppm Na₂SO₄, MgSO₄, MgCl₂, CaCl₂, and NaCl, the ion separation performance of the nanofiltration membrane prepared in the above control example was tested. The experimental results showed that the prepared nanofiltration membrane exhibited rejection rates exceeding 99% for divalent salts Na₂SO₄ and MgSO₄, and a rejection rate of approximately 25% for monovalent salt NaCl. The test results indicate that the nanofiltration membrane prepared in this control example is a typical negatively charged nanofiltration membrane.

[0068] All aspects, embodiments, features, and examples of this invention are to be regarded as illustrative in all respects and are not intended to limit the invention, the scope of which is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0069] The use of headings and sections in this invention is not intended to limit the invention; each section can be applied to any aspect, embodiment or feature of the invention.

[0070] Throughout this invention, wherever a composition is described as having, containing, or including specific components, or wherever a process is described as having, containing, or including specific process steps, it is contemplated that the compositions taught in this invention are also substantially composed of or comprised of the described components, and that the processes taught in this invention are also substantially composed of or comprised of the described process steps.

[0071] It should be understood that the order of the steps or the order in which specific actions are performed is not particularly important, as long as the teachings of this invention remain operable. Furthermore, two or more steps or actions can be performed simultaneously.

[0072] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0073] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated otherwise, any use of the terms first, second, etc., does not indicate any order or importance, but is used to distinguish one element from another.

Claims

1. A method for preparing a high-performance polyamide nanofiltration membrane, characterized in that: The macroporous polyethersulfone substrate surface is thoroughly wetted with an aqueous solution of piperazine, then brought into full contact with an aqueous solution of polymerizable amphiphilic molecules, and subsequently into full contact with an organic solution, thereby positioning the macroporous polyethersulfone substrate surface at the interface between the aqueous solution and the organic solution. This allows the polymerizable amphiphilic molecules to form a monolayer at the interface, which is then polymerized using ultraviolet light-initiated polymerization. Finally, piperazine and trimesoyl chloride undergo a condensation polymerization reaction at the interface. Specifically, the process includes: The macroporous polyethersulfone substrate surface was thoroughly wetted with a piperazine aqueous solution for 10-120 seconds; and, The macroporous polyethersulfone substrate surface is fully wetted with the polymerizable amphiphilic aqueous solution for 10-120 seconds; and, Before contacting the organic solution, the surface of the macroporous polyethersulfone substrate is exposed to ultraviolet light for 20 seconds. The surface of the macroporous polyethersulfone substrate membrane is fully wetted with the organic solution for 30-60 seconds, so that the surface of the macroporous polyethersulfone substrate membrane is located at the interface between the aqueous solution and the organic solution. Piperazine and trimesoyl chloride undergo interfacial condensation polymerization at 25-30°C, and then heat-treated in a forced-air oven or constant-temperature hot water bath at 60-90°C to obtain the high-performance polyamide nanofiltration membrane.

2. The preparation method according to claim 1, characterized in that: The polymerizable amphiphilic molecule includes any one or a combination of two of polymerizable anionic surfactants, cationic surfactants, and zwitterionic surfactants.

3. The preparation method according to claim 2, characterized in that: The polymerizable anionic surfactant includes sodium 11-(methacryloyloxy)undecane-1-sulfonate, the polymerizable cationic surfactant includes 11-(methacryloyloxy)undecane-1-trimethylammonium bromide, and the polymerizable zwitterionic surfactant includes 11-(methacryloyloxy)-3-sulfopropylundecyldimethylammonium.

4. The preparation method according to claim 1, characterized in that: The organic solution comprises pyromellitic acid chloride and an organic solvent; the organic solvent is immiscible with water, and the concentration of pyromellitic acid chloride in the organic solution is 0.5-5 g / L; the organic solution is any one or a combination of two or more of n-hexane, Isopar G, toluene, ethyl acetate and benzene.

5. The preparation method according to claim 1, characterized in that: The heat treatment is performed at a temperature of 60-90℃ for a time of 0.5-1h.

6. The preparation method according to claim 1, characterized in that: The macroporous polyethersulfone substrate membrane is at least one of the following: polyethersulfone porous membrane, polysulfone porous membrane, sulfonated polysulfone porous membrane, polyacrylonitrile porous membrane, polyacrylonitrile-derived porous membrane, synthetic fiber porous membrane, regenerated cellulose porous membrane, polyvinylidene fluoride porous membrane, polyvinylidene fluoride derivative porous membrane, and nylon porous membrane.

7. A high-performance polyamide nanofiltration membrane obtained by the preparation method according to any one of claims 1-6, characterized in that... include: An aqueous solution containing piperazine, an organic solution containing pyromellitic trichomeoyl chloride, and an aqueous solution containing polymerizable amphiphilic molecules, wherein the polymerizable amphiphilic molecules can be polymerized by UV initiation to form a monolayer film; The macroporous polyethersulfone substrate surface is used as the interface between the aqueous solution of piperazine and the organic solution, and the polymerizable amphiphilic molecule is subjected to an ultraviolet-initiated reaction at the interface to form a monolayer film. In addition, the piperazine and trimesoyl chloride are subjected to a condensation polymerization reaction at the interface, thereby forming an ultrathin active separation layer with rich wrinkle morphology on the surface of the macroporous polyethersulfone substrate.

8. The high-performance polyamide nanofiltration membrane according to claim 7, characterized in that: The pore size distribution is 0.3–0.7 nm; the pure water permeation flux is 25–45 L·m⁻²·h⁻¹·bar⁻¹; the retention rate of sodium sulfate is 98.5%–99.8%; the retention rate of various polyvalent cations and polyvalent anions is greater than 95%; and the retention rate of various monovalent cations and monovalent anions is less than 25%.

9. The application of a high-performance polyamide nanofiltration membrane obtained by the preparation method according to any one of claims 1-6 in the rapid separation of divalent or polyvalent salt ions and monovalent salt ions.

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