Method for preparing nanofiltration membrane by enhancing interfacial polymerization or depositing polymer molecules through synergistic effect

Abstract

The invention belongs to the field of separation membrane preparation, and discloses a method for preparing a nanofiltration membrane by enhancing interfacial polymerization or depositing polymer molecules through a synergistic effect, and the method comprises the following steps: (1) taking p-phenylenediamine and paraphthaloyl chloride as monomers, and polymerizing to obtain a poly-p-phenylene terephthamide solution; (2) adding an end-capping reagent and a diluting solvent into the solution to obtain a membrane casting solution, the end-capping reagent being used for providing amido and carboxyl; (3) forming an amido or carboxyl modified poly (p-phenylene terephthamide) membrane by using the membrane casting solution; and (4) taking the nano-filtration membrane as a base membrane, and obtaining the high-performance nano-filtration membrane through interfacial polymerization or polymer molecule deposition by utilizing a synergistic effect. The membrane with the surface rich in amino and carboxyl is obtained through end-capping modification, the membrane serves as a base membrane, a high-molecular polymer is deposited through interfacial polymerization or hydrogen bond interaction to repair pore defects so as to reduce the pore diameter, and the obtained nanofiltration membrane has the advantage of being low in molecular weight cut-off and particularly can serve as an organic solvent resistant nanofiltration membrane.

Description

Technical Field

[0001] This invention belongs to the field of separation membrane preparation, and more specifically, relates to a method for preparing nanofiltration membranes by enhancing interfacial polymerization or depositing polymer molecules through synergistic effects. Background Technology

[0002] Against the backdrop of global water scarcity and the upgrading of industrial separation needs, nanofiltration membranes, with their precise retention of small organic molecules and multivalent ions, have demonstrated irreplaceable application value in fields such as drinking water purification, seawater desalination pretreatment, and biopharmaceutical purification. Interfacial polymerization, as the mainstream technology for preparing ultrathin selective layers of nanofiltration membranes, can efficiently construct separation layers with dense cross-linked structures through the rapid polymerization reaction of monomers at the oil-water interface. Its advantages of simple operation and short preparation cycle have made it a widely adopted method in industry.

[0003] However, traditional interfacial polymerization processes still face significant technical bottlenecks: the diffusion rate of monomers at the two-phase interface is difficult to control precisely, easily leading to uneven selective layer thickness and widened pore size distribution, which in turn restricts the balance between membrane permeability and retention selectivity. To overcome these limitations, researchers have successively tried single modification strategies such as introducing nanoparticle doping, monomer structure modification, and optimization of interfacial reaction conditions. However, a single approach often only improves one aspect of the membrane's performance—for example, while the introduction of nanoparticles can improve the membrane's hydrophilicity, particle aggregation can easily lead to a decrease in interfacial compatibility, thereby damaging the integrity of the separation layer.

[0004] The concept of synergistic effects offers a new approach to addressing the inherent shortcomings of traditional interfacial polymerization. Synergistic effects, by organically combining two or more modification mechanisms (such as component synergy, process synergy, and structural synergy), can achieve performance enhancement. For example, synergistically combining substrate surface pretreatment with the interfacial polymerization process can regulate and improve adsorption and diffusion behavior at the interface through the effects of specific functional groups on the substrate surface, thereby constructing a more uniform and dense selective layer. Currently, although a few studies have mentioned the synergistic modification approach, there is still a lack of exploration of synergistic strategies for traditional interfacial polymerization processes, and further experimental investigation is needed in this area. Summary of the Invention

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, the present invention aims to provide a method for preparing nanofiltration membranes through synergistic effects of interfacial polymerization or polymer deposition. This method involves end-capping modification to obtain amino- or carboxyl-modified poly(p-phenylene terephthalamide) membranes. The presence of amino or carboxyl groups regulates monomer diffusion during interfacial polymerization (furthermore, amino groups can also participate in interfacial polymerization), promoting the formation of more defect-free nanofiltration membranes. Simultaneously, the amino or carboxyl groups deposit polymer molecules through hydrogen bonding interactions to repair pore defects and reduce pore size. The nanofiltration membrane obtained by end-capping modified poly(p-phenylene terephthalamide) of this invention has the characteristic of a low molecular weight cutoff, making it particularly suitable for use as an organic solvent-resistant nanofiltration membrane. It also significantly improves the selective separation and flux of nanofiltration membranes obtained through traditional interfacial polymerization processes.

[0006] To achieve the above objectives, according to one aspect of the present invention, a method for preparing nanofiltration membranes by enhancing interfacial polymerization or depositing polymer molecules through synergistic effects is provided, characterized by comprising the following steps: (1) Using p-phenylenediamine and terephthaloyl chloride as monomers, a poly(p-phenylenediamine) solution was obtained by stirring in a system containing organic solvent and metal salt co-solvent at -4~6℃ through polymerization reaction; (2) Maintain a temperature of -4~6℃, add a capping agent and a diluent to the poly(p-phenylene terephthalamide) solution obtained in step (1), and mix evenly to obtain an amino- or carboxyl-modified poly(p-phenylene terephthalamide) casting solution; wherein, the capping agent is used to provide amino or carboxyl groups; (3) The casting liquid is scraped onto the porous support layer and immersed in the coagulation bath for phase transformation to form an amino or carboxyl-modified poly(p-phenylene terephthalamide) membrane; (4) Using the amino or carboxyl-modified poly(p-phenylene terephthalamide) membrane obtained in step (3) as the base membrane, a high-performance nanofiltration membrane is obtained by interfacial polymerization or deposition of polymer molecules to utilize synergistic effects.

[0007] As a further preferred embodiment of the present invention, in step (1): The concentrations of p-phenylenediamine and terephthaloyl chloride monomers in the poly(p-phenylene terephthalamide) solution are both 0.1~1.0 mol / L; the organic solvent is selected from at least one of dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide. The metal salt co-solvent is selected from at least one of magnesium chloride, sodium chloride, sodium sulfate, magnesium sulfate, calcium chloride, and lithium chloride, and the concentration of the metal salt co-solvent corresponding to the poly(p-phenylene terephthalamide) solution is 50~125 g / L.

[0008] As a further preferred embodiment of the present invention, in step (2): The capping agent is selected from at least one of pyromellitic terephthaloyl chloride, isophthaloyl chloride, terephthaloyl chloride, benzenetrisulfonyl chloride, glutaryl chloride, p-phenylenediamine, m-phenylenediamine, maleic acid chloride, cyclobutanetriacyl chloride, adipyl chloride, cyclobutanetetraacyl chloride, cyclopentanediacyl chloride, cyclopentanetetraacyl chloride, and cyclopropanetriacyl chloride; the concentration of the capping agent after mixing with the poly(p-phenylenediamine) terephthaloyl chloride solution obtained in step (1) is 0.1~1.0 wt%; The diluting solvent is the same type of organic solvent as in step (1), and the amount used is 10-25 wt% of the poly(p-phenylene terephthalamide) solution obtained in step (1).

[0009] As a further preferred embodiment of the present invention, in step (1), the stirring treatment is carried out at a speed of 200~5000 r / min for 1~24 h.

[0010] As a further preferred embodiment of the present invention, in step (3): The coagulation bath is water, or a mixed solution of water and a water-soluble organic solvent; wherein the water-soluble organic solvent is at least one of dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide, phenol, and dimethylacetamide. Preferably, the porous support layer is a nonwoven fabric with a coating thickness of 100~500 µm.

[0011] As a further preferred embodiment of the present invention, in step (4): the interfacial polymerization is to generate a selective layer by condensation reaction of aqueous monomer and oil monomer at the interface of the base film surface; preferably, the interfacial polymerization is to immerse the base film in a solution containing aqueous monomer for 5 to 10 minutes and then take it out. After the surface water droplets are dried, the base film surface is then immersed in a solution containing oil monomer for 15 to 30 minutes. After the surface evaporates, it is heat-treated at 40 to 80 °C for 1 to 10 minutes. More preferably, the interfacial polymerization is an interfacial polymerization of m-phenylenediamine and trimesoyl chloride, or an interfacial polymerization of piperazine and trimesoyl chloride, or an interfacial polymerization of polyethyleneimine and trimesoyl chloride; wherein, When the interfacial polymerization of m-phenylenediamine and trimesoyl chloride is used, the aqueous phase solution is a m-phenylenediamine solution, and the oil phase solution is a mixture of trimesoyl chloride monomer and organic solvent; the concentration of the m-phenylenediamine solution used is 1.0-5.0 wt%, the concentration of the trimesoyl chloride solution used is 0.1-0.5 wt%, and the reaction time is 15 s-10 min; When using interfacial polymerization of piperazine and trimesoyl chloride, the aqueous phase solution is a piperazine solution, and the oil phase solution is a mixture of trimesoyl chloride monomer and organic solvent; the concentration of the piperazine solution used is 0.05-2.0 wt%, the concentration of the trimesoyl chloride solution used is 0.05-0.5 wt%, and the reaction time is 30 s-10 min; When using interfacial polymerization of polyethyleneimine and trimesoyl chloride, the aqueous phase solution is a polyethyleneimine solution, and the oil phase solution is a mixture of trimesoyl chloride monomer and organic solvent; the concentration of the polyethyleneimine solution used is 0.25-2.0 wt%, and the molecular weight of polyethyleneimine is 300-70000 Da; the concentration of the trimesoyl chloride solution used is 0.05-0.5 wt%, and the reaction time is 15 s-30 min; The organic solvent used in the oil phase solution is at least one of octane, cyclohexane, n-hexane, and heptane.

[0012] As a further preferred embodiment of the present invention, in step (4): the deposition of polymer molecules is achieved by immersing the base film in a polymer aqueous solution and maintaining it for 5 min-24 h to form a separation layer, and then immersing the treated film in deionized water for cleaning. Preferably, the polymer used for the deposition of polymer molecules is selected from at least one of polyacrylamide, polyethyleneimine, polyvinyl alcohol, polydimethyldiallylammonium chloride, polyallylamine salt, sodium polyacrylate, polymethacrylic acid, and sodium polystyrene sulfonate, with a molecular weight of 300-70000 Da and a polymer solution concentration of 0.5-2.0 wt%.

[0013] According to another aspect of the present invention, the present invention provides a nanofiltration membrane prepared by the above method.

[0014] According to another aspect of the invention, the present invention provides the application of the above-described nanofiltration membrane in water treatment desalination or in organic solvent-resistant nanofiltration.

[0015] As a further preferred embodiment of the present invention, the organic solvent-resistant nanofiltration is specifically for solvent and drug concentration separation, solvent and solvent separation when different solvents are mixed, light oil and heavy oil separation, or waste solvent recovery.

[0016] Compared with the prior art, the present invention utilizes the above-described technical solutions to directly polymerize p-phenylenediamine and terephthaloyl chloride monomers in an organic solvent system using metal salt ions as a co-solvent. After end-capping modification and dilution, the polymer is formed by phase inversion using a blade coating process. The ultrafiltration membrane obtained through phase inversion has a surface rich in amine and carboxyl groups. This membrane can then be used as a base membrane for traditional interfacial polymerization (e.g., interfacial polymerization of m-phenylenediamine, piperazine, polyethyleneimine, and trimesoyl chloride) or for depositing polymers through hydrogen bonding interactions (when using polymers to modify membrane pores, the molecular weight of the polymer used for pore-shrinking deposition can be, for example, 300-70000 Da) to reduce the pore size, thereby obtaining a high-performance poly(p-phenylenediamine) nanofiltration membrane. The nanofiltration membrane prepared by the present invention through synergistic enhancement of interfacial polymerization or deposition of polymer molecules has better performance than a series of membranes prepared based on traditional poly(p-phenylene terephthalamide). The nanofiltration membrane has a dense separation layer formed on its surface, and its structure is composed of a dense separation layer, a poly(p-phenylene terephthalamide) layer and a support layer. It can be used for water treatment desalination as well as for nanofiltration resistant to organic solvents.

[0017] This invention utilizes monomers containing different functional groups, such as amine and carboxyl groups, to end-cap polymer solutions, resulting in a base membrane (i.e., a poly(p-phenylene terephthalamide) ultrafiltration membrane) with a surface rich in amine and carboxyl groups. This base membrane can be used to prepare nanofiltration membranes through synergistic enhancement of interfacial polymerization or by polymer molecule deposition. The resulting series of different types of membranes exhibit performance far exceeding that of traditional nanofiltration membranes. This method is simple, uses inexpensive raw materials, and can be industrially scaled up, showing promising application prospects.

[0018] This invention provides a method for preparing nanofiltration membranes or depositing polymer molecules through enhanced interfacial polymerization via synergistic effects. The method involves polymerizing p-phenylenediamine and terephthaloyl chloride monomers in one or more organic solvents with one or more metal salt ions as co-solvents at low temperatures to obtain a poly(p-phenylenediamine terephthalamide) solution. Subsequent modification of the end groups results in a base membrane surface with a significantly increased number of amine and carboxyl groups. This allows for direct deposition of polymer molecules to create nanofiltration membranes with reduced pore size or to optimize the interfacial polymerization process. This method enhances the synergistic interaction between the base membrane and the two monomer phases during interfacial polymerization by increasing the number of specific functional groups on the base membrane surface, or directly deposits polymer molecules from the aqueous phase through hydrogen bonding interactions, thereby optimizing surface chemistry and ultimately improving membrane selectivity (and even simultaneously improving permeability). This invention provides a new technical pathway for the preparation of high-efficiency nanofiltration membranes and is of great significance for promoting the application and upgrading of nanofiltration membrane technology in practical separation fields. Taking the following embodiments as examples, based on the method of the present invention, a poly(p-phenylene terephthalamide) membrane is obtained by monomer polymerization followed by end-capping dilution and phase conversion. The surface of this membrane is rich in a large number of carboxyl or amine groups. When the end-capping agent is a diacyl chloride such as terephthaloyl chloride, its surface will be rich in a large number of carboxyl groups. When the end-capping agent is a diamine such as p-phenylenediamine, its surface will be rich in a large number of amine groups. Such a base membrane makes it possible for subsequent synergistic effects to occur. Therefore, the performance of nanofiltration membrane can be improved by enhancing interfacial polymerization through synergistic effects, and nanofiltration membrane can be directly obtained by depositing a polymer rich in amine groups (e.g., polyethyleneimine). This method has never appeared in previous reports. The separation membrane obtained by this method has a high salt ion rejection rate in water or exhibits high flux and low molecular weight cutoff (200-400 Da) in the methanol system, and has high performance, which is superior to the method of preparing poly(p-phenylene terephthalamide) membrane material by dissolving Kevlar fibers.

[0019] As can be seen, the specific synergistic effect of the method of the present invention is manifested in the fact that, since the poly(p-phenylene terephthalamide) membrane obtained in the present invention has a significantly increased number of amine or carboxyl groups on its surface, when a polymer rich in amine groups (such as polyethyleneimine) is deposited on the surface, the synergistic effect between the groups causes the polymer rich in amine groups to interact with the membrane surface, thereby achieving the effect of shrinking pores. When performing conventional interfacial polymerization (such as the interfacial polymerization of m-phenylenediamine, piperazine, polyethyleneimine and trimesoyl chloride), the more amine groups on the surface of the amine-terminated membrane will have a synergistic effect with the amine monomers (such as m-phenylenediamine, piperazine, polyethyleneimine), participating in the reaction with trimesoyl chloride to achieve the effect of performance optimization. The more carboxyl groups on the surface of the carboxyl-terminated membrane will also have a synergistic effect with trimesoyl chloride, making the surface of the prepared nanofiltration membrane rich in carboxyl groups, thereby improving ion rejection.

[0020] In summary, the present invention improves the selective separation and flux of nanofiltration membranes obtained by enhancing interfacial polymerization or deposition of polymer molecules through synergistic effects. Moreover, the method is simple, can be mass-produced industrially, and has good industrial applicability. Attached Figure Description

[0021] Figure 1 The image shows the surface morphology of the membrane obtained by interfacial polymerization in Example 1, as shown by scanning electron microscopy.

[0022] Figure 2 The image shows the surface morphology of the membrane obtained by interfacial polymerization in Example 7, as shown by scanning electron microscopy.

[0023] Figure 3 The image shows the surface morphology of the membrane obtained by interfacial polymerization in Example 13, as shown by scanning electron microscopy.

[0024] Figure 4 The image shows the surface morphology of the membrane prepared in Example 19 using a scanning electron microscope. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0026] Example 1 A method for preparing a m-phenylenediamine trimellityl chloride separation membrane obtained by conventional interfacial polymerization using a carboxyl-modified poly(p-phenylene terephthalamide) membrane as a substrate includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 20 g of magnesium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, add 4.33 g of p-phenylenediamine and stir at 200 r / min for 1 h, then add 8.12 g of terephthaloyl chloride and stir at 2000 r / min for 1 h. (4) Add 0.46 g of terephthaloyl chloride solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 200 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the carboxyl-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the carboxyl-modified poly(p-phenylene terephthalamide) membrane in step (5) was soaked in 1.0 wt% m-phenylenediamine aqueous solution for 10 min, and then the surface of the membrane was dried and treated with 0.1 wt% pyromellitic chlorohexane solution for 15 s. (7) The membrane obtained in step (6) is washed with n-hexane to remove unreacted trimesoyl chloride, and then placed in a 70°C oven for thermal stabilization for 30 s to obtain a m-phenylenediamine trimesoyl chloride separation membrane obtained by conventional interfacial polymerization using a carboxyl-modified poly(p-phenylene terephthalamide) membrane as the substrate.

[0027] Example 2 A method for preparing a m-phenylenediamine trimellityl chloride separation membrane obtained by conventional interfacial polymerization using a carboxyl-modified poly(p-phenylene terephthalamide) membrane as a substrate includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 35 g of calcium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, then add 8.65 g of p-phenylenediamine and stir at 400 r / min for 1 h, then add 16.24 g of terephthaloyl chloride and stir at 2000 r / min for 2.5 h. (4) Add 0.46 g of terephthaloyl chloride solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 250 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the carboxyl-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the carboxyl-modified poly(p-phenylene terephthalamide) membrane in step (5) was soaked in 3.5 wt% m-phenylenediamine aqueous solution for 10 min, and then the surface of the membrane was dried and treated with 0.3 wt% pyromellitic chlorohexane solution for 5 min. (7) The membrane obtained in step (6) is washed with n-hexane to remove unreacted trimesoyl chloride, and then placed in a 70°C oven for 1 min for thermal stabilization to obtain a m-phenylenediamine trimesoyl chloride separation membrane obtained by conventional interfacial polymerization using a carboxyl-modified poly(p-phenylene terephthalamide) membrane as the substrate.

[0028] Example 3 A method for preparing a m-phenylenediamine trimellityl chloride separation membrane obtained by conventional interfacial polymerization using a carboxyl-modified poly(p-phenylene terephthalamide) membrane as a substrate includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 50 g of sodium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, then add 43.25 g of p-phenylenediamine and stir at 600 r / min for 1 h, then add 81.2 g of terephthaloyl chloride and stir at 5000 r / min for 24 h. (4) Add 4.6 g of terephthaloyl chloride solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 250 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the carboxyl-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the carboxyl-modified poly(p-phenylene terephthalamide) membrane in step (5) was soaked in 5.0 wt% m-phenylenediamine aqueous solution for 10 min, and then the surface of the membrane was dried and treated with 0.5 wt% pyromellitic chlorohexane solution for 10 min. (7) The membrane obtained in step (6) is washed with n-hexane to remove unreacted trimesoyl chloride, and then placed in a 70°C oven for 1 min for thermal stabilization to obtain a m-phenylenediamine trimesoyl chloride separation membrane obtained by conventional interfacial polymerization using a carboxyl-modified poly(p-phenylene terephthalamide) membrane as the substrate.

[0029] Example 4 A method for preparing a m-phenylenediamine trimellityl chloride separation membrane obtained by conventional interfacial polymerization using an amino-modified poly(p-phenylene terephthalamide) membrane as a substrate includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 35 g of magnesium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, then add 8.65 g of p-phenylenediamine and stir at 400 r / min for 1 h, then add 16.24 g of terephthaloyl chloride and stir at 2000 r / min for 2.5 h. (4) Add 0.46 g of p-phenylenediamine solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 500 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the amino-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the amino-modified poly(p-phenylene terephthalamide) membrane in step (5) was soaked in 1.0 wt% m-phenylenediamine aqueous solution for 10 min, and then the surface of the membrane was dried and treated with 0.1 wt% pyromellitic chlorohexane solution for 15 s. (7) The membrane obtained in step (6) is washed with n-hexane to remove unreacted trimesoyl chloride, and then placed in a 70°C oven for 1 min for thermal stabilization to obtain a m-phenylenediamine trimesoyl chloride separation membrane obtained by conventional interfacial polymerization using an amino-modified poly(p-phenylene terephthalamide) membrane as the substrate.

[0030] Example 5 A method for preparing a m-phenylenediamine trimellityl chloride separation membrane obtained by conventional interfacial polymerization using an amino-modified poly(p-phenylene terephthalamide) membrane as a substrate includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 35 g of magnesium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, then add 8.65 g of p-phenylenediamine and stir at 400 r / min for 1 h, then add 16.24 g of terephthaloyl chloride and stir at 2000 r / min for 2.5 h. (4) Add 0.46 g of p-phenylenediamine solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 250 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the amino-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the amino-modified poly(p-phenylene terephthalamide) membrane in step (5) was soaked in 3.5 wt% m-phenylenediamine aqueous solution for 10 min, then the moisture on the membrane surface was dried, and the surface was treated with 0.3 wt% pyromellitic chlorohexane solution for 5 min. (7) The membrane obtained in step (6) is washed with n-hexane to remove unreacted trimesoyl chloride, and then placed in a 70°C oven for 1 min for thermal stabilization to obtain a m-phenylenediamine trimesoyl chloride separation membrane obtained by conventional interfacial polymerization using an amino-modified poly(p-phenylene terephthalamide) membrane as the substrate.

[0031] Example 6 A method for preparing a m-phenylenediamine trimellityl chloride separation membrane obtained by conventional interfacial polymerization using an amino-modified poly(p-phenylene terephthalamide) membrane as a substrate includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 35 g of magnesium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, then add 8.65 g of p-phenylenediamine and stir at 400 r / min for 1 h, then add 16.24 g of terephthaloyl chloride and stir at 2000 r / min for 2.5 h. (4) Add 0.46 g of p-phenylenediamine solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 250 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the amino-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the amino-modified poly(p-phenylene terephthalamide) membrane in step (5) was soaked in 5.0 wt% m-phenylenediamine aqueous solution for 10 min, and then the surface of the membrane was dried and treated with 0.5 wt% pyromellitic chlorohexane solution for 10 min. (7) The membrane obtained in step (6) is washed with n-hexane to remove unreacted trimesoyl chloride, and then placed in a 70°C oven for 1 min for thermal stabilization to obtain a m-phenylenediamine trimesoyl chloride separation membrane obtained by conventional interfacial polymerization using an amino-modified poly(p-phenylene terephthalamide) membrane as the substrate.

[0032] Example 7 A method for preparing a piperazine trimellityl chloride separation membrane obtained by conventional interfacial polymerization using a carboxyl-modified poly(p-phenylene terephthalamide) membrane as a substrate includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 35 g of magnesium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, then add 8.65 g of p-phenylenediamine and stir at 400 r / min for 1 h, then add 16.24 g of terephthaloyl chloride and stir at 2000 r / min for 2.5 h. (4) Add 0.46 g of terephthaloyl chloride solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 250 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the carboxyl-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the carboxyl-modified poly(p-phenylene terephthalamide) membrane in step (5) was soaked in 0.05 wt% piperazine aqueous solution for 10 min, and then the surface of the membrane was dried and treated with 0.05 wt% trimesoyl chloride n-hexane solution for 30 s. (7) The membrane obtained in step (6) is washed with n-hexane to remove unreacted trimesoyl chloride, and then placed in a 70°C oven for 1 min for thermal stabilization to obtain a piperazine trimesoyl chloride separation membrane obtained by conventional interfacial polymerization using a carboxyl-modified poly(p-phenylene terephthalamide) membrane as the substrate.

[0033] Example 8 A method for preparing a piperazine trimellityl chloride separation membrane obtained by conventional interfacial polymerization using a carboxyl-modified poly(p-phenylene terephthalamide) membrane as a substrate includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 35 g of magnesium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, then add 8.65 g of p-phenylenediamine and stir at 400 r / min for 1 h, then add 16.24 g of terephthaloyl chloride and stir at 2000 r / min for 2.5 h. (4) Add 0.46 g of terephthaloyl chloride solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 250 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the carboxyl-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the carboxyl-modified poly(p-phenylene terephthalamide) membrane in step (5) was soaked in 1.0 wt% piperazine aqueous solution for 10 min, and then the surface of the membrane was dried and treated with 0.3 wt% trimesoyl chloride n-hexane solution for 5 min. (7) The membrane obtained in step (6) is washed with n-hexane to remove unreacted trimesoyl chloride, and then placed in a 70°C oven for 1 min for thermal stabilization to obtain a piperazine trimesoyl chloride separation membrane obtained by conventional interfacial polymerization using a carboxyl-modified poly(p-phenylene terephthalamide) membrane as the substrate.

[0034] Example 9 A method for preparing a piperazine trimellityl chloride separation membrane obtained by conventional interfacial polymerization using a carboxyl-modified poly(p-phenylene terephthalamide) membrane as a substrate includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 35 g of magnesium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, then add 8.65 g of p-phenylenediamine and stir at 400 r / min for 1 h, then add 16.24 g of terephthaloyl chloride and stir at 2000 r / min for 2.5 h. (4) Add 0.46 g of terephthaloyl chloride solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 250 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the carboxyl-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the carboxyl-modified poly(p-phenylene terephthalamide) membrane in step (5) was soaked in 2.0 wt% piperazine aqueous solution for 10 min, and then the surface of the membrane was dried and treated with 0.5 wt% trimesoyl chloride hexane solution for 10 min. (7) The membrane obtained in step (6) is washed with n-hexane to remove unreacted trimesoyl chloride, and then placed in a 70°C oven for 1 min for thermal stabilization to obtain a piperazine trimesoyl chloride separation membrane obtained by conventional interfacial polymerization using a carboxyl-modified poly(p-phenylene terephthalamide) membrane as the substrate.

[0035] Example 10 A method for preparing a piperazine trimellityl chloride separation membrane obtained by conventional interfacial polymerization using an amino-modified poly(p-phenylene terephthalamide) membrane as a substrate includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 35 g of magnesium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, then add 8.65 g of p-phenylenediamine and stir at 400 r / min for 1 h, then add 16.24 g of terephthaloyl chloride and stir at 2000 r / min for 2.5 h. (4) Add 0.46 g of p-phenylenediamine solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 250 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the amino-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the amino-modified poly(p-phenylene terephthalamide) membrane in step (5) was soaked in 0.05 wt% piperazine aqueous solution for 10 min, then the surface of the membrane was dried, and its surface was treated with 0.05 wt% trimesoyl chloride n-hexane solution for 30 s. (7) The membrane obtained in step (6) is washed with n-hexane to remove unreacted trimesoyl chloride, and then placed in a 70°C oven for 1 min for thermal stabilization to obtain a piperazine trimesoyl chloride separation membrane obtained by conventional interfacial polymerization using an amino-modified poly(p-phenylene terephthalamide) membrane as the substrate.

[0036] Example 11 A method for preparing a piperazine trimellityl chloride separation membrane obtained by conventional interfacial polymerization using an amino-modified poly(p-phenylene terephthalamide) membrane as a substrate includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 35 g of magnesium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, then add 8.65 g of p-phenylenediamine and stir at 400 r / min for 1 h, then add 16.24 g of terephthaloyl chloride and stir at 2000 r / min for 2.5 h. (4) Add 0.46 g of p-phenylenediamine solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 250 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the amino-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the amino-modified poly(p-phenylene terephthalamide) membrane in step (5) was soaked in 1.0 wt% piperazine aqueous solution for 10 min, then the surface of the membrane was dried, and its surface was treated with 0.3 wt% trimesoyl chloride n-hexane solution for 5 min. (7) The membrane obtained in step (6) is washed with n-hexane to remove unreacted trimesoyl chloride, and then placed in a 70°C oven for 1 min for thermal stabilization to obtain a piperazine trimesoyl chloride separation membrane obtained by conventional interfacial polymerization using an amino-modified poly(p-phenylene terephthalamide) membrane as the substrate.

[0037] Example 12 A method for preparing a piperazine trimellityl chloride separation membrane obtained by conventional interfacial polymerization using an amino-modified poly(p-phenylene terephthalamide) membrane as a substrate includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 35 g of magnesium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, then add 8.65 g of p-phenylenediamine and stir at 400 r / min for 1 h, then add 16.24 g of terephthaloyl chloride and stir at 2000 r / min for 2.5 h. (4) Add 0.46 g of p-phenylenediamine solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 250 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the amino-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the amino-modified poly(p-phenylene terephthalamide) membrane in step (5) was soaked in 2.0 wt% piperazine aqueous solution for 10 min, and then the surface of the membrane was dried and treated with 0.5 wt% trimesoyl chloride n-hexane solution for 10 min. (7) The membrane obtained in step (6) is washed with n-hexane to remove unreacted trimesoyl chloride, and then placed in a 70°C oven for 1 min for thermal stabilization to obtain a piperazine trimesoyl chloride separation membrane obtained by conventional interfacial polymerization using an amino-modified poly(p-phenylene terephthalamide) membrane as the substrate.

[0038] Example 13 A method for preparing a polyethyleneimine trimellityl chloride separation membrane obtained by conventional interfacial polymerization using a carboxyl-modified poly(p-phenylene terephthalamide) membrane as a substrate includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 35 g of magnesium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, then add 8.65 g of p-phenylenediamine and stir at 400 r / min for 1 h, then add 16.24 g of terephthaloyl chloride and stir at 2000 r / min for 2.5 h. (4) Add 0.46 g of terephthaloyl chloride solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 250 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the carboxyl-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the carboxyl-modified poly(p-phenylene terephthalamide) membrane in step (5) was soaked in 0.25 wt% of a 300 Da molecular weight polyethyleneimine aqueous solution for 10 min. Then the surface of the membrane was dried and the surface was treated with 0.05 wt% of a pyromellitic chlorohexane solution for 15 s. (7) The membrane obtained in step (6) is washed with n-hexane to remove unreacted trimesoyl chloride, and then placed in an oven at 40°C for 1 min for thermal stabilization. This yields a polyethyleneimine trimesoyl chloride separation membrane obtained by conventional interfacial polymerization using a carboxyl-modified poly(p-phenylene terephthalamide) membrane as the substrate.

[0039] Example 14 A method for preparing a polyethyleneimine trimellityl chloride separation membrane obtained by conventional interfacial polymerization using a carboxyl-modified poly(p-phenylene terephthalamide) membrane as a substrate includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 35 g of magnesium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, then add 8.65 g of p-phenylenediamine and stir at 400 r / min for 1 h, then add 16.24 g of terephthaloyl chloride and stir at 2000 r / min for 2.5 h. (4) Add 0.46 g of terephthaloyl chloride solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 250 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the carboxyl-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the carboxyl-modified poly(p-phenylene terephthalamide) membrane in step (5) was soaked in 1.0 wt% of a 10000 Da molecular weight polyethyleneimine aqueous solution for 5 min, then the surface of the membrane was dried, and its surface was treated with 0.3 wt% of a pyromellitic chlorohexane solution for 15 min. (7) The membrane obtained in step (6) is washed with n-hexane to remove unreacted trimesoyl chloride, and then placed in a 60°C oven for 5 min for thermal stabilization to obtain a polyethyleneimine trimesoyl chloride separation membrane obtained by conventional interfacial polymerization using a carboxyl-modified poly(p-phenylene terephthalamide) membrane as the substrate.

[0040] Example 15 A method for preparing a polyethyleneimine trimellityl chloride separation membrane obtained by conventional interfacial polymerization using a carboxyl-modified poly(p-phenylene terephthalamide) membrane as a substrate includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 35 g of magnesium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, then add 8.65 g of p-phenylenediamine and stir at 400 r / min for 1 h, then add 16.24 g of terephthaloyl chloride and stir at 2000 r / min for 2.5 h. (4) Add 0.46 g of terephthaloyl chloride solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 250 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the carboxyl-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the carboxyl-modified poly(p-phenylene terephthalamide) membrane in step (5) was soaked in a 2.0 wt% aqueous solution of polyethyleneimine with a molecular weight of 70000 Da for 10 min. Then the surface of the membrane was dried and the surface was treated with a 0.5 wt% solution of trimesoyl chloride n-hexane for 30 min. (7) The membrane obtained in step (6) is washed with n-hexane to remove unreacted trimesoyl chloride, and then placed in an oven at 80°C for 10 min for thermal stabilization. This yields a polyethyleneimine trimesoyl chloride separation membrane obtained by conventional interfacial polymerization using a carboxyl-modified poly(p-phenylene terephthalamide) membrane as the substrate.

[0041] Example 16 A method for preparing a polyethyleneimine trimellityl chloride separation membrane obtained by conventional interfacial polymerization using an amino-modified poly(p-phenylene terephthalamide) membrane as a substrate includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 35 g of magnesium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, then add 8.65 g of p-phenylenediamine and stir at 400 r / min for 1 h, then add 16.24 g of terephthaloyl chloride and stir at 2000 r / min for 2.5 h. (4) Add 0.46 g of p-phenylenediamine solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 250 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the amino-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the amino-modified poly(p-phenylene terephthalamide) membrane in step (5) was soaked in a 0.25 wt% aqueous solution of polyethyleneimine with a molecular weight of 300 Da for 10 min. Then the moisture on the membrane surface was dried and the surface was treated with a 0.05 wt% solution of trimesoyl chloride n-hexane for 15 s. (7) The membrane obtained in step (6) is washed with n-hexane to remove unreacted trimesoyl chloride, and then placed in an oven at 40°C for 1 min for thermal stabilization. This yields a polyethyleneimine trimesoyl chloride separation membrane obtained by conventional interfacial polymerization using an amino-modified poly(p-phenylene terephthalamide) membrane as the substrate.

[0042] Example 17 A method for preparing a polyethyleneimine trimellityl chloride separation membrane obtained by conventional interfacial polymerization using an amino-modified poly(p-phenylene terephthalamide) membrane as a substrate includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 35 g of magnesium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, then add 8.65 g of p-phenylenediamine and stir at 400 r / min for 1 h, then add 16.24 g of terephthaloyl chloride and stir at 2000 r / min for 2.5 h. (4) Add 0.46 g of p-phenylenediamine solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 250 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the amino-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the amino-modified poly(p-phenylene terephthalamide) membrane in step (5) was soaked in a 1.0 wt% aqueous solution of polyethyleneimine with a molecular weight of 10000 Da for 5 min. Then the surface of the membrane was dried and the surface was treated with a 0.3 wt% solution of trimesoyl chloride n-hexane for 15 min. (7) The membrane obtained in step (6) is washed with n-hexane to remove unreacted trimesoyl chloride, and then placed in a 60°C oven for 5 min for thermal stabilization to obtain a polyethyleneimine trimesoyl chloride separation membrane obtained by conventional interfacial polymerization using an amino-modified poly(p-phenylene terephthalamide) membrane as the substrate.

[0043] Example 18 A method for preparing a polyethyleneimine trimellityl chloride separation membrane obtained by conventional interfacial polymerization using an amino-modified poly(p-phenylene terephthalamide) membrane as a substrate includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 35 g of magnesium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, then add 8.65 g of p-phenylenediamine and stir at 400 r / min for 1 h, then add 16.24 g of terephthaloyl chloride and stir at 2000 r / min for 2.5 h. (4) Add 0.46 g of p-phenylenediamine solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 250 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the amino-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the amino-modified poly(p-phenylene terephthalamide) membrane in step (5) was soaked in a 2.0 wt% aqueous solution of polyethyleneimine with a molecular weight of 70000 Da for 10 min. Then the surface of the membrane was dried and the surface was treated with a 0.5 wt% solution of trimesoyl chloride n-hexane for 30 min. (7) The membrane obtained in step (6) is washed with n-hexane to remove unreacted trimesoyl chloride, and then placed in an oven at 80°C for 10 min for thermal stabilization. This yields a polyethyleneimine trimesoyl chloride separation membrane obtained by conventional interfacial polymerization using an amino-modified poly(p-phenylene terephthalamide) membrane as the substrate.

[0044] Example 19 A method for preparing a carboxyl-modified poly(p-phenylene terephthalamide) nanofiltration membrane resistant to organic solvents after deposition of a polymer includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 35 g of magnesium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, then add 8.65 g of p-phenylenediamine and stir at 400 r / min for 1 h, then add 16.24 g of terephthaloyl chloride and stir at 2000 r / min for 2.5 h. (4) Add 0.46 g of terephthaloyl chloride solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 250 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the carboxyl-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the carboxyl-modified poly(p-phenylene terephthalamide) membrane obtained in step (5) was soaked in a 1.0 wt% aqueous solution of polyethyleneimine polymer with a molecular weight of 300 Da for 5 min. (7) Use deionized water to wash away the undeposited polyethyleneimine on the membrane in step (6) to obtain a carboxyl-modified poly(p-phenylene terephthalamide) nanofiltration membrane resistant to organic solvents after deposition of polymer.

[0045] Example 20 A method for preparing a carboxyl-modified poly(p-phenylene terephthalamide) nanofiltration membrane resistant to organic solvents after deposition of a polymer includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 35 g of magnesium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, then add 8.65 g of p-phenylenediamine and stir at 400 r / min for 1 h, then add 16.24 g of terephthaloyl chloride and stir at 2000 r / min for 2.5 h. (4) Add 0.46 g of terephthaloyl chloride solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 250 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the carboxyl-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the carboxyl-modified poly(p-phenylene terephthalamide) membrane obtained in step (5) was soaked in a 1.5 wt% aqueous solution of polyethyleneimine polymer with a molecular weight of 10000 Da for 12 h. (7) Use deionized water to wash away the undeposited polyethyleneimine on the membrane in step (6) to obtain a carboxyl-modified poly(p-phenylene terephthalamide) nanofiltration membrane resistant to organic solvents after deposition of polymer.

[0046] Example 21 A method for preparing a carboxyl-modified poly(p-phenylene terephthalamide) nanofiltration membrane resistant to organic solvents after deposition of a polymer includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 35 g of magnesium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, then add 8.65 g of p-phenylenediamine and stir at 400 r / min for 1 h, then add 16.24 g of terephthaloyl chloride and stir at 2000 r / min for 2.5 h. (4) Add 0.46 g of terephthaloyl chloride solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 250 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the carboxyl-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the carboxyl-modified poly(p-phenylene terephthalamide) membrane obtained in step (5) was soaked in a 2.0 wt% aqueous solution of polyethyleneimine polymer with a molecular weight of 70,000 Da for 24 h. (7) Use deionized water to wash away the undeposited polyethyleneimine on the membrane in step (6) to obtain a carboxyl-modified poly(p-phenylene terephthalamide) nanofiltration membrane resistant to organic solvents after deposition of polymer.

[0047] Example 22 A method for preparing an amine-modified poly(p-phenylene terephthalamide) nanofiltration membrane resistant to organic solvents after deposition of a polymer includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 35 g of magnesium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, then add 8.65 g of p-phenylenediamine and stir at 400 r / min for 1 h, then add 16.24 g of terephthaloyl chloride and stir at 2000 r / min for 2.5 h. (4) Add 0.46 g of p-phenylenediamine solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 250 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the amino-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the amino-modified poly(p-phenylene terephthalamide) membrane obtained in step (5) was soaked in a 0.5 wt% aqueous solution of polyethyleneimine polymer with a molecular weight of 300 Da for 5 min. (7) Use deionized water to wash away the undeposited polyethyleneimine on the membrane in step (6) to obtain an amine-modified poly(p-phenylene terephthalamide) nanofiltration membrane resistant to organic solvents after deposition of polymer.

[0048] Example 23 A method for preparing an amine-modified poly(p-phenylene terephthalamide) nanofiltration membrane resistant to organic solvents after deposition of a polymer includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 35 g of magnesium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, then add 8.65 g of p-phenylenediamine and stir at 400 r / min for 1 h, then add 16.24 g of terephthaloyl chloride and stir at 2000 r / min for 2.5 h. (4) Add 0.46 g of p-phenylenediamine solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 250 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the amino-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the amino-modified poly(p-phenylene terephthalamide) membrane obtained in step (5) was soaked in a 1.0 wt% aqueous solution of polyethyleneimine polymer with a molecular weight of 10000 Da for 12 h. (7) Use deionized water to wash away the undeposited polyethyleneimine on the membrane in step (6) to obtain an amine-modified poly(p-phenylene terephthalamide) nanofiltration membrane resistant to organic solvents after deposition of polymer.

[0049] Example 24 A method for preparing an amine-modified poly(p-phenylene terephthalamide) nanofiltration membrane resistant to organic solvents after deposition of a polymer includes the following steps: (1) Take 400 ml of N-methylpyrrolidone solution and add it to a 1 L three-necked flask and heat at 100 °C for 15 min; (2) Add 35 g of magnesium chloride co-solvent to the three-necked flask in step (1), and heat and stir at 100 °C for 30 min; (3) After cooling the three-necked flask in step (2) to room temperature, place it in an ice-water mixing bath to cool, then add 8.65 g of p-phenylenediamine and stir at 400 r / min for 1 h, then add 16.24 g of terephthaloyl chloride and stir at 2000 r / min for 2.5 h. (4) Add 0.46 g of p-phenylenediamine solid to the three-necked flask in step (3) for end-capping treatment, and add 380 ml of N-methylpyrrolidone solution for dilution. At the same time, the temperature is controlled under ice-water bath conditions throughout the process to obtain the diluted end-capped polymer solution. (5) Finally, at room temperature, the polymer solution in step (4) was coated onto the nonwoven fabric with a 250 μm doctor blade and quickly immersed in water for phase inversion, thus obtaining the amino-modified poly(p-phenylene terephthalamide) membrane. (6) At room temperature, the amino-modified poly(p-phenylene terephthalamide) membrane obtained in step (5) was soaked in a 2.0 wt% aqueous solution of polyethyleneimine polymer with a molecular weight of 70,000 Da for 24 h. (7) Use deionized water to wash away the undeposited polyethyleneimine on the membrane in step (6) to obtain an amine-modified poly(p-phenylene terephthalamide) nanofiltration membrane resistant to organic solvents after deposition of polymer.

[0050] Comparative Example 1 A method for preparing a separation membrane by conventional dissolution of para-aramid fibers followed by phase inversion coating to obtain a poly(p-phenylene terephthalamide) membrane, and then using this membrane as a substrate for conventional interfacial polymerization of m-phenylenediamine pyromellitic acid chloride, includes the following steps: (1) Weigh 3 g of potassium hydroxide and dissolve it in 3.5 ml of water. Then add 4 g of para-aramid fiber and 196 g of dimethyl sulfoxide to form a mixed solution system. Heat the solution at 30°C. o A 2 wt% poly(p-phenylene terephthalamide) casting solution was obtained by heating and stirring at C. (2) The casting solution is coated onto the nonwoven fabric using a scraping machine with a scraping blade thickness of 250 μm. The scraped nonwoven fabric is then immersed in deionized water and left to stand for 2 minutes to form a poly(p-phenylene terephthalamide) film. (3) Soak the poly(p-phenylene terephthalamide) membrane in step (2) in a 2.0 wt% aqueous solution of m-phenylenediamine for 10 min, then blow dry the moisture on the surface of the membrane, and treat its surface with a 0.1 wt% solution of pyromellitic chlorohexane for 1 min. (4) The membrane obtained in step (3) is washed with n-hexane to remove unreacted trimesoyl chloride, and then placed in a 70°C oven for 1 min for thermal stabilization. This yields a m-phenylenediamine trimesoyl chloride separation membrane obtained by conventional interfacial polymerization using a poly(p-phenylene terephthalamide) membrane obtained by conventional dissolution of para-aramid fibers and subsequent coating with phase inversion as the substrate.

[0051] Comparative Example 2 A method for preparing a separation membrane by conventional dissolution of para-aramid fibers followed by phase inversion coating to obtain a poly(p-phenylene terephthalamide) membrane, and then using this membrane as a substrate for conventional piperazine-trimethylammonium chloride interfacial polymerization, includes the following steps: (1) Weigh 3 g of potassium hydroxide and dissolve it in 3.5 ml of water. Then add 4 g of para-aramid fiber and 196 g of dimethyl sulfoxide to form a mixed solution system. Heat the solution at 30°C. o A 2 wt% poly(p-phenylene terephthalamide) casting solution was obtained by heating and stirring at C. (2) The casting solution is coated onto the nonwoven fabric using a scraping machine with a scraping blade thickness of 250 μm. The scraped nonwoven fabric is then immersed in deionized water and left to stand for 2 minutes to form a poly(p-phenylene terephthalamide) film. (3) Soak the poly(p-phenylene terephthalamide) membrane in step (2) in 0.2 wt% piperazine aqueous solution for 10 min, then blow dry the moisture on the membrane surface, and treat its surface with 0.1 wt% trimesoyl chloride n-hexane solution for 1 min. (4) The membrane obtained in step (3) is washed with n-hexane to remove unreacted trimesoyl chloride, and then placed in a 70°C oven for thermal stabilization for 1 min to obtain a piperazine trimesoyl chloride separation membrane obtained by conventional interfacial polymerization using a poly(p-phenylene terephthalamide) membrane obtained by conventional dissolution of para-aramid fibers and subsequent coating phase inversion as the substrate.

[0052] Comparative Example 3 A method for preparing a separation membrane by conventional dissolution of para-aramid fibers followed by phase inversion coating to obtain a poly(p-phenylene terephthalamide) membrane, and then using this membrane as a substrate for conventional interfacial polymerization of polyethyleneimine pyromellitic trimethylolpropionate chloride, includes the following steps: (1) Weigh 3 g of potassium hydroxide and dissolve it in 3.5 ml of water. Then add 4 g of para-aramid fiber and 196 g of dimethyl sulfoxide to form a mixed solution system. Heat the solution at 30°C. o A 2 wt% poly(p-phenylene terephthalamide) casting solution was obtained by heating and stirring at C. (2) The casting solution is coated onto the nonwoven fabric using a scraping machine with a scraping blade thickness of 250 μm. The scraped nonwoven fabric is then immersed in deionized water and left to stand for 2 minutes to form a poly(p-phenylene terephthalamide) film. (3) Soak the poly(p-phenylene terephthalamide) membrane in step (2) in a 0.25 wt% aqueous solution of polyethyleneimine for 10 min, then blow dry the moisture on the surface of the membrane, and treat its surface with a 0.1 wt% solution of pyromellitic chlorohexane for 1 min. (4) The membrane obtained in step (3) is washed with n-hexane to remove unreacted trimesoyl chloride, and then placed in a 70°C oven for 1 min for thermal stabilization. This yields a polyethyleneimine trimesoyl chloride separation membrane obtained by conventional interfacial polymerization using a poly(p-phenylene terephthalamide) membrane as the substrate, which is obtained by conventional dissolution of para-aramid fibers and subsequent coating with a phase inversion coating.

[0053] Comparative Example 4 A conventional method for preparing a separation membrane by dissolving para-aramid fibers, then coating with a phase-inversion poly(p-phenylene terephthalamide) membrane, and then redepositing a polymer, includes the following steps: (1) Weigh 3 g of potassium hydroxide and dissolve it in 3.5 ml of water. Then add 4 g of para-aramid fiber and 196 g of dimethyl sulfoxide to form a mixed solution system. Heat the solution at 30°C. o A 2 wt% poly(p-phenylene terephthalamide) casting solution was obtained by heating and stirring at C. (2) The casting solution is coated onto the nonwoven fabric using a scraping machine with a scraping blade thickness of 250 μm. The scraped nonwoven fabric is then immersed in deionized water and left to stand for 2 minutes to form a poly(p-phenylene terephthalamide) film. (3) Soak the poly(p-phenylene terephthalamide) membrane obtained in step (2) in a 1.0 wt% aqueous solution of polyethyleneimine polymer with a molecular weight of 70000 Da for 1 h; (4) Use deionized water to wash away the undeposited polyethyleneimine on the membrane in step (3) to obtain the separation membrane obtained by re-depositing polymers on the poly(p-phenylene terephthalamide) membrane obtained by traditional dissolution of para-aramid fibers and subsequent coating phase conversion.

[0054] Performance testing: The membranes prepared in the above examples and comparative examples were subjected to nanofiltration performance tests in aqueous solutions, nanofiltration performance tests in organic solvents, and end-group functional group density determination. The specific methods are as follows: (1) Nanofiltration performance of aqueous solutions: The performance tests based on aqueous solution nanofiltration were conducted on a cross-flow filtration unit. Before flux testing, each new membrane underwent a stabilization treatment with pure water at 5 bar pressure for 30 minutes. Subsequently, the membrane was subjected to a 45 L / h... -1 Under the specified flow rate, the test pressure was 5 bar, and the test temperature was 25 ± 0.5 ℃. Water flux (P) w , L m -2 h -1 bar -1 Calculate according to the following formula:

[0055] In the formula, V is the permeate volume (L), and A is the effective area of ​​the test membrane (m²). 2 Δt is the time (h) used to collect the required volume of permeate, and ΔP is the transmembrane pressure (bar).

[0056] The formula for calculating the salt rejection rate (R, %) is as follows:

[0057] In the formula, c p and c f These represent the salt concentrations in the permeate and feed solutions, respectively. The feed solution is 2 g / L. -1 Magnesium chloride solution.

[0058] (2) Resistance to organic solvent nanofiltration The organic solvent resistance nanofiltration performance test was conducted on a dead-end filtration unit. Before flux testing, each new membrane was stabilized with pure water at 5 bar for 30 minutes. The test pressure was 5 bar, and the test temperature was 25 ± 0.5 °C. Organic solvent flux (P0.05) was measured. o , L m -2 h -1 bar -1 Calculate according to the following formula:

[0059] In the formula, V is the permeate volume (L), and A is the effective area of ​​the test membrane (m²). 2 Δt is the time (h) used to collect the required volume of permeate, and ΔP is the transmembrane pressure (bar).

[0060] The retention rate (R, %) is calculated using the following formula:

[0061] In the formula, c p and c f These represent the dye concentrations in the permeate and feed solutions, respectively. The feed solution concentration is 20 μmol / L. -1 .

[0062] This invention tested the organic solvent resistance of m-phenylenediamine pyromellitic acid chloride, piperazine pyromellitic acid chloride, polyethyleneimine pyromellitic acid chloride separation membranes, polyethyleneimine separation membranes, and amino- or carboxyl-modified poly(p-phenylene terephthalamide) membranes obtained by synergistically enhanced interfacial polymerization or deposition of polymer molecules. The dyes used were 20 µmol / L, specifically Bengal Rose Red (1017 Da, negatively charged) and Methyl Orange (327 Da, positively charged). The desalination performance in water treatment of m-phenylenediamine pyromellitic acid chloride, piperazine pyromellitic acid chloride, polyethyleneimine pyromellitic acid chloride separation membranes, polyethyleneimine separation membranes, and amino- or carboxyl-modified poly(p-phenylene terephthalamide) membranes obtained by synergistically enhanced conventional interfacial polymerization was also tested. The salts used were sodium chloride, sodium sulfate, and magnesium chloride, with a concentration of 1 g / L. The flux and retention of the separation membranes during long-term operation are shown in Tables 1, 2, 3, and 4. The flux units in the test tables are L / m. -2 bar -1 h -1 .

[0063] (3) Determination of end-group functional group density To quantify the number of carboxyl amine groups on the base film, we need to test the density of carboxyl amine groups on the base film surface.

[0064] By using TBO (a cationic dye (C 15 H 16 N3S + The concentration of negatively charged functional groups on the membrane surface was determined using a molecular weight of 270 g / mol. TBO was dissolved in an aqueous sodium hydroxide solution at pH 11 to prepare a TBO solution (2 mM). The membrane was then compared with the TBO solution (1 cm⁻¹). 2 The membrane (approximately 1 mL of TBO solution) was contacted for 3 min at room temperature (25 °C). Then, the membrane was removed from the glass plate, rinsed, and immersed in a dye-free NaOH solution at pH 11 (>4 hours) to wash away unbound TBO molecules. Next, two 4 cm² membranes were cut. 2The sample was immersed in 10 ml of a 0.2 M NaCl solution (adjusted with hydrochloric acid) at pH 2, with stirring for 30 min. This step releases TBO bound to the carboxyl groups into the solution. The absorbance was measured by UV spectrophotometry at 630 nm. The light absorption was converted to TBO concentration using a calibration curve, and the carboxyl group density on the membrane surface was calculated by dividing the number of TBO molecules by the membrane area.

[0065] The density of carboxyl groups on the surface of the PPTA-based film was tested using Orange II dye (an anionic dye, C...). 16 H 11 N2O4S - The density of charged functional groups on the membrane surface was determined by measuring the molecular weight (350.32 g / mol). Orange II was dissolved in hydrochloric acid aqueous solution at pH 3 to prepare an Orange II solution (2 mM). The membrane was then subjected to an Orange II solution (1 cm⁻¹). 2 The membrane (approximately 1 ml of Orange II solution) was contacted for 3 min at room temperature (25°C). Then, the membrane was removed from the glass plate, rinsed, and immersed in a dye-free hydrochloric acid solution at pH 2 (>4 hours) to wash away unbound Orange II molecules. Next, two 4 cm² membranes were cut. 2 The sample was immersed in 10 ml of a 0.2 M NaCl solution (adjusted with NaOH) at pH 11, and stirred for 30 min. This step releases the carboxyl-bound Orange II into the solution. The light absorption was converted to Orange II concentration using a calibration curve, and the amine density on the membrane surface was calculated by dividing the number of Orange II molecules by the membrane planar area.

[0066] The test results are as follows: Table 1 shows the retention performance and flux of the thin films of Examples 1-6 and Comparative Example 1 on methyl orange in the methanol system and the retention performance and flux of sodium chloride in water treatment desalination. The flux and retention of the present invention are higher than those of Comparative Example 1, and the present invention has better performance. In addition, the total end-group density of the base film is greater than that of Comparative Example 1.

[0067] Table 1

[0068] Table 2 shows the retention performance and flux of the thin films of Examples 7-12 and Comparative Example 2 in the methanol system for methyl orange and the retention performance and flux of sodium sulfate in water treatment desalination. The retention and flux of the present invention are higher than those of Comparative Example 2, and the present invention has better performance. In addition, the total end-group density of the base film is greater than that of Comparative Example 2.

[0069] Table 2

[0070] Table 3 shows the retention performance and flux of the thin films of Examples 13-18 and Comparative Example 3 in the methanol system for methyl orange and the retention performance and flux of magnesium chloride in water treatment desalination. The flux and retention of the present invention are higher than those of Comparative Example 3, and the present invention has better performance. In addition, the total end-group density of the base film is greater than that of Comparative Example 3.

[0071] Table 3

[0072] Table 4 shows the retention performance and flux of the films produced in Examples 19-24 and Comparative Example 4 for Bengal rose red in the methanol system and the retention performance and flux of sodium sulfate in the water system. The retention rate and flux of the present invention are much greater than those of Comparative Example 4. At the same time, it has higher flux for methanol and water, and the total end-group density of the base film is greater than that of Comparative Example 4.

[0073] Table 4

[0074] As can be seen, this invention can enhance the selectivity and flux of nanofiltration membranes through synergistic effects of interfacial polymerization or deposited polymer molecules. Specifically, the synergistic effect manifests in the following ways: Because the poly(p-phenylene terephthalamide) membrane obtained in this invention has a significantly increased number of amine or carboxyl groups on its surface, when a polymer rich in amine groups (e.g., polyethyleneimine) is deposited on the surface, the synergistic effect between the groups causes the amine-rich polymer to interact with the membrane surface, thus achieving a pore-shrinking effect. Furthermore, when performing conventional interfacial polymerization (e.g., interfacial polymerization of m-phenylenediamine, piperazine, polyethyleneimine, and trimesoyl chloride), the amine-terminated membrane surface exhibits a synergistic effect with the amine monomers (e.g., m-phenylenediamine, piperazine, polyethyleneimine), participating in the reaction with trimesoyl chloride to achieve performance optimization. Conversely, the carboxyl groups on the carboxyl-terminated membrane surface also synergistically interact with trimesoyl chloride, resulting in a nanofiltration membrane surface rich in carboxyl groups, thereby improving anion rejection.

[0075] The above embodiments are merely examples. For instance, in addition to nonwoven fabrics, other porous support layer materials with certain mechanical strength can also be used, such as commonly used porous ceramic materials, porous metal meshes (stainless steel, titanium alloys), etc.

[0076] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing nanofiltration membranes by enhancing interfacial polymerization or depositing polymer molecules through synergistic effects, characterized in that, Includes the following steps: (1) Using p-phenylenediamine and terephthaloyl chloride as monomers, a poly(p-phenylenediamine) solution was obtained by stirring in a system containing organic solvent and metal salt co-solvent at -4~6℃ through polymerization reaction; (2) Maintain a temperature of -4~6℃, add a capping agent and a diluent to the poly(p-phenylene terephthalamide) solution obtained in step (1), and mix evenly to obtain an amino- or carboxyl-modified poly(p-phenylene terephthalamide) casting solution; wherein, the capping agent is used to provide amino or carboxyl groups; (3) The casting liquid is scraped onto the porous support layer and immersed in the coagulation bath for phase transformation to form an amino or carboxyl-modified poly(p-phenylene terephthalamide) membrane; (4) Using the amino or carboxyl-modified poly(p-phenylene terephthalamide) membrane obtained in step (3) as the base membrane, a high-performance nanofiltration membrane is obtained by interfacial polymerization or deposition of polymer molecules to utilize synergistic effects.

2. The method as described in claim 1, characterized in that, In step (1): The concentrations of p-phenylenediamine and terephthaloyl chloride monomers in the poly(p-phenylene terephthalamide) solution are both 0.1~1.0 mol / L; the organic solvent is selected from at least one of dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide. The metal salt co-solvent is selected from at least one of magnesium chloride, sodium chloride, sodium sulfate, magnesium sulfate, calcium chloride, and lithium chloride, and the concentration of the metal salt co-solvent corresponding to the poly(p-phenylene terephthalamide) solution is 50~125 g / L.

3. The method as described in claim 1, characterized in that, In step (2): The capping agent is selected from at least one of pyromellitic terephthaloyl chloride, isophthaloyl chloride, terephthaloyl chloride, benzenetrisulfonyl chloride, glutaryl chloride, p-phenylenediamine, m-phenylenediamine, maleic acid chloride, cyclobutanetriacyl chloride, adipyl chloride, cyclobutanetetraacyl chloride, cyclopentanediacyl chloride, cyclopentanetetraacyl chloride, and cyclopropanetriacyl chloride; the concentration of the capping agent after mixing with the poly(p-phenylenediamine) terephthaloyl chloride solution obtained in step (1) is 0.1~1.0 wt%; The diluting solvent is the same type of organic solvent as in step (1), and the amount used is 10-25 wt% of the poly(p-phenylene terephthalamide) solution obtained in step (1).

4. The method as described in claim 1, characterized in that, In step (1), the stirring process is carried out at 200~5000 r / min for 1~24 h.

5. The method as described in claim 1, characterized in that, In step (3): The coagulation bath is water, or a mixed solution of water and a water-soluble organic solvent; wherein the water-soluble organic solvent is at least one of dimethyl sulfoxide, N-methylpyrrolidone, N,N-dimethylformamide, phenol, and dimethylacetamide. Preferably, the porous support layer is a nonwoven fabric with a coating thickness of 100~500 µm.

6. The method as described in claim 1, characterized in that, In step (4): the interfacial polymerization is to generate a selective layer by condensation reaction of aqueous monomer and oil monomer at the interface of the base film surface; preferably, the interfacial polymerization is to immerse the base film in a solution containing aqueous monomer for 5 to 10 minutes and then take it out. After the water droplets on the surface are dried, the base film surface is then immersed in a solution containing oil monomer for 15 to 30 minutes. After the surface evaporates, it is heat-treated at 40 to 80 °C for 1 to 10 minutes. More preferably, the interfacial polymerization is an interfacial polymerization of m-phenylenediamine and trimesoyl chloride, or an interfacial polymerization of piperazine and trimesoyl chloride, or an interfacial polymerization of polyethyleneimine and trimesoyl chloride; wherein, When the interfacial polymerization of m-phenylenediamine and trimesoyl chloride is used, the aqueous phase solution is a m-phenylenediamine solution, and the oil phase solution is a mixture of trimesoyl chloride monomer and organic solvent; the concentration of the m-phenylenediamine solution used is 1.0-5.0 wt%, the concentration of the trimesoyl chloride solution used is 0.1-0.5 wt%, and the reaction time is 15 s-10 min; When using interfacial polymerization of piperazine and trimesoyl chloride, the aqueous phase solution is a piperazine solution, and the oil phase solution is a mixture of trimesoyl chloride monomer and organic solvent; the concentration of the piperazine solution used is 0.05-2.0 wt%, the concentration of the trimesoyl chloride solution used is 0.05-0.5 wt%, and the reaction time is 30 s-10 min; When using interfacial polymerization of polyethyleneimine and trimesoyl chloride, the aqueous phase solution is a polyethyleneimine solution, and the oil phase solution is a mixture of trimesoyl chloride monomer and organic solvent; the concentration of the polyethyleneimine solution used is 0.25-2.0 wt%, and the molecular weight of polyethyleneimine is 300-70000 Da; the concentration of the trimesoyl chloride solution used is 0.05-0.5 wt%, and the reaction time is 15 s-30 min; The organic solvent used in the oil phase solution is at least one of octane, cyclohexane, n-hexane, and heptane.

7. The method as described in claim 1, characterized in that, In step (4): the deposition of polymer molecules involves immersing the base membrane in a polymer aqueous solution and maintaining it for 5 min-24 h to form a separation layer, and then immersing the treated membrane in deionized water for cleaning. Preferably, the polymer used for the deposition of polymer molecules is selected from at least one of polyacrylamide, polyethyleneimine, polyvinyl alcohol, polydimethyldiallylammonium chloride, polyallylamine salt, sodium polyacrylate, polymethacrylic acid, and sodium polystyrene sulfonate, with a molecular weight of 300-70000 Da and a polymer solution concentration of 0.5-2.0 wt%.

8. A nanofiltration membrane prepared by the method described in any one of claims 1-7.

9. The nanofiltration membrane of claim 8 is used for water treatment desalination or for use in organic solvent-resistant nanofiltration.

10. The application as described in claim 9, characterized in that, The organic solvent-resistant nanofiltration is specifically used for solvent and drug concentration and separation, solvent and solvent separation when different solvents are mixed, light oil and heavy oil separation, or waste solvent recovery.

Images