A nanofiltration membrane for the sieving of low molecular weight organic compounds and a method for its preparation

Abstract

The application relates to a nanofiltration membrane for screening low-molecular-weight organic matters and a preparation method thereof, and belongs to the nanofiltration membrane separation field. The membrane is composed of a porous support layer and a sulfonated aromatic polyamide separation layer; the preparation method is as follows: a cosolvent and an inorganic salt are simultaneously added in an aqueous phase solution of interfacial polymerization, and the nanofiltration membrane is prepared from large-size sulfonated aromatic polyamine monomers and polyacyl chloride monomers through interfacial polymerization assisted by the cosolvent and the inorganic salt. The novel membrane preparation method reduces non-selective defects in the membrane. The prepared membrane has high rejection rate for organic matters with molecular weights in the range of 250-400 Da in a water solution and low rejection rate for organic matters with molecular weights in the range of 50-150 Da in the water solution, and the membrane has a significant advantage in organic matter screening in a water solution system. The application is based on the traditional interfacial polymerization process, has mild preparation conditions, simple operation steps and a good industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of nanofiltration membrane separation, and particularly relates to a nanofiltration membrane for screening low molecular weight organic matter and its preparation method. Background Technology

[0002] Membrane separation technology has become a crucial separation technology due to its advantages such as energy saving, environmental friendliness, and high production efficiency. Nanofiltration membranes, in particular, combine pore size sieving with the Donnan effect to retain organic matter with molecular weights in the 200-1000 Da range in aqueous solutions while allowing smaller molecular weight organic matter to pass through. Therefore, nanofiltration membranes can sieve organic matter in aqueous solutions based on differences in molecular weight.

[0003] The aforementioned screening process is involved in many industrial production processes. For example, in the synthesis of glutathione, unreacted amino acids in the aqueous solution need to be removed to purify the product, which requires separating glutathione (307 Da) from the various amino acids (75-147 Da). As another example, in the synthesis of 2-amino-3-hydroxy-3-(4-methylsulfonylphenyl)propionic acid, unreacted glycine in the aqueous solution needs to be extracted and reused in the reaction, which requires separating 2-amino-3-hydroxy-3-(4-methylsulfonylphenyl)propionic acid (259 Da) from glycine (75 Da).

[0004] However, while existing nanofiltration membranes exhibit high rejection rates for target organic compounds with molecular weights less than 400 Da in aqueous solutions, they struggle to maintain low rejection rates for other organic compounds with molecular weights in the 50-150 Da range. Taking the most widely used polypiperazine amide nanofiltration membrane as an example, its poor selectivity for the aforementioned system stems from the piperazine monomer's alicyclic structure and small molecular size, resulting in a small average pore size and low porosity, making it difficult for low-molecular-weight organic compounds to permeate (Angewandte Chemie 134(2022)e202212816). Therefore, replacing piperazine with monomers of larger molecular size and greater molecular rigidity is expected to optimize the average pore size and increase the membrane porosity, thereby improving membrane selectivity. Furthermore, introducing charged groups onto the monomer is expected to further enhance membrane selectivity by strengthening electrostatic repulsion.

[0005] Large-size sulfonated aromatic polyamine monomers can meet the above requirements. However, such monomers, such as 4,4'-diaminobiphenyl-2,2'-disulfonic acid, face serious limitations when preparing nanofiltration membranes via interfacial polymerization. On the one hand, these monomers have poor solubility in water, making it difficult to diffuse uniformly to the organic phase interface to participate in the interfacial polymerization reaction. On the other hand, electrostatic repulsion between charged groups severely hinders the further diffusion of these monomers into the nascent polyamide membrane. This diffusion limitation leads to more non-selective defects in the membrane, limiting the improvement of membrane selectivity. Under existing membrane preparation methods, the molecular weight cutoff of nanofiltration membranes prepared from these monomers is between 900-1500 Da, which cannot achieve a high rejection rate for target organic compounds with a molecular weight less than 400 Da (Journal of Membrane Science 632(2021)119358). Therefore, this invention discloses a novel preparation method: preparing nanofiltration membranes from large-size sulfonated aromatic polyamine monomers and polyacrylamide monomers through interfacial polymerization assisted by a co-solvent and inorganic salt. This novel membrane-forming method promotes the dispersion of these monomers in aqueous solutions, improving their diffusion uniformity. Furthermore, it shields against electrostatic repulsion between sulfonic acid groups, eliminating the hindrance of the nascent polyamide membrane to further diffusion of these monomers. This method also reduces non-selective defects in the membrane. The prepared membrane exhibits high retention rates for organic compounds with molecular weights in the 250-400 Da range in aqueous solutions, and low retention rates for organic compounds with molecular weights in the 50-150 Da range, demonstrating significant advantages in organic matter sieving in aqueous solutions. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a nanofiltration membrane for screening low molecular weight organic matter and a method for preparing the same.

[0007] A nanofiltration membrane for screening low molecular weight organic matter and its preparation method, comprising the following steps:

[0008] (1) Prepare an aqueous solution by dissolving the sulfonated aromatic polyamine monomer, co-solvent, and inorganic salt 1 in water, wherein the concentration of the sulfonated aromatic polyamine monomer is 15-60 mmol / L. -1 The co-solvent volume percentage is 5-35 v / v%, and the inorganic salt concentration is 0.5-1.5 mol L. -1 Prepare an organic phase solution by dissolving polyacrylamide chloride monomers in an organic solvent, wherein the concentration of the polyacrylamide chloride monomers is 0.5-2 g / L. -1 .

[0009] (2) Immerse the porous support layer in the aqueous solution of step (1) for 1-10 minutes; after removing excess aqueous solution from the surface, immerse it in the organic solution of step (1) for 0.5-5 minutes; after the interfacial polymerization reaction, place the obtained nascent polyamide membrane in different media for heat treatment at a temperature of 40-60℃ for 10-30 minutes; after the heat treatment is completed, soak and wash it in water to obtain the nanofiltration membrane.

[0010] The sulfonated aromatic polyamine monomer mentioned in step (1) is one or a mixture of several of the following: 2,4-diaminobenzenesulfonic acid, 2,5-diaminobenzenesulfonic acid, 4,4'-diaminobiphenyl-2,2'-disulfonic acid, 4,4'-diaminodiphenyl ether-2,2'-disulfonic acid, and 4,4'-diaminostilbene-2,2'-disulfonic acid. The co-solvent mentioned in step (1) is one or a mixture of several of the following: methanol, ethanol, isopropanol, toluene, diethyl ether, acetone, ethyl acetate, dimethyl sulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide. The inorganic salt 1 mentioned in step (1) is one or a mixture of several of the following: sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, copper chloride, ferric chloride, zinc chloride, and aluminum chloride. The polyacrylamide monomer mentioned in step (1) is one or a mixture of several of the following: trimesoyl chloride and biphenyltetracarboxylic chloride. The organic solvent mentioned in step (1) is one or a mixture of several of the following: n-hexane, cyclohexane, n-heptane, toluene, chloroform, and carbon tetrachloride. The porous support layer mentioned in step (2) is one of the following: porous polysulfone support layer, porous polyethersulfone support layer, porous polyacrylonitrile support layer, porous polyethylene support layer, porous polypropylene support layer, porous polyvinyl chloride support layer, and porous polyimide support layer. The heat treatment medium mentioned in step (2) is one of the following: air medium or a mixed aqueous solution medium composed of a polyamine and an inorganic salt 2; the polyamine is N,N-dimethylethylenediamine, ethylenediamine, piperazine, m-phenylenediamine, p-phenylenediamine, 4,4-bispiperidine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, or polyethyleneimine (MW = 300 Da - 70000). The mixture is a mixture of one or more of the following: polyamine (MW = 300 Da), polyethyleneimine (MW = 600 Da), polyethyleneimine (MW = 1800 Da), polyethyleneimine (MW = 10000 Da), and polyethyleneimine (MW = 70000 Da); the concentration of the polyamine in the mixed aqueous solution is 0.0025-0.1 wt%; inorganic salt 2 is a mixture of one or more of the following: sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, copper chloride, ferric chloride, zinc chloride, and aluminum chloride; the concentration of inorganic salt 2 in the mixed aqueous solution is 0.5-1.5 mol / L. -1 .

[0011] This invention utilizes large-size sulfonated aromatic polyamine monomers and employs a co-solvent and inorganic salt synergistic assisted interfacial polymerization method to construct a sulfonated aromatic polyamide nanofiltration membrane with a larger intrinsic pore structure, fewer non-selective defects, and stronger negative charge. The prepared membrane, under room temperature and slightly alkaline conditions (pH 7-10), is used for sieving organic compounds of different molecular weights in aqueous solutions. It exhibits high retention rates for organic compounds with molecular weights in the range of 250-400 Da and low retention rates for organic compounds with molecular weights in the range of 50-150 Da, demonstrating significant advantages in organic compound sieving in aqueous systems. This invention is based on a traditional interfacial polymerization process, with mild preparation conditions and simple operation steps, and has promising prospects for industrial applications. Detailed Implementation

[0012] The following are embodiments of the present invention, but the present invention is not limited to the embodiments:

[0013] Example 1:

[0014] An aqueous solution was prepared by dissolving 4,4'-diaminobiphenyl-2,2'-disulfonic acid, ethanol, and sodium chloride in water, wherein the concentration of 4,4'-diaminobiphenyl-2,2'-disulfonic acid was 15 mmol / L. -1 The ethanol volume percentage is 35 v / v, and the sodium chloride concentration is 0.5 mol / L. -1 An organic phase solution was prepared by dissolving trimesoyl chloride in n-hexane, wherein the concentration of trimesoyl chloride was 0.5 g / L. -1 The porous polysulfone support layer was immersed in an aqueous solution for 10 minutes. After removing excess aqueous solution from the surface, it was then immersed in an organic solution for 5 minutes. Following the interfacial polymerization reaction, the nascent polyamide film was heat-treated in a mixed aqueous solution of pentaethylenehexamine and sodium chloride, wherein the concentration of pentaethylenehexamine was 0.0025 wt% and the concentration of sodium chloride was 0.5 mol / L. -1 The heat treatment temperature was 60℃, and the heat treatment time was 10 minutes. After the heat treatment, the membrane was immersed in water for washing to obtain the nanofiltration membrane. Under the test conditions of 25℃, pH = 8.50 ± 0.1, and 0.4 MPa, the separation results of the membrane for 1000 ppm 2-amino-3-hydroxy-3-(4-methylsulfonylphenyl)propionic acid (MW = 259 Da) and 1000 ppm glycine (MW = 75 Da) were as follows: the rejection rate for 2-amino-3-hydroxy-3-(4-methylsulfonylphenyl)propionic acid was 90.5%, the rejection rate for glycine was 20.4%, and the water permeation flux was 5.0 L / m³. -2 h -1 bar -1 .

[0015] Example 2:

[0016] An aqueous solution was prepared by dissolving 4,4'-diaminobiphenyl-2,2'-disulfonic acid, ethanol, and sodium chloride in water, wherein the concentration of 4,4'-diaminobiphenyl-2,2'-disulfonic acid was 60 mmol / L. -1 The ethanol volume percentage is 5 v / v%, and the sodium chloride concentration is 1.5 mol / L. -1 An organic phase solution was prepared by dissolving trimesoyl chloride in n-hexane, wherein the concentration of trimesoyl chloride was 2 g / L. -1 The porous polysulfone support layer was immersed in an aqueous solution for 1 minute. After removing excess aqueous solution from the surface, it was then immersed in an organic solution for 0.5 minutes. Following the interfacial polymerization reaction, the nascent polyamide film was heat-treated in a mixed aqueous solution of pentaethylenehexamine and sodium chloride, wherein the concentration of pentaethylenehexamine was 0.1 wt% and the concentration of sodium chloride was 1.5 mol / L. -1 The heat treatment temperature was 40℃, and the heat treatment time was 30 minutes. After the heat treatment, the membrane was immersed in water for washing to obtain the nanofiltration membrane. Under the test conditions of 25℃, pH = 8.50 ± 0.1, and 0.4 MPa, the separation results of the membrane for 1000 ppm 2-amino-3-hydroxy-3-(4-methylsulfonylphenyl)propionic acid (MW = 259 Da) and 1000 ppm glycine (MW = 75 Da) were as follows: the rejection rate for 2-amino-3-hydroxy-3-(4-methylsulfonylphenyl)propionic acid was 94.9%, the rejection rate for glycine was 48.6%, and the water permeation flux was 4.6 L / m³. -2 h -1 bar -1 .

[0017] Example 3:

[0018] An aqueous solution was prepared by dissolving 4,4'-diaminobiphenyl-2,2'-disulfonic acid, ethanol, and sodium chloride in water, wherein the concentration of 4,4'-diaminobiphenyl-2,2'-disulfonic acid was 30 mmol / L. -1 The ethanol volume percentage is 25 v / v, and the sodium chloride concentration is 0.5 mol / L. -1 An organic phase solution was prepared by dissolving trimesoyl chloride in n-hexane, wherein the concentration of trimesoyl chloride was 1 g / L. -1The porous polysulfone support layer was immersed in an aqueous solution for 5 minutes. After removing excess aqueous solution from the surface, it was then immersed in an organic solution for 1 minute. After interfacial polymerization, the nascent polyamide membrane was heat-treated in an air medium (e.g., an oven) at 50°C for 15 minutes. After heat treatment, it was rinsed in water to obtain the nanofiltration membrane. Under test conditions of 25°C, pH = 9.75 ± 0.1, and 0.4 MPa, the membrane achieved the following separation results for 1000 ppm 2-amino-3-hydroxy-3-(4-methylsulfonylphenyl)propionic acid (MW = 259 Da) and 1000 ppm glycine (MW = 75 Da): a retention rate of 90.4% for 2-amino-3-hydroxy-3-(4-methylsulfonylphenyl)propionic acid and 32.8% for glycine, with a water permeation flux of 13.2 L / m³. -2 h -1 bar -1 .

[0019] Example 4:

[0020] An aqueous solution was prepared by dissolving 4,4'-diaminobiphenyl-2,2'-disulfonic acid, ethanol, and sodium chloride in water, wherein the concentration of 4,4'-diaminobiphenyl-2,2'-disulfonic acid was 30 mmol / L. -1 The ethanol volume percentage is 25 v / v, and the sodium chloride concentration is 0.75 mol / L. -1 An organic phase solution was prepared by dissolving trimesoyl chloride in n-hexane, wherein the concentration of trimesoyl chloride was 1 g / L. -1 The porous polysulfone support layer was immersed in an aqueous solution for 5 minutes. After removing excess aqueous solution from the surface, it was then immersed in an organic solution for 1 minute. After interfacial polymerization, the nascent polyamide membrane was heat-treated in an air medium (e.g., an oven) at 50°C for 15 minutes. After heat treatment, it was rinsed in water to obtain the nanofiltration membrane. Under test conditions of 25°C, pH = 9.75 ± 0.1, and 0.4 MPa, the membrane achieved the following separation results for 1000 ppm 2-amino-3-hydroxy-3-(4-methylsulfonylphenyl)propionic acid (MW = 259 Da) and 1000 ppm glycine (MW = 75 Da): a retention rate of 90.6% for 2-amino-3-hydroxy-3-(4-methylsulfonylphenyl)propionic acid and 32.9% for glycine, with a water permeation flux of 15.0 L / m³. -2 h -1 bar -1 .

[0021] Example 5:

[0022] An aqueous solution was prepared by dissolving 4,4'-diaminobiphenyl-2,2'-disulfonic acid, ethanol, and sodium chloride in water, wherein the concentration of 4,4'-diaminobiphenyl-2,2'-disulfonic acid was 30 mmol / L. -1 The ethanol volume percentage is 25 v / v, and the sodium chloride concentration is 1 mol L. -1 An organic phase solution was prepared by dissolving trimesoyl chloride in n-hexane, wherein the concentration of trimesoyl chloride was 1 g / L. -1 The porous polysulfone support layer was immersed in an aqueous solution for 5 minutes. After removing excess aqueous solution from the surface, it was then immersed in an organic solution for 1 minute. After interfacial polymerization, the nascent polyamide membrane was heat-treated in an air medium (e.g., an oven) at 50°C for 15 minutes. After heat treatment, it was rinsed in water to obtain the nanofiltration membrane. Under test conditions of 25°C, pH = 9.75 ± 0.1, and 0.4 MPa, the membrane showed the following separation results for 1000 ppm 2-amino-3-hydroxy-3-(4-methylsulfonylphenyl)propionic acid (MW = 259 Da) and 1000 ppm glycine (MW = 75 Da): a rejection rate of 88.5% for 2-amino-3-hydroxy-3-(4-methylsulfonylphenyl)propionic acid and 32.0% for glycine, with a water permeation flux of 16.0 L / m³. -2 h -1 bar -1 .

[0023] Example 6:

[0024] An aqueous solution was prepared by dissolving 4,4'-diaminobiphenyl-2,2'-disulfonic acid, ethanol, and sodium chloride in water, wherein the concentration of 4,4'-diaminobiphenyl-2,2'-disulfonic acid was 30 mmol / L. -1 The ethanol volume percentage is 25 v / v, and the sodium chloride concentration is 0.75 mol / L. -1 An organic phase solution was prepared by dissolving trimesoyl chloride in n-hexane, wherein the concentration of trimesoyl chloride was 1 g / L. -1 The porous polysulfone support layer was immersed in an aqueous solution for 5 minutes. After removing excess aqueous solution from the surface, it was then immersed in an organic solution for 1 minute. Following the interfacial polymerization reaction, the nascent polyamide membrane was heat-treated in a mixed aqueous solution of piperazine and sodium chloride, wherein the piperazine concentration was 0.025 wt% and the sodium chloride concentration was 1 mol / L. -1The heat treatment temperature was 50℃, and the heat treatment time was 15 minutes. After the heat treatment, the membrane was immersed in water for washing to obtain the nanofiltration membrane. Under the test conditions of 25℃, pH = 9.50 ± 0.1, and 0.4 MPa, the separation results of the membrane for 1000 ppm 2-amino-3-hydroxy-3-(4-methylsulfonylphenyl)propionic acid (MW = 259 Da) and 1000 ppm glycine (MW = 75 Da) were as follows: the rejection rate for 2-amino-3-hydroxy-3-(4-methylsulfonylphenyl)propionic acid was 90.4%, the rejection rate for glycine was 36.7%, and the water permeation flux was 11.4 L / m³. -2 h -1 bar -1 .

[0025] Example 7:

[0026] An aqueous solution was prepared by dissolving 4,4'-diaminobiphenyl-2,2'-disulfonic acid, ethanol, and sodium chloride in water, wherein the concentration of 4,4'-diaminobiphenyl-2,2'-disulfonic acid was 30 mmol / L. -1 The ethanol volume percentage is 25 v / v, and the sodium chloride concentration is 0.75 mol / L. -1 An organic phase solution was prepared by dissolving trimesoyl chloride in n-hexane, wherein the concentration of trimesoyl chloride was 1 g / L. -1 The porous polysulfone support layer was immersed in an aqueous solution for 5 minutes. After removing excess aqueous solution from the surface, it was then immersed in an organic solution for 1 minute. Following the interfacial polymerization reaction, the nascent polyamide film was heat-treated in a mixed aqueous solution of 4,4-bispiperidine and sodium chloride, wherein the concentration of 4,4-bispiperidine was 0.025 wt% and the concentration of sodium chloride was 1 mol / L. -1 The heat treatment temperature was 50℃, and the heat treatment time was 15 minutes. After the heat treatment, the membrane was immersed in water for washing to obtain the nanofiltration membrane. Under the test conditions of 25℃, pH = 9.00 ± 0.1, and 0.4 MPa, the separation results of the membrane for 1000 ppm 2-amino-3-hydroxy-3-(4-methylsulfonylphenyl)propionic acid (MW = 259 Da) and 1000 ppm glycine (MW = 75 Da) were as follows: the rejection rate for 2-amino-3-hydroxy-3-(4-methylsulfonylphenyl)propionic acid was 91.6%, the rejection rate for glycine was 21.1%, and the water permeation flux was 8.5 L / m³. -2 h -1 bar -1 .

[0027] Example 8:

[0028] An aqueous solution was prepared by dissolving 4,4'-diaminobiphenyl-2,2'-disulfonic acid, ethanol, and sodium chloride in water, wherein the concentration of 4,4'-diaminobiphenyl-2,2'-disulfonic acid was 30 mmol / L. -1 The ethanol volume percentage is 25 v / v, and the sodium chloride concentration is 0.75 mol / L. -1 An organic phase solution was prepared by dissolving trimesoyl chloride in n-hexane, wherein the concentration of trimesoyl chloride was 1 g / L. -1 The porous polysulfone support layer was immersed in an aqueous solution for 5 minutes. After removing excess aqueous solution from the surface, it was then immersed in an organic solution for 1 minute. Following the interfacial polymerization reaction, the nascent polyamide film was heat-treated in a mixed aqueous solution of pentaethylenehexamine and sodium chloride, wherein the concentration of pentaethylenehexamine was 0.025 wt% and the concentration of sodium chloride was 1 mol / L. -1 The heat treatment temperature was 50℃, and the heat treatment time was 15 minutes. After the heat treatment, the membrane was immersed in water for washing to obtain the nanofiltration membrane. Under the test conditions of 25℃, pH = 8.50 ± 0.1, and 0.4 MPa, the separation results of the membrane for 1000 ppm 2-amino-3-hydroxy-3-(4-methylsulfonylphenyl)propionic acid (MW = 259 Da) and 1000 ppm glycine (MW = 75 Da) were as follows: the rejection rate for 2-amino-3-hydroxy-3-(4-methylsulfonylphenyl)propionic acid was 95.1%, the rejection rate for glycine was 34.8%, and the water permeation flux was 3.4 L / m³. -2 h -1 bar -1 .

[0029] Example 9:

[0030] An aqueous solution was prepared by dissolving 4,4'-diaminobiphenyl-2,2'-disulfonic acid, ethanol, and sodium chloride in water, wherein the concentration of 4,4'-diaminobiphenyl-2,2'-disulfonic acid was 30 mmol / L. -1 The ethanol volume percentage is 25 v / v, and the sodium chloride concentration is 0.75 mol / L. -1 An organic phase solution was prepared by dissolving trimesoyl chloride in n-hexane, wherein the concentration of trimesoyl chloride was 1 g / L. -1 The porous polysulfone support layer was immersed in an aqueous solution for 5 minutes. After removing excess aqueous solution from the surface, it was then immersed in an organic solution for 1 minute. Following the interfacial polymerization reaction, the nascent polyamide film was heat-treated in a mixed aqueous solution of polyethyleneimine (MW = 10000 Da) and sodium chloride, wherein the concentration of polyethyleneimine (MW = 10000 Da) was 0.025 wt% and the concentration of sodium chloride was 1 mol / L. -1The heat treatment temperature was 50℃, and the heat treatment time was 15 minutes. After the heat treatment, the membrane was immersed in water for washing to obtain the nanofiltration membrane. Under the test conditions of 25℃, pH = 8.50 ± 0.1, and 0.4 MPa, the separation results of the membrane for 1000 ppm 2-amino-3-hydroxy-3-(4-methylsulfonylphenyl)propionic acid (MW = 259 Da) and 1000 ppm glycine (MW = 75 Da) were as follows: the rejection rate for 2-amino-3-hydroxy-3-(4-methylsulfonylphenyl)propionic acid was 92.7%, the rejection rate for glycine was 29.5%, and the water permeation flux was 5.3 L / m³. -2 h -1 bar -1 .

Claims

1. A method for preparing a nanofiltration membrane for screening low molecular weight organic matter, characterized in that, The steps include the following: (1) Prepare an aqueous solution by dissolving the sulfonated aromatic polyamine monomer, co-solvent, and inorganic salt 1 in water, wherein the concentration of the sulfonated aromatic polyamine monomer is 15-60 mmol / L. -1 The co-solvent volume percentage is 5-35 v / v%, and the inorganic salt concentration is 0.5-1.5 mol L. -1 Prepare an organic phase solution by dissolving polyacrylamide chloride monomers in an organic solvent, wherein the concentration of the polyacrylamide chloride monomers is 0.5-2 g / L. -1 ; (2) Immerse the porous support layer in the aqueous solution of step (1) for 1-10 minutes; After removing excess aqueous solution from the surface, immerse it in the organic phase solution of step (1) for 0.5-5 minutes; after the interfacial polymerization reaction, place the obtained nascent polyamide membrane in different media for heat treatment at a temperature of 40-60 ℃ for 10-30 minutes; after the heat treatment is completed, soak and wash it in water to obtain a nanofiltration membrane. The sulfonated aromatic polyamine monomer mentioned in step (1) is one or a mixture of several of the following: 2,4-diaminobenzenesulfonic acid, 2,5-diaminobenzenesulfonic acid, 4,4'-diaminobiphenyl-2,2'-disulfonic acid, 4,4'-diaminodiphenyl ether-2,2'-disulfonic acid, and 4,4'-diaminostilbene-2,2'-disulfonic acid. The co-solvent mentioned in step (1) is one or a mixture of several of methanol, ethanol, isopropanol, toluene, diethyl ether, acetone, ethyl acetate, dimethyl sulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide; the inorganic salt 1 mentioned in step (1) is one or a mixture of several of sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, copper chloride, ferric chloride, zinc chloride, and aluminum chloride.

2. The method according to claim 1, characterized in that, The polyacryl chloride monomer mentioned in step (1) is one or a mixture of several of pyromellitic tricarboxylic acid chloride and biphenyl tetracarboxylic acid chloride; the organic solvent mentioned in step (1) is one or a mixture of several of n-hexane, cyclohexane, n-heptane, toluene, chloroform, and carbon tetrachloride.

3. The method according to claim 1, characterized in that, The porous support layer mentioned in step (2) is one of the following: porous polysulfone support layer, porous polyethersulfone support layer, porous polyacrylonitrile support layer, porous polyethylene support layer, porous polypropylene support layer, porous polyvinyl chloride support layer, and porous polyimide support layer.

4. The method according to claim 1, characterized in that, The heat treatment medium mentioned in step (2) is either air or a mixed aqueous solution of polyamine and inorganic salt 2; the polyamine is one or a mixture of several of N,N-dimethylethylenediamine, ethylenediamine, piperazine, m-phenylenediamine, p-phenylenediamine, 4,4-bispiperidine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine with MW=300 Da-70000 Da; the inorganic salt 2 is one or a mixture of several of sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, copper chloride, ferric chloride, zinc chloride, and aluminum chloride.

5. The method according to claim 4, characterized in that, Polyethyleneimine is selected from one or a mixture of several of the following: polyethyleneimine with MW=300 Da, polyethyleneimine with MW=600 Da, polyethyleneimine with MW=1800 Da, polyethyleneimine with MW=10000 Da, and polyethyleneimine with MW=70000 Da.

6. The method according to claim 4, characterized in that, The concentration of polyamines was 0.0025-0.1 wt%; the concentration of inorganic salt 2 was 0.5-1.5 mol L. -1 .

7. The nanofiltration membrane prepared according to any one of claims 1-6.

8. The nanofiltration membrane prepared according to any one of claims 1-6 is used to screen organic compounds of different molecular weights in aqueous solution under alkaline conditions of pH 7-10 at room temperature, wherein the different molecular weights of the organic compounds are organic compounds in the range of molecular weight 250-400 Da and organic compounds in the range of molecular weight 50-150 Da.