Preparation method and application of high-flux and high-selectivity polyamide nanofiltration membrane

Abstract

The invention discloses a preparation method and application of a high-flux and high-selectivity polyamide nanofiltration membrane. The water contact angle of the polyamide nanofiltration membrane is less than 65 degrees, the surface potential is less than-30mV when the pH is equal to 7, and the water permeability coefficient of the membrane is gt; the retention rate is 10LMH / bar, and the retention rate for 1000ppm Na2SO4 is gt; the separation factor of monovalent / divalent anions reaches 50 or above. The polyamide nanofiltration membrane can be widely applied to the fields of energy, environment, pharmacy, chemical engineering and the like.

Description

Technical Field

[0001] The invention relates to the technical field of separation membrane materials, and in particular to a preparation method of a high-flux and high-selectivity polyamide nanofiltration membrane and application thereof. Background Art

[0002] Nanofiltration is a type of membrane separation technology with an average pore size of 0.5-2.0 nm and a molecular weight cutoff range of 200-1000 Da. It can be widely used in energy, environment, pharmaceuticals, chemical industry and other fields. Polyamide nanofiltration membrane has become the most widely used nanofiltration membrane variety due to its simple preparation method, good physical and chemical stability and excellent separation performance. However, most of the existing nanofiltration membranes on the market have problems such as low water permeation flux and poor monovalent / divalent salt separation selectivity.

[0003] In order to further improve the permeability selectivity of polyamide nanofiltration membranes, the literature reports the use of surfactants to regulate the interfacial polymerization process, thereby optimizing and regulating the molecular structure and separation performance of polyamide. The published patent CN 118059688A adds cationic surfactant 11-(methacryloyloxy) undecane-1-trimethylammonium bromide to the aqueous solution, and by controlling the interaction between 11-(methacryloyloxy) undecane-1-trimethylammonium bromide and piperazine, it can effectively promote the diffusion of piperazine from the aqueous phase to the oil phase, thereby regulating the interfacial polymerization process to prepare polyamide nanofiltration membranes, and the prepared polyamide nanofiltration membrane has a water permeability coefficient of >25LMH / bar, and the separation factor for monovalent / polyvalent cations is increased to 15. CN 118577145 A uses anionic surfactant sodium dodecyl sulfate to regulate the interfacial polymerization process to prepare polyamide nanofiltration membrane, and promotes the faster and more uniform diffusion of amine monomers on the water-oil interface during the interfacial polymerization process, thereby improving the wettability and hydrophilicity of the membrane surface, and the permeability of the membrane prepared by the method is improved (the water permeability coefficient is increased from 3.83LMH / bar to 13.55LMH / bar), and has made certain research progress in the field of lithium extraction from salt lakes and other single / multivalent cation selective separation (the separation factor of single / multivalent cations is increased to more than 7), the method is simple to operate, the modified material is cheap, the reaction time is short, and the stability is good. However, the surfactants reported are used in the process of preparing nanofiltration membranes by interfacial polymerization, and the main role they play is to promote the diffusion of amine water phase monomers to the oil phase, generate a highly cross-linked polyamide layer, and weaken the negative charge of the polyamide layer, so that the nanofiltration membrane has poor screening performance for single / multivalent anions, which is difficult to meet actual needs.

[0004] This patent invents a method for preparing high-throughput and high-selectivity polyamide nanofiltration membranes by regulating interfacial polymerization using pyridine surfactants, wherein the pyridine surfactants can not only significantly change the water-oil interface properties and reduce the interfacial tension in the process of regulating interfacial polymerization to prepare polyamide nanofiltration membranes, but also can regulate the interfacial polymerization process by adjusting the diffusion rate of the two-phase monomers and the amount of monomers at the reaction interface to generate a polyamide layer with a large specific surface area and strong electronegativity, thereby regulating the structure and properties of the polyamide, thereby improving the water permeability and mono / divalent anion selectivity of the nanofiltration membrane. Compared with other reports on polyamide nanofiltration membranes prepared using surfactant materials, the polyamide nanofiltration membrane invented by this patent can not only significantly improve the water permeability of the nanofiltration membrane (the water permeability coefficient of the nanofiltration membrane is greater than 10LMH / bar), but also the membrane exhibits good screening performance for mono / divalent anions (Cl - with SO 4 2- The separation factor is higher than 50), which has important innovation and practical application value. Summary of the invention

[0005] The invention provides a preparation method of a high-flux and high-selectivity polyamide nanofiltration membrane and application thereof.

[0006] To this end, the technical solution of the present invention is as follows:

[0007] A method for preparing a high-flux and high-selectivity polyamide nanofiltration membrane and its application, characterized in that the polyamide nanofiltration membrane comprises a porous ultrafiltration base membrane and a polyamide dense functional layer. The water contact angle of the polyamide functional layer of the nanofiltration membrane is less than 65°, and the surface potential at pH = 7 is less than -30mV; the water permeability coefficient of the polyamide nanofiltration membrane is greater than 10LMH / bar, and the surface potential of the polyamide nanofiltration membrane is less than 10LMH / bar for 1000ppm Na 2 SO 4 The retention rate is >98%, and the monovalent / divalent anion separation factor is above 50.

[0008] A method for preparing a high-throughput and high-selectivity polyamide nanofiltration membrane and its application, characterized in that the porous ultrafiltration base membrane includes but is not limited to an ultrafiltration membrane with a pore size range of 5nm to 100nm, and the material of the ultrafiltration membrane includes but is not limited to organic, inorganic, metal, etc. A method for preparing a high-throughput and high-selectivity polyamide nanofiltration membrane and its application, the steps are:

[0009] S1, immersing one side of the porous ultrafiltration base membrane in an aqueous monomer solution containing a mixture of a polyamine monomer and a pyridine surfactant for 0.5 min to 5 min, and removing excess aqueous monomer solution from the surface of the ultrafiltration base membrane using a rubber roller or an air knife;

[0010] S2, uniformly coating the organic solution of polyacid chloride on the surface of the ultrafiltration base membrane coated with the aqueous monomer solution obtained in step S1 for 0.5 min to 5 min to form a thin layer of composite polyamide membrane;

[0011] S3, placing the thin layer of composite polyamide membrane obtained in step S2 in an oven at 40°C to 100°C for thermal crosslinking for 5min to 30min, and finally obtaining a polyamide nanofiltration membrane.

[0012] Preferably, the preparation method of the aqueous monomer solution in step S1 is: preparing 0.01 wt.% to 1 wt.% of a polyamine monomer aqueous solution, and then adding 0.1 wt.% to 2 wt.% of a pyridine surfactant to the polyamine monomer aqueous solution.

[0013] Preferably, in step S1, the aqueous monomer solution is coated on the upper surface of the ultrafiltration base membrane, and after waiting for 0.5 to 5 minutes, a rubber roller or an air knife is used to remove excess aqueous solution on the surface of the ultrafiltration base membrane, and then step S2 can be performed.

[0014] Preferably, in step S2, the prepared organic mixed solution is a 0.01wt.% to 0.5wt.% polyacyl chloride organic mixed solution; the organic solvent used to prepare the organic mixed solution includes but is not limited to n-hexane, isoparaffin, n-nonane, and n-decane.

[0015] Preferably, in step S2, the surface of the ultrafiltration base membrane coated with the aqueous monomer solution obtained in step S1 is immersed in an organic mixed solution prepared with polyacyl chlorides for 0.5 min to 5 min, the membrane is taken out, and step S3 can be performed after the organic solvent is completely evaporated.

[0016] A method for preparing a high-throughput and high-selectivity polyamide nanofiltration membrane and its application, characterized in that the polyamine monomers used include but are not limited to aromatic polyamines, aliphatic polyamines, and alicyclic polyamines; wherein the aromatic polyamine monomers include but are not limited to at least one of 2,5-diaminobenzenesulfonic acid, 1,2-phenylenediamine, and 1,3-phenylenediamine. Aliphatic polyamine monomers include but are not limited to at least one of piperazine, 2,5-dimethylpiperazine, polyethyleneimine, and 2,6-dimethylpiperazine; alicyclic polyamine monomers include but are not limited to at least one of cyclobutanediamine and cyclohexanediamine. The pyridine surfactant used is composed of anions and cations, R contains at least one alkyl chain greater than eight carbon atoms, and X is an anionic group, which has the following general chemical structure formula:

[0017]

[0018] The pyridine surfactants include, but are not limited to, at least one of 1-dodecylpyridinium chloride, tetradecylpyridinium chloride, 1-decylpyridinium chloride, stearylpyridinium chloride, hexadecylpyridinium chloride, and N-hexadecylpyridinium bromide.

[0019] A method for preparing a high-flux and high-selectivity polyamide nanofiltration membrane and its application, characterized in that the polyacyl chloride organic solution used in step S2 is a polyacyl chloride organic solution of 0.01wt.% to 0.5wt.%, and the organic solvent includes but is not limited to at least one of n-hexane, isoparaffin, n-nonane, and n-decane. The polyacyl chloride used includes but is not limited to at least one of trimesoyl chloride, benzoyl chloride, and dibenzoyl chloride.

[0020] This preparation method is an interfacial polymerization method, which is simple to operate, has a short reaction time and good stability. It has the advantages of stable industrial preparation and is conducive to industrial scale-up application. In step S1, the addition of pyridine surfactants to the aqueous monomer solution can greatly reduce the water / oil interfacial tension, thereby regulating the rate and concentration of amine monomers diffusing across the interface into the oil / water phase, thereby preparing a polyamide functional layer with high throughput and high selectivity.

[0021] A preparation method of a high-throughput and high-selectivity polyamide nanofiltration membrane and its application can be widely used in the fields of energy, environment, pharmaceuticals, chemical industry, etc.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The high-flux and high-selectivity polyamide nanofiltration membrane prepared by this patent application can be widely used in the fields of energy, environment, pharmaceuticals, chemical industry, etc.; wherein, ① the introduction of pyridine surfactants is conducive to reducing the water / oil interfacial tension and regulating the diffusion rate of two-phase monomers to form a looser polyamide layer, thereby significantly improving the water flux; ② by adding pyridine surfactants to inhibit the diffusion of amine monomers, the surface of the prepared polyamide nanofiltration membrane has a stronger negative charge, thereby improving the membrane's retention performance for divalent anions; in summary, the polyamide separation membrane has both high flux and good monovalent / divalent anion separation performance;

[0024] (2) The method for preparing a high-throughput and high-selectivity polyamide nanofiltration membrane applied for in this patent is a simple one-step interfacial polymerization method. Compared with the traditional graft coating modification method, it not only shortens the preparation time and reduces the production cost, but also improves the comprehensive performance of the polyamide separation membrane, and has good industrial production application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a comparison diagram of the membrane surface Zeta potential curves of the polyamide nanofiltration membrane prepared in Example 2 and Comparative Example 1 of the present invention and the traditional polyamide nanofiltration membrane;

[0026] Figure 2 A comparison chart of the pure water permeability coefficient and monovalent / divalent anion screening performance of the polyamide nanofiltration membrane prepared in Example 2 and Comparative Example 1 of the present invention and the traditional polyamide nanofiltration membrane; DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the following embodiments are by no means intended to limit the present invention in any way.

[0028] Example 1

[0029] A preparation method and application of a high-flux and high-selectivity polyamide nanofiltration membrane, which is prepared by the following steps:

[0030] S1. dissolving piperazine in water to prepare a 0.2 wt. % piperazine aqueous solution; then, adding 0.2 wt. % 1-dodecylpyridinium chloride to the piperazine aqueous solution, stirring and mixing evenly to obtain an aqueous monomer solution; immersing one side of a polysulfone ultrafiltration membrane in the aqueous monomer solution for 2 minutes, and removing excess aqueous monomer solution on the surface of the ultrafiltration base membrane using a rubber roller or an air knife;

[0031] S2, dissolving trimesoyl chloride in n-hexane to prepare a 0.15wt.% trimesoyl chloride organic solution, stirring and mixing to obtain an oil phase monomer solution; uniformly coating the oil phase monomer solution on the surface of the base film coated with the aqueous phase monomer solution obtained in step S1 for 1 minute, and wait until the n-hexane is completely volatilized to form a thin layer of composite polyamide film;

[0032] S3, placing the thin layer of composite polyamide membrane obtained in step S2 in a forced air drying oven, and thermally crosslinking at 60° C. for 5 minutes, to finally obtain a polyamide nanofiltration membrane.

[0033] Example 2

[0034] A method for preparing a high-flux and high-selectivity polyamide nanofiltration membrane and its application, which is different from Example 1 in that 0.2 wt. % of 1-dodecylpyridinium chloride is replaced by 0.4 wt. % of 1-dodecylpyridinium chloride.

[0035] Example 3

[0036] A method for preparing a high-flux and high-selectivity polyamide nanofiltration membrane and its application, which is different from Example 1 in that 0.2 wt. % of 1-dodecylpyridinium chloride is replaced by 2.0 wt. % of 1-dodecylpyridinium chloride.

[0037] Example 4

[0038] A preparation method of a high-flux and high-selectivity polyamide nanofiltration membrane and its application, which is different from Example 1 in that the polysulfone membrane of the porous ultrafiltration base membrane is replaced by a polyethersulfone membrane.

[0039] Example 5

[0040] A method for preparing a high-flux and high-selectivity polyamide nanofiltration membrane and its application, which is different from Example 1 in that the monomer piperazine in the aqueous phase solution is replaced by 2,6-dimethylpiperazine.

[0041] Example 6

[0042] A method for preparing a high-flux and high-selectivity polyamide nanofiltration membrane and its application, which is different from Example 1 in that the monomer trimesoyl chloride in the organic phase solution is replaced with dibenzoyl chloride.

[0043] Example 7

[0044] A method for preparing a high-flux and high-selectivity polyamide nanofiltration membrane and its application, which is different from Example 2 in that the solvent n-hexane in the organic solution for preparing trimesoyl chloride is replaced by isomeric alkanes.

[0045] Example 8

[0046] A method for preparing a high-flux and high-selectivity polyamide nanofiltration membrane and its application, which is different from Example 2 in that the thermal crosslinking condition is changed to 80° C. thermal crosslinking for 3 minutes.

[0047] Example 9

[0048] A method for preparing a high-flux and high-selectivity polyamide nanofiltration membrane and its application, which is different from Example 2 in that the thermal crosslinking condition is changed to thermal crosslinking at 30°C for 10 minutes.

[0049] Example 10

[0050] A method for preparing a high-flux and high-selectivity polyamide nanofiltration membrane and its application, which differs from Example 2 in that: the prepared 0.2wt.% piperazine aqueous solution is replaced by a 1.0wt.% piperazine aqueous solution; the n-hexane solution containing 0.15wt.% trimesoyl chloride is replaced by a n-hexane solution containing 0.5wt.% trimesoyl chloride.

[0051] Embodiment 11

[0052] A method for preparing a high-flux and high-selectivity polyamide nanofiltration membrane and its application, which is different from Example 2 in that 1-dodecylpyridinium chloride is replaced by tetradecylpyridinium chloride.

[0053] Example 12

[0054] A method for preparing a high-flux and high-selectivity polyamide nanofiltration membrane and its application, which is different from Example 2 in that 1-dodecylpyridinium chloride is replaced by 1-decylpyridinium chloride.

[0055] Example 13

[0056] A method for preparing a high-flux and high-selectivity polyamide nanofiltration membrane and its application, which is different from Example 2 in that 1-dodecylpyridinium chloride is replaced by stearylpyridinium chloride.

[0057] Embodiment 14

[0058] A method for preparing a high-flux and high-selectivity polyamide nanofiltration membrane and its application, which is different from Example 2 in that 1-dodecylpyridinium chloride is replaced by hexadecylpyridinium chloride.

[0059] Embodiment 15

[0060] A method for preparing a high-flux and high-selectivity polyamide nanofiltration membrane and its application, which is different from Example 2 in that 1-dodecylpyridinium chloride is replaced by N-hexadecylpyridinium bromide.

[0061] Comparative Example 1

[0062] A polyamide nanofiltration membrane prepared without the use of pyridine surfactants is prepared by the following steps:

[0063] S1. dissolving piperazine in water to prepare a 0.2 wt.% piperazine aqueous solution; immersing one side of a polysulfone ultrafiltration membrane in the piperazine aqueous solution for 2 minutes, and then removing excess piperazine aqueous solution on the surface of the ultrafiltration base membrane using a rubber roller or an air knife;

[0064] S2, dissolving trimesoyl chloride in n-hexane to prepare a 0.15wt.% trimesoyl chloride organic solution, stirring and mixing to obtain an oil phase monomer solution; uniformly coating the oil phase monomer solution on the surface of the base film coated with the aqueous phase monomer solution obtained in step S1 for 1 minute, and wait until the n-hexane is completely volatilized to form a thin layer of composite polyamide film;

[0065] S3: placing the thin layer composite polyamide membrane obtained in step S2 in a forced air drying oven at 60° C. for thermal crosslinking for 5 minutes, and finally obtaining a polyamide nanofiltration membrane.

[0066] Comparative Example 2

[0067] A polyamide nanofiltration membrane prepared by regulation of a non-pyridine surfactant is prepared by the following steps:

[0068] S1, dissolving piperazine in water to prepare a 0.2wt.% piperazine aqueous solution, then adding 0.5wt.% didodecyl dimethyl ammonium bromide to the piperazine aqueous solution, stirring and mixing evenly to obtain an aqueous monomer solution; immersing one side of a polysulfone ultrafiltration membrane in the aqueous monomer solution for 2 minutes, and then removing excess piperazine aqueous solution on the surface of the ultrafiltration base membrane with a rubber roller or an air knife;

[0069] S2, dissolving trimesoyl chloride in n-hexane to prepare a 0.15wt.% trimesoyl chloride organic solution, stirring and mixing to obtain an oil phase monomer solution; uniformly coating the oil phase monomer solution on the surface of the base film coated with the aqueous phase monomer solution obtained in step S1 for 1 minute, and wait until the n-hexane is completely volatilized to form a thin layer of composite polyamide film;

[0070] S3, placing the thin layer of composite polyamide membrane obtained by the treatment in step S2 in a forced air dryer at 60° C. for thermal crosslinking for 5 minutes, and finally obtaining a polyamide nanofiltration membrane.

[0071] Comparative Example 3

[0072] A polyamide nanofiltration membrane prepared by regulation of a non-pyridine surfactant, which differs from Comparative Example 2 in that: 0.5wt.% of didodecyl dimethyl ammonium bromide is replaced by 0.5wt.% of nonylphenol polyether-10; and the thermal crosslinking conditions are adjusted to: thermal crosslinking at 80°C for 3 minutes.

[0073] Performance Test:

[0074] (I) Membrane separation performance test:

[0075] The membrane separation performance was evaluated using a cross-flow test device; the separation performance test conditions were 6 bar, 25 ° C, after pre-pressing for 1 hour, 5 bar, 25 ° C, the prepared polyamide nanofiltration membrane was used as a nanofiltration membrane, and its separation performance was tested for 1000 ppm Na 2 SO 4 The permeate flux and retention rate of the solution and 1000ppm NaCl solution, the permeate flux unit is LMH / bar (liter / square meter / hour / bar).

[0076] The permeation flux was calculated by the following formula (1):

[0077]

[0078] In the formula, J w is the membrane permeation flux (LMH / bar), M is the mass of the permeate passing through the membrane (kg), and ρ is the density of the permeate (kg·m -3 ), E is the effective permeation area of ​​the membrane sample (m 2 ), t is the test time (h), and P is the test pressure (bar).

[0079] The solute concentration of the feed solution and the permeate was measured using a conductivity meter; in addition, the salt rejection was calculated using formula (2):

[0080]

[0081] Where R is the retention rate of the membrane sample (%), C p is the solute concentration in the permeate (mg / L), C f is the solute concentration in the supply solution (mg / L).

[0082] Use 1000ppmNa 2 SO 4 The membrane separation performance was evaluated by 1000 ppm NaCl solution and 1000 ppm NaCl solution, and the NaCl / Na ratio of the polyamide nanofiltration membrane prepared by the interfacial polymerization process regulated by pyridine surfactant and the unmodified polyamide nanofiltration membrane was calculated. 2 SO 4 Separation factor. The permeability of two solutes through the membrane is defined as the separation (S), and the separation factor is calculated by formula (3):

[0083]

[0084] In the formula, R A is the retention rate of NaCl of the membrane sample (%), R B is the Na 2 SO 4 The retention rate (%).

[0085] At least three parallel samples were tested for each membrane sample, and the average value and error range of the test results were calculated.

[0086] The specific test results are shown in Table 1 below.

[0087] Table 1: Selective permeability of polyamide nanofiltration membrane

[0088]

[0089] From the test results in Table 1, we can see that:

[0090] (1) Compared with the polyamide nanofiltration membrane prepared in Comparative Example 1 without adding a pyridine surfactant, the water permeability coefficient of the polyamide nanofiltration membrane prepared in Examples 1 to 15 is significantly improved. Specifically, compared with the water permeability coefficient of 9.17 LMH / bar in Comparative Example 1, the water permeability coefficient of Examples 1 to 15 is increased to 10.71 LMH / bar to 14.60 LMH / bar;

[0091] (2) Compared with the non-pyridine surfactants used in Comparative Examples 2 to 3 and the pyridine surfactants, the pure water permeability coefficient and the separation factor for mono / divalent anions of the polyamide nanofiltration membrane obtained by regulating the use of pyridine surfactants in the present application are higher. Examples 1 to 15 have better permeability and mono / divalent anion screening performance than Comparative Examples 2 to 3, which further illustrates that the pyridine surfactants used in the present invention have a good effect on improving the permeability selectivity of the nanofiltration membrane.

[0092] The permeation selectivity of the polyamide nanofiltration membrane prepared in the examples of the present application is better than that of the polyamide nanofiltration membrane in the comparative example. It can be seen that the polyamide nanofiltration membrane prepared by the interfacial polymerization process regulated by pyridine surfactants exhibits excellent separation performance for monovalent and divalent anions.

[0093] (II) pH stability of membrane

[0094] The solid surface Zeta potential analyzer was used to characterize the potential change on the surface of the polyamide nanofiltration membrane. According to the test, the polyamide nanofiltration membrane prepared in Examples 1 to 15 maintained a change in the Zeta potential on the membrane surface between -49mV and 19mV during the pH change from 10 to 3, showing good pH stability.

[0095] like Figure 1 Shown is a comparison diagram of the membrane surface Zeta potential curves of the polyamide nanofiltration membranes prepared in Example 2 of the present invention and in Comparative Example 1; it can be clearly seen from the figure that the surface Zeta potential of the polyamide nanofiltration membrane of Example 2 increases from -48.81 mV to 3.99 mV during the pH change from 10 to 3, while the surface Zeta potential of the traditional polyamide membrane prepared in Comparative Example 1 increases from -41.10 mV to 18.89 mV during the pH change from 10 to 3; at pH = 7, the surface Zeta potential of the polyamide nanofiltration membrane of Example 2 is -47.08 mV, while the surface Zeta potential of the traditional polyamide membrane is -30.09 mV.

[0096] In summary, the surface charge of the polyamide nanofiltration membrane prepared by the interfacial polymerization process regulated by pyridine surfactants is enhanced in this patent application.

[0097] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a high-throughput and high-selectivity polyamide nanofiltration membrane and its application, characterized in that: The polyamide nanofiltration membrane comprises a porous ultrafiltration base membrane and a polyamide dense functional layer. The water contact angle of the polyamide functional layer of the nanofiltration membrane is less than 65°, and the surface potential is less than -30mV at pH=7; the water permeability coefficient of the polyamide nanofiltration membrane is greater than 10LMH / bar, the retention rate of 1000ppm Na2SO4 is greater than 98%, and the monovalent / divalent anion separation factor reaches more than 50.

2. The method for preparing a high-throughput and high-selectivity polyamide nanofiltration membrane and its application according to claim 1, characterized in that: The porous ultrafiltration base membrane includes but is not limited to an ultrafiltration membrane with a pore size range of 5 nm to 100 nm, and the material of the ultrafiltration membrane includes but is not limited to organic, inorganic, metal, etc.

3. The preparation method and application of a high-throughput and high-selectivity polyamide nanofiltration membrane according to claims 1-2, characterized in that: The film making steps include: S1. Immerse one side of the porous ultrafiltration base membrane in an aqueous solution prepared by mixing a polyamine monomer and a pyridine surfactant for 0.5 to 5 minutes, and use a rubber roller or an air knife to remove excess aqueous solution on the surface of the ultrafiltration base membrane; S2, uniformly coating the organic solution of polyacid chloride on the surface of the ultrafiltration base membrane coated with the aqueous monomer solution obtained in step S1 for 0.5 min to 5 min to form a thin layer of composite polyamide membrane; S3, placing the thin layer of composite polyamide membrane obtained in step S2 in an oven at 40°C to 100°C for thermal crosslinking for 5min to 30min, and finally obtaining a polyamide nanofiltration membrane.

4. The method for preparing a high-throughput and high-selectivity polyamide nanofiltration membrane and its application according to claim 3, characterized in that: The aqueous monomer solution used in step S1 is a mixed solution of 0.01wt.% to 1wt.% of a polyamine monomer and 0.1wt.% to 2wt.% of a pyridine surfactant. The polyamine monomers used include, but are not limited to, aromatic polyamines, aliphatic polyamines, and alicyclic polyamines; wherein, the aromatic polyamine monomers include, but are not limited to, at least one of 2,5-diaminobenzenesulfonic acid, 1,2-phenylenediamine, and 1,3-phenylenediamine. The aliphatic polyamine monomers include, but are not limited to, at least one of piperazine, 2,5-dimethylpiperazine, polyethyleneimine, and 2,6-dimethylpiperazine; the alicyclic polyamine monomers include, but are not limited to, at least one of cyclobutanediamine and cyclohexanediamine. The pyridine surfactant used is composed of anions and cations, R contains at least one alkyl chain greater than eight carbon atoms, and X is an anionic group, which has the following general chemical structure formula: The pyridine surfactants include, but are not limited to, at least one of 1-dodecylpyridinium chloride, tetradecylpyridinium chloride, 1-decylpyridinium chloride, stearylpyridinium chloride, hexadecylpyridinium chloride, and N-hexadecylpyridinium bromide.

5. The method for preparing a high-flux and high-selectivity polyamide nanofiltration membrane and its application according to claim 3, characterized in that: The polyacyl chloride organic solution used in step S2 is a polyacyl chloride organic solution of 0.01 wt.% to 0.5 wt.%, and the organic solvent includes but is not limited to at least one of n-hexane, isoparaffin, n-nonane, and n-decane. The polyacyl chloride used includes but is not limited to at least one of trimesoyl chloride, benzoyl chloride, and dibenzoyl chloride.

6. The method for preparing a high-throughput and high-selectivity polyamide nanofiltration membrane and its application according to claims 1-5 can be widely used in the fields of energy, environment, pharmaceuticals, chemical industry, etc.

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