Composite nanofiltration membrane and preparation method thereof

Abstract

The invention discloses a composite nanofiltration membrane which comprises a base membrane and a functional layer, the functional layer comprises a polymer, polymerization unit monomers of the polymer comprise amine monomers and cyanuric chloride derivatives, the amine monomers comprise aliphatic amine and aromatic amine, the aliphatic amine comprises at least three primary amine or secondary amine groups, and the aromatic amine comprises at least three secondary amine groups. The cyanuric chloride derivative comprises at least one of a compound shown in a formula I and a compound shown in a formula II, and # imgabs0. The nanofiltration membrane provided by the invention has relatively high water flux.

Description

Technical Field

[0001] The invention relates to the technical field of nanofiltration membranes, and in particular to a composite nanofiltration membrane and a preparation method thereof. Background Art

[0002] Nanofiltration membranes are increasingly used in wastewater treatment and material recovery. Some complex industries such as papermaking, textiles, dairy beverages, and pharmaceuticals produce strong alkaline waste liquids during production. Using membrane separation methods to treat these waste liquids not only alleviates the pollution caused by waste liquid discharge to the environment, but also brings certain economic benefits to the company by reusing the treated alkaline liquid. Traditional nanofiltration membrane materials are polyamides, but because the amide bonds are easily broken under strong alkali, resulting in defects in its functional layer, the membrane performance is reduced, and it cannot meet the application requirements of alkaline waste liquids.

[0003] At present, poly(oxazine)amine nanofiltration membranes are generally prepared by interfacial polymerization on a porous base membrane using polyamine monomers as the aqueous phase and halogen-substituted diazine, triazine or tetrazine compounds as the oil phase. However, the flux of poly(oxazine)amine nanofiltration membranes in the prior art is significantly lower than that of polyamide nanofiltration membranes. The low flux is not conducive to the processing efficiency of nanofiltration membranes in downstream applications, which to a certain extent restricts the expanded application of poly(oxazine)amine nanofiltration membrane products. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art to a certain extent. To this end, the present invention provides a nanofiltration membrane and a preparation method thereof. The nanofiltration membrane of the present invention has a high water flux.

[0005] Therefore, in the first aspect of the present invention, the present invention provides a composite nanofiltration membrane, comprising: a base membrane, a functional layer, the functional layer comprising a polymer, the polymerization unit monomer of the polymer comprising an amine monomer and a cyanuric chloride derivative, the amine monomer comprising an aliphatic amine and an aromatic amine, the aliphatic amine comprising at least three primary amine or secondary amine groups, the cyanuric chloride derivative comprising at least one of a compound of formula I and a compound of formula II,

[0006] Therefore, the nanofiltration membrane of the present invention has a higher water flux.

[0007] In some embodiments, the fatty amine includes at least one of polyethyleneimine, tetraethylenepentamine, triethylenetetramine, and pentaethylenehexamine, and the molecular weight of the polyethyleneimine ranges from 300Da to 10000Da.

[0008] In some embodiments, the aromatic amine includes at least one of triaminobenzene, melamine, and triaminonaphthalene.

[0009] In some embodiments, the mass ratio of aliphatic amine to aromatic amine is 3:1 to 15:1.

[0010] In the second aspect of the present invention, the present invention provides a method for preparing the composite nanofiltration membrane of the first aspect, comprising: preparing a base membrane on a support layer by a phase inversion method; and forming a functional layer on the surface of the base membrane. Thus, the method for preparing a nanofiltration membrane provided by the embodiment of the present invention can obtain a nanofiltration membrane with excellent performance.

[0011] In some embodiments, the step of forming a functional layer on the surface of the base film includes: contacting the base film with an aqueous solution, the aqueous solution including an amine monomer; contacting the base film with an oil solution to form a functional layer, the oil solution including a cyanuric chloride derivative.

[0012] In some embodiments, the aqueous solution further includes an aqueous solvent, a catalyst, a proton absorber and a surfactant; the aqueous solution satisfies at least one of the following: (1) the aqueous solvent includes water; (2) the catalyst includes at least one of polyaminopyridine, 4-(NN-dimethylamino)pyridine, and 4-(NN-diallylamine)pyridine, and the catalyst content is 0.1% to 0.8% of the mass of the aqueous solution; (3) the proton absorber includes at least one of sodium carbonate, sodium bicarbonate, sodium hydroxide, potassium hydroxide, pyridine, imidazole, and indole, and the proton absorber content is 0.5% to 2.0% of the mass of the aqueous solution; (4) the surfactant includes sodium dodecyl sulfate and sodium dodecylbenzene sulfonate, and the surfactant content is 0.1% to 3% of the mass of the aqueous solution; (5) the total content of amine monomers is 1% to 8% of the mass of the aqueous solution.

[0013] In some embodiments, the oil phase solution also includes a co-solvent and an organic solvent, and the oil phase solution satisfies at least one of the following: (A) the co-solvent includes ethers, benzene rings, esters, and ketones, and the content of the co-solvent is 0.5% to 5% of the mass of the oil phase solution; (B) the organic solvent includes saturated alkanes; (C) the content of the compound of formula I is 0.2% to 0.4% of the mass of the oil phase solution; the content of the compound of formula II is 0.3% to 0.4% of the mass of the oil phase solution; the total content of the compound of formula I and the compound of formula II is 0.1% to 0.5% of the mass of the oil phase solution, wherein the mass ratio of compound I to compound II is 15:1 to 2:1.

[0014] In some embodiments, in the step of contacting the base film with the aqueous solution, the contact time is 5s to 180s; the contact method includes any one of dipping, rolling, slit, and spraying; and / or, in the step of contacting the base film with the oil phase solution, the contact time is 5s to 180s, and the temperature of the oil phase solution is 50°C to 90°C; the contact method includes any one of dipping, rolling, slit, and spraying.

[0015] In some embodiments, after the step of contacting the basement membrane with the oil phase solution, the step further includes: drying the basement membrane to obtain a nanofiltration membrane; the drying temperature is 60° C. to 90° C., and the time is 1 min to 5 min.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects:

[0017] 1. The present invention uses cyanuric chloride derivatives as oil phase monomers. The cyanuric chloride derivatives have two chlorine atom reaction sites, which can undergo nucleophilic substitution reactions with the amino sites on the water phase monomers. The prepared functional layer has a pore size of appropriate size based on the three-dimensional structure, which is beneficial to the retention rate and flux balance of the membrane.

[0018] 2. The sulfonic acid groups in the oil phase monomer cyanuric chloride derivatives are enriched on the membrane surface, increasing the hydrophilicity of the membrane surface and further improving the nanofiltration membrane flux.

[0019] 3. Aromatic amine monomers have a rigid structure, which improves the mechanical stability of the nanofiltration membrane to a certain extent.

[0020] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. DETAILED DESCRIPTION

[0021] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be understood as limiting the present invention.

[0022] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. Further, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0023] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0024] In this document, the terms “include” or “comprising” are open expressions, that is, including the contents specified in the present invention but not excluding other contents.

[0025] In a first aspect of an embodiment of the present invention, the present invention provides a nanofiltration membrane, comprising: a base membrane; a functional layer, the functional layer comprising a polymer, the polymerization unit monomer of the polymer comprising an amine monomer and a cyanuric chloride derivative, the amine monomer comprising an aliphatic amine and an aromatic amine, the aliphatic amine comprising at least three primary amine or secondary amine groups, the cyanuric chloride derivative comprising at least one of a compound of formula I and a compound of formula II,

[0026]

[0027] The amine monomers provided in the embodiment of the present invention and the cyanuric chloride derivatives undergo polymerization reaction to form a three-dimensional network macromolecular polymer film. The aliphatic amines and aromatic amines in the amine monomers both contain amino groups (-NH 2 , -NH-), the amino group reacts with the chlorine (-Cl-) in the cyanuric chloride derivative by a nucleophilic substitution reaction, and the amino group acts as a nucleophilic agent to attack the chlorine atom in the cyanuric chloride derivative to generate a CN bond, and the amine monomer and the cyanuric chloride derivative are connected by a chemical bond, so that the small molecule monomer becomes a network macromolecular structure, forming a functional layer of the nanofiltration membrane. The two reaction sites of the cyanuric chloride derivative are conducive to the preparation of a loose and porous functional layer, thereby improving the flux of the functional layer. At the same time, the sulfonic acid group in the cyanuric chloride derivative is enriched on the surface of the membrane layer, which increases the hydrophilicity of the membrane surface, thereby further improving the water flux of the nanofiltration membrane. In addition, the rigid structure of the benzene ring in the aromatic amine molecule and the cyanuric chloride derivative improves the mechanical stability of the nanofiltration membrane to a certain extent. Thus, the nanofiltration membrane of the present invention has a higher water flux.

[0028] In some embodiments of the present invention, the fatty amine includes at least one of polyethyleneimine, tetraethylenepentamine, triethylenetetramine, and pentaethylenehexamine, and the molecular weight of the polyethyleneimine ranges from 300Da to 10000Da.

[0029] In the present invention, polyethyleneimine (PEI) is a polyamine polymer having abundant amino groups (primary amine, secondary amine) and hydroxyl functional groups, and polyamine monomers such as tetraethylenepentamine, triethylenetetramine and pentaethylenehexamine have multiple amino groups, and the amino groups can undergo interfacial polymerization reaction with cyanuric chloride derivatives to form a macromolecular network structure with a certain degree of cross-linking. Therefore, the nanofiltration membrane of the present invention has a higher water flux.

[0030] As an example, the molecular weight of polyethyleneimine is 300 Da, 600 Da, 1000 Da, 2000 Da, 3000 Da, 4000 Da, 5000 Da, 6000 Da, 7000 Da, 8000 Da, 9000 Da, 10000 Da, etc.

[0031] In some embodiments of the present invention, the aromatic amine includes at least one of triaminobenzene, melamine, and triaminonaphthalene.

[0032] The aromatic amine provided in the embodiment of the present invention has a rigid structure, which can increase the porosity of the functional layer to improve the flux performance. At the same time, it can also increase the loose structure and surface hydrophilicity of the functional layer. Thus, the water flux of the nanofiltration membrane can be effectively improved.

[0033] In some embodiments of the present invention, the mass ratio of aliphatic amine to aromatic amine is 3:1 to 15:1, preferably 5:1 to 8:1.

[0034] When the mass ratio of the aliphatic amine to the aromatic amine provided in the embodiment of the present invention meets the above conditions, it is beneficial to the polymerization reaction and improves the hydrophilicity of the membrane surface. Therefore, the nanofiltration membrane of the present invention has a higher water flux.

[0035] As an example, the mass ratio is 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, etc.

[0036] In some embodiments of the present invention, the thickness of the base film ranges from 40 to 80 μm, preferably from 50 to 60 μm.

[0037] In some embodiments of the present invention, the molecular weight cutoff range of the base membrane is 3K to 50k, preferably 5K to 10K.

[0038] When the molecular weight cut-off range of the base membrane of the present invention meets the above conditions, it is conducive to forming a thinner and more stable functional layer. Therefore, the nanofiltration membrane of the present invention has higher water flux and stability.

[0039] In a second aspect of the embodiment of the present invention, the present invention provides a method for preparing the composite nanofiltration membrane of the first aspect, comprising: preparing a base membrane on a support layer by a phase inversion method; and forming a functional layer on the surface of the base membrane. Thus, the method for preparing a nanofiltration membrane provided by the embodiment of the present invention can obtain a nanofiltration membrane with excellent performance.

[0040] In some embodiments of the present invention, the step of forming a functional layer on the surface of a base film includes: contacting the base film with an aqueous solution, wherein the aqueous solution includes an amine monomer; contacting the base film with an oil solution to form a functional layer, wherein the oil solution includes a cyanuric chloride derivative.

[0041] In the method for preparing the nanofiltration membrane provided by the embodiment of the present invention, a basement membrane is first prepared, and the basement membrane is a porous matrix. During the process of contacting the aqueous phase solution, the amine monomers in the aqueous phase solution are evenly spread in the shallow layer and surface layer of the nanopores of the basement membrane in the form of a solution. Then, when the basement membrane contacts the oil phase solution, the amine monomers and the cyanuric chloride derivatives rapidly undergo a polymerization reaction to form a functional layer, thereby preparing a nanofiltration membrane with a complete structure. Therefore, the nanofiltration membrane of the present invention has excellent performance.

[0042] In some embodiments of the present invention, the aqueous solution further includes an aqueous solvent, a catalyst, a proton absorber and a surfactant; the aqueous solution satisfies at least one of the following: (1) the aqueous solvent includes water; (2) the catalyst includes at least one of polyaminopyridine, 4-(NN-dimethylamino)pyridine, and 4-(NN-diallylamine)pyridine, and the catalyst content is 0.1% to 0.8% of the mass of the aqueous solution; (3) the proton absorber includes at least one of sodium carbonate, sodium bicarbonate, sodium hydroxide, potassium hydroxide, pyridine, imidazole, and indole, and the proton absorber content is 0.5% to 2.0% of the mass of the aqueous solution; (4) the surfactant includes sodium dodecyl sulfate and sodium dodecylbenzene sulfonate, and the surfactant content is 0.1% to 3% of the mass of the aqueous solution; (5) the total content of amine monomers is 1% to 8% of the mass of the aqueous solution.

[0043] In the present invention, the catalyst mainly plays a catalytic role to accelerate the polymerization reaction. During the polymerization reaction, the reactive group generates protons, and the proton absorber mainly plays a role in combining and neutralizing the protons to promote the reaction. The surfactant mainly improves the hydrophilicity and anti-pollution performance of the membrane surface. Therefore, the nanofiltration membrane of the present invention has excellent water flux.

[0044] As an example, the catalyst content is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, etc., of the mass of the aqueous solution;

[0045] As an example, the content of the proton absorber is 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, 1.8%, 2.0%, etc., based on the mass of the aqueous solution.

[0046] As an example, the content of the surfactant is 0.1%, 0.15%, 0.2%, 0.25%, 3%, etc., based on the mass of the aqueous phase solution.

[0047] As an example, the content of the amine monomer is 1%, 2%, 3%, 4%, 5%, 6%, 8%, etc., of the mass of the aqueous phase solution.

[0048] In some embodiments of the present invention, the oil phase solution also includes a co-solvent and an organic solvent, and the oil phase solution satisfies at least one of the following: (A) the co-solvent includes ethers, benzene rings, esters, and ketones, and the content of the co-solvent is 0.5% to 5% by mass of the oil phase solution; (B) the organic solvent includes saturated alkanes; (C) the content of the compound of formula I is 0.2% to 0.4% by mass of the oil phase solution; the content of the compound of formula II is 0.3% to 0.4% by mass of the oil phase solution; the total content of the compound of formula I and the compound of formula II is 0.1% to 0.5% by mass of the oil phase solution, wherein the mass ratio of the compound of formula I to the compound of formula II is 15:1 to 2:1.

[0049] When the method for preparing the nanofiltration membrane provided by the embodiment of the present invention meets the above conditions, a nanofiltration membrane with excellent performance can be obtained, thereby further improving the flux of the nanofiltration membrane.

[0050] As an example, the content of the co-solvent is 0.5%, 1%, 2%, 3%, 4%, 5%, etc., of the mass of the oil phase solution.

[0051] As an example, the content of the compound of formula I is 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, etc., of the mass of the oil phase solution; the content of the compound of formula II is 0.3%, 0.32%, 0.34%, 0.36%, 0.38%, 0.4%, etc., of the mass of the oil phase solution; the content of the compound of formula I and the compound of formula II is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, etc., of the mass of the oil phase solution; the mass ratio of compound I to compound II is 15:1, 13:1, 12:1, 10:1, 8:1, 6:1, 4:1, 2:1, etc.

[0052] As an example, ethers include at least one of dioxane, tetrahydrofuran, diethylene glycol dimethyl ether, and ethylene glycol dimethyl ether, benzene rings include at least one of toluene and xylene, esters include at least one of tributyl phosphate and triethyl phosphate, and ketones include at least one of acetone and butanone.

[0053] As an example, the saturated alkanes include at least one of ethylcyclohexane, n-hexane, and isoalkanes.

[0054] In some embodiments of the present invention, the synthesis step of the cyanuric chloride derivative comprises: adding 0.05 mol cyanuric chloride and 100 mL xylene to a reaction container, controlling the system temperature to 0-5°C, stirring at a constant speed for 20 minutes, and after uniform dispersion, controlling the feeding speed, slowly adding 0.08 mol aminobenzenesulfonic acid or 6-amino-1-naphthalenesulfonic acid within 1 hour, and using 10% mass fraction of sodium hydroxide to control the system pH value to 6-7 during the process. After the addition is completed, continue stirring for 20 minutes. Wash with water and let stand for stratification, take the upper organic phase and dry it to obtain a solid product.

[0055] In some embodiments of the present invention, the support layer comprises a polyolefin nonwoven fabric.

[0056] In some embodiments of the present invention, the step of preparing a base membrane on a support layer by a phase inversion method includes: mixing polyethersulfone (PES) and / or polysulfone (PS) with a solvent to obtain a casting liquid; contacting the support layer with the casting liquid, and treating it by a phase inversion method to obtain a base membrane.

[0057] In some embodiments of the present invention, the base membrane includes a polyethersulfone (PES) base membrane, a polysulfone (PS) base membrane, and a base membrane mixed with polyethersulfone (PES) and polysulfone (PS); the mass ratio of polysulfone to polyethersulfone is 10:3 to 3:1; the mass concentration range of the mixture of polysulfone and polyethersulfone is 8 to 20%; the solvent includes any one of DMF (N,N-dimethylformamide), DMAC (N,N-dimethylacetamide) and NMP (N-methylpyrrolidone). In the present invention, when polysulfone and polyethersulfone are mixed and applied, a better balance can be obtained in terms of the basic performance of the base membrane and the application adaptability (such as hydrophilicity and mechanical stability).

[0058] In some embodiments of the present invention, in the step of contacting the base film with the aqueous solution, the contact time is 5s to 180s; the contact method includes any one of dipping, rolling, slit coating, and spraying.

[0059] When the method for preparing the nanofiltration membrane provided by the embodiment of the present invention meets the above conditions, the contact time of 5s to 180s ensures that the aqueous solution completely wets the surface of the porous base membrane, which is conducive to preparing a nanofiltration membrane with excellent performance.

[0060] As an example, the contact time is 5s, 10s, 20s, 40s, 60s, 80s, 120s, 140s, 160s, 180s, etc.

[0061] In some embodiments of the present invention, after the base film is in contact with the aqueous solution, the method further comprises: removing excess solution from the surface of the base film by squeezing with a rubber roller or blowing with an air knife.

[0062] In some embodiments of the present invention, in the step of contacting the base film with the oil phase solution, the contact time is 5s to 180s, the temperature of the oil phase solution is 50°C to 90°C; the contact method includes any one of dipping, rolling, slit coating, and spraying.

[0063] In the present invention, the base film is contacted with the aqueous solution and then with the oil phase solution, and the contact time of 5s to 180s ensures that the polymerization reaction is fully carried out. In addition, the di-substitution reaction of the cyanuric chloride derivative is a step-by-step decreasing process, and the substitution reaction can only occur at a temperature above 50°C. Therefore, when the temperature of the oil phase solution is 50°C to 90°C, it is conducive to the polymerization reaction, while avoiding the volatilization of the co-solvent in the oil phase solution, ensuring the stability of the oil phase solution. Thus, the prepared nanofiltration membrane will have excellent performance.

[0064] As an example, the contact time is 5s, 10s, 20s, 40s, 60s, 80s, 120s, 140s, 160s, 180s, etc.

[0065] In some embodiments of the present invention, after the step of contacting the basement membrane with the oil phase solution, the step further includes: drying the basement membrane to obtain a nanofiltration membrane; the drying temperature is 60°C to 90°C, and the time is 1 min to 5 min.

[0066] In the present invention, after the base membrane is in contact with the oil phase solution, the base membrane is dried to remove the organic solvent, promote further cross-linking reaction of the membrane surface layer, and stabilize the pore size and pore structure of the functional layer. If the drying temperature is too high and the drying time is too long, the cross-linking degree of the functional layer will be too high, and the membrane thickness will increase, resulting in a decrease in water flux. Thus, the prepared nanofiltration membrane will have excellent performance.

[0067] The scheme of the present invention will be explained below in conjunction with the embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. Where specific techniques or conditions are not indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used are not indicated by the manufacturer and are all conventional products that can be obtained commercially.

[0068] Embodiment 1:

[0069] (1) Preparation of base membrane: 13% by weight of polyethersulfone was added to the solvent DMF to prepare a casting solution, and a polyethersulfone base membrane was prepared on a polypropylene non-woven fabric by a phase inversion method.

[0070] (2) Preparation of aqueous solution: Add 1% polyethyleneimine (molecular weight 300Da), 0.1% 4-(NN-diallylamine)pyridine, 0.5% sodium hydroxide and 0.3% sodium dodecyl sulfate to deionized water, stir well to dissolve and mix evenly.

[0071] (3) Preparation of oil phase solution: Add 0.2% by mass concentration of the compound of formula I into n-hexane solvent, stir thoroughly to dissolve, and mix evenly.

[0072] (4) Preparation of functional layer: The polyethersulfone base membrane was washed with deionized water to remove surface impurities, and the aqueous solution was dip-coated on the surface of the base membrane for 30 seconds. Then, the excess solution on the surface of the base membrane was blown off with an air knife, and the base membrane was immersed in a 60°C oil phase solution for 10 seconds, then taken out to drain the solvent and placed in an 80°C oven for 3 minutes. The base membrane was washed with deionized water to remove the substances and solvent that did not participate in the reaction, and then immersed in deionized water for more than 12 hours for testing.

[0073] Embodiment 2:

[0074] (1) Preparation of base membrane: 13% by weight of polyethersulfone was added to the solvent DMF to prepare a casting solution, and a polyethersulfone base membrane was prepared on a polypropylene non-woven fabric by a phase inversion method.

[0075] (2) Preparation of aqueous solution: Add 3% polyethyleneimine (molecular weight 1800Da), 0.4% 4-(NN-diallylamine)pyridine, and 0.3% sodium dodecylbenzene sulfonate to deionized water, stir well to dissolve, and mix evenly.

[0076] (3) Preparation of oil phase solution: Add 0.1% of the total mass concentration of the compound of formula I and the compound of formula II (mass ratio of 8:1) and 0.5% of diethylene glycol dimethyl ether to the solvent n-hexane, stir well to dissolve, and mix well.

[0077] (4) Preparation of functional layer: The polyethersulfone base membrane was washed with deionized water to remove surface impurities, and the aqueous solution was dip-coated on the surface of the base membrane for 60 seconds. Then, the excess solution on the surface of the base membrane was blown off with an air knife, and the base membrane was immersed in a 60°C oil phase solution for 30 seconds, then taken out to drain the solvent and placed in an 80°C oven for 3 minutes. The base membrane was washed with deionized water to remove the substances and solvent that did not participate in the reaction, and then immersed in deionized water for more than 12 hours for testing.

[0078] Embodiment 3:

[0079] (1) Preparation of base membrane: 15% by weight of polyethersulfone was added to the solvent DMF to prepare a casting solution, and a polyethersulfone base membrane was prepared on a polypropylene non-woven fabric by a phase inversion method.

[0080] (2) Preparation of aqueous solution: Add 6% polyethyleneimine (molecular weight 10000Da), 2% 1,3,5-triaminobenzene, 0.8% 4-(NN-dimethylamine)pyridine, 2% sodium carbonate, and 3% sodium dodecylbenzene sulfonate in deionized water, stir well to dissolve, and mix evenly.

[0081] (3) Preparation of oil phase solution: Add 0.5% of the total mass concentration of the compound of formula I and the compound of formula II (mass ratio of 5:1) and 5% of tetrahydrofuran to the solvent ethylcyclohexane, stir well to dissolve, and mix well.

[0082] (4) Preparation of functional layer: The polyethersulfone base membrane was washed with deionized water to remove surface impurities, and the aqueous solution was dip-coated on the surface of the base membrane for 20 seconds. Then, the excess solution on the surface of the base membrane was blown off with an air knife, and the base membrane was immersed in a 60°C oil phase solution for 20 seconds, then taken out to drain the solvent and placed in an 80°C oven for 3 minutes. The base membrane was washed with deionized water to remove the substances and solvent that did not participate in the reaction, and then immersed in deionized water for more than 12 hours for testing.

[0083] Embodiment 4:

[0084] (1) Preparation of base membrane: 13% by weight of polyethersulfone was added to the solvent DMF to prepare a casting solution, and a polyethersulfone base membrane was prepared on a polypropylene non-woven fabric by a phase inversion method.

[0085] (2) Prepare an aqueous solution: add 3% polyethyleneimine (molecular weight 300Da), 0.2% 1,3,5-triaminobenzene, 0.3% 4-(NN-dimethylamine)pyridine, and 0.8% sodium carbonate to deionized water, stir thoroughly to dissolve, and mix evenly.

[0086] (3) Preparation of oil phase solution: Add 0.3% by mass concentration of the compound of formula II into n-hexane solvent, stir thoroughly to dissolve, and mix evenly.

[0087] (4) Preparation of functional layer: The polyethersulfone base membrane was washed with deionized water to remove surface impurities, and the aqueous solution A was dip-coated on the surface of the base membrane for 10 seconds. The excess solution was squeezed out with a roller, and then the base membrane was in contact with the aqueous solution B for 10 seconds. The excess solution on the surface of the base membrane was then blown off with an air knife, and the base membrane was immersed in a 60°C oil phase solution for 20 seconds, then taken out to drain the solvent, and placed in an 80°C oven for 3 minutes. The base membrane was washed with deionized water to remove the substances and solvent that did not participate in the reaction, and then immersed in deionized water for more than 12 hours for testing.

[0088] Comparative Example 1:

[0089] (1) Preparation of base membrane: 13% by weight of polyethersulfone was added to the solvent DMF to prepare a casting solution, and a polyethersulfone base membrane was prepared on a polypropylene non-woven fabric by a phase inversion method.

[0090] (2) Preparation of aqueous solution: Add 3% polyethyleneimine (molecular weight 300Da), 0.4% 4-(NN-diallylamine)pyridine, and 0.8% sodium carbonate to deionized water, stir thoroughly to dissolve, and mix evenly.

[0091] (3) Preparation of oil phase solution: Add 0.3% cyanuric chloride to ethylcyclohexane solvent, stir thoroughly to dissolve, and mix evenly.

[0092] (4) Preparation of functional layer: The polyethersulfone base membrane was washed with deionized water to remove surface impurities, and the aqueous solution was dip-coated on the surface of the base membrane for 30 seconds. Then, the excess solution on the surface of the base membrane was blown off with an air knife, and the base membrane was immersed in a 60°C oil phase solution for 10 seconds, then taken out to drain the solvent and placed in an 80°C oven for 3 minutes. The base membrane was washed with deionized water to remove the substances and solvent that did not participate in the reaction, and then immersed in deionized water for more than 12 hours for testing.

[0093] 1. Performance test:

[0094] 1. Test of water flux and retention rate performance of nanofiltration membrane: The test liquid is 2000ppm magnesium sulfate aqueous solution and 2000ppM PEG200 aqueous solution, pH value is 5-8, operating temperature is 25℃, the membrane is under 1MPa operating pressure condition, after running for 30min, the water flux and retention rate of the membrane are tested.

[0095] 2. Test Results

[0096] The test results of the water flux and retention rate performance of magnesium sulfate in the above embodiments and comparative examples are shown in Table 1, and the water flux and retention rate performance of PEG200 are shown in Table 2.

[0097] Table 1 Magnesium sulfate water flux and retention rate performance test results of each embodiment and comparative example

[0098] Serial number Retention rate / % Water flux (LMH) Example 1 95.5 43.1 Example 2 95.3 45.7 Example 3 95.1 47.4 Example 4 95.8 44.3 Comparative Example 1 96.7 25.7

[0099] Table 2 PEG200 water flux and retention rate performance test results of each embodiment and comparative example

[0100] Serial number Retention rate / % Water flux (LMH) Example 1 99.7 50.4 Example 2 99.4 54.3 Example 3 99.1 56.9 Example 4 99.9 49.8 Comparative Example 1 99.5 24.2

[0101] It can be seen from Table 1 and Table 2 that the composite nanofiltration membrane of the present invention has obvious advantages in flux performance and significantly improves water flux while maintaining a stable rejection rate. Therefore, the preparation method of the present invention can effectively improve the water flux of the nanofiltration membrane.

[0102] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0103] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A composite nanofiltration membrane, characterized in that: include: Basement membrane, A functional layer, the functional layer comprises a polymer, the polymerization unit monomers of the polymer comprise amine monomers and cyanuric chloride derivatives, the amine monomers comprise aliphatic amines and aromatic amines, the aliphatic amines comprise at least three primary amine or secondary amine groups, the cyanuric chloride derivatives comprise at least one of the compounds of formula I and formula II, 2. The composite nanofiltration membrane according to claim 1, characterized in that The fatty amine includes at least one of polyethyleneimine, tetraethylenepentamine, triethylenetetramine and pentaethylenehexamine, and the molecular weight of the polyethyleneimine ranges from 300Da to 10000Da.

3. The composite nanofiltration membrane according to claim 1 or 2, characterized in that: The aromatic amine includes at least one of triaminobenzene, melamine and triaminonaphthalene.

4. The composite nanofiltration membrane according to any one of claims 1 to 3, characterized in that: The mass ratio of the aliphatic amine to the aromatic amine is 3:1 to 15:

1.

5. The method for preparing the composite nanofiltration membrane according to any one of claims 1 to 4, characterized in that: include: A base film is prepared on the support layer by a phase inversion method; A functional layer is formed on the surface of the base film.

6. The preparation method according to claim 5, characterized in that: The step of forming a functional layer on the surface of the base film includes: contacting the base film with an aqueous solution, wherein the aqueous solution includes the amine monomer; The base film is contacted with an oil phase solution to form a functional layer, wherein the oil phase solution includes the cyanuric chloride derivative.

7. The preparation method according to claim 6, characterized in that: The aqueous phase solution further includes an aqueous phase solvent, a catalyst, a proton absorber and a surfactant; the aqueous phase solution satisfies at least one of the following: (1) The aqueous phase solvent includes water; (2) The catalyst comprises at least one of polyaminopyridine, 4-(NN-dimethylamino)pyridine, and 4-(NN-diallylamine)pyridine, and the content of the catalyst is 0.1% to 0.8% by mass of the aqueous solution; (3) The proton absorber includes at least one of sodium carbonate, sodium bicarbonate, sodium hydroxide, potassium hydroxide, pyridine, imidazole, and indole, and the content of the proton absorber is 0.5% to 2.0% by mass of the aqueous solution; (4) The surfactant includes sodium dodecyl sulfate and sodium dodecylbenzene sulfonate, and the content of the surfactant is 0.1% to 3% of the mass of the aqueous phase solution; (5) The total content of the amine monomers is 1% to 8% of the mass of the aqueous phase solution.

8. The preparation method according to claim 6, characterized in that: The oil phase solution further includes a co-solvent and an organic solvent, and the oil phase solution satisfies at least one of the following: (A) the cosolvent includes ethers, benzene rings, esters, and ketones, and the content of the cosolvent is 0.5% to 5% of the mass of the oil phase solution; (B) the organic solvent comprises saturated alkanes; (C) The content of the compound of formula I is 0.2% to 0.4% by mass of the oil phase solution; the content of the compound of formula II is 0.3% to 0.4% by mass of the oil phase solution; the total content of the compound of formula I and the compound of formula II is 0.1% to 0.5% by mass of the oil phase solution, wherein the mass ratio of compound I to compound II is 15:1 to 2:

1.

9. The preparation method according to any one of claims 6 to 8, characterized in that: In the step of contacting the base film with the aqueous solution, the contact time is 5s to 180s; the contact method includes any one of dipping, rolling, slit coating, and spraying; And / or, in the step of contacting the base film with the oil phase solution, the contact time is 5s to 180s, the temperature of the oil phase solution is 50°C to 90°C; the contact method includes any one of dipping, rolling, slit coating, and spraying.

10. The preparation method according to any one of claims 6 to 9, characterized in that: After the step of contacting the base film with the oil phase solution, the method further comprises: The base film is dried to obtain a nanofiltration membrane; the drying temperature is 60° C. to 90° C., and the drying time is 1 min to 5 min.

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