A composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin, and its preparation method and application

Abstract

The present invention belongs to the technical field of nanofiltration membrane preparation, and specifically relates to a composite nanofiltration membrane regulated by amino acid modified γ-cyclodextrin, and its preparation method and application. The method comprises the following steps: dissolving an amine compound, an amino acid and γ-cyclodextrin in a solvent and mixing them to obtain an aqueous composite solution; placing the aqueous composite solution on the surface of a base membrane, and depositing the aqueous composite solution in situ to obtain a primary membrane; placing an organic phase solution of an acyl chloride compound on the surface of the primary membrane, performing interfacial polymerization to obtain a composite nanofiltration membrane precursor, and performing heat treatment to obtain a composite nanofiltration membrane regulated by amino acid modified γ-cyclodextrin. The present invention uses a polyacrylonitrile membrane as a substrate, and amino acids, γ-cyclodextrin and polyethyleneimine are coupled to obtain an aqueous composite solution, and an interfacial polymerization method is used to react with 1,3,5-benzenetricarboxylic acid chloride to obtain a polyacrylonitrile nanofiltration membrane having excellent metal cation rejection rates of different valence states and specific separation performance, and has broad prospects in resource recovery and reuse of lithium slag.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanofiltration membrane preparation, and in particular relates to a composite nanofiltration membrane regulated by amino acid-modified gamma-cyclodextrin, and a preparation method and application thereof. Background Art

[0002] With the rapid development of the lithium battery industry, the stockpile of lithium slag generated during lithium ore processing has increased dramatically, and its resource utilization has attracted widespread attention. Currently, the total stockpile of lithium slag in my country has exceeded 10 million tons. This large amount of lithium slag poses environmental regulatory challenges and also raises the need for proper solid waste disposal. Separating and extracting the high-value lithium element from lithium slag not only enables resource recycling but also provides more lithium resources for the lithium battery industry, alleviating my country's tight lithium resource supply and supporting the sustainable development of the new energy industry. Currently, lithium slag is mostly disposed of by landfill or as a low-cost building material. This treatment is costly and has limited effectiveness. Therefore, the scientific disposal and comprehensive utilization of lithium slag has become a bottleneck that needs to be addressed in the development of the lithium battery new energy industry.

[0003] Membrane separation technology is a separation and purification technology widely used in industry and science, including seawater desalination and wastewater treatment. Nanofiltration, a pressure-driven membrane separation process between ultrafiltration and reverse osmosis, is named for its membrane pore size of approximately 1 nm. Applying a certain pressure differential across the membrane allows some solvents and components smaller than the membrane pore size to pass through the membrane, while particles, macromolecules, and salts larger than the membrane pore size are retained by the membrane, achieving separation. Furthermore, by utilizing the Donnan effect, dielectric exclusion, and steric hindrance mechanisms, nanofiltration membranes exhibit varying selectivity for ions of different valence states, with higher retention rates for divalent and multivalent ions than for monovalent ions. This allows them to be used to separate multivalent ions from lithium slag leachates.

[0004] The main problems faced by nanofiltration membranes are flux, ion retention performance, ion selectivity and anti-fouling performance. Traditional commercial nanofiltration membranes are usually negatively charged, and the removal rate of metal cations is relatively low, and they cannot effectively separate metal cations of different valences. Polyacrylonitrile nanofiltration membranes modified only with ordinary polyethyleneimine have certain limitations in separation selectivity, performance stability and anti-fouling ability. These problems need to be solved through technological innovation and modification methods to improve their reliability in practical applications. In existing research, the modification method of introducing positively charged monomers or nanomaterials into the aqueous phase to regulate interfacial polymerization has attracted widespread attention. However, these materials are generally expensive, the synthesis process is complicated, and they are prone to environmental pollution. Summary of the Invention

[0005] To address the above-mentioned issues, the present invention provides a composite nanofiltration membrane modulated by amino acid-modified γ-cyclodextrin, as well as its preparation method and application. The composite nanofiltration membrane utilizes amino acids and cyclodextrin as additives, introduced into an aqueous polyethyleneimine solution. The amino acids and cyclodextrin, acting as additives, both regulate the interfacial polymerization process and participate as monomers in interfacial polymerization. The resulting polyacrylonitrile nanofiltration membrane exhibits excellent retention rates and specific separation properties for metal cations of varying valences. The preparation method is simple, environmentally and ecologically friendly, and can enhance resistance to microbial contamination in applications such as sewage treatment.

[0006] The present invention solves the above technical problems through the following technical solutions.

[0007] One of the purposes of the present invention is to provide a method for preparing a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin, comprising the following steps:

[0008] The amine compound, amino acid and gamma-cyclodextrin are dissolved in a solvent and mixed evenly; the gamma-cyclodextrin coats the amino acid to form a non-covalent inclusion compound, and an aqueous composite solution is obtained.

[0009] The aqueous composite solution is placed on the surface of the base film, and the cyano groups in the base film and the amino groups in the aqueous composite solution undergo addition reaction, thereby in-situ deposition to obtain a primary film.

[0010] An organic phase solution of an acyl chloride compound is placed on the surface of a primary membrane to carry out an interfacial polymerization reaction. The amino groups in the primary membrane and the acyl chloride groups in the organic phase solution of the acyl chloride compound undergo a nucleophilic addition reaction to obtain a composite nanofiltration membrane precursor. The composite nanofiltration membrane precursor is heat-treated at 50°C to 60°C to graft the amino acid-modified γ-cyclodextrin onto the composite nanofiltration membrane to obtain a composite nanofiltration membrane regulated by the amino acid-modified γ-cyclodextrin.

[0011] In some specific embodiments, the mass ratio of the amine compound, the amino acid, and γ-cyclodextrin is 1:0.02-0.05:0.02-0.05.

[0012] In some specific embodiments, the weight percentage of the amine compound in the solvent is 0.5% to 1.5%, the amine compound is polyethyleneimine, and the solvent is water; the weight percentage of the amino acid in the solvent is 0.05% to 0.15%, and the amino acid is selected from one of the basic amino acids.

[0013] In some specific embodiments, the base film is a polyacrylonitrile film, and the in-situ deposition time is 5 min to 10 min.

[0014] In some specific embodiments, the organic phase solution of the acyl chloride compound is prepared by dissolving 1,3,5-benzenetricarboxylic acid chloride in n-hexane, with a mass volume ratio of 1,3,5-benzenetricarboxylic acid chloride to n-hexane of 0.01 g: 2 mL to 50 mL.

[0015] In some specific embodiments, the interfacial polymerization reaction time is 5 min to 10 min.

[0016] In some specific embodiments, the heat treatment time is 10 min to 15 min.

[0017] In some specific embodiments, during the preparation of the aqueous composite solution, the amino acid is first dissolved in a solvent, and then γ-cyclodextrin and the amine compound are added.

[0018] The second object of the present invention is to provide a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin obtained by the above-mentioned preparation method.

[0019] A third object of the present invention is to provide the application of the composite nanofiltration membrane regulated by the amino acid-modified γ-cyclodextrin in lithium separation in lithium-containing solutions.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The preparation method of the composite nanofiltration membrane provided by the present invention uses cyclodextrin as a carrier, which interacts with amino acids to form non-covalent inclusion compounds. The non-covalent inclusion compounds and amine compounds do not react with each other, but only form a uniform mixed solution to obtain an aqueous composite solution. The aqueous composite solution is poured on the surface of the base membrane, and the cyano groups in the base membrane and the amino groups in the aqueous composite solution undergo an addition reaction, and a primary membrane is obtained by in-situ deposition. Finally, an organic phase solution of an acyl chloride compound is placed on the surface of the primary membrane to perform interfacial polymerization. The amino groups in the primary membrane and the acyl chloride groups in the organic phase solution of the acyl chloride compound undergo a nucleophilic addition reaction, and during the interfacial polymerization, the non-covalent inclusion compound also participates in the interfacial polymerization as a monomer, and the polyacrylonitrile nanofiltration membrane is modified. Amino acids with positive charges are grafted on the membrane surface. The synergistic effect between γ-cyclodextrin and histidine enhances the screening effect of the composite membrane on Mg / Li, thereby achieving the purpose of highly selective separation of high-valent cations.

[0022] (2) The polyacrylonitrile nanofiltration membrane prepared by the present invention has positively charged amino acids grafted onto the surface of the composite nanofiltration membrane, which has excellent retention rate of metal cations of different valences and specific separation performance. By introducing amino acids into the membrane material, the hydrophilicity of the membrane can be improved, its anti-pollution ability can be enhanced, and the separation selectivity can be improved. Based on this, a highly selective polyacrylonitrile nanofiltration membrane with antibacterial properties and high flux is developed. The prepared composite nanofiltration membrane is low-cost and environmentally friendly, providing good technical guidance for the preparation of high-performance composite nanofiltration membranes. The composite nanofiltration membrane prepared by this method has excellent retention rate of metal cations of different valences and specific separation performance. It has broad prospects in the resource recovery and reuse of lithium slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the infrared spectrum of the composite nanofiltration membrane and PAN-based membrane prepared in Example 1 of the present invention.

[0024] Figure 2 These are microscopic morphologies of the composite nanofiltration membranes prepared in Example 1 and Comparative Examples 1 to 3 of the present invention.

[0025] Figure 3 This is a graph showing the change in salt retention performance of the composite nanofiltration membranes prepared in Examples 1 to 9 of the present invention.

[0026] in, Figure 3 a is a graph showing the change in salt retention performance with different amounts of amino acids added in Examples 1 to 5, and b is a graph showing the change in salt retention performance with different amounts of γ-cyclodextrin added in Examples 1 and 6 to 9.

[0027] Figure 4 This is a comparison chart of the salt retention performance of the nanofiltration membranes prepared in Example 1 of the present invention and Comparative Examples 1 to 3.

[0028] Figure 5 Salt retention performance diagram of the composite nanofiltration membrane of Example 1 of the present invention in a simulated lithium slag leachate. DETAILED DESCRIPTION

[0029] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0030] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0031] Nanofiltration membranes face challenges primarily in terms of flux, ion retention, ion selectivity, and anti-fouling performance. Traditional commercial nanofiltration membranes are typically negatively charged, resulting in relatively low metal cation removal rates and inability to effectively separate metal cations of varying valences. Polyacrylonitrile nanofiltration membranes modified solely with polyethyleneimine exhibit limitations in separation selectivity, performance stability, and anti-fouling capabilities. Technological innovation and modification methods are needed to address these issues and improve their reliability in practical applications. In existing research, modification methods that introduce positively charged quaternary ammonium salts or MXene nanosheets into the aqueous phase to regulate interfacial polymerization have attracted considerable attention. However, these materials are generally expensive, have complex synthesis processes, and are prone to environmental pollution.

[0032] Based on the above problems, the present invention provides a method for preparing a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin, comprising the following steps:

[0033] S1. The amine compound, amino acid and γ-cyclodextrin are dissolved in a solvent and uniformly mixed, and the γ-cyclodextrin coats the amino acid to form a non-covalent inclusion complex to obtain an aqueous composite solution.

[0034] S2. placing the aqueous composite solution on the surface of the base film, and the cyano groups in the base film and the amino groups in the aqueous composite solution undergo addition reaction, thereby in-situ deposition to obtain a primary film.

[0035] S3. Place the organic phase solution of the acyl chloride compound on the surface of the primary membrane to carry out interfacial polymerization, and obtain a composite nanofiltration membrane precursor through nucleophilic addition reaction between the amino group in the primary membrane and the acyl chloride group in the organic phase solution of the acyl chloride compound. Heat-treat the composite nanofiltration membrane precursor at 50°C to 60°C to graft the amino acid-modified γ-cyclodextrin onto the composite nanofiltration membrane, thereby obtaining a composite nanofiltration membrane regulated by the amino acid-modified γ-cyclodextrin.

[0036] The solvent in the aqueous composite solution of the present invention is immiscible with the solvent in the organic phase solution of the acyl chloride compound. Cyclodextrin is a cyclic oligosaccharide composed of glucopyranose units, and the units are bonded by α-(1-4) bonds to form a truncated cone with a cavity. Cyclodextrin plays an important role as a main body in the inclusion complex of non-covalent interaction. Because cyclodextrin has a hydrophobic interior and a hydrophilic exterior, it can interact with amino acids to form non-covalent inclusion complexes. The non-covalent inclusion complexes and amine compounds do not react with each other, but instead form a uniform mixed solution to obtain an aqueous composite solution. This aqueous composite solution is then poured onto the surface of a base membrane, where cyano groups in the base membrane react with amino groups in the aqueous composite solution to form an in situ deposited nascent membrane. Finally, an organic phase solution of an acyl chloride compound is placed on the surface of the nascent membrane for interfacial polymerization. Nucleophilic addition reactions occur between amino groups in the nascent membrane and acyl chloride groups in the organic phase solution of the acyl chloride compound. During the interfacial polymerization process, the non-covalent inclusion complex also participates as a monomer in the interfacial polymerization, modifying a polyacrylonitrile nanofiltration membrane by grafting positively charged amino acids onto the membrane surface. The synergistic effect between γ-cyclodextrin and histidine enhances the Mg / Li screening ability of the composite membrane, achieving highly selective separation of high-valent cations. The prepared polyacrylonitrile nanofiltration membrane exhibits excellent rejection rates for metal cations of different valence states and specific separation performance. By introducing amino acids into the membrane material, the present invention improves the membrane's hydrophilicity, enhances its anti-pollution ability, and improves separation selectivity. Based on this, a highly selective polyacrylonitrile nanofiltration membrane with antibacterial properties and high flux has been developed. The composite nanofiltration membrane prepared by the present invention is low-cost and environmentally friendly, providing excellent technical guidance for the preparation of high-performance composite nanofiltration membranes. The composite nanofiltration membrane prepared by this method has excellent rejection rates for metal cations of different valence states and specific separation performance. It has broad prospects for the resource recovery and reuse of lithium slag.

[0037] In some specific embodiments, the mass ratio of the amine compound, amino acid, and γ-cyclodextrin is 1:0.02-0.05:0.02-0.05. Both the cyclodextrin and amino acid used in the present invention are green, natural materials. The nanofiltration membrane modified with amino acid-modified γ-cyclodextrin is very environmentally and ecologically friendly and can enhance anti-microbial contamination performance in applications such as sewage treatment.

[0038] In some specific embodiments, the weight percentage of the amine compound in the solvent is 0.5% to 1.5%, the amine compound is polyethyleneimine, and the solvent is water; the weight percentage of the amino acid in the solvent is 0.05% to 0.15%, and the amino acid is selected from one of the basic amino acids.

[0039] In some specific embodiments, the base membrane is a polyacrylonitrile membrane, and the in-situ deposition time is 5 to 10 minutes. The purpose of the in-situ deposition is to evenly disperse the non-covalent inclusion compound on the surface of the polyacrylonitrile membrane base membrane to prevent the non-covalent inclusion compound from agglomerating. After the in-situ deposition is completed, the aqueous composite solution is poured out, and the residual aqueous composite solution on the surface of the polyacrylonitrile membrane is removed using a silica gel roller. The residual aqueous solution on the surface of the polyacrylonitrile membrane is then dried for 5 minutes to obtain a primary membrane.

[0040] In some specific embodiments, the organic phase solution of the acyl chloride compound is prepared by dissolving 1,3,5-benzenetricarboxylic acid chloride in n-hexane, with a mass volume ratio of 1,3,5-benzenetricarboxylic acid chloride to n-hexane of 0.01 g:2 mL to 50 mL. It should be noted that the present invention utilizes a conventional interfacial polymerization method to interfacially polymerize 1,3,5-benzenetricarboxylic acid chloride and polyethyleneimine to form a primary polyamide layer.

[0041] In some specific embodiments, the interfacial polymerization reaction time is 5 min to 10 min.

[0042] In some specific embodiments, the heat treatment time is 10 to 15 minutes. During the heat treatment, the amino acids and cyclodextrin in the non-covalent inclusion complex both regulate the interfacial polymerization process and participate in the interfacial polymerization as monomers, thereby modifying the polyacrylonitrile nanofiltration membrane and grafting positively charged amino acids onto the membrane surface to achieve the purpose of highly selective separation of high-valent cations. The prepared polyacrylonitrile nanofiltration membrane has excellent rejection rate and specific separation performance for metal cations of different valence states.

[0043] In some specific embodiments, during the preparation of the aqueous composite solution, the amino acid is first dissolved in a solvent, and then γ-cyclodextrin and the amine compound are added. It should be noted that during the preparation of the aqueous composite solution of the present invention, the amino acid is dissolved first and then the γ-cyclodextrin. This is because γ-cyclodextrin, with its large cavity and good water solubility, can include the amino acid molecules to form a stable complex.

[0044] The present invention provides a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin obtained by the above-mentioned preparation method. The composite nanofiltration membrane has positively charged amino acids grafted onto its surface, and has excellent rejection rate of metal cations of different valence states and specific separation performance.

[0045] The present invention also provides the use of the composite nanofiltration membrane regulated by the amino acid-modified γ-cyclodextrin in separating lithium from a lithium-containing solution.

[0046] The following is further described through specific examples.

[0047] Example 1

[0048] A method for preparing a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin comprises the following steps:

[0049] S1. Weigh 0.4 g of polyethyleneimine, 0.04 g of amino acid, and 0.03 g of γ-cyclodextrin. Dissolve the amino acid in 40 mL of deionized water first, then add γ-cyclodextrin and polyethyleneimine in sequence and mix well to form a polyethyleneimine aqueous phase composite solution. Weigh 0.0264 g of 1,3,5-benzenetricarboxylic acid chloride and dissolve it in 40 mL of n-hexane to form a 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution.

[0050] S2. Pour the aqueous composite solution onto the surface of the polyacrylonitrile-based membrane to uniformly disperse it on the surface of the polyacrylonitrile membrane. Deposit it in situ at room temperature for 5 minutes. Then pour out the aqueous composite solution. Use a silicone roller to remove the residual aqueous composite solution on the surface of the polyacrylonitrile membrane. Dry it for 5 minutes to remove the residual aqueous solution on the surface of the polyacrylonitrile membrane to obtain a primary membrane.

[0051] S3. Pour the 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution on the surface of the primary membrane to make it evenly dispersed on the surface of the primary membrane, let it stand at room temperature for 5 minutes for interfacial polymerization reaction, then pour out the remaining composite organic phase solution, dry it for 5 minutes to remove the residual composite organic phase solution on the surface of the primary membrane, and obtain a composite nanofiltration membrane precursor. Heat treat the composite nanofiltration membrane precursor in a forced air drying oven at 60°C for 10 minutes to graft the amino acid modified γ-cyclodextrin onto the composite nanofiltration membrane to obtain a composite nanofiltration membrane regulated by amino acid modified γ-cyclodextrin.

[0052] Example 2

[0053] A method for preparing a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin comprises the following steps:

[0054] S1. Weigh 0.4 g polyethyleneimine, 0.01 g amino acid and 0.03 g γ-cyclodextrin, first dissolve the amino acid in 40 mL deionized water, then add γ-cyclodextrin and polyethyleneimine in sequence, mix well to form a polyethyleneimine aqueous phase composite solution; weigh 0.0264 g 1,3,5-benzenetricarboxylic acid chloride and dissolve it in 40 mL n-hexane to form a 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution.

[0055] S2. Pour the aqueous composite solution onto the surface of the polyacrylonitrile-based membrane to uniformly disperse it on the surface of the polyacrylonitrile membrane. Deposit it in situ at room temperature for 5 minutes. Then pour out the aqueous composite solution. Use a silicone roller to remove the residual aqueous composite solution on the surface of the polyacrylonitrile membrane. Dry it for 5 minutes to remove the residual aqueous solution on the surface of the polyacrylonitrile membrane to obtain a primary membrane.

[0056] S3. Pour the 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution on the surface of the primary membrane to make it evenly dispersed on the surface of the primary membrane, and let it stand at room temperature for 5 minutes to undergo interfacial polymerization reaction. Then pour out the remaining composite organic phase solution, dry it for 5 minutes to remove the residual composite organic phase solution on the surface of the primary membrane, and obtain a composite nanofiltration membrane precursor. Heat-treat the composite nanofiltration membrane precursor in a forced air drying oven at 60°C for 10 minutes to graft the amino acid modified γ-cyclodextrin onto the composite nanofiltration membrane to obtain a composite nanofiltration membrane regulated by amino acid modified γ-cyclodextrin.

[0057] Example 3

[0058] A method for preparing a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin comprises the following steps:

[0059] S1. Weigh 0.4 g polyethyleneimine, 0.02 g amino acid and 0.03 g γ-cyclodextrin, first dissolve the amino acid in 40 mL deionized water, then add γ-cyclodextrin and polyethyleneimine in sequence, mix well to form a polyethyleneimine aqueous phase composite solution; weigh 0.0264 g 1,3,5-benzenetricarboxylic acid chloride and dissolve it in 40 mL n-hexane to form a 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution.

[0060] S2. Pour the aqueous composite solution onto the surface of the polyacrylonitrile-based membrane to uniformly disperse it on the surface of the polyacrylonitrile membrane. Deposit it in situ at room temperature for 5 minutes. Then pour out the aqueous composite solution. Use a silicone roller to remove the residual aqueous composite solution on the surface of the polyacrylonitrile membrane. Dry it for 5 minutes to remove the residual aqueous solution on the surface of the polyacrylonitrile membrane to obtain a primary membrane.

[0061] S3. Pour the 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution on the surface of the primary membrane to make it evenly dispersed on the surface of the primary membrane, let it stand at room temperature for 5 minutes for interfacial polymerization reaction, then pour out the remaining composite organic phase solution, dry it for 5 minutes to remove the residual composite organic phase solution on the surface of the primary membrane, and obtain a composite nanofiltration membrane precursor. Heat treat the composite nanofiltration membrane precursor in a forced air drying oven at 60°C for 10 minutes to graft the amino acid modified γ-cyclodextrin onto the composite nanofiltration membrane to obtain a composite nanofiltration membrane regulated by amino acid modified γ-cyclodextrin.

[0062] Example 4

[0063] A method for preparing a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin comprises the following steps:

[0064] S1. Weigh 0.4 g polyethyleneimine, 0.03 g amino acid and 0.03 g γ-cyclodextrin, first dissolve the amino acid in 40 mL deionized water, then add γ-cyclodextrin and polyethyleneimine in sequence, mix well to form a polyethyleneimine aqueous phase composite solution; weigh 0.0264 g 1,3,5-benzenetricarboxylic acid chloride and dissolve it in 40 mL n-hexane to form a 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution.

[0065] S2. Pour the aqueous composite solution onto the surface of the polyacrylonitrile-based membrane to uniformly disperse it on the surface of the polyacrylonitrile membrane. Deposit it in situ at room temperature for 5 minutes. Then pour out the aqueous composite solution. Use a silicone roller to remove the residual aqueous composite solution on the surface of the polyacrylonitrile membrane. Dry it for 5 minutes to remove the residual aqueous solution on the surface of the polyacrylonitrile membrane to obtain a primary membrane.

[0066] S3. Pour the 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution onto the surface of the primary membrane to uniformly disperse it on the surface of the primary membrane, and allow the interfacial polymerization reaction to stand at room temperature for 5 minutes to obtain a composite nanofiltration membrane precursor. Heat-treat the composite nanofiltration membrane precursor in a forced air drying oven at 60°C for 10 minutes to graft the amino acid-modified γ-cyclodextrin onto the composite nanofiltration membrane to obtain a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin.

[0067] Example 5

[0068] A method for preparing a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin comprises the following steps:

[0069] S1. Weigh 0.4 g polyethyleneimine, 0.05 g amino acid and 0.03 g γ-cyclodextrin, first dissolve the amino acid in 40 mL deionized water, then add γ-cyclodextrin and polyethyleneimine in sequence, mix well to form a polyethyleneimine aqueous phase composite solution; weigh 0.0264 g 1,3,5-benzenetricarboxylic acid chloride and dissolve it in 40 mL n-hexane to form a 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution.

[0070] S2. Pour the aqueous composite solution onto the surface of the polyacrylonitrile-based membrane to uniformly disperse it on the surface of the polyacrylonitrile membrane. Deposit it in situ at room temperature for 5 minutes. Then pour out the aqueous composite solution. Use a silicone roller to remove the residual aqueous composite solution on the surface of the polyacrylonitrile membrane. Dry it for 5 minutes to remove the residual aqueous solution on the surface of the polyacrylonitrile membrane to obtain a primary membrane.

[0071] S3. Pour the 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution on the surface of the primary membrane to make it evenly dispersed on the surface of the primary membrane, and let it stand at room temperature for 5 minutes to perform interfacial polymerization reaction. Then pour out the remaining composite organic phase solution, dry it for 5 minutes to remove the residual composite organic phase solution on the surface of the primary membrane, and obtain a composite nanofiltration membrane precursor. Heat-treat the composite nanofiltration membrane precursor in a forced air drying oven at 60°C for 10 minutes to graft the amino acid modified γ-cyclodextrin onto the composite nanofiltration membrane to obtain a composite nanofiltration membrane regulated by amino acid modified γ-cyclodextrin.

[0072] Example 6

[0073] A method for preparing a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin comprises the following steps:

[0074] S1. Weigh 0.4 g of polyethyleneimine, 0.04 g of amino acid, and 0.01 g of γ-cyclodextrin. Dissolve the amino acid in 40 mL of deionized water first, then add γ-cyclodextrin and polyethyleneimine in sequence and mix well to form a polyethyleneimine aqueous phase composite solution. Weigh 0.0264 g of 1,3,5-benzenetricarboxylic acid chloride and dissolve it in 40 mL of n-hexane to form a 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution.

[0075] S2. Pour the aqueous composite solution onto the surface of the polyacrylonitrile-based membrane to uniformly disperse it on the surface of the polyacrylonitrile membrane. Deposit it in situ at room temperature for 5 minutes. Then pour out the aqueous composite solution. Use a silicone roller to remove the residual aqueous composite solution on the surface of the polyacrylonitrile membrane. Dry it for 5 minutes to remove the residual aqueous solution on the surface of the polyacrylonitrile membrane to obtain a primary membrane.

[0076] S3. Pour the 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution on the surface of the primary membrane to make it evenly dispersed on the surface of the primary membrane, and let it stand at room temperature for 5 minutes to perform interfacial polymerization reaction. Then pour out the remaining composite organic phase solution, dry it for 5 minutes to remove the residual composite organic phase solution on the surface of the primary membrane, and obtain a composite nanofiltration membrane precursor. Heat-treat the composite nanofiltration membrane precursor in a forced air drying oven at 60°C for 10 minutes to graft the amino acid modified γ-cyclodextrin onto the composite nanofiltration membrane to obtain a composite nanofiltration membrane regulated by amino acid modified γ-cyclodextrin.

[0077] Example 7

[0078] A method for preparing a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin comprises the following steps:

[0079] S1. Weigh 0.4 g of polyethyleneimine, 0.04 g of amino acid, and 0.02 g of γ-cyclodextrin. Dissolve the amino acid in 40 mL of deionized water first, then add γ-cyclodextrin and polyethyleneimine in sequence and mix well to form a polyethyleneimine aqueous phase composite solution. Weigh 0.0264 g of 1,3,5-benzenetricarboxylic acid chloride and dissolve it in 40 mL of n-hexane to form a 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution.

[0080] S2. Pour the aqueous composite solution onto the surface of the polyacrylonitrile-based membrane to uniformly disperse it on the surface of the polyacrylonitrile membrane. Deposit it in situ at room temperature for 5 minutes. Then pour out the aqueous composite solution. Use a silicone roller to remove the residual aqueous composite solution on the surface of the polyacrylonitrile membrane. Dry it for 5 minutes to remove the residual aqueous solution on the surface of the polyacrylonitrile membrane to obtain a primary membrane.

[0081] S3. Pour the 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution on the surface of the primary membrane to make it evenly dispersed on the surface of the primary membrane, and let it stand at room temperature for 5 minutes to perform interfacial polymerization reaction. Then pour out the remaining composite organic phase solution, dry it for 5 minutes to remove the residual composite organic phase solution on the surface of the primary membrane, and obtain a composite nanofiltration membrane precursor. Heat-treat the composite nanofiltration membrane precursor in a forced air drying oven at 60°C for 10 minutes to graft the amino acid modified γ-cyclodextrin onto the composite nanofiltration membrane to obtain a composite nanofiltration membrane regulated by amino acid modified γ-cyclodextrin.

[0082] Example 8

[0083] A method for preparing a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin comprises the following steps:

[0084] S1. Weigh 0.4 g of polyethyleneimine, 0.04 g of amino acid, and 0.04 g of γ-cyclodextrin. Dissolve the amino acid in 40 mL of deionized water first, then add γ-cyclodextrin and polyethyleneimine in sequence and mix well to form a polyethyleneimine aqueous phase composite solution. Weigh 0.0264 g of 1,3,5-benzenetricarboxylic acid chloride and dissolve it in 40 mL of n-hexane to form a 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution.

[0085] S2. Pour the aqueous composite solution onto the surface of the polyacrylonitrile-based membrane to uniformly disperse it on the surface of the polyacrylonitrile membrane. Deposit it in situ at room temperature for 5 minutes. Then pour out the aqueous composite solution. Use a silicone roller to remove the residual aqueous composite solution on the surface of the polyacrylonitrile membrane. Dry it for 5 minutes to remove the residual aqueous solution on the surface of the polyacrylonitrile membrane to obtain a primary membrane.

[0086] S3. Pour the 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution on the surface of the primary membrane to make it evenly dispersed on the surface of the primary membrane, and let it stand at room temperature for 5 minutes to perform interfacial polymerization reaction. Then pour out the remaining composite organic phase solution, dry it for 5 minutes to remove the residual composite organic phase solution on the surface of the primary membrane, and obtain a composite nanofiltration membrane precursor. Heat-treat the composite nanofiltration membrane precursor in a forced air drying oven at 60°C for 10 minutes to graft the amino acid modified γ-cyclodextrin onto the composite nanofiltration membrane to obtain a composite nanofiltration membrane regulated by amino acid modified γ-cyclodextrin.

[0087] Example 9

[0088] A method for preparing a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin comprises the following steps:

[0089] S1. Weigh 0.4 g of polyethyleneimine, 0.04 g of amino acid, and 0.05 g of γ-cyclodextrin. Dissolve the amino acid in 40 mL of deionized water first, then add γ-cyclodextrin and polyethyleneimine in sequence and mix well to form a polyethyleneimine aqueous phase composite solution. Weigh 0.0264 g of 1,3,5-benzenetricarboxylic acid chloride and dissolve it in 40 mL of n-hexane to form a 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution.

[0090] S2. Pour the aqueous composite solution onto the surface of the polyacrylonitrile-based membrane to uniformly disperse it on the surface of the polyacrylonitrile membrane. Deposit it in situ at room temperature for 5 minutes. Then pour out the aqueous composite solution. Use a silicone roller to remove the residual aqueous composite solution on the surface of the polyacrylonitrile membrane. Dry it for 5 minutes to remove the residual aqueous solution on the surface of the polyacrylonitrile membrane to obtain a primary membrane.

[0091] S3. Pour the 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution onto the surface of the primary membrane to make it evenly dispersed on the surface of the primary membrane, and let it stand at room temperature for 5 minutes for interfacial polymerization reaction. Then pour out the remaining composite organic phase solution, dry it for 5 minutes to remove the residual composite organic phase solution on the surface of the primary membrane, and heat-treat the composite nanofiltration membrane precursor in a forced air drying oven at 60°C for 10 minutes to graft the amino acid modified γ-cyclodextrin onto the composite nanofiltration membrane to obtain a composite nanofiltration membrane regulated by amino acid modified γ-cyclodextrin.

[0092] Comparative Example 1

[0093] A method for preparing a composite nanofiltration membrane comprises the following steps:

[0094] S1. Weigh 0.4 g of polyethyleneimine and dissolve it in 40 mL of deionized water to form a polyethyleneimine aqueous phase composite solution; weigh 0.0264 g of 1,3,5-benzenetricarboxylic acid chloride and dissolve it in 40 mL of n-hexane to form a 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution.

[0095] S2. Pour the aqueous composite solution onto the surface of the polyacrylonitrile-based membrane and deposit it in situ for 5 minutes to make it evenly dispersed on the surface of the polyacrylonitrile membrane. Then pour out the aqueous composite solution and use a silicone roller to remove the residual aqueous composite solution on the surface of the polyacrylonitrile membrane. Dry it for 5 minutes to remove the residual aqueous solution on the surface of the polyacrylonitrile membrane to obtain a primary membrane.

[0096] S3. Pour the 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution on the surface of the primary membrane, let it stand at room temperature for 5 minutes for interfacial polymerization reaction to obtain a composite nanofiltration membrane precursor, and heat-treat the composite nanofiltration membrane precursor in a forced air drying oven at 60°C for 10 minutes to obtain a common polyethyleneimine-modified polyacrylonitrile nanofiltration membrane.

[0097] Comparative Example 2

[0098] A method for preparing a composite nanofiltration membrane comprises the following steps:

[0099] S1. Weigh 0.4 g of polyethyleneimine and 0.04 g of amino acid and dissolve them in 40 mL of deionized water to form a polyethyleneimine aqueous phase composite solution; weigh 0.0264 g of 1,3,5-benzenetricarboxylic acid chloride and dissolve it in 40 mL of n-hexane to form a 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution.

[0100] S2. Pour the aqueous composite solution onto the surface of the polyacrylonitrile-based membrane and deposit it in situ for 5 minutes to make it evenly dispersed on the surface of the polyacrylonitrile membrane. Then pour out the aqueous composite solution and use a silicone roller to remove the residual aqueous composite solution on the surface of the polyacrylonitrile membrane. Dry it for 5 minutes to remove the residual aqueous solution on the surface of the polyacrylonitrile membrane to obtain a primary membrane.

[0101] S3. Pour the 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution onto the surface of the primary membrane, let it stand at room temperature for 5 minutes for interfacial polymerization reaction to obtain a composite nanofiltration membrane precursor, and heat-treat the composite nanofiltration membrane precursor in a forced air drying oven at 60°C for 10 minutes to obtain an amino acid-modified polyacrylonitrile nanofiltration membrane.

[0102] Comparative Example 3

[0103] A method for preparing a composite nanofiltration membrane comprises the following steps:

[0104] S1. Weigh 0.4 g of polyethyleneimine and 0.05 g of γ-cyclodextrin, dissolve them in 40 mL of deionized water to form a polyethyleneimine aqueous phase composite solution; weigh 0.0264 g of 1,3,5-benzenetricarboxylic acid chloride, dissolve it in 40 mL of n-hexane to form a 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution.

[0105] S2. Pour the aqueous composite solution onto the surface of the polyacrylonitrile-based membrane and deposit it in situ for 5 minutes to make it evenly dispersed on the surface of the polyacrylonitrile membrane. Then pour out the aqueous composite solution and use a silicone roller to remove the residual aqueous composite solution on the surface of the polyacrylonitrile membrane. Dry it for 5 minutes to remove the residual aqueous solution on the surface of the polyacrylonitrile membrane to obtain a primary membrane.

[0106] S3. Pour the 1,3,5-benzenetricarboxylic acid chloride composite organic phase solution onto the surface of the primary membrane, let it stand at room temperature for 5 minutes for interfacial polymerization reaction to obtain a composite nanofiltration membrane precursor, and heat-treat the composite nanofiltration membrane precursor in a forced air drying oven at 60°C for 10 minutes to obtain a γ-cyclodextrin modified polyacrylonitrile nanofiltration membrane.

[0107] The morphology and structure of the composite nanofiltration membranes prepared in Examples 1 to 9 and Comparative Examples 1 to 3 were tested. The structures of the composite nanofiltration membranes prepared in Examples 1 to 9 were basically similar, and the effects were similar. The morphology and structure of the composite nanofiltration membrane prepared in Example 1 were described. The composite nanofiltration membrane prepared in Example 1 was named His-γ-CD NF membrane, the nanofiltration membrane prepared in Comparative Example 1 was named PEI-TMC NF membrane, the nanofiltration membrane prepared in Comparative Example 2 was named His NF membrane, and the nanofiltration membrane prepared in Comparative Example 3 was named γ-CD NF membrane. The results are as follows:

[0108] Figure 1 This is the infrared spectrum of the composite nanofiltration membrane and PAN-based membrane prepared in Example 1 of the present invention. Figure 1 As shown in the figure, the interfacial polymer layer of the prepared nanofiltration membrane has been formed on the PAN-based membrane. -1 The stretching vibration peak of amino group appears at 1644cm -1 ~1543cm -1 The significant enhancement of the amide group peak was attributed to the successful preparation of polyacrylonitrile nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin.

[0109] Figure 2 The microscopic morphology of the composite nanofiltration membrane prepared in Example 1 and Comparative Examples 1-3 of the present invention is shown in FIG. Figure 2 a is Example 1, b is Comparative Example 1, c is Comparative Example 2, and d is Comparative Example 3. Figure 2 As shown in the figure, the surface voids of PEI-TMC NF membrane are large and the structure is sparse; the surface voids of His NF membrane are significantly reduced and relatively smooth; the surface voids of γ-CD NF membrane are reduced, but it is relatively loose and the surface is rough; and it can be clearly seen on the surface of His-γ-CD NF membrane that the addition of amino acids and cyclodextrin makes the membrane surface very dense and smooth.

[0110] The composite nanofiltration membranes prepared in Examples 1 to 9 and Comparative Examples 1 to 3 are used to separate lithium from a lithium-containing solution, comprising the following steps:

[0111] Step 1: Cut the composite nanofiltration membranes prepared in Examples 1 to 9 and Comparative Examples 1 to 3 into circular membrane pieces with a diameter of d=4 cm, and conduct tests using a laboratory-prepared salt solution using a cross-flow filtration device.

[0112] Step 2: Prepare the salt solution required for the experiment according to the determined ratio of each ion. The test conditions are 6 Bar and 25±1°C.

[0113] Step 3: Before the experiment, use deionized water to stabilize for 1 hour, and then pass it into the laboratory to prepare salt solution for testing.

[0114] Step 4: After the solution has completely flowed out, sampling should be started. Three sets of parallel samples should be made, and 2 ml of sample should be taken each time. After the filtration is completed, the concentration of metal ions is measured using a flame atomic absorption spectrometer (FAAS, Agilent 240, USA) to calculate the retention efficiency of the composite membrane for magnesium ions.

[0115] Figure 3 This is a graph showing the salt rejection performance changes of the composite nanofiltration membranes prepared in Examples 1 to 9 of the present invention, wherein: Figure 3 Figure a shows the salt retention performance change with different amino acid addition amounts in Examples 1 to 5, and Figure b shows the salt retention performance change with different γ-cyclodextrin addition amounts in Examples 1, 6, and 9. All examples used the same conditions: a total salt solution concentration of 2000 ppm, a magnesium-lithium ion ratio of 30:1, a test pressure of 6 Bar, and a membrane area of ​​3.14 cm. 2 , the test temperature is 25±1℃. Figure 3 As shown in the figure, the modified membrane has the best retention effect when the addition amounts of amino acid and γ-cyclodextrin are 0.04g and 0.03g respectively.

[0116] Figure 4 The salt rejection performance comparison chart of the nanofiltration membranes prepared in Example 1 of the present invention and Comparative Examples 1 to 3 is shown. Comparative Examples 1 to 3 all adopt the same conditions, with a total salt solution concentration of 2000 ppm, a magnesium-lithium ion ratio of 30:1, a test pressure of 6 Bar, and a membrane area of ​​3.14 cm 2 , the test temperature is 25±1℃. Figure 4 As shown, by comparison, it was found that the nanofiltration membrane prepared by adding amino acids and cyclodextrin at the same time had a better retention effect on magnesium ions than the nanofiltration membranes prepared by the other three groups of comparative examples.

[0117] Figure 5Figure 1 shows the salt retention performance of the composite nanofiltration membrane in a simulated lithium slag leachate of Example 1 of the present invention. The salt retention performance conditions for the simulated lithium slag leachate are as follows: the concentration ratio of lithium, magnesium, manganese, calcium, and sodium ions is 1:10:4:20:20, the total salt solution concentration is 1000 ppm, the test pressure is 6 Bar, and the membrane area is 3.14 cm 2 , the test temperature is 25±1℃. Figure 5 As shown, the test found that the nanofiltration membrane prepared in Example 1 has an excellent interception effect on high-valent ions in the multi-element solution, and can realize the extraction of lithium ions in the lithium slag leachate.

[0118] It should be noted that when numerical ranges are mentioned in the present invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints may be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes preferred embodiments. Although preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they understand the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0119] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for preparing a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin, characterized in that: The following steps are involved: The amine compound, amino acid and γ-cyclodextrin are dissolved in a solvent and mixed, and the γ-cyclodextrin coats the amino acid to form a non-covalent inclusion complex, thereby obtaining an aqueous composite solution; The aqueous composite solution is placed on the surface of the base film, and the cyano groups in the base film and the amino groups in the aqueous composite solution undergo addition reaction, thereby in-situ deposition to obtain a primary film; placing an organic phase solution of an acyl chloride compound on the surface of a primary membrane to carry out an interfacial polymerization reaction to obtain a composite nanofiltration membrane precursor, and heat-treating the composite nanofiltration membrane precursor at 50°C to 60°C to graft a non-covalent inclusion compound onto the composite nanofiltration membrane to obtain a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin; The mass ratio of the amine compound, the amino acid and the gamma-cyclodextrin is 1:0.02-0.05:0.02-0.05; the amino acid is selected from one of the basic amino acids; The amine compound is polyethyleneimine, and the base film is polyacrylonitrile film.

2. The method for preparing a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin according to claim 1, characterized in that: The weight percentage of the amine compound in the solvent is 0.5% to 1.5%, and the solvent is water; the weight percentage of the amino acid in the solvent is 0.05% to 0.15%.

3. The method for preparing a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin according to claim 1, characterized in that: The in-situ deposition time is 5 min to 10 min.

4. The method for preparing a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin according to claim 1, characterized in that: The organic phase solution of the acyl chloride compound is prepared by dissolving 1,3,5-benzenetricarboxylic acid chloride in n-hexane, with the mass volume ratio of 1,3,5-benzenetricarboxylic acid chloride to n-hexane being 0.01 g: 2 mL to 50 mL.

5. The method for preparing a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin according to claim 1, characterized in that: The time of interfacial polymerization reaction is 5min~10min.

6. The method for preparing a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin according to claim 1, characterized in that: The heat treatment time is 10min~15min.

7. The method for preparing a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin according to claim 1, characterized in that: During the preparation of the aqueous composite solution, the amino acid is first dissolved in a solvent, and then gamma-cyclodextrin and an amine compound are added.

8. A composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin obtained by the preparation method according to any one of claims 1 to 7.

9. Use of the composite nanofiltration membrane controlled by amino acid-modified γ-cyclodextrin according to claim 8 for lithium separation in a lithium-containing solution.

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