Composite nanofiltration membrane regulated and controlled by amino acid modified gamma-cyclodextrin as well as preparation method and application of composite nanofiltration membrane

Abstract

The invention belongs to the technical field of nanofiltration membrane preparation, and particularly relates to an amino acid modified gamma-cyclodextrin regulated composite nanofiltration membrane as well as a preparation method and application thereof. Comprising the following steps: dissolving an amine compound, amino acid and gamma-cyclodextrin in a solvent, and mixing to obtain a water-phase composite solution; placing the water-phase composite solution on the surface of the base membrane, and performing in-situ deposition to obtain a primary membrane; placing an acyl chloride compound organic phase solution on the surface of the primary membrane, performing interfacial polymerization to obtain a composite nanofiltration membrane precursor, and performing heat treatment to obtain the amino acid modified gamma-cyclodextrin regulated composite nanofiltration membrane. A polyacrylonitrile membrane is used as a substrate, amino acid, gamma-cyclodextrin and polyethyleneimine are coupled to obtain a water-phase composite solution, the water-phase composite solution reacts with 1, 3, 5-benzoyl chloride by adopting an interfacial polymerization method, and the obtained polyacrylonitrile nanofiltration membrane has excellent rejection rate of metal cations with different valence states and specific separation performance and can be used for preparing a high-performance membrane. And the method has a wide prospect in the aspects of resource recycling and reutilization of the lithium slag.

Description

Technical Field

[0001] The invention belongs to the technical field of nanofiltration membrane preparation, and specifically 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 stock of lithium slag generated during the processing of lithium ore has increased dramatically, and its resource utilization has received widespread attention. At present, the total stock of lithium slag in my country has exceeded 10 million tons. The large amount of lithium slag has brought challenges to environmental supervision and also raised the need for proper disposal of solid waste. By separating and extracting high-priced lithium elements in lithium slag, it can not only achieve the recycling of resources, but also provide more lithium resources for the lithium battery industry, alleviate the tight supply of lithium resources in my country, and support the sustainable development of the new energy industry. At present, the treatment of lithium slag is mostly landfill or as a low-cost building material raw material. The cost of treatment is high and the effect is limited. Therefore, the scientific disposal and comprehensive utilization of lithium slag has become a bottleneck that needs to be solved in the development of the lithium battery new energy industry.

[0003] Membrane separation technology is a separation and purification technology widely used in industrial and scientific fields. This technology is widely used in the fields of seawater desalination and wastewater treatment. Among them, nanofiltration is a pressure-driven membrane separation process between ultrafiltration and reverse osmosis. It is named because its membrane pore size is about 1nm. It is a membrane separation process driven by pressure difference. Applying a certain pressure difference on both sides of the membrane can make part of the solvent and components smaller than the membrane pore size pass through the membrane, and particles, macromolecules, salts, etc. larger than the membrane pore size are intercepted by the membrane to achieve the purpose of separation. In addition, by using the Donnan effect, dielectric repulsion and steric hindrance mechanism, nanofiltration membranes have different selectivity for ions of different valence states, and the retention rate of divalent and multivalent ions is higher than that of monovalent ions, so it can be used to separate multivalent ions in lithium slag leachate.

[0004] The main problems faced by nanofiltration membranes are flux, ion retention performance, ion selectivity and anti-pollution performance. Traditional commercial nanofiltration membranes are usually negatively charged, and the removal rate of metal cations is relatively low. They cannot effectively separate metal cations of different valence states. Polyacrylonitrile nanofiltration membranes modified only by ordinary polyethyleneimine have certain limitations in separation selectivity, performance stability and anti-pollution 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 regulating interfacial polymerization by introducing positively charged monomers or nanomaterials into the aqueous phase 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] In order to solve the above problems, the present invention provides a composite nanofiltration membrane regulated by amino acid modified γ-cyclodextrin and its preparation method and application. The composite nanofiltration membrane uses amino acid and cyclodextrin as additives and is introduced into a polyethyleneimine aqueous phase solution. The amino acid and cyclodextrin as additives not only regulate the process of interfacial polymerization but also participate in interfacial polymerization as monomers. The prepared polyacrylonitrile nanofiltration membrane has excellent metal cation rejection rate and specific separation performance of different valence states. The preparation method is simple, very friendly to the environment and ecology, and can enhance the anti-microbial pollution performance 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, and the gamma-cyclodextrin coats the amino acid to form a non-covalent inclusion complex to obtain an aqueous phase composite solution.

[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, and the primary film is deposited in situ.

[0010] An organic phase solution of acyl chloride compounds 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 compounds 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 amino acid-modified γ-cyclodextrin onto the composite nanofiltration membrane to obtain a composite nanofiltration membrane regulated by 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, and the mass volume ratio of 1,3,5-benzenetricarboxylic acid chloride to n-hexane is 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 an 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] The 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 solution.

[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 to interact with amino acids to form a non-covalent inclusion complex. The non-covalent inclusion complex and the amine compound 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 group in the base membrane and the amino group in the aqueous composite solution undergo an addition reaction to obtain a primary membrane 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 group in the primary membrane and the acyl chloride group in the organic phase solution of the acyl chloride compound undergo a nucleophilic addition reaction. During the interfacial polymerization, the non-covalent inclusion complex also participates in the interfacial polymerization as a monomer to modify the polyacrylonitrile nanofiltration membrane, and positively charged amino acids 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 on the surface of the composite nanofiltration membrane, which has excellent retention rate of metal cations in different valence states 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 green and environmentally friendly, and provides 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 in different valence states 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 The microscopic morphology 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 changes in the 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 for different amounts of amino acids added in Examples 1 to 5, and b is a graph showing the change in salt retention performance for 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 simulated lithium slag leaching solution of the composite nanofiltration membrane of Example 1 of the present invention. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are 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 specifically stated, 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] The main problems faced by nanofiltration membranes are flux, ion retention performance, ion selectivity and anti-pollution performance. Traditional commercial nanofiltration membranes are usually negatively charged, and the removal rate of metal cations is relatively low. They cannot effectively separate metal cations of different valence states. Polyacrylonitrile nanofiltration membranes modified only by ordinary polyethyleneimine have certain limitations in separation selectivity, performance stability and anti-pollution ability. It is necessary to solve these problems through technological innovation and modification methods to improve their reliability in practical applications. In existing research, the modification method of introducing positively charged quaternary ammonium salts or Mxene nanosheets into the aqueous phase to regulate interfacial polymerization has attracted widespread attention. However, these materials generally have problems such as high price, complex synthesis process, and easy to cause 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. The γ-cyclodextrin coats the amino acid to form a non-covalent inclusion complex, thereby obtaining 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, and in-situ deposition is performed to obtain a primary film.

[0035] S3. Place an organic phase solution of acyl chloride compounds 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 groups in the primary membrane and the acyl chloride groups in the organic phase solution of acyl chloride compounds. 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, and obtain a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin.

[0036] The solvent in the aqueous phase 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. It plays an important role as a main body in the inclusion complex of non-covalent interaction. Since cyclodextrin has a hydrophobic inner cavity and a hydrophilic outer edge, it can interact with amino acids to form a non-covalent inclusion complex. The non-covalent inclusion complex and the amine compound 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 an addition reaction occurs between the cyano group in the base membrane and the amino group in the aqueous composite solution, 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 for interfacial polymerization. A nucleophilic addition reaction occurs between the amino group in the primary membrane and the acyl chloride group in the organic phase solution of the acyl chloride compound. During the interfacial polymerization, the non-covalent inclusion complex 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, so as to achieve the purpose of highly selective separation of high-valent cations. The prepared polyacrylonitrile nanofiltration membrane has excellent rejection rate of metal cations in different valence states and specific separation performance. The invention introduces amino acids into the membrane material to improve the hydrophilicity of the membrane, enhance its anti-pollution ability, and improve the separation selectivity. Based on this, a highly selective polyacrylonitrile nanofiltration membrane with antibacterial properties and high flux is developed. The composite nanofiltration membrane prepared by the invention is low in cost and environmentally friendly, and provides good technical guidance for the preparation of high-performance composite nanofiltration membranes. The composite nanofiltration membrane prepared by the method has excellent metal cation rejection rates of different valence states and specific separation performance. It has broad prospects in the resource recovery and reuse of lithium slag.

[0037] In some specific embodiments, the mass ratio of the amine compound, the amino acid and the γ-cyclodextrin is 1: 0.02-0.05: 0.02-0.05. The cyclodextrin and the amino acid used in the present invention are both green natural materials. The nanofiltration membrane modified by amino acid-modified γ-cyclodextrin is very friendly to the environment and ecology, and can enhance the anti-microbial pollution 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 film is a polyacrylonitrile film, and the in-situ deposition time is 5 minutes to 10 minutes. The purpose of in-situ deposition is to evenly disperse the non-covalent inclusion compound on the surface of the polyacrylonitrile film base film 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 film is removed using a silica gel roller, and the residual aqueous solution on the surface of the polyacrylonitrile film is removed by drying for 5 minutes to obtain a primary film.

[0040] In some specific embodiments, the organic phase solution of the acyl chloride compound is 1,3,5-benzenetricarboxylic acid chloride dissolved in n-hexane, and the mass volume ratio of 1,3,5-benzenetricarboxylic acid chloride to n-hexane is 0.01 g: 2 mL to 50 mL. It should be noted that the present invention adopts a traditional interfacial polymerization method, and 1,3,5-benzenetricarboxylic acid chloride and polyethyleneimine undergo interfacial polymerization 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 minutes to 15 minutes. During the heat treatment process, the amino acids and cyclodextrin in the non-covalent inclusion complex not only regulate the process of interfacial polymerization but also participate in interfacial polymerization as monomers, modify the polyacrylonitrile nanofiltration membrane, and graft positively charged amino acids on the membrane surface to achieve the purpose of highly selective separation of high-valent cations. The prepared polyacrylonitrile nanofiltration membrane has excellent metal cation rejection rate and specific separation performance 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 an 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 first dissolved and then the γ-cyclodextrin is dissolved, because γ-cyclodextrin has a large cavity and good water solubility, and the amino acid molecules are included to form a stable complex.

[0044] The present invention provides a composite nanofiltration membrane regulated by amino acid-modified gamma-cyclodextrin obtained by the above preparation method. The composite nanofiltration membrane has positively charged amino acids grafted on its surface, and has excellent metal cation retention rate and specific separation performance in different valence states.

[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 invention is further described below 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 polyethyleneimine, 0.04 g amino acid and 0.03 g γ-cyclodextrin, 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, dissolve it in 40 mL 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 make it evenly dispersed on the surface of the polyacrylonitrile membrane, and deposit it in situ at room temperature for 5 minutes. Then pour out the aqueous composite solution, use a silica gel roller to remove the residual aqueous composite solution on the surface of the polyacrylonitrile membrane, and 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, and let the interfacial polymerization reaction stand at room temperature for 5 minutes. 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, and 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, dissolve the amino acid in 40 mL deionized water, then add γ-cyclodextrin and polyethyleneimine in sequence, mix well, and form a polyethyleneimine aqueous phase composite solution; weigh 0.0264 g 1,3,5-benzenetricarboxylic acid chloride, dissolve it in 40 mL n-hexane, and 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 make it evenly dispersed on the surface of the polyacrylonitrile membrane, and deposit it in situ at room temperature for 5 minutes. Then pour out the aqueous composite solution, use a silica gel roller to remove the residual aqueous composite solution on the surface of the polyacrylonitrile membrane, and 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, and dry it for 5 minutes to remove the residual composite organic phase solution on the surface of the primary membrane 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.

[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, dissolve the amino acid in 40 mL deionized water, then add γ-cyclodextrin and polyethyleneimine in sequence, mix well, and form a polyethyleneimine aqueous phase composite solution; weigh 0.0264 g 1,3,5-benzenetricarboxylic acid chloride, dissolve it in 40 mL n-hexane, and 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 make it evenly dispersed on the surface of the polyacrylonitrile membrane, and deposit it in situ at room temperature for 5 minutes. Then pour out the aqueous composite solution, use a silica gel roller to remove the residual aqueous composite solution on the surface of the polyacrylonitrile membrane, and 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, and let the interfacial polymerization reaction stand at room temperature for 5 minutes. 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, and 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, dissolve the amino acid in 40 mL deionized water, then add γ-cyclodextrin and polyethyleneimine in sequence, mix well, and form a polyethyleneimine aqueous phase composite solution; weigh 0.0264 g 1,3,5-benzenetricarboxylic acid chloride, dissolve it in 40 mL n-hexane, and 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 make it evenly dispersed on the surface of the polyacrylonitrile membrane, and deposit it in situ at room temperature for 5 minutes. Then pour out the aqueous composite solution, use a silica gel roller to remove the residual aqueous composite solution on the surface of the polyacrylonitrile membrane, and 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 on the surface of the primary membrane to make it evenly dispersed 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, 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, 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 make it evenly dispersed on the surface of the polyacrylonitrile membrane, and deposit it in situ at room temperature for 5 minutes. Then pour out the aqueous composite solution, use a silica gel roller to remove the residual aqueous composite solution on the surface of the polyacrylonitrile membrane, and 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 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, and 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 polyethyleneimine, 0.04 g amino acid and 0.01 g γ-cyclodextrin, dissolve the amino acid in 40 mL deionized water, then add γ-cyclodextrin and polyethyleneimine in sequence, mix well, and form a polyethyleneimine aqueous phase composite solution; weigh 0.0264 g 1,3,5-benzenetricarboxylic acid chloride, dissolve it in 40 mL n-hexane, and 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 make it evenly dispersed on the surface of the polyacrylonitrile membrane, and deposit it in situ at room temperature for 5 minutes. Then pour out the aqueous composite solution, use a silica gel roller to remove the residual aqueous composite solution on the surface of the polyacrylonitrile membrane, and 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 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, and 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 polyethyleneimine, 0.04 g amino acid and 0.02 g γ-cyclodextrin, dissolve the amino acid in 40 mL deionized water, then add γ-cyclodextrin and polyethyleneimine in sequence, mix well, and form a polyethyleneimine aqueous phase composite solution; weigh 0.0264 g 1,3,5-benzenetricarboxylic acid chloride, dissolve it in 40 mL n-hexane, and 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 make it evenly dispersed on the surface of the polyacrylonitrile membrane, and deposit it in situ at room temperature for 5 minutes. Then pour out the aqueous composite solution, use a silica gel roller to remove the residual aqueous composite solution on the surface of the polyacrylonitrile membrane, and 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 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, and 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 polyethyleneimine, 0.04 g amino acid and 0.04 g γ-cyclodextrin, dissolve the amino acid in 40 mL deionized water, then add γ-cyclodextrin and polyethyleneimine in sequence, mix well, and form a polyethyleneimine aqueous phase composite solution; weigh 0.0264 g 1,3,5-benzenetricarboxylic acid chloride, dissolve it in 40 mL n-hexane, and 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 make it evenly dispersed on the surface of the polyacrylonitrile membrane, and deposit it in situ at room temperature for 5 minutes. Then pour out the aqueous composite solution, use a silica gel roller to remove the residual aqueous composite solution on the surface of the polyacrylonitrile membrane, and 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 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, and 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 polyethyleneimine, 0.04 g amino acid and 0.05 g γ-cyclodextrin, 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, dissolve it in 40 mL 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 make it evenly dispersed on the surface of the polyacrylonitrile membrane, and deposit it in situ at room temperature for 5 minutes. Then pour out the aqueous composite solution, use a silica gel roller to remove the residual aqueous composite solution on the surface of the polyacrylonitrile membrane, and 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 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 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 silica gel 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 polyethyleneimine and 0.04 g amino acid and dissolve them in 40 mL deionized water 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.

[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 silica gel 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 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 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 polyethyleneimine and 0.05 g γ-cyclodextrin, dissolve them in 40 mL deionized water to form a polyethyleneimine aqueous phase composite solution; weigh 0.0264 g 1,3,5-benzenetricarboxylic acid chloride, dissolve it in 40 mL 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 silica gel 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 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 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 composite nanofiltration membranes prepared in Examples 1 to 9 had similar structures and similar effects. The composite nanofiltration membrane prepared in Example 1 was used to illustrate the morphology and structure. 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 polymerization layer of the prepared nanofiltration membrane has been formed on the PAN-based membrane. -1 The stretching vibration peak of the amino group appears at 1644 cm -1 ~1543cm -1 The amide group peak was significantly enhanced, which 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. 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 PEI-TMC NF membrane has large surface voids and a sparse structure; the His NF membrane has significantly fewer surface voids and is relatively smooth; the γ-CD NF membrane has fewer surface voids, but is relatively loose and has a rough surface; and it can be clearly seen from the His-γ-CD NF membrane surface that the addition of amino acids and cyclodextrin causes the membrane surface to become very dense and smooth.

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

[0111] Step 1, the composite nanofiltration membranes prepared in Examples 1 to 9 and Comparative Examples 1 to 3 are cut into circular membrane pieces with a diameter of d=4 cm, and a laboratory-prepared salt solution is used to perform a test 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, and the test conditions are 6 Bar and 25±1°C.

[0113] Step 3: Use deionized water to stabilize for 1 hour before the experiment, and then pass it into the laboratory to prepare a salt solution for the test.

[0114] Step 4, start sampling after the solution has completely flowed out. Three sets of parallel samples should be made, with 2 ml of sample 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 The salt retention performance change diagram of the composite nanofiltration membrane prepared in Examples 1 to 9 of the present invention, wherein: Figure 3 a is a graph showing the change in salt retention performance of different amino acid addition amounts in Examples 1 to 5, and b is a graph showing the change in salt retention performance of different γ-cyclodextrin addition amounts in Examples 1, 6 to 9. All examples adopt the same conditions, the total concentration of the salt solution is 2000ppm, the ratio of magnesium to lithium ions is 30:1, the test pressure is 6Bar, and the membrane area is 3.14cm 2 , the test temperature is 25±1℃. Figure 3 As shown, by comparison, it is shown that when the added amounts of amino acid and γ-cyclodextrin are 0.04 g and 0.03 g respectively, the modified membrane has the best retention effect.

[0116] Figure 4 The salt retention performance comparison chart of the nanofiltration membrane prepared by Example 1 of the present invention and Comparative Examples 1 to 3. Comparative Examples 1 to 3 all adopt the same conditions, the total concentration of the salt solution is 2000ppm, the ratio of magnesium to lithium ions is 30:1, the test pressure is 6Bar, and the membrane area is 3.14cm 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 5The salt retention performance of the composite nanofiltration membrane of Example 1 of the present invention in the simulated lithium slag leachate is shown in Figure 1. The salt retention performance of the simulated lithium slag leachate is as follows: the concentration ratio of lithium, magnesium, manganese, calcium, and sodium ions is 1:10:4:20:20, the total concentration of the salt solution 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, it was found through testing that the nanofiltration membrane prepared in Example 1 has an excellent interception effect on high-valent ions in a multi-element solution, and can realize the extraction of lithium ions in a lithium slag leachate.

[0118] It should be noted that when the present invention involves a numerical range, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can 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 a preferred embodiment. Although the 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 know the basic creative concept. Therefore, the attached 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 can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

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; An organic phase solution of an acyl chloride compound is placed on the surface of a primary membrane to perform an interfacial polymerization reaction to obtain a composite nanofiltration membrane precursor. The composite nanofiltration membrane precursor is heat-treated at 50°C to 60°C to graft a non-covalent inclusion complex onto the composite nanofiltration membrane to obtain a composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin.

2. The method for preparing the composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin according to claim 1, characterized in that: The mass ratio of the amine compound, the amino acid and gamma-cyclodextrin is 1:0.02-0.05:0.02-0.

05.

3. The method for preparing the 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%, 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.

4. The method for preparing the composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin according to claim 1, characterized in that: The base film is a polyacrylonitrile film, and the in-situ deposition time is 5 minutes to 10 minutes.

5. The method for preparing the 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.

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

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

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

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

10. Use of the composite nanofiltration membrane regulated by amino acid-modified γ-cyclodextrin as claimed in claim 9 for lithium separation in a lithium-containing solution.

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