Separation membrane, method for manufacturing the same, and use

Abstract

The present invention relates to a separation membrane, its manufacturing method, and its use in separating magnesium and lithium. The separation membrane comprises a base layer, a porous support layer, a polyamide layer, and a modification layer in this order, and the crosslinked polymer forming the modification layer comprises a structural unit derived from a polyphenol and a structural unit derived from a polyamine, and at least a part of the structural unit derived from a polyphenol is also connected to the polyamide layer through the ortho-position of the phenolic hydroxyl group, and the separation membrane has a pore size of 0.1-0.5 nm and a surface Zeta potential of -5 mV-30 mV. The manufacturing method includes the steps of manufacturing a porous support layer, a polyamide layer, and a modification layer in this order on a base layer, and the method of manufacturing the modification layer includes the steps of: first contacting the polyamide layer side with a polyphenol solution while flowing a polyphenol solution under a first pressure; and second contacting the polyamide layer side with a polyamine solution while flowing a polyamine solution under a second pressure to complete the self-assembly reaction.

Description

Detailed description of the invention

[0001] [Cross-reference of related applications] This application claims the benefits of Chinese application 202210555981.0, filed on 20 May 2022, the contents of which are incorporated herein by reference.

[0002] [Technical field] This invention relates to the field of membranes, and more specifically to separation membranes, methods for producing the same, and uses thereof.

[0003] [Background technology] With the spread of new energy vehicles, the demand for lithium energy is gradually increasing. In China, the majority of lithium resources are contained in the saltwater of salt lakes. Salt lake water contains not only lithium ions but also large amounts of magnesium and sodium ions, making it technically difficult to extract pure lithium resources from salt lakes. Researchers have developed a series of methods and processes to obtain lithium resources, including precipitation, solar ponding, extraction, calcination, membrane separation, and adsorption. Among these, membrane separation and adsorption are the most widely studied.

[0004] However, existing commercially available nanofiltration membranes are not designed to separate magnesium and lithium, and their separation efficiency between magnesium and lithium ions is very low, with magnesium-lithium separation factors typically below 5, making them unsuitable for extracting lithium from salt lakes. Therefore, achieving efficient separation of magnesium and lithium still presents many challenges.

[0005] [Overview of the prefecture] [Problems the invention aims to solve] The object of the present invention is to provide a separation membrane, its manufacturing method, and its use, which have a high density and a high surface electrode potential (Zeta potential), can effectively block magnesium ions when used for separating magnesium and lithium, achieve a high magnesium-lithium separation efficiency, have a large water flux, and a high treatment efficiency, in order to solve the above problems existing in the prior art.

[0006] [Means for Solving the Problems] To achieve the above object, the first aspect of the present invention is to include a base material layer, a porous support layer, a polyamide layer, and a modification layer in this order, the cross-linked polymer forming the modification layer includes a structural unit derived from polyphenol and a structural unit derived from polyamine, and at least a part of the structural unit derived from polyphenol is also connected to the polyamide layer through the ortho position of the phenolic hydroxyl group, to provide a separation membrane with a pore diameter of 0.1 - 0.5 nm and a surface Zeta potential of -5 mV to 30 mV.

[0007] The second aspect of the present invention is to include the steps of manufacturing a porous support layer, a polyamide layer, and a modification layer in this order on a base material layer, the method for manufacturing the modification layer includes performing a first contact between the polyamide layer side of the material including the base material layer, the porous support layer, and the polyamide layer and the polyphenol solution while flowing the polyphenol solution under a first pressure, and then performing a second contact between the polyamide layer side of the material and the polyamine solution while flowing the polyamine solution under a second pressure to complete a self-assembly reaction, and providing a manufacturing method of a separation membrane characterized by this.

[0008] The third aspect of the present invention is to provide a separation membrane manufactured by the above method.

[0009] The fourth aspect of the present invention is to provide the use of the separation membrane according to the first aspect or the third aspect in the separation of magnesium and lithium

[0010] [Advantages of the Invention] The separation membrane according to the present invention has high density and a high surface electrode potential (Zeta potential), and when used for separating magnesium and lithium, it can effectively block magnesium ions while allowing lithium ions to pass through as much as possible, thereby achieving high magnesium-lithium separation efficiency, and also has a large water pass-through rate, resulting in high processing efficiency.

[0011] In the method for producing a separation membrane according to the present invention, a polyphenol solution and a polyamine solution are flowed under first and second pressures, respectively, while a self-assembly reaction of polyamines and polyphenols occurs on a polyamide layer to obtain a separation membrane containing a modified layer. The separation membrane produced thereby has high density and a high surface electrode potential (Zeta potential). When used for the separation of magnesium and lithium, it can effectively block magnesium ions while allowing lithium ions to pass through as much as possible, thereby achieving high magnesium-lithium separation efficiency. Furthermore, it has a large water pass-through rate and high processing efficiency. Moreover, this production method is simple and has the potential for industrialization.

[0012] [Brief description of the drawing] [Figure 1] Infrared spectra of the separation membranes produced in Example 1 and Comparative Examples 1-2 of the present invention. [Figure 2] This curve shows the change in the surface Zeta potential of the separation membrane with respect to the number of self-assembly cycles. [Figure 3] This curve shows the change in the surface Zeta potential of the separation membrane in response to the self-assembly pressure (first pressure / second pressure). [Figure 4] This curve shows the change in the contact angle of the separation membrane in response to the self-assembly pressure (first pressure / second pressure). [Figure 5] This curve shows the change in the contact angle of the separation membrane with respect to the number of self-assembly cycles. [Figure 6] Cross-sectional SEM images of the separation membranes of Comparative Example 1 (Figure 6a) and Example 10 (Figure 6b). [Figure 7] XPS nitrogen element maps of the separation membranes produced in Example 1 and Comparative Example 1.

[0013] [Modes for carrying out the invention] The endpoints of the ranges and any values ​​disclosed herein are not limited to precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to them. With respect to numerical ranges, one or more new numerical ranges can be obtained by combining the endpoint values ​​of each range, the endpoint values ​​of each range and individual dot values, and individual dot values, and these numerical ranges should be considered as specifically disclosed herein.

[0014] In the first embodiment, the present invention comprises a base layer, a porous support layer, a polyamide layer, and a modification layer in this order. The crosslinked polymer forming the modified layer comprises structural units derived from polyphenols and structural units derived from polyamines, and at least a portion of the structural units derived from polyphenols are also connected to the polyamide layer through the ortho position of the phenolic hydroxyl group. The present invention provides a separation membrane with a pore size of 0.1 to 0.5 nm and a surface Zeta potential of -5 mV to 30 mV.

[0015] The inventors have found through research that by including the aforementioned modification layer in the separation membrane, the pore size of the separation membrane can be set to the range of pore size described in the present invention, and the surface Zeta potential of the separation membrane can be set to the range of surface Zeta potential described in the present invention. The separation membrane has high density and a high surface electrode potential, and when used for the separation of lithium and magnesium, it is clear that it makes it easier to block divalent magnesium ions, making it difficult for magnesium ions in the liquid to pass through the separation membrane, while allowing monovalent lithium ions to pass through as much as possible, thereby achieving high magnesium-lithium separation efficiency. Furthermore, due to the combined action of the above-mentioned multiple layers, the separation membrane has a large water pass-through rate, and when used for the separation of magnesium and lithium in a liquid, the processing efficiency is increased.

[0016] In this invention, the pore size of the separation membrane is measured by the polyethylene glycol (PEG) solute transfer method, and the detailed steps are as follows.

[0017] (1) Test the rejection rate of the separation membrane for PEG of various molecular sizes.

[0018] (2) Linear fitting is performed on the PEG size and rejection rate in a log-stochastic coordinate system, and the PEG size corresponding to the 50% rejection rate is taken as the average pore size of the separation membrane.

[0019] In this invention, the surface Zeta potential of the separation membrane is measured by a potential analyzer.

[0020] Furthermore, the separation membrane has a pore size of 0.15 to 0.3 nm and a surface Zeta potential of 1 mV to 10 mV.

[0021] According to the present invention, the modification layer contains a structural unit represented by formula I. [ka]

[0022] In this invention, the inventors have conducted research and, as a result of testing the nitrogen element in the modification layer of the separation membrane using XPS, found that the modification layer of the separation membrane according to the present invention contains structural units represented by formula I, that is, the modification layer contains π-π units formed by a benzene ring-nitrogen atom-benzene ring. * We discovered the presence of electron-conjugated structural units. It was further revealed that at least some of the polyphenol-derived structural units in the modified layer undergo crosslinking reactions with polyamine-derived structural units and / or nitrogen atoms from the polyamide layer via the ortho position of the phenolic hydroxyl group, thereby further reducing the pore size of the separation membrane containing the modified layer, further improving the density of the separation membrane, and further increasing the magnesium-lithium separation efficiency when the separation membrane is used for the separation of magnesium and lithium.

[0023] According to the present invention, the content of the polyphenol-derived structural units on the film surface is 2 × 10 -3 ~5×10 -2 mg / cm 2 Therefore, the content of the polyamine-derived structural units on the film surface is 1 × 10⁻⁶ -3~2.5×10 -2 mg / cm 2 is

[0024] In the present invention, in the separation membrane, the content of the structural unit derived from polyphenol and the structural unit derived from polyamine on the membrane surface of the separation membrane is measured by the following steps.

[0025] After drying a membrane including a base material layer, a porous support layer, and a polyamide layer in a vacuum oven at 60 °C for 24 h, weigh the mass of the membrane and denote it as M n (mg). Place the membrane in a membrane cell, put an aqueous polyphenol solution with a predetermined concentration in the supply tank, cycle it for a certain time under predetermined conditions, then take out the membrane sheet, thoroughly wash the surface of the membrane sheet with deionized water, dry it at 60 °C for 24 h, and then weigh the mass of the membrane and denote it as W n (mg). Next, place the membrane in a membrane cell, put an aqueous polyamine solution with a predetermined concentration in the supply tank, cycle it for a certain time under predetermined conditions, then take out the membrane sheet, thoroughly wash the surface of the membrane sheet with deionized water, dry it at 60 °C for 24 h, and then weigh the mass of the membrane and denote it as N n (mg). Each time the separation membrane is modified, the content P n of polyphenol and the content T n of polyamine on the membrane surface are calculated by the following formulas respectively.

Equation

[0026] Here, when n is greater than 1, M n = N n-1 ; when n = 1, M n is the initial mass of the polyamide membrane sheet.

Equation

[0027] Let the total content of polyphenol on the surface after self-assembly of the separation membrane be ΣPn (n ≧ 1), and the total content of polyamine on the surface be ΣTn (n ≧ 1). Here, n is the number of self-assembly cycles, and S is the effective membrane area (in cm²). 2 )

[0028] In this invention, the inventors have found through research that when the content of polyphenol-derived structural units and polyamine-derived structural units on the membrane surface satisfies the above range, the separation membrane has appropriate density and thickness. This ensures a high magnesium-lithium separation coefficient and water pass-through rate of the separation membrane.

[0029] Furthermore, the content of the polyphenol-derived structural units on the membrane surface is 2.5 × 10⁻⁶. -3 ~5×10 -2 mg / cm 2 Therefore, the content of the polyamine-derived structural units on the film surface is 4 × 10 -3 ~2×10 -2 mg / cm 2 That is the case.

[0030] According to the present invention, the content of N atoms in the modified layer is 13 to 20 at.%.

[0031] In this invention, the N atom content in the modified layer is measured by an X-ray photoelectron spectroscopy analyzer.

[0032] In this invention, when the N atom content in the modified layer satisfies the above range, the separation membrane has a high surface electrode potential, excellent hydrophilicity, and when used for separating magnesium and lithium, it exhibits high magnesium-lithium separation efficiency and a large water pass-through rate.

[0033] Furthermore, the N atom content in the modified layer is 13.5 to 18.5 at.%.

[0034] According to the present invention, the contact angle of the separation membrane is 20 to 60°.

[0035] In this invention, the contact angle of the separation membrane is measured by the following method. The surface contact angle of the composite membrane sample is measured using the static droplet method with a DSA100 surface contact angle analyzer manufactured by KRUSS GmbH in Germany. Before measurement, the sample is dried in a 60°C vacuum oven for 30 minutes to remove moisture from its surface and interior. Then, the dried membrane is attached to a flat glass slide with double-sided tape, and the volume of each water droplet during the test is set to 2 μL. The test is performed immediately 3 seconds after dropping the water droplet onto the surface of the membrane, and the average value of multiple measurements is obtained to determine the final contact angle.

[0036] In this invention, the separation membrane has a contact angle within the range described in the invention, and as a result, the separation membrane has excellent hydrophilicity and water permeability.

[0037] Furthermore, the contact angle of the separation membrane is 20 to 40°.

[0038] According to the present invention, preferably, the thickness of the separation membrane is 100 to 200 μm.

[0039] According to the present invention, preferably, the thickness of the substrate layer is 30 to 150 μm, preferably 50 to 120 μm.

[0040] According to the present invention, preferably, the thickness of the porous support layer is 10 to 100 μm, preferably 30 to 60 μm.

[0041] According to the present invention, preferably the thickness of the polyamide layer is 10 to 500 nm, more preferably 50 to 150 nm.

[0042] According to the present invention, the thickness of the modification layer is preferably 1 to 200 nm, more preferably 10 to 60 nm.

[0043] In this invention, the thicknesses of the separation membrane, porous support layer, and polyamide layer are measured using a spiral micrometer and a scanning electron microscope, and the thickness of the modification layer is obtained by subtracting the thicknesses of the substrate layer, porous support layer, and polyamide layer from the thickness of the separation membrane. Here, the thickness of the substrate layer is the thickness measured before applying the solution of the porous support layer material.

[0044] As a result of their research, the inventors have found that within the thickness range of each layer described above, the layers work well together to give the separation membrane a small pore size and a high Zeta potential. When this separation membrane is used for separating magnesium and lithium, it achieves both high magnesium-lithium separation efficiency and a large water pass-through rate.

[0045] According to the present invention, the material of the base layer is not particularly limited, but may be a material commonly used in the field, having a certain strength, applicable to nanofiltration and reverse osmosis, and providing support. Preferably, the material of the base layer is at least one selected from polyester nonwoven fabric, polyethylene nonwoven fabric, and polypropylene nonwoven fabric.

[0046] According to the present invention, the material of the porous support layer is not particularly limited, but may be a material commonly used in the field that exhibits a certain degree of support and forms a porous structure. More preferably, the material of the porous support layer is at least one selected from polyethersulfone, polysulfone, polyaromatic ether, polybenzimidazole, polyetherketone, polyetheretherketone, polyacrylonitrile, polyvinylidene fluoride, and polyaryletherketone. The porous structure in the porous support layer facilitates the passage of liquid. The number-average molecular weight of the porous support layer material may be 50,000 to 100,000 g / mol.

[0047] According to the present invention, preferably, the polyamide layer is synthesized from a polyamine and a polybasic acid chloride.

[0048] In the present invention, the polyamide layer has an appropriate cross-linked structure, and the amino acids incorporated therein can effectively block divalent magnesium ions.

[0049] Furthermore, the polyamine is at least one selected from polyethyleneimine, triethylenetetramine, tetraethylenepentamine, diethylenetriamine, piperazine, m-phenylenediamine, and p-phenylenediamine, more preferably at least one from polyethyleneimine, piperazine, and polyethylenepolyamine.

[0050] Furthermore, the polybasic acid chloride is at least one selected from trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride, and phthaloyl chloride, more preferably at least one of trimesoyl chloride and terephthaloyl chloride. If there are multiple polybasic acid chlorides, they may be mixed in any proportion, and if the polybasic acid chlorides are trimesoyl chloride and terephthaloyl chloride, the weight ratio of trimesoyl chloride to terephthaloyl chloride may be 1:1 to 10.

[0051] According to the present invention, the modified layer is obtained by a self-assembly reaction between polyphenols and polyamines on a polyamide layer.

[0052] In the present invention, the self-assembly reaction includes the step of first bringing the polyamide layer side of a material comprising a base layer, a porous support layer, and a polyamide layer into contact with the polyphenol solution while flowing the polyphenol solution under a first pressure, and then, while flowing the polyamine solution under a second pressure, bringing the polyamide layer side of the material into contact with the polyamine solution under a second pressure, thereby completing the self-assembly reaction.

[0053] According to the present invention, the polyphenol is one or more selected from tannic acid, tea polyphenols, gallic acid, catechin, lignin, sodium ligninsulfonate, apple polyphenols, grape polyphenols, eriodictyol, naringenin, epicatechin, luteolin, apigenin, kaempferol, myricetin, and genistein, preferably tannic acid and / or tea polyphenols.

[0054] According to the present invention, the polyamine is at least one selected from polyethyleneimine, tetraethylenepentamine, triethylenetetramine, and polyethylenepolyamine.

[0055] According to the present invention, the first pressure and the second pressure are each independently 0.1 to 1.2 MPa.

[0056] In the present invention, when the pressure applied when manufacturing the modified layer satisfies the above range, the separation layer composed of both the modified layer and the polyamide layer has high density, a high content of polyamine-derived structural units in the separation membrane, and further increased hydrophilicity of the separation membrane. Ultimately, the separation membrane exhibits excellent magnesium lithium separation capabilities and water permeability.

[0057] Furthermore, the first pressure and the second pressure are each independently between 0.2 and 1 MPa.

[0058] In the present invention, the polyphenol solution and the polyamine solution are used in amounts such that the mass ratio of polyphenol to polyamine is 0.1 to 10:1.

[0059] In this invention, when the mass ratio of polyphenols to polyamines satisfies the above range, sufficient reaction between polyphenols and polyamines is ensured, and the manufactured separation membrane is ensured to have the pore size required in this invention. In addition, more amino acids remain on the surface of the separation membrane, and as a result, the separation membrane has the high surface Zeta potential and hydrophilicity required in this invention. When the separation membrane is used for separating magnesium and lithium, the rejection rate of divalent magnesium ions is even higher and the water pass-through rate is even greater.

[0060] Furthermore, the polyphenol solution and the polyamine solution are used in amounts such that the mass ratio of polyphenol to polyamine is 0.2 to 6:1, preferably 0.5 to 6:1.

[0061] In the present invention, the concentration of the polyphenol solution is 0.00001 to 1 wt%, preferably 0.0001 to 0.1 wt%.

[0062] In the present invention, the concentration of the polyamine solution is 0.00001 to 1 wt%, preferably 0.0001 to 0.1 wt%.

[0063] In this invention, when the concentrations of the polyphenol solution and the polyamine solution independently satisfy the above range, the manufactured separation membrane has the pore size, surface Zeta potential, and thickness required in this invention, and when used for the separation of magnesium and lithium, it increases the rejection rate against magnesium chloride while maintaining good water permeability.

[0064] In this invention, the temperatures of the first contact and the second contact are independently 10 to 30°C.

[0065] In this invention, when the temperatures of the first and second contacts satisfy the above range, sufficient reaction between polyphenols and polyamines is ensured, the pore size and surface Zeta potential required in this invention are imparted to the manufactured separation membrane, and the magnesium chloride rejection rate and magnesium-lithium separation efficiency when the separation membrane is used for the separation of magnesium and lithium are improved.

[0066] In this invention, the duration of the first contact in a single self-assembly reaction is 1 to 120 minutes.

[0067] In this invention, the duration of the second contact in a single self-assembly reaction is 1 to 120 minutes.

[0068] In this invention, when the first and second contact times in a single self-assembly reaction meet the above range, it not only ensures a sufficient reaction between polyphenols and polyamines, but also appropriately adjusts the density and thickness of the membrane separation layer composed of the polyamide layer and the modified layer, thereby giving the separation membrane produced therein high water permeability and high magnesium lithium separation capability.

[0069] Furthermore, in a single self-assembly reaction, the duration of the first contact is 10 to 60 minutes.

[0070] Furthermore, in a single self-assembly reaction, the duration of the second contact is 10 to 60 minutes.

[0071] In this invention, the inventors have further researched and found that by repeating the following steps and performing self-assembly multiple times according to a method for producing a modified layer on the polyamide layer of a material comprising a substrate layer, a base layer, a porous support layer, and a polyamide layer, a high surface Zeta potential and an even smaller pore size of the separation membrane can be secured, and a high magnesium-lithium separation efficiency can be further secured. Specifically, the number of self-assembly reactions is 1 to 10 times, more preferably 2 to 5 times.

[0072] In one preferred embodiment of the present invention, the water passage rate through the separation membrane is 20 L·m. -2 ·h -1 The above results show that the MgCl2 desalination rate is 99% or higher, and the magnesium-lithium separation coefficient is 70 or higher.

[0073] In a more preferred embodiment of the present invention, the water passage rate through the separation membrane is 20-40 L·m. -2 ·h-1 The MgCl2 desalination rate is over 99%, and the magnesium-lithium separation coefficient is between 100 and 250.

[0074] In a second aspect, the present invention includes the step of manufacturing a porous support layer, a polyamide layer, and a modification layer on a substrate layer in this order. The present invention provides a method for producing a separation membrane, characterized in that, while flowing a polyphenol solution under a first pressure, a first contact is made between the polyamide layer side of a material comprising a base layer, a porous support layer, and a polyamide layer and the polyphenol solution, and then, while flowing a polyamine solution under a second pressure, a second contact is made between the polyamide layer side of the material and the polyamine solution, thereby completing the self-assembly reaction.

[0075] In this invention, polyphenols and polyamines undergo a Michael addition reaction to form a crosslinked structure. The carbon atom in the ortho position of the carbon atom containing the phenolic hydroxyl group on the polyphenol reacts with the polyamine as a reaction site. When the reaction is carried out on the surface of a polyamide layer, the carbon atom in the ortho position of the carbon atom containing the phenolic hydroxyl group on the polyphenol reacts with the amino acid in the polyamide layer as a reaction site.

[0076] In the present invention, a separation membrane is manufactured by a manufacturing method according to a second aspect of the present invention, that is, under first and second pressures, the polyphenol solution and the polyamine solution are flowed while the polyamide layer side of a material including a substrate layer, a porous support layer, and a polyamide layer is sequentially brought into contact with the polyphenol solution and the polyamine solution to react. The polyphenol and polyamine undergo a Michael addition reaction on the surface of the polyamide layer to form a crosslinked structure, and the carbon atoms in the ortho position of carbon atoms where some of the phenolic hydroxyl groups on the polyphenol exist may react with amino acids in the polyamide layer and be connected to the polyamide layer.

[0077] Furthermore, when the polyphenol solution and polyamine solution are kept flowing under the action of the first and second pressures, the resulting separation membrane has a smaller pore size and a higher surface Zeta potential, i.e., a separation membrane as described in the first aspect of the present invention is obtained. Specifically, in the present invention, the self-assembly reaction is carried out in a dynamic environment with a predetermined flow rate, thereby reducing the adsorption of polyphenols or polyamines to the membrane surface and increasing the amount of polyphenols or polyamines bonded to the membrane surface through chemical bonding. As a result, the separation membrane undergoes self-assembly modification, significantly improving its density and increasing its surface Zeta potential.

[0078] The separation membrane produced by the manufacturing method according to the second aspect of the present invention has a pore size within the pore size range described in the present invention and a surface Zeta potential within the surface Zeta potential range described in the present invention. As such, the separation membrane has high density and a high surface electrode potential. When used for the separation of lithium and magnesium, it is clear that it is possible to block divalent magnesium ions, making it difficult for magnesium ions in the liquid to pass through the separation membrane, while allowing monovalent lithium ions to pass through as much as possible, thereby achieving high magnesium-lithium separation efficiency. Furthermore, due to the combined action of the above-mentioned multiple layers, the separation membrane has a large water permeability, and when used for the separation of magnesium and lithium in a liquid, the processing efficiency is increased.

[0079] According to the present invention, the first pressure and the second pressure are each independently 0.1 to 1.2 MPa.

[0080] In the present invention, when the first and second pressures used to manufacture the modified layer independently satisfy the above ranges, the polyphenols and polyamines react more sufficiently, and the resulting separation membrane has the pore size and surface Zeta potential required by the present invention. When used for the separation of magnesium and lithium, it exhibits a high magnesium chloride rejection rate and excellent magnesium-lithium separation efficiency.

[0081] Furthermore, the first pressure and the second pressure are each independently between 0.2 and 1 MPa.

[0082] In the present invention, the self-assembly reaction may be carried out in a cross-flow membrane cell, in which water is circulated into the membrane cell by a water pump, maintaining the water in the membrane cell in a flowing state, and pressure is applied by a pressure regulating valve so that the first and second pressures of the manufacturing process are maintained to satisfy the requirements of the present invention.

[0083] In the present invention, the method for producing the modified layer may be carried out using equipment commonly used in the field, such as a cross-flow membrane cell, which is a simple process and easy to industrialize. Here, when the self-assembly reaction is carried out in a cross-flow membrane cell, for example, after contacting the polyphenol with the material, the polyphenol solution is discharged and the cross-flow membrane cell is repeatedly rinsed with deionized water to wash the polyphenol in the system and also wash the polyphenol on the surface of the material.

[0084] In the present invention, since the solution is continuously supplied to the cell by a pump in a cross-flow membrane cell, the total amount of polyphenols or polyamines in the solution generally exceeds the amount that can adhere to the surface of the membrane and react, thereby ensuring the modified layer required in the present invention. In the present invention, the flow rate of the polyphenol solution and the polyamine solution is not particularly limited, as long as the polyphenol solution and the polyamine solution maintain a flowing state when producing the modified layer. For example, the flow rate of the polyphenol solution or the polyamine solution may be 0.5 to 5 L / min.

[0085] According to the present invention, the polyphenol solution and the polyamine solution are used in amounts such that the mass ratio of polyphenol to polyamine is 0.1 to 10:1.

[0086] In this invention, when the mass ratio of polyphenols to polyamines satisfies the above range, sufficient reaction between polyphenols and polyamines is ensured, and the manufactured separation membrane is ensured to have the pore size required in this invention. In addition, more amino acids remain on the surface of the separation membrane, and as a result, the separation membrane has the high surface Zeta potential and hydrophilicity required in this invention. When the separation membrane is used for separating magnesium and lithium, the rejection rate of divalent magnesium ions is even higher and the water pass-through rate is even greater.

[0087] Furthermore, the polyphenol solution and the polyamine solution are used in amounts such that the mass ratio of polyphenol to polyamine is 0.2 to 6:1, preferably 0.5 to 6:1.

[0088] According to the present invention, the concentration of the polyphenol solution is 0.00001 to 1 wt%, preferably 0.0001 to 0.1 wt%.

[0089] According to the present invention, the concentration of the polyamine solution is 0.00001 to 1 wt%, preferably 0.0001 to 0.1 wt%.

[0090] In this invention, when the concentrations of the polyphenol solution and the polyamine solution independently satisfy the above ranges, the manufactured separation membrane has the pore size, surface Zeta potential, and thickness required in this invention, and when used for the separation of magnesium and lithium, it increases the rejection rate against magnesium chloride while maintaining good water permeability.

[0091] According to the present invention, the temperatures of the first contact and the second contact are independently 10 to 30°C.

[0092] In this invention, when the temperatures of the first and second contacts satisfy the above range, sufficient reaction between polyphenols and polyamines is ensured, the pore size and surface Zeta potential required in this invention are imparted to the manufactured separation membrane, and the magnesium chloride rejection rate and magnesium-lithium separation efficiency when the separation membrane is used for the separation of magnesium and lithium are improved.

[0093] According to the present invention, in a single self-assembly reaction, the duration of the first contact is 1 to 120 minutes.

[0094] According to the present invention, in a single self-assembly reaction, the duration of the second contact is 1 to 120 minutes.

[0095] In this invention, when the first and second contact times in a single self-assembly reaction meet the above range, it not only ensures a sufficient reaction between polyphenols and polyamines, but also appropriately adjusts the density and thickness of the membrane separation layer composed of the polyamide layer and the modified layer, thereby giving the separation membrane produced therein high water permeability and high magnesium lithium separation capability.

[0096] Furthermore, in a single self-assembly reaction, the duration of the first contact is 10 to 60 minutes.

[0097] Furthermore, in a single self-assembly reaction, the duration of the second contact is 10 to 60 minutes.

[0098] In this invention, the inventors have further researched and found that by repeating the following steps and performing self-assembly multiple times according to a method for producing a modified layer on the polyamide layer of a material comprising a substrate layer, a base layer, a porous support layer, and a polyamide layer, a high surface Zeta potential and an even smaller pore size of the separation membrane can be secured, and a high magnesium-lithium separation efficiency can be further secured. Specifically, the number of self-assembly reactions is 1 to 10 times, more preferably 2 to 5 times.

[0099] According to the present invention, the conditions for producing the modified layer include setting the thickness of the modified layer in the separation membrane to 1 to 200 nm, preferably 10 to 60 nm.

[0100] According to the present invention, the polyphenol in the polyphenol solution is one or more selected from tannic acid, tea polyphenol, gallic acid, catechin, lignin, sodium ligninsulfonate, apple polyphenol, grape polyphenol, eriodictyol, naringenin, epicatechin, luteolin, apigenin, kaempferol, myricetin, and genistein, preferably tannic acid and / or tea polyphenol.

[0101] According to the present invention, the polyamine in the polyamine solution is at least one selected from polyethyleneimine, tetraethylenepentamine, triethylenetetramine, and polyethylenepolyamine.

[0102] In the present invention, the method for manufacturing a porous support layer on a substrate layer may be a method commonly used in the art. Preferably, the method for manufacturing a porous support layer includes applying a solution containing the material for the porous support layer onto a substrate layer, performing a phase transition, and obtaining a material containing the substrate layer and the porous support layer.

[0103] In this invention, the specific application method is not particularly limited, but it may be a knife cord.

[0104] According to the present invention, the conditions for the phase transition include immersion in water at 10 to 30°C for 10 to 60 minutes.

[0105] In the present invention, when using the method for manufacturing the porous support layer, when immersed in water, the solvent in the solution containing the porous support layer material gradually separates from the porous support layer, and this phase transition further ensures that a support layer having a porous structure is obtained.

[0106] According to the present invention, the thickness of the substrate layer is preferably 30 to 150 μm, more preferably 50 to 120 μm. The thickness of the substrate layer remains virtually unchanged before and after manufacturing.

[0107] In the present invention, the material of the base layer is at least one selected from polyester nonwoven fabric, polyethylene nonwoven fabric, and polypropylene nonwoven fabric.

[0108] According to the present invention, preferably, the conditions for producing the porous support layer include setting the thickness of the porous support layer in the separation membrane to 10 to 100 μm, more preferably 30 to 60 μm. The thickness may be controlled by controlling the amount of coating, and since the thickness decreases after coating, there will be some difference between the thickness set at the time of coating and the final thickness of the porous support layer of the separation membrane. Typically, the thickness set at the time of coating should be 40 to 60 μm higher than the desired porous support layer of the separation membrane.

[0109] According to the present invention, the concentration of the solution containing the porous support layer material is 10 to 20 wt%.

[0110] According to the present invention, the material of the porous support layer is at least one selected from polyethersulfone, polysulfone, polyaromatic ether, polybenzimidazole, polyetherketone, polyetheretherketone, polyacrylonitrile, polyvinylidene fluoride, and polyaryletherketone.

[0111] According to the present invention, the solvent in the solution containing the material for the porous support layer is at least one selected from N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide.

[0112] In the present invention, the method for producing the solution containing the porous support layer material is not particularly limited, but may be produced by a method commonly used in the art. For example, first, the porous support layer material is dissolved in a solvent and degassed (degassing is performed at 20-40°C for 10-180 minutes) to obtain a solution containing the porous support layer material.

[0113] In the present invention, preferably, after manufacturing the porous support layer, the material is washed, for example, by repeatedly washing it with water.

[0114] According to the present invention, a method for producing the polyamide layer includes the steps of sequentially contacting the surface of the porous support layer of a material comprising a base layer and a porous support layer with an aqueous phase containing a polyamine and an organic phase containing a polybasic acid chloride, and then performing a heat treatment.

[0115] In the present invention, by the above method of sequentially contacting an aqueous phase containing a polyamine with an organic phase containing a polybasic acid chloride, a polyamide layer is obtained by interfacial polymerization. Such a polyamide layer has a crosslinked structure, is dense and thin, has high magnesium-lithium separation efficiency, and has a large water permeability. Here, contact with the aqueous phase and the organic phase may be carried out at room temperature, for example, 23-28°C.

[0116] According to the present invention, the conditions for producing the polyamide layer include setting the thickness of the polyamide layer in the separation membrane to 10 to 500 nm, more preferably 50 to 300 nm.

[0117] According to the present invention, preferably, the time for contacting the porous support layer surface with the aqueous phase containing polyamine is 5 to 100 s, more preferably 10 to 60 s.

[0118] According to the present invention, the time for which the porous support layer surface is in contact with the organic phase containing polybasic acid chloride is 10 to 200 s, more preferably 20 to 120 s.

[0119] According to the present invention, the aqueous phase containing the polyamine and the organic phase containing the polybasic acid chloride are used in amounts such that the mass ratio of the polyamine to the polybasic acid chloride is 0.1 to 10:1.

[0120] Furthermore, the inventors have found that when the mass ratio of polyamine to polybasic acid chloride satisfies the above ratio, the manufactured polyamide layer has an appropriate pore size, ensuring that this polyamide layer has excellent lithium chloride permeability and good inhibitory properties against magnesium chloride. They also found that after modifying the polyamide layer with polyphenols and polyamines, the pore size of the polyamide layer becomes even smaller, the surface Zeta potential is further improved, and ultimately a separation membrane with a specific pore size and surface Zeta potential limited to the first aspect of the present invention is obtained, and when this separation membrane is used for separating magnesium and lithium, the magnesium-lithium separation efficiency is significantly improved.

[0121] Furthermore, the aqueous phase containing the polyamine and the organic phase containing the polybasic acid chloride are used in amounts such that the mass ratio of the polyamine to the polybasic acid chloride is 0.5 to 8:1.

[0122] In the present invention, the organic solvent in the organic phase containing polybasic acid chloride may be at least one of n-hexane, dodecane, n-heptane, and alkane solvent oils (commercially available Isopar E, Isopar G, Isopar H, Isopar L, and Isopar M).

[0123] According to the present invention, the concentration of the aqueous phase containing the polyamine is 0.1 to 10 wt%, more preferably 0.5 to 2.5 wt%.

[0124] According to the present invention, the concentration of the organic phase containing the polybasic acid chloride is 0.01 to 1 wt%, more preferably 0.1 to 0.5 wt%. If there are multiple types of polybasic acid chlorides, they may be mixed in any proportion. For example, if the polybasic acid chlorides are trimesoyl chloride and terephthaloyl chloride, the mass ratio of trimesoyl chloride to terephthaloyl chloride may be 1:1 to 10.

[0125] In this invention, if the concentrations of the aqueous phase containing polyamine and the organic phase containing polybasic acid chloride, the contact time between the porous support layer and the aqueous phase containing polyamine and the organic phase containing polybasic acid chloride, and the mass ratio of polyamine to polybasic acid chloride satisfy the above ranges, the thickness of the manufactured polyamide layer is in the range of 10 to 500 nm.

[0126] In this invention, if the concentrations of the aqueous phase containing polyamine and the organic phase containing polybasic acid chloride satisfy the range limited in this invention, the rejection rate for magnesium ions is improved, and the permeability of monovalent lithium ions is also improved.

[0127] In this invention, neither the volume of the aqueous phase containing polyamine nor the volume of the organic phase containing polybasic acid chloride is particularly limited. As long as the amount of polyamine in the aqueous phase or the amount of polybasic acid chloride in the organic phase can be secured, a suitable polyamide layer having a crosslinked structure can be formed on the film. Preferably, 400 cm³ 2 With respect to the membrane area, the total amount of polyamines in the aqueous phase may be 0.05 to 2 g, and the total amount of polybasic acid chlorides in the organic phase may be 0.0001 to 0.5 g.

[0128] According to the present invention, the polyamine is at least one selected from polyethyleneimine, triethylenetetramine, tetraethylenepentamine, diethylenetriamine, piperazine, m-phenylenediamine, and p-phenylenediamine, more preferably at least one from polyethyleneimine, piperazine, and polyethylenepolyamine.

[0129] According to the present invention, the polybasic acid chloride is at least one selected from trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride, and phthaloyl chloride, and more preferably at least one of trimesoyl chloride and terephthaloyl chloride.

[0130] According to the present invention, the temperature of the heat treatment is 40 to 150°C, and the time of the heat treatment is 0.5 to 10 minutes.

[0131] In this invention, although polyamine and polybasic acid chloride react upon contact, the reaction proceeds more thoroughly when the above heat treatment conditions are met, resulting in a denser polyamide layer. After a modification layer is formed on the surface of this polyamide layer, a separation membrane having a specific pore size as described in the first aspect of this invention is obtained.

[0132] Furthermore, the temperature of the heat treatment is 50 to 120°C, and the duration of the heat treatment is 1 to 5 minutes.

[0133] In the present invention, the manufacturing method further includes the step of immersing the manufactured separation membrane in deionized water to prepare it for use.

[0134] In a third aspect, the present invention provides a separation membrane manufactured by the method described above.

[0135] In a fourth aspect, the present invention provides the use of the separation membrane described in the first or third aspect in the separation of magnesium and lithium (particularly lithium extraction from salt lakes).

[0136] In the present invention, a specific method for using the separation membrane to separate magnesium and lithium includes the steps of: putting saltwater from a salt lake into a supply tank and attaching the separation membrane to a membrane cell; operating the system at pressure I and collecting the primary wastewater filtered by the separation membrane; and putting the primary wastewater into a supply tank as a feed liquid, operating the system at pressure II and collecting the secondary wastewater filtered by the separation membrane.

[0137] In this invention, the saltwater of the salt lake contains 500 ppm or more of magnesium ions and 50 ppm or less of lithium ions.

[0138] In this invention, the Mg in the saltwater of the salt lake 2+ and Li +The mass concentration ratio is 5 or greater.

[0139] In this invention, the pressure I is 0.5 to 2 MPa.

[0140] In this invention, the pressure II is 0.5 to 2 MPa.

[0141] In the present invention, the magnesium ion content in the primary wastewater is 20 ppm or less, and the lithium ion content is 20 ppm or more.

[0142] In this invention, the Mg in the primary wastewater 2+ and Li + The mass concentration ratio is 1 or less.

[0143] In the present invention, the magnesium ion content in the secondary wastewater is 0.5 ppm or less, and the lithium ion content is 25 ppm or more.

[0144] In this invention, Li in the secondary wastewater + Its purity is over 98%.

[0145] In a preferred embodiment of the present invention, when the separation membrane is used for separating magnesium and lithium, the water passage rate is 20 L·m. -2 ·h -1 The above results indicate that the MgCl2 desalination rate is 99% or higher, and the magnesium-lithium separation coefficient is 70 or higher.

[0146] Furthermore, the separation membrane has a water passage rate of 20-40 L·m. -2 ·h -1 The MgCl2 desalination rate is 99% or higher, and the magnesium-lithium separation coefficient is 100-250.

[0147] In a particularly preferred embodiment of the present invention, the separation membrane is manufactured by the following method.

[0148] A polysulfone solution with a polysulfone concentration of 16-19% by weight is applied to a polyester nonwoven fabric (base layer) with a thickness of 75-80 μm using a knife. Next, the material is immersed in water at a temperature of 24-26°C for 45-60 minutes to cause a phase transition of the polysulfone layer on the surface of the polyester nonwoven fabric, forming a porous membrane. Finally, a material containing a base layer and a porous support layer (porous support layer thickness approximately 38-42 μm) is obtained by washing with water 2-3 times.

[0149] The surface of the porous support layer of a material including a base layer and a porous support layer was brought into contact with an aqueous solution containing 0.5-0.6% by weight of polyethyleneimine at 24-26°C for 50-60 seconds, after which the liquid was drained. Subsequently, the upper surface of the support layer was brought into contact with an Isopar E solution containing trimethoyl chloride and terephthaloyl chloride (the mass ratio of polyamine in the aqueous phase containing polyamine to polybasic acid chloride in the organic phase containing polybasic acid chloride was 5-6:1, and the mass ratio of trimethoyl chloride to terephthaloyl chloride was 1:3-5) at 24-26°C for 60-70 seconds, after which the liquid was drained. The membrane was then placed in an oven and heated at 60-70°C for 3-4 minutes to obtain a material including a base layer, a porous support layer, and a polyamide layer.

[0150] A material containing a base layer, a porous support layer, and a polyamide layer was placed in a cross-flow membrane cell. The polyamide layer side of the material was brought into contact with a 0.001-0.005 wt% polyphenol aqueous solution inside the cross-flow membrane cell. The cross-flow membrane cell was operated for 30-35 minutes under conditions of 0.6-0.65 MPa, 25-26°C, and a polyphenol solution flow rate of 2.5-3.5 L / min. After that, the liquid was discharged, and the cross-flow membrane cell was repeatedly rinsed with deionized water to wash away the polyphenols in the system. Polyamine aqueous solution (the polyphenol solution and polyamine solution were used in amounts such that the mass ratio of polyphenol to polyamine was 0.1 to 10:1) was added to a cross-flow membrane cell, and the polyamide layer side of the material was brought into contact with the above solution. The cross-flow membrane cell was operated for 30 to 35 minutes under conditions of 0.6 to 0.65 MPa, 25 to 26°C, and a polyamine solution flow rate of 0.5 to 5 L / min. After that, the liquid was discharged, and the cross-flow membrane cell was repeatedly rinsed with deionized water to wash away any remaining polyamine. In this way, one self-assembly reaction was completed, and by repeating the above procedure, another self-assembly reaction was completed. A separation membrane was obtained.

[0151] In this invention, the pressure refers to gauge pressure.

[0152] The present invention will be described in detail below with reference to examples.

[0153] Isopar E is a commercially available alkane-based solvent oil (purchased from Nishilong Chemical Co., Ltd.).

[0154] In the following embodiments, when bringing a material containing a substrate layer, a porous support layer, and a polyamide layer into contact with a solution in a cross-flow membrane cell, water is circulated into the cross-flow membrane cell by a water pump to maintain the polyphenol solution and polyamine solution in the membrane cell in a flowing state.

[0155] Except for Examples 11-12, in the other examples and comparative examples, the material comprising the base layer and the porous support layer is manufactured by the following method.

[0156] Polysulfone (number-average molecular weight 80,000 g / mol) is dissolved in N,N-dimethylformamide to obtain an 18% by weight polysulfone solution, which is degassed at 25°C for 120 minutes. The polysulfone solution is then applied to a 75 μm thick polyester nonwoven fabric (base layer) using a knife. Next, the material is immersed in water at 25°C for 60 minutes to induce a phase transition in the polysulfone layer on the surface of the polyester nonwoven fabric, forming a porous membrane. Finally, it is washed three times with water to obtain a total thickness of 115 μm and an area of ​​400 cm², including the base layer and the porous support layer (porous support layer thickness 40 μm). 2 Obtain the materials.

[0157] For the membranes produced in the following examples and comparative examples, after production, they were immersed in deionized water for 24 hours, and then various properties and parameters were measured.

[0158] The molecular structure of the separation membrane is characterized and analyzed using a total internal reflection infrared spectrometer (Nicolet 6700).

[0159] The pore size of the separation membrane is measured by the PEG solute transfer method, and the detailed steps are as follows.

[0160] (1) Test the rejection rate of the separation membrane for PEG of various molecular sizes.

[0161] (2) Linear fitting is performed on the PEG size and rejection rate in a log-stochastic coordinate system, and the PEG size corresponding to the 50% rejection rate is taken as the average pore size of the separation membrane.

[0162] The surface Zeta potential of the separation membrane was measured using a Zeta potential analyzer, with the test solution being a 0.001 mol / L KCl aqueous solution (pH 7).

[0163] The nitrogen atom content in the modification layer of the separation membrane is measured by X-ray photoelectron spectroscopy (XPS). This is obtained by irradiating with Al-Kα X-rays using an ESCALAB250 type X-ray photoelectron spectrometer.

[0164] Content of polyphenol-derived structural units and polyamine-derived structural units on the membrane surface of the separation membrane: After drying the film, which includes a base layer, a porous support layer, and a polyamide layer, in a vacuum oven at 60°C for 24 hours, the mass of the film is weighed, and M n (mg) The membrane is placed in a membrane cell, a polyphenol aqueous solution of a predetermined concentration is added to the supply tank, and after a certain period of time under predetermined conditions the membrane sheet is removed, the surface of the membrane sheet is thoroughly washed with deionized water, and after drying at 60°C for 24 hours, the mass of the membrane is weighed, W n (mg) Next, the membrane is placed in a membrane cell, a polyamine aqueous solution of a predetermined concentration is added to the supply tank, and after a certain period of time under predetermined conditions the membrane sheet is removed, the surface of the membrane sheet is thoroughly washed with deionized water, and after drying at 60°C for 24 hours, the mass of the membrane is weighed and N n (mg) is used. For each modification of the separation membrane, the polyphenol content P on the membrane surface is measured. n and the polyamine content T n These are calculated using the following formulas:

number

[0165] Here, if n is greater than 1, M n =N n-1 And, in the case of n=1, M n This is the initial mass of the polyamide film sheet.

number

[0166] Let ΣPn(n≧1) be the total polyphenol content on the surface of the separation membrane after self-assembly, and ΣTn(n≧1) be the total polyamine content on the surface. Here, n is the number of self-assembly cycles, and S is the effective membrane area (in cm²). 2 )

[0167] Here, the contact conditions between the membrane and the aqueous solutions of polyphenol and polyamine correspond to the first pressure, second pressure, temperature and time of the first contact, and temperature and time of the second contact in the self-assembly process in the examples and comparative examples, respectively.

[0168] Contact Angle of Separation Membrane: The surface contact angle of the composite membrane sample is measured using the static droplet method with a DSA100 surface contact angle analyzer manufactured by KRUSS GmbH in Germany. Before measurement, the sample is dried in a 60°C vacuum oven for 30 minutes to remove moisture from the surface and interior. The dried membrane is then attached to a flat glass slide with double-sided tape. Each water droplet used in the test is set to a volume of 2 μL. The test is performed immediately 3 seconds after dropping the water droplet onto the membrane surface, and the average value of multiple measurements is obtained to determine the final contact angle.

[0169] Thickness of the separation membrane and each layer of the separation membrane: The thicknesses of the separation membrane, porous support layer, and polyamide layer were measured using a spiral micrometer and a scanning electron microscope. The thickness of the modification layer was obtained by subtracting the thicknesses of the substrate layer, porous support layer, and polyamide layer from the thickness of the separation membrane. Here, the thickness of the substrate layer is the thickness measured before applying the solution of the porous support layer material.

[0170] Example 1 The surface of the porous support layer of the material, which includes a base layer and a porous support layer, was brought into contact with an aqueous solution (50 mL) containing 0.5 wt% polyethyleneimine at 25°C for 60 seconds, after which the liquid was drained. Subsequently, the upper surface of the support layer was brought into contact with an Isopar E solution (30 mL) containing 0.02 wt% trimethoyl chloride and 0.08 wt% terephthaloyl chloride at 25°C for another 60 seconds, after which the liquid was drained. The membrane was then placed in an oven and heated at 70°C for 3 minutes. The heat-treated product was placed in a cross-flow membrane cell, and the polyamide layer of the material was brought into first contact with a 0.001 wt% tannic acid aqueous solution in the cross-flow membrane cell. The volume of the tannic acid aqueous solution was set to 5 L, and the tannic acid solution was maintained in a flow state at a flow rate of 1.5 L / min. The cross-flow membrane cell was operated at 0.6 MPa and 25°C for 30 min, after which the liquid was discharged, and the cross-flow membrane cell was repeatedly rinsed with deionized water to wash away the tannic acid in the system. 5 L of a 0.004 wt% polyethyleneimine aqueous solution was added to the cross-flow membrane cell, and the polyethyleneimine aqueous solution was maintained in a flow state at a flow rate of 1.5 L / min. The polyamide layer of the material was brought into second contact with the above solution, and the cross-flow membrane cell was operated at 0.6 MPa and 25°C for 30 min. After which the liquid was discharged, and the cross-flow membrane cell was repeatedly rinsed with deionized water to wash away any remaining polyethyleneimine. Thus, one self-assembly reaction was completed, and by repeating the above procedure, another self-assembly reaction was completed. In one self-assembly, the mass ratio of polyphenol to polyamine was 0.25:1. This yielded the separation membrane N1.

[0171] Example 2 The surface of the porous support layer of the material, which includes a base layer and a porous support layer, was brought into contact with an aqueous solution (50 mL) containing 1% by weight of polyethylene polyamine at 25°C for 20 seconds, after which the liquid was drained. Subsequently, the upper surface of the support layer was brought into contact with an Isopar E solution (30 mL) containing 0.18% by weight of trimesoyl chloride and 0.12% by weight of terephthaloyl chloride at 25°C for another 30 seconds, after which the liquid was drained. The membrane was then placed in an oven and heated at 50°C for 5 minutes. The heat-treated product was placed in a cross-flow membrane cell, and the polyamide layer of the material was brought into first contact with a 0.01 wt% tannic acid aqueous solution in the cross-flow membrane cell. The volume of the tannic acid aqueous solution was set to 5 L, and the tannic acid solution was maintained in a flow state at a flow rate of 0.5 L / min. The cross-flow membrane cell was operated at 0.6 MPa and 15°C for 40 min, after which the liquid was discharged, and the solution in the cross-flow membrane cell was repeatedly rinsed with deionized water to wash away any remaining tannic acid. 5 L of a 0.045 wt% polyethyleneimine aqueous solution was added to the cross-flow membrane cell, and the polyethyleneimine aqueous solution was maintained in a flow state at a flow rate of 0.5 L / min. The polyamide layer of the material was brought into second contact with the above solution, and the cross-flow membrane cell was operated at 0.6 MPa and 15°C for 40 min. After which the liquid was discharged, and the cross-flow membrane cell was repeatedly rinsed with deionized water to wash away any remaining polyethyleneimine. Thus, one self-assembly reaction was completed, and by repeating the above procedure, another self-assembly reaction was completed. In one self-assembly, the mass ratio of polyphenol to polyamine was 0.22:1. This yielded the separation membrane N2.

[0172] Example 3 The surface of the porous support layer of the material, which includes a substrate layer and a porous support layer, was brought into contact with an aqueous solution (50 mL) containing 2.5 wt% piperazine at 25°C for 40 seconds, after which the liquid was drained. Subsequently, the upper surface of the support layer was brought into contact with an Isopar E solution (30 mL) containing 0.2 wt% trimethoyl chloride and 0.1 wt% terephthaloyl chloride at 25°C for 100 seconds, after which the liquid was drained. The membrane was then placed in an oven and heated at 110°C for 1 minute. The heat-treated product was placed in a cross-flow membrane cell, and the polyamide layer of the material was brought into first contact with a 0.1 wt% tannic acid aqueous solution in the cross-flow membrane cell. The volume of the tannic acid aqueous solution was set to 5 L, and the tannic acid solution was maintained in a flow state at a flow rate of 5 L / min. The cross-flow membrane cell was operated at 0.6 MPa and 30°C for 20 minutes, after which the liquid was discharged, and the cross-flow membrane cell was repeatedly rinsed with deionized water to wash away any remaining tannic acid. 5 L of a 0.1 wt% polyethyleneimine aqueous solution was added to the cross-flow membrane cell, and the polyethyleneimine aqueous solution was maintained in a flow state at a flow rate of 5 L / min. The polyamide layer of the material was brought into second contact with the above solution, and the cross-flow membrane cell was operated at 0.6 MPa and 30°C for 20 minutes. The liquid was discharged, and the cross-flow membrane cell was repeatedly rinsed with deionized water to wash away any remaining polyethyleneimine. Thus, one self-assembly reaction was completed, and by repeating the above procedure, another self-assembly reaction was completed. In one self-assembly, the mass ratio of polyphenol to polyamine was 1:1. This yielded the separation membrane N3.

[0173] Example 4 Separation membranes were prepared according to the method of Example 1, except that polyethyleneimine was replaced with polyethylene polyamine in the self-assembly reaction. Separation membrane N4 was obtained.

[0174] Example 5 Separation membranes were prepared according to the method of Example 1, except that polyethyleneimine was replaced with tetraethylenepentamine in the self-assembly reaction. Separation membrane N5 was obtained.

[0175] Example 6 Separation membranes were prepared according to the method of Example 1, except that polyethyleneimine was replaced with triethylenetetramine in the self-assembly reaction. Separation membrane N6 was obtained.

[0176] Example 7 A separation membrane was prepared according to the method of Example 1, except that a self-assembly reaction was performed only once. Separation membrane N7 was obtained.

[0177] Example 8 A separation membrane was prepared according to the method of Example 1, except that the self-assembly reaction was carried out a total of three times. Separation membrane N8 was obtained.

[0178] Example 9 A separation membrane was prepared according to the method of Example 1, except that a total of four self-assembly reactions were performed. Separation membrane N9 was obtained.

[0179] Example 10 A separation membrane was prepared according to the method of Example 1, except that a total of five self-assembly reactions were performed. Separation membrane N10 was obtained.

[0180] Example 11 The separation membrane was prepared according to the method of Example 1, except that the material including the base layer and the porous support layer was manufactured by the following method. Polyethersulfone (number average molecular weight 70,000 g / mol) was dissolved in N,N-dimethylformamide to obtain a 20% by weight polyethersulfone solution, which was degassed at 25°C for 120 minutes. Then, the polyethersulfone solution was applied to a 100 μm thick polyethylene nonwoven fabric (base layer) with a knife. Next, the material was immersed in water at 23°C for 20 minutes to cause a phase transition of the polyethersulfone layer on the surface of the polyethylene nonwoven fabric to form a porous membrane. Finally, it was washed with water three times to obtain a total thickness of 135 μm and an area of ​​400 cm², including the base layer and the porous support layer (porous support layer thickness 35 μm). 2 The material was obtained. Separation membrane N11 was obtained.

[0181] Example 12 The separation membrane was prepared according to the method of Example 1, except that the material including the base layer and the porous support layer was manufactured by the following method. Polyacrylonitrile (number average molecular weight 100,000 g / mol) was dissolved in N,N-dimethylformamide to obtain a 15% by weight polyacrylonitrile solution, which was degassed at 25°C for 120 minutes. Then, the polyacrylonitrile solution was applied to a 115 μm thick polypropylene nonwoven fabric (base layer) with a knife. Next, the material was immersed in water at 28°C for 40 minutes to cause a phase transition of the polyacrylonitrile layer on the surface of the polypropylene nonwoven fabric to form a porous membrane. Finally, it was washed three times with water to obtain a total thickness of 160 μm and an area of ​​400 cm², including the base layer and the porous support layer (porous support layer thickness 45 μm). 2 The material was obtained. Separation membrane N12 was obtained.

[0182] Example 13 In the self-assembly reaction, the concentration of tannic acid in the aqueous tannic acid solution was 0.0001 wt%, the concentration of polyethyleneimine in the polyethyleneimine solution was 0.001 wt%, and the mass ratio of polyphenol to polyamine in one self-assembly was 0.1:1. A separation membrane was then prepared according to the method of Example 1. Separation membrane N13 was obtained.

[0183] Example 14 The separation membrane was prepared according to the method of Example 1, except that the first and second pressures during self-assembly were both 0.2 MPa and the solution flow rate was 1.5 L / min. Separation membrane N14 was obtained.

[0184] Example 15 The separation membrane was fabricated according to the method of Example 1, except that the pressures at the first and second contacts during self-assembly were 1 MPa and the solution flow rate was 1.5 L / min in all cases. Separation membrane N15 was obtained.

[0185] Example 16 The separation membrane was fabricated according to the method of Example 1, except that the pressures at the first and second contacts during self-assembly were 0.8 MPa and the solution flow rate was 1.5 L / min in all cases. Separation membrane N16 was obtained.

[0186] Example 17 The separation membrane was fabricated according to the method of Example 1, except that the pressures at the first and second contacts during self-assembly were 0.4 MPa and the solution flow rate was 1.5 L / min in all cases. Separation membrane N17 was obtained.

[0187] Example 18 The surface of the porous support layer of the material, which includes a base layer and a porous support layer, was brought into contact with an aqueous solution (50 mL) containing 0.5 wt% polyethyleneimine at 25°C for 60 seconds, after which the liquid was drained. Subsequently, the upper surface of the support layer was brought into contact with an Isopar E solution (30 mL) containing 0.01 wt% trimethoyl chloride and 0.04 wt% terephthaloyl chloride at 25°C for another 60 seconds, after which the liquid was drained. The membrane was then placed in an oven and heated at 70°C for 3 minutes. The heat-treated product was placed in a cross-flow membrane cell, and the polyamide layer of the material was brought into first contact with a 0.001 wt% tannic acid aqueous solution in the cross-flow membrane cell. The volume of the tannic acid aqueous solution was set to 5 L, and the tannic acid solution was maintained in a flow state at a flow rate of 1.5 L / min. The cross-flow membrane cell was operated at 0.6 MPa and 25°C for 30 min, after which the liquid was discharged, and the cross-flow membrane cell was repeatedly rinsed with deionized water to wash away the tannic acid in the system. 5 L of a 0.004 wt% polyethyleneimine aqueous solution was added to the cross-flow membrane cell, and the polyethyleneimine aqueous solution was maintained in a flow state at a flow rate of 1.5 L / min. The polyamide layer of the material was brought into second contact with the above solution, and the cross-flow membrane cell was operated at 0.6 MPa and 25°C for 30 min. After which the liquid was discharged, and the cross-flow membrane cell was repeatedly rinsed with deionized water to wash away any remaining polyethyleneimine. Thus, one self-assembly reaction was completed, and by repeating the above procedure, another self-assembly reaction was completed. In one self-assembly, the mass ratio of polyphenol to polyamine was 0.25:1. This yielded the separation membrane N18.

[0188] Example 19 In the self-assembly reaction, the concentration of tannic acid in the aqueous tannic acid solution was 0.001 wt%, the concentration of polyethyleneimine in the polyethyleneimine solution was 0.0001 wt%, and the mass ratio of polyphenol to polyamine in one self-assembly was 10:1. Separation membrane N19 was obtained.

[0189] Comparative Example 1 A separation membrane was produced according to the method of Example 1, except that a separation membrane was obtained by heat treatment without performing a self-assembly reaction. Separation membrane D1 was obtained.

[0190] Comparative Example 2 The heat-treated product was placed in a cross-flow membrane cell containing a 0.001 wt% aqueous tannic acid solution, the volume of the aqueous tannic acid solution was increased to 5 L, the tannic acid solution was maintained in a flow state at a flow rate of 1.5 L / min, and the cell was operated at 0.6 MPa and 25°C for 30 minutes. After this, the product was removed to obtain a separation membrane (i.e., contact with aqueous tannic acid solution only once), except that the separation membrane was prepared according to the method of Example 1. Separation membrane D2 was obtained.

[0191] Comparative Example 3 A separation membrane was prepared according to the method of Example 1, except that polyethyleneimine was replaced with polyvinyl alcohol. Separation membrane D3 was obtained.

[0192] Comparative Example 4 A polyacrylonitrile ultrafiltration membrane was placed in a cross-flow membrane cell so that one side was in contact with a 0.001 wt% tannic acid aqueous solution inside the cell. The volume of the tannic acid aqueous solution was 5 L, and the tannic acid solution was maintained in a flow state at a flow rate of 1.5 L / min. The cross-flow membrane cell was operated at 0.6 MPa and 25°C for 30 minutes, after which the liquid was discharged, and the cross-flow membrane cell was repeatedly rinsed with deionized water to wash away the tannic acid in the system. 5 L of a 0.004 wt% polyethyleneimine aqueous solution was added to the cross-flow membrane cell, so that the polyacrylonitrile layer side of the material was in contact with the above solution. The cross-flow membrane cell was operated at 0.6 MPa and 25°C for 30 minutes at a flow rate of 1.5 L / min. After which the liquid was discharged, and the cross-flow membrane cell was repeatedly rinsed with deionized water to wash away the residual polyethyleneimine. In this way, one self-assembly reaction was completed, and by repeating the above procedure, another self-assembly reaction was completed. During a single self-assembly, the mass ratio of polyphenols to polyamines was 0.25:1. This resulted in the acquisition of separation membrane D4.

[0193] Comparative Example 5 The porous support layer of the material, which includes the base layer and the porous support layer, was placed in a cross-flow membrane cell. One side of the porous support layer was brought into initial contact with a 0.001 wt% tannic acid aqueous solution inside the cross-flow membrane cell. The volume of the tannic acid aqueous solution was set to 5 L, and the tannic acid solution was maintained in a flow state with a flow rate of 1.5 L / min. The cross-flow membrane cell was operated at 0.6 MPa and 25°C for 30 minutes, after which the liquid was discharged, and the cross-flow membrane cell was repeatedly rinsed with deionized water to wash away the tannic acid in the system. 5 L of a 0.004 wt% polyethyleneimine aqueous solution is added to a cross-flow membrane cell, the polyethyleneimine solution is maintained in a flow state, and the flow rate is set to 1.5 L / min. A second contact is made between the polyacrylonitrile layer of the material and the above solution. The cross-flow membrane cell is operated at 0.6 MPa and 25°C for 30 min, after which the liquid is discharged, the membrane sheet is removed, and the surface is thoroughly rinsed with deionized water to obtain a porous support layer modified with polyphenols and polyamines. In one self-assembly, the mass ratio of polyphenols to polyamines is 0.25:1. The surface of a porous support layer modified with polyphenols and polyamines was brought into contact with an aqueous solution (50 mL) containing 0.5 wt% polyethyleneimine at 25°C for 60 seconds, after which the liquid was drained. Subsequently, the upper surface of the support layer was brought into contact with an Isopar E solution (30 mL) containing 0.02 wt% trimethoyl chloride and 0.08 wt% terephthaloyl chloride at 25°C for another 60 seconds, after which the liquid was drained. The separation membrane was then prepared according to the method of Example 1, except that the membrane was placed in an oven and heated at 70°C for 3 minutes to obtain a polyamide composite membrane D5 having an intermediate layer of polyamine and polyphenol.

[0194] Comparative Example 6 Instead of placing the heat-treated product into a cross-flow membrane cell to perform a self-assembly reaction, the polyamide layer of the material was brought into contact with an aqueous tannic acid solution in a beaker (i.e., the first pressure was 0 MPa and the tannic acid solution was not flowing), removed after 24 hours, and rinsed repeatedly with deionized water. Then, the polyamide layer of the material was brought into contact with an aqueous polyethyleneimine solution in a beaker (i.e., the second pressure was 0 MPa and the polyethyleneimine solution was not flowing), removed after 24 hours, and rinsed repeatedly with deionized water. Repeating these operations completed another self-assembly reaction and a separation membrane was obtained. The separation membrane was produced according to the method of Example 1, except that in each self-assembly, the volume of the tannic acid solution (or polyamine) in the beaker was set to exceed the amount of tannic acid (or polyamine) that could adhere to the membrane and react. Separation membrane D6 was obtained.

[0195] Comparative Example 7 The surface of the porous support layer of the material, which includes a base layer and a porous support layer, was brought into contact with an aqueous solution (50 mL) containing 0.5 wt% polyethyleneimine at 25°C for 60 seconds, after which the liquid was drained. Subsequently, the upper surface of the support layer was brought into contact with an Isopar E solution (30 mL) containing 0.02 wt% trimethoyl chloride and 0.08 wt% terephthaloyl chloride at 25°C for another 60 seconds, after which the liquid was drained. The membrane was then placed in an oven and heated at 70°C for 3 minutes. The obtained membrane was immersed for 1 minute in 1 L of a 2 wt% tannic acid aqueous solution (first pressure was 0 MPa, and the tannic acid solution was not flowing). After removal, the surface of the membrane was washed with deionized water. Next, the membrane was immersed for 1 minute in 1 L of a 2 wt% polyethyleneimine aqueous solution (second pressure was 0 MPa, and the polyethyleneimine solution was not flowing). In one self-assembly, the mass ratio of polyphenol to polyamine was 1:1. After removing the membrane, the membrane surface was thoroughly rinsed with deionized water to obtain separation membrane D7.

[0196] Comparative Example 8 The separation membrane was prepared according to the method of Example 1, except that the first and second pressures during self-assembly were both 0 MPa and the solution flow rate was 1.5 L / min in all cases. Separation membrane D8 was obtained.

[0197] Comparative Example 9 A separation membrane was prepared according to the method of Example 1, except that the polyamide membrane was first contacted with a polyethyleneimine solution, then with a tannic acid solution, and self-assembly was performed only once. Separation membrane D9 was obtained.

[0198] Figure 1 shows the results of infrared spectral characteristic evaluation of the separation membranes produced in Example 1 and Comparative Examples 1-2.

[0199] In the membrane that has not undergone self-assembly modification with tannic acid and polyethyleneimine (the membrane of Comparative Example 1), the reading was 3388 cm⁻¹. -1 There is one broad peak, which corresponds to unreacted amino acids on the surface of the polyamide, and also at 1507 cm⁻¹. -1A weak signal was observed, which corresponds to the stretching vibration of NH. In the film modified with tannic acid (i.e., the film of Comparative Example 2), the signal was 3364 cm². -1 There is a strong absorption peak at 1507 cm, which corresponds to the phenolic hydroxyl group in the tannic acid molecule, and also at 1507 cm. -1 The signal peak at this point has almost disappeared, which supports the conclusion that amino acids and tannic acid underwent a chemical reaction. In the film where tannic acid and polyethyleneimine underwent two consecutive self-assemblies on the surface of polyamide (film of Example 1), the signal was 3270-3390 cm². -1 There is one broad peak, which corresponds to unreacted amino and unreacted phenolic hydroxyl groups on the modified layer, and also at 1507 cm. -1 The signal was enhanced, which supports the idea that polyethyleneimine was modified on the surface of the membrane. Referring to the operation and infrared images of Comparative Example 2, it was found that in the separation membrane of Example 1, the crosslinked polymer forming the modified layer contained structural units derived from tannic acid and structural units derived from polyamine, and the structural units derived from tannic acid were also connected to the polyamide layer through the ortho position of the phenolic hydroxyl group. The infrared characteristic evaluation results of the separation membranes manufactured in Examples 2 to 19 are similar to those of Example 1 (not shown).

[0200] [Table 1]

[0201] [Table 2]

[0202] As can be seen from Tables 1 and 2, the separation membranes of Examples 1 to 19 have smaller pore sizes and a higher positive charge density in the modified layer compared to Comparative Examples 1 to 9.

[0203] In Comparative Example 2, the thickness of the modified layer is the change in thickness due to tannic acid, and in Comparative Example 3, the thickness of the modified layer is the change in thickness due to the reaction between tannic acid and polyvinyl alcohol.

[0204] Furthermore, the separation membrane according to the present invention has a small pore size and a high surface Zeta potential, and when used for separating magnesium and lithium, it significantly improves the rejection rate against magnesium chloride. In addition, the separation membrane has excellent hydrophilicity and can achieve excellent water permeability.

[0205] As can be seen from Figure 2, as the number of self-assembly cycles increases, the potential of the film surface becomes positively charged, and its absolute value tends to increase. It was found that as the number of self-assembly cycles increases, the content of amino acids (primary, secondary, or tertiary amines) on the film surface improves, which in turn improves the Zeta potential of the film surface.

[0206] As can be seen from Figure 3, during self-assembly, as the self-assembly pressure (i.e., the first pressure / second pressure) increases, the absolute value of the positive potential on the membrane surface increases, indicating that pressure is favorable for reacting high concentrations of polyphenols and polyamines on the membrane surface.

[0207] As can be seen from Figure 4, during self-assembly, as the self-assembly pressure (i.e., the first pressure / second pressure) increases, the content of hydrophilic primary, secondary, or tertiary amine groups on the film surface increases, thereby improving the hydrophilicity of the film surface.

[0208] As can be seen from Figure 5, as the number of self-assembly cycles increases, the content of hydrophilic primary, secondary, or tertiary amine groups on the film surface increases, thereby improving the hydrophilicity of the film surface.

[0209] As can be seen in Figure 6a, the polyamide layer that has not been modified with polyphenols and polyamines is smooth and thin, with a thickness of 85 nm. As can be seen in Figure 6b, when self-assembly modification is performed on the surface of the polyamide layer using polyphenols and polyamines, the surface of the polyamide layer becomes covered with a modified layer with a thickness of approximately 30 nm.

[0210] Figure 7 compares the XPS nitrogen element maps of Example 1 (Figure 7a) and Comparative Example 6 (Figure 7b). As can be seen from this figure, the modified layer of Example 1 has a characteristic peak at 407 eV. This characteristic peak corresponds to the structural unit shown in formula I, namely, the π-π formed by benzene ring-nitrogen atom-benzene ring. * This is a signal peak due to electron conjugation. On the other hand, this signal peak was not observed in Comparative Example 6, which indicates that the structural unit represented by formula I can only be generated under process conditions that drive self-assembly at the pressure of the present invention. One nitrogen atom and two benzene rings of this structural unit undergo a crosslinking reaction, thereby improving the density of the separation membrane and reducing the pore size of the separation membrane.

[0211] Application examples Each of the separation membranes produced in the examples and comparative examples is placed in a cross-flow membrane cell, and the water permeability of the separation membrane is increased over a certain period of time under conditions of 0.6 MPa and a temperature of 25°C. The amount of water that passes through is then calculated using the following formula. J = Q / (A·t) Here, J is the water flow rate (L / m³). 2 h) is where Q is the water permeability (L) and A is the effective membrane area (m²) of the separation membrane. 2 ) and t is time (h). The separation membrane was placed in a cross-flow membrane cell. The raw material liquid in the membrane cell contained either 2000 ppm magnesium chloride or 2000 ppm lithium chloride. After pre-compression at 0.2 MPa for 0.5 hours, permeate was obtained at a pressure of 0.6 MPa and a raw material liquid temperature of 25°C. The concentrations of magnesium chloride and lithium chloride in the permeate were measured using a conductivity meter, and the desalination rate was calculated using the following formula. R(%)=(C f -C P ) / C f ×100% Here, R is the desalting rate, and C f This is the concentration of magnesium chloride or lithium chloride in the raw material liquid (measured by a conductivity meter), and C pThis is the concentration of magnesium chloride or lithium chloride in the permeate (measured by a conductivity meter). The separation membrane was placed in a cross-flow membrane cell. The raw material solution in the membrane cell contained 2000 ppm magnesium chloride and 100 ppm lithium chloride. After pre-compression at 0.2 MPa for 0.5 hours, permeate was obtained at a pressure of 0.6 MPa and a raw material solution temperature of 25°C. The concentrations of magnesium ions and lithium ions in the permeate were measured by ion chromatography. The magnesium-lithium separation coefficient was calculated using the following formula.

number

[0212] [Table 3]

[0213] As can be seen from Table 3, according to the embodiments of the present invention, it is possible to achieve both a large water pass-through rate and high magnesium-lithium separation efficiency. As the number of self-assembly cycles increases, the polyphenol and polyamine content on the membrane surface improves, thereby improving the hydrophilicity and surface Zeta potential of the membrane surface. This improves the membrane's rejection rate against magnesium chloride and improves the magnesium-lithium separation coefficient. On the other hand, as the number of self-assembly cycles increases, the thickness of the modification layer increases, thereby decreasing the water pass-through rate of the membrane. Furthermore, as the operating pressure during self-assembly increases, the reaction proceeds more efficiently, improving the hydrophilicity and surface Zeta potential of the membrane surface, and as a result, the membrane gains improved salt rejection rate and magnesium-lithium separation efficiency.

[0214] Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, several simple modifications can be made to the technical proposal of the present invention, and these simple modifications and combinations, including combining each technical feature in any other suitable manner, should also be considered within the disclosure of the present invention and all fall within the scope of protection of the present invention.

[0215] [Explanation of symbols] 1 modification layer 2. Polyamide layer 3 Porous support layer [Brief explanation of the drawing]

[0216] [Figure 1] These are the infrared spectra of the separation membranes produced in Example 1 and Comparative Examples 1-2 of the present invention. [Figure 2] This curve shows the change in the surface Zeta potential of the separation membrane as the number of self-assembly cycles increases. [Figure 3] This curve shows the change in the surface Zeta potential of the separation membrane in response to the self-assembly pressure (first pressure / second pressure). [Figure 4] This curve shows the change in the contact angle of the separation membrane in response to the self-assembly pressure (first pressure / second pressure). [Figure 5] This curve shows the change in the contact angle of the separation membrane with respect to the number of self-assembly cycles. [Figure 6a] These are cross-sectional SEM images of the separation membranes of Comparative Example 1 (Figure 6a) and Example 10 (Figure 6b). [Figure 6b] These are cross-sectional SEM images of the separation membranes of Comparative Example 1 (Figure 6a) and Example 10 (Figure 6b). [Figure 7a] This is the XPS nitrogen element map of the separation membranes produced in Example 1 and Comparative Example 1. [Figure 7b] This is the XPS nitrogen element map of the separation membranes produced in Example 1 and Comparative Example 1.

Claims

1. A separation membrane used for separating magnesium and lithium, It comprises a base layer, a porous support layer, a polyamide layer, and a modification layer in this order. The crosslinked polymer forming the modified layer comprises structural units derived from polyphenols and structural units derived from polyamines, and at least a portion of the structural units derived from polyphenols are also connected to the polyamide layer through the ortho position of the phenolic hydroxyl group. A separation membrane characterized by having a pore size of 0.1 to 0.5 nm and a surface Zeta potential of -5 mV to 30 mV under conditions of pH 7.

2. The separation membrane according to claim 1, wherein the pore size is 0.15 to 0.3 nm and the surface Zeta potential is 1 mV to 10 mV.

3. The separation membrane according to claim 1, wherein the modification layer includes a structural unit represented by formula I. 【Chemistry 1】

4. The content of the polyphenol-derived structural units on the film surface is 2 × 10 －３ ~5 x 10 -２ The concentration is mg / cm², and the content of the polyamine-derived structural units on the film surface is 1 × 10⁻⁶. －３ ~2.5 x 10 -２ It is mg / cm², Alternatively, the separation membrane according to claim 1, wherein the content of the polyphenol-derived structural units on the membrane surface is 2.5 × 10⁻³ to 5 × 10⁻² mg / cm², and the content of the polyamine-derived structural units on the membrane surface is 4 × 10⁻³ to 2 × 10⁻² mg / cm².

5. The N atom content in the modified layer is 13 to 20 at.%. Alternatively, the separation membrane according to claim 1, wherein the content of N atoms in the modified layer is 13.5 to 18.5 at.%.

6. The contact angle of the separation membrane is 20 to 60°, Alternatively, the separation membrane according to claim 1, wherein the contact angle of the separation membrane is 20 to 40°.

7. The thickness of the separation membrane is 100 to 200 μm. and / or, the thickness of the substrate layer is 30 to 150 μm. And / or, the thickness of the porous support layer is 10 to 100 μm. and / or, the thickness of the polyamide layer is 10 to 500 nm. The separation membrane according to claim 1, and / or, the thickness of the modification layer is 1 to 200 nm.

8. The thickness of the substrate layer is 50 to 120 μm, And / or, the thickness of the porous support layer is 30 to 60 μm. and / or, the thickness of the polyamide layer is 50 to 150 nm. The separation membrane according to claim 1, wherein the thickness of the modification layer is 10 to 60 nm.

9. The material of the base layer is at least one selected from polyester nonwoven fabric, polyethylene nonwoven fabric, and polypropylene nonwoven fabric. The separation membrane according to claim 1, and / or the material of the porous support layer is at least one selected from polyethersulfone, polysulfone, polyaromatic ether, polybenzimidazole, polyetherketone, polyetheretherketone, polyacrylonitrile, polyvinylidene fluoride, and polyaryletherketone.

10. The aforementioned polyamide layer is synthesized from a polyamine and a polybasic acid chloride. and / or, the polyamine is at least one selected from polyethyleneimine, triethylenetetramine, tetraethylenepentamine, diethylenetriamine, piperazine, m-phenylenediamine, and p-phenylenediamine. The separation membrane according to claim 1, and / or, the polybasic acid chloride is at least one selected from trimethoyl chloride, terephthaloyl chloride, isophthaloyl chloride, and phthaloyl chloride.

11. The process includes the steps of manufacturing a porous support layer, a polyamide layer, and a modification layer on a substrate layer in this order, A method for producing the modified layer, characterized in that, under a first pressure, a polyphenol solution is flowed through a polyphenol solution, and a first contact is made between the polyamide layer side of a material including a base layer, a porous support layer, and a polyamide layer and the polyphenol solution, and then under a second pressure, a polyamine solution is flowed through a polyamine solution, thereby completing the self-assembly reaction.

12. The first pressure and the second pressure are each independently 0.1 to 1.2 MPa. and / or, the polyphenol solution and the polyamine solution are used in amounts such that the mass ratio of polyphenol to polyamine is 0.1 to 10:

1. And / or, the concentration of the polyphenol solution is 0.00001 to 1 wt%, The manufacturing method according to claim 11, and / or, the concentration of the polyamine solution is 0.00001 to 1 wt%.

13. The first pressure and the second pressure are each independently 0.2 to 1 MPa, and / or, the polyphenol solution and the polyamine solution are used in amounts such that the mass ratio of polyphenol to polyamine is 0.2 to 6:

1. And / or, the concentration of the polyphenol solution is 0.0001 to 0.1 wt%, The manufacturing method according to claim 11, and / or, the concentration of the polyamine solution is 0.0001 to 0.1 wt%.

14. The temperatures of the first contact and the second contact are, independently, 10 to 30°C. and / or, in a single self-assembly reaction, the duration of the first contact is 1 to 120 min. and / or, in a single self-assembly reaction, the duration of the second contact is 1 to 120 min. And / or, the number of self-assembly reactions is 1 to 10 times. The manufacturing method according to claim 11, wherein the conditions for producing the modified layer include making the thickness of the modified layer in the separation membrane 1 to 200 nm.

15. The polyphenols in the aforementioned polyphenol solution are one or more selected from tannic acid, tea polyphenols, gallic acid, catechin, lignin, sodium ligninsulfonate, apple polyphenols, grape polyphenols, eriodictyol, naringenin, epicatechin, luteolin, apigenin, kaempferol, myricetin, and genistein. The manufacturing method according to claim 11, and / or, the polyamine in the polyamine solution is at least one selected from polyethyleneimine, tetraethylenepentamine, triethylenetetramine, and polyethylenepolyamine.

16. The method for manufacturing the porous support layer is: The manufacturing method according to claim 11, comprising the steps of applying a solution containing a porous support layer material onto a substrate layer, performing a phase transition, and obtaining a material containing the substrate layer and the porous support layer.

17. The conditions for the phase transition include immersion in water at 10 to 30°C for 10 to 60 mins, and / or, the thickness of the substrate layer is 30 to 150 μm. and / or, the material of the base layer is at least one selected from polyester nonwoven fabric, polyethylene nonwoven fabric, and polypropylene nonwoven fabric. And / or, the conditions for manufacturing the porous support layer include making the thickness of the porous support layer in the separation membrane 10 to 100 μm. and / or, the concentration of the solution containing the porous support layer material is 10 to 20 wt%, and / or, the porous support layer material is at least one selected from polyethersulfone, polysulfone, polyaromatic ether, polybenzimidazole, polyetherketone, polyetheretherketone, polyacrylonitrile, polyvinylidene fluoride, and polyaryletherketone. The manufacturing method according to claim 16, and / or the solvent in the solution containing the porous support layer material is at least one selected from N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide.

18. The method for producing the polyamide layer, comprising the steps of sequentially contacting the surface of the porous support layer of a material comprising a base layer and a porous support layer with an aqueous phase containing a polyamine and an organic phase containing a polybasic acid chloride, and then performing a heat treatment, as described in claim 11.

19. The conditions for producing the polyamide layer include making the thickness of the polyamide layer in the separation membrane 10 to 500 nm. And / or, the time for which the porous support layer surface is in contact with the aqueous phase containing polyamine is 5 to 100 s. And / or, the time for which the porous support layer surface is in contact with the organic phase containing polybasic acid chloride is 10 to 200 s. and / or, the aqueous phase containing the polyamine and the organic phase containing the polybasic acid chloride are used in amounts such that the mass ratio of the polyamine to the polybasic acid chloride is 0.1 to 10:

1. And / or, the concentration of the aqueous phase containing the polyamine is 0.1 to 10 wt%, and / or, the concentration of the organic phase containing the polybasic acid chloride is 0.01 to 1 wt%, and / or, the polyamine is at least one selected from polyethyleneimine, triethylenetetramine, tetraethylenepentamine, diethylenetriamine, piperazine, m-phenylenediamine, and p-phenylenediamine. The method for producing the product according to claim 11, and / or the polybasic acid chloride is at least one selected from trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride, and phthaloyl chloride.

20. The manufacturing method according to claim 18, wherein the temperature of the heat treatment is 40 to 150°C and the time of the heat treatment is 0.5 to 10 min.

21. Use of a separation membrane according to any one of claims 1 to 10 in the separation of magnesium and lithium.

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