WO2023222117A1 - 分离膜及其制备方法和应用 - Google Patents

分离膜及其制备方法和应用 Download PDF

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Publication number
WO2023222117A1
WO2023222117A1 PCT/CN2023/095323 CN2023095323W WO2023222117A1 WO 2023222117 A1 WO2023222117 A1 WO 2023222117A1 CN 2023095323 W CN2023095323 W CN 2023095323W WO 2023222117 A1 WO2023222117 A1 WO 2023222117A1
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Prior art keywords
layer
separation membrane
polyamine
porous support
solution
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PCT/CN2023/095323
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English (en)
French (fr)
Inventor
吴长江
张杨
刘轶群
潘国元
于浩
赵慕华
赵国珂
唐功庆
张建华
杜文杰
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中国石油化工股份有限公司
中石化(北京)化工研究院有限公司
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Publication of WO2023222117A1 publication Critical patent/WO2023222117A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0002—Organic membrane manufacture
    • B01D67/0009—Organic membrane manufacture by phase separation, sol-gel transition, evaporation or solvent quenching
    • B01D67/0013—Casting processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/12—Composite membranes; Ultra-thin membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/56—Polyamides, e.g. polyester-amides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/26—Electrical properties
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
    • Y02A20/124—Water desalination
    • Y02A20/131—Reverse-osmosis

Definitions

  • the present invention relates to the field of membranes, and specifically to a separation membrane and its preparation method and application.
  • salt lake brine In addition to lithium ions, salt lake water also contains a large amount of magnesium ions and sodium ions. Extracting pure lithium resources from salt lakes is technically difficult.
  • researchers have developed a series of methods and processes such as precipitation, solar pool, extraction, calcination, membrane separation and adsorption to obtain lithium resources. Among them, membrane separation and adsorption methods are the most widely studied.
  • the purpose of the present invention is to overcome the above-mentioned problems of the prior art and provide a separation membrane and its preparation method and application.
  • the separation membrane has high density and high surface electrode potential (Zeta potential). During the separation of magnesium and lithium, it can better retain magnesium ions, thereby obtaining higher magnesium and lithium separation efficiency. It also has higher water flux and higher treatment efficiency.
  • a first aspect of the present invention provides a separation membrane, which in turn includes a base material layer, a porous support layer, a polyamide layer and a modification layer;
  • the cross-linked polymer forming the modified layer includes structural units provided by tannic acid and structural units provided by polyamines, and at least part of the structural units provided by tannic acid is also connected to the polyamide layer through the ortho position of the phenolic hydroxyl group;
  • the pore diameter of the separation membrane is 0.1-0.5nm, and the surface Zeta potential of the separation membrane is -5mV to 30mV.
  • a second aspect of the present invention provides a method for preparing a separation membrane.
  • the preparation method includes: sequentially preparing a porous support layer, a polyamide layer and a modification layer on a base material layer;
  • the method of preparing the modified layer includes: under the first pressure, while the polyhydric phenol solution is kept flowing, one side of the polyamide layer of the material including the base material layer, the porous support layer, and the polyamide layer is connected with the polyhydric phenol solution. After the first contact with the phenol solution, the polyamide layer side of the material is brought into second contact with the polyamine solution under the second pressure while the polyamine solution remains flowing to complete the self-assembly reaction.
  • a third aspect of the present invention provides a separation membrane prepared by the above method.
  • the fourth aspect of the present invention provides the application of the separation membrane as described in the first aspect or the third aspect in the separation of magnesium and lithium.
  • the separation membrane provided by the present invention has high density and high surface electrode potential (Zeta potential). When it is used for magnesium and lithium separation, it can better intercept magnesium ions and allow lithium ions to pass through as much as possible, thus obtaining a higher It has high magnesium and lithium separation efficiency, and also has high water flux and higher processing efficiency.
  • the preparation method of the separation membrane provided by the present invention, under the first pressure and the second pressure, and under the condition that the polyphenol solution and the polyamine solution are kept flowing, the polyamine and the polyphenol can pass through themselves on the polyamide layer.
  • the assembly reaction obtains a separation membrane containing a modified layer.
  • the separation membrane thus produced has high density and high surface electrode potential (Zeta potential).
  • Zeta potential high surface electrode potential
  • lithium ions are allowed to pass through as much as possible to obtain higher magnesium and lithium separation efficiency. It also has higher water flux and higher processing efficiency.
  • the preparation method has a simple process and has broad industrial prospects.
  • Figure 1 is an infrared spectrum of the separation membrane prepared in Example 1 and Comparative Examples 1-2 of the present invention.
  • Figure 2 shows the surface Zeta potential of the separation membrane as a function of the number of self-assembly times
  • Figure 3 is a curve of the surface Zeta potential of the separation membrane changing with the self-assembly pressure (first pressure/second pressure);
  • Figure 4 shows the change curve of the contact angle of the separation membrane with the self-assembly pressure (first pressure/second pressure);
  • Figure 5 shows the change curve of the contact angle of the separation membrane with the number of self-assembly times
  • Figure 6 is a cross-sectional SEM image of the separation membrane of Comparative Example 1 ( Figure 6a) and Example 10 ( Figure 6b);
  • Figure 7 is the XPS nitrogen element spectrum of the separation membranes prepared in Example 1 and Comparative Example 1.
  • the present invention provides a separation membrane, which sequentially includes a base material layer, a porous support layer, a polyamide layer and a modification layer;
  • the cross-linked polymer forming the modified layer includes structural units provided by polyphenols and structural units provided by polyamines, and at least part of the structural units provided by polyols are also connected to the polyamide layer through the ortho position of the phenolic hydroxyl group;
  • the pore diameter of the separation membrane is 0.1-0.5nm, and the surface Zeta potential of the separation membrane is -5mV to 30mV.
  • the separation membrane includes the modification layer as described above, which can make the separation membrane have the pore size range of the present invention, and make the separation membrane have the surface Zeta potential range of the present invention, indicating that this
  • the separation membrane has high density and high surface electrode potential.
  • it can better repel divalent magnesium ions, making it difficult for magnesium ions in the liquid to pass through the separation membrane, and at the same time, it can make monovalent magnesium ions Lithium ions pass through as much as possible, thereby obtaining higher magnesium and lithium separation efficiency.
  • the separation membrane has a higher water flux, and can have higher processing efficiency when the membrane is applied to the separation of magnesium and lithium in liquid.
  • the pore size of the separation membrane is measured using the polyethylene glycol (PEG) solute transfer method.
  • PEG polyethylene glycol
  • the PEG size corresponding to the 50% rejection rate is the average pore size of the separation membrane.
  • the surface Zeta potential of the separation membrane is measured by a potential analyzer.
  • the pore diameter of the separation membrane is 0.15-0.3 nm, and the surface Zeta potential of the separation membrane is 1 mV to 10 mV.
  • the modification layer includes the structural unit represented by formula I;
  • the modified layer of the separation membrane provided by the present invention contained the structural unit represented by Formula I, that is, there were
  • the ⁇ - ⁇ * electron conjugated structural unit formed by the benzene ring-nitrogen atom-benzene ring further illustrates that at least part of the structural units derived from polyphenols in the modified layer are connected to the structural units derived from polyamines and/or through the ortho position of the phenolic hydroxyl group.
  • the nitrogen atoms from the polyamide layer undergo a cross-linking reaction, further reducing the pore size of the separation membrane containing the modified layer, further improving the density of the separation membrane, thereby improving the magnesium-lithium efficiency of the separation membrane when it is used for magnesium-lithium separation. separation efficiency.
  • the content of the structural units provided by the polyhydric phenol on the membrane surface is 2 ⁇ 10 -3 -5 ⁇ 10 -2 mg/cm 2
  • the content of the structural units provided by the polyamine on the membrane surface is 1 ⁇ 10 -3 -2.5 ⁇ 10 -2 mg/cm 2 .
  • the content of the structural units provided by polyphenols and the structural units provided by polyamines on the membrane surface of the separation membrane follow these steps to measure:
  • the total content of polyphenols on the surface is ⁇ Pn, n ⁇ 1, and the total content of polyamines on the surface is ⁇ Tn, n ⁇ 1;
  • n is the number of self-assembly
  • S is the effective membrane area in cm 2 .
  • the inventor found through research that when the content of the structural units provided by polyphenols and the structural units provided by polyamines on the membrane surface meets the above range, the separation membrane will have appropriate density and thickness, thereby ensuring that the separation membrane It has high magnesium and lithium separation coefficient and water flux.
  • the content of the structural units provided by the polyhydric phenol on the membrane surface is 2.5 ⁇ 10 -3 -5 ⁇ 10 -2 mg/cm 2
  • the content of the structural units provided by the polyamine on the membrane surface is 4 ⁇ 10 -3 -2 ⁇ 10 -2 mg/cm 2 .
  • the content of N atoms in the modification layer is 13-20 at.%.
  • the content of N atoms in the modified layer is measured by an X-ray photoelectron spectrometer.
  • the separation membrane when the content of N atoms in the modified layer meets the above range, the separation membrane can have a high surface electrode potential and excellent hydrophilicity. When it is used for magnesium-lithium separation, it has high magnesium-lithium separation efficiency. and high water flux.
  • the content of N atoms in the modification layer is 13.5-18.5at.%.
  • the contact angle of the separation membrane is 20-60°.
  • the contact angle of the separation membrane is measured according to the following method: use the DSA100 surface contact angle measuring instrument produced by the German KRUSS company to test the surface contact angle of the composite membrane sample by the sessile drop method. Before the test, the sample is heated at 60°C Dry in a vacuum oven for 30 minutes to remove surface and internal moisture, and then paste the dried film on a flat glass slide with double-sided tape. During the test, the volume of each water droplet is 2 ⁇ L. The water droplet is placed on the surface of the film for 3 seconds and is tested immediately. The final contact angle is determined by averaging multiple measurements.
  • the separation membrane has a contact angle in the range described in the present invention, which indicates that the separation membrane has excellent hydrophilicity and can make the separation membrane have excellent water permeability.
  • the contact angle of the separation membrane is 20-40°.
  • the thickness of the separation membrane is 100-200 ⁇ m.
  • the thickness of the base material layer is 30-150 ⁇ m, preferably 50-120 ⁇ m.
  • the thickness of the porous support layer is 10-100 ⁇ m, preferably 30-60 ⁇ m.
  • the thickness of the polyamide layer is 10-500 nm, preferably 50-150 nm.
  • the thickness of the modification layer is 1-200 nm, preferably 10-60 nm.
  • the thickness of the separation membrane, porous support layer, and polyamide layer is measured by a spiral micrometer and a scanning electron microscope, and the thickness of the base material layer, porous support layer, and polyamide layer is subtracted from the thickness of the separation membrane. to obtain the thickness of the modified layer.
  • the thickness of the base material layer is the thickness measured before coating the porous support layer material solution.
  • the inventor of the present invention found in the research that when the thickness range of the above layers is satisfied, the above layers can cooperate better, so that the separation membrane has a small pore size and a high Zeta potential, which can be used for magnesium and lithium separation. , which can take into account higher magnesium and lithium separation efficiency and water flux.
  • the material of the base material layer is not particularly limited, and can be a material commonly used in the field with a certain strength, suitable for nanofiltration or reverse osmosis, and can play a supporting role.
  • the material of the base material layer is selected from polyester non-woven fabric, polyethylene non-woven fabric and At least one of polypropylene nonwoven fabrics.
  • the material of the porous support layer is not particularly limited and can be a material commonly used in the art that can play a certain supporting role and form a porous structure. More preferably, the material of the porous support layer is selected from the group consisting of polyethersulfone, polysulfone, polyarylether, polybenzimidazole, polyetherketone, polyetheretherketone, polyacrylonitrile, polyvinylidene fluoride and polyarylether. At least one of the ketones.
  • the porous structure in the porous support layer allows liquid to flow through it more easily.
  • the number average molecular weight of the material of the porous support layer may be 50,000-100,000 g/mol.
  • the polyamide layer is synthesized from a polyamine and a polybasic acid chloride.
  • the polyamide layer as described above has a more suitable cross-linked structure, and combined with the amino group therein, it can achieve a better interception effect on divalent magnesium ions.
  • the polyamine is selected from at least one of polyethyleneimine, triethylenetetramine, tetraethylenepentamine, diethylenetriamine, piperazine, m-phenylenediamine and p-phenylenediamine, more preferably At least one of polyethyleneimine, piperazine and polyethylenepolyamine.
  • the polybasic acid chloride is selected from at least one of trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride and phthaloyl chloride, more preferably trimesoyl chloride and terephthaloyl chloride at least one of them.
  • the specific types can be mixed in any ratio.
  • the weight ratio of trimesoyl chloride and terephthaloyl chloride can be 1:1-10.
  • the modified layer is obtained by self-assembly reaction of polyphenol and polyamine on the polyamide layer.
  • the self-assembly reaction includes the following steps: under the first pressure, while the polyphenol solution is kept flowing, one side of the polyamide layer of the material including the base material layer, the porous support layer, and the polyamide layer is After the first contact with the polyphenol solution, the polyamide layer side of the material is brought into second contact with the polyamine solution under a second pressure while the polyamine solution remains flowing to complete the self-assembly reaction.
  • the polyphenols are selected from the group consisting of tannic acid, tea polyphenols, gallic acid, catechin, lignin, sodium lignosulfonate, apple polyphenols, grape polyphenols, eriodictyol, and naringenin. , one or more of epicatechin, luteolin, apigenin, kanferol, myricetin and genistein, preferably tannic acid and/or tea polyphenols.
  • the polyamine is selected from at least one of polyethyleneimine, tetraethylenepentamine, triethylenetetramine and polyethylenepolyamine.
  • the first pressure and the second pressure are each independently 0.1-1.2MPa.
  • the pressure applied when preparing the modification layer when controlled to meet the above range, it can ensure that the separation layer composed of the modification layer and the polyamide layer has a higher degree of density, and at the same time, the polyamine provided in the separation membrane can The higher content of structural units makes the separation membrane more hydrophilic, which ultimately makes the separation membrane have excellent magnesium-lithium separation performance and water permeability.
  • first pressure and the second pressure are each independently 0.2-1MPa.
  • the amount of the polyphenol solution and the polyamine solution is such that the mass ratio of the polyphenol to the polyamine is 0.1-10:1.
  • the mass ratio of polyphenols and polyamines when the mass ratio of polyphenols and polyamines is controlled to meet the above range, in addition to ensuring that the polyphenols and polyamines can fully react and ensuring that the separation membrane produced has the pore size required by the present invention, it can also ensure separation.
  • the surface of the membrane contains more residual amino groups, so that the separation membrane has the high surface Zeta potential and hydrophilicity required by the present invention.
  • the separation membrane is used for magnesium-lithium separation, the separation membrane has higher divalent magnesium. Ion rejection and water flux.
  • the amount of the polyphenol solution and the polyamine solution is such that the mass ratio of the polyphenol to the polyamine is 0.2-6:1, preferably 0.5-6:1.
  • the concentration of the polyphenol solution is 0.00001-1wt%, preferably 0.0001-0.1wt%.
  • the concentration of the polyamine solution is 0.00001-1wt%, preferably 0.0001-0.1wt%.
  • controlling the concentrations of the polyphenol solution and the polyamine solution to independently meet the above ranges can ensure that the separation membrane thus produced has the pore size, surface Zeta potential and thickness required by the present invention, and can ensure that the separation membrane is When used for magnesium and lithium separation, it can improve the rejection rate of magnesium chloride while maintaining good water permeability.
  • the temperatures of the first contact and the second contact are independently 10-30°C.
  • the temperature of the first contact and the second contact is controlled to meet the above range, sufficient reaction between the polyphenol and the polyamine can be ensured, so that the prepared separation membrane has the pore size and surface required by the present invention. Zeta potential, thereby improving the magnesium chloride rejection rate and magnesium-lithium separation efficiency when the separation membrane is used for magnesium-lithium separation.
  • the first contact time is 1-120 minutes.
  • the second contact time is 1-120 minutes.
  • the time of the first contact and the second contact is controlled to meet the above range, not only can multiple
  • the full reaction between the polyphenol and the polyamine can also appropriately control the density and thickness of the membrane separation layer composed of the polyamide layer and the modified layer, ultimately making the separation membrane thus produced have high water permeability and high Magnesium and lithium separability.
  • the first contact time is 10-60 minutes.
  • the second contact time is 10-60 minutes.
  • the inventor further discovered in the research that by following the above method of preparing a modified layer on a polyamide layer including a base layer, a base material layer, a porous support layer, and a polyamide layer, and repeating the following steps, multiple processes can be completed.
  • a separation membrane has a higher surface Zeta potential and a smaller pore size, thereby further ensuring a higher magnesium and lithium separation efficiency.
  • the number of self-assembly reactions is 1-10 times, more preferably 2-5 times.
  • the water flux of the separation membrane is greater than or equal to 20L ⁇ m -2 ⁇ h -1 ; the MgCl 2 desalination rate is greater than or equal to 99%; and the magnesium-lithium separation coefficient is greater than or equal to 70.
  • the water flux of the separation membrane is 20-40L ⁇ m -2 ⁇ h -1 ; the MgCl 2 desalination rate is greater than or equal to 99%; the magnesium-lithium separation coefficient is 100-250.
  • the present invention provides a method for preparing a separation membrane, which is characterized in that the preparation method includes the following steps: sequentially preparing a porous support layer, a polyamide layer and a modification layer on the base material layer;
  • the method of preparing the modified layer includes: under the first pressure, while the polyhydric phenol solution is kept flowing, one side of the polyamide layer of the material including the base material layer, the porous support layer, and the polyamide layer is connected with the polyhydric phenol solution. After the first contact with the phenol solution, the polyamide layer side of the material is brought into second contact with the polyamine solution under the second pressure while the polyamine solution remains flowing to complete the self-assembly reaction.
  • the polyhydric phenol and the polyamine can undergo a Michael addition reaction to form a cross-linked structure.
  • the carbon atom adjacent to the carbon atom of the phenolic hydroxyl group on the polyphenol serves as a reaction site to react with the polyamine.
  • the carbon atom adjacent to the carbon atom of the phenolic hydroxyl group on the polyphenol serves as a reaction site to react with the amino group in the polyamide layer.
  • a separation membrane is prepared according to the preparation method provided in the second aspect of the present invention.
  • the separation membrane Under the first pressure and the second pressure, and under the condition that the polyphenol solution and the polyamine solution are kept flowing, the separation membrane will include a base material layer, a porous
  • the polyamide layer side of the material of the support layer and the polyamide layer is contacted with the polyphenol solution and the polyamine solution successively.
  • the polyphenol and the polyamine can undergo a Michael addition reaction on the surface of the polyamide layer to form a cross-linked structure.
  • the carbon atoms adjacent to the carbon atoms of part of the phenolic hydroxyl groups on the polyphenol can react with the amino groups in the polyamide layer and connect with the polyamide layer.
  • the prepared separation membrane can have a small pore size and a high surface Zeta potential, that is, the obtained The separation membrane according to the first aspect of the present invention.
  • controlling the self-assembly reaction process to be carried out in a dynamic environment with a certain flow rate can achieve the purpose of reducing the adsorption of additional polyphenols or polyamines on the membrane surface, thereby achieving more polyphenols or polyamines through chemical bonds. bonded to the membrane surface.
  • the separation membrane is modified by self-assembly, the density of the separation membrane is significantly increased and the separation membrane has a higher surface Zeta potential.
  • the separation membrane prepared by the preparation method provided by the second aspect of the present invention has the pore size range of the present invention, and the separation membrane has the surface Zeta potential range of the present invention, indicating that the separation membrane has high density and high Surface electrode potential, when used for lithium-magnesium separation, can better repel divalent magnesium ions, making it difficult for magnesium ions in the liquid to pass through the separation membrane, and at the same time, it can allow monovalent lithium ions to pass through as much as possible, thereby obtaining a higher High magnesium and lithium separation efficiency. Moreover, under the joint action of the above-mentioned layers, the separation membrane has a higher water flux, and when the membrane is applied to the separation of magnesium and lithium in liquid, it can have higher processing efficiency.
  • the first pressure and the second pressure are each independently 0.1-1.2MPa.
  • the reaction between the polyphenol and the polyamine can be promoted more fully, and the separation membrane thus produced has the properties of the present invention.
  • the required pore size and surface Zeta potential when the prepared separation membrane is used for magnesium and lithium separation, it has a high magnesium chloride rejection rate and excellent magnesium and lithium separation efficiency.
  • first pressure and the second pressure are each independently 0.2-1MPa.
  • the self-assembly reaction can be carried out in a cross-flow membrane tank.
  • the cross-flow membrane tank circulates water into the membrane tank through a water pump, so that the water in the membrane tank is in a flowing state, and pressure is applied through a pressure regulating valve to control the preparation.
  • the first pressure and the second pressure in the process meet the requirements of the present invention.
  • the method for preparing the modified layer can be carried out in conventional equipment in the field, such as a cross-flow membrane tank.
  • This method has a simple process and is easy to be industrialized.
  • the polyphenol solution is discharged, and the cross-flow membrane cell is repeatedly flushed with deionized water to clean the polyphenols in the system. Rinse away the polyphenols on the surface of the material.
  • the pump continuously delivers the solution into the tank. Therefore, the total amount of polyphenols or polyamines in the solution generally exceeds the amount that can be attached to the surface of the membrane to react, which can ensure that the results of the present invention are obtained. Required finishing layer.
  • the flow rate of the polyphenol solution and the polyamine solution there is no particular limit on the flow rate of the polyphenol solution and the polyamine solution, as long as it is ensured that the polyphenol solution and the polyamine solution remain flowing during the preparation of the modification layer, for example, the polyphenol solution or the polyvalent amine solution.
  • the flow rate of the amine solution can be 0.5-5L/min.
  • the amount of the polyphenol solution and the polyamine solution is such that the mass ratio of the polyphenol to the polyamine is 0.1-10:1.
  • the mass ratio of polyphenols and polyamines when the mass ratio of polyphenols and polyamines is controlled to meet the above range, in addition to ensuring that the polyphenols and polyamines can fully react and ensuring that the separation membrane produced has the pore size required by the present invention, it can also ensure separation.
  • the surface of the membrane contains more residual amino groups, so that the separation membrane has the high surface Zeta potential and hydrophilicity required by the present invention.
  • the separation membrane is used for magnesium-lithium separation, the separation membrane has higher divalent magnesium. Ion rejection and water flux.
  • the amount of the polyphenol solution and the polyamine solution is such that the mass ratio of the polyphenol to the polyamine is 0.2-6:1, preferably 0.5-6:1.
  • the concentration of the polyphenol solution is 0.00001-1wt%, preferably 0.0001-0.1wt%.
  • the concentration of the polyamine solution is 0.00001-1wt%, preferably 0.0001-0.1wt%.
  • controlling the concentrations of the polyphenol solution and the polyamine solution to independently meet the above ranges can ensure that the separation membrane thus produced has the pore size, surface Zeta potential and thickness required by the present invention, and can ensure that the separation membrane is When used for magnesium and lithium separation, it can improve the rejection rate of magnesium chloride while maintaining good water permeability.
  • the temperatures of the first contact and the second contact are each independently 10-30°C.
  • the temperature of the first contact and the second contact is controlled to meet the above range, sufficient reaction between the polyphenol and the polyamine can be ensured, so that the prepared separation membrane has the pore size and surface required by the present invention. Zeta potential, thereby improving the magnesium chloride rejection rate and magnesium-lithium separation efficiency when the separation membrane is used for magnesium-lithium separation.
  • the first contact time is 1-120 minutes.
  • the second contact time is 1-120 minutes.
  • the present invention in a self-assembly reaction, when the time of the first contact and the second contact is controlled to meet the above range, not only can the polyphenol and the polyamine be fully reacted, but also the polyamide layer and the modification can be realized.
  • the density and thickness of the membrane separation layer composed of three layers are appropriately controlled, so that the separation membrane thus produced has high water permeability and high magnesium and lithium separation properties.
  • the first contact time is 10-60 minutes.
  • the second contact time is 10-60 minutes.
  • the inventor further discovered in the research that by following the above method of preparing a modified layer on a polyamide layer including a base layer, a base material layer, a porous support layer, and a polyamide layer, and repeating the following steps, multiple processes can be completed.
  • a separation membrane has a higher surface Zeta potential and a smaller pore size, thereby further ensuring a higher magnesium and lithium separation efficiency.
  • the number of self-assembly reactions is 1-10 times, more preferably 2-5 times.
  • the conditions for preparing the modification layer include making the thickness of the modification layer in the separation membrane range from 1 to 200 nm, preferably from 10 to 60 nm.
  • the polyphenols in the polyphenol solution are selected from the group consisting of tannic acid, tea polyphenols, gallic acid, catechin, lignin, sodium lignosulfonate, apple polyphenols, grape polyphenols, and eriodictyol , one or more of naringenin, epicatechin, luteolin, apigenin, kanferol, myricetin and genistein, preferably tannic acid and/or tea polyphenols.
  • the polyamine in the polyamine solution is selected from at least one of polyethyleneimine, tetraethylenepentamine, triethylenetetramine and polyethylenepolyamine.
  • the method for preparing the porous support layer on the base layer can be a method commonly used in this field.
  • the method for preparing the porous support layer includes: coating a solution containing the porous support layer material on the base material layer, and performing phase conversion to obtain a material containing the base material layer and the porous support layer.
  • the specific method of coating is not particularly limited, and a doctor blade can be used for coating.
  • the phase transformation conditions include: soaking in water at 10-30°C for 10-60 minutes.
  • the method for preparing the porous support layer when used as described above, when soaked in water, the solvent in the solution containing the porous support layer material gradually leaves the porous support layer. Through this phase conversion method, it can be further ensured A support layer with a porous structure is obtained.
  • the thickness of the base material layer is 30-150 ⁇ m, more preferably 50-120 ⁇ m. It can be understood that the thickness of the base material layer does not change substantially before and after preparation.
  • the material of the base material layer is selected from at least one of polyester non-woven fabrics, polyethylene non-woven fabrics and polypropylene non-woven fabrics.
  • the conditions for preparing the porous support layer include such that the thickness of the porous support layer in the separation membrane is 10-100 ⁇ m, more preferably 30-60 ⁇ m. It can be understood that the thickness can be controlled by controlling the amount of coating, and since the thickness will collapse after coating, the thickness set during coating is different from the thickness of the porous support layer in the final prepared separation membrane. There will be some differences. Generally, the thickness set during coating is about 40-60 ⁇ m higher than the desired porous support layer in the separation membrane.
  • the concentration of the solution containing the porous support layer material is 10-20 wt%.
  • the porous support layer material is selected from polyethersulfone, polysulfone, polyarylether, polybenzimidazole, polyetherketone, polyetheretherketone, polyacrylonitrile, polyvinylidene fluoride and polyaryletherketone at least one of them.
  • the solvent in the solution containing the porous support layer material is selected from the group consisting of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and dimethyl sulfoxide. of at least one.
  • the preparation method of the solution containing the porous support layer material can be prepared by conventional methods in the art.
  • the porous support layer material is first dissolved in a solvent and degassed (degassed). The soaking can be carried out at 20-40°C for 10-180 min) to obtain a solution containing the porous support layer material.
  • the material can be washed, such as washed with water multiple times.
  • the method for preparing the polyamide layer includes: sequentially contacting the surface of the porous support layer including the material of the base layer and the porous support layer with an aqueous phase containing a polyamine and an organic phase containing a polyvalent acid chloride, and then performing heat treatment.
  • the above-mentioned method of sequentially contacting an aqueous phase containing a polyamine and an organic phase containing a polyvalent acid chloride is used to obtain a polyamide layer through interfacial polymerization.
  • a polyamide layer has a cross-linked structure, and the polyamide layer is not only dense but also very thin. , further ensuring higher magnesium and lithium separation efficiency and water flux.
  • the operation of contacting the aqueous phase and the organic phase can be performed at normal temperature, such as 23-28°C.
  • the conditions for preparing the polyamide layer include making the thickness of the polyamide layer in the separation membrane 10-500 nm, more preferably 50-300 nm.
  • the time for the porous support layer to contact the aqueous phase containing the polyamine is 5-100 s, and more preferably 10-60 s.
  • the time for the porous support layer to contact the organic phase containing the polybasic acid chloride is 10-200s, more preferably 20-120s.
  • the amount of the aqueous phase containing the polyamine and the organic phase containing the polyvalent acid chloride is such that the mass ratio of the polyamine to the polyvalent acid chloride is 0.1-10:1.
  • the inventor of the present invention also found that when the mass ratio of the polyamine and the polycarboxylic acid chloride is controlled to meet the above ratio, it is possible to ensure that the polyamide layer produced has an appropriate pore size and ensures that the polyamide layer has excellent lithium chloride permeability. At the same time, it has good retention of magnesium chloride; at the same time, after the polyamide layer is modified with polyphenols and polyamines, the pore size of the polyamide layer can be further reduced, the surface Zeta potential is further increased, and finally the polyamide layer has the properties of the present invention.
  • the separation membrane defined in the first aspect having a specific pore size and surface Zeta potential has significantly improved magnesium-lithium separation efficiency when the separation membrane is used for magnesium-lithium separation.
  • the amount of the aqueous phase containing the polyamine and the organic phase containing the polyvalent acid chloride is such that the mass ratio of the polyamine to the polyvalent acid chloride is 0.5-8:1.
  • the organic solvent in the organic phase containing polybasic acid chlorides can be n-hexane, dodecane, n-heptane, or alkane solvent naphtha (which can be commercially available Isopar E, Isopar G, Isopar H, Isopar L, and Isopar M). at least one of them.
  • the concentration of the aqueous phase containing polyamine is 0.1-10wt%, more preferably 0.5-2.5wt%.
  • the concentration of the organic phase containing polybasic acid chloride is 0.01-1wt%, more preferably 0.1-0.5wt%.
  • the specific types can be mixed in any ratio.
  • the mass ratio of trimesoyl chloride and terephthaloyl chloride can be 1:1-10.
  • the thickness of the polyamide layer produced can be in the range of 10-500 nm.
  • the concentrations of the aqueous phase containing the polyamine and the organic phase containing the polyvalent acid chloride are controlled to meet the range defined by the present invention, it can also have a higher rejection rate for magnesium ions and at the same time have a higher rejection rate for monovalent lithium ions. Higher transmittance.
  • the volume of the aqueous phase containing the polyvalent amine and the volume of the organic phase containing the polyvalent acid chloride are not particularly limited, as long as the amount of the polyamine in the aqueous phase or the amount of the polyvalent acid chloride in the organic phase can be ensured, A suitable polyamide layer with a cross-linked structure is formed on the membrane.
  • the total amount of polyvalent amines in the aqueous phase can be 0.05-2g
  • the total amount of polyvalent acid chlorides in the organic phase can be 0.0001-0.5g.
  • the polyamine is selected from at least one of polyethyleneimine, triethylenetetramine, tetraethylenepentamine, diethylenetriamine, piperazine, m-phenylenediamine and p-phenylenediamine, more preferably It is at least one of polyethyleneimine, piperazine and polyethylenepolyamine.
  • the polybasic acid chloride is selected from at least one of trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride and phthaloyl chloride, more preferably trimesoyl chloride and terephthaloyl chloride. At least one of the acid chlorides.
  • the temperature of the heat treatment is 40-150°C; the time of the heat treatment is 0.5-10 min.
  • the temperature of the heat treatment is 50-120°C; the time of the heat treatment is 1-5 minutes.
  • the preparation method also includes: soaking the prepared separation membrane in deionized water for later use.
  • the present invention provides a separation membrane prepared by the above method.
  • the present invention provides the application of the separation membrane as described in the first aspect or the third aspect in magnesium and lithium separation (especially lithium extraction from salt lakes).
  • the specific method for using the separation membrane to separate magnesium and lithium includes: loading the salt lake brine into a feed tank, installing the separation membrane on the membrane pool; operating the system under pressure I, and collecting the first-level filtrate filtered by the separation membrane. Produce water; then put the primary product water into the feed tank as the feed liquid, run the system under pressure II, and collect the secondary product water filtered by the separation membrane.
  • the content of magnesium ions in the salt lake brine is greater than or equal to 500 ppm, and the content of lithium ions is less than or equal to 50 ppm.
  • the mass concentration ratio of Mg 2+ and Li + in the salt lake brine is greater than or equal to 5.
  • the pressure I is 0.5-2MPa.
  • the pressure II is 0.5-2MPa.
  • the content of magnesium ions in the primary produced water is less than or equal to 20 ppm, and the content of lithium ions is greater than or equal to 20 ppm.
  • the mass concentration ratio of Mg 2+ and Li + in the primary produced water is less than or equal to 1.
  • the content of magnesium ions in the secondary produced water is less than or equal to 0.5 ppm, and the content of lithium ions is greater than or equal to 25 ppm.
  • the purity of Li + in the secondary produced water is greater than or equal to 98%.
  • the water flux of the separation membrane is greater than or equal to 20L ⁇ m -2 ⁇ h -1 ; the MgCl 2 desalination rate is greater than or equal to 99%; the magnesium-lithium separation coefficient is greater than or equal to 70.
  • the water flux of the separation membrane is 20-40L ⁇ m -2 ⁇ h -1 ; the MgCl 2 desalination rate is greater than or equal to 99%; the magnesium-lithium separation coefficient is 100-250.
  • the separation membrane is prepared according to the following method:
  • the surface of the porous support layer including the material of the base layer and the porous support layer is contacted with an aqueous solution containing 0.5-0.6% by weight polyethyleneimine, and the liquid is drained after contacting for 50-60 seconds at 24-26°C; then, the upper surface of the support layer is Then contact the Isopar E solution containing trimesoyl chloride and terephthaloyl chloride (the mass ratio of the polyamine in the aqueous phase containing the polyamine to the mass ratio of the polyvalent acid chloride in the organic phase containing the polyvalent acid chloride is 5-6: 1.
  • trimesoyl chloride and terephthaloyl chloride are 1:3-5), and the liquid is drained after contact for 60-70 seconds at 24-26°C; then, put the film into the oven and heat it at 60-70°C Heat for 3-4 minutes at high temperature to obtain a material including a base material layer, a porous support layer, and a polyamide layer.
  • the solution in the cross-flow membrane tank is 0.001-0.005 wt% polyphenol aqueous solution, run the cross-flow membrane cell for 30-35 minutes at 0.6-0.65MPa, 25-26°C, and maintain the flow rate of the polyphenol solution at 2.5-3.5L/min, drain the liquid, and use Rinse the cross-flow membrane tank repeatedly with deionized water to clean the polyphenols in the system; add polyamine aqueous solution to the cross-flow membrane tank (the amount of polyphenol solution and polyamine solution is such that the mass ratio of polyphenols to polyamine is 0.1- 10:1), so that the polyamide layer side of the material contacts the above solution, and the cross-flow membrane cell is operated at 0.6-0.65MPa, 25-26°C, and the flow rate of the polyamine solution is maintained at 0.5-5L/min.
  • the pressure refers to gauge pressure.
  • Isopar E is a commercially available alkane solvent oil (purchased from Xilong Chemical Industry).
  • the materials including the base material layer and the porous support layer were prepared according to the following method:
  • the membranes were immersed in deionized water for 24 hours for later use, and then various properties and parameters were measured.
  • the molecular structure of the separation membrane was characterized and analyzed using a total reflection infrared spectrometer (Nicolet 6700).
  • the pore size of the separation membrane measured using the PEG solute transfer method. The detailed steps are as follows:
  • the PEG size corresponding to the 50% rejection rate is the average pore size of the separation membrane.
  • the content of nitrogen atoms in the modified layer of the separation membrane measured by X-ray photoelectron spectroscopy (XPS): obtained by irradiating Al-K ⁇ X-rays on an ESCALAB250 X-ray photoelectron spectrometer.
  • XPS X-ray photoelectron spectroscopy
  • the total content of polyphenols on the surface is ⁇ Pn, n ⁇ 1, and the total content of polyamines on the surface is ⁇ Tn, n ⁇ 1;
  • n is the number of self-assembly
  • S is the effective membrane area in cm 2 .
  • the conditions under which the membrane is contacted with the aqueous solution of polyphenol and the aqueous solution of polyamine respectively correspond to the first pressure, the second pressure, the temperature and time of the first contact and the temperature of the second contact in the self-assembly process in the examples and comparative examples. and time.
  • Contact angle of the separation membrane Use the DSA100 surface contact angle measuring instrument produced by the German KRUSS company to test the surface contact angle of the composite membrane sample by the static drop method. Before the test, the sample was dried in a 60°C vacuum oven for 30 minutes to remove the surface and interior. Moisture, and then stick the dried film on a flat glass slide with double-sided tape. The volume of each water droplet during testing is 2 ⁇ L. The water droplet is placed on the surface of the film for 3 seconds and is tested immediately. After multiple measurements, the average value is taken to determine the final contact. The size of the horn.
  • the thickness of the separation membrane and each layer in the separation membrane The thickness of the separation membrane, porous support layer, and polyamide layer is measured by a spiral micrometer and a scanning electron microscope, and the substrate layer and porous support are subtracted from the thickness of the separation membrane.
  • the thickness of the modified layer is obtained by the thickness of the polyamide layer.
  • the thickness of the base material layer is the thickness measured before coating the porous support layer material solution.
  • the surface of the porous support layer including the material of the base layer and the porous support layer was contacted with an aqueous solution (50 mL) containing 0.5% by weight polyethyleneimine, and the liquid was drained after contacting for 60 seconds at 25°C; then, the upper surface of the support layer was contacted with an aqueous solution containing 0.5 wt% polyethyleneimine.
  • IsoparE solution (30 mL) of 0.02 wt% trimesoyl chloride and 0.08 wt% terephthaloyl chloride was exposed to 25°C for 60 s and then drained; then, the film was placed in an oven and heated at 70°C for 3 min.
  • the heat-treated product into a cross-flow membrane tank so that the polyamide layer side of the material comes into first contact with the 0.001wt% tannic acid aqueous solution in the cross-flow membrane tank.
  • the volume of the tannic acid aqueous solution is 5L, and Keep the tannic acid solution in a flowing state with a flow rate of 1.5L/min.
  • the surface of the porous support layer including the base material layer and the porous support layer was contacted with an aqueous solution (50 mL) containing 1% by weight polyethylene polyamine, and the liquid was drained after contacting for 20 s at 25°C; then, the upper surface of the support layer was contacted with an aqueous solution containing 1 wt% polyethylene polyamine.
  • IsoparE solution (30 mL) of 0.18 wt% trimesoyl chloride and 0.12 wt% terephthaloyl chloride was exposed to 25°C for 30 s and then drained; then, the film was placed in an oven and heated at 50°C for 5 min.
  • the heat-treated product into a cross-flow membrane tank so that the polyamide layer side of the material comes into first contact with the 0.01wt% tannic acid aqueous solution in the cross-flow membrane tank.
  • the volume of the tannic acid aqueous solution is 5L, and Keep the tannic acid solution in a flowing state with a flow rate of 0.5L/min.
  • the surface of the porous support layer including the material of the base layer and the porous support layer was contacted with an aqueous solution (50 mL) containing 2.5% by weight of piperazine, and the liquid was drained after contacting for 40 s at 25°C; then, the upper surface of the support layer was contacted with an aqueous solution containing 0.2% by weight of piperazine.
  • the heat-treated product into a cross-flow membrane tank so that the polyamide layer side of the material comes into first contact with the 0.1wt% tannic acid aqueous solution in the cross-flow membrane tank.
  • the volume of the tannic acid aqueous solution is 5L and makes The tannic acid solution remains in a flowing state with a flow rate of 5L/min.
  • the cross-flow membrane tank is run for 20 minutes at 0.6MPa and 30°C, the liquid is drained and the cross-flow membrane tank is repeatedly flushed with deionized water to clean the remaining tannic acid.
  • Ninic acid add 5L of polyethyleneimine aqueous solution with a concentration of 0.1wt% into the cross-flow membrane tank, and keep the polyethyleneimine water solution in a flowing state.
  • the flow rate is 5L/min, so that one side of the polyamide layer of the material is in contact with the The above solution was subjected to the second contact.
  • the cross-flow membrane cell was run for 20 minutes at 0.6MPa and 30°C, the liquid was drained and the cross-flow membrane cell was repeatedly rinsed with deionized water to wash away the remaining polyethyleneimine; thus completing For a self-assembly reaction, repeat the above operation to complete another self-assembly reaction.
  • the mass ratio of polyphenol and polyamine is 1:1, and the separation membrane N3 is obtained.
  • a separation membrane was prepared according to the method of Example 1, except that in the self-assembly reaction, polyethyleneimine was replaced by polyethylenepolyamine. Separation membrane N4 was prepared.
  • a separation membrane was prepared according to the method of Example 1, except that in the self-assembly reaction, polyethyleneimine was replaced by tetraethylenepentamine. Separation membrane N5 was prepared.
  • a separation membrane was prepared according to the method of Example 1, except that in the self-assembly reaction, polyethyleneimine was replaced by triethylenetetramine. Separation membrane N6 was prepared.
  • the separation membrane was prepared according to the method of Example 1, except that the self-assembly reaction was only performed once. Separation membrane N7 was prepared.
  • the separation membrane was prepared according to the method of Example 1, except that the self-assembly reaction was carried out three times. Separation membrane N8 was prepared.
  • the separation membrane was prepared according to the method of Example 1, except that the self-assembly reaction was carried out four times in total. Separation membrane N9 was prepared.
  • the separation membrane was prepared according to the method of Example 1, except that the self-assembly reaction was carried out five times in total. Separation membrane N10 was prepared.
  • the separation membrane was prepared according to the method of Example 1, except that the materials including the base material layer and the porous support layer were prepared according to the following method: polyethersulfone (number average molecular weight: 70000g/mol) was dissolved in N, N-di In methylformamide, a polyethersulfone solution with a concentration of 20% by weight was prepared and degassed at 25°C for 120 min.
  • the separation membrane was prepared according to the method of Example 1, except that the materials including the substrate layer and the porous support layer were prepared according to the following method: polyacrylonitrile (number average molecular weight: 100000g/mol) was dissolved in N, N-di In methylformamide, a polyacrylonitrile solution with a concentration of 15% by weight was prepared and degassed at 25°C for 120 min.
  • the polyacrylonitrile solution is coated on a polypropylene non-woven fabric (base material layer) with a thickness of 115 ⁇ m using a scraper, and then the material is soaked in water with a temperature of 28°C for 40 minutes, so that the polypropylene non-woven fabric surface becomes
  • the acrylonitrile layer was phase-converted into a porous membrane, and finally washed with water three times to obtain a material with a total thickness of 160 ⁇ m, including a substrate layer and a porous support layer (the thickness of the porous support layer is 45 ⁇ m), with an area of 400 cm2.
  • Separation membrane N12 was prepared.
  • the separation membrane was prepared according to the method of Example 1, except that in the self-assembly reaction, the concentration of tannic acid in the tannic acid aqueous solution was 0.0001wt%, and the concentration of polyethyleneimine in the polyethyleneimine solution was 0.001wt%. In a self-assembly process, the mass ratio of polyphenols to polyamines is 0.1:1. Separation membrane N13 was prepared.
  • a separation membrane was prepared according to the method of Example 1, except that the first pressure and the second pressure during the self-assembly process were both 0.2MPa, and the solution flow rate was both 1.5L/min, to prepare a separation membrane N14.
  • a separation membrane was prepared according to the method of Example 1, except that the pressure of the first contact and the second contact during the self-assembly process was 1 MPa, and the solution flow rate was both 1.5 L/min, to prepare a separation membrane N15.
  • the separation membrane was prepared according to the method of Example 1, except that the pressure of the first contact and the second contact during the self-assembly process was 0.8MPa.
  • the flow rate of the solution was all 1.5L/min, and the separation membrane N16 was obtained.
  • a separation membrane was prepared according to the method of Example 1, except that the pressure of the first contact and the second contact during the self-assembly process was 0.4MPa, and the solution flow rate was both 1.5L/min, to prepare a separation membrane N17.
  • the surface of the porous support layer including the material of the base layer and the porous support layer was contacted with an aqueous solution (50 mL) containing 0.5% by weight polyethyleneimine, and the liquid was drained after contacting for 60 seconds at 25°C; then, the upper surface of the support layer was contacted with an aqueous solution containing 0.5 wt% polyethyleneimine.
  • IsoparE solution (30 mL) of 0.01 wt% trimesoyl chloride and 0.04 wt% terephthaloyl chloride was exposed to 25°C for 60 s and then drained; then, the film was placed in an oven and heated at 70°C for 3 min.
  • the heat-treated product into a cross-flow membrane tank so that the polyamide layer side of the material comes into first contact with the 0.001wt% tannic acid aqueous solution in the cross-flow membrane tank.
  • the volume of the tannic acid aqueous solution is 5L, and Keep the tannic acid solution in a flowing state with a flow rate of 1.5L/min.
  • Tannic acid add 5L of polyethyleneimine aqueous solution with a concentration of 0.004wt% into the cross-flow membrane tank, and keep the polyethyleneimine water solution in a flowing state, with a flow rate of 1.5L/min, so that the polyamide layer of the material is Make a second contact with the above solution on the side.
  • the cross-flow membrane cell is run for 30 minutes at 0.6MPa and 25°C, the liquid is drained and the cross-flow membrane cell is repeatedly rinsed with deionized water to wash away the remaining polyethyleneimine; thus After completing one self-assembly reaction, repeat the above operation to complete another self-assembly reaction.
  • the mass ratio of polyphenol to polyamine is 0.25:1, and the separation membrane N18 is obtained.
  • the separation membrane was prepared according to the method of Example 1, except that in the self-assembly reaction, the concentration of tannic acid in the tannic acid aqueous solution was 0.001wt%, and the concentration of polyethyleneimine in the polyethyleneimine solution was 0.0001wt%. In a self-assembly process, the mass ratio of polyphenols to polyamines is 10:1. Separation membrane N19 was prepared.
  • the separation membrane was prepared according to the method of Example 1, except that no self-assembly reaction was performed, that is, the separation membrane was obtained directly after heat treatment.
  • a separation membrane D1 was prepared.
  • a separation membrane was prepared according to the method of Example 1, except that the heat-treated product was put into a cross-flow membrane tank containing 0.001wt% tannic acid aqueous solution.
  • the volume of the tannic acid aqueous solution was 5L, and the tannic acid aqueous solution was The acid solution was kept in a flowing state with a flow rate of 1.5L/min. After running for 30 minutes at 0.6MPa and 25°C, it was taken out to obtain a separation membrane (that is, it only contacted the tannic acid aqueous solution once).
  • Separation membrane D2 was prepared.
  • a separation membrane was prepared according to the method of Example 1, except that polyethyleneimine was replaced by polyvinyl alcohol. Separation membrane D3 was prepared.
  • the polyacrylonitrile ultrafiltration membrane is loaded into the cross-flow membrane tank, and one side is in contact with the solution in the cross-flow membrane tank.
  • the solution in the cross-flow membrane tank is 0.001wt% tannic acid aqueous solution, and the volume of the tannic acid aqueous solution is 5L. , and keep the tannic acid solution in a flowing state, with a flow rate of 1.5L/min.
  • the cross-flow membrane tank is run for 30 minutes at 0.6MPa and 25°C, the liquid is drained, and the cross-flow membrane tank is rinsed repeatedly with deionized water.
  • a separation membrane was prepared according to the method of Example 1, except that the porous support layer including the substrate layer and the porous support material was installed into the cross-flow membrane. Pool, one side is in first contact with the 0.001wt% tannic acid aqueous solution in the cross-flow membrane pool. The volume of the tannic acid aqueous solution is 5L, and the tannic acid solution is kept in a flowing state, with a flow rate of 1.5L/min.
  • the surface of the porous support layer modified with polyphenol and polyamine was contacted with an aqueous solution (50 mL) containing 0.5 wt% polyethyleneimine, and the liquid was drained after contacting for 60 seconds at 25°C; then, the upper surface of the support layer was contacted with an aqueous solution containing 0.02 wt% polyethylenimine.
  • Isopar E solution (30 mL) of trimesoyl chloride and 0.08 wt% terephthaloyl chloride, contact for 60 seconds at 25°C and then drain; then, place the film in an oven and heat at 70°C for 3 minutes to obtain polyamine-containing Polyamide composite membrane D5 with polyphenol intermediate layer.
  • a separation membrane was prepared according to the method of Example 1. The difference was that the heat-treated product was not put into a cross-flow membrane tank for self-assembly reaction. Instead, the polyamide of the material was directly placed in a beaker containing an aqueous tannic acid solution. One side of the layer is exposed to the tannic acid aqueous solution (that is, the first pressure is 0MPa and the tannic acid solution does not flow), take it out after 24 hours, and rinse it repeatedly with deionized water; then directly place it in a beaker containing the polyethyleneimine aqueous solution.
  • the volume of the tannic acid solution (or polyamine) in the beaker is such that the total amount of tannic acid (or polyamine) exceeds the amount that may be attached to the membrane and react. Separation membrane D6 was obtained.
  • the surface of the porous support layer including the material of the base layer and the porous support layer was contacted with an aqueous solution (50 mL) containing 0.5% by weight polyethyleneimine, and the liquid was drained after contacting for 60 seconds at 25°C; then, the upper surface of the support layer was contacted with an aqueous solution containing 0.5 wt% polyethyleneimine.
  • IsoparE solution (30 mL) of 0.02 wt% trimesoyl chloride and 0.08 wt% terephthaloyl chloride was exposed to 25°C for 60 s and then drained; then, the film was placed in an oven and heated at 70°C for 3 min.
  • a separation membrane was prepared according to the method of Example 1, except that the first pressure and the second pressure during the self-assembly process were both 0 MPa, and the solution flow rate was both 1.5 L/min, to prepare a separation membrane D8.
  • a separation membrane was prepared according to the method of Example 1, except that the polyamide membrane was first contacted with the polyethyleneimine solution and then contacted with the tannic acid solution, and the self-assembly was only once, to prepare the separation membrane D9.
  • Example 1 The separation membranes prepared in Example 1 and Comparative Examples 1-2 were characterized by infrared spectroscopy, and the results are shown in Figure 1.
  • the membrane without self-assembly modification of tannic acid and polyethyleneimine (the membrane of Comparative Example 1) has a broad peak at 3388cm -1 , corresponding to the unreacted amino groups on the polyamide surface, and at the same time at 1507cm - Position 1 shows a weak signal, which also corresponds to the stretching vibration of NH.
  • modification with tannic acid i.e., the membrane of Comparative Example 2
  • there was a strong absorption peak at 3364 cm -1 corresponding to the phenolic hydroxyl group in the tannic acid molecule, and the signal peak at 1507 cm -1 basically disappeared, confirming Amino groups react chemically with tannic acid.
  • the cross-linked polymer forming the modified layer includes structural units provided by tannic acid and structural units provided by polyamines.
  • the tannic acid The structural units provided are also connected to the polyamide layer via the ortho position of the phenolic hydroxyl group.
  • the separation membranes provided in Examples 1-19 have small pore sizes and the modified layer of the separation membrane has a high positive charge density.
  • the thickness of the modified layer in Comparative Example 2 is the thickness change caused by tannic acid
  • the thickness of the modified layer in Comparative Example 3 is the thickness change caused by the reaction of tannic acid and polyvinyl alcohol.
  • the separation membrane provided by the present invention has a small pore size and a high surface Zeta potential.
  • the rejection rate of magnesium chloride can be significantly improved; at the same time, the separation membrane has excellent hydrophilicity. Able to achieve excellent water permeability.
  • the polyamide layer without polyphenol and polyamine modification is smooth and thin, with a thickness of 85nm.
  • polyphenols and polyamines are used to self-assemble on the surface of the polyamide layer. After modification, the surface of the polyamide layer is covered by a modification layer with a thickness of approximately 30 nm. cover.
  • Figure 7 compares the XPS nitrogen element spectra of Example 1 ( Figure 7a) and Comparative Example 6 ( Figure 7b). It can be seen from the figure that the modified layer of Example 1 has a characteristic peak at 407eV, which corresponds to The structural unit shown in Formula I is the signal peak generated by the ⁇ - ⁇ * electron conjugation formed by the benzene ring-nitrogen atom-benzene ring. Comparative Example 6 does not have this signal peak, indicating that the structural unit represented by Formula I can be produced only under the process conditions of the pressure-driven self-assembly of the present invention. One nitrogen atom in this structural unit undergoes a cross-linking reaction with two benzene rings, which increases the density of the separation membrane and further reduces the pore size of the separation membrane.
  • the separation membranes prepared in the Examples and Comparative Examples were put into cross-flow membrane cells respectively, and the water permeability of the separation membrane within a certain period of time was measured at 0.6MPa and a temperature of 25°C, and the water permeability of the separation membrane was measured according to the following formula Calculate the water flux:
  • J Q/(A ⁇ t), where J is the water flux (L/m 2 h), Q is the water permeability (L), A is the effective membrane area of the separation membrane (m 2 ), and t is time. (h).
  • the separation membrane into a cross-flow membrane tank, in which the raw material liquid contains 2000ppm magnesium chloride or 2000ppm lithium chloride. After prepressing at 0.2MPa for 0.5h, the pressure is 0.6MPa and the raw material liquid temperature is 25°C. Obtain the permeate liquid, measure the magnesium chloride and lithium chloride concentrations in the permeate liquid with a conductivity meter, and calculate the salt rejection rate through the following formula:
  • R (%) (C f -C P )/C f ⁇ 100%, where R is the salt rejection rate, C f is the concentration of magnesium chloride or lithium chloride in the raw material liquid (measured by the conductivity meter), and C p is The concentration of magnesium chloride or lithium chloride in the permeate liquid (measured by conductivity meter);
  • the separation membrane into a cross-flow membrane tank.
  • the raw material liquid contains 2000ppm magnesium chloride and 100ppm lithium chloride. After prepressing for 0.5h at 0.2MPa, the pressure is 0.6MPa and the raw material liquid temperature is 25°C.
  • Obtain the permeate liquid measure the concentrations of magnesium ions and lithium ions in the permeate liquid through ion chromatography, and calculate the magnesium-lithium separation coefficient through the following formula:
  • S is the magnesium-lithium separation coefficient
  • C Li, p and C Li, f are the concentrations of lithium ions in the permeate liquid and raw material liquid respectively (measured by ion chromatography);
  • C Mg, p and C Mg, f are the permeate liquid and raw material liquid respectively.
  • the concentration of magnesium ions in the flow liquid and raw material liquid (measured by ion chromatography).
  • the embodiments adopting the technical solution of the present invention have both higher water flux and higher magnesium and lithium separation efficiency.
  • the content of polyphenols and polyamines on the membrane surface increases, which increases the hydrophilicity and surface Zeta potential of the membrane surface.
  • the membrane's rejection rate of magnesium chloride increases, thereby increasing the magnesium-lithium separation coefficient.
  • the thickness of the modified layer increases, which reduces the water flux of the membrane.

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  • Separation Using Semi-Permeable Membranes (AREA)

Abstract

一种分离膜及其制备方法和在镁锂分离中的应用，分离膜依次包括基材层、多孔支撑层、聚酰胺层和修饰层，形成修饰层的交联聚合物包括多元酚提供的结构单元与多元胺提供的结构单元，至少部分多元酚提供的结构单元还通过酚羟基的邻位与聚酰胺层连接，分离膜的孔径为0.1-0.5nm表面Zeta电位为-5mV至30mV；制备方法包括以下步骤：在基材层上依次制备多孔支撑层、聚酰胺层和修饰层，其中，制备修饰层的方法包括：在第一压力下，在多元酚溶液保持流动的情况下，将聚酰胺层一侧与多元酚溶液进行第一接触后，在第二压力下，在多元胺溶液保持流动的情况下，将聚酰胺层一侧与多元胺溶液进行第二接触，完成自组装反应。

Description

分离膜及其制备方法和应用
相关申请的交叉引用
本申请要求2022年05月20日提交的中国专利申请202210555981.0的权益，该申请的内容通过引用被合并于本文。
技术领域
本发明涉及膜领域，具体地涉及一种分离膜及其制备方法和应用。
背景技术
随着新能源汽车的广泛应用，锂能源的需求量也逐步攀升。在我国，绝大多数的锂资源都蕴藏在盐湖卤水中。盐湖水中除了锂离子外，还含有大量的镁离子与钠离子，从盐湖中提取出纯净的锂资源具有较高的技术难度。研究者们开发出沉淀法、太阳池法、萃取法、煅烧法、膜分离法以及吸附法等一系列方法和工艺以获取锂资源。其中，以膜分离法和吸附法研究得最为广泛。
然而，现有的商业纳滤膜不是针对镁锂分离而设计的，其对于镁离子与锂离子的分离效率非常低，镁锂分离系数一般小于5，不能用于盐湖提锂。因此，如何实现高效的镁锂分离仍然面临很多挑战。
发明内容
本发明的目的是为了克服现有技术的存在的上述问题，提供一种分离膜及其制备方法和应用，该分离膜具有高的致密度以及高的表面电极电位(Zeta电位)，将其用于镁锂分离时，具有能够更好的截留镁离子，进而获得较高的镁锂分离效率，同时还具有较高的水通量，处理效率更高。
为了实现上述目的，本发明第一方面提供一种分离膜，所述分离膜依次包括基材层、多孔支撑层、聚酰胺层和修饰层；
其中，形成所述修饰层的交联聚合物包括单宁酸提供的结构单元与多元胺提供的结构单元，至少部分单宁酸提供的结构单元还通过酚羟基的邻位与聚酰胺层连接；
其中，所述分离膜的孔径为0.1-0.5nm，所述分离膜的表面Zeta电位为-5mV至30mV。
本发明第二方面提供了一种分离膜的制备方法，所述制备方法包括：在基材层上依次制备多孔支撑层、聚酰胺层和修饰层；
其中，制备所述修饰层的方法包括：在第一压力下，在多元酚溶液保持流动的情况下，将包括基材层、多孔支撑层、聚酰胺层的材料的聚酰胺层一侧与多元酚溶液进行第一接触后，在第二压力下，在多元胺溶液保持流动的情况下，将所述材料的聚酰胺层一侧与多元胺溶液进行第二接触，完成自组装反应。
本发明第三方面提供了如上所述的方法制备的分离膜。
本发明第四方面提供了如第一方面所述的或第三方面所述的分离膜在镁锂分离中的应用。
本发明提供的分离膜具有高的致密度以及高的表面电极电位(Zeta电位)，将其用于镁锂分离时，能够更好的截留镁离子，同时使得锂离子尽可能的通过，获得较高的镁锂分离效率，同时还具有较高的水通量，处理效率更高。
本发明提供的分离膜的制备方法中，在第一压力以及第二压力下，并且在多元酚溶液和多元胺溶液保持流动的情况下，使得多元胺与多元酚能够在聚酰胺层上通过自组装反应得到包含修饰层的分离膜，由此制得的分离膜具有高的致密度以及高的表面电极电位(Zeta电位)，将其用于镁锂分离时，能够更好的截留镁离子，同时使得锂离子尽可能的通过，获得较高的镁锂分离效率，同时还具有较高的水通量，处理效率更高。且该制备方法工艺简单，具有广阔的产业化前景。
附图说明
图1是本发明实施例1和对比例1-2制备的分离膜的红外光谱图。
图2为分离膜的表面Zeta电位随自组装次数的变化曲线；
图3为分离膜的表面Zeta电位随自组装压力(第一压力/第二压力)的变化曲线；
图4为分离膜的接触角随自组装压力(第一压力/第二压力)的变化曲线；
图5为分离膜的接触角随自组装次数的变化曲线；
图6为对比例1(图6a)和实施例10(图6b)的分离膜的断面SEM图；
图7为实施例1与对比例1制得的分离膜的XPS氮元素图谱。
附图标记说明
1-修饰层；2-聚酰胺层；3-多孔支撑层。
具体实施方式
在本文中所披露的范围的端点和任何值都不限于该精确的范围或值，这些范围或值应当理解为包含接近这些范围或值的值。对于数值范围来说，各个范围的端点值之间、各个范围的端点值和单独的点值之间，以及单独的点值之间可以彼此组合而得到一个或多个新的数值范围，这些数值范围应被视为在本文中具体公开。
第一方面，本发明提供了一种分离膜，所述分离膜依次包括基材层、多孔支撑层、聚酰胺层和修饰层；
其中，形成所述修饰层的交联聚合物包括多元酚提供的结构单元与多元胺提供的结构单元，至少部分多元酚提供的结构单元还通过酚羟基的邻位与聚酰胺层连接；
其中，所述分离膜的孔径为0.1-0.5nm，所述分离膜的表面Zeta电位为-5mV至30mV。
本发明的发明人在研究中发现，分离膜包含如上所述的修饰层，能够使得分离膜具有本发明所述的孔径范围，且使得分离膜具有本发明所述的表面Zeta电位范围，表明该分离膜具有高的致密度以及高的表面电极电位，将其用于锂镁分离时，能够更好的排斥二价镁离子，使得液体中的镁离子不易通过分离膜，同时能够使得一价的锂离子尽可能的通过，从而获得较高的镁锂分离效率。并且，在上述几层的共同作用下，所述分离膜具有较高的水通量，在将膜应用到液体中的镁锂分离时，能够具有更高的处理效率。
本发明中，分离膜的孔径采用聚乙二醇(PEG)溶质传递法测得，其详细步骤如下：
(1)测试分离膜对不同分子尺寸PEG的截留率；
(2)将PEG尺寸与截留率在对数-概率坐标系中进行线性拟合，50％截留率所对应的PEG尺寸为分离膜的平均孔径。
本发明中，分离膜的表面Zeta电位通过电位分析仪测得。
进一步地，所述分离膜的孔径为0.15-0.3nm，所述分离膜的表面Zeta电位为1mV至10mV。
根据本发明，所述修饰层中包括式I所示的结构单元；
本发明中，发明人经研究发现，通过XPS对分离膜的修饰层中的氮元素进行测试时，本发明提供的分离膜的修饰层中包含式I所示的结构单元，即修饰层中存在由苯环-氮原子-苯环形成的π-π*电子共轭结构单元，进一步说明修饰层中至少部分来自多元酚的结构单元通过酚羟基的邻位与来自多元胺的结构单元和/或来自聚酰胺层的氮原子发生交联反应，使得包含该修饰层的分离膜的孔径得到进一步减小，分离膜的致密程度得到进一步提升，进而提高该分离膜用于镁锂分离时的镁锂分离效率。
根据本发明，所述多元酚提供的结构单元在膜表面的含量为2×10-3-5×10-2mg/cm2，所述多元胺提供的结构单元在膜表面的含量为1×10-3-2.5×10-2mg/cm2。
本发明中，分离膜中，多元酚提供的结构单元和多元胺提供的结构单元在所述分离膜的膜表面的含量 按照以下步骤测得：
将包括基材层、多孔支撑层、聚酰胺层的膜在真空烘箱中，60℃下干燥24h后，称量该膜的质量为Mn，mg；将该膜装入膜池，进料罐中为一定浓度的多元酚的水溶液，在一定条件下循环一定时间后，取出膜片，用去离子水将膜片表面冲洗干净后，60℃下干燥24h后，称量膜的质量为Wn，mg；再将膜装入膜池，进料罐中为一定浓度的多元胺的水溶液，在一定条件下循环一定时间后，取出膜片，用去离子水将膜片表面冲洗干净后，60℃下干燥24h后，称量膜的质量为Nn，mg；分离膜每次修饰在膜表面多元酚的含量Pn以及多元胺的含量Tn分别通过以下公式计算得到：
其中，当n大于1时，Mn＝Nn-1；当n＝1时，Mn即为原始聚酰胺膜片的质量；
分离膜经过自组装后表面多元酚的总含量为∑Pn，n≥1，表面多元胺的总含量为∑Tn，n≥1；
其中，n自组装的次数，S为有效膜面积，单位为cm2。
本发明中，发明人经研究发现，当多元酚提供的结构单元和多元胺提供的结构单元在膜表面的含量满足上述范围时，所述分离膜具有合适的致密程度以及厚度，从而保证分离膜具有较高的镁锂分离系数以及水通量。
进一步地，所述多元酚提供的结构单元在膜表面的含量为2.5×10-3-5×10-2mg/cm2，所述多元胺提供的结构单元在膜表面的含量为4×10-3-2×10-2mg/cm2。
根据本发明，所述修饰层中N原子的含量为13-20at.％。
本发明中，所述修饰层中N原子的含量通过X射线光电子能谱分析仪测得。
本发明中，当修饰层中N原子的含量满足上述范围时，能够使得分离膜具有高的表面电极电位以及优异的亲水性，将其用于镁锂分离时，具有高的镁锂分离效率和高的水通量。
进一步地，所述修饰层中N原子的含量为13.5-18.5at.％。
根据本发明，所述分离膜的接触角为20-60°。
本发明中，所述分离膜的接触角按照以下方法测得：使用德国KRUSS公司生产的DSA100型表面接触角测量仪以静滴法测试复合膜样品的表面接触角，测试前将样品在60℃真空烘箱中干燥30min以除去其表面及内部水分，而后将干燥好的膜用双面胶贴于平整载玻片上，测试时每次水滴体积均为2μL，水滴滴于膜表面3s后立即测试，经过多次测量取平均值来确定最终接触角的大小。
本发明中，所述分离膜具有本发明所述范围的接触角，由此表明分离膜具有优异的亲水性，能够使得分离膜具有优异的透水性。
进一步地，所述分离膜的接触角为20-40°。
根据本发明，优选地，所述分离膜的厚度为100-200μm。
根据本发明，优选地，所述基材层的厚度为30-150μm，优选为50-120μm。
根据本发明，优选地，所述多孔支撑层的厚度为10-100μm，优选为30-60μm。
根据本发明，优选地，所述聚酰胺层的厚度为10-500nm，优选为50-150nm。
根据本发明，优选地，所述修饰层的厚度为1-200nm，优选为10-60nm。
本发明中，对于分离膜、多孔支撑层、聚酰胺层的厚度，通过螺旋测微计和扫描电镜进行测定，并通过分离膜的厚度减去基材层、多孔支撑层、聚酰胺层的厚度来获得修饰层的厚度。其中，基材层的厚度即为涂覆多孔支撑层材料溶液之前测定的厚度。
本发明的发明人在研究中发现，满足上述各层的厚度范围时，上述各层能够更好的协同配合，使得分离膜具有小的孔径以及高的Zeta电位，将其用于镁锂分离时，能够兼顾更高的镁锂分离效率和水通量。
根据本发明，所述基材层的材料不受特别的限制，可以为本领域常用的具有一定强度的、适用于纳滤或者反渗透等能够起到依托作用的材料。但优选的，所述基材层的材料选自聚酯无纺布、聚乙烯无纺布和 聚丙烯无纺布中的至少一种。
根据本发明，所述多孔支撑层的材料也不受特别的限制，可以为本领域常用的能够发挥一定支撑作用并能形成多孔结构的材料。更优选的，所述多孔支撑层的材料选自聚醚砜、聚砜、聚芳香醚、聚苯并咪唑、聚醚酮、聚醚醚酮、聚丙烯腈、聚偏氟乙烯和聚芳醚酮中的至少一种。多孔支撑层中的多孔结构，能够使得液体较为容易的从中流通经过。多孔支撑层的材料的数均分子量可以为50000-100000g/mol。
根据本发明，优选地，所述聚酰胺层由多元胺与多元酰氯合成得到。
本发明中，如上所述的聚酰胺层，具有更合适的交联结构，配合其中的氨基能够对二价镁离子进行更好的截留效果。
进一步地，所述多元胺选自聚乙烯亚胺、三乙烯四胺、四乙烯五胺、二乙烯三胺、哌嗪、间苯二胺和对苯二胺中的至少一种，更优选为聚乙烯亚胺、哌嗪和多乙烯多胺中的至少一种。
进一步地，所述多元酰氯选自均苯三甲酰氯、对苯二甲酰氯、间苯二甲酰氯和邻苯二甲酰氯中的至少一种，更优选为均苯三甲酰氯和对苯二甲酰氯中的至少一种。当多元酰氯为多种时，其具体种类可以以任意比例进行混合，如当多元酰氯为均苯三甲酰氯和对苯二甲酰氯时，均苯三甲酰氯和对苯二甲酰氯的重量比可以为1∶1-10。
根据本发明，所述修饰层由多元酚与多元胺在聚酰胺层上通过自组装反应得到。
本发明中，所述自组装反应包括以下步骤：在第一压力下，在多元酚溶液保持流动的情况下，将包括基材层、多孔支撑层、聚酰胺层的材料的聚酰胺层一侧与多元酚溶液进行第一接触后，在第二压力下，在多元胺溶液保持流动的情况下，将所述材料的聚酰胺层一侧与多元胺溶液进行第二接触，完成自组装反应。
根据本发明，所述多元酚选自单宁酸、茶多酚、没食子酸、儿茶酸、木质素、木质素磺酸钠、苹果多酚、葡萄多酚、圣草酚、柚苷配基、表儿茶素、木樨草素、芹菜配基、堪非醇、杨梅黄素和染料木素中的一种或多种，优选单宁酸和/或茶多酚。
根据本发明，所述多元胺选自聚乙烯亚胺、四乙烯五胺、三乙烯四胺和多乙烯多胺中的至少一种。
根据本发明，所述第一压力和所述第二压力各自独立地为0.1-1.2MPa。
本发明中，控制制备所述修饰层时加压的压力满足上述范围时，能够确保由修饰层与聚酰胺层共同构成的分离层具有较高的致密程度，同时使得分离膜中多元胺提供的结构单元含量较高，使分离膜具有更高的亲水性，最终使得该分离膜具有优异的镁锂分离性能和透水性。
进一步地，所述第一压力和所述第二压力各自独立地为0.2-1MPa。
本发明中，所述多元酚溶液与所述多元胺溶液的用量使得多元酚与多元胺的质量比为0.1-10∶1。
本发明中，控制多元酚与多元胺的质量比满足上述范围时，除了能够确保多元酚与多元胺之间能够充分反应，确保制得的分离膜具有本发明要求的孔径外，还能够保证分离膜的表面含有更多的残余氨基，以使得分离膜具有本发明要求的高的表面Zeta电位以及亲水性，将该分离膜用于镁锂分离时，该分离膜具有更高的二价镁离子截留率以及水通量。
进一步地，所述多元酚溶液与所述多元胺溶液的用量使得多元酚与多元胺的质量比为0.2-6∶1，优选为0.5-6∶1。
本发明中，所述多元酚溶液的浓度为0.00001-1wt％，优选为0.0001-0.1wt％。
本发明中，所述多元胺溶液的浓度为0.00001-1wt％，优选为0.0001-0.1wt％。
本发明中，控制多元酚溶液和多元胺溶液的浓度各自独立地满足上述范围，能够确保由此制得的分离膜具有本发明所要求的孔径、表面Zeta电位以及厚度，能够确保将该分离膜用于镁锂分离时，在提高对氯化镁的截留率的同时，保持良好的透水性。
本发明中，所述第一接触和所述第二接触的温度各自独立地为10-30℃。
本发明中，控制所述第一接触和所述第二接触的温度满足上述范围时，能够确保多元酚和多元胺之间充分反应，使得制得的分离膜具有本发明所要求的孔径以及表面Zeta电位，进而提高该分离膜用于镁锂分离时的氯化镁截留率以及镁锂分离效率。
本发明中，在一次自组装反应中，所述第一接触的时间为1-120min。
本发明中，在一次自组装反应中，所述第二接触的时间为1-120min。
本发明中，在一次自组装反应中，控制第一接触和第二接触的时间满足上述范围时，不仅能够确保多 元酚和多元胺之间充分反应，还能够实现对由聚酰胺层以及修饰层构成的膜分离层的致密程度以及厚度进行适当调控，最终使得由此制得的分离膜具有高透水性以及高镁锂分离性。
进一步地，在一次自组装反应中，所述第一接触的时间为10-60min。
进一步地，在一次自组装反应中，所述第二接触的时间为10-60min。
本发明中，发明人在研究中进一步发现，按照上述在包括基体层、基材层、多孔支撑层、聚酰胺层的材料的聚酰胺层上制备修饰层的方法，并重复以下步骤，完成多次自组装时，能够进一步保证分离膜具有较高的表面Zeta电位以及更小的孔径，从而进一步保证获得较高的镁锂分离效率。具体地，所述自组装反应的次数为1-10次，更优选为2-5次。
本发明的一个优选实施方式中，所述分离膜的水通量大于等于20L·m-2·h-1；MgCl2脱盐率大于等于99％；镁锂分离系数大于等于70。
本发明的一个更优选实施方式中，所述分离膜的水通量为20-40L·m-2·h-1；MgCl2脱盐率大于等于99％；镁锂分离系数为100-250。
第二方面，本发明提供了一种分离膜的制备方法，其特征在于，所述制备方法包括以下步骤：在基材层上依次制备多孔支撑层、聚酰胺层和修饰层；
其中，制备所述修饰层的方法包括：在第一压力下，在多元酚溶液保持流动的情况下，将包括基材层、多孔支撑层、聚酰胺层的材料的聚酰胺层一侧与多元酚溶液进行第一接触后，在第二压力下，在多元胺溶液保持流动的情况下，将所述材料的聚酰胺层一侧与多元胺溶液进行第二接触，完成自组装反应。
本发明中，多元酚与多元胺可以发生迈克尔加成反应，形成交联结构。多元酚上酚羟基所在碳原子的邻位碳原子作为反应位点和多元胺进行反应。在聚酰胺层表面上反应时，多元酚上酚羟基所在碳原子的邻位碳原子作为反应位点和聚酰胺层中的氨基反应。
本发明中，按照本发明第二方面提供的制备方法制备分离膜，在第一压力以及第二压力下，并且在多元酚溶液和多元胺溶液保持流动的情况下，将包括基材层、多孔支撑层、聚酰胺层的材料的聚酰胺层一侧先后与多元酚溶液和多元胺溶液进行接触反应，多元酚和多元胺能够在聚酰胺层表面上发生迈克尔加成反应，形成交联结构，并且多元酚上的部分酚羟基所在碳原子的邻位碳原子能够与聚酰胺层中的氨基反应，与聚酰胺层连接。
与此同时，在第一压力和第二压力的作用下以及多元酚溶液和多元胺溶液保持流动的情况下，能够使得制得的分离膜具有小的孔径以及高的表面Zeta电位，即制得本发明第一方面所述的分离膜。具体地，本发明中，控制自组装反应过程在一定流速的动态环境中进行，能够达到减少额外的多元酚或多元胺在膜表面吸附的目的，从而实现更多的多元酚或多元胺通过化学键键合至膜表面。最终使得分离膜经过自组装修饰后，分离膜的致密程度显著增加并且分离膜具有较高的表面Zeta电位。
由本发明第二方面提供的制备方法制得的分离膜具有本发明所述的孔径范围，且使得分离膜具有本发明所述的表面Zeta电位范围，表明该分离膜具有高的致密度以及高的表面电极电位，将其用于锂镁分离时，能够更好的排斥二价镁离子，使得液体中的镁离子不易通过分离膜，同时能够使得一价的锂离子尽可能的通过，从而获得较高的镁锂分离效率。并且，在上述几层的共同作用下，所述分离膜具有较高的水通量，在将该膜应用到液体中的镁锂分离时，能够具有更高的处理效率。
根据本发明，所述第一压力和所述第二压力各自独立地为0.1-1.2MPa。
本发明中，控制制备所述修饰层时第一压力以及第二压力各自独立地满足上述范围时，能够促进多元酚与多元胺反应更加充分，并且使得由此制得的分离膜具有本发明所要求的孔径以及表面Zeta电位，将制得的分离膜用于镁锂分离时，具有高的氯化镁截留率和优异的镁锂分离效率。
进一步地，所述第一压力和所述第二压力各自独立地为0.2-1MPa。
本发明中，所述自组装反应可以在错流膜池中进行，所述错流膜池通过水泵向膜池内循环抽水，使膜池内的水处于流动状态，通过调压阀施加压力，控制制备过程中的第一压力以及第二压力满足本发明的要求。
本发明中，制备所述修饰层的方法可以在本领域中常规的设备中进行即可，例如错流膜池，该方法工艺简单，易产业化。其中，在错流膜池中进行自组装反应时，例如将多元酚和材料接触后，排出多元酚溶液，并用去离子水反复冲洗错流膜池，以洗净系统中的多元酚，也会冲洗净材料表面的多元酚。
本发明中，在错流膜池中，泵持续向池中输送溶液，因此溶液中多元酚或者多元胺的总量一般都会超过膜的表面所能附着从而反应的量，能够保证获得本发明所要求的修饰层。本发明中，对于多元酚溶液和多元胺溶液的流速没有特别限定，只要保证在制备修饰层的过程中，多元酚溶液和多元胺溶保持流动即可，例如所述多元酚溶液或所述多元胺溶液的流速可以为0.5-5L/min。
根据本发明，所述多元酚溶液与所述多元胺溶液的用量使得多元酚与多元胺的质量比为0.1-10∶1。
本发明中，控制多元酚与多元胺的质量比满足上述范围时，除了能够确保多元酚与多元胺之间能够充分反应，确保制得的分离膜具有本发明要求的孔径外，还能够保证分离膜的表面含有更多的残余氨基，以使得分离膜具有本发明要求的高的表面Zeta电位以及亲水性，将该分离膜用于镁锂分离时，该分离膜具有更高的二价镁离子截留率以及水通量。
进一步地，所述多元酚溶液与所述多元胺溶液的用量使得多元酚与多元胺的质量比为0.2-6∶1，优选为0.5-6∶1。
根据本发明，所述多元酚溶液的浓度为0.00001-1wt％，优选为0.0001-0.1wt％。
根据本发明，所述多元胺溶液的浓度为0.00001-1wt％，优选为0.0001-0.1wt％。
本发明中，控制多元酚溶液和多元胺溶液的浓度各自独立地满足上述范围，能够确保由此制得的分离膜具有本发明所要求的孔径、表面Zeta电位以及厚度，能够确保将该分离膜用于镁锂分离时，在提高对氯化镁的截留率的同时，保持良好的透水性。
根据本发明，所述第一接触和所述第二接触的温度各自独立地为10-30℃。
本发明中，控制所述第一接触和所述第二接触的温度满足上述范围时，能够确保多元酚和多元胺之间充分反应，使得制得的分离膜具有本发明所要求的孔径以及表面Zeta电位，进而提高该分离膜用于镁锂分离时的氯化镁截留率以及镁锂分离效率。
根据本发明，在一次自组装反应中，所述第一接触的时间为1-120min。
根据本发明，在一次自组装反应中，所述第二接触的时间为1-120min。
本发明中，在一次自组装反应中，控制第一接触和第二接触的时间满足上述范围时，不仅能够确保多元酚和多元胺之间能够充分反应，还能够实现对由聚酰胺层以及修饰层构成的膜分离层的致密程度以及厚度进行适当调控，最终使得由此制得的分离膜具有高透水性以及高镁锂分离性。
进一步地，在一次自组装反应中，所述第一接触的时间为10-60min。
进一步地，在一次自组装反应中，所述第二接触的时间为10-60min。
本发明中，发明人在研究中进一步发现，按照上述在包括基体层、基材层、多孔支撑层、聚酰胺层的材料的聚酰胺层上制备修饰层的方法，并重复以下步骤，完成多次自组装时，能够进一步保证分离膜具有较高的表面Zeta电位以及更小的孔径，从而进一步保证获得较高的镁锂分离效率。具体地，所述自组装反应的次数为1-10次，更优选为2-5次。
根据本发明，制备修饰层的条件包括使得分离膜中修饰层的厚度为1-200nm，优选为10-60nm。
根据本发明，所述多元酚溶液中的多元酚选自单宁酸、茶多酚、没食子酸、儿茶酸、木质素、木质素磺酸钠、苹果多酚、葡萄多酚、圣草酚、柚苷配基、表儿茶素、木樨草素、芹菜配基、堪非醇、杨梅黄素和染料木素中的一种或多种，优选单宁酸和/或茶多酚。
根据本发明，所述多元胺溶液中的多元胺选自聚乙烯亚胺、四乙烯五胺、三乙烯四胺和多乙烯多胺中的至少一种。
本发明中，在基体层上制备多孔支撑层的方法可以为本领域常用的方法。但优选的，制备多孔支撑层的方法包括：将包含多孔支撑层材料的溶液涂覆在基材层上，进行相转化，得到包含基材层和多孔支撑层的材料。
本发明中，涂覆的具体方式不受特别的限制，可以利用刮刀进行涂覆。
根据本发明，所述相转化的条件包括：在10-30℃的水中浸泡10-60min。
本发明中，采用如上所述的制备多孔支撑层的方法时，当在水中浸泡时，包含多孔支撑层材料的溶液中的溶剂逐渐离开多孔支撑层，通过这种相转化的方法，能够进一步确保获得具有多孔结构的支撑层。
根据本发明，优选地，所述基材层的厚度为30-150μm，更优选为50-120μm。能够理解的是，基材层的厚度，在制备前后基本不发生变化。
本发明中，所述基材层的材料选自聚酯无纺布、聚乙烯无纺布和聚丙烯无纺布中的至少一种。
根据本发明，优选地，制备多孔支撑层的条件包括使得分离膜中多孔支撑层的厚度为10-100μm，更优选为30-60μm。能够理解的是，可以通过控制涂覆的量来控制厚度，并且由于涂覆后，会发生厚度的塌陷，因此涂覆时设定的厚度，与最终制备得到的分离膜中多孔支撑层的厚度会有一些差别。一般的，涂覆时设定的厚度高于希望得到的分离膜中多孔支撑层约40-60μm即可。
根据本发明，所述包含多孔支撑层材料的溶液的浓度为10-20wt％。
根据本发明，所述多孔支撑层材料选自聚醚砜、聚砜、聚芳香醚、聚苯并咪唑、聚醚酮、聚醚醚酮、聚丙烯腈、聚偏氟乙烯和聚芳醚酮中的至少一种。
根据本发明，所述包含多孔支撑层材料的溶液中的溶剂选自N，N-二甲基甲酰胺、N，N-二甲基乙酰胺、N-甲基吡咯烷酮和二甲基亚砜中的至少一种。
本发明中，对于所述包含多孔支撑层材料的溶液的制备方法没有特别限定，可以采用本领域中常规的方法制备，例如，先将多孔支撑层材料溶于溶剂中，并进行脱泡(脱泡可以在20-40℃下进行10-180min)，得到包含多孔支撑层材料的溶液。
本发明中，优选地，在制备多孔支撑层之后，可以对物料进行洗涤，如进行多次水洗。
根据本发明，制备所述聚酰胺层的方法包括：将包括基材层和多孔支撑层的材料的多孔支撑层表面依次接触含有多元胺的水相和含有多元酰氯的有机相，然后进行热处理。
本发明中，采用上述依次接触含有多元胺的水相和含有多元酰氯的有机相的方法，通过界面聚合得到聚酰胺层，这样的聚酰胺层具有交联结构，聚酰胺层不仅致密而且很薄，进一步保证了较高的镁锂分离效率和水通量。其中，接触水相和有机相的操作可以在常温下进行，如23-28℃。
根据本发明，制备聚酰胺层的条件包括使得分离膜中聚酰胺层的厚度为10-500nm，更优选为50-300nm。
根据本发明，优选地，多孔支撑层面接触含有多元胺的水相的时间为5-100s，更优选为10-60s。
根据本发明，多孔支撑层面接触含有多元酰氯的有机相的时间为10-200s，更优选为20-120s。
根据本发明，所述含有多元胺的水相与所述含多元酰氯的有机相的用量使得多元胺与多元酰氯的质量比为0.1-10∶1。
本发明的发明人还发现，当控制多元胺与多元酰氯的质量比满足上述比例时，能够确保制得的聚酰胺层具有合适的孔径，确保该聚酰胺层在具有优异氯化锂透过性的同时对氯化镁具有良好的截留性；与此同时，在该聚酰胺层上采用多元酚与多元胺修饰后，能够使得聚酰胺层的孔径进一步缩小，表面Zeta电位进一步提高，最终得到具有本发明第一方面所限定的具有特定孔径以及表面Zeta电位的分离膜，将该分离膜用于镁锂分离时，具有显著改善的镁锂分离效率。
进一步地，所述含有多元胺的水相与所述含多元酰氯的有机相的用量使得多元胺与多元酰氯的质量比为0.5-8∶1。
本发明中，含有多元酰氯的有机相中的有机溶剂可以为正己烷、十二烷、正庚烷、烷烃溶剂油(可以为市售的Isopar E、Isopar G、Isopar H、Isopar L和IsoparM)中的至少一种。
根据本发明，所述含有多元胺的水相的浓度为0.1-10wt％，进一步优选为0.5-2.5wt％。
根据本发明，所述含多元酰氯的有机相的浓度为0.01-1wt％，更优选为0.1-0.5wt％。当多元酰氯为多种时，其具体种类可以以任意比例进行混合，如当多元酰氯为均苯三甲酰氯和对苯二甲酰氯时，均苯三甲酰氯和对苯二甲酰氯的质量比可以为1∶1-10。
本发明中，通过控制含有多元胺的水相以及含多元酰氯的有机相的浓度、多孔支撑层与含有多元胺的水相以及含有多元酰氯的有机相的接触时间、多元胺与多元酰氯的质量比满足上述范围，能够使得制得的聚酰胺层的厚度在10-500nm的范围内。
本发明中，进一步地，控制含有多元胺的水相以及含多元酰氯的有机相的浓度满足本发明限定的范围时，还能够对于镁离子具有更高截留率的同时，对一价锂离子具有更高的透过率。
本发明中，含有多元胺的水相的体积和含有多元酰氯的有机相的体积都不受特别的限制，只要能够保证水相中的多元胺的量，或者有机相中多元酰氯的量，能够在膜上形成合适的具有交联结构的聚酰胺层。优选的，相对于400cm2的膜面积，水相中多元胺的总量可以为0.05-2g，有机相中的多元酰氯的总量可以为0.0001-0.5g。
根据本发明，所述多元胺选自聚乙烯亚胺、三乙烯四胺、四乙烯五胺、二乙烯三胺、哌嗪、间苯二胺和对苯二胺中的至少一种，更优选为聚乙烯亚胺、哌嗪和多乙烯多胺中的至少一种。
根据本发明，所述多元酰氯选自均苯三甲酰氯、对苯二甲酰氯、间苯二甲酰氯和邻苯二甲酰氯中的至少一种，更优选为均苯三甲酰氯和对苯二甲酰氯中的至少一种。
根据本发明，所述热处理的温度为40-150℃；所述热处理的时间为0.5-10min。
本发明中，能够理解的是，多元胺和多元酰氯接触即会发生反应，但满足上述热处理的条件时，能够保证反应更为充分，获得更加致密的聚酰胺层，确保在其表面制备修饰层后，能够获得本发明第一方面所述的具有特定孔径的分离膜。
进一步地，所述热处理的温度为50-120℃；所述热处理的时间为1-5min。
本发明中，所述制备方法还包括：将制得的分离膜浸泡在去离子水中，备用。
第三方面，本发明提供了如上所述的方法制备的分离膜。
第四方面，本发明提供了如第一方面所述的或第三方面所述的分离膜在镁锂分离(特别是盐湖提锂)中的应用。
本发明中，所述分离膜用于镁锂分离的具体方法包括：将盐湖卤水装入进料罐，膜池上安装所述分离膜；在压力I下运行系统，收集经过分离膜过滤的一级产水；再将一级产水作为进料液装入进料罐，在压力II下运行系统，收集经过分离膜过滤的二级产水。
本发明中，所述盐湖卤水中镁离子的含量大于等于500ppm，锂离子的含量小于等于50ppm。
本发明中，所述盐湖卤水中Mg2+与Li+的质量浓度比大于等于5。
本发明中，所述压力I为0.5-2MPa。
本发明中，所述压力II为0.5-2MPa。
本发明中，所述一级产水中镁离子的含量小于等于20ppm，锂离子的含量大于等于20ppm。
本发明中，所述一级产水中Mg2+与Li+的质量浓度比小于等于1。
本发明中，所述二级产水中镁离子的含量小于等于0.5ppm，锂离子的含量大于等于25ppm。
本发明中，所述二级产水中Li+的纯度大于等于98％。
根据本发明的优选实施方式，用于镁锂分离时，所述分离膜的水通量大于等于20L·m-2·h-1；MgCl2脱盐率大于等于99％；镁锂分离系数大于等于70。
进一步地，所述分离膜的水通量为20-40L·m-2·h-1；MgCl2脱盐率大于等于99％；镁锂分离系数为100-250。
根据本发明一种特别优选的实施方式，按照如下的方法制备分离膜：
将聚砜浓度为16-19重量％的聚砜溶液利用刮刀涂覆在厚度为75-80μm的聚酯无纺布(基材层)上，随即将物料在温度为24-26℃的水中浸泡45-60min，使得聚酯无纺布表面的聚砜层经相转化成多孔膜，最后经2-3次水洗得到包括基材层和多孔支撑层(多孔支撑层厚度约为38-42μm)的材料。
将包括基材层和多孔支撑层的材料的多孔支撑层表面接触含有0.5-0.6重量％聚乙烯亚胺的水溶液，24-26℃下接触50-60s后排液；然后，将支撑层上表面再接触含有均苯三甲酰氯和对苯二甲酰氯的Isopar E溶液(含有多元胺的水相中的多元胺的质量，和含有多元酰氯的有机相中的多元酰氯的质量比为5-6∶1，均苯三甲酰氯和对苯二甲酰氯的质量比为1∶3-5)，24-26℃下接触60-70s后排液；然后，将膜放进烘箱中，在60-70℃下加热3-4min，得到包括基材层、多孔支撑层、聚酰胺层的材料。
将包括基材层、多孔支撑层、聚酰胺层的材料装入错流膜池，使得材料的聚酰胺层一侧接触错流膜池中的溶液，错流膜池中的溶液为0.001-0.005wt％的多元酚水溶液，错流膜池在0.6-0.65MPa、25-26℃下，在保持多元酚溶液的流速为2.5-3.5L/min的条件下运行30-35min后，排液，用去离子水反复冲洗错流膜池，以洗净系统中多元酚；向错流膜池中加入多元胺水溶液(多元酚溶液和多元胺溶液的用量使得多元酚与多元胺的质量比为0.1-10∶1)，使得材料的聚酰胺层一侧接触上述溶液，错流膜池在0.6-0.65MPa、25-26℃下，在保持多元胺溶液的流速为0.5-5L/min的条件下运行30-35min后，排液，用去离子水反复冲洗错流膜池，以洗净残余的多元胺；由此完成了一次自组装反应，重复以上操作再完成一次自组装反应，得到分离膜。
本发明中，所述压力均指表压。
以下将通过实施例对本发明进行详细描述，其中，
Isopar E是市售的烷烃溶剂油(购自西陇化工)。
以下实施例中，在将包括基材层、多孔支撑层、聚酰胺层的材料在错流膜池中和溶液接触时，在错流膜池中，通过水泵向膜池内循环抽水，使膜池内的多元酚溶液和多元胺溶液处于流动状态。
除实施例11-12之外，其他实施例和对比例中，包括基材层和多孔支撑层的材料按照如下的方法制备：
将聚砜(数均分子量为80000g/mol)溶于N，N-二甲基甲酰胺中，制得浓度为18重量％的聚砜溶液，在25℃下脱泡120min。然后，将聚砜溶液利用刮刀涂覆在厚度为75μm的聚酯无纺布(基材层)上，随即将物料在温度为25℃的水中浸泡60min，使得聚酯无纺布表面的聚砜层经相转化成多孔膜，最后经3次水洗得到总厚度为115μm的包括基材层和多孔支撑层(多孔支撑层厚度为40μm)的材料，面积为400cm2。
以下实施例和对比例制备的膜，在完成制备后，将膜浸没在去离子水中24h后以备后用，再进行各种性质和参数的测定。
分离膜的分子结构采用全反射红外光谱分析仪(Nicolet 6700)表征与分析。
分离膜的孔径：采用PEG溶质传递法测得，其详细步骤如下：
(1)测试分离膜对不同分子尺寸PEG的截留率；
(2)将PEG尺寸与截留率在对数-概率坐标系中进行线性拟合，50％截留率所对应的PEG尺寸为分离膜的平均孔径。
分离膜的表面Zeta电位：通过Zeta电位分析仪测定，测试液为0.001mol/L KCl水溶液，pH为7。
分离膜的修饰层中氮原子的含量：通过X射线光电子能谱(XPS)测得：在ESCALAB250型X射线光电子能谱仪上，使用Al-KαX射线辐照得到。
分离膜的膜表面中多元酚提供的结构单元和多元胺提供的结构单元的含量：
将包括基材层、多孔支撑层、聚酰胺层的膜在真空烘箱中，60℃下干燥24h后，称量膜的质量为Mn，mg；将该膜装入膜池，进料罐中为一定浓度的多元酚的水溶液，在一定条件下循环一定时间后，取出膜片，用去离子水将膜片表面冲洗干净后，60℃下干燥24h后，称量膜的质量为Wn，mg；再将膜装入膜池，进料罐中为一定浓度的多元胺的水溶液，在一定条件下循环一定时间后，取出膜片，用去离子水将膜片表面冲洗干净后，60℃下干燥24h后，称量膜的质量为Nn，mg；分离膜每次修饰在膜表面多元酚的含量Pn以及多元胺的含量Tn分别通过以下公式计算得到：
其中，当n大于1时，Mn＝Nn-1；当n＝1时，Mn即为原始聚酰胺膜片的质量；
分离膜经过自组装后表面多元酚的总含量为∑Pn，n≥1，表面多元胺的总含量为∑Tn，n≥1；
其中，n自组装的次数，S为有效膜面积，单位为cm2。
其中，膜与多元酚的水溶液以及多元胺的水溶液接触的条件分别对应于实施例以及对比例中自组装过程的第一压力、第二压力、第一接触的温度和时间以及第二接触的温度和时间。
分离膜的接触角：使用德国KRUSS公司生产的DSA100型表面接触角测量仪以静滴法测试复合膜样品的表面接触角，测试前将样品在60℃真空烘箱中干燥30min以除去其表面及内部水分，而后将干燥好的膜用双面胶贴于平整载玻片上，测试时每次水滴体积均为2μL，水滴滴于膜表面3s后立即测试，经过多次测量取平均值来确定最终接触角的大小。
分离膜以及分离膜中各层的厚度：对于分离膜、多孔支撑层、聚酰胺层的厚度，通过螺旋测微计和扫描电镜进行测定，并通过分离膜的厚度减去基材层、多孔支撑层、聚酰胺层的厚度来获得修饰层的厚度。其中，基材层的厚度即为涂覆多孔支撑层材料溶液之前测定的厚度。
实施例1
将包括基材层和多孔支撑层的材料的多孔支撑层表面接触含有0.5重量％聚乙烯亚胺的水溶液(50mL)，25℃下接触60s后排液；然后，将支撑层上表面再接触含有0.02重量％的均苯三甲酰氯和0.08重量％对苯二甲酰氯的IsoparE溶液(30mL)，25℃下接触60s后排液；然后，将膜放进烘箱中，在70℃下加热3min。
将热处理后的产物装入错流膜池，使得材料的聚酰胺层一侧与错流膜池中的0.001wt％的单宁酸水溶液进行第一接触，单宁酸水溶液的体积是5L，并使得单宁酸溶液保持流动的状态，流速为1.5L/min，错流膜池在0.6MPa、25℃下运行30min后，排液，用去离子水反复冲洗错流膜池，以洗净系统中单宁酸；向错流膜池中加入5L浓度为0.004wt％的聚乙烯亚胺水溶液，并使得聚乙烯亚胺水溶保持流动的状态，流速为1.5L/min，使得材料的聚酰胺层一侧与上述溶液进行第二接触，错流膜池在0.6MPa、25℃下运行30min后，排液，用去离子水反复冲洗错流膜池，以洗净残余的聚乙烯亚胺；由此完成了一次自组装反应，重复以上操作再完成一次自组装反应，一次自组装过程中，多元酚与多元胺的质量比为0.25∶1，得到分离膜N1。
实施例2
将包括基材层和多孔支撑层的材料的多孔支撑层表面接触含有1重量％多乙烯多胺的水溶液(50mL)，25℃下接触20s后排液；然后，将支撑层上表面再接触含有0.18重量％的均苯三甲酰氯和0.12重量％对苯二甲酰氯的IsoparE溶液(30mL)，25℃下接触30s后排液；然后，将膜放进烘箱中，在50℃下加热5min。
将热处理后的产物装入错流膜池，使得材料的聚酰胺层一侧与错流膜池中的0.01wt％的单宁酸水溶液进行第一接触，单宁酸水溶液的体积是5L，并使得单宁酸溶液保持流动的状态，流速为0.5L/min，错流膜池在0.6MPa、15℃下运行40min后，排液，用去离子水反复冲洗错流膜池中的溶液，以洗净残余的单宁酸；向错流膜池中加入5L浓度为0.045wt％的聚乙烯亚胺水溶液，并使得聚乙烯亚胺水溶保持流动的状态，流速为0.5L/min，使得材料的聚酰胺层一侧与上述溶液进行第二接触，错流膜池在0.6MPa、15℃下运行40min后，排液，用去离子水反复冲洗错流膜池，以洗净残余的聚乙烯亚胺；由此完成了一次自组装反应，重复以上操作再完成一次自组装反应，一次自组装过程中，多元酚与多元胺的质量比为0.22∶1，得到分离膜N2。
实施例3
将包括基材层和多孔支撑层的材料的多孔支撑层表面接触含有2.5重量％哌嗪的水溶液(50mL)，25℃下接触40s后排液；然后，将支撑层上表面再接触含有0.2重量％的均苯三甲酰氯和0.1重量％对苯二甲酰氯的Isopar E溶液(30mL)，25℃下接触100s后排液；然后，将膜放进烘箱中，在110℃下加热1min。
将热处理后的产物装入错流膜池，使得材料的聚酰胺层一侧与错流膜池中的0.1wt％的单宁酸水溶液进行第一接触，单宁酸水溶液的体积是5L并使得单宁酸溶液保持流动的状态，流速为5L/min，错流膜池在0.6MPa、30℃下运行20min后，排液，用去离子水反复冲洗错流膜池，以洗净残余的单宁酸；向错流膜池中加入5L浓度为0.1wt％的聚乙烯亚胺水溶液，并使得聚乙烯亚胺水溶保持流动的状态，流速为5L/min，使得材料的聚酰胺层一侧与上述溶液进行第二接触，错流膜池在0.6MPa、30℃下运行20min后，排液，用去离子水反复冲洗错流膜池，以洗净残余的聚乙烯亚胺；由此完成了一次自组装反应，重复以上操作再完成一次自组装反应，一次自组装过程中，多元酚与多元胺的质量比为1∶1，得到分离膜N3。
实施例4
按照实施例1的方法制备分离膜，不同的是，在自组装反应中，将聚乙烯亚胺替换为多乙烯多胺。制得分离膜N4。
实施例5
按照实施例1的方法制备分离膜，不同的是，在自组装反应中，将聚乙烯亚胺替换为四乙烯五胺。制得分离膜N5。
实施例6
按照实施例1的方法制备分离膜，不同的是，在自组装反应中，将聚乙烯亚胺替换为三乙烯四胺。制得分离膜N6。
实施例7
按照实施例1的方法制备分离膜，不同的是，自组装反应只进行一次。制得分离膜N7。
实施例8
按照实施例1的方法制备分离膜，不同的是，自组装反应共进行三次。制得分离膜N8。
实施例9
按照实施例1的方法制备分离膜，不同的是，自组装反应共进行四次。制得分离膜N9。
实施例10
按照实施例1的方法制备分离膜，不同的是，自组装反应共进行五次。制得分离膜N10。
实施例11
按照实施例1的方法制备分离膜，不同的是，包括基材层和多孔支撑层的材料照如下的方法制备：将聚醚砜(数均分子量为70000g/mol)溶于N，N-二甲基甲酰胺中，制得浓度为20重量％的聚醚砜溶液，在25℃下脱泡120min。然后，将聚醚砜溶液利用刮刀涂覆在厚度为100μm的聚乙烯无纺布(基材层)上，随即将物料在温度为23℃的水中浸泡20min，使得聚乙烯无纺布表面的聚醚砜层经相转化成多孔膜，最后经3次水洗得到总厚度为135μm的包括基材层和多孔支撑层(多孔支撑层厚度为35μm)的材料，面积为400cm2。制得分离膜N11。
实施例12
按照实施例1的方法制备分离膜，不同的是，包括基材层和多孔支撑层的材料照如下的方法制备：将聚丙烯腈(数均分子量为100000g/mol)溶于N，N-二甲基甲酰胺中，制得浓度为15重量％的聚丙烯腈溶液，在25℃下脱泡120min。然后，将聚丙烯腈溶液利用刮刀涂覆在厚度为115μm的聚丙烯无纺布(基材层)上，随即将物料在温度为28℃的水中浸泡40min，使得聚丙烯无纺布表面的聚丙烯腈层经相转化成多孔膜，最后经3次水洗得到总厚度为160μm的包括基材层和多孔支撑层(多孔支撑层厚度为45μm)的材料，面积为400cm2。制得分离膜N12。
实施例13
按照实施例1的方法制备分离膜，不同的是，自组装反应中，单宁酸水溶液中单宁酸的浓度为0.0001wt％，聚乙烯亚胺溶液的聚乙烯亚胺的浓度0.001wt％，一次自组装过程中，多元酚与多元胺的质量比为0.1∶1。制得分离膜N13。
实施例14
按照实施例1的方法制备分离膜，不同的是，自组装过程中的第一压力和第二压力均为0.2MPa，溶液流速均为1.5L/min，制得分离膜N14。
实施例15
按照实施例1的方法制备分离膜，不同的是，自组装过程中的第一接触和第二接触的压力为1MPa，溶液流速均为1.5L/min，制得分离膜N15。
实施例16
按照实施例1的方法制备分离膜，不同的是，自组装过程中的第一接触和第二接触的压力为0.8MPa， 溶液流速均为1.5L/min，制得分离膜N16。
实施例17
按照实施例1的方法制备分离膜，不同的是，自组装过程中的第一接触和第二接触的压力为0.4MPa，溶液流速均为1.5L/min，制得分离膜N17。
实施例18
将包括基材层和多孔支撑层的材料的多孔支撑层表面接触含有0.5重量％聚乙烯亚胺的水溶液(50mL)，25℃下接触60s后排液；然后，将支撑层上表面再接触含有0.01重量％的均苯三甲酰氯和0.04重量％对苯二甲酰氯的IsoparE溶液(30mL)，25℃下接触60s后排液；然后，将膜放进烘箱中，在70℃下加热3min。
将热处理后的产物装入错流膜池，使得材料的聚酰胺层一侧与错流膜池中的0.001wt％的单宁酸水溶液进行第一接触，单宁酸水溶液的体积是5L，并使得单宁酸溶液保持流动的状态，流速为1.5L/min错流膜池在0.6MPa、25℃下运行30min后，排液，用去离子水反复冲洗错流膜池，以洗净系统中单宁酸；向错流膜池中加入5L浓度为0.004wt％的聚乙烯亚胺水溶液，并使得聚乙烯亚胺水溶保持流动的状态，流速为1.5L/min，使得材料的聚酰胺层一侧与上述溶液进行第二接触，错流膜池在0.6MPa、25℃下运行30min后，排液，用去离子水反复冲洗错流膜池，以洗净残余的聚乙烯亚胺；由此完成了一次自组装反应，重复以上操作再完成一次自组装反应，一次自组装过程中，多元酚与多元胺的质量比为0.25∶1，得到分离膜N18。
实施例19
按照实施例1的方法制备分离膜，不同的是，自组装反应中，单宁酸水溶液中单宁酸的浓度为0.001wt％，聚乙烯亚胺溶液中聚乙烯亚胺的浓度0.0001wt％，一次自组装过程中，多元酚与多元胺的质量比为10∶1。制得分离膜N19。
对比例1
按照实施例1的方法制备分离膜，不同的是，不进行自组装反应，即在热处理后直接得到分离膜。制得分离膜D1。
对比例2
按照实施例1的方法制备分离膜，不同的是，将热处理后的产物装入含有0.001wt％的单宁酸水溶液的错流膜池中，单宁酸水溶液的体积是5L，并使得单宁酸溶液保持流动的状态，流速为1.5L/min，在0.6MPa、25℃下运行30min后，取出，得到分离膜(即只和单宁酸水溶液中接触了一次)。制得分离膜D2。
对比例3
按照实施例1的方法制备分离膜，不同的是，将聚乙烯亚胺替换成聚乙烯醇。制得分离膜D3。
对比例4
将聚丙烯腈超滤膜装入错流膜池，一侧接触错流膜池中的溶液，错流膜池中的溶液为0.001wt％的单宁酸水溶液，单宁酸水溶液的体积是5L，并使得单宁酸溶液保持流动的状态，流速为1.5L/min，错流膜池在0.6MPa、25℃下运行30min后，排液，用去离子水反复冲洗错流膜池，以洗净系统中单宁酸；向错流膜池中加入5L浓度为0.004wt％的聚乙烯亚胺水溶液，使得材料的聚丙烯腈层一侧接触上述溶液，流速为1.5L/min，错流膜池在0.6MPa、25℃下运行30min后，排液，用去离子水反复冲洗错流膜池，以洗净残余的聚乙烯亚胺；由此完成了一次自组装反应，重复以上操作再完成一次自组装反应，一次自组装过程中，多元酚与多元胺的质量比为0.25∶1，得到分离膜D4。
对比例5
按照实施例1的方法制备分离膜，不同的是，将包括基材层和多孔支撑材料的多孔支撑层装入错流膜 池，一侧与错流膜池中的0.001wt％的单宁酸水溶液进行第一接触，单宁酸水溶液的体积是5L，并使得单宁酸溶液保持流动的状态，流速为1.5L/min错流膜池在0.6MPa、25℃下运行30min后，排液，用去离子水反复冲洗错流膜池，以洗净系统中单宁酸；向错流膜池中加入5L浓度为0.004wt％的聚乙烯亚胺水溶液，并使得聚乙烯亚胺水溶保持流动的状态，流速为1.5L/min，使得材料的聚丙烯腈层一侧与上述溶液进行第二接触，错流膜池在0.6MPa、25℃下运行30min后，排液，取出膜片，用去离子水将表面冲洗干净，得到多元酚与多元胺修饰的多孔支撑层；一次自组装过程中，多元酚与多元胺的质量比为0.25∶1；
将多元酚与多元胺修饰的多孔支撑层表面接触含有0.5重量％聚乙烯亚胺的水溶液(50mL)，25℃下接触60s后排液；然后，将支撑层上表面再接触含有0.02重量％的均苯三甲酰氯和0.08重量％对苯二甲酰氯的Isopar E溶液(30mL)，25℃下接触60s后排液；然后，将膜放进烘箱中，在70℃下加热3min，得到含有多元胺与多元酚中间层的聚酰胺复合膜D5。
对比例6
按照实施例1的方法制备分离膜，不同的是，不将热处理后的产物装入错流膜池进行自组装反应，而是直接在装有单宁酸水溶液的烧杯中，将材料的聚酰胺层一侧接触单宁酸水溶液(即第一压力为0MPa且单宁酸溶液也不流动)中，24h后取出，并用去离子水反复冲洗；然后直接在装有聚乙烯亚胺水溶液的烧杯中，将材料的聚酰胺层一侧接触聚乙烯亚胺水溶液(即第二压力为0MPa且聚乙烯亚胺溶液也不流动)，24h后取出，并用去离子水反复冲洗；重复以上操作再完成一次自组装反应，得到分离膜。其中，每次自组装中，烧杯中单宁酸溶液(或多元胺)的体积使得单宁酸(或多元胺)的总量超过膜上可能附着进而反应的量。得到分离膜D6。
对比例7
将包括基材层和多孔支撑层的材料的多孔支撑层表面接触含有0.5重量％聚乙烯亚胺的水溶液(50mL)，25℃下接触60s后排液；然后，将支撑层上表面再接触含有0.02重量％的均苯三甲酰氯和0.08重量％对苯二甲酰氯的IsoparE溶液(30mL)，25℃下接触60s后排液；然后，将膜放进烘箱中，在70℃下加热3min。
将得到的膜浸入1L浓度为2wt％的单宁酸水溶液中(第一压力为0MPa且单宁酸溶液也不流动)1min，取出后，用去离子水冲洗膜表面；再将膜浸入1L浓度为2wt％的聚乙烯亚胺水溶液中(第二压力为0MPa且聚乙烯亚胺溶液也不流动)1min，一次自组装过程中，多元酚与多元胺的质量比为1∶1，取出后，用去离子水将膜表面冲洗干净，得到分离膜D7。
对比例8
按照实施例1的方法制备分离膜，不同的是，自组装过程中的第一压力和第二压力均为0MPa，溶液流速均为1.5L/min，制得分离膜D8。
对比例9
按照实施例1的方法制备分离膜，不同的是，聚酰胺膜先与聚乙烯亚胺溶液接触后，再于单宁酸溶液进行接触，且自组装只有一次，制得分离膜D9。
对实施例1和对比例1-2制备的分离膜，进行红外光谱表征，结果见图1。
可见，未经单宁酸与聚乙烯亚胺自组装修饰后的膜(对比例1的膜)，在3388cm-1处具有一宽峰，对应于聚酰胺表面未反应的氨基，同时在1507cm-1处显示微弱的信号，也对应于N-H的伸缩振动。经过单宁酸修饰改性(即对比例2的膜)后，3364cm-1处有一强吸收峰，对应于单宁酸分子中的酚羟基，而且1507cm-1处的信号峰基本消失，证实了氨基与单宁酸发生了化学反应。经过单宁酸与聚乙烯亚胺在聚酰胺表面连续两次自组装以后(实施例1的膜)，在3270-3390cm-1处出现一宽峰，对应于修饰层上的未反应的氨基与未反应的酚羟基；同时在1507cm-1处的信号增强，证实了聚乙烯亚胺被修饰到膜的表面。结合对比例2的操作和红外图像，可见对于实施例1的分离膜，形成所述修饰层的交联聚合物包括单宁酸提供的结构单元与多元胺提供的结构单元，所述单宁酸提供的结构单元还通过酚羟基的邻位与聚酰胺层连接。
实施例2-19制得的分离膜的红外表征结果，同实施例1相似(图中未示出)。
表1
*对比例4中为聚丙烯腈超滤膜的厚度。
表2

由表1、表2可以看出，相比于对比例1-9，实施例1-19提供的分离膜具有小的孔径并且分离膜的修饰层具有高的正电荷密度。
其中，对比例2的修饰层厚度是单宁酸带来的厚度变化；对比例3中的修饰层厚度是单宁酸和聚乙烯醇反应带来的厚度变化。
进一步地，本发明提供的分离膜具有小的孔径，高的表面Zeta电位，将其用于镁锂分离时，能够显著提高对氯化镁的截留率；同时，该分离膜具有优异的亲水性，能够实现优异的透水性。
由图2可以看出，随着自组装的次数增加，膜表面电位呈正电性，并且其绝对值表现出增加的趋势。表明随着自组装次数地增加，膜表面的氨基(伯胺、仲胺或者叔胺)的含量增加，致使膜表面Zeta电位提高。
由图3可以看出，随着自组装过程中，随着自组装压力(即第一压力/第二压力)的提高，膜表面的正电位绝对值增加，表明压力可以促使更高含量的多元酚以及多元胺反应至膜表面。
由图4可以看出，随着自组装过程中，随着自组装压力(即第一压力/第二压力)的提高，膜表面具有亲水性的基团伯胺、仲胺或者叔胺的含量增加，使膜表面亲水性提高。
由图5可以看出，随着自组装的次数增加，膜表面具有亲水性的基团伯胺、仲胺或者叔胺的含量增加，使膜表面亲水性提高。
由图6a可以看出，未经多元酚和多元胺修饰的聚酰胺层平滑且较薄，其厚度为85nm，由图6b可以看出，采用多元酚和多元胺在聚酰胺层的表面自组装修饰后，聚酰胺层的表面被厚度约为30nm的修饰层所 覆盖。
图7对比了实施例1(图7a)与对比例6(图7b)的XPS氮元素图谱，由图可以看出，实施例1的修饰层在407eV处具有一个特征峰，该特征峰对应于式I所示的结构单元，即是由苯环-氮原子-苯环形成的π-π*电子共轭产生的信号峰。而对比例6没有该信号峰，说明只有在本发明的压力驱动自组装的工艺条件下，才会产生式I所示的结构单元。该结构单元中一个氮原子与两个苯环发生交联反应，提高了分离膜的致密度，进一步起到了缩小分离膜孔径的作用。
应用例
将实施例以及对比例制得的分离膜分别装入错流膜池中，在0.6MPa下、温度为25℃条件下测得所述分离膜在一定时间内的水透过量，并通过以下公式计算得到水通量：
J＝Q/(A·t)，其中，J为水通量(L/m2h)，Q为水透过量(L)，A为分离膜的有效膜面积(m2)，t为时间(h)。
将分离膜装入错流膜池中，其中的原料液含有2000ppm的氯化镁或2000ppm的氯化锂，在0.2MPa下预压0.5h后，在压力为0.6MPa，原料液温度为25℃下、得到透过液，通过电导率仪测得透过液中的氯化镁和氯化锂浓度，并通过以下公式计算得到脱盐率：
R(％)＝(Cf-CP)/Cf×100％，其中，R为脱盐率，Cf为原料液中氯化镁或氯化锂的浓度(电导率仪测得)，Cp为透过液中氯化镁或氯化锂的浓度(电导率仪测得)；
将分离膜装入错流膜池中，其中的原料液含有2000ppm的氯化镁与100ppm的氯化锂，在0.2MPa下预压0.5h后，在压力为0.6MPa，原料液温度为25℃下、得到透过液，通过离子色谱测得透过液中的镁离子和锂离子的浓度，并通过以下公式计算得到镁锂分离系数：
其中，S为镁锂分离系数，CLi，p和CLi，f分别为透过液和原料液中锂离子的浓度(离子色谱测得)；CMg，p和CMg，f分别为透过液和原料液中镁离子的浓度(离子色谱测得)。
表3

通过表3可以看出，采用本发明技术方案的实施例同时具有更高的水通量和更高的镁锂分离效率。随着自组装次数的增加，膜表面多元酚与多元胺的含量增加，使得膜表面亲水性和表面Zeta电位提高。使膜对氯化镁的截留率增加，从而镁锂分离系数升高。另一方面，自组装次数增加，修饰层的厚度提高，使膜的水通量降低。此外，随着自组装过程中运行压力地提高，促使反应更高效地进行，使得膜表面亲水性和表面Zeta电位提高，从而使膜具有更高的截盐率和镁锂分离效率。
以上详细描述了本发明的优选实施方式，但是，本发明并不限于此。在本发明的技术构思范围内，可以对本发明的技术方案进行多种简单变型，包括各个技术特征以任何其它的合适方式进行组合，这些简单变型和组合同样应当视为本发明所公开的内容，均属于本发明的保护范围。

Claims (18)

  1. 一种分离膜，其特征在于，所述分离膜依次包括基材层、多孔支撑层、聚酰胺层和修饰层；
    其中，形成所述修饰层的交联聚合物包括多元酚提供的结构单元与多元胺提供的结构单元，至少部分多元酚提供的结构单元还通过酚羟基的邻位与聚酰胺层连接；
    其中，所述分离膜的孔径为0.1-0.5nm，所述分离膜的表面Zeta电位为-5mV至30mV。
  2. 根据权利要求1所述的分离膜，其中，所述分离膜的孔径为0.15-0.3nm，所述分离膜的表面Zeta电位为1mV至10mV。
  3. 根据权利要求1或2所述的分离膜，其中，所述修饰层中包含式I所示的结构单元；
  4. 根据权利要求1-3中任意一项所述的分离膜，其中，所述多元酚提供的结构单元在膜表面的含量为2×10-3-5×10-2mg/cm2，优选为2.5×10-3-5×10-2mg/cm2；所述多元胺提供的结构单元在膜表面的含量为1×10-3-2.5×10-2mg/cm2，优选为4×10-3-2×10-2mg/cm2。
  5. 根据权利要求1-4中任意一项所述的分离膜，其中，所述修饰层中N原子的含量为13-20at.％，优选为13.5-18.5at.％。
  6. 根据权利要求1-5中任意一项所述的分离膜，其中，所述分离膜的接触角为20-60°，优选为20-40°。
  7. 根据权利要求1-6中任意一项所述的分离膜，其中，所述分离膜的厚度为100-200μm；
    和/或，所述基材层的厚度为30-150μm，优选为50-120μm；
    和/或，所述多孔支撑层的厚度为10-100μm，优选为30-60μm；
    和/或，所述聚酰胺层的厚度为10-500nm，优选为50-150nm；
    和/或，所述修饰层的厚度为1-200nm，优选为10-60nm。
  8. 根据权利要求1-7中任意一项所述的分离膜，其中，所述基材层的材料选自聚酯无纺布、聚乙烯无纺布和聚丙烯无纺布中的至少一种；
    和/或，所述多孔支撑层的材料选自聚醚砜、聚砜、聚芳香醚、聚苯并咪唑、聚醚酮、聚醚醚酮、聚丙烯腈、聚偏氟乙烯和聚芳醚酮中的至少一种。
  9. 根据权利要求1-8中任意一项所述的分离膜，其中，所述聚酰胺层由多元胺与多元酰氯合成得到；
    和/或，所述多元胺选自聚乙烯亚胺、三乙烯四胺、四乙烯五胺、二乙烯三胺、哌嗪、间苯二胺和对苯二胺中的至少一种，优选为聚乙烯亚胺、哌嗪和多乙烯多胺中的至少一种；
    和/或，所述多元酰氯选自均苯三甲酰氯、对苯二甲酰氯、间苯二甲酰氯和邻苯二甲酰氯中的至少一种，优选为均苯三甲酰氯和对苯二甲酰氯中的至少一种。
  10. 根据权利要求1-9中任意一项所述的分离膜，其中，所述修饰层由多元酚与多元胺在聚酰胺层上通过自组装反应得到；
    优选地，所述多元酚选自单宁酸、茶多酚、没食子酸﹑儿茶酸﹑木质素、木质素磺酸钠、苹果多酚、葡萄多酚、圣草酚、柚苷配基、表儿茶素、木樨草素、芹菜配基、堪非醇、杨梅黄素和染料木素中的一种或多种，优选单宁酸和/或茶多酚；
    优选地，所述多元胺选自聚乙烯亚胺、四乙烯五胺、三乙烯四胺和多乙烯多胺中的至少一种。
  11. 一种分离膜的制备方法，其特征在于，所述制备方法包括以下步骤：在基材层上依次制备多孔支撑层、聚酰胺层和修饰层；
    其中，制备所述修饰层的方法包括：在第一压力下，在多元酚溶液保持流动的情况下，将包括基材层、多孔支撑层、聚酰胺层的材料的聚酰胺层一侧与多元酚溶液进行第一接触后，在第二压力下，在多元胺溶液保持流动的情况下，将所述材料的聚酰胺层一侧与多元胺溶液进行第二接触，完成自组装反应。
  12. 根据权利要求11所述的制备方法，其中，所述第一压力和第二压力各自独立地为0.1-1.2MPa，优选为0.2-1MPa；
    优选地，所述多元酚溶液与所述多元胺溶液的用量使得多元酚与多元胺的质量比为0.1-10∶1，优选为0.2-6∶1；
    优选地，所述多元酚溶液的浓度为0.00001-1wt％，优选为0.0001-0.1wt％；
    优选地，所述多元胺溶液的浓度为0.00001-1wt％，优选为0.0001-0.1wt％。
  13. 根据权利要求11或12所述的制备方法，其中，所述第一接触和所述第二接触的温度各自独立地为10-30℃；
    优选地，在一次自组装反应中，所述第一接触的时间为1-120min，优选为10-60min；
    优选地，在一次自组装反应中，所述第二接触的时间为1-120min，更优选为10-60min；
    优选地，所述自组装反应的次数为1-10次，更优选为2-5次；
    优选地，制备修饰层的条件包括使得分离膜中修饰层的厚度为1-200nm，优选为10-60nm。
  14. 根据权利要求11-13中任意一项所述的制备方法，其中，所述多元酚溶液中的多元酚选自单宁酸、茶多酚、没食子酸﹑儿茶酸﹑木质素、木质素磺酸钠、苹果多酚、葡萄多酚、圣草酚、柚苷配基、表儿茶素、木樨草素、芹菜配基、堪非醇、杨梅黄素和染料木素中的一种或多种，优选单宁酸和/或茶多酚；
    优选地，所述多元胺溶液中的多元胺选自聚乙烯亚胺、四乙烯五胺、三乙烯四胺和多乙烯多胺中的至少一种。
  15. 根据权利要求11-14中任意一项所述的制备方法，其中，制备所述多孔支撑层的方法包括：
    将包含多孔支撑层材料的溶液涂覆在基材层上，进行相转化，得到包含基材层和多孔支撑层的材料；
    优选地，所述相转化的条件包括：在10-30℃的水中浸泡10-60min；
    优选地，所述基材层的厚度为30-150μm，优选为50-120μm；
    优选地，所述基材层的材料选自聚酯无纺布、聚乙烯无纺布和聚丙烯无纺布中的至少一种；
    优选地，制备多孔支撑层的条件包括使得分离膜中多孔支撑层的厚度为10-100μm，更优选为30-60μm；
    优选地，所述包含多孔支撑层材料的溶液的浓度为10-20wt％；
    优选地，所述多孔支撑层材料选自聚醚砜、聚砜、聚芳香醚、聚苯并咪唑、聚醚酮、聚醚醚酮、聚丙烯腈、聚偏氟乙烯和聚芳醚酮中的至少一种；
    优选地，所述包含多孔支撑层材料的溶液中的溶剂选自N，N-二甲基甲酰胺、N，N-二甲基乙酰胺、N-甲基吡咯烷酮和二甲基亚砜中的至少一种。
  16. 根据权利要求11-15中任意一项所述的制备方法，其中，制备所述聚酰胺层的方法包括：将包括基材层和多孔支撑层的材料的多孔支撑层表面依次接触含有多元胺的水相和含有多元酰氯 的有机相，然后进行热处理；
    优选地，制备聚酰胺层的条件包括使得分离膜中聚酰胺层的厚度为10-500nm，更优选为50-300nm；
    优选地，多孔支撑层面接触含有多元胺的水相的时间为5-100s，更优选为10-60s；
    优选地，多孔支撑层面接触含有多元酰氯的有机相的时间为10-200s，更优选为20-120s；
    优选地，所述含有多元胺的水相与所述含多元酰氯的有机相的用量使得多元胺与多元酰氯的质量比为0.1-10∶1，优选为0.5-8∶1；
    优选地，所述含有多元胺的水相的浓度为0.1-10wt％，进一步优选为0.5-2.5wt％；
    优选地，所述含多元酰氯的有机相的浓度为0.01-1wt％，更优选为0.1-0.5wt％；
    优选地，所述多元胺选自聚乙烯亚胺、三乙烯四胺、四乙烯五胺、二乙烯三胺、哌嗪、间苯二胺和对苯二胺中的至少一种，更优选为聚乙烯亚胺、哌嗪和多乙烯多胺中的至少一种；
    优选地，所述多元酰氯选自均苯三甲酰氯、对苯二甲酰氯、间苯二甲酰氯和邻苯二甲酰氯中的至少一种，更优选为均苯三甲酰氯和对苯二甲酰氯中的至少一种。
    优选地，所述热处理的温度为40-150℃，更优选为50-120℃；所述热处理的时间为0.5-10min，更优选为1-5min。
  17. 一种由权利要求11-16中任意一项所述的方法制备的分离膜。
  18. 权利要求1-10和权利要求17中任意一项所述的分离膜在镁锂分离中的应用。
PCT/CN2023/095323 2022-05-20 2023-05-19 分离膜及其制备方法和应用 WO2023222117A1 (zh)

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