A composite ion exchange membrane for ion-selective separation and a method for preparing the same

Abstract

The application discloses a composite ion exchange membrane for ion selective separation and a preparation method thereof. A high-molecular polymer, a charged high-molecular material or a charged inorganic material is blended with an organic solvent to obtain a casting solution by heating and stirring; the obtained casting solution is uniformly coated on both sides of a skeleton material layer to form a wet membrane; the skeleton material layer coated with the wet membrane is immersed in a water bath to form an intermediate porous support layer and an edge porous support layer of the same material on both sides of the skeleton material layer through phase inversion; an amine monomer aqueous solution is coated on the surface of the intermediate porous support layer, the excess water drops on the surface of the intermediate porous support layer are removed, and then an acyl chloride monomer oil phase solution is coated on the surface of the intermediate porous support layer after the coating of the amine monomer aqueous solution to perform interfacial polymerization and drying to form a dense separation layer. The application greatly reduces the membrane area resistance of the composite ion exchange membrane, is simple in operation and easy to realize industrialization.

Description

Technical Field

[0001] This invention relates to a composite ion exchange membrane for selective ion separation and its preparation method, belonging to the field of ion exchange membrane technology. Background Technology

[0002] Due to rapid industrial development, the demand for freshwater is increasing, but the amount of freshwater currently available from groundwater and rivers is limited. In recent years, the use of seawater desalination technology to extract freshwater from abundant seawater has attracted increasing attention from researchers, and seawater desalination has become the most sustainable technology for alleviating water shortages.

[0003] Selective electrodialysis replaces the conventional anion / cation exchange membranes in electrodialysis with monovalent / polyvalent ion separation membranes. The selective separation of monovalent / polyvalent ions by the membrane achieves salt separation, while the directional migration of ions under the influence of an electric field enables high-concentration of monovalent salts. The core component of selective electrodialysis is the monovalent / polyvalent selective ion exchange membrane.

[0004] Currently, the selectivity of monovalent selective ion exchange membranes, formed using thin-layer resins, is very limited and easily decays in application, resulting in poor industrialization performance. To improve the selectivity of monovalent / polyvalent ions, there are three main methods for preparing monovalent / polyvalent selective ion exchange membranes: 1) adding a separation skin layer with the opposite charge to the base membrane surface, utilizing the charge repulsion effect to achieve selective ion permeability; 2) adjusting the degree of cross-linking of the ion exchange membrane to increase its density, utilizing the pore size sieving effect to achieve the retention of polyvalent ions; 3) constructing a polyelectrolyte layer on the base membrane surface to adjust the membrane's affinity, utilizing the difference in interaction forces between ions and the polyelectrolyte layer to achieve ion separation. While these methods improve the selectivity of monovalent / polyvalent ions, they also significantly increase the membrane resistance, which is detrimental to the application and promotion of electrodialysis in seawater desalination. Therefore, a composite ion exchange membrane with superior performance is needed for the separation of monovalent / polyvalent salts. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by providing a composite ion exchange membrane for ion selective separation and its preparation method, thus solving the problems of limited selectivity and high membrane resistance of traditional monovalent / multivalent selective ion exchange membranes.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A composite ion exchange membrane for selective ion separation has an asymmetric structure formed by a dense separation layer, a middle porous support layer, a framework material layer and an edge porous support layer arranged in sequence;

[0007] The dense separation layer is obtained by interfacial polymerization of an aqueous solution of amine monomers and an oil phase solution of acyl chloride monomers;

[0008] Both the intermediate porous support layer and the edge porous support layer are obtained by blending high molecular polymers with charged polymer materials or charged inorganic materials through a non-solvent phase conversion.

[0009] The two sides of the skeleton material layer are coated with casting liquid. After the casting liquid gels, the middle porous support layer and the edge porous support layer formed wrap the skeleton material layer in the middle.

[0010] As a preferred embodiment of a composite ion exchange membrane for selective ion separation, the amine monomer is selected from polyamines, preferably ethylenediamine, hexamethylenediamine, m-phenylenediamine, piperazine, tetraethylpentylamine, diethylenetriamine, and polyethyleneimine.

[0011] The acyl chloride monomers are selected from polyacyl chlorides, and the polyacyl chlorides are pyromellitic trimethylolpropionate chloride and terephthaloyl chloride.

[0012] As a preferred embodiment of the composite ion exchange membrane for selective ion separation, the aqueous solution of the amine monomer has a concentration of 0.1-10 wt%, and the oil phase solution of the acyl chloride monomer is formed by dissolving the acyl chloride monomer in an organic solvent, with a concentration of 0.05-0.5 wt%.

[0013] The organic solvent is n-hexane, N,N-dimethylformamide, N,N-dimethylacetamide, n-heptane, or isoalkanes.

[0014] As a preferred embodiment of a composite ion exchange membrane for selective ion separation, the proportion of polymer added to the intermediate porous support layer and the edge porous support layer is 10-25 wt%.

[0015] The proportion of charged polymer material or charged inorganic material added to the intermediate porous support layer and the edge porous support layer is 0-10wt%.

[0016] As a preferred embodiment of a composite ion exchange membrane for selective ion separation, the polymer is cellulose acetate, polyamide, polysulfone, polyethersulfone, polyphenylene ether, or polypropylene.

[0017] The charged polymer material is a sulfonated polymer or a quaternized polymer;

[0018] The charged inorganic materials are charged MOFs and charged COFs.

[0019] As a preferred embodiment of a composite ion exchange membrane for ion selective separation, the sulfonated polymer is selected from sulfonated polyethersulfone, sulfonated polysulfone, sulfonated polyphenylsulfone, sulfonated polyether ether ketone, sulfonated polyimide, sulfonated polyether imide, sulfonated polyarylether ketone, sulfonated poly / arylene ether, sulfonated polystyrene, and sulfonated polyaniline.

[0020] The quaternized polymer is selected from quaternized polyethyleneimine, quaternized polyaryletherketone, quaternized polyethersulfone, and quaternized polyarylethersulfoneketone.

[0021] As a preferred embodiment of a composite ion exchange membrane for selective ion separation, the skeleton material layer is made of spun fabric with a pore size of 0.05-0.15 mm, spun from polypropylene or polyester synthetic fiber filaments with a diameter of 25-100 μm.

[0022] This invention also provides a method for preparing a composite ion exchange membrane for ion selective separation, comprising the following steps:

[0023] A casting solution is obtained by mixing a polymer, charged polymer material, or charged inorganic material with an organic solvent and heating and stirring.

[0024] The obtained casting solution is evenly coated on both sides of the skeleton material layer to form a wet film.

[0025] The skeleton material layer coated with a wet film is immersed in a water bath, and a middle porous support layer and an edge porous support layer are formed on both sides of the skeleton material layer through phase transformation.

[0026] An aqueous solution of amine monomers is applied to the surface of the intermediate porous support layer. Excess water droplets on the surface of the intermediate porous support layer are removed. Then, an oil phase solution of acyl chloride monomers is applied to the surface of the intermediate porous support layer after the aqueous solution of amine monomers is applied. Interfacial polymerization is carried out and the layer is dried to form a dense separation layer.

[0027] As a preferred method for preparing composite ion exchange membranes for selective ion separation, the organic solvent used for blending with polymers, charged polymers, or charged inorganic materials is N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, or dimethyl sulfoxide.

[0028] As a preferred method for preparing composite ion exchange membranes for selective ion separation, the heating and stirring process for obtaining the casting solution involves a heating temperature of 40-80℃ and a stirring time of 3-7 hours.

[0029] As a preferred method for preparing composite ion exchange membranes for selective ion separation, the framework material layer coated with a wet membrane is immersed in a water bath for a phase transition time of 30-120 s.

[0030] As a preferred embodiment of the method for preparing a composite ion exchange membrane for ion selective separation, the contact time of the aqueous solution of the amine monomer coated on the surface of the intermediate porous support layer is 1-30 min; the reaction time after the oil phase solution of the acyl chloride monomer is coated is 1-30 min.

[0031] During the drying process to form a dense separation layer, it is placed in an oven at 60-120℃ for drying.

[0032] The beneficial effects of this invention are as follows: a casting solution is obtained by mixing a polymer, charged polymer material, or charged inorganic material with an organic solvent and heating and stirring; the casting solution is uniformly coated on both sides of a skeleton material layer to form a wet film; the skeleton material layer coated with the wet film is immersed in a water bath, and a middle porous support layer and an edge porous support layer are formed on both sides of the skeleton material layer through phase transformation; an aqueous solution of amine monomers is coated on the surface of the middle porous support layer, excess water droplets on the surface of the middle porous support layer are removed, and then an oil phase solution of acyl chloride monomers is coated on the surface of the middle porous support layer after coating with the aqueous solution of amine monomers for interfacial polymerization and drying to form a dense separation layer. This invention constructs an ultrathin, dense separation layer with specific ion-sieving channels on the surface of a porous support layer through interfacial polymerization, enabling primary separation of monovalent and multivalent ions. By introducing charged materials into the porous support layer, ion transport is achieved within the pores of the support layer, and the reverse functional groups on the charged polymer material are used for secondary separation of monovalent and multivalent ions. Due to the porous structure of the support layer, the area resistivity of the composite ion exchange membrane is greatly reduced, and this preparation method is simple to operate and easy to industrialize. Attached Figure Description

[0033] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0034] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0035] Figure 1 This is a schematic diagram of the composite ion exchange membrane structure provided in an embodiment of the present invention;

[0036] Figure 2 This is a flowchart of the preparation method of the composite ion exchange membrane for selective ion separation according to an embodiment of the present invention;

[0037] Figure 3This is a schematic diagram illustrating the principle of applying the composite ion exchange membrane of the present invention to electrodialysis for the separation of monovalent and divalent cations;

[0038] Figure 4 The Na concentration chamber provided in this embodiment of the invention + and Mg 2+ Concentration change graph;

[0039] Figure 5 Na, a desalination chamber provided in the embodiments of the present invention + and Mg 2+ Concentration change graph. Detailed Implementation

[0040] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0042] Example 1

[0043] See Figure 1 Embodiment 1 of the present invention provides a composite ion exchange membrane for selective ion separation, having an asymmetric structure formed by a dense separation layer, a middle porous support layer, a framework material layer and an edge porous support layer arranged in sequence;

[0044] The dense separation layer is obtained by interfacial polymerization of an aqueous solution of amine monomers and an oil phase solution of acyl chloride monomers;

[0045] Both the intermediate porous support layer and the edge porous support layer are obtained by blending high molecular polymers with charged polymer materials or charged inorganic materials through a non-solvent phase conversion.

[0046] The skeleton material layer is made of woven or non-woven fabric. Both sides of the skeleton material layer are coated with casting liquid. After the casting liquid gels, the middle porous support layer and the edge porous support layer formed wrap the skeleton material layer in the middle.

[0047] In this embodiment, the amine monomer is selected from polyamines, preferably ethylenediamine, hexamethylenediamine, m-phenylenediamine, piperazine, tetraethylpentylamine, diethylenetriamine, and polyethyleneimine; the acyl chloride monomer is selected from polyacyl chlorides, specifically trimesoyl chloride and terephthaloyl chloride; the aqueous solution concentration of the amine monomer is 0.1-10 wt%, and the oil phase solution of the acyl chloride monomer is obtained by dissolving the acyl chloride monomer in an organic solvent, with a concentration of 0.05-0.5 wt%; the organic solvent is n-hexane, N,N-dimethylformamide, N,N-dimethylacetamide, n-heptane, or isoalkanes.

[0048] In this embodiment, the addition ratio of the polymer in the intermediate porous support layer and the edge porous support layer is 10-25 wt%; the addition ratio of the charged polymer material or charged inorganic material in the intermediate porous support layer and the edge porous support layer is 0-10 wt%.

[0049] The intermediate porous support layer and the edge porous support layer are essentially made of the same material. To distinguish them, the porous support layer that is close to the dense separation layer is defined as the intermediate porous support layer, and the porous support layer that is far from the dense separation layer is defined as the edge porous support layer.

[0050] In this embodiment, the polymer is cellulose acetate, polyamide, polysulfone, polyethersulfone, polyphenylene ether, or polypropylene; the charged polymer is a sulfonated polymer or a quaternized polymer; and the charged inorganic material is a charged MOF or a charged COF. The sulfonated polymer is selected from sulfonated polyethersulfone, sulfonated polysulfone, sulfonated polyphenylene sulfone, sulfonated polyether ether ketone, sulfonated polyimide, sulfonated polyetherimide, sulfonated polyarylether ketone, sulfonated poly(arylene ether), sulfonated polystyrene, and sulfonated polyaniline; the quaternized polymer is selected from quaternized polyethyleneimine, quaternized polyarylether ketone, quaternized polyethersulfone, and quaternized polyarylether sulfone ketone.

[0051] In this embodiment, the woven fabric used for the skeleton material layer has a pore size of 0.05-0.15 mm and is spun from synthetic fibers such as polypropylene and polyester with a diameter of 25-100 μm. The woven fabric serves as a reinforcing mesh for the porous support layer, providing support for the porous support layer. Furthermore, the casting solution can be evenly coated on both sides of the woven fabric and embedded within it through the pores, thereby increasing the mechanical strength and dimensional stability of the porous support layer.

[0052] The composite ion exchange membrane of this invention has an asymmetric structure, and an ultrathin dense separation layer is constructed on the surface of a charged porous support layer via interfacial polymerization. This invention employs a central porous support layer and an edge porous support layer, significantly reducing membrane resistance. Furthermore, this invention constructs an ultrathin dense separation layer with unique ion-sieving channels on the surface of the central porous support layer via interfacial polymerization, performing primary separation of monovalent / multivalent ions; then, by introducing charged materials into the central porous support layer, ion transport is achieved within the pores of the central porous support layer, and secondary separation of monovalent / multivalent ions is performed using the reverse functional groups on the charged polymer material of the edge porous support layer. Compared to traditional monovalent selective ion exchange membranes, the composite ion exchange membrane prepared by this invention exhibits lower membrane resistance and higher ion selectivity, and the preparation method is simple and easily industrialized.

[0053] Example 2

[0054] See Figure 2 Embodiment 2 of the present invention provides a method for preparing a composite ion exchange membrane for ion selective separation, comprising the following steps:

[0055] S1. Mix a polymer, charged polymer material or charged inorganic material with an organic solvent, and heat and stir to obtain a casting solution.

[0056] S2. The obtained casting solution is evenly applied to both sides of the skeleton material layer to form a wet film.

[0057] S3. Immerse the skeleton material layer coated with wet film in a water bath to form a middle porous support layer and an edge porous support layer on both sides of the skeleton material layer through phase transformation.

[0058] S4. Apply an aqueous solution of amine monomers to the surface of the intermediate porous support layer, remove excess water droplets from the surface of the intermediate porous support layer, then apply an oil phase solution of acyl chloride monomers to the surface of the intermediate porous support layer after applying the aqueous solution of amine monomers, perform interfacial polymerization, and dry to form a dense separation layer.

[0059] Specifically, in the preparation of the porous support layer, polysulfone and sulfonated polysulfone were co-dissolved in N,N-dimethylformamide and heated and stirred at 70°C for 7 hours until the solute was completely dissolved to obtain a casting solution. Polysulfone, sulfonated polysulfone, and N,N-dimethylformamide were added according to the proportions in Table 1. The dissolved casting solution was allowed to stand for 15 hours to remove bubbles. Then, a coating machine was used for coating, with the blade thickness set to 400 μm. The casting solution was evenly coated on both sides of the fabric, and the wet film was slowly immersed in a water bath driven by the machine shaft, with a coating linear speed set to 4 m / s. After phase inversion in the water bath, a middle porous support layer and an edge porous support layer were obtained. The middle and edge porous support layers wrapped on both sides of the fabric were soaked in pure water for 20 hours to completely replace the organic solvent. The soaking solution was changed every 5 hours during the soaking period.

[0060] Table 1. Addition ratio of each component in porous support layer A

[0061] A1 11％ 11％ 78％ A2 13％ 9％ 78％ A3 15％ 7％ 78％ A4 17％ 5％ 78％

[0062] Specifically, in the preparation process of the composite ion exchange membrane, a 1 wt% piperazine aqueous solution was prepared as the aqueous phase, and a 0.1 wt% trimesoyl chloride-hexane solution was prepared as the oil phase. The framework material layer prepared in Example 1, along with the middle and edge porous support layers on both sides, were fixed on a stainless steel plate. A polytetrafluoroethylene rectangular frame was used to press the middle and edge porous support layers onto the stainless steel plate to prevent solution outflow. The aqueous phase solution was poured onto the membrane surface and allowed to stand for 1 minute. After that, the solution was poured off, and excess water droplets on the surface were removed using a silicone roller. Then, the oil phase solution was poured onto the membrane surface, reacted for 1 minute, and then poured off. The membrane was then placed in an 80°C forced-air drying oven and dried for 10 minutes to obtain the composite ion exchange membrane.

[0063] Example 3

[0064] The monovalent / divalent ion selectivity experiment was performed on the composite ion exchange membrane obtained by the present invention using porous support layer A3 as a substrate. A schematic diagram of the electrodialysis apparatus is shown below. Figure 3 As shown, from left to right, the components are: anode plate, anode chamber, commercial anion exchange membrane, desalination chamber, composite cation exchange membrane, concentration chamber, commercial anion exchange membrane, cathode chamber, and cathode plate. During operation, the two electrode chambers are connected in series. A mixed solution of 0.1M NaCl + 0.1M MgCl2, a 0.01M KCl solution, and a 0.3M Na2SO4 solution are pumped into the desalination chamber, concentration chamber, and electrode chamber, respectively. An A / m² pressure is applied to the device. 2 After a constant current is applied, ions are selectively transported across the membrane under the influence of the electric field due to the selective permeation effect of the membrane. Figure 4 and Figure 5 These are the Na+ concentration chamber and desalination chamber during electrodialysis, respectively.+ and Mg 2+ Concentration changes over time. (From...) Figure 4 It can be seen that within 4 hours of the start of the experiment, Na + The concentration increased rapidly, while Mg 2+ The concentration increased slowly, and in the following 2 hours, Na... + The transmission speed gradually slowed down, but Mg 2+ The transmission rate increased compared to the previous 4 hours, which is due to the increase in Na in the desalination chamber. + This was due to a decrease in concentration. After 6 hours of the experiment, the Na concentration in the concentration chamber... + The concentration reached its highest value, and subsequently, as the experiment progressed, Na... + The concentration gradually stabilized, but Mg 2+ The concentration continued to increase gradually, due to the Na in the desalination chamber. + Almost all of it has passed through the composite ion exchange membrane into the concentration chamber, while Mg 2+ There are still causes, such as Figure 5 As shown.

[0065] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0066] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A composite ion exchange membrane for selective ion separation, characterized in that, It has an asymmetric structure formed by a dense separation layer, a middle porous support layer, a skeleton material layer and an edge porous support layer arranged in sequence; The dense separation layer is obtained by polymerization of an aqueous solution of amine monomers and an oil phase solution of acyl chloride monomers at the interface of the surface of the intermediate porous support layer. Both the intermediate porous support layer and the edge porous support layer are obtained by blending a polymer with a charged polymer material or a charged inorganic material and then converting the mixture into a solvent-free phase; the intermediate porous support layer and the edge porous support layer are made of the same material. The two sides of the skeleton material layer are coated with casting liquid. After the casting liquid gels, the middle porous support layer and the edge porous support layer formed wrap the skeleton material layer in the middle. An ultrathin and dense separation layer with unique ion sieving channels is constructed on the surface of the intermediate porous support layer through interfacial polymerization to perform primary separation of monovalent / multivalent ions. By introducing charged materials into the intermediate porous support layer, ion transport is realized in the channels of the intermediate porous support layer, and the reverse functional groups on the charged polymer materials of the edge porous support layer are used to perform secondary separation of monovalent / multivalent ions.

2. The composite ion exchange membrane for selective ion separation according to claim 1, characterized in that, The amine monomers are selected from polyamines, and the polyamines used are ethylenediamine, hexamethylenediamine, m-phenylenediamine, piperazine, tetraethylpentylamine, diethylenetriamine, or polyethyleneimine; The acyl chloride monomer is selected from polyacyl chlorides, and the polyacyl chloride is either pyromellitic methyl methacrylate chloride or terephthaloyl chloride.

3. A composite ion exchange membrane for selective ion separation according to claim 2, characterized in that, The aqueous solution of the amine monomer has a concentration of 0.1-10 wt%, and the oil phase solution of the acyl chloride monomer is prepared by dissolving the acyl chloride monomer in an organic solvent, with a concentration of 0.05-0.5 wt%. The organic solvent is n-hexane, N,N-dimethylformamide, N,N-dimethylacetamide, n-heptane, or isoalkanes.

4. The composite ion exchange membrane for selective ion separation according to claim 1, characterized in that, The addition ratio of the polymer in the intermediate porous support layer and the edge porous support layer is 10-25 wt%. The proportion of charged polymer material or charged inorganic material added to the intermediate porous support layer and the edge porous support layer is 0-10wt%.

5. A composite ion exchange membrane for selective ion separation according to claim 1, characterized in that, The polymer is cellulose acetate, polyamide, polysulfone, polyethersulfone, polyphenylene ether, or polypropylene; The charged polymer material is a sulfonated polymer or a quaternized polymer; The charged inorganic material is a charged MOF or a charged COF.

6. A composite ion exchange membrane for selective ion separation according to claim 5, characterized in that, The sulfonated polymer is selected from one or more of sulfonated polyethersulfone, sulfonated polysulfone, sulfonated polyphenylsulfone, sulfonated polyetheretherketone, sulfonated polyimide, sulfonated polyetherimide, sulfonated polyaryletherketone, sulfonated poly / arylene ether, sulfonated polystyrene, and sulfonated polyaniline; The quaternized polymer is selected from one or more of quaternized polyethyleneimine, quaternized polyaryletherketone, quaternized polyethersulfone, and quaternized polyarylethersulfoneketone. The skeleton material layer is made of spun fabric with a pore size of 0.05-0.15mm, and is made of polypropylene and polyester synthetic fiber filaments with a diameter of 25-100μm.

7. A method for preparing a composite ion exchange membrane for ion selective separation as described in any one of claims 1 to 6, characterized in that, Includes the following steps: A casting solution is obtained by mixing a polymer and a charged polymer material or a charged inorganic material with an organic solvent and heating and stirring. The obtained casting solution is evenly coated on both sides of the skeleton material layer to form a wet film. The skeleton material layer coated with a wet film is immersed in a water bath, and a middle porous support layer and an edge porous support layer are formed on both sides of the skeleton material layer through phase transformation. An aqueous solution of amine monomers is applied to the surface of the intermediate porous support layer. Excess water droplets on the surface of the intermediate porous support layer are removed. Then, an oil phase solution of acyl chloride monomers is applied to the surface of the intermediate porous support layer after the aqueous solution of amine monomers is applied. Interfacial polymerization is carried out and the layer is dried to form a dense separation layer.

8. The method for preparing a composite ion exchange membrane for selective ion separation according to claim 7, characterized in that, The organic solvent for blending with polymers and charged polymers or charged inorganic materials is at least one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide; During the heating and stirring process to obtain the casting solution: the heating temperature is 40-80℃, and the stirring time is 3-7h.

9. A method for preparing a composite ion exchange membrane for selective ion separation according to claim 7, characterized in that, The skeleton material layer coated with the wet film is immersed in a water bath, and the phase transformation time is 30-120 seconds.

10. A method for preparing a composite ion exchange membrane for ion selective separation according to claim 7, characterized in that, The contact time between the aqueous solution of the amine monomer and the surface of the intermediate porous support layer is 1-30 min; the reaction time after the oil phase solution of the acyl chloride monomer is applied is 1-30 min. During the drying process to form a dense separation layer, it is placed in an oven at 60-120℃ for drying.

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