Separation membrane and its preparation method

Abstract

This application discloses a separation membrane and its preparation method. The method for preparing the separation membrane includes: providing a casting solution containing particles; forming a base membrane using the casting solution, with particles embedded on the surface of the base membrane; and forming a composite membrane by reacting an oil phase solution with the particles on the surface of the base membrane to obtain the separation membrane. The particles include a core and a shell covering the core. The core includes an aqueous phase solution, which includes a first solute. The oil phase solution includes a second solvent and a second solute. The shell is configured to dissolve at least partially in the second solvent to release at least a portion of the aqueous phase solution. The oil phase solution and the aqueous phase solution undergo an interfacial polymerization reaction to form the composite membrane. The separation membrane disclosed in this application has high water flux and separation efficiency.

Description

Technical Field

[0001] This application relates to the field of membrane separation technology, specifically to separation membranes and their preparation methods. Background Technology

[0002] Membrane separation refers to the process of separating, purifying, and concentrating different substances in a solution by utilizing the selective permeability of a membrane under a certain driving force. Currently, separation membranes are generally classified into four types based on the components they retain, separation mechanism, and pressure difference: microfiltration (MF) membranes, ultrafiltration (UF) membranes, nanofiltration (NF) membranes, and reverse osmosis (RO) membranes. Among these, NF membranes, RO membranes, and some UF membranes with a molecular weight cutoff below 5KD utilize interfacial polymerization technology to react on the surface of a base membrane to form a thin composite membrane, achieving the separation effect.

[0003] The basic principle of interfacial polymerization is to select two immiscible solvents and dissolve two reactive monomers separately in these solvents (typically water and alkanes). When the two solvents come into contact, a dense and thin composite membrane is formed at the interface. Due to its advantages such as fast reaction speed and simple operation, it has been widely used in the preparation of composite membranes such as reverse osmosis (RO) membranes and nanofiltration (NF) membranes. However, the separation performance of these membranes needs further improvement. Summary of the Invention

[0004] The first aspect of this application discloses a method for preparing a separation membrane, comprising: The casting solution is provided and contains particles; A base film is formed using a casting solution, and particles are embedded on the surface of the base film. A composite membrane is formed on the surface of a base membrane by the interaction of an oil phase solution and particles, thus obtaining a separation membrane; The particle includes a core and a shell covering the core. The core includes an aqueous solution, and the aqueous solution includes a first solute. The oil phase solution includes a second solvent and a second solute, and the shell is configured to be at least partially soluble in the second solvent to release at least a portion of the aqueous phase solution; the oil phase solution and the aqueous phase solution undergo an interfacial polymerization reaction to form a composite film.

[0005] This application embeds particles coated with an aqueous solution into the surface of a base membrane. During the interfacial polymerization reaction, the particles dissolve, forming pores on the base membrane surface. This increases the surface roughness and porosity of the base membrane, accelerates the composite membrane bonding process during interfacial polymerization, improves the density of the composite membrane, and enhances its permeability. The oil phase solution gradually dissolves the shell of the particles from top to bottom, allowing it to contact the released aqueous solution and rapidly polymerize on the base membrane surface to form a composite membrane. This improves the problem of pore blockage caused by the formation of the composite membrane within the pores, further enhancing the permeability of the composite membrane. In summary, the separation membrane prepared using this improved interfacial polymerization reaction exhibits high water flux and separation efficiency.

[0006] In some implementations, the particle size is 30nm-80nm.

[0007] In some embodiments, the shell material includes one or more of paraffin wax, beeswax, carnauba wax, gelatin, and gum arabic.

[0008] In some embodiments, the second solvent includes an alkane solvent; optionally, the alkane solvent includes one or more of chain alkanes and cyclic alkanes.

[0009] In some embodiments, the second solvent includes one or more of ethylcyclohexane, ISOPAR G, n-hexane, and cyclohexane.

[0010] In some embodiments, the step of forming a base film using a casting solution includes: coating the casting solution onto a substrate and then placing it in a coagulation bath for phase transformation to form a film, followed by cleaning treatment to obtain a base film with particles embedded on its surface.

[0011] In some embodiments, the base film comprises one or more of polysulfones, polyolefins, polyamides, and polyacrylonitriles; optionally, the base film includes polysulfones: one or more of polysulfones, polyethersulfones, polyethylene, polypropylene, aromatic polyamides, polysulfonamides, and polyacrylonitriles.

[0012] In some embodiments, the first solute comprises an amine monomer and a proton absorber; and satisfies at least one of the following: Amine monomers include one or more of m-phenylenediamine, piperazine, phenylenediamine, and triethylamine; Proton absorbers include one or more of sodium hydroxide, sodium phosphate, camphor sulfonic acid, and sodium bicarbonate.

[0013] In some embodiments, the second solute includes an acyl chloride monomer; optionally, the acyl chloride monomer includes one or more of pyromellitic methyl chloride, phthaloyl chloride, and naphthalenesulfonyl chloride.

[0014] The second aspect of this application provides a separation membrane, including a separation membrane prepared using the method described in the first aspect.

[0015] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0016] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 A schematic diagram illustrating the formation principle of the separation membrane in some embodiments of this application is shown.

[0017] Figure 2 The diagram shows the manufacturing process flow chart of the separation membrane according to some embodiments of this application.

[0018] Figure 3 A schematic diagram of the formation principle of a current method for preparing a separation membrane is shown.

[0019] Figure 4 A schematic diagram of the cross-sectional structure of a base membrane for preparing another existing separation membrane is shown.

[0020] Figure 5 The diagram shows the existing production process flow for preparing separation membranes. Attached image description: 1 Base membrane; 2 Particles; 21 Shell; 22 Core; 3 Oil phase solution; 4 Composite membrane; 5 Pore; 6 Aqueous phase solution; 7 Core-shell structured nanoparticles; 8 Unwinding roller; 9 Oil phase storage device; 10 Aqueous phase storage device; 11 Air knife; 12 Dewatering roller. Detailed Implementation

[0022] The embodiments of this application are described in detail below. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0023] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this application, unless otherwise stated, "multiple" means two or more.

[0024] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this application.

[0025] In this application, the terms "comprising" or "including" are open-ended expressions, meaning they include the content specified in this application but do not exclude other aspects.

[0026] Studies have found that interfacial polymerization reactions are completed on the surface of the base film to form a composite film. The performance of the composite film is greatly related to the surface morphology of the base film. The greater the surface roughness of the base film and the more surface pores, the better the performance of the composite film generated by the interfacial polymerization reaction.

[0027] Currently, the specific process of interfacial polymerization for composite membrane fabrication involves first dipping a layer of aqueous solution containing reactive monomers onto a base membrane, then blowing away excess aqueous solution from the base membrane surface with an air knife, and finally coating the base membrane surface with an oil-phase solution containing another reactive monomer, ultimately reacting to form a composite membrane. This method first requires preparing a base membrane. Currently, most base membranes are modified by adding modifiers or surface grafting to the casting solution to alter the surface morphology. This method makes it difficult to accurately control the surface morphology of the base membrane; furthermore, the interfacial polymerization reaction produces excess aqueous phase, and the aqueous monomers are generally ammonium salts, which cause significant environmental pollution and are detrimental to sustainable development. Specifically: like Figure 3 As shown, in the conventional preparation method, an aqueous solution 6 is dipped into a base membrane 1, forming a thin water film on the surface of the base membrane 1. Then, an oil solution 3 is coated on top, and a polymerization reaction is carried out to generate a composite membrane 4. This method has a drawback: during the formation of the water film, the aqueous solution 6 penetrates into the pores on the surface of the base membrane 1. During the interfacial polymerization reaction, the composite membrane 4 also forms inside the pores of the base membrane 1, which greatly reduces the permeability of the separation membrane.

[0028] like Figure 4 As shown, to improve the surface properties of the base membrane, core-shell structured nanoparticles 7 are added to the casting solution, and the base membrane 1 is prepared using the casting solution to embed the core-shell structured nanoparticles 7 within the base membrane 1. A composite membrane 4 is then fabricated on the surface of the base membrane 1. The resulting separation membrane, through the design of the hydrophilicity and high specific surface area of ​​the core-shell structured nanoparticles 7, achieves improved separation performance, such as improving water flux and desalination rate. However, some drawbacks exist: 1) The core material of the core-shell structured nanoparticles 7 is a solid, and embedding it on the surface of the base membrane 1 does not create pores, not only blocking the channels of the aqueous phase on the surface of the base membrane 1 but also blocking the filtration channels of the separation membrane; 2) It reduces the crosslinking strength of the composite membrane 4, resulting in poor performance and susceptibility to scratches.

[0029] like Figure 5As shown, in the above methods, the interfacial polymerization production process is a two-step process. First, the base film 1 is dipped into an aqueous phase storage device 10 to coat with an aqueous solution, and then coated with an oil phase storage device 9 to coat with an oil phase solution, reacting on the surface of the base film 1 to form a composite film. During this process, the aqueous solution on the surface of the base film 1 needs to be controlled by equipment and processes such as an air knife 11 and a water-squeezing roller 12, making the process cumbersome and difficult to adjust. Furthermore, the aqueous phase coating requires the preparation of a large amount of amine aqueous solution, generating hazardous waste liquid after production, which, if not properly treated, will cause environmental pollution.

[0030] Therefore, a first aspect of the embodiments of this application provides a method for preparing a separation membrane, comprising: The casting solution is provided and contains particles; A base film is formed using a casting solution, and particles are embedded on the surface of the base film. A composite membrane is formed on the surface of a base membrane by the interaction of an oil phase solution and particles, thus obtaining a separation membrane; The particle includes a core and a shell covering the core. The core includes an aqueous solution, and the aqueous solution includes a first solute. The oil phase solution includes a second solvent and a second solute, and the shell is configured to be at least partially soluble in the second solvent to release at least a portion of the aqueous phase solution; the oil phase solution and the aqueous phase solution undergo an interfacial polymerization reaction to form a composite film.

[0031] like Figure 1 As shown, in this embodiment, particles 2 are first added to the casting solution. The structure of the particles 2 includes a core 22 and an outer shell 21. The shell 21 serves to isolate the core 22 from the external environment, preventing premature release of the core 22. After the oil phase solution 3 comes into contact with the particles 2 on the surface of the base film 1, the shell 21 material of the particles 2 dissolves in the second solvent of the oil phase solution 3. This allows the shell 21 to be at least partially broken, exposing the core 22, thus releasing the aqueous phase solution. In this embodiment, the interfacial polymerization reaction is used, with the aqueous phase solution acting as the core 22 encapsulated in the shell 21. The dissolution process of the shell 21 is from top to bottom, with the upper shell 21 dissolving first and then gradually dissolving the lower layers. After the solvent of the oil phase solution 3 dissolves the upper half of the shell 21, the aqueous phase solution is immediately released and reacts with the oil phase solution 3 to form a composite film 4, ultimately obtaining a separation film. Furthermore, a large number of pores 5 are retained on the surface of the base film 1. Therefore: In this embodiment, particles are embedded in the surface layer of the base membrane. This facilitates the uniform distribution of the aqueous solution on the base membrane surface. After dissolution and reaction, these particles create pores on the base membrane surface, increasing its porosity and roughness. This, in turn, increases the water flux of the separation membrane and strengthens the bond between the composite membrane and the base membrane. Higher porosity on the base membrane surface reduces lateral resistance to water flow through the composite membrane, improving the retention and permeation performance of the separation membrane, thereby enhancing its overall separation efficiency.

[0032] The interfacial polymerization reaction provided in this application involves a process where the shell dissolves first in the upper layer and then in the lower layer. After the second solvent of the oil phase solution dissolves the upper half of the shell, the aqueous phase solution is immediately released and reacts with the oil phase solution. This reduces the penetration of the oil phase solution into the pores, allowing the composite membrane to be formed on the surface of the base membrane. This helps to solve the problem of clogging the membrane pores and thus improves the permeability of the composite membrane.

[0033] In addition, such as Figure 2 As shown, the base film 1 with particles embedded in its surface is directly unwound by the unwinding roller 8, and then an oil phase solution is coated on the surface of the base film 1 by the oil phase storage device 9 before proceeding to subsequent processes. In this embodiment, particles that can contain an aqueous phase solution are added during the fabrication of the base film 1. By embedding the material into the base film surface, the step of the base film 1 absorbing the aqueous phase solution in the traditional interfacial polymerization reaction is reduced. This saves on process equipment and operations such as the aqueous phase storage device, air knife, and dewatering roller during production, thus saving costs and reducing the discharge of aqueous phase solution wastewater (amine-containing hazardous wastewater).

[0034] In some embodiments of this application, the particle size is 30nm-80nm.

[0035] As an example, the particle size is 30nm, 35nm, 40nm, 35nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, or any value between two of these.

[0036] The particle size affects the pore size of the formed base membrane surface, which in turn affects the surface roughness, porosity, and other characteristics of the base membrane. In the embodiments of this application, the particle size meets the above conditions, is small, and belongs to the nanoscale. Before the interfacial polymerization reaction, it can be stably embedded in the base membrane surface. During the interfacial reaction, it has a high contact area, which is beneficial to improve the efficiency of the interfacial polymerization reaction and obtain a large porosity, so that the final separation membrane has a high water flux and separation efficiency.

[0037] In some embodiments of this application, the shell material includes one or more of paraffin wax, beeswax, carnauba wax, gelatin, and gum arabic.

[0038] In this embodiment, the shell material can be a material known in the art that is soluble in a second solvent in an oil phase solution. For example, it can be one or more of paraffin wax, beeswax, carnauba wax, gelatin, and gum arabic.

[0039] In some embodiments of this application, the second solvent includes alkane solvents; optionally, the alkane solvent includes one or more of chain alkanes and cyclic alkanes.

[0040] In this embodiment, the second solvent is used to solvent the second solute to form an oil phase solution for participating in the interfacial polymerization reaction; it is also used to dissolve the shell of the particles to release the aqueous phase solution encapsulated within the shell.

[0041] The second solvent may be a solvent known in the art, such as an alkane solvent. As an example, it may be a cyclic alkane or a chain alkane; wherein, the cyclic alkane may contain monocyclic alkanes or alkyl-substituted cyclic alkanes; the chain alkane may contain n-alkanes (straight chains) or isoalkanes (straight chains).

[0042] In some embodiments of this application, the second solvent includes one or more of ethylcyclohexane, ISOPAR G, n-hexane, and cyclohexane.

[0043] In some embodiments of this application, the step of forming a base film using a casting solution includes: coating the casting solution onto a substrate and then placing it in a coagulation bath for phase transformation to form a film, followed by cleaning treatment to obtain a base film with particles embedded on its surface.

[0044] The embodiments of this application can use the existing known phase inversion method to prepare the base membrane, which can obtain a base membrane with a dense surface and a large pore structure in the bulk phase. In this way, the pores of the initially formed base membrane are distributed with particles. After cleaning, the pores of the base membrane surface are smaller, and the particles can be stably embedded and anchored in the base membrane surface. Meanwhile, the pores of the base membrane bulk phase are larger, and the particles are carried away with the cleaning solution. In this way, the base membrane bulk phase can retain a rich pore structure, which is beneficial to improving water flux. The particles embedded in the surface can participate in the interfacial polymerization reaction in subsequent processes and can also play a role in pore formation.

[0045] In some embodiments of this application, the base film comprises one or more of polysulfone, polyolefin, polyamide, and polyacrylonitrile; optionally, the base film includes polysulfone: one or more of polysulfone, polyethersulfone, polyethylene, polypropylene, aromatic polyamide, polysulfonamide, and polyacrylonitrile.

[0046] The base membrane is a porous membrane that provides mechanical support, supporting the composite membrane formed by interfacial polymerization. It also acts as a guide, allowing water molecules to be quickly guided away through the base membrane after passing through the thin composite membrane, thus protecting the composite membrane structure. In the embodiments of this application, the base membrane material can be any material known in the art. For example, it can be one or more of the following: polysulfone, polyethersulfone, polyethylene, polypropylene, aromatic polyamide, polysulfonamide, and polyacrylonitrile.

[0047] In some embodiments of this application, the first solute comprises an amine monomer and a proton absorber; and satisfies at least one of the following: Amine monomers include one or more of m-phenylenediamine, piperazine, phenylenediamine, and triethylamine; Proton absorbers include one or more of sodium hydroxide, sodium phosphate, camphor sulfonic acid, and sodium bicarbonate.

[0048] This application employs interfacial polymerization to form a composite membrane. The aqueous solution participating in the interfacial polymerization reaction can be made of materials known in the art, such as water as the first solvent and amine monomers and proton absorbers as the first solute. Other additives, such as auxiliary solvents and surfactants, can also be added based on actual needs. The amine monomers react with the monomers in the oil phase solution to construct the composite membrane, and the proton absorbers neutralize byproducts, improving reaction efficiency.

[0049] In some embodiments of this application, the second solute includes an acyl chloride monomer; optionally, the acyl chloride monomer includes one or more of pyromellitic methyl chloride, phthaloyl chloride, and naphthalenesulfonyl chloride.

[0050] The embodiments of this application employ interfacial polymerization to form a composite film, and the oil phase solution participating in the interfacial polymerization reaction can be made of materials known in the art. As an example, acyl chloride monomers can react with amine monomers to form a composite film structure.

[0051] In some embodiments of this application, particles can be prepared using an emulsification-solidification method. As an example, the preparation method includes: Provide an aqueous solution; The shell material is dissolved in a solvent to obtain an oil solution; An aqueous solution is dispersed in an oil solution to form an emulsion; wherein, an oil solution is used as the dispersed phase, and the emulsion can be formed by stirring. Interfacial crystallization is performed to form a shell on the surface of an aqueous solution, resulting in particles; the shell can be formed by cooling-induced interfacial crystallization.

[0052] A second aspect of this application provides a separation membrane, including a separation membrane prepared using the method provided in the first aspect.

[0053] The separation membrane obtained by the aforementioned method has high water throughput and separation efficiency.

[0054] The following will explain the solution of this application with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0055]

Preparation of Separation Membranes

[0056] (2) Heat 5g of paraffin and 190g of mineral oil to 60℃-70℃ to melt, add 5g of Span-80 and stir until uniform to obtain oil phase liquid.

[0057] (3) Preheat the aqueous phase liquid to the same temperature as in step (2), slowly add it to the oil phase liquid, and stir with a high-speed shear machine for 15 minutes to form an emulsion in which the aqueous phase liquid droplets are dispersed in the oil phase.

[0058] (4) Cool the emulsion to room temperature. Paraffin crystallizes at the oil-water interface to form a nano solid shell that encapsulates the aqueous droplets with a diameter of about 60 nm.

[0059] (5) Uncoated free paraffin particles were removed by centrifugation and stable core-shell particles were obtained by vacuum drying at 40°C.

[0060] (6) Take 18g of polysulfone and add it to 80g of N,N-dimethylacetamide (DMAC). Heat and stir for 6h to form a uniform casting solution. After cooling, add 2g of core-shell particle material and stir evenly.

[0061] (7) The casting solution is coated on nonwoven fabric and placed in a coagulation bath to transform the phase into a film. The residual solvent and core-shell particles in the base film phase are washed away and used as a base film for later use.

[0062] (8) Dissolve 0.1g of trimesoyl chloride in 100g of ethylcyclohexane to prepare an oil phase solution.

[0063] (9) Immerse the base membrane in the oil phase solution for 1 minute, remove it, put it in an oven to dry, and obtain the separation membrane.

[0064] Example 2 (1) Take 1.5g piperazine and 2.5g camphor sulfonic acid and add them to 80g deionized water. Stir until completely dissolved, add water to 198.5g, and then add 1.5g m-phenylenediamine to the above solution and stir evenly to obtain an aqueous phase.

[0065] (2) Heat 5g of beeswax and 190g of mineral oil to 60℃-70℃ to melt, add 5g of Span-80 and stir until uniform to obtain oil phase liquid.

[0066] (3) Preheat the aqueous phase liquid to the same temperature as in step (2), slowly add it to the oil phase liquid, and stir with a high-speed shear machine for 15 minutes to form an emulsion in which the aqueous phase liquid droplets are dispersed in the oil phase liquid.

[0067] (4) Cool the emulsion to room temperature. The beeswax crystallizes at the oil-water interface to form a nano solid shell that encapsulates the aqueous droplets with a diameter of about 55 nm.

[0068] (5) Uncoated free beeswax particles were removed by centrifugation and stable core-shell particles were obtained by vacuum drying at 40°C.

[0069] (6) Take 20g of polysulfone and add it to 75g of DMAC. Heat and stir for 6 hours to form a uniform casting liquid. After cooling, add 5g of core-shell particle material and stir evenly.

[0070] (7) The casting solution is coated on nonwoven fabric and placed in a coagulation bath to transform the phase into a film. The residual solvent and core-shell particles in the base film phase are washed away and used as a base film for later use.

[0071] (8) Dissolve 0.2g of pyromellitic chloride in 100g of ISOPAR G to prepare an oil phase solution.

[0072] (9) Immerse the base membrane in the oil phase solution for 1 minute, remove it, put it in an oven to dry, and obtain the separation membrane.

[0073] Comparative Example 1 (1) Take 18g of polysulfone and add it to 82g of DMAC, heat and stir for 6h to form a uniform casting solution. (2) The casting solution is coated on the nonwoven fabric, placed in the coagulation bath to transform into a film, and the residual solvent is washed away to prepare the base film for later use.

[0074] (3) Take 2g of triethylamine and 4g of camphor sulfonic acid and add them to 80g of deionized water. Stir until completely dissolved, add water to 100g, and then add 2g of m-phenylenediamine to the above solution and stir evenly to obtain an aqueous solution.

[0075] (4) Dissolve 0.1g of pyromellitic chloride in 100g of ethylcyclohexane to prepare an oil phase solution.

[0076] (5) Immerse the base membrane surface in the aqueous solution for 40 seconds, take it out, blow dry the water and let it stand for 5 minutes, then immerse it in the oil solution for 1 minute, take it out, put it in the oven to dry, and obtain the separation membrane.

[0077] Comparative Example 2 (1) Take 20g of polysulfone and add it to 80g of DMAC, heat and stir for 6h to form a uniform casting solution. (2) The casting solution is coated on the nonwoven fabric, placed in the coagulation bath to transform into a film, and the residual solvent is washed away to prepare the base film for later use.

[0078] (3) Take 1.5g piperazine and 2.5g camphor sulfonic acid and add them to 80g deionized water. Stir until completely dissolved, add water to 100g, and then add 1.5g m-phenylenediamine to the above solution and stir evenly to obtain an aqueous solution.

[0079] (4) Dissolve 0.1g of pyromellitic chloride in 100g of ISOPAR G to prepare an oil phase solution.

[0080] (5) Immerse the base membrane surface in the aqueous solution for 40s, take it out and blow dry the water for 5min, then immerse it in the oil phase for 1min, take it out and put it in the oven to dry to obtain the separation membrane.

[0081] The separation membranes obtained in Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were tested, and the results are shown in Table 1.

[0082] Table 1

[0083] As shown in Table 1, comparing Example 1 and Comparative Example 1, it can be seen that the separation membranes obtained in Example 1 and Comparative Example 1 can both separate and remove NaCl. Comparative Example 1 uses a traditional interfacial polymerization reaction to prepare the separation membrane, which has relatively low water flux and desalination rate. Example 1 of this application uses an improved interfacial polymerization reaction to prepare the separation membrane, which can significantly improve the water flux and also obtain a higher desalination rate.

[0084] Comparing Example 2 and Comparative Example 2, it can be seen that the separation membranes obtained in Example 1 and Comparative Example 1 can both separate and remove NaCl and MgSO4. Furthermore, Example 2 of this application uses an improved interfacial polymerization reaction to prepare the separation membrane, which can significantly increase the water flux and also obtain a higher desalination rate.

[0085] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for preparing a separation membrane, characterized in that, include: A casting solution is provided, the casting solution containing particles; A base film is formed using the casting solution, and the particles are embedded on the surface of the base film. A composite membrane is formed on the surface of the base membrane by reacting the particles with an oil phase solution, thus obtaining a separation membrane; The particle includes a core and a shell covering the core, the core comprising an aqueous solution, and the aqueous solution comprising a first solute; The oil phase solution includes a second solvent and a second solute, and the shell is configured to be at least partially soluble in the second solvent to release at least a portion of the aqueous phase solution; The oil phase solution and the aqueous phase solution undergo an interfacial polymerization reaction to form a composite film.

2. The method according to claim 1, characterized in that, The particle size is 30nm-80nm.

3. The method according to claim 1 or 2, characterized in that, The shell material includes one or more of paraffin wax, beeswax, carnauba wax, gelatin, and gum arabic.

4. The method according to claim 1 or 2, characterized in that, The second solvent includes alkane solvents; optionally, the alkane solvent includes one or more of chain alkanes and cyclic alkanes.

5. The method according to claim 4, characterized in that, The second solvent includes one or more of ethylcyclohexane, ISOPARG, n-hexane, and cyclohexane.

6. The method according to claim 1 or 2, characterized in that, The step of forming a base film using the casting solution includes: coating the casting solution onto the substrate and then placing it in a coagulation bath for phase transformation to form a film, followed by cleaning treatment to obtain the base film with the particles embedded on its surface.

7. The method according to claim 1 or 2, characterized in that, The base film comprises one or more of polysulfone, polyolefin, polyamide, and polyacrylonitrile; optionally, the base film includes polysulfone: one or more of polysulfone, polyethersulfone, polyethylene, polypropylene, aromatic polyamide, polysulfonamide, and polyacrylonitrile.

8. The method according to claim 1 or 2, characterized in that, The first solute comprises an amine monomer and a proton absorber; and satisfies at least one of the following: The amine monomers include one or more of m-phenylenediamine, piperazine, phenylenediamine, and triethylamine; The proton absorber includes one or more of sodium hydroxide, sodium phosphate, camphor sulfonic acid, and sodium bicarbonate.

9. The method according to claim 1 or 2, characterized in that, The second solute includes an acyl chloride monomer; optionally, the acyl chloride monomer includes one or more of pyromellitic methyl chloride, phthaloyl chloride, and naphthalenesulfonyl chloride.

10. A separation membrane, characterized in that, This includes separation membranes prepared using the method described in any one of claims 1 to 9.

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