Preparation method and application of membrane material with specific separation

Abstract

The invention belongs to the technical field of separation membranes, and particularly relates to a preparation method and application of a membrane material with specific separation, and the preparation method of the membrane material with specific separation comprises the following steps: (1) screening an ultrafiltration membrane as a base membrane; (2) preparing a surfactant aqueous solution, and immersing the base membrane in the solution for pretreatment of interfacial polymerization; (3) adopting an interfacial polymerization mode of a low-temperature prepolymerization and normal-temperature curing two-step method to obtain a nanofiltration membrane with uniform pore diameter; and (4) carrying out modification treatment on the surface of the nanofiltration membrane to obtain the membrane material with specific separation. The prepared nanofiltration membrane is large in flux, has a specific separation effect, also has good hydrophilic performance, and can be widely applied to the fields of water treatment and material separation.

Description

Technical Field

[0001] This invention belongs to the field of separation membrane technology, specifically relating to a method for preparing a membrane material with specific separation properties and its application. Background Technology

[0002] With industrial development, accelerated urbanization, and intensified global water scarcity, water treatment faces challenges such as "a wide variety of pollutants, large fluctuations in water quality, and high requirements for resource recovery." Traditional separation technologies (such as sedimentation, filtration, and conventional reverse osmosis) are insufficient to meet the needs of precise treatment, leading to the application of specialized separation membranes. Currently, membrane separation technology is widely used in the water treatment field, characterized by its simple process and easy operation.

[0003] Among the pressure-driven membrane materials currently in use, nanofiltration membranes can effectively separate organic matter and salts, showing broad application prospects in water treatment and solute separation and recovery. However, as can be seen from the nanofiltration membrane preparation process, the diffusion of amine monomers from the aqueous phase to the organic phase for interfacial polymerization is random and difficult to control. This leads to variations in the thickness and pore size of the polyamide separation layer formed by the nanofiltration membrane, affecting the overall performance of the separation layer and limiting the application of nanofiltration membrane materials in the field of material separation.

[0004] The patent CN119746643B, entitled "Preparation Method and Application of LDH Nanonetwork-Assisted Polyamide Nanofiltration Membrane," specifically discloses a method for preparing an LDH nanonetwork-assisted polyamide nanofiltration membrane, comprising the following steps: (1) regionally sealing a porous base membrane with a coating; (2) obtaining a precursor solution, then immersing the porous base membrane in the precursor solution for reaction to obtain an LDH membrane; (3) cleaning and soaking the LDH membrane with an organic solvent, and drying the LDH membrane to obtain a dried LDH membrane; (4) immersing the dried LDH membrane in a mixed aqueous solution of piperazine and LDH nanosheets under vacuum conditions for filtration and drying to obtain an LDH mesh membrane; (5) immersing the LDH mesh membrane in a solution of trimesoyl chloride and hexane for polymerization reaction, washing and drying to obtain an LDH nanonetwork-assisted polyamide nanofiltration membrane. This method of preparing nanofiltration membranes is cumbersome, and the use of nano-ions to construct the auxiliary network inevitably leads to particle stacking, which affects the performance of the separation layer in the interfacial polymerization.

[0005] The patent with publication number CN119455680A, entitled "A High-Permeability Selectivity Beaded Nanofiltration Membrane and Its Preparation Method and Application," specifically discloses a high-permeability selectivity beaded nanofiltration membrane and its preparation method and application, including the following steps: (1) preparing an aqueous solution using an aqueous monomer and a nonionic surfactant, wherein the aqueous monomer is a polyamine monomer and the nonionic surfactant is a polyoxyethylene nonionic surfactant selected from fatty alcohol polyoxyethylene ether, fatty acid polyoxyethylene ether, or fatty amine polyoxyethylene ether; (2) using the aqueous solution obtained in step (1) and the acyl chloride monomer oil phase solution to carry out an interfacial polymerization reaction on a microfiltration substrate to prepare the high-permeability selectivity beaded nanofiltration membrane. This method directly mixes the surfactant with the aqueous phase, which cannot control the pore formation of the interfacial polymerization, resulting in large differences in the overall performance of the membrane material and affecting the overall performance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention proposes a method for preparing a membrane material with specific separation properties and its application. By modifying the surface of the ultrafiltration base membrane with surfactants and performing a two-step interfacial polymerization, the interfacial polymerization is made controllable. Furthermore, the surface of the nanofiltration membrane is grafted and modified to obtain a nanofiltration membrane material that simultaneously possesses specific separation properties and good antifouling performance. The prepared nanofiltration membrane is then applied to water treatment to separate magnesium and lithium ions.

[0007] To achieve the purpose of the invention, the following technical solution is provided: This invention provides a method for preparing a membrane material with specific separation properties. The method involves using a surfactant to modify the surface of an ultrafiltration membrane, followed by a two-step interfacial polymerization process of low-temperature prepolymerization and room-temperature curing to form a separation layer with uniform pore size, resulting in a nanofiltration membrane with uniform pore size. Finally, the surface of the nanofiltration membrane is hydrophilically modified to obtain a membrane material with specific separation properties.

[0008] Furthermore, the method for preparing the membrane material with specific separation includes the following steps: (1) Select an ultrafiltration membrane with an average pore size of 0.1-1 μm and a molecular weight cutoff of 50-100 kDa as the base membrane material; (2) Prepare an aqueous solution of surfactant with a concentration of 0.1-0.5wt%, immerse the ultrafiltration membrane in it, and obtain a surface-modified ultrafiltration membrane material; (3) Prepare a 1-2 wt% piperazine aqueous solution, add a catalyst, adjust the aqueous solution to alkaline, immerse the surface-active modified ultrafiltration membrane obtained in step (2) in the piperazine aqueous solution, and dry it; (4) Prepare an organic phase pyromellitic chloride solution with a concentration of 0.1-0.3wt%, and immerse the ultrafiltration membrane obtained in step (3) in the pyromellitic chloride solution to carry out a two-step interfacial polymerization reaction to obtain a nanofiltration membrane with uniform pore size. (5) Immerse the nanofiltration membrane prepared in step (4) in the modifier, terminate the reaction with ice water, and then neutralize it with sodium hydroxide solution to obtain a nanofiltration membrane material with specific separation.

[0009] Furthermore, the ultrafiltration membrane material is either polysulfone or polyethersulfone.

[0010] Further, in step (2), the ultrafiltration membrane is immersed in a 0.1~0.5 wt% surfactant aqueous solution and shaken at a constant temperature of 30~40℃ for 1~2 hours. After removal, it is rinsed with deionized water until there is no free surfactant on the surface.

[0011] Furthermore, the surfactant is any one or more combinations of anionic, cationic, nonionic, or amphoteric surfactants, wherein anionic surfactants are not used in combination with cationic surfactants.

[0012] Furthermore, the catalyst is any one of triethylamine, pyridine, sodium carbonate, or lithium chloride.

[0013] Further, in step (3), a 1-2 wt% piperazine aqueous solution is prepared, and the pH of the aqueous solution is adjusted according to the type of catalyst selected.

[0014] Furthermore, in step (4), a mixed solution of n-hexane and cyclohexane in a volume ratio of 3:1 is selected as the solvent.

[0015] Furthermore, the specific steps of the two-step interfacial polymerization reaction in step (4) are as follows: first, react at 10°C for 30 seconds to inhibit monomer diffusion, and then react at 25°C for 1 minute to promote uniform cross-linking and produce nanofiltration membrane material with uniform pore size.

[0016] Furthermore, in step (5), the modifier is a mixture of chlorosulfonic acid and dichloromethane in a volume ratio of 1:10.

[0017] Further, in step (5), the nanofiltration membrane is immersed in the modifier and reacted at 0~5℃ for 10-20 minutes. The reaction is terminated with ice water and then neutralized to neutral with 0.1mol / L NaOH solution.

[0018] The present invention also discloses a membrane material with specific separation prepared according to the above preparation method.

[0019] The present invention also discloses the application of a membrane material with specific separation properties for separating magnesium ions and lithium ions in water treatment.

[0020] Furthermore, the application of the membrane material with specific separation includes the following steps: installing the membrane material with specific separation in a cross-flow membrane filtration device, with a filtration pressure of 5~15 bar, to filter water containing magnesium ions and lithium ions.

[0021] Compared with existing technologies, the advantages of this invention are: 1. The nanofiltration membrane of this invention uses a surfactant to modify the surface of an ultrafiltration membrane. The surfactant's amphiphilic properties are utilized to regulate the surface activity of the base membrane. The hydrophobic chains in the surfactant are adsorbed onto the base membrane surface via van der Waals forces, while the exposed hydrophilic groups form uniformly distributed negatively charged sites. This provides electrostatic adsorption sites for subsequent aqueous monomers (such as piperazine), inhibiting random monomer diffusion. Based on surfactant modification, the interfacial polymerization process is optimized using a two-step method of "low-temperature prepolymerization + room-temperature curing" to suppress random monomer diffusion. By providing surface adsorption sites and optimizing the interfacial polymerization process, the controllability of interfacial polymerization is significantly improved, forming a separation layer with uniform pores, ensuring the overall separation effect of the nanofiltration membrane. Subsequently, a low-temperature stepwise reaction is used to graft and modify the nanofiltration membrane surface, adjusting the reaction time to control the degree of sulfonation, ensuring that the introduced -SO3H groups are uniformly distributed on the membrane surface, enhancing the adhesion to divalent ions (such as Ca2+). 2+ Mg 2+ The electrostatic repulsion effect of the graft avoids the membrane pore blockage problem caused by traditional graft modification, and can maintain a large water flux while improving the divalent ion rejection rate.

[0022] 2. The specific separation nanofiltration membrane material prepared by this invention has uniform and smooth pores in its separation layer, high water flux, and a high rejection rate for divalent ions, enabling it to achieve, for example, Mg... 2+ Li + The separation of ions, and the hydrophilic modification of the nanofiltration membrane surface, result in excellent antifouling properties and improved durability in practical applications. Treatment of the ultrafiltration membrane surface with surfactants leverages their amphiphilic characteristics to regulate the surface activity of the base membrane, forming uniformly distributed negatively charged sites. These sites provide electrostatic adsorption sites for subsequent aqueous monomers, influencing the random polymerization of the interfacial polymerization reaction. A two-step interfacial polymerization process is then employed to control the randomness of the polymerization. The nanofiltration membrane prepared in this way exhibits a uniform pore structure in the separation layer, improving its permeability and selectivity. This invention further modifies the separation layer surface, adding electrostatic repulsion to the particle size sieving effect, significantly enhancing the separation of monovalent and divalent ions. The preparation process is simple, adaptable to industrial production, and yields nanofiltration membranes with high water flux, excellent specific separation effect, good durability, and high practicality, making them widely applicable in water treatment. Attached Figure Description

[0023] Figure 1This is a SEM image of the specific separation membrane material in Example 1. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and preferred embodiments. The embodiments given are only for illustrating the present invention and are not intended to limit the scope of the present invention.

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0027] Unless otherwise specified, the experimental methods described in the following examples are conventional methods.

[0028] Example 1 This embodiment provides a method for preparing a membrane material with specific separation capabilities, comprising the following steps: (1) A polysulfone ultrafiltration membrane with a pore size of 0.3 μm and a molecular weight cutoff of 50 kDa was selected as the base membrane material; (2) Prepare a 0.1 wt% sodium dodecyl sulfate (SDS) aqueous solution, immerse the pretreated ultrafiltration membrane in it, and keep it at 40°C for 1.5 hours with constant temperature shaking. After taking it out, rinse it with deionized water. (3) Aqueous phase: Piperazine concentration is 1wt%, 0.5wt% triethylamine is added as catalyst, and pH is adjusted to 8-9; Oil phase: Trimethylolpropionate chloride (TMC) concentration is 0.1wt%, and the solvent is a mixture of n-hexane and cyclohexane (volume ratio 3:1). (4) The surface-pretreated ultrafiltration membrane was immersed in the aqueous solution for 3 minutes and then removed and dried with an air knife; (5) The interface polymerization adopts a two-step method, that is, the membrane material obtained in step (4) is immersed in the oil phase solution, first reacted at 10℃ for 30s to inhibit monomer diffusion, and then reacted at 25℃ for 1min to promote uniform cross-linking, so as to obtain a nanofiltration membrane with uniform pore size. (6) A mixture of chlorosulfonic acid and dichloromethane at a volume ratio of 1:10 was pre-cooled at 0°C. The membrane obtained in step (5) was immersed in the reaction for 15 min, and the reaction was terminated with ice water. The membrane was neutralized with 0.1 mol / mL NaOH aqueous solution and rinsed with deionized water to obtain a nanofiltration membrane with specific separation of the product; the morphology is as follows. Figure 1 As shown.

[0029] Example 2 This embodiment provides a method for preparing a membrane material with specific separation capabilities, including the following steps: (1) A polysulfone ultrafiltration membrane with a pore size of 0.5 μm and a molecular weight cutoff of 100 kDa was selected as the base membrane material; (2) Prepare a 0.5wt% polyethylene glycol aqueous solution, immerse the pretreated ultrafiltration membrane in it, and keep it at a constant temperature of 30°C for 1.5 hours. After taking it out, rinse it with deionized water. (3) Aqueous phase: Piperazine concentration is 1.5wt%, 0.5wt% lithium chloride is added as catalyst, and pH is adjusted to 8-9; Oil phase: Trimethylbenzene chloride (TMC) concentration is 0.3wt%, and the solvent is a mixture of n-hexane and cyclohexane (volume ratio 3:1). (4) The surface-pretreated ultrafiltration membrane was immersed in the aqueous solution for 3 minutes and then removed and dried with an air knife; (5) The interface polymerization adopts a two-step method, that is, the membrane material obtained in step (4) is immersed in the oil phase solution, first reacted at 10℃ for 30s to inhibit monomer diffusion, and then reacted at 25℃ for 1min to promote uniform cross-linking, so as to obtain a nanofiltration membrane with uniform pore size. (6) A mixture of chlorosulfonic acid and dichloromethane in a volume ratio of 1:10 was pre-cooled at 5°C. The membrane obtained in step (5) was immersed in the reaction for 20 min, and the reaction was terminated with ice water. The membrane was neutralized with 0.1 mol / mL NaOH aqueous solution and rinsed with deionized water to obtain a nanofiltration membrane with specific separation.

[0030] Example 3 This embodiment provides a method for preparing a membrane material with specific separation capabilities, including the following steps: (1) A polyethersulfone ultrafiltration membrane with a pore size of 1 μm and a molecular weight cutoff of 80 kDa was selected as the base membrane material; (2) Prepare a 0.5 wt% sodium dodecyl sulfate aqueous solution, immerse the pretreated ultrafiltration membrane in it, and keep it at a constant temperature of 30°C for 1.5 hours. After taking it out, rinse it with deionized water. (3) Aqueous phase: Piperazine concentration is 2wt%, 0.5wt% sodium carbonate is added as catalyst, and pH is adjusted to 8-9; Oil phase: Trimethylbenzene chloride (TMC) concentration is 0.2wt%, and the solvent is a mixture of n-hexane and cyclohexane (volume ratio 3:1). (4) The surface-pretreated ultrafiltration membrane was immersed in the aqueous solution for 3 minutes and then removed and dried with an air knife; (5) The interface polymerization adopts a two-step method, that is, the membrane material obtained in step (4) is immersed in the oil phase solution, first reacted at 10℃ for 30s to inhibit monomer diffusion, and then reacted at 25℃ for 1min to promote uniform cross-linking, so as to obtain a nanofiltration membrane with uniform pore size. (6) A mixture of chlorosulfonic acid and dichloromethane in a volume ratio of 1:10 was pre-cooled at 5°C. The membrane obtained in step (5) was immersed in the reaction for 10 min, and the reaction was terminated with ice water. The membrane was neutralized with 0.1 mol / mL NaOH aqueous solution and rinsed with deionized water to obtain a nanofiltration membrane with specific separation.

[0031] Example 4 This embodiment provides a method for preparing a membrane material with specific separation capabilities, comprising the following steps: (1) A polysulfone ultrafiltration membrane with a molecular weight cutoff of 50 kDa and a diameter of 0.3 μm was selected as the base membrane material; (2) Aqueous phase: Piperazine concentration is 1wt%, 0.5wt% triethylamine is added as catalyst, and pH is adjusted to 8-9; Oil phase: Trimethylolpropionate chloride (TMC) concentration is 0.1wt%, and the solvent is a mixture of n-hexane and cyclohexane (volume ratio 3:1). (3) After immersing the ultrafiltration membrane in the aqueous solution for 3 minutes, remove it and dry it with an air knife; (4) The interfacial polymerization adopts a two-step method, that is, the membrane material obtained in step (4) is immersed in the oil phase solution, and the reaction is carried out at 0℃ for 20s to inhibit monomer diffusion, and then the reaction is carried out at 25℃ for 1min to promote uniform cross-linking. (5) A mixture of chlorosulfonic acid and dichloromethane in a volume ratio of 1:10 was pre-cooled at 0°C. The membrane obtained in step (4) was immersed in the reaction for 15 min, and the reaction was terminated with ice water. The mixture was neutralized with NaOH aqueous solution and rinsed with deionized water to obtain the nanofiltration membrane product.

[0032] Example 5 This embodiment provides a method for preparing a membrane material with specific separation capabilities, comprising the following steps: (1) Select a polyethersulfone ultrafiltration membrane with a pore size of 0.3 μm and a molecular weight cutoff of 50 kDa as the base membrane material; (2) Aqueous phase: Piperazine concentration is 1wt%, 0.5wt% triethylamine is added as catalyst, and pH is adjusted to 8-9; Oil phase: Trimethylolpropionate chloride (TMC) concentration is 0.1wt%, and the solvent is a mixture of n-hexane and cyclohexane (volume ratio 3:1). (3) The surface-pretreated ultrafiltration membrane was immersed in the aqueous solution for 3 minutes and then removed and dried with an air knife; (4) Immerse the membrane material obtained in step (3) in the oil phase solution and react at 25°C for 1 min; (5) The volume ratio of chlorosulfonic acid and dichloromethane mixture is 1:10. Pre-cool at 0℃. Immerse the membrane obtained in step (4) into the reaction for 15 min. Terminate with ice water. Neutralize with NaOH aqueous solution and rinse with deionized water to obtain the product nanofiltration membrane.

[0033] Example 6 This embodiment provides a method for preparing a membrane material with specific separation capabilities, comprising the following steps: (1) A polysulfone ultrafiltration membrane with a pore size of 0.3 μm and a molecular weight cutoff of 50 kDa was selected as the base membrane material; (2) Prepare a 0.1 wt% sodium dodecyl sulfate (SDS) aqueous solution, immerse the pretreated ultrafiltration membrane in it, and keep it at 40°C for 1.5 hours with constant temperature shaking. After taking it out, rinse it with deionized water. (3) Aqueous phase: Piperazine concentration is 1wt%, 0.5wt% triethylamine is added as catalyst, and pH is adjusted to 8-9; Oil phase: Trimethylolpropionate chloride (TMC) concentration is 0.1wt%, and the solvent is a mixture of n-hexane and cyclohexane (volume ratio 3:1). (4) The surface-pretreated ultrafiltration membrane was immersed in the aqueous solution for 3 minutes and then removed and dried with an air knife; (5) The interface polymerization adopts a two-step method, that is, the membrane material obtained in step (4) is immersed in the oil phase solution, first reacted at 10℃ for 30s to inhibit monomer diffusion, and then reacted at 25℃ for 1min to promote uniform cross-linking, thus obtaining the product nanofiltration membrane.

[0034] Example 7 This embodiment provides a method for preparing a membrane material with specific separation capabilities, comprising the following steps: (1) A polysulfone ultrafiltration membrane with a pore size of 0.3 μm and a molecular weight cutoff of 50 kDa was selected as the base membrane material; (2) Prepare a 0.1 wt% aqueous solution of dodecyl dimethyl betaine, immerse the pretreated ultrafiltration membrane in it, shake at room temperature for 1.5 hours, take it out and rinse with deionized water; (3) Aqueous phase: Piperazine concentration is 1wt%, 0.5wt% triethylamine is added as catalyst, and pH is adjusted to 8-9; Oil phase: Trimethylolpropionate chloride (TMC) concentration is 0.1wt%, and the solvent is a mixture of n-hexane and cyclohexane (volume ratio 3:1). (4) The surface-pretreated ultrafiltration membrane was immersed in the aqueous solution for 3 minutes and then removed and dried with an air knife; (5) The interface polymerization adopts a two-step method, that is, the membrane material obtained in step (4) is immersed in the oil phase solution, first reacted at 10℃ for 30s to inhibit monomer diffusion, and then reacted at 25℃ for 1min to promote uniform cross-linking, so as to obtain a nanofiltration membrane material with uniform pore size. (6) A mixture of chlorosulfonic acid and dichloromethane in a volume ratio of 1:10 was pre-cooled at 0°C. The membrane obtained in step (5) was immersed in the reaction for 15 min, and the reaction was terminated with ice water. The membrane was neutralized with 0.1 mol / mL NaOH aqueous solution and rinsed with deionized water to obtain a nanofiltration membrane with specific separation.

[0035] Example 8 This embodiment provides a method for preparing a membrane material with specific separation capabilities, comprising the following steps: (1) A polyethersulfone ultrafiltration membrane with a pore size of 0.1 μm and a molecular weight cutoff of 60 kDa was selected as the base membrane material; (2) Prepare a 0.1 wt% aqueous solution of hexadecyltrimethylammonium bromide, immerse the pretreated ultrafiltration membrane in it, shake it in an 80°C water bath for 1.5 hours, and then rinse it with deionized water. (3) Aqueous phase: Piperazine concentration is 1wt%, 0.5wt% triethylamine is added as catalyst, and pH is adjusted to 8-9; Oil phase: Trimethylolpropionate chloride (TMC) concentration is 0.1wt%, and the solvent is a mixture of n-hexane and cyclohexane (volume ratio 3:1). (4) The surface-pretreated ultrafiltration membrane was immersed in the aqueous solution for 3 minutes and then removed and dried with an air knife; (5) The interface polymerization adopts a two-step method, that is, the membrane material obtained in step (4) is immersed in the oil phase solution, first reacted at 10℃ for 30s to inhibit monomer diffusion, and then reacted at 25℃ for 1min to promote uniform cross-linking, so as to obtain a nanofiltration membrane with uniform pore size. (6) A mixture of chlorosulfonic acid and dichloromethane in a volume ratio of 1:10 was pre-cooled at 0°C, and the membrane was immersed in the reaction for 15 min. The reaction was terminated with ice water, neutralized with 0.1 mol / mL NaOH aqueous solution, and rinsed with deionized water to obtain a nanofiltration membrane with specific separation properties.

[0036] Example 9 This embodiment tests the water flux and salt separation of the nanofiltration membranes prepared in embodiments 1 and 4-6 above, including the following steps: (1) Cut the prepared nanofiltration membrane into membrane sheets of appropriate size according to the size of the membrane tank and place them in the filtration equipment; (2) Test the flux of nanofiltration membrane to pure water at a test pressure of 5~15 bar; (3) Using 1000ppm MgCl2 and 1000ppm LiCl aqueous solutions as feed, respectively, the effect of the membrane material on MgCl2 in the examples was detected by a cross-flow analyzer. 2+ and Li + The selective separability was determined, and the experimental results are shown in Table 1.

[0037] Table 1

[0038] As can be seen from the test data in Table 1, the nanofiltration membrane prepared by surfactant treatment and two-step polymerization in Example 1 has a high pure water flux. Furthermore, after surface modification treatment, the nanofiltration membrane exhibits reduced Mg content. 2+ and Li +The selective separation capability of ions is also good. In Example 4, the ultrafiltration membrane was not treated with surfactant; in Example 5, the two-step polymerization method was not used; and in Example 6, no surface modification treatment was performed. Comparative analysis of the data shows that the combination of surfactant + two-step polymerization + nanofiltration membrane surface modification can obtain nanofiltration membrane materials with optimal water flux and selectivity. However, reducing the steps for controlling the interfacial polymerization reaction, i.e., surfactant treatment / two-step polymerization, will reduce the water flux of the membrane material.

[0039] Furthermore, surface modification of nanofiltration membranes significantly affects their ability to react with Mg. 2+ and Li + Regarding the selective separation effect of ions, the test results of Example 6 show that although the unmodified nanofiltration membrane maintains a good water flux, its selective separation effect is very poor. Furthermore, due to the surface sulfonation modification, the nanofiltration membrane possesses hydrophilic properties. Compared with general membrane materials, the nanofiltration membrane material prepared by this invention has improved surface hydrophilicity, making it easier to wash away pollutants adhering to or deposited on the membrane, and also improving the overall antifouling performance of the membrane material.

[0040] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for producing a membrane material with specifically separated membranes, characterized in that, The surface of the ultrafiltration membrane is modified by surfactant, and on this basis, the ultrafiltration membrane is subjected to low-temperature pre-polymerization and room-temperature curing two-step interfacial polymerization to form a separation layer with uniform pores, so that a nanofiltration membrane with uniform pore size is obtained, and finally the surface of the nanofiltration membrane is subjected to hydrophilic modification to obtain a membrane material with specific separation.

2. A method of producing a membrane material with specific separation according to claim 1, characterized in that, The method comprises the following steps: (1) selecting an ultrafiltration membrane with an average pore size of 0.1-1 μm and a molecular weight cut-off of 50-100 kDa as a base membrane material; (2) preparing a surfactant aqueous solution with a concentration of 0.1-0.5 wt%, immersing the ultrafiltration membrane in the solution, and obtaining a surfactant-modified ultrafiltration membrane material; (3) preparing a piperazine aqueous solution with a concentration of 1-2 wt%, adding a catalyst, adjusting the aqueous solution to be alkaline, immersing the surfactant-modified ultrafiltration membrane obtained in step (2) in the piperazine aqueous solution, and drying; (4) preparing an organic phase trimesoyl chloride solution with a concentration of 0.1-0.3 wt%, immersing the ultrafiltration membrane obtained in step (3) in the trimesoyl chloride solution for two-step interfacial polymerization reaction, and obtaining a nanofiltration membrane with uniform pore size; (5) immersing the nanofiltration membrane prepared in step (4) in a modifier, terminating the reaction with ice water, neutralizing to neutral with a sodium hydroxide solution, and obtaining a nanofiltration membrane material with specific separation.

3. A method of producing a membrane material with specific separation according to claim 2, characterized in that, The ultrafiltration membrane material is any one of polysulfone or polyether sulfone.

4. The method of claim 2, wherein the membrane material is prepared by the steps of: The surfactant is any one or a combination of anionic, cationic, nonionic or zwitterionic surfactants, wherein the anionic surfactant is not mixed with the cationic surfactant.

5. The method for preparing a membrane material with specific separation as described in claim 2, characterized in that, The catalyst is any one of triethylamine, pyridine, sodium carbonate or lithium chloride.

6. The method of claim 2, wherein the membrane material is prepared by the steps of: In step (5), the modifier is a mixture of chlorosulfonic acid and dichloromethane with a volume ratio of 1:

10.

7. The membrane material with specific separation prepared by the preparation method of any one of claims 1-6.

8. The membrane material with specific separation of claim 7 is used for separating magnesium ions and lithium ions in water treatment.

9. Use according to claim 8, wherein the compound is ###00003### or a pharmaceutically acceptable salt thereof. The membrane material with specific separation is installed In a cross-flow membrane filtration device, the filtration pressure is 5-15 bar, and water containing magnesium ions and lithium ions is filtered.

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