A method for preparing a solvent-resistant nanofiltration membrane with a polydopamine / amino-silica intermediate layer

Abstract

The application discloses a preparation method of a solvent-resistant nanofiltration membrane with a polydopamine / amino silica intermediate layer, and belongs to the field of membrane separation technology, and aims at solving the technical problem of low flux and poor stability of the solvent-resistant nanofiltration membrane. The preparation method comprises the following steps: preparing a polyetherimide-based membrane by a phase inversion method-crosslinking method; preparing amino silica nanoparticles by a sol-gel method; preparing a deposition solution containing dopamine, an oxidizing agent and amino silica by using a Tris buffer solution; depositing the polydopamine / amino silica intermediate layer on the upper surface of the polyetherimide-based membrane; performing an interfacial polymerization reaction of piperazine and trimesoyl chloride on the membrane surface on which the intermediate layer is deposited; and obtaining a composite membrane after heat treatment; and activating the composite membrane in an organic solvent to obtain the solvent-resistant nanofiltration membrane with the polydopamine / amino silica intermediate layer. The solvent-resistant nanofiltration membrane is constructed by taking the polyetherimide as a base film, the polydopamine / amino silica as an intermediate layer and polyamide as a separation layer, and has excellent flux and stability, and has a wide application prospect in drug separation, organic solvent recovery and the like.

Description

[Technical Field]

[0001] This invention relates to a method for preparing a solvent-resistant nanofiltration membrane with a polydopamine / amino silica interlayer, belonging to the field of membrane separation technology. [Background Technology]

[0002] Solvent-resistant nanofiltration (OSN) has been used in various industries, such as food, petrochemicals, semiconductors, and especially pharmaceuticals. It is designed not only to separate active pharmaceutical ingredients with molecular weights ranging from 200 Da to 1000 Da from organic solvents, but also to recover valuable organic solvents used in pharmaceutical and chemical synthesis. Solvent-resistant nanofiltration membranes mainly consist of an ultrafiltration base membrane and a separation layer. The polyamide separation layer formed by traditional interfacial polymerization processes is relatively thick, which introduces significant mass transfer resistance during application and is easily peeled off in organic solvents. Therefore, the OSN membrane structure needs to be optimized to improve flux and stability.

[0003] The introduction of an interlayer can significantly affect the structure (thickness and density) of the polyamide separation layer. Polydopamine (PDA), as a functional organic material, exhibits significant advantages in interlayer preparation due to its unique biomimetic properties and chemical multifunctionality. Liu et al. used sodium percarbonate-assisted dopamine oxidative self-polymerization to form a polydopamine interlayer, preparing a highly permeable and selective thin-film composite polyamide nanofiltration membrane. The hydrophilic PDA interlayer can regulate the interfacial polymerization process by controlling the diffusion and storage of amine monomers, constructing a uniform, defect-free separation layer as thin as 8 nm [Journal of Membrane Science, 2025, 718: 123686]. Through oxidative self-polymerization, dopamine can form a uniform polydopamine coating on the base membrane surface. This coating is rich in catechol and amino active functional groups, which can significantly enhance the interfacial bonding strength between the interlayer and the separation layer through hydrogen bonding and π-π stacking effects, thereby effectively suppressing interlayer delamination. More importantly, the amphiphilic nature of the PDA coating allows for tunable surface energy, thereby optimizing permeability to polar solvents and enabling high-throughput transport. Furthermore, the abundant active sites on the PDA surface provide an ideal reaction platform for further functionalization modifications.

[0004] Constructing an inorganic-organic interlayer by blending hydrophilic nanoparticles with polymers can improve the hydrophilicity of the interlayer and increase the free volume of the polymer, thereby providing additional solvent transport channels and further enhancing flux. Among hydrophilic nanoparticles, silica exhibits typical characteristics such as high stability and simple synthesis routes, demonstrating multiple advantages in interlayer applications. Wang et al. modified poly(m-phenylene isophthalamide)-based membranes by using polydopamine-coated silica microspheres as an interlayer, and then prepared polyamide composite nanofiltration membranes through interfacial polymerization. Because both dopamine and silica contain a large number of hydroxyl groups, hydrogen bonding restricts the diffusion of aqueous monomers to the oil-water interface, resulting in a nanotube-like Turing structure on the nanofiltration membrane surface. Its pure water flux is three times that of traditional polyamide nanofiltration membranes [Separation and Purification Technology. 2022, 285: 120390].

[0005] Therefore, this patent leverages the hydrophilicity and adhesiveness of polydopamine to construct a solvent-resistant nanofiltration membrane by introducing amino silica nanoparticles into the polydopamine interlayer. The amino silica in the interlayer forms a well-ordered packing of pores, reducing solvent transport resistance and increasing flux. Simultaneously, its surface amino groups can participate in interfacial polymerization reactions to inhibit the peeling of the separation layer and enhance the bonding strength with the base membrane through hydrogen bonding. Furthermore, the rigid inorganic framework can increase the elastic modulus of the interlayer, suppressing membrane swelling and deformation in highly polar solvents such as methanol, thus enhancing stability. [Summary of the Invention]

[0006] To address the shortcomings of existing technologies, the technical problem solved by this invention is the low flux and poor stability of solvent-resistant nanofiltration membranes.

[0007] The technical solution of this invention to solve the problems of low flux and poor stability of the solvent-resistant nanofiltration membrane is to provide a method for preparing a solvent-resistant nanofiltration membrane with a polydopamine / amino silica interlayer, characterized by the following steps:

[0008] a) Preparation of the base film: 15wt% to 19wt% polyetherimide particles were poured into 100mL to 120mL of N,N-dimethylacetamide solvent, and 2wt% to 4wt% polyvinylpyrrolidone was added as a pore-forming agent. The prepared solution was placed in a 60℃ constant temperature magnetic stirrer and stirred continuously for 8h. After the solution was fully mixed, it was allowed to stand for 12h to remove bubbles. Then, a coating rod with a thickness of 120μm to 250μm was used to uniformly coat the solution onto the surface of the nonwoven fabric and quickly immersed it in a water bath. After the phase inversion was completed, it was immersed in a 6wt% to 12wt% hexamethylenediamine / isopropanol solution and chemically crosslinked at 50℃ to 80℃ to obtain a polyetherimide base film.

[0009] b) Preparation of amino silica nanoparticles: 50 mL of ethanol and 4 mL of deionized water were added to a round-bottom flask and mixed thoroughly. Then, 0.1 mL to 2 mL of ammonia water was added. The round-bottom flask was fixed above a magnetic stirrer and stirred at 100 to 150 rpm for 20 min. Subsequently, 1 mL of tetraethyl silicate was added to the round-bottom flask and stirred for 5 h. Then, 0.1 mL to 1 mL of 3-aminopropyltriethoxysilane was added and stirred for 12 h. After stirring, the solution in the round-bottom flask was transferred to a 50 mL centrifuge tube and centrifuged at 10,000 rpm for 10 min. After centrifugation, the supernatant was poured off, ethanol was added, and the mixture was sonicated for 10 min. The centrifugation operation was repeated four times in total. The solid obtained by centrifugation was placed in a drying oven and vacuum dried at room temperature (25 ± 1 °C) for 12 h to obtain amino silica nanoparticles.

[0010] c) Preparation of the deposition solution: Prepare a Tris buffer solution with a molar concentration of 0.01 mol / L, dissolve dopamine and oxidant in the Tris buffer solution, the mass percentage of dopamine is 0.1 wt% to 2 wt%, and the mass ratio of oxidant to dopamine is 1:10 to 10:1. Then add 0.1 wt% to 10 wt% of the amino silica nanoparticles obtained in step b), and sonicate for 0.5 h to obtain the deposition solution;

[0011] d) Preparation of the intermediate layer: The base film obtained in step a) is fixed in a polytetrafluoroethylene frame, and then the deposition solution obtained in step c) is poured onto the upper surface of the film for 0.5 h to 2.5 h. The temperature of the deposition solution is maintained at 40 ℃ to 80 ℃. After deposition, the film is taken out and ultrasonically cleaned in deionized water for 10 min to obtain the deposited film.

[0012] e) Preparation of polyamide layer: The deposited membrane obtained in step d) is fixed in a polytetrafluoroethylene frame. A piperazine aqueous solution with a mass percentage of 0.1wt% to 1.5wt% is prepared and poured onto the membrane surface. After standing for 5 minutes, the surface solution is poured off. The membrane is then dried at room temperature (25±1℃) for 10 minutes. Then, a pyromellitic methyl chloride / n-hexane solution with a mass percentage of 0.01wt% to 0.5wt% is prepared and poured onto the membrane surface. After standing for 3 minutes, the surface solution is poured off. The membrane is then placed in an oven at 60℃ to 100℃ and dried for 10 minutes to 60 minutes to obtain a composite membrane.

[0013] f) Activation treatment: Immerse the composite membrane obtained in e) in an organic solvent and soak it at 60℃~80℃ for 1min~30min to obtain a solvent-resistant nanofiltration membrane with a polydopamine / amino silica interlayer.

[0014] The oxidant in step c) of the present invention is one or more of ammonium persulfate, potassium persulfate, sodium periodate, potassium periodate, sodium perchlorate, and potassium perchlorate.

[0015] The organic solvent in step f) of the present invention is one or more of methanol, isopropanol, acetone, acetonitrile, tetrahydrofuran, dimethyl sulfoxide, dichloromethane, ethyl acetate, toluene, xylene, n-hexane, cyclohexane, dioxane, N,N-dimethylformamide, N-methylpyrrolidone, acetic acid, ethylene glycol, 1,4-dioxane, and propylene glycol methyl ether. Detailed Implementation

[0016] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0017] The solvent-resistant nanofiltration membrane with a polydopamine / amino silica interlayer prepared in this invention had its permeation performance, namely the membrane flux and rejection rate, determined using a cross-flow filtration device.

[0018] Flux and rejection rate together reflect the membrane's permeation performance, J = V / (A×t), R = (1-C p / C f )×100. Where J is the membrane flux (L·m³). -2 ·h -1 R is the membrane rejection rate (%); V is the permeate volume on the permeate side (L); A is the effective area of ​​the membrane (m²). 2 ); t is the infiltration time (h); C f With C p These represent the concentrations (mg / L) of the solute components in the feed solution and permeate, respectively.

[0019] The degree of swelling reflects the stability of the membrane, SD = (W wet / W dry -1)×100. Where SD is the swelling degree of the membrane (%), W dry and W wet The values ​​are the mass (mg) of the membrane before and after immersion.

[0020] The following describes specific embodiments of the present invention, but the present invention is not limited to these embodiments.

[0021] Example 1.

[0022] a) Preparation of the base film: 17 wt% polyetherimide particles were poured into 100 mL of N,N-dimethylacetamide solvent, and 2 wt% polyvinylpyrrolidone was added as a pore-forming agent. The prepared solution was placed in a 60°C constant temperature magnetic stirrer and stirred continuously for 8 h. After the solution was fully mixed, it was allowed to stand for 12 h to remove bubbles. Then, a coating rod with a thickness of 120 μm was used to uniformly coat the solution onto the surface of the nonwoven fabric, and it was quickly immersed in a water bath. After the phase inversion was completed, it was immersed in a 10 wt% hexamethylenediamine / isopropanol solution and chemically crosslinked at 60°C to obtain a polyetherimide base film.

[0023] b) Preparation of amino silica nanoparticles: 50 mL of ethanol and 4 mL of deionized water were added to a round-bottom flask and mixed thoroughly. Then, 0.75 mL of ammonia was added. The round-bottom flask was fixed above a magnetic stirrer and stirred at 100 r / min for 20 min. Subsequently, 1 mL of tetraethyl silicate was added to the round-bottom flask and stirred for 5 h. Then, 1 mL of 3-aminopropyltriethoxysilane was added and stirred for 12 h. After stirring, the solution in the round-bottom flask was transferred to a 50 mL centrifuge tube and centrifuged at 10000 r / min for 10 min. After centrifugation, the supernatant was poured off, ethanol was added, and the mixture was sonicated for 10 min. The centrifugation operation was repeated four times in total. The solid obtained by centrifugation was placed in a drying oven and vacuum dried at room temperature (25±1℃) for 12 h to obtain amino silica nanoparticles with a diameter of approximately 20 nm.

[0024] c) Preparation of the deposition solution: Prepare a Tris buffer solution with a molar concentration of 0.01 mol / L. Dissolve dopamine and ammonium persulfate in the Tris buffer solution. The mass percentage of dopamine is 0.2 wt%, and the mass ratio of ammonium persulfate to dopamine is 1:1. Then add 0.1 wt% of the amino-silica nanoparticles obtained in step b). After sonication for 0.5 h, the deposition solution is obtained.

[0025] d) Preparation of the intermediate layer: The base film obtained in step a) is fixed in a polytetrafluoroethylene frame, and then the deposition solution obtained in step c) is poured onto the upper surface of the film for 0.5 h. The temperature of the deposition solution is maintained at 60 °C. After deposition, the film is taken out and ultrasonically cleaned in deionized water for 10 min to obtain the deposited film.

[0026] e) Preparation of polyamide layer: The deposited membrane obtained in step d) is fixed in a polytetrafluoroethylene frame. A 0.8 wt% piperazine aqueous solution is prepared and poured onto the membrane surface. After standing for 5 min, the surface solution is poured off and the membrane is dried at room temperature (25±1℃) for 10 min. Then, a 0.2 wt% trimesoyl chloride / n-hexane solution is prepared and poured onto the membrane surface. After standing for 3 min, the surface solution is poured off and the membrane is placed in an 80℃ oven for 10 min to obtain the composite membrane.

[0027] f) Activation treatment: Immerse the composite membrane obtained in e) in n-hexane and soak it at 80°C for 5 min to obtain a solvent-resistant nanofiltration membrane with a polydopamine / amino silica interlayer.

[0028] g) The solvent-resistant nanofiltration membrane with a polydopamine / amino silica interlayer obtained in step f) was tested for permeation performance of a 50 mg / L drug / ethanol solution at room temperature (25 ± 1 °C) and an operating pressure of 0.5 MPa using a cross-flow filtration device. The results showed that the membrane had a flux of 16 L·m⁻¹ for ethanol. -2· h -1 The retention rates of rifampicin, oxytetracycline, vitamin B1, and vitamin B12 were 99%, 88%, 89%, and 99%, respectively; the swelling degrees after soaking in methanol, acetone, and toluene for 24 hours were 1%, 2%, and 1%, respectively.

[0029] Example 2.

[0030] a) Preparation of the base film: 17 wt% polyetherimide particles were poured into 100 mL of N,N-dimethylacetamide solvent, and 2 wt% polyvinylpyrrolidone was added as a pore-forming agent. The prepared solution was placed in a 60°C constant temperature magnetic stirrer and stirred continuously for 8 h. After the solution was fully mixed, it was allowed to stand for 12 h to remove bubbles. Then, a coating rod with a thickness of 120 μm was used to uniformly coat the solution onto the surface of the nonwoven fabric, and it was quickly immersed in a water bath. After the phase inversion was completed, it was immersed in a 10 wt% hexamethylenediamine / isopropanol solution at 60°C for chemical crosslinking to obtain a polyetherimide base film.

[0031] b) Preparation of amino silica nanoparticles: 50 mL of ethanol and 4 mL of deionized water were added to a round-bottom flask and mixed thoroughly. Then, 1 mL of ammonia was added. The round-bottom flask was fixed above a magnetic stirrer and stirred at 100 r / min for 20 min. Subsequently, 1 mL of tetraethyl silicate was added to the round-bottom flask and stirred for 5 h. Then, 1 mL of 3-aminopropyltriethoxysilane was added and stirred for 12 h. After stirring, the solution in the round-bottom flask was transferred to a 50 mL centrifuge tube and centrifuged at 10000 r / min for 10 min. After centrifugation, the supernatant was poured off, ethanol was added, and the mixture was sonicated for 10 min. The centrifugation operation was repeated four times in total. The solid obtained by centrifugation was placed in a drying oven and vacuum dried at room temperature (25±1℃) for 12 h to obtain amino silica nanoparticles with a diameter of approximately 40 nm.

[0032] c) Preparation of the deposition solution: Prepare a Tris buffer solution with a molar concentration of 0.01 mol / L, dissolve dopamine and sodium periodate in the Tris buffer solution, the mass percentage of dopamine is 0.2 wt%, the mass ratio of sodium periodate to dopamine is 1:1, then add 0.2 wt% of the amino silica nanoparticles obtained in step b), and sonicate for 0.5 h to obtain the deposition solution;

[0033] d) Preparation of the intermediate layer: The base film obtained in step a) is fixed in a polytetrafluoroethylene frame, and then the deposition solution obtained in step c) is poured onto the upper surface of the film for 1 hour. The temperature of the deposition solution is maintained at 80°C. After deposition, the film is taken out and ultrasonically cleaned in deionized water for 10 minutes to obtain the deposited film.

[0034] e) Preparation of polyamide layer: The deposited membrane obtained in step d) is fixed in a polytetrafluoroethylene frame. A 0.6 wt% piperazine aqueous solution is prepared and poured onto the membrane surface. After standing for 5 min, the surface solution is poured off. The membrane is then dried at room temperature (25±1℃) for 10 min. Then, a 0.1 wt% trimesoyl chloride / n-hexane solution is prepared and poured onto the membrane surface. After standing for 3 min, the surface solution is poured off. The membrane is then placed in an 80℃ oven and dried for 20 min to obtain the composite membrane.

[0035] f) Activation treatment: Immerse the composite membrane obtained in e) in N,N-dimethylformamide and soak it at 60°C for 10 min to obtain a solvent-resistant nanofiltration membrane with a polydopamine / amino silica interlayer.

[0036] g) The solvent-resistant nanofiltration membrane with a polydopamine / amino silica interlayer obtained in step f) was tested for permeation performance of a 50 mg / L drug / ethanol solution using a cross-flow filtration device at room temperature (25 ± 1 °C) and an operating pressure of 0.5 MPa. The results showed that the membrane had a flux of 19 L·m⁻¹ for ethanol.-2 ·h -1 The retention rates of rifampicin, oxytetracycline, vitamin B1, and vitamin B12 were 95%, 79%, 88%, and 96%, respectively; the swelling degrees after soaking in methanol, acetone, and toluene for 24 hours were 1%, 3%, and 1%, respectively.

[0037] Example 3.

[0038] a) Preparation of the base film: 18 wt% polyetherimide particles were poured into 100 mL of N,N-dimethylacetamide solvent, and 4 wt% polyvinylpyrrolidone was added as a pore-forming agent. The prepared solution was placed in a 60°C constant temperature magnetic stirrer and stirred continuously for 8 h. After the solution was fully mixed, it was allowed to stand for 12 h to remove bubbles. Then, a 120 μm thick coating rod was used to uniformly coat the solution onto the surface of the nonwoven fabric, and it was quickly immersed in a water bath. After the phase inversion was completed, it was immersed in a 6 wt% hexamethylenediamine / isopropanol solution and chemically crosslinked at 60°C to obtain a polyetherimide base film.

[0039] b) Preparation of amino silica nanoparticles: 50 mL of ethanol and 4 mL of deionized water were added to a round-bottom flask and mixed thoroughly. Then, 1.25 mL of ammonia was added. The round-bottom flask was fixed above a magnetic stirrer and stirred at 100 r / min for 20 min. Subsequently, 1 mL of tetraethyl silicate was added to the round-bottom flask and stirred for 5 h. Then, 1 mL of 3-aminopropyltriethoxysilane was added and stirred for 12 h. After stirring, the solution in the round-bottom flask was transferred to a 50 mL centrifuge tube and centrifuged at 10000 r / min for 10 min. After centrifugation, the supernatant was poured off, ethanol was added, and the mixture was sonicated for 10 min. The centrifugation operation was repeated four times in total. The solid obtained by centrifugation was placed in a drying oven and vacuum dried at room temperature (25±1℃) for 12 h to obtain amino silica nanoparticles with a diameter of approximately 60 nm.

[0040] c) Preparation of deposition solution: Prepare a Tris buffer solution with a molar concentration of 0.01 mol / L, dissolve dopamine and potassium persulfate in the Tris buffer solution, the mass percentage of dopamine is 0.2 wt%, the mass ratio of potassium persulfate to dopamine is 1:1, then add 0.3 wt% of the amino silica nanoparticles obtained in step b), and sonicate for 0.5 h to obtain the deposition solution;

[0041] d) Preparation of the intermediate layer: The base film obtained in step a) is fixed in a polytetrafluoroethylene frame, and then the deposition solution obtained in step c) is poured onto the upper surface of the film for 1.5 h. The temperature of the deposition solution is maintained at 60 °C. After deposition, the film is taken out and ultrasonically cleaned in deionized water for 10 min to obtain the deposited film.

[0042] e) Preparation of polyamide layer: The deposited membrane obtained in step d) is fixed in a polytetrafluoroethylene frame. A 0.8 wt% piperazine aqueous solution is prepared and poured onto the membrane surface. After standing for 5 min, the surface solution is poured off. The membrane is then dried at room temperature (25±1℃) for 10 min. Then, a 0.15 wt% trimesoyl chloride / n-hexane solution is prepared and poured onto the membrane surface. After standing for 3 min, the surface solution is poured off. The membrane is then placed in an 80℃ oven and dried for 15 min to obtain the composite membrane.

[0043] f) Activation treatment: Immerse the composite membrane obtained in e) in isopropanol and soak it at 70°C for 15 min to obtain a solvent-resistant nanofiltration membrane with a polydopamine / amino silica interlayer.

[0044] g) The solvent-resistant nanofiltration membrane with a polydopamine / amino silica interlayer obtained in step f) was tested for permeation performance of a 50 mg / L drug / ethanol solution using a cross-flow filtration device at room temperature (25 ± 1 °C) and an operating pressure of 0.5 MPa. The results showed that the membrane had a flux of 23 L·m⁻¹ for ethanol. -2· h -1 The retention rates of rifampicin, oxytetracycline, vitamin B1, and vitamin B12 were 96%, 86%, 90%, and 97%, respectively; the swelling degrees after soaking in methanol, acetone, and toluene for 24 hours were 2%, 3%, and 2%, respectively.

[0045] Example 4.

[0046] a) Preparation of the base film: 18 wt% polyetherimide particles were poured into 100 mL of N,N-dimethylacetamide solvent, and 4 wt% polyvinylpyrrolidone was added as a pore-forming agent. The prepared solution was placed in a 60°C constant temperature magnetic stirrer and stirred continuously for 8 h. After the solution was fully mixed, it was allowed to stand for 12 h to remove bubbles. Then, a coating rod with a thickness of 250 μm was used to uniformly coat the solution onto the surface of the nonwoven fabric, and it was quickly immersed in a water bath. After the phase inversion was completed, it was immersed in a 12 wt% hexamethylenediamine / isopropanol solution and chemically crosslinked at 80°C to obtain a polyetherimide base film.

[0047] b) Preparation of amino silica nanoparticles: 50 mL of ethanol and 4 mL of deionized water were added to a round-bottom flask and mixed thoroughly. Then, 1.5 mL of ammonia was added. The round-bottom flask was fixed above a magnetic stirrer and stirred at 100 r / min for 20 min. Subsequently, 1 mL of tetraethyl silicate was added to the round-bottom flask and stirred for 5 h. Then, 1 mL of 3-aminopropyltriethoxysilane was added and stirred for 12 h. After stirring, the solution in the round-bottom flask was transferred to a 50 mL centrifuge tube and centrifuged at 10000 r / min for 10 min. After centrifugation, the supernatant was poured off, ethanol was added, and the mixture was sonicated for 10 min. The centrifugation operation was repeated four times in total. The solid obtained by centrifugation was placed in a drying oven and vacuum dried at room temperature (25±1℃) for 12 h to obtain amino silica nanoparticles with a diameter of approximately 100 nm.

[0048] c) Preparation of the deposition solution: Prepare a Tris buffer solution with a molar concentration of 0.01 mol / L, dissolve dopamine and ammonium persulfate in the Tris buffer solution, the mass percentage of dopamine is 0.2 wt%, the mass ratio of ammonium persulfate to dopamine is 1:1, then add 0.5 wt% of the amino silica nanoparticles obtained in step b), and sonicate for 0.5 h to obtain the deposition solution;

[0049] d) Preparation of the intermediate layer: The base film obtained in step a) is fixed in a polytetrafluoroethylene frame, and then the deposition solution obtained in step c) is poured onto the upper surface of the film for 2.5 h. The temperature of the deposition solution is maintained at 80 °C. After deposition, the film is taken out and ultrasonically cleaned in deionized water for 10 min to obtain the deposited film.

[0050] e) Preparation of polyamide layer: The deposited membrane obtained in step d) is fixed in a polytetrafluoroethylene frame. A 1.2 wt% piperazine aqueous solution is prepared and poured onto the membrane surface. After standing for 5 min, the surface solution is poured off and the membrane is allowed to stand and dry at room temperature (25±1℃) for 10 min. Then, a 0.3 wt% trimesoyl chloride / n-hexane solution is prepared and poured onto the membrane surface. After standing for 3 min, the surface solution is poured off and the membrane is placed in an 80℃ oven to dry for 25 min to obtain a composite membrane.

[0051] f) Activation treatment: Immerse the composite membrane obtained in e) in N-methylpyrrolidone and soak it at 80°C for 20 min to obtain a solvent-resistant nanofiltration membrane with a polydopamine / amino silica interlayer.

[0052] g) The solvent-resistant nanofiltration membrane with a polydopamine / amino silica interlayer obtained in step f) was tested for permeation performance of a 50 mg / L drug / ethanol solution using a cross-flow filtration device at room temperature (25 ± 1 °C) and an operating pressure of 0.5 MPa. The results showed that the membrane had a flux of 14 L·m⁻¹ for ethanol.-2 ·h -1 The retention rates of rifampicin, oxytetracycline, vitamin B1, and vitamin B12 were 94%, 79%, 69%, and 93%, respectively; the swelling degrees after soaking in methanol, acetone, and toluene for 24 hours were 5%, 5%, and 2%, respectively.

Claims

1. A method for preparing a solvent-resistant nanofiltration membrane with a polydopamine / amino silica interlayer, characterized in that: Includes the following steps: a) Preparation of the base film: 15wt% to 19wt% of polyetherimide particles were poured into 100mL to 120mL of N,N-dimethylacetamide solvent, and 2wt% to 4wt% of polyvinylpyrrolidone was added as a pore-forming agent. The prepared solution was placed in a 60℃ constant temperature magnetic stirrer and stirred continuously for 8h. After the solution was fully mixed, it was allowed to stand for 12h to remove bubbles. Subsequently, a coating rod with a thickness of 120μm to 250μm was selected to uniformly coat the solution onto the surface of the nonwoven fabric and quickly immerse it in a water bath. After the phase inversion was completed, it was immersed in a hexamethylenediamine / isopropanol solution with a mass percentage of 6wt% to 12wt% and chemically crosslinked at 50℃ to 80℃ to obtain a polyetherimide-based film. b) Preparation of amino silica nanoparticles: Add 50 mL of ethanol and 4 mL of deionized water to a round-bottom flask, mix well, and then add 0.1 mL to 2 mL of ammonia water; fix the round-bottom flask above a magnetic stirrer and stir at a speed of 100 r / min to 150 r / min for 20 min. Subsequently, 1 mL of tetraethyl silicate was added to the round-bottom flask and stirred for 5 h. Then, 0.1 mL to 1 mL of 3-aminopropyltriethoxysilane was added and stirred for 12 h. After stirring, the solution in the round-bottom flask was transferred to a 50 mL centrifuge tube and centrifuged at 10000 r / min for 10 min. After centrifugation, the supernatant was poured off, ethanol was added, and the mixture was sonicated for 10 min. The centrifugation was repeated four times in total. The solid obtained by centrifugation was placed in a drying oven and vacuum dried at room temperature for 12 h to obtain amino silica nanoparticles. c) Preparation of the deposition solution: Prepare a Tris buffer solution with a molar concentration of 0.01 mol / L, dissolve dopamine and oxidant in the Tris buffer solution, the mass percentage of dopamine is 0.1 wt% to 2 wt%, and the mass ratio of oxidant to dopamine is 1:10 to 10:

1. Then add 0.1 wt% to 10 wt% of the amino silica nanoparticles obtained in step b), and sonicate for 0.5 h to obtain the deposition solution; d) Preparation of the intermediate layer: The base film obtained in step a) is fixed in a polytetrafluoroethylene frame, and then the deposition solution obtained in step c) is poured onto the upper surface of the film for 0.5 h to 2.5 h. The temperature of the deposition solution is maintained at 40 ℃ to 80 ℃. After deposition, the film is taken out and ultrasonically cleaned in deionized water for 10 min to obtain the deposited film. e) Preparation of polyamide layer: The deposited membrane obtained in step d) is fixed in a polytetrafluoroethylene frame. A piperazine aqueous solution with a mass percentage of 0.1wt% to 1.5wt% is prepared and poured onto the membrane surface. After standing for 5 minutes, the surface solution is poured off and the membrane is allowed to stand and dry at room temperature for 10 minutes. Then, a pyromellitic methyl chloride / n-hexane solution with a mass percentage of 0.01wt% to 0.5wt% is prepared and poured onto the membrane surface. After standing for 3 minutes, the surface solution is poured off and the membrane is placed in an oven at 60℃ to 100℃ and dried for 10 minutes to 60 minutes to obtain a composite membrane. f) Activation treatment: Immerse the composite membrane obtained in e) in an organic solvent and soak it at 60℃~80℃ for 1min~30min to obtain a solvent-resistant nanofiltration membrane with a polydopamine / amino silica interlayer.

2. The method for preparing a solvent-resistant nanofiltration membrane with a polydopamine / amino silica interlayer according to claim 1, characterized in that: In step c), the oxidant is one or more of ammonium persulfate, potassium persulfate, sodium periodate, potassium periodate, sodium perchlorate, and potassium perchlorate.

3. The method for preparing a solvent-resistant nanofiltration membrane with a polydopamine / amino silica interlayer according to claim 1, characterized in that: In step f), the organic solvent is one or more of methanol, isopropanol, acetone, acetonitrile, tetrahydrofuran, dimethyl sulfoxide, dichloromethane, ethyl acetate, toluene, xylene, n-hexane, cyclohexane, N,N-dimethylformamide, N-methylpyrrolidone, acetic acid, ethylene glycol, 1,4-dioxane, and propylene glycol methyl ether.

4. The solvent-resistant nanofiltration membrane with a polydopamine / amino silica interlayer prepared by the preparation method according to any one of claims 1 to 3 is used in organic solvent recovery and drug purification.