Surface protectively modified high-flux solvent-resistant nanofiltration membrane

Abstract

The invention discloses a high-flux solvent-resistant nanofiltration membrane with a protectively modified surface. The preparation method comprises the steps of interfacial polymerization, surface modification, chemical crosslinking and solvent activation. Before overall crosslinking, the nascent state polyamide membrane formed after interfacial polymerization is directly subjected to surface protective modification, the crosslinking degree of a base membrane and a separation skin layer is reduced, meanwhile, the hydrophilicity is improved, and the solvent permeability and the interception performance of the composite membrane are remarkably improved. The method is simple in preparation process, small in material consumption and easy for large-scale industrial production, and has a good application prospect in the aspects of separation and purification of aqueous solution and organic solution systems and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of membrane separation, and particularly relates to a high-flux solvent-resistant nanofiltration membrane with surface protective modification, a preparation method thereof, and an application thereof. Background Art

[0002] Currently, millions of tons of organic solvents are used in the manufacture of pharmaceuticals, petroleum, and various other chemical products. Most of these products are separated from the solvents through heat treatment processes such as distillation, evaporation, and drying crystallization. Compared with traditional energy-intensive thermal separation and recovery processes with high energy consumption and costs such as distillation and evaporation, organic solvent nanofiltration (OSN) technology exhibits great application potential in various fields due to its low energy consumption, mild operating conditions, high separation efficiency, and the ability to be coupled with other conditions. At the same time, the separation and purification of organic solution systems under harsh environments are major requirements for energy conservation, emission reduction, efficient utilization of resources, environmental protection, and sustainable economic development, and also pose major challenges in the field of membrane separation.

[0003] As the core of solvent-resistant nanofiltration technology, improving the separation and stability performance of solvent-resistant nanofiltration membranes has become an urgent problem to be solved. To address these problems, a cross-linking step is usually adopted to improve the chemical and thermal stability of the solvent-resistant membrane. According to literature reports, the currently commonly used "phase inversion-based membrane preparation - interfacial polymerization - solvent cross-linking activation" method results in a membrane with a high degree of internal cross-linking of polyamide after cross-linking activation, showing great solvent resistance and stability; the "gel bath phase inversion cross-linking" method improves the denseness of the membrane by adding a cross-linking agent to the water coagulation bath and cross-linking simultaneously during the phase inversion process; the "liquid-phase cross-linking method" forms a uniform and dense cross-linked membrane in one step by casting a mixed solution containing a cross-linking agent and a polymer. The separation and stability performance of the solvent-resistant nanofiltration membranes prepared by these methods have been improved to a certain extent, but usually the internal structure of the membrane is too dense after cross-linking and difficult to regulate, and a large number of solvent permeation channels are closed, ultimately leading to a significant reduction in the flux of the solvent-resistant nanofiltration membrane. Summary of the Invention

[0004] In view of the technical problem of the low separation membrane flux of the existing technology for organic solution systems, the present invention provides a high-flux solvent-resistant nanofiltration membrane based on surface protective modification, a preparation method thereof, and an application thereof. The present invention improves the hydrophilicity of the membrane surface and has a loose separation layer structure. The prepared solvent-resistant nanofiltration membrane has a high solvent permeability and good separation performance, and is simple to operate and easy to scale up, which is of great significance for the efficient utilization of resources and sustainable development.

[0005] The technical solution of the present invention is as follows: In the first aspect of the present invention, a high-throughput solvent-resistant composite nanofiltration membrane with surface protective modification is disclosed, characterized in that the solvent-resistant composite membrane comprises a base membrane, a nascent separation skin layer in-situ formed on the surface of the base membrane by interfacial polymerization, and a polyhydroxy molecule protective modification layer chemically bonded to the nascent separation skin layer, and the base membrane, the nascent separation skin layer, and the polyhydroxy molecule protective modification layer of the solvent-resistant composite nanofiltration membrane are integrally crosslinked by an aliphatic polyamine compound or an aromatic polyamine compound.

[0006] Preferably, the base membrane is an ultrafiltration membrane or a microfiltration membrane.

[0007] Preferably, the base membrane material contains an imide group capable of undergoing a crosslinking reaction with a polyamine compound.

[0008] Preferably, the nascent separation skin layer is polyamide.

[0009] Preferably, the modification compounds used for the surface protective modification of the separation skin layer include: polyhydroxy compounds, polyhydroxy compounds containing amino groups, or polyamine compounds.

[0010] Preferably, the high-throughput composite nanofiltration membrane with surface protective modification is prepared after integral crosslinking with a binary or polyamine compound.

[0011] Preferably, the ultrathin composite membrane after the integral crosslinking is finally activated by a polar aprotic solvent treatment.

[0012] The second aspect of the present invention discloses a preparation method of a surface-protectively modified high-flux solvent-resistant composite nanofiltration membrane, comprising the following steps: Step 1, preparation of a base membrane: A polyimide base membrane is prepared by a gel bath phase inversion method; Step 2, interfacial polymerization: After the base membrane is fully contacted with an aqueous monomer solution containing an aromatic polyamine compound or also containing other aqueous phase additives for a certain period of time, the aqueous monomer solution on the membrane surface is removed and dried; The surface of the dried membrane is fully contacted with a solution of a first organic solvent containing an aromatic polycarbonyl chloride for a certain period of time to obtain a nascent polyamide composite membrane; Step 3, surface modification: The nascent polyamide composite membrane described in Step 2 is immersed in a second organic solution for a certain period of time, or placed in a third organic solution containing a modifying compound for a certain period of time, or first immersed in the second organic solution for a certain period of time and then placed in the third organic solution containing the modifying compound for a certain period of time, and then taken out to obtain a surface-protectively modified composite nanofiltration membrane; Step 4, chemical crosslinking: The surface-protectively modified composite nanofiltration membrane described in Step 3 is directly immersed in a mixed solution of a crosslinking agent and a fourth organic solvent for overall chemical crosslinking for a certain period of time, and then taken out, and the membrane surface is rinsed with the fourth organic solvent to obtain a surface-protectively modified solvent-resistant composite nanofiltration membrane; Step 5, solvent activation: The surface-protectively modified solvent-resistant composite nanofiltration membrane described in Step 4 is activated in a fifth organic solvent at a certain temperature for a certain period of time, and then taken out, and then rinsed and replaced with a replacement solvent to obtain a surface-protectively modified high-flux solvent-resistant composite nanofiltration membrane.

[0013] Preferably, the aromatic polyamine compounds described in Step 2 include m-phenylenediamine, p-phenylenediamine, other aromatic compounds containing two or more amino groups, or a combination of any two or more of the above.

[0014] Preferably, the aromatic polycarbonyl chlorides described in Step 2 include trimesoyl chloride, other aromatic compounds containing two or more acyl chloride groups, or a combination of any two or more of the above.

[0015] Preferably, the concentration of the aqueous monomer in the aqueous monomer solution during the interfacial polymerization process of the polyamide separation skin layer is 0.01% - 6.0% (mass percentage concentration, the same below); More preferably, the concentration of the aqueous monomer in the aqueous monomer solution is 0.01% - 0.5%; More preferably, the concentration of the aqueous monomer in the aqueous monomer solution is 0.01% - 0.1%.

[0016] Preferably, the concentration of the aromatic polycarbonyl chloride in the organic phase monomer solution during the interfacial polymerization process of the polyamide separation skin layer is 0.01% - 0.50%.

[0017] Preferably, the immersion time of the composite membrane in the second organic solvent containing the modifying compound is 1 second - 60 minutes.

[0018] Preferably, the protective modification compound described in step 4 includes: polyhydroxy compounds, polyhydroxy compounds containing amino groups, or polyamino compounds; more preferably, the protective modification compound is tetrakis(hydroxymethyl)phosphonium chloride (THPC); more preferably, the protective modification compound used is tannic acid; more preferably, the protective modification compound used is D-glucosamine.

[0019] Preferably, the content of the protective modification compound in the aqueous reaction solution containing the surface protective modification compound is 1 mg / kg −1 ~ 10,000 mg / kg −1 .

[0020] Preferably, the contact modification time of the protective modification compound used is from 1 second to 20 minutes.

[0021] Preferably, the aqueous phase additives described in step 2 include polyelectrolytes, surfactants, acid acceptors, or combinations of any two or more of the above.

[0022] Preferably, the cross-linking agent includes ethylenediamine or hexamethylenediamine.

[0023] Preferably, the first organic solvent includes alkanes and other non-polar or weakly polar solvents, or combinations thereof; more preferably, the first organic solvent is n-hexane.

[0024] Preferably, the second organic solvent includes isopropanol or ethanol.

[0025] Preferably, the third organic solvent includes isopropanol, ethanol, DMF and other common organic solvents.

[0026] Preferably, the fourth organic solvent includes isopropanol.

[0027] Preferably, the fifth organic solvent includes N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), or combinations of any two or more of the above.

[0028] Preferably, the replacement solvent includes water, alcohol, or mixtures thereof.

[0029] The third aspect of the present invention discloses an application of a surface-protectively modified high-throughput solvent-resistant composite nanofiltration membrane, which is characterized in that it is used for the separation and purification of solutes and solvents in an aqueous solution system, an organic solvent system, an aqueous solution system containing an organic solvent, or an organic solution system containing water, wherein the molecular weight of the solute in the solution is 200~2000 daltons.

[0030] The technical solution of the present invention has achieved remarkable technical effects and progress and has substantial features.

[0031] The preparation method of the high-flux solvent-resistant nanofiltration membrane based on surface protective modification of the present invention generates a nascent polyamide layer in-situ by interfacial polymerization on an ultrafiltration or microfiltration substrate membrane, and then prepares a polyamide composite membrane by performing surface protective modification with a modified monomer before overall chemical crosslinking, which greatly improves the flux of the composite membrane while ensuring the rejection rate.

[0032] One of the technical features of the present invention is that before overall crosslinking, the nascent polyamide membrane formed after interfacial polymerization is directly subjected to surface protective modification. The active hydroxyl or amino groups contained in the surface modification compound will partially react with the remaining acyl chloride groups during the interfacial polymerization process to form covalent bonds such as ester groups or amide groups, thereby greatly reducing the reaction degree of the acyl chloride groups with the crosslinking agent in the subsequent crosslinking step, reducing the crosslinking degree, increasing the looseness of the composite membrane skin layer, providing additional channels for solvents to a certain extent, and greatly increasing the flux of the composite membrane.

[0033] Another technical feature of the present invention is that the protective modification compound used contains a large number of strongly hydrophilic groups and can form a strong interaction (such as hydrogen bonds) with the nascent polyamide, having an amazing effect of improving the hydrophilicity of the membrane surface. The significant improvement in surface hydrophilicity can effectively reduce the transport resistance, thereby further increasing the flux of the membrane.

[0034] A third technical feature of the present invention is that in the surface protective modification step, instead of using water or other solvents, an alcohol solvent is used to prepare the relevant modified solution for contact reaction with the membrane surface. This not only effectively avoids the hydrolysis of the residual unreacted acyl chloride groups on the membrane surface, but also when the alcohol solvent contacts the membrane surface, it can swell some polyamide small molecule fragments in the polyamide separation skin layer, increasing the looseness of the polyamide separation skin layer, which is beneficial to further increasing the flux of the membrane.

[0035] A fourth technical feature of the present invention is that the high-flux solvent-resistant composite nanofiltration membrane based on surface protective modification is realized by overall chemical crosslinking. The substrate membrane and the modified separation layer are tightly bonded by covalent bonds, and the separation skin layer and the surface modification layer are tightly bonded by covalent bonds such as ester groups or amide groups, ensuring the stability and solvent resistance of the membrane. At the same time, the monomer concentration required in the preparation process is low, the preparation method has a simple process, mild preparation conditions, a wide application range, is easy to scale up and realize industrial production.

[0036] The fifth technical feature of the present invention is that considering the high-temperature environment in the actual industrial process, through long-term and variable-temperature performance tests in the strongly polar aprotic solvent N,N-dimethylformamide (DMF), it is investigated and proved that the high-throughput solvent-resistant composite nanofiltration membrane based on surface protective modification has good stability and temperature resistance in long-term performance operation tests and harsh environments.

[0037] Through the above technical innovations, the present invention has made remarkable technical progress and has excellent application prospects in the field of separation of organic solution systems. Detailed implementation manners

[0038] The present invention will be further described below through specific comparative examples and examples.

[0039] The base membrane is a polyimide (PI) flat ultrafiltration membrane with a cut-off molecular weight of 50,000 Daltons; the aromatic diamine compound used is m-phenylenediamine (MPD); the aromatic tricarboxylic acid chloride used is 1,3,5-benzenetricarbonyl chloride (TMC); the base membrane crosslinking agent used is hexamethylenediamine; the first organic solvent is n-hexane; the second organic solvent is isopropanol or ethanol; the third organic solvent includes other common organic solvents such as isopropanol, ethanol, and DMF; the fourth organic solvent is isopropanol; the fifth organic solvent is DMF; the replacement solvent is ethanol; at 25 °C and a transmembrane pressure difference of 1.0 MPa, with a 100 mg kg −1 rhodamine B (479 Daltons)-ethanol solution to measure the rejection rate and the corresponding solvent flux of the prepared membrane.

[0040] Comparative Example 1: Dissolve the aromatic diamine compound in deionized water with a mass percentage concentration of 0.05% to prepare an aqueous monomer solution.

[0041] Dissolve the aromatic tricarboxylic acid chloride in the first organic solvent with a mass percentage concentration of 0.15% to prepare an organic monomer solution.

[0042] The membrane preparation steps and conditions of the polyamide composite nanofiltration membrane are as follows: Step 1: After contacting the aqueous monomer solution with the surface of the base membrane for 8 s, remove the aqueous monomer solution on the surface of the base membrane and let it air-dry naturally in the air at room temperature. After the air-dried surface of the base membrane is fully contacted with the organic monomer solution for 6 s, remove the organic monomer solution on the membrane surface to obtain a nascent interfacial polymerization composite membrane; Step 2: Put the nascent interfacial polymerization composite membrane obtained in Step 1 into a 10% hexamethylenediamine-isopropanol solution at 60 °C for crosslinking for 30 min to obtain a crosslinked composite membrane; Step 3: After the crosslinked composite nanofiltration membrane obtained in Step 2 is activated with the activation solvent DMF at 80 °C for 30 min, replace it in ethanol for 4 hours to obtain the final solvent-resistant composite nanofiltration membrane.

[0043] The prepared solvent-resistant composite nanofiltration membrane was subjected to 100 mg kg −1 The separation performance of the Rhodamine B-ethanol solution was tested. The retention rate of Rhodamine B was 98.7% and the ethanol permeability was 48.2 L m −2 h −1 MPa −1 .

[0044] Example 1: The aromatic diamine compound is dissolved in deionized water with a mass percentage concentration of 0.05% to prepare an aqueous monomer solution.

[0045] The aromatic triacid chloride is dissolved in a first organic solvent at a mass percent concentration of 0.15% to prepare an organic phase monomer solution.

[0046] Dissolve tetrakis(hydroxymethyl)phosphonium chloride (THPC) in ethanol to a concentration of 60 mg kg -1 THPC-ethanol solution.

[0047] The membrane preparation steps and conditions are as follows: Step 1: After the aqueous monomer solution is in contact with the surface of the base membrane for 8 seconds, the aqueous monomer solution on the surface of the base membrane is removed, and the base membrane is naturally dried in the air at room temperature. After the dried base membrane surface is fully contacted with the organic monomer solution for 6 seconds, the organic monomer solution on the membrane surface is removed to obtain a nascent interfacial polymerization composite membrane; Step 2: After the THPC-ethanol solution is in contact with the above-mentioned nascent interfacial polymerization composite membrane for 120 seconds, a surface protectively modified composite nanofiltration membrane is obtained; Step 3: The composite nanofiltration membrane obtained in step 2 is placed in a hexamethylenediamine-isopropanol solution with a concentration of 10% and a temperature of 60 °C for cross-linking for 30 minutes to obtain a cross-linked composite membrane; Step 4: After the cross-linked composite nanofiltration membrane obtained in step 3 is activated by an activation solvent DMF at 80 °C for 30 minutes, it is replaced in ethanol for 4 hours to obtain the final surface protectively modified solvent-resistant composite nanofiltration membrane.

[0048] The separation performance test results of the prepared surface protective modified solvent-resistant composite nanofiltration membrane are as follows: at 25 °C and a transmembrane pressure difference of 1.0 MPa, using 100 mg kg −1 The separation performance of the Rhodamine B-ethanol solution was tested. The retention rate of Rhodamine B was 99.04%, which was 0.2% higher than that of the control. The ethanol permeability was 80.5 L m −2 h −1 MPa −1 Compared with the control group, the permeability of ethanol increased by 66.7%.

[0049] Example 2:The difference from Example 1 is only that: 50 mg / kg -1 of the THPC-isopropanol solution.

[0050] All other steps are the same as in Example 1; the test conditions are the same as in Comparative Example 1.

[0051] The test results of the separation performance of the prepared solvent-resistant nanofiltration membrane with surface protective modification are as follows: at 25 °C and a transmembrane pressure difference of 1.0 MPa, using 100 mg / kg −1 of the rhodamine B-ethanol solution for the separation performance test. The rejection rate of rhodamine B is 99.34%, and the rejection rate increases by 0.5% compared with the comparative example. The ethanol permeability is 70.6 L m −2 h −1 MPa −1 , and the ethanol permeability increases by 46.5% compared with the comparative example.

[0052] Example 3: The difference from Example 1 is only that: 100 mg / kg -1 of the D-glucosamine (DGM)-ethanol solution.

[0053] All other steps are the same as in Example 1; the test conditions are the same as in Comparative Example 1.

[0054] The test results of the separation performance of the prepared solvent-resistant nanofiltration membrane with surface protective modification are as follows: at 25 °C and a transmembrane pressure difference of 1.0 MPa, using a 100 mg / L rhodamine B-ethanol solution for the separation performance test. The rejection rate of rhodamine B is 98.63%, and the rejection rate remains basically unchanged compared with the comparative example. The ethanol permeability is 77.6 L m −2 h −1 MPa −1 , and the ethanol permeability increases by 60.9% compared with the comparative example.

[0055] Example 4: The difference from Example 3 is only that: after the surface modification post-modification step, the nascent polyamide composite membrane is immersed in the second organic solvent ethanol for 120 s, and then put into 60 mg / kg -1 of the THPC-ethanol solution to contact the above-mentioned nascent interfacial polymerization composite membrane for 120 s.

[0056] All other steps are the same as in Example 1; the test conditions are the same as in Comparative Example 1.

[0057] At 25 °C and a transmembrane pressure difference of 1.0 MPa, using 100 mg / kg −1The separation performance of the Rhodamine B-ethanol solution was tested. The rejection rate of Rhodamine B was 99.12%, and the rejection rate increased by 0.4% compared with the comparative example. The ethanol permeability was 78.61 L m −2 h −1 MPa −1 , and the ethanol permeability increased by 63.1% compared with the comparative example.

[0058] Example 5: The difference from Example 1 is only that: 1000 mg kg −1 of tannic acid (TA)-ethanol solution, the contact time of TA-ethanol solution with the composite membrane was 300 s.

[0059] All other steps were the same as in Example 1; the test conditions were the same as in Comparative Example 1.

[0060] The test results of the separation performance of the prepared solvent-resistant nanofiltration membrane with surface protective modification are as follows: at 25 °C and a transmembrane pressure difference of 1.0 MPa, using 100 mg kg −1 of the Rhodamine B-ethanol solution for separation performance testing. The rejection rate of Rhodamine B was 98.51%, and the rejection rate decreased slightly by 0.2% compared with the comparative example. The ethanol permeability was 65.5 L m −2 h −1 MPa −1 , and the ethanol permeability increased by 35.9% compared with the comparative example.

[0061] Example 6: The aromatic diamine compound was dissolved in deionized water with a mass percentage concentration of 0.05%; the polyelectrolyte "poly(sodium 4-styrenesulfonate) (PSSNa)" with a mass percentage concentration of 0.1%; the acid acceptor Na3P04 with a mass percentage concentration of 0.025% to prepare an aqueous monomer solution.

[0062] The aromatic triacyl chloride was dissolved in the first organic solvent with a mass percentage concentration of 0.15% to prepare an organic monomer solution.

[0063] Tannic acid (TA) was dissolved in ethanol to prepare a TA-ethanol solution with a concentration of 1000 mg kg -1 of TA-ethanol solution, the contact time of TA-ethanol solution with the composite membrane was 300 s.

[0064] All other steps were the same as in Example 1.

[0065] At 25 °C and a transmembrane pressure difference of 1.0 MPa, using 100 mg kg −1The separation performance of the rhodamine B-ethanol solution was tested. The rejection rate of rhodamine B was 98.16%, with a slight decrease of 0.6% in the rejection rate compared with the comparative example. The ethanol permeability was 71.52 L m −2 h −1 MPa −1 , and the ethanol permeability increased by 48.4% compared with the comparative example.

[0066] At room temperature, the membrane was immersed in the polar aprotic solvent N,N-dimethylformamide (DMF) for 30 days, and the separation performance was tested. After 30 days, the rejection rate of rhodamine B was 96.3%, with a slight decrease of 2.4% in the rejection rate compared with the comparative example. The ethanol permeability was 91.24 L m −2 h −1 MPa −1 , and the ethanol permeability increased by 89.1% compared with the comparative example.

[0067] After soaking at room temperature for 30 days, the membrane was transferred to DMF at 80 °C and soaked for 15 days, and the separation performance was tested. After 15 days, the rejection rate of rhodamine B was 97.1%, with a slight decrease of 1.6% in the rejection rate compared with the comparative example. The ethanol permeability was 88.05 L m −2 h −1 MPa −1 , and the ethanol permeability increased by 82.7% compared with the comparative example.

[0068] Example 7: The difference from Example 6 is only that: the concentration of the first organic phase monomer solution is 0.2 wt%.

[0069] All other steps are the same as in Example 1; the test conditions are the same as in Comparative Example 1.

[0070] At 25 °C and a transmembrane pressure difference of 1.0 MPa, a 100 mg kg −1 rhodamine B-ethanol solution was used for the separation performance test. The rejection rate of rhodamine B was 98.18%, with a slight decrease of 0.6% in the rejection rate compared with the comparative example. The ethanol permeability was 58.62 L m −2 h −1 MPa −1 , and the ethanol permeability increased by 21.6% compared with the comparative example.

[0071] Example 8: The difference from Example 6 is only that: the aqueous phase monomer solution does not contain the polyelectrolyte PSSNa, all other steps are the same as in Example 1; the test conditions are the same as in Comparative Example 1.

[0072] At 25 °C and a transmembrane pressure difference of 1.0 MPa, a 100 mg kg−1 The separation performance was tested with a rhodamine B-ethanol solution. The rejection rate of rhodamine B was 97.85%, with a slight decrease of 0.9% in the rejection rate compared with the comparative example. The ethanol permeability was 77.87 L m −2 h −1 MPa −1 , and the ethanol permeability increased by 61.6% compared with the comparative example.

[0073] Example 9: The difference from Example 6 is only that: in the surface modification post-modification step, the nascent polyamide composite membrane was immersed in the second organic solvent ethanol for 300 s and then the membrane surface was rinsed.

[0074] All other steps were the same as in Example 1; the test conditions were the same as in Comparative Example 1.

[0075] At 25 °C and a transmembrane pressure difference of 1.0 MPa, a 100 mg kg −1 rhodamine B-ethanol solution was used for the separation performance test. The rejection rate of rhodamine B was 96.85%, with a slight decrease of 0.3% in the rejection rate compared with the comparative example. The ethanol permeability was 81.53 L m −2 h −1 MPa −1 , and the ethanol permeability increased by 69.1% compared with the comparative example.

[0076] The above examples show that before overall crosslinking, directly performing surface protective modification on the nascent polyamide membrane formed after interfacial polymerization, anchoring through hydroxyl or amino groups, while protecting and modifying the separation skin layer, greatly reducing the reaction degree between the acyl chloride group and the crosslinking agent in the subsequent crosslinking step, reducing the crosslinking degree, increasing the looseness of the composite membrane, providing additional channels for the solvent to a certain extent, and greatly improving the flux of the composite membrane. At the same time, the introduction of hydrophilic groups further reduces the transport resistance of the solvent, significantly improving the separation performance of the composite nanofiltration membrane. And it shows good stability and temperature resistance in long-term performance operation tests and harsh environments.

[0077] It should be noted that the above examples are only specific preferred embodiments of the present invention and do not constitute a limitation to the present invention. Any embodiment falling within the protection scope of the present invention constituted by the features of the claims of the present invention or equivalent features constitutes an infringement of the patent right of the present invention.

Claims

1. A surface-protectively modified high-throughput solvent-resistant composite nanofiltration membrane, characterized in that, It includes a base membrane, a nascent separation cortex in-situ generated on the surface of the base membrane by interfacial polymerization, and a protective modification layer of polyhydroxy molecules chemically bonded to the nascent separation cortex. The base membrane, nascent separation cortex, and protective modification layer of polyhydroxy molecules of the solvent-resistant composite nanofiltration membrane are integrally crosslinked by an aliphatic polyamine compound or an aromatic polyamine compound.

2. The high-throughput solvent-resistant composite nanofiltration membrane with surface protective modification according to claim 1, characterized in that, The base membrane contains imide groups capable of undergoing a crosslinking reaction with polyamine compounds.

3. A surface-protectively modified high-throughput solvent-resistant composite nanofiltration membrane according to claim 1, characterized in that, The separation cortex is polyamide.

4. A high-throughput solvent-resistant composite nanofiltration membrane with surface protective modification according to claim 1, characterized in that The surface modification layer grafted on the separation layer contains groups including hydroxyl groups and amino groups.

5. A method for preparing a surface-protectively modified high-throughput solvent-resistant composite nanofiltration membrane, characterized in that, It includes the following steps: Step 1, base membrane preparation: Prepare a polyimide base membrane by the phase inversion method; Step 2, interfacial polymerization: After the base membrane is fully contacted with an aqueous monomer solution containing an aromatic polyamine compound or other aqueous phase additives simultaneously for a certain period of time, remove the aqueous monomer solution on the membrane surface and air-dry it; Fully contact the air-dried membrane surface with a solution of a first organic solvent containing an aromatic polyacyl chloride for a certain period of time to obtain a nascent polyamide composite membrane; Step 3, surface modification: Immerse the nascent polyamide composite membrane described in Step 2 in a second organic solution for a certain period of time, or place it in a third organic solution containing a modification compound for a certain period of time, or first immerse it in the second organic solution for a certain period of time and then place it in the third organic solution containing the modification compound for a certain period of time, and take it out to obtain a surface-protectively modified composite nanofiltration membrane; Step 4, chemical crosslinking: Immerse the surface-protectively modified composite nanofiltration membrane described in Step 3 directly into a mixed solution of a crosslinking agent and a fourth organic solvent for overall chemical crosslinking for a certain period of time, then take it out and rinse the membrane surface with the fourth organic solvent to obtain a surface-protectively modified solvent-resistant composite agent nanofiltration membrane; Step 5, solvent activation: Immerse the surface-protectively modified solvent-resistant composite agent nanofiltration membrane described in Step 4 in a fifth organic solvent at a certain temperature for activation for a certain period of time, then take it out, and then rinse and displace it with a displacement solvent to obtain a surface-protectively modified high-flux solvent-resistant composite nanofiltration membrane.

6. The preparation method of a surface-protectively modified high-flux solvent-resistant composite nanofiltration membrane according to claim 5, characterized in that, The functional groups of the surface-protective modification compound on the surface of the separation cortex include hydroxyl groups and amino groups.

7. The preparation method of a surface-protectively modified high-flux solvent-resistant composite nanofiltration membrane according to claim 5, characterized in that, The modification compounds used for the surface protection modification of the separation cortex include: polyhydroxy compounds, polyhydroxy compounds containing amino groups, or polyamino compounds; preferably, the protective modification compound is phosphonium chloride tetrakis(hydroxymethyl); preferably, the protective modification compound used is D-glucosamine; preferably, the protective modification compound used is tannic acid; preferably, the content of the protective modification compound in the organic phase solution containing the surface-protective modification compound is 10 mg / L to 2000 mg / L.

8. The preparation method of a surface-protectively modified high-flux solvent-resistant nanofiltration membrane according to claim 5, characterized in that The aromatic polyamine compound includes m-phenylenediamine, p-phenylenediamine, other aromatic compounds containing two or more amino groups, or a combination of any two or more of the above; the aromatic polyacyl chloride includes trimesoyl chloride, other aromatic compounds containing two or more acyl chloride groups, or a combination of any two or more of the above; preferably, the concentration of the aromatic polyamine compound in the aqueous monomer solution in the interfacial polymerization process is 0.01% to 6.0% (mass percentage concentration, the same below); preferably, the concentration of the aromatic polyacyl chloride in the organic monomer solution in the interfacial polymerization process of the polyamide separation skin layer is 0.01% to 0.50%; preferably, the soaking time in the second organic solvent is 0 second to 20 minutes; preferably, the soaking time in the third organic solvent is 0 second to 20 minutes; preferably, the content of the protective modification compound in the aqueous reaction solution containing the surface protective modification compound is 1 mg kg −1 ~ 10000 mg kg −1 ; preferably, the contact modification time of the protective modification compound used is 1 second to 60 minutes.

9. The preparation method of a surface-protectively modified high-flux solvent-resistant nanofiltration membrane according to claim 5, characterized in that The crosslinking agent includes ethylenediamine or hexamethylenediamine; The first organic solvent includes alkanes and other non-polar or weakly polar solvents, or a combination thereof; The second organic solvent includes alcohol solvents such as isopropanol or ethanol; The third organic solvent described above includes other common organic solvents such as isopropanol, ethanol, DMF, etc.; The fourth organic solvent described above includes isopropanol; The fifth organic solvent described above includes N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), or a combination of any two or more of the above; The displacement solvent described above includes water, alcohol, or a mixture thereof.

10. Application of a surface-protectively modified high-throughput solvent-resistant nanofiltration membrane, characterized in that, For the separation and purification of solutes and solvents in organic solvent systems, aqueous solution systems containing organic solvents, or organic solution systems containing water.