Preparation method of zwitterionic anti-pollution nanofiltration membrane for purifying cordycepin
By chemically bonding zwitterionic materials to the surface of nanofiltration membranes to form a stable hydration layer, the problem of nanofiltration membranes being easily fouled by biomolecules is solved, improving water flux and antifouling performance, and enhancing the membrane's separation capacity and stability.
Patent Information
- Application Number
- CN202410963006.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-18
- Publication Date
- 2025-10-28
- Estimated Expiration
- 2044-07-18
AI Technical Summary
Existing nanofiltration membranes are easily contaminated by biomolecules during the cordycepin purification process, leading to membrane pore blockage and affecting normal use. Furthermore, traditional antifouling materials have poor stability and effectiveness.
A zwitterionic antifouling nanofiltration membrane was prepared by introducing zwitterionic materials onto the surface of a nanofiltration membrane through chemical bonding to form a stable hydration layer, thereby improving its resistance to biofouling.
It improves the water flux and biofouling resistance of nanofiltration membranes, enhances the separation ability of biomolecules and membrane stability, and reduces membrane fouling costs.
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Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing an antifouling nanofiltration membrane, belonging to the field of membrane preparation technology. The nanofiltration membrane has advantages such as high pure water flux, high selectivity, and good antifouling effect, and is suitable for fields such as biomolecule purification. Background Technology
[0002] With the development of bioengineering technology, a large number of bioengineered products have emerged. In 1951, German scientist Cunningham observed that the tissues of insects parasitized by Cordyceps militaris did not easily decompose, and subsequently isolated an antibacterial substance from it, naming it cordycepin, or 3'-deoxyadenosine (C3'-deoxyadenosine). 10 H 13 N5O3 (molecular weight 251.24 Da, alkaline) has the structural formula shown in Formula 1. As the first nucleoside antibiotic isolated from fungi, cordycepin has various pharmacological effects, including antitumor, antibacterial, antiviral, anti-inflammatory, and leukemia treatment, and has good prospects for clinical application.
[0003] Cordycepin structural formula
[0004] Currently, cordycepin is primarily extracted from the fermentation broth of Cordyceps militaris. The main process for separating and purifying cordycepin includes centrifugation of the fermentation broth, microfiltration + ultrafiltration to remove large molecular impurities such as proteins and pigments, nanofiltration or electrodialysis to remove inorganic salts, glycine (molecular weight 75.07 Da), and adenine (molecular weight 135.13 Da) and other small biological molecules, and finally crystallization to obtain cordycepin crystals. In the cordycepin / MgSO4 separation process, nanofiltration has advantages over electrodialysis, such as lower energy consumption and simpler process and easier maintenance. However, commercial nanofiltration membranes are generally prone to biomolecular fouling and pore blockage, leading to membrane malfunction. Statistics show that, at the very least, membrane fouling costs still account for 11% of the operating cost of nanofiltration membrane devices. Therefore, it is essential to improve nanofiltration membranes to enhance their antifouling performance and their ability to purify and separate biomolecules.
[0005] There are two common strategies for preparing antifouling nanofiltration membranes: one is to introduce metal nanomaterials, such as silver nanoparticles, to continuously release Ag. +Inactivating biomolecules is clearly unsuitable for separating and purifying them. Another approach is to introduce materials containing hydrophilic groups, such as PEG, which form a hydration layer on the membrane surface through hydrogen bonding with water molecules, thus resisting biomolecule adsorption and contamination. However, PEG is highly susceptible to oxidative damage, significantly reducing its antifouling performance. Therefore, finding alternative antifouling materials with better stability and antifouling properties is essential. Zwitterionic materials are a class of highly efficient antifouling biomedical and engineering materials containing equal numbers of opposite charges. Due to the electrostatically induced hydration layer, the coating surface of zwitterionic polymers exhibits strong resistance to biomolecule adsorption and biofilm formation.
[0006] The hydrophobic methylene group (−CH2−) between the cationic and anionic groups controls the hydrophobic / hydrophilic ratio of the zwitterionic polymer, thus determining its antifouling properties. Shortening the length of the methylene group can effectively enhance the hydrophilicity and antifouling performance of the zwitterionic polymer. Compared with traditional zwitterionic materials such as polyphosphocholine, polysulfobetaine, and polycarboxybetaine, the zwitterionic material synthesized in this invention has directly connected cationic and anionic groups (N... + -O - This invention can form a more stable hydration layer on the surface of nanofiltration membranes, thereby further improving the water flux and anti-biofouling performance of nanofiltration membranes; moreover, the invention uses chemical bonding to introduce zwitterionic materials onto nanofiltration membranes, making the process simpler. Summary of the Invention
[0007] The technical problem to be solved by the present invention is to provide a method for preparing a zwitterionic antifouling nanofiltration membrane for purifying cordycepin, thereby improving the current situation where the antifouling performance of nanofiltration membranes in existing processes is not strong enough.
[0008] To achieve the above objectives, the technical solution adopted by the present invention is: a method for preparing a zwitterionic antifouling nanofiltration membrane for purifying cordycepin, the specific steps of which are as follows:
[0009] (1) Synthesis of zwitterionic materials
[0010] The substances involved in the synthesis of zwitterionic materials are composed of the following mass percentages: oxidant 15-20%, divinyltriamine derivative 15-25%, and the remainder being ultrapure water. The divinyltriamine derivative is added to ultrapure water under ice-water bath stirring conditions, followed by the slow dropwise addition of the oxidant, which is completed within 10 minutes. The mixture is then exposed to air at room temperature with continuous stirring for 5-12 hours. Unoxidized reactants are removed by extraction with dichloromethane. The aqueous solution is freeze-dried for 16-24 hours to obtain the zwitterionic material.
[0011] (2) Preparation of base film
[0012] The casting solution for the base membrane is prepared by mass percentage of the following components: 15-20% film-forming material, 35-50% pore-forming agent, and the remainder being an organic solvent. The film-forming material is dissolved in the solvent, and the pore-forming agent is added. The mixture is heated and stirred until dissolved. After further heating and stirring at 60°C for 12-24 hours, a transparent casting solution is formed. This solution is then allowed to stand for 6-12 hours to remove bubbles. An automatic coating machine is then used to uniformly coat the casting solution onto a nonwoven fabric at a speed of 20-40 mm / s, controlling the film thickness to 100 μm. After being exposed to air for 0-80 seconds, the film is immersed in pure water for phase inversion. The phase-inverted membrane is washed with pure water until no obvious foam is observed in the washing solution to obtain the base membrane, which has a thickness of 150-200 µm. The membrane is then stored immersed in pure water.
[0013] (3) Preparation of zwitterionic antifouling nanofiltration membrane
[0014] The zwitterionic material prepared in (1) was added to ultrapure water and stirred until homogeneous to obtain an aqueous solution with a zwitterionic material mass fraction of 0.1-2%. 1,3,5-benzenetricarboxyl chloride was dissolved in an organic solvent to prepare an oil phase solution with a mass fraction of 0.1-0.3%. 15-25 mL of the aqueous solution was poured onto the surface of the base membrane and kept for 2-5 min. The excess aqueous solution was then wiped off with industrial wiping paper. 15-25 mL of the oil phase solution was then poured in to undergo an interfacial polymerization reaction. After reacting for 1-3 min, the excess oil phase solution was poured off. The membrane was then heat-treated at 50-80℃ for 10-30 min to obtain a zwitterionic antifouling nanofiltration membrane.
[0015] The preferred step (1) is to synthesize zwitterionic materials using one of N,N',N'-trimethyldivinyltriamine, N,N,N',N'-tetraethyldivinyltriamine, or N,N-diethyldivinyltriamine; and the oxidant is one of hydrogen peroxide, potassium permanganate, or potassium dichromate.
[0016] In preferred step (2), the film-forming material of the casting solution is one of polyethersulfone, polyacrylonitrile, or polysulfone.
[0017] In preferred step (2), the pore-forming agent in the casting solution is one of polyethylene glycol, hydroxypropyl cellulose, and polyvinylpyrrolidone; the solvent in the casting solution is one of N,N-dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone.
[0018] The preferred organic solvent in step (3) is one of n-hexane, n-heptane, dodecane, and tetradecane.
[0019] This invention synthesizes a novel zwitterionic material by oxidizing the tertiary amine group of a divinyltriamine derivative. Using this novel zwitterionic material, instead of the traditional aqueous monomer and acyl chloride monomer interfacial polymerization reaction, it is introduced onto a nanofiltration membrane via chemical bonding rather than traditional adhesion, thus preparing a zwitterionic antifouling nanofiltration membrane. The anionic oxygen group of this novel zwitterionic material is directly linked to the cationic quaternary amine group, and the corresponding functional group (i.e., N...)... + -O - Through electrostatically induced hydration, it firmly accommodates water molecules, thus exhibiting excellent hydrophilicity. A hydration layer exists on the surface of the zwitterionic nanofiltration membrane, thereby increasing the water flux of the nanofiltration membrane and providing strong resistance to the adsorption of biomolecules and the formation of biofilms. Beneficial effects
[0020] Since zwitterionic materials are introduced by chemical bonding to replace traditional aqueous monomers, the membrane preparation method of the present invention can use porous support membranes of various materials, and also improves the stability of composite nanofiltration membranes.
[0021] The zwitterionic antifouling nanofiltration membrane prepared by this invention separates zwitterions (N) with equimolar oppositely charged groups in its surface structure. + -O - It has a strong hydration capacity, thereby improving the water flux and biofouling resistance of nanofiltration membranes.
[0022] Furthermore, due to the presence of both anionic and cationic groups, the presence of zwitterions makes the overall surface charge of the nanofiltration membrane neutral, which weakens the influence of charge effect in the separation process and improves the permeability of monovalent and polyvalent ions. Attached Figure Description
[0023] Figure 1 The graphs show the fouling resistance test results of the nanofiltration membrane in Example 1 and Comparative Example 1.
[0024] Figure 2 The image shows a scanning electron microscope (SEM) image of the nanofiltration membrane from Example 3.
[0025] Figure 3 This is a cross-sectional scanning electron microscope image of the nanofiltration membrane from Example 5. Detailed Implementation
[0026] The present invention will be further described in detail below through specific embodiments. However, those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention.
[0027] The zwitterionic nanofiltration membrane prepared by this invention can be used to separate cordycepin and inorganic salts. Therefore, the cordycepin rejection rate, inorganic salt permeation rate, water flux, and antifouling performance are four important parameters for evaluating this nanofiltration membrane.
[0028] The test conditions for water flux, cordycepin rejection rate and inorganic salt permeability were as follows: dead-end filtration device, cordycepin concentration of 2000 mg / L, inorganic salt selected from MgSO4, which is commonly found in cordycepin fermentation broth, concentration of 500 mg / L, test temperature of 25℃, pH=7, and test pressure of 0.6 MPa.
[0029] Cordycepin retention rate is defined as:
[0030] In the formula, R1 represents the cordycepin retention rate, and C p1 and C f1 The concentrations of cordycepin in the permeate and feed solutions are respectively.
[0031] The permeability of MgSO4 is defined as:
[0032] In the formula, R2 represents the cordycepin retention rate, and C p2 and C f2 The concentrations of MgSO4 in the permeate and feed solutions are respectively.
[0033] Water flux is defined as the volume of water that permeates the effective area of the membrane per unit time under unit pressure.
[0034] The antifouling performance of the membrane was measured using a 2000 mg / L cordycepin solution as a simulated pollutant. Each filtration experiment consisted of three cycles, with the following steps for each cycle: (1) filtration with pure water for 30 min to obtain flux P1; (2) filtration with cordycepin solution for 1 h to obtain flux P2; (3) rinsing the membrane with pure water for 20 min, followed by filtration with pure water for 30 min to obtain flux P3. The membrane flux recovery rate (FRR) could be obtained using an equation.
[0035] Membrane flux recovery rate (FRR) is defined as: Example
[0036] (1) 5.5 g of N,N',N”-trimethyldivinyltriamine was added to 24.5 mL of ultrapure water under ice-water bath stirring conditions, followed by slow dropwise addition of 6.5 mL of 30% hydrogen peroxide solution over 10 min. The mixture was continuously stirred in air at room temperature for 12 h, and unoxidized reactants were removed by extraction with dichloromethane. The aqueous solution was freeze-dried for 24 h to obtain the corresponding zwitterionic material.
[0037] (2) The casting solution for the base membrane was prepared by the following components in the following mass percentages: polyethersulfone 17%, polyethylene glycol 37%, and N,N-dimethylacetamide 46%. 17 g of polyethersulfone was dissolved in 46 g of N,N-dimethylacetamide, and then 37 g of polyethylene glycol was added. The mixture was heated and stirred until dissolved. After dissolution, the mixture was heated and stirred at 60°C for 12 h until a transparent casting solution was formed. The solution was then allowed to stand for 8 h to remove bubbles. The casting solution was then uniformly coated onto the nonwoven fabric using an automatic coating machine at a speed of 30 mm / s, controlling the film thickness to be 100 μm. After coating, the nonwoven fabric was left to stand in the air for 20 s before being immersed in pure water for phase inversion. The phase-inverted membrane was washed with pure water until no obvious foam was observed in the washing solution to obtain the base membrane, which had a thickness of 160 µm. The base membrane was then stored in pure water.
[0038] (3) The zwitterionic material prepared in (1) was added to ultrapure water and stirred until homogeneous to obtain a 1 wt% aqueous solution; 1,3,5-benzenetricarboxyl chloride was dissolved in n-heptane to prepare a 0.15 wt% oil solution. 25 mL of the aqueous solution was poured onto the surface of the base membrane and kept for 2 min. After removing the excess aqueous solution, 15 mL of the oil solution was poured in to undergo an interfacial polymerization reaction. After reacting for 1 min, the excess oil solution was removed. After heat treatment at 60℃ for 30 min, the zwitterionic antifouling nanofiltration membrane was obtained.
[0039] The nanofiltration membrane prepared in Example 1 was tested for performance, and the water flux of the nanofiltration membrane was 42.8 L·m. -2 ·h -1 ·bar -1 The cordycepin rejection rate was 97.5%, the MgSO4 permeation rate was 93.8%, and the membrane flux recovery rate was as high as 98%. Example
[0040] (1) 8 g of N,N-diethyldivinyltriamine was added to 26.5 mL of ultrapure water under ice-water bath stirring conditions, followed by slow dropwise addition of 8.5 mL of 30% hydrogen peroxide solution over 10 min. The mixture was exposed to air at room temperature and stirred continuously for 5 h. Unoxidized reactants were removed by extraction with dichloromethane. The aqueous solution was freeze-dried for 20 h to obtain the corresponding zwitterionic material.
[0041] (2) The casting solution for the base membrane was prepared from the following components in the indicated mass percentages: 17% polysulfone, 40% polyethylene glycol, and 43% N,N-dimethylacetamide. 17 g of polysulfone was dissolved in 43 g of N,N-dimethylacetamide, and then 40 g of polyethylene glycol was added. The mixture was heated and stirred until dissolved. After dissolution, the mixture was heated and stirred at 60°C for 12 h until a transparent casting solution was formed. The solution was then allowed to stand for 6 h to remove bubbles. The casting solution was then uniformly coated onto the nonwoven fabric using an automatic coating machine at a speed of 40 mm / s, controlling the film thickness to be 100 μm. After coating, the nonwoven fabric with the casting solution was quickly immersed in pure water for phase inversion. The phase-inverted membrane was washed with pure water until no obvious foam was observed in the washing solution to obtain the base membrane, which had a thickness of 150 µm. The membrane was then stored in pure water.
[0042] (3) The zwitterionic material prepared in (1) was added to ultrapure water and stirred until homogeneous to obtain a 1 wt% aqueous solution; 1,3,5-benzenetricarboxyl chloride was dissolved in n-hexane to prepare a 0.1 wt% oil solution. 25 mL of the aqueous solution was poured onto the surface of the base membrane and kept for 4 min. After removing the excess aqueous solution, 20 mL of the oil solution was poured in to undergo an interfacial polymerization reaction. After reacting for 3 min, the excess oil solution was removed. After heat treatment at 50 °C for 30 min, the zwitterionic antifouling nanofiltration membrane was obtained.
[0043] The nanofiltration membrane prepared in Example 2 was tested for performance. The water flux of the nanofiltration membrane was 40.0 L·m. -2 ·h -1 ·bar -1 The cordycepin rejection rate was 98.1%, the MgSO4 permeation rate was 92.7%, and the membrane flux recovery rate was as high as 96%. Example
[0044] (1) 10 g of N,N,N',N'-tetraethyldivinyltriamine was added to 23 mL of ultrapure water under ice-water bath stirring conditions, followed by 7 mL of 30% potassium permanganate solution added dropwise over 10 min. The mixture was exposed to air at room temperature and stirred continuously for 12 h. Unoxidized reactants were removed by extraction with dichloromethane. The aqueous solution was freeze-dried for 16 h to obtain the corresponding zwitterionic material.
[0045] (2) The casting solution for the base membrane was prepared from the following components in the indicated mass percentages: 15% polyacrylonitrile, 37% hydroxypropyl cellulose, and 48% N,N-dimethylacetamide. 15 g of polyacrylonitrile was dissolved in 48 g of N,N-dimethylacetamide, and then 37 g of hydroxypropyl cellulose was added. The mixture was heated and stirred until dissolved. After further heating and stirring at 60°C for 18 h, a transparent casting solution was formed. The solution was then allowed to stand for 10 h to remove bubbles. The casting solution was then uniformly coated onto the nonwoven fabric using an automatic coating machine at a speed of 20 mm / s, controlling the film thickness to be 100 μm. After coating, the nonwoven fabric with the casting solution was quickly immersed in pure water for phase inversion. The phase-inverted membrane was washed with pure water until no obvious foam was observed in the washing solution, yielding the base membrane with a thickness of 180 µm. The membrane was then stored in pure water.
[0046] (3) The zwitterionic material prepared in (1) was added to ultrapure water and stirred until homogeneous to obtain a 1 wt% aqueous solution; 1,3,5-benzenetricarboxyl chloride was dissolved in dodecane to prepare a 0.15 wt% oil solution. 25 mL of the aqueous solution was poured onto the surface of the base membrane and kept for 2 min. After removing the excess aqueous solution, 25 mL of the oil solution was poured in to undergo an interfacial polymerization reaction. After reacting for 1 min, the excess oil solution was removed. After heat treatment at 80℃ for 10 min, the zwitterionic antifouling nanofiltration membrane was obtained.
[0047] The nanofiltration membrane prepared in Example 3 was tested for performance, and the water flux of the nanofiltration membrane was 43.6 L·m. -2 ·h -1 ·bar -1 The cordycepin rejection rate was 92.0%, the MgSO4 permeation rate was 99.1%, and the membrane flux recovery rate was as high as 97%. Example
[0048] (1) 8 g of N,N',N”-trimethyldivinyltriamine was added to 23 mL of ultrapure water under ice-water bath stirring conditions, followed by 7 mL of 30% potassium dichromate solution added dropwise over 10 min. The mixture was exposed to air at room temperature and stirred continuously for 5 h. Unoxidized reactants were removed by extraction with dichloromethane. The aqueous solution was freeze-dried for 20 h to obtain the corresponding zwitterionic material.
[0049] (2) The casting solution for the base membrane was prepared from the following components in the indicated mass percentages: polysulfone 17%, polyethylene glycol 35%, and N,N-dimethylacetamide 48%. 17 g of polyethersulfone was dissolved in 48 g of N,N-dimethylacetamide, and then 35 g of polyethylene glycol was added. The mixture was heated and stirred until dissolved. After dissolution, the mixture was heated and stirred at 60°C for 15 h until a transparent casting solution was formed. The solution was then allowed to stand for 12 h to remove bubbles. The casting solution was then uniformly coated onto the nonwoven fabric using an automatic coating machine at a speed of 30 mm / s, controlling the film thickness to be 100 μm. After coating, the nonwoven fabric was left to stand in the air for 40 s before being immersed in pure water for phase inversion. The phase-inverted membrane was washed with pure water until no obvious foam was observed in the washing solution, yielding the base membrane with a thickness of 170 µm. The membrane was then stored in pure water.
[0050] (3) The zwitterionic material prepared in (1) was added to ultrapure water and stirred until homogeneous to obtain a 0.1 wt% aqueous solution; 1,3,5-benzenetricarboxyl chloride was dissolved in tetradecane to prepare a 0.15 wt% oil solution. 20 mL of the aqueous solution was poured onto the surface of the base membrane and kept for 5 min. After removing the excess aqueous solution, 20 mL of the oil solution was poured in to undergo an interfacial polymerization reaction. After reacting for 3 min, the excess oil solution was removed. After heat treatment at 60℃ for 20 min, the zwitterionic antifouling nanofiltration membrane was obtained.
[0051] The nanofiltration membrane prepared in Example 4 was tested for performance, and the water flux of the nanofiltration membrane was 43.7 L·m. -2 ·h -1 ·bar -1 The cordycepin rejection rate was 97.9%, the MgSO4 permeation rate was 98.2%, and the membrane flux recovery rate was as high as 98%. Example
[0052] (1) Under ice-water bath stirring conditions, 8 g of N,N,N',N'-tetraethyldivinyltriamine was added to 24 mL of ultrapure water, followed by slow dropwise addition of 8 mL of 30% hydrogen peroxide solution over 10 min. The mixture was exposed to air at room temperature and stirred continuously for 10 h. Unoxidized reactants were removed by extraction with dichloromethane. The aqueous solution was freeze-dried for 24 h to obtain the corresponding zwitterionic material.
[0053] (2) The casting solution for the base membrane was prepared from the following components in the indicated mass percentages: 20% polysulfone, 37% polyvinylpyrrolidone, and 43% N,N-dimethylformamide. 20 g of polysulfone was dissolved in 43 g of N,N-dimethylformamide, and then 37 g of polyvinylpyrrolidone was added. The mixture was heated and stirred until dissolved. The mixture was then heated and stirred at 60°C for 16 h until a transparent casting solution was formed. The solution was then allowed to stand for 8 h to remove bubbles. The casting solution was then uniformly coated onto the nonwoven fabric using an automatic coating machine at a speed of 30 mm / s, controlling the film thickness to be 100 μm. After coating, the nonwoven fabric was left to stand in the air for 60 s before being immersed in pure water for phase inversion. The phase-inverted membrane was washed with pure water until no obvious foam was observed in the washing solution, yielding the base membrane with a thickness of 160 µm. The membrane was then stored in pure water.
[0054] (3) The zwitterionic material prepared in (1) was added to ultrapure water and stirred until homogeneous to obtain a 0.5 wt% aqueous solution; 1,3,5-benzenetricarboxyl chloride was dissolved in n-hexane to prepare a 0.15 wt% oil solution. 20 mL of the aqueous solution was poured onto the surface of the base membrane and kept for 2 min. After removing the excess aqueous solution, 15 mL of the oil solution was poured in to undergo an interfacial polymerization reaction. After reacting for 1 min, the excess oil solution was removed. After heat treatment at 60℃ for 20 min, the zwitterionic antifouling nanofiltration membrane was obtained.
[0055] The nanofiltration membrane prepared in Example 5 was tested for performance, and the water flux of the nanofiltration membrane was 43.1 L·m. -2 ·h -1 ·bar -1 The cordycepin rejection rate was 93.3%, the MgSO4 permeation rate was 99.5%, and the membrane flux recovery rate was as high as 95%. Example
[0056] (1) 8 g of N,N',N”-trimethyldivinyltriamine was added to 24 mL of ultrapure water under ice-water bath stirring conditions, followed by the slow addition of 7.5 mL of 30% potassium permanganate solution over 10 min. The mixture was exposed to air at room temperature and stirred continuously for 12 h. Unoxidized reactants were removed by extraction with dichloromethane. The aqueous solution was freeze-dried for 20 h to obtain the corresponding zwitterionic material.
[0057] (2) The casting solution for the base membrane was prepared from the following components in the indicated mass percentages: 17% polyacrylonitrile, 35% polyethylene glycol, and 48% N-methylpyrrolidone. 17 g of polyacrylonitrile was dissolved in 48 g of N-methylpyrrolidone, and then 35 g of polyethylene glycol was added. The mixture was heated and stirred until dissolved. After dissolution, the mixture was heated and stirred at 60°C for 24 h until a transparent casting solution was formed. The solution was then allowed to stand for 12 h to remove bubbles. The casting solution was then uniformly coated onto the nonwoven fabric using an automatic coating machine at a speed of 20 mm / s, controlling the film thickness to be 100 μm. After coating, the nonwoven fabric was left to stand in the air for 80 s before being immersed in pure water for phase inversion. The phase-inverted membrane was washed with pure water until no obvious foam was observed in the washing solution, yielding the base membrane with a thickness of 200 µm. The base membrane was then stored in pure water.
[0058] (3) The zwitterionic material prepared in (1) was added to ultrapure water and stirred until homogeneous to obtain a 1 wt% aqueous solution; 1,3,5-benzenetricarboxyl chloride was dissolved in n-heptane to prepare a 0.3 wt% oil solution. 15 mL of the aqueous solution was poured onto the surface of the base membrane and kept for 2 min. After removing the excess aqueous solution, 15 mL of the oil solution was poured in to undergo an interfacial polymerization reaction. After reacting for 1 min, the excess oil solution was removed. After heat treatment at 60℃ for 20 min, the zwitterionic antifouling nanofiltration membrane was obtained.
[0059] The nanofiltration membrane prepared in Example 6 was tested for performance, and the water flux of the nanofiltration membrane was 46.2 L·m. -2 ·h -1 ·bar -1 The cordycepin rejection rate was 98.1%, the MgSO4 permeation rate was 90.0%, and the membrane flux recovery rate was as high as 96%. Example
[0060] (1) 8 g of N,N-diethyldivinyltriamine was added to 24 mL of ultrapure water under ice-water bath stirring conditions, followed by the slow addition of 7.5 mL of 30% potassium dichromate solution over 10 min. The mixture was exposed to air at room temperature and stirred continuously for 12 h. Unoxidized reactants were removed by extraction with dichloromethane. The aqueous solution was freeze-dried for 18 h to obtain the corresponding zwitterionic material.
[0061] (2) The casting solution for the base membrane was prepared from the following components in the indicated mass percentages: 17% polyethersulfone, 50% hydroxypropyl cellulose, and 43% N,N-dimethylacetamide. 17 g of polyethersulfone was dissolved in 43 g of N,N-dimethylacetamide, and then 50 g of hydroxypropyl cellulose was added. The mixture was heated and stirred until dissolved. After dissolution, the mixture was heated and stirred at 60°C for 24 h until a transparent casting solution was formed. The solution was then allowed to stand for 6 h to remove bubbles. The casting solution was then uniformly coated onto the nonwoven fabric using an automatic coating machine at a speed of 30 mm / s, controlling the film thickness to be 100 μm. After coating, the nonwoven fabric with the casting solution was quickly immersed in pure water for phase inversion. The phase-inverted membrane was washed with pure water until no obvious foam was observed in the washing solution to obtain the base membrane, which had a thickness of 160 µm. The base membrane was then stored in pure water.
[0062] (3) The zwitterionic material prepared in (1) was added to ultrapure water and stirred evenly to obtain a 2 wt% aqueous solution; 1,3,5-benzenetricarboxyl chloride was dissolved in dodecane to prepare a 0.1 wt% oil solution. 25 mL of the aqueous solution was poured onto the surface of the polyethersulfone ultrafiltration membrane support layer, kept for 2 min, and then the excess aqueous solution was removed. Then 15 mL of the oil solution was poured in to carry out the interfacial polymerization reaction. After reacting for 1 min, the excess oil solution was removed. After heat treatment at 60℃ for 20 min, the zwitterionic antifouling nanofiltration membrane was obtained.
[0063] The nanofiltration membrane prepared in Example 7 was tested for performance, and the water flux of the nanofiltration membrane was 49.3 L·m. -2 ·h -1 ·bar -1 The cordycepin rejection rate was 94.1%, the MgSO4 permeation rate was 99.3%, and the membrane flux recovery rate was as high as 95%. Example
[0064] (1) 10 g of N,N,N',N'-tetraethyldivinyltriamine was added to 23 mL of ultrapure water under ice-water bath stirring conditions, followed by 7 mL of 30% potassium permanganate solution added dropwise over 10 min. The mixture was exposed to air at room temperature and stirred continuously for 12 h. Unoxidized reactants were removed by extraction with dichloromethane. The aqueous solution was freeze-dried for 22 h to obtain the corresponding zwitterionic material.
[0065] (2) The casting solution for the base membrane was prepared from the following components in the indicated mass percentages: polysulfone 17%, polyvinylpyrrolidone 37%, and N,N-dimethylacetamide 46%. 17 g of polysulfone was dissolved in 46 g of N,N-dimethylacetamide, and then 37 g of polyvinylpyrrolidone was added. The mixture was heated and stirred until dissolved. After dissolution, the mixture was heated and stirred at 60°C for 12 h until a transparent casting solution was formed. The solution was then allowed to stand for 6 h to remove bubbles. The casting solution was then uniformly coated onto the nonwoven fabric using an automatic coating machine at a speed of 30 mm / s, controlling the film thickness to be 100 μm. After coating, the nonwoven fabric was left to stand in the air for 40 s before being immersed in pure water for phase inversion. The phase-inverted membrane was washed with pure water until no obvious foam was observed in the washing solution, yielding the base membrane with a thickness of 160 µm. The membrane was then stored in pure water.
[0066] (3) The zwitterionic material prepared in (1) was added to ultrapure water and stirred until homogeneous to obtain a 0.1 wt% aqueous solution; 1,3,5-benzenetricarboxyl chloride was dissolved in tetradecane to prepare a 0.1 wt% oil solution. 25 mL of the aqueous solution was poured onto the surface of the polyethersulfone ultrafiltration membrane support layer, kept for 2 min, and then the excess aqueous solution was removed. Then 20 mL of the oil solution was poured in to undergo interfacial polymerization reaction. After reacting for 2 min, the excess oil solution was removed. After heat treatment at 60℃ for 20 min, the zwitterionic antifouling nanofiltration membrane was obtained.
[0067] The nanofiltration membrane prepared in Example 8 was tested for performance, and the water flux of the nanofiltration membrane was 41.6 L·m. -2 ·h -1 ·bar -1 The cordycepin rejection rate was 92.9%, the MgSO4 permeation rate was 95.2%, and the membrane flux recovery rate was as high as 95%.
[0068] Comparative Example 1:
[0069] Anhydrous piperazine was added to ultrapure water and stirred until homogeneous to obtain a 2 wt% aqueous solution. 1,3,5-Benzotricarboxylic chloride was dissolved in n-hexane to prepare a 0.1 wt% oil solution. 20 mL of the aqueous solution was poured onto the surface of the polyethersulfone ultrafiltration membrane support layer. After maintaining the solution for 2 min, excess aqueous solution was removed. Then, 15 mL of the oil solution was added to initiate an interfacial polymerization reaction. After reacting for 1 min, excess oil solution was removed. The membrane was then heat-treated at 60 °C for 20 min to obtain a nanofiltration membrane.
[0070] The prepared nanofiltration membrane was tested for performance, and its water flux was 22.3 L·m⁻¹. -2 ·h -1 ·bar -1 The cordycepin rejection rate was 80.1%, the MgSO4 permeation rate was 72.6%, and the membrane flux recovery rate was 65%.
Claims
1. A method for preparing a zwitterionic antifouling nanofiltration membrane for purifying cordycepin, the specific steps of which are as follows: (1) Synthesis of zwitterionic materials The substances involved in the synthesis of zwitterionic materials are composed of the following mass percentages: oxidant 15-20%, divinyltriamine derivative 15-25%, and the remainder is ultrapure water; the divinyltriamine derivative is added to ultrapure water under ice-water bath stirring conditions, followed by slow dropwise addition of the oxidant, which is completed within 10 minutes; the mixture is continuously stirred in air at room temperature for 5-12 hours, and unoxidized reactants are removed by extraction with dichloromethane; the aqueous solution is freeze-dried for 16-24 hours to obtain the zwitterionic material; (2) Preparation of base film The casting solution for the base membrane is prepared by the following components in the following mass percentages: 15-20% film-forming material, 35-50% pore-forming agent, and the remainder is organic solvent. The film-forming material is dissolved in the organic solvent, and then the pore-forming agent is added. The mixture is heated and stirred until dissolved. Heating and stirring at 60°C is continued for 12-24 hours until a transparent casting solution is formed. This solution is then allowed to stand for 6-12 hours to remove bubbles. An automatic coating machine is then used to uniformly coat the casting solution onto a nonwoven fabric at a speed of 20-40 mm / s, controlling the film thickness to 100 μm. After being exposed to air for 0-80 seconds, the film is immersed in pure water for phase inversion. The phase-inverted membrane is then washed with pure water until no obvious foam is observed in the washing solution to obtain the base membrane, which has a thickness of 150-200 μm. This base membrane is then stored in pure water. (3) Preparation of zwitterionic antifouling nanofiltration membrane The zwitterionic material prepared in (1) was added to ultrapure water and stirred evenly to obtain an aqueous solution with a zwitterionic material mass fraction of 0.1-2%. 1,3,5-benzenetricarboxyl chloride was dissolved in an organic solvent to prepare an oil phase solution with a mass fraction of 0.1-0.3%. 15-25 mL of the aqueous solution was poured onto the surface of the base membrane and kept for 2-5 min. The excess aqueous solution was wiped off with industrial wiping paper, and then 15-25 mL of the oil phase solution was poured in to undergo interfacial polymerization. After reacting for 1-3 min, the excess oil phase solution was poured off. The zwitterionic antifouling nanofiltration membrane was obtained after heat treatment at 50-80°C for 10-30 min.
2. The preparation method according to claim 1, characterized in that... The main reactant in step (1) for synthesizing zwitterionic materials is one of N,N',N”-trimethyldivinyltriamine, N,N,N',N’-tetraethyldivinyltriamine, and N,N-diethyldivinyltriamine.
3. The preparation method according to claim 1, characterized in that... In step (1), the oxidant is one of hydrogen peroxide, potassium permanganate, or potassium dichromate.
4. The preparation method according to claim 1, characterized in that... In step (2), the film-forming material of the casting solution is one of polyethersulfone, polyacrylonitrile, or polysulfone.
5. The preparation method according to claim 1, characterized in that... In step (2), the pore-forming agent in the casting solution is one of polyethylene glycol, hydroxypropyl cellulose, or polyvinylpyrrolidone.
6. The preparation method according to claim 1, characterized in that... In step (2), the solvent for the casting solution is one of N,N-dimethylacetamide, N,N-dimethylformamide, and N-methylpyrrolidone.
7. The preparation method according to claim 1, characterized in that... The organic solvent mentioned in step (3) is one of n-hexane, n-heptane, dodecane, and tetradecane.
8. A zwitterionic antifouling nanofiltration membrane prepared by the preparation method according to any one of claims 1-7, characterized in that, The nanofiltration membrane has a pure water flux ≥ 40 L·m -2 ·h -1 ·bar -1 In the separation test of cordycepin and MgSO4, the cordycepin retention rate was ≥92%, the MgSO4 permeation rate was ≥90%, and the membrane flux recovery rate was ≥95%, showing a significant anti-biofouling effect.