Chemical bonding zwitter-ion composite membrane and saccharide separation application of chemical bonding zwitter-ion composite membrane

Abstract

The invention provides a high-flux nanofiltration membrane for separating monosaccharide and disaccharide and a preparation method of the high-flux nanofiltration membrane. According to the nanofiltration membrane, the hydrophilicity is improved by hydrolyzing a modified PAN base membrane, an amino-containing zwitterionic material participates in interfacial polymerization, and a PA separation layer is constructed in a chemical bonding mode. Compared with a traditional method, through the synergistic effect of base membrane modification and zwitter-ion introduction, the anti-pollution performance and water flux of the membrane are remarkably improved, and meanwhile high selectivity to monosaccharide and disaccharide is kept. The prepared nanofiltration membrane has excellent performance and long-term stability in the field of saccharide separation, and is suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to a composite membrane chemically bonded with zwitterions, belonging to the technical field of membrane preparation. Background Art

[0002] Carbohydrates are a class of polyhydroxy aldehydes or ketones and their derivatives and condensates, widely existing in nature and being the main products of plant photosynthesis. According to the number of structural units, carbohydrates can be divided into monosaccharides (such as glucose, fructose), disaccharides (such as sucrose, maltose) and polysaccharides (such as starch, cellulose). Among them, monosaccharides and disaccharides have important application values in the fields of food, medicine, bio-chemical engineering, etc.

[0003] In traditional sugar-making industries, the efficient separation of monosaccharides and disaccharides has always been a technical problem. At present, crystallization, chromatographic separation and other methods are mainly used in industry, but these methods have disadvantages such as high energy consumption, complex processes and large pollution. In contrast, membrane separation technology has become an ideal choice for sugar separation due to its advantages of being green and efficient, low energy consumption and easy operation. However, the existing nanofiltration membranes still face the following problems in the separation process of monosaccharides and disaccharides: (1) Insufficient selectivity: The design of traditional nanofiltration membranes mainly focuses on improving the rejection rate of glucose or water flux, but the selective separation effect of monosaccharides and disaccharides is poor, making it difficult to meet the industrial requirements. (2) Limited flux: The pore size of conventional nanofiltration membranes is small, resulting in low water flux and affecting the separation efficiency. (3) Poor anti-fouling performance: During the sugar separation process, organic substances or microorganisms are easily adsorbed on the membrane surface, leading to flux decay and affecting the long-term operation stability.

[0004] To improve the performance of nanofiltration membranes, existing research usually adopts the method of introducing hydrophilic groups (such as PEG) to enhance the hydration layer on the membrane surface, thereby increasing the water flux. However, PEG-based materials are easily oxidized and degraded, with poor long-term stability, which limits their practical applications.

[0005] In recent years, zwitterionic materials have received extensive attention in the biomedical field due to their excellent anti-fouling and hydrophilic properties. Zwitterionic materials are composed of equal amounts of positive and negative charge groups and can form a stable hydration layer through electrostatic induction. The coating surface of zwitterionic polymers has strong resistance to the adsorption of biomolecules and the formation of biofilms, effectively inhibiting the adsorption of pollutants. The hydrophobic methylene group (−CH2−) between the cationic and anionic groups controls the hydrophobic / hydrophilic ratio of the zwitterionic polymer, thus determining its anti-fouling property. Shortening the length of the methylene group can effectively enhance the hydrophilicity and anti-fouling performance of the zwitterionic polymer. Compared with traditional zwitterionic materials such as polyphosphorylcholine, polysulfobetaine, and polycarboxybetaine, the zwitterionic material synthesized in the present invention has the cationic and anionic groups directly connected (N + -O -), reduce the influence of hydrophobic groups, form a more stable hydration layer, and significantly improve the hydrophilicity and anti-fouling performance of the membrane; introduce zwitterionic materials into the separation layer of the nanofiltration membrane through chemical bonding rather than traditional physical coating to enhance the material stability and avoid the shedding problem during long-term use. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a preparation method for a nanofiltration membrane for separating monosaccharides and disaccharides, and to improve the current situation of low flux of the nanofiltration membrane in the existing process.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is: a high-flux nanofiltration membrane for separating monosaccharides and disaccharides and its preparation method, and the specific steps are as follows: (1) Synthesis of zwitterionic materials Dissolve the tertiary amine compound in deionized water, and slowly add an oxidant under stirring at 500 rpm to initiate the oxidation reaction of the tertiary amino group to obtain a zwitterionized solution; dialyze the reaction solution with deionized water for 24 h to remove the residual oxidant, and then freeze-dry to obtain a solid zwitterionic material; wherein, the dosage of the oxidant is 10-20% of the total mass of the reaction system, the dosage of the tertiary amine compound is 5-10%, and the balance is deionized water.

[0008] (2) Preparation of polyacrylonitrile-based membrane Prepare an acid-base reagent solution with a mass fraction of 0.5-5%, immerse the polyacrylonitrile porous membrane in the solution, control the temperature at 25-60 °C, take out the membrane sheet after reacting for 2 h, blot the excess solution with filter paper, and air-dry naturally to obtain a hydrolytically modified polyacrylonitrile-based membrane.

[0009] (3) Interfacial polymerization process Add the zwitterionic material prepared in step (1) to deionized water to prepare an aqueous solution 1 with a mass fraction of 1%; add piperazine (PIP) to deionized water to prepare an aqueous solution 2 with a mass fraction of 1%; mix the aqueous solution 1 and the aqueous solution 2 in proportion to obtain a final aqueous solution; dissolve 1,3,5-benzenetricarbonyl chloride in an organic solvent to prepare an oil-phase solution with a mass fraction of 0.1-0.3%; pour the mixed aqueous solution onto the surface of the base membrane prepared in step (2), let it stand for 2-5 min, then wipe off the excess aqueous solution, and then pour in the oil-phase solution for interfacial polymerization reaction. After reacting for 1-3 min, pour out the excess oil-phase solution, and perform heat treatment at 50-80 °C for 10-30 min to obtain the high-flux nanofiltration membrane.

[0010] Preferably, the main tertiary amine compound for synthesizing the zwitterionic material in step (1) is one of tris(2-aminoethyl)amine, N,N,N',N'-tetraethyldiethylenetriamine, and N,N-diethyldiethylenetriamine.

[0011] Preferably, the oxidant in step (1) is one of hydrogen peroxide, potassium permanganate, and potassium dichromate.

[0012] Preferably, the acid-base reagent in step (2) is one of ethylenediaminetetraacetic acid, alendronic acid, adipic acid, and sodium hydroxide.

[0013] Preferably, the mixing ratio of aqueous solution 1 and aqueous solution 2 in step (3) is 0.1:1, 0.2:1, 0.5:1, or 1:1. Beneficial effects

[0014] 1. Adding a dibasic acid instead of alkali hydrolysis to improve the hydrophilicity of the PAN porous substrate membrane, with simple operation steps and mild conditions at room temperature.

[0015] 2. In the selective layer structure of the composite membrane prepared by the present invention, zwitterions (N + -O - ) with equimolar opposite charge groups are introduced in a chemical bonding manner. Through electrostatic induction hydration, water molecules are firmly accommodated to form a hydration layer, increasing the water flux of the membrane and having strong resistance to the adsorption of biomolecules and the formation of biofilms. Description of the drawings

[0016] Figure 1 It is the surface scanning electron micrograph of the nanofiltration membrane for Comparative Example 1. Figure 2 It is the surface scanning electron micrograph of the nanofiltration membrane for Example 5. Specific embodiments

[0017] 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 only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.

[0018] The high-flux nanofiltration membrane prepared by the present invention can be used to separate glucose and sucrose. Therefore, the rejection rate of sucrose, the permeation rate of glucose, the water flux, and the antifouling performance are four important parameters for evaluating the nanofiltration membrane.

[0019] The test conditions for water flux, sucrose rejection rate, and glucose permeation rate are as follows: dead-end filtration device, sucrose concentration of 1000 mg / L, glucose concentration of 1000 mg / L, test temperature of 25 °C, pH = 7, and test pressure of 0.6 MPa.

[0020] The sucrose rejection rate is defined as:

[0021] In the formula, R1 represents the sucrose rejection rate, C p1 and C f1 represent the sucrose concentrations in the permeate and the feed solution, respectively.

[0022] The glucose permeability is defined as:

[0023] In the formula, R2 represents the sucrose rejection rate, and C p2 and C f2 are the glucose concentrations in the permeate and the feed solution, respectively.

[0024] The water flux is defined as the volume of water passing through the effective area of the membrane per unit time under unit pressure.

[0025] A 1000 mg / L sucrose solution was used as a simulated pollutant to measure the antifouling performance of the membrane. Each filtration experiment consisted of three cycles, and the steps for each cycle were as follows: (1) Filter pure water for 30 min to obtain the flux P1; (2) Filter with the sucrose solution for 1 h to obtain the flux P2; (3) Rinse the membrane with pure water for 20 min, and then filter with pure water for 30 min to obtain the flux P3. The membrane flux recovery rate (FRR) can be obtained through the equation.

[0026] The membrane flux recovery rate (FRR) is defined as: Examples

[0027] (1) 3 g of tris(2-aminoethyl)amine was added to 24.5 mL of deionized water, and then 6.5 mL of 30% potassium dichromate solution was slowly added dropwise under stirring at 500 rpm to initiate the oxidation of the tertiary amine group in tris(2-aminoethyl)amine, thereby making the tertiary amine zwitterionic. Then the reaction solution was dialyzed with deionized water for 24 h to remove the residual potassium dichromate. Finally, the aqueous solution was freeze-dried for 24 h to obtain a solid oxide, i.e., the zwitterionic material.

[0028] (2) An alendronic acid solution with a mass fraction of 0.5% was prepared, and the polyacrylonitrile porous membrane was immersed in the prepared solution, controlling the temperature at 60°C. After deposition for 2 h, the membrane was taken out, and the excess solution was blotted with filter paper and air-dried naturally to obtain the polyacrylonitrile-based membrane.

[0029] (3) Add the zwitterionic material prepared in (1) to deionized water and stir evenly to obtain aqueous solution 1, where the mass fraction of the zwitterionic material in aqueous solution 1 is 1%; add piperazine (PIP) to deionized water and stir evenly to obtain aqueous solution 2, where the mass fraction of piperazine in aqueous solution 2 is 1%. Mix aqueous solution 1 and aqueous solution 2 in a ratio of 0.1:1 to obtain the final aqueous solution. Dissolve 1,3,5-benzenetricarbonyl chloride in an organic solvent to prepare an oil-phase solution, where the mass fraction of 1,3,5-benzenetricarbonyl chloride in the oil-phase solution is 0.15%. Pour the aqueous solution onto the surface of the base membrane. After 2 minutes, use industrial wiping paper to wipe off the excess aqueous solution, then pour in the oil-phase solution to carry out an interfacial polymerization reaction. After 1 minute, pour out the excess oil-phase solution, and heat-treat at 60 °C for 10 minutes to obtain a nanofiltration membrane.

[0030] Perform performance tests on the nanofiltration membrane prepared in Example 1. The water flux of the nanofiltration membrane is 22.8 L·m -2 ·h -1 ·bar -1 , the sucrose rejection rate is 95.5%, the glucose permeation rate is 94.8%, and the membrane flux recovery rate is as high as 95%. Example

[0031] (1) Add 8 g of N,N-diethyldivinyltriamine to 26.5 mL of deionized water, and then slowly drop 6.5 mL of 30% hydrogen peroxide solution under stirring at 500 rpm to initiate the oxidation of the tertiary amine group in tris(2-aminoethyl)amine, thereby making the tertiary amine zwitterionic. Then dialyze the reaction solution with deionized water for 24 h to remove residual hydrogen peroxide. Finally, freeze-dry the aqueous solution for 24 h to obtain a solid oxide, that is, the zwitterionic material.

[0032] (2) Prepare an ethylenediaminetetraacetic acid solution with a mass fraction of 1%, immerse the polyacrylonitrile porous membrane in the prepared solution, and control the temperature at 45 °C. After deposition for 2 h, take out the membrane sheet, suck off the excess solution with filter paper, and air-dry naturally to obtain a polyacrylonitrile base membrane.

[0033] (3) Add the zwitterionic material prepared in (1) to deionized water and stir evenly to obtain aqueous solution 1, where the mass fraction of the zwitterionic material in aqueous solution 1 is 1%; add piperazine (PIP) to deionized water and stir evenly to obtain aqueous solution 2, where the mass fraction of piperazine in aqueous solution 2 is 1%. Mix aqueous solution 1 and aqueous solution 2 in a ratio of 0.5:1 to obtain the final aqueous solution. Dissolve 1,3,5-benzenetricarbonyl chloride in an organic solvent to prepare an oil-phase solution, where the mass fraction of 1,3,5-benzenetricarbonyl chloride in the oil-phase solution is 0.1%. Pour the aqueous solution onto the surface of the substrate membrane. After 2 minutes, use industrial wiping paper to wipe off the excess aqueous solution, and then pour in the oil-phase solution to carry out an interfacial polymerization reaction. After 3 minutes of reaction, pour out the excess oil-phase solution, and obtain a nanofiltration membrane after heat treatment at 50 °C for 10 minutes.

[0034] Perform performance tests on the nanofiltration membrane prepared in Example 2. The water flux of the nanofiltration membrane is 20.0 L·m -2 ·h -1 ·bar -1 , the sucrose rejection rate is 92%, the glucose permeability is 93.7%, and the membrane flux recovery rate is as high as 91%. Example

[0035] (1) Add 3.5 g of tris(2-aminoethyl)amine to 23 mL of deionized water, and then slowly drop 7 mL of 30% potassium permanganate solution under stirring at 500 rpm to initiate the oxidation of the tertiary amine group in tris(2-aminoethyl)amine, thereby making the tertiary amine zwitterionic. Then dialyze the reaction solution with deionized water for 24 h to remove residual potassium permanganate. Finally, freeze-dry the aqueous solution for 24 h to obtain a solid oxide, namely the zwitterionic material.

[0036] (2) Prepare a sodium hydroxide solution with a mass fraction of 2%, immerse the polyacrylonitrile porous membrane in the prepared solution, and control the temperature at 25 °C. After deposition for 2 h, take out the membrane sheet, absorb the excess solution with filter paper, and air-dry it naturally to obtain a polyacrylonitrile substrate membrane.

[0037] (3) Add the zwitterionic material prepared in (1) into deionized water and stir evenly to obtain aqueous solution 1, where the mass fraction of the zwitterionic material in aqueous solution 1 is 1%; add piperazine (PIP) into deionized water and stir evenly to obtain aqueous solution 2, where the mass fraction of piperazine in aqueous solution 2 is 1%. Mix aqueous solution 1 and aqueous solution 2 in a ratio of 0.2:1 to obtain the final aqueous solution. Dissolve 1,3,5-benzenetricarbonyl chloride in an organic solvent to prepare an oil-phase solution, where the mass fraction of 1,3,5-benzenetricarbonyl chloride in the oil-phase solution is 0.2%. Pour the aqueous solution onto the surface of the substrate membrane. After 5 min, use industrial wiping paper to wipe off the excess aqueous solution, and then pour in the oil-phase solution to carry out an interfacial polymerization reaction. After 2 min, pour out the excess oil-phase solution. After heat treatment at 80 °C for 15 min, a nanofiltration membrane is obtained.

[0038] Perform performance tests on the nanofiltration membrane prepared in Example 3. The water flux of the nanofiltration membrane is 26.3 L·m -2 ·h -1 ·bar -1 , the sucrose rejection rate is 91.2%, the glucose permeability is 99.4%, and the membrane flux recovery rate is as high as 93%. Example

[0039] (1) Add 8 g of N,N,N',N'-tetraethyldivinyltriamine into 23 mL of deionized water, and then slowly drop 7 mL of 30% hydrogen peroxide solution under stirring at 500 rpm to initiate the oxidation of the tertiary amine group in tris(2-aminoethyl)amine, thereby making the tertiary amine zwitterionic. Then dialyze the reaction solution with deionized water for 24 h to remove residual hydrogen peroxide. Finally, freeze-dry the aqueous solution for 24 h to obtain a solid oxide, i.e., the zwitterionic material.

[0040] (2) Prepare an adipic acid solution with a mass fraction of 2%. Immerse the polyacrylonitrile porous membrane in the prepared solution and control the temperature at 25 °C. After deposition for 2 h, take out the membrane sheet, blot off the excess solution with filter paper, and air-dry it naturally to obtain a polyacrylonitrile substrate membrane.

[0041] (3) Add the zwitterionic material prepared in (1) to deionized water and stir evenly to obtain aqueous solution 1, where the mass fraction of the zwitterionic material in aqueous solution 1 is 1%; add piperazine (PIP) to deionized water and stir evenly to obtain aqueous solution 2, where the mass fraction of piperazine in aqueous solution 2 is 1%. Mix aqueous solution 1 and aqueous solution 2 in a ratio of 0.1:1 to obtain the final aqueous solution. Dissolve 1,3,5-benzenetricarbonyl chloride in an organic solvent to prepare an oil-phase solution, where the mass fraction of 1,3,5-benzenetricarbonyl chloride in the oil-phase solution is 0.1%. Pour the aqueous solution onto the surface of the base membrane. After maintaining for 3 min, use industrial wiping paper to wipe off the excess aqueous solution, and then pour in the oil-phase solution to carry out an interfacial polymerization reaction. After reacting for 1 min, pour out the excess oil-phase solution, and obtain a nanofiltration membrane after heat treatment at 60 °C for 30 min.

[0042] Perform performance tests on the nanofiltration membrane prepared in Example 4. The water flux of the nanofiltration membrane is 24.5 L·m -2 ·h -1 ·bar -1 , the sucrose rejection rate is 90%, the glucose permeation rate is 96%, and the membrane flux recovery rate is as high as 98%. Example

[0043] (1) Add 8 g of N,N-diethyldivinyltriamine to 24 mL of deionized water, and then slowly drop 8 mL of 30% adipic acid solution under stirring at 500 rpm to initiate the oxidation of the tertiary amine group in tris(2-aminoethyl)amine, thereby making the tertiary amine zwitterionic. Then dialyze the reaction solution with deionized water for 24 h to remove residual hydrogen peroxide. Finally, freeze-dry the aqueous solution for 24 h to obtain a solid oxide, namely the zwitterionic material.

[0044] (2) Prepare an alendronic acid solution with a mass fraction of 1%, immerse the polyacrylonitrile porous membrane in the prepared solution, and control the temperature at 40 °C. After depositing for 2 h, take out the membrane sheet, blot off the excess solution with filter paper, and air-dry it naturally to obtain a polyacrylonitrile base membrane.

[0045] (3) Add the zwitterionic material prepared in (1) to deionized water and stir evenly to obtain aqueous solution 1, where the mass fraction of the zwitterionic material in aqueous solution 1 is 1%; add piperazine (PIP) to deionized water and stir evenly to obtain aqueous solution 2, where the mass fraction of piperazine in aqueous solution 2 is 1%. Mix aqueous solution 1 and aqueous solution 2 in a 1:1 ratio to obtain the final aqueous solution. Dissolve 1,3,5-benzenetricarbonyl chloride in an organic solvent to prepare an oil-phase solution, where the mass fraction of 1,3,5-benzenetricarbonyl chloride in the oil-phase solution is 0.3%. Pour the aqueous solution onto the surface of the substrate membrane. After 2 - 5 min, use industrial wiping paper to wipe off the excess aqueous solution, then pour in the oil-phase solution to carry out an interfacial polymerization reaction. After 1 min, pour out the excess oil-phase solution. After heat treatment at 50 °C for 20 min, a nanofiltration membrane is obtained.

[0046] Perform performance tests on the nanofiltration membrane prepared in Example 5. The water flux of the nanofiltration membrane is 21.5 L·m -2 ·h -1 ·bar -1 , the sucrose rejection rate is 91.3%, the glucose permeability is 93.0%, and the membrane flux recovery rate is as high as 90%. Example

[0047] (1) Add 5 g of tris(2-aminoethyl)amine to 23 mL of deionized water, and then slowly add 6 mL of 30% potassium permanganate solution under stirring at 500 rpm to initiate the oxidation of the tertiary amine group in tris(2-aminoethyl)amine, thereby making the tertiary amine zwitterionic. Then dialyze the reaction solution with deionized water for 24 h to remove residual potassium permanganate. Finally, freeze-dry the aqueous solution for 24 h to obtain a solid oxide, that is, the zwitterionic material.

[0048] (2) Prepare a sodium hydroxide solution with a mass fraction of 5%, immerse the polyacrylonitrile porous membrane in the prepared solution, and control the temperature at 25 °C. After deposition for 2 h, take out the membrane sheet, use filter paper to absorb the excess solution, and air-dry it naturally to obtain a polyacrylonitrile substrate membrane.

[0049] (3) Add the zwitterionic material prepared in (1) to deionized water and stir evenly to obtain aqueous solution 1, where the mass fraction of the zwitterionic material in aqueous solution 1 is 1%; add piperazine (PIP) to deionized water and stir evenly to obtain aqueous solution 2, where the mass fraction of piperazine in aqueous solution 2 is 1%. Mix aqueous solution 1 and aqueous solution 2 in a ratio of 0.5:1 to obtain the final aqueous solution. Dissolve 1,3,5-benzenetricarbonyl chloride in an organic solvent to prepare an oil-phase solution, where the mass fraction of 1,3,5-benzenetricarbonyl chloride in the oil-phase solution is 0.3%. Pour the aqueous solution onto the surface of the substrate membrane. After maintaining for 3 min, use industrial wiping paper to wipe off the excess aqueous solution, and then pour in the oil-phase solution to carry out an interfacial polymerization reaction. After reacting for 1 min, pour out the excess oil-phase solution, and obtain a nanofiltration membrane after heat treatment at 50 °C for 30 min.

[0050] Perform performance tests on the nanofiltration membrane prepared in Example 6. The water flux of the nanofiltration membrane is 23.2 L·m -2 ·h -1 ·bar -1 , the sucrose rejection rate is 91.7%, the glucose permeation rate is 94.1%, and the membrane flux recovery rate is as high as 92%. Example

[0051] (1) Add 8 g of N,N,N',N'-tetraethyldivinyltriamine to 25 mL of deionized water, and then slowly drop 7 mL of 30% hydrogen peroxide solution under stirring at 500 rpm to initiate the oxidation of the tertiary amine group in tris(2-aminoethyl)amine, thereby making the tertiary amine zwitterionic. Then dialyze the reaction solution with deionized water for 24 h to remove residual hydrogen peroxide. Finally, freeze-dry the aqueous solution for 24 h to obtain a solid oxide, that is, the zwitterionic material.

[0052] (2) Prepare an alendronic acid solution with a mass fraction of 0.5%, immerse the polyacrylonitrile porous membrane in the prepared solution, and control the temperature at 60 °C. After depositing for 2 h, take out the membrane sheet, absorb the excess solution with filter paper, and air-dry it naturally to obtain a polyacrylonitrile substrate membrane.

[0053] (3) Add the zwitterionic material prepared in (1) to deionized water and stir evenly to obtain aqueous solution 1, where the mass fraction of the zwitterionic material in aqueous solution 1 is 1%; add piperazine (PIP) to deionized water and stir evenly to obtain aqueous solution 2, where the mass fraction of piperazine in aqueous solution 2 is 1%. Mix aqueous solution 1 and aqueous solution 2 in a ratio of 0.2:1 to obtain the final aqueous solution. Dissolve 1,3,5-benzenetricarbonyl chloride in an organic solvent to prepare an oil-phase solution, where the mass fraction of 1,3,5-benzenetricarbonyl chloride in the oil-phase solution is 0.15%. Pour the aqueous solution onto the surface of the base membrane. After maintaining for 2 min, use industrial wiping paper to wipe off the excess aqueous solution, and then pour in the oil-phase solution to carry out an interfacial polymerization reaction. After reacting for 2 min, pour out the excess oil-phase solution, and obtain a nanofiltration membrane after heat treatment at 60 °C for 10 min.

[0054] Perform performance tests on the nanofiltration membrane prepared in Example 7. The water flux of the nanofiltration membrane is 28.4 L·m -2 ·h -1 ·bar -1 , the sucrose rejection rate is 96.5%, the glucose permeability is 92.6%, and the membrane flux recovery rate is as high as 94%. Example

[0055] (1) Add 10 g of N,N-diethyldivinyltriamine to 24 mL of deionized water, and then slowly drop 5 mL of 30% potassium dichromate solution under stirring at 500 rpm to initiate the oxidation of the tertiary amine group in tris(2-aminoethyl)amine, thereby making the tertiary amine zwitterionic. Then dialyze the reaction solution with deionized water for 24 h to remove the residual potassium dichromate. Finally, freeze-dry the aqueous solution for 24 h to obtain a solid oxide, that is, the zwitterionic material.

[0056] (2) Prepare an ethylenediaminetetraacetic acid solution with a mass fraction of 5%. Immerse the polyacrylonitrile porous membrane in the prepared solution and control the temperature at 25 °C. After depositing for 2 h, take out the membrane sheet, blot off the excess solution with filter paper, and air-dry it naturally to obtain a polyacrylonitrile base membrane.

[0057] (3) Add the zwitterionic material prepared in (1) to deionized water and stir evenly to obtain aqueous solution 1, where the mass fraction of the zwitterionic material in aqueous solution 1 is 1%; add piperazine (PIP) to deionized water and stir evenly to obtain aqueous solution 2, where the mass fraction of piperazine in aqueous solution 2 is 1%. Mix aqueous solution 1 and aqueous solution 2 in a ratio of 0.1:1 to obtain the final aqueous solution. Dissolve 1,3,5-benzenetricarbonyl chloride in an organic solvent to prepare an oil-phase solution, where the mass fraction of 1,3,5-benzenetricarbonyl chloride in the oil-phase solution is 0.1%. Pour the aqueous solution onto the surface of the base membrane. After maintaining for 3 min, use industrial wiping paper to wipe off the excess aqueous solution, and then pour in the oil-phase solution to carry out an interfacial polymerization reaction. After reacting for 1 min, pour out the excess oil-phase solution. After heat treatment at 60 °C for 20 min, a nanofiltration membrane is obtained.

[0058] Perform performance tests on the nanofiltration membrane prepared in Example 8. The water flux of the nanofiltration membrane is 27.2 L·m -2 ·h -1 ·bar -1 , the sucrose rejection rate is 92.6%, the glucose permeability is 94.5%, and the membrane flux recovery rate is as high as 92%.

[0059] Comparative Example 1: Add anhydrous piperazine to deionized water and stir evenly to obtain a 1 wt% aqueous solution; dissolve 1,3,5-benzenetricarbonyl chloride in n-hexane to prepare a 0.1 wt% oil-phase solution. Pour the aqueous solution onto the surface of the support layer polyethersulfone ultrafiltration membrane. After maintaining for 2 min, remove the excess aqueous solution, and then pour in the oil-phase solution to carry out an interfacial polymerization reaction. After reacting for 1 min, remove the excess oil-phase solution. After heat treatment at 60 °C for 20 min, a nanofiltration membrane is obtained.

[0060] Perform performance tests on the prepared nanofiltration membrane. The water flux of the nanofiltration membrane is 14.8 L·m -2 ·h -1 ·bar -1 , the sucrose rejection rate is 90.1%, the glucose permeability is 83.7%, and the membrane flux recovery rate is 70%.

Claims

1. A high-throughput nanofiltration membrane for separating monosaccharides and disaccharides and a preparation method thereof, characterized in that, It includes the following steps: (1) Synthesis of zwitterionic materials Dissolve the tertiary amine compound in deionized water, slowly add an oxidant dropwise under stirring at 500 rpm to initiate the oxidation reaction of the tertiary amino group to obtain a zwitterionized solution; dialyze the reaction solution with deionized water for 24 h to remove the residual oxidant, and then freeze-dry to obtain a solid zwitterionic material; wherein, the dosage of the oxidant is 10-20% of the total mass of the reaction system, the dosage of the tertiary amine compound is 5-10%, and the balance is deionized water; (2) Pretreatment of polyacrylonitrile-based membrane Prepare an acid-base reagent solution with a mass fraction of 0.5-5%, soak the polyacrylonitrile porous membrane in this solution, control the temperature at 25-60 °C, take out the membrane sheet after reacting for 2 h, blot the excess solution with filter paper, and air-dry naturally to obtain a hydrolytically modified polyacrylonitrile-based membrane; (3) Preparation of nanofiltration membrane by interfacial polymerization Add the zwitterionic material prepared in step (1) to deionized water to prepare an aqueous solution 1 with a mass fraction of 1%; add piperazine (PIP) to deionized water to prepare an aqueous solution 2 with a mass fraction of 1%; mix the aqueous solution 1 and the aqueous solution 2 in proportion to obtain the final aqueous solution; dissolve 1,3,5-benzenetricarbonyl chloride in an organic solvent to prepare an organic phase solution with a mass fraction of 0.1-0.3%; pour the mixed aqueous solution onto the surface of the base membrane prepared in step (2), let it stand for 2-5 min and then wipe off the excess aqueous solution, and then pour in the organic phase solution for interfacial polymerization reaction. After reacting for 1-3 min, pour out the excess organic phase solution, and heat-treat at 50-80 °C for 10-30 min to obtain the high-flux nanofiltration membrane.

2. The preparation method according to claim 1, characterized in that, The tertiary amine compound described in step (1) is one of tris(2-aminoethyl)amine, N,N,N',N'-tetraethyldiethylenetriamine, and N,N-diethyldiethylenetriamine.

3. The preparation method according to claim 1, characterized in that, The oxidant in step (1) is one of hydrogen peroxide, potassium permanganate, and potassium dichromate.

4. The preparation method according to claim 1, wherein, The acid-base reagent in step (2) is one of ethylenediaminetetraacetic acid, alendronic acid, adipic acid, and sodium hydroxide.

5. The preparation method according to claim 1, characterized in that The mixing ratio of the aqueous solution 1 and the aqueous solution 2 in step (3) is 0.1:1, 0.2:1, 0.5:1, or 1:

1.

6. A high-throughput nanofiltration membrane prepared by the method according to any one of claims 1-5, characterized in that, The pure water flux of the nanofiltration membrane ≥ 20 L·m -2 ·h -1 ·bar -1 , the rejection rate of sucrose ≥ 90%, and the permeation rate of glucose ≥ 93%.

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