CN108905641B - Nanofiltration membrane and preparation method thereof - Google Patents
Nanofiltration membrane and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a preparation method of a nanofiltration membrane, which comprises the following steps: preparing a polymeric polythiophene triazine polycondensate, (di) modifying the surface of an aluminum oxide nanotube, (tri) preparing a membrane casting solution, and (tetra) preparing a nanofiltration membrane. The invention also discloses the nanofiltration membrane prepared by the preparation method of the nanofiltration membrane. The nanofiltration membrane disclosed by the invention has the advantages of stronger hydrophilicity, higher water flux and ion exchange capacity, stronger pollution resistance, high solvent permeability and high solute rejection rate.
Description
Technical Field
The invention relates to the technical field of membrane filtration, in particular to a nanofiltration membrane and a preparation method thereof.
Background
In recent years, the membrane separation process has been widely used in the technical fields of seawater purification, sewage treatment, pure water production, etc. as a novel high separation, concentration, purification, and purification technology. The membranes used in the membrane separation process must have characteristics such that a part of the substances can pass through and a part of the substances cannot pass through, and generally include four major types, namely microfiltration, ultrafiltration, nanofiltration and reverse osmosis. Nanofiltration membranes are a novel membrane separation technology between ultrafiltration and reverse osmosis. The method is technically characterized in that selective permeation of dissolved components is realized through steric hindrance and electrostatic action, and the pressure of an operating system is far lower than that of a reverse osmosis process, so that selective separation of substances can be realized.
Conventional nanofiltration membranes are flat sheets containing a thick support layer that provides sufficient mechanical strength to withstand high pressures in nanofiltration applications. On the other hand, the thick layer has a great transport resistance, thus hindering solvent permeation, and in addition, it has a low solute rejection rate for ions and compounds having a low molecular weight.
The application publication number is CN 102091539A, Chinese invention patent discloses a preparation method of a nanofiltration membrane, wherein cellulose and polysulfone are taken according to the weight part ratio of 3:97.8, dimethylacetamide DMAC is taken as a solvent, aqueous solution of dilute NaSO3 is taken as an additive according to the weight part ratio of 18, and lithium nitrate is taken as a swelling agent; putting the substances into a reaction kettle, stirring and dissolving, filtering under the pressure of 0.2MPa, removing impurities, removing bubbles to prepare a spinning solution with the temperature of 40 ℃ and the vacuum degree of 0.098 MPa; spinning the prepared spinning stock solution by a dry-jet wet spinning method to prepare a hollow nanofiltration membrane, stretching to volatilize the solvent, immersing into a Dimethylacetamide (DMAC) aqueous solution with the weight ratio of 2 parts, solidifying, preserving pores, removing the solvent and a coagulant in the nanofiltration membrane, and shaping the nanofiltration membrane to prepare a finished product; the nanofiltration membrane prepared by the method can separate harmful substances, bacteria and viruses in water, and the water is alkalescent and is beneficial to absorption by human bodies; promoting metabolism and enhancing immunity. But the solvent resistance thereof can be further improved.
Therefore, a nanofiltration membrane with better transmission performance and higher separation performance, more stable structure and higher mechanical strength is developed, meets the market demand, and has wide market value and application prospect.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides the nanofiltration membrane and the preparation method thereof, the preparation method is simple and easy to implement, the raw materials are easy to obtain, the dependence on equipment is not high, the preparation cost is low, and the nanofiltration membrane is suitable for large-scale production, and has the advantages of stronger hydrophilicity, higher water flux and ion exchange capacity, stronger pollution resistance, high solvent permeability and high solute rejection rate.
In order to achieve the purpose of the invention, the technical scheme adopted by the invention is as follows: a preparation method of a nanofiltration membrane comprises the following steps:
preparation of polymeric polythienyltriazine polycondensate: adding 2, 5-thiophenedicarboxylic acid, 2-vinyl-4, 6-diamino-1, 3, 5-triazine and a polymerization inhibitor into a high-boiling-point solvent, reacting at 160-180 ℃ for 2-3 hours under normal pressure, adding 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and 4-dimethylaminopyridine into the solvent, heating to 200-220 ℃ for primary polycondensation for 4-6 hours, transferring the reaction liquid into a reaction kettle, vacuumizing (500Pa), heating to 240-260 ℃ for secondary polycondensation for 6-8 hours, precipitating in ethanol, performing suction filtration, washing with dichloromethane for 3-5 times, and performing rotary evaporation to remove dichloromethane to obtain a polymeric polythienyltriazine polycondensate;
II, surface modification of the aluminum oxide nanotube: dispersing the alumina nanotube in ethanol to form a dispersion liquid, adding N- (3-triethoxysilylpropyl) glucamide, stirring at 50-60 ℃ for reacting for 8-10 hours, then carrying out suction filtration, and then placing in a vacuum drying oven for drying for 15-18 hours to obtain the surface-modified alumina nanotube;
III, preparing a casting solution: dissolving the polymerized polythiophene triazine polycondensate prepared in the step I, bis (vinylsulfonyl) methane, N' -vinyl bisacrylamide, [3- (methacrylamido) propyl ] dimethyl (3-thiopropyl) ammonium hydroxide inner salt and an initiator in N-methyl pyrrolidone, adding the surface-modified aluminum oxide nanotube prepared in the step II, stirring at room temperature for 1-2 hours, and filtering by using a polytetrafluoroethylene filter membrane with the aperture of 0.1-0.3 mu m to obtain a casting membrane solution;
IV, preparation of a nanofiltration membrane: scraping the casting solution prepared in the step III on a base material with a smooth surface to form a thin-layer liquid film; after the solvent in the thin-layer liquid film is volatilized for a certain time, the thin-layer liquid film is immersed in a hydrogel bath at the temperature of 60-75 ℃ for 3-5 hours, and then the thin-layer liquid film is subjected to phase conversion to form a film.
Preferably, the mass ratio of the 2, 5-thiophenedicarboxylic acid, the 2-vinyl-4, 6-diamino-1, 3, 5-triazine, the polymerization inhibitor, the high-boiling-point solvent, the 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and the 4-dimethylaminopyridine in the step I is 1.26:1:0.3 (10-15: 0.4: 0.3.
Preferably, the polymerization inhibitor is selected from one or more of hydroquinone, 1, 4-naphthoquinone and tetrachloronaphthoquinone; the high boiling point solvent is selected from one or more of dimethyl sulfoxide, N-dimethylformamide and N-methylpyrrolidone.
Preferably, the mass ratio of the alumina nanotubes, the ethanol and the N- (3-triethoxysilylpropyl) glucamide in the step II is (3-5): (10-15): 1.
Furthermore, the mass ratio of the polymerized polythiophene triazine polycondensate to the bis (vinylsulfonyl) methane to the N, N' -vinyl bisacrylamide to the [3- (methacrylamido) propyl ] dimethyl (3-thiopropyl) ammonium hydroxide inner salt to the initiator to the N-methylpyrrolidone to the surface-modified alumina nanotube is 2:0.5:0.2:1 (0.02-0.04) to (12-15) to (0.4-0.8).
Preferably, the initiator is selected from one or more of azobisisobutyronitrile and azobisisoheptonitrile.
Preferably, the alumina nanotubes are prepared in advance, and the preparation method refers to the Chinese patent CN 103073035A.
A nanofiltration membrane is prepared by the preparation method of the nanofiltration membrane.
Adopt the produced beneficial effect of above-mentioned technical scheme to lie in:
1) the nanofiltration membrane provided by the invention has the advantages of simple and feasible preparation method, easily available raw materials, low dependence on equipment and low preparation cost, and is suitable for large-scale production.
2) The nanofiltration membrane provided by the invention overcomes the technical problems of low solvent permeability, low solute rejection rate to ions and compounds with low molecular weight and poor solvent resistance of the traditional nanofiltration membrane in the prior art, and has the advantages of strong hydrophilicity, high water flux and ion exchange capacity, strong pollution resistance, high solvent permeability and high solute rejection rate.
3) The nanofiltration membrane provided by the invention adopts the polymeric polythiophene triazine polycondensate as a membrane material, has good membrane forming property and good weather resistance and antibacterial property, introduces the zwitterion structure, and improves the acid and alkali resistance, the microbial corrosion resistance and the chlorine and other oxidizing substance resistance of the nanofiltration membrane under the synergistic effect with other components and structures through reasonable compatibility of the components, so that the rejection rate of the salts of the membrane is higher, and the colloid and suspended matter pollution resistance is higher; the introduction of polyhydroxy, amino, ionic group and sulfonic group structure can raise the hydrophilicity of the membrane and thus raise the water flux of the membrane.
4) According to the nanofiltration membrane provided by the invention, the surface-modified aluminum oxide nanotube is added, the atomically smooth inner surface of the nanotube can greatly reduce the adsorption force and the friction force when fluid passes through, and the inner hole of the nanotube is the nanofiltration membrane of a transportation channel, so that high permeation rate and high selectivity can be obtained at the same time; on the other hand, the mechanical property and the oxidation resistance of the film can be further improved.
Detailed Description
In order to make the technical solutions of the present invention better understood and make the above features, objects, and advantages of the present invention more comprehensible, the present invention is further described with reference to the following examples. The examples are intended to illustrate the invention only and are not intended to limit the scope of the invention.
The alumina nanotubes described in the following examples of the present invention were prepared in advance by the method described in the Chinese patent of invention CN103073035A, and other raw materials were obtained from Shanghai spring Xin import and export trade Co.
The pure water flux and rejection rate of the nanofiltration membrane are measured by a membrane performance evaluation instrument (MPY-II type membrane performance evaluation instrument of Hangzhou Water treatment center of national ocean office), the test condition is 0.2Mpa, and the effective filtration area of the membrane is 22.22cm2。
Example 1
A preparation method of a nanofiltration membrane comprises the following steps:
preparation of polymeric polythienyltriazine polycondensate: adding 12.6g of 2, 5-thiophenedicarboxylic acid, 10g of 2-vinyl-4, 6-diamino-1, 3, 5-triazine and 3g of hydroquinone into 100g of dimethyl sulfoxide, reacting at 160 ℃ under normal pressure for 2 hours, adding 4g of 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and 3g of 4-dimethylaminopyridine into the dimethyl sulfoxide, heating to 200 ℃, carrying out primary polycondensation for 4 hours, transferring the reaction solution into a reaction kettle, vacuumizing (500Pa), heating to 240 ℃, carrying out polycondensation for 6 hours, precipitating in ethanol, carrying out suction filtration, washing with dichloromethane for 3 times, and carrying out rotary evaporation to remove the dichloromethane to obtain a polymeric polythienyltriazine polycondensate;
II, surface modification of the aluminum oxide nanotube: dispersing 30g of alumina nano tube in 100g of ethanol to form dispersion, then adding 10g of N- (3-triethoxysilylpropyl) glucamide, stirring and reacting at 50 ℃ for 8 hours, then carrying out suction filtration, and then placing in a vacuum drying oven to dry for 15 hours to obtain the surface-modified alumina nano tube;
III, preparing a casting solution: dissolving 20g of the polymeric polythienyltriazine polycondensate prepared in the step I, 5g of bis (vinylsulfonyl) methane, 2g of N, N' -vinyl bisacrylamide, 10g of [3- (methacrylamido) propyl ] dimethyl (3-thiopropyl) ammonium hydroxide inner salt and 0.2g of azobisisobutyronitrile into 120g of N-methylpyrrolidone, adding 4g of the surface-modified aluminum oxide nanotube prepared in the step II, stirring at room temperature for 1 hour, and filtering with a polytetrafluoroethylene filter membrane with the aperture of 0.1 mu m to obtain a casting membrane solution;
IV, preparation of a nanofiltration membrane: scraping the casting solution prepared in the step III on a base material with a smooth surface to form a thin-layer liquid film; after the solvent in the thin-layer liquid film is volatilized for a certain time, the thin-layer liquid film is immersed in a 60 ℃ hydrogel bath for 3 hours, and then phase conversion is carried out to form a film.
A nanofiltration membrane is prepared by the preparation method of the nanofiltration membrane.
Through tests, the pure water flux of the nanofiltration membrane of the embodiment is 93.5L/m2h, the retention rate on magnesium chloride is 98.2%.
Example 2
A preparation method of a nanofiltration membrane comprises the following steps:
preparation of polymeric polythienyltriazine polycondensate: adding 12.6g of 2, 5-thiophenedicarboxylic acid, 10g of 2-vinyl-4, 6-diamino-1, 3, 5-triazine and 3g of 1, 4-naphthoquinone into 115g of N, N-dimethylformamide, reacting for 2.3 hours at the temperature of 166 ℃ under normal pressure, adding 4g of 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and 3g of 4-dimethylaminopyridine into the obtained mixture, heating to 205 ℃, carrying out primary polycondensation for 4.5 hours, transferring the reaction solution into a reaction kettle, vacuumizing (500Pa), heating to 245 ℃, carrying out polycondensation for 6.5 hours, precipitating in ethanol, carrying out suction filtration, washing for 4 times by using dichloromethane, and carrying out rotary evaporation to remove the dichloromethane to obtain a polymeric polythienyltriazine polycondensate;
II, surface modification of the aluminum oxide nanotube: dispersing 35g of alumina nano tube in 120g of ethanol to form a dispersion, adding 10g of N- (3-triethoxysilylpropyl) glucamide, stirring at 53 ℃ to react for 8.5 hours, carrying out suction filtration, and then placing in a vacuum drying oven to dry for 16 hours to obtain the surface-modified alumina nano tube;
III, preparing a casting solution: dissolving 20g of the polymerized polythienyltriazine polycondensate prepared in the step I, 5g of bis (vinylsulfonyl) methane, 2g of N, N' -vinyl bisacrylamide, 10g of [3- (methacrylamido) propyl ] dimethyl (3-thiopropyl) ammonium hydroxide inner salt and 0.25g of azobisisoheptonitrile in 130g of N-methylpyrrolidone, adding 5g of the surface-modified aluminum oxide nanotube prepared in the step II, stirring at room temperature for 1.3 hours, and filtering with a polytetrafluoroethylene filter membrane with the aperture of 0.15 mu m to obtain a casting membrane solution;
IV, preparation of a nanofiltration membrane: scraping the casting solution prepared in the step III on a base material with a smooth surface to form a thin-layer liquid film; after the solvent in the thin-layer liquid film is volatilized for a certain time, the thin-layer liquid film is immersed in a hydrogel bath at 63 ℃ for 3.5 hours, and then phase conversion is carried out to form a film.
A nanofiltration membrane is prepared by the preparation method of the nanofiltration membrane.
Through tests, the pure water flux of the nanofiltration membrane of the embodiment is 94.1L/m2h, the retention rate on magnesium chloride is 98.5%.
Example 3
A preparation method of a nanofiltration membrane comprises the following steps:
preparation of polymeric polythienyltriazine polycondensate: adding 12.6g of 2, 5-thiophenedicarboxylic acid, 10g of 2-vinyl-4, 6-diamino-1, 3, 5-triazine and 3g of tetrachloronaphthoquinone into 125g of N-methylpyrrolidone, reacting at 168 ℃ under normal pressure for 2.5 hours, adding 4g of 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and 3g of 4-dimethylaminopyridine into the mixture, heating to 210 ℃, carrying out primary polycondensation for 5 hours, transferring the reaction solution into a reaction kettle, vacuumizing (500Pa), heating to 250 ℃, carrying out polycondensation for 7 hours, precipitating in ethanol, carrying out suction filtration, washing for 4 times by using dichloromethane, and carrying out rotary evaporation to remove the dichloromethane to obtain a polymeric polythienyltriazine polycondensate;
II, surface modification of the aluminum oxide nanotube: dispersing 40g of alumina nano tube in 132g of ethanol to form a dispersion, adding 10g of N- (3-triethoxysilylpropyl) glucamide, stirring at 55 ℃ for reaction for 9 hours, carrying out suction filtration, and then placing in a vacuum drying oven for drying for 16.5 hours to obtain the surface-modified alumina nano tube;
III, preparing a casting solution: dissolving 20g of the polymeric polythienyltriazine polycondensate prepared in the step I, 5g of bis (vinylsulfonyl) methane, 2g of N, N' -vinyl bisacrylamide, 10g of [3- (methacrylamido) propyl ] dimethyl (3-thiopropyl) ammonium hydroxide inner salt and 0.3g of azobisisobutyronitrile into 135g of N-methylpyrrolidone, adding 6g of the surface-modified aluminum oxide nanotube prepared in the step II, stirring at room temperature for 1.5 hours, and filtering with a polytetrafluoroethylene filter membrane with the aperture of 0.2 mu m to obtain a casting membrane solution;
IV, preparation of a nanofiltration membrane: scraping the casting solution prepared in the step III on a base material with a smooth surface to form a thin-layer liquid film; after the solvent in the thin-layer liquid film is volatilized for a certain time, the thin-layer liquid film is immersed in a hydrogel bath at 69 ℃ for 4.2 hours, and then phase conversion is carried out to form a film.
A nanofiltration membrane is prepared by the preparation method of the nanofiltration membrane.
Through tests, the pure water flux of the nanofiltration membrane of the embodiment is 94.5L/m2h, the retention rate on magnesium chloride is 98.9%.
Example 4
A preparation method of a nanofiltration membrane comprises the following steps:
preparation of polymeric polythienyltriazine polycondensate: adding 12.6g of 2, 5-thiophenedicarboxylic acid, 10g of 2-vinyl-4, 6-diamino-1, 3, 5-triazine and 3g of polymerization inhibitor into 145g of high-boiling-point solvent, reacting at 175 ℃ under normal pressure for 2.8 hours, adding 4g of 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and 3g of 4-dimethylaminopyridine into the mixture, heating to 215 ℃ for primary polycondensation reaction for 5.5 hours, transferring the reaction solution into a reaction kettle, vacuumizing (500Pa), heating to 255 ℃, performing polycondensation reaction for 7.5 hours, precipitating in ethanol, performing suction filtration, washing with dichloromethane for 5 times, and performing rotary evaporation to remove dichloromethane to obtain a polymeric polythienyltriazine polycondensate; the polymerization inhibitor is a mixture formed by mixing hydroquinone, 1, 4-naphthoquinone and tetrachloronaphthoquinone according to the mass ratio of 1:2: 1; the high-boiling-point solvent is a mixture formed by mixing dimethyl sulfoxide, N-dimethylformamide and N-methylpyrrolidone according to the mass ratio of 2:3: 1;
II, surface modification of the aluminum oxide nanotube: dispersing 45g of alumina nano tube in 145g of ethanol to form a dispersion, adding 10g of N- (3-triethoxysilylpropyl) glucamide, stirring at 58 ℃ for reaction for 9.5 hours, carrying out suction filtration, and then placing in a vacuum drying oven for drying for 17.5 hours to obtain the surface-modified alumina nano tube;
III, preparing a casting solution: dissolving 20g of the polymerized polythienyltriazine polycondensate prepared in the step I, 5g of bis (vinylsulfonyl) methane, 2g of N, N' -vinyl bisacrylamide, 10g of [3- (methacrylamido) propyl ] dimethyl (3-thiopropyl) ammonium hydroxide inner salt and 0.35g of initiator in 148g of N-methylpyrrolidone, adding 7.5g of the surface-modified aluminum oxide nanotube prepared in the step II, stirring at room temperature for 1.8 hours, and filtering with a polytetrafluoroethylene filter membrane with the aperture of 0.25 mu m to obtain a casting membrane solution; the initiator is a mixture formed by mixing azodiisobutyronitrile and azodiisoheptonitrile according to the mass ratio of 3: 5;
IV, preparation of a nanofiltration membrane: scraping the casting solution prepared in the step III on a base material with a smooth surface to form a thin-layer liquid film; after the solvent in the thin-layer liquid film is volatilized for a certain time, the thin-layer liquid film is immersed in a hydrogel bath at 73 ℃ for 4.5 hours, and then phase conversion is carried out to form a film.
A nanofiltration membrane is prepared by the preparation method of the nanofiltration membrane.
Through tests, the pure water flux of the nanofiltration membrane of the embodiment is 95.2L/m2h, the retention rate of magnesium chloride is 99.3%.
Example 5
A preparation method of a nanofiltration membrane comprises the following steps:
preparation of polymeric polythienyltriazine polycondensate: adding 12.6g of 2, 5-thiophenedicarboxylic acid, 10g of 2-vinyl-4, 6-diamino-1, 3, 5-triazine and 3g of 1, 4-naphthoquinone into 150g of dimethyl sulfoxide, reacting at 180 ℃ for 3 hours under normal pressure, adding 4g of 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and 3g of 4-dimethylaminopyridine into the obtained mixture, heating to 220 ℃, carrying out primary polycondensation for 6 hours, transferring the reaction solution into a reaction kettle, vacuumizing (500Pa), heating to 260 ℃, carrying out polycondensation for 8 hours, precipitating in ethanol, carrying out suction filtration, washing for 5 times by using dichloromethane, and carrying out rotary evaporation to remove the dichloromethane to obtain a polymeric polythienyltriazine polycondensate;
II, surface modification of the aluminum oxide nanotube: dispersing 50g of alumina nano tube in 150g of ethanol to form a dispersion, adding 10g of N- (3-triethoxysilylpropyl) glucamide, stirring at 60 ℃ for reaction for 10 hours, carrying out suction filtration, and then putting into a vacuum drying oven for drying for 18 hours to obtain the surface-modified alumina nano tube;
III, preparing a casting solution: dissolving 20g of the polymerized polythienyltriazine polycondensate prepared in the step I, 5g of bis (vinylsulfonyl) methane, 2g of N, N' -vinyl bisacrylamide, 10g of [3- (methacrylamido) propyl ] dimethyl (3-thiopropyl) ammonium hydroxide inner salt and 0.4g of azobisisoheptonitrile in 150g of N-methylpyrrolidone, adding 8g of the surface-modified aluminum oxide nanotube prepared in the step II, stirring at room temperature for 2 hours, and filtering by using a polytetrafluoroethylene filter membrane with the aperture of 0.3 mu m to obtain a casting membrane solution;
IV, preparation of a nanofiltration membrane: scraping the casting solution prepared in the step III on a base material with a smooth surface to form a thin-layer liquid film; after the solvent in the thin-layer liquid film is volatilized for a certain time, the thin-layer liquid film is immersed in a hydrogel bath at the temperature of 75 ℃ for 5 hours, and then phase conversion is carried out to form a film.
A nanofiltration membrane is prepared by the preparation method of the nanofiltration membrane.
Through tests, the pure water flux of the nanofiltration membrane of the embodiment is 95.7L/m2h, the retention rate of magnesium chloride is 99.9%.
Comparative example
The composite nanofiltration membrane is prepared by adopting the preparation method disclosed in the invention patent CN105327626B example 1 in China.
Through tests, the pure water flux of the nanofiltration membrane of the comparative example is 93.2L/m2h, the retention rate on magnesium chloride is 96.9%.
According to the test results, the nanofiltration membrane disclosed by the embodiment of the invention has higher pure water flux and higher salt rejection rate.
The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are merely illustrative of the principles of the invention, but that various changes and modifications may be made without departing from the spirit and scope of the invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (8)
1. The preparation method of the nanofiltration membrane is characterized by comprising the following steps:
preparation of polymeric polythienyltriazine polycondensate: adding 2, 5-thiophenedicarboxylic acid, 2-vinyl-4, 6-diamino-1, 3, 5-triazine and a polymerization inhibitor into a high-boiling-point solvent, reacting at 160-180 ℃ for 2-3 hours under normal pressure, adding 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and 4-dimethylaminopyridine into the solvent, heating to 200-220 ℃ for primary polycondensation for 4-6 hours, transferring the reaction liquid into a reaction kettle, vacuumizing to 500Pa, heating to 240-260 ℃ for secondary polycondensation for 6-8 hours, precipitating in ethanol, performing suction filtration, washing with dichloromethane for 3-5 times, and performing rotary evaporation to remove dichloromethane to obtain a polymeric polythienyltriazine polycondensate;
II, surface modification of the aluminum oxide nanotube: dispersing the alumina nanotube in ethanol to form a dispersion liquid, adding N- (3-triethoxysilylpropyl) glucamide, stirring at 50-60 ℃ for reacting for 8-10 hours, then carrying out suction filtration, and then placing in a vacuum drying oven for drying for 15-18 hours to obtain the surface-modified alumina nanotube;
III, preparing a casting solution: dissolving the polymerized polythiophene triazine polycondensate prepared in the step I, bis (vinylsulfonyl) methane, N' -vinyl bisacrylamide, [3- (methacrylamido) propyl ] dimethyl (3-thiopropyl) ammonium hydroxide inner salt and an initiator in N-methyl pyrrolidone, adding the surface-modified aluminum oxide nanotube prepared in the step II, stirring at room temperature for 1-2 hours, and filtering by using a polytetrafluoroethylene filter membrane with the aperture of 0.1-0.3 mu m to obtain a casting membrane solution;
IV, preparation of a nanofiltration membrane: scraping the casting solution prepared in the step III on a base material with a smooth surface to form a thin-layer liquid film; after the solvent in the thin-layer liquid film is volatilized for a certain time, the thin-layer liquid film is immersed in a hydrogel bath at the temperature of 60-75 ℃ for 3-5 hours, and then the thin-layer liquid film is subjected to phase conversion to form a film.
2. The nanofiltration membrane preparation method according to claim 1, wherein in step I, the mass ratio of the 2, 5-thiophenedicarboxylic acid, the 2-vinyl-4, 6-diamino-1, 3, 5-triazine, the polymerization inhibitor, the high boiling point solvent, the 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride and the 4-dimethylaminopyridine is 1.26:1:0.3:10-15:0.4: 0.3.
3. The nanofiltration membrane preparation method according to claim 1, wherein the polymerization inhibitor is one or more selected from hydroquinone, 1, 4-naphthoquinone, and tetrachloronaphthoquinone.
4. The nanofiltration membrane preparation method according to claim 1, wherein the high boiling point solvent is one or more selected from dimethylsulfoxide, N-dimethylformamide and N-methylpyrrolidone.
5. The method for preparing nanofiltration membrane according to claim 1, wherein the mass ratio of the alumina nanotubes to the ethanol to the N- (3-triethoxysilylpropyl) glucamide in the step II is 3-5:10-15: 1.
6. The nanofiltration membrane preparation method according to claim 1, wherein the mass ratio of the polymeric polythienyltriazine polycondensate to bis (vinylsulfonyl) methane to N, N' -vinylbisacrylamide to [3- (methacrylamido) propyl ] dimethyl (3-thiopropyl) ammonium hydroxide to the initiator to N-methylpyrrolidone to the surface-modified alumina nanotubes is 2:0.5:0.2:1:0.02 to 0.04:12 to 15:0.4 to 0.8.
7. The method for preparing nanofiltration membrane according to claim 1, wherein the initiator is one or more selected from azobisisobutyronitrile and azobisisoheptonitrile.
8. A nanofiltration membrane prepared by the method for preparing the nanofiltration membrane of any one of claims 1 to 7.
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