阅读说明：本技术 超滤膜、纳滤膜及其制备和超滤-纳滤可逆转换的方法 (Ultrafiltration membrane, nanofiltration membrane, preparation method thereof and ultrafiltration-nanofiltration reversible conversion method ) 是由 张刚 王晗 杨杰 袁书珊 毛其泽 黄骁 连英甫 严永刚 于 2020-06-02 设计创作，主要内容包括：本发明涉及一种含叔胺结构聚酰胺超滤膜、含叔胺结构聚酰胺纳滤膜及其制备方法,属于高分子材料领域。本发明提供一种聚酰胺分离膜,所述聚酰胺分离膜为含叔胺聚酰胺树脂制得的含叔胺聚酰胺超滤膜。本发明提供了一种新型的超滤分离膜,所得超滤膜通过酸化处理能够转变为纳滤膜；所得纳滤膜通过脱酸处理又可以恢复成超滤膜,进而实现了超滤-纳滤的可逆转换。(The invention relates to a polyamide ultrafiltration membrane containing a tertiary amine structure, a polyamide nanofiltration membrane containing a tertiary amine structure and a preparation method thereof, belonging to the field of high polymer materials. The invention provides a polyamide separation membrane, which is a polyamide ultrafiltration membrane containing tertiary amine prepared from polyamide resin containing tertiary amine. The invention provides a novel ultrafiltration separation membrane, wherein an obtained ultrafiltration membrane can be converted into a nanofiltration membrane through acidification treatment; the nanofiltration membrane can be recovered into an ultrafiltration membrane through deacidification treatment, and then the reversible conversion of ultrafiltration and nanofiltration is realized.)

1. The polyamide separation membrane is characterized by being a tertiary amine-containing polyamide ultrafiltration membrane prepared from tertiary amine-containing polyamide resin.

2. The polyamide separation membrane according to claim 1, wherein the polyamide separation membrane is produced by a method comprising: preparing a membrane casting solution by using a polyamide resin containing tertiary amine, and preparing a polyamide ultrafiltration membrane containing tertiary amine by using the membrane casting solution by adopting the prior art;

further, the polyamide separation membrane is prepared by adopting the following method: adding 16-30 parts of polyamide resin containing tertiary amine and 70-84 parts of solvent into a dissolving kettle, stirring and dissolving at the temperature of 60-200 ℃, centrifuging and filtering after dissolving into a uniform polymer solution, removing solid impurities, and defoaming in vacuum at the temperature of 40-100 ℃ for 2-48 hours to obtain a membrane casting solution; preparing a corresponding flat ultrafiltration membrane or hollow fiber ultrafiltration membrane by using the obtained membrane casting solution;

further, the solvent is any one of 1, 3-dimethyl-2-imidazolidinone, N-methylpyrrolidone, dimethyl sulfoxide, N-dimethylformamide, or N, N-dimethylacetamide.

3. The polyamide separation membrane according to claim 1 or 2, characterized in that the tertiary amine-containing polyamide resin is produced by a method comprising:

dissolving 10-500 parts by weight of aromatic diamine compound, 10-600 parts by weight of tertiary amine-containing diamine compound, 3500-8000 parts by weight of solvent and 50-200 parts by weight of acid-binding agent in a low-temperature reaction kettle filled with 3500-8000 parts by weight of solvent, setting the temperature of the reaction kettle to-10-15 ℃ after the compounds are dissolved and clarified, adding 200-419 parts by weight of aromatic diformyl chloride for 3-5 times, stirring and reacting at-5-25 ℃ for 0.5-10 h, and finally pouring the obtained polymer solution into water while stirring to obtain a tertiary amine-containing polyamide resin linear crude product;

crushing a polyamide resin linear crude product containing tertiary amine, washing the crushed crude product with water and ethanol for 3-5 times, filtering, recovering and recycling filtrate, and drying the collected filter cake at the temperature of 80-120 ℃ for 8-24 hours to obtain purified polyamide resin containing tertiary amine;

further, the aromatic diamine compound has a structural formula of:

at least one of; or:

the aromatic dicarboxylic acid chloride has the structural formula:

at least one of; or:

the solvent is formamide, acetamide, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylformamide, dimethylacetamide, N-methylpropionamide, hexamethylphosphoric triamide, N-methylcaprolactam, N, N-dimethylpropylurea, N, N, N' -tetramethylurea, 1, 3-dimethyl-2-imidazolidinone, N-methylpyrrolidone, N-cyclohexylpyrrolidone, 2-pyrrolidone, quinoline, isoquinoline, diphenylsulfone, benzophenone, sulfolane, dimethylsulfone, dimethylsulfoxide, 2, 4-dimethylsulfolane, N-phenylmorpholine, dimethyl phthalate, diethyl phthalate, 1-methyl-3-propylimidazole bromide salt, 1-methyl-3-isopropylimidazole bromide salt or 1, any one of 3-dipropylimidazole bromide salt; or:

the acid-binding agent is any one of lithium hydroxide, sodium hydroxide, calcium hydroxide, potassium hydroxide, barium hydroxide, trimethylamine, triethylamine, tripropylamine, tri-n-butylamine or tri-t-butylamine.

4. The polyamide separation membrane according to claim 3, wherein the tertiary amine-containing diamine compound is produced by a method comprising: adding 389 parts by weight of N, N' -bis (p-fluorobenzoyl-3-aminopropyl) methylamine, 218-255 parts by weight of p-aminothiophenol or p-aminophenol, 80-300 parts by weight of alkali and 1500-3000 parts by weight of a polar solvent into a reaction kettle, carrying out dehydration reaction for 0.5-2 h at 130-180 ℃ under the protection of nitrogen, then carrying out reaction for 1-12 h at 150-210 ℃, finally cooling the obtained reaction liquid to room temperature, and pouring the reaction liquid into water while stirring to obtain a tertiary amine-containing diamine crude product; and washing the crude product with deionized water for 4-6 times, collecting a filter cake, and drying at the temperature of 80-100 ℃ for 8-24 hours to obtain a purified diamine compound containing tertiary amine, wherein the structural formula of the diamine compound is as follows:

further, the alkali is any one of lithium hydroxide, sodium hydroxide, calcium hydroxide, potassium hydroxide, barium hydroxide, lithium carbonate, sodium carbonate, or potassium carbonate;

further, the polar solvent is any one of N, N-dimethylformamide, N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphoric triamide, N-methylcaprolactam N, N' -tetramethylurea, 1, 3-dimethyl-2-imidazolidinone, or N-methylpyrrolidone.

5. The polyamide separation membrane according to any one of claims 1 to 4, wherein the polyamide separation membrane is improved in corrosion resistance by solvent resistance treatment;

further, the method for improving the corrosion resistance of the polyamide separation membrane through solvent resistance treatment comprises the following steps:

a, immersing a polyamide ultrafiltration membrane containing tertiary amine into a film passivation treating agent, and carrying out passivation treatment at normal temperature for 0.5-48 h to obtain a polyamide passivation ultrafiltration membrane containing tertiary amine; wherein the mass ratio of the tertiary amine-containing polyamide ultrafiltration membrane to the passivation treating agent is as follows: the ultrafiltration membrane containing the tertiary amine polyamide comprises 16-30 parts of tertiary amine polyamide resin and 0.1-100 parts of passivation treating agent, wherein the passivation treating agent of the separation membrane is at least one of concentrated sulfuric acid, concentrated nitric acid, dilute nitric acid, peroxyacetic acid, hypochlorous acid, sodium hypochlorite, potassium permanganate, manganese dioxide, potassium dichromate, potassium perchlorate, potassium chlorate, hydrogen peroxide, ferric sulfate or silver nitrate solution;

b, performing water washing replacement on the polyamide passivated ultrafiltration membrane containing the tertiary amine to remove residual solvent, and combining and entering a solvent recovery system to recover the solvent; then immersing the purified separation membrane into a pore-protecting agent for pore-protecting treatment, and then airing to obtain a corrosion-resistant polyamide separation membrane;

further, in step B, the pore-protecting agent is any one of glycerol, polyethylene glycol 200, polyethylene glycol 400 or polyethylene glycol 600.

6. A method for producing a polyamide separation membrane according to any one of claims 1 to 5, characterized by comprising: preparing a membrane casting solution by using a polyamide resin containing tertiary amine, and preparing a polyamide ultrafiltration membrane containing tertiary amine by using the membrane casting solution by adopting the prior art;

further, the polyamide separation membrane is prepared by adopting the following method: adding 16-30 parts of polyamide resin containing tertiary amine and 70-84 parts of solvent into a dissolving kettle, stirring and dissolving at the temperature of 60-200 ℃, centrifuging and filtering after dissolving into a uniform polymer solution, removing solid impurities, and defoaming in vacuum at the temperature of 40-100 ℃ for 2-48 hours to obtain a membrane casting solution; and preparing a corresponding flat ultrafiltration membrane or hollow fiber ultrafiltration membrane by using the obtained membrane casting solution.

7. The polyamide nanofiltration membrane is characterized in that the polyamide nanofiltration membrane is obtained by introducing an acid structure into a membrane polymer through acidification treatment of a polyamide ultrafiltration membrane containing tertiary amine; wherein the tertiary amine-containing polyamide ultrafiltration membrane is the polyamide separation membrane according to any one of claims 1 to 5; or an ultrafiltration membrane produced by the production method according to claim 6;

further, the acidification treatment is to soak the polyamide ultrafiltration membrane containing the tertiary amine in an acidic solution at 25-40 ℃ for 0.5-48 h, wherein the addition amount of the acidic solution is 5-100 times of the mass of the polyamide resin containing the tertiary amine, and the acid accounts for 0.2-20% of the mass of the polyamide resin containing the tertiary amine;

further, the acidic solution is selected from: at least one aqueous solution of hydrochloric acid, dilute sulfuric acid, formic acid, glacial acetic acid, propionic acid, butyric acid, valeric acid, isovaleric acid, pivalic acid, caproic acid, caprylic acid or isooctanoic acid.

8. A method for realizing ultrafiltration-nanofiltration-ultrafiltration reversible conversion by a separation membrane is characterized by comprising the following steps:

1) preparing a polyamide ultrafiltration membrane containing tertiary amine by using polyamide resin containing tertiary amine;

2) introducing an acid structure into a membrane polymer of the ultrafiltration membrane through acidification treatment on the tertiary amine-containing polyamide ultrafiltration membrane obtained in the step 1) to obtain a tertiary amine-containing polyamide nanofiltration membrane;

3) and 2) deacidifying the tertiary amine-containing polyamide nanofiltration membrane obtained in the step 2) to convert the nanofiltration membrane into an ultrafiltration membrane.

9. The method for realizing ultrafiltration-nanofiltration-ultrafiltration reversible conversion by using the separation membrane according to claim 8, wherein in the step 2), the acidification treatment is to soak the tertiary amine-containing polyamide ultrafiltration membrane in an acidic solution at 25-40 ℃ for 0.5-48 h, wherein the acidic solution is 5-100 times of the mass of the tertiary amine-containing polyamide resin, and the acid accounts for 0.2-20% of the mass of the tertiary amine-containing polyamide resin;

further, the acidic solution is selected from: at least one aqueous solution of hydrochloric acid, dilute sulfuric acid, formic acid, glacial acetic acid, propionic acid, butyric acid, valeric acid, isovaleric acid, pivalic acid, caproic acid, caprylic acid or isooctanoic acid.

10. The method for realizing ultrafiltration-nanofiltration-ultrafiltration reversible conversion by using the separation membrane according to claim 8 or 9, wherein in the step 3), the deacidification treatment is carried out by immersing the tertiary amine-containing polyamide nanofiltration membrane obtained in the step 2) into a deacidification solution and treating the tertiary amine-containing polyamide nanofiltration membrane at 25-40 ℃ for 2-48 h; the deacidifying solution accounts for 5-100 times of the mass of the polyamide resin containing the tertiary amine, wherein the addition amount of the alkali accounts for 0.2-20% of the mass of the polyamide resin containing the tertiary amine;

further, the deacidifying solution is a mixed solution of alkali and an ultrafiltration conversion solvent, and the concentration of the alkali is 0.2-4%; wherein the base is selected from: at least one of lithium hydroxide, sodium hydroxide, potassium hydroxide, barium hydroxide, ammonia water, trimethylamine, triethylamine, tri-tert-butylamine, pyridine, or piperazine; the ultrafiltration conversion solvent is any one of water, methanol, ethanol, glycerol, isopropanol, acetone, tetrahydrofuran, dichloromethane, chloroform, carbon tetrachloride, petroleum ether, cyclohexane, n-hexane or dioxane;

further, in the step 1), the method for preparing the tertiary amine-containing polyamide ultrafiltration membrane by using the tertiary amine-containing polyamide resin comprises the following steps: adding 16-30 parts of polyamide resin containing tertiary amine and 70-84 parts of solvent into a dissolving kettle, stirring and dissolving at the temperature of 60-200 ℃, centrifuging and filtering after dissolving into a uniform polymer solution, removing solid impurities, and defoaming in vacuum at the temperature of 40-100 ℃ for 2-48 hours to obtain a membrane casting solution; preparing a corresponding flat ultrafiltration membrane or hollow fiber ultrafiltration membrane by using the obtained membrane casting solution;

preferably, the tertiary amine-containing polyamide ultrafiltration membrane obtained in the step 1) is subjected to solvation resistance treatment and then to acidification treatment.

Technical Field

The invention relates to a polyamide ultrafiltration membrane containing a tertiary amine structure, a polyamide nanofiltration membrane containing a tertiary amine structure and a preparation method thereof, belonging to the field of high polymer materials.

Background

As a novel separation technology, membrane separation has very important research significance in material separation due to the advantages of low cost, low energy consumption, high efficiency, no pollution, capability of recovering useful materials and the like. The method is widely applied to the fields of food, medicine, biology, energy, water treatment, bionics and the like, has great influence on the production and life of human beings, and becomes one of the most important means in the separation science at present. It is well known that separation membranes are the core of membrane separation processes, and membrane materials are the basis for the development of separation membranes. From the aspects of separation mechanism and application range, the method can be divided into a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, a reverse osmosis membrane, a pervaporation membrane and the like; the biggest factors influencing the use of the separation membrane are membrane separation efficiency, membrane pollution, membrane service life and the like,

the main polymer materials widely used for preparing the separation membrane at present comprise fluorine-containing resin such as polyvinylidene fluoride (PVDF), which has good film forming property and is generally used for preparing ultrafiltration and microfiltration membranes, but the hydrophobicity and the organic solvent corrosion resistance are poor; the sulfone-containing resin such as Polysulfone (PSU), polyether sulfone (PES) and the like has good temperature resistance and film forming property, is generally used for ultrafiltration and nanofiltration membranes, but has poor organic solvent corrosion resistance; polyvinyl chloride (PVC) which is low in cost and general in pore-forming property, but is poor in hydrophobicity, solvent corrosion resistance and temperature resistance; polyamide (PA) and Polyimide (PI) have poor pore forming property, are generally used for nanofiltration and reverse osmosis membranes, and have poor acid and alkali corrosion resistance; polypropylene (PP) is environment-friendly by adopting a thermoforming method, is suitable for a microfiltration membrane, and has poor hydrophobicity, solvent corrosion resistance and heat resistance. Therefore, the preparation of the separation membrane which has high separation efficiency, corrosion resistance, pollution resistance, easy regeneration and high-efficiency circulation and adjustment of the filtering particle size essentially promotes the leap-type development of the separation membrane science and engineering field.

Disclosure of Invention

The invention aims to provide a novel ultrafiltration separation membrane aiming at the defects of the prior art, and the obtained ultrafiltration membrane can be converted into a nanofiltration membrane through acidification treatment; the nanofiltration membrane can be recovered into an ultrafiltration membrane through dechlorination treatment, so that the reversible conversion of ultrafiltration and nanofiltration is realized.

The technical scheme of the invention is as follows:

the first technical problem to be solved by the invention is to provide a polyamide separation membrane, wherein the polyamide separation membrane is a tertiary amine-containing polyamide ultrafiltration membrane prepared from tertiary amine-containing polyamide resin. The polyamide resin containing tertiary amine is obtained by introducing a tertiary amine structure into polyamide, and then the polyamide resin is prepared into an ultrafiltration membrane as a separation membrane.

Further, the polyamide separation membrane is prepared by adopting the following method: preparing a membrane casting solution by using the polyamide resin containing the tertiary amine, and then preparing the polyamide ultrafiltration membrane containing the tertiary amine by adopting the prior art through the membrane casting solution.

Further, the polyamide separation membrane is prepared by adopting the following method: adding 16-30 parts of polyamide resin containing tertiary amine and 70-84 parts of solvent into a dissolving kettle, stirring and dissolving at the temperature of 60-200 ℃, centrifuging and filtering after dissolving into a uniform polymer solution, removing solid impurities, and defoaming in vacuum at the temperature of 40-100 ℃ for 2-48 hours to obtain a membrane casting solution; and preparing a corresponding flat ultrafiltration membrane or hollow fiber ultrafiltration membrane by using the obtained membrane casting solution.

Further, the solvent is any one of 1, 3-dimethyl-2-imidazolidinone, N-methylpyrrolidone, dimethyl sulfoxide, N-dimethylformamide, or N, N-dimethylacetamide.

Further, the tertiary amine-containing polyamide resin is prepared by the following method:

dissolving 10-500 parts by weight of aromatic diamine compound, 10-600 parts by weight of tertiary amine-containing diamine compound, 3500-8000 parts by weight of solvent and 50-200 parts by weight of acid-binding agent in a low-temperature reaction kettle filled with 3500-8000 parts by weight of solvent, setting the temperature of the reaction kettle to-10-15 ℃ after the compounds are dissolved and clarified, adding 200-419 parts by weight of aromatic diformyl chloride for 3-5 times, stirring and reacting at-5-25 ℃ for 0.5-10 h, and finally pouring the obtained polymer solution into water while stirring to obtain a tertiary amine-containing polyamide resin linear crude product;

and (2) crushing the polyamide resin linear crude product containing the tertiary amine, washing the crushed crude product for 3-5 times by using water and ethanol, filtering, recovering and recycling the filtrate, and drying the collected filter cake for 8-24 hours at the temperature of 80-120 ℃ to obtain the purified polyamide resin containing the tertiary amine.

Further, in the above method for producing a tertiary amine-containing polyamide resin, the aromatic diamine compound has a structural formula of:

at least one of (1).

Further, in the above-mentioned process for producing a tertiary amine-containing polyamide resin, the aromatic dicarboxylic acid chloride has the structural formula

At least one of (1).

Further, in the above-mentioned process for producing a polyamide resin containing a tertiary amine, the solvent is formamide, acetamide, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylformamide, dimethylacetamide, N-methylpropionamide, hexamethylphosphoric triamide, N-methylcaprolactam, N, N-dimethylpropylurea, N, N, N' -tetramethylurea, 1, 3-dimethyl-2-imidazolidinone, N-methylpyrrolidone, N-cyclohexylpyrrolidone, 2-pyrrolidone, quinoline, isoquinoline, diphenylsulfone, benzophenone, sulfolane, dimethylsulfone, dimethylsulfoxide, 2, 4-dimethylsulfolane, N-phenylmorpholine, dimethyl phthalate, diethyl phthalate, 1-methyl-3-propylimidazole bromide salt, N-methyl-2-imidazolium bromide salt, N-methyl-2-imidazolidine, N-methyl, Any one of 1-methyl-3-isopropyl imidazole bromide salt or 1, 3-dipropyl imidazole bromide salt.

Further, in the method for producing a tertiary amine-containing polyamide resin, the acid-binding agent is any one of lithium hydroxide, sodium hydroxide, calcium hydroxide, potassium hydroxide, barium hydroxide, trimethylamine, triethylamine, tripropylamine, tri-n-butylamine, and tri-t-butylamine.

Further, in the above method for producing a tertiary amine-containing polyamide resin, the tertiary amine-containing diamine compound is produced by: adding 389 parts by weight of N, N' -bis (p-fluorobenzoyl-3-aminopropyl) methylamine, 218-255 parts by weight of p-aminothiophenol or p-aminophenol, 80-300 parts by weight of alkali and 1500-3000 parts by weight of a polar solvent into a reaction kettle, carrying out dehydration reaction for 0.5-2 h at 130-180 ℃ under the protection of nitrogen, then carrying out reaction for 1-12 h at 150-210 ℃, finally cooling the obtained reaction liquid to room temperature, and pouring the reaction liquid into water while stirring to obtain a tertiary amine-containing diamine crude product; and washing the crude product with deionized water for 4-6 times, collecting a filter cake, and drying at the temperature of 80-100 ℃ for 8-24 hours to obtain a purified diamine compound containing tertiary amine, wherein the structural formula of the diamine compound is as follows:

further, in the above method for producing a diamine compound containing a tertiary amine, the base is any one of lithium hydroxide, sodium hydroxide, calcium hydroxide, potassium hydroxide, barium hydroxide, lithium carbonate, sodium carbonate, or potassium carbonate; the polar solvent is any one of N, N-dimethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoric triamide, N-methylcaprolactam N, N, N' -tetramethylurea, 1, 3-dimethyl-2-imidazolidinone or N-methylpyrrolidone.

Further, the polyamide separation membrane improves its corrosion resistance by a solvent-resistant treatment.

Further, the method for improving the corrosion resistance of the polyamide separation membrane through solvent resistance treatment comprises the following steps:

a, immersing a polyamide ultrafiltration membrane containing tertiary amine into a film passivation treating agent, and carrying out passivation treatment at normal temperature for 0.5-48 h to obtain a polyamide passivation ultrafiltration membrane containing tertiary amine; wherein the mass ratio of the tertiary amine-containing polyamide ultrafiltration membrane to the passivation treating agent is as follows: the ultrafiltration membrane containing the tertiary amine polyamide comprises 16-30 parts of tertiary amine polyamide resin and 0.1-100 parts of passivation treating agent, wherein the passivation treating agent of the separation membrane is at least one of concentrated sulfuric acid, concentrated nitric acid, dilute nitric acid, peroxyacetic acid, hypochlorous acid, sodium hypochlorite, potassium permanganate, manganese dioxide, potassium dichromate, potassium perchlorate, potassium chlorate, hydrogen peroxide, ferric sulfate or silver nitrate solution;

b, performing water washing replacement on the polyamide passivated ultrafiltration membrane containing the tertiary amine to remove residual solvent, and combining and entering a solvent recovery system to recover the solvent; and then immersing the purified separation membrane into a pore-protecting agent for pore-protecting treatment, and airing to obtain the corrosion-resistant polyamide separation membrane.

Further, in the step B, the pore-protecting agent is any one of glycerol, polyethylene glycol 200, polyethylene glycol 400, or polyethylene glycol 600.

The second technical problem to be solved by the present invention is to provide a method for preparing the above polyamide separation membrane, the method comprising: preparing a membrane casting solution by using the polyamide resin containing the tertiary amine, and then preparing the polyamide ultrafiltration membrane containing the tertiary amine by adopting the prior art through the membrane casting solution.

Further, the polyamide separation membrane is prepared by adopting the following method: adding 16-30 parts of polyamide resin containing tertiary amine and 70-84 parts of solvent into a dissolving kettle, stirring and dissolving at the temperature of 60-200 ℃, centrifuging and filtering after dissolving into a uniform polymer solution, removing solid impurities, and defoaming in vacuum at the temperature of 40-100 ℃ for 2-48 hours to obtain a membrane casting solution; and preparing a corresponding flat ultrafiltration membrane or hollow fiber ultrafiltration membrane by using the obtained membrane casting solution.

The third technical problem to be solved by the invention is to provide a polyamide nanofiltration membrane, wherein the polyamide nanofiltration membrane is obtained by introducing an acid structure into a membrane polymer through acidification treatment of the tertiary amine-containing polyamide ultrafiltration membrane.

Further, the acidification treatment is to soak the tertiary amine-containing polyamide ultrafiltration membrane in an acid solution at 25-40 ℃ for 0.5-48 h, wherein the acid solution is 5-100 times of the mass of the tertiary amine-containing polyamide resin, and the addition amount of acid accounts for 0.2-20% of the mass of the tertiary amine-containing polyamide resin.

Further, the acidic solution is selected from: at least one aqueous solution of hydrochloric acid, dilute sulfuric acid, formic acid, glacial acetic acid, propionic acid, butyric acid, valeric acid, isovaleric acid, pivalic acid, caproic acid, caprylic acid or isooctanoic acid.

The fourth technical problem to be solved by the invention is to provide a method for realizing ultrafiltration-nanofiltration-ultrafiltration reversible conversion by a separation membrane, which comprises the following steps:

1) preparing a polyamide ultrafiltration membrane containing tertiary amine by using polyamide resin containing tertiary amine;

2) introducing an acid structure into a membrane polymer of the ultrafiltration membrane through acidification treatment on the tertiary amine-containing polyamide ultrafiltration membrane obtained in the step 1) to obtain a tertiary amine-containing polyamide nanofiltration membrane;

3) and 2) deacidifying the tertiary amine-containing polyamide nanofiltration membrane obtained in the step 2) to convert the nanofiltration membrane into an ultrafiltration membrane.

Further, in the step 2), the acidification treatment refers to soaking the polyamide ultrafiltration membrane containing the tertiary amine in an acidic solution at 25-40 ℃ for 0.5-48 h, wherein the acidic solution is 5-100 times of the mass of the polyamide resin containing the tertiary amine, and the addition amount of acid accounts for 0.2-20% of the mass of the polyamide resin containing the tertiary amine.

Further, the acidic solution is selected from: at least one aqueous solution of hydrochloric acid, dilute sulfuric acid, formic acid, glacial acetic acid, propionic acid, butyric acid, valeric acid, isovaleric acid, pivalic acid, caproic acid, caprylic acid or isooctanoic acid.

Further, in the step 3), the deacidification treatment is to immerse the tertiary amine-containing polyamide nanofiltration membrane obtained in the step 2) into a deacidification solution and treat the polyamide nanofiltration membrane for 2-48 hours at 25-40 ℃; the deacidifying solution is 5-100 times of the mass of the polyamide resin containing the tertiary amine, and the addition amount of the alkali in the deacidifying solution accounts for 0.2-20% of the mass of the polyamide resin containing the tertiary amine.

Further, the deacidifying solution is a mixed solution of alkali and an ultrafiltration conversion solvent, and the concentration of the alkali is 0.2-4%; wherein the base is selected from: at least one of lithium hydroxide, sodium hydroxide, potassium hydroxide, barium hydroxide, ammonia water, trimethylamine, triethylamine, tri-tert-butylamine, pyridine, or piperazine; the ultrafiltration conversion solvent is any one of water, methanol, ethanol, glycerol, isopropanol, acetone, tetrahydrofuran, dichloromethane, chloroform, carbon tetrachloride, petroleum ether, cyclohexane, n-hexane or dioxane.

Further, in the step 1), the method for preparing the tertiary amine-containing polyamide ultrafiltration membrane by using the tertiary amine-containing polyamide resin comprises the following steps: adding 16-30 parts of polyamide resin containing tertiary amine and 70-84 parts of solvent into a dissolving kettle, stirring and dissolving at the temperature of 60-200 ℃, centrifuging and filtering after dissolving into a uniform polymer solution, removing solid impurities, and defoaming in vacuum at the temperature of 40-100 ℃ for 2-48 hours to obtain a membrane casting solution; and preparing a corresponding flat ultrafiltration membrane or hollow fiber ultrafiltration membrane by using the obtained membrane casting solution.

Preferably, in the method, the tertiary amine-containing polyamide ultrafiltration membrane obtained in the step 1) is subjected to solvation resistance treatment and then is subjected to acidification treatment.

In the invention, the raw materials are in parts by weight except for special specifications.

The invention has the beneficial effects that:

1. the invention introduces a weak alkaline tertiary amine structure into a polymer main chain and prepares the polymer main chain into a novel ultrafiltration separation membrane; the obtained ultrafiltration membrane can be converted into a nanofiltration membrane through acidification treatment; the nanofiltration membrane can be recovered into an ultrafiltration membrane through deacidification treatment, and the reversible conversion of ultrafiltration-nanofiltration-ultrafiltration is further realized.

2. The preparation process of the polyamide resin containing the tertiary amine structure is simple in flow, mild in condition and easy to control; except salt generated in the whole reaction process, no other harmful substances are generated, so that the method is environment-friendly; the resin has high molecular weight and high yield.

3. The ultrafiltration membrane and the nanofiltration membrane prepared by the invention have better corrosion resistance (can resist long-term corrosion of aqua regia, halogenated alkane such as chloroform and dichloromethane and strong polar organic solvent such as DMF, NMP and DMSO) after one-step simple solvent-resistant treatment (passivation treatment), can be used for separating organic media, and have excellent temperature resistance and mechanical properties.

4. According to the method, active tertiary amine groups are introduced into a polymer molecular chain in a synthesis stage, and after the polymer molecular chain is subjected to film formation, an original ultrafiltration membrane can be converted into a nanofiltration membrane through acidification treatment, and the flux and the dye retention rate are high; and the original nanofiltration membrane can be converted into an ultrafiltration membrane through dechlorination treatment, the recovery rate of the flux of the ultrafiltration membrane reaches 80-100%, the same membrane material does not need to be replaced, the ultrafiltration/nanofiltration functions can be freely and reversibly switched, and the separation efficiency and the membrane regeneration efficiency of the membrane can be improved, and the service life of the membrane can be prolonged.

5. The invention discovers and provides the reversible and free switching of the ultrafiltration/nanofiltration functions on the same separation membrane for the first time, greatly reduces the unnecessary replacement of membranes and membrane components, investment in disposable equipment and fields, and greatly reduces the production cost.

Drawings

FIG. 1 shows an infrared spectrum (FIG. 1a) and a nuclear magnetic spectrum (FIG. 1b) of the diamine containing a tertiary amine structure obtained in examples 1 to 2.

FIG. 2 is an infrared spectrum of a polyamide resin having a tertiary amine structure obtained in examples 1 to 2.

FIG. 3 is a nuclear magnetic representation of the polyamide resin containing a tertiary amine structure obtained in examples 1 to 2.

FIG. 4 shows pure water flux (FIG. 4a) and dye retention (FIG. 4b) before and after nanofiltration of the tertiary amine-containing polyamide ultrafiltration membrane obtained in examples 1 to 3; wherein, the test process of the water flux and the retention rate is as follows: detecting the volume of pure water permeating through the membrane in unit time and unit area under the pressure of 0.2MPa by adopting an ultrafiltration cup, wherein the volume is water flux, and the percentage content of the concentration of the dye in the solution after membrane filtration in the concentration of the dye before filtration is rejection rate; from the results of fig. 4, it can be seen that: the pure water flux of the prepared ultrafiltration membrane is 600-1100L/(m)²hbar), and the water flux of the filter is changed into 30-190L/(m) after nanofiltration conversion²hbar), the flux has changed by 65 times after the nanofiltration treatment, the effect is very obvious.

FIG. 5 shows polyamides containing tertiary amines obtained in examples 1 to 3The pure water flux of the ultrafiltration membrane obtained after the nanofiltration membrane is subjected to ultrafiltration treatment is shown in the figure, and the water flux of the membrane subjected to nanofiltration treatment is subjected to ultrafiltration treatment again and is increased to 1000L/(m & lt + & gt) of 600-²hbar), has better recovery rate.

Detailed Description

According to the invention, a weakly alkaline tertiary amine structure is introduced into a polyamide main chain by combining a molecular construction method, a separation membrane is prepared by using the weakly alkaline structure of the tertiary amine structure, an acid structure is introduced onto a polymer chain by acid treatment, a certain positive charge is given to the separation membrane, and the mechanism of mutual repulsion of like charges is utilized, so that the whole molecular chain structure of the separation membrane is in a limit relaxation state, the original membrane pore diameter is reduced, and the separation membrane is converted into a nanofiltration membrane from an ultrafiltration membrane; and the treated nanofiltration membrane is subjected to subsequent deacidification treatment, so that the originally charged separation membrane is restored to be electrically neutral, the pore diameter of the membrane is restored to the original ultrafiltration membrane size, and finally the reversible conversion of ultrafiltration-nanofiltration-ultrafiltration is realized.

The present invention is described in detail below by way of examples, it should be noted that the examples are only for the purpose of further illustration, and are not to be construed as limiting the scope of the present invention, and that those skilled in the art can make insubstantial modifications and adaptations of the present invention based on the teachings of the present invention described above.