Acid-resistant nanofiltration membrane and preparation method thereof

Abstract

The invention relates to an acid-resistant nanofiltration membrane and a preparation method thereof, and relates to the technical field of nanofiltration membranes. The acid-resistant nanofiltration membrane comprises a supporting base layer and a functional layer, the functional layer is formed by interfacial polymerization on the supporting base layer, the supporting base layer comprises a polyetherimide-nanomembrane, raw materials of the functional layer comprise an oil-phase solution and a water-phase solution, the oil-phase solution comprises 1, 3, 5-benzene trisulfonyl chloride and an oil-phase solvent, and the water-phase solution comprises 1, 3, 5-benzene trisulfonyl chloride and a water-phase solvent. The water-phase solution comprises piperazine and a water-phase solvent; the method has the effect of improving the acid resistance of the nanofiltration membrane.

Description

Technical Field

[0001] The present application relates to the technical field of nanofiltration membranes, and in particular to an acid-resistant nanofiltration membrane and a preparation method thereof. Background Art

[0002] Nanofiltration membrane is a pressure-driven separation membrane with a pore size of less than 2nm. It is an efficient and energy-saving membrane separation process that can effectively remove multivalent ions and organic compounds. It has important application prospects in water treatment, pharmaceutical and food industries.

[0003] Most commercial nanofiltration membranes contain a functional layer and a porous support layer. The functional layer is mostly a polyamide membrane generated by the interfacial polymerization of trimesoyl chloride and piperazine. The amide bond of the functional layer is easily hydrolyzed under acidic conditions, resulting in the expansion of membrane pores and a significant decrease in the retention rate, thereby reducing the service life of the nanofiltration membrane. Summary of the Invention

[0004] In order to improve the acid resistance of nanofiltration membranes and extend the service life of nanofiltration membranes, the present application provides an acid-resistant nanofiltration membrane and a preparation method thereof.

[0005] In the first aspect, the present application provides an acid-resistant nanofiltration membrane, which adopts the following technical solution: An acid-resistant nanofiltration membrane comprises a supporting substrate and a functional layer. The functional layer is formed by interfacial polymerization on the supporting substrate. The supporting substrate comprises a polyetherimide-nanomembrane. Raw materials of the functional layer comprise an oil phase solution and an aqueous phase solution. The oil phase solution comprises 1,3,5-benzenetrisulfonyl chloride and an oil phase solvent, and the aqueous phase solution comprises piperazine and an aqueous phase solvent.

[0006] By adopting this technical solution, 1,3,5-benzenetrisulfonyl chloride has a chemical structure with three sulfonyl chloride groups attached to a single benzene ring. Piperazine is a cyclic diamine containing two amine groups, which provide crosslinking points and form a three-dimensional network structure. The high reactivity of 1,3,5-benzenetrisulfonyl chloride regulates the interfacial polymerization process, resulting in a high degree of crosslinking in the functional layer. This allows 1,3,5-benzenetrisulfonyl chloride to react with piperazine through interfacial polymerization to produce a high molecular weight and highly crosslinked polysulfonamide separation layer. This crosslinking structure, combined with the strong chemical inertness of the sulfonyl groups, resists acid corrosion and slows degradation. The crosslinking structure also enhances the density of the sodium filtration membrane, reduces defects and porosity, and effectively improves the acid resistance of the nanofiltration membrane, thereby extending its service life.

[0007] Preferably, the aqueous solution further comprises terephthalic acid.

[0008] By adopting the above technical solution, the benzene ring and carboxylic acid group of terephthalic acid are stable in an acidic environment and can fill the microcracks or defects in the polysulfonamide network, reducing H +The carboxylic acid group of terephthalic acid can undergo partial amidation reaction with the amino group of piperazine to generate terephthalic acid-piperazine prepolymer, which forms competitive cross-linking with the main reaction (piperazine and 1,3,5-benzenetrisulfonyl chloride to generate polysulfonamide). The formed polysulfonamide network is denser and has lower porosity, which reduces the acid penetration channel and forms a more complete acid-resistant barrier, effectively improving the acid resistance of the nanofiltration membrane.

[0009] Moreover, the carboxylic acid group of terephthalic acid has strong polarity, which can significantly improve the hydrophilicity of the nanofiltration membrane surface, form a hydration layer, reduce the adsorption of hydrophobic pollutants, and improve the fouling resistance of the nanofiltration membrane.

[0010] Preferably, the aqueous solution also includes sodium lauryl sulfate.

[0011] By adopting the above technical solution, sodium dodecyl sulfate can reduce the interfacial tension between the two phases, promote the diffusion of piperazine into the oil phase, and form a thinner and more uniform functional layer. Sodium dodecyl sulfate prevents the agglomeration of terephthalic acid or piperazine molecules through electrostatic stabilization, ensures the uniform dispersion of the aqueous solution, avoids film formation defects, and thus promotes the improvement of the acid resistance of the nanofiltration membrane.

[0012] Preferably, the mass ratio of piperazine, terephthalic acid, sodium lauryl sulfate and aqueous solvent in the aqueous solution is 1:(0.08-0.16):(0.02-0.06):1000.

[0013] By adopting the above technical solution and controlling the mass ratio of piperazine, terephthalic acid, sodium lauryl sulfate and aqueous solvent within the above range, the acid resistance of the nanofiltration membrane can be effectively improved.

[0014] Preferably, the mass ratio of 1,3,5-benzenetrisulfonyl chloride to the oil phase solvent in the oil phase solution is (1.4-2.4):100.

[0015] By adopting the above technical solution and controlling the mass ratio of 1,3,5-benzenetrisulfonyl chloride and the oil phase solvent within the above range, the acid resistance of the nanofiltration membrane can be effectively improved.

[0016] Preferably, the method for preparing the polyetherimide-nano film comprises the following steps: Polyvinyl pyrrolidone, N,N-dimethylacetamide and MOF-808 are mixed and ultrasonically dispersed, and then polyetherimide is added. The mixture is heated and stirred evenly, and allowed to stand for degassing to form a homogeneous casting solution, which is then coated on the surface of a non-woven fabric, and then cured and washed in sequence to obtain a polyetherimide-nanofilm.

[0017] By adopting the above technical solution, MOF-808, thanks to its use of zirconium as a coordinating metal, possesses excellent acid resistance due to the strong chemical stability of the Zr-O bond. Therefore, MOF-808 nanoparticles are used as a dopant, polyvinylpyrrolidone is used as a pore-forming agent, and the polyetherimide imide ring has a highly conjugated structure, strong chemical inertness, and natural resistance to acid hydrolysis. As a result, the polyetherimide-nanomembrane as a supporting substrate has excellent acid resistance.

[0018] Moreover, the nanoparticles of MOF-808 are dispersed in the polyetherimide matrix to form an "island structure", and MOF-808 is wrapped by the polyetherimide matrix as a dispersed phase; the carboxylic acid groups (from organic ligands) on the surface of MOF-808 that are not completely solvated may form hydrogen bonds with the ether bonds or imide rings in the polyetherimide, so that after the polyetherimide wraps MOF-808, the direct contact of MOF-808 with the acid solution is reduced, and the rigid particles of MOF can inhibit the swelling and deformation of polyetherimide in acid, forming a physical barrier, thereby improving the acid resistance of the polyetherimide-nanomembrane, and then improving the acid resistance of the nanofiltration membrane.

[0019] In addition, the porous structure of MOF-808 absorbs water molecules, forming a hydration layer that reduces the adhesion of pollutants. Furthermore, the positively charged surface of MOF-808's zirconium clusters can electrostatically repel positively charged pollutants in acidic or neutral environments, improving its stain resistance.

[0020] Preferably, the mass ratio of the polyetherimide to MOF-808 is 1:(0.1-0.5).

[0021] By adopting the above technical solution and controlling the mass ratio of polyetherimide and MOF-808 within the above range, the acid resistance of the nanofiltration membrane can be effectively improved.

[0022] Preferably, the modification preparation method of MOF-808 comprises the following steps: MOF-808 and tannic acid were added to deionized water, stirred evenly, and then filtered and dried to obtain modified MOF-808.

[0023] By adopting the above technical solution, tannic acid is a plant polyphenol rich in hydroxyl and polyphenol groups. Tannic acid can form a complex through the coordination between phenolic hydroxyl groups and metal ions on MOF-808, which shows that tannic acid can be well coated on the surface of MOF-808, so that tannic acid is wrapped on the surface of MOF-808. The phenolic hydroxyl groups of tannic acid can be partially protonated in an acidic environment, and by consuming H +The acid corrosion of the MOF-808 skeleton is delayed by using the tannic acid coating layer as a physical barrier to reduce the direct contact of the acid with the zirconium cluster active sites of MOF-808, inhibit the breakage of the Zr-O bond, and further improve the acid resistance of MOF-808. The hydroxyl groups of tannic acid form hydrogen bonds with the carboxylic acid groups of the organic ligands of MOF-808 (such as trimesic acid), thereby improving the compatibility between MOF-808 and polyetherimide.

[0024] In addition, the phenolic hydroxyl groups of tannic acid introduce a large number of hydrophilic groups, which reduce the contact angle of the membrane surface and form a hydration layer to prevent the adsorption of pollutants. The "brush-like" structure formed by tannic acid molecules on the MOF surface increases steric hindrance, hindering large molecular pollutants from approaching the nanofiltration membrane surface, thereby improving the fouling resistance of the nanofiltration membrane.

[0025] Preferably, the mass ratio of MOF-808 to tannic acid is 1:(0.2-0.4) By adopting the above technical solution, the mass ratio of MOF-808 and tannic acid is controlled within the above range, thereby effectively improving the compatibility between MOF-808 and polyetherimide.

[0026] In a second aspect, the present application provides a method for preparing an acid-resistant nanofiltration membrane as in the first aspect, which adopts the following technical solution: A method for preparing an acid-resistant nanofiltration membrane comprises the following steps: S1. Piperazine, terephthalic acid, sodium lauryl sulfate, and an aqueous solvent are mixed and stirred to obtain an aqueous solution; 1,3,5-benzenetrisulfonyl chloride and an oily solvent are mixed and stirred to obtain an oily solution; S2. Immersing the polyetherimide-nanomembrane in an aqueous solution. After the immersion is completed, immersing the soaked polyetherimide-nanomembrane in an oil solution. After the immersion is completed, drying is performed to form a functional layer on the polyetherimide-nanomembrane, thereby preparing an acid-resistant nanofiltration membrane.

[0027] In summary, this application includes at least one of the following beneficial technical effects: 1,3,5-Benzenetrisulfonyl chloride has a chemical structure consisting of three sulfonyl chloride groups attached to a single benzene ring. Piperazine, a cyclic diamine containing two amine groups, provides crosslinking points, forming a three-dimensional network structure. The high reactivity of 1,3,5-Benzenetrisulfonyl chloride regulates the interfacial polymerization process, resulting in a high degree of crosslinking in the functional layer. This allows 1,3,5-Benzenetrisulfonyl chloride to react with piperazine through interfacial polymerization to produce a high-molecular-weight, highly crosslinked polysulfonamide separation layer. This crosslinked structure, combined with the strong chemical inertness of the sulfonyl groups, resists acid corrosion and slows degradation. The crosslinked structure also enhances the density of the sodium filtration membrane, reduces defects and porosity, and effectively improves the acid resistance of the nanofiltration membrane, thereby extending its service life.

[0028] 2. Tannic acid is a plant polyphenol rich in hydroxyl and polyphenol groups. Tannic acid can form complexes through the coordination between phenolic hydroxyl groups and metal ions on MOF-808, which shows that tannic acid can be well coated on the surface of MOF-808, so that tannic acid is wrapped on the surface of MOF-808. The phenolic hydroxyl groups of tannic acid can be partially protonated in an acidic environment, consuming H + The acid corrosion of the MOF-808 skeleton is delayed by using the tannic acid coating layer as a physical barrier to reduce the direct contact of the acid with the zirconium cluster active sites of MOF-808, inhibit the breakage of the Zr-O bond, and further improve the acid resistance of MOF-808. The hydroxyl groups of tannic acid form hydrogen bonds with the carboxylic acid groups of the organic ligands of MOF-808 (such as trimesic acid), thereby improving the compatibility between MOF-808 and polyetherimide. DETAILED DESCRIPTION

[0029] Unless otherwise specified, the raw materials used in this application can be obtained from commercially available raw materials. The following is a further detailed description of this application in conjunction with the examples: Raw materials description: 1,3,5-Benzenetrisulfonyl chloride (CAS No.: 21538-06-78) was provided by Henan Qinpeng Technology Co., Ltd., piperazine (CAS No.: 110-85-0), terephthalic acid (CAS No.: 100-21-0), and sodium lauryl sulfate (CAS No.: 151-21-3) were provided by Shanghai Aladdin Biochemical Technology Co., Ltd., non-woven fabric (specification: QLM-R80) was provided by Zhejiang Qinglan Membrane Technology Co., Ltd., polyetherimide (CAS No.: 61128-46-9) was provided by Shanghai MacLean Biochemical Technology Co., Ltd., tannic acid (CAS No.: 1401-55-48) was provided by Wufeng Chicheng Biotechnology Co., Ltd., and trimesoyl chloride (CAS No.: 4422-95-1) was provided by Hubei Changrun Biopharmaceutical Technology Co., Ltd.

[0030] The present invention discloses an acid-resistant nanofiltration membrane and a method for preparing the same. The membrane comprises a support substrate and a functional layer, the functional layer being formed by interfacial polymerization on the support substrate, the support substrate being a polyetherimide nanofilm. The functional layer is prepared from raw materials comprising an oil-phase solution and an aqueous solution, the oil-phase solution comprising 1,3,5-benzenetrisulfonyl chloride and an oil-phase solvent, and the aqueous solution comprising piperazine and an aqueous solvent.

[0031] Example 1 The preparation method of polyetherimide-nano film comprises the following steps: After mixing 1.3g of polyvinyl pyrrolidone, 60g of N,N-dimethylacetamide and 3g of MOF-808, ultrasonically disperse them for 10 minutes, then add 10g of polyetherimide, and stir at 200r / min at 60°C for 12 hours. After standing and degassing, a homogeneous casting liquid is formed. Use a coating rod to evenly scrape it onto the surface of the non-woven fabric, immediately immerse it in a gel water bath at 25°C. After 30 minutes, soak it in deionized water for 24 hours to prepare a polyetherimide-nanofilm.

[0032] The raw materials of the functional layer include an oil phase solution and an aqueous phase solution. The oil phase solution includes 1,3,5-benzenetrisulfonyl chloride and an oil phase solvent, and the aqueous phase solution includes piperazine and an aqueous phase solvent.

[0033] The oil phase solvent is n-hexane, wherein the mass ratio of 1,3,5-benzenetrisulfonyl chloride to n-hexane is 1.9:100; the water phase solvent is deionized water, and the mass ratio of piperazine to deionized water is 1:1000.

[0034] A method for preparing an acid-resistant nanofiltration membrane comprises the following steps: S1. Mix piperazine and deionized water, stir evenly, and prepare an aqueous phase solution; mix 1,3,5-benzenetrisulfonyl chloride and n-hexane, stir evenly, and prepare an oil phase solution; S2. Immerse the polyetherimide-nanomembrane in the aqueous phase solution. After immersion for 60 seconds, take out the membrane, remove the excess surface solution with filter paper, and then directly immerse it in the oil phase. After immersion for 120 seconds, take out the membrane, and then wash it once with isopropyl alcohol to remove the residual solution. Then put the membrane into a blast drying oven, dry it at 70°C for 30 minutes, and then take it out to form a functional layer on the polyetherimide-nanomembrane, thereby preparing an acid-resistant nanofiltration membrane.

[0035] Example 2 The difference between Example 2 and Example 1 is that the aqueous phase solution further includes terephthalic acid.

[0036] That is, the raw materials of the functional layer include an oil phase solution and an aqueous phase solution. The oil phase solution includes 1,3,5-benzenetrisulfonyl chloride and an oil phase solvent, and the aqueous phase solution includes piperazine, terephthalic acid and an aqueous phase solvent.

[0037] The oil phase solvent is n-hexane, and the mass ratio of 1,3,5-benzenetrisulfonyl chloride to n-hexane is 1.9:100; the water phase solvent is deionized water, and the mass ratio of piperazine, terephthalic acid, and deionized water is 1:0.12:1000.

[0038] A method for preparing an acid-resistant nanofiltration membrane comprises the following steps: S1. Mix piperazine, terephthalic acid, and deionized water, and stir evenly to prepare an aqueous phase solution; mix 1,3,5-benzenetrisulfonyl chloride and n-hexane, and stir evenly to prepare an oil phase solution; S2. Immerse the polyetherimide-nanomembrane in the aqueous phase solution. After immersion for 60 seconds, take out the membrane, remove the excess surface solution with filter paper, and then directly immerse it in the oil phase. After immersion for 120 seconds, take out the membrane, and then wash it once with isopropyl alcohol to remove the residual solution. Then put the membrane into a blast drying oven, dry it at 70°C for 30 minutes, and then take it out to form a functional layer on the polyetherimide-nanomembrane, thereby preparing an acid-resistant nanofiltration membrane.

[0039] Example 3 The difference between Example 3 and Example 3 is that the aqueous phase solution also includes sodium lauryl sulfate.

[0040] That is, the raw materials of the functional layer include an oil phase solution and an aqueous phase solution. The oil phase solution includes 1,3,5-benzenetrisulfonyl chloride and an oil phase solvent. The aqueous phase solution includes piperazine, terephthalic acid, sodium lauryl sulfate and an aqueous phase solvent.

[0041] The oil phase solvent is n-hexane, and the mass ratio of 1,3,5-benzenetrisulfonyl chloride to n-hexane is 1.9:100; the water phase solvent is deionized water, and the mass ratio of piperazine, terephthalic acid, sodium lauryl sulfate, and deionized water is 1:0.12:0.04:1000.

[0042] A method for preparing an acid-resistant nanofiltration membrane comprises the following steps: S1. Mix piperazine, terephthalic acid, and deionized water, and stir evenly to prepare an aqueous phase solution; mix 1,3,5-benzenetrisulfonyl chloride and n-hexane, and stir evenly to prepare an oil phase solution; S2. Immerse the polyetherimide-nanomembrane in the aqueous phase solution. After immersion for 60 seconds, take out the membrane, remove the excess surface solution with filter paper, and then directly immerse it in the oil phase. After immersion for 120 seconds, take out the membrane, and then wash it once with isopropyl alcohol to remove the residual solution. Then put the membrane into a blast drying oven, dry it at 70°C for 30 minutes, and then take it out to form a functional layer on the polyetherimide-nanomembrane, thereby preparing an acid-resistant nanofiltration membrane.

[0043] Example 4 The preparation method of polyetherimide-nano film comprises the following steps: After mixing 1.3g of polyvinyl pyrrolidone, 60g of N,N-dimethylacetamide and 1g of MOF-808, ultrasonically disperse them for 10 minutes, then add 10g of polyetherimide, and stir at 200r / min at 60°C for 12 hours. After standing and degassing, a homogeneous casting liquid is formed. Use a coating rod to evenly scrape it onto the surface of the non-woven fabric, immediately immerse it in a gel water bath at 25°C. After 30 minutes, soak it in deionized water for 24 hours to prepare a polyetherimide-nanofilm.

[0044] The raw materials of the functional layer include an oil phase solution and an aqueous phase solution. The oil phase solution includes 1,3,5-benzenetrisulfonyl chloride and an oil phase solvent. The aqueous phase solution includes piperazine, terephthalic acid, sodium lauryl sulfate and an aqueous phase solvent.

[0045] The oil phase solvent is n-hexane, and the mass ratio of 1,3,5-benzenetrisulfonyl chloride to n-hexane is 1.9:100; the water phase solvent is deionized water, and the mass ratio of piperazine, terephthalic acid, sodium lauryl sulfate, and deionized water is 1:0.08:0.06:1000.

[0046] A method for preparing an acid-resistant nanofiltration membrane comprises the following steps: S1. Mix piperazine, terephthalic acid, and deionized water, and stir evenly to prepare an aqueous phase solution; mix 1,3,5-benzenetrisulfonyl chloride and n-hexane, and stir evenly to prepare an oil phase solution; S2. Immerse the polyetherimide-nanomembrane in the aqueous phase solution. After immersion for 60 seconds, take out the membrane, remove the excess surface solution with filter paper, and then directly immerse it in the oil phase. After immersion for 120 seconds, take out the membrane, and then wash it once with isopropyl alcohol to remove the residual solution. Then put the membrane into a blast drying oven, dry it at 70°C for 30 minutes, and then take it out to form a functional layer on the polyetherimide-nanomembrane, thereby preparing an acid-resistant nanofiltration membrane.

[0047] Example 5 The preparation method of polyetherimide-nano film comprises the following steps: After mixing 1.3g of polyvinyl pyrrolidone, 60g of N,N-dimethylacetamide and 5g of MOF-808, ultrasonically disperse them for 10 minutes, then add 10g of polyetherimide, and stir at 200r / min at 60°C for 12 hours. After standing and degassing, a homogeneous casting liquid is formed. Use a coating rod to evenly scrape it onto the surface of the non-woven fabric, immediately immerse it in a gel water bath at 25°C. After 30 minutes, soak it in deionized water for 24 hours to prepare a polyetherimide-nanofilm.

[0048] The raw materials of the functional layer include an oil phase solution and an aqueous phase solution. The oil phase solution includes 1,3,5-benzenetrisulfonyl chloride and an oil phase solvent. The aqueous phase solution includes piperazine, terephthalic acid, sodium lauryl sulfate and an aqueous phase solvent.

[0049] The oil phase solvent is n-hexane, and the mass ratio of 1,3,5-benzenetrisulfonyl chloride to n-hexane is 1.9:100; the water phase solvent is deionized water, and the mass ratio of piperazine, terephthalic acid, sodium lauryl sulfate, and deionized water is 1:0.16:0.02:1000.

[0050] A method for preparing an acid-resistant nanofiltration membrane comprises the following steps: S1. Mix piperazine, terephthalic acid, and deionized water, and stir evenly to prepare an aqueous phase solution; mix 1,3,5-benzenetrisulfonyl chloride and n-hexane, and stir evenly to prepare an oil phase solution; S2. Immerse the polyetherimide-nanomembrane in the aqueous phase solution. After immersion for 60 seconds, take out the membrane, remove the excess surface solution with filter paper, and then directly immerse it in the oil phase. After immersion for 120 seconds, take out the membrane, and then wash it once with isopropyl alcohol to remove the residual solution. Then put the membrane into a blast drying oven, dry it at 70°C for 30 minutes, and then take it out to form a functional layer on the polyetherimide-nanomembrane, thereby preparing an acid-resistant nanofiltration membrane.

[0051] Example 6 The difference between Example 6 and Example 3 is that the mass ratio of piperazine, terephthalic acid, sodium lauryl sulfate and deionized water is 1:0.06:0.02:1000.

[0052] Example 7 The difference between Example 7 and Example 3 is that the mass ratio of piperazine, terephthalic acid, sodium lauryl sulfate and deionized water is 1:0.18:0.02:1000.

[0053] Example 8 The difference between Example 8 and Example 3 is that the mass ratio of piperazine, terephthalic acid, sodium lauryl sulfate and deionized water is 1:0.12:0.01:1000.

[0054] Example 9 The difference between Example 9 and Example 3 is that the mass ratio of piperazine, terephthalic acid, sodium lauryl sulfate and deionized water is 1:0.12:0.07:1000.

[0055] Example 10 The difference between Example 10 and Example 3 is that the modification preparation method of MOF-808 includes the following steps: 10 g of MOF-808 and 3 g of tannic acid were added to 800 g of deionized water, stirred at 25° C. for 24 h, and then filtered. The filter cake was then washed with deionized water and finally dried in a vacuum drying oven at 60° C. for 12 h to obtain modified MOF-808.

[0056] Example 11 The difference between Example 11 and Example 3 is that the modification preparation method of MOF-808 includes the following steps: 10 g of MOF-808 and 2 g of tannic acid were added to 800 g of deionized water, stirred at 25° C. for 24 h, and then filtered. The filter cake was then washed with deionized water and finally dried in a vacuum drying oven at 60° C. for 12 h to obtain modified MOF-808.

[0057] Example 12 The difference between Example 12 and Example 3 is that the modification preparation method of MOF-808 includes the following steps: 10 g of MOF-808 and 4 g of tannic acid were added to 800 g of deionized water, stirred at 25° C. for 24 h, and then filtered. The filter cake was then washed with deionized water. Finally, the filter cake was placed in a vacuum drying oven at 60° C. and dried for 12 h to obtain modified MOF-808.

[0058] Example 13 The difference between Example 13 and Example 10 is that the mass ratio of MOF-808 to tannic acid is 1:0.1.

[0059] Example 14 The difference between Example 14 and Example 10 is that the mass ratio of MOF-808 to tannic acid is 1:0.5.

[0060] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the polyetherimide-nanomembrane is replaced by a polyetherimide membrane.

[0061] The preparation method of the polyetherimide membrane includes the following steps: mixing 1.3g of polyvinyl pyrrolidone and 60g of N,N-dimethylacetamide, ultrasonically dispersing for 10 minutes, adding 10g of polyetherimide, stirring at 60°C and 200r / min for 12 hours, standing and degassing to form a homogeneous casting liquid, scraping it evenly onto the surface of the non-woven fabric with a coating rod, immediately immersing it in a gel water bath at 25°C, after 30 minutes, and then soaking it in deionized water for 24 hours to obtain the polyetherimide membrane.

[0062] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that 1,3,5-benzenetrisulfonyl chloride is replaced by trimesoyl chloride.

[0063] Performance testing The acid-resistant nanofiltration membranes prepared in Examples 1-14 and Comparative Examples 1-2 were tested for their acid resistance using the following test method: the acid-resistant nanofiltration membranes were tested twice on a cross-flow membrane test bench, namely, performance tests before and after immersion in sulfuric acid solution.

[0064] The water flux and desalination rate performance test of the acid-resistant nanofiltration membrane was completed through a membrane test bench. The test liquid was a 2000ppm magnesium sulfate aqueous solution with a pH value of 6.5-7.5. The operating temperature was 25°C. The membrane was operated at an operating pressure of 0.7MPa for 30 minutes, and then the desalination rate and water flux of the membrane were tested.

[0065] The acid-resistant nanofiltration membrane was tested for its acid resistance using a 10% sulfuric acid solution soaked for one month at 25°C. The membrane was then rinsed repeatedly with deionized water to remove any residual free acid until the pH of the rinse solution stabilized. The membrane's salt rejection and water flux were then measured. See Table 1 for detailed test results.

[0066] Table 1 Specifically combining Example 2 with Example 1, it can be seen that the acid resistance of Example 2 is better than that of Example 1. The difference between Example 2 and Example 1 is that the aqueous phase solution also includes terephthalic acid, which can fill the microcracks or defects in the polysulfonamide network, and the carboxylic acid group of terephthalic acid can undergo partial amidation reaction with the amino group of piperazine to form competitive crosslinking with the main reaction (piperazine and 1,3,5-benzenetrisulfonyl chloride to form polysulfonamide), and the formed polysulfonamide network is denser, thereby improving the acid resistance of the acid-resistant nanofiltration membrane.

[0067] Specifically combining Example 3 with Example 2, it can be seen that Example 3 has better acid resistance than Example 2. The difference between Example 3 and Example 2 is that the aqueous phase solution also includes sodium dodecyl sulfate, which can promote the diffusion of piperazine into the oil phase, and sodium dodecyl sulfate prevents the agglomeration of terephthalic acid or piperazine molecules through electrostatic stabilization, thereby improving the stability of the acid-resistant nanofiltration membrane and avoiding film formation defects of the functional layer, thereby improving the acid resistance of the nanofiltration membrane.

[0068] Specifically combining Example 10 and Example 3, it can be seen that the acid resistance of Example 10 is better than that of Example 3. The difference between Example 10 and Example 3 is that the modification of MOF-808 by tannic acid can not only delay the acid corrosion of the MOF-808 skeleton, but also improve the compatibility between MOF-808 and polyetherimide, effectively improve the acid resistance of the polyetherimide-nanomembrane, and improve the acid resistance of the nanofiltration membrane.

[0069] Specifically combining Example 1 and Comparative Example 1, it can be seen that the acid resistance of Example 1 is better than that of Comparative Example 1. The difference between Example 1 and Comparative Example 1 is that the supporting base layer is a polyetherimide-nanomembrane. On the one hand, MOF-808 itself has excellent acid resistance. On the other hand, the rigid particles of MOF-808 can inhibit the swelling and deformation of polyetherimide in acid, thereby improving the acid resistance of the polyetherimide-nanomembrane, and then improving the acid resistance of the nanofiltration membrane.

[0070] Specifically combining Example 1 and Comparative Example 2, it can be seen that the acid resistance of Example 1 is better than that of Comparative Example 2. The difference between Example 1 and Comparative Example 2 is that 1,3,5-benzenetrisulfonyl chloride is replaced with trimesoyl chloride. 1,3,5-benzenetrisulfonyl chloride has high reactivity, so that the membrane exhibits a higher degree of cross-linking. This cross-linked structure and the strong chemical inertness of the sulfonyl group resist acid corrosion and slow down the degradation process, thereby improving the acid resistance of the functional layer, and then improving the acid resistance of the nanofiltration membrane.

[0071] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. An acid-resistant nanofiltration membrane, characterized in that: The invention comprises a supporting base layer and a functional layer, wherein the functional layer is formed by interfacial polymerization on the supporting base layer, the supporting base layer comprises a polyetherimide-nanomembrane, and the raw materials of the functional layer comprise an oil phase solution and an aqueous phase solution, the oil phase solution comprises 1,3,5-benzenetrisulfonyl chloride and an oil phase solvent, and the aqueous phase solution comprises piperazine and an aqueous phase solvent.

2. An acid-resistant nanofiltration membrane according to claim 1, characterized in that: The aqueous solution also includes terephthalic acid.

3. An acid-resistant nanofiltration membrane according to claim 2, characterized in that: The aqueous phase solution also includes sodium lauryl sulfate.

4. An acid-resistant nanofiltration membrane according to claim 3, characterized in that: The mass ratio of piperazine, terephthalic acid, sodium lauryl sulfate and aqueous solvent in the aqueous solution is 1: (0.08-0.16): (0.02-0.06): 1000.

5. The acid-resistant nanofiltration membrane according to claim 1, characterized in that: The mass ratio of 1,3,5-benzenetrisulfonyl chloride to the oil phase solvent in the oil phase solution is (1.4-2.4):

100.

6. The acid-resistant nanofiltration membrane according to claim 1, characterized in that: The preparation method of the polyetherimide-nano film comprises the following steps: Polyvinyl pyrrolidone, N,N-dimethylacetamide and MOF-808 are mixed and ultrasonically dispersed, and then polyetherimide is added. The mixture is heated and stirred evenly, and allowed to stand for degassing to form a homogeneous casting solution, which is then coated on the surface of a non-woven fabric, and then cured and washed in sequence to obtain a polyetherimide-nanofilm.

7. The acid-resistant nanofiltration membrane according to claim 6, characterized in that: The mass ratio of the polyetherimide to MOF-808 is 1:(0.1-0.5).

8. The acid-resistant nanofiltration membrane according to claim 6, characterized in that: The modification preparation method of MOF-808 comprises the following steps: MOF-808 and tannic acid were added to deionized water, stirred evenly, and then filtered and dried to obtain modified MOF-808.

9. The acid-resistant nanofiltration membrane according to claim 8, characterized in that: The mass ratio of the MOF-808 to tannic acid is 1:(0.2-0.4).

10. A method for preparing the acid-resistant nanofiltration membrane according to any one of claims 1 to 9, characterized in that: The steps include: S1. Piperazine, terephthalic acid, sodium lauryl sulfate, and an aqueous solvent are mixed and stirred to obtain an aqueous solution; 1,3,5-benzenetrisulfonyl chloride and an oily solvent are mixed and stirred to obtain an oily solution; S2. Immersing the polyetherimide-nanomembrane in an aqueous solution. After the immersion is completed, immersing the soaked polyetherimide-nanomembrane in an oil solution. After the immersion is completed, drying is performed to form a functional layer on the polyetherimide-nanomembrane, thereby preparing an acid-resistant nanofiltration membrane.

Images