High-permeability and selective acid-resistant nanofiltration membrane, preparation method and application thereof

Abstract

This application relates to the field of water treatment membrane separation technology, specifically disclosing a high-permeability selective acid-resistant nanofiltration membrane, its preparation method, and its application. A high-permeability selective acid-resistant nanofiltration membrane includes a base membrane and a functional layer formed on the base membrane through interfacial polymerization. The functional layer is prepared by interfacial polymerization of raw materials comprising an oil phase solution and an aqueous phase solution. The oil phase solution is composed of the following raw materials: trimesoyl chloride and n-hexane; the aqueous phase solution is composed of the following raw materials: piperazine, acid-resistant comonomer, carboxylated acid-resistant framework material, surfactant, triethylamine camphorsulfonate, and deionized water. This application can significantly improve the performance degradation of polyamide nanofiltration membranes under strong acid environments and synergistically achieve long-term stable high permeability and high selectivity under acidic environments, ultimately obtaining a high-permeability selective acid-resistant nanofiltration membrane with superior application quality.

Description

Technical Field

[0001] This application relates to the field of water treatment membrane separation technology, and more specifically, to a high-permeability selective acid-resistant nanofiltration membrane, its preparation method, and its application. Background Technology

[0002] Nanofiltration membranes are functional semi-permeable membranes with pore sizes between 1 and 2 nanometers. Their molecular weight cutoff is between that of reverse osmosis membranes and ultrafiltration membranes. As a pressure-driven separation membrane, it has wide applications in the separation, decolorization, and concentration of monovalent and divalent ions due to its unique pore size and Dornan effect.

[0003] However, in many industrial scenarios, such as waste acid recovery from metal smelting, purification of chemical pickling solutions, treatment of lithium battery electrolytes, and separation of products from strong acid catalytic reactions, the material systems are typically characterized by strong acidity, high salinity, and the presence of organic solvents, placing extreme demands on the chemical stability of the separation membrane. Currently, commercially available polyamide composite nanofiltration membranes are typically formed by interfacial polymerization of piperazine (PIP) or m-phenylenediamine (MPD) with trimesoyl chloride (TMC) to create a polyamide active separation layer on a porous support substrate membrane.

[0004] Regarding the aforementioned technologies, the inventors believe that the high water flux of traditional PIP / TMC membranes stems from their relatively loose, hydrophilic polyamide network structure. However, amide bonds form the backbone of polyamides, and in H... + Under catalysis, hydrolysis and breakage easily occur, resulting in poor stability of this structure in acidic media. Furthermore, in acidic environments, the carboxyl groups and other groups on the polyamide chain are protonated, weakening or eliminating the negative charge on the membrane surface, leading to a decrease in the divalent salt rejection rate based on the Donnan effect. At the same time, changes in surface charge and chemical structure can also cause swelling or shrinkage of the polyamide layer, altering its free volume and effective pore size, resulting in unstable water flux and an inability to maintain the initial "high permeability selectivity" advantage.

[0005] To improve acid resistance, the conventional approach is to increase the monomer concentration, extend the reaction time, or perform deep cross-linking post-treatment to increase the cross-linking density and prepare a denser separation layer to block acid molecules from penetrating. However, this often sacrifices the membrane's permeability, leading to a sharp drop in water flux and exposing the inherent contradiction between "high permeability selectivity" and "acid resistance" that is difficult to reconcile.

[0006] Therefore, there is an urgent need to propose a solution to address the aforementioned technical problems. Summary of the Invention

[0007] In order to significantly improve the performance degradation of polyamide nanofiltration membranes in strong acid environments and synergistically achieve long-term stable high permeability and high selectivity in acidic environments, this application provides a high-permeability and selective acid-resistant nanofiltration membrane, its preparation method, and its application.

[0008] In a first aspect, this application provides a highly permeable, selective, acid-resistant nanofiltration membrane, employing the following technical solution: A highly permeable, selective, acid-resistant nanofiltration membrane includes a base membrane and a functional layer formed on the base membrane by interfacial polymerization; The functional layer is prepared by interfacial polymerization of raw materials including oil phase solution and aqueous phase solution; The oil phase solution is composed of the following raw materials by weight percentage: Trimethylbenzene chloride 0.1-1%; The balance is n-hexane; The aqueous solution is composed of the following raw materials by weight percentage: Piperazine 0.5-3%; Acid-resistant comonomer 0.2-0.8%; Carboxylated acid-resistant framework material 0.02-0.05%; Surfactant 0.1-1%; 1-3% of camphor sulfonate triethylamine salt; The remainder is deionized water; The acid-resistant comonomer is composed of triethanolamine and 3,5-diaminobenzenesulfonic acid in a weight ratio of 1:(1-1.2); The carboxylated acid-resistant framework material was prepared by the following steps: S1. After mixing lithium fluoride and hydrochloric acid, add titanium aluminum carbide powder and react at 35-40℃ for 20-24h. After repeated centrifugation and washing with deionized water, collect the bottom precipitate to obtain the pretreated intermediate material. S2. Disperse the pretreated intermediate material obtained in step S1 in deionized water, add aminotrimethylenephosphonic acid, adjust the pH of the solution to 4-5 with alkali, and then reflux at 55-65℃ for 6-8 hours. After repeated centrifugation and washing with ethanol / water mixed solvent, collect the bottom precipitate to obtain the carboxylated intermediate material. S3. Disperse the carboxylated intermediate material obtained in step S2 in a tetramethylammonium hydroxide aqueous solution, treat it at 25-30℃ for 10-12h, then sonicate it at 250-350W for 50-70min in an ice bath, then centrifuge it at 3000-4000rpm for 25-35min to collect the supernatant, and then centrifuge the supernatant at 12000-13000rpm for 25-35min to collect the bottom precipitate, and obtain the carboxylated acid-resistant framework material, and redisperse it in deionized water for later use.

[0009] By adopting the above technical solution, in the preparation of carboxylated acid-resistant framework materials, titanium aluminum carbide powder is first treated with a mixture of hydrochloric acid and lithium fluoride, and the aluminum layer is selectively etched away to obtain a multi-layered sheet-like pretreatment intermediate material. Then, aminotrimethylene phosphonic acid is introduced, and the phosphonic acid group of aminotrimethylene phosphonic acid undergoes a coordination reaction with the -OH / F on the surface of the pretreatment intermediate material, while simultaneously introducing terminal carboxyl groups to obtain a carboxylated intermediate material. Finally, through the linkage of tetramethylammonium hydroxide and ultrasound, the carboxylated intermediate material is exfoliated into few-layer nanosheets, which greatly increases the specific surface area, enabling the obtained carboxylated acid-resistant framework material to be uniformly embedded in the polyamide network. After the application of carboxylated acid-resistant framework materials, their covalent bonding with the polymer network is like driving "steel bars" into soft soil. This structure is extremely stable in acid and is not prone to hydrolytic breakage. It can physically block the excessive swelling and peeling of polyamide chains in acid. Moreover, the rigidity of the carboxylated acid-resistant framework itself distributes the stress of the polyamide chains, reduces the direct attack on the amide bonds, and thus prevents the decrease in selectivity caused by the increase in effective pore size. Furthermore, the carboxylated acid-resistant framework material has a smooth surface and two-dimensional interlayer channels, providing a low-resistance transport path for water molecules.

[0010] For the use of acid-resistant comonomers composed of triethanolamine and 3,5-diaminobenzenesulfonic acid, the large spatial structure of triethanolamine, upon entering the polyamide network, can partially replace the reaction between piperazine and trimesoyl chloride, moderately reducing the crosslinking density of the network. This helps to form a looser, more "open" polymer network, thus tending to increase water flux. Furthermore, the multiple hydroxyl groups introduced are strongly hydrophilic groups, significantly enhancing the hydrophilicity of the functional layer. These hydroxyl groups can stabilize the polyamide network through hydrogen bonding, providing a certain "shielding" protection to ester / amide bonds in acidic environments, thereby improving hydrolytic stability. Qualitative analysis reveals that the sulfonic acid group introduced by 3,5-diaminobenzenesulfonic acid dissociates into negatively charged sulfonate groups in most aqueous environments. This sulfonate group imparts a permanent, high-density negative charge to the separation layer, significantly improving the rejection rate for divalent cations and protecting the amide bond under acidic conditions. Therefore, the complementary synergy between the two properties allows the loosening effect of triethanolamine to offset some of the flux reduction caused by the sulfonic acid monomer, while the high selectivity of the sulfonic acid monomer can compensate for the possible rejection rate loss caused by triethanolamine. This, in turn, is conducive to the synergistic achievement of long-term stable high permeability and high selectivity of nanofiltration membranes in acidic environments.

[0011] Meanwhile, the combination of the aforementioned acid-resistant comonomers and carboxylated acid-resistant skeleton materials not only achieves high selectivity by relying on the stability of the dual charge of sulfonic acid / phosphonic acid under acidic conditions, but also achieves high permeability by relying on the lubrication effect of two-dimensional interlayer channels and hydrophilic groups. Furthermore, the synergistic compounding exhibits excellent acid resistance, thus significantly improving the performance degradation of polyamide nanofiltration membranes in strong acid environments and synergistically achieving long-term stable high permeability and high selectivity in acidic environments, ultimately resulting in a high-permeability, high-selectivity acid-resistant nanofiltration membrane with superior application quality.

[0012] Preferably, in the preparation of the carboxylated acid-resistant skeleton material, the particle size of the titanium aluminum carbide powder in step S1 is 10-20 μm.

[0013] By adopting the above technical solution, firstly, the etching rate of the aluminum layer by mixing hydrochloric acid and lithium fluoride is made uniform, avoiding local "perforation" or structural collapse; secondly, the pre-treated intermediate material obtained after etching is guaranteed to have a suitable interlayer spacing, which is conducive to aminotrimethylene phosphonic acid entering the interlayer and playing a full role; finally, through the linkage of tetramethylammonium hydroxide and ultrasound, high-quality carboxylated acid-resistant skeleton material with large lateral dimensions and few layers can be efficiently peeled out.

[0014] Preferably, in the preparation of the carboxylated acid-resistant skeleton material, the weight ratio of aminotrimethylenephosphonic acid to pretreatment intermediate material in step S2 is (5-10):1.

[0015] By adopting the above technical solution, aminotrimethylenephosphonic acid can form a strong driving force to be extruded into the interlayer of pretreated intermediate material, functionalizing the inner layers rather than just modifying the outermost surface, and forming a dense and flexible organic layer, thereby bringing about the excellent subsequent effects.

[0016] Preferably, in the preparation of the carboxylated acid-resistant skeleton material, the mass concentration of the tetramethylammonium hydroxide aqueous solution in step S3 is 5-10%, and the weight ratio of tetramethylammonium hydroxide to carboxylated intermediate material is (1.5-3.5):1.

[0017] By adopting the above technical solution, the intercalation depth and surface charge density are controlled in a coordinated manner, ensuring that the carboxylated acid-resistant skeleton material enters the membrane preparation system in a state of few layers, high negative charge, and high hydrophilicity. Thus, in an acidic environment, it can act as a rigid skeleton to resist the excessive swelling and peeling of polyamide chains, and also act as a fast water channel to maintain high flux.

[0018] Preferably, the base film is pretreated before use, and the pretreatment steps are as follows: The base membrane was ultrasonically treated in ethanol and deionized water in sequence, then immersed in the pretreatment solution and reacted with shaking at 25-30℃ for 3-4 hours. After rinsing with deionized water, it was dried to obtain the pretreated base membrane. The pretreatment solution is composed of the following raw materials by weight percentage: Polyethyleneimine 1.8-2.2%; 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride 0.08-0.1%; N-hydroxysuccinimide 0.05-0.06%; The remainder is phosphate buffer solution.

[0019] By adopting the above technical solution, during the pretreatment of the base film, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, as an activator, first reacts with the residual carboxyl groups on the surface of the base film to generate an unstable intermediate. Then, N-hydroxysuccinimide immediately reacts with the intermediate to generate a stable amino-reactive NHS ester. The NHS ester then undergoes an amidation reaction with the amino group of polyethyleneimine at 25-30℃, covalently grafting polyethyleneimine onto the surface of the base film to obtain the pretreated base film. Because polyethyleneimine is a highly branched polymer containing a large number of primary and secondary amine groups, it transforms the base membrane surface into an amino-rich active interface, providing a perfect chemical starting point for the subsequent construction of highly permeable and highly selective functional layers. Normally, in a strong acid environment, the polyamide layer and the base membrane rely solely on physical adsorption, which easily leads to interfacial slippage or delamination. However, the use of pretreated base membranes is equivalent to establishing chemical anchoring points between the base membrane and the functional layers, greatly enhancing the interfacial bonding force and preventing interlayer delamination caused by acid penetration. In this way, the overall application quality of the obtained highly permeable and selective acid-resistant nanofiltration membrane can be further improved.

[0020] Preferably, the molecular weight of the polyethyleneimine is 600-1000 Da.

[0021] By adopting the above technical solution, not only is deep penetration of small-molecule polyethyleneimine and pore blockage of large-molecule polyethyleneimine avoided, and the original water flux of the base membrane is preserved to the maximum extent, but uniform and continuous amino groups can also be formed on the surface of the base membrane, providing uniform nucleation sites for the subsequent interfacial polymerization of oil and aqueous solutions. This effectively avoids "pinholes" or "defects" caused by uneven wettability of the base membrane, thus ensuring a high rejection rate. In this way, polyethyleneimine in the above molecular weight range not only enhances the structural stability of the membrane in acid through covalent bonds, but also avoids pore blockage of the base membrane due to its moderate size, perfectly supporting the dual goals of high permeability selectivity and acid resistance.

[0022] Secondly, this application provides a method for preparing a highly permeable, selective, acid-resistant nanofiltration membrane, employing the following technical solution: A method for preparing a highly permeable, selective, acid-resistant nanofiltration membrane includes the following steps: (1) Prepare the raw materials for the base film and the oil phase solution and aqueous phase solution required for the preparation of the functional layer according to the ratio, and prepare the oil phase solution and aqueous phase solution; (2) After rinsing the base membrane with deionized water, place it on clean filter paper to drain naturally, then immerse it in the aqueous solution and let it stand for 110-130 seconds. Remove it to remove the residual liquid on the surface, then immerse it in the oil solution for 55-65 seconds. After removing it again to remove the residual liquid on the surface, heat it at 65-70℃ for 5-8 minutes to form a functional layer, and finally obtain a high-permeability selective acid-resistant nanofiltration membrane.

[0023] By adopting the above technical solution, the above preparation operation is relatively simple. The impregnation method + interfacial polymerization is a mature process for nanofiltration membrane preparation. The parameters are easy to optimize and can form a uniform, complete and defect-free functional layer structure. It is suitable for large-scale industrial production and achieves high-quality preparation of high-permeability selective acid-resistant nanofiltration membranes.

[0024] Preferably, step (2) is specifically set as follows: After rinsing the base film with deionized water, place it on clean filter paper to drain naturally, then immerse it in the aqueous solution and let it stand for 110-130 seconds. Remove it to remove the residual liquid on the surface, then immerse it in the oil solution and let the reaction continue for 55-65 seconds. After removing it again to remove the residual liquid on the surface, heat it at 65-70℃ for 5-8 minutes to form a functional layer. Next, the membrane was placed in a Tris-HCl buffer solution of dopamine hydrochloride and shaken for 2-4 hours. After washing with deionized water, it was placed in a mixed reaction solution containing tetraethyl orthosilicate, ammonia, and ethanol / water solvent and allowed to stand in an ice-water bath for 25-35 minutes. Finally, it was taken out, rinsed with deionized water, and vacuum dried to obtain a high-permeability selective acid-resistant nanofiltration membrane.

[0025] By adopting the above technical solution, dopamine hydrochloride is polymerized into polydopamine for deposition. Polydopamine is rich in catechol and amino groups, which can firmly adhere to almost all solid surfaces under mild conditions. Its abundant functional groups are ideal anchors for subsequent silanization reactions. Then, under the induction of polydopamine, tetraethyl orthosilicate is used to carry out a sol-gel reaction under the catalysis of ammonia to construct a stable, amorphous, and defect-free silica protective layer. This not only provides a top-level chemical inert barrier to resist strong acid erosion, but its microporous structure can further improve selectivity without significantly sacrificing flux. This can significantly improve the stability of the final high-permeability selective acid-resistant nanofiltration membrane in acidic environments.

[0026] Preferably, the concentration of dopamine hydrochloride in the Tris-HCl buffer solution is 10-15 mM; and the concentration of tetraethyl orthosilicate in the mixed reaction solution is 0.1-0.15 wt%.

[0027] By adopting the above technical solution, the polymerization behavior of dopamine hydrochloride in this concentration range perfectly matches the requirements of acid-resistant high-flux membranes; while the in-situ hydrolysis of tetraethyl orthosilicate at this extremely low concentration is not aimed at forming a dense silica layer, but mainly at constructing a nanoscale dot-like anchoring network to form a uniform amorphous silica protective layer; therefore, the above parameters avoid the flux decay trap caused by excessive coating, and by constructing an ultrathin, conformal, and hybrid protective layer, the membrane structure is endowed with extremely strong acid resistance stability while maintaining the initial high permeability.

[0028] Thirdly, this application provides an application of a highly permeable, selective, acid-resistant nanofiltration membrane in the separation, purification, and resource recovery of acidic media.

[0029] In summary, this application has the following beneficial effects: 1. This application uses an acid-resistant comonomer composed of triethanolamine and 3,5-diaminobenzenesulfonic acid in an aqueous solution, and combines it with a specially prepared carboxylated acid-resistant skeleton material for synergistic compounding. This can significantly improve the performance degradation of polyamide nanofiltration membranes in strong acid environments, and synergistically achieve long-term stable high permeability and high selectivity in acidic environments, ultimately obtaining a high-permeability and high-selectivity acid-resistant nanofiltration membrane with better application quality. 2. This application pre-treats the base membrane before use by covalently grafting polyethyleneimine onto the surface of the base membrane, which is equivalent to establishing chemical anchoring points between the base membrane and the functional layer, greatly enhancing the interfacial bonding force and preventing interlayer delamination caused by acid penetration; thus, the overall application quality of the obtained high-permeability selective acid-resistant nanofiltration membrane can be further improved. 3. In this application, after forming a functional layer on the base membrane through interfacial polymerization, polydopamine is first deposited, and then tetraethyl orthosilicate is used to carry out a sol-gel reaction under the catalysis of ammonia water to construct a stable, amorphous, and defect-free silica protective layer. This not only provides a top-level chemical inert barrier to resist strong acid erosion, but its microporous structure can also further improve selectivity without significantly sacrificing flux, thus significantly improving the stability of the high-permeability selective acid-resistant nanofiltration membrane in acidic environments. Detailed Implementation

[0030] The present application will be further described in detail below with reference to preparation examples, embodiments and comparative examples.

[0031] Unless otherwise specified, all raw materials used in the preparation examples, embodiments and comparative examples of this application are commercially available.

[0032] The base membrane is a polyethersulfone ultrafiltration membrane with a molecular weight cutoff of 35 kDa and a thickness of 100 μm; The surfactant is sodium dodecyl sulfate; The pH of the phosphate buffer solution is 7.4; The pH of the Tris-HCl buffer solution is 8.5; The ethanol / water solvent is obtained by mixing ethanol and water in a volume ratio of 4:1.

[0033] Preparation Example 1: A carboxylated acid-resistant framework material was prepared by the following steps: S1. After mixing lithium fluoride and hydrochloric acid, titanium aluminum carbide powder is added. After reacting at 37.5℃ for 22 hours, the bottom precipitate is collected after repeated centrifugation and washing with deionized water to obtain the pretreated intermediate material. S2. Disperse the pretreated intermediate material obtained in step S1 in deionized water at a concentration of 5 mg / mL. After adding aminotrimethylenephosphonic acid, adjust the pH of the solution to 4.5 with alkali. Then, reflux the reaction at 60°C for 7 h. After repeated centrifugation and washing with ethanol / water mixed solvent, collect the bottom precipitate to obtain the carboxylated intermediate material. S3. The carboxylated intermediate material obtained in step S2 is dispersed in a tetramethylammonium hydroxide aqueous solution and treated at 27.5°C for 11 h. Then, it is ultrasonically treated at 300 W for 60 min in an ice bath. After that, it is centrifuged at 3500 rpm for 30 min to collect the supernatant. Then, the supernatant is centrifuged at 12500 rpm for 30 min to collect the bottom precipitate, and the carboxylated acid-resistant framework material is obtained. It is then redispersed in deionized water for storage and later use.

[0034] Note: In the above operations, in step S1, the ratio of lithium fluoride, hydrochloric acid, and titanium aluminum carbide powder is 1g:20mL:1g, and the particle size of the titanium aluminum carbide powder is 15μm. In step S2, the weight ratio of aminotrimethylenephosphonic acid to the pretreatment intermediate is 7.5:1. In step S3, the mass concentration of the tetramethylammonium hydroxide aqueous solution is 7.5%, and the weight ratio of tetramethylammonium hydroxide to the carboxylation intermediate is 2.5:1.

[0035] Preparation Example 2, a carboxylated acid-resistant framework material, differs from Preparation Example 1 in that it is prepared by the following steps: S1. After mixing lithium fluoride and hydrochloric acid, titanium aluminum carbide powder is added. After reacting at 35°C for 24 hours, the bottom precipitate is collected after repeated centrifugation and washing with deionized water to obtain the pretreated intermediate material. S2. Disperse the pretreated intermediate material obtained in step S1 in deionized water at a concentration of 5 mg / mL. After adding aminotrimethylenephosphonic acid, adjust the pH of the solution to 4 with alkali. Then, reflux the reaction at 55°C for 8 hours. After repeated centrifugation and washing with ethanol / water mixed solvent, collect the bottom precipitate to obtain the carboxylated intermediate material. S3. The carboxylated intermediate material obtained in step S2 is dispersed in a tetramethylammonium hydroxide aqueous solution and treated at 25°C for 12 hours. Then, it is ultrasonically treated at 250W for 70 minutes in an ice bath. After that, it is centrifuged at 3000 rpm for 35 minutes to collect the supernatant. Then, the supernatant is centrifuged at 12000 rpm for 35 minutes to collect the bottom precipitate and obtain the carboxylated acid-resistant framework material. It is then redispersed in deionized water for storage and later use.

[0036] Preparation Example 3, a carboxylated acid-resistant framework material, differs from Preparation Example 1 in that it is prepared by the following steps: S1. After mixing lithium fluoride and hydrochloric acid, titanium aluminum carbide powder is added. After reacting at 40°C for 20 hours, the bottom precipitate is collected after repeated centrifugation and washing with deionized water to obtain the pretreated intermediate material. S2. Disperse the pretreated intermediate material obtained in step S1 in deionized water at a concentration of 5 mg / mL. After adding aminotrimethylenephosphonic acid, adjust the pH of the solution to 5 with alkali. Then, reflux the reaction at 65°C for 6 hours. After repeated centrifugation and washing with ethanol / water mixed solvent, collect the bottom precipitate to obtain the carboxylated intermediate material. S3. The carboxylated intermediate material obtained in step S2 is dispersed in a tetramethylammonium hydroxide aqueous solution and treated at 30°C for 10 hours. Then, it is ultrasonically treated at 350W for 50 minutes in an ice bath. After that, it is centrifuged at 4000rpm for 25 minutes to collect the supernatant. Then, the supernatant is centrifuged at 13000rpm for 25 minutes to collect the bottom precipitate, and the carboxylated acid-resistant framework material is obtained. It is then redispersed in deionized water for storage and later use.

[0037] Preparation Example 4, a carboxylated acid-resistant framework material, differs from Preparation Example 1 in that the particle size of the titanium aluminum carbide powder in step S1 is 10 μm.

[0038] Preparation Example 5: A carboxylated acid-resistant framework material, which differs from Preparation Example 1 in that the particle size of the titanium aluminum carbide powder in step S1 is 20 μm.

[0039] Preparation Example 6, a carboxylated acid-resistant framework material, differs from Preparation Example 1 in that the weight ratio of aminotrimethylenephosphonic acid to pretreatment intermediate material in step S2 is 5:1.

[0040] Preparation Example 7, a carboxylated acid-resistant framework material, differs from Preparation Example 1 in that the weight ratio of aminotrimethylenephosphonic acid and pretreatment intermediate material in step S2 is 10:1.

[0041] Preparation Example 8: A carboxylated acid-resistant framework material, which differs from Preparation Example 1 in that the mass concentration of the tetramethylammonium hydroxide aqueous solution in step S3 is 5%, and the weight ratio of tetramethylammonium hydroxide to carboxylated intermediate material is 1.5:1.

[0042] Preparation Example 9: A carboxylated acid-resistant framework material, which differs from Preparation Example 1 in that the mass concentration of the tetramethylammonium hydroxide aqueous solution in step S3 is 10%, and the weight ratio of tetramethylammonium hydroxide to carboxylated intermediate material is 3.5:1.

[0043] Example 1: A high-permeability selective acid-resistant nanofiltration membrane includes a base membrane and a functional layer formed on the base membrane by interfacial polymerization. The functional layer is obtained by interfacial polymerization of an oil phase solution and an aqueous phase solution. The composition and weight percentage of the raw materials of the oil phase solution are shown in Table 1, and the composition and weight percentage of the raw materials of the aqueous phase solution are shown in Table 2. The high-permeability selective acid-resistant nanofiltration membrane is prepared by the following steps: (1) Prepare the raw materials for the base film and the oil phase solution and aqueous phase solution required for the preparation of the functional layer according to the ratio, and prepare the oil phase solution and aqueous phase solution; (2) After rinsing the base membrane with deionized water, place it on clean filter paper to drain naturally, then immerse it in the aqueous solution and let it stand for 120 seconds. Remove it to remove the residual liquid on the surface, then immerse it in the oil solution for 60 seconds. After removing it again to remove the residual liquid on the surface, heat it at 67.5℃ for 6.5 minutes to form a functional layer, and finally obtain a high-permeability selective acid-resistant nanofiltration membrane.

[0044] Note: The acid-resistant comonomer in the above aqueous solution is composed of triethanolamine and 3,5-diaminobenzenesulfonic acid in a weight ratio of 1:1.1, and the carboxylated acid-resistant skeleton material was obtained from Preparation Example 1.

[0045] Example 2, a high-permeability selective acid-resistant nanofiltration membrane, differs from Example 1 in that it is prepared by the following steps: (1) Prepare the raw materials for the base film and the oil phase solution and aqueous phase solution required for the preparation of the functional layer according to the ratio, and prepare the oil phase solution and aqueous phase solution; (2) After rinsing the base membrane with deionized water, place it on clean filter paper to drain naturally, then immerse it in the aqueous solution and let it stand for 110 seconds. Remove it to remove the residual liquid on the surface, then immerse it in the oil solution for 55 seconds. After removing it again to remove the residual liquid on the surface, heat it at 65°C for 8 minutes to form a functional layer, and finally obtain a high-permeability selective acid-resistant nanofiltration membrane.

[0046] Example 3, a high-permeability selective acid-resistant nanofiltration membrane, differs from Example 1 in that it is prepared by the following steps: (1) Prepare the raw materials for the base film and the oil phase solution and aqueous phase solution required for the preparation of the functional layer according to the ratio, and prepare the oil phase solution and aqueous phase solution; (2) After rinsing the base membrane with deionized water, place it on clean filter paper to drain naturally, then immerse it in the aqueous solution and let it stand for 130 seconds. Remove it to remove the residual liquid on the surface, then immerse it in the oil solution for 65 seconds. After removing it again to remove the residual liquid on the surface, heat it at 70°C for 5 minutes to form a functional layer, and finally obtain a high-permeability selective acid-resistant nanofiltration membrane.

[0047] Example 4, a high-permeability selective acid-resistant nanofiltration membrane, differs from Example 1 in that the acid-resistant comonomer in the aqueous solution is composed of triethanolamine and 3,5-diaminobenzenesulfonic acid in a weight ratio of 1:1.

[0048] Example 5, a high-permeability selective acid-resistant nanofiltration membrane, differs from Example 1 in that the acid-resistant comonomer in the aqueous solution is composed of triethanolamine and 3,5-diaminobenzenesulfonic acid in a weight ratio of 1:1.2.

[0049] Example 6, a high-permeability selective acid-resistant nanofiltration membrane, differs from Example 1 in that the carboxylated acid-resistant framework material is obtained from Preparation Example 2.

[0050] Example 7, a high-permeability selective acid-resistant nanofiltration membrane, differs from Example 1 in that the carboxylated acid-resistant framework material is obtained from Preparation Example 3.

[0051] Example 8, a high-permeability selective acid-resistant nanofiltration membrane, differs from Example 1 in that the carboxylated acid-resistant framework material is obtained from Preparation Example 4.

[0052] Example 9, a high-permeability selective acid-resistant nanofiltration membrane, differs from Example 1 in that the carboxylated acid-resistant framework material is obtained from Preparation Example 5.

[0053] Example 10, a high-permeability selective acid-resistant nanofiltration membrane, differs from Example 1 in that the carboxylated acid-resistant framework material was obtained from Preparation Example 6.

[0054] Example 11, a high-permeability selective acid-resistant nanofiltration membrane, differs from Example 1 in that the carboxylated acid-resistant framework material was obtained from Preparation Example 7.

[0055] Example 12, a high-permeability selective acid-resistant nanofiltration membrane, differs from Example 1 in that the carboxylated acid-resistant framework material was obtained from Preparation Example 8.

[0056] Example 13, a high-permeability selective acid-resistant nanofiltration membrane, differs from Example 1 in that the carboxylated acid-resistant framework material was obtained from Preparation Example 9.

[0057] Examples 14-15 describe a high-permeability selective acid-resistant nanofiltration membrane, which differs from Example 1 in that the raw materials and corresponding weight percentages of the oil phase solution are shown in Table 1.

[0058] Table 1. Composition of the oil phase solutions in Examples 1 and 14-15 and their corresponding weight percentages (%) Examples 16-17 describe a high-permeability selective acid-resistant nanofiltration membrane, which differs from Example 1 in that the raw materials and corresponding weight percentages of the aqueous solution are shown in Table 2.

[0059] Table 2. Composition of raw materials and corresponding weight percentages (%) of aqueous solutions in Examples 1, 16-17 Example 18, a high-permeability selective acid-resistant nanofiltration membrane, differs from Example 1 in that the base membrane undergoes pretreatment before use. The pretreatment steps are as follows: The base membrane was subjected to ultrasonic treatment at 200W for 10 min in ethanol and deionized water, then immersed in the pretreatment solution and reacted with shaking at 25℃ for 4 h. After rinsing with deionized water, it was dried to obtain the pretreated base membrane.

[0060] Note: The raw materials and their corresponding weight percentages of the pretreatment solution in the above pretreatment process are shown in Table 3.

[0061] Example 19, a high-permeability selective acid-resistant nanofiltration membrane, differs from Example 18 in that the pretreatment steps are as follows: The base membrane was subjected to ultrasonic treatment at 200W for 10 min in ethanol and deionized water, then immersed in the pretreatment solution and reacted with shaking at 30℃ for 3 h. After rinsing with deionized water, it was dried to obtain the pretreated base membrane.

[0062] Example 20, a high-permeability selective acid-resistant nanofiltration membrane, differs from Example 18 in that the pretreatment steps are as follows: The base membrane was subjected to ultrasonic treatment at 200W for 10 min in ethanol and deionized water, then immersed in the pretreatment solution and reacted with shaking at 27.5℃ for 3.5 h. After rinsing with deionized water, it was dried to obtain the pretreated base membrane.

[0063] Examples 21-22, a high-permeability selective acid-resistant nanofiltration membrane, differ from Example 18 in that the raw materials and corresponding weight percentages of the pretreatment solution are shown in Table 3.

[0064] Table 3. Composition of the pretreatment solutions in Examples 18 and 21-22 and their corresponding weight percentages (%) Example 23, a high-permeability selective acid-resistant nanofiltration membrane, differs from Example 1 in that step (2) is specifically set as follows: After rinsing the base membrane with deionized water, place it on clean filter paper to drain naturally, then immerse it in an aqueous solution and let it stand for 120 seconds. Remove it to remove any residual liquid from the surface, then immerse it in an oil solution for 60 seconds. Remove it again to remove any residual liquid from the surface, and then heat treat it at 67.5℃ for 6.5 minutes to form a functional layer. Next, the membrane was placed in a Tris-HCl buffer solution of dopamine hydrochloride and shaken for 3 hours. After washing with deionized water, it was placed in a mixed reaction solution containing tetraethyl orthosilicate, ammonia, and ethanol / water solvent and allowed to stand in an ice-water bath for 30 minutes. Finally, it was taken out, rinsed with deionized water, and vacuum dried to obtain a high-permeability selective acid-resistant nanofiltration membrane.

[0065] Note: In the above operation, the concentration of dopamine hydrochloride in the Tris-HCl buffer solution was 12.5 mM; the concentration of tetraethyl orthosilicate in the mixed reaction solution was 0.125 wt%, and the pH of the mixed reaction solution was 8.0.

[0066] Example 24, a high-permeability selective acid-resistant nanofiltration membrane, differs from Example 23 in that it is placed in a Tris-HCl buffer solution of dopamine hydrochloride and shaken for 2 hours. After being removed and washed with deionized water, it is placed in a mixed reaction solution containing tetraethyl orthosilicate, ammonia and ethanol / water solvent, and allowed to stand in an ice-water bath for 25 minutes. Finally, it is removed, rinsed with deionized water and vacuum dried to obtain a high-permeability selective acid-resistant nanofiltration membrane.

[0067] Example 25, a high-permeability selective acid-resistant nanofiltration membrane, differs from Example 23 in that it is placed in a Tris-HCl buffer solution of dopamine hydrochloride and shaken for 4 hours. After being removed and washed with deionized water, it is placed in a mixed reaction solution containing tetraethyl orthosilicate, ammonia and ethanol / water solvent, and allowed to stand in an ice-water bath for 35 minutes. Finally, it is removed, rinsed with deionized water and vacuum dried to obtain a high-permeability selective acid-resistant nanofiltration membrane.

[0068] Example 26, a highly permeable selective acid-resistant nanofiltration membrane, differs from Example 23 in that the concentration of dopamine hydrochloride in the Tris-HCl buffer solution is 10 mM; the concentration of tetraethyl orthosilicate in the mixed reaction solution is 0.1 wt%, and the pH of the mixed reaction solution is 8.0.

[0069] Example 27, a highly permeable selective acid-resistant nanofiltration membrane, differs from Example 23 in that the concentration of dopamine hydrochloride in the Tris-HCl buffer solution is 15 mM; the concentration of tetraethyl orthosilicate in the mixed reaction solution is 0.15 wt%, and the pH of the mixed reaction solution is 8.0.

[0070] Comparative Example 1, a highly permeable selective acid-resistant nanofiltration membrane, differs from Example 1 in that triethanolamine and 3,5-diaminobenzenesulfonic acid are not used in the aqueous solution.

[0071] Comparative Example 2, a highly permeable selective acid-resistant nanofiltration membrane, differs from Example 1 in that triethanolamine and carboxylated acid-resistant framework materials are not used in the aqueous solution.

[0072] Comparative Example 3, a highly permeable selective acid-resistant nanofiltration membrane, differs from Example 1 in that 3,5-diaminobenzenesulfonic acid and carboxylated acid-resistant framework materials are not used in the aqueous solution.

[0073] Comparative Example 4, a highly permeable selective acid-resistant nanofiltration membrane, differs from Example 1 in that triethanolamine is not used in the aqueous solution.

[0074] Comparative Example 5, a highly permeable selective acid-resistant nanofiltration membrane, differs from Example 1 in that 3,5-diaminobenzenesulfonic acid is not used in the aqueous solution.

[0075] Comparative Example 6, a high-permeability selective acid-resistant nanofiltration membrane, differs from Example 1 in that no carboxylated acid-resistant framework material is used in the aqueous solution.

[0076] Comparative Example 7, a highly permeable selective acid-resistant nanofiltration membrane, differs from Example 1 in that triethanolamine, 3,5-diaminobenzenesulfonic acid, and carboxylated acid-resistant framework materials are not used in the aqueous solution.

[0077] Performance testing Test samples: The high-permeability selective acid-resistant nanofiltration membranes obtained in Examples 1-27 were selected as test samples 1-27, and the high-permeability selective acid-resistant nanofiltration membranes obtained in Comparative Examples 1-7 were selected as control samples 1-7.

[0078] Test method: A pressure vessel with an inner diameter of 2 inches was used, the test pressure was 0.5 MPa, and the effective membrane area (A) was 25 cm². 2 The test temperature was 25℃, and then the following tests were performed: (1) Desalination rate test: The desalination rate reflects the membrane’s ability to retain ions. In a strong acid environment, magnesium sulfate solution is usually used as the test solution, which can well examine the membrane’s charge repulsion (Downan effect) and sieving performance under acidic conditions.

[0079] Prepare a magnesium sulfate solution with a concentration of 2000 mg / L, then strictly adjust the pH of the solution to 1.0 using analytical grade hydrochloric acid. Calculate the desalination rate after running the test for 30 minutes. Desalination rate (%) = (C f -C p ) / C f ×100%, where C f C represents the feed concentration. p The concentration of the permeate.

[0080] (2) Flux test: Flux measures the permeation rate of the membrane. Using the above-mentioned acidic magnesium sulfate solution, after running under constant temperature and pressure for 30 minutes, accurately measure the volume of permeate collected within a certain time (t, converted to hours h) using a graduated cylinder and stopwatch (V, in liters L), and then calculate the flux: Flux (L·m) -2 ·h -1 ·bar -1 =V / (A×t×P), where P is the test pressure.

[0081] (3) Acid resistance test, which is an accelerated aging test index used to evaluate the cumulative chemical dose that the membrane can withstand in strong acid. "ppm·h" is a commonly used unit in the chemical stability test of membrane materials, representing the cumulative exposure of "concentration (ppm) × time (h)".

[0082] Prepare a strong acid solution of a certain concentration, and completely immerse the membrane sample in the acid solution at a constant temperature of 25°C. Remove the membrane sample every 24 hours, rinse it thoroughly with deionized water, and then test its pure water flux. Stop the test when the pure water flux attenuation rate of the membrane sample reaches more than 50%. Finally, calculate the acid resistance value. Acid resistance value = C × t, where C is the concentration of the soaking solution and t is the total soaking time.

[0083] After performing the above tests on test samples 1-27 and control samples 1-7, the test results are recorded in Table 4.

[0084] Table 4. Test results of test samples 1-27 and control samples 1-7 As can be seen from Examples 1-17 and Comparative Examples 1-7, and Table 4, the use of an acid-resistant comonomer composed of triethanolamine and 3,5-diaminobenzenesulfonic acid in an aqueous solution, combined with a specially prepared carboxylated acid-resistant framework material, can significantly improve the performance degradation of polyamide nanofiltration membranes under strong acid conditions. It also synergistically achieves long-term stable high permeability and high selectivity under acidic conditions. The resulting high-permeability, selective acid-resistant nanofiltration membrane, after the above tests, shows significant improvements in desalination rate, flux, and acid resistance. Furthermore, if any one of triethanolamine, 3,5-diaminobenzenesulfonic acid, and the carboxylated acid-resistant framework material is used alone or in combination, the corresponding effects are limited, and they only have a simple additive effect. Only when all three are used in combination can a synergistic improvement effect (1+1+1>3) be achieved, ultimately resulting in a high-permeability, selective acid-resistant nanofiltration membrane with superior application quality.

[0085] As can be seen from Examples 1 and 18-22 and Table 4, by pretreating the base membrane before use and covalently grafting polyethyleneimine onto the surface of the base membrane, chemical anchoring points are established between the base membrane and the functional layer, which greatly enhances the interfacial bonding force and prevents interlayer delamination caused by acid penetration. In this way, the desalination rate, flux and acid resistance value of the high-permeability selective acid-resistant nanofiltration membrane obtained by the above tests can be further improved.

[0086] As can be seen from Examples 1 and 23-27 and Table 4, after forming a functional layer on the base membrane through interfacial polymerization, polydopamine is first deposited, and then tetraethyl orthosilicate is used to carry out a sol-gel reaction under the catalysis of ammonia water to construct a stable, amorphous, and defect-free silica protective layer. This significantly improves the stability of the high-permeability selective acid-resistant nanofiltration membrane in acidic environments. The desalination rate, flux, and acid resistance value obtained by the above tests are all significantly improved.

[0087] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high permeate selective acid resistant nanofiltration membrane, characterized in that, Includes a base film and a functional layer formed on the base film through interfacial polymerization; The functional layer is prepared by interfacial polymerization of raw materials including oil phase solution and aqueous phase solution; The oil phase solution is composed of the following raw materials by weight percentage: Trimethylbenzene chloride 0.1-1%; The balance is n-hexane; The aqueous solution is composed of the following raw materials by weight percentage: Piperazine 0.5-3%; Acid-resistant comonomer 0.2-0.8%; Carboxylated acid-resistant framework material 0.02-0.05%; Surfactant 0.1-1%; 1-3% of camphor sulfonate triethylamine salt; The remainder is deionized water; The acid-resistant comonomer is composed of triethanolamine and 3,5-diaminobenzenesulfonic acid in a weight ratio of 1:(1-1.2); The carboxylated acid-resistant framework material was prepared by the following steps: S1. After mixing lithium fluoride and hydrochloric acid, add titanium aluminum carbide powder and react at 35-40℃ for 20-24h. After repeated centrifugation and washing with deionized water, collect the bottom precipitate to obtain the pretreated intermediate material. S2. Disperse the pretreated intermediate material obtained in step S1 in deionized water, add aminotrimethylenephosphonic acid, adjust the pH of the solution to 4-5 with alkali, and then reflux at 55-65℃ for 6-8 hours. After repeated centrifugation and washing with ethanol / water mixed solvent, collect the bottom precipitate to obtain the carboxylated intermediate material. S3. Disperse the carboxylated intermediate material obtained in step S2 in a tetramethylammonium hydroxide aqueous solution, treat it at 25-30℃ for 10-12h, then sonicate it at 250-350W for 50-70min in an ice bath, then centrifuge it at 3000-4000rpm for 25-35min to collect the supernatant, and then centrifuge the supernatant at 12000-13000rpm for 25-35min to collect the bottom precipitate, and obtain the carboxylated acid-resistant framework material, and redisperse it in deionized water for later use.

2. The high permeate selective acid resistant nanofiltration membrane according to claim 1, characterized in that: In the preparation of the carboxylated acid-resistant skeleton material, the particle size of the titanium aluminum carbide powder in step S1 is 10-20 μm.

3. The high permeate selective acid resistant nanofiltration membrane according to claim 1, wherein: In the preparation of the carboxylated acid-resistant skeleton material, the weight ratio of aminotrimethylenephosphonic acid and pretreatment intermediate material in step S2 is (5-10):

1.

4. The high permeate selective acid resistant nanofiltration membrane according to claim 1, wherein: In the preparation of the carboxylated acid-resistant skeleton material, the mass concentration of the tetramethylammonium hydroxide aqueous solution in step S3 is 5-10%, and the weight ratio of tetramethylammonium hydroxide to carboxylated intermediate material is (1.5-3.5):

1.

5. The high-permeability selective acid-resistant nanofiltration membrane according to claim 1, characterized in that: The base film undergoes pretreatment before use. The pretreatment steps are as follows: The base membrane was ultrasonically treated in ethanol and deionized water in sequence, then immersed in the pretreatment solution and reacted with shaking at 25-30℃ for 3-4 hours. After rinsing with deionized water, it was dried to obtain the pretreated base membrane. The pretreatment solution is composed of the following raw materials by weight percentage: Polyethyleneimine 1.8-2.2%; 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride 0.08-0.1%; N-hydroxysuccinimide 0.05-0.06%; The remainder is phosphate buffer solution.

6. The high-permeability selective acid-resistant nanofiltration membrane according to claim 5, characterized in that: The molecular weight of the polyethyleneimine is 600-1000 Da.

7. The method for preparing the high-permeability selective acid-resistant nanofiltration membrane according to claim 1, characterized in that: Includes the following steps: (1) Prepare the raw materials for the base film and the oil phase solution and aqueous phase solution required for the preparation of the functional layer according to the ratio, and prepare the oil phase solution and aqueous phase solution; (2) After rinsing the base membrane with deionized water, place it on clean filter paper to drain naturally, then immerse it in the aqueous solution and let it stand for 110-130 seconds. Remove it to remove the residual liquid on the surface, then immerse it in the oil solution for 55-65 seconds. After removing it again to remove the residual liquid on the surface, heat it at 65-70℃ for 5-8 minutes to form a functional layer, and finally obtain a high-permeability selective acid-resistant nanofiltration membrane.

8. The method for preparing the high-permeability selective acid-resistant nanofiltration membrane according to claim 7, characterized in that: Step (2) is specifically set as follows: After rinsing the base film with deionized water, place it on clean filter paper to drain naturally, then immerse it in the aqueous solution and let it stand for 110-130 seconds. Remove it to remove the residual liquid on the surface, then immerse it in the oil solution and let the reaction continue for 55-65 seconds. After removing it again to remove the residual liquid on the surface, heat it at 65-70℃ for 5-8 minutes to form a functional layer. Next, the membrane was placed in a Tris-HCl buffer solution of dopamine hydrochloride and shaken for 2-4 hours. After washing with deionized water, it was placed in a mixed reaction solution containing tetraethyl orthosilicate, ammonia, and ethanol / water solvent and allowed to stand in an ice-water bath for 25-35 minutes. Finally, it was taken out, rinsed with deionized water, and vacuum dried to obtain a high-permeability selective acid-resistant nanofiltration membrane.

9. The method for preparing a high-permeability, selective, acid-resistant nanofiltration membrane according to claim 8, characterized in that: In the Tris-HCl buffer solution of dopamine hydrochloride, the concentration of dopamine hydrochloride is 10-15 mM; in the mixed reaction solution, the concentration of tetraethyl orthosilicate is 0.1-0.15 wt%.

10. The application of the high-permeability selective acid-resistant nanofiltration membrane according to claim 1 in the separation, purification and resource recovery of acidic media.

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