Inorganic-organic hybrid acid-resistant nanofiltration membrane and preparation method thereof

Abstract

This application relates to the field of water treatment membrane separation technology, specifically disclosing an inorganic-organic hybrid acid-resistant nanofiltration membrane and its preparation method. An inorganic-organic hybrid acid-resistant nanofiltration membrane includes a support layer and a separation layer stacked sequentially. The separation layer is prepared by interfacial polymerization of raw materials including oil-phase reactants and aqueous-phase reactants. The aqueous-phase reactants use inorganic nano-sols, which are prepared as follows: first, a silica seed sol is obtained by hydrolysis-condensation reaction of tetraethyl orthosilicate; then, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and perfluorodecyltriethoxysilane are dissolved in anhydrous ethanol and added dropwise to the silica seed sol. After the reaction is completed with stirring, the membrane is purified by centrifugation. The inorganic nanoparticles in this inorganic-organic hybrid acid-resistant nanofiltration membrane are uniformly dispersed, have strong interfacial bonding, and exhibit excellent acid resistance, maintaining stable membrane separation performance during long-term application.

Description

Technical Field

[0001] This application relates to the field of water treatment membrane separation technology, and more specifically, it relates to an inorganic-organic hybrid acid-resistant nanofiltration membrane and its preparation method. 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 an important separation technology, nanofiltration membranes can allow solvent molecules or certain low molecular weight solutes and low-valence ions to pass through, while having a high rejection rate for high-valence ions and large organic molecules. They are widely used in water treatment, food and medicine, resource recycling and many other fields.

[0003] The core structure of nanofiltration membranes is typically a composite membrane, composed of an ultrathin active layer for separation and a porous support layer. The separation layer (active layer), located on the membrane surface, is extremely thin (nanoscale) and is crucial in determining the membrane's separation selectivity. This layer is usually composed of polyelectrolyte materials such as polyamides, and its surface carries a charge. Its nanoscale micropores achieve selective separation through a combination of sieving and Donnan effects (charge repulsion). The support layer, located below the separation layer, primarily provides mechanical strength. It has a porous structure and has a relatively small impact on separation performance, but it does affect the membrane's stability and flux. Studies have shown that separation layers doped with inorganic nanoparticles exhibit varying degrees of improvement in separation efficiency and stability. Currently, the commonly used method for preparing organic / inorganic hybrid membranes is the blending method, which involves directly doping inorganic nanoparticles into the solution used to prepare the separation layer, thus creating a membrane structure with separation capabilities.

[0004] Regarding the aforementioned technologies, the inventors believe that nanoparticles agglomerate due to their high surface energy during application. These agglomerates are essentially "hard lumps" inside the material, which easily lead to stress concentration under stress, becoming the origin of cracks. Furthermore, physical blending relies solely on weak van der Waals forces for bonding, resulting in voids at the interface. Under long-term operation, especially in acidic media and under shear forces, nanoparticles are easily lost, leading to unstable membrane separation performance. Therefore, a solution is urgently needed to address these technical problems. Summary of the Invention

[0005] In order to ensure that the inorganic nanoparticles in the nanofiltration membrane are uniformly dispersed, have strong interfacial bonding, and possess excellent acid resistance, and maintain good membrane separation performance during long-term application, this application provides an inorganic-organic hybrid acid-resistant nanofiltration membrane and its preparation method.

[0006] In a first aspect, this application provides an inorganic-organic hybrid acid-resistant nanofiltration membrane, employing the following technical solution: An inorganic-organic hybrid acid-resistant nanofiltration membrane comprises a support layer and a separation layer stacked sequentially. The separation layer is prepared by interfacial polymerization of raw materials including oil phase reactants and aqueous phase reactants; The aqueous reactants contain 2-3 wt% inorganic nanosol, which is prepared by the following steps: S1. Dissolve tetraethyl orthosilicate in anhydrous ethanol, and add dropwise an ethanol solution containing ammonia while stirring. Stir at 250-350 rpm for 1.5-2.5 h at 23-27℃ to obtain silica seed sol. S2. Cool the silica seed sol obtained in step S1 to 1-5℃, then dissolve N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and perfluorodecyltriethoxysilane in anhydrous ethanol, and then add them dropwise to the silica seed sol and stir to mix, to obtain a modified mixture. S3. Heat the modified mixture obtained in step S2 to 25-30℃ and continue stirring for 6-8 hours. After centrifugation and purification, inorganic nanosol is obtained. In step S1 above, the molar ratio of tetraethyl orthosilicate, anhydrous ethanol, H2O, and NH3 is 1:(9-11):(1.8-2.2):(0.1-0.2). In step S2 above, the molar ratio of N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, perfluorodecyltriethoxysilane, and anhydrous ethanol is (2.8-3.2):1:(330-350). Meanwhile, the molar ratio of tetraethyl orthosilicate, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and perfluorodecyltriethoxysilane is (18-22):(2.8-3.2):1.

[0007] By employing the above technical solution, in the preparation of inorganic nanosols, tetraethyl orthosilicate first undergoes a hydrolysis-condensation reaction under alkaline conditions catalyzed by ammonia water to generate monodisperse silica nanoseeds. The mild reaction conditions and low-speed stirring during this process aim to control the nucleation rate, avoid rapid aggregation, and ensure the acquisition of silica seed sols with controllable particle size. Next, dual functional groups are introduced onto the surface of the silica seeds; N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane provides reactive amino groups, enabling subsequent reactions with... The polyamide layer forms the "anchor" of CN covalent bonds, while the perfluorodecyltriethoxysilane provides hydrophobic / acid-resistant perfluorinated long chains, giving the film acid resistance and anti-swelling properties. The low temperature environment of 0-5℃ during the process is to slow down the hydrolysis rate of silane, so that it preferentially bonds with the silanol groups on the surface of silica nanoseeds, rather than self-polymerizing with each other, ensuring that the modified layer is uniform and dense. Finally, the modification reaction is completed by heating and ripening, and unreacted silane and byproducts are removed by centrifugation to obtain high-purity functionalized inorganic nanosol. When inorganic nanosols are added to aqueous reactants and then undergo interfacial polymerization with oil reactants, the separation layer of the nanofiltration membrane is a three-dimensional hybrid structure consisting of an organic polyamide network and surface-functionalized inorganic nanoparticles interconnected by covalent bonds. The inorganic nanoparticles are uniformly and firmly chemically bonded to the interior and surface of the polyamide network in a monodisperse or primary dispersion state, with no obvious interfacial voids, and can effectively block the penetration and erosion of strong acid molecules, thus maintaining good membrane separation performance stability during long-term application.

[0008] Meanwhile, in step S1, the molar ratio of tetraethyl orthosilicate, anhydrous ethanol, H2O, and NH3 is 1:(9-11):(1.8-2.2):(0.1-0.2), which is beneficial for generating small and uniform silica particles. In step S2, the molar ratio of N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, perfluorodecyltriethoxysilane, and anhydrous ethanol is (2.8-3.2):1:(330-350), which ensures that the membrane has sufficient reaction sites for crosslinking, while also having sufficient fluorine segments to form an effective protective layer, and preventing excessive hydrophobicity of the membrane due to excessive fluorosilane, thus reducing water flux. The molar ratio of tetraethyl orthosilicate, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, and perfluorodecyltriethoxysilane is (18-22):(2.8-3.2):1. This ratio not only constructs a robust silica nanoseed core but also ensures that the inorganic nanosol has sufficient amino reaction sites to guarantee a strong cross-linking bond with polyamide, while preventing excessive coating of the silica nanoseed surface by perfluorinated chains, which could lead to degradation into physical doping. A doping amount of 2-3 wt% in the inorganic nanosol is sufficient to form an effective nanocomposite network; too low a doping level is ineffective, while too high a level may reduce flux due to particle aggregation or hindering polymer chain stacking. Therefore, the selection and combination of the above ratios and amounts ensures the production of a high-quality and stable inorganic-organic hybrid acid-resistant nanofiltration membrane.

[0009] Preferably, the molar ratio of tetraethyl orthosilicate, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and perfluorodecyltriethoxysilane is 20:3:1.

[0010] By adopting the above technical solution, not only can sufficient structural integrity of the silica nanoseed core be provided to ensure its support and prevent it from becoming a stress concentration point under pressure, but also sufficient amino density can be provided to ensure that it forms a strong covalent bond with the polyamide layer rather than physical adsorption. At the same time, a functional layer that effectively shields against acid corrosion is formed at the lowest effective concentration, so that the obtained inorganic nanosol can exert a relatively excellent and stable corresponding effect after application.

[0011] Preferably, in the preparation of inorganic nanosols, step S1 is specifically set as follows: Zirconium oxychloride octahydrate was dissolved in deionized water at a weight ratio of (0.45-0.5):1 to obtain a zirconium source solution. Simultaneously, tetrabutyl titanate and acetylacetone were mixed at a weight ratio of (2.1-2.5):1 to obtain a titanium source solution. Then, tetraethyl orthosilicate was dissolved in anhydrous ethanol, and an ethanol solution containing ammonia was added dropwise with stirring. The mixture was stirred at 250-350 rpm for 1.5-2.5 h at 23-27℃. The zirconium source solution and titanium source solution were then added dropwise to obtain a silica seed sol. The molar ratio of zirconium, titanium and silicon in the silica seed sol is (0.12-0.18):(0.8-0.1):1.

[0012] By adopting the above technical solution, tetrabutyl titanate is easily hydrolyzed and agglomerated. Mixing it with acetylacetone first can significantly reduce the hydrolysis rate, allowing the titanium source to participate in the reaction slowly and controllably, rather than instantly precipitating into agglomerates. This ensures that titanium atoms can insert into the network vacancies of silica one by one. Meanwhile, the zirconium ions provided by the zirconium source solution intervene in the early stage of silica network formation, serving as cross-linking centers and making the formed network structure more compact. In this way, by adding zirconium source solution and titanium source solution, a strong Si-O-Zr / Ti chemical bond bridge is established on silica. Since the Zr / Ti doping enhances the rigidity of the inorganic core and the interface is chemically bonded, the particles are not easy to loosen and fall off under acidic shear force. At the same time, after Zr / Ti is doped into the silica network, in an acidic environment, it can firmly fix the surrounding polyamide chains like an "anchor", effectively inhibiting the swelling of the polyamide layer, thereby maintaining the stability of membrane separation performance in the long term. Therefore, the optimization of the above operations, through Zr-Ti doping, improves the bulk acid resistance and mechanical strength of the inorganic core, and works synergistically with the modification layer formed by N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and perfluorodecyltriethoxysilane, ultimately achieving improved application stability of nanofiltration membranes under harsh acidic conditions.

[0013] By selecting a molar ratio of zirconium, titanium, and silicon in the silica seed sol of (0.12-0.18):(0.8-0.1):1, not only is the basic framework of silica maintained, ensuring the controllability of nanoparticle size, but Zr / Ti doping also ensures a qualitative change in acid resistance and stability of the network structure. At the same time, it also ensures that the surface of the nanoparticles with the three components retains sufficient active groups, laying the foundation for subsequent modification with N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and perfluorodecyltriethoxysilane, thereby ensuring that the final inorganic nanosol has excellent application quality.

[0014] Preferably, the molar ratio of zirconium, titanium and silicon in the silica seed sol is 0.15:0.9:1.

[0015] By adopting the above technical solution, a better compatibility is achieved among acid resistance, structural stability and interfacial activity, which can then play a superior role in the application of inorganic nanosol.

[0016] Preferably, the aqueous phase reactant further contains 1.5-2.5 wt% of a microcapsule repair agent, which is prepared by the following steps: γ-glycidoxypropyltrimethoxysilane was dissolved in toluene at a weight ratio of (3-4):1 to obtain an oil phase solution, and sodium dodecyl sulfate was dissolved in deionized water at a weight ratio of 1:(45-55) to obtain an aqueous phase solution. The oil phase solution was then dropped into the aqueous phase solution under high-speed shearing to obtain a core material emulsion. Then, urea and formaldehyde were added to the core material emulsion, the pH was adjusted to 3.5-4.0, and the mixture was stirred and reacted at 60-70℃ for 2-3 hours. After cooling, filtration and washing, the microcapsule repair agent was obtained. The molar ratio of urea to formaldehyde is 1:(1.5-2). The core-to-wall mass ratio of the microcapsule repair agent is (2.8-3.2):1.

[0017] By adopting the above technical solution, the wall material of the microcapsule (urea-formaldehyde resin) is hydrophilic and can be well dispersed in the aqueous reactants. The core material is γ-glycidoxypropyltrimethoxysilane. When the membrane develops microcracks under long-term operation or acid shear force, the microcapsule ruptures and the γ-glycidoxypropyltrimethoxysilane is released. Its epoxy groups undergo ring-opening reactions with the amino / carboxyl groups of the polyamide layer, while the methoxysilane groups hydrolyze into silanols, which form Si-O-Si or Si-OC covalent bonds with the hydroxyl groups or polyamide chains on the surface of the inorganic nanoparticles. The organic and inorganic phases on both sides of the crack are "stitched" back together by chemical bonds, repairing the interface debonding caused by stress concentration and greatly improving the interfacial bonding strength. Meanwhile, the released γ-glycidoxypropyltrimethoxysilane can still undergo hydrolysis and condensation reactions under acidic conditions. The resulting Si-O-Si bonds exhibit excellent acid resistance, and the repaired area is even more corrosion-resistant than the original physical interface. Furthermore, through chemical bond repair, the membrane's retention rate and mechanical strength are restored, preventing irreversible performance degradation caused by the accumulation of microscopic damage. Thus, the use of microencapsulated repair agents establishes a dynamic repair mechanism in the separation layer, significantly improving the performance stability of the inorganic-organic hybrid acid-resistant nanofiltration membrane during long-term acidic operation.

[0018] Meanwhile, the molar ratio of urea to formaldehyde is 1:(1.5-2), ensuring that the wall material has a certain degree of toughness and density, guaranteeing that the microcapsule repair agent will not break during processing, but will break under control under stress. The core-to-wall mass ratio of the microcapsule repair agent is (2.8-3.2):1, ensuring that the microcapsule repair agent will not suffer from poor repair effects due to insufficient core material, nor will it be prone to premature breakage during storage due to excessively thin wall material, thus exhibiting excellent overall application stability.

[0019] Preferably, the particle size of the microcapsule repair agent is 5-15 μm.

[0020] By employing the above technical solutions, if the particle size is too small, the encapsulation and repair dosage will be insufficient, failing to effectively fill the cracks and easily migrating to the surface during interfacial polymerization, thus compromising the density of the separation layer. If the particle size is too large, it may penetrate the separation layer or block the pores of the support layer, leading to a sharp decrease in membrane flux and even becoming a new source of defects in the membrane structure. The selection of the above-mentioned particle size range ensures that the particle itself can be completely embedded in the separation layer without damaging the structure, while also providing sufficient repair agent to achieve effective self-healing.

[0021] Preferably, the aqueous reactant, in addition to the inorganic nanosol, also contains the following components in parts by weight: 0.2-0.3 parts of 3-aminobenzenesulfonamide; Triethylamine 0.18-0.24 parts; Sodium dodecyl sulfonate 0.1-0.2 parts; 100-110 parts deionized water.

[0022] By adopting the above technical solution, 3-aminobenzenesulfonamide, as a key functional monomer, has sulfonamide and sulfonic acid groups in its molecule that are both strong electron-withdrawing groups. These groups can reduce the electron cloud density of the amide bonds in the polyamide chain, making it more difficult for H to be released under acidic conditions. + Protonated hydrolysis enhances intrinsic acid resistance. The combination of triethylamine and sodium dodecylbenzenesulfonate precisely controls the reaction microenvironment of interfacial polymerization, guiding the polyamide to form a smoother and thinner active layer, reducing surface defects, and thus improving retention stability.

[0023] Secondly, this application provides a method for preparing an inorganic-organic hybrid acid-resistant nanofiltration membrane, employing the following technical solution: A method for preparing an inorganic-organic hybrid acid-resistant nanofiltration membrane includes the following steps: (1) Prepare the supporting layer and the oil phase reactants and aqueous phase reactants required for the preparation of the separation layer according to the proportions; (2) Immerse the support layer from step (1) into the aqueous phase reactant containing inorganic nanosol, remove it to remove the surface liquid, then immerse it in the oil phase reactant, and then remove it again to remove the surface liquid. After heat treatment at 65-75℃ for 10-12 minutes, a separation layer is formed, and finally an inorganic-organic hybrid acid-resistant nanofiltration membrane is obtained.

[0024] 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 a uniform, complete and defect-free layer structure can be formed. It is suitable for large-scale industrial production and achieves high-quality preparation of inorganic-organic hybrid acid-resistant nanofiltration membranes.

[0025] Thirdly, this application provides an application of an inorganic-organic hybrid acid-resistant nanofiltration membrane in the treatment of acidic mining and metallurgical wastewater, the recovery of metal pickling solutions, and the nanofiltration of strong acid organic solvents.

[0026] By adopting the above technical solutions, it is beneficial to achieve efficient retention of heavy metals in acidic wastewater and reuse of acid, significantly reduce the cost of neutralizing agents, and "dialyze" free acid from metal salt solutions to achieve closed-loop reuse of pickling solution, avoid waste acid discharge, and at the same time achieve precise separation of small molecules in acidic organic systems, expanding the application boundaries of nanofiltration in API purification.

[0027] In summary, this application has the following beneficial effects: 1. This application introduces dual functional groups on the surface of monodisperse silica nanoseeds. N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane provides reactive amino groups, while perfluorodecyltriethoxysilane provides hydrophobic / acid-resistant perfluorinated long chains. Inorganic nanosol is obtained through special preparation. After the inorganic nanosol is applied, the separation layer of the nanofiltration membrane is a through-type three-dimensional hybrid structure formed by the covalent interconnection of an organic polyamide network and surface-functionalized inorganic nanoparticles. It not only has no obvious phase interface voids, but also effectively blocks the penetration and erosion of strong acid molecules. Thus, it maintains good membrane separation performance stability during long-term application, and finally obtains an inorganic-organic hybrid acid-resistant nanofiltration membrane with excellent quality and stability. 2. This application uses zirconium source solution and titanium source solution in the preparation of inorganic nanosol to dope Zr / Ti into the silica network, thereby improving the bulk acid resistance and mechanical strength of the inorganic core. It also works synergistically with the modification layer formed by N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and perfluorodecyltriethoxysilane to ultimately improve the application stability of nanofiltration membrane under harsh acidic conditions. 3. This application uses microcapsule repair agents in aqueous reactants. When the membrane develops microcracks under long-term operation or acidic shear stress, the microcapsules rupture and repair through chemical bonds, restoring the membrane's retention rate and mechanical strength. This avoids irreversible performance degradation caused by the accumulation of microscopic damage, and the repaired area is even more corrosion-resistant than the original physical interface. Thus, by constructing a dynamic repair mechanism in the separation layer, the performance stability of the inorganic-organic hybrid acid-resistant nanofiltration membrane under long-term acidic operation is greatly improved. Detailed Implementation

[0028] The present application will be further described in detail below with reference to preparation examples, embodiments and comparative examples.

[0029] Unless otherwise specified, all raw materials used in the preparation examples, embodiments and comparative examples of this application are commercially available.

[0030] The support layer comprises a polymer porous layer and a nonwoven fabric layer stacked sequentially. A 150 μm thick composite support layer is prepared by casting a polysulfone solution onto a polyester nonwoven fabric and then performing a phase inversion method. The polysulfone solution is obtained by stirring Solvay P-3703 polysulfone and DMF solvent at a weight ratio of 1:9 at 60°C for 5 hours. The resulting polymer porous layer has a thickness of 30 μm, a pore size of 1 μm, and a porosity of 70%. The polyester nonwoven fabric has a thickness of 120 μm, a pore size of 10 μm, a porosity of 90%, and a basis weight of 100 g / m². 2 The fiber diameter is 15μm.

[0031] Preparation Example 1: An inorganic nanosol was prepared by the following steps: S1. Dissolve tetraethyl orthosilicate in anhydrous ethanol, and add dropwise an ethanol solution containing ammonia while stirring. Stir at 300 rpm for 2 hours at 25°C to obtain silica seed sol. S2. Cool the silica seed sol obtained in step S1 to 3°C, then dissolve N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and perfluorodecyltriethoxysilane in anhydrous ethanol, and then add them dropwise to the silica seed sol and stir to mix, to obtain a modified mixture. S3. The modified mixture obtained in step S2 is heated to 27.5℃ and stirred for 7 hours. After centrifugation and purification, inorganic nanosol is obtained.

[0032] Note: In step S1 above, the molar ratio of tetraethyl orthosilicate, anhydrous ethanol, H2O and NH3 is 1:10:2:0.15; in step S2 above, the molar ratio of N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, perfluorodecyltriethoxysilane and anhydrous ethanol is 3.0:1:340; at the same time, the molar ratio of tetraethyl orthosilicate, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and perfluorodecyltriethoxysilane is 20:3:1.

[0033] Preparation Example 2, an inorganic nanosol, differs from Preparation Example 1 in that it is prepared by the following steps: S1. Dissolve tetraethyl orthosilicate in anhydrous ethanol, and add dropwise an ethanol solution containing ammonia while stirring. Stir at 250 rpm for 2.5 h at 23°C to obtain silica seed sol. S2. Cool the silica seed sol obtained in step S1 to 1°C, then dissolve N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and perfluorodecyltriethoxysilane in anhydrous ethanol, and then add them dropwise to the silica seed sol and stir to mix, to obtain a modified mixture. S3. The modified mixture obtained in step S2 is heated to 25°C and stirred for 8 hours. After centrifugation and purification, inorganic nanosol is obtained.

[0034] Note: In step S1 above, the molar ratio of tetraethyl orthosilicate, anhydrous ethanol, H2O and NH3 is 1:9:1.8:0.1; in step S2 above, the molar ratio of N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, perfluorodecyltriethoxysilane and anhydrous ethanol is 2.8:1:330.

[0035] Preparation Example 3, an inorganic nanosol, differs from Preparation Example 1 in that it is prepared by the following steps: S1. Dissolve tetraethyl orthosilicate in anhydrous ethanol, and add dropwise an ethanol solution containing ammonia while stirring. Stir at 350 rpm for 1.5 h at 27°C to obtain silica seed sol. S2. Cool the silica seed sol obtained in step S1 to 5°C, then dissolve N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and perfluorodecyltriethoxysilane in anhydrous ethanol, and then add them dropwise to the silica seed sol and stir to mix, to obtain a modified mixture. S3. The modified mixture obtained in step S2 is heated to 30°C and stirred for 6 hours. After centrifugation and purification, inorganic nanosol is obtained.

[0036] Note: In step S1 above, the molar ratio of tetraethyl orthosilicate, anhydrous ethanol, H2O and NH3 is 1:11:2.2:0.2; in step S2 above, the molar ratio of N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, perfluorodecyltriethoxysilane and anhydrous ethanol is 3.2:1:350.

[0037] Preparation Example 4, an inorganic nanosol, differs from Preparation Example 1 in that the molar ratio of tetraethyl orthosilicate, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and perfluorodecyltriethoxysilane is 18:2.8:1.

[0038] Preparation Example 5, an inorganic nanosol, differs from Preparation Example 1 in that the molar ratio of tetraethyl orthosilicate, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, and perfluorodecyltriethoxysilane is 22:3.2:1.

[0039] Preparation Example 6, an inorganic nanosol, differs from Preparation Example 1 in that the molar ratio of tetraethyl orthosilicate, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and perfluorodecyltriethoxysilane is 17:2.7:1.

[0040] Preparation Example 7, an inorganic nanosol, differs from Preparation Example 1 in that the molar ratio of tetraethyl orthosilicate, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, and perfluorodecyltriethoxysilane is 23:3.3:1.

[0041] Preparation Example 8, an inorganic nanosol, differs from Preparation Example 1 in that N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane is not used.

[0042] Preparation Example 9, an inorganic nanosol, differs from Preparation Example 1 in that perfluorodecyltriethoxysilane is not used.

[0043] Preparation Example 10, an inorganic nanosol, differs from Preparation Example 1 in that N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and perfluorodecyltriethoxysilane are not used.

[0044] Preparation Example 11, an inorganic nanosol, differs from Preparation Example 1 in that step S1 is specifically set as follows: Zirconium oxychloride octahydrate was dissolved in deionized water at a weight ratio of 0.475:1 to obtain a zirconium source solution. Simultaneously, tetrabutyl titanate and acetylacetone were mixed at a weight ratio of 2.3:1 to obtain a titanium source solution. Then, tetraethyl orthosilicate was dissolved in anhydrous ethanol, and an ethanol solution containing ammonia was added dropwise with stirring. The mixture was stirred at 300 rpm for 2 hours at 25°C. The zirconium source solution and titanium source solution were then added dropwise to obtain a silica seed sol. The molar ratio of zirconium, titanium and silicon in the silica seed sol is 0.15:0.9:1.

[0045] Preparation Example 12, an inorganic nanosol, differs from Preparation Example 11 in that step S1 is specifically set as follows: Zirconium oxychloride octahydrate was dissolved in deionized water at a weight ratio of 0.45:1 to obtain a zirconium source solution. Simultaneously, tetrabutyl titanate and acetylacetone were mixed at a weight ratio of 2.1:1 to obtain a titanium source solution. Then, tetraethyl orthosilicate was dissolved in anhydrous ethanol, and an ethanol solution containing ammonia was added dropwise while stirring. The mixture was stirred at 250 rpm for 2.5 h at 23 °C. The zirconium source solution and titanium source solution were then added dropwise to obtain a silica seed sol.

[0046] Preparation Example 13, an inorganic nanosol, differs from Preparation Example 11 in that step S1 is specifically set as follows: Zirconium oxychloride octahydrate was dissolved in deionized water at a weight ratio of 0.5:1 to obtain a zirconium source solution. Simultaneously, tetrabutyl titanate and acetylacetone were mixed at a weight ratio of 2.5:1 to obtain a titanium source solution. Then, tetraethyl orthosilicate was dissolved in anhydrous ethanol, and an ethanol solution containing ammonia was added dropwise while stirring. The mixture was stirred at 350 rpm for 1.5 h at 27 °C. The zirconium source solution and titanium source solution were then added dropwise to obtain silica seed sol.

[0047] Preparation Example 14, an inorganic nanosol, differs from Preparation Example 11 in that the molar ratio of zirconium, titanium and silicon in the silica seed sol is 0.12:0.8:1.

[0048] Preparation Example 15, an inorganic nanosol, differs from Preparation Example 11 in that the molar ratio of zirconium, titanium and silicon in the silica seed sol is 0.18:0.1:1.

[0049] Preparation Example 16, an inorganic nanosol, differs from Preparation Example 11 in that the molar ratio of zirconium, titanium and silicon in the silica seed sol is 0.11:0.7:1.

[0050] Preparation Example 17, an inorganic nanosol, differs from Preparation Example 11 in that the molar ratio of zirconium, titanium and silicon in the silica seed sol is 0.19:0.11:1.

[0051] Preparation Example 18, an inorganic nanosol, differs from Preparation Example 11 in that a zirconium source solution was not used.

[0052] Preparation Example 19, an inorganic nanosol, differs from Preparation Example 11 in that it does not use a titanium source solution.

[0053] Preparation Example 20, an inorganic nanosol, differs from Preparation Example 11 in that N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and perfluorodecyltriethoxysilane are not used.

[0054] Preparation Example 21: A microcapsule repair agent was prepared by the following steps: γ-glycidoxypropyltrimethoxysilane was dissolved in toluene at a weight ratio of 3.5:1 to obtain an oil phase solution, and sodium dodecyl sulfate was dissolved in deionized water at a weight ratio of 1:50 to obtain an aqueous phase solution. The oil phase solution was then dropped into the aqueous phase solution under high-speed shearing to obtain a core material emulsion. Then, urea and formaldehyde were added to the core material emulsion, the pH was adjusted to 3.7, and the mixture was stirred at 65°C for 2.5 hours. After cooling, filtration, and washing, the microcapsule repair agent was obtained.

[0055] Note: The molar ratio of urea to formaldehyde is 1:1.75; the core-to-wall mass ratio of the microcapsule repair agent is 3:1. The particle size of the microcapsule repair agent is 10 μm.

[0056] Preparation Example 22, a microcapsule repair agent, differs from Preparation Example 21 in that it is prepared by the following steps: γ-glycidoxypropyltrimethoxysilane was dissolved in toluene at a weight ratio of 3:1 to obtain an oil phase solution, and sodium dodecyl sulfate was dissolved in deionized water at a weight ratio of 1:45 to obtain an aqueous phase solution. The oil phase solution was then dropped into the aqueous phase solution under high-speed shearing to obtain a core material emulsion. Then, urea and formaldehyde were added to the core material emulsion, the pH was adjusted to 3.5, and the mixture was stirred and reacted at 60°C for 3 hours. After cooling, filtration, and washing, the microcapsule repair agent was obtained.

[0057] Note: The molar ratio of urea to formaldehyde is 1:1.5; the core-to-wall mass ratio of the microcapsule repair agent is 2.8:1.

[0058] Preparation Example 23, a microcapsule repair agent, differs from Preparation Example 21 in that it is prepared by the following steps: γ-glycidoxypropyltrimethoxysilane was dissolved in toluene at a weight ratio of 4:1 to obtain an oil phase solution, and sodium dodecyl sulfate was dissolved in deionized water at a weight ratio of 1:55 to obtain an aqueous phase solution. The oil phase solution was then dropped into the aqueous phase solution under high-speed shearing to obtain a core material emulsion. Then, urea and formaldehyde were added to the core material emulsion, the pH was adjusted to 4.0, and the mixture was stirred and reacted at 70°C for 2 hours. After cooling, filtration, and washing, the microcapsule repair agent was obtained.

[0059] Note: The molar ratio of urea to formaldehyde is 1:2; the core-to-wall mass ratio of the microcapsule repair agent is 3.2:1.

[0060] Preparation Example 24, a microcapsule repair agent, differs from Preparation Example 21 in that the microcapsule repair agent has a particle size of 5 μm.

[0061] Preparation Example 25, a microcapsule repair agent, differs from Preparation Example 21 in that the microcapsule repair agent has a particle size of 15 μm.

[0062] Preparation Example 26, a microcapsule repair agent, differs from Preparation Example 21 in that the microcapsule repair agent has a particle size of 4 μm.

[0063] Preparation Example 27, a microcapsule repair agent, differs from Preparation Example 21 in that the microcapsule repair agent has a particle size of 16 μm.

[0064] Example 1: An inorganic-organic hybrid acid-resistant nanofiltration membrane, comprising a support layer and a separation layer stacked sequentially, is prepared by the following steps: (1) Prepare the supporting layer and the oil phase reactants and aqueous phase reactants required for the preparation of the separation layer according to the proportions; (2) Immerse the support layer from step (1) in an aqueous reactant containing inorganic nanosol for 3 minutes, remove it to remove residual liquid on the surface, immerse it in an oil reactant for 35 seconds, remove it again to remove residual liquid on the surface, and then heat-treat it at 65-75℃ for 10-12 minutes (preferably at 70℃ for 11 minutes in this embodiment) to form a separation layer, and finally obtain an inorganic-organic hybrid acid-resistant nanofiltration membrane.

[0065] Note: In the above operations, the oil phase reactant was a hexane solution of benzotricarbonyl chloride, with a weight percentage of 0.1%. The aqueous phase reactant contained 2.5 wt% inorganic nanosol, which was obtained from Preparation Example 1. The components and their corresponding weight parts in the aqueous phase reactant, excluding the inorganic nanosol, are shown in Table 1. The pH of the aqueous phase reactant was 11.

[0066] Examples 2-3 describe an inorganic-organic hybrid acid-resistant nanofiltration membrane. The difference between this membrane and Example 1 is that, apart from the inorganic nanosol, the other components and their corresponding weight parts in the aqueous reactants are shown in Table 1.

[0067] Table 1. Other components and their corresponding weight parts (parts / kg) in the aqueous phase reactants of Examples 1-3 .

[0068] Example 4, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 1 in that 2 wt% inorganic nanosol is used in the aqueous phase reactant.

[0069] Example 5, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 1 in that 3 wt% inorganic nanosol is used in the aqueous phase reactant.

[0070] Example 6, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 1 in that the inorganic nanosol is obtained from Preparation Example 2.

[0071] Example 7, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 1 in that the inorganic nanosol is obtained from Preparation Example 3.

[0072] Example 8, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 1 in that the inorganic nanosol is obtained from Preparation Example 4.

[0073] Example 9, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 1 in that the inorganic nanosol is obtained from Preparation Example 5.

[0074] Example 10, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 1 in that the inorganic nanosol is obtained from Preparation Example 11.

[0075] Example 11, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 1 in that the inorganic nanosol is obtained from Preparation Example 12.

[0076] Example 12, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 1 in that the inorganic nanosol is obtained from Preparation Example 13.

[0077] Example 13, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 1 in that the inorganic nanosol is obtained from Preparation Example 14.

[0078] Example 14, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 1 in that the inorganic nanosol is obtained from Preparation Example 15.

[0079] Example 15, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 1 in that the inorganic nanosol is obtained from Preparation Example 16.

[0080] Example 16, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 1 in that the inorganic nanosol is obtained from Preparation Example 17.

[0081] Example 17, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 1 in that the inorganic nanosol is obtained from Preparation Example 18.

[0082] Example 18, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 1 in that the inorganic nanosol is obtained from Preparation Example 19.

[0083] Example 19, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 1 in that 2 wt% of a microcapsule repair agent is used in the aqueous reactant, which was obtained from Preparation Example 21, and the microcapsule repair agent is used by stirring and mixing with other components in the aqueous reactant.

[0084] Example 20, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 19 in that 1.5 wt% of microcapsule repair agent is also used in the aqueous phase reactants.

[0085] Example 21, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 19 in that 2.5 wt% of microcapsule repair agent is also used in the aqueous phase reactants.

[0086] Example 22, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 19 in that the microcapsule repair agent is obtained from Preparation Example 22.

[0087] Example 23, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 19 in that the microcapsule repair agent is obtained from Preparation Example 23.

[0088] Example 24, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 19 in that the microcapsule repair agent is obtained from Preparation Example 24.

[0089] Example 25, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 19 in that the microcapsule repair agent is obtained from Preparation Example 25.

[0090] Example 26, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 19 in that the microcapsule repair agent is obtained from Preparation Example 26.

[0091] Example 27, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 19 in that the microcapsule repair agent is obtained from Preparation Example 27.

[0092] Comparative Example 1, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 1 in that the inorganic nanosol is obtained from Preparation Example 6.

[0093] Comparative Example 2, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 1 in that the inorganic nanosol is obtained from Preparation Example 7.

[0094] Comparative Example 3, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 1 in that the inorganic nanosol is obtained from Preparation Example 8.

[0095] Comparative Example 4, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 1 in that the inorganic nanosol is obtained from Preparation Example 9.

[0096] Comparative Example 5, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 1 in that the inorganic nanosol is obtained from Preparation Example 10.

[0097] Comparative Example 6, an inorganic-organic hybrid acid-resistant nanofiltration membrane, differs from Example 19 in that the inorganic nanosol is obtained from Preparation Example 20.

[0098] Performance testing Test samples: The inorganic-organic hybrid acid-resistant nanofiltration membranes obtained in Examples 1-27 were selected as test samples 1-27, and the inorganic-organic hybrid acid-resistant nanofiltration membranes obtained in Comparative Examples 1-6 were selected as control samples 1-6.

[0099] Experimental method: The effective area is 44.2 cm². 2The inorganic-organic hybrid acid-resistant nanofiltration membrane was loaded into the acid-resistant cross-flow filtration tank and pre-pressed with deionized water at 2.5 MPa for 30 min to eliminate the initial irreversible compression of the membrane. Switch the feed solution to simulated acidic mining wastewater (pH=1.5, containing 1000ppm MgSO4 and 50ppm Cu). 2+ Adjust the pressure to 2.0 MPa, crossflow velocity to 2 m / s, temperature to 25 ± 1℃, and run stably for 1 hour. Measure the water flux and retention rate after stabilization. The formula for calculating water flux is: F = V / (S·t), where F is the water flux, V is the permeate volume, S is the effective membrane area, and t is the test time. Calculation of retention rate: R = (1 - C) p / C f )×100%, where C p C represents the osmotic concentration. f The concentration of the feed solution; This is recorded as the initial water flux value and the initial retention rate value.

[0100] Then, under the above test conditions, the test was run continuously for 500 hours. During the process, an online pH meter was used to maintain the pH at 1.5 by adding dilute hydrochloric acid. The water flux and rejection rate were measured using the same method. This is recorded as the final water flux value and the final retention rate value.

[0101] Finally, the water flux decay rate and retention rate decay value were calculated. The water flux decay rate = (initial water flux value - final water flux value) / initial water flux value × 100%, and the retention rate decay value = initial retention rate value - final retention rate value. The smaller the water flux decay rate and retention rate decay value, the better the application stability of the inorganic-organic hybrid acid-resistant nanofiltration membrane under acidic media and shear force.

[0102] After performing the above tests on test samples 1-27 and control samples 1-6, the test results are recorded in Table 2.

[0103] Table 2 Test results of test samples 1-27 and control samples 1-6 As can be seen from Examples 1-9 and Comparative Examples 3-5 and Table 2, this application introduces dual functional groups on the surface of monodisperse silica nanoseeds. N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane provides reactive amino groups, while perfluorodecyltriethoxysilane provides hydrophobic / acid-resistant perfluorinated long chains. After special preparation, an inorganic nanosol is obtained, which is then applied to the separation layer. Compared with the case of physical doping only, the application stability of the inorganic-organic hybrid acid-resistant nanofiltration membrane under acidic media and shear force is significantly improved. The water flux attenuation rate and retention rate attenuation values ​​obtained by the above tests are significantly reduced. It was also found that if only one of N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and perfluorodecyltriethoxysilane is used in the preparation of inorganic nanosols, although it can bring about a corresponding improvement, the improvement is limited, and the sum of the improvement brought by using each alone is far less than that of the combination of the two. Therefore, it can be seen that the combination of N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and perfluorodecyltriethoxysilane can bring about a significant improvement effect of 1+1>2. Combined with Comparative Examples 1-2 and Table 2, it can be seen that the molar ratio of tetraethyl orthosilicate, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, and perfluorodecyltriethoxysilane is (18-22):(2.8-3.2):1, which enables the final inorganic nanosol to exhibit excellent and stable application effects. However, if the ratio of the three components is lower or higher than the above range, it will lead to a significant loss in the water flux attenuation rate and retention rate attenuation values ​​obtained in the above tests. This indicates that the specific ratio of the mixture can ensure that the inorganic nanosol has sufficient amino reaction sites to ensure the strong cross-linking with polyamide, and avoid the excessive coating of some perfluorinated chains on the surface of silica nanoseeds, which would lead to degradation into physical doping.

[0104] Combining Examples 1 and 10-14 with Table 2, it can be seen that by using zirconium source solution and titanium source solution in the preparation of inorganic nanosol, Zr / Ti is doped into the silica network, further reducing the water flux attenuation rate and retention rate attenuation value of the final inorganic-organic hybrid acid-resistant nanofiltration membrane as tested above. Furthermore, combining Examples 15-16 with Table 2, it can be seen that controlling the molar ratio of zirconium, titanium, and silicon to (0.12-0.18):(0.8-0.1):1 allows Zr / Ti doping to achieve better results; ratios below or above this range result in less than expected improvements. Combining Examples 17-18 with Table 2, it can be seen that if zirconium source solution or titanium source solution is lacking in the preparation of inorganic nanosol, the improvement effect of Zr and Ti doping alone is limited. Moreover, judging from the performance of water flux attenuation rate and retention rate attenuation value, the combination of the two can bring a significant improvement effect of 1+1>2. Combined with Comparative Examples 5-6 and Table 2, it can be seen that if the preparation of inorganic nanosols lacks the use of N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and perfluorodecyltriethoxysilane, the improvement effect brought by Zr / Ti doping will be significantly reduced. This indicates that Zr / Ti doping can synergistically work with the modification layer formed by N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and perfluorodecyltriethoxysilane, ultimately achieving a significant improvement in the stability of inorganic-organic hybrid acid-resistant nanofiltration membranes under acidic media and shear forces.

[0105] Combining Examples 1 and 19-25 with Table 2, it can be seen that by using microencapsulated repair agents in the aqueous reactants, a dynamic repair mechanism is constructed in the separation layer, which greatly improves the application stability of the inorganic-organic hybrid acid-resistant nanofiltration membrane under acidic media and shear forces. The water flux attenuation rate and retention rate attenuation values ​​obtained from the above tests are significantly reduced. Furthermore, combining Examples 26-27 with Table 2, it can be seen that the particle size of the microencapsulated repair agents is 5-15 μm, ensuring that they are completely embedded in the separation layer without damaging the structure, while also providing sufficient repair agent for effective self-healing. Particle sizes below or above this range do not result in a significant loss of the corresponding improvement effect brought by the microencapsulated repair agents.

[0106] 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. An inorganic-organic hybrid acid-resistant nanofiltration membrane, characterized by, It includes a support layer and a separation layer stacked sequentially; The separation layer is prepared by interfacial polymerization of raw materials including oil phase reactants and aqueous phase reactants; The oil phase reactant is a hexane solution of benzotricarbonyl chloride, with the weight percentage of benzotricarbonyl chloride being 0.1%. The aqueous reactants contain 2-3 wt% inorganic nanosol, which is prepared by the following steps: S1. Dissolve tetraethyl orthosilicate in anhydrous ethanol, and add dropwise an ethanol solution containing ammonia while stirring. Stir at 250-350 rpm for 1.5-2.5 h at 23-27℃ to obtain silica seed sol. S2. Cool the silica seed sol obtained in step S1 to 1-5℃, then dissolve N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and perfluorodecyltriethoxysilane in anhydrous ethanol, and then add them dropwise to the silica seed sol and stir to mix, to obtain a modified mixture. S3. Heat the modified mixture obtained in step S2 to 25-30℃ and continue stirring for 6-8 hours. After centrifugation and purification, inorganic nanosol is obtained. In step S1 above, the molar ratio of tetraethyl orthosilicate, anhydrous ethanol, H2O, and NH3 is 1:(9-11):(1.8-2.2):(0.1-0.2). In step S2 above, the molar ratio of N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, perfluorodecyltriethoxysilane, and anhydrous ethanol is (2.8-3.2):1:(330-350). Meanwhile, the molar ratio of tetraethyl orthosilicate, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and perfluorodecyltriethoxysilane is (18-22):(2.8-3.2):

1.

2. The inorganic-organic hybrid acid-resistant nanofiltration membrane according to claim 1, characterized in that: The molar ratio of tetraethyl orthosilicate, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane and perfluorodecyltriethoxysilane is 20:3:

1.

3. The inorganic-organic hybrid acid-resistant nanofiltration membrane according to claim 1, characterized in that: In the preparation of inorganic nanosols, step S1 is specifically set as follows: Zirconium oxychloride octahydrate was dissolved in deionized water at a weight ratio of (0.45-0.5):1 to obtain a zirconium source solution. Simultaneously, tetrabutyl titanate and acetylacetone were mixed at a weight ratio of (2.1-2.5):1 to obtain a titanium source solution. Then, tetraethyl orthosilicate was dissolved in anhydrous ethanol, and an ethanol solution containing ammonia was added dropwise with stirring. The mixture was stirred at 250-350 rpm for 1.5-2.5 h at 23-27℃. The zirconium source solution and titanium source solution were then added dropwise to obtain a silica seed sol. The molar ratio of zirconium, titanium and silicon in the silica seed sol is (0.12-0.18):(0.8-0.1):

1.

4. The inorganic-organic hybrid acid-resistant nanofiltration membrane according to claim 3, characterized in that: The molar ratio of zirconium, titanium and silicon in the silica seed sol is 0.15:0.9:

1.

5. The inorganic-organic hybrid acid-resistant nanofiltration membrane according to claim 1, characterized in that: The aqueous phase reactants also contain 1.5-2.5 wt% of a microcapsule repair agent, which is prepared by the following steps: γ-glycidoxypropyltrimethoxysilane was dissolved in toluene at a weight ratio of (3-4):1 to obtain an oil phase solution, and sodium dodecyl sulfate was dissolved in deionized water at a weight ratio of 1:(45-55) to obtain an aqueous phase solution. The oil phase solution was then dropped into the aqueous phase solution under high-speed shearing to obtain a core material emulsion. Then, urea and formaldehyde were added to the core material emulsion, the pH was adjusted to 3.5-4.0, and the mixture was stirred and reacted at 60-70℃ for 2-3 hours. After cooling, filtration and washing, the microcapsule repair agent was obtained. The molar ratio of urea to formaldehyde is 1:(1.5-2). The core-to-wall mass ratio of the microcapsule repair agent is (2.8-3.2):

1.

6. The inorganic-organic hybrid acid-resistant nanofiltration membrane according to claim 5, characterized in that: The microcapsule repair agent has a particle size of 5-15 μm.

7. The inorganic-organic hybrid acid-resistant nanofiltration membrane according to claim 1, characterized in that: In addition to the inorganic nano-sol, the aqueous reactants also contain the following components in parts by weight: 0.2-0.3 parts of 3-aminobenzenesulfonamide; Triethylamine 0.18-0.24 parts; Sodium dodecyl sulfonate 0.1-0.2 parts; 100-110 parts deionized water.

8. The method for preparing the inorganic-organic hybrid acid-resistant nanofiltration membrane according to claim 1, characterized in that: Includes the following steps: (1) Prepare the supporting layer and the oil phase reactants and aqueous phase reactants required for the preparation of the separation layer according to the proportions; (2) Immerse the support layer from step (1) into the aqueous phase reactant containing inorganic nanosol, remove it to remove the surface liquid, then immerse it in the oil phase reactant, and then remove it again to remove the surface liquid. After heat treatment at 65-75℃ for 10-12 minutes, a separation layer is formed, and finally an inorganic-organic hybrid acid-resistant nanofiltration membrane is obtained.

9. The application of the inorganic-organic hybrid acid-resistant nanofiltration membrane according to any one of claims 1-7 in the treatment of acidic mining and metallurgical wastewater, recovery of metal pickling solutions, and nanofiltration of strong acid organic solvents.

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