Magnetic quaternized ZIFs nanoparticles and modified ultrafiltration membranes thereof

Abstract

The present invention provides a magnetic quaternized ZIFs nanoparticle and a modified ultrafiltration membrane thereof, belonging to the technical field of ultrafiltration membrane preparation. The preparation method of the ZIFs nanoparticles comprises the following steps: quaternizing an imidazole compound to obtain a quaternized imidazole compound; mixing the quaternized imidazole compound with an imidazole compound, magnetic particles, and solvent 1 to obtain solution 1; mixing a zinc salt with solvent 1 to obtain solution 2; and adding solution 2 dropwise to solution 1 to react and obtain ZIFs nanoparticles. The present invention first prepares ZIFs nanoparticles, and then prepares an ultrafiltration membrane using the nanoparticles under the action of a magnetic field. The magnetic field force can change the distribution of the casting solution containing the magnetic particles, while increasing the distribution density of the filler in the cortex and effectively improving the utilization rate of the filler, thereby improving the microstructure and performance of the membrane, so that the membrane has high pure water flux and flux recovery rate, and has good antibacterial properties.

Description

Technical Field

[0001] The invention relates to the technical field of ultrafiltration membrane preparation, in particular to magnetic quaternized ZIFs nanoparticles and modified ultrafiltration membranes thereof. Background Art

[0002] Ultrafiltration membranes are often asymmetric, consisting of an extremely thin cortex with a defined pore size and a thicker, porous support layer with a sponge-like or finger-like pore structure. The cortex primarily serves as a retaining layer, while the support layer primarily provides support. During the membrane production process using the impregnation-precipitation phase conversion method, the filler density in the support layer is high, while the density in the sieving cortex is relatively low. This not only wastes filler but also hinders the full realization of its potential properties.

[0003] Due to the inherent hydrophobicity of polymer ultrafiltration membranes, they are susceptible to the adsorption and proliferation of bacteria and other microorganisms during the ultrafiltration process, forming a "biofilm" on the membrane surface, which can cause severe organic and biological fouling and significantly reduce the separation performance and service life of the membrane. An increasing number of researchers are introducing hydrophilic and antibacterial fillers to prepare novel composite ultrafiltration membranes to improve the hydrophilicity of the membrane surface, making it difficult for pollutant molecules to pass through and adsorb, thereby significantly enhancing the membrane's antifouling and antibacterial properties. Huang et al. prepared flat ultrafiltration membranes using ferroferric oxide (Fe₃O₄) as a filler and polyvinylidene fluoride as a polymer matrix under both magnetic and non-magnetic conditions. Under the influence of a magnetic field, the magnetic Fe₃O₄ particles in the casting solution aligned along the magnetic field during film formation, resulting in a novel membrane with "lamellar macropores." Ansarie et al. used 8-hydroxyquinoline-modified Fe₃O₄ nanoparticles as a filler to prepare mixed-matrix membranes. The abundant hydroxyl groups on the surface of the composite membranes made them highly hydrophilic, significantly enhancing their permeability and antifouling properties. Zhang et al. successfully fabricated a modified polysulfone ultrafiltration membrane using water-soluble MOF nanoparticles as fillers. By adjusting the content and size of the water-soluble MOF nanoparticles and employing liquid-liquid phase separation techniques, they successfully constructed a uniform porous membrane structure. However, incompatibility between the inorganic nanoparticles and the polymer matrix can cause defects in the composite membrane, such as membrane collapse, particle outflow, and pore blockage. Furthermore, the inorganic nanoparticles can be unevenly distributed on the membrane surface, even agglomerating. Summary of the Invention

[0004] Based on the above, the present invention aims to provide magnetic quaternized ZIFs nanoparticles and modified ultrafiltration membranes thereof. The present invention first prepares magnetic quaternized ZIFs nanoparticles, which are then subjected to a magnetic field to form an ultrafiltration membrane. The magnetic field forces the nanoparticles to alter the distribution of the casting solution containing the magnetic particles, thereby increasing the filler distribution density in the cortex and effectively improving filler utilization, thereby improving the membrane's microstructure and performance.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] One of the technical solutions of the present invention is a method for preparing magnetic quaternized ZIFs nanoparticles, comprising the following steps:

[0007] quaternizing the imidazole compound to obtain a quaternized imidazole compound;

[0008] The quaternized imidazole compound is mixed with the imidazole compound, magnetic particles, and solvent 1 to obtain solution 1; the zinc salt is mixed with solvent 1 to obtain solution 2;

[0009] The solution 2 is added dropwise into the solution 1 to react, thereby obtaining magnetic quaternized ZIFs nanoparticles.

[0010] The second technical solution of the present invention is a magnetic quaternized ZIFs nanoparticle prepared by the above preparation method.

[0011] The third technical solution of the present invention is a method for preparing a modified ultrafiltration membrane, which comprises preparing a casting solution containing the above-mentioned magnetic quaternized ZIFs nanoparticles, and then laying the membrane under the action of a magnetic field to obtain the modified ultrafiltration membrane.

[0012] A fourth technical solution of the present invention is a modified ultrafiltration membrane prepared by the above-mentioned method for preparing the modified ultrafiltration membrane.

[0013] The present invention discloses the following technical effects:

[0014] The present invention can change the distribution of the casting liquid containing magnetic particles through the force of the magnetic field, while increasing the distribution density of the filler in the cortex and effectively improving the utilization rate of the filler, thereby improving the microstructure and performance of the membrane.

[0015] The modified ultrafiltration membrane provided by the invention has high pure water flux and flux recovery rate, and has good antibacterial performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 This is a scanning electron microscope image of the magnetic quaternized ZIF-8 nanoparticles prepared in Example 1;

[0018] Figure 2This is a scanning electron microscope micrograph of a cross section of the ultrafiltration membrane prepared in Example 1;

[0019] Figure 3 The XRD pattern of the magnetic quaternized ZIF-8 nanoparticles prepared in Example 1;

[0020] Figure 4 This is the infrared spectrum of the magnetic quaternized ZIF-8 nanoparticles prepared in Example 1;

[0021] Figure 5 The pure water flux, rejection rate, and flux recovery rate change curves of the ultrafiltration membranes obtained in Comparative Examples 1-2 and Examples 1-8 are shown;

[0022] Figure 6 The curve of the antibacterial rate of the ultrafiltration membrane obtained in Example 4 after different soaking times. DETAILED DESCRIPTION

[0023] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0024] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0025] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0026] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0027] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0028] The present invention provides a method for preparing magnetic quaternized ZIFs nanoparticles, comprising the following steps:

[0029] quaternizing the imidazole compound to obtain a quaternized imidazole compound;

[0030] The quaternized imidazole compound is mixed with the imidazole compound, magnetic particles, and solvent 1 to obtain solution 1; the zinc salt is mixed with solvent 1 to obtain solution 2;

[0031] The solution 2 is added dropwise into the solution 1 to react, thereby obtaining ZIFs nanoparticles.

[0032] In some embodiments of the present invention, the imidazole compound is imidazole, 2-methylimidazole, 2-ethylimidazole, 2-nitroimidazole, benzimidazole, 4,5-dichloroimidazole, 5-chlorobenzimidazole, 5,6-dimethylbenzimidazole, purine, imidazole-2-carboxaldehyde, N-acetylimidazole, methylbenzotriazole, benzimidazole-5-carboxylic acid, N-benzoylimidazole, 2-mercaptoimidazole or 2-hydroxymethylbenzimidazole, preferably imidazole, 2-methylimidazole, 2-ethylimidazole or benzimidazole. The structural formula of the imidazole compound is as follows:

[0033]

[0034]

[0035] The present invention first quaternizes an imidazole compound to obtain a quaternized imidazole compound. The quaternary ammonium group has strong antibacterial properties. The cationic antibacterial quaternary ammonium salt can destroy microbial cell membranes through electrostatic interactions with external microorganisms, causing protein denaturation and enzyme inactivation, thereby killing the bacteria. Introducing the quaternary ammonium salt into an ultrafiltration membrane material imparts excellent antibacterial properties, thereby promoting its large-scale application in the field of water treatment.

[0036] In some embodiments of the present invention, the specific steps of quaternizing the imidazole compound are: adding the imidazole compound to the quaternizing agent, heating and stirring; the stirring temperature is 30°C-80°C, preferably 40°C-70°C, and the stirring time is 12-60h, preferably 24-50h.

[0037] In some embodiments of the present invention, the quaternizing agent is sodium 2-bromoethylsulfonate, sodium 3-bromopropanesulfonate, sodium 3-chloro-2-hydroxypropanesulfonate, sodium chloroacetate, benzyl chloride or a halogenated alkane; the structural formula of the halogenated alkane is RX, wherein R is a C1-C20 alkyl, benzyl or cyclopentyl, and X is Cl, Br or I; preferably sodium 2-bromoethylsulfonate or 1-bromohexadecane; the concentration of the quaternizing agent is 0-3 mol / L, and is not 0, preferably 0.1-1.5 mol / L.

[0038] In some embodiments of the present invention, in the quaternization of the imidazole compound, the molar ratio of the imidazole compound to the quaternizing agent is 1:(1-4), preferably 1:(1.5-2.5).

[0039] After obtaining the quaternized imidazole compound, the present invention mixes the quaternized imidazole compound with the imidazole compound, magnetic particles, and solvent 1 to obtain solution 1; and mixes the zinc salt with solvent 1 to obtain solution 2.

[0040] In some embodiments of the present invention, the magnetic particles are at least one of Fe3O4, γ-Fe2O3, MnO, CoO and NiO (the Fe3O4, γ-Fe2O3, MnO, CoO and NiO are all nanoparticles), preferably Fe3O4, γ-Fe2O3 or NiO; the molar ratio of the magnetic particles, imidazole compounds and quaternized imidazole compounds in the solution 1 is (1-0): (3-1): 1, and is not 0, preferably (0.6-0): (2-1): 1, and is not 0.

[0041] In some embodiments of the present invention, the solvent 1 is at least one of water, methanol (MeOH), acetone, ethanol (EtOH), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), N-methylpyrrolidone (NMP), tetrahydrofuran (THF), dioxane, and methyl ethyl ketone, preferably a mixture of one or two of water, methanol, ethanol, and N,N-dimethylformamide.

[0042] In some embodiments of the present invention, after the mixing, the step of ultrasonicating and stirring the obtained mixed solution is further included; the ultrasonication time is 0-60 min, preferably 20-40 min; the stirring time is 0-60 min, preferably 20-40 min.

[0043] In some embodiments of the present invention, the zinc salt is Zn(NO3)2·6H2O, ZnSO4·6H2O, Zn(CH3COO)2·2H2O, Zn(acac)2·H2O, ZnCl2·H2O, ZnI2·H2O and their corresponding anhydrous salts, preferably Zn(NO3)2·6H2O, ZnSO4·6H2O, Zn(CH3COO)2·2H2O or Zn(acac)2·H2O.

[0044] In some embodiments of the present invention, the molar ratio of the imidazole compound in solution 1 to the zinc element in solution 2 is 4:(1-2).

[0045] After obtaining solution 1 and solution 2, the present invention adds the solution 2 dropwise into the solution 1 to react, thereby obtaining magnetic quaternized ZIFs nanoparticles (denoted as ZIFs nanoparticles).

[0046] In some embodiments of the present invention, the solution 2 is added dropwise to the solution 1 for reaction, and the reaction is a stirring reaction; the stirring reaction time is 12-36 hours, preferably 20-30 hours.

[0047] In some embodiments of the present invention, the solution 2 is added dropwise to the solution 1 for a time of 1-4 hours, preferably 1.5-3 hours. During the experimental process of the present invention, a peristaltic pump is used and the speed of the device is adjusted to control the flow rate of the solution 2, thereby controlling the time of addition. By controlling the rate of addition, the reaction is easily controlled, and the size and morphology of the ZIFs can be precisely regulated. Solution 1 is an organic ligand solution, and solution 2 is a metal ion solution. Solution 2 is added dropwise to the solution 1, i.e., the organic ligand is in excess, and metal ions are added dropwise, which is conducive to the complete coordination of ZIF-8 and quaternized ZIF-8 crystals, making the crystal form complete. If the dropwise addition is too fast, that is, the dropwise addition time is too short, and the reaction time is too short, the ZIF-8 and quaternized ZIF-8 crystals may not be fully coordinated, and the formed crystals may be incomplete and defective. If the dropwise addition is too slow, that is, the dropwise addition time is too long, and the reaction time is too long, impurities in the air or other factors that may affect the experimental results may have more opportunities to enter the reaction system. These impurities may react with the reactants unnecessarily or be adsorbed on the walls of the reaction vessel, resulting in errors in the experimental results. Secondly, too slow a dropwise addition may also cause the reaction process to be affected by unstable factors in the environment, such as temperature changes and humidity changes, which may affect the progress of the reaction and the properties of the final product. Therefore, it is crucial to control the appropriate dropwise addition time.

[0048] In some embodiments of the present invention, after the reaction is completed, the steps of collecting the precipitate in the reaction solution, washing the precipitate, and drying the precipitate are further included.

[0049] The present invention also provides magnetic quaternized ZIFs nanoparticles (denoted as ZIFs nanoparticles) prepared by the above preparation method.

[0050] The present invention also provides a method for preparing a modified ultrafiltration membrane, comprising preparing a casting solution containing the ZIFs nanoparticles, and then laying the membrane under the action of a magnetic field to obtain the modified ultrafiltration membrane.

[0051] In some embodiments of the present invention, the casting solution further includes a porogen, a polymer matrix and a solvent 2; the preparation method of the casting solution is: after the ZIFs nanoparticles are uniformly dispersed in the solvent 2, the porogen is added, and after the porogen is completely dissolved, the polymer matrix is ​​added, and the mixture is stirred for a period of time under certain temperature conditions, and vacuum degassing is performed to obtain the casting solution.

[0052] In some embodiments of the present invention, the solvent 2 is at least one of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide and sulfolane, preferably N,N-dimethylacetamide, N,N-dimethylformamide or N-methylpyrrolidine.

[0053] In some embodiments of the present invention, the mass percentage of the ZIFs nanoparticles in the casting solution is 0-5%, preferably 0-3%, and is not 0.

[0054] In some embodiments of the present invention, the porogen is polyvinyl pyrrolidone, polyethylene glycol, polyacrylamide, hydrolyzed polyacrylamide, polyacrylic acid, polyvinyl alcohol, polyethylene oxide, polymaleic anhydride or polyquaternary ammonium salt, preferably polyvinyl pyrrolidone, polyethylene glycol or polyvinyl alcohol; the mass percentage of the porogen in the casting solution is 0 to 6%.

[0055] In some embodiments of the present invention, the polymer matrix is ​​a polyarylether polymer or a polyimide containing an ether bond; the mass percentage of the polymer matrix in the casting solution is 13%-21%, preferably 15%-18%; the structural formula of the polyarylether polymer is shown in Formula I:

[0056]

[0057] Among them, R1 is

[0058] R2 is

[0059] The structural formula of the polyimide containing ether bonds is one of Formula II-VI:

[0060]

[0061]

[0062] In formula II-VI, n is 30-300.

[0063] In some embodiments of the present invention, the polymer matrix is ​​preferably one of the following structural formulas:

[0064]

[0065]

[0066] Wherein, n is 30-300.

[0067] The ultrafiltration membrane materials selected in the present invention, such as polysulfone, polyethersulfone, polyetherketone, polyetherimide, etc., are all soluble thermoplastic engineering plastics with excellent performance, strong stability, high mechanical strength, good solubility and film-forming properties, and have now become the most commonly used membrane materials in the industry.

[0068] In some embodiments of the present invention, the stirring temperature is 50-80°C, preferably 60-80°C, and the stirring time is 8-12 hours, preferably 10-12 hours.

[0069] After obtaining the casting solution, the present invention lays the casting solution under the action of a magnetic field to obtain the ultrafiltration membrane.

[0070] In some embodiments of the present invention, the film laying is specifically as follows: a clean substrate is loaded onto a coating device, and the distance between the scraper of the coating device and the substrate is adjusted. The prepared casting solution is evenly poured into the material tank of the coating device, and the coating process is quickly started. The process is carried out at room temperature, and the relative movement speed of the scraper and the substrate is constant. After the coating is completed, the substrate is left to stand in the air for a period of time, during which time a magnetic field is applied vertically above the substrate so that the film is in the magnetic field. The resulting magnetized film precursor is then immersed in ultrapure water to obtain a magnetic quaternized ZIFs nanoparticle-modified ultrafiltration membrane (denoted as ultrafiltration membrane).

[0071] In some embodiments of the present invention, the distance between the scraper and the substrate is 50 μm-200 μm, preferably 100 μm; the substrate is a glass plate or a non-woven fabric; the relative speed between the scraper and the substrate is 0-4 m / min, and is not 0, preferably 1-3 m / min; the standing time in the air is 15s-40s, preferably 25s-35s.

[0072] The present invention also provides a modified ultrafiltration membrane prepared by the preparation method described in the above technical solution.

[0073] Fe3O4 is insoluble in water and organic solvents. It has the advantages of small size, high specific surface area, excellent magnetic properties, good dispersibility and hydrophilicity, high reactivity and good thermal stability. It is also biocompatible and degradable, and has special magnetic properties that are different from other materials. ZIFs is a kind of metal particles (Zn 2+ or Co 2+ ) and organic ligands (imidazole and imidazole derivatives) to form a porous material with a unique pore structure and adjustable pore size. It is characterized by high stability, high porosity and organic functionality. Due to its ideal specific surface area and high adjustability, it can maintain good structural stability under various conditions.

[0074] The present invention uses magnetic quaternized ZIFs nanoparticles as hydrophilic fillers to blend and modify ultrafiltration membrane materials, significantly improving the membrane's permeability and anti-fouling properties while also imparting new antibacterial properties to the ultrafiltration membrane. Particles deposited in the ultrafiltration membrane pores and fingerprint region are ineffective and may even cause enrichment and blockage, reducing membrane performance. During the immersion-precipitation phase transformation process, under the action of a magnetic field, the magnetic quaternized ZIFs nanoparticles are oriented and migrate along the magnetic field lines. By utilizing the magnetic field to control the distribution of the magnetic quaternized ZIFs nanoparticles in the membrane, as many of them as possible are dragged from the fingerprint region to the cortex, thereby affecting the membrane's microstructure and performance. This not only enriches the filler and increases filler utilization, but also improves membrane performance. The magnetic quaternized ZIFs nanoparticles are positively charged in solution, and the repulsive force between the particles prevents agglomeration. Furthermore, the hydroxyl groups on the surface of the magnetic quaternized ZIFs nanoparticles form hydrogen bonds with water molecules. This, combined with electrostatic interactions, binds water molecules to the hydration layer on the membrane surface, acting as a barrier to prevent contact and adsorption of pollutant molecules, thereby improving the anti-fouling properties of the ultrafiltration membrane. When the quaternary ammonium cations in the magnetic quaternized ZIFs nanoparticles come into contact with negatively charged bacteria, the long hydrophobic alkyl chains penetrate the cell membrane, causing the extravasation of intracellular substances and killing the bacteria, thereby enhancing the antibacterial properties of the modified membrane.

[0075] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

[0076] Unless otherwise specified, the raw materials and reagents used in the examples can be obtained through commercial channels.

[0077] Example 1

[0078] This embodiment provides an ultrafiltration membrane, and the preparation steps are as follows:

[0079] (1) 0.8211 g (10 mmol) of 2-methylimidazole was added to 0.3 mol / L sodium 2-bromoethylsulfonate, heated to 45°C, stirred for 36 h, centrifuged, and dried to obtain quaternized 2-methylimidazole;

[0080] (2) 0.4640 g (2 mmol) of Fe3O4, 0.3284 g (4 mmol) of 2-methylimidazole, and 0.4264 g (2 mmol) of quaternized 2-methylimidazole were added to 120 ml of the mixed solution (V 甲醇 :V 水 =1:1), ultrasonically for 30 min, stirred for 30 min, and obtained solution 1; 0.2975 g (1 mmol) Zn (NO3) 2·6H2O was added to 60 ml of the mixed solution (V 甲醇 :V 水 =1:1) and stirred to dissolve to obtain solution 2;

[0081] (3) Solution 2 was added dropwise to solution 1 (addition time was 2 h), stirred for 24 h, and then the obtained reaction solution was separated by magnet, the supernatant was poured out, and the black precipitate was washed with a mixed solution of methanol and water and dried to obtain magnetic quaternized ZIF-8 nanoparticles (denoted as ZIF-8 nanoparticles);

[0082] (4) Add 0.05g ZIF-8 nanoparticles to 7.95g dimethylacetamide and ultrasonicate until uniformly dispersed. Then add 0.3g polyvinyl pyrrolidone, and after complete dissolution, add 1.7g PES-C, mechanically stir at 70℃ for 11h, and vacuum degass to obtain a casting solution. Load the casting solution onto a clean non-woven fabric on the coating machine, and adjust the distance between the scraper of the coating machine and the non-woven fabric to 100μm. Pour the prepared casting solution evenly into the material tank of the coating machine and quickly start the coating process. The process is carried out at room temperature, the non-woven fabric is stationary, and the coating speed of the coating machine is 2m / min. After coating, the non-woven fabric is left to stand in the air for 30s. During this period, a magnetic field is applied vertically above the non-woven fabric so that the membrane is in the magnetic field. The obtained magnetized membrane precursor is then immersed in ultrapure water to finally obtain a magnetic ultrafiltration membrane modified with quaternized ZIF-8 nanoparticles (referred to as ultrafiltration membrane).

[0083] Figure 1 This is a scanning electron microscope image of the magnetic quaternized ZIF-8 nanoparticles obtained in Example 1. As can be seen from the figure, Fe3O4 nanoparticles are attached to the quaternized ZIF-8 nanoparticles.

[0084] Figure 2 This is a scanning electron microscope micrograph of the cross section of the magnetized ultrafiltration membrane obtained in Example 1. Figure 3As can be seen from the image, the cross-section of the ultrafiltration membrane prepared in Example 1 exhibits a typical asymmetric structure, consisting of a dense cortex and a finger-like pore support layer. The cortex is relatively thin, resulting in the presence of larger finger-like pores. Magnetic quaternized ZIF-8 nanoparticles are almost absent from the membrane pores, primarily due to the addition of an external magnetic field during the molding process.

[0085] Figure 3 The XRD pattern of the magnetic quaternized ZIF-8 nanoparticles prepared in Example 1. As can be seen from the figure, the magnetic quaternized ZIF-8 nanoparticles have typical characteristics of ZIF-8 crystals at 2θ=7.46°(011), 10.53°(002), 12.85°(112), 14.83°(022), 16.58°(013), 18.18°(222), 22.25°(114), 24.66°(015), 26.84°(431), and 31.63°(35.02), indicating the successful synthesis of ZIF-8. 2+ The quaternized ZIF-8 undergoes coordination, and part of its lattice structure is destroyed, resulting in the disappearance of some characteristic peaks. The characteristic diffraction peaks of the magnetic quaternized ZIF-8 nanoparticles at 2θ = 30.76°, 35.14°, 42.69°, 55.87°, and 63.14° are attributed to the lattice planes (220), (311), (400), (511), and (440) of the Fe3O4 nanoparticles, confirming the presence of Fe3O4 nanoparticles. All of the above proves the successful synthesis of magnetic quaternized ZIF-8 nanoparticles.

[0086] Figure 4 This is the infrared spectrum of the magnetic quaternized ZIF-8 nanoparticles prepared in Example 1. As can be seen from the figure, 3132 and 2927 cm -1 The infrared absorption peaks at 1581 cm-1 are derived from the C—H stretching vibration peaks of the methyl group and the imidazole ring. -1 The stretching vibration peak of C=N in the imidazole ring is 1145 cm -1 The peak at 419cm is the C-N symmetric stretching vibration peak. -1 The peaks corresponding to the stretching vibrations of metal and organic ligands, namely Zn-N, are 1178, 627, and 517 cm -1 The infrared absorption peak belonging to the sulfonic acid group appeared at 558cm -1 The absorption peak at the wave number is another infrared characteristic peak of the sulfonic acid group (530cm -1 ) and the infrared characteristic peaks of Fe-O (580cm -1 ) overlap, which indicates the successful synthesis of magnetic quaternized ZIF-8 nanoparticles.

[0087] Example 2

[0088] This embodiment provides an ultrafiltration membrane, and the preparation steps are as follows:

[0089] (1) 0.8211 g (10 mmol) of 2-methylimidazole was added to 0.3 mol / L sodium 2-bromoethylsulfonate, heated to 45°C, stirred for 36 h, centrifuged, and dried to obtain quaternized 2-methylimidazole;

[0090] (2) 0.4640 g (2 mmol) of Fe3O4, 0.3284 g (4 mmol) of 2-methylimidazole, and 0.4264 g (2 mmol) of quaternized 2-methylimidazole were added to 120 ml of the mixed solution (V 甲醇 :V 水 =1:1), ultrasonically for 30 min, stirred for 30 min, and obtained solution 1; 0.2679 g (1 mmol) ZnSO4·6H2O was added to 60 ml of the mixed solution (V 甲醇 :V 水 =1:1) and stirred to dissolve to obtain solution 2;

[0091] (3) Solution 2 was added dropwise to solution 1 (addition time was 2 h), stirred for 24 h, and then the obtained reaction solution was separated by magnet, the supernatant was poured out, and the black precipitate was washed with a mixed solution of methanol and water and dried to obtain magnetic quaternized ZIF-8 nanoparticles (denoted as ZIF-8 nanoparticles);

[0092] (4) Add 0.1g ZIF-8 nanoparticles to 7.9g dimethylacetamide and ultrasonicate until uniformly dispersed. Then add 0.3g polyvinyl pyrrolidone, add 1.7g PSF after complete dissolution, mechanically stir at 80℃ for 10h, vacuum degassing to obtain a casting solution. Load a clean non-woven fabric on the coating machine, adjust the distance between the scraper of the coating machine and the non-woven fabric to 100μm. Pour the prepared casting solution evenly into the material tank of the coating machine, and quickly start the coating process. The process is carried out at room temperature, the non-woven fabric is stationary, and the coating speed of the coating machine is 2.5m / min. After coating, the non-woven fabric is left to stand in the air for 35s. During this period, a magnetic field is applied vertically above the non-woven fabric so that the membrane is in the magnetic field. The obtained magnetized membrane precursor is then immersed in ultrapure water to finally obtain a magnetic ultrafiltration membrane modified with quaternized ZIF-8 nanoparticles (referred to as ultrafiltration membrane).

[0093] Example 3

[0094] This embodiment provides an ultrafiltration membrane, and the preparation steps are as follows:

[0095] (1) 0.8211 g (10 mmol) of 2-methylimidazole was added to 0.3 mol / L sodium 2-bromoethylsulfonate, heated to 45°C, stirred for 36 h, centrifuged, and dried to obtain quaternized 2-methylimidazole;

[0096] (2) 0.4640 g (2 mmol) of Fe3O4, 0.3284 g (4 mmol) of 2-methylimidazole, and 0.4264 g (2 mmol) of quaternized 2-methylimidazole were added to 120 ml of the mixed solution (V 甲醇 :V 水 =1:1), ultrasonically for 30 min, stirred for 30 min, and obtained solution 1; 0.2975 g (1 mmol) Zn (NO3) 2·6H2O was added to 60 ml of the mixed solution (V 甲醇 :V 水 =1:1) and stirred to dissolve to obtain solution 2;

[0097] (3) Solution 2 was added dropwise to solution 1 (addition time was 2 h), stirred for 24 h, and then the obtained reaction solution was separated by magnet, the supernatant was poured out, and the black precipitate was washed with a mixed solution of methanol and water and dried to obtain magnetic quaternized ZIF-8 nanoparticles (denoted as ZIF-8 nanoparticles);

[0098] (4) Add 0.15g ZIF-8 nanoparticles to 7.85g dimethylacetamide and ultrasonicate until uniformly dispersed. Then add 0.3g polyvinyl pyrrolidone, add 1.7g PEK-C after complete dissolution, mechanically stir at 60℃ for 12h, vacuum degassing to obtain a casting solution. Load a clean non-woven fabric on the coating machine, adjust the distance between the scraper of the coating machine and the non-woven fabric to 100μm. Pour the prepared casting solution evenly into the material trough of the coating machine, and quickly start the coating process. The process is carried out at room temperature, the non-woven fabric is stationary, and the coating speed of the coating machine is 3m / min. After coating, the non-woven fabric is left to stand in the air for 25s. During this period, a magnetic field is applied vertically above the non-woven fabric so that the membrane is in the magnetic field. The obtained magnetized membrane precursor is then immersed in ultrapure water to finally obtain a magnetic ultrafiltration membrane modified with quaternized ZIF-8 nanoparticles (referred to as ultrafiltration membrane).

[0099] Example 4

[0100] This embodiment provides an ultrafiltration membrane, and the preparation steps are as follows:

[0101] (1) 0.8211 g (10 mmol) of 2-methylimidazole was added to 0.3 mol / L sodium 2-bromoethylsulfonate, heated to 45°C, stirred for 36 h, centrifuged, and dried to obtain quaternized 2-methylimidazole;

[0102] (2) 0.4640 g (2 mmol) of Fe3O4, 0.3284 g (4 mmol) of 2-methylimidazole, and 0.4264 g (2 mmol) of quaternized 2-methylimidazole were added to 120 ml of the mixed solution (V 甲醇 :V 水 =1:1), ultrasonically for 30 min, stirred for 30 min, and obtained solution 1; 0.2679 g (1 mmol) ZnSO4·6H2O was added to 60 ml of the mixed solution (V 甲醇 :V 水 =1:1) and stirred to dissolve to obtain solution 2;

[0103] (3) Solution 2 was added dropwise to solution 1 (addition time was 2 h), stirred for 24 h, and then the obtained reaction solution was separated by magnet, the supernatant was poured out, and the black precipitate was washed with a mixed solution of methanol and water and dried to obtain magnetic quaternized ZIF-8 nanoparticles (denoted as ZIF-8 nanoparticles);

[0104] (4) Add 0.2g ZIF-8 nanoparticles to 7.80g dimethylacetamide and sonicate until uniformly dispersed. Then add 0.3g polyvinyl pyrrolidone, add 1.7g PPSU after complete dissolution, mechanically stir at 70℃ for 11h, and vacuum degas to obtain a casting solution. Load a clean non-woven fabric on the coating machine, adjust the distance between the scraper of the coating machine and the non-woven fabric to 100μm. Pour the prepared casting solution evenly into the material tank of the coating machine, and quickly start the coating process. The process is carried out at room temperature, the non-woven fabric is stationary, and the coating speed of the coating machine is 2m / min. After coating, the non-woven fabric is left to stand in the air for 30s. During this period, a magnetic field is applied vertically above the non-woven fabric so that the membrane is in the magnetic field. The obtained magnetized membrane precursor is then immersed in ultrapure water to finally obtain a magnetic ultrafiltration membrane modified with quaternized ZIF-8 nanoparticles (referred to as ultrafiltration membrane).

[0105] Example 5

[0106] This embodiment provides an ultrafiltration membrane, and the preparation steps are as follows:

[0107] (1) 0.6808 g (10 mmol) of imidazole was added to 0.5 mol / L 1-bromohexadecane, heated to 45°C, stirred for 36 h, centrifuged, and dried to obtain quaternized imidazole;

[0108] (2) 0.3194 g (2 mmol) of γ-Fe2O3, 0.2723 g (4 mmol) of imidazole, and 0.5870 g (2 mmol) of quaternized imidazole were added to 120 ml of the mixed solution (V 甲醇 :V 水=1:1), ultrasonically for 30 min, stirred for 30 min, and obtained solution 1; 0.2815 g (1 mmol) Zn(acac)2·H2O was added to 60 ml of the mixed solution (V 甲醇 :V 水 =1:1) and stirred to dissolve to obtain solution 2;

[0109] (3) Solution 2 was added dropwise to solution 1 (addition time was 2.5 h), stirred for 32 h, and then the obtained reaction solution was separated by magnet, the supernatant was discarded, and the black precipitate was washed with a mixed solution of methanol and water and dried to obtain magnetic quaternized ZIF-61 nanoparticles (denoted as ZIF-61 nanoparticles);

[0110] (4) Add 0.05g ZIF-61 nanoparticles to 7.95g dimethylacetamide and ultrasonicate until uniformly dispersed. Then add 0.3g polyvinyl pyrrolidone, and after complete dissolution, add 1.7g PES-C, mechanically stir at 70℃ for 11h, and vacuum degas to obtain a casting solution. Load a clean non-woven fabric on the coating machine, adjust the distance between the scraper of the coating machine and the non-woven fabric to 100μm. Pour the prepared casting solution evenly into the material tank of the coating machine, and quickly start the coating process. The process is carried out at room temperature, the non-woven fabric is stationary, and the coating speed of the coating machine is 2m / min. After coating, the non-woven fabric is left to stand in the air for 30s. During this period, a magnetic field is applied vertically above the non-woven fabric so that the membrane is in the magnetic field. The obtained magnetized membrane precursor is then immersed in ultrapure water to finally obtain a magnetic ultrafiltration membrane modified with quaternized ZIF-61 nanoparticles (referred to as ultrafiltration membrane).

[0111] Example 6

[0112] This embodiment provides an ultrafiltration membrane, and the preparation steps are as follows:

[0113] (1) 0.6808 g (10 mmol) of imidazole was added to 0.5 mol / L 1-bromohexadecane, heated to 45°C, stirred for 36 h, centrifuged, and dried to obtain quaternized imidazole;

[0114] (2) 0.3194 g (2 mmol) of γ-Fe2O3, 0.2723 g (4 mmol) of imidazole, and 0.5870 g (2 mmol) of quaternized imidazole were added to 120 ml of the mixed solution (V 甲醇 :V 水 =1:1), ultrasonically for 30 min, stirred for 30 min, to obtain solution 1; 0.440 g (2 mmol) Zn(CH3COO)2·2H2O was added to 60 ml of the mixed solution (V 甲醇 :V 水 =1:1) and stirred to dissolve to obtain solution 2;

[0115] (3) Solution 2 was added dropwise to solution 1 (addition time was 2.5 h), stirred for 32 h, and then the obtained reaction solution was separated by magnet, the supernatant was discarded, and the black precipitate was washed with a mixed solution of methanol and water and dried to obtain magnetic quaternized ZIF-61 nanoparticles (denoted as ZIF-61 nanoparticles);

[0116] (4) Add 0.1g ZIF-61 nanoparticles to 7.90g dimethylacetamide and ultrasonicate until uniformly dispersed. Then add 0.3g polyvinyl pyrrolidone, add 1.7g PES after complete dissolution, mechanically stir at 80℃ for 10h, and vacuum degas to obtain a casting solution. Load a clean non-woven fabric on the coating machine, adjust the distance between the scraper of the coating machine and the non-woven fabric to 100μm. Pour the prepared casting solution evenly into the material trough of the coating machine, and quickly start the coating process. The process is carried out at room temperature, the non-woven fabric is stationary, and the coating speed of the coating machine is 2.5m / min. After coating, the non-woven fabric is left to stand in the air for 35s. During this period, a magnetic field is applied vertically above the non-woven fabric so that the membrane is in the magnetic field. The obtained magnetized membrane precursor is then immersed in ultrapure water to finally obtain a magnetic ultrafiltration membrane modified with quaternized ZIF-61 nanoparticles (referred to as ultrafiltration membrane).

[0117] Example 7

[0118] (1) 0.6808 g (10 mmol) of imidazole was added to 0.5 mol / L 1-bromohexadecane, heated to 45°C, stirred for 36 h, centrifuged, and dried to obtain quaternized imidazole;

[0119] (2) 0.3194 g (2 mmol) of γ-Fe2O3, 0.2723 g (4 mmol) of imidazole, and 0.5870 g (2 mmol) of quaternized imidazole were added to 120 ml of the mixed solution (V 甲醇 :V 水 =1:1), ultrasonically for 30 min, stirred for 30 min, and obtained solution 1; 0.2815 g (1 mmol) Zn(acac)2·H2O was added to 60 ml of the mixed solution (V 甲醇 :V 水 =1:1) and stirred to dissolve to obtain solution 2;

[0120] (3) Solution 2 was added dropwise to solution 1 (addition time was 2.5 h), stirred for 32 h, and then the obtained reaction solution was separated by magnet, the supernatant was discarded, and the black precipitate was washed with a mixed solution of methanol and water and dried to obtain magnetic quaternized ZIF-61 nanoparticles (denoted as ZIF-61 nanoparticles);

[0121] (4) Add 0.15g ZIF-61 nanoparticles to 7.85g dimethylacetamide and ultrasonicate until uniformly dispersed. Then add 0.3g polyvinyl pyrrolidone, add 1.7g PES after complete dissolution, mechanically stir at 60℃ for 12h, and vacuum degas to obtain a casting solution. Load a clean non-woven fabric on the coating machine, adjust the distance between the scraper of the coating machine and the non-woven fabric to 100μm. Pour the prepared casting solution evenly into the material tank of the coating machine, and quickly start the coating process. The process is carried out at room temperature, the non-woven fabric is stationary, and the coating speed of the coating machine is 3m / min. After coating, the non-woven fabric is left to stand in the air for 25s. During this period, a magnetic field is applied vertically above the non-woven fabric so that the membrane is in the magnetic field. The obtained magnetized membrane precursor is then immersed in ultrapure water to finally obtain a magnetic ultrafiltration membrane modified with quaternized ZIF-61 nanoparticles (referred to as ultrafiltration membrane).

[0122] Example 8

[0123] (1) 0.6808 g (10 mmol) of imidazole was added to 0.5 mol / L 1-bromohexadecane, heated to 45°C, stirred for 36 h, centrifuged, and dried to obtain quaternized imidazole;

[0124] (2) 0.3194 g (2 mmol) of γ-Fe2O3, 0.2723 g (4 mmol) of imidazole, and 0.5870 g (2 mmol) of quaternized imidazole were added to 120 ml of the mixed solution (V 甲醇 :V 水 =1:1), ultrasonically for 30 min, stirred for 30 min, to obtain solution 1; 0.440 g (2 mmol) Zn(CH3COO)2·2H2O was added to 60 ml of the mixed solution (V 甲醇 :V 水 =1:1) and stirred to dissolve to obtain solution 2;

[0125] (3) Solution 2 was added dropwise to solution 1 (addition time was 2.5 h), stirred for 32 h, and then the obtained reaction solution was separated by magnet, the supernatant was poured out, and the black precipitate was washed with a mixed solution of methanol and water and dried to obtain magnetic quaternized ZIF-61 nanoparticles (obtained ZIF-61 nanoparticles);

[0126] (4) Add 0.2g ZIF-61 nanoparticles to 7.8g dimethylacetamide and ultrasonicate until uniformly dispersed. Then add 0.3g polyvinyl pyrrolidone, add 1.7g PEI after complete dissolution, mechanically stir at 80℃ for 10h, vacuum degassing to obtain a casting solution. Load a clean non-woven fabric on the coating machine, adjust the distance between the scraper of the coating machine and the non-woven fabric to 100μm. Pour the prepared casting solution evenly into the material tank of the coating machine, and quickly start the coating process. The process is carried out at room temperature, the non-woven fabric is stationary, and the coating speed of the coating machine is 2.8m / min. After coating, the non-woven fabric is left to stand in the air for 30s. During this period, a magnetic field is applied vertically above the non-woven fabric so that the membrane is in the magnetic field. The obtained magnetized membrane precursor is then immersed in ultrapure water to finally obtain a magnetic ultrafiltration membrane modified with quaternized ZIF-61 nanoparticles (referred to as ultrafiltration membrane).

[0127] Comparative Example 1

[0128] 1.7 g of PES-C was added to 7.6 g of dimethylacetamide and sonicated until uniformly dispersed. Subsequently, 0.3 g of polyvinyl pyrrolidone was added and dissolved completely. The mixture was then magnetically stirred at 70°C for 11 hours and vacuum degassing was performed to obtain a casting solution. A clean glass plate was loaded onto a coating machine, and the distance between the coating machine's scraper and the glass plate was adjusted to 100 μm. The resulting casting solution was evenly poured into the coating machine's trough, and the coating process was quickly initiated. This process was carried out at room temperature, with the scraper stationary and the glass plate moving at a speed of 2 m / min. After coating, the glass plate was allowed to stand in air for 30 seconds. The resulting membrane precursor was then immersed in ultrapure water to obtain a polysulfone ultrafiltration membrane.

[0129] Comparative Example 2

[0130] (1) 0.8211 g (10 mmol) of 2-methylimidazole was added to 0.3 mol / L sodium 2-bromoethylsulfonate, heated to 45°C, stirred for 36 h, centrifuged, and dried to obtain quaternized 2-methylimidazole;

[0131] (2) 0.4640 g (2 mmol) of Fe3O4, 0.3284 g (4 mmol) of 2-methylimidazole, and 0.4264 g (2 mmol) of quaternized 2-methylimidazole were added to 120 ml of the mixed solution (V 甲醇 :V 水 =1:1), ultrasonically for 30 min, stirred for 30 min, and obtained solution 1; 0.2975 g (1 mmol) Zn (NO3) 2·6H2O was added to 60 ml of the mixed solution (V 甲醇 :V 水 =1:1) and stirred to dissolve to obtain solution 2;

[0132] (3) Solution 2 was added dropwise to solution 1 (addition time was 2 h), stirred for 24 h, and then the obtained reaction solution was separated by magnet, the supernatant was poured out, and the black precipitate was washed with a mixed solution of methanol and water and dried to obtain magnetic quaternized ZIF-8 nanoparticles (denoted as ZIF-8 nanoparticles);

[0133] (4) Add 0.1g ZIF-8 nanoparticles to 7.90g dimethylacetamide and ultrasonicate until uniformly dispersed. Then add 0.3g polyvinyl pyrrolidone, add 1.7g PES after complete dissolution, mechanically stir at 60℃ for 12h, and vacuum degas to obtain a casting solution. Load a clean glass plate on the coating machine, adjust the distance between the coating machine's scraper and the glass plate to 100μm. Pour the prepared casting solution evenly into the coating machine's trough, and quickly start the coating process. The process is carried out at room temperature, the scraper is stationary, and the movement speed of the glass plate is 2.5m / min. After coating, the glass plate is left to stand in air for 30s. The obtained membrane precursor is then immersed in ultrapure water to finally obtain a magnetic quaternized ZIF-8 nanoparticle modified ultrafiltration membrane (referred to as ultrafiltration membrane).

[0134] The ultrafiltration performance and antibacterial performance of the ultrafiltration membrane modified with the magnetic quaternized ZIFs nanoparticles prepared in Examples 1 to 8 were tested according to the following method:

[0135] At a pressure of 0.15 MPa, pre-press the membrane to be tested with pure water for 30 minutes, then reduce the pressure to 0.1 MPa. Record the flux value every 5 minutes, and continue measuring for 1 hour. Record the final stable flux as J w1 Replace pure water with 1g / L bovine serum albumin solution, maintain the pressure at 0.1Mpa, record the flux value every 5min, continue measuring for 1h, and record the final stable flux J p ; Then, clean the contaminated membrane with pure water (place the ultrafiltration membrane in the membrane pool upside down and rinse it with pure water for one hour). Then, pass pure water through the cleaned membrane again at 0.1 MPa. Record the flux value every 5 minutes. Continue measuring for 1 hour and record the final stable flux J. w2 .

[0136] J is defined as the permeation flux per unit area per unit time of the membrane, and the calculation formula is as follows:

[0137]

[0138] Where V is the permeate volume (L); A is the membrane area (m 2 ); t represents the penetration time (h).

[0139] The FRR is defined as the flux recovery rate, which is the recovery of the membrane permeability to the pre-fouling level after the fouling-cleaning cycle. The calculation formula is as follows:

[0140]

[0141] R is defined as the retention rate of bovine serum albumin solution. The concentration of bovine serum albumin in the feed solution and permeate is determined by UV-visible spectrophotometry. The calculation formula is as follows:

[0142]

[0143] Among them, C p is the concentration of BSA in the permeate (g / L), C f is the concentration of BSA in the raw material solution (g / L).

[0144] The antibacterial performance of the ultrafiltration membrane was evaluated based on the antibacterial rate using the plate coating method with Escherichia coli and Staphylococcus aureus as indicator bacteria. The specific steps are as follows:

[0145] The bacterial suspension (1.0×10 6 CFU / mL) was added to the UV-sterilized membrane sample and incubated at 37°C for 24 hours. The two bacterial solutions were then applied to solid culture medium, and the inhibition rate was calculated by observing the number of colonies on the culture medium. Each sample was tested three times, and the average result was calculated using the following formula:

[0146]

[0147] Among them, N T is the number of colonies on the ultrafiltration membrane plate; NB is the colony count of the blank control sample plate without membrane sample.

[0148] Table 1 shows the pure water flux, retention rate and flux recovery rate of the ultrafiltration membranes prepared in Comparative Examples 1 to 2 and Examples 1 to 8. Table 2 shows the antibacterial rate measured after the ultrafiltration membrane prepared in Example 4 was immersed in pure water for different times:

[0149] Table 1

[0150]

[0151] Table 2

[0152]

[0153] According to the data in Table 1, the pure water flux, rejection rate and flux recovery rate change curves of the ultrafiltration membranes obtained in Comparative Examples 1 to 2 and Examples 1 to 8 were plotted, as shown in FIG. Figure 5 As shown (Comparative Example 1, Comparative Example 2, and Examples 1-8 correspond to Examples 1-8, respectively).

[0154] From Table 1 and Figure 5It can be seen that the pure water flux and flux recovery rate of the ultrafiltration membrane in comparative example 1, which is not added with any particles, are the lowest, which are 219 L / m 2 h, 48.0%; Comparative Example 2, adding magnetic quaternized ZIFs nanoparticles, but not setting a magnetic field during the molding process, the prepared ultrafiltration membrane pure water flux and flux recovery rate are higher than the first two comparative examples, 489L / m 2 h, 63.0%. In Examples 1 to 4, different contents of magnetic quaternized ZIFs nanoparticles were added, and a magnetic field was set during the molding process. The ultrafiltration membranes prepared by blending and modification were found to have a pure water flux that first increased and then decreased from 575 L / m as the content of magnetic quaternized ZIFs nanoparticles increased from 0.5 (w / v%) to 2 (w / v%). 2 h gradually increased to 640L / m 2 h, and then decreased to 461L / m 2 h; the flux recovery rate increased from 66.8% to 80.4%. In Examples 5 to 8, different amounts of magnetic quaternized ZIFs nanoparticles were added, and a magnetic field was set during the molding process. The ultrafiltration membranes prepared by blending and modification were found to have a pure water flux that first increased and then decreased from 605 L / m as the content of magnetic quaternized ZIFs nanoparticles increased from 0.5 (w / v%) to 2 (w / v%). 2 h gradually increased to 666L / m 2 h, and then decreased to 513 L / m 2 h; the flux recovery rate increased from 67.9% to 81.2%. Although the retention rate of the modified ultrafiltration membrane for bovine serum albumin decreased, it was still above 94%, showing good retention performance.

[0155] According to the data in Table 2, the antibacterial rate curve of the ultrafiltration membrane after different immersion times is drawn, as shown in Figure 2. Figure 6 shown.

[0156] From Table 2 and Figure 6 It can be seen that the antibacterial activity of the ultrafiltration membrane prepared in Example 4 is greater than 90%, and after being immersed for 60 hours, the antibacterial activity is still greater than 83%, indicating that the antibacterial performance of the ultrafiltration membrane modified with magnetic quaternized ZIFs nanoparticles has good stability.

[0157] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing magnetic quaternized ZIFs nanoparticles, characterized in that: The following steps are involved: quaternizing the imidazole compound to obtain a quaternized imidazole compound; The quaternized imidazole compound is mixed with the imidazole compound, magnetic particles, and solvent 1 to obtain solution 1; the zinc salt is mixed with solvent 1 to obtain solution 2; The solution 2 is added dropwise into the solution 1 to react, thereby obtaining the ZIFs nanoparticles.

2. The method for preparing magnetic quaternized ZIFs nanoparticles according to claim 1, wherein The imidazole compound is imidazole, 2-methylimidazole, 2-ethylimidazole, 2-nitroimidazole, benzimidazole, 4,5-dichloroimidazole, 5-chlorobenzimidazole, 5,6-dimethylbenzimidazole, purine, imidazole-2-carboxaldehyde, N-acetylimidazole, benzimidazole-5-carboxylic acid, N-benzoylimidazole, 2-mercaptoimidazole or 2-hydroxymethylbenzimidazole.

3. The method for preparing magnetic quaternized ZIFs nanoparticles according to claim 1, wherein The quaternizing agent used for quaternizing the imidazole compound is sodium 2-bromoethylsulfonate, sodium 3-bromopropylsulfonate, sodium 3-chloro-2-hydroxypropylsulfonate, sodium chloroacetate, benzyl chloride or halogenated alkane; The structural formula of the halogenated alkane is RX, wherein R is a C1-C20 alkyl, benzyl or cyclopentyl, and X is Cl, Br or I; In the reaction of quaternizing the imidazole compound, the molar ratio of the imidazole compound to the quaternizing agent is 1:(1-4).

4. The method for preparing magnetic quaternized ZIFs nanoparticles according to claim 1, wherein The magnetic particles are at least one of Fe3O4, γ-Fe2O3, MnO, CoO and NiO; the molar ratio of the magnetic particles, the imidazole compound and the quaternized imidazole compound in the solution 1 is (1-0): (3-1): 1, and is not 0.

5. The method for preparing magnetic quaternized ZIFs nanoparticles according to claim 1, wherein The zinc salts are Zn(NO3)2·6H2O, ZnSO4·6H2O, Zn(CH3COO)2·2H2O, Zn(acac)2·H2O, ZnCl2·H2O, ZnI2·H2O and their corresponding anhydrous salts.

6. The method for preparing magnetic quaternized ZIFs nanoparticles according to claim 1, wherein The reaction is a stirring reaction; the stirring reaction time is 12-36 hours.

7. Magnetic quaternized ZIFs nanoparticles prepared by the preparation method according to any one of claims 1 to 6.

8. A method for preparing a modified ultrafiltration membrane, characterized in that: A casting solution containing the ZIFs nanoparticles according to claim 1 is prepared, and then a membrane is laid under the action of a magnetic field to obtain the ultrafiltration membrane.

9. The method for preparing a modified ultrafiltration membrane according to claim 8, wherein: The casting solution also includes a porogen, a polymer matrix and a solvent 2.

10. A modified ultrafiltration membrane prepared by the preparation method according to claim 8 or 9.

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