Horizontal orientation ZIF-L composite film and preparation method thereof

Abstract

The invention relates to a horizontally oriented ZIF-L composite film and a preparation method thereof. The membrane comprises a polyacrylonitrile (PAN) base membrane and a separation layer composed of a two-dimensional foliated material ZIF-L. The preparation method comprises the following steps: (1) synthesizing a ZIF-L material at room temperature; (2) preparing a continuously and directionally arranged ZIF-L layer on the PAN base film through an in-situ seed growth method; and (3) carrying out secondary growth treatment on the ZIF-L layer to obtain a complete separation layer. The method has the innovation points that (1) directional arrangement of the ZIF-L crystals is realized by adopting an in-situ seed growth method, and the defect of disordered growth of the ZIF-L in a traditional method is overcome; (2) the separation layer structure is optimized through a secondary growth process, and the selectivity of the membrane is remarkably improved; (3) introducing ZIF-L to construct an efficient water molecule transmission channel, and realizing hydrophilic modification of the membrane surface. The prepared pervaporation membrane shows excellent separation performance, the pure water flux can reach 4000 g.m <-2 >. H <-1 >, the separation factor reaches up to 2100, and the pervaporation membrane has good stability and pollution resistance. The membrane has wide application prospects in the fields of biofuel purification, solvent dehydration and the like.

Description

Technical Field

[0001] The present invention relates to a high-performance membrane for alcohol-water separation, belonging to the technical field of separation membrane preparation. This modified membrane has a high pure water flux, good separation effect on ethanol, and is applicable to fields such as alcohol-water separation. Background Art

[0002] As a new membrane separation process, pervaporation membrane separation technology has shown important application value in the field of liquid mixture separation due to its advantages such as low energy consumption, environmental friendliness, and high separation efficiency. This technology realizes molecular-level separation through the selective permeation and vaporization of membrane materials, and is particularly suitable for systems that are difficult to handle by traditional distillation processes such as azeotropes, near-azeotropes, and heat-sensitive substances.

[0003] In the field of alcohol-water separation, metal-organic framework materials (MOFs) have attracted much attention due to their adjustable pore structures and surface properties. Among them, ZIF-L materials have the following characteristics: (1) a unique two-dimensional leaf-like morphology and a semi-SOD topological structure; (2) a regular pore size of 3.4 Å, which is between the kinetic diameters of water molecules (2.68 Å) and ethanol molecules (4.5 Å), and can produce an accurate molecular sieving effect; (3) the anisotropic structure provides a fast transmission channel for water molecules.

[0004] However, there are the following technical bottlenecks in the preparation of ZIF-L membranes in the prior art: the crystal growth is chaotic and uncontrollable, easily forming a chaotic structure, and it is impossible to achieve oriented horizontal growth; the hydrophilicity of the material is insufficient, affecting the water molecule transmission efficiency. Research shows that the natural growth of ZIF-L crystals tends to be vertically oriented because: (1) the growth rate of crystals in the vertical direction is significantly higher than that in the horizontal direction; (2) the aspect ratio of vertically oriented crystals is more conducive to reducing the surface energy of the system. This growth characteristic makes it difficult to obtain a continuous ZIF-L separation layer with a horizontal orientation by traditional methods. For example, in the comparative document CN202310934028.1, although the prepared ZIF-L layer meets the requirement of oriented growth, the growth orientation is in the vertical direction, and the ZIF-L in the vertical direction has a poor sieving effect on ethanol and water. Because ZIF-L has a crystal structure similar to ZIF-8, Figure 2 shows the hexagonal window-like pore size (∼0.34 nm) and very small four-membered windows on the horizontal orientation plane, which are between the kinetic diameters of water (2.68 Å) and ethanol (4.5 Å). Therefore, dispersing ZIF-L parallel to the membrane surface will show an obvious sieving effect on the water / ethanol mixture. Figure 3 shows the schematic diagram of the horizontal orientation and sorting of ZIF-L by the PEI solution.

[0005] To address the above problems, the present invention innovatively uses polyethyleneimine (PEI) as a regulator. Through its multiple interactions with the surface of ZIF-L crystals (including hydrogen bonds and Zn-N coordination bonds), the horizontal alignment of ZIF-L crystals is achieved, the internal pores are penetrated, and the hydrophilicity of the material is significantly improved. This horizontally oriented ZIF-L layer can fully exert its molecular sieving effect with a pore size of 3.4 Å, providing a new technical solution for the development of high-performance alcohol-water separation membranes. Summary of the Invention

[0006] The object of the present invention is to address the current situation where the membrane flux and separation factor cannot be balanced and well meet the requirements of membrane separation. A high-performance pervaporation membrane for alcohol-water separation is prepared. This method for preparing a high-performance pervaporation membrane has advantages such as high flux and good separation factor, is applicable to the membrane separation process, and can ensure excellent separation effects and long-term stable operation. To achieve the above object, the technical solution adopted by the present invention is: a horizontally oriented ZIF-L composite membrane and its preparation method, and the specific steps are as follows: (1) Synthesis of leaf-like ZIF-L: Dissolve metal nitrate hexahydrate and 2-methylimidazole in water at room temperature according to a mass ratio of 20 - 50%, quickly pour the 2-methylimidazole solution into the metal nitrate hexahydrate, stir for 2 - 4 h, centrifuge three times (6000 - 8000 r / 20 min), wash, and dry at 60 °C for 5 - 8 h, and then grind to obtain ZIF-L powder; (2) Preparation of the oriented ZIF-L seed layer: Dissolve the ZIF-L powder prepared in (1) in a 0.01 - 1 wt% PEI solution, ultrasonically disperse, and then filter it onto a PAN-based membrane. Subsequently, immerse it in the ZIF-L synthesis stock solution and grow at an appropriate temperature for 20 - 40 min, wash, and dry at 60 °C for 4 - 6 h; (3) Secondary growth of the separation layer: Immerse the membrane obtained in (2) again into the ZIF-L synthesis solution with different metal sources and grow at an appropriate temperature for 10 - 30 min, wash and dry to obtain the final composite membrane.

[0007] Preferably, the metal source for synthesizing ZIF-L in step (1) is one of cobalt nitrate hexahydrate, zinc nitrate hexahydrate, or a cobalt-zinc mixed crystal.

[0008] Preferably, the addition amount of ZIF-L powder in step (2) is 0.1 - 4 wt% of the mass of water.

[0009] Preferably, for the secondary growth of the separation layer in step (3): the type of metal ion in the ZIF-L synthesis solution is Zn ion or Co ion.

[0010] The present invention improves the irregular and disordered ZIF-L structure prepared in previous experiments, and uses the method of secondary growth to prepare a continuously and directionally ordered ZIF-L layer. In this study, a PEI solution is used as an adhesive. By controlling the direction of depositing the seed layer, micron-sized ZIF-L nanosheets with PEI as the adhesive are deposited, and then short-time secondary growth is carried out to form a horizontally oriented layer. When the ZIF-L crystal suspension is vacuum filtered, a normal force acts on the ZIF-L crystals near the carrier, that is, the resistance under vacuum. The resistance causes the solution to be transported to the carrier and deposits the ZIF-L crystals on the surface. A large number of ZIF-L particles are well dispersed in the PEI matrix. PEI can form hydrogen bonds with the free hydroxyl groups on the ZIF-L crystals and the support surface, and can also form Zn-N coordination bonds with the zinc cations on the crystal surface. Therefore, adding PEI to the seed solution is crucial for ensuring the firm adhesion of the seed crystals to the support surface, improving the distribution of the ZIF-L material in the membrane, making it horizontally oriented, forming an excellent targeted separation effect, greatly enhancing the selectivity of the membrane, and is the key to ensuring the horizontal growth of the seed crystals. Moreover, by changing the metal source of the growth solution, a heterogeneous ZIF-L membrane (Zn / Co) is prepared, which greatly improves the membrane permeation flux. Beneficial effects

[0011] 1. Structural innovation The horizontal directional arrangement of ZIF-L crystals is achieved through PEI induction, solving the technical problem of the disordered growth (vertical orientation) of crystals in traditional methods, constructing a continuous and ordered molecular transport channel, maximizing the sieving effect of the 3.4 Å pore size, significantly improving the separation performance, and significantly improving the characteristics of the pure ZIF-L (Zn) membrane with poor hydrophilicity and the pure ZIF-L (Co) membrane with poor stability by preparing a ZIF-L heterogeneous membrane. The alcohol-water separation performance is: pure water flux ≥ 4000 g·m⁻²·h⁻¹, separation factor ≥ 2100 2. Functionality of process and materials Innovative "in-situ seed growth + secondary growth" process: The first growth ensures the horizontal orientation of the crystals, and the secondary growth optimizes the integrity of the separation layer; the crystal orientation is achieved through the hydrogen bond and Zn-N coordination of the synergistic effect of PEI, Zn 2+ and Co 2+ heterogeneous interaction enhances the hydrophilicity of the membrane surface and improves the structural stability. Description of the drawings

[0012] Figure 1 It is the surface scanning electron micrograph of the pervaporation membrane in Example 2 Figure 2 It is the pore size structure of ZIF-L in the horizontal direction Figure 3Schematic diagram of the horizontal orientation and sorting of ZIF-L by the PEI solution Detailed implementation manners

[0013] The present invention will be further described in detail below through specific implementation manners. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention.

[0014] The continuously oriented and sorted ZIF-L membrane prepared by the present invention can be used for separating ethanol and water. Therefore, the membrane permeation flux, the ethanol / water separation factor, and the stability performance are three important parameters for evaluating this pervaporation.

[0015] The test conditions for the membrane permeation flux and the ethanol / water separation factor are as follows: pervaporation device, ethanol concentration of 80 - 90%, test temperature of 75°C, and test pressure of 300 Pa.

[0016] The membrane permeation flux (J) is defined as:[[]]

[0017] In the formula, Q represents the total mass of the permeate, g; A represents the effective membrane area, m 2 ; t represents the duration of collection, h.

[0018] The ethanol / water separation coefficient (α) is defined as:[[]]

[0019] In the formula, X A and X B respectively represent the concentrations of ethanol and water in the feed liquid, wt%; Y A and Y B respectively represent the concentrations of ethanol and water in the permeate, wt%.

[0020] Comparative Example 1: (1) Take 0.59 g of Zn(NO3)2·6H2O and 1.30 g of dimethylimidazole (Hmim) and dissolve them separately in 40 mL of water. After stirring and dissolving, quickly pour the dimethylimidazole solution into the zinc nitrate hexahydrate solution and stir at room temperature for 4 h. Collect the two-dimensional ZIF-L crystals by centrifugation three times (8000 rpm, 20 min), wash them 3 times with deionized water, dry them in vacuum at 60°C and grind them to obtain ZIF-L powder.

[0021] (2) Take 0.25 g of the ZIF-L powder prepared in (1) and redissolve it in water, and ultrasonicate it for a period of time to completely dissolve it. Use a vacuum filtration machine to filter it onto a PAN-based membrane. Immerse the filtered PAN-based membrane into the synthesis stock solution of ZIF-L and grow it in a 30°C water bath for 30 min. Take it out, rinse it clean with deionized water, and dry it in an oven at 60°C for 4 - 6 h.

[0022] (3) Dissolve 0.59 g of Zn(NO3)2·6H2O and 1.30 g of dimethylimidazole (Hmim) separately in 40 mL of water. After stirring to dissolve, quickly pour the dimethylimidazole solution into the zinc nitrate hexahydrate solution. Immerse the ZIF-L membrane prepared in (2) again onto the above ZIF-L synthesis stock solution and grow it in a 30 °C water bath for 10 min. Place the grown membrane on a drying rack and let it dry naturally to obtain a high-performance membrane for alcohol-water separation and purification.

[0023] The ZIF-L layer structure prepared in Comparative Example 1 is arranged disorderly. Test the pervaporation membrane prepared in Comparative Example 1, and the membrane permeation flux is 1100 g / m 2 *h, and the alcohol-water separation coefficient is 620. Example

[0024] (1) Dissolve 0.59 g of Zn(NO3)2·6H2O and 1.30 g of dimethylimidazole (Hmim) separately in 40 mL of water. After stirring to dissolve, quickly pour the dimethylimidazole solution into the zinc nitrate hexahydrate solution and stir at room temperature for 4 h. Collect two-dimensional ZIF-L crystals by centrifugation three times (8000 rpm, 20 min), wash them 3 times with deionized water, dry them in a vacuum at 60 °C and grind them to obtain ZIF-L powder.

[0025] (2) Take 0.04 g of the ZIF-L powder prepared in (1) and redissolve it in 0.025 wt% PEI solution, and ultrasonicate for a period of time to completely dissolve it. Use a vacuum filtration machine to filter it onto a PAN-based membrane. Immerse the filtered PAN-based membrane into the ZIF-L synthesis stock solution and grow it in a 30 °C water bath for 30 min. Take it out, rinse it thoroughly with deionized water, and dry it in an oven at 60 °C for 4 - 6 h.

[0026] (3) Dissolve 0.59 g of Zn(NO3)2·6H2O and 1.30 g of dimethylimidazole (Hmim) separately in 40 mL of water. After stirring to dissolve, quickly pour the dimethylimidazole solution into the zinc nitrate hexahydrate solution. Immerse the ZIF-L membrane prepared in (2) again onto the above ZIF-L synthesis stock solution and grow it in a 30 °C water bath for 10 min. Place the grown membrane on a drying rack and let it dry naturally to obtain a high-performance membrane for alcohol-water separation and purification.

[0027] The ZIF-L prepared in Example 1 has a better dispersion effect, and the horizontal orientation arrangement and ZIF-L morphology are both better. Test the pervaporation membrane prepared in Example 1, and the membrane permeation flux is 2500 g / m 2 *h, and the alcohol-water separation coefficient is 1800. After a twelve-hour stability test, the membrane permeation flux can still reach 2300 g / m 2*h, the separation factor can also reach 1700.

[0028] Comparative Example 2: (1) Take 0.59 g of Co(NO3)2·6H2O and 1.30 g of dimethylimidazole (Hmim) and dissolve them separately in 40 mL of water. After stirring to dissolve, quickly pour the dimethylimidazole solution into the cobalt nitrate hexahydrate solution and stir at room temperature for 4 h. Collect the two-dimensional ZIF-L crystals by centrifugation three times (8000 rpm, 20 min), wash them 3 times with deionized water, dry them in a vacuum at 60 °C and grind them to obtain ZIF-L powder.

[0029] (2) Take 0.04 g of the ZIF-L powder prepared in (1) and redissolve it in 0.025 wt% PEI solution, and ultrasonicate it for a period of time to completely dissolve it. Use a vacuum filtration machine to filter it onto a PAN-based membrane. Immerse the filtered PAN-based membrane in the ZIF-L synthesis stock solution and grow it in a 30 °C water bath for 30 min. Take it out, rinse it thoroughly with deionized water, and dry it in an oven at 60 °C for 4 - 6 h.

[0030] (3) Take 0.59 g of Co(NO3)2·6H2O and 1.30 g of dimethylimidazole (Hmim) and dissolve them separately in 40 mL of water. After stirring to dissolve, quickly pour the dimethylimidazole solution into the cobalt nitrate hexahydrate solution. Immerse the ZIF-L membrane prepared in (2) again in the above ZIF-L synthesis stock solution and grow it in a 30 °C water bath for 10 min. Place the grown membrane on a drying rack and let it dry naturally to obtain a high-performance membrane for alcohol-water separation and purification.

[0031] The ZIF-L prepared in Comparative Example 2, compared with the one with Zn 2+ as the central ion, although it has better hydrophilicity, the material is not as complete as the ZIF-L with Zn 2+ as the central ion. The horizontal orientation degree of the prepared ZIF-L layer is 60%, and its stability is poor. Perform pervaporation testing on it, and the membrane permeation flux is 2800 g / m 2 *h, and the alcohol-water separation factor is 900.

[0032] Comparative Example 3: (1) Take 0.59 g of Co(NO3)2·6H2O and 1.30 g of dimethylimidazole (Hmim) and dissolve them separately in 40 mL of water. After stirring to dissolve, quickly pour the dimethylimidazole solution into the cobalt nitrate hexahydrate solution and stir at room temperature for 4 h. Collect the two-dimensional ZIF-L crystals by centrifugation three times (8000 rpm, 20 min), wash them 3 times with deionized water, dry them in a vacuum at 60 °C and grind them to obtain ZIF-L powder.

[0033] (2) Take 0.04 g of the ZIF-L powder prepared in (1) and redissolve it in 0.025 wt% PEI solution. Ultrasonic for a period of time to completely dissolve it. Use a vacuum filtration machine to filter it onto a PAN-based membrane. Immerse the filtered PAN-based membrane in the ZIF-L synthesis stock solution and grow it in a 30 °C water bath for 30 min. Take it out, rinse it with deionized water, and dry it in an oven at 60 °C for 4 - 6 h.

[0034] (3) Take 0.59 g of Zn(NO3)2·6H2O and 1.30 g of dimethylimidazole (Hmim) and dissolve them separately in 40 mL of water. After stirring and dissolving, quickly pour the dimethylimidazole solution into the zinc nitrate hexahydrate solution. Immerse the ZIF-L membrane prepared in (2) again in the above ZIF-L synthesis stock solution and grow it in a 30 °C water bath for 10 min. Place the grown membrane on a drying rack and let it dry naturally to obtain a high-performance membrane for alcohol-water separation and purification.

[0035] The horizontal orientation degree of the ZIF-L layer prepared in Comparative Example 3 is 70%, and there is a certain stacking between the leaves. Perform pervaporation testing on it, and the membrane permeation flux is 2000 g / m 2 *h, and the alcohol-water separation coefficient is 1400. Example

[0036] (1) Take 0.59 g of Zn(NO3)2·6H2O and 1.30 g of dimethylimidazole (Hmim) and dissolve them separately in 40 mL of water. After stirring and dissolving, quickly pour the dimethylimidazole solution into the zinc nitrate hexahydrate solution and stir at room temperature for 4 h. Collect two-dimensional ZIF-L crystals by centrifuging three times (8000 rpm, 20 min), wash them 3 times with deionized water, dry them in a vacuum at 60 °C and grind them to obtain ZIF-L powder.

[0037] (2) Take 0.04 g of the ZIF-L powder prepared in (1) and redissolve it in 0.025 wt% PEI solution. Ultrasonic for a period of time to completely dissolve it. Use a vacuum filtration machine to filter it onto a PAN-based membrane. Immerse the filtered PAN-based membrane in the ZIF-L synthesis stock solution and grow it in a 30 °C water bath for 30 min. Take it out, rinse it with deionized water, and dry it in an oven at 60 °C for 4 - 6 h.

[0038] (3) Take 0.59 g of Co(NO3)2·6H2O and 1.30 g of dimethylimidazole (Hmim) and dissolve them separately in 40 mL of water. After stirring and dissolving, quickly pour the dimethylimidazole solution into the cobalt nitrate hexahydrate solution. Immerse the ZIF-L membrane prepared in (2) again in the above ZIF-L synthesis stock solution and grow it in a 30 °C water bath for 10 min. Place the grown membrane on a drying rack and let it dry naturally to obtain a high-performance membrane for alcohol-water separation and purification.

[0039] The ZIF-L material prepared in Example 2 has a basically plump leaf structure with no obvious defects. The horizontal orientation degree of the prepared ZIF-L layer is 95% and it is well-dispersed. Pervaporation tests were carried out on it, and the membrane permeation flux was 4000 g / m 2 *h, and the alcohol-water separation factor was 2100. After a twelve-hour stability test, the membrane permeation flux could still reach 3800 g / m 2 *h, and the separation factor could also reach 2000. Example

[0040] (1) Take 0.59 g of Zn(NO3)2·6H2O and 1.30 g of dimethylimidazole (Hmim) and dissolve them separately in 40 mL of water. After stirring and dissolving, quickly pour the dimethylimidazole solution into the zinc nitrate hexahydrate solution and stir at room temperature for 4 h. Collect two-dimensional ZIF-L crystals by centrifugation three times (8000 rpm, 20 min), wash them 3 times with deionized water, dry them in a vacuum at 60 °C and grind them to obtain ZIF-L powder.

[0041] (2) Take 0.01 g of the ZIF-L powder prepared in (1) and redissolve it in 0.025 wt% PEI solution, and ultrasonicate it for a period of time to completely dissolve it. Use a vacuum filtration machine to filter it onto a PAN-based membrane, and immerse the filtered PAN-based membrane in the ZIF-L synthesis stock solution and grow it in a 30 °C water bath for 30 min. Take it out, rinse it clean with deionized water, and dry it in an oven at 60 °C for 4 - 6 h.

[0042] (3) Take 0.59 g of Co(NO3)2·6H2O and 1.30 g of dimethylimidazole (Hmim) and dissolve them separately in 40 mL of water. After stirring and dissolving, quickly pour the dimethylimidazole solution into the cobalt nitrate hexahydrate solution. Immerse the ZIF-L membrane prepared in (2) again in the above ZIF-L synthesis stock solution and grow it in a 30 °C water bath for 10 min. Place the grown membrane on a drying rack and let it dry naturally to obtain a high-performance membrane for alcohol-water separation and purification.

[0043] The ZIF-L layer prepared in Example 3 has good horizontal orientation, but there are obvious defects on the surface. Pervaporation tests were carried out on it, and the membrane permeation flux was 3200 g / m 2 *h, and the alcohol-water separation factor was 800. Example

[0044] (1) Take 0.5 g of Zn(NO3)2·6H2O, 0.3 g of Co(NO3)2·6H2O, and 1.30 g of 2-methylimidazole (Hmim), and dissolve them separately in 40 mL of water. After stirring to dissolve, quickly pour the 2-methylimidazole solution into the hexahydrate nitrate solution, and stir at room temperature for 4 h. Collect the two-dimensional ZIF-L crystals by centrifugation three times (8000 rpm, 20 min), wash them 3 times with deionized water, dry them in a vacuum at 60 °C and grind them to obtain ZIF-L powder.

[0045] (2) Take 0.04 g of the ZIF-L powder prepared in (1) and redissolve it in 0.025 wt% PEI solution, and ultrasonicate for a period of time to completely dissolve it. Use a vacuum filtration machine to filter it onto a PAN-based membrane. Immerse the filtered PAN-based membrane in the synthesis stock solution of ZIF-L and grow it in a 30 °C water bath for 30 min. Take it out, rinse it with deionized water, and dry it in an oven at 60 °C for 4 - 6 h.

[0046] (3) Take 0.5 g of Zn(NO3)2·6H2O, 0.3 g of Co(NO3)2·6H2O, and 1.30 g of 2-methylimidazole (Hmim), and dissolve them separately in 40 mL of water. After stirring to dissolve, quickly pour the 2-methylimidazole solution into the hexahydrate nitrate solution. Immerse the ZIF-L membrane prepared in (2) again in the above ZIF-L synthesis stock solution and grow it in a 30 °C water bath for 10 min. Place the grown membrane on a drying rack and let it dry naturally to obtain a high-performance membrane for alcohol-water separation and purification.

[0047] The membrane structure prepared in Example 4 still has certain defects, with some rod-like structures present. Perform pervaporation testing on it. The membrane permeation flux is 2500 g / m 2 *h, and the alcohol-water separation factor is 1500. After a twelve-hour stability test, the membrane permeation flux can still reach 2300 g / m 2 *h, and the separation factor can also reach 1450.

Claims

1. A preparation method of a high-performance pervaporation membrane for alcohol-water separation, characterized in that It includes the following steps: (1) Synthesis of leaf-like ZIF-L: Dissolve metal nitrate hexahydrate and dimethylimidazole in water at room temperature respectively according to the mass ratio of 20-50%, quickly pour the dimethylimidazole solution into the metal nitrate hexahydrate, stir for 2-4 h, centrifuge three times (6000-8000 r / 20 min), wash, dry at 60 °C for 5-8 h, and grind to obtain ZIF-L powder; (2) Preparation of oriented ZIF-L seed layer: Dissolve the ZIF-L powder prepared in (1) in 0.01-1 wt% PEI solution, ultrasonically disperse, filter to PAN-based membrane by suction, then immerse in the ZIF-L synthesis stock solution, grow at appropriate temperature for 20-40 min, wash and dry at 60 °C for 4-6 h; (3) Secondary growth of the separation layer: Immerse the membrane obtained in (2) again into the ZIF-L synthesis solution with different metal sources, grow at appropriate temperature for 10-30 min, wash and dry to obtain the final composite membrane.

2. The preparation method according to claim 1, characterized in that In step (1), the metal source is one of cobalt nitrate hexahydrate and zinc nitrate hexahydrate or a cobalt-zinc mixed crystal.

3. The preparation method according to claim 1, characterized in that In step (1), after centrifugation, use one of water, ethanol, and methanol.

4. The preparation method according to claim 1, wherein The addition amount of ZIF-L powder in step (2) is 0.1-4 wt% of the water mass.

5. A high-performance pervaporation membrane for alcohol-water separation, characterized in that Prepared by the preparation method described in any one of claims 1-4.

6. The high-performance pervaporation membrane according to claim 5, wherein Applied to pervaporation technology for separating ethanol and water, and the membrane shows good stability and anti-pollution performance during long-term use.

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