A hydrophilic pervaporation membrane for ethanol-water azeotrope separation and a method for preparing the same

Abstract

The application belongs to the field of membrane separation technology, and particularly relates to a hydrophilic pervaporation membrane for separating ethanol-water azeotrope and a preparation method thereof. The method comprises the following steps: adding IU particles into a polyvinyl alcohol-chitosan blended solution, and obtaining the hydrophilic pervaporation membrane after cross-linking; and the mass percentage of the IU particles in the polyvinyl alcohol-chitosan blended solution is 20-30 wt%. The application introduces imidazole compound IU modified particles while constructing a polyvinyl alcohol-chitosan mixed matrix membrane, the particles can be well dissolved in the polyvinyl alcohol-chitosan mixed solution, the hydrophilic imidazole groups at both ends of the particles and the hydrophobic fatty chain structure in the middle can be closely arranged in the prepared membrane, so that water molecules can selectively pass through the channel between adjacent hydrophilic groups, thereby improving the separation performance of the membrane. The prepared hydrophilic pervaporation membrane has the advantages of high flux, good separation performance, high film-forming property, low cost, stable structure and performance, and the like, and is suitable for separating ethanol-water systems.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation technology, and specifically relates to a hydrophilic pervaporation membrane for the separation of ethanol-water azeotropes and its preparation method. Background Technology

[0002] Biomass ethanol, due to its high calorific value and lack of pollution, is considered a renewable energy source that can replace many highly polluting, environmentally unsafe, and non-renewable fossil fuels such as petroleum and coal. Ethanol separation is a key step affecting the concentration of ethanol products. Because ethanol and water have similar boiling points and are polar / polar mixtures, traditional separation processes such as isothermal distillation, extractive distillation, or adsorption often require large amounts of energy and expensive third-party components (carriers or extractants) to dehydrate the ethanol, making the separation of ethanol-water azeotropes difficult and economically inefficient. Currently, pervaporation technology based on membrane separation can significantly improve the efficiency of alcohol-water separation. Furthermore, pervaporation equipment is simple and has low energy consumption, making it a promising technology for separating alcohol-water azeotropes.

[0003] In pervaporation technology, membrane development and fabrication are crucial. For alcohol-water separation, membrane materials employ two strategies based on the hydrophilicity or hydrophobicity of the matrix: "alcohol dehydration" and "alcohol collection." In the production of high-concentration ethanol, hydrophilic materials are often preferred, with organic polymer membranes, represented by polyvinyl alcohol, and inorganic membranes, represented by sodium zeolite, being the dominant types. However, inorganic membranes are generally more expensive; therefore, developing organic polymer membranes with excellent separation performance is key to the industrial-scale production of high-concentration bioethanol.

[0004] Polyvinyl alcohol (PVA) is a representative hydrophilic organic material with a main structure of 1,3-propanediol long chains. It is low-cost and easily formed into membranes, making it one of the earliest hydrophilic matrix membranes to enter industrial applications. However, pure PVA membranes suffer from numerous drawbacks, including low mechanical properties and strength, and easy swelling during the separation process leading to reduced permeate flux and separation factor. In the past five years, researchers have prepared mixed matrix membranes by filling PVA membranes with different organic or inorganic particles to increase the free volume within the membrane, thereby improving its pervaporation separation performance. However, modifying PVA membranes still presents challenges: firstly, overcoming the conjugation effect of permeability and selectivity during pervaporation separation; secondly, simultaneously ensuring the compatibility and dispersibility of the filling particles in the membrane solution; and finally, considering the economic practicality of the modified materials.

[0005] To address the aforementioned issues and obtain polyvinyl alcohol (PVA) mixed matrix membranes with stable separation performance and low cost, patents CN109745873A and CN103804828A disclose methods such as incorporating chitosan (CS), another hydrophilic polymer, into PVA, using glutaraldehyde crosslinking modification, and applying it to the dehydration of other alcohols and the adsorption of heavy metal ions. However, despite its high cost-effectiveness, the simple incorporation of chitosan cannot improve the separation effect of ethanol and water because ethanol and water have similar polarities. Therefore, secondary modification of the PVA / CS blend membrane to improve its selectivity for water molecules within the membrane has become an important direction for overcoming the bottleneck of this strategy.

[0006] Currently, secondary modification of PVA / CS blend films is mainly divided into two categories: one is the modification of the chitosan molecules themselves, and the other is the addition of other materials. Examples of the former include Dudek et al.'s crosslinking of phosphorylated chitosan particles with polyvinyl alcohol to form films (Gabriela Dudek, Turczyn Roman, Konieczny Krystyna. Robust poly(vinyl alcohol) membranes containing chitosan / chitosan derivatives microparticles for pervaporative dehydration of ethanol[J]. SEPARATION ANDPURIFICATION TECHNOLOGY, 2020, 234(116094).) and Swastika Choudhury et al.'s reports on several chitosan-coated polyacrylonitrile nanoparticles (CSPAN) crosslinked with maleic acid to form films (Swastika Choudhury, Ray Samit-Kumar. Synthesis of polymer nanoparticles based highly selective membranes by mini-emulsion polymerization for dehydration of 1,4-dioxane and recovery of ethanol from water by pervaporation[J]. JOURNAL OF (MEMBRANESCIENCE, 2021, 617.). However, such methods often suffer from drawbacks such as the modified chitosan failing to disperse well in the mixed matrix membrane, thus affecting separation performance, or the modification methods being relatively cumbersome. Therefore, adding other low-cost and well-dispersible materials to modified blend membranes such as PVA / CS, and further improving the membrane pervaporation performance, is a better strategy. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a hydrophilic pervaporation membrane and its preparation method. By introducing an imidazole compound modified particles while constructing a polyvinyl alcohol-chitosan mixed matrix membrane, the pervaporation membrane can be increased while ensuring good selectivity. Furthermore, the particles can be well dissolved in the polyvinyl alcohol-chitosan mixture, resulting in a dense and uniform membrane.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0009] This invention provides a method for preparing a hydrophilic pervaporation membrane, which generates a pervaporation membrane capable of removing water molecules from ethanol by adding modified particles and blending. The preparation method of this membrane is simple, low-cost, and exhibits good permeability and selectivity for the pervaporation separation of ethanol.

[0010] This invention provides a method for preparing a hydrophilic pervaporation membrane for the separation of ethanol-water azeotropes. The method includes: adding IU particles to a polyvinyl alcohol-chitosan blend solution, mixing, and then crosslinking to obtain the membrane.

[0011] In the above technical solution, the mass percentage of the IU particles in the polyvinyl alcohol-chitosan blend solution is 10-30 wt%.

[0012] In the above technical solution, the mass percentage of the IU particles in the polyvinyl alcohol-chitosan blend solution is 20-30 wt%.

[0013] In the above technical solution, further, in the polyvinyl alcohol-chitosan blend solution, the volume ratio of the polyethylene solution to the chitosan solution is 1:1 to 3, preferably 1:3; the polyvinyl alcohol solution is a 2wt% polyvinyl alcohol aqueous solution, and the chitosan solution is a 2wt% chitosan acetic acid aqueous solution.

[0014] In the above technical solution, the crosslinking agent used for crosslinking is glutaraldehyde, preferably 5 wt% glutaraldehyde; preferably, the amount of glutaraldehyde used is 1 wt%-3 wt% of the total amount of polyvinyl alcohol-chitosan blend solution and IU particles, preferably 2 wt%.

[0015] In the above technical solution, the method further includes the following steps:

[0016] (1) Prepare aqueous solutions of polyvinyl alcohol and chitosan acetic acid;

[0017] (2) Mix polyvinyl alcohol aqueous solution and chitosan acetic acid aqueous solution at a volume ratio of 1:1 to 3 to obtain polyvinyl alcohol-chitosan blend solution;

[0018] (3) Add IU particles to the blend solution, mix at room temperature, then add 5wt% glutaraldehyde, mix at 35-45℃, and sonicate to obtain the injection solution;

[0019] (4) The injection solution is applied to a glass plate and crosslinked at room temperature to obtain the film.

[0020] In the above technical solution, further, in step (1), the preparation of polyvinyl alcohol aqueous solution is as follows: polyvinyl alcohol is dissolved in deionized water and stirred at 85-95°C; the preparation of chitosan acetic acid aqueous solution is as follows: chitosan is dissolved in deionized water and 2wt% glacial acetic acid is added and stirred at room temperature.

[0021] In the above technical solution, further, in step (4), the crosslinking time is 11 to 13 hours.

[0022] The present invention provides a hydrophilic pervaporation membrane for the separation of ethanol-water azeotropes, wherein the vaporization membrane is prepared by the aforementioned preparation method.

[0023] The present invention also provides the application of the aforementioned vaporization membrane in the separation of ethanol and water.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] This invention introduces imidazole compound IU modified particles into a polyvinyl alcohol-chitosan mixed matrix membrane. These particles dissolve well in the polyvinyl alcohol-chitosan mixture. The hydrophilic imidazole groups at both ends and the hydrophobic aliphatic chain structure in the middle of the particles are closely arranged in the prepared membrane, allowing water molecules to selectively pass through the channels of adjacent hydrophilic groups, thereby improving the membrane's separation performance. Polyvinyl alcohol and chitosan are excellent hydrophilic pervaporation membrane materials with strong hydrophilicity and film-forming properties. The mixed membrane material of these two effectively increases its water resistance and thermal stability. The hydrophilic pervaporation membrane prepared by this invention has advantages such as high flux, good separation performance, high film-forming properties, low cost, and stable structure and performance, making it suitable for separating ethanol-water systems. Attached Figure Description

[0026] Figure 1 Here is a surface SEM image of the hydrophilic pervaporation membrane prepared in Example 2;

[0027] Figure 2 This is a cross-sectional SEM image of the hydrophilic pervaporation membrane prepared in Example 2;

[0028] Figure 3 The chemical structural formula of IU;

[0029] Figure 4 TGA curves of PVA, PVA-CS and PVACS-IU membranes with different IU concentrations;

[0030] Figure 5 DTG curves of PVA, PVA-CS, and PVACS-IU membranes with different IU concentrations. Detailed Implementation

[0031] The present invention will be further described below with reference to specific embodiments, but this does not limit the present invention in any way.

[0032] The structural formula of IU is as follows Figure 3As shown, the structure consists of imidazole groups at both ends that are hydrophilic and a fatty acid chain in the middle that is hydrophobic. This invention incorporates IU particles into a PVA / CS membrane. The IU particle structure can form a compact structure in the hybrid membrane, allowing water molecules to selectively pass through the channels of adjacent hydrophilic groups, thereby improving the membrane's separation performance.

[0033] The preparation method of the pervaporation membrane of the present invention is as follows:

[0034] (a) Preparation method of modified particles: The IU particles used in this invention can be prepared according to the method in the literature (Mao, Y., et al., Bola-amphiphile-imidazole embedded GO membrane with enhanced solvent dehydration properties. Journal of Membrane Science, 2020, 595: p. 117545.), or by the following method:

[0035] 1,6-Diisocyanatohexane and histamine were mixed in a 1:2 molar ratio using tetrahydrofuran as a solvent. The resulting mixture was refluxed at 70°C for 10 hours. After the reflux reaction was completed, the reactants were cooled to room temperature, washed three times with tetrahydrofuran, and centrifuged at 5000-7000 rpm for 10 minutes. Finally, the product was vacuum dried at 60-80°C for 48 hours to obtain imidazole-modified particles A.

[0036] (b) Preparation method of polyvinyl alcohol-chitosan blend film: Polyvinyl alcohol is dissolved in deionized water and stirred at 90°C for 1 hour to prepare a 2wt% PVA solution. Chitosan is dissolved in deionized water and 2wt% glacial acetic acid is added and stirred at room temperature for 1 hour to form a 2wt% chitosan solution. The polyvinyl alcohol solution and chitosan solution are mixed in a certain ratio (3:1, 1:1, 1:3) to obtain mixture B, preferably a 1:3 mixing ratio of polyvinyl alcohol and chitosan; this invention uses type 1797 polyvinyl alcohol with a degree of alcoholysis of 96%-98%; and low-viscosity chitosan with a degree of deacetylation of 99%.

[0037] (c) Add appropriate concentrations of particles A (20wt%, 25wt%, 30wt%) to mixture B and stir for 2 hours at room temperature. Add a certain amount of glutaraldehyde (5wt%) as a crosslinking agent and stir for 5 minutes at 40°C. Sonicate the mixture for 15 minutes to obtain casting solution C. Finally, uniformly coat casting solution C onto a vacuum-dried glass plate and crosslink at room temperature for 12 hours. A hydrophilic pervaporation membrane of uniform thickness is obtained.

[0038] Example 1

[0039] Three different PVA / CS pervaporation membranes with varying mixing ratios were prepared. The PVA used was type 1797 polyvinyl alcohol with a degree of alcoholysis of 96%-98%, and the chitosan was low-viscosity chitosan with a degree of deacetylation of 99%. PVA was dissolved in deionized water and stirred at 90°C for 1 h to prepare a 2 wt% PVA solution. CS was dissolved in deionized water, and 2 wt% glacial acetic acid was added and stirred at room temperature for 1 h to form a 2 wt% chitosan solution. PVA and CS were mixed and stirred at ratios of 3:1, 1:1, and 1:3, respectively, for 2 h. 5 wt% glutaraldehyde was added as a crosslinking agent, and the mixture was stirred at 40°C for 5 min to obtain the casting solution. The cooled casting solution was uniformly coated onto a vacuum-dried glass plate and crosslinked at room temperature for 12 h. The resulting PVA / CS mixed matrix membrane was then obtained.

[0040] The three PVA / CS vaporization membranes obtained above were applied to separate an ethanol-water system. The ethanol concentration used was 95 wt%, and the feed temperature was 40 °C. Water was allowed to pass through preferentially via pervaporation. The separation performance of the three membranes is shown in Table 1.

[0041] Table 1 Comparison of PVA / CS membrane separation performance with different mixing ratios

[0042]

[0043]

[0044] Based on the data obtained from pervaporation, it was determined that when the mixing ratio of PVA to CS was 1:3, the membrane had the highest separation index and the best separation performance.

[0045] Example 2

[0046] 0.06 g (20 wt% of the total system) of modified granular IU was dissolved in 12 ml of a PVA / CS mixture (PVA:CS ratio 1:3, each 2 wt%). The mixture was stirred at room temperature for 2 h. 0.24 ml of glutaraldehyde (5 wt%) was added as a crosslinking agent, and the mixture was stirred at 40 °C for 5 min. The mixture was then sonicated for 15 min to obtain a casting solution. This casting solution was uniformly coated onto a vacuum-dried glass plate and crosslinked at room temperature for 12 h. A hydrophilic pervaporation membrane of uniform thickness was obtained. Figure 1 and Figure 2 It can be seen that the vaporization film with added IU particles has a uniform particle distribution, good film-forming performance, and no obvious defects.

[0047] The hydrophilic pervaporation membrane obtained above was applied to an ethanol-water separation system. The ethanol concentration used was 95 wt%, and the feed temperature was 40 °C. Pervaporated water preferentially permeated, with a permeation flux of 118.375 g / (m³). 2The separation factor was 33.346, and the separation index was 3947.333. Compared with the results in Table 1 of Example 1, the addition of IU particles improved the membrane's separation performance.

[0048] Example 3

[0049] 0.06 g (20 wt% of the total system) of modified particles was dissolved in 12 ml of a PVA / CS mixture (PVA:CS ratio 1:3, each 2 wt%). The mixture was stirred at room temperature for 2 h. 0.24 ml of glutaraldehyde (5 wt%) was added as a crosslinking agent. The mixture was stirred at 40 °C for 5 min, and then sonicated for 15 min to obtain a casting solution. This casting solution was uniformly coated onto a vacuum-dried glass plate and crosslinked at room temperature for 12 h. A hydrophilic pervaporation membrane of uniform thickness was obtained.

[0050] The hydrophilic pervaporation membrane obtained above was applied to an ethanol-water separation system. The ethanol concentration used was 95 wt%, and the feed-side temperature was 50 °C. Pervaporated water preferentially permeated, with a permeation flux of 170.986 g / (m²). 2 The separation factor was 22.067, and the separation index was 3773.148. Compared with Example 2, it was found that increasing the temperature increased the permeation flux and decreased the separation factor, which is consistent with the laws of thermodynamics; high temperature increases the mass transfer rate.

[0051] Example 4

[0052] 0.08 g (25 wt% of the total system) of modified particles was dissolved in 12 ml of a PVA / CS mixture (PVA:CS ratio 1:3, each 2 wt%). The mixture was stirred at room temperature for 2 h. 0.24 ml of glutaraldehyde (5 wt%) was added as a crosslinking agent. The mixture was stirred at 40 °C for 5 min, and then sonicated for 15 min to obtain a casting solution. This casting solution was uniformly coated onto a vacuum-dried glass plate and crosslinked at room temperature for 12 h. A hydrophilic pervaporation membrane of uniform thickness was obtained.

[0053] To investigate the thermal stability of the modified particulate films, PVA film, PVA / CS film, and PVACS / IU film were selected, with an IU particle concentration of 25 wt%. Thermogravimetric analysis was performed on the three films at a heating rate of 20 °C. The results are as follows: Figure 4 , Figure 5 As shown. From Figure 5 The data shows that the thermal decomposition of the PVA film begins at 263℃, the PVA / CS film at 278℃, and the PVACS / IU film at 306℃, with the initial thermal decomposition temperatures of the three films increasing sequentially. Figure 4It can be seen that at 250, 300, 400, 500, and 600℃, the residual amounts of the PVA film are 87.37%, 30.83%, 26.88%, 12.63%, and 11.51%, respectively; at the same temperature, the residual amounts of the PVA / CS film are 89.79%, 68.95%, 48.71%, 39.39%, and 35.65%; and at the same temperature, the residual amounts of the PVACS / IU film are 85.69%, 70.92%, 44.71%, 28.22%, and 25.25%. In conclusion, compared with the PVA film, both the PVA / CS film and the PVACS / IU film exhibit better thermal stability, with the PVACS / IU film showing the best thermal stability.

[0054] The PVACS / IU hydrophilic pervaporation membrane obtained above was applied to separate an ethanol-water system. The ethanol concentration used was 95 wt%, and the feed-side temperature was 40 °C. Pervaporated water preferentially permeated, with a permeation flux of 156.694 g / (m³). 2 h), the separation factor was 27.535 and the separation index was 4314.569. Compared with Example 2, the amount of IU added was increased, and the separation performance of the membrane was further improved.

[0055] Example 5

[0056] 0.02 g (10 wt% of the total system) of modified granular IU was dissolved in 12 ml of a PVA / CS mixture with a PVA to CS ratio of 1:3 and a concentration of 2 wt% for each component. The mixture was stirred at room temperature for 2 h. 0.24 ml of glutaraldehyde (5 wt%) was added as a crosslinking agent. The casting solution was obtained according to step (c), and then uniformly coated onto a vacuum-dried glass plate. Crosslinking was performed at room temperature for 12 h. A hydrophilic pervaporation membrane of uniform thickness was obtained.

[0057] The hydrophilic pervaporation membrane obtained above was applied to an ethanol-water separation system. The ethanol concentration used was 95 wt%, and the feed-side temperature was 40 °C. Pervaporated water preferentially permeated, with a permeation flux of 51.512 g / (m³). 2 The separation factor was 55.696, and the separation index was 2869.012. It can be seen that with a small amount of IU particles, the membrane permeation flux was not significantly improved.

[0058] Example 6

[0059] 0.04 g (15 wt% of the total system) of modified granular IU was dissolved in 12 ml of a PVA / CS mixture with a PVA to CS ratio of 1:3 and a concentration of 2 wt% for each component. The mixture was stirred at room temperature for 2 h. 0.24 ml of glutaraldehyde (5 wt%) was added as a crosslinking agent. The casting solution was obtained according to step (c), and then uniformly coated onto a vacuum-dried glass plate. Crosslinking was performed at room temperature for 12 h. A hydrophilic pervaporation membrane of uniform thickness was obtained.

[0060] The hydrophilic pervaporation membrane obtained above was applied to an ethanol-water separation system. The ethanol concentration used was 95 wt%, and the feed-side temperature was 40 °C. Pervaporated water preferentially permeated, with a permeation flux of 75.206 g / (m³). 2 The separation factor (h) was 33.757, and the separation index was 2538.729. This indicates that the membrane permeation flux increased, and the membrane separation performance also improved to some extent.

[0061] Example 7

[0062] 1.00 g (30 wt% of the total system) of modified granular IU was dissolved in 12 ml of a PVA / CS mixture with a PVA to CS ratio of 1:3 and a concentration of 2 wt% for each component. The mixture was stirred at room temperature for 2 h. 0.24 ml of glutaraldehyde (5 wt%) was added as a crosslinking agent. The casting solution was prepared according to step (c) and uniformly coated onto a vacuum-dried glass plate. Crosslinking was carried out at room temperature for 12 h. A hydrophilic pervaporation membrane of uniform thickness was obtained.

[0063] The hydrophilic pervaporation membrane obtained above was applied to an ethanol-water separation system. The ethanol concentration used was 95 wt%, and the feed-side temperature was 40 °C. Pervaporated water preferentially permeated, with a permeation flux of 178.524 g / (m³). 2 The separation factor (h) was 22.424, and the separation index was 4003.222. It can be seen that with an excessive number of IU particles, the membrane permeation flux further increases, but correspondingly, the separation factor decreases, and the membrane's selectivity declines.

[0064] For anyone skilled in the art, many possible variations and modifications can be made to the technical solutions of this invention, or equivalent embodiments can be modified based on the disclosed technical content, without departing from the scope of the technical solutions of this invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this invention without departing from the content of the technical solutions of this invention should still fall within the protection scope of the technical solutions of this invention.

Claims

1. A method for preparing a hydrophilic pervaporation membrane for the separation of ethanol-water azeotropes, characterized in that, The method includes: adding IU particles to a polyvinyl alcohol-chitosan blend solution, mixing, and then crosslinking to obtain the product; The structure of the IU particles is shown in Formula 1: Formula 1; The preparation method of the IU particles includes the following steps: 1,6-diisocyanatohexane and histamine are mixed in tetrahydrofuran at a molar ratio of 1:2, heated under reflux at 70°C for 10 hours, after the reflux reaction is completed, the reactants are cooled to room temperature, washed three times with tetrahydrofuran, centrifuged at 5000-7000 rpm for 10 min, and the obtained product is vacuum dried at 60-80°C for 48 hours.

2. The preparation method according to claim 1, characterized in that, The mass percentage of the IU particles in the polyvinyl alcohol-chitosan blend solution is 10~30 wt%.

3. The preparation method according to claim 2, characterized in that, The mass percentage of the IU particles in the polyvinyl alcohol-chitosan blend solution is 20-30 wt%.

4. The preparation method according to claim 1, characterized in that, In the polyvinyl alcohol-chitosan blend solution, the volume ratio of polyvinyl alcohol solution to chitosan solution is 1:1~3; the polyvinyl alcohol solution is a 2wt% aqueous solution of polyvinyl alcohol, and the chitosan solution is a 2wt% aqueous solution of chitosan acetic acid.

5. The preparation method according to claim 4, characterized in that, The volume ratio of the polyvinyl alcohol solution to the chitosan solution is 1:

3.

6. The preparation method according to claim 1, characterized in that, The crosslinking agent used is glutaraldehyde; the amount of glutaraldehyde used is 1wt%-3wt% of the total amount of polyvinyl alcohol-chitosan blend solution and IU particles.

7. The preparation method according to claim 6, characterized in that, The crosslinking agent used for crosslinking is 5 wt% glutaraldehyde; The amount of glutaraldehyde used is 2 wt% of the total amount of the polyvinyl alcohol-chitosan blend solution and IU particles.

8. The preparation method according to claim 1, characterized in that, The method includes the following steps: (1) Prepare aqueous solutions of polyvinyl alcohol and chitosan acetic acid; (2) Mix polyvinyl alcohol aqueous solution and chitosan acetic acid aqueous solution at a volume ratio of 1:1~3 to obtain polyvinyl alcohol-chitosan blend solution; (3) Add IU particles to the blend solution, mix at room temperature, then add glutaraldehyde, mix at 35~45℃, and sonicate to obtain the injection solution; (4) The injection solution is applied to a glass plate and crosslinked at room temperature to obtain the film.

9. The preparation method according to claim 8, characterized in that, In step (1), the polyvinyl alcohol aqueous solution is prepared by dissolving polyvinyl alcohol in deionized water and stirring at 85~95℃; the chitosan acetic acid aqueous solution is prepared by dissolving chitosan in deionized water and adding 2wt% glacial acetic acid and stirring at room temperature.

10. The preparation method according to claim 8, characterized in that, In step (4), the crosslinking time is 11~13h.

11. A hydrophilic pervaporation membrane for the separation of ethanol-water azeotropes, characterized in that, The vaporization film is prepared by the preparation method described in any one of claims 1 to 10.

12. The application of the vaporization membrane of claim 11 in the separation of ethanol and water.

Images