A sanidine / high molecular polymer pervaporation composite membrane and a preparation method thereof

Abstract

The application discloses a perovskite / high polymer pervaporation composite membrane and a preparation method thereof. The perovskite / high polymer pervaporation composite membrane is prepared by taking silica sol with a certain particle size as a precursor to prepare perovskite, then mixing the dispersed perovskite with a high polymer solution and a crosslinking agent, and coating the mixture to obtain the perovskite / high polymer pervaporation composite membrane. The perovskite contained in the pervaporation composite membrane is a highly hydrophilic material, has the property of preferentially adsorbing water, and the porous perovskite is highly dispersed in the matrix and has the property of promoting the diffusion of water molecules. The surface of the membrane and the membrane can also form special channels for water molecule transmission through the "through" effect of the perovskite, so that the permeation flux and selectivity of the pervaporation composite membrane to the separated components can be simultaneously increased.

Description

Technical Field

[0001] This invention belongs to the field of composite material preparation, specifically relating to a magnolite / polymer pervaporation composite membrane and its preparation method. Background Technology

[0002] Zeolite is an aluminosilicate or silicate material with a three-dimensional interconnected pore network, enabling molecular sieving within a size range of 0.3-0.6 nm. Therefore, zeolite is widely used in the chemical industry as a selective catalyst or adsorbent. An important parameter in zeolite preparation is the Si / Al ratio, which is related to the hydrophilicity of the zeolite membrane. The selective adsorption of hydrophilic sites in zeolite significantly affects water molecule transport. For example, Jiang et al. studied the effect of the Si / Al ratio on the performance of chabazite hollow fiber membranes. When the Si / Al ratio was 2.7, the sheet-like particulate membrane exhibited high flux and low selectivity; when the Si / Al ratio was higher than 2.9, the separation factor reached over 10,000. Increasing the precursor Si / Al ratio to 14 resulted in a flux decrease of approximately 12 kg·m³. -2 ·h -1 (J.Jiang, L. Peng, X. Wang, et al. Effect of Si / Al ratio in the framework on the pervaporation properties of hollow fiber CHA zeolite membranes[J]. Microporous and Mesoporous Materials, 2019, 273(01): 196-202.), Increasing the Al content in zeolite can improve its hydrophilicity. However, most zeolite membranes with low silica content exhibit low acid stability, limiting their use in acidic solutions.

[0003] In zeolite / polymer composite membranes used for pervaporation, the dispersion between the polymer membrane and inorganic materials is a crucial factor affecting their performance. This is due to the contradiction between interfacial defects and chain densification that occur at high zeolite loadings. Mauvesite, like zeolite, belongs to the aluminosilicate family, with a silicon content of approximately 20% and an aluminum content of approximately 60%. It possesses a CAN zeolite topology, with its framework consisting of cages composed of six-membered rings and 12-membered rings. The Na+ outside the framework... + K + Both H2O and other gases can enter the pores of nepheline, which also has the characteristics of large specific surface area and uniform pore size distribution. However, there is still limited research on the use of nepheline zeolite materials for preparing composite membranes.

[0004] Silica is a commonly used filler in the preparation of high-performance composite membranes. When introduced into polymers, it can effectively regulate the physical and chemical structure of the polymer membrane. Silica fillers in composite membranes can increase the hydrophilicity of the membrane and regulate the polymer chain structure, but non-porous silica essentially cannot provide rapid transport channels. This invention uses a coating method to prepare a nepheline / polymer pervaporation composite membrane. First, nepheline with a porous structure is synthesized using silica sol as a precursor. Then, the nepheline, polymer, and crosslinking agent are crosslinked to obtain the pervaporation composite membrane. The nepheline surface contains a large number of hydroxyl groups, which can act as a surface pre-screening layer on the surface of the pervaporation composite membrane. It preferentially adsorbs water molecules by forming hydrogen bonds with them. Furthermore, its porous structure provides rapid channels for water molecule diffusion within the membrane, shortening the diffusion path and reducing diffusion resistance. In addition, its high dispersion within the matrix introduces special channels for ion transport, simultaneously increasing the permeate flux and selectivity for separated components. This method provides new ideas for the development and design of novel structures, and will promote the research of composite materials and their application in the field of pervaporation, which has important theoretical and practical significance. Summary of the Invention

[0005] The purpose of this invention is to provide a pervaporation composite membrane made of magnolite / polymer and its preparation method. The process is simple and environmentally friendly, and the resulting pervaporation composite membrane has good permeation flux and selectivity for the separated components.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A nepheline / polymer pervaporation composite membrane is prepared by first preparing silica sol of a certain particle size using the Stöber method, then using the prepared silica sol as a precursor to prepare nepheline under alkaline conditions via a hydrothermal method; the obtained nepheline is then dispersed and mixed with a polymer solution and a crosslinking agent to form a membrane solution, which is then coated onto a substrate to obtain the nepheline / polymer pervaporation composite membrane.

[0008] The preparation method of the nepheline / polymer pervaporation composite membrane specifically includes the following steps:

[0009] 1) Preparation of silica sol: Stir and mix tetrabutyl orthosilicate, ethanol and deionized water, then add alkaline aqueous solution dropwise at a rate of 0.2 mL per minute to adjust the pH value to between 7 and 9. After stirring evenly, age for a certain period of time to obtain silica sol.

[0010] 2) Preparation of nepheline: The aluminum source is added to the sodium hydroxide aqueous solution and stirred to dissolve, thus obtaining an aluminum-containing alkaline solution; then the prepared silica sol is mixed with the aluminum-containing alkaline solution and stirred evenly, and then placed in a reaction vessel to react for a period of time. The resulting precipitate is washed with deionized water until neutral, and then dried to obtain nepheline.

[0011] 3) Dispersion of nepheline: The prepared nepheline was mixed with deionized water and an aqueous solvent, and stirred using a homogenizer to obtain a uniform nepheline dispersion.

[0012] 4) Preparation of polymer solution: Heat and stir the polymer and solvent to obtain a transparent and uniform polymer solution;

[0013] 5) Preparation of membrane solution: After stirring and mixing the prepared polymer solution, nepheline dispersion and crosslinking agent, let it stand for a period of time to remove air bubbles to obtain the membrane solution;

[0014] 6) Film coating: The prepared film liquid is coated on the substrate and then dried and cooled in a constant temperature oven to obtain the mafia / polymer pervaporation composite membrane.

[0015] Furthermore, in step 1), the volume ratio of tetrabutyl orthosilicate, ethanol, and deionized water is 1:10:1.

[0016] Further, the concentration of the alkaline aqueous solution in step 1) is 5~15 mol / L, and the alkali used is one or more of ammonia, sodium bicarbonate, sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, barium hydroxide, and cesium hydroxide.

[0017] Further, the stirring speed in step 1) is 10~90 r / min.

[0018] Furthermore, the aging time in step 1) is 0.5~24 h.

[0019] Furthermore, the aluminum source mentioned in step 2) is one or more of aluminum hydroxide, sodium aluminate, and aluminum sulfate.

[0020] Further, the concentration of the sodium hydroxide aqueous solution in step 2) is 0.2~5 mol / L.

[0021] Furthermore, in step 2), the amounts of aluminum source and sodium hydroxide are adjusted according to Al / [OH] - The molar ratio is (0.1~1.05):1 for conversion.

[0022] Furthermore, the amount of silica sol used in step 2) is calculated based on a Si / Al molar ratio of (0.04~0.16):1.

[0023] Furthermore, the reaction in step 2) is carried out at a temperature of 100~240 °C for a time of 5~72 h.

[0024] Further, in step 3), the volume ratio of deionized water to aqueous solvent is (0.1~1):1, and the aqueous solvent is one or more of ethanol, glycerol, polyethylene glycol, glycolic acid, triethanolamine, propylene glycol methyl ether, and dimethylformamide.

[0025] Furthermore, in step 3), the amount of magnolite used is 1% of the total mass of the deionized water and aqueous solvent used.

[0026] Furthermore, the homogenizer used in step 3) has a stirring power of 75W and a stirring speed of 8000~30000 r / min.

[0027] Further, the polymer used in step 4) is one or more of the following: chitosan (CS), polyvinyl alcohol (PVA), polyethylene glycol (PEG), polystyrene (PS), polyvinylidene fluoride (PVDF), polyamide resin (PA), polyimide (PI), silsesquioxane (POSS), polydimethylsiloxane (PDMS), fluoroalkyl compounds (PFAS), polyether amide block copolymer (PEBA), styrene-butadiene-styrene block copolymer (SBS), polytetrafluoroethylene (PTFE), and polyarylene sulfone sulfimide (PASSI).

[0028] Furthermore, the solvent used in step 4) is selected from one or more of deionized water, toluene, dimethylformamide, isopropanol, benzamide, etc.

[0029] Further, in step 4), the heating temperature is 50~120 ℃, the time is 1~8 h, and the stirring speed is 10~90 r / min.

[0030] Furthermore, the mass concentration of the polymer solution obtained in step 4) is 1~10wt%.

[0031] Furthermore, in step 5), the amounts of polymer solution and nepheline dispersion are converted according to the mass ratio of polymer to nepheline of 1:(0.0004~0.01).

[0032] Further, the crosslinking agent mentioned in step 5) is one or more of p-toluenesulfonic acid, acetic acid, succinic acid, maleic acid, dimethylaminopropylamine, 2-ethyl-4-methylimidazolium, glyoxal, ethylenediaminetetraacetic acid, and citric acid, and the mass ratio of its amount to the mass of the polymer used is (0.001~1):1.

[0033] Furthermore, in step 5), the settling time is 6~60 h.

[0034] Furthermore, the substrate used in step 6) is any one of nylon 66, nylon 6, polyethersulfone, polytetrafluoroethylene, polyvinylidene fluoride, polypropylene, or mixed cellulose, with a pore size of 0.2 μm to 0.8 μm.

[0035] Further, in step 6), the coating is applied 1 to 10 times at a speed of 5 to 200 mm / s.

[0036] Furthermore, in step 6), the drying temperature is 60~160℃ and the time is 0.5~48 h.

[0037] Furthermore, the thickness of the resulting composite film is 10~100 μm.

[0038] The significant advantages of this invention are:

[0039] This invention controls the size of silica in silica sol by adjusting the hydrolysis conditions of tetraethyl orthosilicate, then uses the obtained silica sol as a precursor to prepare nepheline, and effectively controls the composite membrane structure by regulating the crosslinking reaction between nepheline, polymer, and crosslinking agent, thus constructing the nepheline / polymer pervaporation composite membrane. The surface morphology of this pervaporation composite membrane shows: 1) the surface contains porous nepheline, which preferentially adsorbs small molecules; 2) the surface contains a large number of hydroxyl groups, which can undergo crosslinking reactions with the polymer matrix, improving the selectivity for small molecules; 3) the porous nepheline is highly dispersed in the matrix, exhibiting efficient water molecule diffusion promotion properties; 4) the membrane surface and interior are connected through nepheline, constructing special channels for water molecule transport, which promotes water molecule diffusion. Attached Figure Description

[0040] Figure 1 The XRD patterns are of the magenta prepared in Examples 1-5.

[0041] Figure 2 This is a schematic diagram of the structure of nepheline prepared in Example 1.

[0042] Figure 3 The image shows a SEM image of the magnolite / polyvinyl alcohol pervaporation composite membrane prepared in Example 1.

[0043] Figure 4 SEM image of the polyvinyl alcohol pervaporation composite membrane prepared in Comparative Example 1 without the addition of mahogany dispersion.

[0044] Figure 5 This is a diagram of the experimental setup for conducting a pervaporation evaporation experiment. Detailed Implementation

[0045] A nepheline / polymer pervaporation composite membrane is prepared by the following steps:

[0046] 1) Preparation of silica sol: Butyl orthosilicate, ethanol, and deionized water are mixed at a volume ratio of 1:10:1 and stirred. Then, 5-15 mol / L alkaline aqueous solution is added dropwise at a rate of 0.2 mL per minute to adjust the pH value to between 7 and 9. After stirring evenly, the mixture is aged for 0.5-24 h to obtain silica sol. The stirring speed is 10-90 r / min.

[0047] 2) Preparation of nepheline: An aluminum source was added to a 0.2–5 mol / L sodium hydroxide aqueous solution and stirred until dissolved, yielding an aluminum-containing alkaline solution. The prepared silica sol was then mixed with the aluminum-containing alkaline solution (Al / [OH]). - The molar ratio of Si / Al is 0.1~1.05:1, and the molar ratio of Si / Al is 0.04~0.16:1. After stirring evenly, the mixture is placed in a reaction vessel and reacted at 100~240 ℃ for 5~72 h. The precipitate is washed with deionized water until neutral and dried to obtain magenta.

[0048] 3) Dispersion of nepheline: Deionized water and aqueous solvent were mixed at a volume ratio of (0.1~1):1 as the dispersion solvent. After adding 1% by mass of nepheline to the dispersion solvent, the mixture was stirred using a homogenizer at 75 W and 8000~30000 r / min to obtain a uniform nepheline dispersion.

[0049] 4) Preparation of polymer solution: Heat and stir the polymer and deionized water at 50~120 ℃ and 10~90 r / min for 1~8 h to mix them and obtain a transparent and uniform polymer solution with a mass concentration of 1~10wt%.

[0050] 5) Preparation of membrane solution: The polymer solution, nepheline dispersion and crosslinking agent are mixed at a mass ratio of 1:(0.0004~0.01):(0.001~1), and then allowed to stand for 6~60 h to remove air bubbles to obtain the membrane solution.

[0051] 6) Film coating: The prepared film liquid is coated onto the substrate by scraping (it can be repeatedly coated 1 to 10 times at a scraping speed of 5 to 200 mm / s), and then dried in a constant temperature oven at 60 to 160°C for 0.5 to 48 h. After cooling, the magnolite / polymer pervaporation composite membrane with a thickness of 10 to 100 μm is obtained.

[0052] The alkali used in step 1) is one or more of ammonia, sodium bicarbonate, sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, barium hydroxide, and cesium hydroxide.

[0053] The aluminum source mentioned in step 2) is one or more of aluminum hydroxide, sodium aluminate, and aluminum sulfate.

[0054] The aqueous solvent mentioned in step 3) is one or more of ethanol, glycerol, polyethylene glycol, glycolic acid, triethanolamine, propylene glycol methyl ether, and dimethylformamide.

[0055] The polymer used in step 4) is one or more of the following: chitosan (CS), polyvinyl alcohol (PVA), polyethylene glycol (PEG), polystyrene (PS), polyvinylidene fluoride (PVDF), polyamide resin (PA), polyimide (PI), silsesquioxane (POSS), polydimethylsiloxane (PDMS), fluoroalkyl compounds (PFAS), polyether amide block copolymer (PEBA), styrene-butadiene-styrene block copolymer (SBS), polytetrafluoroethylene (PTFE), and polyarylene sulfone sulfimide (PASSI).

[0056] The crosslinking agent mentioned in step 5) is one or more of p-toluenesulfonic acid, acetic acid, succinic acid, maleic acid, dimethylaminopropylamine, 2-ethyl-4-methylimidazole, glyoxal, ethylenediaminetetraacetic acid, and citric acid.

[0057] The substrate used in step 6) is any one of nylon 66, nylon 6, polyethersulfone, polytetrafluoroethylene, polyvinylidene fluoride, polypropylene, or mixed cellulose, with a pore size of 0.2 μm to 0.8 μm.

[0058] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0059] Example 1:

[0060] (1) Preparation of silica sol: Add 3.5 mL of tetraethyl orthosilicate, 35 mL of ethanol and 3.5 mL of deionized water to a beaker and stir to mix. Then add 0.5 mL of ammonia solution (concentration of 14.8 mol / L) dropwise at a rate of 0.2 mL per minute, adjust the pH value to 7~8, and stir for 30 min to obtain silica sol.

[0061] (2) Preparation of nepheline: 1.0 g sodium aluminate and 2.0 g sodium hydroxide were added to 60 mL of deionized water and stirred for 0.5 h to obtain an aluminum-containing alkaline solution. Then, 4.0 g of the prepared silica sol was mixed with the aluminum-containing alkaline solution (Al / [OH]). - The mixture was stirred until homogeneous and then transferred to a polytetrafluoroethylene reactor. The reaction was carried out at 130 °C for 24 h. The resulting precipitate was washed with deionized water until neutral and dried at 100 °C for 6 h to obtain magenta.

[0062] (3) Dispersion of nepheline: 2.0 g of nepheline, 49 mL of deionized water and 49 mL of ethanol were added to a beaker and mixed using a homogenizer at 75W and 10000 r / min to obtain a uniform nepheline dispersion (after centrifugation at 500 rpm, the undispersed nepheline was taken out, dried and weighed, and the concentration of the nepheline dispersion was calculated to be 0.04 wt%).

[0063] (4) Polymer solution: Add 16 g of polyvinyl alcohol polymer and 184 g of deionized water to a round-bottom flask, heat and stir at 130 °C for 2 h to obtain a transparent and uniform polyvinyl alcohol solution with a mass concentration of 8 wt%.

[0064] (5) Preparation of membrane solution: 100 g polyvinyl alcohol solution, 20 g bainite dispersion and 2 g p-toluenesulfonic acid were added to a beaker and stirred and mixed. The mixture was then allowed to stand for 24 h to remove air bubbles and obtain membrane solution.

[0065] (6) Film coating: Polyvinylidene fluoride with a pore size of 0.2 μm is fixed on the surface of the coating machine platform. The film thickness is adjusted to 650 μm and the scraping speed is 75 mm / s to coat the film. Then, it is placed in a constant temperature oven at 110 ℃ for 4 h to dry and cool. A mafic alumina / polymer pervaporation composite film with a thickness of about 5 μm is obtained on the surface of polyvinylidene fluoride.

[0066] Example 2:

[0067] (1) Preparation of silica sol: Add 4 mL of tetraethyl orthosilicate, 40 mL of ethanol and 4 mL of deionized water to a beaker and stir to mix. Then add 1 mL of ammonia solution (concentration of 14.8 mol / L) dropwise at a rate of 0.2 mL per minute to adjust the pH value to 7~8. After stirring for 30 min, silica sol is obtained.

[0068] (2) Preparation of nepheline: 0.5 g sodium aluminate and 2.0 g sodium hydroxide were added to 60 mL of deionized water and stirred for 0.5 h to obtain an aluminum-containing alkaline solution. Then, 1.0 g of the prepared silica sol was mixed with the aluminum-containing alkaline solution (Al / [OH]). - The mixture was stirred until homogeneous and then transferred to a polytetrafluoroethylene reactor. The reaction was carried out at 150 °C for 48 h. The resulting precipitate was washed with deionized water until neutral and dried at 110 °C for 8 h to obtain magenta.

[0069] (3) Dispersion of nepheline: 1.0 g of nepheline, 10 mL of deionized water and 88 mL of glycerol were added to a beaker and mixed using a homogenizer at 75W and 15000 r / min to obtain a uniform nepheline dispersion (centrifuged at 1000 rpm, the undispersed nepheline was taken out, dried and weighed, and the concentration of the nepheline dispersion was calculated to be 0.2 wt%).

[0070] (4) Polymer solution: Add 10 g chitosan and 90 g deionized water to a round-bottom flask, heat and stir at 110 °C for 2 h to obtain a transparent and uniform chitosan solution with a mass concentration of 10 wt%.

[0071] (5) Preparation of membrane solution: 50 g chitosan solution, 25 g bainite dispersion and 1.5 g maleic acid were added to a beaker and stirred. After stirring and mixing, the mixture was allowed to stand for 12 h to remove air bubbles and obtain membrane solution.

[0072] (6) Film formation by blade coating: Polyethersulfone with a pore size of 0.45 μm is fixed on the surface of the coating machine platform. The film thickness is adjusted to 500 μm and the blade speed is 10 mm / s. The film is coated twice and then placed in a constant temperature oven at 120 ℃ for 10 h. After cooling, a pervaporation composite membrane of mafic alumina / polymer is obtained on the surface of polyethersulfone with a thickness of about 8 μm.

[0073] Example 3:

[0074] (1) Preparation of silica sol: Add 4 mL of tetraethyl orthosilicate, 40 mL of ethanol and 4 mL of deionized water to a beaker and stir to mix. Then add 2 mL of ammonia solution (concentration of 14.8 mol / L) dropwise at a rate of 0.2 mL per minute, adjust the pH value to 7~8, and stir for 30 min to obtain silica sol.

[0075] (2) Preparation of nepheline: 3.0 g of sodium aluminate and 4.0 g of sodium hydroxide were added to 60 mL of deionized water and stirred for 0.5 h to obtain an aluminum-containing alkaline solution. Then, 4.0 g of the prepared silica sol was mixed with the aluminum-containing alkaline solution (Al / [OH]). - The mixture was stirred until homogeneous and then transferred to a polytetrafluoroethylene reactor. The reaction was carried out at 140 °C for 36 h. The resulting precipitate was washed with deionized water until neutral and dried at 130 °C for 3 h to obtain magenta.

[0076] (3) Dispersion of nepheline: 1.8 g of nepheline, 20 mL of deionized water and 78.2 mL of glycerol were added to a beaker and mixed using a homogenizer at 75W and 16000 r / min to obtain a uniform nepheline dispersion (centrifuged at 1500 rpm, the undispersed nepheline was taken out, dried and weighed, and the concentration of the nepheline dispersion was calculated to be 0.05 wt%).

[0077] (4) Polymer solution: Add 1 g of polyethylene glycol and 99 g of deionized water to a round-bottom flask, heat and stir at 80 °C for 3 h to obtain a transparent and uniform polyethylene glycol solution with a mass concentration of 1 wt%.

[0078] (5) Preparation of membrane solution: 100 g polyethylene glycol solution, 10 g bainite dispersion and 3 g citric acid were added to a beaker and stirred and mixed. The mixture was then allowed to stand for 60 h to remove air bubbles and obtain membrane solution.

[0079] (6) Film formation by scraping: Nylon 66 with a pore size of 0.8 μm is fixed on the surface of the coating machine platform, the film thickness is adjusted to 700 μm and the scraping speed is 50 mm / s, and the film is formed by coating 3 times. Then, it is placed in a constant temperature oven at 90 ℃ for 5 h and cooled to obtain a mafia / polymer pervaporation composite film with a thickness of about 10 μm on the surface of nylon 66.

[0080] Example 4:

[0081] (1) Preparation of silica sol: Add 4 mL of tetraethyl orthosilicate, 40 mL of ethanol and 4 mL of deionized water to a beaker and stir to mix. Then add 3 mL of ammonia solution (concentration of 14.8 mol / L) dropwise at a rate of 0.2 mL per minute to adjust the pH value to 7~8. After stirring for 30 min, silica sol is obtained.

[0082] (2) Preparation of nepheline: 5.0 g aluminum sulfate and 4.0 g sodium hydroxide were added to 60 mL of deionized water and stirred for 0.5 h to obtain an aluminum-containing alkaline solution. Then, 4.0 g of the prepared silica sol was mixed with the aluminum-containing alkaline solution (Al / [OH]). - The mixture was stirred until homogeneous and then transferred to a polytetrafluoroethylene reactor. The reaction was carried out at 120 °C for 30 h. The resulting precipitate was washed with deionized water until neutral and dried at 95 °C for 7 h to obtain magenta.

[0083] (3) Dispersion of nepheline: 2.0 g of nepheline, 30 mL of deionized water and 68 mL of dimethylformamide were added to a beaker and mixed using a homogenizer at 75W and 20000 r / min to obtain a uniform nepheline dispersion (centrifuged at 2500 rpm, the undispersed precipitate was taken out, dried and weighed, and the concentration of the nepheline dispersion was calculated to be 0.01 wt%).

[0084] (4) Polymer solution: Add 5.0 g of polydimethylsiloxane and 95.0 g of isopropanol to a round-bottom flask, heat and stir at 70 °C for 1 h to obtain a transparent and uniform polydimethylsiloxane solution with a mass concentration of 5 wt%.

[0085] (5) Preparation of membrane solution: 100 g of polydimethylsiloxane solution, 10 g of bainite dispersion and 1.5 g of ethylenediaminetetraacetic acid were added to a beaker and stirred. After stirring and mixing, the mixture was allowed to stand for 40 h to remove air bubbles and obtain membrane solution.

[0086] (6) Film formation by scraping: Nylon 6 with a pore size of 0.45 μm is fixed on the surface of the coating machine platform, the film thickness is adjusted to 550 μm and the scraping speed is 55 mm / s, and the film is formed by coating 5 times. Then, it is placed in a constant temperature oven at 90 ℃ for 9 h and cooled to obtain a mafia / polymer pervaporation composite film with a thickness of about 15 μm on the surface of nylon 6.

[0087] Example 5:

[0088] (1) Preparation of silica sol: Add 4 mL of tetraethyl orthosilicate, 40 mL of ethanol and 4 mL of deionized water to a beaker and stir to mix. Then add 4 mL of ammonia solution (concentration of 14.8 mol / L) dropwise at a rate of 0.2 mL per minute, adjust the pH value to 7~8, and stir for 30 min to obtain silica sol.

[0089] (2) Preparation of magnolite: 2.0 g aluminum hydroxide and 1.0 g sodium hydroxide were added to 60 mL of deionized water and stirred for 0.5 h to obtain an aluminum-containing alkaline solution. Then, 10.0 g of the prepared silica sol was mixed with the aluminum-containing alkaline solution (Al / [OH]). - The mixture was stirred until homogeneous (molar ratio 1.03:1, Si / Al molar ratio 0.16:1), then transferred to a polytetrafluoroethylene reactor and reacted at 120 °C for 40 h. The resulting precipitate was washed with deionized water until neutral and dried at 110 °C for 8 h to obtain magenta.

[0090] (3) Dispersion of nepheline: 2.0 g of nepheline, 40 mL of deionized water and 58 mL of triethanolamine were added to a beaker and mixed using a homogenizer at 75W and 20000 r / min to obtain a uniform nepheline dispersion (centrifuged at 1600 rpm, the undispersed precipitate was taken out, dried and weighed, and the concentration of the nepheline dispersion was calculated to be 0.02 wt%).

[0091] (4) Polymer solution: 5.0 g of polyether amide block copolymer and 95 g of benzamide were added to a round bottom flask and heated and stirred at 60 °C for 5 h to obtain a transparent and uniform polyether amide block copolymer solution with a mass concentration of 5 wt%.

[0092] (5) Preparation of membrane solution: 100 g of polyether amide block copolymer solution, 50 g of leucite dispersion and 3.5 g of glyoxal were added to a beaker and stirred and mixed. The mixture was then allowed to stand for 60 h to remove air bubbles and obtain membrane solution.

[0093] (6) Film formation by scraping: Polytetrafluoroethylene with a pore size of 0.2 μm is fixed on the surface of the coating machine platform. The film thickness is adjusted to 800 μm and the scraping speed is 75 mm / s. The film is formed by coating 6 times. Then, it is placed in a constant temperature oven at 115 ℃ for 5 h and cooled. A mafic alumina / polymer pervaporation composite film with a thickness of about 20 μm is obtained on the surface of polytetrafluoroethylene.

[0094] Comparative Example 1

[0095] (1) Polymer solution: 16 g of polyvinyl alcohol polymer and 184 g of deionized water were added to a round-bottom flask and heated and stirred at 130 °C for 2 h to obtain a transparent and uniform polyvinyl alcohol solution with a mass concentration of 8 wt%.

[0096] (2) Preparation of membrane solution: 100 g polyvinyl alcohol solution and 2 g p-toluenesulfonic acid were added to a beaker and stirred and mixed. The mixture was allowed to stand for 24 h to remove air bubbles and obtain membrane solution.

[0097] (3) Film coating: Polyvinylidene fluoride with a pore size of 0.2 μm is fixed on the surface of the coating machine platform. The film thickness is adjusted to 650 μm and the scraping speed is 75 mm / s to coat the film. Then, it is placed in a constant temperature oven at 110 ℃ for 4 h to dry and cool. A polymer pervaporation composite film without nepheline is obtained on the surface of polyvinylidene fluoride with a film thickness of about 5 μm.

[0098] Comparative Example 2

[0099] (1) Dispersion of nepheline: 2.0 g of commercially available nepheline (Si / Al molar ratio 1:1), 49 mL of deionized water and 49 mL of ethanol were added to a beaker and mixed using a homogenizer at 75W and 10000 r / min to obtain a uniform nepheline dispersion (after centrifugation at 500 rpm, the undispersed nepheline was taken out, dried and weighed, and the concentration of the nepheline dispersion was calculated to be 0.02 wt%).

[0100] (2) Polymer solution: 16 g of polyvinyl alcohol polymer and 184 g of deionized water were added to a round-bottom flask and heated and stirred at 130 °C for 2 h to obtain a transparent and uniform polyvinyl alcohol solution with a mass concentration of 8 wt%.

[0101] (3) Preparation of membrane solution: 100 g polyvinyl alcohol solution, 40 g bainite dispersion and 2 g p-toluenesulfonic acid were added to a beaker and stirred and mixed. After standing for 24 h to remove air bubbles, the membrane solution was obtained.

[0102] (4) Film coating: Polyvinylidene fluoride with a pore size of 0.2 μm is fixed on the surface of the coating machine platform. The film thickness is adjusted to 650 μm and the scraping speed is 75 mm / s to coat the film. Then, it is placed in a constant temperature oven at 110 ℃ for 4 h to dry and cool. A mafic alumina / polymer pervaporation composite film with a thickness of about 5 μm is obtained on the surface of polyvinylidene fluoride.

[0103] Comparative Example 3

[0104] (1) Preparation of silica sol: Add 3.5 mL of tetraethyl orthosilicate, 35 mL of ethanol and 3.5 mL of deionized water to a beaker and stir to mix. Then add 0.5 mL of ammonia solution (concentration of 14.8 mol / L) dropwise at a rate of 0.2 mL per minute, adjust the pH value to 7~8, and stir for 30 min to obtain silica sol.

[0105] (2) Dispersion of silica: 2.0 g silica sol, 49 mL deionized water and 49 mL ethanol were added to a beaker and mixed using a homogenizer at 75W and 10000 r / min to obtain a uniform silica dispersion (the concentration of the silica dispersion was calculated to be 4.8 wt%).

[0106] (3) Polymer solution: 16 g of polyvinyl alcohol polymer and 184 g of deionized water were added to a round-bottom flask and heated and stirred at 130 °C for 2 h to obtain a transparent and uniform polyvinyl alcohol solution with a mass concentration of 8 wt%.

[0107] (4) Preparation of membrane solution: 100 g polyvinyl alcohol solution, 0.17 g silica dispersion and 2 g p-toluenesulfonic acid were added to a beaker and stirred and mixed. The mixture was then allowed to stand for 24 h to remove air bubbles and obtain membrane solution.

[0108] (5) Film coating: Polyvinylidene fluoride with a pore size of 0.2 μm is fixed on the surface of the coating machine platform. The film thickness is adjusted to 650 μm and the scraping speed is 75 mm / s to coat the film. Then, it is placed in a constant temperature oven at 110 ℃ for 4 h to dry and cool. A silica / polymer pervaporation composite film with a thickness of about 5 μm is obtained on the surface of polyvinylidene fluoride.

[0109] Performance testing:

[0110] 1. Surface morphology

[0111] Figure 3 , 4 The images show scanning electron microscope (SEM) images of the pervaporation composite membrane samples prepared in Example 1 and Comparative Example 1, respectively. As can be seen from the comparison of the images, the nepheline / polyvinyl alcohol pervaporation composite membrane obtained in Example 1 has a highly dispersed surface.

[0112] 2. Pervaporation performance

[0113] The prepared composite membrane was subjected to a pervaporation evaporation experiment. The experimental setup was as follows: Figure 5 It is assembled from a feed tank with heating and stirring, a peristaltic pump, a vacuum pump, a chilled hydrazine, and a membrane tank. Specifically, the pervaporation composite membrane is placed in the center of the membrane tank, with an effective area of ​​12 cm². 2 The feed solution used was a 0.6 mol / L sodium chloride aqueous solution. During the experiment, the feed solution was heated to 40°C and circulated using a peristaltic pump at a flow rate of 80 mL / min. The vacuum level was controlled by a vacuum pump and set at 130 Pa. Permeate was collected using a liquid nitrogen-cooled hydrazine apparatus.

[0114] The separation performance of the composite membrane is measured by its permeate flux and rejection rate to sodium chloride aqueous solution. The permeate flux J is calculated as follows:

[0115] ,

[0116] in: W The weight of the collected permeate; A The effective area of ​​the membrane; t For collection time;

[0117] The retention rate R is calculated as follows:

[0118] ,

[0119] Where: Cf C p These represent the NaCl concentrations at the feed end and the permeation end, respectively.

[0120] Table 1. Pervaporation performance data of various composite membranes

[0121]

[0122] The data in the table show that nepheline prepared using silica as a precursor can significantly improve the permeation flux and rejection rate of the resulting composite membrane.

[0123] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for preparing a nepheline / polymer pervaporation composite membrane, characterized in that, First, silica sol of a certain particle size is prepared by the Stöber method. Then, nepheline is prepared by hydrothermal method using the prepared silica sol as a precursor. The obtained nepheline is then dispersed and mixed with a polymer solution and a crosslinking agent to form a film liquid. The film is then coated on a substrate to obtain the nepheline / polymer pervaporation composite membrane. The preparation of mahogany involves adding an aluminum source to an aqueous sodium hydroxide solution and stirring to dissolve it, thereby obtaining an aluminum-containing alkaline solution. Then, the prepared silica sol is stirred and mixed with the aluminum-containing alkaline solution, placed in a reaction vessel, and reacted using a hydrothermal method for a period of time. The resulting precipitate is washed with deionized water until neutral and then dried to obtain the final product. The aluminum source is one or more of aluminum hydroxide, sodium aluminate, and aluminum sulfate; the concentration of the sodium hydroxide aqueous solution is 0.2~5 mol / L; and the amounts of aluminum source and sodium hydroxide are calculated according to Al / [OH] - The molar ratio is converted to (0.1~1.05):1; the amount of silica sol is converted to Si / Al molar ratio of (0.04~0.16):

1.

2. The method for preparing the nepheline / polymer pervaporation composite membrane according to claim 1, characterized in that, The silica sol is prepared by mixing butyl orthosilicate, ethanol, and deionized water, then adding an alkaline aqueous solution dropwise at a rate of 0.2 mL per minute to adjust the pH to between 7 and 9, stirring until homogeneous, and then aging.

3. The method for preparing the nepheline / polymer pervaporation composite membrane according to claim 2, characterized in that, The volume ratio of tetrabutyl orthosilicate, ethanol and deionized water used is 1:10:1; The concentration of the alkaline aqueous solution is 5~15 mol / L, and the alkali used is one or more of ammonia, sodium bicarbonate, sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, barium hydroxide, and cesium hydroxide.

4. The method for preparing the nepheline / polymer pervaporation composite membrane according to claim 1, characterized in that, The reaction is carried out at a temperature of 100-240 °C for a duration of 5-72 h.

5. The method for preparing the nepheline / polymer pervaporation composite membrane according to claim 1, characterized in that, The preparation of the composite membrane includes the following steps: a) Dispersion of nepheline: The prepared nepheline was mixed with deionized water and an aqueous solvent, and stirred using a homogenizer to obtain a uniform nepheline dispersion. b) Preparation of polymer solution: Heat and stir the polymer and solvent to obtain a transparent and uniform polymer solution; c) Preparation of membrane solution: After stirring and mixing the prepared polymer solution, nepheline dispersion and crosslinking agent, let it stand for a period of time to remove air bubbles to obtain membrane solution; d) Film coating: The prepared film liquid is coated onto the substrate, and then dried and cooled to obtain the mafia / polymer pervaporation composite membrane.

6. The method for preparing the nepheline / polymer pervaporation composite membrane according to claim 5, characterized in that, In step a), the volume ratio of deionized water to aqueous solvent is (0.1~1):1, and the amount of nepheline is 1% of the total mass of deionized water and aqueous solvent used; the aqueous solvent is one or more of ethanol, glycerol, polyethylene glycol, glycolic acid, triethanolamine, propylene glycol methyl ether, and dimethylformamide; the stirring speed is 8000~30000 r / min. The polymer used in step b) is one or more of the following: chitosan, polyvinyl alcohol, polyethylene glycol, polystyrene, polyvinylidene fluoride, polyamide resin, polyimide, silsesquioxane, polydimethylsiloxane, fluoroalkyl compounds, polyetheramide block copolymers, styrene-butadiene-styrene block copolymers, polytetrafluoroethylene, and polyarylate sulfone imide; the solvent used is one or more of the following: deionized water, toluene, dimethylformamide, isopropanol, and benzamide; the heating temperature is 50-120 °C, and the heating time is 1-8 h; the mass concentration of the resulting polymer solution is 1-10 wt%. In step c), the amounts of the polymer solution and the nepheline dispersion are calculated based on a mass ratio of polymer to nepheline of 1:(0.0004~0.01); the crosslinking agent is one or more of p-toluenesulfonic acid, acetic acid, succinic acid, maleic acid, dimethylaminopropylamine, 2-ethyl-4-methylimidazolium, glyoxal, ethylenediaminetetraacetic acid, and citric acid, and its amount is in a mass ratio of (0.001~1):1 with the polymer. The substrate used in step d) is any one of nylon 66, nylon 6, polyethersulfone, polytetrafluoroethylene, polyvinylidene fluoride, polypropylene, or mixed cellulose, with a pore size of 0.2 μm to 0.8 μm; the coating is applied 1 to 10 times at a speed of 5 to 200 mm / s; the drying temperature is 60 to 160℃ and the drying time is 0.5 to 48 h; the thickness of the resulting composite film is 10 to 100 μm.

7. A mahogany / polymer pervaporation composite membrane prepared by the method described in any one of claims 1 to 6.

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