Nanofiltration membranes and methods for making the same

Abstract

The application discloses a kind of nanofiltration membranes, including base film and the nanofiltration layer formed by polymerization reaction on the surface of base film, it is characterized in that the nanofiltration layer is obtained by water-phase solution and oil-phase solution polymerization reaction, piperazine, esterification modified nanocrystalline cellulose and mercapto modified bentonite are added in water phase, 1,3,5-benzene tricarbonyl chloride and amino modified chitosan and the copolymer of graphene oxide are added in oil phase.The application also discloses the preparation method of nanofiltration membrane.Mercapto modified bentonite can form stable complex with amino modified chitosan and the copolymer of graphene oxide, can support the polyamide film formed at interface, to improve the life of nanofiltration membrane.Meanwhile, esterification modified nanocrystalline cellulose can form hydrogen bond on the surface of nanofiltration membrane, improve the hydrophilicity of nanofiltration membrane, to increase flux.

Description

Technical Field

[0001] This invention relates to a filtration membrane, and more particularly to a nanofiltration membrane for water treatment. This invention also relates to a method for preparing the nanofiltration membrane. Background Technology

[0002] Nanofiltration membranes, as a pressure-driven separation membrane, have molecular pore sizes between ultrafiltration and reverse osmosis membranes. They have the advantages of low operating pressure, high flux, and good retention of salts and organic solvents (solute components with a size greater than 1 nm).

[0003] Nanofiltration membranes in water treatment and brine separation are broadly classified into two types: one is an asymmetric structure nanofiltration membrane prepared by immersion precipitation; the other is a thin-layer composite nanofiltration membrane (TFC) prepared by interfacial polymerization, which is widely used in separation and water treatment processes.

[0004] TFC membranes consist of a dense skin layer and a porous support layer. The requirements for the support layer of the composite membrane mainly include suitable pore size and distribution, sufficient water flux and molecular weight cutoff under certain conditions, and good physical and chemical stability. Polymer materials used as base membranes generally include polysulfone, polyarylate, polyvinyl chloride, chlorinated polypropylene, and polycarbonate, although inorganic porous membranes are also used. Polysulfone is inexpensive and readily available, and polysulfone membranes have advantages such as good mechanical strength, resistance to pressure compaction, resistance to microbial degradation, chemical stability, non-toxicity, and minimal impact on the water permeability of the composite membrane. Therefore, most researchers currently use polysulfone membranes as the base membrane for nanofiltration membranes. The dense skin layer is formed by the interfacial polymerization of aqueous phase monomers (PIP) and oil phase monomers (TMC). The thickness of the dense skin layer in the composite membrane is adjustable, changing with the interfacial polymerization conditions. The structure and morphology of the functional layers of the nanofiltration membrane affect the membrane performance. Nanofiltration membranes have long been used to separate mixed salts, especially sodium chloride and sodium sulfate, due to the significant differences in pore size and surface potential. However, their low separation coefficient and low flux for monovalent and divalent salts have made them a challenging problem in water treatment. In recent years, however, researchers have discovered that adding inorganic nanoparticles to the membrane layer can improve the selectivity, mechanical properties, antifouling properties, and permeability of composite membranes. This new type of membrane is called a nanocomposite thin-layer membrane (TFN membrane).

[0005] Titanium dioxide is a white powder with strong hiding and coloring power, high stability, high dispersibility, and non-toxicity. Its surface contains numerous hydroxyl groups, resulting in good dispersibility in water and good polymer compatibility. Currently, some researchers have added titanium dioxide to interfacial polymerization to improve membrane separation performance.

[0006] However, due to their large surface area and strong surface polarity, nanoparticles tend to aggregate easily in polymer substrates and exhibit poor dispersibility in monomer solutions, a problem that remains to be solved. Current research has shown that surface modification of nanoparticles can effectively improve the bonding between inorganic particles and polymer matrices. However, as the concentration of nanoparticles increases, the retention rate decreases, and aggregation remains a serious issue. Summary of the Invention

[0007] The first technical problem to be solved by the present invention is to provide a nanofiltration membrane with good dispersibility and high flux, in view of the above-mentioned technical status.

[0008] The second technical problem to be solved by the present invention is to provide a nanofiltration membrane with good dispersibility and high flux, in view of the above-mentioned technical status.

[0009] The technical solution adopted by the present invention to solve the first technical problem mentioned above is: a nanofiltration membrane, wherein the composite nanofiltration membrane is composed of two parts: one is a base membrane, and the other is a nanofiltration layer obtained by the polymerization reaction of an aqueous phase and an organic phase, wherein piperazine, esterified modified nanocrystalline cellulose and thiol-modified bentonite are added to the aqueous phase, and 1,3,5-benzenetricarboxyl chloride and a copolymer of amino-modified chitosan and graphene oxide are added to the oil phase.

[0010] Preferably, the preparation of the aqueous solution includes the following steps:

[0011] S1. Disperse 1-2g of nanocrystalline cellulose (NCC) in 20-30ml of acetic acid and sonicate for 20-30min. After the nanocrystalline cellulose is evenly dispersed, add 2-6g of acid anhydride and 0.2-0.6g of catalyst in sequence, and stir continuously for 30-40min. Wash the product with ethanol and dry it under vacuum at 50-60℃ for 5 hours to obtain esterified modified nanocrystalline cellulose (C-NCC).

[0012] S2. Weigh 4-6g of bentonite (SCB) into a round-bottom flask containing 50-60ml of glacial acetic acid and sonicate at 60℃ for 10min. Then slowly add 1-2g of dimercaprol and 0.1-0.5g of catalyst while stirring continuously for 30-40min. After the reaction is complete, remove the supernatant, wash the product three times with anhydrous ethanol, and dry the obtained solid in an oven at 70℃ for 5h to obtain the product, mercapto-modified bentonite (SH-SCB).

[0013] S3. Add 0.4-0.5g of piperazine to a beaker containing 100ml of pure water and stir at 30-35℃ for 20-30min to obtain a clear and transparent solution.

[0014] S4. Add 0.02-0.03g of esterified nanocrystalline cellulose and 0.04-0.06g of mercapto-modified bentonite to the above solution, and stir at 30-35℃ for 50-60min to obtain a clear and transparent solution.

[0015] Preferably, the preparation of the oil phase solution includes the following steps:

[0016] S1. Dissolve 1-2g of sodium acetate and 1-2g of sodium carbonate in 100-120ml of distilled water. After complete dissolution, add 1-2g of graphene oxide (GO) to the solution, maintain the temperature at 30-40℃ and stir continuously for 40-50min. In another round-bottom flask, dissolve 0.5-1.5g of chitosan (CS) in 10-20ml of acetic acid, add 80-90ml of ethanol, sonicate for 25-30min, then add 2-3g of aminothiourea, continue sonicating for 10-15min until fully dissolved. Slowly add the solution containing graphene oxide to the mixture, then add 6mol / L sodium hydroxide solution dropwise to adjust the pH of the solution. Finally, raise the temperature to 60℃ and stir continuously. Add 3-5 ml of crosslinking agent and 4-6 ml of concentrated ammonia to the solution, keep the temperature constant and continue stirring. After the reaction is complete, remove the supernatant, wash the microspheres at the bottom with 20 ml of anhydrous ethanol for 30 s, and dry the obtained product in an oven at 50 ℃ for 4 h to obtain the amino-modified chitosan and graphene oxide copolymer NH2-CS-GO.

[0017] S2. Add 0.15-0.2g of 1,3,5-benzenetricarboxyl chloride and 0.03-0.05g of amino-modified chitosan and graphene oxide copolymer to a container containing 100ml of solvent, and stir at 30-35℃ for 30-40min to obtain an oil phase solution.

[0018] Preferably, the diameter of the nanocrystalline cellulose in step S1 is 30-50 nm; the acid anhydride is one or more of succinic anhydride, citric anhydride, or maleic anhydride; the catalyst is one of dibutyltin dilaurate or platinum-diethylenetetramethyldisiloxane; and the catalyst in step S2 is any one of MoS2, benzoic acid, zinc chloride, or platinum-diethylenetetramethyldisiloxane.

[0019] Preferably, the graphene oxide in step S1 has a diameter of 0.2-2 μm and an oxygen content greater than 50% (W / W); the crosslinking agent is one or a combination of hexafluorophosphate and ethylene glycol diglycidyl ether; and the pH of the solution is adjusted to between 10 and 11 using sodium hydroxide. The solvent in step S2 includes one of n-hexane and cyclohexane.

[0020] The technical solution adopted by this invention to solve the second technical problem mentioned above is as follows: The base membrane is immersed in an aqueous solution for 180-240 seconds, then removed and dried to obtain an intermediate membrane. The intermediate membrane is then immersed in an oil solution for 30-60 seconds, removed, and dried in an oven at 60-80°C for 5-7 minutes to obtain a composite nanofiltration membrane.

[0021] Compared with the prior art, the advantages of the present invention are as follows:

[0022] Piperazine and 1,3,5-benzenetriacyl chloride were used as the aqueous and oil phase monomers, respectively. Esterified nanocrystalline cellulose and thiol-modified bentonite were added to the aqueous phase, while an amino-modified chitosan-graphene oxide copolymer was added to the oil phase for interfacial polymerization. In this system, the thiol-modified bentonite forms a stable complex with the amino-modified chitosan-graphene oxide copolymer, supporting the polyamide membrane formed at the interface and thus improving the nanofiltration membrane's lifespan. Simultaneously, the thiol-modified bentonite increases the compatibility between the aqueous and oil phases, promotes polymerization, further enhances the crosslinking degree of the nanofiltration membrane, forms a dense network structure, and improves the rejection rate. Esterified nanocrystalline cellulose forms hydrogen bonds on the nanofiltration membrane surface, increasing its hydrophilicity and thus increasing flux. Furthermore, its antioxidant properties protect the nanofiltration membrane from oxidative damage, extending its lifespan. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the embodiments.

[0024] Example 1

[0025] (1) Disperse 1g of nanocrystalline cellulose (NCC) in 20ml of acetic acid and sonicate for 20min. After the nanocrystalline cellulose is evenly dispersed, add 2g of succinic anhydride and 0.2g of dibutyltin dilaurate in sequence and stir continuously for 30min. Wash the product with ethanol and dry it under vacuum at 50℃ for 5 hours to obtain esterified modified nanocrystalline cellulose (C-NCC).

[0026] (2) Weigh 4g of bentonite (SCB) into a round-bottom flask containing 50ml of glacial acetic acid and sonicate at 60℃ for 10min. Then slowly add 1g of dimercaptopropanol and 0.1g of benzoic acid and stir continuously for 30min. After the reaction is complete, remove the supernatant and wash the product three times with anhydrous ethanol. Place the obtained solid in an oven at 70℃ and dry for 5h to obtain the product mercapto-modified bentonite (SH-SCB).

[0027] (3) Add 0.4g of piperazine to a beaker containing 100ml of pure water and stir at 30℃ for 20min to obtain a clear and transparent solution.

[0028] (4) Add 0.02g of esterified nanocrystalline cellulose and 0.04g of mercapto-modified bentonite to the above solution and stir at 30°C for 50min to obtain a clear and transparent solution.

[0029] (5) Dissolve 1g of sodium acetate and 1g of sodium carbonate in 100ml of distilled water. After they are fully dissolved, add 1g of graphene oxide (GO) to the solution. Keep the temperature at 30℃ and stir continuously for 40min. In another round-bottom flask, dissolve 0.5g of chitosan (CS) in 10ml of acetic acid, add 80ml of ethanol, sonicate for 25min, then add 2g of aminothiourea and continue sonicating for 10min. After they are fully dissolved, slowly add the solution containing graphene oxide to the mixture. Then add 6mol / L sodium hydroxide solution to the mixed solution to adjust the pH of the solution to 10. Raise the temperature to 60℃ and stir continuously. Add 3 ml of ethylene glycol diglycidyl ether and 4 ml of concentrated ammonia to the solution, keep the temperature constant and continue stirring. After the reaction is complete, remove the supernatant, wash the microspheres at the bottom with 20 ml of anhydrous ethanol for 30 s, and dry the obtained product in an oven at 50 ℃ for 4 h to obtain the amino-modified chitosan and graphene oxide copolymer NH2-CS-GO.

[0030] (6) Add 0.15g of 1,3,5-benzenetriacyl chloride and 0.03g of amino-modified chitosan and graphene oxide copolymer to a container containing 100ml of solvent, and stir at 30℃ for 30min to obtain an oil phase solution.

[0031] (7) Immerse the base membrane in the aqueous solution for 180s, then remove it and blow it dry to obtain the intermediate membrane. Immerse the intermediate membrane in the oil solution for 30s, remove it, and dry it in an oven at 60℃ for 5min to obtain the composite nanofiltration membrane.

[0032] Example 2

[0033] (1) Disperse 1.5g of nanocrystalline cellulose (NCC) in 25ml of acetic acid and sonicate for 25min. After the nanocrystalline cellulose is evenly dispersed, add 4g of succinic anhydride and 0.4g of dibutyltin dilaurate in sequence and stir continuously for 35min. Wash the product with ethanol and dry it under vacuum at 55℃ for 5 hours to obtain esterified modified nanocrystalline cellulose (C-NCC).

[0034] (2) Weigh 5g of bentonite (SCB) into a round-bottom flask containing 55ml of glacial acetic acid and sonicate at 60℃ for 10min. Then slowly add 1.5g of dimercaprol and 0.3g of benzoic acid and stir continuously for 35min. After the reaction is complete, remove the supernatant and wash the product three times with anhydrous ethanol. Place the obtained solid in an oven at 70℃ and dry for 5h to obtain the product, mercapto-modified bentonite (SH-SCB).

[0035] (3) Add 0.45g of piperazine to a beaker containing 100ml of pure water and stir at 33℃ for 25min to obtain a clear and transparent solution.

[0036] (4) Add 0.025g of esterified nanocrystalline cellulose and 0.05g of mercapto-modified bentonite to the above solution and stir at 33°C for 55min to obtain a clear and transparent solution.

[0037] (5) Dissolve 1.5g sodium acetate and 1.5g sodium carbonate in 110ml distilled water. After they are fully dissolved, add 1.5g graphene oxide (GO) to the solution. Keep the temperature at 35℃ and stir continuously for 45min. In another round-bottom flask, dissolve 1g chitosan (CS) in 15ml acetic acid, add 85ml ethanol, sonicate for 28min, then add 2.5g aminothiourea and continue sonicating for 13min. After they are fully dissolved, slowly add the solution containing graphene oxide to the mixture. Then add 6mol / L sodium hydroxide solution to the mixture to adjust the pH to 10.5. Raise the temperature to 60℃ and stir continuously. Add 4 ml of ethylene glycol diglycidyl ether and 5 ml of concentrated ammonia to the solution, maintain the temperature and continue stirring. After the reaction is complete, remove the supernatant, wash the microspheres at the bottom with 20 ml of anhydrous ethanol for 30 seconds, and dry the obtained product in an oven at 50 °C for 4 hours to obtain an amino-modified chitosan and graphene oxide copolymer NH. 2- CS-GO.

[0038] (6) Add 0.18g of 1,3,5-benzenetriacyl chloride and 0.04g of amino-modified chitosan and graphene oxide copolymer to a container containing 100ml of solvent, and stir at 33℃ for 35min to obtain an oil phase solution.

[0039] (7) Immerse the base membrane in the aqueous solution for 210s, then remove it and blow it dry to obtain the intermediate membrane. Immerse the intermediate membrane in the oil solution for 45s, remove it, and dry it in an oven at 70℃ for 6min to obtain the composite nanofiltration membrane.

[0040] Example 3

[0041] (1) Disperse 2g of nanocrystalline cellulose (NCC) in 30ml of acetic acid and sonicate for 30min. After the nanocrystalline cellulose is evenly dispersed, add 6g of succinic anhydride and 0.6g of dibutyltin dilaurate in sequence and stir continuously for 40min. Wash the product with ethanol and dry it under vacuum at 60℃ for 5 hours to obtain esterified modified nanocrystalline cellulose (C-NCC).

[0042] (2) Weigh 6g of bentonite (SCB) into a round-bottom flask containing 60ml of glacial acetic acid and sonicate it at 60℃ for 10min. Then slowly add 2g of dimercaptopropanol and 0.5g of benzoic acid and stir continuously for 40min. After the reaction is complete, remove the supernatant and wash the product three times with anhydrous ethanol. Place the obtained solid in an oven at 70℃ and dry it for 5h to obtain the product, mercapto-modified bentonite (SH-SCB).

[0043] (3) Add 0.5g of piperazine to a beaker containing 100ml of pure water and stir at 35℃ for 30min to obtain a clear and transparent solution.

[0044] (4) Add 0.03g of esterified nanocrystalline cellulose and 0.06g of mercapto-modified bentonite to the above solution and stir at 35°C for 60min to obtain a clear and transparent solution.

[0045] (5) Dissolve 2g of sodium acetate and 2g of sodium carbonate in 120ml of distilled water. After they are fully dissolved, add 2g of graphene oxide (GO) to the solution and keep the temperature at 40℃ while stirring continuously for 50min. In another round-bottom flask, dissolve 1.5g of chitosan (CS) in 20ml of acetic acid, add 90ml of ethanol, sonicate for 30min, then add 3g of aminothiourea and continue sonicating for 15min. After they are fully dissolved, slowly add the solution containing graphene oxide to the mixture. Then add 6mol / L sodium hydroxide solution to the mixed solution to adjust the pH of the solution to 11. Then raise the temperature to 60℃ and stir continuously. Add 5 ml of ethylene glycol diglycidyl ether and 6 ml of concentrated ammonia to the solution, keep the temperature constant and continue stirring. After the reaction is complete, remove the supernatant, wash the microspheres at the bottom with 20 ml of anhydrous ethanol for 30 s, and dry the obtained product in an oven at 50 ℃ for 4 h to obtain the amino-modified chitosan and graphene oxide copolymer NH2-CS-GO.

[0046] (6) Add 0.2g of 1,3,5-benzenetriacyl chloride and 0.05g of amino-modified chitosan and graphene oxide copolymer to a container containing 100ml of solvent, and stir at 35℃ for 40min to obtain an oil phase solution.

[0047] (7) Immerse the base membrane in an aqueous solution for 240s, then remove it and blow it dry to obtain the intermediate membrane. Immerse the intermediate membrane in an oil solution for 60s, remove it, and dry it in an oven at 80℃ for 7min to obtain the composite nanofiltration membrane.

[0048] In the comparative examples, only piperazine and 1,3,5-benzenetricarboxylic acid chloride, the two main reactants, were added to the aqueous and oil phases, respectively.

[0049] (1) Add 0.5g of piperazine to a beaker containing 100ml of pure water and stir at 35℃ for 30min to obtain a clear and transparent solution.

[0050] (2) Add 0.2g of 1,3,5-benzenetricarboxyl chloride to a container containing 100ml of n-hexane and stir at 35℃ for 40min to obtain an oil phase solution.

[0051] (3) The base membrane was immersed in the aqueous solution for 240s, then removed and dried to obtain the intermediate membrane. The intermediate membrane was immersed in the oil solution for 60s, removed and dried in an oven at 80℃ for 7min to obtain the composite nanofiltration membrane.

[0052] Test method: A laboratory-made filter was used to test the permeation flux and rejection rate of the nanofiltration membrane to magnesium sulfate solution under a certain pressure. All experiments were performed in parallel three times, and the average value was taken.

[0053] The permeation flux (P, L·m) of a nanofiltration membrane under a certain pressure −2 ·h −1 ·bar −1 The retention rate (R, %) and the rejection rate (R, %) are calculated by the following formulas: (1 bar = 10⁵ Pa)

[0054] P = V / A / Δt / Δp (1)

[0055] R = (1 – cp / cf) × 100% (2)

[0056] In the formula: V (L) is the volume of permeate collected; A (m³) is the volume of permeate collected. 2 Δt (h) is the effective membrane area; Δp (bar) is the time taken to collect the permeate sample; Δp (bar) is the pressure applied to the membrane by the nitrogen device during the experiment; cp (mol / L) is the concentration of the solute in the permeate; cf (mol / L) is the concentration of the solute in the feed solution. The concentration of the solution is calculated from the absorbance of the solution, which is measured using a UV-Vis spectrophotometer.

[0057]

[0058] As can be seen from the above results, the nanofiltration membrane obtained by the present invention has excellent performance.

[0059] To verify the lifespan of the nanofiltration membrane, it was run for an extended period using the above testing method. Changes in flux and rejection rate were measured every day for 30 consecutive days, and the average value was taken. The results are as follows:

[0060]

[0061] As can be seen from the above results, after long-term testing, the nanofiltration membrane obtained by the method of the present invention still maintains a good flux and rejection rate, and has the effect of long life.

Claims

1. A nanofiltration membrane, comprising a base membrane and a nanofiltration layer formed by a polymerization reaction on the surface of the base membrane, characterized in that... The nanofiltration layer is obtained by polymerization reaction of an aqueous solution and an oil solution. The aforementioned aqueous solution includes the following components and their weight ratios: Piperazine 0.4-0.5 parts; 0.02-0.03 parts of esterified modified nanocrystalline cellulose; Thiol-modified bentonite 0.04-0.06; 100 parts water; The aforementioned oil phase solution comprises the following components and their weight ratios: 0.15-0.2 parts of 1,3,5-benzotricarboxylic acid chloride; 0.03-0.05 parts of an amino-modified copolymer of chitosan and graphene oxide; 100 parts organic solvent; In the aforementioned amino-modified chitosan and graphene oxide copolymer, the weight ratio of chitosan to graphene oxide is 0.5~1.5:1~2.

2. The nanofiltration membrane according to claim 1, characterized in that... The base membrane is a polysulfone or polyethersulfone type ultrafiltration membrane.

3. The nanofiltration membrane according to claim 1, characterized in that... The amino-modified chitosan and graphene oxide copolymer is prepared by the following steps: In the first container, dissolve 1-2g of sodium acetate and 1-2g of sodium carbonate in 100-120ml of distilled water. After they are fully dissolved, add 1-2g of graphene oxide to the solution and stir to obtain solution one. In the second container, dissolve 0.5-1.5g of chitosan in 10-20ml of acetic acid, add 80-90ml of ethanol, sonicate, then add 2-3g of aminothiourea, continue sonicating until fully dissolved to obtain solution two. Solution 1 was added to Solution 2, and sodium hydroxide solution was added dropwise to adjust the pH of the solution. The mixture was stirred, and a crosslinking agent and ammonia were added to the solution. The mixture was stirred continuously. After the reaction was completed, the supernatant was removed, and the microspheres at the bottom were taken, washed, and dried to obtain an amino-modified chitosan and graphene oxide copolymer.

4. The nanofiltration membrane according to claim 3, characterized in that... The graphene oxide has a diameter of 0.2-2 μm and an oxygen content (W / W) greater than 50%.

5. The nanofiltration membrane according to claim 3, characterized in that... The crosslinking agent is at least one of hexafluorophosphate and ethylene glycol diglycidyl ether.

6. The nanofiltration membrane according to claim 3, characterized in that... Adjust the pH of the solution to between 10 and 11 using sodium hydroxide.

7. The nanofiltration membrane according to claim 1, characterized in that... The aqueous solution is obtained through the following steps: S1. Disperse 1-2g of nanocrystalline cellulose in 20-30ml of acetic acid, sonicate, and after the nanocrystalline cellulose is evenly dispersed, add 2-6g of acid anhydride and 0.2-0.6g of the first catalyst in sequence, and stir continuously for 30-40min. Wash and dry the product to obtain 3-4g of esterified modified nanocrystalline cellulose. S2. Weigh 4-6g of bentonite into a third container containing 50-60ml of glacial acetic acid, sonicate, and then slowly add 1-2g of dimercaptopropanol and 0.1-0.5g of the second catalyst while stirring continuously. After the reaction is complete, remove the supernatant, wash the product, and dry it to obtain 2-3g of mercapto-modified bentonite. S3. Add 0.4-0.5g of piperazine to the fourth container containing pure water, stir, and obtain a clear and transparent solution; S4. Take 0.02-0.03g of esterified nanocrystalline cellulose from S1 and 0.04-0.06g of mercapto-modified bentonite from S2 and add them to the clear and transparent solution in S3. Stir to obtain a clear and transparent aqueous solution.

8. The nanofiltration membrane according to claim 7, characterized in that... The nanocrystalline cellulose has a diameter of 30-50 nm.

9. The nanofiltration membrane according to claim 7, characterized in that... The acid anhydride is at least one of succinic anhydride, citric anhydride, or maleic anhydride.

10. The nanofiltration membrane according to claim 7, characterized in that... The first catalyst is at least one of dibutyltin dilaurate or platinum-diethylenetetramethyldisiloxane.

11. The nanofiltration membrane according to claim 4, characterized in that... The second catalyst is at least one of MoS2, benzoic acid, zinc chloride, and platinum-diethylenetetramethyldisiloxane.

12. The nanofiltration membrane according to claim 1, characterized in that... The oil phase solution is obtained through the following steps: A copolymer of 1,3,5-benzenetriacyl chloride and amino-modified chitosan and graphene oxide was added to an organic solvent and stirred to obtain an oil phase solution.

13. The nanofiltration membrane according to claim 1, characterized in that... The organic solvent is at least one of n-hexane and cyclohexane.

14. A method for preparing the nanofiltration membrane according to any one of claims 1 to 13, characterized in that... Includes the following steps: The base membrane is immersed in an aqueous solution, then removed and dried to obtain an intermediate membrane. The intermediate membrane is then immersed in an oil solution, then removed and dried to obtain a composite nanofiltration membrane.

Images