Preparation method of reverse osmosis membrane for portable lightweight PEM water electrolysis oxygen production equipment

Abstract

The invention relates to a preparation method of a reverse osmosis membrane for portable lightweight PEM water electrolysis oxygen production equipment, and belongs to the technical field of reverse osmosis membranes. The ultra-thin reverse osmosis membrane obtained by doping the modified multi-walled carbon nanotubes has high water flux and can meet the water flow requirement of an oxygen generator; the pure water conductivity of the prepared reverse osmosis membrane is lower than 5 [mu] S / cm, and the requirement of a PEM oxygenerator on pure water can be met; in addition, trace metal ions in pure water prepared by the reverse osmosis membrane are in ppb level, damage to a membrane electrode of a PEM oxygen generator is small, and the service life of the oxygen generator can be effectively prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of reverse osmosis membranes and relates to a method for preparing a reverse osmosis membrane used in a portable lightweight PEM water electrolysis oxygen production device. Background Art

[0002] PEM electrolysis of water to produce hydrogen has high requirements for water, and there is also a problem of water consumption during use. Therefore, by adding a pure water filter membrane to the oxygen production equipment, users can get water nearby to produce oxygen; it can truly achieve portability and lightweight, and at the same time eliminate the anxiety of not being able to produce oxygen after the pure water is consumed. The core of pure water filtration equipment is the pure water filter membrane, and reverse osmosis membrane technology has developed rapidly in recent decades and has been widely used in seawater and brackish water desalination, pure water and ultrapure water preparation, and wastewater treatment.

[0003] Therefore, it is necessary to prepare a reverse osmosis membrane that can be used in PEM water electrolysis oxygen production equipment. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a reverse osmosis membrane used in a portable lightweight PEM water electrolysis oxygen production device. The reverse osmosis membrane prepared by the present invention has high water flux, low pure water conductivity and high NaCl retention rate.

[0005] The purpose of the present invention can be achieved through the following technical solutions: A method for preparing a reverse osmosis membrane used in a portable lightweight PEM water electrolysis oxygen production device comprises the following steps: S1, adding multi-walled carbon nanotubes to a mixed acid solution of sulfuric acid and nitric acid, heating to 70-80°C and refluxing for 5-6 hours, washing until the solution pH is 6.5-7.5, and drying to obtain acidified multi-walled carbon nanotubes; S2. Under nitrogen protection, polylysine and deionized water are stirred evenly to form a polylysine solution, and polyvinyl alcohol and acidified multi-walled carbon nanotubes are added and mixed evenly, and stirred at room temperature for 6 to 9 hours. After the stirring is completed, the mixture is naturally cooled to room temperature, and the product is collected for vacuum distillation. After drying at 90°C for 8 hours, modified multi-walled carbon nanotubes are obtained, wherein the mass ratio of the polylysine solution, polyvinyl alcohol and acidified multi-walled carbon nanotubes is 60:10:(10-15); S3, dissolving m-phenylenediamine monomer in ultrapure water at room temperature to prepare an aqueous solution with a concentration of 6-12wt%, and uniformly dispersing the modified multi-walled carbon nanotubes with the aqueous solution to obtain an MPD dispersion, first soaking the polysulfone ultrafiltration bottom membrane in pure water for 20 hours, blowing the surface pure water with nitrogen, and then laying the polysulfone ultrafiltration bottom membrane on a glass plate, and then immersing it in the MPD dispersion, soaking for 10-15 minutes and then taking it out, removing the excess water phase on the surface with nitrogen until there are no obvious droplets, and obtaining a polysulfone support membrane; S4, dissolving trimesoyl chloride monomer in n-hexane at room temperature to prepare an organic phase solution, and then immersing the polysulfone support membrane obtained in step S3 in the organic phase solution, forming a composite layer on the surface of the polysulfone support membrane through interfacial polymerization reaction, taking out after 1 to 3 minutes, and drying in air to obtain a primary ecological composite membrane; S5. After heat-treating the nascent composite membrane, wash the membrane surface with deionized water for 3 to 5 times to remove unreacted monomers and solvents, thereby obtaining a reverse osmosis membrane used in the portable lightweight PEM water electrolysis oxygen production equipment.

[0006] As a preferred technical solution of the present invention, in step S1, the volume ratio of concentrated sulfuric acid to concentrated nitric acid in the mixed acid solution is 3:1.

[0007] As a preferred technical solution of the present invention, in step S1, the dosage ratio of the multi-walled carbon nanotubes to the mixed acid solution is 0.3-0.5 mg / mL.

[0008] As a preferred technical solution of the present invention, in step S1, the drying temperature is 90-95°C and the drying time is 8-12 hours.

[0009] As a preferred technical solution of the present invention, in step S2, the mass fraction of the polylysine solution is 10-15%.

[0010] As a preferred technical solution of the present invention, in step S3, the solid-liquid ratio of the modified multi-walled carbon nanotubes to the aqueous phase solution in the MPD dispersion is (1-5): 100 g / mL.

[0011] As a preferred technical solution of the present invention, in step S4, the concentration of the organic phase solution is 0.1-0.5wt%.

[0012] As a preferred technical solution of the present invention, in step S5, the temperature of the heat treatment is 65-75°C and the time is 20-30 minutes.

[0013] In the present invention, acidified multi-walled carbon nanotubes are obtained by acidifying multi-walled carbon nanotubes, and metaphenylenediamine and trimesoyl chloride are polymerized to form a polyamide active layer, which can be used as a functional nanofiller and composited with polyamide to form a reverse osmosis membrane with excellent separation performance. After the acidification treatment, the surface of the carbon nanotubes is provided with carboxyl functional groups, which enhances the interface interaction between the carbon nanotubes and the polymer matrix, and is conducive to improving the separation performance of the membrane.

[0014] After the acid treatment, the carbon nanotubes are modified by polylysine and polyvinyl alcohol. The acid treatment before the modification can remove impurities on the surface of the carbon nanotubes and increase the oxygen-containing functional groups (such as carboxyl, hydroxyl, etc.) on the surface, thereby improving their hydrophilicity and chemical reaction activity. This treatment makes it easier for polylysine to interact with carbon nanotubes to form a more stable modified product. In addition, the acid treatment can also improve the dispersibility of carbon nanotubes, further broadening their application range in various fields.

[0015] At the same time, polyvinyl alcohol has good water solubility and film-forming properties. It can form a uniform coating on the surface of acidified multi-walled carbon nanotubes, thereby effectively preventing the agglomeration and precipitation of acidified multi-walled carbon nanotubes. The addition of polylysine further enhances the interaction between carbon nanotubes and polyvinyl alcohol, so that the modified carbon nanotubes can be more evenly dispersed in the reverse osmosis membrane. And in order to avoid the weakening of the bonding force between polyamide membranes due to the high hygroscopicity and poor water resistance of polyvinyl alcohol, the material strength decreases. Therefore, the strength of the material can be increased by acidifying multi-walled carbon nanotubes. Carbon nanotubes themselves have the characteristics of high strength and high toughness. Adding them to the reverse osmosis membrane can significantly improve the mechanical strength of the membrane, which helps the reverse osmosis membrane maintain stable separation performance and structural integrity during long-term use, which enables the membrane to better intercept impurities and ions in the water while ensuring sufficient water flux.

[0016] Adding modified multi-walled carbon nanotubes during the polymerization of m-phenylenediamine and trimesoyl chloride to form a polyamide active layer can improve its compatibility with the polymer matrix and reduce the risk of chemical corrosion and degradation, which helps to extend the service life of the membrane and maintain stable separation performance.

[0017] And because modified multi-walled carbon nanotubes can give the membrane surface more hydrophilic groups, thereby improving the hydrophilicity of the membrane, which helps to reduce the pollution and scaling of the membrane surface and improve the separation efficiency and stability of the membrane. Because modified multi-walled carbon nanotubes can improve the hydrophilicity and chemical stability of the membrane surface, they can enhance the anti-fouling performance of the membrane.

[0018] Beneficial effects of the present invention: The ultra-thin reverse osmosis membrane obtained by doping modified multi-walled carbon nanotubes in the present invention has a high water flux and can meet the water flow requirement of the oxygen generator; the pure water conductivity of the prepared reverse osmosis membrane is lower than 5μS / cm, which can meet the pure water requirement of the PEM oxygen generator; and the trace metal ions in the pure water prepared by the reverse osmosis membrane are at the ppb level, which has little damage to the membrane electrode of the PEM oxygen generator and can effectively improve the service life of the oxygen generator. DETAILED DESCRIPTION

[0019] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0020] In the following examples and comparative examples: Multi-walled carbon nanotubes: purchased from Zhejiang Yamei Nanotechnology Co., Ltd.; polylysine: purchased from Shanghai Yuanye Biotechnology Co., Ltd.; polyvinyl alcohol: purchased from Sichuan Lai Te Ju Xin Pharmaceutical Excipients Co., Ltd.; meta-phenylenediamine: purchased from Shandong Yu Kang Chemical Co., Ltd.; trimesoyl chloride: purchased from Hubei Jiahui Xingcheng Biotechnology Co., Ltd.

[0021] Example 1 S1. Add multi-walled carbon nanotubes to a mixed acid solution of sulfuric acid and nitric acid, heat to 70°C and reflux for 5 hours, wash until the solution pH is 6.5, and dry at 90°C for 8 hours to obtain acidified multi-walled carbon nanotubes, wherein the volume ratio of concentrated sulfuric acid to concentrated nitric acid in the mixed acid solution is 3:1, and the dosage ratio of the multi-walled carbon nanotubes to the mixed acid solution is 0.3 mg / mL; S2. Under nitrogen protection, polylysine and deionized water were stirred evenly to form a polylysine solution with a mass fraction of 10%, and polyvinyl alcohol and acidified multi-walled carbon nanotubes were added and mixed evenly, and stirred at room temperature for 6 hours. After the stirring was completed, the mixture was naturally cooled to room temperature, and the product was collected for vacuum distillation. After drying at 90°C for 8 hours, modified multi-walled carbon nanotubes were obtained, wherein the mass ratio of the polylysine solution, polyvinyl alcohol and acidified multi-walled carbon nanotubes was 60:10:10; S3, dissolving m-phenylenediamine monomer in ultrapure water at room temperature to prepare an aqueous solution with a concentration of 6wt%, and uniformly dispersing the modified multi-walled carbon nanotubes with the aqueous solution to obtain an MPD dispersion, first soaking the polysulfone ultrafiltration bottom membrane in pure water for 20 hours, blowing the surface pure water with nitrogen, then laying the polysulfone ultrafiltration bottom membrane on a glass plate, and then immersing it in the MPD dispersion, taking it out after soaking for 10 minutes, and removing the excess water phase on the surface with nitrogen until there are no obvious droplets, to obtain a polysulfone support membrane, wherein the solid-liquid ratio of the modified multi-walled carbon nanotubes to the aqueous solution in the MPD dispersion is 1:100 g / mL; S4, dissolving trimesoyl chloride monomer in n-hexane at room temperature to prepare an organic phase solution with a concentration of 0.1wt%, and then immersing the polysulfone support membrane obtained in step S3 in the organic phase solution, forming a composite layer on the surface of the polysulfone support membrane through interfacial polymerization reaction, taking out after 1 minute, and drying in air to obtain a primary ecological composite membrane; S5. Heat-treat the nascent composite membrane at 65° C. for 20 min, wash the membrane surface with deionized water three times to remove unreacted monomers and solvent, and obtain a reverse osmosis membrane used in the portable lightweight PEM water electrolysis oxygen production equipment.

[0022] Example 2 S1. Add multi-walled carbon nanotubes to a mixed acid solution of sulfuric acid and nitric acid, heat to 75°C and reflux for 5.5h, wash until the solution pH is 7, and dry at 93°C for 10h to obtain acidified multi-walled carbon nanotubes, wherein the volume ratio of concentrated sulfuric acid to concentrated nitric acid in the mixed acid solution is 3:1, and the dosage ratio of the multi-walled carbon nanotubes to the mixed acid solution is 0.4mg / mL; S2. Under nitrogen protection, polylysine and deionized water were stirred evenly to form a polylysine solution with a mass fraction of 13%, and polyvinyl alcohol and acidified multi-walled carbon nanotubes were added and mixed evenly, and stirred at room temperature for 7 hours. After the stirring was completed, the mixture was naturally cooled to room temperature, and the product was collected for vacuum distillation. After drying at 90°C for 8 hours, modified multi-walled carbon nanotubes were obtained, wherein the mass ratio of the polylysine solution, polyvinyl alcohol and acidified multi-walled carbon nanotubes was 60:10:13; S3, dissolving m-phenylenediamine monomer in ultrapure water at room temperature to prepare an aqueous solution with a concentration of 8wt%, and uniformly dispersing the modified multi-walled carbon nanotubes with the aqueous solution to obtain an MPD dispersion, first soaking the polysulfone ultrafiltration bottom membrane in pure water for 20 hours, blowing the surface pure water with nitrogen, then laying the polysulfone ultrafiltration bottom membrane on a glass plate, and then immersing it in the MPD dispersion, taking it out after soaking for 13 minutes, and removing the excess water phase on the surface with nitrogen until there are no obvious droplets, to obtain a polysulfone support membrane, wherein the solid-liquid ratio of the modified multi-walled carbon nanotubes to the aqueous solution in the MPD dispersion is 3:100 g / mL; S4, dissolving trimesoyl chloride monomer in n-hexane at room temperature to prepare an organic phase solution with a concentration of 0.3wt%, and then immersing the polysulfone support membrane obtained in step S3 in the organic phase solution, forming a composite layer on the surface of the polysulfone support membrane through interfacial polymerization reaction, taking out after 2 minutes, and drying in air to obtain a primary ecological composite membrane; S5. Heat-treating the nascent composite membrane at 70° C. for 25 min, washing the membrane surface with deionized water 4 times to remove unreacted monomers and solvent, and obtaining a reverse osmosis membrane used in the portable lightweight PEM water electrolysis oxygen production equipment.

[0023] Example 3 S1. Add multi-walled carbon nanotubes to a mixed acid solution of sulfuric acid and nitric acid, heat to 80°C and reflux for 6 hours, wash until the solution pH is 7.5, and dry at 95°C for 12 hours to obtain acidified multi-walled carbon nanotubes, wherein the volume ratio of concentrated sulfuric acid to concentrated nitric acid in the mixed acid solution is 3:1, and the dosage ratio of the multi-walled carbon nanotubes to the mixed acid solution is 0.5 mg / mL; S2. Under nitrogen protection, polylysine and deionized water were stirred evenly to form a polylysine solution with a mass fraction of 15%, and polyvinyl alcohol and acidified multi-walled carbon nanotubes were added and mixed evenly, and stirred at room temperature for 9 hours. After the stirring was completed, the mixture was naturally cooled to room temperature, and the product was collected for vacuum distillation. After drying at 90°C for 8 hours, modified multi-walled carbon nanotubes were obtained, wherein the mass ratio of the polylysine solution, polyvinyl alcohol and acidified multi-walled carbon nanotubes was 60:10:15; S3, dissolving m-phenylenediamine monomer in ultrapure water at room temperature to prepare an aqueous solution with a concentration of 12wt%, and uniformly dispersing the modified multi-walled carbon nanotubes with the aqueous solution to obtain an MPD dispersion, first soaking the polysulfone ultrafiltration bottom membrane in pure water for 20 hours, blowing the surface pure water with nitrogen, then laying the polysulfone ultrafiltration bottom membrane on a glass plate, and then immersing it in the MPD dispersion, taking it out after soaking for 10-15 minutes, and removing the excess water phase on the surface with nitrogen until there are no obvious droplets, to obtain a polysulfone support membrane, wherein the solid-liquid ratio of the modified multi-walled carbon nanotubes to the aqueous solution in the MPD dispersion is 1:100 g / mL; S4, dissolving trimesoyl chloride monomer in n-hexane at room temperature to prepare an organic phase solution with a concentration of 0.5wt%, and then immersing the polysulfone support membrane obtained in step S3 in the organic phase solution, forming a composite layer on the surface of the polysulfone support membrane through interfacial polymerization reaction, taking out after 3 minutes, and drying in air to obtain a primary ecological composite membrane; S5. Heat-treating the nascent composite membrane at 75° C. for 30 min, washing the membrane surface with deionized water 5 times to remove unreacted monomers and solvent, and obtaining a reverse osmosis membrane used in the portable lightweight PEM water electrolysis oxygen production equipment.

[0024] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the multi-walled carbon nanotubes in Comparative Example 1 are not subjected to acidification treatment, and the other operations are the same.

[0025] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the step S2 is not performed in Comparative Example 2, and the other operations are the same.

[0026] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the multi-walled carbon nanotubes in Comparative Example 3 are not processed through steps S1 and S2, and the other operations are the same.

[0027] Performance Testing: 1. Water permeation flux and retention rate: Prepare a sodium chloride solution with a concentration of 2 g / L, and test for 1 h after pre-pressing for 1 h at a pressure of 1.55 MPa and a flow rate of 3 L / min. Record the conductivity and volume of the filtrate, and calculate the water permeation flux and retention rate according to formula (1) and formula (2), respectively.

[0028] Formula (1): J / Vp = At, where J represents water permeation flux, in units of L·m -2 ·h -1 ; Vp is the volume passed, unit is L; A is the effective area of ​​the membrane, unit is m 2 ; Formula (2): R = (1-Cp / Cf) × 100%, R is the apparent retention rate of salt ions, %; Cp represents the salt ion concentration in the permeate, mg / L; Cf represents the salt ion concentration in the raw material solution, mg / L; 2. Test the contact angle of the reverse osmosis membrane using a water contact angle tester; 3. Test the conductivity of pure water using a conductivity tester; The test results are shown in the following table:

[0029] According to the above data, the reverse osmosis membrane prepared by the present invention has high water flux, low pure water conductivity and high NaCl retention rate.

[0030] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a reverse osmosis membrane used in a portable lightweight PEM water electrolysis oxygen production device, characterized in that: The following steps are involved: S1, adding multi-walled carbon nanotubes to a mixed acid solution of sulfuric acid and nitric acid, heating to 70-80°C and refluxing for 5-6 hours, washing until the solution pH is 6.5-7.5, and drying to obtain acidified multi-walled carbon nanotubes; S2. Under nitrogen protection, polylysine and deionized water are stirred evenly to form a polylysine solution, and polyvinyl alcohol and acidified multi-walled carbon nanotubes are added and mixed evenly, and stirred at room temperature for 6 to 9 hours. After the stirring is completed, the mixture is naturally cooled to room temperature, and the product is collected for vacuum distillation. After drying at 90°C for 8 hours, modified multi-walled carbon nanotubes are obtained, wherein the mass ratio of the polylysine solution, polyvinyl alcohol and acidified multi-walled carbon nanotubes is 60:10:(10-15); S3, dissolving m-phenylenediamine monomer in ultrapure water at room temperature to prepare an aqueous solution with a concentration of 6-12wt%, and uniformly dispersing the modified multi-walled carbon nanotubes with the aqueous solution to obtain an MPD dispersion, first soaking the polysulfone ultrafiltration bottom membrane in pure water for 20 hours, blowing the surface pure water with nitrogen, and then laying the polysulfone ultrafiltration bottom membrane on a glass plate, and then immersing it in the MPD dispersion, soaking for 10-15 minutes and then taking it out, removing the excess water phase on the surface with nitrogen until there are no obvious droplets, and obtaining a polysulfone support membrane; S4, dissolving trimesoyl chloride monomer in n-hexane at room temperature to prepare an organic phase solution, and then immersing the polysulfone support membrane obtained in step S3 in the organic phase solution, forming a composite layer on the surface of the polysulfone support membrane through interfacial polymerization reaction, taking out after 1 to 3 minutes, and drying in air to obtain a primary ecological composite membrane; S5. After heat-treating the nascent composite membrane, wash the membrane surface with deionized water for 3 to 5 times to remove unreacted monomers and solvents, thereby obtaining a reverse osmosis membrane used in the portable lightweight PEM water electrolysis oxygen production equipment.

2. The method for preparing a reverse osmosis membrane used in a portable lightweight PEM water electrolysis oxygen production device according to claim 1, characterized in that: In step S1, the volume ratio of concentrated sulfuric acid to concentrated nitric acid in the mixed acid solution is 3:

1.

3. The method for preparing a reverse osmosis membrane used in a portable lightweight PEM water electrolysis oxygen production device according to claim 1, characterized in that: In step S1, the dosage ratio of the multi-walled carbon nanotubes to the mixed acid solution is 0.3-0.5 mg / mL.

4. The method for preparing a reverse osmosis membrane used in a portable lightweight PEM water electrolysis oxygen production device according to claim 1, characterized in that: In step S1, the drying temperature is 90-95° C. and the drying time is 8-12 hours.

5. The method for preparing a reverse osmosis membrane used in a portable lightweight PEM water electrolysis oxygen production device according to claim 1, characterized in that: In step S2, the mass fraction of the polylysine solution is 10-15%.

6. The method for preparing a reverse osmosis membrane used in a portable lightweight PEM water electrolysis oxygen production device according to claim 1, characterized in that: In step S3, the solid-liquid ratio of the acidified multi-walled carbon nanotubes to the aqueous phase solution in the MPD dispersion is (1-5): 100 g / mL.

7. The method for preparing a reverse osmosis membrane used in a portable lightweight PEM water electrolysis oxygen production device according to claim 1, characterized in that: In step S4, the concentration of the organic phase solution is 0.1-0.5 wt %.

8. The method for preparing a reverse osmosis membrane used in a portable lightweight PEM water electrolysis oxygen production device according to claim 1, characterized in that: In step S5, the heat treatment temperature is 65-75° C. and the time is 20-30 min.

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