CN116272371A - Method for preparing reverse osmosis membrane with high boric acid rejection rate by utilizing ultraviolet light modification process - Google Patents

Abstract

The invention relates to a method for preparing a reverse osmosis membrane with a high boric acid rejection rate by an ultraviolet light modification process. The supporting membrane is soaked in an aqueous phase solution containing 2-sulfoethyl methacrylate additive and an ultraviolet photoinitiator; Immerse in the oil phase solution for interfacial polymerization reaction. During the process, place the film under ultraviolet light for irradiation; use a solution containing n-hexyl methacrylate to rinse the surface of the film, and then apply ultraviolet light irradiation; place the film at 70~ Heat treatment at 90°C to prepare a reverse osmosis membrane containing 2-sulfoethyl methacrylate ultraviolet polymerization reaction product and n-hexyl methacrylate chemically grafted. The H ₃ BO ₃ rejection rate of the reverse osmosis membrane prepared by this method is increased from 83.82% to 92.47%, and the NaCl rejection rate is increased from 98.89% to 99.19%. The preparation method of the invention is simple, efficient, easy to implement, and can greatly increase the boric acid rejection rate of the prepared membrane under the premise of ensuring water flux.

Description

A method for preparing reverse osmosis membrane with high boric acid rejection rate by using ultraviolet light modification process

technical field

The invention relates to a method for preparing a reverse osmosis membrane with a high boric acid rejection rate by using an ultraviolet light modification process, combining two processes of ultraviolet enhanced interfacial polymerization and ultraviolet grafting modification, respectively for the main part and the surface area of the separation layer of the reverse osmosis membrane Targeted optimization is carried out to improve the boric acid interception performance of the reverse osmosis membrane, which belongs to the field of composite reverse osmosis membrane preparation.

Background technique

Reverse osmosis membrane technology has been widely used in seawater desalination, wastewater/sewage treatment, food processing, drinking water purification and other fields due to its characteristics of stability and high efficiency, mild operating conditions and easy integration and scale-up. Seawater desalination is the most common application field of reverse osmosis membrane technology. Under normal circumstances, salt water cannot be directly used in human production and life. It is necessary to use appropriate desalination methods to turn salt water that cannot be directly used into fresh water that can be directly used. In recent years, a large number of researchers have devoted themselves to improving the water permeability coefficient and sodium chloride rejection rate of reverse osmosis membranes. For the membrane seawater desalination technology with reverse osmosis membrane as the core, in order to make the water quality of the desalinated water meet the regulations of my country and some other countries on the upper limit of boron content in drinking water and the water quality requirements of some crop irrigation water, reverse osmosis membrane More than 90% of boron in seawater needs to be removed. Therefore, it is of great significance to prepare reverse osmosis membranes with high salt rejection and high boric acid rejection. In seawater, boron mainly exists in the form of boric acid (H ₃ BO ₃ ). However, due to the weak hydrolysis ability and small molecular size of H ₃ BO ₃ , it is difficult for the common reverse osmosis membranes to pass through the electrostatic repulsion effect and steric potential. The effective interception of H ₃ BO ₃ is achieved by the resistance effect, which hinders the further popularization and application of reverse osmosis membrane technology.

At present, the common methods to improve the boric acid rejection rate of reverse osmosis membrane can be divided into two categories. One is to strengthen the compactness of the reverse osmosis membrane, thereby enhancing the transmembrane mass transfer resistance of boric acid molecules; the other is to reasonably regulate the interaction between boric acid molecules and the reverse osmosis membrane. Both of them can improve the H ₃ BO ₃ interception performance of the reverse osmosis membrane to a certain extent. Therefore, combining the above two methods is expected to improve the H ₃ BO ₃ interception performance of the reverse osmosis membrane more effectively. Studies have found that the main body of an ideal reverse osmosis membrane with high H ₃ BO ₃ rejection performance should not only have a dense structure, but also have a strong interaction with H ₃ BO ₃ to slow down the transfer of H ₃ BO ₃ in the membrane speed. At the same time, the ideal reverse osmosis membrane with high H ₃ BO ₃ rejection performance should have a non-polar or weakly polar surface to reduce the interaction between the membrane surface and H ₃ BO ₃ containing polar groups in the raw material solution and prevent H ₃ BO ₃ is enriched on the membrane surface. Li et al. used the "swelling-embedding-shrinking" strategy to embed 4-nitrobenzenesulfonyl chloride (NBS) containing sulfonic acid groups into the polyamide (PA) separation layer of the reverse osmosis membrane. First, the ethanol solution dissolved in NBS is poured on the surface of the reverse osmosis membrane. Ethanol has a strong affinity for the PA material, so it can swell the PA separation layer of the reverse osmosis membrane and increase the size of the PA chain gap in the separation layer. After entering the swollen separation layer, the ethanol gradually volatilized, and the PA chains shrank, and finally the NBS was fixed in the membrane separation layer. The embedding of NBS reduces the size of the PA chain gaps within the membrane separation layer. In addition, the sulfonic acid groups in the membrane can inhibit the rapid diffusion of H ₃ BO ₃ in the membrane through strong intermolecular interactions. Under the influence of the above two factors, after embedding NBS into the PA separation layer of the reverse osmosis membrane, the H ₃ BO ₃ rejection rate of the reverse osmosis membrane increased from 82.12% to 93.10%, and the NaCl rejection rate increased from 99.20% to 99.57%. (Li Y.,Wang S.,Song X.,Zhou Y.,Shen H.,Cao X.,Zhang P.,Gao C.,Highboron removal polyamide reverse osmosis membranes by swelling induced embedding of a sulfonyl molecular plug,Journal of Membrane Science [J], 2020, 597: 117716.). However, NBS containing a rigid benzene ring structure easily blocked the water transfer channels in the inner part of the membrane, so the water flux of the reverse osmosis membrane decreased from ∼33.8 L·m ⁻² ·h ⁻¹ to ∼16.9 L·m ⁻² ·h ^-1 (The raw material solution is an aqueous solution of 32000mg/L sodium chloride and 5mg/L boric acid, and the test pressure is 5.5MPa). Li et al. used a strategy similar to "swelling-embedding-shrinking" to embed capric acid molecules containing non-polar alkyl chains into the PA separation layer of reverse osmosis membranes to prepare reverse osmosis membranes with high H ₃ BO ₃ interception performance. permeable membrane. After non-polar capric acid molecules are embedded in the reverse osmosis membrane, the polarity of the membrane surface is significantly reduced, and the density of the separation layer is improved, thereby improving the H ₃ BO ₃ rejection rate of the reverse osmosis membrane (Li Yunhao, Li Aiai, Yang Binbin, Yu Junjie, Wang Kaizhen, Zhou Yong, Gao Congjie, High deboronation reverse osmosis membrane prepared by swelling and embedding fatty acid molecules, Chinese Journal of Chemical Industry [J], 2020, 71:1343-1351+1896). Under the optimal membrane process conditions, the H ₃ BO ₃ rejection rate of the prepared reverse osmosis membrane increased from 47.85% to 77.32%, and the NaCl rejection rate increased from 90.36% to 96.46%. However, the hydrophilicity of the membrane surface decreased due to the intercalation of nonpolar capric acid molecules. Therefore, the water flux of the reverse osmosis membrane is reduced from ~37.6L·m ^-2 ·h ^-1 to ~28.0L·m ^-2 ·h ^-1 (the raw material solution is 2000mg/L sodium chloride, 5mg/L boric acid aqueous solution, the test pressure is 1.55MPa). It is worth noting that swelling the PA separation layer of the reverse osmosis membrane may cause some PA materials with low molecular weight to dissolve from the membrane separation layer, which may cause irreparable damage to the membrane structure. In summary, it is difficult to increase the boric acid rejection rate of the reverse osmosis membrane without compromising the water flux of the reverse osmosis membrane. However, the present invention provides a method for preparing a reverse osmosis membrane with a high boric acid rejection rate combined with an ultraviolet light-enhanced interfacial polymerization process and an ultraviolet grafting modification process, which can achieve a high boric acid rejection rate while ensuring the water flux of the membrane. Substantially improved.

Contents of the invention

The invention provides a method for preparing a reverse osmosis membrane with a high boric acid rejection rate by using an ultraviolet light modification process. This method can optimize the interaction between the membrane material and boric acid molecules while improving the compactness of the reverse osmosis membrane. The method can improve the boric acid rejection rate and the sodium chloride rejection rate of the reverse osmosis membrane while ensuring the produced water flux of the prepared membrane. The present invention is realized through the following technical solutions as shown in Figure 2:

A method for preparing a reverse osmosis membrane with a high boric acid rejection rate using an ultraviolet light modification process of the present invention comprises the following process:

1) soaking the supporting membrane in an aqueous phase solution containing 2-sulfoethyl methacrylate additive and ultraviolet photoinitiator;

2) Immerse the membrane in the oil phase solution to carry out interfacial polymerization reaction, and irradiate the membrane under ultraviolet lamp during the process;

3) Rinse the film surface with a solution containing n-hexyl methacrylate, and then apply ultraviolet light irradiation;

4) heat-treating the membrane at 70-90° C. to prepare a reverse osmosis membrane containing 2-sulfoethyl methacrylate ultraviolet polymerization reaction product and n-hexyl methacrylate chemically grafted.

The mass fraction of 2-sulfoethyl methacrylate in the aqueous phase solution in the step 1) is 0.1%-1.5%.

The step 1) soaking the membrane in the aqueous solution for 10-90s.

The ultraviolet photoinitiator in the step 1) is 2,2-diethoxyacetophenone, and its mass fraction is 0.02%-0.5%.

The oil phase solution in the step 2) is a n-heptane solution containing trimesoyl chloride, and the mass fraction of trimesoyl chloride is 0.15%.

The step 2) immersing the membrane in the oil phase solution for 10-90s to carry out the interfacial polymerization reaction.

Said step 3) irradiating with ultraviolet light for 10-90s.

The mass fraction of n-hexyl methacrylate in the solution containing n-hexyl methacrylate in step 3) is 0.1%-8.0%.

The step 4) heat treatment for 3-10 minutes.

By adopting the above-mentioned technical scheme, the polysulfone ultrafiltration membrane is used as a substrate, and the reverse osmosis membrane is prepared through an interfacial polymerization process between an aqueous phase solution containing m-phenylenediamine and an n-heptane oil phase solution containing trimesoyl chloride. The aqueous phase solution used in the interfacial polymerization process includes 2-sulfoethyl methacrylate, m-phenylenediamine, (±)-camphor-10-sulfonic acid, triethylamine, sodium dodecylsulfonate and 2, 2-diethoxyacetophenone; the oil phase solution is n-heptane solution containing only 0.15% trimesoyl chloride in mass concentration. 2-sulfoethyl methacrylate (SMA) with ultraviolet light-induced polymerization activity is selected as the water phase additive. During the process of ultraviolet light-enhanced interfacial polymerization, it is difficult to diffuse into the oil phase by using SMA containing sulfonic acid groups. The characteristics of the deep part of the interfacial polymerization reaction zone successfully enriched the SMA polymerization product in the main part of the PA separation layer. This method not only improves the density of the main part of the separation layer, but also utilizes the strong intermolecular interaction force between the sulfonic acid group and H ₃ BO ₃ to strengthen the interaction between the main part of the separation layer and the H ₃ BO ₃ in the membrane, and slow down the H 3 BO 3 in the membrane. ₃ The transmission speed of BO ₃ in the membrane realizes the optimization of the main part of the PA separation layer.

After the interfacial polymerization reaction, add n-hexyl methacrylate (HMA) with ultraviolet light-induced polymerization activity to the n-hexane solvent that rinses the surface of the reverse osmosis membrane. The HMA is grafted onto the surface area of the PA separation layer. This method significantly weakens the polarity of the surface of the separation layer, inhibits the enrichment of H ₃ BO ₃ containing polar groups on the membrane surface, and realizes the optimization of the surface area of the PA separation layer.

Combined with the above strategies, a reverse osmosis membrane with optimized body and surface was prepared. The H ₃ BO ₃ rejection rate of the reverse osmosis membrane prepared by this method increased from 83.82% to 92.47%, and the NaCl rejection rate increased from 98.89% to 99.19%. . (The raw material solution is an aqueous solution containing 32000mg/L of sodium chloride and 5mg/L of boron, the operating pressure is 5.50MPa, and the test temperature is 25°C). A method for preparing a reverse osmosis membrane with a high boric acid rejection rate using an ultraviolet light modification process of the present invention can improve the boric acid rejection rate of the prepared membrane without damaging the reverse osmosis membrane product water flux and sodium chloride rejection rate . The invention has the advantages of simple operation, time-saving and high-efficiency, mild modification conditions, and no damage to the separation layer structure of the reverse osmosis membrane. In addition, the prepared reverse osmosis membrane with high boric acid rejection rate has the characteristics of high product water flux and high sodium chloride rejection rate. The invention is not only applicable to the preparation of the reverse osmosis membrane, but also applicable to the development of other separation membranes prepared based on the interface polymerization process and the graft modification process.

Description of drawings:

FIG. 1 is a scanning electron microscope image of the surface structure of the reverse osmosis membrane prepared in Example 4.

Fig. 2 is a schematic diagram of the membrane-making process of the reverse osmosis membrane with high boric acid rejection rate in the present invention.

Detailed ways

The present invention is further described in detail below in conjunction with specific examples, with the polysulfone ultrafiltration membrane as the substrate, through the interface between the aqueous phase solution containing m-phenylenediamine and the n-heptane oil phase solution containing trimesoyl chloride Polymerization process to prepare reverse osmosis membrane. The aqueous phase solution used in the interfacial polymerization process includes 2-sulfoethyl methacrylate, m-phenylenediamine, (±)-camphor-10-sulfonic acid, triethylamine, sodium dodecylsulfonate and 2, 2-diethoxyacetophenone; the oil phase solution is n-heptane solution containing only 0.15% trimesoyl chloride in mass concentration. 2-sulfoethyl methacrylate (SMA) with ultraviolet light-induced polymerization activity is selected as the water phase additive. During the process of ultraviolet light-enhanced interfacial polymerization, it is difficult to diffuse into the oil phase by using SMA containing sulfonic acid groups. The characteristics of the deep part of the interfacial polymerization reaction zone enrich the SMA polymerization product in the main part of the PA separation layer; after that, through the ultraviolet grafting modification process, HMA is chemically grafted to the surface of the reverse osmosis membrane separation layer, thereby weakening the membrane surface The polarity of the membrane surface reduces the attraction of H ₃ BO ₃ on the surface of the membrane to optimize the surface area of the separation layer; it is expected that the main part of the separation layer of the reverse osmosis membrane and the The surface area is optimized separately to improve the H ₃ BO ₃ interception performance of the reverse osmosis membrane.

Example 1

1) The preparation contains 0.20% 2-sulfoethyl methacrylate, 3.0% m-phenylenediamine, 3.9% (±)-camphor-10-sulfonic acid, 1.9% triethylamine, 0.15% dodecane An aqueous phase solution of sodium sulfonate and 0.02% 2,2-diethoxyacetophenone, soak the support membrane in the aqueous phase solution for 10 seconds, remove the aqueous phase solution, and dry;

2) Prepare a n-heptane oil phase solution containing a mass concentration of 0.15% trimesoyl chloride, then immerse the film obtained in step 1) in the oil phase solution for 10s to carry out interfacial polymerization reaction, during which the film is placed under a UV lamp irradiation;

3) Prepare a n-hexane solution containing 0.1% n-hexyl methacrylate in mass concentration, then use 0.1 wt% n-hexyl methacrylate n-hexane solution to rinse the membrane surface, and then apply 10s of ultraviolet light irradiation;

4) heat-treat the membrane obtained in step 3) at 70° C. for 3 minutes to prepare a composite reverse osmosis membrane with high boric acid rejection.

Tested at 5.50MPa and 25°C by using 5mg/L boric acid molecules and 32000mg/L sodium chloride aqueous solution, the product water flux of the prepared reverse osmosis membrane was lower than 44.69L/(m ² ·h), chlorine The sodium chloride rejection rate exceeds 98.89%, and the boric acid rejection rate exceeds 83.82%.

Example 2

1) The preparation contains 1.5% 2-sulfoethyl methacrylate, 3.0% m-phenylenediamine, 3.9% (±)-camphor-10-sulfonic acid, 1.9% triethylamine, 0.15% dodecane An aqueous phase solution of sodium sulfonate and 0.5% 2,2-diethoxyacetophenone, soak the support membrane in the aqueous phase solution for 90 seconds, remove the aqueous phase solution, and dry;

2) Prepare an n-heptane oil phase solution containing a mass concentration of 0.15% trimesoyl chloride, then immerse the film obtained in step 1) in the oil phase solution for 90 seconds to carry out interfacial polymerization, during which the film is placed under a UV lamp irradiation;

3) Prepare a n-hexane solution containing 8% n-hexyl methacrylate in mass concentration, then use 8wt% n-hexyl methacrylate n-hexane solution to rinse the film surface, and then apply 90s of ultraviolet light irradiation;

4) heat-treat the membrane obtained in step 3) at 90° C. for 10 minutes to prepare a composite reverse osmosis membrane with high boric acid rejection.

Tested at 5.50MPa and 25°C by using 5mg/L boric acid molecules and 32000mg/L sodium chloride aqueous solution, the product water flux of the prepared reverse osmosis membrane was lower than 40.95L/(m ² ·h), chlorine The sodium chloride rejection rate is lower than 99.19%, and the boric acid rejection rate is lower than 92.47%.

Example 3

1) Preparation containing 0.10% 2-sulfoethyl methacrylate, 3.0% m-phenylenediamine, 3.9% (±)-camphor-10-sulfonic acid, 1.9% triethylamine, 0.15% dodecane An aqueous phase solution of sodium sulfonate and 0.04% 2,2-diethoxyacetophenone, soak the support membrane in the aqueous phase solution for 60 seconds, remove the aqueous phase solution, and dry;

2) Prepare a n-heptane oil phase solution containing a mass concentration of 0.15% trimesoyl chloride, then immerse the film obtained in step 1) in the oil phase solution for 60 seconds to carry out interfacial polymerization reaction, during which the film is placed under a UV lamp irradiation;

3) Prepare a n-hexane solution containing 6% n-hexyl methacrylate in mass concentration, then use 6wt% n-hexyl methacrylate n-hexane solution to rinse the film surface, and then apply 60s of ultraviolet light irradiation;

4) heat-treat the membrane obtained in step 3) at 80° C. for 5 minutes to prepare a composite reverse osmosis membrane with high boric acid rejection.

At 5.50MPa and 25°C, using 5mg/L boric acid molecules and 32000mg/L sodium chloride aqueous solution to test, the product water flux of the prepared reverse osmosis membrane is more than 38.64L/(m ² ·h), chlorination The sodium rejection rate exceeds 98.89%, and the boric acid rejection rate exceeds 83.82%.

Example 4

1) The preparation contains 0.20% 2-sulfoethyl methacrylate, 3.0% m-phenylenediamine, 3.9% (±)-camphor-10-sulfonic acid, 1.9% triethylamine, 0.15% dodecane An aqueous phase solution of sodium sulfonate and 0.02% 2,2-diethoxyacetophenone; soak the support membrane in the aqueous phase solution for 60 seconds, remove the aqueous phase solution, and dry;

2) Prepare a n-heptane oil phase solution containing a mass concentration of 0.15% trimesoyl chloride, then immerse the film obtained in step 1) in the oil phase solution for 60 seconds to carry out interfacial polymerization reaction, during which the film is placed under a UV lamp irradiation;

3) Prepare a n-hexane solution containing 6% n-hexyl methacrylate in mass concentration, then use 6wt% n-hexyl methacrylate n-hexane solution to rinse the film surface, and then apply 60s of ultraviolet light irradiation;

4) heat-treat the membrane obtained in step 3) at 80° C. for 5 minutes to prepare a composite reverse osmosis membrane with high boric acid rejection. The electron microscope pictures of the prepared film surface are shown in Fig. 1 .

Tested at 5.50MPa and 25°C by using 5mg/L boric acid molecules and 32000mg/L sodium chloride aqueous solution, the product water flux, sodium chloride rejection rate and boric acid rejection rate of the prepared reverse osmosis membrane were respectively 40.95 L/(m ² ·h), 99.19% and 92.47%.

comparative example

Li et al. (Li Y., Wang S., Song X., Zhou Y., Shen H., Cao X., Zhang P., Gao C., High boron removal polyamide reverse osmosis membranes by swelling induced embedding of a sulfonyl molecular plug, Journal of Membrane Science[J],2020,597:117716.) The prepared reverse osmosis membrane was tested at 5.50MPa and 25°C with an aqueous sodium chloride solution containing 5mg/L of boric acid molecules and 32000mg/L, and obtained The product water flux, sodium chloride rejection rate and boric acid rejection rate of the prepared reverse osmosis membrane were 16.90L/(m ² ·h), 99.57% and 93.10%, respectively.

Embodiments 1 to 4 adopt the method of the present invention to prepare a reverse osmosis membrane whose main body and surface are optimized, and under the premise of a small loss of water flux, the retention rate of sodium chloride and the retention rate of boric acid are all improved; wherein The optimum concentration of additive is 0.2wt%, and the optimum concentration of n-hexyl methacrylate in n-hexane solution is 6.0wt%, as shown in Example 4, the produced water flux of the prepared reverse osmosis membrane under this condition, The rejection rates of sodium chloride and boric acid were 40.95L/(m ² ·h), 99.19% and 92.47%, respectively. Compared with the comparative example, both have higher sodium chloride rejection rate and boric acid rejection rate, but Experimental Example 4 has more excellent water flux. In summary, the composite reverse osmosis membrane with high boric acid rejection rate prepared by the combination of ultraviolet light-enhanced interfacial polymerization process and ultraviolet grafting modification process has more excellent water flux, sodium chloride rejection rate and boric acid rejection rate.

The invention relates to a method for preparing a reverse osmosis membrane with a high boric acid rejection rate by an ultraviolet light modification process, which combines two processes of ultraviolet enhanced interfacial polymerization and ultraviolet graft modification to separately carry out the main part and the surface area of the separation layer of the reverse osmosis membrane Targeted optimization; preparation of an aqueous phase solution containing both 2-sulfoethyl methacrylate additive and UV photoinitiator; soaking the support membrane in the above aqueous phase solution to fully infiltrate the support membrane; remove the membrane surface After the excess water phase solution, soak the membrane in the oil phase solution for interfacial polymerization, and apply ultraviolet light to the membrane surface; remove the excess oil phase solution on the membrane surface, and rinse the membrane with a solution containing n-hexyl methacrylate After rinsing, UV radiation was applied to the membrane surface. After the membrane is dried, a reverse osmosis membrane with high boric acid rejection is obtained. The preparation method of the invention is simple, efficient, easy to implement, and can greatly improve the boric acid rejection rate of the prepared membrane under the premise of ensuring water flux.

A method for preparing a reverse osmosis membrane with a high boric acid rejection rate disclosed and proposed by the present invention can be realized by those skilled in the art by referring to the content of this article and appropriately changing the conditions and routes. Although the method and preparation of the present invention The technology has been described through preferred implementation examples, and it is obvious that those skilled in the art can modify or recombine the methods and technical routes described herein without departing from the content, spirit and scope of the present invention to realize the final preparation technology. In particular, it should be pointed out that all similar substitutions and modifications will be obvious to those skilled in the art, and they are all considered to be included in the spirit, scope and content of the present invention.

Claims (9)

1. The method for preparing the reverse osmosis membrane with high boric acid rejection rate by utilizing the ultraviolet light modification process is characterized by comprising the following steps of:

1) Immersing the support film in an aqueous solution containing a 2-sulfoethyl methacrylate additive and an ultraviolet initiator;

2) Soaking the film in the oil phase solution for interfacial polymerization reaction, and placing the film under an ultraviolet lamp for irradiation in the process;

3) Rinsing the film surface with a solution containing n-hexyl methacrylate, and then applying ultraviolet light irradiation;

4) And (3) placing the membrane in a temperature of 70-90 ℃ for heat treatment to prepare a reverse osmosis membrane containing 2-sulfoethyl methacrylate ultraviolet polymerization reaction products and n-hexyl methacrylate chemical grafting.

2. The method according to claim 1, wherein the mass fraction of 2-sulfoethyl methacrylate in the aqueous phase solution of step 1) is 0.1% to 1.5%.

3. The method of claim 1, wherein the step 1) is immersing the membrane in the aqueous solution for 10 to 90 seconds.

4. The method according to claim 1, wherein the ultraviolet initiator in the step 1) is 2, 2-diethoxyacetophenone, and the mass fraction thereof is 0.02% -0.5%.

5. The method according to claim 1, wherein the oil phase solution in the step 2) is an n-heptane solution containing trimesic acid chloride, and the mass fraction of trimesic acid chloride is 0.15%.

6. The method of claim 1, wherein the step 2) is performed by immersing the membrane in the oil phase solution for 10 to 90 seconds to perform interfacial polymerization.

7. The method of claim 1, wherein said step 3) is ultraviolet light irradiation for 10 to 90 seconds.

8. The method according to claim 1, wherein the mass fraction of n-hexyl methacrylate in the solution containing n-hexyl methacrylate in step 3) is 0.1% to 8.0%.

9. The method according to claim 1, wherein the step 4) is a heat treatment for 3 to 10 minutes.

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