Preparation method of seawater desalination membrane

Abstract

The invention belongs to the field of separation membranes, and particularly relates to a preparation method of a seawater desalination membrane, which comprises the following steps: a) providing a base membrane; b) coating the front surface of the base membrane with an ionic liquid containing a polyamine monomer, and then drying until the surface of the base membrane is dry; c) coating the front surface of the surface-dried base membrane with an ionic liquid containing a multi-element acyl chloride monomer, and then carrying out drying treatment to obtain a nascent state polyamide separation membrane; d) sequentially soaking the nascent state polyamide separation membrane in treating fluid containing m-phenylenediamine and sodium pyrosulfite at high temperature; and e) sequentially washing the separation membrane treated in the step d) with water and soaking the separation membrane in a glycerol aqueous solution, then coating the front surface of the separation membrane with a polyvinyl alcohol solution, and drying to obtain the seawater desalination membrane.The seawater desalination membrane prepared by the method has good initial performance and stability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of separation membrane, and particularly relates to a preparation method of a seawater desalination membrane. BACKGROUND

[0002] The seawater desalination membrane is generally composed of a non-woven fabric layer, a porous support layer and a separation layer. The porous support layer currently used more is formed on the surface of the non-woven fabric layer by phase inversion of polysulfone / DMF, and the separation layer is formed on the porous support layer by interfacial polymerization of polyamine monomers and polyacyl chloride monomers. The separation performance of the seawater desalination membrane is mainly determined by the structure (pore size, porosity, thickness, roughness, surface charge and hydrophilicity, etc.) and the chemical properties (functional groups, bond energy, crosslinking degree, etc.) of the separation layer, so that the separation performance of the seawater desalination membrane can be regulated by controlling the interfacial polymerization process of the polyamine monomers and the polyacyl chloride monomers.

[0003] The seawater desalination membrane is a product mainly used in high-salt and high-pressure environment, and has high requirements for the separation performance and long-term stability of the membrane sheet. However, the existing preparation method cannot effectively control the interfacial polymerization process of the polyamine monomers and the polyacyl chloride monomers, resulting in obvious deficiencies in the initial performance and stability of the membrane sheet. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a preparation method of a seawater desalination membrane, and the seawater desalination membrane prepared by the method has good initial performance and stability.

[0005] The present application provides a preparation method of a seawater desalination membrane, comprising the following steps:

[0006] a) providing a base membrane;

[0007] In step a), the front surface of the base membrane is a porous support layer, and the back surface is a non-woven fabric layer;

[0008] b) coating a polyamine monomer solution on the front surface of the base membrane, and then drying to surface dryness;

[0009] In step b), the solvent of the polyamine monomer solution is imidazole acetate ionic liquid;

[0010] c) coating a polyacyl chloride monomer solution on the front surface of the surface-dried base membrane to perform interfacial polymerization, and then performing drying treatment to obtain a nascent polyamide separation membrane;

[0011] In step c), the solvent of the polyacyl chloride monomer solution is one or more of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium dicyanamide, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium bis-trifluoromethylsulfonylimide and 1-butyl-3-methylimidazolium trifluoromethanesulfonate;

[0012] d) sequentially immersing the nascent polyamide separation membrane in a first treatment solution and a second treatment solution;

[0013] In step d), the components of the first treatment solution include m-phenylenediamine and 1-pentyl-3-methylimidazolium acetate; the components of the second treatment solution include sodium pyrosulfite; the temperature of the immersion in the first treatment solution and the second treatment solution is 60-80°C;

[0014] e) sequentially immersing the separation membrane treated in step d) in water and glycerol aqueous solution, then coating a polyvinyl alcohol solution on the front side of the separation membrane, drying to obtain a seawater desalination membrane.

[0015] Preferably, in step b), the polyamine monomer in the polyamine monomer solution is m-phenylenediamine; the content of the polyamine monomer in the polyamine monomer solution is 1-4wt%.

[0016] Preferably, in step b), the imidazole acetate ionic liquid is 1-pentyl-3-methylimidazolium acetate.

[0017] Preferably, in step c), the polyacyl chloride monomer in the polyacyl chloride monomer solution is trimesoyl chloride and / or adipoyl chloride; the content of the polyacyl chloride monomer in the polyacyl chloride monomer solution is 0.2-0.4wt%.

[0018] Preferably, in step c), the temperature of the drying treatment is 60-100°C; the time of the drying treatment is 1-3min.

[0019] Preferably, in step d), the content of the m-phenylenediamine in the first treatment solution is 0.1-0.5wt%; the content of the 1-pentyl-3-methylimidazolium acetate in the first treatment solution is 1-5wt%; the content of the sodium pyrosulfite in the second treatment solution is 0.1-0.5wt%.

[0020] Preferably, in step d), the time of the immersion in the first treatment solution and the second treatment solution is 1-2min.

[0021] Preferably, in step e), the water washing process includes:

[0022] First, rinse in water at 40-60℃, then rinse in water at 70-80℃, and finally rinse in water at 40-60℃.

[0023] Preferably, the first rinse takes 0.5 to 1 minute; the second rinse takes 15 to 20 minutes; and the third rinse takes 0.5 to 1 minute.

[0024] Preferably, in step e), the glycerol content in the glycerol aqueous solution is 1-5 wt%; the soaking temperature of the glycerol aqueous solution is 10-40°C; and the soaking time of the glycerol aqueous solution is 2-3 min.

[0025] Compared with the prior art, the present invention provides a method for preparing a seawater desalination membrane, comprising the following steps: a) providing a base membrane; in step a), the front side of the base membrane is a porous support layer and the back side is a non-woven fabric layer; b) coating the front side of the base membrane with a polyamine monomer solution, and then drying it until the base membrane is surface dry; in step b), the solvent of the polyamine monomer solution is an imidazole acetate ionic liquid; c) coating the surface-dried base membrane with a polyacrylamide chloride monomer solution to perform an interfacial polymerization reaction, and then drying it to obtain a nascent polyamide separation membrane; in step c), the solvent of the polyacrylamide chloride monomer solution is 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium dicyanamide, or 1-butyl-3-methylimidazolium tetrafluoroborate. One or more of borates, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and 1-butyl-3-methylimidazolium trifluoromethanesulfonate are selected; d) the nascent polyamide separation membrane is sequentially immersed in a first treatment solution and a second treatment solution; in step d), the first treatment solution comprises m-phenylenediamine and 1-pentyl-3-methylimidazolium acetate; the second treatment solution comprises sodium metabisulfite; the immersion temperature in both the first and second treatment solutions is 60~80℃; e) the separation membrane after step d) is sequentially washed with water and immersed in an aqueous glycerol solution, then coated with a polyvinyl alcohol solution on the front side of the separation membrane, and dried to obtain a seawater desalination membrane. This invention optimizes the preparation method of the seawater desalination membrane, especially by optimizing the selection of solvents for the polyamine monomer solution and the polyacrylamide chloride monomer solution, thereby improving the stability and controllability of the interfacial polymerization reaction and laying the foundation for improving the membrane separation performance. Building upon this, the membrane performance was further enhanced by sequentially immersing the membrane after the interfacial polymerization reaction in a high-temperature treatment solution containing m-phenylenediamine and sodium metabisulfite. Specifically, immersion in the high-temperature treatment solution containing m-phenylenediamine allows for a secondary reaction on the membrane surface, thus avoiding potential structural defects caused by insufficient primary reaction; immersion in the high-temperature treatment solution containing sodium metabisulfite removes chlorine and prevents oxidation, further improving the membrane's stability. This invention, by optimizing the preparation method of seawater desalination membranes, ensures that the nascent membrane after interfacial polymerization can overcome the trade-off effect to a maximum extent, enabling the membrane to maintain a high desalination rate while also possessing good flux. Simultaneously, this method effectively avoids potential structural defects on the membrane surface, improves the membrane's operational stability, and has promising prospects for industrial application. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] This invention provides a method for preparing a seawater desalination membrane, comprising the following steps:

[0028] a) Provide a base film;

[0029] b) Coat the front side of the base film with a polyamine monomer solution, and then dry until the base film is surface dry;

[0030] c) Coat the front side of the surface-dried base membrane with a polyacrylamide chloride monomer solution for interfacial polymerization, and then dry it to obtain a nascent polyamide separation membrane.

[0031] d) The nascent polyamide separation membrane is sequentially immersed in the first treatment solution and the second treatment solution;

[0032] e) The separation membrane processed in step d) is washed with water and soaked in an aqueous glycerol solution in sequence. Then, a polyvinyl alcohol solution is coated on the front side of the separation membrane and dried to obtain a seawater desalination membrane.

[0033] In the preparation method provided by the present invention, in step a), the front side of the base film is a porous support layer and the back side is a non-woven fabric layer; wherein, the composition of the porous support layer is preferably one or more of polysulfone, polyethersulfone, and polyvinylidene fluoride; the average pore size of the porous support layer is preferably 10~50nm, specifically 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, or 50nm; the thickness of the porous support layer is preferably 20~50μm, specifically 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, or 50μm; the thickness of the non-woven fabric layer is preferably 80~120μm, specifically 80μm, 85μm, 90μm, 95μm, 100μm, 105μm, 110μm, 115μm, or 120μm.

[0034] In the preparation method provided by the present invention, in step b), the polyamine monomer in the polyamine monomer solution is preferably m-phenylenediamine; the content of the polyamine monomer in the polyamine monomer solution is preferably 1~4 wt%, specifically 1 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, 2.5 wt%, 2.6 wt%, 2.7 wt%, 2.8 wt%, 2.9 wt%, 3 wt%, 3.1 wt%, 3.2 wt%, 3.3 wt%, 3.4 wt%, 3.5 wt%, 3.6 wt%, 3.7 wt%, 3.8 wt%, 3.9 wt%, or 4 wt%.

[0035] In the preparation method provided by the present invention, in step b), the solvent of the polyamine monomer solution is an imidazole acetate ionic liquid; the imidazole acetate ionic liquid is preferably 1-pentyl-3-methylimidazole acetate.

[0036] In the preparation method provided by the present invention, in step c), the coated polyacrylamide chloride monomer solution undergoes an interfacial polymerization reaction with the polyamine monomer solution on the surface of the base film to form a polyamide layer, and then the polyamide layer is further crosslinked by drying treatment.

[0037] In the preparation method provided by the present invention, in step c), the polyacrylamide chloride monomer in the polyacrylamide chloride monomer solution is preferably pyromellitic acid trimethylolpropionate chloride and / or adipyl chloride; the content of the polyacrylamide chloride monomer in the polyacrylamide chloride monomer solution is preferably 0.2~0.4 wt%, specifically 0.2 wt%, 0.21 wt%, 0.22 wt%, 0.23 wt%, 0.24 wt%, 0.25 wt%, 0.26 wt%, 0.27 wt%, 0.28 wt%, 0.29 wt%, 0.3 wt%, 0.31 wt%, 0.32 wt%, 0.33 wt%, 0.34 wt%, 0.35 wt%, 0.36 wt%, 0.37 wt%, 0.38 wt%, 0.39 wt%, or 0.4 wt%.

[0038] In the preparation method provided by the present invention, in step c), the solvent of the polyacrylamide chloride monomer solution is one or more of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium dicyandiamide, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and 1-butyl-3-methylimidazolium trifluoromethanesulfonate.

[0039] In the preparation method provided by the present invention, in step c), the coating amount of the polyacrylamide chloride monomer solution is preferably 20~30 g / m². 2 Specifically, it can be 20g / m 2 21g / m 2 22g / m 2 23g / m 2 24g / m 2 25g / m 2 26g / m 2 27g / m 2 28g / m 2 29g / m 2 Or 30g / m 2 .

[0040] In the preparation method provided by the present invention, in step c), the temperature of the drying treatment is preferably 60~100℃, specifically 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃ or 100℃; the drying time is preferably 1~3min, specifically 1min, 1.5min, 2min, 2.5min or 3min.

[0041] In the preparation method provided by this invention, in step d), the first treatment solution comprises m-phenylenediamine, 1-pentyl-3-methylimidazolium acetate, and water; wherein, the main function of the m-phenylenediamine is to undergo a secondary reaction with the reactive groups on the membrane surface; the content of the m-phenylenediamine in the first treatment solution is preferably 0.1~0.5 wt%, specifically 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, 0.4 wt%, 0.45 wt%, or 0.5 wt%; the main function of the 1-pentyl-3-methylimidazolium acetate is to stabilize the reaction interface and promote the reaction; the content of the 1-pentyl-3-methylimidazolium acetate in the first treatment solution is preferably 1~5 wt%, specifically 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or 5 wt%.

[0042] In the preparation method provided by the present invention, in step d), the temperature for soaking in the first treatment solution is 60~80℃, specifically 60℃, 62℃, 65℃, 67℃, 70℃, 72℃, 75℃, 77℃ or 80℃; the soaking time in the first treatment solution is preferably 1~2 min, specifically 1 min, 1.1 min, 1.2 min, 1.3 min, 1.4 min, 1.5 min, 1.6 min, 1.7 min, 1.8 min, 1.9 min or 2 min.

[0043] In the preparation method provided by the present invention, in step d), the components of the second treatment liquid include sodium metabisulfite and water; wherein, the main function of the sodium metabisulfite is to remove chlorine and prevent oxidation; the content of sodium metabisulfite in the second treatment liquid is preferably 0.1~0.5wt%, specifically 0.1wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt%, or 0.5wt%.

[0044] In the preparation method provided by the present invention, in step d), the temperature for soaking in the second treatment solution is 60~80℃, specifically 60℃, 62℃, 65℃, 67℃, 70℃, 72℃, 75℃, 77℃ or 80℃; the soaking time in the second treatment solution is preferably 1~2min, specifically 1min, 1.1min, 1.2min, 1.3min, 1.4min, 1.5min, 1.6min, 1.7min, 1.8min, 1.9min or 2min.

[0045] In the preparation method provided by the present invention, in step e), the water washing process preferably includes: first rinsing in water at 40~60℃, then rinsing in water at 70~80℃, and then rinsing in water at 40~60℃ for a third time; wherein, the time for the first rinsing is preferably 0.5~1 min, specifically 0.5 min, 0.6 min, 0.7 min, 0.8 min, 0.9 min or 1 min; the time for the second rinsing is preferably 15~20 min, specifically 15 min, 16 min, 17 min, 18 min, 19 min or 20 min; and the time for the third rinsing is preferably 0.5~1 min, specifically 0.5 min, 0.6 min, 0.7 min, 0.8 min, 0.9 min or 1 min.

[0046] In the preparation method provided by the present invention, the purpose of soaking in the glycerol aqueous solution in step e) is to fill the pores of the separation membrane and prevent the membrane pores from collapsing during subsequent drying and storage, which would cause structural changes and affect performance.

[0047] In the preparation method provided by the present invention, in step e), the glycerol content in the glycerol aqueous solution is preferably 1 to 5 wt%, specifically 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or 5 wt%.

[0048] In the preparation method provided by the present invention, in step e), the soaking temperature of the glycerol aqueous solution is preferably 10~40℃, specifically 10℃, 15℃, 20℃, 25℃ (room temperature), 30℃, 35℃ or 40℃; the soaking time of the glycerol aqueous solution is preferably 2~3min, specifically 2min, 2.1min, 2.2min, 2.3min, 2.4min, 2.5min, 2.6min, 2.7min, 2.8min, 2.9min or 3min.

[0049] In the preparation method provided by the present invention, in step e), the purpose of coating with polyvinyl alcohol solution is to form a protective layer on the surface of the polyamide separation layer of the separation membrane to prevent damage to the membrane surface.

[0050] In the preparation method provided by the present invention, in step e), the number-average molecular weight of polyvinyl alcohol in the polyvinyl alcohol solution is preferably 10,000 to 40,000, more preferably 15,000 to 30,000, and most preferably 19,800 to 26,400; the concentration of the polyvinyl alcohol solution is preferably 0.5 to 5 wt%, specifically 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or 5 wt%.

[0051] In the preparation method provided by this invention, in step e), the dry coating amount of the polyvinyl alcohol solution is preferably 0.05~0.5 g / m². 2 Specifically, it can be 0.05g / m 2 0.1g / m 2 0.15g / m 2 0.2g / m 2 0.25g / m 2 0.3g / m 2 0.35g / m 2 0.4g / m 2 0.45g / m 2 or 0.5g / m 2 .

[0052] This invention optimizes the preparation method of seawater desalination membranes, particularly by optimizing the selection of solvents for the polyamine monomer solution and the polyacrylamide chloride monomer solution. This enhances the stability and controllability of the interfacial polymerization reaction, laying the foundation for improved membrane separation performance. Furthermore, by sequentially immersing the membrane after the interfacial polymerization reaction in a high-temperature treatment solution containing m-phenylenediamine and sodium metabisulfite, membrane performance is further improved. Specifically, immersion in the high-temperature treatment solution containing m-phenylenediamine allows for a secondary reaction on the membrane surface, thus avoiding potential structural defects caused by insufficient primary reaction; immersion in the high-temperature treatment solution containing sodium metabisulfite removes chlorine and prevents oxidation, further improving membrane stability. This invention, by optimizing the preparation method of seawater desalination membranes, ensures that the nascent membrane after interfacial polymerization can overcome the trade-off effect to a maximum extent, enabling the membrane to maintain a high desalination rate while also possessing good flux. Simultaneously, this method effectively avoids potential structural defects on the membrane surface, improves the membrane's operational stability, and has promising prospects for industrial application.

[0053] For clarity, the following examples and comparative models will be used to provide a detailed description.

[0054] Example 1

[0055] A method for preparing a seawater desalination membrane includes the following steps:

[0056] 1) Provide a base film;

[0057] In step 1), the front side of the base film is a polysulfone porous support layer (average pore size of 30nm and thickness of 30μm), and the back side is a non-woven fabric layer (thickness of 100μm).

[0058] 2) Coat the front side of the base film with a polyamine monomer solution, and then dry until the base film is surface dry;

[0059] In step 2), the polyamine monomer in the polyamine monomer solution is m-phenylenediamine, and the m-phenylenediamine content is 3.3 wt%; the solvent of the polyamine monomer solution is imidazole acetate ionic liquid.

[0060] 3) Coat the front side of the surface-dried base membrane with a polyacrylamide chloride monomer solution for interfacial polymerization reaction, and then dry it to obtain a nascent polyamide separation membrane;

[0061] In step 3), the polyacrylamide chloride monomer in the polyacrylamide chloride monomer solution is pyromellitic acid trimethylolpropionate chloride, and the content of pyromellitic acid trimethylolpropionate chloride is 0.28 wt%; the solvent of the polyacrylamide chloride monomer solution is 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt; the drying temperature is 80°C and the time is 2 min.

[0062] 4) The nascent polyamide separation membrane is sequentially immersed in the first treatment solution and the second treatment solution;

[0063] In step 4), the first treatment solution comprises 0.1 wt% m-phenylenediamine, 2 wt% 1-pentyl-3-methylimidazolium acetate, and the remainder is water; the second treatment solution comprises 0.2 wt% sodium metabisulfite, and the remainder is water; the soaking temperature is 75°C and the soaking time is 2 min.

[0064] 5) The separation membrane processed in step 4) is washed with water and soaked in glycerol aqueous solution in sequence. Then, polyvinyl alcohol solution is coated on the front side of the separation membrane and dried to obtain a seawater desalination membrane.

[0065] In step 5), the water washing process includes: first rinsing in water at 50°C for 1 minute, then rinsing in water at 75°C for 20 minutes, and then rinsing in water at 50°C for 1 minute.

[0066] In step 5), the glycerol content in the glycerol aqueous solution is 2 wt%; the soaking temperature of the glycerol aqueous solution is 25°C, and the soaking time is 3 min.

[0067] In step 5), the number-average molecular weight of the polyvinyl alcohol is 19800~26400, the concentration of the polyvinyl alcohol solution is 2wt%, and the dry coating weight is 0.15g / m². 2 .

[0068] Example 2

[0069] A method for preparing a seawater desalination membrane, referring to Example 1, differs only in that the m-phenylenediamine content in the polyamine monomer solution is 2.8 wt%.

[0070] Example 3

[0071] A method for preparing a seawater desalination membrane, referring to Example 1, differs only in that: the m-phenylenediamine content in the polyamine monomer solution is 2.7 wt%, and the trimesoyl chloride content in the polyacrylamide chloride monomer solution is 0.25 wt%.

[0072] Example 4

[0073] A method for preparing a seawater desalination membrane, referring to Example 1, differs only in that: the m-phenylenediamine content in the polyamine monomer solution is 3.4 wt%, and the trimesoyl chloride content in the polyacrylamide chloride monomer solution is 0.3 wt%.

[0074] Comparative Example 1

[0075] A method for preparing a seawater desalination membrane, referring to Example 1, differs only in that: the solvent in the polyamine monomer solution is RO water, and the solvent in the polyacrylamide chloride monomer solution is Isopar G.

[0076] Comparative Example 2

[0077] A method for preparing a seawater desalination membrane, referring to Example 3, differs only in that: the solvent in the polyamine monomer solution is RO water, and the solvent in the polyacrylamide chloride monomer solution is Isopar G.

[0078] Comparative Example 3

[0079] A method for preparing a seawater desalination membrane, referring to Example 1, differs only in that the solvent in the polyacrylamide chloride monomer solution is Isopar G.

[0080] Comparative Example 4

[0081] A method for preparing a seawater desalination membrane, referring to Example 1, differs only in that the solvent in the polyamine monomer solution is RO water.

[0082] Comparison of membrane flux and desalination rate

[0083] Flux and desalination rate of the seawater desalination membranes prepared in Examples 1-4 and Comparative Examples 1-4 were tested using a 32000 mg / L NaCl aqueous solution at 800 psi pressure, a test solution temperature of 25 ± 1 °C, and a test solution pH of 7.0 ± 0.5. The differences in preparation conditions between Examples 1-4 and Comparative Examples 1-4, as well as the results of the flux and desalination rate tests, are summarized in Table 1.

[0084] Table 1. Flux and desalination rate test results of Examples 1-4 and Comparative Examples 1-4

[0085]

[0086] As can be seen from Table 1, the desalination rate and flux of the embodiment can be maintained at a high level, which is significantly better than that of the comparative example.

[0087] Comparative Example 5

[0088] A method for preparing a seawater desalination membrane, referring to Example 1, except that the nascent polyamide separation membrane is not treated in step 4).

[0089] Stability test

[0090] The seawater desalination membranes prepared in Example 1 and Comparative Example 5 were subjected to operational stability tests. The tests were conducted using a 32000 mg / L NaCl aqueous solution at 800 psi pressure, a test solution temperature of 25 ± 1 °C, and a test solution pH of 7.0 ± 0.5. The tests were performed continuously for 2 hours, with permeate volume measured every 20 minutes. The results are shown in Table 2.

[0091] Table 2 Results of Operational Stability Test

[0092]

[0093] As shown in Table 2, compared to Comparative Example 5, the membrane desalination rate stability of Example 1 is significantly improved. This indicates that immersing the membrane that has completed the interfacial polymerization reaction in a high-temperature treatment solution containing m-phenylenediamine can improve the membrane's operational stability.

[0094] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a seawater desalination membrane, characterized in that, Includes the following steps: a) Provide a base film; In step a), the front side of the base film is a porous support layer, and the back side is a non-woven fabric layer; b) Coat the front side of the base film with a polyamine monomer solution, and then dry until the base film is surface dry; In step b), the solvent for the polyamine monomer solution is an imidazole acetate ionic liquid; c) Coat the front side of the surface-dried base membrane with a polyacrylamide chloride monomer solution for interfacial polymerization, and then dry it to obtain a nascent polyamide separation membrane. In step c), the solvent of the polyacrylamide chloride monomer solution is one or more of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium dicyanamide, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and 1-butyl-3-methylimidazolium trifluoromethanesulfonate. d) The nascent polyamide separation membrane is sequentially immersed in the first treatment solution and the second treatment solution; In step d), the first treatment solution comprises m-phenylenediamine and 1-pentyl-3-methylimidazolium acetate; the second treatment solution comprises sodium metabisulfite; and the immersion temperature in both the first and second treatment solutions is 60~80℃. e) The separation membrane processed in step d) is washed with water and soaked in an aqueous glycerol solution in sequence. Then, a polyvinyl alcohol solution is coated on the front side of the separation membrane and dried to obtain a seawater desalination membrane.

2. The preparation method according to claim 1, characterized in that, In step b), the polyamine monomer in the polyamine monomer solution is m-phenylenediamine; the content of the polyamine monomer in the polyamine monomer solution is 1~4 wt%.

3. The preparation method according to claim 1, characterized in that, In step b), the imidazole acetate ionic liquid is 1-pentyl-3-methylimidazolium acetate.

4. The preparation method according to claim 1, characterized in that, In step c), the polyacryl chloride monomer in the polyacryl chloride monomer solution is pyromellitic acid trimethylolpropionate chloride and / or adipoyl chloride; the content of the polyacryl chloride monomer in the polyacryl chloride monomer solution is 0.2~0.4wt%.

5. The preparation method according to claim 1, characterized in that, In step c), the drying temperature is 60~100℃; the drying time is 1~3min.

6. The preparation method according to claim 1, characterized in that, In step d), the content of m-phenylenediamine in the first treatment solution is 0.1~0.5 wt%; the content of 1-pentyl-3-methylimidazolium acetate in the first treatment solution is 1~5 wt%; and the content of sodium metabisulfite in the second treatment solution is 0.1~0.5 wt%.

7. The preparation method according to claim 1, characterized in that, In step d), the soaking time in both the first and second treatment solutions is 1 to 2 minutes.

8. The preparation method according to claim 1, characterized in that, In step e), the water washing process includes: First, rinse in water at 40-60℃, then rinse in water at 70-80℃, and finally rinse in water at 40-60℃.

9. The preparation method according to claim 8, characterized in that, The first rinse lasts for 0.5 to 1 minute; the second rinse lasts for 15 to 20 minutes; and the third rinse lasts for 0.5 to 1 minute.

10. The preparation method according to claim 1, characterized in that, In step e), the glycerol content in the glycerol aqueous solution is 1-5 wt%; the soaking temperature of the glycerol aqueous solution is 10-40℃; and the soaking time of the glycerol aqueous solution is 2-3 min.

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