Composite membranes, their preparation methods and applications

Abstract

This invention relates to composite membranes, their preparation methods, and applications. The preparation method includes the following steps: an interfacial polymerization reaction is carried out on the surface of a porous support membrane using an aqueous solution containing polyamines and an oil solution containing polyacrylamide chlorides to form a polyamide layer. The solvent in the oil solution containing polyacrylamide chlorides is methyl silicone oil. A hydrophilic polyphenol aqueous solution, a urea aqueous solution, and a lysine aqueous solution are sequentially placed on the surface of the polyamide layer away from the porous support membrane to obtain the composite membrane. The temperature of the lysine aqueous solution is 50℃-80℃. This preparation method effectively reduces the residual amine content while enabling the prepared composite membrane to possess both high desalination rate and high water flux.

Description

Technical Field

[0001] This invention relates to the field of water treatment membrane technology, and in particular to composite membranes, their preparation methods, and applications. Background Technology

[0002] In the process of preparing composite membranes using interfacial polymerization, m-phenylenediamine, a commonly used aqueous monomer, may have residual residues that affect the membrane's performance and stability. Therefore, post-treatment is a key step in removing unreacted amines and optimizing the membrane structure and performance.

[0003] Currently, post-processing mainly includes heat treatment and chemical treatment. Heat treatment promotes the cross-linking and curing of the polyamide layer by controlling temperature and time. For example, after interfacial polymerization, a 90°C water bath treatment for 1 minute can replace traditional oven heating, which can reduce the residual amine content to a certain extent while enhancing the density of the polyamide layer and improving the desalination rate of the composite membrane. However, excessively high temperatures can easily lead to membrane pore shrinkage and reduce the water flux of the membrane. Chemical treatment modifies the polyamide membrane at room temperature using nitrous acid solution. Through diazotization, it combines with amino groups on the membrane surface, thereby reducing the residual amine content on the membrane surface and regulating the separation layer structure to improve the desalination rate of the composite membrane. However, the groups introduced by the diazotization reaction or the surface structure rearrangement caused often increase the resistance to water molecule permeation, thereby reducing the water flux of the membrane.

[0004] Therefore, there is an urgent need to provide a method for preparing composite membranes that can effectively reduce residual amine content while maintaining high desalination rate and high water flux. Summary of the Invention

[0005] Therefore, it is necessary to provide a composite membrane, its preparation method, and its application to address the above problems. This preparation method can effectively reduce the residual amine content while enabling the prepared composite membrane to have both high desalination rate and high water flux.

[0006] A method for preparing a composite membrane includes the following steps:

[0007] An interfacial polymerization reaction is carried out on the surface of a porous support membrane to form a polyamide layer by an aqueous solution containing polyamines and an oil solution containing polyacrylamide chlorides. The solvent in the oil solution containing polyacrylamide chlorides is methyl silicone oil.

[0008] A hydrophilic polyphenol aqueous solution, a urea aqueous solution, and a lysine aqueous solution are sequentially placed on the surface of the polyamide layer away from the porous support membrane to obtain a composite membrane, wherein the temperature of the lysine aqueous solution is 50℃-80℃.

[0009] In one embodiment, the mass fraction of the hydrophilic polyphenol in the aqueous solution is 0.5%-1.5%;

[0010] And / or, the hydrophilic polyphenol is selected from at least one of resorcinol, phloroglucinol, and tannic acid.

[0011] In one embodiment, the mass fraction of urea in the urea aqueous solution is 1%-5%.

[0012] In one embodiment, the lysine aqueous solution contains 1%-2% by mass of lysine;

[0013] And / or, the aqueous solution of lysine contains an acidification catalyst, wherein the acidification catalyst is selected from sulfuric acid and / or hydrochloric acid.

[0014] In one embodiment, the aqueous phase solution containing polyamine contains an acid scavenger, wherein the mass fraction of the acid scavenger in the aqueous phase solution containing polyamine is 0.1%-0.5%.

[0015] In one embodiment, the mass fraction of the polyamine in the aqueous solution containing the polyamine is 0.5%-1.5%;

[0016] And / or, the polyamine is selected from at least one of m-phenylenediamine, diethylenetriamine, or triethylenetetramine.

[0017] In one embodiment, the mass fraction of the polyacrylamide chloride in the oil phase solution containing polyacrylamide chloride is 0.1%-0.5%;

[0018] And / or, the polyacryl chloride is selected from at least one of pyromellitic methyl chloride, terephthaloyl chloride, biphenyl polyacryl chloride, or cyanuric chloride.

[0019] In one embodiment, the specific steps for forming a polyamide layer by interfacial polymerization of an aqueous solution containing polyamine and an oil solution containing polyacrylamide chloride on the surface of a porous support membrane are as follows: the aqueous solution containing polyamine and the oil solution containing polyacrylamide chloride are placed sequentially on the same surface of the porous support membrane, and the polyamide layer is formed by heat treatment.

[0020] A composite membrane prepared using the aforementioned method.

[0021] Application of the aforementioned composite membrane in a water treatment device.

[0022] In the preparation method of the composite membrane of this invention, an interfacial polymerization method is used to form a polyamide layer on the surface of a porous support membrane. During this process, methyl silicone oil is used as the oil phase solvent. Taking advantage of the non-volatile and highly hydrophobic properties of methyl silicone oil, a small amount of methyl silicone oil remains on the polyamide layer after interfacial polymerization. This ensures that the residual polyacrylamide chlorides on the polyamide layer are not easily hydrolyzed, reserving reactive sites for subsequent reactions. When hydrophilic polyphenol aqueous solution, urea aqueous solution, and lysine aqueous solution are sequentially placed on the surface of the polyamide layer, the residual amines on the polyamide layer dissolve, significantly reducing the content of residual amines. Simultaneously, the hydrophilic polyphenols react with the residual polyacrylamide chlorides, grafting polyhydroxy compounds onto the surface of the polyamide layer. The surface hydrophilicity of the composite membrane is significantly improved, thereby increasing its water flux. Urea, with its strong hydrogen bonding ability, can form new hydrogen bonds with the amide groups on the polyamide chain segments, replenishing the hydrogen bond network damaged by the dissolution of polyamines, enhancing the structural stability of the polyamide layer, and enabling the composite membrane to maintain a high desalination rate. Under specific temperature conditions, lysine undergoes self-assembly on the surface of the polyamide layer through hydrogen bonding. At the same time, its amino groups undergo polymerization with the residual polyphenol groups on the membrane, forming a two-dimensional network structure firmly attached to the membrane surface. This two-dimensional network structure connects with the hydrogen bond sites on the surface of the polyamide layer, effectively increasing the hydrogen bond network density and introducing a large number of amino and carboxyl hydrophilic groups, thereby achieving a synergistic improvement in the desalination rate and water flux of the composite membrane.

[0023] Therefore, the method for preparing the composite membrane of the present invention can effectively reduce the residual amine content while enabling the prepared composite membrane to have both high desalination rate and high water flux. Detailed Implementation

[0024] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments or examples only and is not intended to limit the invention. The optional range of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0026] The method for preparing the composite membrane provided by the present invention includes the following steps:

[0027] An interfacial polymerization reaction is carried out on the surface of a porous support membrane to form a polyamide layer by an aqueous solution containing polyamines and an oil solution containing polyacrylamide chlorides. The solvent in the oil solution containing polyacrylamide chlorides is methyl silicone oil.

[0028] A hydrophilic polyphenol aqueous solution, a urea aqueous solution, and a lysine aqueous solution are sequentially placed on the surface of the polyamide layer away from the porous support membrane to obtain a composite membrane, wherein the temperature of the lysine aqueous solution is 50℃-80℃.

[0029] In this invention, an aqueous solution containing polyamines and an oil solution containing polyacrylamide chlorides are subjected to interfacial polymerization on the surface of a porous support membrane to form a polyamide layer. In this process, methyl silicone oil is used as the oil phase solvent. Taking advantage of the non-volatile and highly hydrophobic properties of methyl silicone oil, after the interfacial polymerization is completed, methyl silicone oil remains on the polyamide layer in liquid form. Due to its strong hydrophobicity and high interfacial tension, it can effectively prevent the polyacrylamide chlorides remaining on the polyamide layer from contacting water molecules in the environment, significantly inhibiting the hydrolysis reaction of the polyacrylamide chlorides and reserving reactive sites for subsequent reactions with hydrophilic polyphenols.

[0030] When an aqueous solution of hydrophilic polyphenols is placed on the surface of a polyamide layer, the hydrophilic polyphenols, being rich in ortho-phenolic hydroxyl groups, act as strong hydrogen bond donors. They can form stronger competitive hydrogen bonds with the amide groups on the surface of the polyamide layer, effectively displacing and promoting the dissolution of residual amines from the polyamide. At the same time, the hydrophilic polyphenols react with residual polyacrylamide chlorides to graft polyhydroxy compounds onto the surface of the polyamide layer, significantly improving the surface hydrophilicity of the composite membrane and thus increasing the water flux of the composite membrane.

[0031] When an aqueous urea solution is placed on the surface of a polyamide layer, the small size of urea molecules allows them to easily diffuse into the free volume pores of the polyamide layer. Through hydrogen bonding, the original hydrogen bonds between polyamide molecular chains are weakened, increasing the mobility of the chain segments and inducing micro-swelling of the polyamide layer. This increases the surface volume and the inter-chain spacing, effectively releasing deep-seated residual amines that are physically embedded or weakly bound by hydrogen bonds, causing them to dissolve and further reducing the content of residual amines. At the same time, urea, with its strong hydrogen bonding ability, can form new hydrogen bonds with the amide groups on the polyamide chain segments, replenishing the hydrogen bond network damaged by the dissolution of polyamines and enhancing the structural stability of the polyamide layer. This allows the composite membrane to maintain a high desalination rate.

[0032] When an aqueous solution of lysine is placed on the surface of a polyamide layer, under specific temperature and pH conditions, lysine is electrostatically adsorbed onto the polyamide surface and then arranged in an orderly manner through intermolecular hydrogen bonding, i.e., self-assembly occurs on the surface of the polyamide layer. Simultaneously, the amino groups of lysine can polymerize with the polyphenol groups remaining on the membrane surface to form a firmly attached two-dimensional network structure. This two-dimensional network structure connects with the hydrogen bonding sites on the surface of the polyamide layer, effectively increasing the hydrogen bond network density, correspondingly increasing the crosslinking density of the polyamide layer, reducing the free volume pores, and enhancing the size sieving effect, thereby improving the desalination rate of the composite membrane. On the other hand, the large number of amino and carboxyl hydrophilic groups introduced by the lysine molecule significantly enhances the hydrophilicity of the composite membrane surface, forming a dense hydration layer on the composite membrane surface, reducing water transport resistance, thereby increasing the water flux of the composite membrane, and thus achieving a synergistic improvement in the desalination rate and water flux of the composite membrane.

[0033] Therefore, the method for preparing the composite membrane of the present invention first uses interfacial polymerization to form a polyamide layer on the surface of a porous support membrane, wherein methyl silicone oil is used as the oil phase solvent, and then hydrophilic polyphenol aqueous solution, urea aqueous solution and lysine aqueous solution are sequentially placed on the surface of the polyamide layer. Under this synergistic effect, the residual amine content can be effectively reduced, while the prepared composite membrane has both high desalination rate and high water flux.

[0034] It should be noted that in this invention, during the process of placing the hydrophilic polyphenol aqueous solution, urea aqueous solution and lysine aqueous solution on the surface of the polyamide layer, since all three use water as a solvent, they provide a dissolution and diffusion medium for residual amines, allowing the residual amines on the polyamide layer to dissolve. In conjunction with the hydrophilic polyphenols and urea, the residual amines on the polyamide layer can be deeply removed, significantly reducing the content of residual amines.

[0035] Optionally, the mass fraction of hydrophilic polyphenols in the aqueous solution of hydrophilic polyphenols is 0.5%-1.5%. By controlling the mass fraction of hydrophilic polyphenols, it is possible to effectively ensure the dissolution of residual amines on the polyamide layer while ensuring that they react fully with the residual polyacrylamide chlorides, grafting polyhydroxy compounds onto the surface of the polyamide layer, significantly improving the surface hydrophilicity of the composite membrane, thereby increasing the water flux of the composite membrane.

[0036] Furthermore, the hydrophilic polyphenol is selected from at least one of resorcinol, phloroglucinol, and tannic acid, preferably resorcinol and / or phloroglucinol.

[0037] In one embodiment, the temperature of the hydrophilic polyphenol aqueous solution is 20°C-30°C.

[0038] Optionally, the mass fraction of urea in the urea aqueous solution is 1%-5%. By controlling the mass fraction of urea, the polyamide molecular chains can undergo moderate swelling, promoting further dissolution of residual amines inside the polyamide layer. This further reduces the residual amine content and allows for the formation of a dynamic hydrogen bond network with the amide groups of the polyamide layer through hydrogen bonding. This replenishes the hydrogen bond network damaged by the dissolution of residual amines, maintains the structural integrity of the polyamide layer, and ensures that the composite membrane still has a high desalination rate.

[0039] In one embodiment, the temperature of the urea aqueous solution is 20°C-30°C.

[0040] Optionally, the mass fraction of lysine in the lysine aqueous solution is 1%-2%. By controlling the mass fraction of lysine, this setting facilitates the self-assembly of a monolayer hydrogen bond network structure on the surface of the polyamide layer, which interweaves with the original hydrogen bond network of the polyamide, thereby improving the strength of the hydrogen bond network and enhancing the structural stability of the composite membrane. At the same time, it introduces a large number of hydrophilic groups, thereby improving the hydrophilicity of the composite membrane and thus increasing the water flux of the composite membrane.

[0041] Optionally, an acidic catalyst is added to the lysine aqueous solution, wherein the acidification catalyst is selected from sulfuric acid and / or hydrochloric acid, preferably sulfuric acid; this setting can catalyze the polymerization reaction of lysine and polyphenols, while regulating the self-assembly order, thereby forming a denser and more stable two-dimensional network under milder conditions, further improving the desalination rate of the composite membrane.

[0042] In order to better remove the hydrochloric acid generated by the interfacial polymerization reaction and ensure the forward reaction of the polymerization of polyamine and polyacrylamide chloride, the aqueous phase solution containing polyamine contains an acid absorber, wherein the mass fraction of the acid absorber in the aqueous phase solution containing polyamine is 0.1%-0.5%.

[0043] Furthermore, the acid absorbent is selected from at least one of triethylamine, sodium hydroxide, potassium hydroxide, sodium carbonate, trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, potassium phosphate, and dipotassium hydrogen phosphate, preferably triethylamine.

[0044] Optionally, the mass fraction of the polyamine in the aqueous solution containing polyamine is 0.5%-1.5%; the mass fraction of the polyacrylamide in the oil solution containing polyacrylamide is 0.1%-0.5%. By controlling the mass fraction of polyamine in the aqueous solution and the mass fraction of polyacrylamide in the oil solution, it is beneficial to allow the polyamine and polyacrylamide to react fully and form a relatively dense polyamide layer, which is beneficial to maintaining a high desalination rate of the composite membrane.

[0045] Optionally, the polyamine is selected from at least one of m-phenylenediamine, diethylenetriamine, or triethylenetetramine, preferably m-phenylenediamine.

[0046] Optionally, the polyacryl chloride is selected from at least one of pyromellitic methyl chloride, terephthaloyl chloride, biphenyl polyacryl chloride or cyanuric chloride, preferably pyromellitic methyl chloride.

[0047] It should be noted that, in this invention, the solvent of the aqueous phase solution is water.

[0048] In this invention, the specific steps for forming a polyamide layer by interfacial polymerization of an aqueous solution containing polyamine and an oil solution containing polyacrylamide chloride on the surface of a porous support membrane are as follows: the aqueous solution containing polyamine and the oil solution containing polyacrylamide chloride are placed sequentially on the same surface of the porous support membrane, and the polyamide layer is formed by heat treatment.

[0049] In one embodiment, in the step of forming the polyamide layer by heat treatment, the heat treatment temperature is 90°C-110°C, and the heat treatment time is 2 min-4 min. This setting can further ensure the integrity and uniformity of the crosslinking of the polyamide separation layer, and further improve the salt rejection performance and water flux of the composite membrane.

[0050] In one embodiment, the porous support membrane is selected from at least one of polysulfone membrane, polypropylene membrane or polyacrylonitrile membrane. Polysulfone is inexpensive and readily available, simple to prepare, has good mechanical strength, good compressive strength, stable chemical properties, is non-toxic, and can resist biodegradation. Therefore, the support membrane is preferably a polysulfone membrane.

[0051] It should be noted that, in this invention, the specific method for placing the hydrophilic polyphenol aqueous solution, urea aqueous solution, and lysine aqueous solution on the surface of the polyamide layer away from the porous support membrane is not particularly limited. Specifically, in one embodiment, the hydrophilic polyphenol aqueous solution, urea aqueous solution, and lysine aqueous solution are placed on the surface of the polyamide layer away from the porous support membrane by means of coating, spraying, soaking, or impregnation.

[0052] Furthermore, this invention also provides a composite membrane prepared using the aforementioned method. This composite membrane possesses the properties of low residual amine content, high desalination rate, and high water flux.

[0053] Furthermore, the present invention also provides an application of the aforementioned composite membrane in a water treatment device.

[0054] In one embodiment, the water treatment device can be a water purifier. When the composite membrane is applied in the water purifier, during the water purification process, the raw water to be purified enters from the separation layer of the composite membrane, and the raw water permeates through the composite membrane under pressure to form pure water.

[0055] In one embodiment, the water treatment device may also be a seawater desalination device.

[0056] The composite membrane, its preparation method, and its applications will be further described below through specific embodiments. However, those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, specific conditions in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0057] Example 1

[0058] Aqueous solution was prepared by uniformly mixing m-phenylenediamine, triethylamine, and water, wherein the mass fraction of m-phenylenediamine in the aqueous solution was 2% and the mass fraction of triethylamine was 1%. Oil solution was prepared by uniformly mixing pyromellitic acid chloride and methyl silicone oil, wherein the mass fraction of pyromellitic acid chloride in the oil solution was 0.15%. Phloroglucinol and water were mixed to prepare an aqueous solution of phloroglucinol, wherein the mass fraction of phloroglucinol in the aqueous solution was 1%. Urea and water were mixed to prepare an aqueous solution of urea, wherein the mass fraction of urea in the aqueous solution was 2%. Lysine, sulfuric acid, and water were mixed to prepare an aqueous solution of lysine, wherein the mass fraction of lysine in the aqueous solution was 1%, and the temperature of the aqueous solution of lysine was 65°C.

[0059] The above aqueous solution was applied to the surface of the polysulfone support membrane. After standing for 60 seconds, the excess aqueous solution was poured off, and the membrane surface was dried with cold air. Then, the above oil solution was applied to the same surface of the polysulfone support membrane. After standing for 30 seconds, the excess oil solution was poured off, and after draining for 30 seconds, the membrane was placed in a 100°C forced-air drying oven for 2 minutes to form a polyamide layer, thus obtaining a pre-fabricated composite membrane. The pre-fabricated composite membrane was then immersed in a phloroglucinol aqueous solution for 30 seconds and then removed. Next, it was immersed in a urea aqueous solution for 40 seconds, and finally immersed in a lysine aqueous solution for 5 minutes before being removed to obtain the composite membrane.

[0060] Example 2

[0061] Aqueous solution was prepared by uniformly mixing m-phenylenediamine, triethylamine, and water, wherein the mass fraction of m-phenylenediamine in the aqueous solution was 1.5% and the mass fraction of triethylamine was 1%. Oil solution was prepared by uniformly mixing pyromellitic acid chloride and methyl silicone oil, wherein the mass fraction of pyromellitic acid chloride in the oil solution was 0.2%. Resorcinol and water were mixed to prepare resorcinol aqueous solution, wherein the mass fraction of resorcinol in the resorcinol aqueous solution was 0.5%. Urea and water were mixed to prepare urea aqueous solution, wherein the mass fraction of urea in the urea aqueous solution was 1%. Lysine, sulfuric acid, and water were mixed to prepare lysine aqueous solution, wherein the mass fraction of lysine in the lysine aqueous solution was 2%, and the temperature of the lysine aqueous solution was 80℃.

[0062] The above aqueous solution was applied to the surface of the polysulfone support membrane. After standing for 60 seconds, the excess aqueous solution was poured off, and the membrane surface was dried with cold air. Then, the above oil solution was applied to the same surface of the polysulfone support membrane. After standing for 30 seconds, the excess oil solution was poured off, and after draining for 30 seconds, the membrane was placed in a 100°C forced-air drying oven for 2 minutes to form a polyamide layer, thus obtaining a pre-fabricated composite membrane. The pre-fabricated composite membrane was then immersed in a phloroglucinol aqueous solution for 30 seconds and then removed. Next, it was immersed in a urea aqueous solution for 40 seconds, and finally immersed in a lysine aqueous solution for 5 minutes before being removed to obtain the composite membrane.

[0063] Example 3

[0064] Aqueous solution was prepared by uniformly mixing m-phenylenediamine, triethylamine, and water, wherein the mass fraction of m-phenylenediamine and triethylamine in the aqueous solution was 1%; oil solution was prepared by uniformly mixing trimesoyl chloride and methyl silicone oil, wherein the mass fraction of trimesoyl chloride in the oil solution was 0.1%; aqueous solution was prepared by mixing tannic acid and water, wherein the mass fraction of tannic acid was 1%; aqueous solution was prepared by mixing urea and water, wherein the mass fraction of urea in the aqueous solution was 3%; aqueous solution was prepared by mixing lysine, sulfuric acid, and water, wherein the mass fraction of lysine in the aqueous solution was 1.5%, and the temperature of the aqueous solution was 50°C.

[0065] The above aqueous solution was applied to the surface of the polysulfone support membrane. After standing for 60 seconds, the excess aqueous solution was poured off, and the membrane surface was dried with cold air. Then, the above oil solution was applied to the same surface of the polysulfone support membrane. After standing for 30 seconds, the excess oil solution was poured off, and after draining for 30 seconds, the membrane was placed in a 100°C forced-air drying oven for 2 minutes to form a polyamide layer, thus obtaining a pre-fabricated composite membrane. The pre-fabricated composite membrane was then immersed in a phloroglucinol aqueous solution for 30 seconds and then removed. Next, it was immersed in a urea aqueous solution for 40 seconds, and finally immersed in a lysine aqueous solution for 5 minutes before being removed to obtain the composite membrane.

[0066] Example 4

[0067] Example 4 differs from Example 1 only in that the mass fraction of phloroglucinol in the aqueous solution is 0.4%; all other conditions are the same, resulting in a composite membrane.

[0068] Example 5

[0069] Example 5 differs from Example 1 only in that the mass fraction of phloroglucinol in the aqueous solution is 1.6%; all other conditions are the same, resulting in a composite membrane.

[0070] Example 6

[0071] The only difference between Example 6 and Example 1 is that the mass fraction of urea in the urea aqueous solution is 0.5%; all other conditions are the same, and a composite membrane is obtained.

[0072] Example 7

[0073] Example 7 differs from Example 1 only in that the mass fraction of urea in the urea aqueous solution is 6%; all other conditions are the same, resulting in a composite membrane.

[0074] Example 8

[0075] Compared with Example 1, Example 8 differs only in that the mass fraction of lysine in the lysine aqueous solution is 0.8%; all other conditions are the same, and a composite membrane is obtained.

[0076] Example 9

[0077] Compared with Example 1, Example 9 differs only in that the mass fraction of lysine in the lysine aqueous solution is 2.5%; all other conditions are the same, and a composite membrane is obtained.

[0078] Example 10

[0079] Compared with Example 1, Example 10 differs only in that triethylamine is not added in the step of preparing the aqueous solution; all other conditions are the same, and a composite membrane is obtained.

[0080] Example 11

[0081] Compared with Example 1, Example 11 differs only in that sulfuric acid is not added in the step of preparing the lysine aqueous solution; all other conditions are the same, and a composite membrane is obtained.

[0082] Comparative Example 1

[0083] Compared with Example 1, Comparative Example 1 differs only in that, in the step of preparing the oil phase solution, an isoparaffin solvent (Isopar-L) is used instead of methyl silicone oil; all other conditions are the same, and a composite membrane is obtained.

[0084] Comparative Example 2

[0085] Compared with Example 1, Comparative Example 2 differs only in that the temperature of the lysine aqueous solution is 45°C; all other conditions are the same, and a composite membrane is obtained.

[0086] Comparative Example 3

[0087] Compared with Example 1, Comparative Example 3 differs only in that the temperature of the lysine aqueous solution is 85°C; all other conditions are the same, and a composite membrane is obtained.

[0088] Comparative Example 4

[0089] Compared with Example 1, Comparative Example 4 differs only in that the pre-prepared composite membrane was immersed in a urea aqueous solution for 30 seconds, then immersed in a phloroglucinol aqueous solution for 30 seconds and then removed, and finally immersed in a lysine aqueous solution for 5 minutes and then removed to obtain the composite membrane.

[0090] Comparative Example 5

[0091] Compared with Example 1, Comparative Example 5 differs only in that the pre-prepared composite membrane was immersed in a phloroglucinol aqueous solution for 30 seconds and then removed, followed by immersion in a lysine aqueous solution for 5 minutes and then removed, and finally immersed in a urea aqueous solution for 30 seconds and then removed to obtain the composite membrane.

[0092] Comparative Example 6

[0093] Compared with Example 1, Comparative Example 6 differs only in that the pre-prepared composite membrane was immersed in lysine aqueous solution for 5 minutes and then removed, followed by immersion in phloroglucinol aqueous solution for 30 seconds and then removed, and finally immersed in urea aqueous solution for 30 seconds and then removed to obtain the composite membrane.

[0094] Comparative Example 7

[0095] Compared with Example 1, Comparative Example 7 is only different in that it does not contain the step of immersing the pre-made composite membrane in a phloroglucinol aqueous solution. That is, the pre-made composite membrane is directly immersed in a urea aqueous solution for 30 seconds and then immersed in a lysine aqueous solution for 5 minutes before being taken out to obtain the composite membrane.

[0096] Comparative Example 8

[0097] Compared with Example 1, Comparative Example 8 is only different in that it does not contain the step of immersing the pre-made composite membrane in a urea aqueous solution. That is, the pre-made composite membrane is directly immersed in a phloroglucinol aqueous solution for 30 seconds and then immersed in a lysine aqueous solution for 5 minutes before being taken out to obtain the composite membrane.

[0098] Comparative Example 9

[0099] Compared with Example 1, Comparative Example 9 differs only in that it does not include the step of immersing the pre-prepared composite membrane in a lysine aqueous solution. Instead, the pre-prepared composite membrane is directly immersed in a phloroglucinol aqueous solution for 30 seconds, and then immersed in a urea aqueous solution for 30 seconds before being removed to obtain the composite membrane.

[0100] Comparative Example 10

[0101] Comparative Example 10 differs from Example 1 only in that it does not include the step of immersing the pre-made composite membrane in a phloroglucinol aqueous solution, a urea aqueous solution, and a lysine aqueous solution. In other words, the pre-made composite membrane obtained is the composite membrane.

[0102] The composite membranes prepared in Examples 1 to 11 and Comparative Examples 1 to 10 were subjected to performance tests. The test conditions were as follows: test pressure was 1.55 MPa, concentrate flow rate was 1.0 GPM, ambient temperature was 25°C, concentrate pH was 6.5-7.5, and concentrate was 2000 ppm sodium chloride aqueous solution. The test results are shown in Table 1.

[0103] Table 1

[0104]

[0105] It should be noted that in Table 1, the membrane water flux (F) is calculated by the volume of water passing through the composite membrane within a certain time period, and the formula is: F=V / (A×T), where V is the volume of water passing through the composite membrane per unit time, A is the effective membrane area, and T is time.

[0106] The rejection rate (R) is calculated using the concentrations of the feed liquid and the permeate liquid. The formula is: R = (1 - C1 / C0) × 100%, where C1 is the concentration of the permeate liquid and C0 is the concentration of the feed liquid.

[0107] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0108] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a composite membrane, characterized in that, Includes the following steps: An interfacial polymerization reaction is carried out on the surface of a porous support membrane to form a polyamide layer by an aqueous solution containing polyamines and an oil solution containing polyacrylamide chlorides. The solvent in the oil solution containing polyacrylamide chlorides is methyl silicone oil. A hydrophilic polyphenol aqueous solution, a urea aqueous solution, and a lysine aqueous solution are sequentially placed on the surface of the polyamide layer away from the porous support membrane to obtain a composite membrane, wherein the temperature of the lysine aqueous solution is 50℃-80℃.

2. The method for preparing the composite membrane according to claim 1, characterized in that, The mass fraction of hydrophilic polyphenols in the aqueous solution is 0.5%-1.5%; And / or, the hydrophilic polyphenol is selected from at least one of resorcinol, phloroglucinol, and tannic acid.

3. The method for preparing the composite membrane according to claim 1, characterized in that, The mass fraction of urea in the urea aqueous solution is 1%-5%.

4. The method for preparing the composite membrane according to claim 1, characterized in that, The mass fraction of lysine in the lysine aqueous solution is 1%-2%; And / or, the aqueous solution of lysine contains an acidification catalyst, wherein the acidification catalyst is selected from sulfuric acid and / or hydrochloric acid.

5. The method for preparing the composite membrane according to claim 1, characterized in that, The aqueous solution containing polyamine contains an acid absorbent, wherein the mass fraction of the acid absorbent in the aqueous solution containing polyamine is 0.5%-1.5%.

6. The method for preparing the composite membrane according to claim 1, characterized in that, The mass fraction of the polyamine in the aqueous solution containing polyamine is 1%-2%; And / or, the polyamine is selected from at least one of m-phenylenediamine, diethylenetriamine, or triethylenetetramine.

7. The method for preparing the composite membrane according to claim 1, characterized in that, The mass fraction of the polyacryl chloride in the oil phase solution containing polyacryl chloride is 0.1%-0.5%; And / or, the polyacryl chloride is selected from at least one of pyromellitic trimethylolpropionate chloride, terephthaloyl chloride, and biphenyl polyacryl chloride.

8. The method for preparing the composite membrane according to any one of claims 1 to 7, characterized in that, The specific steps for forming a polyamide layer by interfacial polymerization of an aqueous solution containing polyamine and an oil solution containing polyacryl chloride on the surface of a porous support membrane are as follows: The aqueous solution containing polyamine and the oil solution containing polyacryl chloride are placed sequentially on the same surface of the porous support membrane, and the polyamide layer is formed by heat treatment.

9. A composite membrane prepared by the method for preparing a composite membrane according to any one of claims 1 to 8.

10. The application of the composite membrane as described in claim 9 in a water treatment device.

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