Composite membranes, methods of making and using the same

Abstract

The present application relates to a composite membrane and its preparation method and application, wherein the preparation method of the composite membrane comprises the following steps: providing a reverse osmosis membrane comprising a support membrane and a dense layer arranged in a stack; preparing a mixed solution of sodium phosphate, sodium hydroxide and water, sequentially placing the mixed solution and a triethylamine solution containing calcium nitrate on the surface of the dense layer away from the support membrane, forming hydroxyapatite nanoparticles through heat treatment, and then placing an aqueous solution of bovine serum albumin on the surface of the dense layer away from the support membrane to form a hydrophilic anti-pollution layer, thereby obtaining the composite membrane, wherein the mass ratio of bovine serum albumin to calcium nitrate is greater than or equal to 1:20. When the composite membrane prepared by the preparation method is applied to water treatment, it can maintain high desalination rate and high water flux while still having excellent anti-pollution performance.

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] Reverse osmosis is a highly efficient and energy-saving water treatment method that has been widely used in seawater desalination, drinking water treatment, and water reuse. However, reverse osmosis membranes are easily fouled during use, leading to a decrease in water flux and a shortened lifespan, thus hindering their application.

[0003] To improve the antifouling performance of reverse osmosis membranes, an antifouling layer is usually formed on the surface of the membrane. Currently, there are two main ways to form the antifouling layer: First, a hydrophilic polymer is directly coated onto the surface of the reverse osmosis membrane to form the antifouling layer. However, the antifouling layer formed by this method is very prone to peeling off during use. Second, a hydrophilic substance is cross-linked on the surface of the reverse osmosis membrane to form the antifouling layer. However, the antifouling layer formed by this method has a relatively dense cross-linking, which increases the resistance of the reverse osmosis membrane and leads to a decrease in the water flux of the reverse osmosis membrane.

[0004] This shows that reverse osmosis membranes prepared by traditional methods still cannot maintain high water flux while also having high antifouling performance. 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. When the composite membrane prepared by this method is applied to water treatment, it can maintain a high desalination rate and high water flux while still exhibiting excellent antifouling performance.

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

[0007] A reverse osmosis membrane is provided, the reverse osmosis membrane comprising a support membrane and a dense layer stacked together;

[0008] Sodium phosphate, sodium hydroxide, and water are prepared into a mixed solution. The mixed solution and a triethylamine solution containing calcium nitrate are sequentially placed on the surface of the dense layer away from the supporting membrane. After heat treatment, hydroxyapatite nanoparticles are formed. Then, an aqueous solution of bovine serum albumin is placed on the surface of the dense layer away from the supporting membrane to form a hydrophilic antifouling layer, thus obtaining a composite membrane. The mass ratio of bovine serum albumin to calcium nitrate is greater than or equal to 1:20.

[0009] In one embodiment, the mass ratio of bovine serum albumin to calcium nitrate is 1:20 to 1:10.

[0010] In one embodiment, the mass ratio of water in the mixed solution to triethylamine in the triethylamine solution containing calcium nitrate is 1:1 to 5:1.

[0011] In one embodiment, the mass fraction of sodium phosphate in the mixed solution is 1%-3%;

[0012] And / or, the mass fraction of sodium hydroxide in the mixed solution is 0.1%-1%.

[0013] In one embodiment, the mass fraction of bovine serum albumin in the bovine serum albumin aqueous solution is 0.05%-0.3%.

[0014] In one embodiment, the heat treatment temperature is 60°C-80°C, and the heat treatment time is 3 min-5 min.

[0015] In one embodiment, the method for preparing the reverse osmosis membrane includes the following steps: placing an aqueous solution and an oil solution sequentially on the same surface of the supporting membrane, and then heat-treating to form a dense layer to obtain the reverse osmosis membrane, wherein the aqueous solution includes a polyamine and the oil solution includes a polyacrylamide.

[0016] A composite membrane prepared using the aforementioned method.

[0017] Application of the aforementioned composite membrane in a water treatment device.

[0018] In the preparation method of the composite membrane of the present invention, when a mixed solution of sodium phosphate, sodium hydroxide, and water, and a triethylamine solution containing calcium nitrate are sequentially placed on the surface of the dense layer of the reverse osmosis membrane, an interface is formed on the surface of the dense layer due to the low compatibility between water and triethylamine. This allows an interfacial reaction to occur between sodium phosphate, sodium hydroxide, and calcium nitrate, forming hydroxyapatite nanoparticles uniformly distributed on the surface of the dense layer. Simultaneously, when an aqueous solution of bovine serum albumin is placed on the surface of the dense layer, the hydroxyapatite nanoparticles react with the bovine serum albumin to form a hydrophilic antifouling layer. This hydrophilic antifouling layer is firmly attached to the surface of the dense layer and is not easily detached during use. With a relatively loose three-dimensional network structure, the composite membrane can effectively reduce water resistance and increase water flux. Furthermore, the presence of uniformly sized hydroxyapatite nanoparticles effectively increases the water production channels, further enhancing the water flux. Moreover, the mass ratio of bovine serum albumin to calcium nitrate is greater than or equal to 1:20, resulting in an excess of bovine serum albumin on the hydrophilic antifouling layer. This effectively complexes divalent metal salt ions (such as calcium and magnesium ions) in the water, greatly increasing the solubility of divalent metal ions on the composite membrane surface. This effectively prevents the formation of fouling such as calcium carbonate and magnesium carbonate on the composite membrane surface, thereby significantly improving the antifouling performance of the composite membrane.

[0019] Therefore, when the composite membrane of the present invention is applied to water treatment, it can maintain a high desalination rate and high water flux while still exhibiting excellent antifouling performance. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is an electron microscope image of the composite membrane prepared in Example 1 of the present invention;

[0022] Figure 2 This is an electron microscope image of the composite membrane prepared in Comparative Example 3 of the present invention;

[0023] Figure 3 This is an electron microscope image of the composite membrane prepared in Comparative Example 5 of the present invention. 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] S1, providing a reverse osmosis membrane, the reverse osmosis membrane comprising a support membrane and a dense layer stacked together.

[0028] In step S1, the method for preparing the reverse osmosis membrane includes the following steps: placing an aqueous solution and an oil solution sequentially on the same surface of the supporting membrane, and then heat-treating to form a dense layer to obtain the reverse osmosis membrane. The aqueous solution comprises a polyamine, and the oil solution comprises a polyacrylamide chloride. It can be understood that the polyamine and polyacrylamide chloride form a polyamide layer, i.e., a dense layer, through interfacial polymerization, thereby ensuring that the composite membrane has a high desalination rate.

[0029] In one embodiment, the mass fraction of the polyamine in the aqueous phase solution is 1%-3%, and the mass fraction of the polyacrylamide in the oil phase solution is 0.1%-0.5%. This arrangement facilitates a sufficient reaction between the polyamine and the polyacrylamide to form a complete and dense layer, which further helps to ensure that the composite membrane has a high desalination rate.

[0030] Further, the polyamine is selected from at least one of m-phenylenediamine, polyamine, p-phenylenediamine, and tetraethylenepentamine, preferably m-phenylenediamine; the polyacryl chloride is selected from at least one of pyromellitic chloride, isophthaloyl chloride, and terephthaloyl chloride, preferably pyromellitic chloride.

[0031] 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, in one embodiment, the aqueous solution further includes an acid scavenger, the mass fraction of which is 0.5%-3%.

[0032] 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.

[0033] In one embodiment, in the step of forming a dense layer through heat treatment, the heat treatment temperature is 75°C-100°C, and the heat treatment time is 2 min-4 min. This configuration further ensures the integrity and uniformity of the crosslinking of the dense layer, further improving the desalination rate and water flux of the composite membrane.

[0034] In one embodiment, the solvent of the oil phase solution is selected from isoparaffin solvents, and the isoparaffin solvent is selected from at least one of Isopar-E, Isopar-G, and Isopar-L; the solvent of the aqueous phase solution is water.

[0035] In one embodiment, the support membrane is selected from at least one of polysulfone membrane, polypropylene membrane or polyacrylonitrile membrane. Polysulfone is inexpensive and readily available, simple to form, has good mechanical strength, good compressive strength, stable chemical properties, is non-toxic, and can resist biodegradation. Therefore, polysulfone membrane is preferred as the support membrane.

[0036] S2, sodium phosphate, sodium hydroxide and water are prepared into a mixed solution, the mixed solution and a triethylamine solution containing calcium nitrate are placed sequentially on the surface of the dense layer away from the supporting membrane, and hydroxyapatite nanoparticles are formed by heat treatment. Then, an aqueous solution of bovine serum albumin is placed on the surface of the dense layer away from the supporting membrane to form a hydrophilic antifouling layer, and a composite membrane is obtained, wherein the mass ratio of bovine serum albumin to calcium nitrate is greater than or equal to 1:20.

[0037] In step S2, when the mixed solution and the triethylamine solution containing calcium nitrate come into contact on the surface of the dense layer, due to the low compatibility between water and triethylamine, an interface is formed on the surface of the dense layer. This allows the reaction between sodium phosphate, sodium hydroxide, and calcium nitrate to occur at the interface formed by water and triethylamine, i.e., an interfacial reaction. This effectively prevents the formation of large hydroxyapatite particles, and subsequently, hydroxyapatite nanoparticles are formed on the surface of the dense layer and are uniformly distributed. The reaction formula for the preparation of hydroxyapatite nanoparticles by the reaction between sodium phosphate, sodium hydroxide, and calcium nitrate is as follows:

[0038] 10Ca(NO3)2+6Na3PO4+2NaOH+18H2O→Ca 10 (PO4)6(OH)2+20NaNO3.

[0039] When an aqueous solution of bovine serum albumin is placed on the surface of the dense layer away from the supporting membrane, the hydroxyapatite nanoparticles on the dense layer react with the bovine serum albumin to form a hydrophilic antifouling layer. On the one hand, compared to the antifouling layer formed by directly coating the surface of the reverse osmosis membrane with hydrophilic polymers, this hydrophilic antifouling layer can be firmly attached to the surface of the dense layer and is not easy to fall off during use. On the other hand, compared to the antifouling layer formed by cross-linking hydrophilic substances on the surface of the reverse osmosis membrane, this hydrophilic antifouling layer has a relatively loose three-dimensional network structure, which can effectively reduce the water resistance of the composite membrane and increase the water flux of the composite membrane. At the same time, due to the presence of hydroxyapatite nanoparticles, the permeate channels can be effectively increased, further improving the water flux of the composite membrane.

[0040] Meanwhile, by controlling the mass ratio of bovine serum albumin to calcium nitrate to be greater than or equal to 1:20, when hydroxyapatite nanoparticles react with bovine serum albumin, the bovine serum albumin is in excess. This results in the hydrophilic antifouling layer containing excess bovine serum albumin, which can effectively complex divalent metal salt ions (such as calcium ions and magnesium ions) in water. This greatly increases the solubility of divalent metal ions on the surface of the composite membrane, thereby effectively preventing the formation of fouling such as calcium carbonate and magnesium carbonate on the surface of the composite membrane and greatly improving the antifouling performance of the composite membrane.

[0041] It should be noted that in the present invention, in the reaction between hydroxyapatite nanoparticles and bovine serum albumin, in addition to the complexation reaction, there is also a self-assembly behavior. The mechanism of the complexation reaction is mainly as follows: calcium ions on the surface of hydroxyapatite nanoparticles and carboxyl or amino groups in bovine serum albumin molecules are combined through coordinate bonds to form a stable bovine serum albumin-hydroxyapatite complex, which allows the hydrophilic antifouling layer to be firmly attached to the surface of the dense layer and is not easy to fall off during use. At the same time, since hydroxyapatite nanoparticles contain hydroxyl groups and bovine serum albumin is rich in carboxyl and amino groups, the two will also spontaneously form a self-assembly structure through electrostatic interaction and hydrogen bonding, thereby synergistically forming a hydrophilic antifouling layer with a relatively loose three-dimensional network structure through the complexation reaction. This allows the hydrophilic antifouling layer to effectively reduce the water resistance of the composite membrane and increase the water flux of the composite membrane.

[0042] In addition, it should be noted that in the field of reverse osmosis membranes, bovine serum albumin is usually used as a contaminant to test the antifouling performance of reverse osmosis membranes. However, this application is the first to utilize the interaction between bovine serum albumin and hydroxyapatite nanoparticles to form a hydrophilic antifouling layer, which is used to improve the antifouling performance and water flux of the composite membrane.

[0043] Therefore, when the composite membrane of the present invention is applied to water treatment, it can maintain a high desalination rate and high water flux while still exhibiting excellent antifouling performance.

[0044] Optionally, the mass ratio of bovine serum albumin to calcium nitrate is 1:20 to 1:10. This setting helps to better ensure that the hydrophilic antifouling layer contains excess bovine serum albumin, further improving the solubility of divalent metal ions on the surface of the composite membrane, and thus better improving the antifouling performance of the composite membrane.

[0045] Optionally, the mass ratio of water in the mixed solution to triethylamine in the triethylamine solution containing calcium nitrate is 1:1 to 5:1. This setting, by adjusting the mass ratio of water to triethylamine, allows for a better formation of a stable interface between the two substances. This prevents the formation of large hydroxyapatite particles during the reaction between sodium phosphate, sodium hydroxide, and calcium nitrate to form hydroxyapatite, resulting in smaller, more uniformly sized, and more evenly dispersed hydroxyapatite nanoparticles. This facilitates better reaction with bovine serum albumin to form a hydrophilic antifouling layer, while also increasing the water production channels, further improving the antifouling performance and water flux of the composite membrane.

[0046] Optionally, the mass fraction of sodium phosphate in the mixed solution is 1%-3%; the mass fraction of sodium hydroxide in the mixed solution is 0.1%-1%; and the mass fraction of calcium nitrate in the triethylamine solution containing calcium nitrate is 1%-3%. This configuration, by controlling the amounts of sodium phosphate, sodium hydroxide, and calcium nitrate, allows for a sufficient reaction among the three components, resulting in the formation of smaller, uniformly distributed hydroxyapatite nanoparticles.

[0047] Optionally, the mass fraction of bovine serum albumin in the aqueous solution is 0.05%-0.3%. This configuration allows for sufficient complexation reaction and self-assembly between bovine serum albumin and hydroxyapatite nanoparticles to form a firmly connected hydrophilic antifouling layer. It also ensures that the bovine serum albumin is in excess, resulting in a surplus on the surface of the hydrophilic antifouling layer. This effectively complexes divalent metal ions during water treatment, preventing fouling on the surface of the hydrophilic antifouling layer and thus improving the antifouling performance and water flux of the composite membrane.

[0048] Optionally, the heat treatment temperature is 60℃-80℃, and the heat treatment time is 3min-5min. This setting facilitates a more complete reaction between sodium phosphate, sodium hydroxide, and calcium nitrate, resulting in better formation of hydroxyapatite nanoparticles.

[0049] Furthermore, this invention also provides a composite membrane prepared using the aforementioned method. When applied to water treatment, this composite membrane maintains excellent antifouling properties while preserving high desalination rates and high water flux.

[0050] Furthermore, the present invention also provides an application of the aforementioned composite membrane in a water treatment device.

[0051] In one embodiment, the water treatment device can be a water purifier. When the reverse osmosis 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 reverse osmosis membrane, and the raw water passes through the reverse osmosis membrane under pressure to form pure water.

[0052] In one embodiment, the water treatment device may also be a seawater desalination device.

[0053] 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.

[0054] Example 1

[0055] 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 trimesoyl chloride and isoparaffin solvent (Isopar-L), wherein the mass fraction of trimesoyl chloride in the oil solution was 0.2%. Mixed solution was prepared by mixing sodium phosphate, sodium hydroxide, and water, wherein the mass fraction of sodium phosphate in the mixed solution was 2% and the mass fraction of sodium hydroxide was 0.5%. Triethylamine solution containing calcium nitrate was prepared by uniformly mixing calcium nitrate and triethylamine, wherein the mass fraction of calcium nitrate in the triethylamine solution containing calcium nitrate was 2%, and the mass ratio of water to triethylamine in the mixed solution was 3:1. Bovine serum albumin (BSA) was prepared by mixing bovine serum albumin (BSA) and water, wherein the mass fraction of BSA in the bovine serum albumin aqueous solution was 0.2%, and the mass ratio of BSA to calcium nitrate was 1:15.

[0056] The above aqueous solution is applied to the surface of the polysulfone support membrane. After standing for 60 seconds, the excess aqueous solution is poured off, and the membrane surface is dried with cold air. Then, the above oil solution is applied to the same surface of the polysulfone support membrane. After standing for 30 seconds, the excess oil solution is poured off, and after draining, the membrane is placed in an 80°C oven for 2 minutes to obtain a reverse osmosis membrane. The reverse osmosis membrane includes a stacked support membrane and a dense layer.

[0057] The above-described mixed solution was applied to the surface of the dense layer away from the support membrane. After standing for 30 seconds, the excess mixed solution was poured off, and the mixture was air-dried. Then, the above-described triethylamine solution containing calcium nitrate was applied to the surface of the dense layer away from the support membrane. After standing for 30 seconds, the excess triethylamine solution containing calcium nitrate was poured off, and the hydroxyapatite nanoparticles were dried in a 60°C oven. Then, a bovine serum albumin aqueous solution was applied to the surface of the dense layer away from the support membrane. After standing for 30 seconds, the excess bovine serum albumin aqueous solution was poured off, and the mixture was air-dried to form a hydrophilic antifouling layer, thus obtaining a composite membrane.

[0058] Example 2

[0059] 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% and the mass fraction of triethylamine was 0.5%. Oil solution was prepared by uniformly mixing trimesoyl chloride and isoparaffin solvent (Isopar-L), wherein the mass fraction of trimesoyl chloride in the oil solution was 0.15%. Mixed solution was prepared by mixing sodium phosphate, sodium hydroxide, and water, wherein the mass fraction of sodium phosphate in the mixed solution was 1% and the mass fraction of sodium hydroxide was 0.1%. Triethylamine solution containing calcium nitrate was prepared by uniformly mixing calcium nitrate and triethylamine, wherein the mass fraction of calcium nitrate in the triethylamine solution containing calcium nitrate was 1%, and the mass ratio of water to triethylamine in the triethylamine solution containing calcium nitrate was 1:1. Bovine serum albumin (BSA) was prepared by mixing bovine serum albumin (BSA) and water, wherein the mass fraction of BSA in the bovine serum albumin aqueous solution was 0.05%, and the mass ratio of BSA to calcium nitrate was 1:20.

[0060] The above aqueous solution is applied to the surface of the polysulfone support membrane. After standing for 60 seconds, the excess aqueous solution is poured off, and the membrane surface is dried with cold air. Then, the above oil solution is applied to the same surface of the polysulfone support membrane. After standing for 30 seconds, the excess oil solution is poured off, and after draining, the membrane is placed in an 80°C oven for 3 minutes to obtain a reverse osmosis membrane. The reverse osmosis membrane includes a stacked support membrane and a dense layer.

[0061] The above-described mixed solution was applied to the surface of the dense layer away from the support membrane. After standing for 30 seconds, the excess mixed solution was poured off, and the mixture was air-dried. Then, the above-described triethylamine solution containing calcium nitrate was applied to the surface of the dense layer away from the support membrane. After standing for 30 seconds, the excess triethylamine solution containing calcium nitrate was poured off, and the hydroxyapatite nanoparticles were dried in a 60°C oven. Then, a bovine serum albumin aqueous solution was applied to the surface of the dense layer away from the support membrane. After standing for 30 seconds, the excess bovine serum albumin aqueous solution was poured off, and the mixture was air-dried to form a hydrophilic antifouling layer, thus obtaining a composite membrane.

[0062] Example 3

[0063] 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 3%; an oil solution was prepared by uniformly mixing pyromellitic trimethylolpropionate (PPS) and isoparaffin solvent (Isopar-L), wherein the mass fraction of PPS was 0.4%; a mixed solution was prepared by uniformly mixing sodium phosphate, sodium hydroxide, and water, wherein the mass fraction of sodium phosphate was 3% and the mass fraction of sodium hydroxide was 1%; a triethylamine solution containing calcium nitrate was prepared by uniformly mixing calcium nitrate and triethylamine, wherein the mass fraction of calcium nitrate in the triethylamine solution containing calcium nitrate was 3%, and the mass ratio of water to triethylamine in the triethylamine solution containing calcium nitrate was 5:1; and a bovine serum albumin (BSA) aqueous solution was prepared by mixing bovine serum albumin and water, wherein the mass fraction of bovine serum albumin in the bovine serum albumin aqueous solution was 0.3%, and the mass ratio of bovine serum albumin to calcium nitrate was 1:10.

[0064] The above aqueous solution is applied to the surface of the polysulfone support membrane. After standing for 60 seconds, the excess aqueous solution is poured off, and the membrane surface is dried with cold air. Then, the above oil solution is applied to the same surface of the polysulfone support membrane. After standing for 30 seconds, the excess oil solution is poured off, and after draining, the membrane is placed in an 80°C oven for 3 minutes to obtain a reverse osmosis membrane. The reverse osmosis membrane includes a stacked support membrane and a dense layer.

[0065] The above-described mixed solution was applied to the surface of the dense layer away from the support membrane. After standing for 30 seconds, the excess mixed solution was poured off and the mixture was air-dried. Then, the above-described triethylamine solution containing calcium nitrate was applied to the surface of the dense layer away from the support membrane. After standing for 30 seconds, the excess triethylamine solution containing calcium nitrate was poured off and the hydroxyapatite nanoparticles were dried in an oven at 80°C. Then, bovine serum albumin aqueous solution was applied to the surface of the dense layer away from the support membrane. After standing for 30 seconds, the excess bovine serum albumin aqueous solution was poured off and the mixture was air-dried to form a hydrophilic antifouling layer, thus obtaining the composite membrane.

[0066] Example 4

[0067] Example 4 differs from Example 1 only in that the mass fraction of sodium phosphate in the mixed solution is 0.5%, while 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 sodium phosphate in the mixed solution is 4%, while all other conditions are the same, resulting in a composite membrane.

[0070] Example 6

[0071] Example 6 differs from Example 1 only in that the mass fraction of calcium nitrate in the triethylamine solution containing calcium nitrate is 0.15%, the mass ratio of bovine serum albumin to calcium nitrate is 2:15, and all other conditions are the same, resulting in a composite membrane.

[0072] Example 7

[0073] Example 7 differs from Example 1 only in that the mass fraction of calcium nitrate in the triethylamine solution containing calcium nitrate is 4%, the mass ratio of bovine serum albumin to calcium nitrate is 1:20, and all other conditions are the same, resulting in a composite membrane.

[0074] Example 8

[0075] Example 8 differs from Example 1 only in that the mass fraction of bovine serum albumin in the aqueous solution is 0.4%, the mass ratio of bovine serum albumin to calcium nitrate is 1:5, and all other conditions are the same, resulting in a composite membrane.

[0076] Example 9

[0077] Example 9 differs from Example 1 only in that the mass fraction of calcium nitrate in the triethylamine solution containing calcium nitrate is 2%, the mass fraction of bovine serum albumin in the bovine serum albumin aqueous solution is 0.1%, and the mass ratio of bovine serum albumin to calcium nitrate is 3:10. All other conditions are the same, resulting in a composite membrane.

[0078] Example 10

[0079] Example 10 differs from Example 1 only in that the mass fraction of calcium nitrate in the triethylamine solution containing calcium nitrate is 1%, the mass fraction of bovine serum albumin in the bovine serum albumin aqueous solution is 0.1%, and the mass ratio of bovine serum albumin to calcium nitrate is 9:1. All other conditions are the same, resulting in a composite membrane.

[0080] Example 11

[0081] Example 11 differs from Example 1 only in that the mass ratio of water to triethylamine in the mixed solution containing calcium nitrate is 1:2, while all other conditions are the same, resulting in a composite membrane.

[0082] Example 12

[0083] Example 12 differs from Example 1 only in that the mass ratio of water to triethylamine in the mixed solution containing calcium nitrate is 8:1, while all other conditions are the same, resulting in a composite membrane.

[0084] Comparative Example 1

[0085] Compared with Example 1, Comparative Example 1 differs only in that a calcium nitrate aqueous solution is used instead of a triethylamine solution containing calcium nitrate. That is, calcium nitrate and water are mixed evenly to prepare a calcium nitrate aqueous solution, wherein the mass fraction of calcium nitrate in the calcium nitrate aqueous solution is 2%, and all other conditions are the same, to obtain a composite membrane.

[0086] Comparative Example 2

[0087] Compared with Example 1, Comparative Example 2 differs only in that the mass fraction of bovine serum albumin in the bovine serum albumin aqueous solution is 0.2%, the mass ratio of bovine serum albumin to calcium nitrate is 1:25, and all other conditions are the same, resulting in a composite membrane.

[0088] Comparative Example 3

[0089] Comparative Example 3 differs from Example 1 only in that a polyvinyl alcohol aqueous solution is used instead of a bovine serum albumin aqueous solution, and the mass fraction of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 0.2%. All other conditions are the same, and the result is as follows. Figure 2 The composite membrane shown.

[0090] Comparative Example 4

[0091] Compared with Example 1, Comparative Example 4 differs only in that nano-titanium dioxide and water are prepared into a titanium dioxide solution with a mass fraction of 1%; the titanium dioxide solution is applied to the surface of the dense layer away from the support membrane, left to stand for 30 seconds, and then the excess titanium dioxide solution is poured off and air-dried; then bovine serum albumin aqueous solution is applied to the surface of the dense layer away from the support membrane, left to stand for 30 seconds, and then the excess bovine serum albumin aqueous solution is poured off and air-dried to form a hydrophilic antifouling layer. All other conditions are the same, and a composite membrane is obtained.

[0092] Comparative Example 5

[0093] 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% and the mass fraction of triethylamine was 0.5%; and oil solution was prepared by uniformly mixing pyromellitic tricarboxylate chloride and isoparaffin solvent (Isopar-L), wherein the mass fraction of pyromellitic tricarboxylate chloride in the oil solution was 0.15%.

[0094] The above aqueous solution is applied to the surface of the polysulfone support membrane. After standing for 60 seconds, the excess aqueous solution is poured off, and the membrane surface is dried with cold air. Then, the above oil solution is applied to the same surface of the polysulfone support membrane. After standing for 30 seconds, the excess oil solution is poured off, and after draining, the membrane is placed in an 80°C oven for 2 minutes to obtain a reverse osmosis membrane. The reverse osmosis membrane includes a stacked support membrane and a dense layer.

[0095] A 0.2% (w / w) aqueous solution of polyvinyl alcohol and a 0.5% (w / w) aqueous solution of glutaraldehyde were mixed and then coated onto the dense layer surface of the reverse osmosis membrane. After 30 seconds, excess solution was discarded, and the membrane was finally placed in an 80°C oven for 3 minutes to obtain the desired result. Figure 3 The composite membrane shown.

[0096] The composite membranes prepared in Examples 1 to 12 and Comparative Examples 1 to 5 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 calcium chloride aqueous solution. The test results are shown in Table 1.

[0097] Table 1

[0098]

[0099] Meanwhile, the antifouling performance of the composite membranes prepared in Examples 1 to 12 and Comparative Examples 1 to 5 was tested. The test conditions were as follows: test pressure of 1.55 MPa, concentrate flow rate of 1.0 GPM, ambient temperature of 25ºC, and concentrate pH of 6.5-7.5. The antifouling performance was tested with concentrate of 2000 ppm sodium chloride + 100 ppm sodium humate as feed water. After 100 hours of continuous operation, the membrane was cleaned, and then the performance was tested with concentrate of 2000 ppm calcium chloride as feed water. The test results are shown in Table 2.

[0100] Table 2

[0101]

[0102] It should be noted that in Tables 1 and 2, the membrane water flux (F) is calculated by the volume of water passing through the composite membrane within a certain time, 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.

[0103] 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.

[0104] The formula for calculating the water flux recovery rate is: (water flux of the composite membrane after fouling / water flux of the initial composite membrane) × 100%.

[0105] from Figure 1As can be seen from the results, the composite membrane prepared in Example 1 has a relatively obvious blade structure on its surface, indicating that even after the formation of the hydrophilic antifouling layer, the blade structure of the composite membrane is still visible. This indicates that the hydrophilic antifouling layer is relatively thin and has a relatively loose three-dimensional network structure, which is beneficial to improving the water flux and antifouling performance of the composite membrane.

[0106] from Figure 2 As can be seen from the data, in Comparative Example 3, the use of polyvinyl alcohol aqueous solution instead of bovine serum albumin aqueous solution resulted in a thicker hydrophilic antifouling layer, and the surface structure of the composite membrane was basically covered, affecting the water flux of the composite membrane.

[0107] from Figure 3 As can be seen from Comparative Example 5, an antifouling layer is formed on the surface of the reverse osmosis membrane by cross-linking polyvinyl alcohol and glutaraldehyde. Because the cross-linking of this antifouling layer is relatively dense, the surface morphology of the composite membrane is completely covered by the antifouling coating, and the antifouling layer becomes significantly thicker, which increases the resistance of the reverse osmosis membrane and leads to a decrease in the water flux of the composite membrane.

[0108] 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.

[0109] 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: A reverse osmosis membrane is provided, the reverse osmosis membrane comprising a support membrane and a dense layer stacked together; Sodium phosphate, sodium hydroxide, and water are prepared into a mixed solution. The mixed solution and a triethylamine solution containing calcium nitrate are sequentially placed on the surface of the dense layer away from the supporting membrane. After heat treatment, hydroxyapatite nanoparticles are formed. Then, an aqueous solution of bovine serum albumin is placed on the surface of the dense layer away from the supporting membrane to form a hydrophilic antifouling layer, thus obtaining a composite membrane. The mass ratio of bovine serum albumin to calcium nitrate is greater than or equal to 1:

20.

2. The method for preparing the composite membrane according to claim 1, characterized in that, The mass ratio of bovine serum albumin to calcium nitrate is 1:20 to 1:

10.

3. The method for preparing the composite membrane according to claim 1, characterized in that, The mass ratio of water in the mixed solution to triethylamine in the triethylamine solution containing calcium nitrate is 1:1 to 5:

1.

4. The method for preparing the composite membrane according to claim 1, characterized in that, The mass fraction of sodium phosphate in the mixed solution is 1%-3%; And / or, the mass fraction of sodium hydroxide in the mixed solution is 0.1%-1%.

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

6. The method for preparing the composite membrane according to claim 1, characterized in that, The mass fraction of bovine serum albumin in the bovine serum albumin aqueous solution is 0.05%-0.3%.

7. The method for preparing the composite membrane according to claim 1, characterized in that, The heat treatment temperature is 60℃-80℃, and the heat treatment time is 3min-5min.

8. The method for preparing the composite membrane according to any one of claims 1 to 7, characterized in that, The method for preparing the reverse osmosis membrane includes the following steps: placing an aqueous phase solution and an oil phase solution sequentially on the same surface of the supporting membrane, and then heat-treating to form a dense layer to obtain the reverse osmosis membrane, wherein the aqueous phase solution includes a polyamine and the oil phase solution includes a polyacrylamide chloride.

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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