Composite membrane as well as preparation method and application thereof

Abstract

The invention relates to a composite membrane as well as a preparation method and application thereof, and the preparation method of the composite membrane comprises the following steps: providing a reverse osmosis membrane which comprises a support membrane and a compact layer which are laminated; 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, away from the supporting membrane, of the compact layer, hydroxyapatite nano-particles are formed through heat treatment, then an aqueous solution of bovine serum albumin is placed on the surface, away from the supporting membrane, of the compact layer, and a hydrophilic anti-pollution layer is formed; the mass ratio of the bovine serum albumin to the calcium nitrate is greater than or equal to 1: 20. When the composite membrane prepared by the preparation method is applied to water treatment, high desalination rate and high water flux can be maintained, and meanwhile, the composite membrane still has excellent anti-pollution performance.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment membranes, in particular to a composite membrane and a preparation method and application thereof. Background Art

[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 contaminated during use, resulting in reduced water flux and shortened service life, which hinders their application.

[0003] To improve the anti-fouling performance of reverse osmosis membranes, an anti-fouling layer is typically formed on the surface of the membrane. Currently, there are two main methods for forming this anti-fouling layer: First, a hydrophilic polymer is directly coated on the surface of the membrane to form the anti-fouling layer. However, this anti-fouling layer is prone to shedding during use. Second, a hydrophilic substance is cross-linked on the surface of the membrane to form the anti-fouling layer. However, this method creates a denser cross-linking layer, which increases the resistance of the membrane and reduces its water flux.

[0004] It can be seen that the reverse osmosis membrane prepared by traditional methods still cannot maintain high water flux while also having high anti-pollution performance. Summary of the Invention

[0005] Based on this, it is necessary to provide a composite membrane and its preparation method and application to address the above problems. The composite membrane prepared by this preparation method can maintain high desalination rate and high water flux while still having excellent anti-pollution performance when used in water treatment.

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

[0007] A reverse osmosis membrane is provided, comprising a support membrane and a dense layer arranged in a stacked manner;

[0008] Sodium phosphate, sodium hydroxide and water are prepared into a mixed solution, and the mixed solution and a triethylamine solution containing calcium nitrate are placed in sequence on the surface of the dense layer away from the support membrane, and hydroxyapatite nanoparticles are formed through heat treatment. Then, an aqueous solution of bovine serum albumin is placed on the surface of the dense layer away from the support membrane to form a hydrophilic anti-fouling layer, thereby obtaining a composite membrane, wherein the mass ratio of the bovine serum albumin to the calcium nitrate is greater than or equal to 1:20.

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

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

[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 phase solution and an oil phase solution on the same surface of the support membrane in sequence, 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 polyacyl chloride.

[0016] A composite membrane prepared by adopting the composite membrane preparation method.

[0017] An application of the composite membrane in a water treatment device.

[0018] In the preparation method of the composite membrane of the present invention, a mixed solution prepared by 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. Due to the low compatibility of water and triethylamine, an interface is formed on the surface of the dense layer, so that an interfacial reaction occurs between the sodium phosphate, sodium hydroxide and calcium nitrate to form hydroxyapatite nanoparticles uniformly distributed on the surface of the dense layer; at the same time, 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 anti-pollution layer. The hydrophilic anti-pollution layer can be firmly connected to the surface of the dense layer and is not easy to fall off during use. On the other hand, It has a relatively loose three-dimensional network structure, which can effectively reduce the resistance of the composite membrane to water and improve the water flux of the composite membrane. At the same time, due to the presence of hydroxyapatite nanoparticles with uniform particle size, it can effectively increase the water production channel, further improving the water flux of the composite membrane; moreover, since the mass ratio of bovine serum albumin to the calcium nitrate is greater than or equal to 1:20, the hydrophilic anti-pollution layer contains excess bovine serum albumin, which can effectively complex divalent metal salt ions (such as calcium ions and magnesium ions) in water, greatly increasing the solubility of divalent metal ions on the surface of the composite membrane, effectively avoiding the formation of scale such as calcium carbonate and magnesium carbonate on the surface of the composite membrane, thereby greatly improving the anti-pollution 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 a high water flux while still having excellent anti-pollution performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[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 DESCRIPTION

[0024] To facilitate understanding of the present invention, the present invention 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. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the technical field of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments or embodiments and are not intended to limit the present invention. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of related listed items, including any two related listed items, any more related listed items, or the combination of all related listed items.

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

[0027] S1, providing a reverse osmosis membrane, wherein the reverse osmosis membrane includes a support membrane and a dense layer arranged in a stacked manner.

[0028] In step S1, the method for preparing a reverse osmosis membrane includes the following steps: placing an aqueous solution and an oily solution sequentially on the same surface of a support membrane, and then heat-treating the solution to form a dense layer to obtain the reverse osmosis membrane, wherein the aqueous solution includes a polyamine and the oily solution includes a polyacyl chloride. It is understood that the polyamine and the polyacyl chloride form a polyamide layer, i.e., a dense layer, through an interfacial polymerization reaction, thereby ensuring that the composite membrane has a high salt rejection rate.

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

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

[0031] In order to better remove the hydrochloric acid generated by the interfacial polymerization reaction and ensure the forward polymerization reaction of the polyamine and the polyacyl chloride, in one embodiment, the aqueous phase solution also includes an acid scavenger, and the mass fraction of the acid scavenger in the aqueous phase solution is 0.5%-3%.

[0032] Furthermore, the acid scavenger 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 minutes-4 minutes. This configuration can further ensure the integrity and uniformity of the cross-linking of the dense layer, further improving the salt rejection rate and water flux of the composite membrane.

[0034] In one embodiment, the solvent of the oil phase solution is selected from an isoparaffin solvent, 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 a polysulfone membrane, a polypropylene membrane or a polyacrylonitrile membrane, wherein polysulfone is cheap and readily available, simple to prepare, has good mechanical strength, good pressure resistance, stable chemical properties, is non-toxic, and can resist biodegradation. Therefore, the support membrane is preferably a polysulfone membrane.

[0036] S2, sodium phosphate, sodium hydroxide and water are prepared into a mixed solution, the mixed solution and the triethylamine solution containing calcium nitrate are placed in sequence on the surface of the dense layer away from the support membrane, and hydroxyapatite nanoparticles are formed through heat treatment, and then an aqueous solution of bovine serum albumin is placed on the surface of the dense layer away from the support membrane to form a hydrophilic anti-fouling layer, thereby obtaining a composite membrane, wherein the mass ratio of the bovine serum albumin to the 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 of water and triethylamine, the water and triethylamine form an interface on the surface of the dense layer. This allows the reaction between the sodium phosphate, sodium hydroxide, and calcium nitrate to proceed at the interface formed by the water and triethylamine, i.e., an interfacial reaction occurs. This effectively prevents the formation of large particles of hydroxyapatite, and subsequently forms hydroxyapatite nanoparticles on the surface of the dense layer, with uniform distribution. The reaction formula for preparing 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 support membrane, the hydroxyapatite nanoparticles on the dense layer will react with the bovine serum albumin to form a hydrophilic anti-pollution layer. On the one hand, compared with the anti-pollution layer formed by directly coating a hydrophilic polymer on the surface of the reverse osmosis membrane, the hydrophilic anti-pollution layer can be firmly connected to the surface of the dense layer and is not easy to fall off during use; on the other hand, compared with the anti-pollution layer formed by cross-linking the surface of the reverse osmosis membrane with a hydrophilic substance, the hydrophilic anti-pollution layer has a relatively loose three-dimensional network structure, which can effectively reduce the resistance of the composite membrane to water and improve the water flux of the composite membrane. At the same time, due to the presence of hydroxyapatite nanoparticles, the water production channel can be effectively increased, further improving the water flux of the composite membrane.

[0040] At the same time, by controlling the mass ratio of the bovine serum albumin to the calcium nitrate to be greater than or equal to 1:20, the bovine serum albumin is in excess when the hydroxyapatite nanoparticles react with the bovine serum albumin, resulting in excess bovine serum albumin on the hydrophilic anti-fouling layer. This can effectively complex divalent metal salt ions (such as calcium ions and magnesium ions) in water, greatly increasing the solubility of divalent metal ions on the surface of the composite membrane, thereby effectively avoiding the formation of scale such as calcium carbonate and magnesium carbonate on the surface of the composite membrane, and greatly improving the anti-fouling performance of the composite membrane.

[0041] It should be noted that in the present invention, in addition to the complexation reaction, self-assembly behavior also occurs during the reaction between hydroxyapatite nanoparticles and bovine serum albumin. The mechanism of the complexation reaction is mainly that the calcium ions on the surface of the hydroxyapatite nanoparticles bind to the carboxyl groups or amino groups in the bovine serum albumin molecules through coordination bonds to form a stable bovine serum albumin-hydroxyapatite complex, so that the hydrophilic anti-fouling layer can be firmly connected to the surface of the dense layer and is not easy to fall off during use; at the same time, since the hydroxyapatite nanoparticles contain hydroxyl groups and the bovine serum albumin is rich in carboxyl groups and amino groups, the two will spontaneously form a self-assembled structure through electrostatic interaction and hydrogen bonds, thereby synergistically reacting to form a hydrophilic anti-fouling layer with a relatively loose three-dimensional network structure, so that the hydrophilic anti-fouling layer can effectively reduce the resistance of the composite membrane to water and improve 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 pollutant to test the anti-pollution performance of reverse osmosis membranes. This application is the first to use the interaction between bovine serum albumin and hydroxyapatite nanoparticles to form a hydrophilic anti-pollution layer to improve the anti-pollution 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 a high water flux while still having excellent anti-pollution performance.

[0044] Optionally, the mass ratio of the bovine serum albumin to the calcium nitrate is 1:20-1:10. This configuration helps to better ensure that the hydrophilic anti-fouling layer contains excess bovine serum albumin, further improve the solubility of divalent metal ions on the composite membrane surface, and better improve the anti-fouling 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 1:1-5:1. With this arrangement, by adjusting the mass ratio of water to triethylamine, a stable interface can be formed between water and triethylamine, thereby preventing the formation of large hydroxyapatite particles during the reaction between sodium phosphate, sodium hydroxide, and calcium nitrate to form hydroxyapatite. This allows the formation of small, uniformly sized, and evenly dispersed hydroxyapatite nanoparticles, which are conducive to better reaction with bovine serum albumin to form a hydrophilic anti-fouling layer. This also increases the number of water production channels, further improving the anti-fouling 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%. By adjusting the amounts of sodium phosphate, sodium hydroxide, and calcium nitrate, sufficient reaction between the three can be achieved, thereby better forming small, 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 the bovine serum albumin and the hydroxyapatite nanoparticles to form a firmly connected hydrophilic anti-fouling layer, while also ensuring an excess of bovine serum albumin, thereby ensuring that the surface of the hydrophilic anti-fouling layer contains excess bovine serum albumin. This effectively complexes divalent metal ions during water treatment, preventing the formation of dirt on the surface of the hydrophilic anti-fouling layer, thereby improving the anti-fouling performance and water flux of the composite membrane.

[0048] Optionally, the heat treatment temperature is 60° C.-80° C., and the heat treatment time is 3 min-5 min. This configuration is conducive to more complete reaction between sodium phosphate, sodium hydroxide and calcium nitrate, and better formation of hydroxyapatite nanoparticles.

[0049] The present invention also provides a composite membrane prepared by the composite membrane preparation method. When used in water treatment, the composite membrane can maintain high desalination rate and high water flux while still having excellent anti-pollution performance.

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

[0051] In one embodiment, the water treatment device can be a purifier. When the reverse osmosis membrane is used 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 application will be further described below through the following specific examples. However, those skilled in the art will understand that the following examples are intended only to illustrate the present invention and should not be construed as limiting the scope of the present invention. Where specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, for which the manufacturer is not specified, are all commercially available conventional products.

[0054] Example 1

[0055] Metaphenylenediamine, triethylamine, and water were uniformly mixed to form an aqueous phase solution, wherein the mass fraction of metaphenylenediamine in the aqueous phase solution was 1.5% and the mass fraction of triethylamine was 1%. Trimesoyl chloride and an isoparaffin solvent (Isopar-L) were uniformly mixed to form an oil phase solution, wherein the mass fraction of trimesoyl chloride in the oil phase solution was 0.2%. Sodium phosphate, sodium hydroxide, and water were uniformly mixed to form a mixed solution, wherein the mass fraction of sodium phosphate in the mixed solution was 2% and the mass fraction of sodium hydroxide in the mixed solution was 0.5%. Calcium nitrate and triethylamine were uniformly mixed to form a triethylamine solution containing calcium nitrate, 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 triethylamine solution containing calcium nitrate was 3:1. Bovine serum albumin and water were mixed to form a bovine serum albumin aqueous solution, wherein the mass fraction of bovine serum albumin in the bovine serum albumin aqueous solution was 0.2%, and the mass ratio of bovine serum albumin to calcium nitrate was 1:15.

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

[0057] The above-mentioned mixed solution is applied on the surface of the dense layer away from the support membrane, and after standing for 30 seconds, the excess mixed solution is poured out and dried in the shade. The above-mentioned triethylamine solution containing calcium nitrate is applied on the surface of the dense layer away from the support membrane, and after standing for 30 seconds, the excess triethylamine solution containing calcium nitrate is poured out, and the hydroxyapatite nanoparticles are dried in a 60°C oven; then, the bovine serum albumin aqueous solution is applied to the surface of the dense layer away from the support membrane, and after standing for 30 seconds, the excess bovine serum albumin aqueous solution is poured out and dried in the shade to form a hydrophilic anti-pollution layer to obtain a composite membrane.

[0058] Example 2

[0059] Metaphenylenediamine, triethylamine, and water were uniformly mixed to form an aqueous phase solution, wherein the mass fraction of metaphenylenediamine in the aqueous phase solution was 1% and the mass fraction of triethylamine was 0.5%. Trimesoyl chloride and an isoparaffin solvent (Isopar-L) were uniformly mixed to form an oil phase solution, wherein the mass fraction of trimesoyl chloride in the oil phase solution was 0.15%. Sodium phosphate, sodium hydroxide, and water were uniformly mixed to form a mixed solution, wherein the mass fraction of sodium phosphate in the mixed solution was 1% and the mass fraction of sodium hydroxide in the mixed solution was 0.1%. Calcium nitrate and triethylamine were uniformly mixed to form a triethylamine solution containing calcium nitrate, 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 and water were mixed to form a bovine serum albumin aqueous solution, wherein the mass fraction of bovine serum albumin in the bovine serum albumin aqueous solution was 0.05%, and the mass ratio of bovine serum albumin to calcium nitrate was 1:20.

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

[0061] The above-mentioned mixed solution is applied on the surface of the dense layer away from the support membrane, and after standing for 30 seconds, the excess mixed solution is poured out and dried in the shade. The above-mentioned triethylamine solution containing calcium nitrate is applied on the surface of the dense layer away from the support membrane, and after standing for 30 seconds, the excess triethylamine solution containing calcium nitrate is poured out, and the hydroxyapatite nanoparticles are dried in a 60°C oven; then, the bovine serum albumin aqueous solution is applied to the surface of the dense layer away from the support membrane, and after standing for 30 seconds, the excess bovine serum albumin aqueous solution is poured out and dried in the shade to form a hydrophilic anti-pollution layer to obtain a composite membrane.

[0062] Example 3

[0063] Metaphenylenediamine, triethylamine, and water were uniformly mixed to form an aqueous phase solution, wherein the mass fraction of metaphenylenediamine in the aqueous phase solution was 3% and the mass fraction of triethylamine was 3%; trimesoyl chloride and an isoparaffin solvent (Isopar-L) were uniformly mixed to form an oil phase solution, wherein the mass fraction of trimesoyl chloride in the oil phase solution was 0.4%; sodium phosphate, sodium hydroxide, and water were uniformly mixed to form a mixed solution, wherein the mass fraction of sodium phosphate in the mixed solution was 3% and the mass fraction of sodium hydroxide in the mixed solution was 1%; calcium nitrate and triethylamine were uniformly mixed to form a triethylamine solution containing calcium nitrate, 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; bovine serum albumin and water were mixed to form a bovine serum albumin aqueous solution, 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-mentioned aqueous phase solution is applied to the surface of the polysulfone support membrane, and after standing for 60 seconds, the excess aqueous phase solution is poured out, and the membrane surface is blown dry with cold air. Then, the above-mentioned oil phase solution is applied to the same surface of the polysulfone support membrane, and after standing for 30 seconds, the excess oil phase solution is poured out. After draining, it is placed in an 80°C oven for 3 minutes to obtain a reverse osmosis membrane, wherein the reverse osmosis membrane includes a stacked support membrane and a dense layer.

[0065] The above-mentioned mixed solution is applied on the surface of the dense layer away from the support membrane, and after standing for 30 seconds, the excess mixed solution is poured out and dried in the shade. The above-mentioned triethylamine solution containing calcium nitrate is applied on the surface of the dense layer away from the support membrane, and after standing for 30 seconds, the excess triethylamine solution containing calcium nitrate is poured out, and the hydroxyapatite nanoparticles are dried in an 80°C oven; then, a bovine serum albumin aqueous solution is applied to the surface of the dense layer away from the support membrane, and after standing for 30 seconds, the excess bovine serum albumin aqueous solution is poured out, and the membrane is dried in the shade to form a hydrophilic anti-pollution layer to obtain a composite membrane.

[0066] Example 4

[0067] Compared with Example 1, Example 4 differs only in that the mass fraction of sodium phosphate in the mixed solution is 0.5%, and the other conditions are the same to obtain a composite membrane.

[0068] Example 5

[0069] Compared with Example 1, Example 5 differs only in that the mass fraction of sodium phosphate in the mixed solution is 4%, and the other conditions are the same to obtain a composite membrane.

[0070] Example 6

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

[0072] Example 7

[0073] Compared with Example 1, Example 7 differs 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 the other conditions are the same to obtain a composite membrane.

[0074] Example 8

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

[0076] Example 9

[0077] Example 9 is different 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. Other conditions are the same, and a composite membrane is obtained.

[0078] Example 10

[0079] Example 10 is different 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. 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 the mass ratio of water in the mixed solution to triethylamine in the triethylamine solution containing calcium nitrate is 1:2, and other conditions are the same to obtain a composite membrane.

[0082] Example 12

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

[0084] Comparative Example 1

[0085] Comparative Example 1 is different from Example 1 only in that a calcium nitrate aqueous solution is used to replace the triethylamine solution containing calcium nitrate, that is, calcium nitrate and water are uniformly mixed to prepare a calcium nitrate aqueous solution, wherein the mass fraction of calcium nitrate in the calcium nitrate aqueous solution is 2%, and the other conditions are the same to obtain a composite membrane.

[0086] Comparative Example 2

[0087] Comparative Example 2 is compared with Example 1, except that the mass fraction of bovine serum albumin in the bovine serum albumin aqueous solution is 0.2%, and the mass ratio of bovine serum albumin to calcium nitrate is 1:25. Other conditions are the same, and a composite membrane is obtained.

[0088] Comparative Example 3

[0089] Comparative Example 3 is different 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%. Other conditions are the same, and the following is obtained: Figure 2 The composite membrane shown.

[0090] Comparative Example 4

[0091] The only difference between Comparative Example 4 and Example 1 is 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, and the excess titanium dioxide solution is poured out after standing for 30 seconds, and then dried in the shade; then the bovine serum albumin aqueous solution is applied to the surface of the dense layer away from the support membrane, and the excess bovine serum albumin aqueous solution is poured out after standing for 30 seconds, and dried in the shade to form a hydrophilic anti-pollution layer. The other conditions are the same to obtain a composite membrane.

[0092] Comparative Example 5

[0093] Metaphenylenediamine, triethylamine and water are uniformly mixed to prepare an aqueous phase solution, wherein the mass fraction of metaphenylenediamine in the aqueous phase solution is 1%, and the mass fraction of triethylamine is 0.5%. Trimesoyl chloride and an isoparaffin solvent (Isopar-L) are uniformly mixed to prepare an oil phase solution, wherein the mass fraction of trimesoyl chloride in the oil phase solution is 0.15%.

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

[0095] Mix a 0.2% polyvinyl alcohol aqueous solution with a 0.5% glutaraldehyde aqueous solution, and then apply it on the surface of the dense layer of the reverse osmosis membrane. After 30 seconds, pour out the excess solution, and finally put it in an 80℃ oven for 3 minutes to obtain the following: 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: a test pressure of 1.55 MPa, a concentrate flow rate of 1.0 GPM, an ambient temperature of 25°C, a concentrate pH value of 6.5-7.5, and a 2000 ppm calcium chloride aqueous solution. The test results are shown in Table 1.

[0097] Table 1

[0098]

[0099] At the same time, the anti-pollution 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: the test pressure was 1.55 MPa, the concentrated water flow rate was 1.0 GPM, the ambient temperature was 25°C, the concentrated water pH value was 6.5-7.5, and the anti-pollution performance test was carried out under the inlet conditions of 2000 ppm sodium chloride + 100 ppm sodium humate. After 100 hours of continuous operation, the membrane was cleaned, and then the performance test was carried out under the inlet conditions of 2000 ppm calcium chloride in the concentrated 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 in a certain period of 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 retention rate (R) is calculated by the concentration of the feed liquid and the concentration of the permeate. The calculation formula is: R=(1-C1 / C0)×100%, where C1 is the concentration of the permeate and C0 is the concentration of the feed liquid.

[0104] The calculation formula of water flux recovery rate is: (water flux of composite membrane after pollution / water flux of initial composite membrane) × 100%.

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

[0106] from Figure 2 It can be seen that in Comparative Example 3, since polyvinyl alcohol aqueous solution is used instead of bovine serum albumin aqueous solution, the thickness of the formed hydrophilic anti-fouling layer is thicker, and the surface structure of the composite membrane has been basically covered, affecting the water flux of the composite membrane.

[0107] from Figure 3 It can be seen that in Comparative Example 5, an anti-pollution layer is formed by cross-linking polyvinyl alcohol and glutaraldehyde on the surface of the reverse osmosis membrane. The anti-pollution layer is densely cross-linked, so that the surface morphology of the composite membrane has been completely covered by the anti-pollution coating. The anti-pollution layer is significantly thickened, which increases the resistance of the reverse osmosis membrane and causes the water flux of the composite membrane to decrease.

[0108] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned 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 above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A method for preparing a composite film, characterized in that: The steps include: A reverse osmosis membrane is provided, comprising a support membrane and a dense layer arranged in a stacked manner; Sodium phosphate, sodium hydroxide and water are prepared into a mixed solution, and the mixed solution and a triethylamine solution containing calcium nitrate are placed in sequence on the surface of the dense layer away from the support membrane, and hydroxyapatite nanoparticles are formed through heat treatment. Then, an aqueous solution of bovine serum albumin is placed on the surface of the dense layer away from the support membrane to form a hydrophilic anti-fouling layer, thereby obtaining a composite membrane, wherein the mass ratio of the bovine serum albumin to the calcium nitrate is greater than or equal to 1:

20.

2. The method for preparing a composite film according to claim 1, wherein The mass ratio of the bovine serum albumin to the calcium nitrate is 1:20-1:

10.

3. The method for preparing a composite film according to claim 1, wherein The mass ratio of water in the mixed solution to triethylamine in the triethylamine solution containing calcium nitrate is 1:1-5:

1.

4. The method for preparing a composite film according to claim 1, wherein 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 a composite membrane according to claim 1, wherein: The mass fraction of calcium nitrate in the triethylamine solution containing calcium nitrate is 1%-3%.

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

7. The method for preparing a composite membrane according to claim 1, wherein: The temperature of the heat treatment is 60° C.-80° C., and the time of the heat treatment is 3 min-5 min.

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

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

10. Use of the composite membrane according to claim 9 in a water treatment device.

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