Reverse osmosis membrane and its preparation method and application

Abstract

The present invention relates to a reverse osmosis membrane and a preparation method and application thereof, wherein the preparation method of the reverse osmosis membrane comprises the following steps: a linear polyquaternary ammonium salt containing a hydroxyl group, a polyamine and water are formulated into an aqueous phase solution, wherein the mass ratio of the linear polyquaternary ammonium salt containing a hydroxyl group to the polyamine is 1:3-1:350, and the pH of the aqueous phase solution is greater than or equal to 10.0; the aqueous phase solution and an oil phase solution containing polyacyl chloride are sequentially placed on the same surface of a porous support membrane, and a polyamide / polyquaternary ammonium salt separation layer is formed through heat treatment to obtain a prefabricated membrane; the prefabricated membrane is rinsed with a small molecule polyol aqueous solution to obtain a reverse osmosis membrane, wherein the temperature of the small molecule polyol aqueous solution is 70°C-90°C. The reverse osmosis membrane prepared by this preparation method can have high rejection rate, high water flux and excellent antibacterial performance when applied to water treatment.

Description

Technical Field

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

[0002] Reverse osmosis is a highly efficient and energy-saving technology that has been widely used in drinking water treatment, seawater desalination, brackish water desalination, and water reuse. However, reverse osmosis membranes prepared using traditional interfacial polymerization methods are susceptible to microbial growth on the membrane surface during use, resulting in a significant decrease in the membrane's water flux. Furthermore, while reverse osmosis membranes have a high salt rejection rate, their retention rate for small organic molecules such as glycerol is still low. These small organic molecules remaining in the produced water provide a nutrient source for microbial growth, leading to microbial proliferation and negatively impacting the produced water quality.

[0003] It can be seen that traditional reverse osmosis membranes still find it difficult to have high retention rate, high water flux and excellent antibacterial performance. Summary of the Invention

[0004] Based on this, it is necessary to provide a reverse osmosis membrane and its preparation method and application to address the above problems. The reverse osmosis membrane prepared by this preparation method can have high retention rate, high water flux and excellent antibacterial performance when used in water treatment.

[0005] A method for preparing a reverse osmosis membrane comprises the following steps:

[0006] A linear polyquaternium salt containing hydroxyl groups, a polyamine, and water are formulated into an aqueous solution, wherein the mass ratio of the linear polyquaternium salt containing hydroxyl groups to the polyamine is 1:3-1:350, and the pH of the aqueous solution is greater than or equal to 10.0;

[0007] placing the aqueous solution and the oily solution containing polyacyl chloride on the same surface of a porous support membrane in sequence, and subjecting the membrane to heat treatment to form a separation layer to obtain a prefabricated membrane;

[0008] The prefabricated membrane is rinsed with a small molecule polyol aqueous solution to obtain a reverse osmosis membrane, wherein the temperature of the small molecule polyol aqueous solution is 70° C.-90° C.

[0009] In one embodiment, the mass fraction of the linear polyquaternary ammonium salt containing hydroxyl groups in the aqueous solution is 0.01%-0.5%;

[0010] And / or, the mass fraction of the polyamine in the aqueous solution is 1.5%-3.5%.

[0011] In one embodiment, the mass fraction of the polyacyl chloride in the oil phase solution containing the polyacyl chloride is 0.1%-0.3%.

[0012] In one embodiment, the mass fraction of the small molecule polyol in the small molecule polyol aqueous solution is 5%-20%.

[0013] In one embodiment, the linear polyquaternium salt containing a hydroxyl group is polyquaternium-10.

[0014] In one embodiment, the small molecule polyol has 2-3 carbon atoms.

[0015] In one embodiment, in the step of preparing an aqueous solution by combining a linear polyquaternary ammonium salt containing a hydroxyl group, a polyamine and water, triethylamine is used to adjust the pH of the aqueous solution to 10.0-12.0.

[0016] In one embodiment, the heat treatment temperature is 100°C-120°C, and the heat treatment time is 1 min-3 min;

[0017] And / or, the rinsing treatment time is 1 min-5 min.

[0018] A reverse osmosis membrane prepared by adopting the reverse osmosis membrane preparation method.

[0019] An application of the reverse osmosis membrane in a water treatment device.

[0020] In the preparation method of the reverse osmosis membrane of the present invention, when the aqueous phase solution and the oil phase solution are in contact, the polyamine and the polyacyl chloride undergo an interfacial polymerization reaction to form a polyamide layer. In this process, since a linear polyquaternary ammonium salt containing hydroxyl groups is added to the aqueous phase solution, and the mass ratio of the linear polyquaternary ammonium salt containing hydroxyl groups and the polyamine and the pH of the aqueous phase solution are controlled, on the one hand, the polar groups uniformly distributed in the linear polyquaternary ammonium salt containing hydroxyl groups can be fully and reasonably utilized, the diffusion speed and diffusion depth of the polyamine into the oil phase solution are reduced and controlled within a suitable range, so that the formed separation layer has a thin thickness and a high degree of crosslinking. Moderate characteristics, thereby effectively reducing the permeation resistance of the reverse osmosis membrane and improving the water flux of the reverse osmosis membrane; on the other hand, the linear polyquaternary ammonium salt containing hydroxyl groups is interspersed in the polyamide molecular chain with its linear structure to form a separation layer. Since the polyquaternary ammonium salt molecules are more inclined to fill the excessive free volume in the separation layer, the free volume distribution of the separation layer can be uniform, which is beneficial to improving the retention rate of the reverse osmosis membrane; moreover, the linear polyquaternary ammonium salt containing hydroxyl groups is rich in positively charged quaternary ammonium groups, which form negatively charged carboxyl groups formed with residual acyl chlorides to form zwitterion-like hydration channels, further improving the water flux of the reverse osmosis membrane.

[0021] When heat treatment is performed, the hydroxyl groups in the linear polyquaternary ammonium salt containing hydroxyl groups react with the residual acyl chloride groups under high temperature and high pH conditions, so that the linear polyquaternary ammonium salt containing hydroxyl groups is chemically bonded to the polyamide molecules to form a separation layer, thereby improving the operational stability of the separation layer; and the linear polyquaternary ammonium salt containing hydroxyl groups itself has antibacterial properties, so that the reverse osmosis membrane has antibacterial properties; when rinsing treatment is performed, under the action of a small molecule polyol aqueous solution at a specific temperature, the polyamide / polyquaternary ammonium salt molecular chains creep, eliminating larger gaps in the separation layer and making its free volume distribution more uniform, which is beneficial to further improving the retention rate of the reverse osmosis membrane, and at the same time inducing some quaternary ammonium groups of the linear polyquaternary ammonium salt containing hydroxyl groups to migrate to the surface of the separation layer and exist on the surface of the separation layer in the form of molecular brushes to form an antibacterial layer, giving the reverse osmosis membrane excellent antibacterial properties without affecting the water flux of the reverse osmosis membrane.

[0022] Therefore, the reverse osmosis membrane prepared by the present invention can have high retention rate, high water flux and excellent antibacterial performance when applied to water treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is an electron microscope image of the reverse osmosis membrane prepared in Example 1 of the present invention;

[0024] Figure 2 This is an electron microscope image of the reverse osmosis membrane prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0025] 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.

[0026] 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.

[0027] The method for preparing a reverse osmosis membrane provided by the present invention comprises the following steps:

[0028] A linear polyquaternium salt containing hydroxyl groups, a polyamine, and water are formulated into an aqueous solution, wherein the mass ratio of the linear polyquaternium salt containing hydroxyl groups to the polyamine is 1:3-1:350, and the pH of the aqueous solution is greater than or equal to 10.0;

[0029] placing the aqueous solution and the oily solution containing polyacyl chloride on the same surface of a porous support membrane in sequence, and subjecting the membrane to heat treatment to form a separation layer to obtain a prefabricated membrane;

[0030] The prefabricated membrane is rinsed with a small molecule polyol aqueous solution to obtain a reverse osmosis membrane, wherein the temperature of the small molecule polyol aqueous solution is 70° C.-90° C.

[0031] Specifically, when the aqueous solution and the oil phase solution containing polyacyl chlorides are sequentially placed on the same surface of the porous support membrane, the aqueous solution and the oil phase solution contact to form a water-oil interface, and the polyamine in the aqueous solution and the polyacyl chloride in the oil phase solution undergo interfacial polymerization at the water-oil interface to form a polyamide layer. In this process, the linear polyquaternary ammonium salt containing hydroxyl groups is introduced into the aqueous solution, and the mass ratio of the linear polyquaternary ammonium salt containing hydroxyl groups and the polyamine is controlled, which has the following three effects: 1. It can fully and reasonably utilize the polar groups uniformly distributed in the linear polyquaternary ammonium salt containing hydroxyl groups, reduce the diffusion speed and diffusion depth of m-phenylenediamine into the oil phase solution and control them within a suitable range, so that the formed The separation layer is characterized by a thin thickness and a moderate degree of cross-linking, which can effectively reduce the permeation resistance of the reverse osmosis membrane and improve the water flux of the reverse osmosis membrane; ② The linear polyquaternary ammonium salt containing hydroxyl groups is interspersed in the polyamide molecular chain with its linear structure to form a polyamide / polyquaternary ammonium salt separation layer. Compared with the star-shaped polyquaternary ammonium salt, the linear structure does not interfere with the orderly arrangement of the polyamide molecules and can fill the excessive free volume in the separation layer, ensuring a high retention rate while further improving the water flux of the reverse osmosis membrane; ③ The linear polyquaternary ammonium salt containing hydroxyl groups is rich in positively charged quaternary ammonium groups, which form negatively charged carboxyl groups formed by residual acyl chlorides to form zwitterionic hydration channels, further improving the water flux of the reverse osmosis membrane.

[0032] During heat treatment, since the pH of the aqueous solution is 10.0-12.0, the hydroxyl groups in the linear polyquaternary ammonium salt containing hydroxyl groups can react with the residual acyl chloride groups under high temperature and high pH conditions, so that the linear polyquaternary ammonium salt containing hydroxyl groups and the polyamide molecules are chemically bonded to form a separation layer, thereby improving the operational stability of the separation layer.

[0033] When the prefabricated membrane is rinsed with a small molecule polyol aqueous solution, the small molecule polyol aqueous solution is used as the rinsing solution, and the temperature of the small molecule polyol aqueous solution is controlled. That is, under the synergistic effect of high temperature, the small molecule polyol is used as a small molecule plasticizer to penetrate into the separation layer, thereby promoting the creep of the polyamide / polyquaternary ammonium salt molecular chains, eliminating excessive free volume holes in the separation layer, and making the free volume distribution more uniform, which is conducive to further improving the retention rate of the reverse osmosis membrane. At the same time, because the linear polyquaternary ammonium salt containing hydroxyl groups has high molecular chain flexibility and the quaternary ammonium group has strong hydrophilicity and positive charge, under the induction effect of the small molecule polyol solution and high temperature, the quaternary ammonium group migrates to the surface of the separation layer and exists in the form of a molecular brush on the surface of the separation layer to form an antibacterial layer, giving the reverse osmosis membrane excellent antibacterial properties. Compared with conventional continuous antibacterial coating, this method does not increase the permeation resistance of the reverse osmosis membrane, that is, it does not sacrifice the water flux of the reverse osmosis membrane.

[0034] Therefore, the reverse osmosis membrane prepared by the present invention can have high retention rate, high water flux and excellent antibacterial performance when applied to water treatment.

[0035] It should be noted that the linear polyquaternary ammonium salt containing hydroxyl groups in the reverse osmosis membrane of the present invention, a portion of which exists in the form of filling chains in the larger free volume between the polyamide chain segments and is chemically bonded to the polyamide molecules, thereby improving the uniformity of the distribution of the free volume in the separation layer structure and further improving the rejection rate of the reverse osmosis membrane, especially the rejection rate of small molecule organic matter; the other portion exists in the form of molecular brushes on the surface of the separation layer to form an antibacterial layer, which gives the reverse osmosis membrane excellent and long-lasting antibacterial properties without sacrificing the water flux of the reverse osmosis membrane.

[0036] Optionally, the mass fraction of the linear polyquaternary ammonium salt containing hydroxyl groups in the aqueous phase solution is 0.01%-0.5%; the mass fraction of the polyamine in the aqueous phase solution is 1.5%-3.5%; such an arrangement can be made by adjusting the mass fraction of the linear polyquaternary ammonium salt containing hydroxyl groups in the aqueous phase solution and the mass fraction of the polyamine in the aqueous phase solution, so as to better regulate the mass ratio of the linear polyquaternary ammonium salt containing hydroxyl groups and the polyamine, so that the formed separation layer has the characteristics of thinner thickness and moderate density, which is beneficial to further improve the water flux and retention rate of the reverse osmosis membrane, and further improve the antibacterial performance of the reverse osmosis membrane.

[0037] Furthermore, the linear polyquaternium salt containing hydroxyl groups is preferably polyquaternium-10.

[0038] In one embodiment, the polyamine is preferably m-phenylenediamine.

[0039] Optionally, the mass fraction of the polyacyl chloride in the oil phase solution containing the polyacyl chloride is 0.1%-0.3%; such a setting can enable the polyacyl chloride to fully react with the polyamine in the aqueous phase solution to better form a complete high polyamide separation layer, which is beneficial to further improve the retention rate of the reverse osmosis membrane.

[0040] Furthermore, the polybasic acid chloride is preferably trimesoyl chloride.

[0041] Optionally, the mass fraction of the small molecule polyol in the small molecule polyol aqueous solution is 5%-20%; such a setting can better adjust the free volume distribution of the separation layer by adjusting the mass fraction of the small molecule polyol in the small molecule polyol aqueous solution, making it more uniform, and further improving the retention rate of the reverse osmosis membrane; at the same time, it is conducive to better synergistic high temperature action, so that the linear polyquaternary ammonium salt containing hydroxyl groups migrates to the surface of the separation layer to form a uniform antibacterial layer, further improving the antibacterial performance of the reverse osmosis membrane.

[0042] Optionally, the carbon number of the small molecule polyol is 2-3, and more preferably, the small molecule polyol is selected from at least one of ethylene glycol, propylene glycol, and glycerol.

[0043] It can be understood that when the prefabricated membrane is rinsed with a small molecule polyol aqueous solution having a specific temperature in the present invention, the small molecule polyol enters between the polyamide molecular segments and causes them to peristalsis, which, on the one hand, makes the free volume distribution of the separation layer more uniform, and on the other hand, can induce some quaternary ammonium groups of the linear polyquaternary ammonium salt containing hydroxyl groups to migrate to the surface of the separation layer and exist in the form of molecular brushes on the surface of the separation layer to form an antibacterial layer, further improving the water flux, retention rate and antibacterial performance of the reverse osmosis membrane.

[0044] Optionally, the rinsing treatment lasts for 1-5 minutes. This configuration is beneficial for better improving the uniformity of the free volume in the separation layer structure and better ensuring that some quaternary ammonium groups of the linear polyquaternary ammonium salt containing hydroxyl groups are present in the form of molecular brushes on the surface of the separation layer to form an antibacterial layer, further improving the water flux, retention rate, and antibacterial performance of the reverse osmosis membrane.

[0045] Optionally, in the step of preparing an aqueous phase solution from a linear polyquaternary ammonium salt containing hydroxyl groups, a polyamine, and water, triethylamine is used to adjust the pH of the aqueous phase solution to 10.0-12.0. This arrangement is conducive to ensuring the smooth progress of the interfacial polymerization reaction between the polyamine and the polyacyl chloride, which is conducive to obtaining a separation layer with better integrity and further improving the retention rate of the reverse osmosis membrane. At the same time, the hydroxyl groups in the linear polyquaternary ammonium salt are involved in the reaction, so that they are connected to the separation layer in the form of chemical bonds, thereby avoiding gradual loss during actual use, which leads to a weakening of the antibacterial effect.

[0046] Optionally, the heat treatment temperature is 100°C-120°C, and the heat treatment time is 1-3 minutes. This configuration further ensures the integrity and uniformity of the cross-linking of the separation layer, and promotes the reaction between the hydroxyl groups in the linear polyquaternium salt and the residual acyl chloride, further improving the rejection rate, water flux, and antibacterial durability of the reverse osmosis membrane.

[0047] In one embodiment, the porous support membrane is selected from at least one of a polysulfone membrane, a polypropylene membrane or a polyacrylonitrile membrane, wherein polysulfone is cheap and easy to obtain, 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.

[0048] In one embodiment, the solvent of the aqueous phase solution is water; 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.

[0049] At the same time, the present invention also provides a reverse osmosis membrane prepared by the preparation method of the reverse osmosis membrane. Specifically, the reverse osmosis membrane includes a porous support membrane, a separation layer, and an antibacterial layer arranged in a stacked manner, wherein linear polyquaternary ammonium salt molecules containing hydroxyl groups are interspersed in polyamide molecules to form the separation layer, and some quaternary ammonium groups of the linear polyquaternary ammonium salt containing hydroxyl groups are distributed on the surface of the separation layer in the form of molecular brushes to form the antibacterial layer. When applied to water treatment, the reverse osmosis membrane can have high retention rate, high water flux, and excellent antibacterial performance, thereby ensuring the operational stability of the water treatment system, extending its service life, and having low energy consumption and reducing costs.

[0050] In one embodiment, the separation layer has a thickness of 120 nm to 160 nm.

[0051] In addition, the present invention also provides an application of the reverse osmosis membrane in a water treatment device.

[0052] 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.

[0053] In another embodiment, the water treatment device may also be a seawater desalination device.

[0054] The reverse osmosis membrane, its preparation method, and its application will be further described below by 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 procedures 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.

[0055] Example 1

[0056] Polyquaternium-10, m-phenylenediamine, triethylamine and water are mixed to form an aqueous phase solution, wherein the pH of the aqueous phase solution is 10.0, and the mass fraction of polyquaternium-10 and the mass fraction of m-phenylenediamine in the aqueous phase solution is 0.15%, and the mass fraction of m-phenylenediamine is 2.5%; trimesoyl chloride and Isopar G are mixed to form an oil phase solution, wherein the mass fraction of trimesoyl chloride in the oil phase solution is 0.15%; glycerol and water are mixed to form a glycerol aqueous solution, wherein the mass fraction of glycerol in the glycerol aqueous solution is 5%, and the temperature of the glycerol aqueous solution is 70°C.

[0057] After the polysulfone support membrane is immersed in the above-mentioned aqueous solution for 1 minute, the excess aqueous solution is taken out and removed, and then the above-mentioned oil phase solution is coated on the surface of the polysulfone support membrane. After standing for 1 minute, the excess oil phase solution is poured out and drained. After that, it is placed in a 100°C oven for heat treatment for 2 minutes to form a separation layer to obtain a prefabricated membrane; the prefabricated membrane is immersed in a glycerol aqueous solution for 3 minutes, and then taken out to obtain Figure 1 The reverse osmosis membrane shown, wherein the thickness of the separation layer in the reverse osmosis membrane is 130 nm.

[0058] Example 2

[0059] Polyquaternium-10, m-phenylenediamine, triethylamine, and water are mixed to form an aqueous solution, wherein the pH of the aqueous solution is 12.0, and the mass fraction of polyquaternium-10 and the mass fraction of m-phenylenediamine in the aqueous solution is 0.01%, and the mass fraction of m-phenylenediamine is 1.5%. Trimesoyl chloride and Isopar G are mixed to form an oily solution, wherein the mass fraction of trimesoyl chloride in the oily solution is 0.3%. Ethylene glycol and water are mixed to form an ethylene glycol aqueous solution, wherein the mass fraction of ethylene glycol in the ethylene glycol aqueous solution is 12%, and the temperature of the ethylene glycol aqueous solution is 80°C.

[0060] After the polysulfone support membrane is immersed in the above-mentioned aqueous phase solution for 1 minute, the excess aqueous phase solution is taken out and removed, and then the above-mentioned oil phase solution is applied to the surface of the polysulfone support membrane. After standing for 1 minute, the excess oil phase solution is poured out and drained. After that, it is placed in a 110°C oven for heat treatment for 2 minutes to form a separation layer to obtain a prefabricated membrane; the prefabricated membrane is immersed in an ethylene glycol aqueous solution for 2 minutes, and then taken out to obtain a reverse osmosis membrane, wherein the thickness of the separation layer in the reverse osmosis membrane is 123 nm.

[0061] Example 3

[0062] Polyquaternium-10, m-phenylenediamine, triethylamine and water are mixed to form an aqueous phase solution, wherein the pH of the aqueous phase solution is 11.0, and the mass fraction of polyquaternium-10 and the mass fraction of m-phenylenediamine in the aqueous phase solution is 0.5%, and the mass fraction of m-phenylenediamine is 3.5%; trimesoyl chloride and Isopar G are mixed to form an oil phase solution, wherein the mass fraction of trimesoyl chloride in the oil phase solution is 0.2%; propylene glycol and water are mixed to form a propylene glycol aqueous solution, wherein the mass fraction of propylene glycol in the propylene glycol aqueous solution is 20%, and the temperature of the propylene glycol aqueous solution is 90°C.

[0063] After the polysulfone support membrane is immersed in the above-mentioned aqueous phase solution for 1 minute, the excess aqueous phase solution is taken out and removed, and then the above-mentioned oil phase solution is applied to the surface of the polysulfone support membrane. After standing for 1 minute, the excess oil phase solution is poured out and drained. After that, it is placed in a 120°C oven for heat treatment for 1 minute to form a separation layer to obtain a prefabricated membrane; the prefabricated membrane is immersed in a propylene glycol aqueous solution for 5 minutes, and then taken out to obtain a reverse osmosis membrane, wherein the thickness of the separation layer in the reverse osmosis membrane is 135 nm.

[0064] Example 4

[0065] Compared with Example 1, Example 4 differs only in that, in the aqueous solution, the mass fraction of polyquaternium-10 is 0.008%, and the other conditions are the same, to obtain a reverse osmosis membrane, wherein the thickness of the separation layer in the reverse osmosis membrane is 198 nm.

[0066] Example 5

[0067] Compared with Example 1, Example 5 differs only in that, in the aqueous solution, the mass fraction of polyquaternium-10 is 0.8%, and other conditions are the same, to obtain a reverse osmosis membrane, wherein the thickness of the separation layer in the reverse osmosis membrane is 202 nm.

[0068] Example 6

[0069] Compared with Example 1, Example 6 differs only in that the mass fraction of glycerol in the glycerol aqueous solution is 3%, and the other conditions are the same, thereby obtaining a reverse osmosis membrane, wherein the thickness of the separation layer in the reverse osmosis membrane is 137 nm.

[0070] Example 7

[0071] Compared with Example 1, Example 7 differs only in that the mass fraction of glycerol in the glycerol aqueous solution is 22%, and other conditions are the same, thereby obtaining a reverse osmosis membrane, wherein the thickness of the separation layer in the reverse osmosis membrane is 128 nm.

[0072] Example 8

[0073] Compared with Example 1, Example 8 differs only in that the pH of the aqueous solution is 13.0, and the other conditions are the same, thereby obtaining a reverse osmosis membrane, wherein the thickness of the polyamide separation layer in the reverse osmosis membrane is 118 nm.

[0074] Example 9

[0075] The only difference between Example 9 and Example 1 is that methanol is used instead of glycerol. Other conditions are the same, and a reverse osmosis membrane is obtained, wherein the thickness of the separation layer in the reverse osmosis membrane is 135 nm.

[0076] Comparative Example 1

[0077] An aqueous solution was prepared by mixing m-phenylenediamine, triethylamine, and water, wherein the pH of the aqueous solution was 10.0 and the mass fraction of m-phenylenediamine in the aqueous solution was 2.5%. An oil solution was prepared by mixing trimesoyl chloride and Isopar G, wherein the mass fraction of trimesoyl chloride in the oil solution was 0.15%.

[0078] After the polysulfone support membrane is immersed in the above aqueous solution for 1 minute, the excess aqueous solution is taken out and removed, and then the above oil phase solution is coated on the surface of the polysulfone support membrane. After standing for 1 minute, the excess oil phase solution is poured out and drained. After that, the membrane is placed in a 100°C oven for heat treatment for 2 minutes to form a separation layer. Figure 2 The reverse osmosis membrane shown, wherein the thickness of the separation layer in the reverse osmosis membrane is 280 nm.

[0079] Comparative Example 2

[0080] m-phenylenediamine, triethylamine, and water are mixed to form an aqueous solution, wherein the pH of the aqueous solution is 12.0, and the mass fraction of m-phenylenediamine in the aqueous solution is 1.5%; trimesoyl chloride and Isopar G are mixed to form an oily solution, wherein the mass fraction of trimesoyl chloride in the oily solution is 0.30%; ethylene glycol and water are mixed to form an ethylene glycol aqueous solution, wherein the mass fraction of ethylene glycol in the ethylene glycol aqueous solution is 12%.

[0081] After the polysulfone support membrane is immersed in the above-mentioned aqueous phase solution for 1 minute, the excess aqueous phase solution is taken out and removed, and then the above-mentioned oil phase solution is applied to the surface of the polysulfone support membrane. After standing for 1 minute, the excess oil phase solution is poured out and drained. After that, it is placed in a 100°C oven for heat treatment for 2 minutes to form a separation layer to obtain a prefabricated membrane; the prefabricated membrane is immersed in an ethylene glycol aqueous solution at a temperature of 80°C for 3 minutes, and then taken out to obtain a reverse osmosis membrane, wherein the thickness of the separation layer in the reverse osmosis membrane is 295 nm.

[0082] Comparative Example 3

[0083] Comparative Example 3 is different from Example 1 only in that polyquaternium-7 is used instead of polyquaternium-10, and other conditions are the same to obtain a reverse osmosis membrane, wherein the thickness of the separation layer in the reverse osmosis membrane is 195 nm.

[0084] Comparative Example 4

[0085] Comparative Example 4 is different from Example 1 only in that dodecyltrimethylammonium chloride is used instead of polyquaternium-10, and other conditions are the same to obtain a reverse osmosis membrane, wherein the thickness of the separation layer in the reverse osmosis membrane is 178 nm.

[0086] Comparative Example 5

[0087] Comparative Example 5 is compared with Example 1, except that, in the aqueous solution, the mass fraction of polyquaternium-10 is 0.003%, and the other conditions are the same, to obtain a reverse osmosis membrane, wherein the thickness of the separation layer in the reverse osmosis membrane is 188 nm.

[0088] Comparative Example 6

[0089] Comparative Example 6 is compared with Example 1, except that, in the aqueous solution, the mass fraction of polyquaternium-10 is 3.0%, and the other conditions are the same, to obtain a reverse osmosis membrane, wherein the thickness of the separation layer in the reverse osmosis membrane is 109 nm.

[0090] Comparative Example 7

[0091] Comparative Example 7 is different from Example 1 only in that the temperature of the glycerol aqueous solution is 60° C., and other conditions are the same to obtain a reverse osmosis membrane, wherein the thickness of the separation layer in the reverse osmosis membrane is 134 nm.

[0092] Comparative Example 8

[0093] Comparative Example 8 is different from Example 1 only in that the temperature of the glycerol aqueous solution is 100° C., and other conditions are the same to obtain a reverse osmosis membrane, wherein the thickness of the separation layer in the reverse osmosis membrane is 208 nm.

[0094] Comparative Example 9

[0095] Comparative Example 9 is different from Example 1 only in that water is used instead of the glycerol aqueous solution, the water temperature is 75° C., and other conditions are the same to obtain a reverse osmosis membrane, wherein the thickness of the separation layer in the reverse osmosis membrane is 125 nm.

[0096] Comparative Example 10

[0097] Comparative Example 10 is different from Example 1 only in that PEG-200 is used instead of the glycerol aqueous solution, the temperature of the PEG-200 aqueous solution is 75° C., and the other conditions are the same to obtain a reverse osmosis membrane, wherein the thickness of the separation layer in the reverse osmosis membrane is 126 nm.

[0098] Comparative Example 11

[0099] Compared with Example 1, Comparative Example 11 differs only in that, in the step of preparing the aqueous solution, triethylamine is not added, the pH of the aqueous solution is 8.6, and the other conditions are the same, to obtain a reverse osmosis membrane, wherein the thickness of the separation layer in the reverse osmosis membrane is 94 nm.

[0100] The reverse osmosis membranes prepared in Examples 1 to 9 and Comparative Examples 1 to 11 were tested for water flux, rejection rate, and antibacterial performance. The test results are shown in Table 1. The specific test methods are as follows:

[0101] The test conditions for water flux and retention rate are as follows: the test pressure is 1.03 MPa, the concentrated water flow rate is 4.5 L / min, the ambient temperature is 25°C, the concentrated water pH value is 6.8-7.2, and a mixed aqueous solution containing 1000 ppm of sodium chloride and 100 ppm of glycerol is used as the inlet water.

[0102] Antibacterial performance test: The antibacterial effect was quantitatively detected by the shake flask method. The reverse osmosis membrane was cut into 1 cm × 3 cm samples and rinsed with pure water for 24 hours. The above samples were then placed in a 150 mL conical flask, and 70 mL of PBS buffer and 500 μL of Escherichia coli suspension were added respectively. Finally, the conical flask was fixed on a shaking shaker and shaken at 120 r / min for 24 hours. Then, 500 μL of the shaken sample liquid was taken, appropriately diluted with PBS buffer, and live bacteria culture was performed to calculate the antibacterial rate.

[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 reverse osmosis 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 reverse osmosis membrane per unit time, A is the effective membrane area, and T is time.

[0106] The retention rate (R) is calculated by the concentration of the feed solution 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 solution.

[0107] The calculation formula of the antibacterial rate is 1-C A / C B ×100%, where C A is the number of viable bacteria in the sample, C B is the number of viable cells in the blank.

[0108] from Figures 1 to 2 It can be seen that the thickness of the separation layer of the reverse osmosis membrane prepared in Example 1 and Comparative Example 1 is 130 nm and 280 nm, respectively. This is mainly because after the aqueous solution introduces polyquaternium-10, it produces a strong hydrogen bond with m-phenylenediamine, inhibiting the diffusion of m-phenylenediamine into the organic phase, thereby reducing the thickness of the separation layer.

[0109] Meanwhile, as shown in Table 1, compared to Example 1 and Example 4 to Example 5, controlling the mass fraction of the linear polyquaternary ammonium salt containing hydroxyl is within a suitable range, which is conducive to improving the water flux and antibacterial performance of reverse osmosis membrane; compared to Example 1 and Example 6 to Example 7, controlling the mass fraction of small molecule polyol in the small molecule polyol aqueous solution is within a suitable range, which is conducive to improving the retention rate and antibacterial performance of reverse osmosis membrane; compared to Example 1 and Example 8, the pH of the aqueous phase solution is too high and can affect the retention rate and antibacterial performance of reverse osmosis membrane; compared to Example 1 and Example 9, controlling the carbon number of small molecule polyol is within a suitable range, which is conducive to improving the retention rate and antibacterial performance of reverse osmosis membrane.

[0110] Compared with Example 1 and Comparative Example 1, since no linear polyquaternium salt containing hydroxyl groups was added and no glycerol aqueous solution was used for rinsing treatment in Comparative Example 1, its water flux, the retention rate of NaCl and the retention rate of organic small molecule glycerol were all reduced; Compared with Comparative Example 1 and Comparative Example 2, since no linear polyquaternium salt containing hydroxyl groups was added in Comparative Example 2, its permeation flux and retention rate were basically close to those in Comparative Example 1, indicating that only post-rinsing treatment failed to improve the separation performance of the reverse osmosis membrane; Compared with Example 1 and Comparative Example 3, since the star-shaped polyquaternium salt was used in Comparative Example 3, it was difficult for it to penetrate the network structure of the separation layer well. The structure of the gap makes the free volume distribution of the separation layer structure uneven, thereby affecting the rejection rate of the reverse osmosis membrane for small molecular organic matter. At the same time, due to the large steric hindrance of the star-shaped polyquaternium salt, it cannot migrate well to the surface of the separation layer, thereby affecting the antibacterial rate of the reverse osmosis membrane; compared with Example 1 and Comparative Example 4, since the antibacterial material in Comparative Example 4 does not contain polar groups, it is impossible to slow down the diffusion speed and diffusion depth of the polyamine to the oil phase solution, resulting in a thicker thickness of the formed separation layer, which affects the water flux of the reverse osmosis membrane; compared with Example 1 and Comparative Examples 5 to 6, due to the polyquaternium-10 and m-phenylene in Comparative Examples 5 to 6, the antibacterial material in Comparative Example 4 does not contain polar groups, it is impossible to slow down the diffusion speed and diffusion depth of the polyamine to the oil phase solution, thereby affecting the water flux of the reverse osmosis membrane. The mass ratio of diamine is not within an appropriate range, so that the diffusion speed and diffusion depth of m-phenylenediamine to the oil phase solution are not within an appropriate range, resulting in the thickness of the formed separation layer being too thick or too thin, affecting the water flux and retention rate of the reverse osmosis membrane; compared with Example 1 and Comparative Examples 7 to 8, since the temperature of the glycerol aqueous solution in Comparative Examples 7 to 8 is not within an appropriate range, the migration effect of polyquaternium-10 and the free volume distribution effect of the separation layer structure are affected, thereby affecting the retention rate and antibacterial rate of the reverse osmosis membrane for small molecular organic matter; compared with Example 1 and Comparative Example 9, since the rinsing solution in Comparative Example 9 is water, Affect the migration effect of polyquaternium salt -10 and the free volume distribution effect of the separation layer structure, thereby affecting the rejection rate and antibacterial rate of the reverse osmosis membrane for small molecule organic matter; compared with Example 1 and Comparative Example 10, since the rinsing solution in Comparative Example 10 is PEG-200, it has a large molecular weight and is difficult to enter the polyamide molecular segment, affecting the migration effect of polyquaternium salt -10 and the free volume distribution effect of the separation layer structure, thereby affecting the rejection rate and antibacterial rate of the reverse osmosis membrane for small molecule organic matter; compared with Example 1 and Comparative Example 11, the pH of the aqueous phase solution is too low, which affects the rejection rate and antibacterial performance of the reverse osmosis membrane.

[0111] 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.

[0112] 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 reverse osmosis membrane, characterized in that: The steps include: A linear polyquaternium salt containing hydroxyl groups, a polyamine, and water are formulated into an aqueous solution, wherein the mass ratio of the linear polyquaternium salt containing hydroxyl groups to the polyamine is 1:3-1:350, and the pH of the aqueous solution is greater than or equal to 10.0; placing the aqueous solution and the oily solution containing polyacyl chloride on the same surface of a porous support membrane in sequence, and subjecting the membrane to heat treatment to form a separation layer to obtain a prefabricated membrane; The prefabricated membrane is rinsed with a small molecule polyol aqueous solution to obtain a reverse osmosis membrane, wherein the temperature of the small molecule polyol aqueous solution is 70° C.-90° C., and the mass fraction of the small molecule polyol in the small molecule polyol aqueous solution is 5%-20%.

2. The method for preparing a reverse osmosis membrane according to claim 1, wherein The mass fraction of the linear polyquaternary ammonium salt containing hydroxyl groups in the aqueous phase solution is 0.01%-0.5%; And / or, the mass fraction of the polyamine in the aqueous solution is 1.5%-3.5%.

3. The method for preparing a reverse osmosis membrane according to claim 1, wherein The mass fraction of the polyacyl chloride in the oil phase solution containing the polyacyl chloride is 0.1%-0.3%.

4. The method for preparing a reverse osmosis membrane according to claim 1, wherein The linear polyquaternium salt containing hydroxyl groups is polyquaternium-10.

5. The method for preparing a reverse osmosis membrane according to claim 1, wherein Small molecule polyols have 2-3 carbon atoms.

6. The method for preparing a reverse osmosis membrane according to claim 1, wherein In the step of preparing an aqueous solution by mixing a linear polyquaternary ammonium salt containing hydroxyl groups, a polyamine and water, triethylamine is used to adjust the pH of the aqueous solution to 10.0-12.

0.

7. The method for preparing a reverse osmosis membrane according to any one of claims 1 to 6, characterized in that: The heat treatment temperature is 100°C-120°C, and the heat treatment time is 1min-3min; And / or, the rinsing treatment time is 1 min-5 min.

8. A reverse osmosis membrane prepared by the method for preparing a reverse osmosis membrane according to any one of claims 1 to 7.

9. Use of the reverse osmosis membrane according to claim 8 in a water treatment device.

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