Reverse osmosis membrane and its preparation method and application

Abstract

The present invention relates to the field of separation membranes, and discloses a reverse osmosis membrane, a method for preparing the reverse osmosis membrane, and an application of the reverse osmosis membrane in a water treatment process. The reverse osmosis membrane comprises a support layer and a polyamide separation layer, wherein one surface of the polyamide separation layer is bonded to the support layer, and the other surface is surface-modified with an ammonium salt containing epoxy groups, so that the epoxy groups in the ammonium salt containing epoxy groups are cross-linked with the polyamide. The reverse osmosis membrane provided by the present invention improves the hydrophilicity of the membrane by cross-linking the ammonium salt containing epoxy groups on the surface of the polyamide membrane, so that the membrane surface carries a positive charge, and the membrane's anti-pollution ability to cationic surfactants or other positively charged pollutants is improved; and, by cross-linking the epoxy groups in the ammonium salt containing epoxy groups with the polyamide, the cross-linking density of the reverse osmosis membrane separation layer is increased, further improving the salt rejection rate of the membrane.

Description

Technical Field

[0001] The present invention relates to the field of separation membranes, and in particular to a reverse osmosis membrane, a method for preparing the reverse osmosis membrane, and application of the reverse osmosis membrane in a water treatment process. Background Art

[0002] Membrane separation technology emerged in the early 20th century and rapidly gained popularity after the 1960s. Because it combines the functions of separation, concentration, purification, and refinement with high efficiency, energy conservation, environmental protection, molecular-level filtration, simple filtration processes, and ease of control, it has been widely used in fields such as food, medicine, biology, environmental protection, chemical engineering, metallurgy, energy, petroleum, water treatment, electronics, and biomimetics, generating significant economic and social benefits and becoming one of the most important methods in separation science today.

[0003] The core of membrane separation technology lies in the separation membrane. Based on pore size, membranes can be categorized into microfiltration, ultrafiltration, nanofiltration, and reverse osmosis membranes. Reverse osmosis membranes have become a key technology in water treatment due to their excellent separation performance for small organic molecules and inorganic salt ions, safety, environmental friendliness, and ease of operation. To date, reverse osmosis membranes have been primarily used in seawater and brackish water desalination, hard water softening, reclaimed water recovery, industrial wastewater treatment, and ultrapure water production. Currently, the mainstream product on the market utilizes interfacial polymerization, where a polyamide film is bonded to the surface of a microporous support membrane. The typical process is described in detail in US Pat. No. 4,277,344. This type of reverse osmosis membrane product not only offers high salt rejection, but also excellent water permeability, a wide pH range (2-12), and low operating pressure. However, membrane fouling remains a significant factor that impacts membrane performance and reduces its service life. Membrane fouling refers to the irreversible phenomenon of adsorption and deposition on the membrane surface or within the membrane pores caused by physical or chemical interactions between microparticles, colloids, or macromolecules in the feed solution in contact with the membrane, or by concentration polarization, which causes the concentration of certain solutes on the membrane surface to exceed their solubility, as well as mechanical interactions. This causes the membrane pore size to decrease or become clogged, leading to a significant decrease in membrane flux and separation characteristics. Flux attenuation and reduced membrane separation capacity caused by the adsorption of pollutants on the membrane surface and within the pores, particularly protein adsorption, are the primary causes of membrane flux attenuation. Current solutions involve preventing membrane fouling and performing post-treatment. Compared to post-treatment, the research and development of anti-fouling composite reverse osmosis membrane materials is the most fundamental and direct approach to addressing this issue.

[0004] In order to improve the anti-pollution ability of polyamide composite membranes, a lot of work has been done at home and abroad, mainly focusing on surface modification and surface coating.

[0005] There are many methods for modifying membrane surfaces, such as increasing the hydrophilicity of the membrane surface through surfactant treatment (Desalination, 1998, 115: 15-32); U.S. Patent No. 5,028,453 uses plasma treatment to introduce hydrophilic groups on the membrane surface, thereby improving the anti-fouling properties of the composite membrane. Currently, plasma treatment is limited by technical conditions and costs and cannot be achieved in large-scale production; U.S. Patent No. 5,151,183 uses fluorine gas to fluorinate the membrane surface to improve the anti-fouling properties of the membrane. At the same time, fluorine gas treatment can easily break the polyamide molecular chains on the membrane surface, thereby affecting the separation performance and service life of the membrane.

[0006] Therefore, a reverse osmosis membrane with a simple preparation method and excellent fouling resistance is needed. Summary of the Invention

[0007] The purpose of the present invention is to overcome the defect of poor pollution resistance of existing reverse osmosis membranes and to provide a reverse osmosis membrane with simple preparation method and excellent pollution resistance, a preparation method thereof and the application of the reverse osmosis membrane in a water treatment process.

[0008] After in-depth research, the inventors of the present invention found that, on the one hand, cross-linking an ammonium salt containing epoxy groups to the surface of a polyamide membrane improves the hydrophilicity of the membrane and makes the membrane surface positively charged, thereby improving the membrane's resistance to contamination by cationic surfactants or other positively charged pollutants; and, by cross-linking the epoxy groups in the ammonium salt containing epoxy groups with the polyamide, the cross-linking density of the reverse osmosis membrane separation layer is increased, further improving the salt rejection rate of the membrane, thereby completing the present invention.

[0009] That is, on the one hand, the present invention provides a reverse osmosis membrane, which includes a support layer and a polyamide separation layer, wherein one surface of the polyamide separation layer is bonded to the support layer, and the other surface is surface-modified with an ammonium salt containing epoxy groups, so that the epoxy groups in the ammonium salt containing epoxy groups are cross-linked with the polyamide.

[0010] The present invention also provides a method for preparing a reverse osmosis membrane, which comprises the following steps:

[0011] (1) forming a polyamide separation layer on one surface of the support layer to obtain a composite membrane;

[0012] (2) In the presence of a curing agent, the composite film obtained in step (1) is contacted with an ammonium salt containing an epoxy group, so that the epoxy groups in the ammonium salt containing an epoxy group react with the polyamide through a cross-linking reaction.

[0013] The present invention also provides a reverse osmosis membrane prepared by the method.

[0014] In addition, the present invention also provides application of the reverse osmosis membrane in a water treatment process.

[0015] According to the reverse osmosis membrane of the present invention, since an ammonium salt containing epoxy groups is cross-linked on the surface of the polyamide membrane, the hydrophilicity of the membrane is improved, and the membrane surface is given a positive charge, thereby improving the membrane's resistance to pollution by cationic surfactants or other positively charged pollutants; and, through cross-linking of the epoxy groups in the ammonium salt containing epoxy groups with the polyamide, the cross-linking density of the separation layer of the reverse osmosis membrane is increased, further improving the salt rejection rate of the membrane.

[0016] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0017] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0018] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0019] The present invention provides a reverse osmosis membrane, which comprises a support layer and a polyamide separation layer, wherein one surface of the polyamide separation layer is bonded to the support layer, and the other surface is surface-modified with an ammonium salt containing epoxy groups, so that the epoxy groups in the ammonium salt containing epoxy groups are cross-linked with the polyamide.

[0020] In the present invention, by cross-linking an ammonium salt containing epoxy groups on the surface of a polyamide membrane, the hydrophilicity of the membrane is increased, and the membrane surface is given a positive charge, thereby improving the membrane's resistance to cationic surfactants or other positively charged pollutants. Furthermore, by cross-linking the epoxy groups in the ammonium salt containing epoxy groups with the polyamide, the cross-linking density of the reverse osmosis membrane separation layer is increased, further improving the salt rejection rate of the membrane. In the present invention, the salt rejection rate of the reverse osmosis membrane of the present invention is preferably 99.5% or more, more preferably 99.6% or more, more preferably 99.7% or more, more preferably 99.8% or more, and even more preferably 99.9% or more.

[0021] In addition, under the condition of meeting the above-mentioned desalination rate, the water flux of the reverse osmosis membrane is preferably 40L / m 2 h or more, more preferably 45 L / m 2 h or more, preferably 60L / m 2 h or less, more preferably 50 L / m2 The water flux of the reverse osmosis membrane can be specifically exemplified as: 40 L / m 2 h, 41L / m 2 h, 42L / m 2 h, 43L / m 2 h, 44L / m 2 h, 45L / m 2 h, 46L / m 2 h, 47L / m 2 h, 48L / m 2 h, 49L / m 2 h, 50L / m 2 h, 55L / m 2 h, 58L / m 2 h or 60L / m 2 h et al.

[0022] In the present invention, in order to enable the obtained reverse osmosis membrane to better combine excellent anti-fouling performance, high water flux and salt rejection rate, it is preferred that the polyamide separation layer has a surface-modified membrane with a thickness of 0.005-0.5 μm, more preferably a surface-modified membrane with a thickness of 0.01-0.1 μm, and even more preferably a surface-modified membrane with a thickness of 0.02-0.05 μm after surface modification. Specific examples of the thickness of the surface-modified membrane include: 0.005 μm, 0.01 μm, 0.02 μm, 0.03 μm, 0.04 μm, 0.05 μm, 0.06 μm, 0.07 μm, 0.08 μm, 0.09 μm, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, or 0.5 μm.

[0023] In the present invention, one surface of the polyamide separation layer is bonded to the support layer, and the other surface is surface-modified with an epoxy-containing ammonium salt, such that the epoxy groups in the epoxy-containing ammonium salt cross-link with the polyamide. The epoxy-containing ammonium salt can be any substance capable of modifying the surface of the polyamide separation layer, such that the epoxy groups in the epoxy-containing ammonium salt cross-link with the polyamide. The epoxy-containing ammonium salt can contain one or more epoxy groups, preferably one or two, and more preferably one.

[0024] The above-mentioned ammonium salt containing an epoxy group is preferably an ammonium halide salt, more preferably an ammonium chloride salt, an ammonium bromide salt or an ammonium iodide salt, and further preferably an ammonium chloride salt. As such epoxy group-containing ammonium salts, for example, one or more of 2,3-epoxypropyltrimethylammonium chloride, 2,3-epoxypropyltriethylammonium chloride, 1,2-epoxypropyldimethyldodecylammonium chloride, diethyl-2,3-epoxypropyl-[3-(methyldimethoxy)]silylpropylammonium chloride, 3-epoxypropyltrimethylammonium bromide, 2,3-epoxypropyltriethylammonium bromide, 1,2-epoxypropyldimethyldodecylammonium bromide, diethyl-2,3-epoxypropyl-[3-(methyldimethoxy)]silylpropylammonium bromide, 3-epoxypropyltrimethylammonium iodide, 2,3-epoxypropyltriethylammonium iodide, 1,2-epoxypropyldimethyldodecylammonium iodide and diethyl-2,3-epoxypropyl-[3-(methyldimethoxy)]silylpropylammonium iodide can be selected. Preferably, the ammonium salt containing an epoxy group is selected from one or more of 2,3-epoxypropyltrimethylammonium chloride, 2,3-epoxypropyltriethylammonium chloride, 1,2-epoxypropyldimethyldodecylammonium chloride, diethyl-2,3-epoxypropyl-[3-(methyldimethoxy)]silylpropylammonium chloride, 3-epoxypropyltrimethylammonium bromide, 2,3-epoxypropyltriethylammonium bromide, 1,2-epoxypropyldimethyldodecylammonium bromide, and diethyl-2,3-epoxypropyl-[3-(methyldimethoxy)]silylpropylammonium bromide; more preferably, the ammonium salt containing an epoxy group is selected from one or more of 2,3-epoxypropyltrimethylammonium chloride, 2,3-epoxypropyltriethylammonium chloride, 1,2-epoxypropyldimethyldodecylammonium chloride and diethyl-2,3-epoxypropyl-[3-(methyldimethoxy)]silylpropylammonium chloride.

[0025] According to the present invention, the polyamide separation layer is a polyamide thin film having a cross-linked polyamide structure and formed on the surface of the support layer and in contact with the support layer. The thickness of the polyamide separation layer can vary within a wide range. To achieve better synergy between the polyamide separation layer, the support layer, and the surface-modified membrane, and to enable the resulting reverse osmosis membrane to better combine excellent pollution resistance, high water flux, and salt rejection, the thickness of the polyamide separation layer is preferably 0.01-1 μm, more preferably 0.05-0.8 μm, more preferably 0.05-0.5 μm, more preferably 0.05-0.3 μm, and even more preferably 0.05-0.2 μm. Specific examples of the thickness of the polyamide separation layer include 0.01 μm, 0.02 μm, 0.05 μm, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, and 1 μm.

[0026] The polyamide separation layer of the present invention is preferably obtained by interfacial polymerization of the polyamine and the polyacid chloride.

[0027] In the present invention, the term "interfacial polymerization" refers to a polymerization reaction carried out at the interface (or on the organic phase side of the interface) between two immiscible solutions containing two monomers dissolved therein.

[0028] In the present invention, the type of polyamine is not particularly limited and may be any amine compound commonly used in the art for preparing polyamides. For example, it may be one or more of m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, piperazine, and mesitylenetriamine; m-phenylenediamine is preferred. Furthermore, when performing interfacial polymerization, the polyamine is preferably used in the form of a solution. The solvent for dissolving the polyamine may be a solvent that is incompatible with the solvent for dissolving the polyacyl chloride, described later, and inert to the polyamine. Such a solvent may be, for example, one or more of water, methanol, and acetonitrile; water is preferred.

[0029] In addition, there is no particular limitation on the concentration of the polyamine in the polyamine solution and can be selected conventionally in the art. For example, the concentration of the polyamine in the polyamine solution can be 0.5-10% by weight, preferably 1-5% by weight. Specifically, the concentration of the polyamine in the polyamine solution can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% by weight.

[0030] In the present invention, the type of the polyacyl chloride is not particularly limited and can be any acyl chloride compound commonly used in the art for preparing polyamides. For example, it can be one or more of trimesoyl chloride, isophthaloyl chloride, and terephthaloyl chloride, preferably trimesoyl chloride.

[0031] Furthermore, when performing interfacial polymerization, the polyacyl chloride is preferably used in the form of a solution. The solvent for dissolving the polyacyl chloride may be a solvent that is incompatible with the solvent for dissolving the polyamine and inert to the polyacyl chloride. Such a solvent may be, for example, an organic solvent, preferably one or more of n-hexane, dodecane, n-heptane, Isopar E, Isopar G, Isopar H, Isopar L, and Isopar M.

[0032] In addition, there is no particular limitation on the concentration of the polyacyl chloride in the polyacyl chloride solution, and it can be a conventional choice in the art. For example, the concentration of the polyacyl chloride in the polyacyl chloride solution can be 0.025-1% by weight, preferably 0.05-0.5% by weight. The concentration of the polyacyl chloride in the polyacyl chloride solution can specifically be 0.025% by weight, 0.05% by weight, 0.10% by weight, 0.20% by weight, 0.30% by weight, 0.40% by weight, 0.50% by weight, 0.60% by weight, 0.70% by weight, 0.80% by weight, 0.90% by weight, or 1% by weight, etc.

[0033] The amounts of the polyamine and the polyacyl chloride used can vary within a wide range. Preferably, the mass concentration ratio of the polyamine to the polyacyl chloride is 1-100:1, more preferably 5-50:1, further preferably 10-40:1, further preferably 15-35:1, and further preferably 18-25:1. Specific mass concentration ratios of the polyamine to the polyacyl chloride include 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, 21:1, 22:1, 23:1, 24:1, 25:1, or 30:1.

[0034] The method for interfacially polymerizing the polyamine and the polyacyl chloride to obtain the polyamide separation layer of the present invention is not particularly limited, and may be any conventional contact method used in the art for interfacial polymerization of polyamines and polyacyl chlorides. In the present invention, the support layer is preferably contacted sequentially with a solution containing the polyamine and a solution containing the polyacyl chloride, followed by heat treatment.

[0035] According to the present invention, there is no particular limitation on the conditions for the interfacial polymerization reaction and they may be any conventional choice in the art. For example, when the support layer is sequentially contacted with a solution containing a polyamine and a solution containing a polyacyl chloride, the contact time between the support layer and the solution containing the polyamine is 5-100 seconds, preferably 10-60 seconds (for example, 10 seconds, 20 seconds, 30 seconds, 40 seconds, 50 seconds, or 60 seconds); and the contact time between the support layer and the solution containing the polyacyl chloride is 5-100 seconds, preferably 10-60 seconds (for example, 10 seconds, 20 seconds, 30 seconds, 40 seconds, 50 seconds, or 60 seconds). The temperature during the above contact may be 10-40° C. (for example, 25° C.).

[0036] In addition, when performing the above-mentioned heat treatment, the heat treatment conditions include: a heat treatment temperature of 40-150°C and a heat treatment time of 0.5-20 minutes; preferably, the heat treatment conditions include: a heat treatment temperature of 50-120°C and a heat treatment time of 1-10 minutes. Here, the heat treatment temperature can be, for example, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, or 120°C. The heat treatment time can be, for example, 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, or 10 minutes.

[0037] According to the present invention, the support layer is not particularly limited and can be made of any existing material having a certain strength and capable of being used for nanofiltration and reverse osmosis membranes. Typically, the support layer can be made of one or more of polyester, polyacrylonitrile, polyvinylidene fluoride, phenolphthalein-type non-sulfonated polyarylethersulfone, polyethersulfone, and polysulfone. Furthermore, the support layer can have a single-pore or multi-pore structure.

[0038] According to one embodiment of the present invention, the support layer includes a polyester non-woven fabric layer and a polymer layer attached to the surface of the polyester non-woven fabric layer and made of at least one of polyacrylonitrile, polyvinylidene fluoride, phenolphthalein-type non-sulfonated polyarylethersulfone, polyethersulfone, and polysulfone. The polyester non-woven fabric layer may have a thickness of 60-100 μm, and the polymer layer may have a thickness of 10-50 μm.

[0039] In addition, in the present invention, the thickness of the support layer can vary within a wide range. In order to achieve better synergy between the support layer, the polyamide separation layer, and the surface-modified membrane, so that the resulting reverse osmosis membrane can better combine excellent pollution resistance, high water flux, and salt rejection, the thickness of the support layer is preferably 90-150 μm, more preferably 100-120 μm. Specific examples of the thickness of the support layer include: 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, 120 μm, 125 μm, 130 μm, 135 μm, 140 μm, 145 μm, or 150 μm.

[0040] The present invention also provides a method for preparing the above-mentioned reverse osmosis membrane, which comprises the following steps:

[0041] (1) forming a polyamide separation layer on one surface of the support layer to obtain a composite membrane;

[0042] (2) In the presence of a curing agent, the composite film obtained in step (1) is contacted with an ammonium salt containing an epoxy group, so that the epoxy groups in the ammonium salt containing an epoxy group react with the polyamide through a cross-linking reaction.

[0043] In the method of the present invention, the support layer is not particularly limited and can be made of any existing material having a certain strength and capable of being used for nanofiltration and reverse osmosis membranes. Typically, the support layer can be made of one or more of polyester, polyacrylonitrile, polyvinylidene fluoride, phenolphthalein-type non-sulfonated polyarylethersulfone, polyethersulfone, and polysulfone. Furthermore, the support layer can have a monoporous or multiporous structure.

[0044] According to one embodiment of the present invention, the support layer includes a polyester non-woven fabric layer and a polymer layer attached to the surface of the polyester non-woven fabric layer and made of at least one of polyacrylonitrile, polyvinylidene fluoride, phenolphthalein-type non-sulfonated polyarylethersulfone, polyethersulfone, and polysulfone. The polyester non-woven fabric layer may have a thickness of 60-100 μm, and the polymer layer may have a thickness of 10-50 μm.

[0045] In addition, in the method of the present invention, the thickness of the support layer can vary within a wide range. In order to achieve a better synergistic effect between the support layer, the polyamide separation layer, and the modified membrane obtained in the subsequent step (2), so that the obtained reverse osmosis membrane can better have excellent pollution resistance, high water flux and salt rejection, the thickness of the support layer is preferably 90-150 μm, more preferably 100-120 μm. Specific examples of the thickness of the support layer include: 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm, 120 μm, 125 μm, 130 μm, 135 μm, 140 μm, 145 μm, or 150 μm.

[0046] According to the method of the present invention, in step (1), a composite membrane is obtained by forming a polyamide separating layer on a surface of a supporting layer. As a method for forming a polyamide separating layer on a surface of a supporting layer, it is preferably obtained by subjecting a polyamine and a polyacyl chloride to interfacial polymerization. There is no particular limitation on the mode of subjecting the polyamine and the polyacyl chloride to interfacial polymerization to obtain the polyamide separating layer. Various conventional contact modes can be used in this area to subject polyamine and the polyacyl chloride to interfacial polymerization. In the method of the present invention, it is preferred that the supporting layer is contacted with a solution containing a polyamine and a solution containing a polyacyl chloride in sequence, and then heat-treated.

[0047] In the method of the present invention, the type of polyamine is not particularly limited and may be any amine compound commonly used in the art for preparing polyamides. For example, it may be one or more of m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, piperazine, and mesitylenetriamine; m-phenylenediamine is preferred. Furthermore, during interfacial polymerization, the polyamine is preferably used in solution. The solvent for dissolving the polyamine may be a solvent that is incompatible with the solvent for dissolving the polyacyl chloride, described later, and inert to the polyamine. Such a solvent may be, for example, one or more of water, methanol, and acetonitrile; water is preferred.

[0048] In addition, there is no particular limitation on the concentration of the polyamine in the polyamine solution and can be selected conventionally in the art. For example, the concentration of the polyamine in the polyamine solution can be 0.5-10% by weight, preferably 1-5% by weight. Specifically, the concentration of the polyamine in the polyamine solution can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% by weight.

[0049] In the method of the present invention, the type of the polyacyl chloride is not particularly limited and can be any acyl chloride compound commonly used in the art for preparing polyamides. For example, it can be one or more of trimesoyl chloride, isophthaloyl chloride, and terephthaloyl chloride; preferably trimesoyl chloride.

[0050] Furthermore, when performing interfacial polymerization, the polyacyl chloride is preferably used in the form of a solution. The solvent for dissolving the polyacyl chloride may be a solvent that is incompatible with the solvent for dissolving the polyamine and inert to the polyacyl chloride. Such a solvent may be, for example, an organic solvent, preferably one or more of n-hexane, dodecane, n-heptane, Isopar E, Isopar G, Isopar H, Isopar L, and Isopar M.

[0051] In addition, there is no particular limitation on the concentration of the polyacyl chloride in the polyacyl chloride solution, and it can be a conventional choice in the art. For example, the concentration of the polyacyl chloride in the polyacyl chloride solution can be 0.025-1% by weight, preferably 0.05-0.5% by weight. The concentration of the polyacyl chloride in the polyacyl chloride solution can specifically be 0.025% by weight, 0.05% by weight, 0.10% by weight, 0.20% by weight, 0.30% by weight, 0.40% by weight, 0.50% by weight, 0.60% by weight, 0.70% by weight, 0.80% by weight, 0.90% by weight, or 1% by weight, etc.

[0052] In the method of the present invention, the amounts of the polyamine and the polyacyl chloride can vary within a wide range. Preferably, the mass concentration ratio of the polyamine to the polyacyl chloride is 1-100:1, more preferably 5-50:1, further preferably 10-40:1, further preferably 15-35:1, and further preferably 18-25:1. Specific mass concentration ratios of the polyamine to the polyacyl chloride include 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, 21:1, 22:1, 23:1, 24:1, 25:1, or 30:1.

[0053] According to the method of the present invention, there is no particular limitation on the conditions for the interfacial polymerization reaction, and any of the conventional methods in the art may be employed. For example, when the support layer is sequentially contacted with a solution containing a polyamine and a solution containing a polyacyl chloride, the contact time between the support layer and the solution containing the polyamine is 5-100 seconds, preferably 10-60 seconds (e.g., 10 seconds, 20 seconds, 30 seconds, 40 seconds, 50 seconds, or 60 seconds); and the contact time between the support layer and the solution containing the polyacyl chloride is 5-100 seconds, preferably 10-60 seconds (e.g., 10 seconds, 20 seconds, 30 seconds, 40 seconds, 50 seconds, or 60 seconds). The temperature during the above contact may be 10-40° C. (e.g., 25° C.).

[0054] In addition, after the support layer is sequentially contacted with a solution containing a polyamine and a solution containing a polyacyl chloride, and then subjected to heat treatment, the heat treatment conditions include: a heat treatment temperature of 40-150°C and a heat treatment time of 0.5-20 minutes; preferably, the heat treatment conditions include: a heat treatment temperature of 50-120°C and a heat treatment time of 1-10 minutes. Here, the heat treatment temperature can be, for example, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, or 120°C. The heat treatment time can be, for example, 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, or 10 minutes.

[0055] In addition, in the method of the present invention, the thickness of the polyamide separation layer formed can vary within a wide range. In order to better cooperate with the support layer and the surface modified membrane obtained in the following step (2), so that the obtained reverse osmosis membrane can better have excellent pollution resistance, high water flux and desalination rate, the thickness of the polyamide separation layer is preferably 0.01-1 μm, more preferably 0.05-0.8 μm, more preferably 0.05-0.5 μm, more preferably 0.05-0.3 μm, and more preferably 0.05-0.2 μm. Specific examples of the thickness of the polyamide separation layer include: 0.01 μm, 0.02 μm, 0.05 μm, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm or 1 μm.

[0056] According to the method of the present invention, step (2) modifies the surface of the polyamide separation layer of the composite membrane by contacting the composite membrane obtained in step (1) with an ammonium salt containing epoxy groups in the presence of a curing agent, so that the epoxy groups in the ammonium salt containing epoxy groups react with the polyamide to form a cross-linking reaction. In order to enable the resulting reverse osmosis membrane to better have excellent pollution resistance, high water flux and salt rejection rate, it is preferred that a surface modified film with a thickness of 0.005-0.5 μm is formed on the surface of the polyamide separation layer after step (2), more preferably a surface modified film with a thickness of 0.01-0.1 μm is formed, and even more preferably a surface modified film with a thickness of 0.02-0.05 μm is formed. Specific examples of the thickness of the surface modification film include 0.005 μm, 0.01 μm, 0.02 μm, 0.03 μm, 0.04 μm, 0.05 μm, 0.06 μm, 0.07 μm, 0.08 μm, 0.09 μm, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, and 0.5 μm.

[0057] There is no particular limitation on the manner in which the composite membrane obtained in step (1) is contacted with the ammonium salt containing epoxy groups, and various contacting methods conventionally used in the art may be employed. Preferably, the implementation process of step (2) comprises: immersing the composite membrane obtained in step (1) in a solution containing a curing agent and an ammonium salt containing epoxy groups, removing the composite membrane and performing a heat treatment to obtain a dry composite membrane, and then storing the dry composite membrane in a dry state at 10-40°C.

[0058] In the method of the present invention, the conditions for the heat treatment include: a temperature of 25-120° C. and a time of 1-15 min; preferably, the conditions for the heat treatment include: a temperature of 40-100° C. and a time of 2-10 min.

[0059] In addition, the storage time in a dry state at 10-40° C. may be more than 1 hour, for example, 1-720 hours, preferably 12-360 hours.

[0060] According to the method of the present invention, the curing agent is not particularly limited and can be any curing agent commonly used in the art, for example, a phenolic curing agent or an amine curing agent, preferably a phenolic curing agent. The curing agent may be, for example, one or more of 2,4,6-tris(dimethylaminomethyl)phenol, phenol, o-cresol, m-cresol, resorcinol, nonylphenol, bisphenol A, salicylic acid, benzyldimethylamine, triethanolamine, bicyclic amidine, triethylamine, pyridine, N-diglycidylaniline, N-diglycidyl-p-toluidine, N-ethyl-N-glycidylaniline, N-ethyl-N-glycidyl-o-toluidine, tetraethylammonium bromide, tetrabutylammonium bromide, diethylenetriamine, triethylenetetramine, polyethylenepolyamine, benzyl alcohol, 2,4-imidazole, 1-benzyl-2-ethylimidazole, 2-methylimidazole, and 1-aminoethyl-2-methylimidazole; preferably one or more of 2,4,6-tris(dimethylaminomethyl)phenol, phenol, m-cresol, and resorcinol.

[0061] According to the method of the present invention, the epoxy-containing ammonium salt can be used as long as it is capable of modifying the surface of the polyamide separation layer so that the epoxy groups in the epoxy-containing ammonium salt cross-link with the polyamide. The epoxy-containing ammonium salt can contain one or more epoxy groups, preferably one or two, and more preferably one.

[0062] The above-mentioned ammonium salt containing an epoxy group is preferably an ammonium halide salt, more preferably an ammonium chloride salt, an ammonium bromide salt or an ammonium iodide salt, and further preferably an ammonium chloride salt. As such epoxy group-containing ammonium salts, for example, one or more of 2,3-epoxypropyltrimethylammonium chloride, 2,3-epoxypropyltriethylammonium chloride, 1,2-epoxypropyldimethyldodecylammonium chloride, diethyl-2,3-epoxypropyl-[3-(methyldimethoxy)]silylpropylammonium chloride, 3-epoxypropyltrimethylammonium bromide, 2,3-epoxypropyltriethylammonium bromide, 1,2-epoxypropyldimethyldodecylammonium bromide, diethyl-2,3-epoxypropyl-[3-(methyldimethoxy)]silylpropylammonium bromide, 3-epoxypropyltrimethylammonium iodide, 2,3-epoxypropyltriethylammonium iodide, 1,2-epoxypropyldimethyldodecylammonium iodide and diethyl-2,3-epoxypropyl-[3-(methyldimethoxy)]silylpropylammonium iodide can be selected. Preferably, the ammonium salt containing an epoxy group is selected from one or more of 2,3-epoxypropyltrimethylammonium chloride, 2,3-epoxypropyltriethylammonium chloride, 1,2-epoxypropyldimethyldodecylammonium chloride, diethyl-2,3-epoxypropyl-[3-(methyldimethoxy)]silylpropylammonium chloride, 3-epoxypropyltrimethylammonium bromide, 2,3-epoxypropyltriethylammonium bromide, 1,2-epoxypropyldimethyldodecylammonium bromide and diethyl-2,3-epoxypropyl-[3-(methyldimethoxy)]silylpropylammonium bromide; more preferably, the ammonium salt containing an epoxy group is selected from one or more of 2,3-epoxypropyltrimethylammonium chloride, 2,3-epoxypropyltriethylammonium chloride, 1,2-epoxypropyldimethyldodecylammonium chloride and diethyl-2,3-epoxypropyl-[3-(methyldimethoxy)]silylpropylammonium chloride.

[0063] According to the method of the present invention, an ammonium salt containing epoxy groups is cross-linked to the surface of a polyamide by heat treatment under the action of a curing agent to form the surface-modified film. In the solution containing the curing agent and the ammonium salt containing epoxy groups, the content of the ammonium salt containing epoxy groups is 0.1-50 parts by weight, preferably 0.25-25 parts by weight, and more preferably 0.5-20 parts by weight, relative to 100 parts by weight of the solvent; the content of the curing agent is 0.0001-10 parts by weight, preferably 0.001-5 parts by weight, and more preferably 0.05-2 parts by weight.

[0064] In the solution containing the curing agent and the ammonium salt containing an epoxy group, the content of the ammonium salt containing an epoxy group, relative to 100 parts by weight of the solvent, can be specifically exemplified by: 0.1 parts by weight, 0.25 parts by weight, 0.3 parts by weight, 0.4 parts by weight, 0.5 parts by weight, 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 8 parts by weight, 10 parts by weight, 12 parts by weight, 14 parts by weight, 16 parts by weight, 18 parts by weight, 20 parts by weight, 25 parts by weight, 30 parts by weight, 40 parts by weight or 50 parts by weight, etc.

[0065] In the solution containing the curing agent and the ammonium salt containing an epoxy group, the content of the curing agent relative to 100 parts by weight of the solvent can be specifically 0.0001 parts by weight, 0.0005 parts by weight, 0.001 parts by weight, 0.002 parts by weight, 0.003 parts by weight, 0.004 parts by weight, 0.005 parts by weight, 0.01 parts by weight, 0.02 parts by weight, 0.03 parts by weight, 0.04 parts by weight, 0.05 parts by weight, 0.08 parts by weight, 0.1 parts by weight, 0.12 parts by weight, 0.14 parts by weight, 0.16 parts by weight, 0.18 parts by weight, 0.2 parts by weight, 0.5 parts by weight, 1 part by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 10 parts by weight, 20 parts by weight or 50 parts by weight.

[0066] In addition, from the perspective of fully forming the surface modified film, under the premise of meeting the above-mentioned concentration, the mass ratio of the ammonium salt containing epoxy groups to the curing agent is preferably 0.1-1000:1, more preferably 0.5-500:1, further preferably 1-200:1, and further preferably 1-100:1.

[0067] According to the method of the present invention, a polyamide separation layer is immersed in a solution of an ammonium salt containing epoxy groups and a curing agent, and then taken out and subjected to heat treatment to obtain a dry composite membrane; the dry composite membrane is stored in a dry state at 10-40°C for a certain period of time to complete the cross-linking reaction; the quaternary ammonium salt group acts as an accelerator for epoxy curing and slowly promotes further cross-linking reaction between the epoxy groups and the polyamide separation layer, ultimately obtaining a reverse osmosis membrane with a high salt rejection rate and high pollution resistance.

[0068] The present invention also provides a reverse osmosis membrane prepared by the method.

[0069] In addition, the present invention also provides the use of the reverse osmosis membrane in a water treatment process.

[0070] The present invention will be described in detail below through examples, but the present invention is not limited to the following examples.

[0071] In the following examples and preparation examples, the water flux, salt rejection and pollution resistance of the reverse osmosis membrane were tested using the following methods.

[0072] (1) Initial water flux of reverse osmosis membrane: The reverse osmosis membrane was placed in a membrane tank and pre-pressed at 1.2 MPa for 0.5 h. The water permeation of the reverse osmosis membrane was measured at a pressure of 1.55 MPa and a temperature of 25°C within 1 h and calculated using the following formula:

[0073] Q1=J / (A·t), where J is the water permeability (L), Q1 is the water flux (L / m 2 h), A is the effective membrane area of the reverse osmosis membrane (m 2 ), t is time (h).

[0074] (2) Salt rejection rate of reverse osmosis membrane: After the reverse osmosis membrane is placed in the membrane tank and pre-pressed at 1.2 MPa for 0.5 h, the concentration change of sodium chloride in the original aqueous solution with an initial concentration of 2000 ppm and the permeate is measured at a pressure of 1.55 MPa and a temperature of 25°C within 1 h, and the salt rejection rate is calculated using the following formula:

[0075] R=(C p -C f ) / C p ×100%, where R is the desalination rate, C p is the concentration of sodium chloride in the original solution, C f is the concentration of sodium chloride in the permeate.

[0076] (3) The pollution resistance of the reverse osmosis membrane was tested as follows: the reverse osmosis membrane was placed in a membrane pool and pre-pressed at 1.2 MPa for 0.5 h. The water permeation of the reverse osmosis membrane was measured at a pressure of 1.55 MPa and a temperature of 25 °C within 1 h, and the water flux was calculated by the following formula: Q1 = J / (A·t), where J is the water permeation (L) and Q1 is the water flux (L / m 2 h), A is the effective membrane area of the reverse osmosis membrane (m 2 ), t is time (h). The circulating test liquid was replaced with a mixed aqueous solution containing NaCl and cetyltrimethylammonium bromide (wherein the concentration of NaCl was 2000ppm and the concentration of cetyltrimethylammonium bromide was 1000ppm). After running for 6 hours at a pressure of 1.55MPa and a temperature of 25°C, the water flux Q2 of the reverse osmosis membrane was measured at a pressure of 1.55MPa and a temperature of 25°C. Then, after rinsing the reverse osmosis membrane with clean water for 0.5 hours, the water flux Q3 when the circulating liquid was a 2000ppm NaCl aqueous solution was measured at a pressure of 1.55MPa and a temperature of 25°C. The water flux decrease rate D of the reverse osmosis membrane was calculated by the following formula:

[0077] D = (Q1 - Q2) / Q1 × 100%. The water flux recovery rate H of the reverse osmosis membrane after water washing is calculated using the following formula: H = Q3 / Q1 × 100%. The lower the water flux decline rate and the higher the water flux recovery rate, the better the reverse osmosis membrane's anti-fouling performance.

[0078] (4) Thickness measurement: A Hitachi S-4800 high-resolution field emission scanning electron microscope (FESEM) was used to observe the cross-sectional morphology of the membrane and obtain the thickness of the membrane.

[0079] In addition, in the following examples and preparation examples, 2,3-epoxypropyltrimethylammonium chloride, 2,3-epoxypropyltriethylammonium chloride, 1,2-epoxypropyldimethyldodecylammonium chloride, diethyl-2,3-epoxypropyl-[3-(methyldimethoxy)]silylpropylammonium chloride, m-phenylenediamine, trimesoyl chloride, and hexadecyltrimethylammonium bromide were purchased from J&K Technology Co., Ltd.; Isopar E was purchased from Xilong Chemical Co., Ltd.; and other chemical reagents were purchased from Sinopharm Chemical Reagent Co., Ltd.

[0080] The support layer was prepared by a phase inversion method, and the specific steps were as follows: polysulfone (number average molecular weight of 80,000) was dissolved in N,N-dimethylformamide to prepare a polysulfone solution with a concentration of 18 weight%, and the solution was allowed to stand and degas at 25°C for 120 minutes. Then, the polysulfone solution was coated on a polyester non-woven fabric with a thickness of 75 μm using a scraper to obtain an initial membrane, which was then soaked in water at a temperature of 25°C for 60 minutes to allow the polysulfone layer on the surface of the polyester non-woven fabric to undergo phase conversion into a porous membrane. Finally, the support layer with a total thickness of 115 μm was obtained after three water washes.

[0081] Preparation Example 1

[0082] The upper surface of the support layer (the surface of the polysulfone layer, the same below) was contacted with a 2 wt% aqueous solution of m-phenylenediamine at 25° C. for 10 seconds, and then the liquid was drained. Then, the upper surface of the support layer was contacted with an Isopar E solution containing a 0.1 wt% trimesoyl chloride solution at 25° C. for 10 seconds, and then the liquid was drained. Then, the membrane was placed in an oven and heated at 70° C. for 3 minutes to obtain a reverse osmosis membrane M1, which included a support layer and a separation layer, wherein the thickness of the separation layer was 0.15 μm.

[0083] After soaking the resulting reverse osmosis membrane M1 in water for 24 hours, its water flux Q1 and NaCl (2000 ppm) rejection rate were measured at a pressure of 1.55 MPa and a temperature of 25°C. The results are shown in Table 1. Furthermore, its fouling resistance was tested under the same temperature and pressure conditions. After operating in a mixed aqueous solution containing 2000 ppm NaCl and 1000 ppm hexadecyltrimethylammonium bromide for 6 hours, its water flux Q2 and its water flux after washing were measured. The water flux decline rate and water flux recovery rate of the reverse osmosis membrane were calculated from these results, as shown in Table 1.

[0084] Preparation Example 2

[0085] The reverse osmosis membrane M1 prepared according to the method of Preparation Example 1 was immersed in an aqueous solution containing 2 wt% polyvinyl alcohol and 0.1 wt% glutaraldehyde at a pH of 2 at 25°C for 30 seconds. After removal, the membrane was placed in a 70°C oven and heated for 5 minutes to produce a fouling-resistant reverse osmosis membrane M2 having a surface-modified membrane formed on the upper surface of the polyamide separation layer. The surface-modified membrane had a thickness of 0.12 μm.

[0086] The resulting reverse osmosis membrane M2 was soaked in water for 24 hours, and its water flux Q1 and NaCl (2000 ppm) rejection rate were measured at a pressure of 1.55 MPa and a temperature of 25°C. The results are shown in Table 1. Furthermore, its fouling resistance was tested under the same temperature and pressure conditions. After running the membrane in a mixed aqueous solution containing 2000 ppm NaCl and 1000 ppm hexadecyltrimethylammonium bromide for 6 hours, its water flux Q2 and water flux Q3 after washing were measured. The water flux decline rate and water flux recovery rate of the reverse osmosis membrane were calculated from these results, as shown in Table 1.

[0087] Example 1

[0088] The reverse osmosis membrane M1 prepared according to the method of Preparation Example 1 was immersed in an aqueous solution containing 5 wt% 2,3-epoxypropyltrimethylammonium chloride and 0.5 wt% 2,4,6-tris(dimethylaminomethyl)phenol at 25°C for 30 seconds. After removal, the membrane was placed in a 70°C oven and heated for 5 minutes to obtain a dry reverse osmosis membrane. After storing the reverse osmosis membrane in a dry state at 25°C for 7 days, a fouling-resistant reverse osmosis membrane N1 was obtained, which had a surface-modified membrane formed on the polyamide separation layer. The thickness of the surface-modified membrane was 0.025 μm.

[0089] After soaking the resulting reverse osmosis membrane N1 in water for 24 hours, its water flux Q1 and NaCl (2000 ppm) rejection rate were measured at a pressure of 1.55 MPa and a temperature of 25°C. The results are shown in Table 1. Furthermore, its fouling resistance was tested under the same temperature and pressure conditions. After operating in a mixed aqueous solution containing 2000 ppm NaCl and 1000 ppm hexadecyltrimethylammonium bromide for 6 hours, its water flux Q2 and water flux Q3 after washing were measured. The water flux decline rate and water flux recovery rate of the reverse osmosis membrane were calculated from these results. The results are shown in Table 1.

[0090] Example 2

[0091] Reverse osmosis membrane M1, prepared according to the method of Preparation Example 1, was immersed in an aqueous solution containing 3 wt% 2,3-epoxypropyltriethylammonium chloride and 2 wt% 2,4,6-tris(dimethylaminomethyl)phenol at 25°C for 1 minute. After removal, the membrane was placed in a 40°C oven and heated for 10 minutes to obtain a dry reverse osmosis membrane. This reverse osmosis membrane was stored dry at 25°C for 3 days to obtain a fouling-resistant reverse osmosis membrane N2 with a surface-modified membrane formed on the polyamide separation layer. The thickness of the surface-modified membrane was 0.022 μm.

[0092] The resulting reverse osmosis membrane N2 was soaked in water for 24 hours, and its water flux Q1 and NaCl (2000 ppm) rejection rate were measured at a pressure of 1.55 MPa and a temperature of 25°C. The results are shown in Table 1. Furthermore, its fouling resistance was tested under the same temperature and pressure conditions. After operating in a mixed aqueous solution containing 2000 ppm NaCl and 1000 ppm hexadecyltrimethylammonium bromide for 6 hours, its water flux Q2 and water flux Q3 after washing were measured. The water flux decline rate and water flux recovery rate of the reverse osmosis membrane were calculated from these results, as shown in Table 1.

[0093] Example 3

[0094] At 25°C, the reverse osmosis membrane M1 prepared according to the method of Preparation Example 1 was immersed in an aqueous solution containing 10% by weight of 1,2-epoxypropyldimethyldodecylammonium chloride and 0.05% by weight of 2,4,6-tris(dimethylaminomethyl)phenol for 10 seconds. After removal, the membrane was placed in a 60°C oven and heated for 7 minutes to obtain a dry reverse osmosis membrane. After storing the reverse osmosis membrane in a dry state at 25°C for 15 days, a fouling-resistant reverse osmosis membrane N3 was obtained, which had a surface-modified membrane formed on the surface of the polyamide separation layer. The thickness of the surface-modified membrane was 0.038 μm.

[0095] The resulting reverse osmosis membrane N3 was soaked in water for 24 hours, and its water flux Q1 and NaCl (2000 ppm) rejection rate were measured at a pressure of 1.55 MPa and a temperature of 25°C. The results are shown in Table 1. Furthermore, its fouling resistance was tested under the same temperature and pressure conditions. After operating in a mixed aqueous solution containing 2000 ppm NaCl and 1000 ppm hexadecyltrimethylammonium bromide for 6 hours, its water flux Q2 and water flux Q3 after washing were measured. The water flux decline rate and water flux recovery rate of the reverse osmosis membrane were calculated from these results, as shown in Table 1.

[0096] Example 4

[0097] The method for preparing a reverse osmosis membrane was carried out according to Example 1, except that diethyl-2,3-epoxypropyl-[3-(methyldimethoxy)]silylpropyl ammonium chloride was used instead of 2,3-epoxypropyltrimethylammonium chloride to obtain a pollution-resistant reverse osmosis membrane N4 having a surface modified membrane formed on the surface of the polyamide separation layer, wherein the thickness of the surface modified membrane was 0.03 μm.

[0098] The resulting reverse osmosis membrane N4 was soaked in water for 24 hours, and its water flux Q1 and NaCl (2000 ppm) rejection rate were measured at a pressure of 1.55 MPa and a temperature of 25°C. The results are shown in Table 1. Furthermore, its fouling resistance was tested under the same temperature and pressure conditions. After operating in a mixed aqueous solution containing 2000 ppm NaCl and 1000 ppm hexadecyltrimethylammonium bromide for 6 hours, its water flux Q2 and water flux Q3 after washing were measured. The water flux decline rate and water flux recovery rate of the reverse osmosis membrane were calculated from these results, as shown in Table 1.

[0099] Example 5

[0100] The method for preparing a reverse osmosis membrane was followed as in Example 1, except that 2,4,6-tris(dimethylaminomethyl)phenol was replaced by resorcinol to obtain a fouling-resistant reverse osmosis membrane N5 having a surface modified membrane formed on the surface of the polyamide separation layer, wherein the thickness of the surface modified membrane was 0.02 μm.

[0101] After the resulting reverse osmosis membrane N5 was soaked in water for 24 hours, its water flux Q1 and NaCl (2000 ppm) rejection rate were measured at a pressure of 1.55 MPa and a temperature of 25°C. The results are shown in Table 1. Furthermore, its fouling resistance was tested under the same temperature and pressure conditions. After operating in a mixed aqueous solution containing 2000 ppm NaCl and 1000 ppm hexadecyltrimethylammonium bromide for 6 hours, its water flux Q2 and water flux Q3 after washing were measured. The water flux decline rate and water flux recovery rate of the reverse osmosis membrane were calculated from these results. The results are shown in Table 1.

[0102] Example 6

[0103] The method for preparing a reverse osmosis membrane was followed as in Example 1, except that phenol was used instead of 2,4,6-tris(dimethylaminomethyl)phenol to obtain a fouling-resistant reverse osmosis membrane N6 having a surface modified membrane formed on the surface of the polyamide separation layer, wherein the thickness of the surface modified membrane was 0.017 μm.

[0104] The resulting reverse osmosis membrane N6 was soaked in water for 24 hours, and its water flux Q1 and NaCl (2000 ppm) rejection rate were measured at a pressure of 1.55 MPa and a temperature of 25°C. The results are shown in Table 1. Furthermore, its fouling resistance was tested under the same temperature and pressure conditions. After running the membrane in a mixed aqueous solution containing 2000 ppm NaCl and 1000 ppm hexadecyltrimethylammonium bromide for 6 hours, its water flux Q2 and the water flux Q3 after washing were measured. The water flux decline rate and water flux recovery rate of the reverse osmosis membrane were calculated from these results, as shown in Table 1.

[0105] Example 7

[0106] The method for preparing a reverse osmosis membrane was followed as in Example 1, except that 2,4,6-tris(dimethylaminomethyl)phenol was replaced by m-cresol to obtain a fouling-resistant reverse osmosis membrane N7 having a surface modified membrane formed on the surface of the polyamide separation layer, wherein the thickness of the surface modified membrane was 0.035 μm.

[0107] The resulting reverse osmosis membrane N7 was soaked in water for 24 hours, and its water flux Q1 and NaCl (2000 ppm) rejection rate were measured at a pressure of 1.55 MPa and a temperature of 25°C. The results are shown in Table 1. Furthermore, its fouling resistance was tested under the same temperature and pressure conditions. After running the membrane in a mixed aqueous solution containing 2000 ppm NaCl and 1000 ppm hexadecyltrimethylammonium bromide for 6 hours, its water flux Q2 and the water flux Q3 after washing were measured. The water flux decline rate and water flux recovery rate of the reverse osmosis membrane were calculated from these results, as shown in Table 1.

[0108] Example 8

[0109] The reverse osmosis membrane was prepared according to the method of Example 1, except that the concentration of 2,3-epoxypropyltrimethylammonium chloride was 1 wt %. The membrane was placed in a 40° C. oven and heated for 6 min to obtain a fouling-resistant reverse osmosis membrane N8 having a surface modified membrane formed on the surface of the polyamide separation layer, wherein the thickness of the surface modified membrane was 0.015 μm.

[0110] The resulting reverse osmosis membrane N8 was soaked in water for 24 hours, and its water flux Q1 and NaCl (2000 ppm) rejection rate were measured at a pressure of 1.55 MPa and a temperature of 25°C. The results are shown in Table 1. Furthermore, its fouling resistance was tested under the same temperature and pressure conditions. After running the membrane in a mixed aqueous solution containing 2000 ppm NaCl and 1000 ppm hexadecyltrimethylammonium bromide for 6 hours, its water flux Q2 and water flux Q3 after washing were measured. The water flux decline rate and water flux recovery rate of the reverse osmosis membrane were calculated from these results, as shown in Table 1.

[0111] Example 9

[0112] The method for preparing a reverse osmosis membrane was carried out according to Example 1, except that the concentration of 2,3-epoxypropyltrimethylammonium chloride was 20% by weight. The membrane was placed in an oven at 100°C and heated for 3 minutes to obtain a fouling-resistant reverse osmosis membrane N9 having a surface modified membrane formed on the surface of the polyamide separation layer, wherein the thickness of the surface modified membrane was 0.046 μm.

[0113] The resulting reverse osmosis membrane N9 was soaked in water for 24 hours, and its water flux Q1 and NaCl (2000 ppm) rejection rate were measured at a pressure of 1.55 MPa and a temperature of 25°C. The results are shown in Table 1. Furthermore, its fouling resistance was tested under the same temperature and pressure conditions. After running the membrane in a mixed aqueous solution containing 2000 ppm NaCl and 1000 ppm hexadecyltrimethylammonium bromide for 6 hours, its water flux Q2 and water flux Q3 after washing were measured. The water flux decline rate and water flux recovery rate of the reverse osmosis membrane were calculated from these results, as shown in Table 1.

[0114] Table 1

[0115]

[0116] It can be seen from the results in Table 1 that, compared with the reverse osmosis membranes provided in the preparation examples, the reverse osmosis membranes prepared using Examples 1-9 of the present invention have excellent water flux, higher salt rejection, and stronger anti-pollution properties to cationic surfactants.

[0117] In addition, the preparation method of the reverse osmosis membrane provided by the present invention is simple and has great industrial application prospects.

[0118] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

[0119] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0120] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A reverse osmosis membrane comprising a support layer and a polyamide separation layer, characterized in that: One surface of the polyamide separation layer is bonded to the support layer, and the other surface is surface-modified with an ammonium salt containing epoxy groups, so that the epoxy groups in the ammonium salt containing epoxy groups are cross-linked with the polyamide; The preparation method of the reverse osmosis membrane comprises: 1) forming a polyamide separation layer on one surface of the support layer to obtain a composite membrane; 2) Immersing the composite membrane of step (1) in a solution containing a curing agent and an ammonium salt containing an epoxy group, taking it out and performing a heat treatment to obtain a dry composite membrane, and then storing the dry composite membrane in a dry state at 10-40° C. for 12-360 hours. The curing agent is 2,4,6-tris(dimethylaminomethyl)phenol or phenol, The ammonium salt containing epoxy group is 2,3-epoxypropyltrimethylammonium chloride, The reverse osmosis membrane has a desalination rate of more than 99.5%.

2. The reverse osmosis membrane according to claim 1, wherein After the surface modification, a surface modified membrane with a thickness of 0.005-0.5 μm is formed on the surface of the polyamide separation layer.

3. The reverse osmosis membrane according to claim 1, wherein After the surface modification, a surface modification film with a thickness of 0.01-0.1 μm is formed on the surface of the polyamide separation layer.

4. The reverse osmosis membrane according to claim 1, wherein The polyamide separation layer is obtained by interfacial polymerization of polyamine and polyacid chloride.

5. The reverse osmosis membrane according to claim 4, wherein The mass concentration ratio of the polyamine to the polyacyl chloride is 1-100:

1.

6. The reverse osmosis membrane according to claim 4, wherein The polyamine is one or more of m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, piperazine and s-phenylenediamine, and the polyacid chloride is one or more of trimesoyl chloride, isophthaloyl chloride and terephthaloyl chloride.

7. The reverse osmosis membrane according to any one of claims 1 to 6, wherein The support layer is made of one or more of polyester, polyacrylonitrile, polyvinylidene fluoride, phenolphthalein type non-sulfonated polyarylethersulfone, polyethersulfone and polysulfone.

8. The reverse osmosis membrane according to any one of claims 1 to 6, wherein The thickness of the support layer is 90-150 μm; the thickness of the polyamide separation layer is 0.01-1 μm.

9. The reverse osmosis membrane according to claim 8, wherein The thickness of the support layer is 100-120 μm; the thickness of the polyamide separation layer is 0.05-0.5 μm.

10. A method for preparing a reverse osmosis membrane, the method comprising the following steps: (1) forming a polyamide separation layer on one surface of the support layer to obtain a composite membrane; (2) contacting the composite film obtained in step (1) with an ammonium salt containing an epoxy group in the presence of a curing agent, so that the epoxy groups in the ammonium salt containing an epoxy group react with the polyamide through a cross-linking reaction; Wherein, the curing agent is 2,4,6-tris(dimethylaminomethyl)phenol or phenol, The ammonium salt containing epoxy group is 2,3-epoxypropyltrimethylammonium chloride, The implementation process of step (2) includes: immersing the composite membrane obtained in step (1) in a solution containing a curing agent and an ammonium salt containing an epoxy group, taking it out and performing a heat treatment to obtain a dry composite membrane, and then storing the dry composite membrane in a dry state at 10-40° C. for 12-360 hours.

11. The method according to claim 10, wherein: In the solution containing the curing agent and the ammonium salt containing epoxy groups, relative to 100 parts by weight of the solvent, the content of the ammonium salt containing epoxy groups is 0.1-50 parts by weight; the content of the curing agent is 0.0001-10 parts by weight.

12. The method according to claim 11, wherein In the solution containing the curing agent and the ammonium salt containing epoxy groups, relative to 100 parts by weight of the solvent, the content of the ammonium salt containing epoxy groups is 0.25-25 parts by weight; the content of the curing agent is 0.001-5 parts by weight.

13. The method according to claim 12, wherein: In the solution containing the curing agent and the ammonium salt containing epoxy groups, relative to 100 parts by weight of the solvent, the content of the ammonium salt containing epoxy groups is 0.5-20 parts by weight; and the content of the curing agent is 0.05-2 parts by weight.

14. The method according to claim 10, wherein: The mass ratio of the ammonium salt containing epoxy groups to the curing agent is 0.1-1000:

1.

15. The method according to claim 14, wherein The mass ratio of the ammonium salt containing epoxy groups to the curing agent is 0.5-500:

1.

16. The method according to claim 15, wherein The mass ratio of the ammonium salt containing epoxy groups to the curing agent is 1-200:

1.

17. The method according to claim 16, wherein The mass ratio of the ammonium salt containing epoxy groups to the curing agent is 1-100:

1.

18. The method according to claim 10, wherein The conditions of the heating treatment include: temperature of 25-120° C. and time of 1-15 min.

19. The method according to claim 18, wherein The conditions of the heating treatment include: temperature of 40-100° C. and time of 2-10 minutes.

20. The method according to claim 10, wherein The process of forming the polyamide separation layer in step (1) comprises: contacting the support layer with a solution containing polyamine and a solution containing polyacyl chloride in sequence, and then performing heat treatment.

21. The method according to claim 20, wherein The mass concentration ratio of the polyamine to the polyacyl chloride is 1-100:

1.

22. The method according to claim 20, wherein The polyamine is one or more of m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, piperazine and mesitylenetriamine.

23. The method according to claim 20, wherein The polybasic acid chloride is one or more of trimesoyl chloride, isophthaloyl chloride and terephthaloyl chloride.

24. The method according to claim 20, wherein the conditions of the heat treatment include: The temperature is 40-150°C and the time is 0.5-20 minutes.

25. The method according to claim 24, wherein The heat treatment conditions include: temperature of 50-120° C. and time of 1-10 min.

26. The method according to any one of claims 10 to 25, wherein: The support layer is made of one or more of polyester, polyacrylonitrile, polyvinylidene fluoride, phenolphthalein type non-sulfonated polyarylethersulfone, polyethersulfone and polysulfone.

27. A reverse osmosis membrane prepared by the method according to any one of claims 10 to 26.

28. Use of the reverse osmosis membrane according to any one of claims 1 to 9 and claim 27 in a water treatment process.

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