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: oil, a surfactant and water are mixed to form an oil-in-water nanoemulsion, wherein the surfactant includes a nonionic surfactant, the average particle size of the oil-in-water nanoemulsion is 80nm-200nm, and the polydispersity index is ≤0.3; an aqueous solution of an inorganic metal salt and the oil-in-water nanoemulsion are sequentially placed on the same surface of a support membrane, dendritic crystals are formed by heat treatment, and the mass ratio of the inorganic metal salt to the oil-in-water nanoemulsion is 1:50-1:30; a polyamide separation layer is prepared on the surface of the support membrane distributed with dendritic crystals by reverse interfacial polymerization to obtain a reverse osmosis membrane. The reverse osmosis membrane prepared by the preparation method can maintain a high water flux while maintaining a high salt rejection rate 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 (RO) is a highly efficient and energy-efficient water treatment method widely used in seawater desalination, drinking water treatment, and water reuse. Numerous methods exist for preparing RO membranes, with interfacial polymerization being a common method. However, RO membranes prepared using conventional interfacial polymerization methods struggle to achieve both high salt rejection and high water flux. Summary of the Invention

[0003] Based on this, it is necessary to provide a reverse osmosis membrane and its preparation method and application to address the above problems. When the reverse osmosis membrane prepared by this preparation method is used in water treatment, it can maintain a high desalination rate while also having a high water flux.

[0004] A method for preparing a reverse osmosis membrane comprises the following steps:

[0005] Mixing oil, a surfactant, and water to prepare an oil-in-water nanoemulsion, wherein the surfactant includes a nonionic surfactant, and the average particle size of the oil-in-water nanoemulsion is 80 nm to 200 nm, and the polydispersity index is ≤0.3;

[0006] placing an aqueous solution of an inorganic metal salt and the oil-in-water nanoemulsion on the same surface of a support membrane in sequence, and forming dendritic crystals through heat treatment, wherein the mass ratio of the inorganic metal salt to the oil-in-water nanoemulsion is 1:50-1:30;

[0007] A polyamide separation layer is prepared on the surface of the support membrane on which the dendritic crystals are distributed by reverse interfacial polymerization to obtain a reverse osmosis membrane.

[0008] In one embodiment, in the step of preparing the oil-in-water nanoemulsion, the volume ratio of the oil to the water is 1:200-1:100.

[0009] In one embodiment, the mass fraction of the oil in the oil-in-water nanoemulsion is 0.1%-0.8%;

[0010] And / or, the mass fraction of the surfactant in the oil-in-water nanoemulsion is 20%-40%.

[0011] In one embodiment, the surfactant further includes an ionic surfactant, and the mass ratio of the non-ionic surfactant to the ionic surfactant is 5:1-10:1.

[0012] In one embodiment, the mass fraction of the inorganic metal salt in the aqueous solution of the inorganic metal salt is 1%-5%.

[0013] In one embodiment, the oil is selected from at least one of alkanes, stearates, and tributyl citrate;

[0014] And / or, the nonionic surfactant is selected from at least one of Tween 80, alkylphenol polyoxyethylene ether, and alkyl alcohol polyoxyethylene ether;

[0015] And / or, the inorganic metal salt is selected from at least one of sodium chloride, potassium chloride, magnesium chloride and calcium chloride.

[0016] In one embodiment, in the step of forming dendrites by heat treatment, the heat treatment temperature is 50° C.-80° C., and the heat treatment time is 3 min-5 min.

[0017] In one embodiment, in the step of preparing a polyamide separation layer on the surface of the support membrane on which the dendritic crystals are distributed by reverse interfacial polymerization, an oil phase solution and an aqueous phase solution are sequentially placed on the surface of the support membrane on which the dendritic crystals are distributed, and a polyamide separation layer is prepared by heat treatment, wherein the oil phase solution contains polyacyl chloride and the aqueous phase solution contains polyamine.

[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, by controlling the average particle size and polydispersity index of the oil-in-water nanoemulsion, the nano oil droplets in the nanoemulsion are uniformly dispersed in water, thereby ensuring the long-term stability of the nanoemulsion; at the same time, by controlling the mass ratio of the inorganic metal salt and the oil-in-water nanoemulsion, a significant concentration gradient difference and surface tension difference are provided between the aqueous solution of the inorganic metal salt and the oil-in-water nanoemulsion, thereby causing a significant capillary phenomenon to occur when the aqueous solution of the inorganic metal salt and the oil-in-water nanoemulsion come into contact, thereby promoting the rapid penetration and diffusion of the inorganic metal salt into the water of the nanoemulsion, and due to the nanoemulsion Nano-oil droplets are evenly dispersed in the water of the rice emulsion, creating numerous tiny pore structures between the nano-oil droplets. This induces the inorganic metal salt to diffuse into the water along a dendritic permeation path formed between the nano-oil droplets. During heat treatment, the inorganic metal salt precipitates and forms dendritic crystals distributed on the surface of the support membrane. The presence of these dendritic crystals greatly increases the specific surface area of ​​the water-oil interface during the subsequent reverse interfacial polymerization to prepare the polyamide separation layer, resulting in a large specific surface area for the polyamide separation layer. This significantly improves the water flux of the reverse osmosis membrane while not affecting the salt rejection rate of the reverse osmosis membrane. Furthermore, by using reverse interfacial polymerization to prepare the polyamide separation layer, the dendritic crystal morphology is effectively maintained, allowing interfacial polymerization to occur on the crystal surface and forming a separation layer with a high specific surface area, thus avoiding the problem of water dissolution and destruction of the crystal structure.

[0021] Therefore, when the reverse osmosis membrane of the present invention is applied to water treatment, it can maintain a high desalination rate while also having a high water flux. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is an electron microscope image of the reverse osmosis membrane prepared in Example 1 of the present invention;

[0023] Figure 2 This is an electron microscope image of the reverse osmosis membrane prepared in Comparative Example 6 of the present invention. DETAILED DESCRIPTION

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

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

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

[0027] S1, oil, surfactant and water are mixed to form an oil-in-water nanoemulsion, wherein the surfactant includes a nonionic surfactant, the average particle size of the oil-in-water nanoemulsion is 80nm-200nm, and the polydispersity index is ≤0.3. It can be understood that in step S1, in the oil-in-water nanoemulsion, the oil is dispersed in the water in the form of nanodroplets, that is, the nano-oil droplets are dispersed in the water to form an emulsion, and by controlling the average particle size and polydispersity index of the oil-in-water nanoemulsion, the nano-oil droplet particle size in the oil-in-water nanoemulsion is small and the size distribution is uniform, and it can be evenly dispersed in water, ensuring the long-term stability of the oil-in-water nanoemulsion. Moreover, since the nano-oil droplets are evenly dispersed in water, many tiny pore structures are formed between the nano-oil droplets. These pore structures are similar to capillaries, which can drive the aqueous solution of the inorganic metal salt in the subsequent step S2 to penetrate and diffuse into the nanoemulsion through surface tension, and the path of penetration and diffusion is dendritic.

[0028] Optionally, in the step of preparing the oil-in-water nanoemulsion, the volume ratio of the oil to the water is 1:200-1:100; such a setting can better form the oil-in-water nanoemulsion by adjusting the volume ratio of oil to water.

[0029] Optionally, the mass fraction of the oil in the oil-in-water nanoemulsion is 0.1%-0.8%; the mass fraction of the surfactant in the oil-in-water nanoemulsion is 20%-40%. Such an arrangement can adjust the mass fractions of the oil and surfactant in the oil-in-water nanoemulsion, thereby facilitating the formation of an oil-in-water nanoemulsion with smaller particle size, uniform particle size distribution, and higher stability, thereby facilitating better penetration and diffusion of the inorganic metal salt into the water of the nanoemulsion in the subsequent step S2.

[0030] Furthermore, the oil is selected from at least one of alkanes, stearates, and tributyl citrate, preferably alkanes, and the alkane is selected from a mixture of normal alkanes and isoalkanes or straight-chain alkanes, and more preferably liquid paraffin.

[0031] Optionally, the surfactant further comprises an ionic surfactant, and the mass ratio of the nonionic surfactant to the ionic surfactant is 5:1-10:1. With this arrangement, by compounding the nonionic surfactant and the ionic surfactant, the nonionic surfactant is used to reduce interfacial tension, and the ionic surfactant provides electrostatic stabilization, thereby effectively regulating the particle size distribution of the nanoemulsion, better obtaining a water-in-oil nanoemulsion with a smaller and more uniform particle size, and thus better ensuring the long-term stability of the water-in-oil nanoemulsion.

[0032] Furthermore, the nonionic surfactant is selected from long-chain fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, alkyl alcohol polyoxyethylene ether, polyoxyethylene alkylamine, polyoxyethylene alkylamide and polyethers, preferably two or more of Tween 80, alkylphenol polyoxyethylene ether and alkyl alcohol polyoxyethylene ether.

[0033] Optionally, the ionic surfactant is preferably an anionic surfactant, and the anionic surfactant is preferably at least one of sodium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium stearate, and sodium lauryl sulfate.

[0034] In one embodiment, the preparation method of the oil-in-water nanoemulsion is as follows: oil, surfactant and water are mixed and placed in a hot water bath for ultrasonic treatment, and then placed in an ice water bath to cool to room temperature to obtain the oil-in-water nanoemulsion, wherein the hot water bath temperature is 90°C-110°C, preferably 100°C, and the ultrasonic treatment time is 0.5h-2h.

[0035] S2, placing an aqueous solution of an inorganic metal salt and the oil-in-water nanoemulsion on the same surface of a support membrane in sequence, and forming dendritic crystals through heat treatment, wherein the mass ratio of the inorganic metal salt to the oil-in-water nanoemulsion is 1:50-1:30.

[0036] In step S2, the present invention controls the mass ratio of the inorganic metal salt and the oil-in-water nanoemulsion so that there is a significant concentration gradient difference between the aqueous solution of the inorganic metal salt and the oil-in-water nanoemulsion, thereby causing a significant surface tension difference between the aqueous solution of the inorganic metal salt and the oil-in-water nanoemulsion. Therefore, when the aqueous solution of the inorganic metal salt and the oil-in-water nanoemulsion contact the surface of the support membrane, a significant capillary phenomenon occurs, prompting the inorganic metal salt to quickly penetrate and diffuse into the water of the nanoemulsion. Moreover, in this process, since nano-oil droplets are uniformly dispersed in the water of the oil-in-water nanoemulsion, many tiny pore structures are formed between the nano-oil droplets, inducing the inorganic metal salt to penetrate and diffuse into the water along the pore structure between the nano-oil droplets to form a dendritic penetration path. When heat treated, the inorganic metal salt will precipitate and form dendritic crystals, which then form dendritic crystals distributed on the surface of the support membrane. The presence of the dendritic crystals correspondingly increases the specific surface area of ​​the support membrane.

[0037] Optionally, the mass fraction of the inorganic metal salt in the aqueous solution of the inorganic metal salt is 1%-5%. This configuration allows for the regulation of the mass fraction of the inorganic metal salt in the aqueous solution of the inorganic metal salt, thereby regulating the concentration difference and surface tension difference between the aqueous solution of the inorganic metal salt and the nanoemulsion, thereby enhancing the capillary action of the inorganic metal salt in the nanoemulsion and forming a dendritic permeation path.

[0038] Furthermore, the inorganic metal salt is selected from at least one of sodium chloride, potassium chloride, magnesium chloride and calcium chloride.

[0039] Optionally, the heat treatment temperature is 50° C.-80° C., and the heat treatment time is 3 min-5 min. This configuration can better ensure that the inorganic metal salt precipitates to form dendritic crystals.

[0040] In one embodiment, the support membrane is selected from at least one of a polysulfone membrane, a polypropylene membrane or a polyacrylonitrile membrane, wherein polysulfone is cheap and readily available, simple to prepare, has good mechanical strength, good pressure resistance, stable chemical properties, is non-toxic, and can resist biodegradation. Therefore, the support membrane is preferably a polysulfone membrane.

[0041] S3, preparing a polyamide separation layer on the surface of the support membrane on which the dendritic crystals are distributed by reverse interfacial polymerization to obtain a reverse osmosis membrane.

[0042] It should be noted that in step S3, compared with traditional interfacial polymerization, reverse interfacial polymerization means first placing the oil phase solution on the surface of the support membrane, and then placing the aqueous phase solution on the surface of the support membrane. Specifically, the oil phase solution and the aqueous phase solution are placed in sequence on the surface of the support membrane on which the dendritic crystals are distributed, and a polyamide separation layer is prepared by heat treatment, wherein the oil phase solution contains polyacyl chloride and the aqueous phase solution contains polyamine.

[0043] It can be understood that when the oil phase solution and the aqueous phase solution are placed in sequence on the surface of the support membrane on which the dendritic crystals are distributed, the aqueous phase solution and the oil phase solution will contact on the surface of the support membrane to form a water-oil interface. Since the dendritic crystals are distributed on the surface of the support membrane, the water-oil interface is formed on the dendritic crystals, so that the water-oil interface has a large specific surface area. Correspondingly, the polyamide separation layer formed by the interfacial polymerization reaction of polyamine and polyacyl chloride at the water-oil interface also has a large specific surface area, thereby significantly improving the water flux of the reverse osmosis membrane without affecting the desalination rate of the reverse osmosis membrane.

[0044] At the same time, in order to prevent the aqueous solution from destroying the morphology of the dendritic crystals on the surface of the support membrane and affecting the specific surface area of ​​the support membrane, the present invention first places the oil phase solution on the surface of the support membrane to form a protective layer, and then places the aqueous solution on the surface of the support membrane. The formation of the protective layer can effectively prevent the aqueous solution from directly contacting the dendritic crystals, avoiding the problem of the crystal structure being destroyed by water dissolving the crystals on the surface of the support membrane, ensuring that the polyamide separation layer has a large specific surface area, thereby improving the water flux of the reverse osmosis membrane. On the other hand, it can make the oil phase and the crystals have good compatibility, facilitating the interfacial polymerization reaction of polyacyl chlorides and polyamines on the surface of the support membrane to form a polyamide separation layer, ensuring a high salt rejection rate of the reverse osmosis membrane.

[0045] It can be seen that the present invention adopts the method of exchanging the water phase and the oil phase in order to place them on the surface of the support membrane on which the dendritic crystals are distributed, that is, using reverse interfacial polymerization, which can effectively ensure the morphology of the dendritic crystals on the surface of the support membrane, so that the interfacial polymerization occurs on the crystal surface and forms a separation layer with a high specific surface area, avoiding the problem of the crystals on the surface of the support membrane being dissolved by water and destroying the crystalline structure.

[0046] Therefore, when the reverse osmosis membrane of the present invention is applied to water treatment, it can maintain a high desalination rate while also having a high water flux.

[0047] It should be noted that since the newly prepared reverse osmosis membrane is usually soaked in water, the inorganic metal salt crystals will dissolve in water and detach from the reverse osmosis membrane, thereby correspondingly increasing the water production channel and further improving the water flux of the reverse osmosis membrane.

[0048] In one embodiment, the mass fraction of the polyamine in the aqueous phase solution is 1%-3%, and the mass fraction of the polyacyl chloride in the oil phase solution is 0.1%-0.5%. This configuration facilitates sufficient reaction between the polyamine and the polyacyl chloride to form a relatively dense polyamide separation layer, which helps the reverse osmosis membrane maintain a high salt rejection rate.

[0049] Furthermore, the polyamine is selected from at least one of m-phenylenediamine, piperazine, p-phenylenediamine, and tetraethylenepentamine, preferably m-phenylenediamine; the polyacyl chloride is selected from at least one of trimesoyl chloride, isophthaloyl chloride, and terephthaloyl chloride, preferably trimesoyl chloride.

[0050] In order to better remove the hydrochloric acid generated by the interfacial polymerization reaction and ensure the forward polymerization reaction of the polyamine and the polyacyl chloride, in the present invention, the aqueous phase solution also includes an acid scavenger, and the mass fraction of the acid scavenger in the aqueous phase solution is 0.5%-3%.

[0051] Furthermore, the acid scavenger is selected from at least one of triethylamine, sodium hydroxide, potassium hydroxide, sodium carbonate, trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, potassium phosphate, and dipotassium hydrogen phosphate, preferably triethylamine.

[0052] In one embodiment, in the step of forming the polyamide separation layer through heat treatment, the heat treatment temperature is 70°C to 90°C, and the heat treatment time is 2 minutes to 4 minutes. This configuration further ensures the integrity and uniformity of the crosslinking of the polyamide separation layer, further improving the salt rejection rate and water flux of the reverse osmosis membrane.

[0053] In one embodiment, the solvent of the oil phase solution is selected from an isoparaffin solvent, and the isoparaffin solvent is selected from at least one of Isopar-E, Isopar-G, and Isopar-L; the solvent of the aqueous phase solution is water.

[0054] The present invention also provides a reverse osmosis membrane prepared by the reverse osmosis membrane preparation method. When used in water treatment, the reverse osmosis membrane can maintain a high desalination rate while also having a high water flux.

[0055] In addition, the present invention also provides an application of the reverse osmosis composite membrane in a water treatment device.

[0056] 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.

[0057] In one embodiment, the water treatment device may also be a seawater desalination device.

[0058] 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.

[0059] Example 1

[0060] Liquid paraffin, Tween 80, sodium lauryl sulfate, and water were mixed and ultrasonically treated in a hot water bath at 100°C for 1 hour. The mixture was then cooled to room temperature in an ice-water bath to obtain an oil-in-water nanoemulsion. The volume ratio of liquid paraffin to water was 1:200, the average particle size of the oil-in-water nanoemulsion was 100 nm, and the polydispersity index was ≤0.25. In the oil-in-water nanoemulsion, the mass fraction of liquid paraffin was 0.1%, the mass fraction of Tween 80 was 20%, and the mass fraction of sodium lauryl sulfate was 2%. Metaphenylenediamine, triethylamine, and water were uniformly mixed to prepare an aqueous phase solution. The mass fraction of metaphenylenediamine and the mass fraction of triethylamine in the aqueous phase solution was 1%, and the mass fraction of triethylamine was 0.5%. Trimesoyl chloride and an isoparaffin solvent (Isopar-L) were uniformly mixed to prepare an oil phase solution. The mass fraction of trimesoyl chloride in the oil phase solution was 0.15%.

[0061] An aqueous solution of sodium chloride is applied to the surface of a polysulfone support membrane, and after standing for 60 seconds, excess sodium chloride aqueous solution is poured out, and the membrane surface is air-dried, wherein the mass fraction of sodium chloride in the aqueous solution of sodium chloride is 10%; the above-mentioned oil-in-water nanoemulsion is poured onto the air-dried polysulfone support membrane surface, and after standing for 60 seconds, excess nanoemulsion is poured out, and the membrane is placed in a 50°C forced air drying oven for heat treatment for 5 minutes to form dendritic crystals distributed on the surface of the polysulfone support membrane, wherein the mass ratio of sodium chloride to the oil-in-water nanoemulsion is 1:50.

[0062] The above oil phase solution was applied to the surface of the polysulfone support membrane with dendritic crystals, and after standing for 30 seconds, the excess oil phase solution was poured out and the membrane surface was dried in the shade; then the above water phase solution was applied to the surface of the polysulfone support membrane that absorbed the oil phase solution, and after standing for 60 seconds, the excess water phase solution was poured out, and finally the membrane was placed in an 80°C forced air drying oven for heat treatment for 2 minutes, and the membrane was taken out to obtain the following: Figure 1 The reverse osmosis membrane shown.

[0063] Example 2

[0064] Liquid paraffin, Tween 80, sodium lauryl sulfate, and water were mixed and ultrasonically treated in a hot water bath at 85°C for 1.5 hours. The mixture was then cooled to room temperature in an ice-water bath to obtain an oil-in-water nanoemulsion. The volume ratio of liquid paraffin to water was 1:150, the average particle size of the oil-in-water nanoemulsion was 95 nm, and the polydispersity index was ≤0.24. In the oil-in-water nanoemulsion, the mass fraction of liquid paraffin was 0.5%, the mass fraction of Tween 80 was 30%, and the mass fraction of sodium lauryl sulfate was 6%. Metaphenylenediamine, triethylamine, and water were uniformly mixed to prepare an aqueous phase solution. The mass fraction of metaphenylenediamine and the mass fraction of triethylamine in the aqueous phase solution was 2%. Trimesoyl chloride and an isoparaffin solvent (Isopar-L) were uniformly mixed to prepare an oil phase solution. The mass fraction of trimesoyl chloride in the oil phase solution was 0.3%.

[0065] An aqueous solution of sodium chloride is applied to the surface of a polysulfone support membrane, and after standing for 60 seconds, excess sodium chloride aqueous solution is poured out, and the membrane surface is air-dried, wherein the mass fraction of sodium chloride in the aqueous solution of sodium chloride is 10%; the above-mentioned oil-in-water nanoemulsion is poured onto the air-dried polysulfone support membrane surface, and after standing for 60 seconds, excess nanoemulsion is poured out, and the membrane is placed in a 60°C forced air drying oven and heated for 4 minutes to form dendritic crystals distributed on the surface of the polysulfone support membrane, wherein the mass ratio of sodium chloride to the oil-in-water nanoemulsion is 1:40.

[0066] The above oil phase solution is applied to the surface of the polysulfone support membrane with dendritic crystals distributed thereon, and after standing for 30 seconds, the excess oil phase solution is poured out, and the membrane surface is dried in the shade; then the above aqueous phase solution is applied to the surface of the polysulfone support membrane that has absorbed the oil phase solution, and after standing for 60 seconds, the excess aqueous phase solution is poured out, and finally the membrane is placed in a 75°C forced air drying oven for heat treatment for 4 minutes, and then taken out to obtain a reverse osmosis membrane.

[0067] Example 3

[0068] Liquid paraffin, Tween 80, sodium lauryl sulfate, and water were mixed and ultrasonically treated in a hot water bath at 85°C for 1.5 hours. The mixture was then cooled to room temperature in an ice-water bath to obtain an oil-in-water nanoemulsion. The volume ratio of liquid paraffin to water was 1:100, the average particle size of the oil-in-water nanoemulsion was 100 nm, and the polydispersity index was ≤0.25. In the oil-in-water nanoemulsion, the mass fraction of liquid paraffin was 0.8%, the mass fraction of Tween 80 was 35%, and the mass fraction of sodium lauryl sulfate was 5%. Metaphenylenediamine, triethylamine, and water were uniformly mixed to prepare an aqueous phase solution. The mass fraction of metaphenylenediamine and the mass fraction of triethylamine in the aqueous phase solution was 3%. Trimesoyl chloride and an isoparaffin solvent (Isopar-L) were uniformly mixed to prepare an oil phase solution. The mass fraction of trimesoyl chloride in the oil phase solution was 0.4%.

[0069] An aqueous solution of sodium chloride is applied to the surface of a polysulfone support membrane, and after standing for 60 seconds, excess sodium chloride aqueous solution is poured out, and the membrane surface is air-dried, wherein the mass fraction of sodium chloride in the aqueous solution of sodium chloride is 10%; the above-mentioned oil-in-water nanoemulsion is poured onto the air-dried polysulfone support membrane surface, and after standing for 60 seconds, excess nanoemulsion is poured out, and the membrane is placed in an 80°C forced air drying oven for heat treatment for 5 minutes to form dendritic crystals distributed on the surface of the polysulfone support membrane, wherein the mass ratio of sodium chloride to the oil-in-water nanoemulsion is 1:30.

[0070] The above oil phase solution is applied to the surface of the polysulfone support membrane with dendritic crystals distributed thereon, and after standing for 30 seconds, the excess oil phase solution is poured out, and the membrane surface is dried in the shade; then the above water phase solution is applied to the surface of the polysulfone support membrane that has absorbed the oil phase solution, and after standing for 60 seconds, the excess water phase solution is poured out, and finally the membrane is placed in a 90°C forced air drying oven for heat treatment for 2 minutes, and then taken out to obtain a reverse osmosis membrane.

[0071] Example 4

[0072] Example 4 is different from Example 1 only in that the volume ratio of liquid paraffin to water is 1:300, the mass fraction of liquid paraffin in the oil-in-water nanoemulsion is 0.1%, and the other conditions are the same. An oil-in-water nanoemulsion and a reverse osmosis membrane are obtained, wherein the average particle size of the oil-in-water nanoemulsion is 110 nm and the polydispersity index is ≤0.27.

[0073] Example 5

[0074] Example 5 is different from Example 1 only in that the volume ratio of liquid paraffin to water is 1:50, the mass fraction of liquid paraffin in the oil-in-water nanoemulsion is 0.8%, and the other conditions are the same. An oil-in-water nanoemulsion and a reverse osmosis membrane are obtained, wherein the average particle size of the oil-in-water nanoemulsion is 115 nm and the polydispersity index is ≤0.28.

[0075] Example 6

[0076] Compared with Example 1, Example 6 differs only in that, in the oil-in-water nanoemulsion, the mass fraction of Tween 80 is 30%, and the mass fraction of sodium lauryl sulfate is 2%, while the other conditions are the same. An oil-in-water nanoemulsion and a reverse osmosis membrane are obtained, wherein the average particle size of the oil-in-water nanoemulsion is 100 nm and the polydispersity index is ≤0.27.

[0077] Example 7

[0078] Compared with Example 1, Example 7 differs only in that, in the oil-in-water nanoemulsion, the mass fraction of Tween 80 is 30%, and the mass fraction of sodium lauryl sulfate is 8%, while the other conditions are the same. An oil-in-water nanoemulsion and a reverse osmosis membrane are obtained, wherein the average particle size of the oil-in-water nanoemulsion is 98 nm and the polydispersity index is ≤0.27.

[0079] Example 8

[0080] The only difference between Example 8 and Example 1 is that sodium lauryl sulfate is not contained in the oil-in-water nanoemulsion. Other conditions are the same. An oil-in-water nanoemulsion and a reverse osmosis membrane are obtained, wherein the average particle size of the oil-in-water nanoemulsion is 105 nm and the polydispersity index is ≤0.28.

[0081] Example 9

[0082] Compared with Example 1, Example 9 differs only in that the mass fraction of liquid paraffin in the oil-in-water nanoemulsion is 0.05%, and the other conditions are the same. An oil-in-water nanoemulsion and a reverse osmosis membrane are obtained, wherein the average particle size of the oil-in-water nanoemulsion is 100 nm and the polydispersity index is ≤0.25.

[0083] Example 10

[0084] Compared with Example 1, Example 10 differs only in that the mass fraction of liquid paraffin in the oil-in-water nanoemulsion is 1.0%, and other conditions are the same. An oil-in-water nanoemulsion and a reverse osmosis membrane are obtained, wherein the average particle size of the oil-in-water nanoemulsion is 120 nm and the polydispersity index is ≤0.28.

[0085] Example 11

[0086] Compared with Example 1, Example 11 differs only in that, in the oil-in-water nanoemulsion, the mass fraction of Tween 80 is 18%, and the mass fraction of sodium lauryl sulfate is 1%, while other conditions are the same. An oil-in-water nanoemulsion and a reverse osmosis membrane are obtained, wherein the average particle size of the oil-in-water nanoemulsion is 100 nm and the polydispersity index is ≤0.27.

[0087] Example 12

[0088] Compared with Example 1, Example 12 differs only in that, in the oil-in-water nanoemulsion, the mass fraction of Tween 80 is 40%, and the mass fraction of sodium lauryl sulfate is 6%, while other conditions are the same. An oil-in-water nanoemulsion and a reverse osmosis membrane are obtained, wherein the average particle size of the oil-in-water nanoemulsion is 94 nm and the polydispersity index is ≤0.27.

[0089] Example 13

[0090] Compared with Example 1, Example 13 differs only in that the mass fraction of sodium chloride in the sodium chloride aqueous solution is 0.5%, and other conditions are the same to obtain a reverse osmosis membrane.

[0091] Example 14

[0092] Example 14 is different from Example 1 only in that the mass fraction of sodium chloride in the sodium chloride aqueous solution is 8%, and other conditions are the same to obtain a reverse osmosis membrane.

[0093] Example 15

[0094] Compared with Example 1, Example 15 differs only in that tributyl citrate is used instead of liquid paraffin, alkylphenol polyoxyethylene ether is used instead of Tween 80, and an aqueous solution of potassium chloride is used instead of an aqueous solution of sodium chloride. Other conditions are the same to obtain a reverse osmosis membrane.

[0095] Comparative Example 1

[0096] Comparative Example 1 is compared with Example 1, except that the volume ratio of liquid paraffin to water is 1:50, the average particle size of the oil-in-water nanoemulsion is 250 nm, the polydispersity index is ≤0.41, and in the oil-in-water nanoemulsion, the mass fraction of liquid paraffin is 0.5%, the mass fraction of Tween 80 is 20%, and the mass fraction of sodium lauryl sulfate is 4%, and the other conditions are the same to obtain a reverse osmosis membrane.

[0097] Comparative Example 2

[0098] Comparative Example 2 is compared with Example 1, except that the volume ratio of liquid paraffin to water is 1:20, the average particle size of the oil-in-water nanoemulsion is 200 nm, the polydispersity index is about 0.52, and in the oil-in-water nanoemulsion, the mass fraction of liquid paraffin is 0.6%, the mass fraction of Tween 80 is 30%, and the mass fraction of sodium lauryl sulfate is 3%, and the other conditions are the same to obtain a reverse osmosis membrane.

[0099] Comparative Example 3

[0100] Comparative Example 3 is compared with Example 1, except that the mass ratio of sodium chloride to oil-in-water nanoemulsion is 1:100, and other conditions are the same to obtain a reverse osmosis membrane.

[0101] Comparative Example 4

[0102] Comparative Example 4 is compared with Example 1, except that the mass ratio of sodium chloride to oil-in-water nanoemulsion is 1:10, and other conditions are the same to obtain a reverse osmosis membrane.

[0103] Comparative Example 5

[0104] The only difference between Comparative Example 5 and Example 1 is that it does not contain the step of applying the water-in-water oil-type nanoemulsion on the surface of the polysulfone support membrane. That is, an aqueous solution of sodium chloride is applied to the surface of the polysulfone support membrane, and after standing for 60 seconds, the excess sodium chloride aqueous solution is poured out, and the membrane is placed in a 60°C forced air drying oven for heat treatment for 4 minutes to form sodium chloride crystals distributed on the surface of the polysulfone support membrane.

[0105] The above oil phase solution was applied to the surface of a polysulfone support membrane with sodium chloride crystals distributed thereon, and after standing for 30 seconds, the excess oil phase solution was poured out and the membrane surface was dried in the shade; other conditions were kept the same to obtain a reverse osmosis membrane.

[0106] Comparative Example 6

[0107] Comparative Example 6 is different from Example 1 only in that the step of applying the aqueous solution of sodium chloride to the surface of the polysulfone support membrane is not included. That is, the water-in-oil nanoemulsion in Example 1 is directly applied to the surface of the polysulfone support membrane, and after standing for 60 seconds, the excess nanoemulsion is poured out and the membrane surface is dried in the shade; the above oil phase solution is applied to the surface of the polysulfone support membrane containing the nanoemulsion, and after standing for 30 seconds, the excess oil phase solution is poured out and the membrane surface is dried in the shade; the other conditions are the same, and the following is obtained: Figure 2 The reverse osmosis membrane shown.

[0108] Comparative Example 7

[0109] Comparative Example 7 is different from Example 1 only in that the above-mentioned aqueous solution is applied to the surface of the polysulfone support membrane with dendritic crystals distributed thereon, and after standing for 60 seconds, the excess aqueous solution is poured out, and the membrane surface is dried in the shade; then the above-mentioned oil phase solution is applied to the surface of the polysulfone support membrane that has absorbed the aqueous solution, and after standing for 30 seconds, the excess oil phase solution is poured out, and finally the membrane is placed in an 80°C forced air drying oven for heat treatment for 2 minutes. The other conditions are the same to obtain a reverse osmosis membrane.

[0110] The reverse osmosis membranes prepared in Examples 1 to 15 and Comparative Examples 1 to 7 were subjected to performance tests. The test conditions were as follows: a test pressure of 1.55 MPa, a brine flow rate of 1.0 GPM, an ambient temperature of 25°C, a brine pH of 6.5-7.5, and a brine solution of 2000 ppm sodium chloride. The test results are shown in Table 1.

[0111] Table 1

[0112]

[0113] 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.

[0114] The retention rate (R) is calculated by the concentration of the feed liquid and the concentration of the permeate. The calculation formula is: R=(1-C1 / C0)×100%, where C1 is the concentration of the permeate and C0 is the concentration of the feed liquid.

[0115] from Figure 1 It can be seen that the surface of the reverse osmosis membrane prepared in Example 1 has a large number of interconnected leaf-like structures, which can effectively increase the specific surface area of ​​the reverse osmosis membrane and effectively improve the water flux of the reverse osmosis membrane.

[0116] from Figure 2 It can be seen that in Comparative Example 6, since dendritic crystals cannot be formed, the number of granular protrusions on the surface of the separation layer formed increases. Compared with the blade-like structure, the reverse osmosis membrane has a very small specific surface area, thereby affecting the water flux of the reverse osmosis membrane.

[0117] 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.

[0118] 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: Mixing oil, a surfactant, and water to prepare an oil-in-water nanoemulsion, wherein the surfactant includes a nonionic surfactant, the average particle size of the oil-in-water nanoemulsion is 80 nm to 200 nm, the polydispersity index is ≤0.3, and the volume ratio of the oil to the water is 1:200 to 1:100; An aqueous solution of an inorganic metal salt and the oil-in-water nanoemulsion are sequentially placed on the same surface of a support membrane, and subjected to heat treatment to form dendritic crystals, wherein the mass ratio of the inorganic metal salt to the oil-in-water nanoemulsion is 1:50-1:30, and the mass fraction of the inorganic metal salt in the aqueous solution of the inorganic metal salt is 1%-5%; A polyamide separation layer is prepared on the surface of the support membrane on which the dendritic crystals are distributed by reverse interfacial polymerization to obtain a reverse osmosis membrane.

2. The method for preparing a reverse osmosis membrane according to claim 1, wherein The mass fraction of the oil in the oil-in-water nanoemulsion is 0.1%-0.8%; And / or, the mass fraction of the surfactant in the oil-in-water nanoemulsion is 20%-40%.

3. The method for preparing a reverse osmosis membrane according to claim 2, wherein The surfactant further comprises an ionic surfactant, and the mass ratio of the nonionic surfactant to the ionic surfactant is 5:1-10:

1.

4. The method for preparing a reverse osmosis membrane according to claim 1, wherein The oil is selected from at least one of alkanes, stearates, and tributyl citrate; And / or, the nonionic surfactant is selected from at least one of Tween 80, alkylphenol polyoxyethylene ether, and alkyl alcohol polyoxyethylene ether; And / or, the inorganic metal salt is selected from at least one of sodium chloride, potassium chloride, magnesium chloride and calcium chloride.

5. The method for preparing a reverse osmosis membrane according to claim 1, wherein In the step of forming dendrites by heat treatment, the temperature of the heat treatment is 50° C.-80° C., and the time of the heat treatment is 3 min-5 min.

6. The method for preparing a reverse osmosis membrane according to any one of claims 1 to 5, characterized in that: In the step of preparing a polyamide separation layer on the surface of the support membrane on which the dendritic crystals are distributed by reverse interfacial polymerization, an oil phase solution and an aqueous phase solution are sequentially placed on the surface of the support membrane on which the dendritic crystals are distributed, and a polyamide separation layer is prepared by heat treatment, wherein the oil phase solution contains polyacyl chloride and the aqueous phase solution contains polyamine.

7. A reverse osmosis membrane prepared by the method for preparing a reverse osmosis membrane according to any one of claims 1 to 6.

8. Use of the reverse osmosis membrane according to claim 7 in a water treatment device.

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