Reverse osmosis membrane as well as preparation method and application thereof

Abstract

The invention discloses a reverse osmosis membrane with stable performance and a preparation method and application thereof.The reverse osmosis membrane comprises a supporting layer and a separation function layer formed on the supporting layer, and the separation function layer is a polyamide layer and is of a hollow wrinkle structure formed by a thin film with a certain thickness. The reverse osmosis dry membrane with stable performance, longer shelf life and stable pressure resistance can be obtained by regulating and controlling the thickness of the membrane and the hollow wrinkled structure.

Description

Technical Field

[0001] This invention belongs to the field of reverse osmosis membranes, and particularly relates to a stable reverse osmosis membrane, its preparation method, and its application. Background Technology

[0002] Reverse osmosis (RO), also known as reverse osmosis membrane technology, is one of the most advanced water treatment technologies today, with wide applications such as seawater desalination, pure water production, and concentration and separation of aqueous solutions. Currently, the mainstream RO membrane on the market is the aromatic polyamide composite RO membrane, which consists of a non-woven fabric support layer, a porous carrier intermediate layer, and a polyamide desalination layer. In practical applications, RO membranes still face a series of problems. For example, during operation, membrane fouling easily occurs, reducing the permeate flow rate. Professional chemical cleaning is necessary to restore the permeate flow. Even in applications with good water quality, the permeate flow rate decreases significantly due to increased compaction, and this loss is almost irreversible. Therefore, to solve the problem of permeate flow loss during RO operation, it is not enough to simply improve the membrane's anti-fouling ability; the pressure resistance and stability of the RO membrane are equally important.

[0003] On the other hand, for ease of storage and transportation, composite membranes are often stored in a dry state during actual production. Therefore, various humectants, such as glycerin, inorganic salts, and organic salts, are used in the composite membrane preparation process. While these humectants help maintain pore size and moisture, they also cause swelling of the polyamide desalination layer, resulting in irreversible negative impacts on the separation performance of the composite membrane. Furthermore, this swelling effect intensifies during membrane storage, shortening the membrane's shelf life and affecting product lifespan. To a certain extent, this also leads to a decrease in the pressure resistance stability of the polyamide composite membrane.

[0004] Current technologies for improving membrane pressure resistance mainly focus on enhancing the pressure resistance of the polyamide separation layer. For example, CN117380002A obtained a stable composite membrane by changing the aqueous phase monomer formulation; CN214131099U inserted a cross-linked polyamide porous membrane support layer as an intermediate layer between the base membrane and the polyamide desalination layer to improve the pressure resistance stability of the composite membrane. However, these methods all have certain negative effects on the performance of the composite membrane, such as a decrease in water production or desalination rate.

[0005] Therefore, there is still a need in the field to develop a reverse osmosis membrane with stable performance and a longer lifespan. Summary of the Invention

[0006] To address the above technical problems, the present invention aims to provide a reverse osmosis membrane with stable performance and longer shelf life, and a method for preparing the same. By controlling the morphology of polyamide, the long-term operational stability of the reverse osmosis membrane is improved, and its shelf life is significantly extended.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a reverse osmosis membrane with stable performance.

[0009] The reverse osmosis membrane includes a support layer and a separation functional layer formed on the support layer. The inventors have discovered that a separation functional layer with a specific raised, pleated unit structure can have a more stable rigid structure, resulting in a better balance between the water permeability and swelling resistance of the polyamide membrane, while also improving storage stability.

[0010] The support layer provides strength to the separation functional layer, and its material and pore size are not particularly limited. Specifically, the support layer material may include at least one of polysulfone, polyethersulfone, polyester, polyphenylene sulfide, polyphenylene sulfide sulfone, and polyphenylene ether. Specifically, the support layer is formed by coating the support layer material onto a polyester nonwoven fabric layer. Specifically, the separation functional layer is a polyamide layer with specific raised pleated units formed by the reaction of polyfunctional amines and polyfunctional acyl halides on the support layer, such as... Figure 1 .

[0011] The polyamide layer of the present invention has a raised, wrinkled unit structure, which is obtained by reacting polyfunctional amines and polyfunctional acyl halides.

[0012] The polyfunctional amine may specifically be one or more of the following: m-phenylenediamine, p-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 2,4-diaminotoluene, 2,6-diaminotoluene, 2,4-diaminoanisole, amylin, xylene diamine, 1,2-ethylenediamine, 1,2-propylenediamine, tris(2-aminoethyl)amine, 1,3-diaminocyclohexane, 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, piperazine, 2,5-dimethylpiperazine, and 4-aminomethylpiperazine; preferably one or more of the following: m-phenylenediamine, p-phenylenediamine, and 2,5-dimethylpiperazine.

[0013] The polyfunctional acyl halogen can be one or more of the following: pyromellitic chlorobenzene chloride, isophthaloyl chloride, terephthaloyl chloride, benzenetrisulfonyl chloride, benzenedisulfonyl chloride, glutaryl halide, adipyl halide, and cyclohexane-1,3,5-tricarboxylic acid chloride, preferably at least one of pyromellitic chlorobenzene chloride, isophthaloyl chloride, and terephthaloyl chloride.

[0014] As known from existing technology, a reverse osmosis membrane is a composite semi-permeable membrane composed of a support layer and a separation functional layer formed on the support layer. The separation functional layer is a polyamide layer, obtained by interfacial polymerization of polyfunctional amines in the aqueous phase and polyfunctional halides in the organic phase on the support layer. As most people skilled in the art agree, the specific process of interfacial polymerization involves the aqueous monomer polyfunctional amine starting from the base membrane surface, breaking through the water-oil phase interface, diffusing into the oil phase, and reacting with the polyfunctional halides in the oil phase to form the polyamide layer. Once formed, the polyamide layer inhibits further contact and reaction between the aqueous and oil phase monomers; therefore, the interfacial polymerization reaction is a self-inhibiting reaction. Because the diffusion rate of aqueous monomers at different sites varies slightly, the final polyamide layer morphology appears as a hollow, raised, pleated unit structure at different heights perpendicular to the base membrane surface (e.g., ...). Figure 1 (As shown).

[0015] The polyamide layer of this invention has a raised wrinkle unit structure. In images obtained by observing the cross-section of the above-mentioned separated functional layer using scanning electron microscopy, transmission electron microscopy, etc., a protrusion between two adjacent low points in the cross-section of the polyamide layer (polyamide film) is defined as a raised wrinkle unit structure (e.g., Figure 2 In this invention, the protrusion height H of the polyamide layer containing the hollow structure is defined as the vertical height from the top of the protruding pleated unit to the support layer, and the cross-sectional perimeter of a protruding pleated unit structure is defined as D, that is, the perimeter of the outer edge of a protruding pleated unit structure within a cross section, as shown in the attached figure. Figure 2 The lengths of the solid and dashed lines shown in the attached diagram are for illustrative purposes only. The height H of the polyamide layer protrusion is directly related to the performance of the reverse osmosis membrane. When H is <140nm, although it has high permeability, the ion removal rate is low. When H >310nm, the ion removal rate increases, but water permeability is hindered. Therefore, H is preferably between 140nm and 310nm to achieve a better balance between permeate flow and salt removal rate. When H and D are large, the polyamide layer has a higher specific surface area and better water permeability, but its salt removal rate will be affected and reduced. At the same time, it will be affected by compaction during long-term operation, resulting in poor stability. Therefore, D is preferably between 350nm and 700nm, and more preferably between 400nm and 650nm.

[0016] Furthermore, in this invention, the thickness of the top of the raised pleated unit is defined as the top thickness A of the polyamide layer. The top of the raised pleat is the thinnest part of the polyamide layer as a whole, which has the greatest impact on the salt removal rate and is also the position where the deformation due to swelling of the humectant is the greatest. Therefore, the top thickness A of the polyamide layer should be above 10 nm, preferably above 12 nm, and more preferably above 15 nm. However, when A is too high, it will affect the water permeability, so it should not exceed 35 nm, preferably not more than 32 nm, and more preferably not more than 30 nm.

[0017] To improve the storage stability of the reverse osmosis membrane and reduce the impact of humectant swelling on the deformation of the polyamide layer's raised wrinkle units, the ratio of the polyamide layer's raised height H to the top thickness A is not less than 6, preferably not less than 8. This raised structure has a more stable rigidity. At the same time, to ensure the stability of the polyamide layer, the ratio of the polyamide layer's raised height H to the top thickness A is not more than 25, preferably not more than 22, more preferably not more than 20. Even more preferably, the ratio of the polyamide layer's raised height H to the top thickness A is 10-18, which has a better effect on resisting humectant swelling.

[0018] On the other hand, the present invention found that when the product of the cross-sectional perimeter D of the raised pleated unit and the top thickness A of the polyamide layer further satisfies 5000-13000, preferably 8200-12500, the water permeability and anti-swelling stability of the polyamide film can be better balanced, ensuring that there are no excessively weak defects and improving storage stability.

[0019] The specific testing method for the aforementioned parameters such as the polyamide layer protrusion height, the top thickness of the polyamide layer, and the perimeter of the cross-section of the protruding fold unit is to take cross-sectional photographs using a transmission electron microscope. In any number of cross-sectional photographs, the "polyamide layer protrusion height", "polyamide layer top thickness", and "protruding fold unit cross-sectional perimeter" of each protruding fold unit in each cross-sectional photograph are calculated, and the average value of each parameter of each protruding fold unit in multiple cross-sections is calculated.

[0020] The reverse osmosis membrane of the present invention has a yellow index of 5-30, preferably 8-20, in its separation functional layer. This ensures a good crosslinking density of polyamide and also provides better water permeability. On the other hand, it also ensures the stability and anti-swelling effect of the raised structural unit, thereby improving the storage life of the reverse osmosis membrane.

[0021] The yellow index described in this invention is measured using a colorimeter. For details of the measurement method, please refer to the specific implementation section.

[0022] In a second aspect, the present invention provides a method for preparing a reverse osmosis membrane, the method being used to prepare the aforementioned reverse osmosis membrane, the preparation method comprising the following steps:

[0023] S1: After the support layer comes into contact with the aqueous phase solution of a polyfunctional amine, it comes into contact with the organic phase solution of a polyfunctional acyl halide to obtain the polyamide layer;

[0024] S2: Post-treatment of the reverse osmosis membrane.

[0025] In one embodiment of the present invention, the support layer in S1 includes at least one of polysulfone, polyethersulfone, polyester, polyphenylene sulfide, polyphenylene sulfide sulfone, and polyphenylene ether, preferably a polysulfone or polyethersulfone support layer, more preferably a polysulfone support layer. Preferably, the polysulfone support layer is obtained by coating a polysulfone solution onto a nonwoven fabric layer and then subjecting it to phase inversion. The concentration of the polysulfone solution is preferably 15-20 wt%, such as 15, 18, 19, or 20 wt%. The preparation method of the support layer can be carried out using well-known techniques in the field, and there is no particular limitation thereto.

[0026] As a support layer, in order to provide sufficient support, the thickness of the support layer is at least 100 μm, preferably 120 μm or more, more preferably 125 μm or more, and in order to ensure the removal rate, the thickness should be less than 150 μm, preferably less than 145 μm.

[0027] In one embodiment of the present invention, the mass concentration of the polyfunctional amine in the aqueous solution of the polyfunctional amine can be 1-5 wt%, such as 1 wt%, 2 wt%, 3 wt%, 4 wt%, or 5 wt%.

[0028] In one embodiment of the present invention, the mass concentration of the polyfunctional acyl halide in the organic phase solution can be 0.05-0.3 wt%, such as 0.05 wt%, 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, or 0.3 wt%. The solvent in the organic phase solution can include one or more of aliphatic alkanes, aromatic alkanes, and haloalkanes, preferably aliphatic alkanes, specifically including at least one of n-hexane, n-decane, dodecane, tridecane, Isopar G, Isopar L, and Isopar H.

[0029] In one embodiment of the present invention, the contact time between the support layer and the polyfunctional amine aqueous solution can be 15-30 s, such as 18, 20, 23, 25, or 28 s, and the contact time between the support layer and the polyfunctional acyl halide organic solution can be 10-300 s, such as 20, 35, 40, 50, 60, 80, 100, 120, 160, 200, 250, or 300 s.

[0030] In a preferred embodiment of the present invention, the aqueous solution further includes an acid receiver selected from a weak base, a buffer pair consisting of a weak base and an acid, an alkali metal hydroxide, carbonate, and bicarbonate, or an organic compound; wherein the weak base includes triethylamine and sodium phosphate; the buffer pair includes triethylamine hydrochloride and triethylamine camphor sulfonate; the alkali metal hydroxide, carbonate, and bicarbonate include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, and potassium bicarbonate; the organic compound includes tetramethylammonium hydroxide and tetraethylammonium hydroxide; preferably, the acid receiver is triethylamine camphor sulfonate; preferably, the aqueous solution contains 1.1–3.5 wt% triethylamine and 2.3–6.5 wt% camphor sulfonic acid; more preferably, the pH of the aqueous solution is 9–12.

[0031] In one embodiment of the present invention, the post-treatment of the reverse osmosis membrane specifically includes rinsing, oxidation post-treatment, and moisturizing treatment of the membrane.

[0032] In one embodiment of the present invention, the reverse osmosis membrane forming the polyamide layer is rinsed with hot water, preferably rinsing in hot water at 60-90°C for 2-5 minutes, and more preferably rinsing in hot water for 2-3 minutes, which can improve desalination performance and water permeability.

[0033] In one embodiment of the invention, the post-oxidation treatment involves contacting the reverse osmosis membrane, after hot water rinsing, with an oxidant solution. The oxidant solution includes an aqueous solution of nitrite and its salts. Since aqueous solutions of nitrite readily decompose and produce gas, it is preferable to generate nitrite sequentially through, for example, the reaction of nitrite with an acidic solution. This can be achieved by using sodium nitrite and controlling the pH of the oxidant solution. The pH of the oxidant solution is preferably controlled to be 2-4, such as 2, 2.5, 3, 3.5, or 4. Preferably, the concentration of the oxidant solution can be 0.1-0.5 wt%, such as 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, or 0.5 wt%.

[0034] The contact time between the reverse osmosis membrane and the oxidant solution can be 0.5-5 min, such as 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 min. The preferred temperature of the oxidant solution is 15-40℃, but room temperature can usually be chosen.

[0035] Preferably, after the reverse osmosis membrane has been rinsed with hot water and then contacted with the oxidant solution, it is rinsed with a reducing agent solution. The reducing agent includes, for example, one or more of sodium metabisulfite, sodium bisulfite, sodium thiosulfate, and sodium sulfite. Preferably, the concentration of the reducing agent solution can be 0.5-2 wt%, such as 0.5, 1, 1.5, or 2 wt%, and the rinsing time can be 0.5-3 min, such as 0.5, 1, 1.5, 2, 2.5, or 3 min.

[0036] Preferably, the reverse osmosis membrane can be rinsed with water before being rinsed with a reducing agent after contacting the oxidant solution, in order to remove excess oxidant from the membrane surface. After rinsing with the reducing agent solution, it can also be rinsed with water before proceeding with subsequent processing operations.

[0037] In one embodiment of the present invention, the moisturizing treatment involves contacting the aforementioned treated reverse osmosis membrane with a moisturizing agent solution.

[0038] The humectant solution contains at least one of glycerin, citric acid, sodium acetate, and glucose. The humectant solution also contains an anti-swelling agent, which is an active polyether compound, and at least one end of the active polyether compound contains a group that can react with an amino group.

[0039] The reactive polyether compound may contain one or more of the following groups: allyl (H2C=CH-CH2-), epoxy, isocyanate (-N=C=O), silyl, etc.

[0040] Preferably, the epoxy group includes glycidyl ether type epoxy group with a structure such as -CH2-CH(O)CH2, and may also include aliphatic epoxy type, such as cyclohexane oxide type.

[0041] Preferably, the silyl group has a structure including -Si(OR)3 or -Si(OR)2R', wherein OR may include -OCH3, -OC2H5, etc., and R' includes -CH3.

[0042] Preferably, the weight-average molecular weight of the active polyether compound is 300-1500, more preferably 300-1200, and the concentration of the active polyether compound in the humectant solution is 0.01%-0.5wt%, such as 0.01wt%, 0.05wt%, 0.08wt%, 0.1wt%, 0.12wt%, 0.15wt%, 0.2wt%, 0.25wt%, 0.28wt%, 0.3wt%, 0.35wt%, 0.4wt%, 0.45wt%, and 0.5wt%; the concentration of the humectant in the humectant solution is 1%-20wt%, such as 1wt%, 2wt%, 5wt%, 10wt%, 15wt%, and 20wt%.

[0043] In one embodiment of the present invention, the contact method between the reverse osmosis membrane and the humectant solution includes spraying, immersion, or back coating, and the contact time between the reverse osmosis membrane and the humectant solution is 0.5 min to 6 min, such as 1, 2, 5, or 6 min, preferably 0.5 to 2 min; preferably, the temperature of the humectant solution can be 25 to 90°C, and different humectants can be selected for use.

[0044] The reverse osmosis membrane described in this invention, after being moisturized, is dried and stored as a dry membrane sheet.

[0045] The reverse osmosis membrane post-treatment process described in this invention can further control the microstructure of the polyamide layer obtained by interfacial polymerization, forming a specific raised pleated unit structure in the polyamide layer, thereby obtaining a reverse osmosis membrane with long-term operational stability and significantly improved storage life.

[0046] A third aspect of the present invention provides the application of the above-described high-performance reverse osmosis membrane in a water treatment assembly or water treatment method.

[0047] The water treatment component can be any component or device that can be applied to the water treatment process and is equipped with the reverse osmosis membrane of the present invention, and also includes the preparation of such components or devices; the component can be, for example, a spiral wound membrane component and a disc tube flat sheet membrane component, or a household / commercial reverse osmosis water purifier, an industrial boiler feedwater reverse osmosis pure water device, an industrial wastewater reuse reverse osmosis device, etc.; the water treatment method can be, for example, brackish water wastewater reuse, drinking water production, etc.

[0048] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0049] This invention designs and controls the microstructure of the polyamide layer to obtain a more stable raised, wrinkled structure, maintaining the structural stability of the polyamide layer and reducing the swelling effect of traditional humectants on the polyamide layer. During long-term use, the water production is more stable and less prone to decay, while also maintaining pressure resistance. Simultaneously, during dry membrane storage, it also alleviates the continuous swelling effect of humectants on the polyamide layer, significantly extending the service life of the dry membrane. Furthermore, the preparation method of this invention is green and safe, simple to operate, low in production cost, and easy to industrialize. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the reverse osmosis membrane structure of the present invention, wherein 1 is a polyamide layer, 2 is a polysulfone support layer, and 3 is a polyester nonwoven fabric support layer;

[0051] Figure 2This is a schematic diagram of the raised pleated unit structure of the present invention, wherein A is the thickness of the top of the polyamide layer of the raised pleated unit 1, H is the protrusion height of the polyamide layer of the raised pleated unit 3, and D is the perimeter of the cross section of the raised pleated unit 2. Detailed Implementation

[0052] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0053] The sources of raw materials used in the embodiments and comparative examples of this invention are shown in Table 1. Unless otherwise specified, all raw materials are commercially available conventional raw materials.

[0054] Table 1 Information on Main Raw Materials

[0055]

[0056]

[0057] Test methods for polyamide films in the examples and comparative examples:

[0058] (1) Measurement of polyamide layer height and raised wrinkle unit parameters: First, the sample was embedded in a water-soluble polymer to prepare ultrathin sections for transmission electron microscopy (TEM). Any polymer capable of maintaining the sample shape could be used as the water-soluble polymer; for example, SPI-PON812 resin could be used for embedding. The sections were then placed in a 60°C oven for 48 hours to cure, followed by cooling to room temperature. For easier cross-sectional observation, ultrathin sections were cut using an ultramicrotome. Cross-sectional images of the obtained ultrathin sections were taken using TEM at a magnification of 100,000. The cross-sectional images were then analyzed using ImageJ image analysis software to determine the polyamide layer height and related parameters of the raised wrinkle unit (e.g., ...). Figure 2 Example). By taking any three sets of cross-sectional photographs using a TEM, the height of the polyamide layer protrusions, the thickness at the top of the polyamide layer, and the perimeter of the cross-section of the protruding wrinkle unit were measured, and the average value was calculated.

[0059] (2) Yellow Index Test Method:

[0060] The nonwoven fabric and porous support layer of the reverse osmosis membrane were peeled off, leaving the support layer and polyamide layer. The polyamide layer was placed face down on a glass plate, and the polysulfone was dissolved and removed by solvent immersion. Since the residual amine will also show color after oxidation, N,N-dimethylformamide (DMF) was used as the solvent to remove polysulfone and free coloring impurities as thoroughly as possible. The sample on the glass plate was rinsed with DMF, and the removal of polysulfone was verified by adding methanol to the surface of the polyamide separation layer. If white flocculent polysulfone precipitates, it was rinsed again with fresh DMF and methanol was added for verification until no polysulfone flocculent precipitates. The sample was washed with methanol until the DMF content in the eluent was less than 1 ppm. The sample was then transferred to a vacuum oven and vacuum dried at 150°C for 24 hours to obtain a glass plate loaded with the polyamide separation layer to be tested. The yellow index of the separation layer could be determined by measuring the transmittance using a colorimeter. The colorimeter used was Hunter Lab VIS, and the test method was based on standard ASTM E313C.

[0061] (3) Evaluation of desalination rate and permeability

[0062] Desalination rate and permeate flux are two important parameters for evaluating the separation performance of reverse osmosis membranes. This invention evaluates the separation performance of reverse osmosis membranes according to GB / T32373-2015 "Test Methods for Reverse Osmosis Membranes".

[0063] Desalination rate (R) is defined as: under certain operating conditions, the salt concentration (C) of the feed solution... f ) and the salt concentration in the permeate (C p The difference between the two is then divided by the feed solution salt concentration (C). f ), as in formula (1).

[0064]

[0065] Permeation flux is defined as the volume of water that permeates through a unit membrane area per unit time under certain operating conditions, and its unit is L / (m²). 2 ·h).

[0066] The operating conditions used for the reverse osmosis membrane performance determination in this invention are as follows: the feed solution is a 2000ppm sodium chloride aqueous solution, the solution pH is 7.0±0.5, the operating pressure is 1.55MPa, and the operating temperature is 25℃.

[0067] (4) Evaluation of long-cycle pressure resistance performance

[0068] a. Routine performance test: After stabilizing for 1 hour, measure the initial permeate flow rate F1 and desalination rate R1 of the membrane according to the performance test method (3);

[0069] b. Long-term pressure stability test: The membrane that has undergone routine performance testing will continue to operate under the above test conditions for 100 hours. Record the permeate flow rate F2 and the desalination rate R2 at this point, and calculate the membrane flux decline rate.

[0070] Flux change rate = (Fluorescence after 100h - Flux at steady state after 1h) / Flux at steady state after 1h × 100%.

[0071] The lower the flux change rate, the better the pressure resistance stability.

[0072] (5) Evaluation of the storage stability of dry film sheets

[0073] The prepared reverse osmosis dry membrane sheets were placed in a constant temperature and humidity environment. Membrane sheets were cut at regular intervals for performance testing after different storage periods. To accelerate the experimental process, the membrane sheets were stored in an air-exposed but light-protected environment. Performance changes were recorded after one week of storage.

[0074] The preparation method of the polysulfone-based membrane support layer in the comparative examples and embodiments of the present invention is as follows: Polysulfone is dissolved in N,N-dimethylformamide to prepare a solution with a solid content of 18wt%. The polysulfone solution is coated onto the surface of nonwoven fabric using a wet film preparation device with a thickness of 250 micrometers. After being left in the air for 4-5 seconds, the nonwoven fabric is immersed in room temperature pure water. After immersion for 5 minutes, the phase inversion is completed. The polysulfone-based membrane that has completed the phase inversion is then immersed in room temperature pure water. The water is changed every 2 hours to thoroughly clean the residual solvent, thereby obtaining a polysulfone-based membrane with a porous support layer supported on nonwoven fabric. The membrane is then cut for later use.

[0075] Example 1

[0076] S1: Prepare an aqueous solution of 2.5 wt% m-phenylenediamine; contact the polysulfone-supported membrane with the aqueous solution for 30 s; after removing excess water from the membrane surface, react it with an isopar G isoalkane solution containing 0.15 wt% trimesoyl chloride for 30 s, and the interface will undergo polycondensation to form a polyamide composite membrane. Remove excess oil phase with an air knife, and allow the composite membrane to air dry vertically for 1 min.

[0077] S2: The composite membrane is rinsed with hot water at a temperature of 80℃ for 2 minutes.

[0078] S3: Immerse the composite membrane obtained in S2 in a 0.2wt% nitrous acid solution with pH=3 for 1 min at room temperature, then rinse it with pure water, and then immerse it in a 0.5wt% sodium sulfite solution for 1 min, followed by rinsing with pure water.

[0079] S4: The polyamide composite membrane after post-treatment in S3 is immersed in an aqueous solution of glycerol containing active dielyl-terminated polyether. The concentration of glycerol in the solution is 6 wt%, the concentration of active dielyl-terminated polyether is 0.1 wt%, and the solution temperature is 80℃. After immersion for 1 min, the excess solution on the front side of the polyamide composite membrane is removed with an air knife, and then it is dried in a 60℃ oven for 6 min to obtain a reverse osmosis membrane.

[0080] Examples 2-6

[0081] Examples 2-6 were prepared using the same method as Example 1, with the main difference being the post-processing conditions, as detailed in Table 2.

[0082] Comparative Examples 1-2

[0083] Compared with Example 1, the post-processing conditions are different, but the rest are the same as in Example 1, as detailed in Table 2.

[0084] Table 2. Main preparation parameters for Examples 1-6 and Comparative Examples 1-2

[0085]

[0086]

[0087] Table 3. Measurement of indicators for each embodiment and comparative example.

[0088] A / nm D / nm H / nm H / A D*A Yellow Index Example 1 20.2 432 220 10.89 8726.4 15 Example 2 25.0 360 202 8.08 9000 27 Example 3 19.3 580 270 13.99 11194 7 Example 4 18.3 690 300 16.39 12627 14 Example 5 15.0 450 145 9.67 6750 16 Example 6 19.2 523 230 11.98 10041.6 15 Comparative Example 1 24.5 688 200 8.16 16856 12 Comparative Example 2 18.0 223 140 7.78 4014 14

[0089] Table 4 Performance results of each embodiment and comparative example

[0090]

[0091] In summary, compared with the comparative example, by adjusting the interfacial polymer membrane structure parameters through the above embodiments, a reverse osmosis membrane with more stable performance, longer shelf life, and better pressure resistance can be obtained. The present invention has been described in detail with reference to specific embodiments, but it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

Claims

1. A reverse osmosis membrane, the reverse osmosis membrane comprising a support layer and a separation functional layer formed on the support layer, the separation functional layer being a polyamide layer having raised corrugated units, characterized in that, The following conditions must be met: a. The cross-sectional perimeter D of the raised folded unit structure is 350nm-700nm; b. The thickness A of the top layer of the polyamide layer is 10-35 nm; c. The product of the cross-sectional perimeter D of the raised pleated unit structure and the top thickness A of the polyamide layer is 5000-13000.

2. The reverse osmosis membrane according to claim 1, characterized in that, The cross-sectional perimeter D of the raised pleated unit structure is 400-650 nm, and the product of the cross-sectional perimeter D of the raised pleated unit structure and the top thickness A of the polyamide layer is 8200-12500.

3. The reverse osmosis membrane according to claim 1 or 2, characterized in that, It also satisfies condition d. d. The height H of the polyamide layer protrusion is 140-310 nm.

4. The reverse osmosis membrane according to claim 3, characterized in that, Condition e is also met. e. The ratio of the protrusion height H of the polyamide layer to the top thickness A of the polyamide layer is 6-25, preferably 8-22, and more preferably 10-18.

5. The reverse osmosis membrane according to claim 4, characterized in that, It also satisfies condition f. f. The yellow index Y is 5-30, preferably 8-20.

6. A method for preparing a reverse osmosis membrane, characterized in that, Includes the following steps: S1: After the support layer comes into contact with the aqueous phase solution of a polyfunctional amine, it comes into contact with the organic phase solution of a polyfunctional acyl halide to obtain the polyamide layer; S2: Post-treatment of the reverse osmosis membrane; The post-treatment includes hot water rinsing, oxidation post-treatment, and moisturizing treatment of the reverse osmosis membrane. The moisturizing treatment involves contacting the reverse osmosis membrane with a moisturizing agent solution, which includes an anti-swelling agent. The anti-swelling agent is an active polyether compound, and at least one end of the active polyether compound contains a group that can react with an amino group.

7. The preparation method according to claim 6, characterized in that, The anti-swelling additive contains one or more of the following groups that can react with amino groups: allyl, epoxy, isocyanate, and silyl; preferably, the weight-average molecular weight of the active polyether compound is 300-1500, more preferably 300-1200; preferably, the concentration of the active polyether in the humectant solution is 0.01-0.5 wt%.

8. The preparation method according to claim 6 or 7, characterized in that, The post-processing moisturizing treatment also satisfies at least one of the following conditions: (1) The moisturizer includes at least one of glycerin, citric acid, sodium acetate, and glucose; (2) The concentration of the humectant in the humectant solution is 1-20 wt%; (3) The contact time for moisturizing treatment is 0.5 min to 6 min; (4) The temperature of the humectant solution is 25-90℃.

9. The preparation method according to claim 8, characterized in that, The hot water rinsing specifically involves treating the reverse osmosis membrane that forms the polyamide layer with hot water at 60-90°C for 2-5 minutes, preferably 2-3 minutes.

10. The preparation method according to claim 9, characterized in that, The oxidation post-treatment involves contacting the reverse osmosis membrane, after hot water rinsing, with an oxidant solution, and also satisfies at least one of the following conditions: (1) The oxidizing agent solution includes an aqueous solution of nitrite and its salt, the pH of the oxidizing agent solution is 2-4, and the concentration of the oxidizing agent solution is preferably 0.1-0.5 wt%. (2) The contact time between the reverse osmosis membrane and the oxidant solution is 0.5-5 min; (3) The temperature of the oxidant solution is 15-40℃; (4) After the reverse osmosis membrane comes into contact with the oxidant solution, it is rinsed with a reducing agent solution and water. The reducing agent includes one or more of sodium metabisulfite, sodium bisulfite, sodium thiosulfate, and sodium sulfite. The concentration of the reducing agent solution is preferably 0.5-2wt%, and the rinsing time of the reducing agent solution is preferably 0.5-3min.

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