Polyamide reverse osmosis membrane with high organic interception rate and anti-pollution and preparation method and application thereof

Abstract

The application belongs to the technical field of reverse osmosis membrane preparation, and particularly relates to a polyamide reverse osmosis membrane with high organic matter interception rate and anti-pollution, and a preparation method and application thereof; the polyamide reverse osmosis membrane comprises, in sequence, a substrate layer, a porous support layer and a functional separation layer; the functional separation layer comprises cross-linked polyamide and AAEM / NVP copolymer, and the cross-linked polyamide and the AAEM / NVP copolymer in the functional separation layer are connected through a chemical bond. The application can effectively improve the organic matter interception performance and anti-pollution performance of the reverse osmosis membrane under the premise of maintaining high flux and high desalination rate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of reverse osmosis membrane preparation, and particularly relates to a polyamide reverse osmosis membrane with high organic matter interception rate and anti-pollution, and a preparation method and application thereof. BACKGROUND

[0002] Currently, the mainstream commercial reverse osmosis membrane is a composite membrane with a three-layer composite structure, taking polyester non-woven fabric as a substrate, taking polysulfone porous membrane as an intermediate support layer, and taking cross-linked aromatic polyamide ultra-thin layer as a surface actual functional separation layer. By adjusting the thickness and cross-linking degree of the cross-linked aromatic polyamide layer, reverse osmosis membranes with different flux and desalination rates can be obtained, so as to achieve different degrees of interception of water-soluble substances such as salt ions and macromolecular organic matters. Therefore, reverse osmosis membranes are often used in application fields with desalination as the main purpose, such as domestic tap water purification, industrial pure water production, industrial wastewater reuse, and seawater desalination.

[0003] However, in addition to the field with desalination as the main purpose, reverse osmosis membranes are also often used for filtering total organic carbon (TOC) in pure water in the semiconductor and display panel industries. When a silicon wafer or a display panel is cleaned using pure water, if the residual amount of TOC in the water is too high, the silicon wafer or the panel will be contaminated, thereby greatly increasing the product failure rate. For example, as a typical scenario of a storage chip company, the conductivity of the pure water to be treated is generally about 1-5 μS / cm, and the TOC concentration is in the range of 200-500 ppb; in order to improve the chip yield, it is necessary to further filter the pure water using a reverse osmosis membrane, and the conductivity of the produced water is expected to be <1 μS / cm, the TOC concentration is expected to be <50 ppb, and the water production is expected to be as large as possible.

[0004] Unlike salt ions with charge repulsion effect, small-molecule organic matter constituting TOC generally has no charge effect, which makes reverse osmosis membranes unable to use the charge repulsion effect of the carboxyl and amino groups inside the cross-linked aromatic polyamide to intercept TOC, but only rely on the "pore size screening" effect of the Angstrom-level pores inside the cross-linked polyamide. Therefore, the interception rate of the existing reverse osmosis membranes for TOC is generally significantly lower than that for salt ions. In particular, it is more difficult to improve the removal rate of TOC while maintaining as high a water permeation flux as possible, and there are relatively few relevant targeted studies.

[0005] In addition, whether the reverse osmosis membrane is applied in the desalination field or the TOC removal field, it will encounter the problem of flux decline due to membrane pollution during use. This is mainly because the cross-linked aromatic polyamide material is generally hydrophilic, and some organic pollutants such as proteins, surfactants, emulsified hydrocarbons, and microorganisms with strong hydrophobicity can easily be adsorbed on the membrane surface through hydrophobic molecular interactions, and are difficult to clean. This makes it necessary to frequently clean the reverse osmosis membrane with acid and alkali during operation.

[0006] In order to improve the anti-fouling performance of reverse osmosis membranes, there are many literatures and patents researches, which mainly focus on improving the hydrophilicity of the reverse osmosis membrane surface, reducing the roughness of the membrane surface and making the membrane surface tend to be electrically neutral. Despite so many researches on anti-fouling coating of reverse osmosis membranes, considering the acid and alkali resistance and oxidation resistance of the coating material, the main method of the patent reports with industrial value is to introduce hydrophilic polymers such as polyvinyl alcohol (such as patent document CN102921315A, patent document CN105008031A, patent document CN105008031A), polyethylene glycol (such as patent document CN102363113A, patent document CN1180876C), polyoxazoline (such as patent document CN101605592A), polyacrylic acid (such as patent document CN111787997A, patent document CN105611994A, patent document CN110536743A) and the like on the surface of the reverse osmosis membrane.

[0007] Among the anti-fouling reverse osmosis membranes that have been industrialized, polyethylene glycol and polyoxazoline have been introduced to the surface of the reverse osmosis membrane due to the presence of active groups that are easy to react, and have shown good anti-fouling performance. Although polyvinylpyrrolidone (PVP) has excellent anti-fouling performance, it cannot directly form chemical bonds with the amino groups, carboxyl groups and the like of the cross-linked aromatic polyamide on the surface of the reverse osmosis membrane due to the absence of reactive active groups in the side chain of the polymer. The existing research is to introduce a strong hydrogen bond formed by a tannic acid intermediate layer containing polyphenol to the surface of the reverse osmosis membrane (Wu J, Wang Z, Yan W, et al. Improving the hydrophilicity and fouling resistance of RO membranes by surface immobilization of PVP based on a metal-polyphenol precursor layer [J]. Journal of Membrane Science, 2015, 496: 58-69. DOI: 10.1016 / j.memsci.2015.08.044.). However, since polyvinylpyrrolidone is not chemically bonded to the membrane surface, simple acid and alkali cleaning can easily break the hydrogen bond, causing the coating to be lost, thus lacking commercial significance.

[0008] Therefore, it is of great significance to develop a polyamide reverse osmosis membrane with high organic matter retention and anti-fouling for improving the retention effect of the reverse osmosis membrane and reducing the operating cost of the reverse osmosis membrane. SUMMARY

[0009] The present application aims at solving the problems of the prior art in improving the anti-fouling and TOC interception of reverse osmosis membranes, and provides a polyamide reverse osmosis membrane with high organic matter interception rate and anti-fouling, a preparation method and application thereof.

[0010] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions.

[0011] In a first aspect, a polyamide reverse osmosis membrane with high organic matter interception rate and anti-fouling is provided, which comprises, in sequence, a substrate layer, a porous support layer and a functional separation layer; the functional separation layer comprises cross-linked polyamide and AAEM / NVP copolymer, and the cross-linked polyamide and the AAEM / NVP copolymer in the functional separation layer are connected by chemical bonds.

[0012] According to the polyamide reverse osmosis membrane provided by the present application, in some embodiments, in the functional separation layer, the AAEM / NVP copolymer is connected by chemical bonds formed between acetylacetyl groups of side chains thereof and terminal amino groups of the cross-linked polyamide and / or by chemical bonds formed between the terminal amino groups and diazonium salts obtained after diazotization.

[0013] In the present application, the functional separation layer comprises chemical bonds formed between acetylacetyl groups and terminal amino groups of the cross-linked polyamide, azo groups and phenolic hydroxyl groups. Among them, the azo groups are derived from chemical groups formed by the reaction of diazonium salts with acetylacetyl groups of the copolymer, as shown in the accompanying drawings, and the phenolic hydroxyl groups are derived from chemical groups formed by the hydrolysis of unreacted diazonium salts at high temperatures, as shown in the accompanying drawings. Figure 3 As shown in the accompanying drawings, the azo groups in the functional separation layer can further improve the cross-linking degree of the cross-linked polyamide desalination layer and improve the TOC interception rate of small molecule organic matter; the phenolic hydroxyl groups in the functional separation layer are derived from chemical groups formed by the hydrolysis of unreacted diazonium salts at high temperatures, as shown in the accompanying drawings. Figure 4 As shown in the accompanying drawings, the phenolic hydroxyl groups in the functional separation layer can increase the hydrophilicity inside the polyamide desalination layer and improve the permeation flux, and on the other hand, the hydrogen bonding between the phenolic hydroxyl groups and the amide bonds can be used to make no loss of desalination rate.

[0014] According to the polyamide reverse osmosis membrane provided by the present application, in some embodiments, the AAEM / NVP copolymer is a product obtained by radical polymerization reaction of acetylacetoxyethyl methacrylate (AAEM) and N-vinyl pyrrolidone (NVP) as monomers.

[0015] In some embodiments, the side chain of the AAEM / NVP copolymer contains acetylacetyl groups with reactivity and pyrrolidone groups with hydrophilicity, and the chemical structure is as shown in formula (I):

[0016]

[0017] wherein x, y are positive integers (e.g., each independently selected from 10, 12, 13, 15, 17, 18, 19, 20, 25, 30, 36, 40, 45, 50, 55, 60, 65, 70, 75, 80, 86, 90, 95, 100, 500, etc.), and satisfy the relationship x / (x+y) in the range of 0.05 to 0.3; for example, x / (x+y) is 0.055, 0.06, 0.07, 0.08, 0.1, 0.12, 0.15, 0.18, 0.2, 0.22, 0.24, 0.25, 0.26, 0.28.

[0018] In this context, the AAEM / NVP copolymer can be obtained by using a free radical copolymerization technique known in the art, which will not be described in detail. The solvent used in the free radical copolymerization is not particularly limited, as long as it can dissolve AAEM and NVP, such as N-methylpyrrolidone, dimethylformamide, dimethylacetamide, acetonitrile, tetrahydrofuran, dimethyl sulfoxide, dioxane, etc. N-methylpyrrolidone is preferred in consideration of the solubility of the AAEM / NVP copolymer in the solvent. The initiator used in the free radical copolymerization is not particularly limited, and can be selected from redox initiators, azo initiators, etc., as long as it can generate free radicals. Azo initiators, such as azobisisobutyronitrile initiators, are preferred in consideration of the solvent compatibility and the polymerization temperature. The solid content of the copolymer synthesized finally in the solvent can be in the range of 5% to 60%, preferably in the range of 10% to 50%, and further preferably in the range of 30% to 45%. In the present application, the copolymer obtained after the free radical polymerization of AAEM and NVP in the solvent does not need to be separated and purified, and can be used directly.

[0019] In some embodiments, the AAEM / NVP copolymer has a weight average molecular weight of greater than or equal to 5,000 and less than or equal to 1,000,000, preferably greater than or equal to 10,000 and less than or equal to 800,000, more preferably greater than or equal to 50,000 and less than or equal to 500,000. The AAEM / NVP copolymer can have a weight average molecular weight of, for example, 5,500, 5,800, 6,000, 6,500, 7,000, 7,500, 8,000, 9,000, 10,000, 11,000, 12,000, 15,000, 18,000, 20,000, 30,000, 40,000, 50,000, 60,000, 80,000, 100,000, 120,000, 150,000, 200,000, 300,000, 550,000, 600,000, 850,000, 900,000.

[0020] In some embodiments, the cross-linked polyamide is obtained by interfacial polycondensation reaction on the surface of the porous support layer using an aqueous solution containing m-phenylenediamine and triethyl phosphate and an oil solution containing trimesoyl chloride. In this context, the aromatic cross-linked polyamide layer can be a functional layer commonly found in reverse osmosis membranes of the prior art, and its preparation process can be referred to the prior art, which is not described here in detail.

[0021] In some embodiments, the substrate layer is selected from one or more of polyester nonwoven fabric, polyethylene porous film, and polypropylene porous film.

[0022] In some embodiments, the porous support layer is selected from one or more of polysulfone porous support layer, polyethersulfone porous support layer, and polyacrylonitrile porous support layer.

[0023] The method of bonding between the substrate layer and the porous support layer is well known to those skilled in the art, which is not described here in detail.

[0024] In some embodiments, the functional separation layer of the polyamide reverse osmosis membrane has a static contact angle of greater than or equal to 20° and less than or equal to 40°; for example, the static contact angle is 22°, 24°, 25°, 28°, 30°, 32°, 34°, 35°, 36°, 38°.

[0025] The static contact angle test can be understood as follows: after the polyamide reverse osmosis membrane is dried in a hot air oven at 80°C for 24 hours, 2 microliters of deionized water is dropped onto the surface of the functional separation layer of the reverse osmosis membrane to perform the static contact angle test process, and the contact angle after 10 seconds from the dropping of the pure water droplet to the surface of the functional separation layer.

[0026] In some embodiments, the surface zeta potential value of the functional separation layer is -35 mV to -10 mV at pH = 6.5. For example, the surface zeta potential value is -32 mV, -30 mV, -28 mV, -25 mV, -22 mV, -20 mV, -18 mV, -15 mV, -12 mV.

[0027] In some embodiments, the polyamide reverse osmosis membrane has a salt rejection rate (Rs) of 99.6% and above (e.g., 99.7%, 99.75%, 99.8%, 99.85%, 99.9%, 99.92%, 99.95%), a TOC removal rate (Rt) of 85% and above (e.g., 86%, 87%, 88%, 89%, 90%, 92%, 94%, 95%), and a permeate flux of 60 L / (m 2 ·h) and above (e.g., 62 L / (m 2 ·h), 65 L / (m 2 ·h), 68 L / (m 2 ·h), 70 L / (m 2 ·h), 72 L / (m 2 ·h), 75 L / (m 2 ·h).

[0028] For example, the polyamide reverse osmosis membrane has a salt rejection rate of 99.6% and above, a i-propanol rejection rate of 85% and above, and a permeate flux of 60 L / (m 2 ·h) and above after filtering a water solution with a temperature of 25°C, a pH of 7.0, a sodium chloride concentration of 1500-2000 mg / L, and an i-propanol concentration of 100 mg / L for 1 hour under a pressure of 1.03 MPa.

[0029] In some embodiments, the polyamide reverse osmosis membrane has a flux reduction rate of greater than or equal to 5% and less than or equal to 25% (e.g., 6%, 7%, 8%, 10%, 12%, 15%, 16%, 18%, 20%, 22%, 24%) after contamination, and a flux recovery rate of greater than or equal to 98% and less than or equal to 100% (e.g., 98.2%, 98.5%, 98.8%, 99%, 99.2%, 99.4%, 99.5%, 99.6%, 99.8%, 99.9%) after cleaning.

[0030] In a second aspect, a method for preparing the polyamide reverse osmosis membrane as described above is provided, comprising the following steps:

[0031] S1, performing an interfacial polycondensation reaction on the surface of the porous support layer by mixing an aqueous solution containing m-phenylenediamine and triethyl phosphate with an oil solution containing trimesoyl chloride to form a cross-linked aromatic polyamide-I, thereby obtaining a nascent reverse osmosis membrane;

[0032] S2, the nascent reverse osmosis membrane obtained in step S1 is contacted with a post-crosslinking aqueous solution to react, and then washed in hot water to form a crosslinked aromatic polyamide-II, thereby obtaining a secondary reverse osmosis membrane;

[0033] Preferably, the post-crosslinking aqueous solution contains m-phenylenediamine and an alcohol additive;

[0034] Preferably, the alcohol additive is selected from any one of methanol, ethanol, isopropanol, ethylene glycol, and glycerol;

[0035] The secondary crosslinking reaction of the crosslinked aromatic polyamide with m-phenylenediamine in the post-crosslinking aqueous solution is not particularly limited, as long as the residual acyl chloride groups on the surface of the crosslinked aromatic polyamide can further react with the amino groups of m-phenylenediamine;

[0036] The crosslinked aromatic polyamide formed by the interfacial polycondensation using the post-crosslinking aqueous solution to contact the surface of the crosslinked aromatic polyamide not only enables the unreacted acyl chloride groups remaining on the surface to continue to react with the amino groups, reduces the proportion of carboxyl-terminated linear polyamides on the surface and inside of the crosslinked aromatic polyamide, and preliminarily reduces the size of the Angstrom-level "pores", but also increases the content of terminal amino groups on the surface of the crosslinked polyamide;

[0037] S3, the secondary reverse osmosis membrane obtained in step S2 is contacted with an aqueous solution containing an AAEM / NVP copolymer to react, and then washed in hot water to form a crosslinked aromatic polyamide-III, thereby obtaining a tertiary reverse osmosis membrane;

[0038] The chemical bond formed by the acetylacetyl groups of the AAEM / NVP copolymer and the terminal amino groups on the surface of the crosslinked aromatic polyamide further crosslinks part of the amino groups on the surface of the membrane, increases the crosslinking degree, and further reduces the size of the Angstrom-level "pores" inside the crosslinked aromatic polyamide. In addition, since the oil phase solvent containing trimesoyl chloride remains inside the crosslinked aromatic polyamide, and the pyrrolidone ring of the AAEM / NVP copolymer has a certain surface activity, the AAEM / NVP copolymer is more easily introduced into the loose structure inside the crosslinked aromatic polyamide;

[0039] S4, the tertiary reverse osmosis membrane obtained in step S3 is first immersed in a nitrous acid aqueous solution to react, and then immersed in an aqueous solution containing sodium sulfite and the AAEM / NVP copolymer to react, and then washed in hot water, thereby obtaining the polyamide reverse osmosis membrane.

[0040] The residual part of the terminal amino group after the reaction of the crosslinked aromatic polyamide with the AAEM / NVP copolymer can react with nitrous acid to form diazonium salt, which can further react with the acetyl acetyl group of the AAEM / NVP copolymer, thereby further increasing the surface grafting amount of the AAEM / NVP copolymer, and again reducing the size of the "pore" of the crosslinked aromatic polyamide.

[0041] In the present application, the polyamide reverse osmosis membrane with high organic matter retention and anti-pollution can have the above-mentioned performance characteristics (for example, the static contact angle of the functional separation layer in the polyamide reverse osmosis membrane is greater than or equal to 20° and less than or equal to 40°; and / or, the surface Zeta potential value of the functional separation layer is -35mV to -10mV at pH = 6.5; and / or, the salt rejection rate (Rs) of the polyamide reverse osmosis membrane is 99.6% and above, the TOC removal rate (Rt) is 85% and above, the permeate flux is 60L / (m 2 ·h) and above; the flux decline rate of the polyamide reverse osmosis membrane after pollution is greater than or equal to 5% and less than or equal to 25%, and the flux recovery rate after cleaning is greater than or equal to 98% and less than or equal to 100%) without being limited to a specific preparation method.

[0042] In the preparation method of the present application, the expressions "I", "II", "III" and "primary", "secondary", "tertiary" and the like have no specific meaning and are only used to represent the operation process between steps.

[0043] According to the preparation method provided by the present application, in step S1:

[0044] Regarding the aqueous solution containing m-phenylenediamine and triethyl phosphate, the mass concentration of m-phenylenediamine can be in the range of 0.5% to 10%, preferably in the range of 1% to 7%, in terms of mass percentage; the mass concentration of triethyl phosphate can be in the range of 0.05% to 1%, preferably in the range of 0.1% to 0.8%, and further preferably in the range of 0.2% to 0.5%. In order to obtain a crosslinked aromatic polyamide desalination layer with higher flux and salt rejection rate, the mass concentration ratio of m-phenylenediamine to triethyl phosphate in the aqueous solution can be in the range of 20:1 to 5:1, preferably in the range of 20:1 to 8:1, and further preferably in the range of 15:1 to 8:1.

[0045] Regarding the temperature of the aqueous solution, it can be 0 to 100°C, preferably 5 to 60°C, and further preferably 20 to 45°C.

[0046] As for the way of contacting the aqueous solution containing m-phenylenediamine and triethyl phosphate with the surface of the porous support layer, as long as the aqueous solution can be uniformly contacted with the surface of the base film, the aqueous solution can be uniformly coated on the surface of the base film by coating, or the base film can be directly immersed in the aqueous solution.

[0047] As for the contacting time of the aqueous solution with the base film, it can be 5 seconds to 10 minutes, preferably 10 seconds to 2 minutes. Then, the excess aqueous solution on the surface of the base film needs to be removed. The removal method is not limited as long as the aqueous solution can be uniformly infiltrated on the surface of the base film and there is no visible water droplet on the surface of the base film. The method of vertically placing the base film to allow the aqueous solution to flow down naturally and then naturally drying can be used, or a squeeze roller or air knife can be directly used to remove most of the excess aqueous solution, and then the remaining aqueous solution can be further removed by natural air drying or oven drying. Then, the oil phase solution containing trimesoyl chloride is uniformly coated on the surface of the base film, and the interfacial polycondensation reaction occurs on the surface to form a cross-linked aromatic polyamide desalination layer.

[0048] As for the interfacial polycondensation reaction of m-phenylenediamine and trimesoyl chloride, it not only occurs in the pores of the porous support layer, but also occurs in the non-porous part of the surface of the porous support layer, and finally the cross-linked aromatic polyamide desalination layer is combined with the porous support layer in a "physical fitting" manner.

[0049] As for the temperature of the static interfacial polycondensation reaction, it is mainly determined by the temperature of the oil phase solution, which can be 10-40℃, preferably 15-35℃, and further preferably 20-30℃. As for the time of the static contact interfacial polycondensation reaction, it can be 0.5 seconds to 5 minutes, preferably 5 seconds to 2 minutes, and further preferably 10 seconds to 1 minute. When the time of the static contact interfacial polycondensation reaction is less than 0.5 seconds, the interfacial polycondensation reaction is insufficient and a complete polyamide desalination layer cannot be formed; when the time of the static contact interfacial polycondensation reaction is more than 5 minutes, the formed polyamide desalination layer is too thick, the membrane permeation flux is too low, and the production efficiency is reduced.

[0050] As for the concentration of trimesoyl chloride in the oil phase solution, it can be in the range of 0.05% to 1% by mass, preferably in the range of 0.08% to 0.5%, and further preferably in the range of 0.1% to 0.3%. In order to form a cross-linked aromatic polyamide desalination layer with higher flux and desalination rate, the ratio between the concentration of m-phenylenediamine in the aqueous solution and the concentration of trimesoyl chloride in the oil phase solution can be limited, for example, 30:1 to 5:1, preferably 15:1 to 5:1, and further preferably 15:1 to 10:1.

[0051] Next, the excess oil phase solution on the membrane surface needs to be removed. The method for removing the oil phase solution is not limited as long as the polyamide desalination layer is not damaged. For example, the oil phase solvent can be volatilized by directly using an oven, the membrane can be vertically placed to allow the oil phase solution to naturally flow down and then naturally air-dried, or a physical method such as a guide roller, air knife, water knife, etc. can be used to directly remove the solvent.

[0052] According to the preparation method provided by the present application, in step S2:

[0053] The concentration of the m-phenylenediamine contained in the post-crosslinking aqueous solution can be in the range of 0.001% to 1% by mass, preferably in the range of 0.005% to 0.5% by mass, and further preferably in the range of 0.01% to 0.1% by mass. In order to promote the diffusion of the m-phenylenediamine into the crosslinked aromatic polyamide, an alcohol additive can be added. As the alcohol additive, methanol, ethanol, isopropanol, ethylene glycol, glycerol, etc. can be selected; the concentration of the alcohol additive contained in the post-crosslinking aqueous solution can be in the range of 1% to 20% by mass, and preferably in the range of 5% to 10% by mass. The temperature of the post-crosslinking aqueous solution containing the m-phenylenediamine can be 0°C to 100°C, preferably 20°C to 90°C, and further preferably 60°C to 85°C.

[0054] The method for contacting the post-crosslinking aqueous solution containing the m-phenylenediamine with the crosslinked aromatic polyamide can be any method that allows the aqueous solution to uniformly contact the surface of the crosslinked aromatic polyamide, for example, the aqueous solution can be uniformly coated on the surface of the membrane by coating, or the reverse osmosis membrane can be directly immersed in the aqueous solution.

[0055] The contact time of the post-crosslinking aqueous solution with the crosslinked aromatic polyamide can be, for example, 5 seconds to 10 minutes, and preferably 10 seconds to 2 minutes. The contact temperature of the post-crosslinking aqueous solution with the crosslinked aromatic polyamide is mainly determined by the temperature of the post-crosslinking aqueous solution, and can be, for example, 45°C to 100°C, preferably 60°C to 95°C, and further preferably 75°C to 90°C.

[0056] The hot water cleaning method can be, for example, directly immersing the reverse osmosis membrane in hot water. The temperature of the hot water can be, for example, 45°C to 100°C, preferably 60°C to 95°C, and further preferably 75°C to 90°C. The immersion time can be, for example, 5 seconds to 10 minutes, preferably 10 seconds to 2 minutes, and further preferably 30 seconds to 1 minute.

[0057] According to the preparation method provided by the present application, in step S3:

[0058] The reaction formula for the specific reaction is as shown in Figure 1 ;

[0059] The concentration of the aqueous solution containing the AAEM / NVP copolymer can be, for example, in the range of 0.001% to 1%, preferably in the range of 0.01% to 0.5%, and further preferably in the range of 0.01% to 0.1%, in terms of mass percentage. The contact temperature of the aqueous solution containing the AAEM / NVP copolymer with the crosslinked aromatic polyamide is mainly determined by the temperature of the aqueous solution containing the AAEM / NVP copolymer, and can be, for example, in the range of 45°C to 100°C, preferably in the range of 60°C to 95°C, and further preferably in the range of 75°C to 90°C. The contact time of the aqueous solution containing the AAEM / NVP copolymer with the crosslinked aromatic polyamide can be, for example, in the range of 5 seconds to 10 minutes, preferably in the range of 10 seconds to 2 minutes, and further preferably in the range of 30 seconds to 1 minute.

[0060] The way of cleaning in hot water can be, for example, directly immersing the reverse osmosis membrane in hot water. The temperature of the hot water can be, for example, in the range of 45°C to 100°C, preferably in the range of 60°C to 95°C, and further preferably in the range of 75°C to 90°C. The time of immersing in hot water can be, for example, in the range of 5 seconds to 10 minutes, preferably in the range of 10 seconds to 2 minutes, and further preferably in the range of 30 seconds to 1 minute.

[0061] According to the preparation method provided by the present application, in step S4:

[0062] The reaction formula of the crosslinked aromatic polyamide reacting with nitrous acid to form diazonium salt is shown as Figure 2 .

[0063] The aqueous solution of nitrous acid can be, for example, formed by adjusting the pH value of the aqueous solution of sodium nitrite to be acidic by hydrochloric acid; the sodium nitrite reacts with hydrochloric acid to form nitrous acid, and the terminal amino group is converted into diazonium salt by reacting with the nitrous acid.

[0064] The concentration of the aqueous solution of nitrous acid can be, for example, in the range of 0.05% to 1%, preferably in the range of 0.1% to 0.5%, and further preferably in the range of 0.2% to 0.4%, in terms of mass percentage; the pH value of the aqueous solution of nitrous acid can be, for example, in the range of 1 to 5, preferably in the range of 2 to 4, and further preferably in the range of 2 to 3.

[0065] The immersing time of the reverse osmosis membrane in the aqueous solution of nitrous acid can be, for example, in the range of 5 seconds to 24 hours, preferably in the range of 10 seconds to 2 hours, and further preferably in the range of 10 seconds to 60 seconds.

[0066] Subsequently, the reverse osmosis membrane is immersed in an aqueous solution containing sodium sulfite and AAEM / NVP copolymer; the reaction formula of the AAEM / NVP copolymer with the diazonium salt is shown as Figure 3 .

[0067] In the aqueous solution containing the AAEM / NVP copolymer and sodium sulfite, the concentration of sodium sulfite, for example, can be in the range of 0.1% to 10%, preferably in the range of 0.2% to 5%, and further preferably in the range of 0.5% to 2%, in terms of mass percentage; and the concentration of the AAEM / NVP copolymer, for example, can be in the range of 0.001% to 1%, preferably in the range of 0.01% to 0.5%, and further preferably in the range of 0.01% to 0.1%, in terms of mass percentage.

[0068] The time for which the reverse osmosis membrane is immersed in the aqueous solution containing the AAEM / NVP copolymer and sodium sulfite, for example, can be in the range of 5 seconds to 24 hours, preferably in the range of 10 seconds to 1 hour, and further preferably in the range of 10 seconds to 60 seconds.

[0069] To better promote the reaction of the AAEM / NVP copolymer with the diazonium salt in the cross-linked aromatic polyamide, the concentration ratio of sodium sulfite and the AAEM / NVP copolymer and the temperature can be limited. The concentration ratio of sodium sulfite and the AAEM / NVP copolymer, for example, can be in the range of 200:1 to 10:1, preferably in the range of 150:1 to 50:1, and further preferably in the range of 100:1 to 50:1.

[0070] Finally, the reverse osmosis membrane is cleaned with hot water to obtain a final reverse osmosis membrane; in this operation, the unreacted diazonium salt remaining in the cross-linked aromatic polyamide is hydrolyzed into phenolic hydroxyl groups, and the reaction formula is as shown in Figure 4 .

[0071] The way for cleaning the reverse osmosis membrane with hot water, for example, can be directly immersing the reverse osmosis membrane in hot water; the temperature of the hot water, for example, can be in the range of 45°C to 100°C, preferably in the range of 60°C to 95°C, and further preferably in the range of 75°C to 90°C; and the time for which the reverse osmosis membrane is immersed in the hot water, for example, can be in the range of 5 seconds to 10 minutes, preferably in the range of 10 seconds to 2 minutes, and further preferably in the range of 30 seconds to 1 minute.

[0072] Herein, the way for the AAEM / NVP copolymer to form a chemical bond with the cross-linked aromatic polyamide includes both the reaction of the acetoacetyl active group in the AAEM / NVP copolymer with the terminal amino group remaining before the nitrous acid treatment and the reaction of the acetoacetyl active group in the AAEM / NVP copolymer with the diazonium salt after the nitrous acid treatment.

[0073] In one aspect, the acetoacetyl group in the AAEM / NVP copolymer crosslinks the crosslinked aromatic polyamide, which together with the crosslinking reaction of the m-phenylenediamine and the polyamide residual acyl chloride group, reduces the size of the Angstrom-level "pores" of the functional separation layer, and the diazonium salt formed can continue to react with the acetoacetyl group of the AAEM / NVP copolymer, thereby further increasing the surface grafting amount of the AAEM / NVP copolymer, again reducing the size of the Angstrom-level "pores" in the crosslinked aromatic polyamide, thereby improving the retention of uncharged organic matter and maintaining a high desalination rate. On the other hand, the copolymer embedded in the crosslinked aromatic polyamide promotes the transfer of water molecules due to the hydrophilicity of the pyrrolidone ring, not only compensating for the increase in water permeability resistance caused by the introduction of the surface copolymer, avoiding the loss of flux, but also forming a PVP "polymer brush" on the surface of the crosslinked polyamide, which is chemically bonded firmly, reducing the adhesion of pollutants on the membrane surface, and improving the anti-fouling property of the membrane.

[0074] In a third aspect, there is provided a use of the polyamide reverse osmosis membrane as described above or the polyamide reverse osmosis membrane prepared by the method as described above in the field of desalination.

[0075] According to the application, in some embodiments, the polyamide reverse osmosis membrane is used in the fields of household water purification, industrial pure water production, industrial wastewater treatment, and removal of organic matter from pure water used in the semiconductor industry. In this context, the specific application steps and operating conditions of the polyamide reverse osmosis membrane can be conventional operations in the art, which will not be described here.

[0076] Acetoacetyl methacrylate ethyl ester (AAEM) is a kind of methacrylic acid monomer, which contains two active groups, one is the end group double bond, and the other is the end group acetoacetyl group. Among them, the end group double bond can make AAEM copolymerize with N-vinyl pyrrolidone (NVP) and other monomers to form a copolymer; the end group acetoacetyl group will make the hydrogen (-H) on the middle methylene group very active due to the conjugation effect of the double carbonyl group, and it is easy to react with amino, aldehyde group, diazonium salt and other groups to form a firm chemical bond. The application utilizes the reactivity of the acetoacetyl group in AAEM and the good hydrophilicity and anti-protein adhesion performance of NVP copolymer to form AAEM / polyvinyl pyrrolidone copolymer containing acetoacetyl active group by free radical polymerization of AAEM and NVP, and graft it to the surface and inside of the crosslinked aromatic polyamide functional separation layer of the reverse osmosis membrane. On the premise of being able to maintain high flux, the organic matter retention performance and anti-fouling performance of the reverse osmosis membrane are effectively improved. The introduction of AAEM / NVP copolymer in the polyamide desalination layer not only significantly improves the organic matter retention performance and anti-fouling performance without losing permeation flux, but also maintains a high desalination rate.

[0077] Compared with the prior art, the technical scheme of the present application has at least the following beneficial effects:

[0078] The polyamide reverse osmosis membrane provided by the present application maintains high reverse osmosis membrane flux and desalination rate, and improves organic matter interception and anti-pollution performance; in addition, the technical scheme of the present application is easy to realize industrialization. BRIEF DESCRIPTION OF DRAWINGS

[0079] Figure 1 A reaction formula schematic diagram of the reaction between the AAEM / NVP copolymer and the terminal amino group of the crosslinked aromatic polyamide is shown;

[0080] Figure 2 A reaction formula schematic diagram of the reaction between the residual terminal amino group in the crosslinked aromatic polyamide and nitrous acid to form diazonium salt is shown;

[0081] Figure 3 A reaction formula schematic diagram of the reaction between the AAEM / NVP copolymer and the diazonium salt formed by the crosslinked aromatic polyamide is shown;

[0082] Figure 4 A reaction formula schematic diagram of the reaction between the residual unreacted diazonium salt in the crosslinked aromatic polyamide and the hydrolysis to form phenolic hydroxyl is shown. DETAILED DESCRIPTION

[0083] In order to enable a detailed understanding of the technical features and contents of the present application, the preferred embodiments of the present application will be described in more detail below. Although the preferred embodiments of the present application are described in the examples, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. If no specific conditions are indicated in the examples, the conventional conditions or the conditions recommended by the manufacturer are used.

[0084] If not specifically stated, the raw materials used in the following examples or comparative examples are all commercially available conventional raw materials; the main raw material information is shown in Table 1 below:

[0085] Table 1

[0086]

[0087]

[0088] The synthesis method of the AAEM / NVP copolymer used in each embodiment of the present application includes the following steps:

[0089] (1) Preparation of primer solution and preheating of initiator: 210 g of N-methyl pyrrolidone was weighed in a 1 L four-necked round-bottom flask, which was placed in a water bath, and the stirrer speed was set to 100-150 rpm. The nitrogen main valve and branch valve were opened to ensure stable nitrogen emission. 40 g of N-methyl pyrrolidone and 0.96 g of azobisisobutyronitrile were weighed, shaken until completely dissolved, and then added to the four-necked round-bottom flask, which was heated to 78°C;

[0090] (2) Preparation of dropping solution and dropping reaction: 60 g of N-methyl pyrrolidone, a total of 240 g of AAEM and NVP, and 1.44 g of azobisisobutyronitrile were mixed to prepare a dropping solution, and the dropping solution was shaken uniformly;

[0091] The prepared dropping solution was added to the four-necked round-bottom flask at a constant speed, and the reaction temperature was maintained at 78±1°C. The dropping time was about 2 h. The molar ratio of AAEM to the total molar amount of monomers (AAEM and NVP) was adjusted according to different embodiments.

[0092] (3) Preparation of post-treatment solution and post-treatment: 26 g of N-methyl pyrrolidone and 1.2 g of azobisisobutyronitrile were mixed to prepare a post-treatment solution, which was shaken until completely dissolved, and then added to the four-necked round-bottom flask. The system was controlled to react at 80±1°C for 2 h. Finally, the nitrogen was stopped, and the system temperature was reduced to room temperature to obtain an AAEM / NVP copolymer with a solid content of 40%.

[0093] Structural characterization and test methods

[0094] The structural characterization and test methods of the reverse osmosis membrane obtained in each example or comparative example are described as follows:

[0095] (1) Contact angle

[0096] The reverse osmosis membrane to be tested was soaked in pure water for 12 hours, then dried in a 60°C oven for 24 hours, and then placed in an environment with a temperature of 25±2°C and a humidity of 40%-60%. A 2 μL drop of deionized water was dropped onto the surface of the functional separation layer of the reverse osmosis membrane during the static contact angle test process using an OCA25 video optical contact angle measuring instrument produced by Dataphysics Company. The contact angle was taken 10 seconds after the pure water drop landed on the surface of the functional separation layer.

[0097] (2) Zeta potential

[0098] The to-be-tested reverse osmosis membrane was soaked in pure water for 12 hours, then dried in a 60℃ oven for 24 hours, and then the Zeta potential at pH = 6.5 was tested by using a SurPASS solid surface Zeta potential tester produced by Anton Paar Company, with 1mM potassium chloride solution as the mobile phase and a flow channel gap of 100±5μm.

[0099] (3) Desalination rate (Rs), TOC removal rate (Rt) and permeate flux

[0100] Desalination rate and permeate flux are two important parameters for evaluating the separation performance of reverse osmosis membranes. According to the content in GB / T32373-2005 "Reverse Osmosis Membrane Test Method", the separation performance of the reverse osmosis membrane was evaluated.

[0101] Desalination rate (Rs) is defined as the difference between the salt concentration of the feed solution (Cf,s) and the salt concentration of the permeate solution (Cp,s) under certain operating conditions, divided by the salt concentration of the feed solution (Cf,s). The calculation formula is as follows:

[0102]

[0103] TOC removal rate (Rt) is defined as the difference between the isopropyl alcohol concentration of the feed solution (Cf,t) and the isopropyl alcohol concentration of the permeate solution (Cp,t) under certain operating conditions, divided by the salt concentration of the feed solution (Cf,t). The calculation formula is as follows:

[0104]

[0105] Permeate flux is defined as the volume of water per unit membrane area per unit time under certain operating conditions, and its unit is L / (m 2 ·h);

[0106] The performance test conditions of the reverse osmosis membrane were as follows: the feed solution was 2000mg / L sodium chloride and 100mg / L isopropyl alcohol aqueous solution, the temperature was 25℃, the solution pH was 7.0, the operating pressure was 1.55MPa, and the continuous operation time was 60 minutes.

[0107] (4) Anti-pollution performance

[0108] Triton X-100 was used as a model pollutant, and the flux decline rate after pollution and the flux recovery rate after cleaning were used to characterize the anti-pollution performance of reverse osmosis.

[0109] Flux decline rate after pollution = (F1-F2) / F1;

[0110] Flux recovery rate after cleaning = F3 / F1;

[0111] Wherein:

[0112] F1 is the flux of the membrane to be tested after being filtered for 1 hour under a pressure of 1.03 MPa against a water solution of 25°C, pH 7.0, and sodium chloride concentration of 2000 mg / L;

[0113] F2 is the flux after adding Triton X-100 to the aforementioned sodium chloride water solution to a concentration of 100 mg / L and continuing to run for 48 hours;

[0114] F3 is the flux after the membrane is first cleaned in a sodium hydroxide solution of 35°C, pH 12.0 for 1 hour, then in hydrochloric acid of 25°C, pH 2.0 for 1 hour, and finally filtered for 1 hour under a pressure of 1.03 MPa against a water solution of 25°C, pH 7.0, and sodium chloride concentration of 2000 mg / L.

[0115] Comparative Example 1

[0116] The reverse osmosis membrane was prepared using a pilot production line, and the steps were as follows:

[0117] S1, under the condition of 25°C, a dimethylformamide solution containing 16.5wt% polysulfone was uniformly coated on a polyester non-woven fabric substrate, the thickness of the wet coating layer was 150μm, after staying in the air for 1.5 seconds, it was immersed in deionized water of 15°C for 1 minute, and then in deionized water of 70°C for 2 minutes, to obtain a base membrane containing a non-woven fabric substrate and a porous polysulfone support layer;

[0118] The base membrane obtained as above was soaked in an aqueous phase solution containing m-phenylenediamine (content of 2.0wt%) and triethyl phosphate (content of 0.2wt%) for 30 seconds, then the base membrane was pulled out of the aqueous phase solution tank along the vertical direction upward, and then the excess aqueous phase solution on the surface was removed using a rubber squeeze roller; then a n-decane oil phase solution containing trimesoyl chloride (content of 0.11wt%) was uniformly coated on the surface of the base membrane, after standing for 30 seconds of reaction, the excess oil phase solution on the surface was removed, to obtain a nascent reverse osmosis membrane including a non-woven fabric substrate, a porous support layer, and a polyamide desalination layer;

[0119] S2, the nascent reverse osmosis membrane obtained as above was cleaned in hot water of 80°C for 3 minutes,

[0120] S3, then it was immersed in a sodium nitrite aqueous solution (pH 3.0, solute content of 0.3wt%, using hydrochloric acid to adjust pH) for 1 minute, then in a sodium sulfite reducing aqueous solution (60°C, solute content of 1wt%) for 1 minute, and finally cleaned in hot water of 90°C for 2 minutes, to obtain the final reverse osmosis membrane.

[0121] The prepared reverse osmosis membrane was characterized and tested for contact angle, Zeta potential, flux, desalination rate, TOC removal rate, and anti-fouling property, and the test results are recorded in Tables 2 and 3, respectively.

[0122] Comparative Example 2

[0123] A reverse osmosis membrane was prepared using a pilot production line, and the steps were as follows:

[0124] S1, a dimethylformamide solution containing 16.5wt% polysulfone was uniformly coated on a polyester non-woven fabric substrate at 25°C, the thickness of the wet coating was 150μm, after staying in the air for 1.5 seconds, it was immersed in deionized water at 15°C for 1 minute, and then immersed in deionized water at 70°C for 2 minutes to obtain a base membrane containing a non-woven fabric substrate and a polysulfone porous support layer;

[0125] The base membrane obtained as above was soaked in an aqueous phase solution containing m-phenylenediamine (content of 2.0wt%) and triethyl phosphate (content of 0.2wt%) for 30 seconds, then the base membrane was pulled out of the aqueous phase solution tank along the vertical direction upwards, and then the excess aqueous phase solution on the surface was removed using a rubber squeeze roller; then a n-decane oil phase solution containing trimesoyl chloride (content of 0.11wt%) was uniformly coated on the surface of the base membrane, after standing for 30 seconds, the excess oil phase solution on the surface was removed, and a nascent reverse osmosis membrane including a non-woven fabric substrate, a porous support layer and a polyamide desalination layer was obtained;

[0126] S2, the nascent reverse osmosis membrane obtained as above was first immersed in a post-crosslinking aqueous solution containing 0.05wt% m-phenylenediamine and 5wt% ethylene glycol at 80°C for 1 minute, and then washed in hot water at 80°C for 1 minute;

[0127] S3, then immersed in an aqueous solution containing 0.05wt% AAEM / NVP copolymer at 80°C for 1 minute, and then washed in hot water at 80°C for 1 minute;

[0128] S4, then immersed in a sodium nitrite aqueous solution with a solute content of 0.3wt% and a pH of 3.0 (pH adjusted using hydrochloric acid) for 1 minute, and then immersed in an aqueous solution containing 1wt% sodium sulfite and 0.05wt% AAEM / NVP copolymer at 60°C for 1 minute, and finally washed in hot water at 90°C for 2 minutes to obtain the final reverse osmosis membrane.

[0129] In the AAEM / NVP copolymer, the value of x / (x+y) representing the ratio of the molar amount of AAEM to the total molar amount of monomers is 0.02, and the weight average molecular weight of the AAEM / NVP copolymer is 100,000.

[0130] The prepared reverse osmosis membrane was characterized and tested for contact angle, Zeta potential, flux, desalination rate, TOC removal rate, and anti-fouling performance, and the test results are recorded in Tables 2 and 3, respectively.

[0131] Comparative Example 3

[0132] The preparation steps of the reverse osmosis membrane refer to Comparative Example 2, except that the content of ethylene glycol in the post-crosslinking aqueous solution in step S2 is replaced from 5wt% to 10wt%; the remaining steps are the same as those in Comparative Example 2.

[0133] The prepared reverse osmosis membrane was characterized and tested for contact angle, Zeta potential, flux, desalination rate, TOC removal rate, and anti-fouling performance, and the test results are recorded in Tables 2 and 3, respectively.

[0134] Comparative Example 4

[0135] The preparation steps of the reverse osmosis membrane refer to Example 1, except that the value of the mole ratio of AAEM to the total moles of monomers x / (x+y) in the AAEM / NVP copolymer in steps S3 and S4 is replaced by 0.5, and the weight average molecular weight of the AAEM / NVP copolymer is kept unchanged at 100,000; the remaining steps are the same as those in Example 1.

[0136] The prepared reverse osmosis membrane was characterized and tested for contact angle, Zeta potential, flux, desalination rate, TOC removal rate, and anti-fouling performance, and the test results are recorded in Tables 2 and 3, respectively.

[0137] Example 1

[0138] A reverse osmosis membrane was prepared using a pilot production line, and the steps were as follows:

[0139] S1, at 25°C, a dimethylformamide solution containing 16.5wt% polysulfone was uniformly coated on a polyester non-woven fabric substrate, the thickness of the wet coating layer was 150μm, after staying in the air for 1.5 seconds, it was immersed in deionized water at 15°C for 1 minute, and then immersed in deionized water at 70°C for 2 minutes, to obtain a base membrane containing a non-woven fabric substrate and a polysulfone porous support layer;

[0140] The base membrane obtained as above was immersed in an aqueous phase solution containing m-phenylenediamine (content of 2.0wt%) and triethyl phosphate (content of 0.2wt%) for 30 seconds, then the base membrane was pulled out of the aqueous phase solution tank along the vertical direction upwards, and then the surface excess aqueous phase solution was removed using a rubber squeeze roller; then a n-decane oil phase solution containing trimesoyl chloride (content of 0.11wt%) was uniformly coated on the surface of the base membrane, after standing for 30 seconds, the surface excess oil phase solution was removed, and a nascent reverse osmosis membrane including a non-woven fabric substrate, a porous support layer, and a polyamide desalination layer was obtained.

[0141] S2, the nascent reverse osmosis membrane obtained above is first immersed in a post-crosslinking aqueous solution containing 0.05wt% m-phenylenediamine and 10wt% ethylene glycol at 80℃ for 1 minute, and then washed in hot water at 80℃ for 1 minute;

[0142] S3, then immersed in an aqueous solution containing 0.05wt% AAEM / NVP copolymer at 80℃ for 1 minute, and then washed in hot water at 80℃ for 1 minute;

[0143] S4, then immersed in a sodium nitrite aqueous solution with a solute content of 0.3wt% and a pH of 3.0 (the pH is adjusted using hydrochloric acid), for 1 minute, and then immersed in an aqueous solution containing 1wt% sodium sulfite and 0.05wt% AAEM / NVP copolymer at 60℃ for 1 minute, and finally washed in hot water at 90℃ for 2 minutes to obtain the final reverse osmosis membrane.

[0144] In the AAEM / NVP copolymer, the value of x / (x+y) is 0.05, and the weight average molecular weight of the AAEM / NVP copolymer is 100,000.

[0145] The prepared reverse osmosis membrane is characterized and tested in terms of contact angle, Zeta potential, flux, desalination rate, TOC removal rate, and anti-pollution performance, and the test results are recorded in Tables 2 and 3, respectively.

[0146] Example 2

[0147] The reverse osmosis membrane is prepared using a pilot production line, and the operation steps refer to Example 1, except that the value of x / (x+y) of the AAEM molar amount in the AAEM / NVP copolymer in steps S3 and S4 is replaced by 0.15 instead of 0.05; the remaining steps are the same as in Example 1.

[0148] The prepared reverse osmosis membrane is characterized and tested in terms of contact angle, Zeta potential, flux, desalination rate, TOC removal rate, and anti-pollution performance, and the test results are recorded in Tables 2 and 3, respectively.

[0149] Example 3

[0150] The reverse osmosis membrane is prepared using a pilot production line, and the operation steps refer to Example 1, except that the value of x / (x+y) of the AAEM molar amount in the AAEM / NVP copolymer in steps S3 and S4 is replaced by 0.30 instead of 0.05; the remaining steps are the same as in Example 1.

[0151] The prepared reverse osmosis membranes were characterized and tested for contact angle, Zeta potential, flux, desalination rate, TOC removal rate, and anti-fouling performance, and the test results are recorded in Tables 2 and 3, respectively.

[0152] Example 4

[0153] The reverse osmosis membranes were prepared using the pilot production line, and the operation steps referred to Example 1, except that the value of the mole ratio of the AAEM in the AAEM / NVP copolymer to the total moles of monomers x / (x+y) in steps S3 and S4 was replaced by 0.15 from 0.05, and the weight average molecular weight of the AAEM / NVP copolymer was replaced by 200,000 from 100,000; the remaining steps were the same as in Example 1.

[0154] The prepared reverse osmosis membranes were characterized and tested for contact angle, Zeta potential, flux, desalination rate, TOC removal rate, and anti-fouling performance, and the test results are recorded in Tables 2 and 3, respectively.

[0155] Example 5

[0156] The reverse osmosis membranes were prepared using the pilot production line, and the operation steps referred to Example 1, except that the value of the mole ratio of the AAEM in the AAEM / NVP copolymer to the total moles of monomers x / (x+y) in steps S3 and S4 was replaced by 0.15 from 0.05, and the weight average molecular weight of the AAEM / NVP copolymer was replaced by 300,000 from 100,000; the remaining steps were the same as in Example 1.

[0157] The prepared reverse osmosis membranes were characterized and tested for contact angle, Zeta potential, flux, desalination rate, TOC removal rate, and anti-fouling performance, and the test results are recorded in Tables 2 and 3, respectively.

[0158] Example 6

[0159] The reverse osmosis membranes were prepared using the pilot production line, and the operation steps referred to Example 1, except that the value of the mole ratio of the AAEM in the AAEM / NVP copolymer to the total moles of monomers x / (x+y) in steps S3 and S4 was replaced by 0.15 from 0.05, and the weight average molecular weight of the AAEM / NVP copolymer was replaced by 500,000 from 100,000; the remaining steps were the same as in Example 1.

[0160] The prepared reverse osmosis membranes were characterized and tested for contact angle, Zeta potential, flux, desalination rate, TOC removal rate, and anti-fouling performance, and the test results are recorded in Tables 2 and 3, respectively.

[0161] Example 7

[0162] The reverse osmosis membrane was prepared by using the pilot production line, and the operation steps were referred to those in Example 1, except that the value of the mole ratio of the AAEM in the AAEM / NVP copolymer to the total moles of monomers x / (x+y) in steps S3 and S4 was replaced by 0.15, and the weight average molecular weight of the AAEM / NVP copolymer was replaced by 300,000; and,

[0163] The content of the AAEM / NVP copolymer in the aqueous solution containing the AAEM / NVP copolymer in step S3 was replaced by 0.01wt%, and the content of the AAEM / NVP copolymer in the aqueous solution containing sodium sulfite and the AAEM / NVP copolymer in step S4 was replaced by 0.01wt%;

[0164] The remaining steps were the same as those in Example 1.

[0165] The prepared reverse osmosis membrane was characterized and tested in terms of contact angle, Zeta potential, flux, desalination rate, TOC removal rate, and anti-fouling performance, and the test results are recorded in Tables 2 and 3, respectively.

[0166] Example 8

[0167] The reverse osmosis membrane was prepared by using the pilot production line, and the operation steps were referred to those in Example 1, except that the value of the mole ratio of the AAEM in the AAEM / NVP copolymer to the total moles of monomers x / (x+y) in steps S3 and S4 was replaced by 0.15, and the weight average molecular weight of the AAEM / NVP copolymer was replaced by 300,000; and,

[0168] The content of the AAEM / NVP copolymer in the aqueous solution containing the AAEM / NVP copolymer in step S3 was replaced by 0.10wt%, and the content of the AAEM / NVP copolymer in the aqueous solution containing sodium sulfite and the AAEM / NVP copolymer in step S4 was replaced by 0.10wt%;

[0169] The remaining steps were the same as those in Example 1.

[0170] The prepared reverse osmosis membrane was characterized and tested in terms of contact angle, Zeta potential, flux, desalination rate, TOC removal rate, and anti-fouling performance, and the test results are recorded in Tables 2 and 3, respectively.

[0171] Example 9

[0172] The reverse osmosis membrane was prepared by using the pilot production line, and the operation steps were referred to those in Example 1, except that the percentage content of m-phenylenediamine in the aqueous solution for post-crosslinking in step S2 was replaced by 0.01wt%, and,

[0173] The value of the mole ratio x / (x+y) of the AAEM in the AAEM / NVP copolymer described in steps S3 and S4 to the total monomers is replaced by 0.15 instead of 0.05, and the weight average molecular weight of the AAEM / NVP copolymer is replaced by 500,000 instead of 100,000;

[0174] The remaining steps are the same as in Example 1.

[0175] The prepared reverse osmosis membranes are characterized and tested in terms of contact angle, Zeta potential, flux, desalination rate, TOC removal rate, and anti-fouling performance, and the test results are recorded in Tables 2 and 3, respectively.

[0176] Example 10

[0177] The reverse osmosis membranes are prepared using a pilot production line, and the operation steps refer to Example 1, except that the content of m-phenylenediamine in the post-crosslinking aqueous solution of step S2 is changed from 0.05wt% to 0.10wt%, and

[0178] The value of the mole ratio x / (x+y) of the AAEM in the AAEM / NVP copolymer described in steps S3 and S4 to the total monomers is replaced by 0.15 instead of 0.05, and the weight average molecular weight of the AAEM / NVP copolymer is replaced by 500,000 instead of 100,000;

[0179] The remaining steps are the same as in Example 1.

[0180] The prepared reverse osmosis membranes are characterized and tested in terms of contact angle, Zeta potential, flux, desalination rate, TOC removal rate, and anti-fouling performance, and the test results are recorded in Tables 2 and 3, respectively.

[0181] Example 11

[0182] The reverse osmosis membranes are prepared using a pilot production line, and the operation steps refer to Example 10, except that the ethylene glycol in the post-crosslinking aqueous solution of step S2 is replaced by methanol; the remaining steps are unchanged.

[0183] The prepared reverse osmosis membranes are characterized and tested in terms of contact angle, Zeta potential, flux, desalination rate, TOC removal rate, and anti-fouling performance, and the test results are recorded in Tables 2 and 3, respectively.

[0184] Example 12

[0185] The reverse osmosis membranes are prepared using a pilot production line, and the operation steps refer to Example 10, except that the ethylene glycol in the post-crosslinking aqueous solution of step S2 is replaced by ethanol; the remaining steps are unchanged.

[0186] The prepared reverse osmosis membranes were characterized and tested in terms of contact angle, Zeta potential, flux, desalination rate, TOC removal rate, and anti-fouling performance, and the test results are recorded in Table 2 and Table 3, respectively.

[0187] Example 13

[0188] The reverse osmosis membranes were prepared by using the pilot production line, and the operation steps were referred to Example 10, except that the ethylene glycol in the post-crosslinking aqueous solution in step S2 was replaced by isopropyl alcohol, and the remaining steps were unchanged.

[0189] The prepared reverse osmosis membranes were characterized and tested in terms of contact angle, Zeta potential, flux, desalination rate, TOC removal rate, and anti-fouling performance, and the test results are recorded in Table 2 and Table 3, respectively.

[0190] Example 14

[0191] The reverse osmosis membranes were prepared by using the pilot production line, and the operation steps were referred to Example 10, except that the ethylene glycol in the post-crosslinking aqueous solution in step S2 was replaced by isopropyl alcohol, and the remaining steps were unchanged.

[0192] The prepared reverse osmosis membranes were characterized and tested in terms of contact angle, Zeta potential, flux, desalination rate, TOC removal rate, and anti-fouling performance, and the test results are recorded in Table 2 and Table 3, respectively.

[0193] Table 2: Partial process conditions and test results of each example and comparative example

[0194]

[0195]

[0196] Table 3: Test results of the membranes obtained in each example and comparative example

[0197]

[0198]

[0199] From the overall comparison of Comparative Examples 1-4 and Examples 1-14, it can be seen that when the molar ratio x / (x+y) of AAEM in the AAEM / NVP copolymer is less than 0.05 or greater than 0.3, it is difficult to react with the amino group or diazonium salt converted from the amino group in the polyamide desalination layer to form a chemical bond, and the obtained reverse osmosis membrane has no obvious improvement in anti-fouling performance and isopropyl alcohol rejection rate.

[0200] As can be seen from the comparative example 4 and the examples 1-3, when the molar ratio x / (x+y) of AAEM in the AAEM / NVP copolymer is in the range of 0.05-0.30, the grafting of the AAEM / NVP copolymer on the crosslinked aromatic polyamide via chemical bonds can significantly improve the isopropanol removal rate and the anti-fouling performance while keeping the flux and the desalination rate almost unchanged, and the improvement effect increases with the increase of the value of x / (x+y) in the AAEM / NVP copolymer.

[0201] When the molar ratio x / (x+y) of AAEM in the AAEM / NVP copolymer is in the range of 0.05-0.30, and the weight average molecular weight of the AAEM / NVP copolymer increases, the TOC removal rate and the anti-fouling performance of the reverse osmosis membrane increase, and the desalination rate also slightly increases.

[0202] When the molar ratio x / (x+y) of AAEM in the AAEM / NVP copolymer is in the range of 0.05-0.30, and the concentration of the AAEM / NVP copolymer reacting with the crosslinked aromatic polyamide increases, the TOC removal rate and the anti-fouling performance of the reverse osmosis membrane can be further improved.

[0203] When the concentration of the m-phenylenediamine in the post-crosslinking aqueous solution decreases, the isopropanol removal rate and the anti-fouling performance slightly decrease, but are still significantly higher than those of the reverse osmosis membrane prepared when the molar ratio x / (x+y) of AAEM in the AAEM / NVP copolymer is less than 0.05 or greater than 0.3.

[0204] As can be seen from the examples 10-13, since the methanol, ethanol, isopropanol and ethylene glycol all have relatively low surface tension, they can all promote the diffusion of the m-phenylenediamine into the crosslinked aromatic polyamide, and help to accelerate the reaction with the residual acyl chloride of the crosslinked aromatic polyamide, and the organic matter removal rate and the anti-fouling performance of the obtained reverse osmosis membrane are all quite good.

[0205] As can be seen from the example 14 and the examples 10-13, compared with the methanol, ethanol, isopropanol and ethylene glycol, since the surface tension of the glycerol is relatively high, the diffusion of the m-phenylenediamine into the crosslinked aromatic polyamide is relatively weak, and thus the organic matter removal rate and the anti-fouling performance of the obtained reverse osmosis membrane are also relatively weak.

[0206] The above has described the embodiments of the present application, and the above description is exemplary and is not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those skilled in the art without departing from the spirit of the present application.

Claims

1. A polyamide reverse osmosis membrane with high organic matter rejection rate and anti-fouling properties, comprising, in sequence: A substrate layer, a porous support layer, and a functional separation layer; characterized in that the functional separation layer comprises: a crosslinked aromatic polyamide and an AAEM / NVP copolymer, wherein the AAEM / NVP copolymer is connected to the crosslinked aromatic polyamide through a chemical bond formed between the acetoacetyl group of its side chain and the terminal amino group of the crosslinked aromatic polyamide and / or through a chemical bond formed between the acetoacetyl group of its side chain and the diazonium salt obtained after diazotization of the terminal amino group; The AAEM / NVP copolymer is a product obtained by free radical polymerization of acetyl acetoxyethyl methacrylate and N-vinylpyrrolidone as monomers. The side chains of the AAEM / NVP copolymer contain reactive acetoacetyl groups and hydrophilic pyrrolidone groups, and its chemical structure is shown in formula (I): In the formula, x and y are positive integers, and the value of the relation x / (x+y) ranges from 0.05 to 0.

3.

2. The polyamide reverse osmosis membrane according to claim 1, characterized in that, The weight-average molecular weight of the AAEM / NVP copolymer is greater than or equal to 5,000 and less than or equal to 1,000,000.

3. The polyamide reverse osmosis membrane according to claim 2, characterized in that, The weight-average molecular weight of the AAEM / NVP copolymer is greater than or equal to 10,000 and less than or equal to 800,000.

4. The polyamide reverse osmosis membrane according to claim 2, characterized in that, The weight-average molecular weight of the AAEM / NVP copolymer is greater than or equal to 50,000 and less than or equal to 500,000.

5. The polyamide reverse osmosis membrane according to any one of claims 1-4, characterized in that, The crosslinked aromatic polyamide is obtained by interfacial polycondensation reaction on the surface of the porous support layer using an aqueous solution containing m-phenylenediamine and triethyl phosphate and an oil solution containing trimesoyl chloride.

6. The polyamide reverse osmosis membrane according to any one of claims 1-4, characterized in that, The substrate layer is selected from one or more of polyester nonwoven fabric, polyethylene porous film, and polypropylene porous film; and / or The porous support layer is selected from one or more of polysulfone porous support layers, polyethersulfone porous support layers, and polyacrylonitrile porous support layers.

7. The polyamide reverse osmosis membrane according to any one of claims 1-4, characterized in that, The static contact angle of the functional separation layer in the polyamide reverse osmosis membrane is greater than or equal to 20° and less than or equal to 40°; and / or At pH = 6.5, the surface Zeta potential of the functional separation layer is -35 mV to -10 mV.

8. The polyamide reverse osmosis membrane according to any one of claims 1-4, characterized in that, The polyamide reverse osmosis membrane has a desalination rate (Rs) of 99.6% or higher, a TOC removal rate (Rt) of 85% or higher, and a permeation flux of 60 L / (m²). 2 ·h) and above.

9. The polyamide reverse osmosis membrane according to any one of claims 1-4, characterized in that, The polyamide reverse osmosis membrane exhibits a flux reduction rate of ≥5% and ≤25% after fouling; and a flux recovery rate of ≥98% and ≤100% after cleaning.

10. The method for preparing the polyamide reverse osmosis membrane according to any one of claims 1-9, characterized in that, Includes the following steps: S1. An aqueous solution containing m-phenylenediamine and triethyl phosphate and an oil solution containing pyromellitic methyl chloride are subjected to an interfacial polycondensation reaction on the surface of a porous support layer to form cross-linked aromatic polyamide-I, thus obtaining a nascent reverse osmosis membrane. S2. The primary reverse osmosis membrane obtained in step S1 is reacted with the post-crosslinked aqueous solution, and then washed in hot water to form crosslinked aromatic polyamide-II, thus obtaining a secondary reverse osmosis membrane. S3. The secondary reverse osmosis membrane obtained in step S2 is reacted with an aqueous solution containing AAEM / NVP copolymer, and then washed in hot water to form cross-linked aromatic polyamide-III, thus obtaining a tertiary reverse osmosis membrane. S4. The three-stage reverse osmosis membrane obtained in step S3 is first immersed in an aqueous solution of nitrous acid for reaction, then immersed in an aqueous solution containing sodium sulfite and AAEM / NVP copolymer for reaction, and then washed with hot water to obtain the polyamide reverse osmosis membrane.

11. The preparation method according to claim 10, characterized in that, The post-crosslinking aqueous solution described in step S2 contains m-phenylenediamine and alcohol additives; The alcohol additive is selected from any one of methanol, ethanol, isopropanol, ethylene glycol, and glycerol.

12. The application of the polyamide reverse osmosis membrane according to any one of claims 1-9 or the polyamide reverse osmosis membrane prepared by the preparation method according to claim 10 or 11 in the field of desalination.

13. The application according to claim 12, characterized in that, The polyamide reverse osmosis membrane is used in household water purification, industrial pure water production, industrial wastewater treatment, and organic matter removal from pure water used in the semiconductor industry.

Images