Method for preparing a composite reverse osmosis membrane and composite reverse osmosis membrane prepared thereby

Abstract

The present application relates to a preparation method of composite reverse osmosis membrane and the composite reverse osmosis membrane prepared by the method. The method comprises: preparing a casting solution, wherein the casting solution comprises a polymer and a solvent; applying the casting solution on a support material to form a base film; sequentially contacting the base film with an aqueous solution comprising an amine monomer, an oil phase solution comprising an acid chloride monomer to form a polyamide desalination layer; sequentially contacting the base film with an aqueous solution comprising polyethyleneimine and thioctic acid, an aqueous solution comprising a dialdehyde compound; and post-treatment. The method is simple in process, high in production efficiency, and suitable for industrial scale production. The composite reverse osmosis membrane prepared by the method can be continuously operated in an aqueous solution comprising sodium hypochlorite, and the fluctuation range of flux and desalination rate is small.

Description

Technical Field

[0001] This invention relates to a method for preparing a composite reverse osmosis membrane and the composite reverse osmosis membrane prepared therefrom, and more specifically to the field of composite reverse osmosis membranes capable of continuous operation in an aqueous solution containing sodium hypochlorite with small fluctuations in flux and desalination rate. Background Technology

[0002] Reverse osmosis (RO) technology is a core process for seawater desalination, wastewater reuse, and high-end water treatment, and it has the advantages of high efficiency (>99%) desalination rate and low energy consumption.

[0003] However, traditional polyamide reverse osmosis membranes face a severe problem of oxidative failure: the amide bonds in their desalination layer are easily attacked by residual chlorine in the water (such as sodium hypochlorite), leading to chemical bond breakage and irreversible structural degradation, which in turn causes an increase in membrane flux and a deterioration in desalination performance.

[0004] To avoid this problem, current processes require strict limits on the residual chlorine concentration in the influent (<0.1 ppm). However, this measure promotes the growth of microorganisms on the membrane surface, leading to severe biofouling and significantly increasing cleaning frequency and operating costs. Therefore, developing a composite reverse osmosis membrane that can effectively maintain flux and desalination rate in wastewater with high residual chlorine content has become a research focus for many professionals in this field.

[0005] CN118987994A discloses an antioxidant polyamide reverse osmosis composite membrane and its preparation method. The membrane uses a flat sheet ultrafiltration membrane as the base membrane. In addition to ordinary polyamines, N-monosubstituted hydroxylamines are introduced into the aqueous solution. The membrane then undergoes interfacial polymerization with acyl chloride monomers to form a reverse osmosis membrane, thereby introducing a hydroxylamine structure into the polyamide layer. Furthermore, the reverse osmosis membrane is immersed in an alcohol solution containing N-disubstituted hydroxylamine compounds for secondary interfacial polymerization, thereby introducing a hydroxylamine structure protective layer on the surface.

[0006] The resulting antioxidant composite reverse osmosis membrane exhibited an initial flux of 25.7–34.5 L·m⁻¹ for a 0.2% sodium chloride aqueous solution. -2 ·h -1 Within this range, after 12 hours of operation in an aqueous solution of sodium hypochlorite with a mass concentration of 0.05% (i.e., after oxidation treatment), the flux was 30.2–39.5 L·m⁻¹. -2 ·h -1 Within this range, the difference between the initial desalination rate and the desalination rate after oxidation treatment is in the range of -0.1 to -1.7.

[0007] In this patent document, hydroxylamine structures are introduced into both the bulk structure and the protective layer. Hydroxylamine compounds possess excellent antioxidant properties; however, when introduced into the polyamide bulk structure or during secondary interfacial polymerization, the acyl chloride groups react with amino or hydroxyl groups, which significantly weakens the antioxidant properties of the hydroxylamine compounds themselves. Furthermore, the resulting antioxidant composite reverse osmosis membrane exhibits an initial desalination rate of only 98.0% at most, and a desalination rate of only 97.4% after oxidation treatment.

[0008] CN115337800A discloses a high desalination and antioxidant polyamide reverse osmosis membrane, which includes a polysulfone ultrafiltration support membrane, a first polyamide layer formed on the polysulfone ultrafiltration support membrane, and a second polyamide layer containing a dihydrazide compound formed on the first polyamide layer. The membrane surface crosslinking density is enhanced by immersing the reverse osmosis membrane in a second aqueous solution containing a dihydrazide compound to undergo secondary interfacial polymerization, thereby improving its desalination rate. The formed second polyamide layer can serve as an attack site for active chlorine, thereby reducing the damage of active chlorine to the first polyamide layer.

[0009] In this patent document, a dihydrazide-based compound is directly introduced onto the membrane surface as a sacrificial layer, causing sodium hypochlorite to preferentially attack the amide groups on the surface, thereby protecting the important internal polyamide desalination layer. However, during the long-term operation of the reverse osmosis membrane, when the surface sacrificial layer is exhausted, the internal polyamide desalination layer will still be attacked, resulting in a significant reduction in its desalination rate. Furthermore, the flux measured after the obtained high desalination and antioxidant polyamide reverse osmosis membrane was immersed in a sodium hypochlorite solution with an effective chlorine concentration of 500 ppm for 24 hours and then reduced by immersing it in a 1% sodium sulfite solution (i.e., after chlorine resistance) showed a significant increase compared to the initial flux, and the desalination rate after chlorine resistance was also significantly lower than the initial desalination rate; that is, the fluctuation range of flux and desalination rate was relatively large.

[0010] CN113967415A discloses a chlorine-resistant reverse osmosis membrane, which includes a support layer, a polyamide layer disposed on the support layer, and a protective layer disposed on the polyamide layer. The raw material of the protective layer includes a specific diamine, which is a diamine substance with a hydrocarbon group on a benzene ring. The protective layer is introduced on the surface of the reverse osmosis membrane by reacting the specific diamine with the residual acyl chloride groups on the membrane surface through secondary interfacial polymerization by dissolving the specific diamine in an aqueous solution containing an acid-binding agent. However, unlike CN115337800A, the formed protective layer does not have attack sites for active chlorine. Instead, it prevents the attack of active chlorine through the steric hindrance effect of the specific diamine, thereby keeping the membrane surface stable. However, the large steric hindrance itself will lead to a decrease in the reactivity with the acyl chloride groups, resulting in uneven secondary interfacial polymerization and too few reaction sites on the membrane surface. As a result, additional defects are generated during continuous operation, causing a sharp drop in the desalination rate. After soaking the obtained chlorine-resistant reverse osmosis membrane in an aqueous solution with a sodium hypochlorite concentration of 1000 ppm for 10 hours, the desalination rate was found to be approximately 0.4% lower than the initial desalination rate. Furthermore, the flux of the obtained reverse osmosis membrane was not examined in this patent document. Summary of the Invention

[0011] The problem the invention aims to solve

[0012] The purpose of this invention is to solve the above-mentioned problems existing in the prior art and to provide a method for preparing a chlorine-resistant composite reverse osmosis membrane and a composite reverse osmosis membrane prepared therefrom.

[0013] Solution for solving the problem

[0014] The inventors conducted in-depth research and discovered that:

[0015] After forming the polyamide desalination layer, a coating layer with antioxidant properties (i.e., chlorine resistance) can be introduced on the basis of a conventional reverse osmosis membrane by first physically applying an aqueous solution containing polyethyleneimine and thioctic acid to its surface, and then adding dialdehyde compounds through a secondary physical surface application to crosslink the coating layer via a Schiff base reaction between polyethyleneimine and dialdehyde compounds.

[0016] The reactions or interactions between the carboxyl groups and disulfide bonds in thioctic acid, the abundant hydrogen bonds in polyethyleneimine, and dialdehydes, as well as the cross-linking effect between the coating layer and the surface of the polyamide desalination layer, allow the coating layer to adhere firmly to the surface of the reverse osmosis membrane without easily falling off.

[0017] Lipoic acid is a natural small molecule and a coenzyme in biology. It is widely available and can undergo ring-opening polymerization under mild conditions. The pH > 7 of aqueous solutions containing polyethyleneimine also provides conditions for its binding with lipoic acid. In aqueous solutions containing polyethyleneimine, the carboxyl groups of lipoic acid react with the ionized hydroxyl groups provided by polyethyleneimine, thereby dissolving in the aqueous solution through deprotonation. During the evaporation of the solvent (i.e., water), ring-opening polymerization occurs, leading to self-assembly and the formation of a thin film. The presence of disulfide bonds in lipoic acid and secondary amine groups in polyethyleneimine significantly enhances the antioxidant properties of reverse osmosis membranes.

[0018] Lipoic acid is slightly soluble in water, exhibiting very low solubility. However, it can dissolve in aqueous solutions containing polyethyleneimine. This is because aqueous solutions containing polyethyleneimine are alkaline, allowing lipoic acid to dissolve in these solutions through carboxyl deprotonation. After deprotonation, the evaporating solvent (i.e., water) induces its ring-opening polymerization, leading to self-assembly and the formation of a thin film that prevents the dissociation of the disulfide bonds in lipoic acid after the solvent (i.e., water) evaporates.

[0019] The amino group in polyethyleneimine can undergo a Schiff base reaction with the carbonyl group in dialdehyde compounds. The dialdehyde compounds can also react with the polyamide desalination layer. That is, the dialdehyde compounds act as an intermediate medium, crosslinking with the desalination layer on the one hand and with the coating layer on the other, thereby fixing the coating layer on the surface of the desalination layer.

[0020] The carbonyl group in dialdehyde compounds can also undergo a Schiff base reaction with the amino group in the polyamide layer, thereby further crosslinking the polyamide desalination layer and improving the antioxidant performance of the reverse osmosis membrane.

[0021] This invention provides a method for preparing a composite reverse osmosis membrane, which includes the following steps:

[0022] A casting solution is prepared, wherein the casting solution comprises a polymer and a solvent;

[0023] The casting solution is applied to a support material to form a base film;

[0024] The base film is sequentially contacted with an aqueous solution containing amine monomers and an oil solution containing acyl chloride monomers to form a polyamide desalination layer;

[0025] It is then contacted sequentially with an aqueous solution containing polyethyleneimine and lipoic acid, and an aqueous solution containing dialdehyde compounds;

[0026] Post-processing.

[0027] The preparation method of the present invention, wherein the polymer is at least one selected from bisphenol A type polysulfone, polyethersulfone, and polyarylsulfone, and the supporting material is nonwoven fabric; the amine monomer is an amine monomer having two or more amino groups, preferably, the amine monomer is at least one selected from m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, mesitylenetriamine, 2,4-diaminotoluene, 2,5-diaminotoluene, 2,6-diaminotoluene, polyetheramine, polyethyleneimine, diaminobenzenesulfonic acid, and 3,5-diaminobenzoic acid, based on the total mass of the aqueous solution containing the amine monomer, the amine... The concentration of the monomer is 0.1 wt% to 5 wt%; the acyl chloride monomer is an aromatic acyl chloride monomer having two or more acyl chloride groups, preferably, the acyl chloride monomer is selected from at least one of pyromellitic trimethylbenzene chloride, isophthaloyl chloride, biphenyl dimethylbenzene chloride, terephthaloyl chloride, o-fluorobenzoyl chloride, 3-fluorobenzoyl chloride, 4-fluorobenzoyl chloride, 3,5-difluorobenzoyl chloride, 2,5-difluorobenzoyl chloride, and 4-nitrobenzenesulfonyl chloride, and the concentration of the acyl chloride monomer is 0.01 wt% to 0.5 wt% based on the total mass of the oil phase solution containing the acyl chloride monomer.

[0028] In the preparation method of the present invention, the number average molecular weight of the polyethyleneimine is in the range of 1,000 to 100,000 g / mol. Preferably, based on the total mass of the aqueous solution containing polyethyleneimine and thioctic acid, the content of the polyethyleneimine is 0.05 wt% to 2 wt%.

[0029] The preparation method of the present invention, wherein the content of lipoic acid is 0.01wt% to 1wt% based on the total mass of the aqueous solution containing polyethyleneimine and lipoic acid.

[0030] The preparation method of the present invention, wherein the dialdehyde compound is an aliphatic dialdehyde compound and / or an aromatic dialdehyde compound, preferably, the dialdehyde compound is selected from at least one of glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, adipaldehyde, o-phthalaldehyde, terephthalaldehyde, and iso-phthalaldehyde, and the concentration of the dialdehyde compound is 0.01wt% to 0.5wt% based on the total mass of the aqueous solution containing the dialdehyde compound.

[0031] The present invention also provides a composite reverse osmosis membrane prepared by the above method, which comprises, from bottom to top:

[0032] Supporting materials;

[0033] A base film, wherein the base film is formed by a casting solution comprising a polymer and a solvent;

[0034] A polyamide desalination layer, which is formed by the polymerization of amine monomers and acyl chloride monomers;

[0035] A protective layer formed by treatment with polyethyleneimine, thioctic acid, and dialdehyde compounds.

[0036] The composite reverse osmosis membrane of the present invention, wherein the polymer is at least one selected from bisphenol A type polysulfone, polyethersulfone, and polyarylsulfone, and the supporting material is nonwoven fabric; the amine monomer is an amine monomer having two or more amino groups, preferably, the amine monomer is at least one selected from m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, mesitylenetriamine, 2,4-diaminotoluene, 2,5-diaminotoluene, 2,6-diaminotoluene, polyetheramine, polyethyleneimine, diaminobenzenesulfonic acid, and 3,5-diaminobenzoic acid, based on the total mass of the aqueous solution containing the amine monomer, the amine... The concentration of the acyl chloride monomer is 0.1 wt% to 5 wt%; the acyl chloride monomer is an aromatic acyl chloride monomer having two or more acyl chloride groups, preferably, the acyl chloride monomer is selected from at least one of pyromellitic trimethylbenzene chloride, isophthaloyl chloride, biphenyl dimethylbenzene chloride, terephthaloyl chloride, o-fluorobenzoyl chloride, 3-fluorobenzoyl chloride, 4-fluorobenzoyl chloride, 3,5-difluorobenzoyl chloride, 2,5-difluorobenzoyl chloride, and 4-nitrobenzenesulfonyl chloride, and the concentration of the acyl chloride monomer is 0.01 wt% to 0.5 wt% based on the total mass of the oil phase solution containing the acyl chloride monomer.

[0037] The composite reverse osmosis membrane of the present invention has a number-average molecular weight of polyethyleneimine in the range of 1,000 to 100,000 g / mol. Preferably, the content of polyethyleneimine is 0.05 wt% to 2 wt% based on the total mass of the aqueous solution containing polyethyleneimine and thioctic acid.

[0038] The composite reverse osmosis membrane of the present invention, wherein the content of the lipoic acid is 0.01wt% to 1wt% based on the total mass of the aqueous solution containing polyethyleneimine and lipoic acid.

[0039] The composite reverse osmosis membrane of the present invention, wherein the dialdehyde compound is an aliphatic dialdehyde compound and / or an aromatic dialdehyde compound, preferably, the dialdehyde compound is selected from at least one of glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, adipaldehyde, o-phthalaldehyde, terephthalaldehyde, and iso-phthalaldehyde, and the concentration of the dialdehyde compound is 0.01wt% to 0.5wt% based on the total mass of the aqueous solution containing the dialdehyde compound.

[0040] The effects of the invention

[0041] The method of the present invention is simple, does not involve secondary interfacial polymerization, has high production efficiency, and the raw materials are readily available, making it suitable for large-scale industrial production.

[0042] The chlorine-resistant and antioxidant composite reverse osmosis membrane obtained by the method of this invention has a flux higher than 21GFD and a desalination rate higher than 99.5% for aqueous solutions with a sodium chloride concentration of 2000ppm. After operating in an aqueous solution with a sodium hypochlorite concentration of 1000ppm for 24 hours, the fluctuation range of flux and desalination rate is small and the desalination rate still remains above 99.4%. Detailed Implementation

[0043] Various exemplary embodiments, features, and aspects of the present invention will be described in detail below. The term "exemplary" as used herein means "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as superior to or better than other embodiments.

[0044] Furthermore, to better illustrate the present invention, numerous specific details are set forth in the following detailed embodiments. Those skilled in the art should understand that the present invention can be practiced without certain specific details. In other instances, methods, means, apparatus, and steps well known to those skilled in the art have not been described in detail in order to highlight the spirit of the present invention.

[0045] Unless otherwise stated, all units used in this specification are international standard units, and all numerical values ​​and ranges appearing in this invention should be understood to include systematic errors that are unavoidable in industrial production.

[0046] In this specification, the word "may" has two meanings: to perform a certain process and not to perform a certain process.

[0047] In this specification, references to "some specific / preferred embodiments," "other specific / preferred embodiments," "implementation," etc., refer to specific elements (e.g., features, structures, properties, and / or characteristics) related to that embodiment, which are included in at least one of the embodiments described herein and may or may not be present in other embodiments. Furthermore, it should be understood that these elements may be combined in any suitable manner in various embodiments.

[0048] In this specification, the range of values ​​referred to as "value A to value B" refers to the range including the endpoint values ​​A and B.

[0049] This invention provides a method for preparing a composite reverse osmosis membrane, which includes the following steps:

[0050] A casting solution is prepared, wherein the casting solution comprises a polymer and a solvent;

[0051] The casting solution is applied to a support material to form a base film;

[0052] The base film is sequentially contacted with an aqueous solution containing amine monomers and an oil solution containing acyl chloride monomers to form a polyamide desalination layer;

[0053] It is then contacted sequentially with an aqueous solution containing polyethyleneimine and lipoic acid, and an aqueous solution containing dialdehyde compounds;

[0054] Post-processing.

[0055] The preparation method of this invention uses a polymer selected from at least one of bisphenol A type polysulfone, polyethersulfone, and polyarylsulfone. Preferably, the number average molecular weight of the polymer is in the range of 60,000 to 90,000 g / mol. The solvent is not particularly limited, as long as it can dissolve the polymer; examples include N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), acetone, and N-methylpyrrolidone (NMP). Preferably, based on the total mass of the casting solution, the concentration of the polymer is in the range of 16 wt% to 20 wt%.

[0056] The supporting material is non-woven fabric. There are no particular limitations on the material of the non-woven fabric. Examples include polypropylene fiber, polyester PET fiber, and natural fibers.

[0057] The amine monomer is an amine monomer having two or more amino groups. Preferably, the amine monomer is selected from at least one of m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, mesitylenetriamine, 2,4-diaminotoluene, 2,5-diaminotoluene, 2,6-diaminotoluene, polyetheramine, polyethyleneimine, diaminobenzenesulfonic acid, and 3,5-diaminobenzoic acid.

[0058] Based on the total mass of the aqueous solution containing amine monomers, the concentration of the amine monomers is 0.1 wt% to 5 wt%, preferably 1 wt% to 4 wt%.

[0059] The acyl chloride monomer is an aromatic acyl chloride monomer having two or more acyl chloride groups. Preferably, the acyl chloride monomer is selected from at least one of pyromellitic trimethylbenzene chloride, isophthaloyl chloride, biphenyl dimethylbenzene chloride, terephthaloyl chloride, o-fluorobenzoyl chloride, 3-fluorobenzoyl chloride, 4-fluorobenzoyl chloride, 3,5-difluorobenzoyl chloride, 2,5-difluorobenzoyl chloride, and 4-nitrobenzenesulfonyl chloride. Based on the total mass of the oil phase solution containing the acyl chloride monomer, the concentration of the acyl chloride monomer is 0.01wt% to 0.5wt%.

[0060] The oil phase solution also contains solvents such as cyclohexane, Isopar G, n-hexane, Isopar E, m-xylene, p-xylene, o-xylene, dichloromethane, cyclohexanone, n-pentane, n-heptane, and propylene oxide.

[0061] In the preparation method of the present invention, the number average molecular weight of the polyethyleneimine is in the range of 1,000 to 100,000 g / mol, preferably in the range of 10,000 to 70,000 g / mol.

[0062] The polyethyleneimine of the present invention is preferably dendritic polyethyleneimine, the structure of which can be exemplified as follows.

[0063]

[0064] Based on the total mass of the aqueous solution containing polyethyleneimine and thioctic acid, the content of polyethyleneimine is 0.05wt% to 2wt%, preferably in the range of 0.5wt% to 1wt%.

[0065] Based on the total mass of the aqueous solution containing polyethyleneimine and thioctic acid, the content of thioctic acid is 0.01wt% to 1wt%, preferably in the range of 0.05wt% to 0.5wt%.

[0066] The structure of the thioctic acid of the present invention can be exemplified as follows.

[0067]

[0068] The preparation method of the present invention, wherein the dialdehyde compound is an aliphatic dialdehyde compound and / or an aromatic dialdehyde compound, preferably, the dialdehyde compound is selected from at least one of glyoxal, malondialdehyde, butyraldehyde, glutaraldehyde, adipaldehyde, o-phthalaldehyde, terephthalaldehyde, and isophthalaldehyde.

[0069] Based on the total mass of the aqueous solution containing dialdehyde compounds, the concentration of the dialdehyde compounds is 0.01wt% to 0.5wt%, preferably in the range of 0.1wt% to 0.2wt%.

[0070] Post-processing includes drying, with no particular restrictions on temperature and time; for example, drying can be done at 60°C for 5-10 minutes.

[0071] The present invention also provides a composite reverse osmosis membrane prepared by the above method, which comprises, from bottom to top:

[0072] Supporting materials;

[0073] A base film, wherein the base film is formed by a casting solution comprising a polymer and a solvent;

[0074] A polyamide desalination layer, which is formed by the polymerization of amine monomers and acyl chloride monomers;

[0075] A protective layer formed by treatment with polyethyleneimine, thioctic acid, and dialdehyde compounds.

[0076] The limitations on supporting materials, polymers, solvents, amine monomers, acyl chloride monomers, polyethyleneimine, thioctic acid, and dialdehyde compounds are as described above.

[0077] Example

[0078] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0079] Comparative Example 1:

[0080] Conventional composite reverse osmosis membranes were prepared via interfacial polymerization of polyamines and polyacrylamide chlorides. Specifically, a bisphenol A type polysulfone (number average molecular weight in the range of 78,000–82,000 g / mol, casting solution concentration of 18 wt%, composition of bisphenol A type polysulfone and DMF) base membrane was prepared by a solvent-free phase inversion method. The polysulfone base membrane was then immersed in an aqueous solution of m-phenylenediamine (3.0 wt%) for 120 s to fully absorb the amine monomers. After drying the surface water droplets, it was immersed in an oil solution of trimesoyl chloride (0.3 wt%) for 180 s to form a polyamide separation layer. Isopar G was used as the oil solvent. The membrane was then dried in an oven at 60 °C for 5 min.

[0081] Example 1

[0082] A conventional composite reverse osmosis membrane was prepared by interfacial polymerization of polyamines and polyacrylamide chlorides. Specifically, a bisphenol A type polysulfone (same as Comparative Example 1) base membrane was prepared by a solvent-free phase inversion method. The polysulfone base membrane was then immersed in an aqueous solution of m-phenylenediamine (3.0 wt%) for 120 s to allow for sufficient absorption of the amine monomers. After drying the surface water droplets, it was immersed in an oil solution of trimesoyl chloride (0.3 wt%) for 180 s to form a polyamide separation layer. Isopar G was used as the oil solvent. After drying the residual solvent, the composite reverse osmosis membrane was immersed in an aqueous solution of polyethyleneimine (0.05 wt%), a number-average molecular weight of 1000 g / mol, and lipoic acid (0.05 wt%) for 30 s. Next, the composite reverse osmosis membrane was immersed in an aqueous solution of glutaraldehyde (0.2 wt%) for 30 s. Finally, it was dried in a 60°C oven for 5 min to obtain an antioxidant composite reverse osmosis membrane.

[0083] Example 2

[0084] A conventional composite reverse osmosis membrane was prepared by interfacial polymerization of polyamines and polyacrylamide chlorides. Specifically, a bisphenol A type polysulfone (same as Comparative Example 1) base membrane was prepared by a solvent-free phase inversion method. The polysulfone base membrane was then immersed in an aqueous solution of m-phenylenediamine (3.0 wt%) for 120 s to allow for sufficient absorption of the amine monomers. After drying the surface water droplets, it was immersed in an oil solution of trimesoyl chloride (0.3 wt%) for 180 s to form a polyamide separation layer. Isopar G was used as the oil solvent. After drying the residual solvent, the composite reverse osmosis membrane was immersed in an aqueous solution of polyethyleneimine (0.05 wt%), a number average molecular weight of 100,000 g / mol, and lipoic acid (0.01 wt%) for 30 s. Next, the composite reverse osmosis membrane was immersed in an aqueous solution of glutaraldehyde (0.2 wt%) for 30 s. Finally, it was dried in a 60°C oven for 5 min to obtain an antioxidant composite reverse osmosis membrane.

[0085] Example 3

[0086] A conventional composite reverse osmosis membrane was prepared by interfacial polymerization of polyamines and polyacrylamide chlorides. Specifically, a bisphenol A type polysulfone (same as Comparative Example 1) base membrane was prepared by a solvent-free phase inversion method. The polysulfone base membrane was then immersed in an aqueous solution of m-phenylenediamine (3.0 wt%) for 120 s to allow for sufficient absorption of the amine monomers. After drying the surface water droplets, it was immersed in an oil solution of trimesoyl chloride (0.3 wt%) for 180 s to form a polyamide separation layer. Isopar G was used as the oil solvent. After drying the residual solvent, the composite reverse osmosis membrane was immersed in an aqueous solution of polyethyleneimine (2 wt%), a number-average molecular weight of 1000 g / mol, and thioctic acid (1 wt%) for 30 s. Next, the composite reverse osmosis membrane was immersed in an aqueous solution of glutaraldehyde (0.2 wt%) for 30 s. Finally, it was dried in a 60°C oven for 5 min to obtain an antioxidant composite reverse osmosis membrane.

[0087] Example 4

[0088] A conventional composite reverse osmosis membrane was prepared by interfacial polymerization of polyamines and polyacrylamide chlorides. Specifically, a bisphenol A type polysulfone (same as Comparative Example 1) base membrane was prepared by a solvent-free phase inversion method. The polysulfone base membrane was then immersed in an aqueous solution of m-phenylenediamine (3.0 wt%) for 120 s to allow for sufficient absorption of the amine monomers. After drying the surface water droplets, it was immersed in an oil solution of trimesoyl chloride (0.3 wt%) for 180 s to form a polyamide separation layer. Isopar G was used as the oil solvent. After drying the residual solvent, the composite reverse osmosis membrane was immersed in an aqueous solution of polyethyleneimine (2 wt%), with a number average molecular weight of 100,000 g / mol and a lipoic acid content of 0.5 wt% for 30 s. Next, the composite reverse osmosis membrane was immersed in an aqueous solution of glutaraldehyde (0.2 wt%) for 30 s. Finally, it was dried in a 60°C oven for 5 min to obtain an antioxidant composite reverse osmosis membrane.

[0089] Example 5

[0090] A conventional composite reverse osmosis membrane was prepared by interfacial polymerization of polyamines and polyacrylamide chlorides. Specifically, a bisphenol A type polysulfone (same as Comparative Example 1) base membrane was prepared by a solvent-free phase inversion method. The polysulfone base membrane was then immersed in an aqueous solution of m-phenylenediamine (3.0 wt%) for 120 s to allow for sufficient absorption of the amine monomers. After drying the surface water droplets, it was immersed in an oil solution of trimesoyl chloride (0.3 wt%) for 180 s to form a polyamide separation layer. Isopar G was used as the oil solvent. After drying the residual solvent, the composite reverse osmosis membrane was immersed in an aqueous solution of polyethyleneimine (0.05 wt%), a number average molecular weight of 100,000 g / mol, and lipoic acid (0.01 wt%) for 30 s. Next, the composite reverse osmosis membrane was immersed in an aqueous solution of glutaraldehyde (0.01 wt%) for 30 s. Finally, it was dried in a 60°C oven for 5 min to obtain an antioxidant composite reverse osmosis membrane.

[0091] Example 6

[0092] A conventional composite reverse osmosis membrane was prepared by interfacial polymerization of polyamines and polyacrylamide chlorides. Specifically, a bisphenol A type polysulfone (same as Comparative Example 1) base membrane was prepared by a solvent-free phase inversion method. The polysulfone base membrane was then immersed in an aqueous solution of m-phenylenediamine (3.0 wt%) for 120 s to allow for sufficient absorption of the amine monomers. After drying the surface water droplets, it was immersed in an oil solution of trimesoyl chloride (0.3 wt%) for 180 s to form a polyamide separation layer. Isopar G was used as the oil solvent. After drying the residual solvent, the composite reverse osmosis membrane was immersed in an aqueous solution of polyethyleneimine (0.05 wt%, molecular weight 100,000 g / mol), thioctic acid (0.01 wt%) for 30 s. Next, the composite reverse osmosis membrane was immersed in an aqueous solution of glutaraldehyde (0.5 wt%) for 30 s. Finally, it was dried in a 60°C oven for 5 min to obtain an antioxidant composite reverse osmosis membrane.

[0093] Example 7

[0094] A conventional composite reverse osmosis membrane was prepared by interfacial polymerization of polyamines and polyacrylamide chlorides. Specifically, a bisphenol A type polysulfone (same as Comparative Example 1) base membrane was prepared by a solvent-free phase inversion method. The polysulfone base membrane was then immersed in an aqueous solution of m-phenylenediamine (3.0 wt%) for 120 s to allow for sufficient absorption of the amine monomers. After drying the surface water droplets, it was immersed in an oil solution of trimesoyl chloride (0.3 wt%) for 180 s to form a polyamide separation layer. Isopar G was used as the oil solvent. After drying the residual solvent, the composite reverse osmosis membrane was immersed in an aqueous solution of polyethyleneimine (0.05 wt%, molecular weight 100,000 g / mol), thioctic acid (0.01 wt%) for 30 s. Next, the composite reverse osmosis membrane was immersed in an aqueous solution of terephthalaldehyde (0.5 wt%) for 30 s. Finally, it was dried in a 60°C oven for 5 min to obtain an antioxidant composite reverse osmosis membrane.

[0095] Performance testing:

[0096] The membrane performance of Comparative Example 1 was compared with that of Examples 1-7 above.

[0097] Membrane performance testing: The desalination rate and flux of 5 groups of membranes were tested at an operating pressure of 225 psi (concentrate circulation) with an aqueous solution of 2000 ppm NaCl. (5 groups of membranes were tested for each comparative example and the average value was taken.) Then, after adding 1000 ppm sodium hypochlorite and running for 24 h (i.e. after oxidation treatment), the desalination rate and flux of the membranes were tested again.

[0098] The test results before and after oxidation treatment are shown in Table 1 below (concentrate circulation).

[0099] Table 1

[0100]

[0101] As shown in Table 1, compared with Comparative Example 1, the composite reverse osmosis membranes obtained by Examples 1-7 of the present invention have both excellent water flux and desalination rate, and can operate continuously and stably in aqueous solutions containing sodium hypochlorite with small fluctuations in flux and desalination rate.

[0102] It should be noted that although the technical solution of the present invention has been described with specific examples, those skilled in the art will understand that the present invention should not be limited thereto.

[0103] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing a composite reverse osmosis membrane, characterized in that, It includes the following steps: A casting solution is prepared, wherein the casting solution comprises a polymer and a solvent; The casting solution is applied to a support material to form a base film; The base film is sequentially contacted with an aqueous solution containing amine monomers and an oil solution containing acyl chloride monomers to form a polyamide desalination layer; The base film with the polyamide desalting layer formed is sequentially contacted with an aqueous solution containing polyethyleneimine and thioctic acid, and an aqueous solution containing dialdehyde compounds. Post-processing.

2. The preparation method according to claim 1, wherein the polymer is at least one selected from bisphenol A type polysulfone, polyethersulfone, and polyarylsulfone, and the supporting material is nonwoven fabric; the amine monomer is an amine monomer having two or more amino groups; and the acyl chloride monomer is an aromatic acyl chloride monomer having two or more acyl chloride groups.

3. The preparation method according to claim 1 or 2, wherein the amine monomer is at least one selected from m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, pyromellitic triamine, 2,4-diaminotoluene, 2,5-diaminotoluene, 2,6-diaminotoluene, polyetheramine, polyethyleneimine, diaminobenzenesulfonic acid, and 3,5-diaminobenzoic acid, and the concentration of the amine monomer is 0.1 wt% to 5 wt% based on the total mass of the aqueous solution containing the amine monomer; and the acyl chloride monomer is at least one selected from pyromellitic tricarboxylic acid chloride, isophthaloyl chloride, biphenyl dicarboxylic acid chloride, terephthaloyl chloride, o-fluorobenzoyl chloride, 3-fluorobenzoyl chloride, 4-fluorobenzoyl chloride, 3,5-difluorobenzoyl chloride, 2,5-difluorobenzoyl chloride, and 4-nitrobenzenesulfonyl chloride, and the concentration of the acyl chloride monomer is 0.01 wt% to 0.5 wt% based on the total mass of the oil solution containing the acyl chloride monomer.

4. The preparation method according to claim 1 or 2, wherein the number-average molecular weight of the polyethyleneimine is in the range of 1000 to 100000 g / mol.

5. The preparation method according to claim 1 or 2, wherein the content of polyethyleneimine is 0.05wt% to 2wt% based on the total mass of the aqueous solution containing polyethyleneimine and thioctic acid.

6. The preparation method according to claim 1 or 2, wherein the content of lipoic acid is 0.01 wt% to 1 wt% based on the total mass of the aqueous solution containing polyethyleneimine and lipoic acid.

7. The preparation method according to claim 1 or 2, wherein the dialdehyde compound is an aliphatic dialdehyde compound and / or an aromatic dialdehyde compound.

8. The preparation method according to claim 1 or 2, wherein the dialdehyde compound is at least one selected from glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, adipaldehyde, o-phthalaldehyde, terephthalaldehyde, and isophthalaldehyde, and the concentration of the dialdehyde compound is 0.01wt% to 0.5wt% based on the total mass of the aqueous solution containing the dialdehyde compound.

9. A composite reverse osmosis membrane prepared by the preparation method according to any one of claims 1 to 8, characterized in that, From bottom to top, it includes: Supporting materials; A base film, wherein the base film is formed by a casting solution comprising a polymer and a solvent; A polyamide desalination layer, which is formed by the polymerization of amine monomers and acyl chloride monomers; A protective layer formed by treatment with polyethyleneimine, thioctic acid, and dialdehyde compounds.

10. The composite reverse osmosis membrane according to claim 9, wherein the polymer is at least one selected from bisphenol A type polysulfone, polyethersulfone, and polyarylsulfone, and the supporting material is nonwoven fabric; the amine monomer is an amine monomer having two or more amino groups; and the acyl chloride monomer is an aromatic acyl chloride monomer having two or more acyl chloride groups.

11. The composite reverse osmosis membrane according to claim 9 or 10, wherein the amine monomer is at least one selected from m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, pyromellitic triamine, 2,4-diaminotoluene, 2,5-diaminotoluene, 2,6-diaminotoluene, polyetheramine, polyethyleneimine, diaminobenzenesulfonic acid, and 3,5-diaminobenzoic acid, and the concentration of the amine monomer is 0.1 wt% to 5 wt% based on the total mass of the aqueous solution containing the amine monomer; and the acyl chloride monomer is at least one selected from pyromellitic tricarboxylic acid, isophthaloyl chloride, biphenyl dicarboxylic acid, terephthaloyl chloride, o-fluorobenzoyl chloride, 3-fluorobenzoyl chloride, 4-fluorobenzoyl chloride, 3,5-difluorobenzoyl chloride, 2,5-difluorobenzoyl chloride, and 4-nitrobenzenesulfonyl chloride, and the concentration of the acyl chloride monomer is 0.01 wt% to 0.5 wt% based on the total mass of the oil phase solution containing the acyl chloride monomer.

12. The composite reverse osmosis membrane according to claim 9 or 10, wherein the number-average molecular weight of the polyethyleneimine is in the range of 1000 to 100000 g / mol.

13. The composite reverse osmosis membrane according to claim 9 or 10, wherein the content of the polyethyleneimine is 0.05 wt% to 2 wt% based on the total mass of the aqueous solution containing polyethyleneimine and thioctic acid.

14. The composite reverse osmosis membrane according to claim 9 or 10, wherein the content of the lipoic acid is 0.01 wt% to 1 wt% based on the total mass of the aqueous solution containing polyethyleneimine and lipoic acid.

15. The composite reverse osmosis membrane according to claim 9 or 10, wherein the dialdehyde compound is an aliphatic dialdehyde compound and / or an aromatic dialdehyde compound.

16. The composite reverse osmosis membrane according to claim 9 or 10, wherein the dialdehyde compound is at least one selected from glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, adipaldehyde, o-phthalaldehyde, terephthalaldehyde, and isophthalaldehyde, and the concentration of the dialdehyde compound is 0.01wt% to 0.5wt% based on the total mass of the aqueous solution containing the dialdehyde compound.

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