Oxidation-resistant seawater desalination film and preparation method thereof

Abstract

The invention relates to the technical field of water treatment, in particular to an oxidation-resistant seawater desalination film and a preparation method thereof. The oxidation-resistant seawater desalination membrane sequentially comprises a non-woven fabric layer, a polysulfone base layer and a polyamide layer from bottom to top, the polyamide layer is prepared from the following raw materials in parts by weight: 3 to 5 parts of 4, 4-diaminodiphenyl, 1 to 3 parts of o-phenylenediamine, 1 to 5 parts of a sulfydryl modified cobalt-based metal organic framework, 2 to 4 parts of an auxiliary agent, 0.5 to 1.5 parts of an acyl chloride monomer and 100 to 140 parts of an isoparaffin solvent. According to the seawater desalination membrane disclosed by the invention, the oxidation resistance of the seawater desalination membrane is improved for a long time under the condition that the separation performances such as water yield and desalination rate are ensured.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of water treatment, in particular to an oxidation-resistant seawater desalination membrane and a preparation method thereof. BACKGROUND

[0002] The global water resource shortage problem is increasingly prominent, and seawater desalination technology has become a key means for alleviating the contradiction between fresh water supply and demand. Reverse osmosis technology has occupied a dominant position in the field of seawater desalination due to its high efficiency and energy saving, and the comprehensive performance of seawater desalination membranes as the core component of reverse osmosis technology directly determines the operation stability and economy of the entire desalination system. After years of development, seawater desalination membranes have evolved from early homogeneous membranes to current widely used composite membrane structures. Such composite membranes have good desalination performance and water permeation efficiency due to reasonable interlayer design, and in particular, composite membranes with polyamide as the functional layer have become the mainstream choice in commercial seawater desalination projects due to mature preparation process and excellent separation effect, which promotes the scale application of seawater desalination technology.

[0003] In the actual operation process of seawater desalination membranes, microorganisms in seawater are prone to grow on the membrane surface to form biological pollution, which leads to an increase in the permeation resistance of the membrane and a decrease in the separation performance. The industry generally adds chlorine-containing disinfectants to the water inlet system to inhibit the reproduction of microorganisms to ensure the normal operation of the membrane. However, this measure poses a serious challenge to the polyamide functional layer. The specific structure in the polyamide molecular chain is easily attacked by active chlorine generated by the disinfectant, which causes molecular chain degradation and membrane pore structure deterioration, and further leads to desalination performance degradation and water flux abnormal fluctuation of the membrane, thereby shortening the service life of the membrane. This problem of insufficient oxidation resistance not only increases the replacement frequency and operation and maintenance cost of the membrane component, but also may fall into a vicious cycle of oxidation damage and microbial pollution due to the need to balance the disinfection effect and membrane damage, which seriously restricts the long-term stable operation of the seawater desalination system. Therefore, developing seawater desalination membranes with high desalination rate, high flux and excellent oxidation resistance has become a core direction for promoting the sustainable development of seawater desalination technology, and has important significance for improving the economy and sustainability of the desalination system. SUMMARY

[0004] In order to effectively improve the oxidation resistance of the reverse osmosis membrane without reducing the separation performance of the membrane, the application provides an oxidation-resistant seawater desalination membrane and a preparation method thereof.

[0005] In a first aspect, the application provides an oxidation-resistant seawater desalination membrane, which adopts the following technical solution: An oxidation-resistant seawater desalination membrane, from bottom to top, is a non-woven fabric layer, a polysulfone base layer and a polyamide layer; the raw materials of the polyamide layer include, by weight: 3-5 parts of 4,4-diaminobiphenyl, 1-3 parts of o-phenylenediamine, 1-5 parts of a thiol-modified cobalt metal organic framework, 2-4 parts of an auxiliary agent, 0.5-1.5 parts of an acyl chloride monomer and 100-140 parts of an isomeric alkane solvent.

[0006] The present application cooperates the structures of 4,4-diaminobiphenyl and o-phenylenediamine to improve the tensile strength and other mechanical properties of the material, and to enhance the long-term stability of the material. The acyl chloride monomer forms a dense polyamide layer structure with them, thereby enhancing the oxidation resistance stability of the material. The thiol-modified cobalt metal organic framework is added, which has the effects of anti-oxidation, antibacterial and water guiding, and is used as a water phase component to improve the oxidation resistance of the overall membrane layer. The seawater desalination membrane maintains stable water flux and desalination rate in a chlorine-containing seawater environment, thereby maintaining excellent separation performance and prolonging the service life of the membrane.

[0007] The polyamide layer serves as the core functional layer. The aromatic rings provided by o-phenylenediamine and 4,4-diaminobiphenyl effectively improve the mechanical strength, chemical resistance and thermal stability of the polyamide layer. The conjugated system of the biphenyl structure can also absorb ultraviolet light to improve the aging resistance. The amine molecules in the present application have a more stable mechanical structure in the polyamide backbone formed by the cross-linking reaction with the acyl chloride monomer, forming a dense three-dimensional polyamide network to enhance the resistance of the membrane to oxidation corrosion. On this basis, the cobalt metal organic framework is introduced, which is modified by thiol. The surface-exposed thiol chemical activity is much higher than that of the amide bond of polyamide, and can preferentially react with active chlorine in seawater to improve the oxidation resistance of the membrane. The cobalt ions in the framework can destroy the phospholipid bilayer of the microbial cell membrane and inhibit the synthesis of microbial proteins, effectively improving the biofouling problem on the membrane surface and further improving the oxidation resistance of the membrane. At the same time, the six-coordinated cobalt metal organic framework has a porous cage structure, which can provide a fast transmission channel for water molecules to ensure stable water flux. The modified cobalt metal organic framework can be fixed in the polyamide layer to avoid its shedding under long-term seawater erosion, ensuring the durability of the anti-oxidation and seawater desalination, and prolonging the service life. The auxiliary agent optimizes the dispersibility and reactivity of each component in the system to avoid local oxidation resistance weakness and uneven desalination caused by component agglomeration or insufficient reaction, so that the seawater desalination membrane can maintain stable separation performance in a chlorine-containing seawater environment for a long time, significantly prolonging the service life of the membrane.

[0008] The polysulfone base layer and the polyamide layer interact to form stable interlayer bonding, ensuring the stability of the overall performance of the membrane, and the interaction between the components forms a dense structure, stabilizing the water flux and desalination rate, so that the seawater desalination membrane of the application can accurately intercept the salt ions in seawater, ensuring high desalination rate of the membrane, and the dense structure can also reduce the path of active chlorine penetrating into the membrane, thereby improving the oxidation resistance.

[0009] Preferably, the preparation method of the mercapto-modified cobalt-based metal organic framework comprises the following steps: dissolving cobalt nitrate and 2,5-dihydroxyterephthalic acid in N-methylpyrrolidone, reacting at 110-120 DEG C for 10-12 h to obtain a cobalt-based metal organic framework, dispersing in an ethanol aqueous solution, adding 3-aminopropyltriethoxysilane, stirring for 5-8 h to obtain an aminated cobalt-based metal organic framework; then dispersing in an ethanol solution, adding 3-mercaptopropionic acid, stirring, adding 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride, stirring under nitrogen protection for 8-10 h, centrifuging, washing, and drying to obtain a mercapto-modified cobalt-based metal organic framework.

[0010] More preferably, the mass ratio of the aminated cobalt-based metal organic framework and 3-mercaptopropionic acid is (7-10):1.

[0011] The mercapto group introduced after amination of the cobalt-based metal organic framework can react with active chlorine, avoiding direct attack of active chlorine on the amide bond structure of the polyamide layer, reducing oxidative damage to the amide bond, and thereby improving the oxidation resistance. The inventors have found that the optimal antioxidant effect is achieved when the ratio of the aminated cobalt-based metal organic framework and 3-mercaptopropionic acid is within the range of the application. This may be because the aminated cobalt-based metal organic framework is partially modified by the mercapto group, and the remaining amino group can participate in the polymerization reaction of the separation layer by reacting with the amine in the water phase and the acid chloride monomer, so that the cobalt-based metal organic framework is firmly anchored in the separation layer based on covalent bonds, and the introduced mercapto group better plays the role of chlorine ion oxidation resistance. Too much 3-mercaptopropionic acid can consume too much amino group, which is not conducive to the participation of the cobalt-based metal organic framework in cross-linking to achieve stable adhesion. Too little 3-mercaptopropionic acid reduces the introduced mercapto group, which deteriorates the antioxidant effect.

[0012] Preferably, the mass ratio of 4,4-diaminobiphenyl and o-phenylenediamine is 3:1.

[0013] Preferably, the raw materials of the polysulfone base layer include 20-25 parts of polysulfone, 5-8 parts of hydroxyapatite, 4-7 parts of polyvinylpyrrolidone, and 60-75 parts of N,N-dimethylformamide.

[0014] In the polysulfone base layer, the polysulfone provides basic mechanical support for the membrane body, the molecular chain forms hydrogen bonds with the hydroxyl groups on the surface of the hydroxyapatite, and the hydroxyapatite forms interaction with the modified cobalt-based metal organic framework through the surface calcium ions, thereby constructing a stable interlayer strong interaction network, strengthening the combination tightness of the polyamide layer and the polysulfone base layer, and improving the tensile strength and overall structural stability of the membrane.

[0015] Preferably, the acyl chloride monomer is trimesoyl chloride and 1,2-benzenedisulfonyl dichloride in a mass ratio of (2-4):1.

[0016] The inventors found that by selecting trimesoyl chloride and 1,2-benzenedisulfonyl dichloride as the composite acyl chloride monomer, and by allowing the two to jointly crosslink with 4,4-diaminobiphenyl and o-phenylenediamine, stable amide bonds and sulfonamide bonds are formed in the polyamide layer, and a three-dimensional network structure with compactness and oxidation resistance is constructed. Not only can it accurately intercept salt ions in seawater to ensure high desalination rate, but also can enhance the regularity of the polyamide main chain and improve the mechanical properties of the membrane, avoiding deformation and damage of the membrane under high pressure working conditions. Further enhance the resistance of the polyamide layer to active chlorine, strengthen the overall oxidation resistance effect, and significantly prolong the long-term operation life of the membrane.

[0017] Preferably, the auxiliary agent includes camphorsulfonic acid, sodium dodecyl sulfonate and sodium hydroxide in a mass ratio of (3-5):1:1.

[0018] Preferably, the isomeric alkane solvent includes one or more of Isopar G, isododecane, Isopar H, isomyristyl, and isodecane.

[0019] In a second aspect, the application provides a preparation method of an oxidation-resistant seawater desalination membrane, which adopts the following technical scheme: a preparation method of an oxidation-resistant seawater desalination membrane, comprising the following steps: S1: spraying a polysulfone base layer casting solution onto a non-woven fabric, and then placing the thin film in a water coagulation liquid to obtain a base film; S2: dispersing 4,4-diaminobiphenyl, o-phenylenediamine, a modified cobalt-based metal organic framework, and an auxiliary agent in water, and ultrasonic dispersing for 30-40 min to obtain an aqueous solution; S3: dissolving acyl chloride monomers in an isomeric alkane solvent, and ultrasonic dispersing for 30-40 min to obtain an oil phase solution; S4: immersing the upper surface of the base film in the aqueous solution for 60-90 s, then immersing the upper surface of the base film in the oil phase solution for 40-70 s, and then taking out and drying to obtain the oxidation-resistant seawater desalination membrane.

[0020] Preferably, the drying is vacuum heat treatment at 60-75℃ for 15-25 min.

[0021] In summary, the application includes at least one of the following beneficial technical effects: 1. By the mutual cooperation of 4, 4-diaminobiphenyl and o-phenylenediamine structure, the tensile strength and other mechanical properties of the material are improved, the long-term stability of the material is enhanced, and the acyl chloride monomer forms a dense polyamide layer structure, which enhances the oxidation resistance stability of the material; then the mercapto-modified cobalt-based metal organic framework is added, which has the effects of anti-oxidation, antibacterial and water guiding, and is used as the water phase component together, which improves the oxidation resistance of the whole membrane layer, so that the seawater desalination membrane maintains stable water flux and desalination rate in the chlorine-containing seawater environment, thereby maintaining excellent separation performance and prolonging the service life of the membrane.

[0022] 2. The mercapto introduced after the amination of the cobalt-based metal organic framework can react with active chlorine, avoiding the direct attack of active chlorine on the amide bond structure of the polyamide layer, reducing the oxidative damage of the amide bond, and further improving the oxidation resistance. DETAILED DESCRIPTION

[0023] The raw materials used in the present application are as follows: hydroxyapatite (average particle size 20 nm) is purchased from Beijing Deke Island Gold Technology Co., Ltd.; the others are conventional commercially available brands or obtained by conventional preparation process.

[0024] Preparation Example 1 Preparation of mercapto-modified cobalt-based metal organic framework: (1) 12.1 g of cobalt nitrate hexahydrate and 7.8 g of 2, 5-dihydroxyterephthalic acid were dissolved in 100 ml of N-methylpyrrolidone, ultrasonicated for 30 min, transferred to a polytetrafluoroethylene reaction kettle, and reacted at 110°C for 10 h. The cobalt-based metal organic framework was obtained by filtration. (2) 10 g of the cobalt-based metal organic framework was dispersed in 300 ml of an ethanol aqueous solution (volume ratio 1:1), 8 g of 3-aminopropyltriethoxysilane was added, and after stirring at room temperature for 5 h, centrifugation, washing with anhydrous ethanol 3 times (50 ml each time), and vacuum drying at 60°C for 6 h, the amino-modified cobalt-based metal organic framework was obtained. (3) 5 g of the amino-modified cobalt-based metal organic framework was dispersed in 100 ml (v / v = 1 / 1) of an ethanol aqueous solution, 0.6 g of 3-mercaptopropionic acid was added, after stirring and dissolving, 1.1 g of carbodiimide hydrochloride was added, stirring was carried out at room temperature under nitrogen protection for 8 h, then centrifugation was carried out, washing was carried out 3 times with an ethanol aqueous solution, washing was carried out 2 times with water, and vacuum drying was carried out at 60°C for 8 h, thereby obtaining the mercapto-modified cobalt-based metal organic framework.

[0025] Preparation Example 2 Preparation of the thiol-modified cobalt-based metal organic framework: (1) 12.1 g of cobalt nitrate hexahydrate and 7.8 g of 2,5-dihydroxyterephthalic acid were dissolved in 100 ml of N-methylpyrrolidone, and ultrasonic treatment was performed for 30 min. The solution was transferred to a polytetrafluoroethylene reaction kettle, and reaction was performed at 110°C for 10 h. Filtration was performed to obtain a cobalt-based metal organic framework. (2) 10 g of the cobalt-based metal organic framework was dispersed in 300 ml of an ethanol aqueous solution (volume ratio 1:1), 8 g of 3-aminopropyltriethoxysilane was added, stirring was performed at room temperature for 5 h, centrifugal collection was performed, washing was performed with anhydrous ethanol three times (50 ml each time), and vacuum drying was performed at 60°C for 6 h to obtain an aminated cobalt-based metal organic framework. (3) 4.6 g of the aminated cobalt-based metal organic framework was dispersed in 100 ml of an ethanol aqueous solution (v:v=1:1), 1 g of 3-mercaptopropionic acid was added, stirring was performed until dissolution, 1.1 g of carbodiimide hydrochloride was added, stirring was performed at room temperature under nitrogen protection for 8 h, centrifugal collection was performed, washing was performed with an ethanol aqueous solution three times, washing was performed with water two times, and vacuum drying was performed at 60°C for 8 h to obtain a thiol-modified cobalt-based metal organic framework.

[0026] Preparation Example 3 Preparation of the thiol-modified cobalt-based metal organic framework: (1) 12.1 g of cobalt nitrate hexahydrate and 7.8 g of 2,5-dihydroxyterephthalic acid were dissolved in 100 ml of N-methylpyrrolidone, and ultrasonic treatment was performed for 30 min. The solution was transferred to a polytetrafluoroethylene reaction kettle, and reaction was performed at 110°C for 10 h. Filtration was performed to obtain a cobalt-based metal organic framework. (2) 10 g of the cobalt-based metal organic framework was dispersed in 300 ml of an ethanol aqueous solution (volume ratio 1:1), 8 g of 3-aminopropyltriethoxysilane was added, stirring was performed at room temperature for 5 h, centrifugal collection was performed, washing was performed with anhydrous ethanol three times (50 ml each time), and vacuum drying was performed at 60°C for 6 h to obtain an aminated cobalt-based metal organic framework. (3) 5.3 g of the aminated cobalt-based metal organic framework was dispersed in 100 ml of an ethanol aqueous solution (v:v=1:1), 0.3 g of 3-mercaptopropionic acid was added, stirring was performed until dissolution, 1.1 g of carbodiimide hydrochloride was added, stirring was performed at room temperature under nitrogen protection for 8 h, centrifugal collection was performed, washing was performed with an ethanol aqueous solution three times, washing was performed with water two times, and vacuum drying was performed at 60°C for 8 h to obtain a thiol-modified cobalt-based metal organic framework.

[0027] Preparation Example 4 Preparation of modified cobalt-based metal organic framework: (1) 12.1 g of cobalt nitrate hexahydrate and 7.8 g of 2,5-dihydroxyterephthalic acid were dissolved in 100 ml of N-methylpyrrolidone, ultrasonic for 30 min, transferred to a polytetrafluoroethylene reaction kettle, constant temperature reaction at 110℃ for 10 h, filtration to obtain cobalt-based metal organic framework, (2) 10 g of cobalt-based metal organic framework was dispersed in 300 ml of ethanol aqueous solution (volume ratio 1:1), 8 g of 3-aminopropyl triethoxysilane was added, stirred at room temperature for 5 h, then centrifuged, washed with anhydrous ethanol for 3 times (50 ml each time), vacuum dried at 60℃ for 6 h, to obtain amino-modified cobalt-based metal organic framework.

[0028] Preparation Example 5 Preparation of cobalt-based metal organic framework: (1) 12.1 g of cobalt nitrate hexahydrate and 7.8 g of 2,5-dihydroxyterephthalic acid were dissolved in 100 ml of N-methylpyrrolidone, ultrasonic for 30 min, transferred to a polytetrafluoroethylene reaction kettle, constant temperature reaction at 110℃ for 10 h, filtration to obtain cobalt-based metal organic framework.

[0029] Example 1 An oxidation-resistant seawater desalination membrane and a preparation method thereof, comprising the following steps: S1: Preparation of casting solution: 20 g of polysulfone was dissolved in 72 g of N,N-dimethylformamide, then 3 g of hydroxyapatite and 5 g of polyvinylpyrrolidone were added, the above raw materials were mixed and placed, defoaming and filtering to obtain the casting solution; the casting solution was uniformly sprayed on the non-woven fabric (thickness 80 μm, air permeability 2.5 cc / cm 2 / s) through a slot die coating head, and after coating, the film was placed in a water coagulation liquid to obtain a base film; S2: 3 g of 4,4-diaminobiphenyl, 1 g of o-phenylenediamine, 2 g of the thiol-modified cobalt-based metal organic framework prepared in Preparation Example 1 and 3 g of an additive were dispersed in 91 g of water, ultrasonic dispersion for 40 min to obtain an aqueous phase solution; the additive was camphor sulfonic acid, sodium dodecyl sulfonate and sodium hydroxide with a mass ratio of 3:1:1; S3: 0.5 g of an acid chloride monomer was dissolved in 99.5 g of IsoparG, ultrasonic dispersion for 30 min to obtain an oil phase solution; the acid chloride monomer was isophthaloyl chloride and 1,2-benzenedisulfonyl dichloride with a mass ratio of 2:1; S4: the upper surface of the base film was immersed in the aqueous phase solution for 80 s, the residual aqueous phase solution on the surface of the base film was removed with a rubber roller, then the upper surface of the base film was immersed in the oil phase solution for 70 s, and the obtained product was vacuum dried at 60℃ for 25 min to obtain the oxidation-resistant seawater desalination membrane.

[0030] Example 2 An oxidation-resistant seawater desalination membrane and a preparation method thereof, comprising the following steps: S1: Preparation of casting solution: 20 g of polysulfone was dissolved in 72 g of N,N-dimethylformamide, then 3 g of hydroxyapatite and 5 g of polyvinylpyrrolidone were added, the above raw materials were mixed and placed, defoaming and filtering to obtain a casting solution; the casting solution was uniformly sprayed on the non-woven fabric (thickness 80 μm, air permeability 2.5 cc / cm 2 / s) through a slot die coating head, and after coating, the film was placed in a water coagulation solution to obtain a base film; S2: 2 g of 4,4-diaminobiphenyl, 2 g of o-phenylenediamine, 2 g of the thiol-modified cobalt-based metal organic framework prepared in Preparation Example 1, and 3 g of an additive were dispersed in 91 g of water, and ultrasonic dispersion was performed for 40 min to obtain an aqueous phase solution; the additive was camphorsulfonic acid, sodium dodecylsulfate, and sodium hydroxide with a mass ratio of 3:1:1; S3: 0.5 g of an acid chloride monomer was dissolved in 99.5 g of IsoparG, and ultrasonic dispersion was performed for 30 min to obtain an oil phase solution; the acid chloride monomer was isophthaloyl chloride and 1,2-benzenedisulfonyl dichloride with a mass ratio of 2:1; S4: the upper surface of the base film was immersed in the aqueous phase solution for 80 s, the residual aqueous phase solution on the surface of the base film was removed with a rubber roller, then the upper surface of the base film was immersed in the oil phase solution for 70 s, and the base film was taken out and dried in a vacuum oven at 60°C for 25 min to obtain an oxidation-resistant seawater desalination membrane.

[0031] Example 3 An oxidation-resistant seawater desalination membrane and a preparation method thereof, comprising the following steps: S1: Preparation of casting solution: 20 g of polysulfone was dissolved in 72 g of N,N-dimethylformamide, then 3 g of hydroxyapatite and 5 g of polyvinylpyrrolidone were added, the above raw materials were mixed and placed, defoaming and filtering to obtain a casting solution; the casting solution was uniformly sprayed on the non-woven fabric (thickness 80 μm, air permeability 2.5 cc / cm 2 / s) through a slot die coating head, and after coating, the film was placed in a water coagulation solution to obtain a base film; S2: 3 g of 4,4-diaminobiphenyl, 1 g of o-phenylenediamine, 2 g of the thiol-modified cobalt-based metal organic framework prepared in Preparation Example 2, and 3 g of an additive were dispersed in 91 g of water, and ultrasonic dispersion was performed for 40 min to obtain an aqueous phase solution; the additive was camphorsulfonic acid, sodium dodecylsulfate, and sodium hydroxide with a mass ratio of 3:1:1; S3: 0.5 g of an acid chloride monomer was dissolved in 99.5 g of IsoparG, and ultrasonic dispersion was performed for 30 min to obtain an oil phase solution; the acid chloride monomer was isophthaloyl chloride and 1,2-benzenedisulfonyl dichloride with a mass ratio of 2:1; S4: the upper surface of the base film was immersed in the aqueous phase solution for 80 s, the residual aqueous phase solution on the surface of the base film was removed with a rubber roller, then the upper surface of the base film was immersed in the oil phase solution for 70 s, and the base film was taken out and dried in a vacuum oven at 60°C for 25 min to obtain an oxidation-resistant seawater desalination membrane.

[0032] Example 4 An oxidation-resistant seawater desalination membrane and a preparation method thereof, comprising the following steps: S1: Preparation of casting solution: 20g of polysulfone is dissolved in 72g of N,N-dimethylformamide, then 3g of hydroxyapatite and 5g of polyvinylpyrrolidone are added, the above raw materials are uniformly mixed and placed, defoaming and filtering to obtain the casting solution; the casting solution is uniformly sprayed on non-woven fabric (thickness 80μm, air permeability 2.5cc / cm 2 / s) through a slot die coating head, and after coating, the film is placed in a water coagulation solution to obtain a base film; S2: 3g of 4,4-diaminobiphenyl, 1g of o-phenylenediamine, 2g of the thiol-modified cobalt-based metal-organic framework prepared in Preparation Example 3 and 3g of an additive are dispersed in 91g of water, and ultrasonic dispersion is performed for 40min to obtain an aqueous phase solution; the additive is camphorsulfonic acid, sodium dodecylsulfate and sodium hydroxide with a mass ratio of 3:1:1; S3: 0.5g of an acid chloride monomer is dissolved in 99.5g of IsoparG, and ultrasonic dispersion is performed for 30min to obtain an oil phase solution; the acid chloride monomer is trimesoyl chloride and 1,2-benzenedisulfonyl dichloride with a mass ratio of 2:1; S4: the upper surface of the base film is immersed in the aqueous phase solution for 80s, the residual aqueous phase solution on the surface of the base film is removed with a rubber roller, then the upper surface of the base film is immersed in the oil phase solution for 70s, and the base film is taken out and dried at 60°C in a vacuum for 25min to obtain the oxidation-resistant seawater desalination membrane.

[0033] Example 5 An oxidation-resistant seawater desalination membrane and a preparation method thereof, comprising the following steps: S1: Preparation of casting solution: 20g of polysulfone is dissolved in 72g of N,N-dimethylformamide, then 3g of hydroxyapatite and 5g of polyvinylpyrrolidone are added, the above raw materials are uniformly mixed and placed, defoaming and filtering to obtain the casting solution; the casting solution is uniformly sprayed on non-woven fabric (thickness 80μm, air permeability 2.5cc / cm 2 / s) through a slot die coating head, and after coating, the film is placed in a water coagulation solution to obtain a base film; S2: 3g of 4,4-diaminobiphenyl, 1g of o-phenylenediamine, 2g of the thiol-modified cobalt-based metal-organic framework prepared in Preparation Example 1 and 3g of an additive are dispersed in 91g of water, and ultrasonic dispersion is performed for 40min to obtain an aqueous phase solution; the additive is camphorsulfonic acid, sodium dodecylsulfate and sodium hydroxide with a mass ratio of 3:1:1; S3: 0.5g of an acid chloride monomer is dissolved in 99.5g of IsoparG, and ultrasonic dispersion is performed for 30min to obtain an oil phase solution; the acid chloride monomer is trimesoyl chloride; S4: the upper surface of the base film is immersed in the aqueous phase solution for 80s, the residual aqueous phase solution on the surface of the base film is removed with a rubber roller, then the upper surface of the base film is immersed in the oil phase solution for 70s, and the base film is taken out and dried at 60°C in a vacuum for 25min to obtain the oxidation-resistant seawater desalination membrane.

[0034] Example 6 An oxidation-resistant seawater desalination membrane and a preparation method thereof, comprising the following steps: S1: Preparation of casting solution: 20 g of polysulfone is dissolved in 72 g of N,N-dimethylformamide, then 3 g of hydroxyapatite and 5 g of polyvinylpyrrolidone are added, the above raw materials are uniformly mixed and placed, defoaming and filtering to obtain a casting solution; the casting solution is uniformly sprayed on a non-woven fabric (thickness 80 μm, air permeability 2.5 cc / cm 2 / s) through a slot die coater, and after coating, the film is placed in a water coagulation solution to obtain a base film; S2: 3 g of 4,4-diaminobiphenyl, 1 g of o-phenylenediamine, 2 g of the thiol-modified cobalt-based metal organic framework prepared in Preparation Example 1, and 3 g of an additive are dispersed in 91 g of water, and ultrasonic dispersion is performed for 40 min to obtain an aqueous phase solution; the additive is camphor sulfonic acid, sodium dodecyl sulfonate and sodium hydroxide with a mass ratio of 3:1:1; S3: 0.5 g of an acyl chloride monomer is dissolved in 99.5 g of IsoparG, and ultrasonic dispersion is performed for 30 min to obtain an oil phase solution; the acyl chloride monomer is 1,2-benzenedisulfonyl dichloride; S4: the upper surface of the base film is immersed in the aqueous phase solution for 80 s, the residual aqueous phase solution on the surface of the base film is removed with a rubber roller, then the upper surface of the base film is immersed in the oil phase solution for 70 s, and the base film is taken out and dried in a vacuum oven at 60°C for 25 min to obtain an oxidation-resistant seawater desalination membrane.

[0035] Example 7 An oxidation-resistant seawater desalination membrane and a preparation method thereof, comprising the following steps: S1: Preparation of casting solution: 20 g of polysulfone is dissolved in 72 g of N,N-dimethylformamide, then 3 g of hydroxyapatite and 5 g of polyvinylpyrrolidone are added, the above raw materials are uniformly mixed and placed, defoaming and filtering to obtain a casting solution; the casting solution is uniformly sprayed on a non-woven fabric (thickness 80 μm, air permeability 2.5 cc / cm 2 / s) through a slot die coater, and after coating, the film is placed in a water coagulation solution to obtain a base film; S2: 3 g of 4,4-diaminobiphenyl, 1 g of o-phenylenediamine, 2 g of the thiol-modified cobalt-based metal-organic framework prepared in Preparation Example 1, and 3 g of an auxiliary agent were dispersed in 91 g of water, and ultrasonic dispersion was performed for 40 min to obtain an aqueous phase solution; the auxiliary agent was camphorsulfonic acid, sodium dodecylsulfate, and sodium hydroxide at a mass ratio of 3:1:1; S3: 0.5 g of an acid chloride monomer was dissolved in 99.5 g of IsoparG, and ultrasonic dispersion was performed for 30 min to obtain an oil phase solution; the acid chloride monomer was isophthaloyl chloride and 1,2-benzenedisulfonyl dichloride at a mass ratio of 2:1; S4: the upper surface of the base membrane was immersed in the aqueous phase solution for 80 s, the residual aqueous phase solution on the surface of the base membrane was removed using a rubber roller, the upper surface of the base membrane was then immersed in the oil phase solution for 70 s, and the base membrane was taken out and dried in a vacuum at 60°C for 25 min to obtain the oxidation-resistant seawater desalination membrane.

[0036] Comparative Example 1 An oxidation-resistant seawater desalination membrane and a preparation method thereof, comprising the following steps: S1: Preparation of a casting solution: 20 g of polysulfone was dissolved in 72 g of N,N-dimethylformamide, 3 g of hydroxyapatite, and 5 g of polyvinylpyrrolidone were added, the above raw materials were mixed and left to stand, and the casting solution was obtained after degassing and filtration; the casting solution was uniformly sprayed on a non-woven fabric (thickness 80 μm, air permeability 2.5 cc / cm 2 / s) through a slit coating head, and after coating, the membrane was left to stand in a water coagulation solution to obtain a base membrane; S2: 3 g of 4,4-diaminobiphenyl, 1 g of o-phenylenediamine, 2 g of the thiol-modified cobalt-based metal-organic framework prepared in Preparation Example 4, and 3 g of an auxiliary agent were dispersed in 91 g of water, and ultrasonic dispersion was performed for 40 min to obtain an aqueous phase solution; the auxiliary agent was camphorsulfonic acid, sodium dodecylsulfate, and sodium hydroxide at a mass ratio of 3:1:1; S3: 0.5 g of an acid chloride monomer was dissolved in 99.5 g of IsoparG, and ultrasonic dispersion was performed for 30 min to obtain an oil phase solution; the acid chloride monomer was isophthaloyl chloride and 1,2-benzenedisulfonyl dichloride at a mass ratio of 2:1; S4: the upper surface of the base membrane was immersed in the aqueous phase solution for 80 s, the residual aqueous phase solution on the surface of the base membrane was removed using a rubber roller, the upper surface of the base membrane was then immersed in the oil phase solution for 70 s, and the base membrane was taken out and dried in a vacuum at 60°C for 25 min to obtain the oxidation-resistant seawater desalination membrane.

[0037] Comparative Example 2 An oxidation-resistant seawater desalination membrane and a preparation method thereof, comprising the following steps: S1: Preparation of a casting solution: 20 g of polysulfone was dissolved in 72 g of N,N-dimethylformamide, 3 g of hydroxyapatite, and 5 g of polyvinylpyrrolidone were added, the above raw materials were mixed and left to stand, and the casting solution was obtained after degassing and filtration; the casting solution was uniformly sprayed on a non-woven fabric (thickness 80 μm, air permeability 2.5 cc / cm 2After coating, the film is placed in a water coagulation solution to obtain a base film; S2: 4g 4,4-diaminobiphenyl, 2g thiol-modified cobalt-based metal organic framework prepared in preparation example 1 and 3g auxiliary are dispersed in 91g water, ultrasonic dispersion for 40min to obtain an aqueous phase solution; the auxiliary is camphorsulfonic acid, sodium dodecyl sulfonate and sodium hydroxide with a mass ratio of 3:1:1; S3: 0.5g acyl chloride monomer is dissolved in 99.5g IsoparG, ultrasonic dispersion for 30min to obtain an oil phase solution; the acyl chloride monomer is isophthaloyl chloride and 1,2-benzenedisulfonyl dichloride with a mass ratio of 2:1; S4: the upper surface of the base film is immersed in the aqueous phase solution for 80s, the residual aqueous phase solution on the surface of the base film is removed by a rubber roller, then the upper surface of the base film is immersed in the oil phase solution for 70s, and the base film is taken out and dried in a vacuum oven at 60℃ for 25min to obtain the oxidation-resistant seawater desalination membrane.

[0038] Comparative example 3 An oxidation-resistant seawater desalination membrane and a preparation method thereof, comprising the following steps: S1: preparation of casting solution: 20g of polysulfone is dissolved in 72g of N,N-dimethylformamide, then 3g of hydroxyapatite and 5g of polyvinylpyrrolidone are added, the above raw materials are uniformly mixed and placed, defoaming and filtering to obtain a casting solution; the casting solution is uniformly sprayed on a non-woven fabric (thickness 80μm, air permeability 2.5cc / cm 2 After coating, the film is placed in a water coagulation solution to obtain a base film; S2: 4g 4,4-diaminobiphenyl, 2g thiol-modified cobalt-based metal organic framework prepared in preparation example 1 and 3g auxiliary are dispersed in 91g water, ultrasonic dispersion for 40min to obtain an aqueous phase solution; the auxiliary is camphorsulfonic acid, sodium dodecyl sulfonate and sodium hydroxide with a mass ratio of 3:1:1; S3: 0.5g acyl chloride monomer is dissolved in 99.5g IsoparG, ultrasonic dispersion for 30min to obtain an oil phase solution; the acyl chloride monomer is isophthaloyl chloride and 1,2-benzenedisulfonyl dichloride with a mass ratio of 2:1; S4: the upper surface of the base film is immersed in the aqueous phase solution for 80s, the residual aqueous phase solution on the surface of the base film is removed by a rubber roller, then the upper surface of the base film is immersed in the oil phase solution for 70s, and the base film is taken out and dried in a vacuum oven at 60℃ for 25min to obtain the oxidation-resistant seawater desalination membrane.

[0039] Comparative example 4 An oxidation-resistant seawater desalination membrane and a preparation method thereof, comprising the following steps: S1: Preparation of casting solution: 20 g of polysulfone was dissolved in 72 g of N,N-dimethylformamide, then 3 g of hydroxyapatite and 5 g of polyvinylpyrrolidone were added, the above raw materials were mixed and placed, defoamed and filtered to obtain a casting solution; the casting solution was uniformly sprayed on non-woven fabric (thickness 80 μm, air permeability 2.5 cc / cm 2 / s) by a slot die coater, and after coating, the film was placed in a water coagulation solution to obtain a base film; S2: 3 g of 4,4-diaminobiphenyl, 1 g of o-phenylenediamine and 3 g of an auxiliary were dispersed in 93 g of water, and ultrasonic dispersion was performed for 40 min to obtain an aqueous phase solution; the auxiliary was camphor sulfonic acid, sodium dodecyl sulfonate and sodium hydroxide with a mass ratio of 3:1:1; S3: 0.5 g of an acid chloride monomer was dissolved in 99.5 g of IsoparG, and ultrasonic dispersion was performed for 30 min to obtain an oil phase solution; the acid chloride monomer was trimesoyl chloride and 1,2-benzenedisulfonyl dichloride with a mass ratio of 2:1; S4: the upper surface of the base film was immersed in the aqueous phase solution for 80 s, the residual aqueous phase solution on the surface of the base film was removed by a rubber roller, then the upper surface of the base film was immersed in the oil phase solution for 70 s, and the base film was taken out and dried in a vacuum oven at 60°C for 25 min to obtain an oxidation-resistant seawater desalination membrane.

[0040] Performance detection The oxidation-resistant seawater desalination membranes prepared in Examples 1-7 and Comparative Examples 1-4 were subjected to oxidation resistance performance testing: first, the initial water flux and desalination rate were tested, and the test results are shown in Table 1; then the above oxidation-resistant seawater desalination membranes were immersed in a sodium hypochlorite aqueous solution with a concentration of 2000 ppm, and after immersion for 24 h, the water flux and desalination rate of the reverse osmosis membranes were detected. The test conditions of the water flux and desalination rate of the oxidation-resistant seawater desalination membranes before and after sodium hypochlorite immersion were: operating pressure 800 psi, NaCl aqueous solution concentration 32 g / L, and solution temperature 25°C.

[0041] Table 1: Oxidation resistance performance test results According to Examples 1-7 of the present application, the water flux and desalination rate of the seawater desalination membranes before and after oxidation were maintained at a high desalination rate and stable water flux, and the oxidation resistance performance and membrane stability were good compared with Comparative Examples 1-4.

[0042] According to Examples 1-4 and Comparative Examples 1-4 of the present application, after the aminated cobalt-based metal organic framework was modified by a mercapto group, the amino group therein could participate in the polymerization reaction of the separation layer by reacting with the amine in the aqueous phase and the acid chloride monomer, thereby increasing the crosslinking density of the separation layer and improving the stability of the separation layer. The introduced mercapto group better played the role of resistance to oxidation of chloride ions. Within the scope of the present application, both the grafting of anti-oxidation groups and the attachment of organic frameworks were considered, and therefore the seawater desalination membrane with the best oxidation resistance could be obtained.

[0043] From Comparative Example 1 and Examples 5-6, it can be seen that both trimesoyl chloride and 1,2-benzenedisulfonyl dichloride are crosslinked with 4,4-diaminobiphenyl and o-phenylenediamine to form stable amide bonds and sulfonamide bonds in the polyamide layer, and a three-dimensional network structure with compactness and oxidation resistance is constructed.

[0044] The above are preferred embodiments of the present application, and are not intended to limit the protection scope of the present application, so: any equivalent changes made in structure, shape, principle, etc. according to the present application should be covered within the protection scope of the present application.

Claims

1. An oxidation-resistant seawater desalination membrane, characterized in that, From bottom to top, the layers are a non-woven fabric layer, a polysulfone base layer, and a polyamide layer; By weight, the raw materials of the polyamide layer include: 3-5 parts of 4,4-diaminobiphenyl, 1-3 parts of o-phenylenediamine, 1-5 parts of mercapto-modified cobalt-based metal-organic framework, 2-4 parts of additives, 0.5-1.5 parts of acyl chloride monomers and 100-140 parts of isoparaffin solvent.

2. The oxidation-resistant seawater desalination membrane according to claim 1, characterized in that, The preparation method of the thiol-modified cobalt-based metal-organic framework includes: dissolving cobalt nitrate and 2,5-dihydroxyterephthalic acid in N-methylpyrrolidone, reacting at a constant temperature of 110-120℃ for 10-12 h to obtain a cobalt-based metal-organic framework, dispersing it in an ethanol aqueous solution, adding 3-aminopropyltriethoxysilane, stirring for 5-8 h to obtain an aminated cobalt-based metal-organic framework; further dispersing it in an ethanol solution, adding 3-mercaptopropionic acid, stirring and adding 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, stirring under nitrogen protection for 8-10 h, centrifuging, washing, and drying to obtain a thiol-modified cobalt-based metal-organic framework.

3. The oxidation-resistant seawater desalination membrane according to claim 2, characterized in that, The mass ratio of the aminated cobalt-based metal-organic framework to 3-mercaptopropionic acid is (7-10):

1.

4. The oxidation-resistant seawater desalination membrane according to claim 1, characterized in that, The raw materials for the polysulfone base layer include: 20-25 parts polysulfone, 5-8 parts hydroxyapatite, 4-7 parts polyvinylpyrrolidone, and 60-75 parts N,N-dimethylformamide.

5. The oxidation-resistant seawater desalination membrane according to claim 1, characterized in that, The acyl chloride monomers are pyromellitic trimethylol chloride and 1,2-benzenedisulfonyl dichloride in a mass ratio of (2-4):

1.

6. The oxidation-resistant seawater desalination membrane according to claim 1, characterized in that, The additives include camphor sulfonic acid, sodium dodecyl sulfonate, and sodium hydroxide in a mass ratio of (3-5):1:

1.

7. The oxidation-resistant seawater desalination membrane according to claim 1, characterized in that, The isoparaffin solvent includes one or more of Isopar G, isododecane, Isopar H, isotetradecane, and isodecanane.

8. The method for preparing the oxidation-resistant seawater desalination membrane according to any one of claims 1-7, characterized in that, Includes the following steps: S1: Spray the polysulfone base casting solution onto the nonwoven fabric, let it stand, and then place the film in an aqueous coagulation solution to obtain the base film; S2: Disperse 4,4-diaminobiphenyl, o-phenylenediamine, mercapto-modified cobalt-based metal-organic framework and additives in water, and ultrasonically disperse for 30-40 min to obtain an aqueous phase solution; S3: Dissolve acyl chloride monomers in isoparaffin solvent, and ultrasonically disperse for 30-40 min to obtain an oil phase solution; S4: Immerse the upper surface of the base film in the aqueous phase solution for 60-90 s, then immerse the upper surface of the base film in the oil phase solution for 40-70 s, remove and dry to obtain an oxidation-resistant seawater desalination membrane.

9. The method for preparing the oxidation-resistant seawater desalination membrane according to claim 8, characterized in that, The drying process involves vacuum heat treatment at 60-75°C for 15-25 minutes.

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