High-flux chlorine-resistant and acid-alkali-resistant reverse osmosis composite membrane and preparation method thereof

Abstract

According to the high-flux chlorine-resistant and acid-alkali-resistant reverse osmosis composite membrane and the preparation method thereof, a porous supporting layer is sequentially immersed into a first water-phase solution, an organic-phase solution, a second water-phase solution and a third water-phase solution, ester bonds are formed through esterification reaction of water-soluble monomers, chlorine attack sites do not exist on the ester bonds, the chlorine resistance can be effectively improved, and the reverse osmosis composite membrane can be used for preparing the high-flux chlorine-resistant and acid-alkali-resistant reverse osmosis composite membrane. The reverse osmosis membrane with high flux and high desalination rate is obtained; the composite membrane is subjected to surface grafting modification, and the reverse osmosis active layer is covered with the protective layer, so that the chlorine resistance, acid resistance and alkali resistance of the membrane are greatly improved, and the service life of the membrane is prolonged; the preparation method has the characteristics of simplicity, convenience in operation, cheap and easily available raw materials, large-scale industrial production and the like, and can be widely applied to brackish water treatment and seawater desalination.

Description

Technical Field

[0001] The present application generally relates to the technical field of reverse osmosis composite membranes, and specifically relates to a high-throughput, chlorine-resistant, acid- and alkali-resistant reverse osmosis composite membrane and a preparation method thereof. Background Art

[0002] With the continuous growth of population and rapid industrialization, the demand for fresh water is increasing and becoming more urgent. To meet the challenge of water shortage worldwide, sustainable water management methods such as seawater desalination, wastewater treatment and water reuse must be adopted. Membrane-based water treatment technologies, including nanofiltration (NF) and reverse osmosis (RO), have attracted much attention due to their unique advantages over other processes in terms of simplicity, scalability, small footprint and energy efficiency, and also provide opportunities to solve the problem of water shortage.

[0003] For nearly half a century, polyamide thin-layer composite membranes (PA-TFC) have been the key to seawater desalination and wastewater reuse due to their excellent separation efficiency. PA-TFC membranes are usually formed on a porous substrate through an interfacial polymerization (IP) reaction, where two monomers react violently near the interface of two immiscible phases to form a dense cross-linked separation layer. This is a highly selective barrier that only allows water molecules to pass through effectively and retains the target solute.

[0004] Although PA-TFC membranes have been widely used in NF and RO, they still have many limitations. While improving the solute retention rate, it actually hinders the membrane permeability, especially in the presence of active chlorine, which leads to membrane deactivation and affects the membrane's treatment efficiency. Summary of the invention

[0005] In view of the above-mentioned defects or deficiencies in the prior art, it is desired to provide a high-flux chlorine-resistant, acid-resistant and alkali-resistant reverse osmosis composite membrane and a preparation method thereof, which is not restricted by traditional amine monomers, can not only control the structure of the separation layer to improve the permeability, but also increase the resistance to solutes in the composite structure of the membrane, and can improve the chlorine tolerance of the membrane.

[0006] In a first aspect, the present application provides a method for preparing a high-flux chlorine-resistant, acid-resistant and alkali-resistant reverse osmosis composite membrane, the method comprising:

[0007] (1) adding a catalyst having a mass concentration of 0.1% to 1% to an aqueous solution of a water-soluble monomer having a mass concentration of 0.05% to 8% to obtain a first aqueous phase solution, wherein the water-soluble monomer has a phenolic hydroxyl group structure;

[0008] (2) dissolving an acyl chloride aromatic compound having a mass concentration of 0.01% to 10% in an alkane solvent to obtain an organic phase solution;

[0009] (3) dissolving a polyaldehyde organic compound having a mass concentration of 0.02% to 1% in water, and adjusting the pH value of the solution to 8 to 12 to obtain a second aqueous phase solution;

[0010] (4) dissolving a hydroxy alcohol polymer having a mass concentration of 0.05% to 1% in water, and adjusting the pH value of the solution to 2 to 6 to obtain a third aqueous phase solution;

[0011] (5) The porous support layer is sequentially immersed in a first aqueous phase solution, an organic phase solution, a second aqueous phase solution, and a third aqueous phase solution to prepare a high-flux chlorine-resistant, acid-resistant, and alkali-resistant reverse osmosis composite membrane.

[0012] Optionally, the phenolic hydroxyl group is expressed as Formula I, and the water-soluble monomer is a structure containing at least one compound of Formula I;

[0013]

[0014] Wherein, the method for obtaining the first aqueous phase solution comprises:

[0015] Dissolving a water-soluble monomer having a mass concentration of 0.05% to 8% in water, adding a catalyst having a mass concentration of 0.1% to 1%, dissolving by magnetic stirring and performing ultrasonic defoaming to obtain the first aqueous phase solution;

[0016] Optionally, the mass concentration of the aqueous solution of the water-soluble monomer is 0.05% to 1%.

[0017] Optionally, the water-soluble monomer includes one or more of tannic acid, catechin, gallic acid, caffeic acid, curcumin, quercetin, anthocyanidin, resveratrol, vanillin, ellagic acid, ferulic acid and salicylic acid;

[0018] The catalyst includes one or more of triethylamine, pyridine, imidazole, tetramethylpiperidine, morpholine, cyclohexylamine, benzylamine, N,N-dimethylethylamine and thiourea.

[0019] Optionally, the acyl chloride aromatic compound is a structure containing at least one compound of formula II;

[0020]

[0021] The method for obtaining the organic phase solution comprises:

[0022] Dissolving an acyl chloride aromatic compound with a mass concentration of 0.01% to 10% in an alkane solvent, dissolving by magnetic stirring and performing ultrasonic defoaming to obtain the organic phase solution;

[0023] Optionally, the mass concentration of the acyl chloride aromatic compound is 0.01% to 1%.

[0024] Optionally, the acyl chloride aromatic compound includes one or more of trimesoyl chloride, isophthaloyl chloride, o-phthaloyl chloride, 5-isocyanatoisophthaloyl chloride, mm-biphenyltetracarboxylic acid chloride, om-biphenyltetracarboxylic acid chloride, op-biphenyltetracarboxylic acid chloride, 5-chloroformyloxyisophthaloyl chloride and biphenylhexacarboxylic acid chloride;

[0025] The alkane solvent includes one or more of n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, Isopar G, Isopar E, Isopar H and Isopar C.

[0026] Optionally, the method for obtaining the second aqueous phase solution comprises:

[0027] Dissolving a polyaldehyde organic compound with a mass concentration of 0.02% to 1% in water, and dissolving by magnetic stirring, adding an appropriate amount of sodium hydroxide to adjust the pH value of the solution to 8 to 12, dissolving by magnetic stirring again, and performing ultrasonic defoaming to obtain a second aqueous phase solution;

[0028] Wherein, the polyaldehyde organic compound includes one or more of glutaraldehyde, o-phthalaldehyde, terephthalaldehyde, adipaldehyde, malondialdehyde, succinaldehyde and salicylaldehyde.

[0029] Optionally, the method for obtaining the third aqueous phase solution comprises:

[0030] The hydroxy alcohol polymer with a mass concentration of 0.05% to 1% is heated and dissolved in water at 50° C. to 90° C., and after cooling, an appropriate amount of sulfuric acid is added to adjust the pH value of the solution to 2 to 6, and the second aqueous phase solution is obtained after dissolving by magnetic stirring and ultrasonic defoaming;

[0031] Wherein, the hydroxy alcohol polymer includes one or more of polyvinyl alcohol, polyethylene glycol and polypropylene glycol.

[0032] Optionally, the porous support layer is one or more of polysulfone, polyethersulfone, polyvinylidene fluoride, polypropylene, polytetrafluoroethylene and polyimide generated on the non-woven fabric by phase inversion method through an ultrafiltration membrane with a molecular weight cutoff in the range of 10kDa to 200kDa.

[0033] Optionally, the method for preparing a high-flux chlorine-resistant, acid-resistant and alkali-resistant reverse osmosis composite membrane comprises:

[0034] The porous support layer is immersed in the first aqueous phase solution for 1 min to 10 min, immersed in the organic phase solution for 30s to 90s after drying, rinsed and dried at 40°C to 90°C for 5min to 30min, then immersed in the second aqueous phase solution for 1min to 5min, immersed in the third aqueous phase solution for 1min to 10min after drying, cleaned and dried at 40°C to 90°C for 5min to 30min to obtain a high-flux chlorine-resistant and acid-alkali-resistant reverse osmosis composite membrane.

[0035] In a second aspect, the present application provides a high-throughput chlorine-resistant, acid-resistant and alkali-resistant reverse osmosis composite membrane, which is prepared by any of the methods described above.

[0036] The technical solution provided by the embodiments of the present application may have the following beneficial effects:

[0037] The high-flux chlorine-resistant, acid-resistant and alkali-resistant reverse osmosis composite membrane and the preparation method thereof provided in the embodiments of the present application utilize the esterification reaction of water-soluble monomers to form ester bonds. There are no chlorine attack sites on the ester bonds, which can effectively improve the chlorine resistance to obtain a reverse osmosis membrane with a high flux and a high desalination rate. The composite membrane is then surface-grafted and modified, and a protective layer is covered on the reverse osmosis active layer, thereby greatly improving the chlorine resistance, acid resistance and alkali resistance of the membrane and extending the life of the membrane. The method has the characteristics of simple preparation method, convenient operation, cheap and readily available raw materials, and large-scale industrial production, and can be widely used in brackish water treatment and seawater desalination. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Other features, objects and advantages of the present application will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0039] Figure 1 A schematic diagram of the structure of a high-throughput chlorine-resistant, acid-resistant and alkali-resistant reverse osmosis composite membrane provided in an embodiment of the present application;

[0040] Figure 2 A SEM cross-sectional view of a polyamide composite membrane provided as a comparative example of the present application;

[0041] Figure 3 This is a SEM cross-sectional view of a polyester composite film provided in Example 1 of the present application;

[0042] Figure 4 This is a SEM cross-sectional view of a polyester composite film with a protective layer provided in Example 2 of the present application;

[0043] Figure 5 This is a SEM cross-sectional view of a polyester composite film with a protective layer provided in Example 3 of the present application;

[0044] Figure 6This is a SEM cross-sectional view of a polyester composite film with a protective layer provided in Example 4 of the present application;

[0045] Figure 7 This is a SEM cross-sectional view of a polyester composite film with a protective layer provided in Example 5 of the present application. DETAILED DESCRIPTION

[0046] The present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It is also necessary to explain that, for ease of description, only the parts related to the invention are shown in the accompanying drawings.

[0047] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0048] After research, it was found that the existing PA-TFC membrane has the following disadvantages or shortcomings:

[0049] 1) There is a trade-off between membrane permeability and selectivity, which hinders the simultaneous improvement of membrane permeability and solute retention rate.

[0050] 2) Since the water permeability of the membrane is inversely proportional to the thickness of the membrane, and the rapid progress of the IP reaction and the high diffusion rate of the amine monomer result in the thickness of the separation layer ranging from tens of nanometers to hundreds of nanometers, it is difficult to accurately control the IP process.

[0051] 3) In the presence of active chlorine, the membrane will corrode the polyamide skeleton of the membrane through N-chlorination reaction of amide linkage (-CONH-) and ring chlorination reaction through Orton rearrangement, resulting in the cleavage of the cross-linked network of the active layer, thereby increasing the amount of salt and water passing through the membrane, causing membrane deactivation and affecting treatment efficiency.

[0052] The present application provides a method for preparing a high-flux chlorine-resistant, acid-resistant and alkali-resistant reverse osmosis composite membrane, the method comprising:

[0053] (1) Dissolving a water-soluble monomer with a mass concentration of 0.05% to 8% in water, adding a catalyst with a mass concentration of 0.1% to 1%, dissolving by magnetic stirring and performing ultrasonic defoaming to obtain the first aqueous phase solution.

[0054] In each embodiment of the present application, the amount of catalyst added is based on the total amount of the water-soluble monomer aqueous solution. The mass concentration of the water-soluble monomer aqueous solution in different embodiments can be adjusted as needed. Preferably, the water-soluble monomer is added in an amount with a mass concentration of 0.05% to 1% of the total mass of the aqueous solution.

[0055] (2) dissolving an acyl chloride aromatic compound with a mass concentration of 0.01% to 10% in an alkane solvent, dissolving by magnetic stirring and performing ultrasonic defoaming to obtain the organic phase solution.

[0056] In each embodiment of the present application, the amount of the acyl chloride aromatic compound added is based on the total amount of the organic phase solution. The mass concentration of the acyl chloride aromatic compound in different embodiments can be adjusted as needed. Preferably, the mass concentration of the acyl chloride aromatic compound is 0.01% to 1%.

[0057] (3) dissolving a polyaldehyde organic compound having a mass concentration of 0.02% to 1% in water, and dissolving by magnetic stirring, adding an appropriate amount of sodium hydroxide to adjust the pH value of the solution to 8 to 12, dissolving by magnetic stirring again, and performing ultrasonic defoaming to obtain a second aqueous phase solution.

[0058] In each embodiment of the present application, the amount of the polyaldehyde organic compound and the pH regulator added is based on the total amount of the second aqueous phase solution. The mass concentration of the acyl chloride aromatic compound in different embodiments can be adjusted as needed, preferably, the mass concentration of the polyaldehyde organic compound is 0.02% to 0.5%.

[0059] (4) Dissolving a hydroxy alcohol polymer having a mass concentration of 0.05% to 1% in water by heating at 50° C. to 90° C., adding an appropriate amount of sulfuric acid to adjust the pH value of the solution to 2 to 6 after cooling, dissolving by magnetic stirring and performing ultrasonic defoaming to obtain a second aqueous phase solution.

[0060] In each embodiment of the present application, the amount of hydroxy alcohol polymer and pH regulator added is based on the total amount of the third aqueous phase solution. The mass concentration of the acyl chloride aromatic compound in different embodiments can be adjusted as needed, preferably, the mass concentration of the polyaldehyde organic compound is 0.05% to 0.5%.

[0061] (5) The porous support layer is immersed in the first aqueous phase solution for 1 min to 10 min, immersed in the organic phase solution for 30 s to 90 s after drying, rinsed and dried at 40°C to 90°C for 5 min to 30 min, and then immersed in the second aqueous phase solution for 1 min to 5 min. After drying, it is immersed in the third aqueous phase solution for 1 min to 10 min, cleaned and dried at 40°C to 90°C for 5 min to 30 min to obtain a high-flux chlorine-resistant and acid-alkali-resistant reverse osmosis composite membrane.

[0062] Specifically, the porous support layer is one or more of polysulfone, polyethersulfone, polyvinylidene fluoride, polypropylene, polytetrafluoroethylene and polyimide generated on the non-woven fabric by phase inversion method through an ultrafiltration membrane with a molecular weight cutoff in the range of 10kDa to 200kDa.

[0063] It should be noted that in the embodiments of the present application, the porous support layer can be immersed in each solution by coating or immersion, and the present application does not limit this. For example, in the embodiments of the present application, a surface coating method can be used. When a protective layer is generated on the porous support layer, the thickness of the protective layer is related to the concentration and time. The higher the concentration, the thicker it is; the longer the time, the thicker it is, but there is a limit. In the embodiments of the present application, different immersion methods can be selected according to the requirements such as the thickness of the protective layer.

[0064] In addition, in the above preparation method, step (1), step (2), and step (3) can be performed simultaneously or sequentially, and the present application does not limit this.

[0065] Wherein, the phenolic hydroxyl group is expressed as Formula I, and the water-soluble monomer is a structure containing at least one compound of Formula I;

[0066]

[0067] Exemplarily, the water-soluble monomers include one or more of tannic acid, catechin, gallic acid, caffeic acid, curcumin, quercetin, anthocyanidin, resveratrol, vanillin, ellagic acid, ferulic acid and salicylic acid.

[0068] The acyl chloride aromatic compound is a structure containing at least one compound of formula II;

[0069]

[0070] Exemplarily, the acyl chloride aromatic compound includes one or more of trimesoyl chloride, isophthaloyl chloride, o-phthaloyl chloride, 5-isocyanatoisophthaloyl chloride, mm-biphenyltetracarboxylic acid chloride, om-biphenyltetracarboxylic acid chloride, op-biphenyltetracarboxylic acid chloride, 5-chloroformyloxyisophthaloyl chloride and biphenylhexacarboxylic acid chloride.

[0071] In the embodiment of the present application, a water-soluble monomer with a phenolic hydroxyl group can undergo an esterification reaction with an acyl chloride aromatic compound to form a reverse osmosis active layer on a porous support layer to form a polyester composite membrane, which is a reverse osmosis composite membrane. Compared with the polyamide composite membrane generated by using m-phenylenediamine, o-phenylenediamine or p-phenylenediamine monomers and acyl chloride aromatic compounds in the prior art, there is no chlorine attack site on the ester bond on the polyester composite membrane, which can effectively improve the chlorine resistance.

[0072] In the embodiments of the present application, different polyester stereostructures can be generated by changing the combination of water-soluble monomers and acyl chloride aromatic compounds, and different steric hindrances can be used to delay hydrolysis. Stereohindrance refers to the phenomenon of hindering or slowing down chemical reactions due to the limitation of spatial configuration within or between molecules. It is closely related to the spatial structure of the molecule. The larger the molecular volume, the more complex its internal and external spatial configuration, and the more obvious the steric hindrance effect.

[0073] The molecular geometry of the polyester stereostructure, such as straight chain, ring, branched, etc., will affect the interaction between molecules and the reaction process. Increasing steric hindrance can also prevent the membrane from hydrolyzing under alkaline conditions. For example, in the embodiment of the present application, the branched molecules generated by tannic acid and trimesoyl chloride may be difficult to approach other molecules due to steric hindrance, thereby slowing down the reaction rate.

[0074] Illustratively, the catalyst includes one or more of triethylamine, pyridine, imidazole, tetramethylpiperidine, morpholine, cyclohexylamine, benzylamine, N,N-dimethylethylamine and thiourea.

[0075] In the present application, by adding a catalyst to the first aqueous phase solution, the esterification reaction can be promoted or the interfacial mass transfer efficiency can be improved, and the formation of reverse osmosis can be accelerated. By adjusting the reaction pH value of the interfacial polymerization, the diffusion rate of the water-soluble monomer at the interface of the two phases is increased, which is beneficial to the formation of a dense reverse osmosis layer and enhances the chemical stability of the reverse osmosis.

[0076] Illustratively, the alkane solvent includes one or more of n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, Isopar G, Isopar E, Isopar H and Isopar C.

[0077] In the embodiments of the present application, alkane solvents with different viscosities and surface tensions can be selected. By changing the type of solvent, reverse osmosis composite membranes with different surface roughness can be generated. When low viscosity and low surface tension solvents are used, the surface morphology of the membrane is rougher; when high viscosity and high surface tension solvents are used, the surface morphology of the membrane is smoother, thereby obtaining membranes with different anti-pollution properties.

[0078] For example, the low viscosity and low surface tension solvent of n-decane can be used to generate a rougher membrane surface with good anti-fouling performance.

[0079] In an embodiment of the present application, a polyaldehyde organic compound in the second aqueous phase solution undergoes an aldol condensation reaction with the polyester of the reverse osmosis active layer, and then cross-links with a hydroxyl alcohol polymer in the third aqueous phase solution to form a protective layer on the surface of the polyester composite membrane layer. In the present application, a graft copolymerization method is used to form a protective layer on the surface of the composite membrane to prevent the reverse osmosis active layer on the membrane surface from swelling, thereby improving the protective effect.

[0080] It should also be noted that in the embodiments of the present application, the protective layer is a protective layer formed by a reverse osmosis active layer generated by a first aqueous phase solution and an organic phase solution and a surface coating generated by a second aqueous phase solution and a third aqueous phase solution. The protective effect is achieved by wrapping the reverse osmosis active layer with the coating to obtain a high-throughput, chlorine-resistant, acid- and alkali-resistant reverse osmosis composite membrane.

[0081] Specifically, the polyaldehyde organic compound includes one or more of glutaraldehyde, o-phthalaldehyde, terephthalaldehyde, adipaldehyde, malondialdehyde, succinaldehyde and salicylaldehyde. The hydroxy alcohol polymer includes one or more of polyvinyl alcohol, polyethylene glycol and polypropylene glycol.

[0082] like Figure 1 As shown, in the present application, a protective layer 200 is arranged on the upper layer of the porous support 100, and the protective layer 200 is used to prevent the reverse osmosis skeleton from being corroded by chlorine or to reduce the chlorination sites in the reverse osmosis chain, thereby improving the tolerance of the reverse osmosis composite membrane to chlorine, while enhancing or maintaining the membrane separation performance; dirt can be adsorbed to the membrane surface through hydrophobic action, hydrogen bonding, van der Waals attraction and electrostatic action, and the protective layer can improve the anti-fouling performance of the membrane by reducing the adsorption effect between the dirt and the membrane surface.

[0083] Comparative Example

[0084] Preparation of polyamide composite membrane

[0085] Prepare a 2% m-phenylenediamine aqueous solution: add 2 g of m-phenylenediamine into 100 mL of water, stir magnetically to dissolve, and defoam by ultrasonic for 30 seconds to obtain an aqueous phase solution.

[0086] Prepare 0.1% trimesoyl chloride solution: add 0.1 g of trimesoyl chloride into 100 mL of n-hexane and stir magnetically to dissolve to obtain an organic phase solution.

[0087] After the polyethersulfone membrane with a molecular weight cutoff of 20 kDa was immersed in the aqueous solution for 2 minutes, the excess solution was removed by rolling with a rubber roller until there were no obvious water drops on the membrane surface, and then the membrane was immersed in the organic solution for interfacial polymerization for 60 seconds. The membrane surface was cleaned with n-hexane and dried in an oven at 60°C for 5 minutes to obtain a polyamide composite membrane. The SEM cross-sectional view of the product is shown in FIG. Figure 2 shown.

[0088] Example 1

[0089] Preparation of polyester composite film

[0090] Prepare 0.5% tannic acid aqueous solution: add 0.5 g of tannic acid into 100 mL of water, stir magnetically to dissolve, add 200 μL of triethylamine, stir magnetically to dissolve again, and defoam by ultrasonic for 30 s to obtain an aqueous solution.

[0091] Prepare 0.1% trimesoyl chloride solution: add 0.1 g of trimesoyl chloride into 100 mL of n-hexane and stir magnetically to dissolve to obtain an organic phase solution.

[0092] After the polyethersulfone membrane with a molecular weight cutoff of 20 kDa was immersed in the aqueous solution for 2 minutes, the excess solution was removed by rolling with a rubber roller until there were no obvious water drops on the membrane surface, and then the membrane was immersed in the organic solution for interfacial polymerization for 60 seconds. The membrane surface was cleaned with n-hexane and dried in an oven at 60°C for 5 minutes to obtain a reverse osmosis composite membrane. The SEM cross-sectional view of the product is shown in FIG. Figure 3 shown.

[0093] Example 2

[0094] Preparation of polyester composite film with protective layer

[0095] Prepare a 0.5% tannic acid aqueous solution: add 0.5 g of tannic acid to 100 mL of water, stir magnetically to dissolve, add 200 μL of triethylamine, stir magnetically to dissolve again, and defoam by ultrasonication for 30 seconds to obtain a first aqueous phase solution.

[0096] Prepare 0.1% trimesoyl chloride solution: add 0.1 g of trimesoyl chloride into 100 mL of n-hexane and stir magnetically to dissolve to obtain an organic phase solution.

[0097] Prepare 0.04% glutaraldehyde aqueous solution: add 160 μL of 25% glutaraldehyde solution to 100 mL of water, stir magnetically to dissolve, add appropriate amount of sodium hydroxide, stir magnetically to dissolve again, adjust pH value to 8-9, and ultrasonically defoam for 30 seconds to obtain a second aqueous phase solution.

[0098] Prepare 0.1% polyvinyl alcohol aqueous solution: add 0.1 g of polyvinyl alcohol to 100 mL of water, heat to 90° C. until dissolved, add appropriate amount of sulfuric acid, stir magnetically to dissolve again, adjust the pH value to 3-4, and ultrasonically defoam for 30 seconds to obtain a third aqueous phase solution.

[0099] After the polyethersulfone membrane with a molecular weight cutoff of 20 kDa was immersed in the first aqueous phase solution for 2 minutes, the excess solution was removed with a rubber roller until there were no obvious water drops on the membrane surface, and then the membrane was immersed in an organic solution for interfacial polymerization for 60 seconds. The membrane surface was cleaned with n-hexane and dried in an oven at 60°C for 5 minutes. Then, the membrane was immersed in the second aqueous phase solution for grafting for 5 minutes, and the excess solution was removed with a rubber roller until there were no obvious water drops on the membrane surface. Then, the membrane was immersed in the third aqueous phase solution for protective layer coating for 2 minutes. The membrane surface was cleaned with deionized water and dried in an oven at 60°C for 5 minutes to obtain a reverse osmosis composite membrane with a protective layer. The SEM cross-sectional view of the product is shown in the figure. Figure 4 shown.

[0100] Example 3

[0101] Preparation of polyester composite film with protective layer

[0102] Prepare a 0.8% caffeic acid aqueous solution: add 0.8 g of caffeic acid to 100 mL of water, stir magnetically to dissolve, add 0.1 g of imidazole, stir magnetically to dissolve again, and ultrasonically defoam for 30 seconds to obtain a first aqueous phase solution.

[0103] Prepare a 0.2% isophthaloyl chloride solution: add 0.2 g of isophthaloyl chloride into 100 mL of n-octane and stir magnetically to dissolve to obtain an organic phase solution.

[0104] Prepare 0.05% malondialdehyde aqueous solution: add 0.05 g malondialdehyde into 100 mL water, stir magnetically to dissolve, add appropriate amount of sodium hydroxide, stir magnetically to dissolve again, adjust pH value to 8-9, and defoam by ultrasonic for 30 seconds to obtain the second aqueous phase solution.

[0105] Prepare 0.15% polyethylene glycol aqueous solution: add 0.15 g polyethylene glycol to 100 mL water, heat to 80° C. until dissolved, add appropriate amount of sulfuric acid, stir magnetically to dissolve again, adjust pH to 3-4, and ultrasonically defoam for 30 seconds to obtain the third aqueous phase solution.

[0106] After the polyethersulfone membrane with a molecular weight cutoff of 50 kDa was immersed in the first aqueous phase solution for 2 minutes, the excess solution was removed with a rubber roller until there were no obvious water drops on the membrane surface, and then the membrane was immersed in an organic solution for interfacial polymerization for 90 seconds, and the membrane surface was cleaned with n-octane, and dried in an oven at 50°C for 10 minutes, and then the membrane was immersed in the second aqueous phase solution for grafting for 3 minutes, and the excess solution was removed with a rubber roller until there were no obvious water drops on the membrane surface, and then the membrane was immersed in the third aqueous phase solution for protective layer coating for 1 minute, and the membrane surface was cleaned with deionized water. After drying in an oven at 50°C for 10 minutes, a reverse osmosis composite membrane with a protective layer was obtained. The SEM cross-sectional view of the product is shown in the figure. Figure 5 shown.

[0107] Example 4

[0108] Preparation of polyester composite film with protective layer

[0109] Prepare a 1.0% curcumin aqueous solution: add 1.0 g of curcumin to 100 mL of water, stir magnetically to dissolve, add 0.15 g of thiourea, stir magnetically to dissolve again, and defoam by ultrasonication for 30 seconds to obtain a first aqueous phase solution.

[0110] Prepare 0.2% 5-isocyanatoisophthaloyl chloride solution: add 0.2 g of 5-isocyanatoisophthaloyl chloride into 100 mL of n-heptane and stir magnetically to dissolve to obtain an organic phase solution.

[0111] Prepare 0.06% salicylaldehyde aqueous solution: add 0.06 mL of salicylaldehyde to 100 mL of water, stir magnetically to dissolve, add appropriate amount of sodium hydroxide, stir magnetically to dissolve again, adjust pH value to 8-9, and ultrasonically defoam for 30 seconds to obtain a second aqueous phase solution.

[0112] Prepare 0.09% polypropylene glycol aqueous solution: add 0.09 g of polypropylene glycol to 100 mL of water, heat to 70° C. until dissolved, add appropriate amount of sulfuric acid, stir magnetically to dissolve again, adjust the pH value to 3-4, and ultrasonically defoam for 30 seconds to obtain a third aqueous phase solution.

[0113] After the polysulfone membrane with a molecular weight cutoff of 20 kDa was immersed in the first aqueous phase solution for 2 minutes, the excess solution was removed with a rubber roller until there were no obvious water drops on the membrane surface, and then the membrane was immersed in an organic solution for interfacial polymerization for 70 seconds. The membrane surface was cleaned with n-heptane and dried in an oven at 70°C for 5 minutes. Then, the membrane was immersed in the second aqueous phase solution for grafting for 4 minutes, and the excess solution was removed with a rubber roller until there were no obvious water drops on the membrane surface. Then, the membrane was immersed in the third aqueous phase solution for protective layer coating for 3 minutes. The membrane surface was cleaned with deionized water and dried in an oven at 70°C for 5 minutes to obtain a reverse osmosis composite membrane with a protective layer. The SEM cross-sectional view of the product is shown in the figure. Figure 6 shown.

[0114] Example 5

[0115] Preparation of polyester composite film with protective layer

[0116] Prepare a 0.4% catechin aqueous solution: add 0.4 g of catechin to 100 mL of water, stir magnetically to dissolve, add 0.15 g of morpholine, stir magnetically to dissolve again, and defoam by ultrasonic for 30 seconds to obtain a first aqueous phase solution.

[0117] Prepare 0.08% phthaloyl chloride solution: add 0.08 g of phthaloyl chloride into 100 mL of n-decane and stir magnetically to dissolve to obtain an organic phase solution.

[0118] Prepare 0.15% adipaldehyde aqueous solution: add 150 μL of adipaldehyde to 100 mL of water, stir magnetically to dissolve, add appropriate amount of sodium hydroxide, stir magnetically to dissolve again, adjust pH value to 8-9, and defoam by ultrasonic for 30 seconds to obtain the second aqueous phase solution.

[0119] Prepare 0.1% polyethylene glycol aqueous solution: add 0.1 g polyethylene glycol to 100 mL water, heat to 80° C. until dissolved, add appropriate amount of sulfuric acid, stir magnetically to dissolve again, adjust pH to 3-4, and ultrasonically defoam for 30 seconds to obtain the third aqueous phase solution.

[0120] After the polyethersulfone membrane with a molecular weight cutoff of 40 kDa was immersed in the first aqueous phase solution for 2 minutes, the excess solution was removed with a rubber roller until there were no obvious water drops on the membrane surface, and then the membrane was immersed in an organic solution for interfacial polymerization reaction for 40 seconds, and the membrane surface was cleaned with n-decane, and dried in an oven at 60°C for 7 minutes, and then the membrane was immersed in the second aqueous phase solution for grafting for 4 minutes, and the excess solution was removed with a rubber roller until there were no obvious water drops on the membrane surface, and then the membrane was immersed in the third aqueous phase solution for protective layer coating for 2 minutes, and the membrane surface was cleaned with deionized water. After drying in an oven at 60°C for 7 minutes, a reverse osmosis composite membrane with a protective layer was obtained. The SEM cross-sectional view of the product is shown in the figure. Figure 7 shown.

[0121] All the membranes prepared above were tested using a cross-flow reverse osmosis filtration system. The test indicators included water permeability and salt retention rate. The test method was as follows:

[0122] The membrane was placed in the membrane assembly, and 2000ppm NaCl aqueous solution was filtered at a temperature of 24°C, a pH value of 8-9, and a pressure of 2MPa. After compacting the membrane sample for 1 hour, the pressure was adjusted to 1.6MPa. After stabilization, the permeate volume and the conductivity of the effluent and influent were tested every 10 minutes, and the corresponding water permeation and salt retention rate were calculated.

[0123] The membrane sample was soaked in a 2000ppm NaClO aqueous solution for one week. After cleaning the membrane surface, the 2000ppm NaCl aqueous solution was filtered at a temperature of 24°C, a pH value of 8-9, and a pressure of 2MPa. After compacting the membrane sample for 1 hour, the pressure was adjusted to 1.6MPa. After stabilization, the permeate volume and the conductivity of the effluent and influent were tested every 10 minutes, and the corresponding water permeation and salt retention rate after chlorine pollution were calculated. The membrane performance data obtained from the test are shown in Table 1.

[0124] Table 1 Properties of the films obtained in the comparative examples and examples 1-5

[0125]

[0126] From the above comparison, it can be seen that the water-soluble monomer reverse osmosis composite membrane has generally higher water permeability than the polyamide composite membrane, and the salt retention rate can also be maintained at a high level; although the water permeability decreases slightly after adding the coating, it can well protect the membrane from chlorine attack and keep the membrane separation performance unaffected.

[0127] The water-soluble monomer reverse osmosis composite membrane containing a protective layer of the present invention has high water permeability and high desalination rate. The presence of the protective layer can also greatly improve the chlorine resistance of the membrane and extend the life of the membrane. It has the characteristics of simple preparation method, convenient operation, cheap and easy-to-obtain raw materials, large-scale industrial production, etc., and can be widely used in brackish water treatment and seawater desalination.

[0128] It should be understood that the terms "first" and "second" in the embodiments of the present application are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0129] Unless otherwise defined, the technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art in the technical field of the present invention. The terms used herein are only for describing specific implementation purposes and are not intended to limit the present invention. Terms such as "setting" and the like appearing in this article can mean that one component is directly attached to another component, or that one component is attached to another component through an intermediate. Features described in this article in one embodiment may be applied to another embodiment alone or in combination with other features, unless the feature is not applicable in the other embodiment or otherwise specified.

[0130] The present invention has been described through the above-mentioned embodiments, but it should be understood that the above-mentioned embodiments are only for the purpose of example and illustration, and are not intended to limit the present invention to the described embodiments. It can be understood by those skilled in the art that more variations and modifications can be made according to the teachings of the present invention, and these variations and modifications all fall within the scope of the protection claimed by the present invention.

Claims

1. A method for preparing a high-throughput chlorine-resistant, acid-resistant and alkali-resistant reverse osmosis composite membrane, characterized in that: The method comprises: (1) adding a catalyst having a mass concentration of 0.1% to 1% to an aqueous solution of a water-soluble monomer having a mass concentration of 0.05% to 8% to obtain a first aqueous phase solution, wherein the water-soluble monomer has a phenolic hydroxyl group structure; (2) dissolving an acyl chloride aromatic compound having a mass concentration of 0.01% to 10% in an alkane solvent to obtain an organic phase solution; (3) dissolving a polyaldehyde organic compound having a mass concentration of 0.02% to 1% in water, and adjusting the pH value of the solution to 8 to 12 to obtain a second aqueous phase solution; (4) dissolving a hydroxy alcohol polymer having a mass concentration of 0.05% to 1% in water, and adjusting the pH value of the solution to 2 to 6 to obtain a third aqueous phase solution; (5) The porous support layer is sequentially immersed in a first aqueous phase solution, an organic phase solution, a second aqueous phase solution, and a third aqueous phase solution to prepare a high-flux chlorine-resistant, acid-resistant, and alkali-resistant reverse osmosis composite membrane.

2. The method according to claim 1, characterized in that The phenolic hydroxyl group is expressed as Formula I, and the water-soluble monomer is a structure containing at least one compound of Formula I; Wherein, the method for obtaining the first aqueous phase solution comprises: Dissolving a water-soluble monomer having a mass concentration of 0.05% to 8% in water, adding a catalyst having a mass concentration of 0.1% to 1%, dissolving by magnetic stirring and performing ultrasonic defoaming to obtain the first aqueous phase solution; Optionally, the mass concentration of the aqueous solution of the water-soluble monomer is 0.05% to 1%.

3. The method according to claim 1, characterized in that The water-soluble monomers include one or more of tannic acid, catechin, gallic acid, caffeic acid, curcumin, quercetin, anthocyanidin, resveratrol, vanillin, ellagic acid, ferulic acid and salicylic acid; The catalyst includes one or more of triethylamine, pyridine, imidazole, tetramethylpiperidine, morpholine, cyclohexylamine, benzylamine, N,N-dimethylethylamine and thiourea.

4. The method according to claim 1, characterized in that: The acyl chloride aromatic compound is a structure containing at least one compound of formula II; The method for obtaining the organic phase solution comprises: Dissolving an acyl chloride aromatic compound with a mass concentration of 0.01% to 10% in an alkane solvent, dissolving by magnetic stirring and performing ultrasonic defoaming to obtain the organic phase solution; Optionally, the mass concentration of the acyl chloride aromatic compound is 0.01% to 1%.

5. The method according to claim 1, characterized in that The acyl chloride aromatic compound includes one or more of trimesoyl chloride, isophthaloyl chloride, o-phthaloyl chloride, 5-isocyanatoisophthaloyl chloride, mm-biphenyltetracarboxylic acid chloride, om-biphenyltetracarboxylic acid chloride, op-biphenyltetracarboxylic acid chloride, 5-chloroformyloxyisophthaloyl chloride and biphenylhexacarboxylic acid chloride; The alkane solvent includes one or more of n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, Isopar G, Isopar E, Isopar H and Isopar C.

6. The method according to claim 1, characterized in that The method for obtaining the second aqueous phase solution comprises: Dissolving a polyaldehyde organic compound with a mass concentration of 0.02% to 1% in water, and dissolving by magnetic stirring, adding an appropriate amount of sodium hydroxide to adjust the pH value of the solution to 8 to 12, dissolving by magnetic stirring again, and performing ultrasonic defoaming to obtain a second aqueous phase solution; Wherein, the polyaldehyde organic compound includes one or more of glutaraldehyde, o-phthalaldehyde, terephthalaldehyde, adipaldehyde, malondialdehyde, succinaldehyde and salicylaldehyde.

7. The method according to claim 1, characterized in that The method for obtaining the third aqueous phase solution comprises: The hydroxy alcohol polymer with a mass concentration of 0.05% to 1% is heated and dissolved in water at 50° C. to 90° C., and after cooling, an appropriate amount of sulfuric acid is added to adjust the pH value of the solution to 2 to 6, and the second aqueous phase solution is obtained after dissolving by magnetic stirring and ultrasonic defoaming; Wherein, the hydroxy alcohol polymer includes one or more of polyvinyl alcohol, polyethylene glycol and polypropylene glycol.

8. The method according to claim 1, characterized in that The porous support layer is an ultrafiltration membrane with a molecular weight cutoff in the range of 10kDa to 200kDa, and one or more of polysulfone, polyethersulfone, polyvinylidene fluoride, polypropylene, polytetrafluoroethylene and polyimide are generated on the non-woven fabric by phase inversion method.

9. The method according to claim 1, characterized in that: The method for preparing a high-flux chlorine-resistant, acid-resistant and alkali-resistant reverse osmosis composite membrane comprises: The porous support layer is immersed in the first aqueous phase solution for 1 min to 10 min, immersed in the organic phase solution for 30s to 90s after drying, rinsed and dried at 40°C to 90°C for 5min to 30min, then immersed in the second aqueous phase solution for 1min to 5min, immersed in the third aqueous phase solution for 1min to 10min after drying, cleaned and dried at 40°C to 90°C for 5min to 30min to obtain a high-flux chlorine-resistant and acid-alkali-resistant reverse osmosis composite membrane.

10. A high-throughput chlorine-resistant, acid-resistant and alkali-resistant reverse osmosis composite membrane, characterized in that: It is prepared by the method according to any one of claims 1 to 9.

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