Method for producing a reverse osmosis membrane

Abstract

The application belongs to the technical field of semi-permeable membrane preparation, and particularly relates to a preparation method of a reverse osmosis membrane. The preparation method comprises the following steps: (1) cleaning a support layer for standby; blending a binary amine, a modified additive and water to obtain an aqueous phase for standby; blending an aromatic acyl chloride, a co-solvent and an organic solvent to obtain an oil phase A for standby, and blending a dynamic crosslinking monomer and an organic solvent to obtain an oil phase B for standby; (2) placing the support layer at the bottom of a container, mixing the aqueous phase and a catalyst uniformly, and then adding them into the container; adding the oil phase A into the container to perform a first condensation reaction, adding the oil phase B to perform a second condensation reaction after the reaction is completed, and obtaining the reverse osmosis membrane through post-processing. The application introduces a Schiff base-phenyl ring bridging structure and a dynamic crosslinking bond imine bond through a dynamic crosslinking monomer, and cooperates with dodecyl ethoxy sulfobetaine, so that the reverse osmosis membrane has good desalination rate and water flux while improving the chlorine resistance and pollution resistance of the reverse osmosis membrane.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semi-permeable membrane preparation, and particularly relates to a preparation method of a reverse osmosis membrane. BACKGROUND

[0002] Reverse osmosis is a membrane separation sewage treatment method, which refers to applying a pressure higher than the water permeation pressure to sewage water to make water molecules in the sewage flow from a high-concentration region (the sewage side) to a low-concentration region (the clean water side) through a membrane material against the natural permeation tendency, thereby improving the sewage treatment efficiency. The membrane material used is also called a reverse osmosis membrane or an RO membrane, which is a composite membrane material for intercepting impurities such as salts, organic matter and microorganisms in sewage based on the principle of reverse osmosis, and is currently basically prepared by a free interface polymerization method. The membrane structure of the reverse osmosis membrane generally includes a non-woven fabric layer, a support layer and an active separation layer. The support layer is a composite material of various materials such as polysulfone, polyether ketone and polyether sulfone, which mainly provides an attachment carrier during interface polymerization and also has a certain selective permeability. The active separation layer, as the core component of the reverse osmosis membrane, is mainly responsible for removing pollutants, and polyamide is commonly used at present.

[0003] With the increasing strictness of the requirements for the purity and efficiency of sewage purification, polyamide materials are more widely used due to their advantages of high desalination rate, high flux and high pressure resistance. However, the polyamide itself has insufficient anti-pollution property, so that the purification efficiency is often difficult to reach the theoretical value. In addition, the N-H bond exposed in the polyamide structure is easily attacked by free chlorine ions, which causes the decomposition of the polyamide and affects the service life of the reverse osmosis membrane. How to improve the defects of polyamide is one of the concerns of the industry and academia. In particular, there is a trade-off effect between high desalination rate, high flux, and resistance to pollution and chlorine, so people hope to find a method that can balance the trade-off effect and have good desalination rate and water flux on the one hand, and good resistance to pollution and chlorine on the other hand, with a good service life.

[0004] Chinese Patent CN109012186A discloses a preparation method of an anti-pollution modified reverse osmosis membrane, which comprises the following steps: polymerizing hydrochloric acid dopamine on the surface of an ultrafiltration base membrane to obtain a modified ultrafiltration base membrane coated with dopamine; contacting the modified ultrafiltration base membrane with aromatic polyamines; and then contacting the modified ultrafiltration base membrane with aromatic polyacyl chlorides to perform substitution reaction between the aromatic polyamines and the aromatic polyacyl chlorides.

[0005] The patent has the following drawbacks: the polydopamine formed by the self-polymerization of dopamine hydrochloride is a non-crosslinked polymer with a crosslinking degree much smaller than that of polyamide, resulting in a much larger molecular swelling coefficient of polydopamine than that of polyamide; moreover, the polydopamine and polyamide are simply attached to each other, and the polyamide is not etched by acid or alkali or chemically grafted. When both are immersed in a water environment for a long time, the dopamine hydrochloride membrane layer will easily fall off due to the swelling effect. The swelling-shrinkage cycle will cause fatigue damage at the interface between the coating and the polyamide, making it difficult to guarantee the life of the reverse osmosis membrane.

[0006] Chinese patent CN110201563A discloses a method for preparing a chlorine-resistant and fouling-resistant polyamide reverse osmosis membrane, including preparing two types of polyamide reverse osmosis membranes; preparing an organic nanofiber dispersion for later use; preparing an MOFs aqueous dispersion for later use; and performing surface modification on the two types of polyamide reverse osmosis membranes to obtain a chlorine-resistant and fouling-resistant polyamide reverse osmosis membrane.

[0007] The preparation of organic nanofiber dispersions in this patent requires multiple steps such as grinding, centrifugation, and filtration. The preparation of MOFs aqueous dispersions involves microwave reaction and multiple centrifugal washing. The multi-step modification results in low production efficiency, cumbersome process, and long single modification cycle (each soaking, rinsing, and drying takes several hours), making it difficult to carry out continuous production. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing a reverse osmosis membrane, which further improves the chlorine resistance and fouling resistance of the reverse osmosis membrane, while enabling the reverse osmosis membrane to have both good desalination rate and water flux.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] The method for preparing the reverse osmosis membrane according to the present invention includes the following steps:

[0011] (1) Clean the support layer for later use; mix the diamine, the modifier and water to obtain the aqueous phase for later use; mix the aromatic acyl chloride, the cosolvent and the organic solvent A to obtain the oil phase A for later use; mix the dynamic crosslinking monomer with the organic solvent B to obtain the oil phase B for later use.

[0012] (2) Place the support layer at the bottom of the container, mix the aqueous phase and the catalyst, and add them into the container; add oil phase A into the container for a first condensation reaction, and after the reaction is complete, add oil phase B for a second condensation reaction, and then obtain the reverse osmosis membrane after post-treatment.

[0013] in:

[0014] In step (1), the support layer is one of polysulfone, polyethersulfone, polyetherketone or sulfonated polyethersulfone, and the thickness of the support layer is 45~70μm; during cleaning, the support layer is placed in the cleaning solution and water in sequence for ultrasonic cleaning.

[0015] In step (1), the cleaning solution used during cleaning is prepared according to a mass ratio of fatty alcohol polyoxyethylene ether to water of 1:(30~40), the mass ratio of the support layer to the cleaning solution is 1000:(2000~2500), the mass ratio of the support layer to water is 1000:(2500~3000), the ultrasonic power in the cleaning solution is 180~220W, and the ultrasonic time is 3~5min; the ultrasonic power in the water is 180~220W, and the ultrasonic time is 3~5min.

[0016] In step (1), the diamine is m-phenylenediamine, the modifying agent is dodecyl ethoxysulfobetaine, the aromatic acyl chloride is trimesoyl chloride, the dynamic crosslinking monomer is 4-aminobenzaldehyde, organic solvent A and organic solvent B are both N,N-dimethylformamide, and the cosolvent is prepared by mixing 1,3-dimethyl-2-imidazolinone and N,N-dimethylpropenylurea in a mass ratio of (320~400):(90~110).

[0017] In step (1), the mass ratio of the support layer, diamine, modifier and water is 1000:450:(80~100):(4500~5500); the mass ratio of the support layer, aromatic acyl chloride, cosolvent and organic solvent A is 1000:(680~720):(410~510):(5800~6800); the mass ratio of the support layer, dynamic crosslinking monomer and organic solvent B is 1000:(520~560):(1800~2000).

[0018] In step (2), the catalyst is sodium p-toluenesulfonate and 4-dimethylaminopyridine. The mass ratio of the modifier, sodium p-toluenesulfonate and 4-dimethylaminopyridine in the aqueous phase is (80~100):(24~40):(56~65).

[0019] In step (2), the mixing temperature is 0~5℃. After the aqueous phase and catalyst are mixed and added to the container, the liquid level is 1.8~3.5mm higher than the support layer height.

[0020] In step (2), the temperature of the first condensation reaction is 35~45℃ and the time of the first condensation reaction is 30~40min; the temperature of the second condensation reaction is 30~40℃ and the time of the second condensation reaction is 35~45min.

[0021] In step (2), the post-treatment includes water washing and vacuum drying. The water washing temperature is 30~40℃ and the water washing time is 40~60min. The vacuum drying pressure is 0.03~0.04MPa, the vacuum drying temperature is 45~50℃, and the vacuum drying time is 4~6h.

[0022] The membrane product includes a reverse osmosis membrane, a feed water channel network, an outlet water pipe, and a fiberglass shell. The reverse osmosis membrane consists of modified polyamide and a support layer. The modified polyamide portion of the reverse osmosis membrane is placed outwards and alternately stacked with the feed water channel network. It is then rolled around the outlet water pipe. During rolling, both ends of the reverse osmosis membrane are fixed with sealant. After rolling, both ends are fixed with end caps. Sealant is injected to fill the gap between the end caps and the reverse osmosis membrane. After heating and curing, the entire membrane is installed in the fiberglass shell to obtain the membrane product.

[0023] The sealant is made of polyurethane, with a curing temperature of 60~70℃ and a curing time of 75~95min.

[0024] The beneficial effects of this invention are as follows:

[0025] (1) The present invention introduces a dynamic crosslinking monomer, which forms amide and imine bonds with m-phenylenediamine and pyromellitic chloride through acyl chloride-amine condensation and aldehyde-amine condensation, thereby introducing a Schiff base-benzene ring bridging structure and dynamic crosslinking bond, i.e. imine bond, to obtain modified polyamide, thereby improving the chlorine resistance of traditional polyamide.

[0026] The Schiff base-benzene ring bridging structure enhances the packing density of the polymerized molecular chains, reduces the diffusion rate of chlorine within the material, and lowers the contact frequency, thereby reducing the breakage of amide bonds within the modified polyamide. Simultaneously, the nitrogen atom in the imine bond is conjugated with the benzene ring, further reducing the reactivity of the imine bond, making it less susceptible to chlorine damage compared to amide bonds. In an acidic environment (high-chlorine environment), the imine bond undergoes hydrolytic breakage. During regeneration, the environment returns to neutral, and the free aldehyde or ketone recombines with the amine, regenerating the imine bond, reconstructing the crosslinking network, restoring the material's mechanical properties, and imparting dynamic crosslinking characteristics. The membrane material has a certain shape memory function, making it less prone to deformation in high chlorine environments. When subjected to pressure, pollution, or slight chemical erosion, the modified polyamide network can dissipate energy or adapt to changes through bond recombination, reducing permanent damage. This helps to balance the trade-off effect between high crosslinking degree (higher crosslinking degree results in greater amide group density and higher desalination efficiency) and flexibility / chlorine resistance. On the one hand, it maintains a high amide group density, and on the other hand, the dynamic crosslinking structure can provide the modified polyamide with chlorine resistance, which is beneficial to maintaining the stability of the long-term water flux and desalination rate of the polyamide.

[0027] (2) The modifying agent of this invention is an amphoteric surfactant (e.g., dodecyl ethoxysulfonyl betaine). When blended with m-phenylenediamine, the amphoteric polar groups in the amphoteric surfactant (e.g., the sulfonic acid groups and quaternary ammonium groups (-N) in dodecyl ethoxysulfonyl betaine) +(CH3)2-) imparts strong hydrophilicity to m-phenylenediamine, trimesoyl chloride, and dynamic crosslinking monomers. Through electrostatic interaction, it improves the contact between m-phenylenediamine, trimesoyl chloride, and dynamic crosslinking monomers at the oil-water interface, thereby enhancing the uniformity of the modified polyamide. During the formation of the modified polyamide, the long-chain alkyl and quaternary ammonium groups of dodecyl ethoxysulfobetaine are enriched on the surface of the modified polyamide through molecular entanglement and electrostatic interaction, forming a sulfonic acid-based hydrophilic layer. This hydrophilic surface reduces the adsorption force of pollutants (especially organic matter, colloids, and microorganisms) on the membrane surface, thereby improving the antifouling properties of the reverse osmosis membrane.

[0028] (3) The present invention uses a co-solvent (1,3-dimethyl-2-imidazolinone and N,N-dimethylpropenylurea). 1,3-dimethyl-2-imidazolinone can improve the solubility and diffusion ability of trimesoyl chloride in the oil phase. The urea group in N,N-dimethylpropenylurea acts as a hydrogen bond acceptor, promoting diffusion between the water and oil phases and reducing the viscosity of the oil phase. The two work together to reduce the interfacial tension between oil and water, promote the rapid dispersion of trimesoyl chloride and dynamic crosslinking monomers in the aqueous phase, and make the dynamic crosslinking structure more uniformly distributed in the modified polyamide, thereby improving the overall chlorine resistance and mechanical strength. The polar environment formed by the co-solvent is conducive to attracting the sulfonic acid groups (-SO3) of dodecylethoxysulfonyl betaine. - The polar end is closer to the oil-water interface, which is conducive to the formation of the sulfonic acid hydrophilic layer and further improves the antifouling properties of the reverse osmosis membrane. Attached Figure Description

[0029] Figure 1 This is a SEM image of the reverse osmosis membrane in Example 1. Detailed Implementation

[0030] The present invention will now be described and illustrated in detail with reference to the embodiments.

[0031] Example 1

[0032] A cleaning solution was prepared by mixing fatty alcohol polyoxyethylene ether and deionized water at a mass ratio of 1:35. 1000g of a 55μm thick polysulfone support layer was placed in 2200g of the cleaning solution and sonicated at 200W for 3.5min. The layer was then removed, placed in 2600g of deionized water, and sonicated at 200W for 3.5min. The layer was then dried and set aside. 450g of m-phenylenediamine was weighed and added to 5kg of deionized water and mixed thoroughly. Then, 90g of dodecylethoxysulfonate was added and mixed thoroughly to obtain the aqueous phase. 700g of trimesoyl chloride was weighed and added to 5.95kg of N,N-dimethylformamide. Then, 360g of the co-solvent 1,3-dimethyl-2-imidazolinone and 100g of N,N-dimethylpropenylurea were added and mixed thoroughly to obtain oil phase A. 540g of 4-aminobenzaldehyde was weighed and added to 1.95kg of N,N-dimethylformamide and mixed thoroughly to obtain oil phase B.

[0033] 1000g of polysulfone support layer was placed at the bottom of the reaction tank. The prepared aqueous phase was mixed with 30g of sodium p-toluenesulfonate catalyst and 60g of 4-dimethylaminopyridine at 4℃ and then slowly added to the reaction tank. The liquid level was equal to the height of the support layer plus 2.5mm. The prepared oil phase A was added to the reaction tank and reacted at 37℃ in a nitrogen atmosphere for 36min. The prepared oil phase B was added to the reaction tank and reacted at 34℃ in a nitrogen atmosphere for 42min. After the reaction was completed, the membrane was removed, washed with water at 35℃ for 45min, and then vacuum dried at 46℃ and 0.035MPa for 4.5h to obtain the reverse osmosis membrane.

[0034] With the modified polyamide portion of the reverse osmosis membrane facing outwards, it is alternately stacked with the inlet water flow channel mesh and then rolled around the outlet pipe. During rolling, both ends of the reverse osmosis membrane are fixed with polyurethane sealant, and after rolling, both ends are fixed with end caps. Polyurethane sealant is injected to fill the gap between the end caps and the membrane. The membrane is then heated and cured at 62°C for 80 minutes. Finally, the entire membrane is installed in a fiberglass shell, and the inlet and outlet water flow directions are marked to obtain the membrane product.

[0035] Example 2

[0036] A cleaning solution was prepared by mixing fatty alcohol polyoxyethylene ether and deionized water at a mass ratio of 1:33. 1000 g of a 60 μm thick polyethersulfone support layer was placed in 2300 g of the cleaning solution and sonicated at 190 W for 4.5 min. The layer was then removed, placed in 2900 g of deionized water, and sonicated at 190 W for 4.5 min. The layer was then dried and set aside. 450 g of m-phenylenediamine was weighed and added to 5.2 kg of deionized water and mixed thoroughly. Then, 95 g of dodecyl ethoxysulfonate was added and mixed thoroughly to obtain the aqueous phase. 710 g of trimesoyl chloride was weighed and added to 6.25 kg of N,N-dimethylformamide. Then, 340 g of 1,3-dimethyl-2-imidazolinone and 95 g of N,N-dimethylpropenylurea were mixed thoroughly to obtain oil phase A. 550 g of 4-aminobenzaldehyde was weighed and added to 2.0 kg of N,N-dimethylformamide and mixed thoroughly to obtain oil phase B.

[0037] 1000g of polyethersulfone support layer was placed at the bottom of the reaction tank. The prepared aqueous phase was mixed with 36g of sodium p-toluenesulfonate catalyst and 63g of 4-dimethylaminopyridine at 2℃ and then slowly added to the reaction tank. The liquid level was equal to the support layer height plus 3.2mm. The prepared oil phase A was added to the reaction tank and reacted at 42℃ in a nitrogen atmosphere for 32min. The prepared oil phase B was added to the reaction tank and reacted at 38℃ in a nitrogen atmosphere for 38min. After the reaction was completed, the membrane was removed, washed with water at 38℃ for 55min, and then vacuum dried at 46℃ and 0.035MPa for 5.5h to obtain the reverse osmosis membrane.

[0038] With the modified polyamide portion of the reverse osmosis membrane facing outwards, it is alternately stacked with the inlet water flow channel mesh and then rolled around the outlet pipe. During rolling, both ends of the reverse osmosis membrane are fixed with polyurethane sealant, and after rolling, both ends are fixed with end caps. Polyurethane sealant is injected to fill the gap between the end caps and the membrane. The membrane is then heated and cured at 68°C for 80 minutes. Subsequently, the entire membrane is installed in a fiberglass shell, and the inlet and outlet water flow directions are marked to obtain the membrane product.

[0039] Example 3

[0040] A cleaning solution was prepared by mixing fatty alcohol polyoxyethylene ether and deionized water at a mass ratio of 1:30. 1000 g of a 70 μm thick sulfonated polyethersulfone support layer was placed in 2500 g of the cleaning solution and sonicated at 220 W for 5 min. The layer was then removed, placed in 3000 g of deionized water, sonicated at 220 W for 5 min, and dried. 450 g of m-phenylenediamine was weighed and added to 4.5 kg of deionized water and mixed thoroughly. Then, 80 g of dodecyl ethoxysulfonate was added and mixed thoroughly to obtain the aqueous phase. 680 g of trimesoyl chloride was weighed and added to 5.8 kg of N,N-dimethylformamide. Then, 400 g of the co-solvent 1,3-dimethyl-2-imidazolinone and 110 g of N,N-dimethylpropenylurea were added and mixed thoroughly to obtain oil phase A. 520 g of 4-aminobenzaldehyde was weighed and added to 1.8 kg of N,N-dimethylformamide and mixed thoroughly to obtain oil phase B.

[0041] 1000g of sulfonated polyethersulfone support layer was placed at the bottom of the reaction tank. The prepared aqueous phase was mixed with 40g of sodium p-toluenesulfonate catalyst and 65g of 4-dimethylaminopyridine at 5℃ and then slowly added to the reaction tank. The liquid level was equal to the support layer height plus 3.5mm. The prepared oil phase A was added to the reaction tank and reacted at 45℃ in a nitrogen atmosphere for 30min. The prepared oil phase B was added to the reaction tank and reacted at 40℃ in a nitrogen atmosphere for 35min. After the reaction was completed, the membrane was removed, washed with water at 30℃ for 60min, and then vacuum dried at 50℃ and 0.03MPa for 4h to obtain the reverse osmosis membrane.

[0042] With the modified polyamide portion of the reverse osmosis membrane facing outwards, it is alternately stacked with the inlet water flow channel mesh and then rolled around the outlet pipe. During rolling, both ends of the reverse osmosis membrane are fixed with polyurethane sealant, and after rolling, both ends are fixed with end caps. Polyurethane sealant is injected to fill the gap between the end caps and the membrane. The membrane is then heated and cured at 60°C for 95 minutes. Finally, the entire membrane is installed in a fiberglass shell, and the inlet and outlet water flow directions are marked to obtain the membrane product.

[0043] Example 4

[0044] A cleaning solution was prepared by mixing fatty alcohol polyoxyethylene ether and deionized water at a mass ratio of 1:40. 1000g of a 45μm thick polyetherketone support layer was placed in 2000g of the cleaning solution and sonicated at 180W for 3 minutes. The layer was then removed, placed in 2500g of deionized water, and sonicated at 180W for 3 minutes. The layer was then dried and set aside. 450g of m-phenylenediamine was weighed and added to 5.5kg of deionized water and mixed thoroughly. Then, 100g of dodecyl ethoxysulfonate was added and mixed thoroughly to obtain the aqueous phase. 720g of trimesoyl chloride was weighed and added to 6.8kg of N,N-dimethylformamide. Then, 320g of the co-solvent 1,3-dimethyl-2-imidazolinone and 90g of N,N-dimethylpropenylurea were added and mixed thoroughly to obtain oil phase A. 560g of 4-aminobenzaldehyde was weighed and added to 2.0kg of N,N-dimethylformamide and mixed thoroughly to obtain oil phase B.

[0045] 1000g of polyetherketone support layer was placed at the bottom of the reaction tank. The prepared aqueous phase was mixed with 24g of sodium p-toluenesulfonate catalyst and 56g of 4-dimethylaminopyridine at 0℃ and then slowly added to the reaction tank. The liquid level was equal to the support layer height plus 1.8mm. The prepared oil phase A was added to the reaction tank and reacted at 35℃ in a nitrogen atmosphere for 40min. The prepared oil phase B was added to the reaction tank and reacted at 30℃ in a nitrogen atmosphere for 45min. After the reaction was completed, the membrane was removed, washed with water at 40℃ for 40min, and then vacuum dried at 45℃ and 0.04MPa for 6h to obtain the reverse osmosis membrane.

[0046] With the modified polyamide portion of the reverse osmosis membrane facing outwards, it is alternately stacked with the inlet water flow channel mesh and then rolled around the outlet water pipe. During rolling, the two ends of the reverse osmosis membrane are fixed with polyurethane sealant, and after rolling, the two ends are fixed with end caps. Polyurethane sealant is injected to fill the gap between the end caps and the membrane. It is then heated and cured at 70°C for 75 minutes. Subsequently, the whole thing is installed in a fiberglass shell, and the inlet and outlet water flow directions are marked to obtain the membrane product.

[0047] The reaction tanks described in Examples 1-4 are commercially available products.

[0048] Comparative Example 1

[0049] Without adding any modifying agents, the remaining operating steps and raw materials used are the same as in Example 1.

[0050] Comparative Example 2

[0051] The modifying agent was replaced with sodium dodecyl sulfate, and the remaining operating steps and raw materials were the same as in Example 1.

[0052] Comparative Example 3

[0053] Without adding dynamic crosslinking monomers, the remaining operation steps and raw materials are the same as in Example 1.

[0054] Comparative Example 4

[0055] The dynamic crosslinking monomer was replaced with p-phenylenediamine, and the remaining operating steps and raw materials were the same as in Example 1.

[0056] Comparative Example 5

[0057] Without adding a co-solvent, the remaining operating steps and raw materials are the same as in Example 1.

[0058] Comparative Example 6

[0059] Without adding 1,3-dimethyl-2-imidazolinone, the remaining operating steps and raw materials are the same as in Example 1.

[0060] Comparative Example 7

[0061] Without adding N,N-dimethylpropenylurea, the remaining operating steps and raw materials used are the same as in Example 1.

[0062] Implementation effect

[0063] The reverse osmosis membranes prepared in Examples 1-4 and Comparative Examples 1-7 were taken, and their effective area was 0.35m². 2 ±0.2cm 2 Following the steps described in Example 1, reverse osmosis membranes were prepared and sequentially labeled as samples 1 to 11.

[0064] Prepare sodium chloride aqueous solution (both 1500 mg / L and 68000 mg / L), sodium hypochlorite aqueous solution (4500 ppm free chlorine, for use as a chlorine corrosion solution), humic acid solution (150 mg / L, for use as an organic pollutant solution), and E. coli bacterial solution (10... 8 (CFU / mL, used as a biological contaminant solution).

[0065] Chlorine and pollution resistance test: Samples 1-11 were soaked in pure water for 1 hour, then removed and treated with 1500 mg / L sodium chloride aqueous solution at 0.8 MPa for 1 hour. After 55 minutes of water inlet, the temperature was set to 25 ± 0.5℃, and 68000 mg / L sodium chloride aqueous solution was introduced at an operating pressure of 1.98 MPa and an inlet flow rate of 0.8 L / min. After the product water stabilized, the product water volume, salt concentration on the product water side and salt concentration on the inlet water side were recorded once after 15 minutes. J0 and R0 can be calculated.

[0066] Subsequently, sodium hypochlorite aqueous solution was continuously bubbled into samples 1-11, and compaction was carried out at 1.5 MPa for 24 h. Afterward, water was introduced for 35 min, followed by the introduction of humic acid solution and E. coli culture (volume ratio 3.5:1), and treatment at 1.5 MPa for 24 h for later use. The temperature was set at 25±0.5℃, with 68000 mg / L sodium chloride aqueous solution bubbled in, an operating pressure of 1.98 MPa, and an influent flow rate of 0.8 L / min. After the product water stabilized, the product water volume, salt concentration on the product water side, and salt concentration on the influent side were recorded after 100 h. Jt and R can be calculated from these results. t Thus, ΔJ and ΔR are obtained.

[0067] Water flux calculation (J, unit L·m) -2 ·h -1 ):

[0068] Where V represents the product water volume (in L); A represents the effective area of ​​the reverse osmosis membrane (m²). 2 ); t represents the collection time (h). The effective area refers to the active separation layer area that is not covered by sealant and can directly contact the incoming water.

[0069] Desalination rate calculation (R):

[0070] C p Indicates the salt concentration (mg / L) on the product water side; C f This indicates the salt concentration (mg / L) on the inlet side.

[0071] Calculation of water flux attenuation rate (ΔJ):

[0072] Where J0 represents the initial water flux; J t This indicates the water flow rate 100 hours after the test.

[0073] Calculation of desalination rate decline rate (ΔR):

[0074] Where R0 represents the initial desalination rate; R t This indicates the desalination rate after 100 hours of testing.

[0075] The specific test results are shown in Table 1.

[0076] Table 1. Performance test results of reverse osmosis membranes

[0077]

[0078] As shown in Table 1, the present invention exhibits higher initial water flux and initial desalination rate. Furthermore, the reverse osmosis membrane is less prone to failure and blockage in environments with high chlorine, high organic pollution, and biological pollution, meaning that the decline rate of water flux and desalination rate is gradual. The present invention balances high desalination rate and chlorine resistance by introducing a Schiff base-benzene ring bridging structure and dynamic imine bonds through dynamically crosslinked monomers; a zwitterionic surfactant forms a sulfonic acid-based hydrophilic layer to inhibit pollutant adhesion; and a co-solvent ensures uniform distribution of the dynamically crosslinked structure. Through the synergistic effect of these three elements at the microscopic level, the trade-off effect of traditional polyamides is overcome, achieving a balance between high desalination rate, high water flux, and long-term stability.

Claims

1. A method for producing a reverse osmosis membrane, characterized by, The method comprises the following steps: (1) washing the support layer for standby; blending the binary amine, the modified additive and water to obtain an aqueous phase for standby; blending the aromatic acyl chloride, the cosolvent and the organic solvent to obtain an oil phase A for standby, and blending the dynamic crosslinking monomer and the organic solvent to obtain an oil phase B for standby; (2) placing the support layer at the bottom of a container, mixing the aqueous phase and the catalyst uniformly, and then adding them into the container; adding the oil phase A into the container to perform a first condensation reaction, adding the oil phase B to perform a second condensation reaction after the first condensation reaction is completed, and obtaining the reverse osmosis membrane through post-processing; In step (1), the binary amine is m-phenylenediamine, the modified additive is dodecyl ethoxy sulfobetaine, the aromatic acyl chloride is trimesoyl chloride, the dynamic crosslinking monomer is 4-aminobenzaldehyde, the organic solvent is N,N-dimethylformamide, and the cosolvent is prepared from 1,3-dimethyl-2-imidazolidinone and N,N-dimethylacryl urea according to a mass ratio of (320-400):(90-110). In step (2), the catalyst comprises sodium p-toluenesulfonate and 4-dimethylamino pyridine, and the mass ratio of the modified additive, the sodium p-toluenesulfonate and the 4-dimethylamino pyridine is (80-100):(24-40):(56-65) based on the mass of the modified additive in the aqueous phase; the first condensation reaction temperature is 35-45 DEG C, and the first condensation reaction time is 30-40 min; the second condensation reaction temperature is 30-40 DEG C, and the second condensation reaction time is 35-45 min.

2. The method for producing a reverse osmosis membrane according to claim 1, characterized by, In step (1), the support layer is one of polysulfone, polyether sulfone, polyether ketone or sulfonated polyether sulfone, and the thickness of the support layer is 45-70 mu m; the support layer is sequentially placed in a cleaning solution and water for ultrasonic cleaning during washing.

3. The method for producing a reverse osmosis membrane according to claim 2, characterized by, In step (1), the cleaning solution used during washing is prepared according to a mass ratio of fatty alcohol polyoxyethylene ether to water of 1:(30-40), the mass ratio of the support layer to the cleaning solution is 1000:(2000-2500), and the mass ratio of the support layer to water is 1000:(2500-3000).

4. The method of producing a reverse osmosis membrane according to claim 1, characterized by, In step (1), when the aqueous phase is prepared, the mass ratio of the support layer, the binary amine, the modified additive and water is 1000:450:(80-100):(4500-5500).

5. The method of producing a reverse osmosis membrane according to claim 1, wherein When the oil phase A is prepared, the mass ratio of the support layer, the aromatic acyl chloride, the cosolvent and the organic solvent is 1000:(680-720):(410-510):(5800-6800); when the oil phase B is prepared, the mass ratio of the support layer, the dynamic crosslinking monomer and the organic solvent is 1000:(520-560):(1800-2000).

6. The method of producing a reverse osmosis membrane according to claim 1, wherein In step (2), the mixing temperature is 0-5 DEG C, and after the aqueous phase and the catalyst are mixed and added into the container, the liquid level is 1.8-3.5 mm higher than the height of the support layer.

7. The method of producing a reverse osmosis membrane according to claim 1, wherein In step (2), the post-processing comprises water washing and vacuum drying, the water washing temperature is 30-40 DEG C, the water washing time is 40-60 min; the vacuum drying pressure is 0.03-0.04 MPa, the vacuum drying temperature is 45-50 DEG C, and the vacuum drying time is 4-6 h.

Images