Reverse osmosis membrane with high flux and high salt rejection rate as well as preparation method and application of reverse osmosis membrane

Abstract

The invention relates to the technical field of membrane separation, in particular to a high-flux high-salt rejection rate reverse osmosis membrane as well as a preparation method and application thereof. The preparation method comprises the following steps: sequentially contacting a porous base membrane with a water phase solution and an oil phase solution to generate an interfacial polymerization reaction to form a primary reverse osmosis membrane, and sequentially contacting the primary reverse osmosis membrane with a nitrous acid or salt solution thereof and a hydrosulfite solution to obtain the reverse osmosis membrane with high flux and high salt rejection rate, the water-phase solution contains a water-phase cosolvent, and the oil-phase solution contains an oil-phase cosolvent. According to the preparation method, cosolvents are creatively added into a water-phase solution and an oil-phase solution in an interfacial polymerization reaction process to regulate and control the microstructure of a polyamide layer, and a diazo reaction promotes further crosslinking of residual aniline groups, so that in-situ densification regulation and control of a polyamide network structure are realized; the trade-off effect of the water flux and the salt rejection rate of the traditional reverse osmosis membrane is successfully broken through.

Description

Technical Field

[0001] The present invention relates to the technical field of membrane separation, and specifically relates to a high-flux and high-salt rejection reverse osmosis membrane, a preparation method thereof, and an application thereof. Background Art

[0002] Reverse osmosis membranes are widely used in water treatment and seawater desalination. Currently, reverse osmosis membranes still have problems of high energy consumption and low water flux, which limits their further application. However, increasing the water flux of reverse osmosis membranes often leads to a decrease in their salt rejection rate. Therefore, how to further improve the water flux of reverse osmosis membranes while ensuring a high salt rejection rate has always been a research hotspot in the field of membrane separation.

[0003] The classic structure of reverse osmosis membranes is a composite structure, which consists of a bottom non-woven fabric, a middle porous substrate membrane, and an upper separation layer. The polyamide upper separation layer is prepared by interfacial polymerization of an oil-phase monomer polyacyl chloride and an aqueous-phase monomer polyamine. Existing technologies such as CN114950165A, CN111569675A, and CN105169971A add a co-solvent to the oil phase or the aqueous phase to increase the miscibility of the oil phase and the aqueous phase, promote the diffusion of polyamine monomers into the oil phase, and form a "large leaf" structure, thereby significantly improving the flux of reverse osmosis membranes. However, adding a co-solvent only in the aqueous phase or the oil phase will cause a bottleneck in the increase of the flux. To ensure the maximization of the membrane flux, the inventor attempts to add a co-solvent to both the aqueous solution and the oil solution. Especially when the addition amount of the co-solvent in the aqueous solution is greater than 1%, it is found that it causes the loosening of the polyamide network and leads to a decrease in the salt rejection rate of the reverse osmosis membrane.

[0004] After post-treatment of the polyamide membrane by diazotization, the diazotization reagent reacts with aniline to form an intermediate diazonium salt, and the diazonium salt further undergoes a coupling reaction with the benzene ring to produce an azo structure, increasing the cross-linking degree and denseness of the polymer network, thereby improving the salt rejection rate, but this is also accompanied by a decrease in the water flux.

[0005] Based on the above background, in order to further improve the water flux of reverse osmosis membranes while ensuring a high salt rejection rate, it is necessary to improve the existing preparation method of reverse osmosis membranes. Summary of the Invention

[0006] The first object of the present invention is to provide a preparation method of a high-flux and high-salt rejection reverse osmosis membrane, which is simple and has a low cost.

[0007] The second object of the present invention is to provide a high-flux and high-salt rejection reverse osmosis membrane, which has a high water flux and a high salt rejection rate.

[0008] The third object of the present invention is to provide an application of a high-flux and high-salt rejection reverse osmosis membrane, which has a broad application prospect.

[0009] To achieve the above object, the technical solution adopted by the present invention is as follows: A method for preparing a high-flux and high-salt rejection reverse osmosis membrane, which comprises successively contacting a porous substrate membrane with an aqueous solution and an oil-phase solution to carry out an interfacial polymerization reaction to form a primary reverse osmosis membrane, and successively contacting the primary reverse osmosis membrane with a nitrous acid or its salt solution and a hydrogen sulfite solution, thereby obtaining the high-flux and high-salt rejection reverse osmosis membrane; the aqueous solution contains an aqueous co-solvent, and the concentration of the aqueous co-solvent in the aqueous solution is 1-95 wt%; the oil-phase solution contains an oil-phase co-solvent.

[0010] Further, the aqueous solution comprises a polyamine monomer, an aqueous co-solvent and water, and the oil-phase solution comprises a polyacyl chloride monomer, an oil-phase co-solvent and an alkane solvent.

[0011] Further, the aqueous co-solvent is one or more of alcohol solvents, ketone solvents, and ether solvents that are miscible with water but do not react with amino groups; the oil-phase co-solvent is one or more of ester solvents, ketone solvents, and ether solvents that are miscible with alkane solvents but do not react with acyl chlorides; the concentration of the oil-phase co-solvent in the oil-phase solution is 0.01-20 wt%.

[0012] Further, the aqueous co-solvent is selected from one or more of ethanol, n-propanol, isopropanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerol, acetone, methyl ethyl ketone, ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl ether acetate; the oil-phase co-solvent is selected from one or more of ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, dimethyl oxalate, diethyl oxalate, dipropyl oxalate, dimethyl malonate, diethyl malonate, dimethyl succinate, diethyl succinate, acetone, methyl ethyl ketone, 2-pentanone, 3-pentanone, ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol dipropyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, diethylene glycol dibutyl ether, diethylene glycol ethyl ether acetate, diethylene glycol ethyl ether butyrate, diethylene glycol diacetate, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetraethylene glycol dimethyl ether.

[0013] Further, the concentration of nitrite in the nitrous acid or its salt solution is 0.005 - 5 wt%, the solution temperature is 4 - 50 °C, and the pH is 1 - 7; the contact time of the primary reverse osmosis membrane with the nitrous acid or its salt solution is 5 - 1800 s; the concentration of the hydrogen sulfite solution is 0.05 - 5 wt%, the temperature is 4 - 50 °C, and the pH is 1 - 7; the contact time of the reverse osmosis membrane treated with the nitrous acid or its salt solution with the hydrogen sulfite solution is 5 - 1800 s.

[0014] Further, the contact time of the surface of the porous substrate membrane with the aqueous solution is 1 - 300 s; the time of the interfacial polymerization reaction is 1 - 300 s.

[0015] Further, the concentration of the polyamine monomer in the aqueous solution is 0.5 - 5 wt%; the polyamine monomer is selected from one or more of o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 1,3,5-triaminobenzene, diaminotoluene, benzidine, and diaminonaphthalene; the concentration of the polyacyl chloride monomer in the oil phase solution is 0.01 - 5 wt%; the polyacyl chloride monomer is selected from one or more of trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride, biphenyl-4,4'-dicarbonyl chloride, terphenyl-4,4'',4'''-tricarbonyl chloride, biphenyl-3,3',4,4'-tetracarbonyl chloride, naphthalene-1,4-dicarbonyl chloride, naphthalene-1,3,5-tricarbonyl chloride, naphthalene-1,2,4,5-tetracarbonyl chloride, malonyl chloride, succinyl chloride, glutaroyl chloride, and adipoyl chloride; the alkane solvents are selected from one or more of hexane, heptane, octane, nonane, decane, undecane, dodecane, Isopar C, Isopar E, Isopar G, Isopar H, Isopar L, and Isopar M.

[0016] Further, the material of the porous substrate membrane is selected from one of polysulfone, polyethersulfone, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, polyimide, polyetherimide, polyacrylonitrile, polyphenylene ether, polyphenylene sulfide, polyether ketone, and polyarylether ketone.

[0017] A high-flux and high-salt rejection reverse osmosis membrane is prepared by using the above-mentioned preparation method.

[0018] The application of the above high-flux and high-salt rejection reverse osmosis membrane in the field of water treatment.

[0019] The beneficial technical effects of the present invention are as follows: First, the present invention innovatively adds co-solvents to both the aqueous solution and the oil-phase solution during the interfacial polymerization reaction to regulate the microstructure of the polyamide layer. On the one hand, by forming a loose polymer network and a leaf-like surface morphology, the water flux of the reverse osmosis membrane is significantly improved; in response to the subsequent problem of reduced salt rejection rate, the present invention performs diazotization post-treatment on the as-prepared reverse osmosis membrane. The diazo reaction promotes the further cross-linking of residual aniline groups, realizing in-situ densification regulation of the polyamide network structure, and successfully breaking through the trade-off effect between the water flux and salt rejection rate of traditional reverse osmosis membranes.

[0020] Secondly, the present invention adds co-solvents to the aqueous and oil-phase solutions to promote the diffusion of amine monomers during the interfacial polymerization process. By selecting the co-solvents for the aqueous and oil phases, the amine group content of the as-prepared reverse osmosis membrane accounts for more than 20% of the total nitrogen content, increasing the residual density of unreacted aniline functional groups on the surface of the as-prepared polyamide membrane and providing sufficient reaction sites for subsequent functionalization modification.

[0021] Finally, the present invention creatively immerses the membrane in sodium bisulfite solution immediately after soaking in sodium nitrite solution, thereby further improving the rejection rate of the reverse osmosis membrane. Description of the Drawings

[0022] Figure 1 are scanning electron microscope (SEM) images of the surfaces of the reverse osmosis membranes obtained in Examples 1-9, where the magnification of a1-i1 is 10,000; the magnification of a2-i2 is 50,000. Among them, a-i respectively correspond to the SEM images of the surfaces of the reverse osmosis membranes obtained in Examples 1-9; Figure 2 are scanning electron microscope (SEM) images of the surfaces of the reverse osmosis membranes obtained in Comparative Examples 1-5, where the magnification of a1-e1 is 10,000; the magnification of a2-e2 is 50,000. Among them, a-e respectively correspond to the SEM images of the surfaces of the reverse osmosis membranes obtained in Comparative Examples 1-5. Detailed Embodiments

[0023] The following content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should all be regarded as belonging to the protection scope of the present invention. The specific conditions not specified in the examples are carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used, unless otherwise specified, are all conventional products obtained through commercial channels.

[0024] Example 1 Example 1 provides a method for preparing a high-flux and high-salt-rejection reverse osmosis membrane. The specific preparation process is as follows: (1) Prepare an aqueous solution Add m-phenylenediamine, camphorsulfonic acid, triethylamine, and isopropanol to water to prepare a homogeneous and transparent aqueous solution. The concentrations of each component in the aqueous solution are as follows: m-phenylenediamine 3 wt%, camphorsulfonic acid 3 wt%, triethylamine 2 wt%, and isopropanol 50 wt%.

[0025] (2) Prepare an oil-phase solution Add trimesoyl chloride and ethyl acetate to Isopar G to prepare a homogeneous and transparent oil-phase solution. The concentrations of each component in the oil-phase solution are as follows: trimesoyl chloride 0.2 wt% and ethyl acetate 5 wt%.

[0026] (3) Contact the surface of the polysulfone-based membrane with the aqueous solution prepared in step (1) for 10 s, remove the excess aqueous solution on the surface, contact the membrane layer formed by the aqueous solution with the oil-phase solution prepared in step (2) to carry out an interfacial polymerization reaction for 10 s. After the reaction is completed, remove the excess oil-phase solution on the surface, perform heat treatment at 90 °C for 360 s, and obtain a primary reverse osmosis membrane after rinsing; (4) Immerse the primary reverse osmosis membrane obtained in step (3) in a sodium nitrite solution with a concentration of 0.3 wt%, a temperature of 25 °C, and a pH of 3 for 60 s, and then immerse it in a sodium bisulfite solution with a concentration of 1 wt%, a temperature of 25 °C, and a pH of 3 for 60 s. After the immersion is completed, obtain the high-flux and high-salt rejection reverse osmosis membrane after rinsing.

[0027] Example 2 Example 2 provides a method for preparing a high-flux and high-salt rejection reverse osmosis membrane. The specific preparation process is as follows: (1) Prepare an aqueous solution Add diaminotoluene, camphorsulfonic acid, triethylamine, and methyl ethyl ketone to water to prepare a homogeneous and transparent aqueous solution. The concentrations of each component in the aqueous solution are as follows: diaminotoluene 5 wt%, camphorsulfonic acid 3 wt%, triethylamine 2 wt%, and methyl ethyl ketone 1 wt%.

[0028] (2) Prepare an oil-phase solution Add diphthaloyl chloride and dimethyl oxalate to nonane to prepare a homogeneous and transparent oil-phase solution. The concentrations of each component in the oil-phase solution are as follows: diphthaloyl chloride 0.5 wt% and dimethyl oxalate 15 wt%.

[0029] (3) Contact the surface of the polyimide-based membrane with the aqueous solution prepared in step (1) for 8 s, remove the excess aqueous solution on the surface, contact the membrane layer formed by the aqueous solution with the oil-phase solution prepared in step (2) to carry out an interfacial polymerization reaction for 15 s. After the reaction is completed, remove the excess oil-phase solution on the surface, perform heat treatment at 40 °C for 600 s, and obtain a primary reverse osmosis membrane after rinsing; (4) Immerse the nascent reverse osmosis membrane obtained in step (3) in a sodium nitrite solution with a concentration of 0.1 wt%, a temperature of 4 °C, and a pH of 1 for 5 s, and then immerse it in a sodium bisulfite solution with a concentration of 1 wt%, a temperature of 4 °C, and a pH of 1 for 5 s. After the immersion is completed, rinse to obtain the high-flux and high-salt rejection reverse osmosis membrane.

[0030] Example 3 Example 3 provides a method for preparing a high-flux and high-salt rejection reverse osmosis membrane, and the specific preparation process is as follows: (1) Prepare an aqueous solution Add diaminonaphthalene, camphorsulfonic acid, triethylamine, and ethylene glycol monoethyl ether to water to prepare a homogeneous and transparent aqueous solution. The concentrations of the components in the aqueous solution are as follows: diaminonaphthalene 3 wt%, camphorsulfonic acid 3 wt%, triethylamine 2 wt%, and ethylene glycol monoethyl ether 10 wt%.

[0031] (2) Prepare an oil phase solution Add trimesoyl chloride and diethyl ether to Isopar G to prepare a homogeneous and transparent oil phase solution. The concentrations of the components in the oil phase solution are as follows: trimesoyl chloride 0.2 wt% and diethyl ether 5 wt%.

[0032] (3) Contact the surface of the polytetrafluoroethylene-based membrane with the aqueous solution prepared in step (1) for 30 s, remove the excess aqueous solution on the surface, contact the membrane layer formed by the aqueous solution with the oil phase solution prepared in step (2) to carry out an interfacial polymerization reaction for 30 s. After the reaction is completed, remove the excess oil phase solution on the surface, heat-treat at 60 °C for 500 s, and rinse to obtain a nascent reverse osmosis membrane; (4) Immerse the nascent reverse osmosis membrane obtained in step (3) in a sodium nitrite solution with a concentration of 0.5 wt%, a temperature of 15 °C, and a pH of 3 for 30 s, and then immerse it in a potassium bisulfite solution with a concentration of 0.5 wt%, a temperature of 15 °C, and a pH of 3 for 1200 s. After the immersion is completed, rinse to obtain the high-flux and high-salt rejection reverse osmosis membrane.

[0033] Example 4 Example 4 provides a method for preparing a high-flux and high-salt rejection reverse osmosis membrane, and the specific preparation process is as follows: (1) Prepare an aqueous solution Add m-phenylenediamine, camphorsulfonic acid, triethylamine, and ethylene glycol monoethyl ether to water to prepare a homogeneous and transparent aqueous solution. The concentrations of the components in the aqueous solution are as follows: m-phenylenediamine 4 wt%, camphorsulfonic acid 3 wt%, triethylamine 2 wt%, and ethylene glycol monoethyl ether 30 wt%.

[0034] (2) Prepare an oil phase solution Naphthalene tricarbonyl chloride and diethyl oxalate were added to Isopar L to prepare a homogeneous and transparent oil-phase solution. The concentrations of the components in the oil-phase solution were as follows: naphthalene tricarbonyl chloride 1 wt%, diethyl oxalate 20 wt%.

[0035] (3)The surface of the polysulfone-based membrane was contacted with the aqueous solution prepared in step (1) for 80 s to remove the excess aqueous solution on the surface. The membrane layer formed by the aqueous solution was contacted with the oil-phase solution prepared in step (2) to carry out an interfacial polymerization reaction for 80 s. After the reaction was completed, the excess oil-phase solution on the surface was removed, and heat treatment was carried out at 100 °C for 300 s. After rinsing, a primary reverse osmosis membrane was obtained; (4)The primary reverse osmosis membrane obtained in step (3) was first immersed in a potassium nitrite solution with a concentration of 0.7 wt%, a temperature of 40 °C, and a pH of 6 for 120 s, and then immersed in a sodium bisulfite solution with a concentration of 0.7 wt%, a temperature of 40 °C, and a pH of 6 for 120 s. After soaking, the high-flux and high-salt rejection reverse osmosis membrane was obtained after rinsing.

[0036] Example 5 Example 5 provides a method for preparing a high-flux and high-salt rejection reverse osmosis membrane. The specific preparation process is as follows: (1)Prepare an aqueous solution m-Phenylenediamine, camphorsulfonic acid, triethylamine, diethylene glycol monoethyl ether acetate, and isopropanol were added to water to prepare a homogeneous and transparent aqueous solution. The concentrations of the components in the aqueous solution were as follows: m-phenylenediamine 5 wt%, camphorsulfonic acid 3 wt%, triethylamine 2 wt%, diethylene glycol monoethyl ether acetate 5 wt%, isopropanol 30 wt%.

[0037] (2)Prepare an oil-phase solution Trimesoyl chloride and triethylene glycol dimethyl ether were added to nonane to prepare a homogeneous and transparent oil-phase solution. The concentrations of the components in the oil-phase solution were as follows: trimesoyl chloride 1 wt%, triethylene glycol dimethyl ether 3 wt%.

[0038] (3)The surface of the polyphenylene oxide-based membrane was contacted with the aqueous solution prepared in step (1) for 100 s to remove the excess aqueous solution on the surface. The membrane layer formed by the aqueous solution was contacted with the oil-phase solution prepared in step (2) to carry out an interfacial polymerization reaction for 100 s. After the reaction was completed, the excess oil-phase solution on the surface was removed, and heat treatment was carried out at 120 °C for 100 s. After rinsing, a primary reverse osmosis membrane was obtained; (4)The primary reverse osmosis membrane obtained in step (3) was first immersed in a sodium nitrite solution with a concentration of 2 wt%, a temperature of 50 °C, and a pH of 2 for 5 s, and then immersed in a sodium bisulfite solution with a concentration of 2 wt%, a temperature of 50 °C, and a pH of 2 for 10 s. After soaking, the high-flux and high-salt rejection reverse osmosis membrane was obtained after rinsing.

[0039] Example 6 Example 6 provides a method for preparing a high-flux and high-salt rejection reverse osmosis membrane, and the specific preparation process is as follows: (1)Prepare an aqueous solution Add m-phenylenediamine, camphorsulfonic acid, triethylamine, isopropanol, and diethylene glycol monomethyl ether to water to obtain a homogeneous and transparent aqueous solution. The concentrations of each component in the aqueous solution are as follows: m-phenylenediamine 3 wt%, camphorsulfonic acid 3 wt%, triethylamine 2 wt%, isopropanol 35 wt%, and diethylene glycol monomethyl ether 30 wt%.

[0040] (2)Prepare an oil-phase solution Add trimesoyl chloride and ethyl acetate to Isopar G to obtain a homogeneous and transparent oil-phase solution. The concentrations of each component in the oil-phase solution are as follows: trimesoyl chloride 0.5 wt% and ethyl acetate 2 wt%.

[0041] (3)Contact the surface of the polysulfone substrate membrane with the aqueous solution prepared in step (1) for 200 s, remove the excess aqueous solution on the surface, contact the membrane layer formed by the aqueous solution with the oil-phase solution prepared in step (2) to carry out an interfacial polymerization reaction for 200 s. After the reaction is completed, remove the excess oil-phase solution on the surface, and perform heat treatment at 150 °C for 6 s. After rinsing, a primary reverse osmosis membrane is obtained; (4)Immerse the primary reverse osmosis membrane obtained in step (3) in a sodium nitrite solution with a concentration of 4 wt%, a temperature of 30 °C, and a pH of 4 for 10 s, and then immerse it in a sodium bisulfite solution with a concentration of 4 wt%, a temperature of 30 °C, and a pH of 4 for 30 s. After the immersion is completed, the high-flux and high-salt rejection reverse osmosis membrane is obtained after rinsing.

[0042] Example 7 Example 7 provides a method for preparing a high-flux and high-salt rejection reverse osmosis membrane, and the specific preparation process is as follows: (1)Prepare an aqueous solution Add m-phenylenediamine, camphorsulfonic acid, triethylamine, and diethylene glycol to water to obtain a homogeneous and transparent aqueous solution. The concentrations of each component in the aqueous solution are as follows: m-phenylenediamine 3 wt%, camphorsulfonic acid 3 wt%, triethylamine 2 wt%, and diethylene glycol 30 wt%.

[0043] (2)Prepare an oil-phase solution Add trimesoyl chloride, ethyl acetate, and 2-pentanone to Isopar G to obtain a homogeneous and transparent oil-phase solution. The concentrations of each component in the oil-phase solution are as follows: trimesoyl chloride 0.2 wt%, ethyl acetate 2 wt%, and 2-pentanone 2 wt%.

[0044] (3) Contact the surface of the polysulfone-based membrane with the aqueous solution prepared in step (1) for 300 s, remove the excess aqueous solution on the surface, contact the membrane layer formed by the aqueous solution with the oil-phase solution prepared in step (2) to carry out an interfacial polymerization reaction for 300 s, remove the excess oil-phase solution on the surface after the reaction is completed, perform heat treatment at 90 °C for 360 s, and obtain a primary reverse osmosis membrane after rinsing; (4) Immerse the primary reverse osmosis membrane obtained in step (3) first in a sodium nitrite solution with a concentration of 5 wt%, a temperature of 32 °C, and a pH of 3 for 8 s, and then immerse it in a sodium bisulfite solution with a concentration of 5 wt%, a temperature of 32 °C, and a pH of 3 for 10 s. After the immersion is completed, obtain the high-flux and high-salt rejection reverse osmosis membrane after rinsing.

[0045] Example 8 Example 8 provides a method for preparing a high-flux and high-salt rejection reverse osmosis membrane. The specific preparation process is as follows: (1) Prepare an aqueous solution Add m-phenylenediamine, camphorsulfonic acid, triethylamine, and isopropanol to water to prepare a homogeneous and transparent aqueous solution. The concentrations of the components in the aqueous solution are as follows: m-phenylenediamine 3 wt%, camphorsulfonic acid 3 wt%, triethylamine 2 wt%, and isopropanol 60 wt%.

[0046] (2) Prepare an oil-phase solution Add trimesoyl chloride, ethyl acetate, and diethylene glycol diethyl ether to Isopar G to prepare a homogeneous and transparent oil-phase solution. The concentrations of the components in the oil-phase solution are as follows: trimesoyl chloride 0.2 wt%, ethyl acetate 2 wt%, and diethylene glycol diethyl ether 0.3 wt%.

[0047] (3) Contact the surface of the polysulfone-based membrane with the aqueous solution prepared in step (1) for 300 s, remove the excess aqueous solution on the surface, contact the membrane layer formed by the aqueous solution with the oil-phase solution prepared in step (2) to carry out an interfacial polymerization reaction for 300 s, remove the excess oil-phase solution on the surface after the reaction is completed, perform heat treatment at 90 °C for 360 s, and obtain a primary reverse osmosis membrane after rinsing; (4) Immerse the primary reverse osmosis membrane obtained in step (3) first in a sodium nitrite solution with a concentration of 0.5 wt%, a temperature of 25 °C, and a pH of 3 for 60 s, and then immerse it in a sodium bisulfite solution with a concentration of 2 wt%, a temperature of 25 °C, and a pH of 3 for 60 s. After the immersion is completed, obtain the high-flux and high-salt rejection reverse osmosis membrane after rinsing.

[0048] Example 9 Example 9 provides a method for preparing a high-flux and high-salt rejection reverse osmosis membrane. The specific preparation process is as follows: (1) Prepare an aqueous solution Add m - phenylenediamine, camphorsulfonic acid, triethylamine, and acetone to water to prepare a homogeneous and transparent aqueous solution. The concentrations of each component in the aqueous solution are as follows: m - phenylenediamine 3 wt%, camphorsulfonic acid 3 wt%, triethylamine 2 wt%, and acetone 5 wt%.

[0049] (2)Prepare an oil - phase solution Add trimesoyl chloride, ethyl acetate, and ethylene glycol diethyl ether to Isopar G to prepare a homogeneous and transparent oil - phase solution. The concentrations of each component in the oil - phase solution are as follows: trimesoyl chloride 0.2 wt%, ethyl acetate 2 wt%, and ethylene glycol diethyl ether 1.5 wt%.

[0050] (3)Contact the surface of the polysulfone - based membrane with the aqueous solution prepared in step (1) for 300 s, remove the excess aqueous solution on the surface, contact the membrane layer formed by the aqueous solution with the oil - phase solution prepared in step (2) to carry out an interfacial polymerization reaction for 300 s. After the reaction is completed, remove the excess oil - phase solution on the surface, perform heat treatment at 90 °C for 360 s, and obtain a primary reverse osmosis membrane after rinsing; (4)First soak the primary reverse osmosis membrane obtained in step (3) in a sodium nitrite solution with a concentration of 0.5 wt%, a temperature of 20 °C, and a pH of 3 for 30 s, and then soak it in a sodium bisulfite solution with a concentration of 1 wt%, a temperature of 25 °C, and a pH of 3 for 60 s. After the soaking is completed, obtain the high - flux and high - salt rejection reverse osmosis membrane after rinsing.

[0051] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that: Step (4) is omitted, and the rest is the same as Example 1.

[0052] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that: Isopropanol is not added to the aqueous solution, and ethyl acetate is not added to the oil - phase solution. The rest is the same as Example 1.

[0053] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that: Isopropanol is not added to the aqueous solution, and the rest is the same as Example 1.

[0054] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that: Ethyl acetate is not added to the oil - phase solution, and the rest is the same as Example 1.

[0055] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that: The sodium bisulfite soaking step in step (4) is omitted, and the rest is the same as Example 1.

[0056] Test Example 1 The surfaces of the reverse osmosis membranes obtained in Examples 1-9 and Comparative Examples 1-5 were observed using a scanning electron microscope. The results are shown respectively in Figure 1 and Figure 2 . It can be seen from Figure 1 that the membrane surfaces of Examples 1-9 all exhibited larger "blade" - shaped structures. This structure facilitated by the co - solvent method significantly improved the water flux of the reverse osmosis membrane.

[0057] Test Example 2 In order to detect the performance of the reverse osmosis membranes obtained in Examples 1-9 and Comparative Examples 1-5, a cross - flow filtration device was used in this experiment to test the water flux and salt rejection rate of the seawater desalination membranes. The effective membrane area of a single rectangular test unit was 42 cm². A sodium chloride solution with a mass concentration of 32 g / L (3.2 wt%) was used as the feed solution, and the feed solution temperature was controlled at 25.0 ± 0.2 °C. After a 3 - hour pre - pressing treatment under an operating pressure of 800 psi (5.5 MPa), filtrate was collected for 30 minutes. The volume of filtrate produced per unit time and per unit membrane area was the water flux (LMH). The salt rejection rate (%) = (feed solution conductivity - filtrate conductivity) / feed solution conductivity. The results of the water flux and salt rejection rate of each reverse osmosis membrane are shown in Table 1.

[0058] Table 1 Results of water flux and salt rejection rate of reverse osmosis membranes in different examples and comparative examples Combining the examples and comparative examples, it can be seen that for the reverse osmosis membranes obtained by post - treatment with nitrous acid and sodium bisulfite, when only the aqueous co - solvent is added without adding the oil - phase co - solvent, the membrane flux and salt rejection rate are not high; when only the oil - phase co - solvent is added without adding the aqueous co - solvent, the membrane flux of the reverse osmosis membrane obtained by post - treatment with nitrous acid and sodium bisulfite is high, but the salt rejection rate is low. Only when both the aqueous co - solvent and the oil - phase co - solvent are present, the membrane flux and salt rejection rate of the reverse osmosis membrane obtained by post - treatment with nitrous acid and sodium bisulfite are both very high.

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, not to limit it. The basic principles and main features of the present invention have been described using specific implementation schemes above. Based on the present invention, some modifications or replacements can be made, but these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the present invention claimed.

Claims

1. A method for preparing a high-throughput reverse osmosis membrane with high salt rejection rate, characterized in that, The porous substrate membrane is successively contacted with an aqueous solution and an oil-phase solution to carry out an interfacial polymerization reaction to form a primary reverse osmosis membrane, and the primary reverse osmosis membrane is successively contacted with a nitrous acid or its salt solution and a hydrogen sulfite solution to obtain the high-flux and high-salt rejection reverse osmosis membrane; the aqueous solution contains an aqueous co-solvent, and the concentration of the aqueous co-solvent in the aqueous solution is 1-95 wt%; the oil-phase solution contains an oil-phase co-solvent.

2. The preparation method according to claim 1, characterized in that, The aqueous solution includes a polyamine monomer, an aqueous co-solvent and water, and the oil-phase solution includes a polyacyl chloride monomer, an oil-phase co-solvent and an alkane solvent.

3. The preparation method according to claim 1, characterized in that, The aqueous co-solvent is one or more of an alcohol solvent, a ketone solvent, and an ether solvent that are miscible with water but do not react with amino groups; the oil-phase co-solvent is one or more of an ester solvent, a ketone solvent, and an ether solvent that are miscible with the alkane solvent but do not react with acyl chloride; the concentration of the oil-phase co-solvent in the oil-phase solution is 0.01-20 wt%.

4. The preparation method according to claim 1, wherein The aqueous co-solvent is selected from one or more of ethanol, n-propanol, isopropanol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerol, acetone, methyl ethyl ketone, diethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl ether acetate; the oil-phase co-solvent is selected from one or more of ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, dimethyl oxalate, diethyl oxalate, dipropyl oxalate, dimethyl malonate, diethyl malonate, dimethyl succinate, diethyl succinate, acetone, methyl ethyl ketone, 2-pentanone, 3-pentanone, diethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol dipropyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, diethylene glycol dibutyl ether, diethylene glycol ethyl ether acetate, diethylene glycol ethyl ether butyrate, diethylene glycol diacetate, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetraethylene glycol dimethyl ether.

5. The preparation method according to claim 1, characterized in that The concentration of nitrite in the nitrous acid or its salt solution is 0.005-5 wt%, the solution temperature is 4-50 °C, and the pH is 1-7; the contact time of the primary reverse osmosis membrane with the nitrous acid or its salt solution is 5-1800 s; the concentration of the hydrogen sulfite solution is 0.05-5 wt%, the temperature is 4-50 °C, and the pH is 1-7; the contact time of the reverse osmosis membrane treated with the nitrous acid or its salt solution with the hydrogen sulfite solution is 5-1800 s.

6. The preparation method of the high-flux and high-salt rejection reverse osmosis membrane according to claim 1, characterized in that, The contact time of the surface of the porous substrate membrane with the aqueous solution is 1-300 s; the time of the interfacial polymerization reaction is 1-300 s.

7. The preparation method of the high-flux and high-salt rejection reverse osmosis membrane according to claim 2, wherein, The concentration of the polyamine monomer in the aqueous solution is 0.5-5 wt%; the polyamine monomer is selected from one or more of o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 1,3,5-triaminobenzene, diaminotoluene, biphenylenediamine, and diaminonaphthalene; the concentration of the polyacyl chloride monomer in the oil phase solution is 0.01-5 wt%; the polyacyl chloride monomer is selected from one or more of trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride, biphenyldicarbonyl chloride, terphthaloyl chloride, benzophenonetetracarbonyl chloride, naphthalenedicarbonyl chloride, naphthalenetricarbonyl chloride, naphthalenetetracarbonyl chloride, malonyl chloride, succinyl chloride, glutaroyl chloride, and adipoyl chloride; the alkane solvent is selected from one or more of hexane, heptane, octane, nonane, decane, undecane, dodecane, Isopar C, Isopar E, Isopar G, Isopar H, Isopar L, and Isopar M.

8. The preparation method of the high-flux and high-salt rejection reverse osmosis membrane according to claim 1, wherein, The material of the porous base membrane is selected from one of polysulfone, polyethersulfone, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, polyimide, polyetherimide, polyacrylonitrile, polyphenylene ether, polyphenylene sulfide, polyether ketone, and polyarylether ketone.

9. A high-flux reverse osmosis membrane with high salt rejection rate, characterized in that It is prepared by using the preparation method according to any one of claims 1-8.

10. Use of the high-flux and high-salt rejection reverse osmosis membrane according to claim 9 in the field of water treatment.

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