Preparation method and application of ternary multifunctional three-dimensional framework mediated high ammonia nitrogen selectivity polyamide reverse osmosis membrane

Abstract

The invention discloses a preparation method and application of a ternary multifunctional three-dimensional framework mediated high ammonia nitrogen selectivity polyamide reverse osmosis membrane, and belongs to the technical field of membrane separation. The method comprises the following steps: 1, preparing a high-molecular copolymer; 2, preparing a polysulfone support layer by adopting a non-solvent induced phase inversion method; 3, preparing a polyamide reverse osmosis membrane by adopting an interfacial polymerization method; and 4, preparing the polyamide reverse osmosis membrane with high ammonia nitrogen selectivity. Through reasonable design of the structure and distribution of the group of the ternary multifunctional three-dimensional structure high-molecular copolymer, the copolymer can react with the acyl chloride group on the surface of the polyamide active layer to form a covalent amido bond, and the covalent amido bond is anchored on the surface of the polyamide layer in situ to construct the functional layer. The functional layer not only can significantly improve the surface potential of the membrane, but also can increase the inherent concentration of ammonia nitrogen on the surface of the membrane, thereby increasing the diffusion resistance, finally realizing the repulsive force to the ammonia nitrogen, and improving the interception capability of the grafted membrane to the ammonia nitrogen. The operation process is simple and mild, the whole membrane preparation process is not changed, and industrialization is easy.

Description

Technical Field

[0001] The present invention belongs to the technical field of membrane separation, and in particular relates to a preparation method and application of a high ammonia nitrogen selectivity polyamide reverse osmosis membrane mediated by a ternary multifunctional stereostructure. Background Art

[0002] With the acceleration of industrialization and the rapid advancement of urbanization, the problem of water shortage is becoming increasingly serious worldwide, especially in areas with scarce water resources. Seeking new water supply has become an important issue for social development. In this context, the development and utilization of unconventional water resources has gradually become a key way to alleviate the pressure on water resources. Among them, the resource treatment and high-quality reuse of domestic sewage has become an important part of water conservation and source of income. Compared with traditional domestic sewage treatment technology that degrades pollutants at the cost of high energy consumption, material consumption and greenhouse gas emissions, membrane separation technology can achieve precise separation and purification without phase change and low energy consumption. Among them, the reverse osmosis membrane (RO) with excellent separation performance has the outstanding advantage of strongly retaining salt ions, pathogenic microorganisms and difficult-to-degrade organic matter, and has become the core unit of high-quality water recycling and reuse technology at home and abroad.

[0003] In recent years, anaerobic biotechnology has attracted much attention because of its ability to recover energy while treating sewage. It can efficiently convert organic pollutants in domestic sewage into bioenergy-methane, greatly improve the energy self-sufficiency rate of the treatment process, and meet the current low-carbon and sustainable development guidelines for sewage treatment. Therefore, the construction of an anaerobic (such as anaerobic membrane bioreactor AnMBR)-reverse osmosis membrane coupled sewage treatment system has the potential to achieve the simultaneous recovery of water resources and energy. In addition, in the production of high-quality recycled water, the most common is the double membrane process of low-pressure membrane-high-pressure membrane series, among which low-pressure membrane filtration technology (such as ultrafiltration (UF) technology) is usually used as the first step of the double membrane water treatment technology to remove particulate matter, colloids, etc. in the effluent of the previous biological treatment to reduce the possibility of contamination of the subsequent high-pressure membrane. Therefore, the construction of an anaerobic-ultrafiltration-reverse osmosis membrane coupled sewage treatment system is expected to become an important window leading the innovation in the field of low-carbon and high-quality in-situ reuse treatment of sewage. However, it is difficult to effectively remove nitrogen and phosphorus pollutants in the anaerobic process, and they can only be converted into ammonia nitrogen and phosphate, which enter the membrane filtration process with the effluent. Ultrafiltration membranes that rely on size screening have no interception capacity for small molecules such as ammonia nitrogen, and the downstream coupled RO membrane has poor interception capacity for ammonia nitrogen. On the one hand, this will cause the ammonia nitrogen content in the RO produced water to exceed the standard by a large margin, posing a greater threat to water eutrophication and human health; on the other hand, it will also cause the loss of ammonia nitrogen in the concentrate, thereby reducing the recovery efficiency of nutrients such as nitrogen and phosphorus. Although adding a biochemical denitrification process to the front end of RO, or adding additional treatment steps to the back end, such as biochar adsorption or chemical oxidation, can reduce the ammonia nitrogen concentration in the recycled water to a safe range, this will also increase energy consumption, material consumption and greenhouse gas emissions. Therefore, strengthening the ammonia nitrogen interception efficiency of the RO membrane itself can promote the development of a low-carbon and high-quality reuse strategy for domestic sewage from the root.

[0004] At present, the membrane regulation and modification strategy to enhance the retention performance of RO membranes for small-sized ions / molecules is mainly to perform in-situ grafting modification on the surface of the separation layer, introduce functional groups with specific functions, change the surface structure or chemical properties of the membrane material, reduce the nonspecific adsorption of target ions / molecules on the membrane surface, and thus achieve efficient removal. However, existing research has limitations in the regulation of the micro-nano structure of the membrane surface. It is impossible to directionally regulate the specific structure of the membrane surface to form a functional layer with a spatial three-dimensional architecture with multi-level protection and multiple functions, while maintaining excellent salt rejection and water flux, and enhancing the ammonia nitrogen retention efficiency of the RO membrane. In addition, improper modification methods can easily cause damage to the main structure of the membrane, leading to membrane defects, which in turn seriously damages the separation performance of the membrane. In addition, the presence of the functional layer may increase the mass transfer resistance of water molecules, resulting in a decrease in transmembrane water flux and increased operating costs, which greatly limits its industrial application in the modification of the surface of the separation membrane. Therefore, how to ensure high ammonia nitrogen retention efficiency and stable chemical structure while overcoming the shortcomings of harsh modification conditions, great damage to the membrane surface structure, and complicated operation process is a problem that needs to be faced in the current large-scale production of high ammonia nitrogen retention RO membranes. The present invention is based on the above technical background and is developed to solve the current problems. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a preparation method and application of a high ammonia nitrogen selectivity polyamide reverse osmosis membrane mediated by a ternary multifunctional stereostructure.

[0006] The present invention rationally designs the structure and distribution of the ternary multifunctional three-dimensional polymer copolymer group, so that it can react with the acyl chloride group on the surface of the polyamide active layer to form a covalent amide bond and in situ anchor on the surface of the polyamide layer to construct a functional layer. The functional layer can not only significantly increase the membrane surface potential, but also increase the inherent concentration of ammonia nitrogen on the membrane surface, thereby increasing the diffusion resistance, and finally achieve the repulsion of ammonia nitrogen and improve the ammonia nitrogen interception capacity of the grafted membrane.

[0007] A method for preparing a polyamide reverse osmosis membrane with high ammonia nitrogen selectivity mediated by a ternary multifunctional stereostructure is specifically completed by the following steps:

[0008] 1. Preparation of polymer copolymers:

[0009] Under the protection of nitrogen atmosphere, amine monomer A, zwitterionic monomer B, amine monomer C and free radical polymerization initiator are added to a mixed solvent of dimethyl sulfoxide and deionized water, and the mixture is heated and stirred for a period of time to obtain a reaction product; the reaction product is dialyzed, concentrated by rotary evaporation and freeze-dried to obtain a high molecular copolymer;

[0010] The structural formula of the polymer copolymer described in step 1 is: Wherein, the value ranges of m, n and h are all 0.1 to 0.8, and m+n+h=1;

[0011] Second, the polysulfone support layer was prepared by a non-solvent induced phase inversion method;

[0012] ①, adding the dried polysulfone particles into the organic solvent, and then sealing, heating, mechanically stirring, naturally degassing, and decompressing to obtain the casting solution;

[0013] ②, under constant temperature and humidity conditions, use a scraper to evenly apply the casting solution on the non-woven fabric, then completely immerse it in a coagulation bath for a period of time, take the non-woven fabric out of the coagulation bath, and obtain a polysulfone support layer;

[0014] 3. Preparation of polyamide reverse osmosis membrane by interfacial polymerization:

[0015] ① Dissolve the aromatic diamine monomer in pure water, add the interfacial polymerization additive, stir evenly to obtain an aqueous solution;

[0016] ②, dissolving polyacyl chloride monomers in an alkane organic solvent, and ultrasonically vibrating to obtain an oil phase solution;

[0017] ③, immersing the polysulfone support layer in the aqueous solution for a period of time, taking it out and evenly blowing it with an air gun to remove the residual aqueous solution on its surface, thereby obtaining a purged support layer;

[0018] ④, immersing the purged support layer into the oil phase solution to undergo polycondensation reaction, taking it out after the reaction is completed, and then using an alkane organic solvent to evenly clean the surface to obtain a polyamide reverse osmosis primary membrane;

[0019] ⑤, placing the polyamide reverse osmosis primary membrane in a constant temperature oven for heat treatment to obtain a polyamide reverse osmosis membrane;

[0020] 4. Preparation of high ammonia nitrogen selectivity polyamide reverse osmosis membrane:

[0021] ①, dissolving the high molecular copolymer prepared in step 1 into a solvent to obtain a grafting modification solution;

[0022] ②. Pour the grafted modified solution onto the surface of the primary polyamide reverse osmosis membrane to carry out the grafting reaction for a period of time. After the grafting reaction is completed, pour out the excess grafted modified solution and place it in an oven for heat treatment for a period of time to obtain a high ammonia nitrogen selectivity polyamide reverse osmosis membrane mediated by a ternary multifunctional three-dimensional structure.

[0023] Principles and key technical points of the present invention:

[0024] The present invention is based on the unique charge characteristics and rich molecular chain configurations of zwitterions, so that zwitterion monomers and amine monomers are blended to undergo Michael addition or Schiff base reaction, thereby realizing the molecular design and synthesis of a ternary multifunctional polymer; then, a covalent amide bond is formed by the reaction between the terminal amine group of the polymer molecule and the acyl chloride group on the surface of the polyamide active layer, so that the ternary multifunctional polymer is in situ anchored on the surface of the polyamide layer, and the specific structure of the membrane surface is directionally regulated to form a functional layer with a spatial three-dimensional structure with multi-level protection and multiple functions. While maintaining an excellent salt interception rate, it can intercept more than 99.25% of ammonia nitrogen in the solution, and its water permeability is also greatly improved.

[0025] Compared with the prior art, the technical advantages of the present invention are:

[0026] 1. The ternary multifunctional polymer molecules with different spatial configurations designed in the present invention provide a complex specific micro-nano structure for the membrane surface, and the selectivity of the RO membrane for ammonia nitrogen is significantly improved by finely regulating the distribution of functional groups in the space;

[0027] 2. The present invention overcomes the limitations of single polymer-modified membrane surface functionalization. Compared with the prior art that relies on a single effect to enhance the membrane's ammonia nitrogen retention capacity, the protonated primary amine groups in the functional layer constructed in the present invention act as tentacles to effectively enhance the inherent concentration of ammonia nitrogen on the membrane surface, forming a reverse concentration gradient from the membrane surface to the feed liquid, and increasing the diffusion resistance of ammonia nitrogen mass transfer; the positively charged amine groups that run through the spatial structure will also exert electrostatic repulsion on the positively charged ammonium ions, synchronously blocking and controlling ammonia nitrogen from penetrating the spatial structure, and effectively preventing ammonia nitrogen from invading the separation layer. At the same time, the outer layer of the spatial structure is covered with a hydrophilic amphiphilic functional layer, which can protect the internal ammonia nitrogen blocking and controlling core functional unit while enhancing the water flux, thereby achieving efficient ammonia nitrogen retention efficiency of the RO membrane during long-term operation;

[0028] 3. The functional layer of the ternary multifunctional three-dimensional structure constructed in the present invention provides the reverse osmosis membrane with higher mechanical strength and structural stability, effectively avoiding the problem that traditional film materials are easily deformed or damaged under high pressure, so that the membrane exhibits longer service life and stability under complex operating conditions;

[0029] 4. The operation process of the present invention is simple and mild, has strong designability, does not change the overall film-making process, and is easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 are scanning electron microscope images of the surfaces of three polyamide reverse osmosis membranes prepared in Comparative Example 1, Example 1 and Example 5;

[0031] Figure 2 It is the hydrophilicity graph of the surface of nine kinds of polyamide reverse osmosis membranes prepared in comparative example 1 and examples 1-8;

[0032] Figure 3 1 is a comparison chart of water permeability and sodium chloride retention of nine polyamide reverse osmosis membranes prepared in Comparative Example 1 and Examples 1-8;

[0033] Figure 4 It is a diagram showing the retention efficiency of nine polyamide reverse osmosis membranes prepared in Comparative Example 1 and Examples 1-8 for ammonia nitrogen in ammonium chloride solution. DETAILED DESCRIPTION

[0034] Specific implementation method 1: This implementation method is a method for preparing a high ammonia nitrogen selectivity polyamide reverse osmosis membrane mediated by a ternary multifunctional three-dimensional structure, which is specifically completed according to the following steps:

[0035] 1. Preparation of polymer copolymers:

[0036] Under the protection of nitrogen atmosphere, amine monomer A, zwitterionic monomer B, amine monomer C and free radical polymerization initiator are added to a mixed solvent of dimethyl sulfoxide and deionized water, and the mixture is heated and stirred for a period of time to obtain a reaction product; the reaction product is dialyzed, concentrated by rotary evaporation and freeze-dried to obtain a high molecular copolymer;

[0037] The structural formula of the polymer copolymer described in step 1 is: Wherein, the value ranges of m, n and h are all 0.1 to 0.8, and m+n+h=1;

[0038] Second, the polysulfone support layer was prepared by a non-solvent induced phase inversion method;

[0039] ①, adding the dried polysulfone particles into the organic solvent, and then sealing, heating, mechanically stirring, naturally degassing, and decompressing to obtain the casting solution;

[0040] ②, under constant temperature and humidity conditions, use a scraper to evenly apply the casting solution on the non-woven fabric, then completely immerse it in a coagulation bath for a period of time, take the non-woven fabric out of the coagulation bath, and obtain a polysulfone support layer;

[0041] 3. Preparation of polyamide reverse osmosis membrane by interfacial polymerization:

[0042] ① Dissolve the aromatic diamine monomer in pure water, add the interfacial polymerization additive, stir evenly to obtain an aqueous solution;

[0043] ②, dissolving polyacyl chloride monomers in an alkane organic solvent, and ultrasonically vibrating to obtain an oil phase solution;

[0044] ③, immersing the polysulfone support layer in the aqueous solution for a period of time, taking it out and evenly blowing it with an air gun to remove the residual aqueous solution on its surface, thereby obtaining a purged support layer;

[0045] ④, immersing the purged support layer into the oil phase solution to undergo polycondensation reaction, taking it out after the reaction is completed, and then using an alkane organic solvent to evenly clean the surface to obtain a polyamide reverse osmosis primary membrane;

[0046] ⑤, placing the polyamide reverse osmosis primary membrane in a constant temperature oven for heat treatment to obtain a polyamide reverse osmosis membrane;

[0047] 4. Preparation of high ammonia nitrogen selectivity polyamide reverse osmosis membrane:

[0048] ①, dissolving the high molecular copolymer prepared in step 1 into a solvent to obtain a grafting modification solution;

[0049] ②. Pour the grafted modified solution onto the surface of the primary polyamide reverse osmosis membrane to carry out the grafting reaction for a period of time. After the grafting reaction is completed, pour out the excess grafted modified solution and place it in an oven for heat treatment for a period of time to obtain a high ammonia nitrogen selectivity polyamide reverse osmosis membrane mediated by a ternary multifunctional three-dimensional structure.

[0050] The preparation method of this embodiment is carried out according to the following steps: first, a ternary multifunctional polymer with a unique spatial stereoscopic configuration is designed, and then a polyamide composite reverse osmosis membrane is prepared by a non-solvent induced phase inversion method and an interfacial polymerization method. Then, the amino groups rich in the ternary multifunctional polymer designed are used to undergo a condensation reaction with the acyl chloride groups on the membrane surface, and the amine groups are anchored in situ on the surface of the polyamide layer to construct a functional layer with a specific spatial stereoscopic structure. The protonated primary amine groups in the constructed functional layer can effectively increase the inherent concentration of ammonia nitrogen on the membrane surface as tentacles, form a reverse concentration gradient from the membrane surface to the feed liquid, and increase the diffusion resistance of ammonia nitrogen mass transfer; the positively charged amine groups running through the spatial structure will also exert electrostatic repulsion on the positively charged ammonium ions, synchronously block and control ammonia nitrogen from penetrating the spatial structure, and effectively prevent ammonia nitrogen from invading the separation layer. At the same time, the outer layer of the spatial structure is covered with a hydrophilic amphiphilic functional layer, which can protect the internal ammonia nitrogen blocking core functional unit while improving the water flux, thereby realizing the efficient retention of ammonia nitrogen by the RO membrane during long-term operation. Through the above method, the problem of poor ammonia nitrogen retention performance of conventional reverse osmosis membranes is overcome. While maintaining an excellent salt rejection rate, more than 99.25% of ammonia nitrogen in the solution can be retained, and its water permeability is also greatly improved. The present invention also provides a high ammonia nitrogen selectivity polyamide reverse osmosis membrane prepared by the above preparation method, which shows broad application prospects in the fields of high-quality reuse of domestic sewage. The method of this embodiment does not need to change the overall membrane preparation process during the scale-up process, and is easy to industrialize.

[0051] Specific embodiment 2: The difference between this embodiment and specific embodiment 1 is that the amine monomer A described in step 1 is a mixture of one or both of 2-aminoethyl methacrylate and 2-aminoethyl methacrylate hydrochloride; the zwitterionic monomer B described in step 1 is [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl)ammonium hydroxide, 2-methacryloyloxyethyl phosphorylcholine, N-(3-sulfopropyl)-N-methacryloyloxyethyl-N,N-dimethylammonium betaine, N,N-dimethylaminoethyl methyl The invention relates to a method for preparing the polymerization product of the present invention, wherein the polymerization product comprises one or more of methyl acrylate, N,N-dimethylaminopropyl acrylamide, 3-[(3-acrylamidopropyl)dimethylammonium]propane-1-sulfonate and 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt; the amine monomer C described in step 1 is a mixture of one or two of acryloyloxyethyltrimethylammonium chloride and methacryloyloxyethyltrimethylammonium chloride; the free radical polymerization initiator described in step 1 is 2,2'-azobisisobutyronitrile. The other steps are the same as those in the first embodiment.

[0052] Specific implementation method three: This implementation method is different from specific implementation method one or two in that: the amount of the free radical polymerization initiator described in step one is 0.1% to 0.6% of the total molar number of the amine monomer A, the zwitterionic monomer B and the amine monomer C; the volume ratio of dimethyl sulfoxide and deionized water in the mixed solvent of dimethyl sulfoxide and deionized water described in step one is 1:(1 to 3); the molar ratio of the amine monomer A, the zwitterionic monomer B and the amine monomer C described in step one is (0.01 to 10):(0.01 to 10):(0.01 to 10); the volume ratio of the total mass of the amine monomer A, the zwitterionic monomer B and the amine monomer C to the mixed solvent of dimethyl sulfoxide and deionized water is (5g to 50g):(250mL to 1000mL). The other steps are the same as specific implementation method one or two.

[0053] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that: in step 1, stirring is performed at 60°C to 100°C for 6h to 48h; in step 1, deionized water is used as a solvent to dialyze the reaction product 6 to 20 times; the temperature of the rotary evaporation concentration in step 1 is 30°C to 70°C, the time of the rotary evaporation concentration is 0.5h to 10h, the temperature of the freeze drying is -60°C to -30°C, and the time of the freeze drying is 0.5h to 10h. The other steps are the same as those of specific embodiments 1 to 3.

[0054] Specific implementation method 5: This implementation method is different from specific implementation methods 1 to 4 in that: the organic solvent described in step 2① is one or more of N-methylpyrrolidone, N,N-dimethylformamide and N,N-dimethylacetamide; the mass fraction of polysulfone in the casting solution described in step 2① is 10% to 25%; the temperature of the heating mechanical stirring described in step 2① is 50℃ to 80℃, the speed of the mechanical stirring is 150r / min to 300r / min, and the time of the mechanical stirring is 2h to 24h; the temperature of the natural degassing described in step 2① is room temperature, and the time of the natural degassing is 3h to 12h; the process of the degassing under reduced pressure described in step 2① is vacuum drying degassing under reduced pressure, and the time of the degassing under reduced pressure is 0.5h to 2h in a vacuum drying oven at room temperature of 25℃ and a vacuum pressure gauge of 0.03 to 0.06MPa. The other steps are the same as those of specific implementation methods 1 to 4.

[0055] Specific implementation method 6: The difference between this implementation method and specific implementation methods 1 to 5 is that: the temperature of the constant temperature and humidity conditions described in step 2② is 20℃~30℃, and the relative humidity is 30%~60%; the height of the scraper described in step 2② is 100μm~300μm; the coagulation bath described in step 2② is 20℃~30℃, and the coagulation bath is tap water, anhydrous ethanol or dimethyl sulfoxide; the time of immersion in the coagulation bath in step 2② is 2min~4min. The other steps are the same as specific implementation methods 1 to 5.

[0056] Specific implementation 7: The difference between this implementation and specific implementations 1 to 6 is that: the aromatic diamine monomer described in step 3① is a mixture of one or more of o-phenylenediamine, m-phenylenediamine and p-phenylenediamine; the interfacial polymerization additive described in step 3① is a mixture of one or more of camphorsulfonic acid, triethylamine, dimethyl sulfoxide, sodium dodecyl sulfate and sodium dodecyl sulfonate; the mass fraction of the aromatic diamine monomer in the aqueous phase solution described in step 3① is 1% to 4%, and the mass fraction of the interfacial polymerization additive is 0.05% to 4%; the polyacyl chloride monomer described in step 3② is a mixture of one or more of trimesoyl chloride, terephthaloyl chloride and o-phthaloyl chloride; the organic solvent described in step 3② is a mixture of one or more of n-hexane, cyclohexane and isoparaffin Isopar-G; the mass fraction of the polyacyl chloride monomer in the oil phase solution described in step 3② is 0.05% to 0.50%. The other steps are the same as specific implementations 1 to 6.

[0057] Specific embodiment eight: This embodiment differs from specific embodiments one to seven in that: in step three (3), the time for immersing the polysulfone support layer in the aqueous solution is 30s to 120s; in step three (3), the time for evenly blowing with an air gun after taking it out is 30s to 120s, and the pressure during blowing is 0.5MPa to 1.0MPa; the time for the polycondensation reaction described in step three (4) is 30s to 120s; the alkane organic solvent described in step three (4) is one or a mixture of n-hexane, cyclohexane and isoparaffin Isopar-G; the temperature of the heat treatment described in step three (5) is 50°C to 100°C, and the time of the heat treatment is 2min to 60min. The other steps are the same as those of specific embodiments one to seven.

[0058] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that: the solvent described in step 4 ① is a mixture of one or more of water, methanol and dimethyl sulfoxide; the concentration of the high molecular copolymer in the grafting modification solution described in step 4 ① is 0.01 g / L to 20 g / L; the time of the grafting reaction described in step 4 ② is 10 s to 6 h; the temperature of the heat treatment described in step 4 ② is 50°C to 100°C, and the time of the heat treatment is 2 min to 60 min; the volume ratio of the grafting modification solution described in step 4 ② to the area of ​​the polyamide reverse osmosis primary membrane is (50 mL to 250 mL): (250 cm 2 ~500cm 2 ). The other steps are the same as those in Specific Embodiments 1 to 8.

[0059] Specific implementation method ten: This implementation method is the application of a high ammonia nitrogen selectivity polyamide reverse osmosis membrane mediated by a ternary multifunctional three-dimensional structure in water treatment.

[0060] The preparation method of this embodiment is carried out according to the following steps: first, a ternary multifunctional polymer with a unique spatial stereoscopic configuration is designed, and then a polyamide composite reverse osmosis membrane is prepared by a non-solvent induced phase inversion method and an interfacial polymerization method. Then, the amino groups rich in the ternary multifunctional polymer designed are used to undergo a condensation reaction with the acyl chloride groups on the membrane surface, and the amine groups are anchored in situ on the surface of the polyamide layer to construct a functional layer with a specific spatial stereoscopic structure. The protonated primary amine groups in the constructed functional layer can effectively increase the inherent concentration of ammonia nitrogen on the membrane surface as tentacles, form a reverse concentration gradient from the membrane surface to the feed liquid, and increase the diffusion resistance of ammonia nitrogen mass transfer; the positively charged amine groups running through the spatial structure will also exert electrostatic repulsion on the positively charged ammonium ions, synchronously block and control ammonia nitrogen from penetrating the spatial structure, and effectively prevent ammonia nitrogen from invading the separation layer. At the same time, the outer layer of the spatial structure is covered with a hydrophilic amphiphilic functional layer, which can protect the internal ammonia nitrogen blocking core functional unit while improving the water flux, thereby realizing the efficient retention of ammonia nitrogen by the RO membrane during long-term operation. Through the above method, the problem of poor ammonia nitrogen retention performance of conventional reverse osmosis membranes is overcome. While maintaining an excellent salt rejection rate, more than 99.25% of ammonia nitrogen in the solution can be retained, and its water permeability is also greatly improved. The present invention also provides a high ammonia nitrogen selectivity polyamide reverse osmosis membrane prepared by the above preparation method, which shows broad application prospects in the fields of high-quality reuse of domestic sewage. The method of this embodiment does not need to change the overall membrane preparation process during the scale-up process, and is easy to industrialize.

[0061] The following examples are used to verify the beneficial effects of the present invention:

[0062] Example 1: A method for preparing a polyamide reverse osmosis membrane with high ammonia nitrogen selectivity mediated by a ternary multifunctional stereostructure, which is specifically completed by the following steps:

[0063] 1. Preparation of polymer copolymers:

[0064] Under nitrogen atmosphere protection, 4.40 g of 2-aminoethyl methacrylate, 7.82 g of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl)ammonium hydroxide, 12.2 g of methacryloyloxyethyltrimethylammonium chloride and 0.10 g of 2,2'-azobisisobutyronitrile were added to a mixed solvent of 250 mL of dimethyl sulfoxide and 500 mL of deionized water, and stirred at 70° C. for 48 h to obtain a reaction product; the reaction product was dialyzed 10 times using deionized water as a solvent, concentrated by rotary evaporation, and freeze-dried to obtain a polymer copolymer;

[0065] The amount of the free radical polymerization initiator used in step 1 is 0.1% to 0.6% of the total molar number of the amine monomer A, the zwitterionic monomer B and the amine monomer C;

[0066] The temperature of the rotary evaporation concentration in step 1 is 50° C., the time of the rotary evaporation concentration is 8 hours, the temperature of the freeze-drying is -60° C., and the time of the freeze-drying is 5 hours;

[0067] The structural formula of the polymer copolymer described in step 1 is:

[0068] Where m is 0.25, n is 0.25, and h is 0.5;

[0069] Second, the polysulfone support layer was prepared by a non-solvent induced phase inversion method;

[0070] ①, adding the dried polysulfone particles into N-methylpyrrolidone, and then sealing, heating, mechanically stirring, naturally degassing, and vacuum decompression degassing to obtain a casting solution;

[0071] The mass fraction of polysulfone in the casting solution described in step 2① is 20%;

[0072] The temperature of the heating mechanical stirring described in step 2① is 70°C, the speed of the mechanical stirring is 200r / min, and the time of the mechanical stirring is 16h;

[0073] The temperature of natural degassing described in step 2① is room temperature, and the time of natural degassing is 12h;

[0074] The process of degassing under reduced pressure in step 2① is vacuum drying and degassing under reduced pressure, that is, in a vacuum drying oven, at room temperature of 25°C and a vacuum pressure gauge of 0.06MPa, the time of degassing under reduced pressure is 2h;

[0075] ②, under constant temperature and humidity conditions, use a scraper to evenly scrape the casting solution on the non-woven fabric, then completely immerse it in a coagulation bath for a period of time, and take the non-woven fabric out of the coagulation bath at a temperature of 25°C after 2 minutes to obtain a polysulfone support layer;

[0076] The temperature of the constant temperature and humidity conditions described in step 2② is 25°C and the relative humidity is 45%;

[0077] The height of the scraper described in step 2② is 150 μm;

[0078] 3. Preparation of polyamide reverse osmosis membrane by interfacial polymerization:

[0079] ① Dissolve m-phenylenediamine and triethylamine in pure water and stir evenly to obtain an aqueous solution;

[0080] The mass fraction of phenylenediamine in the aqueous phase solution described in step 3① is 2%, and the mass fraction of triethylamine is 1.1%;

[0081] ②, dissolve trimesoyl chloride in isoparaffin Isopar-G, and ultrasonically vibrate to obtain an oil phase solution;

[0082] The mass fraction of trimesoyl chloride in the oil phase solution described in step 3② is 0.10%;

[0083] ③, immersing the polysulfone support layer in the aqueous solution for a period of time, taking it out and evenly blowing it with an air gun to remove the residual aqueous solution on its surface, thereby obtaining a purged support layer;

[0084] In step 3③, the polysulfone support layer is immersed in the aqueous solution for 40 seconds;

[0085] After taking out in step 3③, the time for evenly blowing with an air gun is 40 seconds, and the pressure during blowing is 0.7MPa;

[0086] ④. Immerse the purged support layer in the oil phase solution for 60 seconds to undergo polycondensation reaction. After the reaction is completed, take it out and use isoparaffin Isopar-G to evenly clean the surface to obtain a polyamide reverse osmosis primary membrane.

[0087] ⑤, placing the polyamide reverse osmosis primary membrane in a constant temperature oven for heat treatment to obtain a polyamide reverse osmosis membrane;

[0088] The temperature of the heat treatment in step 3⑤ is 60°C, and the time of the heat treatment is 10 minutes;

[0089] 4. Preparation of high ammonia nitrogen selectivity polyamide reverse osmosis membrane:

[0090] ①, dissolving the high molecular copolymer prepared in step 1 into a solvent to obtain a grafting modification solution;

[0091] The solvent described in step 4① is water;

[0092] The concentration of the high molecular copolymer in the graft modification solution described in step 4① is 1 g / L;

[0093] ②, pouring the grafting modification solution onto the surface of the polyamide reverse osmosis primary membrane to carry out the grafting reaction. After the grafting reaction is completed, pouring out the excess grafting modification solution, and then putting it into an oven for heat treatment for a period of time to obtain a high ammonia nitrogen selectivity polyamide reverse osmosis membrane mediated by a ternary multifunctional three-dimensional structure;

[0094] The grafting reaction time described in step 4② is 5 minutes;

[0095] The heat treatment temperature in step 4② is 50°C and the heat treatment time is 5 minutes;

[0096] The volume of the grafting modification solution in step 4② is 150 mL, and the area of ​​the polyamide reverse osmosis primary membrane is 250 cm2 .

[0097] Example 2: The difference between this example and Example 1 is that the concentration of the high molecular copolymer in the grafting modification solution described in step 4① is 5 g / L. The other steps and parameters are the same as those in Example 1.

[0098] Embodiment 3: The difference between this embodiment and embodiment 1 is that the solvent described in step 4① is a mixture of water and methanol, wherein the volume ratio of water to methanol is 1:1. The other steps and parameters are the same as those in embodiment 1.

[0099] Example 4: The difference between this example and Example 1 is that the grafting reaction time in step 4② is 15 minutes. The other steps and parameters are the same as those in Example 1.

[0100] Example 5: The difference between this example and Example 1 is that the method for preparing the polymer copolymer in step 1 is different. The method for preparing the polymer copolymer in step 1 of this example is as follows:

[0101] 1. Preparation of polymer copolymers:

[0102] Under nitrogen atmosphere protection, 4.40 g of 2-aminoethyl methacrylate, 8.26 g of 2-methacryloyloxyethyl phosphorylcholine, 12.2 g of methacryloyloxyethyl trimethylammonium chloride and 0.10 g of 2,2'-azobisisobutyronitrile were added to a mixed solvent of 250 mL of dimethyl sulfoxide and 500 mL of deionized water, and stirred at 80° C. for 24 h to obtain a reaction product; the reaction product was dialyzed 15 times using deionized water as a solvent, concentrated by rotary evaporation, and freeze-dried to obtain a polymer copolymer;

[0103] The temperature of the rotary evaporation concentration in step 1 is 60° C., the time of the rotary evaporation concentration is 5 hours, the temperature of the freeze-drying is -60° C., and the time of the freeze-drying is 5 hours;

[0104] The structural formula of the polymer copolymer described in step 1 is:

[0105] Where m is 0.25, n is 0.25, and h is 0.5.

[0106] Example 6: The difference between this example and Example 5 is that the concentration of the high molecular copolymer in the grafting modification solution described in step 4① is 5 g / L. The other steps and parameters are the same as those in Example 5.

[0107] Embodiment 7: The difference between this embodiment and embodiment 5 is that the solvent described in step 4① is a mixture of water and methanol, wherein the volume ratio of water to methanol is 1:1. The other steps and parameters are the same as those in embodiment 5.

[0108] Example 8: This example is different from Example 5 in that the grafting reaction time in step 4 ② is 15 minutes. The other steps and parameters are the same as those in Example 5.

[0109] Comparative Example 1: A composite reverse osmosis membrane comprising a polysulfone support layer and a polyamide separation layer was prepared by a non-solvent induced phase inversion method and an interfacial polymerization method, which was specifically completed by the following steps:

[0110] 1. Preparation of polysulfone support layer by non-solvent induced phase inversion method:

[0111] ①, adding the dried polysulfone particles into N-methylpyrrolidone, and then sealing, heating, mechanically stirring, naturally degassing, and vacuum decompression degassing to obtain a casting solution;

[0112] The mass fraction of polysulfone in the casting solution described in step 2① is 20%;

[0113] The temperature of the heating mechanical stirring described in step 2① is 70°C, the speed of the mechanical stirring is 200r / min, and the time of the mechanical stirring is 14h;

[0114] The temperature of natural degassing described in step 2① is room temperature, and the time of natural degassing is 12h;

[0115] The process of degassing under reduced pressure in step 2① is vacuum drying and degassing under reduced pressure, that is, in a vacuum drying oven, at room temperature of 25°C and a vacuum pressure gauge of 0.06MPa, the time of degassing under reduced pressure is 2h;

[0116] ②, under constant temperature and humidity conditions, use a scraper to evenly scrape the casting solution on the non-woven fabric, then completely immerse it in a coagulation bath for a period of time, and take the non-woven fabric out of the coagulation bath at a temperature of 25°C after 2 minutes to obtain a polysulfone support layer; the constant temperature and humidity conditions described in step 2② are 25°C and 45% relative humidity;

[0117] The height of the scraper described in step 2② is 150 μm;

[0118] 2. Preparation of polyamide reverse osmosis membrane by interfacial polymerization:

[0119] ① Dissolve m-phenylenediamine in pure water and stir evenly to obtain an aqueous solution;

[0120] The mass fraction of the intermediate phenylenediamine in the aqueous solution in step 2① is 2%;

[0121] ① Dissolve m-phenylenediamine and triethylamine in pure water and stir evenly to obtain an aqueous solution;

[0122] The mass fraction of phenylenediamine in the aqueous phase solution described in step 2① is 2%, and the mass fraction of triethylamine is 1.1%;

[0123] ②, dissolve trimesoyl chloride in isoparaffin Isopar-G, and ultrasonically vibrate to obtain an oil phase solution;

[0124] The mass fraction of trimesoyl chloride in the oil phase solution described in step 2② is 0.10%;

[0125] ③, immersing the polysulfone support layer in the aqueous solution for a period of time, taking it out and evenly blowing it with an air gun to remove the residual aqueous solution on its surface, thereby obtaining a purged support layer;

[0126] In step 2③, the polysulfone support layer is immersed in the aqueous solution for 40 seconds;

[0127] After taking out in step 2③, the time for evenly blowing with an air gun is 40 seconds, and the pressure during blowing is 0.7MPa;

[0128] ④. Immerse the purged support layer in the oil phase solution for 60 seconds to undergo polycondensation reaction. After the reaction is completed, take it out and use isoparaffin Isopar-G to evenly clean the surface to obtain a polyamide reverse osmosis primary membrane.

[0129] ⑤, placing the polyamide reverse osmosis primary membrane in a constant temperature oven for heat treatment to obtain a polyamide reverse osmosis membrane;

[0130] The temperature of the heat treatment in step 2⑤ is 50°C, and the time of the heat treatment is 5 minutes.

[0131] Test Example 1:

[0132] The three polyamide layer reverse osmosis membranes prepared in Comparative Example 1, Example 1 and Example 5 were observed using a scanning electron microscope to observe the surface morphology of the membranes. The results are as follows: Figure 1 As shown in the figure, the surfaces of the polyamide layers of Comparative Example 1 and Examples 1 and 5 all present a typical leaf-like structure, and the surface structure has not changed significantly, and is still a typical peak-valley structure of the polyamide membrane. This indicates that when the functional layer is constructed on the surface of the polyamide membrane by the secondary grafting method, the membrane surface structure is not significantly damaged, and the grafted material does not undergo a cross-linking reaction and aggregate on the surface of the grafted membrane.

[0133] Test Example 2:

[0134] The surface physicochemical properties of the reverse osmosis membrane, hydrophilicity, were further evaluated and analyzed using the OCA contact angle meter from Dataphysics of Germany. The specific steps are as follows: Cut the pre-vacuum dried membrane sample into pieces of appropriate size and fix them on a glass slide with double-sided tape, making sure that the membrane surface faces upward. Place the glass slide on the sample platform, squeeze out a 2μL water droplet by rotating the micro-syringe and drop it on the surface of the membrane sample. After 10 seconds, the morphology of the water droplet on the membrane surface is photographed using the instrument's image capture software, and the contact angle of the membrane surface is calculated using the instrument's own contact angle analysis software. The same membrane sample was tested at 6 different locations, and 3 parallel samples of each type of membrane were tested. The average of all results is the contact angle of the membrane.

[0135] The hydrophilicity test results of the nine polyamide layer reverse osmosis membrane surfaces prepared in Comparative Example 1 and Examples 1-8 are as follows: Figure 2 As shown, after grafting the directed designed amphiphilic molecules, the contact angle of the grafted membrane was significantly reduced compared with the blank polyamide composite membrane, indicating that the introduction of hydrophilic primary amine groups and amphiphilic molecular groups greatly improved the hydrophilicity of the membrane surface.

[0136] Test Example 3:

[0137] Water permeability and NaCl retention rate test: Use pure water to pre-press the membrane sample at an operating pressure of 16 bar for 1.5 hours, and the test is carried out under cross-flow filtration conditions with an operating pressure of 15.5 bar, a water temperature of 25°C, and a cross-flow rate of 22.4 cm / s. When the effluent water quality is stable, take the effluent from the membrane pool to measure the volume, and calculate the water permeability; Use pure water to pre-press the membrane sample at an operating pressure of 16 bar for 1.5 hours, prepare a 2000 mg / L NaCl aqueous solution, and test under cross-flow filtration conditions with an operating pressure of 15.5 bar, a water temperature of 25°C, and a cross-flow rate of 22.4 cm / s. When the effluent water quality is stable, take the inlet water solution and the effluent from the permeation side to test the solution conductivity with a conductivity meter, and convert it into NaCl concentration in the inlet water solution and the effluent from the permeation side based on the conductivity measurement data to calculate the NaCl retention rate.

[0138] The hydrophilicity test results of the nine polyamide layer reverse osmosis membrane surfaces prepared in Comparative Example 1 and Examples 1-8 are as follows: Figure 3 As shown in Figure 2, the water flux of all modified membranes exceeded 3.20 Lm -2 h -1 bar -1 That is, the water flux of the high ammonia nitrogen selectivity polyamide reverse osmosis membrane mediated by the ternary multifunctional stereostructure prepared in Examples 1-8 is higher than that of the blank polyamide reverse osmosis membrane prepared in Comparative Example 1 (1.89 Lm -2 h -1 bar -1) has been greatly improved. The NaCl rejection rate of the high ammonia nitrogen selectivity polyamide reverse osmosis membrane mediated by the ternary multifunctional stereoscopic framework prepared in Examples 1-8 remained constant (>99.00%), which was higher than that of the polyamide reverse osmosis membrane in Comparative Example 1 (98.50%). The results show that the ternary multifunctional stereoscopic polymer copolymer has been successfully grafted and anchored on the surface of the polyamide separation layer. Due to the presence of super hydrophilic amphiphilic groups in the ternary multifunctional stereoscopic polymer copolymer, the hydrophilicity of the membrane surface can be greatly improved while maintaining the compactness of the polyamide separation layer, thereby improving its water flux.

[0139] Test Example 4:

[0140] Ammonia nitrogen retention rate test: Use pure water to pre-press each membrane sample at an operating pressure of 16 bar for 1.5 hours, prepare 50 mg / LN (NH4Cl) solution, and test under the cross-flow filtration conditions of operating pressure of 15.5 bar, water temperature of 25 ° C, and cross-flow rate of 22.4 cm / s. When the effluent water quality is stable, take the inlet water and the effluent from the permeate side to test the ammonia nitrogen concentration in the solution according to the national standard method, and calculate the ammonia nitrogen retention rate.

[0141] The test results of the ammonia nitrogen interception efficiency of the nine polyamide layer reverse osmosis membranes prepared in Comparative Example 1 and Examples 1-8 are as follows: Figure 4 As shown, compared with the polyamide reverse osmosis blank membrane prepared in Comparative Example 1, the high ammonia nitrogen selective polyamide reverse osmosis membrane mediated by the ternary multifunctional stereoscopic structure prepared in Examples 1-8 has a very large improvement in the interception rate of ammonia nitrogen in simulated domestic sewage. Among them, the blank membrane has a retention rate of less than 90% for ammonia nitrogen, and the high ammonia nitrogen selective polyamide reverse osmosis membrane mediated by the ternary multifunctional stereoscopic structure has a retention rate of more than 97.30% for ammonia nitrogen. Among them, the modified membrane prepared in Example 8 with the best effect has a retention rate of 99.25% for ammonia nitrogen.

[0142] In summary, the high ammonia nitrogen selective polyamide reverse osmosis membrane prepared by the present invention has excellent ammonia nitrogen separation performance and water transmission rate, and shows broad application prospects in the field of high-quality reuse of domestic sewage.

Claims

1. A method for preparing a polyamide reverse osmosis membrane with high ammonia nitrogen selectivity mediated by a ternary multifunctional stereostructure, characterized in that The preparation method is specifically completed according to the following steps:

1. Preparation of polymer copolymers: Under the protection of nitrogen atmosphere, amine monomer A, zwitterionic monomer B, amine monomer C and free radical polymerization initiator are added to a mixed solvent of dimethyl sulfoxide and deionized water, and the mixture is heated and stirred for a period of time to obtain a reaction product; the reaction product is dialyzed, concentrated by rotary evaporation and freeze-dried to obtain a high molecular copolymer; The structural formula of the polymer copolymer described in step 1 is: Wherein, the value ranges of m, n and h are all 0.1 to 0.8, and m+n+h=1; Second, the polysulfone support layer was prepared by a non-solvent induced phase inversion method; ①, adding the dried polysulfone particles into the organic solvent, and then sealing, heating, mechanically stirring, naturally degassing, and decompressing to obtain the casting solution; ②, under constant temperature and humidity conditions, use a scraper to evenly apply the casting solution on the non-woven fabric, then completely immerse it in a coagulation bath for a period of time, take the non-woven fabric out of the coagulation bath, and obtain a polysulfone support layer; 3. Preparation of polyamide reverse osmosis membrane by interfacial polymerization: ① Dissolve the aromatic diamine monomer in pure water, add the interfacial polymerization additive, stir evenly to obtain an aqueous solution; ②, dissolving polyacyl chloride monomers in an alkane organic solvent, and ultrasonically vibrating to obtain an oil phase solution; ③, immersing the polysulfone support layer in the aqueous solution for a period of time, taking it out and evenly blowing it with an air gun to remove the residual aqueous solution on its surface, thereby obtaining a purged support layer; ④, immersing the purged support layer into the oil phase solution to undergo polycondensation reaction, taking it out after the reaction is completed, and then using an alkane organic solvent to evenly clean the surface to obtain a polyamide reverse osmosis primary membrane; ⑤, placing the polyamide reverse osmosis primary membrane in a constant temperature oven for heat treatment to obtain a polyamide reverse osmosis membrane; 4. Preparation of high ammonia nitrogen selectivity polyamide reverse osmosis membrane: ①, dissolving the high molecular copolymer prepared in step 1 into a solvent to obtain a grafting modification solution; ②. Pour the grafted modified solution onto the surface of the primary polyamide reverse osmosis membrane to carry out the grafting reaction for a period of time. After the grafting reaction is completed, pour out the excess grafted modified solution and place it in an oven for heat treatment for a period of time to obtain a high ammonia nitrogen selectivity polyamide reverse osmosis membrane mediated by a ternary multifunctional three-dimensional structure.

2. The method for preparing a high ammonia nitrogen selectivity polyamide reverse osmosis membrane mediated by a ternary multifunctional stereostructure according to claim 1, characterized in that The amine monomer A in step 1 is a mixture of one or both of 2-aminoethyl methacrylate and 2-aminoethyl methacrylate hydrochloride; the zwitterionic monomer B in step 1 is [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl)ammonium hydroxide, 2-methacryloyloxyethyl phosphorylcholine, N-(3-sulfopropyl)-N-methacryloyloxyethyl-N,N-dimethylammonium betaine, N,N-dimethylaminoethyl methyl methacrylate, N,N-dimethyl The method comprises the following steps: the step of preparing the polymerization product: a mixture of one or more of 1,2-diaminopropyl acrylamide, 3-[(3-acrylamidopropyl)dimethylammonium]propane-1-sulfonate and 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt; the amine monomer C in step one is a mixture of one or two of acryloyloxyethyltrimethylammonium chloride and methacryloyloxyethyltrimethylammonium chloride; and the free radical polymerization initiator in step one is 2,2'-azobisisobutyronitrile.

3. The method for preparing a high ammonia nitrogen selectivity polyamide reverse osmosis membrane mediated by a ternary multifunctional stereostructure according to claim 1, characterized in that The amount of the free radical polymerization initiator used in step one is 0.1% to 0.6% of the total molar number of the amine monomer A, the zwitterionic monomer B and the amine monomer C; the volume ratio of dimethyl sulfoxide and deionized water in the mixed solvent of dimethyl sulfoxide and deionized water in step one is 1:(1 to 3); the molar ratio of the amine monomer A, the zwitterionic monomer B and the amine monomer C in step one is (0.01 to 10):(0.01 to 10):(0.01 to 10); the volume ratio of the total mass of the amine monomer A, the zwitterionic monomer B and the amine monomer C to the mixed solvent of dimethyl sulfoxide and deionized water is (5g to 50g):(250mL to 1000mL).

4. The method for preparing a high ammonia nitrogen selectivity polyamide reverse osmosis membrane mediated by a ternary multifunctional stereostructure according to claim 1, characterized in that In step one, stirring is performed at 60°C to 100°C for 6h to 48h; in step one, the reaction product is dialyzed 6 to 20 times using deionized water as a solvent; the temperature of the rotary evaporation concentration in step one is 30°C to 70°C, the time of the rotary evaporation concentration is 0.5h to 10h, the temperature of the freeze-drying is -60°C to -30°C, and the time of the freeze-drying is 0.5h to 10h.

5. The method for preparing a high ammonia nitrogen selectivity polyamide reverse osmosis membrane mediated by a ternary multifunctional stereostructure according to claim 1, characterized in that The organic solvent described in step 2① is one or more of N-methylpyrrolidone, N,N-dimethylformamide and N,N-dimethylacetamide; the mass fraction of polysulfone in the casting solution described in step 2① is 10% to 25%; the temperature of the heating mechanical stirring described in step 2① is 50℃ to 80℃, the speed of the mechanical stirring is 150r / min to 300r / min, and the time of the mechanical stirring is 2h to 24h; the temperature of the natural degassing described in step 2① is room temperature, and the time of the natural degassing is 3h to 12h; the process of the reduced pressure degassing described in step 2① is vacuum drying reduced pressure degassing, in a vacuum drying oven, at room temperature of 25℃ and a vacuum pressure gauge of 0.03 to 0.06MPa, the time of the reduced pressure degassing is 0.5h to 2h.

6. The method for preparing a high ammonia nitrogen selectivity polyamide reverse osmosis membrane mediated by a ternary multifunctional stereostructure according to claim 1, characterized in that The temperature of the constant temperature and humidity conditions described in step 2② is 20℃~30℃, and the relative humidity is 30%~60%; the height of the scraper described in step 2② is 100μm~300μm; the coagulation bath described in step 2② is 20℃~30℃, and the coagulation bath is tap water, anhydrous ethanol or dimethyl sulfoxide; the immersion time in the coagulation bath in step 2② is 2min~4min.

7. The method for preparing a high ammonia nitrogen selectivity polyamide reverse osmosis membrane mediated by a ternary multifunctional stereostructure according to claim 1, characterized in that The aromatic diamine monomer described in step 3① is a mixture of one or more of o-phenylenediamine, m-phenylenediamine and p-phenylenediamine; the interfacial polymerization additive described in step 3① is a mixture of one or more of camphorsulfonic acid, triethylamine, dimethyl sulfoxide, sodium dodecyl sulfate and sodium dodecyl sulfonate; the mass fraction of the aromatic diamine monomer in the aqueous phase solution described in step 3① is 1% to 4%, and the mass fraction of the interfacial polymerization additive is 0.05% to 4%; the polyacyl chloride monomer described in step 3② is a mixture of one or more of trimesoyl chloride, terephthaloyl chloride and phthaloyl chloride; the organic solvent described in step 3② is a mixture of one or more of n-hexane, cyclohexane and isoparaffin Isopar-G; the mass fraction of the polyacyl chloride monomer in the oil phase solution described in step 3② is 0.05% to 0.50%.

8. The method for preparing a high ammonia nitrogen selectivity polyamide reverse osmosis membrane mediated by a ternary multifunctional stereostructure according to claim 1, characterized in that In step 3③, the time for immersing the polysulfone support layer in the aqueous solution is 30s to 120s; the time for evenly blowing with an air gun after taking out in step 3③ is 30s to 120s, and the pressure during blowing is 0.5MPa to 1.0MPa; the time for the polycondensation reaction described in step 3④ is 30s to 120s; the alkane organic solvent described in step 3④ is one or a mixture of n-hexane, cyclohexane and isoalkane Isopar-G; the temperature of the heat treatment described in step 3⑤ is 50°C to 100°C, and the time of the heat treatment is 2min to 60min.

9. The method for preparing a high ammonia nitrogen selectivity polyamide reverse osmosis membrane mediated by a ternary multifunctional stereostructure according to claim 1, characterized in that The solvent described in step 4① is a mixture of one or more of water, methanol and dimethyl sulfoxide; the concentration of the high molecular copolymer in the grafting modification solution described in step 4① is 0.01g / L~20g / L; the time of the grafting reaction described in step 4② is 10s~6h; the temperature of the heat treatment described in step 4② is 50℃~100℃, and the heat treatment time is 2min~60min; the volume ratio of the grafting modification solution described in step 4② to the area of ​​the polyamide reverse osmosis primary membrane is (50mL~250mL):(250cm 2 ~500cm 2 ).

10. Application of a ternary multifunctional three-dimensional framework-mediated high ammonia nitrogen selectivity polyamide reverse osmosis membrane prepared by the preparation method according to claim 1, characterized in that A ternary multifunctional stereostructure-mediated high ammonia nitrogen selectivity polyamide reverse osmosis membrane is used in water treatment.

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