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

Abstract

A preparation method and application of a ternary multifunctional three-dimensional architecture-mediated high ammonia nitrogen-selective polyamide reverse osmosis membrane, which belongs to the field of membrane separation technology. Method: First, prepare a polymer copolymer; second, prepare a polysulfone support layer by non-solvent induced phase inversion method; third, prepare a polyamide reverse osmosis membrane by interfacial polymerization method; fourth, prepare a high ammonia nitrogen-selective polyamide reverse osmosis membrane. By reasonably designing the structure and distribution of the ternary multifunctional three-dimensional architecture polymer copolymer groups, the present invention enables them to react with the acyl chloride groups on the surface of the polyamide active layer to form covalent amide bonds 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 ammonia nitrogen concentration on the membrane surface, thereby increasing the diffusion resistance, and finally jointly realizing the repulsive force for ammonia nitrogen and improving the retention ability of the grafted membrane for ammonia nitrogen. The operation process of the present invention is simple and mild, does not change the overall membrane preparation process, and is easy to industrialize.

Description

Technical Field

[0001] The present invention belongs to the technical field of membrane separation, and particularly relates to a preparation method and application of a high ammonia nitrogen selective polyamide reverse osmosis membrane mediated by a ternary multifunctional three-dimensional architecture. Background Art

[0002] With the acceleration of the industrialization process and the rapid advancement of urbanization, the problem of water resource shortage has become increasingly severe globally. Especially in water-scarce regions, seeking new water source supplies has become an important topic for social development. Against this background, the development and utilization of unconventional water resources have gradually become a key approach to alleviating water resource pressure. Among them, the resource treatment and high-quality reuse of domestic sewage have become an important part of water conservation and water source expansion. Compared with traditional domestic sewage treatment technologies that degrade 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 with low energy consumption. Among them, reverse osmosis membranes (RO) with excellent separation performance have the outstanding advantage of strongly retaining salt ions, pathogenic microorganisms, and refractory organic compounds, and have become the core unit of high-quality water regeneration and reuse technologies at home and abroad.

[0003] In recent years, anaerobic biotechnology has attracted much attention because it can recover energy while treating sewage. It can efficiently convert organic pollutants in domestic sewage into bioenergy - methane, greatly improving the energy self - sufficiency rate of the treatment process and conforming to the current low - carbon and sustainable development guidelines for sewage treatment. Therefore, constructing an anaerobic (such as anaerobic membrane bioreactor AnMBR) - reverse osmosis membrane coupled sewage treatment system has the potential to achieve the synchronous recovery of water resources and energy. In addition, in the production of high - quality reclaimed water, the most common is the dual - membrane process of low - pressure membrane - high - pressure membrane in series. Among them, low - pressure membrane filtration technology (such as ultrafiltration (UF) technology) is usually used as the first step of the dual - membrane water treatment technology to remove particulate matter, colloids, etc. in the effluent of the previous biological treatment, so as to reduce the possibility of pollution to the subsequent high - pressure membrane. Therefore, constructing 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 of sewage treatment. However, the anaerobic process is difficult to effectively remove nitrogen and phosphorus pollutants, and can only convert them into ammonia nitrogen and phosphate, which enter the membrane filtration process with the effluent. The ultrafiltration membrane relying on size screening has no retention ability for small - molecule substances such as ammonia nitrogen, and the downstream coupled RO membrane has poor retention ability for ammonia nitrogen. On the one hand, it will cause the ammonia nitrogen content in the RO product water to exceed the standard significantly, posing a great threat to water eutrophication and human health; on the other hand, it will also lead to the loss of ammonia nitrogen in the concentrate, thus reducing the recovery efficiency of nutrients such as nitrogen and phosphorus. Although adding a biochemical denitrification process at the front end of RO or adding additional treatment steps at the back end, such as biochar adsorption or chemical oxidation, can reduce the ammonia nitrogen concentration in the reclaimed water to a safe range, this will also increase energy consumption, material consumption and greenhouse gas emissions. Therefore, strengthening the ammonia nitrogen retention efficiency of the RO membrane itself can promote the development of the low - carbon and high - quality reuse strategy of domestic sewage from the root cause.

[0004] At present, the membrane regulation and modification strategies for enhancing the retention performance of RO membranes towards small-sized ions / molecules mainly involve in-situ grafting modification treatment on the surface of the separation layer. By introducing functional groups with specific functions, the surface structure or chemical properties of the membrane material are changed, reducing the non-specific adsorption of target ions / molecules on the membrane surface, and thus achieving their efficient removal. However, the existing research has limitations in the regulation of the micro-nano structure on the membrane surface, unable to directionally regulate the specific structure on the membrane surface to form a functional layer with a three-dimensional architecture with multi-level protection and multiple functions, while maintaining excellent salt rejection rate and water flux, and enhancing the ammonia nitrogen retention efficiency of RO membranes. Moreover, improper modification methods are likely to cause damage to the main structure of the membrane, leading to membrane defects, and thus seriously damaging 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 the transmembrane water flux and an increase in the operating cost, greatly limiting its industrial application in modifying the separation membrane surface. Therefore, how to overcome the disadvantages of harsh modification conditions, large damage to the membrane surface structure, and complex and cumbersome operation process while ensuring high ammonia nitrogen retention efficiency and stable chemical structure is a problem that needs to be faced for the large-scale production of high ammonia nitrogen retention RO membranes. The present invention is developed and improved based on the above technical background to solve the current problems. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a preparation method and application of a high ammonia nitrogen selective polyamide reverse osmosis membrane mediated by a ternary multi-functional three-dimensional architecture.

[0006] By reasonably designing the structure and distribution of the ternary multi-functional three-dimensional architecture polymer copolymer groups, the present invention enables them to react with the acyl chloride groups on the surface of the polyamide active layer to form covalent amide bonds 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 ammonia nitrogen concentration on the membrane surface, thereby increasing the diffusion resistance, and finally jointly achieving the repulsive force against ammonia nitrogen and enhancing the retention ability of the grafted membrane towards ammonia nitrogen.

[0007] A preparation method of a high ammonia nitrogen selective polyamide reverse osmosis membrane mediated by a ternary multi-functional three-dimensional architecture is specifically completed according to the following steps:

[0008] I. Preparation of the polymer copolymer:

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

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

[0011] II. Prepare a polysulfone support layer by the non-solvent induced phase inversion method;

[0012] ①. Add dry polysulfone particles to an organic solvent, then seal, heat with mechanical stirring, naturally degas, and degas under reduced pressure to obtain a casting solution;

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

[0014] III. Prepare a polyamide reverse osmosis membrane by the interfacial polymerization method:

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

[0016] ②. Dissolve a polyfunctional acyl chloride monomer in an alkane organic solvent and ultrasonically oscillate to obtain an oil phase solution;

[0017] ③. Immerse the polysulfone support layer in the aqueous solution for a period of time, take it out, and evenly blow it with an air gun to remove the residual aqueous solution on its surface to obtain a blown support layer;

[0018] ④. Immerse the blown support layer in the oil phase solution to carry out a polycondensation reaction. After the reaction is completed, take it out and evenly wash the surface with an alkane organic solvent to obtain a polyamide reverse osmosis primary membrane;

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

[0020] IV. Prepare a high ammonia nitrogen selective polyamide reverse osmosis membrane:

[0021] ①. Dissolve the high molecular copolymer prepared in step one in a solvent to obtain a graft modification solution;

[0022] ②. Pour the graft modification solution onto the surface of the polyamide reverse osmosis primary membrane and carry out a graft reaction for a period of time. After the graft reaction is completed, pour out the excess graft modification solution, and then put it into the oven for heat treatment for a period of time to obtain a high ammonia nitrogen selective polyamide reverse osmosis membrane mediated by a ternary multifunctional three-dimensional framework.

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

[0024] Based on the unique charge characteristics and rich molecular chain configurations of zwitterions, the zwitterionic monomer is blended with the amine monomer to undergo Michael addition or Schiff base reaction, realizing the molecular design and synthesis of ternary multifunctional polymers. Then, covalent amide bonds are formed through the reaction between the amine groups at the ends of the polymer molecules and the acyl chloride groups on the surface of the polyamide active layer, achieving the in-situ anchoring of the ternary multifunctional polymer on the surface of the polyamide layer, directionally regulating the specific structure on the membrane surface, and forming a functional layer with a three-dimensional architecture with multi-level protection and multiple functions. While maintaining excellent salt rejection rate, it can retain more than 99.25% of ammonia nitrogen in the solution, and its water permeability performance has also been greatly improved.

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

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

[0027] 2. The present invention overcomes the limitations of membrane surface functionalization by single polymer modification. Compared with the prior art that relies on a single effect to improve the ammonia nitrogen retention ability of the membrane, the protonated primary amine groups in the functional layer constructed in the present invention can effectively increase the inherent concentration of ammonia nitrogen on the membrane surface as a touchable, forming an inverse 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 throughout the spatial architecture will also exert an electrostatic repulsive force on the positively charged ammonium ions, simultaneously blocking the penetration of ammonia nitrogen through the spatial architecture and effectively preventing the intrusion of ammonia nitrogen into the separation layer. At the same time, the outer layer of the spatial architecture is covered with a hydrophilic amphoteric functional layer, which can protect the internal ammonia nitrogen blocking core functional unit while increasing the water flux, realizing the high-efficiency ammonia nitrogen retention performance of the RO membrane during long-term operation.

[0028] 3. The functional layer with a ternary multifunctional three-dimensional architecture constructed in the present invention provides higher mechanical strength and structural stability for the reverse osmosis membrane, effectively avoiding the problems that traditional thin film materials are prone to deformation or damage under high pressure, making the membrane show a longer service life and stability under complex operating conditions.

[0029] 4. The operation process of the present invention is simple, mild, highly designable, does not change the overall membrane-making process, and is easy to industrialize. Description of the Drawings

[0030] Figure 1 are the 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 are the hydrophilicity diagrams of the surfaces of nine polyamide reverse osmosis membranes prepared in Comparative Example 1 and Examples 1-8.

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

[0033] Figure 4 It is an interception efficiency chart of ammonia nitrogen in ammonium chloride solution by nine polyamide reverse osmosis membranes prepared in Comparative Example 1 and Examples 1-8. Detailed implementation manners

[0034] Detailed implementation manner 1: A preparation method of a ternary multifunctional three-dimensional architecture-mediated polyamide reverse osmosis membrane with high ammonia nitrogen selectivity is specifically completed according to the following steps:

[0035] I. Preparation of a polymer copolymer:

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

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

[0038] II. Preparation of a polysulfone support layer by the non-solvent induced phase inversion method;

[0039] ①. Dry polysulfone particles are added to an organic solvent, and then sealed, heated and mechanically stirred, naturally degassed, and vacuum degassed to obtain a casting solution;

[0040] ②. Under constant temperature and humidity conditions, the casting solution is evenly scraped onto a non-woven fabric with a doctor blade, and then it is completely immersed in a coagulation bath for a period of time, and the non-woven fabric is taken out of the coagulation bath to obtain a polysulfone support layer;

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

[0042] ①. An aromatic diamine monomer is dissolved in pure water, and then an interfacial polymerization additive is added and stirred evenly to obtain an aqueous solution;

[0043] ②. A polyfunctional acyl chloride monomer is dissolved in an alkane organic solvent and ultrasonically oscillated to obtain an oil phase solution;

[0044] ③. The polysulfone support layer is immersed in the aqueous solution for a period of time, taken out and evenly purged with an air gun to remove the residual aqueous solution on its surface to obtain a purged support layer;

[0045] ④. Immerse the purged support layer into the oil-phase solution for polycondensation reaction. After the reaction ends, take it out and then uniformly wash the surface with an alkane organic solvent to obtain a polyamide reverse osmosis nascent membrane;

[0046] ⑤. Heat-treat the polyamide reverse osmosis nascent membrane in a constant-temperature oven to obtain a polyamide reverse osmosis membrane;

[0047] IV. Preparation of a highly ammonia-nitrogen-selective polyamide reverse osmosis membrane:

[0048] ①. Dissolve the high molecular copolymer prepared in Step 1 into a solvent to obtain a graft-modified solution;

[0049] ②. Pour the graft-modified solution onto the surface of the polyamide reverse osmosis nascent membrane and conduct a graft reaction for a period of time. After the graft reaction is completed, pour out the excess graft-modified solution, and then place it in an oven for heat treatment for a period of time to obtain a highly ammonia-nitrogen-selective polyamide reverse osmosis membrane mediated by a ternary multifunctional three-dimensional framework.

[0050] The preparation method of this embodiment is carried out according to the following steps: First, a ternary multifunctional polymer with a unique spatial three-dimensional configuration is designed directionally. Then, a polyamide composite reverse osmosis membrane is prepared by the non-solvent induced phase inversion method and the interfacial polymerization method. Then, the polycondensation reaction occurs between the amine groups rich in the directionally designed ternary multifunctional polymer and the acyl chloride groups on the membrane surface, and it is in-situ anchored on the surface of the polyamide layer to construct a functional layer with a specific spatial three-dimensional framework. The protonated primary amine groups in the constructed functional layer can effectively increase the inherent ammonia-nitrogen concentration on the membrane surface as a handle, forming an inverse concentration gradient from the membrane surface to the feed liquid, increasing the diffusion resistance of ammonia-nitrogen mass transfer; the positively charged amine groups penetrating the spatial framework will also exert an electrostatic repulsion on the positively charged ammonium ions, simultaneously blocking the penetration of ammonia-nitrogen through the spatial framework, effectively preventing ammonia-nitrogen from invading the separation layer. At the same time, the outer layer of the spatial framework is covered with a hydrophilic amphoteric functional layer, which can improve the water flux while protecting the internal ammonia-nitrogen blocking core functional unit, realizing the efficient interception of ammonia-nitrogen by the RO membrane during long-term operation. Through the above method, the problem of poor ammonia-nitrogen interception performance of conventional reverse osmosis membranes is overcome. While maintaining an excellent salt rejection rate, it can intercept more than 99.25% of ammonia-nitrogen in the solution, and its water permeability performance has also been greatly improved. The present invention also provides a highly ammonia-nitrogen-selective polyamide reverse osmosis membrane prepared by the above preparation method, and this polyamide reverse osmosis membrane shows broad application prospects in the fields such as 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] Embodiment 2: The difference between this embodiment and Embodiment 1 is as follows: The amine monomer A described in Step 1 is one or a mixture of two of 2-aminoethyl methacrylate and 2-aminoethyl methacrylate hydrochloride; the zwitterionic monomer B described in Step 1 is [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide, 2-methacryloyloxyethyl phosphorylcholine, N-(3-sulfopropyl)-N-methacryloyloxyethyl-N,N-dimethylammonium betaine, N,N-dimethylaminoethyl methacrylate, N,N-dimethylaminopropyl acrylamide, 3-[(3-acrylamidopropyl)dimethylammonio]propane-1-sulfonate, and 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium] propane-1-sulfonate inner salt, one or a mixture of several; the amine monomer C described in Step 1 is one or a mixture of two of acryloyloxyethyl trimethylammonium chloride and methacryloyloxyethyl trimethylammonium chloride; the radical polymerization initiator described in Step 1 is 2,2'-azobisisobutyronitrile. Other steps are the same as those in Embodiment 1.

[0052] Embodiment 3: The difference between this embodiment and one of Embodiments 1 or 2 is as follows: The amount of the radical polymerization initiator described in Step 1 is 0.1% - 0.6% of the total molar amount of the amine monomer A, the zwitterionic monomer B, and the amine monomer C; the volume ratio of dimethyl sulfoxide to deionized water in the mixed solvent of dimethyl sulfoxide and deionized water described in Step 1 is 1:(1 - 3); the molar ratio of the amine monomer A, the zwitterionic monomer B, and the amine monomer C described in Step 1 is (0.01 - 10):(0.01 - 10):(0.01 - 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 - 50g):(250mL - 1000mL). Other steps are the same as those in Embodiment 1 or 2.

[0053] Embodiment 4: The difference between this embodiment and one of Embodiments 1 to 3 is as follows: Stirring is carried out at 60°C - 100°C for 6h - 48h in Step 1; the reaction product is dialyzed 6 - 20 times using deionized water as a solvent in Step 1; the temperature of the rotary evaporation concentration described in Step 1 is 30°C - 70°C, and the time of the rotary evaporation concentration is 0.5h - 10h. The temperature of the freeze-drying is -60°C - -30°C, and the time of the freeze-drying is 0.5h - 10h. Other steps are the same as those in Embodiments 1 to 3.

[0054] Specific Embodiment 5: The differences between this embodiment and any one of Specific Embodiments 1 to 4 are as follows: 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% - 25%; the temperature of the heating mechanical stirring in Step 2① is 50°C - 80°C, the speed of the mechanical stirring is 150 r / min - 300 r / min, and the time of the mechanical stirring is 2 h - 24 h; the temperature of the natural defoaming in Step 2① is room temperature, and the time of the natural defoaming is 3 h - 12 h; the process of the reduced-pressure defoaming in Step 2① is vacuum drying reduced-pressure defoaming. In the vacuum drying oven, under the conditions of normal temperature 25°C and vacuum pressure gauge 0.03 - 0.06 MPa, the time of the reduced-pressure defoaming is 0.5 h - 2 h. Other steps are the same as those in Specific Embodiments 1 to 4.

[0055] Specific Embodiment 6: The differences between this embodiment and any one of Specific Embodiments 1 to 5 are as follows: The temperature of the constant temperature and humidity conditions described in Step 2② is 20°C - 30°C, and the relative humidity is 30% - 60%; the height of the doctor blade described in Step 2② is 100 μm - 300 μm; the coagulation bath described in Step 2② is at 20°C - 30°C, and the coagulation bath is tap water, absolute ethanol, or dimethyl sulfoxide; the time of immersion in the coagulation bath in Step 2② is 2 min - 4 min. Other steps are the same as those in Specific Embodiments 1 to 5.

[0056] Specific Embodiment 7: The differences between this embodiment and any one of Specific Embodiments 1 to 6 are as follows: The aromatic diamine monomer described in Step 3① is one or a mixture of several of o-phenylenediamine, m-phenylenediamine, and p-phenylenediamine; the interfacial polymerization additive described in Step 3① is one or a mixture of several of camphorsulfonic acid, triethylamine, dimethyl sulfoxide, sodium dodecyl sulfate, and sodium dodecyl sulfonate; the mass fraction of the aromatic diamine monomer in the aqueous solution in Step 3① is 1% - 4%, and the mass fraction of the interfacial polymerization additive is 0.05% - 4%; the polyvalent acyl chloride monomer described in Step 3② is one or a mixture of several of trimesoyl chloride, terephthaloyl chloride, and phthaloyl chloride; the organic solvent described in Step 3② is one or a mixture of several of n-hexane, cyclohexane, and isoparaffin Isopar-G; the mass fraction of the polyvalent acyl chloride monomer in the oil phase solution in Step 3② is 0.05% - 0.50%. Other steps are the same as those in Specific Embodiments 1 to 6.

[0057] Embodiment 8: The difference between this embodiment and any one of Embodiments 1 to 7 is as follows: In step 3③, the time for immersing the polysulfone support layer in the aqueous solution is 30 s to 120 s; in step 3③, the time for uniformly purging with an air gun after taking out is 30 s to 120 s, and the pressure during purging is 0.5 MPa to 1.0 MPa; in step 3④, the time for the polycondensation reaction is 30 s to 120 s; in step 3④, the alkane organic solvent is one or a mixture of several of n-hexane, cyclohexane, and Isopar-G; in step 3⑤, the temperature of the heat treatment is 50 °C to 100 °C, and the time of the heat treatment is 2 min to 60 min. Other steps are the same as those in Embodiments 1 to 7.

[0058] Embodiment 9: The difference between this embodiment and any one of Embodiments 1 to 8 is as follows: In step 4①, the solvent is one or a mixture of several of water, methanol, and dimethyl sulfoxide; in step 4①, the concentration of the polymer copolymer in the graft modification solution is 0.01 g / L to 20 g / L; in step 4②, the time for the graft reaction is 10 s to 6 h; in step 4②, the temperature of the heat treatment is 50 °C to 100 °C, and the time of the heat treatment is 2 min to 60 min; in step 4②, the volume ratio of the graft modification solution to the area of the polyamide reverse osmosis primary membrane is (50 mL to 250 mL):(250 cm 2 ~500 cm 2 ). Other steps are the same as those in Embodiments 1 to 8.

[0059] Embodiment 10: This embodiment is an application of a ternary multifunctional three-dimensional structure-mediated high-ammonia-nitrogen-selective polyamide reverse osmosis membrane 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 three-dimensional configuration is designed directionally. Then, a polyamide composite reverse osmosis membrane is prepared by the non-solvent induced phase inversion method and the interfacial polymerization method. Then, the polycondensation reaction occurs between the amino groups rich in the directionally designed ternary multifunctional polymer and the acyl chloride groups on the membrane surface, and it is in-situ anchored on the surface of the polyamide layer to construct a functional layer with a specific three-dimensional structure. The protonated primary amino groups in the constructed functional layer can effectively increase the inherent ammonia nitrogen concentration on the membrane surface as a handle, forming an inverse concentration gradient from the membrane surface to the feed liquid, increasing the diffusion resistance of ammonia nitrogen mass transfer; the positively charged amine groups penetrating the three-dimensional structure will also exert an electrostatic repulsion on the positively charged ammonium ions, simultaneously blocking the penetration of ammonia nitrogen through the three-dimensional structure, effectively preventing ammonia nitrogen from invading the separation layer. At the same time, the outer layer of the three-dimensional structure is covered with a hydrophilic amphiphilic functional layer, which can protect the internal ammonia nitrogen blocking core functional unit while increasing the water flux, realizing the efficient interception of ammonia nitrogen by the RO membrane during long-term operation. Through the above method, the problem of poor ammonia nitrogen interception performance of conventional reverse osmosis membranes is overcome. While maintaining an excellent salt rejection rate, it can intercept more than 99.25% of ammonia nitrogen in the solution, and its water permeability performance has also been greatly improved. The present invention also provides a high ammonia nitrogen selective polyamide reverse osmosis membrane prepared by the above preparation method, and this polyamide reverse osmosis membrane shows broad application prospects in the fields such as 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 preparation method of a high ammonia nitrogen selective polyamide reverse osmosis membrane mediated by a ternary multifunctional three-dimensional structure is specifically completed according to the following steps:

[0063] I. Preparation of a polymer copolymer:

[0064] Under the protection of a nitrogen atmosphere, 4.40 g of 2-aminoethyl methacrylate, 7.82 g of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide, 12.2 g of methacryloyloxyethyl trimethyl ammonium chloride, and 0.10 g of 2,2'-azobisisobutyronitrile are 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 is dialyzed 10 times, rotary evaporated and concentrated, and freeze-dried using deionized water as a solvent to obtain a polymer copolymer;

[0065] The dosage of the radical polymerization initiator in step I is 0.1% - 0.6% of the total molar amount of amine monomer A, zwitterionic monomer B, and amine monomer C;

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

[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] II. Prepare a polysulfone support layer by non-solvent induced phase inversion method;

[0070] ① Add dry polysulfone particles to N-methylpyrrolidone, and then seal, heat, mechanically stir, naturally defoam, and vacuum decompression defoam to obtain a casting solution;

[0071] The mass fraction of polysulfone in the casting solution described in Step 2 ① is 20%;

[0072] The temperature of the mechanical stirring with heating in Step 2 ① is 70°C, the speed of mechanical stirring is 200 r / min, and the time of mechanical stirring is 16 h;

[0073] The temperature of natural defoaming in Step 2 ① is room temperature, and the time of natural defoaming is 12 h;

[0074] The process of decompression defoaming in Step 2 ① is vacuum drying decompression defoaming, that is, in a vacuum drying oven, at a normal temperature of 25°C and a vacuum pressure gauge of 0.06 MPa, the time of decompression defoaming is 2 h;

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

[0076] The temperature of the constant temperature and humidity conditions in Step 2 ② is 25°C, and the relative humidity is 45%;

[0077] The height of the scraper in Step 2 ② is 150 μm;

[0078] III. Prepare a 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 m-phenylenediamine in the aqueous solution described in Step 3 ① is 2%, and the mass fraction of triethylamine is 1.1%;

[0081] ②. Dissolve trimesoyl chloride in isoparaffin Isopar-G, and perform ultrasonic oscillation 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. Immerse the polysulfone support layer in the aqueous solution for a period of time, take it out, and uniformly blow it with an air gun to remove the residual aqueous solution on its surface, obtaining the blown support layer;

[0084] In step ③③, the time for immersing the polysulfone support layer in the aqueous solution is 40 s;

[0085] In step ③③, the time for uniformly blowing with an air gun after taking it out is 40 s, and the pressure during blowing is 0.7 MPa;

[0086] ④. Immerse the blown support layer in the oil-phase solution for 60 s to carry out a polycondensation reaction. After the reaction is completed, take it out, and then uniformly clean the surface with isoparaffin Isopar-G to obtain a polyamide reverse osmosis primary membrane;

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

[0088] In step ③⑤, the temperature of the heat treatment is 60 °C, and the time of the heat treatment is 10 min;

[0089] IV. Preparation of a polyamide reverse osmosis membrane with high ammonia nitrogen selectivity:

[0090] ①. Dissolve the high molecular copolymer prepared in step one in a solvent to obtain a graft-modified solution;

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

[0092] In step ④①, the concentration of the high molecular copolymer in the graft-modified solution is 1 g / L;

[0093] ②. Pour the graft-modified solution onto the surface of the polyamide reverse osmosis primary membrane to carry out a grafting reaction. After the grafting reaction is completed, pour out the excess graft-modified solution, and then put it into an oven for heat treatment for a period of time to obtain a polyamide reverse osmosis membrane with high ammonia nitrogen selectivity mediated by a ternary multi-functional three-dimensional framework;

[0094] In step ④②, the time of the grafting reaction is 5 min;

[0095] In step ④②, the temperature of the heat treatment is 50 °C, and the time of the heat treatment is 5 min;

[0096] In step ④②, the volume of the graft-modified solution 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 polymer copolymer in the graft modification solution described in step ④① is 5 g / L. Other steps and parameters are the same as those in Example 1.

[0098] Example 3: The difference between this example and Example 1 is that the solvent described in step ④① is a mixed solution of water and methanol, and the volume ratio of water to methanol is 1:1. Other steps and parameters are the same as those in Example 1.

[0099] Example 4: The difference between this example and Example 1 is that the graft reaction time described in step ④② is 15 min. 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] I. Preparation of the polymer copolymer:

[0102] Under the protection of a nitrogen atmosphere, 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 are 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 is dialyzed 15 times using deionized water as the solvent, rotary evaporated and concentrated, and freeze-dried to obtain the polymer copolymer;

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

[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 polymer copolymer in the graft modification solution described in step ④① is 5 g / L. Other steps and parameters are the same as those in Example 5.

[0107] Example 7: The difference between this example and Example 5 is that the solvent described in step ④① is a mixed solution of water and methanol, and the volume ratio of water to methanol is 1:1. Other steps and parameters are the same as those in Example 5.

[0108] Example 8: The difference between this example and Example 5 is that the grafting reaction time described in Step 4 ② is 15 min. 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 the non-solvent induced phase inversion method and the interfacial polymerization method. Specifically, it was completed according to the following steps:

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

[0111] ①. Add dry polysulfone particles to N-methylpyrrolidone, and then seal, heat with mechanical stirring, naturally defoam, and perform vacuum decompression defoaming to obtain a casting solution;

[0112] The mass fraction of polysulfone in the casting solution described in Step 2 ① is 20%;

[0113] The temperature of the mechanical stirring with heating described in Step 2 ① is 70 °C, the speed of mechanical stirring is 200 r / min, and the time of mechanical stirring is 14 h;

[0114] The temperature of the natural defoaming described in Step 2 ① is room temperature, and the time of natural defoaming is 12 h;

[0115] The process of decompression defoaming described in Step 2 ① is vacuum drying decompression defoaming, that is, in a vacuum drying oven, at a normal temperature of 25 °C and a vacuum pressure gauge of 0.06 MPa, the decompression defoaming time is 2 h;

[0116] ②. Under constant temperature and humidity conditions, use a doctor blade to evenly coat the casting solution on the non-woven fabric, and then immerse it completely in the coagulation bath for a period of time. Take out the non-woven fabric from the coagulation bath at a temperature of 25 °C after 2 min to obtain a polysulfone support layer; the temperature of the constant temperature and humidity conditions described in Step 2 ② is 25 °C, and the relative humidity is 45%;

[0117] The height of the doctor blade described in Step 2 ② is 150 μm;

[0118] II. Preparation of the polyamide reverse osmosis membrane by the interfacial polymerization method:

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

[0120] The mass fraction of m-phenylenediamine in the aqueous solution described in Step 2 ① is 2%;

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

[0122] In step 2①, the mass fraction of m-phenylenediamine in the aqueous solution is 2%, and the mass fraction of triethylamine is 1.1%.

[0123] ② Dissolve trimesoyl chloride in Isopar-G (isoparaffin), and ultrasonically oscillate to obtain an oil-phase solution.

[0124] In step 2②, the mass fraction of trimesoyl chloride in the oil-phase solution is 0.10%.

[0125] ③ Immerse the polysulfone support layer in the aqueous solution for a period of time, take it out, and evenly blow it with an air gun to remove the residual aqueous solution on its surface, obtaining a blown support layer.

[0126] In step 2③, the time for immersing the polysulfone support layer in the aqueous solution is 40 s.

[0127] In step 2③, the time for evenly blowing with an air gun after taking out is 40 s, and the pressure during blowing is 0.7 MPa.

[0128] ④ Immerse the blown support layer in the oil-phase solution for 60 s to carry out a polycondensation reaction. After the reaction ends, take it out, and then evenly clean the surface with Isopar-G (isoparaffin) to obtain a polyamide reverse osmosis primary membrane.

[0129] ⑤ Place the polyamide reverse osmosis primary membrane in a constant-temperature oven for heat treatment to obtain a polyamide reverse osmosis membrane.

[0130] In step 2⑤, the temperature of the heat treatment is 50 °C, and the time of the heat treatment is 5 min.

[0131] Test example 1:

[0132] Observe the surface morphology characteristics of the three polyamide layer reverse osmosis membranes prepared in Comparative Example 1, Example 1, and Example 5 by scanning electron microscopy. The results are as Figure 1 shown; the surfaces of the polyamide layers in Comparative Example 1 and Examples 1 and 5 all exhibit a typical leaf-like structure, and the surface structure has not changed significantly, still being the typical peak-valley structure of a polyamide membrane. This indicates that when constructing a functional layer on the surface of a polyamide membrane by the secondary grafting method, the surface structure of the membrane is not significantly damaged, and the grafting material does not crosslink 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 ternary multifunctional three-dimensional framework-mediated high ammonia nitrogen selective polyamide reverse osmosis membrane 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 indicate that the ternary multifunctional three-dimensional framework polymer copolymer has been successfully grafted and anchored on the surface of the polyamide separation layer. Due to the presence of super-hydrophilic zwitterionic groups in the ternary multifunctional three-dimensional framework polymer copolymer, while maintaining the compactness of the polyamide separation layer, the hydrophilicity of the membrane surface can be greatly improved, thereby increasing its water flux.

[0139] Test Example 4:

[0140] Ammonia nitrogen retention rate test: Each membrane sample was pre-pressed with pure water at an operating pressure of 16 bar for 1.5 h. A 50 mg / L N(NH4Cl) solution was prepared, and the test was carried out under the cross-flow filtration conditions of 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 water quality of the effluent was stable, the ammonia nitrogen concentration in the feed liquid of the inlet water and the effluent on the permeate side was measured according to the national standard method, and the ammonia nitrogen retention rate was calculated.

[0141] The test results of the ammonia nitrogen retention efficiency on the surfaces of the nine polyamide layer reverse osmosis membranes prepared in Comparative Example 1 and Examples 1-8 are as Figure 4 shown. Compared with the blank polyamide reverse osmosis membrane prepared in Comparative Example 1, the ammonia nitrogen retention rate of the ternary multifunctional three-dimensional framework-mediated high ammonia nitrogen selective polyamide reverse osmosis membrane prepared in Examples 1-8 for ammonia nitrogen in simulated domestic sewage increased significantly. The ammonia nitrogen retention rate of the blank membrane was less than 90%, and the ammonia nitrogen retention rate of the ternary multifunctional three-dimensional framework-mediated high ammonia nitrogen selective polyamide reverse osmosis membrane exceeded 97.30%. The ammonia nitrogen retention rate of the modified membrane prepared in Example 8 with the best effect reached 99.25%.

[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, showing broad application prospects in the field of high-quality reuse of domestic sewage.

Claims

1. A preparation method of a ternary multifunctional three-dimensional structure-mediated polyamide reverse osmosis membrane with high ammonia nitrogen selectivity, characterized in that The preparation method is specifically completed according to the following steps: I. Preparation of a polymer copolymer: Under the protection of a nitrogen atmosphere, amine monomer A, zwitterionic monomer B, amine monomer C, and a free radical polymerization initiator are added to a mixed solvent of dimethyl sulfoxide and deionized water, heated and stirred for a period of time to obtain a reaction product; the reaction product is dialyzed, rotary evaporated and concentrated, and freeze-dried to obtain a polymer copolymer; The structural formula of the polymer copolymer described in Step 1 is as follows: Among them, the value ranges of m, n, and h are all 0.1 to 0.8, and m + n + h = 1; II. Preparation of a polysulfone support layer by the non-solvent induced phase inversion method; ①. Dry polysulfone particles are added to an organic solvent, and then sealed, heated with mechanical stirring, naturally degassed, and vacuum degassed to obtain a casting solution; ②. Under constant temperature and humidity conditions, the casting solution is evenly coated on the non-woven fabric with a scraper, and then completely immersed in a coagulation bath for a period of time. The non-woven fabric is taken out of the coagulation bath to obtain a polysulfone support layer; III. Preparation of a polyamide reverse osmosis membrane by interfacial polymerization: ①. Aromatic diamine monomers are dissolved in pure water, and then interfacial polymerization additives are added and stirred evenly to obtain an aqueous solution; ②. Polyvalent acyl chloride monomers are dissolved in an alkane organic solvent and ultrasonically oscillated to obtain an oil phase solution; ③. The polysulfone support layer is immersed in the aqueous solution for a period of time, taken out, and evenly blown with an air gun to remove the residual aqueous solution on its surface to obtain a blown support layer; ④. The blown support layer is immersed in the oil phase solution for polycondensation reaction. After the reaction is completed, it is taken out and the surface is evenly cleaned with an alkane organic solvent to obtain a polyamide reverse osmosis primary membrane; ⑤. The polyamide reverse osmosis primary membrane is heat-treated in a constant temperature oven to obtain a polyamide reverse osmosis membrane; IV. Preparation of a polyamide reverse osmosis membrane with high ammonia nitrogen selectivity: ①. The polymer copolymer prepared in step I is dissolved in a solvent to obtain a graft modification solution; ②. The graft modification solution is poured on the surface of the polyamide reverse osmosis primary membrane for a graft reaction for a period of time. After the graft reaction is completed, the excess graft modification solution is poured out, and then heat-treated in an oven for a period of time to obtain a polyamide reverse osmosis membrane with high ammonia nitrogen selectivity mediated by a ternary multifunctional three-dimensional structure.

2. The preparation method of a ternary multifunctional three-dimensional structure-mediated high ammonia nitrogen-selective polyamide reverse osmosis membrane according to claim 1, characterized in that The amine monomer A described in Step 1 is one or a mixture of two of 2-aminoethyl methacrylate and 2-aminoethyl methacrylate hydrochloride; the zwitterionic monomer B described in Step 1 is one or a mixture of several of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide, 2-methacryloyloxyethyl phosphorylcholine, N-(3-sulfopropyl)-N-methacryloyloxyethyl-N,N-dimethylammonium betaine, N,N-dimethylaminoethyl methacrylate, N,N-dimethylaminopropyl acrylamide, 3-[(3-acrylamidopropyl)dimethylammonio] propane-1-sulfonate, and 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium] propane-1-sulfonate inner salt; the amine monomer C described in Step 1 is one or a mixture of two of acryloyloxyethyl trimethylammonium chloride and methacryloyloxyethyl trimethylammonium chloride; the radical polymerization initiator described in Step 1 is 2,2'-azobisisobutyronitrile.

3. The preparation method of a ternary multifunctional three-dimensional structure-mediated high ammonia nitrogen-selective polyamide reverse osmosis membrane according to claim 1, characterized in that The amount of the radical polymerization initiator described in Step 1 is 0.1% to 0.6% of the total molar amount of the amine monomer A, the zwitterionic monomer B, and the amine monomer C; the volume ratio of dimethyl sulfoxide to deionized water in the mixed solvent of dimethyl sulfoxide and deionized water described in Step 1 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 1 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 (5 g to 50 g):(250 mL to 1000 mL).

4. The preparation method of a ternary multifunctional three-dimensional architecture-mediated high ammonia nitrogen-selective polyamide reverse osmosis membrane according to claim 1, characterized in that In Step 1, stir at 60°C to 100°C for 6 h to 48 h; in Step 1, dialyze the reaction product 6 to 20 times using deionized water as a solvent; the temperature of the rotary evaporation concentration described in Step 1 is 30°C to 70°C, and the time of the rotary evaporation concentration is 0.5 h to 10 h. The temperature of the freeze-drying is -60°C to -30°C, and the time of the freeze-drying is 0.5 h to 10 h.

5. The preparation method of a ternary multifunctional three-dimensional architecture-mediated high ammonia nitrogen-selective polyamide reverse osmosis membrane according to claim 1, characterized in that The organic solvent described in Step 2① is one or several 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°C to 80°C, the speed of the mechanical stirring is 150 r / min to 300 r / min, and the time of the mechanical stirring is 2 h to 24 h; the temperature of the natural defoaming described in Step 2① is room temperature, and the time of the natural defoaming is 3 h to 12 h; the process of the vacuum defoaming described in Step 2① is vacuum drying and vacuum defoaming. In the vacuum drying oven, under the conditions of normal temperature 25°C and vacuum pressure gauge 0.03 to 0.06 MPa, the time of the vacuum defoaming is 0.5 h to 2 h.

6. The preparation method of a ternary multifunctional three-dimensional framework-mediated high ammonia nitrogen-selective polyamide reverse osmosis membrane according to claim 1, characterized in that In Step 2②, the temperature of the constant temperature and humidity condition is 20°C to 30°C, and the relative humidity is 30% to 60%; in Step 2②, the height of the scraper is 100 μm to 300 μm; in Step 2②, the coagulation bath is at 20°C to 30°C, and the coagulation bath is tap water, absolute ethanol or dimethyl sulfoxide; in Step 2②, the immersion time in the coagulation bath is 2 min to 4 min.

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

8. The preparation method of a ternary multifunctional three-dimensional framework-mediated high ammonia nitrogen-selective polyamide reverse osmosis membrane according to claim 1, characterized in that In Step 3③, the immersion time of the polysulfone support layer in the aqueous solution is 30 s to 120 s; in Step 3③, the uniform blowing time with an air gun after taking out is 30 s to 120 s, and the pressure during blowing is 0.5 MPa to 1.0 MPa; in Step 3④, the time of the polycondensation reaction is 30 s to 120 s; in Step 3④, the alkane organic solvent is one or a mixture of several of n-hexane, cyclohexane and isoparaffin Isopar-G; in Step 3⑤, the temperature of the heat treatment is 50°C to 100°C, and the time of the heat treatment is 2 min to 60 min.

9. The preparation method of a ternary multifunctional three-dimensional structure-mediated high ammonia nitrogen-selective polyamide reverse osmosis membrane according to claim 1, characterized in that The solvent described in Step 4① is one or a mixture of several of water, methanol, and dimethyl sulfoxide; the concentration of the polymer copolymer in the graft modification solution described in Step 4① is 0.01 g / L to 20 g / L; the time for the graft reaction described in Step 4② is 10 s to 6 h; the temperature of the heat treatment described in Step 4② is 50 °C to 100 °C, and the time for the heat treatment is 2 min to 60 min; the volume ratio of the graft modification solution to the area of the polyamide reverse osmosis primary membrane described in Step 4② is (50 mL to 250 mL):(250 cm 2 to 500 cm 2 ).

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

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