A method for preparing a charged hydrogel polyamide double network reverse osmosis membrane

Abstract

A method for preparing a charged hydrogel polyamide double network reverse osmosis membrane, which relates to a method for preparing a reverse osmosis membrane. The purpose of the present invention is to solve the problem that the reverse osmosis membrane prepared by the existing method has multiple-step reactions and insufficient binding force of different structural and effective layers. The present invention constructs a charged hydrogel polyamide double network layer on the membrane surface through an interface-initiated free radical polymerization reaction, and enhances the electrical properties of the membrane through the presence of the charged hydrogel, thereby limiting the dissolution of ions in the water on the membrane surface and the diffusion of ions in the membrane, thereby reducing the number of ions passing through the membrane. At the same time, the hydrogel improves the hydrophilicity of the membrane, which is beneficial to the transmission of water molecules in the membrane and the improvement of the anti-pollution performance of the membrane. Method: 1. Prepare a polymer solution; 2. Prepare a reverse osmosis membrane; 3. Clean the membrane. The double network reverse osmosis membrane prepared by the present invention has a wide and uniform distribution of charged groups, which is beneficial to the efficient separation of salt and water. The present invention can obtain a charged hydrogel polyamide double network reverse osmosis membrane.

Description

Technical Field

[0001] The invention relates to a method for preparing a reverse osmosis membrane. Background Art

[0002] Since seawater and brackish water desalination technology is not affected by climate and can provide stable water supply around the clock, it has become an important way for countries around the world to cope with fresh water shortages. Reverse osmosis membrane desalination technology has been studied since the 1970s. After decades of development, it has become one of the main means of seawater desalination and brackish water desalination, accounting for about 65% of the global seawater desalination market share. Reverse osmosis desalination technology mainly uses external pressure higher than the osmotic pressure of seawater to allow water molecules to pass through the reverse osmosis membrane to obtain fresh water, and has high energy consumption. Therefore, how to improve the efficiency of reverse osmosis desalination and reduce the cost of fresh water production is the focus of the development of reverse osmosis desalination technology.

[0003] Reverse osmosis membranes achieve effective separation of ions and water molecules in water by constructing a non-porous polyamide separation layer. Brine separation performance is an important indicator for measuring the filtration performance of reverse osmosis membranes, which is often controlled by the composition and structure of the polyamide functional layer. In order to construct the optimal polyamide structure, researchers have made great efforts and summarized many rules. The rough surface of the polyamide membrane can increase the effective area of ​​water transfer during the filtration process, thereby improving the water permeability of the reverse osmosis membrane. Hydrophilic materials such as metal organic frameworks are introduced into the polyamide layer to promote the transmission of water molecules and enhance the separation performance of the membrane and brine. In addition, constructing an intermediate layer between the polyamide functional layer and the base membrane can also effectively improve the water permeability of the reverse osmosis membrane. At the same time, the pollution problem faced by the reverse osmosis membrane during use also seriously restricts its application in the field of seawater desalination.

[0004] Existing methods for preparing reverse osmosis membranes often only focus on improving the brine separation performance of reverse osmosis membranes, or on the anti-fouling modification of the polyamide structure of reverse osmosis membranes. Therefore, in order to achieve the improvement of the brine separation performance and anti-fouling performance of reverse osmosis membranes, two or even multiple steps of reaction are usually required to construct the target performance of the membrane one by one. At the same time, the lack of binding force between different structural and functional layers puts the stability of reverse osmosis membranes to the test. Summary of the invention

[0005] The purpose of the present invention is to solve the problems of multi-step reaction and insufficient binding force of different structural effect layers in reverse osmosis membranes prepared by existing methods, and to provide a method for preparing a charged hydrogel polyamide double network reverse osmosis membrane.

[0006] The present invention constructs a charged hydrogel polyamide double network layer on the membrane surface through an interface-initiated free radical polymerization reaction, and the existence of the charged hydrogel enhances the electrical properties of the membrane, thereby limiting the dissolution of ions in water on the membrane surface and the diffusion of ions in the membrane, thereby reducing the number of ions passing through the membrane. At the same time, the hydrogel improves the hydrophilicity of the membrane, which is beneficial to the transmission of water molecules in the membrane and the improvement of the membrane's anti-pollution performance.

[0007] A method for preparing a charged hydrogel polyamide double network reverse osmosis membrane is specifically completed by the following steps:

[0008] 1. Prepare polymer liquid:

[0009] ①, adding m-phenylenediamine, ionic group polymer monomer and cross-linking agent into deionized water, stirring with magnetic force to obtain aqueous polymer solution;

[0010] The ionic group polymer monomer described in step 1① is an organic substance having an ionic group and a carbon-carbon double bond;

[0011] The cross-linking agent described in step 1① is an organic substance with two carbon-carbon double bonds;

[0012] The mass fraction of the intermediate phenylenediamine in the aqueous phase polymerization solution in step 1① is 1.0% to 10%, the mass fraction of the polymer monomer with ionic groups is 0.001% to 10%, and the mass fraction of the cross-linking agent is 0.001% to 10%;

[0013] ②, add trimesoyl chloride and photoinitiator to the organic solvent, stir evenly to obtain an organic phase polymerization liquid;

[0014] The mass fraction of trimesoyl chloride in the organic phase polymerization solution described in step 1② is 0.05% to 0.5%, and the concentration of the photoinitiator is 0.001 to 0.1 g / mL;

[0015] 2. Preparation of reverse osmosis membrane:

[0016] ① Fix the cleaned membrane on the glass plate, pour deionized water on the membrane surface, and after the membrane is moistened, pour out the water on the surface and blow dry the membrane surface;

[0017] ② Pour the aqueous polymer solution on the membrane surface, and after the membrane is wetted, pour out the aqueous polymer solution on the surface and remove the residual droplets on the surface;

[0018] ③, pour the organic phase polymerization liquid on the membrane surface and place it under ultraviolet light to react, thereby obtaining a charged hydrogel polyamide double network reverse osmosis membrane;

[0019] 3. Cleaning membrane:

[0020] The charged hydrogel polyamide double network reverse osmosis membrane was cleaned with deionized water and then stored in deionized water.

[0021] Advantages of the present invention:

[0022] 1. The present invention has low requirements on the material of the base membrane when preparing the charged hydrogel polyamide double network reverse osmosis membrane, and has a wide range of applicable membrane modification;

[0023] Second, the double-network reverse osmosis membrane prepared by the present invention has a wide and uniform distribution of charged groups, which is conducive to the efficient separation of salt and water;

[0024] 3. The process equipment of the present invention is simple, easy to operate, has a short process cycle, and has low requirements on the operating environment;

[0025] Fourth, the charged hydrogel polyamide double network reverse osmosis membrane prepared by the present invention has good salt water separation performance. Compared with the traditional polyamide membrane, the water flux and salt selectivity are significantly improved;

[0026] 5. The charged hydrogel polyamide double network reverse osmosis membrane prepared by the present invention has good anti-pollution performance. In the pollution experiment, its water flux is significantly enhanced compared with the polyamide membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Scanning electron microscope surface images and surface roughness images of the charged hydrogel polyamide double network reverse osmosis membranes prepared in Examples 1, 2, 3, and 4;

[0028] Figure 2 The XPS full spectrum of the charged hydrogel polyamide double network reverse osmosis membrane prepared in Examples 1, 2, 3 and 4;

[0029] Figure 3 The change trends of flux and selectivity of charged hydrogel polyamide double network reverse osmosis membranes prepared in Examples 1, 2, 3 and 4;

[0030] Figure 4 The flux variation trend of the charged hydrogel polyamide double network reverse osmosis membrane prepared in Examples 1, 2, 3 and 4 during the pollution process. DETAILED DESCRIPTION

[0031] Specific implementation method 1: This implementation method is a method for preparing a charged hydrogel polyamide double network reverse osmosis membrane, which is specifically completed by the following steps:

[0032] 1. Prepare polymer liquid:

[0033] ①, adding m-phenylenediamine, ionic group polymer monomer and cross-linking agent into deionized water, stirring with magnetic force to obtain aqueous polymer solution;

[0034] The ionic group polymer monomer described in step 1① is an organic substance having an ionic group and a carbon-carbon double bond;

[0035] The cross-linking agent described in step 1① is an organic substance with two carbon-carbon double bonds;

[0036] The mass fraction of the intermediate phenylenediamine in the aqueous phase polymerization solution in step 1① is 1.0% to 10%, the mass fraction of the polymer monomer with ionic groups is 0.001% to 10%, and the mass fraction of the cross-linking agent is 0.001% to 10%;

[0037] ②, add trimesoyl chloride and photoinitiator to the organic solvent, stir evenly to obtain an organic phase polymerization liquid;

[0038] The mass fraction of trimesoyl chloride in the organic phase polymerization solution described in step 1② is 0.05% to 0.5%, and the concentration of the photoinitiator is 0.001 to 0.1 g / mL;

[0039] 2. Preparation of reverse osmosis membrane:

[0040] ① Fix the cleaned membrane on the glass plate, pour deionized water on the membrane surface, and after the membrane is moistened, pour out the water on the surface and blow dry the membrane surface;

[0041] ② Pour the aqueous polymer solution on the membrane surface, and after the membrane is wetted, pour out the aqueous polymer solution on the surface and remove the residual droplets on the surface;

[0042] ③, pour the organic phase polymerization liquid on the membrane surface and place it under ultraviolet light to react, thereby obtaining a charged hydrogel polyamide double network reverse osmosis membrane;

[0043] 3. Cleaning membrane:

[0044] The charged hydrogel polyamide double network reverse osmosis membrane was cleaned with deionized water and then stored in deionized water.

[0045] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the ionic group polymer monomer described in step 1① is any one of 3-sulfonate propyl methacrylate potassium salt, methacryloyloxyethyl trimethylammonium chloride solution, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, 2-methacryloyloxyethyl phosphorylcholine, carboxybetaine methacrylate and carboxybetaine acrylamide, or a combination of several of them in any ratio. The other steps are the same as those in specific embodiment 1.

[0046] Specific embodiment 3: This embodiment differs from specific embodiment 1 or 2 in that: the crosslinking agent described in step 1① is any one of polyethylene glycol diacrylate, N,N-methylenebis(acrylamide) and N,N-dimethylacryloylcystine or a combination of several of them in any ratio; the magnetic stirring described in step 1① is magnetic stirring at 300r / min for 0.1h to 6h. The other steps are the same as those of specific embodiment 1 or 2.

[0047] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the organic solvent in step 1② is any one of Isopar-G, benzene, xylene, n-hexane and cyclohexane or a combination of several of them in any ratio. The other steps are the same as those of specific embodiments 1 to 3.

[0048] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that the photoinitiator described in step 1 ② is any one of 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropanone, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone and diphenylacetone. The other steps are the same as those of specific embodiments 1 to 4.

[0049] Specific embodiment 6: This embodiment differs from specific embodiments 1 to 5 in that the membrane described in step ① in step 2 is any one of polysulfone membrane, polyethersulfone membrane, polyvinyl chloride membrane and polyvinylidene fluoride membrane. The other steps are the same as those of specific embodiments 1 to 5.

[0050] Specific implementation method 7: The difference between this implementation method and specific implementation methods 1 to 6 is that: the cleaned membrane described in step 2 (1) means: soaking the membrane in isopropanol for 5h to 6h, then washing it with deionized water for 3 to 5 times, and storing it in deionized water; the wetting described in step 2 (2) means: after the liquid is poured on the membrane surface, it is left to stand for 1min to 10min for the liquid to contact, and the liquid enters the membrane pores through capillary action. The other steps are the same as those of specific implementation methods 1 to 6.

[0051] Specific implementation eight: This implementation differs from specific implementations one to seven in that: the fixing described in step two ① is: using a 1 cm thick hollow polytetrafluoroethylene plate to clamp the membrane on the glass plate along the four sides through a binder clip, and adding a hollow rubber pad between the membrane and the plate to prevent the polymer solution from leaking; the middle hollow area is the membrane modification area, and the plate thickness can be used to accommodate the aqueous polymer solution and the organic polymer solution; the blowing and drying of the membrane surface described in step two ① is: using an air gun to spray nitrogen to blow dry the water on the membrane surface, leaving only part of the deionized water inside the membrane pores to prevent the aqueous polymer solution from penetrating deeply into the membrane pores. The other steps are the same as specific implementations one to seven.

[0052] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that: the removal of residual surface droplets in step 2② is to use an air gun to spray nitrogen to gently blow off the residual surface droplets, leaving only the ultra-thin liquid layer adsorbed on the membrane surface. The other steps are the same as specific embodiments 1 to 8.

[0053] Specific embodiment 10: This embodiment differs from specific embodiments 1 to 9 in that the reaction under ultraviolet light in step 2 (3) is to induce the photoinitiator in the organic phase to generate free radicals under the ultraviolet light for 10 minutes of stable operation, and the free radicals induce the ionic group polymer monomer and the crosslinking agent to polymerize at the interface of the organic phase and the aqueous phase to generate a hydrogel layer, and at the same time, phenylenediamine and trimesoyl chloride are polymerized to generate a polyamide layer, and the reaction time under ultraviolet light is 1 minute to 10 minutes. The other steps are the same as those of specific embodiments 1 to 9.

[0054] The following examples are used to verify the beneficial effects of the present invention:

[0055] Embodiment 1: The preparation method of polyamide film is specifically completed according to the following steps:

[0056] 1. Prepare polymer liquid:

[0057] ①, add m-phenylenediamine, ionic group polymer monomer and cross-linking agent into deionized water, stir magnetically at 300r / min for 6h to obtain aqueous polymer solution;

[0058] The ionic group polymer monomer described in step 1① is 3-sulfonate propyl methacrylate potassium salt;

[0059] The cross-linking agent described in step 1① is polyethylene glycol diacrylate;

[0060] The mass fraction of the intermediate phenylenediamine in the aqueous phase polymerization solution described in step 1① is 2%, the mass fraction of the polymer monomer with ionic groups is 0.0%, and the mass fraction of the cross-linking agent is 0.0%;

[0061] ②, add trimesoyl chloride and photoinitiator to the organic solvent, stir evenly to obtain an organic phase polymerization liquid;

[0062] The organic solvent described in step 1② is Isopar-G;

[0063] The photoinitiator described in step 1② is 1-hydroxycyclohexyl phenyl ketone;

[0064] The mass fraction of trimesoyl chloride in the organic phase polymerization solution described in step 1② is 0.1%, and the concentration of the photoinitiator is 0.00 g / mL;

[0065] 2. Preparation of reverse osmosis membrane:

[0066] ① Fix the cleaned membrane on the glass plate, pour deionized water on the membrane surface, and after the membrane is moistened, pour out the water on the surface and blow dry the membrane surface;

[0067] The process for cleaning the membrane in step 2 is as follows: soak the membrane in isopropanol for 6 hours, then wash it three times with deionized water, and then store it in deionized water;

[0068] The wetting described in step 2① is to pour the liquid on the membrane surface and let it stand, waiting for the liquid to contact for 2 minutes, and the liquid enters the membrane pores through capillary action;

[0069] The membrane described in step 2① is a polyethersulfone ultrafiltration membrane with a molecular weight cutoff of 20k Daltons;

[0070] The fixing in step 2① is as follows: the membrane is clamped on the glass plate along the four sides by a 1 cm thick hollow polytetrafluoroethylene plate through a binder clip, and a hollow rubber pad is added between the membrane and the plate to prevent the polymer solution from leaking; the middle hollow area is the membrane modification area, and the thickness of the plate can be used to accommodate the aqueous phase polymer solution and the organic phase polymer solution;

[0071] The step 2① of blowing the membrane surface dry is to use an air gun to spray nitrogen to blow dry the water on the membrane surface, leaving only a portion of deionized water inside the membrane pores to prevent the aqueous polymer solution from penetrating deeply into the membrane pores;

[0072] ② Pour the aqueous polymer solution on the membrane surface, and after the membrane is wetted, pour out the aqueous polymer solution on the surface and remove the residual droplets on the surface;

[0073] The step 2② of removing the residual droplets on the surface is as follows: using an air gun to spray nitrogen to gently blow off the residual droplets on the surface, leaving only the ultra-thin liquid layer adsorbed on the membrane surface;

[0074] ③, pour the organic phase polymerization liquid on the membrane surface and place it under ultraviolet light to react to obtain a polyamide membrane;

[0075] The reaction under ultraviolet light in step 2③ is as follows: under the ultraviolet light which runs stably for 10 minutes, the photoinitiator in the organic phase is induced to generate free radicals, and the free radicals induce the ionic group polymer monomer and the crosslinking agent to polymerize at the interface between the organic phase and the aqueous phase to form a hydrogel layer, and at the same time, phenylenediamine and trimesoyl chloride are polymerized to form a polyamide layer, and the reaction time under ultraviolet light is 2 minutes;

[0076] 3. Cleaning membrane:

[0077] The polyamide membrane was washed three times with deionized water and then stored in deionized water.

[0078] Embodiment 2: A method for preparing a charged hydrogel polyamide double network reverse osmosis membrane is specifically completed by the following steps:

[0079] 1. Prepare polymer liquid:

[0080] ①, add m-phenylenediamine, ionic group polymer monomer and cross-linking agent into deionized water, stir magnetically at 300r / min for 6h to obtain aqueous polymer solution;

[0081] The ionic group polymer monomer described in step 1① is 3-sulfonate propyl methacrylate potassium salt;

[0082] The cross-linking agent described in step 1① is polyethylene glycol diacrylate;

[0083] The mass fraction of the aqueous phase polymer solution in the aqueous phase polymer solution in step 1① is 2%, the mass fraction of the ionic group polymer monomer is 0.2%, and the mass fraction of the cross-linking agent is 0.2%;

[0084] ②, add trimesoyl chloride and photoinitiator to the organic solvent, stir evenly to obtain an organic phase polymerization liquid;

[0085] The organic solvent described in step 1② is Isopar-G;

[0086] The photoinitiator described in step 1② is 1-hydroxycyclohexyl phenyl ketone;

[0087] The mass fraction of trimesoyl chloride in the organic phase polymerization solution described in step 1② is 0.1%, and the concentration of the photoinitiator is 0.01 g / mL;

[0088] 2. Preparation of reverse osmosis membrane:

[0089] ① Fix the cleaned membrane on the glass plate, pour deionized water on the membrane surface, and after the membrane is moistened, pour out the water on the surface and blow dry the membrane surface;

[0090] The process for cleaning the membrane in step 2 is as follows: soak the membrane in isopropanol for 6 hours, then wash it three times with deionized water, and then store it in deionized water;

[0091] The wetting described in step 2① is to pour the liquid on the membrane surface and let it stand, waiting for the liquid to contact for 2 minutes, and the liquid enters the membrane pores through capillary action;

[0092] The membrane described in step 2① is a polyethersulfone ultrafiltration membrane with a molecular weight cutoff of 20k Daltons;

[0093] The fixing in step 2① is as follows: the membrane is clamped on the glass plate along the four sides by a 1 cm thick hollow polytetrafluoroethylene plate through a binder clip, and a hollow rubber pad is added between the membrane and the plate to prevent the polymer solution from leaking; the middle hollow area is the membrane modification area, and the thickness of the plate can be used to accommodate the aqueous phase polymer solution and the organic phase polymer solution;

[0094] The step 2① of blowing the membrane surface dry is to use an air gun to spray nitrogen to blow dry the water on the membrane surface, leaving only a portion of deionized water inside the membrane pores to prevent the aqueous polymer solution from penetrating deeply into the membrane pores;

[0095] ② Pour the aqueous polymer solution on the membrane surface, and after the membrane is wetted, pour out the aqueous polymer solution on the surface and remove the residual droplets on the surface;

[0096] The step 2② of removing the residual droplets on the surface is as follows: using an air gun to spray nitrogen to gently blow off the residual droplets on the surface, leaving only the ultra-thin liquid layer adsorbed on the membrane surface;

[0097] ③, pour the organic phase polymerization liquid on the membrane surface and place it under ultraviolet light to react, thereby obtaining a charged hydrogel polyamide double network reverse osmosis membrane;

[0098] The reaction under ultraviolet light in step 2③ is as follows: under the ultraviolet light which runs stably for 10 minutes, the photoinitiator in the organic phase is induced to generate free radicals, and the free radicals induce the ionic group polymer monomer and the crosslinking agent to polymerize at the interface between the organic phase and the aqueous phase to form a hydrogel layer, and at the same time, phenylenediamine and trimesoyl chloride are polymerized to form a polyamide layer, and the reaction time under ultraviolet light is 2 minutes;

[0099] 3. Cleaning membrane:

[0100] The charged hydrogel polyamide double network reverse osmosis membrane was washed three times with deionized water and then stored in deionized water.

[0101] Embodiment 3: The difference between this embodiment and embodiment 2 is that the mass fraction of the phenylenediamine in the aqueous phase polymer solution described in step 1① is 2%, the mass fraction of the ionic group polymer monomer is 0.8%, and the mass fraction of the cross-linking agent is 0.2%. The other steps and parameters are the same as those in embodiment 2.

[0102] Embodiment 4: The difference between this embodiment and embodiment 2 is that the mass fraction of the phenylenediamine in the aqueous phase polymer solution described in step 1① is 2%, the mass fraction of the ionic group polymer monomer is 1.6%, and the mass fraction of the cross-linking agent is 0.2%. The other steps and parameters are the same as those in embodiment 2.

[0103] Figure 1 Scanning electron microscope surface images and surface roughness images of the charged hydrogel polyamide double network reverse osmosis membranes prepared in Examples 1, 2, 3, and 4;

[0104] from Figure 1It can be seen that the charged hydrogel polyamide double network layer grows continuously on the surface of the polyethersulfone membrane. The surfaces of the gel layers corresponding to Examples 1, 2, 3 and 4 are all node-shaped and leaf-shaped structures, and their surface roughnesses are 26.2nm, 47.6nm, 50.8nm and 56.5nm, respectively, indicating that with the increase of the charged hydrogel content, the roughness of the hydrogel on the membrane surface increases; and the large surface roughness gives the membrane a larger water flow area, which is beneficial to the membrane water production.

[0105] Figure 2 The XPS full spectrum of the charged hydrogel polyamide double network reverse osmosis membrane prepared in Examples 1, 2, 3 and 4;

[0106] from Figure 2 It can be seen that the charged hydrogel polyamide double network layer is continuously coated on the surface of the polysulfone membrane, because the N element representing the polyamide network appears on its surface, and the introduction of the polymer monomer with ionic groups makes the S element appear on the membrane surface, which confirms the formation of the charged hydrogel network structure;

[0107] The membrane filtration device, which was built with a nanofiltration reverse osmosis cup produced by STERLITECH, USA, was used to evaluate the water production performance and anti-fouling performance of the membrane. The membrane desalination performance was tested using NaCl solution (the concentration of NaCl solution was 2g / L) as the mother liquid. Figure 3 As shown; the membrane anti-fouling performance was tested using a NaCl and humic acid composite solution (the concentrations of NaCl and humic acid in the NaCl and humic acid composite solution were 2 g / L and 300 mg / L, respectively) as the mother solution. Figure 4 shown.

[0108] Figure 3 The change trends of flux and selectivity of charged hydrogel polyamide double network reverse osmosis membranes prepared in Examples 1, 2, 3 and 4;

[0109] Depend on Figure 3 It can be seen that with the increase of hydrogel content, the water permeability coefficient of the membrane gradually increases, and the water production efficiency of the membrane gradually improves; at the same time, the introduction of charged hydrogel significantly improves the water-salt selectivity of the membrane, thereby improving the separation efficiency of salt and water.

[0110] Figure 4 The flux variation trend of the charged hydrogel polyamide double network reverse osmosis membrane prepared in Examples 1, 2, 3 and 4 during the pollution process.

[0111] Depend on Figure 4It can be seen that after 3 hours of humic acid solution filtration pollution, the flux of the charged hydrogel polyamide double network reverse osmosis membrane prepared in Examples 1, 2, 3 and 4 was reduced to 75%, 82%, 87% and 85% of the initial membrane flux, respectively; after simple rinsing with deionized water, the flux of the charged hydrogel polyamide double network reverse osmosis membrane prepared in Examples 1, 2, 3 and 4 was restored to 90%, 97%, 98% and 97% of the initial membrane flux, respectively; compared with the polyamide membrane prepared in Example 1, the anti-pollution performance of the charged hydrogel polyamide double network reverse osmosis membrane is significantly improved.

Claims

1. A method for preparing a charged hydrogel polyamide double network reverse osmosis membrane, characterized in that The preparation method is specifically completed according to the following steps:

1. Prepare polymer liquid: ①, adding m-phenylenediamine, ionic group polymer monomer and cross-linking agent into deionized water, stirring with magnetic force to obtain aqueous polymer solution; The ionic group polymer monomer described in step 1① is an organic substance having an ionic group and a carbon-carbon double bond; The cross-linking agent described in step 1① is an organic substance with two carbon-carbon double bonds; The mass fraction of the intermediate phenylenediamine in the aqueous phase polymerization solution in step 1① is 1.0% to 10%, the mass fraction of the polymer monomer with ionic groups is 0.001% to 10%, and the mass fraction of the cross-linking agent is 0.001% to 10%; The ionic group polymer monomer described in step 1① is any one of 3-sulfonate propyl methacrylate potassium salt, methacryloyloxyethyl trimethylammonium chloride solution, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, 2-methacryloyloxyethyl phosphorylcholine, carboxybetaine methacrylate and carboxybetaine acrylamide, or a combination of several of them in any ratio; The cross-linking agent described in step 1① is any one of polyethylene glycol diacrylate, N,N-methylenebis(acrylamide) and N,N-dimethylacryloylcystine or a combination of several of them in any ratio; ②, add trimesoyl chloride and photoinitiator to the organic solvent, stir evenly to obtain an organic phase polymerization liquid; The organic solvent described in step 1② is any one of Isopar-G, benzene, xylene, n-hexane and cyclohexane, or a combination of several of them in any ratio; The photoinitiator described in step 1② is any one of 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropanone, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone and diphenylacetone; The mass fraction of trimesoyl chloride in the organic phase polymerization solution described in step 1② is 0.05% to 0.5%, and the concentration of the photoinitiator is 0.001 to 0.1 g / mL; 2. Preparation of reverse osmosis membrane: ① Fix the cleaned membrane on the glass plate, pour deionized water on the membrane surface, and after the membrane is moistened, pour out the water on the surface and blow dry the membrane surface; ② Pour the aqueous polymer solution on the membrane surface, and after the membrane is wetted, pour out the aqueous polymer solution on the surface and remove the residual droplets on the surface; ③, pour the organic phase polymerization liquid on the membrane surface and place it under ultraviolet light to react, thereby obtaining a charged hydrogel polyamide double network reverse osmosis membrane; 3. Cleaning membrane: The charged hydrogel polyamide double network reverse osmosis membrane was cleaned with deionized water and then stored in deionized water.

2. The method for preparing a charged hydrogel polyamide double network reverse osmosis membrane according to claim 1, characterized in that The magnetic stirring described in step 1① is magnetic stirring at 300 r / min for 0.1 h to 6 h.

3. The method for preparing a charged hydrogel polyamide double network reverse osmosis membrane according to claim 1, characterized in that The membrane described in ① in step 2 is any one of a polysulfone membrane, a polyethersulfone membrane, a polyvinyl chloride membrane and a polyvinylidene fluoride membrane.

4. The method for preparing a charged hydrogel polyamide double network reverse osmosis membrane according to claim 1, characterized in that The cleaned membrane described in step ① of step 2 means: immersing the membrane in isopropanol for 5h to 6h, then washing it with deionized water for 3 to 5 times, and storing it in deionized water; the wetting described in step ② of step 2 means: after pouring the liquid on the membrane surface, let it stand and wait for the liquid to contact for 1min to 10min, and the liquid enters the membrane pores by capillary action.

5. The method for preparing a charged hydrogel polyamide double network reverse osmosis membrane according to claim 1, characterized in that The fixation described in step 2① is as follows: use a 1 cm thick hollow polytetrafluoroethylene plate to clamp the membrane on the glass plate along the four sides through long tail clips, and add a hollow rubber pad between the membrane and the plate to prevent the leakage of the polymer solution; the middle hollow area is the membrane modification area, and the plate thickness can be used to accommodate the aqueous phase polymer solution and the organic phase polymer solution; the drying of the membrane surface described in step 2① is as follows: use an air gun to spray nitrogen to dry the water on the membrane surface, and only retain part of the deionized water inside the membrane pores to prevent the aqueous phase polymer solution from penetrating deeply into the membrane pores.

6. The method for preparing a charged hydrogel polyamide double network reverse osmosis membrane according to claim 1, characterized in that The removal of residual droplets on the surface described in step 2② is to use nitrogen gas sprayed from an air gun to gently blow off the residual droplets on the surface, leaving only an ultra-thin liquid layer adsorbed on the membrane surface.

7. The method for preparing a charged hydrogel polyamide double network reverse osmosis membrane according to claim 1, characterized in that The reaction under ultraviolet light described in step 2③ is as follows: under stable ultraviolet light operation for 10 minutes, the photoinitiator in the organic phase is triggered to produce free radicals, and the free radicals trigger the polymerization reaction of the ionic group polymer monomer and the cross-linking agent at the interface between the organic phase and the aqueous phase to form a hydrogel layer. At the same time, phenylenediamine and trimesoyl chloride are polymerized to form a polyamide layer. The reaction time under ultraviolet light is 1 minute to 10 minutes.

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