A highly fouling-resistant reverse osmosis membrane and its preparation method

Abstract

This invention discloses a highly fouling-resistant reverse osmosis membrane and its preparation method, belonging to the field of reverse osmosis membrane preparation technology. The preparation method of the highly fouling-resistant reverse osmosis membrane includes the following steps: Step 1: A base membrane is attached to a stainless steel plate and immersed in a modified diamine solution for adsorption, followed by immersion in a hexane solution containing trimesoyl chloride for adsorption. The membrane is then removed, dried, and a pretreated base membrane is obtained. Step 2: The pretreated base membrane is fixed in a polytetrafluoroethylene (PTFE) frame. A modified grafting solution is then poured onto the pretreated base membrane. After reaction, unreacted solution is removed, and the membrane is washed, soaked, and dried to obtain a grafted base membrane. Step 3: Modified cellulose is added to a tris(hydroxymethyl)aminomethane hydrochloride buffer solution. After stirring and mixing, a sedimentation solution is obtained. The grafted base membrane is immersed in the sedimentation solution, shaken, washed, and dried to obtain a highly fouling-resistant reverse osmosis membrane. The reverse osmosis membrane prepared by this method exhibits excellent antifouling performance.

Description

Technical Field

[0001] This invention belongs to the field of reverse osmosis membrane preparation technology, specifically relating to a highly fouling-resistant reverse osmosis membrane and its preparation method. Background Technology

[0002] In traditional reverse osmosis membrane technology applications, poor antifouling performance is the core bottleneck restricting its long-term stable operation. Due to the extremely small pore size of reverse osmosis membranes, when treating complex water qualities such as industrial wastewater and municipal sewage, suspended solids, organic matter, microorganisms, and colloids in the wastewater easily form deposits or biofilms on the membrane surface, leading to pore blockage, increased mass transfer resistance, and consequently, decreased permeate flow and reduced desalination rate. Furthermore, traditional membrane materials are sensitive to changes in feed water quality. When the concentration of pollutants in the raw water fluctuates or when it contains oxidants such as residual chlorine, the membrane surface is prone to chemical damage, further accelerating performance degradation.

[0003] Patent CN102921314A discloses a composite reverse osmosis membrane with an interpenetrating network desalination layer and its preparation method. The desalination layer is composed of a three-dimensional network formed by the interpenetration of polymeric nanogels and polyamides. The preparation method involves pre-adding well-dispersed hydrophilic and / or lipophilic polymeric nanogels to the solvents of solutions A and / or B, preparing an aqueous phase A solution containing m-phenylenediamine and / or p-phenylenediamine, and preparing an organic phase B solution containing trimesoyl chloride. Solutions A and B are then brought into full contact on a porous support for interfacial reaction. The membrane is then rinsed with deionized water, moisturized with glycerol, and dried. This yields a reverse osmosis membrane with high antifouling capabilities. However, although the prepared reverse osmosis membrane has made some progress in antifouling, there is still room for improvement in practical applications. On the one hand, while the interpenetrating network structure formed by the polymeric nanogels and polyamides can block some pollutants, its interception effect for some highly polar or small-sized pollutants still needs to be strengthened. On the other hand, although the addition of hydrophilic and / or lipophilic polymer nanogels improves the hydrophilicity or lipophilicity of the membrane surface, under complex water quality conditions, pollutants may still gradually accumulate on the membrane surface, leading to a decrease in membrane flux and a decline in desalination performance. Summary of the Invention

[0004] The purpose of this invention is to provide a highly fouling-resistant reverse osmosis membrane and its preparation method, in order to solve the technical problem of poor fouling resistance of reverse osmosis membranes in the prior art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a method for preparing a highly fouling-resistant reverse osmosis membrane, comprising the following steps:

[0007] Step 1: The prepared base film is attached to a stainless steel plate, immersed in a modified diamine solution, and then immersed in a hexane solution containing trimesoyl chloride. The film is then removed, dried, and the pretreated base film is obtained.

[0008] Step 2: Fix the pretreated base film on a polytetrafluoroethylene plate frame, then pour the modified grafting solution onto the pretreated base film. After the reaction, remove the unreacted solution, wash, soak, and dry to obtain the grafted base film.

[0009] Step 3: Add the modified cellulose to the tris(hydroxymethyl)aminomethane hydrochloride buffer solution, stir and mix to obtain the deposition solution, immerse the grafted membrane in the deposition solution, shake, wash and dry to obtain a highly fouling-resistant reverse osmosis membrane.

[0010] Preferably, in step one, the preparation method of the base film is as follows: polysulfone, polyethylene glycol and N,N-dimethylformamide are mixed in a mass ratio of (14-20)g:(1-3)g:(76-85)g, heated and stirred at 80-85℃ for 7-9h, and then allowed to stand at room temperature for 10-12h to degas. The degassed mixed solution is then poured into the solution tank of a film scraper, a nonwoven fabric is installed, and the mixed solution is evenly scraped onto the nonwoven fabric with a scraper. Then, it is added to cold water at 14.5-15.5℃ for 60-90s to solidify, then soaked and replaced in room temperature water at 24.5-25.5℃ for 60-75s, and washed in hot water at 64.5-65.5℃ for 120-150s to obtain the base film.

[0011] Preferably, the method for preparing the modified diamine solution in step one includes the following steps:

[0012] Q1: Add 4-nitroaniline, 4-nitrophthalic anhydride, N,N-dimethylacetamide and toluene to a container, heat and stir the reaction under a nitrogen atmosphere, cool, add distilled water, stir, filter, wash, and vacuum dry to obtain a pale yellow substance 1;

[0013] Q2: Add the pale yellow substance 1, Pd / C and methanol to a high-pressure reactor, introduce hydrogen gas, heat to react, filter while hot, rotary evaporate, crystallize, wash and dissolve to obtain a modified diamine solution.

[0014] The synthesis reaction formula for the modified diamine in the above process is as follows:

[0015]

[0016] The mass spectrometry analysis results of the pale yellow object 1 were: m / z: 313.03 (100.0%), 314.04 (15.5%), 315.04 (2.3%), 314.03 (1.1%); the mass spectrometry analysis results of the modified diamine were: m / z: 253.09 (100.0%), 254.09 (15.3%), 255.09 (1.7%), 254.08 (1.1%).

[0017] Preferably, in Q1, the ratio of 4-nitroaniline, 4-nitrophthalic anhydride, N,N-dimethylacetamide, and toluene is (12.1-15.5) g : (18.2-20.4) g : (80-120) mL : (100-140) mL, the temperature is raised to 160-170℃, and the reaction time is 8-12 h; in Q2, the ratio of pale yellow substance 1, Pd / C, and methanol is (5-7.5) g : (0.31-0.44) g : (200-300) mL, hydrogen gas is introduced to maintain the pressure in the autoclave at 3-4 MPa, the heating temperature is 60-65℃, and the reaction time is 6-8 h.

[0018] Preferably, in step one, the sample is immersed in a modified diamine solution for 20-25 seconds, the modified diamine solution having a mass fraction of 3 wt%, and immersed in a hexane solution containing trimesoyl chloride for 10-15 seconds, the hexane solution containing trimesoyl chloride having a mass fraction of 0.1 wt%.

[0019] Preferably, in step two, the preparation method of the modified grafting solution is as follows: (10-12)g of polyvinyl alcohol is added to deionized water, and the pH is adjusted to 3-3.2 with 1mol / L hydrochloric acid. Then, (1.42-1.54)g of sodium periodate is added, and the mixture is stirred and reacted for 10-12 hours in the dark. Then, 0.1mol / L sodium thiosulfate solution and 0.1mol / L hydrochloric acid solution are added dropwise alternately. Finally, sodium sulfate is added for salting out, filtered, washed, added to distilled water, and stirred to dissolve, thus obtaining the modified grafting solution.

[0020] The synthesis reaction formula for the modified grafted product in the above process is as follows:

[0021]

[0022] Preferably, in step two, the concentration of the modified grafting solution is (10-12) g / L, the reaction time is 20-25 min, the soaking time is 20-24 h, and the water is changed every two hours during the soaking process.

[0023] Preferably, in step three, the method for preparing modified cellulose is as follows: (10.12-11.06)g of aminosulfonic acid is added to (40-50)mL of N,N-dimethylformamide, stirred and mixed to dissolve, then (1.5-2.5)g of cellulose is added, and the mixture is stirred and mixed again. The mixture is heated at 70-80℃ for 0.5-1.5h. After the reaction is completed, the mixture is washed, dialyzed, and freeze-dried to obtain modified cellulose.

[0024] Preferably, in step three, the ratio of modified cellulose to tris(hydroxymethyl)aminomethane hydrochloride buffer solution is (0.2-0.5) g: (90-120) mL, the pH of the tris(hydroxymethyl)aminomethane hydrochloride buffer solution is 8.5, and the solution is shaken at 170-190 rpm for 4-8 hours.

[0025] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0026] This invention constructs a basic separation layer through interfacial polymerization, then grafts a strongly hydrophilic polyvinyl alcohol layer through Schiff base reaction, significantly enhancing hydrophilicity and forming a hydration barrier. Finally, it further enhances hydrophilicity, provides strong electrostatic repulsion, and improves surface smoothness by depositing a strongly hydrophilic and negatively charged sulfonated cellulose layer. The synergistic effect of each functional layer constructs a highly efficient antifouling barrier from three aspects: hydrophilization, charge repulsion, and surface smoothing, endowing the reverse osmosis membrane with excellent antifouling performance while maintaining good desalination capacity. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1: This example provides a method for preparing a base film. The specific steps are as follows: P-3500LCD MB7 polysulfone, polyethylene glycol with an average molecular weight of 6000, and N,N-dimethylformamide are mixed in a mass ratio of 17g:2g:80g. After heating and stirring at 85°C for 7 hours, the mixture is allowed to stand at room temperature for 12 hours to remove bubbles. Then, the degassed mixture is poured into the solution tank of a film scraper. A nonwoven fabric is installed, and the mixture is evenly scraped onto the nonwoven fabric with a scraper. Then, it is added to cold water at 15°C for 60 seconds to solidify, then immersed in room temperature water at 25°C for 60 seconds to displace, and finally washed in hot water at 65°C for 120 seconds to obtain the base film.

[0029] This embodiment provides a method for preparing a modified diamine solution, including the following steps:

[0030] Q1: Add 13.8g of 4-nitroaniline, 19.3g of 4-nitrophthalic anhydride, 100mL of N,N-dimethylacetamide and 120mL of toluene to a container, heat to 170℃ and stir for 12h under a nitrogen atmosphere, cool, add distilled water, stir, filter, wash, and vacuum dry to obtain a pale yellow substance 1.

[0031] Q2: Add 6.25g of pale yellow substance 1, 0.37g of Pd / C and 250mL of methanol to a high-pressure reactor, introduce hydrogen gas to maintain the pressure in the high-pressure reactor at 3MPa, heat at 65℃ for 8h, filter while hot, rotary evaporate, crystallize, wash and dissolve to obtain a modified diamine solution.

[0032] This embodiment provides a method for preparing a modified grafting solution. The specific steps are as follows: 11g of polyvinyl alcohol is added to deionized water, the pH is adjusted to 3 with 1mol / L hydrochloric acid, then 1.48g of sodium periodate is added, and the mixture is stirred and reacted for 12h in the dark. Then, 0.1mol / L sodium thiosulfate solution and 0.1mol / L hydrochloric acid solution are added dropwise alternately. Finally, sodium sulfate is added for salting out, filtered, washed, added to distilled water, and stirred to dissolve, thus obtaining the modified grafting solution.

[0033] This embodiment provides a method for preparing modified cellulose. The specific steps are as follows: 10.54g of aminosulfonic acid is added to 45mL of N,N-dimethylformamide, stirred and mixed to dissolve, then 2g of cellulose is added, and the mixture is stirred and mixed again. The mixture is heated at 75℃ for 1h. After the reaction is completed, the mixture is washed, dialyzed, and freeze-dried to obtain modified cellulose.

[0034] This embodiment provides a method for preparing a highly fouling-resistant reverse osmosis membrane, comprising the following steps:

[0035] Step 1: The prepared base film is attached to a stainless steel plate and immersed in a 3 wt% modified diamine solution for 20 seconds. Then it is immersed in a 0.1 wt% n-hexane solution containing trimesoyl chloride for 10 seconds. After removal and drying, the pretreated base film is obtained.

[0036] Step 2: Fix the pretreated base film on a polytetrafluoroethylene plate frame, then pour 11 g / L modified grafting solution onto the pretreated base film. After reacting for 20 min, remove the unreacted solution, wash, soak for 24 h, changing the water every two hours during the soaking process, and then dry to obtain the grafted base film.

[0037] Step 3: Add 0.35g of modified cellulose to 110mL of tris(hydroxymethyl)aminomethane hydrochloride buffer solution (pH=8.5), stir and mix to obtain a deposition solution, immerse the grafted membrane in the deposition solution, shake at 190rpm for 8h, wash and dry to obtain a highly fouling-resistant reverse osmosis membrane.

[0038] Example 2: This example provides a method for preparing a base film. The specific steps are as follows: P-3500LCD MB7 polysulfone, polyethylene glycol with an average molecular weight of 6000, and N,N-dimethylformamide are mixed in a mass ratio of 14g:3g:85g. After heating and stirring at 85°C for 7 hours, the mixture is allowed to stand at room temperature for 12 hours to remove bubbles. Then, the degassed mixture is poured into the solution tank of a film scraper. A nonwoven fabric is installed, and the mixture is evenly scraped onto the nonwoven fabric with a scraper. Then, it is added to cold water at 15°C for 60 seconds to solidify, then immersed in room temperature water at 25°C for 60 seconds to displace, and finally washed in hot water at 65°C for 120 seconds to obtain the base film.

[0039] This embodiment provides a method for preparing a modified diamine solution, including the following steps:

[0040] Q1: Add 12.1g of 4-nitroaniline, 18.2g of 4-nitrophthalic anhydride, 120mL of N,N-dimethylacetamide and 140mL of toluene to a container, heat to 170℃ and stir for 12h under a nitrogen atmosphere, cool, add distilled water, stir, filter, wash, and vacuum dry to obtain a pale yellow substance 1;

[0041] Q2: Add 7.5g of pale yellow substance 1, 0.31g of Pd / C and 200mL of methanol to a high-pressure reactor, introduce hydrogen gas to maintain the pressure in the high-pressure reactor at 3MPa, heat at 65℃ for 8h, filter while hot, rotary evaporate, crystallize, wash and dissolve to obtain a modified diamine solution.

[0042] This embodiment provides a method for preparing a modified grafting solution. The specific steps are as follows: 10g of polyvinyl alcohol is added to deionized water, the pH is adjusted to 3 with 1mol / L hydrochloric acid, then 1.42g of sodium periodate is added, and the mixture is stirred and reacted for 12h in the dark. Then, 0.1mol / L sodium thiosulfate solution and 0.1mol / L hydrochloric acid solution are added dropwise alternately. Finally, sodium sulfate is added for salting out, filtered, washed, and added to distilled water. The mixture is stirred and dissolved to obtain the modified grafting solution.

[0043] This embodiment provides a method for preparing modified cellulose. The specific steps are as follows: 10.12g of aminosulfonic acid is added to 50mL of N,N-dimethylformamide, stirred and mixed to dissolve, then 2.5g of cellulose is added, and the mixture is stirred and mixed again. The mixture is heated at 75℃ for 1h. After the reaction is completed, the mixture is washed, dialyzed, and freeze-dried to obtain modified cellulose.

[0044] This embodiment provides a method for preparing a highly fouling-resistant reverse osmosis membrane, comprising the following steps:

[0045] Step 1: The prepared base film is attached to a stainless steel plate and immersed in a 3 wt% modified diamine solution for 20 seconds. Then it is immersed in a 0.1 wt% n-hexane solution containing trimesoyl chloride for 10 seconds. After removal and drying, the pretreated base film is obtained.

[0046] Step 2: Fix the pretreated base film on a polytetrafluoroethylene plate frame, then pour 11 g / L modified grafting solution onto the pretreated base film. After reacting for 20 min, remove the unreacted solution, wash, soak for 24 h, changing the water every two hours during the soaking process, and then dry to obtain the grafted base film.

[0047] Step 3: Add 0.2g of modified cellulose to 120mL of tris(hydroxymethyl)aminomethane hydrochloride buffer solution (pH=8.5), stir and mix to obtain a deposition solution, immerse the grafted membrane in the deposition solution, shake at 190rpm for 8h, wash and dry to obtain a highly fouling-resistant reverse osmosis membrane.

[0048] Example 3: This example provides a method for preparing a base film. The specific steps are as follows: P-3500LCD MB7 polysulfone, polyethylene glycol with an average molecular weight of 6000, and N,N-dimethylformamide are mixed in a mass ratio of 20g:1g:76g. After heating and stirring at 85°C for 7 hours, the mixture is allowed to stand at room temperature for 12 hours to remove bubbles. Then, the degassed mixture is poured into the solution tank of a film scraper. A nonwoven fabric is installed, and the mixture is evenly scraped onto the nonwoven fabric with a scraper. Then, the mixture is added to cold water at 15°C for 60 seconds to solidify, then immersed in room temperature water at 25°C for 60 seconds to displace the solidified mixture, and finally washed in hot water at 65°C for 120 seconds to obtain the base film.

[0049] This embodiment provides a method for preparing a modified diamine solution, including the following steps:

[0050] Q1: Add 15.5g of 4-nitroaniline, 20.4g of 4-nitrophthalic anhydride, 80mL of N,N-dimethylacetamide and 100mL of toluene to a container, heat to 170℃ and stir for 12h under a nitrogen atmosphere, cool, add distilled water, stir, filter, wash, and vacuum dry to obtain a pale yellow substance 1;

[0051] Q2: Add 5g of pale yellow substance 1, 0.44g of Pd / C and 300mL of methanol to a high-pressure reactor, introduce hydrogen gas to maintain the pressure in the high-pressure reactor at 3MPa, heat at 65℃ for 8h, filter while hot, rotary evaporate, crystallize, wash and dissolve to obtain a modified diamine solution.

[0052] This embodiment provides a method for preparing a modified grafting solution. The specific steps are as follows: 12g of polyvinyl alcohol is added to deionized water, and the pH is adjusted to 3 with 1mol / L hydrochloric acid. Then, 1.54g of sodium periodate is added, and the mixture is stirred and reacted for 12h in the dark. Then, 0.1mol / L sodium thiosulfate solution and 0.1mol / L hydrochloric acid solution are added dropwise alternately. Finally, sodium sulfate is added for salting out, filtered, washed, and added to distilled water. The mixture is stirred and dissolved to obtain the modified grafting solution.

[0053] This embodiment provides a method for preparing modified cellulose. The specific steps are as follows: 11.06g of aminosulfonic acid is added to 40mL of N,N-dimethylformamide, stirred and mixed to dissolve, then 1.5g of cellulose is added, and the mixture is stirred and mixed again. The mixture is heated at 75℃ for 1h. After the reaction is completed, the mixture is washed, dialyzed, and freeze-dried to obtain modified cellulose.

[0054] This embodiment provides a method for preparing a highly fouling-resistant reverse osmosis membrane, comprising the following steps:

[0055] Step 1: The prepared base film is attached to a stainless steel plate and immersed in a 3 wt% modified diamine solution for 20 seconds. Then it is immersed in a 0.1 wt% n-hexane solution containing trimesoyl chloride for 10 seconds. After removal and drying, the pretreated base film is obtained.

[0056] Step 2: Fix the pretreated base film on a polytetrafluoroethylene plate frame, then pour 11 g / L modified grafting solution onto the pretreated base film. After reacting for 20 min, remove the unreacted solution, wash, soak for 24 h, changing the water every two hours during the soaking process, and then dry to obtain the grafted base film.

[0057] Step 3: Add 0.5g of modified cellulose to 90mL of tris(hydroxymethyl)aminomethane hydrochloride buffer solution (pH=8.5), stir and mix to obtain a deposition solution, immerse the grafted membrane in the deposition solution, shake at 190rpm for 8h, wash and dry to obtain a highly fouling-resistant reverse osmosis membrane.

[0058] Example 4: This example provides a method for preparing a base film. The specific steps are as follows: P-3500LCD MB7 polysulfone, polyethylene glycol with an average molecular weight of 6000, and N,N-dimethylformamide are mixed in a mass ratio of 15g:1.5g:78g. After heating and stirring at 85°C for 7 hours, the mixture is allowed to stand at room temperature for 12 hours to remove bubbles. Then, the degassed mixture is poured into the solution tank of a film scraper. A nonwoven fabric is installed, and the mixture is evenly scraped onto the nonwoven fabric with a scraper. Then, the mixture is added to cold water at 15°C for 60 seconds to solidify, then immersed in room temperature water at 25°C for 60 seconds to displace the mixture, and finally washed in hot water at 65°C for 120 seconds to obtain the base film.

[0059] This embodiment provides a method for preparing a modified diamine solution, including the following steps:

[0060] Q1: Add 13.2g of 4-nitroaniline, 18.7g of 4-nitrophthalic anhydride, 85mL of N,N-dimethylacetamide and 110mL of toluene to a container, heat to 170℃ and stir for 12h under a nitrogen atmosphere, cool, add distilled water, stir, filter, wash, and vacuum dry to obtain a pale yellow substance 1.

[0061] Q2: Add 5.5g of pale yellow substance 1, 0.34g of Pd / C and 220mL of methanol to a high-pressure reactor, introduce hydrogen gas to maintain the pressure in the high-pressure reactor at 3MPa, heat at 65℃ for 8h, filter while hot, rotary evaporate, crystallize, wash and dissolve to obtain a modified diamine solution.

[0062] This embodiment provides a method for preparing a modified grafting solution. The specific steps are as follows: 10.5g of polyvinyl alcohol is added to deionized water, and the pH is adjusted to 3 with 1mol / L hydrochloric acid. Then, 1.45g of sodium periodate is added, and the mixture is stirred and reacted for 12h in the dark. Then, 0.1mol / L sodium thiosulfate solution and 0.1mol / L hydrochloric acid solution are added dropwise alternately. Finally, sodium sulfate is added for salting out, filtered, washed, and added to distilled water. The mixture is stirred and dissolved to obtain the modified grafting solution.

[0063] This embodiment provides a method for preparing modified cellulose. The specific steps are as follows: 10.28g of aminosulfonic acid is added to 42mL of N,N-dimethylformamide, stirred and mixed to dissolve, then 1.8g of cellulose is added, and the mixture is stirred and mixed again. The mixture is heated at 75°C for 1 hour. After the reaction is completed, the mixture is washed, dialyzed, and freeze-dried to obtain modified cellulose.

[0064] This embodiment provides a method for preparing a highly fouling-resistant reverse osmosis membrane, comprising the following steps:

[0065] Step 1: The prepared base film is attached to a stainless steel plate and immersed in a 3 wt% modified diamine solution for 20 seconds. Then it is immersed in a 0.1 wt% n-hexane solution containing trimesoyl chloride for 10 seconds. After removal and drying, the pretreated base film is obtained.

[0066] Step 2: Fix the pretreated base film on a polytetrafluoroethylene plate frame, then pour 11 g / L modified grafting solution onto the pretreated base film. After reacting for 20 min, remove the unreacted solution, wash, soak for 24 h, changing the water every two hours during the soaking process, and then dry to obtain the grafted base film.

[0067] Step 3: Add 0.3g of modified cellulose to 95mL of tris(hydroxymethyl)aminomethane hydrochloride buffer solution (pH=8.5), stir and mix to obtain a deposition solution, immerse the grafted membrane in the deposition solution, shake at 190rpm for 8h, wash, and dry to obtain a highly fouling-resistant reverse osmosis membrane.

[0068] Comparative Example 5: This embodiment provides a method for preparing a base film. The specific steps are as follows: P-3500LCD MB7 polysulfone, polyethylene glycol with an average molecular weight of 6000, and N,N-dimethylformamide are mixed in a mass ratio of 18g:2.5g:82g. After heating and stirring at 85°C for 7 hours, the mixture is allowed to stand at room temperature for 12 hours to remove bubbles. Then, the degassed mixture is poured into the solution tank of a film scraper. A nonwoven fabric is installed, and the mixture is evenly scraped onto the nonwoven fabric with a scraper. Then, the mixture is added to cold water at 15°C for 60 seconds to solidify, then soaked in room temperature water at 25°C for 60 seconds to displace the mixture, and finally washed in hot water at 65°C for 120 seconds to obtain the base film.

[0069] This embodiment provides a method for preparing a modified diamine solution, including the following steps:

[0070] Q1: Add 14.9g of 4-nitroaniline, 19.8g of 4-nitrophthalic anhydride, 115mL of N,N-dimethylacetamide and 130mL of toluene to a container, heat to 170℃ and stir for 12h under a nitrogen atmosphere, cool, add distilled water, stir, filter, wash, and vacuum dry to obtain a pale yellow substance 1;

[0071] Q2: Add 7g of pale yellow substance 1, 0.41g of Pd / C and 280mL of methanol to a high-pressure reactor, introduce hydrogen gas to maintain the pressure in the high-pressure reactor at 3MPa, heat at 65℃ for 8h, filter while hot, rotary evaporate, crystallize, wash and dissolve to obtain a modified diamine solution.

[0072] This embodiment provides a method for preparing a modified grafting solution. The specific steps are as follows: 11.5g of polyvinyl alcohol is added to deionized water, and the pH is adjusted to 3 with 1mol / L hydrochloric acid. Then, 1.51g of sodium periodate is added, and the mixture is stirred and reacted for 12h in the dark. Then, 0.1mol / L sodium thiosulfate solution and 0.1mol / L hydrochloric acid solution are added dropwise alternately. Finally, sodium sulfate is added for salting out, filtered, washed, and added to distilled water. The mixture is stirred and dissolved to obtain the modified grafting solution.

[0073] This embodiment provides a method for preparing modified cellulose. The specific steps are as follows: 10.97g of aminosulfonic acid is added to 48mL of N,N-dimethylformamide, stirred and mixed to dissolve, then 2.3g of cellulose is added, and the mixture is stirred and mixed again. The mixture is heated at 75℃ for 1h. After the reaction is completed, the mixture is washed, dialyzed, and freeze-dried to obtain modified cellulose.

[0074] This embodiment provides a method for preparing a highly fouling-resistant reverse osmosis membrane, comprising the following steps:

[0075] Step 1: The prepared base film is attached to a stainless steel plate and immersed in a 3 wt% modified diamine solution for 20 seconds. Then it is immersed in a 0.1 wt% n-hexane solution containing trimesoyl chloride for 10 seconds. After removal and drying, the pretreated base film is obtained.

[0076] Step 2: Fix the pretreated base film on a polytetrafluoroethylene plate frame, then pour 11 g / L modified grafting solution onto the pretreated base film. After reacting for 20 min, remove the unreacted solution, wash, soak for 24 h, changing the water every two hours during the soaking process, and then dry to obtain the grafted base film.

[0077] Step 3: Add 0.4g of modified cellulose to 115mL of tris(hydroxymethyl)aminomethane hydrochloride buffer solution (pH=8.5), stir and mix to obtain a deposition solution, immerse the grafted membrane in the deposition solution, shake at 190rpm for 8h, wash, and dry to obtain a highly fouling-resistant reverse osmosis membrane.

[0078] Comparative Example 1: Compared with Example 1, Comparative Example 1 did not add modified diamine solution during the preparation of the high antifouling reverse osmosis membrane, and all other conditions remained unchanged.

[0079] Comparative Example 2: Compared with Example 1, Comparative Example 2 did not add modified cellulose during the preparation of the high antifouling reverse osmosis membrane, and all other conditions remained unchanged.

[0080] Experimental Example: The samples prepared according to Examples 1-5 and Comparative Examples 1-2 were subjected to performance testing. The prepared samples were placed in different pollutant solutions, immersed and rinsed, and then their water flux was measured. Water flux (F) is the volume (V) of water passing through a unit membrane area (A) per unit time (t) under certain operating conditions. The calculation formula is F = V / (A·t). The test results are shown in Table 1:

[0081] Table 1

[0082]

[0083] As shown in Table 1, the antifouling performance of the reverse osmosis membrane can be effectively improved by using the methods of Examples 1-5. A comparison between Comparative Example 1 and Examples 1-5 reveals that adding modified diamine solution can effectively improve the antifouling performance of the reverse osmosis membrane; a comparison between Comparative Example 2 and Examples 1-5 reveals that adding modified cellulose can effectively improve the antifouling performance of the reverse osmosis membrane.

[0084] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0085] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a high antifouling reverse osmosis membrane, characterized by, It comprises the following steps: Step one: the prepared base film is pasted on the stainless steel plate, immersed in the modified diamine solution, then immersed in the n-hexane solution containing triformyl chloride, taken out, dried, and the pretreated base film is obtained; Step two: the pretreated base film is fixed in the polytetrafluoroethylene plate frame, then the modified grafting solution is poured onto the pretreated base film, after reaction, the unreacted solution is removed, washed, soaked, and dried, and the grafted base film is obtained; Step three: the modified cellulose is added to the tris(hydroxymethyl)aminomethane hydrochloride buffer solution, after stirring and mixing, the deposition solution is obtained, the grafted base film is immersed in the deposition solution, oscillated, washed, and dried, and the high anti-pollution reverse osmosis membrane is obtained; In the step one, the preparation method of the modified diamine solution comprises the following steps: Q1: 4-nitroaniline, 4-nitrobenzoic anhydride, N,N-dimethylacetamide and toluene are added to a container, and stirring reaction is carried out under nitrogen atmosphere after heating, then cooling, adding distilled water, stirring, filtering, washing, and vacuum drying to obtain a light yellow object; Q2: the light yellow object, Pd / C and methanol are added to an autoclave, hydrogen is introduced, and heating reaction is carried out, after the reaction is completed, hot filtration is carried out, rotary evaporation is carried out, crystallization is carried out, washing is carried out, and dissolution is carried out to obtain the modified diamine solution; In the step two, the preparation method of the modified grafting solution is as follows: (10-12) g of polyvinyl alcohol is added to deionized water, 1 mol / L hydrochloric acid is used to adjust the pH to 3-3.2, then (1.42-1.54) g of sodium periodate is added, stirring reaction is carried out in dark environment for 10-12 h, then 0.1 mol / L sodium thiosulfate solution and 0.1 mol / L hydrochloric acid solution are alternately added dropwise, finally sodium sulfate is added for salting out, filtering, washing, adding to distilled water, stirring and dissolving to obtain the modified grafting solution.

2. The method of claim 1, wherein the method further comprises the step of: In the step one, the preparation method of the base film is as follows: poly sulfone, polyethylene glycol and N,N-dimethyl formamide are mixed in a mass ratio of (14-20) g:(1-3) g:(76-85) g, after heating and stirring at 80-85℃ for 7-9 h, room temperature standing for 10-12 h for defoaming, then the defoamed mixed solution is poured into the solution tank of the film coater, non-woven fabric is installed, the mixed solution is uniformly scraped onto the non-woven fabric by the scraper, then it is added to cold water at 14.5-15.5℃ for coagulation for 60-90 s, 24.5-25.5℃ normal temperature water immersion replacement for 60-75 s, and hot water at 64.5-65.5℃ for cleaning for 120-150 s to obtain the base film. ​ 3. The method of claim 1, wherein the method further comprises the step of: The Q1, 4-nitroaniline, 4-nitrobenzoic anhydride, N, N-dimethylacetamide and toluene are used in a ratio of (12.1-15.5) g: (18.2-20.4) g: (80-120) mL: (100-140) mL, heated to 160-170℃, and the reaction time is 8-12h; the Q2, the light yellow object, Pd / C and methanol are used in a ratio of (5-7.5) g: (0.31-0.44) g: (200-300) mL, hydrogen is introduced to keep the pressure in the autoclave at 3-4MPa, the heating temperature is 60-65℃, and the reaction time is 6-8h. ​ 4. The method of claim 1, wherein the method further comprises the step of adding a polyamine to the polyamide membrane. In the step one, the dipping time in the modified diamine solution is 20-25s, the mass fraction of the modified diamine solution is 3wt%, and the dipping time in the n-hexane solution containing triformylchloride is 10-15s, and the mass fraction of the n-hexane solution containing triformylchloride is 0.1wt%.

5. The method of claim 1, wherein the method further comprises the step of: In the step two, the concentration of the modified grafting solution is (10-12) g / L, the reaction time is 20-25min, and the soaking time is 20-24h, and the water is changed every two hours during the soaking process. ​ 6. The method of claim 1, wherein the method further comprises the step of: In the step three, the preparation method of the modified cellulose is as follows: (10.12-11.06) g of sulfamic acid is added to (40-50) mL of N, N-dimethylformamide, after stirring, mixing and dissolving, (1.5-2.5) g of cellulose is added, and the mixture is continuously stirred and mixed, heated at 70-80℃ for 0.5-1.5h, after the reaction is completed, the product is washed, dialyzed, and freeze-dried to obtain the modified cellulose. ​ 7. The method of claim 1, wherein the method further comprises the step of: In the step three, the use amount ratio of the modified cellulose and the tris(hydroxymethyl)aminomethane hydrochloride buffer solution is (0.2-0.5) g: (90-120) mL, the pH of the tris(hydroxymethyl)aminomethane hydrochloride buffer solution is 8.5, and the oscillation speed is 170-190rpm for 4-8h. ​

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