Preparation method of alkali-resistant reverse osmosis membrane and alkali-resistant reverse osmosis membrane

Abstract

The invention discloses a preparation method of an alkali-resistant reverse osmosis membrane and the alkali-resistant reverse osmosis membrane. The preparation method of the alkali-resistant reverse osmosis membrane comprises the following steps: (1) adding a polymer into an organic solvent in a heating and stirring state, and stirring for a period of time after charging is completed, so as to obtain a mixed solution; (2) cooling the mixed solution, continuing to add a pore-foaming agent, and stirring for a period of time after charging is completed to obtain a precursor solution; (3) performing vacuum defoaming treatment on the precursor solution to obtain a membrane casting solution; (4) loading the membrane casting solution on a carrier, and then carrying out gel bath treatment to obtain a base membrane; and (5) sequentially infiltrating the base membrane in the aqueous phase solution and the organic phase solution for crosslinking treatment to obtain the alkali-resistant reverse osmosis membrane. Wherein the water phase solution is prepared from diethylenetriamine and polyethyleneimine; the organic phase solution comprises cyanuric chloride. The process is simple, and the obtained membrane has excellent alkali resistance.

Description

Technical Field

[0001] This invention relates to the technical field of reverse osmosis membranes, and more specifically, to a method for preparing an alkali-resistant reverse osmosis membrane and the alkali-resistant reverse osmosis membrane itself. Background Technology

[0002] Reverse osmosis membranes are a key membrane separation technology that uses high pressure to separate water or other solutions from a solution, thereby purifying or concentrating substances. They are widely used in water treatment, wastewater treatment, and seawater desalination. In reverse osmosis membranes, the base membrane is the crucial component supporting the entire membrane structure, determining its mechanical properties, chemical stability, and separation efficiency. The applicant of this application has filed Chinese invention patent CN119258820A, which discloses a method for preparing a reverse osmosis membrane and the membrane itself. By introducing polyethersulfone and polymerizing it at the interface, the membrane's heat resistance, chemical stability, mechanical strength, hydrophilicity, biocompatibility, and solute rejection rate are significantly improved compared to traditional polysulfone-based membranes. However, since existing reverse osmosis membranes mostly use polyamide as the selective layer material, the amide bonds in its molecular structure are highly susceptible to nucleophilic attack by hydroxide ions (OH⁻) under strongly alkaline conditions, leading to amide bond breakage and rapid degradation of membrane performance. Summary of the Invention

[0003] To further improve alkali resistance while maintaining good separation performance, this invention provides a method for preparing an alkali-resistant reverse osmosis membrane and the alkali-resistant reverse osmosis membrane itself. The technical solution is as follows:

[0004] A method for preparing an alkali-resistant reverse osmosis membrane, characterized by comprising the following steps:

[0005] (1) Add the polymer to the organic solvent under heating and stirring conditions. After the addition is completed, stir for a period of time to obtain a mixture;

[0006] (2) After cooling the mixture, continue to add the pore-forming agent. After the addition is complete, stir for a period of time to obtain the precursor solution;

[0007] (3) Vacuum degassing treatment is performed on the precursor solution to obtain the casting solution;

[0008] (4) Load the casting solution onto the carrier and then perform a gel bath treatment to obtain the base film;

[0009] (5) The base membrane is sequentially immersed in an aqueous solution and an organic solution for crosslinking treatment to obtain an alkali-resistant reverse osmosis membrane; wherein the aqueous solution includes diethylenetriamine and polyethyleneimine; and the organic solution includes cyanuric chloride.

[0010] The advantages of the preparation method of the present invention are: (1) Polyethyleneimine contains a large number of primary, secondary, and tertiary amine groups, and its large polymer structure participates in the formation of a more stable three-dimensional network with greater steric hindrance. This network physically forms a dense barrier, which can effectively hinder OH - It penetrates and attacks the interior of the membrane; simultaneously, the amine-triazine bond formed by the reaction of polyethyleneimine with cyanuric chloride has a chemical stability far exceeding that of the amide bond in traditional polyamide membranes; furthermore, the large number of unreacted amine groups on the polyethyleneimine chain can react with OH groups in the solution. - Acid-base neutralization occurs, playing a buffering and sacrificial protection role. (2) Diethylenetriamine, as a small molecule polyamine monomer, can form a highly cross-linked basic network with cyanuric chloride through synergy with polyethyleneimine, ensuring a high desalination rate and the integrity of the separation layer structure. (3) Cyanuric chloride has strong chemical corrosion resistance and is inherently more alkali resistant than traditional acyl chlorides (such as trimesoyl chloride). The polymer network skeleton formed by it with polyethyleneimine and diethylenetriamine is completely free of carbonyl structure and does not contain amide bonds that are easily hydrolyzed by alkali, thus eliminating the main alkali degradation sites at the molecular level.

[0011] As a further improvement to the above-mentioned method for preparing alkali-resistant reverse osmosis membrane: in step (1), the polymer is polysulfone or polyethersulfone; the organic solvent is N,N-dimethylformamide; the polymer is added when the temperature reaches 50-60°C, and the mixture is stirred for 24-36 hours after the addition is completed.

[0012] As a further improvement to the above-mentioned method for preparing alkali-resistant reverse osmosis membrane: in step (2), the mixture is cooled to 20-40°C before adding the pore-forming agent, and the mixture is stirred for 12-24 hours after the addition is completed; the pore-forming agent is polyvinylpyrrolidone-K30 or polyethylene glycol; the mass ratio of organic solvent, polymer and pore-forming agent is (75-85):(15-25):(1-5).

[0013] As a further improvement to the above-mentioned method for preparing alkali-resistant reverse osmosis membranes:

[0014] In step (3), the precursor solution is degassed under vacuum at 50°C for 6 to 12 hours;

[0015] In step (4), nonwoven fabric is used as a carrier, and casting solution at a temperature of 20-40°C is loaded onto the nonwoven fabric and subjected to a gel bath treatment in pure water at 10-40°C for 1-10 minutes.

[0016] As a further improvement to the above-mentioned method for preparing alkali-resistant reverse osmosis membranes: step (5) includes the following steps performed sequentially:

[0017] The base membrane was immersed in an aqueous solution. After immersion, it was removed and the surface of the base membrane was cleaned with compressed air.

[0018] The base membrane is then immersed in an organic phase solution. After immersion, it is removed and the surface of the base membrane is rinsed with deionized water to obtain an alkali-resistant reverse osmosis membrane.

[0019] As a further improvement to the above-mentioned method for preparing alkali-resistant reverse osmosis membrane: in the aqueous solution, the mass fraction of diethylenetriamine is 0.5-3.5 wt%, and the mass fraction of polyethyleneimine is 0.05-0.1 wt%; the base membrane is immersed in the aqueous solution for 1-5 minutes.

[0020] As a further improvement to the above-mentioned method for preparing alkali-resistant reverse osmosis membrane: the mass fraction of cyanuric chloride in the organic phase solution is 0.05-2 wt%; the base membrane is immersed in the organic phase solution for 5-60 seconds.

[0021] As a further improvement to the above-mentioned method for preparing alkali-resistant reverse osmosis membranes, it also includes post-treatment of the base membrane after wetting with an organic phase solution, specifically including the following steps:

[0022] The base film was immersed in a positively charged dielectric solution. After immersion, it was removed and the surface of the base film was rinsed with deionized water.

[0023] The base membrane is then immersed in a negatively charged medium solution. After immersion, it is removed and the surface of the base membrane is rinsed with deionized water to obtain an alkali-resistant reverse osmosis membrane.

[0024] Therefore, based on the principle of like charges repelling each other, by forming a negatively charged coating on the outermost layer of the membrane that generates a strong electrostatic repulsion force against OH-, the OH- is prevented from approaching and contacting the membrane surface, thereby improving alkali resistance. At the same time, the added coating also forms a physical barrier, delaying the attack of OH- on the polymer network skeleton and restraining its excessive swelling, making it more durable in alkaline environments.

[0025] As a further improvement to the above-mentioned method for preparing alkali-resistant reverse osmosis membranes:

[0026] The positively charged dielectric solution is a mixture of polyallylamine hydrochloride and sodium chloride, with a pH of 3.5–4.5, a mass fraction of polyallylamine hydrochloride of 0.05–0.15 wt%, and a mass fraction of sodium chloride of 0.5–0.7 wt%; the base film is immersed in the positively charged dielectric solution for 10–20 minutes;

[0027] The negative charge medium solution is a mixture of sodium polystyrene sulfonate and sodium chloride, with a pH of 3.5–4.5, a sodium polystyrene sulfonate mass fraction of 0.05–0.15 wt%, and a sodium chloride mass fraction of 0.5–0.7 wt%; the base film is immersed in the negative charge medium solution for 10–20 minutes;

[0028] The post-processing procedure is performed twice.

[0029] Therefore, polyallylamine hydrochloride is a weak polycation, and sodium polystyrene sulfonate is a strong polyanion. The combination of the two can form a dense, uniform, and stable composite coating. Specifically, the surface layer of sodium polystyrene sulfonate can remain in a dissociated state under strongly alkaline conditions, stably carrying a negative charge, thus continuously and efficiently repelling OH- ions. Furthermore, the π-π stacking interactions between the benzene rings in the sodium polystyrene sulfonate molecular chain enhance the rigidity and interaction forces of the polymer chain, resulting in a denser and stronger coating.

[0030] The alkali-resistant reverse osmosis membrane is prepared by the above-described method for preparing alkali-resistant reverse osmosis membranes.

[0031] In summary, the preparation method of the alkali-resistant reverse osmosis membrane of the present invention is simple in process and low in material cost. The resulting alkali-resistant reverse osmosis membrane not only has a good separation effect, but also has significantly improved alkali resistance. It can operate stably and continuously at a high flux under high pressure conditions, has a wider range of applications, and is highly practical.

[0032] The present invention will be further described below through specific embodiments. Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Detailed Implementation

[0033] The present invention will now be clearly and completely described. Those skilled in the art will be able to implement the present invention based on this description. Before describing the present invention, it should be particularly noted that:

[0034] The technical solutions and features provided in the various parts of this invention, including the following description, can be combined with each other without conflict.

[0035] Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0036] Regarding the terminology and units used in this invention: The terms "comprising," "having," and any variations thereof in the specification, claims, and related parts of this invention are intended to cover non-exclusive inclusion.

[0037] Example 1

[0038] The method for preparing the alkali-resistant reverse osmosis membrane in this embodiment includes the following steps:

[0039] (1) Add N,N-dimethylformamide to a three-necked flask, place the three-necked flask in an electric heating mantle and heat it while stirring. When the temperature reaches 60°C, add polyethersulfone to the N,N-dimethylformamide. After the addition is complete, stir for 24 hours to obtain a mixture.

[0040] (2) When the temperature of the mixture is lowered to 25°C, polyvinylpyrrolidone-K30 is added and the mixture is stirred for 12 hours to obtain the precursor solution; wherein, the mass ratio of N,N-dimethylformamide, polyethersulfone and polyvinylpyrrolidone-K30 is 75:15:3.

[0041] (3) The precursor solution was degassed under vacuum at 50°C for 12 hours to obtain the casting solution.

[0042] (4) Using a doctor blade with a blade spacing of 150 μm and a moving speed of 10 m / min, the casting solution at a temperature of 40 °C is loaded onto the nonwoven fabric. Then, a gel bath treatment is performed in pure water at 15 °C for 10 minutes to allow N,N-dimethylformamide and pure water to exchange and solidify into a film, thus obtaining the base film.

[0043] (5) Polyamidation treatment of the base film, specifically:

[0044] First, the base membrane is immersed in an aqueous solution for 5 minutes. After immersion, it is removed and the surface of the base membrane is cleaned with compressed air. The aqueous solution is a mixture of diethylenetriamine and polyethyleneimine, wherein the mass fraction of diethylenetriamine is 0.5 wt% and the mass fraction of polyethyleneimine is 0.05 wt%.

[0045] The base membrane was then immersed in the organic phase solution for 60 seconds. After immersion, it was removed and the surface of the base membrane was rinsed with deionized water to obtain the alkali-resistant reverse osmosis membrane. The organic phase solution was a 0.05 wt% cyanuric chloride solution (the solvent was n-hexane, the same below).

[0046] The test results showed that the pure water flux of the alkali-resistant reverse osmosis membrane was 42.5 L / (m²). 2 The original sodium chloride desalination rate was 98.50%. After statically immersing the membrane in a 1 wt% NaOH solution for 30 days, the sodium chloride desalination rate was 98.45%.

[0047] Example 2

[0048] Compared with Example 1, the difference in the preparation method of the alkali-resistant reverse osmosis membrane in this example is that the mass ratio of N,N-dimethylformamide, polyethersulfone, and polyvinylpyrrolidone-K30 is 75:15:1.

[0049] The test results showed that the pure water flux of the alkali-resistant reverse osmosis membrane was 41.2 L / (m²). 2The original sodium chloride desalination rate was 98.67%. After the membrane was statically immersed in a 1 wt% NaOH solution for 30 days, the sodium chloride desalination rate was 98.61%.

[0050] Example 3

[0051] Compared with Example 1, the difference in the preparation method of the alkali-resistant reverse osmosis membrane in this example is that the mass ratio of N,N-dimethylformamide, polyethersulfone, and polyvinylpyrrolidone-K30 is 85:25:5.

[0052] The test results showed that the pure water flux of the alkali-resistant reverse osmosis membrane was 39.6 L / (m²). 2 The original sodium chloride desalination rate was 99.23%. After statically immersing the membrane in a 1 wt% NaOH solution for 30 days, the sodium chloride desalination rate was 99.10%.

[0053] Example 4

[0054] Compared with Example 1, the difference in the preparation method of the alkali-resistant reverse osmosis membrane in this example is that the mass fraction of diethylenetriamine is 1.5 wt%, the mass fraction of polyethyleneimine is 0.075 wt%, and the mass fraction of cyanuric chloride is 0.5 wt%.

[0055] The tested pure water flux of the alkali-resistant reverse osmosis membrane was 39.8 L / (m²). 2 The original sodium chloride desalination rate was 99.05%. After statically immersing the membrane in a 1 wt% NaOH solution for 30 days, the sodium chloride desalination rate was 98.99%.

[0056] Example 5

[0057] Compared with Example 1, the difference in the preparation method of the alkali-resistant reverse osmosis membrane in this example is that the mass fraction of diethylenetriamine is 2.5 wt%, the mass fraction of polyethyleneimine is 0.1 wt%, and the mass fraction of cyanuric chloride is 1 wt%.

[0058] The tested pure water flux of the alkali-resistant reverse osmosis membrane was 38.2 L / (m²). 2 The original sodium chloride desalination rate was 99.81%. After the membrane was statically immersed in a 1 wt% NaOH solution for 30 days, the sodium chloride desalination rate was 99.75%.

[0059] Example 6

[0060] Compared with Example 1, the difference in the preparation method of the alkali-resistant reverse osmosis membrane in this example is that the mass fraction of diethylenetriamine is 3.5 wt%, the mass fraction of polyethyleneimine is 0.1 wt%, and the mass fraction of cyanuric chloride is 1.5 wt%.

[0061] The test results showed that the pure water flux of the alkali-resistant reverse osmosis membrane was 37.5 L / (m²). 2 The original sodium chloride desalination rate was 99.73%. After statically immersing the membrane in a 1 wt% NaOH solution for 30 days, the sodium chloride desalination rate was 99.66%.

[0062] Example 7

[0063] Compared with Example 1, the difference in the preparation method of the alkali-resistant reverse osmosis membrane in this example is that the mass fraction of diethylenetriamine is 2 wt%, the mass fraction of polyethyleneimine is 0.06 wt%, and the mass fraction of cyanuric chloride is 0.1 wt%.

[0064] The test results showed that the pure water flux of the alkali-resistant reverse osmosis membrane was 39.5 L / (m²). 2 The original sodium chloride desalination rate was 99.24%. After statically immersing the membrane in a 1 wt% NaOH solution for 30 days, the sodium chloride desalination rate was 99.12%.

[0065] Example 8

[0066] Compared with Example 1, the difference in the preparation method of the alkali-resistant reverse osmosis membrane in this example is that the mass fraction of diethylenetriamine is 3 wt%, the mass fraction of polyethyleneimine is 0.09 wt%, and the mass fraction of cyanuric chloride is 2 wt%.

[0067] The tested pure water flux of the alkali-resistant reverse osmosis membrane was 37.8 L / (m²). 2 The original sodium chloride desalination rate was 99.75%. After the membrane was statically immersed in a 1 wt% NaOH solution for 30 days, the sodium chloride desalination rate was 99.73%.

[0068] Example 9

[0069] Compared with Example 1, the preparation method of the alkali-resistant reverse osmosis membrane in this example differs in that it further includes post-treatment of the base membrane after wetting the organic phase solution. The post-treatment is as follows: the base membrane is immersed in a positively charged medium solution for 15 minutes, and after immersion, it is removed and the surface of the base membrane is rinsed with deionized water. The positively charged medium solution is a mixture of polyallylamine hydrochloride and sodium chloride, with a pH of 4, a mass fraction of 0.1 wt% for polyallylamine hydrochloride, and a mass fraction of 0.58 wt% for sodium chloride. Then, the base membrane is immersed in a negatively charged medium solution for 15 minutes, and after immersion, it is removed and the surface of the base membrane is rinsed with deionized water. The negatively charged medium solution is a mixture of sodium polystyrene sulfonate and sodium chloride, with a pH of 4, a mass fraction of 0.1 wt% for sodium polystyrene sulfonate, and a mass fraction of 0.58 wt% for sodium chloride.

[0070] The tested pure water flux of the alkali-resistant reverse osmosis membrane was 38.8 L / (m²). 2 The original sodium chloride desalination rate was 99.81%. After the membrane was statically immersed in a 1 wt% NaOH solution for 30 days, the sodium chloride desalination rate was 99.80%.

[0071] Example 10

[0072] Compared with Example 9, the difference in the preparation method of the alkali-resistant reverse osmosis membrane in this example is that the post-treatment process is performed twice.

[0073] The test results showed that the pure water flux of the alkali-resistant reverse osmosis membrane was 37.5 L / (m²). 2 The original sodium chloride desalination rate was 99.87%. After the membrane was statically immersed in a 1 wt% NaOH solution for 30 days, the sodium chloride desalination rate was 99.85%.

[0074] Compare with Example 1

[0075] Compared with Example 1, the difference in the preparation method of the reverse osmosis membrane in this comparative example is that the aqueous solution does not contain diethylenetriamine.

[0076] The tested pure water flux of the alkali-resistant reverse osmosis membrane was 43.2 L / (m²). 2 The original sodium chloride desalination rate was 98.43%. After statically immersing the membrane in a 1 wt% NaOH solution for 30 days, the sodium chloride desalination rate was 97.26%.

[0077] Compare with Example 2

[0078] Compared with Example 1, the difference in the preparation method of the reverse osmosis membrane in this comparative example is that the aqueous phase solution is a 3 wt% m-phenylenediamine solution and the organic phase solution is a 1 wt% trimesoyl chloride solution.

[0079] The test results showed that the pure water flux of the alkali-resistant reverse osmosis membrane was 32.5 L / (m²). 2 The original sodium chloride desalination rate was 99.84%. After statically immersing the membrane in a 1 wt% NaOH solution for 30 days, the sodium chloride desalination rate was 97.41%.

[0080] The pure water flux and sodium chloride desalination rate of the reverse osmosis membranes in the above examples and control examples were tested according to the "Test Methods for Reverse Osmosis Membranes" (GB / T 32373-2015), as follows:

[0081] 1. Take several (no fewer than 4) samples. The samples should be free of obvious defects such as wrinkles and damage. The size of the samples should meet the requirements of completely covering the sealing ring of the evaluation cell. The effective membrane area of ​​the samples in the evaluation cell should not be less than 2.5 × 10⁻⁶. -3 m 2 Prepare a 32,000 ppm sodium chloride solution and adjust the pH to 7.5 ± 0.5.

[0082] 2. Immerse the sample in deionized water or distilled water for 30 minutes;

[0083] 3. Pure water flux test: Take a sample and put it into the evaluation cell. Turn on the water supply pump and slowly adjust the operating pressure to 55 bar for cross-flow filtration. Maintain the temperature at 25℃±0.5℃. After running stably for 30 minutes, collect the permeate produced after passing through the sample with a measuring cup (no less than 30 ml for a single sample). Use a stopwatch to calculate the time required and calculate the pure water flux.

[0084] Sodium chloride desalination rate test: Fresh samples or samples soaked in alkaline solution for 30 days are placed in the evaluation tank, the booster pump is turned on, the operating pressure is adjusted to 55 bar, and the temperature is adjusted to 25℃±0.5℃; after running stably under constant pressure for 24 hours, the total dissolved solids (TDS) content of the original solution (sodium chloride solution) and the permeate are determined according to GB / T 5750.4.

[0085] 4. After the test is completed, slowly reduce the operating pressure to below 0.05MPa and turn off the booster pump or water supply pump.

[0086] The pure water flux is calculated using the following formula:

[0087]

[0088] In the formula, J is the pure water flux, with units of L / (m³). 2 ﹒ h); V is the volume of the graduated cylinder sample, in L; T is the sampling time, in h; A is the effective area of ​​the sample, in m². 2 .

[0089] The sodium chloride desalination rate is calculated using the following formula:

[0090]

[0091] In the formula, R is the sodium chloride desalination rate, in units of %; C P The total dissolved solids (TDS) of the permeate is expressed in mg / L; C f The TDS of the stock solution is expressed in mg / L.

[0092] The foregoing has described the relevant content of the present invention. Those skilled in the art will be able to implement the present invention based on these descriptions. All other embodiments obtained by those skilled in the art based on the above description of the present invention without inventive effort should fall within the scope of protection of the present invention.

Claims

1. A method for making an alkali-resistant reverse osmosis membrane, characterized by: The method comprises the following steps: (1) adding a polymer into an organic solvent under heating and stirring, stirring for a period of time after the addition is completed, and obtaining a mixed solution; (2) continuing to add a pore-forming agent after the mixed solution is cooled, stirring for a period of time after the addition is completed, and obtaining a precursor solution; (3) performing vacuum defoaming treatment on the precursor solution, and obtaining a casting solution; (4) loading the casting solution onto a carrier, and then performing gel bath treatment, and obtaining a base film; (5) sequentially immersing the base film in an aqueous solution and an organic solution for cross-linking treatment, and obtaining the alkali-resistant reverse osmosis membrane; the aqueous solution comprises diethylene triamine and polyethylene imine; the organic solution comprises cyanuric chloride.

2. The method of making an alkaline-resistant reverse osmosis membrane according to claim 1, wherein: In step (1), the polymer is polysulfone or polyether sulfone; the organic solvent is N,N-dimethylformamide; the polymer is added when the temperature reaches 50-60 DEG C, and stirring is performed for 24-36 hours after the addition is completed.

3. The method of making an alkaline-resistant reverse osmosis membrane according to claim 1, wherein: In step (2), the mixed solution is cooled to 20-40 DEG C before the pore-forming agent is added, and stirring is performed for 12-24 hours after the addition is completed; the pore-forming agent is polyvinylpyrrolidone-K30 or polyethylene glycol; the mass ratio of the organic solvent, the polymer and the pore-forming agent is (75-85):(15-25):(1-5).

4. The method for preparing the alkali-resistant reverse osmosis membrane according to claim 1, wherein: In step (3), the precursor solution is subjected to vacuum defoaming treatment at 50 DEG C for 6-12 hours; In step (4), the casting solution at a temperature of 20-40 DEG C is loaded onto a non-woven fabric carrier, and the gel bath treatment is performed in pure water at 10-40 DEG C for 1-10 minutes.

5. The method of making an alkaline-resistant reverse osmosis membrane according to claim 1, wherein: Step (5) comprises the following steps performed in sequence: immersing the base film in the aqueous solution, taking out the base film after the immersion is completed, and blowing the surface of the base film with compressed air; then immersing the base film in the organic solution, taking out the base film after the immersion is completed, and washing the surface of the base film with deionized water, thereby obtaining the alkali-resistant reverse osmosis membrane.

6. The method of making an alkaline-resistant reverse osmosis membrane according to claim 5, wherein: In the aqueous solution, the mass fraction of diethylene triamine is 0.5-3.5 wt%, and the mass fraction of polyethylene imine is 0.05-0.1 wt%; the base film is immersed in the aqueous solution for 1-5 minutes.

7. The method of making an alkaline-resistant reverse osmosis membrane according to claim 5, wherein: In the organic solution, the mass fraction of cyanuric chloride is 0.05-2 wt%; the base film is immersed in the organic solution for 5-60 seconds.

8. The method of making an alkaline-resistant reverse osmosis membrane according to claim 5, wherein: The method further comprises the following steps for post-treatment of the base film after the immersion in the organic solution: immersing the base film in a positive charge medium solution, taking out the base film after the immersion is completed, and washing the surface of the base film with deionized water; then immersing the base film in a negative charge medium solution, taking out the base film after the immersion is completed, and washing the surface of the base film with deionized water, thereby obtaining the alkali-resistant reverse osmosis membrane.

9. The method for preparing the alkali-resistant reverse osmosis membrane according to claim 8, wherein: the positive charge medium solution is a mixed solution of polyallylamine hydrochloride and sodium chloride, the pH is 3.5-4.5, the mass fraction of polyallylamine hydrochloride is 0.05-0.15 wt%, and the mass fraction of sodium chloride is 0.5-0.7 wt%; the base film is immersed in the positive charge medium solution for 10-20 minutes. The negative charge medium solution is a mixture of sodium polystyrene sulfonate and sodium chloride, the pH is 3.5-4.5, the mass fraction of sodium polystyrene sulfonate is 0.05-0.15wt%, and the mass fraction of sodium chloride is 0.5-0.7wt%; the base film is soaked in the negative charge medium solution for 10-20 minutes. The post-treatment process is performed twice.

10. An alkali-resistant reverse osmosis membrane, characterized by: The alkali-resistant reverse osmosis membrane is prepared by the method of any one of claims 1-9.

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