High boron removal reverse osmosis membrane based on functionalized ionic liquid modification and preparation method thereof

Abstract

The application relates to the field of membrane separation technology, and particularly discloses a high desorption reverse osmosis membrane based on functionalized ionic liquid modification and a preparation method thereof. The reverse osmosis membrane comprises a base film and an interface functional layer formed on the surface of the base film. The interface functional layer is a polyamide functional layer formed by interface polymerization reaction of acyl chloride monomers and aromatic amine monomers. The interface functional layer is further modified by cis-diol functionalized ionic liquid to firmly anchor the ionic liquid in the polyamide network. The high desorption reverse osmosis membrane based on functionalized ionic liquid modification provided by the application is a reverse osmosis membrane with specific boron removal function. By introducing the cis-diol functionalized ionic liquid into the reverse osmosis membrane, the specific complexation reaction of the ionic liquid with boric acid is utilized to solve the problem of boron desorption under neutral conditions, and the obvious limitations faced by the existing solutions are avoided.

Description

Technical Field

[0001] This invention relates to the field of membrane separation technology, specifically to a high-boron-deionization reverse osmosis membrane based on functionalized ionic liquid modification and its preparation method. Background Technology

[0002] Reverse osmosis (RO) technology has become the mainstream technology for seawater desalination, brackish water desalination, and industrial wastewater reuse due to its high efficiency and energy saving. Currently, commercially available reverse osmosis membranes (RO membranes) are mainly based on aromatic polyamide (PA) materials, which are prepared by the interfacial polymerization reaction of m-phenylenediamine (MPD) and trimesoyl chloride (TMC).

[0003] With the increasing severity of water scarcity, the performance requirements for reverse osmosis (RO) membranes are becoming increasingly stringent, particularly in boron removal, which faces significant challenges. Boron removal is a naturally occurring trace element in seawater (concentration approximately 4.5–5.0 mg / L) and a common pollutant in some industrial wastewater (such as wastewater from glass manufacturing, semiconductor cleaning, and geothermal power generation). Excessive boron intake can be toxic to plant growth and affect human health (e.g., reproductive system toxicity). Therefore, the World Health Organization (WHO) and national drinking water standards have extremely strict limits on boron (typically 0.5–2.4 mg / L, with some higher standards requiring a content <0.3 mg / L). However, the form of boron in aqueous solutions is significantly affected by pH: for example, under acidic conditions and pH < 9.0, boron mainly exists as the electrically neutral borate molecule B(OH)3; only under alkaline conditions (pH > 9.24) does it convert to the negatively charged borate ion B(OH)4. - .

[0004] Existing polyamide reverse osmosis membranes (RO membranes) mainly rely on size sieving and the Donnan effect (electrostatic repulsion) for retention. However, because neutral boric acid molecules are small (kinetic diameter of about 0.28 nm) and uncharged, they can easily pass through the traditional polyamide separation (functional) layer on the RO membrane. Therefore, under the normal water treatment operating pH (6.5-8.0), the boron retention rate of ordinary RO membranes is usually only 40-60%, which is far from meeting the water use standards.

[0005] To address the difficulty of boron removal under neutral conditions (pH 6.5–8.0), existing technologies have primarily employed the following strategies, but all have significant limitations, such as: Strategy 1: High pH operation process (two-stage RO membrane or alkali adjustment): By adding alkaline agents such as sodium hydroxide to the influent, the pH value is raised to 10.0-11.0, thereby forcing neutral boric acid to convert into negatively charged borate ions (B(OH)4). -While the electrostatic repulsion of membranes can improve the rejection rate, this strategy has certain drawbacks, such as: ① High operating costs: It requires a large amount of acid and alkali reagents and usually requires a two-stage RO system to meet the standards, resulting in a significant increase in equipment investment and energy consumption; ② Poor membrane stability: Polyamide RO membranes are prone to hydrolysis and degradation under strongly alkaline conditions, leading to an irreversible decrease in the desalination rate and shortening the membrane's lifespan; ③ Complex operation: It requires a complex online pH monitoring and callback system, increasing the difficulty of operation and maintenance.

[0006] Strategy 2: Surface grafting or coating modification: After film formation, a polymer layer containing boron adsorption groups (such as polyphenols and sugars) is grafted onto the film surface through methods such as UV initiation and plasma treatment. However, this strategy also has obvious drawbacks, such as: ① Complex process: It requires additional reaction steps and equipment, making it difficult to achieve continuous large-scale production; ② Insufficient stability: The physical coating layer is prone to peeling off during high-pressure shearing and cleaning processes, and if chemical grafting is not properly controlled, it may damage the original polyamide separation layer structure.

[0007] Strategy 3: Traditional Ionic Liquid Doping: In recent years, some studies have attempted to dope ordinary ionic liquids (such as imidazole and pyridine) into membranes to improve hydrophilicity. However, this method also has corresponding drawbacks, such as: ① Single function: Traditional ionic liquids mainly focus on adjusting free volume or hydrophilicity, and lack specific recognition functional groups for boron molecules (such as cis-diol structures), resulting in insignificant boron removal effect; ② Environmental toxicity concerns: Some ionic liquids containing fluoride anions or specific cations have poor biodegradability and pose potential environmental risks. Summary of the Invention

[0008] The purpose of this invention is to provide a high-boron-removing reverse osmosis membrane based on functionalized ionic liquid modification and its preparation method, aiming to solve the problem of difficult boron removal from ordinary RO membranes under neutral pH conditions and overcome the limitations of the prior art.

[0009] To achieve the above objectives, the present invention is implemented through the following technical solution: This invention provides a high-boron-deionization reverse osmosis membrane based on functionalized ionic liquid modification. The reverse osmosis membrane includes a base membrane and an interfacial functional layer formed on the surface of the base membrane. The interfacial functional layer is a polyamide functional layer formed by interfacial polymerization of acyl chloride monomer and aromatic amine monomer. The interfacial functional layer is further modified with cis-diol functionalized ionic liquid to achieve the ionic liquid firmly anchored in the polyamide network.

[0010] Specifically, the high boron removal reverse osmosis membrane based on functionalized ionic liquid modification provided by this invention is a reverse osmosis membrane with specific boron removal function. By introducing cis-diol functionalized ionic liquid into the reverse osmosis membrane, the problem of difficult boron removal under neutral conditions is solved by utilizing its specific complexation reaction with boric acid, and it does not bring about the obvious limitations faced by existing solutions.

[0011] Furthermore, a high-boron-deboron reverse osmosis membrane based on functionalized ionic liquid modification: the base membrane is a polysulfone-based membrane.

[0012] This invention also provides a method for preparing a high-boron-desorption reverse osmosis membrane based on functionalized ionic liquid modification, the method comprising the following steps: S1. Hydrolysis: Dissolve the biomass sugar in water and stir to hydrolyze it into sugar acid; S2, Neutralization: Under ice-water bath and magnetic stirring conditions, the organic quaternary ammonium base solution is added dropwise to the sugar-acid solution. The temperature is controlled to prevent local overheating that could lead to caramelization of the sugar. After the addition is complete, stirring continues until the solution becomes a colorless, transparent, viscous liquid and the pH value stabilizes at neutral, thus obtaining a cis-diol functionalized ionic liquid. S3. Preparation of aqueous phase: Mix pH adjuster, aromatic amine monomer, cis-diol functionalized ionic liquid with water and stir until homogeneous to obtain aqueous phase; S4. Preparation of oil phase liquid: Add acyl chloride monomer to organic solvent and stir evenly to obtain oil phase liquid; S5. Interfacial polymerization reaction: Immerse the base film in the aqueous phase liquid, remove it and remove excess water from the surface, then pour an excess of oil phase liquid onto the surface of the base film to carry out the interfacial polymerization reaction, let it stand and remove excess oil phase liquid, and dry it. S6. Reverse osmosis post-treatment: Immerse the dried membrane in hot water to remove residual amine, then transfer it sequentially to sodium bisulfite solution and glycerol solution for soaking, and dry to obtain a high boron removal reverse osmosis membrane modified with cis-diol functionalized ionic liquid.

[0013] Furthermore, a method for preparing a high-boron-deionized reverse osmosis membrane based on functionalized ionic liquid modification: the biomass sugar in step S1 is selected from D-gluconic acid-δ-lactone or D-mannonic acid.

[0014] Furthermore, a method for preparing a high-boron-deionized reverse osmosis membrane based on functionalized ionic liquid modification: in step S2, the concentration of the organic quaternary ammonium alkali solution is 40-50 wt%, and the temperature is controlled not to exceed 25℃.

[0015] Furthermore, a method for preparing a high-boron-deionized reverse osmosis membrane based on functionalized ionic liquid modification: the organic quaternary ammonium base in step S2 is selected from choline hydroxide or betaine.

[0016] Specifically, choline hydroxide can be prepared from choline chloride (vitamin B4), for example, by converting choline chloride into choline hydroxide through ion exchange.

[0017] Furthermore, a method for preparing a high-boron-deionized reverse osmosis membrane based on functionalized ionic liquid modification: in step S3, the concentration of the pH adjuster in the aqueous phase is 2.0–5.0 wt%, the concentration of the aromatic amine monomer is 1.5–4.0 wt%, and the concentration of the cis-diol functionalized ionic liquid is 1.0–3.0 wt%.

[0018] Furthermore, a method for preparing a high-boron-deionized reverse osmosis membrane based on functionalized ionic liquid modification: the pH adjuster is triethylamine hydrochloride, and the aromatic amine monomer is selected from any one of o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, and benzidine.

[0019] Furthermore, a method for preparing a high-boron-deionized reverse osmosis membrane based on functionalized ionic liquid modification: the concentration of the acyl chloride monomer in the oil phase of step S4 is 0.05-0.25 wt%.

[0020] Furthermore, a method for preparing a high-boron-deionized reverse osmosis membrane based on functionalized ionic liquid modification: the acyl chloride monomer is selected from any one of trimesoyl chloride, isophthaloyl chloride, and terephthaloyl chloride, and the organic solvent is selected from any one of ethylcyclohexane, cyclohexane, n-hexane, n-heptane, and isoparaffin solvents.

[0021] The beneficial effects of this invention are: This invention relates to a high-boron-removing reverse osmosis membrane modified with functionalized ionic liquids, which possesses the following characteristics: ① Specific recognition mechanism: This invention introduces a functionalized ionic liquid with a cis-diol structure into the polymerized aqueous phase at the reverse osmosis membrane interface for the first time. The ortho-hydroxyl groups on the anion of this ionic liquid can undergo a specific complexation reaction with boric acid under neutral pH conditions, converting neutral boric acid molecules into negatively charged complexed anions, thereby achieving efficient boron retention through electrostatic repulsion; ② Green and stable: The functionalized ionic liquid raw materials selected in this invention are derived from vitamin B4 (choline hydroxide can be obtained from vitamin B4 through ion exchange) and biomass sugars. They are non-toxic and biodegradable, and during the high-temperature post-treatment of reverse osmosis, the ionic liquid can be firmly anchored in the polyamide network through hydrogen bonding and potential esterification, resulting in stable performance; ③ High antifouling and water flux: The unique properties (high hydrophilicity) of the functionalized ionic liquid synergistically enhance the antifouling ability and water flux of the reverse osmosis membrane.

[0022] The method for preparing a high-boron-deionization reverse osmosis membrane based on functionalized ionic liquid modification provided by this invention also includes immersion treatment in sodium bisulfite solution (reducing agent), which has the following effects: ① Protecting the membrane material: The core of the reverse osmosis membrane is the polyamide functional layer, which is easily oxidized and degraded, leading to a decrease in desalination rate and a shortened membrane life. Immersion treatment in sodium bisulfite solution can react with residual oxidizing substances, preventing oxidative damage to the membrane material; ② Inhibiting microbial fouling: The surface of the reverse osmosis membrane is prone to the growth of microorganisms due to feed water quality issues, forming a biofilm. This not only clogs the membrane pores and reduces flux but also secretes metabolic products that corrode the membrane elements. Sodium bisulfite can slowly release sulfite ions in water, creating a reducing environment that is unfavorable to the growth and reproduction of aerobic microorganisms. It can also react with oxidizing substances produced by microbial metabolism, further inhibiting microbial activity. In addition, immersion treatment in sodium bisulfite solution can also remove residual metal oxide fouling (such as high-valence oxides of iron and manganese) from the membrane surface by reducing high-valence metal ions to soluble low-valence ions, making them easier to remove through subsequent cleaning.

[0023] The preparation method of the high boron removal reverse osmosis membrane based on functionalized ionic liquid modification provided by this invention also includes immersion in a glycerol solution, which has the following effects: ① Preventing membrane flux decay: Reverse osmosis dry membranes are prone to water loss and shrinkage, leading to membrane pore closure and irreversible decay of water flux. Glycerol, as a polyol humectant, contains hydroxyl groups in its molecules, which can combine with water molecules through hydrogen bonds to form a breathable and moisturizing membrane on the membrane surface, locking in moisture and reducing water evaporation; ② Preventing membrane dry-state damage: Dry membrane materials become hard and brittle, and are easily damaged by mechanical stress. Glycerol, as a plasticizer, can penetrate into the internal structure of the membrane, reduce the interaction forces between polymer chains, increase the flexibility and extensibility of the membrane, and prevent membrane rupture caused by drying; In addition, glycerol can also act as a protective liquid, forming a hydrophobic barrier on the membrane surface, reducing the contact between the membrane and external pollutants, and extending the service life of the membrane. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 The image shows a scanning electron microscope (SEM) image of the reverse osmosis membrane in Comparative Example 1. Figure 2 This is a scanning electron microscope image of the high boron removal reverse osmosis membrane modified with functionalized ionic liquid in Example 1. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] Example 1

[0028] This embodiment 1 provides a high boron removal reverse osmosis membrane based on functionalized ionic liquid modification. The reverse osmosis membrane includes a polysulfone-based membrane and an interface functional layer formed on the surface of the polysulfone-based membrane. The interface functional layer is a polyamide functional layer formed by interfacial polymerization of acyl chloride monomer and aromatic amine monomer. The interface functional layer is also modified with cis-diol functionalized ionic liquid to achieve that the ionic liquid is firmly anchored in the polyamide network. The above-described method for preparing a high-boron-desorption reverse osmosis membrane based on functionalized ionic liquid modification includes the following specific steps: S1. Hydrolysis: Dissolve 17.8g (about 0.1mol) of biomass sugar (D-gluconic acid-δ-lactone) in 50.0ml of deionized water and stir at room temperature for 30 minutes to completely hydrolyze it into D-gluconic acid; S2, Neutralization: Under ice-water bath and magnetic stirring conditions, 21.5 g of organic quaternary ammonium base solution (50.0 wt% choline hydroxide solution) was slowly added dropwise to the above D-gluconic acid solution, with the temperature controlled below 25°C to prevent local overheating and caramelization of sugars; after the addition was complete, stirring was continued for 2 hours until the solution became a colorless, transparent, viscous liquid and the pH value stabilized at neutral (pH 7.0 ± 0.2), thus obtaining cis-diol functionalized ionic liquid; S3. Preparation of the aqueous phase: The pH adjuster (triethylamine hydrochloride), the aromatic amine monomer (m-phenylenediamine), and the cis-diol functionalized ionic liquid are mixed with deionized water and stirred until homogeneous to obtain the aqueous phase; wherein the concentrations of triethylamine hydrochloride, m-phenylenediamine, and the functionalized ionic liquid in the aqueous phase are 3.5wt%, 2.5wt%, and 1.0wt%, respectively. S4. Preparation of oil phase: Add 0.15g of acyl chloride monomer (pyromellitic trimethylol chloride) to 99.85g of organic solvent (ethylcyclohexane), stir evenly to obtain oil phase; S5. Interfacial polymerization reaction: Immerse the polysulfone-based membrane in the functional aqueous phase liquid for 20 seconds, remove it and use a roller to remove excess water from the surface of the polysulfone-based membrane. Then pour excess oil phase liquid onto the surface of the polysulfone-based membrane to carry out the interfacial polymerization reaction for 30 seconds. After removing the excess oil phase liquid, place it in a 90°C oven to dry for 120 seconds. S6. Reverse osmosis post-treatment: Immerse the dried membrane in hot water at 70°C for 240 seconds to remove residual amines on the membrane surface, then transfer it to a 0.5wt% sodium bisulfite solution for 40 seconds, then transfer it to a 7.0wt% glycerol solution for 40 seconds, and finally place it in an oven at 70°C for 90 seconds to dry, thereby obtaining a high-boron-deionized reverse osmosis membrane modified with cis-diol functionalized ionic liquid.

[0029] Example 2

[0030] The difference between Example 2 and Example 1 is that in Example 2, the biomass sugar (D-gluconic acid-δ-lactone) in Example 1 is replaced with D-mannonic acid, while the other conditions are the same.

[0031] Example 3

[0032] The difference between Example 3 and Example 1 is that in Example 3, the organic quaternary ammonium base (choline hydroxide) in Example 1 is replaced with betaine, while the other conditions are the same.

[0033] Example 4

[0034] The difference between Example 4 and Example 1 is that in Example 4, the amount of cis-diol functionalized ionic liquid added to the aqueous phase of Example 1 is increased from 1.0 wt% to 2.0 wt%, while the other conditions remain the same.

[0035] Example 5

[0036] The difference between Example 5 and Example 1 is that in Example 5, the amount of cis-diol functionalized ionic liquid added to the aqueous phase of Example 1 is increased from 1.0 wt% to 3.0 wt%, while the other conditions remain the same.

[0037] Comparative Example 1

[0038] The difference between Comparative Example 1 and Example 1 is that no cis-diol functionalized ionic liquid was added to the aqueous phase of Comparative Example 1, while the other conditions were the same.

[0039] test: The reverse osmosis membranes of Examples 1 to 5 and Comparative Example 1 were subjected to relevant performance tests (including flux-removal rate tests and membrane property analysis).

[0040] (1) Flux-Removal Rate Test: According to the test platform required by the national standard GB / T 32373-2025, a 2000ppm NaCl + 5ppm boric acid solution was prepared and mixed evenly as the test solution for later use. Under the test conditions of 1.55MPa operating pressure, 25±1℃ temperature and pH value of 7.5±0.5, the permeate flow rate and NaCl desalination rate of the membrane were tested. At the same time, the boron content in the feed water and the permeate water was detected by ion chromatography and the boron removal rate was calculated. The results are shown in Table 1.

[0041] Table 1 shows the performance test results of the reverse osmosis membranes in Examples 1-5 and Comparative Example 1.

[0042] As can be seen from the membrane test results of Examples 1-5 and Comparative Example 1 in Table 1, the reverse osmosis membrane of Comparative Example 1 has a water production rate of 28.66 GFD, a NaCl removal rate of 99.39%, and a boron removal rate of 58.32%, which is close to the performance of conventional industrial membrane products on the market. However, the membrane test performance of Examples 1-5 shows that the water production rate is significantly higher than that of the membrane of Comparative Example 1. This is mainly attributed to the fact that the sugar acid in the functionalized ionic liquid carries a large number of hydrophilic hydroxyl groups, and the introduction of hydrophilic hydroxyl groups significantly improves the water production rate of the membrane. Regarding the NaCl removal rate, the reverse osmosis membranes of Examples 1-5 were no less efficient than those of Comparative Example 1. This improvement was mainly due to the introduction of functionalized ionic liquids, which filled the defects generated during the interfacial polymerization process. The significant improvement in boron removal rate is the core of this application. It can be seen that the boron removal rate of Comparative Example 1 membrane was only 58.32%, while the boron removal rates of the membranes of Examples 1-5 were all maintained above 75.0%. This improvement in boron removal rate is mainly attributed to the cis-diol content in the functionalized ionic liquid. Cis-diol reacts with boric acid under neutral conditions... The molecules undergo a reversible esterification reaction to form stable five- or six-membered cyclic complexes, converting neutral boric acid into negatively charged complex anions, which are then efficiently retained by the negatively charged polyamide membrane surface through the Donnan effect. The membrane boron removal rates in Examples 1, 4, and 5 also confirm this trend. As the content of functionalized ionic liquid increases, the boron removal rate shows an increasing trend. However, functionalized ionic liquids have a surfactant effect, and adding too much functionalized ionic liquid to the aqueous phase will affect the degree of interfacial polymerization reaction, which will lead to a decrease in the sodium chloride removal rate.

[0043] (2) Physicochemical property analysis of membranes: The reverse osmosis membranes of Example 1 and Comparative Example 1 were analyzed by scanning electron microscopy (SEM), and the results are as follows: Figure 1 and Figure 2 As shown, a comparison of SEM images reveals that the membrane surface blade structure without the addition of functionalized ionic liquid in the aqueous phase is smaller. Figure 1), while membranes with functionalized ionic liquids added to the aqueous phase ( Figure 2 The surface blade structure is significantly enlarged and increased in number. This is because the functionalized ionic liquid has the function of a surfactant. The addition of the functionalized ionic liquid helps to increase the diffusion rate of m-phenylenediamine molecules to the polymerization reaction interface, and also simultaneously increases the surface tension of the interface, forming more and larger micro blade structures.

[0044] (3) Contact angle test: The reverse osmosis membranes of Examples 1 to 5 and Comparative Example 1 were tested for contact angle. The results are shown in Table 2.

[0045] Table 2 shows the test results of the reverse osmosis membrane contact angle in Examples 1-5 and Comparative Example 1.

[0046] The contact angle test data in Table 2 above further confirms the introduction of functional ionic liquids; the contact angle of the reverse osmosis membrane in Comparative Example 1 is 56.5°, while the contact angles of the reverse osmosis membranes in Examples 1 to 5 are between 29° and 37°. It can be seen that the contact angle value is significantly reduced, which indicates that the hydrophilicity of the membrane surface is significantly improved. This is because the sugar acid molecules in the functionalized ionic liquid contain a large number of hydroxyl groups, and the introduction of surface hydrophilic hydroxyl groups is beneficial to improving the membrane's antifouling ability and cleaning and recovery effect, as well as increasing the membrane water flux and enhancing the boron retention capacity.

[0047] The above-described preferred embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of the invention. Any obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A high-boron-desorption reverse osmosis membrane based on functionalized ionic liquid modification, characterized in that, The reverse osmosis membrane includes a base membrane and an interfacial functional layer formed on the surface of the base membrane. The interfacial functional layer is a polyamide functional layer formed by interfacial polymerization of acyl chloride monomer and aromatic amine monomer. The interfacial functional layer is also modified with cis-diol functionalized ionic liquid to achieve the ionic liquid firmly anchored in the polyamide network.

2. The high boron removal reverse osmosis membrane based on functionalized ionic liquid modification according to claim 1, characterized in that, The base membrane is a polysulfone base membrane.

3. A method for preparing a high-boron-desorption reverse osmosis membrane based on functionalized ionic liquid modification according to claim 1 or 2, characterized in that, The method includes the following steps: S1. Hydrolysis: Dissolve the biomass sugar in water and stir to hydrolyze it into sugar acid; S2, Neutralization: Under ice-water bath and magnetic stirring conditions, the organic quaternary ammonium base solution is added dropwise to the sugar-acid solution. The temperature is controlled to prevent local overheating that could lead to caramelization of the sugar. After the addition is complete, stirring continues until the solution becomes a colorless, transparent, viscous liquid and the pH value stabilizes at neutral, thus obtaining a cis-diol functionalized ionic liquid. S3. Preparation of aqueous phase: Mix pH adjuster, aromatic amine monomer, cis-diol functionalized ionic liquid with water and stir until homogeneous to obtain aqueous phase; S4. Preparation of oil phase liquid: Add acyl chloride monomer to organic solvent and stir evenly to obtain oil phase liquid; S5. Interfacial polymerization reaction: Immerse the base film in the aqueous phase liquid, remove it and remove excess water from the surface, then pour an excess of oil phase liquid onto the surface of the base film to carry out the interfacial polymerization reaction, let it stand and remove excess oil phase liquid, and dry it. S6. Reverse osmosis post-treatment: Immerse the dried membrane in hot water to remove residual amine, then transfer it sequentially to sodium bisulfite solution and glycerol solution for soaking, and dry to obtain a high boron removal reverse osmosis membrane modified with cis-diol functionalized ionic liquid.

4. The method for preparing a high-boron-desorption reverse osmosis membrane based on functionalized ionic liquid modification according to claim 3, characterized in that, The biomass sugar mentioned in step S1 is selected from D-gluconic acid-δ-lactone or D-mannonic acid.

5. The method for preparing a high-boron-desorption reverse osmosis membrane based on functionalized ionic liquid modification according to claim 3, characterized in that, In step S2, the concentration of the organic quaternary ammonium alkali solution is 40-50 wt%, and the temperature is controlled to not exceed 25°C.

6. A method for preparing a high-boron-desorption reverse osmosis membrane based on functionalized ionic liquid modification according to claim 3 or 5, characterized in that, The organic quaternary ammonium base mentioned in step S2 is selected from choline hydroxide or betaine.

7. The method for preparing a high-boron-desorption reverse osmosis membrane based on functionalized ionic liquid modification according to claim 3, characterized in that, In step S3, the concentration of the pH adjuster in the aqueous phase is 2.0–5.0 wt%, the concentration of the aromatic amine monomer is 1.5–4.0 wt%, and the concentration of the cis-diol functionalized ionic liquid is 1.0–3.0 wt%.

8. A method for preparing a high-boron-desorption reverse osmosis membrane based on functionalized ionic liquid modification according to claim 3 or 7, characterized in that, The pH adjuster is triethylamine hydrochloride, and the aromatic amine monomer is selected from any one of o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, and benzidine.

9. The method for preparing a high-boron-desorption reverse osmosis membrane based on functionalized ionic liquid modification according to claim 3, characterized in that, The concentration of the acyl chloride monomer in the oil phase of step S4 is 0.05 to 0.25 wt%.

10. A method for preparing a high-boron-desorption reverse osmosis membrane based on functionalized ionic liquid modification according to claim 3 or 9, characterized in that, The acyl chloride monomer is selected from any one of trimesoyl chloride, isophthaloyl chloride, and terephthaloyl chloride, and the organic solvent is selected from any one of ethylcyclohexane, cyclohexane, n-hexane, n-heptane, and isoparaffin solvents.

Images