Reverse osmosis membrane with ultrathin functional layer and preparation method of reverse osmosis membrane

Abstract

The invention belongs to the technical field of reverse osmosis membranes, and particularly relates to a preparation method of a reverse osmosis membrane with an ultrathin functional layer, which comprises the following steps: (1) preparing a membrane casting solution; (2) forming an ultrafiltration porous support layer; (3) forming a polyamide / polyester functional layer: sequentially contacting the ultrafiltration support layer with an organic phase solution I containing a polyamine / polyphenol monomer and an acid-binding agent and an organic phase solution II containing polyacyl chloride; (4) post-treatment; (5) drying; in the interfacial polymerization process, a strong-polarity organic solvent is adopted to replace pure water to serve as a carrier solvent of polyamine / polyphenol, the limitation of a traditional water / oil interface is broken through, and the method has the advantages that the monomer selection range is greatly expanded, a functional layer is ultrathin, the surface smoothness is improved, hydrolysis of multi-acyl chloride is avoided, the crosslinking degree of the functional layer is improved, and the service life of the functional layer is prolonged. The surface charge property of the membrane is improved, the process is simple, commercialized popularization is easy, and the comprehensive performance of the membrane is improved.

Description

Technical Field

[0001] This invention belongs to the field of reverse osmosis membrane technology, and specifically relates to a method for preparing a reverse osmosis membrane with an ultrathin functional layer. Background Technology

[0002] Reverse osmosis (RO) technology is widely used in water resource recycling processes such as seawater desalination, wastewater treatment, and desalination of bitter water due to its advantages of high efficiency, energy saving, environmental friendliness, and low cost. RO technology separates impurities such as salt, bacteria, and viruses from water through a semi-permeable membrane driven by pressure, thereby obtaining high-quality fresh water. As the core of reverse osmosis technology, the performance of the reverse osmosis membrane directly determines the economic indicators and environmental benefits of the water treatment technology.

[0003] Commercially available reverse osmosis membranes are mostly polyamide (PA) thin-layer composite membranes prepared by interfacial polymerization, primarily composed of a porous support layer and an ultrathin separation layer. This asymmetric membrane structure allows the reverse osmosis membrane to maintain high mechanical strength while exhibiting excellent selectivity and permeation performance. The separation performance and antifouling properties of reverse osmosis membranes mainly depend on the surface structure and properties of the polyamide functional layer. Therefore, research on the modification of the functional layer has become a major direction for improving the performance of reverse osmosis membranes.

[0004] To prepare high-flux, low-energy-consumption reverse osmosis membranes, researchers have conducted various modification studies, mainly including the following aspects: 1. Introducing small-molecule additives into the aqueous or oil phase to alter the properties of the co-solubility zone during interfacial polymerization, thereby obtaining high-flux reverse osmosis membranes with improved performance. 2. Preparing ultrathin desalination layers by introducing metal nano-intermediate layers, utilizing the lower water transport resistance of the ultrathin desalination layer to obtain high-flux reverse osmosis membranes. For example, patent CN114028959A discloses a method for preparing ultrathin desalination layer reverse osmosis composite membranes, introducing metal hydroxide nanowires as intermediate layers into the interfacial polymerization process to alter the solvent environment of the miscible zone, thereby obtaining an ultrathin desalination layer. 3. Constructing a nanoparticle intermediate layer on the base membrane surface, utilizing the high hydrophilicity and porosity of nanoparticles to form good water permeation channels. For example, patent CN112023731A discloses a method for preparing high-flux, low-pressure reverse osmosis membranes, achieving a high-flux reverse osmosis process under low-pressure driving conditions by constructing a nano-silica particle intermediate layer on the base membrane surface. 4. Surface grafting modification imparts unique surface properties to the PA layer, enhancing its permeation performance, antifouling performance, and chlorine resistance. 5. Developing and introducing novel interfacial polymerization monomers to prepare active functional layers fundamentally solves a series of membrane fouling problems associated with traditional monomer-based membrane fabrication. While introducing metal nanoparticles or inorganic nanoparticle interlayers can effectively improve the flux of reverse osmosis membranes, these methods also present some challenges. For example, the poor compatibility between metal / inorganic nanoparticles and the polysulfone support / functional layer leads to decreased membrane stability and durability. These membrane fabrication processes are typically complex and difficult to scale up for mass production, limiting their practical applications. Furthermore, interfacial polymerization often involves the simplification of polyamine / polyphenol monomers. In traditional water / oil interfacial polymerization, the polarity of water limits the types of polyamine / polyphenol monomers that can participate in the reaction. Moreover, the presence of water can cause hydrolysis of polyacrylamide chlorides, making it difficult to control the surface charge of the membrane and reducing the crosslinking degree of the functional layer.

[0005] Therefore, although significant progress has been made in the modification of reverse osmosis membranes to improve membrane performance, further optimization of processes and addressing the shortcomings of existing technologies are still needed to achieve large-scale application and sustainable development of reverse osmosis membranes. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies by proposing a method for preparing a reverse osmosis membrane with an ultrathin functional layer.

[0007] Specifically, this is achieved through the following technical solutions: A method for preparing a reverse osmosis membrane with an ultrathin functional layer includes the following steps: (1) Preparation of casting solution: The polymer is added to an organic solvent, heated and stirred until the polymer is completely dissolved to prepare a polymer solution as a casting solution; (2) Formation of an ultrafiltration porous support layer: The casting solution is coated onto a nonwoven fabric support layer, and an ultrafiltration porous support layer is formed by phase inversion. (3) Formation of polyamide / polyester functional layer: The ultrafiltration support layer is sequentially contacted with an organic phase solution I containing polyamine / polyphenol monomers and an acid-binding agent and an organic phase solution II containing polyacryl chlorides to form a polyamide / polyester functional layer. (4) Post-processing: The polyamide / polyester functional layer formed above is subjected to post-treatment, which includes acid cleaning, pure water cleaning and pore preservation treatment in sequence. (5) Drying: The post-treated membrane is then dried.

[0008] The polymer is selected from one or more of polyethersulfone, polysulfone, polyacrylonitrile, polyimide, polyvinylidene fluoride, and sulfonated polyethersulfone.

[0009] The organic solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpyrrolidone, and dimethyl sulfoxide.

[0010] The polymer concentration in the casting solution is 10-25%.

[0011] The polyamine / polyphenol monomer is selected from one or more of the following: m-phenylenediamine, o-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 4,4,4,4-methylethanetetraphenylamine, tris(4-aminophenyl)amine, 1,3,5-tris(4-aminophenyl)benzene, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenol, 4,4',4"-triaminotriphenylmethane, 4,4',4''-methylenetriphenol, perhydroxyl columnar aromatic compounds, biphenyl-based compounds, biphenylamine-based compounds, cyclodextrin, and piperazine.

[0012] The solvent in the organic phase solution I is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0013] The acid-binding agent in the organic phase solution I is selected from one or more of sodium hydroxide, potassium hydroxide, and triethylamine camphor sulfonate.

[0014] The concentration of polyamine / polyphenol monomers in the organic phase solution I is 1-5%, and the concentration of acid-binding agent is 0.03-3%.

[0015] The polyacryl chloride monomer is selected from one or more of phthaloyl chloride, biphenyl chloride, oxaloyl chloride, terephthaloyl chloride, trimesoyl chloride, and isophthaloyl chloride.

[0016] The solvent in the organic phase solution II is selected from one or more of the following: n-hexane, cyclohexane, ethylcyclohexane, n-heptane, tetrahydrofuran, isoparaffins, chloroform, toluene, and m-xylene.

[0017] The concentration of polyacrylamide chloride monomer in the organic phase solution II is 0.05-1.0%.

[0018] The acid solution used for pickling is selected from one or more of citric acid, malic acid, sodium bisulfate, hydrochloric acid, sulfurous acid, and hypochlorous acid, and the concentration of the acid solution is 0.5-20%.

[0019] The pore-preserving treatment uses 3-10% glycerol as a pore-preserving agent.

[0020] The drying temperature is 50-120℃, and the time is 1-10 minutes.

[0021] Beneficial effects: This invention overcomes the limitations of traditional water / oil interfaces by using a highly polar organic solvent instead of pure water as the carrier solvent for polyamines / polyphenols during interfacial polymerization, achieving an innovative transformation of the oil / oil (organic phase I / organic phase II) interface. The specific beneficial effects are as follows: 1. Expanded the range of single-agent selection.

[0022] This invention uses a highly polar organic solvent as a carrier solvent for polyamines / polyphenols, which greatly improves the solubility of various polyamine / polyphenol monomers, thus expanding the selection of monomer molecules in interfacial polymerization.

[0023] 2. The functional layer is made thinner and the surface smoothness is improved.

[0024] Strongly polar organic solvents are not only good solvents for polyamines / polyphenols, but also for polyacryl chlorides. During interfacial polymerization, this characteristic results in a much higher diffusion rate of polyacryl chlorides into organic phase I compared to the diffusion rate of polyamines / polyphenols into organic phase II. This reverse diffusion reaction mode is beneficial for forming ultrathin and smooth functional layers, which helps reduce water transport resistance and contaminant adhesion, thereby improving membrane flux and antifouling performance.

[0025] 3. Avoid hydrolysis of polyacrylamide chlorides and improve the cross-linking degree of functional layers.

[0026] In traditional water / oil interfacial polymerization, the presence of water causes the polyacryl chloride to hydrolyze, generating carboxylic acids, which affects the crosslinking degree of the functional layer and the membrane performance. This invention uses an anhydrous organic solvent system, fundamentally solving the problem of polyacryl chloride hydrolysis, increasing the crosslinking degree of the functional layer, and thus further improving the membrane's separation performance.

[0027] 4. The process is simple and easy to commercialize and promote.

[0028] The process of this invention is simple and easy to implement, requiring no complex equipment or operating steps. The method of this invention is also easier to scale up for production and reduce production costs.

[0029] 5. Improve the overall performance of the membrane.

[0030] The reverse osmosis membrane prepared by the method of this invention has high flux, high selectivity, good antifouling performance, and greatly expands the application scenarios of the membrane. Attached Figure Description

[0031] Figure 1 This is a SEM image of the surface of the cross-linked polyimide (XP84) ultrafiltration membrane prepared in Example 1 of this invention; Figure 2 This is a SEM image of the surface of the thin-layer composite reverse osmosis membrane prepared in Example 3 of the present invention; Figure 3 This is a cross-sectional SEM image of the thin-layer composite reverse osmosis membrane prepared in Example 3 of the present invention; Figure 4 This is a SEM image of the surface of the thin-layer composite reverse osmosis membrane prepared in Comparative Example 1 of this invention; Figure 5 This is a cross-sectional SEM image of the thin-layer composite reverse osmosis membrane prepared in Comparative Example 1 of this invention; Figure 6 This is an AFM image of the surface of the thin-layer composite reverse osmosis membrane prepared in Example 3 of this invention; Figure 7 This is an AFM image of the surface of the thin-layer composite reverse osmosis membrane prepared in Comparative Example 1 of this invention; Figure 8 This is a diffusion rate diagram of m-phenylenediamine and pyromellitic acid chloride under the conditions of Comparative Example 1 of this invention; Figure 9 This is a diffusion rate diagram of m-phenylenediamine and pyromellitic acid chloride under the conditions of Example 2 of the present invention. Detailed Implementation

[0032] The specific embodiments of the present invention will be described in further detail below, but the present invention is not limited to these embodiments. Any improvements or substitutions based on the basic spirit of these embodiments shall still fall within the scope of protection claimed by the claims of the present invention.

[0033] Example 1 A method for preparing a reverse osmosis membrane with an ultrathin functional layer includes the following steps: (1) Preparation of casting solution: Polyimide was added to an N,N-dimethylformamide solution, heated and stirred until completely dissolved, and then allowed to stand to remove bubbles to obtain a casting solution with a polyimide concentration of 22%. (2) Formation of an ultrafiltration porous support layer: The above casting solution was coated onto a nonwoven fabric and phase-inverted in pure water to form a polyimide ultrafiltration membrane. The polyimide ultrafiltration membrane was placed in a 120 g / L isopropanol solvent of 1,6-hexanediamine for crosslinking at room temperature for 10-16 hours. The crosslinking agent was then washed with isopropanol. Finally, the membrane was subjected to a pore-preserving treatment with a PEG400 / isopropanol solvent at a volume ratio of 3:2 to obtain a crosslinked polyimide (XP84) ultrafiltration porous support layer. (3) Formation of polyamide / polyester functional layer: The XP84 base membrane was placed in pure water for 1-10 minutes to remove the pore-retaining agent. After soaking, the XP84 base membrane was removed and drained. Then, it was immersed in an N,N-dimethylformamide solution (organic phase solution I) with a concentration of 3wt% m-phenylenediamine and 0.04wt% sodium hydroxide for 20 seconds. The XP84 base membrane was then removed and the surface water droplets were removed. Next, the XP84 ultrafiltration base membrane was immersed in an ethylcyclohexane solution with 0.2wt% trimesoyl chloride for 20 seconds to form a polyamide functional layer / polyester functional layer. (4) Post-processing: The polyamide / polyester functional layer formed above was washed sequentially with 10 wt% citric acid solution for 4 min, washed with pure water for 1 min, and then immersed in 5 wt% glycerol solution for pore preservation treatment for 1 min to obtain a thin-layer composite separation membrane. (5) Drying: The thin-layer composite separation membrane was dried in a 65℃ oven for 3 min to obtain the thin-layer composite reverse osmosis membrane.

[0034] Example 2 The preparation method is the same as in Example 1, except that the concentration of trimesoyl chloride in the organic phase solution II is 0.4 wt% in the preparation of the thin-layer composite reverse osmosis membrane. Other preparation steps and conditions are exactly the same.

[0035] Example 3 The preparation method is the same as in Example 1, except that the concentration of trimesoyl chloride in the organic phase solution II is 0.6 wt% in the preparation of the thin-layer composite reverse osmosis membrane. Other preparation steps and conditions are exactly the same.

[0036] Example 4 The preparation method is the same as in Example 1, except that the concentration of trimesoyl chloride in the organic phase solution II is 0.8 wt% in the preparation of the thin-layer composite reverse osmosis membrane. Other preparation steps and conditions are exactly the same.

[0037] Example 5 The preparation method is the same as in Example 1, except that the concentration of trimesoyl chloride in the organic phase solution II is 1.0 wt% in the preparation of the thin-layer composite reverse osmosis membrane. Other preparation steps and conditions are exactly the same.

[0038] Example 6 The preparation method is the same as in Example 1, except that in the preparation of the thin-layer composite reverse osmosis membrane, the amine-containing monomer in organic phase solution I is 3 wt% 3,3'-diaminobenzidine, and the concentration of trimesoyl chloride in organic phase solution II is 0.8 wt%. Other preparation steps and conditions are exactly the same.

[0039] Comparative Example 1 Thin-layer composite reverse osmosis membranes were prepared using the method described in Example 1, with the difference being that in the preparation of the thin-layer composite membrane, after the XP84 base membrane was drained, it was immersed in pure water (aqueous phase) containing 3 wt% m-phenylenediamine and 0.04 wt% sodium hydroxide for 20 s. The XP84 base membrane was then removed and surface water droplets were removed. Next, the XP84 ultrafiltration base membrane was immersed in 0.4 wt% trimesoyl chloride in ethylcyclohexane organic phase solution II for 20 s to form a polyamide functional layer / polyester functional layer. Other preparation steps and conditions were exactly the same.

[0040] II. Diaphragm Performance Testing Experimental methods Using a NaCl aqueous solution with a concentration of 1500 ppm as the feed liquid, the desalination rate and throughput of Examples 1-5 and Comparative Example 1 were tested under the conditions of operating pressure of 0.69 MPa and temperature of 25 °C. The results are shown in Table 1 (concentrate circulation).

[0041] Table 1

[0042] As shown in Table 1, compared with the comparative reverse osmosis membranes, the thin-layer composite reverse osmosis membranes prepared in Examples 1-6 using the method of this invention, with the polar organic solvent N,N-dimethylformamide instead of pure water as a good solvent for the polyamine (organic phase I), exhibited significantly improved permeate flux. This is because N,N-dimethylformamide is not only a good solvent for polyamines but also for polyacrylamide chlorides, resulting in a much higher diffusion rate of trimesoyl chloride into organic phase I compared to the diffusion rate of m-phenylenediamine into ethylcyclohexane (organic phase II). Figure 9As shown), the polyamide functional layer grows towards the XP84 porous support layer, resulting in a thinner functional layer and significantly increasing the membrane permeation flux. Figure 3 As shown, the thickness of the polyamide layer in Example 3 is only 20 to 30 nanometers, while that in Comparative Example 1 (as shown) Figure 5 The thickness of the polyamide layer (as shown) is approximately 120 to 130 nanometers. As demonstrated in Example 1, when the concentration of trimesoyl chloride is too low, the thin-layer composite membrane exhibits low retention capacity for monovalent salts. This is because insufficient trimesoyl chloride diffuses into organic phase I, resulting in the formation of mostly low-molecular-weight, short-chain polyamides. With increasing trimesoyl chloride concentration, a dense, defect-free polyamide functional layer is obtained. While the flux of the thin-layer composite membrane decreases slightly, its retention capacity for monovalent salts significantly improves. When the trimesoyl chloride concentration is 0.80 wt%, the removal rate of monovalent salts by the thin-layer composite membrane reaches over 99.0%. Furthermore, under long-term testing, the flux decline of the thin-layer composite membranes prepared in Examples 3 and 4 is significantly lower than that in Comparative Example 1. This is because the resulting polyamide functional layer is smoother, and the interfacial polymerization reaction at the anhydrous interface fundamentally solves the problem of acyl chloride hydrolysis, reducing the electronegativity of the membrane surface and effectively improving the antifouling ability of the resulting thin-layer composite membrane. Further increasing the concentration of trimesoyl chloride, as shown in Example 5, resulted in insufficient m-phenylenediamine molecules available for reaction when the trimesoyl chloride diffused into organic phase I, leading to the formation of many low-molecular-weight polymers and defects in the polyamide functional layer. This resulted in increased flux and decreased desalination of the thin-layer composite membrane. In Example 6, a polyamide reverse osmosis membrane was prepared by dissolving 3 wt% 3,3'-diaminobenzidine in N,N-dimethylformamide, which also yielded a reverse osmosis membrane with both high flux and high desalination. In conventional processes, 3,3'-diaminobenzidine is almost insoluble in water. Using N,N-dimethylformamide instead of water as a solvent for polyamines can greatly expand the selection of polyamines in interfacial polymerization.

[0043] Figure 1 This is a SEM image of the surface of the cross-linked polyimide (XP84) ultrafiltration membrane prepared in Example 1 of the present invention. As can be seen from the figure, the surface of the ultrafiltration membrane exhibits a typical porous structure.

[0044] Figure 2 This is a SEM image of the surface of the thin-layer composite reverse osmosis membrane prepared in Example 3 of the present invention; as can be seen from the figure, the surface of the composite membrane exhibits a smooth and defect-free dense structure.

[0045] Figure 3 This is a cross-sectional SEM image of the thin-layer composite reverse osmosis membrane prepared in Example 3 of the present invention. As can be seen from the figure, the composite membrane is composed of multiple layers, and the thickness of the polyamide (PA) layer is as low as 20 to 30 nanometers.

[0046] Figure 4This is a SEM image of the thin-layer composite reverse osmosis membrane prepared in Comparative Example 1 of this invention. As can be seen from the image, the surface of the composite membrane exhibits a typical "lotus leaf" structure of polyamide reverse osmosis membrane, and has large "peaks and valleys".

[0047] Figure 5 This is a cross-sectional SEM image of the thin-layer composite reverse osmosis membrane prepared in Comparative Example 1 of the present invention. As can be seen from the figure, the composite membrane is composed of multiple layers, and the thickness of the polyamide (PA) layer is between 120 and 130 nanometers, which is much higher than the thickness of the polyamide functional layer in Example 3.

[0048] Figure 6 The image shows the surface AFM of the thin-layer composite reverse osmosis membrane prepared in Example 3 of this invention. As can be seen from the image, the average surface roughness (Ra) is 2.01 nanometers, which means that the surface is very smooth, but there are some nanometer-sized protrusions and depressions.

[0049] Figure 7 The image shows the surface AFM pattern of the thin-layer composite reverse osmosis membrane prepared in Comparative Example 1 of this invention. As can be seen from the image, the average surface roughness (Ra) is 36.8 nanometers, which is much higher than that of Example 3.

[0050] Figure 8 This is a graph showing the diffusion rate of m-phenylenediamine from water to pure ethylcyclohexane and the diffusion rate of trimesoyl chloride from ethylcyclohexane to pure water under the condition of no support layer in Comparative Example 1 of this invention. It should be noted that trimesoyl chloride cannot exist in a dissolved state when it diffuses into pure water. Its acyl chloride group is directly hydrolyzed into carboxylic acid. The concentration measured in water is the concentration in the state of hydrolysis into carboxylic acid.

[0051] Figure 9 This is a graph showing the diffusion rates of m-phenylenediamine from N,N-dimethylformamide to pure ethylcyclohexane and trimesoyl chloride from ethylcyclohexane to pure N,N-dimethylformamide under the support-free condition of Example 2 of the present invention. As shown in the graph, due to the greater solubility of m-phenylenediamine and trimesoyl chloride in N,N-dimethylformamide solution, m-phenylenediamine hardly diffuses into the ethylcyclohexane solution, while trimesoyl chloride rapidly diffuses into the N,N-dimethylformamide solution. The polyamide functional layer grows towards the XP84 porous support layer, and its diffusion rate is significantly greater than that of the N,N-dimethylformamide solution. Figure 8 The diffusion rate of intermediate phenylenediamine into ethylcyclohexane solution.

[0052] It should be noted that the above examples are merely some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and other modifications are possible. All modifications directly or indirectly derived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a reverse osmosis membrane with an ultrathin functional layer, characterized in that, Includes the following steps: (1) Preparation of casting solution: The polymer is added to an organic solvent, heated and stirred until the polymer is completely dissolved to prepare a polymer solution as a casting solution; (2) Formation of an ultrafiltration porous support layer: The casting solution is coated onto a nonwoven fabric support layer, and an ultrafiltration porous support layer is formed by phase inversion. (3) Formation of polyamide / polyester functional layer: The ultrafiltration support layer is sequentially contacted with an organic phase solution I containing polyamine / polyphenol monomers and an acid-binding agent and an organic phase solution II containing polyacryl chlorides to form a polyamide / polyester functional layer. (4) Post-processing: The polyamide / polyester functional layer formed above is subjected to post-treatment, which includes acid cleaning, pure water cleaning and pore preservation treatment in sequence. (5) Drying: The post-treated membrane is then dried.

2. The method for preparing a reverse osmosis membrane with an ultrathin functional layer as described in claim 1, characterized in that, The polymer is selected from one or more of polyethersulfone, polysulfone, polyacrylonitrile, polyimide, polyvinylidene fluoride, and sulfonated polyethersulfone; the organic solvent is selected from one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpyrrolidone, and dimethyl sulfoxide; the polymer concentration in the casting solution is 10-25%.

3. The method for preparing a reverse osmosis membrane with an ultrathin functional layer as described in claim 1, characterized in that, The polyamine / polyphenol monomer is selected from one or more of the following: m-phenylenediamine, o-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 4,4,4,4-methylethanetetraphenylamine, tris(4-aminophenyl)amine, 1,3,5-tris(4-aminophenyl)benzene, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenol, 4,4',4"-triaminotriphenylmethane, 4,4',4''-methylenetriphenol, perhydroxyl columnar aromatic compounds, biphenyl-based compounds, biphenylamine-based compounds, cyclodextrin, and piperazine.

4. The method for preparing a reverse osmosis membrane with an ultrathin functional layer as described in claim 1, characterized in that, The acid-binding agent in the organic phase solution I is selected from one or more of sodium hydroxide, potassium hydroxide, and triethylamine camphor sulfonate.

5. The method for preparing a reverse osmosis membrane with an ultrathin functional layer as described in claim 1, characterized in that, The concentration of polyamine / polyphenol monomers in the organic phase solution I is 1-5%, and the concentration of acid-binding agent is 0.03-3%.

6. The method for preparing a reverse osmosis membrane with an ultrathin functional layer as described in claim 1, characterized in that, The polyacryl chloride monomer is selected from one or more of phthaloyl chloride, biphenyl chloride, oxaloyl chloride, terephthaloyl chloride, trimesoyl chloride, and isophthaloyl chloride.

7. The method for preparing a reverse osmosis membrane with an ultrathin functional layer as described in claim 1, characterized in that, The concentration of polyacrylamide chloride monomer in the organic phase solution II is 0.05-1.0%.

8. The method for preparing a reverse osmosis membrane with an ultrathin functional layer as described in claim 1, characterized in that, The acid solution used for pickling is selected from one or more of citric acid, malic acid, sodium bisulfate, hydrochloric acid, sulfurous acid, and hypochlorous acid, and the concentration of the acid solution is 0.5-20%.

9. The method for preparing a reverse osmosis membrane with an ultrathin functional layer as described in claim 1, characterized in that, The pore-preserving treatment uses 3-10% glycerol as a pore-preserving agent.

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