A high-flux fouling-resistant polyamide reverse osmosis membrane prepared by interfacial polymerization regulated by imidazole-based surfactants and a preparation method thereof

Abstract

The present invention discloses a high-throughput fouling-resistant polyamide reverse osmosis membrane prepared by regulating interfacial polymerization using imidazole-based surfactants, its preparation method and application. The polyamide reverse osmosis membrane regulates the molecular behavior of interfacial polymerization by using imidazole-based surfactants and is prepared from polyamine monomers and polyacyl chlorides. The polyamide membrane has a high specific surface area, and its cross-section is a hierarchical structure formed by multiple layers of stacked cavities, enabling the membrane to have a rejection rate of over 99%, an ultra-high water permeability coefficient (>4 LMH / bar), a high membrane surface potential, good hydrophilicity, and good fouling resistance to both positively and negatively charged and neutral pollutants; the preparation process of the polyamide reverse osmosis membrane is convenient and efficient, and its application in industrial production is conducive to improving industrial production efficiency, reducing production costs, and having strong equipment adaptability, and it has good application prospects in separation and purification in fields such as water treatment, medical and health, and food production.

Description

Technical Field

[0001] The present invention relates to the technical field of functional membrane materials, and particularly relates to a high-flux anti-fouling polyamide reverse osmosis membrane prepared by regulating interfacial polymerization using an imidazole-based surfactant and a preparation method thereof. Background Art

[0002] With the rapid development of industrialization and urbanization in China, the water resource crisis has become increasingly severe, seriously affecting the sustainable development of human society. Reverse osmosis membranes have excellent monovalent salt rejection performance and can maximize the recycling of water resources. Among them, thin-film composite polyamide membranes are the most widely used reverse osmosis membrane varieties in large-scale applications at present due to their excellent separation selectivity and good chemical stability. However, polyamide reverse osmosis membranes face a trade-off effect between permeability and selectivity during actual use, and are easily fouled by membrane pollution, resulting in attenuation of membrane performance and shortening of membrane life. Therefore, the development of high-flux anti-fouling reverse osmosis membranes is the current research focus in the membrane field.

[0003] Currently, grafting / coating modification methods are commonly used to hydrophilically modify the membrane surface (CN 116785941 A and CN116785942A) to improve the anti-fouling performance of the membrane, but they cannot break through the limitation of the trade-off effect between selective permeability performances. The publicly disclosed patents CN 114130218 A, CN 114570218 B, and CN 117160254 B use anionic surfactants to regulate the interfacial polymerization process to prepare polyamide reverse osmosis membranes, breaking the trade-off effect between selective permeability performances and achieving an improvement in the selective permeability performance of the membrane. This method is simple and easy to operate, the modification materials are inexpensive, the reaction time is short, and the stability is good, having good industrial prospects.

[0004] However, the above-mentioned publicly disclosed patents mainly use anionic surfactants to regulate the interfacial polymerization to prepare polyamide reverse osmosis membranes, but the prepared reverse osmosis membranes show strong negative charges (less than -30 mV under neutral conditions) and hydrophobicity (water contact angle greater than 70°), and are easily fouled by pollutants in the water body (especially positively charged pollutants) during actual application, resulting in a large attenuation of flux and requiring frequent cleaning and maintenance, thus increasing the membrane usage cost. Therefore, it is of great value to develop a new type of surfactant for regulating interfacial polymerization to prepare high-flux, hydrophilic and weakly charged anti-fouling reverse osmosis membranes.

[0005] This patent invents a preparation method for high-flux antifouling polyamide reverse osmosis membranes by regulating interfacial polymerization using imidazole-based cationic surfactants. It can not only significantly improve the water permeability of the reverse osmosis membrane (membrane water permeability coefficient > 5 LMH / bar, superior to the water permeability of the reported reverse osmosis membranes), but also significantly enhance the hydrophilicity of the reverse osmosis membrane surface (water contact angle on the membrane surface < 60°, solid-liquid interfacial free energy > 80 mJ m -2 ), and at the same time, it greatly enhances the surface potential of the reverse osmosis membrane in a neutral water environment and weakens the negative charge of the membrane (membrane surface charge > -20 eV at pH = 7), which has important innovation and practical application value. Compared with other reported anionic surfactants, the imidazole-based cationic surfactant used in this patent can not only significantly change the properties of the water-oil interface, reduce the interfacial tension, and affect the diffusion behavior of interfacial polymerization monomers during the process of regulating interfacial polymerization to prepare polyamide reverse osmosis membranes, thereby regulating the structure and properties of the polyamide formed by interfacial polymerization to generate a polyamide functional layer with a rich cavity structure and high water permeability, but also stably embed in the polyamide layer to change the hydrophilicity and charge properties of the membrane, exerting multiple advantages. Summary of the Invention

[0006] The present invention provides a new method for preparing high-flux antifouling polyamide reverse osmosis membranes by regulating interfacial polymerization using imidazole-based surfactants.

[0007] For this purpose, the technical solution of the present invention is as follows:

[0008] A high-flux antifouling polyamide reverse osmosis membrane prepared by regulating interfacial polymerization using imidazole-based surfactants, wherein the polyamide reverse osmosis membrane comprises a porous ultrafiltration substrate membrane and a polyamide dense functional layer; among them, the polyamide dense functional layer is prepared on the surface of the porous ultrafiltration substrate membrane by interfacial polymerization of a polyamine monomer and a polyacyl chloride monomer; the cross-section of the polyamide functional layer has a multi-level structure feature formed by stacking of large pores, its effective specific surface area > 1.2, the average area of lotus leaves > 0.03 μm 2 , the height of the polyamide layer > 250 nm, the water contact angle < 60°, the solid-liquid interfacial free energy > 80 mJ m -2 , the surface charge at pH = 7 > -30 eV; the water permeability coefficient of the polyamide functional layer > 5 LMH / bar, and the rejection rate of 2000 ppm NaCl > 99%.

[0009] The multi-level structure of the polyamide functional layer can achieve multi-layer filtration of the feed liquid to ensure that the separated permeate has high purity. The high specific surface area can greatly increase the water permeability coefficient. The water contact angle is low, and the hydrophilicity of the membrane surface is good. A hydration layer is formed on the membrane surface to prevent pollutants from adhering to the membrane surface. Moreover, the embedding of cationic surfactants can effectively weaken the negative charge on the membrane surface. The weakening of the negative charge on the membrane surface is beneficial to reducing the electrostatic interaction force between the membrane surface and negatively charged small molecule pollutants, and the anti-fouling performance of the membrane is significantly improved; according to the application examples of the present application, the effective specific surface area of the polyamide functional layer is further preferably 1.6-3.6, the height of the polyamide layer is further preferably 500 nm-800 nm, and the surface charge at pH = 7 is > -20 eV.

[0010] Among them, the polyamine monomers used include, but are not limited to, aromatic polyamines, aliphatic polyamines, cycloaliphatic polyamines, etc. Aromatic polyamine monomers include, but are not limited to, at least one of m-phenylenediamine, p-phenylenediamine, o-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 2,4-diaminotoluene, 2,6-diaminotoluene, N,N'-dimethyl-m-phenylenediamine, 2,4-diaminoanisole, amiphenol, xylylenediamine; aliphatic polyamine monomers include, but are not limited to, at least one of ethylenediamine, propylenediamine, tris(2-aminoethyl)amine, N-phenylethylenediamine; cycloaliphatic polyamine monomers include, but are not limited to, 1,3-diaminocyclohexane, 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, etc. One or more of the above polyamine components can be selected and used in combination, and aromatic amino compounds such as m-phenylenediamine are preferably used.

[0011] Among them, the polyacyl chlorides used include, but are not limited to, aromatic polyacyl chlorides, aliphatic polyacyl chlorides, cycloaliphatic polyacyl chlorides, etc. Aromatic polyacyl chloride monomers include, but are not limited to, at least one of trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride, biphenyl-4,4'-dicarbonyl dichloride, naphthalene-1,4-dicarbonyl dichloride, benzenetrisulfonyl chloride, benzenedisulfonyl chloride, chlorosulfonyl phthaloyl chloride; aliphatic polyacyl chloride monomers include, but are not limited to, at least one of propanedicarbonyl dichloride, butanedicarbonyl dichloride, pentanedicarbonyl dichloride, propanetricarbonyl trichloride, butanetricarbonyl trichloride, pentanetricarbonyl trichloride, glutaroyl chloride, adipoyl chloride; cycloaliphatic polyacyl chloride monomers include, but are not limited to, cyclopropanetricarbonyl chloride, cyclobutanetetracarbonyl chloride, cyclopentanetricarbonyl chloride, cyclopentanetetracarbonyl chloride, cyclohexanetricarbonyl chloride, tetrahydrofurantetracarbonyl chloride, cyclopentanedicarbonyl chloride, cyclobutanedicarbonyl chloride, cyclohexanedicarbonyl chloride, tetrahydrofurandicarbonyl chloride, etc. One or more of the above polyacyl chloride components can be selected and used in combination, and aromatic acyl chloride compounds such as 1,3,5-benzenetricarbonyl chloride are preferably used.

[0012] Preferably, the imidazole-based surfactant is composed of an imidazole group-containing cation and an anion, and has the following chemical structure:

[0013]

[0014] In the formula, at least one of R1 and R2 is an alkyl chain with more than eight carbon atoms, and X is an anionic group.

[0015] More preferably, the imidazole-based surfactant can specifically be selected from but not limited to at least one of 1,2-dodecyl-3-hydroxyethylimidazolium hexafluorophosphate, 1,2-dodecyl-3-hydroxyethylimidazolium tetrafluoroborate, 1-hydroxyethyl-2-dodecyl-3-dimethylimidazolium chloride, 1-dodecyl-3-methylimidazolium chloride ([C12mim]Cl), 1-hydroxyethyl-3-hexadecylimidazolium hydrogen sulfate, 1-hydroxyethyl-3-octadecylimidazolium p-toluenesulfonate, 1-hydroxyethyl-3-pentadecylimidazolium dicyanamide, 1-hydroxyethyl-3-hexadecylimidazolium bis(trifluoromethanesulfonyl)imide, 1-hydroxyethyl-3-decylimidazolium perchlorate, and 1-sulfopropyl-3-dodecylimidazolium betaine.

[0016] A high-flux fouling-resistant polyamide reverse osmosis membrane prepared by regulating interfacial polymerization using an imidazole-based surfactant, which is formed by compositing the aforementioned polyamide functional layer on the surface of a porous ultrafiltration substrate membrane; the porous ultrafiltration substrate membrane includes but is not limited to high-molecular ultrafiltration membranes such as cellulose acetate membranes, polyethersulfone membranes, polyvinylidene fluoride membranes, polysulfone membranes, and polyacrylonitrile membranes with a pore size range of 10 nm to 100 nm, or inorganic ultrafiltration membranes such as ceramic membranes. In this composite polyamide reverse osmosis membrane, the porous ultrafiltration substrate membrane mainly acts as a substrate to support the polyamide functional layer, that is, to increase the mechanical strength of the membrane in a composite form to expand the applicable range of the functional membrane.

[0017] A preparation method of the high-flux fouling-resistant polyamide reverse osmosis membrane prepared by regulating interfacial polymerization using the above-mentioned imidazole-based surfactant, the steps are as follows:

[0018] S1. Immerse one side of the porous ultrafiltration substrate membrane into the aqueous monomer solution prepared by blending a polyamine monomer and a surfactant for 0.5 min to 5 min, and use a rubber roller or an air knife to remove the excess aqueous monomer solution on the surface of the ultrafiltration substrate membrane;

[0019] S2. Uniformly coat the organic solution of polyacyl chloride on the surface of the carrier coated with the aqueous monomer solution obtained in step S1 for 0.5 min to 5 min to form a thin-film composite polyamide membrane;

[0020] S3. Place the thin-film composite polyamide membrane obtained in step S2 at 40 °C to 180 °C for thermal cross-linking for 1 min to 10 min to finally obtain the polyamide reverse osmosis membrane.

[0021] The preparation method is an interfacial polymerization method, which is simple in operation, short in reaction time, and good in stability, having the advantage of stable industrial preparation and being conducive to industrial scale-up application. Among them, in step S1, adding an imidazole surfactant to the aqueous monomer solution can greatly reduce the interfacial tension between the aqueous phase and the oil phase, and then regulate the rate and concentration of the cross-interfacial diffusion of amine / acyl chloride monomers into the oil / water phase, thereby realizing the preparation of a polyamide functional layer with the above-mentioned characteristic structure.

[0022] Preferably, the preparation method of the aqueous monomer solution in step S1 is: preparing an aqueous solution of a polyamine monomer with a mass fraction of 0.1 wt.% to 5 wt.%, and then adding 0.1 wt.% to 10 wt.% of an imidazole surfactant to the aqueous polyamine monomer solution.

[0023] Preferably, in step S1, after the aqueous monomer solution is coated on the upper surface of the porous ultrafiltration substrate membrane and left for 0.5 min to 5 min, the excess aqueous monomer solution on the membrane is poured out, and then step S2 can be carried out.

[0024] Preferably, in step S2, in the organic mixture, the mass fraction of the polyacyl chloride is 0.01 wt.% to 5 wt.%; the organic solvents used for preparing the organic mixture include but are not limited to n-hexane, isoparaffin, n-nonane, and n-decane.

[0025] Preferably, in step S2, after the carrier and the membrane intermediate I thereon are immersed in the organic mixture prepared from polyacyl chloride for 0.5 min to 15 min, the membrane is taken out and left standing for 1 min to wait for the organic solvent to volatilize, and then step S3 can be carried out.

[0026] An application of a high-flux anti-fouling polyamide reverse osmosis membrane prepared by regulating interfacial polymerization using an imidazole surfactant, specifically: using the polyamide reverse osmosis membrane as a reverse osmosis membrane for solution desalination treatment, solute concentration, separation and purification, etc.

[0027] Compared with the prior art, the beneficial effects of this application are as follows:

[0028] (1) The high-flux anti-fouling polyamide reverse osmosis membrane prepared in this application solves the problems of the decline of membrane properties caused by typical small-molecule organic pollutants and the secondary pollution caused by them, and the inability to simultaneously improve the anti-fouling properties against different types of pollutants. Among them, ① the introduction of the imidazole surfactant is beneficial to reducing the water-oil interfacial tension, inducing a strong Marangoni effect, and regulating the reaction interdiffusion of amine monomers and acyl chlorides, improving the effective specific surface area of the polyamide functional membrane, and significantly increasing the water flux; ② the embedding of the imidazole surfactant in the polyamide layer improves the hydrophilicity of the polyamide reverse osmosis membrane and weakens the negative charge, improving the anti-fouling performance of the membrane; In summary, the polyamide separation membrane has high flux, high rejection rate and good anti-fouling performance;

[0029] (2) The preparation method of the polyamide reverse osmosis membrane of this application is a simple interfacial polymerization method. Compared with the traditional graft coating modification method, it not only shortens the preparation time and cost, but also improves the comprehensive performance of the polyamide separation membrane, and has good industrial production application value; Description of the Drawings

[0030] Figure 1 It is a scanning electron microscope comparison diagram of the membrane surface morphology of the polyamide reverse osmosis membranes prepared in Example 2 and Comparative Example 1 of the present invention;

[0031] Figure 2 It is a scanning electron microscope diagram and a transmission electron microscope diagram of the membrane cross-section morphology of the polyamide reverse osmosis membranes prepared in Example 2 and Comparative Example 1 of the present invention;

[0032] Figure 3 It is a comparison diagram of the membrane surface Zeta potential curves of the polyamide reverse osmosis membranes prepared in Example 2 and Comparative Example 1 of the present invention;

[0033] Figure 4 It is a comparison diagram of the membrane surface water contact angle curves of the polyamide reverse osmosis membranes prepared in Example 2 and Comparative Example 1 of the present invention and the membrane surface water contact angle of the traditional polyamide membrane;

[0034] Figure 5 It is a comparison diagram of the anti-fouling performance of the high-flux and high-rejection anti-fouling polyamide composite membrane prepared in Example 3 of the present invention against the traditional polyamide membrane. Detailed Embodiments

[0035] The following further describes the present invention in conjunction with the drawings and specific embodiments, but the following embodiments are by no means any limitation to the present invention.

[0036] Example 1

[0037] A high-flux anti-fouling polyamide reverse osmosis membrane prepared by regulating interfacial polymerization with an imidazole surfactant is prepared by the following steps:

[0038] S1. Dissolve m-phenylenediamine in water to prepare a 2.0 wt.% m-phenylenediamine aqueous solution; then, add 2.0 wt.% of 1-dodecyl-3-methylimidazolium chloride to the m-phenylenediamine aqueous solution, stir and mix evenly to obtain an aqueous monomer solution; Immerse one side of the polysulfone ultrafiltration membrane in the aqueous monomer solution for 2 min, and use a rubber roller or an air knife to remove the excess aqueous monomer solution on the surface of the ultrafiltration substrate membrane;

[0039] S2. Dissolve trimesoyl chloride in n - hexane to prepare a 0.1 wt.% trimesoyl chloride organic solution, stir and mix evenly to obtain an oil - phase monomer solution; evenly coat the oil - phase monomer solution on the surface of the base film coated with the aqueous - phase monomer solution obtained in step S1 for 1 min, and place it in the air for 2 min to completely volatilize n - hexane, generating a thin - layer composite polyamide membrane;

[0040] S3. Place the thin - layer composite polyamide membrane obtained in step S2 in a forced - air drying oven and conduct thermal cross - linking at 60 °C for 10 min to finally prepare a polyamide reverse - osmosis membrane.

[0041] Example 2

[0042] A high - flux anti - fouling polyamide reverse - osmosis membrane prepared by regulating interfacial polymerization using an imidazole - based surfactant, which is different from Example 1 in that 2.0 wt.% of 1 - dodecyl - 3 - methylimidazolium chloride is replaced by 5.0 wt.% of 1 - dodecyl - 3 - methylimidazolium chloride.

[0043] Example 3

[0044] A high - flux anti - fouling polyamide reverse - osmosis membrane prepared by regulating interfacial polymerization using an imidazole - based surfactant, which is different from Example 1 in that 2.0 wt.% of 1 - dodecyl - 3 - methylimidazolium chloride is replaced by 10.0 wt.% of 1 - dodecyl - 3 - methylimidazolium chloride.

[0045] Example 4

[0046] A high - flux anti - fouling polyamide reverse - osmosis membrane prepared by regulating interfacial polymerization using an imidazole - based surfactant, which is different from Example 2 in that the thermal cross - linking conditions are changed to thermal cross - linking at 100 °C for 3 min.

[0047] Example 5

[0048] A high - flux anti - fouling polyamide reverse - osmosis membrane prepared by regulating interfacial polymerization using an imidazole - based surfactant, which is different from Example 2 in that the thermal cross - linking conditions are changed to thermal cross - linking at 40 °C for 10 min.

[0049] Example 6

[0050] A high - flux anti - fouling polyamide reverse - osmosis membrane prepared by regulating interfacial polymerization using an imidazole - based surfactant, which is different from Example 1 in that the solvent n - hexane in the organic solution for preparing trimesoyl chloride is replaced by isoparaffin Isopar G.

[0051] Example 7

[0052] A high-flux fouling-resistant polyamide reverse osmosis membrane prepared by regulating interfacial polymerization with an imidazole surfactant, which is different from Example 1 in that: the polysulfone membrane as the porous ultrafiltration substrate membrane is replaced with a polyacrylonitrile membrane.

[0053] Example 8

[0054] A high-flux fouling-resistant polyamide reverse osmosis membrane prepared by regulating interfacial polymerization with an imidazole surfactant, which is different from Example 1 in that: the polysulfone membrane as the porous ultrafiltration substrate membrane is replaced with a polyethersulfone membrane.

[0055] Example 9

[0056] A high-flux fouling-resistant polyamide reverse osmosis membrane prepared by regulating interfacial polymerization with an imidazole surfactant, which is different from Example 1 in that: the 2.0 wt.% m-phenylenediamine aqueous solution prepared in step S1 is replaced with a 5.0 wt.% m-phenylenediamine aqueous solution; the n-hexane solution containing 0.1 wt.% trimesoyl chloride is replaced with a n-hexane solution containing 5.0 wt.% trimesoyl chloride.

[0057] Example 10

[0058] A high-flux fouling-resistant polyamide reverse osmosis membrane prepared by regulating interfacial polymerization with an imidazole surfactant, which is different from Example 1 in that: 1-dodecyl-3-methylimidazolium chloride is replaced with 1,2-dodecyl-3-hydroxyethylimidazolium hexafluorophosphate.

[0059] Example 11

[0060] A high-flux fouling-resistant polyamide reverse osmosis membrane prepared by regulating interfacial polymerization with an imidazole surfactant, which is different from Example 1 in that: 1-dodecyl-3-methylimidazolium chloride is replaced with 1-sulfopropyl-3-dodecylimidazolium betaine.

[0061] Example 12

[0062] A high-flux fouling-resistant polyamide reverse osmosis membrane prepared by regulating interfacial polymerization with an imidazole surfactant, which is prepared by the following steps:

[0063] S1. Dissolve m-phenylenediamine in water to prepare a 2.0 wt.% m-phenylenediamine aqueous solution; then, add 2.0 wt.% of 1-sulfopropyl-3-dodecylimidazolium betaine to the m-phenylenediamine aqueous solution, stir and mix evenly to obtain an aqueous phase monomer solution; immerse one side of the polysulfone ultrafiltration membrane in the aqueous phase monomer solution for 2 min, and use a rubber roller or an air knife to remove the excess aqueous phase monomer solution on the surface of the ultrafiltration substrate membrane;

[0064] S2. Dissolve trimesoyl chloride in n-decane to prepare a 0.1 wt.% trimesoyl chloride organic solution, stir and mix evenly to obtain an oil-phase monomer solution; uniformly coat the oil-phase monomer solution on the surface of the base film coated with the aqueous-phase monomer solution obtained in step S1 for 5 min, and place it in the air for 20 min to completely volatilize the n-decane, generating a thin-film composite polyamide membrane;

[0065] S3. Place the thin-film composite polyamide membrane obtained in step S2 in a forced-air drying oven and thermally crosslink it at 180 °C for 1 min to finally obtain a polyamide reverse osmosis membrane.

[0066] Example 13

[0067] A high-flux fouling-resistant polyamide reverse osmosis membrane prepared by regulating interfacial polymerization using an imidazole surfactant, which is different from Example 12 in that 2.0 wt.% of 1-sulfopropyl-3-dodecylimidazolium inner salt is replaced by 2.0 wt.% of 1,2-didodecyl-3-hydroxyethylimidazolium tetrafluoroborate.

[0068] Comparative Example 1

[0069] A polyamide reverse osmosis membrane prepared without using a surfactant for regulation is prepared by the following steps:

[0070] S1. Dissolve m-phenylenediamine in water to prepare a 2.0 wt.% m-phenylenediamine aqueous solution; immerse one side of the polysulfone ultrafiltration membrane in the m-phenylenediamine aqueous solution for 2 min, and use a rubber roller or an air knife to remove the excess m-phenylenediamine aqueous solution on the surface of the ultrafiltration base membrane;

[0071] S2. Dissolve trimesoyl chloride in n-hexane to prepare a 0.1 wt.% trimesoyl chloride organic solution, stir and mix evenly to obtain an oil-phase monomer solution; uniformly coat the oil-phase monomer solution on the surface of the base film coated with the aqueous-phase monomer solution obtained in step S1 for 1 min, and place it in the air for 2 min to completely volatilize the n-hexane, generating a thin-film composite polyamide membrane;

[0072] S3. Place the thin-film composite polyamide membrane obtained in step S2 in a forced-air drying oven and thermally crosslink it at 60 °C for 10 min to finally obtain a polyamide reverse osmosis membrane.

[0073] Comparative Example 2

[0074] A polyamide reverse osmosis membrane prepared by regulating using a non-imidazole surfactant is prepared by the following steps:

[0075] S1. Dissolve m-phenylenediamine in water to prepare a 2.0 wt.% m-phenylenediamine aqueous solution. Then, add 5.0 wt.% nonylphenol polyether-10 to the m-phenylenediamine aqueous solution and stir to mix evenly to obtain an aqueous monomer solution. Immerse one side of the polysulfone ultrafiltration membrane in the aqueous monomer solution for 2 min, and use a rubber roller or air knife to remove the excess aqueous monomer solution on the surface of the ultrafiltration base membrane.

[0076] S2. Dissolve trimesoyl chloride in n-hexane to prepare a 0.1 wt.% trimesoyl chloride organic solution, stir to mix evenly to obtain an oil-phase monomer solution. Uniformly coat the oil-phase monomer solution on the surface of the base membrane coated with the aqueous monomer solution obtained in step S1 for 1 min, and place it in the air for 2 min to completely volatilize the n-hexane to form a thin-film composite polyamide membrane.

[0077] S3. Place the thin-film composite polyamide membrane obtained in step S2 in a blast dryer and thermally crosslink it at 180 °C for 2 min to finally prepare a polyamide reverse osmosis membrane.

[0078] Comparative Example 3

[0079] A polyamide reverse osmosis membrane prepared by controlling with a non-imidazole surfactant, which is different from Comparative Example 1 in that: replace 5.0 wt.% nonylphenol polyether-10 with 5.0 wt.% polysorbate-20; adjust the thermal crosslinking conditions to: thermally crosslink at 80 °C for 5 min.

[0080] Comparative Example 4

[0081] A polyamide reverse osmosis membrane prepared by controlling with a non-imidazole surfactant, which is different from Comparative Example 1 in that: replace 5.0 wt.% nonylphenol polyether-10 with 5.0 wt.% glyceryl stearate; adjust the thermal crosslinking conditions to: thermally crosslink at 40 °C for 20 min.

[0082] Comparative Example 5:

[0083] A high-flux and fouling-resistant polyamide reverse osmosis membrane prepared without using a surfactant for control, which is prepared by the following steps:

[0084] S1. Dissolve m-phenylenediamine in water to prepare a 5.0 wt.% m-phenylenediamine aqueous solution. Immerse one side of the polysulfone ultrafiltration membrane in the m-phenylenediamine aqueous solution for 2 min, and use a rubber roller or air knife to remove the excess m-phenylenediamine aqueous solution on the surface of the ultrafiltration base membrane.

[0085] S2. Dissolve trimesoyl chloride in n - hexane to prepare a 5 wt.% trimesoyl chloride organic solution, stir and mix evenly to obtain an oil - phase monomer solution; uniformly coat the oil - phase monomer solution on the surface of the base film coated with the aqueous - phase monomer solution obtained in step S1 for 5 min, and place it in the air for 2 min to completely volatilize n - hexane, generating a thin - film composite polyamide membrane;

[0086] S3. Place the thin - film composite polyamide membrane obtained in step S2 in a forced - air dryer and thermally cross - link it at 60 °C for 10 min to finally obtain a polyamide reverse - osmosis membrane.

[0087] Performance test:

[0088] (I) Membrane microstructure test:

[0089] As Figure 1 shown are the scanning electron microscopy (SEM) images of the membrane surface morphologies of the polyamide reverse - osmosis membranes prepared in Comparative Example 1 and Example 2, specifically the SEM images of the surface of their polyamide functional layers. From the comparison results of the two figures, it can be seen that Comparative Example 1 was prepared by the traditional polyimide membrane preparation method. From its SEM image, it can be observed that the area of the leaf - like structure on the surface of the traditional polyimide reverse - osmosis membrane is small, while the area of the leaf - like structure on the membrane surface of the polyamide reverse - osmosis membrane prepared in Example 2 of the present application is large, that is, it has a super - high specific surface area.

[0090] Similarly, the membrane surface morphologies of the polyamide functional layers in the polyamide reverse - osmosis membranes prepared in other examples of the present application also have the same morphological structural characteristics as those in Example 2. According to the SEM results, the effective specific surface area of the surface of the polyamide functional layer prepared by the method of the present application > 1.2, specifically between 1.2 and 3.6; among them, the lotus leaf area > 0.03 μm 2 .

[0091] As Figure 2 shown are the SEM images and transmission electron microscopy (TEM) images of the cross - section morphologies of the polyamide functional layers in Example 2 and Comparative Example 1; among them, in Figure 2 , figure (a) is the SEM image of the cross - section morphology of the polyamide reverse - osmosis membrane prepared in Comparative Example 1, and figure (b) is the SEM image of the cross - section morphology of the polyamide reverse - osmosis membrane prepared in Example 2; from the comparison of these two figures, it can be seen that the polyamide functional layer in Comparative Example 1 here is a single - layer structure, while the cross - section of the polyamide functional layer in Example 2 has a multi - level structure formed by stacking large pores and there are multiple large cavities. In Figure 2Among them, Figure (c) is a transmission electron microscope image of the cross-sectional morphology of the polyamide reverse osmosis membrane prepared in Comparative Example 1, and Figure (d) is a transmission electron microscope image of the cross-sectional morphology of the polyamide reverse osmosis membrane prepared in Example 2; it can be clearly measured from these two figures that the cross-sectional height of the polyamide functional layer in Example 2 reaches 759.4 nm, while the height of the traditional polyamide functional layer in Comparative Example 1 is only 159.4 nm.

[0092] Similarly, the cross-sectional morphology of the polyamide functional layer in the polyamide reverse osmosis membranes prepared in other examples of the present application also has a microstructure similar to that of Comparative Example 1, and the cross-sectional height of the polyamide functional layer ranges between 250 nm and 800 nm.

[0093] (II) Membrane separation performance test:

[0094] The membrane separation performance evaluation was obtained by testing with a cross-flow test device; among them, the separation performance test conditions were pre-pressed for 1 hour at 20 bar and 25 °C, and then under the conditions of 15 bar and 25 °C, the prepared polyamide reverse osmosis membrane was used as the reverse osmosis membrane to test its rejection rate and permeation flux for a 2000 ppm sodium chloride solution. The flux unit is LMH / bar (liters per square meter per hour per bar).

[0095] The permeation flux was calculated by the following formula (1):

[0096]

[0097] In the formula, J w is the membrane permeation flux (LMH / bar), M is the mass of the permeate passing through the membrane sheet (kg), p is the density of the permeate (kg·m -3 ), E is the effective permeation area of the membrane sample (m 2 ), t is the test time (h), and P is the test pressure (bar).

[0098] The conductivity meter was used to measure the concentrations of the feed liquid and the permeate; the salt rejection rate was calculated by formula (2):

[0099]

[0100] In the formula, R is the salt rejection rate of the membrane sample (%), C p is the salt concentration of the permeate (mg / L), and C f is the salt concentration of the feed liquid (mg / L).

[0101] At least 3 parallel samples of each membrane sample were tested, and the average value and error range of the test results were calculated.

[0102] The specific test results are shown in Table 1 below.

[0103] Table 1: Specific Surface Area, Polyamide Layer Height and Permeation Selectivity Performance of Polyamide Reverse Osmosis Membrane

[0104]

[0105] It can be seen from the test results in Table 1 that:

[0106] (1) Compared with the polyamide reverse osmosis membrane prepared without adding imidazole-based surfactant in Comparative Example 1, when the polyamide reverse osmosis membranes prepared in Examples 1 to 12 are used as reverse osmosis membranes, while maintaining a high rejection rate, the water permeability coefficient has doubled. Specifically, compared with the water permeability coefficient of 1.86 LMH / bar in Comparative Example 1, the water permeation flux in Examples 1 to 12 has increased to 5.08 LMH / bar to 8.21 LMH / bar;

[0107] (2) Compared with the use of non-imidazole-based surfactants and imidazole-based surfactants in Comparative Examples 2 to 5, the specific surface area and AFM detection height of the polyamide reverse osmosis membrane regulated by the imidazole-based surfactant in this application are higher than those in the comparative examples. Examples 1 - 12 have better selective permeation performance than Comparative Examples 2 - 5, which further shows that the imidazole-based surfactant used in the present invention has a better effect on improving the selective permeation performance of the RO membrane.

[0108] In addition, the selective permeation performance of the polyamide reverse osmosis membrane with a high specific surface area in this application is much higher than that of the polyamide reverse osmosis membrane prepared by introducing other non-imidazole-based surfactants reported currently. The performance comparison with the latest literature reports is shown in Table 2 below.

[0109] Table 2: Comparison of Permeation Selectivity Performance of Polyamide Reverse Osmosis Membrane

[0110] Using other types of surfactants Permeation coefficient Rejection rate of NaCl Ref Tween 80 0.72 99.60 [1] Sodium dodecyl trimethyl sulfate (SDS) 1.8 98.2 [2] Benzalkonium chloride (BAC) 1.66 99.60 [3] Sodium dodecyl trimethyl sulfate (SDS) 0.73 94.54 <![CDATA [4] > Cetyltrimethylammonium bromide (CTAB) 3.84 98.50 <![CDATA [5] > PF127 / SDS 2.26 99.5 <![CDATA [6] > Commercial membrane CR100 3.32 99.51 Self-test

[0111] (III) pH Stability of the Membrane

[0112] The surface potential change of the polyamide reverse osmosis membrane was characterized using a solid surface zeta potential analyzer. After testing, during the pH change from 10 to 3 for the polyamide reverse osmosis membranes prepared in Examples 1 to 12, the surface zeta potential change of the membrane remained between -15 mV and 8 mV, showing good pH stability.

[0113] Such as Figure 3Figure 1 shows the comparison chart of the membrane surface Zeta potential curves of the polyamide reverse osmosis membranes prepared in Example 2 of the present invention and Comparative Example 1; it can be clearly seen from the figure that for the polyamide reverse osmosis membrane of Example 2, during the pH change from 10 to 3, the zeta potential of the membrane surface changes from -17.28 mV to 4.58 mV, while for the traditional polyamide membrane prepared in Comparative Example 1, during the pH change from 10 to 3, the surface potential of the membrane changes from -50.98 mV to 5.52 mV, showing better pH stability; when pH = 7, the zeta potential of the surface of the polyamide reverse osmosis membrane of Example 2 is -13.36 mV, while the zeta potential of the surface of the traditional polyamide membrane is -46.23 mV.

[0114] In summary, the polyamide reverse osmosis membrane prepared in this application has achieved an increase in the Zeta potential of the membrane surface.

[0115] (IV) Hydrophilicity of the membrane

[0116] A water contact angle measuring instrument is used to characterize the change in the hydrophilicity of the surface of the polyamide reverse osmosis membrane. After testing, the water contact angles of the polyamide reverse osmosis membranes prepared in Examples 1 to 12 are between 48° and 30°, showing good hydrophilicity.

[0117] As Figure 4 Figure 2 shows the comparison chart of the membrane surface water contact angles of the polyamide reverse osmosis membranes prepared in Example 2 of the present invention and Comparative Example 1 and the membrane surface water contact angle curve of the traditional polyamide membrane; it can be clearly seen from the figure that the water contact angle of the traditional polyamide reverse osmosis membrane is 78°, and the water contact angle of the polyamide reverse osmosis membrane prepared in Example 2 is 42°; compared with Comparative Example 1, in Example 2, by introducing an imidazole-based surfactant to regulate the membrane structure, the imidazole head groups of the imidazole-based surfactant embedded on the membrane surface have more hydrogen bond acceptors, making the membrane surface have good hydrophilicity and achieving an improvement in the hydrophilicity of the membrane surface.

[0118] (V) Membrane anti-fouling performance test:

[0119] Dodecyl trimethyl ammonium bromide (DTAB), sodium dodecyl sulfate (SDS), positively charged model macromolecular pollutant lysozyme (LYZ), positively charged model macromolecular pollutant bovine serum albumin (BSA), and neutral pollutant bisphenol A (BPA) are used as model pollutants to evaluate the membrane fouling resistance performance. These are typical representative examples of different electrically charged organic pollutants in water systems. Specifically, during the fouling test, DTAB, SDS, LYZ, and BSA are respectively added to a 2000 ppm NaCl solution, and the concentrations of the above four pollutants are 200 ppm, and the concentration of BPA is 50 ppm.

[0120] The normalized flux decay rate (%) of the polyamide reverse osmosis membrane prepared by regulating the interfacial polymerization process with imidazole surfactants and the unmodified polyamide reverse osmosis membrane was evaluated.

[0121] The specific measurement steps of the Flux decay rate are as follows: 1) Under the conditions of 15 bar and a cross-flow velocity of 14 cm / s, use a feed aqueous solution containing 2000 ppm of NaCl to pre-press the RO system for 60 minutes to determine the baseline permeate flux and salt rejection rate; 2) Add 200 ppm of the aforementioned model pollutant to the aforementioned feed aqueous solution and operate the RO system under the same conditions as in step 1) until the volume of the permeate is 200 mL; 3) Wash the polyamide composite reverse osmosis membrane with deionized water more than 3 times at a water circulation flow rate of 3 L / min, with each cycle lasting 10 minutes; 4) Use a feed aqueous solution containing 2000 mg / L of NaCl to measure the permeate flux and salt rejection rate again.

[0122] Among them, the calculation formula of the Flux decay rate is as follows:

[0123] Flux reduction rate (%) = [1 - (permeate flux in step 2) / (permeate flux in step 1)] × 100%;

[0124] Flux recovery rate (%) = (permeate flux in step 4) / (permeate flux in step 1) × 100%.

[0125] The specific test results are shown in Table 3 below.

[0126] Table 3: Fouling resistance performance of polyamide reverse osmosis membrane

[0127]

[0128] It can be seen from the test results in Table 3 that the permeate flux of the polyamide reverse osmosis membrane prepared in the examples of this application and the selective permeation performance before and after the fouling resistance test are significantly better than those of the polyamide reverse osmosis membrane in the comparative examples. It can be seen that the polyamide reverse osmosis membrane prepared by regulating the interfacial polymerization process with imidazole surfactants shows excellent fouling resistance performance against positively charged, neutrally charged, and negatively charged organic pollutants.

[0129] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0130] References:

[0131] [1] HAN X, WANG Z, WANG J. Preparation of highly selective reverse osmosis membranes by introducing a nonionic surfactant in the organic phase[J]. Journal of Membrane Science, 2022, 651.

[0132] [2] SHEN Q, SONG Q, MAI Z, et al. When self-assembly meets interfacial polymerization[J]. Science Advances, 2023, 9(18): eadf6122.

[0133] [3] PARK S-J, LEE M-S, CHOI W, et al. Biocidal surfactant-assisted fabrication of thin film composite membranes with excellent and durable anti-biofouling performance[J]. Chemical Engineering Journal, 2022, 431.

[0134] [4] KLAYSOM C, HERMANS S, GAHLAUT A, et al. Polyamide / Polyacrylonitrile (PA / PAN) thin film composite osmosis membranes: Film optimization, characterization and performance evaluation[J]. Journal of Membrane Science, 2013, 445: 25 - 33.

[0135] [5] MANSOURPANAH Y, MADAENI S S, RAHIMPOUR A. Fabrication and development of interfacial polymerized thin-film composite nanofiltration membrane using different surfactants in organic phase;study of morphology and performance[J]. Journal of Membrane Science, 2009, 343(1-2): 219-28.

[0136] [6] LI Y, CHEN T-H, YU C-Y, et al. Facile polyamide microstructure adjustment of the composite reverse osmosis membrane assisted by PF127 / SDS mixed micelles for improving seawater desalination performance[J]. Desalination, 2022, 521.

Claims

1. A high-throughput, pollution-resistant polyamide reverse osmosis membrane prepared by interfacial polymerization regulated by imidazole surfactants, characterized in that: The polyamide reverse osmosis membrane comprises a porous ultrafiltration base membrane and a polyamide dense functional layer; wherein the polyamide dense functional layer is prepared on the surface of the porous ultrafiltration base membrane by interfacial polymerization of polyamine monomers and polyacyl chloride monomers; the effective specific surface area of ​​the polyamide functional layer is greater than 1.2, and the average surface area of ​​the lotus leaf is greater than 0.03 μm 2 , polyamide layer height>250 nm, water contact angle<60°, solid-liquid interface free energy>80 mJ m -2 , surface charge at pH=7>-20 eV; water permeability coefficient of polyamide functional layer>5 LMH / bar, retention rate of 2,000 ppm NaCl>99%; The imidazole surfactant includes at least one of 1,2-dodecyl-3-hydroxyethyl imidazole hexafluorophosphate, 1,2-dodecyl-3-hydroxyethyl imidazole tetrafluoroborate, 1-hydroxyethyl-2-dodecyl-3-dimethyl imidazole chloride, 1-dodecyl-3-methyl imidazole chloride, 1-hydroxyethyl-3-hexadecyl imidazole hydrogen sulfate, 1-hydroxyethyl-3-octadecyl imidazole p-toluene sulfonate, 1-hydroxyethyl-3-pentadecyl imidazole dinitrile amine, 1-hydroxyethyl-3-hexadecyl imidazole bis(trifluoromethanesulfonyl)imide, 1-hydroxyethyl-3-decyl imidazole perchlorate, and 1-sulfopropyl-3-dodecyl imidazole inner salt; The steps of the preparation method of high-flux pollution-resistant polyamide reverse osmosis membrane are as follows: S1, immersing one side of the porous carrier in an aqueous solution prepared by mixing polyamine monomers and surfactants for 0.5 min to 5 min, and removing excess aqueous solution on the surface of the carrier with a rubber roller or an air knife; the carrier is a porous ultrafiltration base membrane; S2, uniformly coating the organic solution of polyacid chloride on the surface of the carrier coated with the aqueous monomer solution obtained in step S1 for 0.5 min to 5 min to form a thin layer of composite polyamide film; S3, placing the thin layer composite polyamide membrane obtained in step S2 at 40°C to 180°C for thermal crosslinking for 1 min to 10 min, and finally obtaining a polyamide reverse osmosis membrane.

2. The high-throughput, pollution-resistant polyamide reverse osmosis membrane prepared by interfacial polymerization regulated by imidazole surfactants according to claim 1, characterized in that: The porous ultrafiltration base membrane includes a polymer ultrafiltration membrane or an inorganic ultrafiltration membrane with a pore size ranging from 10 nm to 100 nm. The polymer ultrafiltration membrane includes a cellulose acetate membrane, a polyethersulfone membrane, a polyvinylidene fluoride membrane, a polysulfone membrane or a polyacrylonitrile membrane, and the inorganic ultrafiltration membrane includes a ceramic membrane.

3. The high-throughput, pollution-resistant polyamide reverse osmosis membrane prepared by interfacial polymerization regulated by imidazole surfactants according to claim 1, characterized in that: The polyacyl chlorides used include aromatic polyacyl chlorides, aliphatic polyacyl chlorides, and alicyclic polyacyl chlorides; wherein the aromatic polyacyl chlorides include at least one of trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride, biphenyl dicarboxylic acid chloride, naphthalene dicarboxylic acid chloride, benzene trisulfonyl chloride, benzene disulfonyl chloride, and chlorosulfonyl phthaloyl chloride; the aliphatic polyacyl chlorides include at least one of propanedioyl chloride, butanedioyl chloride, glutaric acid chloride, propanedioyl chloride, butanedioyl chloride, glutaric acid chloride, glutaric acid chloride, and adipoyl chloride; the alicyclic polyacyl chlorides include at least one of cyclopropane tricarboxylic acid chloride, cyclobutane tetracarboxylic acid chloride, cyclopentane tricarboxylic acid chloride, cyclopentane tetracarboxylic acid chloride, cyclohexane tricarboxylic acid chloride, tetrahydrofuran tetracarboxylic acid chloride, cyclopentane dicarboxylic acid chloride, cyclobutane dicarboxylic acid chloride, cyclohexane dicarboxylic acid chloride, and tetrahydrofuran dicarboxylic acid chloride.

4. The high-throughput, pollution-resistant polyamide reverse osmosis membrane prepared by interfacial polymerization regulated by imidazole surfactants according to claim 1, characterized in that: The polyamine monomers used include aromatic polyamines, aliphatic polyamines, and alicyclic polyamines; wherein the aromatic polyamine monomers include at least one of meta-phenylenediamine, para-phenylenediamine, o-phenylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 2,4-diaminotoluene, 2,6-diaminotoluene, N,N'-dimethyl meta-phenylenediamine, 2,4-diaminoanisole, amphenol, and benzyl diamine; the aliphatic polyamine monomers include at least one of ethylenediamine, propylenediamine, tris(2-aminoethyl)amine, and N-phenylethylenediamine; and the alicyclic polyamine monomers include at least one of 1,3-diaminocyclohexane, 1,2-diaminocyclohexane, and 1,4-diaminocyclohexane.

5. A method for preparing a high-throughput, pollution-resistant polyamide reverse osmosis membrane prepared by interfacial polymerization regulated by an imidazole surfactant as claimed in claim 1, characterized in that: The steps are: S1, immersing one side of the porous carrier in an aqueous solution prepared by mixing a polyamine monomer and a surfactant for 0.5 min to 5 min, and removing excess aqueous solution on the surface of the carrier with a rubber roller or an air knife; The carrier is a porous ultrafiltration base membrane; S2, uniformly coating the organic solution of polyacid chloride on the surface of the carrier coated with the aqueous monomer solution obtained in step S1 for 0.5 min to 5 min to form a thin layer of composite polyamide film; S3, placing the thin layer composite polyamide membrane obtained in step S2 at 40°C to 180°C for thermal crosslinking for 1 min to 10 min, and finally obtaining a polyamide reverse osmosis membrane.

6. The method for preparing a high-throughput, pollution-resistant polyamide reverse osmosis membrane prepared by interfacial polymerization regulated by imidazole surfactants according to claim 5, characterized in that: The aqueous monomer solution used in step S1 is a mixed solution of 0.1 wt.%~5 wt.% of a polyamine monomer and 0.1 wt.%~10 wt.% of an imidazole surfactant; the polyacyl chloride organic solution used in step S2 is a polyacyl chloride organic solution of 0.01 wt.%~5 wt.%, and the organic solvent includes at least one of n-hexane, isoparaffin, n-nonane, and n-decane.

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