High-efficiency antifouling and sterilizing reverse osmosis composite membrane and preparation method thereof

Abstract

The application belongs to the technical field of reverse osmosis membrane manufacturing, and particularly relates to a high-efficiency antifouling and sterilization reverse osmosis composite membrane and a preparation method thereof. The high-efficiency antifouling and sterilization reverse osmosis composite membrane is formed by forming a polyamide desalination layer on a polysulfone base film, and then coating a copolymer of a zwitterion with double bonds and thioctic acid on the surface of the polyamide desalination layer. The zwitterion is any one of SBMA, VPPS and VPES. The product has the advantages of high flux, high desalination rate, excellent antifouling performance, stable operation and the like. The preparation method has the advantages of simple process, high industrial production efficiency, low cost, rapid copolymerization reaction and no need of additional catalyst, and is suitable for large-scale coating production.

Description

Technical Field

[0001] This invention belongs to the field of reverse osmosis membrane manufacturing technology, specifically relating to a high-efficiency antifouling and bactericidal reverse osmosis composite membrane and its preparation method. Background Technology

[0002] Due to their excellent desalination performance and superior mechanical stability, aromatic polyamide reverse osmosis membranes have been widely used in seawater desalination and the production of ultrapure water from brackish water. However, during production, storage, and practical applications, they inevitably suffer from organic and biological contamination such as proteins, bacteria, and microorganisms. This significantly impairs the desalination and permeate performance of composite membranes and increases storage and cleaning costs. Therefore, there is an urgent need to develop a high-performance composite reverse osmosis membrane that combines antifouling and bactericidal properties without reducing its desalination and flux. By integrating the advantages of reverse osmosis membranes and enhancing their antifouling and bactericidal properties, composite membranes offer significant advantages in production, storage, and the treatment and recycling of saline organic wastewater.

[0003] Currently, enhancing the antifouling and bactericidal performance of composite reverse osmosis membranes mainly involves optimization in three areas: the base membrane, the desalination layer, and the surface functional layer. Regarding the base membrane, functionalized nanoparticles can be introduced to improve its dispersibility and introduce additional water channels to increase permeate flux. For example, patent CN 114768543 adds modified titanium dioxide nanoparticles to the casting solution, improving water flux and antifouling capability. While modifying nanoparticles can improve dispersibility, the modification method is complex, and the high density of nanoparticles makes them prone to sedimentation. Bactericidal capability requires the introduction of additional polymers on the surface, increasing process complexity and uncertainty. Regarding the desalination layer, antifouling and bactericidal substances can be introduced into the aqueous or oil phase. For example, patent CN 110711504 introduces copper-coated titanium dioxide into the base solution. Compared to patent CN114768543, this solves the problem of introducing additional bactericidal polymers, but it still cannot solve the dispersion and sedimentation problems. This leads to uneven surface distribution of the desalination layer, affecting product stability. Regarding the functional layer, antifouling and bactericidal polymers are grafted onto the desalination layer surface by reacting residual acyl chloride or carboxyl groups with amino compounds, or by directly coating the surface with antifouling and bactericidal substances to achieve these functions. For example, patent CN 112827368 grafts fluorine-containing substances onto the surface of residual acyl chloride groups to achieve antifouling, and guanidine compounds to achieve bactericidal activity. However, this method carries the risk of hydrolysis of the surface acyl chloride groups, and the fluorine-containing substances increase hydrophobicity, thus affecting permeation flux. In general, simplifying the process for industrial production and selecting appropriate antifouling and bactericidal substances are particularly important.

[0004] CN118388801A discloses a self-aggregation-induced polymerization zwitterionic hydrogel based on thioctic acid and its preparation method. The method involves reacting thioctic acid with an amine monomer containing a tertiary amine group to obtain a thioctic acid intermediate containing a tertiary amine group and an amide bond. This intermediate is further reacted with β-propiolactone or 1,3-propanesulfonate to obtain a thioctic acid zwitterionic monomer, and the gel exhibits excellent antifouling properties. However, in the field of reverse osmosis membrane applications, the synthesis steps are complex, the preparation cycle is long, and it involves the use of numerous organic reagents. Secondly, the swelling properties of the thioctic acid zwitterionic hydrogel are not shown in the patent, but hydrogels generally have swelling characteristics, and they are prone to swelling during long-term operation, leading to performance degradation or even complete loss of function. Furthermore, the hydrogel is at risk of water loss during storage, which is detrimental to the long-term storage of reverse osmosis membranes. Finally, after coating with the hydrogel solution, it takes 12 hours for polymerization to form a hydrogel, and it also needs to be soaked in water for 1-3 days to remove unreacted monomers, which is difficult to achieve in practical applications. Considering practical applications and cost-effectiveness, the thioctic acid-based zwitterionic hydrogel prepared by patent CN118388801A is not suitable for the actual production and application of reverse osmosis membranes. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by proposing a highly efficient antifouling and bactericidal reverse osmosis composite membrane and its preparation method.

[0006] Specifically, this is achieved through the following technical solutions:

[0007] One objective of this invention is to provide a highly efficient antifouling and antibacterial reverse osmosis composite membrane, which is formed on a polysulfone-based membrane with a polyamide desalination layer, and then coated on the surface of the polyamide desalination layer with a copolymer of zwitterionic acid and thioctic acid with double bonds; the zwitterionic acid includes any one or more of 3-[dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]azonyl]propane-1-sulfonate (SBMA), 1-(3-sulfopropyl)-2-vinylpyridinium inner salt (VPPS), and 1-[(4-vinylphenyl)methyl]-4-(2-sulfoethyl)pyridinium inner salt (VPES).

[0008] The second objective of this invention is to provide a method for preparing a highly efficient antifouling and antibacterial reverse osmosis composite membrane, comprising the following steps:

[0009] (1) Preparation of copolymer solution: Thioctic acid and zwitterion were dissolved in ethanol to prepare copolymer solution;

[0010] (2) A polysulfone-based membrane is prepared by a non-solvent phase inversion method. Then, the membrane is immersed in an aqueous solution of amine monomers. After immersion, the surface water droplets are dried. Then, it is immersed in an oil solution of acyl chloride monomers. After immersion, a polyamide desalination layer is formed. The solvent is dried, and then a copolymer solution is coated. After drying with hot air, a copolymer layer is formed, thus obtaining a high-efficiency antifouling and antibacterial reverse osmosis composite membrane.

[0011] The concentration of thioctic acid in the copolymer solution is 0.05 g / mL to 1.0 g / mL.

[0012] The mass ratio of thioctic acid to zwitterions in the copolymer solution is 10:1-2:1.

[0013] The hot air drying temperature is 55-70℃, and the time is 8-15 minutes.

[0014] Furthermore, the hot air drying temperature is 60°C and the time is 10 minutes.

[0015] The coating is an dip coating, and the coating is performed simultaneously with the winding process.

[0016] The mass concentration of the amine monomers in the aqueous solution is 1wt%-9wt%; the amine monomers include aromatic amines and aliphatic amines, such as aniline, diphenylamine, cyclohexanediamine, m-phenylenediamine, p-phenylenediamine, piperazine, o-phenylenediamine, diethanolamine, ethylenediamine, propylenediamine, butanediamine, hexanediamine, triethanolamine, polyetheramine, and polyethyleneimine, etc.

[0017] The mass concentration of the acyl chloride monomer in the oil phase solution is 0.01wt%-5wt%; the solvent is selected from any one or more of ISOPAR G, ISOPAR E, ISOPAR R, dichloromethane, toluene, and xylene; and the acyl chloride monomer includes any one or more of pyromellitic tricarboxylic chloride, isophthaloyl chloride, biphenyl dicarboxylic chloride, terephthaloyl chloride, and pyromellitic tetracarboxylic chloride.

[0018] Beneficial effects:

[0019] The product of this invention has advantages such as high throughput, high desalination rate, excellent antifouling performance, and stable operation.

[0020] The preparation method of the present invention is simple, has high industrial production efficiency, low cost, rapid copolymerization reaction, and does not require additional catalysts, making it suitable for large-scale coating production.

[0021] Lipoic acid is a biomass coenzyme that can be easily extracted from many plants and animals. It is soluble in most organic solvents, and its concentration increases through solvent evaporation at room temperature. The proximity of disulfide bonds initiates ring-opening polymerization, followed by a click reaction with zwitterions containing double bonds to form copolymers with disulfide bonds. The presence of disulfide bonds, hydrophilic carboxyl groups, and zwitterions enhances the binding to the desalination layer, ensuring firm adhesion to its surface. It also enhances the hydrophilicity of the composite membrane surface, improving its antifouling properties. The dynamic disulfide bonds effectively inhibit bacterial growth and enable self-healing after external physical damage, effectively preventing damage caused by friction during reverse osmosis membrane winding. Attached Figure Description

[0022] Figure 1 This is a process flow diagram for preparing the high-efficiency antifouling and bactericidal reverse osmosis composite membrane of the present invention. Detailed Implementation

[0023] 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.

[0024] Example 1

[0025] A method for preparing a high-efficiency antifouling and antibacterial reverse osmosis composite membrane includes the following steps:

[0026] (1) Dissolve lipoic acid and SBMA in ethanol to prepare a copolymer solution with a lipoic acid concentration of 0.5 g / mL and a lipoic acid to SBMA mass ratio of 3:1;

[0027] (2) A polysulfone-based membrane was prepared by a non-solvent phase inversion method. The membrane was then immersed in an aqueous solution of 5.0 wt% m-phenylenediamine for 20 s. After the surface water droplets were dried by nitrogen, it was immersed in an oil solution of 2.0 wt% trimesoyl chloride for 30 s to form a polyamide desalination layer. The solvent was then dried, and the membrane was passed through a copolymer solution. Finally, it was dried with hot air at 60 °C for 10 min to obtain a reverse osmosis composite membrane. The oil solvent used was ISOPAR G.

[0028] Example 2

[0029] A method for preparing a high-efficiency antifouling and antibacterial reverse osmosis composite membrane includes the following steps:

[0030] (1) Dissolve lipoic acid and SVBA in ethanol to prepare a copolymer solution with a lipoic acid concentration of 0.5 g / mL and a lipoic acid to SVBA mass ratio of 3:1;

[0031] (2) A polysulfone-based membrane was prepared by a non-solvent phase inversion method. The membrane was then immersed in an aqueous solution of 5.0 wt% m-phenylenediamine for 20 s. After the surface water droplets were dried by nitrogen, it was immersed in an oil solution of 2.0 wt% trimesoyl chloride for 30 s to form a polyamide desalination layer. The solvent was then dried, and the membrane was passed through a copolymer solution. Finally, it was dried with hot air at 60 °C for 10 min to obtain a reverse osmosis composite membrane. The oil solvent used was ISOPAR G.

[0032] Example 3

[0033] A method for preparing a high-efficiency antifouling and antibacterial reverse osmosis composite membrane includes the following steps:

[0034] (1) Dissolve lipoic acid and VPES in ethanol to prepare a copolymer solution with a lipoic acid concentration of 0.5 g / mL and a lipoic acid to VPES mass ratio of 3:1;

[0035] (2) A polysulfone-based membrane was prepared by a non-solvent phase inversion method. The membrane was then immersed in an aqueous solution of 5.0 wt% m-phenylenediamine for 20 s. After the surface water droplets were dried by nitrogen, it was immersed in an oil solution of 2.0 wt% trimesoyl chloride for 30 s to form a polyamide desalination layer. The solvent was then dried, and the membrane was passed through a copolymer solution. Finally, it was dried with hot air at 60 °C for 10 min to obtain a reverse osmosis composite membrane. The oil solvent used was ISOPAR G.

[0036] Example 4

[0037] A method for preparing a high-efficiency antifouling and antibacterial reverse osmosis composite membrane includes the following steps:

[0038] (1) Dissolve lipoic acid and SBMA in ethanol to prepare a copolymer solution with a lipoic acid concentration of 0.5 g / mL and a lipoic acid to SBMA mass ratio of 10:1;

[0039] (2) A polysulfone-based membrane was prepared by a non-solvent phase inversion method. The membrane was then immersed in an aqueous solution of 5.0 wt% m-phenylenediamine for 20 s. After the surface water droplets were dried by nitrogen, it was immersed in an oil solution of 2.0 wt% trimesoyl chloride for 30 s to form a polyamide desalination layer. The solvent was then dried, and the membrane was passed through a copolymer solution. Finally, it was dried with hot air at 60 °C for 10 min to obtain a reverse osmosis composite membrane. The oil solvent used was ISOPAR G.

[0040] Example 5

[0041] A method for preparing a high-efficiency antifouling and antibacterial reverse osmosis composite membrane includes the following steps:

[0042] (1) Dissolve lipoic acid and SBMA in ethanol to prepare a copolymer solution with a lipoic acid concentration of 0.5 g / mL and a lipoic acid to SBMA mass ratio of 2:1;

[0043] (2) A polysulfone-based membrane was prepared by a non-solvent phase inversion method. The membrane was then immersed in an aqueous solution of 5.0 wt% m-phenylenediamine for 20 s. After the surface water droplets were dried by nitrogen, it was immersed in an oil solution of 2.0 wt% trimesoyl chloride for 30 s to form a polyamide desalination layer. The solvent was then dried, and the membrane was passed through a copolymer solution. Finally, it was dried with hot air at 60 °C for 10 min to obtain a reverse osmosis composite membrane. The oil solvent used was ISOPAR G.

[0044] Comparative Example 1:

[0045] A method for preparing a high-efficiency antifouling and antibacterial reverse osmosis composite membrane differs from Example 1 in that it does not include the copolymer solution step, i.e., the polysulfone-based membrane is prepared sequentially by a non-solvent phase inversion method, followed by the formation of a polyamide desalination layer and drying.

[0046] Performance testing:

[0047] The membrane performance of Comparative Example 1 was compared with that of Examples 1-5 above. Membrane performance testing: The desalination rate and flux changes of the membranes in the examples and comparative examples were tested before and after contamination with 100 ppm bovine serum albumin in a 2000 ppm NaCl aqueous solution at an operating pressure of 225 psi (concentrate circulation).

[0048] The test results for NaCl and bovine serum albumin solutions are shown in Table 1 below (concentrate circulation):

[0049] Table 1

[0050]

[0051] As shown in Table 1, the embodiments obtained by the present invention, after introducing antifouling and bactericidal copolymers on the surface of the desalination layer, compared with the comparative example, showed a significant increase in flux and desalination rate when running in NaCl solution, and even after contamination by bovine serum albumin, there was no significant change in flux and desalination.

[0052] The composite reverse osmosis membranes prepared in Examples 1-5 and Comparative Example 1 were immersed in Staphylococcus aureus and Escherichia coli culture medium (CFU = 300 / mL) and cultured at 37°C for 24 h. The percentage reduction in the number of bacteria was calculated to determine the antibacterial performance of the membrane.

[0053] The antibacterial test results are shown in Table 2 below:

[0054] Table 2

[0055] sample Staphylococcus aureus E. coli Example 1 99.45 99.25 Example 2 99.20 99.22 Example 3 99.32 98.95 Example 4 98.91 98.86 Example 5 99.65 99.54 Comparative Example 1 0 0

[0056] As can be seen from Table 2, coating the desalination layer with the copolymer solution has a superior antibacterial effect compared to the uncoated layer.

Claims

1. A high-efficiency antifouling and antibacterial reverse osmosis composite membrane, characterized in that, The high-efficiency antifouling and antibacterial reverse osmosis composite membrane is formed by forming a polyamide desalination layer on a polysulfone-based membrane, and then coating the surface of the polyamide desalination layer with a copolymer of zwitterionic acid and thioctic acid with double bonds; the zwitterionic acid is any one or more of SBMA, VPPS, and VPES.

2. The high-efficiency antifouling and antibacterial reverse osmosis composite membrane as described in claim 1, characterized in that, Includes the following steps: (1) Preparation of copolymer solution: Thioctic acid and zwitterion were dissolved in ethanol to prepare copolymer solution; (2) A polysulfone-based membrane is prepared by a non-solvent phase inversion method. The membrane is then immersed in an aqueous solution of amine monomers. After immersion, the surface water droplets are dried. The membrane is then immersed in an oil solution of acyl chloride monomers. After immersion, a polyamide desalination layer is formed. The solvent is dried, and the membrane is then coated in a copolymer solution and dried with hot air to form a copolymer layer. This yields a high-efficiency antifouling and antibacterial reverse osmosis composite membrane.

3. The high-efficiency antifouling and antibacterial reverse osmosis composite membrane as described in claim 2, characterized in that, The concentration of thioctic acid in the copolymer solution is 0.05 g / mL to 1.0 g / mL.

4. The high-efficiency antifouling and antibacterial reverse osmosis composite membrane as described in claim 2, characterized in that, The mass ratio of thioctic acid to zwitterions in the copolymer solution is 10:1-2:

1.

5. The high-efficiency antifouling and antibacterial reverse osmosis composite membrane as described in claim 2, characterized in that, The hot air drying temperature is 55-70℃, and the time is 8-15 minutes.

6. The high-efficiency antifouling and antibacterial reverse osmosis composite membrane as described in claim 5, characterized in that, The hot air drying temperature is 60°C and the time is 10 minutes.

Images