A reverse osmosis membrane with both sterilization and antifouling functions and a preparation method thereof

Abstract

This invention discloses a reverse osmosis membrane with both bactericidal and antifouling functions, and its preparation method. In the reverse osmosis membrane of this invention, the guanidine compound grafted onto the bottom layer acts as a cationic bactericide, which can target and bind to bacterial lipopolysaccharides through electrostatic adsorption to disrupt the cell membrane, achieving highly efficient contact sterilization. The zwitterionic copolymer on the surface forms a stable interfacial hydration layer protective barrier through strong hydration, effectively inhibiting pollutant deposition and bacterial adhesion, thereby achieving the dual functions of bactericidal and antifouling.

Description

Technical Field

[0001] This invention relates to the field of membrane separation and water treatment technology, and in particular to a reverse osmosis membrane with both sterilization and antifouling functions and its preparation method. Background Technology

[0002] Reverse osmosis (RO) membranes have been widely used in various fields such as water softening, wastewater recycling, seawater desalination, pharmaceuticals, and salt separation due to their advantages of low cost, high energy efficiency, and environmental benefits. However, membrane fouling, especially biofouling, has consistently been a major bottleneck restricting the long-term stable operation of RO systems. During the RO process, residual microorganisms in the feed water adhere to, proliferate, and secrete extracellular polymers on the membrane surface, forming a dense biofilm. This biofouling not only leads to a sharp decline in membrane flux, reduced desalination rate, and increased operating pressure differential, significantly increasing energy consumption and cleaning frequency, but also, once formed, is difficult to completely remove with conventional physical cleaning and chemical disinfection, causing irreversible damage to the membrane elements.

[0003] Currently, common reverse osmosis membrane modification strategies often only address either antifouling or sterilization issues, making it difficult to balance long-term effectiveness with high separation performance. Simple hydrophilic modification (such as polyethylene glycol modification) can reduce initial adhesion, but it lacks the ability to kill already attached microorganisms, eventually leading to biofilm formation. On the other hand, conventional antibacterial agents (such as silver nanoparticles or free quaternary ammonium salts) are prone to leaching and loss during long-term operation, resulting in a decline in antibacterial effect and potentially posing a risk of secondary environmental pollution.

[0004] Therefore, there is an urgent need to develop a reverse osmosis membrane material with a reasonable structural design, stable chemical bonding, and both high-efficiency sterilization and long-term antifouling functions to solve the technical bottleneck of the aforementioned biological pollution. Summary of the Invention

[0005] The present invention aims to at least partially solve one of the technical problems in the related art.

[0006] Therefore, embodiments of the present invention propose a reverse osmosis membrane with both bactericidal and antifouling functions and a method for preparing the same.

[0007] In a first aspect, the present invention proposes a method for preparing a reverse osmosis membrane that combines sterilization and antifouling functions, comprising the following steps:

[0008] (1) Dissolve monomers containing epoxy groups and monomers containing zwitterionic structures in a mixed solution of water and alcohol, add a thermal initiator, carry out free radical copolymerization under inert gas protection, and obtain polyepoxy zwitterionic copolymers after purification and drying. (2) The polyamide active layer of the pretreated commercial reverse osmosis membrane is contacted with an aqueous solution of guanidine compound and heated to react. After the reaction is completed, it is washed to obtain a primary modified membrane grafted with bactericidal components. (3) The primary modified membrane is brought into contact with the polyepoxy zwitterionic copolymer solution and heated for cross-linking reaction. After cleaning, a reverse osmosis membrane with dual functions of sterilization and antifouling is obtained.

[0009] Furthermore, the molar ratio of the monomer containing the epoxy group to the monomer containing the zwitterionic structure is (3~5):1.

[0010] Furthermore, the epoxy-containing monomer includes glycidyl methacrylate.

[0011] Furthermore, the monomer containing the zwitterionic structure includes at least one of methacryloylethyl sulfobetaine and carboxylate betaine methacrylate.

[0012] Furthermore, the thermal initiator includes azobisisobutyronitrile (AIBN).

[0013] Furthermore, the temperature of the free radical copolymerization reaction in step (1) is 50~60℃ and the time is 6~8h.

[0014] Furthermore, the pretreatment process of the commercial reverse osmosis membrane includes immersing the commercial reverse osmosis membrane in ultrapure water for 20-40 minutes to remove the surface protectant.

[0015] Furthermore, the guanidine compound includes at least one of sulfaguanidine and chlorhexidine gluconate.

[0016] Furthermore, in step (2), the concentration of the guanidine compound aqueous solution is 1~2 g / L.

[0017] Furthermore, in step (2), the heating reaction temperature is 50~60℃ and the time is 20~40min.

[0018] Furthermore, in step (3), the concentration of the polyepoxy zwitterionic copolymer solution is 1~2 g / L.

[0019] Furthermore, in step (3), the crosslinking reaction is carried out at a temperature of 50-60°C for 4-6 hours.

[0020] Furthermore, the polyepoxy zwitterionic copolymer solution also includes the auxiliary agent hexamethylenetetramine.

[0021] Secondly, the present invention provides a reverse osmosis membrane with both bactericidal and antifouling functions prepared by the method proposed in the first aspect above.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: The guanidine compound grafted onto the bottom layer of the reverse osmosis membrane of this invention acts as a cationic bactericide. It can target and bind to bacterial lipopolysaccharides through electrostatic adsorption to destroy the cell membrane, thereby achieving highly efficient contact sterilization. The zwitterionic copolymer on the surface forms a stable interfacial hydration layer protective barrier through strong hydration, which effectively inhibits the deposition of pollutants and bacterial adhesion, thus achieving the dual functions of sterilization and antifouling.

[0023] The bilayer functionalization of this invention does not sacrifice the membrane's retention capacity. The reverse osmosis membrane maintains a NaCl rejection rate of over 98.37%, and the improved surface hydrophilicity increases the pure water flux to over 36.2 LMH. The functional layer, fixed by chemical covalent grafting, exhibits excellent stability. After six repeated cycle tests, the modified membrane still maintains a bactericidal rate of over 97% against Escherichia coli and Staphylococcus aureus, demonstrating stable and long-lasting antibacterial efficacy. Attached Figure Description

[0024] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a flowchart of the preparation method of the reverse osmosis membrane with both sterilization and antifouling functions of the present invention; Figure 2 Infrared spectra of different membrane samples (commercial reverse osmosis membrane, ROS, ROSP), where, Figure 2 (b) is Figure 2 Enlarged view of a portion of (a); Figure 3 SEM and AFM images of different membrane samples (commercial reverse osmosis membrane, ROS, ROSP), where, Figure 3 Image (a) is a SEM image. Figure 3 (b) is the AFM diagram. Detailed Implementation

[0025] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0026] The following description, in conjunction with the accompanying drawings, describes the reverse osmosis membrane with both bactericidal and antifouling functions proposed in this invention and its preparation method.

[0027] like Figure 1 As shown, the method for preparing the reverse osmosis membrane with both sterilization and antifouling functions of the present invention includes the following steps: (1) Dissolve monomers containing epoxy groups and monomers containing zwitterionic structures in a mixed solution of water and alcohol, add a thermal initiator, carry out free radical copolymerization under inert gas protection, and obtain polyepoxy zwitterionic copolymers after purification and drying. (2) The polyamide active layer of the pretreated commercial reverse osmosis membrane is contacted with an aqueous solution of guanidine compound and heated to react. After the reaction is completed, it is washed to obtain a primary modified membrane grafted with bactericidal components. (3) The primary modified membrane is brought into contact with the polyepoxy zwitterionic copolymer solution and heated for cross-linking reaction. After cleaning, a reverse osmosis membrane with dual functions of sterilization and antifouling is obtained.

[0028] Step (1) is the synthesis process of zwitterionic copolymer. The monomer containing epoxy groups and the monomer containing zwitterionic structure are dissolved in a mixed solution of water and alcohol, a thermal initiator is added, and a free radical copolymerization reaction is carried out under the protection of inert gas. After purification and drying, a polyepoxy zwitterionic copolymer is obtained.

[0029] In some embodiments, the molar ratio of the epoxy-containing monomer to the zwitterionic monomer is (3-5):1. The epoxy-containing monomer includes glycidyl methacrylate (GMA), and the zwitterionic monomer includes at least one of methacryloyl ethyl sulfobetaine (SBMA) and carboxylate betaine methacrylate (CBMA).

[0030] In some embodiments, the water-alcohol mixture is a mixture of water and methanol in equal mass ratios.

[0031] In some embodiments, the thermal initiator includes azobisisobutyronitrile (AIBN), and the mass concentration of the thermal initiator in the mixed solution of water and alcohol is 0.1% to 0.2%.

[0032] The temperature of the free radical copolymerization reaction in step (1) is 50~60℃ and the time is 6~8h. The inert gas includes either nitrogen or argon.

[0033] Step (2) involves constructing the bactericidal coating on the bottom layer of the reverse osmosis membrane. The pretreated polyamide active layer of the commercial reverse osmosis membrane is contacted with an aqueous solution of a guanidine compound and heated to react. After the reaction is complete, the membrane is cleaned to obtain a primary modified membrane grafted with bactericidal components. The pretreatment process of the commercial reverse osmosis membrane involves immersing it in ultrapure water for 20-40 minutes to remove the surface protectant, thus exposing the polyamide active layer.

[0034] The guanidine compound includes at least one of sulfaguanidine (SG) and chlorhexidine gluconate (CHG). In step (2), the concentration of the aqueous solution of the guanidine compound is 1~2 g / L, and the heating reaction temperature in step (2) is 50~60℃, and the time is 20~40 min.

[0035] Step (3) is the process of constructing the antifouling coating on the surface of the reverse osmosis membrane. The primary modified membrane obtained in step (2) is brought into contact with the polyepoxy zwitterionic copolymer solution obtained in step (1) and heated for cross-linking reaction. After cleaning, a reverse osmosis membrane with dual functions of sterilization and antifouling is obtained.

[0036] In step (3), the concentration of the polyepoxy zwitterionic copolymer solution is 1~2 g / L, the temperature of the crosslinking reaction is 50~60℃, and the time is 4~6 h.

[0037] In some embodiments, the polyepoxy zwitterionic copolymer solution further includes the auxiliary agent hexamethylenetetramine, wherein the mass concentration of hexamethylenetetramine in the polyepoxy zwitterionic copolymer solution is 0.2~0.3 g / L.

[0038] The reverse osmosis membrane of the present invention is prepared by the method of the present invention. The guanidine compound grafted into the bottom layer of the reverse osmosis membrane of the present invention acts as a cationic bactericide, which can target and bind to bacterial lipopolysaccharides through electrostatic adsorption to destroy the cell membrane, thereby achieving highly efficient contact sterilization. The zwitterionic copolymer on the surface forms a stable interfacial hydration layer protective barrier through strong hydration, which effectively inhibits the deposition of pollutants and bacterial adhesion.

[0039] The present invention will be described in detail below with reference to the embodiments, wherein the commercial reverse osmosis membrane is RO1 (Zhongke Ruiyang Company).

[0040] Example 1 (1) Glycidyl methacrylate (GMA) and methacryloyl ethyl sulfobetaine (SBMA) in a molar ratio of 4:1 were dissolved in a mixed solution of deionized water and methanol in an equal mass ratio, wherein the mass concentration of glycidyl methacrylate (GMA) in the mixed solution was 0.9% and the mass concentration of methacryloyl ethyl sulfobetaine (SBMA) was 6.8%. The mixture was stirred at 500 r / min for 10 min at 25 °C. Then, azobisisobutyronitrile (AIBN) thermal initiator with a mass concentration of 0.1% was added, and the mixture was stirred for another 10 min under nitrogen protection. The mixture was heated at 60 °C for 6 h. After the reaction was completed, the reaction was terminated by an ice bath. The product was washed three times with methanol, freeze-dried, and collected to obtain the zwitterionic copolymer (PGS).

[0041] (2) The commercial reverse osmosis membrane was immersed in ultrapure water for 30 min to remove the surface protectant. The polyamide active layer of the pretreated commercial reverse osmosis membrane was contacted with a 1 g / L sulfanilamide (SG) solution and reacted at 60 °C for 20 min. After the reaction was completed, the membrane was rinsed with ultrapure water to obtain the primary modified membrane, named ROS.

[0042] (3) The polyurethane layer of the primary modified membrane was contacted with a 1 g / L PGS solution (containing 0.2 g / L hexamethylenetetramine) and the reaction was continued at 60 °C for 4 h. After the reaction was completed, the membrane was thoroughly rinsed three times with ultrapure water to obtain a modified ROSP membrane with both bactericidal and antifouling functions.

[0043] Example 2 (1) Glycidyl methacrylate (GMA) and methacryloyl ethyl sulfobetaine (SBMA) in a molar ratio of 4:1 were dissolved in a mixed solution of deionized water and methanol in an equal mass ratio, wherein the mass concentration of glycidyl methacrylate (GMA) in the mixed solution was 0.9% and the mass concentration of methacryloyl ethyl sulfobetaine (SBMA) was 6.8%. The mixture was stirred at 500 r / min for 10 min at 25 °C. Then, azobisisobutyronitrile (AIBN) thermal initiator with a mass concentration of 0.1% was added, and the mixture was stirred for another 10 min under nitrogen protection. The mixture was heated at 60 °C for 6 h. After the reaction was completed, the reaction was terminated by an ice bath. The product was washed three times with methanol, freeze-dried, and collected to obtain the zwitterionic copolymer (PGS).

[0044] (2) The commercial reverse osmosis membrane was immersed in ultrapure water for 30 min to remove the surface protectant. The polyamide active layer of the pretreated commercial reverse osmosis membrane was contacted with a 1 g / L chlorhexidine gluconate (CHG) solution and reacted at 60 °C for 20 min. After the reaction was completed, the membrane was rinsed with ultrapure water to obtain the primary modified membrane.

[0045] (3) The polyurethane layer of the primary modified membrane was contacted with a 1 g / L PGS solution (containing 0.2 g / L hexamethylenetetramine) and the reaction was continued at 60 °C for 4 h. After the reaction was completed, the membrane was thoroughly rinsed three times with ultrapure water to obtain the modified membrane CHG-PGS with both bactericidal and antifouling functions.

[0046] Example 3 (1) Glycidyl methacrylate (GMA) and carboxylate betaine methacrylate (CBMA) in a molar ratio of 4:1 were dissolved in a mixed solution of deionized water and methanol in an equal mass ratio, wherein the mass concentration of glycidyl methacrylate (GMA) in the mixed solution was 0.9% and the mass concentration of carboxylate betaine methacrylate (CBMA) was 6.8%. The mixture was stirred at 500 r / min for 10 min at 25 °C. Then, azobisisobutyronitrile (AIBN) thermal initiator with a mass concentration of 0.1% was added, and the mixture was stirred for another 10 min under nitrogen protection. The mixture was heated at 60 °C for 6 h. After the reaction was completed, the reaction was terminated by an ice bath. The product was washed three times with methanol, freeze-dried, and collected to obtain zwitterionic copolymer (PGC).

[0047] (2) The commercial reverse osmosis membrane was immersed in ultrapure water for 30 min to remove the surface protectant. The polyamide active layer of the pretreated commercial reverse osmosis membrane was contacted with a 1 g / L sulfanilamide (SG) solution and reacted at 60 °C for 20 min. After the reaction was completed, the membrane was rinsed with ultrapure water to obtain the primary modified membrane.

[0048] (3) The polyurethane layer of the primary modified membrane was contacted with a 1 g / L PGC solution (containing 0.2 g / L hexamethylenetetramine) and the reaction was continued at 60 °C for 4 h. After the reaction was completed, the membrane was thoroughly rinsed three times with ultrapure water to obtain the modified membrane SG-PGC with both bactericidal and antifouling functions.

[0049] Example 4 (1) Glycidyl methacrylate (GMA) and carboxylate betaine methacrylate (CBMA) in a molar ratio of 4:1 were dissolved in a mixed solution of deionized water and methanol in an equal mass ratio, wherein the mass concentration of glycidyl methacrylate (GMA) in the mixed solution was 0.9% and the mass concentration of carboxylate betaine methacrylate (CBMA) was 6.8%. The mixture was stirred at 500 r / min for 10 min at 25 °C. Then, azobisisobutyronitrile (AIBN) thermal initiator with a mass concentration of 0.1% was added, and the mixture was stirred for another 10 min under nitrogen protection. The mixture was heated at 60 °C for 6 h. After the reaction was completed, the reaction was terminated by an ice bath. The product was washed three times with methanol, freeze-dried, and collected to obtain zwitterionic copolymer (PGC).

[0050] (2) The commercial reverse osmosis membrane was immersed in ultrapure water for 30 min to remove the surface protectant. The polyamide active layer of the pretreated commercial reverse osmosis membrane was contacted with a 1 g / L chlorhexidine gluconate (CHG) solution and reacted at 60 °C for 20 min. After the reaction was completed, the membrane was rinsed with ultrapure water to obtain the primary modified membrane.

[0051] (3) The polyurethane layer of the primary modified membrane was contacted with a 1 g / L PGC solution (containing 0.2 g / L hexamethylenetetramine) and the reaction was continued at 60 °C for 4 h. After the reaction was completed, the membrane was thoroughly rinsed three times with ultrapure water to obtain the modified membrane CHG-PGC with both bactericidal and antifouling functions.

[0052] Comparative Example 1 A commercially available unmodified reverse osmosis membrane (Pristine RO) was used as a blank control. It was immersed in ultrapure water for 30 min to remove the surface protectant before use.

[0053] Comparative Example 2 Commercial reverse osmosis membranes were immersed in ultrapure water for 30 min to remove surface protectants. The polyamide active layer of the pretreated commercial reverse osmosis membrane was then contacted with a 1 g / L sulfanilamide (SG) solution and reacted at 60 °C for 20 min. After the reaction was complete, the membrane was rinsed with ultrapure water to obtain the primary modified membrane ROS.

[0054] Comparative Example 3 (1) Glycidyl methacrylate (GMA) and methacryloyl ethyl sulfobetaine (SBMA) in a molar ratio of 4:1 were dissolved in a mixed solution of deionized water and methanol in an equal mass ratio, wherein the mass concentration of glycidyl methacrylate (GMA) in the mixed solution was 0.9% and the mass concentration of methacryloyl ethyl sulfobetaine (SBMA) was 6.8%. The mixture was stirred at 500 r / min for 10 min at 25 °C. Then, azobisisobutyronitrile (AIBN) thermal initiator with a mass concentration of 0.1% was added, and the mixture was stirred for another 10 min under nitrogen protection. The mixture was heated at 60 °C for 6 h. After the reaction was completed, the reaction was terminated by an ice bath. The product was washed three times with methanol, freeze-dried, and collected to obtain the zwitterionic copolymer (PGS).

[0055] (2) The commercial reverse osmosis membrane was immersed in ultrapure water for 30 min to remove the surface protectant. The polyamide active layer of the pretreated commercial reverse osmosis membrane was contacted with 1 g / L PGS solution (containing 0.2 g / L hexamethylenetetramine) and the reaction was continued at 60 °C for 4 h. After the reaction was completed, the membrane was thoroughly rinsed three times with ultrapure water to obtain the modified membrane PGC.

[0056] Experimental Example 1 The structures of different membrane samples were characterized using Fourier transform infrared spectroscopy (FT-IR), and the test results are as follows: Figure 2 As shown, where, Figure 2 (b) is Figure 2 A magnified view of a portion of (a). FT-IR spectroscopy analysis shows that, compared to the RO membrane, the SG-modified ROS membrane exhibits better performance at 1147 cm⁻¹. 1 A new characteristic absorption peak appeared at [value missing], which is attributed to the characteristic stretching vibration of the guanidinium group in the SG molecule. Subsequently, after further introducing the zwitterionic copolymer PGS into the ROS membrane, the ROSP membrane exhibited a peak at 1488 cm⁻¹. 1 956 cm 1 and 1039 cm 1 Three distinct absorption peaks were newly added, corresponding to the quaternary ammonium groups (CN) in PGS. + ) and sulfonate groups (–SO3) The stretching and contraction vibrations indicate that PGS has been successfully constructed on the membrane surface.

[0057] The morphology of the films before and after modification was characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM), such as... Figure 3 As shown, where, Figure 3 Image (a) is a SEM image. Figure 3 (b) is the AFM diagram. According to... Figure 3 It was found that the RO membrane surface exhibited a typical polyamide wrinkled structure with an arithmetic mean roughness (Ra) of 42.0 ± 2.5 nm. After modification with SG (ROS membrane), the surface roughness did not change significantly (46.6 ± 2.2 nm), and the continuous wrinkled skeleton was still maintained, indicating that SG grafting did not cause significant macroscopic morphology reconstruction. After further reaction with PGS (ROSP membrane), the overall wrinkled structure of the surface was still discernible, but Ra increased to 51.0 ± 2.9 nm, meaning an increase in the effective specific area of ​​the membrane surface. At the same time, the sulfur element distribution on the ROSP membrane surface showed a continuous and uniform signal characteristic, and no obvious local enrichment or agglomeration patches were observed, indicating that the SG and PGS-related components had good coverage uniformity on the membrane surface. These results indicate that the layer-by-layer assembly strategy achieved a controllable improvement in membrane surface roughness while maintaining the integrity and coverage uniformity of the polyamide layer, providing a structural basis for improving water flux.

[0058] Experimental Example 2 The zeta potential of different membrane samples was measured using a solid surface zeta potential meter at pH=7. To reduce the influence of experimental error, each membrane sample was tested three times. The test results are shown in Table 1.

[0059] Table 1:

[0060] Test results show that the surface of the original RO membrane (Comparative Example 1) is negatively charged due to the ionization of carboxyl groups at the ends of the polyamide layer. After SG modification, the negative charge on the surface of the ROS membrane (Comparative Example 2) decreased to -22.37 mV, which may be due to the SG molecules consuming the negatively charged -COOH on the RO membrane surface. After modification with zwitterionic polymers PGS or PGC, the surface zeta potential of the membrane samples in Examples 1-4 increased significantly. This phenomenon is due to zwitterionic charge shielding, which helps in the formation of the interfacial hydration layer, thereby improving the membrane's antifouling performance.

[0061] Experimental Example 3 The hydrophilicity of the membrane surface was measured using an optical contact angle meter in static drop mode. A 3 μL droplet of ultrapure water was added to a dry membrane sample measuring 1 cm × 1 cm, and the static contact angle was recorded. Three locations were tested for each sample, and the average value was taken as the final result. The test results are shown in Table 2.

[0062] Table 2:

[0063] Test results show that the unmodified original RO membrane (Comparative Example 1) has a high surface water contact angle of approximately 71.5° due to the inherent properties of the polyamide layer. The ROS membrane (Comparative Example 2), modified only by the bottom guanidine compound (SG), has a lower contact angle, decreasing to approximately 48.7°. After further modification with a zwitterionic copolymer on the surface, the surface water contact angle of the membrane samples in Examples 1-4 is significantly reduced. This significant decrease in water contact angle directly demonstrates that the dual modification strategy successfully constructed a very strong hydrophilic interface on the membrane surface. This is mainly due to the zwitterionic structure's ability to form a dense and stable electrically neutral hydration layer on the membrane surface, effectively reducing the membrane's surface energy and thus increasing hydrophilicity. The construction of this strong hydrophilic interface reduces the transport resistance of water molecules into the membrane, effectively increasing the membrane's pure water permeation flux. Furthermore, this dense hydration barrier thermodynamically greatly hinders the direct contact between organic matter and bacteria and the membrane surface, providing a solid physicochemical basis for "anti-organic fouling" and "anti-bioadhesion."

[0064] Test Example 4 (1) Water flux test: Under the conditions of 25±5 °C and 0.8 MPa, the membrane sample was pre-pressed for 30 min (0.1 MPa) using a cross-flow filtration device. The permeate flow rate of the membrane was then recorded, and the pure water permeate flux J (unit: L·m) was calculated according to formula (1). -2 ·h -1 ): J = V / (A×t) Formula (1) Where V is the volume of water permeating the membrane (L), and A is the effective membrane area (m²). 2), where t is the filtering time (h).

[0065] (2) Retention rate test: Using 0.5 g / L NaCl solution as feed liquid, filter test is performed according to step (1), and the retention rate is calculated according to formula (2).

[0066] Retention rate = (1-C1 / C0)×100% Formula (2) Where C0 and C1 are the concentrations of NaCl in the solution before and after filtration, respectively.

[0067] As shown in Table 3, the pure water flux of the membrane samples in Examples 1-4 reached 36.2 L·m. -2 ·h -1 The concentration was significantly higher than that of Comparative Example 1 and Comparative Example 2, while maintaining a NaCl rejection rate of over 98%, indicating that the zwitterionic functional layer constructed on the membrane surface effectively maintained the membrane's separation accuracy while improving hydrophilicity.

[0068] Table 3:

[0069] Experimental Example 5 Antimicrobial performance evaluation: *Escherichia coli* and *Staphylococcus aureus* were used as microbial models. A 1 cm × 1 cm sample of the membrane to be tested was inoculated with 20 μL of the bacterial stock solution (10... 5 The membrane samples (CFU / mL) were brought into full contact with the bacterial solution. The membrane samples in contact with the bacterial solution were incubated in a 37°C thermostatic incubator for 24 hours. The antibacterial rate of the membrane samples was then calculated using the plate count method, and the test results are shown in Table 4. Compared with the unmodified original RO membrane (Comparative Example 1), the finally modified membranes (Examples 1-4) exhibited extremely high bactericidal rates of nearly 99% against both *Escherichia coli* and *Staphylococcus aureus*, demonstrating the excellent broad-spectrum antibacterial performance of SG / CHG. Furthermore, after six repeated cycles, the bactericidal rate of the modified membrane against *Escherichia coli* and *Staphylococcus aureus* remained above 97%, indicating stable and long-lasting antibacterial efficacy, demonstrating the excellent stability of the functional layer fixed through chemical covalent grafting.

[0070] Table 4:

[0071] Experimental Example 6 Evaluation of anti-biofilm adhesion performance: *Escherichia coli* and *Staphylococcus aureus* were used as microbial models. A 1 cm × 1 cm sample of the test membrane was immersed in 1 mL of a 10% concentration of [unspecified solution]. 8 The bacterial suspension was incubated at CFU / mL in a 37°C incubator for 48 h. Subsequently, it was cultured using LIVE / DEAD BacLight. TMThe bacterial activity assay kit was used to fluorescently stain the biofilm on the reverse osmosis membrane surface. The biofilm thickness was then observed and measured using a laser scanning confocal microscope. The results are shown in Table 5. The results showed that the original RO membrane (Comparative Example 1) was covered with a large number of bacteria, forming a dense biofilm (12.93 μm and 10.37 μm). Bacterial adhesion was reduced on the surface of the SG-modified ROS membrane (Comparative Example 2). In contrast, the membrane samples from Examples 1-4 showed only a very small number of sparse bacteria attached to their surfaces, with almost no complete biofilm formation, demonstrating excellent anti-bioadhesion capabilities. This is mainly due to the dual bactericidal and antifouling protection mechanism constructed from the SG / CHG and zwitterionic polymers PGS / PGC on the membrane surface. Specifically, the guanidinium groups in the SG / CHG molecules disrupt the bacterial cell membrane through electrostatic interaction, achieving contact sterilization. Simultaneously, the strong hydration of the PGS / PGC structure forms a dense hydration layer on the membrane surface, effectively blocking the interaction between bacteria and the membrane surface, thereby inhibiting initial bacterial adhesion.

[0072] Table 5:

[0073] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms may refer to different embodiments or examples. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0074] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0075] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for preparing a reverse osmosis membrane with both sterilization and antifouling functions, characterized in that, Includes the following steps: (1) Dissolve monomers containing epoxy groups and monomers containing zwitterionic structures in a mixed solution of water and alcohol, add a thermal initiator, carry out free radical copolymerization under inert gas protection, and obtain polyepoxy zwitterionic copolymers after purification and drying. (2) The polyamide active layer of the pretreated commercial reverse osmosis membrane is contacted with an aqueous solution of guanidine compound and heated to react. After the reaction is completed, it is washed to obtain a primary modified membrane grafted with bactericidal components. (3) The primary modified membrane is brought into contact with the polyepoxy zwitterionic copolymer solution and heated for cross-linking reaction. After cleaning, a reverse osmosis membrane with dual functions of sterilization and antifouling is obtained.

2. The method as described in claim 1, characterized in that, The molar ratio of the monomer containing the epoxy group to the monomer containing the zwitterionic structure is (3~5):

1.

3. The method as described in claim 1, characterized in that, The monomer containing epoxy groups includes glycidyl methacrylate; And / or, the monomer containing the zwitterionic structure includes at least one of methacryloylethyl sulfobetaine and carboxylate betaine methacrylate; And / or, the thermal initiator includes azobisisobutyronitrile.

4. The method as described in claim 1, characterized in that, The temperature of the free radical copolymerization reaction in step (1) is 50~60℃ and the time is 6~8h.

5. The method as described in claim 1, characterized in that, The pretreatment process of the commercial reverse osmosis membrane includes immersing the commercial reverse osmosis membrane in ultrapure water for 20-40 minutes to remove the surface protectant.

6. The method as described in claim 1, characterized in that, The guanidine compound includes at least one of sulfaguanidine and chlorhexidine gluconate.

7. The method as described in claim 1, characterized in that, In step (2), the concentration of the guanidine compound aqueous solution is 1~2 g / L; And / or, the heating reaction in step (2) is carried out at a temperature of 50~60℃ for a time of 20~40min.

8. The method as described in claim 1, characterized in that, The concentration of the polyepoxy zwitterionic copolymer solution in step (3) is 1~2 g / L; And / or, the temperature of the crosslinking reaction in step (3) is 50~60℃ and the time is 4~6h.

9. The method as described in claim 8, characterized in that, The polyepoxy zwitterionic copolymer solution also includes the auxiliary agent hexamethylenetetramine.

10. A reverse osmosis membrane with both sterilization and antifouling functions, characterized in that, Prepared by the method described in any one of claims 1 to 9.

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