Bacteriostatic ultrafiltration membrane applied to MBR (Membrane Bioreactor) sewage treatment as well as preparation method and application of bacteriostatic ultrafiltration membrane

Abstract

The invention discloses a bacteriostatic ultrafiltration membrane applied to MBR (Membrane Bioreactor) sewage treatment as well as a preparation method and application thereof. The preparation method comprises the following steps: S1, pretreating an ultrafiltration membrane; s2, placing the pretreated ultrafiltration membrane on a suction filtration device, pouring a polymeric dopamine solution into a funnel of the suction filtration device, starting a suction filtration pump, washing the membrane surface with deionized water after the suction filtration process is finished, and drying to obtain a modified ultrafiltration membrane; and S3, completely soaking the modified ultrafiltration membrane obtained in the step S2 by using a bacteriostatic agent solution, and drying to obtain the bacteriostatic ultrafiltration membrane. The prepared polyvinylidene fluoride ultrafiltration membrane doped with the natural mixed antibacterial agent is safe, non-toxic, green and environment-friendly, multiple experiments show that the water flux, the retention rate and the antibacterial activity of the membrane are considered, the antibacterial rate on escherichia coli and staphylococcus aureus is high, and the synergistic effect of resisting adhesion of bacteria and killing bacteria is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of ultrafiltration membranes, and in particular relates to an antibacterial ultrafiltration membrane used in MBR sewage treatment, a preparation method and an application thereof. Background Art

[0002] With population growth, urbanization, and the increasing use of freshwater resources, freshwater shortages have become an increasingly serious problem worldwide. MBR (Mechanical Filters or MBRs) combine membrane separation technology with biological treatment processes to effectively intercept microorganisms and macromolecular organic matter, ensuring high and stable effluent quality. They also offer high removal rates for suspended solids, organic matter, and bacteria, enabling compliance with stricter discharge standards or reuse requirements. They play a vital role in wastewater treatment and seawater desalination. However, biofouling is a common problem in MBR processes and is considered a major factor contributing to reduced membrane flux and service life. Biofouling is caused by bacteria on the membrane surface. Due to bacterial motility, secretion, and reproduction, biofouling is currently considered the most destructive and difficult to control form of membrane fouling. When membrane separation technology is used to treat wastewater containing microorganisms, microorganisms spontaneously adhere to the membrane surface to form a biofilm, leading to irreversible fouling and reduced water flux. Therefore, an ultrafiltration membrane with antibacterial properties is highly desirable to prevent biofilm formation on the membrane surface and ensure long-term membrane service life. Introducing antimicrobial materials onto the membrane surface is an important method for improving the membrane's antimicrobial capacity. However, organic antimicrobial agents have limited application in membrane manufacturing due to their poor chemical stability and short duration of action. Although inorganic antimicrobial agents are widely used in industry due to their good stability and safety, they also have problems such as low antimicrobial rate and high price. Invention content In view of this, the present invention aims to propose an antibacterial ultrafiltration membrane for use in MBR sewage treatment, as well as a preparation method and application thereof, to solve at least one technical problem in the background technology.

[0003] To achieve the above object, the technical solution created by the present invention is implemented as follows: A method for preparing an antibacterial ultrafiltration membrane used in MBR sewage treatment comprises the following steps: S1: pre-treating the ultrafiltration membrane; S2: placing the pretreated ultrafiltration membrane on a filtration device, pouring the polymerized dopamine solution into the funnel of the filtration device, turning on the filtration pump, and after the filtration process is completed, washing the membrane surface with deionized water and drying it to obtain a modified ultrafiltration membrane; S3: completely soaking the modified ultrafiltration membrane obtained in step S2 with an antibacterial agent solution, and drying the membrane to obtain an antibacterial ultrafiltration membrane.

[0004] Furthermore, the ultrafiltration membrane in step S1 is one of PVDF membrane, PVC membrane, PAN membrane, PP membrane, PES membrane, PTFE membrane, and PS membrane.

[0005] Furthermore, the pretreatment in step S1 includes soaking the ultrafiltration membrane in deionized water, washing it with deionized water, and then drying it for storage; The soaking time is 20-28h.

[0006] Furthermore, the preparation of the polymerized dopamine solution in step S2 includes adding the dopamine solution buffer solution to the buffer solution, stirring magnetically for 8-12 minutes at 20-30°C, and ultrasonically dispersing for 8-12 minutes at room temperature. The buffer solution is a Tris-HCl buffer solution with a pH of 8-9; The concentration of the polymerized dopamine solution is 0.4-0.6 mg·mL -1 ; Dopamine solution and buffer solution.

[0007] Furthermore, the drying in step S2 is performed at 55-65° C. and the drying time is 5-7 hours.

[0008] Further, the antibacterial agent solution includes placing the antibacterial agent into an ethanol solution; The antibacterial agent in step S3 includes one or more of baicalin, chlorogenic acid and emodin.

[0009] Furthermore, the antibacterial agent in step S3 is baicalin, chlorogenic acid and emodin; The mass ratio of baicalin / chlorogenic acid / emodin is (0~2):(0~2):(0~2); Preferably, the mass ratio of baicalin / chlorogenic acid / emodin is 2:2:2.

[0010] Furthermore, the soaking time in step S3 is 25-35 minutes; The temperature of the oven in step S3 is 55-65° C. and the time is 11-13 hours.

[0011] The antibacterial ultrafiltration membrane prepared by the above-mentioned method for preparing an antibacterial ultrafiltration membrane used in MBR sewage treatment.

[0012] The antibacterial ultrafiltration membrane prepared by the above-mentioned method for preparing an antibacterial ultrafiltration membrane used in MBR sewage treatment is used in MBR sewage treatment.

[0013] Natural antibacterial agents are environmentally friendly, widely available, and highly safe. Examples include chitosan, baicalin, chlorogenic acid, and emodin. Baicalin's antibacterial mechanism primarily involves disrupting bacterial cell walls and membranes, inhibiting bacterial protein synthesis. Chlorogenic acid's antibacterial mechanism primarily involves inhibiting the activity of enzymes essential for bacterial growth and reproduction. Emodin's antibacterial mechanism primarily involves reducing the synthesis of adenosine triphosphate, a key energy-producing enzyme in bacteria, resulting in a lack of energy and difficulty maintaining normal life activities. All three natural antibacterial agents exhibit some antibacterial activity, but the results are not ideal. Natural mixed antibacterial agents, by adjusting the ratio of the three natural antibacterial agents, enhance their synergistic antibacterial capacity, exhibiting superior antibacterial efficacy compared to the individual agents alone. The synergistic antibacterial mechanism of the natural mixed antibacterial agent is as follows: 1. Chlorogenic acid binds to the active site of the enzyme, while baicalin alters the enzyme's spatial structure, jointly disrupting bacterial energy metabolism; and 2. Chlorogenic acid increases the permeability of the bacterial cell membrane, allowing bacterial contents to leak out. Baicalin can inhibit bacterial cell wall synthesis, and the combination of baicalin and emodin can more effectively destroy bacterial integrity. 3. Baicalin and emodin can jointly interfere with bacterial nucleic acid metabolism and protein synthesis, such as inhibiting DNA and RNA synthesis and protein translation, hindering bacterial reproduction through various pathways. Furthermore, natural mixed antibacterial agents offer enhanced antibacterial efficacy, high safety, and low cost, garnering significant attention and rapid development in recent years.

[0014] Compared with the prior art, the antibacterial ultrafiltration membrane, preparation method and application for MBR wastewater treatment created by the present invention have the following advantages: The polyvinylidene fluoride ultrafiltration membrane doped with a natural antimicrobial agent produced in this application exhibits excellent antimicrobial properties against both Escherichia coli and Staphylococcus aureus. Furthermore, the membrane's hydrophilicity is further enhanced, resulting in increased water flux. Compared to polyvinylidene fluoride ultrafiltration membranes doped with heavy metal antimicrobial agents such as copper and silver, the polyvinylidene fluoride ultrafiltration membrane doped with a natural mixed antimicrobial agent produced in this application is safe, non-toxic, and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings: Figure 1 Surface SEM images of the PVDF membrane and modified membrane of the embodiment of the present application (a1 and a2 are SEM images of M0, b1 and b2 are SEM images of M0', c1 and c2 are SEM images of M5, d1 and d2 are SEM images of M10, and e1 and e2 are SEM images of M15); Figure 2Surface AFM images of the PVDF membrane and the modified membrane according to the embodiment of the present application (a is the surface AFM image of M0, b is the surface AFM image of M0', c is the surface AFM image of M5, d is the surface AFM image of M10, and e is the surface AFM image of M15); Figure 3 Membrane properties of the PVDF membrane and modified membrane of the embodiment of the present application (a is Zeta potential, b is contact angle); Figure 4 The pure water flux and BSA retention rate of the PVDF membrane and modified membrane in the examples of this application; Figure 5 The normalized water flux of the PVDF membrane and the modified membrane of the embodiment of the present application (a is Escherichia coli, b is Staphylococcus aureus); Figure 6 The flux recovery rates of the PVDF membrane and modified membrane of the present application example (a is Escherichia coli, b is Staphylococcus aureus); Figure 7 CLSM images of the PVDF membrane and modified membrane of the present application before dynamic cleaning of E. coli contamination; Figure 8 CLSM images of the PVDF membrane and modified membrane of the embodiment of the present application before cleaning of Staphylococcus aureus dynamic contamination; Figure 9 The antibacterial efficiency of the PVDF membrane and modified membrane of the examples of the present application against Escherichia coli and Staphylococcus aureus (a is Escherichia coli, b is Staphylococcus aureus). DETAILED DESCRIPTION

[0016] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0017] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0018] A method for preparing an antibacterial ultrafiltration membrane comprises the following steps: Step 1: Select a suitable ultrafiltration membrane, such as polysulfone or polyethersulfone. Rinse the membrane with deionized water to remove any impurities and protective agents on the membrane surface, then dry and store.

[0019] Step 2, Polydopamine Coating: Add a certain concentration of dopamine to a Tris-HCl buffer solution at a pH of approximately 8.5. Place the pretreated ultrafiltration membrane on a filtration unit. Next, pour the prepared dopamine solution into the filtration unit's funnel and start the filtration pump. Due to the filtration process, the dopamine molecules in the solution polymerize on the membrane surface, gradually forming a coating. After the filtration process is complete, rinse the membrane surface with deionized water and place it in a 60°C oven.

[0020] Step 3: Select an appropriate antimicrobial agent, install the membrane in a frame equipped with a gasket, pour the prepared antimicrobial solution into the membrane, and allow it to soak completely for a period of time. Because polydopamine has strong adhesion, it can interact with the antimicrobial agent, such as through physical adsorption or chemical bonding, causing the antimicrobial agent to adhere to the membrane surface.

[0021] According to an embodiment of the present invention, in step 1, the commercial PVDF membrane was soaked in deionized water for 24 hours to remove glycerol from the surface of the commercial membrane. The membrane was then washed with deionized water and dried for storage. The pure membrane was designated as M0 membrane.

[0022] According to an embodiment of the present invention, the step 2 contains 0.5 mg·mL -1 The dopamine solution was added to 10 mM Tris-HCl buffer solution (pH 8.5) and placed in a beaker with magnetic stirring at 25°C for 10 minutes. The mixture was then ultrasonically dispersed at room temperature for 10 minutes to obtain a PDA nanoparticle dispersion. The dopamine nanoparticles in the solution continuously undergo self-polymerization, so the solution should be prepared immediately before use. 0.5 mg mL -1 The treated commercial PVDF membrane was fixed to a filtration device and the polydopamine solution was poured into it. After the filtration process was completed, the membrane surface was washed with deionized water and then dried in a 60°C oven for 6 hours. The modified membrane was named M0' membrane.

[0023] According to an embodiment of the present invention, the antibacterial agent in step 3 is a natural mixed antibacterial agent. Natural mixed antibacterial agents are composed of a mixture of multiple natural ingredients that synergistically inhibit the growth and reproduction of microorganisms (such as bacteria and fungi). The natural mixed antibacterial agent selected in the present invention is a solution of baicalin, chlorogenic acid, and emodin. The mass ratio of baicalin / chlorogenic acid / emodin is (0-2):(0-2):(0-2). Multiple tests have shown that the optimal mass ratio for the combination with the best antibacterial effect is 2:2:2. Ethanol solutions of the antibacterial composition at concentrations of 5, 10, and 15% are prepared in a 100 mL volumetric flask. The mass ratio of baicalin / chlorogenic acid / emodin in the 5, 10, and 15% solutions is 2:2:2. The membrane is then mounted in a frame equipped with a gasket, and the prepared solution is poured in, allowing it to completely soak for 30 minutes. The membrane is then dried in a 60°C oven for 12 hours. The membranes modified with natural mixed antibacterial agents were named M5, M10, and M15 membranes.

[0024] 1) Surface SEM images of PVDF membrane and modified membrane observed in this example; The surface of the M0 membrane is characterized by numerous porous structures and a large number of pores with a pore diameter of approximately 82.62 nm, indicating a large specific surface area. After PDA modification, the pore size and porosity of the M0' membrane decreased. This is due to the formation of a PDA interlayer after dopamine self-polymerizes on the M0 membrane surface, covering the membrane pores and significantly reducing water flux during filtration. The adhesive properties of PDA were utilized to adhere the natural mixed antibacterial agent to the membrane surface. With increasing concentration of the natural mixed antibacterial agent, the membrane surface became denser, the pore size and porosity decreased, and the smoothness increased, indicating successful membrane modification.

[0025] 2) Surface AFM images of PVDF membrane and modified membrane observed in this example; Compared to membrane M0, membrane M0' exhibited reduced Ra and Rq values, indicating a significant reduction in membrane surface roughness. PDA modification of PVDF membranes, after initially increasing surface hydrophilicity, establishes good surface coverage, further increasing surface energy. This effect is partially offset by pore blockage (as demonstrated by SEM and pure water flux). Consequently, as membrane pores become blocked, the surface roughness decreases from 38.4 ± 3.6 nm to 30.1 ± 2.1 nm. However, the roughness of membranes M5, M10, and M15 decreased slightly to 32.7 ± 3.2 nm, 32.4 ± 2.8 nm, and 32.2 ± 3.0 nm, respectively, due to the loading of the natural mixed antibacterial agent on the membrane surface. Since foulants tend less to adhere to smooth surfaces, a clear link between antifouling performance and membrane surface roughness is evident.

[0026] In this example, the membrane properties of PVDF membrane and modified membrane were observed: Zeta potential and contact angle; At a solution pH of 7.4, the zeta potentials of the M0, M0', M5, M10, and M15 membranes were approximately -15.95 mV, -20.29 mV, -24.23 mV, -28.86 mV, and -34.97 mV, respectively. PDA modification deprotonates the phenolic hydroxyl groups in alkaline conditions, resulting in a negative charge. Natural pollutants are generally negatively charged in the environment. Therefore, due to the electrostatic repulsion between the negatively charged membrane and the negatively charged pollutants, the membrane has a low affinity for these pollutants. The negative zeta potential values within the solution pH range of 3-9 are due to the weakly negative charge of baicalin and emodin, and the negative charge of chlorogenic acid, resulting in an overall negative charge for the natural antibacterial mixture. This results in the transformation of the originally electronegative M0' membrane surface to a more negatively charged one. Furthermore, PDA forms a hydration layer, preventing foulants from adsorbing onto the membrane surface.

[0027] After PDA modification, the water contact angle of the original M0 membrane decreased from 59.21° to 34.27°. This phenomenon also indicates that the hydrophilic groups of PDA (such as phenolic hydroxyl groups) migrated to the membrane surface, increasing the membrane's hydrophilicity, and that the PDA layer was successfully introduced into the M0 membrane surface. The contact angle increased slightly with increasing concentrations of the natural mixed antibacterial agent. It is well known that the wettability of a membrane surface, as assessed by the contact angle, depends on the surface chemical composition, roughness, and porosity. The presence of the natural mixed antibacterial agent on the M0' membrane surface caused it to accumulate, resulting in a slight increase in roughness, but this was not a major factor affecting the contact angle. On the other hand, the reduction in porosity also reduced the contact area with water.

[0028] 4) This example observes the pure water flux and BSA retention rate of PVDF membrane and modified membrane; The pure water flux and BSA rejection of the original M0 membrane were 245.13 L·m -2 ·h -1 bar -1 and 68.35%. Since the pore size of the membrane surface is large and uneven at this time, the large pores on the membrane surface cannot effectively intercept BSA molecules, so the retention rate is low. The appropriate amount of PDA modification on the M0 membrane can improve the hydrophilicity of the membrane surface and reduce the permeation resistance of water molecules. The pure water flux of the membrane decreased from 245.13 L·m -2 ·h -1 bar -1 Reduced to 173.83 L·m -2 ·h -1 bar -1 At the same time, PDA covered part of the membrane pores, preventing BSA molecules from passing through the membrane, which may be the reason for the increase in BSA retention rate (76.63%). When the concentration of natural mixed antibacterial agents increased from 5% to 15%, the pure water flux of the membrane increased from 153.62 L·m -2 ·h -1 bar -1 Reduced to 132.31 L·m -2 ·h -1 bar -1 , the BSA retention rate increased from 82.13% to 87.59%. This is because increasing the concentration of the natural mixed antibacterial agent on the membrane surface makes the membrane surface denser, partially blocking the pores, which increases the membrane resistance and dominates the process. Therefore, the pure water flux decreases with increasing natural mixed antibacterial agent concentration. A denser membrane surface is more conducive to improving the retention rate of M5, M10, and M15 membranes.

[0029] 5) This example observes the normalized water flux of PVDF membrane and modified membrane; The presence of E. coli resulted in the largest decrease in normalized flux of the original M0 membrane, at 35.71%, and the lowest flux recovery rate, at 45.93%. Modification with a PDA layer significantly enhanced its anti-biofouling performance, with a normalized flux reaching 48.96% and a flux recovery rate of 56.21%. This improvement can be attributed to the anti-adhesion properties of PDA, primarily due to its enhanced hydrophilicity. Water molecules are initially attracted to the hydrophilic layer, forming an interfacial hydration layer that reduces the adsorption of contaminants. Increasing the concentration of the natural mixed antibacterial agent from 5% to 15% increased the normalized flux from 56.72% to 70.01%. This is because the membrane's strong hydrophilicity prevents contaminants and bacteria from adhering to it. Furthermore, the natural mixed antibacterial agent exhibits excellent antibacterial activity. The combined effects of these two factors significantly enhance the normalized flux.

[0030] The original M0 membrane experienced the largest decrease in normalized flux, 25.13%, due to the presence of Staphylococcus aureus. Compared to Escherichia coli, S. aureus exhibited the same normalized water flux variation trend. The M15 membrane demonstrated excellent antibacterial activity, with a normalized flux of 56.79%, sharing the same bactericidal mechanism as E. coli. Combined with basic membrane characterization, the M10 membrane demonstrated excellent antibacterial activity, further reducing bacterial attachment and growth, and extending the lifespan of ultrafiltration membranes in combating biofouling.

[0031] 6) This example observes the flux recovery rate of PVDF membrane and modified membrane; When the membrane was contaminated with E. coli, the original M0 membrane had the lowest flux recovery rate, at 45.61%. The flux recovery rate of the modified membranes was significantly greater than that of the original M0 membrane. Among them, the M10 membrane had the highest flux recovery rate, at 72.47%, indicating that hydrophilicity can enhance its antifouling ability. Water molecules are attracted to the hydrophilic layer, forming an interfacial hydration layer. This not only inhibits the adhesion of pollutants to the membrane surface, but also minimizes the possibility of pollutants penetrating the membrane pores. In addition, the natural mixed antibacterial agent can destroy the bacterial cell membrane and inhibit the synthesis of bacterial proteins, affecting its metabolic process. Therefore, it will show an excellent flux recovery rate after hydraulic cleaning.

[0032] When the membrane was contaminated with Staphylococcus aureus, the membrane showed the same flux recovery rate trend compared to Escherichia coli. However, under S. aureus contamination, the original M0 membrane showed a lower flux recovery rate of 38.73%. At the same time, although the M10 membrane showed the best flux recovery rate of 62.21%, the flux recovery rate was significantly reduced compared to E. coli contamination. In addition, the same problem was found in other modified membranes. This is because Staphylococcus aureus has a thicker bacterial cell membrane, resulting in different antibacterial effects. In addition, the antibacterial effect of Staphylococcus aureus is slightly worse than that of E. coli, and the biofilm load is greater, which is less likely to be washed off by hydraulic cleaning.

[0033] 7) In this example, CLSM images of PVDF membrane and modified membrane before cleaning of E. coli dynamic contamination were observed; Compared to M0 and M0', the number of live cells on the M5, M10, and M15 membranes decreased, while the number of dead cells gradually increased, demonstrating their excellent bactericidal properties. This directly proves that the goal of mitigating biofouling is achieved by killing bacteria. As the concentration of the natural mixed antibacterial agent on the membrane surface increases, the number of dead cells increases, while the number of live cells decreases, indicating that the natural mixed antibacterial agent has an antibacterial effect, which is consistent with the CLSM results.

[0034] 8) This example shows CLSM images of PVDF membrane and modified membrane before cleaning of Staphylococcus aureus dynamic contamination. CLSM images of bacteria in contact with the M0 membrane revealed abundant green fluorescence, indicating active bacteria on the M0 membrane surface and poor biofouling resistance. Compared to the M0 membrane, the M0' membrane began to exhibit red fluorescence, indicating damaged bacteria. This is due to the hydrophilic PDA loading, which effectively weakened the interaction between the bacteria and the membrane surface. A small number of ruptured cells were observed, indicating a disruption of the cell barrier. After hydraulic cleaning, the number of both live and dead cells decreased. Dead cells can be fixed to the membrane surface through electrostatic attraction, while loose bacteria on the membrane surface may be washed away by hydraulic cleaning.

[0035] Furthermore, in the M5, M10, and M15 membranes, the number of live cells further decreased, while the number of dead cells significantly increased, demonstrating that the modified membranes not only inactivate bacteria and inhibit their growth and reproduction, but also exhibit good recovery efficiency after hydraulic cleaning. Although biofilms gradually form on the membrane surface, they are in a loose and reversible state and can be easily removed with simple hydraulic cleaning.

[0036] 9) This example observes the antibacterial efficiency of PVDF membrane and modified membrane against Escherichia coli and Staphylococcus aureus; The M0' membrane exhibited antibacterial rates of 15.97% and 14.31% against Escherichia coli and Staphylococcus aureus, respectively. The results indicate that the prepared M0' membrane exhibits a certain degree of antibacterial activity, which is attributed to the deprotonation of the phenolic hydroxyl groups in polydopamine, resulting in a negative charge and electrostatic repulsion with negatively charged bacteria. The M5, M10, and M15 membranes exhibited significantly improved antibacterial efficiencies against E. coli and S. aureus, reaching 54.26% and 49.73%, 85.61% and 79.75%, and 87.63% and 81.39%, respectively. The main antibacterial mechanisms are as follows: 1. Chlorogenic acid binds to the active site of the enzyme, while baicalin alters the enzyme's spatial structure, jointly disrupting bacterial energy metabolism; 2. Chlorogenic acid increases bacterial cell membrane permeability, allowing bacterial contents to leak out, while emodin inhibits bacterial cell wall synthesis. The combination of chlorogenic acid and emodin effectively disrupts bacterial integrity; 3. Baicalin and emodin can jointly disrupt bacterial nucleic acid metabolism and protein synthesis. The three antibacterial agents in the natural antibacterial blend act synergistically to enhance antibacterial activity. 2. Polydopamine provides a strong connection between the natural antibacterial blend and the membrane, ensuring a stable bond between the functional layer and the basement membrane. A small amount of hydrophilic polydopamine enhances the hydrophilicity of the membrane surface, effectively weakening the interaction between bacteria and the membrane. The natural antibacterial blend kills Staphylococcus aureus by disrupting the phospholipid bilayer, a mechanism consistent with its antibacterial effect on Escherichia coli. The two bacteria exhibited different inhibition rates. While the overall trend remained consistent with that of E. coli, the inhibition efficiency decreased. This difference is attributed to structural differences in the cell walls of the two bacteria. E. coli, a Gram-positive bacterium, has a cell wall thickness of 20-80 nm; Staphylococcus aureus, a Gram-negative bacterium, has a relatively loose cell wall thickness of 10-15 nm. The cell walls of the two bacteria are disrupted by the natural antibacterial blend, but these differences in cell wall structure can have different effects on the membrane's antibacterial efficacy.

[0037] The natural mixed antibacterial agent selected in the present invention is a solution of a combination of baicalin, chlorogenic acid and emodin. The synergistic antibacterial principle of the natural mixed antibacterial agent is: 1. The combination of chlorogenic acid and emodin can more effectively destroy the integrity of bacteria. 2. Baicalin and emodin can jointly interfere with the nucleic acid metabolism and protein synthesis of bacteria. Therefore, the prepared composite antibacterial membrane has excellent antibacterial properties. After multiple experiments, taking into account the water flux, retention rate and antibacterial properties of the membrane, the M10 membrane is the best membrane choice for the present invention. Its antibacterial rates against Escherichia coli and Staphylococcus aureus are 85.61% and 79.75%, respectively, achieving a synergistic effect of anti-adhesion and killing bacteria.

[0038] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing an antibacterial ultrafiltration membrane for use in MBR sewage treatment, characterized by: The steps include: S1: pre-treating the ultrafiltration membrane; S2: placing the pretreated ultrafiltration membrane on a filtration device, pouring the polymerized dopamine solution into the funnel of the filtration device, turning on the filtration pump, and after the filtration process is completed, washing the membrane surface with deionized water and drying it to obtain a modified ultrafiltration membrane; S3: completely soaking the modified ultrafiltration membrane obtained in step S2 with an antibacterial agent solution, and drying the membrane to obtain an antibacterial ultrafiltration membrane.

2. The method for preparing an antibacterial ultrafiltration membrane for use in MBR sewage treatment according to claim 1, wherein: The ultrafiltration membrane in step S1 is one of PVDF membrane, PVC membrane, PAN membrane, PP membrane, PES membrane, PTFE membrane and PS membrane.

3. The method for preparing an antibacterial ultrafiltration membrane for use in MBR sewage treatment according to claim 1, wherein: The pretreatment in step S1 includes soaking the ultrafiltration membrane in deionized water, washing it with deionized water, and then drying it for storage; The soaking time is 20-28h.

4. The method for preparing an antibacterial ultrafiltration membrane for use in MBR sewage treatment according to claim 1, wherein: The preparation of the polymerized dopamine solution in step S2 includes adding the dopamine solution buffer solution to the buffer solution, stirring magnetically for 8-12 minutes at 20-30°C, and ultrasonically dispersing for 8-12 minutes at room temperature. The buffer solution is a Tris-HCl buffer solution with a pH of 8-9; The concentration of the polymerized dopamine solution is 0.4-0.6 mg·mL -1 ; Dopamine solution and buffer solution.

5. The method for preparing an antibacterial ultrafiltration membrane for use in MBR sewage treatment according to claim 1, wherein: The drying temperature in step S2 is 55-65° C., and the drying time is 5-7 hours.

6. The method for preparing an antibacterial ultrafiltration membrane for use in MBR sewage treatment according to claim 1, wherein: The bacteriostatic solution comprises placing the bacteriostatic agent into an ethanol solution; The antibacterial agent in step S3 includes one or more of baicalin, chlorogenic acid and emodin.

7. The method for preparing an antibacterial ultrafiltration membrane for use in MBR sewage treatment according to claim 6, wherein: The antibacterial agents in step S3 are baicalin, chlorogenic acid and emodin; The mass ratio of baicalin / chlorogenic acid / emodin is (0~2):(0~2):(0~2); Preferably, the mass ratio of baicalin / chlorogenic acid / emodin is 2:2:

2.

8. The method for preparing an antibacterial ultrafiltration membrane for use in MBR sewage treatment according to claim 1, wherein: The soaking time in step S3 is 25-35 minutes; The temperature of the oven in step S3 is 55-65° C. and the time is 11-13 hours.

9. An antibacterial ultrafiltration membrane prepared by the method for preparing an antibacterial ultrafiltration membrane for MBR wastewater treatment according to any one of claims 1 to 8.

10. The method for preparing an antibacterial ultrafiltration membrane for MBR wastewater treatment according to any one of claims 1 to 8, wherein the antibacterial ultrafiltration membrane prepared is used for MBR wastewater treatment.

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