A hydrogel promoting phase inversion film and a patterning, hydrophilic and antibacterial functionalization preparation method and application thereof

Abstract

This invention discloses a hydrogel-promoted phase inversion membrane and its patterning, hydrophilic antibacterial functionalization preparation method and application, relating to the field of materials technology. This invention provides a hydrogel-promoted phase inversion (HFPS) ​​membrane, utilizing a hydrogel template to replace the water bath in traditional non-solvent-induced phase separation (NIPS). By controlling the hydrogel surface pattern and altering the hydrogel temperature, its internal network structure and solvent / non-solvent diffusion behavior are regulated, thereby controlling the phase inversion kinetics and achieving patterned construction of the membrane surface and adjustment of membrane pore size distribution, molecular weight cutoff, and water flux. Furthermore, by leveraging the triple mechanism of slow phase separation kinetics in HFPS (extending the migration time of the segregating agent), interfacial physical constraints (preventing segregating agent loss), and gravity-assisted segregation (promoting surface enrichment), uniform and high-coverage enrichment of hydrophilic additives (tannic acid / polyvinylpyrrolidone) is achieved on the membrane surface, and silver ions are anchored and reduced to nano-silver particles, thus constructing a hydrophilic antibacterial functional layer on the membrane surface.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, specifically relating to a hydrogel-promoted phase inversion membrane and its patterning, hydrophilic antibacterial functionalization preparation method and application. Background Technology

[0002] Membrane separation technology is widely used in water treatment, biomedicine, and other fields, but its operational efficiency is severely limited by membrane fouling. Membrane fouling, caused by the deposition of organic matter, inorganic matter, and microorganisms on the membrane surface or blockage within the membrane pores, leads to decreased membrane flux, deteriorated separation performance, increased operating costs, and even shortened membrane lifespan. To mitigate membrane fouling, researchers are mainly conducting research and technological development in two directions: physical construction (surface patterning) and chemical modification (surface modification).

[0003] In terms of physical construction, patterned membrane fabrication technology improves the hydrodynamic properties of the membrane surface by introducing patterned structures, and inhibits pollutant deposition by enhancing local shear stress and inducing vortices. Currently, the main methods for patterned membrane fabrication include: ① Phase separation microplasticity method: Fine templates are prepared using photolithography, and then a casting solution is coated onto the template surface to replicate the pattern. However, the average pore size of the membrane obtained by this method is relatively large (0.89-0.91 μm), making it difficult to effectively retain small-sized pollutants such as proteins, thus limiting its application. ② Nanoimprint lithography method: Patterns are directly replicated onto the membrane surface using a mold under high temperature and pressure. However, this method easily damages the internal pore structure of the membrane, leading to a decrease in water flux. ③ Surface printing method: Patterns are constructed on the membrane surface through 3D printing or inkjet printing. However, the equipment cost is high, the fabrication speed is slow, and it is difficult to scale up applications. In contrast, the hydrogel-induced phase inversion (HFPS) ​​method (④) uses a high-water-content hydrogel as a pattern template, replacing the coagulation bath in the solvent-induced phase separation process with a hydrogel. Patterned membranes are prepared directly during the phase inversion process, offering advantages such as simplicity, speed, and ease of implementation, thus possessing significant application potential. However, patterned membranes prepared by the existing HFPS method suffer from problems such as large pore size (30-90 nm) and low retention rates (less than 20% retention for 500 kDa dextran and only about 40% for polyethylene glycol), making it difficult to control the membrane structure and surface functional layers for specific separation requirements.

[0004] In terms of chemical modification, surface segregation modification technology is a highly efficient in-situ modification method for membrane surfaces. Its principle involves incorporating additives containing hydrophilic segments into the casting solution. These additives spontaneously migrate towards the membrane / water interface during phase inversion, reducing interfacial free energy and forming a hydrophilic functional layer on the membrane surface. However, in traditional non-solvent-induced phase separation (NIPS) processes, the rapid and difficult-to-control phase inversion rate presents a dilemma for surface segregating agents: on the one hand, if the migration rate is insufficient, the polymer network quickly solidifies, trapping the segregating agent within the membrane matrix, resulting in "under-segregation" and low surface functional layer coverage; on the other hand, if the segregating agent is too hydrophilic, it easily diffuses directly into the coagulation bath and is lost, resulting in "over-segregation," wasting functional materials and causing uneven surface distribution. Therefore, traditional NIPS methods struggle to form a uniform, continuous, and stable functional layer on the membrane surface, weakening the expected antifouling effect.

[0005] In summary, relying solely on patterned structures to improve hydrodynamic properties can only passively alleviate pollutant deposition to a certain extent, and its resistance to highly adhesive biological contaminants (such as bacteria and biofilms) is insufficient. Furthermore, existing surface segregation techniques struggle to form uniform functional layers. Currently, there is no systematic technical solution that integrates HFPS-based patterned films, temperature control, surface segregation, and antibacterial modification. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a hydrogel-promoted phase inversion membrane and its patterning, hydrophilic antibacterial functionalization preparation method and application.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for preparing a hydrogel-promoted phase transformation membrane, comprising the following steps: S1. Pour the hydrogel solution into the mold and solidify to form a hydrogel template; S2. Control the temperature of the hydrogel template to obtain a hydrogel template with a temperature of 10-30℃; S3 Place the casting solution on the surface of the hydrogel template at a temperature of 10-30℃, use a scraper to form a film, and after the liquid on the film surface has completely solidified, remove the film and immerse it in water to obtain the hydrogel-promoted phase inversion membrane. This invention selects agar hydrogels with temperatures ranging from 10 to 30°C as templates based on the temperature dependence of their gelation behavior and mechanical properties. Specifically, when the temperature is above 30°C, the cross-linking density of the agar gel network decreases significantly, leading to incomplete gelation or difficulty in solidification. Simultaneously, the mechanical strength of the hydrogel decreases substantially, making it difficult to maintain the structural stability and dimensional fidelity required for use as a template. Conversely, when the temperature is below 10°C, the agar hydrogel undergoes significant volume shrinkage, which compromises the structural accuracy of the template and is detrimental to the subsequent preparation of patterned films.

[0008] Through extensive experimentation, the inventors of this application discovered that by employing the hydrogel-promoted phase inversion membrane preparation method of this invention and controlling the hydrogel template temperature to 10-30℃, it is possible to regulate its internal network structure and solvent / non-solvent diffusion behavior, thereby controlling the phase inversion kinetics and achieving directional adjustment of membrane pore size, pore size distribution, molecular weight cutoff, and water flux. Furthermore, combining the HFPS method with surface segregation technology achieves the following synergistic effects: slow phase separation kinetics provide sufficient migration time for the segregating agent; interfacial physical constraints prevent segregating agent loss; and gravity-assisted segregation promotes surface enrichment. These three factors work together to construct a uniform, continuous, and highly covered hydrophilic functional layer on the membrane surface. As a preferred embodiment of the preparation method described in this invention, the hydrogel solution comprises a hydrogel monomer, a crosslinking agent, an initiator, and water.

[0009] Preferably, the concentration of the hydrogel monomer is 1.0-10.0%, the concentration of the crosslinking agent is 0-5.0%, and the concentration of the initiator is 0-1.0%.

[0010] As a preferred embodiment of the preparation method of the present invention, it includes at least one of the following (a)-(c): (a) The hydrogel monomer is one or more of agar, gelatin, sodium alginate, chitosan, polyacrylamide, polyvinyl alcohol, sodium polyacrylate, and acrylate. (b) The crosslinking agent is one or more of polyvinyl alcohol, sodium carboxymethyl cellulose, ethylene glycol dicarboxylic acid, polyoxymethylene alcohol, calcium chloride, and calcium carbonate; (c) The initiator includes lithium phenyl-2,4,6-trimethylbenzoylphosphinate, ammonium persulfate, Irgacure 184, and Irgacure 2959.

[0011] As a preferred embodiment of the preparation method described in this invention, the casting solution comprises 10-20% polymer, 0-40% additives, and 40-90% solvent by mass percentage.

[0012] As a preferred embodiment of the preparation method of the present invention, it includes at least one of the following (a)-(c): (a) The polymer includes at least one of polyethersulfone, polyvinylidene fluoride, polysulfone, and cellulose acetate; (b) The additives include one or more of polyethylene glycol, glycerol, isobutanol, polyvinylpyrrolidone (PVP), and tannic acid (TA); (c) The solvent includes one or more of N'N-dimethylacetamide, N'N-dimethylformamide, N-methylpyrrolidone, and dimethyl sulfoxide.

[0013] As a preferred embodiment of the preparation method of the present invention, the preparation method further includes step S4: immersing the hydrogel-promoted phase inversion membrane obtained in step S3 in silver nitrate solution to obtain a nano-silver modified antibacterial membrane.

[0014] Preferably, the concentration of the silver nitrate solution is 0-60 mM, and the soaking time is 0-24 h.

[0015] In a preferred embodiment of the preparation method of the present invention, the thickness of the film formed by the doctor blade in step S3 is 100-400 μm; the drying time is 1-10 min; and the soaking time is 24-48 h.

[0016] As a preferred embodiment of the preparation method of the present invention, the mold shape in step S1 includes trapezoidal columnar, prismatic, and cylindrical.

[0017] Preferably, the mold in step S1 is trapezoidal columnar in shape.

[0018] More preferably, the trapezoidal columnar pattern includes a small-sized trapezoidal columnar pattern with an upper base × lower base × height of 100 × 200 × 100 μm or a large-sized trapezoidal columnar pattern with an upper base × lower base × height of 200 × 400 × 200 μm, and the center-to-center distance of the pattern is about 500 μm.

[0019] The present invention also provides a hydrogel-promoted phase transformation membrane prepared by the preparation method described above.

[0020] The present invention also provides the application of the hydrogel-promoted phase transformation membrane in the field of water treatment.

[0021] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a hydrogel-promoted phase inversion membrane and its patterning and hydrophilic antibacterial functionalization preparation method, which has the following advantages: (1) It solves the problem of poor separation performance of patterned membranes prepared by the existing HFPS method. By adjusting the temperature of the hydrogel, the pore size of the membrane surface can be directionally adjusted (average pore size adjusted from 7.95 nm to 4.00 nm) and the molecular weight cutoff can be adjusted (from 372.5 kDa to 57.8 kDa). While maintaining a high water flux (918-1177 LMH / bar), the retention performance is significantly improved (the retention rate of bovine serum albumin (BSA) is increased from 65% to over 99.5%). (2) The problem of uneven distribution of functional layers in traditional NIPS surface segregation technology has been solved. By utilizing the triple mechanism of hydrogel-driven slow phase separation kinetics, interfacial physical constraints and gravity-assisted segregation, the uniform enrichment of hydrophilic additives on the membrane surface is achieved; (3) Synergistic antifouling effect of patterning and antibacterial modification was achieved. Antifouling patterns were replicated on the surface of temperature-controlled HFPS membranes to significantly inhibit pollutant deposition. Silver ions were anchored and reduced in situ using a uniform hydrophilic functional layer on the membrane surface to form uniformly distributed silver nanoparticles (AgNPs), which endowed the membrane with long-lasting and stable antibacterial and antifouling capabilities. Attached Figure Description

[0022] Figure 1 The images are scanning electron microscope (SEM) images, where a is an SEM image of the patternless planar membrane prepared in Comparative Example 1; b is an SEM image of the 25℃ hydrogel-controlled patternless planar membrane prepared in Example 2; c is an SEM image of the patternless planar membrane prepared in Example 3; d is an SEM image of the patternless planar membrane prepared in Example 4; e is an SEM image of the patternless planar membrane prepared in Example 5; and f is an SEM image of the patterned membrane prepared in Example 6.

[0023] Figure 2 The graph shows the test results of pure water flux and rejection rate. In the graph, NIPS corresponds to the patternless planar membrane prepared in Example 1; HFPS-25 corresponds to the patternless planar membrane prepared in Example 2; HFPS-25 corresponds to the patternless planar membrane prepared in Example 3; HFPS-15 corresponds to the patternless planar membrane prepared in Example 4; HFPS-10 corresponds to the patternless planar membrane prepared in Example 5; and HFPS-10-P corresponds to the patterned membrane prepared in Example 6.

[0024] Figure 3 The graph shows the results of the antifouling performance test. HFPS-10 corresponds to the unpatterned planar membrane prepared in Example 5, and HFPS-10-P corresponds to the patterned membrane prepared in Example 6.

[0025] Figure 4 This is a schematic diagram of the membrane surface pattern and a scanning electron microscope image.

[0026] Figure 5 The images are scanning electron microscope images of the membranes prepared in Comparative Examples 2 and 3, and Examples 7 and 8. N-4TAP corresponds to the non-solvent-induced phase separation hydrophilic modified membrane prepared in Comparative Example 2; N-4TAP-40Ag corresponds to the conventional non-solvent-induced phase separation hydrophilic antibacterial modified membrane prepared in Comparative Example 3; H-4TAP corresponds to the hydrogel-promoted phase inversion patternless planar membrane prepared in Example 7; and H-4TAP-40Ag corresponds to the hydrogel-promoted phase inversion patternless planar membrane prepared in Example 8.

[0027] Figure 6 Scanning electron microscope images of the membranes prepared in Comparative Examples 2 and 3, and Examples 7 and 8.

[0028] Figure 7The graph shows the test results of pure water flux and rejection rate for comparative examples 2 and 3, and examples 7, 8 and 9.

[0029] Figure 8 The figures show the static antibacterial ability test results for Comparative Examples 2 and 3, and Examples 7 and 8. N-4TAP corresponds to the non-solvent-induced phase separation hydrophilic modified membrane prepared in Comparative Example 2; N-4TAP-40Ag corresponds to the conventional non-solvent-induced phase separation hydrophilic antibacterial modified membrane prepared in Comparative Example 3; H-4TAP corresponds to the hydrogel-promoted phase inversion patternless planar membrane prepared in Example 7; and H-4TAP-40Ag corresponds to the hydrogel-promoted phase inversion patternless planar membrane prepared in Example 8.

[0030] Figure 9 The figures show the dynamic antibacterial ability test results for Comparative Examples 2 and 3, and Examples 7, 8, and 9. N-4TAP corresponds to the non-solvent-induced phase separation hydrophilic modified membrane prepared in Example 2; N-4TAP-40Ag corresponds to the conventional non-solvent-induced phase separation hydrophilic antibacterial modified membrane prepared in Example 3; H-4TAP corresponds to the hydrogel-promoted phase inversion patternless planar membrane prepared in Example 7; H-4TAP-40Ag corresponds to the hydrogel-promoted phase inversion patternless planar membrane prepared in Example 8; and HP-4TAP-40Ag corresponds to the hydrogel-promoted phase inversion patterned membrane prepared in Example 9. Detailed Implementation

[0031] The following detailed embodiments further illustrate the above-described content of the present invention. However, this should not be construed as limiting the scope of the present invention to the following embodiments. Unless otherwise specified, the experimental methods used in the embodiments are conventional methods, and the materials and reagents used are commercially available.

[0032] Example 1 This embodiment provides a method for preparing a patternless planar membrane that promotes phase transformation using hydrogel, comprising the following steps: (1) Based on the mass percentage of the casting solution, weigh 18% polyethersulfone, 20% polyethylene glycol 400 and 62% N'N-dimethylacetamide, mix them, heat and stir at 80°C for 12 h, let stand to remove air bubbles, and obtain the casting solution. (2) Mix agar and water in a mass ratio of 5:95, heat to boiling, let stand for 15 min to remove air bubbles to obtain agar hydrogel solution, pour the agar hydrogel solution into a patternless template, wait 30 min to solidify, and obtain a patternless hydrogel template. (3) Take out the patternless hydrogel template and place it in a temperature control device until the temperature of the patternless hydrogel template reaches 30°C; (4) Dry the surface moisture of the patternless hydrogel template, place the casting liquid on the surface of the patternless hydrogel template, form a film with a scraper, and after the liquid on the surface of the film is completely dry, remove the film and soak it in water to obtain the patternless planar film.

[0033] Example 2 This embodiment provides a method for preparing a patternless planar membrane that promotes phase transformation using hydrogel. The difference between this method and that of Embodiment 1 is only in step (3). Specifically, step (3) of this embodiment is: take out the patternless hydrogel template and place it in a temperature control device until the temperature of the patternless hydrogel template reaches 25°C.

[0034] Example 3 This embodiment provides a method for preparing a patternless planar membrane that promotes phase transformation using hydrogel. The difference between this method and that of Embodiment 1 is only in step (3). Specifically, step (3) of this embodiment is: take out the patternless hydrogel template and place it in a temperature control device until the temperature of the patternless hydrogel template reaches 20°C.

[0035] Example 4 This embodiment provides a method for preparing a patternless planar membrane that promotes phase transformation using hydrogel. The difference between this method and that of Embodiment 1 is only in step (3). Specifically, step (3) of this embodiment is: take out the patternless hydrogel template and place it in a temperature control device until the temperature of the patternless hydrogel template reaches 15°C.

[0036] Example 5 This embodiment provides a method for preparing a patternless planar membrane that promotes phase transformation using hydrogel. The difference between this method and that of Embodiment 1 is only in step (3). Specifically, step (3) of this embodiment is: take out the patternless hydrogel template and place it in a temperature control device until the temperature of the patternless hydrogel template reaches 10°C.

[0037] Example 6 This embodiment provides a method for preparing a hydrogel-promoted phase transformation patterned film, comprising the following steps: (1) Based on the mass percentage of the casting solution, weigh 18% polyethersulfone, 20% polyethylene glycol 400 and 62% N'N-dimethylacetamide, mix them, heat and stir at 80°C for 12 h, let stand to remove air bubbles, and obtain the casting solution. (2) Mix agar and water in a mass ratio of 5:95, heat to boiling, and let stand for 15 minutes to remove air bubbles to obtain an agar hydrogel solution. Pour the agar hydrogel solution into a trapezoidal pattern template with a cross-section of 200*400*200 μm and a spacing of about 500 μm. Figure 4 In the process of curing, wait 30 minutes to obtain the patterned hydrogel template; (3) Take out the patterned hydrogel template and place it in a temperature control device until the temperature of the patternless hydrogel template reaches 10°C; (4) Dry the surface moisture of the unpatterned hydrogel template, place the casting liquid on the surface of the patterned hydrogel template, form a film with a scraper, and after the liquid on the surface of the film is completely dry, remove the film and soak it in water to obtain the patterned film.

[0038] Example 7 This embodiment provides a method for preparing a patternless planar membrane that promotes phase transformation using hydrogel, comprising the following steps: (1) Based on the mass percentage of the casting solution, weigh 18% polyethersulfone, 15% polyethylene glycol 400, 0.4% polyvinylpyrrolidone, 0.8% tannic acid and 65.8% N'N-dimethylacetamide, mix them, heat and stir at 80°C for 12 h, let stand to remove air bubbles, and obtain the casting solution. (2) Mix agar and water in a mass ratio of 5:95, heat to boiling, let stand for 15 min to remove air bubbles to obtain agar hydrogel solution, pour the agar hydrogel solution into a patternless template, wait 30 min to solidify, and obtain a patternless hydrogel template. (3) Take out the patternless hydrogel template and place it in a temperature control device until the temperature of the patternless hydrogel template is 10℃; (4) Dry the surface moisture of the patternless hydrogel template, place the casting liquid on the surface of the patternless hydrogel template, form a film with a scraper, and after the liquid on the surface of the film is completely dry, remove the film and soak it in water to obtain the patternless planar film.

[0039] Example 8 This embodiment provides a method for preparing a patternless planar membrane that promotes phase transformation using hydrogel, comprising the following steps: (1) Based on the mass percentage of the casting solution, weigh 18% polyethersulfone, 15% polyethylene glycol 400, 0.4% polyvinylpyrrolidone, 0.8% tannic acid and 65.8% N'N-dimethylacetamide, mix them, heat and stir at 80°C for 12 h, let stand to remove air bubbles, and obtain the casting solution. (2) Mix agar and water in a mass ratio of 5:95, heat to boiling, let stand for 15 min to remove air bubbles, pour the above agar hydrogel solution into the patternless template, wait 30 min to solidify, and obtain the patternless hydrogel template. (3) Take out the patternless hydrogel template and place it in a temperature control device until the temperature of the patternless hydrogel template is 10℃; (4) Dry the surface moisture of the patternless hydrogel template, place the casting liquid on the surface of the patternless hydrogel template, and form a film with a scraper. After the liquid on the surface of the film is completely dry, remove the film and soak it in water to obtain a patternless planar film. (5) The patternless planar membrane is placed in a 40 mM silver nitrate solution and soaked for 12 h. After soaking, the surface is cleaned 3-4 times to obtain the patternless planar membrane.

[0040] Example 9 This embodiment provides a method for preparing a hydrogel-promoted phase transformation patterned film, including the following steps: (1) Based on the mass percentage of the casting solution, weigh 18% polyethersulfone, 15% polyethylene glycol 400, 0.4% polyvinylpyrrolidone, 0.8% tannic acid and 65.8% N'N-dimethylacetamide, mix them, heat and stir at 80°C for 12 h, let stand to remove air bubbles, and obtain the casting solution. (2) Mix agar and water in a mass ratio of 5:95, heat to boiling, let stand for 15 min to remove air bubbles, and then pour the above agar hydrogel solution into a trapezoidal pattern template with a cross-section of 200*400*200μm and a spacing of 500μm. Figure 4 In the process of curing, wait 30 minutes to obtain the patterned hydrogel template; (3) Take out the patterned hydrogel template and place it in a temperature control device until the temperature of the patterned hydrogel template is 10℃; (4) Dry the surface of the patterned hydrogel template, place the casting liquid on the surface of the patterned hydrogel template, and form a film with a scraper. After the liquid on the surface of the film is completely dry, remove the film and soak it in water to obtain a patterned film. (5) The patterned film is placed in a 40 mM silver nitrate solution and soaked for 12 h. After soaking, the surface is cleaned 3-4 times to obtain the patterned film.

[0041] Comparative Example 1 This comparative example provides a conventional method for preparing a non-solvent-induced phase separation membrane, which is a patternless planar membrane, comprising the following steps: (1) Based on the mass percentage of the casting solution, weigh 18% polyethersulfone, 20% polyethylene glycol 400 and 62% N'N-dimethylacetamide, mix them, heat and stir at 80°C for 12 h, let stand to remove air bubbles, and obtain the casting solution. (2) Place the casting solution on a smooth glass plate, scrape the film with a 200 μm doctor blade, place the glass plate together with the film layer in deionized water, and after the film is formed and cured and automatically detaches from the glass plate, continue to soak for 24 h to obtain the non-solvent phase separation membrane.

[0042] Comparative Example 2 This comparative example provides a method for preparing a non-solvent-induced phase separation hydrophilic modified membrane, which is a patternless planar membrane, including the following steps: (1) Based on the mass percentage of the casting solution, weigh 18% polyethersulfone, 15% polyethylene glycol 400, 0.4% polyvinylpyrrolidone, 0.8% tannic acid and 65.8% N'N-dimethylacetamide, mix them, heat and stir at 80°C for 12 h, let stand to remove air bubbles, and obtain the casting solution. (2) Place the casting solution on a smooth glass plate, scrape the film with a 200 μm doctor blade, place the glass plate along with the film layer in deionized water, and after the film is formed and cured and automatically detaches from the glass plate, continue to soak for 24 h to obtain a non-solvent phase separation hydrophilic modified film.

[0043] Comparative Example 3 This comparative example provides a traditional method for preparing a non-solvent-induced phase separation hydrophilic antibacterial modified membrane, which is a patternless planar membrane, including the following steps: (1) Weigh 18% polyethersulfone, 15% polyethylene glycol 400, 0.4% polyvinylpyrrolidone, 0.8% tannic acid and 65.8% N'N-dimethylacetamide according to the mass percentage of casting solution, mix them, heat and stir at 80°C for 12 h, and let stand to remove air bubbles.

[0044] (2) Place the casting solution on a smooth glass plate, scrape the film with a 200 μm doctor blade, place the glass plate along with the film layer in deionized water, and after the film is formed and cured and automatically detaches from the glass plate, continue to soak for 24 h to obtain a hydrophilic modified patternless planar film. (3) The above membrane is placed in 40 mM silver nitrate solution and soaked for 12 h. After soaking, the membrane is taken out and the surface is cleaned 3-4 times to obtain the non-solvent phase separation hydrophilic antibacterial modified membrane.

[0045] Example of effect The membranes prepared in Examples 1-8 and Comparative Examples 1-3 were characterized and their performance tested, as detailed below: 1. Observation using a scanning electron microscope.

[0046] 2. Pure water flux test: The pure water flux of the membrane is evaluated by measuring the volume of the filtrate after filtration at 0.1 MPa (25℃) for 30 min using a dead-end filter. Before the experiment, the membrane is pre-pressurized at 0.15 MPa (25℃) for 30 min.

[0047] The formula for calculating pure water flux is: Jw = V / A*t. In the formula, Jw is the pure water flux, V (L) is the permeate flow rate, A (m2) is the effective membrane area, and t (h) is the test time.

[0048] 3. Retention rate test: Using a 1 g / L bovine serum albumin solution as the filtrate, the membrane was filtered for 30 min at 0.1 MPa (25℃) using a dead-end filter. The concentration of bovine serum albumin before and after filtration was measured at a wavelength of 280 nm using a UV spectrophotometer, and the membrane retention rate was calculated.

[0049] The retention rate is calculated using the formula: R = 1 - Cp / Cf * 100%. In the formula, R is the retention rate, and Cp and Cf (mg·L⁻¹) are the concentrations of bovine serum albumin solution in the filtrate and feed solution, respectively.

[0050] 4. Anti-pollution ability test: Using a 1 g / L bovine serum albumin solution as the filtrate, 200 mL of filtrate was filtered using a cross-flow filtration device at a flow rate of 0.5 m / s under 0.1 MPa (25℃) conditions. Then, it was rinsed with pure water at a flow rate of 0.8 m / s, and the cycle was repeated 3 times. The real-time throughput J of 10 mL of filtrate was calculated.

[0051] The formula for calculating the flux decline rate is: J / J0 = J / J0*100%. In the formula, J / J0 is the flux decline rate, J is the real-time flux per 10 mL of filtrate filtered, and J0 is the initial flux.

[0052] 5. Antibacterial activity test: Antibacterial tests were conducted using Staphylococcus aureus and Escherichia coli. All strains were first incubated in LB broth at 37°C with shaking at 150 rpm for 24 hours before collection. The bacterial suspension was diluted to the working bacterial concentration using PBS buffer (102). 7 CFU·mL⁻¹).

[0053] 6. Static antibacterial ability: First, spread the bacterial suspension evenly on the surface of an LB agar plate with a sterile cotton swab and let it stand for 10 minutes; then, cut the membrane sample into 1 cm diameter round pieces, sterilize them by ultraviolet irradiation for 15 minutes, and place them face down on the plate; finally, place the plate in a 37℃ incubator overnight and evaluate the antibacterial performance of the membrane by observing the inhibition zone.

[0054] 7. Dynamic Antibacterial Capability: First, the device was sterilized by filtration with 75% ethanol for 30 minutes, followed by rinsing with deionized water at 1.5 bar pressure. Then, 150 mL of E. coli suspension was filtered at 1 bar pressure for filtration testing. Flux decay was continuously monitored throughout the experiment, and the dynamic antibacterial performance of the membrane was evaluated using normalized flux (J / J0). After the test, the membrane was sequentially immersed in 2.5% (v / v) glutaraldehyde and 20% (v / v), 40% (v / v), 60% (v / v), 80% (v / v), and 100% (v / v) ethanol solutions for stabilization and dehydration. Finally, the surface morphology of the fouled membrane was observed using SEM.

[0055] The normalized flux (J / J0) is calculated using the formula: J / J0 = J / J0 * 100%. In the formula, J / J0 is the flux decrease rate, J is the real-time flux per 10 mL of filtrate filtered, and J0 is the initial flux.

[0056] The results are as follows: Figure 1 The scanning electron microscope images of Comparative Example 1 and Examples 2-6 show that the membranes prepared using the hydrogel-promoted phase separation method of the present invention (Examples 2-6) have larger pore sizes and more pores on their surface. As the temperature decreases, it is clearly observed that the pore size of the membranes prepared by the hydrogel-promoted phase separation method becomes smaller and more uniformly distributed. This indicates that the present invention successfully achieves temperature-directed control of the membrane surface pore size through hydrogel.

[0057] Figure 2 This is a comparison chart of the pure water flux and rejection rate for Example 1 and Examples 1-6. Compared with membranes prepared by conventional non-solvent-induced phase separation, the pure water flux of the membrane prepared by the hydrogel-promoted phase separation method of this invention is increased by 236%-302%, and the rejection rate can be improved by controlling the temperature. As the hydrogel temperature decreases, the pure water flux of the membrane decreases from 1177.00 LMH / bar to 918.45 LMH / bar, while the rejection rate of 1 g / L bovine serum albumin (BSA) solution increases from 67.53% to 99.39%, further confirming the feasibility of controlling the membrane surface pore size by hydrogel temperature. In particular, the patterned membrane prepared by the hydrogel-promoted phase separation method of this invention can maintain its original rejection performance while achieving a higher pure water flux after temperature control.

[0058] Figure 3 This is a comparison chart of the antifouling capabilities of Examples 5 and 6. Due to the successful addition of an antifouling pattern to the membrane surface, the antifouling performance of Example 5 was significantly superior to that of Example 5 without a pattern in all three cycles of antifouling tests, achieving both improved membrane separation performance and enhanced membrane surface antifouling capability.

[0059] Figure 5 , Figure 6 The images shown are scanning electron microscope (SEM) images and photographs of Comparative Examples 2 and 3, and Examples 7 and 8. Due to the introduction of the hydrophilic functional layer, Comparative Example 3 and Example 7 successfully generated nano-silver particles in situ on the membrane surface, and the nano-silver distribution on the surface of Example 8 was more dense and uniform. Figure 5 It can also be visually observed that the distribution of yellow nano-silver on the surface of Comparative Example 3 is uneven and exhibits obvious mottled patterns, while the surface nano-silver in Example 8 is significantly darker in color and more uniformly distributed. This demonstrates that the hydrogel-promoted phase separation method of the present invention can optimize the traditional surface segregation process and achieve a more uniform construction of the functional layer on the membrane surface.

[0060] Figure 7 The graphs show a comparison of the pure water flux and rejection rate for Comparative Examples 2 and 3, and Examples 7, 8, and 9. Compared with membranes prepared by traditional solvent-free phase separation, the membranes prepared by the hydrogel-promoted phase separation method of the present invention still have a significant advantage in pure water flux and can maintain a high BSA rejection rate.

[0061] Figure 8 The figures show a comparison of the static antibacterial capabilities of Comparative Examples 2 and 3, and Examples 7 and 8. It can be seen that Example 8 exhibits antibacterial effects against both Escherichia coli and Staphylococcus aureus, and possesses a significantly larger inhibition zone compared to Comparative Example 3, demonstrating that the antibacterial film prepared in this invention has a more effective antibacterial surface functional layer.

[0062] Figure 9 This is a comparison of the dynamic antibacterial activity of Comparative Examples 2 and 3, and Examples 7, 8, and 9. Figure 8 The results were consistent; Example 8 exhibited significantly stronger dynamic antibacterial properties compared to Comparative Example 3. After patterning, Example 9 showed an even stronger antibacterial effect.

[0063] Finally, it should be noted that the above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing a hydrogel-promoted phase transformation membrane, characterized in that, Includes the following steps: S1. Pour the hydrogel solution into the mold and solidify to form a hydrogel template; S2. Control the temperature of the hydrogel template to obtain a hydrogel template with a temperature of 10-30℃; S3. Place the casting solution on the surface of the hydrogel template at a temperature of 10-30℃, use a scraper to form a film, and after the liquid on the film surface has completely solidified, remove the film and immerse it in water to obtain the hydrogel-promoted phase inversion membrane.

2. The preparation method according to claim 1, characterized in that, The hydrogel solution comprises hydrogel monomers, crosslinking agents, initiators, and water.

3. The preparation method according to claim 2, characterized in that, Includes at least one of the following (a)-(c): (a) The hydrogel monomer is one or more of agar, gelatin, sodium alginate, chitosan, polyacrylamide, polyvinyl alcohol, sodium polyacrylate, and acrylate. (b) The crosslinking agent is one or more of polyvinyl alcohol, sodium carboxymethyl cellulose, ethylene glycol dicarboxylic acid, polyoxymethylene alcohol, calcium chloride, and calcium carbonate; (c) The initiator includes lithium phenyl-2,4,6-trimethylbenzoylphosphinate, ammonium persulfate, Irgacure 184, and Irgacure 2959.

4. The preparation method according to claim 1, characterized in that, The casting solution comprises 10-20% polymer, 0-40% additives, and 40-90% solvent by mass percentage.

5. The preparation method according to claim 4, characterized in that, Includes at least one of the following (a)-(c): (a) The polymer includes at least one of polyethersulfone, polyvinylidene fluoride, polysulfone, and cellulose acetate; (b) The additives include one or more of polyethylene glycol, glycerol, isobutanol, polyvinylpyrrolidone, and tannic acid; (c) The solvent includes one or more of N'N-dimethylacetamide, N'N-dimethylformamide, N-methylpyrrolidone, and dimethyl sulfoxide.

6. The preparation method according to claim 1, characterized in that, The preparation method further includes step S4: immersing the hydrogel-promoted phase inversion membrane obtained in step S3 in silver nitrate solution to obtain a nano-silver modified antibacterial functional membrane.

7. The preparation method according to claim 1, characterized in that, In step S3, the thickness of the film formed by the scraper is 100-400 μm; the curing time is 1-10 min; and the soaking time is 24-48 h.

8. The preparation method according to claim 1, characterized in that, The mold shape in step S1 includes trapezoidal columnar, prismatic, and cylindrical.

9. The hydrogel-promoted phase inversion membrane prepared by the preparation method according to any one of claims 1-8.

10. The application of the hydrogel-promoted phase inversion membrane according to claim 9 in the field of water treatment.

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