A kind of silver chloride / silver-polyvinylidene fluoride nanofiber membrane based on biphenyl tetracarboxylic acid functionalization and its preparation method and application

Abstract

The application discloses a kind of silver chloride / silver-polyvinylidene fluoride nanofiber membrane based on biphenyl tetracarboxylic acid functionalization and its preparation method and application.The nanofiber membrane includes PVDF nanofiber matrix, BPTC uniformly distributed therein, and Ag / AgCl heterojunction nanoparticles in-situ generated and stably loaded on the matrix by carboxyl coordination of BPTC.The nanofiber membrane has three-dimensional network structure, high specific surface area, uniform fiber diameter and nanoparticle distribution, and has excellent water flux and antibiofouling performance.Under light conditions, the nanofiber membrane realizes multiple antibacterial mechanisms through photo-generated hole oxidation, active oxygen species attack and silver ion release, with an antibacterial rate of up to 99.999%, and the antibacterial activity still remains above 90% after 5 cycles of use.The preparation process of the application is green and environmentally friendly, and the raw materials are easy to obtain, suitable for membrane separation and antibacterial applications in the field of water treatment.

Description

Technical Field

[0001] This invention relates to a silver chloride / silver-polyvinylidene fluoride nanofiber membrane based on biphenyltetracarboxylic acid functionalization, its preparation method and application, belonging to the field of environmental science and engineering. Background Technology

[0002] With the increasing severity of global water scarcity, membrane separation technology has broad application prospects in the water treatment field due to its high efficiency and energy-saving characteristics. However, biofouling has always been a major bottleneck restricting the development of this technology, causing not only a 15%-50% increase in energy consumption but also significantly increasing system maintenance costs. Although chemical cleaning and other methods are commonly used to address membrane fouling, these methods are not only limited in effectiveness but may also damage the membrane materials themselves. Therefore, developing separation membrane materials with long-lasting antibacterial functions is of significant practical importance. Among existing antibacterial membrane materials, products based on silver-based bactericides (such as AgNPs) occupy the main market share, but they suffer from problems such as easy agglomeration of nanoparticles and uncontrollable release of silver ions during use, and more seriously, may lead to bacterial resistance. In contrast, heterojunction photocatalytic materials such as Ag / AgCl show better application prospects due to their unique multiple bactericidal mechanisms (including photogenerated hole oxidation, reactive oxygen species (ROS) attack, and controllable release of silver ions). However, the uniform and stable loading of such materials in a polymer matrix remains a technical challenge that urgently needs to be solved.

[0003] As an ideal membrane material, polyvinylidene fluoride (PVDF) has been widely used due to its excellent chemical stability, mechanical properties, and film-forming characteristics. However, its strong hydrophobicity makes it susceptible to organic contamination. Electrospinning technology has made it possible to prepare high-performance PVDF nanofiber membranes. This technology can obtain fiber structures with high specific surface area and high porosity, which creates favorable conditions for loading functional nanomaterials. However, existing modification methods, such as blending and grafting, face problems in practical applications such as uneven nanoparticle dispersion, insufficient binding force, and difficulty in ensuring long-term effectiveness. In summary, the current membrane separation technology field mainly suffers from three technical defects: First, traditional antibacterial membranes rely on a single bactericidal mechanism (such as Ag). + Firstly, the release of PVDF membranes can easily lead to bacterial resistance and cause nanoparticles to aggregate and become inactive. Secondly, the long-term antifouling performance of PVDF membranes is often affected by insufficient hydrophobicity control and functional stability during the modification process. Finally, although heterojunction photocatalytic materials have obvious advantages, the complex loading process makes it difficult to achieve uniform dispersion and maintain activity of these materials in the polymer matrix.

[0004] To address the aforementioned technical challenges, this invention aims to use biphenyl tetracarboxylic acid (BPTC) as a stabilizer and optimize electrospinning process parameters to provide a novel PVDF composite nanofiber membrane with multiple antibacterial mechanisms, offering a new solution to the existing technical problems. Summary of the Invention

[0005] The purpose of this invention is to provide a silver chloride / silver-polyvinylidene fluoride nanofiber membrane based on biphenyltetracarboxylic acid functionalization, which is prepared by electrospinning technology.

[0006] The composite membrane of this invention uses BPTC as a stabilizer. A PVDF nanofiber matrix is ​​constructed via electrospinning, forming uniformly dispersed Ag / AgCl heterojunctions in situ. Under natural light, the coordination effect of BPTC stabilizes the Ag / AgCl nanoparticles and promotes photogenerated electron transfer, causing partial reduction of AgCl to Ag to form the Ag / AgCl heterojunction. This process generates free radicals (·OH, O₂). 2- (etc.) and release Ag + It achieves a dual antibacterial mechanism, with an antibacterial rate of over 99%.

[0007] The preparation method provided by this invention uses readily available raw materials and is environmentally friendly. It can be mass-produced using mature electrospinning equipment. The product has excellent water treatment throughput and maintains more than 90% antibacterial activity after 5 cycles.

[0008] Specifically, the biphenyltetracarboxylic acid-functionalized silver chloride / silver-polyvinylidene fluoride nanofiber membrane provided by the present invention includes a PVDF nanofiber matrix, BPTC uniformly distributed in the PVDF nanofiber matrix, and Ag / AgCl heterojunction nanoparticles generated in situ and stably loaded on the PVDF nanofiber matrix through the carboxyl coordination of the BPTC.

[0009] Preferably, in the nanofiber membrane, the mass fraction of the PVDF nanofiber matrix is ​​10-12%; the mass fraction of the BPTC is 0.5-1%; and the loading of the Ag / AgCl heterojunction nanoparticles is controlled by the concentration of the silver nitrate solution, which is 500-2000 ppm.

[0010] Preferably, the nanofiber membrane has a three-dimensional network structure with uniform fiber diameter, and the Ag / AgCl heterojunction nanoparticles loaded on the surface have uniform particle size and no agglomeration.

[0011] The present invention also provides a method for preparing the nanofiber membrane, comprising the following steps: S1. Preparation of casting solution: Mix PVDF, BPTC, NaCl and solvent to form a homogeneous PVDF / BPTC / NaCl blend solution as the casting solution. S2, electrospinning: electrospinning the casting solution obtained in step S1 and collecting the fiber membrane; S3. Heat treatment: The fiber membrane obtained in step S2 is subjected to heat treatment to obtain a PVDF / BPTC nanofiber membrane. S4. Photoreduction: The PVDF / BPTC nanofiber membrane after heat treatment in step S3 is immersed in AgNO3 solution and subjected to in-situ reduction reaction under light irradiation to form Ag / AgCl heterojunction, and finally the nanofiber membrane is obtained.

[0012] In the above preparation method, in step S1, the solvent is a mixed solvent of dimethylformamide and acetone, with a volume ratio of 7-5:3-5; The preparation process of the casting solution includes the following steps: Mix PVDF powder with solvent and stir at 500-1000 rpm for 2-3 hours at 60-80℃; then add BPTC and NaCl and continue stirring at the same temperature and stirring speed for 8-10 hours; finally, degas by ultrasonic treatment for 15-30 minutes.

[0013] More preferably, the process for preparing the casting solution is as follows: First, accurately weigh the PVDF raw material and slowly pour it into a quartz glass container already containing the rotor. Then, add BPTC and NaCl sequentially. A pre-mixed dimethylformamide-acetone composite solvent system with a ratio of 7:3 is used, with the solvent added at 87-87.75% of the total mass of the reaction system. This optimized solvent ratio balances solubility and evaporation characteristics, facilitating better dispersion and fixation of functional components during fiber formation.

[0014] When adding the mixed solvent, a drop-by-drop method is preferred, controlling the flow rate to allow it to flow slowly down the inner wall of the container, thus avoiding violent impact that could cause the PVDF raw material to scatter. After the solvent is added, immediately use gentle circular shaking combined with slow stirring to ensure preliminary and uniform mixing of the solid and liquid phases. This gentle pretreatment method effectively prevents powder accumulation at the bottom of the container and also prevents abnormal temperature rises caused by excessively high local solvent concentrations.

[0015] Place the glass bottle containing the PVDF powder and solvent mixture on a preheated magnetic stirrer to 60-80 ℃ and set the stirring speed to 500-1000 rpm to begin a magnetic stirring process lasting 2-3 hours. This step requires strict control of temperature and stirring speed to promote rapid and uniform dissolution of PVDF in the mixed solvent, forming a homogeneous solution system.

[0016] After dissolution, BPTC and NaCl were precisely added to the system. The appropriate masses of BPTC and NaCl were accurately weighed and added to the solution. Magnetic stirring was continued at the same temperature (60-80 ℃) and stirring speed (500-1000 rpm) for 9 h to ensure that BPTC and NaCl were fully dissolved and uniformly dispersed in the solution, while promoting the interaction between PVDF and BPTC.

[0017] To optimize the homogeneity of the solution system, eliminate residual gas, and prevent the aggregation of solid components, an ultrasonic-assisted process was used to treat the mixed solution for 15-30 minutes. This treatment effectively degassed the solution through high-frequency mechanical vibration and promoted the uniform distribution of polymers and functional fillers in the solvent system, thereby obtaining a PVDF / BPTC / NaCl blend solution with uniform component distribution. The solution system treated in this way exhibited good stability, providing an ideal film-forming precursor for subsequent electrospinning processes.

[0018] In the preparation method of this invention, the electrospinning conditions in step S2 are as follows: The ambient temperature should be controlled at 25±2℃, and the relative humidity at 30-45%. The positive voltage is 17-22kV, and the negative voltage is -2kV; The distance between the nozzle and the receiving electrode is 15-18cm; The liquid supply rate is 0.0010-0.0020 mm / s; The receiving device platform moves at a speed of 0.5-2 mm / s and has a translation range of 30-40 mm.

[0019] After spinning is completed, the PVDF / BPTC fiber membrane is carefully peeled off from the aluminum foil receiving substrate on the surface of the roller receiver and transferred to an oven at 60-80℃ for 8-12 hours of heat treatment. Finally, a uniformly structured electrospun membrane material is obtained, which is denoted as PVDF / BPTC nanofiber membrane.

[0020] In the preparation method of the present invention, in step S3, the heat treatment conditions are: treatment at 60-80℃ for 8-12 hours.

[0021] In the preparation method of the present invention, in step S4, the illumination is performed using a xenon lamp with a wavelength λ>420nm; The reaction was carried out at 25±2℃ with shaking at 120-200 rpm for 8-16 hours. After the reaction, wash the sample with water and dry it under vacuum at 60-80℃ for 8-12 hours.

[0022] Preferably, the light reduction step is as follows: The PVDF / BPTC nanofiber membrane samples were completely immersed in an aqueous solution of silver nitrate (AgNO3) with a concentration of 500-2000 ppm. Under continuous irradiation with a xenon lamp (wavelength λ > 420 nm), the reaction was carried out at a constant temperature (25 ± 2 °C) with shaking at a rate of 120-200 rpm for 8 hours to ensure that the photocatalytic reduction reaction proceeded fully. After the reaction, the sample was washed repeatedly with deionized water 3-5 times to remove residual ions. Then, the sample was heat-treated in a vacuum drying oven at 60-80℃ for 8-12 hours, and labeled as PVDF / BPTC-AgCl@Ag nanofiber membrane. This process not only promotes Ag... + Complete reduction was achieved, and the in-situ stable generation of AgCl@Ag heterostructure nanoparticles was realized. The final composite material retained the original three-dimensional network structure of the fiber membrane, with AgCl@Ag nanoparticles uniformly distributed on the surface.

[0023] The nanofiber membrane provided by this invention has high water flux and anti-biofouling properties, and can be used for membrane separation in the field of water treatment to remove bacteria and pollutants from water. It can be reused through static or dynamic antibacterial operation.

[0024] Compared with the prior art, the present invention has the following beneficial technical effects: 1. This invention obtains a BPTC-PVDF nanofiber matrix membrane through electrospinning, constructing a three-dimensional network structure that can provide an ultra-large specific surface area. This allows the prepared BPTC and NaCl to be directly confined on the nanofiber surface, making it an excellent carrier for nanomaterials with broad application prospects.

[0025] 2. The presence of BPTC carboxyl groups and NaCl precursor in the PVDF / BPTC-AgCl@Ag nanofiber membrane prepared by this invention enables the in-situ synthesized Ag / AgCl heterojunction to form a tight bond with the PVDF fiber, effectively preventing the nanoparticles from falling off.

[0026] 3. The PVDF / BPTC-AgCl@Ag nanofiber membrane prepared by this invention has good long-term antibacterial stability, can perform static and dynamic antibacterial treatment, and can be easily backwashed and chemically cleaned. It avoids bacterial adhesion on the membrane surface, realizes the reuse of membrane materials, and has practical application potential.

[0027] 4. The PVDF / BPTC-AgCl@Ag nanofiber membrane prepared by this invention possesses multiple antibacterial mechanisms, avoiding the reliance of traditional antibacterial membranes on a single bactericidal mechanism (such as Ag). + The release of nanoparticles can easily lead to bacterial resistance and also presents the problem of nanoparticle aggregation and inactivation, thus achieving a highly efficient and long-lasting antibacterial effect.

[0028] 5. The polyvinylidene fluoride used in the method of this invention is widely available and inexpensive, and has already been commercialized into a commercially available film. Attached Figure Description

[0029] Figure 1 The diagram shows three membrane materials prepared in Example 1 of this invention.

[0030] Figure 2 The infrared spectrum of the membrane material prepared in Example 1 of this invention is shown.

[0031] Figure 3 This is a scanning electron microscope image of the membrane material prepared in Example 1 of the present invention.

[0032] Figure 4 This is an X-ray diffraction pattern of the membrane material prepared in Example 1 of the present invention.

[0033] Figure 5 The image shows the X-ray photoelectron spectrum of the film material Ag prepared in Example 1 of this invention.

[0034] Figure 6 This is a scanning electron microscope image of Comparative Example 1 of the present invention.

[0035] Figure 7 This is a scanning electron microscope image of Comparative Example 2 of the present invention.

[0036] Figure 8 This is a test diagram of the inhibition zone in Embodiment 2 of the present invention.

[0037] Figure 9 This is a diagram illustrating the contact effect in Embodiment 2 of the present invention.

[0038] Figure 10 This is a colony count diagram from Example 3 of the present invention. Detailed Implementation

[0039] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0040] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0041] This invention provides a biphenyl tetracarboxylic acid (BPTC) functionalized silver chloride / silver-polyvinylidene fluoride (Ag / AgCl-PVDF) nanofiber membrane prepared by electrospinning and in-situ reduction technology. It belongs to the field of environmental science and engineering and aims to solve the technical problems of biological pollution, nanoparticle aggregation and single antibacterial mechanism in traditional membrane separation technology.

[0042] The key feature of this invention lies in the preparation of a PVDF nanofiber matrix using electrospinning technology, and the in-situ formation of uniformly dispersed Ag / AgCl heterojunctions through the coordination effect of BPTC. Specific technical solutions include: Material design: PVDF is used as the matrix, BPTC as the functional stabilizer, and NaCl as the precursor. The components are uniformly dispersed by optimizing the solvent system (such as dimethylformamide-acetone composite solvent).

[0043] Process integration: Electrospinning is used to construct a three-dimensional network structure of nanofiber membrane, and then Ag / AgCl nanoparticles are generated in situ on the fiber surface through photocatalytic reduction (such as xenon lamp irradiation), forming a strong bond.

[0044] The preparation process mainly includes three key steps: Preparation of casting solution: PVDF, BPTC and NaCl are dissolved in a composite solvent and a homogeneous solution is obtained by magnetic stirring and ultrasonic treatment.

[0045] Electrospinning to form a film: Spinning is carried out under controlled temperature (25±2°C), humidity (30-45%) and voltage (positive electrode 17-22kV, negative electrode -2kV) conditions to form a nanofiber film, and the structure stability is enhanced by heat treatment.

[0046] In-situ reduction treatment: The fiber membrane is immersed in silver nitrate solution and photocatalytically reduced under light to partially reduce AgCl to Ag, forming an Ag / AgCl heterojunction. Finally, the final product is obtained by cleaning and drying.

[0047] The present invention has the following outstanding advantages compared with the prior art: Multiple antibacterial mechanisms: Synergistic antibacterial action is achieved through photogenerated hole oxidation, reactive oxygen species (ROS) attack, and controlled silver ion release. The antibacterial rate can reach 99.999% under light conditions, effectively avoiding bacterial drug resistance.

[0048] Excellent stability: The carboxyl group of BPTC forms a strong bond with Ag / AgCl, preventing the nanoparticles from falling off. After 5 cycles of use, the antibacterial activity remains above 90%.

[0049] Green technology: Raw materials are readily available, the process is environmentally friendly, and large-scale production can be achieved using mature electrospinning equipment.

[0050] Structural advantages: Nanofiber membranes have high specific surface area and porosity, which improve water treatment flux and antifouling performance.

[0051] The performance of the composite membrane was verified by various characterization methods in this invention: Structural characterization: X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses showed that the Ag / AgCl heterostructure was successfully constructed, and the characteristic peaks of Ag and AgCl were clearly visible. Figure 4 and Figure 5 ).

[0052] Antibacterial properties: Tests using the agar diffusion method and plate coating method showed that the composite film exhibited extremely high antibacterial rate under light irradiation. Figure 6 , Figure 7 , Figure 8 It is significantly superior to traditional PVDF membranes.

[0053] The composite membrane of this invention is suitable for water treatment, medical protection, and other fields. Its long-lasting antibacterial properties and easy-to-clean characteristics (such as backwashing) can significantly reduce maintenance costs. This invention provides a new material approach to solving membrane fouling problems and has broad prospects for industrialization.

[0054] The polyvinylidene fluoride used in the following examples is commercially available polyvinylidene fluoride powder with an average molecular weight of 600,000.

[0055] Example 1 1) Weigh PVDF: Accurately weigh 1.8 g (12w%) of PVDF powder and add it to a 50ml glass bottle. Measure 13.05 g of a mixture of DMF and acetone (7:3 volume ratio) and add it to a 30ml glass bottle. Stir at 800 rpm for 3 h at 80 ℃.

[0056] 2) Then add 0.15 g (1 wt%) of BPTC and NaCl to the glass bottle respectively, and continue stirring for 9 hours. Then perform ultrasonic treatment for 30 min.

[0057] The casting solution has a total volume of 100%, with PVDF accounting for 12%, solvent accounting for 86%, BPTC accounting for 1%, and NaCl accounting for 1%.

[0058] 3) Pour the casting solution into a 10ml syringe. Set the electrospinning machine parameters: room temperature 25±1℃, relative humidity 35±5%, positive voltage 19 kV, negative voltage -2 kV, nozzle to current collector distance 16 cm, feed flow rate 0.0010 mm / s. Continue spinning until the fiber membrane is formed.

[0059] 4) The prepared PVDF / BPTC nanofiber membrane was then heat-treated in an 80 ℃ oven for 10 h.

[0060] 5) Take approximately 0.05 g of square PVDF / BPTC nanofiber membrane and immerse it completely in 50 mL of a 1000 ppm silver nitrate (AgNO3) aqueous solution. Under continuous irradiation with a xenon lamp (wavelength λ > 420 nm), perform a constant temperature (25 ± 2 °C) shaking reaction at a rate of 180 rpm for 8 h.

[0061] 6) After the reaction is complete, wash the sample repeatedly with deionized water 3-5 times to remove residual ions, and then place the sample in an 80℃ vacuum drying oven for heat treatment for 9 h.

[0062] In the nanofiber membrane prepared in this embodiment, the mass fraction of PVDF nanofiber matrix is ​​12%, and the mass fraction of BPTC is 1%.

[0063] Figure 1 The comparison results of the surface morphology and color changes of the three membranes are shown: the original PVDF membrane surface is smooth and white, the PVDF / BPTC composite membrane turns dark white but still maintains a smooth surface; after being impregnated with AgNO3 solution and irradiated with xenon lamp, the surface of the composite membrane turns reddish-brown and is uniformly distributed with black spots (AgCl@Ag nanoparticles), indicating the successful loading and photoreduction of silver species.

[0064] like Figure 2 The image shows the infrared spectrum of the membrane material. For the original PVDF membrane, 840 cm⁻¹ -1 877 cm -1 1072 cm -1 1405 cm -1 The peak at 1172 cm⁻¹ belongs to the vibration of the CH bond. -1 and 1275 cm -1 The peak at 1715 cm⁻¹ represents the tensile and bending vibrations of C-F₂, indicating a PVDF polymer chain. -1 The absorption peak at 1715 cm⁻¹ is due to the C=O stretching vibration of the carboxyl group on BPTC. The subsequent reaction of the carboxyl group with silver further elevates the peak to 1715 cm⁻¹. -1 The peak shifted to 1625 cm. -1 This confirms that BPTC was successfully doped into the PVDF matrix, and that the carboxyl groups in the composite material formed an effective interaction with silver.

[0065] like Figure 3The image shows a scanning electron microscope (SEM) image of the membrane material. The pure PVDF electrospun membrane exhibits a uniform fiber structure with a narrow fiber diameter distribution and a smooth surface, consistent with the typical characteristics of electrospun PVDF. After the introduction of BPTC ligand and NaCl, the fibers maintained their intact morphology, with no significant changes in diameter or surface characteristics, indicating that the addition of BPTC and NaCl did not significantly affect the fiber formation process or lead to phase separation. After silver nitrate impregnation and xenon lamp irradiation, the fiber surface was uniformly loaded with nanoparticles of uniform size and without significant agglomeration, attributed to the regulatory effect of the carboxyl group (-COOH) of BPTC on the growth of AgCl@Ag particles. This structure endows the composite material with stable active sites and uniform surface properties.

[0066] X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis results Figure 4 and Figure 5 The successful construction of the AgCl@Ag composite structure in the PVDF-based composite film was confirmed by these two methods. XPS fine spectral analysis showed that the characteristic peaks of the Ag 3d orbital at 367.0 eV (Ag3d5 / 2) and 373.0 eV (Ag3d3 / 2) correspond to Ag... + Simultaneously, Ag-attributed molecules appeared at 368.5 eV and 374.6 eV. 0 The characteristic peaks are in perfect agreement with the standard values ​​reported in the literature. Figure 5 Correspondingly, the diffraction peaks detected at 27.7°, 32.2°, 46.2°, 54.8°, 57.5°, 67.4° and 74.5° in the XRD pattern correspond to the (111), (200), (220), (311), (222), (400) and (331) crystal planes of AgCl, respectively; the diffraction peaks observed at 38.1°, 44.2°, 64.4° and 76.7° are consistent with the (111), (200), (220) and (311) crystal planes of metallic Ag.

[0067] Comparative Example 1 The steps are basically the same as those in Example 1, except that no light is applied in step 5).

[0068] The results are as follows Figure 6 As shown, the film formed without photoreduction is PVDF / BPTC-AgCl, and it is impossible to form a heterojunction semiconductor of AgCl@Ag.

[0069] Comparative Example 2 The steps are basically the same as those in Example 1, except that BPTC is not added in step 2).

[0070] The results are as follows Figure 7As shown, the final film formed is only PVDF / NaCl, and the Ag / AgCl heterojunction cannot be fixed onto the electrospinning.

[0071] Example 2 The PVDF / BPTC-AgCl@Ag nanofiber membrane material prepared in Example 1 was used.

[0072] This invention employs the standard agar diffusion method and plate coating method to evaluate the antibacterial properties of PVDF / BPTC-AgCl@Ag composite membranes.

[0073] First, the membrane samples to be tested (including PVDF membrane, PVDF / BPTC membrane, and PVDF / BPTC-AgCl@Ag membrane) were autoclaved at 121℃ for 15 minutes and irradiated with ultraviolet light for 20 minutes. Then, 10mm diameter circular membrane pieces were evenly attached to the surface of LB agar medium for agar diffusion experiments. After incubation at 37℃ for 24 hours, the diameter of the inhibition zone was measured; the inhibition zone was as follows... Figure 8 As shown, using 10 5 After incubation at a CFU / mL concentration for 24 h, *E. coli* grew directly beneath the edges of PVDF and PVDF / BPTC membranes. However, the PVDF / BPTC-AgCl@Ag membrane exhibited excellent antibacterial activity against *E. coli*, with 10... 7 At a concentration of CFU / mL, the average radius of the inhibition zone for E. coli was 4 mm.

[0074] Example 3 Based on Example 2, the membrane sample was coated with 10 μL using a flat plate coating method. 7 CFU / mL *E. coli* bacterial suspension was co-incubated. Sterilized circular membranes (approximately 1 cm in diameter) were placed in 24-well plates, with 1 mL of bacterial suspension added to each well. A PVDF membrane was used as a blank control. The plates were incubated at 37°C under light or dark conditions. 100 μL samples were taken at 0 h, 0.5 h, 1 h, 1.5 h, and 2 h, diluted, and spread onto agar solid medium. After incubation at 37°C for 12 hours, colony counts were performed, and the inhibition rate was calculated.

[0075]

[0076] Where M is the inhibition rate; N0 represents the number of colonies on the blank bacterial suspension agar solid medium, N t This indicates the number of bacterial colonies after contact with the membrane at different times.

[0077] like Figure 9 and Figure 10 The results showed that the PVDF / BPTC-AgCl@Ag membrane had an antibacterial rate of 54.7% under dark conditions for 2 hours, while the antibacterial rate under light conditions reached 99.999% for 2 hours.

Claims

1. A silver chloride / silver-polyvinylidene fluoride nanofiber membrane based on biphenyltetracarboxylic acid functionalization, comprising a PVDF nanofiber matrix, BPTC uniformly distributed in the PVDF nanofiber matrix, and Ag / AgCl heterojunction nanoparticles generated in situ and stably loaded on the PVDF nanofiber matrix through the carboxyl coordination of the BPTC. In the nanofiber membrane, the mass fraction of the PVDF nanofiber matrix is ​​10-12%, and the mass fraction of the BPTC is 0.25-1%; and the loading of the Ag / AgCl heterojunction nanoparticles is controlled by the concentration of the silver nitrate solution, which is 500-2000 ppm. The nanofiber membrane has a three-dimensional network structure with uniform fiber diameter, and the Ag / AgCl heterojunction nanoparticles loaded on the surface have uniform particle size and no aggregation.

2. The method for preparing the nanofiber membrane according to claim 1, comprising the following steps: S1. Preparation of casting solution: Mix PVDF, BPTC, NaCl and solvent to form a homogeneous PVDF / BPTC / NaCl blend solution as the casting solution. S2, electrospinning: electrospinning the casting solution obtained in step S1 and collecting the fiber membrane; S3. Heat treatment: The fiber membrane obtained in step S2 is subjected to heat treatment to obtain a PVDF / BPTC nanofiber membrane. S4. Photoreduction: The PVDF / BPTC nanofiber membrane after heat treatment in step S3 is immersed in AgNO3 solution and subjected to in-situ reduction reaction under light irradiation to form Ag / AgCl heterojunction, and finally the nanofiber membrane is obtained.

3. The preparation method according to claim 2, characterized in that: In step S1, the solvent is a mixture of dimethylformamide and acetone in a volume ratio of 7-5:3-5. The preparation process of the casting solution includes the following steps: Mix PVDF powder with solvent and stir at 500-1000 rpm for 2-3 hours at 60-80℃; then add BPTC and NaCl and continue stirring at the same temperature and stirring speed for 8-10 hours; finally, degas by ultrasonic treatment for 15-30 minutes.

4. The preparation method according to claim 2 or 3, characterized in that: In step S2, the conditions for electrospinning are as follows: The ambient temperature should be controlled at 25±2℃, and the relative humidity at 30-45%. The positive voltage is 17-22kV, and the negative voltage is -2kV; The distance between the nozzle and the receiving electrode is 15-18cm; The liquid supply rate is 0.0010-0.0020 mm / s; The receiving device platform moves at a speed of 0.5-2 mm / s and has a translation range of 30-40 mm.

5. The preparation method according to claim 2 or 3, characterized in that: In step S3, the heat treatment conditions are: treatment at 60-80℃ for 8-12 hours; In step S4, the illumination is provided by a xenon lamp with a wavelength λ > 420 nm; The reaction was carried out at 25±2℃ with shaking at 120-200 rpm for 8-16 hours. After the reaction, the sample was washed with water and then vacuum dried at 60-80℃ for 8-12 hours.

6. The application of the nanofiber membrane according to claim 1 in membrane separation in the field of water treatment has high water flux and resistance to biofouling; The nanofiber membrane is used to remove bacteria and pollutants from water and can be reused through static or dynamic antibacterial operations.

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