A method for preparing a nanofiber tubular membrane based on a separable magnetic particle anti-fouling function

Abstract

This invention discloses a method for preparing a magnetic nanofiber tubular membrane based on the antifouling function of separable magnetic particles, comprising the following steps: 1) thoroughly mixing equal volumes of iron salt solution and fumaric acid solution and then subjecting the mixture to ultrasonic treatment, followed by a hydrothermal reaction; 2) thoroughly mixing the solid product obtained in step 1) with a sulfiding agent-ethanol solution at a certain mass ratio, and then continuing the hydrothermal reaction to obtain Fe3S4 magnetic catalytic particles; 3) weaving polyester fibers into a braided tube and nesting it on axially stacked magnetic tubes to form a magnetic braided tube; 4) dissolving the fiber-forming polymer in a solvent to obtain a uniform and stable spinning solution; using the magnetic braided tube obtained in step 3) as a receiver, the spinning solution obtained in step 4) is spun into a magnetic nanofiber tubular membrane using electrospinning technology; 6) loading the magnetic catalytic particles obtained in step 2) onto the surface of the membrane obtained in step 5), thereby obtaining the Fe3S4 / magnetic nanofiber tubular membrane.

Description

Technical Field

[0001] This invention relates to the field of membrane separation technology, and specifically to a method for preparing a nanofiber tubular membrane based on the antifouling function of separable magnetic particles. Background Technology

[0002] Membrane separation technology is one of the effective ways to efficiently treat complex wastewater, but membrane fouling severely limits the performance and application cost of membrane materials. Actual wastewater is characterized by high concentration, complex composition, and strong chemical stability, often containing large amounts of soluble components (dyes, antibiotics, sugars, proteins, phenols, aldehydes, etc.) and insoluble components (humus, microorganisms, oil, dust, sand, and other inorganic impurities). This type of wastewater is difficult to degrade and easily accumulates on the membrane surface, forming a stable fouling layer. This reduces the flux and separation efficiency of the membrane material, significantly shortens its lifespan, and substantially increases the economic costs of washing and replacing the membrane.

[0003] Chemical cleaning is a widely used method for cleaning membrane fouling. Depending on the cleaning agent, it can be categorized into alkaline cleaning, acid cleaning, enzymatic cleaning, disinfectant cleaning, and combined cleaning. Sodium hypochlorite is a common membrane fouling cleaning agent, characterized by its strong oxidizing and inactivating properties, quickly removing organic pollutants deposited on the membrane surface and within the membrane pores. However, high concentrations of sodium hypochlorite can react with organic matter to generate disinfection byproducts with "three-fold" toxicity (mutagenic, carcinogenic, and teratogenic), severely affecting effluent quality and impacting the metabolism of aquatic organisms, threatening the food chain. Therefore, some research is currently focusing on using oxidants such as ozone and hydrogen peroxide (H2O2) to replace sodium hypochlorite for membrane fouling cleaning. Although these oxidants can achieve good cleaning results, they also produce highly toxic disinfection byproducts during the cleaning process, causing irreversible chemical damage to the membrane material. Furthermore, these oxidants are ineffective at removing most inorganic pollutants.

[0004] Numerous studies in recent years have demonstrated that catalyst-coupled membranes exhibit excellent treatment effects on various types of complex wastewater under the influence of physical fields such as light, electricity, and sound. Among these effects, the catalyst, acting as the main oxidant, generates reactive oxygen species (ROS) such as hydroxyl radicals, superoxide anions, and singlet oxygen under suitable conditions. ROS can not only oxidize and degrade various organic pollutants but also inhibit membrane fouling, effectively extending the service life of membrane materials. Chinese invention patent CN202310381227.4 discloses a ferrous oxide particle (Fe... 2+ The method of inducing H2O2 for in-situ acid production from organic pollutants to control membrane fouling mainly involves Fe 2+The hydroxyl radicals generated by the Fenton reaction with H2O2 oxidize organic pollutants on the membrane surface, thus achieving antifouling. Although the Fenton reaction is highly oxidizing and easy to operate, it requires the addition of large amounts of iron salts and H2O2, resulting in a large amount of iron sludge and causing excessive iron levels in the effluent. Chinese invention patent CN202010218286.6 discloses an electrochemical system for membrane fouling control in membrane bioreactors (MBRs). This system combines advanced electrochemical oxidation with the MBR process, utilizing the strong electric field of electrochemical oxidation to accelerate the degradation of organic pollutants and promote microbial metabolism, thereby inhibiting membrane fouling to some extent. An electrochemical-MBR coupling system can directly embed the electrochemical module into the MBR system, avoiding the need for additional devices. However, the process parameters and maintenance costs of the electrochemical module severely limit its practical application.

[0005] Photocatalytic coupling membrane systems are a rapidly developing type of multi-physics field (light field) coupled membrane system in recent years. Due to their green, environmentally friendly, energy-efficient, and high-efficiency characteristics, they have attracted widespread attention in the treatment of textile wastewater and other similar wastewater. A photocatalytic coupling membrane system mainly consists of photocatalyst particles and a separation membrane module. Through the catalytic oxidation of the photocatalyst, organic pollutants in the water and those attached to the membrane surface can be efficiently oxidized and degraded, thereby achieving the purification of organic wastewater and effective prevention of membrane fouling. It has advantages such as high degradation rate, strong selectivity, and convenient operation. Based on their composition and operation mode, photocatalytic coupling membrane systems can be divided into two types: photocatalyst suspended membrane systems and photocatalyst supported membrane systems. For example, Professor Sheydaei's research group proposed a photocatalyst suspended membrane system composed of polypropylene hollow fiber membranes and cerium-doped zinc oxide (Ce-ZnO) nanoparticles. This system can efficiently degrade simulated Active Orange-29 wastewater under visible light irradiation and, to a certain extent, inhibit membrane fouling. When the photocatalyst exists in the wastewater in a suspended system, the catalyst particles are in full contact with the pollutants, promoting the adsorption, diffusion, and oxidative degradation of pollutant molecules on the catalyst surface. The above technology was published in *Ultrasonics Sonochemistry*, 2019, Vol. 56, pp. 361-371, in the article titled: "Systematic comparison of sono-synthesized Ce-, La- and Ho-doped ZnO nanoparticles and application of the optimum catalyst in a visible light-assisted continuous sono-photocatalytic membrane reactor," specifically Mohsen Sheydaei, Marzieh Fattahi, Leila Ghalamchi, et al. However, most photocatalyst particles have only nanoscale spatial dimensions, making them highly susceptible to loss or clogging of membrane pores, leading to reduced water output and decreased water quality. In contrast, the catalysts in photocatalyst-supported membrane systems are mostly immobilized on the base membrane through physical and chemical methods, which can largely avoid the aforementioned catalyst loss problems. Professor Zinadini's research group proposed a method for preparing a photocatalytic nanofiltration membrane of multi-walled carbon nanotube-doped zinc oxide nanoparticles (ZnO / MWCNTs) blended with polyether sulfone (PES). The ZnO / MWCNTs / PES photocatalytic nanofiltration membrane obtained by one-step coating method has the characteristics of high rejection rate, simple preparation and strong anti-fouling properties.Similarly, Professor Ding Changkun's research group proposed a method to prepare a graphene@titanium dioxide (GO@TiO2) supported PES ultrafiltration membrane through a layer-by-layer self-assembly method. This membrane can efficiently degrade methylene blue under ultraviolet light and maintain a high flux recovery rate. The above technologies were published in *Membrane Science*, 2017, Vol. 529, pp. 133-141, titled "Development of antibiofouling polyethersulfone mixed matrix NF membrane using photocatalytic activity of ZnO / MWCNTs nanocomposite"; and in *Membrane Science*, 2022, Vol. 659, No. 120789, titled "Improving photocatalytic performance of PES membrane by layer-by-layer self-assembly of GO@TiO2". Photocatalytic performance [J], Journal of Membrane Science, 2022, 659, 120789. In the above methods, although the catalyst particles supported on the membrane surface can undergo catalytic reactions under light irradiation, the damage to the membrane substrate from long-term ultraviolet radiation is significant. Moreover, when the catalyst on the membrane surface is deactivated, both the catalyst and the separation membrane fail, further increasing the cost of membrane replacement. Furthermore, for some inorganic pollutants in wastewater, the catalyst cannot degrade and remove them, leading to clogging and scaling over long periods, resulting in a significant decrease in flux.

[0006] Inspired by the natural phenomenon of "pulling out a radish and bringing out the mud," this study utilizes the ability of separable magnetic catalytic particles to rapidly load and remove catalytic particles on the surface of a nanofiber tubular membrane with nested magnetic tubes. Combined with the catalytic particles' ability to remove organic pollutants, a non-fouling nanofiber tubular membrane with separable catalysts has been developed and prepared. This is of great significance for solving the urgent and complex wastewater pollution problem and alleviating membrane fouling. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a Fe3S4 / magnetic nanofiber tubular membrane, which combines separable magnetic iron tetrasulfide (Fe3S4) catalyst particles with a nanofiber tubular membrane nested with stacked magnetic tubes for membrane fouling control. This combined membrane effectively prevents pollutant deposition on the membrane surface, reducing membrane fouling. Furthermore, it allows for catalyst particle renewal without replacing the membrane material, improving the membrane's antifouling performance. The Fe3S4 / magnetic nanofiber tubular membrane consists of Fe3S4 particles obtained through continuous hydrothermal methods and electrospinning techniques, respectively, and a nanofiber tubular membrane nested with stacked magnetic tubes. In application, the Fe3S4 particles are magnetically adsorbed onto the membrane surface, and then assembled into a membrane module for operation in cross-flow mode. Under conditions of low light and the presence of persulfate (PMS), the Fe3S4 nanofiber tubular membrane system can efficiently treat various simulated wastewaters (dyes, antibiotics, drugs, etc.) while significantly eliminating membrane fouling. After operation, Fe3S4 particles can be detached from the membrane surface by an external magnetic field for cleaning and reloading, enabling recycling. The Fe3S4 / magnetic nanofiber tubular membrane achieves highly efficient antifouling through its detachable modular design without the use of subsequent cleaning agents, significantly extending the membrane's lifespan while avoiding the generation of highly toxic byproducts during traditional membrane cleaning.

[0008] This invention provides a method for preparing magnetic nanofiber tubular membranes based on the antifouling function of separable magnetic particles, comprising the following steps:

[0009] 1) Equal volumes of iron salt solution and fumaric acid solution are thoroughly mixed and ultrasonically treated, then transferred to a hydrothermal reactor and reacted at a certain temperature. After a period of time, the resulting solid product is centrifuged, washed, and dried. The iron salt solution is either ferric chloride hexahydrate (FeCl3·6H2O) solution or ferric nitrate nonahydrate (Fe(NO3)3·9H2O) solution, preferably FeCl3·6H2O solution, with a mass fraction of 5–15 wt%. The fumaric acid solution has a mass fraction of 1–10 wt%. The ultrasonic treatment time is 10–30 min, and the ultrasonic frequency is 20–40 kHz. The reaction temperature is 100–150 °C, and the reaction time is 5–20 h.

[0010] 2) Synthesis of Fe3S4 particles: The solid product obtained in step 1) is thoroughly mixed with a sulfiding agent-ethanol solution at a certain mass ratio, and then transferred to a hydrothermal reactor for reaction at a certain temperature. After a period of time, the obtained solid product is centrifuged, washed, and dried to obtain Fe3S4 magnetic catalytic particles; the sulfiding agent-ethanol solution is a thioacetamide (TAA) ethanol solution with a mass fraction of 1-10 wt%; the mass ratio of the solid product to the sulfiding agent-ethanol solution is 1:200-1:1000; the reaction temperature is 100-150℃, and the reaction time is 5-15 h;

[0011] 3) Preparation of magnetic braided tube matrix: Polyester (PET) fibers are braided into PET fiber braided tubes with a regular mesh structure using a braiding machine, and then nested on stacked magnetic tubes to form a magnetic braided tube matrix; the PET fiber braided tube is woven from a certain number of spindles, with an inner diameter of 0.5-1.5 mm and an outer diameter of 2-5 mm; the number of spindles can be 8-64, the braiding angle is 30-60°, and the braiding pitch is 0.1-10 mm;

[0012] 4) Spinning solution preparation: After thoroughly drying a certain mass of fiber-forming polymer powder, add it to the corresponding solvent and stir at a certain temperature for 12 hours to obtain a uniform and stable spinning solution; the fiber-forming polymer powder includes one of polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyethersulfone (PES), poly(m-phenylene isophthalamide) (PMIA), and polyimide (PI); the mass concentration of the spinning solution is 10-20 wt%; the solvent is one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and acetone;

[0013] 5) Spinning: After the spinning solution obtained in step 4) is allowed to stand or degassed under vacuum, it is loaded into a syringe and electrospun using the magnetic braided tube substrate obtained in step 3) as the receiver. After a period of time, the resulting nanofiber tubular membrane with nested stacked magnetic tubes is placed in a vacuum oven for thorough drying to obtain a magnetic nanofiber tubular membrane. The drying temperature of the vacuum oven is 60 to 100°C and the vacuum pressure is -50 to -30 Pa.

[0014] 6) The Fe3S4 magnetic catalytic particles obtained in step 2) are uniformly loaded onto the surface of the magnetic nanofiber tubular membrane obtained in step 5) to obtain the Fe3S4 / magnetic nanofiber tubular membrane; the loading amount of the Fe3S4 magnetic catalytic particles is 0.5-10 g / 10 cm, preferably 2-5 g / 10 cm.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] This invention provides a universal method for preparing nanofiber tubular membranes based on the antifouling function of separable magnetic particles. Magnetic Fe3S4 particles are prepared via a continuous hydrothermal method and loaded onto the surface of a nanofiber-magnetic braided tube matrix obtained by electrospinning, forming an Fe3S4 / nanofiber tubular membrane. Due to the separability of magnetic particles under an external magnetic field, this system can loosen and remove contaminant particles attached to the membrane surface during the loading and separation of Fe3S4 particles, significantly mitigating membrane fouling. Moreover, under conditions of low light and the presence of PMS, it exhibits enhanced removal effects on various contaminants (including dyes, drugs, antibiotics, etc.) and membrane fouling. Furthermore, the antifouling performance of this membrane system was comprehensively evaluated using different contaminants (bovine serum albumin, sodium alginate, and humic acid). Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the magnetic nanofiber tubular membrane structure prepared in Example 1;

[0018] Figure 2 This is a photograph of the magnetic nanofiber tubular membrane prepared in Example 1 after loading Fe3S4.

[0019] Figure 3 The actual removal effect of the Fe3S4 / magnetic nanofiber tubular membrane prepared in Example 1 on various pollutants, namely bisphenol A (BPA), gentian violet (CV), sodium alginate (HA), methyl orange (MO), ofloxacin (OFL), (Phenol), rhodamine B (RhB), sulfamethoxazole (SMX), and methylene blue (MB).

[0020] Figure 4 The antifouling performance of the Fe3S4 / magnetic nanofiber tubular membrane prepared in Example 1 against pollutants such as bovine serum albumin, sodium alginate, and humic acid is shown.

[0021] The following are the labeling elements in the figure:

[0022] 1-Magnetic tube, 2-Fiber braided tube, 3-Nanofiber layer. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below in conjunction with specific embodiments. The following embodiments are for illustrative purposes only and do not limit the scope of the invention. Furthermore, it should be understood that after reading the above description of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0024] Example 1

[0025] This embodiment illustrates the preparation of Fe3S4 / magnetic nanofiber tubular membranes, including the preparation of magnetic Fe3S4 particles and magnetic polyvinylidene fluoride (PVDF) nanofiber tubular membranes:

[0026] 1) Dissolve 12.8g FeCl3·6H2O and 5.6g fumaric acid in 120mL of ultrapure water respectively. Mix the two thoroughly and stir at 500rpm for 30min to obtain a clear orange-yellow solution. After sonication for 10min, transfer the solution to a hydrothermal reactor and react at 100℃ for 6h. After the reaction, collect the product by centrifugation, wash with ultrapure water and anhydrous ethanol, and dry to obtain a solid product for later use.

[0027] 2) Disperse 10g of the solid product obtained in step 1) in 2000mL of anhydrous ethanol containing 50g TAA by ultrasonication. After ultrasonic treatment for 30min, transfer the mixture into a hydrothermal reactor and keep it at 120℃ for 12h. After the reaction is completed, collect the product by centrifugation, wash it with ultrapure water and anhydrous ethanol and dry it to obtain magnetic Fe3S4 particles.

[0028] 3) The PET filaments are wound onto 48 yarn tubes and woven into 16-strand mesh braided tubes by a high-speed braiding machine. These are then nested around a magnetic tube of a certain length to obtain a magnetic PET fiber braided tube.

[0029] 4) Preparation of electrospinning solution: Weigh a certain amount of PVDF powder and add it to a 3 / 7 volume ratio of acetone / DMAc mixed solvent. After dissolving by mechanical stirring at 60°C, a PVDF spinning solution with a mass fraction of 12wt% is prepared.

[0030] 5) Load the electrospinning solution obtained in step 4) into an electrospinning syringe, and use the magnetic PET fiber braided tube obtained in step 3) as a receiver to perform electrospinning; Electrospinning process parameters: Positive voltage: 15kV, negative voltage: -5kV; Syringe needle diameter: No. 19; Receiving distance: 8cm; Receiver rotation speed: 600rpm; Spinning temperature: 30±2℃; Spinning humidity: 60±10%;

[0031] 6) Place the nanofiber tubular membrane obtained in step 5) into a vacuum oven to dry (drying temperature: 70℃; vacuum pressure: -50Pa; drying time: 12h, to obtain a magnetic PVDF nanofiber tubular membrane);

[0032] 7) Load the magnetic Fe3S4 particles prepared in step 2) onto the surface of the magnetic PVDF nanofiber tubular membrane prepared in step 6) to obtain the Fe3S4 / magnetic PVDF nanofiber tubular membrane.

[0033] The Fe3S4 / magnetic nanofiber tubular membrane prepared in Example 1 was subjected to visible light irradiation (cross-flow mode, membrane area 9.5 cm²). 2 Operating pressure = 0.02 MPa; Irradiation source: 1W LED, λ = 380~1000nm, I = ~6.25±0.45mWcm -2 The initial concentration of contaminants in the solution was 10 mg·L⁻¹. -1 The PMS initial concentration (5 mM) showed a removal efficiency exceeding 86% for various pollutants, including bisphenol A (BPA), gentian violet (CV), sodium alginate (HA), methyl orange (MO), ofloxacin (OFL), phenol, rhodamine B (RhB), sulfamethoxazole (SMX), and methylene blue (MB); except for HA-contaminated wastewater (with a flux of 68 L / min). -1 ·m -2 ·h· -1 Other pollutant wastewater flux was maintained at 90–115 L. -1 ·m -2 ·h· -1 Furthermore, as the separation / loading of magnetic Fe3S4 particles continued to circulate, the membrane flux remained relatively stable, demonstrating excellent antifouling performance.

[0034] Example 2

[0035] This embodiment illustrates the preparation of Fe3S4 / magnetic nanofiber tubular membranes, including the preparation of magnetic Fe3S4 particles and magnetic polyacrylonitrile (PAN) nanofiber tubular membranes:

[0036] 1) Dissolve 6.4g FeCl3·6H2O and 2.8g fumaric acid in 60mL of ultrapure water respectively. Mix the two thoroughly and stir at 500rpm for 30min to obtain a clear orange-yellow solution. After sonication for 10min, transfer the solution to a hydrothermal reactor and react at 100℃ for 6h. After the reaction, collect the product by centrifugation, wash with ultrapure water and anhydrous ethanol, and dry to obtain a solid product for later use.

[0037] 2) Disperse 5g of the solid product obtained in step 1) in 1000mL of anhydrous ethanol containing 25g TAA by ultrasonication. After ultrasonic treatment for 30min, transfer the mixture into a hydrothermal reactor and keep it at 120℃ for 12h. After the reaction is completed, collect the product by centrifugation, wash it with ultrapure water and anhydrous ethanol and dry it to obtain magnetic Fe3S4 particles.

[0038] 3) The PET filaments are wound onto 48 yarn tubes and woven into 16-strand mesh braided tubes by a high-speed braiding machine. These are then nested around a magnetic tube of a certain length to obtain a magnetic PET fiber braided tube.

[0039] 4) Preparation of electrospinning solution: Weigh a certain amount of PAN powder and add it to DMF. After dissolving it by mechanical stirring at 60°C, a PAN spinning solution with a mass fraction of 15 wt% is prepared.

[0040] 5) Load the electrospinning solution obtained in step 4) into an electrospinning syringe, and use the magnetic PET fiber braided tube obtained in step 3) as a receiver to perform electrospinning; Electrospinning process parameters: positive voltage, 15kV, negative voltage, -5kV; syringe needle diameter: 19; receiving distance: 10cm; receiver rotation speed: 800rpm; spinning temperature: 28±2℃; spinning humidity: 50±10%.

[0041] 6) Place the nanofiber tubular membrane obtained in step 5) into a vacuum oven for drying (drying temperature: 80℃; vacuum pressure: -50Pa; drying time: 12h) to obtain a PAN nanofiber tubular membrane;

[0042] 7) Load the magnetic Fe3S4 particles prepared in step 2) onto the surface of the PAN nanofiber tubular membrane prepared in step 6) to obtain the Fe3S4 / magnetic PAN nanofiber tubular membrane.

[0043] Example 3

[0044] This embodiment illustrates the preparation of magnetic Fe3S4 / magnetic nanofiber tubular membranes, including the preparation of magnetic Fe3S4 particles and magnetic polyethersulfone (PES) nanofiber tubular membranes:

[0045] 1) Dissolve 6.4g FeCl3·6H2O and 2.8g fumaric acid in 60mL of ultrapure water respectively. Mix the two thoroughly and stir at 500rpm for 30min to obtain a clear orange-yellow solution. After sonication for 10min, transfer the solution to a hydrothermal reactor and react at 100℃ for 6h. After the reaction is completed, collect the product by centrifugation, wash with ultrapure water and anhydrous ethanol, and dry to obtain a solid product for later use.

[0046] 2) Disperse 5g of the solid product obtained in step 1) in 1000mL of anhydrous ethanol containing 25g TAA by ultrasonication. After ultrasonic treatment for 30min, transfer the mixture into a hydrothermal reactor and keep it at 120℃ for 12h. After the reaction is completed, collect the product by centrifugation, wash it with ultrapure water and anhydrous ethanol and dry it to obtain magnetic Fe3S4 particles.

[0047] 3) The PET filaments are wound onto 48 yarn tubes and woven into 16-strand mesh braided tubes by a high-speed braiding machine. These are then nested around a magnetic tube of a certain length to obtain a magnetic PET fiber braided tube.

[0048] 4) Preparation of electrospinning solution: Weigh a certain amount of PES powder and add it to DMAc. After dissolving it by mechanical stirring at 60°C, a PES spinning solution with a mass fraction of 20 wt% is prepared.

[0049] 5) Load the electrospinning solution obtained in step 4) into an electrospinning syringe, and use the magnetic PET fiber braided tube obtained in step 3) as a receiver to perform electrospinning; Electrospinning process parameters: positive voltage, 18kV, negative voltage, -5kV; syringe needle diameter: 18 gauge; receiving distance: 8cm; receiver rotation speed: 1000rpm; spinning temperature: 26±2℃; spinning humidity: 65±10%.

[0050] 6) Place the nanofiber tubular membrane obtained in step 5) into a vacuum oven for drying (drying temperature: 70℃; vacuum pressure: -50Pa; drying time: 12h) to obtain a PES nanofiber tubular membrane;

[0051] 7) Load the magnetic Fe3S4 particles prepared in step 2) onto the surface of the PES nanofiber tubular membrane prepared in step 6) to obtain the Fe3S4 / magnetic PES nanofiber tubular membrane.

[0052] Example 4

[0053] This embodiment illustrates the preparation of Fe3S4 / magnetic nanofiber tubular membranes, including the preparation of magnetic Fe3S4 particles and magnetic poly(m-phenylene isophthalamide) (PMIA) nanofiber tubular membranes:

[0054] 1) Dissolve 6.4g FeCl3·6H2O and 2.8g fumaric acid in 60mL of ultrapure water respectively. Mix the two thoroughly and stir at 500rpm for 30min to obtain a clear orange-yellow solution. After sonication for 10min, transfer the solution to a hydrothermal reactor and react at 100℃ for 6h. After the reaction is completed, collect the product by centrifugation, wash with ultrapure water and anhydrous ethanol, and dry to obtain a solid product for later use.

[0055] 2) Disperse 2.5g of the solid product obtained in step 1) in 500mL of anhydrous ethanol containing 12.5g of TAA by ultrasonication. After ultrasonic treatment for 30min, transfer the mixture into a hydrothermal reactor and keep it at 120℃ for 12h. After the reaction is completed, collect the product by centrifugation, wash it with ultrapure water and anhydrous ethanol and dry it to obtain magnetic Fe3S4 particles.

[0056] 3) The PET filaments are wound onto 48 yarn tubes and woven into 16-strand mesh braided tubes by a high-speed braiding machine. These are then nested around a magnetic tube of a certain length to obtain a magnetic PET fiber braided tube.

[0057] 4) Preparation of electrospinning solution: Weigh a certain amount of PMIA powder and add it to a DMAc / lithium chloride (LiCl) mixed solvent. After dissolving by mechanical stirring at 60°C, a PMIA spinning solution with a mass fraction of 12.5 wt% is prepared; wherein, the mass fraction of LiCl is 2 wt%.

[0058] 5) Load the electrospinning solution obtained in step 4) into an electrospinning syringe, and use the magnetic PET fiber braided tube obtained in step 3) as a receiver to perform electrospinning; Electrospinning process parameters: positive voltage, 15kV, negative voltage, -5kV; syringe needle diameter: 19 gauge; receiving distance: 8cm; receiver rotation speed: 600rpm; spinning temperature: 32±2℃; spinning humidity: 70±10%.

[0059] 6) Place the nanofiber tubular membrane obtained in step 5) into a vacuum oven for drying (drying temperature: 60℃; vacuum pressure: -50Pa; drying time: 12h) to obtain PMIA nanofiber tubular membrane;

[0060] 7) Load the magnetic Fe3S4 particles prepared in step 2) onto the surface of the PMIA nanofiber tubular membrane prepared in step 6) to obtain the Fe3S4 / magnetic PMIA nanofiber tubular membrane.

[0061] Example 5

[0062] This embodiment illustrates the preparation of Fe3S4 / magnetic nanofiber tubular membranes, including the preparation of magnetic Fe3S4 particles and magnetic polyimide (PI) nanofiber tubular nanofiber membranes:

[0063] 1) Dissolve 19.2g FeCl3·6H2O and 8.4g fumaric acid in 180mL of ultrapure water respectively. Mix the two thoroughly and stir at 500rpm for 30min to obtain a clear orange-yellow solution. After sonication for 10min, transfer the solution to a hydrothermal reactor and react at 100℃ for 6h. After the reaction, collect the product by centrifugation, wash with ultrapure water and anhydrous ethanol, and dry to obtain a solid product for later use.

[0064] 2) Disperse 15g of the solid product obtained in step 1) in 3000mL of anhydrous ethanol containing 75g TAA by ultrasonication. After ultrasonic treatment for 30min, transfer the mixture into a hydrothermal reactor and keep it at 120℃ for 12h. After the reaction is completed, collect the product by centrifugation, wash it with ultrapure water and anhydrous ethanol and dry it to obtain magnetic Fe3S4 particles.

[0065] 3) The PET filaments are wound onto 48 yarn tubes and woven into 16-strand mesh braided tubes by a high-speed braiding machine. These are then nested around a magnetic tube of a certain length to obtain a magnetic PET fiber braided tube.

[0066] 4) Preparation of electrospinning solution: Weigh a certain mass of PI powder and add it to a DMF / DMAc mixed solvent with a volume ratio of 2 / 8. After dissolving by mechanical stirring at 70°C, a PI spinning solution with a mass fraction of 14wt% is prepared.

[0067] 5) Load the electrospinning solution obtained in step 4) into an electrospinning syringe, and use the magnetic PET fiber braided tube obtained in step 3) as a receiver to perform electrospinning; Electrospinning process parameters: positive voltage, 15kV, negative voltage, -5kV; syringe needle diameter: 21 gauge; receiving distance: 10.5cm; receiver rotation speed: 600rpm; spinning temperature: 35±2℃; spinning humidity: 40±10%.

[0068] 6) Place the nanofiber tubular membrane obtained in step 5) into a vacuum oven for drying (drying temperature: 70℃; vacuum pressure: -40Pa; drying time: 12h) to obtain a PI nanofiber tubular membrane;

[0069] 7) Load the magnetic Fe3S4 particles prepared in step 2) onto the surface of the PI nanofiber tubular membrane prepared in step 6) to obtain the Fe3S4 / PI nanofiber tubular membrane.

Claims

1. A method for preparing a magnetic nanofiber tubular membrane based on the antifouling function of separable magnetic particles, characterized in that... Includes the following steps: 1) Mix equal volumes of iron salt solution and fumaric acid solution thoroughly and then sonicate them. Transfer the mixture to a hydrothermal reactor and react at a certain temperature. After a period of time, centrifuge, wash and dry the resulting solid product. 2) Synthesis of Fe3S4 particles: The solid product obtained in step 1) is thoroughly mixed with the sulfiding agent-ethanol solution at a certain mass ratio, and then transferred to a hydrothermal reactor for reaction at a certain temperature. After a period of time, the obtained solid product is centrifuged, washed and dried to obtain Fe3S4 magnetic catalytic particles. 3) Preparation of magnetic braided tube matrix: Polyester fibers are braided into polyester fiber braided tubes with regular mesh structure by a braiding machine, and then nested on stacked magnetic tubes to form magnetic braided tube matrix; 4) Spinning solution preparation: After a certain mass of fiber-forming polymer powder is fully dried, it is added to the corresponding solvent and stirred at a certain temperature for 12 hours to obtain a uniform and stable spinning solution. 5) Spinning: After the spinning solution obtained in step 4) is allowed to stand or degassed in a vacuum, it is loaded into a syringe and electrospinned using the magnetic braided tube substrate obtained in step 3) as the receiver. After a period of time, the nanofiber tubular membrane with stacked magnetic tubes is placed in a vacuum oven to dry thoroughly, thus obtaining a magnetic nanofiber tubular membrane. 6) Load the Fe3S4 magnetic catalytic particles obtained in step 2) onto the surface of the magnetic nanofiber tubular membrane obtained in step 5) to obtain the Fe3S4 / magnetic nanofiber tubular membrane.

2. The method for preparing a magnetic nanofiber tubular membrane based on the antifouling function of separable magnetic particles as described in claim 1, characterized in that: The iron salt solution in step 1) is either ferric chloride hexahydrate (FeCl3·6H2O) solution or ferric nitrate nonahydrate (Fe(NO3)3·9H2O) solution, with a mass fraction of 5–15 wt%; the fumaric acid solution has a mass fraction of 1–10 wt%; the ultrasonic treatment time is 10–30 min, and the ultrasonic frequency is 20–40 kHz; the reaction temperature is 100–150 °C, and the reaction time is 5–20 h.

3. The method for preparing a magnetic nanofiber tubular membrane based on the antifouling function of separable magnetic particles as described in claim 1, characterized in that: Step 2) The vulcanizing agent-ethanol solution is a thioacetamide (TAA) ethanol solution with a mass fraction of 1-10 wt%; the mass ratio of the solid product to the vulcanizing agent-ethanol solution is 1:200-1:1000; the reaction temperature is 100-150℃ and the reaction time is 5-15h.

4. The method for preparing a magnetic nanofiber tubular membrane based on the antifouling function of separable magnetic particles as described in claim 1, characterized in that: Step 4) The fiber-forming polymer powder includes one of polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyethersulfone (PES), poly(m-phenylene isophthalamide) (PMIA), and polyimide (PI); the mass concentration of the spinning solution is 10-20 wt%; the solvent is one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and acetone; the vacuum oven drying temperature is 60-100℃, and the vacuum pressure is -50 to -30 Pa.

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