A long-acting and durable photo-thermal-photo-catalytic synergistic nanofiber membrane and a preparation method and application thereof

Abstract

This invention discloses a long-lasting and durable photothermal-photocatalytic synergistic nanofiber membrane, its preparation method, and its applications. A spinning solution containing titanium, silicon, silver precursors, and a polymer template agent is prepared, and a precursor fiber membrane is constructed via electrospinning. After two-stage temperature-controlled calcination, amorphous silica flexible buffer nodes are generated in the continuous titanium dioxide phase, resulting in in-situ silver generation. A polypyrrole shell is constructed on the fiber surface through in-situ polymerization, yielding a TiO2 / SiO2 / Ag / PPy nanofiber membrane. The stress dissipation of the SiO2 flexible nodes and the physical protection and toughening effect of the PPy shell enhance the membrane's mechanical properties and cycle stability. This membrane exhibits a high interfacial water evaporation rate under simulated sunlight, a high photocatalytic degradation rate of methylene blue within 2 hours, and high quality retention after 50 cycles. It combines photothermal and photocatalytic properties with long-lasting durability, showing broad application prospects in dyeing and printing wastewater treatment and reclaimed water preparation.

Description

Technical Field

[0001] This invention belongs to the field of water treatment and environmental catalytic materials technology, specifically relating to a long-lasting and durable photothermal-photocatalytic synergistic nanofiber membrane, its preparation method, and its application. Background Technology

[0002] With rapid socio-economic development and continuous industrialization, water pollution has become an increasingly serious problem. In particular, the complex wastewater discharged from the dyeing and printing industry, due to its high color, complex composition, and high content of recalcitrant organic matter, poses a serious threat to the ecological environment. Therefore, in the field of water treatment, there is an urgent need to develop a green treatment technology that achieves more thorough degradation, lower energy consumption, and no secondary pollution.

[0003] Photocatalysis, with its advantages of mild reaction conditions, high degradation rate, wide applicability, and energy saving, has become a promising water treatment technology. In the research of semiconductor photocatalysts, titanium dioxide (TiO2) has attracted widespread attention due to its high stability, non-toxicity, and low cost. To address the problem of powdered catalysts easily agglomerating in water and being difficult to recycle and reuse, researchers often attempt to load them onto substrates or prepare nanofiber membranes using electrospinning. However, traditional pure TiO2 membranes, after high-temperature calcination and crystallization, are prone to stress concentration at grain boundaries, leading to significant fiber brittleness and easy membrane breakage during water treatment. If physical coating or external binders are used to fix TiO2 onto flexible substrates, there is a risk of peeling and loss during long-term recycling, and the binders can also obscure catalytic active sites.

[0004] Therefore, developing a long-lasting and durable photocatalytic nanofiber membrane and its preparation method is of great practical significance. Summary of the Invention

[0005] Technical problem to be solved: The present invention aims to solve the problems of poor mechanical properties, insufficient cycle stability and low light energy utilization efficiency of existing photocatalytic membrane materials, and to provide a long-lasting and durable photothermal-photocatalytic synergistic nanofiber membrane, its preparation method and application.

[0006] Purpose of the invention: The purpose of this invention is to provide a long-lasting and durable photothermal-photocatalytic synergistic nanofiber membrane, its preparation method and application. This photothermal-photocatalytic synergistic nanofiber membrane can have high photocatalytic degradation efficiency under visible light and can achieve water purification through interfacial water evaporation.

[0007] To achieve the above objectives, this application provides the following technical solution: A method for preparing a long-lasting and durable photothermal-photocatalytic synergistic nanofiber membrane includes the following steps: S1. Add 0.005-0.2g of silver acetate to 3-5mL of anhydrous ethanol by mass-volume ratio, stir until dissolved, add 0.2-0.5g of polyvinylpyrrolidone, and continue stirring for 10-30 minutes to obtain the first solution; mix 3-5mL of anhydrous ethanol, 3-5mL of glacial acetic acid, and 0.1-0.3mL of tetraethyl orthosilicate, stir for 5-10 minutes until homogeneous, add 1-2mL of tetrabutyl titanate, and continue stirring for 5-10 minutes to obtain a clear and homogeneous second solution; pour the second solution into the first solution, stir for 5-10 minutes, add 0.2-0.5g of polyethylene oxide, and stir for 5-10 minutes to obtain a metal complex solution; S2. Electrospinning: The metal complex solution is transferred as the spinning solution into a syringe with a metal needle. The injection speed is 1.2-2 mL / h, the applied voltage is 12-15 kV, the receiving distance is 12-20 cm, and the temperature is controlled at 25±2℃ and the relative humidity is 40±5%. Electrospinning is carried out for 6 hours to obtain the precursor fiber membrane of the nanofiber membrane. S3. Two-stage temperature-controlled calcination: The obtained precursor fiber membrane is placed in an alumina crucible, and then the crucible is placed in a muffle furnace. Under an air atmosphere, the temperature is first slowly increased to 250-300℃ at a rate of 1-3℃ / min, and then held at a constant temperature for 1-3 hours for pre-oxidation buffering. Then, the temperature is continued to be increased to 450-500℃ at a rate of 1-3℃ / min, and held at a constant temperature for 1-3 hours to allow the polymer template to be completely pyrolyzed and volatilized, thus obtaining a TiO2 / SiO2 / Ag nanofiber membrane. S4. Dissolve 0.8-1.2g of ferric chloride (FeCl3) in 50mL of deionized water and stir for 10-15 minutes to prepare an oxidant solution; ultrasonically disperse 0.8-1.5mL of pyrrole monomer in 50mL of deionized water for 5-10 minutes to form a pyrrole suspension; then immerse the TiO2 / SiO2 / Ag nanofiber membrane obtained in S3 in the pyrrole suspension for 10-30 minutes to obtain a pyrrole suspension containing the membrane; subsequently, add the oxidant solution to the pyrrole suspension containing the membrane and allow it to stand at room temperature for 5-60 minutes to undergo an in-situ polymerization reaction to obtain a composite membrane; after the reaction is complete, take out the obtained composite membrane and place it in an oven to dry, then immerse it in deionized water for 5-15 minutes, and place it in the oven to dry again. After 2-4 alternating soaking-drying cycles, remove the residual FeCl3 to obtain a TiO2 / SiO2 / Ag nanofiber membrane with polypyrrole loading.

[0008] Further, in step S1, the molar ratio of silver acetate, tetraethyl orthosilicate, and tetrabutyl titanate is (0.005~0.05):(0.1~0.30):1.

[0009] Further, in step S1, 0.005-0.2g of silver acetate is added to 4mL of anhydrous ethanol at a mass-to-volume ratio and stirred until dissolved. Then, 0.2-0.5g of polyvinylpyrrolidone is added and stirred for another 20 minutes to obtain a first solution. 4mL of anhydrous ethanol, 4mL of glacial acetic acid, and 0.2mL of tetraethyl orthosilicate are mixed and stirred for 5 minutes until homogeneous. Then, 1.5mL of tetrabutyl titanate is added and stirred for another 5 minutes to obtain a clear and homogeneous second solution. The second solution is poured into the first solution and stirred for 10 minutes. Then, 0.2-0.5g of polyethylene oxide is added and stirred for another 10 minutes to obtain a metal complex solution.

[0010] Furthermore, in step S2, the electrospinning conditions are as follows: the feed speed is set to 1.5 mL / h; a 15 kV DC high voltage is applied between the needle and the silicone paper-coated roller; and the receiving distance is fixed at 15 cm.

[0011] Furthermore, the two-stage calcination process in step S3 specifically involves: slowly raising the temperature to 280°C at a rate of 2°C / min and holding it at that temperature for 1.5 hours for pre-oxidation buffering; then continuing to raise the temperature to 500°C at a rate of 2°C / min and holding it at that temperature for 3 hours to allow the polymer template to completely pyrolyze and volatilize, thereby generating a TiO2 / SiO2 / Ag nanofiber membrane.

[0012] Further, in step S4, 1g of ferric chloride (FeCl3) is dissolved in 50mL of deionized water and stirred for 15 minutes to prepare an oxidant solution; 1.2mL of pyrrole monomer is ultrasonically dispersed in 50mL of deionized water for 5 minutes to form a pyrrole suspension.

[0013] Further, in step S4, the TiO2 / SiO2 / Ag nanofiber membrane is immersed in a pyrrole suspension for 20 minutes to obtain a pyrrole suspension containing the membrane. Then, an oxidant solution is added to the pyrrole suspension containing the membrane, and the mixture is allowed to stand at room temperature for 10 minutes to undergo an in-situ polymerization reaction.

[0014] Furthermore, in step S4, the composite membrane is taken out and placed in an oven to dry, then immersed in deionized water for 10 minutes, and then placed in the oven to dry again. The residual FeCl3 is removed by three alternating soaking-drying cycles.

[0015] A long-lasting and durable photothermal-photocatalytic synergistic nanofiber membrane prepared by any of the above preparation methods.

[0016] This application also discloses the application of long-lasting and durable photothermal-photocatalytic synergistic nanofiber membranes in the treatment of dyeing and printing wastewater and the preparation of reclaimed water.

[0017] Explanation of the principle: Inside the fiber, through two-stage calcination, amorphous silica flexible buffer nodes are generated in situ within the continuous titanium dioxide phase. These nodes effectively dissipate the concentrated stress generated during the high-temperature crystallization of titanium dioxide grains, preventing cracks at grain boundaries due to excessive stress. Outside the fiber, the in-situ polymerized polypyrrole (PPy) shell not only acts as a physical protective layer, absorbing and dispersing external forces, but its own flexibility further enhances the overall fracture resistance of the fiber. This synergistic stress dissipation and enhancement mechanism significantly improves the flexibility and self-supporting mechanical properties of the nanofiber membrane. The embedded Ag nanoparticles form a Schottky barrier with titanium dioxide, acting as electron trapping centers to effectively suppress the recombination of photogenerated electron-hole pairs, prolonging hole lifetime and thus improving photocatalytic efficiency. The PPy shell on the outside of the fiber has broad-spectrum absorption and efficient photothermal conversion characteristics, which can convert absorbed light energy into heat energy, forming a local heating at the solid-liquid interface. On the one hand, it drives the evaporation of interfacial water, and on the other hand, it provides heat energy for the photocatalytic reaction, accelerating the reaction rate. In addition, the heterojunction interface formed between PPy and titanium dioxide / Ag further promotes the cross-interfacial transport and separation of photogenerated charges.

[0018] This application provides a long-lasting and durable photothermal-photocatalytic synergistic nanofiber membrane, its preparation method, and its application. Compared with the prior art, it has the following advantages: 1. This invention effectively dissipates concentrated stress generated by high-temperature crystallization by constructing flexible SiO2 buffer nodes within nanofibers. Combined with the in-situ polymerization of a PPy shell on the fiber skeleton surface, this PPy shell not only absorbs and disperses external forces but also protects the internal structure. This synergistic stress dissipation mechanism significantly improves the flexibility and overall self-supporting mechanical properties of the nanofiber membrane, resulting in a 94.1% quality retention rate after 50 water treatment cycles. 2. This invention enhances the photothermal and photocatalytic performance of the composite membrane by embedding Ag particles and a PPy shell. Inside the fiber, Ag nanoparticles form a Schottky barrier with TiO2. Ag acts as an electron trapping center, promoting the transfer of photogenerated electrons generated in the TiO2 bulk phase to Ag, thereby effectively suppressing electron-hole recombination and extending hole lifetime. Outside the fiber, the PPy shell exhibits broadband light absorption and photothermal conversion characteristics. After absorbing light energy, PPy converts it into heat energy, causing localized heating at the solid-liquid interface. This localized heat not only promotes the evaporation rate of interfacial water to reach 2.46 kg·m³, but also... -2 ·h -1 It also accelerated the photocatalytic degradation reaction rate, achieving a degradation rate of up to 99.1% for methylene blue within 2 hours. In addition, the heterojunction interface between the PPy shell and TiO2 / Ag further promoted the cross-interface charge transport. 3. The nanofiber membrane prepared by this invention has a self-supporting structure, requiring no additional substrate or binder, thus avoiding the problem of catalyst shedding. It is also easy to separate and recover from the reaction system, simplifying the water treatment process. Attached Figure Description

[0019] Figure 1 This is a scanning electron microscope image of the photothermal-photocatalytic synergistic nanofiber membrane prepared in Example 1 of this application; Figure 2 This is a scanning electron microscope image of the photothermal-photocatalytic synergistic nanofiber membrane prepared in Example 2 of this application; Figure 3 This is a schematic diagram of the photothermal-photocatalytic synergistic nanofiber membrane evaporation prepared in this application. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Unless otherwise specified below, the specifications and manufacturer information of all raw materials used in the various embodiments of this application are commercially available: Polyvinylpyrrolidone (PVP, Mw=1300000g / mol), polyethylene oxide (PEO, Mw=600000g / mol), tetrabutyl titanate (TBOT), methylene blue (MB), tetraethyl orthosilicate (TEOS), and pyrrole (Py) were all purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; anhydrous ethanol was purchased from Shanghai Lingfeng Chemical Reagent Co., Ltd.; glacial acetic acid was purchased from Shanghai Runjie Technology Development Co., Ltd.; silver acetate was purchased from Sinopharm Chemical Reagent Co., Ltd.; and ferric chloride (FeCl3) was purchased from Shanghai Titan Technology Co., Ltd.

[0022] Example 1: This example provides a method for preparing a long-lasting and durable photothermal-photocatalytic synergistic nanofiber membrane, comprising the following steps: S1. Precursor preparation: At room temperature, measure 4 mL of anhydrous ethanol and 0.02 g of silver acetate and stir for 20 minutes. Then add 0.25 g of polyvinylpyrrolidone and stir for another 20 minutes to form a homogeneous solution A. Measure 4 mL of anhydrous ethanol, 4 mL of glacial acetic acid, and 0.2 mL of tetraethyl orthosilicate and stir for 5 minutes. Then add 1.5 mL of tetrabutyl titanate and stir for another 5 minutes to form a clear and homogeneous solution B. Pour solution B into solution A and stir for 10 minutes. Add 0.25 g of polyethylene oxide and stir for another 10 minutes to finally form a metal complex solution.

[0023] S2. Electrospinning: The above metal complex solution was transferred into a syringe with a metal needle, and the injection speed was set to 1.5 mL / h. A 15 kV DC high voltage was applied between the needle and the silicone paper-coated roller, and the receiving distance was fixed at 15 cm. The temperature was controlled at 25 ± 2 °C and the relative humidity at 40 ± 5%. Spinning continued for 6 hours to obtain the precursor of the nanofiber membrane.

[0024] S3. Two-stage temperature-controlled calcination: The obtained precursor film is placed in an alumina crucible, and then the crucible is placed in a muffle furnace. First, the temperature is slowly increased to 280°C at a rate of 2°C / min, and then held at a constant temperature for 1.5 hours for pre-oxidation buffering. Then, the temperature is increased to 500°C at a rate of 2°C / min, and held at a constant temperature for 3 hours to allow the polymer template to be completely pyrolyzed and volatilized, generating a TiO2 / SiO2 / Ag nanofiber film.

[0025] The electron microscope image of the sample in step S3 is shown below. Figure 1 As shown, the fibers are uniformly web-like.

[0026] S4. In-situ polymerization reaction: 1.2 mL of pyrrole (Py) monomer was weighed and dispersed in 50 mL of deionized water, and sonicated for 5 minutes to form a uniform suspension. The TiO2 / SiO2 / Ag nanofiber membrane obtained in S3 was immersed in the pyrrole suspension for 20 minutes to allow the monomer to be fully adsorbed onto the fiber surface. Separately, 1 g of ferric chloride (FeCl3) was weighed and dissolved in 50 mL of deionized water, and stirred for 15 minutes to prepare an oxidant solution. This FeCl3 solution was slowly poured into the pyrrole suspension containing the membrane, and the reaction was allowed to proceed at room temperature for 10 minutes, resulting in in-situ polymerization of polypyrrole (PPy) on the membrane surface. After the reaction, the resulting composite membrane was removed and dried in an oven; then it was immersed in deionized water for 10 minutes and dried again in the oven. The above immersion and drying steps were repeated 3 times to remove residual FeCl3, finally obtaining a TiO2 / SiO2 / Ag nanofiber membrane with polypyrrole loading.

[0027] Example 2 differs from Example 1 only in that the reaction is allowed to stand at room temperature for 20 minutes.

[0028] The electron microscope image of the sample in step S4 is shown below. Figure 2 As shown, polypyrrole is uniformly loaded on the fiber surface.

[0029] Example 3 differs from Example 1 only in that the reaction is allowed to stand at room temperature for 30 minutes.

[0030] Example 4 differs from Example 1 only in that the reaction is allowed to stand at room temperature for 40 minutes.

[0031] Comparative Example 1 differs from Example 1 only in that tetraethyl orthosilicate is not added. This is because, during high-temperature calcination, the titanium dioxide grains undergo disordered growth and severe sintering, forming a highly rigid continuous inorganic crystal network. This structure leads to severe stress concentration at the grain boundaries, making S4 impossible.

[0032] Comparative Example 2 differs from Example 1 only in that silver acetate is not added.

[0033] Comparative Example 3 differs from Example 1 only in that S1-S3 are implemented and S4 is omitted.

[0034] Comparative Example 4 differs from Example 1 only in that it does not contain tetraethyl orthosilicate and S4 is omitted.

[0035] Comparative Example 5 differs from Example 1 only in that silver acetate is not added and step S4 is omitted.

[0036] Performance Testing and Evaluation: To evaluate the mechanical properties of the membrane, the tensile strength testing and calculation process is as follows: First, the prepared membrane is cut into 50 mm × 10 mm pieces, and its initial width and thickness are accurately measured. Then, the membrane is fixed flat and vertically in the upper and lower clamps of a universal testing machine. A constant tensile rate of 5 mm / min is set at room temperature for uniform stretching until the membrane fractures. The instrument automatically records the force-displacement curve during the stretching process and the maximum tensile load (F) before fracture.

[0037] The specific formula for calculating fracture strength (σ) is as follows: .

[0038] Where σ represents the tensile strength in megapascals (MPa); F represents the maximum tensile load that the membrane can withstand before tensile fracture in newtons (N); b represents the initial width of the test membrane in millimeters (mm); and d represents the initial thickness of the test membrane in millimeters (mm).

[0039] Photocatalytic degradation tests were conducted on samples from Examples 1-4 and Comparative Examples 2-5: Using MB as a model pollutant, 20 mg of inorganic nanofiber membrane was placed in a glass beaker (100 mL, 10 mg / L) containing the pollutant solution under simulated irradiation conditions. Before irradiation, the beaker was kept in the dark for 30 min to reach adsorption-desorption equilibrium. Then, the beaker was irradiated under a solar simulator. During irradiation, approximately 3 mL of solution was drawn every 30 min, and the degradation solution was evaluated in the wavelength range of 600 nm to 700 nm using a UV-Vis spectrophotometer with deionized water as a reference. The degradation efficiency (η) was obtained using the following formula: .

[0040] in This indicates the quality of the membrane after 50 tests. This indicates the initial mass of the membrane.

[0041] The quality retention rates of the samples from Examples 1-4 and Comparative Examples 2-5 after cyclic testing up to the 50th cycle are shown in Table 1.

[0042] Photothermal evaporation tests were conducted on samples from Examples 1-4 and Comparative Examples 2-5. The membrane was cut into a 1×6 cm rectangle, and both sides were immersed in two identical water tanks (4 cm×4 cm×4 cm). The evaporation area was set to 1×2 cm. Water transfer was achieved through capillary action, thus establishing a suspended evaporation mode. Figure 3 As shown, the evaporation device was irradiated with a solar simulator and placed on a balance to record mass changes. The solar-driven photothermal evaporation performance of the evaporator was evaluated using deionized water under one solar irradiation.

[0043] A xenon lamp equipped with an AM 1.5G filter (CME-Xe3000F, China) was used to simulate sunlight and vertically illuminate the evaporator. The distance between the light source and the evaporator surface was maintained at 15cm, so that the light intensity reaching the membrane surface was one standard solar radiation (1000 W / m²). 2 The mass change of water was recorded in real time using a digital balance (Sartorius, readability d=0.0001g). Water evaporation rate (ER, kg·m³) -2 ·h -1 ) is calculated using the following formula: .

[0044] in S is the mass loss of water (kg), and S is the interfacial water evaporation area (m²). 2 ), where t is the evaporation time (h).

[0045] The photothermal evaporation rates of samples in Examples 1-4 and Comparative Examples 2-5 are shown in Table 1.

[0046] Antibacterial tests were performed on samples from Examples 1-4 and Comparative Examples 2-5: For the antibacterial test, 0.1 g of nanofiber membrane was cut into fragments and sterilized by UV light, then placed in sterile petri dishes. 100 μL of a bacterial suspension in the logarithmic growth phase (concentration approximately 1 × 10⁻⁶) was aspirated. 6CFU / mL (using Escherichia coli or Staphylococcus aureus as indicator bacteria) was added to the surface of the membrane sample to ensure full contact and absorption. After incubation at 37°C for 24 hours, the sample was transferred to sterile phosphate-buffered saline (PBS) and eluted with vigorous shaking. The eluent was serially diluted, plated on nutrient agar plates, and cultured. Colony forming units (CFU) were counted, and the antibacterial rate of the membrane was calculated using an untreated blank sample as a control. The results are shown in Table 1.

[0047] Performance evaluation and data comparison: The samples prepared in the above embodiments and comparative examples were tested together, and the data are shown in the table below: Table 1. Membrane performance data of each embodiment and comparative example. .

[0048] Table 2 Cyclic degradation performance of each example and comparative example .

[0049] By comparing the various test data, it can be found that Example 2 exhibits better overall performance in terms of tensile strength, water evaporation rate, mass retention rate after 50 cycles, methylene blue degradation rate, and antibacterial rate. Observing the data from Examples 1-4 shows that adjusting the reaction time of in-situ polymerization of polypyrrole affects the fluctuation of various properties. With the extension of polymerization time, the tensile strength and photothermal evaporation rate of the membrane steadily increase, which confirms that polypyrrole can effectively improve the macroscopic mechanical properties and light absorption conversion capacity of the material; however, the photocatalytic degradation rate shows a trend of first increasing and then decreasing, indicating that the appropriate polypyrrole shell thickness is the key to balancing photothermal synergy and effective exposure of catalytic active sites. Comparative Examples 1 and 4, due to the absence of tetraethyl orthosilicate in the preparation process, lack amorphous silica buffer nodes within the fiber skeleton, resulting in the inability of the membrane to form a self-supporting structure between the two water tanks, and thus preventing S4. Meanwhile, the data from Comparative Examples 3 and 5 show that, without a polypyrrole shell, the film fractures after more than ten cycles, and the photothermal evaporation rate is relatively low. Furthermore, the data from Comparative Examples 2 and 5 confirm that the lack of silver acetate leads to the loss of the membrane's antibacterial function and a significant decrease in the antibacterial rate. Overall, the above data reflect the synergistic mechanism of the various raw material components in the membrane construction process.

[0050] In summary, through reasonable component selection and structural design, this invention has successfully prepared a nanofiber membrane with excellent mechanical properties, efficient photothermal-photocatalytic synergistic performance, and long-lasting durability, which has significant application potential in the field of water treatment.

[0051] The embodiments selected in the above materials are for ease of understanding and not for limiting the process method. Those skilled in the art can easily modify the process flow or transfer it to other cases without inventive change. If these modifications also fall under the category of similar claims or similar technology of this invention, then the intent of this invention also includes these modifications.

Claims

1. A method for preparing a long-lasting photo-thermal-photo-catalytic synergistic nanofiber membrane, characterized in that, Includes the following steps: S1. Add 0.005-0.2g of silver acetate to 3-5mL of anhydrous ethanol by mass-volume ratio, stir until dissolved, add 0.2-0.5g of polyvinylpyrrolidone, and continue stirring for 10-30 minutes to obtain the first solution; mix 3-5mL of anhydrous ethanol, 3-5mL of glacial acetic acid, and 0.1-0.3mL of tetraethyl orthosilicate, stir for 5-10 minutes until homogeneous, add 1-2mL of tetrabutyl titanate, and continue stirring for 5-10 minutes to obtain a clear and homogeneous second solution; pour the second solution into the first solution, stir for 5-10 minutes, add 0.2-0.5g of polyethylene oxide, and stir for 5-10 minutes to obtain a metal complex solution; S2. Electrospinning: The metal complex solution is transferred as the spinning solution into a syringe with a metal needle. The injection speed is 1.2-2 mL / h, the applied voltage is 12-15 kV, the receiving distance is 12-20 cm, and the temperature is controlled at 25±2℃ and the relative humidity is 40±5%. Electrospinning is carried out for 6 hours to obtain the precursor fiber membrane of the nanofiber membrane. S3. Two-stage temperature-controlled calcination: The obtained precursor fiber membrane is placed in an alumina crucible, and then the crucible is placed in a muffle furnace. Under an air atmosphere, the temperature is first slowly increased to 250-300℃ at a rate of 1-3℃ / min, and then held at a constant temperature for 1-3 hours for pre-oxidation buffering. Then, the temperature is continued to be increased to 450-500℃ at a rate of 1-3℃ / min, and held at a constant temperature for 1-3 hours to allow the polymer template to be completely pyrolyzed and volatilized, thus obtaining a TiO2 / SiO2 / Ag nanofiber membrane. S4. Dissolve 0.8-1.2g of ferric chloride (FeCl3) in 50mL of deionized water and stir for 10-15 minutes to prepare an oxidant solution; ultrasonically disperse 0.8-1.5mL of pyrrole monomer in 50mL of deionized water for 5-10 minutes to form a pyrrole suspension; then immerse the TiO2 / SiO2 / Ag nanofiber membrane obtained in S3 in the pyrrole suspension for 10-30 minutes to obtain a pyrrole suspension containing the membrane; subsequently, add the oxidant solution to the pyrrole suspension containing the membrane and allow it to stand at room temperature for 5-60 minutes to undergo an in-situ polymerization reaction to obtain a composite membrane; after the reaction is complete, take out the obtained composite membrane and place it in an oven to dry, then immerse it in deionized water for 5-15 minutes, and place it in the oven to dry again. After 2-4 alternating soaking-drying cycles, remove the residual FeCl3 to obtain a TiO2 / SiO2 / Ag nanofiber membrane with polypyrrole loading.

2. The method for preparing a long-lasting and durable photothermal-photocatalytic synergistic nanofiber membrane according to claim 1, characterized in that: In step S1, the molar ratio of silver acetate, tetraethyl orthosilicate, and tetrabutyl titanate is (0.005~0.05):(0.1~0.30):

1.

3. The method for preparing the long-lasting and durable photothermal-photocatalytic synergistic nanofiber membrane according to claim 1, characterized in that: In step S1, 0.005-0.2 g of silver acetate is added to 4 mL of anhydrous ethanol by mass-volume ratio and stirred until dissolved. Then, 0.2-0.5 g of polyvinylpyrrolidone is added and stirred for another 20 minutes to obtain a first solution. 4 mL of anhydrous ethanol, 4 mL of glacial acetic acid, and 0.2 mL of tetraethyl orthosilicate are mixed and stirred for 5 minutes until homogeneous. Then, 1.5 mL of tetrabutyl titanate is added and stirred for another 5 minutes to obtain a clear and homogeneous second solution. The second solution is poured into the first solution and stirred for 10 minutes. Then, 0.2-0.5 g of polyethylene oxide is added and stirred for another 10 minutes to obtain a metal complex solution.

4. The method for preparing a long-lasting and durable photothermal-photocatalytic synergistic nanofiber membrane according to claim 1, characterized in that: In step S2, the electrospinning conditions are as follows: the feed speed is set to 1.5 mL / h; a 15 kV DC high voltage is applied between the needle and the silicone paper-coated roller; and the receiving distance is fixed at 15 cm.

5. The method for preparing a long-lasting and durable photothermal-photocatalytic synergistic nanofiber membrane according to claim 1, characterized in that: The two-stage calcination process in step S3 is as follows: the temperature is slowly increased to 280°C at a rate of 2°C / min and held at a constant temperature for 1.5 hours for pre-oxidation buffering; then the temperature is increased to 500°C at a rate of 2°C / min and held at a constant temperature for 3 hours to allow the polymer template to be completely pyrolyzed and volatilized, generating a TiO2 / SiO2 / Ag nanofiber membrane.

6. The method for preparing a long-lasting and durable photothermal-photocatalytic synergistic nanofiber membrane according to claim 1, characterized in that: In step S4, 1g of ferric chloride (FeCl3) is dissolved in 50mL of deionized water and stirred for 15 minutes to prepare an oxidant solution; 1.2mL of pyrrole monomer is ultrasonically dispersed in 50mL of deionized water for 5 minutes to form a pyrrole suspension.

7. The method for preparing a long-lasting and durable photothermal-photocatalytic synergistic nanofiber membrane according to claim 1, characterized in that: In step S4, the TiO2 / SiO2 / Ag nanofiber membrane is immersed in a pyrrole suspension for 20 minutes to obtain a pyrrole suspension containing the membrane. Then, an oxidant solution is added to the pyrrole suspension containing the membrane, and the mixture is allowed to stand at room temperature for 10 minutes to undergo an in-situ polymerization reaction.

8. The method for preparing a long-lasting and durable photothermal-photocatalytic synergistic nanofiber membrane according to claim 1, characterized in that: In step S4, the composite membrane is taken out and placed in an oven to dry, then immersed in deionized water for 10 minutes, and then placed in the oven to dry again. This process of alternating immersion-drying cycles is repeated three times to remove residual FeCl3.

9. A long-lasting and durable photothermal-photocatalytic synergistic nanofiber membrane prepared by the preparation method according to any one of claims 1-8.

10. The application of the long-lasting and durable photothermal-photocatalytic synergistic nanofiber membrane according to claim 9 in the treatment of dyeing and printing wastewater and the preparation of reclaimed water.

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