F-doped titanium dioxide / PVDF (Polyvinylidene Fluoride) composite fiber membrane as well as preparation method and application thereof

Abstract

The invention discloses an F-doped titanium dioxide / PVDF (polyvinylidene fluoride) composite fiber membrane as well as a preparation method and application thereof, belongs to the technical field of synthetic fiber membranes, and solves the problem of low catalytic efficiency of a conventional / PVDF composite membrane material in the field of photocatalysis. Comprising the following steps: preparing a PVDF fiber membrane by adopting an electrostatic spinning method; the preparation method comprises the following steps: uniformly mixing an organic solvent and deionized water, dropwise adding a titanium source under violent stirring, and continuously stirring for 0.5-3 hours to obtain a titanium source solution; and simultaneously adding the PVDF fiber membrane and a titanium source solution into a high-temperature reaction kettle, carrying out hydrothermal reaction to obtain a primary fiber membrane, fishing out the primary fiber membrane after the reaction is finished, repeatedly washing the primary fiber membrane with ethanol and deionized water for 3 times, and drying the primary fiber membrane in a drying oven at 40-70 DEG C for 2-24 hours after washing is finished to obtain the F-doped / PVDF composite fiber membrane. The method is suitable for photocatalytic degradation scenes.

Description

Technical Field

[0001] This invention belongs to the field of synthetic fiber membrane technology, specifically relating to an F-doped membrane. / PVDF composite fiber membrane and its preparation method. Background Technology

[0002] Titanium dioxide ( Nanoparticles are widely used in photocatalysis due to their low cost, non-toxicity, high efficiency, and excellent chemical stability, but... It has a narrow optical response range and a high recombination rate of photogenerated carriers, and Since the materials are in powder form, they are often difficult to separate, recycle, and reuse in practical applications, and can easily cause secondary pollution to the environment. Therefore, photocatalysis-membrane coupling technology has become one of the current research hotspots in the field of photocatalysis. By loading powdered materials onto fibers to prepare photocatalytic material / fiber composite membranes, both recyclability and environmental pollution can be improved.

[0003] Polyvinylidene fluoride (PVDF) is a well-known piezoelectric polymer with excellent chemical, thermal, and mechanical properties. The polar bonds in its molecular structure form electric dipoles, which effectively improve the transport rate and separation efficiency of photogenerated carriers when used as a photocatalyst support. Furthermore, when subjected to external pressure, the PVDF photocatalytic film can generate an internal electric field, further enhancing the transport rate and separation efficiency of photogenerated carriers within the photocatalyst, thereby improving the photocatalytic degradation efficiency.

[0004] Methods for preparing PVDF composite membranes include solvent casting (see CN111905811A, CN111916716A), blade coating (CN102728240A), and spin coating (CN113161546A). Composite membranes prepared by these methods are typically used as protective layers for lithium-ion battery lithium metal sheets, but their pore structures are not suitable for photocatalysis. Membrane materials used in photocatalysis ideally have interconnected macropores to facilitate mass transfer. Fiber membrane materials prepared using electrospinning have a nonwoven fabric structure (see CN102704190A), but this method only... The preparation of composite materials by loading them onto PVDF fiber membranes solves the problem of the difficulty in separating, recycling, and reusing powder materials. The problem of low photocatalytic efficiency has not been solved. Summary of the Invention

[0005] This invention provides an F-doped / PVDF composite fiber membrane, its preparation method and application, aiming to solve the current The problem of low catalytic efficiency of PVDF composite membrane materials in the field of photocatalysis.

[0006] Firstly, the object of this invention is to provide an F-doped... The preparation method of PVDF composite fiber membrane includes the following steps: S1: PVDF fiber membranes were prepared by electrospinning. S2: Mix organic solvent and deionized water evenly, add titanium source dropwise under vigorous stirring, and continue stirring for 0.5~3h to obtain titanium source solution; S3: The PVDF fiber membrane and titanium source solution are simultaneously added to a high-temperature reactor for hydrothermal reaction to obtain a preliminary fiber membrane. After the reaction is complete, the preliminary fiber membrane is removed and washed repeatedly three times with ethanol and deionized water. After washing, it is dried in an oven at 40-70 °C for 2-24 hours to obtain F-doped material. / PVDF composite fiber membrane.

[0007] Furthermore, a preferred embodiment is provided: S1 includes: S11: Mix organic solvent and acetone evenly to prepare a mixed solution; S12: Add polyvinylidene fluoride powder to the mixed solution, heat and dissolve in a water bath at 40~80℃ for 2~8h, let stand for 2-8h after complete dissolution to remove excess air bubbles, and obtain electrospinning solution. S13: Electrospin the electrospinning solution to obtain a PVDF fiber membrane.

[0008] Furthermore, a preferred embodiment is provided: the organic solvent in S11 is at least one selected from N,N-dimethylformamide, N,N-diethylformamide, dimethyl sulfoxide, dimethylacetamide, N-methyl-2-pyrrolidone, and ethylene glycol monomethyl ether, and the volume ratio of the organic solvent to acetone is 4~1.5:1.

[0009] Furthermore, a preferred embodiment is provided: the mass of the polyvinylidene fluoride powder in S12 is 10% to 30% of the mass of the mixed solution.

[0010] Furthermore, a preferred embodiment is provided: the process conditions for the electrospinning method are as follows: spinning voltage 12~16 kV, feed speed 0.6~1.5 mL / h, receiving distance 18~25 cm, spinning humidity 20~45%, and spinning temperature 20~40 ℃.

[0011] Furthermore, a preferred embodiment is provided: the organic solvent in S2 is at least one of methanol, ethanol, ethylene glycol, isopropanol, n-propanol, n-butanol, and glycerol, and the volume ratio of the organic solvent to deionized water is 30~10:1.

[0012] Furthermore, a preferred embodiment is provided: the titanium source in S2 is at least one of tetrabutyl titanate, ethyl titanate, titanium tetrachloride, titanium trichloride, isopropyl titanate, and isobutyl titanate, and the volume ratio of the titanium source to the organic solvent is 40~20:1.

[0013] Furthermore, a preferred embodiment is provided: in S3, the hydrothermal reaction temperature is 110~170 ℃, and the hydrothermal reaction time is 2-18 h.

[0014] Secondly, the object of the present invention is to provide an F-doped material prepared by the preparation method described in any one or more of the above-described schemes. / PVDF composite fiber membrane.

[0015] Thirdly, the object of the present invention is to provide a photocatalyst comprising the aforementioned F doping. / PVDF composite fiber membrane.

[0016] Compared with the prior art, the advantages of the present invention are: 1. This invention produces PVDF fiber membranes through electrospinning, and can simultaneously achieve this through a simple one-step hydrothermal method. F-doping modification and F-doping In-situ growth on PVDF films improves... It improves the photocatalytic efficiency of uranium while avoiding the drawbacks of powdered photocatalysts, such as easy agglomeration and difficulty in separation and reuse.

[0017] 2. F-doped modified It exhibits excellent photocatalytic reduction performance for uranium (U(VI)) and can achieve photocatalytic reduction of U(VI) without the addition of a hole scavenger, thus solving the problem that most photocatalytic reactions require the addition of a hole scavenger.

[0018] 3. F doping PVDF composite fiber membranes can achieve photocatalytic reduction of U(VI) at high acidity, specifically at pH=2 and an initial U(VI) concentration of 10. Under these conditions, after 2 hours of photocatalytic reaction, the removal rate of U(VI) reached as high as 70%.

[0019] 4. The prepared composite fiber membrane has good flexibility, high tensile strength, excellent hydrophilicity, and is easy to separate from water, and has good recyclability.

[0020] In summary, the F-doped material prepared by the method proposed in this invention... PVDF composite fiber membrane has excellent mechanical properties, can be bent and folded at will, and has a tensile strength of up to 2.0 MPa. It also has excellent hydrophilicity, with a contact angle in the range of 23.5~32.1°.

[0021] Without the addition of a hole trap, and at a relatively acidic pH of 2, photocatalytic reduction and fixation of uranium U(VI) were achieved, with a removal rate exceeding 70% after 2 hours of photocatalytic reaction. ; This invention is applicable to photocatalytic degradation scenarios. Attached Figure Description

[0022] Figure 1 The F-doped sample obtained in Embodiment 2 of this invention has a hydrothermal temperature of 150 °C and a hydrothermal reaction time of 2 h. SEM image of PVDF composite fiber membrane; Figure 2 The F-doped sample obtained in Embodiment 3 of this invention has a hydrothermal temperature of 150 °C and a hydrothermal reaction time of 6 h. SEM image of PVDF composite fiber membrane; Figure 3 The F-doped sample obtained in Embodiment 4 of this invention has a hydrothermal temperature of 150 °C and a hydrothermal reaction time of 10 h. SEM image of PVDF composite fiber membrane; Figure 4 The F-doped sample obtained in Embodiment 5 of this invention has a hydrothermal temperature of 150 °C and a hydrothermal reaction time of 14 h. SEM image of PVDF composite fiber membrane; Figure 5 The F-doped sample obtained in Embodiment 6 of this invention has a hydrothermal temperature of 150 °C and a hydrothermal reaction time of 18 h. SEM image of PVDF composite fiber membrane; Figure 6 The F-doped sample obtained in Embodiment 7 of this invention has a hydrothermal temperature of 110 °C and a hydrothermal reaction time of 10 h. SEM image of PVDF composite fiber membrane; Figure 7 The F-doped sample obtained in Embodiment 8 of this invention has a hydrothermal temperature of 130 °C and a hydrothermal reaction time of 10 h. SEM image of PVDF composite fiber membrane; Figure 8 The F-doped sample obtained in Embodiment 9 of this invention has a hydrothermal temperature of 170 °C and a hydrothermal reaction time of 10 h. Digital photograph of PVDF composite fiber membrane; Figure 9The pure PVDF fiber membranes and F-doped membranes prepared in Comparative Examples 1 and Embodiments 2 to 5 of this invention are examples of the present invention. Contact angle test results of PVDF composite fiber membrane; Figure 10 The pure PVDF fiber membrane and F-doped membrane prepared in Comparative Example 1 and Embodiment 4 of this invention are examples of the present invention. Stress-strain curve of PVDF composite fiber membrane; Figure 11 The F-doped sample obtained in Embodiment 4 of the present invention Digital photograph of PVDF composite fiber membrane; Figure 12 As comparative examples 1-2 of the present invention, the pure PVDF fiber membrane prepared in embodiment four... Nanoparticles and F-doped XRD pattern of PVDF composite fiber membrane; Figure 13 In Experiment 1 of this invention, different hydrothermal times affected PVDF- Photocatalytic performance diagram showing the effect of fiber composite membrane on U(VI) reduction; Figure 14 An F-doped variety as described in specific embodiment one of the present invention A flowchart of the preparation method of PVDF composite fiber membrane. Detailed Implementation

[0023] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application can also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of this application with unnecessary detail.

[0024] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0026] Implementation Method 1: An F-doped The preparation method of PVDF composite fiber membrane includes the following steps: S1: PVDF fiber membranes were prepared by electrospinning. S11: A mixed solution is prepared by uniformly mixing an organic solvent with acetone; the organic solvent is at least one selected from N,N-dimethylformamide (DMF), N,N-diethylformamide (DEF), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAC), N-methyl-2-pyrrolidone (NMP), and ethylene glycol monomethyl ether (EGME), preferably N,N-dimethylformamide (DMF). The volume ratio of the organic solvent to acetone is 10 to 1:1. Preferably, the volume ratio is 4 to 1.5:1.

[0027] S12: Add polyvinylidene fluoride (PVDF) powder to the mixed solution, heat and dissolve in a water bath at 40-80°C for 2-8 hours, and let stand for 2-8 hours after complete dissolution to remove excess air bubbles, thereby obtaining an electrospinning solution; wherein the mass of the polyvinylidene fluoride powder is 10%-30% of the mass of the mixed solution. Preferably, the mass of the PVDF powder is 18% of the mass of the mixed solution obtained in step (1).

[0028] S13: Electrospin the electrospinning solution to obtain a PVDF fiber membrane. The process conditions for the electrospinning method are: spinning voltage 12~16 kV, feed speed 0.6~1.5 mL / h, receiving distance 18~25 cm, spinning humidity 20~45%, and spinning temperature 20~40 ℃.

[0029] S2: Mix organic solvent and deionized water thoroughly. Add titanium source dropwise under vigorous stirring for 0.5-3 hours to obtain titanium source solution. The organic solvent is at least one of methanol, ethanol, ethylene glycol, isopropanol, n-propanol, n-butanol, and glycerol. Preferably, ethylene glycol is selected as the organic solvent. The volume ratio of the organic solvent to deionized water is 30-10:1. Preferably, the volume ratio is 18-12:1. The titanium source is at least one of tetrabutyl titanate, ethyl titanate, titanium tetrachloride, titanium trichloride, isopropyl titanate, and isobutyl titanate. Preferably, titanium trichloride is selected as the titanium source. The volume ratio of the titanium source to the organic solvent is 100-10:1. Preferably, the volume ratio is 40-20:1.

[0030] S3: The PVDF fiber membrane and titanium source solution are simultaneously added to a high-temperature reactor for hydrothermal reaction to obtain a preliminary fiber membrane. The hydrothermal reaction temperature is 110~170 ℃, preferably 150 ℃, and the hydrothermal reaction time is 2~18 h. After the reaction is complete, the preliminary fiber membrane is taken out and washed repeatedly three times with ethanol and deionized water. After washing, it is dried in an oven at 40~70 ℃ for 2~24 hours to obtain F-doped membrane. / PVDF composite fiber membrane.

[0031] This embodiment obtains PVDF fiber membranes via electrospinning technology, requiring no other treatment, and utilizes a hydrothermal method for in-situ growth on its surface. Simultaneously, using PVDF as the source of F, to achieve F-doping modification. The F-doped material prepared in this way... PVDF composite fiber membranes possess excellent hydrophilicity, mechanical properties, and photocatalytic performance. They can efficiently reduce uranium (VI) in water without the need for sacrificial agents, and are easy to recycle and reuse, significantly improving the performance and efficiency of photocatalytic materials in practical applications.

[0032] This invention provides an F-doped PVDF composite fiber membrane and its preparation method: in-situ growth of PVDF membrane on the surface using a hydrothermal method. At the same time, PVDF can also be used as an F source for... F-doping modification can be achieved through a simple one-step hydrothermal method. The F-doping modification and in-situ growth on PVDF films not only improved The photocatalytic efficiency for uranium is improved while avoiding the drawbacks of powdered photocatalysts, such as easy agglomeration and difficulty in separation and reuse. The prepared composite fiber membrane exhibits good flexibility and is easy to separate, and the F-doped modification further enhances its effectiveness. It exhibits excellent photocatalytic reduction performance for uranium (VI).

[0033] Implementation Method Two: This embodiment is an F-doped method as described in Embodiment 1. Further examples illustrate the preparation method of PVDF composite fiber membranes.

[0034] An F-doped The preparation method of PVDF composite fiber membrane includes the following steps: (1) Mix 12 ml of N,N-dimethylformamide (DMF) with 6 ml of acetone solution to prepare a mixed solution; (2) Weigh 2.88 g of polyvinylidene fluoride (PVDF) powder and add it to the mixed solution. Heat it in a water bath at 50 °C for 4 h to dissolve it. After it is completely dissolved, let it stand for 2 h to remove excess air bubbles and obtain the electrospinning solution. (3) The spinning solution obtained in step (2) is electrospun at room temperature, with a voltage of 14 kV, a distance of 15 cm between the needle and the collector, an injection speed of 1.0 ml / h, an ambient temperature of 20-30 ℃, and a humidity of 30-50%, to obtain a PVDF fiber membrane. (4) Mix 60 mL of ethylene glycol and 4 mL of deionized water evenly, and add 2 mL of TiCl3 dropwise under vigorous stirring for 0.5 h.

[0035] (5) The PVDF fiber membrane prepared in step (3) and the solution prepared in step (4) are added together into a high-temperature reactor and reacted at 150 °C for 2 h. After the reaction is complete, the membrane is taken out and washed repeatedly with ethanol and deionized water 3 times. It is then dried in an oven at 60 °C for 24 h to obtain F doping. / PVDF composite fiber membrane.

[0036] The product obtained in this embodiment SEM image of PVDF composite fiber membrane as shown below Figure 1 As shown, by Figure 1 It can be seen that the flexible PVDF fiber membrane prepared using the method and conditions described in this embodiment is composed of randomly oriented nanofibers, and its surface is not loaded with... Nanoparticles.

[0037] Implementation Method 3: The steps of this embodiment are the same as those in Embodiment 2, except that the hydrothermal reaction time in step (5) is changed to 6 hours.

[0038] The product obtained in this embodiment SEM image of PVDF composite fiber membrane as shown below Figure 2 As shown, by Figure 2 It can be seen that the flexible PVDF fiber membrane prepared using the method and conditions described in this embodiment has a surface loaded with sporadic particles. Nanoparticles It appears as nano-flowers and is unevenly distributed.

[0039] Implementation Method Four: The steps of this embodiment are the same as those in Embodiment 2, except that the hydrothermal reaction time in step (5) is changed to 10h.

[0040] The product obtained in this embodiment SEM image of PVDF composite fiber membrane as shown below Figure 3 As shown, by Figure 3It can be seen that the flexible PVDF fiber membrane prepared using the method and conditions described in this embodiment has a large amount of [unclear text - possibly related to surface loading]. Nanoparticles It exhibits a nano-flower-like appearance and is evenly distributed.

[0041] Implementation Method 5: The steps of this embodiment are the same as those in Embodiment 2, except that the hydrothermal reaction time in step (5) is changed to 14 hours.

[0042] The product obtained in this embodiment SEM image of PVDF composite fiber membrane as shown below Figure 4 As shown, by Figure 4 It can be seen that the flexible PVDF fiber membrane prepared by the method and conditions described in this embodiment has a large amount of nanoflower-like structures loaded on its surface. Nanoparticles, and Some families reunited.

[0043] Implementation Method Six: The steps of this embodiment are the same as those in Embodiment 2, except that the hydrothermal reaction time in step (5) is changed to 18h.

[0044] The product obtained in this embodiment SEM image of PVDF composite fiber membrane as shown below Figure 5 As shown, by Figure 5 It can be seen that the PVDF fiber membrane prepared by the method and conditions described in this embodiment has a large amount of nanofloral material loaded on its surface. Nanoparticles, and The aggregation phenomenon is obvious, and it is easy to peel off.

[0045] Comparing embodiments two to six, with a hydrothermal temperature of 150 °C, the F-doped samples obtained from different hydrothermal reactions... SEM images of the PVDF composite fiber membrane show that the hydrothermal reaction time is 10 h. The load is most uniform on the surface of the PVDF fiber membrane.

[0046] Implementation Method Seven: The steps of this embodiment are as described in Embodiment 2, except that the hydrothermal reaction temperature in step (5) is set to 110 °C and the hydrothermal reaction time is set to 10 h.

[0047] The product obtained in this embodiment SEM image of PVDF composite fiber membrane as shown below Figure 6 As shown, by Figure 6 It can be seen that the flexible PVDF fiber membrane prepared using the method and conditions described in this embodiment failed to have its surface loaded with [material]. Nanoparticles.

[0048] Implementation Method Eight: The steps of this embodiment are as described in Embodiment 2, except that the hydrothermal reaction temperature in step (5) is set to 130 °C and the hydrothermal reaction time is set to 10 h.

[0049] The product obtained in this embodiment SEM image of PVDF composite fiber membrane as shown below Figure 7 As shown, by Figure 7 It can be seen that the flexible PVDF fiber membrane prepared using the method and conditions described in this embodiment failed to have a surface loading capacity. Nanoparticles.

[0050] Implementation Method Nine: The steps of this embodiment are as described in Embodiment 2, except that the hydrothermal reaction temperature in step (5) is set to 170 °C and the hydrothermal reaction time is set to 10 h.

[0051] The product obtained in this embodiment Digital photos of PVDF composite fiber membranes are shown below. Figure 8 As shown, by Figure 8 It can be seen that the PVDF fiber membrane has carbonized due to the excessively high temperature.

[0052] Comparing Embodiment 4 and Embodiments 7 to 9, F-doped samples obtained after 10 hours of hydrothermal reaction at different hydrothermal temperatures were compared. SEM and digital images of the PVDF composite fiber membrane show that 150 ℃ is the optimal hydrothermal reaction temperature.

[0053] Comparative Example 1: (1) Mix 12 ml of N,N-dimethylformamide (DMF) with 6 ml of acetone solution to prepare a mixed solution; (2) Weigh 2.88 g of polyvinylidene fluoride (PVDF) powder and add it to the mixed solution. Heat it in a water bath at 50 °C for 4 h to dissolve it. After it is completely dissolved, let it stand for 2 h to remove excess air bubbles and obtain the electrospinning solution. (3) Electrospinning is performed on the spinning solution obtained in step (2) at room temperature, with a voltage of 14 kV, a distance of 15 cm between the needle and the collector, an injection speed of 1.0 ml / h, an ambient temperature of 20-30 ℃, and a humidity of 30-50% to obtain a PVDF fiber membrane.

[0054] Comparative Example 2: (1) Mix 60 mL of ethylene glycol and 4 mL of deionized water evenly, and add 2 mL of TiCl3 dropwise under vigorous stirring for 0.5 h.

[0055] (2) Add the solution prepared in step (1) to a high-temperature reactor and react at 150 °C for 10 h. After the reaction is complete, centrifuge and wash the obtained powder material repeatedly with ethanol and deionized water three times. Dry it in an oven at 60 °C for 24 h to obtain the final product. Nanoparticles.

[0056] Comparative Examples 1, and the pure PVDF fiber membranes and F-doped membranes prepared in Examples 2 to 6 The contact angle of the PVDF composite fiber membrane is as follows: Figure 9 As shown, the PVDF fiber membrane has a contact angle of 153.2° and is a hydrophobic material, produced through hydrothermal growth on its surface. Afterwards, the composite fiber membrane exhibits excellent hydrophilicity, with a contact angle ranging from 23.5 to 32.1°.

[0057] Comparative Example 1, Pure PVDF Fiber Membrane and F-doped Membrane prepared in Embodiment 4 The stress-strain curve of the PVDF composite fiber membrane is as follows: Figure 10 As shown, The loading of nanoparticles on the surface of the PVDF fiber membrane improves its tensile strength; F doping... The tensile strength of the PVDF composite fiber membrane reaches 2.0 MPa.

[0058] F-doped sample obtained in Implementation Method 4 Digital photos of PVDF composite fiber membranes, such as Figure 11 As shown, the composite fiber membrane has excellent mechanical properties and can be bent, folded, and knotted at will.

[0059] Comparative Examples 1-2, the pure PVDF fiber membrane prepared in Embodiment 4, Nanoparticles and F-doped The XRD pattern of the PVDF composite fiber membrane is as follows: Figure 12 As shown, the results demonstrate that the present invention can grow on the surface of PVDF fiber membranes. Nanoparticles are bronze phase .

[0060] Experimental example: Add a 10 mg / L U(VI) solution to a 100 ml jacketed quartz cup equipped with circulating water (25±1℃), then use a solution of a certain concentration... The pH of the solution was adjusted to 2. 40 mg of the composite fiber membrane prepared in methods two to six were added to the above solution, and the solution was continuously irradiated for 120 min in air using a 300 W xenon lamp as the light source. During the photocatalytic process, 1 ml of the reaction solution was taken at regular intervals and filtered using a 0.22 μm nylon needle filter. The concentration of soluble U in the filtrate was measured using an ICAP7400 inductively coupled plasma optical emission spectrometer (ICP-OES). PVDF- The efficiency of photocatalytic reduction of U(VI) by fiber composite membrane is given by the formula. It means that, among them This indicates the concentration of soluble U at time t min during photocatalysis. This represents the concentration of U before photocatalytic reduction. All experimental results were fitted using a modified first-order kinetic function, as shown in the formula: , This indicates the residual amount of soluble U. It is a pseudo-first-order dynamic constant.

[0061] In the experimental example, different hydrothermal times affected PVDF- The photocatalytic performance of fiber composite membranes affected by the reduction of U(VI) is as follows: Figure 13 As shown, at pH=2, TFM exhibited the best reduction capacity with a hydrothermal time of 10 h, achieving a removal rate of 70% after 60 μm photocatalysis. When the hydrothermal time was too short, the removal rate decreased due to the presence of impurities on the composite membrane. The low load results in low removal efficiency, while when the hydrothermal time is too long, although the load... While the number of particles increases, they tend to cluster, which can reduce removal efficiency.

Claims

1. A F-doped A method for producing a F-doped The method comprises the following steps: S1: obtaining a PVDF fiber membrane by electrospinning; S2: uniformly mixing an organic solvent and deionized water, and adding a titanium source drop by drop under vigorous stirring, and continuously stirring for 0.5-3 h to obtain a titanium source solution; S3: the PVDF fiber membrane and the titanium source solution are simultaneously added to a high-temperature reaction kettle to perform a hydrothermal reaction, a preliminary fiber membrane is obtained, after the reaction is completed, the preliminary fiber membrane is fished out, and is repeatedly washed with ethanol and deionized water for 3 times, after the washing is completed, the preliminary fiber membrane is dried in an oven at 40-70 ℃ for 2-24 hours, and an F-doped / PVDF composite fiber membrane is obtained.

2. A F-doped A method for producing a PVDF composite fiber membrane, characterized by, The S1 comprises: S11: uniformly mixing an organic solvent and acetone to obtain a mixed solution; S12: adding polyvinylidene fluoride powder into the mixed solution, heating and dissolving in a water bath at 40-80 DEG C for 2-8 h, and then standing for 2-8 h to remove excess bubbles to obtain an electrospinning solution; S13: electrospinning the electrospinning solution to obtain a PVDF fiber membrane.

3. A F-doped according to claim 2 A method for producing a PVDF composite fiber membrane, characterized by, The organic solvent in the S11 is at least one of N, N-dimethylformamide, N, N-diethylformamide, dimethyl sulfoxide, dimethylacetamide, N-methyl-2-pyrrolidone and ethylene glycol monomethyl ether, and the volume ratio of the organic solvent to acetone is 4-1.5:

1.

4. A F-doped according to claim 2 Method for producing a composite fiber membrane of PVDF, characterized by, The mass of the polyvinylidene fluoride powder in the S12 is 10%-30% of the mass of the mixed solution.

5. A F-doped according to claim 1 A method for producing a PVDF composite fiber membrane, characterized by, The process conditions of the electrospinning method are as follows: spinning voltage 12-16 kV, pushing speed 0.6-1.5 mL / h, receiving distance 18-25 cm, spinning humidity 20-45%, and spinning temperature 20-40 DEG C.

6. A F-doped according to claim 1 Method for producing a composite fiber membrane of PVDF, characterized by, The organic solvent in the S2 is at least one of methanol, ethanol, ethylene glycol, isopropyl alcohol, n-propanol, n-butanol and glycerol, and the volume ratio of the organic solvent to deionized water is 30-10:

1.

7. A F-doped according to claim 1 A method for producing a PVDF composite fiber membrane, characterized by, The titanium source in the S2 is at least one of butyl titanate, ethyl titanate, titanium tetrachloride, titanium trichloride, isopropyl titanate and isobutyl titanate, and the volume ratio of the titanium source to the organic solvent is 40-20:

1.

8. A F-doped according to claim 1 A method for producing a PVDF composite fiber membrane, characterized by, In the S3, the hydrothermal reaction temperature is 110-170 DEG C, and the hydrothermal reaction time is 2-18 h.

9. An F-doped / PVDF composite fiber membrane prepared by the method of any one of claims 1-8.​ 10. A photocatalyst characterized by comprising: F-doped as claimed in claim 9 / PVDF composite fiber membranes.

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