A method of preparing a janus membrane hydrophobic layer from a modified hydrophobic polymer nanofiber

Abstract

The application belongs to the technical field of membrane materials, and particularly relates to a method for preparing a Janus membrane hydrophobic layer from modified hydrophobic polymer nanofibers. The method uses secondary deep exfoliation to obtain single-layer high-fluorinated graphene oxide nanosheets, which are used as hydrophobic polymer additives in the preparation of the hydrophobic layer in the electrospinning process to induce the formation of uniform bead structures, promote the formation of finer nanofibers, more microspheres, and larger pore diameters. The Janus membrane prepared with the hydrophobic layer can significantly improve the permeation flux and / or oil-water separation efficiency in the oil-water separation process, and has excellent cycle stability.

Description

A method for preparing a hydrophobic layer of a Janus membrane using modified hydrophobic polymer nanofibers Technical Field

[0001] This invention belongs to the field of membrane materials technology. More specifically, it relates to a method for preparing a Janus membrane hydrophobic layer using modified hydrophobic polymer nanofibers. Background Technology

[0002] Wastewater from industries such as petrochemicals, textiles, metal mining, and food processing contains oil pollutants, which can cause serious water pollution and disrupt aquatic ecosystems once it enters the aquatic environment. Given the current international environment and my country's ever-increasing crude oil imports, separating and treating oily wastewater (especially oil-in-water emulsions) can effectively protect the environmental balance while enabling resource recovery and reuse. Among existing oil-water separation technologies, membrane separation technology has advantages such as simplicity, high efficiency, convenient operation, and wide applicability, and has attracted widespread attention from the academic community in the field of oil-water separation over the past few decades.

[0003] Electrospinning is considered an ideal technology for preparing oil-water separation membrane materials because it allows for convenient and effective control of the chemical composition, porosity, and micro / nano structure of the membrane material. To improve the separation performance of membrane materials, low surface energy materials (such as silica particles, graphene, and polyfluorinated compounds) are often used to further enhance the hydrophobicity of the polymer membrane material. For example, Chinese patent application CN114452840A provides a graphene oxide-modified separation membrane based on electrostatic spraying. The resulting graphene oxide-modified separation membrane has both a hydrophilic surface layer and a hydrophobic mass transfer layer, enabling long-term stable operation and exhibiting excellent antifouling, antiwetting, desalination, and permeation flux. It is a high-performance hydrophilic-hydrophobic "Janus" composite membrane, but its permeation flux does not exceed 60 L / m³. 2 The efficiency of graphene oxide still needs improvement. Fluorinated graphene oxide materials possess a two-dimensional planar structure of graphene and exhibit strong hydrophobicity due to the presence of fluorine atoms. With its high aspect ratio and high specific surface area, it exhibits good interaction with polymers and can be used as an additive to improve hydrophobic film materials. The preparation methods of fluorinated graphene oxide materials mainly include: (1) fluorinated graphite exfoliation oxidation, (2) refluorination of graphene oxide, and (3) vapor deposition using CH4 and SF6 as carbon sources and fluorinating agents. Among these, the fluorinated graphite exfoliation oxidation method is simple to operate, easy to mass-produce, and has higher application potential. However, the graphene materials prepared using fluorinated graphite exfoliation oxidation have a low degree of exfoliation and poor particle uniformity, resulting in poor film formation. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the defects and shortcomings of the graphene material prepared by the exfoliation and oxidation of fluorinated graphite in the prior art, which are difficult to guarantee the degree of exfoliation, have poor particle uniformity, and have poor film formation effect. The present invention provides a method for preparing the hydrophobic layer of Janus membrane by modified hydrophobic polymer nanofibers.

[0005] The purpose of this invention is to provide an application of the method.

[0006] The above-mentioned objective of this invention is achieved through the following technical solution:

[0007] This invention protects a method for preparing a Janus membrane hydrophobic layer using modified hydrophobic polymer nanofibers, comprising the following steps:

[0008] S1. Fluorinated graphite is dispersed in an acidic reagent, followed by oxidation treatment with an oxidant, and then post-treatment to obtain first-stage deep exfoliated fluorinated graphene oxide; repeat the above steps to obtain second-stage deep exfoliated fluorinated graphene oxide; the second-stage deep exfoliation is to use the reagent used in the traditional first-stage exfoliation in two separate applications, that is, to prepare high-fluorinated graphene oxide material under the condition that the total amount of reagent used and the total exfoliation time remain unchanged.

[0009] S2. After fully dissolving the hydrophobic polymer in the organic solvent, stir thoroughly to obtain a hydrophobic polymer solution;

[0010] S3. Add the secondary deep exfoliated fluorinated graphene oxide obtained in step S1 to an organic solvent, disperse it fully, and then mix it thoroughly with the hydrophobic polymer solution obtained in step S2 to obtain a spinning solution.

[0011] S4. Electrospin the spinning solution obtained in step S3 on the surface of the hydrophilic layer, and the resulting layer on the surface of the hydrophilic layer is the Janus membrane hydrophobic layer.

[0012] Through extensive preliminary research, the applicant has, for the first time, discovered that by dividing the reagents used in the traditional single-step exfoliation process into two applications—that is, by keeping the total reagent usage and total exfoliation time constant—highly fluorinated graphene oxide materials can be prepared. The resulting highly fluorinated graphene oxide exhibits a uniform structure and high dispersion, which is more conducive to ensuring the structural stability and separation performance of the membrane material. When used as a hydrophobic polymer additive in the electrospinning process to participate in the preparation of the hydrophobic layer, it can induce the formation of a uniform beaded structure, promoting the generation of finer nanofibers and more microspheres. The finer the nanofibers, the greater the spacing between them, which is beneficial for the formation of larger pores in the hydrophobic layer. Janus membranes prepared using this hydrophobic layer significantly improve the permeate flux and / or oil-water separation efficiency in the oil-water separation process and exhibit excellent cycling stability.

[0013] Furthermore, the hydrophobic layer thickness of the Janus membrane is 2–8 μm.

[0014] Preferably, the electrospinning time is 10 to 20 minutes.

[0015] Preferably, the acidic reagent is one or more of sulfuric acid, phosphoric acid, or nitric acid.

[0016] Preferably, in step S1, the oxidant is potassium permanganate or potassium dichromate.

[0017] Preferably, in step S1, the post-processing includes stopping the oxidation reaction, adding ice, allowing the mixture to stand and separate into layers, collecting, washing, and drying.

[0018] Optionally, the oxidation reaction can be stopped by reacting hydrogen peroxide with potassium permanganate or potassium dichromate.

[0019] Specifically, the purpose of adding ice is to cool the liquid and provide sufficient water (the ice will melt) so that the fluorinated graphene oxide prepared by exfoliation and oxidation floats on the surface of the liquid.

[0020] Preferably, the hydrophobic polymer is one or more of polyvinylidene fluoride-hexafluoropropylene copolymer, polystyrene, polyvinylidene fluoride, polyvinyl chloride, and polyethylene.

[0021] Preferably, in steps S1 and S2, the organic solvent is one or more of N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, and acetone.

[0022] Preferably, in step S4, the material of the hydrophilic layer is one or more of polyacrylonitrile, polyethersulfone, polyvinylidene fluoride, polyvinyl alcohol, and cellulose acetate.

[0023] Preferably, in step S2, the mixing ratio of the hydrophobic polymer to the organic solvent is 2-8:16 g / mL.

[0024] Preferably, in step S3, the mixing ratio of the secondary deep exfoliated fluorinated graphene oxide (FGO) to the organic solvent is 0.1–1:4 g / mL. This invention also requires reasonable control of the amount of secondary deep exfoliated fluorinated graphene oxide (FGO). Reducing the amount of FGO will decrease the number of microspheres in the hydrophobic layer membrane structure, while increasing the amount of FGO will increase the number of microspheres, resulting in a morphology similar to that of single-exfoliated FGO, and the microspheres will become irregular. Furthermore, if the amount of FGO is too high, it will aggregate, leading to a significant decrease in the performance of the resulting Janus membrane.

[0025] This invention also protects the application of the preparation method in the field of membrane separation technology.

[0026] The present invention has the following beneficial effects: The present invention provides a method for preparing a Janus membrane hydrophobic layer by modifying hydrophobic polymer nanofibers. The method obtains a single layer of highly fluorinated graphene oxide nanosheets by using a two-stage deep exfoliation process. When the graphene oxide nanosheets are used as a hydrophobic polymer additive in the electrospinning process, they can induce the formation of a uniform beaded structure, promote the generation of finer nanofibers, more microspheres, and larger pore sizes. The Janus membrane prepared with this as the hydrophobic layer can significantly improve the permeation flux and / or oil-water separation efficiency in the oil-water separation process, and has excellent cycle stability. Attached Figure Description

[0027] Figure 1 shows the surface morphology (a) of the secondary exfoliated FGO / PVDF-HP hydrophobic layer prepared in Example 1 and the statistical data (b) of its nanofiber diameter distribution.

[0028] Figure 2 shows the SEM image (a) of the morphology of the PVDF-HP hydrophobic layer surface prepared in Comparative Example 1 and the statistical diagram (b) of its nanofiber diameter distribution data.

[0029] Figure 3 shows the surface morphology SEM image (a) of the FGO / PVDF-HP hydrophobic layer prepared in Comparative Example 2 after one-time exfoliation and the statistical data of nanofiber diameter distribution (b).

[0030] Figure 4 is a statistical chart of the surface roughness of the hydrophobic layers prepared by Comparative Example 1 without FGO (a), Comparative Example 2 with one-time exfoliated FGO (b), and Example 1 with two-time exfoliated FGO (c).

[0031] Figure 5 shows the permeation flux and oil-water separation efficiency of Janus membranes with hydrophobic layers of no FGO (Comparative Example 1), one-time exfoliated FGO (Comparative Example 2), and two-time exfoliated FGO (Example 1) (Example 1); and the permeation flux and oil-water separation efficiency of Janus membranes prepared with two-time exfoliated FGO at different electrospinning times (Example 1-20 min, Example 2-10 min, and Comparative Example 3-30 min) (b).

[0032] Figure 6 shows the oil-water separation performance of the Janus membrane material obtained in Example 1: the separation process of heavy oil / water mixture (a), the cyclic separation stability and reusability of heavy oil / water mixture (b), the separation process of light oil / water mixture (c), and the cyclic separation stability and reusability of light oil / water mixture (d). Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0034] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0035] The preparation methods for the hydrophilic layers of the Janus membranes in the examples and comparative examples were both achieved through the following steps:

[0036] 1. Preparation of the hydrophilic layer of the Janus membrane: Polyacrylonitrile (PAN) powder was dried in an oven for 6 hours. 10 g of PAN powder was added to 40 mL of DMF solvent, and the mixture was mechanically stirred at 60 °C for 12 hours to obtain a 10 wt% PAN solution. PAN nanofiber membrane material was prepared by electrospinning. Specific electrospinning parameters were: voltage 21 kV, electrospinning flow rate 1.0 mL / h, receiving distance 15 cm, and receiving time 240 min. After electrospinning, the PAN nanofiber membrane was placed in a hot press for hot pressing to improve its mechanical strength and stability. The hot pressing temperature was 120 °C, and the hot pressing time was 2 min. The hot-pressed PAN nanofiber membrane served as the hydrophilic layer of the Janus membrane.

[0037] 2. The methods for determining permeation flux and oil-water separation efficiency are conventional methods, specifically:

[0038] (1) Permeation flux: The test procedure is shown in Figure 6. The membrane (with known membrane area) is sandwiched between two glass tubes and placed vertically. Oil and water are added to red dye (Oil Red) and blue dye (Methyl Blue), respectively. The mixture is poured into the upper glass tube, and oil and water are separated under gravity. The volume of liquid collected in the bottom layer per unit time is recorded, and the permeation flux (L / m³) is calculated. 2 ·h).

[0039] (2) Retention rate (representing oil-water separation efficiency): The experimental procedure is consistent with the permeation flux. The total organic carbon (TOC, reflecting the oil content in the liquid) of the bottom collected liquid is measured, and the TOC of the original oil or water is measured at the same time. The retention rate (R) is calculated according to the following formula:

[0040]

[0041] Where C0 is the original TOC of oil or water, C e TOC for collecting liquid at the bottom layer.

[0042] 3. Roughness was measured using an atomic force microscope.

[0043] 4. The morphology of the hydrophobic layer was determined by scanning electron microscopy. The obtained SEM images were used to obtain a statistical data graph of the nanofiber diameter distribution of the hydrophobic layer using ImageJ software.

[0044] Example 1: Preparation of Janus membrane with FGO / PVDF-HP hydrophobic layer after secondary exfoliation

[0045] (1) Preparation of fluorinated graphene oxide (FGO) by secondary deep exfoliation

[0046] 4 g of fluorinated graphene (fluorination degree 60%) was dispersed in 200 mL of concentrated sulfuric acid / concentrated phosphoric acid (volume ratio 9:1) solution and stirred at 50 °C for 2 h. Then, 9 g of potassium permanganate powder was slowly added, and the mixture was stirred at 90 °C for 4 h. The mixed solution was poured into ice water, and then 5 mL of hydrogen peroxide (30%) was added. After sufficient settling and separation, the brown solid at the top of the liquid surface was collected. The mixture was centrifuged at 6000 rpm for 30 min, washed with 30 wt% hydrochloric acid and anhydrous ethanol to remove residual impurities, dried, and then subjected to secondary exfoliation following the above steps to obtain secondary deep exfoliated fluorinated graphene oxide material.

[0047] (2) Preparation of FGO / PVDF-HP mixed solution by secondary exfoliation

[0048] PVDF-HP (polyvinylidene fluoride-hexafluoropropylene) powder was dried in an oven for 6 hours. Then, 5 g of PVDF-HP was dissolved in 16 mL of DMF and stirred at 50 °C for 6 hours to prepare a viscous PVDF-HP solution. Next, 0.4 g of secondary exfoliated FGO particles were added to 4 mL of acetone, and the mixture was sonicated for 3 hours to obtain a uniformly dispersed mixture. This mixture was then combined with the PVDF-HP solution and stirred for another 3 hours to obtain an electrospinning casting solution. The spinning solution ratios are shown in Table 1.

[0049] (3) Electrospinning of hydrophilic PAN nanofiber layer to prepare secondary exfoliated FGO / PVDF-HP hydrophobic layer

[0050] After degassing the electrospinning casting solution, a hydrophobic layer of secondary exfoliated FGO / PVDF-HP nanofibers was prepared on the surface of the hydrophilic PAN nanofiber support layer by electrospinning. After drying in air, a Janus membrane with PAN as the hydrophilic layer and secondary exfoliated FGO / PVDF-HP as the hydrophobic layer was obtained. The electrospinning process parameters are shown in Table 2.

[0051] Table 1. FGO / PVDF-HP spinning solution ratio

[0052]

[0053] Table 2 Electrospinning parameters

[0054]

[0055] Example 2: Preparation of Janus membrane with FGO / PVDF-HP hydrophobic layer after secondary exfoliation

[0056] The difference from Example 1 is that the electrospinning time in step (2) is changed to 10 min.

[0057] Other steps and parameters are the same as in Example 1.

[0058] Example 3: Preparation of Janus membrane with FGO / PVDF-HP hydrophobic layer after secondary exfoliation

[0059] The difference from Example 1 is that the electrospinning time in step (2) is changed to 15 min.

[0060] Other steps and parameters are the same as in Example 1.

[0061] Comparative Example 1: Preparation of Janus membrane with PVDF-HP as hydrophobic layer

[0062] (1) Preparation of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HP) polymer solution

[0063] PVDF-HP powder was dried in an oven for 6 hours. Then, 5 g of PVDF-HP was dissolved in 16 mL of N,N-dimethylformamide (DMF) and stirred at 50 °C for 6 hours to prepare a viscous PVDF-HP solution. Then, 4 mL of acetone was added and stirring was continued for 3 hours to obtain an electrospinning casting solution. The spinning solution ratio (except that no FGO was added, all other parameters were the same) is shown in Table 1.

[0064] (2) Electrospinning of hydrophilic PAN nanofiber layer to prepare PVDF-HP hydrophobic layer

[0065] After degassing the electrospinning casting solution, a hydrophobic PVDF-HP nanofiber hydrophobic layer was prepared on the surface of the hydrophilic PAN nanofiber support layer by electrospinning. After drying in air, a Janus membrane material with PAN as the hydrophilic layer and PVDF-HP as the hydrophobic layer was obtained. The electrospinning process parameters are shown in Table 2.

[0066] Comparative Example 2: Preparation of Janus membrane with FGO / PVDF-HP hydrophobic layer after single-step exfoliation

[0067] (1) Preparation of fluorinated graphene oxide (FGO) by single-step exfoliation:

[0068] 4 g of fluorinated graphene (fluorination degree 60%) was dispersed in 400 mL of concentrated sulfuric acid / concentrated phosphoric acid (volume ratio 9:1) solution and stirred at 50 °C for 4 h. Then, 18 g of potassium permanganate powder was slowly added, and the mixture was stirred at 90 °C for 8 h. The mixture was poured into ice water, and then 10 mL of hydrogen peroxide (30%) was added. After sufficient settling and separation, the brown solid at the top of the liquid surface was collected. The mixture was centrifuged at 6000 rpm for 30 min, washed with 30 wt% hydrochloric acid and anhydrous ethanol to remove residual impurities, and then dried to obtain a single-layer deep-exfoliated fluorinated graphene oxide material.

[0069] (2) Preparation of FGO / PVDF-HP mixed solution by single-step stripping:

[0070] PVDF-HP powder was dried in an oven for 6 hours. Then, 5 g of PVDF-HP was dissolved in 16 mL of DMF and stirred at 50 °C for 6 hours to prepare a viscous PVDF-HP solution. Next, 0.4 g of single-peeled FGO particles were added to 4 mL of acetone, and the mixture was sonicated for 3 hours to obtain a uniformly dispersed solution. This solution was then mixed with the PVDF-HP solution and stirred for another 3 hours to obtain an electrospinning casting solution. The spinning solution ratios are shown in Table 1.

[0071] (3) Electrospinning of hydrophilic PAN nanofiber layer to prepare a single-exfoliation FGO / PVDF-HP hydrophobic layer:

[0072] After degassing the electrospinning casting solution, a single-exfoliated FGO / PVDF-HP nanofiber hydrophobic layer was prepared on the surface of the hydrophilic PAN nanofiber support layer by electrospinning. After drying in air, a Janus membrane material with PAN as the hydrophilic layer and single-exfoliated FGO / PVDF-HP as the hydrophobic layer was obtained. The electrospinning process parameters are shown in Table 2.

[0073] Comparative Example 3: Janus membrane with FGO / PVDF-HP hydrophobic layer after secondary stripping

[0074] The difference from Example 1 is that the electrospinning time in step (2) is changed to 30 min.

[0075] Other steps and parameters are the same as in Example 1.

[0076] Performance testing

[0077] (1) Morphology and particle size determination

[0078] The morphology of the obtained Janus membrane hydrophobic layer was measured using scanning electron microscopy, and the diameter distribution of the nanofibers in the hydrophobic layer was further measured using ImageJ software. The results are shown in Figures 1-3. The thickness of the secondary exfoliated FGO / PVDF-HP hydrophobic layer obtained in Example 1 is approximately 5 μm, composed of nanofilaments and microspheres, with a uniform structure (Figure 1a). The average diameter of the nanofilaments is 0.195 μm (Figure 1b). The interlocking stacking of finer nanofibers can form a larger pore structure, which helps to improve the permeation flux in the oil-water separation process. The hydrophobic layers of the Janus membranes obtained in Examples 2-3 have basically the same morphological structure as those in Example 1.

[0079] The morphology of the hydrophobic layer of the Janus membrane obtained in Comparative Example 1 is shown in Figure 2. It consists only of nanowires (Figure 2a), and the average diameter of the obtained nanowires is 0.355 μm (Figure 2b), which is relatively thick.

[0080] The morphology of the hydrophobic layer of the Janus membrane obtained in Comparative Example 2 is shown in Figure 3. It consists of nanowires and microspheres, but the number of microspheres formed is small and the shape is irregular (Figure 3a). The average diameter of the nanowires is 0.296 μm (Figure 3b). The diameter is lower than that of the Janus membrane without FGO, but it is still relatively thick, which is not conducive to the improvement of membrane performance.

[0081] (2) Roughness measurement

[0082] The surface roughness results of the Janus hydrophobic layers in Examples 1, 1, and 2 are shown in Figure 4. The hydrophobic layer obtained in Example 1 formed more nanospheres, significantly improving the surface roughness of the resulting hydrophobic layer (543 nm, as shown in Figure 4c). This helps to enhance the surface wettability difference between the hydrophilic and hydrophobic layers of the Janus membrane, thereby improving oil-water separation efficiency. The hydrophobic layers of the Janus membranes obtained in Examples 2 and 3 have essentially the same roughness as those in Example 1.

[0083] The surface roughness of the hydrophobic layers obtained in Comparative Example 1 and Comparative Example 2 were 408 nm (Fig. 4a) and 437 nm (Fig. 4b), respectively. The low roughness is not conducive to improving the surface wettability difference between the hydrophilic and hydrophobic layers of the Janus membrane.

[0084] (3) Determination of separation performance

[0085] Figure 5 shows the results of permeation flux and oil-water separation efficiency. Compared with Janus membranes without FGO or with a single-time stripped FGO / PVDF-HP hydrophobic layer, the Janus membrane with a double-time stripped FGO / PVDF-HP hydrophobic layer (i.e., 2-time FGO / PVDF-HP) showed improved permeation flux and oil-water separation efficiency, with a separation efficiency >95% and a permeation flux >17000 L / m. 2The permeation flux and oil-water separation efficiency of the Janus membrane obtained in Example 2 are shown in Figure 5b. The separation efficiency is >90%, and the permeation flux is >28000 L / m. 2 •h; The Janus membrane obtained in Comparative Example 1 (i.e., the PVDF-HP in Figure 5a) had a low oil-water separation efficiency of <90% and a low permeation flux of <12000 L / m 2 •h; The oil-water separation efficiency of the Janus membrane obtained in Comparative Example 2 (i.e., the 1-time FGO / PVDF-HP in Figure 5a) is still low, <91%, and the permeation flux is <12500 L / m 2 •h; The Janus membrane obtained in Comparative Example 3 (Fig. 5b) has a thicker hydrophobic layer (approximately 10 μm), resulting in a significantly reduced oil-water separation efficiency, below 70%.

[0086] The stability and reusability of the Janus membrane obtained in Example 1 for the cyclic separation of oil / water mixtures were further determined. The results are shown in Figure 6. As can be seen from the figure, the Janus membrane completes the complete separation of oil and water in a heavy oil / water mixture in about 20 seconds (Figure 6a), and completes the separation of oil and water in a light oil / water mixture in about 44 seconds (Figure 6c). This indicates that the Janus membrane has a good separation effect on both heavy oil / water mixtures and light oil / water mixtures.

[0087] When separating oil and water from a heavy oil / water mixture, after a period of circulation (Figure 6b), the permeation flux changes very little, remaining essentially at 18000 L / m³. 2 The oil-water separation efficiency decreased to about 94.5% of the initial efficiency after the third use. With continued use, the oil-water separation efficiency gradually recovered, eventually reaching about 96.5%.

[0088] When separating oil and water from a light oil / water mixture, after a period of circulation (Figure 6d), the permeation flux changed little, remaining essentially at 5500 L / m³. 2 The oil-water separation efficiency remained very stable, consistently around 99%. The Janus membranes obtained in Examples 2 and 3 exhibited essentially the same membrane separation performance as those in Example 1.

[0089] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a Janus membrane hydrophobic layer using modified hydrophobic polymer nanofibers, characterized in that, A method for preparing a Janus membrane hydrophobic layer using modified hydrophobic polymer nanofibers includes the following steps: S1, dispersing fluorinated graphite in an acidic reagent, then adding an oxidant for oxidation treatment, followed by post-treatment to obtain first-stage deeply exfoliated fluorinated graphene oxide; repeating the above steps to obtain second-stage deeply exfoliated fluorinated graphene oxide; S2, fully dissolving the hydrophobic polymer in an organic solvent and stirring thoroughly to obtain a hydrophobic polymer solution; S3, adding the second-stage deeply exfoliated fluorinated graphene oxide obtained in step S1 to an organic solvent, dispersing thoroughly, and then mixing thoroughly with the hydrophobic polymer solution obtained in step S2 to obtain a spinning solution; S4, electrospinning the spinning solution obtained in step S3 on the surface of a hydrophilic layer, forming the Janus membrane hydrophobic layer on the surface of the hydrophilic layer; the electrospinning time is 10-20 min; the hydrophobic polymer is one or more of polyvinylidene fluoride-hexafluoropropylene copolymer, polystyrene, polyvinylidene fluoride, polyvinyl chloride, and polyethylene; the mixing ratio of the second-stage deeply exfoliated fluorinated graphene oxide to the organic solvent is 0.1-1:

4. g / mL; the mixing ratio of the hydrophobic polymer to the organic solvent is 2~8:16 g / mL; the thickness of the hydrophobic layer of the Janus membrane is 2~8 μm.

2. The method for preparing a Janus membrane hydrophobic layer using modified hydrophobic polymer nanofibers according to claim 1, characterized in that, The acidic reagent is one or more of sulfuric acid, phosphoric acid, or nitric acid.

3. The method for preparing a Janus membrane hydrophobic layer using modified hydrophobic polymer nanofibers according to claim 1, characterized in that, In step S1, the oxidant is potassium permanganate or potassium dichromate.

4. The method for preparing a Janus membrane hydrophobic layer using modified hydrophobic polymer nanofibers according to claim 1, characterized in that, In steps S1 and S2, the organic solvent is one or more of N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, and acetone.

5. The method for preparing a Janus membrane hydrophobic layer using modified hydrophobic polymer nanofibers according to claim 1, characterized in that, In step S4, the hydrophilic layer is made of one or more of the following materials: polyacrylonitrile, polyethersulfone, polyvinylidene fluoride, polyvinyl alcohol, and cellulose acetate.

6. The application of the modified hydrophobic polymer nanofibers according to any one of claims 1 to 5 in the preparation of the Janus membrane hydrophobic layer in the field of membrane separation technology.

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