High-flux gradient fiber membrane and preparation method thereof

Abstract

The invention provides a large-flux gradient fiber membrane and a preparation method thereof, and the fiber membrane is mainly prepared from the following raw materials in percentage by mass: 55-83 wt% of an organic solvent, 9-30 wt% of polyvinylidene fluoride, 1-20 wt% of a pore-forming agent and 0.5-15 wt% of an additive. Through effective proportioning of the raw materials, the fiber membrane has relatively high pollution resistance and corrosion resistance and relatively long service life.

Description

Technical Field

[0001] The invention belongs to the technical field of membrane separation, and in particular to a large-flux gradient fiber membrane and a preparation method thereof. Background Art

[0002] At present, the rapid progress of society is accompanied by severe challenges of water pollution, which not only threatens the survival of humans and other organisms, but also poses a major constraint on my country's economic development. Therefore, the effective treatment and recycling of water resources has become a key issue to be resolved.

[0003] Within the existing market scope, the ultrafiltration membrane industry is showing a trend of expanding market size. The main driving forces behind this growth include: the country's increased efforts in environmental protection and water resources management, the iterative upgrading of water treatment technology, the accelerated pace of new urbanization, and the increased demand for high-quality water resources brought about by the improvement of residents' living standards. Despite the booming industry, it still faces a series of limitations and challenges, such as pressure for technological innovation, instability in raw material costs, fierce market competition, and the need to further improve product performance and service life. The ultrafiltration membrane market undoubtedly has broad development potential and good future prospects, but at the same time, companies in the industry also need to continue to adapt to the new market environment and technical standards, and consolidate their competitive advantages through technological innovation and excellent services.

[0004] However, it is worth noting that most of the polymer membranes currently used in the market are easily damaged by pollutants such as organic colloids, proteins, microorganisms and suspended inorganic particles in the solution. At the same time, acid and alkali substances in the water will also corrode the membrane fibers. Especially in the alkaline or acid washing process during on-site operation, these operations will damage the membrane, resulting in a decrease in the separation performance of the membrane and a shortened service life.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The first purpose of the present invention is to provide a large-flux gradient fiber membrane, which has strong anti-pollution and anti-corrosion capabilities and a long service life through the effective ratio of raw materials.

[0007] The second object of the present invention is to provide a method for preparing the above-mentioned large-flux gradient fiber membrane, which is simple to operate, has mild operating conditions, and will not cause harm to the environment and operators.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted: The invention provides a large-flux gradient fiber membrane, which is mainly prepared from the following raw materials by weight percentage: 55-83wt% of an organic solvent, 9-30wt% of polyvinylidene fluoride, 1-20wt% of a pore-forming agent and 0.5-15wt% of an additive.

[0009] Preferably, as a further feasible implementation scheme, it is mainly prepared from the following raw materials, by mass percentage: 60-81wt% of organic solvent, 9.5-25wt% of polyvinylidene fluoride, 2-15wt% of pore-forming agent, and 0.8-13wt% of additives.

[0010] Preferably, as a further feasible embodiment, the material is mainly prepared from the following raw materials, by mass percentage: 80 wt % of organic solvent, 10 wt % of polyvinylidene fluoride, 9 wt % of pore-forming agent and 1 wt % of additive.

[0011] Preferably, as a further feasible embodiment, the material is mainly prepared from the following raw materials, by mass percentage: 80 wt % of organic solvent, 10 wt % of polyvinylidene fluoride, 9 wt % of pore-forming agent and 1 wt % of additive.

[0012] Preferably, the organic solvent is at least one of dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide and N-methylpyrrolidone.

[0013] Preferably, the pore-forming agent is at least one of polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 800, polyethylene glycol 1000, polyethylene glycol 2000, polyvinyl pyrrolidone K17, polyvinyl pyrrolidone K30, and polyvinyl pyrrolidone K90.

[0014] Preferably, the additive is a graphene oxide / zirconium oxide nanocomposite material.

[0015] Among the above raw materials, organic solvents, as the core solvent of the present invention, can effectively dissolve polyvinylidene fluoride, can affect the fluidity of the casting agent stock solution in the present invention and the phase separation rate in the film forming process; it helps to form more microporous structures, thereby improving the water flux of the fiber membrane. Polyvinylidene fluoride, as the main material of the fiber membrane, can determine the mechanical strength and chemical stability of the membrane. An appropriate amount of polyvinylidene fluoride can form a tough membrane structure to resist the erosion of water flow and chemical substances, and the hydrophobicity of polyvinylidene fluoride helps to reduce the adsorption of pollutants on the membrane surface.

[0016] The pore-forming agent plays a role in forming pores in the process of forming the high-flux gradient fiber membrane of the present invention. An appropriate amount of pore-forming agent can form a uniform and through-hole channel structure, thereby improving the water flux and anti-fouling performance of the membrane. The use of the additive, namely graphene oxide / zirconium oxide (GO / ZrO2) nanocomposite material, can significantly improve the separation efficiency and durability of the membrane; graphene oxide can enhance the mechanical strength and osmotic pressure resistance of the membrane due to its unique two-dimensional structure and excellent mechanical properties; zirconium oxide can improve the acid and alkali resistance and high temperature resistance of the membrane due to its good chemical stability and thermal stability; the combined use of the two can further enhance the comprehensive performance of the membrane.

[0017] The use of organic solvents and pore-forming agents makes the membrane have more microporous structures and more uniform pore size distribution, thus achieving the dual goals of high flux and high separation efficiency. At the same time, the hydrophobicity of polyvinylidene fluoride also helps to improve the separation efficiency of the membrane. The use of pore-forming agents and additives not only improves the water flux and anti-pollution performance of the membrane, but also enhances the mechanical strength of the membrane through interaction with polyvinylidene fluoride. The pore structure formed by the pore-forming agent helps to reduce the deposition of pollutants on the membrane surface, and the introduction of additives further improves the durability of the membrane. The synergistic effect of polyvinylidene fluoride and additives makes the membrane have excellent chemical and thermal stability; the chemical corrosion resistance of polyvinylidene fluoride can resist the erosion of various chemical substances, and the introduction of additives further improves the acid and alkali resistance and high temperature resistance of the membrane. This synergistic effect enables the membrane to maintain structural integrity and stable performance in various harsh water conditions and cleaning processes.

[0018] The present invention also provides a method for preparing the above-mentioned high-flux gradient fiber membrane, comprising the following steps: The organic solvent and the stored water are mixed in a certain proportion, and the temperature is raised to obtain a gel bath for use; Pour polyvinylidene fluoride, pore-forming agent, organic solvent and additives into a stirring kettle in sequence, heat and stir until completely dissolved, and then perform degassing treatment to obtain a film casting stock solution; The film casting stock solution is sent to the spraying device through a pump and a pipeline, and the inner lining support pipe passes through the spraying device, and the film casting stock solution is evenly sprayed on the surface of the support pipe; The support tube sprayed with the film casting solution is cooled and solidified in a gel bath and a water bath to form a uniform polyvinylidene fluoride coating on the surface of the support tube; The support tube with polyvinylidene fluoride coating was immersed in glycerol solution to obtain a high-flux gradient fiber membrane.

[0019] Preferably, in the step of heating and stirring until complete dissolution, the heating temperature is 60-80° C. and the stirring time is 15-17 h.

[0020] Preferably, in the step of uniformly spraying the film casting stock solution on the surface of the support tube, the film casting stock solution is sprayed at 0.5MPa-4MPa.

[0021] Preferably, in the gel bath and water bath cooling and curing step, the temperature of the gel bath and the water bath are both 40-60°C.

[0022] Through the carefully designed preparation steps, the present invention realizes the efficient production of high-flux gradient fiber membranes. From the mixing, dissolution and degassing of raw materials, to the spraying of the casting solution, the gel bath and water bath cooling and solidification, to the final glycerol solution soaking treatment, each step is subject to specific parameters to ensure the continuity and stability of the preparation process and improve production efficiency. The preparation method of the present invention uses environmentally friendly raw materials and processes, reducing the emission of harmful substances and energy consumption.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention introduces an inner lining support tube during the preparation process, which is tightly combined with polyvinylidene fluoride. The structure of the high-flux gradient fiber membrane of the present invention is significantly strengthened, which can improve the membrane's ability to resist compression, tension and bending, so that the high-flux gradient fiber membrane of the present invention is not easy to be damaged during long-term use, and can effectively extend the service life of the membrane. The careful selection of pore-forming agents and additives and their reasonable ratio with polyvinylidene fluoride make the membrane of the present invention have a gradient pore structure and high porosity. This structure not only improves the water flux of the membrane, but also ensures a good interception effect, so that the membrane can efficiently remove impurities during the filtration process while reducing energy consumption. The addition of graphene oxide / zirconium oxide nanocomposite (GO / ZrO2) not only increases the porosity of the membrane, but also significantly improves the hydrophilicity of the membrane. The improvement of hydrophilicity helps to reduce the adsorption of pollutants on the membrane surface and reduce the risk of membrane contamination, thereby reducing the cleaning frequency and cleaning cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the following detailed description of the preferred embodiment.The drawings are only for the purpose of illustrating the preferred embodiments and are not to be construed as limiting the invention. In the attached picture: Figure 1 A grid diagram of a high-flux gradient fiber membrane according to an embodiment of the present invention; Figure 2 This is an enlarged view of the grid-shaped holes of the high-flux gradient fiber membrane according to an embodiment of the present invention; Figure 3 A cross-sectional view of a high-flux gradient fiber membrane grid according to an embodiment of the present invention; Figure 4 This is a microscopic view of a high-flux gradient fiber membrane according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be appreciated by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work, all belong to the scope of protection of the present invention. If specific conditions are not indicated in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0026] Example 1 The specific preparation process of the high flux gradient fiber membrane of this embodiment is carried out according to the following steps: Take 40g of dimethylformamide and 60g of pure water and mix them, and heat them to obtain a gel bath for use; 9 g of polyvinylidene fluoride, 6 g of polyethylene glycol 1000, 7 g of polyvinyl pyrrolidone K17, 78 g of dimethylformamide and 13 g of GO / ZrO2 were sequentially poured into a stirring kettle, stirred for 16 h to dissolve under heating conditions of 70 ° C, and then degassed for 12 h to obtain a casting solution; The film casting stock solution is sent to the spraying device through a pump and a pipeline under the operating condition of 4MPa, and the inner lining support pipe is passed through the spraying device, and the film casting stock solution is evenly sprayed on the surface of the support pipe; The support tube sprayed with the film casting solution is cooled and solidified in a 50°C gel bath and a water bath to form a uniform polyvinylidene fluoride coating on the surface of the support tube; The support tube with polyvinylidene fluoride coating was immersed in glycerol solution for 12 hours to obtain a high-flux gradient fiber membrane.

[0027] Example 2 The specific preparation process of the high flux gradient fiber membrane of this embodiment is carried out according to the following steps: Take 55 g of dimethylformamide and 45 g of pure water and mix them, and heat them to obtain a gel bath for use; 10 g of polyvinylidene fluoride, 9 g of polyethylene glycol 400, 11 g of polyvinyl pyrrolidone K90, 55 g of dimethylformamide and 15 g of GO / ZrO2 were sequentially poured into a stirring kettle, stirred for 15 h to dissolve under heating conditions of 60 ° C, and then degassed for 12 h to obtain a casting solution; The film casting stock solution is sent to the spray device through a pump and a pipeline under the operating condition of 1.5MPa, and the inner lining support pipe passes through the spray device, and the film casting stock solution is evenly sprayed on the surface of the support pipe; The support tube sprayed with the film casting solution is cooled and solidified in a 55°C gel bath and a water bath to form a uniform polyvinylidene fluoride coating on the surface of the support tube; The support tube with polyvinylidene fluoride coating was immersed in glycerol solution for 12 hours to obtain a high-flux gradient fiber membrane.

[0028] Example 3 The specific preparation process of the high flux gradient fiber membrane of this embodiment is carried out according to the following steps: Mix 30 g of dimethyl sulfoxide and 70 g of pure water, and heat to obtain a gel bath for later use; 9.5 g of polyvinylidene fluoride, 1 g of polyethylene glycol 2000, 1 g of polyvinyl pyrrolidone K90, 83 g of dimethyl sulfoxide and 5.5 g of GO / ZrO2 were sequentially poured into a stirring kettle, stirred for 17 h to dissolve under heating conditions of 75 ° C, and then degassed for 12 h to obtain a casting solution; The film casting stock solution is sent to the spraying device through a pump and a pipeline under the operating condition of 3MPa, and the inner lining support pipe passes through the spraying device, and the film casting stock solution is evenly sprayed on the surface of the support pipe; The support tube sprayed with the film casting solution is cooled and solidified in a 60°C gel bath and a water bath to form a uniform polyvinylidene fluoride coating on the surface of the support tube; The support tube with polyvinylidene fluoride coating was immersed in glycerol solution for 12 hours to obtain a high-flux gradient fiber membrane.

[0029] Example 4 The specific preparation process of the high flux gradient fiber membrane of this embodiment is carried out according to the following steps: Take 45 g of N,N-dimethylacetamide and 55 g of pure water and mix them, and heat them to obtain a gel bath for use; 30 g of polyvinylidene fluoride, 4 g of polyethylene glycol 600, 5.5 g of polyvinyl pyrrolidone K17, 60 g of N,N-dimethylacetamide and 0.5 g of GO / ZrO2 were sequentially poured into a stirring kettle, stirred for 16 h to dissolve under heating conditions of 65 ° C, and then degassed for 12 h to obtain a casting solution; The film casting stock solution is sent to the spray device through a pump and a pipeline under the operating condition of 1MPa, and the inner lining support pipe is passed through the spray device, and the film casting stock solution is evenly sprayed on the surface of the support pipe; The support tube sprayed with the film casting solution is cooled and solidified in a 45°C gel bath and a water bath to form a uniform polyvinylidene fluoride coating on the surface of the support tube; The support tube with polyvinylidene fluoride coating was immersed in glycerol solution for 12 hours to obtain a high-flux gradient fiber membrane.

[0030] Example 5 The specific preparation process of the high flux gradient fiber membrane of this embodiment is carried out according to the following steps: Take 35 g of N,N-dimethylacetamide and 65 g of pure water and mix them, and heat them to obtain a gel bath for use; 10 g of polyvinylidene fluoride, 2 g of polyethylene glycol 800, 7 g of polyvinyl pyrrolidone K30, 80 g of N, N-dimethylacetamide and 1 g of GO / ZrO2 were sequentially poured into a stirring kettle, stirred for 16 h to dissolve under heating conditions of 60 ° C, and then degassed for 12 h to obtain a casting solution; The film casting stock solution is sent to the spraying device through a pump and a pipeline under the operating condition of 0.5MPa, and the inner lining support pipe passes through the spraying device, and the film casting stock solution is evenly sprayed on the surface of the support pipe; The support tube sprayed with the film casting solution is cooled and solidified in a 40°C gel bath and a water bath to form a uniform polyvinylidene fluoride coating on the surface of the support tube; The support tube with polyvinylidene fluoride coating was immersed in glycerol solution for 12 hours to obtain a high-flux gradient fiber membrane.

[0031] Example 6 The specific preparation process of the high flux gradient fiber membrane of this embodiment is carried out according to the following steps: Mix 40 g of N-methylpyrrolidone and 60 g of pure water, and heat to obtain a gel bath for later use; 9 g of polyvinylidene fluoride, 2 g of polyethylene glycol 600, 7 g of polyvinyl pyrrolidone K17, 81 g of N-methyl pyrrolidone and 1 g of GO / ZrO2 were sequentially poured into a stirring kettle, stirred for 15 h to dissolve under heating conditions of 75 ° C, and then degassed for 12 h to obtain a casting solution; The film casting stock solution is sent to the spray device through a pump and a pipeline under the operating condition of 3.5MPa, and the inner lining support pipe passes through the spray device, and the film casting stock solution is evenly sprayed on the surface of the support pipe; The support tube sprayed with the film casting solution is cooled and solidified in a 55°C gel bath and a water bath to form a uniform polyvinylidene fluoride coating on the surface of the support tube; The support tube with polyvinylidene fluoride coating was immersed in glycerol solution for 12 hours to obtain a high-flux gradient fiber membrane.

[0032] Example 7 The specific preparation process of the high flux gradient fiber membrane of this embodiment is carried out according to the following steps: Take 35g of N-methylpyrrolidone and 65g of pure water and mix them, and then heat them to obtain a gel bath for use; 25 g of polyvinylidene fluoride, 0.5 g of polyethylene glycol 2000, 0.5 g of polyvinyl pyrrolidone K17, 73.2 g of N-methyl pyrrolidone and 1 g of GO / ZrO2 were sequentially poured into a stirring kettle, stirred for 17 h to dissolve under heating conditions of 75 ° C, and then degassed for 12 h to obtain a casting solution; The film casting stock solution is sent to the spray device through a pump and a pipeline under the operating condition of 2.5MPa, and the inner lining support pipe passes through the spray device, and the film casting stock solution is evenly sprayed on the surface of the support pipe; The support tube sprayed with the film casting solution is cooled and solidified in a 60°C gel bath and a water bath to form a uniform polyvinylidene fluoride coating on the surface of the support tube; The support tube with polyvinylidene fluoride coating was immersed in glycerol solution for 12 hours to obtain a high-flux gradient fiber membrane.

[0033] Comparative Example 1 The specific preparation steps of the fiber membrane are basically the same as those in Example 1, except that GO / ZrO2 and the inner lining support tube are not added, and the core liquid is introduced.

[0034] Comparative Example 2 The specific preparation steps of the fiber membrane are basically the same as those in Example 2, except that GO / ZrO2 and the inner lining support tube are not added, and the core liquid is introduced.

[0035] Comparative Example 3 The specific preparation steps of the fiber membrane are basically the same as those in Example 3, except that GO / ZrO2 and the inner lining support tube are not added, and the core liquid is introduced.

[0036] Comparative Example 4 The specific preparation steps of the fiber membrane are basically the same as those in Example 4, except that GO / ZrO2 and the inner lining support tube are not added, and the core liquid is introduced.

[0037] Comparative Example 5 The specific preparation steps of the fiber membrane are basically the same as those in Example 5, except that GO / ZrO2 and the inner lining support tube are not added, and the core liquid is introduced.

[0038] Comparative Example 6 The specific preparation steps of the fiber membrane are basically the same as those in Example 6, except that GO / ZrO2 and the inner lining support tube are not added, and the core liquid is introduced.

[0039] Comparative Example 7 The specific preparation steps of the fiber membrane are basically the same as those in Example 7, except that GO / ZrO2 and the inner lining support tube are not added, and the core liquid is introduced.

[0040] Experimental Example 1 The fiber membranes prepared in the embodiments and comparative examples were placed in a sewage treatment process at room temperature and operated for 3 days before sampling and testing. The test results were calculated using the formula, and the test results are shown in Table 1.

[0041] Table 1. Test results

[0042] Based on the above data, we can draw the following conclusions: From Examples 1 to 7, it can be seen that the present invention can produce a high-flux gradient fiber membrane with excellent performance (by precisely controlling the mass percentages of organic solvent (55-83wt%), polyvinylidene fluoride (9-30wt%), pore-forming agent (1-20wt%) and additive (0.5-15wt%). Figure 1-Figure 4 ). This ratio makes the membrane perform well in terms of tensile strength, water flux, rejection rate and water contact angle.

[0043] The fiber membranes in Examples 1-7 are superior to the comparative examples in various performance indicators, especially in water flux and tensile strength. The tensile strength values ​​generally exceed 130 MPa, which shows that the combined use of GO / ZrO2 and the inner lining support tube added by the present invention makes the fiber membrane more stable in structure and can withstand large external forces without being easily damaged. In terms of water flux, the fiber membranes of the embodiments also show excellent performance. The water flux of each embodiment is much higher than that of the comparative example, especially Examples 2, 3, 5 and 6, whose water flux has reached more than 1200 L / (m2.h). This shows that the fiber membrane with added GO / ZrO2 has higher permeability and permeability, and can better meet the large flux requirements in sewage treatment. It is further proved that each component in the present invention is indispensable and there is an optimal ratio range between the components. Only by reaching such an optimal ratio range can the membrane of the present invention perform at its best.

[0044] Regarding the membrane lacking GO / ZrO2 and the inner lining support tube in the comparative example, its tensile strength is extremely low, all below 4MPa, far lower than the embodiment, further emphasizing the contribution of GO / ZrO2 and the inner lining support tube to the membrane strength in the present invention. By introducing the inner lining support tube and uniformly spraying the casting film stock solution on its surface to form a polyvinylidene fluoride coating, the high-flux gradient fiber membrane of the present invention is structurally strengthened, thereby improving the mechanical stability of the membrane. This can be seen from the comparison of the tensile strength of the embodiment and the comparative example. Even without considering the influence of the additive (such as the raw material ratio of Comparative Example 1 and Example 1 is similar, but Comparative Example 1 does not mention the inner lining support tube), the tensile strength of the embodiment is much higher than that of the comparative example, which proves the reinforcing effect of the inner lining support tube on the membrane strength. It also further proves the synergistic effect of the components in the present invention. When the components are missing, the performance of the high-flux gradient fiber membrane of the present invention will be seriously affected, and its performance will be greatly reduced and far lower than the embodiment.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high flux gradient fiber membrane, characterized in that: The invention is mainly prepared from the following raw materials by weight percentage: 55-83wt% of organic solvent, 9-30wt% of polyvinylidene fluoride, 1-20wt% of pore-forming agent and 0.5-15wt% of additives.

2. The high flux gradient fiber membrane according to claim 1, characterized in that: The invention is mainly prepared from the following raw materials by weight percentage: 60-81wt% of organic solvent, 9.5-25wt% of polyvinylidene fluoride, 2-15wt% of pore-forming agent and 0.8-13wt% of additive.

3. The high flux gradient fiber membrane according to claim 1, characterized in that: The invention is mainly prepared from the following raw materials by weight percentage: 80 wt % of organic solvent, 10 wt % of polyvinylidene fluoride, 9 wt % of pore-forming agent and 1 wt % of additive.

4. The high flux gradient fiber membrane according to any one of claims 1 to 3, characterized in that: The organic solvent is at least one of dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide and N-methylpyrrolidone.

5. The high flux gradient fiber membrane according to any one of claims 1 to 3, characterized in that: The pore-forming agent is at least one of polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 800, polyethylene glycol 1000, polyethylene glycol 2000, polyvinyl pyrrolidone K17, polyvinyl pyrrolidone K30, and polyvinyl pyrrolidone K90.

6. The high flux gradient fiber membrane according to any one of claims 1 to 3, characterized in that: The additive is a graphene oxide / zirconium oxide nanocomposite material.

7. A method for preparing a high-flux gradient fiber membrane according to any one of claims 1 to 6, characterized in that: The steps include: The organic solvent and the stored water are mixed in a certain proportion, and the temperature is raised to obtain a gel bath for use; Pour polyvinylidene fluoride, pore-forming agent, organic solvent and additives into a stirring kettle in sequence, heat and stir until completely dissolved, and then perform degassing treatment to obtain a film casting stock solution; The film casting stock solution is sent to the spraying device through a pump and a pipeline, and the inner lining support pipe passes through the spraying device, and the film casting stock solution is evenly sprayed on the surface of the support pipe; The support tube sprayed with the film casting solution is cooled and solidified in a gel bath and a water bath to form a uniform polyvinylidene fluoride coating on the surface of the support tube; The support tube with polyvinylidene fluoride coating was immersed in glycerol solution to obtain a high-flux gradient fiber membrane.

8. The method for preparing a high-flux gradient fiber membrane according to claim 7, characterized in that: In the step of heating and stirring until completely dissolved, the heating temperature is 60-80° C. and the stirring time is 15-17 hours.

9. The method for preparing a high-flux gradient fiber membrane according to claim 7, characterized in that: In the step of uniformly spraying the film casting stock solution on the surface of the support tube, the film casting stock solution is sprayed at 0.5MPa-4MPa.

10. The method for preparing a high-flux gradient fiber membrane according to any one of claims 7 to 9, characterized in that: In the gel bath and water bath cooling and solidification step, the temperature of the gel bath and the water bath are both 40-60°C.

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