Method for preparing filter membrane and filter membrane prepared thereby

Abstract

The present invention relates to a method for preparing a filtration membrane, comprising the steps of: preparing a first solution by dissolving at least polyamide 6 and a polyether block amide in formic acid wherein the weight ratio of polyamide 6 to polyether block amide is limited to 5: 1; preparing a second solution by adding acetic acid to the first solution wherein the weight ratio of acetic acid to formic acid is limited to 3: 1 and the weight ratio of polyamide 6 to polyether block amide in the second solution is limited to 15 wt%; and electrospinning the second solution, thereby depositing fibers comprising polyamide 6 and polyether block amides on a substrate selected from polyethylene terephthalate. The invention also relates to a filtration membrane prepared by said method.

Description

Technical Field

[0001] This invention relates to a method for preparing a filter membrane and a filter membrane prepared by the method. In particular, this invention relates to a method for preparing a filter membrane using a polymeric compound and a filter membrane prepared by the method. Background Technology

[0002] Polyamide 6 (commonly known as PA6) is a commonly used material for the fabrication of water filtration membranes, offering significant technical advantages such as mechanical strength, chemical resistance, toughness, and processability. PA6 membranes exhibit strong mechanical properties, particularly during filtration operations, maintaining structural integrity under pressure differentials and mechanical stress. Its tolerance to various contaminants and fluids enhances membrane life and performance. PA6's inherent toughness allows for extended use and cleaning cycles without substantial degradation. Its industrial processability (e.g., electrospinning) enables the creation of customized membrane structures to meet precise filtration requirements.

[0003] However, PA6 does have some drawbacks that may hinder its application in the preparation of water filtration membranes. These drawbacks include its sensitivity to moisture absorption, limited resistance to ultraviolet radiation (current technology utilizes UV lamps for sterilization), potential thermal degradation at high temperatures, and a tendency to warp during processing if adequate cooling and forming conditions are not maintained. These factors affect the pore size and overall filtration efficiency of the membrane, highlighting the importance of careful handling and environmental control during production.

[0004] To compensate for the shortcomings of PA6 discussed above, especially its thermal degradation at high temperatures and its tendency to warp during processing if sufficient cooling and molding conditions are not maintained, it may be a feasible option to use a composite material comprising at least two materials (one of which is PA6) to prepare water filtration membranes to meet specific filtration needs and desired membrane properties.

[0005] Using polyether block amide (commonly known as PEBAX) as a material for the preparation of composites for water filtration membranes is a viable option, offering numerous advantages that overcome the shortcomings of PA6. PEBAX's inherent flexibility and resilience make it an excellent choice, particularly when the manufactured membrane can withstand deformation or stretching during filtration. Its excellent UV resistance and chemical resistance ensure longevity and performance, effectively resisting a wide range of aquatic contaminants. Furthermore, PEBAX's low water absorption enhances structural integrity and long-term filtration efficiency, key attributes for maintaining optimal membrane function. Combined with strong mechanical strength, PEBAX membranes maintain structural integrity under pressure differentials and mechanical stresses in filtration systems. The material's customizability allows for tailored membrane properties, such as pore size, surface chemistry, and permeability, to be tailored to specific filtration requirements. Considering PEBAX's thermal stability across various temperature ranges and its biocompatibility in selected applications, it becomes a versatile and reliable material choice for producing water filtration membranes with excellent flexibility, durability, and specialized properties.

[0006] The present invention aims to solve the above-mentioned problems by providing a composite comprising PA6 and PEBAX for the preparation of water filtration membranes. Alternatively, the present invention at least provides an alternative to the public. Summary of the Invention

[0007] This invention relates to a method for preparing a filter membrane, comprising the steps of: preparing a first solution by dissolving at least polyamide 6 and polyether block amide in formic acid, wherein the weight ratio of polyamide 6 to polyether block amide is limited to 5:1; preparing a second solution by adding acetic acid to the first solution, wherein the weight ratio of acetic acid to formic acid is limited to 3:1, and the weight ratio of polyamide 6 to polyether block amide in the second solution is limited to 15 wt%; and electrospinning the second solution, thereby depositing fibers comprising polyamide 6 and polyether block amide on a substrate selected from polyethylene terephthalate.

[0008] In one embodiment, the weight ratio of polyamide 6 to polyether block amide is limited to 4:1.

[0009] In one embodiment, the weight ratio of polyamide 6 to polyether block amide is limited to 3:1.

[0010] In one embodiment, the weight ratio of polyamide 6 to polyether block amide is limited to 2:1.

[0011] In one embodiment, the weight ratio of polyamide 6 to polyether block amide is limited to 1:1.

[0012] In one embodiment, the weight ratio of acetic acid to formic acid is limited to 2:1.

[0013] In one embodiment, the weight ratio of acetic acid to formic acid is limited to 1:1.

[0014] In one embodiment, the weight ratio of polyamide 6 to polyether block amide in the second solution is limited to 12 wt%.

[0015] In one embodiment, the weight ratio of polyamide 6 to polyether block amide in the second solution is limited to 10 wt%.

[0016] In one embodiment, the weight ratio of polyamide 6 to polyether block amide in the second solution is limited to 8 wt%.

[0017] In one embodiment, the method further includes the step of adding an additive selected from aluminum hydroxide oxide, polyhexamethylene biguanide, polyethyleneimine, chlorhexidine, or a combination thereof to the second solution, wherein the amount of the additive in the second solution is limited to 5 wt%.

[0018] Preferably, the fiber is a nanofiber.

[0019] The present invention also relates to a filter membrane comprising: polyamide 6; polyether block amide; and a PET substrate; wherein polyamide 6 and polyether block amide are deposited on the PET substrate in the form of fibers by electrospinning, wherein the solution for electrospinning is prepared by the following steps: preparing a first solution by dissolving polyamide 6 and polyether block amide in formic acid, wherein the weight ratio of polyamide 6 to polyether block amide is limited to 5:1; preparing a solution for electrospinning by adding acetic acid to the first solution, wherein the weight ratio of acetic acid to formic acid is limited to 3:1, and the weight ratio of polyamide 6 to polyether block amide in the second solution is limited to 15 wt%.

[0020] In one embodiment, the weight ratio of polyamide 6 to polyether block amide is limited to 4:1.

[0021] In one embodiment, the weight ratio of polyamide 6 to polyether block amide is limited to 3:1.

[0022] In one embodiment, the weight ratio of polyamide 6 to polyether block amide is limited to 2:1.

[0023] In one embodiment, the weight ratio of polyamide 6 to polyether block amide is limited to 1:1.

[0024] In one embodiment, the weight ratio of acetic acid to formic acid is limited to 2:1.

[0025] In one embodiment, the weight ratio of acetic acid to formic acid is limited to 1:1.

[0026] In one embodiment, the weight ratio of polyamide 6 to polyether block amide in the second solution is limited to 12 wt%.

[0027] In one embodiment, the weight ratio of polyamide 6 to polyether block amide in the second solution is limited to 10 wt%.

[0028] In one embodiment, the weight ratio of polyamide 6 to polyether block amide in the second solution is limited to 8 wt%.

[0029] Preferably, the fiber is a nanofiber.

[0030] More preferably, the membrane can filter out at least 99% of E. coli bacteria.

[0031] More preferably, the membrane can filter out at least 99% of particles larger than 3 micrometers. Attached Figure Description

[0032] Some embodiments of the present invention will now be described with reference to the accompanying drawings, in which:

[0033] Figure 1 This is a schematic diagram showing the electrospinning process; and

[0034] Figure 2 This is a setting used for performance testing. Detailed Implementation

[0035] The invention will now be described by way of example in the following paragraphs with reference to the accompanying drawings. The objects, features, and aspects of this disclosure are disclosed in or apparent from the following description. It will be understood by those skilled in the art that the following description is merely a description of exemplary embodiments and is not intended to limit the broader aspects of the disclosure embodied in the exemplary constructions.

[0036] It should be noted that, unless otherwise defined, the technical or scientific terms used in the embodiments of this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar expressions used in the embodiments of this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components.

[0037] Unless otherwise specified, the following chemicals are commercially available and can be used directly without special treatment, and may contain impurities (such as residual solvents or byproducts).

[0038] - Polyamide 6 (PA6)

[0039] - Polyether block amide (PEBAX)

[0040] -Polyethylene terephthalate (PET)

[0041] - Aluminum hydroxide oxide

[0042] - Polyhexamethylene biguanide

[0043] - Polyethyleneimine

[0044] -Chlorhexidine

[0045] - Acetic acid

[0046] -Formic acid

[0047] Unless otherwise stated, percentages herein refer to weight percentages. The chemicals used in this specification are merely illustrative for ease of explanation and should be understood to have no limiting effect on the invention.

[0048] Preparation of electrospinning solution

[0049] The following describes the preparation of the electrospinning solution used in this invention.

[0050] The weight percentage (wt%) of the polymer (e.g., PA6) is calculated as follows:

[0051]

[0052] Where M is the mass of the corresponding chemical.

[0053] For the sake of simplicity, Table 1-12 below shows different electrospinning solutions prepared with different parameters.

[0054] Table 1

[0055] Example 1 Example 2 Example 3 Example 4 Example 5 PA6 50g 40g 30g 20g 10g PEBAX 10g 10g 10g 10g 10g Acetic acid 517.5g 431.25g 345g 258.75g 172.5g Formic acid 172.5g 143.75g 115g 86.25g 57.5g solution 750g 625g 500g 375g 250g additive 0％ 0％ 0％ 0％ 0％ wt% 8％ 8％ 8％ 8％ 8％

[0056] Table 2

[0057] Example 1 Example 2 Example 3 Example 4 Example 5 PA6 50g 40g 30g 20g 10g PEBAX 10g 10g 10g 10g 10g Acetic acid 460g 383.33g 306.67g 230g 153.33g Formic acid 230g 191.67g 153.33g 115g 76.67g solution 750g 625g 500g 375g 250g additive 0％ 0％ 0％ 0％ 0％ wt% 8％ 8％ 8％ 8％ 8％

[0058] Table 3

[0059]

[0060]

[0061] Table 4

[0062] Example 1 Example 2 Example 3 Example 4 Example 5 PA6 50g 40g 30g 20g 10g PEBAX 10g 10g 10g 10g 10g Acetic acid 405g 337.5g 270g 202.5g 135g Formic acid 135g 112.5g 90g 67.5g 45g solution 600g 500g 400g 300g 200g additive 0％ 0％ 0％ 0％ 0％ wt% 10％ 10％ 10％ 10％ 10％

[0063] Table 5

[0064] Example 1 Example 2 Example 3 Example 4 Example 5 PA6 50g 40g 30g 20g 10g PEBAX 10g 10g 10g 10g 10g Acetic acid 360g 300g 240g 180g 120g Formic acid 180g 150g 120g 90g 60g solution 600g 500g 400g 300g 200g additive 0％ 0％ 0％ 0％ 0％ wt% 10％ 10％ 10％ 10％ 10％

[0065] Table 6

[0066] Example 1 Example 2 Example 3 Example 4 Example 5 PA6 50g 40g 30g 20g 10g PEBAX 10g 10g 10g 10g 10g Acetic acid 270g 225g 180g 135g 90g Formic acid 270g 225g 180g 135g 90g solution 600g 500g 400g 300g 200g additive 0％ 0％ 0％ 0％ 0％ wt% 10％ 10％ 10％ 10％ 10％

[0067] Table 7

[0068]

[0069]

[0070] Table 8

[0071] Example 1 Example 2 Example 3 Example 4 Example 5 PA6 50g 40g 30g 20g 10g PEBAX 10g 10g 10g 10g 10g Acetic acid 293.33g 244.44g 195.56g 146.67g 97.78g Formic acid 146.67g 122.22g 97.78g 73.33g 48.89g solution 500g 416.67g 333.33g 250g 166.67g additive 0％ 0％ 0％ 0％ 0％ wt% 12％ 12％ 12％ 12％ 12％

[0072] Table 9

[0073] Example 1 Example 2 Example 3 Example 4 Example 5 PA6 50g 40g 30g 20g 10g PEBAX 10g 10g 10g 10g 10g Acetic acid 220g 183.33g 146.67g 110g 73.33g Formic acid 220g 183.33g 146.67g 110g 73.33g solution 500g 416.67g 333.33g 250g 166.67g additive 0％ 0％ 0％ 0％ 0％ wt% 12％ 12％ 12％ 12％ 12％

[0074] Table 10

[0075]

[0076]

[0077] Table 11

[0078] Example 1 Example 2 Example 3 Example 4 Example 5 PA6 50g 40g 30g 20g 10g PEBAX 10g 10g 10g 10g 10g Acetic acid 226.67g 188.89g 151.11g 113.33g 75.56g Formic acid 113.33g 94.44g 75.56g 56.67g 37.78g solution 400g 333.33g 266.67g 200g 133.33g additive 0％ 0％ 0％ 0％ 0％ wt% 15％ 15％ 15％ 15％ 15％

[0079] Table 12

[0080] Example 1 Example 2 Example 3 Example 4 Example 5 PA6 50g 40g 30g 20g 10g PEBAX 10g 10g 10g 10g 10g Acetic acid 170g 141.67g 113.33g 85g 56.67 Formic acid 170g 141.67g 113.33g 85g 56.67 solution 400g 333.33g 266.67g 200g 133.33g additive 0％ 0％ 0％ 0％ 0％ wt% 15％ 15％ 15％ 15％ 15％

[0081] Example 1

[0082] The following is a detailed description of the steps involved in preparing the electrospinning solution as described in Example 1 of Table 1: First, weigh out 50 g of PA6 and 10 g of PEBAX. In a mixing container, combine these polymers with 172.5 g of formic acid and stir thoroughly until completely dissolved. Next, in a separate container, measure out 517.5 g of acetic acid. Transfer the formic acid solution containing the dissolved PA6 and PEBAX to the acetic acid and mix the components until a homogeneous solution is formed. Check the homogeneity of the solution and ensure that all components are fully dissolved. Confirm that the total weight of the electrospinning solution is 750 g. Store the prepared solution properly, labeling its contents and any relevant safety information. The solution can then be used for the desired electrospinning application following the appropriate procedures for the electrospinning process.

[0083] Example 2

[0084] The following is a detailed description of the steps involved in preparing the electrospinning solution as described in Example 2 of Table 1: First, weigh out 40 g of PA6 and 10 g of PEBAX. In a mixing container, combine these polymers with 143.75 g of formic acid and stir thoroughly until completely dissolved. Next, in a separate container, measure out 431.25 g of acetic acid. Transfer the formic acid solution containing the dissolved PA6 and PEBAX to the acetic acid and mix the components until a homogeneous solution is formed. Check the homogeneity of the solution and ensure that all components are fully dissolved. Confirm that the total weight of the electrospinning solution is 625 g. Properly store the prepared solution, labeling its contents and any relevant safety information. The solution can then be used for the desired electrospinning application following the appropriate procedures for the electrospinning process.

[0085] Example 3

[0086] The following is a detailed description of the steps involved in preparing the electrospinning solution as described in Example 3 of Table 1: First, weigh out 30 g of PA6 and 10 g of PEBAX. In a mixing container, combine these polymers with 115 g of formic acid and stir thoroughly until completely dissolved. Next, in a separate container, measure out 345 g of acetic acid. Transfer the formic acid solution containing the dissolved PA6 and PEBAX to the acetic acid and mix the components until a homogeneous solution is formed. Check the homogeneity of the solution and ensure that all components are fully dissolved. Confirm that the total weight of the electrospinning solution is 500 g. Properly store the prepared solution, labeling its contents and any relevant safety information. The solution can then be used for the desired electrospinning application following the appropriate procedures for the electrospinning process.

[0087] Example 4

[0088] The following is a detailed description of the steps involved in preparing the electrospinning solution as described in Example 4 of Table 1: First, weigh out 20 g of PA6 and 10 g of PEBAX. In a mixing container, combine these polymers with 86.25 g of formic acid and stir thoroughly until completely dissolved. Next, in a separate container, measure 258.75 g of acetic acid. Transfer the formic acid solution containing the dissolved PA6 and PEBAX to the acetic acid and mix the components until a homogeneous solution is formed. Check the homogeneity of the solution and ensure that all components are fully dissolved. Confirm that the total weight of the electrospinning solution is 375 g. Store the prepared solution properly, labeling its contents and any relevant safety information. The solution can then be used for the desired electrospinning application following the appropriate procedures for the electrospinning process.

[0089] Example 5

[0090] The following is a detailed description of the steps involved in preparing the electrospinning solution as described in Example 5 of Table 1: First, weigh out 10 g of PA6 and 10 g of PEBAX. In a mixing container, combine these polymers with 57.5 g of formic acid and stir thoroughly until completely dissolved. Next, in a separate container, measure out 172.5 g of acetic acid. Transfer the formic acid solution containing the dissolved PA6 and PEBAX to the acetic acid and mix the components until a homogeneous solution is formed. Check the homogeneity of the solution and ensure that all components are fully dissolved. Confirm that the total weight of the electrospinning solution is 250 g. Properly store the prepared solution, labeling its contents and any relevant safety information. The solution can then be used for the desired electrospinning application following the appropriate procedures for the electrospinning process.

[0091] To provide additional functionality to the filter membrane, additives can be added to the electrospinning solution prior to the electrospinning process. These additives can be selected from aluminum hydroxide oxide, polyhexamethylene biguanide, polyethyleneimine, chlorhexidine, or combinations thereof. The amount of additives in the electrospinning solution is limited to 5 wt%.

[0092] Aluminum hydroxide oxide, polyhexamethylene biguanide, polyethyleneimine, and chlorhexidine possess various beneficial effects and properties for filter membranes, especially in water filtration systems. Aluminum hydroxide oxide is used in filter membranes due to its adsorption properties. Because it can bind to certain heavy metals and other contaminants, it helps remove these substances from water. Polyhexamethylene biguanide is a polymer known for its antibacterial properties. In filter membranes, it helps inhibit the growth of bacteria and other microorganisms, thus preventing biofouling and ensuring filter life and effectiveness. Polyethyleneimine is a polymer that can be used in filter membranes to improve filtration efficiency. It helps remove fine particles and impurities from water through adsorption or other mechanisms. Chlorhexidine is a preservative and disinfectant commonly used in healthcare settings. In filter membranes, it can be used to prevent the growth of bacteria and algae, thus keeping the filtration system clean and hygienic. Overall, these substances play an important role in improving the performance, durability, and hygiene of filter membranes, particularly in water treatment and purification processes. It is worth noting that the specific uses and effects of these substances in filter membranes can vary depending on the membrane design, the target contaminants, and the intended application.

[0093] Electrospinning process for preparing filter membranes

[0094] The electrospinning solution prepared according to Table 1-12 above needs to be electrospinned to prepare a filter membrane, such as... Figure 1As shown. The electrospinning technology used in this disclosure is prior art; therefore, for the sake of brevity, a detailed description will not be provided. In short, in the embodiments described herein, the electrospinning apparatus 100 is equipped with a bracket 102, which houses an electrospinning needle connected to the electrospinning solution. Figure 1 (Not shown in the image). The device 100 has a lower conductor 104 connected to a first potential and an upper conductor 106 connected to a second potential opposite to the first potential. The potential difference between the upper and lower conductors establishes an electric field gradient on the nonwoven PET substrate 108 and the electrospinning needle, thereby guiding the electrospun fibers 110 toward the substrate 108. A continuous electrospinning process deposits polymer nanofibers onto the PET substrate, forming a felt-like structure on the PET substrate. For example, the process parameters for electrospinning are as follows:

[0095] - Orifice size 0.6-1.0mm (to control the flow rate of the polymer solution on the lower conductor)

[0096] -CE voltage -40 to -10kV (lower conductor voltage)

[0097] -SE voltage: 10-80kV (upper conductor voltage)

[0098] -Distance from CE to substrate: 30 to 130 mm (distance from bottom conductor to substrate)

[0099] -Distance from SE to substrate: 150-250mm (distance from top conductor to substrate)

[0100] - Chamber temperature: 18-30℃

[0101] -Chamber humidity: 10-50%

[0102] - Substrate tension control: 40-110N (tensile force of the substrate)

[0103] - Operating linear speed: 1-40m / min (substrate moves through the conductor)

[0104] Experiments and optimizations can be conducted to adjust process parameters for desired fiber morphology and arrangement. For example, to meet filtration requirements, at least one layer (preferably 7 or 8 layers) of nanofibers can be deposited on a substrate. Figure 2 As shown, the filter membranes prepared by the above electrospinning process need to undergo performance testing. This includes a 3-micron microsphere reduction test and a bacterial (E. coli MTCC 68) reduction test. The membranes used in these tests include PA6 and PABEX at a weight ratio of 3:1.

[0105] Figure 2Setup 200 is shown, comprising a bottom container 202, a filter container 204 assembled on the bottom container 202, and a filter 206 including a filter membrane 208. As can be seen, the filter 206 is located between the bottom container 202 and the filter container 204. The experiment begins by pouring 2 liters of distilled water into the filter container 204 for rinsing. Then, 10 liters of sample liquid 210 are poured into the filter container 204 for filtration. The liquid passes through the filter 206 under gravity. The filtered sample liquid, i.e., the filtered liquid 212, is collected in the bottom container 202 and then analyzed.

[0106] Analysis of the experimental results of reducing 1-3 micrometer microspheres

[0107] The purpose of this experiment was to evaluate the ability of gravity filter cartridges to reduce 3-micron microspheres. Table 13 summarizes the experimental conditions and results.

[0108] Table 13.3 Results of Experiments on Reduction of Microspheres

[0109]

[0110] Analysis of the results of the 2-bacterial (Escherichia coli MTCC 68) reduction test The purpose of this experiment was to evaluate the bacteria reduction capability of gravity filter cartridges. Table 14 summarizes the experimental conditions and results.

[0111] Table 14. Results of the bacterial (Escherichia coli MTCC 68) reduction test

[0112] The test results show that the membrane can filter out at least 99% of E. coli bacteria and at least 99% of particles larger than 3 micrometers.

[0113] The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. For those skilled in the art, some improvements and modifications can be made to the present invention without departing from the principles of the invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not limited to the embodiments shown herein, but should be accorded the widest scope consistent with the principles, novel features, and equivalents disclosed herein. It should be understood that each specific numerical point of the parameter described in the context of the embodiments can be considered as an end value of the numerical range of the parameter in the embodiments of the present invention. In other words, the end value is also included in the numerical range. It should be understood that, in embodiments according to the present invention, each value within the numerical range can also be an end value of another numerical range of the parameter.

Claims

1. A method for preparing a filtration membrane comprising the steps of: i) preparing a first solution by dissolving at least polyamide 6 and polyether block amide in formic acid, wherein the weight ratio of polyamide 6 to polyether block amide is limited to 5:1; ii) preparing a second solution by adding acetic acid to the first solution, wherein the weight ratio of acetic acid to formic acid is limited to 3:1, and the weight ratio of polyamide 6 to polyether block amide in the second solution is limited to 15 wt%; and iii) electrospinning the second solution, thereby depositing fibers comprising polyamide 6 and polyether block amide on a substrate selected from polyethylene terephthalate.

2. The method according to claim 1, wherein the weight ratio of polyamide 6 to polyether block amide is limited to 3:

1.

3. The method according to claim 1, wherein the weight ratio of polyamide 6 to polyether block amide is limited to 1:

1.

4. The method according to claim 1, wherein the weight ratio of acetic acid to formic acid is limited to 2:

1.

5. The method according to claim 1, wherein the weight ratio of acetic acid to formic acid is limited to 1:

1.

6. The method according to claim 1, wherein the weight ratio of polyamide 6 to polyether block amide in the second solution is limited to 12 wt%.

7. The method according to claim 1, wherein the weight ratio of polyamide 6 to polyether block amide in the second solution is limited to 10 wt%.

8. The method according to claim 1, wherein the weight ratio of polyamide 6 to polyether block amide in the second solution is limited to 8 wt%.

9. The method according to claim 1, wherein the method further comprises the step of adding an additive selected from aluminum hydroxide oxide, polyhexamethylene biguanide, polyethylene imine, chlorhexidine, or a combination thereof to the second solution, wherein the amount of the additive in the second solution is limited to 5 wt%.

10. The method according to claim 1, wherein the fibers are nanofibers.

11. A filtration membrane comprising: • polyamide 6; • polyether block amide; and • a PET substrate; characterized in that polyamide 6 and polyether block amide are deposited in the form of fibers on the PET substrate by electrospinning, wherein the solution for electrospinning is prepared by: - preparing a first solution by dissolving polyamide 6 and polyether block amide in formic acid, wherein the weight ratio of polyamide 6 to polyether block amide is limited to 5:1; - preparing the solution for electrospinning by adding acetic acid to the first solution, wherein the weight ratio of acetic acid to formic acid is limited to 3:1, and the weight ratio of polyamide 6 to polyether block amide in the second solution is limited to 15 wt%.

12. The filtration membrane according to claim 11, wherein the weight ratio of polyamide 6 to polyether block amide is limited to 3:

1.

13. The filtration membrane according to claim 11, wherein the weight ratio of polyamide 6 to polyether block amide is limited to 1:

1.

14. The filtration membrane according to claim 11, wherein the weight ratio of acetic acid to formic acid is limited to 2:

1.

15. The filtration membrane of claim 11, wherein the weight ratio of acetic acid to formic acid is limited to 1 :

1.

16. The filtration membrane of claim 11, wherein the weight ratio of polyamide 6 to polyether block amide in the second solution is limited to 12 wt%.

17. The filtration membrane of claim 11, wherein the weight ratio of polyamide 6 to polyether block amide in the second solution is limited to 8 wt%.

18. The filtration membrane of claim 11, wherein the fibers are nanofibers.

19. The filtration membrane of claim 11, the membrane can filter out at least 99% of E. coli bacteria.

20. The filtration membrane of claim 11, the membrane can filter out at least 99% of particles greater than 3 microns.

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