A nanofiber membrane for gas filtration and a method for preparing the same

Abstract

The application belongs to the technical field of composite fiber diaphragm, and particularly relates to a nanofiber membrane for gas filtration and a preparation method thereof. The method comprises the following steps: polyvinyl alcohol and polyacrylic acid are respectively configured into 8-10wt% and 13-16.4wt% aqueous solutions; when the aqueous solutions are prepared, graphene oxide or hydrophilic modified graphene is added into one of the solutions and uniformly mixed to obtain a "core" spinning solution, and the other solution is a "shell" spinning solution; the two spinning solutions are spun into a nanometer thin film by using a coaxial electrospinning process; the residual solvent in the thin film is removed by heating at 70-80 degrees Celsius for 2-4 hours; and finally, the nanofiber membrane for gas filtration is obtained by heating and crosslinking at 100-150 degrees Celsius for 12-24 hours. The application effectively increases the filtration effect of the fiber membrane by adding graphene oxide or hydrophilic modified graphene.

Description

Technical Field

[0001] This invention belongs to the field of composite fiber membrane technology, specifically relating to a nanofiber membrane that can be used for gas filtration and its preparation method. Background Technology

[0002] Electrospinning is widely used in the preparation of fiber membranes due to its ease of operation. In recent years, with increasing environmental protection requirements, polyvinyl alcohol / polyacrylic acid (PVA / PAA) composite fibers, which do not require the addition of organic solvents in the electrospinning process, have become increasingly popular. Existing PVA / PAA fiber membranes undergo cross-linking via heating after spinning. Even when heated to a highly elastic state, the degree of cross-linking is limited, resulting in limited mechanical strength. Furthermore, when used as an adsorbent, the gas adsorption and filtration efficiency is approximately 80%. CN110144726A discloses that LiOH solution treatment converts unreacted polyacrylic acid on the surface of the polyvinyl alcohol / polyacrylic acid composite fiber into lithium polyacrylate, enhancing lithium-ion conductivity; however, the LiOH solution treatment also significantly reduces the porosity and pore size distribution of the composite nanofiber membrane. CN107881645A discloses increasing the surface roughness of the PVA / PAA fiber membrane by adding silica, thereby increasing the filtration effect. None of the above-mentioned publications address a method that can effectively improve both the degree of cross-linking and the adsorption effect of PVA / PAA simultaneously. Summary of the Invention

[0003] The purpose of this invention is to provide a nanofiber membrane that can be used for gas filtration and a method for preparing the same. By adding graphene oxide or hydrophilically modified graphene, the crosslinking of PVA and PAA is enhanced to increase the filtration performance and mechanical properties of the nanomembrane.

[0004] This invention provides a method for preparing a nanofiber membrane that can be used for gas filtration, comprising the following steps:

[0005] Polyvinyl alcohol and polyacrylic acid were prepared into aqueous solutions of 8-10 wt% and 13-16.4 wt%, respectively.

[0006] When preparing the aqueous solution, graphene oxide or hydrophilic modified graphene is added to one of the solutions and mixed evenly to obtain the "core" spinning solution, while the other solution is the "shell" spinning solution.

[0007] Two spinning solutions were spun into nanofilms using a coaxial electrospinning process.

[0008] The residual solvent in the film is removed by heating at 70-80 degrees Celsius for 2-4 hours, and finally crosslinked by heating at 100-150 degrees Celsius for 12-24 hours to obtain a nanofiber membrane that can be used for gas filtration.

[0009] Furthermore, the amount of graphene added to the "nuclear" spinning solution is 0.5-2g / 100ml.

[0010] Furthermore, the graphene has a particle size of 50-700 nm.

[0011] Furthermore, the graphene has a particle size of 50-500 nm.

[0012] Furthermore, the specific steps of the coaxial electrospinning process are as follows: two spinning solutions are injected at the same injection speed of 10ul / min, the distance from the needle to the roller is 15cm, the voltage is 10kv, the humidity is 30-45%, and a nanofilm of a certain thickness is spun using a coaxial electrospinning device.

[0013] This invention provides a nanofiber membrane that can be used for gas filtration, prepared by any of the methods described above.

[0014] Compared with existing technologies, the present invention effectively increases the filtration effect of fiber membranes by adding graphene oxide or hydrophilic modified graphene. Detailed Implementation

[0015] To enable those skilled in the art to better understand the technical solutions in this application, the present invention will be further described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0016] Polyvinyl alcohol and polyacrylic acid were prepared into 100 ml aqueous solutions of 8-10 wt% and 13-16.4 wt%, respectively. At this ratio, the two polymers had the same number of crosslinking groups, which was beneficial to improving the crosslinking effect. During the preparation of the aqueous solutions, graphene oxide or hydrophilically modified graphene was added to one solution and mixed evenly to obtain a "core" spinning solution, while the other solution was a "shell" spinning solution. Appropriate amounts of graphene oxide and hydrophilically modified graphene effectively improved the degree of crosslinking of the composite fibers and enhanced the filtration performance of the composite fiber membrane. Preferably, the amount of graphene oxide or hydrophilically modified graphene added was 0.5-2 g. Too little addition would result in a negligible improvement in the crosslinking effect, while too much addition would reduce the structure of the nanomembrane. Two spinning solutions were injected at the same injection rate of 10 μL / min, with a needle-to-roll distance of 15 cm, a voltage of 10 kV, and a humidity of 30-45%. A nanofilm of a certain thickness was spun using a coaxial electrospinning device. The film was then heated at 70-80 degrees Celsius for 2-4 hours to remove residual solvents. Finally, the film was heated at 100-150 degrees Celsius for 12-24 hours to crosslink, thus obtaining a nanofiber membrane that can be used for gas filtration.

[0017] Unless otherwise stated, the filtration efficiency test mentioned in this article refers to the percentage of 0.3-micron particles filtered, and the testing equipment is a filtration efficiency tester.

[0018] Examples 1-7

[0019] Polyvinyl alcohol (PVA) and polyacrylic acid (PAA) were dissolved in deionized water to prepare 8.8 wt% and 14.4 wt% aqueous solutions, respectively. 0.5 g of graphene oxide was added to 100 ml of the prepared PVA aqueous solution and mixed thoroughly to obtain the "core" spinning solution. The other prepared 14.4 wt% PAA aqueous solution was the "shell" spinning solution. 100 ml of each spinning solution was injected into an electrospinning device through a needle to spin nanofilms. The residual solvent in the film was removed by heating at 80°C for 2 hours, and finally crosslinked at 100°C for 12-24 hours to obtain a nanofiber membrane suitable for gas filtration. The particle size of the added graphene is shown in Table 1.

[0020] Table 1

[0021]

[0022]

[0023] The filtration effect of the nanofiber membrane prepared in Example 1 is shown in Table 2.

[0024] Table 2

[0025] Sample 1 2 89.7 Sample 2 3 95.5 Sample 3 4 97.2 Sample 4 5 98.9

[0026] The filtration effects of the nanofiber membranes prepared in Examples 2-7 are shown in Table 3.

[0027] Table 3

[0028] Example 2 3 95.1 Example 3 3 94.8 Example 4 3 94.0 Example 5 3 93.1 Example 6 3 91.9 Example 7 3 90.3

[0029] Example 8

[0030] Polyvinyl alcohol (PVA) and polyacrylic acid (PAA) were dissolved in deionized water to prepare 8.8 wt% and 14.4 wt% aqueous solutions, respectively. 2.0 g of graphene oxide was added to 100 ml of the prepared PVA aqueous solution and mixed thoroughly to obtain the "core" spinning solution. The other prepared 14.4 wt% PAA aqueous solution was the "shell" spinning solution. 100 ml of each spinning solution was injected into an electrospinning device through a needle to spin nanofilms. The films were heated at 80°C for 2 hours to remove residual solvent, and finally heated at 150°C for 12-24 hours to crosslink, yielding nanofiber membranes suitable for gas filtration. The added graphene particles had a diameter of 100-200 nm.

[0031] Example 9

[0032] Polyvinyl alcohol and polyacrylic acid were dissolved in deionized water to prepare 8.8 wt% and 14.4 wt% aqueous solutions, respectively. 0.5 g of graphene oxide was added to 100 ml of the prepared polyacrylic acid aqueous solution and mixed thoroughly to obtain the "core" spinning solution. The other prepared 8.8 wt% polyvinyl alcohol aqueous solution was the "shell" spinning solution. 100 ml of each spinning solution was injected into an electrospinning device through a needle to spin nanofilms. The residual solvent in the film was removed by heating at 70°C for 4 hours, and finally crosslinked at 100°C for 12-24 hours to obtain a nanofiber membrane suitable for gas filtration. The added graphene particle size was 100-200 nm.

[0033] Example 10

[0034] Polyvinyl alcohol and polyacrylic acid were dissolved in deionized water to prepare 8.8 wt% and 14.4 wt% aqueous solutions, respectively. 2.0 g of graphene oxide was added to 100 ml of the prepared polyacrylic acid aqueous solution and mixed thoroughly to obtain the "core" spinning solution. The other prepared 8.8 wt% polyvinyl alcohol aqueous solution was the "shell" spinning solution. 100 ml of each spinning solution was injected into an electrospinning device through a needle to spin nanofilms. The films were heated at 80°C for 2 hours to remove residual solvent, and finally heated at 150°C for 12-24 hours to crosslink, yielding nanofiber membranes suitable for gas filtration. The added graphene particles had a diameter of 100-200 nm.

[0035] Example 11

[0036] Polyvinyl alcohol (PVA) and polyacrylic acid (PAA) were dissolved in deionized water to prepare 8.0 wt% and 13.0 wt% aqueous solutions, respectively. 1.0 g of graphene oxide was added to 100 ml of the prepared PVA aqueous solution and mixed thoroughly to obtain the "core" spinning solution. The other prepared 13.0 wt% PAA aqueous solution was the "shell" spinning solution. 100 ml of each spinning solution was injected into an electrospinning device through a needle to spin nanofilms. The films were heated at 75°C for 2 hours to remove residual solvent, and finally crosslinked at 120°C for 12-24 hours to obtain nanofiber membranes suitable for gas filtration. The added graphene particles had a diameter of 100-200 nm.

[0037] Example 12

[0038] Polyvinyl alcohol (PVA) and polyacrylic acid (PAA) were dissolved in deionized water to prepare 8.0 wt% and 13.0 wt% aqueous solutions, respectively. 1.5 g of graphene oxide was added to 100 ml of the prepared PVA aqueous solution and mixed thoroughly to obtain the "core" spinning solution. The other prepared PAA aqueous solution was the "shell" spinning solution. 100 ml of each spinning solution was injected into an electrospinning device through a needle to spin nanofilms. The films were heated at 75°C for 2 hours to remove residual solvent, and finally heated at 120°C for 12-24 hours to crosslink, yielding nanofiber membranes suitable for gas filtration. The added graphene particles had a diameter of 200-300 nm.

[0039] Example 13

[0040] Polyvinyl alcohol (PVA) and polyacrylic acid (PAA) were dissolved in deionized water to prepare 10.0 wt% and 16.4 wt% aqueous solutions, respectively. 1.0 g of graphene oxide was added to 100 ml of the prepared PVA aqueous solution and mixed thoroughly to obtain the "core" spinning solution. The other prepared PAA aqueous solution was the "shell" spinning solution. 100 ml of each spinning solution was injected into an electrospinning device through a needle to spin nanofilms. The films were heated at 80°C for 2 hours to remove residual solvent, and finally heated at 130°C for 12-24 hours to crosslink, yielding nanofiber membranes suitable for gas filtration. The added graphene particles had a diameter of 300-400 nm.

[0041] Example 14

[0042] Polyvinyl alcohol and polyacrylic acid were dissolved in deionized water to prepare 10.0 wt% and 16.4 wt% aqueous solutions, respectively. 1.0 g of graphene oxide was added to 100 ml of the prepared polyacrylic acid aqueous solution and mixed thoroughly to obtain the "core" spinning solution. Another prepared polyvinyl alcohol aqueous solution was used as the "shell" spinning solution. 100 ml of each spinning solution was injected into an electrospinning device through a needle to spin nanofilms. The residual solvent in the film was removed by heating at 80°C for 2 hours, and finally crosslinked at 130°C for 12-24 hours to obtain a nanofiber membrane suitable for gas filtration. The added graphene particle size was 400-500 nm.

[0043] Example 15

[0044] Polyvinyl alcohol and polyacrylic acid were dissolved in deionized water to prepare 8.0 wt% and 13.0 wt% aqueous solutions, respectively. 1.5 g of graphene oxide was added to 100 ml of the prepared polyacrylic acid aqueous solution and mixed thoroughly to obtain the "core" spinning solution. Another prepared polyvinyl alcohol aqueous solution was used as the "shell" spinning solution. 100 ml of each spinning solution was injected into an electrospinning device through a needle to spin nanofilms. The films were heated at 75°C for 2 hours to remove residual solvent, and finally heated at 120°C for 12-24 hours to crosslink, yielding nanofiber membranes suitable for gas filtration. The added graphene particles had a diameter of 100-200 nm.

[0045] Example 16

[0046] Polyvinyl alcohol (PVA) and polyacrylic acid (PAA) were dissolved in deionized water to prepare 10.0 wt% and 16.4 wt% aqueous solutions, respectively. 1.5 g of graphene oxide was added to 100 ml of the prepared PAA aqueous solution and mixed thoroughly to obtain the "core" spinning solution. Another prepared PVA aqueous solution was used as the "shell" spinning solution. 100 ml of each spinning solution was injected into an electrospinning device through a needle to spin nanofilms. The films were heated at 80°C for 2 hours to remove residual solvent, and finally crosslinked at 130°C for 12-24 hours to obtain nanofiber membranes suitable for gas filtration. The added graphene particles had a diameter of 200-300 nm.

[0047] Example 17

[0048] The graphene added to the "nuclear" spinning solution is hydrophilic modified graphene, and the rest is the same as in Example 2.

[0049] Example 18

[0050] The graphene added to the "nuclear" spinning solution is hydrophilic modified graphene, and the rest is the same as in Example 8.

[0051] Example 19

[0052] The graphene added to the "nuclear" spinning solution is hydrophilic modified graphene, and the rest is the same as in Example 9.

[0053] Example 20

[0054] The graphene added to the "nuclear" spinning solution is hydrophilic modified graphene, and the rest is the same as in Example 10.

[0055] Comparative Example 1

[0056] Polyvinyl alcohol and polyacrylic acid were dissolved in deionized water to prepare aqueous solutions of 8.8 wt% and 14.4 wt% respectively. 100 ml of each spinning solution was injected into an electrospinning apparatus via a needle to spin nanofilms. Residual solvents in the films were removed by heating at 80°C for 2 hours, and finally, crosslinking was performed at 100°C for 12-24 hours to obtain nanofiber membranes suitable for gas filtration.

[0057] The filtration effects of the nanofiber membranes prepared in Examples 8-20 and Comparative Example 1 are shown in Table 4.

[0058] Table 4

[0059] Example 8 3 93.6 Example 9 3 94.5 Example 10 3 92.3 Example 11 3 94.3 Example 12 3 93.7 Example 13 3 93.0 Example 14 3 91.2 Example 15 3 93.1 Example 16 3 92.7 Example 17 3 91.0 Example 18 3 89.5 Example 19 3 90.7 Example 20 3 88.8 Comparative Example 1 3 86.5

[0060] Based on the filtration effects presented in Tables 2, 3, and 4, the addition of graphene oxide or hydrophilically modified graphene effectively increased the filtration efficiency of the nanofiber membrane compared to the membrane without graphene. Preferably, the graphene oxide particle size is 50-500 nm.

Claims

1. A method for preparing a nanofiber membrane that can be used for gas filtration, comprising the following steps: Polyvinyl alcohol and polyacrylic acid were prepared into aqueous solutions of 8-10 wt% and 13-16.4 wt%, respectively. When preparing the aqueous solution, graphene oxide or hydrophilic modified graphene is added to one of the solutions and mixed evenly to obtain the "core" spinning solution, while the other solution is the "shell" spinning solution. Two spinning solutions were spun into nanofilms using a coaxial electrospinning process. The residual solvent in the film is removed by heating at 70-80 degrees Celsius for 2-4 hours, and finally crosslinked by heating at 100-150 degrees Celsius for 12-24 hours to obtain a nanofiber membrane that can be used for gas filtration. The amount of graphene added to the "core" spinning solution is 0.5-2g / 100ml.

2. The method according to claim 1, characterized in that, The graphene has a particle size of 50-700 nm.

3. The method according to claim 2, characterized in that, The graphene has a particle size of 50-500 nm.

4. The method according to claim 2, characterized in that, The specific steps of the coaxial electrospinning process are as follows: two spinning solutions are injected at the same injection speed of 10ul / min, the distance from the needle to the roller is 15cm, the voltage is 10kv, the humidity is 30-45%, and a nanofilm of a certain thickness is spun using a coaxial electrospinning device.

5. A nanofiber membrane for gas filtration, prepared by the method described in any one of claims 1 to 4.

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