Preparation method of a beaded sodium alginate nanofiber membrane

Abstract

The application belongs to the technical field of nanometer materials, and particularly discloses a preparation method of a string-bead-shaped sodium alginate nanofiber membrane, which is used for air purification. The method comprises the following steps: (1) preparing SA aqueous solution and PEO aqueous solution respectively, mixing the SA aqueous solution and the PEO aqueous solution according to a proportion of 9:1 to obtain SA / PEO solution with a concentration of 2.4%-2.8%, and adding ethanol and triton into the SA / PEO solution to prepare a spinning solution; (2) electrospinning the spinning solution to obtain a sodium alginate nanofiber membrane; (3) placing the sodium alginate nanofiber membrane in anhydrous ethanol for 1 min, then placing the sodium alginate nanofiber membrane in a calcium chloride crosslinking solution with a concentration of 5.0% for 1 min to perform calcium ion crosslinking, and then performing freeze-drying on the sodium alginate nanofiber membrane after the calcium ion crosslinking. The string-bead-shaped sodium alginate nanofiber membrane with high efficiency and low resistance can be simply obtained by regulating the concentration of the SA / PEO solution.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterials technology, and particularly relates to a method for preparing a beaded sodium alginate nanofiber membrane. Background Technology

[0002] Air contains particulate matter carrying bacteria and viruses, and air filtration is considered one of the most effective technologies to mitigate this problem. Compared to membrane filters, fiber filters have always attracted attention due to their advantages such as ease of mass production, cost-effectiveness, variety of materials, and energy efficiency.

[0003] Currently, there are various techniques for preparing fiber filters, such as stretching, spin bonding, template methods, and melt blowing. Electrospun fibers, due to their controllable diameter and morphology, interconnected pore structure, and high specific surface area and porosity, are considered a simple and universal top-down method for preparing high-efficiency nanofiber membranes. Electrospun nanofiber membranes with interconnected pore structures show great promise for applications in air purification.

[0004] Currently, electrospun nanofiber membranes are mainly formed by the random deposition of smooth-surfaced fibers. The stacking structure is relatively simple, and the fiber membrane is relatively dense, which is not conducive to the permeation of air and liquid, resulting in high filtration resistance. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing beaded sodium alginate nanofiber membranes, which effectively solves the problem of high filtration resistance in existing electrospun nanofiber membranes.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a beaded sodium alginate nanofiber membrane includes the following steps: S1, preparation of spinning solution: Prepare aqueous solutions of sodium alginate (SA) and sodium phenolate (PEO) separately, and mix the SA and PEO solutions in a ratio of 9:1 to obtain an SA / PEO solution with a solute mass concentration of 2.4% to 2.8%. Add ethanol and Triton to the SA / PEO solution dropwise, stir for a period of time to obtain the spinning solution, and then centrifuge and degas the spinning solution for later use.

[0008] S2. Electrospin the centrifuged and deaerated spinning solution to obtain a sodium alginate nanofiber membrane.

[0009] S3. Place the sodium alginate nanofiber membrane in anhydrous ethanol and let it stand for 1 minute. Then, immerse it in a 5.0% calcium chloride crosslinking solution for 1 minute to perform calcium ion crosslinking. Finally, freeze-dry the sodium alginate nanofiber membrane after calcium ion crosslinking.

[0010] Further, in step S1, the proportions of ethanol and Triton in the spinning solution are 10w% and 0.8w%, respectively.

[0011] Further, in step S1, the solute mass concentration of the SA / PEO solution is 2.6%.

[0012] Furthermore, in step S1, the centrifugation degassing condition is centrifugation at 3000 r / min for 10 min.

[0013] Further, in step S2, the electrospinning process conditions include: a spinning voltage of 30kV, a feed speed of 0.01mL / min, a receiving distance of 18cm, a receiving roller speed of 180-200r / min, a spinning environment controlled at a temperature of 15-25℃ and a humidity of 20-30%, and a spinning needle moving speed of 10cm / min.

[0014] The beneficial technical effects of this invention are: it achieves the control of the beaded hierarchical structure of sodium alginate nanofiber membranes without the need for expensive nano-additives and various materials, or cumbersome experimental preparation steps. This invention can easily obtain highly efficient, low-resistance beaded sodium alginate nanofiber membranes by adjusting the concentration of the SA / PEO solution. Attached Figure Description

[0015] Figure 1 These are SEM images of sodium alginate nanofiber membranes of Examples 1-3 and Comparative Example 1 of the present invention. In the figure, (A) is the sodium alginate nanofiber membrane of Example 1, (B) is the sodium alginate nanofiber membrane of Example 2, (C) is the sodium alginate nanofiber membrane of Example 3, and (D) is the sodium alginate nanofiber membrane of Comparative Example 1.

[0016] Figure 2 These are steady-state shear diagrams (A) and tensile rheological diagrams (B) of the spinning solutions of Examples 1-3 and Comparative Example 1 of the present invention;

[0017] Figure 3 These are pore size distribution diagrams of sodium alginate nanofiber membranes from Examples 1-3 and Comparative Example 1 of the present invention. Detailed Implementation

[0018] The present invention will now be described with reference to the accompanying drawings, embodiments, and comparative examples.

[0019] The chemical formulas involved in this invention are explained as follows: SA—sodium alginate, PEO—polyethylene oxide.

[0020] A method for preparing a beaded sodium alginate nanofiber membrane includes the following steps: S1, preparation of spinning solution: Prepare aqueous solutions of sodium alginate (SA) and sodium phenolate (PEO) separately, and mix them in a 9:1 ratio to obtain an SA / PEO solution with a solute mass concentration of 2.4%–2.8%. Add ethanol and Triton to the SA / PEO solution dropwise, stir for 5 hours to obtain the spinning solution, and centrifuge the spinning solution at 3000 r / min for 10 minutes to remove bubbles before use. The proportions of ethanol and Triton in the spinning solution are 10 wt% and 0.8 wt%, respectively.

[0021] S2. The centrifuged and deaerated spinning solution is electrospun to obtain a sodium alginate nanofiber membrane. In some specific embodiments, the centrifuged and deaerated spinning solution is slowly added to a 20mL syringe, avoiding the generation of air bubbles during this process. A No. 22 stainless steel spinning needle is used for electrospinning, and a roller is used for receiving the spinneret. The electrospinning process conditions include: spinning voltage of 30kV, feed speed of 0.01mL / min, receiving distance of 18cm, receiving roller speed of 180-200r / min, spinning environment control of temperature of 15-25℃ and humidity of 20-30%, and spinning needle moving speed of 10cm / min.

[0022] S3. Crosslinking and drying of sodium alginate nanofiber membrane: First, place the sodium alginate nanofiber membrane in anhydrous ethanol and let it stand for 1 minute. Then, immerse it in a 5.0% calcium chloride crosslinking solution for 1 minute to perform calcium ion crosslinking. After that, take out the sodium alginate nanofiber membrane after calcium ion crosslinking and place it directly in a vacuum freeze dryer for freeze drying.

[0023] The present invention will be further illustrated below with specific examples.

[0024] Example 1

[0025] (1) Prepare SA aqueous solution and PEO aqueous solution separately, and mix SA aqueous solution and PEO aqueous solution in a ratio of 9:1 to obtain SA / PEO solution with a solute mass concentration of 2.4%. Add ethanol and Triton to SA / PEO solution dropwise, stir together for 5 hours to obtain spinning solution. Centrifuge the spinning solution at 3000 r / min for 10 min to remove bubbles and set aside for later use. The proportions of ethanol and Triton in the spinning solution are 10 w% and 0.8 w%, respectively.

[0026] (2) The centrifuged and deaerated spinning solution is electrospun to obtain a sodium alginate nanofiber membrane. Specifically, the centrifuged and deaerated spinning solution is slowly added to a 20mL syringe, avoiding the generation of air bubbles during this process. A No. 22 stainless steel spinning needle is used for electrospinning, and a roller is used for receiving. The electrospinning process conditions include: spinning voltage of 30kV, feed speed of 0.01mL / min, receiving distance of 18cm, receiving roller speed of 180-200r / min, spinning environment control of temperature of 15-25℃ and humidity of 20-30%, and spinning needle moving speed of 10cm / min.

[0027] (3) First, place the sodium alginate nanofiber membrane in anhydrous ethanol and let it stand for 1 minute. Then, immerse it in a 5.0% calcium chloride crosslinking solution for 1 minute to perform calcium ion crosslinking. After that, take out the sodium alginate nanofiber membrane after calcium ion crosslinking and place it directly in a vacuum freeze dryer for freeze drying.

[0028] Example 2

[0029] The difference from Example 1 is that the solute mass concentration of the SA / PEO solution in step (1) is 2.6%.

[0030] Example 3

[0031] The difference from Example 1 is that the solute mass concentration of the SA / PEO solution in step (1) is 2.8%.

[0032] Comparative Example 1

[0033] The difference from Example 1 is that the solute mass concentration of the SA / PEO solution in step (1) is 3.0%.

[0034] The sodium alginate nanofiber membranes of Examples 1-3 and Comparative Example 1 were characterized by SEM, such as... Figure 1As shown, the sodium alginate nanofiber membrane of Example 1 (SA / PEO solution concentration of 2.4%) exhibits a beaded fiber structure, but its fiber-forming performance is poor, and it is difficult to observe a complete beaded fiber structure. With increasing SA / PEO solution concentration, the increased molecular chain interaction forces lead to slower creep recovery of the molecular chains during the spinning process, resulting in a greater tendency to form a stable fiber structure. Therefore, the sodium alginate nanofiber membranes of Example 2 (SA / PEO solution concentration of 2.6%) and Example 3 (SA / PEO solution concentration of 2.8%) show a very obvious beaded fiber structure. In contrast, the beaded and other hierarchical structures of Comparative Example 1 (SA / PEO solution concentration of 3.0%) completely disappear, and the fiber as a whole appears smooth. From the effect of SA / PEO solution concentration on spinning performance, the beaded hierarchical structure effect is most significant and the fiber-forming performance is better when the SA / PEO solution concentration is around 2.6% and 2.8%.

[0035] To investigate the effect of SA / PEO solution concentration on the stretching process of the spinning solution, the steady-state shear and tensile rheological behavior of the spinning solutions in Examples 1-3 and Comparative Example 1 were characterized, such as... Figure 2 As shown. By Figure 2 (A) It can be seen that the spinning solution exhibits a trend of shear thinning under shear action. As the concentration of SA / PEO solution decreases, the zero-shear viscosity of the spinning solution decreases from 20 Pa·s to 6 Pa·s, proving that the molecular chain entanglement concentration decreases with decreasing solute concentration. Meanwhile, from Figure 2 (B) It can be seen that as the concentration of SA / PEO solution decreases, the breaking time of the stretched filament decreases from 10s to 2.5s. After the power-law thinning region, the diameter exhibits an exponential thinning trend characteristic of elastic solutions. The steady-state shear and tensile rheological behavior of the spinning solution both reflect that with the decrease of SA / PEO solution concentration, the jet surface of the spinning solution after leaving the spinneret is more easily deformed, making it easier to generate uneven fibers, thus obtaining the desired beaded fiber structure.

[0036] The pore size of the sodium alginate nanofiber membranes in Examples 1-3 and Comparative Example 1 was studied, such as... Figure 3 As shown, the sodium alginate nanofiber membrane prepared in Comparative Example 1 has the smallest pore size and the narrowest pore size distribution. With decreasing SA / PEO solution concentration, the pore size of the sodium alginate nanofiber membrane significantly increases, and the pore size distribution gradually widens. This is because as the SA / PEO solution concentration decreases, the size and number of fiber beads increase, increasing the gaps between fibers, thereby increasing the pore size of the sodium alginate nanofiber membrane. This further confirms that beaded sodium alginate nanofiber membranes can be obtained by controlling the SA / PEO solution concentration.

[0037] The air filtration performance of sodium alginate nanofiber membranes from Examples 1-3 and Comparative Example 1 was studied. The densely packed, smooth sodium alginate nanofiber membrane prepared in Comparative Example 1 showed a relatively stable filtration effect for aerosol particles of different sizes, with a filtration efficiency exceeding 99%. However, the dense sodium alginate nanofiber membrane exhibited a relatively large pressure drop of 330 Pa. Among the sodium alginate nanofiber membranes prepared in Examples 1-3, the pressure drop of the sodium alginate nanofiber membrane prepared in Example 2 was measured to be 100 Pa. Further evaluation of the filtration performance of the sodium alginate nanofiber membranes was conducted by calculating the quality factor (QF = -ln(1-η) / ΔP). The sodium alginate nanofiber membrane from Example 2 (SA / PEO solution concentration of 2.6%) showed the highest quality factor, reaching 0.0284 Pa. -1 Therefore, among Examples 1-3, the sodium alginate nanofiber membrane in Example 2 has the most ideal gas filtration effect.

[0038] In summary, this invention achieves the control of the beaded hierarchical structure of sodium alginate nanofiber membranes without the need for expensive nano-additives and various materials, or cumbersome experimental preparation steps. This invention allows for the simple and efficient acquisition of low-resistance beaded sodium alginate nanofiber membranes by adjusting the concentration of the SA / PEO solution.

[0039] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for preparing a beaded sodium alginate nanofiber membrane, characterized in that, Includes the following steps: S1. Preparation of spinning solution: Prepare SA aqueous solution and PEO aqueous solution separately, and mix them in a 9:1 ratio to obtain an SA / PEO solution with a solute mass concentration of 2.6%. Add ethanol and Triton to the SA / PEO solution dropwise, and stir for a period of time to obtain the spinning solution. Centrifuge and degas the spinning solution for later use. The proportions of ethanol and Triton in the spinning solution are 10 w% and 0.8 w%, respectively. S2. Electrospinning the centrifuged and degassed spinning solution to obtain sodium alginate nanofiber membrane. The conditions for centrifugation and degassing are: centrifugation at 3000 r / min for 10 min; The electrospinning process conditions include: a spinning voltage of 30kV, a feed speed of 0.01mL / min, a receiving distance of 18cm, a receiving roller speed of 180-200 r / min, a spinning environment controlled at a temperature of 15-25℃ and a humidity of 20-30%, and a spinning needle moving speed of 10cm / min. S3. The sodium alginate nanofiber membrane is placed in anhydrous ethanol and allowed to stand for 1 minute. Then, it is immersed in a 5.0% calcium chloride crosslinking solution for 1 minute to perform calcium ion crosslinking. The calcium ion crosslinked sodium alginate nanofiber membrane is then freeze-dried. The beaded sodium alginate nanofiber membrane is used for air filtration.

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