Rough porous oriented cellulose acetate nanofiber and method of making and use thereof

Abstract

The present application relates to a kind of rough porous oriented cellulose acetate nanofiber preparation method, comprising the following steps: preparing precursor solution by preparing cellulose acetate solution and CDs-PVA composite pore-forming agent;Nanofiber bundle is prepared by using electrospinning precursor solution;CDs-PVA composite pore-forming agent in nanofiber bundle matrix is removed, and rough porous structure oriented cellulose acetate nanofiber bundle is obtained.The present application also relates to a kind of rough porous oriented cellulose acetate nanofiber prepared based on the above method, the average fiber diameter of oriented cellulose acetate nanofiber bundle is 150-300 nanometers, porosity is 81%-87%, average pore size is 0.7-1.8 microns, channel communication rate is greater than 80%, and a kind of rough porous oriented cellulose acetate nanofiber is applied, several oriented cellulose acetate nanofiber bundles are parallelly arranged into sheet shape and edge sealing to obtain membrane type liquid filtration medium.The present application makes the tensile strength of the filament bundle under the high-speed operation of the hub, and simultaneously improves the pore size of the filament bundle after hole making.

Description

Technical Field

[0001] This invention pertains to chemical equipment, and in particular relates to a rough, porous, oriented cellulose acetate nanofiber, its preparation method, and its applications. Background Technology

[0002] Electrospinning is a highly efficient and economical method for producing large quantities of micro and nanofibers. Based on electrostatic forces, an electric field is used to excite a viscous polymer precursor solution into an extremely fine jet, which then rapidly dries and solidifies in air, thus producing high-performance fiber materials. Electrospun acetate nanofibers exhibit chemical resistance and biodegradability; however, in actual production, the fibers obtained through this method are often quite disordered.

[0003] In domestic and international research, high-speed rotating hubs are widely used as receiving devices for the preparation of oriented nanofiber materials. However, this method is prone to causing fiber breakage, severely impacting production efficiency and product yield. Furthermore, traditional acetate nanofiber products require a high-pressure environment for effective operation as a filter medium, resulting in low filtration efficiency and significant energy waste. Summary of the Invention

[0004] The purpose of this invention is to address the above-mentioned problems by providing a method for preparing coarse and porous oriented cellulose acetate nanofibers.

[0005] Another objective of this invention is to address the aforementioned problems by providing a coarse, porous, oriented cellulose acetate nanofiber.

[0006] Another object of the present invention is to provide a rough and porous oriented cellulose acetate nanofiber in response to the above-mentioned problems.

[0007] This invention creatively proposes a method for preparing coarse, porous, oriented cellulose acetate nanofibers, comprising the following steps:

[0008] A precursor solution was prepared by mixing cellulose acetate solution and CDs-PVA composite porogen.

[0009] Nanofiber bundles were prepared from precursor solutions by electrospinning.

[0010] By removing the CDs-PVA composite porogen from the nanofiber bundle matrix, a rough, porous structure of oriented cellulose acetate nanofiber bundles is obtained.

[0011] On the one hand, polyvinyl alcohol (PVA) has a coating and dispersing effect on carbon quantum dots (CDs), preventing them from agglomerating and giving the oriented cellulose acetate nanofiber bundles a smaller pore size. On the other hand, the physical composite and appropriate cross-linking of carbon quantum dots and polyvinyl alcohol with cellulose acetate form mixed fibers, which improves the breaking elongation of the nanofiber bundles and the pore connectivity.

[0012] In the above-mentioned method for preparing coarse and porous oriented cellulose acetate nanofibers, the CDs-PVA composite pore-forming agent contains water-soluble carbon quantum dots and polyvinyl alcohol solution.

[0013] In the above-mentioned method for preparing rough and porous oriented cellulose acetate nanofibers, the water-soluble carbon quantum dots use at least one of chitosan, lignin, and glucose as the carbon source.

[0014] In the above-mentioned method for preparing rough and porous oriented cellulose acetate nanofibers, carbon quantum dots are prepared by hydrothermal method, thermal decomposition method, ultrasonic method, radiation synthesis or microemulsion method.

[0015] In the above-mentioned method for preparing rough and porous oriented cellulose acetate nanofibers, the method for preparing water-soluble carbon quantum dots is as follows: the carbon source material is dispersed evenly in a solvent at a solid-liquid ratio of 0.2-0.5g:20ml, heated at 180-200℃ for 4-12h, cooled to room temperature, filtered, and the filtrate is freeze-dried to obtain water-soluble carbon quantum dots.

[0016] Furthermore, after the filtrate is freeze-dried, it is completely dispersed in water again, filtered, and then freeze-dried to obtain water-soluble carbon quantum dots.

[0017] Furthermore, the dispersion filtration uses a 200nm filter needle.

[0018] In the above-mentioned method for preparing rough and porous oriented cellulose acetate nanofibers, the mass ratio of water-soluble carbon quantum dots to polyvinyl alcohol is 0.0001-0.001:1-3.

[0019] In the above-mentioned method for preparing rough and porous oriented cellulose acetate nanofibers, the polyvinyl alcohol solution contains 8-16 wt% polyvinyl alcohol with a degree of polymerization of 2400-2500 and a degree of alcoholysis of 98-99%.

[0020] In the above-mentioned method for preparing coarse and porous oriented cellulose acetate nanofibers, the cellulose acetate solution contains 8-14 wt% cellulose acetate.

[0021] In the above-mentioned method for preparing coarse and porous oriented cellulose acetate nanofibers, the mass ratio of the cellulose acetate solution to the CDs-PVA composite pore-forming agent is 40:60 to 50:50.

[0022] In the above-mentioned method for preparing coarse and porous oriented cellulose acetate nanofibers, the electrospinning method is as follows: the precursor solution is injected through a syringe and received by a hub. The metal needle of the syringe is connected to the positive terminal of a high-voltage power supply, and the grounding device of the hub is connected to the negative terminal of the high-voltage power supply. The syringe advance speed is set to 0.5-2 mL / h, and the hub rotation speed is 800-1500 r / min.

[0023] By changing the polymer concentration ratio, hub rotation speed, and propulsion speed, oriented fibers can be obtained in a stable and controllable manner, thus solving the problems of poor fiber adsorption capacity and low filtration efficiency.

[0024] In one embodiment, the method for preparing coarse, porous, oriented cellulose acetate nanofibers includes the following steps:

[0025] (1) Preparation of carbon quantum dots

[0026] The carbon source material was magnetically stirred and dispersed evenly in a solvent at a solid-liquid ratio of 0.2–0.5 g: 20 ml. After heating at 180–200 °C for 4–12 h, the mixture was cooled to room temperature. The solution was filtered through a 200 nm filter needle and then freeze-dried to obtain a solid powder. The solid powder was then completely dispersed in water again and filtered through a 200 nm filter needle once more. The solution was then freeze-dried to obtain water-soluble carbon quantum dots.

[0027] (2) Preparation of CDs-PVA composite pore-forming agent

[0028] Polyvinyl alcohol is mixed with water and heated and stirred for more than 12 hours using a heated magnetic stirrer at a temperature of 60-100°C to obtain a colorless, transparent and viscous polyvinyl alcohol solution containing 8-16 wt% polyvinyl alcohol with a degree of polymerization of 2400-2500 and a degree of alcoholysis of 98-99%.

[0029] Water-soluble carbon quantum dots were added to a polyvinyl alcohol solution and heated and stirred for 18–24 h at a stirring temperature of 60–100 °C to obtain a CDs-PVA composite porogen with a mass ratio of water-soluble carbon quantum dots to polyvinyl alcohol of 0.0001–0.001:2–8.

[0030] (3) Preparation of precursor solution

[0031] A cellulose acetate solution with a concentration of 8–14 wt% was prepared by mixing cellulose acetate and acetone solvent. The solution was then sonicated for 2–4 hours using an ultrasonic device to obtain a colorless, clear, and viscous cellulose acetate solution.

[0032] A cellulose acetate solution and a CDs-PVA composite porogen were mixed at a mass ratio of 40:60 to 50:50 and stirred at room temperature for 10 to 12 hours to obtain a precursor solution.

[0033] (4) Electrospinning

[0034] The precursor solution is injected through a syringe, which is connected to an injection pump and received through a hub. The metal needle of the syringe is connected to the positive terminal of a high-voltage power supply, and the grounding device of the hub is connected to the negative terminal of the high-voltage power supply. The needle is a stainless steel needle with an outer diameter of 0.2–1 mm and an inner diameter of 0.15–0.9 mm.

[0035] The syringe propulsion speed is set to 0.5–2 mL / h, the positive power supply voltage to 10–20 kV, the receiving distance to 10–15 cm, and the hub rotation speed to 800–1500 r / min. After the device is in operation, the nanofibers can be received by the receiving hub without a large amount of scattering, thus obtaining a nanofiber bundle.

[0036] (5) Drying

[0037] The received nanofiber bundles were dried in a vacuum drying oven to remove residual solvent from the fibers. The operating temperature was set to 35–45°C, the vacuum degree to 5–15 Pa, and the drying time to 5–10 hours.

[0038] (6) Rinse

[0039] The dried nanofiber bundles were placed in a constant temperature water bath and rinsed with flowing high-temperature deionized water. The temperature of the high-temperature deionized water was controlled at 60-95℃ to remove excess CDs-PVA composite porogen. After drying, oriented cellulose acetate nanofiber bundles with a rough porous structure were obtained.

[0040] This invention creatively proposes a coarse and porous oriented cellulose acetate nanofiber, wherein the oriented cellulose acetate nanofiber bundle has an average fiber diameter of 150-300 nanometers, a porosity of 81%-87%, an average pore size of 0.7-1.8 micrometers, and a pore connectivity of greater than 80%.

[0041] The present invention also creatively proposes an application of rough and porous oriented cellulose acetate nanofibers, characterized in that: several segments of the oriented cellulose acetate nanofiber bundles are arranged in parallel into a sheet, and the edges of the sheet are sealed with resin material to obtain a membrane-type liquid filter medium.

[0042] Compared with the prior art, the advantages of the present invention are as follows:

[0043] This invention improves the performance of cellulose acetate by using CDs-PVA composite pore-forming agent, reduces the fiber breakage rate under high-speed operation of wheel hub, and enables the minimum fiber diameter of oriented cellulose acetate nanofiber bundles to reach 150nm, the porosity to reach 87%, the average pore size to reach 0.7 micrometers, and the pore connectivity rate to reach over 80%.

[0044] The fibers prepared by this invention have high parallelism and good orientation.

[0045] This invention improves the tensile strength of nanofiber bundles by 8.7 MPa during electrospinning.

[0046] The membrane-type liquid filter medium prepared by this invention has a filtration efficiency of up to 99.6% and a pressure drop of 0.04 MPa. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the electrospinning process in this invention.

[0048] Figure 2 This is an electron microscope image of a rough, porous, oriented cellulose acetate nanofiber bundle according to the present invention.

[0049] Figure 3 This is a magnified view of the surface of a rough, porous, oriented cellulose acetate nanofiber bundle according to the present invention.

[0050] Figure 4 This is a cross-sectional view of a rough, porous, oriented cellulose acetate nanofiber according to the present invention.

[0051] In the diagram, there is a syringe pump (1), a syringe (2), a high-voltage power supply (3), and a hub (4). Detailed Implementation

[0052] The following specific examples further illustrate this point;

[0053] The present invention will be further illustrated below with specific examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0054] Example 1

[0055] The method for preparing rough, porous, oriented cellulose acetate nanofibers includes the following steps:

[0056] (1) Preparation of carbon quantum dots

[0057] 0.5g of chitosan was magnetically stirred and dispersed evenly in 20ml of deionized water, and then heated at 200℃ for 4h for hydrothermal reaction. After cooling to room temperature, the mixture was filtered with a 200nm filter needle, and the filtrate was freeze-dried to obtain a solid powder.

[0058] The solid powder was completely dispersed again in deionized water and filtered again with a 200nm filter needle. The filtrate was then freeze-dried to obtain water-soluble carbon quantum dots.

[0059] (2) Preparation of CDs-PVA composite pore-forming agent

[0060] 2.18g of polyvinyl alcohol with an average degree of polymerization of 2400 and a degree of alcoholysis of 98% was mixed with 25ml of deionized water to prepare a polyvinyl alcohol concentration of 8wt%. The solution was heated and stirred on a heated magnetic stirrer for more than 12 hours at a temperature of 75℃ to obtain a colorless, transparent and viscous polyvinyl alcohol solution.

[0061] 0.1 mg of water-soluble carbon quantum dots were added to a polyvinyl alcohol solution and heated and stirred for 24 h at a stirring temperature of 90 °C to obtain a CDs-PVA composite porogen.

[0062] (3) Preparation of precursor solution

[0063] A 10 wt% cellulose acetate solution was prepared by mixing cellulose acetate and acetone solvent. The solution was then sonicated for 2 hours to obtain a colorless, clear, and viscous cellulose acetate solution.

[0064] A cellulose acetate solution and a CDs-PVA composite porogen were mixed at a mass ratio of 40:60 and stirred at room temperature for 12 hours to obtain a precursor solution.

[0065] (4) Electrospinning

[0066] like Figure 1 As shown, the precursor solution is injected through syringe 2. Syringe 2 is connected to syringe pump 1 and received through hub 4. The metal needle of syringe 2 is connected to the positive terminal of high voltage power supply 3, and the grounding device of hub 4 is connected to the negative terminal of high voltage power supply 3. The needle is a stainless steel needle with an outer diameter of 0.2 to 1 mm and an inner diameter of 0.15 to 0.9 mm.

[0067] The syringe propulsion speed was set to 1.5 mL / h, the positive power supply voltage to 10 kV, the receiving distance to 10 cm, and the hub rotation speed to 1500 r / min. After the device was running, the nanofibers were received by the receiving hub without much scattering, and nanofiber bundles were obtained.

[0068] (5) Drying

[0069] The received nanofiber bundles were dried in a vacuum drying oven to remove residual solvent from the fibers. The operating temperature was set to 40°C, the vacuum degree to 10Pa, and the drying time to 6 hours.

[0070] (6) Rinse

[0071] The dried nanofiber bundles were placed in an 80°C constant-temperature water bath in deionized water for 2 hours, and then rinsed with flowing high-temperature deionized water (temperature controlled at 80°C) to remove excess CDs-PVA composite porogen. The bundles were then dried in a vacuum drying oven at 40°C and 10 Pa for 6 hours to obtain the desired product. Figure 2 , 3 The image shows a directional cellulose acetate nanofiber bundle with a rough, porous structure, with a cross-sectional electron microscope image of the fiber as shown below. Figure 4 As shown, the surface of the fiber matrix becomes rough due to the lack of CDs-PVA composite pore-forming agent, and irregular pores are formed inside, while cellulose acetate retains its original shape.

[0072] Example 2

[0073] The method for preparing rough, porous, oriented cellulose acetate nanofibers includes the following steps:

[0074] (1) Preparation of carbon quantum dots

[0075] 0.2g of lignin was magnetically stirred and dispersed evenly in 20ml of deionized water, and then heated at 180℃ for 12h for hydrothermal reaction. After cooling to room temperature, the solution was filtered with a 200nm filter needle and freeze-dried to obtain a solid powder.

[0076] The solid powder was completely dispersed again in deionized water and filtered again with a 200nm filter needle. The filtrate was then freeze-dried to obtain water-soluble carbon quantum dots.

[0077] (2) Preparation of CDs-PVA composite pore-forming agent

[0078] 4.76g of polyvinyl alcohol with an average degree of polymerization of 2500 and a degree of alcoholysis of 99% was mixed with 25ml of deionized water to prepare a polyvinyl alcohol concentration of 16wt%. The solution was heated and stirred on a heated magnetic stirrer for more than 12 hours at a temperature of 75℃ to obtain a colorless, transparent and viscous polyvinyl alcohol solution.

[0079] 0.1 mg of water-soluble carbon quantum dots were added to a polyvinyl alcohol solution and heated and stirred for 24 h at a stirring temperature of 80 °C to obtain a CDs-PVA composite porogen.

[0080] (3) Preparation of precursor solution

[0081] A 10 wt% cellulose acetate solution was prepared by mixing cellulose acetate and acetone solvent. The solution was then sonicated for 2 hours to obtain a colorless, clear, and viscous cellulose acetate solution.

[0082] A cellulose acetate solution and a CDs-PVA composite porogen were mixed at a mass ratio of 50:50 and stirred at room temperature for 12 hours to obtain a precursor solution.

[0083] (4) Electrospinning

[0084] like Figure 1 As shown, the precursor solution is injected through syringe 2. Syringe 2 is connected to syringe pump 1 and received through hub 4. The metal needle of syringe 2 is connected to the positive terminal of high voltage power supply 3, and the grounding device of hub 4 is connected to the negative terminal of high voltage power supply 3. The needle is a stainless steel needle with an outer diameter of 0.2 to 1 mm and an inner diameter of 0.15 to 0.9 mm.

[0085] The syringe propulsion speed was set to 1.5 mL / h, the positive power supply voltage to 10 kV, the receiving distance to 10 cm, and the hub rotation speed to 1200 r / min. After the device was running, the nanofibers were received by the receiving hub without much scattering, and nanofiber bundles were obtained.

[0086] (5) Drying

[0087] The received nanofiber bundles were dried in a vacuum drying oven to remove residual solvent from the fibers. The operating temperature was set to 45°C, the vacuum degree to 10Pa, and the drying time to 6 hours.

[0088] (6) Rinse

[0089] The dried nanofiber bundles were placed in a constant temperature water bath at 80℃ in deionized water for 2 hours, and then rinsed with flowing high-temperature deionized water at 80℃ to remove excess CDs-PVA composite porogen. The bundles were then dried in a vacuum drying oven at 45℃ and 10Pa for 6 hours to obtain oriented cellulose acetate nanofiber bundles with a rough porous structure.

[0090] Example 3

[0091] The method for preparing rough, porous, oriented cellulose acetate nanofibers includes the following steps:

[0092] (1) Preparation of carbon quantum dots

[0093] Disperse 0.5g of glucose evenly in 20ml of deionized water by magnetic stirring, then heat at 180℃ for 12h for hydrothermal reaction. After cooling to room temperature, filter with a 200nm filter needle and freeze-dry the filtrate to obtain a solid powder, which is water-soluble carbon quantum dots.

[0094] (2) Preparation of CDs-PVA composite pore-forming agent

[0095] 4.76g of polyvinyl alcohol with an average degree of polymerization of 2500 and a degree of alcoholysis of 99% was mixed with 25ml of deionized water to prepare a polyvinyl alcohol concentration of 16wt%. The solution was heated and stirred on a heated magnetic stirrer for more than 12 hours at a temperature of 75℃ to obtain a colorless, transparent and viscous polyvinyl alcohol solution.

[0096] 0.2 mg of water-soluble carbon quantum dots were added to a polyvinyl alcohol solution and heated and stirred for 18 h at a stirring temperature of 90 °C to obtain a CDs-PVA composite porogen.

[0097] (3) Preparation of precursor solution

[0098] A cellulose acetate solution with a concentration of 14 wt% was prepared by mixing cellulose acetate and acetone solvent. The solution was then sonicated for 2 hours using an ultrasonic device to obtain a colorless, clear, and viscous cellulose acetate solution.

[0099] A cellulose acetate solution and a CDs-PVA composite porogen were mixed at a mass ratio of 50:50 and stirred at room temperature for 12 hours to obtain a precursor solution.

[0100] (4) Electrospinning

[0101] like Figure 1 As shown, the precursor solution is injected through syringe 2. Syringe 2 is connected to syringe pump 1 and received through hub 4. The metal needle of syringe 2 is connected to the positive terminal of high voltage power supply 3, and the grounding device of hub 4 is connected to the negative terminal of high voltage power supply 3. The needle is a stainless steel needle with an outer diameter of 0.2 to 1 mm and an inner diameter of 0.15 to 0.9 mm.

[0102] The syringe propulsion speed was set to 2 mL / h, the positive power supply voltage to 20 kV, the receiving distance to 15 cm, and the hub rotation speed to 1500 r / min. After the device was running, the nanofibers were received by the receiving hub without much scattering, and nanofiber bundles were obtained.

[0103] (5) Drying

[0104] The received nanofiber bundles were dried in a vacuum drying oven to remove residual solvent from the fibers. The operating temperature was set to 45°C, the vacuum degree to 10Pa, and the drying time to 6 hours.

[0105] (6) Rinse

[0106] The dried nanofiber bundles were placed in a constant temperature water bath at 80℃ in deionized water for 2 hours, and then rinsed with flowing high-temperature deionized water at 80℃ to remove excess CDs-PVA composite porogen. The bundles were then dried in a vacuum drying oven at 45℃ and 10Pa for 6 hours to obtain oriented cellulose acetate nanofiber bundles with a rough porous structure.

[0107] Comparative Example 1

[0108] The method for preparing oriented cellulose acetate nanofibers includes the following steps:

[0109] (1) Preparation of pore-forming agent

[0110] 2.18 g of polyvinyl alcohol with an average degree of polymerization of 2400 and a degree of alcoholysis of 98% was mixed with 25 ml of deionized water to prepare a polyvinyl alcohol concentration of 8 wt%. The solution was heated and stirred on a heated magnetic stirrer for more than 12 hours at a temperature of 75 °C to obtain a colorless, transparent and viscous polyvinyl alcohol solution, which was then used as a pore-forming agent.

[0111] (2) Preparation of precursor solution

[0112] A 10 wt% cellulose acetate solution was prepared by mixing cellulose acetate and acetone solvent. The solution was then sonicated for 2 hours to obtain a colorless, clear, and viscous cellulose acetate solution.

[0113] A cellulose acetate solution and a porogen were mixed at a mass ratio of 40:60 and stirred at room temperature for 12 hours to obtain a precursor solution.

[0114] (3) Electrospinning

[0115] like Figure 1 As shown, the precursor solution is injected through syringe 2. Syringe 2 is connected to syringe pump 1 and received through hub 4. The metal needle of syringe 2 is connected to the positive terminal of high voltage power supply 3, and the grounding device of hub 4 is connected to the negative terminal of high voltage power supply 3. The needle is a stainless steel needle with an outer diameter of 0.2 to 1 mm and an inner diameter of 0.15 to 0.9 mm.

[0116] The syringe propulsion speed was set to 1.5 mL / h, the positive power supply voltage to 10 kV, the receiving distance to 10 cm, and the hub rotation speed to 1500 r / min. After the device was running, the nanofibers were received by the receiving hub without much scattering, and nanofiber bundles were obtained.

[0117] (4) Drying

[0118] The received nanofiber bundles were dried in a vacuum drying oven to remove residual solvent from the fibers. The operating temperature was set to 40°C, the vacuum degree to 10Pa, and the drying time to 6 hours.

[0119] (5) Rinse

[0120] The dried nanofiber bundles were placed in a constant temperature water bath at 80°C in deionized water for 2 hours, and then rinsed with flowing high-temperature deionized water at 80°C to remove excess pore-forming agent. The bundles were then dried in a vacuum drying oven at 40°C and 10Pa for 6 hours to obtain cellulose acetate nanofiber bundles.

[0121] Comparative Example 2

[0122] The method for preparing oriented cellulose acetate nanofibers includes the following steps:

[0123] (1) Preparation of carbon quantum dots

[0124] Chitosan was magnetically stirred and dispersed evenly in deionized water at a solid-liquid ratio of 0.5g:20ml. Then, it was heated at 200℃ for 4h to carry out a hydrothermal reaction. After cooling to room temperature, it was filtered with a 200nm filter needle, and the filtrate was freeze-dried to obtain a solid powder.

[0125] The solid powder was completely dispersed again in deionized water and filtered again with a 200nm filter needle. The filtrate was then freeze-dried to obtain water-soluble carbon quantum dots.

[0126] (2) Preparation of precursor solution

[0127] A 10 wt% cellulose acetate solution was prepared by mixing cellulose acetate and acetone solvent. The solution was then sonicated for 2 hours to obtain a colorless, clear, and viscous cellulose acetate solution.

[0128] A cellulose acetate solution and water-soluble carbon quantum dots were mixed at a mass ratio of 40:4.8 and stirred at room temperature for 12 hours to obtain a precursor solution.

[0129] (3) Electrospinning

[0130] like Figure 1 As shown, the precursor solution is injected through syringe 2. Syringe 2 is connected to syringe pump 1 and received through hub 4. The metal needle of syringe 2 is connected to the positive terminal of high voltage power supply 3, and the grounding device of hub 4 is connected to the negative terminal of high voltage power supply 3. The needle is a stainless steel needle with an outer diameter of 0.2 to 1 mm and an inner diameter of 0.15 to 0.9 mm.

[0131] The syringe propulsion speed was set to 1.5 mL / h, the positive power supply voltage to 10 kV, the receiving distance to 10 cm, and the hub rotation speed to 1500 r / min. After the device was running, the nanofibers were received by the receiving hub without much scattering, and nanofiber bundles were obtained.

[0132] (4) Drying

[0133] The received nanofiber bundles were dried in a vacuum drying oven to remove residual solvent from the fibers. The operating temperature was set to 40°C, the vacuum degree to 10Pa, and the drying time to 6 hours.

[0134] (5) Rinse

[0135] The dried nanofiber bundles were placed in a constant temperature water bath at 80°C in deionized water for 2 hours, and then rinsed with flowing high-temperature deionized water at 80°C to remove excess carbon quantum dots. The bundles were then dried in a vacuum drying oven at 40°C and 10 Pa for 6 hours to obtain cellulose acetate nanofiber bundles.

[0136] The present invention tested the tensile properties of the nanofiber bundles obtained in step (4) of Examples 1-3 and step (3) of Comparative Examples 1 and 2. The test method was in accordance with the standard GB / T1040.3-2006 Determination of tensile properties of plastics Part 3: Test conditions for films and sheets. The results are shown in Table 1 below:

[0137] Table 1

[0138] Tensile strength Example 1 8.7MPa Example 2 8.2MPa Example 3 8.6MPa Comparative Example 1 7.6MPa Comparative Example 2 6.5MPa

[0139] The results show that the present invention improves the tensile strength of nanofiber bundles during electrospinning. The oriented nanofiber bundles obtained by electrospinning with CDs-PVA composite porogen and cellulose acetate composite (Example 1) have significantly improved tensile strength compared with the oriented nanofiber bundles obtained by using only polyvinyl alcohol as a porogen (Comparative Example 1) or the oriented nanofiber bundles obtained by using only carbon quantum dots as a porogen (Comparative Example 2).

[0140] The parameters of the cellulose acetate nanofiber bundles prepared in Examples 1-3 and Comparative Examples 1 and 2 of this invention were tested according to the standards ASTM C457-06 Porosity Test, GB / T 32361-2015 Separation Membrane Pore Size Test Method (Bubble Point and Average Flow Rate Method), and DIN EN 993-1:2019 Dense Molded Refractory Articles – Test Methods – Part 1: Determination of Bulk Density, Apparent Porosity and True Porosity. The results are shown in Table 2 below.

[0141] Table 2

[0142]

[0143]

[0144] The results show that the present invention has high porosity, small average pore size, and high pore connectivity. The oriented nanofiber bundles obtained by electrospinning with CDs-PVA composite porogen and cellulose acetate (Example 1) have significantly reduced pore size and improved porosity and pore connectivity compared with the oriented nanofiber bundles obtained by using only polyvinyl alcohol as a porogen (Comparative Example 1). Compared with the oriented nanofiber bundles obtained by using only carbon quantum dots as a porogen (Comparative Example 2), the pore connectivity and porosity are significantly improved, and the average pore size is also lower. The combination of polyvinyl alcohol and carbon quantum dots makes the pore distribution more uniform and fine.

[0145] Application Examples 1-5 correspond to the preparation of a certain amount of cellulose acetate nanofiber bundles according to Examples 1-3 and Comparative Examples 1 and 2, respectively. The oriented cellulose acetate nanofiber bundles are cut into several small segments of 5 cm, arranged in parallel into a sheet of 5 cm × 5 cm, and the edges of the sheet are sealed with epoxy resin to obtain a membrane-type liquid filter medium.

[0146] The parameters of the membrane-type liquid filter media prepared in Examples 1-3 and Comparative Examples 1 and 2 of this invention were tested according to the standard GB / T26114-2010 General Technical Specification for Filters for Liquid Filtration. The results are shown in Table 3 below:

[0147] Table 3

[0148] Filtration efficiency resistance pressure drop Example 1 99.5％ 0.4MPa Example 2 99.6％ 0.4MPa Example 3 99.5％ 0.5MPa Comparative Example 1 99.1％ 0.7MPa Comparative Example 2 99.2％ 0.9MPa

[0149] The results show that the membrane-type liquid filter medium manufactured by this invention has higher filtration efficiency and lower pressure drop due to its good orientation, small pore size, high porosity and high permeability. As a result, it has wide applications in water treatment fields such as microfiltration, ultrafiltration, nanofiltration, and membrane bioreactors, as well as in biological, medical and environmental fields such as high temperature air filtration and adsorption.

[0150] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

[0151] Although this paper frequently uses terms such as cellulose acetate, CDs-PVA composite porogen, precursor solution, carbon source, carbon quantum dots, polyvinyl alcohol, membrane liquid filter media, and oriented cellulose acetate nanofiber bundles, these terms are used merely for the convenience of describing and explaining the essence of the invention. Interpreting them as any additional limitation would contradict the spirit of the invention.

Claims

1. A method for preparing coarse, porous, oriented cellulose acetate nanofibers, characterized in that, Includes the following steps: A precursor solution was prepared by mixing cellulose acetate solution and CDs-PVA composite porogen. Nanofiber bundles were prepared from precursor solutions by electrospinning. By removing the CDs-PVA composite porogen from the nanofiber bundle matrix, a rough porous structure of oriented cellulose acetate nanofiber bundles is obtained. The CDs-PVA composite porogen contains water-soluble carbon quantum dots and a polyvinyl alcohol solution.

2. The method for preparing rough, porous, oriented cellulose acetate nanofibers as described in claim 1, characterized in that: The water-soluble carbon quantum dots use at least one of chitosan, lignin, and glucose as the carbon source.

3. The method for preparing rough, porous, oriented cellulose acetate nanofibers as described in claim 2, characterized in that: The method for preparing the water-soluble carbon quantum dots is as follows: the carbon source material is dispersed evenly in a solvent at a solid-liquid ratio of 0.2~0.5g:20ml, heated for a certain time and then cooled to room temperature. After filtration, the filtrate is freeze-dried to obtain water-soluble carbon quantum dots.

4. The method for preparing rough, porous, oriented cellulose acetate nanofibers as described in claim 3, characterized in that: The mass ratio of the water-soluble carbon quantum dots to polyvinyl alcohol is 0.0001~0.001:2~8.

5. The method for preparing rough, porous, oriented cellulose acetate nanofibers as described in claim 3, characterized in that: The polyvinyl alcohol solution contains 8-16 wt% polyvinyl alcohol with a degree of polymerization of 2400-2500 and a degree of alcoholysis of 98-99%. The cellulose acetate solution contains 8-14 wt% cellulose acetate.

6. The method for preparing rough, porous, oriented cellulose acetate nanofibers as described in claim 3, characterized in that: The mass ratio of the cellulose acetate solution to the CDs-PVA composite porogen is 40:60~50:

50.

7. The method for preparing rough, porous, oriented cellulose acetate nanofibers as described in claim 1, characterized in that: The electrospinning method involves injecting the precursor solution through a syringe and receiving it through a hub. The metal needle of the syringe is connected to the positive terminal of a high-voltage power supply, and the grounding device of the hub is connected to the negative terminal of the high-voltage power supply. The syringe propulsion speed is set to 0.5~2mL / h, and the hub rotation speed is 800~1500r / min.

8. A rough, porous, oriented cellulose acetate nanofiber prepared by the method according to any one of claims 1-7, characterized in that: The oriented cellulose acetate nanofiber bundles have an average fiber diameter of 150-300 nanometers, a porosity of 81%-87%, an average pore size of 0.7-1.8 micrometers, and a pore connectivity of greater than 80%.

9. An application of the rough, porous, oriented cellulose acetate nanofibers as described in claim 8, characterized in that: Several segments of the oriented cellulose acetate nanofiber bundles are arranged in parallel into a sheet, and the edges of the sheet are sealed with resin material to obtain a membrane-type liquid filter medium.

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