CN114225711A

CN114225711A - Electrostatic spinning nanofiber membrane and preparation method and application thereof

Info

Publication number: CN114225711A
Application number: CN202111595405.0A
Authority: CN
Inventors: 孙润军; 魏亮; 杜馨禹; 刘呈坤; 董洁; 王秋实
Original assignee: Xian Polytechnic University
Current assignee: Xian Polytechnic University
Priority date: 2021-12-23
Filing date: 2021-12-23
Publication date: 2022-03-25

Abstract

The invention discloses an electrostatic spinning nanofiber membrane as well as a preparation method and application thereof, and belongs to the technical field of membrane materials. Through blending modification of polylactic acid and cellulose acetate, the mechanical strength and the hydrophilic effect of the nanofiber membrane can be effectively improved, and the nanofiber membrane has an excellent dye adsorption effect. The polylactic acid and the cellulose acetate adopted by the invention are biodegradable materials, and the degradation products are lactic acid and glucose, so that the polylactic acid and the cellulose acetate have no toxic or side effect and do not cause secondary pollution to the environment. The cellulose acetate can improve the mechanical strength of the nanofiber fibrous membrane, and simultaneously has the function of adsorbing heavy metal ions and pigments. The nanofiber membrane prepared by electrostatic spinning can effectively filter impurities below the micron level. The invention has simple process, easily obtained raw materials and low cost; the prepared nanofiber membrane has good water permeability, hydrolysis resistance, degradability and swelling resistance, and can be used for manufacturing durable and long-acting filter materials.

Description

Electrostatic spinning nanofiber membrane and preparation method and application thereof

Technical Field

The invention belongs to the technical field of membrane materials, and particularly relates to an electrostatic spinning nanofiber membrane as well as a preparation method and application thereof.

Background

In recent years, the demand of water resources is increasing year by year due to the continuous increase of population, and the pollution of the water environment is more serious due to the rapid development of industry, so the phenomena of water resource shortage and water environment pollution become more severe. Therefore, in the face of emerging water pollution challenges, the development of novel multifunctional, high value-added filter materials is urgent.

Scholars began research relating to liquid filtration technology as early as the 19 th century. Compared with the traditional separation technology, the membrane separation technology is concerned by the advantages of low energy consumption, high efficiency, wide application range, simple equipment operation and the like. By the 20 th century, microfiltration, ultrafiltration, nanofiltration and other related liquid filtration technologies have rapidly developed. The nano-scale material can show novel and remarkable physical and chemical properties through artificial design, and the nano-scale polymer is used as an important component of the nano-scale material, thereby showing good application value in the aspect of wastewater treatment with high specific surface area and other excellent properties.

However, the existing nano materials still have certain defects in the using process, the non-degradability and non-regenerability of most raw materials can cause secondary pollution to the environment to a certain extent, and the nano materials have poor mechanical properties and are limited to a certain extent in the actual using process, so that the development of environment-friendly nano film adsorbing materials has important value.

Disclosure of Invention

In order to overcome the problems in the prior art, the invention aims to provide an electrostatic spinning nanofiber membrane as well as a preparation method and application thereof, wherein the preparation method has the advantages of simple process, easily obtained raw materials and low cost; the prepared nanofiber membrane has good water permeability, hydrolysis resistance, degradability and swelling resistance, and can be used for manufacturing durable and long-acting filter materials.

The invention is realized by the following technical scheme:

the invention discloses a preparation method of an electrostatic spinning nanofiber membrane, which comprises the following steps:

step 1: dissolving polylactic acid in an organic solvent, and fully stirring to obtain a uniform polylactic acid solution;

step 2: adding cellulose acetate into the polylactic acid solution obtained in the step (1), and fully stirring to obtain a polylactic acid/cellulose acetate spinning solution;

and step 3: and (3) performing electrostatic spinning by using the polylactic acid/cellulose acetate spinning solution obtained in the step (2) as a spinning solution, and drying the obtained product to obtain the electrostatic spinning nanofiber membrane.

Preferably, in the polylactic acid/cellulose acetate spinning solution, the mass fraction of the polylactic acid is 8-14%, and the mass fraction of the cellulose acetate is 1-7%.

Preferably, in step 1, the organic solvent is one or more of dichloromethane, chloroform, acetone, N-dimethylformamide, glacial acetic acid and trifluoroacetic acid.

Preferably, in the step 1, the stirring speed is 200-700 r/min, and the stirring time is 6-12 h.

Preferably, in the step 2, the stirring speed is 200-700 r/min, and the stirring time is 4-10 h.

Preferably, in step 3, the electrostatic spinning is performed by using a needle electrostatic spinning device.

Further preferably, the parameters of electrospinning include: the voltage range of the high-voltage electrostatic field is 14-22 kv, the propelling speed of the injector is 0.4-2 ml/h, the spinning receiving distance is 15-20 cm, the rotating speed of the collecting roller is 100-600 r/min, and the collecting roller is made of aluminum, titanium or stainless steel.

Preferably, in the step 3, a vacuum oven is adopted for drying, the drying temperature is 40-70 ℃, and the drying time is 6-8 hours.

The invention also discloses the electrostatic spinning nanofiber membrane prepared by the preparation method, the diameter of the nanofiber is 100-700 nm, and the unevenness rate is less than or equal to 35%; 30mg of nanofiber membrane has the adsorption capacity of more than 80 mg.g for Congo red dye^-1The removal rate is more than or equal to 75 percent; the elongation at break is more than 36 percent, and the breaking strength is more than 4 MPa.

The invention also discloses application of the electrostatic spinning nanofiber membrane in removing organic dye pollutants.

Compared with the prior art, the invention has the following beneficial technical effects:

according to the preparation method of the electrostatic spinning nanofiber membrane, the polylactic acid and the cellulose acetate are blended and modified, so that the mechanical strength and the hydrophilic effect of the nanofiber membrane can be effectively improved, and the nanofiber membrane has an excellent dye adsorption effect. The polylactic acid and the cellulose acetate adopted by the invention are biodegradable materials, and the degradation products are lactic acid and glucose, so that the polylactic acid and the cellulose acetate have no toxic or side effect and do not cause secondary pollution to the environment. The cellulose acetate can improve the mechanical strength of the nanofiber fibrous membrane, and simultaneously has the function of adsorbing heavy metal ions and pigments. The nanofiber membrane prepared by electrostatic spinning can effectively filter impurities below the micron level.

Further, in the polylactic acid/cellulose acetate spinning solution, the mass fractions of polylactic acid and cellulose acetate are too small, the entanglement degree of polymer molecular chains is poor, the spinning jet flow is discontinuous and is not uniformly acted by an electric field force, the ejected fiber bundle is not sufficiently stretched, the solvent is not completely volatilized, and the nano-fibers are not continuous enough and more beads are formed; the mass fraction of the nano-fiber and the nano-fiber is too large, the action of the electric field force on the spinning solution in the spinning process is weakened, the diameter of the nano-fiber is increased, and the uniformity is poor.

Furthermore, the organic solvent adopts one or more of dichloromethane, trichloromethane, acetone, N-dimethylformamide, glacial acetic acid and trifluoroacetic acid, so that the polylactic acid and the cellulose acetate can be fully dissolved at the same time, and the phase separation phenomenon cannot occur.

Further, in the step 1, the stirring speed is 200-700 r/min, the stirring time is 6-12 h, and the polylactic acid and the cellulose acetate can be fully dissolved and the two polymers can be uniformly mixed.

Furthermore, needle type electrostatic spinning equipment is adopted for electrostatic spinning, the adjustment operation of spinning parameters is simple, and the unevenness of the diameters of the nano fibers prepared by the equipment is low.

Furthermore, the voltage is in the range of 14-22 kV, the electric field force has better drafting effect on the spinning solution and overcomes the surface tension of the spinning solution, so that jet flow is split, and the drawing and the thinning of the nano fibers are facilitated; when the propelling speed of the injector is 0.4-2 mL/h, the unevenness of the diameter of the jet flow stable nanofiber is low, the propelling speed of the injector is too high, the charge quantity carried by the spinning solution is increased, the probability of column refinement of the spinning solution under the action of an electric field force is increased, and the unevenness of the fiber diameter is increased; the propelling speed of the injector is too low, and the spinning solution can be changed into nano particles under the action of electric field force and can not form fibers; the spinning receiving distance is 15-20 cm, the rotating speed of the roller is 100-600 r/min, the collecting roller is made of aluminum, titanium or stainless steel, the nano fibers can be effectively stretched and refined, and the collecting efficiency is high.

Further, a vacuum oven is adopted for drying, the drying temperature is 40-70 ℃, the drying time is 6-8 hours, residual organic solvent on the surface of the nanofiber membrane can be effectively removed, and the structure of the nanofiber membrane cannot be damaged under the condition.

The electrostatic spinning nanofiber membrane prepared by the preparation method has the advantages that the surface of the fiber membrane is flat and smooth, and the fiber thickness is uniform; the fiber membrane has certain hydrophilicity, average strength and elongation at break, and has better mechanical property.

When the electrospun nanofiber membrane is used as a sewage filtering material, the nanofiber membrane has a higher specific surface area, which provides more adsorption areas and binding sites compared with a traditional filter membrane, and simultaneously, the addition of the acetate fibers improves the hydrophilicity and the flux of the membrane, improves the anti-fouling capacity of the membrane to a certain extent, and prolongs the service life of the fiber membrane in sewage treatment; meanwhile, polylactic acid and cellulose acetate are degradable environment-friendly materials, and secondary pollution of the adsorbed filter membrane to the environment can be effectively prevented.

Drawings

FIG. 1 is a diagram of an object of an electrospun nanofiber membrane prepared according to the present invention;

FIG. 2 is a Scanning Electron Microscope (SEM) image of the nanofiber membrane prepared in example 1;

FIG. 3 is a fiber diameter distribution diagram of the nanofiber membrane prepared in example 1;

FIG. 4 is a Scanning Electron Microscope (SEM) image of the nanofiber membrane prepared in example 2;

FIG. 5 is a fiber diameter distribution diagram of the nanofiber membrane prepared in example 2;

FIG. 6 is a Scanning Electron Microscope (SEM) image of the nanofiber membrane prepared in example 3;

FIG. 7 is a graph showing a distribution of fiber diameters of the nanofiber membrane prepared in example 3;

FIG. 8 is a Scanning Electron Microscope (SEM) image of the nanofiber membrane prepared in example 4;

FIG. 9 is a graph of the fiber diameter distribution of the nanofiber membrane prepared in example 4;

FIG. 10 is a graph showing the relationship between the adsorption capacity of the nanofiber membranes and the CA powder prepared in examples 1 to 4 for Congo red dye and the amount of the adsorbent used;

FIG. 11 is a graph showing the relationship between the removal rate of Congo red dye and the amount of adsorbent used in the nanofiber membranes and CA powders prepared in examples 1 to 4;

FIG. 12 is a graph showing the relationship between adsorption capacity and adsorption time of the nanofiber membranes and CA powders prepared in examples 1 to 4 for Congo red dye;

FIG. 13 is a graph showing the relationship between the removal rate of Congo red dye and the adsorption time of the nanofiber films and CA powders obtained in examples 1 to 4;

FIG. 14 is a water contact angle test chart of the nanofiber membranes prepared in examples 1 to 4.

Detailed Description

The electrostatic spinning is an efficient technology for manufacturing the nano-fiber, on one hand, the electrostatic spinning nano-fiber composite filter material has high filtering efficiency, and compared with the traditional filter material, the filtering efficiency is improved by 70% or more; secondly, the water flux is large. Compared with the traditional filter material, the electrostatic spinning nanofiber scaffold has low gram weight, high porosity, high permeability and controllable pore diameter, provides a platform for combining the functions of filtration and adsorption, captures targeted molecules on the surface of the nanofiber and can effectively remove pollutants; the nanofiber material is used as a filtering material, so that the adsorption capacity and the filtering efficiency can be obviously improved, and the nanofiber material has important application value and prospect in the field of filtering. However, due to the nature of the nanofiber membrane, the nanofiber membrane generally has the defect of insufficient mechanical strength, and a reinforcing material needs to be added into the spinning solution to improve the mechanical property of the fiber membrane; meanwhile, most high polymers cannot be naturally degraded, and the filtered waste materials may cause secondary pollution to the environment, so whether the selected materials are naturally degradable or not needs to be considered.

Cellulose acetate is a reproducible natural adsorbent, and a functional nano-cellulose adsorbent with a function of adsorbing metal ions can be prepared by carrying out chemical reaction on hydroxyl of cellulose. The method has great potential objective value for developing cellulose adsorbent applied to separation and filtration of drinking water. Polylactic acid can be used as a high molecular polymer for improving the spinnability of cellulose due to the properties of no toxicity, good biocompatibility, degradability, no damage to water, insolubility in water and the like.

The invention will be further explained with reference to the following figures and specific examples:

example 1

Dissolving 1.353g of polylactic acid in 10ml of trifluoroacetic acid, and stirring for 12 hours by using a magnetic stirrer with the rotating speed of 200r/min to completely dissolve the polylactic acid to obtain uniform polylactic acid electrostatic spinning solution;

adding 0.168g of cellulose acetate into the obtained polylactic acid electrostatic spinning solution, and magnetically stirring at the rotating speed of 700r/min for 4 hours to completely dissolve the cellulose acetate to obtain uniform polylactic acid/cellulose acetate electrostatic spinning solution;

carrying out electrostatic spinning by taking the prepared spinning solution as a raw material, wherein the spinning process parameter is high-voltage electrostatic field voltage of 14kv, the propelling speed of an injector is 0.4ml/h, the receiving distance is 15cm, and the rotating speed of a collecting roller is 100 r/min;

the prepared nanofiber membrane is placed in a vacuum oven and dried in vacuum at 40 ℃ for 8h to remove residual solvent, and the Scanning Electron Microscope (SEM) image of the obtained polylactic acid/cellulose acetate nanofiber membrane is shown in FIG. 2.

Example 2

Dissolving 1.336g of polylactic acid in 10ml of mixed solution (volume ratio is 3:1:1) of dichloromethane, acetone and glacial acetic acid, and stirring for 10 hours by using a magnetic stirrer with the rotating speed of 400r/min to completely dissolve the polylactic acid to obtain uniform polylactic acid electrostatic spinning solution;

adding 0.401g of cellulose acetate into the obtained polylactic acid electrostatic spinning solution, and magnetically stirring at the rotating speed of 600r/min for 6 hours to completely dissolve the cellulose acetate to obtain uniform polylactic acid/cellulose acetate electrostatic spinning solution;

carrying out electrostatic spinning by taking the prepared spinning solution as a raw material, wherein the spinning process parameter is high-voltage electrostatic field voltage of 16kv, the propelling speed of an injector is 0.8ml/h, the receiving distance is 16cm, and the rotating speed of a collecting roller is 400 r/min;

the prepared nanofiber membrane is placed in a vacuum oven and dried at 50 ℃ for 7h in vacuum to remove residual solvent, and a Scanning Electron Microscope (SEM) image of the polylactic acid/cellulose acetate nanofiber membrane is shown in FIG. 3.

Example 3

1.7262g of polylactic acid is dissolved in 10ml of mixed solution (volume ratio is 3:1:1) of trichloromethane, N-dimethylformamide and glacial acetic acid, and a magnetic stirrer with the rotating speed of 600r/min is used for stirring for 8 hours to completely dissolve the polylactic acid, so that uniform polylactic acid electrostatic spinning solution is obtained;

adding 0.719g of cellulose acetate into the obtained polylactic acid electrostatic spinning solution, and magnetically stirring at the rotating speed of 700r/min for 4 hours to completely dissolve the cellulose acetate to obtain uniform polylactic acid/cellulose acetate electrostatic spinning solution;

carrying out electrostatic spinning by taking the prepared spinning solution as a raw material, wherein the spinning process parameter is high-voltage electrostatic field voltage of 18kv, the propelling speed of an injector is 1.4ml/h, the receiving distance is 18cm, and the rotating speed of a collecting roller is 500 r/min;

the obtained nanofiber membrane was placed in a vacuum oven and vacuum dried at 60 ℃ for 7h to remove the residual solvent, and the Scanning Electron Microscope (SEM) image of the polylactic acid/cellulose acetate nanofiber membrane is shown in fig. 4.

Example 4

Dissolving 2.634g of polylactic acid in 10ml of mixed solution (volume ratio is 9: 1) of trifluoroacetic acid and glacial acetic acid, and stirring for 6 hours by using a magnetic stirrer with the rotating speed of 700r/min to completely dissolve the polylactic acid to obtain uniform polylactic acid electrostatic spinning solution;

adding 1.317g of cellulose acetate into the obtained polylactic acid electrostatic spinning solution, and magnetically stirring for 4 hours at the rotating speed of 700r/min to completely dissolve the cellulose acetate to obtain uniform polylactic acid/cellulose acetate electrostatic spinning solution;

carrying out electrostatic spinning by taking the prepared spinning solution as a raw material, wherein the spinning process parameter is high-voltage electrostatic field voltage of 20kv, the propelling speed of an injector is 2.0ml/h, the receiving distance is 20cm, and the rotating speed of a collecting roller is 600 r/min;

the obtained nanofiber membrane was placed in a vacuum oven and vacuum dried at 70 ℃ for 6h to remove residual solvent, and the Scanning Electron Microscope (SEM) image of the polylactic acid/cellulose acetate nanofiber membrane obtained is shown in fig. 5.

Fig. 1 is a real object diagram of the electrospun nanofiber membrane prepared by the present invention, and it can be seen from the diagram that the nanofiber membrane has a flat and smooth surface, a uniform texture, and a certain flexibility.

As can be seen from the graphs in FIGS. 2 to 9, the nanofiber membranes prepared in the examples 1 to 4 have uniform fineness and excellent appearance, the average diameter is 250 to 350nm, the overall diameter is 100 to 700nm, and the irregularity rate is less than or equal to 35%.

FIGS. 10 to 13 are the adsorption tests of the nanofiber membranes and Cellulose Acetate (CA) powders prepared in examples 1 to 4 on Congo red dye of 100mg/L, and the results show that the nanofiber membranes prepared by the method of the present invention have a better adsorption effect on Congo red dye than cellulose acetate, and the adsorption capacity of 30mg of the nanofiber membranes can reach 80mg g^-1Above, the removal rate is more than or equal to 75 percent.

Fig. 10 is a graph showing the relationship between the adsorption capacity of the nanofiber membranes and the CA powder prepared in examples 1 to 4 for congo red dye and the amount of the adsorbent, and it can be seen from the graph that the nanofiber membranes have better adsorption capacity for the dye than cellulose acetate, and when the amount of the membranes is increased from 10mg to 50mg, the adsorption capacity is decreased, because the concentration of the dye is not changed due to the increase in the amount of the membranes under the condition of a certain volume and concentration of the dye, which results in a certain decrease in the adsorption capacity per unit mass of the membranes.

FIG. 11 is a graph showing the relationship between the removal rate of Congo red dye and the amount of adsorbent in the nanofiber membranes and CA powder prepared in examples 1 to 4, wherein it can be seen that the removal rate gradually increases when the amount of the fiber membrane is increased from 10mg to 50mg, and the removal percentage increases with the increase of the amount of the membrane. This is due to the fact that the amount of the film used is increased, the adsorbable surface area is increased, more active sites can be provided to be bound, the concentration of the dye is reduced, and the removal rate is increased.

Fig. 12 is a graph showing the relationship between the adsorption capacity of the nanofiber membrane and the adsorption time of the CA powder prepared in examples 1 to 4 for congo red dye, and it can be seen from the graph that the adsorption capacity of the membrane for dye increases with the increase of the adsorption time, the adsorption equilibrium time is about 6 hours, after reaching equilibrium, the adsorption capacity does not continue to increase with the increase of the time, after 6 hours, because the surface mesh channels of the nanofiber membrane are covered and blocked, the dye is difficult to enter the interior and combine with the adsorption sites, so the adsorption process is slow, after reaching equilibrium, the active sites are occupied by a large amount, and the adsorption reaches a saturated state.

FIG. 13 is a graph showing the relationship between the removal rate of Congo red dye and the adsorption time of the nanofiber membranes and CA powder prepared in examples 1-4, wherein the removal rate of Congo red dye increases with the increase of the adsorption time, the adsorption equilibrium time is about 6h, and after the balance is reached, the removal rate does not increase with the increase of the adsorption time; the adsorption of the fiber membrane comprises two processes of quick adsorption and slow adsorption; wherein the rapid adsorption stage is physical adsorption caused by the high specific surface area of the nanofiber membrane, and the excellent network structure of the fiber membrane provides a favorable channel for the adsorption of the dye in the process. After the adsorption is balanced, the adsorption reaches a saturated state because the surface reticular channels of the adsorbent are covered and blocked.

FIG. 14 is a water contact angle test chart of the nanofiber membranes prepared in examples 1-4, which shows that the prepared nanofiber membranes have certain hydrophilicity.

The following table shows the mechanical property test data of the nanofiber membranes prepared in examples 1 to 4, and the experimental results show that the nanofiber membranes prepared by the present invention have good mechanical strength and stretchability.

Name (R)	Elongation at break/%	Tensile strength/MPa	Breaking Strength/cN
				Example 1	36.5％	4.12	78.27
Example 2	40％	5.63	88.91
				Example 3	39.3％	4.89	90.27
Example 4	38.6％	4.15	92.21

Claims

1. The preparation method of the electrostatic spinning nanofiber membrane is characterized by comprising the following steps:

2. The method for preparing an electrospun nanofiber membrane according to claim 1, characterized in that in the polylactic acid/cellulose acetate spinning solution, the mass fraction of polylactic acid is 8-14%, and the mass fraction of cellulose acetate is 1-7%.

3. The method for preparing electrostatic spinning nanofiber membrane according to claim 1, wherein in step 1, the organic solvent is one or more of dichloromethane, chloroform, acetone, N-dimethylformamide, glacial acetic acid and trifluoroacetic acid.

4. The method for preparing the electrospun nanofiber membrane of claim 1, wherein in the step 1, the stirring speed is 200-700 r/min, and the stirring time is 6-12 h.

5. The method for preparing the electrospun nanofiber membrane of claim 1, wherein in the step 2, the stirring speed is 200-700 r/min, and the stirring time is 4-10 h.

6. The method for preparing electrospun nanofiber membrane according to claim 1, wherein in step 3, needle-type electrospinning equipment is used for electrospinning.

7. The method of claim 6, wherein the parameters of electrospinning include: the voltage range of the high-voltage electrostatic field is 14-22 kv, the propelling speed of the injector is 0.4-2 ml/h, the spinning receiving distance is 15-20 cm, the rotating speed of the collecting roller is 100-600 r/min, and the collecting roller is made of aluminum, titanium or stainless steel.

8. The preparation method of the electrospun nanofiber membrane according to claim 1, wherein in the step 3, a vacuum oven is adopted for drying, the drying temperature is 40-70 ℃, and the drying time is 6-8 hours.

9. The electrostatic spinning nanofiber membrane prepared by the preparation method according to any one of claims 1 to 8, wherein the diameter of the nanofiber is 100-700 nm, and the irregularity is less than or equal to 35%; 30mg of nanofiber membrane has the adsorption capacity of more than 80 mg.g for Congo red dye^-1The removal rate is more than or equal to 75 percent; the elongation at break is more than 36 percent, and the breaking strength is more than 4 MPa.

10. Use of the electrospun nanofiber membrane of claim 9 as a sewage filtration material.