WO2021004458A1

WO2021004458A1 - Ion exchange-type nanofiber skeleton three-dimensional separation material having controllable structure, and preparation method for same

Info

Publication number: WO2021004458A1
Application number: PCT/CN2020/100690
Authority: WO
Inventors: 王栋; 刘轲; 程盼; 郭启浩; 刘琼珍; 程芹; 李沐芳; 赵青华
Original assignee: 武汉纺织大学
Priority date: 2019-07-08
Filing date: 2020-07-07
Publication date: 2021-01-14
Also published as: JP2021531953A; JP7270993B2; CN110327900B; CN114245757A; CN114245757B; CN110327900A

Abstract

Provided are an ion exchange-type nanofiber skeleton three-dimensional separation material having a controllable structure and a preparation method for the same. The preparation method comprises preparing nanofibers by means of a melt spinning process, pre-dispersing the nanofibers, preparing a suspension of pre-crosslinked nanofibers, and freeze-drying cross-linking, thereby obtaining a nanofiber skeleton three-dimensional separation material having structural stability, a large specific surface area, and a high adsorbing capacity. The microstructure of the nanofiber skeleton three-dimensional separation material is adjusted and controlled by adjusting and controlling the composition of the suspension of pre-crosslinked nanofibers and the manner of freezing. Adding different quantities of polyelectrolytes to the suspension of pre-crosslinked nanofibers enables the ion exchange-type nanofiber skeleton three-dimensional separation material to have various structures, high strength, and high adsorbing capacity. The entire preparation process has simple operations, is suitable for mass production, and provides superior product performance, thereby providing wide applicability in the fields of filtration, heat insulation, and adsorbing materials, and the like.

Description

Structure-controllable ion-exchange type nano-fiber skeleton three-dimensional separation material and preparation method thereof

Technical field

The invention belongs to the technical field of functional nano-adsorption materials, and in particular relates to a three-dimensional separation material with a controllable structure of an ion exchange type nanofiber skeleton and a preparation method thereof.

Background technique

Sponge structure material is a three-dimensional porous material with high specific surface area and good adsorption. It is often used for water or air pollution filtration and adsorption and other separation treatments, and the treatment effect is remarkable. Among them, polyvinyl alcohol sponges are often used in the preparation of adsorption materials due to their high water absorption. Polyvinyl alcohol sponge is obtained by cross-linking, foaming and curing of polyvinyl alcohol molecular chains through a cross-linking agent, but the current domestic production process of polyvinyl alcohol sponge water-absorbing materials mostly uses backward starch filling and foaming methods. When this method is used for production, the environmental pollution is serious, the subsequent processing procedures are long, the starch cannot be completely washed, and the starch and acid catalyst cannot be completely recycled, which is not conducive to saving resources and cutting costs; and the adsorption performance of the sponge material needs to be further improved. Therefore, there is an urgent need to develop and improve the structure and preparation process of high-absorption sponge materials, so as to save energy consumption, reduce production costs, improve cost performance, and promote the large-scale production and application of such absorbent materials.

Chinese invention patent CN107051408A discloses a method for preparing a three-dimensional nanofiber hydrophobic sponge that can repeatedly absorb oil. The method obtains the cellulose acetate/polyethylene oxide nanofiber membrane by electrostatic spinning; after the nanofiber membrane is cross-linked and pulverized, a dispersant is added, and after the dispersion is uniform, freeze-drying is performed to obtain a nanofiber sponge; The fiber sponge is hydrophobically modified to obtain a nanofiber hydrophobic sponge that can repeatedly absorb oil. Although the material can be used for the treatment of oily sewage and has good adsorption performance, its shortcomings are (1) The method uses electrospinning to prepare nanofiber membranes. Electrospinning is compared with melt spinning, and the process and The cost is relatively high, and it cannot be the best choice for large-scale production; (2) Cross-linking the nanofiber membrane and then pulverizing it will easily cause the problem of uneven cross-linking. The strength of the sponge obtained by freeze-drying this method is low. (3) The mechanical pulverization is used in the preparation, which easily causes the problems of irregular shape of the fiber membrane, poor fluidity and low fluidity.

Chinese invention patent CN106009056B discloses a polymer nanofiber-based aerogel material and a preparation method thereof. In this method, polymer nanofibers are prepared by melt blending, drawing, and extraction, and then the polymer nanofibers are directly formed into a dispersion in an aqueous solvent, and then crosslinking agents such as polyvinyl alcohol and chitosan are added, and crosslinked by heating After freezing and drying, a polymer nanofiber-based aerogel is obtained. The disadvantage of this method is that the polymer nanofibers are directly dispersed in an aqueous solvent and then cross-linked. When the solvent is an aqueous solution, the dispersion effect is not good; when the solvent is a mixed solvent composed of water and organic solvents, freeze and dry At this time, it is not conducive to the uniform shaping of the aerogel material, resulting in low strength of the prepared nanofiber-based aerogel. In addition, the crosslinking agent and nanofibers are both polymer matrixes, resulting in low porosity after crosslinking.

Summary of the invention

In view of the above-mentioned defects in the prior art, the purpose of the present invention is to provide a structure-controllable ion exchange nanofiber skeleton three-dimensional separation material and a preparation method thereof. The preparation method includes the steps of melt spinning and dispersion of nanofibers, preparation of pre-crosslinked nanofiber suspension, and freeze-drying crosslinking. By adjusting the content of polyelectrolyte in the pre-crosslinked nanofiber suspension and the freeze-drying method, An ion-exchange type nanofiber skeleton three-dimensional separation material with diversified structures, high strength and high adsorption capacity.

The purpose of the present invention is also to provide a method for preparing nanofiber hollow ball sponge material. The preparation method includes the steps of melt spinning and dispersion of nanofibers, preparation of pre-crosslinked nanofiber suspension, freeze-drying and crosslinking, etc., thereby obtaining a nanofiber hollow ball sponge material with stable structure, high specific surface area and large adsorption capacity. It can be widely used for adsorption in water pollution.

In order to achieve the above objectives, the present invention adopts the following technical solutions to achieve:

A structure-controllable ion-exchange nanofiber skeleton three-dimensional separation material. The ion-exchange nanofiber skeleton three-dimensional separation material comprises polymer nanofibers and the polymer nanofibers are freeze-dried and crosslinked with the polymer nanofibers to form a porous Structured polyelectrolyte; by adjusting the content of the polyelectrolyte and/or the freeze-drying method, the porous structure of the ion-exchange nanofiber skeleton three-dimensional separation material is adjusted; the surface of the polymer nanofiber contains active Group, the crosslinking agent is any one or more of polyaldehyde and polyacid.

The present invention uses polymer nanofibers as the skeleton material of the three-dimensional separation material. The high aspect ratio and high strength of the nanofibers endow the three-dimensional separation material with good mechanical strength; and then select the multi-aldehyde or multi-acid cross-linking agent and combine it with the polymer The electrolyte is cross-linked by freeze drying. Polyelectrolytes include polycations and polyanions, which endow the three-dimensional separation material with good electrostatic adsorption and ion exchange performance, thereby achieving selective adsorption. By simply adjusting the polyelectrolyte content and freezing methods, an ion-exchange type nanofiber skeleton three-dimensional separation material with diversified structures and high strength and high adsorption capacity can be obtained.

A method for preparing a structure-controllable ion-exchange nanofiber skeleton three-dimensional separation material includes the following steps:

S1. Prepare polymer nanofiber aggregates by melt spinning, the surface of which contains active groups;

S2. Disperse the polymer nanofiber aggregates obtained in step S1 in a dispersion solvent, and after a uniform polymer nanofiber dispersion is formed, the dispersion solvent is removed by centrifugal separation to obtain a dispersed polymer nanofiber monofilament ; Here the dispersion solvent and the aforementioned poor solvent are both solvents that can make the polymer nanofiber aggregates dispersed well, but will not dissolve the polymer nanofiber aggregates;

S3. Disperse the polymer nanofiber monofilament obtained in step S2 in deionized water, add a crosslinking agent, and stir the pre-crosslinking reaction to obtain a pre-crosslinked nanofiber suspension;

S4. Add a polyelectrolyte solution to the pre-crosslinked nanofiber suspension obtained in step S3, and obtain a functionalized nanofiber suspension after emulsification;

S5. Put the functionalized nanofiber suspension obtained in step S4 into a mold and freeze-dry to obtain a three-dimensional separation material with a controllable structure of ion exchange nanofiber skeleton;

The structure of the ion exchange nanofiber skeleton three-dimensional separation material is adjusted by adjusting the content of the polyelectrolyte solution and/or the freeze-drying method.

The above technical solution provides a complete set of preparation processes from polymer melt spinning to nanofiber skeleton three-dimensional separation material molding. Each of the above-mentioned operations is interrelated. The entire preparation process is simple to operate, suitable for large-scale production, and has excellent product performance, which provides an effective way for the mass and high-efficiency production of high-adsorption three-dimensional separation materials with diversified structures.

A preparation method of nanofiber hollow ball sponge material includes the following steps:

S1. Preparation of thermoplastic polymer nanofibers: the thermoplastic polymer and cellulose acetate butyrate are melt blended to prepare thermoplastic polymer nanofibers by a phase separation method;

S2. Preparation of dispersion: disperse the thermoplastic polymer nanofiber assembly prepared in the above steps in a poor solvent to form a uniform dispersion;

S3. Preparation of pure nanofibers: centrifugal dispersion of the nanofiber suspension prepared in the above steps to remove poor solvents to obtain pure nanofibers after dispersion;

S4. Preparation of nanofiber vacuoles: adding water, crosslinking agent and surfactant to the pure nanofibers prepared in the above steps, and emulsifying to obtain nanofiber foam;

S5. Preparation of sponge material: Put the nanofiber foam prepared in the above steps into a mold, and freeze-dry to obtain a nanofiber hollow ball sponge material.

The thermoplastic polymer nanofibers are prepared by melt spinning and phase separation methods, and then the polymer nanofibers are dispersed into monofilaments, and then the polymer nanofiber monofilaments, crosslinking agent and surfactant are made into nanofiber bubbles in water. Because the polymer nanofiber monofilament is well dispersed, it can maintain a high pore structure after freeze-drying, and significantly increase the adsorption capacity. The entire preparation cycle is short, which is suitable for large-scale mass production of sponge absorbent materials, and has high production efficiency and low production cost. The nanofiber hollow ball sponge material prepared in this way has good performance, and also has certain ion exchange and three-dimensional separation functions, and can be widely used in filtration, heat insulation, adsorption materials and other fields.

The chemical crosslinking agent is polyhydric aldehydes and polyacids. By adding polyhydric aldehydes and polyacid crosslinking agents, the active groups such as hydroxyl or amino groups in the polymer nanofibers and the aldehyde or carboxyl groups in the crosslinking agent are formed by esterification, acetal, hemiacetal or hydrogen bonding The cross-linked network structure increases the hydrophilic properties of the nanofiber hollow ball sponge material, and the size of the hollow ball is smaller and the particle size distribution is more uniform, thereby giving the nanofiber hollow ball sponge material a high specific surface area and improving its adsorption performance.

Beneficial effect

Compared with the prior art, the structure-controllable ion exchange nanofiber skeleton three-dimensional separation material and the preparation method thereof provided by the present invention have the following beneficial effects:

(1) The structure-controllable ion exchange nanofiber skeleton three-dimensional separation material provided by the present invention uses polymer nanofibers as the skeleton material of the three-dimensional separation material. The high aspect ratio and high strength of the nanofibers give the three-dimensional separation material good Mechanical strength; then select polyaldehyde or polyacid cross-linking agent, and cross-link it with polyelectrolyte through freeze-drying. Polyelectrolytes include polycations and polyanions, which endow the three-dimensional separation material with good electrostatic adsorption and ion exchange performance, thereby achieving selective adsorption. The use of multi-aldehyde or multi-acid small molecule cross-linking agent to cross-link polymer nanofibers and polyelectrolytes can increase the cross-linking point and enrich the cross-linked network structure, thereby increasing the porosity and strength of the three-dimensional separation material. By simply adjusting the polyelectrolyte content and freezing methods, the occurrence of the cross-linking process is adjusted, thereby adjusting the microstructure, and obtaining an ion-exchange type nanofiber skeleton three-dimensional separation material with high strength and high adsorption capacity with diversified structures. It can be widely used in filtration, heat insulation, adsorption materials and other fields.

(2) The method for preparing a structure-controllable ion-exchange nanofiber skeleton three-dimensional separation material provided by the present invention includes a complete set of preparation processes from polymer melt spinning to rice fiber skeleton three-dimensional separation material molding. First, the melt spinning method is used to prepare polymer nanofibers, which is convenient for large-scale production of nanofiber raw materials. However, polymer nanofibers produced by melt-spinning mass production usually exist in the form of polymer nanofiber aggregates due to mutual entanglement or bonding, which makes them easy to agglomerate in aqueous solution and difficult to uniformly disperse to form nanofiber monofilaments. . Therefore, in the present invention, polymer nanofiber aggregates prepared by melt spinning are dispersed and stripped into nanofiber monofilaments in a mixed solvent composed of water and alcohol or water and acid organic solvent, and then the mixed solvent is removed by centrifugation. In this process, the nanofiber monofilament can basically maintain the original high dispersion state. Next, the nanofiber monofilament is sequentially mixed with the small molecule crosslinking agent and the polyelectrolyte solution to form a uniform nanofiber suspension; and finally freeze-dried to obtain a structure-controllable ion exchange nanofiber skeleton three-dimensional separation material. Each of the above-mentioned operations is interrelated. The entire preparation process is simple to operate, suitable for large-scale production, and has excellent product performance, which provides an effective way for the mass and high-efficiency production of high-adsorption three-dimensional separation materials with diversified structures.

(3) The nanofiber hollow ball sponge material provided by the present invention firstly prepares thermoplastic polymer nanofibers by melt spinning and phase separation, then disperses the polymer nanofibers into monofilaments, and then combines the polymer nanofiber monofilaments with The cross-linking agent and the surfactant are made into nanofiber vacuoles in water. Because the polymer nanofiber monofilament is well dispersed, it can maintain a high pore structure after freeze-drying, and significantly increase the adsorption capacity. The entire preparation cycle is short, which is suitable for large-scale mass production of sponge absorbent materials, and has high production efficiency and low production cost. By adding surfactants such as sodium lauryl sulfate, the dissolution of sodium lauryl sulfate and water molecules have a better diffusion effect in the nanofiber material, increasing the specific surface area of the nanofiber hollow ball sponge material , Improve its adsorption performance. In addition, the present invention selects polymer nanofibers with active groups (such as hydroxyl, amino, etc.) on the surface, and crosslinks them with a crosslinking agent containing aldehyde groups or carboxyl groups, so that the prepared sponge material has a certain ion exchange function. The nanofiber hollow ball sponge material prepared in this way has good performance and can be well used in the fields of filtration, heat insulation, adsorption materials and the like.

Description of the drawings

In Figure 1, a and b are both electron micrographs of the nanofiber hollow ball sponge material prepared in Example 1 of the present invention;

In Figure 2 (a), (b), (c), (d), (e), (f) are PVA-co-PE nanofiber porous three-dimensional separation material and chitosan porous three-dimensional separation material (comparative example) 6) Polyethyleneimine porous three-dimensional separation material, crosslinked PVA-co-PE nanofiber porous three-dimensional separation material (comparative example 5), crosslinked chitosan blended PVA-co-PE nanofiber porous three-dimensional separation The infrared spectrum of the material (Example 28) and the cross-linked polyethyleneimine blended PVA-co-PE nanofiber porous three-dimensional separation material (Example 33);

Figure 3 (a), (b), (c), (d), (e) are the electron micrographs of the ion-exchange nanofiber skeleton three-dimensional separation materials prepared in Examples 28 to 32;

(A), (b), (c), and (d) in Figure 4 are electron micrographs of the ion-exchange nanofiber skeleton three-dimensional separation materials prepared in Comparative Examples 5-8, respectively.

Detailed ways

The following will give a clear and complete description of the technical solutions of the various embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, common in the art All other embodiments obtained by technicians without creative work fall within the protection scope of the present invention.

Example 1

A kind of nanofiber hollow ball sponge material, which is composed of a thermoplastic polymer nanofiber with a mass fraction of 90% and a chemical crosslinking agent with a mass fraction of 10% by entangled and stacked sponge material; the thermoplastic polymer nanofiber It is prepared from 20% by mass polyamide and 80% cellulose acetate butyrate through a melt blending phase separation method; the chemical crosslinking agent is glutaraldehyde. The preparation method includes the following steps:

S1. Preparation of thermoplastic polymer nanofibers: melt blending of polyamide and cellulose acetate butyrate to prepare thermoplastic polymer nanofibers using a phase separation method, as follows:

a) Mix 20% of polyamide and 80% of cellulose acetate butyrate uniformly, extrude and pelletize in a twin-screw extruder with a processing temperature of 200°C to prepare polyamide/cellulose acetate butyrate Composite materials.

b) The polyamide/cellulose acetate butyrate composite material obtained in step a) is spun and drawn on a melt spinning machine to obtain a composite fiber, wherein the spinning machine processing temperature is 200°C, and the drawing rate is 20m/min.

c) The composite fiber obtained in step b) is refluxed in acetone at 60°C for 72 hours to extract cellulose acetate butyrate, and the composite fiber after extraction of cellulose acetate butyrate is dried at room temperature to prepare a 50-500nm diameter Polyamide nanofibers.

S2. Preparation of a suspension: the polyamide nanofibers prepared in the above steps are dispersed in an alcohol-water mixed solvent to form a uniform suspension, wherein the volume ratio of water to the alcoholic organic solvent is 5:1. The mass ratio of the alcohol-water mixed solvent is 0.05:1.

S3. Preparation of pure nanofibers: the nanofiber suspension prepared in the above steps is centrifuged and dispersed, and the centrifugal dispersion is placed in a high-speed centrifuge for 5 minutes at a speed of 9000r/min, and the mixed solvent of alcohol and water is removed to obtain the dispersed Pure nanofiber.

S4. Preparation of nanofiber vacuoles: adding water, crosslinking agent glutaraldehyde and surfactant sodium lauryl sulfate to the pure nanofibers prepared in the above steps, where the mass fraction of sodium lauryl sulfate is the total mass of the solution 0.25%, emulsify in an emulsifier for 12 minutes, and obtain nanofiber vacuoles after emulsification.

S5. Preparation of sponge material: Put the nanofiber vacuoles prepared in the above steps into a mold and freeze-dry at a freezing temperature of -30°C, a freezing time of 5h, and a drying time of 30h. After freeze-drying, a nanofiber hollow ball sponge is obtained material.

Referring to FIG. 1, it can be seen that the nanofiber hollow sphere sponge material prepared in Example 1 is composed of a number of nanofiber entanglements, and the hollow interior is hollow. The hollow spheres have a uniform particle size and are stacked to form a loose sponge structure.

Examples 2～4

Examples 2 to 4 provide a method for preparing nanofiber hollow ball sponge material. Compared with Example 1, the difference is that the mass percentage of the thermoplastic polymer nanofibers and the chemical crosslinking agent is changed. Except for the above differences, other operations are roughly the same, so I won't repeat them here. The specific parameters are shown in Table 1 below.

Two oil aqueous solutions were prepared, one of which included n-hexane and the other included dodecane, and the above solutions were weighed for adsorption performance testing. The results are shown in Table 1.

Table 1:

It can be seen from Table 1 that when the content of thermoplastic polymer nanofibers is 90% to 99% and the content of chemical crosslinking agent is 1% to 10%, the performance of the absorption of oily substances n-hexane and dodecane The strong adsorption performance indicates that the nanofiber hollow ball sponge material prepared by the present invention has better performance, relatively uniform particle size distribution, and strong adsorption performance.

Examples 5-7

Examples 5-7 provide a method for preparing nanofiber hollow ball sponge material. Compared with Example 1, the difference is that the chemical crosslinking agent of this example is citric acid, and the content of citric acid is changed. Except for the above differences, other operations are roughly the same, so I won't repeat them here. The specific parameters are shown in Table 2 below.

Two aqueous solutions were prepared, one of which included lysozyme and the other of which included bovine serum albumin, and the above-mentioned solutions were weighed for adsorption performance testing. The results are shown in Table 2.

Table 2:

实施例Example	柠檬酸含量Citric acid content	溶菌酶吸附率(mg/g)Lysozyme adsorption rate (mg/g)	牛血清蛋白吸附率(mg/g)Adsorption rate of bovine serum albumin (mg/g)
实施例5Example 5	10％10%	14001400	11001100
实施例6Example 6	8％8%	10001000	900900
实施例7Example 7	1％1%	700700	600600

It can be seen from Table 2 that when the chemical crosslinking agent is citric acid with a content of 1% to 10%, the prepared nanofiber hollow ball sponge material has better adsorption performance for lysozyme and bovine serum albumin in the aqueous solution.

Examples 8-12

Examples 8-12 provide a method for preparing nanofiber hollow ball sponge material. Compared with Example 1, the difference is that the centrifugal dispersion time and the centrifugal dispersion speed in step S3 are changed. Except for the above differences, the other operations are roughly the same, and will not be repeated here. The specific parameters are shown in Table 3.

Two oily aqueous solutions were prepared, one of which included n-hexane and the other included dodecane, and the above-mentioned solutions were weighed for adsorption performance testing. The results are shown in Table 3.

table 3:

It can be seen from Table 3 that when the centrifugal dispersion time is 4-6min and the centrifugal dispersion rotation speed is 8000-12000r/min, it shows strong adsorption performance when adsorbing oily substances n-hexane and dodecane. It shows that the nanofiber hollow ball sponge material prepared by the present invention has good performance, relatively uniform particle size distribution and strong adsorption performance.

Examples 13-15

Examples 13-15 provide a method for preparing nanofiber hollow ball sponge material. Compared with Example 1, the difference is that the content of the surfactant added in step S4 is changed. Except for the above differences, the other operations are roughly the same, and will not be repeated here. The specific parameters are shown in Table 4.

Two oil aqueous solutions were prepared, one of which included n-hexane and the other included dodecane, and the above-mentioned solutions were weighed for adsorption performance testing. The results are shown in Table 4.

Table 4:

It can be seen from Table 4 that when the surfactant content is 0.05% to 5%, it exhibits strong adsorption performance when adsorbing oily substances n-hexane and dodecane, indicating that the nanofiber hollowed out prepared by the present invention The ball sponge material has better performance, more uniform particle size distribution, and strong adsorption performance.

Examples 16-18

Examples 16 to 18 provide a method for preparing nanofiber hollow ball sponge material. Compared with Example 1, the difference is that the emulsification time in the emulsifier in step S4 is changed. Except for the above differences, the other operations are roughly the same, and will not be repeated here. The specific parameters are shown in Table 5.

Two oily aqueous solutions were prepared, one of which included n-hexane and one of which included dodecane, and the above-mentioned solutions were weighed for adsorption performance testing. The results are shown in Table 5.

table 5:

It can be seen from Table 5 that when the emulsification time of the emulsifier is 10-20 min, it exhibits strong adsorption performance when adsorbing oily substances n-hexane and dodecane, indicating that the nanofiber hollow sphere prepared by the present invention The sponge material has better performance, more uniform particle size distribution, and strong adsorption performance.

Examples 19-27

Examples 19-27 provide a method for preparing nanofiber hollow ball sponge material. Compared with Example 1, the difference is that the temperature, freezing time and drying time obtained by freeze-drying in step S5 are changed. Except for the above differences, the other operations are roughly the same, and will not be repeated here. The specific parameters are shown in Table 6.

Prepare different concentrations of copper ions, chromium ions, and oily aqueous solutions. The oily substances include n-hexane and dodecane. Weigh the above solutions for adsorption performance testing. The results are shown in Table 6.

Table 6:

It can be seen from Table 7 that the freeze-drying temperature is ﹣80～﹣10℃, the freezing time is 4～6h, and the drying time is 24～72h. It has a strong performance when adsorbing oily substances n-hexane and dodecane. The adsorption performance indicates that the nanofiber hollow ball sponge material prepared by the present invention has better performance, more uniform particle size distribution, and strong adsorption performance.

Comparative example 1

Comparative Example 1 provides a method for preparing nanofiber hollow sphere sponge material. Compared with Example 1, the difference is that the chemical crosslinking agent for preparing nanofiber hollow sphere sponge material in this method is citric acid. Add 0.5%. Except for the above differences, other operations are roughly the same, so I won't repeat them here.

Two aqueous solutions were prepared, one of which included lysozyme and the other of which included bovine serum albumin, and the above-mentioned solutions were weighed for adsorption performance testing. The results are shown in Table 7.

Comparative example 2

Comparative Example 2 provides a method for preparing a nanofiber hollow ball sponge material. Compared with Example 1, the difference is that the method does not perform centrifugal dispersion in step S3 of preparing the nanofiber hollow ball sponge material. Except for the above differences, other operations are roughly the same, so I won't repeat them here.

Prepare different concentrations of copper ions, chromium ions, and oil-containing aqueous solutions. The oily substances include n-hexane and dodecane. Weigh the above-mentioned solutions for adsorption performance testing. The results are shown in Table 7.

Comparative example 3

Comparative Example 3 provides a method for preparing nanofiber hollow ball sponge material. Compared with Example 1, the difference is that the drying in step S5 of preparing the nanofiber hollow ball sponge material in this method is drying at room temperature. Except for the above differences, other operations are roughly the same, so I won't repeat them here.

Table 7:

It can be seen from Examples 5-7 and Comparative Example 1 that when the content of citric acid is low, it is not conducive to the adsorption of lysozyme and bovine serum albumin in the aqueous solution by the nanofiber hollow ball sponge material. It can be seen from Examples 8-12 and Comparative Example 2 that without centrifugal dispersion, the adsorption performance is lower when the oily substances n-hexane and dodecane are adsorbed. It can be seen from Examples 19-27 and Comparative Example 3 that the freeze-dried nanofiber hollow sphere sponge material has good adsorption performance for adsorbing oily substances n-hexane and dodecane.

Example 28

A three-dimensional separation material with a controllable structure of ion exchange nanofiber skeleton, and its preparation method is as follows:

S1. Mix ethylene-vinyl alcohol copolymer (PVA-co-PE) and cellulose acetate butyrate at a mass ratio of 20%:80%, and then extrude them in a twin-screw extruder at a processing temperature of 180°C , Granulation to obtain ethylene-vinyl alcohol copolymer/cellulose acetate butyrate composite material;

Then, the ethylene-vinyl alcohol copolymer/cellulose acetate butyrate composite material is melt-spun and drawn to obtain an ethylene-vinyl alcohol copolymer/cellulose acetate butyrate composite fiber aggregate; wherein the melt spinning The processing temperature is 200℃, and the drawing rate is 20m/min;

The ethylene-vinyl alcohol copolymer/cellulose acetate butyrate composite fiber aggregate was refluxed in acetone at 60°C for 72 hours, the cellulose acetate butyrate was extracted and removed, and then dried to obtain ethylene-vinyl alcohol with a diameter of about 200 nm Copolymer nanofiber aggregates.

S2. Disperse the ethylene-vinyl alcohol copolymer nanofiber aggregates obtained in step S1 in a mixed solvent composed of water and ethanol (volume ratio of 5:1) (the mass of the ethylene-vinyl alcohol copolymer nanofiber aggregates 5% of the mass of the mixed solvent), after high-speed dispersion to obtain a uniform polymer nanofiber dispersion, the mixed solvent in the dispersion is removed by centrifugal separation to obtain a dispersed ethylene-vinyl alcohol copolymer nanofiber monofilament . Ethylene-vinyl alcohol copolymer nanofiber aggregates are easily dispersed in a mixed solvent of water and ethanol to form nanofiber monofilaments. In the process of removing the solvent by centrifugal separation, the nanofiber monofilaments can basically maintain the original high dispersion state.

S3. Disperse the ethylene-vinyl alcohol copolymer nanofiber monofilament obtained in step S2 in deionized water, add glutaraldehyde, and stir for 6 hours, after the pre-crosslinking reaction occurs, a pre-crosslinked nanofiber suspension is obtained; wherein In the pre-crosslinked nanofiber suspension, the mass fraction of ethylene-vinyl alcohol copolymer nanofiber monofilaments is 3%; the volume fraction of the crosslinking agent is 1%.

S4. Add chitosan solution to the pre-crosslinked nanofiber suspension obtained in step S3, and obtain a functionalized nanofiber suspension after emulsification; wherein, the chitosan is 0.5% of the total mass of the functionalized nanofiber suspension .

S5. Put the functionalized nanofiber suspension obtained in step S4 into a mold, and perform non-directional freeze-drying (the freezing temperature is -40°C, the freezing time is 5h, and the drying time is 30h) to obtain ion exchange nanofibers The skeleton three-dimensional separation material.

Please refer to FIG. 2, it can be seen from the curve (a), OH stretching absorption peak pure PVA-co-PE porous three-dimensional nanofiber separation material appears at 3298cm ^{^-1,} 2941cm ^-1 and 2906cm ^-1 of the fat Group CH stretch absorption peak, 1095cm ^-1 is the absorption peak of CC skeleton vibration. As can be seen from the curve (e), a broad peak near 3276cm ^-1 is OH and NH stretching vibration absorption mixing, 2935cm ^-1 is the stretching vibration absorption peak of CH aliphatic, 1062cm ^-1 is the stretching vibration of the COC Absorption peak. This shows that the ethylene-vinyl alcohol copolymer and chitosan have cross-linked with glutaraldehyde, and no carbonyl absorption peak is observed at 1720 cm ^-1 , indicating that the aldehyde group in glutaraldehyde has completely reacted.

Referring to FIG. 3, it can be seen that the microstructure of the ion exchange type nanofiber skeleton three-dimensional separation material prepared in this embodiment is a microsphere-like ordered porous structure.

Examples 29 to 38

Compared with Example 28, the structure-controllable ion exchange nanofiber skeleton three-dimensional separation material provided by Examples 29 to 38 is different in that the type, content, freezing method and freezing temperature of polyelectrolyte are shown in Table 8. Others are substantially the same as Embodiment 28, and will not be repeated here.

Please refer to FIG. 2, it can be seen from the curve (C), for a simple separation of polyethyleneimine porous three-dimensional material, the absorption at 2935 and 2832cm ^-1 CH stretching vibration peak _2, 1455cm ^-1 at ₂ is CH the plane bending vibration absorption peaks, 1650cm ^-1 and 1581cm ^-1 is NH bending vibration at the primary and secondary amines absorption peak, 1360cm ^-1 and 1073cm ^-1 CN stretching vibration at the primary and secondary amine absorption peak . It can be seen from curve (f) that a new absorption peak appears at 1641 cm ^-1 , which corresponds to the C=N stretching vibration formed after polyethyleneimine is cross-linked with glutaraldehyde, indicating successful cross-linking (Example 33) .

Table 8

Specific surface area test method: use specific surface area analyzer (Micrometrics, ASPS2020, USA)

The N ₂ adsorption isotherm curve of the test sample at 373K is used to calculate the specific surface area of the sample through the Brunauer–Emmett–Tellet (BET) model.

Water flux test method: put a fixed-size sample into the permeability test device, pour deionized water, let the deionized water pass through the sample under the action of gravity, record the volume of deionized water passing through the sample within 1 min, ion

The water flux per unit area of water through the sample is calculated by the following formula:

Where: J is the pure water flux, L/(m ² ·h); A is the effective membrane area, m ² , A is defined in this experiment as 0.000314m ² ; T is the filtration time, h; V is the time period T The volume of the filtrate that passes through the sample.

Adsorption capacity test method: Weigh 0.2g of yeast RNA powder and dissolve it in a beaker containing 100ml 0.1M Tris-Hcl buffer, then put 0.05g sample into it, and place the beaker in a water bath shaker after sealing. Oscillate at 150r/min for 24h at ℃. Use an ultra-micro spectrophotometer to test the concentration of RNA in the solution before and after adsorption. The adsorption capacity of the sample is calculated by the following formula:

Where: Q is the adsorption capacity of the sample for RNA, mg/g; C ₀ is the initial concentration of RNA in the solution,

C _t is the concentration of RNA in the solution after sample adsorption; V is the volume of RNA solution.

Table 9

Table 9 shows the performance test results of Examples 28 to 38. In combination with Figure 3, it can be seen that when the content of chitosan is low, non-directional freezing (Example 28) is used, and the three-dimensional separation material obtained is microsphere-like ordered porous Structure, and because chitosan belongs to polycation electrolyte, it has anion exchange function. When the content of chitosan remains unchanged and is changed to directional freezing (Example 29), the porous structure of the three-dimensional separation material becomes a disordered porous structure as shown in Figure 3 (b), which is a honeycomb-like structure. Structure and spherical porous structure nested in it. Compared with Example 28, its specific surface area, compressive strength and adsorption capacity are improved. When the chitosan content continues to increase and directional freezing is used, a sheet-like or honeycomb-like ordered porous structure can be obtained. Among them, the overall performance of the honeycomb ordered porous structure is the best. When the content of chitosan is high and non-directional freezing is used (Example 32), a disordered porous structure as shown in Figure 3(e) is obtained, which has relatively poor adsorption performance.

The porous structure and adsorption performance can also be adjusted by changing the type of polyelectrolyte, so as to obtain three-dimensional separation materials with different ion exchange types.

Examples 39-41

Compared with Example 28, the structure-controllable ion exchange nanofiber skeleton three-dimensional separation material provided in Examples 39 to 41 is different in that the ethylene-vinyl alcohol copolymer in step S1 is replaced with polyamide 6; The glutaraldehyde in step S3 is replaced by citric acid, the mass fraction of polyamide 6 nanofiber monofilament in step S3 is 5%; the chitosan in step S4 is replaced by sodium alginate. Among them, the chitosan content, freezing method and freezing temperature are shown in Table 10. Others are substantially the same as Embodiment 28, and will not be repeated here.

Table 10

Comparative example 4

Compared with Example 28, the structure-controllable ion exchange nanofiber skeleton three-dimensional separation material provided in Comparative Example 4 is different in that it does not include step S2, that is, the ethylene-vinyl alcohol copolymer nanofiber aggregate is not processed Pre-dispersion.

Comparative example 5

Compared with Example 28, the structure-controllable ion exchange nanofiber skeleton three-dimensional separation material provided by Comparative Example 5 is different in that, in step S4, no chitosan is added. Others are substantially the same as Embodiment 28, and will not be repeated here.

Please refer to Figure 2. It can be seen from the curve (d) that after the PVA-co-PE nanofiber porous three-dimensional separation material is cross-linked with glutaraldehyde, the stretching vibration absorption peak of COC appears at 1062 cm ^-1 , indicating the successful cross-linking Joint reaction.

Comparative example 6～8

The preparation methods of the ion exchange three-dimensional separation materials provided in Comparative Examples 6-8 are as follows:

(1) Add glutaraldehyde to the chitosan solution and obtain a functionalized solution after emulsification.

(2) Put the functionalized solution obtained above into a mold and perform directional freeze-drying (freezing temperature -190°C, freezing time 5h, drying time 30h) to obtain ion exchange type three-dimensional separation material. Among them, the content of chitosan in Comparative Examples 6-8 is 0.5%, 1.5% and 3%, respectively.

Please refer to Figure 2. It can be seen from the curve (b) that the broad peak of 3700-3200cm ^{-1 is} the mixed absorption peak of OH and NH stretching vibration, and the double peak near 2977cm ^-1 is the stretching of -CH ₃ and -CH ₂ Vibration absorption peak, 1075cm ^-1 is the absorption peak of CC skeleton vibration, the absorption peak at 1641cm ^-1 corresponds to C=N stretching vibration, indicating that chitosan successfully crossed under the action of crosslinking agent glutaraldehyde United (Comparative Example 6).

Table 11

From the performance test results of Examples 39 to 41 in Table 11, it can be seen that when the crosslinking agent is citric acid and the polyelectrolyte is sodium alginate, cation exchange nanofibers with different porous structures can be obtained by freeze drying and crosslinking. The skeleton three-dimensional separation material. The specific surface area and porosity are high, and it can selectively adsorb RNA, and the adsorption capacity can reach 380mg/g. It can be seen from Comparative Example 4 that when the ethylene-vinyl alcohol copolymer nanofiber aggregates are not pre-dispersed, the ethylene-vinyl alcohol copolymer nanofiber aggregates are difficult to be well dispersed into single fibers in water, resulting in the final production The specific surface area and porosity of the obtained three-dimensional separation material are significantly reduced, and the compressive strength and adsorption performance are also significantly reduced. It can be seen from Comparative Example 5 that when polyelectrolyte chitosan is not added, the obtained three-dimensional separation material structure is shown in Figure 4 (a), showing a disordered structure, and its selective adsorption performance is significantly reduced, almost impossible Absorb RNA or lysozyme. It can be seen from Comparative Examples 6-8 that when only chitosan and glutaraldehyde are used for cross-linking, the specific surface area and porosity of the obtained three-dimensional separation material are significantly reduced, resulting in a significant reduction in its adsorption performance. Therefore, the present invention can obtain a nanofiber skeleton three-dimensional separation material with a controllable and diversified structure through reasonable selection and design of raw material components and matching with the preparation method of the present invention, which provides an effective way for the industrial application of functional adsorption materials.

In summary, the present invention provides a complete set of preparation processes from polymer melt spinning to three-dimensional separation of rice fiber skeleton materials. By adjusting the composition of the pre-crosslinked nanofiber suspension and the freezing method, the microstructure of the three-dimensional separation material of the nanofiber skeleton is adjusted. When polyelectrolytes of different contents are added to the pre-crosslinked nanofiber suspension, an ion exchange type nanofiber skeleton three-dimensional separation material with diversified structures and high strength and high adsorption capacity can be obtained. The entire preparation process is simple to operate, suitable for large-scale production, and has excellent product performance, which provides an effective way for mass and high-efficiency production of high-adsorption three-dimensional separation materials with diversified structures. It can be widely used in filtration, heat insulation, adsorption materials and other fields.

The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited to this. Anyone familiar with the technical field within the technical scope disclosed by the present invention, according to the technical solution of the present invention The equivalent replacement or change of the inventive concept thereof shall be covered by the protection scope of the present invention.

Claims

A structured controllable ion exchange nanofiber skeleton three-dimensional separation material, characterized in that the ion exchange nanofiber skeleton three-dimensional separation material comprises polymer nanofibers and freeze-dried with the polymer nanofibers through a crosslinking agent Cross-linked to form a porous structure polyelectrolyte; by adjusting the content of the polyelectrolyte and/or the freeze-drying method, the porous structure of the ion exchange nanofiber skeleton three-dimensional separation material is adjusted; the polymer nano The fiber surface contains active groups, and the crosslinking agent is any one or more of polyaldehyde and polyacid.
The structure-controllable ion-exchange nanofiber skeleton three-dimensional separation material according to claim 1, wherein the polymer nanofiber is one of ethylene-vinyl alcohol copolymer nanofiber or polyamide nanofiber ; The crosslinking agent is glutaraldehyde or citric acid.
The structure-controllable ion-exchange nanofiber skeleton three-dimensional separation material according to claim 2, wherein the porous structure comprises a microsphere-like ordered porous structure, a sheet-like ordered porous structure, and a honeycomb-like ordered porous structure And disordered porous structure.
A method for preparing a structure-controllable ion exchange nanofiber skeleton three-dimensional separation material, which is characterized in that it comprises the following steps:

S1. Prepare polymer nanofiber aggregates by melt spinning, the surface of which contains active groups;

S2. Disperse the polymer nanofiber aggregates obtained in step S1 in a dispersion solvent, and after a uniform polymer nanofiber dispersion is formed, the dispersion solvent is removed by centrifugal separation to obtain a dispersed polymer nanofiber monofilament ；

S3. Disperse the polymer nanofiber monofilament obtained in step S2 in deionized water, add a small molecule crosslinking agent, and stir the pre-crosslinking reaction to obtain a pre-crosslinked nanofiber suspension;

S4. Add a polyelectrolyte solution to the pre-crosslinked nanofiber suspension obtained in step S3, and obtain a functionalized nanofiber suspension after emulsification;

S5. Put the functionalized nanofiber suspension obtained in step S4 into a mold and freeze-dry to obtain a three-dimensional separation material with a controllable structure of ion exchange nanofiber skeleton;

The structure of the ion exchange nanofiber skeleton three-dimensional separation material is adjusted by adjusting the content of the polyelectrolyte solution and/or the freeze-drying method.
The method for preparing a structure-controllable ion exchange nanofiber skeleton three-dimensional separation material according to claim 4, wherein in step S4, the polyelectrolyte solution is a chitosan solution, a polyethyleneimine solution, One of sodium alginate solution, polyacrylic acid solution and polyacrylamide solution; the mass of the polyelectrolyte is 0.5% to 5% of the mass of the pre-crosslinked nanofiber suspension; in step S5, the freezing Drying methods include directional freeze-drying and non-directional freeze-drying.
The method for preparing a structure-controllable ion-exchange nanofiber skeleton three-dimensional separation material according to claim 4, characterized in that, in step S5, the freezing temperature of the freeze-drying is -196～-10°C, and the freezing time It is 4 to 6 hours, and the drying time is 24 to 72 hours.
The method for preparing a structure-controllable ion exchange nanofiber skeleton three-dimensional separation material according to claim 4, characterized in that, in step S2, the dispersion solvent is composed of water and alcohol or water and acid organic solvent The mixed solvent; in the mixed solvent, the volume ratio of water and organic solvent is (1.2-10):1; the mass of the polymer nanofiber aggregate is 0.5%-10% of the mass of the mixed solvent .
The preparation method of the structure-controllable ion exchange nanofiber skeleton three-dimensional separation material according to claim 7, wherein the centrifugal separation time is 4-10 min, and the centrifugal rotation speed is 8000-12000 r/min to remove The mixed solvent.
The method for preparing a structure-controllable ion-exchange nanofiber skeleton three-dimensional separation material according to claim 4, wherein, in step S3, in the pre-crosslinked nanofiber suspension, the polymer nanofiber The mass fraction of the monofilament is 0.5%-10%; the volume fraction of the crosslinking agent is 0.5%-20%.
The method for preparing a structure-controllable ion-exchange nanofiber skeleton three-dimensional separation material according to claim 9, wherein the small molecule crosslinking agent is any one or more of polyaldehyde and polyacid.
The method for preparing a structure-controllable ion exchange nanofiber skeleton three-dimensional separation material according to claim 4, wherein, in step S1, the polymer nanofiber aggregate is a thermoplastic polymer nanofiber aggregate, The thermoplastic polymer nanofiber aggregates include, but are not limited to, one or more of ethylene-vinyl alcohol copolymer nanofiber aggregates and polyamide nanofiber aggregates.
A preparation method of nanofiber hollow ball sponge material, characterized in that it comprises the following steps:

S1. Preparation of thermoplastic polymer nanofibers: the thermoplastic polymer and cellulose acetate butyrate are melt blended to prepare thermoplastic polymer nanofibers by a phase separation method;

S2. Preparation of a suspension: the thermoplastic polymer nanofibers prepared in the above steps are dispersed in a poor solvent to form a uniform suspension;

S3. Preparation of pure nanofibers: centrifugal dispersion of the nanofiber suspension prepared in the above steps to remove poor solvents to obtain pure nanofibers after dispersion;

S4. Preparation of nanofiber vacuoles: adding water, a crosslinking agent and a surfactant to the pure nanofibers prepared in the above steps, and obtaining nanofiber vacuoles after emulsification;

S5. Preparation of sponge material: Put the nanofiber bubble prepared in the above steps into a mold, and freeze-dry to obtain a nanofiber hollow ball sponge material.
The method for preparing nanofiber hollow ball sponge material according to claim 12, wherein the nanofiber hollow ball sponge material is made of thermoplastic polymer nanofibers with a mass fraction of 90% to 99% and a mass fraction of 1% to 1%. A sponge material composed of 10% chemical cross-linking agent intertwined and stacked; the chemical cross-linking agent is a polyhydric aldehyde and a polyacid.
The method for preparing nanofiber hollow spherical sponge material according to claim 12, wherein the method for preparing thermoplastic polymer nanofibers in step S1 comprises the following preparation steps:

a) Mix 5-40% of thermoplastic polymer material and 60-95% of cellulose acetate butyrate uniformly, extrude and pelletize in a twin-screw extruder at a processing temperature of 140-240°C to prepare Thermoplastic polymer/cellulose acetate butyrate composite material;

b) The thermoplastic polymer/cellulose acetate butyrate composite material obtained in step a) is spun and drawn on a melt spinning machine to obtain a composite fiber. The processing temperature of the spinning machine is 130-270°C and the drawing The extension rate is 8～30m/min;

c) The composite fiber obtained in step b) is refluxed in acetone at 50-70°C for 70-75 hours to extract cellulose acetate butyrate, and the composite fiber after extraction of cellulose acetate butyrate is dried at room temperature to prepare a diameter of 50～500nm thermoplastic poly nanofiber.
The method for preparing nanofiber hollow ball sponge material according to claim 12, wherein the poor solvent in step S2 is a mixture of water and alcoholic organic solvent, wherein the volume ratio of water to alcoholic organic solvent is ( 1.2-10):1, the mass ratio of the thermoplastic polymer nanofibers and the alcohol-water mixed solvent is (0.005-10):1.
The method for preparing nanofiber hollow ball sponge material according to claim 12, wherein the centrifugal dispersion in step S3 is centrifugation in a high-speed centrifuge for 4-6 minutes, and the centrifugal rotation speed is 8000-12000r/min to remove alcohol and Mixed solvent of water.
The method for preparing nanofiber hollow spherical sponge material according to claim 12, wherein the surfactant in step S4 is sodium lauryl sulfate, and its mass fraction is 0.05% to 5 of the total mass of the solution. %.
The method for preparing nanofiber hollow ball sponge material according to claim 12, wherein in step S5, the freeze-drying temperature is -80～﹣10℃, the freezing time is 4-6h, and the drying time is 24-72h .