CN114210208A

CN114210208A - Preparation method of ultraviolet light driven nanofiber membrane capable of converting wettability

Info

Publication number: CN114210208A
Application number: CN202111536771.9A
Authority: CN
Inventors: 李斐然; 霍天威; 潘昀路; 赵学增
Original assignee: Harbin Institute of Technology
Current assignee: Harbin Institute of Technology
Priority date: 2021-12-15
Filing date: 2021-12-15
Publication date: 2022-03-22
Anticipated expiration: 2041-12-15
Also published as: CN114210208B

Abstract

The invention relates to the field of preparation of nanofiber materials, in particular to a preparation method of a nanofiber membrane with ultraviolet light driven and wettability convertible, which comprises the following steps: s1, adding perfluorooctyl trimethoxy silane into absolute ethyl alcohol for hydrolysis, adding P25-TiO2 particles for stirring, volatilizing to obtain dry TiO2-PFOS particle solid blocks, and crushing; s2, mixing N, N-dimethylformamide and acetone in proportion, adding PVDF-HFP, stirring until the PVDF-HFP is completely dissolved, and then adding TiO2 fluoride particles, and stirring to obtain an electrostatic spinning solution; s3, carrying out electrostatic spinning on the electrostatic spinning solution, volatilizing N, N-dimethylformamide and acetone in the spinning process to leave a PVDF-HFP-TiO2-PFOS nanofiber membrane, and removing the residual solution to obtain the nanofiber membrane capable of converting the wettability of the super-wetting membrane.

Description

Preparation method of ultraviolet light driven nanofiber membrane capable of converting wettability

Technical Field

The invention relates to the field of preparation of nanofiber materials, in particular to a preparation method of a nanofiber membrane with ultraviolet light driven and wettability convertible.

Background

In recent years, environmental pollution caused by leakage of marine petroleum and discharge of industrial waste water has been increasingly serious, and the treatment amount of waste water has been gradually increased, and the conventional separation methods of waste water mainly include physical treatment methods including gravity separation, centrifugal separation, and the like, and chemical treatment methods such as combustion methods and the like, which are energy-consuming and inefficient and easily cause secondary pollution.

Aiming at the defects, the selective super-infiltration membrane separation mode has the characteristics of high efficiency, environmental friendliness, repeatability, special selectivity and the like, and has unique advantages in oil-water separation application. The super-wetting membrane with single wettability can be a super-hydrophobic super-hydrophilic oil membrane, a super-hydrophilic underwater super-oleophobic membrane, a super-hydrophilic super-oleophobic membrane and the like. These super-wetting membranes can separate immiscible oil-water mixtures and emulsions in an "oil-through water-blocking" or "water-through oil-blocking" manner, respectively.

Although the selective super-wetting membrane separation mode has many advantages, for more complex oil-water environment, the wettability and the oil-passing or water-passing separation mode need to be changed instantly to realize separation according to needs, and the requirement of single selective wettability is difficult to meet. Therefore, the development of super-wetting films with switchable wettability is of great significance.

Disclosure of Invention

The invention provides a preparation method of a nanofiber membrane with ultraviolet light driven and switchable wettability, and aims to switch the wettability of a super-wetting membrane.

The above purpose is realized by the following technical scheme:

a preparation method of an ultra-wet nanofiber membrane with ultraviolet-driven switchable wettability comprises the following steps:

s1, adding perfluorooctyl trimethoxy silane to anhydrousHydrolyzing in ethanol, adding P25-TiO₂Stirring the particles to obtain a solution I, volatilizing the solution I to obtain dried TiO₂-solid mass of PFOS particles, eventually made in a finely divided state to obtain fluorinated TiO₂Particles;

s2, mixing N, N-dimethylformamide and acetone in proportion, adding PVDF-HFP, stirring until the PVDF-HFP is completely dissolved to obtain a solution II, and adding the fluorinated TiO₂Adding the particles into the solution II, and stirring to obtain an electrostatic spinning solution;

s3, carrying out electrostatic spinning on the electrostatic spinning solution, volatilizing N, N-dimethylformamide and acetone in the spinning process to leave PVDF-HFP-TiO₂Heating the PFOS nanofiber membrane to dry the residual solvent on the surface, and obtaining the ultra-wet nanofiber membrane with the target object ultraviolet light driving convertible wettability.

Drawings

FIG. 1 shows;

fig. 2 and 3 show SEM images of uv-driven switchable wettability nanofiber membranes prepared in accordance with the present invention;

FIG. 4 shows different TiO electrospinning solutions₂The change curve of the hydrophobic angle corresponding to the nanofiber membrane prepared under the content and static spinning voltage;

FIG. 5 shows the hydrophobic angle size versus FTIR image curves of the nanofiber membrane after various UV irradiation and heating treatments;

FIG. 6 shows images of different oils and water on the surface of the nanofiber membrane before UV irradiation, and images of the contact angles of oil and water in air;

FIG. 7 shows images of different oils and water on the surface of the nanofiber membrane after UV irradiation, as well as underwater oil contact angle and water contact angle in air;

FIG. 8 shows water contact angle change curves for the nanofiber membrane during UV-heating cycles;

FIG. 9 shows water contact angle change images of the nanofiber membrane under UV-heat cycling;

FIGS. 10(a) and 10(b) are schematic diagrams illustrating that the nanofiber membrane is used for separating a layered oil-water mixture in an oil-water-blocking mode and a water-oil-blocking mode before and after ultraviolet irradiation;

FIGS. 10(c) and 10(d) are photographs comparing the effect of the nanofiber membrane separating a water-in-oil emulsion and an oil-in-water emulsion, respectively;

FIG. 10(e) is the separation efficiency of the nanofiber membrane for separating a stratified oil-water mixture;

FIG. 10(f) is the nanofiber membrane separation water-in-oil emulsion separation efficiency.

Detailed Description

step one, fluoridizing TiO₂Preparation of the particles: adding perfluorooctyl trimethoxysilane (PFOS) into absolute ethanol, stirring and hydrolyzing for 10min, wherein the mass ratio of the perfluorooctyl trimethoxysilane to the absolute ethanol is 1.7 to 10, and adding P25-TiO under the condition of magnetic stirring₂Continuously stirring particles at normal temperature for 1 hour to obtain a liquid I, then placing the liquid I into an evaporation pan and placing the evaporation pan into an oven, heating the evaporation pan at 90 ℃ for about 1 hour until the solvent is completely volatilized, and taking out the heated liquid until a dried solid TiO particle block is obtained₂PFOS, and TiO agglomeration of the dried particulate solid₂Putting PFOS into a grinding bowl, grinding and finely crushing to obtain fluorinated TiO₂The particles are ready for use;

step two, preparing an electrostatic spinning solution: mixing and stirring N, N-Dimethylformamide (DMF) and acetone according to a ratio, wherein the mass ratio of the N, N-Dimethylformamide (DMF) to the acetone is 7: 3, adding PVDF-HFP under the condition of magnetic stirring to obtain a solution II, namely a powder-free electrostatic spinning solution, wherein the content of the PVDF-HFP in the solution II is 10% by mass percentage, and continuously stirring for about 1 hour at normal temperature until the PVDF-HFP is completely dissolved. Fluorinated TiO₂Gradually adding the particles into the electrostatic spinning solution under the condition of vigorous stirring, and continuously stirring for more than 2 hours to obtain the electrostatic spinning solution, wherein the TiO in the electrostatic spinning solution is calculated according to the mass percentage₂PFOS content 2.9% -16.5%.

Step three, preparation of the super-wetting fiber membrane: putting the electrostatic spinning solution obtained in the step two into a 5ml medical injector for electrostatic spinning; the electrostatic spinning voltage is 12-24 kv, the distance between the medical syringe needle and the receiver is 15cm, the flow rate of the electrostatic spinning solution is controlled to be 1ml/h, the receiver adopts a high-speed rotating drum aluminum foil receiver, the rotating speed is 100r/min, N, N-Dimethylformamide (DMF) and acetone volatilize in the spinning process, and the nano-fiber membrane is left at the end of the roller. Heating and drying the residual solvent on the surface after the fiber film is removed to obtain the ultra-wet nano fiber film with the target object ultraviolet light driven and the convertible wettability;

wherein the differently fluorinated TiO₂The content of the electrostatic spinning solution is as follows according to the mass percentage: 0%, 2.9%, 9.0%, 13.1%, 16.3%. The electrostatic spinning voltages correspond to: 12kV, 15kV, 18kV, 21kV and 24 kV.

For example, 1000. mu.l of perfluorooctyltrimethoxysilane was measured, added to 100ml of ethanol under magnetic stirring, and hydrolyzed under magnetic stirring at normal temperature for 10 minutes. Then 10g of P25-TiO was added to the solution₂The powder was magnetically stirred at room temperature for 1 hour. The solution was then poured into an evaporation dish and placed in an oven at 90 ℃ for about 1 hour until the solvent was completely evaporated. Taking out the dried fluoridized powder, putting the fluoridized powder into a grinding bowl, grinding the fluoridized powder into fine powder, and storing the fine powder for later use. 21g of DMF and 9g of acetone were weighed out and mixed in a 50ml beaker, and 3.3g of PVDF-HFP were weighed out and added to the solution, and the mixture was magnetically stirred at room temperature for 1 hour until completely dissolved. Then taking the prepared fluorinated TiO₂Several grams (0g, 1g, 3.3g, 5g, 6.5g) of the powder was gradually added in small portions to PVDF-HFP electrospinning solution under magnetic stirring, and magnetic stirring was carried out at normal temperature for more than 2 hours to form an electrospinning solution. The above electrospun solution was placed in a 5ml medical plastic syringe equipped with a 0.5mm diameter stainless steel needle. The distance between the needle and the receiving drum was 15cm, the advancing speed of the syringe was 1ml/h, the electrospinning voltage was set to a specific value (12kV, 15kV, 18kV, 21kV, 24kV), and the drum rotation speed was 100 r/min. After spinning is finished, a layer of PVDF-HFP-TiO is formed on the surface of the aluminum foil₂-PFOS nanofiber membranes. Placing the fiber membrane in an oven to be dried for 5-6 hours at 60 ℃ to obtain the ultra-wet nano fiber with ultraviolet-driven convertible wettabilityAnd (5) maintaining the membranes.

The nanofiber membrane has super-hydrophobicity and super-lipophilicity in the original state, the water contact angle WCA is larger than 150 degrees, the membrane is covered on a stainless steel net serving as a support, and a layered oil-water mixture and a water-in-oil emulsion can be directly separated in an oil-feeding and water-blocking mode. The membrane is placed under an ultraviolet lamp for 1cm, after 2-10 minutes of irradiation, the super-hydrophobic and super-oleophilic state can be changed into a super-hydrophilic and underwater super-oleophobic state, the underwater oleophobic angle is larger than 160 degrees, and the membrane is placed on a stainless steel net to serve as a support to directly separate a layered oil-water mixture and an oil-in-water emulsion in a 'water-passing and oil-blocking' mode. And (3) putting the nanofiber membrane subjected to ultraviolet irradiation into an oven, and heating for 10-30 minutes at 90 ℃, wherein the wettability can be restored to be super-hydrophobic. This uv-heating cycle can be repeated more than 15 times.

The preparation method has the characteristics of simple operation, high separation efficiency, environmental friendliness and the like, and selects the PVDF-HFP polymer material with excellent chemical stability and pollution resistance and the fluoride modified TiO₂Granules were prepared by electrospinning PVDF-HFP/DMF/acetone/TiO in solution₂TiO in PFOS₂Controlling the PFOS content and the electrostatic spinning voltage, and preparing the super-wetting nanofiber membrane with ultraviolet-driven switching wettability. And the influence of the powder content and the voltage on the wettability and the light-induced transformation of the fiber membrane is researched and applied to oil-water separation.

Wherein the PVDF-HFP material is purchased from Sigma-Aldrich company, N, N-Dimethylformamide (DMF) and acetone are purchased from local Baida experimental equipment, P25-TiO₂Purchased from Tianjin Baima science and technology, Inc., and perfluoro octyl trimethoxysilane purchased from Shanghai Mielin Biotechnology, Inc.

The SEM picture shot by the method is obtained by a Scios2 scanning electron microscope provided by Sammerfo, an FTIR image is obtained by an FTIR-650S infrared spectrometer provided by Tianjin Hongkong science and technology Limited, and the water content in the oil is measured by a Karl Fischer moisture tester MKC-710B.

Claims

1. A preparation method of an ultra-wet nanofiber membrane with switchable wettability driven by ultraviolet is characterized by comprising the following steps:

s1, adding perfluorooctyl trimethoxy silane into absolute ethyl alcohol for hydrolysis, and adding P25-TiO₂Stirring the particles to obtain a solution I, volatilizing the solution I to obtain dried TiO₂-solid mass of PFOS particles, finally making said solid mass in a finely divided state to obtain fluorinated modified TiO₂Particles;

s2, mixing N, N-dimethylformamide and acetone in proportion, adding PVDF-HFP, stirring until the PVDF-HFP is completely dissolved to obtain a solution II, and carrying out fluorination modification on the TiO₂Adding the particles into the solution II, and stirring to obtain an electrostatic spinning solution;

2. The method according to claim 1, wherein in S1, the hydrolysis process: stirring for 10min, adding P25-TiO under magnetic stirring₂Continuously stirring the particles for 1h at normal temperature; and (3) volatilizing the solution I: putting the liquid into an evaporating dish and putting the evaporating dish into an oven, and heating the evaporating dish for 50 to 70min at 90 ℃; the process of making the solid block into a fine crushing state: and (5) putting the solid block into a grinding bowl for grinding.

3. The method according to claim 2 or 1, wherein in S1, perfluorooctyltrimethoxysilane and P25-TiO are added₂Is 1.7 to 10.

4. The preparation method according to claim 1, wherein in the step S2, PVDF-HFP is subjected to a stirring process: continuously stirring for 50-70 min at normal temperature; the preparation process of the electrostatic spinning solution comprises the following steps: fluorinated modified TiO₂The particles are gradually added into the electrostatic spinning solution under the condition of vigorous stirring, and the mixture is continuously stirred for more than 2 hours.

5. The production method according to claim 4 or 1, wherein in S2, the mass ratio of N, N-dimethylformamide to acetone is 7 to 3.

6. The method according to claim 5, wherein the PVDF-HFP content of the solution II and the TiO content of the electrospinning solution are 10% by mass in the S2₂PFOS content 2.9% -16.5%.

7. The production method according to claim 6 or 1, wherein in the step (3), the electrospinning solution is placed in a 5ml medical syringe to be electrospun; the electrostatic spinning voltage is 12 kv-24 kv, the distance between the medical injector needle and the receiver is 15cm, the flow rate of the electrostatic spinning solution is controlled to be 1ml/h, the receiver adopts a rotating drum aluminum foil receiver, and the rotating speed is 100 r/min.

8. The method according to claim 7, wherein in S3, the heating and drying process: and (3) drying the nanofiber membrane for 5 to 6 hours at the temperature of 60 ℃ in an oven.

9. The preparation method according to claim 8 or 1, wherein the super-infiltrated nanofiber membrane is placed at a position 1cm below an ultraviolet lamp, and can be changed from a super-hydrophobic super-oleophilic state to a super-hydrophilic underwater super-oleophobic state after being irradiated for 3-10 minutes.

10. The preparation method according to claim 9, wherein the nano fiber membrane in the super-hydrophilic and super-hydrophobic state can be restored to the super-hydrophobic state after being placed in an oven and heated at 90 ℃ for 10-30 minutes.