阅读说明：本技术 一种基于氟化氧化石墨烯纳米片的疏水性电纺丝纳米纤维膜及其制备方法与应用 (Hydrophobic electrospinning nanofiber membrane based on fluorinated graphene oxide nanosheets and preparation method and application thereof ) 是由 于洋 吴婉霖 陈达 于�玲 于 2021-07-05 设计创作，主要内容包括：本发明属于膜材料技术领域,具体公开了一种基于氟化氧化石墨烯纳米片的疏水性电纺丝纳米纤维膜及其制备方法与应用。以氟化石墨颗粒替代普通石墨颗粒,采用修改Hummers法制备高氟化氧化石墨烯纳米片材料,可以直接获得强疏水性二维碳纳米材料,避免了氧化石墨烯还原处理所带来的制备成本与环境污染问题。氟化石墨颗粒因包含一定的C-F键,呈现出高疏水性与优异的化学稳定性。氟化氧化石墨烯纳米片具有独特的二维片状结构,同时所具有的氟基团赋予了其高疏水性,能够作为添加剂材料制备超疏水性纳米纤维膜材料,并应用于膜蒸馏领域,为膜蒸馏产业化提供一种新的制膜工艺。(The invention belongs to the technical field of membrane materials, and particularly discloses a fluorinated graphene oxide nanosheet-based hydrophobic electrospun nanofiber membrane and a preparation method and application thereof. Graphite fluoride particles are used for replacing common graphite particles, a Hummers method is modified to prepare the high-fluorination graphene oxide nanosheet material, the high-hydrophobicity two-dimensional carbon nanomaterial can be directly obtained, and the problems of preparation cost and environmental pollution caused by reduction treatment of graphene oxide are solved. The graphite fluoride particles have high hydrophobicity and excellent chemical stability because of containing a certain C-F bond. The fluorinated graphene oxide nanosheet has a unique two-dimensional sheet structure, and the fluorine group endows the fluorinated graphene oxide nanosheet with high hydrophobicity, so that the fluorinated graphene oxide nanosheet can be used as an additive material to prepare a super-hydrophobic nanofiber membrane material, is applied to the field of membrane distillation, and provides a new membrane preparation process for the industrialization of the membrane distillation.)

1. A preparation method of a hydrophobic electrospun nanofiber membrane based on fluorinated graphene oxide nanosheets is characterized by comprising the following steps:

(1) dispersing carbon fluoride in concentrated sulfuric acid/concentrated phosphoric acid solution, stirring, adding potassium permanganate, and continuously stirring to obtain a mixed solution; adding the obtained mixed solution into ice water, then adding hydrogen peroxide, standing, and collecting a solid on the top of a liquid level to obtain a highly fluorinated graphene oxide nanosheet;

(2) ultrasonically dispersing the obtained highly fluorinated graphene oxide nanosheet in a dimethylformamide solvent, dissolving a polyvinylidene fluoride polymer in a dimethylformamide/acetone mixed solvent, then mixing the two solutions to obtain a uniformly dispersed solution, taking the uniformly dispersed solution as an electrospinning polymer solution, and carrying out electrostatic spinning to obtain hydrophobic electrospinning based on the fluorinated graphene oxide nanosheet.

2. The method of claim 1, wherein: the concentration of the highly fluorinated graphene oxide nanosheets in the electrospinning polymer solution in the step (2) is 1-10 wt%.

3. The method of claim 1, wherein: and (3) the concentration of the highly fluorinated graphene oxide nanosheets in the electrospinning polymer solution in the step (2) is 2-6 wt%.

4. The method of claim 1, wherein: the mass-to-volume ratio of the carbon fluoride to the concentrated sulfuric acid/concentrated phosphoric acid solution in the step (1) is 1 g-50 mL: 1g to 200 mL.

5. The method of claim 1, wherein:

the mass ratio of the potassium permanganate to the carbon fluoride in the step (1) is 6-12: 2; the volume mass ratio of the hydrogen peroxide to the carbon fluoride in the step (1) is 8-15 mL: 4g of the total weight.

6. The method of claim 1, wherein: and (3) the concentration of the polyvinylidene fluoride polymer in the electrospinning polymer solution in the step (2) is 8-15 wt%.

7. The method of claim 1, wherein: the concentration of dimethylformamide in the electrospinning polymer solution in the step (2) is 40-48 wt%; the concentration of acetone is 40-48 wt%.

8. The method of claim 1, wherein: the stirring temperature for the first time in the step (1) is 40-60 ℃, and the stirring time is 2-6 h; the temperature of the second stirring is 80-90 ℃, and the stirring time is 6-24 hours.

9. A hydrophobic electrospun nanofiber membrane based on fluorinated graphene oxide nanosheets, prepared by the method of any one of claims 1-8.

10. Use of the hydrophobic electrospun nanofiber membrane based on fluorinated graphene oxide nanoplatelets according to claim 9 in the field of membrane distillation.

Technical Field

The invention belongs to the technical field of membrane materials, and particularly relates to a fluorinated graphene oxide nanosheet-based hydrophobic electrospun nanofiber membrane and a preparation method and application thereof.

Background

In recent years, two-dimensional carbon nanomaterials including graphene oxide, reduced graphene oxide and graphene are widely applied to the field of novel membrane material preparation as additive materials. The two-dimensional carbon nano material can obviously increase the conductivity of the polymer electrospinning solution, thereby promoting the generation of more uniform nano-fiber filaments. Compared with graphene oxide, the graphene nano material has strong hydrophobicity, but the large-scale application of the graphene nano material is limited to a great extent by the excessively high preparation cost at present. The graphene oxide nano material can remove functional groups on the surface of the graphene oxide to a certain extent through subsequent reduction treatment, and the corresponding nano material is called reduced graphene oxide. Because the proportion of the non-oxidation area is improved, the hydrophobicity of the reduced graphene oxide nanosheet is enhanced. In terms of hydrophilicity and hydrophobicity, the reduced graphene oxide nano material is between graphene oxide and graphene. The hydrophobicity of the reduced graphite oxide nanosheet is directly related to the reduction degree thereof, at present, the reduced graphene oxide nanosheet is prepared by adopting strong reducing agents such as hydrazine hydrate, dimethylhydrazine, sodium borohydride and hydroiodic acid, harsh conditions such as high temperature and the like are generally required, and meanwhile, the adopted reducing agents can cause potential secondary pollution to the environment.

Disclosure of Invention

In order to overcome the defects and shortcomings of the prior art, the invention mainly aims to provide a preparation method of a hydrophobic electrospun nanofiber membrane based on fluorinated graphene oxide nanosheets.

The invention also aims to provide the hydrophobic electrospun nanofiber membrane based on the fluorinated graphene oxide nanosheet prepared by the method.

The invention further aims to provide application of the hydrophobic electrospun nanofiber membrane based on the fluorinated graphene oxide nanosheet in the field of membrane distillation.

The purpose of the invention is realized by the following scheme:

a preparation method of a hydrophobic electrospun nanofiber membrane based on fluorinated graphene oxide nanosheets comprises the following steps:

(1) dispersing carbon fluoride in concentrated sulfuric acid/concentrated phosphoric acid solution, stirring, adding potassium permanganate, and continuously stirring to obtain a mixed solution; adding the obtained mixed solution into ice water, then adding hydrogen peroxide, standing, and collecting a solid on the top of a liquid level to obtain a highly fluorinated graphene oxide nanosheet;

(2) ultrasonically dispersing the obtained highly fluorinated graphene oxide nanosheet in a dimethylformamide solvent, dissolving a polyvinylidene fluoride polymer in a dimethylformamide/acetone mixed solvent, then mixing the two solutions to obtain a uniformly dispersed solution, taking the uniformly dispersed solution as an electrospinning polymer solution, and carrying out electrostatic spinning to obtain the hydrophobic electrospinning nanofiber membrane based on the fluorinated graphene oxide nanosheet.

The mass-to-volume ratio of the carbon fluoride to the concentrated sulfuric acid/concentrated phosphoric acid solution in the step (1) is 1 g-50 mL: 1g to 200mL, preferably 1 g: 100 mL.

The volume ratio of the concentrated sulfuric acid to the concentrated phosphoric acid in the concentrated sulfuric acid/concentrated phosphoric acid solution in the step (1) is 6: 1-12: 1, and preferably 9: 1.

The mass ratio of the potassium permanganate to the carbon fluoride in the step (1) is 6-12: 2, preferably 9: 2.

The volume mass ratio of the hydrogen peroxide to the carbon fluoride in the step (1) is 8-15 mL: 4g of the total weight of the mixture; preferably 10 mL: 4g of the total weight.

The stirring temperature for the first time in the step (1) is 40-60 ℃, and the stirring time is 2-6 h; the temperature of the second stirring is 80-90 ℃, and the stirring time is 6-24 hours.

The concentration of the highly fluorinated graphene oxide nanosheets in the electrospinning polymer solution in the step (2) is 1-10 wt%, preferably 2-6 wt%, and most preferably 4 wt%.

The concentration of the polyvinylidene fluoride polymer in the electrospinning polymer solution in the step (2) is 8-15 wt%, and preferably 12 wt%.

The concentration of the dimethylformamide in the electrospinning polymer solution in the step (2) is 40-48 wt%, preferably 41-44.0 wt%, and the concentration of the acetone is 40-48 wt%, preferably 41-44.0 wt%.

A hydrophobic electrospun nanofiber membrane based on fluorinated graphene oxide nanosheets is prepared by the method.

An application of a hydrophobic electrospun nanofiber membrane based on fluorinated graphene oxide nanosheets in the field of membrane distillation.

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

graphite fluoride particles are used for replacing common graphite particles, and a Hummers method is modified to prepare a highly Fluorinated Graphene Oxide (FGO) nanosheet material, so that a highly hydrophobic two-dimensional carbon nanomaterial can be directly obtained, and the problems of preparation cost and environmental pollution caused by reduction treatment of graphene oxide are solved. The graphite fluoride particles have high hydrophobicity and excellent chemical stability because of containing a certain C-F bond. The fluorinated graphene oxide nanosheet has a unique two-dimensional sheet structure, and the fluorine group endows the fluorinated graphene oxide nanosheet with high hydrophobicity, so that the fluorinated graphene oxide nanosheet can be used as an additive material to prepare a super-hydrophobic nanofiber membrane material, is applied to the field of membrane distillation, and provides a new membrane preparation process for the industrialization of the membrane distillation.

Drawings

FIG. 1 shows the nanofiber dimensions of nanofiber membranes under different fluorinated graphene oxide nanosheet doping conditions; wherein (a) is FGO ENMs-1; (b) is FGO ENMs-2; (c) is FGO ENMs-4; (d) is FGO ENMs-6.

Fig. 2 shows membrane distillation permeation flux and rejection rate of the nanofiber membrane under different fluorinated graphene oxide nanosheet doping conditions.

FIG. 3 is a stability system analysis of the best membrane material.

Detailed Description

The present invention will be described in further detail with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.

The reagents used in the examples are commercially available without specific reference.

Example 1

(1)4g of carbon fluoride (degree of fluorination: 60%) was dispersed in 400mL of a concentrated sulfuric acid/concentrated phosphoric acid (volume ratio: 9:1) solution, stirred at 50 ℃ for 4 hours, slowly added with 18g of potassium permanganate powder, and stirred at 90 ℃ overnight. The mixed solution was poured into ice water, and 10mL of hydrogen peroxide (30%) was added thereto. After sufficient settling, a brown solid at the top of the liquid surface was collected. Centrifuging at 6000rpm for 1h, and washing with 30 wt% hydrochloric acid and anhydrous ethanol to remove residual impurities.

(2) Ultrasonically dispersing 2 wt% of the highly fluorinated graphene oxide nanosheet material (FGO) prepared above in a dimethylformamide solvent, while dissolving a certain amount of polyvinylidene fluoride polymer in the dimethylformamide/acetone mixed solvent. And mixing and stirring the two solutions to form a uniform dispersion solution, using the uniform dispersion solution as an electrospinning polymer solution, and performing electrostatic spinning (the electrostatic spinning parameters are shown in table 2) to obtain the nanofiber membrane. The specific proportioning parameters are shown in table 1:

TABLE 1 electrospinning solution ratio

TABLE 2 Electrostatic spinning parameters

Example 2

Referring to example 1, the addition amount of the highly fluorinated graphene oxide nanosheets in step (2) was changed to 1 wt%, and the amounts of dimethylformamide and acetone used were 43.5%.

Example 3

Referring to example 1, the addition amount of the highly fluorinated graphene oxide nanosheets in step (2) was changed to 4 wt%, and the amounts of dimethylformamide and acetone used were 42%.

Example 4

Referring to example 1, the addition amount of the highly fluorinated graphene oxide nanosheets in step (2) was changed to 6 wt%, and the amounts of dimethylformamide and acetone used were 41%.

The FGO addition amounts of the prepared electrospun nanofiber membranes were 1 wt%, 2 wt%, 4 wt% and 6 wt%, respectively, and were expressed as FGO ENMs-1, FGO ENMs-2, FGO ENMs-4 and FGO ENMs-6, respectively. The original polyvinylidene fluoride nanofiber membranes served as control membranes PVDF ENMs.

Application examples

(1) Characterization of the Membrane Material

The nanofiber diameter distribution of the prepared nanofiber membrane was measured from the scanning electron microscope Image using Image J software. After the ratio of the pixel to the actual distance is determined, the diameter of at least one hundred nanofibers is measured manually, and it is ensured that no identical nanofibers are repeatedly measured during the measurement process. And calculating the statistical result by Gaussian fitting to obtain the diameter distribution and the average diameter of the nano fibers of the nano fiber membrane.

(2) Membrane distillation performance test of membrane material

The membrane distillation performance of the prepared electrospun nanofiber membrane was evaluated by a laboratory scale air gap membrane distillation test platform. In this apparatus, the effective membrane area for mass transfer was 2.32cm²The thickness of the air gap is 4 mm. NaCl at a concentration of 3.5 wt% was placed as simulated seawater into the round bottom flask immersed in an oil bath to maintain the desired temperature of 70 ℃. The temperature of the condensate was maintained at 10 ℃. A stainless steel plate is used as the condensing plate for condensing the water vapor. The cross-flow rate of feed liquid and condensate was maintained at 10L/h by means of a peristaltic pump. Before measurement, the air gap membrane distillation system is started to operate for 30 minutes in advance so that enough time is available for the system to reach a stable state, and then the membrane performance of different electrospinning nanofiber membranes is measured. The salt concentration was measured by a conductivity meter (INESA Scientific Instrument co., ltd.ddsj-308F). Each film sample was tested in triplicate and averaged.

The formula for the permeate flux is as follows:

J＝m/(A×t)

wherein, J (L/m)²h) Is the permeation flux, m (kg) is the weight of distilled water, A (m)²) Is the membrane area, and t (h) represents the duration of the operation.

The salt rejection was calculated according to the following equation:

SR＝(C_f-C_p)/C_f×100

wherein SR (%) represents the salt rejection, C_f(g/L) and C_p(g/L) represents the salt concentration of the feed solution and the permeate water, respectively.

(3) Determination of Long-term stability of the film

The best membrane was selected for long-term running experiments to verify the stability of its performance.

As can be seen from fig. 1, the nanofibers become smaller by adding FGO.

As can be seen from fig. 2, the addition of FGO increases the water flux and rejection of the electrospun nanofiber membrane.

As can be seen from fig. 3, the polyvinylidene fluoride electrospun nanofiber membrane having an FGO content of 4 wt% has strong stability in a long-term membrane distillation operation.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.