阅读说明：本技术 可切换乳液型油水分离纳米抗菌膜及其制备方法 (Switchable emulsion type oil-water separation nano antibacterial film and preparation method thereof ) 是由 武艺 王栋 徐桂林 刘轲 夏明� 程芹 徐佳 陈媛丽 于 2021-09-10 设计创作，主要内容包括：本发明提供了一种可切换乳液型油水分离纳米抗菌膜及其制备方法。该纳米抗菌膜包括经过亲水处理的支撑基底、分别不对称设置于所述支撑基底上下表面的超疏水纳米纤维层和超亲水纳米纤维层；所述超疏水纳米纤维层由第一纳米纤维层、同时负载于所述第一纳米纤维层表面和内部的纳米抗菌粒子和疏水改性剂三者复合而成；所述超亲水纳米纤维层由第二纳米纤维层和负载于所述第二纳米纤维层表面和内部的纳米抗菌粒子复合而成。本发明利用可切换乳液型油水分离纳米抗菌膜的不同润湿性可以选择性地分离水包油乳液和油包水乳液。(The invention provides a switchable emulsion type oil-water separation nano antibacterial film and a preparation method thereof. The nano antibacterial film comprises a support substrate subjected to hydrophilic treatment, and a super-hydrophobic nanofiber layer and a super-hydrophilic nanofiber layer which are respectively and asymmetrically arranged on the upper surface and the lower surface of the support substrate; the super-hydrophobic nanofiber layer is formed by compounding a first nanofiber layer, nano antibacterial particles and a hydrophobic modifier, wherein the nano antibacterial particles and the hydrophobic modifier are loaded on the surface and the inside of the first nanofiber layer simultaneously; the super-hydrophilic nanofiber layer is formed by compounding a second nanofiber layer and nano antibacterial particles loaded on the surface and inside of the second nanofiber layer. The invention can selectively separate oil-in-water emulsion and water-in-oil emulsion by utilizing different wettabilities of the switchable emulsion type oil-water separation nano antibacterial film.)

1. A switchable emulsion type oil-water separation nano antibacterial film is characterized in that: the switchable emulsion type oil-water separation nano antibacterial film comprises a supporting substrate, and a super-hydrophobic nanofiber layer and a super-hydrophilic nanofiber layer which are respectively and asymmetrically arranged on the upper surface and the lower surface of the supporting substrate;

the super-hydrophobic nanofiber layer is formed by compounding a first nanofiber layer, nano antibacterial particles and a hydrophobic modifier, wherein the nano antibacterial particles and the hydrophobic modifier are loaded on the surface and the inside of the first nanofiber layer simultaneously;

the super-hydrophilic nanofiber layer is formed by compounding a second nanofiber layer and nano antibacterial particles loaded on the surface and inside of the second nanofiber layer;

the thickness of the super-hydrophobic nanofiber layer is 10-15 mu m, and the pore diameter is 150-250 nm; the thickness of the super-hydrophilic nanofiber layer is 10-15 mu m, and the pore diameter is 150-250 nm;

the oil-water separation efficiency of the switchable emulsion type oil-water separation nano antibacterial film reaches 99% or more.

2. The switchable emulsion type oil-water separation nano antibacterial film of claim 1, wherein: the support substrate is a hydrophilic PP modified membrane with micron pore size.

3. The switchable emulsion type oil-water separation nano antibacterial film of claim 1, wherein: the first nanofiber layer and the second nanofiber layer are respectively one of a PVA-co-PE nanofiber membrane, a polyester fiber nanofiber membrane with the surface subjected to hydrophilic modification treatment and a nylon nanofiber membrane with the surface subjected to hydrophilic modification treatment.

4. The switchable emulsion type oil-water separation nano antibacterial film of claim 1, wherein: the nano antibacterial particles are ZIF-8 particles, and the average particle size is 30-70 nm.

5. The switchable emulsion type oil-water separation nano antibacterial film of claim 1, wherein: the hydrophobic modifier is a fluorosilane modifier and is loaded on the second nanofiber layer by a chemical vapor deposition method.

6. The switchable emulsion type oil-water separation nano antibacterial film of claim 1, wherein: the switchable emulsion type oil-water separation nano antibacterial film can separate oil-in-water type emulsion or water-in-oil type emulsion by adjusting the surface separation sequence of the super-hydrophilic surface and the super-hydrophobic surface which are asymmetrically arranged.

7. The switchable emulsion type oil-water separation nano antibacterial film of claim 1, wherein: the contact angle of the super-hydrophobic nanofiber layer is larger than 150 degrees; the contact angle of the super-hydrophilic nanofiber layer is close to 0 degree; the switchable emulsion type oil-water separation nano antibacterial film has the antibacterial performance of 99% or more.

8. A preparation method of the switchable emulsion type oil-water separation nano antibacterial film as claimed in any one of claims 1 to 7, which is characterized in that: the method comprises the following steps:

s1, preparing nanofiber slurry with super-hydrophilic characteristics;

s2, uniformly spraying nanofiber slurry on the upper surface and the lower surface of a hydrophilic PP modified membrane supporting substrate by adopting a spraying method, and then drying to obtain a hydrophilic composite membrane compounded by a middle hydrophilic PP modified membrane supporting substrate and a super-hydrophilic nanofiber membrane three-layer membrane structure loaded on the upper surface and the lower surface of the supporting substrate;

s3, loading the nano antibacterial particles on the surface and inside of the hydrophilic composite membrane by adopting an ultrasonic treatment method to obtain the hydrophilic antibacterial composite membrane with the upper and lower surfaces loaded with the nano antibacterial particles;

s4, sealing one surface of the hydrophilic antibacterial composite membrane by using a double-sided adhesive tape, and depositing a fluorosilane modifier on the other surface of the hydrophilic antibacterial composite membrane by using a chemical vapor deposition method to obtain a composite membrane of which one surface is a super-hydrophilic nanofiber layer and the other surface is a super-hydrophobic nanofiber layer, namely the switchable emulsion type oil-water separation nano antibacterial membrane with the hydrophilic properties on the upper surface and the lower surface being asymmetrically arranged.

9. The method for preparing the switchable emulsion type oil-water separation nano antibacterial film according to claim 8, wherein the switchable emulsion type oil-water separation nano antibacterial film comprises the following steps: in step S1, the diameter of the nanofibers in the nanofiber slurry is 200-400 nm.

10. The method for preparing the switchable emulsion type oil-water separation nano antibacterial film according to claim 8, wherein the switchable emulsion type oil-water separation nano antibacterial film comprises the following steps: in step S4, the processing time of the chemical vapor deposition method is 8-16 h.

Technical Field

The invention relates to the technical field of oil-water separation membrane preparation, in particular to a switchable emulsion type oil-water separation nano antibacterial membrane and a preparation method thereof.

Background

Along with the acceleration of the urbanization and industrialization process, the problems of oil pollutants and petroleum leakage in the water body are increasingly prominent, great harm is caused to human health, water environment and ecological environment balance, and the oil-polluted water source becomes one of important problems which need to be solved urgently in the whole world.

After oil stains enter a water body, oil-water mixtures of four types of floating oil, dispersed oil, emulsified oil and dissolved oil can be formed, wherein the floating oil and the dispersed oil are easy to agglomerate into a continuous oil layer due to large particle sizes, and can be easily removed by the traditional methods of adsorption, sedimentation and mechanical oil skimming; for the separation of stable emulsified oil and dissolved oil, although a certain separation effect can be obtained by the traditional demulsification technology such as a sedimentation method, a biological method, an ultra-micro-filtration membrane separation method and the like, the defects of high energy consumption and low treatment efficiency still exist. Therefore, there is a need to develop a novel high-efficiency oil-water emulsion separation material.

In recent years, nanofiber membranes are increasingly applied to the field of oil-water separation due to the characteristics of easiness in preparation, large specific surface area, good mechanical properties and the like, but fibers in nanofiber membranes prepared by the traditional electrostatic spinning technology are in a disordered state or a unidirectional arrangement state, and lack of three-dimensional structures inside the fiber membranes, so that the porosity and the pore size are not favorable for realizing oil-water separation.

The invention patent with the application number of CN201910299527.1 discloses a nanofiber membrane, a preparation method thereof and application thereof in oil-water separation. The nanofiber membrane comprises a crisscross nanofiber membrane; and polytetrafluoroethylene nanoparticles for modifying the surface of the crossed nanofiber membrane. The demulsification of the water-in-oil emulsion or the oil-in-water emulsion can be realized through the combined action of the three-dimensional topological structure and the surface chemical component modification of the cross-shaped nanofiber membrane, so that the high-efficiency oil-water separation is realized.

The invention patent with the application number of CN201910758509.5 discloses a preparation method of an oil-water separation composite membrane added with COFs. The electrostatic spinning technology is combined with a Covalent Organic Framework (COFs), nanofibers with good modifiability and the COFs which contain a large number of amphiphilic group hydroxyl groups and have ultrahigh porosity and ultrahigh specific surface area are blended and modified, the problem of wettability of a polymer in oil water is solved, the roughness of a composite membrane is improved, super-amphiphilic, underwater super-oleophobic property in air and super-hydrophobic property under oil are realized, the membrane can be accurately designed according to the properties of different oil-water mixtures, and oil-in-water and water-in-oil mixtures can be simultaneously separated.

The invention patent with the application number of CN201911177599.5 discloses a preparation method and application of an emulsion separation membrane with controllable wettability. The method is characterized in that cobalt salt is used as electrolyte, and a plurality of layers of cobalt hydroxide nanosheets are deposited on the surface of a stainless steel net in a self-assembly manner through an electrodeposition technology to obtain the emulsion separation membrane with super-hydrophilic/underwater super-oleophobic properties, so that the oil-in-water emulsion can be separated. The surface modification of fluorosilane can be intelligently converted into a super-hydrophobic/underwater super-lipophilic oil film, so that the separation of water-in-oil emulsion is realized.

However, the preparation method of the oil-water separation membrane has the defects of single functionality, complicated process, difficulty in large-scale production, few types of separated emulsions and the like, and the separation membrane blocks micropores due to the attachment of various water pollutants or bacteria in the long-term use process, so that the separation efficiency is obviously reduced, and the service life of the separation membrane is influenced.

In view of the above, there is a need to design an improved switchable emulsion type oil-water separation nano antibacterial film and a preparation method thereof to solve the above problems.

Disclosure of Invention

The invention aims to provide a switchable emulsion type oil-water separation nano antibacterial film and a preparation method thereof.

In order to achieve the purpose, the invention provides a switchable emulsion type oil-water separation nano antibacterial film which comprises a supporting substrate, a super-hydrophobic nanofiber layer and a super-hydrophilic nanofiber layer, wherein the super-hydrophobic nanofiber layer and the super-hydrophilic nanofiber layer are respectively and asymmetrically arranged on the upper surface and the lower surface of the supporting substrate;

the super-hydrophobic nanofiber layer is formed by compounding a first nanofiber layer, nano antibacterial particles and a hydrophobic modifier, wherein the nano antibacterial particles and the hydrophobic modifier are loaded on the surface and the inside of the first nanofiber layer simultaneously;

the super-hydrophilic nanofiber layer is formed by compounding a second nanofiber layer and nano antibacterial particles loaded on the surface and inside of the second nanofiber layer;

the thickness of the super-hydrophobic nanofiber layer is 10-15 mu m, and the pore diameter is 150-250 nm; the thickness of the super-hydrophilic nanofiber layer is 10-15 mu m, and the pore diameter is 150-250 nm;

the oil-water separation efficiency of the switchable emulsion type oil-water separation nano antibacterial film reaches 99% or more. As a further improvement of the present invention, the support substrate is a hydrophilic PP modified membrane with micron pore size.

As a further improvement of the invention, the first nanofiber layer and the second nanofiber layer are respectively one of a PVA-co-PE nanofiber membrane, a polyester fiber nanofiber membrane with the surface subjected to hydrophilic modification treatment and a nylon nanofiber membrane with the surface subjected to hydrophilic modification treatment.

As a further improvement of the invention, the nano antibacterial particles are ZIF-8 particles, and the average particle size is 30-70 nm.

As a further improvement of the present invention, the hydrophobic modifier is a fluorosilane modifier, which is loaded on the second nanofiber layer by a chemical vapor deposition method.

As a further improvement of the present invention, the switchable emulsion type oil-water separation nano antibacterial film can separate an oil-in-water emulsion or a water-in-oil emulsion by adjusting the surface separation order of the super hydrophilic surface and the super hydrophobic surface which are asymmetrically disposed.

As a further improvement of the invention, the contact angle of the superhydrophobic nanofiber layer is greater than 150 °; the contact angle of the super-hydrophilic nanofiber layer is close to 0 degree; the switchable emulsion type oil-water separation nano antibacterial film has the antibacterial performance of 99% or more.

In order to realize the purpose, the invention also provides a preparation method of the switchable emulsion type oil-water separation nano antibacterial film, which comprises the following steps:

s1, preparing nanofiber slurry with super-hydrophilic characteristics;

s2, uniformly spraying nanofiber slurry on the upper surface and the lower surface of a hydrophilic PP modified membrane supporting substrate by adopting a spraying method, and then drying to obtain a hydrophilic composite membrane compounded by a middle hydrophilic PP modified membrane supporting substrate and a super-hydrophilic nanofiber membrane three-layer membrane structure loaded on the upper surface and the lower surface of the supporting substrate;

s3, loading the nano antibacterial particles on the surface and inside of the hydrophilic composite membrane by adopting an ultrasonic treatment method to obtain the hydrophilic antibacterial composite membrane with the upper and lower surfaces loaded with the nano antibacterial particles;

s4, sealing one surface of the hydrophilic antibacterial composite membrane by using a double-sided adhesive tape, and depositing a fluorosilane modifier on the other surface of the hydrophilic antibacterial composite membrane by using a chemical vapor deposition method to obtain a composite membrane of which one surface is a super-hydrophilic nanofiber layer and the other surface is a super-hydrophobic nanofiber layer, namely the switchable emulsion type oil-water separation nano antibacterial membrane with the hydrophilic properties on the upper surface and the lower surface being asymmetrically arranged.

As a further improvement of the invention, in step S1, the diameter of the nanofibers in the nanofiber slurry is 200-400 nm.

As a further improvement of the invention, in step S4, the treatment time of the chemical vapor deposition method is 8-16 h.

The invention has the beneficial effects that:

1. the switchable emulsion type oil-water separation nano antibacterial membrane provided by the invention is arranged in a three-layer composite structure, wherein a support substrate adopts a PP membrane subjected to hydrophilic modification treatment, the pore diameter of the PP membrane is larger and the PP membrane is in a micron-sized size, and the PP membrane mainly plays a role in supporting a nanofiber membrane and permeating liquid; the super-hydrophilic nanofiber layer is arranged on one surface of the supporting substrate, PVA-co-PE nanofibers or nanofibers with modified surfaces are used as raw materials, the surfaces of the super-hydrophilic nanofiber layer can contain abundant hydroxyl groups, and the super-hydrophilic nanofiber layer has super-hydrophilic characteristics; the super-hydrophobic nanofiber layer arranged on the other surface of the supporting substrate is subjected to nano antibacterial particle loading and fluorosilane modification treatment to show a super-hydrophobic characteristic, and under the synergistic effect of low surface adhesion and ZIF-8 nano antibacterial particles, zinc ions and imidazole groups in ZIF-8, including active oxygen groups generated under illumination, can destroy RNA of bacteria, inactivate the bacteria, can effectively repel and kill the bacteria (staphylococcus aureus and escherichia coli), and has excellent antibacterial performance. According to the invention, the oil-in-water type emulsion or the water-in-oil type emulsion is specifically and selectively separated by adjusting the surface separation sequence of the super-hydrophilic surface and the super-hydrophobic surface which are asymmetrically arranged on the nano antibacterial composite membrane, so that the oil-water separation of different emulsion types is switched.

2. According to the preparation method of the switchable emulsion type oil-water separation nano antibacterial membrane, the PP membrane subjected to hydrophilic modification is used as a supporting substrate, and then the nano fibers with super-hydrophilic characteristics are sprayed on two sides of the hydrophilic PP membrane supporting substrate to obtain the upper nano fiber layer and the lower nano fiber layer, wherein the surfaces of the upper nano fiber layer and the lower nano fiber layer can contain abundant hydroxyl groups, and the super-hydrophilic characteristics are presented. Then, when the nanofiber membrane on one surface is modified into a hydrophobic property through fluorosilane, the nanofiber composite membrane can effectively repel and kill bacteria under the synergistic effect of the low adhesion property of the hydrophobic surface and the ZIF-8 nano antibacterial particles; the hydrophobic modification is carried out on one surface, the other surface is sealed by the double faced adhesive tape, the treatment can be torn off after the hydrophobic treatment while the super-hydrophilic characteristic of the treatment is kept, the double faced adhesive tape is used for protecting the covered surface from being modified by the hydrophobic modification, the protected surface is tightly attached to the base material without a gap, so that when vapor deposition is carried out, fluorosilane steam enters the protected layer from the gap, the hydrophilicity of the unmodified surface is kept, and the asymmetric arrangement of the hydrophilic performance of the upper surface and the lower surface of the nano composite film is realized. The invention can selectively separate oil-in-water emulsion and water-in-oil emulsion by utilizing different wettabilities of the switchable emulsion type oil-water separation nano antibacterial film.

3. According to the preparation method of the switchable emulsion type oil-water separation nano antibacterial film, the hydrophilic nano fibers with proper sizes are selected, so that the nano fiber aperture required by emulsion separation can be prepared by a simple spraying method; and the water-in-oil and oil-in-water emulsion type oil-water pollutants can be simultaneously separated by utilizing the asymmetric wettability of two surfaces of the nanofiber composite membrane.

4. According to the preparation method of the switchable emulsion type oil-water separation nano antibacterial film, ZIF-8 nano antibacterial particles are loaded on the surfaces of an upper nanofiber layer and a lower nanofiber layer, the ZIF-8 nano antibacterial particles form granular convex MOF micro-nano structures on the surfaces and the interiors of nanofibers with nanometer apertures and three-dimensional staggered, the roughness of the nanofiber layers is increased, and therefore convex hydrophilic nano particle structures are formed on the surfaces of the hydrophilic layers, and convex super-hydrophobic nano particle structures are formed on the surfaces of the hydrophobic layers after hydrophobic modification. The protruding micro-nano structure can perform a synergistic effect with the nanofiber layer, and the oil-water separation efficiency is promoted together. When the oil-in-water emulsion is separated, the hydrophilic layer is arranged above, on the basis of demulsification of the hydrophilic nanofibers, water molecules are preferentially captured in the MOF micro-nano structure on the surface of the membrane to form a continuous water layer, and the liquid membrane allows water to rapidly pass through by virtue of gravity and generates strong repulsive force to an oil phase, so that efficient oil-water separation is realized. When the water-in-oil emulsion is separated, the hydrophobic layer is on the upper part, and on the basis of demulsification of the super-hydrophobic nanofiber layer, the super-hydrophobic convex MOF micro-nano structure can capture oil drops preferentially to form a continuous oil layer, so that efficient separation of the water-in-oil emulsion is successfully realized.

Drawings

FIG. 1 is a schematic view of the preparation of the switchable emulsion type oil-water separation nano antibacterial film provided by the present invention.

Fig. 2 is a scanning electron microscope photograph of the switchable emulsion type oil-water separation nano antibacterial film and an element distribution diagram of the modified nano fiber film provided by the present invention (the scale bar in fig. 2 a is 100 μm, the scale bar in fig. 2 b is 20 μm, the scale bar in fig. 2 c is 5 μm, the scale bar in fig. 2 d is 2 μm, the scale bar in fig. 2 e is 2 μm, and the scale bar in fig. 2 f is 2 μm).

FIG. 3 is an optical photograph of the switchable emulsion type oil-water separation nano-antibacterial film provided by the present invention for separating water-in-toluene and water-in-toluene, respectively.

FIG. 4 is a test of the antibacterial property of the switchable emulsion type oil-water separation nano antibacterial film provided by the invention to Escherichia coli and Staphylococcus aureus.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in detail with reference to the accompanying drawings and specific embodiments.

It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and/or processing steps closely related to the aspects of the present invention are shown in the drawings, and other details not closely related to the present invention are omitted.

In addition, it is also to be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

Referring to fig. 1, the present invention provides a method for preparing a switchable emulsion type oil-water separation nano antibacterial film, comprising the following steps:

s1, preparing nanofiber slurry with super-hydrophilic characteristics;

s2, uniformly spraying nanofiber slurry on the upper surface and the lower surface of a hydrophilic PP modified membrane supporting substrate by adopting a spraying method, and then drying to obtain a hydrophilic composite membrane compounded by a middle hydrophilic PP modified membrane supporting substrate and a super-hydrophilic nanofiber membrane three-layer membrane structure loaded on the upper surface and the lower surface of the supporting substrate;

s3, loading the nano antibacterial particles on the surface and inside of the hydrophilic composite membrane by adopting an ultrasonic treatment method to obtain the hydrophilic antibacterial composite membrane with the upper and lower surfaces loaded with the nano antibacterial particles;

s4, sealing one surface of the hydrophilic antibacterial composite membrane by using a double-sided adhesive tape, and depositing a fluorosilane modifier on the other surface of the hydrophilic antibacterial composite membrane by using a chemical vapor deposition method to obtain a composite membrane of which one surface is a super-hydrophilic nanofiber layer and the other surface is a super-hydrophobic nanofiber layer, namely the switchable emulsion type oil-water separation nano antibacterial membrane with the hydrophilic properties on the upper surface and the lower surface being asymmetrically arranged.

Preferably, in step S1, the diameter of the nanofibers in the nanofiber slurry is 200 to 400 nm.

Preferably, in step S4, the chemical vapor deposition method is performed for 8 to 16 hours.

The switchable emulsion type nanofiber membrane for oil-water separation and the preparation method thereof provided by the invention are described below with reference to specific examples.

Example 1

The embodiment 1 provides a preparation method of a switchable emulsion type oil-water separation nano antibacterial film, which comprises the following steps:

s1, preparation of PVA-co-PE (ethylene/vinyl alcohol copolymer) nanofiber slurry:

firstly, preparing PVA-co-PE nanofiber slurry: dispersing PVA-co-PE nano-fibers in a mixed solvent of isopropanol and water (the gram-weight ratio of the water to the isopropanol to the PVA-co-PE nano-fibers is 50: 50: 3), and uniformly stirring by using a beater to obtain PVA-co-PE nano-fiber slurry.

S2, preparation of a hydrophilic composite membrane:

and uniformly spraying PVA-co-PE nanofiber slurry on the upper surface and the lower surface of the hydrophilic PP modified membrane by adopting a spraying method, and naturally airing to obtain a hydrophilic composite membrane formed by compounding a middle hydrophilic PP modified membrane supporting substrate and a super-hydrophilic nanofiber membrane three-layer membrane loaded on the upper surface and the lower surface of the supporting substrate.

S3, antibacterial loading of the PVA-co-PE nanofiber hydrophilic composite membrane:

and (3) placing the prepared PVA-co-PE nanofiber hydrophilic composite membrane in a ZIF-8 dispersion liquid (the concentration is 1-10 wt%), carrying out ultrasonic treatment for 30min, and naturally airing to obtain the nanofiber membrane with the ZIF-8 loaded on the surface, wherein the nanofiber membrane is marked as a hydrophilic antibacterial composite membrane.

S4, preparation of the asymmetric wettability switchable emulsion type oil-water separation nanofiber membrane:

one side of the PVA-co-PE nanofiber hydrophilic antibacterial composite membrane is sealed by a double faced adhesive tape, the other side of the PVA-co-PE nanofiber hydrophilic antibacterial composite membrane is deposited on the surface of the nanofiber membrane by a chemical vapor deposition method through perfluorooctyl trichlorosilane (10mL of a mixed solution of 1% volume fraction perfluorooctyl trichlorosilane and ethanol), the surface of the deposited PVA-co-PE nanofiber membrane is super-hydrophobic, the PVA-co-PE nanofiber membrane sealed by the double faced adhesive tape keeps the super-hydrophilic characteristic of the PVA-co-PE nanofiber membrane, the PVA-co-PE nanofiber composite membrane with the two sides set with the asymmetric wetting characteristics is obtained, and the PVA-co-PE nanofiber composite membrane with the two sides set with the asymmetric wetting characteristics is the switchable emulsion type oil-water separation nanofiber membrane.

In this way, a schematic diagram of the switchable emulsion type oil-water separation nanofiber membrane prepared in this embodiment 1 is shown in fig. 1. As can be seen from fig. 1, the pore size of the support substrate hydrophilic modified PP film in the switchable emulsion type oil-water separation nano antibacterial film prepared in this embodiment is large, and is micron-sized, and mainly plays a role in supporting the PVA-co-PE nanofiber film and the penetrating liquid. The PVA-co-PE nanofiber membranes sprayed on two sides of the hydrophilic PP membrane are ethylene/vinyl alcohol copolymers, the surfaces of the ethylene/vinyl alcohol copolymers contain rich hydroxyl groups, and the ethylene/vinyl alcohol copolymers are super-hydrophilic before modification. When the PVA-co-PE nanofiber membrane on one surface is modified into a hydrophobic property through fluorosilane, the PVA-co-PE nanofiber membrane can effectively reject and kill bacteria (staphylococcus aureus and escherichia coli) under the synergistic effect of low surface adhesion and ZIF-8 antibacterial particles. Therefore, the oil-in-water emulsion and the water-in-oil emulsion can be selectively separated by utilizing the different wettabilities of the switchable emulsion type oil-water separation nano antibacterial film.

The three-layer fiber film composite structure of the switchable emulsion type oil-water separation nano antibacterial film can be clearly seen from a in fig. 2 and b in fig. 2. After modification with perfluorooctyltrichlorosilane, the elemental composition of one side of the PVA-co-PE membrane is shown as d-F in fig. 2, and it can be seen that the F element is distributed throughout the cross section of the modified PVA-co-PE membrane, and the concentration gradually decreases from top to bottom (shown as d in fig. 2).

Please refer to the optical photographs of the switchable emulsion type oil-water separation nano-antibacterial film shown in fig. 3 for filtering toluene in water and water in toluene in water, respectively. According to the different wettabilities of different surfaces of the nanofiber membrane and the principle of oil-water immiscibility, when the oil-in-water emulsion is separated, the nanofiber membrane with the hydrophilic surface faces upwards (shown as a in figure 3); when separating the water-in-oil emulsion, we faced the hydrophobic side nanofiber membrane upwards (shown as b in fig. 3).

A in FIG. 3 is a photograph before and after the nanofiber membrane separation of toluene in water; b in fig. 3 is a photograph before and after the nanofiber membrane separation of water-in-toluene. It can be seen from the figure that transparent homogeneous phase solution (water or toluene) can be obtained from the two emulsions after the two emulsions are separated and filtered by the nanofiber membrane, which indicates that the asymmetrically arranged switchable emulsion type oil-water separation nano antibacterial membrane prepared in this example 1 can effectively separate different types of emulsions.

Please refer to fig. 4 for the antibacterial property test of the switchable emulsion type oil-water separation nano antibacterial film against escherichia coli and staphylococcus aureus. As can be seen from fig. 4, compared with the pure PVA-co-PE nanofiber membrane, an obvious zone of inhibition appears around the [email protected] PVA-co-PE membrane (switchable emulsion type oil-water separation nano-antibacterial membrane) with the ZIF-8 antibacterial particles loaded on the surface, which indicates that the switchable emulsion type oil-water separation nano-antibacterial membrane prepared in this embodiment 1 has good antibacterial performance at the same time.

Example 2

The difference from example 1 is that: in step S1, the nanofibers are polyester nanofibers whose surfaces have undergone hydrophilic modification, and the rest are the same as those in embodiment 1, and are not described herein again.

The nano antibacterial film prepared in the example 2 is subjected to an oil-water separation experiment, and the oil-water separation efficiency reaches 99%.

Example 3

The difference from example 1 is that: in step S1, the nanofibers are nylon nanofibers whose surfaces have undergone hydrophilic modification, and the rest are the same as those in embodiment 1, and are not described herein again.

The nano antibacterial film prepared in the example 3 is subjected to an oil-water separation experiment, and the oil-water separation efficiency reaches 98%.

Comparative example 1

The difference from example 1 is that: the procedure of ultrasonic loading of the antibacterial nanoparticles of step S3 is not performed.

Carrying out an oil-water separation experiment and an antibacterial performance test on the nano composite film prepared in the comparative example 1, wherein the oil-water separation efficiency reaches 95%; the antibacterial performance was 30%, which is much lower than that of example 1.

It should be noted that, as will be understood by those skilled in the art, the fluorosilane modifier used in the present invention may also be one of perfluorodecyltriethoxysilane and perfluoroheptadecyltrimethoxysilane, which can perform superhydrophobic modification treatment on the nanofiber layer. The concentration of the ZIF-8 dispersion liquid and the deposition amount of the perfluorooctyl trichlorosilane can influence the performance of the prepared nanofiber membrane to a certain extent, but the nanofiber membrane can achieve excellent antibacterial effect and hydrophobic effect after the two treatments.

In conclusion, the invention provides a switchable emulsion type oil-water separation nano antibacterial film and a preparation method thereof. The nano antibacterial film comprises a support substrate subjected to hydrophilic treatment, and a super-hydrophobic nanofiber layer and a super-hydrophilic nanofiber layer which are respectively and asymmetrically arranged on the upper surface and the lower surface of the support substrate; the super-hydrophobic nanofiber layer is formed by compounding a first nanofiber layer, nano antibacterial particles and a hydrophobic modifier, wherein the nano antibacterial particles and the hydrophobic modifier are loaded on the surface and the inside of the first nanofiber layer simultaneously; the super-hydrophilic nanofiber layer is formed by compounding a second nanofiber layer and nano antibacterial particles loaded on the surface and inside of the second nanofiber layer. The invention can selectively separate oil-in-water emulsion and water-in-oil emulsion by utilizing different wettabilities of the switchable emulsion type oil-water separation nano antibacterial film.

Although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the spirit and scope of the present invention.