Polytetrafluoroethylene film for separating emulsion mixture and preparation method thereof

Abstract

The invention provides a polytetrafluoroethylene film for separating an emulsion mixture and a preparation method of the polytetrafluoroethylene film, and belongs to the technical field of functional materials and laser micromachining. The invention provides a polytetrafluoroethylene film for separating an emulsion mixture. The polytetrafluoroethylene film comprises a polytetrafluoroethylene film and a copper oxide nanowire, the polytetrafluoroethylene film contains a plurality of micro through holes, and the copper oxide nanowires grow on the surfaces of the inner walls of the micro through holes. The method comprises the following steps: constructing micro-through holes with good hole shapes in a polytetrafluoroethylene film by utilizing picosecond laser, presetting a film containing metal elements for the micro-through holes, performing chemical copper plating, and performing high-temperature and high-pressure heat treatment to generate copper oxide nanowires on the surfaces of the inner walls of the micro-through holes in situ; therefore, the polytetrafluoroethylene film for separating the emulsion mixture is obtained, and the problem that an oil-water separation film constructed by laser at present is difficult to be applied to separation of the emulsion mixture is solved.

Description

Technical Field

[0001] The invention relates to the technical field of functional materials and laser micro-machining, and in particular to a polytetrafluoroethylene film for separating an emulsion mixture and a preparation method thereof. Background Art

[0002] As the source of human life, water pollution has always attracted widespread attention. At present, many industries and fields, such as the petroleum industry, catering industry, metallurgy industry, mining industry, textile and leather industry, and national defense industry, produce a large amount of oily wastewater every year, including oily emulsion systems. If they are directly discharged, they will cause serious pollution to the water body; at the same time, frequent crude oil spills will cause a large number of deaths of animals and plants in the ocean and rivers, causing serious damage to their ecological balance. Therefore, how to deal with oily wastewater, including emulsion systems, will become a global problem and challenge in solving environmental pollution problems.

[0003] In order to separate oily wastewater, distillation, gravity, centrifugation, flotation, adsorption, coagulation, salting out and biological methods can be used according to the different physical, chemical and biological characteristics of water and oil phases. However, these methods still have the disadvantages of high energy consumption, low efficiency, narrow scope of application and possible secondary pollution, which greatly limits their scope of application. Therefore, it is particularly urgent to develop a low-cost, high-efficiency and widely applicable oil-water separation technology.

[0004] Due to the inconsistency of the surface tension of the oil phase and the water phase, the wetting properties on the surface of some functional materials are inconsistent. By utilizing this difference in wettability, under the action of the liquid's own gravity or external pressure, one component can be selectively allowed to penetrate through the film micropores, while the other component cannot penetrate through the film micropores, thereby achieving the separation of the oil-water mixture. Compared with traditional separation technology, membrane separation technology has the advantages of low operating cost, high separation efficiency, no secondary pollution and a wide range of applications.

[0005] At present, many technologies can be applied to the preparation of oil-water separation membranes, such as spraying, sol-gel, electrospinning, etc. Compared with the above methods, laser processing technology can process a wide range of materials and has the advantages of better processing area selectivity, less pollution, and non-contact. In particular, laser processing technology can perform precision processing with the help of computer software control, so it has great advantages in the preparation of oil-water separation membranes.

[0006] However, the oil-water separation film directly constructed by laser processing technology has good effects in separating floating oil (particle size>100 μm), dispersed oil (particle size between 10 μm~100 μm) and water mixtures, but the effect in separating emulsion mixtures (particle size between 0.1 μm~10 μm) is poor. The reason is that it is limited by the laser wavelength, the focal length of the focusing lens, the magnification of the beam expander and the waist radius, making the current minimum theoretical laser spot diameter about 10 μm. Therefore, the diameter of the through hole constructed in the film by laser is usually much larger than the diameter of the droplet in the emulsion system, resulting in the oil phase and the water phase in the emulsion system being able to penetrate through the through hole of the film, which makes it difficult to use the laser-constructed oil-water separation film to separate emulsion mixtures. Summary of the invention

[0007] In view of the deficiencies of the above prior art, the present invention provides a polytetrafluoroethylene film for separating emulsion mixtures and a preparation method thereof. By combining laser construction technology, chemical plating technology and heat treatment technology, microchannels and super-hydrophobic surfaces suitable for separating emulsion mixtures are constructed on the polytetrafluoroethylene film, thereby solving the problem that the current laser-constructed oil-water separation film is difficult to apply to separating emulsion mixtures.

[0008] To achieve the above purpose, the specific technical solutions of the present invention are as follows:

[0009] A polytetrafluoroethylene film for separating an emulsion mixture comprises a polytetrafluoroethylene (PTFE) film and copper oxide (CuO) nanowires; the polytetrafluoroethylene film contains a plurality of micro-through holes, and the copper oxide nanowires grow on the inner wall surfaces of the micro-through holes.

[0010] Preferably, the diameter of the micro-through hole is 30-70 μm.

[0011] Preferably, the growth length of the copper oxide nanowires is 20 to 40 μm.

[0012] Preferably, the distance between adjacent micro-through holes is 80-130 μm.

[0013] Preferably, the thickness of the polytetrafluoroethylene film is 0.3 ~ 1.50 mm.

[0014] The method for preparing the polytetrafluoroethylene film for separating an emulsion mixture comprises the following steps:

[0015] (1) Constructing micro-through holes in a polytetrafluoroethylene film of a certain thickness;

[0016] (2) immersing the polytetrafluoroethylene film of step (1) in a solution containing metal ions or metal complex ions, and after ultrasonic treatment and static treatment, taking out and drying, obtaining a polytetrafluoroethylene film in which the inner wall surface of the micro-through hole and the outer surface of the polytetrafluoroethylene film are covered with a solid film of metal elements; the metal ions in the solid film of metal elements serve as catalytic active species, and ultrasonic treatment is used to allow the solution of metal ions or metal complex ions to penetrate into the micro-nano structure of the inner wall surface of the micro-through hole of the polytetrafluoroethylene film etched by laser, so as to facilitate the deposition of metal ions or metal complex ions in the grooves or holes of these micro-nano structures; and then static treatment is performed for a period of time, so that more metal ions or metal complex ions can be deposited in the inner surface grooves or holes of the micro-through hole of the polytetrafluoroethylene film.

[0017] (3) Cleaning the polytetrafluoroethylene film of step (2); the purpose of cleaning is to clean the solid film of metal elements on the outer surface of the polytetrafluoroethylene film, while the solid film of metal elements on the inner wall surface of the micro-through hole is not completely cleaned; since the surface of the polytetrafluoroethylene film is relatively smooth, the solid film of metal elements on the surface is easy to clean, while the inner wall of the micro-through hole is covered with a large number of grooves and hole structures, and the solid film of metal elements inside is not easy to clean;

[0018] (4) chemically copper plating the polytetrafluoroethylene film after cleaning in step (3) to metallize the inner wall surface of the micro-through hole;

[0019] (5) performing laser surface roughening on the inner wall surface of the micro-through hole of the polytetrafluoroethylene film in step (4), so that a large number of composite rough structures of micrometer size and nanometer size are generated on the inner wall surface of the micro-through hole;

[0020] (6) The polytetrafluoroethylene film in step (5) is heat treated at high temperature and high pressure to generate copper oxide (CuO) nanowires on the inner wall surface of the micro-through holes, thereby obtaining a polytetrafluoroethylene film that can be used to separate the emulsion mixture.

[0021] Preferably, in step (1), the specific operation of constructing the micro-through holes is: laying a polytetrafluoroethylene film of a certain thickness on a copper plate with a smooth surface, then setting the diameter of the micro-through holes and the distance between adjacent holes, adjusting the processing parameters of the femtosecond laser, and constructing micro-through holes for oil-water separation in the polytetrafluoroethylene film; the laser wavelength is an ultraviolet band laser.

[0022] Preferably, in step (2), the metal ions or metal complex ions include one or more of palladium, iron, nickel, copper, zinc, aluminum, manganese, molybdenum, gold, ruthenium, tungsten, rhodium and silver.

[0023] Preferably, in step (2), the power of the ultrasonic treatment is 120 to 180 W, the time of the ultrasonic treatment is 20 to 60 s, and the time of the static treatment is 60 to 150 s.

[0024] Preferably, in step (3), the cleaning solvent is water or 95% ethanol, and the cleaning time is 5 to 20 s.

[0025] Preferably, in step (4), the time of the chemical copper plating is 8 to 15 min, and the plating solution of the chemical copper plating is composed of 10 g / L CuSO4·5H2O, 15 ml / L formaldehyde, 30 g / L EDTA·2Na, 40 g / L potassium sodium tartrate, 10 mg / L α,α′-bipyridine, 100 mg / L potassium ferrocyanide, and 10 mg / L polyethylene glycol; the temperature of the plating solution is 50°C, and the pH of the plating solution is 12.5; the chemical copper plating time cannot be too short or too long, because too short a copper plating time will result in less copper plating layer generated in the micro-through hole, which will directly affect the subsequent generation of copper oxide nanowires; while too long a copper plating time will result in the generation of too much copper plating layer, and in severe cases, the laser-constructed micro-through hole will be completely blocked and closed, causing it to lose its oil-water separation performance.

[0026] Preferably, in step (6), the heat treatment is carried out in oxygen, and the oxygen flow rate is 10 to 30 mL / min.

[0027] Preferably, in step (6), the heat treatment pressure is 4 to 5 MPa, the heat treatment temperature is 200 to 250°C, and the heat treatment time is 6 to 24 h; the oxygen is introduced to promote the rapid oxidation reaction of copper to generate copper oxide nanowires, and the high pressure can allow the copper oxide nanowires to grow rapidly in the range of 200 to 250°C. At the same time, the temperature is lower than the melting point of polytetrafluoroethylene and will not affect the micro-nano structure on the polytetrafluoroethylene film.

[0028] The thickness of the polytetrafluoroethylene film of the present invention is selected between 0.3 and 1.50 mm, and the film should not be too thin or too thick. Because in the separation process of the emulsion mixture, the separation is mainly achieved by relying on the gravity of the emulsion, and a too thin polytetrafluoroethylene film is difficult to support a certain weight of the emulsion mixture; and a too thick polytetrafluoroethylene film will make it difficult for the femtosecond laser to etch micro-through holes for oil-water separation. The polytetrafluoroethylene film is laid flat on a copper plate with a smooth surface for drilling, so that the laser will first etch micro-through holes in the polytetrafluoroethylene film, and then the laser will etch the copper plate. Under the action of the laser etching Coulomb explosion, a large number of copper particles will be ejected and reacted in the etched grooves or holes on the inner surface of the micro-through holes, which can become active species for subsequent chemical copper plating, inducing it to undergo a chemical copper plating reaction.

[0029] The present invention chooses to use femtosecond laser for processing and the wavelength is in the ultraviolet band because the etching threshold of polytetrafluoroethylene film is relatively high. As is known to all, the pulse width of femtosecond laser is in the order of femtoseconds, corresponding to a high peak power of laser etching. At the same time, the wavelength of ultraviolet band laser is short, the frequency is high, and the corresponding single photon energy is high. In the process of etching polytetrafluoroethylene film, photochemical action is mainly used, so that micro-through holes with good hole shape can be constructed in the polytetrafluoroethylene film. The present invention controls the diameter of the micro-through hole drilled by laser to 30 ~ 70 μm, and through subsequent surface roughening and heat treatment, the growth length of copper oxide nanowires is controlled to 20 ~ 40 μm. If the diameter of the micro-through hole is too small, it is easy for the generated copper oxide nanowires to completely block the through hole, and lose the function of emulsion separation; if the diameter of the micro-through hole is too large, it will cause the through hole to be unable to be completely covered by the generated copper oxide nanowires, so that the effect of separating the emulsion is deteriorated.

[0030] Compared with the prior art, the present invention is beneficial in that:

[0031] (1) The present invention achieves effective regulation of the separation efficiency of the emulsion mixture (i.e., the emulsion separation effect) and the oil flux (i.e., the speed of emulsion separation) by effectively regulating the diameter and pore density of the micropores of the polytetrafluoroethylene oil-water separation membrane and by coordinating the length and richness of the copper oxide nanowires in the micropores.

[0032] (2) The present invention combines laser construction technology, chemical plating technology and heat treatment technology to prepare hydrophobic copper oxide nanowires on the inner wall of the micro-through holes of the polytetrafluoroethylene oil-water separation membrane, thereby reducing the diameter of the laser-etched micro-through holes and solving the problem that the polytetrafluoroethylene membrane constructed solely by laser technology is difficult to use in separating emulsion mixtures. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The micro-through hole array structure constructed in the polytetrafluoroethylene film by femtosecond laser;

[0034] Figure 2 This is a local enlarged image of the micro-through holes in the polytetrafluoroethylene film after laser drilling.

[0035] Figure 3 This is a diagram showing the structure of conical micro-nano protrusions on the surface of polytetrafluoroethylene after laser surface roughening;

[0036] Figure 4 a is a schematic diagram of the static contact angle of water on the surface of polytetrafluoroethylene film; Figure 4 b is a schematic diagram of the static contact angle of oil (1,2-dichloroethane) on the surface of polytetrafluoroethylene film;

[0037] Figure 5 The morphology of copper oxide nanowires generated on the inner surface of micro-through-holes in polytetrafluoroethylene film after heat treatment for 4 hours;

[0038] Figure 6 This is a local enlarged image of the copper oxide nanowires on the inner surface of the micro-through hole. DETAILED DESCRIPTION

[0039] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] The invention provides a polytetrafluoroethylene film for separating an emulsion mixture, comprising a polytetrafluoroethylene (PTFE) film and copper oxide (CuO) nanowires; the polytetrafluoroethylene film contains a plurality of micro-through holes, and the copper oxide nanowires grow on the inner wall surfaces of the micro-through holes.

[0041] The growth length of the copper oxide nanowires is 20 to 40 μm.

[0042] In some examples, the diameter of the micro-through hole is 30-70 μm.

[0043] In some examples, the distance between adjacent holes and the center of the micro-through holes is 80-130 μm.

[0044] In some examples, the thickness of the polytetrafluoroethylene film is 0.3 to 1.50 mm.

[0045] The method for preparing the polytetrafluoroethylene film for separating an emulsion mixture comprises the following steps:

[0046] (1) Laser drilling: Select a certain thickness of polytetrafluoroethylene as the film for preparing the emulsion mixture separation, spread it flat on a smooth copper plate, then set the hole diameter and the distance between adjacent holes, adjust the processing parameters of the femtosecond laser, and construct micro-through holes for oil-water separation in the polytetrafluoroethylene film;

[0047] (2) Pre-setting a thin film containing metal elements: immersing the polytetrafluoroethylene film of step (1) in a solution containing metal ions or metal complex ions, and after ultrasonic treatment and static treatment for a period of time, taking it out and drying it to obtain a polytetrafluoroethylene film in which the inner wall surface of the micro-through hole and the outer surface of the polytetrafluoroethylene film are covered with a solid thin film of metal elements;

[0048] (3) Cleaning: Cleaning the polytetrafluoroethylene film in step (2);

[0049] (4) Chemical copper plating: chemically plating the polytetrafluoroethylene film cleaned in step (3) with copper;

[0050] (5) Laser surface roughening: using a laser with appropriate parameters to roughen the inner wall surface of the micro-through hole of the polytetrafluoroethylene film in step (4), so that a large number of micron-sized and nano-sized composite rough structures are generated on the inner wall surface of the micro-through hole;

[0051] (6) Heat treatment: The polytetrafluoroethylene film material in step (5) is placed in a high temperature and high pressure reactor for heat treatment, so that copper oxide (CuO) nanowires are generated on the inner wall surface of the micro-through hole, thereby obtaining a polytetrafluoroethylene film material that can be used to separate the emulsion mixture.

[0052] In some examples, in step (2), the metal ions or metal complex ions include one or more of palladium, iron, nickel, copper, zinc, aluminum, manganese, molybdenum, gold, ruthenium, tungsten, rhodium, and silver.

[0053] In some examples, in step (2), the power of the ultrasonic treatment is 120 to 180 W, the time of the ultrasonic treatment is 20 to 60 s, and the time of the static treatment is 60 to 150 s.

[0054] In some examples, in step (3), the cleaning solvent is water or 95% ethanol, and the cleaning time is 5 to 20 seconds.

[0055] In some examples, in step (6), the heat treatment is performed in oxygen, and the oxygen flow rate is 10 to 30 mL / min; the heat treatment pressure is 4 to 5 MPa, the heat treatment temperature is 200 to 250 °C, and the heat treatment time is 6 to 24 h.

[0056] Example 1

[0057] A polytetrafluoroethylene film for separating an emulsion mixture, the preparation steps are as follows:

[0058] (1) Thin film laser drilling: The hole diameter is designed to be 50 μm, the distance between adjacent holes is 120 μm, and a femtosecond laser with a wavelength of 355 nm and a focused spot diameter of 20 μm is used for drilling. The drilling parameters are: laser power of 10 W, pulse frequency of 200 kHz, and scanning speed of 150 mm / s. Figure 1 This is a micro-through hole array structure constructed in a polytetrafluoroethylene film by femtosecond laser. Figure 2 This is a local enlarged image of the micro-through holes in the polytetrafluoroethylene film after laser drilling.

[0059] (2) Pre-setting a film containing metal elements: Place the polytetrafluoroethylene film after laser drilling in step (1) in a 1.5 mol / L PdCl2 solution and perform ultrasonic treatment for 60 s using an ultrasonic cleaner with a power of 120 W. Then, place the film at rest for 90 s and take it out and place it in a 110 °C oven to dry for 2 h.

[0060] (3) Cleaning: Rinse the polytetrafluoroethylene film obtained in step (2) in distilled water for 10 s.

[0061] (4) Chemical copper plating: The polytetrafluoroethylene film cleaned in step (3) is placed in a chemical plating solution for chemical copper plating. The chemical plating solution used is composed of 10 g / L CuSO4·5H2O, 15 ml / L formaldehyde, 30 g / L EDTA·2Na, 40 g / L potassium sodium tartrate, 10 mg / L α,α′-bipyridine, 100 mg / L potassium ferrocyanide, and 10 mg / L polyethylene glycol. During the chemical plating, the temperature is controlled to be 50°C, the pH value is 12.5, and the chemical plating time is 12 min.

[0062] (5) Laser surface roughening: The polytetrafluoroethylene film obtained in step (4) was placed on a laser processing platform, and a femtosecond laser with a wavelength of 355 nm and a focused spot diameter of 20 μm was used to roughen the surface of the polytetrafluoroethylene film by a grid scanning method. The roughening parameters were: laser power of 4.0 W, pulse frequency of 400 kHz, scanning speed of 1500 mm / s, and scanning spacing of 25 μm. Figure 3 This is a diagram of the conical micro-nano protrusion structure on the surface of polytetrafluoroethylene after laser surface roughening. Figure 4 4a and 4b are schematic diagrams of the static contact angles of water and oil (1,2-dichloroethane) on the surface of the polytetrafluoroethylene film, respectively. It can be seen that the prepared polytetrafluoroethylene film shows good superhydrophobicity and superoleophilicity.

[0063] (6) Heat treatment: The polytetrafluoroethylene film prepared in step (5) was placed in a high temperature and high pressure reactor for heat treatment at an oxygen flow rate of 20 mL min -1 The heat treatment pressure was 4 MPa, the heat treatment temperature was 230 ℃, and the heat treatment time was 2h, 4 h, 6 h, 8 h, 10 h, 12 h, and 24 h, respectively. Figure 5 This is the morphology of copper oxide nanowires generated on the inner wall surface of the micro-through-holes in the polytetrafluoroethylene film after heat treatment for 4 hours. Figure 6 This is a local enlarged image of the copper oxide nanowires on the inner wall surface of the micro-through hole after heat treatment for 4 hours.

[0064] (7) Emulsion separation test: An emulsion mixture was prepared with 1,2-dichloroethane and water in a volume ratio of 48:2. The separation efficiency and separation rate (oil flux) of the emulsion mixture were tested using the polytetrafluoroethylene film obtained in step (6). The test results are shown in Table 1.

[0065] Table 1: Separation efficiency and oil flux of polytetrafluoroethylene membranes for separation of emulsion mixtures with different heat treatment times

[0066]

[0067] It can be seen from Table 1 that with the continuous increase of heat treatment time, the oil flux of the polytetrafluoroethylene membrane separating the emulsion mixture continues to decrease, while the corresponding separation efficiency continues to increase. When the heat treatment time is not less than 6 h, the emulsion separation effect exceeds 99.0%.

[0068] Example 2

[0069] (1) Thin film laser drilling: The hole diameters were designed to be 30 μm, 40 μm, 50 μm, 60 μm, and 70 μm, respectively, and the distance between adjacent holes was 50 μm. A femtosecond laser with a wavelength of 355 nm and a focused spot diameter of 20 μm was used for drilling. The drilling parameters were: laser power of 9 W, pulse frequency of 400 kHz, and scanning speed of 150 mm / s.

[0070] (2) Pre-setting a thin film containing metal elements: Place the thin film after laser drilling in step (1) in a 1.5 mol / L PdCl2 solution, and ultrasonically treat it in a 130 W ultrasonic cleaning machine for 50 s. Then, let it stand for a preferably 120 s, and then take it out and place it in a 110 °C oven to dry for 2 h.

[0071] (3) Cleaning: Rinse the polytetrafluoroethylene film in step (2) in 96% ethanol for 15 s.

[0072] (4) Chemical copper plating: The polytetrafluoroethylene film material cleaned in step (3) is placed in a chemical plating solution for chemical copper plating. The chemical plating solution is composed of 10 g / L CuSO4·5H2O, 15 ml / L formaldehyde, 30 g / L EDTA·2Na, 40 g / L potassium sodium tartrate, 10 mg / L α,α′-bipyridine, 100 mg / L potassium ferrocyanide, and 10 mg / L polyethylene glycol. During the chemical plating, the temperature is controlled to be 50°C, the pH value is 12.5, and the chemical plating time is 10 min.

[0073] (5) Laser surface roughening: The polytetrafluoroethylene film obtained in step (4) was placed on a laser processing platform. A femtosecond laser with a wavelength of 355 nm and a focused spot diameter of 20 μm was used to roughen the surface of the polytetrafluoroethylene film by a grid scanning method. The roughening parameters were: laser power of 4.5 W, pulse frequency of 200 kHz, scanning speed of 1300 mm / s, and scanning spacing of 30 μm.

[0074] (6) Heat treatment: The polytetrafluoroethylene film material prepared in step (5) was placed in a high temperature and high pressure reactor for heat treatment at an oxygen flow rate of 20 mL min -1 The heat treatment pressure is preferably 5 MPa, the heat treatment temperature is preferably 220 °C, and the heat treatment time is preferably 10 h.

[0075] (7) Emulsion separation test: An emulsion mixture was prepared with 1,2-dichloroethane and water in a volume ratio of 48:2. The separation efficiency and separation rate (oil flux) of the emulsion mixture were tested using the polytetrafluoroethylene film obtained in step (6). The test results are shown in Table 2.

[0076] Table 2: Efficiency and oil flux of polytetrafluoroethylene membranes with different micropore diameters in separating emulsion mixtures

[0077]

[0078] It can be seen from Table 2 that with the continuous increase in the aperture of the laser-etched micro-through holes, the oil flux of the polytetrafluoroethylene membrane separating the emulsion mixture continues to increase, while the corresponding oil-water separation efficiency continues to decrease.

[0079] The above specific embodiments describe the implementation of the present invention in detail, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the claims and technical concept of the present invention, the technical solution of the present invention can be modified and changed in many simple ways, and these simple modifications all belong to the protection scope of the present invention.

Claims

1. A polytetrafluoroethylene membrane for separating an emulsion mixture, characterized in that: It comprises a polytetrafluoroethylene film and copper oxide nanowires; the polytetrafluoroethylene film contains a plurality of micro-through holes, and the copper oxide nanowires grow on the inner wall surfaces of the micro-through holes.

2. A polytetrafluoroethylene membrane for separating an emulsion mixture according to claim 1, characterized in that: The diameter of the micro-through hole is 30-70 μm.

3. A polytetrafluoroethylene film for separating an emulsion mixture according to claim 1, characterized in that: The growth length of the copper oxide nanowires is 20 to 40 μm.

4. A polytetrafluoroethylene film for separating an emulsion mixture according to claim 1, characterized in that: The distance between adjacent micro-through holes is 80-130 μm.

5. A polytetrafluoroethylene membrane for separating an emulsion mixture according to claim 1, characterized in that: The thickness of the polytetrafluoroethylene film is 0.3 to 1.50 mm.

6. A method for preparing a polytetrafluoroethylene film for separating an emulsion mixture, characterized in that: The following steps are involved: (1) Constructing micro-through holes in a polytetrafluoroethylene film of a certain thickness; (2) immersing the polytetrafluoroethylene film of step (1) in a solution containing metal ions or metal complex ions, and after ultrasonic treatment and static treatment, taking out and drying, to obtain a polytetrafluoroethylene film in which the inner wall surface of the micro-through hole and the outer surface of the polytetrafluoroethylene film are covered with a solid film of the metal element; (3) cleaning the polytetrafluoroethylene film of step (2); (4) chemically copper plating the polytetrafluoroethylene film cleaned in step (3); (5) roughening the inner wall surface of the micro-through hole of the polytetrafluoroethylene film in step (4) so ​​that a large number of composite rough structures of micrometer size and nanometer size are generated on the inner wall surface of the micro-through hole; (6) The polytetrafluoroethylene film in step (5) is heat treated at high temperature and high pressure to generate copper oxide nanowires on the inner wall surface of the micro-through holes, thereby obtaining a polytetrafluoroethylene film for separating the emulsion mixture.

7. The method for preparing a polytetrafluoroethylene film for separating an emulsion mixture according to claim 6, characterized in that: The specific operation of constructing the micro-through holes is: laying a polytetrafluoroethylene film of a certain thickness on a copper plate with a smooth surface, then setting the diameter of the micro-through holes and the distance between adjacent holes, adjusting the processing parameters of the femtosecond laser, and constructing micro-through holes for oil-water separation in the polytetrafluoroethylene film.

8. The method for preparing a polytetrafluoroethylene film for separating an emulsion mixture according to claim 6, characterized in that: The power of the ultrasonic treatment is 120 to 180 W, the time of the ultrasonic treatment is 20 to 60 s, and the time of the static treatment is 60 to 150 s.

9. The method for preparing a polytetrafluoroethylene film for separating an emulsion mixture according to claim 6, characterized in that: The heat treatment is carried out in oxygen, and the oxygen flow rate is 10 to 30 mL / min.

10. The method for preparing a polytetrafluoroethylene film for separating an emulsion mixture according to claim 6, characterized in that: The heat treatment pressure is 4-5 MPa, the heat treatment temperature is 200-250°C, and the heat treatment time is 6-24 h.

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