CN111744369A - Janus-type distillation membrane with resistance to wetting and oil pollution, and preparation method and application thereof - Google Patents

Abstract

The invention relates to a Janus type distillation membrane with wetting resistance and oil stain resistance, and a preparation method and application thereof, wherein the distillation membrane comprises a base membrane, one side of the base membrane is a hydrophilic cortex, the other side of the base membrane is a fully-hydrophobic cortex, and the hydrophilic cortex is a polydopamine layer; the whole hydrophobic cortex layer is a PAL layer modified by dopamine. The Janus type distillation membrane has an asymmetric structure in the membrane thickness direction, one surface of the distillation membrane is hydrophilic, the other surface of the distillation membrane is super-hydrophobic, and the distillation membrane has good wetting resistance, pollution resistance and thermal stability. The membrane preparation method for membrane distillation is simple, low in cost and environment-friendly. The asymmetric all-hydrophobic membrane has good wetting resistance and pollution resistance, can treat high-salt oily sewage, has good stability, can basically achieve 100 percent of desalination, and keeps stable flux in long-time use.

Description

Janus-type distillation membrane with resistance to wetting and oil pollution, and preparation method and application thereof

technical field

The invention relates to a Janus-type distillation membrane with resistance to wetting and oil pollution, a preparation method and application thereof, and belongs to the technical field of bionic interface material technology and membrane distillation technology.

Background technique

Membrane distillation technology is a heat-driven membrane separation process, which uses a microporous hydrophobic membrane as the separation medium and the vapor pressure difference on both sides of the membrane as the driving force for mass transfer, so that the steam molecules on the hot side pass through the membrane pores and are condensed and enriched on the cold side. To achieve high-efficiency separation of water and pollutants, high-quality separation products can be obtained. The membrane distillation process has the advantages of up to 100% salt rejection rate, lower operating temperature, low-grade thermal energy such as waste energy, and lower requirements for membrane mechanical properties. It shows good separation effect and huge market potential in challenging water supply treatment.

However, with the development of the water industry and the needs of ecological protection, membrane distillation technology faces more complex treatment objects, such as industrial wastewater with complex components, polluted seawater or brackish water, oily wastewater, dye wastewater, etc. During operation, the durability of the membrane is greatly challenged and suffers from the dual constraints of membrane wetting and membrane fouling. Influence the application and promotion of distillation membranes. The ideal distillation membrane should have the characteristics of resistance to wetting, anti-pollution, high permeability, low thermal conductivity, and high thermal stability. The fully hydrophobic membrane has good stability and good hydrophobicity and oleophobicity in the air, but it has underwater lipophilicity and will be polluted by oily feedwater; although the hydrophilic composite membrane in the air has anti-pollution performance, it is not effective. Wetting of the membrane by low surface energy species is inhibited.

Chinese patent document CN107020017A discloses an anti-pollution composite distillation membrane and its preparation method and application. The composite membrane uses a polytetrafluoroethylene microfiltration membrane as a base membrane. Hydrophilic modification was performed on the hot side by interfacial polymerization to prepare a hydrophilic-hydrophobic composite distillation membrane with good anti-fouling ability. Although the membrane has good anti-fouling ability, it has poor performance in treating oily sewage and wastewater containing low surface energy substances (such as surfactants). Complex industrial wastewater is not applicable.

Chinese patent document CN108404685A relates to a method for preparing a distillation membrane for high permeability, wetting resistance and anti-pollution membrane distillation. The method steps are as follows: Step 1: Electrospin a hydrophobic polymer spinning solution to obtain a hydrophobic polymer spinning solution. Porous fiber membrane; second step: use electrostatic spray to spray the superhydrophobic skin layer spinning solution on the hydrophobic base film to obtain a superhydrophobic skin layer; third step: use electrostatic spray to spray the superhydrophilic skin layer spinning solution on the superhydrophobic skin layer , obtaining an asymmetric super-wetting composite nanofiber distillation membrane; the fourth step: drying the asymmetric super-wetting composite nanofiber distillation membrane. Since this method uses electrospinning to prepare the base film, there will be a problem of uneven film, and the production efficiency of electrospinning is low, and the mass and rapid production of the film cannot be realized, resulting in limited promotion of the film.

SUMMARY OF THE INVENTION

Aiming at the deficiencies of the prior art, the present invention provides a Janus-type distillation membrane with resistance to wetting and oil pollution, and a preparation method and application thereof. It is fully sparse and has good wetting resistance, anti-pollution performance and thermal stability. Modified on the basis of commercial membranes, the membrane can be quickly prepared by simple deposition and spraying methods, which solves the problem that commercial membranes are easily wetted by oil-containing liquids and low surface tension substances, and can be well applied to membrane distillation processes. , can be used to treat oily high-salt wastewater.

In order to solve the above problems, the present invention is achieved through the following technical solutions:

A Janus type distillation membrane resistant to wetting and oil pollution, comprising a base membrane, one side of the base membrane is a hydrophilic skin layer, the other side is a fully hydrophobic skin layer, and the hydrophilic skin layer is a polydopamine layer; the The fully hydrophobic skin layer is a fully hydrophobic material layer modified by dopamine.

A preparation method of a Janus-type distillation membrane resistant to wetting and oil pollution, comprising the following steps:

The first step is to prepare the hydrophilic skin layer:

The basement membrane is placed in a dopamine buffer solution and shaken to make the polydopamine evenly attached to the surface of the membrane, and then rinsed with deionized water to obtain a hydrophilic cortex basement membrane;

The second step is to prepare a fully hydrophobic skin layer:

(1) Add the fully sparse layer material to the Tirs-HCl buffer solution and sonicate to obtain a suspension, add dopamine to the suspension, stir and react at room temperature for 1-4 hours, wash the reacted product to neutrality, and dry , a dopamine-modified fully sparse layer material was obtained;

(2) Add absolute ethanol and ammonia or separate toluene to the dopamine-modified fully sparse layer material, and after ultrasonically mixing uniformly, add tetraethoxysilane (TEOS) and a fluorinating agent to fluoride at room temperature, and ultrasonically crush, Obtain a well-mixed fully phobic material suspension;

The third step, preparation of Janus type distillation membrane

The uniformly mixed fully hydrophobic material suspension is sprayed onto the other side of the hydrophilic skin base film prepared in the first step, and dried to obtain a Janus-type distillation film with resistance to wetting and oil pollution.

Preferably according to the present invention, in the first step, the concentration of dopamine in the dopamine buffer solution is 0.125-0.5 g/L.

Preferably according to the present invention, in the first step, the dopamine buffer solution is a Tirs-HCl buffer solution of dopamine, the concentration of the Tirs-HCl buffer solution is 10 mM, and pH=8.5. Tris-HCl buffer solution kept the reaction system at a constant pH.

Preferably according to the present invention, in the first step, the base film is a PTFE film, a PTFE film, a PVDF film or a PP film, and the size of the base film is 3*8cm.

Further preferably, the base film is a PTFE film.

Preferably according to the present invention, in the first step, the membrane is shaken in the dopamine buffer solution at a rotational speed of 50-300 r/min, a temperature of 20-30° C., and a shaking time of 3-6 hours.

According to a preferred embodiment of the present invention, in the second step (1), the fully sparse layer material is one of attapulgite PAL, carbon nanotube (CNT) or nanocellulose (CNF).

Most preferably, in the second step (1), the fully sparse layer material is attapulgite PAL.

Preferably according to the present invention, in the second step (1), when the all-sparse layer material is attapulgite PAL, the attapulgite PAL is activated first, and then added to the Tirs-HCl buffer solution, and the attapulgite PAL is activated as The attapulgite PAL was added to the hydrochloric acid solution and stirred for activation. After activation, it was washed with deionized water to pH 6, then dried in a vacuum oven to constant weight, and ground into powder.

When the fully sparse layer material is carbon nanotube (CNT) or nanocellulose (CNF), it is directly added to the Tirs-HCl buffer solution without activation.

Further preferably, the concentration of attapulgite PAL in the hydrochloric acid solution is 0.1 g/mL; the concentration of the hydrochloric acid solution is C _HCl = 1 mol/L; the stirring speed is 650 rpm; and the drying temperature is 105° C.

Preferably according to the present invention, in the second step (1), the concentration of the fully sparse layer material in the suspension is 0.001-0.002 g/L.

Further preferably, the concentration of the fully sparse layer material in the suspension is 0.0017 g/L.

Preferably according to the present invention, in the second step (1), after adding dopamine, the concentration of dopamine in the suspension is 0.05-1.5 g/L.

Preferably according to the present invention, in the second step (1), drying is vacuum drying at 60° C. for 10 hours.

Preferably according to the present invention, in the second step (2), the mass-volume ratio of the dopamine-modified fully sparse layer material to absolute ethanol is: (0.1-0.3): (8-10), unit, g/mL, dopamine The mass-volume ratio of the modified fully sparse layer material to ammonia water is: (0.1-0.3):(0.5-3), unit, g/mL.

Preferably according to the present invention, in the second step (2), the mass-volume ratio of the dopamine-modified fully sparse layer material to absolute ethanol is: (0.1-0.3): (40-60), unit, g/mL.

Preferably according to the present invention, in the second step (2), the mass-volume ratio of the dopamine-modified fully sparse layer material to tetraethoxysilane (TEOS) is: (0.1-0.3): (5-15), unit, g/μL.

Preferably according to the present invention, in the second step (2), the fluorinating agent is 1H, 1H, 2H, 2H-perfluorodecyl triethoxysilane (PFDTES), 1H, 1H, 2H, 2H-perfluorodecyl The volume ratio of triethoxysilane (PFDTES) to absolute ethanol is: (0.1-0.3): (8-10).

Preferably according to the present invention, in the second step (2), ultrasonic fragmentation is performed using a cell disruptor, the power is 288W, and the fragmentation time is 40 minutes.

According to a preferred embodiment of the present invention, in the third step, the amount of the suspension solution of the fully sparse material sprayed is 6 mL.

In the preparation method of the present invention, taking attapulgite PAL as an example of the all sparse layer material, acidizing PAL can disperse the nanorods, remove the impurity part and dissolve the inner layer, which is convenient for subsequent fluorination treatment. Grinding can form mesopores and micropores, which can effectively modify the structure and properties of PAL. TEOS and PFDTES form a fluorinated polysiloxane coating through hydrolysis and condensation to wrap PAL, forming a convex and microporous structure on the surface of PAL, forming a re-entrant structure, so that the coating formed after the suspension spraying has super-hydrophobic, super-phobic properties oil properties. In the preparation process of PAL suspension, the modification of PAL with dopamine utilizes its adhesion to make the PAL coating more firmly attached to the membrane surface, and the dopamine modification will not affect the properties of PAL, but it will make PAL agglomerate and affect the dispersion effect; TEOS Hydrolysis and condensation with PFDTES to form fluorinated polysiloxane can also bridge and induce the aggregation of PAL nanorods. Therefore, PAL is uniformly dispersed using a cell disruptor to form a relatively stable and uniform suspension.

Compared with the existing membrane distillation membrane, the Janus type distillation membrane of the present invention with resistance to wetting and oil pollution has the following beneficial effects:

1. The wetting-resistant and oil-resistant Janus-type distillation membrane of the present invention adopts the method of depositing dopamine to prepare the hydrophilic cortex. The amine group can self-polymerize on the surface of any material to form an ultra-thin hydrophilic polydopamine layer. The formed hydrophilic layer will not affect the properties of the base membrane itself, will not reduce the flux of the membrane, and is firmly attached to the membrane surface. Due to the hydrophilic properties of the coating, the membrane can achieve underwater oleophobicity and pollution resistance, and prevent the decrease of flux and effluent quality caused by the blockage of membrane pores by pollutants such as oil droplets; and the preparation of the hydrophilic skin layer is simple, fast and effective. Environmental friendly.

2. The wetting-resistant and oil-resistant Janus-type distillation membrane of the present invention uses modified PAL to prepare a fully sparse skin layer, and the dopamine-modified PAL is highly viscous and has a micro-nano structure suitable for constructing a biomimetic super fully sparse coating. , nanochannels and layered silicate micropores can easily form reentrant structures. The fully hydrophobic modified PAL suspension is sprayed onto the surface of the polytetrafluoroethylene (PTFE) membrane by a spray gun, and the spraying is uniform. It is superhydrophobic and can prevent the wetting of liquids with low surface tension including mineral oil, surfactants (such as: sodium lauryl sulfate, etc.), n-tetradecane, etc. The coating is firmly attached to the membrane surface and is not easy to fall off, so that the membrane has good stability, and the material cost is low and easy to obtain. This is the first time that PAL is used to prepare membranes for membrane distillation.

3. The method for producing a membrane for membrane distillation provided by the present invention is simple and low in cost, and is more environmentally friendly. The asymmetric fully hydrophobic membrane has good wetting resistance and anti-pollution properties, can treat high-salt oily wastewater, and has good stability, which can basically reach 100% desalination, and the flux remains stable in long-term use.

Description of drawings

1 is a scanning electron microscope picture of the superhydrophobic surface of the Janus film prepared by the method of Example 1.

FIG. 2 is a scanning electron microscope picture of the hydrophilic surface of the Janus membrane prepared by the method of Example 1. FIG.

3 is a photo of the contact angle of water in air of the superhydrophobic surface of the Janus membrane prepared by the method of Example 1.

4 is a photograph of the underwater oil contact angle of the hydrophilic surface of the Janus membrane prepared by the method of Example 1.

FIG. 5 is a schematic diagram of the flux and salt cut effect of testing the stability of the Janus membrane distillation process by the method of Example 2. FIG.

FIG. 6 is a schematic diagram of the flux resistance and salt cut-off effect of the Janus membrane distillation process being tested by the method of Example 2. FIG.

FIG. 7 is a schematic diagram showing the anti-oil fouling flux and salt interception effect of the Janus membrane distillation process using the method of Example 2. FIG.

Detailed ways

The present invention will be further described below with reference to specific embodiments and accompanying drawings to better understand the present invention, but the protection scope of the present invention is not limited to this.

The raw materials involved in the present invention are all prior art unless otherwise specified.

Example 1

A preparation method of a Janus-type distillation membrane resistant to wetting and oil pollution, the steps are as follows:

(1) Add dopamine to 10 mM Tirs-HCl buffer solution with pH=8.5 to make the concentration of dopamine solution 0.5 g/L. A commercial PTFE membrane with a size of 3*8cm was placed in the PDA solution and shaken under the conditions of 100r/min and 25°C, so that the PDA was evenly attached to the surface of the membrane.

(2) Rinse the membrane surface with deionized water at least three times to obtain a hydrophilic skin basement membrane;

(3) 5 g of PAL was added to 50 mL of a hydrochloric acid solution with a concentration of C _HCl = 1 M and stirred for 2 h for activation, and the stirring speed was 650 rpm. It was then washed with deionized water to pH 6, then dried to constant weight in a 105°C vacuum oven, and the dried PAL was ground to a powder.

(4) Take 0.1 g of PAL activated in step (3) and add it to 60 mL of Tirs-HCl buffer solution for sonication, then add dopamine to the uniformly mixed suspension to make the concentration reach 0.05-1.5 g/L, and stir at room temperature for 3 After the solution was fully mixed, it was centrifuged and washed to neutrality, and vacuum-dried at 60° C. for 10 hours to obtain PAL modified with dopamine.

(5) Take 0.1 g of the dopamine-modified PAL in step (4), add 8.6 mL of absolute ethanol, 1.4 mL of ammonia water, ultrasonically treat for 1 hour, and then add 10 μL of tetraethoxysilane (TEOS), 0.12 mL to the mixture 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (PFDTES), stirred at room temperature for 16 hours, and then disrupted with an ultrasonic cell disrupter at 288W for 40 minutes to obtain a fully mixed PAL suspension .

(6) Under the pressure of 0.2MPaN ₂ , use a spray gun to spray 4mL of the PAL suspension onto the other side of the vertically placed hydrophilic skin base film, put it into a vacuum oven at 80 ° C to dry for 6 hours, and then get the prepared Janus membrane.

The two sides of the Janus membrane are shown in Figure 1 and Figure 2, respectively. The hydrophilicity and hydrophobicity of both sides of the membrane were tested, and it was found that the water contact angle of the hydrophobic surface was above 160°, as shown in Figure 3; Wetted with mineral oil.

Example 2

A preparation method of a Janus-type distillation membrane resistant to wetting and oil pollution, the steps are as follows:

(1) Add dopamine to 10 mM Tirs-HCl buffer solution with pH=8.5 to make the concentration of dopamine solution 0.5 g/L. Put the commercial PVDF membrane with a size of 3*8cm into the PDA solution and shake it under the condition of 100r/min and the temperature of 25℃, so that the PDA is evenly attached to the surface of the membrane;

(2) Rinse the membrane surface with deionized water at least three times to obtain a hydrophilic skin basement membrane;

(3) Add 0.1 g of CNTs to 50 mL of Tirs-HCl buffer solution for sonication, then add dopamine to the uniformly mixed suspension to make the concentration 0.05-1.5 g/L, and stir at room temperature for 3 hours. After the solution is fully mixed , which were centrifuged and washed to neutrality, and vacuum-dried at 60 °C for 10 h to obtain dopamine-modified CNTs.

(4) Take 0.1 g of dopamine-modified CNT, add it to 50 mL of toluene, ultrasonically treat it for 30 minutes, and then add 10 μL of tetraethoxysilane (TEOS), 0.12 mL of 1H, 1H, 2H, 2H-perfluorodecane to the mixture triethoxysilane (PFDTES), stirred at room temperature for 15 hours, and then disrupted with an ultrasonic cell disrupter at 288 W for 40 minutes to obtain a completely homogeneously mixed CNT suspension.

(5) Under the pressure of 0.2MPaN ₂ , use a spray gun to spray 4mL of CNT suspension onto the other side of the vertically placed hydrophilic skin base film, and then put it into a vacuum oven at 80 °C to dry for 6 hours, and the prepared Janus film.

Example 3

A preparation method of a Janus-type distillation membrane resistant to wetting and oil pollution, the steps are as follows:

(1) Add dopamine to 10 mM Tirs-HCl buffer solution with pH=8.5 to make the concentration of dopamine solution 0.5 g/L. A commercial PP film with a size of 3*8cm was placed in the PDA solution and shaken under the conditions of 100 r/min and temperature of 25 °C, so that the PDA was evenly attached to the surface of the film.

(2) Rinse the membrane surface with deionized water at least three times to obtain a hydrophilic skin basement membrane;

(3) Add 0.1 g of CNF to 50 mL of Tirs-HCl buffer solution for sonication, then add dopamine to the well-mixed suspension to make the concentration reach 0.05-1.5 g/L, and stir at room temperature for 3 hours. After the solution is well mixed, it is centrifuged and washed until neutral. And vacuum-dried at 60 °C for 10 hours to obtain dopamine-modified CNFs.

(4) Take dopamine-modified CNF, add 8.6 mL of absolute ethanol and 1.4 mL of ammonia water, and ultrasonically treat for 1 hour. Then, 10 μL of tetraethoxysilane (TEOS) and 0.12 mL of 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES) were added to the mixture, and the mixture was stirred at room temperature for 20 hours. The crusher was crushed at 300W power for 40 minutes to obtain a CNF suspension that was mixed completely and uniformly.

(5) Use a spray gun to spray 4 mL of CNF suspension onto the other side of the vertically placed hydrophilic skin base film, and then put it into a vacuum oven at 80°C to dry for 6 hours to obtain the prepared Janus film.

Experimental example

Membrane distillation experiments were performed using the Janus membrane prepared in Example 1.

This example uses a direct contact membrane distillation process to evaluate the membrane. The hot side was 3.5wt.% sodium chloride aqueous solution (simulating seawater salinity) at 65°C, the cold side was deionized water at 25°C, the flow rate on both sides was controlled at 0.5L/min, and the effective membrane area was 24cm ² . The normalized flux is calculated according to J/J ₀ , where J is the real-time flux LMH (L/m ² /h), and J ₀ is the initial flux LMH (L/m when the membrane flux is stable) ² /h). The results are shown in Figure 5. The membrane has good stability within 20 hours of operation, the salt rejection rate is nearly 100%, and the pure water flux is basically stable.

Wetting resistance test of the membrane: the hot side is 65°C, the cold side is deionized water at 25°C, the flow rate on both sides is controlled at 0.5L/min, and the effective membrane area is 24cm ² . At the beginning, 0.1 mM SDS was added to the salt solution of 3.5 wt% NaCl. After the system was running for 2 hours, SDS was added to the hot side to make the solution SDS concentration 0.2 mM. After that, SDS was added to the hot side every 2 hours, so that the solution SDS concentration was 0.3mM, 0.4mM. The pure water flux and salt rejection of the pristine PTFE membrane and the prepared Janus membrane were tested by the same method. The test results of the two membranes are shown in Figure 6. The salt rejection of both membranes was nearly 100% within 8 hours of operation, but the pure water flux of the modified membrane was higher than that of the original membrane.

The anti-oil pollution test of the membrane: the hot side is 65°C, the cold side is deionized water at 25°C, the flow rate on both sides is controlled at 0.5L/min, and the effective membrane area is 24cm ² . Take 80mg of mineral oil and 1mL of TWEEN80, add it to 1000ml of 3.5% NaCl solution, use a homogenizer to stir at 10,000rpm for 5 minutes and then ultrasonicate for 10 minutes to obtain an oil-water mixture. Use this mixture as the feed solution to test the prepared Janus The pure water flux and salt rejection rate of the membrane, the results are shown in Figure 7. Under water, the original film is not resistant to mineral oil wetting, and oil droplets will directly wet the film. The Janus membrane has a stable flux within 6 hours of operation, and the salt rejection rate is nearly 100%.

Claims (10)

1. A Janus-type distillation membrane of wetting resistance and anti-oil pollution, comprising a base film, one side of the base film is a hydrophilic skin layer, and the other side is a fully hydrophobic skin layer, and the hydrophilic skin layer is a polydopamine layer; The fully thin cortex described above is the PAL layer modified with dopamine. 2. a preparation method of the Janus-type distillation membrane of wetting resistance and oil-resistance, comprising the steps as follows: The first step is to prepare the hydrophilic skin layer: The basement membrane is placed in a dopamine buffer solution and shaken to make the polydopamine evenly attached to the surface of the membrane, and then rinsed with deionized water to obtain a hydrophilic cortex basement membrane; The second step is to prepare a fully hydrophobic skin layer: (1) Add the fully sparse layer material to the Tirs-HCl buffer solution and sonicate to obtain a suspension, add dopamine to the suspension, stir and react at room temperature for 1-4 hours, wash the reacted product to neutrality, and dry , a dopamine-modified fully sparse layer material was obtained; (2) Add absolute ethanol and ammonia or separate toluene to the dopamine-modified fully sparse layer material, and after ultrasonically mixing uniformly, add tetraethoxysilane (TEOS) and a fluorinating agent to fluoride at room temperature, and ultrasonically crush, Obtain a well-mixed fully phobic material suspension; The third step, preparation of Janus type distillation membrane The uniformly mixed fully hydrophobic material suspension is sprayed onto the other side of the hydrophilic skin base film prepared in the first step, and dried to obtain a Janus-type distillation film with resistance to wetting and oil pollution. 3. preparation method according to claim 2 is characterized in that, in the first step, in the PDA buffer solution, the concentration of dopamine is 0.125-0.5g/L, and the PDA buffer solution is the Tirs-HCl buffer solution of dopamine, and the Tirs-HCl buffer solution The HCl buffer solution was 10 mM, pH=8.5. 4. preparation method according to claim 2 is characterized in that, described base film is PTFE film, PTFE film, PVDF film or PP film, base film size is 3*8cm, further preferably, described base film The membrane is a PTFE membrane, and the membrane is shaken in a dopamine PDA buffer solution at a speed of 50-300 r/min, a temperature of 20-30° C., and a shaking time of 3-6 hours. 5. preparation method according to claim 2, is characterized in that, in the second step (1), described full sparse layer material is attapulgite PAL, carbon nanotube (CNT) or nanocellulose (CNF) One of; most preferably, in the second step (1), the material of the fully sparse layer is attapulgite PAL. 6. preparation method according to claim 5 is characterized in that, in second step (1), when all sparse layer material is attapulgite attapulgite PAL, first attapulgite PAL is activated, then adds In Tirs-HCl buffer solution, attapulgite PAL is activated by adding attapulgite PAL to hydrochloric acid solution and stirring for activation. After activation, it is washed with deionized water to pH 6, then dried in a vacuum oven to constant weight, and ground. To powder, the concentration of attapulgite PAL in the hydrochloric acid solution is 0.1 g/mL; the concentration of the hydrochloric acid solution is C _HCl = 1 mol/L; the stirring speed is 650 rpm; and the drying temperature is 105 ° C. 7. preparation method according to claim 2 is characterized in that, in the second step (1), the concentration of all sparse layer material in the suspension is 0.001-0.002g/L, preferably, in the suspension The concentration of the sparse layer material is 0.0017 g/L; after adding dopamine, the concentration of dopamine in the suspension is 0.05-1.5 g/L; drying is vacuum drying at 60° C. for 10 hours. 8. preparation method according to claim 2 is characterized in that, in the second step (2), the mass volume ratio of the fully sparse layer material of dopamine modification and dehydrated alcohol is: (0.1-0.3): (8- 10), unit, g/mL, the mass-volume ratio of dopamine-modified fully sparse layer material to ammonia water is: (0.1-0.3):(0.5-3), unit, g/mL; The mass-volume ratio of tetraethoxysilane (TEOS) is: (0.1-0.3):(5-15), unit, g/μL. 9. preparation method according to claim 2 is characterized in that, in the second step (2), the fluorinating agent is 1H, 1H, 2H, 2H-perfluorodecyl triethoxysilane (PFDTES), 1H The volume ratio of ,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES) to absolute ethanol is: (0.1-0.3):(8-10). 10 . The preparation method according to claim 2 , wherein in the second step (2), ultrasonic fragmentation is performed using a cell disruptor, the power is 288W, and the fragmentation time is 40 minutes. 11 .

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