ZIF-8-based multi-scale high-permeability super-hydrophobic membrane for membrane distillation

Abstract

The invention relates to a preparation method of a high-permeability super-hydrophobic membrane for membrane distillation, which comprises the following steps: preparing a PVDF (Polyvinylidene Fluoride) membrane containing ZIF-8 through a one-step method, then mixing the prepared ZIF-8 nanoparticles and a silane coupling agent in ethanol, heating and stirring to form milk white liquid, taking a resin material as a reinforcing material, and preparing the high-permeability super-hydrophobic membrane for membrane distillation. And spraying the prepared coating liquid onto a PVDF (Polyvinylidene Fluoride) membrane containing ZIF-8 by adopting a spraying method to form the super-hydrophobic membrane. The method has the advantages that the in-situ growth ZIF-8 and the sprayed ZIF-8 are different in forming process, the formed particle sizes are different, the particle size range of the one-step in-situ growth ZIF-8 is 500-1000 nm, the particle size range of the sprayed ZIF-8 is 200-400 nm, multiple scales are formed through combination of the ZIF-8 and the sprayed ZIF-8, and the formed film has good permeability and hydrophobicity; the resin material in the coating greatly enhances the durability of the membrane, and is beneficial to long-term efficient and stable operation of the membrane distillation process; spray generated by the selected nozzle is uniform in distribution, and an excellent effect can be achieved in the jet flow application field requiring covering of one area. The preparation method is simple, and the prepared super-hydrophobic membrane has wide application.

Description

Technical Field

[0001] The invention relates to a high-permeability super-hydrophobic membrane, in particular to a high-permeability super-hydrophobic membrane for membrane distillation and a preparation method thereof, belonging to the technical field of membrane preparation. Background Art

[0002] Fresh water, as an important component of the life-sustaining system, is a limited resource that is unevenly distributed on Earth. Although 97.4% of the Earth's surface is covered by oceans and salt lakes, only about 2.6% is fresh water. Due to the small proportion of fresh water in the world, many areas cannot obtain safe and clean drinking water, and cost-effective, reliable and successful methods are urgently needed to treat local raw water sources.

[0003] In recent years, membrane distillation (MD), as a new type of heat-driven membrane technology, has shown good application prospects in the field of wastewater treatment due to its mild operating conditions, high water production rate, good separation performance, and the use of industrial waste heat. In addition, compared with traditional pressure-driven membrane technologies such as nanofiltration and reverse osmosis, membrane distillation does not require high quality of raw water. When treating high-concentration and difficult-to-degrade wastewater, high-quality output water can be obtained, and it has been used to treat typical wastewater.

[0004] Although membrane distillation technology has great advantages, membrane distillation as a separation technology also has many imperfections, which is the main reason why the technology has not been applied on a large scale in industry so far: ① The permeability of the membrane is low, and the membrane is easily wetted; ② After long-term use, the performance of the membrane is greatly reduced and lacks durability. Therefore, how to improve the air permeability, hydrophobicity and durability of the membrane in membrane distillation has become a hot topic of research. There is a ZIF-8 dual-scale super hydrophobic membrane for membrane distillation. Nano- and micro-sized ZIF-8 particles are synthesized, mixed and hydrophobically modified by POTS, and then deposited on a PTFE substrate by a spray method. The membrane prepared by this method reduces the membrane porosity as the ZIF-8 coating is deposited, and the ZIF-8 particles are easy to fall off after long-term use, and the nano- and micro-sized ZIF-8 particles are not easy to be evenly distributed on the membrane surface.

[0005] The invention prepares a PVDF membrane containing ZIF-8 by a one-step method, wherein the ZIF-8 grows uniformly on the membrane, and suitable silane coupling agents and resin materials are selected for the prepared ZIF-8 nanoparticles, and the prepared ZIF-8 nanoparticles are prepared into a coating according to a suitable ratio, and the coating is sprayed onto the PVDF membrane containing the uniformly grown ZIF-8 according to a specific spraying route by a spray gun. The in-situ grown ZIF-8 and the sprayed ZIF-8 have different formation processes, and the formed particle sizes are different, so that the surface coating has a multi-layered and uniform concave-convex structure, and the hydrophobic property of the membrane is improved. Moreover, the resin material in the coating greatly enhances the durability of the membrane, prevents the ZIF-8 from falling off, and is conducive to the long-term, efficient and stable operation of the membrane distillation process. Summary of the invention

[0006] Step 1) Synthesis of PVDF membrane containing ZIF-8: The functional material solution is prepared by the following components in mass percentage: 10%-15% PVDF powder, 1.8%-3.6% zinc acetate dihydrate, 1.8%-10.8% 2-methylimidazole, and the rest is NMP solution. Add PVDF powder to NMP solution, stir it hydrothermally at 55-65°C until it is completely dissolved, then add zinc acetate dihydrate and 2-methylimidazole and continue to stir it hydrothermally at 55-65°C to form a casting solution, use a scraper to scrape the film, and then immerse it in pure water to form a PVDF membrane containing ZIF-8; Step 2) Preparation of coating: 1.8%-3.6% zinc acetate dihydrate, 1.8%-10.8% 2-methylimidazole, 1.3-6.5% silane coupling agent material, 1.3-2.6% resin material, and the rest is anhydrous ethanol. Zinc acetate dihydrate and 2-methylimidazole are used to synthesize ZIF-8 nanoparticles at 20-25°C, the silane coupling agent material is added to anhydrous ethanol and stirred, and the prepared ZIF-8 nanoparticles are added to the solution, and the resin material is added after ultrasonic treatment until it is evenly dispersed, and the ZIF-8@silane coupling agent@resin coating is prepared after ultrasonic treatment until it is evenly dispersed; Step 3): Preparation of super-hydrophobic film: fix the PVDF film containing ZIF-8 on a glass plate, clean the spray gun with deionized water, pour the coating prepared in step (2) into the spray gun filling barrel, tilt the nozzle 30-90° and place it above the substrate at a height of 10-20 cm, adjust the spray gun air pressure to spray the coating onto the PVDF film surface according to the specified spraying route at a spraying pressure of 0.3-0.5 MPa, and spray for 10-15 s. Finally, dry the sprayed PVDF film in a 55°C-70°C oven to obtain a super-hydrophobic film.

[0007] Preferably, the silane coupling agent material in step 2) is one or more of 3-glycidoxypropyltriethoxysilane, polydimethylsiloxane, vinyltrimethoxysilane, and 1H,1H,2H,2H-perfluorooctyltriethoxysilane.

[0008] Preferably, the resin material in step 2) is one or more of epoxy resin, silicone rubber, and phenolic resin.

[0009] Preferably, the spray gun nozzle in step 3) is a solid cone nozzle or a fan-shaped nozzle.

[0010] Preferably, the spraying route in step 3) is one of S-shaped, square and circular.

[0011] The present invention also provides a method for preparing a high permeability super hydrophobic membrane for membrane distillation: a high permeability super hydrophobic membrane is prepared, characterized in that the water contact angle of the super hydrophobic membrane is 140.3-164.2°, and the permeability is 8.7-22.3 kg·m -2 ·h -1 After 100 hours of continuous use, the water contact angle value decreased by 1.8%-3.9%, and the permeability value decreased by 1.7%-3.6%.

[0012] Compared with the prior art, the present invention has the following beneficial effects: The invention prepares a PVDF membrane containing ZIF-8 by a one-step method, wherein ZIF-8 grows uniformly on the membrane, the formation of ZIF-8 reduces the density of a PVDF matrix, increases the porosity of the matrix, and the formed membrane has good permeability; then, the ZIF-8 modified coating is sprayed onto the membrane surface by using different spraying routes and spraying heights, the in-situ grown ZIF-8 and the sprayed ZIF-8 have different formation processes, and the formed particle sizes are different, the particle size range of the in-situ grown ZIF-8 by the one-step method is 500-1000nm, and the particle size range of the sprayed ZIF-8 is 200-400nm, and the combination of the two forms a multi-scale, so that The surface coating has a multi-level, uniform concavo-convex structure, so that there are more air gaps between the membrane surface and the feed liquid, and these air gaps can reduce the contact area between the droplet and the membrane surface, prevent the liquid from penetrating into the pores of the membrane, thereby enhancing the hydrophobicity of the membrane material, and the evaporated gas can enter the pores through the air gap, which is conducive to the transmission of steam in the membrane pores, thereby increasing the permeation of the material; while obtaining the super-hydrophobic film of high permeability, the resin material in the coating greatly enhances the durability of the film, which is conducive to the long-term, efficient and stable operation of the membrane distillation process; the spray generated by the selected nozzle is evenly distributed, and can play an excellent effect for the jet application field requiring to cover an area. The manufacturing method of the present invention is simple, and the prepared high-permeability super-hydrophobic film has a wide range of uses. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is the spraying process condition diagram; Figure 2 The data graphs of high permeability superhydrophobic membranes of various examples; Figure 3 is a picture of ZIF-8 particles prepared in Example 1; Figure 4 This is a picture of the high permeability super hydrophobic membrane prepared in Example 1 Figure 5 The surface SEM image of the high permeability super-hydrophobic membrane prepared in Example 3; Figure 6 Water contact angle image of the high permeability super hydrophobic film prepared in Example 5; Figure 7 It is the nozzle style model diagram and spraying effect diagram; Figure 8 Map the spray route for the spray gun; Fig. 9 Schematic diagram of nozzle height and nozzle tilt angle. Implementation

[0014] The present invention is further described below in conjunction with specific embodiments. Example

[0015] Step 1) Synthesis of PVDF membrane containing ZIF-8: The functional material solution is prepared by the following components in mass percentage: 10.0% PVDF powder, 1.8% zinc acetate dihydrate, 1.8% 2-methylimidazole, and the rest is NMP solution. Add PVDF powder to NMP solution, stir it hydrothermally at 55°C until it is completely dissolved, then add zinc acetate dihydrate and 2-methylimidazole and continue to stir it hydrothermally at 55°C until a casting solution is formed. After using a scraper to scrape the film, immerse it in pure water to form a PVDF membrane containing ZIF-8; Step 2) Preparation of coating: 1.8% zinc acetate dihydrate, 3.6% 2-methylimidazole, 1.3% 3-glycidoxypropyltriethoxysilane, 1.3% epoxy resin, and the rest is anhydrous ethanol. Zinc acetate dihydrate and 2-methylimidazole are used to synthesize ZIF-8 nanoparticles at 20°C, and the silane coupling agent material is added to anhydrous ethanol and stirred, and then 1.3% of the prepared ZIF-8 nanoparticles are added to the solution. After ultrasonic treatment until uniform dispersion, the resin material is added and ultrasonic treatment is performed until uniform dispersion is obtained to prepare ZIF-8@silane coupling agent@resin coating; Step 3): Preparation of super-hydrophobic film: Fix the PVDF film containing ZIF-8 on a glass plate, clean the spray gun with deionized water, pour the coating prepared in step (2) into the spray gun filling barrel, the nozzle of the spray gun is a fan-shaped nozzle, the nozzle is tilted 30° and placed above the substrate, the height is 10 cm, adjust the spray gun air pressure to spray the coating on the surface of the PVDF film in an S-shaped route with a spraying pressure of 0.3MPa, the spraying time is 10s, and finally the sprayed PVDF film is dried in a 55°C oven to obtain a super-hydrophobic film. The water contact angle of the super-hydrophobic film is 140.3°, and the permeability is 8.7 kg·m -2 ·h -1 After 100 hours of continuous use, the water contact angle was 135.9°, the decrease rate was 3.1%, and the penetration rate was 8.4 kg·m -2 ·h -1 , a decrease rate of 3.4%. Example

[0016] Step 1) Synthesis of PVDF membrane containing ZIF-8: The functional material solution is prepared by the following components in mass percentage: 11.0% PVDF powder, 1.8% zinc acetate dihydrate, 3.6% 2-methylimidazole, and the rest is NMP solution. Add PVDF powder to NMP solution, stir it hydrothermally at 55°C until it is completely dissolved, then add zinc acetate dihydrate and 2-methylimidazole and continue to stir it hydrothermally at 55°C until a casting solution is formed. After using a scraper to scrape the film, soak it in pure water to form a PVDF membrane containing ZIF-8; Step 2) Preparation of coating: 1.8% zinc acetate dihydrate, 1.8% 2-methylimidazole, 1.3% 3-glycidoxypropyltriethoxysilane, 1.3% silicone rubber, and the rest is anhydrous ethanol. Zinc acetate dihydrate and 2-methylimidazole are used to synthesize ZIF-8 nanoparticles at 20°C, and the silane coupling agent material is added to anhydrous ethanol and stirred, and then 1.3% of the prepared ZIF-8 nanoparticles are added to the solution. After ultrasonic treatment until uniform dispersion, the resin material is added and ultrasonic treatment is performed until uniform dispersion to prepare ZIF-8@silane coupling agent@resin coating; Step 3): Preparation of super-hydrophobic film: Fix the PVDF film containing ZIF-8 on a glass plate, clean the spray gun with deionized water, pour the coating prepared in step (2) into the spray gun filling barrel, the nozzle of the spray gun is a fan-shaped nozzle, the nozzle is tilted 30° and placed above the substrate, the height is 10cm, adjust the spray gun air pressure to spray the coating to the surface of the PVDF film according to the S-shaped spray route with a spray pressure of 0.4MPa, the spray time is 12s, and finally the sprayed PVDF film is dried in a 60°C oven to obtain a super-hydrophobic film. The water contact angle of the super-hydrophobic film is 143.6°, and the permeability is 10.4kg·m -2 ·h -1 After 100 hours of continuous use, its water contact angle was 139.3°, with a decrease rate of 3.0%, and its penetration was 10.1 kg·m -2 ·h -1 , a decrease of 2.9%. Example

[0017] Step 1) Synthesis of PVDF membrane containing ZIF-8: The functional material solution is prepared by the following components in mass percentage: 12.0% PVDF powder, 1.8% zinc acetate dihydrate, 5.4% 2-methylimidazole, and the rest is NMP solution. Add PVDF powder to NMP solution, stir it hydrothermally at 60°C until it is completely dissolved, then add zinc acetate dihydrate and 2-methylimidazole and continue to stir it hydrothermally at 60°C until a casting solution is formed. After using a scraper to scrape the film, soak it in pure water to form a PVDF membrane containing ZIF-8; Step 2) Preparation of coating: 1.8% zinc acetate dihydrate, 3.6% 2-methylimidazole, 1.3% 3-glycidoxypropyltriethoxysilane, 1.3% polydimethylsiloxane, 2.6% silicone rubber, and the rest is anhydrous ethanol. Zinc acetate dihydrate and 2-methylimidazole are used to synthesize ZIF-8 nanoparticles at 25°C, and the silane coupling agent material is added to anhydrous ethanol and stirred, and then 2.6% of the prepared ZIF-8 nanoparticles are added to the solution. After ultrasonic treatment until uniform dispersion, the resin material is added and ultrasonic treatment is performed until uniform dispersion is obtained to prepare ZIF-8@silane coupling agent@resin coating; Step 3): Preparation of super-hydrophobic film: Fix the PVDF film containing ZIF-8 on a glass plate, clean the spray gun with deionized water, pour the coating prepared in step (2) into the spray gun filling barrel, the nozzle of the spray gun is a solid cone, the nozzle is tilted 45° and placed above the substrate, the height is 15cm, adjust the spray gun air pressure to spray the coating to the surface of the PVDF film according to the square spray route with a spray pressure of 0.5MPa, the spray time is 13s, and finally the sprayed PVDF film is dried in a 70°C oven to obtain a super-hydrophobic film. The water contact angle of the super-hydrophobic film is 153.4°, and the permeability is 15.3kg·m -2 ·h -1 After 100 hours of continuous use, the water contact angle was 149.4°, the decrease rate was 2.6%, and the penetration rate was 14.9 kg·m -2 ·h -1 , a decrease of 2.6%. Example

[0018] Step 1) Synthesis of PVDF membrane containing ZIF-8: The functional material solution is prepared by the following components in mass percentage: 13.0% PVDF powder, 3.6% zinc acetate dihydrate, 7.2% 2-methylimidazole, and the rest is NMP solution. Add PVDF powder to NMP solution, stir it hydrothermally at 65°C until it is completely dissolved, then add zinc acetate dihydrate and 2-methylimidazole and continue to stir it hydrothermally at 65°C until a casting solution is formed. After using a scraper to scrape the film, soak it in pure water to form a PVDF membrane containing ZIF-8; Step 2) Preparation of coating: 1.8% zinc acetate dihydrate, 7.2% 2-methylimidazole, 1.3% vinyl trimethoxysilane, 2.6% 1H, 1H, 2H, 2H-perfluorooctyl triethoxysilane, 1.3% phenolic resin, and the rest is anhydrous ethanol. Zinc acetate dihydrate and 2-methylimidazole are used to synthesize ZIF-8 nanoparticles at 25°C, and the silane coupling agent material is added to anhydrous ethanol and stirred, and then 2.6% of the prepared ZIF-8 nanoparticles are added to the solution, and the resin material is added after ultrasonic treatment until it is evenly dispersed, and the ZIF-8@silane coupling agent@resin coating is prepared; Step 3): Preparation of super-hydrophobic film: Fix the PVDF film containing ZIF-8 on a glass plate, clean the spray gun with deionized water, pour the coating prepared in step (2) into the spray gun filling barrel, the nozzle of the spray gun is a solid cone, the nozzle is tilted 90° and placed above the substrate, the height is 15 cm, adjust the spray gun air pressure to 0.3MPa spray pressure according to the square spray route to spray the coating to the surface of the PVDF film, the spraying time is 13s, and finally the sprayed PVDF film is dried in a 70°C oven to obtain a super-hydrophobic film. The water contact angle of the super-hydrophobic film is 161.6°, and the permeability is 22.3kg·m -2 ·h -1 After 100 h of continuous use, its water contact angle was 158.4°, with a decrease rate of 2.0%, and its penetration was 21.8 kg·m -2 ·h -1 , a decrease of 2.2%. Example

[0019] Step 1) Synthesis of PVDF membrane containing ZIF-8: The functional material solution is prepared by the following components in mass percentage: 14.0% PVDF powder, 3.6% zinc acetate dihydrate, 9.0% 2-methylimidazole, and the rest is NMP solution. Add PVDF powder to NMP solution, stir it hydrothermally at 60°C until it is completely dissolved, then add zinc acetate dihydrate and 2-methylimidazole and continue to stir it hydrothermally at 60°C until a casting solution is formed. After using a scraper to scrape the film, soak it in pure water to form a PVDF membrane containing ZIF-8; Step 2) Preparation of coating: 3.6% zinc acetate dihydrate, 7.2% 2-methylimidazole, 2.6% polydimethylsiloxane, 2.6% 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane, 2.6% epoxy resin, 1.3% phenolic resin, and the rest is anhydrous ethanol. Zinc acetate dihydrate and 2-methylimidazole are used to synthesize ZIF-8 nanoparticles at 20°C, and the silane coupling agent material is added to anhydrous ethanol and stirred, and then 3.9% of the prepared ZIF-8 nanoparticles are added to the solution, and the resin material is added after ultrasonic treatment until it is evenly dispersed, and the ZIF-8@silane coupling agent@resin coating is made after ultrasonic treatment until it is evenly dispersed; Step 3): Preparation of super-hydrophobic film: Fix the PVDF film containing ZIF-8 on a glass plate, clean the spray gun with deionized water, pour the coating prepared in step (2) into the spray gun filling barrel, the nozzle of the spray gun is a solid cone, the nozzle is tilted 90° and placed above the substrate, the height is 20cm, adjust the spray gun air pressure to spray the coating on the surface of the PVDF film according to the circular spray route with a spray pressure of 0.4MPa, the spray time is 15s, and finally the sprayed PVDF film is dried in a 70°C oven to obtain a super-hydrophobic film. The water contact angle of the super-hydrophobic film is 164.6°, and the permeability is 18.1 kg·m -2 ·h -1 After 100 hours of continuous use, the water contact angle was 161.6°, the decrease rate was 1.8%, and the penetration rate was 17.8 kg·m -2 ·h -1 , a decrease of 1.7%. Example

[0020] Step 1) Synthesis of PVDF membrane containing ZIF-8: The functional material solution is prepared by the following components in mass percentage: 15.0% PVDF powder, 3.6% zinc acetate dihydrate, 10.8% 2-methylimidazole, and the rest is NMP solution. Add PVDF powder to NMP solution, stir it hydrothermally at 65°C until it is completely dissolved, then add zinc acetate dihydrate and 2-methylimidazole and continue to stir it hydrothermally at 65°C until a casting solution is formed. After using a scraper to scrape the film, soak it in pure water to form a PVDF membrane containing ZIF-8; Step 2) Preparation of coating: 3.6% zinc acetate dihydrate, 9.0% 2-methylimidazole, 1.3% 3-glycidoxypropyltriethoxysilane, 2.6% polydimethylsiloxane, 1.3% vinyltrimethoxysilane, 2.6% epoxy resin, 1.3% phenolic resin, and the rest is anhydrous ethanol. Zinc acetate dihydrate and 2-methylimidazole are used to synthesize ZIF-8 nanoparticles at 20°C, and the silane coupling agent material is added to anhydrous ethanol and stirred, and then 5.2% of the prepared ZIF-8 nanoparticles are added to the solution, and the resin material is added after ultrasonic treatment until it is evenly dispersed, and the ZIF-8@silane coupling agent@resin coating is made after ultrasonic treatment until it is evenly dispersed; Step 3): Preparation of super-hydrophobic film: Fix the PVDF film containing ZIF-8 on a glass plate, clean the spray gun with deionized water, pour the coating prepared in step (2) into the spray gun filling barrel, the nozzle of the spray gun is a fan-shaped nozzle, the nozzle is tilted 60° and placed above the substrate, the height is 15cm, adjust the spray gun air pressure to spray the coating on the surface of the PVDF film according to the circular spraying route with a spraying pressure of 0.5MPa, the spraying time is 15s, and finally the sprayed PVDF film is dried in a 70°C oven to obtain a super-hydrophobic film. The water contact angle of the super-hydrophobic film is 159.9°, and the permeability is 20.4kg·m -2 ·h -1 After 100 hours of continuous use, the water contact angle was 154.5°, the decline rate was 2.8%, and the penetration rate was 19.9 kg·m -2 ·h -1 , a decrease rate of 2.5%. Example

[0021] Step 1) Synthesis of PVDF membrane containing ZIF-8: The functional material solution is prepared by the following components in mass percentage: 14.0% PVDF powder, 3.6% zinc acetate dihydrate, 9.0% 2-methylimidazole, and the rest is NMP solution. Add PVDF powder to NMP solution, stir it hydrothermally at 55°C until it is completely dissolved, then add zinc acetate dihydrate and 2-methylimidazole and continue to stir it hydrothermally at 55°C until a casting solution is formed. After using a scraper to scrape the film, soak it in pure water to form a PVDF membrane containing ZIF-8; Step 2) Preparation of coating: 3.6% zinc acetate dihydrate, 10.8% 2-methylimidazole, 3.9% 3-glycidoxypropyltriethoxysilane, 2.6% polydimethylsiloxane, 2.6% epoxy resin, 1.3% silicone rubber, 1.3% phenolic resin, and the rest is anhydrous ethanol. Zinc acetate dihydrate and 2-methylimidazole are used to synthesize ZIF-8 nanoparticles at 25°C, and the silane coupling agent material is added to anhydrous ethanol and stirred, and then 6.5% of the prepared ZIF-8 nanoparticles are added to the solution. After ultrasonic treatment until uniform dispersion, the resin material is added and ultrasonic treatment is performed until uniform dispersion to prepare ZIF-8@silane coupling agent@resin coating; Step 3): Preparation of super-hydrophobic film: Fix the PVDF film containing ZIF-8 on a glass plate, clean the spray gun with deionized water, pour the coating prepared in step (2) into the spray gun filling barrel, the nozzle of the spray gun is a fan-shaped nozzle, the nozzle is tilted 60° and placed above the substrate, the height is 15cm, adjust the spray gun air pressure to spray the coating to the surface of the PVDF film according to the square spraying route with a spraying pressure of 0.5MPa, the spraying time is 15s, and finally the sprayed PVDF film is dried in a 70°C oven to obtain a super-hydrophobic film. The water contact angle of the super-hydrophobic film is 160.8°, and the permeability is 16.8kg·m -2 ·h -1 After 100 hours of continuous use, the water contact angle was 154.6°, the decrease rate was 3.9%, and the penetration rate was 16.2 kg·m -2 ·h -1 , a decrease rate of 3.6%.

Claims

1. A method for preparing a high permeability super-hydrophobic membrane for membrane distillation, characterized in that: The following steps are involved: (1) Synthesis of PVDF membrane containing ZIF-8: The functional material solution is prepared by the following components in mass percentage: 10%-15% PVDF powder, 1.8%-3.6% zinc acetate dihydrate, 1.8%-10.8% 2-methylimidazole, and the rest is NMP solution. Add PVDF powder to NMP solution, stir it hydrothermally at 55-65°C until it is completely dissolved, then add zinc acetate dihydrate and 2-methylimidazole and continue to stir it hydrothermally at 55-65°C until a casting solution is formed. After using a scraper to scrape the film, soak it in pure water to form a PVDF membrane containing ZIF-8; (2) Preparation of coating: 1.8%-3.6% zinc acetate dihydrate, 1.8%-10.8% 2-methylimidazole, 1.3-6.5% silane coupling agent material, 1.3-2.6% resin material, and the rest is anhydrous ethanol. Zinc acetate dihydrate and 2-methylimidazole are used to synthesize ZIF-8 nanoparticles at 20-25°C. The silane coupling agent material is added to anhydrous ethanol and stirred. The prepared ZIF-8 nanoparticles are added to the solution. After ultrasonic treatment until the nanoparticles are evenly dispersed, the resin material is added. After ultrasonic treatment until the nanoparticles are evenly dispersed, the ZIF-8@silane coupling agent@resin coating is prepared. (3) Preparation of super-hydrophobic film: fix the PVDF film containing ZIF-8 on a glass plate, clean the spray gun with deionized water, pour the coating prepared in step (2) into the filling barrel of the spray gun, the nozzle of the spray gun is a solid cone nozzle or a fan nozzle, the nozzle is tilted at a certain angle and placed at a certain height above the substrate, adjust the air pressure of the spray gun and spray the coating onto the surface of the PVDF film according to a spraying route of S shape, square or circle, spray for a certain time, and finally dry the sprayed PVDF film in an oven at 55°C-70°C to obtain a super-hydrophobic film.

2. The method for preparing a high permeability super-hydrophobic membrane for membrane distillation according to claim 1, characterized in that: The silane coupling agent material is one or more of 3-glycidoxypropyltriethoxysilane, polydimethylsiloxane, vinyltrimethoxysilane, and 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane.

3. The resin material according to claim 1 is one or more of epoxy resin, silicone rubber, and phenolic resin.

4. The preparation of the super-hydrophobic film according to claim 1: the nozzle inclination angle is 30-90°.

5. Preparation of super hydrophobic film according to claim 1: the spraying time of the coating is 10-15s.

6. The preparation of the super-hydrophobic film according to claim 1: the height of the nozzle is 10-20 cm.

7. The preparation of the super-hydrophobic film according to claim 1: the spray gun nozzle is a solid cone nozzle or a fan-shaped nozzle.

8. A method for preparing a high permeability super hydrophobic membrane for membrane distillation according to any one of claims 1 to 7: a high permeability super hydrophobic membrane prepared, characterized in that: The water contact angle of the membrane is 140.3-164.2°, and the permeability is 8.7-22.3 kg·m -2 ·h -1 After 100 hours of recycling, the water contact angle value decreased by 1.8%-3.9%, and the permeability value decreased by 1.7%-3.6%.

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