A ZIF-8-based multi-scale high-permeability superhydrophobic membrane for membrane distillation

Abstract

This invention relates to a method for preparing a high-permeability superhydrophobic membrane for membrane distillation. The invention involves a one-step process to prepare a ZIF-8-containing PVDF membrane. The prepared ZIF-8 nanoparticles are then mixed with a silane coupling agent in ethanol and heated and stirred until a milky white liquid is formed. A resin material is used as a reinforcing material, and the prepared coating liquid is sprayed onto the ZIF-8-containing PVDF membrane to form a superhydrophobic membrane. The advantages of this invention are that the in-situ grown ZIF-8 and the sprayed ZIF-8 are formed through different processes, resulting in different particle sizes. The ZIF-8 particles grown in situ in the one-step method have a particle size range of 500-1000 nm, while the sprayed ZIF-8 particles have a particle size range of 200-400 nm. The combination of these two methods creates a multi-scale membrane with good permeability and hydrophobic properties. The resin material in the coating greatly enhances the membrane's durability, which is beneficial for the long-term, efficient, and stable operation of the membrane distillation process. The selected nozzle produces a uniform spray distribution, which is highly effective for applications requiring coverage of a specific area. The manufacturing method of this invention is simple, and the superhydrophobic membrane prepared has a wide range of applications.

Description

Technical Field

[0001] This invention relates to a high-permeability superhydrophobic membrane, specifically to a high-permeability superhydrophobic membrane for membrane distillation and its preparation method, belonging to the field of membrane preparation technology. Background Technology

[0002] Freshwater, as a vital component of life-sustaining systems, is a limited and unevenly distributed resource on Earth. Although 97.4% of the Earth's surface is covered by oceans and salt lakes, freshwater accounts for only about 2.6%. Due to the small proportion of freshwater globally, many regions lack access to safe and clean drinking water, creating an urgent need for cost-effective, reliable, and successful methods to treat local raw water sources.

[0003] In recent years, membrane distillation (MD), as a novel heat-driven membrane technology, has shown promising application prospects in wastewater treatment due to its mild operating conditions, high water production rate, good separation performance, and ability to utilize industrial waste heat. Furthermore, compared to traditional pressure-driven membrane technologies such as nanofiltration and reverse osmosis, membrane distillation has lower requirements for raw water quality and can produce high-quality permeate when treating high-concentration, recalcitrant wastewater, thus it has been used to treat typical wastewater.

[0004] Although membrane distillation technology has significant advantages, it still has many imperfections as a separation technique, which is the main reason why it has not yet been widely used in industry: ① The membrane permeability is low, and the membrane is easily wetted; ② After long-term use, the membrane performance deteriorates significantly, lacking durability. Therefore, improving the permeability, hydrophobicity, and durability of membranes in membrane distillation has become a research hotspot. A dual-scale superhydrophobic ZIF-8 membrane for membrane distillation has been developed. ZIF-8 particles of both nano and micron sizes were synthesized, mixed, and modified with POTS hydrophobicity before being deposited onto a PTFE substrate using a spray method. However, the membrane porosity decreases with the deposition of the ZIF-8 coating, and the ZIF-8 particles are prone to detachment after long-term use. Furthermore, the nano and micron-sized ZIF-8 particles are not easily evenly distributed on the membrane surface.

[0005] This invention prepares a PVDF membrane containing ZIF-8 in a one-step process. ZIF-8 grows uniformly on the membrane. The prepared ZIF-8 nanoparticles are formulated into a coating by selecting appropriate silane coupling agents and resin materials in a suitable ratio. The coating is then sprayed onto the PVDF membrane containing uniformly grown ZIF-8 using a spray gun along a specific spraying route. The in-situ grown ZIF-8 and the sprayed ZIF-8 are formed using different processes, resulting in different particle sizes. This gives the surface coating a multi-layered and uniform uneven structure, improving the hydrophobic properties of the membrane. Furthermore, the resin material in the coating greatly enhances the membrane's durability, preventing ZIF-8 from falling off, which is beneficial for the long-term, efficient, and stable operation of the membrane distillation process. Summary of the Invention

[0006] Step 1) Synthesis of ZIF-8-containing PVDF membrane: The feed solution of the functionalized material is prepared by the following components in the following mass percentages: PVDF powder 10%-15%, zinc acetate dihydrate 1.8%-3.6%, 2-methylimidazole 1.8%-10.8%, and the remainder is NMP solution. PVDF powder is added to the NMP solution and hydrothermally stirred at 55-65℃ until completely dissolved. Then, zinc acetate dihydrate and 2-methylimidazole are added, and hydrothermal stirring is continued at 55-65℃ until a casting solution is formed. After casting using a film scraper, the membrane is immersed in pure water to form a ZIF-8-containing PVDF membrane.

[0007] Step 2) Coating Preparation: Zinc acetate dihydrate 1.8%-3.6%, 2-methylimidazole 1.8%-10.8%, silane coupling agent 1.3-6.5%, resin 1.3-2.6%, with the remainder being anhydrous ethanol. ZIF-8 nanoparticles are synthesized using zinc acetate dihydrate and 2-methylimidazole at 20-25℃. The silane coupling agent is added to anhydrous ethanol and stirred. The prepared ZIF-8 nanoparticles are then added to the solution and ultrasonically treated until uniformly dispersed. The resin is then added and ultrasonically treated until uniformly dispersed to obtain the ZIF-8@silane coupling agent@resin coating.

[0008] Step 3): Preparation of superhydrophobic film: Fix the PVDF film containing ZIF-8 onto a glass plate, clean the spray gun with deionized water, pour the coating prepared in step (2) into the spray gun filler bucket, tilt the nozzle 30-90° above the substrate at a height of 10-20cm, adjust the air pressure of the spray gun to spray the coating onto the surface of the PVDF film at a spraying pressure of 0.3-0.5MPa according to the specified spraying route, and spray for 10-15s. Finally, dry the sprayed PVDF film in an oven at 55℃-70℃ to obtain the superhydrophobic film.

[0009] Preferably, the silane coupling agent material in step 2) is one or more of 3-epoxypropoxypropyltriethoxysilane, polydimethylsiloxane, vinyltrimethoxysilane, and 1H,1H,2H,2H-perfluorooctyltriethoxysilane.

[0010] Preferably, the resin material in step 2) is one or more of epoxy resin, silicone rubber, and phenolic resin.

[0011] Preferably, in step 3), the spray gun nozzle is either a solid cone nozzle or a fan-shaped nozzle.

[0012] Preferably, the spraying route in step 3) is one of S-shape, square, or circle.

[0013] This invention also provides a method for preparing a high-permeability superhydrophobic membrane for membrane distillation: the prepared high-permeability superhydrophobic membrane is characterized by having a water contact angle of 140.3-164.2° and a permeability of 8.7-22.3 kg·m³. -2 ·h -1 After 100 hours of continuous use, the water contact angle decreased by 1.8%-3.9%, and the permeability decreased by 1.7%-3.6%.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] This invention prepares a ZIF-8-containing PVDF membrane in a one-step process. ZIF-8 grows uniformly on the membrane, reducing the density and increasing the porosity of the PVDF matrix, resulting in a membrane with good permeability. Then, a ZIF-8 modified coating is sprayed onto the membrane surface using different spraying routes and heights. The in-situ grown ZIF-8 and the sprayed ZIF-8 have different formation processes, resulting in different particle sizes. The ZIF-8 particles grown in situ using the one-step method have a particle size range of 500-1000 nm, while the sprayed ZIF-8 particles have a particle size range of 200-400 nm. The combination of these two methods creates a multi-scale structure, enabling… The surface coating possesses a multi-layered, uniform uneven structure, creating more air gaps between the membrane surface and the feed liquid. These air gaps reduce the contact area between the droplets and the membrane surface, preventing liquid from penetrating into the membrane pores and thus enhancing the hydrophobicity of the membrane material. Meanwhile, evaporated gas can enter the pores through these air gaps, facilitating vapor transport within the membrane pores and increasing the material's permeation capacity. While achieving a high-permeability superhydrophobic membrane, the resin material in the coating significantly enhances the membrane's durability, contributing to the long-term, efficient, and stable operation of the membrane distillation process. The selected nozzle produces a uniform spray distribution, providing excellent performance for applications requiring spray coverage of a specific area. This invention features a simple manufacturing method, and the resulting high-permeability superhydrophobic membrane has a wide range of applications. Attached Figure Description

[0016] Figure 1 This is a diagram showing the spraying process conditions;

[0017] Figure 2 Data graphs for high-permeability superhydrophobic membranes in various examples;

[0018] Figure 3 Images of ZIF-8 particles prepared in Example 1;

[0019] Figure 4 Image of the high-permeability superhydrophobic membrane prepared in Example 1.

[0020] Figure 5The surface SEM image of the high-permeability superhydrophobic membrane prepared in Example 3;

[0021] Figure 6 The image shows the water contact angle of the high-permeability superhydrophobic membrane obtained in Example 5;

[0022] Figure 7 This includes a model diagram of the nozzle style and a diagram showing the spraying effect.

[0023] Figure 8 A spray gun spraying route diagram;

[0024] Figure 9 This is a schematic diagram showing the nozzle height and nozzle tilt angle. Implementation

[0025] The present invention will be further described below with reference to specific embodiments. Example

[0026] Step 1) Synthesis of ZIF-8-containing PVDF membrane: The feed solution of the functionalized material is prepared by the following components in the following mass percentages: PVDF powder 10.0%, zinc acetate dihydrate 1.8%, 2-methylimidazole 1.8%, and the remainder is NMP solution. PVDF powder is added to the NMP solution and hydrothermally stirred at 55°C until completely dissolved. Then, zinc acetate dihydrate and 2-methylimidazole are added, and hydrothermally stirred at 55°C until a casting solution is formed. After casting using a film scraper, the membrane is immersed in pure water to form a ZIF-8-containing PVDF membrane.

[0027] Step 2) Preparation of the coating: 1.8% zinc acetate dihydrate, 3.6% 2-methylimidazole, 1.3% 3-epoxypropoxypropyltriethoxysilane, 1.3% epoxy resin, and the remainder anhydrous ethanol. ZIF-8 nanoparticles were synthesized using zinc acetate dihydrate and 2-methylimidazole at 20℃. The silane coupling agent was added to anhydrous ethanol and stirred. Then, 1.3% of the prepared ZIF-8 nanoparticles were added to the solution. After ultrasonic treatment until uniform dispersion, the resin material was added and ultrasonically treated until uniform dispersion was achieved to prepare the ZIF-8@silane coupling agent@resin coating.

[0028] Step 3): Preparation of the superhydrophobic film: The PVDF film containing ZIF-8 is fixed on a glass plate. The spray gun is cleaned with deionized water. The coating prepared in step (2) is poured into the spray gun filler. The nozzle of the spray gun is a fan-shaped nozzle, tilted at 30° above the substrate at a height of 10cm. The air pressure of the spray gun is adjusted to a spraying pressure of 0.3MPa, and the coating is sprayed onto the surface of the PVDF film in an S-shaped path for 10s. Finally, the sprayed PVDF film is dried in an oven at 55℃ to obtain the superhydrophobic film. The water contact angle of the superhydrophobic film is 140.3°, and the permeation is 8.7 kg·m³. -2·h -1 After 100 hours of continuous use, its water contact angle was 135.9°, with a decrease rate of 3.1%, and its permeability was 8.4 kg·m³. -2 ·h -1 The decline rate was 3.4%. Example

[0029] Step 1) Synthesis of ZIF-8-containing PVDF membrane: The feed solution of the functionalized material is prepared by the following components in the following mass percentages: PVDF powder 11.0%, zinc acetate dihydrate 1.8%, 2-methylimidazole 3.6%, and the remainder is NMP solution. PVDF powder is added to the NMP solution and hydrothermally stirred at 55°C until completely dissolved. Then, zinc acetate dihydrate and 2-methylimidazole are added, and hydrothermally stirred at 55°C until a casting solution is formed. After casting using a film scraper, the membrane is immersed in pure water to form a ZIF-8-containing PVDF membrane.

[0030] Step 2) Preparation of the coating: Zinc acetate dihydrate 1.8%, 2-methylimidazole 1.8%, 3-epoxypropoxypropyltriethoxysilane 1.3%, silicone rubber 1.3%, and the remainder is anhydrous ethanol. ZIF-8 nanoparticles were synthesized using zinc acetate dihydrate and 2-methylimidazole at 20℃. The silane coupling agent was added to anhydrous ethanol and stirred. Then, 1.3% of the prepared ZIF-8 nanoparticles were added to the solution. After ultrasonic treatment until uniform dispersion, the resin material was added and ultrasonically treated until uniform dispersion was achieved to prepare the ZIF-8@silane coupling agent@resin coating.

[0031] Step 3): Preparation of the superhydrophobic film: The PVDF film containing ZIF-8 is fixed on a glass plate. The spray gun is cleaned with deionized water. The coating prepared in step (2) is poured into the spray gun filler. The nozzle of the spray gun is a fan-shaped nozzle, tilted at 30° above the substrate at a height of 10cm. The air pressure of the spray gun is adjusted to a spraying pressure of 0.4MPa, and the coating is sprayed onto the surface of the PVDF film in an S-shaped spraying path for 12s. Finally, the sprayed PVDF film is dried in a 60℃ oven to obtain the superhydrophobic film. The water contact angle of the superhydrophobic film is 143.6°, and the permeation 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 permeability was 10.1 kg·m³. -2 ·h -1 The decline rate was 2.9%. Example

[0032] Step 1) Synthesis of ZIF-8-containing PVDF membrane: The feed solution of the functionalized material is prepared by the following components in the following mass percentages: PVDF powder 12.0%, zinc acetate dihydrate 1.8%, 2-methylimidazole 5.4%, and the remainder is NMP solution. PVDF powder is added to the NMP solution and hydrothermally stirred at 60°C until completely dissolved. Then, zinc acetate dihydrate and 2-methylimidazole are added, and hydrothermally stirred at 60°C until a casting solution is formed. After casting using a film scraper, the membrane is immersed in pure water to form a ZIF-8-containing PVDF membrane.

[0033] Step 2) Preparation of the coating: Zinc acetate dihydrate 1.8%, 2-methylimidazole 3.6%, 3-epoxypropoxypropyltriethoxysilane 1.3%, polydimethylsiloxane 1.3%, silicone rubber 2.6%, and the remainder being anhydrous ethanol. ZIF-8 nanoparticles were synthesized using zinc acetate dihydrate and 2-methylimidazole at 25°C. The silane coupling agent was added to anhydrous ethanol and stirred. Then, 2.6% of the prepared ZIF-8 nanoparticles were added to the solution. After ultrasonic treatment until uniform dispersion, the resin material was added and ultrasonically treated until uniform dispersion was achieved to prepare the ZIF-8@silane coupling agent@resin coating.

[0034] Step 3): Preparation of the superhydrophobic film: The PVDF film containing ZIF-8 is fixed on a glass plate. The spray gun is cleaned with deionized water. The coating prepared in step (2) is poured into the spray gun filler. The nozzle of the spray gun is a solid cone, tilted at 45° above the substrate at a height of 15cm. The air pressure of the spray gun is adjusted to a spraying pressure of 0.5MPa, and the coating is sprayed onto the surface of the PVDF film in a square spraying path for 13s. Finally, the sprayed PVDF film is dried in a 70℃ oven to obtain the superhydrophobic film. The water contact angle of the superhydrophobic film is 153.4°, and the permeation is 15.3kg·m. -2 ·h -1 After 100 hours of continuous use, its water contact angle was 149.4°, with a decrease rate of 2.6%, and its permeability was 14.9 kg·m³. -2 ·h -1 The decline rate was 2.6%. Example

[0035] Step 1) Synthesis of ZIF-8-containing PVDF membrane: The feed solution of the functionalized material is prepared by the following components in the following mass percentages: PVDF powder 13.0%, zinc acetate dihydrate 3.6%, 2-methylimidazole 7.2%, and the remainder is NMP solution. PVDF powder is added to the NMP solution and hydrothermally stirred at 65°C until completely dissolved. Then, zinc acetate dihydrate and 2-methylimidazole are added, and hydrothermally stirred at 65°C until a casting solution is formed. After casting using a film scraper, the membrane is immersed in pure water to form a ZIF-8-containing PVDF membrane.

[0036] Step 2) Preparation of the coating: Zinc acetate dihydrate 1.8%, 2-methylimidazole 7.2%, vinyltrimethoxysilane 1.3%, 1H,1H,2H,2H-perfluorooctyltriethoxysilane 2.6%, phenolic resin 1.3%, and the remainder being anhydrous ethanol. ZIF-8 nanoparticles were synthesized using zinc acetate dihydrate and 2-methylimidazole at 25°C. The silane coupling agent was added to anhydrous ethanol and stirred. Then, 2.6% of the prepared ZIF-8 nanoparticles were added to the solution. After ultrasonic treatment until uniform dispersion, the resin material was added and ultrasonically treated until uniform dispersion was achieved to prepare the ZIF-8@silane coupling agent@resin coating.

[0037] Step 3): Preparation of the superhydrophobic film: The PVDF film containing ZIF-8 is fixed on a glass plate. The spray gun is cleaned with deionized water. The coating prepared in step (2) is poured into the spray gun filler. The nozzle of the spray gun is a solid cone, tilted at 90° above the substrate at a height of 15 cm. The air pressure of the spray gun is adjusted to a spraying pressure of 0.3 MPa, and the coating is sprayed onto the surface of the PVDF film in a square spraying path for 13 seconds. Finally, the sprayed PVDF film is dried in a 70°C oven to obtain the superhydrophobic film. The water contact angle of the superhydrophobic film is 161.6°, and the permeation is 22.3 kg·m³. -2 ·h -1 After 100 hours of continuous use, its water contact angle was 158.4°, with a decrease rate of 2.0%, and its permeability was 21.8 kg·m³. -2 ·h -1 The decline rate was 2.2%. Example

[0038] Step 1) Synthesis of ZIF-8-containing PVDF membrane: The feed solution of the functionalized material is prepared by the following components in the following mass percentages: PVDF powder 14.0%, zinc acetate dihydrate 3.6%, 2-methylimidazole 9.0%, and the remainder is NMP solution. PVDF powder is added to the NMP solution and hydrothermally stirred at 60°C until completely dissolved. Then, zinc acetate dihydrate and 2-methylimidazole are added, and hydrothermally stirred at 60°C until a casting solution is formed. After casting using a film scraper, the membrane is immersed in pure water to form a ZIF-8-containing PVDF membrane.

[0039] Step 2) Preparation of the coating: Zinc acetate dihydrate 3.6%, 2-methylimidazole 7.2%, polydimethylsiloxane 2.6%, 1H,1H,2H,2H-perfluorooctyltriethoxysilane 2.6%, epoxy resin 2.6%, phenolic resin 1.3%, and the remainder being anhydrous ethanol. ZIF-8 nanoparticles were synthesized using zinc acetate dihydrate and 2-methylimidazole at 20℃. The silane coupling agent was added to anhydrous ethanol and stirred. Then, 3.9% of the prepared ZIF-8 nanoparticles were added to the solution. After ultrasonic treatment until uniform dispersion, the resin material was added and ultrasonically treated until uniform dispersion was achieved to prepare the ZIF-8@silane coupling agent@resin coating.

[0040] Step 3): Preparation of the superhydrophobic film: The PVDF film containing ZIF-8 is fixed on a glass plate. The spray gun is cleaned with deionized water. The coating prepared in step (2) is poured into the spray gun filler. The nozzle of the spray gun is a solid cone, tilted at 90° above the substrate at a height of 20cm. The air pressure of the spray gun is adjusted to a spraying pressure of 0.4MPa, and the coating is sprayed onto the surface of the PVDF film in a circular spraying path for 15s. Finally, the sprayed PVDF film is dried in a 70℃ oven to obtain the superhydrophobic film. The water contact angle of the superhydrophobic film is 164.6°, and the permeation is 18.1 kg·m³. -2 ·h -1 After 100 hours of continuous use, its water contact angle was 161.6°, with a decrease rate of 1.8%, and its permeability was 17.8 kg·m³. -2 ·h -1 The decline rate was 1.7%. Example

[0041] Step 1) Synthesis of ZIF-8-containing PVDF membrane: The feed solution of the functionalized material is prepared by the following components in the following mass percentages: PVDF powder 15.0%, zinc acetate dihydrate 3.6%, 2-methylimidazole 10.8%, and the remainder is NMP solution. PVDF powder is added to the NMP solution and hydrothermally stirred at 65°C until completely dissolved. Then, zinc acetate dihydrate and 2-methylimidazole are added, and hydrothermally stirred at 65°C until a casting solution is formed. After casting using a film scraper, the membrane is immersed in pure water to form a ZIF-8-containing PVDF membrane.

[0042] Step 2) Preparation of the coating: Zinc acetate dihydrate 3.6%, 2-methylimidazole 9.0%, 3-epoxypropoxypropyltriethoxysilane 1.3%, polydimethylsiloxane 2.6%, vinyltrimethoxysilane 1.3%, epoxy resin 2.6%, phenolic resin 1.3%, and the remainder being anhydrous ethanol. ZIF-8 nanoparticles were synthesized using zinc acetate dihydrate and 2-methylimidazole at 20℃. The silane coupling agent was added to anhydrous ethanol and stirred. Then, 5.2% of the prepared ZIF-8 nanoparticles were added to the solution. After ultrasonic treatment until uniform dispersion, the resin material was added and ultrasonically treated until uniform dispersion was achieved to prepare the ZIF-8@silane coupling agent@resin coating.

[0043] Step 3): Preparation of the superhydrophobic film: The PVDF film containing ZIF-8 is fixed on a glass plate. The spray gun is cleaned with deionized water. The coating prepared in step (2) is poured into the spray gun filler container. The nozzle of the spray gun is a fan-shaped nozzle, tilted at 60° above the substrate at a height of 15cm. The air pressure of the spray gun is adjusted to a spraying pressure of 0.5MPa, and the coating is sprayed onto the surface of the PVDF film in a circular spraying path for 15s. Finally, the sprayed PVDF film is dried in a 70℃ oven to obtain the superhydrophobic film. The water contact angle of the superhydrophobic film is 159.9°, and the permeation is 20.4kg·m. -2 ·h -1 After 100 hours of continuous use, its water contact angle was 154.5°, with a decrease rate of 2.8%, and its permeability was 19.9 kg·m³. -2 ·h -1 The decline rate was 2.5%. Example

[0044] Step 1) Synthesis of ZIF-8-containing PVDF membrane: The feed solution of the functionalized material is prepared by the following components in the following mass percentages: PVDF powder 14.0%, zinc acetate dihydrate 3.6%, 2-methylimidazole 9.0%, and the remainder is NMP solution. PVDF powder is added to the NMP solution and hydrothermally stirred at 55°C until completely dissolved. Then, zinc acetate dihydrate and 2-methylimidazole are added, and hydrothermally stirred at 55°C until a casting solution is formed. After casting using a film scraper, the membrane is immersed in pure water to form a ZIF-8-containing PVDF membrane.

[0045] Step 2) Preparation of the coating: Zinc acetate dihydrate 3.6%, 2-methylimidazole 10.8%, 3-epoxypropoxypropyltriethoxysilane 3.9%, polydimethylsiloxane 2.6%, epoxy resin 2.6%, silicone rubber 1.3%, phenolic resin 1.3%, and the remainder being anhydrous ethanol. ZIF-8 nanoparticles were synthesized using zinc acetate dihydrate and 2-methylimidazole at 25℃. The silane coupling agent was added to anhydrous ethanol and stirred. Then, 6.5% of the prepared ZIF-8 nanoparticles were added to the solution. After ultrasonic treatment until uniform dispersion, the resin material was added and ultrasonically treated until uniform dispersion was achieved to prepare the ZIF-8@silane coupling agent@resin coating.

[0046] Step 3): Preparation of the superhydrophobic film: The PVDF film containing ZIF-8 is fixed on a glass plate. The spray gun is cleaned with deionized water. The coating prepared in step (2) is poured into the spray gun filler container. The nozzle of the spray gun is a fan-shaped nozzle, tilted at 60° above the substrate at a height of 15cm. The air pressure of the spray gun is adjusted to a spraying pressure of 0.5MPa, and the coating is sprayed onto the surface of the PVDF film in a square spraying path for 15s. Finally, the sprayed PVDF film is dried in a 70℃ oven to obtain the superhydrophobic film. The water contact angle of the superhydrophobic film is 160.8°, and the permeation is 16.8kg·m. -2 ·h -1 After 100 hours of continuous use, its water contact angle was 154.6°, with a decrease rate of 3.9%, and its permeability was 16.2 kg·m³. -2 ·h -1 The decline rate was 3.6%.

Claims

1. A method for preparing a high-permeability superhydrophobic membrane for membrane distillation, characterized in that, Includes the following steps: (1) Synthesis of ZIF-8-containing PVDF membrane: The functional material solution is prepared by the following components in mass percentage: PVDF powder 10%-15%, zinc acetate dihydrate 1.8%-3.6%, 2-methylimidazole 1.8%-10.8%, and the remainder is NMP solution; PVDF powder is added to NMP solution and hydrothermally stirred at 55-65°C until completely dissolved. Then zinc acetate dihydrate and 2-methylimidazole are added and hydrothermally stirred at 55-65°C until the functional material solution is formed. After the membrane is coated using a coating machine, it is immersed in pure water to form a ZIF-8-containing PVDF membrane. (2) Preparation of coating: The raw materials of the coating are 1.8%-3.6% zinc acetate dihydrate, 1.8%-10.8% 2-methylimidazole, 1.3%-6.5% silane coupling agent, 1.3%-2.6% resin, and the remainder is anhydrous ethanol. ZIF-8 nanoparticles are synthesized by zinc acetate dihydrate and 2-methylimidazole at 20-25°C. After adding the silane coupling agent to anhydrous ethanol and stirring, ZIF-8 nanoparticles are added. After ultrasonic treatment until uniform dispersion, the resin is added and ultrasonic treatment is performed until uniform dispersion to prepare ZIF-8@silane coupling agent@resin coating. (3) Preparation of superhydrophobic film: Fix the PVDF film containing ZIF-8 onto a glass plate, clean the spray gun with deionized water, pour the coating prepared in step (2) into the spray gun filler bucket, the nozzle of the spray gun is either 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 in an S-shaped, square or circular spraying route, spray for a certain time, and finally dry the sprayed PVDF film in an oven at 55°C-70°C to obtain the superhydrophobic film.

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

3. The method for preparing a high-permeability superhydrophobic membrane for membrane distillation according to claim 1, characterized in that: The resin material is one or more of epoxy resin, silicone rubber, and phenolic resin.

4. The method for preparing a high-permeability superhydrophobic membrane for membrane distillation according to claim 1, characterized in that: Preparation of superhydrophobic film: The nozzle tilt angle is 30-90°.

5. The method for preparing a high-permeability superhydrophobic membrane for membrane distillation according to claim 1, characterized in that: The coating application time is 10-15 seconds.

6. The method for preparing a high-permeability superhydrophobic membrane for membrane distillation according to claim 1, characterized in that: The nozzle height is 10-20cm.

7. A high-permeability superhydrophobic membrane prepared by the method for preparing a high-permeability superhydrophobic membrane for membrane distillation according to any one of claims 1-6, characterized in that, The membrane has a water contact angle of 140.3-164.2° and a permeation rate of 8.7-22.3 kg·m⁻²·h⁻¹. After 100 hours of use, the water contact angle decreases by 1.8%-3.9% and the permeation rate decreases by 1.7%-3.6%.

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