Preparation method and application of hydrophobic carbon nanotube composite polyvinylidene fluoride photo-thermal hydrophobic membrane

Abstract

The application relates to the technical field of membrane distillation, in particular to a preparation method of a hydrophobic carbon nanotube composite polyvinylidene fluoride photo-thermal hydrophobic membrane, which comprises the following steps: S1. mixing water, ethanol and 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane to obtain a hydrophobic modifier; S2. mixing carbon nanotubes, ammonia and the hydrophobic modifier to obtain a black suspension; S3. centrifuging, washing and drying the black suspension solution to obtain hydrophobic carbon nanotube powder; S4. mixing acetone and N, N-dimethylformamide, adding polyvinylidene fluoride and the hydrophobic carbon nanotube powder to obtain a spinning solution; and S5. electrospinning the spinning solution into a film, and then drying the film to obtain the hydrophobic carbon nanotube composite polyvinylidene fluoride photo-thermal hydrophobic membrane. The modified carbon nanotubes can be used as photo-thermal particles to increase the photo-thermal utilization rate of the hydrophobic membrane, polyvinylidene fluoride is used as the main structure of the hydrophobic membrane to provide mechanical strength and certain hydrophobicity, the photo-thermal utilization rate is coordinated in the application of solar membrane distillation, and the comprehensive performance is improved.

Description

Technical Field

[0001] This invention relates to the field of membrane distillation technology, specifically to a method for preparing a hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic membrane. Background Technology

[0002] Membrane distillation (MD) is an emerging heat-driven membrane separation process. A hydrophobic membrane serves as the separation medium, and the driving force is provided by the temperature difference between the solutions on both sides of the membrane. This allows volatile components (such as water vapor) to pass through the membrane pores and condense on the permeate side, while simultaneously blocking non-volatile components (such as salts) from passing through, thus achieving desalination. Compared to desalination technologies such as reverse osmosis and conventional distillation, MD exhibits significant advantages, such as insensitivity to feed solution salt concentration, high salt rejection rate, simple equipment, and modularity. However, temperature polarization is one of the main challenges currently facing membrane distillation technology. This refers to the temperature at the feed solution-side membrane interface being lower than the feed solution bulk temperature, resulting in a reduced effective transmembrane temperature difference, thereby decreasing flux and increasing energy loss during membrane distillation.

[0003] Photothermal film distillation (PMD) technology typically involves enriching photothermal materials into a film, utilizing solar energy to achieve a photothermal conversion effect and locally heating the film surface, thereby alleviating temperature polarization and improving energy utilization efficiency. Among these technologies, carbon-based photothermal nanomaterials, such as carbon nanotubes, are widely used in PMD film preparation due to their relatively low cost and broad-spectrum light absorption capabilities.

[0004] Therefore, how to develop a high-flux, high-liquid-in-pressure, durable photothermal hydrophobic membrane based on CNTs materials to ensure its sustainable and stable operation in the treatment of high-salt wastewater and seawater desalination is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing a hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film, which solves the problem of poor overall performance of traditional photothermal hydrophobic films.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film, comprising the following steps:

[0007] S1. Mix water, ethanol and 1H,1H,2H,2H-perfluorodecyltriethoxysilane and stir at room temperature for 15 minutes to obtain a hydrophobic modifier;

[0008] S2. Add carbon nanotubes and a certain amount of ammonia water to the hydrophobic modifier in step (1) and stir at 65°C for 12 hours to obtain a black suspension;

[0009] S3. The black suspension solution obtained in step (2) is centrifuged, washed with ethanol and water, and then placed in a forced-air drying oven at 80°C for 12 to 24 hours to obtain hydrophobic carbon nanotube powder.

[0010] S4. Mix acetone and N,N-dimethylformamide at a mass ratio of 9:1, and add a certain amount of polyvinylidene fluoride and hydrophobic carbon nanotube powder obtained in step (3). Stir at 50°C for 6 hours to obtain spinning solution.

[0011] S5. A certain amount of the spinning solution obtained in step (4) is drawn out with a syringe, put into the injection pump, and the liquid volume, pushing speed, spinning distance, rotation speed and voltage parameters are adjusted. The resulting spinning membrane is placed in a vacuum drying oven and dried at 80°C for 12 hours to obtain a hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic membrane.

[0012] Preferably, the mass ratio of water, ethanol and 1H,1H,2H,2H-perfluorodecyltriethoxysilane in step S1 is 50:5:1.

[0013] Preferably, the mass ratio of carbon nanotubes in step S2 to 1H,1H,2H,2H-perfluorodecyltriethoxysilane in step S1 is 1:2, and the amount of ammonia added is 3 mL.

[0014] Preferably, in step S3, the centrifugation speed is 3000-8000 rpm, and the number of washing cycles is 3-5.

[0015] Preferably, in step S4, the mass fractions of polyvinylidene fluoride and hydrophobic carbon nanotube powder are 12 wt% and 1.0 wt%, respectively.

[0016] Preferably, in step S5, the spinning solution volume is 10-20 mL, the dispensing speed is 0.5-1.0 mL / h, the spinning distance is 10-20 cm, the spinning speed is 300-1000 rpm, and the voltage is 10.0-16.0 kV.

[0017] This invention provides a method for preparing a photothermal hydrophobic film composed of hydrophobic carbon nanotubes and polyvinylidene fluoride. It has the following beneficial effects:

[0018] 1. This invention modifies carbon nanotubes to be hydrophobic. Carbon nanotubes possess rich surface structures, strong photothermal conversion capabilities (99.9% light absorption rate), and excellent hydrophobicity, effectively resisting water penetration. The polyvinylidene fluoride (PVDF) used is hydrophobic, and the mixture of acetone and N,N-dimethylformamide at a mass ratio of 9:1 facilitates continuous and stable electrospinning. The designed photothermal hydrophobic membrane utilizes modified carbon nanotubes as photothermal particles to increase the photothermal utilization rate and enhance the hydrophobicity. PVDF serves as the main structural component, providing mechanical strength and a degree of hydrophobicity. After electrospinning, the relationship between photothermal utilization rate, liquid entry pressure, and membrane distillation flux is balanced, improving overall performance and increasing the water production efficiency of the photothermal membrane distillation system.

[0019] 2. The raw materials for this invention are widely available, and the electrospinning process is simple and efficient. The hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic membrane prepared can achieve a hydrophobic angle of up to 146.7°, a maximum liquid ingress pressure of up to 2.4 bar, and a membrane flux of up to 1.78 kg·m³. -2 ·h -1 The conductivity of the produced water is less than 5.0 μS / cm. Attached Figure Description

[0020] Figure 1 This is a photograph of the hydrophobic membrane product obtained in Embodiment 1 of the present invention.

[0021] Figure 2 The electron microscope structure and hydrophobic angle measurement diagram of the hydrophobic film product prepared in Embodiment 1 of the present invention are shown.

[0022] Figure 3 This is a performance diagram of the hydrophobic membrane product prepared in Embodiment 1 of the present invention;

[0023] Figure 4 This is a photograph of the hydrophobic membrane product obtained in Embodiment 2 of the present invention;

[0024] Figure 5 The electron microscope structure and hydrophobic angle measurement diagram of the hydrophobic film product prepared in Embodiment 2 of the present invention are shown.

[0025] Figure 6 This is a performance diagram of the hydrophobic membrane product obtained in Embodiment 2 of the present invention;

[0026] Figure 7 This is a photograph of the hydrophobic membrane product prepared in Comparative Example 1 of the present invention.

[0027] Figure 8 The electron microscope structure and hydrophobic angle measurement diagram of the hydrophobic film product prepared in Comparative Example 1 of this invention are shown.

[0028] Figure 9This is a performance diagram of the hydrophobic membrane product prepared in Comparative Example 1 of the present invention;

[0029] Figure 10 This is a photograph of the hydrophobic membrane product prepared in Comparative Example 2 of the present invention.

[0030] Figure 11 The electron microscope structure and hydrophobic angle measurement diagram of the hydrophobic film product prepared in Comparative Example 2 of this invention are shown.

[0031] Figure 12 This is a performance diagram of the hydrophobic membrane product prepared in Comparative Example 2 of the present invention;

[0032] Figure 13 This is a comparison chart of the salt rejection rate and membrane flux of the hydrophobic membranes obtained in Embodiments 1 and 2, and Comparative Examples 1 and 2 of the present invention. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1:

[0035] like Figure 1-3 As shown, this embodiment of the invention provides a method for preparing a hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film, comprising the following steps:

[0036] S1. Mix 100g water, 10g ethanol and 2g 1H,1H,2H,2H-perfluorodecyltriethoxysilane and stir at room temperature for 15 minutes to obtain a hydrophobic modifier;

[0037] S2. Add 1g of carbon nanotubes and 3mL of ammonia water to the hydrophobic modifier in step (1) and stir at 65°C for 12 hours to obtain a black suspension;

[0038] S3. The black suspension solution obtained in step (2) is centrifuged at 3500 rpm and washed three times with ethanol and water respectively. Then it is placed in a forced-air drying oven and dried at 80°C for 12 hours to obtain hydrophobic carbon nanotube powder.

[0039] S4. Mix acetone and N,N-dimethylformamide at a mass ratio of 9:1 and weigh 26.1g. Then add 3.6g of polyvinylidene fluoride and 0.3g of hydrophobic carbon nanotube powder obtained in step (3) and stir at 50°C for 6 hours to obtain spinning solution.

[0040] S5. Take 25 mL of the spinning solution obtained in step (4) with a syringe, put it into the injection pump, and set the liquid volume to 20 mL, the liquid pushing speed to 0.5 mL / h, the spinning distance to 15 cm, the rotation speed to 500 rpm, and the voltage to 14.0 kV. Then put the obtained spinning membrane into a vacuum drying oven and dry it at 80°C for 12 hours to obtain a hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic membrane.

[0041] The surface of the hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film prepared in Example 1 was characterized using a scanning electron microscope, and the water contact angle (WCA) of the hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film obtained in Example 1 was measured using a contact angle meter. Figure 1 This is a photograph of the resulting hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film. Figure 2 The image shows a surface electron microscope (SEM) image of the obtained hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film. The inset image shows the hydrophobic angle measurement. Figure 3 The image shows the performance of the resulting hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film.

[0042] according to Figure 1 It can be seen that the product surface has no obvious defects such as delamination, breakage, or local aggregation; the surface is smooth, and the color is blackish-gray. According to... Figure 2 It can be seen that the surface of the hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film exhibits a porous morphology of mesh fibers, and there is no aggregation of hydrophobic carbon nanoparticles and PVDF. The hydrophobic angle in air is 149°.

[0043] The liquid inlet pressure (LEP) of the membrane was tested using a static liquid inlet pressure tester, and the obtained data was 2.4 bar.

[0044] The membrane performance was tested using a photothermal membrane distillation apparatus, with a feed solution containing 3.5 wt% sodium chloride, a permeate side temperature of 10 °C, and a membrane surface irradiance of 1 kW·m. -2 The membrane size exposed to light is 3*8 cm. The photothermal desalination performance of the hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic membrane obtained in Example 1 was tested, and the results are as follows: Figure 3 As shown.

[0045] Depend on Figure 3 It can be seen that at 1kW·m -2 Under light intensity, the feed liquid temperature reached a maximum of 26.7℃, and the mass increase was 15.12g within 3 hours. The calculated permeation flux of the hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic membrane was 2.1 kg·m³. -2 ·h -1 The salt rejection rate can reach 99.991%, and the conductivity of the produced water is less than 5.0 μS / cm.

[0046] Example 2:

[0047] like Figure 4-6 As shown, this embodiment of the invention provides a method for preparing a hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film, comprising the following steps:

[0048] S1. Mix 100g water, 10g ethanol and 2g 1H,1H,2H,2H-perfluorodecyltriethoxysilane and stir at room temperature for 15 minutes to obtain a hydrophobic modifier;

[0049] S2. Add 1g of carbon nanotubes and 3mL of ammonia water to the hydrophobic modifier in step (1) and stir at 65°C for 12 hours to obtain a black suspension;

[0050] S3. The black suspension solution obtained in step (2) is centrifuged at 3500 rpm and washed three times with ethanol and water respectively. Then it is placed in a forced-air drying oven and dried at 80°C for 12 hours to obtain hydrophobic carbon nanotube powder.

[0051] S4. Mix acetone and N,N-dimethylformamide at a mass ratio of 9:1 and weigh 26.1g. Then add 3.6g of polyvinylidene fluoride and 0.15g of hydrophobic carbon nanotube powder obtained in step (3) and stir at 50°C for 6 hours to obtain spinning solution.

[0052] S5. Take 25 mL of the spinning solution obtained in step (4) with a syringe, put it into the injection pump, and set the liquid volume to 20 mL, the liquid pushing speed to 0.5 mL / h, the spinning distance to 15 cm, the rotation speed to 500 rpm, and the voltage to 14.0 kV. Then put the obtained spinning membrane into a vacuum drying oven and dry it at 80°C for 12 hours to obtain a hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic membrane.

[0053] The surface of the hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film prepared in Example 2 was characterized using a scanning electron microscope, and the water contact angle (WCA) of the hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film obtained in Example 2 was measured using a contact angle meter. Figure 4 This is a photograph of the resulting hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film. Figure 5 The image shows a surface electron microscope (SEM) image of the obtained hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film. The inset image shows the hydrophobic angle measurement. Figure 6 The image shows the performance of the resulting hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film.

[0054] according to Figure 4 It can be seen that the product surface has no obvious defects such as delamination, breakage, or local aggregation; the surface is smooth, and the color is light gray. According to... Figure 5It can be seen that the surface of the hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film exhibits a porous morphology of mesh fibers, and there is no aggregation of hydrophobic carbon nanoparticles and PVDF. The hydrophobic angle in air is 147.8°.

[0055] The liquid ingress pressure (LEP) of the membrane was tested using a static liquid ingress pressure tester, and the obtained data was 2.2 bar.

[0056] The membrane performance was tested using a photothermal membrane distillation apparatus, with a feed solution containing 3.5 wt% sodium chloride, a permeate side temperature of 10 °C, and a membrane surface irradiance of 1 kW·m. -2 The size of the membrane exposed to light is 3*8cm. The photothermal desalination performance of the hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic membrane obtained in Example 2 was tested, and the results are as follows: Figure 6 As shown.

[0057] according to Figure 6 It can be seen that at 1kW·m -2 Under light intensity, the feed liquid temperature reached a maximum of 26.6℃, and the mass increase was 11.66g within 3 hours. The calculated permeation flux of the hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic membrane was 1.62 kg·m³. -2 ·h -1 The salt rejection rate reached 99.985%, and the conductivity of the produced water was less than 5.0 μS / cm.

[0058] Comparative Example 1:

[0059] like Figure 7-9 As shown in the comparative example, the present invention provides a method for preparing a hydrophobic polyvinylidene fluoride membrane, comprising the following steps:

[0060] (1) Mix acetone and N,N-dimethylformamide at a mass ratio of 9:1 and weigh 26.4g. Then add 3.6g of polyvinylidene fluoride and stir at 50°C for 6 hours to obtain the spinning solution.

[0061] (2) Draw 25 mL of the spinning solution obtained in step (1) into the injection pump and set the parameters as follows: liquid volume 20 mL, injection speed 0.5 mL / h, spinning distance 15 cm, rotation speed 500 rpm, voltage 14.0 kV. Place the obtained spinning membrane into a vacuum drying oven and dry it at 80 °C to obtain a polyvinylidene fluoride hydrophobic membrane.

[0062] The surface of the polyvinylidene fluoride hydrophobic film obtained in Comparative Example 1 was characterized using a scanning electron microscope, and the water contact angle (WCA) of the polyvinylidene fluoride hydrophobic film obtained in Comparative Example 1 was measured using a contact angle meter. Figure 7 The image shows the actual product of the obtained polyvinylidene fluoride hydrophobic membrane. Figure 8The image shows a surface electron microscope (SEM) image of the obtained polyvinylidene fluoride (PVDF) hydrophobic film. The inset image shows the hydrophobic angle measurement. Figure 9 The diagram shows the performance of the obtained polyvinylidene fluoride hydrophobic membrane.

[0063] according to Figure 7 It can be seen that the product surface has no obvious defects such as delamination, breakage, or local aggregation; the surface is smooth and the color is white. According to... Figure 8 It can be seen that the surface of the polyvinylidene fluoride hydrophobic film exhibits a porous morphology of mesh fibers, and PVDF does not show aggregation. The hydrophobic angle in air is 137.6°.

[0064] The liquid ingress pressure (LEP) of the membrane was tested using a static liquid ingress pressure tester, and the obtained data was 1.4 bar.

[0065] The membrane performance was tested using a photothermal membrane distillation apparatus, with a feed solution containing 3.5 wt% sodium chloride, a permeate side temperature of 10 °C, and a membrane surface irradiance of 1 kW·m. -2 The membrane size exposed to light was 3*8cm. The photothermal desalination performance of the polyvinylidene fluoride hydrophobic membrane obtained in Comparative Example 1 was tested, and the results are as follows: Figure 9 As shown.

[0066] according to Figure 9 It can be seen that at 1kW·m -2 Under light intensity, the feed liquid temperature reached a maximum of 24.6℃, and the mass increase was 9.87g within 3 hours. The calculated permeation flux of the hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic membrane was 1.37 kg·m³. -2 ·h -1 The salt rejection rate is 99.986%, and the conductivity of the produced water is less than 5.0 μS / cm.

[0067] Comparative Example 2:

[0068] like Figure 10-13 As shown in the comparative example, this invention provides a method for preparing a carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film, comprising the following steps:

[0069] (1) Mix acetone and N,N-dimethylformamide at a mass ratio of 9:1 and weigh 26.25g. Then add 3.6g of polyvinylidene fluoride and 0.15g of carbon nanotube powder. Stir at 50°C for 6 hours to obtain spinning solution.

[0070] (2) Take 25 mL of the spinning solution obtained in step (1) with a syringe, put it into the injection pump, and set the parameters as follows: liquid volume 20 mL, liquid pushing speed 0.5 mL / h, spinning distance 15 cm, rotation speed 500 rpm, voltage 14.0 kV. Then put the obtained spinning membrane into a vacuum drying oven and dry it at 80 °C to obtain a carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic membrane.

[0071] The surface of the carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film obtained in Comparative Example 2 was characterized using a scanning electron microscope, and the water contact angle (WCA) of the carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film obtained in Comparative Example 2 was measured using a contact angle meter. Figure 10 This is a photograph of the resulting carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film. Figure 11 The image shows a surface electron microscope (SEM) image of the obtained carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film. The inset image shows the hydrophobic angle measurement. Figure 12 The image shows the performance of the obtained carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film.

[0072] according to Figure 10 It can be seen that the product surface has no obvious defects such as delamination, breakage, or local aggregation; the surface is smooth, and the color is light gray. According to... Figure 11 It can be seen that the carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film exhibits a porous morphology of mesh fibers on its surface, without aggregation, and has a hydrophobic angle of 142.6° in air.

[0073] The liquid ingress pressure (LEP) of the membrane was tested using a static liquid ingress pressure tester, and the obtained data was 1.8 bar.

[0074] The membrane performance was tested using a photothermal membrane distillation apparatus, with a feed solution containing 3.5 wt% sodium chloride, a permeate side temperature of 10 °C, and a membrane surface irradiance of 1 kW·m. -2 The size of the membrane exposed to light is 3*8cm. The photothermal desalination performance of the polyvinylidene fluoride hydrophobic membrane obtained in Comparative Example 2 was tested, and the results are as follows: Figure 12 As shown.

[0075] Depend on Figure 12 It can be seen that at 1kW·m -2 Under light intensity, the feed liquid temperature reached a maximum of 25.5℃, and the mass increase was 11.15g within 3 hours. The calculated permeation flux of the hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic membrane was 1.55 kg·m³. -2 ·h -1 The salt rejection rate reached 99.984%, and the conductivity of the produced water was less than 5.0 μS / cm.

[0076] The hydrophobic membranes obtained in Examples 1 and 2, and Comparative Examples 1 and 2, were tested for condensation conductivity before and after passing through a photothermal membrane distillation system. The values ​​are shown in Table 1. Conductivity was measured using a conductivity meter. The salt rejection rate of different hydrophobic membranes was calculated, and the membrane flux was compared. Figure 13 As shown. The hydrophobic films obtained in Examples 1 and 2, and Comparative Examples 1 and 2 were tested using a dead-end liquid ingress pressure testing system. The test conditions were as follows: the cut area was 19.625 cm². 2 The dried membrane sample was placed in the dead-end membrane module. 20 mL of deionized water was added to the storage tank and pressure was applied by nitrogen gas to force the deionized water into the ultrafiltration cup. The pressure was gradually increased in increments of 0.1 bar and held for 1 minute at each pressure. When the first droplet appeared at the bottom of the module, the pressure value at this time was recorded as LEP. The values ​​are shown in Table 2.

[0077] Table 1. Condensation conductivity before and after hydrophobic film testing in Examples 1 and 2, and Comparative Examples 1 and 2.

[0078] Before testing (μS / cm) After testing (μS / cm) Example 1 2.05 2.63 Example 2 2.15 2.83 Comparative Example 1 2.10 3.16 Comparative Example 2 2.14 2.96

[0079] Table 2. Liquid Inlet Pressure (LEP) of Examples 1 and 2, and Comparative Examples 1 and 2

[0080] LEP (bar) Example 1 2.4 Example 2 2.2 Comparative Example 1 1.4 Comparative Example 2 1.8

[0081] The hydrophobic angle of the hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film can reach 149°, and the static liquid ingress pressure can reach 2.4 bar. At 1 kW·m -2 Under light intensity, the membrane's permeation flux can reach 2.1 kg·m³. -2 ·h -1 The salt rejection rate reaches 99.991%, and the conductivity of the produced water is less than 5.0 μS / cm. It can better balance the relationship between the hydrophobicity of the photothermal membrane, the liquid inlet pressure, and the membrane flux.

[0082] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a hydrophobic carbon nanotube composite polyvinylidene fluoride photothermal hydrophobic film, characterized in that: The method comprises the following steps: S1. mixing water, ethanol and 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and stirring at room temperature for 15 minutes to obtain a hydrophobic modifier, the mass ratio of water, ethanol and 1H,1H,2H,2H-perfluorodecyltriethoxysilane being 50:5:1; S2. adding carbon nanotubes and a certain amount of ammonia water into the hydrophobic modifier of step (1), and stirring at 65°C for 12 hours to obtain a black suspension, the mass ratio of carbon nanotubes to 1H,1H,2H,2H-perfluorodecyltriethoxysilane in step S1 being 1:2, and the amount of ammonia water added being 3mL; S3. centrifuging the black suspension solution obtained in step (2), and washing with ethanol and water, and then placing in a blast drying oven for drying treatment at 80°C for 12-24 hours to obtain hydrophobic carbon nanotube powder; S4. mixing acetone and N,N-dimethylformamide according to a mass ratio of 9:1, and adding a certain amount of polyvinylidene fluoride and the hydrophobic carbon nanotube powder obtained in step (3), and stirring at 50°C for 6 hours to obtain a spinning solution, the mass fractions of polyvinylidene fluoride and hydrophobic carbon nanotube powder being 12wt% and 1.0wt%, respectively; S5. extracting a certain amount of the spinning solution obtained in step (4) with a syringe, placing in a syringe pump, and adjusting the liquid amount, liquid pushing speed, spinning distance, rotation speed, voltage parameters, and placing the obtained spinning film in a vacuum drying oven for drying at 80°C for 12 hours to obtain a hydrophobic carbon nanotube composite polyvinylidene fluoride photo-thermal hydrophobic film, the liquid amount of the spinning solution being 10-20mL, the liquid pushing speed being 0.5-1.0mL / h, the spinning distance being 10-20cm, the rotation speed being 300-1000rpm, and the voltage being 10.0-16.0kV.

2. The preparation method of the hydrophobic carbon nanotube composite polyvinylidene fluoride photo-thermal hydrophobic membrane according to claim 1, characterized in that: The rotation speed of the centrifugation in step S3 is 3000-8000rpm, and the washing times are 3-5 times.

3. Application of the hydrophobic carbon nanotube composite polyvinylidene fluoride photo-thermal hydrophobic film prepared by the method of any one of claims 1-2 to solar film distillation.

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