A super-hydrophobic porous composite membrane material and a preparation method thereof

Abstract

The application provides a super-hydrophobic porous composite film material and a preparation method thereof, and belongs to the technical field of composite film material preparation.The preparation method comprises the following steps: adding a cobalt nitrate hexahydrate solution into a 2-methyl imidazole solution containing graphene oxide, and obtaining a ZIF-67 / graphene oxide composite material through reaction; then, spraying a suspension of the ZIF-67 / graphene oxide composite material on a modified polyvinylidene fluoride surface, drying, transferring to an ethyl lauric acid ethanol solution, reacting for a period of time, taking out, and drying to obtain the super-hydrophobic porous composite film material.The super-hydrophobic porous composite film material prepared by the application has a water contact angle of 162.35 degrees and a sliding angle of 2 degrees, has excellent hydrophobic characteristics, excellent self-cleaning performance, high mechanical strength and good durability, and meets the actual use requirements.

Description

Technical Field

[0001] This invention relates to the field of composite membrane material preparation technology, specifically to a superhydrophobic porous composite membrane material and its preparation method. Background Technology

[0002] Superhydrophobicity generally refers to a surface property where the contact angle of a water droplet on a solid surface is greater than 150° and less than 180°, and the roll-off angle is less than 10°. The key to constructing superhydrophobic film materials is to build a rough surface with micro- and nano-structures and reduce the surface energy of the film material. In existing technologies, inorganic materials with large specific surface areas and small dimensions are usually used to prepare superhydrophobic surfaces.

[0003] Metal-organic frameworks (MOFs), also known as porous coordination polymers, are porous materials mainly formed by the interaction of inorganic metals and organic ligands through coordination bonds. MOFs combine the advantages of both organic and inorganic materials, exhibiting characteristics such as large specific surface area and low density, making composite materials prepared using MOFs as raw materials more functionally diverse. Zeolitic imidazolate frameworks (ZIFs) are a crucial type of MOF material. They are cage-like compounds with a zeolite topology formed by the coordination of N atoms on imidazolium rings with divalent transition metal ions. They not only possess the large specific surface area and large pore size of MOF materials but also the high thermal stability and excellent chemical stability of zeolite structures. In the preparation of superhydrophobic materials, they can replace traditional inorganic nanomaterials in constructing micro / nano rough surfaces and improving the hydrophobic properties of materials. Therefore, research on hydrophobic film materials based on ZIFs has received increasing attention. In addition, fluorinated silane coupling agents are usually used in the preparation of existing superhydrophobic membrane materials to reduce the surface energy of the membrane. However, fluorinated silane coupling agents have certain toxicity and are not ideal in terms of environmental protection and safety.

[0004] Therefore, it is of great significance to develop a superhydrophobic porous composite membrane material based on ZIFs that conforms to the concept of green and environmentally friendly development. Summary of the Invention

[0005] In view of this, the present invention provides a method for preparing a superhydrophobic porous composite membrane material, comprising the following steps:

[0006] (1) Dissolve 2-methylimidazole in methanol solution, then add a certain proportion of graphene oxide to the system, and after ultrasonic dispersion, obtain solution A; dissolve cobalt nitrate hexahydrate in methanol solution to obtain solution B;

[0007] (2) Add the solution B to the solution A while stirring, continue stirring for 0.5-1.0 h, centrifuge, wash and dry to obtain ZIF-67 / graphene oxide composite material;

[0008] (3) Polyvinylidene fluoride was immersed in potassium hydroxide solution for reaction. After the reaction was completed, it was washed and dried to obtain modified polyvinylidene fluoride.

[0009] (4) Add deionized water to the ZIF-67 / graphene oxide composite material described in step (2) and disperse it evenly under ultrasonic conditions to obtain a suspension;

[0010] (5) Spray the suspension described in step (4) onto the surface of the modified polyvinylidene fluoride described in step (3) for the first drying treatment. Then, immerse the product after the drying treatment in a wood wax acid ethanol solution, let it stand for a certain period of time, take it out, and perform a second drying to obtain a superhydrophobic porous composite membrane material.

[0011] Furthermore, the mass ratio of graphene oxide to 2-methylimidazole in step (1) is 1:10-18.

[0012] Furthermore, the molar ratio of 2-methylimidazole and cobalt nitrate hexahydrate in step (1) is 2.5-5.8:1.

[0013] Furthermore, in step (2), the centrifugation speed is 5500-8000 rpm and the centrifugation time is 3-8 min. Preferably, the centrifugation speed is 7000 rpm and the centrifugation time is 5 min.

[0014] Furthermore, step (2) involves repeated washing with methanol multiple times, preferably three times.

[0015] Furthermore, in step (2), the drying temperature is 100-145℃ and the drying time is 15-25h. Preferably, the drying temperature is 120℃ and the drying time is 18h.

[0016] Furthermore, the concentration of the potassium hydroxide solution in step (3) is 3-5.5 mol / L, preferably 3.5 mol / L.

[0017] Furthermore, in step (3), the reaction temperature is 60-65℃ and the reaction time is 1.0-1.7h. Preferably, the reaction temperature is 60℃ and the reaction time is 1.5h.

[0018] Furthermore, in step (3), the product is washed repeatedly with pure water, preferably three times.

[0019] Furthermore, in step (3), the drying temperature is 60-65℃ and the drying time is 0.5-0.8h. Preferably, the drying temperature is 62℃ and the drying time is 0.7h.

[0020] Furthermore, in step (4), the mass-to-volume ratio of the ZIF-67 / graphene oxide composite material to deionized water is 0.01-0.05:100.

[0021] Furthermore, in step (4), the ultrasonic power is 300-800W and the ultrasonic time is 0.3-1.0h. Preferably, the ultrasonic power is 300W and the ultrasonic time is 0.5h.

[0022] Furthermore, in step (5), the temperature of the first drying process is 60-65℃ and the drying time is 0.5-1.2h. Preferably, the temperature of the first drying process is 60℃ and the drying time is 0.8h.

[0023] Furthermore, the concentration of the ceramide ethanol solution in step (5) is 8-13 g / L, preferably 10 g / L.

[0024] Furthermore, after step (5), the sample is taken out after a standing time of 1-3 hours, preferably 2 hours.

[0025] Furthermore, in step (5), the second drying temperature is 80-95℃ and the second drying time is 1-2h. Preferably, the second drying temperature is 85℃ and the second drying time is 1h.

[0026] The present invention also provides a superhydrophobic porous composite membrane material prepared according to the method.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] Because ZIF-67 has a high surface energy, its particles tend to agglomerate to reduce surface area, resulting in poor dispersibility. Poor dispersibility can easily lead to poor particle uniformity on the surface of the composite membrane material and blockage of membrane pores. To solve this problem, this invention grows ZIF-67 in situ on the surface of graphene oxide and combines it with ultrasonic dispersion technology to improve the dispersibility of ZIF-67, which helps to improve the hydrophobicity and self-cleaning properties of the composite membrane material.

[0029] This invention improves the surface roughness and hydrophobicity of a membrane material by spraying a ZIF-67 / graphene oxide composite material onto the surface of modified polyvinylidene fluoride. Then, modification with wood wax acid further reduces the surface energy of the composite membrane, successfully producing a superhydrophobic porous composite membrane material.

[0030] Existing superhydrophobic membrane materials typically use fluorinated silane coupling agents to reduce membrane surface energy during preparation. However, these agents are toxic and their environmental and safety aspects are not ideal. Therefore, this invention utilizes the biomass material lignosulfonic acid in the preparation of superhydrophobic composite membrane materials, improving the safety of the membrane material and making it environmentally friendly, in line with the concept of sustainable development.

[0031] The superhydrophobic porous composite membrane material provided by this invention has a water contact angle of up to 162.35° and a sliding angle of 2°, exhibiting excellent hydrophobic properties, as well as superior self-cleaning ability, high mechanical strength, and good durability, thus meeting practical application requirements. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0033] Unless otherwise specified, the test methods or experimental methods described in the following examples are all conventional methods; unless otherwise specified, the raw materials and additives are obtained from conventional commercial sources or prepared by conventional methods.

[0034] The cobalt nitrate hexahydrate used in the following examples or comparative examples was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. 2-Methylimidazole was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. Graphene oxide was purchased from Kaina Carbon New Materials Co., Ltd. Polyvinylidene fluoride was purchased from Shanghai Maclean Biochemical Co., Ltd. Caulic acid was purchased from Shanghai Maclean Biochemical Co., Ltd.

[0035] Hydrophobicity testing method: The static contact angle and sliding angle of the material were tested using an SDC-350 contact angle measuring instrument manufactured by Dongguan Shengding Precision Instruments Co., Ltd. Water droplets were placed on the surface of the membrane material under test, and the static contact angle and sliding angle were calculated using the instrument's built-in software system to determine the surface condition of the membrane material. The test was conducted at room temperature, using deionized water as the reagent, with a volume of 8µL each time. The same sample was tested 5 times at different sites, and the average value was taken.

[0036] Self-cleaning test method: Fix the membrane material on the glass substrate and tilt it at a 30° angle. Sprinkle an appropriate amount of black chalk dust on the tilted surface and observe the condition of the tilted surface after water rinsing to determine the self-cleaning performance.

[0037] Durability testing method: The composite membrane material was placed in air, and the contact angle was tested on the 10th, 50th, 100th, 160th, 230th and 310th days. The tests were conducted at room temperature.

[0038] Example 1

[0039] A method for preparing a superhydrophobic porous composite membrane material, comprising the following specific steps:

[0040] (1) Weigh 1.5426 g (18.79 mmol) of 2-methylimidazole and dissolve it in 50 mL of methanol solution. Then add 0.1585 g of graphene oxide to the system and disperse it evenly by ultrasonication. The ultrasonic power is 550 W and the ultrasonication time is 0.7 h to obtain solution A. Dissolve 1.15 g (3.95 mmol) of cobalt nitrate hexahydrate in 50 mL of methanol solution to obtain solution B.

[0041] (2) Add the solution B to the solution A while stirring, continue stirring for 0.8 h, centrifuge at 7000 rpm for 5 min, wash three times with methanol, and dry at 120℃ for 18 h to obtain ZIF-67 / graphene oxide composite material.

[0042] (3) Immerse polyvinylidene fluoride in a 3.5 mol / L potassium hydroxide solution and react at 60°C for 1.5 h. After the reaction is complete, wash with pure water three times and dry at 62°C for 0.7 h to obtain modified polyvinylidene fluoride.

[0043] (4) Weigh 0.03g of ZIF-67 / graphene oxide composite material and add it to 100ml of deionized water, and disperse it evenly under ultrasonic conditions. The ultrasonic power is 300W and the ultrasonic time is 0.5h to obtain a suspension.

[0044] (5) Spray the suspension described in step (4) onto the surface of the modified polyvinylidene fluoride described in step (3), dry it at 60°C for 0.8h, then immerse the product after drying in a 10g / L ethanol solution of wood wax acid, let it stand for 2h, take it out and dry it at 85°C for 1h to obtain a superhydrophobic porous composite membrane material.

[0045] Example 2

[0046] A method for preparing a superhydrophobic porous composite membrane material, comprising the following specific steps:

[0047] (1) Weigh 1.5426 g of 2-methylimidazole (18.79 mmol) and dissolve it in 50 mL of methanol solution. Then add 0.1372 g of graphene oxide to the system and disperse it evenly by ultrasonication to obtain solution A. Dissolve 1.15 g of cobalt nitrate hexahydrate (3.95 mmol) in 50 mL of methanol solution to obtain solution B.

[0048] (2) Add the solution B to the solution A while stirring, continue stirring for 0.5 h, centrifuge at 5500 rpm for 3 min, wash three times with methanol, and dry at 100℃ for 15 h to obtain ZIF-67 / graphene oxide composite material.

[0049] (3) Immerse polyvinylidene fluoride in a 3 mol / L potassium hydroxide solution and react at 60°C for 1.0 h. After the reaction is complete, wash with pure water three times and dry at 60°C for 0.5 h to obtain modified polyvinylidene fluoride.

[0050] (4) Weigh 0.01g of ZIF-67 / graphene oxide composite material and add it to 100ml of deionized water, and disperse it evenly under ultrasonic conditions. The ultrasonic power is 300W and the ultrasonic time is 0.3h to obtain a suspension.

[0051] (5) Spray the suspension described in step (4) onto the surface of the modified polyvinylidene fluoride described in step (3), dry it at 65°C for 0.5h, then immerse the product after drying in an ethanol solution of wood wax acid with a concentration of 8g / L, let it stand for 1h, take it out and dry it at 80°C for 1h to obtain a superhydrophobic porous composite membrane material.

[0052] Example 3

[0053] A method for preparing a superhydrophobic porous composite membrane material, comprising the following specific steps:

[0054] (1) Weigh 1.5426 g (18.79 mmol) of 2-methylimidazole and dissolve it in 50 mL of methanol solution. Then add 0.1191 g of graphene oxide to the system and disperse it evenly by ultrasonication to obtain solution A. Dissolve 1.15 g (3.95 mmol) of cobalt nitrate hexahydrate in 50 mL of methanol solution to obtain solution B.

[0055] (2) Add the solution B to the solution A while stirring, continue stirring for 1.0 h, centrifuge at 8000 rpm for 8 min, wash three times with methanol, and dry at 145℃ for 25 h to obtain ZIF-67 / graphene oxide composite material.

[0056] (3) Immerse polyvinylidene fluoride in a 5.5 mol / L potassium hydroxide solution and react at 65°C for 1.7 h. After the reaction is complete, wash three times with pure water and dry at 65°C for 0.8 h to obtain modified polyvinylidene fluoride.

[0057] (4) Weigh 0.05g of ZIF-67 / graphene oxide composite material and add it to 100ml of deionized water. Disperse it evenly under ultrasonic conditions. The ultrasonic power is 800W and the ultrasonic time is 1.0h to obtain a suspension.

[0058] (5) Spray the suspension described in step (4) onto the surface of the modified polyvinylidene fluoride described in step (3), dry it at 60°C for 1.2 h, then immerse the product after drying in a 13 g / L ethanol solution of wood wax acid, let it stand for 3 h, take it out and dry it at 95°C for 2 h to obtain a superhydrophobic porous composite membrane material.

[0059] Comparative Example 1

[0060] A method for preparing a superhydrophobic porous composite membrane material, comprising the following specific steps:

[0061] (1) Weigh 2-methylimidazole (1.5426 g, 18.79 mmol) and dissolve it in 50 mL of methanol solution. Disperse it evenly by ultrasonication with a power of 550 W and an ultrasonication time of 0.7 h to obtain solution A; dissolve cobalt nitrate hexahydrate (1.15 g, 3.95 mmol) in 50 mL of methanol solution to obtain solution B;

[0062] (2) Add the solution B to the solution A while stirring, continue stirring for 0.8 h, centrifuge at 7000 rpm for 5 min, wash three times with methanol, and dry at 120℃ for 158 h to obtain ZIF-67 material;

[0063] (3) Immerse polyvinylidene fluoride in a 3.5 mol / L potassium hydroxide solution and react at 60°C for 1.5 h. After the reaction is complete, wash with pure water three times and dry at 62°C for 0.7 h to obtain modified polyvinylidene fluoride.

[0064] (4) Weigh 0.03g of ZIF-67 material and add it to 100ml of deionized water, and disperse it evenly under ultrasonic conditions. The ultrasonic power is 300W and the ultrasonic time is 0.5h to obtain a suspension.

[0065] (5) Spray the suspension described in step (4) onto the surface of the modified polyvinylidene fluoride described in step (3), dry it at 60°C for 0.8h, then immerse the product after drying in a 10g / L ethanol solution of wood wax acid, let it stand for 2h, take it out and dry it at 85°C for 1h to obtain a superhydrophobic porous composite membrane material.

[0066] Comparative Example 2

[0067] A method for preparing a superhydrophobic porous composite membrane material, comprising the following specific steps:

[0068] (1) Weigh 1.5426 g (18.79 mmol) of 2-methylimidazole and dissolve it in 50 mL of methanol solution. Then add 0.1585 g of graphene oxide to the system and disperse it evenly by ultrasonication. The ultrasonic power is 550 W and the ultrasonication time is 0.7 h to obtain solution A. Dissolve 1.15 g (3.95 mmol) of cobalt nitrate hexahydrate in 50 mL of methanol solution to obtain solution B.

[0069] (2) Add the solution B to the solution A while stirring, continue stirring for 0.8 h, centrifuge at 7000 rpm for 5 min, wash three times with methanol, and dry at 120℃ for 158 h to obtain ZIF-67 / graphene oxide composite material.

[0070] (3) Immerse polyvinylidene fluoride in a 3.5 mol / L potassium hydroxide solution and react at 60°C for 1.5 h. After the reaction is complete, wash with pure water three times and dry at 62°C for 0.7 h to obtain modified polyvinylidene fluoride.

[0071] (4) Weigh 0.03g of ZIF-67 / graphene oxide composite material and add it to 100ml of deionized water. Disperse it evenly under ultrasonic conditions. The ultrasonic power is 300W and the ultrasonic time is 0.5h to obtain a suspension.

[0072] (5) Spray the suspension from step (4) onto the surface of the modified polyvinylidene fluoride from step (3) and dry it at 60°C for 0.8 h to obtain a porous composite membrane material.

[0073] Performance testing

[0074] 1) The hydrophobicity and self-cleaning properties of the composite membrane materials provided in the test examples and comparative examples are shown in Table 1.

[0075] Table 1

[0076]

[0077] As shown in Table 1, compared to Comparative Examples 1 and 2, the composite membrane material prepared in this embodiment of the invention has a contact angle as high as 162.35°, exhibiting significant superhydrophobic properties. Simultaneously, the composite membrane material prepared in this embodiment of the invention has a low sliding angle, as low as 2°, allowing black chalk dust on the membrane surface to be easily washed away by water flow. Therefore, the composite membrane material prepared in this embodiment of the invention also possesses excellent self-cleaning properties.

[0078] (ii) The durability of the composite membrane materials in the test examples and comparative examples is expressed as contact angle. The test results are shown in Table 2.

[0079] Table 2

[0080]

[0081] As shown in Table 2, the contact angle of the composite membrane material prepared by this invention decreased by only 2.64° after being placed in air for 310 days, indicating that the composite membrane material prepared by this invention has excellent durability. In contrast, the contact angles of the composite membrane materials prepared in Comparative Example 1 and Comparative Example 2 both decreased significantly.

[0082] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a superhydrophobic porous composite membrane material, characterized in that, Includes the following steps: (1) Dissolve 2-methylimidazole in methanol solution, then add a certain proportion of graphene oxide to the system, and after ultrasonic dispersion, obtain solution A; dissolve cobalt nitrate hexahydrate in methanol solution to obtain solution B; (2) Add the solution B to the solution A while stirring, continue stirring for 0.5-1.0 h, centrifuge, wash and dry to obtain ZIF-67 / graphene oxide composite material; (3) Polyvinylidene fluoride was immersed in potassium hydroxide solution for reaction. After the reaction was completed, it was washed and dried to obtain modified polyvinylidene fluoride. (4) Add deionized water to the ZIF-67 / graphene oxide composite material described in step (2) and disperse it evenly under ultrasonic conditions to obtain a suspension; (5) Spray the suspension described in step (4) onto the surface of the modified polyvinylidene fluoride described in step (3) for the first drying treatment. Then, immerse the product after the drying treatment in a wood wax acid ethanol solution, let it stand for a certain time, take it out, and perform a second drying to obtain a superhydrophobic porous composite membrane material. The mass ratio of graphene oxide to 2-methylimidazole in step (1) is 1:10-18; The molar ratio of 2-methylimidazole and cobalt nitrate hexahydrate in step (1) is 2.5-5.8:1; The reaction temperature in step (3) is 60-65℃, and the reaction time is 1.0-1.7h; The concentration of the ceramide ethanol solution in step (5) is 8-13 g / L.

2. The method for preparing the superhydrophobic porous composite membrane material according to claim 1, characterized in that, The drying temperature in step (2) is 100-145℃, and the drying time is 15-25h.

3. The method for preparing the superhydrophobic porous composite membrane material according to claim 1, characterized in that, The drying temperature in step (3) is 60-65℃ and the drying time is 0.5-0.8h.

4. The method for preparing the superhydrophobic porous composite membrane material according to claim 1, characterized in that, In step (4), the mass-to-volume ratio of the ZIF-67 / graphene oxide composite material to deionized water is 0.01-0.05:

100.

5. The superhydrophobic porous composite membrane material prepared by the method according to any one of claims 1-4.

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