Heterogeneous carbon nanotube and oil-water separation membrane prepared therefrom

Abstract

The present invention relates to the technical field of oil-water separation membrane preparation, specifically a heterogeneous carbon nanotube and an oil-water separation membrane prepared therefrom. The heterogeneous carbon nanotube is obtained by grafting a titanium dioxide / carbon nanotube composite material with a hydrophilic and oleophobic modifier; the oil-water separation membrane preparation includes the following components: by mass fraction, 5-15% of heterogeneous carbon nanotube, 60-70% of N,N-dimethylacetamide, 15-25% of polyacrylonitrile, 2-8% of polyvinylpyrrolidone, and 2-4% of a defoaming agent. In the present invention, a hydrophilic and oleophobic modification is performed on carbon nanotubes, and then an oil-water separation membrane with excellent hydrophilic and oleophobic properties is prepared therefrom, which can well realize oil-water separation, and in addition, it also has a certain anti-pollution ability and can maintain a good separation efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of oil-water separation membrane preparation, in particular to a heterogeneous carbon nanotube and an oil-water separation membrane prepared therefrom. Background Art

[0002] The basic treatment method for oily wastewater is oil-water separation, and membrane separation technology plays an important role in this. At present, super-hydrophobic separation membranes are commonly used in membrane separation technology, which can achieve the selective penetration and absorption of oil in oil-water mixtures and the separation effect of repelling water. However, since the density of water is greater than that of oil, water tends to form a barrier layer on the surface of the hydrophobic membrane, thereby preventing the penetration of oil. In addition, this type of membrane is easily contaminated or even blocked by selectively permeable oil, resulting in a rapid decrease in separation efficiency. The hydrophilic separation membrane can selectively absorb the permeated water and repel the oil, which can effectively avoid the formation of a barrier layer and overcome the defects of the hydrophobic separation membrane.

[0003] In recent years, with the development of one-dimensional nanomaterials, especially carbon nanotubes, good application prospects have been shown. The inherent hydrophobicity of carbon nanotubes makes them an extremely attractive candidate for oil-water separation. Due to their good film-forming properties and excellent processing performance, highly dispersed carbon nanotubes are widely used to construct oil-water separation membranes.

[0004] Based on this, the present invention will perform hydrophilic and oleophobic modification on carbon nanotubes, and then use them to prepare an oil-water separation membrane for efficiently separating oil and water. Summary of the invention

[0005] The purpose of the present invention is to provide a heterogeneous carbon nanotube and an oil-water separation membrane prepared therefrom to solve the problems raised in the prior art.

[0006] To achieve the above object, the first aspect of the present invention provides the following technical solutions:

[0007] A heterogeneous carbon nanotube is obtained by grafting a titanium dioxide / carbon nanotube composite material with a hydrophilic and oleophobic modifier.

[0008] Furthermore, the method for preparing the heterogeneous carbon nanotubes comprises the following steps:

[0009] Step 1: (1) Add carbon nanotubes, concentrated sulfuric acid and concentrated nitric acid into a container, stir and mix evenly, then heat to 50-100°C, soak for 0.5-3h, filter, wash with water until neutral, and dry to obtain acidified carbon nanotubes; (2) Add acidified carbon nanotubes and 50-80v / v% ethanol solution into a container, ultrasonically disperse for 1-2h, adjust the pH to 9-10, and then drop 2.5-5v / v% tetrabutyl titanate anhydrous ethanol solution therein while stirring. After the dropwise addition is complete, continue stirring and reacting for 1-12h, and finally filter, wash, and dry to obtain a titanium dioxide / carbon nanotube composite material;

[0010] Step 2: (1) Add N,N'-vinylbisacrylamide and tetrahydrofuran into a container, stir and mix them evenly, then add perfluoro-2,5-dimethyl-3,6-dioxanoic acid, dicyclohexylcarbodiimide and 1-hydroxybenzotriazole into it under a nitrogen environment, and heat it to 50-80°C, stir and react for 1-24 hours, terminate the reaction, filter and dry to obtain product A; (2) Add product A, acrylic acid, polyethylene glycol diacrylate and ammonium persulfate solution into a container, stir and mix them evenly, stir and react at 70-85°C for 1-6 hours, terminate the reaction, separate ammonium persulfate and obtain product B; (3) Add product B, 3-mercaptopropyltrimethoxysilane and a photoinitiator into a container, stir and mix them evenly, irradiate under 350-370nm ultraviolet light for 1-20 minutes, terminate the reaction and obtain a hydrophilic-oleophobic modifier;

[0011] Step 3: Add the titanium dioxide / carbon nanotube composite material, the hydrophilic-oleophobic modifier and 50-80 v / v% ethanol solution into a container, stir and mix evenly, and soak at 45-60° C. for 0.5-3 h to obtain heterogeneous carbon nanotubes.

[0012] Furthermore, the ratio of the carbon nanotubes, concentrated sulfuric acid and concentrated nitric acid is (0.5-2) g:20 mL:30 mL.

[0013] Furthermore, the carbon nanotubes include but are not limited to any one of single-walled carbon nanotubes, double-walled carbon nanotubes and multi-walled carbon nanotubes.

[0014] Furthermore, in the embodiment of the present invention, the carbon nanotubes are preferably multi-walled carbon nanotubes.

[0015] Since multi-walled carbon nanotubes have more defects on their surfaces than single-walled carbon nanotubes and double-walled carbon nanotubes, they can be better treated by acidification, thereby generating more active groups on their surfaces.

[0016] Furthermore, the ratio of the acidified carbon nanotubes, the 50-80 v / v% ethanol solution and the 2.5-5 v / v% anhydrous ethanol solution of tetrabutyl titanate is (0.5-2) g:100 mL:100 mL.

[0017] Since titanium dioxide has hydrophilic and oleophobic properties, the present invention is designed to deposit it on carbon nanotubes so that the carbon nanotubes show good hydrophilic and oleophobic properties; and in order to enhance the bonding force between titanium dioxide and carbon nanotubes, the carbon nanotubes are acidified in the scheme so that their surface obtains more active groups (-COOH) that can generate titanium dioxide in situ, thereby allowing titanium dioxide to be evenly generated on the carbon nanotubes and more tightly bonded to them. On the other hand, carbon nanotubes also have the defects of poor mechanical strength and easy agglomeration. By depositing titanium dioxide, their mechanical strength can be enhanced to a certain extent and their dispersibility can be improved to a certain extent.

[0018] Furthermore, the mass ratio of the N,N'-vinylbisacrylamide, perfluoro-2,5-dimethyl-3,6-dioxanononanoic acid, dicyclohexylcarbodiimide and 1-hydroxybenzotriazole is 1:(5.5-7):(0.1-0.5):(0.1-0.5).

[0019] Furthermore, the mass ratio of the product A, acrylic acid, polyethylene glycol diacrylate and ammonium persulfate is 5:(0.5~1):(0.5~1):(0.05~0.1).

[0020] Furthermore, the mass ratio of the product B, 3-mercaptopropyltrimethoxysilane and the photoinitiator is 1:(0.5~1):(0.03~0.06).

[0021] In order to enhance the hydrophilic and oleophobic properties of titanium dioxide / carbon nanotubes, the present invention further promotes the amidation reaction of N,N'-vinylbisacrylamide and perfluoro-2,5-dimethyl-3,6-dioxanononanoic acid to prepare product A; then initiates polymerization with acrylic acid and polyethylene glycol to prepare product B; finally, through a click reaction, reacts with 3-mercaptopropyltrimethoxysilane to prepare a hydrophilic and oleophobic modifier. The hydrophilic-oleophobic modifier contains abundant carboxyl and hydroxyl groups, which can enhance the hydrophilicity of titanium dioxide / carbon nanotubes, and also contains oleophobic components (fluoroalkyl groups) to enhance the oleophobicity of titanium dioxide / carbon nanotubes. On the other hand, the fluorine in the hydrophilic-oleophobic modifier can also form hydrogen bonding forces with carboxyl and hydroxyl groups, further converting the originally hydrophobic fluorine into hydrophilic, that is, the hydrophilic-oleophobic modifier has extremely excellent hydrophilic-oleophobic properties. Finally, due to the use of 3-mercaptopropyltrimethoxysilane end-capping, the hydrophilic-oleophobic modifier can also be used as a coupling agent, and the titanium dioxide / carbon nanotubes can be enhanced and modified by using the hydrophilic-oleophobic modifier, and the hydrophilic-oleophobic properties of titanium dioxide / carbon nanotubes can be enhanced, and the dispersion performance is also better, so the separation effect of the prepared oil-water separation membrane for water and oil is also more excellent.

[0022] Furthermore, the mass ratio of the titanium dioxide / carbon nanotube composite material, the hydrophilic-oleophobic modifier and the 50-80 v / v% ethanol solution is 2:(1-2):10.

[0023] The second aspect of the present invention provides an oil-water separation membrane prepared from the heterogeneous carbon nanotubes.

[0024] Furthermore, the preparation method of the oil-water separation membrane is as follows: (1) adding heterogeneous carbon nanotubes to N,N-dimethylacetamide, ultrasonically dispersing for 1 to 15 minutes, then adding polyacrylonitrile, polyvinyl pyrrolidone and a defoaming agent thereto, heating to 50 to 70°C and stirring for 1 to 6 hours to obtain a casting liquid; (2) pouring the casting liquid onto a scraping plate, scraping it evenly with a scraper, placing it at room temperature for 10 to 60 minutes, then injecting clean water into the scraping plate, soaking it for 24 to 48 hours, taking it out, and finally drying it at 50 to 70°C, and trimming it to obtain an oil-water separation membrane.

[0025] Furthermore, the oil-water separation membrane preparation includes the following components: by mass fraction, 5-15% heterogeneous carbon nanotubes, 60-70% N,N-dimethylacetamide, 15-25% polyacrylonitrile, 2-8% polyvinyl pyrrolidone, and 2-4% defoaming agent.

[0026] Furthermore, the pouring amount of the casting solution is not less than 2 mL / cm 2 .

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

[0028] 1. The present invention obtains heterogeneous carbon nanotubes with hydrophilic and oleophobic properties by modifying carbon nanotubes to be hydrophilic and oleophobic, and then uses the heterogeneous carbon nanotubes with polyacrylonitrile to prepare an oil-water separation membrane with excellent hydrophilic and oleophobic properties. The oil-water separation membrane has the ability to quickly penetrate water and can well block oil;

[0029] 2. Due to the filling of heterogeneous carbon nanotubes in the oil-water separation membrane, the surface of the oil-water separation membrane becomes smoother, which is not conducive to the accumulation of pollutants and also improves the anti-pollution ability of the oil-water separation membrane to a certain extent. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] It should be noted that the purchasers of all raw materials involved in the present invention are not subject to any special restrictions and exemplarily include: In the following embodiments: the sources of the raw materials used are as follows:

[0032] Multi-walled carbon nanotubes with a purity of 99%, a diameter of 50 nm, and a length of 10 μm, item number: 100288, were purchased from Xianfeng Nano Co., Ltd.;

[0033] Tetrabutyl titanate with a purity of 99%, N,N-dimethylacetamide with a purity of 99%, polyacrylonitrile with a purity of 99%, CAS number: 25014-41-9, item number: 25014-41-9, acrylic acid with a purity of 99%, were purchased from Hubei Yongkuo Technology Co., Ltd.;

[0034] N,N'-vinylbisacrylamide with a purity of 99%, perfluoro-2,5-dimethyl-3,6-dioxanonanoic acid with a purity of 99%, dicyclohexylcarbodiimide with a purity of 99%, and 1-hydroxybenzotriazole with a purity of 99% were all purchased from JACS-Zhengzhou Jacks Chemical Products Co., Ltd.;

[0035] Polyethylene glycol diacrylate with a purity of 99.5%, 3-mercaptopropyltrimethoxysilane with a purity of 99%, and polyvinyl pyrrolidone with a purity of 99.5% were all purchased from Hubei Jusheng Technology Co., Ltd.

[0036] Example 1: A heterogeneous carbon nanotube and an oil-water separation membrane prepared therefrom:

[0037] 1. Preparation of heterogeneous carbon nanotubes:

[0038] Step 1: (1) Add multi-walled carbon nanotubes, 98wt% concentrated sulfuric acid and 65wt% concentrated nitric acid in a ratio of 2g:20mL:30mL into a container, stir and mix evenly, then heat to 75°C, soak for 1.5h, filter, wash with clean water until neutral, and dry to obtain acidified carbon nanotubes; (2) Add the acidified carbon nanotubes and 70v / v% ethanol solution into a container, ultrasonically disperse for 2h, add 28wt% ammonia water to adjust the pH to 9, and then add 4v / v% tetrabutyl titanate anhydrous ethanol solution dropwise thereto under stirring (wherein, the ratio of the acidified carbon nanotubes, 70v / v% ethanol solution and 4v / v% tetrabutyl titanate anhydrous ethanol solution is 1.5g:100mL:100mL), after the addition is complete, continue to stir and react for 12h, and finally filter, wash and dry to obtain a titanium dioxide / carbon nanotube composite material;

[0039] Step 2: (1) Add 10 parts of N,N'-vinylbisacrylamide and 100 parts of tetrahydrofuran into a container, stir and mix evenly, then add 60 parts of perfluoro-2,5-dimethyl-3,6-dioxanoic acid, 3 parts of dicyclohexylcarbodiimide and 3 parts of 1-hydroxybenzotriazole under nitrogen atmosphere, heat to 70°C, stir and react for 12 hours, terminate the reaction, filter and dry to obtain product A; (2) Add 50 parts of product A and 8 (3) adding 40 parts of product B, 25 parts of 3-mercaptopropyltrimethoxysilane and 2 parts of photoinitiator into a container, stirring and mixing evenly, irradiating under 350nm ultraviolet light for 10 minutes, and terminating the reaction to obtain a hydrophilic and oleophobic modifier;

[0040] Step 3: Add 30 parts of titanium dioxide / carbon nanotube composite material, 22.5 parts of hydrophilic oleophobic modifier and 150 parts of 70 v / v% ethanol solution into a container, stir and mix evenly, and soak at 50° C. for 2 hours to obtain heterogeneous carbon nanotubes;

[0041] 2. Preparation of oil-water separation membrane: (1) Add 36 parts of heterogeneous carbon nanotubes to 186 parts of N,N-dimethylacetamide, and ultrasonically disperse for 10 minutes. Then, add 54 parts of polyacrylonitrile, 18 parts of polyvinyl pyrrolidone and 6 parts of defoaming agent, heat to 60°C and stir for 4 hours to obtain a casting solution; (2) Pour the casting solution onto a scraping plate (pouring volume 2 mL / cm 2), after being evenly scraped with a scraper, it was placed at room temperature for 60 minutes, and then clean water was injected into the scraper plate, soaked for 48 hours, taken out, and finally dried at 60°C. After trimming, an oil-water separation membrane was obtained; wherein, the components used in the preparation of the oil-water separation membrane are: by mass fraction, 12% heterogeneous carbon nanotubes, 62% N,N-dimethylacetamide, 18% polyacrylonitrile, 6% polyvinyl pyrrolidone, and 2% defoaming agent.

[0042] Example 2: A heterogeneous carbon nanotube and an oil-water separation membrane prepared therefrom:

[0043] 1. Preparation of heterogeneous carbon nanotubes:

[0044] Step 1: (1) Add multi-walled carbon nanotubes, 98wt% concentrated sulfuric acid and 65wt% concentrated nitric acid in a ratio of 2g:20mL:30mL into a container, stir and mix evenly, then heat to 75°C, soak for 1.5h, filter, wash with clean water until neutral, and dry to obtain acidified carbon nanotubes; (2) Add the acidified carbon nanotubes and 70v / v% ethanol solution into a container, ultrasonically disperse for 2h, add 28wt% ammonia water to adjust the pH to 9, and then add 4v / v% tetrabutyl titanate anhydrous ethanol solution dropwise thereto under stirring (wherein the ratio of the acidified carbon nanotubes, 70v / v% ethanol solution and 4v / v% tetrabutyl titanate anhydrous ethanol solution is 0.5g:100mL:100mL), after the addition is complete, continue to stir and react for 12h, and finally filter, wash and dry to obtain a titanium dioxide / carbon nanotube composite material;

[0045] Step 2: (1) Add 10 parts of N,N'-vinylbisacrylamide and 100 parts of tetrahydrofuran into a container, stir and mix evenly, then add 55 parts of perfluoro-2,5-dimethyl-3,6-dioxanoic acid, 3 parts of dicyclohexylcarbodiimide and 3 parts of 1-hydroxybenzotriazole under nitrogen atmosphere, heat to 70°C, stir and react for 12 hours, terminate the reaction, filter and dry to obtain product A; (2) Add 50 parts of product A and 5 (3) adding 40 parts of product B, 20 parts of 3-mercaptopropyltrimethoxysilane and 2 parts of photoinitiator into a container, stirring and mixing evenly, irradiating under 350nm ultraviolet light for 10 minutes, and terminating the reaction to obtain a hydrophilic and oleophobic modifier;

[0046] Step 3: Add 30 parts of titanium dioxide / carbon nanotube composite material, 15 parts of hydrophilic oleophobic modifier and 150 parts of 70v / v% ethanol solution into a container, stir and mix evenly, and soak at 50°C for 2h to obtain heterogeneous carbon nanotubes;

[0047] 2. Preparation of oil-water separation membrane: (1) Add 36 parts of heterogeneous carbon nanotubes to 186 parts of N,N-dimethylacetamide, and ultrasonically disperse for 10 minutes. Then, add 54 parts of polyacrylonitrile, 18 parts of polyvinyl pyrrolidone and 6 parts of defoaming agent, heat to 60°C and stir for 4 hours to obtain a casting solution; (2) Pour the casting solution onto a scraping plate (pouring volume 2 mL / cm 2 ), after being evenly scraped with a scraper, it was placed at room temperature for 60 minutes, and then clean water was injected into the scraper plate, soaked for 48 hours, taken out, and finally dried at 60°C. After trimming, an oil-water separation membrane was obtained; wherein, the components used in the preparation of the oil-water separation membrane are: by mass fraction, 12% heterogeneous carbon nanotubes, 62% N,N-dimethylacetamide, 18% polyacrylonitrile, 6% polyvinyl pyrrolidone, and 2% defoaming agent.

[0048] Example 3: A heterogeneous carbon nanotube and an oil-water separation membrane prepared therefrom:

[0049] 1. Preparation of heterogeneous carbon nanotubes:

[0050] Step 1: (1) Add multi-walled carbon nanotubes, 98wt% concentrated sulfuric acid and 65wt% concentrated nitric acid in a ratio of 2g:20mL:30mL into a container, stir and mix evenly, then heat to 75°C, soak for 1.5h, filter, wash with clean water until neutral, and dry to obtain acidified carbon nanotubes; (2) Add the acidified carbon nanotubes and 70v / v% ethanol solution into a container, ultrasonically disperse for 2h, add 28wt% ammonia water to adjust the pH to 9, and then add 4v / v% tetrabutyl titanate anhydrous ethanol solution dropwise thereto under stirring (wherein the ratio of the acidified carbon nanotubes, 70v / v% ethanol solution and 4v / v% tetrabutyl titanate anhydrous ethanol solution is 2g:100mL:100mL), after the addition is complete, continue to stir and react for 12h, and finally filter, wash and dry to obtain a titanium dioxide / carbon nanotube composite material;

[0051] Step 2: (1) 10 parts of N,N'-vinylbisacrylamide and 100 parts of tetrahydrofuran were added into a container, stirred and mixed evenly, and then 70 parts of perfluoro-2,5-dimethyl-3,6-dioxanoic acid, 3 parts of dicyclohexylcarbodiimide and 3 parts of 1-hydroxybenzotriazole were added thereto under a nitrogen environment, and the temperature was raised to 70°C, and the reaction was stirred for 12 hours. The reaction was terminated, and the product A was obtained by suction filtration and drying; (2) 50 parts of the product A and 100 parts of tetrahydrofuran were added into a container, and the mixture was stirred and mixed evenly. 10 parts of acrylic acid, 10 parts of polyethylene glycol diacrylate and 0.8 parts of ammonium persulfate solution are added into a container, stirred and mixed evenly, stirred and reacted at 75°C for 4 hours, the reaction is terminated, and the ammonium persulfate is separated to obtain product B; (3) 40 parts of product B, 40 parts of 3-mercaptopropyltrimethoxysilane and 2 parts of photoinitiator are added into a container, stirred and mixed evenly, irradiated under 350nm ultraviolet light for 10 minutes, the reaction is terminated, and a hydrophilic and oleophobic modifier is obtained;

[0052] Step 3: Add 30 parts of titanium dioxide / carbon nanotube composite material, 30 parts of hydrophilic oleophobic modifier and 150 parts of 70v / v% ethanol solution into a container, stir and mix evenly, and soak at 50°C for 2h to obtain heterogeneous carbon nanotubes;

[0053] 2. Preparation of oil-water separation membrane: (1) Add 36 parts of heterogeneous carbon nanotubes to 186 parts of N,N-dimethylacetamide, and ultrasonically disperse for 10 minutes. Then, add 54 parts of polyacrylonitrile, 18 parts of polyvinyl pyrrolidone and 6 parts of defoaming agent, heat to 60°C and stir for 4 hours to obtain a casting solution; (2) Pour the casting solution onto a scraping plate (pouring volume 2 mL / cm 2 ), after being evenly scraped with a scraper, it was placed at room temperature for 60 minutes, and then clean water was injected into the scraper plate, soaked for 48 hours, taken out, and finally dried at 60°C. After trimming, an oil-water separation membrane was obtained; wherein, the components used in the preparation of the oil-water separation membrane are: by mass fraction, 12% heterogeneous carbon nanotubes, 62% N,N-dimethylacetamide, 18% polyacrylonitrile, 6% polyvinyl pyrrolidone, and 2% defoaming agent.

[0054] Based on Example 1, comparative examples 1 to 5 are set, as shown below:

[0055] Comparative Example 1: Comparative Example 1 is based on Example 1, with the following modifications: no acid treatment is performed on the carbon nanotubes, and other processes remain unchanged, specifically:

[0056] A heterogeneous carbon nanotube and an oil-water separation membrane prepared therefrom:

[0057] 1. Preparation of heterogeneous carbon nanotubes:

[0058] Step 1: Add carbon nanotubes and 70v / v% ethanol solution into a container, ultrasonically disperse for 2h, add 28wt% ammonia water to adjust the pH to 9, and then add 4v / v% tetrabutyl titanate anhydrous ethanol solution dropwise therein under stirring (wherein, the ratio of carbon nanotubes, 70v / v% ethanol solution and 4v / v% tetrabutyl titanate anhydrous ethanol solution is 1.5g:100mL:100mL), after the addition is completed, continue to stir and react for 12h, and finally filter, wash and dry to obtain a titanium dioxide / carbon nanotube composite material;

[0059] Step 2: (1) Add 10 parts of N,N'-vinylbisacrylamide and 100 parts of tetrahydrofuran into a container, stir and mix evenly, then add 60 parts of perfluoro-2,5-dimethyl-3,6-dioxanoic acid, 3 parts of dicyclohexylcarbodiimide and 3 parts of 1-hydroxybenzotriazole under nitrogen atmosphere, heat to 70°C, stir and react for 12 hours, terminate the reaction, filter and dry to obtain product A; (2) Add 50 parts of product A and 8 (3) adding 40 parts of product B, 25 parts of 3-mercaptopropyltrimethoxysilane and 2 parts of photoinitiator into a container, stirring and mixing evenly, irradiating under 350nm ultraviolet light for 10 minutes, and terminating the reaction to obtain a hydrophilic and oleophobic modifier;

[0060] Step 3: Add 30 parts of titanium dioxide / carbon nanotube composite material, 22.5 parts of hydrophilic oleophobic modifier and 150 parts of 70 v / v% ethanol solution into a container, stir and mix evenly, and soak at 50° C. for 2 hours to obtain heterogeneous carbon nanotubes;

[0061] 2. Preparation of oil-water separation membrane: (1) Add 36 parts of heterogeneous carbon nanotubes to 186 parts of N,N-dimethylacetamide, and ultrasonically disperse for 10 minutes. Then, add 54 parts of polyacrylonitrile, 18 parts of polyvinyl pyrrolidone and 6 parts of defoaming agent, heat to 60°C and stir for 4 hours to obtain a casting solution; (2) Pour the casting solution onto a scraping plate (pouring volume 2 mL / cm 2 ), after being evenly scraped with a scraper, it was placed at room temperature for 60 minutes, and then clean water was injected into the scraper plate, soaked for 48 hours, taken out, and finally dried at 60°C. After trimming, an oil-water separation membrane was obtained; wherein, the components used in the preparation of the oil-water separation membrane are: by mass fraction, 12% heterogeneous carbon nanotubes, 62% N,N-dimethylacetamide, 18% polyacrylonitrile, 6% polyvinyl pyrrolidone, and 2% defoaming agent.

[0062] Comparative Example 2: Comparative Example 2 is based on Example 1, with the following modifications: titanium dioxide is not generated in situ on the acidified carbon nanotubes, and other processes remain unchanged, specifically:

[0063] A heterogeneous carbon nanotube and an oil-water separation membrane prepared therefrom:

[0064] 1. Preparation of heterogeneous carbon nanotubes:

[0065] Step 1: (1) adding multi-walled carbon nanotubes, 98wt% concentrated sulfuric acid and 65wt% concentrated nitric acid into a container in a ratio of 2g:20mL:30mL, stirring and mixing evenly, then heating to 75°C, soaking for 1.5h, filtering, washing with clean water until neutral, and drying to obtain acidified carbon nanotubes;

[0066] Step 2: (1) Add 10 parts of N,N'-vinylbisacrylamide and 100 parts of tetrahydrofuran into a container, stir and mix evenly, then add 60 parts of perfluoro-2,5-dimethyl-3,6-dioxanoic acid, 3 parts of dicyclohexylcarbodiimide and 3 parts of 1-hydroxybenzotriazole under nitrogen atmosphere, heat to 70°C, stir and react for 12 hours, terminate the reaction, filter and dry to obtain product A; (2) Add 50 parts of product A and 8 (3) adding 40 parts of product B, 25 parts of 3-mercaptopropyltrimethoxysilane and 2 parts of photoinitiator into a container, stirring and mixing evenly, irradiating under 350nm ultraviolet light for 10 minutes, and terminating the reaction to obtain a hydrophilic and oleophobic modifier;

[0067] Step 3: Add 30 parts of acidified carbon nanotubes, 22.5 parts of hydrophilic oleophobic modifier and 150 parts of 70 v / v% ethanol solution into a container, stir and mix evenly, and soak at 50° C. for 2 hours to obtain heterogeneous carbon nanotubes;

[0068] 2. Preparation of oil-water separation membrane: (1) Add 36 parts of heterogeneous carbon nanotubes to 186 parts of N,N-dimethylacetamide, and ultrasonically disperse for 10 minutes. Then, add 54 parts of polyacrylonitrile, 18 parts of polyvinyl pyrrolidone and 6 parts of defoaming agent, heat to 60°C and stir for 4 hours to obtain a casting solution; (2) Pour the casting solution onto a scraping plate (pouring volume 2 mL / cm 2), after being evenly scraped with a scraper, it was placed at room temperature for 60 minutes, and then clean water was injected into the scraper plate, soaked for 48 hours, taken out, and finally dried at 60°C. After trimming, an oil-water separation membrane was obtained; wherein, the components used in the preparation of the oil-water separation membrane are: by mass fraction, 12% heterogeneous carbon nanotubes, 62% N,N-dimethylacetamide, 18% polyacrylonitrile, 6% polyvinyl pyrrolidone, and 2% defoaming agent.

[0069] Comparative Example 3: Comparative Example 3 is based on Example 1, with the following adjustments: no hydrophilic oleophobic modifier is prepared, and other processes remain unchanged, specifically:

[0070] A heterogeneous carbon nanotube and an oil-water separation membrane prepared therefrom:

[0071] 1. Preparation of heterogeneous carbon nanotubes:

[0072] Step 1: (1) Add multi-walled carbon nanotubes, 98wt% concentrated sulfuric acid and 65wt% concentrated nitric acid in a ratio of 2g:20mL:30mL into a container, stir and mix evenly, then heat to 75°C, soak for 1.5h, filter, wash with clean water until neutral, and dry to obtain acidified carbon nanotubes; (2) Add acidified carbon nanotubes and 70v / v% ethanol solution into a container, ultrasonically disperse for 2h, add 28wt% ammonia water to adjust the pH to 9, and then add 4v / v% tetrabutyl titanate anhydrous ethanol solution dropwise thereto under stirring (wherein, the ratio of the acidified carbon nanotubes, 70v / v% ethanol solution and 4v / v% tetrabutyl titanate anhydrous ethanol solution is 1.5g:100mL:100mL), after the addition is complete, continue to stir and react for 12h, and finally filter, wash and dry to obtain heterogeneous carbon nanotubes (titanium dioxide / carbon nanotube composite materials);

[0073] 2. Preparation of oil-water separation membrane: (1) Add 36 parts of heterogeneous carbon nanotubes to 186 parts of N,N-dimethylacetamide, and ultrasonically disperse for 10 minutes. Then, add 54 parts of polyacrylonitrile, 18 parts of polyvinyl pyrrolidone and 6 parts of defoaming agent, heat to 60°C and stir for 4 hours to obtain a casting solution; (2) Pour the casting solution onto a scraping plate (pouring volume 2 mL / cm 2 ), after being evenly scraped with a scraper, it was placed at room temperature for 60 minutes, and then clean water was injected into the scraper plate, soaked for 48 hours, taken out, and finally dried at 60°C. After trimming, an oil-water separation membrane was obtained; wherein, the components used in the preparation of the oil-water separation membrane are: by mass fraction, 12% heterogeneous carbon nanotubes, 62% N,N-dimethylacetamide, 18% polyacrylonitrile, 6% polyvinyl pyrrolidone, and 2% defoaming agent.

[0074] Comparative Example 4: Comparative Example 4 is based on Example 1, with the following adjustments: Product B is directly used as the hydrophilic oleophobic modifier, and other processes remain unchanged, specifically:

[0075] A heterogeneous carbon nanotube and an oil-water separation membrane prepared therefrom:

[0076] 1. Preparation of heterogeneous carbon nanotubes:

[0077] Step 1: (1) Add multi-walled carbon nanotubes, 98wt% concentrated sulfuric acid and 65wt% concentrated nitric acid in a ratio of 2g:20mL:30mL into a container, stir and mix evenly, then heat to 75°C, soak for 1.5h, filter, wash with clean water until neutral, and dry to obtain acidified carbon nanotubes; (2) Add the acidified carbon nanotubes and 70v / v% ethanol solution into a container, ultrasonically disperse for 2h, add 28wt% ammonia water to adjust the pH to 9, and then add 4v / v% tetrabutyl titanate anhydrous ethanol solution dropwise thereto under stirring (wherein, the ratio of the acidified carbon nanotubes, 70v / v% ethanol solution and 4v / v% tetrabutyl titanate anhydrous ethanol solution is 1.5g:100mL:100mL), after the addition is complete, continue to stir and react for 12h, and finally filter, wash and dry to obtain a titanium dioxide / carbon nanotube composite material;

[0078] Step 2: (1) Add 10 parts of N,N'-vinylbisacrylamide and 100 parts of tetrahydrofuran into a container, stir and mix evenly, then add 60 parts of perfluoro-2,5-dimethyl-3,6-dioxanoic acid, 3 parts of dicyclohexylcarbodiimide and 3 parts of 1-hydroxybenzotriazole under nitrogen environment, heat to 70°C, stir and react for 12 hours, terminate the reaction, filter and dry to obtain product A; (2) Add 50 parts of product A, 8 parts of acrylic acid, 8 parts of polyethylene glycol diacrylate and 0.8 parts of ammonium persulfate solution into a container, stir and mix evenly, stir and react at 75°C for 4 hours, terminate the reaction, separate ammonium persulfate and obtain a hydrophilic and oleophobic modifier (product B);

[0079] Step 3: Add 30 parts of titanium dioxide / carbon nanotube composite material, 22.5 parts of hydrophilic oleophobic modifier and 150 parts of 70 v / v% ethanol solution into a container, stir and mix evenly, and soak at 50° C. for 2 hours to obtain heterogeneous carbon nanotubes;

[0080] 2. Preparation of oil-water separation membrane: (1) Add 36 parts of heterogeneous carbon nanotubes to 186 parts of N,N-dimethylacetamide, and ultrasonically disperse for 10 minutes. Then, add 54 parts of polyacrylonitrile, 18 parts of polyvinyl pyrrolidone and 6 parts of defoaming agent, heat to 60°C and stir for 4 hours to obtain a casting solution; (2) Pour the casting solution onto a scraping plate (pouring volume 2 mL / cm 2), after being evenly scraped with a scraper, it was placed at room temperature for 60 minutes, and then clean water was injected into the scraper plate, soaked for 48 hours, taken out, and finally dried at 60°C. After trimming, an oil-water separation membrane was obtained; wherein, the components used in the preparation of the oil-water separation membrane are: by mass fraction, 12% heterogeneous carbon nanotubes, 62% N,N-dimethylacetamide, 18% polyacrylonitrile, 6% polyvinyl pyrrolidone, and 2% defoaming agent.

[0081] Comparative Example 5: Comparative Example 5 is based on Example 1, with the following modifications: directly using multi-walled carbon nanotubes to prepare the oil-water separation membrane, and other processes remain unchanged, specifically:

[0082] 1. Preparation of oil-water separation membrane: (1) Add 36 parts of multi-walled carbon nanotubes to 186 parts of N,N-dimethylacetamide, and ultrasonically disperse for 10 minutes. Then, add 54 parts of polyacrylonitrile, 18 parts of polyvinyl pyrrolidone and 6 parts of defoaming agent, heat to 60°C and stir for 4 hours to obtain a casting solution; (2) Pour the casting solution onto a scraping plate (pouring volume 2 mL / cm 2 ), after being evenly scraped with a scraper, it was placed at room temperature for 60 minutes, and then clean water was injected into the scraper plate, soaked for 48 hours, taken out, and finally dried at 60°C. After trimming, an oil-water separation membrane was obtained; wherein, the components used in the preparation of the oil-water separation membrane are: by mass fraction, 12% heterogeneous carbon nanotubes, 62% N,N-dimethylacetamide, 18% polyacrylonitrile, 6% polyvinyl pyrrolidone, and 2% defoaming agent.

[0083] Performance test: The relevant performance tests of the oil-water separation membranes prepared in Examples 1 to 3 and Comparative Examples 1 to 5 are as follows:

[0084] (1) Hydrophilicity: At room temperature, drop 2 μL of pure water on the oil-water separation membrane and use an OSA200 contact angle meter to quickly measure the contact angle of the membrane. Tests were performed at three different locations on each membrane and the average value was taken as the final contact angle of the membrane. The smaller the contact angle, the better the hydrophilicity.

[0085] (2) Membrane flux: Prepare 1 g / L peanut oil emulsion (containing 0.1 g / L sodium dodecyl sulfate as an emulsifier); filter the peanut emulsion using an oil-water separation membrane at a pressure of 0.15 MPa; record the time required to filter a certain volume of peanut oil emulsion, and calculate the membrane flux according to J=V / A·T; where J is the membrane flux (L / (m 2 ·h); V is the sampling volume (L); T is the filtration time (h); A is the effective area of ​​the membrane (m 2 );

[0086] (3) Anti-pollution: After completing the membrane flux test (2), the oil-water separation membrane was cleaned 5 times with clean water and then another membrane flux test was performed.

[0087] The specific results are shown in Table 1:

[0088] Table 1

[0089]

[0090] Result analysis: From the data in Table 1 above, it can be seen that the hydrophilicity and oleophobicity of heterogeneous carbon nanotubes can be significantly enhanced by the acidification treatment of carbon nanotubes, the in-situ generation of titanium dioxide and the preparation of hydrophilic and oleophobic modifiers. The oil-water separation membrane prepared by the carbon nanotubes has the ability to penetrate water at a high speed and can well block oil. In addition, the anti-pollution performance of the oil-water separation membrane is also enhanced due to the filling of the heterogeneous carbon nanotubes in the oil-water separation membrane, which greatly improves the oil-water separation efficiency.

[0091] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

Claims

1. A heterogeneous carbon nanotube, characterized in that: The titanium dioxide / carbon nanotube composite material is grafted with a hydrophilic and oleophobic modifier; the specific preparation method comprises the following steps: Step 1: (1) Add carbon nanotubes, concentrated sulfuric acid and concentrated nitric acid into a container, stir and mix evenly, then heat to 50-100°C, soak for 0.5-3h, filter, wash with water until neutral, and dry to obtain acidified carbon nanotubes; (2) Add acidified carbon nanotubes and 50-80v / v% ethanol solution into a container, ultrasonically disperse for 1-2h, adjust the pH to 9-10, and then drop 2.5-5v / v% tetrabutyl titanate anhydrous ethanol solution therein while stirring. After the dropwise addition is complete, continue stirring and reacting for 1-12h, and finally filter, wash, and dry to obtain a titanium dioxide / carbon nanotube composite material; Step 2: (1) Add N,N'-vinylbisacrylamide and tetrahydrofuran into a container, stir and mix them evenly, then add perfluoro-2,5-dimethyl-3,6-dioxanoic acid, dicyclohexylcarbodiimide and 1-hydroxybenzotriazole into it under a nitrogen environment, and heat it to 50-80°C, stir and react for 1-24 hours, terminate the reaction, filter and dry to obtain product A; (2) Add product A, acrylic acid, polyethylene glycol diacrylate and ammonium persulfate solution into a container, stir and mix them evenly, stir and react at 70-85°C for 1-6 hours, terminate the reaction, separate ammonium persulfate and obtain product B; (3) Add product B, 3-mercaptopropyltrimethoxysilane and a photoinitiator into a container, stir and mix them evenly, irradiate under 350-370nm ultraviolet light for 1-20 minutes, terminate the reaction and obtain a hydrophilic-oleophobic modifier; Step 3: Add the titanium dioxide / carbon nanotube composite material, the hydrophilic-oleophobic modifier and 50-80 v / v% ethanol solution into a container, stir and mix evenly, and soak at 45-60° C. for 0.5-3 h to obtain heterogeneous carbon nanotubes.

2. The heterogeneous carbon nanotube according to claim 1, characterized in that: In step 1, the ratio of the carbon nanotubes, concentrated sulfuric acid and concentrated nitric acid is (0.5-2) g: 20 mL: 30 mL; the ratio of the acidified carbon nanotubes, 50-80 v / v% ethanol solution and 2.5-5 v / v% tetrabutyl titanate anhydrous ethanol solution is (0.5-2) g: 100 mL: 100 mL.

3. The heterogeneous carbon nanotube according to claim 2, characterized in that: The carbon nanotubes include any one of single-walled carbon nanotubes, double-walled carbon nanotubes and multi-walled carbon nanotubes.

4. The heterogeneous carbon nanotube according to claim 1, characterized in that: In step 2, the mass ratio of N,N'-vinylbisacrylamide, perfluoro-2,5-dimethyl-3,6-dioxanoic acid, dicyclohexylcarbodiimide and 1-hydroxybenzotriazole is 1:(5.5~7):(0.1~0.5):(0.1~0.5); the mass ratio of product A, acrylic acid, polyethylene glycol diacrylate and ammonium persulfate is 5:(0.5~1):(0.5~1):(0.05~0.1); the mass ratio of product B, 3-mercaptopropyltrimethoxysilane and photoinitiator is 1:(0.5~1):(0.03~0.06).

5. The heterogeneous carbon nanotube according to claim 1, characterized in that: In step 3, the mass ratio of the titanium dioxide / carbon nanotube composite material, the hydrophilic-oleophobic modifier and the 50-80 v / v% ethanol solution is 2:(1-2):

10.

6. An oil-water separation membrane prepared from the heterogeneous carbon nanotubes according to any one of claims 1 to 5.

7. The oil-water separation membrane according to claim 6, characterized in that: The preparation method of the oil-water separation membrane is as follows: (1) adding heterogeneous carbon nanotubes to N,N-dimethylacetamide, ultrasonically dispersing for 1 to 15 minutes, then adding polyacrylonitrile, polyvinyl pyrrolidone and a defoaming agent thereto, heating to 50 to 70°C and stirring for 1 to 6 hours to obtain a casting liquid; (2) pouring the casting liquid onto a scraping plate, scraping it evenly with a scraper, placing it at room temperature for 10 to 60 minutes, then injecting clean water into the scraping plate, soaking it for 24 to 48 hours, taking it out, and finally drying it at 50 to 70°C, and trimming it to obtain an oil-water separation membrane.

8. The oil-water separation membrane according to claim 7, characterized in that: The oil-water separation membrane preparation comprises the following components: by mass fraction, 5-15% heterogeneous carbon nanotubes, 60-70% N,N-dimethylacetamide, 15-25% polyacrylonitrile, 2-8% polyvinyl pyrrolidone, and 2-4% defoaming agent.

9. The oil-water separation membrane according to claim 7, characterized in that: The pouring volume of the casting solution is not less than 2 mL / cm 2 .

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