Preparation method of composite carbon nanotube functional filter membrane

Abstract

The application belongs to the technical field of functional membrane material preparation, and particularly relates to a preparation method of a composite carbon nanotube functional filter membrane with a layer-by-layer assembly structure, which comprises the following steps: preparing a composite membrane by hot pressing PTFE microporous membrane and PET non-woven material; adding a surfactant and a binder to carbon nanotube powder after activation treatment to obtain a carbon nanotube composite liquid; preparing titanium dioxide as a rigid intercalation material; preparing iron oxide as a rigid intercalation material; diluting the carbon nanotube composite liquid with water, and then adding the titanium dioxide or the iron oxide as the rigid intercalation material and uniformly spraying the mixture on the surface of the composite membrane by a spraying method. The obtained composite carbon nanotube functional filter membrane can be used for effective filtration of sewage.

Description

Technical Field

[0001] This invention belongs to the field of functional membrane material preparation technology, specifically relating to a method for preparing a composite carbon nanotube functional filter membrane with a layer-by-layer assembly structure. Background Technology

[0002] Membrane separation technology, a novel separation technology developed through the interdisciplinary collaboration of materials science and engineering, has garnered significant attention in scientific research and industrial applications due to its unique advantages and performance. Currently, in the field of water treatment, membrane separation technology effectively addresses the high filtration quality requirements that traditional water treatment technologies struggle to meet, thus solving water pollution problems more efficiently. However, with the advancement of science and technology, single-function membrane separation technologies are no longer sufficient to meet technological demands.

[0003] Carbon nanotubes were discovered by Lijima in 1991 on the cathode surface using the arc discharge method. Carbon nanotube films constructed from them have a tunable microstructure surface, high mechanical strength, good mechanical, electrical and adsorption properties, and a long service life, enabling repeated recycling. In recent years, they have been extensively studied and widely used in dye filtration, oil-water separation, composite materials and other fields.

[0004] Patent CN107602927A discloses a method for preparing and applying a carbon nanotube composite membrane. This method involves blending cellulose, carbon nanotubes, and poly(N-isopropylacrylamide) gel nanospheres with an ionic liquid to prepare a near-infrared laser-responsive composite membrane material, applicable to applications such as dye concentration control in textile printing and dyeing. The carbon nanotube composite membrane prepared by this method exhibits a small difference in absorbance to the dye solution, indicating a low dye removal rate.

[0005] Patent CN116550317A discloses a method for preparing a multi-scale titanium dioxide fiber / carbon nanotube membrane composite photocatalyst. The method primarily involves preparing TiO2 fibers on the surface of carbon nanotube arrays using microemulsion electrospinning while simultaneously stretching the arrays, resulting in the multi-scale TiO2 fiber / carbon nanotube membrane. This method effectively addresses the problem of poor mechanical properties in carbon nanotube membranes. Observations after photocatalysis show that the membrane requires a certain time to effectively adsorb dye solutions. This invention improves upon this feature for efficient dye filtration, resulting in a composite carbon nanotube functional filter membrane that effectively separates dye solutions in a short time. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing a composite carbon nanotube functional filter membrane with good hydrophilicity.

[0007] To address the above problems, this invention provides a method for preparing a composite carbon nanotube functional filtration membrane, comprising the following steps:

[0008] 1) Preparation of organic membrane support:

[0009] A composite membrane was prepared by hot pressing PTFE microporous membrane (pore size 0.45 μm) with PET nonwoven material;

[0010] 2) Preparation of carbon nanotube composite liquid:

[0011] After carbon nanotube powder is activated, a surfactant is added and mixed uniformly (after uniform stirring, ultrasonic vibration is performed for 30-90 min) to obtain a carbon nanotube / surfactant mixture. A binder is added to the carbon nanotube / surfactant mixture and mixed uniformly (mechanical stirring for 10-20 min, ultrasonic vibration for 20-40 min; a total of 2-4 cycles of "mechanical stirring-ultrasonic vibration" are performed) to obtain a carbon nanotube composite liquid (uniformly dispersed carbon nanotube composite liquid). The mass ratio of carbon nanotubes to surfactant is 1:1-2, and the volume ratio of binder to carbon nanotube / surfactant mixture is 2:3-4.

[0012] 3) Preparation of titanium dioxide as a rigid intercalation material:

[0013] Titanium tetrachloride was hydrolyzed, and the precipitate was obtained after centrifugation. The precipitate was washed with water and then dried and calcined to obtain titanium dioxide (titanium dioxide particles).

[0014] 4) Preparation of iron oxide as a rigid intercalation material:

[0015] Ferric chloride was placed in a reaction vessel and subjected to a hydrothermal reaction under the action of a reducing agent. The hydrothermal reaction temperature was in the range of 140–240℃, and the time was 10–18 h. After the reaction was completed, the mixture was centrifuged (7000–10000 rpm, 25–55 min), and the precipitate obtained by centrifugation was washed with water to obtain the precursor FeCO3. The reducing agent was ascorbic acid or uric acid.

[0016] The precursor FeCO3 was calcined at a high temperature of 400-600℃ for 1-3 hours to obtain iron oxide (iron oxide particles).

[0017] At least one of the above steps 3) and 4) must be performed;

[0018] 5) Preparation of composite carbon nanotube functional filtration membranes:

[0019] Add pure water to the composite solution obtained in step 2) to dilute it, wherein the weight ratio of composite solution to pure water is 1:4 to 6, to obtain a diluted solution;

[0020] Then, the rigid intercalation material obtained in step 3) or step 4) is mixed evenly with the diluent and then evenly sprayed onto the film surface obtained in step 1) using a spraying method.

[0021] The ratio of the rigid intercalation material to the diluent is 0.005–0.01 g / 30 ml.

[0022] Note: The purpose of dilution is to create a flowing pattern, which facilitates subsequent spraying.

[0023] As an improvement to the preparation method of the composite carbon nanotube functional filter membrane of the present invention, step 1):

[0024] PTFE microporous membrane and PET nonwoven material are conveyed to the same hot press roller via two independent conveyor rollers, and subjected to a temperature of 150–290°C and a pressure of 1.5–6 kg / cm². 2 A composite membrane (a hydrophilic PTFE filter membrane) is prepared by hot pressing under pressure.

[0025] As a further improvement to the preparation method of the composite carbon nanotube functional filter membrane of the present invention, step 2):

[0026] The surfactant is Triton X-100 or sodium dodecylbenzenesulfonate; the binder is waterborne polyurethane or waterborne epoxy resin.

[0027] As a further improvement to the preparation method of the composite carbon nanotube functional filter membrane of the present invention, step 2): activation methods include plasma treatment, heat treatment, hydrogen peroxide or acid treatment.

[0028] For example, heat treatment involves calcining carbon nanotube powder at 400±20℃ for 120±20 min to activate it, resulting in activated carbon nanotube powder.

[0029] As a further improvement to the preparation method of the composite carbon nanotube functional filter membrane of the present invention, step 3):

[0030] Add 100±10ml of pure water to 10ml of titanium tetrachloride, then add 0.5g of agar, and hydrolyze at 90~100℃ for 90±10min. Then, centrifuge (6000~10000rpm for 10~40min) to separate the precipitate, and wash the precipitate with pure water.

[0031] The washed precipitate is first dried (drying at 80-110℃ for 20-40 minutes to obtain a grayish-white powder), and then calcined at 300-600℃ for 50-70 minutes (preferably calcined at 400℃ for 60 minutes) to obtain titanium dioxide (titanium dioxide particles with a particle size of about 40-60 nm).

[0032] Note: The presence of agar effectively prevents particle aggregation and improves solution stability; washing the precipitate with pure water is to obtain a purer precipitate.

[0033] As a further improvement to the preparation method of the composite carbon nanotube functional filter membrane of the present invention, step 4) is as follows: 0.0012 mol ferric chloride hexahydrate is added to 15±1 ml of water and stirred evenly (until a uniform red color is achieved). Then, 0.6 M sodium carbonate solution of 6±1 ml is added and stirred (stirring time is 10±2 min). Then, 6±1 ml of glycerol and 0.4-0.5 g (preferably 0.42 g) ascorbic acid are added and stirred evenly (until a uniform black color is achieved). The mixture is then reacted at 180±10℃ for 16±1 h, centrifuged (centrifuged at 8000-10000 rpm for 35-45 min), and the precipitate is washed with water to obtain the precursor FeCO3. Subsequently, the precursor FeCO3 is calcined at 500±50℃ for 2±0.2 h to obtain iron oxide.

[0034] Note: In the hydrothermal process of preparing ferric oxide using ferric chloride, sodium carbonate mainly acts as a mineralizing agent and pH adjuster, influencing the chemical equilibrium and physical conditions of the reaction system. Specifically, as a mineralizing agent, it can increase the solubility of the solute in the hydrothermal solution and alter the coefficient of its solubility with temperature. As a pH buffer, it can regulate the acidity or alkalinity of the reaction system, promoting the hydrolysis and precipitation of the iron source, thus significantly impacting the formation process of ferric oxide and the properties of the final product.

[0035] That is, the present invention uses an appropriate amount of sodium carbonate to preliminarily adjust the pH value of the solution and can effectively prevent the aggregation of the product, and then uses ascorbic acid or uric acid as a reducing agent to reduce the solution.

[0036] As a further improvement to the preparation method of the composite carbon nanotube functional filter membrane of the present invention, step 5):

[0037] When the rigid intercalation material is mixed evenly with the diluent, a magnetic stirrer at 200-600 rpm is used, and the stirring time is 4-10 hours.

[0038] During spraying, the spraying distance is set to 8-20cm, and the spraying time for each spraying is set to 3-8s (that is, the amount of spray liquid used per square centimeter is about 0.13-0.15ml). After each spraying, dry at 45-70℃ for 5-10min (that is, spray and dry before the next spraying and drying); the number of spraying times is 2-3.

[0039] This invention selects rigid nanomaterials with different structures as intercalation materials, studies the supporting and modifying effects of the microstructure of the intercalation materials on the pore structure of carbon nanotube membranes, analyzes the influence of the surface chemical properties of the intercalation materials on the physicochemical properties of the membrane surface and internal network channels, and ultimately establishes a composite carbon nanotube functional filtration membrane with high-efficiency wastewater treatment capabilities. Compared with existing carbon nanotube composite membrane preparation processes, this method is more efficient and convenient, and its production equipment and experimental environment have higher tolerance. This invention achieves the preparation of functional composite membranes by controlling the preparation of carbon nanotube composite liquid, the implementation of spraying technology, and the construction of intercalation materials. The resulting composite membrane demonstrates high application value in the field of membrane filtration.

[0040] This invention focuses on membrane separation technology and aims to prepare a composite carbon nanotube functional filtration membrane with a layered assembly structure to achieve effective filtration of wastewater. Furthermore, it improves the microstructure of the carbon nanotube membrane by constructing rigid intercalation materials, thereby enhancing the performance of the composite membrane.

[0041] The key advantage of this invention lies in the carbon nanotube composite membrane preparation technology, which endows the composite membrane with a series of superior properties. Firstly, the contact angle measurement shows that all values ​​are less than 30°, indicating excellent hydrophilicity, a characteristic particularly important in wastewater treatment. During filtration, it effectively intercepts dye and oil molecules in wastewater, significantly improving filtration efficiency and water purity. Furthermore, the high separation efficiency of this carbon nanotube composite membrane ensures that wastewater filtered through the membrane meets water quality standards, addressing the issue of sustainable water resource utilization and achieving environmental protection. Simultaneously, the design of this composite membrane considers practical application convenience and economy. Its composite process is simple and efficient, and the addition of rigid intercalation provides self-support, avoiding the possibility of collapse due to pressure during repeated use. During the experiment, the membrane was consistently subjected to a pressure of -0.1 MPa, and no significant changes were observed after the experiment, demonstrating excellent stability, reducing replacement frequency and maintenance costs, and indicating broad market application prospects.

[0042] Traditional in-situ polymerization methods for preparing carbon nanotube membranes are complex, typically involving multiple steps, including catalyst preparation, carbon source introduction, and high-temperature treatment. Furthermore, the chemicals used are often toxic, posing potential risks to the environment and the health of operators. However, this invention utilizes a spray coating method to prepare composite carbon nanotube functional filtration membranes in a single step, simplifying the manufacturing process and avoiding the use of toxic chemicals. Overall, this invention achieves a simple and efficient preparation process by optimizing material selection and manufacturing procedures, reducing production costs and improving efficiency. The flexibility of this process allows for rapid response to market demands, catering to various application scales, from small-batch customization to large-scale production. Moreover, its high separation efficiency not only enhances the reuse value of water resources but also makes a positive contribution to environmental protection.

[0043] Meanwhile, compared with the current carbon nanotube membrane preparation process, the method mentioned in this invention is more convenient and efficient, which can meet the needs of small-batch or large-batch production in a short time. It has significant advantages in terms of production efficiency, cost control and environmental friendliness, and has shown great potential and value in practical applications.

[0044] The key inventive point of this invention lies in selecting rigid nanomaterials with different structures as intercalation materials and employing a spray coating method to prepare composite carbon nanotube functional filter membranes, which is highly efficient and convenient. Specifically, titanium dioxide and iron oxide are selected as intercalation materials. Optimal parameters for preparation were determined through multiple experiments, overcoming the shortcomings of commercially available titanium dioxide, such as easy agglomeration, and iron oxide, such as excessive impurities. Furthermore, optimal parameter ranges were set in both the preparation process of the intercalation materials and the preparation process of the composite carbon nanotube functional filter membrane to increase the quality of the product.

[0045] In summary, this invention addresses the drawbacks of complex carbon nanotube membrane synthesis methods and stringent equipment requirements by employing a spray coating method to prepare a composite carbon nanotube functional filter membrane. The invention demonstrates that this membrane preparation method is simple and efficient. Attached Figure Description

[0046] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0047] Figure 1 This is a photograph of the PTFE membrane in an embodiment of the present invention.

[0048] Figure 2 This is a photograph of the composite carbon nanotube functional filter membrane in an embodiment of the present invention.

[0049] Figure 3 This is a photograph of a composite carbon nanotube functional filter membrane using titanium dioxide as an intercalating material in an embodiment of the present invention.

[0050] Figure 4 This is a photograph of a composite carbon nanotube functional filter membrane using iron oxide as an intercalating material in an embodiment of the present invention.

[0051] Figure 5 This is a SEM image of the composite carbon nanotube functional filter membrane in an embodiment of the present invention.

[0052] Figure 6 This is a SEM image of titanium dioxide in an embodiment of the present invention.

[0053] Figure 7 This is a SEM image of iron oxide in an embodiment of the present invention.

[0054] Figure 8 The image shows the ultraviolet absorption spectrum of Application Example I of the present invention. The samples in the image, from left to right, are methylene blue solution, filtrate of membrane in Application Example a, filtrate of membrane in Application Example b, filtrate of membrane in Application Example c, and water.

[0055] Figure 9 The image shows the ultraviolet absorption spectrum of Application Example II of the present invention. The samples in the image, from left to right, are a neutral red solution, the filtrate of the membrane in Application Example a, the filtrate of the membrane in Application Example b, the filtrate of the membrane in Application Example c, and water.

[0056] Figure 10 The image shows the ultraviolet absorption spectrum of application example III of the present invention. The samples in the image, from left to right, are an oil-water emulsion, the filtrate of the membrane in application example a, the filtrate of the membrane in application example b, the filtrate of the membrane in application example c, and water. Detailed Implementation

[0057] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0058] The ingredients used in the invention process and subsequent experiments of this invention are all commercially available, for example:

[0059] PTFE microporous membrane (0.45μm), Maiborui Biomembrane Technology Co., Ltd.;

[0060] 8% aqueous polyurethane solution, Shenzhen Yoshida Chemical Co., Ltd.

[0061] PET nonwoven fabric, Changzhou Yinghan Nonwoven Fabric Co., Ltd.;

[0062] Carbon nanotubes, a product of Suzhou CarbonFeng Graphene Technology Co., Ltd.

[0063] Titanium tetrachloride, a product of Hangzhou Mike Chemical Instrument Co., Ltd.

[0064] Agar, a product of Hangzhou Mike Chemical Instrument Co., Ltd.

[0065] Ferric chloride hexahydrate, a product of Hangzhou Mike Chemical Instrument Co., Ltd.

[0066] Sodium carbonate, a product of Hangzhou Mike Chemical Instrument Co., Ltd.

[0067] Ascorbic acid, a product of Hangzhou Mike Chemical Instrument Co., Ltd.

[0068] Glycerol, a product of Hangzhou Mike Chemical Instrument Co., Ltd.

[0069] Methylene blue dye (MB) and neutral red dye (NR) are products of Sinopharm Chemical Reagent Co., Ltd.

[0070] Golden Dragon soybean oil, a product of Shanghai Kerry Foods Co., Ltd.

[0071] Sodium dodecyl sulfate (SDS), a product of Tianjin Zhiyuan Chemical Reagent Co., Ltd.

[0072] The pure water used in the experiment was all Wahaha purified water.

[0073] Experimental Instruments: Circulating water ring multi-purpose vacuum pump (Shanghai Lichen Instrument Technology Co., Ltd.); Magnetic heating stirrer (Shanghai Lichen Instrument Technology Co., Ltd.); FA224 electronic balance (Shanghai Shunyu Hengping Scientific Instrument Co., Ltd.); Dead end filter (Hangzhou Mike Chemical Instrument Co., Ltd.); Cary 60UV-Vis (Agilent Technologies); Field emission scanning electron microscope (ZEISS, UK); Electric airbrush (Guangdong Xiangkong Technology Co., Ltd.); JY-PHb contact angle meter (Shanghai Bingjing Instrument Equipment Co., Ltd.); Electric thermostatic drying oven (Shanghai Senxin Experimental Instrument Co., Ltd.); Muffle furnace (KSL-1100X) (Hefei Kejing Materials Technology Co., Ltd.); Centrifuge (TGL-20B-C) (Shanghai Anting Scientific Instrument Factory); Laminating machine (TH-PUR, Wuxi Xianhe Automation Equipment Co., Ltd.).

[0074] Example 1

[0075] (1) Preparation of hydrophilic PFFE filter membrane

[0076] A PTFE microporous membrane (0.45 μm pore size) and PET nonwoven material are conveyed to the same hot press roller via two independent conveyor rollers, and subjected to a pre-set temperature of 290°C and a pressure of 6 kg / cm². 2 A composite membrane, which is a hydrophilic PTFE filter membrane, is prepared by hot pressing under pressure. The composite membrane is then rolled into rolls using a winding machine for later use.

[0077] The thickness of the PTFE microporous membrane is 0.0015 mm, and the thickness of the nonwoven material is 0.1710 mm.

[0078] (2) Preparation of carbon nanotube composite liquid

[0079] The mass ratio of carbon nanotube powder to Triton X-100 surfactant was set to 1:1.

[0080] First, carbon nanotube powder is placed in a muffle furnace and activated by calcination at 400°C for 120 minutes to obtain activated carbon nanotube powder.

[0081] Then, Triton X-100 surfactant was added to the activated carbon nanotube powder, and after being thoroughly stirred with a glass rod, it was placed in a CNC ultrasonic cleaner and ultrasonically vibrated for 45 minutes to obtain a mixture of carbon nanotubes and surfactant.

[0082] Subsequently, an 8% aqueous polyurethane solution and a carbon nanotube / surfactant mixture were mixed at a volume ratio of 2:3. The mixture was then mechanically stirred at 800 rpm for 15 minutes on a magnetic stirrer and ultrasonically vibrated for 30 minutes. The mechanical stirring-ultrasonic vibration process was repeated twice to obtain a uniformly dispersed carbon nanotube composite solution.

[0083] (3) Preparation of intercalation material titanium dioxide

[0084] Add 10 ml of titanium tetrachloride and 100 ml of pure water to a three-necked flask, followed by 0.5 g of agar. Hydrolyze the titanium tetrachloride at 100°C for 90 min in the presence of the agar additive. The presence of agar effectively prevents particle aggregation and improves solution stability. Then, centrifuge at 8000 rpm for 20 min to separate the precipitate. Wash the precipitate 2-3 times with pure water (to obtain a relatively pure precipitate).

[0085] Then, the washed titanium dioxide powder was dried in an oven at 100°C for 30 minutes to obtain a grayish-white powder. The powder was then calcined in a muffle furnace at 400°C for 60 minutes to obtain titanium dioxide particles (with a particle size of approximately 40-60 nm).

[0086] (4) Preparation of intercalated material iron oxide

[0087] Add 0.0012 mol ferric chloride hexahydrate to 15 ml of water and stir until a uniform red color appears. Then add 6 ml of 0.6 M sodium carbonate solution and stir for 10 min. Next, add 6 ml of glycerol and 0.42 g of ascorbic acid and stir until a uniform black color appears. Then place the mixture in a reaction vessel and react at 180 °C for 16 h. After centrifuging at 10,000 rpm for 40 min, wash the precipitate three times with water to obtain the precursor FeCO3. Then calcine the precursor in a muffle furnace at 500 °C for 2 h to obtain the target product, iron oxide particles.

[0088] (5) Preparation of composite carbon nanotube functional filter membrane

[0089] The following three options are included:

[0090] a) Preparation of carbon nanotube composite filter membrane

[0091] Take 5ml of the carbon nanotube composite liquid obtained in step (2), add pure water to make up to 30ml, stir at 400rpm for 8h under normal temperature and pressure conditions, place it in a spray bottle and use an electric spray gun to spray evenly for 5s at a distance of 15cm from the PTFE membrane side of the "hydrophilic PTFE filter membrane" obtained in step (1), that is, the amount of spray liquid used per square centimeter is about 0.14ml, and then use an oven to dry it at 50℃ for 10 minutes, and repeat the "spraying---drying" steps twice. The resulting product is named composite carbon nanotube functional filter membrane.

[0092] b) Preparation of composite carbon nanotube functional filter membranes with titanium dioxide as intercalating material

[0093] Take 5 ml of the carbon nanotube composite liquid obtained in step (2), add pure water to make up to 30 ml, add 0.01 g of titanium dioxide obtained in step (3), and stir at 400 rpm for 8 h under normal temperature and pressure conditions using a magnetic stirrer; the subsequent spraying steps are the same as in scheme a, and the resulting product is named titanium dioxide composite carbon nanotube functional filter membrane.

[0094] c) Preparation of composite carbon nanotube functional filtration membranes with iron oxide as intercalating material

[0095] Take 5 ml of the carbon nanotube composite liquid obtained in step (2), add pure water to make up to 30 ml, add 0.005 g of iron oxide obtained in step (4), stir at 400 RPM for 8 h under normal temperature and pressure conditions using a magnetic stirrer, and the subsequent spraying steps are the same as in scheme a. The resulting product is named iron oxide composite carbon nanotube functional filter membrane.

[0096] Experiment 1

[0097] The experimental method was as follows: a circulating water ring multi-purpose vacuum pump and a dead-end filter were used to filter the solution to calculate the flux. During the experiment, the vacuum pump pressure was controlled at -0.1 MPa. After the power was turned on and the liquid volume passing through the filter membrane stabilized, the liquid volume passing through the membrane per unit time was calculated to obtain the flux.

[0098] Flux formula

[0099]

[0100] Where: J — flux of solution through the membrane (Lm) -2 h -1 V—Volume of solution permeating through the membrane per unit time (L); A—Effective area of ​​solution permeating through the membrane (m²) 2 ); t — the time (h) for the solution to permeate through the membrane.

[0101] Table 1. Relevant performance indicators of composite carbon nanotube functional filter membranes

[0102]

[0103] As shown in Table 1, the titanium dioxide composite carbon nanotube functional filter membrane has a higher flux and a smaller water contact angle. When the contact angle is less than 90 degrees, the surface is considered hydrophilic, and the smaller the angle, the better the hydrophilicity. Therefore, the titanium dioxide composite carbon nanotube functional filter membrane is the preferred option.

[0104] Application Example I: Filtration of Methylene Blue Solution

[0105] 5 mg of methylene blue dye powder was added to 1 L of pure water and stirred at 1200 RPM for 8 hours at room temperature and pressure using a magnetic stirrer to obtain a homogeneous methylene blue dispersion. The solution was then filtered using a dead-end filtration device, i.e., using three composite membranes at a pressure of -0.1 MPa. During filtration, the sprayed surface was kept upwards, meaning the methylene blue dispersion was in contact with the sprayed surface. Subsequently, ultraviolet absorption spectra of the solutions before and after filtration were measured, and the results are shown below. Figure 8 As shown.

[0106] The specific flux effects are shown in Table 2 below:

[0107] Table 2. Filtration data of methylene blue solution by composite carbon nanotube functional filtration membrane.

[0108]

[0109]

[0110] Experiments showed that the carbon nanotube membranes prepared by all three methods exhibited significant filtration effects, producing clear filtrates with no obvious differences. However, the membrane obtained by method b had a higher flux, and... Figure 8 It is evident that the UV spectrum of the filtrate in scheme b is closer to that of water, indicating that scheme b is more effective.

[0111] Application Example II: Filtration of Neutral Red Solution

[0112] Add 5 mg of neutral red dye powder to 1 L of pure water and stir at 1200 RPM for 8 hours using a magnetic stirrer under normal temperature and pressure to obtain a homogeneous neutral red dispersion solution. Then, filter the solution using a dead-end filtration device, i.e., using three composite membranes at a pressure of -0.1 MPa, with the sprayed surface facing upwards during filtration. Perform UV absorption spectroscopy on the solutions before and after filtration. The results are shown below. Figure 9 As shown.

[0113] The specific flux effects are shown in Table 3 below:

[0114] Table 3. Filtration data of neutral red solution by composite carbon nanotube functional filtration membrane.

[0115]

[0116] Experiments showed that the carbon nanotube membranes prepared by all three methods exhibited significant filtration effects, producing clear filtrates with no obvious differences. However, the membrane obtained by method b had a higher flux, and... Figure 9 It is evident that the UV spectrum of the filtrate in scheme b is closer to that of water, indicating that scheme b is more effective.

[0117] Application Example III: Filtration of Oil-Water Emulsions

[0118] 1 ml of soybean oil and 30 mg of surfactant SDS were added to 99 ml of pure water. The mixture was stirred at 1200 RPM for 12 hours under ambient temperature and pressure using a magnetic stirrer to obtain a homogeneous oil-water emulsion. This emulsion was then filtered using a dead-end filtration system, i.e., using three composite membranes at a pressure of -0.1 MPa. During filtration, the coated surface was kept upwards, and UV absorption spectra were measured for both the coated and filtered solutions. The results are as follows: Figure 10 As shown.

[0119] The specific flux effects are shown in Table 4 below:

[0120] Table 4. Filtration data of oil-water emulsion by composite carbon nanotube functional filtration membranes

[0121]

[0122]

[0123] Experiments showed that the carbon nanotube membranes prepared by all three methods exhibited significant filtration effects, producing clear filtrates with no obvious differences. However, the membrane obtained by method b had a higher flux, and... Figure 10 It is evident that the UV spectrum of the filtrate in scheme b is closer to that of water, indicating that scheme b is the most effective.

[0124] Comparative Example 1: The preparation of the intercalation material titanium dioxide in "step 3") is cancelled. In step 5) scheme b), "titanium dioxide" is directly replaced with commercially available "titanium dioxide (purity ≥ 99.8%, particle size 60nm, rutile type)", and the rest is the same as in step 5) scheme b).

[0125] The resulting membranes were tested according to Application Examples I through III. Measurements showed that the membrane prepared in Comparative Example 1 had a water contact angle of 34.3° and a pure water flux of 42.1421 Lm. -2 h -1 The results are as follows:

[0126] Table 5. Filtration performance of the composite carbon nanotube functional filter membrane in Comparative Example 1

[0127] Filtration of methylene blue solution Filtration of neutral red solution Filtration of oil-water emulsions <![CDATA[Flux (Lm -2 h -1 )]]> 22.4237 29.8584 15.582 Filtration effect The filtrate is pale blue. The filtrate is pale red. The filtrate is slightly milky white.

[0128] Experiments showed that although the composite carbon nanotube functional filter membrane prepared using purchased titanium dioxide had good hydrophilicity, its filtration effect and flux were significantly lower than those of scheme b in the filtration experiments of methylene blue solution, neutral red solution, and oil-water emulsion.

[0129] Comparative Example 2: "Preparation of intercalation material iron oxide in step 4)" is cancelled, and "iron oxide" in step 5) scheme c) is directly replaced with commercially available "iron oxide (purity ≥ 99%, product specification 300 mesh)", the rest is the same as step 5) scheme c).

[0130] The resulting membrane was operated according to Application Examples I to III. Measurements showed that the membrane prepared in Comparative Example 2 had a water contact angle of 35.2° and a pure water flux of 33.4465 Lm. -2 h -1 The results obtained are compared with those of the iron oxide composite carbon nanotube functional filter membrane of the present invention (Scheme c) as follows:

[0131] Table 6. Filtration performance of composite carbon nanotube functional filter membranes in comparative examples

[0132] Filtration of methylene blue solution Filtration of neutral red solution Filtration of oil-water emulsions <![CDATA[Flux (Lm -2 h -1 )]]> 18.5953 21.1223 9.2339 Filtration effect The filtrate is pale blue. The filtrate is pale red. The filtrate is slightly milky white.

[0133] Experiments showed that although the composite carbon nanotube functional filter membrane prepared using purchased iron oxide had good hydrophilicity, its filtration effect and flux were significantly lower than those of scheme c in the filtration experiments of methylene blue solution, neutral red solution, and oil-water emulsion. Therefore, it can be seen that the iron oxide prepared in the laboratory has better performance.

[0134] Finally, it should be noted that the above examples are merely some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a composite carbon nanotube functional filter membrane for separating dye solutions, characterized in that... Includes the following steps: 1) Preparation of organic membrane support: A composite membrane is prepared by hot pressing PTFE microporous membrane with PET nonwoven material; 2) Preparation of carbon nanotube composite liquid: After carbon nanotube powder is activated, a surfactant is added and mixed uniformly to obtain a carbon nanotube / surfactant mixture. A binder is added to the carbon nanotube / surfactant mixture and mixed uniformly to obtain a carbon nanotube composite liquid. The mass ratio of carbon nanotubes to surfactant is 1:1~2, and the volume ratio of binder to carbon nanotube / surfactant mixture is 2:3~4. 3) Preparation of titanium dioxide as a rigid intercalation material: Titanium tetrachloride was hydrolyzed, centrifuged to obtain a precipitate, and the precipitate was washed with water and then dried and calcined to obtain titanium dioxide. 4) Preparation of iron oxide as a rigid intercalation material: Ferric chloride was placed in a reaction vessel and subjected to a hydrothermal reaction under the action of a reducing agent. The hydrothermal reaction temperature was in the range of 140~240℃ and the time was 10~18h. After the reaction was completed, the mixture was centrifuged, and the precipitate obtained by centrifugation was washed with water to obtain the precursor FeCO3. The reducing agent was ascorbic acid or uric acid. The precursor FeCO3 was calcined at a high temperature of 400~600℃ for 1~3h to obtain iron oxide; At least one of the above steps 3) and 4) must be performed; 5) Preparation of composite carbon nanotube functional filtration membranes: In step 2), pure water is added to dilute the composite solution, wherein the weight ratio of composite solution to pure water is 1:4~6, to obtain a diluted solution. Then, the rigid intercalation material obtained in step 3) or step 4) is mixed evenly with the diluent and then evenly sprayed onto the film surface obtained in step 1) using a spraying method. The ratio of the rigid intercalating material to the diluent is 0.005~0.01g:30ml.

2. The method for preparing a composite carbon nanotube functional filter membrane for separating dye solutions according to claim 1, characterized in that... Step 1): PTFE microporous membrane and PET nonwoven material are conveyed to the same hot press roller via two independent conveyor rollers, and subjected to a temperature of 150~290℃ and a pressure of 1.5~6kg / cm². 2 Composite membranes are prepared by hot pressing under pressure.

3. The method for preparing a composite carbon nanotube functional filter membrane for separating dye solutions according to claim 2, characterized in that... Step 2): The surfactant is Triton X-100 or sodium dodecylbenzenesulfonate; the binder is waterborne polyurethane or waterborne epoxy resin.

4. The method for preparing a composite carbon nanotube functional filter membrane for separating dye solutions according to claim 3, characterized in that... Step 2): Activation methods include plasma treatment, heat treatment, hydrogen peroxide or acid treatment.

5. A method for preparing a composite carbon nanotube functional filter membrane for separating dye solutions according to any one of claims 1 to 4, characterized in that... Step 3): Add 100±10ml of pure water to 10ml of titanium tetrachloride, then add 0.5g of agar, and hydrolyze at 90~100℃ for 90±10min. Then, centrifuge to separate the precipitate and wash the precipitate with pure water. The washed precipitate is first dried, and then calcined at 300~600℃ for 50~70 minutes to obtain titanium dioxide.

6. The method for preparing a composite carbon nanotube functional filter membrane for separating dye solutions according to claim 5, characterized in that... Step 4): Add 0.0012 mol ferric chloride hexahydrate to 15±1 ml of water, stir evenly, then add 0.6 M sodium carbonate solution (6±1 ml) and stir again. Then add 6±1 ml glycerol and 0.4~0.5 g ascorbic acid and stir evenly. Then react at 180±10℃ for 16±1 h, centrifuge, wash the precipitate with water to obtain the precursor FeCO3. Then calcine the precursor FeCO3 at 500±50℃ for 2±0.2 h to obtain iron oxide.

7. The method for preparing a composite carbon nanotube functional filter membrane for separating dye solutions according to claim 6, characterized in that... Step 5): When the rigid intercalation material is mixed evenly with the diluent, a magnetic stirrer at 200-600 rpm is used, and the stirring time is 4-10 hours. During spraying, the spraying distance should be set to 8~20cm, the spraying time for each spraying should be set to 3~8s, and after each spraying, dry at 45~70℃ for 5~10min; the number of spraying times should be 2~3.

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