Processing technology of conductive CNT nanofiltration membrane for water treatment

Abstract

The invention discloses a processing technology of a conductive CNT nanofiltration membrane for water treatment, and relates to the technical field of nanofiltration membranes. The preparation method comprises the following steps: adding an N, N-dimethylformamide solvent into a conical flask, stirring in a water bath environment, adding a pore-forming agent and polyethersulfone powder, and stirring to prepare a membrane casting solution 1; adding N, N-dimethylformamide into a conical flask, then transferring the carboxylated multi-walled carbon nanotube powder and the graphene slurry, performing ultrasonic treatment, then transferring to a water bath environment, adding polyethersulfone powder, and stirring to prepare a membrane casting solution 2; pouring the membrane casting solution 1 on a glass plate, adjusting the thickness of a membrane scraping knife to form a membrane, then rapidly inverting the membrane casting solution 2 at the starting end, rapidly scraping the membrane at a uniform speed by using the membrane scraping knife until the membrane is formed, staying in air, placing the glass plate in a solidification water bath at normal temperature, standing, taking out the glass plate, and soaking the membrane in deionized water for later use. The nano-filtration membrane prepared by the method has high conductivity and can be used for highly treating pollutants, so that the nano-filtration membrane has wide application in the aspect of water treatment.

Description

Technical Field

[0001] The invention relates to the technical field of nanofiltration membranes, and in particular to a processing technology of a conductive CNT nanofiltration membrane for water treatment. Background Art

[0002] Nanofiltration membranes are widely used in the deep treatment of domestic sewage, the compliance and reuse of industrial wastewater. However, the high energy consumption and membrane fouling in the application of nanofiltration membranes seriously restrict their further promotion and application. Conductive separation membranes have membrane retention and conductivity properties, and can show good water flux, selective retention and anti-membrane fouling properties under the action of an external electric field. They are considered to be one of the suitable ways to solve the problems of high energy consumption and membrane fouling of nanofiltration membranes. However, there are problems such as limited improvement in membrane conductivity and poor treatment efficiency of pollutants in the process of blended conductive modification of organic membranes. Therefore, it is very necessary to develop a conductive separation membrane with high conductivity and high treatment efficiency. Summary of the invention

[0003] The purpose of the present invention is to provide a processing technology for a conductive CNT nanofiltration membrane for water treatment to solve the problems raised in the above background technology.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A processing technology for a conductive CNT nanofiltration membrane for water treatment comprises the following steps:

[0006] (1) Preparation of casting solution 1: N,N-dimethylformamide solvent is placed in a conical flask, stirred in a water bath, pore-forming agent and polyethersulfone powder are added, stirred to obtain casting solution 1, and allowed to stand for degassing;

[0007] (2) Preparation of casting solution 2: N,N-dimethylformamide was placed in a conical flask, and then the carboxylated multi-walled carbon nanotube powder and graphene slurry were transferred into the conical flask through a funnel. The conical flask was sealed and placed in an ultrasonic oscillator for ultrasonic treatment. After that, the solution was transferred to a water bath, polyethersulfone powder was added and stirred to obtain casting solution 2, which was then allowed to stand for degassing.

[0008] (3) Pour the casting liquid 1 onto the glass plate, adjust the thickness of the scraper to scrape until a film is formed, and then quickly invert the casting liquid 2 at the starting end, use the scraper to quickly scrape at a uniform speed until a film is formed, and allow air to remain. Place the glass plate in a coagulation water bath at room temperature, let it stand, then transfer it to another clear coagulation water bath, let it stand, then take out the film and soak it in deionized water for later use.

[0009] Preferably, the specific preparation steps of the conductive CNT nanofiltration membrane for water treatment are:

[0010] (1) Preparation of casting solution 1: Take 40-50 parts of N,N-dimethylformamide, 3-5 parts of pore-forming agent, and 8-15 parts of polyethersulfone powder by weight, take N,N-dimethylformamide solvent in a conical flask, stir in a water bath at a temperature of 58-60° C., add the pore-forming agent and polyethersulfone powder, stir for 3-4.5 hours, and prepare casting solution 1, and let it stand for degassing for 10-12 hours;

[0011] (2) Preparation of casting solution 2: 40-50 parts of N,N-dimethylformamide, 8-16 parts of carboxylated multi-walled carbon nanotubes and 10-20 parts of graphene slurry are taken by weight, and N,N-dimethylformamide is placed in a conical flask, and then the carboxylated multi-walled carbon nanotube powder and graphene slurry are transferred through a funnel. The conical beaker is sealed and placed in an ultrasonic oscillator, and ultrasonically treated at a temperature of 60-68°C and a frequency of 28-68kHz for 30-50min, and then transferred to a water bath at a temperature of 58-60°C, polyethersulfone powder with a weight of 0.5-0.8 times that of the carboxylated multi-walled carbon nanotubes is added, and the mixture is stirred at a speed of 550-690rpm for 6.5-6.9h to obtain casting solution 2, which is then allowed to stand for degassing for 8-12h;

[0012] (3) Pour casting solution 1 onto a glass plate, adjust the thickness of the scraper to scrape until a film is formed, and then quickly invert casting solution 2 at the starting end, use a 250 μm scraper to quickly scrape at a uniform speed until a film is formed. After the air stays for 50-80 seconds, place the glass plate in a coagulation water bath at room temperature, let it stand for 20-30 minutes, then transfer it to another clear coagulation water bath, let it stand for 3-5 hours, then take it out and soak the film in deionized water for later use.

[0013] Preferably, the pore-forming agent in step (1) is polyethylene glycol.

[0014] Preferably, the volume content of graphene in the graphene slurry in step (2) is 5-8%.

[0015] Preferably, in step (3), the volume ratio of casting liquid 1 to casting liquid 2 is 1:1.5-1:1.8.

[0016] In summary, due to the adoption of the above technology, the beneficial effects of the present invention are:

[0017] The present invention uses organic polyethersulfone as the base membrane, uses carboxylated multi-walled carbon nanotubes and graphene as conductive modification materials, and uses a mixed phase conversion method to modify the conductive nanofiltration functional membrane active layer, thereby obtaining a conductive nanofiltration functional membrane with good conductivity stability;

[0018] The modified conductive membrane (the active layer of the conductive nanofiltration functional membrane is the functional cortex of the modified conductive membrane) is prepared by an improved co-mixed phase conversion method, and its filtration performance is optimized. The hydrophilicity of the modified conductive membrane is improved, the roughness is reduced, the electrochemical properties are stable, and it can operate stably under both acidic and neutral conditions.

[0019] The modified conductive membrane prepared by the present invention has separation characteristics of characteristic pollutants in water and anti-pollution characteristics under the action of an external electric field. Under the action of an external electric field, the conductive nanofiltration membrane can stably alleviate membrane pollution. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0021] Example 1

[0022] The specific preparation steps of the conductive CNT nanofiltration membrane for water treatment are:

[0023] (1) Preparation of casting solution 1: 50 parts by weight of N,N-dimethylformamide, 3 parts of pore-forming agent, and 15 parts of polyethersulfone powder were taken. The N,N-dimethylformamide solvent was placed in a conical flask and stirred in a water bath at 60°C. The pore-forming agent and polyethersulfone powder were added and stirred for 4.5 hours to obtain casting solution 1. The solution was allowed to stand for degassing for 12 hours.

[0024] (2) Preparation of casting solution 2: 50 parts of N,N-dimethylformamide, 8 parts of carboxylated multi-walled carbon nanotubes and 20 parts of graphene slurry were taken by weight, and N,N-dimethylformamide was placed in a conical flask, and then the carboxylated multi-walled carbon nanotube powder and graphene slurry were transferred into the conical flask through a funnel. The conical flask was sealed and placed in an ultrasonic oscillator. The mixture was ultrasonically treated at a temperature of 68°C and a frequency of 68kHz for 30 minutes, and then transferred to a water bath at a temperature of 58°C, and polyethersulfone powder (0.8 times the weight of the carboxylated multi-walled carbon nanotubes) was added. The mixture was stirred at a speed of 690rpm for 6.5 hours to obtain casting solution 2, and the mixture was allowed to stand for degassing for 8 hours;

[0025] (3) Pour the casting solution 1 onto the glass plate, adjust the thickness of the scraper to scrape until a film is formed, and then quickly invert the casting solution 2 at the starting end, use a 250 μm scraper to quickly scrape at a uniform speed until a film is formed. After the air stays for 80 seconds, place the glass plate in a coagulation water bath at room temperature, let it stand for 20 minutes, then transfer it to another clear coagulation water bath, let it stand for 3-5 hours, then take it out and soak the film in deionized water for later use.

[0026] The pore-forming agent in step (1) is polyethylene glycol.

[0027] The volume content of graphene in the graphene slurry of step (2) is 8%.

[0028] In step (3), the volume ratio of casting liquid 1 to casting liquid 2 is 1:1.8.

[0029] Example 2

[0030] The specific preparation steps of the conductive CNT nanofiltration membrane for water treatment are:

[0031] (1) Preparation of casting solution 1: 40 parts by weight of N,N-dimethylformamide, 3 parts of pore-forming agent, and 8 parts of polyethersulfone powder were taken. The N,N-dimethylformamide solvent was placed in a conical flask and stirred in a water bath at a temperature of 58° C. The pore-forming agent and polyethersulfone powder were added and stirred for 3 h to obtain casting solution 1, which was then allowed to stand for degassing for 12 h.

[0032] (2) Preparation of casting solution 2: Take 50 parts of N,N-dimethylformamide, 16 parts of carboxylated multi-walled carbon nanotubes and 20 parts of graphene slurry by weight, put N,N-dimethylformamide in a conical flask, and then transfer the carboxylated multi-walled carbon nanotube powder and graphene slurry through a funnel. Seal the conical beaker and put it in an ultrasonic oscillator. Ultrasonic treatment is carried out at a temperature of 68°C and a frequency of 68kHz for 50 minutes. Then, transfer it to a water bath environment at a temperature of 58°C, add polyethersulfone powder (0.8 times the weight of carboxylated multi-walled carbon nanotubes), stir at a speed of 690rpm for 6.5 hours, and prepare casting solution 2. Let it stand for degassing for 12 hours;

[0033] (3) Pour casting liquid 1 onto a glass plate, adjust the thickness of the scraper to scrape until a film is formed, and then quickly invert casting liquid 2 at the starting end, use a 250 μm scraper to quickly scrape at a uniform speed until a film is formed. After the air stays for 50 seconds, place the glass plate in a coagulation water bath at room temperature, let it stand for 30 minutes, then transfer it to another clear coagulation water bath, let it stand for 5 hours, then take it out and soak the film in deionized water for later use.

[0034] The pore-forming agent in step (1) is polyethylene glycol.

[0035] The volume content of graphene in the graphene slurry of step (2) is 5%.

[0036] In step (3), the volume ratio of casting liquid 1 to casting liquid 2 is 1:1.8.

[0037] Example 3

[0038] The specific preparation steps of the conductive CNT nanofiltration membrane for water treatment are:

[0039] (1) Preparation of casting solution 1: Take 50 parts of N,N-dimethylformamide, 5 parts of pore-forming agent, and 10 parts of polyethersulfone powder by weight, take N,N-dimethylformamide solvent in a conical flask, stir in a water bath at a temperature of 60°C, add the pore-forming agent and polyethersulfone powder, stir for 3 hours, and prepare casting solution 1, and let it stand for degassing for 12 hours;

[0040] (2) Preparation of casting solution 2: 50 parts of N,N-dimethylformamide, 16 parts of carboxylated multi-walled carbon nanotubes and 10 parts of graphene slurry were taken by weight, and N,N-dimethylformamide was placed in a conical flask, and then the carboxylated multi-walled carbon nanotube powder and graphene slurry were transferred into the conical flask through a funnel. The conical flask was sealed and placed in an ultrasonic oscillator. Ultrasonic treatment was performed at a temperature of 68°C and a frequency of 58kHz for 50 minutes, and then the solution was transferred to a water bath at a temperature of 58°C, polyethersulfone powder was added, and the mixture was stirred at a speed of 550 rpm for 6.9 hours to obtain casting solution 2, which was then allowed to stand for degassing for 12 hours;

[0041] (3) Pour casting liquid 1 onto a glass plate, adjust the thickness of the scraper to scrape until a film is formed, and then quickly invert casting liquid 2 at the starting end, use a 250 μm scraper to quickly scrape at a uniform speed until a film is formed. After the air stays for 80 seconds, place the glass plate in a coagulation water bath at room temperature, let it stand for 20 minutes, then transfer it to another clear coagulation water bath, let it stand for 5 hours, then take it out and soak the film in deionized water for later use.

[0042] The pore-forming agent in step (1) is polyethylene glycol.

[0043] The volume content of graphene in the graphene slurry of step (2) is 8%.

[0044] In step (3), the volume ratio of casting liquid 1 to casting liquid 2 is 1:1.8.

[0045] Comparative Example 1

[0046] The specific preparation steps of the conductive CNT nanofiltration membrane for water treatment are:

[0047] (1) Preparation of casting solution 1: 50 parts by weight of N,N-dimethylformamide and 5 parts of pore-forming agent were taken, and N,N-dimethylformamide solvent was placed in a conical flask, stirred in a water bath at 60°C, and the pore-forming agent was added, stirred for 3 hours to obtain casting solution 1, and allowed to stand for degassing for 12 hours;

[0048] (2) Preparation of casting solution 2: 50 parts by weight of N,N-dimethylformamide, 16 parts of carboxylated multi-walled carbon nanotubes and 10 parts of graphene slurry were taken, and N,N-dimethylformamide was placed in a conical flask, and then the carboxylated multi-walled carbon nanotube powder and graphene slurry were transferred into the conical flask through a funnel. The conical flask was sealed and placed in an ultrasonic oscillator, and ultrasonically treated at a temperature of 68°C and a frequency of 58kHz for 50min, and then transferred to a water bath at a temperature of 58°C to obtain casting solution 2, which was allowed to stand for degassing for 12h;

[0049] (3) Pour casting liquid 1 onto a glass plate, adjust the thickness of the scraper to scrape until a film is formed, and then quickly invert casting liquid 2 at the starting end, use a 250 μm scraper to quickly scrape at a uniform speed until a film is formed. After the air stays for 80 seconds, place the glass plate in a coagulation water bath at room temperature, let it stand for 20 minutes, then transfer it to another clear coagulation water bath, let it stand for 5 hours, then take it out and soak the film in deionized water for later use.

[0050] The pore-forming agent in step (1) is polyethylene glycol.

[0051] The volume content of graphene in the graphene slurry of step (2) is 8%.

[0052] In step (3), the volume ratio of casting liquid 1 to casting liquid 2 is 1:1.8.

[0053] Comparative Example 2

[0054] The specific preparation steps of the conductive CNT nanofiltration membrane for water treatment are:

[0055] (1) Preparation of casting solution 1: Take 50 parts of N,N-dimethylformamide, 5 parts of pore-forming agent, and 10 parts of polyethersulfone powder by weight, take N,N-dimethylformamide solvent in a conical flask, stir in a water bath at a temperature of 60°C, add the pore-forming agent and polyethersulfone powder, stir for 3 hours, and prepare casting solution 1, and let it stand for degassing for 12 hours;

[0056] (2) Preparation of casting solution 2: 50 parts of N,N-dimethylformamide, 16 parts of multi-walled carbon nanotubes and 10 parts of graphene slurry were taken by weight, and N,N-dimethylformamide was placed in a conical flask, and then multi-walled carbon nanotube powder and graphene slurry were transferred into the conical flask through a funnel. The conical flask was sealed and placed in an ultrasonic oscillator. Ultrasonic treatment was performed at a temperature of 68°C and a frequency of 58kHz for 50 minutes, and then the solution was transferred to a water bath at a temperature of 58°C, polyethersulfone powder was added, and the mixture was stirred at a speed of 550 rpm for 6.9 hours to obtain casting solution 2, which was then allowed to stand for degassing for 12 hours;

[0057] (3) Pour casting liquid 1 onto a glass plate, adjust the thickness of the scraper to scrape until a film is formed, and then quickly invert casting liquid 2 at the starting end, use a 250 μm scraper to quickly scrape at a uniform speed until a film is formed. After the air stays for 80 seconds, place the glass plate in a coagulation water bath at room temperature, let it stand for 20 minutes, then transfer it to another clear coagulation water bath, let it stand for 5 hours, then take it out and soak the film in deionized water for later use.

[0058] Preferably, the pore-forming agent in step (1) is polyethylene glycol.

[0059] Preferably, the volume content of graphene in the graphene slurry in step (2) is 8%.

[0060] Detection:

[0061] (1) Electrochemical properties: conductivity

[0062] The conductivity of the membrane was measured using a four-point probe conductivity meter RTS-8 (Four Probe Technology (Guangzhou), China). The greater the conductivity, the better the conductive performance. Before the test, the membrane was pressed into a circle with a diameter of 12 mm. During the test, the four probes were fully in contact with the membrane material. The correction coefficient was determined according to the shape characteristics of each membrane. The value was read after the display stabilized. The final result was the average of 18 measurements.

[0063] (2) Experimental studies were conducted on membrane fouling control to examine the effects of modified conductive membranes on Congo red (CR) and methylene blue (MB), characteristic pollutants in printing and dyeing wastewater, under the action of an electric field.

[0064] Table 1

[0065]

[0066] From the comparison of the data of Examples 1-3 and Comparative Examples 1-2 in Table 1, it can be seen that the present invention uses organic polyethersulfone as the base membrane, utilizes carboxylated multi-walled carbon nanotubes and graphene as conductive modification materials, and uses a mixed phase conversion method to conduct conductive modification on the active layer of the conductive nanofiltration functional membrane, thereby obtaining a conductive nanofiltration functional membrane with good conductivity stability.

[0067] An improved co-mixed phase transformation method is used to prepare a modified conductive membrane (the active layer of the conductive nanofiltration functional membrane is the functional cortex of the modified conductive membrane), and its filtration performance is optimized. The hydrophilicity of the modified conductive membrane is improved, the roughness is reduced, the electrochemical properties are stable, and it can operate stably under both acidic and neutral conditions.

[0068] The modified conductive membrane prepared by the present invention has separation characteristics of characteristic pollutants in water and anti-pollution characteristics under the action of an external electric field. Under the action of an external electric field, the conductive nanofiltration membrane can stably alleviate membrane pollution.

[0069] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0070] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

Claims

1. A process for producing a conductive CNT nanofiltration membrane for water treatment, characterized in that: The steps include: (1) Preparation of casting solution 1: N,N-dimethylformamide solvent is placed in a conical flask, stirred in a water bath, pore-forming agent and polyethersulfone powder are added, stirred to obtain casting solution 1, and allowed to stand for degassing; (2) Preparation of casting solution 2: N,N-dimethylformamide was placed in a conical flask, and then the carboxylated multi-walled carbon nanotube powder and graphene slurry were transferred into the conical flask through a funnel. The conical flask was sealed and placed in an ultrasonic oscillator for ultrasonic treatment. After that, the solution was transferred to a water bath, polyethersulfone powder was added and stirred to obtain casting solution 2, which was then allowed to stand for degassing. (3) Pour the casting liquid 1 onto the glass plate, adjust the thickness of the scraper to scrape until a film is formed, and then quickly invert the casting liquid 2 at the starting end, use the scraper to quickly scrape at a uniform speed until a film is formed, and allow air to remain. Place the glass plate in a coagulation water bath at room temperature, let it stand, then transfer it to another clear coagulation water bath, let it stand, then take out the film and soak it in deionized water for later use.

2. The processing technology of a conductive CNT nanofiltration membrane for water treatment according to claim 1, characterized in that: The specific preparation steps of the conductive CNT nanofiltration membrane for water treatment are: (1) Preparation of casting solution 1: Take 40-50 parts of N,N-dimethylformamide, 3-5 parts of pore-forming agent, and 8-15 parts of polyethersulfone powder by weight, take N,N-dimethylformamide solvent in a conical flask, stir in a water bath at a temperature of 58-60° C., add the pore-forming agent and polyethersulfone powder, stir for 3-4.5 hours, and prepare casting solution 1, and let it stand for degassing for 10-12 hours; (2) Preparation of casting solution 2: 40-50 parts of N,N-dimethylformamide, 8-16 parts of carboxylated multi-walled carbon nanotubes and 10-20 parts of graphene slurry are taken by weight, and N,N-dimethylformamide is placed in a conical flask, and then the carboxylated multi-walled carbon nanotube powder and graphene slurry are transferred through a funnel. The conical beaker is sealed and placed in an ultrasonic oscillator, and ultrasonically treated at a temperature of 60-68°C and a frequency of 28-68kHz for 30-50min, and then transferred to a water bath at a temperature of 58-60°C, polyethersulfone powder with a weight of 0.5-0.8 times that of the carboxylated multi-walled carbon nanotubes is added, and the mixture is stirred at a speed of 550-690rpm for 6.5-6.9h to obtain casting solution 2, which is then allowed to stand for degassing for 8-12h; (3) Pour casting solution 1 onto a glass plate, adjust the thickness of the scraper to scrape until a film is formed, and then quickly invert casting solution 2 at the starting end, use a 250 μm scraper to quickly scrape at a uniform speed until a film is formed. After the air stays for 50-80 seconds, place the glass plate in a coagulation water bath at room temperature, let it stand for 20-30 minutes, then transfer it to another clear coagulation water bath, let it stand for 3-5 hours, then take it out and soak the film in deionized water for later use.

3. The processing technology of a conductive CNT nanofiltration membrane for water treatment according to claim 2, characterized in that: The pore-forming agent in step (1) is polyethylene glycol.

4. The processing technology of a conductive CNT nanofiltration membrane for water treatment according to claim 2, characterized in that: The volume content of graphene in the graphene slurry in step (2) is 5-8%.

5. The processing technology of a conductive CNT nanofiltration membrane for water treatment according to claim 2, characterized in that: In step (3), the volume ratio of the casting liquid 1 to the casting liquid 2 is 1:1.5-1:1.8.

Images