A method and system for continuous batch purification of single-walled carbon nanotubes

Abstract

This invention belongs to the field of nanomaterial preparation and purification technology, and relates to a method and system for continuous batch purification of single-walled carbon nanotubes. This method rapidly evaporates metal catalyst impurity particles in carbon nanotubes through a high-temperature region generated by an electric arc discharge, achieving the purification effect. Furthermore, by controlling the diameter of the pipe introducing carbon nanotube powder and the flow rate of the transported gas, the content and residence time of carbon nanotubes entering the arc region from the electrode gun can be controlled, enabling continuous batch purification of single-walled carbon nanotubes. The beneficial technical effects of this invention are that the purification efficiency can reach 150–300 g / min, and the purity after purification can be increased from 40% to over 95%. This invention achieves rapid dry purification, avoiding waste acid pollution caused by traditional acid washing purification. Simultaneously, the high temperature of the electric arc also improves the graphitization degree of the carbon nanotubes, enabling continuous batch purification and possessing significant commercial application value.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial preparation and purification post-processing technology, specifically relating to a method and system for continuous batch purification of single-walled carbon nanotubes. Background Technology

[0002] Carbon nanotubes (CNTs) possess excellent electrical conductivity, mechanical properties, and photoelectric characteristics, making them widely applicable in various fields such as conductive pastes, reinforcing additives, transparent conductive films, and electromagnetic shielding. They are an indispensable cutting-edge material for the development of high-tech industries. In the preparation of carbon nanotubes, metallic catalysts such as iron, cobalt, and nickel are typically used, with the metal catalyst encapsulated within the carbon nanotube powder in the resulting product. Especially in the currently used high-temperature plasma arc method for preparing single-walled carbon nanotubes, not only is a significant amount of metal catalyst removed, but also byproducts such as crystalline carbon generated at high temperatures. Generally, to obtain commercially viable carbon nanotube products, impurities such as metal catalyst particles need to be removed—this is the purification process.

[0003] Traditional purification methods include acid washing and high-temperature methods. Acid washing typically uses acidic solutions such as hydrochloric acid to react with a metal catalyst, achieving removal. While relatively low-cost, acid washing generates large amounts of waste acid and liquid, creating significant environmental pressure. High-temperature methods involve heating under vacuum to temperatures above the boiling point of the metal catalyst, causing the metal particles to evaporate and achieving purification. High-temperature methods generally require high-purity raw materials, placing high demands on the raw materials, resulting in long production cycles and stringent requirements for equipment vacuum levels and insulation. Currently, the preparation of high-purity carbon nanotubes generally employs a combination of these two purification methods. For example, CN 113860289 A discloses a purification method using a mixture of oxidant and dilute acid. CN 116835572A discloses a process of first expanding aggregated carbon nanotubes, then subjecting them to high-temperature oxidation, and finally acid washing. CN 115403034 A discloses a high-purity, high-conversion-rate purification method for single-walled carbon nanotubes (SUVs). This method combines high-temperature treatment of dispersed SUV powder with mixed acid treatment. While this combination of methods is currently the main purification process, it is complex, costly, and causes significant damage to the SUVs. Furthermore, these methods can only perform intermittent purification and cannot achieve continuous purification. Summary of the Invention

[0004] This invention discloses a method and system for continuous batch purification of single-walled carbon nanotubes, in order to solve the above-mentioned and other potential problems of the prior art.

[0005] To address the aforementioned problems, the technical solution of this invention is: a method for continuous batch purification of single-walled carbon nanotubes. This method uses the high-temperature region generated by an arc discharge device as a heat source to rapidly evaporate the metal catalyst impurity particles in the carbon nanotubes, thereby achieving the effect of purifying the carbon nanotubes. Furthermore, by controlling the pipe diameter and airflow rate of the pipe introducing carbon nanotube powder to control the carbon nanotube content and residence time entering the arc region from the electrode gun, continuous batch purification can be performed to obtain high-purity, highly graphitized single-walled carbon nanotubes.

[0006] The method specifically includes the following steps:

[0007] S1) The prepared single-walled carbon nanotubes are mechanically sheared to obtain carbon nanotube powder of a certain particle size that is initially dispersed and placed in the feeding unit for later use.

[0008] S2) Remove the air from the system, fill it with an argon atmosphere, and start the plasma arc device at a certain power to make the core region of the arc reach the required high temperature.

[0009] S3) Introduce arc-igniting gas to guide the powder carbon tube in the feeding unit through the electrode gun to the core area of ​​the arc, control the residence time, and introduce an appropriate amount of etching agent to make the metal catalyst in the carbon tube evaporate rapidly.

[0010] S4) Driven by the purge airflow, the purified product enters the collection system for collection.

[0011] Furthermore, the average particle size D50 of the carbon nanotube powder initially dispersed after mechanical shearing in S1) is 15-150 micrometers;

[0012] Furthermore, the power of the plasma arc device in S2) is 50 to 500 kW, and the temperature of the core region reaches 4000 to 8000 °C;

[0013] Furthermore, in S3), the arc-igniting gas, which is also the gas for conveying carbon nanotube powder, is high-purity argon, with a gas flow rate of 10–500 L / min, the diameter of the electrode gun outlet is 0.5–15 cm, and the residence time of the material in the core high-temperature zone is 0.01–0.5 s.

[0014] The etching agent is at least one of water vapor, hydrogen, carbon dioxide, and hydrogen sulfide gas, and is introduced after being mixed with the arc-igniting gas argon, with the introduced flow rate accounting for 0.1% to 15% of the argon flow rate.

[0015] Furthermore, the purified product in step S4) is a single-walled carbon nanotube with a purity of over 95%, and its Raman spectroscopy... G / I D Greater than 80.

[0016] Furthermore, the purification efficiency of the method can reach 150-300 g / min, enabling continuous batch processing and possessing significant commercial application value.

[0017] Another object of the present invention is to provide a system for realizing the above-described method for continuous batch purification of single-walled carbon nanotubes, the system comprising:

[0018] The feeding unit is used to store the single-walled carbon nanotubes to be purified;

[0019] The electrode gun is used as a cathode to initiate an arc while simultaneously introducing the material to be processed into the core area.

[0020] Graphite anode, used to generate an electric arc with the electrode gun;

[0021] The purification unit is used to form the high-temperature core region to complete the purification of the material;

[0022] The collection unit is used to collect the processed products under the influence of airflow.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] (1) This invention proposes for the first time to use the high temperature electric arc method to purify carbon nanotubes. This dry purification process avoids the waste liquid pollution caused by traditional wet processes such as acid washing, and does not require subsequent cumbersome processes such as washing and drying, which greatly simplifies the purification process.

[0025] (2) The present invention adopts a purification method of controlling the airflow to transport carbon tubes into the high-temperature zone of the electric arc to evaporate catalyst metals. By controlling the airflow, raw materials can be continuously input and products can be output, which can effectively realize batch preparation.

[0026] (3) In the single-walled carbon nanotubes prepared by plasma arc method, in addition to removing metal catalyst particles, there are also byproducts such as crystalline carbon generated at high temperature. The present invention can conveniently mix a specific etching agent into the carrier gas argon, which can effectively etch the crystalline carbon components in the raw material single-walled carbon nanotubes that are difficult to remove without damaging the carbon nanotubes, and further improve the purification effect.

[0027] (4) The present invention allows the raw carbon nanotubes to undergo a second high-temperature treatment by electric arc, which can further improve the crystallinity of single-walled carbon nanotubes during the high-temperature treatment process, and improve the quality of carbon nanotubes while purifying them. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of a system for continuous batch purification of single-walled carbon nanotubes according to the present invention.

[0029] Figure 2This is a schematic diagram of a scanning electron microscope image of the carbon nanotube raw material before purification in Example 1 of the present invention.

[0030] Figure 3 This is a schematic diagram of a scanning electron microscope image of the purified single-walled carbon nanotube product in Example 1 of the present invention.

[0031] Figure 4 This is a schematic diagram comparing the Raman spectra of carbon nanotubes before and after purification in Example 1 of the present invention.

[0032] Figure 5 This is a schematic diagram comparing the thermogravimetric spectra of carbon nanotubes before and after purification in Example 1 of the present invention.

[0033] Figure 6 This is a schematic diagram of a transmission electron microscope image of the carbon nanotube raw material before purification in Example 1 of the present invention.

[0034] Figure 7 This is a schematic diagram of a transmission electron microscope image of the purified carbon nanotube product in Example 1 of the present invention.

[0035] Figure 8 This is a schematic diagram of a scanning electron microscope image of the purified single-walled carbon nanotube product in Example 2 of the present invention.

[0036] In the picture:

[0037] 1. Feeding unit, 2. Electrode gun, 3. Purification unit, 4. Graphite anode, 5. Collection unit. Specific implementation methods

[0038] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0039] This invention discloses a method for continuous batch purification of single-walled carbon nanotubes, which specifically includes the following steps:

[0040] S1) The single-walled carbon nanotubes to be purified are mechanically sheared to obtain carbon nanotube powder with a certain particle size that is initially dispersed, for later use.

[0041] S2) Empty the air, fill with a protective atmosphere, start the plasma arc device, and make the core area of ​​the arc reach the preset temperature under a certain power.

[0042] S3) Introduce arc-igniting gas to pass the carbon nanotube powder and etching agent obtained in S1) through the electrode gun to the core area of ​​the arc, where they stay for a certain period of time to allow the metal catalyst in the carbon nanotube powder to evaporate rapidly and some of the crystalline carbon to be removed.

[0043] S4) Driven by the purge airflow, the purified product enters for collection.

[0044] The average particle size D50 of the carbon nanotube powder initially dispersed after mechanical shearing in S1) is 15-150 micrometers.

[0045] The protective atmosphere in S2) is argon; the power of the plasma arc device is 50-500kW, and the preset temperature is 4000-8000℃.

[0046] The flow rate of the arc-igniting gas in S3) is 10-500 L / min, the diameter of the electrode gun outlet is 0.5-15 cm, and the residence time of the material in the core high-temperature zone is 0.01-0.5 s.

[0047] The flow rate of the etchant is 0.1% to 15% of the flow rate of the arc-starting gas.

[0048] The arc-igniting gas is high-purity argon; the etching agent is at least one of water vapor, hydrogen, carbon dioxide, or hydrogen sulfide.

[0049] The purified product described in S4) is a single-walled carbon nanotube with a purity of over 95%, and its Raman spectroscopy... G / I D Greater than 80.

[0050] The purification efficiency of the method can reach 150-300 g / min.

[0051] A single-walled carbon nanotube, characterized in that the single-walled carbon nanotube is obtained by purification using the method described above. Figure 1 As shown, the system for the above-described method of continuous batch purification of single-walled carbon nanotubes includes:

[0052] Feeding unit 1 is used to store single-walled carbon nanotubes to be purified;

[0053] Electrode gun 2 is used as a cathode to initiate an arc while simultaneously introducing the material to be processed into the core area.

[0054] Graphite anode 4 is used to generate an electric arc with the electrode gun;

[0055] Purification unit 3 is used to form the high-temperature core region to complete the purification of materials;

[0056] Collection unit 5 is used to collect the processed products under the influence of airflow.

[0057] Example 1

[0058] The prepared single-walled carbon nanotube sheet or filament primary products were mechanically sheared to obtain initially dispersed carbon nanotube powder with an average particle size D50 of 50 micrometers, which was then placed in the feeding unit for later use. A vacuum pump was used to evacuate the system and remove air, followed by argon atmosphere replacement. The power was set to 300kW, and the plasma arc device was started, raising the average temperature of the arc core region to 4500℃. Argon gas, which also served as the feed gas, was introduced through a hollow electrode gun to guide the carbon nanotube powder from the feeding unit to the arc core region. The feed gas flow rate was controlled at 150L / min, the electrode gun outlet diameter was 10cm, and the residence time of the raw material in the high-temperature zone was controlled at 0.2s. 10L / min of water vapor was introduced into the argon gas as an etchant, causing the metal catalyst in the carbon nanotubes to evaporate rapidly while etching away some of the crystalline carbon. The outlet switch was opened, and the purified product was collected by the purge gas flow into the collection system for sampling and characterization.

[0059] Scanning electron microscope images of carbon nanotube raw materials before purification are shown below. Figure 1 As shown in the image, this invention uses single-walled carbon nanotubes prepared by plasma arc method. Scanning electron microscopy (SEM) images reveal numerous randomly distributed particles within the bundles of thin, straight single-walled carbon nanotubes. These particles, ranging in size from tens to hundreds of nanometers, are crystalline carbon-coated metal nanoparticles. Due to the carbon layer coating the metal surface, conventional acid washing purification processes are insufficient to remove the catalyst metal within the coating. The purification method described in this embodiment utilizes an etchant that can etch away the crystalline carbon coating at high temperatures without damaging the carbon nanotubes. Simultaneously, the internal metal particles rapidly evaporate under the high-temperature environment of the arc, achieving highly efficient purification. Figure 2 Comparison of purified scanning electron microscope images Figure 1 It can be seen that most of the carbon-coated metal particles have been completely removed, and there are no obvious metal catalyst particles remaining between the straight tube bundles. Furthermore, through... Figure 3 Raman spectroscopy results before and after purification show that the D peak, representing defects, is significantly weakened in the purified sample, indicating that purification improved the crystallinity of the product. Meanwhile, Raman I... G / I D The concentration increased from 18.7 before purification to 52.5 after purification. Figure 4 In this embodiment, the purified sample and the unpurified sample were subjected to thermogravimetric analysis. The final residue decreased from 56.6% before purification to 3.4% after purification, indicating that most of the metal impurities were removed after purification. The unpurified single-walled carbon nanotube raw material was as follows: Figure 5As shown, there are distinct black particles of varying sizes between the linear carbon nanotubes; these are the metal catalyst particles, some of which are coated with multiple carbon shells, forming a core-shell structure. After purification in this example, as... Figure 6 Transmission electron microscopy (TEM) images of the purified sample show that the crystalline carbon shell was partially etched by the etchant, resulting in the removal of all metal catalyst particles within the shell, leaving only an empty shell structure. Simultaneously, the linear, vertical single-walled carbon nanotube bundles remained intact. Both test and analysis results demonstrate the excellent purification effect of this method.

[0060] Example 2

[0061] The prepared single-walled carbon nanotube sheet or filament primary products were mechanically sheared to obtain initially dispersed carbon nanotube powder with an average particle size D50 of 50 micrometers, which was then placed in the feeding unit for later use. A vacuum pump was used to evacuate the system and remove air, followed by argon atmosphere replacement. The power was set to 300kW, and the plasma arc device was started, raising the average temperature of the arc core region to 4500℃. Argon gas, which also served as the raw material transport gas, was introduced through a hollow electrode gun, guiding the carbon nanotube powder from the feeding unit to the arc core region. The transport gas flow rate was controlled at 150L / min, the electrode gun outlet diameter was 10cm, and the residence time of the raw material in the high-temperature zone was controlled at 0.2s. Carbon dioxide at a flow rate of 15L / min was introduced into the argon transport gas as an etchant, causing the metal catalyst in the carbon nanotubes to evaporate rapidly while etching away some of the crystalline carbon. The outlet switch was opened, and the purified product was collected by the purge gas flow into the collection system for sampling and characterization.

[0062] Scanning electron microscope images of the purified product are shown below. Figure 7 As shown, no obvious catalyst particles were found between the tightly packed carbon nanotube bundles, and the sample surface showed no other impurities besides the tube bundles, indicating a very significant purification effect.

[0063] Example 3

[0064] The prepared single-walled carbon nanotube sheet or filament primary products were mechanically sheared to obtain initially dispersed carbon nanotube powder with an average particle size D50 of 50 micrometers, which was then placed in the feeding unit for later use. A vacuum pump was used to evacuate the system and remove air, followed by purging with an argon atmosphere. The power was set to 300kW, and the plasma arc device was started, raising the average temperature of the arc core region to 4500℃. Argon gas, which also served as the feed gas, was introduced through a hollow electrode gun, guiding the carbon nanotube powder from the feeding unit to the arc core region. The feed gas flow rate was controlled at 150L / min, the electrode gun outlet diameter was 10cm, and the residence time of the raw material in the high-temperature zone was controlled at 0.2s. 20L / min of hydrogen gas was introduced into the argon gas as an etchant, causing the metal catalyst in the carbon nanotubes to evaporate rapidly while etching away some of the crystalline carbon. The outlet switch was opened, and the purified product was collected by the purge gas flow into the collection system for sampling and characterization.

[0065] Table 1. Comparison of sample performance parameters before and after purification using different etchants in Examples 1, 2, and 3.

[0066]

[0067]

[0068] As can be seen from the results in Table 1 above, Examples 1, 2, and 3 used different etching agents. Compared with the raw carbon nanotubes, the purified product exhibited higher Raman spectral density. G / I D All three etchants showed significant improvements, with the highest improvement observed in Example 1. Thermogravimetric (TG) residues in the purified products were significantly reduced, indicating that the purity was increased to over 90%, with the water vapor etching used in Example 1 showing the best effect. The three etchants had little impact on purification efficiency, all achieving around 250 g / min, enabling continuous batch purification.

[0069] Example 4

[0070] The prepared single-walled carbon nanotube sheet or filament primary products were mechanically sheared to obtain initially dispersed carbon nanotube powder with an average particle size D50 of 100 micrometers, which was then placed in the feeding unit for later use. A vacuum pump was used to evacuate the system and remove air, followed by argon atmosphere replacement. The power was set to 400kW, and the plasma arc device was started, raising the average temperature of the arc core region to 6500℃. Argon gas, which also serves as the raw material transport gas, was introduced through a hollow electrode gun, guiding the carbon nanotube powder from the feeding unit to the arc core region. The transport gas flow rate was controlled at 300L / min, the electrode gun outlet diameter was selected as 5cm, and the residence time of the raw material in the high-temperature zone was controlled at 0.05s. 10L / min of water vapor was introduced into the argon transport gas as an etchant, causing the metal catalyst in the carbon nanotubes to evaporate rapidly while etching away some of the crystalline carbon. The outlet switch was opened, and the purified product was collected by the purge gas flow into the collection system.

[0071] Example 5

[0072] The prepared single-walled carbon nanotube sheet or filament primary products were mechanically sheared to obtain initially dispersed carbon nanotube powder with an average particle size D50 of 80 micrometers, which was then placed in the feeding unit for later use. A vacuum pump was used to evacuate the system and remove air, followed by argon atmosphere replacement. The power was set to 450kW, and the plasma arc device was started, raising the average temperature of the arc core region to 7500℃. Argon gas, which also serves as the raw material transport gas, was introduced through a hollow electrode gun, guiding the carbon nanotube powder from the feeding unit to the arc core region. The transport gas flow rate was controlled at 350L / min, the electrode gun outlet diameter was selected as 8cm, and the residence time of the raw material in the high-temperature zone was controlled at 0.1s. 20L / min of water vapor was introduced into the argon transport gas as an etchant, causing the metal catalyst in the carbon nanotubes to evaporate rapidly while etching away some of the crystalline carbon. The outlet switch was opened, and the purified product entered the collection system for collection under the purge gas flow.

[0073] Example 6

[0074] The prepared single-walled carbon nanotube sheet or filament primary products were mechanically sheared to obtain initially dispersed carbon nanotube powder with an average particle size D50 of 30 micrometers, which was then placed in the feeding unit for later use. A vacuum pump was used to evacuate the system and remove air, followed by argon atmosphere replacement. The power was set to 250kW, and the plasma arc device was started, raising the average temperature of the arc core region to 4500℃. Argon gas, which also served as the raw material transport gas, was introduced through a hollow electrode gun, guiding the carbon nanotube powder from the feeding unit to the arc core region. The transport gas flow rate was controlled at 50L / min, the electrode gun outlet diameter was selected at 8cm, and the residence time of the raw material in the high-temperature zone was controlled at 0.1s. 20L / min of hydrogen gas was introduced into the argon transport gas as an etchant, causing the metal catalyst in the carbon nanotubes to evaporate rapidly while etching away some of the crystalline carbon. The outlet switch was opened, and the purified product entered the collection system for collection under the purge gas flow.

[0075] Example 7

[0076] The prepared single-walled carbon nanotube sheet or filament primary products were mechanically sheared to obtain initially dispersed carbon nanotube powder with an average particle size D50 of 50 micrometers, which was then placed in the feeding unit for later use. A vacuum pump was used to evacuate the system and remove air, followed by argon atmosphere replacement. The power was set to 400kW, and the plasma arc device was started, raising the average temperature of the arc core region to 6500℃. Argon gas, which also served as the raw material transport gas, was introduced through a hollow electrode gun, guiding the carbon nanotube powder from the feeding unit to the arc core region. The transport gas flow rate was controlled at 150L / min, the electrode gun outlet diameter was 10cm, and the residence time of the raw material in the high-temperature zone was controlled at 0.1s. Hydrogen sulfide at a flow rate of 10L / min was introduced into the argon gas as an etchant, causing the metal catalyst in the carbon nanotubes to evaporate rapidly while etching away some of the crystalline carbon. The outlet switch was opened, and the purified product was collected by the purge gas flow into the collection system.

[0077] The above provides a detailed description of a method and system for continuous batch purification of single-walled carbon nanotubes provided in the embodiments of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and its core ideas; furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

[0078] Certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The terms "comprising" and "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising / including but not limited to". "Approximately" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect within a certain margin of error. The following descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of illustrating the general principles of this application and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appended claims.

[0079] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the product or system that includes said element.

[0080] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0081] The foregoing description illustrates and describes several preferred embodiments of this application. However, as previously stated, it should be understood that this application is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the application concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of this application should be within the protection scope of the appended claims.

Claims

1. A method for continuous batch purification of single-walled carbon nanotubes, characterized in that, The method uses the high-temperature region generated by electric arc discharge as a heat source, introduces carbon nanotube powder and etching agent into the high-temperature region through arc-igniting gas, and controls the residence time of carbon nanotubes to rapidly evaporate the metal catalyst in the carbon nanotube powder and remove some of the crystalline carbon, thereby achieving continuous batch purification of single-walled carbon nanotubes. The method specifically includes the following steps: S1) The single-walled carbon nanotubes to be purified are mechanically sheared to obtain carbon nanotube powder with a certain particle size that is initially dispersed, for later use. The average particle size D50 of the carbon nanotube powder initially dispersed after mechanical shearing is 15~150 micrometers; S2) Empty the air, fill with a protective atmosphere, start the plasma arc device, and make the core area of ​​the arc reach the preset temperature under a certain power. The protective atmosphere is argon; the power of the plasma arc device is 50~500kW, and the preset temperature is 4000~8000℃. S3) Introduce arc-igniting gas to pass the carbon nanotube powder and etchant obtained from S1) through the electrode gun to the core area of ​​the arc, where they remain for a certain period of time to allow the metal catalyst in the carbon nanotube powder to evaporate rapidly and to remove some of the crystalline carbon. The flow rate of the arc-igniting gas is 10~500L / min, the diameter of the electrode gun outlet is 0.5~15cm, and the residence time of the material in the core high-temperature zone is 0.01~0.5s. The flow rate of the etchant is 0.1% to 15% of the arc-starting gas flow rate; The arc-igniting gas is high-purity argon; the etching agent is at least one of water vapor, hydrogen, carbon dioxide, or hydrogen sulfide gas. S4) Driven by the purge airflow, the purified product enters for collection.

2. The method according to claim 1, characterized in that, The purified product described in S4) is a single-walled carbon nanotube with a purity of over 95%, and its Raman spectroscopy... G / I D Greater than 80.

3. The method according to claim 2, characterized in that, The purification efficiency of the method can reach 150~300g / min.

4. A single-walled carbon nanotube, characterized in that, The single-walled carbon nanotubes were purified using any one of the methods described in claims 1-3.

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