Single-walled carbon nanotube metal catalyst, method for preparing same, and use thereof

Abstract

The application provides a single-wall carbon nanotube metal catalyst and a preparation method and application thereof, a special dispersion process is adopted to treat carbon nanotubes, a carbon nanotube dispersion liquid is obtained, the type of metal and the amount of additive are selected, an impregnation method is adopted to prepare the carbon nanotube catalyst, and a stage temperature rising procedure and a continuous stirring process are adopted to prepare the carbon nanotube metal catalyst with small size of active nanometal sites and high orientation. The catalyst function of the application is mainly designed for Fenton reaction, and focuses on decomposing pollutants with benzene ring structure in natural water bodies; and the concentration of methyl blue dye molecules in water bodies can be significantly reduced when the metal loading is less than 10wt%. The application develops a batch of carbon nanotube catalysts based on the principle of low cost and rapid synthesis, the manufacturing process cost is low, the roasting process has high environmental tolerance, and no adhesive is needed in the process, so that the cost is reduced and the environmental pollution is reduced.

Description

Technical Field

[0001] This application belongs to the field of catalysis technology, and in particular relates to a single-walled carbon nanotube metal catalyst, its preparation method and application. Background Technology

[0002] With the rapid development of industries such as textiles, pharmaceuticals, chemicals, leather tanning, and food processing, the production and use of organic dyes has become a widespread phenomenon globally, causing serious environmental pollution problems. my country is one of the world's largest dye processors and producers, and also the world's largest exporter of textiles. Currently, there are over 100,000 types of synthetic dyes available for sale, and the annual production and consumption of dyes exceeds 7 × 10⁻⁶. 5 Tons. The large-scale production and application of dyes directly generate substantial amounts of colored wastewater. In natural environments, organic dye molecules in water degrade slowly or are non-biodegradable, accumulating in the human body through the food chain. The carcinogenic risks of these organic compounds have been reported in medicine. Furthermore, they cause water discoloration, obstruct natural light, and threaten aquatic ecosystems.

[0003] Organic dyes are typically composed of acridine, anthraquinone, diphenylmethane, xanthane, and methylene blue, all of which are aromatic compounds. Currently, methods for treating these organic pollutants mainly include precipitation, adsorption, biodegradation, and advanced oxidation processes (AOPs). The principle of AOPs is that H₂O₂ reacts with an iron-containing catalyst in an acidic environment to undergo a redox reaction, generating hydroxyl radicals in solution; this process is also known as the Fenton reaction. Some studies have reported that Fe₃O₄ and Fe₂O₃ magnetic powders possess high adsorption capacity and effective catalytic reaction performance for the organic dye molecule methylene blue, and their paramagnetism facilitates the separation and recovery of it from water using magnets. However, in practical applications, magnetic nanoparticles tend to aggregate, reducing the catalytic reaction rate, and the recovery rate is low, easily lost with water flow, resulting in poor catalytic performance. Furthermore, existing carbon nanotube-supported catalysts suffer from complex preparation processes, low efficiency, high cost, and poor catalytic performance. Summary of the Invention

[0004] This application is made in view of the above-mentioned issues, and its purpose is to provide a single-walled carbon nanotube metal catalyst, its preparation method and application, to solve the problems of easy agglomeration of nano-metal cluster particles, decreased catalytic performance and difficulty in recovery in the Fenton reaction.

[0005] To achieve the above objectives, this application provides a process for in-situ loading of nano-terminal clusters on single-walled carbon nanotubes using an impregnation method. By selecting the type of metal and controlling the dosage, a nano-cluster metal catalyst is prepared, and it is verified that the catalyst can effectively accelerate the rate of the Fenton reaction, thereby achieving the harmless treatment of organic dye wastewater.

[0006] The first aspect of this application provides a method for preparing a single-walled carbon nanotube metal catalyst, comprising the following steps: (1) Preparation of carbon nanotube dispersion: 1) Add hydroxylated carbon nanotubes and deionized water at a mass ratio of 1:1 to 1:3, and pre-disperse in a water bath at room temperature using ultrasonication for 1-2 hours. The ultrasonication time should not be too short, otherwise the carbon nanotube aggregates will not open sufficiently, which can easily lead to local enrichment of catalyst metal in subsequent processes. The purpose of pre-dispersion is to expose the surface of the carbon nanotubes, increase the number of active sites for metal nanoparticle deposition, and at the same time initially remove carbon black and other carbon nanotube byproducts.

[0007] 2) Transfer the carbon nanotube aqueous solution to an ultrasonic cell disruptor. Using the instrument's built-in No. 6 frequency converter, set the ultrasonic output power to 325-520W, and control the frequency converter to intermittently output ultrasonic waves (2s on, 5s off output cycle) for 20-40 minutes. The ultrasonic output power needs to be controlled within a reasonable range. If the power is lower than 325W, the carbon nanotubes may not disperse evenly, resulting in clumps of carbon nanotube precipitates in the solution; if the power is higher than 520W, the carbon nanotubes will be highly fragmented, leading to a reduction in the specific surface area of ​​the carrier. Compared to water bath ultrasonic dispersion, the ultrasonic probe (frequency converter) of the ultrasonic cell disruptor allows for higher output power, resulting in more uniform material dispersion. Experimental studies have shown that it is more suitable for dispersing self-aggregating materials such as carbon nanotubes, which is beneficial for the subsequent preparation of this application. Simultaneously, to prevent the continuous accumulation of heat in the material during high-power ultrasonication, which could reduce the dispersion effect, the ultrasonic output needs to be intermittent to prevent the solution from evaporating excessively due to high temperature. The output power of the No. 6 frequency converter meets these requirements. While performing ultrasonic dispersion, place a basin of 40ml ice water inside the blender and immerse the reagent bottle in the ice water to maintain the material temperature at around 0℃ and prevent the solution from boiling due to excessively high material temperature. The ultrasonic crushing time should not be too long, otherwise the carbon nanotubes will be mechanically broken, causing the tube length to shrink, reducing the specific surface area of ​​the catalyst, and decreasing the catalytic efficiency.

[0008] 3) Let the dispersed carbon nanotube solution stand for 5 minutes to remove impurities such as precipitated carbon black and amorphous carbon. Transfer the solution to 1 ml centrifuge tubes and centrifuge at 10,000-15,000 rpm for 10-15 minutes. After centrifugation, use a pipette to remove 50%-70% of the supernatant volume from the centrifuge tubes to obtain a highly dispersed carbon nanotube aqueous solution. The supernatant should account for approximately 50%-70% of the total solution mass, and the amount of supernatant removed should not exceed 80% to avoid removing carbon black precipitate and introducing impurities. The centrifugation speed and time should be no less than 10,000 rpm and 10 minutes, respectively. This step ensures thorough precipitation of the aggregated carbon nanotubes in the solution.

[0009] (2) Preparation of the mixture: 1) Weigh at least one of Fe(NO3)3·9H2O, Cu2(NO3)4·5H2O and Co(NO3)2·6H2O, add deionized water, stir evenly and sonicate in a water bath to obtain an aqueous solution of metal salt.

[0010] 2) Mix the metal salt solutions obtained in the previous step with the carbon nanotube aqueous solution at a volume ratio of 3:2 to obtain the catalyst precursor required for the impregnation method. The ratio of metal salt solution to carbon nanotube solution directly determines the loading amount of metal oxide on carbon nanotubes. The amount of carbon nanotube solution should not be less than 1 ml, otherwise the metal oxide catalyst will sinter and form clusters on the surface of carbon nanotubes, reducing the effective area of ​​the catalyst and hindering the recovery of organic dye wastewater.

[0011] (3) Preparation of carbon nanotube catalysts by impregnation method: 1) Transfer the above-mentioned mixed solution of carbon nanotubes and metal salts to a 20ml beaker, add a magnetic rotor, and stir at a speed of not less than 500rpm while impregnating the carbon nanotubes for 12 hours. The stirring speed should not be less than 500rpm; the purpose of high-speed stirring is to ensure that the metal salt solution and carbon nanotubes are fully mixed so that a nano-metal catalyst with uniform particle size can be prepared in the subsequent calcination process. If the stirring speed is too low, the metal oxide will be unevenly loaded on the carbon nanotubes, and the catalyst's anti-sintering ability and stability will easily decrease. Then, transfer the solution to an electric furnace, first evaporate the moisture, and then calcine at high temperature to form the desired shape.

[0012] 2) After calcination, the carbon nanotubes were naturally cooled to room temperature, annealed, and then transferred to a vacuum drying oven for further drying at 80°C for 8 hours.

[0013] In any embodiment, the mass ratio of the hydroxylated carbon nanotubes to deionized water is 1:1-2.

[0014] Ideally, during pre-dispersion, the mass ratio of carbon nanotubes to water should be kept at 1:2 to prevent excessive carbon nanotube concentration from causing a large amount of self-agglomeration, which would affect the degree of dispersion.

[0015] In any embodiment, the concentration of metal ions in the aqueous solution of the metal salt is controlled between 0.019 mol / L and 0.022 mol / L. 5 ml of deionized water is added to each solution, stirred until homogeneous, and then sonicated in a water bath for 2 minutes to obtain the aqueous solution corresponding to each metal salt.

[0016] In any embodiment, the water is initially evaporated in the electric furnace at 90-95℃ for 2-3 hours. The temperature of the concentrated precursor solution should not exceed 100℃ to prevent the catalyst-supported metal clusters from becoming too large due to excessively rapid concentration. Then, the temperature is increased to 400-480℃ at a rate of 30℃ / min for high-temperature calcination for 3 hours, followed by natural cooling and annealing after the heating device is turned off. A heating temperature not lower than 400℃ will result in poor bonding between the carbon nanotubes and the metal oxides, making it easier for the catalyst's active sites to detach.

[0017] A second aspect of this application also provides a single-walled carbon nanotube metal catalyst, which is prepared by the above-described method.

[0018] In any embodiment, the catalyst is a carbon nanotube catalyst supported on at least one nanometal particle selected from Fe, Co, and Cu.

[0019] In any embodiment, the length of the carbon nanotube catalyst is distributed in the range of 200 nm to 20 μm, and the diameter is distributed in the range of 1 to 50 nm; the metal nanoparticles uniformly loaded on the surface of the carbon nanotube catalyst have a length of 40 to 60 nm and a width of 10 to 15 nm, and the metal nanoparticles are cylindrical metal oxides.

[0020] In any embodiment, the metal nanoparticles are uniformly distributed along the axial direction of the outer wall of the carbon nanotube.

[0021] A third aspect of this application also provides the application of a single-walled carbon nanotube metal catalyst, specifically its use in the treatment of organic dye wastewater using the catalyst described above or prepared by the method described above.

[0022] In any embodiment, the organic dye wastewater treatment includes a catalytic reaction of methylene blue or methyl orange organic dyes. It primarily treats aromatic compounds such as acridine, anthraquinone, diphenylmethane, xanthracene, and methylene blue found in the organic dyes.

[0023] The beneficial effects of this application are: 1) This invention develops a carbon nanotube catalyst based on an impregnation process, exhibiting good adaptability and replaceability to different types of metals. The carbon nanotube catalyst of this invention has low manufacturing cost, high environmental tolerance during the calcination process, and the carbon nanotubes prepared by calcination in air have high dispersion and do not aggregate due to the high-temperature calcination process.

[0024] 2) The carbon nanotube catalyst developed in this invention exhibits good dispersibility and numerous loading sites; the redox reaction conditions are mild, enabling rapid oxidation of organic dye molecules in water at ambient temperature and pressure. The heterojunction formed by the metal nanoparticles and carbon nanotubes improves the electron-hole separation rate, generating more hydroxyl radicals. The catalysts supported on Fe, Co, and Cu nanoparticles demonstrate faster reaction kinetics and faster rate constants for the Fenton reaction of methylene blue molecules.

[0025] 3) The active nano-metal sites on the carbon nanotube catalyst of the present invention are small enough to form metal rod-shaped oxides with a length of only 40 nm and a width of only 10 nm; at the same time, the orientation is high and they are basically distributed along the tube axis of the carbon nanotube.

[0026] 4) The catalyst function of this invention is primarily designed for the Fenton reaction, focusing on the decomposition of pollutants containing benzene ring structures in natural water bodies; and it can significantly reduce the concentration of methylene blue dye molecules in water bodies even with a metal loading of less than 10 wt%. This invention develops a batch of carbon nanotube catalysts based on the principles of low cost and rapid synthesis, forming nano-metal oxides through hydroxyl groups modified on the outer wall of carbon nanotubes. This process requires no binder, reducing costs and environmental pollution.

[0027] 5) The carbon nanotube catalyst of this invention has a more convenient process and higher mechanical strength, remaining intact even in a water bath with a 650W ultrasonic probe. Furthermore, thanks to the designed staged temperature rise program and continuous stirring process, the carbon nanotube catalyst of this invention will not aggregate or clump due to high-temperature calcination, eliminating the need for additional oxidants to introduce oxygen-containing functional groups, resulting in more dispersed catalytic active sites. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the process flow for preparing the single-walled carbon nanotube metal catalyst of this application; Figure 2 This is a schematic diagram of a carbon nanotube catalyst supported on nano-metal particles, which is a single-walled carbon nanotube metal catalyst of this application. Figure 3 SEM images of the carbon nanotube catalysts obtained in Comparative Example 1 and Example 1; Figure 4 The images show the UV-Vis spectra of the single-walled carbon nanotube metal catalyst and the control group in this application. Figure 5 This is a normalized graph showing the first-order catalytic reaction rates of the single-walled carbon nanotube metal catalyst and the control group in this application. Figure 6 SEM images of commercial carbon nanotubes (b) and the dispersed carbon nanotube catalyst prepared in this invention. Figure 7The Raman spectrum of the single-walled carbon nanotube metal catalyst of this application; Detailed Implementation The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the single-walled carbon nanotube metal catalyst, its preparation method, and its applications. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of essentially the same structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of providing a full understanding of this application by those skilled in the art and are not intended to limit the subject matter of the claims.

[0029] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0030] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0031] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0032] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0033] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0034] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0035] This invention aims to develop a single-walled carbon nanotube catalyst to address the problems of easy agglomeration of nano-metal clusters, decreased catalytic performance, and difficult recovery in the Fenton reaction. A process for in-situ loading of nano-terminated clusters onto single-walled carbon nanotubes was developed based on an impregnation method. A series of nano-cluster metal catalysts were prepared by changing the type and dosage of metal, and the catalysts were verified to effectively accelerate the Fenton reaction rate, providing a method for the harmless treatment of organic dye wastewater.

[0036] Catalyst supports need to possess stable chemical properties and high specific surface area, while also exhibiting a certain degree of resistance to sintering. Carbon nanotubes are tubular structures formed by carbon atoms bonding through sp2 hybridization, interconnected by a planar hexagonal lattice, and bent at a certain curvature. Typically, carbon nanotubes are classified into single-walled and multi-walled types, with wall thicknesses ranging from 1-100 nm and tube lengths reaching μm or even cm levels, and specific surface areas generally ranging from 100-1200 m². 2 / g, while the specific surface area of ​​existing zeolite molecular sieve catalysts is about 600m². 2 Approximately / g. As a quasi-one-dimensional material, the unique molecular structure endows carbon nanotubes with excellent electrical and chemical stability, making them resistant to acids and alkalis while remaining stable at high temperatures up to 3000K.

[0037] Compared to conventional zeolite catalyst supports, the surface curvature of carbon nanotubes results in a higher electron cloud density on the inner wall of the large π bonds compared to the outer wall. This is expected to alter the electron cloud density distribution on the surface of the metal clusters on the outer wall, and the confinement effect of the tubular structure itself will further modify the catalytic performance of the active sites. The high carrier mobility of carbon nanotubes leads to the formation of a heterojunction structure between the iron oxide and the carbon nanotubes, which is beneficial for electron-hole separation and recombination under illumination, further increasing the rate of the Fenton reaction. Based on these advantages, carbon nanotubes are very suitable as supports for nanoscale metal active sites for the preparation of highly efficient Fenton reaction catalysts.

[0038] Carbon nanotubes naturally aggregate into clusters, making them difficult to dissolve in common solvents such as water, DMF, and DMSO. To ensure that the impregnation method can produce nanoscale metal catalyst clusters, a special dispersion process is required. The carbon nanotube dispersion process of this invention is compatible with common solvents and produces a uniformly dispersed carbon nanotube suspension.

[0039] Example 1 A method for preparing a single-walled carbon nanotube metal catalyst includes the following steps: S1. Preparation of carbon nanotube dispersion: S11. The single-walled carbon nanotubes used in this invention were purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd. The outer wall of the tubes was modified with hydroxyl groups to increase their solubility in aqueous solution. 20 mg of carbon nanotubes were accurately weighed using an electronic balance, and 5 ml of deionized water was added. The mixture was then ultrasonically pre-dispersed in a water bath at room temperature for 2 hours.

[0040] S12. Transfer the above-mentioned carbon nanotube aqueous solution to an ultrasonic cell disruptor. Using a No. 6 frequency converter, set the ultrasonic parameters to 455W and cycle the process for 2 seconds on and 5 seconds off for 20 minutes. While ultrasonically dispersing, place the reagent bottle in an ice-water bath to maintain the material temperature at around 0°C.

[0041] S13. Let the dispersed carbon nanotube solution stand for 5 minutes, then centrifuge at 12000 rpm for 10-15 minutes. Use a pipette to remove 500 μL of the supernatant from the centrifuge tube.

[0042] S14. Weigh 44.43 mg of experimentally pure Fe(NO3)3·9H2O, add 5 ml of deionized water, stir well, and sonicate in a water bath for 2 min.

[0043] S2. Preparation of carbon nanotube catalysts by impregnation method: S21. Transfer the above mixed solution of carbon nanotubes and metal salts to a 20ml beaker, add a magnetic rotor and stir at 1200rpm, while stirring and impregnating the carbon nanotubes for 12h.

[0044] S22. The solution is then transferred to an electric furnace and treated at 90°C for 2-3 hours to initially evaporate the water and concentrate the precursor solution; then the temperature is increased to 400°C at 30°C / min and calcined for 3 hours.

[0045] S23. After calcination, the carbon nanotubes are naturally cooled to room temperature, annealed, and then transferred to a vacuum drying oven for further drying for 8 hours to obtain the product.

[0046] Example 2 This embodiment uses the same method as Embodiment 1, except that in S14, 23.21 mg of experimentally pure Cu2(NO3)4·5H2O is weighed.

[0047] Example 3 This embodiment uses the same method as Example 1, except that in S14, 29.98 mg of experimentally pure Co(NO3)2·6H2O is weighed.

[0048] Comparative Example 1 The comparative example uses the same method as Example 1, except that in S22, the solution is then transferred to an electric furnace and heated to 400°C at a rate of 30°C / min for calcination for 3 hours.

[0049] Experimental analysis was performed on the carbon nanotube catalysts prepared above: 1 mg of the carbon nanotube catalyst prepared above was weighed and added to 1 ml of H₂O₂ (3 wt%), 3 ml of deionized water, and 1 ml of 200 mg / L methylene blue solution. The solution was adjusted to pH 6 using hydrochloric acid (pH 5), and then transferred to a UV spectrophotometer cuvette and allowed to stand. The UV spectroscopy sampling interval was set to 30 min, and the spectral scanning range was from 280 to 1000 nm. The change in the absorption peak of the methylene blue solution over 2 h was recorded. The surface morphology, elemental distribution, and chemical bond composition of the prepared catalyst were evaluated using SEM-EDS and Raman spectroscopy. Figure 3 In the image (a), the carbon nanotube catalyst is agglomerated by direct high-temperature calcination, and in the image (b), the highly dispersed carbon nanotube catalyst is processed by the variable-temperature program of the present invention.

[0050] according to Figure 4 The results show that the concentration of methylene blue dye molecules has a linear relationship with the main absorption peak (600 nm) in the ultraviolet spectrum. In this invention, the absorption peak intensity at 600 nm at 0 min is taken as the initial residual dye concentration C0. The reaction rate constant of the Fenton reaction is calculated with reference to the first-order reaction kinetic model to evaluate the catalyst. Figure 5The results showed that all three catalysts effectively accelerated the catalytic oxidation rate of methylene blue molecules, with the catalytic reaction rate decreasing in the order of Cu / XFS20 > Fe / XFS20 > Co / XFS20. Cu / XFS20 and Fe / XFS20 exhibited similar catalytic performance, reducing the concentration of methylene blue dye to 37% of its initial value within 120 min, while the control group only reduced it to 55%. Figure 4 Ultraviolet spectroscopy evaluation of carbon nanocatalysts catalyzing the methyl blue Fenton reaction: (a) Fe nanoparticle loading (b) Co nanoparticle loading (c) Cu nanoparticle loading (d) No nano-metal particle loading (e) Blank control group.

[0051] Figure 6 SEM characterization results showed that the prepared carbon nanotube catalyst had a length distribution between 200 nm and 20 μm, and a diameter distribution between 1 and 50 nm. Compared with commercially available carbon nanotubes, the carbon nanotubes prepared in this invention have a high degree of dispersion, with metal nanoparticles uniformly grown on the surface, approximately 40 nm in length, and distributed along the diameter direction of the carbon nanotubes. The high dispersion of the carbon nanotubes provides more loading sites for the metal particles, resulting in a higher decomposition rate in the catalytic reaction of methylene blue molecules. Figure 6 In the image, (a) represents commercially available carbon nanotubes, and (b) represents the dispersed carbon nanotube catalyst prepared in this invention (taking Fe / XFS20 as an example).

[0052] according to Figure 7 Raman spectroscopy characterization results revealed characteristic peaks of carbon nanotubes, with a G peak appearing near 1590 cm⁻¹, which was identified as originating from the vibration of C-C bonds on the carbon nanotube axis; 1550-1585 cm⁻¹ -1 A small G' peak appears at 1350 cm⁻¹, indicating that this peak originates from the vibration of C-C bonds in the circumferential direction of the carbon nanotube. -1 The D peak at I mainly originates from the sp3 hybridization bonding of C atoms. G / I D =13.46, which may be due to the additional O atoms introduced onto the C atoms during the CVD growth of carbon nanotubes or the high-temperature annealing of nano-metal particles under load.

[0053] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing a single-walled carbon nanotube metal catalyst, characterized in that, Includes the following steps: (1) Preparation of carbon nanotube dispersion: 1) Add hydroxylated carbon nanotubes and deionized water at a mass ratio of 1:1 to 1:3, and pre-disperse them in a water bath at room temperature for 1-2 hours using ultrasonication. 2) Transfer the carbon nanotube aqueous solution into the ultrasonic cell wall disruptor, set the ultrasonic output power to 325-520W, and control the frequency converter to open and close the ultrasonic output for 20-40 minutes. 3) Let the dispersed carbon nanotube solution stand for 5 minutes, then put the solution into 1 ml centrifuge tubes and centrifuge at 10000-15000 rpm for 10-15 minutes. After centrifugation, use a pipette to remove 50%-70% of the volume of the supernatant in the centrifuge tube to obtain a highly dispersed carbon nanotube aqueous solution. (2) Preparation of the mixture: 1) Weigh at least one of Fe(NO3)3·9H2O, Cu2(NO3)4·5H2O and Co(NO3)2·6H2O, add deionized water, stir evenly and sonicate in a water bath to obtain an aqueous solution of metal salt; 2) The metal salt solution obtained in step (2) is mixed with the carbon nanotube aqueous solution at a volume ratio of 3:2 to obtain the catalyst precursor required for the impregnation method; (3) Preparation of carbon nanotube catalysts by impregnation method: 1) Transfer the mixed solution of catalyst precursor to a 20ml beaker, add a magnetic rotor and stir at a speed of not less than 500rpm, while stirring and impregnating carbon nanotubes for 12h; then transfer the solution to an electric furnace, first evaporate the water, and then calcine at high temperature to form the shape. 2) After calcination, the carbon nanotubes are naturally cooled to room temperature, annealed, and then transferred to a vacuum drying oven for drying.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the hydroxylated carbon nanotubes to deionized water is 1:1-2.

3. The preparation method according to claim 1, characterized in that, The concentration of metal ions in the aqueous solution of the metal salt is controlled between 0.019 mol / L and 0.022 mol / L.

4. The preparation method according to claim 1, characterized in that, In the electric furnace, the water is initially evaporated by treating at 90-95℃ for 2-3 hours, and then the temperature is increased to 400-480℃ at 30℃ / min for high-temperature calcination and shaping for 3 hours. After that, the heating device is turned off and the furnace is allowed to cool and anneal naturally.

5. A single-walled carbon nanotube metal catalyst, characterized in that, Carbon nanotube catalysts are obtained by any one of the preparation methods of claims 1-4.

6. The single-walled carbon nanotube metal catalyst according to claim 5, characterized in that, The carbon nanotube catalyst has a length distribution of 200 nm to 20 μm and a diameter distribution of 1 to 50 nm.

7. The single-walled carbon nanotube metal catalyst according to claim 5, characterized in that, The metal nanoparticles uniformly loaded on the surface of the carbon nanotube catalyst have a length of 40-60 nm and a width of 10-15 nm.

8. The single-walled carbon nanotube metal catalyst according to claim 5, characterized in that, The metal nanoparticles are uniformly distributed along the axial direction of the outer wall of the carbon nanotube, and the metal nanoparticles are cylindrical metal oxides.

9. An application of a single-walled carbon nanotube metal catalyst, characterized in that, The application of the catalyst prepared by any one of claims 1 to 3 or the catalyst prepared by any one of claims 4 to 8 in the treatment of organic dye wastewater.

10. The application according to claim 9, characterized in that, The organic dye wastewater treatment includes the catalytic reaction of organic dyes such as methylene blue or methyl orange.

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