Method for modifying and refining carbon black from waste tire pyrolysis

Abstract

The application discloses a kind of waste tyre pyrolysis carbon black modification refining method, belong to solid waste resource utilization field.The method includes: after being pretreated by crushing, magnetic separation, screening to pyrolysis carbon black crude product, in turn, supercritical CO2 extraction pre-refining and low temperature plasma depth refining modification are carried out, finally, by grading collection, obtain refined modified carbon black, CO2 produced by extraction is recycled and applied.The application passes through supercritical CO2 extraction, and pre-clears carbon black pore and loosens inorganic ash, and then active free radicals generated by low temperature plasma penetrate into pore interior to carry out depth ash stripping and oxygen-containing functional group introduction, break through the limitation that traditional plasma modification only acts on the surface of particle, realize the uniform modification of carbon black from surface to interior.No waste water discharge in whole process, environmental protection advantage is remarkable, the PAHs residual amount of obtained product is ≤2mg / kg, ash content is ≤2.0%, can be widely applied in rubber products, plastic color masterbatch and asphalt modification and the like field.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization, specifically to a method for modifying and refining carbon black from waste tire pyrolysis. Background Technology

[0002] With the continuous growth of car ownership, the amount of waste tires generated is increasing year by year. Pyrolysis, as one of the mainstream technologies for the resource utilization of waste tires, can convert waste tires into pyrolysis oil, pyrolysis gas, and pyrolysis carbon black. Among these, pyrolysis carbon black accounts for approximately 30% to 35% of the tire's mass, and its high-value utilization is a key link in realizing a closed-loop industrial chain for the pyrolysis of waste tires.

[0003] However, the addition of large amounts of inorganic reinforcing fillers (such as silica and calcium carbonate) and functional additives (such as zinc oxide) during tire manufacturing results in crude pyrolysis carbon black generally exhibiting defects such as high ash content (typically 15%–22%), high residual polycyclic aromatic hydrocarbons (PAHs), surface coating by tar and other organic matter, blocked pore structure, and a lack of surface-active functional groups. These problems hinder the direct reuse of pyrolysis carbon black in rubber products or plastic masterbatches, leading to poor dispersibility, weak interfacial bonding, and a reinforcing effect far inferior to industrial carbon black, severely limiting its market value and application scope.

[0004] Existing technologies for the refining and modification of pyrolysis carbon black are mainly divided into two categories: wet and dry methods.

[0005] Wet processes are represented by acid washing, alkaline washing, or combined acid-alkali treatment. For example, Chinese patent CN108530951A discloses a two-step acid washing deashing method using hydrochloric acid and hydrofluoric acid, which can reduce ash content to a low level. However, such methods generate large amounts of acidic or alkaline wastewater, have high treatment costs, and pose risks of equipment corrosion and secondary pollution, resulting in significant environmental pressure.

[0006] Dry processing mainly includes high-temperature heat treatment, mechanochemical modification, and low-temperature plasma treatment. Among these, low-temperature plasma technology has attracted considerable attention due to its ability to introduce oxygen-containing active functional groups onto the carbon black surface, improving surface polarity and rubber compatibility. For example, Chinese patent CN113801376B discloses a method for modifying pyrolyzed carbon black powder using low-temperature plasma. However, existing research and engineering practice show that the highly active free radicals generated by low-temperature plasma have limited depth of action, mainly concentrated on the outer surface of carbon black particles, and are difficult to penetrate into the nanoscale pores. This results in the inability to effectively remove the tar coating and ash particles from the inner walls of the pores, leading to an uneven modification effect with a "deep outside, shallow inside" characteristic.

[0007] Supercritical CO2 extraction technology has been used to remove PAHs from carbon black. For example, US Patent 8728324B2 discloses a method for reducing the PAH content of carbon black using supercritical CO2 extraction. However, this technology is mainly used for the post-processing of ordinary industrial carbon black, with a single function, and has not yet addressed the pore opening of pyrolysis carbon black or its synergistic effect with subsequent surface modification.

[0008] In summary, the existing technology lacks a method that can deeply remove organic and inorganic impurities from the pores of pyrolysis carbon black, achieve uniform surface chemical modification of the outer surface and inner walls of the pores of carbon black, and enable continuous industrial production without wastewater discharge. Summary of the Invention

[0009] (a) Technical problems to be solved This invention aims to overcome the shortcomings of existing technologies and provide a method for modifying and refining pyrolysis carbon black from waste tires, thereby simultaneously solving the following technical problems: incomplete removal of tar and ash from the pores of pyrolysis carbon black, plasma modification only acting on the outer surface of particles, uneven modification, and large wastewater discharge and high environmental protection costs in wet processes.

[0010] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: A method for modifying and refining pyrolysis carbon black from waste tires includes the following steps: S1. Raw material pretreatment: The crude pyrolysis carbon black is crushed, magnetically separated, and sieved to obtain pretreated carbon black with a moisture content of ≤0.5%; S2, Supercritical CO2 extraction pre-purification: The pretreated carbon black is fed into a supercritical extraction vessel. Under the conditions of temperature 40-60℃ and pressure 8-12MPa, supercritical CO2 is introduced and an entrainer accounting for 5%-8% of the CO2 mass flow rate is added. The extraction residence time is 30-60min. S3. Low-temperature plasma deep refining and modification: The carbon black obtained in step S2 is depressurized and sent to a dual dielectric barrier discharge low-temperature plasma reactor for treatment in a mixed atmosphere of argon and oxygen, wherein oxygen accounts for 5% to 10% of the total volume of the mixed atmosphere, the discharge power is 80 to 120W, and the treatment time is 5 to 10 minutes. S4. Finished product collection: The carbon black obtained in step S3 is graded and collected to obtain refined modified carbon black; the CO2 generated during extraction is recovered and recycled to step S2.

[0011] Further, in step S2, the entrainer is at least one of anhydrous ethanol, isopropanol, acetone, and ethyl acetate.

[0012] Preferably, the entrainer is anhydrous ethanol.

[0013] Furthermore, in step S2, the supercritical extraction vessel is a continuous extraction vessel with a gas-solid countercurrent contact internal component, in which carbon black passes through from top to bottom, and the mixed fluid of supercritical CO2 and entrainer passes through from bottom to top in a countercurrent manner.

[0014] Furthermore, in step S3, the dual-dielectric barrier discharge low-temperature plasma reactor adopts a coaxial cylindrical structure with a discharge gap of 2–8 mm.

[0015] Furthermore, in step S3, carbon black is transported in a dispersed phase through the plasma discharge region by pneumatic conveying, with argon as the carrier gas.

[0016] Furthermore, between steps S2 and S3, the process includes introducing the supercritical extracted carbon black into a pressure relief buffer chamber, where a slightly positive pressure inert gas atmosphere is maintained.

[0017] Furthermore, in step S1, the magnetic separation adopts a permanent magnet drum magnetic separator with a magnetic field strength of 3000 to 8000 Gauss; the screening adopts a vibrating screen with a screen mesh of 60 to 120 mesh.

[0018] Furthermore, in step S3, oxygen accounts for 6% to 9% of the total volume of the mixed atmosphere.

[0019] Furthermore, in step S4, the grading adopts a two- or three-stage cascaded cyclone grading method.

[0020] The technical concept of this invention lies in using supercritical CO2 extraction as a pre-process step for low-temperature plasma modification, constructing a synergistic process route of physical unblocking and chemical modification. Supercritical CO2 combines the density of a liquid with the diffusion coefficient of a gas, exhibiting low viscosity and zero surface tension. It can penetrate into the nanoscale pores of pyrolysis carbon black, dissolving and extracting organic impurities such as tar and polycyclic aromatic hydrocarbons that clog the pores. Simultaneously, the removal of organic impurities pre-exfoliates and loosens the inorganic ash encapsulated within, opening mass transfer channels for subsequent active particles to enter the pores. Building upon this, the high-energy electrons and active free radicals (·O, ·OH, etc.) generated by the subsequent low-temperature plasma treatment not only act on the outer surface of the carbon black particles but also diffuse along the unblocked pore channels to the inner pore walls, further bombarding and stripping residual ash. Simultaneously, oxygen-containing active functional groups such as hydroxyl and carboxyl groups are controllably introduced onto the outer surface and inner pore walls of the carbon black, achieving uniform modification of the carbon black from the surface to the interior.

[0021] (III) Beneficial Effects The purpose of this invention is to provide a method for modifying and refining pyrolysis carbon black from waste tires, which has the following beneficial effects: (1) The entire process is free of wastewater, strong acids and alkalis, and organic solvents. Supercritical CO2 is recycled and reused. Organic impurities are condensed, recovered, and utilized as resources. This meets the requirements of green chemical industry and dual-carbon policy, and has significant environmental advantages. (2) The supercritical CO2 extraction pre-purification has a synergistic effect on the unblocking effect of carbon black pores and the deep modification effect of low temperature plasma. It breaks through the limitation that traditional plasma modification can only act on the outer surface of particles, and realizes the deep removal of organic impurities inside the pores of cracked carbon black, the targeted stripping of ash and the simultaneous introduction of surface functional groups inside and outside, significantly improving the uniformity and depth of modification. (3) Supercritical CO2 extraction pre-purification removes most of the tar and PAHs, which greatly reduces the ineffective consumption of active free radicals in the subsequent low-temperature plasma treatment, improves energy utilization, and enhances modification efficiency. (4) The process can be operated continuously, and the materials can be continuously transferred between each process, which is suitable for large-scale industrial production. Attached Figure Description

[0022] Figure 1 This is an overall process flow diagram of the method for modifying and refining pyrolysis carbon black from waste tires according to the present invention. Detailed Implementation

[0023] The following will refer to the appendix in the examples of this invention. Figure 1 The technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1 This embodiment provides a method for modifying and refining pyrolysis carbon black from waste tires, including the following steps: S1. Raw material pretreatment: Take crude pyrolysis carbon black obtained from the thermal cracking of waste tires. After testing, the ash content is 18.5%, the total content of polycyclic aromatic hydrocarbons (PAHs) is 125 mg / kg, and the content of volatile organic compounds (VOCs) is 0.52%.

[0025] After being crushed to a particle size of ≤5mm by a jaw crusher, the material is fed into a permanent magnet drum separator with a magnetic field strength of 5000 Gauss to remove residual steel wire debris from the pyrolysis process. The magnetically separated material is then fed into a vibrating screen with a mesh size of 80. The material passing through the screen is the pretreated carbon black, and its moisture content is 0.3% as tested.

[0026] S2. Supercritical CO2 Extraction Pre-purification: The pretreated carbon black obtained in step S1 is continuously fed into a supercritical extraction vessel equipped with a gas-solid countercurrent contact internal component via a screw feeder. The carbon black passes through the extraction vessel from top to bottom under gravity. Simultaneously, liquid CO2 from the CO2 storage tank is pressurized and heated to a supercritical state by a high-pressure pump, and then mixed with anhydrous ethanol from the entrainer storage tank (the entrainer accounts for 6% of the CO2 mass flow rate) to form a mixed fluid, which passes through the carbon black layer countercurrently from bottom to top. The system temperature inside the extraction vessel is maintained at 50℃, and the pressure is maintained at 10MPa. The extraction residence time is controlled to be 45min by adjusting the carbon black feed rate. During this process, the mixed fluid of supercritical CO2 and anhydrous ethanol penetrates into the pores of the carbon black, dissolving, extracting, and carrying away organic impurities such as tar and PAHs. At the same time, the removal of organic impurities pre-peels and loosens the coated inorganic ash, thus opening up the pore structure of the carbon black. The extracted CO2 fluid containing organic impurities is discharged from the top of the extraction vessel and sent to the CO2 recovery and circulation system; the extracted carbon black is discharged from the bottom of the extraction vessel.

[0027] S3. Low-Temperature Plasma Deep Refining and Modification: The carbon black obtained in step S2 is first introduced into a pressure relief buffer chamber, which is filled with argon gas to maintain a slightly positive pressure environment and prevent the newly exposed active surfaces of the carbon black from being oxidized by air during the pressure relief process. The depressurized carbon black, using argon gas as the carrier gas, is pneumatically conveyed into a coaxial cylindrical dual-dielectric barrier discharge low-temperature plasma reactor in a dispersed phase. Quartz glass is filled between the inner and outer electrodes of the reactor as a dielectric barrier layer, with a discharge gap of 5 mm. A mixture of argon and oxygen is continuously introduced into the reactor, with oxygen accounting for 8% of the total volume of the mixed atmosphere. The plasma power supply is turned on, and the discharge power is adjusted to 100W to generate a uniform and stable dielectric barrier discharge plasma. The carbon black particles pass through the discharge region in a dispersed state, with a residence time of 8 minutes. In the plasma region, high-energy electrons collide with gas molecules to generate a large number of highly active free radicals such as ·O and ·OH. These active particles act on the outer surface of carbon black particles on the one hand, and penetrate into the inner wall of the pores along the pore channels cleared in step S2 on the other hand, further bombarding and stripping the residual inorganic ash. At the same time, oxygen-containing active functional groups such as hydroxyl and carboxyl groups are introduced controllably on the outer surface of carbon black and the inner wall of the pores, so as to achieve uniform and deep modification from the surface to the inside.

[0028] S4. Finished Product Collection: The carbon black processed in step S3 is fed into a two-stage cyclone classifier via airflow for classification to obtain products within the target particle size range. The remaining ultrafine powder is collected by a bag filter. The resulting product is refined modified carbon black.

[0029] The CO2 fluid containing organic impurities discharged in step S2 enters the CO2 recovery and recycling system. It sequentially passes through a pressure reducing separator to separate the organic impurities, a condenser to liquefy the CO2, and a compressor unit to pressurize it. The liquid CO2 is then returned to the CO2 storage tank and recycled back to step S2. The separated organic impurities can be collected and utilized as fuel oil.

[0030] The performance indicators of the refined modified carbon black obtained in this embodiment were tested as follows: ash content was 1.8%, PAHs residue was 1.5 mg / kg, VOCs residue was 0.06%, specific surface area increased by 45% compared with the pretreatment, DBP oil absorption value increased by 28% compared with the pretreatment, and the content of oxygen-containing functional groups on the surface (determined by Boehm titration) increased by 160% compared with the pretreatment.

[0031] Example 2 This embodiment provides a method for modifying and refining pyrolysis carbon black from waste tires, including the following steps: S1. Raw material pretreatment: Take crude carbon black obtained from the thermal pyrolysis of waste tires, with an ash content of 15.8%, a total PAH content of 98 mg / kg, and a VOC content of 0.41%. After crushing, remove iron by a permanent magnet drum separator, and then screen by a vibrating screen to obtain pretreated carbon black with a moisture content of 0.4%.

[0032] S2. Supercritical CO2 Extraction Pre-purification: The pretreated carbon black obtained in step S1 is fed into a supercritical extraction vessel. The system temperature is maintained at 40℃, the pressure is maintained at 8MPa, supercritical CO2 is introduced, and isopropanol, an entrainer accounting for 5% of the CO2 mass flow rate, is added. The extraction residence time is controlled at 60min.

[0033] S3. Low-Temperature Plasma Deep Refining and Modification: After depressurizing the carbon black obtained in step S2, it is fed into a coaxial cylindrical dual-dielectric barrier discharge low-temperature plasma reactor with a discharge gap of 2 mm. A mixture of argon and oxygen is introduced into the reactor, with oxygen accounting for 5% of the total volume of the mixed atmosphere. The discharge power is 80 W, and the residence time of the carbon black in the discharge region is 10 min.

[0034] S4. Finished Product Collection: The carbon black obtained in step S3 is subjected to three-stage cyclone separation and bag filter collection to obtain refined modified carbon black. The CO2 containing organic impurities generated during extraction is recovered and recycled back to step S2.

[0035] The performance indicators of the refined modified carbon black obtained in this embodiment are as follows: ash content is 1.9%, PAHs residue is 1.8 mg / kg, VOCs residue is 0.07%, specific surface area is increased by 41% compared with the pretreatment, DBP oil absorption value is increased by 26% compared with the pretreatment, and the content of oxygen-containing functional groups on the surface is increased by 152% compared with the pretreatment.

[0036] Example 3 This embodiment provides a method for modifying and refining pyrolysis carbon black from waste tires, including the following steps: S1. Raw material pretreatment: Take crude carbon black obtained from the thermal pyrolysis of waste tires, with an ash content of 22.0%, a total PAH content of 156 mg / kg, and a VOC content of 0.63%. After crushing, remove iron by a permanent magnet drum separator, and then screen by a vibrating screen to obtain pretreated carbon black with a moisture content of 0.2%.

[0037] S2. Supercritical CO2 Extraction Pre-purification: The pretreated carbon black obtained in step S1 is fed into a continuous supercritical extraction vessel equipped with a gas-solid countercurrent contact internal component. The system temperature is maintained at 60℃, the pressure at 12MPa, and supercritical CO2 is introduced along with an entrainer accounting for 8% of the CO2 mass flow rate. The entrainer is a mixture of anhydrous ethanol and acetone in a 1:1 mass ratio. The extraction residence time is controlled at 30 min.

[0038] S3. Low-Temperature Plasma Deep Refining and Modification: The carbon black obtained in step S2 is first introduced into a pressure relief buffer chamber, which is filled with nitrogen to maintain a slightly positive pressure environment. Then, using argon as the carrier gas, it is pneumatically conveyed as a dispersed phase into a coaxial cylindrical dual-dielectric barrier discharge low-temperature plasma reactor with a discharge gap of 8 mm. A mixture of argon and oxygen is introduced into the reactor, with oxygen accounting for 10% of the total volume of the mixed atmosphere. The discharge power is 120 W, and the residence time of the carbon black in the discharge region is 5 min.

[0039] S4. Finished Product Collection: The carbon black obtained in step S3 is subjected to two-stage cyclone separation and bag filter collection to obtain refined modified carbon black. The CO2 containing organic impurities generated during extraction is recovered and recycled to step S2.

[0040] The performance indicators of the refined modified carbon black obtained in this embodiment are as follows: ash content is 2.0%, PAHs residue is 2.0 mg / kg, VOCs residue is 0.09%, specific surface area is increased by 43% compared with the pretreatment, DBP oil absorption value is increased by 27% compared with the pretreatment, and surface oxygen functional group content is increased by 155% compared with the pretreatment.

[0041] Comparative Example 1 This comparative example provides a method for modifying pyrolysis carbon black without a supercritical CO2 extraction pre-purification step, to verify the synergistic effect of supercritical CO2 extraction pre-purification and low-temperature plasma deep purification modification.

[0042] The difference between this comparative example and Example 1 is that step S2 is omitted, that is, the pretreated carbon black obtained in step S1 is directly subjected to the low-temperature plasma treatment in step S3, and the other conditions are exactly the same as those in Example 1.

[0043] The performance indicators of the carbon black obtained in this comparative example were as follows: ash content was 14.2%, PAHs residue was 78 mg / kg, VOCs residue was 0.45%, specific surface area increased by only 12% compared with the pretreatment, DBP oil absorption value increased by only 8% compared with the pretreatment, and the content of oxygen-containing functional groups on the surface increased by 65% ​​compared with the pretreatment.

[0044] A comparison of Comparative Example 1 and Example 1 shows that, in the absence of a supercritical CO2 extraction pre-purification step, the low-temperature plasma treatment has a very limited effect on ash removal, reducing the ash content only from 18.5% to 14.2%, while the residual levels of PAHs and VOCs remain high. This is because the carbon black pores are blocked by organic impurities such as tar, preventing the active free radicals generated by the plasma from effectively penetrating into the pores. The modification effect is limited to the outer surface of the particles, and the overall purification and modification effect is far inferior to that of Example 1.

[0045] Comparative Example 2 This comparative example provides a method for refining pyrolysis carbon black without a low-temperature plasma deep refining and modification step, in order to further verify the synergistic effect of the two-step process.

[0046] The difference between this comparative example and Example 1 is that step S3 is omitted, that is, the carbon black obtained in step S2 is directly collected as a finished product in step S4 after depressurization, without low-temperature plasma treatment, and the other conditions are exactly the same as in Example 1.

[0047] The performance indicators of the carbon black obtained in this comparative example were as follows: ash content was 8.5%, PAHs residue was 16 mg / kg, VOCs residue was 0.15%, specific surface area increased by 28% compared with the pretreatment, DBP oil absorption value increased by 18% compared with the pretreatment, and surface oxygen functional group content increased by 20% compared with the pretreatment.

[0048] Comparison of Example 2 and Example 1 shows that although supercritical CO2 extraction alone can partially remove organic impurities, reducing PAHs from 125 mg / kg to 16 mg / kg and producing a certain ash loosening effect, reducing ash content from 18.5% to 8.5%, the ash residue is still high due to the lack of deep stripping and chemical modification steps from plasma treatment, and the introduction of oxygen-containing functional groups on the surface is very limited, failing to improve the surface chemical properties of carbon black.

[0049] Summary of experimental data Table 1 below summarizes the test results of key performance indicators for each embodiment and comparative example.

[0050] Table 1. Comparison of performance indicators between each embodiment and the comparative example Results Analysis The data in Table 1 clearly shows that: (1) Examples 1 to 3 of the present invention organically combine two steps: supercritical CO2 extraction pre-purification and low-temperature plasma deep purification modification. Significant technical effects have been achieved in ash removal, PAHs and VOCs removal, specific surface area and DBP oil absorption value enhancement, and the introduction of oxygen-containing functional groups on the surface. The resulting refined modified carbon black has a PAHs residue ≤2.0 mg / kg and a VOCs residue ≤0.1%.

[0051] (2) Comparative Example 1 only used low-temperature plasma treatment (without supercritical CO2 extraction pre-purification), and Comparative Example 2 only used supercritical CO2 extraction treatment (without low-temperature plasma modification). Comparing Example 1 with Comparative Example 1 and Comparative Example 2 respectively, it can be found that Example 1 is significantly better than both in all indicators. Moreover, the effect of Example 1 is not a simple sum of Comparative Example 1 and Comparative Example 2, but shows a significant synergistic gain effect. Specifically, the PAHs removal rate of Example 1 (98.8%) is much higher than that of Comparative Example 1 (37.6%) and Comparative Example 2 (87.2%), and the ash removal rate (90.3%) is much higher than that of Comparative Example 1 (23.2%) and Comparative Example 2 (54.1%).

[0052] (3) The mechanism of the above-mentioned synergistic effect can be explained as follows: Supercritical CO2 extraction pre-purification first dissolves and removes organic impurities such as tar and PAHs that clog the pores of carbon black, while loosening the inorganic ash coated in the organic impurities, thus opening up mass transfer channels for subsequent plasma active particles to penetrate deep into the pores; on this basis, the highly active free radicals generated by low-temperature plasma can smoothly penetrate into the pores, achieving further mineralization and degradation of organic residues on the inner wall and targeted bombardment and stripping of ash particles, while simultaneously introducing oxygen-containing functional groups on the inner and outer surfaces of carbon black. Without the unblocking step of supercritical CO2 extraction, plasma active particles can only act on the outer surface of the particles and are basically ineffective inside the pores; without the deep purification step of plasma, the complete stripping of ash and the full introduction of surface functional groups cannot be achieved.

[0053] (4) Examples 1 to 3 adopted different combinations of process parameters, and all of them achieved excellent technical results, indicating that the method of the present invention has good process adaptability and stability within the parameter range defined in the claims, and has a significant improvement effect on pyrolysis carbon black crude products from different sources and with different initial ash contents.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for modifying and refining pyrolysis carbon black from waste tires, characterized in that, Includes the following steps: S1. Raw material pretreatment: The crude pyrolysis carbon black is crushed, magnetically separated, and sieved to obtain pretreated carbon black with a moisture content of ≤0.5%; S2, Supercritical CO2 extraction pre-purification: The pretreated carbon black is fed into a supercritical extraction vessel. Under the conditions of temperature 40-60℃ and pressure 8-12MPa, supercritical CO2 is introduced and an entrainer accounting for 5%-8% of the CO2 mass flow rate is added. The extraction residence time is 30-60min. S3. Low-temperature plasma deep refining and modification: The carbon black obtained in step S2 is depressurized and sent to a dual dielectric barrier discharge low-temperature plasma reactor for treatment in a mixed atmosphere of argon and oxygen, wherein oxygen accounts for 5% to 10% of the total volume of the mixed atmosphere, the discharge power is 80 to 120W, and the treatment time is 5 to 10 minutes. S4. Finished product collection: The carbon black obtained in step S3 is graded and collected to obtain refined modified carbon black; the CO2 generated during extraction is recovered and recycled to step S4.

2. The method according to claim 1, characterized in that, In step S2, the entrainer is at least one of anhydrous ethanol, isopropanol, acetone, and ethyl acetate.

3. The method according to claim 2, characterized in that, The entrainer is anhydrous ethanol.

4. The method according to claim 1, characterized in that, In step S2, the supercritical extraction vessel is a continuous extraction vessel with a gas-solid countercurrent contact internal component. Carbon black passes through from top to bottom, while the mixed fluid of supercritical CO2 and entrainer passes through from bottom to top in a countercurrent manner.

5. The method according to claim 1, characterized in that, In step S3, the dual-dielectric barrier discharge low-temperature plasma reactor adopts a coaxial cylindrical structure with a discharge gap of 2-8 mm.

6. The method according to claim 1, characterized in that, In step S3, carbon black is transported in a dispersed phase through the plasma discharge region by pneumatic conveying, with argon as the carrier gas.

7. The method according to claim 1, characterized in that, Between steps S2 and S3, the process also includes introducing the supercritical extracted carbon black into a pressure relief buffer chamber, where a slightly positive pressure inert gas atmosphere is maintained.

8. The method according to claim 1, characterized in that, In step S1, the magnetic separation uses a permanent magnet drum magnetic separator with a magnetic field strength of 3000 to 8000 Gauss; the screening uses a vibrating screen with a screen mesh of 60 to 120 mesh.

9. The method according to claim 1, characterized in that, In step S3, oxygen accounts for 6% to 9% of the total volume of the mixed atmosphere.

10. The method according to claim 1, characterized in that, In step S4, the grading adopts a two-stage or three-stage cascade cyclone grading method.

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