A method and system for heavy metal adsorption and carbon capture from waste plastic-based porous carbon

Abstract

The application provides a waste plastic-based porous carbon heavy metal adsorption and carbon capture method and system, and belongs to the technical field of solid waste resource utilization, water pollution treatment and gas separation. The method is aimed at the problems that the existing waste plastic carbon production, heavy metal wastewater treatment and CO2 capture are mutually separated, and the carbon material after adsorbing heavy metals is difficult to dispose. The method mixes waste plastic and molten salt for pyrolysis and water washing to obtain waste plastic-based porous carbon; the waste plastic-based porous carbon is used to treat heavy metal wastewater, and the solid-liquid separation is carried out to obtain metal-loaded porous carbon; the metal-loaded porous carbon is dehydrated, dried and heat-treated in an inert atmosphere, so that the metal components from the wastewater form a metal-loaded phase, and a CO2 adsorption material for adsorbing CO2-containing gas is obtained. The system comprises a porous carbon preparation unit, a heavy metal adsorption unit, a solid-liquid separation and drying unit, a heat treatment unit and a CO2 capture unit connected in sequence, realizes the continuous transfer and cascade utilization of the same batch of carbon material, and reduces the secondary pollution risk.

Description

Technical Field

[0001] This invention belongs to the fields of solid waste resource utilization, water pollution control and gas separation technology, and specifically relates to a method and system for adsorption and capture of heavy metals and carbon on porous carbon based on waste plastics. Background Technology

[0002] With the widespread use of plastic products in packaging, construction, transportation, and industrial production, the amount of waste plastics generated is constantly increasing. Waste plastics have a high carbon content, but their complex composition and long natural degradation cycle mean that landfilling or direct incineration can easily lead to resource waste and potentially generate waste gas, residue, and other environmental problems. Therefore, converting waste plastics into carbon materials with adsorption properties has become an important research direction for the resource utilization of waste plastics. Existing technologies can convert waste plastics into porous carbon materials through pyrolysis, carbonization, chemical activation, or molten salt-assisted pyrolysis. Among these, using zinc chloride, potassium chloride, or other inorganic salts as activators or pore-forming media can promote pore formation during the pyrolysis process of waste plastics. The resulting porous carbon materials can be used for electrochemical energy storage, liquid-phase pollutant adsorption, or gas adsorption.

[0003] On the other hand, wastewater from industries such as electroplating, metallurgy, mining, and metal processing may contain metallic components such as copper, nickel, lead, zinc, cadmium, and chromium. Porous carbon materials, with their large specific surface area and abundant pore structure, can adsorb metallic components from wastewater through pore adsorption, surface complexation, or ion exchange. However, after adsorbing metallic components, porous carbon materials form metal-loaded porous carbon. Existing treatment methods typically involve desorption and regeneration of the metal-loaded porous carbon, incineration, or disposal as solid waste containing heavy metals. Desorption and regeneration produce metal-containing regenerated liquid, requiring further metal separation and wastewater treatment; direct high-temperature treatment may also cause some metals and their chlorine-containing compounds to volatilize or migrate, increasing the difficulty of tail gas treatment and secondary pollution control. Therefore, how to continue utilizing porous carbon after heavy metal adsorption, and how to safely treat the metallic components within it, are problems that need to be solved in the engineering application of heavy metal adsorption technology.

[0004] Solid-state adsorption is a technical approach for the separation and capture of carbon dioxide-containing gases, and porous carbon materials can be used as carbon dioxide adsorbents. The carbon dioxide adsorption performance of porous carbon materials is not only related to specific surface area but also influenced by microporous structure, surface functional groups, metallic phases, metal loading, and the composition of moisture and impurities in the gas to be treated. Loading some metal components onto porous carbon may alter the material's surface properties, but it may also clog pores, reduce the effective adsorption space, or migrate during adsorption and regeneration. Therefore, it cannot be directly assumed that any metal-loaded porous carbon is suitable for carbon dioxide capture, nor can porous carbon that has adsorbed heavy metals be directly loaded into a carbon dioxide adsorption device without proper conversion treatment and material access measures.

[0005] Existing technologies for preparing porous carbon from waste plastics, adsorbing heavy metals from wastewater, and capturing carbon dioxide are mostly set up independently around their respective treatment targets. Waste plastic carbon production technologies typically focus on pyrolysis conditions and pore structure; heavy metal wastewater treatment technologies typically focus on removal rate, adsorption capacity, and adsorbent regeneration; and carbon dioxide capture technologies typically focus on adsorption capacity, gas selectivity, and regeneration performance. These technologies lack a continuous material relationship for the same batch of porous carbon materials, especially lacking measures for solid-liquid separation, dehydration, drying, and transfer when metal-loaded porous carbon transitions from the wet wastewater treatment stage to the heat treatment stage. They also lack a systematic arrangement for metal retention, volatile matter interception, and chlorine-containing gas treatment during the heat treatment process.

[0006] Furthermore, existing technologies typically fail to differentiate between suitable metal components for retention and those requiring priority recovery or stabilization based on the properties of the metal components in metal-loaded porous carbon. They also lack a processing mechanism linking the heat-treated material to the required metal stability and adsorption performance for carbon dioxide capture, and fails to address the subsequent disposal of the material. After multiple adsorption and desorption cycles, carbon dioxide adsorption materials may experience adsorption performance degradation, pulverization, or metal migration, requiring further processing of the decommissioned material and its contained metals. Additionally, if the washing liquid generated from molten salt-assisted pyrolysis is simply concentrated and reused, changes in salt composition and impurity accumulation may negatively impact subsequent carbon production processes.

[0007] Therefore, it is necessary to improve the material connection and equipment connection between the preparation of waste plastic-based porous carbon, heavy metal wastewater adsorption, metal-loaded porous carbon conversion and carbon dioxide capture, so that the same batch of porous carbon material can be continuously transferred in different treatment stages, and the molten salt recovery, metal-loaded material treatment, carbon dioxide adsorption material regeneration and final metal disposal can be rationally arranged. Summary of the Invention

[0008] The present invention aims to solve at least one of the technical problems existing in the prior art, and to provide a method and system for adsorption and capture of heavy metals and carbon based on porous carbon in waste plastics.

[0009] This invention provides a method for adsorption of heavy metals and capture of carbon in porous carbon based on waste plastics, comprising the following steps: S1: Waste plastics are mixed with molten salt and pyrolyzed under an inert atmosphere. The salt-containing carbon material obtained from the pyrolysis is washed with water to obtain waste plastic-based porous carbon. S2: The waste plastic-based porous carbon is used to treat heavy metal wastewater, so that the metal components in the heavy metal wastewater are adsorbed onto the waste plastic-based porous carbon, and metal-loaded porous carbon is obtained after solid-liquid separation. S3: The metal-loaded porous carbon is dehydrated and dried, and then heat-treated under an inert atmosphere to cause the metal components from the heavy metal wastewater to undergo phase transformation and remain loaded on the surface and in the pores of the metal-loaded porous carbon, thus obtaining a CO2 adsorption material. S4: Bring the CO2-containing gas into contact with the CO2 adsorption material, so that the CO2 in the CO2-containing gas is adsorbed by the CO2 adsorption material.

[0010] Furthermore, the molten salt is a ZnCl2-KCl mixed molten salt; after the molten salt washing solution generated by water washing is concentrated, dried and its composition is adjusted, it is returned to step S1 and mixed with the waste plastic.

[0011] Specifically, in steps S2 and S3, the solid-liquid separation, dehydration, and drying are all carried out in a closed state, and the dried metal-loaded porous carbon is transferred to the heat treatment position in a closed manner.

[0012] Specifically, in step S3, the gas generated by heat treatment is sequentially condensed, particles are intercepted, and chlorine-containing gas is purified, and the resulting condensate and intercepted material are sent to the metal recovery process.

[0013] Preferably, in step S4, the CO2 adsorption material is packed into an adsorption bed, and the CO2-containing gas that has undergone particulate matter removal and condensate separation is introduced into the adsorption bed.

[0014] Specifically, the CO2 concentration at the gas outlet of the adsorption bed is obtained. When the CO2 concentration reaches the breakthrough concentration, the supply of the CO2-containing gas to the adsorption bed is stopped, and the CO2 adsorption material is desorbed and regenerated. The working CO2 adsorption capacity of the CO2 adsorption material after desorption and regeneration is obtained. If the working CO2 adsorption capacity is not lower than the recovery limit, the process returns to step S4. If it is lower than the recovery limit, the CO2 adsorption material is sent to the metal recovery process or the stabilization process.

[0015] Further, the metal leaching concentration and CO2 working adsorption capacity of the material obtained by heat treatment of the metal-loaded porous carbon are obtained. The conversion conditions are that the metal leaching concentration does not exceed the leaching limit and the CO2 working adsorption capacity is not lower than the lower limit of working adsorption capacity. When the metal leaching concentration does not exceed the leaching limit but the CO2 working adsorption capacity is lower than the lower limit of working adsorption capacity, the heat treatment temperature or holding time is adjusted and heat treatment is performed again to obtain the metal leaching concentration and CO2 working adsorption capacity again. When the conversion conditions are met, the CO2 adsorption material is sent to step S4. If the conversion conditions are still not met, the CO2 adsorption material is sent to the metal recovery process or the stabilization process. When the metal leaching concentration exceeds the leaching limit, the CO2 adsorption material is sent to the metal recovery process or the stabilization process.

[0016] Another aspect of the present invention provides a porous carbon heavy metal adsorption and carbon capture system based on waste plastics, comprising: The porous carbon preparation unit is used to mix waste plastics with molten salt, pyrolyze them under an inert atmosphere, and wash the salt-containing carbon material obtained by pyrolysis with water to obtain waste plastic-based porous carbon. A heavy metal adsorption unit is connected to the porous carbon preparation unit and is used to bring the waste plastic-based porous carbon into contact with heavy metal wastewater, so that the metal components in the heavy metal wastewater are adsorbed onto the waste plastic-based porous carbon. A solid-liquid separation and drying unit is connected to the heavy metal adsorption unit and is used to perform solid-liquid separation, dehydration and drying on the material output from the heavy metal adsorption unit to obtain metal-loaded porous carbon. A heat treatment unit, connected to the solid-liquid separation and drying unit, is used to heat treat the metal-loaded porous carbon under an inert atmosphere, causing the metal components from the heavy metal wastewater to undergo phase transformation and remain loaded on the surface and pores of the metal-loaded porous carbon, thereby obtaining a CO2 adsorption material; and The CO2 capture unit is connected to the heat treatment unit and is used to bring the CO2 adsorption material into contact with the CO2-containing gas to adsorb the CO2 in the CO2-containing gas.

[0017] Furthermore, the system also includes a closed transfer mechanism, a condensation unit, a particle interception unit, a chlorine-containing gas purification unit, and a metal recovery unit; the closed transfer mechanism is disposed between the solid-liquid separation and drying unit and the heat treatment unit, the gas outlet of the heat treatment unit is sequentially connected to the condensation unit, the particle interception unit, and the chlorine-containing gas purification unit, and the material collection outlets of the condensation unit and the particle interception unit are respectively connected to the metal recovery unit.

[0018] Specifically, the system further includes a material testing mechanism, a CO2 outlet testing mechanism, a regeneration unit, a material switching mechanism, a stabilization unit, and a control unit; the material testing mechanism is located in the material output path of the heat treatment unit and the regeneration unit respectively; the CO2 outlet testing mechanism is located at the gas outlet of the CO2 capture unit; the regeneration unit is connected to the CO2 capture unit; the material switching mechanism is connected to the heat treatment unit, the regeneration unit, the CO2 capture unit, the metal recovery unit, and the stabilization unit respectively; the control unit is connected to the material testing mechanism, the CO2 outlet testing mechanism, the CO2 outlet testing mechanism, the material switching ... The outlet detection mechanism, the heat treatment unit, the regeneration unit, and the material switching mechanism are connected to control the CO2 adsorbent material to enter the CO2 collection unit, return to the heat treatment unit for further heat treatment, or enter the metal recovery unit or the stabilization treatment unit based on the metal leaching concentration and CO2 working adsorption capacity obtained by the material detection mechanism. The regeneration unit is also controlled based on the CO2 concentration obtained by the CO2 outlet detection mechanism, so that the desorbed and regenerated CO2 adsorbent material returns to the CO2 collection unit or enters the metal recovery unit or the stabilization treatment unit according to its CO2 working adsorption capacity.

[0019] The beneficial effects of this invention are as follows: This invention sequentially connects the preparation of porous carbon based on waste plastics, adsorption of heavy metal wastewater, thermal treatment and conversion of metal-loaded porous carbon, and CO2 capture. This allows the metal components from heavy metal wastewater to become the loading components in the CO2 adsorption material after thermal treatment, achieving continuous transfer and cascade utilization of the same batch of carbon materials. At the same time, through the closed separation and transfer of metal-loaded porous carbon, the condensation and purification of thermal treatment tail gas, the access detection of converted materials, the regeneration and withdrawal of CO2 adsorption materials, and the recycling of molten salt washing liquid, a closed-loop treatment system combining material conversion, safety control, and recycling is formed. Attached Figure Description

[0020] Figure 1 The flowchart illustrates the operation control of a waste plastic-based porous carbon heavy metal adsorption and carbon capture method according to a specific embodiment of the present invention. Figure 2 This is a connection block diagram of a waste plastic-based porous carbon heavy metal adsorption and carbon capture system according to a specific embodiment of the present invention. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] like Figure 1As shown in the figure, a method for adsorption and capture of heavy metals in porous carbon based on waste plastics provided by a specific embodiment of the present invention includes the following steps: S1: Waste plastics are mixed with molten salt and pyrolyzed under an inert atmosphere. The salt-containing carbon material obtained from the pyrolysis is washed with water to obtain waste plastic-based porous carbon. S2: The waste plastic-based porous carbon is used to treat heavy metal wastewater, so that the metal components in the heavy metal wastewater are adsorbed onto the waste plastic-based porous carbon, and metal-loaded porous carbon is obtained after solid-liquid separation. S3: The metal-loaded porous carbon is dehydrated and dried, and then heat-treated under an inert atmosphere to cause the metal components from the heavy metal wastewater to undergo phase transformation and remain loaded on the surface and in the pores of the metal-loaded porous carbon, thus obtaining a CO2 adsorption material. S4: Bring the CO2-containing gas into contact with the CO2 adsorption material, so that the CO2 in the CO2-containing gas is adsorbed by the CO2 adsorption material.

[0023] In one embodiment, steps S1 to S4 are performed sequentially according to the material formation order. The waste plastic-based porous carbon obtained in step S1 serves as the heavy metal adsorbent in step S2, the metal-loaded porous carbon obtained in step S2 serves as the heat treatment target in step S3, and the CO2 adsorbent obtained in step S3 serves as the solid adsorbent in step S4. The continuous process includes temporary storage, transportation, sampling, or detection procedures between each step. However, the carbon material output from the previous step should constitute the material input for the next step to maintain a continuous material relationship between the same batch of carbon material in the heavy metal adsorption, heat treatment conversion, and CO2 capture stages. The normal main process is suitable for heavy metal wastewater for which previous heat treatment tests have confirmed that the metal components can be retained in the carbon material, and where the metal leaching concentration and CO2 adsorption capacity of the heat-treated material meet the conversion conditions.

[0024] Specifically, the waste plastics include one or more of polyethylene, polypropylene, polystyrene, and polyethylene terephthalate. Before being mixed with molten salt, the waste plastics undergo sorting, washing, drying, crushing, and impurity removal to remove attached oil, silt, and metallic impurities. For raw materials containing polyvinyl chloride or other halogenated plastics, their chlorine content is tested before entering the pyrolysis process. When the chlorine content exceeds the processing capacity of the pyrolysis equipment and exhaust gas purification device, the chlorinated plastics are separated or dechlorinated to prevent chlorine-containing gases generated during pyrolysis from corroding the equipment or exceeding the exhaust gas purification capacity.

[0025] Further, the molten salt in step S1 is a ZnCl2-KCl mixed molten salt. The molar ratio of ZnCl2 to KCl can be 1:1 to 3:1, and the mass ratio of the mixed molten salt to waste plastic can be 2:1 to 10:1. ZnCl2 and KCl are dried before use to reduce the impact of their adsorbed moisture on the pyrolysis process. After mixing the mixed molten salt with the waste plastic, the mixture is heated to 500-900℃ under nitrogen or argon protection and held at that temperature for 1-4 hours, followed by cooling under inert gas protection. The above ratios and pyrolysis conditions are used to illustrate the feasible range and do not indicate that all ratios represent the eutectic composition of the ZnCl2-KCl system.

[0026] Based on the above basic implementation method, the molten salt is a ZnCl2-KCl mixed molten salt; after the molten salt washing solution generated by water washing is concentrated, dried and its composition is adjusted, it is returned to step S1 and mixed with the waste plastic.

[0027] Furthermore, during the washing process, water is brought into full contact with the salt-containing carbon material, allowing the ZnCl2 and KCl adhering to the surface and pores of the carbon material to transfer into the molten salt washing solution. The washing can employ staged washing, agitation washing, or ultrasonic-assisted washing. The washing endpoint is determined by detecting the conductivity, chloride ion content, or zinc and potassium content of the final washing solution. The solids after washing are separated to obtain waste plastic-based porous carbon, and the resulting molten salt washing solution enters a separate molten salt recovery path, not mixing with the heavy metal wastewater treatment solution generated in step S2.

[0028] Furthermore, the molten salt washing solution is concentrated and dehydrated to obtain recovered salt. The zinc and potassium content in the recovered salt is tested, and ZnCl2 or KCl is added according to the test results to restore the composition of the recovered salt to the range used in step S1. After drying, it is returned to step S1 for use. When the accumulation of organic matter, ash, or non-target inorganic impurities in the recovered salt affects the melting state of the mixed molten salt or the formation of porous carbon, the recovered salt is purified or a portion of the recovered salt is discharged and new salt is added. This forms a molten salt circulation path of washing solution collection, concentration and dehydration, component detection, salt replenishment, and return for use.

[0029] In one specific embodiment, in steps S2 and S3, the solid-liquid separation, dehydration, and drying are all carried out in a closed state, and the dried metal-loaded porous carbon is transferred to the heat treatment position in a closed manner.

[0030] In this embodiment, the "closed state" refers to the process where, after the metal-loaded porous carbon is discharged from the heavy metal adsorption unit, it is treated in a solid-liquid separation device, dehydration device, drying device, and transfer container with a closed material channel to prevent the escape of heavy metal-containing droplets and carbon dust. The liquid obtained from solid-liquid separation is returned to the heavy metal wastewater treatment process, enters a further treatment process, or enters the metal recovery process according to the concentration of residual heavy metals therein, and is not directly incorporated into the molten salt washing solution recovery path.

[0031] Furthermore, the metal-loaded porous carbon after solid-liquid separation undergoes controlled washing based on its soluble salt content to reduce the entry of unadsorbed free metal salts and water-soluble impurities into the heat treatment unit; the washing liquid is combined with the liquid obtained from solid-liquid separation for further processing. The metal-loaded porous carbon is then dehydrated and dried until its moisture content meets the feed requirements of the heat treatment unit. Under laboratory conditions, the drying endpoint can be determined by continuous weighing until the quality stabilizes; in industrial operation, the drying endpoint can be determined by detecting the moisture content of the material. The dried metal-loaded porous carbon is then transferred to the heat treatment location via a sealed container or a closed conveyor system.

[0032] In another specific embodiment, in step S3, the gas generated by heat treatment is sequentially condensed, particles are trapped, and chlorine-containing gas is purified, and the resulting condensate and trapped material are sent to the metal recovery process.

[0033] In this embodiment, the transformation form of the metal component in the metal-supported porous carbon is related to the type of metal, the original valence state, the adsorbed anions, the heat treatment temperature, the holding time, and the atmosphere. The metal phase formed after heat treatment can include elemental metals, metal oxides, metal salts, or other metal-containing solid phases, and is not limited to a specific compound. The metal phase in the heat-treated material is determined using X-ray diffraction, X-ray photoelectron spectroscopy, or other detection methods capable of characterizing the metal valence state and phase, and a metal material balance is performed by combining the metal content in the material before and after heat treatment and in the exhaust gas collection.

[0034] Specifically, considering that zinc, lead, cadmium, and some of their compounds may volatilize or migrate with particles during heat treatment, the gas discharged from the heat treatment unit first enters the condensation unit, where condensable metal components and metal-containing vapors form condensate. Uncondensed metal-containing particles and aerosols are collected by the particle retention unit, and the remaining gas enters the chlorine-containing gas purification unit for absorption or purification. Samples of the condensate, particle retention material, and absorbent produced by the chlorine-containing gas purification unit are taken for testing. Materials containing recyclable metals are sent to the metal recovery process, while materials unsuitable for recovery are disposed of after stabilization treatment. The heat treatment exhaust gas is not directly emitted before completing condensation, particle retention, and chlorine-containing gas purification.

[0035] In another specific embodiment, in step S4, the CO2 adsorption material is filled into an adsorption bed, and the CO2-containing gas that has undergone particulate matter removal and condensate separation is introduced into the adsorption bed.

[0036] Furthermore, the adsorption bed is equipped with a support structure for supporting the CO2 adsorption material and a trapping structure for preventing carbon material from being carried out by the gas flow. Before the CO2-containing gas enters the adsorption bed, particulate matter and free condensate that may clog the pores of the carbon material are removed. When the CO2-containing gas contains acidic gases, oil mist, or other impurities that compete with CO2 for adsorption or cause the migration of metal components, appropriate gas pretreatment should be performed according to the verified tolerance range of the CO2 adsorption material.

[0037] Specifically, the CO2-containing gas can be pretreated combustion flue gas or industrial process gas. During CO2 capture, the CO2-containing gas is passed through the adsorption bed in a predetermined flow direction, and the CO2 concentration at the inlet and outlet of the adsorption bed is detected. The working CO2 adsorption capacity is a dynamic adsorption capacity determined based on the amount of CO2 entering and leaving the adsorption bed under the same gas composition, temperature, pressure, flow rate, and adsorption endpoint conditions. It is used to compare the actual adsorption performance of different batches of materials or the same material before and after regeneration.

[0038] In another specific embodiment, the CO2 concentration at the gas outlet of the adsorption bed is obtained. When the CO2 concentration reaches the breakthrough concentration, the supply of the CO2-containing gas to the adsorption bed is stopped, and the CO2 adsorption material is desorbed and regenerated. The working CO2 adsorption capacity of the CO2 adsorption material after desorption and regeneration is obtained. If the working CO2 adsorption capacity is not lower than the recovery limit, the process returns to step S4. If it is lower than the recovery limit, the CO2 adsorption material is sent to the metal recovery process or the stabilization process.

[0039] Specifically, the breakthrough concentration is the allowable outlet concentration determined based on the CO2 content requirements of the CO2 capture target in the outlet gas. When the CO2 outlet detection agency detects that the CO2 concentration at the outlet of the adsorption bed reaches the breakthrough concentration, it stops supplying CO2-containing gas to the adsorption bed or switches the CO2-containing gas to another adsorption bed, and then desorbs and regenerates the CO2 adsorption material that has reached the breakthrough state.

[0040] Furthermore, desorption regeneration can employ methods such as heated desorption, reduced pressure desorption, vacuum desorption, or inert gas purging desorption, selecting one based on the adsorption mechanism and thermal stability of the CO2 adsorbent material. The CO2-rich gas generated during desorption is collected and then used in subsequent utilization, compression, or storage processes. After regeneration, the material's working CO2 adsorption capacity is retested under the same test conditions as when the working CO2 adsorption capacity was determined. Materials reaching the recovery limit are returned to step S4; materials not reaching the recovery limit are removed from the CO2 capture process, preventing insufficiently performing materials from repeatedly returning to the adsorption bed. The regenerated material can also be tested periodically for target metal retention, particle pulverization, or metal content in the particles at the adsorption bed outlet; materials exceeding permissible limits are removed from use.

[0041] In another specific embodiment, the metal leaching concentration and working CO2 adsorption capacity of the CO2 adsorbent material after heat treatment are obtained. The conversion conditions are that the metal leaching concentration does not exceed the leaching limit and the working CO2 adsorption capacity is not lower than the lower limit of the working adsorption capacity. When the metal leaching concentration does not exceed the leaching limit but the working CO2 adsorption capacity is lower than the lower limit of the working adsorption capacity, the heat treatment temperature or holding time is adjusted and heat treatment is performed again to obtain the metal leaching concentration and the working CO2 adsorption capacity again. If the conversion conditions are met, the CO2 adsorbent material is sent to step S4. If the conversion conditions are still not met, the CO2 adsorbent material is sent to the metal recovery process or the stabilization process. When the metal leaching concentration exceeds the leaching limit, the CO2 adsorbent material is sent to the metal recovery process or the stabilization process.

[0042] Furthermore, the metal leaching concentration is obtained by sampling and leaching tests on the heat-treated CO2 adsorbent material, and the metal content in the leachate is determined using inductively coupled plasma atomic emission spectrometry, atomic absorption spectrometry, or other metal content detection methods. The metal leaching concentration refers to the target metal concentration measured after preparing the leachate according to the determined leaching test method. The leaching limit is determined based on the application scenario of the CO2 adsorbent material, the material contact conditions, and applicable environmental safety requirements.

[0043] Specifically, the lower limit of the working adsorption capacity is the minimum working CO2 adsorption capacity required for the CO2 adsorbent material to enter the CO2 capture unit, and the lower limit of reuse is the minimum working CO2 adsorption capacity required for the desorbed and regenerated CO2 adsorbent material to re-enter the CO2 capture unit. These lower limits should be determined under the same CO2 adsorption test conditions. When the metal leaching concentration of the heat-treated material meets the requirements but the working CO2 adsorption capacity is insufficient, the heat treatment temperature or holding time is adjusted within the verified heat treatment range, and the material is heat-treated again and retested. When the metal leaching concentration exceeds the leaching limit, or the conversion conditions are still not met after reheat treatment, the material is no longer sent to the CO2 capture unit, but instead sent to the metal recovery process or stabilization process according to the metal type and content. The metal recovery process separates and enriches the metals in the material and exhaust gas collection; the stabilization process solidifies or chemically stabilizes metal-containing materials unsuitable for recovery, and after the leaching test meets the treatment requirements, the material enters the subsequent treatment stage.

[0044] In one specific implementation, such as Figure 2 As shown, a porous carbon heavy metal adsorption and carbon capture system based on waste plastics is provided, comprising: The porous carbon preparation unit is used to mix waste plastics with molten salt, pyrolyze them under an inert atmosphere, and wash the salt-containing carbon material obtained by pyrolysis with water to obtain waste plastic-based porous carbon. A heavy metal adsorption unit is connected to the porous carbon preparation unit and is used to bring the waste plastic-based porous carbon into contact with heavy metal wastewater, so that the metal components in the heavy metal wastewater are adsorbed onto the waste plastic-based porous carbon. A solid-liquid separation and drying unit is connected to the heavy metal adsorption unit and is used to perform solid-liquid separation, dehydration and drying on the material output from the heavy metal adsorption unit to obtain metal-loaded porous carbon. A heat treatment unit, connected to the solid-liquid separation and drying unit, is used to heat treat the metal-loaded porous carbon under an inert atmosphere, causing the metal components from the heavy metal wastewater to undergo phase transformation and remain loaded on the surface and pores of the metal-loaded porous carbon, thereby obtaining a CO2 adsorption material; and The CO2 capture unit is connected to the heat treatment unit and is used to bring the CO2 adsorption material into contact with the CO2-containing gas to adsorb the CO2 in the CO2-containing gas.

[0045] In this embodiment, the connections between the units include direct or indirect connections formed through pipelines, closed conveying mechanisms, transfer containers, or intermediate storage equipment. A solid material path for waste plastic-based porous carbon is formed between the porous carbon preparation unit and the heavy metal adsorption unit; a solid-liquid separation, dehydration, drying, and transfer path for metal-loaded porous carbon is formed between the heavy metal adsorption unit, the solid-liquid separation and drying unit, and the heat treatment unit; and a transfer path for CO2 adsorbent material is formed between the heat treatment unit and the CO2 capture unit. Each material path is equipped with a closable material inlet and outlet to prevent the mixing of molten salt washing liquid, heavy metal wastewater treatment liquid, and metal-containing solid materials.

[0046] Specifically, the porous carbon preparation unit may include crushing equipment, mixing equipment, a pyrolysis furnace, and washing equipment; the heavy metal adsorption unit may employ adsorption tanks or adsorption columns; the solid-liquid separation and drying unit may include filtration equipment or centrifugal separation equipment and drying equipment; the heat treatment unit includes a heat treatment furnace with an inert gas inlet and a gas outlet; and the CO2 capture unit includes an adsorption bed for filling with CO2 adsorbent material, a CO2-containing gas inlet, and a gas outlet. The above equipment can be set up separately according to the processing scale, or some conveying, heating, or gas supply equipment can be shared without causing cross-contamination of materials.

[0047] In one specific embodiment, the system further includes a closed transfer mechanism, a condensation unit, a particle interception unit, a chlorine-containing gas purification unit, and a metal recovery unit; the closed transfer mechanism is disposed between the solid-liquid separation and drying unit and the heat treatment unit, the gas outlet of the heat treatment unit is sequentially connected to the condensation unit, the particle interception unit, and the chlorine-containing gas purification unit, and the material collection outlets of the condensation unit and the particle interception unit are respectively connected to the metal recovery unit.

[0048] Furthermore, the closed transfer mechanism includes a closed hopper, a closed transfer container, a closed screw conveyor mechanism, or a pneumatic conveyor mechanism. Its inlet end is connected to the solid material outlet of the solid-liquid separation and drying unit, and its outlet end is connected to the inlet of the heat treatment unit. The closed transfer mechanism maintains a closed material channel during the transfer of metal-loaded porous carbon and, when necessary, uses inert gas purging to reduce the escape of metal-containing dust and the entry of external air and moisture into the heat treatment unit.

[0049] Furthermore, the condensation unit is equipped with a sealed collection container for collecting condensate, the particulate retention unit is equipped with a replaceable filter assembly for collecting metal-containing particles, and the chlorine-containing gas purification unit is equipped with an absorbent inlet, a purified gas outlet, and an absorbent outlet. The condensate and particulate retention are respectively transported to the metal recovery unit. The absorbent produced by the chlorine-containing gas purification unit, after being tested for metal and chloride ion content, is sent to either the metal recovery process or the waste liquid treatment process. All collection containers and transport paths are kept sealed to prevent secondary pollution from volatile metal components and chlorine-containing components generated during heat treatment.

[0050] In one specific embodiment, the system further includes a material testing mechanism, a CO2 outlet testing mechanism, a regeneration unit, a material switching mechanism, a stabilization treatment unit, and a control unit; the material testing mechanism is located in the material output path of the heat treatment unit and the regeneration unit respectively, the CO2 outlet testing mechanism is located at the gas outlet of the CO2 capture unit, the regeneration unit is connected to the CO2 capture unit, and the material switching mechanism is connected to the heat treatment unit, the regeneration unit, the CO2 capture unit, the metal recovery unit, and the stabilization treatment unit respectively; the control unit is connected to the material testing mechanism, the regeneration unit, the CO2 capture unit, the metal recovery unit, and the stabilization treatment unit respectively. The CO2 outlet detection mechanism, the heat treatment unit, the regeneration unit, and the material switching mechanism are connected to control the CO2 adsorbent material to enter the CO2 collection unit, return to the heat treatment unit for further heat treatment, or enter the metal recovery unit or the stabilization treatment unit based on the metal leaching concentration and CO2 working adsorption capacity obtained by the material detection mechanism. The regeneration unit is also controlled based on the CO2 concentration obtained by the CO2 outlet detection mechanism, so that the desorbed and regenerated CO2 adsorbent material returns to the CO2 collection unit or enters the metal recovery unit or the stabilization treatment unit according to its CO2 working adsorption capacity.

[0051] Specifically, the material testing mechanism includes sampling components installed on the material output paths of the heat treatment unit and the regeneration unit, as well as testing equipment for determining the metal leaching concentration and CO2 working adsorption capacity of the samples. The material testing mechanism obtains representative samples through the sampling components, and the metal leaching concentration and CO2 working adsorption capacity are determined by offline testing equipment; the test results are input to the control unit. The CO2 outlet testing mechanism includes a CO2 concentration detection device installed at the gas outlet of the CO2 capture unit; the material switching mechanism includes valves, conveying equipment, or switchable material outlets installed on each material path to change the conveying direction of the CO2 adsorbent material.

[0052] Further, the control unit executes the following control process: After heat treatment, the material testing mechanism obtains the metal leaching concentration and CO2 working adsorption capacity of the CO2 adsorbent material; when the metal leaching concentration does not exceed the leaching limit and the CO2 working adsorption capacity is not lower than the lower limit of the working adsorption capacity, the material switching mechanism is controlled to send the CO2 adsorbent material into the CO2 collection unit; when the metal leaching concentration meets the requirements but the CO2 working adsorption capacity is insufficient, the material switching mechanism is controlled to return the material to the heat treatment unit, and the heat treatment unit is controlled to perform heat treatment again according to the adjusted heat treatment temperature or holding time, and the sample is re-sampled and tested after the second heat treatment; when the metal leaching concentration exceeds the leaching limit or the conversion conditions are still not met after the second heat treatment, the material is sent to the metal recovery unit or the stabilization treatment unit. When the CO2 outlet concentration reaches the breakthrough concentration, the control unit stops or switches the CO2-containing gas entering the corresponding adsorption bed and starts the regeneration unit. When the CO2 working adsorption capacity of the regenerated material is not lower than the recovery limit, the control material returns to the CO2 capture unit. When it is lower than the recovery limit, the control material exits the CO2 capture unit and enters the metal recovery unit or the stabilization treatment unit. The metal phase refers to the metal-containing solid phase that originates from heavy metal wastewater and exists on the surface or in the pores of the carbon material after heat treatment. It does not mean that different metals form the same valence state or the same compound. The CO2 adsorption material referred to in this specification refers to the material formed by heat treatment of metal-loaded porous carbon, which is intended to be used for or used for CO2 adsorption. Among them, the CO2 adsorption material that meets the conversion conditions enters the CO2 capture step, and the material that does not meet the conversion conditions enters the re-heat treatment, metal recovery or stabilization treatment path.

[0053] In one specific embodiment, a method for adsorption of heavy metals and capture of CO2 in porous carbon based on waste plastics is provided for treating copper-containing wastewater. As Example 1, it specifically includes the following steps.

[0054] 10g of waste plastic was selected as the carbon source. The waste plastic was sorted, washed and dried to remove oil, mud and other water-soluble impurities adhering to its surface, then crushed and magnetically separated to remove any metal impurities mixed in.

[0055] The chlorine content in the pretreated waste plastics is detected. If the waste plastics contain polyvinyl chloride (PVC) or other halogenated plastics that would cause the pyrolysis exhaust gas to exceed the treatment capacity of the exhaust gas purification device, the corresponding halogenated plastics are separated, or dechlorination treatment is performed before pyrolysis. This embodiment uses low-chlorine waste plastics that meet the feeding requirements of the pyrolysis equipment.

[0056] Weigh out ZnCl2 and KCl respectively, and prepare a ZnCl2-KCl mixed molten salt with a molar ratio of ZnCl2 to KCl of 2:1. The total mass of the mixed molten salt is 50g.

[0057] After pre-drying, ZnCl2 and KCl are cooled under conditions that isolate them from ambient moisture. 10g of pretreated waste plastic and 50g of mixed molten salt are added to a mixing device and thoroughly mixed to disperse the mixed molten salt among the waste plastic. In this embodiment, the ZnCl2-KCl system is referred to as the mixed molten salt, and the molar ratio is not directly considered as the eutectic composition.

[0058] The mixed materials were loaded into a pyrolysis furnace, and nitrogen was introduced to replace the air inside the furnace, maintaining a nitrogen flow rate of 300 mL / min during the pyrolysis process. The pyrolysis furnace was heated to 750°C at a heating rate of 5°C / min and held at 750°C for 2 hours to allow the waste plastics to undergo pyrolysis and carbonization.

[0059] After the heat preservation period, heating is stopped, and the pyrolysis furnace is allowed to cool naturally under nitrogen protection. Once the material temperature has dropped to a level suitable for safe removal, the salt-containing carbon material is removed from the pyrolysis furnace. The gases generated during pyrolysis enter the pyrolysis tail gas treatment device through the pyrolysis furnace gas outlet.

[0060] Salt-containing carbon materials are added to a washing device and subjected to staged washing with deionized water, allowing ZnCl2 and KCl from the surface and pores of the carbon materials to enter the molten salt washing solution. The completion of the washing process is determined by detecting the conductivity, chloride ion content, or zinc and potassium content of the final washing solution.

[0061] After washing, solid-liquid separation is performed to obtain waste plastic-based porous carbon and molten salt washing solution. The waste plastic-based porous carbon is dried until its quality is stable and then stored in a sealed container.

[0062] The molten salt washing solution is collected separately, concentrated, and dehydrated to obtain recovered salt. The zinc and potassium content in the recovered salt is tested, and ZnCl2 or KCl is added based on the test results to restore the composition of the recovered salt to that used in this embodiment. After drying, it is returned to the mixing step. The molten salt washing solution is not mixed with the liquid generated from subsequent heavy metal wastewater treatment.

[0063] Preparation of Cu² + Simulated heavy metal wastewater with an initial concentration of 100 mg / L was prepared, with the pH adjusted to 5–6 and the temperature maintained at 25°C. Waste plastic-based porous carbon was added to the simulated heavy metal wastewater at a dosage of 1 g / L, and the mixture was contacted for 120 min under constant temperature and shaking conditions.

[0064] Wastewater samples were taken before and after adsorption, and Cu² was determined using inductively coupled plasma atomic emission spectrometry or atomic absorption spectrometry. + Concentration, based on Cu² before and after adsorption + The copper adsorption capacity is calculated based on the concentration change and the actual mass of porous carbon input. This embodiment does not predefine the copper adsorption capacity and removal rate; both are determined by actual test results.

[0065] After adsorption, the mixture is filtered or centrifuged in a closed solid-liquid separation device to obtain copper-loaded porous carbon and the adsorption treatment solution. The residual Cu²⁺ in the adsorption treatment solution is then detected. + Based on the concentration, the adsorption treatment liquid will be discharged into the subsequent wastewater treatment process or returned to the heavy metal adsorption process according to the test results.

[0066] Based on the residual soluble copper salts in the copper-loaded porous carbon, a small amount of deionized water was used for controlled washing, and the washing solution was combined with the adsorption treatment solution. The copper-loaded porous carbon was dehydrated and dried until the continuous weighing results were stable, and then the dried copper-loaded porous carbon was transferred to the heat treatment location through a sealed transfer container.

[0067] Samples were taken from the dried copper-loaded porous carbon to detect the copper loading, and the weight loss process of the copper-loaded porous carbon and the temperature range in which the adsorbed copper components were transformed were determined by thermogravimetric analysis.

[0068] The remaining copper-loaded porous carbon was loaded into a heat treatment furnace, and nitrogen was introduced to replace the air inside the furnace. Heat treatment was then carried out under nitrogen protection. The heat treatment temperature and holding time were determined based on the aforementioned thermogravimetric analysis results, so that the copper components adsorbed on the surface and in the pores of the carbon material underwent a phase transformation, while avoiding significant burn-off of the carbon skeleton or severe collapse of the pore structure.

[0069] The gases generated during heat treatment sequentially pass through a condensation unit, a particulate retention unit, and a chlorine-containing gas purification unit. The condensate and particulate retention materials are collected and their copper content is analyzed; the collected material containing recoverable copper components is sent to the metal recovery process.

[0070] After heat treatment, the material is cooled under nitrogen protection to obtain the CO2 adsorbent material to be approved for entry. X-ray diffraction and X-ray photoelectron spectroscopy are performed on the material to determine the phase and valence state of the copper component. This detection is only used to characterize the heat treatment conversion result and is not the sole basis for directly accepting the material into the CO2 capture step.

[0071] The heat-treated material was sampled and its metal leaching concentration was tested under uniform leaching test conditions; at the same time, its working CO2 adsorption capacity was tested under fixed CO2 gas composition, temperature, pressure, flow rate and adsorption endpoint conditions.

[0072] When the metal leaching concentration does not exceed the leaching limit and the working CO2 adsorption capacity is not lower than the lower limit of the working adsorption capacity, the material is deemed to meet the conversion conditions for entering the CO2 capture step.

[0073] When the metal leaching concentration meets the requirements but the working CO2 adsorption capacity is below the lower limit of the working adsorption capacity, the heat treatment temperature or holding time is adjusted within the validated treatment range based on the results of thermogravimetric analysis, phase analysis, and pore structure analysis. The material is then heat-treated again, and the metal leaching concentration and working CO2 adsorption capacity are re-tested. Material that meets the conversion conditions after the second treatment enters the CO2 capture step; material that still does not meet the conversion conditions enters the metal recovery process or stabilization process.

[0074] When the metal leaching concentration exceeds the leaching limit, the material is not sent to the CO2 capture step, but is directly sent to the metal recovery process or the stabilization process.

[0075] CO2 adsorption material that meets the conversion conditions is packed into an adsorption bed, which is equipped with a material support structure and a particle trapping structure. Before the CO2-containing gas enters the adsorption bed, particulate matter removal and condensate separation are performed to prevent particulate matter and free water from clogging the pores of the CO2 adsorption material.

[0076] Under conditions of stable inlet gas composition, temperature, pressure, and flow rate, CO2-containing gas is passed through the adsorption bed. The CO2 concentration at the inlet and outlet of the adsorption bed is measured separately, and the working CO2 adsorption capacity is determined based on the changes in CO2 concentration at the inlet and outlet.

[0077] When the CO2 concentration at the adsorption bed outlet reaches the breakthrough concentration, the flow of CO2-containing gas into the adsorption bed is stopped, and the CO2 adsorption material is desorbed and regenerated. The breakthrough concentration is determined based on the CO2 content requirements of the target CO2 capture medium in the outlet gas.

[0078] Based on the adsorption characteristics of the CO2 adsorbent material, regeneration is achieved by one of the following methods: heating desorption, depressurization desorption, vacuum desorption, or inert gas purging desorption, and the CO2-rich gas produced by desorption is collected.

[0079] After regeneration, the CO2 working adsorption capacity of the material is retested under the same CO2 adsorption conditions as the initial test. When the CO2 working adsorption capacity is not lower than the recovery limit, the material is returned to the CO2 adsorption bed for continued use; when the CO2 working adsorption capacity is lower than the recovery limit, the material is removed from the CO2 capture process and sent to the metal recovery process or stabilization process according to the copper content and leaching characteristics of the material. The selection of the metal recovery path and the stabilization process is determined based on the target metal type, the total metal content in the material, the metal content in the exhaust gas, and the feed requirements of the metal recovery process adopted.

[0080] Therefore, this embodiment forms a material cascade utilization process that includes waste plastics to prepare porous carbon, porous carbon adsorbing copper ions, copper-loaded porous carbon thermal treatment conversion, post-conversion material access, CO2 adsorption, desorption regeneration, and the withdrawal of failed materials.

[0081] In another specific embodiment, this embodiment is basically the same as the previous embodiment, except that: after the waste plastic is mixed with ZnCl2-KCl mixed molten salt, it is heated to 600°C at a determined heating rate under nitrogen protection, and kept at 600°C for 2 hours, and then naturally cooled under nitrogen protection.

[0082] The obtained salt-containing carbon material was washed with water, subjected to solid-liquid separation and drying according to the method in Example 1, and then used to treat Ni²-containing materials. + Wastewater. After adsorption, the nickel-loaded porous carbon is dehydrated, dried, and transferred in a sealed environment before undergoing heat treatment. The heat-treated material only enters the CO2 capture step when both the metal leaching concentration and the working CO2 adsorption capacity meet the conversion conditions; materials that do not meet the conversion conditions are either heat-treated again or removed according to the path in Example 1.

[0083] This example illustrates that porous carbon based on waste plastics can be prepared using different pyrolysis temperatures, but it does not presuppose that the material obtained at 600℃ necessarily has a higher content of oxygen-containing functional groups or better heavy metal adsorption performance without characterization data.

[0084] In another specific embodiment, this embodiment is basically the same as Embodiment 1, except that: the mass ratio of ZnCl2-KCl mixed molten salt to waste plastic is 8:1, the pyrolysis temperature is 850℃, and the holding time is 3h. After pyrolysis, cooling, washing with water, and drying, another type of waste plastic-based porous carbon is obtained.

[0085] Treatment of Cu²-containing waste plastic-based porous carbon + and Ni² + Mixed heavy metal wastewater was treated. After adsorption, the loading of copper and nickel in the metal-supported porous carbon was measured, and the heat treatment conditions were determined based on the thermal conversion characteristics of the two metal components. After heat treatment, the leaching concentrations of copper and nickel were measured, and the working CO2 adsorption capacity of the material was also measured. The material was only sent to the CO2 capture step when the leaching values ​​of each target metal met the requirements and the working CO2 adsorption capacity reached the lower limit of the working adsorption capacity.

[0086] This embodiment illustrates that under mixed heavy metal wastewater conditions, the loading, phase composition, and leaching risk of different metal components should be considered separately, and the suitability of materials for CO2 capture should not be determined solely based on the total metal content.

[0087] In another specific embodiment, this embodiment uses waste plastic-based porous carbon prepared in Example 1 to treat Zn²⁺-containing materials. + Pb² + Or Cd² +Heavy metal wastewater. After adsorption, the metal-loaded porous carbon undergoes closed-loop solid-liquid separation, dehydration, drying, and closed-loop transfer.

[0088] Before heat treatment, the volatilization risk is determined based on the type and load of the metal. During heat treatment, the exhaust gas is sequentially passed through a condensation unit, a particulate trapping unit, and a chlorine-containing gas purification unit. The target metal content in the solid material, condensate, particulate trappings, and purification absorbent after heat treatment is measured to determine the distribution of the target metal in each material.

[0089] Materials whose metal leaching concentration meets the requirements after heat treatment and whose working CO2 adsorption capacity reaches the lower limit of working adsorption capacity can proceed to the CO2 capture step; materials whose metal leaching concentration exceeds the leaching limit, whose target metal volatilization loss is too large, or whose working CO2 adsorption capacity is insufficient will not proceed to the CO2 capture step, but will instead be included in the metal recovery process or stabilization treatment process along with the collected condensate and particulate residue.

[0090] This embodiment illustrates that metals such as Pb, Cd, and Zn, which have the risk of volatilization or migration, cannot be automatically used as functional components in CO2 adsorption materials. Instead, the treatment path should be determined after exhaust gas collection, metal material balance, and material access testing.

[0091] In summary, the above embodiments can at least form the following technical relationships: This invention sequentially connects the preparation of waste plastic-based porous carbon, heavy metal wastewater adsorption, metal-loaded porous carbon thermal treatment conversion, and CO2 capture, so that the carbon material formed in the previous stage can be directly used as the treatment object in the next stage, realizing the continuous transfer and cascade utilization of the same batch of carbon material. This invention utilizes the metal components adsorbed on porous carbon in heavy metal wastewater to form a metal phase loaded on the carbon material through heat treatment. This eliminates the need to add metal salts to the carbon material and reduces the situation where porous carbon after heavy metal adsorption is directly disposed of as waste adsorbent. Before entering the heat treatment unit, the metal-loaded porous carbon undergoes solid-liquid separation, dehydration, drying, and closed transfer, which can reduce the amount of residual wastewater entering the heat treatment process and reduce the risk of heavy metal droplets and carbon dust escaping during separation, drying, and transfer. The gas generated during heat treatment is sequentially condensed, particulate intercepted, and chlorine-containing gas purified to collect volatile or migrating metal components with particles. The condensate and particulate intercepted are then sent to the metal recovery process, reducing the risk of secondary pollution caused by metal migration and chlorine-containing gas emissions during heat treatment. This invention determines the subsequent path of the material based on the metal leaching concentration and CO2 adsorption capacity of the heat-treated material. Only materials that simultaneously meet the requirements of metal stability and CO2 adsorption performance are allowed to enter the CO2 capture unit, thus avoiding the direct use of materials with high metal leaching risk or insufficient CO2 adsorption performance for gas treatment. For materials that do not meet the conversion conditions, they can be heat-treated again based on the test results; materials that still do not meet the requirements after re-treatment will enter the metal recycling or stabilization process, thus forming a closed loop of testing, re-treatment, re-testing, and rejection of unqualified materials. During CO2 capture, the breakthrough state of the material is determined based on the CO2 concentration at the outlet of the adsorption bed, and the CO2 adsorption material that has reached the breakthrough state is desorbed and regenerated. After the regenerated material is tested for working adsorption capacity, it can be reused or withdrawn, so that the recycling and final treatment of CO2 adsorption material have a clear path. The molten salt washing solution generated by water washing is concentrated, dehydrated, analyzed for components, and replenished with salt before being returned to the porous carbon preparation process, forming an independent molten salt recovery path, reducing the consumption of ZnCl2 and KCl and the discharge of salt-containing washing solution.

[0092] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for adsorption of heavy metals and capture of carbon in porous carbon based on waste plastics, characterized in that, Includes the following steps: S1: Waste plastics are mixed with molten salt and pyrolyzed under an inert atmosphere. The salt-containing carbon material obtained from the pyrolysis is washed with water to obtain waste plastic-based porous carbon. S2: The waste plastic-based porous carbon is used to treat heavy metal wastewater, so that the metal components in the heavy metal wastewater are adsorbed onto the waste plastic-based porous carbon, and metal-loaded porous carbon is obtained after solid-liquid separation. S3: The metal-loaded porous carbon is dehydrated and dried, and then heat-treated under an inert atmosphere to cause the metal components from the heavy metal wastewater to undergo phase transformation and remain loaded on the surface and in the pores of the metal-loaded porous carbon, thereby obtaining a CO2 adsorption material. S4: Bring the CO2-containing gas into contact with the CO2 adsorption material, so that the CO2 in the CO2-containing gas is adsorbed by the CO2 adsorption material.

2. The method for adsorption of heavy metals and capture of carbon in porous carbon based on waste plastics according to claim 1, characterized in that, The molten salt is a ZnCl2-KCl mixed molten salt; the molten salt washing solution generated by water washing is concentrated, dried and its composition is adjusted for reuse.

3. The method for adsorption of heavy metals and capture of carbon in porous carbon based on waste plastics according to claim 1, characterized in that, The solid-liquid separation, dehydration, and drying are all carried out in a closed state, and the dried metal-loaded porous carbon is then transferred in a closed manner to the heat treatment location.

4. The method for adsorption of heavy metals and capture of carbon in porous carbon based on waste plastics according to claim 1, characterized in that, In step S3, the gas generated by heat treatment is sequentially condensed, particles are trapped, and chlorine-containing gas is purified, and the resulting condensate and trapped material are sent to the metal recovery process.

5. The method for adsorption of heavy metals and capture of carbon in porous carbon based on waste plastics according to claim 1, characterized in that, In step S4, the CO2 adsorption material is packed into the adsorption bed, and the CO2-containing gas that has undergone particulate matter removal and condensate separation is introduced into the adsorption bed.

6. The method for adsorption of heavy metals and capture of carbon in porous carbon based on waste plastics according to claim 5, characterized in that, Obtain the CO2 concentration at the gas outlet of the adsorption bed. When the CO2 concentration reaches the breakthrough concentration, stop feeding the CO2-containing gas into the adsorption bed and desorb and regenerate the CO2 adsorption material. Obtain the working CO2 adsorption capacity of the CO2 adsorption material after desorption and regeneration. If the working CO2 adsorption capacity is not lower than the recovery limit, return to step S4. If it is lower than the recovery limit, send the CO2 adsorption material into the metal recovery process or the stabilization process.

7. The method for adsorption and capture of heavy metals and carbon in porous carbon based on waste plastics according to any one of claims 1 to 6, characterized in that, The metal leaching concentration and working CO2 adsorption capacity of the CO2 adsorbent material after heat treatment are obtained, and the conversion conditions are that the metal leaching concentration does not exceed the leaching limit and the working CO2 adsorption capacity is not lower than the lower limit of the working adsorption capacity.

8. A porous carbon heavy metal adsorption and carbon capture system based on waste plastics, characterized in that, include: The porous carbon preparation unit is used to mix waste plastics with molten salt, pyrolyze them under an inert atmosphere, and wash the salt-containing carbon material obtained by pyrolysis with water to obtain waste plastic-based porous carbon. A heavy metal adsorption unit is connected to the porous carbon preparation unit and is used to bring the waste plastic-based porous carbon into contact with heavy metal wastewater, so that the metal components in the heavy metal wastewater are adsorbed onto the waste plastic-based porous carbon. A solid-liquid separation and drying unit is connected to the heavy metal adsorption unit and is used to perform solid-liquid separation, dehydration and drying on the material output from the heavy metal adsorption unit to obtain metal-loaded porous carbon. A heat treatment unit, connected to the solid-liquid separation and drying unit, is used to heat treat the metal-loaded porous carbon under an inert atmosphere, so that the metal components from the heavy metal wastewater undergo phase transformation and remain loaded on the surface and pores of the metal-loaded porous carbon, thereby obtaining a CO2 adsorption material. as well as The CO2 capture unit is connected to the heat treatment unit and is used to bring the CO2 adsorption material into contact with the CO2-containing gas to adsorb the CO2 in the CO2-containing gas.

9. The waste plastic-based porous carbon heavy metal adsorption and carbon capture system according to claim 8, characterized in that, The system also includes a closed transfer mechanism, a condensation unit, a particle interception unit, a chlorine-containing gas purification unit, and a metal recovery unit; the closed transfer mechanism is located between the solid-liquid separation and drying unit and the heat treatment unit; the gas outlet of the heat treatment unit is sequentially connected to the condensation unit, the particle interception unit, and the chlorine-containing gas purification unit; and the material collection outlets of the condensation unit and the particle interception unit are respectively connected to the metal recovery unit.

10. The waste plastic-based porous carbon heavy metal adsorption and carbon capture system according to claim 9, characterized in that, The system further includes a material testing mechanism, a CO2 outlet testing mechanism, a regeneration unit, a material switching mechanism, a stabilization unit, and a control unit. The material testing mechanism is located in the material output paths of both the heat treatment unit and the regeneration unit. The CO2 outlet testing mechanism is located at the gas outlet of the CO2 collection unit. The regeneration unit is connected to the CO2 collection unit. The material switching mechanism is connected to the heat treatment unit, the regeneration unit, the CO2 collection unit, the metal recovery unit, and the stabilization unit. The control unit is connected to the material testing mechanism, the CO2 outlet testing mechanism, the material switching ... The material detection mechanism, the heat treatment unit, the regeneration unit, and the material switching mechanism are connected to control the CO2 adsorbent material to enter the CO2 collection unit, return to the heat treatment unit for further heat treatment, or enter the metal recovery unit or the stabilization treatment unit based on the metal leaching concentration and CO2 working adsorption capacity obtained by the material detection mechanism. The regeneration unit is also controlled based on the CO2 concentration obtained by the CO2 outlet detection mechanism, so that the desorbed and regenerated CO2 adsorbent material returns to the CO2 collection unit or enters the metal recovery unit or the stabilization treatment unit according to its CO2 working adsorption capacity.

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