Process for preparing carbon-based composite adsorption material by using neodymium iron boron oil sludge solid waste, product prepared by process and application of product in flue gas demercuration

Abstract

The invention provides a process for preparing a carbon-based composite adsorption material by using neodymium iron boron oil sludge solid waste, a product thereof and application of the product in flue gas demercuration, and particularly comprises the following steps: in a nitrogen atmosphere, pyrolyzing and carbonizing the neodymium iron boron oil sludge solid waste after polymerizing the neodymium iron boron oil sludge solid waste, adding strong acid into the pyrolyzed and carbonized product, and stirring for reaction, thereby obtaining the carbon-based composite adsorption material. Filtering to obtain a carbon material and rare earth iron ion mixed solution; adding oxalic acid into the rare earth iron ion mixed solution, filtering and separating to obtain an iron-rich solution, mixing and reacting with the carbon material, and performing heat treatment to obtain the carbon-based composite adsorption material. The acidified and modified carbon material is obtained through pyrolysis and acid treatment processes, the acidified and modified carbon material has a rich functional group structure, meanwhile, the residual quantity of rare earth ions in an iron-rich solution is controlled, oxygen vacancies with high oxidation performance are generated, and a final product has two efficient mercury removal centers at the same time and has a wide application prospect in flue gas mercury removal.

Description

Technical Field

[0001] This invention relates to the field of solid waste recycling and material preparation, specifically to a process for preparing carbon-based composite adsorbent materials from neodymium iron boron sludge solid waste, the resulting products, and their application in flue gas mercury removal. More specifically, it relates to a method for synthesizing a novel carbon-based composite adsorbent material for flue gas mercury removal and the resulting products. Background Technology

[0002] Sintered neodymium iron boron (Nd2Fe14B, or Nd-Fe-B for short) magnets are considered the third generation of rare-earth permanent magnet materials after samarium cobalt permanent magnets. Since their discovery in 1983, they remain the most powerful permanent magnet materials. However, in the production process of sintered Nd-Fe-B magnets, the utilization rate of raw materials is generally only 60% to 70%. The waste generated can be roughly classified into three types according to their form: oily sludge waste, solid blocky production waste, and a small amount of powdery waste. Among these, oily sludge waste is the largest amount of waste generated in each process. It is mainly a slurry-like waste (organic matter accounting for 40% to 60%) coated with oily organic matter, generated during the machining process.

[0003] Currently, the industrial treatment of NdFeB oily sludge solid waste both domestically and internationally involves first subjecting the sludge to high-temperature oxidation roasting, followed by the extraction and recovery of rare earth elements (Re) using a wet process. While this treatment method is widely used industrially, it still has two drawbacks. First, high-temperature oxidation roasting only converts organic matter into CO2 emissions, failing to effectively utilize the approximately 50% oily organic matter by mass. Second, the 64% Fe species in NdFeB fails to be converted into value-added industrial products; even with recovery, trace amounts of rare earth elements often remain in the Fe species, leading to a decrease in product purity.

[0004] Therefore, there is an urgent need to develop a new method for recycling and reusing neodymium iron boron sludge solid waste. Summary of the Invention

[0005] One objective of this invention is to overcome the shortcomings and deficiencies of existing technologies and, with the aim of effectively utilizing the organic matter and Fe species in NdFeB oil sludge solid waste, provide a process for preparing carbon-based composite adsorbent materials from NdFeB oil sludge solid waste. This method effectively utilizes neglected byproducts in NdFeB oil sludge solid waste to prepare carbon-based composite adsorbent materials with high efficiency in flue gas mercury removal. The preparation process is simple and cost-effective.

[0006] The objective of this invention is achieved through the following solution:

[0007] A process for preparing carbon-based composite adsorbent materials using neodymium iron boron oil sludge solid waste includes the following steps:

[0008] Under a nitrogen atmosphere, NdFeB oil sludge solid waste is thermally polymerized and then pyrolyzed and carbonized. Strong acid is added to the pyrolysis and carbonization products and the mixture is stirred and reacted. After filtration, acidified carbon materials and a mixed solution of rare earth iron ions are obtained.

[0009] Oxalic acid was added to the rare earth iron ion mixed solution to adjust the pH to 1.5-3.0, resulting in rare earth oxalate precipitate, which was then separated by filtration to obtain an iron-rich solution.

[0010] The carbon material was added to the iron-rich solution, and potassium hydroxide was added under stirring conditions to adjust the pH to alkaline. The aging reaction yielded a carbon-based composite adsorbent precursor.

[0011] The carbon-based composite adsorbent precursor was heat-treated under a nitrogen atmosphere to obtain the carbon-based composite adsorbent.

[0012] Preferably, the thermal polymerization temperature is 160–250℃ and the thermal polymerization time is 1–2 hours.

[0013] Preferably, the strong acid is either nitric acid or hydrochloric acid, and the concentration of the strong acid is 2–5 mol / L.

[0014] As a preferred method, after adding a strong acid, the mixture is stirred at 80–90°C for 4–5 hours.

[0015] Preferably, the ratio of the total mass of carbon material to the mass of iron in the iron-rich solution is 3:1 to 1:3.

[0016] Preferably, the aging reaction temperature is 60–65°C and the aging reaction time is 1–1.5 h.

[0017] Preferably, the heat treatment temperature is 300–600℃.

[0018] This invention combines a wet acid treatment process with a co-precipitation process to prepare a novel carbon-based composite adsorption material. The key technology in the above chemical preparation process for preparing highly efficient flue gas mercury removal adsorption materials lies in the mutual doping of carbon materials with the active centers of iron-rare earth (Fe-Re) composite oxides. The specific reaction principle is as follows:

[0019] First, acid-modified carbon materials are obtained through pyrolysis and acid treatment. These acid-modified carbon materials possess abundant functional group structures on their surface, serving as effective adsorption centers for mercury species. Simultaneously, neodymium iron boron (NdFeB) is dissolved to its ionic state during acid treatment, followed by precipitation of industrially recoverable rare earth elements using oxalic acid. During this process, pH control is crucial, determining the residual amount of rare earth ions in the subsequent iron-rich solution, which further influences the high-oxidation-performance oxygen vacancies generated by a small amount of Re doping in the Fe oxide. Ultimately, the prepared novel carbon-based composite adsorption material possesses two highly efficient mercury removal centers: functional groups and oxygen vacancies.

[0020] Another objective of this invention is to provide a carbon-based composite adsorbent material prepared using the above method.

[0021] Another object of the present invention is to provide the application of the above-mentioned carbon-based composite adsorbent material in mercury removal from flue gas.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0023] This invention proposes a novel approach to the recycling of NdFeB oil sludge solid waste. Aiming to effectively utilize the organic matter and Fe species within the NdFeB oil sludge solid waste, it simultaneously recovers rare earth oxalates and prepares a highly active flue gas mercury removal adsorbent. Specifically, the carbon-based composite adsorbent material of this invention originates from a neglected byproduct of NdFeB oil sludge solid waste, representing an effective utilization of waste. Therefore, the process is low-cost and more environmentally friendly, effectively overcoming the shortcomings of existing technologies that fail to fully utilize NdFeB oil sludge solid waste. Attached Figure Description

[0024] Figure 1 XPS image of the carbon-based composite adsorbent material of this invention. Detailed Implementation

[0025] The present invention will be further analyzed below with reference to specific embodiments.

[0026] As mentioned above, this embodiment provides a process for preparing carbon-based composite adsorbent materials using neodymium iron boron oil sludge solid waste, along with the resulting product and its application. The prepared carbon-based composite adsorbent material possesses two highly efficient mercury removal centers: functional groups and oxygen vacancies. The process includes the following steps:

[0027] S1. Under a nitrogen atmosphere, the NdFeB oil sludge solid waste is thermally polymerized and then pyrolyzed and carbonized. Nitric acid or hydrochloric acid with a concentration of 2-5 mol / L is added to the pyrolysis and carbonization products. The mixture is stirred and reacted at 80-90℃ for 4-5 hours. After filtration, a mixed solution of carbon material and rare earth iron ions is obtained.

[0028] S2. Oxalic acid is added to the rare earth iron ion mixed solution to adjust the pH to 1.5-3.0, rare earth oxalate precipitate is generated, and after filtration and separation, an iron-rich solution is obtained.

[0029] S3. Add the carbon material to the iron-rich solution, add potassium hydroxide under stirring to adjust the pH to alkaline, and age at 60-65°C for 1-1.5 h to obtain the carbon-based composite adsorbent precursor.

[0030] S4. Under a nitrogen atmosphere, the carbon-based composite adsorbent precursor is heat-treated to obtain the carbon-based composite adsorbent.

[0031] In one preferred embodiment, the heat polymerization temperature in step S1 is 160-250°C and the heat polymerization time is 1-2 hours. Those skilled in the art can select according to actual needs. For example, the heat polymerization temperature can be 160°C, 180°C, 200°C, 220°C or 250°C, and the heat polymerization time can be 1 hour, 1.5 hours or 2 hours. There is no limitation here.

[0032] In one preferred embodiment, the concentration of nitric acid or hydrochloric acid in step S1 is 3 mol / L.

[0033] In one preferred embodiment, the pH is adjusted to 2.0 to 3.0 in step S3.

[0034] In one preferred embodiment, the mass ratio of carbon material to Fe element in iron-rich solution in step S3 is 3:1 to 1:3. Those skilled in the art can choose according to actual needs, such as 3:1, 3:2, 1:1, 1:2 or 1:3, which is not limited here.

[0035] In one preferred embodiment, the heat treatment temperature in step S4 is 300-600°C. Those skilled in the art can select the appropriate temperature according to actual needs, such as 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, or 650°C, which is not limited here.

[0036] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0037] Example 1

[0038] Under a nitrogen atmosphere, NdFeB oil sludge solid waste was thermally polymerized at a certain low temperature for 1 hour, followed by pyrolysis and carbonization at 600℃ for 1 hour. 3 mol / L hydrochloric acid was added to the pyrolysis products, and the reaction was stirred at 80℃ for 4 hours. The acidified carbon material and the NdFeB ion mixed solution were separated by filtration. Oxalic acid was added to the above rare earth iron ion mixed solution to adjust the pH to 2, and the precipitated rare earth oxalate was recovered by filtration to obtain an iron-rich solution (containing a small amount of rare earth ions). The acidified carbon material was added to the iron-rich solution at a carbon-to-Fe element mass ratio of 1:1, and KOH solution was slowly added while stirring to adjust the pH to 9. The solution was then aged at 60℃ for 1 hour to obtain a carbon-based composite adsorbent precursor. Under a nitrogen atmosphere, the carbon-based composite adsorbent precursor was heat-treated at 500℃ for 3 hours to finally obtain the desired carbon-based composite adsorbent. The obtained adsorbent was used in a simulated flue gas mercury removal experiment. The simulated flue gas contained 45 μg / m³ of mercury. 3 Hg 0, Composed of 10% CO2, 5% O2 and N2, with a total gas flow rate of 1 L / min and a space velocity of 240,000 h⁻¹.-1 The adsorption temperature was 150 ℃. The effect of low-temperature thermal polymerization temperature on the mercury removal performance of the adsorbent material is shown in Table 1.

[0039] Table 1. Effect of low-temperature thermal polymerization temperature on mercury removal performance of adsorbent materials

[0040] Low temperature thermal polymerization temperature Mercury removal efficiency (%) 160 59.3 200 65.8 250 57.9

[0041] Table 1 shows that the adsorbent material prepared at a thermal polymerization temperature of 200℃ exhibits the highest mercury removal efficiency. If the temperature is too low, the polymerization reaction will be incomplete, leading to an unstable carbon framework structure; while if the temperature is too high, excessive carbonization of the organic components will reduce the content of functional groups on the carbon surface, thereby weakening the chemisorption capacity for mercury. Therefore, controlling the thermal polymerization temperature between 160 and 250℃, preferably 200℃, helps to form a carbon material with a stable structure and abundant active sites.

[0042] Example 2

[0043] Under a nitrogen atmosphere, NdFeB oil sludge solid waste was thermally polymerized at 200℃ for 1 hour, followed by pyrolysis and carbonization at 600℃ for 1 hour. A strong acid of 3 mol / L was added to the pyrolysis products, and the mixture was stirred at 80℃ for 4 hours. The acidified carbon material and the NdFe ion mixed solution were separated by filtration. Oxalic acid was added to the above rare earth iron ion mixed solution to adjust the pH to 2, and the precipitated rare earth oxalate was recovered by filtration to obtain an iron-rich solution (containing a small amount of rare earth ions). The acidified carbon material was added to the iron-rich solution at a carbon-to-Fe element mass ratio of 1:1, and KOH solution was slowly added while stirring to adjust the pH to 9. The mixture was then aged at 60℃ for 1 hour to obtain a carbon-based composite adsorbent precursor. Under a nitrogen atmosphere, the carbon-based composite adsorbent precursor was heat-treated at 500℃ for 3 hours to finally obtain the desired carbon-based composite adsorbent. The obtained adsorbent was then subjected to a mercury removal experiment simulating flue gas. The effect of strong acid type on the mercury removal performance of adsorbent material is shown in Table 2.

[0044] Table 2. Effect of strong acid type on mercury removal performance of adsorbent materials

[0045] Types of strong acids Mercury removal efficiency (%) sulfuric acid 45.6 hydrochloric acid 65.8 Nitric acid 53.3

[0046] Example 3

[0047] Under a nitrogen atmosphere, NdFeB oil sludge solid waste was thermally polymerized at 200℃ for 1 hour, followed by pyrolysis and carbonization at 600℃ for 1 hour. A certain concentration of hydrochloric acid was added to the pyrolysis products, and the mixture was stirred at 80℃ for 4 hours. The acidified carbon material and the NdFeB ion mixed solution were separated by filtration. Oxalic acid was added to the above rare earth iron ion mixed solution to adjust the pH to 2, and the precipitated rare earth oxalate was recovered by filtration to obtain an iron-rich solution (containing a small amount of rare earth ions). The acidified carbon material was added to the iron-rich solution at a carbon-to-Fe element mass ratio of 1:1, and KOH solution was slowly added while stirring to adjust the pH to 9. The mixture was then aged at 60℃ for 1 hour to obtain a carbon-based composite adsorbent precursor. Under a nitrogen atmosphere, the carbon-based composite adsorbent precursor was heat-treated at 500℃ for 3 hours to finally obtain the desired carbon-based composite adsorbent. The obtained adsorbent was subjected to a mercury removal experiment simulating flue gas. The effect of hydrochloric acid concentration on the mercury removal performance of the adsorbent is shown in Table 3.

[0048] Table 3. Effect of hydrochloric acid concentration on the mercury removal performance of adsorbent materials

[0049] hydrochloric acid concentration Mercury removal efficiency (%) 2 mol / L 58.6 3 mol / L 65.8 5 mol / L 51.3

[0050] Table 3 shows that the adsorbent material exhibits the highest mercury removal efficiency when the hydrochloric acid concentration is 3 mol / L. Too low a concentration may result in insufficient leaching of iron and rare earth elements, inadequate acidification of the carbon material, and a limited number of surface functional groups; too high a concentration may excessively corrode the carbon skeleton, damaging its structure and reducing effective loading sites. Therefore, controlling the hydrochloric acid concentration between 2 and 5 mol / L, preferably 3 mol / L, balances the acidification modification and structural stability of the product.

[0051] Example 4

[0052] Under a nitrogen atmosphere, NdFeB oil sludge solid waste was thermally polymerized at 200℃ for 1 hour, followed by pyrolysis and carbonization at 600℃ for 1 hour. 3 mol / L hydrochloric acid was added to the pyrolysis products, and the mixture was stirred at 80℃ for 4 hours. The acidified carbon material and the NdFe ion mixed solution were separated by filtration. Oxalic acid was added to the rare earth iron ion mixed solution to adjust the pH to a specific value, and the precipitated rare earth oxalate was recovered by filtration to obtain an iron-rich solution (containing a small amount of rare earth ions). The acidified carbon material was added to the iron-rich solution at a carbon-to-Fe element mass ratio of 1:1, and KOH solution was slowly added while stirring to adjust the pH to 9. The mixture was then aged at 60℃ for 1 hour to obtain a carbon-based composite adsorbent precursor. Under a nitrogen atmosphere, the carbon-based composite adsorbent precursor was heat-treated at 500℃ for 3 hours to finally obtain the desired carbon-based composite adsorbent. The obtained adsorbent was then used in a simulated flue gas mercury removal experiment. The effect of pH value on the mercury removal performance of the adsorbent material is shown in Table 4.

[0053] Table 4. Effect of pH value on mercury removal performance of adsorbent materials

[0054] pH value Mercury removal efficiency (%) 1.5 69.3 2 65.8 3 50.6 3.5 47.9

[0055] Table 4 shows that excessively low pH (e.g., 1.5) leads to incomplete rare earth precipitation and high rare earth residue. Although this forms a more active Fe-RE composite oxide, the excessive loss of high-value rare earths is detrimental to rare earth recovery and indirectly increases process costs. Excessively high pH (e.g., 3.5) causes ferric oxalate precipitation to mix with rare earth oxalate precipitation, increasing iron impurities in the recovered rare earth and reducing the mercury removal performance of the Fe-RE composite oxide. Appropriately controlling the pH between 2.0 and 3.0 can achieve a balance between rare earth recovery and oxygen vacancy generation, ensuring optimal product performance.

[0056] Example 5

[0057] Under a nitrogen atmosphere, NdFeB oil sludge solid waste was thermally polymerized at 200℃ for 1 hour, followed by pyrolysis and carbonization at 600℃ for 1 hour. 3 mol / L hydrochloric acid was added to the pyrolysis products, and the mixture was stirred at 80℃ for 4 hours. The acidified carbon material and the NdFe ion mixed solution were separated by filtration. Oxalic acid was added to the rare earth iron ion mixed solution to adjust the pH to 2, and the precipitated rare earth oxalate was recovered by filtration to obtain an iron-rich solution (containing a small amount of rare earth ions). The acidified carbon material was added to the iron-rich solution according to a specific mass ratio of carbon material to Fe, and KOH solution was slowly added while stirring to adjust the pH to 9. The mixture was then aged at 60℃ for 1 hour to obtain a carbon-based composite adsorbent precursor. Under a nitrogen atmosphere, the carbon-based composite adsorbent precursor was heat-treated at 500℃ for 3 hours to finally obtain the desired carbon-based composite adsorbent. The obtained adsorbent was then used in a simulated flue gas mercury removal experiment. The effect of the mass ratio of carbon materials to Fe elements on the mercury removal performance of the adsorbent materials is shown in Table 5.

[0058] Table 5. Effect of the mass ratio of carbon materials to Fe on the mercury removal performance of the adsorbent materials.

[0059] Mass ratio of carbon materials to Fe elements Mercury removal efficiency (%) 3:1 50.6 1:1 65.8 1:3 59.3

[0060] Table 5 shows that the mercury removal efficiency is highest when the mass ratio of carbon material to iron is 1:1. Excessive carbon content results in insufficient active metal sites; while excessive iron content leads to iron oxide agglomeration, blocking some pores and reducing the specific surface area. Therefore, controlling the mass ratio of carbon to iron material to iron in the range of 3:1 to 1:3, preferably 1:1, can achieve a synergistic enhancement of functional group adsorption and the catalytic effect of metal oxide sites.

[0061] Example 6

[0062] Under a nitrogen atmosphere, NdFeB oil sludge solid waste was thermally polymerized at 200℃ for 1 hour, followed by pyrolysis and carbonization at 600℃ for 1 hour. 3 mol / L hydrochloric acid was added to the pyrolysis products, and the mixture was stirred at 80℃ for 4 hours. The acidified carbon material and the NdFe ion mixed solution were separated by filtration. Oxalic acid was added to the above rare earth iron ion mixed solution to adjust the pH to 2, and the precipitated rare earth oxalate was recovered by filtration to obtain an iron-rich solution (containing a small amount of rare earth ions). The acidified carbon material was added to the iron-rich solution at a carbon-to-Fe element mass ratio of 1:1, and KOH solution was slowly added while stirring to adjust the pH to 9. The mixture was then aged at 60℃ for 1 hour to obtain a carbon-based composite adsorbent precursor. Under a nitrogen atmosphere, the carbon-based composite adsorbent precursor was heat-treated at a certain temperature for 3 hours to finally obtain the desired carbon-based composite adsorbent. The obtained adsorbent was subjected to a mercury removal experiment simulating flue gas. The effect of heat treatment temperature on the mercury removal performance of the adsorbent is shown in Table 6.

[0063] Table 6. Effect of heat treatment temperature on mercury removal performance of adsorbent materials

[0064] Heat treatment temperature Mercury removal efficiency (%) 300 66.6 500 65.8 600 61.3

[0065] As shown in Table 6, the mercury removal performance is optimal when the temperature is approximately 300–500℃. However, excessively high temperatures (≥600℃) cause oxygen vacancy rearrangement and removal of surface functional groups, resulting in a decrease in mercury removal performance.

[0066] Comparative Example 1

[0067] To further verify the superiority of the product of this invention, carbon-based composite adsorbent materials were prepared under optimal conditions and comparative experiments were conducted:

[0068] Under a nitrogen atmosphere, NdFeB oil sludge solid waste was thermally polymerized at 200℃ for 1 hour, followed by pyrolysis and carbonization at 600℃ for 1 hour. 3 mol / L hydrochloric acid was added to the pyrolysis product, and the reaction was stirred at 80℃ for 4 hours. The acidified carbon material and the NdFe ion mixed solution were separated by filtration. Oxalic acid was added to the above rare earth iron ion mixed solution to adjust the pH to 2, and the precipitated rare earth oxalate was recovered by filtration to obtain an iron-rich solution (containing a small amount of rare earth ions). The acidified carbon material was added to the iron-rich solution at a carbon-to-Fe element mass ratio of 1:1, and KOH solution was slowly added while stirring to adjust the pH to 9. The mixture was then aged at 60℃ for 1 hour to obtain a carbon-based composite adsorbent precursor. Under a nitrogen atmosphere, the carbon-based composite adsorbent precursor was heat-treated at 500℃ for 3 hours to finally obtain the desired carbon-based composite adsorbent. The O1s-XPS spectrum of this product is shown below. Figure 1As shown, after peak separation of the spectrum, it can be seen that the ratio of oxygen vacancy content to lattice oxygen content in the sample is 1.22, indicating that abundant oxygen vacancies have been generated on its surface.

[0069] The obtained adsorbent material was subjected to a mercury removal experiment simulating flue gas. Its performance was compared with other common mercury removal products. According to literature reports (Chemical Engineering Journal, 2020, 388, 124220), commercial activated carbon, under the same test conditions (45 μg / m³), showed superior performance. 3 Hg 0, Composed of 10% CO2, 5% O2 and N2, with a total gas flow rate of 1 L / min and a space velocity of 240,000 h⁻¹. -1 The mercury removal efficiency of Fe2O3 / SiO2 under the same test conditions (adsorption temperature 150 °C) is less than 8%; according to literature reports (Separation and Purifcation Technology, 2024, 338, 126569), the mercury removal efficiency of Fe2O3 / SiO2 under the same test conditions is less than 15%.

[0070] The above embodiments are not intended to limit the present invention, and the present invention is not limited to the above embodiments. Any embodiment that meets the requirements of the present invention is within the protection scope of the present invention.

Claims

1. A process for preparing carbon-based composite adsorbent materials using neodymium iron boron oil sludge solid waste, characterized in that, The process includes the following steps: Under a nitrogen atmosphere, NdFeB oil sludge solid waste is thermally polymerized and then pyrolyzed and carbonized. Strong acid is added to the pyrolysis and carbonization products and the mixture is stirred and reacted. After filtration, acidified carbon materials and a mixed solution of rare earth iron ions are obtained. Oxalic acid was added to the rare earth iron ion mixed solution to adjust the pH to 1.5-3.0, resulting in rare earth oxalate precipitate, which was then separated by filtration to obtain an iron-rich solution. The carbon material was added to the iron-rich solution, and potassium hydroxide was added under stirring conditions to adjust the pH to alkaline. The aging reaction yielded a carbon-based composite adsorbent precursor. The carbon-based composite adsorbent precursor was heat-treated at 300–600°C under a nitrogen atmosphere to obtain the carbon-based composite adsorbent.

2. The process according to claim 1, characterized in that, The heat polymerization temperature is 160–250℃, and the heat polymerization time is 1–2 hours.

3. The process according to claim 1, characterized in that, The strong acid can be either nitric acid or hydrochloric acid.

4. The process according to claim 3, characterized in that, The concentration of strong acid is 2–5 mol / L.

5. The process according to claim 4, characterized in that, After adding a strong acid, stir the mixture at 80–90°C for 4–5 hours.

6. The process according to claim 1, characterized in that, The mass ratio of carbon materials to Fe elements is 3:1 to 1:

3.

7. The process according to claim 5, characterized in that, The mass ratio of carbon material to Fe element is 1:

1.

8. The process according to claim 1, characterized in that, The aging reaction temperature is 60-65℃, and the aging reaction time is 1-1.5h.

9. A carbon-based composite adsorbent material, characterized in that, It is prepared using the process described in any one of claims 1-8.

10. The application of the carbon-based composite adsorbent material as described in claim 9 in mercury removal from flue gas.

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