Preparation process of active biochar

Abstract

The invention provides a preparation process of active biochar. The preparation process comprises the following steps: S1, raw material pretreatment; S2, cross-linking enhancement treatment; S3, polymer microsphere blending; the active biochar prepared by the method has high specific surface area, a multi-stage pore structure and rich surface active sites, shows excellent performance in the fields of heavy metal adsorption, organic pollutant degradation and electrochemical energy storage, realizes resource utilization of waste wood after typhoon, and has environmental benefits and economic values.

Description

Technical Field

[0001] The present invention relates to the technical field of biochar preparation, and in particular to a process for preparing activated biochar. Background Art

[0002] Typhoons often cause trees to fall due to strong winds, especially in coastal areas and densely vegetated areas. If not properly handled, fallen trees not only occupy land resources and hinder urban greening restoration, but may also produce greenhouse gases such as methane as they decay, further burdening the environment. Although some fallen trees are crushed and used for biomass fuel, papermaking, or landscaping, overall utilization remains low. Due to the lack of systematic recycling and high-value-added processing, a large amount of wood is landfilled or incinerated, resulting in a waste of resources and a loss of economic value.

[0003] Converting typhoon-downed trees into activated biochar can significantly improve their resource utilization. Activated biochar, with its high specific surface area, rich pore structure, and abundant surface functional groups, is widely used in wastewater treatment, soil remediation, and electrochemical energy storage. However, traditional preparation methods struggle to simultaneously optimize both pore structure and surface active groups, limiting adsorption performance. Summary of the Invention

[0004] In view of this, the present invention proposes a preparation process of activated biochar to solve the above problems.

[0005] The technical solution of the present invention is achieved as follows:

[0006] A process for preparing activated biochar comprises the following steps:

[0007] S1. Raw material pretreatment: Trees fallen after the typhoon were collected, impurities removed, and cut into wood segments ≤ 5 cm. The wood segments were immersed in a complex enzyme solution and shaken. The wood segments were then crushed using a grinder to a particle size of 1-3 mm. The wood segments were then dried with hot air to a moisture content of ≤ 10% to obtain wood pellets.

[0008] S2. Crosslinking and strengthening treatment: Prepare a crosslinking solution, immerse the wood particles in the crosslinking solution, vacuum impregnate at 75-85°C for 1.8-2.2 hours, and then heat at 115-125°C for 2.5-3.5 hours to induce esterification and etherification reactions to obtain crosslinked wood particles;

[0009] S3 polymer microsphere blending: polyacrylic acid microspheres and polyethyleneimine microspheres prepared by emulsion polymerization, mixed in a mass ratio of 1:1 to obtain mixed microspheres; cross-linked wood particles and mixed microspheres in a mass ratio of 100:4-10;

[0010] S4. Gradient pyrolysis-dynamic oxidation coupling: Under a nitrogen atmosphere, the temperature was raised to 300°C at 5°C / min and held for 0.9-1.1 h. An O2 / N2 mixture containing 4-6% O2 was then introduced, and the temperature was raised to 400°C at 10°C / min and held for 0.8-1.2 h. After that, the mixture was switched to pure N2 and then raised to 500°C and held for 2 h to form a mesoporous structure. The temperature was then raised to 600°C at 15°C / min and held for 1 h to expand the microporous structure and obtain pyrolytic carbon.

[0011] S5. Deep Activation: Choline oxalate and FeCl3 were mixed and stirred until a deep eutectic solvent was formed; the pyrolytic carbon was immersed in the deep eutectic solvent, ultrasonically shaken, and then filtered and dried to obtain iron-doped deep eutectic solvent-activated porous carbon;

[0012] S6. Post-treatment: Immerse the iron-doped deep eutectic solvent-activated porous carbon in an ethylenediamine ethanol solution, filter, and vacuum dry to obtain activated biochar.

[0013] Furthermore, the fallen trees in S1 are selected from coniferous forests or broad-leaved forests with a lignin content of ≥25%, the time of falling is ≤30 days, and the impurities removed include branches and leaves, sand and gravel, soil, metal foreign matter, and bark.

[0014] Furthermore, the complex enzyme solution in S1 contains 4-6 U / g lignin peroxidase and 8-12 U / g xylanase, has a pH of 4.2-4.8, is shaken at 40-50°C for 5-7h, and the hot air drying temperature is 75-85°C.

[0015] Furthermore, the cross-linking solution in S2 contains 14-16 wt% glycerol, 8-12 wt% citric acid, 4.5-5.5 wt% tannic acid, and 0.4-0.6 wt% toluenesulfonic acid, and the solid-liquid ratio of the wood particles to the cross-linking solution is 1:4-6 g / mL.

[0016] Furthermore, the particle size of the polyacrylic acid microspheres in S3 is 50-100 nm, the surface contains -COOH functional groups and -COOH ≥ 0.8 mmol / g; the particle size of the polyethyleneimine microspheres is 80-150 nm, the surface contains -NH2 functional groups and -NH2 ≥ 1.2 mmol / g.

[0017] Furthermore, the flow rate of the O2 / N2 mixed gas in S4 is 0.1-0.5 L / min, and the ventilation cycle is 30 s every 10 min.

[0018] Furthermore, the choline oxalate in S5 is prepared by reacting choline chloride and oxalic acid in a molar ratio of 1:2. When choline oxalate is mixed with FeCl3, it is mixed in a mass ratio of 8-10:1 and stirred at 75-85°C to form a low eutectic solvent; the solid-liquid ratio of the pyrolytic carbon to the low eutectic solvent is 1:2.5-3.5 g / mL; the ultrasonic oscillation is carried out at 70-90°C, the ultrasonic power is 200-500W, the ultrasonic frequency is 20-40kHz, the ultrasonic oscillation is 1.8-2.2h, and after filtration, it is dried at 110-130°C for 2-4h.

[0019] Furthermore, the concentration of the ethylenediamine ethanol solution in S6 is 4-6 wt %, the treatment temperature is 55-65° C., the treatment time is 1.5-2.5 h, the drying temperature is 100-110° C., and the drying time is 10-15 h.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The present invention effectively degrades lignin and constructs a three-dimensional cross-linked network by soaking in a complex enzyme solution and a cross-linking solution, providing a stable skeleton for pore development;

[0022] (2) The present invention forms a hierarchical and rich pore structure through the coupling process of polymer microsphere blending and gradient pyrolysis-dynamic oxidation, and at the same time introduces oxygen-containing and nitrogen-containing functional groups such as carboxyl and pyridine-N to increase the functional group density of biochar.

[0023] (3) The present invention realizes micropore expansion and high-density anchoring of Fe-N coordination structure through deep activation, and further grafts amino groups in post-processing. The final product has high specific surface area, multi-level pore structure and abundant surface active sites, and exhibits excellent performance in the fields of heavy metal adsorption, organic pollutant degradation and electrochemical energy storage. At the same time, it realizes the resource utilization of waste wood after typhoon, and has both environmental benefits and economic value. DETAILED DESCRIPTION

[0024] In order to better understand the technical content of the present invention, specific examples are provided below to further illustrate the present invention.

[0025] Unless otherwise specified, the experimental methods used in the examples of the present invention are all conventional methods.

[0026] Unless otherwise specified, the materials, reagents, etc. used in the examples of the present invention can be obtained from commercial sources.

[0027] Example 1

[0028] A process for preparing activated biochar comprises the following steps:

[0029] S1. Raw material pretreatment: Trees that fell after a typhoon were collected, impurities removed, and cut into 1 cm segments. The segments were immersed in a complex enzyme solution and shaken. The segments were then crushed to a particle size of 1 mm using a grinder and dried with hot air at 75°C to a moisture content of 10% to obtain wood pellets. The fallen trees were selected from coniferous forests with a lignin content ≥25%. The trees were fallen for 1-10 days. Impurities removed included branches, leaves, sand, soil, metal foreign matter, and bark. The complex enzyme solution contained 4 U / g lignin peroxidase and 8 U / g xylanase, with a pH of 4.2. The treatment was performed at 40°C with shaking for 7 hours.

[0030] S2. Cross-linking and Strengthening Treatment: A cross-linking solution was prepared and the wood particles were immersed in the solution under vacuum at 75°C for 2.2 hours. The solution was then heated at 115°C for 3.5 hours to induce esterification and etherification reactions, resulting in cross-linked wood particles. The cross-linking solution contained 14 wt% glycerol, 8 wt% citric acid, 4.5 wt% tannic acid, and 0.4 wt% toluenesulfonic acid. The solid-to-liquid ratio (g / mL) of wood particles to cross-linking solution was 1:4.

[0031] S3. Polymer Microsphere Blending: Polyacrylic acid microspheres and polyethyleneimine microspheres were prepared by emulsion polymerization and mixed in a 1:1 mass ratio to produce mixed microspheres. Crosslinked wood particles and the mixed microspheres were mixed in a 100:4 mass ratio. The polyacrylic acid microspheres had a particle size of 50 nm and contained surface -COOH functional groups at a -COOH concentration of 0.8 mmol / g. The polyethyleneimine microspheres had a particle size of 80 nm and contained surface -NH2 functional groups at a -NH2 concentration of 1.2 mmol / g.

[0032] S4. Gradient pyrolysis-dynamic oxidation coupling: Under a nitrogen atmosphere, the temperature was increased at 5°C / min to 300°C and held for 0.9 h. An O2 / N2 mixture containing 4% O2 was then introduced at a flow rate of 0.1 L / min for 30 seconds every 10 min. The temperature was then increased at 10°C / min to 400°C and held for 0.8 h. After this, the mixture was switched to pure N2 and then heated to 500°C and held for 2 h to form a mesoporous structure. The temperature was then increased at 15°C / min to 600°C and held for 1 h to expand the microporous structure, resulting in pyrolytic carbon.

[0033] S5. Deep Activation: Mix choline oxalate and FeCl3 in a mass ratio of 8:1 and stir at 75°C until a deep eutectic solvent is formed. Immerse the pyrolytic carbon in the deep eutectic solvent at a solid-to-liquid ratio of 1:2.5 g / mL. Ultrasonicate the carbon and filter and dry it to obtain the iron-doped deep eutectic solvent-activated porous carbon. Ultrasonication is performed at 70°C, with a power of 200 W and a frequency of 20 kHz for 2.2 hours. After filtration, the carbon is dried at 110°C for 4 hours. The choline oxalate is prepared by reacting choline chloride with oxalic acid in a molar ratio of 1:2.

[0034] S6. Post-treatment: The iron-doped deep eutectic solvent-activated porous carbon was immersed in a 4 wt% ethylenediamine ethanol solution at 55° C. for 2.5 h, filtered, and then vacuum-dried at 100° C. for 15 h to obtain activated biochar.

[0035] Example 2

[0036] A process for preparing activated biochar comprises the following steps:

[0037] S1. Raw material pretreatment: Collect fallen trees after the typhoon, remove impurities, and cut them into 3 cm wood segments; immerse the wood segments in a complex enzyme solution for shaking treatment, then use a crusher to crush the wood segments to a particle size of 2 mm, and dry them with hot air to a moisture content of 8% to obtain wood pellets. The fallen trees are selected from coniferous forests with a lignin content of ≥25%. The time of falling is 11-20 days. The impurities removed include branches and leaves, sand and gravel, soil, metal foreign matter, and bark. The complex enzyme solution contains 5U / g lignin peroxidase and 10U / g xylanase, with a pH of 4.5. It is shaken at 45°C for 6 hours, and the hot air drying temperature is 80°C.

[0038] S2. Cross-linking and Strengthening Treatment: A cross-linking solution was prepared and the wood particles were immersed in the cross-linking solution at 75-85°C for 2 hours under vacuum. The solution was then heated at 120°C for 3 hours to induce esterification and etherification reactions, thereby producing cross-linked wood particles. The cross-linking solution contained 15 wt% glycerol, 10 wt% citric acid, 5.0 wt% tannic acid, and 0.5 wt% toluenesulfonic acid. The solid-to-liquid ratio of the wood particles to the cross-linking solution was 1:5 (g / mL).

[0039] S3. Polymer Microsphere Blending: Polyacrylic acid microspheres and polyethyleneimine microspheres were prepared by emulsion polymerization and mixed in a 1:1 mass ratio to produce mixed microspheres. Crosslinked wood particles and the mixed microspheres were mixed in a 100:7 mass ratio. The polyacrylic acid microspheres had a particle size of 80 nm, surface-containing -COOH functional groups at a -COOH concentration of 1.0 mmol / g. The polyethyleneimine microspheres had a particle size of 120 nm, surface-containing -NH2 functional groups at a -NH2 concentration of 1.5 mmol / g.

[0040] S4. Gradient pyrolysis-dynamic oxidation coupling: Under a nitrogen atmosphere, the temperature was increased at 5°C / min to 300°C and held for 1.0 h. An O2 / N2 mixture containing 5% O2 was then introduced at a flow rate of 0.3 L / min, with a 30-second aeration cycle every 10 min. The temperature was then increased at 10°C / min to 400°C and held for 1.0 h. After this, the mixture was switched to pure N2 and then heated to 500°C and held for 2 h to form a mesoporous structure. The temperature was then increased at 15°C / min to 600°C and held for 1 h to expand the microporous structure, resulting in pyrolytic carbon.

[0041] S5. Deep Activation: Mix choline oxalate and FeCl3 in a 9:1 mass ratio and stir at 80°C until a deep eutectic solvent is formed. Immerse the pyrolytic carbon in the deep eutectic solvent at a solid-to-liquid ratio of 1:3.0 g / mL. Ultrasonicate the carbon and filter and dry it to obtain the iron-doped deep eutectic solvent-activated porous carbon. Ultrasonication is performed at 80°C, with an ultrasonic power of 350 W and a frequency of 30 kHz for 2.0 h. After filtration, the carbon is dried at 120°C for 3 h. The choline oxalate is prepared by reacting choline chloride with oxalic acid in a 1:2 molar ratio.

[0042] S6. Post-treatment: The iron-doped deep eutectic solvent-activated porous carbon was immersed in a 5 wt% ethylenediamine ethanol solution at 60° C. for 2.0 h, filtered, and then vacuum-dried at 105° C. for 12.5 h to obtain activated biochar.

[0043] Example 3

[0044] A process for preparing activated biochar comprises the following steps:

[0045] S1. Raw material pretreatment: Collect fallen trees after the typhoon, remove impurities, and cut them into 5 cm wood segments; immerse the wood segments in a complex enzyme solution for shaking treatment, then use a crusher to crush the wood segments to a particle size of 3 mm, and dry them with hot air to a moisture content of 6% to obtain wood pellets. The fallen trees are selected from broad-leaved forests with a lignin content ≥25%. The time of falling is 21-30 days. The impurities removed include branches and leaves, sand and gravel, soil, metal foreign matter, and bark. The complex enzyme solution contains 6U / g lignin peroxidase and 12U / g xylanase, with a pH of 4.8. It is shaken at 50°C for 5 hours, and the hot air drying temperature is 85°C.

[0046] S2. Cross-linking and Strengthening Treatment: A cross-linking solution was prepared and the wood particles were immersed in the solution under vacuum at 85°C for 1.8 hours. The solution was then heated at 125°C for 2.5 hours to induce esterification and etherification reactions, resulting in cross-linked wood particles. The cross-linking solution contained 16 wt% glycerol, 12 wt% citric acid, 5.5 wt% tannic acid, and 0.6 wt% toluenesulfonic acid. The solid-to-liquid ratio (g / mL) of wood particles to cross-linking solution was 1:6.

[0047] S3. Polymer Microsphere Blending: Polyacrylic acid microspheres and polyethyleneimine microspheres were prepared by emulsion polymerization and mixed in a 1:1 mass ratio to produce mixed microspheres. Crosslinked wood particles and the mixed microspheres were mixed in a 100:10 mass ratio. The polyacrylic acid microspheres had a particle size of 100 nm, surface-containing -COOH functional groups at a -COOH concentration of 1.2 mmol / g. The polyethyleneimine microspheres had a particle size of 150 nm, surface-containing -NH2 functional groups at a -NH2 concentration of 1.8 mmol / g.

[0048] S4. Gradient pyrolysis-dynamic oxidation coupling: Under a nitrogen atmosphere, the temperature was increased at 5°C / min to 300°C and held for 1.1 hours. An O2 / N2 mixture containing 6% O2 was then introduced at a flow rate of 0.5 L / min, with a 30-second aeration cycle every 10 minutes. The temperature was then increased at 10°C / min to 400°C and held for 1.2 hours. After this, the mixture was switched to pure N2 and then heated to 500°C and held for 2 hours to form a mesoporous structure. The temperature was then increased at 15°C / min to 600°C and held for 1 hour to expand the microporous structure, resulting in pyrolytic carbon.

[0049] S5. Deep Activation: Mix choline oxalate and FeCl3 in a 10:1 mass ratio and stir at 85°C until a deep eutectic solvent is formed. Immerse the pyrolytic carbon in the deep eutectic solvent at a solid-to-liquid ratio of 1:3.5 g / mL. Ultrasonicate the carbon and filter and dry it to obtain the iron-doped deep eutectic solvent-activated porous carbon. Ultrasonication is performed at 90°C, with an ultrasonic power of 2500 W and an ultrasonic frequency of 40 kHz for 1.8 hours. After filtration, the carbon is dried at 130°C for 2 hours. The choline oxalate is prepared by reacting choline chloride with oxalic acid in a 1:2 molar ratio.

[0050] S6. Post-treatment: The iron-doped deep eutectic solvent-activated porous carbon was immersed in a 6 wt% ethylenediamine ethanol solution at 65° C. for 1.5 h, filtered, and then vacuum-dried at 110° C. for 10 h to obtain activated biochar.

[0051] Comparative Example 1

[0052] Compared with Example 2, this comparative example differs in that no complex enzyme solution is used for soaking in step S1.

[0053] Comparative Example 2

[0054] The difference between this comparative example and Example 2 is that no cross-linking solution is used for immersion, that is, step S3 is entered after step S1 is completed.

[0055] Comparative Example 3

[0056] The difference between this comparative example and Example 2 is that no polymer microspheres are used for blending, that is, step S4 is entered after step S2 is completed.

[0057] Comparative Example 4

[0058] Compared with Example 2, this comparative example differs in that step S4 is as follows: under a nitrogen atmosphere, the temperature is raised to 600° C. at a rate of 5° C. / min and kept at this temperature for 2.0 h to obtain pyrolytic carbon.

[0059] Comparative Example 5

[0060] The difference between this comparative example and Example 2 is that step S5 is not performed, that is, step S6 is entered after step S4 is completed.

[0061] Comparative Example 6

[0062] Compared with Example 2, this comparative example is different in that the biochar in this comparative example is commercially available.

[0063] Performance testing

[0064] 1.1 Detection of pore structure and surface functional group density

[0065] The total specific surface area of ​​the biochars prepared in Examples 1-3 and Comparative Examples 1-5 was measured using the BET specific surface area method, and the measurements were performed five times, with the average values ​​reported in Table 1. The functional group density of the biochars prepared in Examples 1-3 and Comparative Examples 1-5 was measured five times, with the average values ​​reported in Table 1.

[0066] Table 1

[0067]

[0068] 1.2 Adsorption capacity detection

[0069] Methylene blue was selected as the adsorption target at an initial concentration of 50 mg / L. Equal amounts of biochar prepared in Examples 1-3 and Comparative Examples 1-6 were used for adsorption in a 1 L volume at 2 g / L. Adsorption was performed for 24 hours. After adsorption, the concentration of methylene blue in the adsorbed solution was measured, and the adsorption rate was calculated. Five measurements were performed, and the average values ​​were recorded in Table 2. The adsorption rate was calculated using the following formula:

[0070] Where C0 is the initial concentration and C1 is the concentration after adsorption.

[0071] Table 2

[0072]

[0073] As can be seen from Table 1, the activated biochar prepared by the present invention has a rich pore structure and surface functional groups. Therefore, it has better adsorption performance, which can also be reflected from Table 2.

[0074] By comparing Example 2 with Comparative Example 1, the S1 step of Example 2 is soaked in a complex enzyme solution, in which the lignin peroxidase catalyzes the breaking of the β-O-4 bond in the lignin, decomposing the lignin macromolecules into oligomers or monomers. Xylanase hydrolyzes the xylan chains in the hemicellulose, destroying the cross-linked structure of the hemicellulose, lignin and cellulose. The degradation of lignin and hemicellulose exposes the cellulose skeleton, reducing the pore collapse caused by the rapid release of volatiles during pyrolysis, while reducing the coke residue during pyrolysis, avoiding pore blockage. In addition, after soaking in the complex enzyme solution, more active sites are exposed, which is conducive to the penetration of the subsequent cross-linking solution.

[0075] By comparing Example 2 with Comparative Example 2, the S2 step of Example 2 is soaked in a cross-linking solution to optimize the pore structure and surface chemical properties of the wood particles. The glycerol forms ether bonds with the cellulose hydroxyl groups to construct a flexible three-dimensional network, inhibiting subsequent pyrolysis shrinkage, thereby improving the macropore retention rate. The carboxyl group of citric acid esterifies with the phenolic hydroxyl group of lignin to generate a heat-stable cross-linking bridge, thereby increasing the subsequent mesopore volume. The pyrocatechol of tannic acid penetrates into the nanopores and is converted into a rigid carbon skeleton during subsequent pyrolysis, thereby improving the pore collapse resistance. Toluenesulfonic acid acts as a catalyst to promote the improvement of the cross-linking degree. Therefore, the cross-linked network constructed by soaking in a cross-linking solution pre-solidifies the carbon skeleton before pyrolysis, which can prevent the carbon skeleton from collapsing during pyrolysis, thereby retaining more mesopores and macropores. The ester bonds and ether bonds formed by the cross-linking reaction can enhance the mechanical strength of the carbon skeleton and avoid pore collapse caused by structural shrinkage during pyrolysis. The carboxyl and phenolic hydroxyl groups introduced by cross-linking react with Fe in S5. 3+ The formation of coordination bonds (Fe-OC) promotes uniform dispersion of Fe and prevents agglomeration. The carboxyl groups (-COOH) introduced by crosslinking can also strengthen the interfacial bonding with the -NH2 on the surface of the microspheres through hydrogen bonding, improving the uniformity of the blend.

[0076] By comparing Example 2 with Comparative Example 3, in step S3 of Example 2, polymer microspheres are used for blending. Polyacrylic acid microspheres and polyethyleneimine microspheres are thermally decomposed in step S4, releasing gases such as CO2, NH3, and H2O, forming nanoscale pores. The -COOH on the surface of the polyacrylic acid microspheres is partially converted into oxygen-containing functional groups such as imide (-CONH-) and carboxylate (COO-) during thermal decomposition. The -NH2 on the surface of the polyethyleneimine microspheres is thermally decomposed to form nitrogen-containing functional groups such as pyridine-N and pyrrole-N. The nitrogen-containing functional groups (-NH2, pyridine-N) react with Fe in S5. 3+ Form coordination bonds (Fe-N), promote uniform dispersion of Fe and avoid agglomeration.

[0077] Comparing Example 2 with Comparative Example 4, the S4 gradient pyrolysis-dynamic oxidation coupled process of Example 2, through staged temperature control and the introduction of dynamic oxidation, improved the pore richness and surface functional group density of the biochar compared to single nitrogen atmosphere pyrolysis. This is because the staged pyrolysis control enables the formation of multi-scale pores. The periodic introduction of oxygen introduces oxygen-containing functional groups (-COOH, -OH), enhancing surface activity.

[0078] Comparing Example 2 with Comparative Example 5, Example 2 shows that S5 was soaked in a deep eutectic solvent. The deep eutectic solvent molecules can dissolve ash or residual organic matter within the pores, reducing pore blockage. The polar environment of the deep eutectic solvent may promote the rearrangement of aromatization structures in the pyrolytic carbon, forming more micropores. Furthermore, soaking in the deep eutectic solvent further introduces oxygen-containing functional groups such as -COOH and -OH, while the iron species provide metal active sites, achieving acid-base and redox synergistic adsorption.

[0079] Comparing Example 2 with Comparative Example 6, the activated biochar produced by the present invention possesses both a rich pore structure and surface functional groups, resulting in higher adsorption performance compared to commercially available biochar. While the biochar produced in Comparative Example 6 possesses abundant pores, its low content of surface functional groups results in poor overall adsorption performance.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A process for preparing activated biochar, characterized in that: The following steps are involved: S1. Raw material pretreatment: Trees fallen after the typhoon were collected, impurities removed, and cut into wood segments ≤ 5 cm. The wood segments were immersed in a complex enzyme solution and shaken. The wood segments were then crushed using a grinder to a particle size of 1-3 mm. The wood segments were then dried with hot air to a moisture content of ≤ 10% to obtain wood pellets. S2. Crosslinking and strengthening treatment: Prepare a crosslinking solution, immerse the wood particles in the crosslinking solution, vacuum impregnate at 75-85°C for 1.8-2.2 hours, and then heat at 115-125°C for 2.5-3.5 hours to induce esterification and etherification reactions to obtain crosslinked wood particles; S3 polymer microsphere blending: polyacrylic acid microspheres and polyethyleneimine microspheres prepared by emulsion polymerization, mixed in a mass ratio of 1:1 to obtain mixed microspheres; cross-linked wood particles and mixed microspheres in a mass ratio of 100:4-10; S4. Gradient pyrolysis-dynamic oxidation coupling: Under a nitrogen atmosphere, the temperature was raised to 300°C at 5°C / min and held for 0.9-1.1 h. An O2 / N2 mixture containing 4-6% O2 was then introduced, and the temperature was raised to 400°C at 10°C / min and held for 0.8-1.2 h. After that, the mixture was switched to pure N2 and then raised to 500°C and held for 2 h to form a mesoporous structure. The temperature was then raised to 600°C at 15°C / min and held for 1 h to expand the microporous structure and obtain pyrolytic carbon. S5. Deep Activation: Choline oxalate and FeCl3 were mixed and stirred until a deep eutectic solvent was formed; the pyrolytic carbon was immersed in the deep eutectic solvent, ultrasonically shaken, and then filtered and dried to obtain iron-doped deep eutectic solvent-activated porous carbon; S6. Post-treatment: Immerse the iron-doped deep eutectic solvent-activated porous carbon in an ethylenediamine ethanol solution, filter, and vacuum dry to obtain activated biochar.

2. The process for preparing activated biochar according to claim 1, wherein: The fallen trees in S1 are selected from coniferous forests or broad-leaved forests with a lignin content of ≥25%, and the time of falling is ≤30 days. The impurities removed include branches and leaves, sand and gravel, soil, metal foreign matter, and bark.

3. The process for preparing activated biochar according to claim 1, wherein: The complex enzyme solution in S1 contains 4-6 U / g lignin peroxidase and 8-12 U / g xylanase, has a pH of 4.2-4.8, is shaken at 40-50° C. for 5-7 hours, and the hot air drying temperature is 75-85° C.

4. The process for preparing activated biochar according to claim 1, wherein: The cross-linking solution in S2 contains 14-16 wt% glycerol, 8-12 wt% citric acid, 4.5-5.5 wt% tannic acid, and 0.4-0.6 wt% toluenesulfonic acid. The solid-liquid ratio of the wood particles to the cross-linking solution is 1:4-6 g / mL.

5. The process for preparing activated biochar according to claim 1, wherein: The particle size of the polyacrylic acid microspheres in S3 is 50-100 nm, and the surface contains -COOH functional groups with -COOH≥0.8 mmol / g; the particle size of the polyethyleneimine microspheres is 80-150 nm, and the surface contains -NH2 functional groups with -NH2≥1.2 mmol / g.

6. The process for preparing activated biochar according to claim 1, wherein: The flow rate of the O2 / N2 mixed gas in S4 is 0.1-0.5 L / min, and the ventilation cycle is 30 seconds every 10 minutes.

7. The process for preparing activated biochar according to claim 1, wherein: The choline oxalate in S5 is prepared by reacting choline chloride and oxalic acid in a molar ratio of 1:

2. When choline oxalate is mixed with FeCl3, it is mixed in a mass ratio of 8-10:1 and stirred at 75-85°C to form a deep eutectic solvent; the solid-liquid ratio of the pyrolytic carbon to the deep eutectic solvent is 1:2.5-3.5 g / mL; the ultrasonic oscillation is carried out at 70-90°C, the ultrasonic power is 200-500W, the ultrasonic frequency is 20-40kHz, the ultrasonic oscillation is 1.8-2.2h, and after filtration, it is dried at 110-130°C for 2-4h.

8. The process for preparing activated biochar according to claim 1, wherein: The concentration of the ethylenediamine ethanol solution in S6 is 4-6 wt %, the treatment temperature is 55-65° C., the treatment time is 1.5-2.5 h, the drying temperature is 100-110° C., and the drying time is 10-15 h.

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