Preparation method of magnetic hydrothermal biochar-based heavy metal adsorption material

Abstract

This invention provides a method for preparing a magnetic hydrothermal biochar-based heavy metal adsorbent material, belonging to the field of environmental functional materials technology. It selects inexpensive, renewable, and easily modifiable natural biomass as raw material, and obtains a magnetic porous carbon framework through one-step hydrothermal carbonization. Then, epoxy groups are introduced using green electron beam radiation grafting technology. Finally, high-density amino functional groups are grafted onto the surface of the magnetic hydrothermal biochar through a dual-amino synergistic ring-opening reaction involving small-molecule polyamines with any one of ethylenediamine (EDA), triethylenetetramine (TETA), polyethyleneimine (PEI), and diethylenetriamine (DETA). The prepared adsorbent material possesses high adsorption capacity, rapid adsorption kinetics, and convenient magnetic separation and recovery performance, effectively solving the bottleneck problems of insufficient adsorption performance and difficulty in recovery of existing biomass adsorbents.

Description

Technical Field

[0001] This invention relates to the field of environmental functional materials technology, and in particular to a method for preparing a magnetic hydrothermal biochar-based heavy metal adsorbent material. Background Technology

[0002] With the rapid development of modern industry, heavy metal pollution has become a major problem threatening the ecological environment and human health. Hexavalent chromium Cr(VI) has the characteristics of high toxicity, strong oxidizing properties, easy migration and difficulty in natural degradation. It is listed as a Group 1 carcinogen by the International Agency for Research on Cancer and is widely found in industrial wastewater such as electroplating, leather making and dyeing. Adsorption technology is regarded as one of the treatment methods with the greatest potential for engineering application due to its simple operation, low energy consumption and high treatment efficiency. Current research faces multiple challenges: (1) Insufficient adsorption efficiency and selectivity: Traditional adsorbents (such as activated carbon and natural minerals) generally have problems such as limited specific surface area and single active sites, resulting in low adsorption capacity and slow adsorption rate for Cr(VI); (2) Biomass-based materials rely solely on physical pore adsorption when unmodified, making it difficult to accurately capture anionic Cr(VI), with a fast adsorption saturation rate and low compliance rate; (3) Difficult material recovery: Traditional powder or block biochar is difficult to separate from water bodies quickly after adsorption, which can easily cause secondary pollution. In addition, it lacks magnetic response performance and cannot achieve convenient magnetic separation and recovery.

[0003] Currently, both domestically and internationally, surface modification of biochar is mainly achieved through methods such as chemical cross-linking or coating. Methods for preparing hydroxyapatite-modified loofah-based heavy metal adsorbent materials include: a method for preparing loofah-based magnetic adsorbent materials (CN201510086076.5); a method for preparing magnetic egg white / loofah adsorbent materials (CN202210854421.5); and a method for preparing magnetic egg white / loofah adsorbent materials (CN201610142259.9). While these technologies improve the adsorption performance of biomass materials to some extent, they also suffer from problems such as complex preparation methods, the need for chemical initiators, and difficulty in large-scale production. More importantly, existing biomass adsorbents generally lack efficient magnetic separation capabilities, requiring centrifugation or filtration after adsorption saturation, resulting in high energy consumption and cumbersome operation. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a method for preparing a dual-amino-modified magnetic hydrothermal bamboo charcoal-based adsorbent material using bamboo powder as raw material. This method involves hydrothermal carbonization, magnetization, and a combination of electron beam radiation grafting and ring-opening techniques. The application of this material in the treatment and adsorption separation of wastewater containing high-valence heavy metals is explored.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing magnetic hydrothermal biochar-based heavy metal adsorbent materials.

[0006] 1. Preparation of magnetic hydrothermal biochar First, natural biomass materials, such as bamboo powder, loofah sponge, corn cob, and osmanthus, are collected and ground into powder. 200-mesh sieves are used to obtain 10 g of the above biomass powder, which is then mixed with ethylene glycol at an appropriate ratio (1 / 6~1 / 8, g / mL). The mixture is magnetically stirred for 30 min to form suspension A. 5~8 g of FeCl3·6H2O and 15~20 g of anhydrous sodium acetate are dissolved in 100~150 mL of ethylene glycol and sonicated to form solution B. Solution A is quickly poured into suspension B, and the mixture is magnetically stirred for 30 min to obtain a homogeneous mixture. Then, the solution is transferred to a 500 mL high-temperature, high-pressure reactor. The reactor is placed in an electrically heated constant-temperature drying oven, and the temperature is adjusted to 150~200 ℃ for 10~15 h. After the reaction, the mixture is washed with ultrapure water and dried in a vacuum drying oven at 60 ℃ for 5 h to obtain magnetic hydrothermal biochar.

[0007] 2. Preparation of magnetic hydrothermal biochar radiation-grafted GMA The magnetic hydrothermal biochar was dried at 60–100 °C for 3–6 hours. 0.5–2.0 g of the dried magnetic hydrothermal biochar was accurately weighed into a polyethylene bag and vacuum-sealed. A 30%–40% (w / w) glycidyl methacrylate (GMA) methanol solution was prepared and purged with nitrogen for 10–30 minutes to remove dissolved oxygen. The GMA solution was injected into the polyethylene bag containing the magnetic hydrothermal biochar, heat-sealed, and then subjected to electron beam irradiation grafting at an electron accelerator. Irradiation conditions: radiation dose rate 20 kGy / pass, total absorbed dose 100–200 kGy. After irradiation, the biochar was filtered under reduced pressure, repeatedly washed with methanol and deionized water, and dried at 60–80 °C to constant weight to obtain PGMA-g-magnetic hydrothermal biochar.

[0008] 3. Preparation of dual-amino modified bamboo powder adsorbent materials First, take 1.0 g of PGMA-g-magnetic hydrothermal biochar sample into a 100 mL three-necked flask, add 50 mL of ultrapure water, and add an aqueous solution containing 2.5–4.5 mL of ethylenediamine. Stir at 60–80 °C for 30–60 min. Then, using a syringe, add 10–20 mL of any one of triethylenetetramine (TETA), polyethyleneimine (PEI), or diethylenetriamine (DETA) at a rate of 10 mL / min to the three-necked flask, and continue stirring for 5–8 h. Wash the crude product with deionized water and anhydrous ethanol until neutral, and dry at 80 °C for 5–8 h. Finally, filter to obtain the diamine-modified magnetic hydrothermal biochar adsorbent material.

[0009] Compared with the prior art, the present invention has the following advantages: This invention selects inexpensive, renewable, and easily modifiable natural biomass as raw material. A magnetic porous carbon framework is obtained through one-step hydrothermal carbonization. Then, epoxy groups are introduced using green electron beam radiation grafting technology. Finally, high-density amino functional groups are grafted onto the surface of the magnetic hydrothermal bamboo charcoal through a dual-amine synergistic ring-opening reaction involving any of the following small-molecule polyamines: ethylenediamine (EDA), triethylenetetramine (TETA), polyethyleneimine (PEI), and diethylenetriamine (DETA). The prepared adsorbent material possesses high adsorption capacity, rapid adsorption kinetics, and convenient magnetic separation and recovery performance, effectively solving the bottleneck problems of insufficient adsorption performance and difficulty in recovery of existing biomass adsorbents.

[0010] 2. This invention uses natural biomass as raw material, which is widely available, inexpensive and readily available, realizing the resource utilization of agricultural and forestry waste, and has important significance in being green, low-carbon and sustainable; 3. This invention combines hydrothermal carbonization and magnetization processes to endow biomass materials with excellent superparamagnetic properties (saturation magnetization intensity can reach 30-60 emu / g). After adsorption saturation, solid-liquid separation can be achieved quickly by applying an external magnetic field, avoiding the high energy consumption of centrifugation or filtration and significantly reducing recycling costs. 4. This invention uses electron beam radiation grafting technology, which can complete the grafting polymerization of GMA on the surface of magnetic hydrothermal bamboo charcoal in one step at room temperature and pressure. No chemical initiator needs to be added, avoiding the problems of initiator residue and secondary pollution in traditional chemical grafting methods. It has outstanding advantages such as simple operation, strong controllability, low energy consumption, and green environmental protection.

[0011] 5. This invention introduces a high density of amino active sites on the surface of bamboo charcoal through a dual-amino synergistic modification strategy using EDA and polyamine compounds (such as triethylenetetramine (TETA), polyethyleneimine (PEI), diethylenetriamine (DETA), etc.). EDS and XPS test results show that the nitrogen content on the surface of the dual-amino modified adsorbent material can reach 8.11%, which is much higher than that of the single-amino modified material.

[0012] 6. The adsorbent materials prepared by this invention exhibit excellent adsorption performance for Cr(VI). Static adsorption experiments show that, under the conditions of pH=2 and 298.15 K, the maximum adsorption capacity of one of the dual-amino modified magnetic hydrothermal carbon composite materials for Cr(VI) can reach 438.1 mg / g, which is much higher than that of unmodified hydrothermal bamboo charcoal (46.5 mg / g) and single GMA grafted intermediate (40.9 mg / g). 7. The adsorbent material prepared by this invention has rapid adsorption kinetics characteristics. Most pollutants are rapidly adsorbed within 60 minutes and adsorption equilibrium is reached within 240 minutes. The adsorption behavior conforms to the pseudo-second-order kinetic model (R²>0.999), indicating that chemisorption is the dominant process. 8. The adsorbent material prepared by this invention has good regeneration and reuse performance. After 5 adsorption-desorption cycles, the removal rate of Cr(VI) can still be maintained at more than 75%, which has good economic value. Attached Figure Description

[0013] Figure 1 This is a synthetic route diagram for PEI / EDA-g-PGMA-MBC.

[0014] Figure 2 This is the synthetic route diagram for DETA / EDA-g-PGMA-MBC.

[0015] Figure 3 SEM images of MBC (Figures (a), (b) and (c)) and DETA / EDA-g-PGMA-MBC (Figures (d), (e) and (f)).

[0016] Figure 4 The effect of pH on the adsorption capacity of TETA / EDA-g-PGMA-MGC.

[0017] Figure 5 The effect of time on the adsorption performance of Cr(VI) and the linear fitting of pseudo-first-order and pseudo-second-order kinetics (TETA / EDA-g-PGMA-MGC). Detailed Implementation

[0018] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0019] Example 1: (1) Pass bamboo powder through a 200-mesh sieve, take 10 g of bamboo powder and mix with 80 mL of ethylene glycol, stir magnetically for 30 minutes to form suspension A. (2) Dissolve 6.75 g of FeCl3·6H2O and 18.0 g of anhydrous sodium acetate in 150 mL of ethylene glycol, and sonicate to form solution B. (3) Pour solution A into suspension B, sonicate for 30 minutes, put the mixture into a high-temperature and high-pressure reactor, and hydrothermally react at 180 °C for 12 hours. After cooling, collect the product with a magnet, wash with ethanol, and vacuum dry at 60 °C for 12 hours to obtain magnetic hydrothermal bamboo charcoal (labeled as: MBC). (4) Accurately weigh 1.0 g of MBC into a PE bag and vacuum seal it. Prepare a 30% GMA methanol solution and purge with nitrogen for 15 minutes. 100 mL of GMA solution was injected, and after heat sealing, it was irradiated under an electron accelerator at a radiation dose rate of 20 kGy / pass and a total dose of 160 kGy. After irradiation, the solution was filtered under reduced pressure, washed repeatedly with methanol and deionized water, and dried at 60 °C to obtain PGMA-g-MBC. (5) 1.0 g of PGMA-g-MBC was placed in a three-necked flask, 50 mL of ultrapure water was added, and 4.5 mL of ethylenediamine aqueous solution was added. The mixture was stirred at 60 °C for 1 h, and 10.0 mL of polyethyleneimine (molecular weight 1800) solution was injected at a rate of 10 mL / min. The mixture was stirred at 60 °C for 5 h. After the reaction, the mixture was washed with deionized water and anhydrous ethanol until neutral and dried at 80 °C for 5 h to obtain PEI / EDA-g-PGMA-MBC. The synthesis route is shown in the figure. Figure 1 As shown. (6) Take 20 mL of Cr(VI) solution (200 mg / L), add 20 mg of adsorbent, adjust pH=2 with 0.1 M HCl, and shake in a constant temperature water bath shaker at 25 ℃ for 24 hours. (7) Take the supernatant and filter it through a 0.45 μm filter membrane. Use the diphenylcarbazide colorimetric method to determine the absorbance at 543 nm and calculate the adsorption amount. It was determined that the adsorption amount of Cr(VI) by PEI / EDA-g-PGMA-MBC was 385.6 mg / g.

[0020] Example 2: (1) Pass the loofah powder through a 200-mesh sieve, take 10 g of loofah powder and mix it with 60 mL of ethylene glycol, stir magnetically for 30 minutes to form suspension A. (2) Dissolve 6.0 g of FeCl3·6H2O and 20.0 g of anhydrous sodium acetate in 100 mL of ethylene glycol, and sonicate to form solution B. (3) Pour solution A into suspension B, sonicate for 30 minutes, put the mixture into a high-temperature and high-pressure reactor, and hydrothermally react at 200 °C for 12 hours. After cooling, collect the product with a magnet, wash with ethanol, and vacuum dry at 60 °C for 12 hours to obtain magnetic hydrothermal loofah charcoal (labeled as: MLC). (4) Accurately weigh 1.0 g of MLC into a PE bag and vacuum seal it. Prepare a 40% GMA methanol solution and purge with nitrogen for 30 minutes. 100 mL of GMA solution was injected, and after heat sealing, it was irradiated under an electron accelerator at a radiation dose rate of 20 kGy / pass and a total dose of 200 kGy. After irradiation, the solution was filtered under reduced pressure, washed repeatedly with methanol and deionized water, and dried at 60 °C to obtain PGMA-g-MLC. (5) 1.0 g of PGMA-g-MLC was placed in a three-necked flask, 50 mL of ultrapure water was added, and 3.0 mL of ethylenediamine aqueous solution was added. The mixture was stirred at 80 °C for 30 min, and 10.0 mL of diethylenetriamine (DETA) solution was injected at a rate of 10 mL / min. The mixture was stirred at 80 °C for 8 hours. After the reaction, the mixture was washed with deionized water and anhydrous ethanol until neutral and dried at 80 °C for 5 h to obtain DETA / EDA-g-PGMA-MLC. (6) Take 10 mL of Cr(VI) solution (200 mg / L), add 20 mg of adsorbent, adjust the pH to 2 with 0.1 M HCl, and shake in a constant temperature water bath shaker at 25 ℃ for 24 hours. (7) Filter the supernatant through a 0.45 μm filter membrane, and measure the absorbance at 543 nm using the diphenylcarbazide colorimetric method to calculate the adsorption amount. The adsorption amount of Cr(VI) by PEI / EDA-g-PGMA-MLC was determined to be 243.3 mg / g.

[0021] Example 3: (1) Pass osmanthus powder through a 200-mesh sieve, take 10 g of osmanthus powder and mix with 70 mL of ethylene glycol, stir magnetically for 30 minutes to form suspension A. (2) Dissolve 5.0 g of FeCl3·6H2O and 15.0 g of anhydrous sodium acetate in 120 mL of ethylene glycol, and sonicate to form solution B. (3) Pour solution A into suspension B, sonicate for 30 minutes, put the mixture into a high-temperature and high-pressure reactor, and hydrothermally react at 200 °C for 10 hours. After cooling, collect the product with a magnet, wash with ethanol, and vacuum dry at 60 °C for 12 hours to obtain magnetic hydrothermal osmanthus char (labeled as: MGC). (4) Accurately weigh 1.0 g of MGC into a PE bag and vacuum seal it. Prepare a 30% GMA methanol solution and purge with nitrogen for 30 minutes. 100 mL of GMA solution was injected, and after heat sealing, it was irradiated under an electron accelerator at a radiation dose rate of 20 kGy / pass and a total dose of 180 kGy. After irradiation, the solution was filtered under reduced pressure, washed repeatedly with methanol and deionized water, and dried at 60 °C to obtain PGMA-g-MGC. (5) 1.0 g of PGMA-g-MGC was placed in a three-necked flask, 50 mL of ultrapure water was added, and 2.5 mL of ethylenediamine aqueous solution was added. 15.0 mL of triethylenetetramine (TETA) was injected at a rate of 10 mL / min, and the mixture was stirred at 60 °C for 8 hours. After the reaction, the mixture was washed with deionized water and anhydrous ethanol until neutral, and dried at 80 °C for 5 h to obtain TETA / EDA-g-PGMA-MGC. The synthesis route is shown in the figure. Figure 2 As shown. (6) Take 20 mL of Cr(VI) solution (200 mg / L), add 20 mg of adsorbent, adjust pH=2 with 0.1M HCl, and shake in a constant temperature water bath shaker at 25 ℃ for 24 hours. (7) Take the supernatant and filter it through a 0.45 μm filter membrane. Use the diphenylcarbazide colorimetric method to determine the absorbance at 543 nm and calculate the adsorption amount. It was determined that the adsorption amount of Cr(VI) by TETA / EDA-g-PGMA-MGC was 195.6 mg / g.

[0022] Example 4: (1) Pass corn cobs through a 200-mesh sieve, take 10 g of bamboo powder and mix with 80 mL of ethylene glycol, stir magnetically for 30 minutes to form suspension A. (2) Dissolve 6.75 g of FeCl3·6H2O and 20.0 g of anhydrous sodium acetate in 150 mL of ethylene glycol, and sonicate to form solution B. (3) Pour solution A into suspension B, sonicate for 30 minutes, load the mixture into a high-temperature and high-pressure reactor, and hydrothermally react at 200°C for 10 hours. After cooling, collect the product with a magnet, wash with ethanol, and vacuum dry at 60°C for 12 hours to obtain magnetic hydrothermal corn char (labeled as: MYC). (4) Accurately weigh 1.0 g of MYC into a PE bag and vacuum seal it. Prepare a 30% GMA methanol solution and purge with nitrogen for 15 minutes. Inject 100 mL of GMA solution, heat seal, and irradiate under an electron accelerator with a radiation dose rate of 20 kGy / pass and a total dose of 160 kGy. After irradiation, the sample was filtered under reduced pressure, washed repeatedly with methanol and deionized water, and dried at 60°C to obtain PGMA-g-MYC. (5) 1.0 g of PGMA-g-MYC was placed in a three-necked flask, 50 mL of ultrapure water was added, and 4.5 mL of ethylenediamine aqueous solution was added. 20.0 mL of polyethyleneimine (molecular weight 1800) solution was injected at a rate of 10 mL / min, and the mixture was stirred at 60°C for 8 hours. After the reaction, the sample was washed with deionized water and anhydrous ethanol until neutral, and dried at 80°C for 5 h to obtain PEI / EDA-g-PGMA-MYC. (6) 20 mL of Cr(VI) solution (200 mg / L) was taken, 20 mg of adsorbent was added, the pH was adjusted to 2 with 0.1 M HCl, and the sample was shaken in a constant temperature water bath shaker at 25°C for 24 hours. (7) The supernatant was filtered through a 0.45 μm filter membrane, and the absorbance was measured at 543 nm using the diphenylcarbazide colorimetric method to calculate the adsorption amount. The adsorption amount of Cr(VI) by PEI / EDA-g-PGMA-MYC was determined to be 307.3 mg / g.

[0023] Example 5: (1) Bamboo powder was passed through a 200-mesh sieve. 10 g of bamboo powder was mixed with 60 mL of ethylene glycol and magnetically stirred for 30 minutes to form suspension A. (2) 7.25 g of FeCl3·6H2O and 17.5 g of anhydrous sodium acetate were dissolved in 120 mL of ethylene glycol and ultrasonically treated to form solution B. (3) Solution A was poured into suspension B and ultrasonically treated for 30 minutes. The mixture was then placed in a high-temperature and high-pressure reactor and hydrothermally reacted at 200°C for 12 hours. After cooling, the product was collected with a magnet, washed with ethanol, and vacuum dried at 60°C for 12 hours to obtain magnetic hydrothermal bamboo charcoal (labeled as: MBC). (4) 1.0 g of MBC was accurately weighed into a PE bag and vacuum sealed. A 40% GMA methanol solution was prepared and nitrogen gas was passed through for 15 minutes. 100 mL of GMA solution was injected, and after heat sealing, the bag was irradiated under an electron accelerator with a radiation dose rate of 20 kGy / pass and a total dose of 180 kGy. After irradiation, the sample was filtered under reduced pressure, washed repeatedly with methanol and deionized water, and dried at 60°C to obtain PGMA-g-MBC. (5) 1.0 g of PGMA-g-MBC was placed in a three-necked flask, 50 mL of ultrapure water was added, and 4.5 mL of ethylenediamine aqueous solution was added. The mixture was stirred at 70°C for 30 min. 10.0 mL of diethylenetriamine (DETA) solution was injected at a rate of 10 mL / min, and the mixture was stirred at 70°C for 5 hours. After the reaction, the sample was washed with deionized water and anhydrous ethanol until neutral, and dried at 80°C for 5 h to obtain DETA / EDA-g-PGMA-MBC. (6) 20 mL of Cr(VI) solution (200 mg / L) was taken, 20 mg of adsorbent was added, the pH was adjusted to 2 with 0.1 MHCl, and the mixture was shaken in a constant temperature water bath shaker at 25°C for 24 hours. (7) The supernatant was filtered through a 0.45 μm filter membrane, and the absorbance was measured at 543 nm using the diphenylcarbazide colorimetric method. The adsorption amount was calculated. The adsorption amount of DETA / EDA-g-PGMA-MBC for Cr(VI) was determined to be 423.7 mg / g.

[0024] SEM images of unmodified magnetic hydrothermal bamboo charcoal (MBC) are shown below. Figure 3 As shown in (a), (b), and (c), the SEM images of DETA / EDA-g-PGMA-MBC obtained by this method are as follows: Figure 3 As shown in (d), (e), and (f).

[0025] from Figure 4 Static adsorption experimental data showed that, under the conditions of pH=2 and 298.15 K, the maximum adsorption capacity of one of the dual-amino modified magnetic hydrothermal carbon composite materials for Cr(VI) reached 438.1 mg / g, which was much higher than that of unmodified hydrothermal bamboo charcoal (46.5 mg / g) and single GMA grafting intermediate (40.9 mg / g).

[0026] Figure 5 It can be seen that most pollutants are rapidly adsorbed within 60 minutes and adsorption equilibrium is reached within 240 minutes. The adsorption behavior conforms to the pseudo-second-order kinetic model (R²>0.999), indicating that chemical adsorption is dominant. The adsorbent material has good regeneration and reuse performance. After 5 adsorption-desorption cycles, the removal rate of Cr(VI) can still be maintained above 75%, which has good economic value.

[0027] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for preparing a magnetic hydrothermal biochar-based heavy metal adsorbent material, characterized in that, Includes the following steps: (1) Preparation of magnetic hydrothermal biochar: Natural biomass was ground into powder, sieved, and the biomass powder was mixed with ethylene glycol at a ratio of (1 / 6~1 / 8) g / mL. The mixture was magnetically stirred for 30 min to form suspension A. 5~8 g FeCl3·6H2O and 15~20 g anhydrous sodium acetate were dissolved in 100~150 mL of ethylene glycol and ultrasonically treated to form solution B. Solution A was poured into solution B and magnetically stirred for 30 min to obtain a homogeneous mixture. The mixture was transferred to a high-temperature and high-pressure reactor and reacted in an electric thermostatic drying oven at 150~200℃ for 10~15 h. After the reaction, the mixture was washed with ultrapure water and vacuum dried at 60℃ for 5 h to obtain magnetic hydrothermal biochar. (2) Preparation of magnetic hydrothermal biochar irradiated with GMA: The magnetic hydrothermal biochar was dried at 60-100℃ for 3-6 h; 0.5-2.0 g of dried magnetic hydrothermal biochar was weighed and placed into a polyethylene bag and vacuum sealed; a 30%-40% mass fraction glycidyl methacrylate (GMA) methanol solution was prepared and purged with nitrogen for 10-30 min to remove oxygen; the GMA solution was injected into the polyethylene bag, heat-sealed, and then irradiated with electron beam under an electron accelerator with a radiation dose rate of 20 kGy / pass and a total absorbed dose of 100-200 kGy; after irradiation, the bag was filtered under reduced pressure, washed repeatedly with methanol and deionized water, and dried at 60-80℃ to constant weight to obtain PGMA-g-magnetic hydrothermal biochar. (3) Preparation of bisamine-modified adsorbent material: 1.0 g of PGMA-g-magnetic hydrothermal biochar was placed in a three-necked flask, 50 mL of ultrapure water was added, and 2.5-4.5 mL of ethylenediamine aqueous solution was added. The mixture was stirred at 60-80 °C for 30-60 min. 10-20 mL of any one of triethylenetetramine (TETA), polyethyleneimine (PEI), or diethylenetriamine (DETA) was added to the three-necked flask at a rate of 10 mL / min. The mixture was stirred and reacted for 5-8 h. The crude product was washed with deionized water and anhydrous ethanol until neutral, dried at 80 °C for 5-8 h, and filtered to obtain bisamine-modified magnetic hydrothermal biochar adsorbent material.

2. The preparation method of a magnetic hydrothermal biochar-based heavy metal adsorbent material according to claim 1, characterized in that, The natural biomass is one of bamboo powder, loofah sponge, corn cob or osmanthus, and is screened to obtain 200-mesh powder, with a dosage of 10g.

3. The method for preparing a magnetic hydrothermal biochar-based heavy metal adsorbent material according to claim 1, characterized in that, The prepared dual-amino modified magnetic hydrothermal biochar adsorbent material is applied to the treatment and adsorption separation of wastewater containing high-valence heavy metals.

4. The method for preparing a magnetic hydrothermal biochar-based heavy metal adsorbent material according to claim 1, characterized in that, The magnetic hydrothermal biochar has a saturation magnetization of 30–60 emu / g and exhibits superparamagnetic properties. After adsorption saturation, it can achieve rapid solid-liquid separation by applying an external magnetic field.

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