A method for phytoremediation of heavy metal containing biomass derived from a process

Abstract

This invention belongs to the field of environmental engineering technology, and specifically discloses a method for treating phytoremediation-derived biomass containing heavy metals. This method utilizes bone meal to immobilize heavy metals in the biomass through a co-hydrothermal process, controlling the leaching of Cd within a safe threshold range and Zn far below the safe threshold. This ensures that the resulting hydrothermal carbon composite material does not pose an ecological risk due to excessive heavy metal release. Furthermore, the hydrothermal carbon composite material obtained by this method possesses characteristics such as uniformity, porosity, and a large specific surface area, exhibiting excellent heavy metal adsorption capacity, thus enabling its reuse as a soil remediation agent. This method eliminates the need for separating heavy metals from the phytoremediation-derived biomass, is simple in process, and avoids problems such as acid washing wastewater pollution and treatment.

Description

Technical Field

[0001] This invention belongs to the field of environmental engineering technology, specifically, it relates to a method for treating heavy metal-containing biomass derived from phytoremediation. Background Technology

[0002] With the acceleration of industrialization and modernization, the situation of heavy metal pollution in soil is far from optimistic, and its remediation remains a top priority. The most common sources of heavy metal pollution in soil include cadmium, nickel, copper, arsenic, and lead. Traditional remediation technologies include physical remediation, chemical remediation, and bioremediation, among which phytoremediation has become the most popular technology in recent years.

[0003] Phytoremediation is a low-cost and effective remediation method. Its principle involves plants absorbing, extracting, and transferring heavy metals from the soil, accumulating them in their roots, stems, and leaves, thus achieving in-situ soil remediation. However, the residual biomass after remediation may contain large amounts of heavy metals, and improper handling can still cause secondary pollution.

[0004] Traditional methods for treating heavy metal-containing biomass derived from phytoremediation generally include incineration, landfill, and biogas fermentation. These methods have many problems, such as high energy consumption, easy pollution, and low energy utilization.

[0005] Current research includes techniques for converting heavy metal-containing biomass into porous biochar through preliminary carbonization followed by high-temperature carbonization with phosphoric acid, allowing for its reuse in soil remediation. However, this technology requires acid washing to remove heavy metals after obtaining the porous biochar, and precipitation of the acid washing solution to separate these heavy metals. Furthermore, the key to this technology's ability to reuse the obtained porous biochar for heavy metal contamination remediation lies in the fact that the heavy metals have already been separated and removed from the porous biochar, leaving it in a "heavy metal-free" state. Nevertheless, this technology suffers from complex processes and wastewater generation during acid washing due to the heavy metal separation operation.

[0006] Therefore, how to efficiently and rationally treat heavy metal-containing biomass derived from phytoremediation still requires further research. Summary of the Invention

[0007] To address the problems of complex processes and acid washing waste pollution associated with existing technologies that treat phytoremediation-derived heavy metal-containing biomass through carbonization and heavy metal separation, the inventors of this invention, based on long-term research on biomass, have proposed a novel method for treating phytoremediation-derived heavy metal-containing biomass. This method eliminates the need for heavy metal separation from the biomass, simplifies the process, and the resulting hydrothermal char can still be used as a soil / water remediation agent to treat heavy metal-contaminated soil / water bodies.

[0008] The present invention specifically adopts the following technical solution:

[0009] A method for treating phytoremediation-derived heavy metal-containing biomass, comprising the following steps:

[0010] Heavy metal-containing biomass and bone meal are mixed in a mass ratio of 0.1 to 5:1, and then mixed with 10 to 20 times the total mass of water. The mixture is subjected to a hydrothermal reaction at 120°C to 260°C for 60 to 150 minutes to obtain a hydrothermal carbon composite material.

[0011] Generally, a stirring rate of 180 rpm to 220 rpm is sufficient to ensure that the hydrothermal reaction proceeds fully.

[0012] Generally, the heating rate can be controlled at 3℃ / min to 5℃ / min.

[0013] Generally, after the hydrothermal reaction is complete, the temperature drops to room temperature within 60 to 120 minutes.

[0014] It should be noted that the ratios of the three raw materials required for the hydrothermal reaction above—heavy metal-containing biomass, bone meal, and water—refer to the proportions of their effective contents in the reaction system. If the heavy metal-containing biomass and / or bone meal contain some water, then the amount of water added should be reduced by this portion.

[0015] Generally, the first step is to test the moisture content of biomass and bone meal containing heavy metals in order to accurately determine the actual amount of biomass, bone meal, and added water used.

[0016] Heavy metal-containing biomass refers to the state of woody plant materials that have a certain ability to extract heavy metals after phytoremediation, in which heavy metals have been enriched. These woody plants are preferably Quercus texana, Salix willow, and Populus L.

[0017] Generally, bone meal comes from the waste bones produced after meat consumption.

[0018] Preferably, the bone meal is bovine bone meal, pork bone meal, sheep bone meal, or fish bone meal; more preferably, it is feed grade.

[0019] Generally, the particle size of biomass containing heavy metals and bone meal should be controlled between 40 and 100 mesh. If the particle size of the two sources is larger, appropriate grinding treatment can be carried out first.

[0020] The above-mentioned treatment method provided by the present invention, firstly, relies on the natural mineral components hydroxyapatite (Ca(PO4)6(OH)2), mineral elements, and a large amount of protein-derived organic matter contained in bone meal. These components react with heavy metals in biomass powder during hydrothermal processes through surface complexation (such as oxygen-containing groups, nitrogen-containing groups, etc.), cation exchange and precipitation (phosphate or carbonate), electrostatic attraction, and cation-π bonds. This process significantly immobilizes heavy metals during hydrothermal treatment, resulting in a Cd leaching amount of less than 0.50 mg·kg⁻¹. -1 The leaching amount of Zn is at most 10 mg / kg to 11 mg / kg, far below the safety threshold of 25 mg / kg. This ensures that the obtained hydrothermal carbon composite material does not pose an ecological risk due to excessive heavy metal leaching, which is also a prerequisite for the reuse of this hydrothermal carbon composite material. Secondly, bone meal and heavy metal-containing biomass undergo dehydration, decarboxylation, decomposition, and carbonization processes in the hydrothermal reaction. The resulting hydrothermal carbon composite material has characteristics such as uniformity, porosity, and large specific surface area, and has good heavy metal adsorption capacity, thus it can be used again as a soil / water remediation agent. Thirdly, this treatment method only requires one hydrothermal step to treat phytoremediation-derived heavy metal-containing biomass. The heavy metals contained therein do not need to be separated and precipitated by acid washing, which greatly simplifies the treatment process and does not generate waste acid or other waste, making it more environmentally friendly. Moreover, the co-hydrothermal carbonization technology also has advantages over other carbonization technologies, such as no dehydration required, low reaction temperature, simple operation, and higher carbon yield. Fourth, this treatment method can process large quantities of waste materials such as heavy metal-containing biomass derived from phytoremediation and waste bones generated after meat consumption, turning them into valuable resources and transforming them into safe, green, and reusable composite materials, which has extremely high application prospects. Fifth, this treatment method does not require pretreatment such as drying of heavy metal-containing biomass or bone meal, saving energy.

[0021] When the hydrothermal carbon composite material prepared by the processing method of this invention is applied to soil remediation, on the one hand, the nitrogen, phosphorus, calcium and other mineral elements in the bone meal can promote plant nutrient absorption and improve the rhizosphere environment; on the other hand, the porous structure of the hydrothermal carbon composite material itself is more conducive to the colonization and survival of microorganisms, and improves the physical properties of the soil, thus comprehensively enhancing soil fertility. Attached Figure Description

[0022] Figure 1This is a SEM image of the hydrothermal carbon composite material prepared by the processing method of Example 1 of the present invention;

[0023] Figure 2 This is a BET result diagram of the hydrothermal carbon composite material prepared by the processing method of Example 1 of the present invention;

[0024] Figure 3 The image shows the FTIR spectrum of the hydrothermal carbon composite material prepared by the processing method of Example 1 of the present invention.

[0025] Figure 4 The image shows the XRD pattern of the hydrothermal carbon composite material (BHM / BM) prepared by the processing method of Example 1 of the present invention.

[0026] Figure 5 The adsorption isotherm of Cd on the hydrothermal carbon composite material obtained by the processing method of Example 1 of the present invention is shown.

[0027] Figure 6 The adsorption isotherm of Zn on the hydrothermal carbon composite material obtained by the processing method of Embodiment 1 of the present invention is shown. Detailed Implementation

[0028] The following specific embodiments describe the method for treating phytoremediation-derived heavy metal-containing biomass provided by the present invention. However, those skilled in the art will understand that the following embodiments are merely specific examples of the present invention and are not intended to limit the scope thereof. Rather, these embodiments are provided to explain the principles of the present invention and its practical application, thereby enabling other those skilled in the art to understand the various embodiments of the present invention and various modifications suitable for specific intended applications.

[0029] Example 1

[0030] This embodiment provides a method for treating phytoremediation-derived heavy metal-containing biomass, which yields a hydrothermal carbon composite material via a co-hydrothermal method. The specific method is as follows:

[0031] First, the heavy metal-containing Norfolk oak is ground into powder of 40-100 mesh to obtain biomass powder, and bovine bone powder with a particle size of 40-100 mesh is weighed out.

[0032] Then, mix 1g of biomass powder and 5g of bovine bone powder evenly and add them to 100mL of deionized water. Place them together in a high-pressure stirred reactor and stir evenly. Set the heating rate to 5℃ / min. When the temperature reaches 260℃, keep it at a stirring rate of 180rpm~220rpm for 150min to carry out the hydrothermal reaction.

[0033] Finally, the hydrothermal product was cooled to room temperature within 120 minutes, filtered, and the filter residue was washed with water three times. The filter residue was then dried at 100°C for 24 hours to obtain the hydrothermal carbon composite material.

[0034] The hydrothermal carbon composite materials obtained by the above treatment methods were characterized by SEM, BET, FTIR, and XRD, respectively, as shown in the figures. Figures 1-4 As shown.

[0035] from Figure 1 As can be seen, the material composition after hydrothermal reaction treatment mainly consists of hydrothermal carbon components derived from biomass containing heavy metals and inorganic mineral components derived from bovine bone meal, and combined with... Figure 2 The BET test results of the hydrothermal carbon composite material (PB / BM) show that it has a porous structure, which is beneficial for the adsorption of heavy metals.

[0036] from Figure 3 As can be seen, the hydrothermal carbon composite material contains a large number of oxygen-containing functional groups. This feature plays a key role in the stabilization of heavy metals during the hydrothermal process and in the adsorption of heavy metals in the subsequent adsorption performance evaluation. It indicates that the product system is rich in performance characteristics that can stabilize the initial heavy metals and can subsequently re-adsorb heavy metals.

[0037] from Figure 4 It can be seen that the hydrothermal carbon composite material contains a large number of hydroxyapatite characteristic peaks, which is attributed to the characteristics of the raw material bovine bone meal. It can also be found that the heavy metals Cd and Zn originally present in the biomass ash during the hydrothermal process are fixed in the hydrothermal carbon composite material in the form of CdCO3 and Zn3(PO4)2, respectively. This indicates that Cd and Zn were successfully stabilized during the hydrothermal process.

[0038] The adsorption performance of the hydrothermal carbon composite material obtained in this embodiment was tested using batch adsorption experiments and adsorption isotherm analysis. Specifically, in the batch adsorption experiment, for the Cd adsorption performance test, solutions with Cd concentrations of 0, 0.1 mg / L, 1 mg / L, 5 mg / L, 15 mg / L, 25 mg / L, 50 mg / L, and 75 mg / L were used; for the Zn adsorption performance test, solutions with Zn concentrations of 0, 5 mg / L, 10 mg / L, 15 mg / L, 20 mg / L, 25 mg / L, 30 mg / L, 35 mg / L, 40 mg / L, and 100 mg / L were used. Furthermore, at the above initial concentrations, under the conditions of T = 298.15 K and pH = 6.0 ± 0.05, 2 g / L of hydrothermal carbon composite material was added, and the mixture was shaken in a horizontal shaker at 180 r / min for 24 h. After filtration with 0.45 μmol, the supernatant was used to determine the Cd and Zn concentrations using ICP-MS. e (Equilibrium adsorption capacity, mg / L) is the ordinate, Ce Adsorption isotherms were plotted at (solute equilibrium concentration, mg / L). The adsorption isotherms are shown below. Figure 5 and Figure 6 As shown. From Figure 5 and Figure 6 As can be seen, the hydrothermal carbon composite material still retains adsorption properties for Cd and Zn.

[0039] Example 2

[0040] First, the willow tree containing heavy metals is ground into powder of 40-100 mesh to obtain biomass powder, and pig bone powder with a particle size of 40-100 mesh is weighed out.

[0041] Then, mix 5g of biomass powder and 1g of pork bone powder evenly and add them to 200mL of water. Place them together in a high-pressure stirred reactor and stir evenly. Set the heating rate to 5℃ / min. When the temperature reaches 260℃, keep it at a stirring rate of 180rpm~220rpm for 150min to carry out the hydrothermal reaction.

[0042] Finally, the hydrothermal product was cooled to room temperature within 120 minutes, filtered, and the filter residue was washed with water three times. The filter residue was then dried at 100°C for 24 hours to obtain the hydrothermal carbon composite material.

[0043] Example 3

[0044] First, the heavy metal-containing Quercus nucifera is ground into powder of 40-100 mesh to obtain biomass powder, and sheep bone powder with a particle size of 40-100 mesh is weighed out.

[0045] Then, mix 5g of biomass powder and 10g of sheep bone powder evenly and add them to 150mL of water. Place them together in a high-pressure stirred reactor and stir evenly. Set the heating rate to 4℃ / min. When the temperature reaches 200℃, keep it at a stirring rate of 180rpm~220rpm for 90min to carry out the hydrothermal reaction.

[0046] Finally, the hydrothermal product was cooled to room temperature within 120 minutes, filtered, and the filter residue was washed with water three times. The filter residue was then dried at 100°C for 24 hours to obtain the hydrothermal carbon composite material.

[0047] Example 4

[0048] First, the poplar tree containing heavy metals is ground into powder of 40-100 mesh to obtain biomass powder, and fish bone powder with a particle size of 40-100 mesh is weighed out.

[0049] Then, mix 0.5g of biomass powder and 5g of fish bone powder evenly and add them to 55mL of water. Place them together in a high-pressure stirred reactor and stir evenly. Set the heating rate to 5℃ / min. When the temperature reaches 180℃, keep it at a stirring rate of 180rpm to 220rpm for 60min to carry out the hydrothermal reaction.

[0050] Finally, the hydrothermal product was cooled to room temperature within 120 minutes, filtered, and the filter residue was washed with water three times. The filter residue was then dried at 100°C for 24 hours to obtain the hydrothermal carbon composite material.

[0051] Example 5

[0052] The similarities between this embodiment and Embodiment 1 will not be repeated here; only the differences from Embodiment 1 will be described. The difference between this embodiment and Embodiment 1 is that the hydrothermal reaction temperature is 120°C; otherwise, it is the same as described in Embodiment 1, and a hydrothermal carbon composite material is obtained.

[0053] To verify the influence of the process method and process parameters in the above-mentioned treatment method of the present invention on the performance of the finally obtained hydrothermal carbon composite material, the following comparative experiments were conducted.

[0054] Comparative Example 1

[0055] The similarities between this comparative example and Example 1 will not be repeated here; only the differences from Example 1 will be described. The difference between this comparative example and Example 1 is that equal amounts of biomass powder and bovine bone powder were mixed evenly and then added to a tube furnace under a nitrogen atmosphere for pyrolysis. A heating rate of 5°C / min was set, and when the temperature reached 600°C, it was held for 150 minutes and then cooled to room temperature to obtain the pyrolyzed biochar composite material. In other words, this comparative example uses the same raw materials as in Example 1, but replaces them with a co-pyrolysis method to prepare the composite carbon material.

[0056] Comparative Example 2

[0057] The similarities between this comparative example and Example 1 will not be repeated here; only the differences from Example 1 will be described. The difference between this comparative example and Example 1 is that an equal mass of heavy metal-free *Quercus nucifera* was used as the biomass source; the rest is the same as described in Example 1, resulting in a comparative carbon composite material.

[0058] Comparative Example 3

[0059] The similarities between this comparative example and Example 1 will not be repeated here; only the differences from Example 1 will be described. The difference between this comparative example and Example 1 is that the hydrothermal reaction temperature was adjusted from 260°C to 300°C; otherwise, it is the same as described in Example 1, and a comparative carbon composite material was obtained.

[0060] Comparative Example 4

[0061] The similarities between this comparative example and Example 1 will not be repeated here; only the differences from Example 1 will be described. The difference between this comparative example and Example 1 is that the hydrothermal reaction temperature was adjusted from 260°C to 100°C; otherwise, it was the same as described in Example 1, and a comparative carbon composite material was obtained.

[0062] Comparative Example 5

[0063] The similarities between this comparative example and Example 1 will not be repeated here; only the differences from Example 1 will be described. The difference between this comparative example and Example 1 is that the heat preservation time was adjusted from 150 min to 300 min; otherwise, it was the same as described in Example 1, and a comparative carbon composite material was obtained.

[0064] Comparative Example 6

[0065] The similarities between this comparative example and Example 1 will not be repeated here; only the differences from Example 1 will be described. The difference between this comparative example and Example 1 is that the heat preservation time was adjusted from 150 min to 30 min; otherwise, it was the same as described in Example 1, and a comparative carbon composite material was obtained.

[0066] Comparative Example 7

[0067] The similarities between this comparative example and Example 1 will not be repeated here; only the differences from Example 1 will be described. The difference between this comparative example and Example 1 is that the amount of deionized water added for the hydrothermal reaction was adjusted from 100 mL to 300 mL; otherwise, it was the same as described in Example 1, and a comparative carbon composite material was obtained.

[0068] Comparative Example 8

[0069] The similarities between this comparative example and Example 1 will not be repeated here; only the differences from Example 1 will be described. The difference between this comparative example and Example 1 is that the amount of deionized water added for the hydrothermal reaction was adjusted from 100 mL to 50 mL; otherwise, it was the same as described in Example 1, and a hydrothermal carbon composite material was obtained.

[0070] Comparative Example 9

[0071] The similarities between this comparative example and Example 1 will not be repeated here; only the differences from Example 1 will be described. The difference between this comparative example and Example 1 is that the amount of biomass added (1g) and bone meal added (5g) was adjusted to 10g of biomass added and 1g of bone meal added; the rest is the same as described in Example 1, and a hydrothermal carbon composite material was obtained.

[0072] Comparative Example 10

[0073] The similarities between this comparative example and Example 1 will not be repeated here; only the differences from Example 1 will be described. The difference between this comparative example and Example 1 is that the amount of biomass added (1g) and bone meal added (5g) was adjusted to 1g of biomass added and 15g of bone meal added; the rest is the same as described in Example 1, and a hydrothermal carbon composite material was obtained.

[0074] It should be noted that, in the above embodiments and comparative examples provided by the present invention, in order to facilitate laboratory preservation, the heavy metal-containing biomass and bone meal used are all raw materials that are almost water-free. That is, the effective component content of each raw material is approximately equal to its actual usage.

[0075] However, the processing method provided by the present invention is not limited to this. In some schemes, if the biomass containing heavy metals and / or bone meal contains some moisture, there is no need to perform pretreatment such as drying. It is only necessary to determine its moisture content and then weigh the raw materials whose effective components meet the proportion range in the scheme of the present invention.

[0076] It should be noted that, in this invention, the first step in evaluating the performance of the hydrothermal carbon composite material obtained by the above treatment method is a safety assessment, specifically the stability of the heavy metals within it. Only if its heavy metal stability is excellent and it does not pose an environmental risk due to excessive release can it be considered that the treatment is appropriate. Based on this, its adsorption performance on heavy metals in soil or water when applied to soil remediation or water body remediation is then evaluated.

[0077] 1. The safety evaluation method specifically adopts the TCLP (Toxicity Characteristic Leaching Procedure), the standard toxicity leaching method recommended by the U.S. Environmental Protection Agency.

[0078] The specific method is as follows: Prepare the extraction solution (glacial acetic acid solution with pH 2.88 ± 0.05). The ratio (sample mass / extraction solution volume) of the carbon composite material sample obtained in each example and comparative example to the extraction solution is 1 / 20. Shake at 30 rpm at room temperature for 18 hours. After completion, let stand for 30 minutes, filter the supernatant using a 0.45 μm filter membrane, and test the heavy metal concentration using ICP-MS. The heavy metal leaching thresholds for solid waste are Cd: 0.5 mg / kg and Zn: 25 mg / kg.

[0079] 2. Heavy metal samples were collected using a heavy metal absorption device and then analyzed using ICP-OES. Specific methods can be found in reference 1 (Xiao et al., 2018. DOI: 10.1016 / j.cej.2018.04.133). The vapor above the reaction system in each of the above embodiments and comparative examples was monitored during the preparation process to assess the risk of heavy metal gaseous escape.

[0080] 3. The adsorption performance of the carbon composite materials obtained in the above examples and comparative examples for heavy metals was tested using batch adsorption experiments and adsorption isotherm methods.

[0081] The safety evaluation results of the hydrothermal carbon composite materials of Examples 1 to 5 and the comparative carbon composite materials of Comparative Examples 1 to 10 are shown in Table 1 below.

[0082] Table 1. Safety evaluation results of the hydrothermal carbon composite materials of Examples 1-5 and the comparative carbon composite materials of Comparative Examples 1-10.

[0083]

[0084]

[0085] The monitoring results of heavy metal gaseous emission of the hydrothermal carbon composite materials of Examples 1 to 5 and the comparative carbon composite materials of Comparative Examples 1 to 10 are shown in Table 2 below.

[0086] Table 2. Heavy metal leaching monitoring results of hydrothermal carbon composite materials from Examples 1 to 5 and comparative carbon composite materials from Comparative Examples 1 to 10.

[0087]

[0088]

[0089] The adsorption performance of heavy metals on the hydrothermal carbon composite materials of Examples 1 to 5 and the comparative carbon composite materials of Comparative Examples 1 to 10 is shown in Table 3 below.

[0090] Table 3 shows the adsorption performance of heavy metals on the hydrothermal carbon composite materials of Examples 1-5 and the comparative carbon composite materials of Comparative Examples 1-10.

[0091]

[0092] As shown in Tables 1-3 above, the hydrothermal carbon composite material obtained by the processing method provided in each embodiment of the present invention can firstly fix the heavy metals in the raw material—heavy metal-containing biomass. Its fixation efficiency for Cd ensures that the leaching amount meets the threshold requirement of 0.5 mg / kg, while the fixation efficiency for Zn ensures that the leaching amount is only 10 mg / kg to 11 mg / kg at most, which is far below the threshold requirement of 25 mg / kg. The heavy metal fixation effect is excellent, preventing it from flowing into the environment and causing safety risks. Secondly, the prepared hydrothermal carbon composite material still has the ability to adsorb heavy metals and can be put back into the soil or water body to adsorb the heavy metals therein.

[0093] Specifically, in Comparative Example 1, the conventional composite material preparation method of co-pyrolysis was used to treat biomass and bone meal containing heavy metals. It was found that due to the generally high pyrolysis temperature, heavy metals were released in a gaseous state, which inevitably caused environmental pollution. This method did not fundamentally solve the problem of secondary pollution caused by heavy metals in the biomass after phytoremediation.

[0094] By comparing the adsorption performance of hydrothermal carbon composite materials for heavy metals obtained from heavy metal-containing biomass and heavy metal-free biomass under the same process in Example 1 and Comparative Example 2, it can be seen that in the embodiments of the present invention, although the raw materials contain some heavy metals, they have been mainly fixed through the action of bone meal, and the re-adsorption capacity of the final hydrothermal carbon composite material for heavy metals is not severely degraded. The reason for this is mainly that the heavy metals in the heavy metal-containing biomass are primarily fixed by the action of bone meal, while the re-adsorption capacity of the obtained hydrothermal carbon composite material mainly depends on the carbonization products of the biomass. Therefore, the inherent heavy metals in the raw materials do not fundamentally affect its re-adsorption performance.

[0095] By comparing Examples 3 and 4 with Example 1, it can be seen that excessively high or low hydrothermal temperatures cannot simultaneously satisfy the fixation of Cd and Zn and the good adsorption capacity. The main reason is that if the hydrothermal temperature is too low, the degree of hydrolysis and carbonization will be reduced, and effective groups will not be formed to fix Cd and Zn. On the other hand, excessively high temperatures may cause some heavy metal gases to escape.

[0096] By comparing Comparative Examples 5 and 6 with Example 1, it can be seen that excessively long heat preservation time will cause the fixed Cd and Zn to become unstable, increasing the risk of secondary pollution of heavy metals; while shorter heat preservation time will also lead to insufficient reaction and affect the leaching amount of Cd and Zn, which will still increase the risk of secondary pollution of heavy metals.

[0097] By comparing Examples 7 and 8 with Example 1, it can be seen that during the co-hydrothermal reaction, a higher water content leads to a greater degree of hydrolysis and an increase in the amount of H in the system. + Increased water content is detrimental to the fixation of Cd and Zn; while lower water content leads to insufficient hydrothermal reaction and cannot effectively fix Cd and Zn.

[0098] By comparing Examples 9 and 10 with Example 1, it can be seen that a smaller material ratio leads to a dilution of heavy metal concentrations that cannot be specifically analyzed; a higher material composition results in fewer effective components in the bone meal, thereby reducing the fixation rate of Cd and Zn.

[0099] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for treating phytoremediation-derived heavy metal-containing biomass, characterized in that, Including the following steps: Heavy metal-containing biomass and bone meal are mixed in a mass ratio of 0.1 to 5:1, and then mixed with water at a mass ratio of 10 to 20 times the total mass of the heavy metal-containing biomass and bone meal. The mixture is subjected to a hydrothermal reaction at 120°C to 260°C for 60 to 150 minutes to obtain a hydrothermal carbon composite material.

2. The processing method according to claim 1, characterized in that, The heavy metal-containing biomass refers to woody plants containing heavy metals derived from phytoremediation.

3. The processing method according to claim 2, characterized in that, The woody plant is selected from any one of the following: Quercus nucifera, willow, and poplar, or a mixture of at least two of them.

4. The processing method according to claim 1, characterized in that, The bone meal is selected from any one of beef bone meal, pork bone meal, sheep bone meal, and fish bone meal, or a mixture of at least two of them.

5. The processing method according to any one of claims 1 to 4, characterized in that, The hydrothermal reaction was carried out at a stirring rate of 180 rpm to 220 rpm.

6. The processing method according to any one of claims 1 to 4, characterized in that, The particle size of both the heavy metal-containing biomass and the bone meal is 40 mesh to 100 mesh.

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