A preparation method and application of a biomass-derived carbon material for absorbing heavy metal ions from soil

Abstract

The present application relates to the field of soil purification and hydrogen energy technology, and specifically relates to a preparation method of biomass-derived carbon material for absorbing heavy metal ions from soil, comprising the following steps: S1, transplanting plants in soil contaminated by heavy metals, and obtaining plants containing heavy metal ions after normal planting and cultivation for two months; S2, cleaning and freeze-drying the plants containing heavy metal ions to obtain dried plants retaining original tissue structure; S3, calcining the freeze-dried plants retaining original tissue structure, and obtaining carbonized biomass-derived carbon material after cooling. The present application innovates the method for obtaining biomass-derived carbon material, and the preparation process is simple. When the biomass-derived carbon material is used as a catalyst for alkaline water electrolysis hydrogen production, it shows a low hydrogen evolution overpotential. Meanwhile, the biomass-derived carbon material proposed can purify soil and realize high-value utilization of biomass resources in the field of new energy, showing good innovation.

Description

Technical Field

[0001] This invention relates to the fields of soil purification and hydrogen energy technology, specifically to a method for preparing and applying biomass-derived carbon materials that absorb heavy metal ions from soil. Background Technology

[0002] Heavy metal pollution mainly includes the contamination of soil by heavy metals and their compounds. This pollution is caused by the use of fertilizers, electronic waste, pesticides, herbicides, and industrial waste treatment. It is estimated that more than 50,000 sites covering approximately 200,000 hectares worldwide are affected by heavy metal pollution. With continuous social development, strong industrialization and urbanization, and rising living standards, the intensity of heavy metal pollution in soil is escalating. Traditional heavy metal contaminated soil remediation technologies have mitigated heavy metal pollution in soil to some extent, but they have significant drawbacks. In addition, traditional methods often cannot completely extract metals tightly bound to the soil matrix. The removal of pollutants may require the extraction of large amounts of soil, resulting in a reduction of land available for agriculture or other purposes. These methods are often time-consuming, and the management and remediation processes of contaminated soil may pose health risks to workers.

[0003] Currently, hydrogen energy is widely recognized as a green and clean energy source for the 21st century and an ideal energy alternative due to its wide availability, high heat release during combustion, and the fact that its combustion product is water, which is non-toxic and has high energy density. Among all hydrogen production methods, water electrolysis has attracted widespread attention due to its advantages such as high product purity, high efficiency, and environmental friendliness. However, in practice, a relatively high voltage (usually >1.8V) is required to overcome the activation barrier of the electrolysis reaction. The two-electron transfer in the cathodic hydrogen evolution reaction (HER) and four-electron coupled anodic oxygen evolution reaction (OER) pathways leads to a large overpotential and greatly reduces the kinetics of water electrolysis. Therefore, in order to reduce the activation energy of HER and OER and minimize the overpotential to improve energy conversion efficiency, highly efficient electrocatalysts must be used. Currently, Pt is the most ideal catalyst for HER, but the scarcity and high cost of precious metal Pt-based materials limit their large-scale application. Biomass-based carbon, on the other hand, has attracted great interest and widespread application due to its environmental friendliness, unique structural characteristics, and high stability. Biomass, as a naturally abundant renewable resource with diverse structures, is an alternative sustainable source.

[0004] The actual annual crop yield is approximately 14.6 billion tons, and the amount of domestic or livestock waste is approximately 10 billion tons. This biomass is usually discarded or directly incinerated, causing pollution and urgent environmental problems, and resulting in low energy efficiency.

[0005] In conclusion, developing a method for preparing and applying biomass-derived carbon materials that absorb heavy metal ions from soil remains a critical issue that urgently needs to be addressed in the fields of soil remediation and hydrogen energy technology. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of this invention is to provide a method for preparing and applying biomass-derived carbon materials that absorb heavy metal ions from soil.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for preparing biomass-derived carbon materials that absorb heavy metal ions from soil includes the following steps:

[0009] S1. Transplant the plants into soil contaminated with heavy metals and cultivate them normally for two months to obtain plants containing heavy metal ions.

[0010] S2. The plants containing heavy metal ions are cleaned and freeze-dried to obtain dried plants that retain their original tissue structure.

[0011] S3. Calcining the freeze-dried plants while preserving their original tissue structure, and then cooling them, yields carbonized biomass-derived carbon materials.

[0012] The present invention is further configured such that, in step S1, the plant is one of the following: Sedum aizoon, lettuce, spinach, leek, and rapeseed.

[0013] The present invention is further configured such that, in step S1, the soil contaminated with heavy metals is mainly soil contaminated by one or more of Cd ions, Cr ions, Pb ions, Cu ions, and Ni ions, and the heavy metal ion pollution level in the soil is 1–1000 mg·kg⁻¹. －1 Preferably 1–200 mg·kg －1 .

[0014] The present invention is further configured such that, in step S2, before freeze-drying the plants containing heavy metal ions, the plants containing heavy metal ions need to be washed three times with deionized water.

[0015] The present invention is further configured such that, in step S2, the freeze-drying temperature is -45 to -55°C, the vacuum pressure is 5 to 10 Pa, and the freeze-drying time is 24 to 72 h.

[0016] The present invention is further configured such that: in step S3, the calcination temperature is 400℃~700℃, the heating rate is 5℃ / min, and the calcination time is 120min.

[0017] A method for preparing biomass-derived carbon materials that absorb heavy metal ions from soil yields biomass-derived carbon materials, including Sedum aizoon-derived carbon materials, lettuce-derived carbon materials, spinach-derived carbon materials, leek-derived carbon materials, and rapeseed-derived carbon materials.

[0018] The present invention is further configured such that the biomass-derived carbon material can be used in alkaline water electrolysis for hydrogen production.

[0019] Beneficial effects

[0020] Compared with known public technologies, the technical solution provided by this invention has the following advantages:

[0021] Beneficial effects:

[0022] (1) Compared with the prior art, the present invention provides a method for preparing and applying biomass-derived carbon materials that absorb heavy metal ions from soil. The present invention prepares biomass-derived carbon materials by planting plants in soil contaminated with heavy metals, allowing the plants to absorb heavy metal ions from the soil, and then freeze-drying and calcining the plants that have absorbed heavy metals. The method for obtaining biomass-derived carbon materials is innovative and the preparation process is simple. When this biomass-derived carbon material is used as an alkaline water electrolysis hydrogen production catalyst, it exhibits a low hydrogen evolution overpotential.

[0023] (2) The biomass-derived carbon material proposed in this invention purifies the soil and processes plants that have absorbed heavy metal ions to obtain biomass-derived carbon material. Biomass resources are not only reused, but when this biomass-derived carbon material is used as an alkaline water electrolysis hydrogen production catalyst, it also shows good performance in the field of water electrolysis hydrogen production. It provides an important reference for the high-value utilization of biomass resources in the new energy field and shows good innovation. Attached Figure Description

[0024] Figure 1 This is the basic preparation process of the bio-derived carbon materials in this invention;

[0025] Figure 2 This is an optical photograph of *Sedum aizoon* cultivated in heavy metal-contaminated soil for two months in Example 1 of this invention.

[0026] Figure 3 An optical photograph of Sedum aizoon after freeze-drying in Example 1 of this invention;

[0027] Figure 4 An optical photograph of Sedum morganianum after carbonization in Example 1 of this invention;

[0028] Figure 5 This is a SEM image of the Southeast Sedum after carbonization in this invention;

[0029] Figure 6 This is a SEM image and elemental distribution diagram of the carbon material derived from Sedum aizoon in this invention;

[0030] Figure 7 This is an optical photograph of lettuce grown in heavy metal-contaminated soil for two months in Example 2 of this invention;

[0031] Figure 8 An optical photograph of the freeze-dried lettuce in Example 2 of this invention;

[0032] Figure 9 This is an optical photograph of the carbonized lettuce in Example 2 of this invention;

[0033] Figure 10 This is a SEM image of the carbonized lettuce used in this invention;

[0034] Figure 11 This is a SEM image and elemental distribution diagram of the lettuce-derived carbon material in this invention;

[0035] Figure 12 This is an optical photograph of chives grown in heavy metal-contaminated soil for two months in Example 3 of this invention;

[0036] Figure 13 This is a SEM image and elemental distribution diagram of the chive-derived carbon material in this invention;

[0037] Figure 14 This is a graph showing the overpotential test results of alkaline water hydrogen production using biomass-derived carbon materials in this invention. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0039] The present invention will be further described below with reference to embodiments.

[0040] Example 1

[0041] Please refer to Figures 1-14 As shown, a method for preparing biomass-derived carbon materials that absorb heavy metal ions from soil includes the following steps:

[0042] Step 1: Transplant the Sedum aizoon into soil contaminated with Cd ions, where the Cd ion concentration is 150 mg / kg. -1After two months of normal watering and cultivation, Sedum aizoon containing heavy metal Cd ions was obtained and kept for later use.

[0043] Step 2: Wash the obtained Sedum aizoon with deionized water. After washing, freeze dry it in a freeze dryer at -50°C and 8Pa pressure for 48 hours to obtain dried Sedum aizoon with its original tissue structure intact.

[0044] Step 3: Place the freeze-dried Sedum aizoon in a tube furnace and heat it to 600°C at a heating rate of 5°C / min under the protection of inert gas Ar and hold it at that temperature for 2 hours. After cooling with the furnace, carbonized Sedum aizoon-derived carbon material is obtained for later use.

[0045] In this embodiment, the Southeast Sedum at each stage is as follows: Figure 2-4 As shown, Figure 2 and Figure 3 The images show Sedum aizoon after being cultivated in soil containing heavy metal Cd ions for two months and after freeze-drying. The comparison clearly shows that the freeze-dried Sedum aizoon retained its original tissue structure and morphology. Because freeze-drying preserves the original microstructure, it effectively retains the absorbed heavy metal Cd ions within the plant tissue. Figure 4 After high-temperature calcination under inert gas protection, *Sedum aizoon* is clearly completely carbonized into a black color. After thorough grinding, a fine powder is obtained. Subsequent microscopic morphology and structural analysis were performed. Figure 5 It can be seen that the Sedum aizoon-derived carbon material prepared in Example 1 consists of loose micron-sized particles, and the material is very rough, thus possessing a high specific surface area. Figure 6 SEM images and energy dispersive spectroscopy analysis showed that C and Cd elements were uniformly distributed in the Sedum aizoon-derived carbon material, indicating that Sedum aizoon absorbed a large amount of Cd elements from the soil, confirming the presence of Cd elements. After freeze-drying and carbonization, the Cd elements were loaded into the carbon matrix. The prepared Sedum aizoon-derived carbon material will be used as a catalyst material in electrocatalytic water splitting.

[0046] Example 2

[0047] Please refer to Figures 1-14 As shown, a method for preparing biomass-derived carbon materials that absorb heavy metal ions from soil includes the following steps:

[0048] Step 1: Transplant the lettuce into soil contaminated with Cu ions, where the Cu ion concentration is 60 mg / kg. -1 After two months of normal watering and cultivation, lettuce containing heavy metal Cu ions was obtained and put into use.

[0049] Step 2: Wash the lettuce obtained above with deionized water, and then freeze-dry it in a freeze dryer at -50℃ and 8Pa pressure for 72 hours to obtain lettuce that retains its original tissue structure.

[0050] Step 3: Place the freeze-dried lettuce in a tube furnace and heat it to 550°C at a heating rate of 5°C / min under the protection of inert gas Ar and hold it at that temperature for 4 hours. After cooling with the furnace, carbonized lettuce-derived carbon material is obtained for later use.

[0051] In this embodiment, lettuce at each stage, such as Figures 7-9 As shown, Figure 7 and Figure 8 The photos show lettuce grown in soil containing heavy metal copper ions for two months and lettuce after freeze-drying. Figure 9 (a) shows the carbonized lettuce before grinding, and (b) shows the carbonized lettuce after grinding. By comparison, it can be clearly seen that the lettuce retains its original tissue structure and morphology after freeze-drying. Because freeze-drying can preserve the original microstructure, it can effectively retain the absorbed heavy metal Cu ions in the plant tissue structure. Figure 4 Lettuce calcined at high temperature under inert gas protection is clearly visibly carbonized into a black color. After thorough grinding, it yields a fine powder, which is then analyzed for its microstructure and structure. Figure 10 It can be seen that the lettuce-derived carbon material prepared in Example 2 is in the form of rods and granules. Figure 11 SEM images and energy dispersive spectroscopy analysis showed that C and Cu elements were uniformly distributed in the lettuce-derived carbon material, indicating that lettuce absorbed Cu elements from the soil, confirming the presence of Cu elements. After freeze-drying and carbonization, Cu elements were loaded into the carbon matrix. The prepared lettuce-derived carbon material will be used as a catalyst material in electrocatalytic water splitting.

[0052] Example 3

[0053] Please refer to Figures 1-14 As shown, a method for preparing biomass-derived carbon materials that absorb heavy metal ions from soil includes the following steps:

[0054] Step 1: Transplant the chives into soil contaminated with Pb ions, where the concentration of Pb ions in the soil is 45 mg / kg. -1 After two months of normal watering and cultivation, chives containing heavy metal Pb ions were obtained and put into use.

[0055] Step 2: Wash the chives obtained above with deionized water, and then freeze-dry them in a freeze dryer at -50℃ and 8Pa pressure for 36 hours to obtain dried chives that retain their original tissue structure.

[0056] Step 3: Place the freeze-dried chives in a tube furnace and heat them to 500°C at a heating rate of 10°C / min under the protection of inert gas Ar. Hold the temperature for 6 hours. After cooling with the furnace, carbonized chive-derived carbon material is obtained for later use.

[0057] In this embodiment, Figure 12 These are photos of lettuce grown in soil containing heavy metal copper ions for two months. Figure 13 It can be seen that the leek-derived carbon material prepared in Example 3 is a micron-sized sheet-like particle. SEM energy dispersive spectroscopy analysis shows that C and Pd elements are uniformly distributed in the lettuce-derived carbon material, indicating that the lettuce has absorbed Pd elements from the soil. The prepared leek-derived carbon material will be used as a catalyst material in electrocatalytic water splitting.

[0058] In summary, the morphological and elemental analyses of the biomass-derived carbon materials in Examples 1-3 demonstrate that the biomass plants have the ability to absorb heavy metal ions from heavy metal-contaminated soil, providing feasibility for the purification of heavy metal-contaminated soil. Furthermore, freeze-drying the plants preserves their original microstructure, and carbonization yields biomass carbon materials with different microstructures, providing feasibility for the application of biomass-derived carbon materials in the new energy field.

[0059] Comparative Example 1

[0060] Please refer to Figures 1-14 As shown, a method for preparing biomass-derived carbon materials that absorb heavy metal ions from soil is generally the same as that in Example 1. The main difference is that Sedum aizoon is directly cultivated in soil without heavy metal pollution and then processed through the same process as in Example 1 to obtain a comparative sample of Sedum aizoon-derived carbon materials.

[0061] Comparative Example 2

[0062] Please refer to Figures 1-14 As shown, a method for preparing biomass-derived carbon materials that absorb heavy metal ions from soil is generally the same as that in Example 2. The main difference is that lettuce is directly cultivated in soil without heavy metal pollution and then processed through the same process as in Example 2 to obtain a comparative sample of lettuce-derived carbon materials.

[0063] Comparative Example 3

[0064] Please refer to Figures 1-14As shown, a method for preparing biomass-derived carbon materials that absorb heavy metal ions from soil is generally the same as that in Example 3. The main difference is that chives are directly cultivated in soil without heavy metal pollution and then processed through the same process as in Example 3 to obtain a chive-derived carbon material comparison sample.

[0065] Tests and experiments:

[0066] The alkaline water hydrogen production performance of biomass-derived carbon materials was analyzed using a CHI760E electrochemical workstation from Shanghai Chenhua Instruments Co., Ltd. A three-electrode system was employed, with a graphite rod as the counter electrode, an Hg / HgO electrode as the reference electrode, and the working electrode prepared by ultrasonically dropping a mixture of biomass-derived carbon materials obtained in Examples 1-3 and Comparative Examples 1-3 onto nickel foam in a mixture of Nafion solution and ethanol. The electrolyte was a 1.0 M KOH solution, and the test temperature was room temperature. Linear sweep voltammetry (LSV) was used for measurement at 2 mV / s. -1 The scanning rate was used to perform overpotential tests on alkaline water hydrogen production using different biomass-derived carbon materials at different current densities. (See attached data). Figure 14 See Table 1.

[0067] Table 1: Overpotential of Alkaline Hydrogen Production from Biomass-Derived Carbon Materials

[0068]

[0069] As shown in Table 1, a comparison of the hydrogen evolution performance data of alkaline water electrolysis in Examples 1-3 and Comparative Examples 1-3 reveals that the hydrogen evolution performance of the biomass-derived carbon materials prepared in Examples 1-3 of this invention is significantly better than that of the respective biomass-derived carbon materials in Comparative Examples 1-3. Specifically, the Sedum aizoon-derived carbon material in Example 1, under a current density of -10 mA / cm², exhibits significantly better hydrogen evolution performance in water electrolysis. -2 At that time, the overpotential was 174.2V, which showed good hydrogen evolution performance.

[0070] This invention involves planting plants in heavy metal-contaminated soil, allowing the plants to absorb heavy metal ions from the soil. The plants, having absorbed the heavy metals, are then freeze-dried and calcined to produce biomass-derived carbon material. This innovative method for obtaining biomass-derived carbon material is simple to implement. When used as a catalyst in alkaline water electrolysis for hydrogen production, this biomass-derived carbon material exhibits a low hydrogen evolution overpotential. This invention not only purifies the soil but also processes plants that have absorbed heavy metal ions to obtain biomass-derived carbon material. This not only achieves the reuse of biomass resources (solving the pollution and pressing environmental problems caused by the usual disposal or direct incineration of biomass in existing technologies, and improving energy efficiency), but also demonstrates good performance (low hydrogen evolution overpotential) when used as a catalyst in alkaline water electrolysis for hydrogen production. This provides important insights for the high-value utilization of biomass resources in the new energy field and demonstrates significant innovation.

[0071] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or basic characteristics. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all changes falling within the meaning and scope of the equivalents of the claims are intended to be included within the scope of the invention. Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing biomass-derived carbon materials that absorb heavy metal ions from soil, characterized in that, Includes the following steps: S1. Transplanting plants into soil contaminated with heavy metals and cultivating them normally for two months yields plants containing heavy metal ions; the plants are one of the following: Sedum aizoon, lettuce, spinach, leek, or rapeseed; the soil contaminated with heavy metals is mainly contaminated with one or more of the following ions: Cd, Cr, Pb, Cu, and Ni, and the heavy metal ion contamination level in the soil is 1–1000 mg / kg. －1 ; S2. The plants containing heavy metal ions are cleaned and freeze-dried to obtain dried plants that retain their original tissue structure. Before freeze-drying the plants containing heavy metal ions, they need to be cleaned three times with deionized water. The freeze-drying temperature is -45~-55℃, the vacuum pressure is 5~10Pa, and the freeze-drying time is 24~72h. S3. The freeze-dried plants, retaining their original tissue structure, are calcined and cooled to obtain carbonized biomass-derived carbon materials; the calcination temperature is 400℃~700℃, the heating rate is 5℃ / min, and the calcination time is 120min.

2. The method for preparing biomass-derived carbon materials that absorb heavy metal ions from soil according to claim 1, characterized in that, Including carbon materials derived from Sedum aizoon, lettuce, spinach, leek, and rapeseed; The biomass-derived carbon material is used in alkaline water electrolysis for hydrogen production.

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