Modified biochar material for repairing copper-polluted planting soil and preparation method of modified biochar material

Abstract

The invention discloses a modified biochar material for repairing copper-polluted planting soil and a preparation method of the modified biochar material, and belongs to the technical field of ecological restoration. The preparation method comprises the following steps: firstly, cleaning, drying and crushing tobacco straws, pyrolyzing at 600 DEG C, cooling, soaking in a 0.1 mol / L HCl solution overnight, carrying out suction filtration, washing, and drying to obtain original biochar; ball-milling the original biochar, uniformly mixing with 0.5 mol / L of MgCl2 solution, drying, carrying out secondary pyrolysis and cooling to obtain the magnesium chloride modified biochar, and carrying out ball-milling treatment to obtain a final product. The biochar material subjected to magnesium chloride and ball milling treatment is rich in pore structure, and the chelating ability with copper ions is enhanced, so that the bio-availability of the copper ions in the soil is reduced, the soil quality is improved, plant growth is promoted, and the biochar material is suitable for large-scale application in copper-contaminated soil remediation.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ecological restoration, and particularly relates to a modified biochar material for restoring copper-polluted planting soil and a preparation method thereof. BACKGROUND

[0002] Copper is an essential micronutrient for plants, but in recent years, due to human activities such as irrigation with contaminated river water, air pollution caused by mining, and improper use of copper-based agricultural chemicals, the concentration of copper in the soil has accumulated significantly, far exceeding the natural background value. Excessive copper not only seriously affects crop yields, but also poses a threat to public health through the food chain. Therefore, it is imperative to take effective measures to reduce the transfer of copper from the soil to plants.

[0003] Biochar is a low-cost potential adsorbent with high negative charge density, large specific surface area, and abundant surface functional groups. It can change the distribution of heavy metals in the soil through various mechanisms such as electrostatic attraction, ion exchange, precipitation, and complexation, reducing their mobility and bioavailability. In addition, the alkalinity of biochar can increase the soil pH, thereby inhibiting the dissolution of heavy metals such as cadmium and mercury. Its porous structure also provides a suitable habitat for soil microorganisms, enhancing microbial activity and soil fertility. Tobacco straw, as an abundant biomass waste, can be used as a raw material for biochar after carbonization. Tobacco straw biochar can effectively restore contaminated soil and support sustainable agricultural development. Meanwhile, by modifying biochar with MgCl2, metal oxide MgO can be introduced onto its surface, which helps to form complexes with metal cations through lone pair electrons. In addition, Mg 2+ can exchange with divalent metal cations to immobilize heavy metals. Currently, MgCl2-modified biochar can effectively remove Pb(II), Cr(VI), As(II), and Cu(II) from water bodies. However, the immobilization effect of MgCl2-modified biochar on copper in soil and its mechanism still need further research. SUMMARY

[0004] The present application proposes a modified biochar material for restoring copper-polluted planting soil and a preparation method thereof, aiming to effectively reduce copper pollution in the soil, reduce the migration and accumulation of heavy metals to crops, and thus reduce the potential risks to human health caused by excessive heavy metals in crops.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0006] Technical purpose one: a preparation method of a modified biochar material, comprising the following steps:

[0007] The process of washing, drying, crushing, pyrolyzing, and soaking tobacco straw in acid yields raw biochar.

[0008] The original biochar was mixed with magnesium chloride solution, dried, and then pyrolyzed a second time to obtain magnesium chloride modified biochar.

[0009] The obtained magnesium chloride-modified biochar was ball-milled to obtain modified biochar material.

[0010] This invention uses waste tobacco straw from the field as raw material, combined with magnesium chloride and ball milling modification, which increases the pH and surface roughness of the biochar, forming a richer pore structure. Simultaneously, the magnesium chloride modification process introduces Mg-O bonds into the biochar surface, increasing the number of surface functional groups such as -OH, -COOH, and CO, thereby significantly enhancing the adsorption capacity of copper ions.

[0011] Tobacco straw, a waste product of the tobacco industry, is abundant and easy to collect. As a biomass feedstock, tobacco straw has a higher content of nutrients such as nitrogen, phosphorus, and potassium compared to wheat and corn straw, especially nitrogen, giving it higher nutritional value among biomass feedstocks. Nicotine and other nitrogen-containing compounds in tobacco straw decompose at high temperatures to generate pyridine nitrogen, pyrrole nitrogen, and graphitic nitrogen, providing additional complexing sites for copper ion adsorption, thus significantly enhancing its chemisorption capacity. Furthermore, tobacco straw is rich in alkaline metal oxides such as potassium, calcium, and magnesium; these minerals further improve the removal efficiency of copper ions through chemical fixation. Its high organic carbon, cellulose, and lignin content, as well as low ash content, contribute to improved thermal stability of biochar, resulting in a larger specific surface area and rich pore structure, thereby significantly enhancing adsorption capacity. Therefore, biochar prepared from tobacco straw exhibits excellent performance in remediating contaminated soil and provides an important pathway for promoting sustainable agricultural development.

[0012] Furthermore, the parameters for both pyrolysis processes were: nitrogen atmosphere, nitrogen flow rate 0.2 L / min, heating rate 10 °C / min, temperature 600 °C, and time 120 min.

[0013] Furthermore, the acid soaking refers to soaking in a 0.1 mol / L HCl solution overnight.

[0014] Furthermore, the parameters for the ball milling process are: ball-to-material ratio of 100:1, rotation speed of 500 rpm, and ball milling time of 1 hour.

[0015] Furthermore, the ratio of ball-milled modified biochar to magnesium chloride solution is 1g:12mL, and the concentration of magnesium chloride solution is 0.5mol / L.

[0016] Furthermore, the parameters for the mixing process are: time 12h, temperature 25℃, and rotation speed 500rpm.

[0017] Technical objective 2: A modified biochar material prepared using the above preparation method.

[0018] Technical objective three: Application of a modified biochar material in the remediation of copper-contaminated planting soil.

[0019] Furthermore, the modified biochar material is applied to copper-contaminated soil at a mass ratio of 0.5%, wherein the concentration of copper ions in the soil is 600 mg / kg.

[0020] Compared with the prior art, the present invention has the following advantages and technical effects:

[0021] This invention modifies biochar by using magnesium chloride and ball milling. The resulting modified biochar material has a rich pore structure and enhanced chelation ability with copper ions (II), thereby reducing the bioavailability of copper ions in the soil, improving soil quality and promoting plant growth.

[0022] This invention applies modified biochar material to the remediation of copper-contaminated tobacco soil. Pot experiments show that after applying the modified biochar, not only was the available copper content in the soil and the copper content in tobacco plants significantly reduced, but the soil nutrient content was also increased, soil quality was improved, and the adverse effects of copper pollution on the soil were effectively reduced.

[0023] The modified biochar material provided by this invention can efficiently remediate copper-contaminated soil. The raw material is waste tobacco straw from farmland, and the preparation process is simple and easy to operate. This material demonstrates advantages of high efficiency and low cost in addressing soil copper pollution, while simultaneously realizing the resource utilization of biomass solid waste. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0025] Figure 1 Scanning electron microscope (SEM) images and EDS elemental maps of the original biochar, magnesium chloride-modified biochar, ball-milled magnesium chloride-modified biochar in Example 1, and ball-milled modified biochar in Comparative Example 1.

[0026] Figure 2 The infrared spectra of the original biochar, magnesium chloride-modified biochar, and ball-milled magnesium chloride-modified biochar in Example 1, and the ball-milled modified biochar in Comparative Example 1 are shown.

[0027] Figure 3XPS images of the original biochar, magnesium chloride-modified biochar, and ball-milled magnesium chloride-modified biochar in Example 1, and the ball-milled modified biochar in Comparative Example 1.

[0028] Figure 4 The images show the XRD patterns of the original biochar, magnesium chloride-modified biochar, and ball-milled magnesium chloride-modified biochar in Example 1, as well as the ball-milled modified biochar in Comparative Example 1.

[0029] Figure 5 To investigate the effects of applying different types of biochar materials on tobacco growth in copper-contaminated soil. Detailed Implementation

[0030] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0031] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0032] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0033] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0034] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0035] This invention provides a method for preparing modified biochar material. First, tobacco straw is washed, dried, and pulverized, then pyrolyzed at 600℃ and cooled. Next, it is soaked overnight in a 0.1 mol / L HCl solution, filtered, washed, and dried to obtain raw biochar. The obtained raw biochar is mixed with a 0.5 mol / L MgCl2 solution, dried, and then subjected to a second pyrolysis and cooling to obtain magnesium chloride-modified biochar. This modified biochar is then ball-milled to obtain the final product. The biochar material treated with magnesium chloride and ball milling has a rich pore structure and enhanced chelation ability with copper (II) ions, thereby reducing the bioavailability of copper ions in the soil, improving soil quality, and promoting plant growth. This material has superior performance, is easy to operate, is natural and environmentally friendly, and has low cost, making it suitable for large-scale application in the remediation of copper-contaminated soil.

[0036] In one specific embodiment, a method for preparing a modified biochar material includes the following steps:

[0037] (1) The tobacco straw was washed with ultrapure water and dried, crushed into particles smaller than 1 mm, and then pyrolyzed at 600℃ for 120 min. After cooling to room temperature, crude biochar was obtained. The crude biochar was soaked in 0.1 mol / L HCl solution overnight, washed with ultrapure water, and dried at 70℃ to obtain raw biochar.

[0038] (2) The original biochar obtained in step (1) is mixed evenly with 0.5 mol / L MgCl2 solution, dried, pyrolyzed twice, and cooled to obtain magnesium chloride modified biochar;

[0039] (3) The obtained magnesium chloride modified biochar was ball-milled to obtain ball-milled magnesium chloride modified biochar material.

[0040] In the following preferred embodiments of the present invention, the pyrolysis in step (1) is carried out in a tube furnace under an inert gas atmosphere, with a nitrogen flow rate of 0.2 L / min and a heating rate of 10 °C / min.

[0041] In the following preferred embodiments of the present invention, the ratio of the amount of raw biochar to magnesium chloride solution in step (2) is 1g:12mL, and the concentration of the magnesium chloride solution is 0.5mol / L.

[0042] Modification with metals or metal compounds can significantly increase the porosity and the number of oxygen-containing functional groups on the surface of biochar. This invention uses magnesium chloride to modify biochar, introducing a metal oxide (MgO) onto its surface. This facilitates complexation with metal cations via lone pair electrons and further enhances its adsorption capacity through the exchange interaction between magnesium ions and divalent metal cations.

[0043] In the following preferred embodiments of the present invention, the mixing parameters in step (2) are: time 12h, temperature 25℃, and rotation speed 500rpm.

[0044] In the following preferred embodiments of the present invention, the parameters for the secondary pyrolysis in step (2) are: nitrogen atmosphere, nitrogen flow rate 0.2 L / min, heating rate 10 °C / min, temperature 600 °C, and time 120 min. After cooling to room temperature, the product is filtered and washed with ultrapure water and then transferred to a 70 °C oven to dry to constant weight.

[0045] In the following preferred embodiments of the present invention, the parameters for ball milling in step (3) are: ball-to-material ratio 100:1, rotation speed 500 rpm, and ball milling time 1 h.

[0046] The modified biochar material was applied to the remediation of copper-contaminated planting soil. The specific method was as follows: the biochar material was uniformly mixed at a mass ratio of 0.5% and applied to copper-contaminated soil with a copper ion concentration of 600 mg / kg. The treated soil was used for pot experiments to observe the effect of the material on the growth of tobacco seedlings.

[0047] Unless otherwise specified, "room temperature" in this invention refers to 25±2℃.

[0048] The raw materials, reagents, instruments and equipment used in this invention can all be purchased from the market or prepared by existing methods.

[0049] The technical solution of the present invention will be further illustrated by the following embodiments.

[0050] Example 1

[0051] A method for preparing modified biochar material includes the following steps:

[0052] (1) Preparation of tobacco straw biochar: Waste tobacco straw was collected from a tobacco field in Henan Province, cleaned with ultrapure water, dried at 70°C, and then crushed to a particle size of less than 1 mm. The crushed sample was then transferred to a tube furnace and pyrolyzed at 600°C (heating rate of 10°C / min, N2 flow rate of 0.2 L / min) for 120 min. After cooling to room temperature, crude biochar was obtained. The crude biochar was soaked in 0.1 mol / L HCl solution overnight to remove impurities. After being filtered and washed with ultrapure water, it was dried at 70°C to obtain the original biochar.

[0053] (2) The raw biochar obtained in step (1) was placed in a 0.5 mol / L MgCl2 solution (the ratio of raw biochar to magnesium chloride solution was 1 g: 12 mL, and the concentration of magnesium chloride solution was 0.5 mol / L). The sample was stirred continuously for 12 h using a constant temperature water bath magnetic stirrer (temperature 25℃, speed 500 rpm). The sample was then dried at 70℃ to constant weight. The dried sample was transferred to a tube furnace and subjected to secondary pyrolysis at 600℃ (heating rate 10℃ / min, N2 flow rate 0.2 L / min) for 120 min. After the sample cooled to room temperature, it was filtered and washed with ultrapure water and then dried at 70℃ to constant weight to obtain magnesium chloride modified biochar.

[0054] (3) The magnesium chloride modified biochar obtained in step (2) was ball-milled for 1 hour at a ball-to-material ratio of 100:1 and a rotation speed of 500 rpm to obtain ball-milled magnesium chloride modified biochar.

[0055] Comparative Example 1

[0056] A method for preparing ball-milled modified biochar includes the following steps:

[0057] (1) Preparation of tobacco straw biochar: Waste tobacco straw was collected from a tobacco field in Henan Province, cleaned with ultrapure water, dried at 70°C, and then crushed to a particle size of less than 1 mm. The crushed sample was then transferred to a tube furnace and pyrolyzed at 600°C (heating rate of 10°C / min, N2 flow rate of 0.2 L / min) for 120 min. After cooling to room temperature, crude biochar was obtained. The crude biochar was soaked in 0.1 mol / L HCl solution overnight to remove impurities. After being filtered and washed with ultrapure water, it was dried at 70°C to obtain the original biochar.

[0058] (2) The raw biochar obtained in step (1) was ball-milled for 1 hour at a ball-to-material ratio of 100:1 and a rotation speed of 500 rpm to obtain ball-milled modified biochar.

[0059] Measurement indicators and methods:

[0060] The surface morphology and microstructure of biochar were analyzed using a scanning electron microscope (SEM-EDS) equipped with energy-dispersive X-ray spectroscopy (EDS). The nitrogen adsorption isotherm of the biochar was determined at 77 K using a fully automated surface area and porosity analyzer. Fourier transform infrared spectroscopy was used for infrared spectroscopy analysis of the biochar. XPS full spectrum (1350-0 eV) and fine elemental spectral scanning were performed using X-ray photoelectron spectroscopy. X-ray diffraction (XRD) tests of the biochar were performed using an X-ray diffractometer, with a scanning range of 5° to 90° and a scanning rate of 10° / min.

[0061] Figure 1 The images show 20 μm scanning electron microscope (SEM) images and EDS elemental maps of the original biochar, magnesium chloride-modified biochar, and ball-milled magnesium chloride-modified biochar in Example 1, as well as the ball-milled modified biochar in Comparative Example 1. Figure 1 As shown, the original biochar has a smooth surface with few pores, varying in size and irregular shape, and mostly exists in block form. Magnesium chloride-modified biochar has a wrinkled and rough surface, with a pore structure dominated by small pores, and noticeable tiny particles and fine powdery substances adhering to it. Ball milling further enhances the roughness of the biochar surface. Magnesium chloride modification significantly increases the magnesium content on the biochar surface.

[0062] Figure 2 The infrared spectra of the original biochar, magnesium chloride-modified biochar, and ball-milled magnesium chloride-modified biochar in Example 1, and the ball-milled modified biochar in Comparative Example 1, are used to characterize the composition of their surface functional groups. From... Figure 2 It can be seen from this that it is approximately 3400cm -1 The peak belongs to the hydroxyl (-OH) vibration peak. It appears at 1628 cm⁻¹. -1 The peak is caused by the C=C vibration of the aromatic ring or olefin. 1440 cm⁻¹ -1 The vibration peaks at 1163 and 865 cm⁻¹ are attributed to the stretching vibrations of -COOH, while those at 1163 and 865 cm⁻¹ are attributed to the stretching vibrations of -COOH. -1 The peaks at 471 cm⁻¹ are attributed to stretching vibrations of aliphatic CO and CH bonds, respectively. Magnesium chloride-modified biochar and ball-milled magnesium chloride-modified biochar showed peaks at 471 cm⁻¹. -1 There are high-intensity Mg-O vibration peaks. Magnesium chloride-modified biochar enhances the peak intensity of -OH and C=C and introduces CO and Mg-O bonds.

[0063] Figure 3 XPS spectra of the original biochar, magnesium chloride-modified biochar, and ball-milled magnesium chloride-modified biochar in Example 1, as well as the ball-milled modified biochar in Comparative Example 1. The surface elemental composition of the biochar was analyzed by X-ray photoelectron spectroscopy (XPS). Figure 3 As can be seen, peaks corresponding to O1s, C1s, and Cl2p were identified at 531.8, 289.9, and 198.7 eV, respectively, while Mg1s appeared only in MgT and BMgT materials at 1303.0 eV.

[0064] Figure 4The XRD patterns of the original biochar, magnesium chloride-modified biochar, and ball-milled magnesium chloride-modified biochar in Example 1, as well as the ball-milled modified biochar in Comparative Example 1, illustrate their crystal phase structure and mineral composition. The XRD patterns of the original biochar and ball-milled modified biochar show a CaCO3 peak (JCPDS card #85-0512). The magnesium chloride-modified biochar and ball-milled magnesium chloride-modified biochar show peaks of pure MgO at 36.9°, 42.8°, 62.2°, 74.5°, and 78.4° (JCPDS card #75-0447).

[0065] Comparative Example 1

[0066] Same as Example 1, except that in step (2), the concentration of magnesium chloride solution is 0.25 mol / L, and modified biochar material is obtained.

[0067] Comparative Example 2

[0068] Same as Example 1, except that in step (2), the concentration of the magnesium chloride solution is 1.0 mol / L, and the modified biochar material is obtained.

[0069] Application Example 1

[0070] Experimental variety: The tested tobacco variety was Yunyan 87. The soil samples were taken from a tobacco field in Henan Province at a depth of 0-20 cm.

[0071] Experimental Procedure: After the soil was naturally air-dried, animal and plant residues were removed, and the soil was sieved through a 20-mesh sieve. The basic properties of the soil were as follows: pH 7.13, organic matter 18.92 g / kg, available nitrogen 440.69 mg / kg, available phosphorus 25.05 mg / kg, available potassium 480.54 mg / kg, and copper content 21 mg / kg. Tobacco seedlings were transplanted when they reached the four-leaf stage. Using the original biochar, magnesium chloride-modified biochar, and ball-milled magnesium chloride-modified biochar from Example 1, as well as the ball-milled modified biochar from Comparative Example 1, as raw materials, the following four experimental groups and four control groups were set up, with three replicates for each group. The average value was calculated. In the soil with added exogenous copper pollutants, the concentration of copper ions was 600 mg / kg. In the biochar addition experiment, the percentage of biochar added to soil was 0.5%:99.5%.

[0072] Control group 1 (CK group): No exogenous copper contaminants were added, and no biochar was added, i.e., normal treatment.

[0073] Control group 2 (Cu group): Exogenous copper contaminants were added, but no biochar was added, i.e., 600 mg / kg Cu. 2+ .

[0074] Experimental Group 1 (Group T): Exogenous copper contaminants were added, along with raw biochar, i.e., raw biochar + 600 mg / kg Cu. 2+ .

[0075] Experimental Group 2 (BT Group): Exogenous copper contaminants were added, along with ball-milled modified biochar (i.e., ball-milled modified biochar + 600 mg / kg Cu). 2+ .

[0076] Experimental Group 3 (MgT Group): Exogenous copper contaminants were added, along with magnesium chloride-modified biochar, i.e., magnesium chloride-modified biochar + 600 mg / kg Cu. 2+ .

[0077] Experimental group 4 (BMgT group): Exogenous copper contaminants were added, along with ball-milled magnesium chloride-modified biochar, i.e., ball-milled magnesium chloride-modified biochar + 600 mg / kg Cu. 2+ .

[0078] Comparative Example 1: Exogenous copper contaminants were added, along with the modified biochar material prepared in Comparative Example 1.

[0079] Comparative Example 2: Exogenous copper contaminants were added, along with the modified biochar material prepared in Comparative Example 2.

[0080] The cultivation conditions were 25 / 22℃ (day / night), light intensity 8000 lx, and watering with 50 mL of deionized water every 3 days. Thirty days after transplanting the tobacco seedlings, the rhizosphere soil was harvested, air-dried, sieved, and stored in self-sealing bags; the root and aboveground samples were blanched at 105℃ and then dried at 75℃ to constant weight.

[0081] Results and Analysis:

[0082] Available copper content in the soil was extracted using diethylenetriaminepentaacetic acid (DTPA) and triethanolamine (TEA), and total copper content was determined by atomic absorption spectrophotometry. Samples were digested using concentrated HNO3-H2O2 via microwave, and their Cu content was determined by atomic absorption spectrophotometry (AAS). Results are shown in Tables 1-3 and... Figure 5 As shown.

[0083] Table 1. Soil available copper and total copper content

[0084] Total copper content (mg / kg) Available copper content (mg / kg) Control group 1 20.33±3.21d 12.39±1.93f Control group 2 558.00±11.00c 370.23±13.92a Test group 1 575.00±12.29b 339.11±11.85 bc Test group 2 582.33±11.93 ab 349.21±5.51b Test group 3 582.00±2.65 ab 256.74±8.41e Test group 4 592.00±6.08a 266.16±9.79 de Comparative example 1 group 576.02±5.56b 324.86±11.23c Comparative example 2 group 591.09±6.17a 274.73±8.67d

[0085] Table 2 Copper content in tobacco seedlings

[0086] Aboveground part (mg / kg) Root (mg / kg) Control group 1 9.23±2.32e 21.67±1.42d Control group 2 149.53±5.50a 356.40±5.50 ab Test group 1 128.00±5.00b 336.70±6.33c Test group 2 110.63±4.07c 349.53±11.93 ab Test group 3 81.67±8.39d 347.60±13.37 abc Test group 4 74.73±5.06d 358.73±7.88a Comparative example 1 group 119.12±5.82 bc 350.09±7.41 ab Comparative example 2 group 78.51±7.51d 344.93±2.57 bc

[0087] Table 3 Soil physicochemical properties

[0088] Cation exchange capacity pH Organic carbon (g / kg) Alkaline hydrolysis nitrogen (mg / kg) Available phosphorus (mg / kg) Available potassium (mg / kg) Available magnesium (mg / kg) Control group 1 13.63±0.25a 6.28±0.14c 11.57±0.72e 461.04±7.81c 29±0.96e 534.67±9.29c 168.83±0.93 de Control group 2 12.04±0.21c 5.33±0.08e 11.67±0.40d 176.58±4.39f 25.9±0.62f 509.67±9.45d 208.7±7.38c Test group 1 12.71±0.15b 6.25±0.14 cd 14.3±0.40c 353.95±6.50e 25.63±0.4f 349±7.21f 169.82±3.75 de Test group 2 12.85±0.23b 5.95±0.13d 13.7±0.36 bc 360.72±5.51e 25.77±0.7f 388±13.53e 164.77±7.00e Test group 3 13.01±0.17b 7.79±0.08a 15.77±0.21a 392.22±6.82d 53.7±1.87c 603.33±9.02b 229.61±4.89a Test group 4 13.07±0.21b 7.69±0.19a 16.57±0.31a 518.75±7.25a 67±2.55a 641±10.44a 219.47±5.46b Comparative example 1 group 12.06±0.28c 6.37±0.32c 14.93±0.54d 359.75±2.92e 49.08±2.79d 544.15±9.75c 175.34±6.25d Comparative example 2 group 12.01±0.35c 7.21±0.36b 15.91±0.30 ab 496.06±12.51b 61.78±1.48b 603.26±8.78b 238.12±6.16a

[0089] The results in the table above show that the magnesium-modified biochar prepared by treatment with 0.5 mol / L magnesium chloride solution exhibits the best performance. Higher concentrations of magnesium chloride solution may affect the adsorption capacity of copper ions, thereby reducing the remediation effect of the biochar. The ball-milled magnesium chloride-modified biochar prepared in this invention, after application in copper-contaminated soils, significantly improved soil fertility and soil quality. Simultaneously, it effectively reduced the content of available copper in the soil and the accumulation of copper in plants, fully demonstrating the excellent adsorption performance of this biochar material for copper ions. This characteristic indicates that the prepared modified biochar has significant advantages in remediating copper-contaminated soils and provides an effective solution for soil environmental protection. Furthermore, the application of this biochar material also provides new ideas and methods for the resource utilization of biomass solid waste.

[0090] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a modified biochar material, characterized in that, Includes the following steps: The process of washing, drying, crushing, pyrolyzing, and soaking tobacco straw in acid yields raw biochar. The original biochar was mixed with magnesium chloride solution, dried, and then pyrolyzed a second time to obtain magnesium chloride modified biochar. The obtained magnesium chloride-modified biochar was ball-milled to obtain ball-milled magnesium chloride-modified biochar material.

2. The method for preparing the modified biochar material according to claim 1, characterized in that, The conditions for both pyrolysis processes were: nitrogen atmosphere, nitrogen flow rate 0.2 L / min, heating rate 10 °C / min, temperature 600 °C, and time 120 min.

3. The method for preparing the modified biochar material according to claim 1, characterized in that, The acid soaking was performed by soaking overnight in a 0.1 mol / L HCl solution.

4. The method for preparing the modified biochar material according to claim 1, characterized in that, The conditions for ball milling are: ball-to-material ratio of 100:1, rotation speed of 500 rpm, and ball milling time of 1 hour.

5. The method for preparing the modified biochar material according to claim 1, characterized in that, The ratio of raw biochar to magnesium chloride solution is 1g:12mL, and the concentration of magnesium chloride solution is 0.5mol / L.

6. The method for preparing the modified biochar material according to claim 1, characterized in that, The conditions for the mixing process are: 12 hours, 25°C, and 500 rpm.

7. A modified biochar material prepared by the preparation method according to any one of claims 1-6.

8. The application of the modified biochar material as described in claim 7 in the remediation of copper-contaminated planting soil.

9. The application according to claim 8, characterized in that, The modified biochar material was applied to copper-contaminated soil at a mass ratio of 0.5%, and the concentration of copper ions in the soil was 600 mg / kg.

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