A method for preparing trace element and positive charge modified yak dung biochar

Abstract

This invention relates to the field of biochar technology, specifically disclosing a method for preparing yak manure biochar modified with trace elements and positive charge. By modifying it with trace elements such as boron, molybdenum, manganese, zinc, and selenium, combined with positive charge modification with glycine, the biochar prepared can significantly enhance its binding ability with plant roots, improve the water and fertilizer retention capacity of the soil, promote the growth of pasture, and is suitable for soil remediation and improvement in the northwestern Sichuan plateau region.

Description

Technical Field

[0001] This invention relates to the field of biochar technology, specifically a method for preparing yak dung biochar modified with trace elements and positive charge. Background Technology

[0002] In the high-altitude pastoral areas of northwestern Sichuan, where forest resources are scarce and coal is expensive, many herders choose yak dung as fuel. Yak dung, the excrement of yaks grazing on pasture, is rich in nitrogen and carbon after drying or baking. It has a low ignition point, is easily ignited in the low-oxygen environment of the plateau, and burns without producing an odor, while also generating a gentle flame. However, most of the stoves in the tents where residents live in the pastoral areas lack chimneys. This results in smoke and particulate matter (PM2.5) produced during the combustion of yak dung, which seriously affects the health of herders and the atmospheric environment of the high-altitude pastoral areas. Therefore, changing the way yak dung resources are utilized and replacing combustion with new technologies is particularly important.

[0003] With rapid industrialization and urbanization, soil pollution and degradation have become increasingly serious problems. Traditional soil remediation methods are often costly, time-consuming, and have limited effectiveness. Biochar, as an environmentally friendly soil conditioner, has attracted widespread attention due to its excellent adsorption properties and soil improvement effects. However, the application of existing biochar in soil remediation and grassland restoration still has certain limitations, such as insufficient adsorption capacity and poor stability.

[0004] Currently, yak manure biomass carbonization is gradually being accepted and favored as a new and environmentally friendly treatment method. Due to regional environmental factors, the heavy metal content in yak manure biochar is much lower than that in other types of biochar, making it more suitable as fertilizer to be applied to the soil, supplementing soil nutrients, enhancing soil fertility, and promoting the growth of pasture. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing yak manure biochar modified with trace elements and positive charge, which solves the problems of insufficient adsorption performance and poor stability of existing biochar, enhances the binding ability of biochar with plant roots, improves the water and fertilizer retention performance of soil, and increases the biomass of forage grass.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] The preparation method of yak dung biochar modified with trace elements and positive charge is as follows:

[0008] Step (1): Dry, grind and sieve the yak dung to obtain pretreated yak dung;

[0009] Step (2): Add boric acid, ammonium molybdate, manganese sulfate, zinc sulfate, and sodium selenate to deionized water, stir evenly to obtain a trace element mixed solution, add calcium hydroxide solution to the trace element mixed solution, stir evenly, let stand, filter out the precipitate, dry, and obtain trace element additive.

[0010] Step (3): Mix the pretreated yak manure with trace element additives and stir for 1-2 hours to obtain trace element modified yak manure. Under nitrogen protection, pyrolyze the trace element modified yak manure to obtain trace element modified yak manure biochar.

[0011] Step (4): Mix the trace element modified yak dung biochar with glycine and react at 80-100℃ for 1-2 hours. After the reaction is completed, dry the mixture to obtain trace element and positive charge modified yak dung biochar.

[0012] As a limitation of the present invention, in step (2), the mass ratio of boric acid, ammonium molybdate, manganese sulfate, zinc sulfate and sodium selenate is (5-7):(9-11):(3-5):1:(0.04-0.06).

[0013] As a limitation of the present invention, in step (3), the mass of the trace element additive accounts for 1% to 5% of the total mass of the pretreated yak manure.

[0014] As a limitation of the present invention, the mass ratio of the trace element modified yak dung biochar to glycine is 1:(5-10).

[0015] As a limitation of the present invention, during the pyrolysis treatment, the pyrolysis temperature is controlled at 400-600°C and the pyrolysis time is 2-6 hours.

[0016] As a limitation of the present invention, step (3) specifically includes:

[0017] Pretreated yak dung is mixed with trace element additives and stirred for 1-2 hours to obtain trace element modified yak dung. Under nitrogen protection, trace element modified yak dung, attapulgite clay and potassium dihydrogen phosphate are mixed and pyrolyzed to obtain trace element modified yak dung biochar.

[0018] As a limitation of this invention, the mass ratio of trace element modified yak dung, attapulgite soil, and potassium dihydrogen phosphate is (5-10):(0.5-1.5):(1-3).

[0019] As a limitation of the present invention, step (4) specifically includes:

[0020] Mix yak dung with sawdust, add Bacillus subtilis and Trichoderma harzianum inoculants, compost, and aerobic ferment for 50-70 days. Turn the compost over every 8-12 days. After fermentation, dry and crush the fermentation products to obtain composted yak dung.

[0021] Trace element modified yak manure biochar was mixed with composted yak manure and ball-milled thoroughly. After ball milling, it was mixed with glycine and reacted for 1-2 hours. After the reaction was completed, it was dried to obtain trace element and positively charged modified yak manure biochar.

[0022] Trace element and positive charge modified yak dung biochar obtained according to any of the above preparation methods.

[0023] As a limitation of this invention, the trace element and positive charge modified yak dung biochar can be used for soil remediation, with a dosage of 0.5 to 2.0 kg per square meter of soil.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] Yak manure biochar deposited with trace elements can replenish the lack of trace elements in the soil, promoting pasture growth. Adding attapulgite effectively increases the specific surface area, average pore size, and total pore volume of the biochar, facilitating the attachment of nutrients such as potassium dihydrogen phosphate and trace elements that promote pasture growth. The addition of composted yak manure enhances the fertility of the biochar. Glycine-modified biochar has a positively charged surface, resulting in stronger adsorption properties, effectively adsorbing heavy metals and organic pollutants in the soil. Ball milling enriches the pore structure of the biochar, enhancing its adsorption and ion exchange capacity. The modified biochar exhibits good stability, is not easily decomposed, and can remain in the soil for a long time, continuously improving its condition. The preparation method of this biochar is simple, low-cost, and easy for large-scale production and application. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Yak dung was collected from the cattle shed of the Ruoergai Alpine Wetland Ecological Station in Hongyuan County, Aba Prefecture, Sichuan Province; attapulgite soil (200 mesh) was provided by Huachuan Mineral Products Processing Plant in Lingshou County; and Bacillus subtilis inoculant (5×10⁻⁶) was used. 7 CFU / g), Trichoderma harzianum inoculum (1×10) 8 CFU / g was provided by Jiangsu Pengyao Lianye Biotechnology.

[0028] Example 1: A method for preparing yak dung biochar modified with trace elements and positive charge, specifically as follows:

[0029] Step 1: Pretreatment of yak dung

[0030] 1000g of fresh yak dung is dried, ground, and passed through a 100-mesh sieve to obtain pretreated yak dung.

[0031] Step 2: Deposition of trace elements

[0032] Add 6g boric acid, 10g ammonium molybdate, 4g manganese sulfate, 1g zinc sulfate, and 0.05g sodium selenate to 100ml deionized water and stir until homogeneous to obtain a trace element mixed solution. Add 100ml of 0.02mol / L calcium hydroxide solution to the trace element mixed solution, stir until homogeneous, let stand, filter out the precipitate, and dry to obtain the trace element additive.

[0033] Step 3: Preparation of trace element modified yak dung biochar

[0034] Pretreated yak manure was mixed with trace element additives and stirred for 1 hour to obtain trace element modified yak manure. Under nitrogen as a protective gas, the trace element modified yak manure was pyrolyzed to obtain trace element modified yak manure biochar. The mass of the trace element additives accounted for 3% of the total mass of the pretreated yak manure. The pyrolysis temperature was 500℃ and the pyrolysis time was 2 hours.

[0035] Step 4: Preparation of trace element and positive charge modified yak dung biochar

[0036] Glycine was mixed with deionized water to prepare a 1 mol / L glycine solution. Trace element modified yak dung biochar was soaked in the glycine solution for modification. The ratio of trace element modified yak dung biochar to glycine was 1:5. The pH was maintained at 8, and the reaction was carried out for 2 hours. After the reaction was completed, it was dried at 400℃ for 0.5 hours to obtain trace element and positive charge modified yak dung biochar.

[0037] Example 2: A method for preparing yak dung biochar modified with trace elements and positive charge, specifically as follows:

[0038] Step 1: Pretreatment of yak dung

[0039] 1000g of fresh yak dung is dried, ground, and passed through a 100-mesh sieve to obtain pretreated yak dung.

[0040] Step 2: Deposition of trace elements

[0041] Add 6g boric acid, 10g ammonium molybdate, 4g manganese sulfate, 1g zinc sulfate, and 0.05g sodium selenate to 100ml deionized water and stir until homogeneous to obtain a trace element mixed solution. Add 100ml of 0.02mol / L calcium hydroxide solution to the trace element mixed solution, stir until homogeneous, let stand, filter out the precipitate, and dry to obtain the trace element additive.

[0042] Step 3: Preparation of trace element modified yak dung biochar

[0043] Pretreated yak manure was mixed with trace element additives and stirred for 1 hour to obtain trace element modified yak manure. Under nitrogen as a protective gas, the trace element modified yak manure was pyrolyzed to obtain trace element modified yak manure biochar. The mass of the trace element additives accounted for 1% of the total mass of the pretreated yak manure. The pyrolysis temperature was 500℃ and the pyrolysis time was 2 hours.

[0044] Step 4: Preparation of trace element and positive charge modified yak dung biochar

[0045] Glycine was mixed with deionized water to prepare a 1 mol / L glycine solution. Trace element modified yak dung biochar was soaked in the glycine solution for modification. The ratio of trace element modified yak dung biochar to glycine was 1:5. The pH was maintained at 8, and the reaction was carried out for 2 hours. After the reaction was completed, it was dried at 400℃ for 0.5 hours to obtain trace element and positive charge modified yak dung biochar.

[0046] Example 3: A method for preparing yak dung biochar modified with trace elements and positive charge, specifically as follows:

[0047] Step 1: Pretreatment of yak dung

[0048] 1000g of fresh yak dung is dried, ground, and passed through a 100-mesh sieve to obtain pretreated yak dung.

[0049] Step 2: Deposition of trace elements

[0050] Add 6g boric acid, 10g ammonium molybdate, 4g manganese sulfate, 1g zinc sulfate, and 0.05g sodium selenate to 100ml deionized water and stir until homogeneous to obtain a trace element mixed solution. Add 100ml of 0.02mol / L calcium hydroxide solution to the trace element mixed solution, stir until homogeneous, let stand, filter out the precipitate, and dry to obtain the trace element additive.

[0051] Step 3: Preparation of trace element modified yak dung biochar

[0052] Pretreated yak manure was mixed with trace element additives and stirred for 1 hour to obtain trace element modified yak manure. Under nitrogen as a protective gas, the trace element modified yak manure was pyrolyzed to obtain trace element modified yak manure biochar. The mass of the trace element additives accounted for 5% of the total mass of the pretreated yak manure. The pyrolysis temperature was 500℃ and the pyrolysis time was 2 hours.

[0053] Step 4: Preparation of trace element and positive charge modified yak dung biochar

[0054] Glycine was mixed with deionized water to prepare a 1 mol / L glycine solution. Trace element modified yak dung biochar was soaked in the glycine solution for modification. The ratio of trace element modified yak dung biochar to glycine was 1:5. The pH was maintained at 8, and the reaction was carried out for 2 hours. After the reaction was completed, it was dried at 400℃ for 0.5 hours to obtain trace element and positive charge modified yak dung biochar.

[0055] Example 4: A method for preparing yak dung biochar modified with trace elements and positive charge, specifically as follows:

[0056] Step 1: Pretreatment of yak dung

[0057] 1000g of fresh yak dung is dried, ground, and passed through a 100-mesh sieve to obtain pretreated yak dung.

[0058] Step 2: Deposition of trace elements

[0059] Add 6g boric acid, 10g ammonium molybdate, 4g manganese sulfate, 1g zinc sulfate, and 0.05g sodium selenate to 100ml deionized water and stir until homogeneous to obtain a trace element mixed solution. Add 100ml of 0.02mol / L calcium hydroxide solution to the trace element mixed solution, stir until homogeneous, let stand, filter out the precipitate, and dry to obtain the trace element additive.

[0060] Step 3: Preparation of trace element modified yak dung biochar

[0061] Pretreated yak manure was mixed with trace element additives and stirred for 1 hour to obtain trace element modified yak manure. The trace element modified yak manure was then mixed with 200g of attapulgite clay, 400g of potassium dihydrogen phosphate, and 200g of deionized water, stirred evenly, and air-dried at room temperature to obtain mixed biochar. Under nitrogen protection, the mixed biochar was pyrolyzed to obtain trace element modified yak manure biochar. The pyrolysis temperature was 500℃ and the pyrolysis time was 2 hours.

[0062] Step 4: Preparing composted yak manure

[0063] Mix yak dung and sawdust at a mass ratio of 2.5:1, add 0.05% of Bacillus subtilis inoculant and 0.05% of Trichoderma harzianum inoculant by mass of the total mass of yak dung and sawdust, compost, and aerobic ferment for 60 days. Turn the compost over every 10 days. After fermentation is complete, dry and crush the fermentation products to obtain composted yak dung.

[0064] Step 5: Preparation of trace element and positive charge modified yak dung biochar

[0065] Glycine was mixed with deionized water to prepare a 1 mol / L glycine solution. Trace element-modified yak manure biochar and composted yak manure were mixed at a mass ratio of 5:1 and thoroughly ball-milled for 6 hours at a speed of 550 rpm using 5 mm diameter grinding balls. The grinding direction was reversed every 30 minutes during milling. After milling, the biochar was soaked in a glycine solution at a ratio of 1:5 (trace element-modified yak manure biochar to glycine), maintaining the pH of the glycine solution at 8. The reaction was carried out for 2 hours. After soaking, the biochar was dried at 400℃ for 0.5 hours to obtain trace element and positively charged modified yak manure biochar.

[0066] Based on Example 1, comparative experiments were conducted, specifically Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4, as described below:

[0067] Comparative Example 1: This comparative example relates to a method for preparing yak dung biochar modified with trace elements and positive charge. The only difference from Example 1 is the absence of manganese sulfate and zinc sulfate. Specifically:

[0068] Step 1: Pretreatment of yak dung

[0069] 1000g of fresh yak dung is dried, ground, and passed through a 100-mesh sieve to obtain pretreated yak dung.

[0070] Step 2: Deposition of trace elements

[0071] Add 6g boric acid, 10g ammonium molybdate, and 0.05g sodium selenate to 100ml deionized water and stir until homogeneous to obtain a trace element mixed solution. Add 100ml of 0.02mol / L calcium hydroxide solution to the trace element mixed solution, stir until homogeneous, let stand, filter out the precipitate, and dry to obtain the trace element additive.

[0072] Step 3: Preparation of trace element modified yak dung biochar

[0073] Pretreated yak manure was mixed with trace element additives and stirred for 1 hour to obtain trace element modified yak manure. Under nitrogen as a protective gas, the trace element modified yak manure was pyrolyzed to obtain trace element modified yak manure biochar. The mass of the trace element additives accounted for 3% of the total mass of the pretreated yak manure. The pyrolysis temperature was 500℃ and the pyrolysis time was 2 hours.

[0074] Step 4: Preparation of trace element and positive charge modified yak dung biochar

[0075] Trace element modified yak dung biochar was soaked in a glycine solution for modification. The ratio of trace element modified yak dung biochar to glycine was 1:5. The pH was maintained at 8, and the reaction was carried out for 2 hours. After the reaction was completed, it was dried at 400℃ for 0.5 hours to obtain trace element and positive charge modified yak dung biochar.

[0076] Comparative Example 2: This comparative example relates to a method for preparing trace element- and positively charged modified yak dung biochar, differing from Example 1 only in that boric acid and ammonium molybdate are not added. Specifically:

[0077] Step 1: Pretreatment of yak dung

[0078] 1000g of fresh yak dung is dried, ground, and passed through a 100-mesh sieve to obtain pretreated yak dung.

[0079] Step 2: Deposition of trace elements

[0080] Add 4g of manganese sulfate, 1g of zinc sulfate, and 0.05g of sodium selenate to 100ml of deionized water and stir until homogeneous to obtain a trace element mixed solution. Add 100ml of 0.02mol / L calcium hydroxide solution to the trace element mixed solution, stir until homogeneous, let stand, filter out the precipitate, and dry to obtain the trace element additive.

[0081] Step 3: Preparation of trace element modified yak dung biochar

[0082] Pretreated yak manure was mixed with trace element additives and stirred for 1 hour to obtain trace element modified yak manure. Under nitrogen as a protective gas, the trace element modified yak manure was pyrolyzed to obtain trace element modified yak manure biochar. The mass of the trace element additives accounted for 3% of the total mass of the pretreated yak manure. The pyrolysis temperature was 500℃ and the pyrolysis time was 2 hours.

[0083] Step 4: Preparation of trace element and positive charge modified yak dung biochar

[0084] Trace element modified yak dung biochar was soaked in a glycine solution for modification. The ratio of trace element modified yak dung biochar to glycine was 1:5. The pH was maintained at 8, and the reaction was carried out for 2 hours. After the reaction was completed, it was dried at 400℃ for 0.5 hours to obtain trace element and positive charge modified yak dung biochar.

[0085] Comparative Example 3: This comparative example relates to a method for preparing trace element and positive charge modified yak dung biochar, differing from Example 1 only in that sodium selenate was not added. Specifically:

[0086] Step 1: Pretreatment of yak dung

[0087] 1000g of fresh yak dung is dried, ground, and passed through a 100-mesh sieve to obtain pretreated yak dung.

[0088] Step 2: Deposition of trace elements

[0089] Add 6g boric acid, 10g ammonium molybdate, 4g manganese sulfate, and 1g zinc sulfate to 100ml deionized water and stir until homogeneous to obtain a trace element mixed solution. Add 100ml of 0.02mol / L calcium hydroxide solution to the trace element mixed solution, stir until homogeneous, let stand, filter out the precipitate, and dry to obtain the trace element additive.

[0090] Step 3: Preparation of trace element modified yak dung biochar

[0091] Pretreated yak manure was mixed with trace element additives and stirred for 1 hour to obtain trace element modified yak manure. Under nitrogen as a protective gas, the trace element modified yak manure was pyrolyzed to obtain trace element modified yak manure biochar. The mass of the trace element additives accounted for 3% of the total mass of the pretreated yak manure. The pyrolysis temperature was 500℃ and the pyrolysis time was 2 hours.

[0092] Step 4: Preparation of trace element and positive charge modified yak dung biochar

[0093] Trace element modified yak dung biochar was soaked in a glycine solution for modification. The ratio of trace element modified yak dung biochar to glycine was 1:5. The pH was maintained at 8, and the reaction was carried out for 2 hours. After the reaction was completed, it was dried at 400℃ for 0.5 hours to obtain trace element and positive charge modified yak dung biochar.

[0094] Comparative Example 4: This comparative example relates to a method for preparing yak dung biochar, differing from Example 1 only in that glycine was not used to modify the yak dung biochar. Specifically:

[0095] Step 1: Pretreatment of yak dung

[0096] 1000g of fresh yak dung is dried, ground, and passed through a 100-mesh sieve to obtain pretreated yak dung.

[0097] Step 2: Deposition of trace elements

[0098] Add 6g boric acid, 10g ammonium molybdate, 4g manganese sulfate, 1g zinc sulfate, and 0.05g sodium selenate to 100ml deionized water and stir until homogeneous to obtain a trace element mixed solution. Add 100ml of 0.02mol / L calcium hydroxide solution to the trace element mixed solution, stir until homogeneous, let stand, filter out the precipitate, and dry to obtain the trace element additive.

[0099] Step 3: Preparation of trace element modified yak dung biochar

[0100] Pretreated yak manure was mixed with trace element additives and stirred for 1 hour to obtain trace element modified yak manure. Under nitrogen as a protective gas, the trace element modified yak manure was pyrolyzed to obtain trace element modified yak manure biochar. The mass of the trace element additives accounted for 3% of the total mass of the pretreated yak manure. The pyrolysis temperature was 500℃ and the pyrolysis time was 2 hours.

[0101] Testing experiment:

[0102] Yak dung biochar samples were prepared according to the processes in Examples 1, 2, 3, 4, Comparative Examples 1, 2, 3, and 4.

[0103] Surface potential test: After crushing the yak dung biochar sample, wet it with deionized water, filter out the excess water, put 1g of sample into the glass sample cell, press the sample tightly with the stopper, seal it well, and measure the surface potential of the yak dung biochar. The electrolyte solution is a 0.001mol / L potassium chloride solution.

[0104] Soil fertility test: The experimental soil was collected from the alpine grassland of Hongyuan County, Aba Prefecture, Sichuan Province. After the soil was collected, it was sieved through a 2mm sieve and air-dried. A certain amount of the air-dried soil sample was weighed and placed into flowerpots, filling a total of 45 flowerpots. The pots were divided into 9 groups of 5 pots each. Eight groups were randomly selected, and different samples of yak manure biochar were mixed into the flowerpots at an application rate of 1 kg / m³. 2 The remaining group served as a control, with an equal amount of experimental soil added to the sample. Seeds of the same batch and specification were selected and sown. Then, the seedlings with uniform growth were transplanted into the same number of pots. The forage was watered and treated for pests according to the normal forage growth cycle. Once the forage growth stabilized, the changes in forage biomass in each group were measured, using the control group as a benchmark. Soil samples were taken from each group and the control group. A permeameter was used to simulate rainfall, and the changes in soil water retention capacity in each group were measured, using the control group's soil water retention capacity as a benchmark.

[0105] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Surface potential (mV) +25 +23 +27 +31 +21 +19 +24 -5 Pasture biomass (%) +31 +25 +36 +43 +23 +21 +26 +17 Soil water retention capacity (%) +30 +28 +32 +35 +23 +22 +25 +13

[0106] Conclusion: Based on the test data, it can be seen that the surface potential, pasture biomass, and soil water retention capacity of the trace element and positively charged modified trace element yak manure biochar prepared in Example 1 are superior to those of Comparative Examples 1, 2, 3, and 4.

[0107] As can be seen from Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3, the deposition of multiple trace elements is beneficial to promoting the growth of pasture.

[0108] As can be seen from Example 1 and Comparative Example 4, without glycine modification, yak manure biochar carries a negative charge, has a low surface potential, is prone to reacting with anions in the soil, has a weak binding capacity with roots, and is not conducive to the absorption of trace elements by forage grass.

[0109] It will be apparent to those skilled in the art that the present 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 the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing trace element and positive charge modified yak dung biochar, characterized in that: Specifically: Step (1): Dry, grind and sieve fresh yak dung to obtain pretreated yak dung; Step (2): Add boric acid, ammonium molybdate, manganese sulfate, zinc sulfate, and sodium selenate to deionized water, stir evenly to obtain a trace element mixed solution, add calcium hydroxide solution to the trace element mixed solution, stir evenly, let stand, filter out the precipitate, dry, and obtain trace element additive. Step (3): Mix the pretreated yak manure with trace element additives and stir for 1-2 hours to obtain trace element modified yak manure. Under nitrogen protection, mix the trace element modified yak manure, attapulgite clay and potassium dihydrogen phosphate, and pyrolyze to obtain trace element modified yak manure biochar. Step (4): Mix yak dung with sawdust, add Bacillus subtilis and Trichoderma harzianum, compost, and aerobic ferment for 50-70 days. Turn the compost over every 8-12 days. After fermentation, dry and crush the fermentation product to obtain composted yak dung. Mix micronutrient-modified yak dung biochar with composted yak dung and ball mill thoroughly. After ball milling, mix with glycine and react for 1-2 hours. After reaction, dry to obtain micronutrient-modified and positively charged yak dung biochar.

2. The method for preparing trace element and positively charged modified yak dung biochar according to claim 1, characterized in that: In step (2), the mass ratio of boric acid, ammonium molybdate, manganese sulfate, zinc sulfate, and sodium selenate is (5-7):(9-11):(3-5):1:(0.04-0.06).

3. The method for preparing trace element and positively charged modified yak dung biochar according to claim 1, characterized in that: In step (3), the mass of the trace element additive accounts for 1% to 5% of the total mass of the pretreated yak manure.

4. The method for preparing trace element and positively charged modified yak dung biochar according to claim 1, characterized in that: The mass ratio of trace element modified yak manure biochar to glycine is 1:(5-10).

5. The method for preparing trace element and positively charged modified yak dung biochar according to claim 1, characterized in that: In step (3), the pyrolysis temperature is 400-600℃ and the pyrolysis time is 2-6h.

6. The method for preparing trace element and positively charged modified yak dung biochar according to claim 1, characterized in that: The mass ratio of trace element modified yak dung, attapulgite soil, and potassium dihydrogen phosphate is (5-10):(0.5-1.5):(1-3).

7. Trace element and positive charge modified yak dung biochar obtained by the preparation method according to any one of claims 1 to 6.

8. The trace element and positive charge modified yak dung biochar according to claim 7, characterized in that: This trace element and positively charged modified yak manure biochar can be used for soil remediation, with a dosage of 0.5–2.0 kg per square meter of soil.