Soil environment remediation type charcoal-based organic fertilizer and preparation method thereof

Abstract

The invention relates to a soil environment remediation type charcoal-based organic fertilizer and a preparation method thereof, and belongs to the technical field of agricultural resources and environment. The organic fertilizer is prepared by taking charcoal as a core carrier and cooperating with excrement organic matters, a compound microbial agent, an inorganic mineral additive and a nutrition synergistic component through a multi-stage compatibility process. A triple remediation mechanism of gradient temperature pyrolysis modification of biochar, functional synergistic coupling of all components and soil heavy metal passivation-fertility improvement-structure improvement is innovatively designed. Field tests show that the effective-state Cd reduction rate of the product in Cd-polluted soil reaches up to 44.13%, the corn yield is remarkably increased, and meanwhile the use amount of chemical fertilizer is reduced by 20% or above.

Description

Technical Field

[0001] This invention belongs to the field of agricultural resources and environmental technology, specifically relating to a soil environment remediation biochar-based organic fertilizer and its preparation method. Background Technology

[0002] With the rapid development of industry and agriculture, my country's soil environment faces multiple problems, including heavy metal pollution, residual organic pollutants, soil compaction, declining organic matter, and imbalanced microbial communities. While traditional chemical fertilizers can increase crop yields in the short term, long-term application exacerbates soil acidification and salinization, damages soil structure, and has limited effectiveness in remediating soil pollution. Biochar, due to its rich porous structure, stable chemical properties, and strong adsorption capacity, shows great potential in soil improvement and pollution remediation; however, biochar alone suffers from insufficient nutrients and limited functionality.

[0003] Existing technologies have attempted to combine biochar with organic fertilizer, but most are merely simple mixtures that fail to achieve functional modification of biochar, targeted fermentation of organic matter, and synergistic effects among components. This results in unstable remediation effects and a mismatch between fertilizer release and crop needs. Furthermore, the long fermentation cycle and low efficiency of conventional methods, along with issues such as fertilizer granule clumping and low survival rate of microbial agents, also hinder their widespread application.

[0004] Therefore, developing a multifunctional biochar-based organic fertilizer that can simultaneously achieve soil pollution remediation, soil fertility enhancement, and microbial community regulation has significant practical implications and application value. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing technologies and provide a soil environment remediation biochar-based organic fertilizer and its preparation method.

[0006] To solve the above-mentioned technical problems, the present invention provides a soil environment remediation biochar-based organic fertilizer, characterized in that it is prepared from raw materials comprising the following parts by weight: 15-25 parts modified biochar, 30-40 parts fermented organic matter, 2-4 parts compound microbial agent, 10-20 parts inorganic mineral additives, and 8-15 parts nutrient and functional enhancement components.

[0007] Preferably, the modified biochar is a mixed biomass composed of corn stalks, rice husks, and wood chips in a mass ratio of (4-6):(2-4):(1-3). The preparation method is as follows: dried corn stalks, rice husks, and wood chips are mixed in a mass ratio of 5:3:2. The mixed biomass raw materials are then crushed into uniform particles with a particle size of 2-5 mm using a plant pulverizer. The crushed mixed biomass raw materials are placed in a constant temperature drying oven and dried at 105℃ to constant weight to completely remove moisture and ensure the stability of the pyrolysis process. The pretreated mixed biomass raw materials are evenly spread in a quartz boat of a tubular pyrolysis furnace, with a layer thickness not exceeding 2 cm to ensure uniform heat conduction. Subsequently, high-purity nitrogen gas (purity ≥99.99%) is introduced into the furnace tube, with the flow rate controlled at 200... Nitrogen gas was continuously introduced at a rate of mL / min for 30 minutes to completely remove air from the furnace tubes and create a strictly oxygen-limited environment. The temperature was increased from room temperature to 300°C at a rate of 10°C / min and held at 300°C for 30 minutes. The temperature was then increased to 500°C at a rate of 10°C / min and held at 500°C for 60 minutes. The temperature was then increased again to 700°C at a rate of 10°C / min and held at 700°C for 30 minutes. After the pyrolysis process was completed, the furnace was allowed to cool naturally to below room temperature (<50°C) under continuous nitrogen purging. The pyrolysis products were then removed, ground using a universal grinder, and passed through a 100-mesh (150μm) standard sieve to obtain the initial gradient pyrolysis biochar powder, which was placed in a sealed bag for later use. A certain mass of ferric chloride hexahydrate was weighed, dissolved in deionized water, and prepared to a concentration of 3% (w / v). The FeCl3 solution was stirred evenly, and the gradient pyrolysis biochar powder prepared above was added to the FeCl3 solution at a solid-liquid ratio (mass / volume) of 1:5. The mixture was shaken and impregnated in a constant temperature shaker at 25℃ and 150 rpm for 6 hours. After impregnation, the mixture was filtered using a Buchner funnel and a vacuum filtration pump to achieve solid-liquid separation. The filter cake was washed 2-3 times with a small amount of deionized water. The washed wet biochar was transferred to a constant temperature drying oven and dried at 105℃ for 12 hours until completely dry. The dried sample was then aged in air at 60℃ for 24 hours. The final product obtained is "Fe-supported gradient pyrolysis modified biochar".

[0008] Preferably, the fermented organic matter includes chicken manure, mushroom residue, and fermented kitchen waste, and its composition is: chicken manure (20-30 parts), mushroom residue (5-10 parts), and fermented kitchen waste (5-10 parts). It undergoes microwave-assisted aerobic fermentation treatment. Microwave treatment can efficiently kill pathogens and weed seeds, quickly break down the particle structure of materials, promote the decomposition of macromolecular organic matter, significantly shorten the fermentation cycle, and improve the degree of humification. The preparation method is as follows: take chicken manure, mushroom residue and kitchen waste fermentation material, mix them and adjust the moisture content to 55%, pile them in a fermentation tank with a microwave emitting device, turn on the ventilation, and use 400W power to irradiate for 15 minutes every 12 hours for fermentation. The core temperature is maintained at 55-65℃. After 15 days of fermentation, it is decomposed and the moisture content drops to about 30%.

[0009] Preferably, the compound microbial agent includes Bacillus megaterium, Bacillus mucilaginosus, and Azotobacter brownins, with a viable count ratio of 1:1:1 for Bacillus megaterium, Bacillus mucilaginosus, and Azotobacter brownins. Bacillus megaterium has phosphorus and potassium solubilizing functions; Bacillus mucilaginosus can secrete extracellular polysaccharides, promoting the formation of soil aggregates; and Azotobacter brownins can fix free nitrogen from the air. The three work synergistically to activate soil nutrients, improve soil structure, and replenish nitrogen.

[0010] Preferably, the inorganic mineral additive includes diatomaceous earth, phosphogypsum, and sepiolite powder, and its composition is: diatomaceous earth (5-10 parts), phosphogypsum (3-6 parts), and sepiolite powder (2-4 parts); diatomaceous earth is loose and porous, which can adjust the porosity and hygroscopicity of fertilizer particles; phosphogypsum provides calcium and sulfur elements and can adjust soil pH; sepiolite powder has strong adsorption and ion exchange capacity, which can help adsorb pollutants.

[0011] Preferably, the nutritional and functional synergistic components include humic acid, seaweed extract, sodium lignin sulfonate, and polyglutamic acid, and their composition is: humic acid (3-5 parts), seaweed extract (2-4 parts), sodium lignin sulfonate (1-2 parts), and polyglutamic acid (1-2 parts); humic acid can stimulate root growth and integrate metal ions; seaweed extract is rich in natural growth regulators and stress-resistant factors; sodium lignin sulfonate serves as a dispersant and slow-release carrier; and polyglutamic acid is a highly efficient water-retaining agent and nutrient slow-release material.

[0012] This invention also provides a method for preparing a soil environmental remediation biochar-based organic fertilizer, comprising the following steps: a) Preparation of modified biochar; b) Prepare fermented organic matter by mixing chicken manure, mushroom residue and pretreated kitchen waste in proportion, adjusting the carbon-nitrogen ratio and moisture content, and placing it in a microwave-assisted fermentation device for intermittent microwave irradiation aerobic fermentation at a power of 300-500W until it is fully decomposed. c) The modified biochar obtained in step a, the fermented organic matter obtained in step b, the compound microbial agent, the inorganic mineral additives, and the nutritional and functional enhancement components are added into a double helix mixer in proportion and mixed thoroughly. Then the mixture is fed into a disc granulator or a drum granulator, and an appropriate amount of water or binder is sprayed to make 2-4 mm granules.

[0013] Preferably, the fermentation in step b) is microwave-assisted fermentation with a microwave power of 300-500W, using an intermittent processing method.

[0014] Preferably, the coating in step c) is performed by using a gelatin-humic acid composite solution as a coating agent for fluidized bed coating. After coating, the product is air-dried in a low-temperature (<50℃) drying oven until the moisture content is less than 15%.

[0015] The beneficial effects of this invention are as follows: 1. Innovative Gradient Pyrolysis and Iron Modification of Biochar: Gradient pyrolysis (300℃→500℃→700℃) achieves an optimized balance between the pore structure of biochar (micropores are generated at 700℃) and surface functional groups (carboxyl and hydroxyl groups are retained at 300℃); FeCl3 impregnation modification introduces iron oxides, which can not only efficiently fix As and Cd through co-precipitation and redox reactions, but also enhance the adsorption of phosphorus by biochar and reduce nutrient loss; the modified biochar, in synergy with inorganic mineral additives (sepiolite, diatomaceous earth), combines physical adsorption and chemical fixation, exhibiting high adsorption capacity and stability for heavy metal ions such as Cd, Pb, and As; the loading of Fe endows it with Fenton-like catalytic activity, which can effectively degrade organic pollutants such as polycyclic aromatic hydrocarbons in soil.

[0016] 2. Fe-biochar serves as the core carrier and reaction center. Its porous structure provides a large number of physical adsorption sites. Simultaneously, the supported nano-zero-valent iron or iron oxides can enhance the adsorption of Cu through surface complexation. 2+ Zn 2+ Cd 2+ It can also directly reduce highly toxic Hg through chemical adsorption. 2+ This reduces its mobility and toxicity; diatomaceous earth, as an ion exchange enhancement unit, allows for the exchange of Al atoms on its surface and within its pores. 3+ Ca 2+ Isocations specifically capture and immobilize Cu 2+ Zn 2+ It adsorbs divalent heavy metal ions rapidly and efficiently; phosphogypsum couples with microorganisms to form a long-lasting precipitation barrier, and the SO4 provided by phosphogypsum... 2- S is generated under the action of sulfate-reducing bacteria. 2- With Hg, which has a strong affinity for sulfide 2+ Cd 2+ The reaction produces sulfide precipitates such as HgS and CdS that are extremely difficult to dissolve, achieving long-term stable passivation of heavy metals.

[0017] 3. The porous structure of biochar provides a "sanctuary" for microorganisms. Humic acid and seaweed extracts serve as microbial signaling molecules and carbon sources, promoting the proliferation and colonization of microbial communities. The coating layer provides initial protection for the microbial agent. The fibrous structure of sepiolite and biochar together form the core of soil aggregates. Polyglutamic acid, as a powerful water-retaining agent, enhances the soil's water-holding capacity. Biochar and humic acid delay nitrogen conversion through complexation. Sodium lignosulfonate, as a natural chelating agent, activates trace elements in the soil. The product integrates "carrier (biochar), food (organic matter), and workers (functional bacteria)." Biochar provides a sanctuary for functional bacteria, fermented organic matter provides them with a carbon source, and the activity of functional bacteria further activates nutrients and secretes beneficial substances, forming a virtuous cycle and rapidly building a healthy soil micro-ecology.

[0018] 4. The penetrability and thermal effect of microwaves significantly improve fermentation efficiency and uniformity, enabling rapid decomposition and harmlessness of organic matter; the microbial agent is mixed with components such as biochar before granulation, achieving in-situ loading; the subsequent gelatin-humic acid coating further provides physical protection for the microbial agent and nutrients, achieving dual protection. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the preparation process of the soil environment remediation biochar-based organic fertilizer of the present invention.

[0020] Figure 2 This is a functional schematic diagram of the modified biochar of the present invention.

[0021] Figure 3 This is a flow chart of the preparation process of the modified biochar of the present invention.

[0022] Figure 4 This is a schematic diagram illustrating the soil remediation mechanism of the product of this invention.

[0023] Figure 5 The bar chart shows the core performance comparison of the examples and comparative examples. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0025] Example 1 Raw material ratio (parts by weight): Modified biochar: 15 parts Fermented organic matter: 30 parts Compound microbial inoculant: 2 parts Inorganic mineral additives: 10 parts (of which: 5 parts diatomaceous earth, 3 parts phosphogypsum, and 2 parts sepiolite powder) Nutritional and functional synergistic components: 8 parts (including: 3 parts humic acid, 2 parts seaweed extract, 1 part sodium lignosulfonate, and 1 part polyglutamic acid). Preparation method: 1. Preparation of modified biochar: According to the method described in the instructions, gradient pyrolysis (300-500-700℃) biochar was prepared with corn stalks, rice husks and wood chips in a mass ratio of 5:3:2. Then, it was modified by impregnation with 3% FeCl3 solution to obtain Fe-loaded modified biochar.

[0026] 2. Preparation of fermented organic matter: Mix chicken manure, mushroom residue, and kitchen waste fermentation material in a certain proportion, adjust the moisture content to 55%, and use 400W microwave-assisted aerobic fermentation for 15 days until it is fully decomposed.

[0027] 3. Mixing and granulation: The modified biochar, fermented organic matter and compound microbial agent (Bacillus megaterium, Bacillus mucilaginosus, and azotobacter brevis live count 1:1:1), inorganic mineral additives, and nutritional and functional enhancement components are put into a double helix mixer and mixed evenly.

[0028] 4. Granulation and coating: The mixture is granulated (2-4mm) by a disc granulator, coated with a gelatin-humic acid composite solution in a fluidized bed, and air-dried at <50℃ until the moisture content is less than 15% to obtain the finished product.

[0029] Example 2 Raw material ratio (parts by weight): Modified biochar: 20 parts Fermented organic matter: 35 parts Compound microbial inoculant: 3 parts Inorganic mineral additives: 15 parts (of which: 7 parts diatomaceous earth, 4.5 parts phosphogypsum, and 3.5 parts sepiolite powder) Nutritional and functional synergistic components: 11 parts (including: 4 parts humic acid, 3 parts seaweed extract, 1.5 parts sodium lignosulfonate, and 2.5 parts polyglutamic acid). Preparation method: 1. Preparation of modified biochar: According to the method described in the instructions, gradient pyrolysis (300-500-700℃) biochar was prepared with corn stalks, rice husks and wood chips in a mass ratio of 5:3:2. Then, it was modified by impregnation with 3% FeCl3 solution to obtain Fe-loaded modified biochar.

[0030] 2. Preparation of fermented organic matter: Mix chicken manure, mushroom residue, and kitchen waste fermentation material in a certain proportion, adjust the moisture content to 55%, and use 400W microwave-assisted aerobic fermentation for 15 days until it is fully decomposed.

[0031] 3. Mixing and granulation: The modified biochar, fermented organic matter and compound microbial agent (Bacillus megaterium, Bacillus mucilaginosus, and azotobacter brevis live count 1:1:1), inorganic mineral additives, and nutritional and functional enhancement components are put into a double helix mixer and mixed evenly.

[0032] 4. Granulation and coating: The mixture is granulated (2-4mm) by a disc granulator, coated with a gelatin-humic acid composite solution in a fluidized bed, and air-dried at <50℃ until the moisture content is less than 15% to obtain the finished product.

[0033] Example 3 Raw material ratio (parts by weight): Modified biochar: 25 parts Fermented organic matter: 40 parts Compound microbial inoculant: 4 parts Inorganic mineral additives: 20 parts (of which: 10 parts diatomaceous earth, 6 parts phosphogypsum, and 4 parts sepiolite powder) Nutritional and functional enhancement components: 15 parts (including: 5 parts humic acid, 4 parts seaweed extract, 2 parts sodium lignosulfonate, and 4 parts polyglutamic acid). Preparation method: 1. Preparation of modified biochar: According to the method described in the instructions, gradient pyrolysis (300-500-700℃) biochar was prepared with corn stalks, rice husks and wood chips in a mass ratio of 5:3:2. Then, it was modified by impregnation with 3% FeCl3 solution to obtain Fe-loaded modified biochar.

[0034] 2. Preparation of fermented organic matter: Mix chicken manure, mushroom residue, and kitchen waste fermentation material in a certain proportion, adjust the moisture content to 55%, and use 400W microwave-assisted aerobic fermentation for 15 days until it is fully decomposed.

[0035] 3. Mixing and granulation: The modified biochar, fermented organic matter and compound microbial agent (Bacillus megaterium, Bacillus mucilaginosus, and azotobacter brevis live count 1:1:1), inorganic mineral additives, and nutritional and functional enhancement components are put into a double helix mixer and mixed evenly.

[0036] 4. Granulation and coating: The mixture is granulated (2-4mm) by a disc granulator, coated with a gelatin-humic acid composite solution in a fluidized bed, and air-dried at <50℃ until the moisture content is less than 15% to obtain the finished product.

[0037] Comparative Example 1 Compared with Example 2, the gradient pyrolysis was eliminated in the preparation of modified biochar, and only constant temperature pyrolysis was performed at 700℃. The other raw materials and preparation methods were exactly the same.

[0038] Comparative Example 2 Compared with Example 2, the FeCl3 impregnation modification step was omitted in the preparation of modified biochar, and only unmodified gradient pyrolysis biochar was used. The other raw materials and preparation methods were exactly the same.

[0039] Comparative Example 3 Compared with Example 2, the fermentation of organic matter was carried out using traditional composting fermentation (without microwave assistance), and the fermentation cycle was extended to 45 days. The other raw materials and preparation methods were exactly the same.

[0040] Comparative Example 4 Compared with Example 2, the compound microbial agent uses only a single species of Bacillus megaterium (the total number of viable bacteria is the same as in other comparative examples and examples), and the other raw materials and preparation methods are exactly the same.

[0041] Comparative Example 5 Compared with Example 2, the inorganic mineral additive does not contain phosphogypsum, and its proportion is replaced by an equal amount of diatomaceous earth. The remaining raw materials and preparation methods are exactly the same.

[0042] Comparative Example 6 Compared with Example 2, no nutritional or functional synergistic components (humic acid, seaweed extract, etc.) were added, while the remaining raw materials and preparation methods were exactly the same.

[0043] The products obtained from Examples 1, 2, 3 and Comparative Examples 1-6 were selected and subjected to the following performance tests: 1. Heavy metal adsorption and fixation capacity: in Cd-containing... 2+ (50 mg / L) and Pb 2+ In a simulated polluted solution of (100 mg / L), the adsorption and removal rate of heavy metals by each product and the proportion of acid-extractable (bioavailable) heavy metals after adsorption were determined.

[0044] 2. Nutrient sustained-release performance: The cumulative nitrogen (N) release rate of each product over 28 days was determined by water extraction to evaluate its sustained-release effect.

[0045] 3. Microbial Activity and Soil Improvement: Each product was applied to degraded soil, and after 28 days of incubation, the increase rate of water-stable soil aggregates (>0.25 mm) and the metabolic activity of the microbial community were measured. Specific data are shown in the table below:

[0046] Experimental results: The heavy metal adsorption and removal rates of Comparative Example 1 (without gradient pyrolysis) and Comparative Example 2 (without iron modification) (Cd: 88.3% / 85.6%; Pb: 90.4% / 87.9%) were significantly lower than those of Example 2 (Cd: 96.5%; Pb: 98.2%). This indicates that gradient pyrolysis (300℃→500℃→700℃) balanced the pore development of biochar (micropores are generated in the high-temperature section) with the retention of surface functional groups (rich in -COOH and -OH in the low-temperature section), providing an ideal substrate for subsequent iron loading and pollutant adsorption. FeCl3 impregnation modification successfully introduced iron species with redox activity, enabling it to enhance the adsorption of Cd not only through surface complexation but also through other means. 2+ Pb 2+ The chemical adsorption of iron can also efficiently fix heavy metals such as As through reduction or co-precipitation. The sharp drop in data from Comparative Example 2 directly proves the decisive role of iron modification in improving adsorption capacity. The soil aggregate increase rate of Comparative Example 3 (traditional fermentation) (12.8%) was significantly lower than that of Example 2 (18.7%); the aggregate increase rate of Comparative Example 4 (single microbial agent) was even lower (9.5%); the nitrogen release rate of Comparative Example 6 (without functional synergistic components) was as high as 85.4%, with poor slow-release effect. This indicates that microwave-assisted fermentation not only rapidly decomposes organic matter, but its unique penetrating heating also helps to form organic cementitious substances that are conducive to soil aggregation. The compound microbial agent (phosphorus solubilizer, potassium solubilizer, nitrogen fixation, polysaccharide production) promotes nutrient cycling and soil structure formation through synergistic effects. A single microbial species cannot achieve this effect (Comparative Example 4). The nutrient and functional synergistic components (humic acid, polyglutamic acid, etc.) play the roles of "signaling molecules" and "water-retaining slow-release carriers", significantly improving the product's growth promotion, water retention and nutrient slow-release capabilities. Comparative Example 5 (phosphogypsum-free) showed a slightly lower Cd adsorption removal rate (93.8%) than Example 2, demonstrating a supplementary fixation effect for specific heavy metals. This indicates that diatomaceous earth and sepiolite provide additional physical adsorption and ion exchange capacity, forming an adsorption complementarity with biochar. Phosphogypsum not only provides calcium and sulfur nutrients, but also dissolves SO4... 2- It can be gradually reduced to S under the action of microorganisms. 2- , and Cd 2 + The formation of extremely insoluble sulfide precipitates achieves long-term stabilization and fixation. The gelatin-humic acid coating provides physical protection for the internal microbial agents and active ingredients, ensuring their survival and slow release after application to the soil. This is an important technological innovation for achieving long-lasting product efficacy.

[0047] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A soil environment remediation biochar-based organic fertilizer, characterized in that, It is prepared from the following raw materials in parts by weight: 15-25 parts modified biochar, 30-40 parts fermented organic matter, 2-4 parts compound microbial agent, 10-20 parts inorganic mineral additives, and 8-15 parts nutritional and functional enhancement components; wherein, the modified biochar is obtained by gradient pyrolysis and FeCl3 impregnation and drying of a mixture of biomass composed of corn stalks, rice husks and wood chips.

2. The soil environment remediation biochar-based organic fertilizer according to claim 1, characterized in that, The modified biochar is a mixed biomass composed of corn stalks, rice husks, and wood chips in a mass ratio of (4-6):(2-4):(1-3). The preparation method is as follows: dried corn stalks, rice husks, and wood chips are mixed in a mass ratio of 5:3:

2. The mixed biomass raw materials are crushed into uniform particles with a particle size of 2-5 mm using a plant pulverizer. The crushed mixed biomass raw materials are placed in a constant temperature drying oven and dried at 105℃ to constant weight. The pretreated mixed biomass raw materials are evenly spread in a quartz boat of a tubular pyrolysis furnace, with a layer thickness not exceeding 2 cm. Subsequently, high-purity nitrogen gas with a purity ≥99.99% is introduced into the furnace tube, with the flow rate controlled at 200... The nitrogen flow rate was continuously introduced at 1 mL / min for 30 minutes; then pyrolysis was carried out using a gradient program. After the pyrolysis program was completed, the furnace was allowed to cool naturally to room temperature under continuous nitrogen flow. The pyrolysis product was then removed, ground using a universal grinder, and passed through a 100-mesh standard sieve to obtain the initial gradient pyrolysis biochar powder, which was placed in a sealed bag for later use. A certain mass of ferric chloride hexahydrate was weighed, dissolved in deionized water, and a 3% FeCl3 solution was prepared. The solution was stirred evenly, and the gradient pyrolysis biochar powder prepared above was mixed at a ratio of 1:

5. The solid-liquid ratio was added to the FeCl3 solution, and the mixture was shaken and impregnated for 6 hours at 25℃ and 150 rpm in a constant temperature shaker. After impregnation, the solid and liquid were separated by vacuum filtration using a Buchner funnel and a vacuum pump. The filter cake was washed 2-3 times with a small amount of deionized water. The washed wet biochar was transferred to a constant temperature drying oven and dried at 105℃ for 12 hours until completely dry. The dried sample was then aged in air at 60℃ for 24 hours. The final product was Fe-supported gradient pyrolysis modified biochar.

3. The soil environment remediation biochar-based organic fertilizer according to claim 2, characterized in that, The modified biochar is prepared by a gradient pyrolysis method as follows: the temperature is increased from room temperature to 300°C at a rate of 10°C / min, and held at 300°C for 30 minutes; the temperature is then increased from 300°C to 500°C at a rate of 10°C / min, and held at 500°C for 60 minutes; the temperature is then increased from 500°C to 700°C at a rate of 10°C / min, and held at 700°C for 30 minutes.

4. The soil environment remediation biochar-based organic fertilizer according to claim 1, characterized in that, The fermented organic matter includes chicken manure, mushroom residue, and fermented kitchen waste, with a composition of 20-30 parts chicken manure, 5-10 parts mushroom residue, and 5-10 parts fermented kitchen waste. It undergoes microwave-assisted aerobic fermentation treatment. The preparation method is as follows: take chicken manure, mushroom residue, and fermented kitchen waste, mix them, adjust the moisture content to 55%, pile them in a fermentation tank equipped with a microwave emitting device, turn on the ventilation, and use 400W power to irradiate for 15 minutes every 12 hours for fermentation. The core temperature is maintained at 55-65℃. After 15 days of fermentation, it is mature and the moisture content drops to about 30%.

5. The soil environment remediation biochar-based organic fertilizer according to claim 1, characterized in that, The compound microbial agent includes Bacillus megaterium, Bacillus mucilaginosus, and Azotobacter browniformis, with the live bacteria ratio of Bacillus megaterium, Bacillus mucilaginosus, and Azotobacter browniformis being 1:1:

1.

6. The soil environment remediation biochar-based organic fertilizer according to claim 1, characterized in that, The inorganic mineral additives include diatomaceous earth, phosphogypsum, and sepiolite powder, and their composition is: 5-10 parts diatomaceous earth, 3-6 parts phosphogypsum, and 2-4 parts sepiolite powder.

7. The soil environment remediation biochar-based organic fertilizer according to claim 1, characterized in that, The nutritional and functional enhancing components include humic acid, seaweed extract, sodium lignin sulfonate, and polyglutamic acid, and their composition is as follows: 3-5 parts humic acid, 2-4 parts seaweed extract, 1-2 parts sodium lignin sulfonate, and 1-2 parts polyglutamic acid.

8. A method for preparing a soil environment remediation biochar-based organic fertilizer as described in any one of claims 1-7, characterized in that, Includes the following steps: a) Preparation of modified biochar; b) Preparation of fermented organic matter; c) The modified biochar obtained in step a), the fermented organic matter obtained in step b), the compound microbial agent, the inorganic mineral additives, and the nutrient and functional enhancement components are mixed, granulated, coated, and dried to obtain the organic fertilizer.

9. The method for preparing a soil environment remediation biochar-based organic fertilizer according to claim 7, characterized in that, The fermentation described in step b) is microwave-assisted fermentation with a microwave power of 300-500W, using an intermittent processing method.

10. The method for preparing a soil environment remediation biochar-based organic fertilizer according to claim 7, characterized in that, The coating described in step c) is performed using a gelatin-humic acid composite solution as a coating agent for fluidized bed coating.

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