Phosphoric acid modified charcoal-based multifunctional soil conditioner and preparation method thereof

Abstract

The invention provides a phosphoric acid modified charcoal-based multifunctional soil conditioner and a preparation method thereof, and relates to the technical field of soil improvement. The soil conditioner is of a three-layer structure and sequentially comprises an inner core, an interlayer and a shell from inside to outside. The weight ratio of the inner core to the interlayer to the shell is (1-2): (3-4): (5-6); the inner core is prepared from fulvic acid, wheat bran, trace elements and auxiliary materials; the interlayer is prepared from bacillus subtilis, a porous material and an auxiliary material; the porous material is nano zeolite or montmorillonite; the shell is prepared from phosphoric acid modified charcoal, urea, sodium polyacrylate, bentonite, a cross-linking agent and an auxiliary material. By preparing the soil conditioner with a core-interlayer-shell three-layer structure, integrated improvement of salt reduction, recarburization, microbe promotion and fertilizer supply of soil is realized, the action period of the soil conditioner is prolonged, and the improvement efficiency of the coastal saline-alkali soil is improved.

Description

Technical Field

[0001] This invention provides a phosphoric acid-modified biochar-based multifunctional soil conditioner and its preparation method, belonging to the field of soil improvement technology. Background Technology

[0002] Soil salinization, lack of organic matter, and low microbial activity are key issues restricting the sustainable development of agriculture, especially in coastal saline-alkali areas. Long-term seawater immersion leads to high soil salinity (usually ≥3g / kg), high pH (8.0-9.5), and low organic carbon content (≤10g / kg). High salinity increases the osmotic pressure of the soil solution, making it difficult for plant roots to absorb water, easily causing physiological drought and severely inhibiting plant growth. Moreover, the saline-alkali environment greatly limits the activity and diversity of soil microorganisms, hinders soil nutrient cycling, and results in low soil fertility and low utilization value. Currently, there are numerous methods for improving coastal saline-alkali land. Soil conditioners, as the core materials for improving such soils, directly determine the improvement effect based on their performance. However, existing technologies have certain limitations. Traditional conditioners often focus on a single function, such as reducing salinity or supplementing fertilizer. For example, applying biochar alone can increase organic matter but has limited salinity-reducing effects. Applying microbial agents alone can improve the microecology but is easily inactivated by high-salt environments, making it difficult to achieve synergistic treatment of salinity reduction, carbon increase, microbial promotion, and fertilizer supply. Beneficial microorganisms such as Bacillus subtilis have a survival rate of less than 30% in the high-salt, high-pH environment of saline-alkali land (after 15 days of application) and lack effective protection mechanisms, making it difficult for the microbial community to form a dominant group, with an effect cycle of only 1-2 months. Nitrogen in conventional conditioners, such as urea, is easily lost with irrigation water and is prone to adsorption conflicts when mixed with biochar and microbial agents, failing to match the nutrient requirements of plant growth. In existing technologies, although there have been attempts to combine biochar with microbial agents and fertilizers, a layered encapsulation structure has not been adopted, which fails to solve the synergistic problems of microbial agent protection, nutrient slow release, and biochar salt reduction. Summary of the Invention

[0003] Based on this, the present invention provides a phosphoric acid-modified biochar-based multifunctional soil conditioner and its preparation method. The present invention achieves integrated improvement of soil salinity reduction, carbon increase, microbial growth promotion, and nutrient supply by preparing a soil conditioner with a three-layer structure of core-interlayer-outer shell, thereby extending the action period of the soil conditioner and improving the efficiency of coastal saline-alkali land improvement.

[0004] The present invention is specifically implemented using the following technical solutions: A phosphoric acid modified biochar-based multifunctional soil conditioner has a three-layer structure, consisting of a core, an interlayer, and an outer shell from the inside out. The weight ratio of the core, interlayer, and outer shell is 1~2:3~4:5~6; The core is prepared from fulvic acid, wheat bran, trace elements and auxiliary materials; The interlayer is prepared from Bacillus subtilis, porous materials, and auxiliary materials; the porous material is nano-zeolite or montmorillonite. The outer shell is made of phosphoric acid modified biochar, urea, sodium polyacrylate, bentonite, crosslinking agent and auxiliary materials.

[0005] Preferably, the weight percentage of each raw material in the core is as follows: 60-70% fulvic acid; Wheat bran 15-20%; Trace elements 5-8%; Core auxiliary materials 5-12%.

[0006] Preferably, the weight percentage of each raw material in the interlayer is as follows: Bacillus subtilis 65-90%; Nano-zeolite or montmorillonite 10-35%; 5-10% of the interlayer auxiliary materials.

[0007] Preferably, the weight percentages of each raw material in the outer shell are as follows: Phosphoric acid modified biochar 40-50%; Urea 15-20%; Sodium polyacrylate 10-15%; Bentonite 8-12%; Crosslinking agent 3-5%; The rest are auxiliary materials for the outer shell.

[0008] Preferably, the preparation method of the phosphoric acid modified biochar is to crush the biomass raw material and then pyrolyze it under nitrogen protection; then crush the pyrolyzed biomass to obtain biochar; mix the biochar and a phosphoric acid solution with a mass concentration of 85% at a mass ratio of 1:2~2.2, activate it at 100℃ for 2 hours, and finally obtain the phosphoric acid modified biochar after washing and drying.

[0009] More preferably, the specific surface area of ​​the phosphoric acid modified biochar is ≥500 m². 2 / g, carbon content ≥75%, porosity ≥60%.

[0010] Preferably, the core auxiliary material is sodium carboxymethyl cellulose; The interlayer auxiliary material is trehalose; The outer shell auxiliary material is talc.

[0011] Preferably, the trace element is at least one of Fe, Mn, Zn, and Cu.

[0012] This invention also includes a method for preparing the phosphoric acid-modified biochar-based multifunctional soil conditioner, comprising the following steps: S1, Kernel Preparation Mix fulvic acid, wheat bran, trace elements and core auxiliary materials in a certain proportion, and add deionized water to make a mixture with a mass concentration of 20-30%. After homogenization, the mixture is initially shaped by a granulator and dried to obtain core particles with a particle size of 0.1-0.2 cm. S2, the inner and outer layers are covered with an interlayer. S2-1, One-time coating Prepare an aqueous solution of interlayer auxiliary material with a mass concentration of 5-8% by adding water, and adjust the pH to 7.0-7.5; The core particles are immersed in the aqueous solution of the interlayer auxiliary material, stirred at 30-35°C for 30-40 minutes, removed and dried to obtain one-time coated particles; S2-2, Microbial Agent Filling Bacillus subtilis was mixed with porous material, and a small amount of deionized water was added to make a paste, which was then uniformly coated onto the surface of the primary coated particles. S2-3, Secondary coating: Repeat steps S2-1 to S2-2 to obtain composite particles with coated interlayers; S3, Covering shell Phosphoric acid-modified biochar, urea, sodium polyacrylate, bentonite, and shell auxiliary materials are mixed in proportion and deionized water is added to prepare a suspension with a mass concentration of 15-20%. The composite particles with the coating layer are added to the suspension and stirred at room temperature for 60-90 minutes, during which the crosslinking agent is added in 3-4 batches with an interval of 15-20 minutes between each batch. After filtration, the solid particles are first pre-freeze-dried, and then vacuum-dried. After sieving, the surface is functionalized to obtain a phosphate-modified biochar-based multifunctional soil conditioner.

[0013] Preferably, the surface functionalization treatment involves spraying 0.5-1 wt% talc powder and 1-2 wt% polyvinyl alcohol onto the sieved particles, followed by drying.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The multifunctional soil conditioner of this invention has a three-layer structure. The phosphoric acid-modified biochar in the outer shell can adsorb soil salts and slowly release nutrients to create a suitable microenvironment, increasing the survival rate of microorganisms in the interlayer to over 60%. The fulvic acid in the core can re-stimulate the activity of roots and microorganisms after a long period of application. The layered protection can effectively ensure the long-term effectiveness of each layer, achieving the effects of rapid activation, medium-term microbial preservation, and long-term improvement.

[0015] This invention utilizes phosphoric acid-modified biochar to prepare the outer shell, increasing the functional groups on the surface of the biochar and enhancing its adsorption capacity for slow-release phosphorus.

[0016] This invention utilizes the temperature- and salt-sensitive properties of sodium polyacrylate to ensure that the nutrient release rate in the soil conditioner matches the needs of plant growth, and avoids activity inhibition caused by direct contact with microbial agents, thus solving the conflict problem between nutrients and microbial agents in traditional compound conditioners.

[0017] This invention employs a layer-by-layer self-assembly technology, which simplifies the process while enhancing the compressive strength of the particles, making it suitable for mechanized use and reducing production and usage costs. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly described below.

[0019] Figure 1 This is a schematic diagram of the structure of a phosphoric acid-modified biochar-based multifunctional soil conditioner. Detailed Implementation

[0020] This invention provides a method for preparing a phosphoric acid-modified biochar-based multifunctional soil conditioner. The core lies in the precise design and material synergy of a three-layer structure (core, interlayer, and outer shell) to achieve integrated soil salinization, slow nutrient release, microbial agent preservation, and plant growth promotion. Specifically, the method includes the following steps: fulvic acid (core), Bacillus subtilis (interlayer), phosphoric acid-modified biochar, and urea (outer shell) are prepared into granules according to a specific ratio and process, and then applied to the target soil. The preparation method of the phosphoric acid-modified biochar in this invention involves pulverizing biomass raw materials (corn stalks or bamboo charcoal) and then pyrolyzing them under nitrogen protection (350℃ for 2 hours); then pulverizing the pyrolyzed biomass to obtain biochar; mixing the biochar with an 85% phosphoric acid solution at a mass ratio of 1:2, activating it at 100℃ for 2 hours, and finally washing and drying to obtain the phosphoric acid-modified biochar.

[0021] To further illustrate the present invention, the following detailed description is provided in conjunction with embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0022] The test soil was located in Huanghekou Town, Kenli District, Dongying City, Shandong Province.

[0023] Example 1 A phosphoric acid modified biochar-based multifunctional soil conditioner has a three-layer structure, consisting of a core, an interlayer, and an outer shell from the inside out. The weight ratio of the core, interlayer, and outer shell is 2:3:5; The weight percentages of each raw material in the core are as follows: 14% fulvic acid; 3% wheat bran; Trace elements (nitrogen, phosphorus, potassium, calcium, sodium, magnesium, etc.) 1%; Core auxiliary material (sodium carboxymethyl cellulose) 2%.

[0024] The weight percentages of each raw material in the interlayer are as follows: Bacillus subtilis 22.5%; Nano zeolite 4.5%; Sandwich auxiliary material (trehalose) 3%.

[0025] Preferably, the weight percentages of each raw material in the outer shell are as follows: Phosphoric acid modified biochar 25%; 10% urea; Sodium polyacrylate 7.5%; 5% bentonite; Crosslinking agent: ethylene glycol dimethacrylate 2.5%; The rest are auxiliary materials for the outer shell (talc).

[0026] The preparation method of the phosphoric acid modified biochar-based multifunctional soil conditioner includes the following steps: S1, Kernel Preparation Mix fulvic acid, wheat bran, trace elements and core auxiliary materials in a certain proportion, and add deionized water to make a mixture with a mass concentration of 25%. After homogenization, the mixture is initially shaped by a granulator and dried to obtain core particles with a particle size of 0.2 cm. S2, the inner and outer layers are covered with an interlayer. S2-1, One-time coating Prepare a 6% (w / w) aqueous solution of interlayer auxiliary material by adding water, and adjust the pH to 7.0; The core particles are immersed in the aqueous solution of the interlayer auxiliary material, stirred at 35°C for 40 minutes, removed and dried to obtain one-time coated particles; S2-2, Microbial Agent Filling Bacillus subtilis was mixed with porous material, and a small amount of deionized water was added to make a paste, which was then uniformly coated onto the surface of the primary coated particles. S2-3, Secondary coating: Repeat steps S2-1 to S2-2 to obtain composite particles with coated interlayers; S3, Covering shell Phosphoric acid-modified biochar, urea, sodium polyacrylate, bentonite, and shell auxiliary materials are mixed in proportion and deionized water is added to prepare a suspension with a mass concentration of 20%. The composite particles with the coating layer were added to the suspension and stirred at room temperature for 90 minutes, during which the crosslinking agent was added in four portions, with each portion 20 minutes apart. After filtration, the solid particles are first pre-freeze-dried, and then vacuum-dried. After sieving, the surface is functionalized to obtain a phosphate-modified biochar-based multifunctional soil conditioner.

[0027] Preferably, the surface functionalization treatment involves spraying 0.5 wt% talc powder and 1 wt% polyvinyl alcohol onto the sieved particles, followed by drying. A pot experiment was conducted using soil from the experimental area of ​​Dongying City, Shandong Province, with 28 kg / mu applied to the soil surface. Ryegrass seeds were sown in the first layer, followed by normal irrigation and management. After 45 days of planting, plant and soil samples were collected and analyzed. The planting and management of ryegrass in the following examples and comparative examples are the same as in Example 1.

[0028] Example 2 After covering the outer shell, no surface functionalization treatment is performed. Other components and preparation methods are the same as in Example 1. A soil conditioner is obtained by direct drying. It is applied to the soil surface at 28 kg / mu and ryegrass is planted. After that, normal irrigation and management are carried out.

[0029] Example 3 Montmorillonite was used instead of nano-zeolite when making the interlayer. Other components and preparation methods were the same as in Example 1. A soil conditioner was obtained by direct drying. It was applied to the soil surface at a rate of 28 kg / mu and ryegrass was planted. After that, normal irrigation and management were carried out.

[0030] Example 4 After the core is prepared, the sandwich layer is skipped and the core is wrapped directly with the outer shell. The other components and preparation methods are the same as in Example 1, resulting in a soil conditioner. It is applied to the soil surface at 28 kg / mu and ryegrass is planted. After that, normal irrigation and management are carried out.

[0031] Example 5 When making the outer shell, unmodified biochar powder was used, and the other components and preparation method were the same as in Example 1, resulting in a soil conditioner. It was applied to the soil surface at a rate of 28 kg / acre and ryegrass was planted, followed by normal irrigation and management.

[0032] Control Example (CK) Plant ryegrass without adding any other materials and water and manage it normally.

[0033] Table 1 Soil physical properties

[0034] Table 2 Soil chemical properties

[0035] Table 3 Plant biomass and root characteristics

[0036] Table 4 Soil Quality Index

[0037] Table 5 Physicochemical Properties of Conditioner Granules

[0038] This invention produces a soil conditioner that can rapidly increase crop yield and provide long-term ecological restoration for coastal saline-alkali land, achieving a synergistic effect of salt reduction, fertilization, and growth promotion. This verifies the feasibility of the three-layer structure and phosphate modification technology of this invention. Using this soil conditioner to improve soil results in a 30-40% increase in soil salinity, an increase in the 15-day survival rate of Bacillus subtilis to over 65%, and an extension of the nutrient release period to over 90 days.

[0039] This invention utilizes the synergistic effect of phosphoric acid-modified biochar, microbial agents, and fertilizers to prepare a layered phosphoric acid-modified biochar-based multifunctional soil conditioner. This conditioner has significant advantages in the improvement of saline-alkali land, effectively regulating soil pH, adsorbing nutrients, increasing organic matter content, and improving soil structure. Furthermore, the product exhibits stable performance and has promising application prospects.

[0040] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A phosphoric acid modified biochar based multifunctional soil conditioner, characterized in that, The soil conditioner is a three-layer structure, from inside to outside, the core, the sandwich and the shell; The weight ratio of the core, the sandwich and the shell is 1-2:3-4:5-6; The core is prepared from fulvic acid, wheat bran, trace elements and auxiliary materials; The sandwich is prepared from Bacillus subtilis, porous material and auxiliary materials; the porous material is nano zeolite or montmorillonite; The shell is prepared from phosphoric acid modified biochar, urea, sodium polyacrylate, bentonite, crosslinking agent and auxiliary materials.

2. The phosphoric acid modified biochar based multifunctional soil conditioner as claimed in claim 1, wherein, The weight percentage of each raw material in the core is as follows: Fulvic acid 60-70%; Wheat bran 15-20%; Trace elements 5-8%; Core auxiliary material 5-12%.

3. The phosphoric acid modified biochar based multifunctional soil conditioner as claimed in claim 1, wherein, The weight percentage of each raw material in the sandwich is as follows: Bacillus subtilis 65-90%; Nano zeolite or montmorillonite 10-35%; Sandwich auxiliary material 5-10%.

4. The phosphoric acid modified biochar based multifunctional soil conditioner as claimed in claim 1, wherein, The weight percentage of each raw material in the shell is as follows: Phosphoric acid modified biochar 40-50%; Urea 15-20%; Sodium polyacrylate 10-15%; Bentonite 8-12%; Crosslinking agent 3-5%; The rest is shell auxiliary material.

5. The phosphoric acid modified biochar based multifunctional soil conditioner as claimed in claim 1, wherein, The preparation method of the phosphoric acid modified biochar is to crush the biomass raw material and pyrolyze it under nitrogen protection; then crush the pyrolyzed biomass to obtain biochar; mix the biochar with a phosphoric acid solution with a mass concentration of 85% at a mass ratio of 1:2-2.2, activate at 100℃ for 2h, and finally wash and dry to obtain the phosphoric acid modified biochar.

6. The phosphoric acid-modified biochar-based multifunctional soil conditioner according to claim 5, wherein, The specific surface area of the phosphoric acid modified biochar is ≥500 m 2 / g, the carbon content is ≥75%, and the porosity is ≥60%.

7. The phosphoric acid modified biochar based multifunctional soil conditioner according to claim 1, wherein The core auxiliary material is sodium carboxymethyl cellulose; The sandwich auxiliary material is trehalose; The shell auxiliary material is talc powder.

8. The phosphoric acid modified biochar based multifunctional soil conditioner as claimed in claim 1, wherein, The trace elements are at least one of Fe, Mn, Zn and Cu.

9. The method for preparing the phosphoric acid-modified biochar-based multifunctional soil conditioner according to any one of claims 1 to 8, characterized in that, The steps include: S1, preparing the core Mix fulvic acid, wheat bran, trace elements and core auxiliary materials in proportion, add deionized water to prepare a mixed solution with a mass concentration of 20-30%; After homogenizing the mixed solution, it is initially formed by a granulator, and then dried to obtain core particles with a particle size of 0.1-0.2cm; S2, coating the sandwich on the inner layer S2-1, primary coating Prepare a sandwich auxiliary material aqueous solution with a mass concentration of 5-8% by adding water to the sandwich auxiliary material, and adjust the pH to 7.0-7.5; Soak the core particles in the sandwich auxiliary material aqueous solution, stir at 30-35℃ for 30-40min, take out and dry to obtain primary coated particles; S2-2, filling of bacterial agent Mix Bacillus subtilis with porous material, add a small amount of deionized water to make a paste, and uniformly coat the surface of the primary coated particles; S2-3, secondary coating: repeat steps S2-1-S2-2 to obtain sandwich coated composite particles; S3, covering the shell Mix phosphoric acid modified biochar, urea, sodium polyacrylate, bentonite and shell auxiliary materials in proportion, add deionized water to prepare a suspension with a mass concentration of 15-20%; The coated sandwich composite particles are added into the suspension, stirred at room temperature for 60-90 min, and the crosslinking agent is added for 3-4 times with an interval of 15-20 min each time; After filtration, the solid particles are first pre-frozen and dried, and then vacuum dried; After sieving, surface functionalization treatment is performed to obtain the phosphoric acid modified biochar-based multifunctional soil conditioner.

10. The preparation method of the phosphoric acid modified biochar-based multifunctional soil conditioner as described in claim 9, characterized in that, The surface functionalization treatment is to spray 0.5-1 wt% talcum powder and 1-2 wt% polyvinyl alcohol on the sieved particles, and finally perform drying treatment.

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