Nitrogen-alkali coupling modified biochar and preparation method thereof, nitrogen-alkali coupling modified biochar-based bacterial fertilizer and preparation method and application of nitrogen-alkali coupling modified biochar-based bacterial fertilizer

Abstract

The invention provides nitrogen-alkali coupling modified biochar and a preparation method thereof, nitrogen-alkali coupling modified biochar-based bacterial fertilizer and a preparation method and application of the nitrogen-alkali coupling modified biochar-based bacterial fertilizer. The preparation method of the nitrogen-alkali coupling modified biochar comprises the following steps: step S101, mixing blocky eucommia branches with urea, and uniformly grinding; then, carrying out first modification reaction in a protective atmosphere to obtain nitrogen modified biochar; step S102, impregnating the nitrogen-modified biochar in an aqueous solution of inorganic alkali, and then carrying out a second modification reaction in a protective atmosphere; then, washing with a washing solution to obtain the nitrogen-alkali coupling modified biochar. The pore structure of the biochar is optimized through nitrogen-alkali coupling modification, and the porosity, specific surface area and active sites are increased, so that the immobilization and release effects of the nitrogen-alkali coupling modified biochar on microorganisms are improved, the leaching rate of nitrogen, phosphorus and potassium nutrients is reduced, the slow release effect is improved, and the effective utilization rate of the nitrogen, phosphorus and potassium nutrients is improved.

Description

Technical Field

[0001] The present application relates to the technical field related to modified biochar-based bacterial fertilizers, and specifically provides a nitrogen-base coupled modified biochar and a preparation method thereof, a nitrogen-base coupled modified biochar-based bacterial fertilizer and a preparation method and use thereof. Background Art

[0002] As a new type of microbial agent carrier, biochar has good pore structure and chemical properties, which can improve the nutrient content of soil by improving the survival rate and stability of microbial agents in the soil.

[0003] Biochar as a carrier of microbial agents mainly relies on its adsorption capacity, and the adsorption capacity of biochar mainly depends on the specific surface area and surface functional groups of biochar; surface nutrients are also the key to biochar as a carrier of microbial agents. Only by providing the nutrients required by microorganisms can the microbial agents play a role in a long-term and efficient manner. However, biochar prepared by traditional methods is easily affected by various factors, resulting in small porosity and specific surface area, low microbial load, and poor nutrient slow-release leaching effect. Summary of the invention

[0004] In view of this, the present application provides a nitrogen-alkali coupled modified biochar and a preparation method thereof, a nitrogen-alkali coupled modified biochar-based bacterial fertilizer and a preparation method and use thereof.

[0005] In a first aspect of the present application, the present application provides a method for preparing nitrogen-base coupled modified biochar, which comprises the following steps:

[0006] Step S101, mixing and grinding the blocky Eucommia ulmoides branches and urea at a weight ratio of 1: (0.5-1.5) evenly; then, performing a first modification reaction in a protective atmosphere to obtain nitrogen-modified biochar; wherein the temperature of the first modification reaction is selected from (400-600)°C;

[0007] Step S102, the nitrogen-modified biochar is first immersed in an aqueous solution of an inorganic base, and then a second modification reaction occurs in a protective atmosphere; thereafter, it is washed with a washing liquid until the pH value of the washing liquid is in the range of (6.5 to 7.5) to obtain the nitrogen-base coupled modified biochar; wherein the temperature of the second modification reaction is selected from (700 to 1000)°C.

[0008] In some optional embodiments, in step S101, the weight ratio of the block of Eucommia ulmoides branches and the urea is 1:(0.8-1.2); for example, 1:0.8, 1:0.85, 1:0.9, 1:0.95, 1:1, 1:1.05, 1:1.1, 1:1.15 or 1:1.2, etc.

[0009] In some optional embodiments, in step S101, the block of Eucommia branches and trunks are obtained by first crushing the Eucommia branches and trunks (particle size ≤ 10 mesh; for example, 10 mesh, 15 mesh, 16 mesh, 17 mesh, 18 mesh, 19 mesh, 20 mesh, 25 mesh, 30 mesh, 40 mesh, 45 mesh, 50 mesh, 55 mesh, 60 mesh, 65 mesh, 70 mesh, 75 mesh, 80 mesh, 85 mesh, 90 mesh, 95 mesh or 100 mesh, etc.), and then drying them (temperature is (60-80)°C, for example, 60°C, 65°C, 70°C, 75°C or 80°C, etc.; time is (5-10) hours, for example, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours or 10 hours, etc.).

[0010] In some optional embodiments, in step S101, the temperature of the first modification reaction is selected from (450-550)°C; for example, 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C or 550°C, etc.

[0011] In some optional embodiments, in step S101, the time of the first modification reaction is selected from (1 to 5) hours; for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours.

[0012] In some optional embodiments, in step S102, the aqueous solution of inorganic base is selected from an aqueous solution of inorganic base with a concentration of (10-30) wt%; for example, 10 wt%, 15 wt%, 20 wt%, 25 wt% or 30 wt%, etc. In some specific embodiments, in step S102, the aqueous solution of inorganic base is selected from an aqueous solution of inorganic base with a concentration of 15 wt%.

[0013] In some optional embodiments, in step S102, the inorganic base is selected from at least one of sodium hydroxide and potassium hydroxide. In some specific embodiments, in step S102, the inorganic base is selected from sodium hydroxide.

[0014] In some optional embodiments, in step S102, the washing liquid is selected from at least one of an aqueous solution of hydrogen chloride and water. Further, the washing liquid is selected from at least one of an aqueous solution of hydrogen chloride with a concentration of (1 to 20) wt% (e.g., 1 wt%, 5 wt%, 10 wt%, 15 wt% or 20 wt%, etc.) and water. Further, the washing liquid includes an aqueous solution of hydrogen chloride with a concentration of (1 to 20) wt% and water. In some specific embodiments, the washing liquid includes an aqueous solution of hydrogen chloride with a concentration of 10 wt% and water.

[0015] In some optional embodiments, in step S102, the temperature of the second modification reaction is selected from (700-900)°C; for example, 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C or 900°C, etc.

[0016] In some optional embodiments, in step S102, the time of the second modification reaction is selected from (1 to 5) hours; for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours.

[0017] In the second aspect of the present application, the present application provides a nitrogen-base coupled modified biochar prepared by the preparation method described in the first aspect of the present application.

[0018] In a third aspect of the present application, the present application provides a method for preparing a nitrogen-alkali coupled modified biochar-based bacterial fertilizer, which comprises the following steps:

[0019] Step S201: The nitrogen-base coupling modified biochar and the coprecipitated Al 2 O 3 -SiO 2 The gel is mixed evenly; wherein the nitrogen-base coupling modified biochar and the co-precipitated Al 2 O 3 -SiO 2 The gel weight ratio is 1:(0.1-0.5);

[0020] Step S202, mixing the mixture obtained in step S201 with the bacterial solution and culturing the mixture; then performing solid-liquid separation and drying to obtain the nitrogen-base coupled modified biochar-based bacterial fertilizer; wherein the weight ratio of the mixture to the bacterial solution is 1:(0.5-1.5); and the number of effective live bacteria in the bacterial solution is ≥600 million / g.

[0021] In some optional embodiments, in step S201, the co-precipitated Al 2 O 3 -SiO 2 The gel was prepared by the following preparation method: first, a sodium aluminate aqueous solution and a sodium silicate aqueous solution were mixed evenly to form a colloidal system; then, CO was introduced into the colloidal system. 2 Gas to make Al 2 O 3 and SiO 2 Co-precipitation; finally, after washing and drying, the co-precipitated Al 2 O3 -SiO 2 gel.

[0022] In some optional embodiments, the concentration of the sodium aluminate aqueous solution is (0.3-0.7) mol / L; for example, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L, 0.5 mol / L, 0.55 mol / L, 0.6 mol / L, 0.65 mol / L or 0.7 mol / L, etc.

[0023] In some optional embodiments, the sodium silicate aqueous solution is prepared by mixing sodium silicate and deionized water in a weight ratio of 1:(2-6); for example, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:55 or 1:6, etc.

[0024] In some optional embodiments, the weight ratio of the sodium aluminate aqueous solution to the sodium silicate aqueous solution is 1:(4-8); for example, 1:4, 1:4.5, 1:5, 1:55, 1:6, 1:6.5, 1:7, 1:7.5 or 1:8, etc.

[0025] In some optional embodiments, in step S201, the nitrogen-base coupling modified biochar and the co-precipitated Al 2 O 3 -SiO 2 The weight ratio of the gel is 1:(0.2-0.3); for example, 1:0.2, 1:0.21, 1:0.22, 1:0.23, 1:0.24, 1:0.25, 1:0.26, 1:0.27, 1:0.28, 1:0.29, 1:0.3, 1:0.31, 1:0.32, 1:0.33, 1:0.34, 1:0.35, 1:0.36, 1:0.37, 1:0.38, 1:0.39 or 1:0.4, etc.

[0026] In some optional embodiments, in step S202, the weight ratio of the third mixture to the bacterial liquid is 1:(0.7-1.3); for example, 1:0.7, 1:0.75, 1:0.8, 1:0.85, 1:0.9, 1:0.95, 1:1, 1:1.05, 1:1.1, 1:1.15, 1:1.2, 1:1.25 or 1:1.3, etc.

[0027] In some optional embodiments, in step S202, the content of organic matter in the bacterial liquid is ≥ 60 wt%.

[0028] In some specific embodiments, in step S202, the effective live bacteria in the bacterial solution include Bacillus subtilis and Bacillus licheniformis. In some optional embodiments, the ratio of the effective live bacteria count of the Bacillus subtilis and the effective live bacteria count of the Bacillus licheniformis in the bacterial solution is 1:(0.2-0.3); for example, 1:0.2, 1:0.21, 1:0.22, 1:0.23, 1:0.24, 1:0.25, 1:0.26, 1:0.27, 1:0.28, 1:0.29 or 1:0.3, etc. In some specific embodiments, the ratio of the effective live bacteria count of the Bacillus subtilis and the effective live bacteria count of the Bacillus licheniformis in the bacterial solution is 1:0.25.

[0029] In some optional embodiments, in step S202, the conditions for culturing the bacteria are: temperature of (30-35)°C (for example, 30°C, 31°C, 32°C, 33°C, 34°C or 35°C, etc.), shaking speed of (100-140) r / min (for example, 100 r / min, 110 r / min, 120 r / min, 130 r / min or 140 r / min, etc.), time of (0.5-2) hours (for example, 0.5 hours, 1 hour, 1.5 hours, 2 hours, etc.).

[0030] In the fourth aspect of the present application, the present application provides a nitrogen-alkali coupled modified biochar-based bacterial fertilizer prepared by the preparation method described in the third aspect of the present application.

[0031] In the fifth aspect of the present application, the present application provides a use of the nitrogen-alkali coupled modified biochar-based bacterial fertilizer described in the fourth aspect of the present application in a slow-release fertilizer.

[0032] This application has the following beneficial effects:

[0033] The present application optimizes the pore structure of biochar through nitrogen-base coupling modification, increases the porosity, specific surface area and active sites, thereby improving the fixation and release effect of nitrogen-base coupling modified biochar on microorganisms, and reducing the leaching rate of nitrogen, phosphorus and potassium nutrients, improving the slow-release effect, and improving the effective utilization rate of nitrogen, phosphorus and potassium nutrients. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 are the SEM images of nitrogen-base coupling modified biochars MEB-700-1 and MEB-900-1.

[0035] Figure 2 These are the XRD spectra of nitrogen-base coupled modified biochars MEB-700-1, MEB-700-2, MEB-800-1, MEB-800-2, MEB-900-1 and MEB-900-2.

[0036] Figure 3 It is the FTIR spectra of nitrogen-base coupled modified biochars MEB-800-1, MEB-800-2, MEB-900-1 and MEB-900-2.

[0037] Figure 4 This is the XPS spectrum of nitrogen-base coupling modified biochar MEB-900-1. DETAILED DESCRIPTION

[0038] The present application discloses nitrogen-base coupled modified biochar and its preparation method, nitrogen-base coupled modified biochar-based bacterial fertilizer and its preparation method and use. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve it. It is particularly important to point out that all similar substitutions and modifications are obvious to those skilled in the art, and they are all deemed to be included in this application. The methods and applications of this application have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of this application to implement and apply the technology of this application.

[0039] In order to make the purpose, technical solutions and advantages of the present application clearer, the implementation scheme of the present application will be further described in detail below in conjunction with examples.

[0040] Preparation Examples 1 to 17 of Nitrogen-Base Coupling Modified Biochar:

[0041] In preparation examples 1 to 17, the specific preparation method of nitrogen-base coupling modified biochar includes the following steps:

[0042] Step S101, the Eucommia ulmoides branches are first crushed (controlling the particle size <18 mesh), and then dried (conditions: temperature is 75°C, time is 6 hours) to obtain block Eucommia ulmoides branches; the block Eucommia ulmoides branches and urea in a weight ratio of 1: (0.5-1.5) are mixed and ground evenly; then, a first modification reaction occurs in a nitrogen atmosphere (conditions: temperature is (400-600)°C, time is (1-5) hours), and nitrogen-modified biochar is obtained;

[0043] Step S102, after the nitrogen-modified biochar is cooled to room temperature, the nitrogen-modified biochar is first stirred for 0.5 hour and immersed for 12 hours in a 15wt% sodium hydroxide aqueous solution, and then solid-liquid separation and drying (conditions: temperature is 75°C, time is 6 hours); then a second modification reaction occurs in a nitrogen atmosphere (conditions: temperature is (700-900)°C, time is (1-5) hours); then washed with a washing liquid (a 10wt% hydrogen chloride aqueous solution and water are used in combination) until the pH value of the washing liquid = 7.0, and dried (conditions: temperature is 75°C, time is 6 hours) to obtain nitrogen-base coupling modified biochar.

[0044] Among them, the conditions selected in the preparation examples 1 to 17 of nitrogen-base coupling modified biochar are shown in Table 1.

[0045] Table 1 Selection of conditions in preparation examples 1 to 17 of nitrogen-base coupling modified biochar:

[0046]

[0047]

[0048] The nitrogen-base coupling modified biochar MEB-700-1 of Preparation Example 1 and the nitrogen-base coupling modified biochar MEB-900-1 of Preparation Example 5 were selected for scanning electron microscope (SEM) analysis. The SEM images of the nitrogen-base coupling modified biochar MEB-700-1 and MEB-900-1 are as follows: Figure 1 shown.

[0049] The nitrogen-base coupling modified biochar MEB-700-1 of Preparation Example 1, the nitrogen-base coupling modified biochar MEB-700-2 of Preparation Example 2, the nitrogen-base coupling modified biochar MEB-800-1 of Preparation Example 3, the nitrogen-base coupling modified biochar MEB-800-2 of Preparation Example 4, the nitrogen-base coupling modified biochar MEB-900-1 of Preparation Example 5 and the nitrogen-base coupling modified biochar MEB-900-2 of Preparation Example 6 were selected for X-ray diffraction (XRD) analysis. Among them, the XRD spectra of the nitrogen-base coupling modified biochar MEB-700-1, MEB-700-2, MEB-800-1, MEB-800-2, MEB-900-1 and MEB-900-2 are as follows: Figure 2 shown.

[0050] The nitrogen-base coupled modified biochar MEB-800-1 of Preparation Example 3, the nitrogen-base coupled modified biochar MEB-800-2 of Preparation Example 4, the nitrogen-base coupled modified biochar MEB-900-1 of Preparation Example 5, and the nitrogen-base coupled modified biochar MEB-900-2 of Preparation Example 6 were selected for Fourier Transform Infrared Spectroscopy (FTIR) analysis. Among them, the FTIR spectra of the nitrogen-base coupled modified biochar MEB-800-1, MEB-800-2, MEB-900-1, and MEB-900-2 are as follows: Figure 3 shown.

[0051] Depend on Figure 3 It can be seen that the nitrogen-base coupling modified biochar MEB-900-1 has a peak at 468 cm -1 、1110cm -1 、1420cm-1 、1580cm -1 and 2450cm -1 The stretching vibration peak appeared at 2450cm -1 The stretching vibration peak at 1580cm corresponds to the stretching vibration of hydroxyl (-OH); -1 、1420cm -1 and 1110cm -1 The stretching vibration peaks at correspond to C=C, O=CO and COC groups, respectively, which indicates that C=C, O=CO and COC groups appear in the nitrogen-base coupling modified biochar, and these functional groups play an important role in the nitrogen-base coupling modified biochar.

[0052] The nitrogen-base coupled modified biochar MEB-900-1 of Preparation Example 5 was selected for X-ray Photoelectron Spectroscopy (XPS) analysis. The XPS spectrum of the nitrogen-base coupled modified biochar MEB-900-1 is as follows: Figure 4 shown.

[0053] Depend on Figure 4 It can be seen that it confirms Figure 3 C=C, O=CO and COC groups appeared in the medium nitrogen base coupling modified biochar MEB-900-1.

[0054] It can be seen that the present application can effectively improve the structure of biochar through high-temperature pyrolysis and nitrogen-base coupling modification methods. High-temperature carbonization can enhance the biological activity of biochar. It may be that more active functional groups are formed during the high-temperature treatment, thereby enhancing its biological activity; NaOH acts as a pore-forming agent in the activation process, which will promote the formation of abundant microporous pores inside the biochar; urea modification can increase the microporosity and nitrogen doping content; in short, nitrogen-base coupling modification causes a large number of wrinkles to form on the surface of biochar, increases the specific surface area and active sites, improves the electron density and alkalinity of carbon, and is conducive to the fixation of microorganisms on the microporous surface.

[0055] Preparation of nitrogen-modified biochar Comparative Example 1:

[0056] In the preparation comparative example 1, the specific preparation method of the nitrogen-modified biochar-based fertilizer comprises the following steps:

[0057] The Eucommia ulmoides branches and trunks are first crushed (controlling the particle size <18 mesh) and then dried (conditions: temperature is 75°C and time is 6 hours) to obtain block-shaped Eucommia ulmoides branches and trunks; the block-shaped Eucommia ulmoides branches and trunks are mixed with urea in a weight ratio of 1:1 and ground evenly; then, a first modification reaction occurs in a nitrogen atmosphere (conditions: temperature is 500°C and time is 2 hours) to obtain nitrogen-modified biochar.

[0058] Preparation of alkali-modified biochar Comparative Example 2:

[0059] In the preparation comparative example 2, the specific preparation method of the alkali-modified biochar comprises the following steps:

[0060] First, the Eucommia ulmoides branches are crushed (the particle size is controlled to be less than 18 meshes) to obtain block-shaped Eucommia ulmoides branches; then, the block-shaped Eucommia ulmoides branches are placed in a 15wt% sodium hydroxide aqueous solution, stirred for 0.5 hours, immersed for 12 hours, and then separated from the solid and liquid and dried (conditions: temperature is 75°C, time is 6 hours); finally, a second modification reaction occurs in a nitrogen atmosphere (conditions: temperature is 900°C, time is 1 hour), and then washed with a washing liquid (a 10wt% hydrogen chloride aqueous solution and water are used in combination) until the pH value of the washing liquid is 7.0, and dried (conditions: temperature is 75°C, time is 6 hours) to obtain alkali-modified biochar.

[0061] Examples 1 to 19 and Comparative Examples 1 to 2 of modified biochar-based bacterial fertilizers:

[0062] In Examples 1 to 19 and Comparative Examples 1 to 2, the preparation method of the modified biochar-based fertilizer specifically includes the following steps:

[0063] Step S201, modifying biochar (nitrogen-base coupling modified biochar, or nitrogen-modified biochar, or alkali-modified biochar) and coprecipitating Al in a weight ratio of 1: (0.1-0.5) 2 O 3 -SiO 2 The gel was mixed evenly; among them, the coprecipitated Al 2 O 3 -SiO 2 The gel was prepared by the following preparation method: first, a sodium aluminate aqueous solution (concentration of 0.5 mol / L) and a sodium silicate aqueous solution (prepared by sodium silicate and deionized water in a weight ratio of 1:4) were mixed evenly to form a colloidal system; then, CO was introduced into the colloidal system. 2 Gas to make Al 2 O 3 and SiO 2 Finally, after washing and drying, the coprecipitated Al 2 O 3 -SiO 2 gel;

[0064] Step S202, the mixture obtained in step S201 and the bacterial solution are mixed at a weight ratio of 1:1 and cultured (conditions: temperature of (30-35)°C, shaking speed of (100-140) r / min, time of (0.5-2) hours); then solid-liquid separation (placed in a centrifuge, centrifuged at a speed of (4000-6000) r / min) and dried (conditions: at (35-40)°C air-dried under conditions) to obtain modified biochar-based fertilizer (nitrogen-alkali coupling modified biochar-based fertilizer, or nitrogen-modified biochar-based fertilizer, or alkali-modified biochar-based fertilizer); wherein the content of organic matter in the bacterial solution is ≥60wt%, and the number of effective live bacteria is ≥600 million / g, the effective live bacteria in the bacterial solution include Bacillus subtilis and Bacillus licheniformis, and the ratio of the effective live bacteria number of Bacillus subtilis to the effective live bacteria number of Bacillus licheniformis in the bacterial solution is 1:0.25.

[0065] Table 2 Condition selection in Examples 1 to 19 and Comparative Examples 1 to 2 of modified biochar-based fertilizers:

[0066]

[0067] Evaluation of the slow-release performance of modified biochar-based fertilizer:

[0068] This application uses a soil column leaching test to evaluate the slow-release performance of modified biochar-based fertilizer. There are 22 treatment groups in the soil column leaching test, including 1 blank control group and 21 test groups. Three soil columns are set up for each group, totaling 66 soil columns. Among them, the soil column is an acrylic transparent tube with an inner diameter of 5 cm and a height of 35 cm, with multiple small holes with a diameter of 1 mm at the bottom; a 50mL triangular flask is placed under the soil column to collect the leaching solution.

[0069] Filling of soil column: First, evenly apply vaseline on the inner wall of the soil column to increase the friction between the soil and the inner wall to prevent preferential flow; then, lay nylon mesh (300 mesh), quartz sand (particle size is (6-8) mesh, thickness is 3cm, quartz sand is soaked in dilute hydrochloric acid and rinsed with pure water before laying) and nylon mesh (300 mesh) in the bottom of the soil column in order from bottom to top to prevent the loss of soil filled at the bottom of the soil column; then, fill the soil (Among them, 5wt% of modified biochar-based fertilizer was added to the soil filled in the experimental group, and no modified biochar-based fertilizer was added to the soil filled in the blank control group), the marginal soil was compacted; finally, 2 layers of nylon mesh (300 mesh, for uniform water distribution) and quartz sand (particle size of (6-8) mesh, thickness of 3cm, quartz sand was soaked in dilute hydrochloric acid and rinsed with pure water before laying, in order to reduce the disturbance of water flow to the soil surface) were laid from the lower right to the top of the soil surface.

[0070] The leaching solution was collected from each soil column at 0 hours, 24 hours, 48 ​​hours, 72 hours, 96 hours, 120 hours, 144 hours and 168 hours, and the nitrogen, phosphorus and potassium contents in the leaching solution were determined.

[0071] The nitrogen, phosphorus and potassium content of each treatment group was the average value of the nitrogen, phosphorus and potassium content of three repeated soil columns.

[0072] Table 3 Measurement results of soil column leaching test in Examples 1 to 19 and Comparative Examples 1 to 2 of modified biochar-based bacterial fertilizers:

[0073]

[0074] As can be seen from Table 3, the nitrogen-base coupling modified biochar of the present application can significantly reduce the leaching rate of nitrogen, phosphorus, and potassium nutrients, improve the slow-release effect, and improve the effective utilization rate of nitrogen, phosphorus, and potassium nutrients. This is because the present application optimizes the pore structure of biochar through nitrogen-base coupling modification, increases the porosity, specific surface area, and active sites, thereby improving the fixation and release effect of nitrogen-base coupling modified biochar on microorganisms, and reduces the leaching rate of nitrogen, phosphorus, and potassium nutrients, improves the slow-release effect, and improves the effective utilization rate of nitrogen, phosphorus, and potassium nutrients.

[0075] By comparing Example 7 and Comparative Examples 1 to 2, it can be seen that compared with the nitrogen-modified biochar obtained only through the first modification reaction and the alkali-modified biochar obtained only through the second modification reaction, the nitrogen-base coupled modified biochar obtained by the combination of the first modification reaction and the second modification reaction used in the present application can significantly reduce the leaching rate of nitrogen, phosphorus and potassium nutrients, enhance the slow release effect, and improve the effective utilization rate of nitrogen, phosphorus and potassium nutrients.

[0076] By comparing Examples 1 to 4, 7, and 11 to 13, it can be seen that the temperature and time of the second modification reaction can affect the slow-release fertilizer effect of the nitrogen-base coupling modified biochar on the nitrogen-base coupling modified biochar-based bacterial fertilizer. Among them, the gain of the temperature of the second modification reaction on the slow-release fertilizer effect is from best to worst: 900℃>1000℃>800℃>700℃.

[0077] By comparing Examples 7 and 14 to 17, it can be seen that the weight ratio of the block of Eucommia ulmoides branches and urea can slightly affect the slow-release fertilizer effect of the nitrogen-base coupling modified biochar on the nitrogen-base coupling modified biochar-based bacterial fertilizer. By comparing Examples 7 and 18 to 19, it can be seen that the temperature of the first modification reaction can affect the slow-release fertilizer effect of the nitrogen-base coupling modified biochar on the nitrogen-base coupling modified biochar-based bacterial fertilizer. Among them, the temperature of the first modification reaction has an effect on the slow-release fertilizer effect from best to worst: 500℃>600℃>400℃.

[0078] The nitrogen-base coupled modified biochar and its preparation method, the nitrogen-base coupled modified biochar-based bacterial fertilizer and its preparation method and use provided by the present application are introduced in detail above. This article uses specific examples to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea. It should be pointed out that for technical personnel in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

Claims

1. A method for preparing nitrogen-base coupled modified biochar, characterized in that: It includes the following steps: Step S101, mixing and grinding the blocky Eucommia ulmoides branches and urea at a weight ratio of 1: (0.5-1.5) evenly; then, performing a first modification reaction in a protective atmosphere to obtain nitrogen-modified biochar; wherein the temperature of the first modification reaction is selected from (400-600)°C; Step S102, the nitrogen-modified biochar is first immersed in an aqueous solution of an inorganic base, and then a second modification reaction occurs in a protective atmosphere; thereafter, it is washed with a washing liquid until the pH value of the washing liquid is in the range of (6.5 to 7.5) to obtain the nitrogen-base coupled modified biochar; wherein the temperature of the second modification reaction is selected from (700 to 1000)°C.

2. The preparation method according to claim 1, characterized in that: In step S101, the temperature of the first modification reaction is selected from (450-550)°C; And / or, in step S101, the time of the first modification reaction is selected from (1 to 5) hours.

3. The preparation method according to claim 1, characterized in that: In step S102, the aqueous solution of inorganic base is selected from an aqueous solution of inorganic base with a concentration of (10-30) wt%; And / or, in step S102, the inorganic base is selected from at least one of sodium hydroxide and potassium hydroxide.

4. The preparation method according to claim 1, characterized in that: In step S102, the washing liquid is selected from at least one of an aqueous solution of hydrogen chloride and water.

5. The preparation method according to claim 1, characterized in that: In step S102, the temperature of the second modification reaction is selected from (700-900)°C; And / or, the time of the second modification reaction is selected from (1 to 5) hours.

6. A nitrogen-base coupled modified biochar prepared by the preparation method according to any one of claims 1 to 5.

7. A method for preparing nitrogen-alkali coupled modified biochar-based fertilizer, characterized in that: It includes the following steps: Step S201, uniformly mixing the nitrogen-base coupling modified biochar and the co-precipitated Al2O3-SiO2 gel according to claim 6; wherein the weight ratio of the nitrogen-base coupling modified biochar to the aluminum sol is 1:(0.1-0.5); Step S202, mixing the mixture obtained in step S201 with the bacterial solution and culturing the mixture; then performing solid-liquid separation and drying to obtain the nitrogen-base coupled modified biochar-based bacterial fertilizer; wherein the weight ratio of the mixture to the bacterial solution is 1:(0.5-1.5); and the number of effective live bacteria in the bacterial solution is ≥600 million / g.

8. The preparation method according to claim 7, characterized in that: In step S201, the weight ratio of the nitrogen-base coupling modified biochar to the co-precipitated Al2O3-SiO2 gel is 1:(0.2-0.3).

9. The preparation method according to claim 7, characterized in that: In step S202, the effective live bacteria in the bacterial solution include Bacillus subtilis and Bacillus licheniformis.

10. The preparation method according to claim 9, characterized in that: The ratio of the effective viable bacteria count of the Bacillus subtilis to the effective viable bacteria count of the Bacillus licheniformis in the bacterial solution is 1:(0.2-0.3).

11. A nitrogen-alkali coupled modified biochar-based fertilizer prepared by the preparation method according to any one of claims 7 to 10.

12. Use of the nitrogen-alkali coupled modified biochar-based fertilizer as claimed in claim 11 in slow-release fertilizer.

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