A nitrogen-base coupled modified biochar and its preparation method, a nitrogen-base coupled modified biochar-based bacterial fertilizer and its preparation method and use

Abstract

The present application provides a nitrogen-alkali coupled modified biochar, a preparation method thereof, a nitrogen-alkali coupled modified biochar-based bacterial fertilizer, a preparation method thereof and uses. The preparation method of the nitrogen-alkali coupled modified biochar includes: Step S101, mixing and grinding the massive Eucommia ulmoides Oliv. branches with urea; then, performing a first modification reaction in a protective atmosphere to obtain a nitrogen-modified biochar; Step S102, impregnating the nitrogen-modified biochar in an aqueous solution of an inorganic base first and then performing a second modification reaction in a protective atmosphere; then, washing with a washing solution to obtain the nitrogen-alkali coupled modified biochar. The present application optimizes the pore structure of the biochar through nitrogen-alkali coupling modification, increases the porosity, specific surface area and active sites, thereby improving the fixation and release effects of the nitrogen-alkali coupled modified biochar on microorganisms, reducing the leaching rate of nitrogen, phosphorus and potassium nutrients, enhancing the slow-release effect, and improving the effective utilization rate of nitrogen, phosphorus and potassium nutrients.

Description

Technical Field

[0001] The present application relates to the technical field of modified biochar-based bacterial fertilizers, and specifically 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. Background Art

[0002] As a new type of microbial inoculant carrier, biochar can improve the nutrient content of soil by enhancing the survival rate and stability of microbial inoculants in soil due to its good pore structure and chemical properties.

[0003] Biochar acts as a microbial inoculant carrier mainly relying on its adsorption ability, and the adsorption ability of biochar mainly depends on the specific surface area and surface functional groups of biochar; the nutrients on the surface are also crucial for biochar to be used as a microbial inoculant carrier. Only by providing the nutrients required by microorganisms can the microbial inoculant play a lasting and efficient role. However, the biochar prepared by traditional methods is easily affected by various factors, resulting in small porosity and specific surface area, low microbial loading, and poor nutrient slow-release and leaching effects. 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 the first aspect of the present application, a preparation method of a nitrogen-alkali coupled modified biochar is provided, which includes the following steps:

[0006] Step S101: Mix and grind blocky Eucommia ulmoides branches and urea with a weight ratio of 1:(0.5 - 1.5) evenly; then, carry out 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: Immerse the nitrogen-modified biochar in an aqueous solution of an inorganic base first, and then carry out a second modification reaction in a protective atmosphere; then, wash with a washing solution until the pH value of the washing solution is within the range of (6.5 - 7.5) to obtain the nitrogen-alkali coupled modified biochar; wherein, the temperature of the second modification reaction is selected from (700 - 1000)°C.

[0008] In some optional embodiments, in step S101, the weight ratio of the blocky Eucommia ulmoides branches to 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 alternative embodiments, in step S101, the blocky Eucommia ulmoides Oliv. branches and stems are obtained by first subjecting Eucommia ulmoides Oliv. branches and stems to comminution treatment (particle size ≤ 10 mesh; such as 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 subjecting them to drying treatment (temperature is (60 - 80) °C, such as 60 °C, 65 °C, 70 °C, 75 °C or 80 °C, etc.; time is (5 - 10) hours, such as 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 alternative embodiments, in step S101, the temperature of the first modification reaction is selected from (450 - 550) °C; such as 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 alternative embodiments, in step S101, the time of the first modification reaction is selected from (1 - 5) hours; such as 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 alternative embodiments, in step S102, the aqueous solution of the inorganic base is selected from aqueous solutions of inorganic bases with a concentration of (10 - 30) wt%; such as 10 wt%, 15 wt%, 20 wt%, 25 wt% or 30 wt%, etc. In some specific embodiments, in step S102, the aqueous solution of the inorganic base is selected from an aqueous solution of an inorganic base with a concentration of 15 wt%.

[0013] In some alternative 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 alternative 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 - 20) wt% (such as 1 wt%, 5 wt%, 10 wt%, 15 wt% or 20 wt%, etc.) and water. Still further, the washing liquid includes an aqueous solution of hydrogen chloride with a concentration of (1 - 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 alternative 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 alternative embodiments, in step S102, the time of the second modification reaction is selected from (1 - 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 - alkali coupled modified biochar prepared by the preparation method described in the first aspect of the present application.

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

[0019] Step S201: Mix the nitrogen - alkali coupled modified biochar described in the second aspect of the present application and coprecipitated Al 2 O 3 -SiO 2 gel evenly; wherein, the weight ratio of the nitrogen - alkali coupled modified biochar to the coprecipitated Al 2 O 3 -SiO 2 gel is 1:(0.1 - 0.5);

[0020] Step S202: Mix the mixture obtained in step S201 and the bacterial liquid and carry out bacterial strain cultivation; then carry out solid - liquid separation and drying to obtain the nitrogen - alkali coupled modified biochar - based bacterial fertilizer; wherein, the weight ratio of the mixture to the bacterial liquid is 1:(0.5 - 1.5); and the effective viable bacteria count in the bacterial liquid is ≥ 600 million / g.

[0021] In some alternative embodiments, in step S201, the coprecipitated Al 2 O 3 -SiO 2 gel is prepared by the following preparation method: First, mix the aqueous solution of sodium aluminate and the aqueous solution of sodium silicate evenly to form a colloidal system; then, introduce CO 2 gas into the colloidal system to cause coprecipitation of Al 2 O 3 and SiO 2 ; finally, after washing and drying, obtain coprecipitated Al 2 O3 -SiO 2 gel

[0022] In some alternative 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 alternative embodiments, the sodium silicate aqueous solution is prepared from sodium silicate and deionized water with 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 alternative 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 alternative embodiments, in step S201, the weight ratio of the nitrogen - base - coupled modified biochar to the coprecipitated Al 2 O 3 -SiO 2 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 alternative embodiments, in step S202, the weight ratio of the third mixture to the bacterial solution 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 alternative embodiments, in step S202, the content of organic matter in the bacterial solution is ≥60 wt%.

[0028] In some specific embodiments, in step S202, the effective viable bacteria in the bacterial liquid include Bacillus subtilis and Bacillus licheniformis. In some alternative embodiments, the ratio of the number of effective viable bacteria of Bacillus subtilis to the number of effective viable bacteria of Bacillus licheniformis in the bacterial liquid 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 number of effective viable bacteria of Bacillus subtilis to the number of effective viable bacteria of Bacillus licheniformis in the bacterial liquid is 1:0.25.

[0029] In some alternative embodiments, in step S202, the conditions for culturing the bacterial strain are: the temperature is (30 - 35)°C (such as 30°C, 31°C, 32°C, 33°C, 34°C, or 35°C, etc.), the oscillation speed is (100 - 140) r / min (such as 100 r / min, 110 r / min, 120 r / min, 130 r / min, or 140 r / min, etc.), and the time is (0.5 - 2) hours (such as 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 the use of the nitrogen - alkali coupled modified biochar - based bacterial fertilizer described in the fourth aspect of the present application in slow - release and controlled - release fertilizers.

[0032] The present application has the following beneficial effects:

[0033] The present application optimizes the pore structure of biochar through nitrogen - alkali coupling modification, increases the porosity, specific surface area, and active sites, thereby improving the fixation and release effects of nitrogen - alkali coupled modified biochar on microorganisms, reducing the leaching rate of nitrogen, phosphorus, and potassium nutrients, enhancing 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 - alkali coupled modified biochars MEB - 700 - 1 and MEB - 900 - 1.

[0035] Figure 2 are the XRD spectra of nitrogen - alkali 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 These are 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 coupled modified biochar MEB-900-1. Detailed implementation manners

[0038] This application discloses nitrogen-base coupled modified biochars and their preparation methods, nitrogen-base coupled modified biochar-based bacterial fertilizers and their preparation methods and uses. Those skilled in the art can draw on the content of this article and appropriately modify the process parameters to achieve. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included in this application. The methods and applications of this application have been described through preferred embodiments, and those related can obviously make changes or appropriate changes and combinations to 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] To make the purpose, technical solutions and advantages of this application clearer, the implementation solutions of this application will be further described in detail below in conjunction with embodiments.

[0040] Preparation Examples 1 - 17 of Nitrogen-Alkali Coupled Modified Biochar:

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

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

[0043] Step S102: After the nitrogen-modified biochar is cooled to room temperature, the nitrogen-modified biochar is first stirred in a 15 wt% sodium hydroxide aqueous solution for 0.5 hours and impregnated for 12 hours, then subjected to solid-liquid separation and dried (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, it is washed with a washing solution (a combination of an aqueous solution of 10 wt% hydrogen chloride and water) until the pH value of the wash liquor = 7.0, and dried (conditions: temperature is 75 °C, time is 6 hours) to obtain the nitrogen-base coupled modified biochar.

[0044] Among them, the condition selections in Preparation Examples 1 to 17 of the nitrogen-alkali coupled modified biochar are shown in Table 1.

[0045] Table 1 Condition selections in Preparation Examples 1 to 17 of the nitrogen-alkali coupled modified biochar:

[0046]

[0047]

[0048] Select the nitrogen-alkali coupled modified biochar MEB-700-1 of Preparation Example 1 and the nitrogen-alkali coupled modified biochar MEB-900-1 of Preparation Example 5 for Scanning Electron Microscope (SEM) analysis. Among them, the SEM images of the nitrogen-alkali coupled modified biochars MEB-700-1 and MEB-900-1 are as Figure 1 shown.

[0049] Select the nitrogen-alkali coupled modified biochar MEB-700-1 of Preparation Example 1, the nitrogen-alkali coupled modified biochar MEB-700-2 of Preparation Example 2, the nitrogen-alkali coupled modified biochar MEB-800-1 of Preparation Example 3, the nitrogen-alkali coupled modified biochar MEB-800-2 of Preparation Example 4, the nitrogen-alkali coupled modified biochar MEB-900-1 of Preparation Example 5, and the nitrogen-alkali coupled modified biochar MEB-900-2 of Preparation Example 6 for X-ray Diffraction (XRD) analysis. Among them, the XRD spectra of the nitrogen-alkali coupled modified biochars MEB-700-1, MEB-700-2, MEB-800-1, MEB-800-2, MEB-900-1, and MEB-900-2 are as Figure 2 shown.

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

[0051] It can be seen from Figure 3 that the nitrogen-alkali coupled modified biochar MEB-900-1 has absorption peaks at 468 cm -1 、1110 cm -1 、1420 cm-1 , 1580 cm -1 and 2450 cm -1 showed stretching vibration peaks. Among them, the stretching vibration peak at 2450 cm -1 corresponded to the stretching vibration of the hydroxyl group (-OH); the stretching vibration peaks at 1580 cm -1 , 1420 cm -1 and 1110 cm -1 corresponded to the C=C, O=C-O and C-O-C groups respectively. Thus, it was indicated that the C=C, O=C-O and C-O-C groups appeared in the nitrogen-base coupled modified biochar, and these functional groups played an important role in the nitrogen-base coupled modified biochar.

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

[0053] From Figure 4 it was known that it confirmed Figure 3 that the C=C, O=C-O and C-O-C groups appeared in the nitrogen-base coupled modified biochar MEB-900-1.

[0054] Thus, it can be seen that the structure of the biochar can be effectively improved by the high-temperature pyrolysis and nitrogen-base coupled modification method. High-temperature carbonization can enhance the biological activity of the biochar, probably because more active functional groups are formed during the high-temperature treatment process, thereby enhancing its biological activity; NaOH plays the role of a pore-forming agent during the activation process, which will promote the formation of abundant micropores inside the biochar; urea modification can increase the microporosity and nitrogen doping content; in short, nitrogen-base coupled modification makes the biochar surface form a large number of wrinkles, 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 micropore surface.

[0055] Preparation Comparative Example 1 of Nitrogen-Modified Biochar:

[0056] In the preparation of Comparative Example 1, the specific preparation method of the nitrogen-modified biochar-based bacterial fertilizer included the following steps:

[0057] The Eucommia ulmoides branches were first subjected to crushing treatment (controlling the particle size <18 mesh), and then subjected to drying treatment (conditions: temperature 75 °C, time 6 hours) to obtain block-shaped Eucommia ulmoides branches; the block-shaped Eucommia ulmoides branches and urea with a weight ratio of 1:1 were mixed and ground evenly; then, a first modification reaction was carried out in a nitrogen atmosphere (conditions: temperature 500 °C, time 2 hours) to obtain nitrogen-modified biochar.

[0058] Preparation Comparative Example 2 of Alkali-Modified Biochar:

[0059] In the preparation of Comparative Example 2, the specific preparation method of the alkali-modified biochar includes the following steps:

[0060] First, the Eucommia ulmoides branches are crushed (the particle size is controlled to be <18 mesh) to obtain block-shaped Eucommia ulmoides branches; then, the block-shaped Eucommia ulmoides branches are placed in a 15 wt% sodium hydroxide aqueous solution, stirred for 0.5 hours first, then impregnated for 12 hours, and then subjected to solid-liquid separation and drying (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 solution (a combined use of an aqueous solution of 10 wt% hydrogen chloride and water) until the pH value of the wash liquor = 7.0, and dried (conditions: temperature is 75 °C, time is 6 hours) to obtain the alkali-modified biochar.

[0061] Examples 1 - 19 and Comparative Examples 1 - 2 of Modified Biochar-Based Bacterial Fertilizer:

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

[0063] Step S201. Mix the modified biochar (nitrogen-alkali coupled modified biochar, or nitrogen-modified biochar, or alkali-modified biochar) and coprecipitated Al 2 O 3 -SiO 2 gel in a weight ratio of 1:(0.1 - 0.5); wherein, the coprecipitated Al 2 O 3 -SiO 2 gel is prepared by the following preparation method: First, mix an aqueous solution of sodium aluminate (concentration 0.5 mol / L) and an aqueous solution of sodium silicate (which is prepared from sodium silicate and deionized water in a weight ratio of 1:4) in a weight ratio of 1:6 to form a colloidal system; then, introduce CO 2 gas into the colloidal system to cause coprecipitation of Al 2 O 3 and SiO 2 ; finally, after washing and drying, obtain the coprecipitated Al 2 O 3 -SiO 2 gel;

[0064] Step S202: Mix the mixture obtained in Step S201 and the bacterial solution with a weight ratio of 1:1 and conduct bacterial strain cultivation (conditions: temperature is (30 - 35) °C, oscillation speed is (100 - 140) r / min, time is (0.5 - 2) hours); then conduct solid-liquid separation (place in a centrifuge and conduct centrifugal separation under the condition of a rotation speed of (4000 - 6000) r / min) and drying (conditions: air dry under the condition of (35 - 40) °C) to obtain modified biochar-based bacterial fertilizer (nitrogen-alkali coupling modified biochar-based bacterial fertilizer, or nitrogen-modified biochar-based bacterial fertilizer, or alkali-modified biochar-based bacterial fertilizer); wherein, the content of organic matter in the bacterial solution ≥ 60 wt%, the effective viable count ≥ 600 million / g, the effective viable bacteria in the bacterial solution include Bacillus subtilis and Bacillus licheniformis, and the ratio of the effective viable count of Bacillus subtilis to the effective viable count of Bacillus licheniformis in the bacterial solution is 1:0.25.

[0065] Table 2 Condition selection in Examples 1 - 19 and Comparative Examples 1 - 2 of the modified biochar-based bacterial fertilizer:

[0066]

[0067] Evaluation of the Sustained-Release Performance of Modified Biochar-Based Bacterial Fertilizer:

[0068] This application uses a soil column leaching test to evaluate the slow-release performance of the modified biochar-based bacterial fertilizer. A total of 22 treatment groups are set up in the soil column leaching test, including 1 blank control group and 21 test groups. 3 soil columns are set 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, and multiple small holes with a diameter of 1 mm are opened at the bottom; a 50 mL Erlenmeyer flask is placed below the soil column to collect the leaching solution.

[0069] Filling of the 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 and prevent preferential flow; then, lay a nylon mesh (300 mesh), quartz sand (particle size is (6 - 8) mesh, thickness is 3 cm, and the quartz sand is soaked in dilute hydrochloric acid and rinsed with pure water before laying), and a nylon mesh (300 mesh) in sequence from bottom to top at the bottom of the soil column to prevent the soil filled at the bottom of the soil column from flowing away; then, fill the soil (wherein, 5 wt% of the modified biochar-based bacterial fertilizer is added to the soil filled in the test group, and no modified biochar-based bacterial fertilizer is added to the soil filled in the blank control group), and compact the edge soil; finally, lay 2 layers of nylon mesh (300 mesh, the function is to distribute water evenly) and quartz sand (particle size is (6 - 8) mesh, thickness is 3 cm, and the quartz sand is soaked in dilute hydrochloric acid and rinsed with pure water before laying, the function is to reduce the disturbance of the water flow to the soil surface layer) from bottom to top on the soil surface layer.

[0070] Leachate was collected from each soil column at 0 h, 24 h, 48 h, 72 h, 96 h, 120 h, 144 h, and 168 h, and the contents of nitrogen, phosphorus, and potassium in the leachate were measured.

[0071] Among them, the contents of nitrogen, phosphorus, and potassium in each treatment group were the average values of the contents of nitrogen, phosphorus, and potassium in 3 replicated soil columns.

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

[0073]

[0074] As can be seen from Table 3, the nitrogen-alkali coupled modified biochar of the present application can significantly reduce the leaching rates of nitrogen, phosphorus, and potassium nutrients, improve the slow-release effect, and increase the effective utilization rate of nitrogen, phosphorus, and potassium nutrients. This is because the pore structure of the biochar is optimized by nitrogen-alkali coupling modification in the present application, increasing the porosity, specific surface area, and active sites, thereby improving the fixation and release effects of nitrogen-alkali coupled modified biochar on microorganisms, reducing the leaching rates of nitrogen, phosphorus, and potassium nutrients, improving the slow-release effect, and increasing the effective utilization rate of nitrogen, phosphorus, and potassium nutrients.

[0075] By comparing Example 7 with Comparative Examples 1-2, 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-alkali coupled modified biochar obtained by combining the first modification reaction and the second modification reaction in the present application can significantly reduce the leaching rates of nitrogen, phosphorus, and potassium nutrients, improve the slow-release effect, and increase the effective utilization rate of nitrogen, phosphorus, and potassium nutrients.

[0076] By comparing Examples 1-4, 7, 11-13, it can be seen that the temperature and time of the second modification reaction can affect the slow and controlled release fertilizer effect of nitrogen-alkali coupled modified biochar on nitrogen-alkali coupled modified biochar-based bacterial fertilizer. Among them, the order of the gain of the temperature of the second modification reaction on the slow and controlled release fertilizer effect from good to bad is: 900 °C > 1000 °C > 800 °C > 700 °C.

[0077] By comparing Example 7 with Examples 14-17, it can be seen that the weight ratio of massive Eucommia ulmoides branches to urea can slightly affect the slow and controlled release fertilizer effect of nitrogen-alkali coupled modified biochar on nitrogen-alkali coupled modified biochar-based bacterial fertilizer. By comparing Example 7 with Examples 18-19, it can be seen that the temperature of the first modification reaction can affect the slow and controlled release fertilizer effect of nitrogen-alkali coupled modified biochar on nitrogen-alkali coupled modified biochar-based bacterial fertilizer. Among them, the order of the gain of the temperature of the first modification reaction on the slow and controlled release fertilizer effect from good to bad is: 500 °C > 600 °C > 400 °C.

[0078] The above has introduced in detail the nitrogen-alkali coupled modified biochar provided by the present application, its preparation method, the nitrogen-alkali coupled modified biochar-based bacterial fertilizer, its preparation method and uses. Specific examples are used in this article to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application. It should be noted that for those skilled in the art of this technology, without departing from the principle of the present application, several improvements and modifications can still be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. 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; wherein the weight ratio of the nitrogen-base coupling modified biochar to the co-precipitated Al2O3-SiO2 gel is 1:0.25; 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; The preparation method of the nitrogen-base coupling modified biochar comprises 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 S202, the effective live bacteria in the bacterial solution include Bacillus subtilis and Bacillus licheniformis.

3. The preparation method according to claim 2, 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).

4. 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.

5. 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.

6. 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.

7. 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.

8. A nitrogen-alkali coupled modified biochar-based fertilizer prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the nitrogen-alkali coupled modified biochar-based bacterial fertilizer as claimed in claim 8 in slow-release fertilizer.

Images