Carbon-based controlled-release fertilizer as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of fertilizers, and discloses a carbon-based slow / controlled-release fertilizer as well as a preparation method and application thereof. The preparation method of the carbon-based slow / controlled-release fertilizer comprises the following steps: mixing biochar, peroxyacetic acid oxidized lignin, starch acetate, an acidic catalyst and a solvent to obtain a mixed solution, adjusting the pH value of the mixed solution, and carrying out a cross-linking reaction to obtain a compound; mixing the compound, urea and a solvent, carrying out a first reaction, mixing a product obtained after the reaction, kaolin and polyvinyl alcohol, and carrying out a second reaction, so as to obtain a urea-loaded compound; and mixing the urea-loaded compound, tetraethoxysilane, hexadecyltrimethoxysilane and a solvent, and carrying out a hydrolysis reaction to obtain the carbon-based slow / controlled-release fertilizer. The carbon-based slow / controlled-release fertilizer effectively reduces the release rate of urea, reduces the dissolution of nutrients and improves the controlled-release performance.

Description

Technical Field

[0001] The present invention relates to the technical field of biological fertilizers, and in particular to a carbon-based slow-release fertilizer and a preparation method and application thereof. Background Art

[0002] With the continuous development of global agriculture, fertilizers play a vital role in increasing crop yields and ensuring food security. However, the extensive use of traditional chemical fertilizers has brought about a series of severe environmental and resource problems. Traditional chemical fertilizers are characterized by rapid solubility. After being applied to the soil, the nutrients in them will quickly dissolve and release, which causes a large amount of nutrients that are not absorbed and utilized by crops to enter the water body through rainwater erosion, surface runoff and other channels, which not only wastes precious resources, but may also lead to soil acidification, compaction and other phenomena of soil quality degradation, affecting the soil's aeration, water retention and fertility retention capacity, which is not conducive to the long-term healthy growth of crops.

[0003] In order to solve these drawbacks of traditional fertilizers, slow-release fertilizer technology came into being. Slow-release fertilizer can release nutrients slowly and continuously according to the growth needs of crops, thereby improving fertilizer utilization, reducing nutrient loss, reducing environmental pollution risks, and simplifying fertilization operations to a certain extent, saving labor costs.

[0004] Among the many research and development directions of slow-release fertilizers, carbon-based materials have attracted much attention due to their unique physical and chemical properties. Biochar is a typical carbon-based material, which is formed by pyrolysis of biomass (such as wood, crop straw, etc.) under anaerobic or hypoxic conditions. Biochar has a rich pore structure, a large specific surface area, and surface functional groups (such as hydroxyl, carboxyl, carbonyl, etc.). These characteristics enable it to adsorb and fix fertilizer nutrients, and regulate the release rate of nutrients through the synergy of physical adsorption and chemical action. However, the adsorption and slow-release effect of biochar on some fertilizers may not be ideal, and its stability in long-term soil environment needs to be improved.

[0005] Therefore, biochar is modified to overcome the shortcomings of biochar materials in the field of slow-release fertilizers and develop carbon-based slow-release fertilizers with better performance to meet the urgent needs of modern agriculture for efficient and environmentally friendly fertilizers. Summary of the invention

[0006] The object of the present invention is to provide a carbon-based slow-release fertilizer and a preparation method and application thereof, so as to solve the problem that the existing carbon-based slow-release fertilizer has poor fertilizer adsorption and slow-release effects.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing a carbon-based slow-release fertilizer, comprising the following steps:

[0009] (1) mixing biochar, peracetic acid oxidized lignin, acetate starch, an acid catalyst and a solvent to obtain a mixed solution, adjusting the pH value of the mixed solution, and performing a cross-linking reaction to obtain a composite;

[0010] (2) mixing the composite, urea and a solvent to carry out a first reaction, mixing the product obtained after the reaction, kaolin and polyvinyl alcohol to carry out a second reaction to obtain a composite loaded with urea;

[0011] (3) The urea-loaded composite, tetraethoxysilane, hexadecyltrimethoxysilane and a solvent are mixed and subjected to a hydrolysis reaction to obtain a carbon-based slow-release fertilizer.

[0012] Preferably, the mass ratio of the biochar, peracetic acid oxidized lignin and acetate starch in step (1) is 1-5:3-8:5-10.

[0013] Preferably, the mass of the acidic catalyst in step (1) is 2 to 5% of the total mass of the modified biochar, peracetic acid oxidized lignin and acetate starch.

[0014] Preferably, the ratio of the modified biochar to the solvent in step (1) is 1-5 g: 30-50 mL.

[0015] Preferably, the acidic catalyst in step (1) comprises a sulfuric acid solution.

[0016] Preferably, the concentration of the sulfuric acid solution is 96-98%.

[0017] Preferably, the solvent in step (1) comprises at least one of dimethyl sulfoxide (DMSO) or N,N-dimethylformamide (DMF).

[0018] Preferably, the target pH value in step (1) is 3-5.

[0019] Preferably, the temperature of the cross-linking reaction in step (1) is 70 to 90° C., and the time of the cross-linking reaction is 40 to 80 minutes.

[0020] Preferably, in step (2), the usage ratio of the complex, urea and solvent is 4-6 g: 0.2-0.7 g: 20-30 mL.

[0021] Preferably, in step (2), the mass ratio of the composite, kaolin and polyvinyl alcohol is 4-6:0.3-1:0.1-0.3.

[0022] Preferably, in step (2), the temperature of the first reaction is 120-140° C., and the time of the first reaction is 1-3 h.

[0023] Preferably, in step (2), the temperature of the second reaction is 120-140° C., and the time of the second reaction is 1-3 h.

[0024] Preferably, in step (3), the ratio of the urea-loaded complex, tetraethoxysilane, hexadecyltrimethoxysilane and solvent is 1-2 g: 0.5-1.5 g: 0.5-1.5 g: 30-50 mL.

[0025] Preferably, the solvent in step (3) comprises at least one of water and an alcohol solution.

[0026] Preferably, the temperature of the hydrolysis reaction in step (3) is 40 to 80° C., and the time of the hydrolysis reaction is 20 to 40 minutes.

[0027] Preferably, after the hydrolysis reaction in step (3) is completed, post-treatment is also included;

[0028] The post-treatment method comprises: dispersing the product obtained after the hydrolysis reaction at 20-30° C. for 12-24 hours, then separating it, washing the separated precipitate with an alcohol solution, and finally drying it to obtain a carbon-based slow-release fertilizer.

[0029] The invention also provides a carbon-based slow-release fertilizer prepared by the preparation method of the carbon-based slow-release fertilizer.

[0030] The invention also provides application of a carbon-based slow-release fertilizer in crop planting.

[0031] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0032] The carbon-based slow-release fertilizer provided by the present invention comprises the following steps: first, biochar, peracetic acid oxidized lignin, and acetate starch are reacted under the action of an acidic catalyst, and the oxygen-containing functional groups on the surface of the biochar react with the peracetic acid oxidized lignin, the peracetic acid oxidized lignin, and the hydroxyl groups of the acetate starch to form ether bonds, thereby achieving cross-linking among the three, thereby forming a pore structure with a more stable structure; and the molecular force among the three also promotes the stability of the cross-linked structure, so that nutrients need to diffuse along a complex path when released, increasing the distance and difficulty for nutrients to reach the soil solution; thereby extending the release time of the nutrients. Secondly, the cross-linked product of the above three is mixed with fertilizer urea. Since biochar, peracetic acid oxidized lignin, and acetate starch can effectively adsorb urea and wrap urea at the same time, kaolin contains a large number of hydroxyl groups, which can undergo grafting polymerization reaction with biochar and polyvinyl alcohol. Due to its adsorption performance, biochar and urea can be closely combined, thereby delaying the release rate of urea and prolonging the sustained release time. At the same time, the effective combination of biochar, urea and kaolin can better exert the controlled release characteristics, improve the utilization rate of fertilizers, save costs and resources, and promote the growth of crops. Kaolin can also be used as a nutrient for crop growth to promote crop growth; finally, silane is used for hydrophobic modification, and due to the extremely low surface tension of silicone, hydrophobic Si atoms will gather and arrange on the surface of the membrane shell during the film formation process, making the membrane shell hydrophobic, further reducing the release rate of urea, reducing the dissolution of nutrients, and improving the controlled release performance. DETAILED DESCRIPTION

[0033] The present invention provides a method for preparing a carbon-based slow-release fertilizer, comprising the following steps:

[0034] (1) mixing biochar, peracetic acid oxidized lignin, acetate starch, an acid catalyst and a solvent to obtain a mixed solution, adjusting the pH value of the mixed solution, and performing a cross-linking reaction to obtain a composite;

[0035] (2) mixing the composite, urea and a solvent to carry out a first reaction, mixing the product obtained after the reaction, kaolin and polyvinyl alcohol to carry out a second reaction to obtain a composite loaded with urea;

[0036] (3) The urea-loaded composite, tetraethoxysilane, hexadecyltrimethoxysilane and a solvent are mixed and subjected to a hydrolysis reaction to obtain a carbon-based slow-release fertilizer.

[0037] In the present invention, the mass ratio of the biochar, peracetic acid oxidized lignin and acetate starch in step (1) is preferably 1-5:3-8:5-10, more preferably 2-4:4-7:6-9, and more preferably 2.5-3.5:5-6:7-8.

[0038] In the present invention, the mass of the acidic catalyst in step (1) is preferably 2-5% of the total mass of the modified biochar, peracetic acid oxidized lignin and acetate starch, more preferably 2.5-4.5%, and more preferably 3-4%.

[0039] In the present invention, the usage ratio of the modified biochar and the solvent in step (1) is preferably 1-5 g: 30-50 mL, more preferably 2-4 g: 35-48 mL, and more preferably 2.5-3.5 g: 40-45 mL.

[0040] In the present invention, the acidic catalyst in step (1) preferably comprises a sulfuric acid solution.

[0041] In the present invention, the concentration of the sulfuric acid solution is preferably 96 to 98%, more preferably 96.5 to 97.5%, and even more preferably 97%.

[0042] In the present invention, the solvent in step (1) includes at least one of dimethyl sulfoxide (DMSO) or N,N-dimethylformamide (DMF).

[0043] In the present invention, the reagent for adjusting the pH value of the mixed solution in step (1) is preferably an acid solution;

[0044] The acid solution is preferably a hydrochloric acid solution; the concentration of the hydrochloric acid is preferably 37%.

[0045] In the present invention, the target pH value in step (1) is preferably 3 to 5, more preferably 3.5 to 4.5, and even more preferably 4.

[0046] In the present invention, the temperature of the cross-linking reaction in step (1) is preferably 70 to 90°C, more preferably 72 to 88°C, and more preferably 75 to 80°C; the time of the cross-linking reaction is preferably 40 to 80 min, more preferably 45 to 70 min, and more preferably 50 to 60 min.

[0047] In the present invention, after the cross-linking reaction in step (1) is completed, post-treatment is also included;

[0048] The post-treatment includes: separating the product obtained after the cross-linking reaction is completed, washing the separated precipitate with ethanol and water in sequence, and finally drying to obtain a composite.

[0049] In the present invention, the usage ratio of the complex, urea and solvent in step (2) is preferably 4-6 g: 0.2-0.7 g: 20-30 mL, more preferably 4.5-5.5 g: 0.3-0.6 g: 22-28 mL, and more preferably 5-5.2 g: 0.4-0.5 g: 24-25 mL.

[0050] In the present invention, the solvent in step (2) is preferably water.

[0051] In the present invention, the mass ratio of the composite, kaolin and polyvinyl alcohol in step (2) is preferably 4-6: 0.3-1: 0.1-0.3, more preferably 4.5-5.5: 0.4-0.9: 0.15-0.28, and more preferably 5-5.2: 0.5-0.8: 0.18-0.25.

[0052] In the present invention, the temperature of the first reaction in step (2) is preferably 120-140°C, more preferably 125-135°C, and more preferably 128-130°C; the time of the first reaction is preferably 1-3h, more preferably 1.5-2.5h, and more preferably 1.75-2h.

[0053] In the present invention, after the first reaction in step (2) is completed, post-treatment is also included;

[0054] The post-treatment comprises: drying the product obtained after the first reaction is completed, and then cooling the temperature to 20-30°C.

[0055] In the present invention, the temperature of the second reaction in step (2) is preferably 120-140°C, more preferably 125-135°C, and more preferably 128-130°C; the time of the second reaction is preferably 1-3h, more preferably 1.5-2.5h, and more preferably 1.75-2h.

[0056] In the present invention, after the second reaction in step (2) is completed, post-treatment is also included;

[0057] The post-treatment includes: separating the product obtained after the second reaction is completed, washing the separated precipitate with ethanol and water in sequence, and finally drying to obtain a urea-loaded composite.

[0058] In the present invention, the usage ratio of the urea-loaded complex, tetraethoxysilane, hexadecyltrimethoxysilane and solvent in step (3) is preferably 1-2 g: 0.5-1.5 g: 0.5-1.5 g: 30-50 mL, more preferably 1.2-1.8 g: 0.7-1.2 g: 0.7-1.2 g: 35-45 mL, and more preferably 1.3-1.5 g: 0.8-1 g: 0.8-1 g: 38-40 mL.

[0059] In the present invention, the solvent in step (3) comprises at least one of water and an alcohol solution.

[0060] In the present invention, the temperature of the hydrolysis reaction in step (3) is preferably 40 to 80°C, more preferably 45 to 75°C, and more preferably 60 to 70°C; the time of the hydrolysis reaction is preferably 20 to 40 min, more preferably 25 to 35 min, and more preferably 28 to 30 min.

[0061] In the present invention, after the hydrolysis reaction in step (3) is completed, post-treatment is also included;

[0062] The post-treatment method comprises: dispersing the product obtained after the hydrolysis reaction at 20-30° C. for 12-24 hours, then separating it, washing the separated precipitate with an alcohol solution, and finally drying it to obtain a carbon-based slow-release fertilizer.

[0063] The invention also provides a carbon-based slow-release fertilizer prepared by the preparation method of the carbon-based slow-release fertilizer.

[0064] The invention also provides application of a carbon-based slow-release fertilizer in crop planting.

[0065] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0066] Example 1

[0067] A method for preparing a carbon-based slow-release fertilizer comprises the following steps:

[0068] (1) 1 g of biochar, 5 g of peracetic acid oxidized lignin, 5 g of acetate starch, 0.25 g of 98 wt % sulfuric acid solution and 30 mL of dimethyl sulfoxide were mixed to obtain a mixed solution, and then a 37 wt % hydrochloric acid solution was added to adjust the pH value of the mixed solution to 4, and the mixed solution was stirred at 70° C. for 60 min for cross-linking reaction. After the cross-linking reaction was completed, the obtained product was separated, and the separated precipitate was washed with ethanol and water in turn, and finally dried to obtain a composite;

[0069] (2) 4 g of the complex, 0.5 g of urea and 30 mL of deionized water were mixed and reacted at 140° C. for 1 h. After the reaction, the obtained product was dried and cooled to 25° C.; then the cooled product, 0.5 g of kaolin and 0.3 g of polyvinyl alcohol were mixed and reacted at 140° C. for 1 h. After the reaction, the obtained product was separated, and the separated precipitate was washed with ethanol and water in turn, and finally dried to obtain a urea-loaded complex;

[0070] (3) 1.2 g of the urea-loaded complex, 0.5 g of tetraethoxysilane, 0.5 g of hexadecyltrimethoxysilane and 30 mL of ethanol solution (the volume ratio of ethanol to water is 3:1) were mixed, and a hydrolysis reaction was carried out at 40°C for 30 min. After the hydrolysis reaction was completed, the obtained product was dispersed at 20°C for 12 h and then separated. The separated precipitate was washed with an alcohol solution and finally dried to obtain a carbon-based slow-release fertilizer.

[0071] Example 2

[0072] A method for preparing a carbon-based slow-release fertilizer comprises the following steps:

[0073] (1) 5 g of biochar, 4 g of peracetic acid oxidized lignin, 10 g of acetate starch, 0.5 g of 98 wt % sulfuric acid solution and 30 mL of dimethyl sulfoxide were mixed to obtain a mixed solution, and then a 37 wt % hydrochloric acid solution was added to adjust the pH value of the mixed solution to 4, and the mixed solution was stirred at 70° C. for 40 min for cross-linking reaction. After the cross-linking reaction was completed, the obtained product was separated, and the separated precipitate was washed with ethanol and water in turn, and finally dried to obtain a composite;

[0074] (2) 5 g of the complex, 0.2 g of urea and 30 mL of deionized water were mixed and reacted at 135° C. for 1.5 h. After the reaction, the obtained product was dried and cooled to 25° C.; then the cooled product, 1 g of kaolin and 0.3 g of polyvinyl alcohol were mixed and reacted at 135° C. for 1 h. After the reaction, the obtained product was separated, and the separated precipitate was washed with ethanol and water in turn, and finally dried to obtain a urea-loaded complex;

[0075] (3) 2 g of the urea-loaded complex, 1.5 g of tetraethoxysilane, 0.5 g of hexadecyltrimethoxysilane and 50 mL of ethanol solution (the volume ratio of ethanol to water is 3:1) are mixed, and a hydrolysis reaction is carried out at 50° C. for 20 min. After the hydrolysis reaction is completed, the obtained product is dispersed at 20° C. for 12 to 24 h and then separated. The separated precipitate is washed with an alcohol solution and finally dried to obtain a carbon-based slow-release fertilizer.

[0076] Example 3

[0077] A method for preparing a carbon-based slow-release fertilizer comprises the following steps:

[0078] (1) 2.5 g of biochar, 6.5 g of peracetic acid oxidized lignin, 8 g of acetate starch, 0.5 g of 98 wt % sulfuric acid solution and 30 mL of dimethyl sulfoxide were mixed to obtain a mixed solution, and then a 37 wt % hydrochloric acid solution was added to adjust the pH value of the mixed solution to 4, and the mixed solution was stirred at 80° C. for 55 min for cross-linking reaction. After the cross-linking reaction was completed, the obtained product was separated, and the separated precipitate was washed with ethanol and water in turn, and finally dried to obtain a composite;

[0079] (2) 4 g of the complex, 0.7 g of urea and 30 mL of deionized water were mixed and reacted at 130° C. for 2 h. After the reaction, the obtained product was dried and cooled to 25° C.; then the cooled product, 0.8 g of kaolin and 0.25 g of polyvinyl alcohol were mixed and reacted at 130° C. for 1 h. After the reaction, the obtained product was separated, and the separated precipitate was washed with ethanol and water in turn, and finally dried to obtain a urea-loaded complex;

[0080] (3) 1.2 g of the urea-loaded complex, 1 g of tetraethoxysilane, 1.5 g of hexadecyltrimethoxysilane and 50 mL of ethanol solution (the volume ratio of ethanol to water is 3:1) were mixed, and a hydrolysis reaction was carried out at 50°C for 25 min. After the hydrolysis reaction was completed, the obtained product was dispersed at 20°C for 12 h and then separated. The separated precipitate was washed with an alcohol solution and finally dried to obtain a carbon-based slow-release fertilizer.

[0081] Example 4

[0082] A method for preparing a carbon-based slow-release fertilizer comprises the following steps:

[0083] (1) 4 g of biochar, 7 g of peracetic acid oxidized lignin, 6.8 g of acetate starch, 0.5 g of 98 wt % sulfuric acid solution and 30 mL of dimethyl sulfoxide were mixed to obtain a mixed solution, and then a 37 wt % hydrochloric acid solution was added to adjust the pH value of the mixed solution to 4, and the mixed solution was stirred at 85° C. for 40 min for cross-linking reaction. After the cross-linking reaction was completed, the obtained product was separated, and the separated precipitate was washed with ethanol and water in turn, and finally dried to obtain a composite;

[0084] (2) 5.6 g of the complex, 0.5 g of urea and 30 mL of deionized water were mixed and reacted at 120° C. for 2.5 h. After the reaction, the obtained product was dried and cooled to 25° C.; then the cooled product, 1 g of kaolin and 0.1 g of polyvinyl alcohol were mixed and reacted at 120° C. for 1.5 h. After the reaction, the obtained product was separated, and the separated precipitate was washed with ethanol and water in turn, and finally dried to obtain a urea-loaded complex;

[0085] (3) 1.8 g of the urea-loaded complex, 0.5 g of tetraethoxysilane, 0.5 g of hexadecyltrimethoxysilane and 50 mL of ethanol solution (the volume ratio of ethanol to water is 3:1) were mixed, and a hydrolysis reaction was carried out at 40°C for 20 min. After the hydrolysis reaction was completed, the obtained product was dispersed at 20°C for 12 h and then separated. The separated precipitate was washed with an alcohol solution and finally dried to obtain a carbon-based slow-release fertilizer.

[0086] Comparative Example 1

[0087] A method for preparing a carbon-based slow-release fertilizer comprises the following steps:

[0088] (1) 4 g of biochar, 0.5 g of urea and 30 mL of deionized water were mixed and reacted at 140 ° C for 1 h. After the reaction, the obtained product was dried and cooled to 25 ° C; then the cooled product, 0.5 g of kaolin and 0.3 g of polyvinyl alcohol were mixed and reacted at 140 ° C for 1 h. After the reaction, the obtained product was separated, and the separated precipitate was washed with ethanol and water in turn, and finally dried to obtain a urea-loaded composite;

[0089] (3) 1.2 g of the urea-loaded complex, 0.5 g of tetraethoxysilane, 0.5 g of hexadecyltrimethoxysilane and 30 mL of ethanol solution (the volume ratio of ethanol to water is 3:1) were mixed, and a hydrolysis reaction was carried out at 40°C for 30 min. After the hydrolysis reaction was completed, the obtained product was dispersed at 20°C for 12 h and then separated. The separated precipitate was washed with an alcohol solution and finally dried to obtain a carbon-based slow-release fertilizer.

[0090] Comparative Example 2

[0091] A method for preparing a carbon-based slow-release fertilizer comprises the following steps:

[0092] (1) 1 g of biochar, 5 g of peracetic acid oxidized lignin, 5 g of acetate starch, 0.25 g of 98 wt % sulfuric acid solution and 30 mL of dimethyl sulfoxide were mixed to obtain a mixed solution, and then a 37 wt % hydrochloric acid solution was added to adjust the pH value of the mixed solution to 4, and the mixed solution was stirred at 70° C. for 60 min for cross-linking reaction. After the cross-linking reaction was completed, the obtained product was separated, and the separated precipitate was washed with ethanol and water in turn, and finally dried to obtain a composite;

[0093] (2) 4 g of the complex, 0.5 g of urea and 30 mL of deionized water were mixed and reacted at 140° C. for 1 h. After the reaction, the product was dried and cooled to 25° C.; then the cooled product, 0.5 g of kaolin and 0.3 g of polyvinyl alcohol were mixed and reacted at 140° C. for 1 h. After the reaction, the product was separated, and the separated precipitate was washed with ethanol and water in turn, and finally dried to obtain a carbon-based slow-release fertilizer.

[0094] Performance Testing

[0095] The slow-release effects of the carbon-based slow-release fertilizers prepared in Examples 1 to 4 and Comparative Examples 1 to 2 were verified. The verification method referred to GB / T23348-2009 slow-release fertilizers. The results are shown in Table 1.

[0096] Table 1 The slow-release effect of carbon-based slow-release fertilizer in Examples 1 to 4 and Comparative Examples 1 to 2

[0097]

[0098]

[0099] It can be seen from Table 1 that, compared with Comparative Examples 1 to 2, the carbon-based slow-release fertilizers prepared in Examples 1 to 4 have good slow-release effects, and the nutrient release period can reach more than 150 days, which can be well applied to crop growth.

[0100] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a carbon-based slow-release fertilizer, characterized in that: The following steps are involved: (1) mixing biochar, peracetic acid oxidized lignin, acetate starch, an acid catalyst and a solvent to obtain a mixed solution, adjusting the pH value of the mixed solution, and performing a cross-linking reaction to obtain a composite; (2) mixing the composite, urea and a solvent to carry out a first reaction, mixing the product obtained after the reaction, kaolin and polyvinyl alcohol to carry out a second reaction to obtain a composite loaded with urea; (3) The urea-loaded complex, tetraethoxysilane, hexadecyltrimethoxysilane and a solvent are mixed and subjected to a hydrolysis reaction to obtain a carbon-based slow-release fertilizer.

2. The method for preparing a carbon-based slow-release fertilizer according to claim 1, characterized in that: The mass ratio of the biochar, peracetic acid oxidized lignin and acetate starch in step (1) is 1-5:3-8:5-10; And / or, the mass of the acidic catalyst in step (1) is 2-5% of the total mass of the modified biochar, peracetic acid oxidized lignin and acetate starch; And / or, the ratio of the modified biochar to the solvent in step (1) is 1-5 g: 30-50 mL.

3. The method for preparing the carbon-based slow-release fertilizer according to claim 1, characterized in that: The acidic catalyst in step (1) comprises a sulfuric acid solution; And / or, the concentration of the sulfuric acid solution is 96-98%; and / or, the solvent in step (1) comprises at least one of dimethyl sulfoxide or N,N-dimethylformamide; And / or, the target pH value in step (1) is 3-5; And / or, the temperature of the cross-linking reaction in step (1) is 70-90° C., and the time of the cross-linking reaction is 40-80 min.

4. The method for preparing a carbon-based slow-release fertilizer according to claim 1, characterized in that: The ratio of the complex, urea and solvent used in step (2) is 4-6 g: 0.2-0.7 g: 20-30 mL; And / or, in step (2), the mass ratio of the composite, kaolin and polyvinyl alcohol is 4-6:0.3-1:0.1-0.

3.

5. The method for preparing a carbon-based slow-release fertilizer according to claim 1, characterized in that: In step (2), the temperature of the first reaction is 120-140° C., and the time of the first reaction is 1-3 hours; And / or, in step (2), the temperature of the second reaction is 120-140° C., and the time of the second reaction is 1-3 h.

6. The method for preparing a carbon-based slow-release fertilizer according to claim 1, characterized in that: The ratio of the urea-loaded composite, tetraethoxysilane, hexadecyltrimethoxysilane and solvent used in step (3) is 1-2 g: 0.5-1.5 g: 0.5-1.5 g: 30-50 mL; And / or, the solvent in step (3) includes at least one of water and an alcohol solution.

7. The method for preparing a carbon-based slow-release fertilizer according to claim 1, characterized in that: The temperature of the hydrolysis reaction in step (3) is 40-80° C., and the time of the hydrolysis reaction is 20-40 min.

8. The method for preparing a carbon-based slow-release fertilizer according to claim 1, characterized in that: After the hydrolysis reaction in step (3) is completed, post-treatment is also included; The post-treatment method comprises: dispersing the product obtained after the hydrolysis reaction at 20-30° C. for 12-24 hours, then separating it, washing the separated precipitate with an alcohol solution, and finally drying it to obtain a carbon-based slow-release fertilizer.

9. The carbon-based slow-release fertilizer obtained by the method for preparing the carbon-based slow-release fertilizer according to any one of claims 1 to 8.

10. Use of the carbon-based slow-release fertilizer according to claim 9 in crop planting.

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