A fertilizer for remediation of heavy metals in soil and a preparation method thereof

Abstract

The application relates to the technical field of fertilizers, and discloses a fertilizer for soil heavy metal remediation and a preparation method thereof. The fertilizer is prepared from modified biochar, urea, superphosphoric acid calcium, potassium chloride, magnesium sulfate heptahydrate, diatomite, calcium-magnesium phosphate fertilizer, potassium dihydrogen phosphate, potassium silicate, sodium carboxymethyl cellulose and deionized water. The modified biochar is prepared from biochar powder, N, N-dimethylformamide, potassium humate powder, triethylamine and 1,4-butanediol diglycidyl ether. The biochar powder is prepared from corn stalks through pyrolysis. The fertilizer can realize remediation of soil heavy metals.

Description

Technical Field

[0001] This invention relates to the field of fertilizer technology, specifically to a fertilizer for soil heavy metal remediation and its preparation method. Background Technology

[0002] With the increasing intensification of agriculture and industrial activities, soil heavy metal pollution has become a prominent problem. This pollution not only damages soil structure and reduces soil fertility, but also accumulates in the human body through the food chain, harming human health. Meanwhile, as a major agricultural country, my country generates a large amount of agricultural waste, specifically corn stalks, every year. Traditional burning methods not only waste resources but also cause air pollution. Therefore, realizing the resource-based reuse of corn stalks is of great significance for promoting the green and sustainable development of agriculture.

[0003] Patent CN103910567B discloses a rice-specific organic-inorganic compound fertilizer, composed of nitrogen fertilizer, nitrogen fertilizer synergist, phosphate fertilizer, potassium fertilizer, trace elements, and beneficial element fertilizers. The effective components of this rice-specific organic-inorganic compound fertilizer contain the following mass percentages: nitrogen 6-9%; phosphorus pentoxide 4-6%; potassium oxide 6-8%; zinc 0.2-0.6%; and silicon 0.2-0.6%. However, this fertilizer cannot remediate heavy metal pollution in soil, which limits its application scope. Summary of the Invention

[0004] The purpose of this invention is to provide a fertilizer for soil heavy metal remediation and its preparation method, so as to solve the problems existing in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A fertilizer for soil heavy metal remediation, the fertilizer being prepared from modified biochar, urea, superphosphate, potassium chloride, magnesium sulfate heptahydrate, diatomaceous earth, calcium magnesium phosphate, potassium dihydrogen phosphate, potassium silicate, sodium carboxymethyl cellulose, and deionized water. The modified biochar is prepared from biochar powder, N,N-dimethylformamide, potassium humate powder, triethylamine, and 1,4-butanediol diglycidyl ether. The biochar powder is prepared from corn stalks through pyrolysis.

[0006] Furthermore, the mass ratio of biochar powder, N,N-dimethylformamide, potassium humate powder, triethylamine, and 1,4-butanediol diglycidyl ether is 10:70-90:7-9:1.0-1.5:1.5-2.5.

[0007] Furthermore, the mass ratio of modified biochar, urea, superphosphate, potassium chloride, magnesium sulfate heptahydrate, diatomaceous earth, calcium magnesium phosphate fertilizer, potassium dihydrogen phosphate, potassium silicate, sodium carboxymethyl cellulose, and deionized water is 30:1-1.5:3.0-5.0:0.5-1.2:0.5-1.5:10-15:5-10:1-3:3-8:0.5-2:10-25.

[0008] A method for preparing a fertilizer for heavy metal remediation in soil includes the following steps: (1) Place corn stalks in a tubular pyrolysis furnace, heat to 450-600℃ under nitrogen protection, and pyrolyze at this temperature for 60-90 minutes. Then cool to 20-25℃, crush and pass through a 100-200 mesh sieve to obtain biochar powder. (2) Under nitrogen protection, biochar powder, solvent, potassium humate powder and catalyst are mixed in a closed reactor and stirred at 800-1000 rpm for 30-60 minutes at 40-60℃. Then, 1,4-butanediol diglycidyl ether is added dropwise. After the addition is complete, the temperature is raised to 80-100℃ and stirring is continued for 6-12 hours. The mixture is filtered and vacuum dried at 100-110℃ for 4-6 hours. Finally, it is pulverized and passed through a 100-200 mesh sieve to obtain modified biochar. (3) Mix modified biochar, urea, superphosphate, potassium chloride, magnesium sulfate heptahydrate, diatomaceous earth, calcium magnesium phosphate fertilizer, potassium dihydrogen phosphate, potassium silicate and sodium carboxymethyl cellulose. Stir at 100-200 rpm for 20-30 minutes, then add deionized water. Then granulate the mixture using a roller extrusion granulator to obtain fertilizer granules with a particle size of 3-5 mm. Finally, dry the mixture.

[0009] Furthermore, in step (1), the temperature is increased to 450-600℃ at a heating rate of 10-15℃ / min.

[0010] Furthermore, in step (2), 1,4-butanediol diglycidyl ether is added dropwise over 1-2 hours.

[0011] Furthermore, the catalyst in step (2) is triethylamine.

[0012] Furthermore, the solvent in step (2) is N,N-dimethylformamide.

[0013] Furthermore, in step (3), deionized water is added by spraying.

[0014] Furthermore, the drying process in step (3) specifically involves hot air drying at 70-80℃ for 40-60 minutes.

[0015] Compared with the prior art, the beneficial effects achieved by the present invention are: 1. In this invention, corn stalks undergo pyrolysis to form biochar with a high specific surface area and porosity. Under the catalysis of triethylamine, the hydroxyl groups on the surface of the biochar and the hydroxyl groups on the potassium humate molecules undergo a ring-opening addition reaction with the epoxy groups at both ends of the 1,4-butanediol diglycidyl ether molecule, thereby loading potassium humate onto the surface and pores of the biochar to form modified biochar. In addition, some potassium humate is firmly loaded onto the porous surface and pores of the biochar through physical adsorption and hydrogen bonding, which can also form stable modified biochar. In addition to providing phosphorus nutrition, calcium magnesium phosphate and potassium dihydrogen phosphate release phosphate ions after dissolution, which can react with lead ions, cadmium ions, etc. in the soil to form phosphate minerals with low solubility in the soil environment, thus achieving chemical passivation of heavy metals. Potassium silicate provides silicate ions and potassium ions. Silicate ions can promote the formation of soil aggregates and can react with some heavy metals, while potassium ions help plants grow healthily. Sodium carboxymethyl cellulose, as a binder, achieves binding and hydration through its molecular chains during granulation. Detailed Implementation

[0016] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0017] A fertilizer for soil heavy metal remediation, the fertilizer being prepared from modified biochar, urea, superphosphate, potassium chloride, magnesium sulfate heptahydrate, diatomaceous earth, calcium magnesium phosphate, potassium dihydrogen phosphate, potassium silicate, sodium carboxymethyl cellulose, and deionized water. The modified biochar is prepared from biochar powder, N,N-dimethylformamide, potassium humate powder, triethylamine, and 1,4-butanediol diglycidyl ether. The biochar powder is prepared from corn stalks through pyrolysis.

[0018] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0019] Example 1

[0020] (1) Place corn stalks in a tubular pyrolysis furnace, heat them to 450°C at a heating rate of 10°C / min under nitrogen protection, and pyrolyze them at this temperature for 60 minutes. Then cool them to 20°C, crush them and pass them through a 100-mesh sieve to obtain biochar powder.

[0021] (2) Under nitrogen protection, biochar powder, N,N-dimethylformamide, potassium humate powder and triethylamine were mixed in a closed reactor and stirred at 800 rpm for 30 minutes at 40°C. Then, 1,4-butanediol diglycidyl ether was added dropwise over 1 hour. After the addition was completed, the temperature was raised to 80°C and stirring was continued for 6 hours. The mixture was filtered and vacuum dried at 100°C for 4 hours. Finally, it was pulverized and passed through a 100-mesh sieve to obtain modified biochar. The mass ratio of biochar powder, N,N-dimethylformamide, potassium humate powder, triethylamine and 1,4-butanediol diglycidyl ether was 10:70:7:1.0:1.5.

[0022] (3) Modified biochar, urea, superphosphate, potassium chloride, magnesium sulfate heptahydrate, diatomaceous earth, calcium magnesium phosphate fertilizer, potassium dihydrogen phosphate, potassium silicate, and sodium carboxymethyl cellulose were mixed and stirred at 100 rpm for 20 minutes. Then, deionized water was added by spraying. The mixture was then granulated using a roller extrusion granulator to obtain fertilizer granules with a particle size of 3 mm. Finally, the granules were dried with hot air at 70°C for 40 minutes. The mass ratio of modified biochar, urea, superphosphate, potassium chloride, magnesium sulfate heptahydrate, diatomaceous earth, calcium magnesium phosphate fertilizer, potassium dihydrogen phosphate, potassium silicate, sodium carboxymethyl cellulose, and deionized water was 30:1:3.0:0.5:0.5:10:5:1:3:0.5:10.

[0023] Example 2

[0024] (1) Place corn stalks in a tubular pyrolysis furnace, heat them to 525°C at a heating rate of 12.5°C / min under nitrogen protection, and pyrolyze them at this temperature for 75 minutes. Then cool them to 22°C, crush them and pass them through a 150-mesh sieve to obtain biochar powder.

[0025] (2) Under nitrogen protection, biochar powder, N,N-dimethylformamide, potassium humate powder and triethylamine were mixed in a closed reactor and stirred at 900 rpm for 45 minutes at 50°C. Then, 1,4-butanediol diglycidyl ether was added dropwise over 1.5 hours. After the addition was completed, the temperature was raised to 90°C and stirring was continued for 9 hours. The mixture was filtered and vacuum dried at 105°C for 5 hours. Finally, it was pulverized and passed through a 150-mesh sieve to obtain modified biochar. The mass ratio of biochar powder, N,N-dimethylformamide, potassium humate powder, triethylamine and 1,4-butanediol diglycidyl ether was 10:80:8:1.25:2.0.

[0026] (3) Modified biochar, urea, superphosphate, potassium chloride, magnesium sulfate heptahydrate, diatomaceous earth, calcium magnesium phosphate fertilizer, potassium dihydrogen phosphate, potassium silicate, and sodium carboxymethyl cellulose were mixed and stirred at 150 rpm for 25 minutes. Then, deionized water was added by spraying. The mixture was then granulated using a roller extrusion granulator to obtain fertilizer granules with a particle size of 4 mm. Finally, the granules were dried with hot air at 75°C for 50 minutes. The mass ratio of modified biochar, urea, superphosphate, potassium chloride, magnesium sulfate heptahydrate, diatomaceous earth, calcium magnesium phosphate fertilizer, potassium dihydrogen phosphate, potassium silicate, sodium carboxymethyl cellulose, and deionized water was 30:1.25:4.0:0.85:1.0:12.5:7.5:2:5.5:1.25:17.5.

[0027] Example 3

[0028] (1) Place corn stalks in a tubular pyrolysis furnace, heat them to 600°C at a heating rate of 15°C / min under nitrogen protection, and pyrolyze them at this temperature for 90 minutes. Then cool them to 25°C, crush them and pass them through a 200-mesh sieve to obtain biochar powder.

[0029] (2) Under nitrogen protection, biochar powder, N,N-dimethylformamide, potassium humate powder and triethylamine were mixed in a closed reactor and stirred at 1000 rpm for 60 minutes at 60°C. Then, 1,4-butanediol diglycidyl ether was added dropwise over 2 hours. After the addition was completed, the temperature was raised to 100°C and stirring was continued for 12 hours. The mixture was filtered and vacuum dried at 110°C for 6 hours. Finally, it was pulverized and passed through a 200-mesh sieve to obtain modified biochar. The mass ratio of biochar powder, N,N-dimethylformamide, potassium humate powder, triethylamine and 1,4-butanediol diglycidyl ether was 10:90:9:1.5:2.5.

[0030] (3) Modified biochar, urea, superphosphate, potassium chloride, magnesium sulfate heptahydrate, diatomaceous earth, calcium magnesium phosphate fertilizer, potassium dihydrogen phosphate, potassium silicate, and sodium carboxymethyl cellulose were mixed and stirred at 200 rpm for 30 minutes. Then, deionized water was added by spraying. The mixture was then granulated using a roller extrusion granulator to obtain fertilizer granules with a particle size of 5 mm. Finally, the granules were dried with hot air at 80°C for 60 minutes. The mass ratio of modified biochar, urea, superphosphate, potassium chloride, magnesium sulfate heptahydrate, diatomaceous earth, calcium magnesium phosphate fertilizer, potassium dihydrogen phosphate, potassium silicate, sodium carboxymethyl cellulose, and deionized water was 30:1.5:5.0:1.2:1.5:15:10:3:8:2:25.

[0031] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that 1,4-butanediol diglycidyl ether is not added.

[0032] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the biochar powder is not modified; unmodified biochar powder is used directly.

[0033] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that potassium dihydrogen phosphate and potassium silicate are not added.

[0034] Soil was contaminated with cadmium nitrate aqueous solution to achieve a cadmium content of 3 mg / kg, while maintaining a moisture content of 60% of field capacity. Fertilizer was added at 1% of soil weight. The soil was incubated at 25℃ for 60 days. A separate sample of contaminated soil without fertilizer was used as a blank control. Each treatment was replicated in triplicate.

[0035] The air-dried soil sample was ground and passed through a 2 mm sieve. 10.0 g of the soil sample was weighed into an Erlenmeyer flask, and 20.0 mL of DTPA extraction reagent (0.005 mol / L DTPA + 0.1 mol / L triethanolamine + 0.001 mol / L CaCl2, pH adjusted to 7.3 with dilute hydrochloric acid or sodium hydroxide solution) was added. The flask was placed in a shaker and shaken at 180 rpm for 2 hours at 20°C. The mixture was then vacuum filtered through a 0.45 μm filter membrane. The concentration of cadmium in the filtrate was determined using inductively coupled plasma mass spectrometry (ICP-MS). The passivation rate of available cadmium (%) was calculated as follows: [(C0-C1) / C0] × 100%, where C0 is the concentration of available cadmium (mg / kg) in the unfertilized contaminated soil, and C1 is the concentration of available cadmium (mg / kg) in the fertilized soil.

[0036] Table 1 below shows the performance analysis results of the embodiments and comparative examples of the present invention.

[0037] Table 1

[0038] Experimental data from the examples and comparative examples show that the modified biochar in this invention utilizes its high specific surface area and porous structure to physically adsorb and retain heavy metal ions in the soil. Simultaneously, the carboxyl and phenolic hydroxyl functional groups of humic acid on its surface can chelate with heavy metal ions to form relatively stable complexes, thereby achieving chemical fixation of heavy metals. The phosphate ions released after the phosphate component dissolves can react with lead ions, cadmium ions, etc., to form phosphate minerals that are chemically stable and have low solubility in the soil environment. The silicate ions released by the potassium silicate component help promote the formation of soil aggregates and improve soil structure, while its potassium ions can serve as an essential nutrient for plant growth, thus synergistically achieving soil remediation.

[0039] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A fertilizer for remediation of heavy metals in soil, characterized in that, The fertilizer is prepared from modified biochar, urea, superphosphate, potassium chloride, magnesium sulfate heptahydrate, diatomaceous earth, calcium magnesium phosphate, potassium dihydrogen phosphate, potassium silicate, sodium carboxymethyl cellulose, and deionized water. The modified biochar is prepared from biochar powder, N,N-dimethylformamide, potassium humate powder, triethylamine, and 1,4-butanediol diglycidyl ether. The biochar powder is prepared from corn stalks through pyrolysis.

2. The fertilizer for remediation of heavy metals in soil according to claim 1, characterized in that The mass ratio of biochar powder, N,N-dimethylformamide, potassium humate powder, triethylamine, and 1,4-butanediol diglycidyl ether is 10:70-90:7-9:1.0-1.5:1.5-2.

5.

3. The fertilizer for soil heavy metal remediation according to claim 1, characterized in that... The mass ratio of modified biochar, urea, superphosphate, potassium chloride, magnesium sulfate heptahydrate, diatomaceous earth, calcium magnesium phosphate fertilizer, potassium dihydrogen phosphate, potassium silicate, sodium carboxymethyl cellulose, and deionized water is 30:1-1.5:3.0-5.0:0.5-1.2:0.5-1.5:10-15:5-10:1-3:3-8:0.5-2:10-25.

4. A method for preparing a fertilizer for soil heavy metal remediation, applied to the fertilizer for soil heavy metal remediation as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) Place corn stalks in a tubular pyrolysis furnace, heat to 450-600℃ under nitrogen protection, and pyrolyze at this temperature for 60-90 minutes. Then cool to 20-25℃, crush and pass through a 100-200 mesh sieve to obtain biochar powder. (2) Under nitrogen protection, biochar powder, solvent, potassium humate powder and catalyst are mixed in a closed reactor and stirred at 800-1000 rpm for 30-60 minutes at 40-60℃. Then, 1,4-butanediol diglycidyl ether is added dropwise. After the addition is complete, the temperature is raised to 80-100℃ and stirring is continued for 6-12 hours. The mixture is filtered and vacuum dried at 100-110℃ for 4-6 hours. Finally, it is pulverized and passed through a 100-200 mesh sieve to obtain modified biochar. (3) Mix modified biochar, urea, superphosphate, potassium chloride, magnesium sulfate heptahydrate, diatomaceous earth, calcium magnesium phosphate fertilizer, potassium dihydrogen phosphate, potassium silicate and sodium carboxymethyl cellulose. Stir at 100-200 rpm for 20-30 minutes, then add deionized water. Then granulate the mixture using a roller extrusion granulator to obtain fertilizer granules with a particle size of 3-5 mm. Finally, dry the mixture.

5. A method for preparing a fertilizer for heavy metal remediation in soil according to claim 4, characterized in that... In step (1), the temperature is increased to 450-600℃ at a rate of 10-15℃ / minute.

6. A method for preparing a fertilizer for heavy metal remediation in soil according to claim 4, characterized in that... In step (2), 1,4-butanediol diglycidyl ether is added dropwise over 1-2 hours.

7. A method for preparing a fertilizer for heavy metal remediation in soil according to claim 4, characterized in that... The catalyst in step (2) is triethylamine.

8. A method for preparing a fertilizer for heavy metal remediation in soil according to claim 4, characterized in that... The solvent in step (2) is N,N-dimethylformamide.

9. A method for preparing a fertilizer for soil heavy metal remediation according to claim 4, characterized in that... In step (3), deionized water is added by spraying.

10. A method for preparing a fertilizer for soil heavy metal remediation according to claim 4, characterized in that... The drying process in step (3) specifically involves hot air drying at 70-80℃ for 40-60 minutes.

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