Fertilizer for reducing cadmium ion absorption of crops and preparation method thereof
By preparing a compound fertilizer consisting of thiol-modified LDH and activated biochar, the problem of cadmium ion absorption by crops has been solved, achieving stable fixation and reduction of cadmium ions, thus ensuring the safety of agricultural products.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- TECH CENT FOR SOIL AGRI & RURAL ECOLOGY & ENVIRONMENT MINIST OF ECOLOGY & ENVIRONMENT
- Filing Date
- 2026-03-11
- Publication Date
- 2026-05-12
AI Technical Summary
Existing technologies are insufficient to effectively reduce crop absorption of cadmium ions. Traditional passivating agents are unstable in acidic environments and pose a risk of secondary release. Furthermore, agronomic measures are not easy to implement, and physical remediation is costly.
Thiol-modified LDH and activated biochar were prepared. Thiol-modified LDH with both layered structure and strong cadmium adsorption performance was formed through hydrothermal reaction and etching. Combined with activated biochar as a porous carrier, a compound fertilizer was formed to achieve specific complexation and cascade fixation of cadmium ions.
It significantly reduces the bioavailability of cadmium ions in the soil, reduces the absorption of cadmium ions by crop roots and their translocation to the aboveground parts, ensures the quality and safety of agricultural products, and improves the passivation efficiency of cadmium ions in the soil.
Smart Images
Figure CN122010632A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of fertilizer technology, specifically to a fertilizer that reduces crop absorption of cadmium ions and its preparation method. Background Technology
[0002] Cadmium is a heavy metal element with strong biotoxicity. It easily accumulates in soil and is difficult to degrade, making it one of the major pollutants in my country's arable land, seriously threatening the quality and safety of agricultural products and human health. Currently, cadmium pollution exists to varying degrees in arable land in many parts of my country. Crops grown in polluted soil easily absorb cadmium ions from the soil, which then accumulate in the grains, stems, and leaves. After entering the human body through the food chain, it can cause continuous damage to organs such as the kidneys and bones.
[0003] Currently, remediation strategies for cadmium pollution in soil mainly encompass physical engineering remediation, chemical passivation remediation, and agronomic control measures. Physical remediation methods, such as topsoil replacement or deep tillage, are thorough but involve large-scale engineering projects, are costly, and can damage the original soil structure. Agronomic measures, such as water management or variety selection, can reduce cadmium absorption to some extent, but their operability is limited by natural conditions and variety characteristics, making them difficult to apply universally. Chemical passivation remediation primarily involves applying lime, calcium silicate materials, or phosphate materials to increase soil pH or form precipitates with cadmium ions, thereby reducing their available content in the soil. However, these traditional passivating agents often have limited functionality, focusing only on the immediate fixation of cadmium in the soil and neglecting the nutrient absorption process by crop roots and the cadmium transport mechanisms within plants. Furthermore, some passivating agents are unstable in acidic environments, posing a risk of secondary release.
[0004] Therefore, there is a need to propose a fertilizer that can reduce crop absorption of cadmium ions and its preparation method. Summary of the Invention
[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a fertilizer that reduces the absorption of cadmium ions by crops and a method for preparing the same.
[0006] This invention provides a method for preparing a fertilizer that reduces crop absorption of cadmium ions, comprising the following steps:
[0007] S1: Preparation of thiol-modified LDH
[0008] Magnesium nitrate hexahydrate and aluminum nitrate nonahydrate were dissolved in deionized water, and then sodium hydroxide solution and 3-mercaptopropyltrimethoxysilane were added to carry out a hydrothermal reaction to obtain mercapto-modified LDH.
[0009] S2: Preparation of activated biochar
[0010] After washing, drying, crushing, and pyrolyzing the rice husks, they are then soaked in a potassium hydroxide solution for activation to obtain activated biochar.
[0011] S3: Preparation of compound fertilizer
[0012] The above-mentioned thiol-modified LDH, activated biochar, urea, diammonium phosphate, potassium sulfate, humic acid and binder are put into a double helix conical mixer, 6-8 wt% deionized water is added and stirred and mixed evenly, then compound microbial agent is added, and stirring and mixing is continued for 5-10 minutes. Then, the mixture is granulated, dried and sieved to obtain compound fertilizer.
[0013] Furthermore, by weight, the raw material composition of the compound fertilizer is as follows: 18-22 parts thiol-modified LDH, 20-25 parts activated biochar, 6-8 parts urea, 10-12 parts diammonium phosphate, 2-3 parts potassium sulfate, 8-10 parts humic acid, 1-2 parts binder and 3-5 parts compound microbial inoculant.
[0014] Furthermore, the binder is sodium carboxymethyl cellulose.
[0015] Furthermore, the compound microbial agent is composed of Bacillus subtilis, Bacillus mucilaginosus, and Saccharomyces cerevisiae in a mass ratio of (2-3):(1.4-1.6):1.
[0016] Furthermore, S1 includes the following steps:
[0017] S1.1: Add magnesium nitrate hexahydrate and aluminum nitrate nonahydrate to deionized water at a ratio of (1.3-1.4)g:1g:(10-12)mL, and stir thoroughly until dissolved to obtain a mixed salt solution;
[0018] S1.2: Under nitrogen protection, add 2 mol / L sodium hydroxide solution to the above mixed salt solution, adjust the pH to 9, and then add 3-mercaptopropyltrimethoxysilane while stirring. Continue stirring for 30-40 min, then transfer to a hydrothermal reactor and hydrothermally crystallize at 120-130℃ for 10-12 h. After cooling, filter, wash with deionized water until neutral, vacuum dry and grind to obtain mercapto-modified LDH.
[0019] Furthermore, the amount of 3-mercaptopropyltrimethoxysilane added is 1.8-2% of the volume of the mixed salt solution.
[0020] Furthermore, S2 includes the following steps:
[0021] S2.1: After washing the rice husks, dry them at 100-110℃ to constant weight, then crush them and pass them through a 40-mesh sieve to obtain rice husk powder.
[0022] S2.2: The above rice husk powder is pyrolyzed at 600-700℃ in anoxic conditions for 2-3 hours, then soaked in 2 mol / L potassium hydroxide solution for 8-10 hours, and then filtered, washed until neutralized and dried to obtain activated biochar.
[0023] A fertilizer that reduces crop absorption of cadmium ions, prepared by any of the above-described methods for preparing a fertilizer that reduces crop absorption of cadmium ions.
[0024] The present invention has the following advantages:
[0025] 1. In this invention, magnesium nitrate hexahydrate and aluminum nitrate nonahydrate are first dissolved to form a mixed salt solution. Then, sodium hydroxide solution is added to induce a co-precipitation reaction, generating a MgLDH layered precursor. Subsequently, 3-mercaptopropyltrimethoxysilane is added to graft thiol groups onto the surface of the LDH layered structure through silane coupling. A hydrothermal crystallization reaction at 120-130℃ is then performed to achieve stable loading of the thiol groups, ultimately forming a thiol-modified LDH that combines a layered structure with strong cadmium adsorption properties. When added to fertilizer, the thiol groups loaded on its surface can undergo a specific complexation reaction with free cadmium ions in the soil, forming a stable and water-insoluble Cd-S complex. Simultaneously, its layered structure can further fix exchangeable cadmium ions in the soil through ion exchange and physical adsorption, converting them into residual cadmium that is not easily absorbed by crops. This significantly reduces the bioavailability of cadmium ions in the soil, thereby effectively reducing the absorption of cadmium ions by crop roots and their translocation to the aboveground parts, resulting in a significant reduction in cadmium accumulation in crops and ensuring the safety of agricultural products.
[0026] 2. In this invention, rice husks are pyrolyzed to form biochar with a porous structure, which is then activated by soaking in potassium hydroxide solution. This process increases the specific surface area of the biochar through etching, thereby optimizing its adsorption performance. When the activated biochar is added to fertilizer, it acts as a porous carrier to achieve efficient dispersion of thiol-modified LDH, preventing its aggregation and deactivation. The two work together to achieve cascade fixation of cadmium ions through physical adsorption capture and chemical complexation stabilization, thereby synergistically improving the passivation efficiency of cadmium ions in the soil and reducing the absorption and translocation of cadmium ions by crops from the source. Attached Figure Description
[0027] Figure 1 This is a flowchart illustrating the preparation method of a fertilizer that reduces crop absorption of cadmium ions, as used in an embodiment of the present invention. Detailed Implementation
[0028] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this invention.
[0029] Example 1: A method for preparing a fertilizer that reduces crop absorption of cadmium ions, such as... Figure 1 As shown, it includes the following steps:
[0030] S1: Preparation of thiol-modified LDH
[0031] S1.1: Add magnesium nitrate hexahydrate and aluminum nitrate nonahydrate to deionized water at a ratio of 1.3g:1g:10mL, and stir thoroughly until dissolved to obtain a mixed salt solution;
[0032] S1.2: Under nitrogen protection, 2 mol / L sodium hydroxide solution was added to the above mixed salt solution to adjust the pH to 9. Then, 3-mercaptopropyltrimethoxysilane was added while stirring, and stirring was continued for 30 min. The mixture was then transferred to a hydrothermal reactor and hydrothermally crystallized at 120 °C for 10 h. After cooling, the mixture was filtered, washed with deionized water until neutral, vacuum dried, and ground to obtain mercapto-modified LDH. The amount of 3-mercaptopropyltrimethoxysilane added was 1.8% of the volume of the mixed salt solution.
[0033] S2: Preparation of activated biochar
[0034] S2.1: After washing the rice husks, dry them at 100℃ to constant weight, then crush them and pass them through a 40-mesh sieve to obtain rice husk powder.
[0035] S2.2: The above rice husk powder was pyrolyzed at 600℃ in an oxygen-deficient environment for 2 hours, then soaked in 2 mol / L potassium hydroxide solution for 8 hours, and then filtered, washed until neutral and dried to obtain activated biochar;
[0036] S3: Preparation of compound fertilizer
[0037] The above-mentioned thiol-modified LDH, activated biochar, urea, diammonium phosphate, potassium sulfate, humic acid, and sodium carboxymethyl cellulose were put into a double-helix conical mixer, 6 wt% deionized water was added and stirred until uniform, then the compound microbial agent was added, and stirring was continued for 5 minutes. After granulation, drying and sieving, the compound fertilizer was obtained. The raw material composition of the compound fertilizer by mass parts is: 18 parts thiol-modified LDH, 20 parts activated biochar, 6 parts urea, 10 parts diammonium phosphate, 2 parts potassium sulfate, 8 parts humic acid, 1 part sodium carboxymethyl cellulose and 3 parts compound microbial agent. The compound microbial agent is composed of Bacillus subtilis, Bacillus mucilaginosus and Saccharomyces cerevisiae in a mass ratio of 2:1.4:1.
[0038] Example 2: A method for preparing a fertilizer that reduces crop absorption of cadmium ions, such as... Figure 1 As shown, it includes the following steps:
[0039] S1: Preparation of thiol-modified LDH
[0040] S1.1: Add magnesium nitrate hexahydrate and aluminum nitrate nonahydrate to deionized water at a ratio of 1.35g:1g:11mL, and stir thoroughly until dissolved to obtain a mixed salt solution;
[0041] S1.2: Under nitrogen protection, 2 mol / L sodium hydroxide solution was added to the above mixed salt solution to adjust the pH to 9. Then, 3-mercaptopropyltrimethoxysilane was added while stirring, and stirring was continued for 35 min. The mixture was then transferred to a hydrothermal reactor and hydrothermally crystallized at 125 °C for 11 h. After cooling, the mixture was filtered, washed with deionized water until neutral, vacuum dried, and ground to obtain mercapto-modified LDH. The amount of 3-mercaptopropyltrimethoxysilane added was 1.9% of the volume of the mixed salt solution.
[0042] S2: Preparation of activated biochar
[0043] S2.1: After washing the rice husks, dry them at 105℃ to constant weight, then crush and pass them through a 40-mesh sieve to obtain rice husk powder.
[0044] S2.2: The above rice husk powder was pyrolyzed at 650℃ in an oxygen-deficient environment for 2.5h, then soaked in 2mol / L potassium hydroxide solution for 9h, and then filtered, washed until neutral and dried to obtain activated biochar;
[0045] S3: Preparation of compound fertilizer
[0046] The above-mentioned thiol-modified LDH, activated biochar, urea, diammonium phosphate, potassium sulfate, humic acid, and sodium carboxymethyl cellulose were put into a double-helix conical mixer. 7 wt% deionized water was added and stirred until uniform. Then, the compound microbial agent was added and stirred for another 7.5 min. After granulation, drying, and sieving, the compound fertilizer was obtained. The raw material composition of the compound fertilizer, by mass, is as follows: 20 parts thiol-modified LDH, 22.5 parts activated biochar, 7 parts urea, 11 parts diammonium phosphate, 2.5 parts potassium sulfate, 9 parts humic acid, 1.5 parts sodium carboxymethyl cellulose, and 4 parts compound microbial agent. The compound microbial agent is composed of Bacillus subtilis, Bacillus mucilaginosus, and Saccharomyces cerevisiae in a mass ratio of 2.5:1.5:1.
[0047] Example 3: A method for preparing a fertilizer that reduces crop absorption of cadmium ions, such as... Figure 1 As shown, it includes the following steps:
[0048] S1: Preparation of thiol-modified LDH
[0049] S1.1: Add magnesium nitrate hexahydrate and aluminum nitrate nonahydrate to deionized water at a ratio of 1.4g:1g:12mL, and stir thoroughly until dissolved to obtain a mixed salt solution;
[0050] S1.2: Under nitrogen protection, 2 mol / L sodium hydroxide solution was added to the above mixed salt solution to adjust the pH to 9. Then, 3-mercaptopropyltrimethoxysilane was added while stirring, and stirring was continued for 40 min. The mixture was then transferred to a hydrothermal reactor and hydrothermally crystallized at 130 °C for 12 h. After cooling, the mixture was filtered, washed with deionized water until neutral, vacuum dried, and ground to obtain mercapto-modified LDH. The amount of 3-mercaptopropyltrimethoxysilane added was 2% of the volume of the mixed salt solution.
[0051] S2: Preparation of activated biochar
[0052] S2.1: After washing the rice husks, dry them at 110℃ to constant weight, then crush them and pass them through a 40-mesh sieve to obtain rice husk powder.
[0053] S2.2: The above rice husk powder was pyrolyzed at 700℃ in an oxygen-deficient environment for 3 hours, then soaked in 2 mol / L potassium hydroxide solution for 10 hours, and then filtered, washed until neutralized and dried to obtain activated biochar;
[0054] S3: Preparation of compound fertilizer
[0055] The above-mentioned thiol-modified LDH, activated biochar, urea, diammonium phosphate, potassium sulfate, humic acid, and sodium carboxymethyl cellulose were put into a double-helix conical mixer, 8 wt% deionized water was added and stirred until uniform, then the compound microbial agent was added, and stirring was continued for 10 minutes. After granulation, drying and sieving, the compound fertilizer was obtained. The raw material composition of the compound fertilizer by mass parts is: 22 parts thiol-modified LDH, 25 parts activated biochar, 8 parts urea, 12 parts diammonium phosphate, 3 parts potassium sulfate, 10 parts humic acid, 2 parts sodium carboxymethyl cellulose and 5 parts compound microbial agent. The compound microbial agent is compounded by Bacillus subtilis, Bacillus mucilaginosus and Saccharomyces cerevisiae in a mass ratio of 3:1.6:1.
[0056] Comparative Example 1 differs from Example 1 in that the thiol-modified LDH in step S3 is removed.
[0057] Comparative Example 2 differs from Example 1 in that 3-mercaptopropyltrimethoxysilane is removed in step S1.2.
[0058] Comparative Example 3 differs from Example 1 in that the thiol-modified LDH in step S3 is replaced with an equal amount of activated biochar.
[0059] Comparative Example 4 differs from Example 1 in that the activated biochar in step S3 is replaced with an equal amount of mercapto-modified LDH removal.
[0060] Test example:
[0061] Pot experiment: 24 pots, each containing 5 kg of cadmium-contaminated soil, were divided into 8 groups: Example 1 group, Example 2 group, Example 3 group, Comparative Example 1 group, Comparative Example 2 group, Comparative Example 3 group, Comparative Example 4 group, and control group, with 3 pots in each group. Each group was treated with compound fertilizer at a rate of 550 kg / mu. The control group received no fertilizer. Examples 1-3 and Comparative Example 1-4 groups were treated with the compound fertilizers prepared in Examples 1-3 and Comparative Example 1-4, respectively. The fertilizers were evenly incorporated into the soil, and rice seeds were sown. Conventional water and fertilizer management was implemented until maturity. The available cadmium content in the soil, and the cadmium content in the rice roots, stems, leaves, and grains were then measured. The average values were taken, and the results are shown in Table 1.
[0062] Table 1: Results of Compound Fertilizer Efficiency Test
[0063] Available cadmium content in soil (mg / kg) Cadmium content in rice roots (mg / kg) Cadmium content in rice stems and leaves (mg / kg) Cadmium content in rice grains (mg / kg) Example 1 Group 0.17 10.3 1.9 0.05 Example 2 group 0.15 9.6 1.6 0.04 Example 3 Group 0.12 9.2 1.4 0.02 Comparative Example 1 0.94 27.1 6.5 0.31 Comparative Example 2 0.69 21.5 4.2 0.22 Comparative Example 3 Groups 0.63 19.6 3.8 0.17 Comparative Example 4 Groups 0.37 14.8 2.9 0.13 Blank group 1.48 39.2 8.5 0.46
[0064] As shown in Table 1, in Comparative Example 1 without the addition of thiol-modified LDH, the cadmium content in the soil, rice roots, stems, leaves, and grains after application of the prepared compound fertilizer was significantly higher than that in Example 1. In Comparative Example 2, when unmodified LDH was directly added, although the cadmium content in the soil, rice roots, stems, leaves, and grains after application was lower than that in Comparative Example 1, it was still higher than that in Example 1. This shows that by first dissolving magnesium nitrate hexahydrate and aluminum nitrate nonahydrate to form a mixed salt solution, and then adding sodium hydroxide solution to undergo a co-precipitation reaction to generate a MgLDH layered precursor, followed by the addition of 3-mercaptopropyltrimethoxysilane through silane coupling, thiol groups are grafted onto the LDH layered structure. The surface is then subjected to a hydrothermal crystallization reaction at 120-130℃ to achieve stable loading of thiol groups, ultimately forming a thiol-modified LDH with both a layered structure and strong cadmium adsorption properties. When added to fertilizer, the thiol groups loaded on its surface can undergo a specific complexation reaction with free cadmium ions in the soil to form a stable and water-insoluble Cd-S complex. At the same time, its layered structure can further fix exchangeable cadmium ions in the soil through the dual effects of ion exchange and physical adsorption, converting them into residual cadmium that is not easily absorbed by crops. This significantly reduces the bioavailability of cadmium ions in the soil, thereby effectively reducing the absorption of cadmium ions by crop roots and their translocation to the aboveground parts, achieving a significant reduction in cadmium accumulation in crops and ensuring the quality and safety of agricultural products.
[0065] Furthermore, in Comparative Examples 3 and 4, when only one of activated biochar or thiol-modified LDH was added, the resulting compound fertilizers showed higher effective cadmium content in the soil, as well as higher cadmium content in rice roots, stems, leaves, and grains compared to Example 1. This demonstrates that by pyrolyzing rice husks to form porous biochar, followed by activation by soaking in potassium hydroxide solution, the specific surface area of the biochar is increased through etching, thus optimizing its adsorption performance. When activated biochar is added to the fertilizer, it acts as a porous carrier to achieve efficient dispersion of thiol-modified LDH, preventing its aggregation and deactivation. The two work together to achieve cascade fixation of cadmium ions through physical adsorption capture and chemical complexation stabilization, synergistically improving the passivation efficiency of cadmium ions in the soil and reducing the absorption and translocation of cadmium ions by crops from the source.
[0066] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims. Parts not described in detail in this specification are prior art known to those skilled in the art.
Claims
1. A method for preparing a fertilizer that reduces crop absorption of cadmium ions, characterized in that, Includes the following steps: S1: Preparation of thiol-modified LDH Magnesium nitrate hexahydrate and aluminum nitrate nonahydrate were dissolved in deionized water, and then sodium hydroxide solution and 3-mercaptopropyltrimethoxysilane were added to carry out a hydrothermal reaction to obtain mercapto-modified LDH. S2: Preparation of activated biochar After washing, drying, crushing, and pyrolyzing the rice husks, they are then soaked in a potassium hydroxide solution for activation to obtain activated biochar. S3: Preparation of compound fertilizer The above-mentioned thiol-modified LDH, activated biochar, urea, diammonium phosphate, potassium sulfate, humic acid and binder are put into a double helix conical mixer, 6-8 wt% deionized water is added and stirred and mixed evenly, then compound microbial agent is added, and stirring and mixing is continued for 5-10 minutes. Then, the mixture is granulated, dried and sieved to obtain compound fertilizer.
2. The method for preparing a fertilizer that reduces crop absorption of cadmium ions according to claim 1, characterized in that, By weight, the raw material composition of compound fertilizer is as follows: 18-22 parts thiol-modified LDH, 20-25 parts activated biochar, 6-8 parts urea, 10-12 parts diammonium phosphate, 2-3 parts potassium sulfate, 8-10 parts humic acid, 1-2 parts binder and 3-5 parts compound microbial agent.
3. The method for preparing a fertilizer that reduces crop absorption of cadmium ions according to claim 2, characterized in that, The binder is sodium carboxymethyl cellulose.
4. The method for preparing a fertilizer that reduces crop absorption of cadmium ions according to claim 2, characterized in that, The compound microbial agent is composed of Bacillus subtilis, Bacillus mucilaginosus, and Saccharomyces cerevisiae in a mass ratio of (2-3):(1.4-1.6):
1.
5. A method for preparing a fertilizer that reduces crop absorption of cadmium ions according to claim 1, characterized in that, S1 includes the following steps: S1.1: Add magnesium nitrate hexahydrate and aluminum nitrate nonahydrate to deionized water at a ratio of (1.3-1.4)g:1g:(10-12)mL, and stir thoroughly until dissolved to obtain a mixed salt solution; S1.2: Under nitrogen protection, add 2 mol / L sodium hydroxide solution to the above mixed salt solution, adjust the pH to 9, and then add 3-mercaptopropyltrimethoxysilane while stirring. Continue stirring for 30-40 min, then transfer to a hydrothermal reactor and hydrothermally crystallize at 120-130℃ for 10-12 h. After cooling, filter, wash with deionized water until neutral, vacuum dry and grind to obtain mercapto-modified LDH.
6. A method for preparing a fertilizer that reduces crop absorption of cadmium ions according to claim 5, characterized in that, The amount of 3-mercaptopropyltrimethoxysilane added is 1.8-2% of the volume of the mixed salt solution.
7. The method for preparing a fertilizer that reduces crop absorption of cadmium ions according to claim 1, characterized in that, S2 includes the following steps: S2.1: After washing the rice husks, dry them at 100-110℃ to constant weight, then crush them and pass them through a 40-mesh sieve to obtain rice husk powder. S2.2: The above rice husk powder is pyrolyzed at 600-700℃ in anoxic conditions for 2-3 hours, then soaked in 2 mol / L potassium hydroxide solution for 8-10 hours, and then filtered, washed until neutralized and dried to obtain activated biochar.
8. A fertilizer that reduces crop absorption of cadmium ions, characterized in that, It is prepared by a method for preparing a fertilizer that reduces the absorption of cadmium ions by crops, as described in any one of claims 1-7.