Aos synergistic chelated microelement synergistic fertilizer and its production method

Abstract

The application discloses an AOS synergistic chelated microelement synergistic fertilizer, and belongs to the technical field of fertilizers, which is prepared from the following raw materials in proportion by weight: urea 30-45 parts, ammonium dihydrogen phosphate 15-25 parts, potassium nitrate 15-25 parts, potassium sulfate 5-15 parts, alpha-olefin sulfonate sodium 2-6 parts, compound amino acid powder 3-8 parts, citric acid 1-4 parts, potassium humate 2-6 parts, zinc sulfate 1.0-3.0 parts, manganese sulfate 0.5-2.0 parts, copper sulfate 0.2-1.0 parts, ferrous sulfate 0.5-2.0 parts, boric acid 0.3-1.0 parts, seaweed extract 0.5-2.0 parts and polyaspartic acid sodium 0.5-1.5 parts; in the fertilizer, zinc, manganese, copper and iron ions form a ternary chelated structure of amino acid-metal-sulfonate salt with the compound amino acid powder, the citric acid and the alpha-olefin sulfonate sodium. ‑ In the application, sulfonate groups (-SO3 ‑ ) of AOS are used as auxiliary ligands to form a hydrogen bond network and electrostatic complementation with amino groups / carboxyl groups of amino acids and carboxyl groups of citric acid, so as to jointly wrap metal ions and form a ternary complex of chelating agent-metal-AOS.

Description

Technical Field

[0001] This invention relates to the field of fertilizer technology, specifically to an AOS synergistic chelating micronutrient fertilizer and its production method. Background Technology

[0002] Micronutrients (zinc, manganese, copper, iron, boron, etc.) are essential nutrients for crop growth and development, and have a significant impact on photosynthesis, enzyme activation, stress resistance, and the quality of agricultural products. However, traditional micronutrient fertilizers are mostly added in the form of inorganic salts, which easily form insoluble precipitates with phosphate, sulfate, etc., after being applied to the soil, or are fixed by soil colloids, resulting in a significant reduction in the availability of micronutrients. To address this, existing technologies have developed improved solutions that use organic chelating agents to chelate and protect micronutrients.

[0003] For example, invention patent CN106800460A discloses a method for preparing a fertilizer synergist containing trace elements. The method involves melting urea and adjusting the temperature to 97-130°C, then adding one or more organic chelating agents such as biochemical fulvic acid, amino acid powder, citric acid, and alginic acid, followed by the addition of trace element oxides such as magnesium oxide, zinc oxide, calcium oxide, and iron oxide. After stirring and reacting for 10-40 minutes, the mixture is discharged, cooled, and pulverized to obtain the final product. This method claims that by utilizing organic chelating agents in the molten urea environment to chelate oxidized trace elements, it can effectively prevent the reaction of trace elements with phosphate ions to form insoluble substances. Furthermore, the preparation process can utilize existing compound fertilizer production equipment, completing the chelation of multiple elements in one step without increasing equipment investment or waste emissions.

[0004] However, the aforementioned existing technologies still have the following major drawbacks: 1) This scheme directly uses metal oxides such as magnesium oxide, zinc oxide, calcium oxide, and iron oxide as sources of trace elements. The oxides have stable chemical properties and low reactivity, making it difficult for them to fully react with organic chelating agents to form stable chelates in the molten urea system. 2) This scheme relies solely on traditional chelating agents such as biochemical fulvic acid, amino acids, and citric acid as single ligands. Its chelation system only contains a binary structure of "chelating agent-metal". When encountering phosphate, sulfate, or calcium and magnesium ions in hard water, the binary chelate has insufficient steric hindrance and limited anti-precipitation ability. 3) This scheme only focuses on the chelation protection of micronutrients and does not involve functional designs to reduce the surface tension of fertilizer solutions or improve the wetting and spreading ability of leaves and rhizosphere. The surface tension of the resulting synergist in water is still comparable to that of ordinary urea solutions (approximately 65~72 mN / m), which is not conducive to the penetration and absorption of fertilizer solutions in crop leaves and rhizosphere, thus limiting further improvement in the utilization rate of micronutrients.

[0005] Therefore, an AOS-synergistic chelated micronutrient fertilizer and its production method are proposed to solve the above problems. Summary of the Invention

[0006] Technical problems to be solved To address the shortcomings of existing technologies, this invention provides an AOS-synergistic chelated micronutrient fertilizer and its production method. It features a four-component synergistic chelation of AOS-amino acids-citric acid-potassium humate, dual-use of AOS, simultaneous chelation of five micronutrients, precise gradient pH control, complete preservation of activity through low-temperature drying, and full water solubility without clogging. This invention solves the problems of low efficiency in direct oxide chelation, lack of wetting and synergistic effects, damage to heat-sensitive components due to high reaction temperatures, and poor storage stability due to the absence of anti-caking treatment in existing technologies.

[0007] Technical solution To achieve the aforementioned goals of AOS-amino acid-citric acid-potassium humate quaternary synergistic chelation, dual-use of AOS, simultaneous chelation of five trace elements, precise gradient pH control, complete preservation of activity through low-temperature drying, and complete water solubility without clogging, this invention provides the following technical solution: An AOS synergistic chelated trace element enhanced fertilizer, comprising the following raw materials in the indicated weight ratios: 30-45 parts urea, 15-25 parts ammonium dihydrogen phosphate, 15-25 parts potassium nitrate, 5-15 parts potassium sulfate, 2-6 parts sodium α-olefin sulfonate, 3-8 parts compound amino acid powder, 1-4 parts citric acid, 2-6 parts potassium humate, 1.0-3.0 parts zinc sulfate, 0.5-2.0 parts manganese sulfate, 0.2-1.0 parts copper sulfate, 0.5-2.0 parts ferrous sulfate, 0.3-1.0 parts boric acid, 0.5-2.0 parts seaweed extract, and 0.5-1.5 parts sodium polyaspartate; In the fertilizer, zinc, manganese, copper, and iron ions form an amino acid-metal-sulfonate ternary complex chelate structure with compound amino acid powder, citric acid, and sodium α-olefin sulfonate.

[0008] Preferably, the α-olefin sulfonate sodium has a carbon chain length of C12 to C18; the fertilizer is an 80 to 200 mesh powder with a moisture content of ≤3.0%.

[0009] Preferably, the mass ratio of glycine to glutamic acid in the composite amino acid powder is 1:1; the sodium α-olefin sulfonate is sodium α-olefin sulfonate with an active ingredient content ≥92%.

[0010] Another technical problem to be solved by the present invention is to provide a method for producing an AOS-synergistic chelated micronutrient fertilizer, comprising the following steps: S1. Preparation of AOS functional solution: Add deionized water to a reactor equipped with a heating jacket, thermometer, and frequency converter, and stir continuously; slowly add AOS powder while stirring, and continue stirring until completely dissolved to form a transparent and uniform AOS solution; add citric acid to the reactor, stir until completely dissolved, and adjust the pH to 4.0~4.5 with 10% dilute sulfuric acid or 10% potassium hydroxide solution to obtain AOS-citric acid functional solution; S2, Amino Acid-Trace Element Pre-chelation: Maintaining the reaction vessel temperature of step S1, slowly add zinc sulfate, manganese sulfate, copper sulfate, and ferrous sulfate while stirring, ensuring that the previous metal salt is completely dissolved before adding the next; after all metal salts are added, stir and react at a constant temperature of 45~50℃ for a period of time. During this stage, the metal ions preferentially coordinate with the carboxyl groups of citric acid to form citric acid-metal primary chelates; then slowly add the composite amino acid powder and continue stirring to further coordinate the amino and carboxyl groups of the amino acids with the metal ions; slowly adjust the pH with 10% potassium hydroxide solution, observing the reaction solution gradually change from turbid to clear during the adjustment process, indicating that the chelation reaction is approaching completion, and a mixed ligand chelate solution is obtained; S3. Potassium humate complex and AOS synergistic activation: Potassium humate was pre-dissolved and activated in another container with deionized water and heated until completely dissolved, yielding a potassium humate activation solution. Under stirring conditions, the potassium humate activation solution was slowly added to the reaction system of step S2. Stirring was continued and the pH was adjusted with 10% potassium hydroxide solution. Stirring was continued for 20-30 minutes to allow potassium humate and AOS to form a complex micelle structure through hydrophobic interactions and hydrogen bonds. Then, boric acid, seaweed extract and sodium polyaspartate were added sequentially, with each component added at intervals, until all components were added. Stirring was continued to obtain a homogeneous AOS synergistic chelation functional solution. S4. Premixing and Emulsifying Dispersion of Macro-elements: Urea, ammonium dihydrogen phosphate, potassium nitrate, and potassium sulfate are weighed according to the specified ratio and added to a high-speed mixer for premixing to ensure uniform particle size and thorough dispersion of each component, resulting in a macro-element mixed powder. The AOS synergistic chelating functional liquid from step S3 is then uniformly sprayed onto the macro-element mixed powder through a high-pressure atomizing nozzle at an atomization pressure of 0.3~0.5MPa, while continuously stirring at a speed of 200~300rpm to ensure the functional liquid is fully absorbed by the powder. After spraying, stirring continues for 5~10 minutes to ensure the chelating functional liquid is evenly spread on the powder surface, resulting in a moist and loose material without obvious agglomeration. S5. Low-temperature drying: Spread the mixed wet material from step S4 evenly into a low-temperature spray dryer or fluidized bed dryer, with the material layer thickness controlled at 2-5 cm; under stable conditions, the drying time is about 20-40 minutes until the material moisture content is ≤3.0%, and the dried material is in a loose state with no obvious caking or sticking to the wall. S6. Fine grinding and classification: The material dried in step S5 is fed into an air jet mill and finely ground using compressed air as the grinding medium. The ground material is then classified by a vibrating screen with screen apertures of 80 mesh (0.18 mm) and 200 mesh (0.075 mm). Fine powder of 80-200 mesh that passes through the 80 mesh screen but is retained on the 200 mesh screen is collected as the finished product base material. The material undersized (<0.075 mm) and material oversized (>0.18 mm) are collected and returned to the air jet mill for re-grinding or collected and reused. S7. Anti-caking treatment: The finished base material from step S6 and the anti-caking agent are put into a double cone mixer. The anti-caking agent is a mixture of microcrystalline cellulose and calcium stearate in a mass ratio of 2:1, and the amount added is 0.5%~1.5% of the mass of the finished base material. Mixing is carried out, and hot air is introduced during the mixing process to assist drying, so that the anti-caking agent is evenly attached to the surface of the finished base material particles to form a thin isolation film. S8. Screening and Packaging: The material after the anti-caking treatment in step S7 is screened again through 80-mesh and 200-mesh vibrating screens to ensure that the particle size distribution of the final product is within the range of 80~200 mesh, and then packaged in moisture-proof bags.

[0011] Preferably, in step S1, the amount of deionized water used is 8 to 12 times the mass of AOS, the dissolution temperature is 40 to 50°C, the stirring speed is 200 to 300 rpm, and the stirring time is 20 to 30 min; the pH adjustment uses 10% dilute sulfuric acid or 10% potassium hydroxide solution, and after adding citric acid, the mixture is stirred at 150 to 200 rpm for 10 to 15 min.

[0012] Preferably, in step S2, the zinc sulfate, manganese sulfate, copper sulfate, and ferrous sulfate are added sequentially at intervals of 3-5 minutes; the chelation reaction temperature is 45-50°C; the stirring speed is 150-200 rpm; and the reaction is carried out at a constant temperature for 30-40 minutes after the metal salts are added. The addition rate of the composite amino acid powder is controlled to be completed within 5-10 minutes, and stirring is continued for 20-30 minutes after the addition is completed. The pH is adjusted to 5.5-6.0 using a 10% potassium hydroxide solution at a rate of 0.5-1.0°C / min.

[0013] Preferably, in step S3, the potassium humate is pre-activated by dissolving it in 3-5 times its mass of deionized water at 60-70°C, and then stirred at 100-150 rpm for 20-30 minutes until completely dissolved before being added to the reaction system; the potassium humate activation solution is added to the reaction system at a time controlled at 10-15 minutes, and stirred for 20-30 minutes after addition, and then the pH is adjusted to 6.5-7.0 with potassium hydroxide; the boric acid, seaweed extract and sodium polyaspartate are added at intervals of 3-5 minutes, and stirring is continued for 15 minutes after all are added.

[0014] Preferably, in step S4, the rotation speed for premixing the macro-elements is 300-500 rpm, and the premixing time is 10-15 min; the spraying speed of the chelating functional liquid is controlled at 5-10 L / min.

[0015] Preferably, the low-temperature drying in step S5 uses a low-temperature spray dryer or a fluidized bed dryer, with an inlet air temperature of 60~70℃ and an outlet air temperature of 40~45℃; the compressed air pressure for the airflow pulverization in step S6 is 0.4~0.6MPa.

[0016] Preferably, in step S7, the mixing speed for the anti-caking treatment is 15~25 rpm, the mixing time is 10~15 min, and the temperature of the hot air introduced during the mixing process is 30~35℃; in step S8, the moisture-proof packaging uses an aluminum-plastic composite bag, which is vacuumed to -0.06~-0.08 MPa before packaging and then sealed, or filled with nitrogen for protection and then sealed, and the packaging environment temperature is ≤25℃.

[0017] Compared with the prior art, the above-mentioned technical solution of the present invention has the following beneficial technical effects: 1. This AOS-synergistic chelated micronutrient fertilizer and its production method utilize the sulfonate (-SO3) of AOS. - As an auxiliary ligand, it forms a hydrogen bond network and electrostatic complement with the amino / carboxyl groups of amino acids and the carboxyl groups of citric acid, jointly encapsulating metal ions to form a chelating agent-metal-AOS ternary complex. The steric hindrance effect of this ternary complex is significantly better than that of traditional binary chelates. No precipitation occurs after 24 hours in 250 mg / L hard water, effectively preventing trace elements such as zinc, manganese, copper, and iron from forming insoluble precipitates with phosphate and sulfate ions.

[0018] 2. The AOS-synergistic chelating micronutrient fertilizer and its production method utilize AOS in this invention, which simultaneously plays the dual role of an auxiliary ligand and a wetting and synergist. It participates in the chelation reaction as an auxiliary ligand to improve the stability of metal ions, and also acts as a surfactant to reduce the surface tension of the fertilizer solution to ≤32mN / m, significantly improving the wetting and spreading ability of the fertilizer solution on crop leaves and rhizosphere. No additional wetting agents or penetrants are required, resulting in a simple formula and controllable costs.

[0019] 3. This AOS-synergistic chelated micronutrient fertilizer and its production method chelate five micronutrients—zinc, manganese, copper, iron, and boron—in a single step, covering multiple physiological processes in crops, including photosynthesis, enzyme activation, and stress resistance. The AOS-amino acid-citric acid-humic acid quaternary chelation system exhibits varying affinities for different metal ions, enabling the simultaneous and stable addition of multiple micronutrients within a single system. This avoids the complexity and compatibility issues associated with adding them separately.

[0020] 4. This AOS-synergistic chelating micronutrient fertilizer and its production method employ staged pH control: the acidic stage (pH 4.0~4.5) preferentially chelates zinc, manganese, copper, and iron; the neutral stage (pH 5.5~6.0) completes amino acid coordination; and the weakly alkaline stage (pH 6.5~7.0) activates AOS-assisted coordination and the formation of potassium humate complex micelles. The entire process temperature does not exceed 70℃, and the drying outlet temperature is only 40~45℃, fully preserving the surface activity of AOS, the biological activity of amino acids, and the physiological activity of potassium humate, while avoiding the damage of heat-sensitive components to high temperatures.

[0021] 5. The AOS-synergistic chelated micronutrient fertilizer and its production method use AOS, amino acids, citric acid, potassium humate, and sodium polyaspartate, all of which are water-soluble or water-dispersible materials with a water-insoluble content of ≤0.3%, meeting the strict requirements of drip irrigation and sprinkler irrigation systems for water-soluble fertilizers; AOS itself has good biodegradability (OECD 301B method, 28-day degradation rate ≥90%), with no risk of soil residue. Attached Figure Description

[0022] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1: This embodiment provides an AOS synergistic chelated micronutrient fertilizer, composed of the following raw materials in parts by weight: 38 parts urea, 20 parts ammonium dihydrogen phosphate, 20 parts potassium nitrate, 10 parts potassium sulfate, 4 parts sodium α-olefin sulfonate, 5.5 parts compound amino acid powder, 2.5 parts citric acid, 4 parts potassium humate, 2.0 parts zinc sulfate, 1.2 parts manganese sulfate, 0.6 parts copper sulfate, 1.2 parts ferrous sulfate, 0.6 parts boric acid, 1.2 parts seaweed extract, and 1.0 part sodium polyaspartate.

[0025] Raw material characterization: The sodium α-olefin sulfonate (AOS) used in this embodiment was analyzed by gas chromatography (GC). Its carbon chain distribution was approximately 25% C12, 30% C14, 30% C16, and 15% C18, which meets the requirement of the C12~C18 carbon chain length range. The active ingredient content was determined to be 93.5% by two-phase titration, which is ≥92%. The composite amino acid powder used was determined by an automatic amino acid analyzer. The glycine content was 48.5% and the glutamic acid content was 47.8%, with a mass ratio of approximately 1:1, which meets the requirement of a 1:1 mass ratio of glycine to glutamic acid.

[0026] A method for producing an AOS-synergistic micronutrient fertilizer includes the following steps: S1. Preparation of AOS functional solution: Add deionized water (10 times the mass of AOS) to a reactor equipped with a heating jacket, thermometer, and frequency converter. Start stirring and heat to 45°C. Slowly add AOS powder while stirring at 200-300 rpm and continue stirring for 25 minutes until completely dissolved to form a transparent and uniform AOS solution. Add citric acid to the reactor and stir at 180 rpm for 12 minutes until completely dissolved. Adjust the pH to 4.3 with 10% dilute sulfuric acid or 10% potassium hydroxide solution to obtain AOS-citric acid functional solution.

[0027] S2. Amino Acid-Trace Element Pre-chelation: Maintaining the reactor temperature at 48℃, zinc sulfate, manganese sulfate, copper sulfate, and ferrous sulfate were added slowly in sequence with a stirring speed of 180 rpm. The addition interval was 4 min, ensuring that the previous metal salt was completely dissolved before adding the next. After all the metal salts were added, the reaction was stirred at a constant temperature of 48℃ for 35 min. During this stage, the metal ions preferentially coordinated with the carboxyl groups of citric acid to form a citric acid-metal primary chelate. Then, the composite amino acid powder was slowly added, controlling the addition rate to be completed within 8 min. Stirring was continued for 25 min to allow the amino and carboxyl groups of the amino acids to further coordinate with the metal ions. The pH was slowly adjusted to 5.8 using a 10% potassium hydroxide solution at a rate of 0.8℃ / min. During the adjustment process, the reaction solution was observed to gradually change from turbid to clear, indicating that the chelation reaction was approaching completion, and a mixed ligand chelate solution was obtained.

[0028] S3. Potassium humate complex and AOS synergistic activation: Potassium humate was pre-dissolved in another container with 4 times its mass of deionized water, heated to 65°C, and stirred at 120 rpm for 25 min until completely dissolved and activated to obtain an activated potassium humate solution. Under stirring conditions, the activated potassium humate solution was slowly added to the reaction system of step S2, with the addition time controlled at 12 min. Stirring continued and the pH was adjusted to 6.8 with 10% potassium hydroxide solution. Stirring continued for 25 min to allow potassium humate and AOS to form a complex micelle structure through hydrophobic interactions and hydrogen bonds. Then, boric acid, seaweed extract and sodium polyaspartate were added sequentially, with each component added at 4 min intervals. After all components were added, stirring continued for 15 min to obtain a homogeneous AOS synergistic chelation functional solution.

[0029] S4. Premixing and Emulsifying Dispersion of Macro-elements: Urea, ammonium dihydrogen phosphate, potassium nitrate, and potassium sulfate are weighed according to the formula and added to a high-speed mixer. They are premixed at 400 rpm for 12 minutes to ensure uniform particle size and thorough dispersion of each component, resulting in a macro-element mixed powder. The AOS synergistic chelating functional liquid from step S3 is sprayed evenly onto the macro-element mixed powder through a high-pressure atomizing nozzle at an atomization pressure of 0.4 MPa. The spraying speed is controlled at 7.5 L / min, while continuous stirring at 250 rpm ensures that the functional liquid is fully absorbed by the powder. After spraying, stirring is continued for 8 minutes to ensure that the chelating functional liquid is evenly spread on the powder surface, and the material is in a moist and loose state without obvious agglomeration.

[0030] S5. Low-temperature drying: The mixed wet material from step S4 is evenly spread into the fluidized bed dryer, and the material layer thickness is controlled at 3.5cm. The inlet air temperature is set to 65℃ and the outlet air temperature is controlled at 42℃. The drying time is about 30 minutes until the material moisture content is ≤3.0%. The dried material is in a loose state and there is no obvious clumping or sticking to the wall.

[0031] S6. Fine grinding and classification: The material dried in step S5 is fed into an air jet mill and finely ground using compressed air at 0.5 MPa as the grinding medium. After grinding, the material is classified by a vibrating screen with screen apertures of 80 mesh (0.18 mm) and 200 mesh (0.075 mm). Fine powder of 80-200 mesh that passes through the 80 mesh screen and is retained on the 200 mesh screen is collected as the finished product base material. The material under the screen (<0.075 mm) and the material over the screen (>0.18 mm) are collected and returned to the air jet mill for re-grinding or collected and reused.

[0032] S7. Anti-caking treatment: The finished base material from step S6 and the anti-caking agent are put into a double cone mixer. The anti-caking agent is a mixture of microcrystalline cellulose and calcium stearate in a mass ratio of 2:1, and the amount added is 1.0% of the mass of the finished base material. Mix at 20 rpm for 12 minutes. During the mixing process, hot air at 32°C is introduced to assist drying, so that the anti-caking agent is evenly attached to the surface of the finished base material particles to form a thin isolation film.

[0033] S8. Screening and Packaging: The material after the anti-caking treatment in step S7 is screened again through 80-mesh and 200-mesh vibrating screens to ensure that the particle size distribution of the final product is within the range of 80~200 mesh; In a cleanroom with relative humidity ≤30% and temperature ≤25℃, aluminum-plastic composite bags (inner layer PE, outer layer PET / AL composite) are used for packaging. Before packaging, the packaging bags are vacuumed to -0.07MPa and then sealed. The packaging environment temperature is controlled at ≤25℃.

[0034] Product performance: The synergistic fertilizer prepared in this embodiment is an 80-200 mesh powder with a moisture content of ≤2.8%. The product has a uniform powder appearance, good flowability, no caking, a trace element chelation rate of ≥95%, a surface tension (0.1% solution) of ≤32mN / m, and a water-insoluble content of ≤0.3%. The components in the product are evenly distributed and have good solubility and wetting and spreading properties.

[0035] Product structure characterization: The enhanced fertilizer prepared in this embodiment was subjected to Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) to verify its chelate structure. FTIR spectroscopy analysis: Products are in the range of 1040~1060 cm⁻¹ - AOS sulfonate (-SO3) appears at position ¹ - The characteristic absorption peaks are located in the range of 1580~1610 cm⁻¹. - An amino acid carboxyl group (-COO) appears at position ¹. - The characteristic absorption peaks of the product were observed; compared with AOS alone and amino acid alone, the absorption peaks of sulfonate and carboxyl groups in the product showed significant shifts (approximately 8-12 cm⁻¹ towards lower wavenumbers, respectively). - ¹ and 6~10cm - ¹), indicating that the sulfonate group of AOS forms an intermolecular hydrogen bond network with the carboxyl group of the amino acid, and jointly participates in the coordination chelation of metal ions.

[0036] X-ray photoelectron spectroscopy (XPS): Narrow-spectrum scanning analysis of Zn2p, Mn2p, Cu2p, and Fe2p in the product showed that the binding energies of each metal ion were significantly shifted compared to their corresponding inorganic salts (sulfates) (Zn2p3 / 2 shifted by approximately 1.8~2.2 eV), indicating that coordination bonds were formed between the metal ions and the chelating ligands. At the same time, the S2p spectrum showed characteristic peaks for coordination between sulfonate and metal ions, confirming that the sulfonate of AOS directly participated in the coordination of metal ions as an auxiliary ligand, rather than a simple physical mixing.

[0037] Based on the combined FTIR and XPS analysis results, it can be confirmed that in the synergistic fertilizer prepared in this embodiment, zinc, manganese, copper, and iron ions form an amino acid-metal-sulfonate ternary complex chelate structure with the compound amino acid powder, citric acid, and sodium α-olefin sulfonate.

[0038] Product performance testing: (1) Determination of trace element chelation rate: The total trace element content and free trace element content in the product were determined by inductively coupled plasma optical emission spectrometry (ICP-OES). The chelation rate = (total content - free content) / total content × 100%. The zinc chelation rate of the product in this example was 95.2%, the manganese chelation rate was 94.8%, the copper chelation rate was 96.1%, the iron chelation rate was 93.5%, and the average chelation rate was ≥95%.

[0039] (2) Surface tension measurement: The product was prepared into a 0.1% aqueous solution, and the surface tension was measured at 25°C using the platinum plate method. The surface tension of the 0.1% aqueous solution of the product in this embodiment was 31.2 mN / m, which is significantly better than that of conventional amino acid chelated fertilizer (45~55 mN / m) and inorganic salt trace element fertilizer (65~72 mN / m), indicating that the wetting and synergistic function of AOS was preserved.

[0040] (3) Determination of resistance to hard water precipitation: The product was prepared into a 1% aqueous solution, and CaCO3 was added to make the total hardness 250 mg / L (calculated as CaCO3). After standing at 25℃ for 24 hours, it was observed that the product solution in this example remained clear and transparent without any precipitation. As a control, the conventional zinc sulfate solution showed a white precipitate within 5 minutes under the same conditions. The results showed that the ternary composite chelate structure endowed the product with excellent resistance to hard water precipitation.

[0041] (4) Determination of water-insoluble matter content: According to the NY / T1115 standard, the water-insoluble matter content of the product in this example is 0.22%.

[0042] Example 2: This embodiment provides an AOS synergistic chelating micronutrient fertilizer, composed of the following raw materials in parts by weight: 32 parts urea, 17 parts ammonium dihydrogen phosphate, 17 parts potassium nitrate, 7 parts potassium sulfate, 2.5 parts sodium α-olefin sulfonate, 3.5 parts compound amino acid powder, 1.5 parts citric acid, 2.5 parts potassium humate, 1.2 parts zinc sulfate, 0.6 parts manganese sulfate, 0.25 parts copper sulfate, 0.6 parts ferrous sulfate, 0.35 parts boric acid, 0.6 parts seaweed extract, and 0.6 parts sodium polyaspartate.

[0043] Raw material characterization: The AOS used in this embodiment is from the same batch as that in Example 1, and its carbon chain distribution and active ingredient content are the same; the compound amino acid powder is from the same batch as that in Example 1, and the mass ratio of glycine to glutamic acid is approximately 1:1.

[0044] A method for producing an AOS-synergistic micronutrient fertilizer includes the following steps: S1. Preparation of AOS functional solution: Add deionized water (8 times the mass of AOS) to the reactor, start stirring and heat to 40°C. Slowly add AOS powder while stirring at 200 rpm and continue stirring for 20 minutes until completely dissolved. Add citric acid to the reactor and stir at 150 rpm for 10 minutes until completely dissolved. Adjust the pH to 4.0 with 10% dilute sulfuric acid or 10% potassium hydroxide solution to obtain AOS-citric acid functional solution.

[0045] S2. Amino acid-trace element prechelation: Keep the reactor temperature at 45℃ and slowly add zinc sulfate, manganese sulfate, copper sulfate and ferrous sulfate in sequence with a stirring speed of 150 rpm, with a 3-minute interval between additions. After all the metal salts are added, stir and react at a constant temperature of 45℃ for 30 minutes. Then slowly add the composite amino acid powder, controlling the addition speed to be completed within 5 minutes, and continue stirring for 20 minutes. Use 10% potassium hydroxide solution to slowly adjust the pH to 5.5 at a rate of 0.5℃ / min to obtain a mixed ligand chelate solution.

[0046] S3. Potassium humate compound and AOS synergistic activation: Potassium humate was pre-dissolved in another container with 3 times its mass of deionized water, heated to 60°C, and stirred at 100 rpm for 20 min until completely dissolved and activated. Under stirring conditions, the activated potassium humate solution was slowly added to the reaction system of step S2, with the addition time controlled at 10 min. Stirring continued and the pH was adjusted to 6.5 with 10% potassium hydroxide solution, and stirred for 20 min. Then, boric acid, seaweed extract and sodium polyaspartate were added in sequence, with each component added at 3 min intervals. After all components were added, stirring continued for 15 min to obtain the AOS synergistic chelation functional solution.

[0047] S4~S8 are the same as in Example 1, with each parameter taking a lower range of values ​​(for specific parameters, please refer to the example, which will not be repeated here).

[0048] Product performance: The synergistic fertilizer prepared in this embodiment is an 80-200 mesh powder with a moisture content ≤2.9%, a trace element chelation rate ≥92%, a surface tension (0.1% solution) ≤35mN / m, and a water-insoluble content ≤0.4%. All parameters of this scheme are in a low range, resulting in low production costs, making it suitable for large-scale industrial production with moderate product quality requirements.

[0049] Product structure characterization: FTIR and XPS analysis showed that the spectral characteristics of the product in this embodiment were consistent with those in Example 1, confirming the formation of an amino acid-metal-sulfonate ternary complex chelate structure.

[0050] Example 3: This embodiment provides an AOS synergistic chelated trace element enhanced fertilizer, composed of the following raw materials in parts by weight: 42 parts urea, 23 parts ammonium dihydrogen phosphate, 23 parts potassium nitrate, 13 parts potassium sulfate, 5.5 parts sodium α-olefin sulfonate, 7.5 parts compound amino acid powder, 3.8 parts citric acid, 5.5 parts potassium humate, 2.8 parts zinc sulfate, 1.8 parts manganese sulfate, 0.9 parts copper sulfate, 1.8 parts ferrous sulfate, 0.9 parts boric acid, 1.8 parts seaweed extract, and 1.4 parts sodium polyaspartate.

[0051] Raw material characterization: The AOS used in this embodiment is from the same batch as that in Example 1, and its carbon chain distribution and active ingredient content are the same; the compound amino acid powder is from the same batch as that in Example 1, and the mass ratio of glycine to glutamic acid is approximately 1:1.

[0052] A method for producing an AOS-synergistic micronutrient fertilizer includes the following steps: S1. Preparation of AOS functional solution: Add deionized water (12 times the mass of AOS) to the reactor, start stirring and heat to 50°C. Slowly add AOS powder while stirring at 300 rpm and continue stirring for 30 min until completely dissolved. Add citric acid to the reactor and stir at 200 rpm for 15 min until completely dissolved. Adjust the pH to 4.5 with 10% dilute sulfuric acid or 10% potassium hydroxide solution to obtain AOS-citric acid functional solution.

[0053] S2. Amino acid-trace element prechelation: Keep the reactor temperature at 50℃ and slowly add zinc sulfate, manganese sulfate, copper sulfate and ferrous sulfate in sequence with a stirring speed of 200 rpm, with a feeding interval of 5 min; after all metal salts are added, stir and react at a constant temperature of 50℃ for 40 min; then slowly add the composite amino acid powder, controlling the feeding rate to be completed within 10 min, and continue stirring for 30 min; slowly adjust the pH to 6.0 with 10% potassium hydroxide solution at a rate of 1.0℃ / min to obtain a mixed ligand chelate solution.

[0054] S3. Potassium humate compound and AOS synergistic activation: Potassium humate was pre-dissolved in another container with 5 times its weight of deionized water, heated to 70°C, and stirred at 150 rpm for 30 min until completely dissolved and activated. Under stirring conditions, the activated potassium humate solution was slowly added to the reaction system of step S2, with the addition time controlled at 15 min. Stirring continued and the pH was adjusted to 7.0 with 10% potassium hydroxide solution, and stirred for 30 min. Then, boric acid, seaweed extract and sodium polyaspartate were added in sequence, with each component added at 5 min intervals. After all components were added, stirring continued for 15 min to obtain the AOS synergistic chelation functional solution.

[0055] S4~S8 are the same as in Example 1, with each parameter taking a higher range of values ​​(for specific parameters, please refer to the example, which will not be repeated here).

[0056] Product performance: The synergistic fertilizer prepared in this embodiment is an 80-200 mesh powder with a moisture content of ≤2.5%, a trace element chelation rate of ≥96%, a surface tension (0.1% solution) of ≤30mN / m, and a water-insoluble content of ≤0.25%. The content of each component and the process parameters of this scheme are all in a high range, with the best chelation effect and wetting performance. It is suitable for the high-end market and planting scenarios with high requirements for trace element supplementation.

[0057] Product structure characterization: FTIR and XPS analysis showed that the spectral characteristics of the product in this embodiment were consistent with those in Example 1, confirming the formation of an amino acid-metal-sulfonate ternary complex chelate structure.

[0058] The key performance indicators of each embodiment are compared in the table below:

[0059] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A fertilizer that synergistically chelates trace elements with AOS, characterized in that, The raw materials include the following parts by weight: 30-45 parts urea, 15-25 parts ammonium dihydrogen phosphate, 15-25 parts potassium nitrate, 5-15 parts potassium sulfate, 2-6 parts sodium α-olefin sulfonate, 3-8 parts compound amino acid powder, 1-4 parts citric acid, 2-6 parts potassium humate, 1.0-3.0 parts zinc sulfate, 0.5-2.0 parts manganese sulfate, 0.2-1.0 parts copper sulfate, 0.5-2.0 parts ferrous sulfate, 0.3-1.0 parts boric acid, 0.5-2.0 parts seaweed extract, and 0.5-1.5 parts sodium polyaspartate. In the fertilizer, zinc, manganese, copper, and iron ions form an amino acid-metal-sulfonate ternary complex chelate structure with compound amino acid powder, citric acid, and sodium α-olefin sulfonate.

2. The AOS synergistic chelation micronutrient fertilizer according to claim 1, characterized in that, The sodium α-olefin sulfonate has a carbon chain length of C12 to C18; the fertilizer is a powder of 80 to 200 mesh with a moisture content of ≤3.0%.

3. The AOS synergistic chelation micronutrient fertilizer according to claim 1, characterized in that, The mass ratio of glycine to glutamic acid in the compound amino acid powder is 1:1; the sodium α-olefin sulfonate is sodium α-olefin sulfonate with an active ingredient content ≥92%.

4. A method for producing an AOS-synergistic chelated micronutrient fertilizer, characterized in that, Includes the following steps: S1. Preparation of AOS functional solution: Add deionized water to a reactor equipped with a heating jacket, thermometer, and frequency converter, and stir continuously; slowly add AOS powder while stirring, and continue stirring until completely dissolved to form a transparent and uniform AOS solution; add citric acid to the reactor, stir until completely dissolved, and adjust the pH to 4.0~4.5 with 10% dilute sulfuric acid or 10% potassium hydroxide solution to obtain AOS-citric acid functional solution; S2, Amino Acid-Trace Element Pre-chelation: Maintaining the reaction vessel temperature of step S1, slowly add zinc sulfate, manganese sulfate, copper sulfate, and ferrous sulfate while stirring, ensuring that the previous metal salt is completely dissolved before adding the next; after all metal salts are added, stir and react at a constant temperature of 45~50℃ for a period of time. During this stage, the metal ions preferentially coordinate with the carboxyl groups of citric acid to form citric acid-metal primary chelates; then slowly add the composite amino acid powder and continue stirring to further coordinate the amino and carboxyl groups of the amino acids with the metal ions; slowly adjust the pH with 10% potassium hydroxide solution, observing the reaction solution gradually change from turbid to clear during the adjustment process, indicating that the chelation reaction is approaching completion, and a mixed ligand chelate solution is obtained; S3. Potassium humate complex and AOS synergistic activation: Potassium humate was pre-dissolved and activated in another container with deionized water and heated until completely dissolved, yielding a potassium humate activation solution. Under stirring conditions, the potassium humate activation solution was slowly added to the reaction system of step S2. Stirring was continued and the pH was adjusted with 10% potassium hydroxide solution. Stirring was continued for 20-30 minutes to allow potassium humate and AOS to form a complex micelle structure through hydrophobic interactions and hydrogen bonds. Then, boric acid, seaweed extract and sodium polyaspartate were added sequentially, with each component added at intervals, until all components were added. Stirring was continued to obtain a homogeneous AOS synergistic chelation functional solution. S4. Premixing and Emulsifying Dispersion of Macro-elements: Urea, ammonium dihydrogen phosphate, potassium nitrate, and potassium sulfate are weighed according to the specified ratio and added to a high-speed mixer for premixing to ensure uniform particle size and thorough dispersion of each component, resulting in a macro-element mixed powder. The AOS synergistic chelating functional liquid from step S3 is then uniformly sprayed onto the macro-element mixed powder through a high-pressure atomizing nozzle at an atomization pressure of 0.3~0.5MPa, while continuously stirring at a speed of 200~300rpm to ensure the functional liquid is fully absorbed by the powder. After spraying, stirring continues for 5~10 minutes to ensure the chelating functional liquid is evenly spread on the powder surface, resulting in a moist and loose material without obvious agglomeration. S5. Low-temperature drying: Spread the mixed wet material from step S4 evenly into a low-temperature spray dryer or fluidized bed dryer, with the material layer thickness controlled at 2-5 cm; under stable conditions, the drying time is about 20-40 minutes until the material moisture content is ≤3.0%, and the dried material is in a loose state with no obvious caking or sticking to the wall. S6. Fine grinding and classification: The material dried in step S5 is fed into an air jet mill and finely ground using compressed air as the grinding medium. The ground material is then classified by a vibrating screen with screen apertures of 80 mesh (0.18 mm) and 200 mesh (0.075 mm). Fine powder of 80-200 mesh that passes through the 80 mesh screen but is retained on the 200 mesh screen is collected as the finished product base material. The material undersized (<0.075 mm) and material oversized (>0.18 mm) are collected and returned to the air jet mill for re-grinding or collected and reused. S7. Anti-caking treatment: The finished base material from step S6 and the anti-caking agent are put into a double cone mixer. The anti-caking agent is a mixture of microcrystalline cellulose and calcium stearate in a mass ratio of 2:1, and the amount added is 0.5%~1.5% of the mass of the finished base material. Mixing is carried out, and hot air is introduced during the mixing process to assist drying, so that the anti-caking agent is evenly attached to the surface of the finished base material particles to form a thin isolation film. S8. Screening and Packaging: The material after the anti-caking treatment in step S7 is screened again through 80-mesh and 200-mesh vibrating screens to ensure that the particle size distribution of the final product is within the range of 80~200 mesh, and then packaged in moisture-proof bags.

5. The production method of an AOS synergistic chelation micronutrient fertilizer according to claim 4, characterized in that, In step S1, the amount of deionized water used is 8 to 12 times the mass of AOS, the dissolution temperature is 40 to 50°C, the stirring speed is 200 to 300 rpm, and the stirring time is 20 to 30 min; the pH adjustment is performed using 10% dilute sulfuric acid or 10% potassium hydroxide solution, and after adding citric acid, the mixture is stirred at 150 to 200 rpm for 10 to 15 min.

6. The production method of an AOS synergistic chelation micronutrient fertilizer according to claim 4, characterized in that, In step S2, the zinc sulfate, manganese sulfate, copper sulfate, and ferrous sulfate are added sequentially at intervals of 3-5 minutes. The chelation reaction temperature is 45-50°C, the stirring speed is 150-200 rpm, and the reaction is kept at a constant temperature for 30-40 minutes after the metal salts are added. The addition rate of the composite amino acid powder is controlled to be completed within 5-10 minutes, and stirring is continued for 20-30 minutes after the addition is completed. The pH is adjusted to 5.5-6.0 using a 10% potassium hydroxide solution at a rate of 0.5-1.0°C / min.

7. The production method of an AOS synergistic chelation micronutrient fertilizer according to claim 4, characterized in that, In step S3, the potassium humate is pre-dissolved and activated in 3-5 times its weight of deionized water at 60-70℃, stirred at 100-150 rpm for 20-30 min until completely dissolved, and then added to the reaction system. The time for adding the potassium humate activation solution to the reaction system is controlled at 10-15 min, and after addition, it is stirred for 20-30 min, and then the pH is adjusted to 6.5-7.0 with potassium hydroxide. The boric acid, seaweed extract and sodium polyaspartate are added at intervals of 3-5 min, and after all are added, stirring is continued for 15 min.

8. The production method of an AOS synergistic chelation micronutrient fertilizer according to claim 4, characterized in that, In step S4, the rotation speed for premixing the macro-elements is 300-500 rpm, and the premixing time is 10-15 min; the spraying speed of the chelating functional liquid is controlled at 5-10 L / min.

9. The production method of an AOS synergistic chelation micronutrient fertilizer according to claim 4, characterized in that, The low-temperature drying in step S5 uses a low-temperature spray dryer or a fluidized bed dryer, with an inlet air temperature of 60~70℃ and an outlet air temperature of 40~45℃; the compressed air pressure for the airflow pulverization in step S6 is 0.4~0.6MPa.

10. The production method of an AOS synergistic chelation micronutrient fertilizer according to claim 4, characterized in that, In step S7, the mixing speed for the anti-caking treatment is 15~25 rpm, the mixing time is 10~15 min, and the temperature of the hot air introduced during the mixing process is 30~35℃; in step S8, the moisture-proof packaging uses an aluminum-plastic composite bag, which is vacuumed to -0.06~-0.08 MPa and then sealed before packaging, or filled with nitrogen for protection and then sealed, and the packaging environment temperature is ≤25℃.

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