Chelation optimization method of amino acid-containing water-soluble fertilizer added with sugar alcohol

Abstract

The invention provides a sugar alcohol-added amino acid-containing water-soluble fertilizer chelation optimization method, which comprises the following steps: S1, constructing a step-by-step chelation system: carrying out chelation reaction on sugar alcohol, amino acid and a salt solution containing calcium, magnesium and iron elements step by step in sequence to obtain a chelation solution; s2, implementing process monitoring and feedback regulation and control: in the chelation reaction process, monitoring the chelation reaction proceeding degree by using a rapid detection auxiliary system, and dynamically adjusting reaction parameters based on the chelation reaction proceeding degree; and S3, stability treatment after chelating: carrying out subsequent treatment on the chelated chelating liquid. Through systematic integration of four technical links of step-by-step chelation, sugar alcohol modification, process monitoring and stability treatment, three technical problems of multi-ion competitive coordination, unstable batch quality and poor product compatibility are solved at the same time.

Description

Technical Field

[0001] This invention belongs to the field of water-soluble fertilizer technology, specifically relating to a chelation optimization method for amino acid-containing water-soluble fertilizers with added sugar alcohols. Background Technology

[0002] Water-soluble fertilizers, as an important component of modern agricultural production systems, offer the core value of providing crops with rapid and efficient nutrient replenishment through irrigation or foliar spraying. Among these, water-soluble fertilizers containing amino acids not only possess the nutritional functions of traditional water-soluble fertilizers but are also highly favored because amino acids themselves, as physiologically active substances, can stimulate crop metabolism and enhance stress resistance. However, in practical applications, when adding micronutrients such as calcium, magnesium, and iron to amino acid-containing liquid fertilizer systems, a long-standing technical challenge emerges: these metal ions readily antagonize other components in the fertilizer system or undergo hydrolysis and precipitation, leading to a sharp decline in nutrient availability. This often results in clogged pipes and nozzles after fertilizer application, and the actual absorption and utilization rate by crops is far lower than the theoretical value.

[0003] To stabilize these metal ions and prevent precipitation, chelation technology is crucial. Sugar alcohols, such as xylitol, mannitol, and sorbitol, are widely studied and applied in the development of micronutrient fertilizers due to their plant-derived origin, high safety, and the ability of multiple hydroxyl groups in their molecular structure to form stable complexes with metal ions. However, existing technologies for producing amino acid-containing water-soluble fertilizers using sugar alcohol chelation still have several systemic defects that urgently need to be addressed.

[0004] First, most existing technologies employ a "one-pot" mixed chelation process, where sugar alcohols, amino acids, and various metal salts are added to the reaction system all at once or sequentially. This method ignores the inherent differences in affinity and competitive reactions between different metal ions and different chelating agents. For example, iron ions are more likely to stably bind with sugar alcohols in a slightly acidic environment, while calcium and magnesium ions perform better under near-neutral conditions. Placing ions with different properties in the same reaction environment inevitably leads to incomplete chelation of some ions, while potentially wasting an excessive amount of chelating agent, failing to achieve precise and efficient chelation.

[0005] Secondly, existing processes rely too heavily on rigid controls for the chelation process. Key parameters such as reaction temperature, time, and pH value depend on fixed empirical values, lacking a flexible adjustment mechanism for different batches of raw materials. More importantly, there is a lack of real-time, rapid monitoring of the chelation reaction process during production. Typically, offline sampling and laboratory analysis are relied upon, but the results are severely delayed and cannot be used to guide production control for the current batch, leading to large fluctuations in product quality and significant raw material waste.

[0006] Furthermore, the physicochemical stability of the final product of sugar alcohol-amino acid compound chelated liquid fertilizer prepared by existing technology, especially its compatibility with other fertilizers commonly used in agricultural production (such as potassium dihydrogen phosphate), is often overlooked. Many products are stable when stored alone, but once mixed with fertilizers such as phosphorus sources, they immediately produce a large amount of flocculation or precipitation. This not only renders nutrients ineffective but may also cause physical blockage of irrigation systems, greatly limiting their practical application value.

[0007] To address the aforementioned issues, while some technical solutions have been attempted to improve the situation—for example, some patents focus on the chelation of sugar alcohols with specific elements (such as calcium)—they have failed to provide a systematic solution for multi-element competitive chelation; some studies have optimized single reaction parameters, but have not established a complete closed-loop process from reaction and monitoring to post-treatment. Therefore, it is necessary to design an optimized chelation method for amino acid-containing water-soluble fertilizers with added sugar alcohols. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies, a chelation optimization method for amino acid-containing water-soluble fertilizers with added sugar alcohols is provided.

[0009] To achieve the above objectives, the present invention provides the following technical solution: A chelation optimization method for amino acid-containing water-soluble fertilizers with added sugar alcohols, comprising the following steps: S1. Constructing a stepwise chelation system: Sugar alcohols, amino acids and salt solutions containing calcium, magnesium and iron elements are chelated stepwise in sequence to obtain a chelate solution; S2. Implementation of process monitoring and feedback control: During the chelation reaction, a rapid detection auxiliary system is used to monitor the progress of the chelation reaction and dynamically adjust the reaction parameters based on this. S3. Post-chelation stability treatment: Perform subsequent treatment on the chelated solution after chelation.

[0010] The chelation reaction carried out in a sequential stepwise manner as described in step S1 is as follows: First, the sugar alcohol and iron salt are subjected to a first-stage chelation reaction at a pH of 4.5-5.5 and a temperature of 45-55℃ for 15-25 minutes. Then, calcium salt was added and a second-stage chelation reaction was carried out at pH 6.0-7.0 and temperature 35-45℃ for 20-40 minutes. Finally, amino acids and magnesium salts are added, and a third-stage chelation reaction is carried out at a pH of 7.0-8.0 and a temperature of 40-50℃ for 25-35 minutes.

[0011] In the first-stage chelation reaction, the sugar alcohol used is a complex of xylitol and mannitol, with a mass ratio of 1:1 to 3:1.

[0012] The xylitol and mannitol were modified before use. The modification process included the following steps: reacting xylitol, mannitol and plant-derived organic acids at 65-75°C for 90-120 minutes, wherein the mass ratio of xylitol, mannitol and plant-derived organic acids was 1:0.1 to 1:0.3.

[0013] The plant-derived organic acid is a mixture of citric acid and malic acid, and the mass ratio of citric acid to malic acid is 1:1 to 2:1.

[0014] In the third-stage chelation reaction, the amino acid used is a complex of glycine and glutamic acid, with a mass ratio of 2:1 to 4:1.

[0015] Before each chelation reaction, the pH value of the system was precisely controlled by adding a pH adjuster composed of citric acid and boric acid, wherein the mass ratio of citric acid to boric acid was 1:1 to 1:2.

[0016] The mass ratio of calcium salt to sugar alcohol is 1:2-3, the mass ratio of iron salt to sugar alcohol is 1:1.5-2, and the mass ratio of magnesium salt to sugar alcohol is 1:2.5-3.

[0017] In step S2, the rapid detection auxiliary system is a portable chelation rate detection reagent based on colorimetric reaction. After the reaction, a sample is taken for detection. If the chelation rate is less than 90%, sugar alcohol is added and the reaction continues for 10 minutes to ensure that the final chelation rate is greater than 90%.

[0018] The post-chelation stability treatment described in step S3 includes the following steps: a compatibility test is conducted between the chelating solution and potassium dihydrogen phosphate at a mass of 5%-10% to ensure that the mixture does not precipitate or flocculate within 48 hours of standing at 25°C; if precipitation or flocculation occurs during the compatibility test, triethanolamine at a mass of 0.5%-2% of the total mass of sugar alcohols and amino acids in the chelating solution is added to the chelating solution as a stabilizer.

[0019] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: 1. This invention achieves precise control of the chelation environment for different metal ions by constructing a stepwise chelation system. The stepwise chelation system fully considers the unique coordination characteristics of the three types of metal ions. By creating the most suitable reaction environment for each ion, it effectively avoids the problem of incomplete chelation caused by multi-ion competitive coordination, and ensures that each metal ion can form a stable chelation structure with the corresponding ligand.

[0020] 2. Regarding the specific component selection, this invention uses a xylitol-mannitol complex as the main sugar alcohol for the first-stage chelation and modifies it. This modification involves reacting xylitol and mannitol with plant-derived organic acids under specific conditions, introducing additional carboxyl functional groups into the sugar alcohol molecules. This structural modification enhances the coordination ability of the sugar alcohol molecules, enabling them to form a stable chelate network with more connection points with iron ions. Simultaneously, the glycine-glutamic acid complex used in the third-stage chelation, through the synergistic coordination of the amino and carboxyl groups, constructs a chelate with magnesium ions with a more spatially rational configuration.

[0021] 3. This invention establishes a comprehensive process monitoring and feedback control mechanism. The portable chelation rate detection reagent based on a colorimetric reaction can monitor the chelation reaction process in real time. When the chelation rate fails to meet the expected standard, the system can adjust the reaction process promptly by adding sugar alcohol. This dynamic control mechanism ensures that each batch of product maintains a stable high chelation rate, effectively overcoming the shortcomings of traditional fixed-parameter processes when facing raw material fluctuations.

[0022] 4. In the post-chelation stability treatment stage, this invention simulates actual application scenarios by conducting compatibility tests between the chelating solution and potassium dihydrogen phosphate. When precipitation or flocculation occurs during the test, an appropriate amount of triethanolamine is added as a stabilizer to further consolidate the structural stability of the metal chelate. This post-treatment method improves the compatibility of the product with common agricultural fertilizers, ensuring that the final product maintains stable chemical properties and physical state under actual use conditions. The entire technical solution, from stepwise chelation to process monitoring and then to stability treatment, provides a guarantee for improving the quality of amino acid-containing water-soluble fertilizers with added sugar alcohols. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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] In the specific embodiments of this application, the sources of various main raw materials are briefly described as follows: Xylitol: Purchased from Beijing Bairuiji Biotechnology Co., Ltd., CAS No. 87-99-0 Mannitol: Purchased from Shandong Lusen Biotechnology Co., Ltd., CAS No.: 87-78-5 Citric acid: Purchased from Guangdong Mingtong Biotechnology Co., Ltd., CAS No. 77-92-9 Malic acid: Purchased from Shandong Xinxiong Biotechnology Co., Ltd., CAS No. 97-67-6 Glycine: Purchased from Shandong Xinxiong Biotechnology Co., Ltd. Glutamic acid: purchased from Shandong Xinxiong Biotechnology Co., Ltd. Boric acid: purchased from Shandong Xinxiong Biotechnology Co., Ltd., CAS number 10043-35-3 Potassium dihydrogen phosphate: Purchased from Shandong Xinxiong Biotechnology Co., Ltd., CAS No. 7778-77-0 Triethanolamine: Purchased from Shandong Jinyueyuan New Materials Co., Ltd. CAS No.: 102-71-6 Calcium chloride: Purchased from Shandong Shangshan Chemical Co., Ltd., CAS No. 10043-52-4 Magnesium chloride: Purchased from Jinan Fuhao Chemical Co., Ltd. CAS No. 7786-30-3 Ferric chloride: purchased from Shandong Guohua Chemical Co., Ltd., CAS No. 7705-08-0 The technical solution of this application is as follows: A chelation optimization method for amino acid-containing water-soluble fertilizers with added sugar alcohols, comprising the following steps: S1. Constructing a stepwise chelation system: Sugar alcohols, amino acids and salt solutions containing calcium, magnesium and iron elements are chelated stepwise in sequence to obtain a chelate solution; S2. Implementation of process monitoring and feedback control: During the chelation reaction, a rapid detection auxiliary system is used to monitor the progress of the chelation reaction and dynamically adjust the reaction parameters based on this. S3. Post-chelation stability treatment: Perform subsequent treatment on the chelated solution after chelation.

[0025] The chelation reaction carried out in a sequential stepwise manner as described in step S1 is as follows: First, the sugar alcohol and iron salt are subjected to a first-stage chelation reaction at a pH of 4.5-5.5 and a temperature of 45-55℃ for 15-25 minutes. Then, calcium salt was added and a second-stage chelation reaction was carried out at pH 6.0-7.0 and temperature 35-45℃ for 20-40 minutes. Finally, amino acids and magnesium salts are added, and a third-stage chelation reaction is carried out at a pH of 7.0-8.0 and a temperature of 40-50℃ for 25-35 minutes.

[0026] In the first-stage chelation reaction, the sugar alcohol used is a complex of xylitol and mannitol, with a mass ratio of 1:1 to 3:1.

[0027] The xylitol and mannitol were modified before use. The modification process included the following steps: reacting xylitol, mannitol and plant-derived organic acids at 65-75°C for 90-120 minutes, wherein the mass ratio of xylitol, mannitol and plant-derived organic acids was 1:0.1 to 1:0.3.

[0028] The plant-derived organic acid is a mixture of citric acid and malic acid, and the mass ratio of citric acid to malic acid is 1:1 to 2:1.

[0029] In the third-stage chelation reaction, the amino acid used is a complex of glycine and glutamic acid, with a mass ratio of 2:1 to 4:1.

[0030] Before each chelation reaction, the pH value of the system was precisely controlled by adding a pH adjuster composed of citric acid and boric acid, wherein the mass ratio of citric acid to boric acid was 1:1 to 1:2.

[0031] The mass ratio of calcium salt to sugar alcohol is 1:2-3, the mass ratio of iron salt to sugar alcohol is 1:1.5-2, and the mass ratio of magnesium salt to sugar alcohol is 1:2.5-3.

[0032] In step S2, the rapid detection auxiliary system is a portable chelation rate detection reagent based on colorimetric reaction. After the reaction, a sample is taken for detection. If the chelation rate is less than 90%, sugar alcohol is added and the reaction continues for 10 minutes to ensure that the final chelation rate is greater than 90%.

[0033] The post-chelation stability treatment described in step S3 includes the following steps: a compatibility test is conducted between the chelating solution and potassium dihydrogen phosphate at a mass of 5%-10% to ensure that the mixture does not precipitate or flocculate within 48 hours of standing at 25°C; if precipitation or flocculation occurs during the compatibility test, triethanolamine at a mass of 0.5%-2% of the total mass of sugar alcohols and amino acids in the chelating solution is added to the chelating solution as a stabilizer.

[0034] This invention systematically integrates four technical steps: stepwise chelation, sugar alcohol modification, process monitoring, and stability treatment, thereby solving three major technical challenges: multi-ion competitive coordination, batch quality instability, and poor product compatibility.

[0035] The present invention will be described in detail below through examples and comparative examples, but the scope of protection of the present invention is not limited to these examples. Unless otherwise specified, the chemical reagents and raw materials used in the following examples and comparative examples are all conventional commercially available products.

[0036] Example 1 This embodiment provides a chelation optimization method for amino acid-containing water-soluble fertilizers with added sugar alcohols. First, the sugar alcohol is modified by mixing xylitol and mannitol at a mass ratio of 3:1, and then reacting it with plant-derived organic acids at a mass ratio of 1:0.3 at 75°C for 90 minutes. The plant-derived organic acids used are a mixture of citric acid and malic acid at a mass ratio of 2:1. Next, a stepwise chelation system is constructed. In the first step, the modified sugar alcohol is chelated with ferric chloride at a mass ratio of 1:2 at pH 5.5 and temperature 55°C for 15 minutes. In the second step, calcium chloride is added, and a second chelation reaction is carried out at a mass ratio of calcium chloride to sugar alcohol of 1:3 at pH 7.0 and temperature 35°C for 20 minutes. In the third step, amino acids and magnesium chloride are added. The amino acid is a complex of glycine and glutamic acid at a mass ratio of 4:1, and the magnesium chloride is mixed with sugar alcohol at a mass ratio of 1:3. A third chelation reaction is carried out at pH 8.0 and temperature 40°C for 25 minutes. Before each chelation reaction, the pH of the system was precisely controlled by adding a pH adjuster composed of citric acid and boric acid in a 1:2 mass ratio. During the second-stage chelation reaction, a portable chelation rate detection reagent based on a colorimetric reaction was used for monitoring. When the chelation rate was detected to be less than 90%, sugar alcohol was added and the reaction continued for 10 minutes. Finally, post-chelation stability treatment was performed. The compatibility of the chelated solution with 10% potassium dihydrogen phosphate was tested, and the solution was allowed to stand at 25°C for 48 hours. If precipitation or flocculation occurred, triethanolamine (2% of the total mass of sugar alcohol and amino acids) was added to the chelated solution as a stabilizer.

[0037] Example 2 In this embodiment, the similarities to those in Embodiment 1 will not be repeated, and the differences are as follows: This embodiment provides another chelation optimization method for amino acid-containing water-soluble fertilizers with added sugar alcohols. First, the sugar alcohol is modified by mixing xylitol and mannitol at a mass ratio of 1:1, and then reacting it with plant-derived organic acids at a mass ratio of 1:0.1 at 65°C for 120 minutes. The plant-derived organic acids used are a mixture of citric acid and malic acid at a mass ratio of 1:1. Next, a stepwise chelation system is constructed. In the first step, the modified sugar alcohol and iron salt at a mass ratio of 1:1.5 undergo a first-stage chelation reaction at pH 4.5 and 45°C for 25 minutes. In the second step, calcium salt is added, and a second-stage chelation reaction is carried out at pH 6.0 and 45°C at a mass ratio of 1:2, with the calcium salt to sugar alcohol at a mass ratio of 1:2, for 40 minutes. In the third step, amino acids and magnesium salt are added. The amino acid is a complex composed of glycine and glutamic acid at a mass ratio of 2:1, and the magnesium salt is mixed with sugar alcohol at a mass ratio of 1:2.5, undergoing a third-stage chelation reaction at pH 7.0 and 50°C for 35 minutes. Before each chelation reaction, the pH of the system was precisely controlled by adding a pH adjuster composed of citric acid and boric acid in a 1:1 mass ratio. During the second-stage chelation reaction, a portable chelation rate detection reagent based on a colorimetric reaction was used for monitoring. When the chelation rate was detected to be less than 90%, sugar alcohol was added and the reaction continued for 10 minutes. Finally, post-chelation stability treatment was performed. The compatibility of the chelated solution with 5% potassium dihydrogen phosphate was tested, and the solution was allowed to stand at 25°C for 48 hours. If precipitation or flocculation occurred, triethanolamine (0.5% of the total mass of sugar alcohol and amino acids) was added to the chelated solution as a stabilizer.

[0038] Example 3 In this embodiment, the similarities to those in Embodiment 1 will not be repeated, and the differences are as follows: This embodiment provides another method for chelating and optimizing amino acid-containing water-soluble fertilizers with added sugar alcohols. First, sugar alcohol modification is performed by mixing xylitol and mannitol at a mass ratio of 2:1, and then reacting them with plant-derived organic acids at a mass ratio of 1:0.2 at 70°C for 105 minutes. The plant-derived organic acids used are a mixture of citric acid and malic acid at a mass ratio of 1.5:1. Next, a stepwise chelation system was constructed. First, the modified sugar alcohol and iron salt were chelated at a mass ratio of 1:1.75 at pH 5.0 and 50°C for 20 minutes. Second, calcium salt was added, and a second chelation reaction was carried out at a mass ratio of 1:2.5 at pH 6.5 and 40°C for 30 minutes. Third, amino acids and magnesium salts were added. The amino acid mixture consisted of glycine and glutamic acid at a mass ratio of 3:1, and the magnesium salt was mixed with sugar alcohol at a mass ratio of 1:2.75. A third chelation reaction was carried out at pH 7.5 and 45°C for 30 minutes. Before each chelation reaction, the pH was precisely controlled by adding a pH adjuster composed of citric acid and boric acid at a mass ratio of 1:1.5. During the second chelation reaction, a portable chelation rate detection reagent based on a colorimetric reaction was used for monitoring. When the chelation rate was detected to be less than 90%, sugar alcohol was added, and the reaction continued for another 10 minutes. Finally, a chelation stability treatment was performed. The compatibility of the chelating solution with 7.5% potassium dihydrogen phosphate by weight was tested. The solution was left to stand at 25°C for 48 hours. If precipitation or flocculation occurred, triethanolamine (1.25% of the total weight of sugar alcohol and amino acids) was added to the chelating solution as a stabilizer.

[0039] Comparative Example 1 In this comparative example, the similarities with Example 1 will not be repeated, and the differences are as follows: Instead of using a stepwise chelation process, sugar alcohols, amino acids, and three metal salts (calcium, magnesium, and iron) are added to the reaction system all at once and reacted uniformly for 60 minutes at pH 6.5 and temperature 45°C.

[0040] Comparative Example 2 In this comparative example, the similarities with Example 2 will not be repeated, and the differences are as follows: Sugar alcohols are not modified; the chelation reaction is carried out directly using a complex of xylitol and mannitol.

[0041] Comparative Example 3 In this comparative example, the similarities with Example 3 will not be repeated, and the differences are as follows: Instead of using a rapid detection system for process monitoring and feedback control, the reaction time is fixed, and sugar alcohol is not added based on the chelation rate.

[0042] Comparative Example 4 In this comparative example, the similarities with Example 1 will not be repeated, and the differences are as follows: No chelation stabilization treatment is performed, meaning no compatibility test is conducted with potassium dihydrogen phosphate, and no triethanolamine stabilizer is added.

[0043] Comparative Example 5 In this comparative example, the similarities with Example 2 will not be repeated, and the differences are as follows: The stepwise chelation sequence was changed, with magnesium salt chelation performed first, followed by calcium salt chelation, and finally iron salt chelation.

[0044] Comparative Example 6 In this comparative example, the similarities with Example 3 will not be repeated, and the differences are as follows: Use the single sugar alcohol sorbitol instead of the xylitol and mannitol complex.

[0045] Performance Test Results and Analysis The performance of the samples prepared in the three examples and six comparative examples above was tested. The test methods included: determining the chelation rate of calcium, magnesium and iron elements by EDTA titration; determining the stability of the solution after mixing with 5% potassium dihydrogen phosphate by visual inspection and turbidimeter, and recording whether precipitation or flocculation occurred within 48 hours; determining the change in the content of metal elements in the solution after 3 months of storage by atomic absorption spectrometry, and calculating the nutrient retention rate. The test results are shown in Table 1.

[0046] Table 1 Analysis of Test Results

[0047] As shown in Table 1, the stepwise chelation system fundamentally solves the problem of multi-ion competitive coordination by creating an optimal reaction environment for each metal ion. Specifically, iron ions preferentially chelate with sugar alcohols under slightly acidic conditions, avoiding premature hydrolysis under neutral conditions; subsequently, calcium ions react under near-neutral conditions, and finally, magnesium ions form stable complexes with amino acids in a weakly alkaline environment. This sequential and differentiated reaction pathway makes the "one-pot" mixed chelation process used in Comparative Example 1 pale in comparison. The calcium chelation rate of 82.3%, the magnesium chelation rate of 78.6%, and the iron chelation rate of 85.4% in Comparative Example 1 are all significantly lower, precisely because different metal ions interfere with each other in the same reaction system, failing to achieve their respective optimal chelation states.

[0048] Sugar alcohol modification played a crucial role in improving chelation efficiency. By reacting xylitol and mannitol with plant-derived organic acids, carboxyl functional groups were successfully introduced into the sugar alcohol molecules. This structural modification significantly enhanced the coordination ability of sugar alcohols with metal ions and the stability of the chelates. Comparative Example 2, which was not modified, showed significantly lower calcium chelation rates (88.7%), magnesium chelation rates (86.2%), and iron chelation rates (89.1%) compared to the corresponding Example 2. This directly demonstrates that the introduction of carboxyl functional groups can indeed form a stable chelate network structure with more connection points. Similarly, Comparative Example 6, which used sorbitol alone instead of the xylitol and mannitol complex, also showed a lower chelation rate, indicating a synergistic effect between different sugar alcohol molecules in the chelation of specific metal ions. A specific ratio of xylitol to mannitol can form a more stable multi-component coordination structure.

[0049] The implementation of process monitoring and feedback control mechanisms ensured the stability of product quality. The rapid detection method based on colorimetric reactions could promptly identify incomplete chelation during the reaction process and dynamically adjust the levels by adding sugar alcohol. Comparative Example 3 lacked this feedback mechanism and relied solely on a fixed reaction time. Its calcium chelation rate (87.9%), magnesium chelation rate (85.7%), and iron chelation rate (88.5%) were all lower than those of the corresponding Example 3. This indicates that in actual production, due to factors such as batch-to-batch variations in raw materials, fixed process parameters cannot guarantee that each batch of product will achieve the optimal chelation state, while a dynamic control mechanism can effectively address this uncertainty.

[0050] Post-chelation stabilization treatment is a crucial step in ensuring the product's performance in practical applications. By conducting compatibility tests between the chelated solution and potassium dihydrogen phosphate, and adding triethanolamine as a stabilizer when stability issues arose, precipitation problems that occurred when the product was mixed with common phosphate fertilizers in actual use were effectively prevented. Although Comparative Example 4 had a higher chelation rate, it did not undergo post-stabilization treatment, resulting in significant precipitation when mixed with potassium dihydrogen phosphate. Furthermore, after three months of storage, its nutrient retention rate was only 82.6%, far lower than the 94.7% of Example 1. This clearly demonstrates that compatibility testing and stabilizer addition are essential for ensuring the long-term stability and practical application effectiveness of the product.

[0051] The rationality of the stepwise chelation sequence was also experimentally verified. Comparative Example 5 changed the chelation sequence, first performing magnesium salt chelation, then calcium salt chelation, and finally iron salt chelation. The chelation rates of all chelation methods decreased significantly. This confirms that the chelation sequence of iron, then calcium, and finally magnesium determined in this invention is a scientific choice based on the characteristics of each metal ion. Changing this optimized sequence would disrupt the established optimal reaction pathway.

[0052] Test results show that this invention, through the organic combination of four technical steps—stepwise chelation system, sugar alcohol modification treatment, process monitoring and feedback control, and post-chelation stability treatment—forms a complete and self-consistent process. Each step collectively contributes to the excellent performance of the final product in terms of chelation rate, stability, and compatibility.

[0053] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A chelation optimization method for amino acid-containing water-soluble fertilizers with added sugar alcohols, characterized in that, The method includes the following steps: S1. Constructing a stepwise chelation system: Sugar alcohols, amino acids and salt solutions containing calcium, magnesium and iron elements are chelated stepwise in sequence to obtain a chelate solution; S2. Implementation of process monitoring and feedback control: During the chelation reaction, a rapid detection auxiliary system is used to monitor the progress of the chelation reaction and dynamically adjust the reaction parameters based on this. S3. Post-chelation stability treatment: Perform subsequent treatment on the chelated solution after chelation.

2. The chelation optimization method for amino acid-containing water-soluble fertilizers with added sugar alcohols according to claim 1, characterized in that, The chelation reaction carried out in a sequential stepwise manner as described in step S1 is as follows: First, the sugar alcohol and iron salt are subjected to a first-stage chelation reaction at a pH of 4.5-5.5 and a temperature of 45-55℃ for 15-25 minutes. Then, calcium salt was added and a second-stage chelation reaction was carried out at pH 6.0-7.0 and temperature 35-45℃ for 20-40 minutes. Finally, amino acids and magnesium salts are added, and a third-stage chelation reaction is carried out at a pH of 7.0-8.0 and a temperature of 40-50℃ for 25-35 minutes.

3. The chelation optimization method for amino acid-containing water-soluble fertilizers with added sugar alcohols according to claim 2, characterized in that, In the first-stage chelation reaction, the sugar alcohol used is a complex of xylitol and mannitol, with a mass ratio of 1:1 to 3:

1.

4. The chelation optimization method for amino acid-containing water-soluble fertilizers with added sugar alcohols according to claim 3, characterized in that, The xylitol and mannitol were modified before use. The modification process included the following steps: reacting xylitol, mannitol and plant-derived organic acids at 65-75°C for 90-120 minutes, wherein the mass ratio of xylitol, mannitol and plant-derived organic acids was 1:0.1 to 1:0.

3.

5. The chelation optimization method for amino acid-containing water-soluble fertilizers with added sugar alcohols according to claim 4, characterized in that, The plant-derived organic acid is a mixture of citric acid and malic acid, and the mass ratio of citric acid to malic acid is 1:1 to 2:

1.

6. The chelation optimization method for amino acid-containing water-soluble fertilizers with added sugar alcohols according to claim 2, characterized in that, In the third-stage chelation reaction, the amino acid used is a complex of glycine and glutamic acid, with a mass ratio of 2:1 to 4:

1.

7. The chelation optimization method for amino acid-containing water-soluble fertilizers with added sugar alcohols according to claim 2, characterized in that, Before each chelation reaction, the pH value of the system was precisely controlled by adding a pH adjuster composed of citric acid and boric acid, wherein the mass ratio of citric acid to boric acid was 1:1 to 1:

2.

8. The chelation optimization method for amino acid-containing water-soluble fertilizers with added sugar alcohols according to claim 2, characterized in that, The mass ratio of calcium salt to sugar alcohol is 1:2-3, the mass ratio of iron salt to sugar alcohol is 1:1.5-2, and the mass ratio of magnesium salt to sugar alcohol is 1:2.5-3.

9. The chelation optimization method for amino acid-containing water-soluble fertilizers with added sugar alcohols according to claim 1, characterized in that, In step S2, the rapid detection auxiliary system is a portable chelation rate detection reagent based on colorimetric reaction. After the reaction, a sample is taken for detection. If the chelation rate is less than 90%, sugar alcohol is added and the reaction continues for 10 minutes to ensure that the final chelation rate is greater than 90%.

10. The chelation optimization method for amino acid-containing water-soluble fertilizers with added sugar alcohols according to claim 1, characterized in that, The post-chelation stability treatment described in step S3 includes the following steps: a compatibility test is conducted between the chelating solution and potassium dihydrogen phosphate at a mass of 5%-10% to ensure that the mixture does not precipitate or flocculate within 48 hours of standing at 25°C; if precipitation or flocculation occurs during the compatibility test, triethanolamine at a mass of 0.5%-2% of the total mass of sugar alcohols and amino acids in the chelating solution is added to the chelating solution as a stabilizer.

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