A citric acid chelated trace element fertilizer synergist and a preparation method thereof

Abstract

The application provides a citric acid chelated trace element fertilizer synergist and a preparation method thereof, and belongs to the technical field of trace element fertilizers for agriculture. The citric acid chelated trace element fertilizer synergist is prepared by first performing an acid-base neutralization reaction on calcium carbonate and citric acid monohydrate, and then performing a double decomposition reaction on the sulfate salt (single or compound) of trace elements and the calcium citrate solution. The two-step reaction has high efficiency and does not need a pH regulator, thereby solving the problems of the existing technology, such as the difficulty in separating the byproduct of soluble sulfate, the generation of the charged citric acid chelate, and the uneven distribution of elements after the compound of the citric acid chelated trace elements. The content of the trace elements in the citric acid chelated trace elements prepared by the application is 10.2-15.2%, the types and content of the trace elements can be accurately adjusted, the purity of the byproduct calcium sulfate dihydrate is more than 98%, and the byproduct can be sold or deeply processed as raw materials, thereby bringing additional profits for the production enterprises.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of microelement fertilizers for agriculture, and particularly relates to a citric acid chelated microelement fertilizer synergist and a preparation method thereof. BACKGROUND

[0002] Fertilizers are substances that supply plants with the nutrients they need, providing essential elements such as nitrogen, phosphorus, and potassium. However, they often lack trace elements such as iron, manganese, zinc, copper, boron, molybdenum, and chlorine, which are crucial for plant growth and development. Citric acid is a tricarboxylic acid that contains three carboxyl groups (-COOH) and can form carboxylate ions (-COO - ) with metal ions in their oxidized state, forming stable complexes with metal ions. Adding citric acid chelates of trace elements to fertilizers can increase their stability and solubility, reduce their fixation and precipitation, and make them more easily absorbed and utilized by plants. Additionally, citric acid chelates can adjust soil pH, improve soil conditions, and enhance plant growth, yield, and crop quality and disease resistance. Common citric acid chelated trace elements include iron, manganese, zinc, and copper.

[0003] Currently, the main method for preparing citric acid chelated trace elements is to react soluble salts of elements such as zinc, magnesium, and manganese (such as sulfate or chloride) with citric acid at high temperatures. To promote the reaction, an alkaline substance such as sodium hydroxide or ammonia is usually added to adjust the reaction environment to be alkaline, thereby forming byproducts of sulfate. These highly soluble sulfates are very difficult to separate from citric acid chelates, and a portion often enters the citric acid chelate product, affecting the purity of the product and its absorption by plants. Additionally, since the reaction occurs in an alkaline environment, with free negatively charged hydroxide ions in the solution, to maintain the overall electrical neutrality of the solution, some citric acid chelates need to carry a positive charge, resulting in a mixture of neutral citric acid chelates, positively charged citric acid chelates, and negatively charged hydroxyl compounds. The charged citric acid chelates are difficult to release trace elements in the soil, affecting the absorption of trace elements by crops. Furthermore, when different trace elements need to be added to fertilizers, the common practice is to physically mix several different citric acid chelated salts in solid form. This approach cannot ensure uniform distribution of different particle sizes of citric acid chelated salts in the product, affecting the appearance of the product and the absorption of trace elements by crops.

[0004] In summary, there is an urgent need to develop a new preparation method to address the problems of existing citric acid chelated trace element production technology, such as the difficulty of separating soluble sulfate byproducts, the generation of charged citric acid chelates, and the uneven distribution of multiple citric acid chelated trace elements after compounding. SUMMARY

[0005] Therefore, the present application aims to provide a citric acid chelated trace element fertilizer synergist and a preparation method thereof.

[0006] To achieve the above object, the present application provides the following technical solutions.

[0007] The present application provides a preparation method of a citric acid chelated trace element fertilizer synergist, comprising the following steps:

[0008] (1) mixing calcium carbonate and citric acid monohydrate solution to perform acid-base neutralization reaction, obtaining calcium citrate solution and carbon dioxide gas;

[0009] (2) mixing sulfate and the calcium citrate solution obtained in step (1) to perform double decomposition reaction, centrifuging to obtain calcium sulfate precipitate and citrate solution;

[0010] (3) performing vacuum drying treatment on the citrate solution obtained in step (2) to obtain citric acid chelated trace element fertilizer synergist.

[0011] Preferably, the mass ratio of citric acid monohydrate to water in the citric acid monohydrate solution in step (1) is 1:1.1-4, and the molar ratio of calcium carbonate to citric acid monohydrate is 1:0.7-5.5.

[0012] Preferably, the temperature of the acid-base neutralization reaction in step (1) is 20-100℃, the pH of the acid-base neutralization reaction is 3-5, and the end time of the acid-base neutralization is determined by the absence of carbon dioxide gas emission.

[0013] Preferably, the sulfate in step (2) is a single salt or mixed salt containing trace elements.

[0014] Preferably, the sulfate in step (2) includes one or more of zinc sulfate monohydrate, zinc sulfate heptahydrate, magnesium sulfate monohydrate, magnesium sulfate heptahydrate, copper sulfate pentahydrate, ferrous sulfate heptahydrate, manganese sulfate monohydrate, and manganese sulfate tetrahydrate.

[0015] Preferably, the molar ratio of the sulfate to citric acid monohydrate in step (2) is 1:1-2.5.

[0016] Preferably, the temperature of the double decomposition reaction in step (2) is 20-100℃, the pH of the double decomposition reaction is 4-7, and the time of the double decomposition reaction is 60-70min.

[0017] Preferably, the temperature of the centrifugation in step (2) is 25-30 DEG C, the rotation speed of the centrifugation is 5500-6500 r / min, and the centrifugation time is 10-20 min.

[0018] Preferably, the temperature of the vacuum drying treatment in step (3) is 80-120 DEG C, and the vacuum degree of the vacuum drying treatment is 5-10 kPa.

[0019] The application also provides the citric acid chelated trace element fertilizer synergist prepared by the preparation method.

[0020] Compared with the prior art, the application has the following beneficial effects:

[0021] (1) Compared with the prior art, the by-products produced in the process of preparing the citric acid chelated trace element are carbon dioxide in gaseous form and calcium sulfate dihydrate in precipitated form, which are very easy to completely separate from the main product, thus solving the problem of separation of the by-product soluble sulfate from the main product in the traditional method.

[0022] (2) In the preparation process, as the by-products are continuously removed from the reaction system, the reaction driving force is increased, and the balance is continuously moved to the intended reaction, so that the citric acid chelation reaction originally requiring high temperature and addition of excessive alkali to promote can occur in a nearly neutral environment, thus improving the reaction efficiency and avoiding the problem of production of charged citric acid chelates that are difficult for crops to absorb.

[0023] (3) In the preparation of the citric acid chelated trace element, different citric acid chelated salts are simultaneously crystallized, dried and discharged in an instant in one drying tower, so that the uniform distribution of various trace elements in the product is ensured, the product has uniform particle size and good consistency, and the problem of uneven distribution of elements in the traditional physical compounding and mixing is solved.

[0024] (4) The by-products carbon dioxide and calcium sulfate dihydrate produced in the preparation of the citric acid chelated trace element have very high purity and can be sold as raw materials or further processed, thus bringing additional profits to the production enterprises.

[0025] (5) The preparation method provided by the application is simple, low in cost, mild in reaction conditions, high in reaction efficiency, green and environmentally friendly in the preparation process, and suitable for industrialized large-scale production. DETAILED DESCRIPTION

[0026] The application provides a preparation method of a citric acid chelated trace element fertilizer synergist, which comprises the following steps:

[0027] (1) mixing calcium carbonate and citric acid monohydrate solution to perform acid-base neutralization reaction, so as to obtain a calcium citrate solution and carbon dioxide;

[0028] (2) mixing the sulfate with the calcium citrate solution obtained in step (1) to perform a double decomposition reaction, centrifuging to obtain a calcium sulfate and a citrate solution;

[0029] (3) performing vacuum drying treatment on the citrate solution obtained in step (2) to obtain a citric acid chelated trace element fertilizer synergist.

[0030] In the present application, calcium carbonate is mixed with a citric acid monohydrate solution to perform an acid-base neutralization reaction to obtain a calcium citrate solution and carbon dioxide.

[0031] In the present application, the mass ratio of citric acid monohydrate to water in the citric acid monohydrate solution is preferably 1:1.1-4, further preferably 1:1.5-3.5, more further preferably 1:2-3, and still further preferably 1:2.5; the molar ratio of calcium carbonate to citric acid monohydrate is preferably 1:0.7-5.5, further preferably 1:1-5, more further preferably 1:1.5-4.5, and still further preferably 1:2-4; the temperature of the acid-base neutralization reaction is preferably 20-100℃, further preferably 30-90℃, more further preferably 40-80℃, and still further preferably 50-70℃; the pH of the acid-base neutralization reaction is preferably 3-5, further preferably 3.5-4.5, and more further preferably 4; and the end time of the acid-base neutralization is preferably determined according to the absence of carbon dioxide gas emission.

[0032] In the present application, the sulfate is mixed with the above-obtained calcium citrate solution to perform a double decomposition reaction, and centrifuging to obtain a calcium sulfate and a citrate solution.

[0033] In the present application, the sulfate is preferably a single salt or a mixed salt containing trace elements, further preferably includes trace element sulfates containing different numbers of crystal water, more preferably includes sulfates of zinc, magnesium, copper, manganese, iron and the like; the sulfate preferably includes one or more of zinc sulfate monohydrate, zinc sulfate heptahydrate, magnesium sulfate monohydrate, magnesium sulfate heptahydrate, copper sulfate pentahydrate, ferrous sulfate heptahydrate, manganese sulfate monohydrate and manganese sulfate tetrahydrate, further preferably includes zinc sulfate monohydrate and / or magnesium sulfate heptahydrate, more preferably includes zinc sulfate monohydrate and / or manganese sulfate monohydrate, and further preferably includes magnesium sulfate heptahydrate and / or manganese sulfate monohydrate; the mass ratio of zinc sulfate monohydrate to manganese sulfate monohydrate is preferably 5-6:1; the molar ratio of the sulfate to citric acid monohydrate is preferably 1:1-2.5, further preferably 1:1.5-2; the temperature of the double decomposition reaction is preferably 20-100℃, further preferably 30-90℃, more preferably 40-80℃, and further preferably 50-70℃; the pH of the double decomposition reaction is preferably 4-7, further preferably 4.5-6.5, more preferably 5-6, and further preferably 5.5; the time of the double decomposition reaction is preferably 60-70min, further preferably 62-68min, more preferably 64-66min, and further preferably 65min; the temperature of the centrifugation is preferably 25-30℃, further preferably 26-29℃, and more preferably 27-28℃; the speed of the centrifugation is preferably 5500-6500r / min, further preferably 5600-6300r / min, and more preferably 5800-6000r / min; and the time of the centrifugation is preferably 10-20min, further preferably 12-18min, more preferably 14-16min, and further preferably 15min.

[0034] In the present application, the citrate solution obtained above is subjected to vacuum drying treatment to obtain a citric acid chelated trace element fertilizer synergist.

[0035] In the present application, the temperature of the vacuum drying treatment is preferably 80-120℃, further preferably 90-110℃, more preferably 95-105℃, and further preferably 100℃; the vacuum degree of the vacuum drying treatment is preferably 5-10kPa, further preferably 6-9kPa, and more preferably 7-8kPa; and the time of the vacuum drying is preferably determined according to the constant weight of the citric acid chelated trace element obtained.

[0036] The present application also provides the citric acid chelated trace element fertilizer synergist obtained by the preparation method.

[0037] The technical solutions provided by the application will be described in detail below in conjunction with the embodiments, but they should not be understood as limiting the scope of protection of the application.

[0038] Example 1

[0039] A preparation method of a citric acid chelated trace element fertilizer synergist, comprising the following steps:

[0040] (1) 70 g of monohydrated citric acid is dissolved in 150 ml of water, slowly heated to 60℃, 20 g of calcium carbonate is slowly added while stirring, constant temperature stirring until the calcium carbonate is completely dissolved and no carbon dioxide gas is released, to obtain a calcium citrate solution and carbon dioxide;

[0041] (2) the temperature of the calcium citrate solution is raised to 80℃, 35 g of monohydrated zinc sulfate is slowly added while stirring, after 60 min of double decomposition reaction, centrifugation is performed at 25℃ and 5500 r / min for 15 min, filtration is performed, to obtain calcium sulfate dihydrate and a citrate solution;

[0042] (3) the citrate solution is evaporated to constant weight under the conditions of a vacuum degree of 5 kPa and a temperature of 80℃, to obtain 78.7 g of white zinc citrate; the calcium sulfate dihydrate is washed with 10 ml of deionized water twice, and then dried in a vacuum drying oven at 50℃ for 12 h, to obtain 29.8 g of white calcium sulfate dihydrate powder.

[0043] Example 2

[0044] A preparation method of a citric acid chelated trace element fertilizer synergist, comprising the following steps:

[0045] (1) 70 g of monohydrated citric acid is dissolved in 150 ml of water, slowly heated to 60℃, 20 g of calcium carbonate is slowly added while stirring, constant temperature stirring until the calcium carbonate is completely dissolved and no carbon dioxide gas is released, to obtain a calcium citrate solution and carbon dioxide;

[0046] (2) 50 g of magnesium sulfate heptahydrate is slowly added into the calcium citrate solution while stirring, after 60 min of double decomposition reaction, centrifugation is performed at 30℃ and 6500 r / min for 10 min, filtration is performed, to obtain calcium sulfate dihydrate and a citrate solution;

[0047] (3) the citrate solution is evaporated to constant weight under the conditions of a vacuum degree of 10 kPa and a temperature of 120℃, to obtain 75.7 g of white magnesium citrate; the calcium sulfate dihydrate is washed with 10 ml of deionized water twice, and then dried in a vacuum drying oven at 50℃ for 12 h, to obtain 31 g of white calcium sulfate dihydrate powder.

[0048] Example 3

[0049] A preparation method of a citric acid chelated trace element fertilizer synergist, comprising the following steps:

[0050] (1) 70 g of citric acid monohydrate is dissolved in 150 ml of water, slowly heated to 60℃, 20 g of calcium carbonate is slowly added while stirring, constant temperature stirring until the calcium carbonate is completely dissolved and no carbon dioxide gas is released, to obtain a calcium citrate solution and carbon dioxide;

[0051] (2) The temperature of the calcium citrate solution is reduced to 30℃, 30 g of manganese sulfate monohydrate is slowly added while stirring, and the metathesis reaction is carried out for 60 min, then centrifuged at 28℃ and 6000 r / min for 20 min, filtered, to obtain calcium sulfate dihydrate and a citrate solution;

[0052] (3) The citrate solution is evaporated to constant weight under the conditions of a vacuum degree of 8 kPa and a temperature of 90℃, to obtain 73 g of light coffee-colored manganese citrate; the calcium sulfate dihydrate is washed with 10 ml of deionized water twice, and then dried in a vacuum drying oven at 50℃ for 12 h, to obtain 33 g of white calcium sulfate dihydrate powder.

[0053] Example 4

[0054] A preparation method of a citric acid chelated trace element fertilizer synergist, comprising the following steps:

[0055] (1) 70 g of citric acid monohydrate is dissolved in 150 ml of water, slowly heated to 60℃, 20 g of calcium carbonate is slowly added while stirring, constant temperature stirring until the calcium carbonate is completely dissolved and no carbon dioxide gas is released, to obtain a calcium citrate solution and carbon dioxide;

[0056] (2) The temperature of the calcium citrate solution is increased to 90℃, a mixed sulfate (mass ratio of 30:5) of 35 g of zinc sulfate monohydrate and manganese sulfate monohydrate is slowly added while stirring, and the metathesis reaction is carried out for 60 min, then centrifuged at 26℃ and 5800 r / min for 15 min, filtered, to obtain calcium sulfate dihydrate and a citrate solution;

[0057] (3) The citrate solution is evaporated to constant weight under the conditions of a vacuum degree of 6 kPa and a temperature of 100℃, to obtain 81.1 g of white zinc-manganese citrate mixture; the calcium sulfate dihydrate is washed with 10 ml of deionized water twice, and then dried in a vacuum drying oven at 50℃ for 12 h, to obtain 31.3 g of white calcium sulfate dihydrate powder.

[0058] Comparative Example 1

[0059] A preparation method of a citric acid chelate, comprising the following steps:

[0060] (1) mixed 25 g of citric acid monohydrate, 10.7 g of zinc sulfate monohydrate with 30 mL of water, adjusted the pH value of the mixed solution to 5.3 with 25% ammonia water, reacted at 50°C and 500 r / min for 2 h, stood for 30 min, and then extracted by filtration to obtain solution 1 and precipitate 1;

[0061] (2) added 100 mL of ethanol to the solution 1 obtained in step (1) to obtain solution 2 and precipitate 2; dried the precipitate 1 and the precipitate 2 at 25°C and a vacuum degree of 1 bar for 24 h to obtain citric acid chelated zinc.

[0062] Test Example 1

[0063] The content of elemental zinc in the citric acid chelated zinc prepared in Example 1 and Comparative Example 1 was determined by referring to "6.2 Plasma emission spectrometry" in "Chemical Industry Standard of the People's Republic of China NY / T 1974-2010", and calculated according to formula (1).

[0064]

[0065] In the formula,

[0066] c is the mass concentration of the sample obtained from the working curve, g / mL;

[0067] c0 is the mass concentration of zinc in the blank solution obtained from the working curve, g / mL;

[0068] D is the dilution multiple of the sample solution when measured;

[0069] 250 is the volume of the sample solution, mL;

[0070] m is the mass of the sample, g;

[0071] 10 6 is the conversion coefficient from gram to microgram;

[0072] Similarly, the content of elemental magnesium in the citric acid chelated magnesium prepared in Examples 2-4 and the content of elemental manganese in the citric acid chelated manganese were determined by referring to the "Plasma emission spectrometry" for magnesium and manganese recorded in "Chemical Industry Standard of the People's Republic of China NY / T 1974-2010", and calculated according to formula (1) respectively. In the calculation, the working curve of Zn above was replaced by the working curve of magnesium and manganese in turn, and the results are shown in Table 1.

[0073] Table 1 Content of trace elements in citric acid chelated trace elements

[0074]

[0075]

[0076] Test Example 2

[0077] The purity of the calcium sulfate dihydrate prepared in Examples 1-4 was determined and calculated according to the method and formula of 5.3.2 in the Chinese Chemical Industry Standard HG / T 5346-2018, and the results are shown in Table 2.

[0078] Table 2 Purity of calcium sulfate dihydrate

[0079] Group Purity (%) Example 1 99.2 Example 2 99.4 Example 3 98.0 Example 4 98.2

[0080] In conclusion, the present application does not need to use pH regulator and organic solvent ethanol in the process of preparing citric acid chelated trace elements, and the content of trace elements is higher.

[0081] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should be considered as the protection scope of the present application.

Claims

1. A method of preparing a citric acid chelated micronutrient fertilizer synergist, characterized by, The method comprises the following steps: (1) mixing calcium carbonate with citric acid monohydrate solution to perform acid-base neutralization reaction, obtaining calcium citrate solution and carbon dioxide gas; The mass ratio of citric acid monohydrate to water in the citric acid monohydrate solution is 1:1.1-4, and the molar ratio of calcium carbonate to citric acid monohydrate is 1:0.7-5.5; (2) mixing sulfate with the calcium citrate solution obtained in step (1) to perform double decomposition reaction, centrifuging to obtain calcium sulfate precipitate and citrate solution; The sulfate is single salt or mixed salt containing trace elements; The molar ratio of the sulfate to citric acid monohydrate is 1:1-2.5; (3) performing vacuum drying treatment on the citrate solution obtained in step (2) to obtain citrate chelated trace element fertilizer synergist.

2. The production method according to claim 1, characterized by, The temperature of the acid-base neutralization reaction in step (1) is 20-100°C, the pH of the acid-base neutralization reaction is 3-5, and the end time of the acid-base neutralization is determined by no carbon dioxide gas being emitted.

3. The preparation method according to claim 1, characterized in that, The temperature of the double decomposition reaction in step (2) is 20-100°C, the pH of the double decomposition reaction is 4-7, and the time of the double decomposition reaction is 60-70 min.

4. The production method according to claim 1, characterized by, The temperature of the centrifuging in step (2) is 25-30°C, the rotation speed of the centrifuging is 5500-6500 r / min, and the time of the centrifuging is 10-20 min.

5. The method of claim 1, wherein, The temperature of the vacuum drying treatment in step (3) is 80-120°C, and the vacuum degree of the vacuum drying treatment is 5-10 kPa.

6. The citrate chelated trace element fertilizer synergist obtained by the preparation method in any one of claims 1-5.

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