Preparation method of modified fulvic acid and application thereof in fertilizers

Abstract

The application belongs to the technical field of fertilizers, and provides a preparation method of modified fulvic acid and application of the modified fulvic acid in fertilizers.The preparation method of the modified fulvic acid comprises the following steps: step 1, dissolving fulvic acid in deionized water, ultrasonic activation, after reaction, drying to obtain activated fulvic acid; step 2, dissolving the activated fulvic acid in a sodium hydroxide solution, heating to 40-45 DEG C for 10-15 min, after cooling, adjusting pH, adding a polymer monomer and an initiator, heating to 40-45 DEG C for 3-3.5 h, and drying to obtain modified fulvic acid. The application introduces new functional groups, such as amide groups, into fulvic acid molecules through chemical reactions, so as to enhance the chelating capacity or adsorption performance of the fulvic acid on specific nutrient elements, thereby effectively preventing the fixation of the elements in soil, and improving the absorption efficiency of the elements by plants.

Description

Technical Field

[0001] This invention belongs to the field of fertilizer technology, specifically relating to the preparation method of modified fulvic acid and its application in fertilizers. Background Technology

[0002] Fertilizers can be classified into three types based on their chemical and biological active components: inorganic fertilizers, organic fertilizers, and bio-fertilizers. Inorganic fertilizers, also known as mineral fertilizers, contain large amounts of nitrogen, phosphorus, and potassium, offering advantages such as rapid fertilization and low price. However, their nutrient composition is limited, and long-term use is not conducive to improving soil fertility and can place a heavy burden on the land. Furthermore, the increasing use of chemical fertilizers each year corresponds to extremely low yield increases. Currently, organic fertilizers made from organic matter and bio-fertilizers containing large amounts of beneficial live bacteria are favored because they can improve soil fertility and enhance the quality of agricultural products. However, their use is limited due to their slower onset of action and higher price.

[0003] Fulvic acid is a type of organic compound with a relatively small molecular weight and numerous active functional groups, found in both acids and alkalis. It is widely distributed in nature and has immense development potential. Fulvic acid possesses functions such as improving soil quality, increasing fertilizer utilization, stimulating crop growth, enhancing crop resistance, and improving product quality. When combined with conventional fertilizers, fulvic acid can significantly improve fertilizer utilization, making it a promising candidate for agricultural applications. There are two main sources of fulvic acid: one is extracted from straw and other materials through biological fermentation, known as biochemical fulvic acid; the other is extracted from minerals, known as mineral-derived fulvic acid. Biochemical fulvic acid is an aromatic organic acid, primarily composed of C, H, O, and N, containing various active groups such as hydroxyl, carboxyl, methoxy, and carbonyl groups. It is an amorphous macromolecular organic mixture. Most biochemical fulvic acid can be obtained through the biological fermentation of materials such as straw, sawdust, and animal manure, and it can also be synthesized artificially. In agriculture, biochemical fulvic acid can improve crop resistance to stress, enhance soil fertility and water retention, and synergistically enhance the effects of other nutrients.

[0004] With the deepening of basic applications and research on fulvic acid, the introduction of new functional groups or grafting of polymers onto fulvic acid macromolecules has received increasing attention. This invention introduces new functional groups, such as amide groups, into fulvic acid molecules through chemical reactions to enhance their chelating ability or adsorption performance for specific nutrients. This effectively prevents the fixation of these elements in the soil and improves the absorption efficiency of plants. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing modified fulvic acid and its application in fertilizers. By introducing new functional groups, such as amide groups, into fulvic acid molecules through chemical reactions, the chelation capacity or adsorption performance of fulvic acid is enhanced, thereby effectively preventing the fixation of these elements in the soil and improving the absorption efficiency of plants.

[0006] The objective of this invention can be achieved through the following technical solutions: The first aspect of this invention provides a method for preparing modified fulvic acid, comprising the following steps: Step 1: Dissolve fulvic acid in deionized water, activate it by sonication, and after the reaction is complete, dry it to obtain activated fulvic acid; Step 2: Dissolve activated fulvic acid in sodium hydroxide solution, heat to 40-45℃ and react for 10-15 minutes. After cooling, adjust the pH, add polymer monomer and initiator, heat to 40-45℃ and react for 3-3.5 hours. After drying, obtain modified fulvic acid.

[0007] In a preferred embodiment of the present invention, the ratio of fulvic acid to deionized water in step 1 is 1g:10mL.

[0008] In a preferred embodiment of the present invention, the ultrasonic power in step 1, ultrasonic activation, is 80-100W.

[0009] In a preferred embodiment of the present invention, the ultrasonic temperature in step 1, ultrasonic activation, is 50-60°C, and the ultrasonic time is 1-1.5 hours.

[0010] As a preferred embodiment of the present invention, the ratio of activated fulvic acid, sodium hydroxide solution, polymer monomer and initiator in step 2 is 1g:100mL:0.05~0.20g:0.0015~0.01g.

[0011] As a preferred embodiment of the present invention, the polymer monomer in step 2 is at least one of acrylic acid and acrylamide.

[0012] As a preferred embodiment of the present invention, the initiator in step 2 is one of ammonium persulfate and potassium persulfate.

[0013] In a preferred embodiment of the present invention, the mass fraction of sodium hydroxide in step 2 is 5%.

[0014] In a preferred embodiment of the present invention, the pH is adjusted to 6.5 to 7.5 in step 2.

[0015] The second aspect of this invention provides the application of the modified fulvic acid prepared by the above-described method in fertilizers.

[0016] The beneficial effects of this invention are: This invention provides a method for preparing modified fulvic acid. By adding polymeric reactants and activating fulvic acid to undergo a copolymerization reaction, new functional groups, such as amide groups, are introduced into the fulvic acid molecule to enhance its chelating ability or adsorption performance for specific nutrients. The amide groups can enhance the coordination ability with metal ions. The number of hydroxyl groups is also increased. By improving the hydroxyl groups introduced at specific positions, the water solubility of fulvic acid and its binding sites with other molecules (such as phosphate and metal ions) can be significantly improved, thereby enhancing its adsorption and exchange performance. This can effectively prevent the fixation of these elements in the soil and improve the absorption efficiency of plants.

[0017] The present invention provides a method for preparing modified fulvic acid, which has a simple process, simple operation, low equipment requirements, and is suitable for industrial production.

[0018] This invention also provides the application of modified fulvic acid prepared by the above-described method in fertilizers. Applying modified fulvic acid as a synergistic fertilizer to the soil can reduce the fixation of inorganic phosphorus, activate fixed phosphorus in the soil, and increase the content of available phosphorus in the soil. This is because the polar groups such as amide and hydroxyl groups in modified fulvic acid interact with the hydroxyl groups on the surface of soil clay minerals to form hydrogen bonds, reducing and hindering the hydration of hydroxyl groups on the surface of clay minerals, thus limiting the exchange with phosphorus and reducing phosphorus adsorption. Simultaneously, since phosphorus in soil usually exists in the form of negatively charged ions, the interaction between modified fulvic acid and soil surface groups, and the presence of the negatively charged copolymer on the soil solid phase surface, facilitates the adsorption of cations while repelling anions. This effect is beneficial for the retention of negatively charged phosphorus ions in the soil liquid phase. Therefore, applying modified fulvic acid to the soil can reduce the fixation of phosphorus, resulting in less phosphorus fixation in the soil and effectively improving the effectiveness of phosphate fertilizer. Detailed Implementation

[0019] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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.

[0020] Obviously, the following description is merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios without inventive effort. Furthermore, it is understood that although the effort involved in such development may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, modifications to design, manufacturing, or production based on the disclosed technical content are merely conventional technical means and should not be construed as insufficient disclosure. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of actually identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Moreover, the following description is provided to enable those skilled in the art to fully understand this application and is not intended to limit the subject matter of the claims.

[0021] Example Example 1 This example provides a method for preparing modified fulvic acid, including the following steps: Step 1: Dissolve 1g of fulvic acid in 10mL of deionized water and activate it by ultrasonication at 80W and 50℃ for 1h. After the reaction is complete, dry it in an oven at 60℃ to obtain activated fulvic acid. Step 2: Dissolve 1g of activated fulvic acid in 100mL of sodium hydroxide solution (mass fraction 5%), heat to 40℃ and react for 10min, cool and adjust pH to 6.5, add 0.05g of acrylic acid and 0.0015g of ammonium persulfate, heat to react for 3h, and dry to obtain modified fulvic acid.

[0022] Example 2 The only difference compared to Example 1 is: Step 1: Dissolve 1g of fulvic acid in 10mL of deionized water and activate it by ultrasonication at 80W and 50℃ for 1h. After the reaction is complete, dry it in an oven at 60℃ to obtain activated fulvic acid. Step 2: Dissolve 1g of activated fulvic acid in 100mL of sodium hydroxide solution (mass fraction 5%), heat to 40℃ and react for 10min, cool and adjust pH to 6.5, add 0.05g of acrylamide and 0.0015g of ammonium persulfate, heat to 40℃ and react for 3h, and dry to obtain modified fulvic acid.

[0023] Example 3 The only difference compared to Example 1 is: Step 2: Dissolve 1g of activated fulvic acid in 100mL of sodium hydroxide solution (mass fraction 5%), heat to 40℃ and react for 10min, cool and adjust pH to 6.5, add 0.10g of acrylic acid and 0.0045g of ammonium persulfate, heat to 40℃ and react for 3h, and dry to obtain modified fulvic acid.

[0024] Example 4 The only difference compared to Example 1 is: Step 2: Dissolve 1g of activated fulvic acid in 100mL of sodium hydroxide solution (mass fraction 5%), heat to 40℃ and react for 10min, cool and adjust pH to 6.5, add 0.15g of acrylic acid and 0.0075g of ammonium persulfate, heat to 40℃ and react for 3h, and dry to obtain modified fulvic acid.

[0025] Example 5 The only difference compared to Example 1 is: Step 2: Dissolve 1g of activated fulvic acid in 100mL of sodium hydroxide solution (mass fraction 5%), heat to 40℃ and react for 10min, cool and adjust pH to 6.5, add 0.20g of acrylic acid and 0.01g of ammonium persulfate, heat to 40℃ and react for 3h, and dry to obtain modified fulvic acid.

[0026] Example 6 The only difference compared to Example 1 is: Step 2: Dissolve 1g of activated fulvic acid in 100mL of sodium hydroxide solution (mass fraction 5%), heat to 40℃ and react for 10min, cool and adjust pH to 6.5, add 0.10g acrylic acid, 0.10g acrylamide and 0.01g ammonium persulfate, heat to 40℃ and react for 3h, and dry to obtain modified fulvic acid.

[0027] Example 7 The only difference compared to Example 1 is: Step 1: Dissolve 1g of fulvic acid in 10mL of deionized water and activate it by ultrasonication at 100W and 60℃ for 1h. After the reaction is complete, dry it in a 60℃ oven to obtain activated fulvic acid.

[0028] Example 8 The only difference compared to Example 1 is: Step 2: Dissolve 1g of activated fulvic acid in 100mL of sodium hydroxide solution (mass fraction 5%), heat to 40℃ and react for 10min, cool and adjust pH to 7.5, add 0.05g of acrylic acid and 0.0015g of ammonium persulfate, heat to 40℃ and react for 3h, and dry to obtain modified fulvic acid.

[0029] Comparative Example Comparative Example 1 The only difference compared to Example 1 is: Step 1: Dissolve 1g of fulvic acid in 10mL of deionized water and activate it by ultrasonication at 80W and 50℃ for 1h. After the reaction is complete, dry it in an oven at 60℃ to obtain modified fulvic acid.

[0030] Comparative Example 2 The only difference compared to Example 1 is: Step 2: Dissolve 1g of activated fulvic acid in 100mL of sodium hydroxide solution (mass fraction 5%), heat to 40℃ and react for 10min, cool and adjust pH to 6.5, add 0.035g of acrylic acid and 0.00010g of ammonium persulfate, heat to 40℃ and react for 3h, and dry to obtain modified fulvic acid.

[0031] Comparative Example 3 The only difference compared to Example 1 is: Step 2: Dissolve 1g of activated fulvic acid in 100mL of sodium hydroxide solution (mass fraction 5%), heat to 40℃ and react for 10min, cool and adjust pH to 6.5, add 0.25g of acrylic acid and 0.015g of ammonium persulfate, heat to 40℃ and react for 3h, and dry to obtain modified fulvic acid.

[0032] Performance testing (1) Indoor incubation experiment on the effect of modified humic acid in activating soil phosphorus Test soil: The test soil was gray desert soil with a relatively clayey texture and medium fertility. The sampling depth was 0-20 cm. The total phosphorus content was 0.67 g / kg, available phosphorus was 17.39 mg / kg, total potassium was 23.0 mg / kg, available potassium was 249.0 mg / kg, total nitrogen was 0.87 g / kg, CEC was 16.2 mmol / kg, organic matter was 15.2 g / kg, and pH was 8.17. Eleven 1mm soil samples (30g each) were placed in 7.5cm diameter petri dishes. 14mL of 0.5% (V / V) modified humic acid aqueous solution obtained in Examples 1-8 and Comparative Examples 1-3 were added to each dish. Distilled water was added to bring the soil moisture to field capacity. One control soil sample with an equal volume of distilled water was also added. The dishes were placed in a 25±1℃ constant temperature incubator. Water was added periodically during the incubation process to maintain soil moisture at field capacity. The petri dishes were removed at 4, 7, 15, and 30 days of incubation. After air-drying, the available phosphorus content of the soil was measured. The test results are shown in Table 1. Table 1

[0033] As shown in Table 1, compared to Comparative Examples 1-3, Examples 1-8 showed a greater increase in the content of available phosphorus in the soil. In Comparative Example 1, the modified fulvic acid was only activated without grafting polymers. In Comparative Examples 2-3, the amount of acrylic acid added during the preparation of modified fulvic acid exceeded the limits specified in this invention. Comparative Example 1 showed the lowest increase in the content of available phosphorus in the soil. This indicates that the modified fulvic acid molecules contain a large number of polar groups such as amide and hydroxyl groups, which can interact with hydroxyl groups on the soil surface to form hydrogen bonds, limiting the exchange with phosphorus and thus reducing the adsorption of fixed phosphorus. Applying modified fulvic acid to the soil reduces phosphorus fixation; less phosphorus fixation in the soil improves the effectiveness of phosphate fertilizer.

[0034] (2) Fertilizer effect test of modified humic acid on green vegetables The experiment was conducted in farmland. The tested variety was tetraploid Suzhou Green. The farmland was divided into multiple plots, each 20m in size. The control group received no treatment. Ten days after planting, the modified fulvic acid obtained in Examples 1-8 and Comparative Examples 1-3 was applied, respectively. The harvest period was 70 days. The results of the green vegetable traits and yield are shown in Table 2. Table 2

[0035] As shown in Table 1, compared to Comparative Examples 1-3, the plant height of the bok choy in Examples 1-8 was generally higher. Specifically, the plant height in Example 1 was 19.02 cm, while the plant height in Comparative Example 1 was only 16.77 cm. This indicates that the application of modified fulvic acid helps promote plant growth. Furthermore, the number of leaves, total number of leaves, and yield per plot in the examples were generally higher than in Comparative Examples 1-3. Therefore, it can be seen that the application of modified fulvic acid can significantly promote the growth of bok choy, increase plant height, number of leaves, and total number of leaves, thereby significantly increasing the average yield per plot.

[0036] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0037] It should be understood that in the various embodiments of this application, the sequence number of each process does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the implementation regulations of this application.

[0038] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application are available on the market or can be prepared by existing methods.

[0039] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions, and all technical features and optional technical features of this application can be combined to form new technical solutions.

[0040] 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 method for preparing modified fulvic acid, characterized in that, Includes the following steps: Step 1: Dissolve fulvic acid in deionized water, activate it by sonication, and after the reaction is complete, dry it to obtain activated fulvic acid; Step 2: Dissolve activated fulvic acid in sodium hydroxide solution, heat to 40-45℃ and react for 10-15 minutes. After cooling, adjust the pH, add polymer monomer and initiator, heat to 40-45℃ and react for 3-3.5 hours. After drying, obtain modified fulvic acid.

2. The method for preparing modified fulvic acid according to claim 1, characterized in that, In step 1, the ratio of fulvic acid to deionized water is 1g:10mL.

3. The method for preparing modified fulvic acid according to claim 1, characterized in that, In step 1, the ultrasonic power during ultrasonic activation is 80-100W.

4. The method for preparing modified fulvic acid according to claim 1, characterized in that, In step 1, the ultrasonic activation temperature is 50-60℃ and the ultrasonic time is 1-1.5h.

5. The method for preparing modified fulvic acid according to claim 1, characterized in that, In step 2, the ratio of activated fulvic acid, sodium hydroxide solution, polymer monomer and initiator is 1g:100mL:0.05~0.20g:0.0015~0.01g.

6. The method for preparing modified fulvic acid according to claim 1, characterized in that, The polymer monomer mentioned in step 2 is at least one of acrylic acid and acrylamide.

7. The method for preparing modified fulvic acid according to claim 1, characterized in that, The initiator mentioned in step 2 is either ammonium persulfate or potassium persulfate.

8. The method for preparing modified fulvic acid according to claim 1, characterized in that, In step 2, the mass fraction of sodium hydroxide is 5%.

9. The method for preparing modified fulvic acid according to claim 1, characterized in that, In step 2, adjust the pH to 6.5–7.

5.

10. The application of modified humic acid prepared by the method according to any one of claims 1 to 9 in fertilizers.

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