A method for preparing mineral-derived fulvic acid and its application

Abstract

This invention belongs to the field of fertilizers, specifically relating to a method for preparing mineral-derived fulvic acid, comprising: crushing, washing, and activation: adding washed weathered coal to a reaction vessel, adding distilled vinegar and citric acid to obtain activated weathered coal; acid extraction: adding a 10% hydrochloric acid solution to the activated weathered coal, stirring thoroughly, separating the solid and liquid phases using an 800-mesh sieve, and drying to obtain fulvic acid. The preparation method of this invention is simple and can significantly improve the extraction rate of fulvic acid, while producing fulvic acid with low impurity content.

Description

Technical Field

[0001] This invention belongs to the field of fertilizers and relates to a method for preparing mineral-derived fulvic acid and its application. Background Technology

[0002] Fulvic acid (FA) is the water-soluble fraction of humic acid. It is a component with numerous oxygen-containing functional groups, high chemical and biological activity, and good solubility, making it widely used in industry, agriculture, fisheries, medicine, and animal husbandry. In recent years, numerous studies have been conducted in China on the extraction, separation, and purification of FA. These studies are of practical significance for expanding the sources of FA raw materials, rationally utilizing my country's abundant low-rank coal resources, and meeting market demand for pure FA. However, fulvic acid is difficult to separate from general humic acid resources; therefore, the extraction, application, and basic research of fulvic acid have become important research topics both domestically and internationally in recent years.

[0003] Based on the characteristics of the resources and the needs of applications, there are six methods for extracting fulvic acid from mineral sources: acid extraction, alkali dissolution and acid precipitation, sulfuric acid-acetone method, ion exchange resin method, chemical degradation method, and electrodialysis method. The main methods are the sulfuric acid-acetone method and the ion exchange resin method. The principle of the sulfuric acid-acetone method is to add sulfuric acid to weathered coal, initiating a double decomposition reaction. The H+ ions in the sulfuric acid replace the metal ions of the calcium and magnesium salts of fulvic acid, making the fulvic acid free. This free fulvic acid can be dissolved by acetone containing a small amount of water (10-20%), while the resulting coal powder residue and the generated calcium sulfate salt are insoluble. This allows the fulvic acid to be extracted. After evaporating the solvent, low-ash fulvic acid is obtained. The ion exchange resin method uses a strong acid-type ion exchange resin to replace sulfuric acid in the metal ions of the fulvic acid salts, releasing the fulvic acid. Since the ion exchange resin and the residue are insoluble in water, water is used to extract the generated fulvic acid. Ion exchange resins and weathered coal residues are separated by sieving due to their different particle sizes. The recovered ion exchange resins are regenerated with dilute hydrochloric acid and reused. Currently, both the sulfuric acid-acetone method and the ion exchange resin method for producing fulvic acid have certain drawbacks: the main disadvantages of the sulfuric acid-acetone method are the relatively low extraction rate of fulvic acid from weathered coal and the problem of recovering the solvent acetone, which are also the main reasons for the high production cost of this method; although the ion exchange resin method has a higher extraction rate, the resin regeneration process is more complex and energy-intensive, especially when the water-to-coal ratio of the reaction is increased to improve purity, the energy consumption is even greater.

[0004] Ge Hongguang et al. from the Department of Chemistry at Hanzhong Normal University conducted a study on the separation of fulvic acid from peat. Based on the principle that fulvic acid dissolves in acidic acetone solution, they used a mixed solvent of acetone, water, and sulfuric acid to separate and determine the content of fulvic acid in Mianxian peat. Chen Xiaoling et al. from the Department of Chemical Engineering at Huainan Institute of Technology studied the extraction process of humic acid from Chaohu peat. They used NaOH, Na2CO3, and mixed solutions of NaOH and Na2CO3 as extractants. Because humic acid in peat has colloidal characteristics and forms a relatively viscous aggregate with the residue, making separation difficult, a water-soluble cationic flocculant was added to the solid-liquid phase after extraction. This allowed the ultrafine residue particles to flocculate into larger particles. Furthermore, this flocculant did not react with the sodium humate solution, thus reducing the ash content of the humic acid in the product. Zhang Yujun et al. used a mixed acid oxidation extraction method to extract fulvic acid from raw coal. Oxidation reduces the molecular weight of the raw coal, and this method is particularly effective for coals with low fulvic acid content, achieving an extraction rate of up to 72.1%. Gao Jianren et al. provided a method for preparing fulvic acid salts from low-rank coal using a composite photocatalyst. The method includes the following steps: mixing low-rank coal powder with water, adjusting the pH to 8-11 with alkali, stirring for 1-2 hours, adding an oxidant, reacting at 25-55℃ for 1-3 hours, separating the solid and liquid phases to obtain a humate solution, adding a composite photocatalyst, and then stirring under ultraviolet light for 2-6 hours. After solid-liquid separation, the solution is evaporated to dryness to obtain the fulvic acid salt product. This method can improve the yield of fulvic acid salts from low-rank coal; however, the photocatalyst is relatively expensive, increasing production costs. Tian Hongzhe et al. used peat as raw material, extracting with a dilute alkali solution, purifying with a cationic surfactant as a precipitant, and purifying with resin adsorption of metal ions to obtain high-purity fulvic acid.

[0005] Currently, the existing technology for preparing fulvic acid is relatively complex and has a long preparation cycle. Moreover, most fulvic acid on the market is dark in color, which can have a negative impact on the leaves or fruit surfaces of crops after spraying. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing mineral-derived fulvic acid and its application. The specific technical solution is as follows:

[0007] A method for preparing mineral-derived fulvic acid includes the following steps:

[0008] Crushing: Weathered coal is air-dried under natural conditions, then crushed and sieved to below 100 mesh;

[0009] Washing: Weigh the pulverized sample into a centrifuge tube, add distilled water and shake to wash three times, then centrifuge. The mass-to-volume ratio of weathered coal to distilled water is 1:5-15 (w / v). Remove the centrifuge tube, discard the supernatant and set aside.

[0010] Activation: Add the washed weathered coal to the reaction vessel, add distilled acetic acid and citric acid, stir and mix evenly, and react at 40-60℃ for 30-60 min to obtain activated weathered coal; the mass-volume ratio of weathered coal, distilled acetic acid and citric acid is 5-10:20:2-10 (w / v / w).

[0011] Acid extraction: Add a 10% hydrochloric acid solution to the activated weathered coal. The mass-volume ratio of weathered coal to 10% hydrochloric acid solution is 1-5:5-20 (w / v). Stir thoroughly at 30-45℃ for 0.5-2 hours. Separate the solid and liquid using an 800-mesh sieve. Wash the residue three times with distilled water. Collect and combine the filtrates.

[0012] Drying: Evaporate using a rotary evaporator and then vacuum dry. The temperature range of the rotary evaporator is 60-70℃ to obtain fulvic acid.

[0013] Preferably, the volume-to-mass ratio of distilled vinegar and citric acid is 10:20:4-8.

[0014] Preferably, in the activation process, the reaction temperature is 40-50℃ and the reaction time is 40-50 min. More specifically, in the activation process, the reaction temperature is 45℃ and the reaction time is 45 min.

[0015] Preferably, the acid extraction is carried out at a temperature of 40°C for a reaction time of 1 min.

[0016] The mineral-derived fulvic acid prepared by this invention has applications in agricultural production.

[0017] By adopting the above technical solution, the present invention has the following beneficial effects:

[0018] The activator composed of distilled vinegar and citric acid in the preparation method of this invention can significantly improve the extraction rate of fulvic acid. The activator enables the reaction of humic acid with calcium, magnesium, iron, aluminum, etc., to form insoluble substances in a reverse manner. Furthermore, the reaction temperature and time during activation have a significant impact on the extraction rate of fulvic acid; a reaction temperature of 45℃ and a reaction time of 45 min can significantly improve the extraction rate. In addition, the fulvic acid prepared by this invention has a lower impurity content, the resulting liquid has a lighter color, and it has less impact on crops. Attached Figure Description

[0019] Figure 1 : Spectrum of fulvic acid prepared by treatment 8 Detailed Implementation

[0020] 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.

[0021] The present invention will be further explained below with reference to specific embodiments.

[0022] Example 1: Extraction of fulvic acid

[0023] Raw material: Weathered coal (Changzhi Coal Mine, Shanxi Province; total humic acid content 53.02%, fulvic acid content 35.15%, moisture content 13.28%).

[0024] Extraction method:

[0025] Crushing: Weathered coal is air-dried under natural conditions, then crushed and sieved to below 100 mesh;

[0026] Washing: Weigh 10g of sample into a centrifuge tube, add distilled water and shake to wash three times, then centrifuge. The mass-to-volume ratio of weathered coal to distilled water is 1:8 (w / v). Remove the centrifuge tube, discard the supernatant and set aside.

[0027] Activation: Washed weathered coal is added to a reaction vessel, and distilled vinegar and citric acid in different proportions are added. The mixture is stirred and mixed evenly. After reacting at 40-60℃ for 30-60 minutes, activated weathered coal is obtained.

[0028] Acid extraction: Add a 10% hydrochloric acid solution to the activated weathered coal, stir thoroughly at 40°C for 1 hour, separate the solid and liquid using an 800-mesh sieve, wash the residue three times with distilled water, collect and combine the filtrates;

[0029] Drying: Evaporate using a rotary evaporator and then vacuum dry at a temperature of 65°C to obtain fulvic acid.

[0030] Example 2: Specific Extraction Method

[0031] Solution 1:

[0032] Crushing: Weathered coal is air-dried under natural conditions, then crushed and sieved to below 100 mesh;

[0033] Washing: Weigh 10g of sample into a centrifuge tube, add distilled water and shake to wash three times, then centrifuge. The mass-volume ratio of weathered coal to distilled water is 1:8 (w / v). Remove the centrifuge tube, discard the supernatant and set aside.

[0034] Activation: Add the washed weathered coal to the reaction vessel, add 20 mL of distilled vinegar, stir and mix evenly, and react at 45°C for 45 min to obtain activated weathered coal.

[0035] Acid extraction: Add 30 mL of 10% hydrochloric acid solution to the activated weathered coal, stir thoroughly at 40℃ for 1 h, separate solid and liquid using an 800-mesh sieve, wash the residue three times with distilled water, collect and combine the filtrates;

[0036] Drying: Evaporate using a rotary evaporator and then vacuum dry at a temperature of 65°C to obtain fulvic acid.

[0037] Solution 2:

[0038] Crushing: Weathered coal is air-dried under natural conditions, then crushed and sieved to below 100 mesh;

[0039] Washing: Weigh 10g of sample into a centrifuge tube, add distilled water and shake to wash three times, then centrifuge. The mass-volume ratio of weathered coal to distilled water is 1:8 (w / v). Remove the centrifuge tube, discard the supernatant and set aside.

[0040] Activation: Add the washed weathered coal to the reaction vessel, add 20 mL of distilled vinegar and 2 g of citric acid, stir and mix evenly, and react at 45°C for 45 min to obtain activated weathered coal.

[0041] Acid extraction: Add 30 mL of 10% hydrochloric acid solution to the activated weathered coal, stir thoroughly at 40℃ for 1 h, separate solid and liquid using an 800-mesh sieve, wash the residue three times with distilled water, collect and combine the filtrates;

[0042] Drying: Evaporate using a rotary evaporator and then vacuum dry at a temperature of 65°C to obtain fulvic acid.

[0043] Treatment 3-4: Based on treatment 2, only adjust the amount of citric acid, and keep the other conditions unchanged.

[0044] Treatment 6: Based on Treatment 2, replace distilled vinegar with nitric acid, keeping all other conditions unchanged.

[0045] Process 7:

[0046] Crushing: Weathered coal is air-dried under natural conditions, then crushed and sieved to below 100 mesh;

[0047] Washing: Weigh 10g of sample into a centrifuge tube, add distilled water and shake to wash three times, then centrifuge. The mass-volume ratio of weathered coal to distilled water is 1:8 (w / v). Remove the centrifuge tube, discard the supernatant and set aside.

[0048] Activation: Add the washed weathered coal to the reaction vessel, add 20 mL of distilled vinegar and 5 g of citric acid, stir and mix evenly, and react at 40°C for 60 min to obtain activated weathered coal.

[0049] Acid extraction: Add 30 mL of 10% hydrochloric acid solution to the activated weathered coal, stir thoroughly at 40℃ for 1 h, separate solid and liquid using an 800-mesh sieve, wash the residue three times with distilled water, collect and combine the filtrates;

[0050] Drying: Evaporate using a rotary evaporator and then vacuum dry at a temperature of 65°C to obtain fulvic acid.

[0051] Treatments 8-10: Based on treatment 7, only the activation temperature and time are changed, while all other conditions remain the same.

[0052] For specific adjustments, please refer to Tables 1 and 2.

[0053] Table 1: Distilled vinegar and citric acid in different ratios

[0054]

[0055] Table 2: Different activation temperatures and times

[0056]

[0057] Example 3: Furic Acid Extraction Rate Test

[0058] Test method: Refer to the extraction rate test method in "Jiao Yuangang, Extraction of fulvic acid from weathered coal".

[0059] Test Results: Table 3 shows that the activator composed of distilled vinegar and citric acid can significantly improve the extraction rate of fulvic acid. However, when the amount of citric acid added is small, the reaction between humic acid and calcium, magnesium, iron, aluminum, etc., to form insoluble substances cannot proceed in reverse, resulting in a poor activation effect. The optimal mass-volume ratio of distilled vinegar to citric acid is 50 mL: 4-8 g. Furthermore, under strongly acidic conditions, the extraction rate of fulvic acid remains low.

[0060] The reaction temperature and time during activation have a significant impact on the extraction rate of fulvic acid. When the reaction temperature is 45℃ and the reaction time is 45min, the extraction rate of fulvic acid is 42.8%.

[0061] In addition, at the same concentration, treatments 1 and 6 dissolved in water to produce a dark gray-black liquid; treatments 2-5 and 7-10 dissolved in water to produce a light brown liquid; that is, treatments 2-5 and 7-10 had a lower impact on the crop surface.

[0062] Table 3: Extraction rate of fulvic acid in different treatments 1-10

[0063]

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it.

Claims

1. A method for preparing mineral-derived fulvic acid, characterized in that, It includes the following steps: Crushing: Weathered coal is air-dried under natural conditions, then crushed and sieved to below 100 mesh; Washing: Weigh the pulverized sample into a centrifuge tube, add distilled water and shake to wash three times, then centrifuge. The mass-volume ratio of weathered coal to distilled water is 1:5-15. Remove the centrifuge tube, discard the supernatant and set aside. Activation: Add the washed weathered coal to the reaction vessel, add distilled vinegar and citric acid, stir and mix evenly, and react at 40-50℃ for 30-50 min to obtain activated weathered coal; the mass-volume ratio of weathered coal, distilled vinegar and citric acid is 5-10g: 20ml: 2-10g. Acid extraction: Add a 10% hydrochloric acid solution to the activated weathered coal. The mass-volume ratio of weathered coal to 10% hydrochloric acid solution is 1-5:5-20. Stir thoroughly at 30-45℃ for 0.5-2 hours. Separate the solid and liquid using an 800-mesh sieve. Wash the residue three times with distilled water. Collect and combine the filtrates. Drying: Evaporate using a rotary evaporator and then vacuum dry. The temperature range of the rotary evaporator is 60-70℃ to obtain fulvic acid.

2. The preparation method according to claim 1, characterized in that, The mass-volume ratio of weathered coal, distilled vinegar, and citric acid is 10g:20ml:4-8g.

3. The preparation method according to claim 2, characterized in that, During the activation process, the reaction temperature was 45℃ and the reaction time was 45 min.

4. The preparation method according to any one of claims 1-3, characterized in that, The acid extraction process was carried out at a temperature of 40°C for 1 hour.

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