A method for low-cost preparation of dual-effect fertilizer based on humic acid in coal and its application

Abstract

This invention discloses a method for preparing dual-effect fertilizers at low cost based on humic acid in coal and its application, belonging to the field of humic acid preparation in coal. The purpose is to simplify the production process of humic acid compound fertilizer and reduce production costs. It includes the following steps: (1) after pulverizing weathered coal, the pulverized weathered coal is mixed with potassium hydroxide solution and stirred continuously for 0.25~4h to obtain a first reaction mixture; (2) the first reaction mixture is subjected to solid-liquid separation to obtain an alkaline extract; (3) a small molecule alcohol is added to the alkaline extract to precipitate the solution, and then solid-liquid separation is performed to obtain a third reaction solution and a third precipitate; (4) the third precipitate is dried. In the precipitation experiment, the potassium humate extraction rate of 500 mg / 10 mL ethanol precipitation can reach 96%; in the experiment of extracting humic acid from weathered coal, the potassium humate extraction amount reached 1.416 g, and ethanol precipitation is better than the existing acid precipitation. This invention can be used for soil improvement and has good effects.

Description

Technical Field

[0001] This application relates to the field of humic acid preparation from coal, specifically a method for low-cost preparation of dual-effect fertilizers based on humic acid from coal and its application. Based on the alkali-dissolution-acid-precipitation method for extracting humic acid from weathered coal, this application improves the production process to prepare potassium humate, a dual-effect waste material. Furthermore, it employs an acid-free process, avoiding the generation of waste acid and reducing subsequent disposal costs, thus demonstrating high economic and environmental benefits and warranting large-scale promotion and application. Background Technology

[0002] Humic acid is widely found in peat, lignite, and weathered coal, and its main elemental composition is carbon, hydrogen, oxygen, nitrogen, and sulfur. The content of the main elements in humic acid varies slightly depending on the origin, but it is mostly dominated by carbon and oxygen, while nitrogen, hydrogen, and sulfur are relatively less abundant. Dry humic acid has a conchoidal, gel-like appearance and a relative density between 1.330 and 1.448. As a naturally occurring, non-structurally complex organic compound, humic acid plays an important role in agriculture, forestry, animal husbandry, fisheries, industry, environmental protection, and medicine.

[0003] In the late 19th century, humic acid began to be used abroad, while in my country, research on its industrial applications and soil improvement began in the 1960s. As an important organic component of coal, humic acid is extracted primarily based on the weakly acidic characteristics of its carboxyl and phenolic hydroxyl groups in its molecular structure.

[0004] Currently, weathered coal is commonly used as raw material, and humic acid extraction is employed to extract humic acid. This method mainly utilizes the principle of alkali dissolution and acid precipitation. First, humic acid in the raw material is converted into water-soluble humate salts using an alkaline solution. Then, the humate salts are converted into water-insoluble humic acid using an acidic solution, achieving effective separation from impurities. During the alkali dissolution process, the carboxyl groups in the humic acid undergo a neutralization reaction with the alkali, generating humate salts and water. For example, when sodium hydroxide is used, the reaction equation is: R(COOH)₄ + 4NaOH → R(COONa)₄ + 4H₂O. During the acid precipitation process, the humate salts undergo a neutralization reaction with the acid, regenerating humic acid and the corresponding salts. For example, when hydrochloric acid is used, the reaction equation is: R(COONa)₄ + 4HCl → R(COOH)₄ + 4NaCl (in a specific example, under stirring conditions...). In this method, an inorganic acid (such as hydrochloric acid or sulfuric acid) is slowly added to the alkaline extract without precipitate until the pH of the mixture drops to around 1-2. At this point, humic acid will precipitate out in large quantities as a flocculent gel. Then, solid-liquid separation is performed again, and the precipitate is collected to obtain wet humic acid. The washed wet humic acid is then placed in an oven or drying device at 60-80℃ for low-temperature drying to prevent changes in properties caused by high temperatures. The dried blocky product is then pulverized and sieved to obtain a brownish-black powdered humic acid product. This method is characterized by its simple operation and high extraction efficiency, and is widely used in laboratories and industrial production.

[0005] Humic acid, as an excellent fertilizer, contains elements such as carbon, hydrogen, oxygen, and nitrogen necessary for plant growth, and can also improve the utilization rate of nitrogen, phosphorus, and potassium fertilizers, thus exhibiting a good yield-increasing effect. How to further reduce production costs while simplifying the production process has always been a pressing technical problem for researchers. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing dual-effect fertilizers at low cost based on humic acid in coal and its application, so as to simplify the production process of humic acid compound fertilizer and reduce production costs.

[0007] To achieve the above objectives, this application adopts the following technical solution:

[0008] A method for preparing a dual-effect fertilizer includes the following steps:

[0009] (1) After pulverizing the weathered coal, the pulverized weathered coal is mixed with potassium hydroxide solution at a solid-liquid ratio of 1:5~25 and stirred continuously for 0.25~4h to obtain the first reaction mixture;

[0010] (2) The first reaction mixture was subjected to solid-liquid separation to obtain coal slag residue and alkaline extract, respectively;

[0011] (3) Add small molecule alcohol to alkaline extract to precipitate the solution, then perform solid-liquid separation to obtain the third reaction solution and the third precipitate respectively;

[0012] (4) The third precipitate is dried to obtain the dual-effect fertilizer.

[0013] It also includes the following steps:

[0014] (5) The third reaction solution was distilled to obtain the fifth small molecule alcohol solution and the fifth residual liquid, respectively;

[0015] The fifth small molecule alcohol solution is returned to step (3) for reuse.

[0016] In step (1), 1g of weathered coal requires 5mL~25mL of potassium hydroxide solution.

[0017] In step (1), the lumpy weathered coal is crushed and passed through a 20-60 mesh sieve, and then the sieved weathered coal is mixed with potassium hydroxide solution.

[0018] In step (1), the concentration of the potassium hydroxide solution is 1%-4%. Specifically, the mass fraction of the potassium hydroxide solution is 1%-4%, that is, 100g of solution contains 1-4g of potassium hydroxide.

[0019] In step (1), the solid-liquid ratio of weathered coal to potassium hydroxide solution is 1:5~10, and the stirring time is 1.0~2.0H.

[0020] In step (2), the first reaction mixture is subjected to solid-liquid separation to obtain coal slag residue and alkaline extract, respectively; the coal slag residue is washed with water and the aqueous solution generated from washing is mixed with the alkaline extract; then a small molecule alcohol is added to the alkaline extract mixed with the aqueous solution generated from washing.

[0021] In step (3), the volume of the small molecule alcohol is 30% to 85% of the sum of the volumes of the small molecule alcohol and the alkaline extract.

[0022] Further, in step (3), the volume of the small molecule alcohol is 50% to 72% of the sum of the volumes of the small molecule alcohol and the alkaline extract. Preferably, in step (3), the volume of the small molecule alcohol is 60% to 70% of the sum of the volumes of the small molecule alcohol and the alkaline extract.

[0023] In step (4), the third precipitate is dried at a temperature of 60-80°C.

[0024] The small molecule alcohols are C1 to C4 alcohols.

[0025] The small molecule alcohol is selected from any one of methanol, ethanol, n-propanol or isopropanol.

[0026] The dual-effect fertilizer prepared by the aforementioned method.

[0027] The aforementioned method is applied to the preparation of potassium humate.

[0028] To address the aforementioned problems, this application provides a method for preparing dual-effect fertilizers at low cost based on humic acid in coal and its application. In this application, the weathered coal raw material is first pretreated. The lumpy weathered coal is crushed and sieved (usually 20-60 mesh) to increase its contact area with the subsequent solution, thereby improving extraction efficiency. Subsequently, alkaline leaching is performed. The pretreated coal powder is mixed with a sodium hydroxide solution of a certain concentration (commonly 1%-4%) at a certain solid-liquid ratio (e.g., 1:5 to 1:10), and reacted for approximately 1-2 hours under continuous stirring. During this process, humic acid is converted into soluble sodium humate and enters the solution.

[0029] After the alkaline dissolution reaction is complete, solid-liquid separation is performed. The mixture after the reaction is separated by centrifugation or filtration to obtain a dark brown alkaline extract (crude extract) containing sodium humate and insoluble coal slag residue. To improve purity, the crude extract can be allowed to settle or filtered a second time to remove fine suspended particles. A small molecule alcohol is then added to the alkaline extract to precipitate a solid, followed by solid-liquid separation to obtain the third reaction solution and the third precipitate. Finally, the third precipitate is dried at 60-80℃ to obtain the dual-effect fertilizer. Attached Figure Description

[0030] The present invention will be described by way of example and with reference to the accompanying drawings, wherein:

[0031] Figure 1 The amount of potassium humate precipitated at different methanol concentrations is 500 mg / 10 mL.

[0032] Figure 2 The amount of potassium humate precipitated at different amounts of ethanol is 500 mg / 10 mL.

[0033] Figure 3 The amount of potassium humate precipitated at different amounts of n-propanol is 500 mg / 10 mL.

[0034] Figure 4 The amount of potassium humate precipitated at different amounts of ethanol is 100 mg / 10 mL.

[0035] Figure 5 The amount of potassium humate precipitated at different amounts of ethanol is 300 mg / 10 mL.

[0036] Figure 6 Comparison of ethanol precipitation and hydrochloric acid precipitation in the extraction of humic acid from weathered coal. Detailed Implementation

[0037] All features disclosed in this specification, or steps in all methods or processes disclosed herein, may be combined in any way, except for mutually exclusive features and / or steps.

[0038] As indicated in this specification and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of expressly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains.

[0040] Any feature disclosed in this specification, unless otherwise stated, may be replaced by other equivalent or similar features. That is, unless otherwise stated, each feature is merely one example of a series of equivalent or similar features.

[0041] As mentioned earlier, humic acid is an excellent fertilizer that can improve the utilization rate of nitrogen, phosphorus, and potassium fertilizers by plants. Therefore, it is common practice to apply potassium fertilizer in addition to humic acid when using it as a fertilizer. To address this, this application uses humic acid from coal as a raw material to prepare a dual-effect fertilizer. This method not only simplifies the processing procedure and reduces the generation of waste acid, but also enables the preparation of a dual-effect fertilizer. In this embodiment, the purpose of adding the drying group is to dry the commercially available potassium humate containing moisture, in order to accurately calculate the precipitation rate, along with the experimental group. The control group, on the other hand, contains insoluble impurities in the commercially available potassium humate, which affects the calculation of the precipitation rate.

[0042] Example 1

[0043] Weigh 2 g of weathered coal sample and 0.45 g of KOH, disperse them in 30 mL of water, and stir for 30 min to obtain the first reaction mixture. Separate the first reaction mixture into solid and liquid components to obtain coal slag residue and an alkaline extract. Wash the coal slag residue once with water, and combine the resulting aqueous solution with the alkaline extract. Add a certain amount of a small molecule alcohol (the amount of which can be determined experimentally and can be selected from methanol, ethanol, n-propanol, or isopropanol) as a precipitant to the alkaline extract containing the washing solution. Shake vigorously for 5 min, centrifuge, dry, and weigh. The results show that potassium humate was successfully prepared in this application.

[0044] Furthermore, after solid-liquid separation during acid precipitation, the liquid is a mixture of alcohol and water, which can be used to regenerate the alcohol through methods such as distillation. The regenerated alcohol can be reused, effectively reducing production costs and minimizing pollutant generation.

[0045] Example 2

[0046] (1) Drying group

[0047] 500 mg of potassium humate was weighed and placed in a 50 mL centrifuge tube. The tube was then dried in an 80 ℃ oven for 12 h, and the weight was recorded as a control to eliminate the influence of moisture in the reagent. The data in the table shows that even without the addition of small molecule alcohol, precipitates formed; these were not potassium humate but impurities. To avoid impurities affecting the calculation of the precipitation rate, in the control group, the weighed potassium humate was dissolved, centrifuged to separate the impurities, dried, and the weight recorded.

[0048] (2) Extraction of humic acid from weathered coal in the experimental group (alkali dissolution method)

[0049] Commercial reagent simulation: Weigh 500 mg of potassium humate into a 50 mL centrifuge tube, add 10 mL of distilled water, and shake vigorously. Then, add different amounts of methanol and continue shaking vigorously for 5 min. Centrifuge at 7000 r / min (centrifugation speed for humic acid in the alkali dissolution and acid precipitation method) to separate potassium humate, and dry in an 80 ℃ oven for 12 h, then weigh and record the results.

[0050] The methanol addition amounts were 0 mL, 5 mL, 10 mL, 15 mL, 20 mL, and 25 mL, respectively. The experimental results are shown in Table 1 below. Figure 1 As shown in the figure. A control group with 0 mL of added methanol was used for comparative analysis.

[0051] Table 1. Precipitation amount of 500 mg / 10 mL potassium humate at different methanol concentrations

[0052]

[0053] The experimental results show that when the amount of methanol added is 25 mL, the amount of methanol accounts for 71% of the total volume, and the precipitation rate is 91.2%.

[0054] Example 3

[0055] (1) Drying group

[0056] Weigh 500 mg of potassium humate into a 50 mL centrifuge tube, dry it in an 80 ℃ oven for 12 h, weigh and record the result as a comparison to eliminate the influence of moisture in the reagent.

[0057] (2) Extraction of humic acid from weathered coal in the experimental group (alkali dissolution method)

[0058] Commercial reagent simulation: Weigh 500 mg of potassium humate into a 50 mL centrifuge tube, add 10 mL of distilled water, and shake vigorously. Then, add different amounts of ethanol and continue shaking vigorously for 5 min. Centrifuge at 7000 r / min (centrifugation speed for humic acid in the alkali dissolution and acid precipitation method) to separate potassium humate, and dry in an 80 ℃ oven for 12 h, then weigh and record the results.

[0059] The amounts of ethanol added were 0 mL, 5 mL, 7 mL, 8 mL, 9 mL, 10 mL, 20 mL, and 25 mL, respectively. The experimental results are shown in Table 2 below. Figure 2 As shown in the figure. A control group with 0 mL of added ethanol was used for comparative analysis.

[0060] Table 2. Precipitation amount of 500 mg / 10 mL potassium humate at different ethanol concentrations

[0061]

[0062] The experimental results show that when 20 mL of ethanol is added, the ethanol accounts for 66% of the total volume, and the precipitation rate is 96.0%.

[0063] Example 4

[0064] (1) Drying group

[0065] Weigh 500 mg of potassium humate into a 50 mL centrifuge tube, dry it in an 80 ℃ oven for 12 h, weigh and record the result as a comparison to eliminate the influence of moisture in the reagent.

[0066] (2) Extraction of humic acid from weathered coal in the experimental group (alkali dissolution method)

[0067] Commercial reagent simulation: Weigh 500 mg of potassium humate into a 50 mL centrifuge tube, add 10 mL of distilled water, and shake vigorously. Then, add different amounts of n-propanol and shake vigorously for 5 min. Centrifuge at 7000 r / min (centrifugation speed for humic acid in the alkali dissolution and acid precipitation method) to separate potassium humate, and dry in an 80 ℃ oven for 12 h, then weigh and record the results.

[0068] The amounts of n-propanol added were 0 mL, 5 mL, 10 mL, 15 mL, 20 mL, and 25 mL, respectively. The experimental results are shown in Table 3 below. Figure 3 As shown. A control group with 0 mL of n-propanol was used for comparative analysis.

[0069] Table 3. Precipitation amount of 500 mg / 10 mL potassium humate at different amounts of n-propanol

[0070]

[0071] The experimental results show that when 25 mL of n-propanol is added, the amount of n-propanol accounts for 71% of the total volume, and the precipitation rate is 95.0%.

[0072] Example 5

[0073] (1) Drying group

[0074] Weigh 100 mg of potassium humate into a 50 mL centrifuge tube, dry it in an 80 ℃ oven for 12 h, weigh and record the result as a comparison to eliminate the influence of moisture in the reagent.

[0075] (2) Extraction of humic acid from weathered coal in the experimental group (alkali dissolution method)

[0076] Commercial reagent simulation: Weigh 100 mg of potassium humate into a 50 mL centrifuge tube, add 10 mL of distilled water, and shake vigorously. Then, add different amounts of ethanol and continue shaking vigorously for 5 min. Centrifuge at 7000 r / min (centrifugation speed for humic acid in the alkali dissolution and acid precipitation method) to separate potassium humate, and dry in an 80 ℃ oven for 12 h, then weigh and record the results.

[0077] The amounts of ethanol added were 0 mL, 5 mL, 10 mL, and 20 mL, respectively. The experimental results are shown in Table 4 below. Figure 4 As shown in the figure. A control group with 0 mL of added ethanol was used for comparative analysis.

[0078] Table 4. Precipitation amount of 100 mg / 10 mL potassium humate at different ethanol concentrations

[0079]

[0080] The experimental results show that for low concentrations of potassium humate (100 mg / 10 mL), when 20 mL of ethanol is added, the ethanol accounts for 66% of the total volume, and the precipitation rate is 84.0%.

[0081] Example 6

[0082] (1) Drying group

[0083] Weigh 300 mg of potassium humate into a 50 mL centrifuge tube, dry it in an 80 ℃ oven for 12 h, weigh and record the result as a comparison to eliminate the influence of moisture in the reagent.

[0084] (2) Extraction of humic acid from weathered coal in the experimental group (alkali dissolution method)

[0085] Commercial reagent simulation: Weigh 300 mg of potassium humate into a 50 mL centrifuge tube, add 10 mL of distilled water, and shake vigorously. Then, add different amounts of ethanol and continue shaking vigorously for 5 min. Centrifuge at 7000 r / min (centrifugation speed for humic acid in the alkali dissolution and acid precipitation method) to separate potassium humate, and dry in an 80 ℃ oven for 12 h, then weigh and record the results.

[0086] The amounts of ethanol added were 0 mL, 5 mL, 10 mL, and 20 mL, respectively. The experimental results are shown in Table 5 below. Figure 5 As shown in the figure. A control group with 0 mL of added ethanol was used for comparative analysis.

[0087] Table 5. Precipitation amount of 300 mg / 10 mL potassium humate at different ethanol concentrations

[0088]

[0089] The experimental results show that when the concentration of potassium humate (300 mg / 10 mL) is low and the amount of ethanol added is 20 mL, the amount of ethanol accounts for 66% of the total volume and the precipitation rate is 92.1%.

[0090] Example 7

[0091] To reduce the impact of catalysts and oxidants on precipitation, weathered coal samples with moderate extraction yields, only subject to alkali dissolution and acid precipitation, were selected as the control group. The amount of coal residue in the three groups was similar, which indirectly proves the consistency of the alkali dissolution effect of humic acid (Residue is the amount of residue; the residue amount corresponding to the Acid precipitation group was 0.791g, the residue amount corresponding to the group with 10mL ethanol was 0.799g, and the residue amount corresponding to the group with 20mL ethanol was 0.802g). Figure 6In the figures, "Acid precipitation" represents the experimental results using the existing alkaline dissolution and acid precipitation method. 10 mL and 20 mL correspond to the results obtained when 10 mL and 20 mL of ethanol were added, respectively. The acid precipitation method utilizes the low solubility of humic acid in acidic solutions to separate it. In this experiment, taking 2 g of weathered coal as an example, approximately 5 mL of concentrated hydrochloric acid (37% by mass) is typically needed to adjust the pH of the potassium humate solution to 1 for better humic acid separation. However, during pH adjustment, the hydrochloric acid first neutralizes excess potassium hydroxide from the alkaline dissolution stage, further increasing the amount of hydrochloric acid used. Without considering the adsorption of potassium chloride produced by acid-base neutralization by humic acid, under ideal conditions, the solid separated by the alkaline dissolution and acid precipitation method is humic acid, not potassium humate. As a control group, the amount of humic acid extracted by the alkaline dissolution and acid precipitation method was 1.196 g. The product obtained by alkali dissolution followed by ethanol precipitation is potassium humate. Therefore, with 10 mL of ethanol, the amount of potassium humate precipitated is 1.117 g, and with 20 mL of ethanol, the amount of precipitate exceeds that of humic acid obtained by acid precipitation by 1.416 g. In practical applications, potassium humate has a wider range of applications and is more closely aligned with actual needs due to its good water solubility and dual nutrient supply (humic acid and potassium fertilizer).

[0092] In this application, alcohol is used as a precipitant to replace acid precipitation for the extraction of potassium humate. The alcohol method improves the environmental friendliness and economy of potassium humate extraction and allows for the direct preparation of potassium humate, which is closer to practical needs. In precipitation experiments, the extraction rate of potassium humate precipitated with 500 mg / 10 mL ethanol reached 96%; in experiments extracting humic acid from weathered coal, the extraction yield of potassium humate reached 1.416 g, demonstrating that ethanol precipitation is superior to existing acid precipitation methods.

[0093] This invention is not limited to the specific embodiments described above. The invention extends to any new feature or combination disclosed in this specification, as well as any new method or process step or combination disclosed herein.

Claims

1. A method for preparing a dual-effect fertilizer, characterized in that, Includes the following steps: (1) After pulverizing the weathered coal, the pulverized weathered coal is mixed with potassium hydroxide solution at a solid-liquid ratio of 1:5~25 and stirred continuously for 0.25~4h to obtain the first reaction mixture; (2) The first reaction mixture was subjected to solid-liquid separation to obtain coal slag residue and alkaline extract, respectively; (3) Add small molecule alcohol to alkaline extract to precipitate the solution, then perform solid-liquid separation to obtain the third reaction solution and the third precipitate respectively; (4) The third precipitate is dried to obtain the dual-effect fertilizer.

2. The method according to claim 1, characterized in that, It also includes the following steps: (5) The third reaction solution was distilled to obtain the fifth small molecule alcohol solution and the fifth residual liquid, respectively; The fifth small molecule alcohol solution is returned to step (3) for reuse.

3. The method according to claim 1, characterized in that, In step (1), the concentration of potassium hydroxide solution is 1%-4%.

4. The method according to claim 1, characterized in that, In step (1), the solid-liquid ratio of weathered coal to potassium hydroxide solution is 1:5~10, and the stirring time is 1.0~2.0H.

5. The method according to claim 1, characterized in that, In step (2), the first reaction mixture is subjected to solid-liquid separation to obtain coal slag residue and alkaline extract, respectively; the coal slag residue is washed with water, and the resulting aqueous solution is mixed with the alkaline extract; Then, add a small molecule alcohol to the alkaline extract containing the aqueous solution produced by washing.

6. The method according to any one of claims 1 to 5, characterized in that, In step (3), the volume of the small molecule alcohol is 30% to 85% of the sum of the volumes of the small molecule alcohol and the alkaline extract.

7. The method according to claim 1, characterized in that, In step (4), the third precipitate is dried at a temperature of 60-80°C.

8. The method according to any one of claims 1 to 7, characterized in that, The small molecule alcohol is selected from any one of methanol, ethanol, n-propanol or isopropanol.

9. The dual-effect fertilizer prepared by the method according to any one of claims 1 to 7.

10. The application of the method described in any one of claims 1 to 7, wherein the method is applied to the preparation of potassium humate.

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