High-quality humic acid extracted from weathered coal, preparation method thereof, and method for co-producing high-humic acid organic fertilizer

Abstract

The present invention provides high-quality humic acid extracted from weathered coal, a preparation method thereof, and a method for co-producing high-humic acid organic fertilizer. The method comprises physical treatment of weathered coal, stacking, activation, dissolution, filtration, precipitation of humic acid from the extract, and production of high-humic acid organic fertilizer from the extraction residue. The present invention overcomes the technical difficulties in the prior art of humic acid extraction from weathered coal, such as the complex, time-consuming process with low yield, and the low comprehensive benefit of a single product. According to the characteristics of the weathered coal raw material, the yield of humic acid is improved through physical-chemical coupling reaction conversion, and a high-yield extraction of humic acid from weathered coal is achieved through a solid-phase reaction of stacking thermochemical reaction and oxidative activation to obtain humic acid. The residual humic acid that has been activated but not extracted is then compounded with aquaculture waste to achieve the combination of the residual humic acid from the weathered coal and the organic matter in the aquaculture waste, and the coupling of humic acid and organic matter, to obtain high-humic acid organic fertilizer, with diversified products, thereby maximizing the comprehensive economic benefits of weathered coal conversion.

Description

Technical Field

[0001] The present invention belongs to the technical field of transformation and utilization of weathered coal resources, and particularly relates to high-quality humic acid extracted from weathered coal, a preparation method thereof, and a method for co-producing high-humic acid organic fertilizer. Background Art

[0002] Weathered coal is a low-quality coal resource. It's formed when lignite, bituminous coal, and anthracite are exposed to air, where their organic components are oxidized by oxygen. This increases the oxygen content, moisture content, and volatile matter, reducing the calorific value, ignition point, and hydrogen / carbon (H / C) ratio. China has abundant reserves of weathered coal, approximately 100 billion tons, primarily distributed in Inner Mongolia, Shanxi, Xinjiang, and Yunnan. Due to its low calorific value and high oxygen content, weathered coal is unsuitable as a power generation fuel, and its economic value is not fully realized. However, weathering leads to the formation of regenerated humic acid. The total humic acid content in weathered coal ranges from 30% to 70%, sometimes reaching over 80%. Humic acid can be extracted as a chemical raw material.

[0003] Humic acid is a high-molecular polymer found in soil, water, peat, lignite, and weathered coal. Peat forms lignite through diagenesis, and as temperature and pressure gradually increase, it transforms into bituminous coal through metamorphism. When lignite and bituminous coal are exposed to air, their organic components are oxidized by oxygen through weathering, forming weathered coal, which is further subdivided into weathered lignite and weathered bituminous coal. The development of weathered coal provides resources for the extraction of humic acid, making it a common raw material for humic acid production in industrial production. The humic acid skeleton is composed of one or more aromatic rings randomly connected through alkane and ether bonds, with side chains containing oxygen-containing functional groups such as -COOH, C=O, and -OH, forming a complex polymer mixture. Due to its unique physical and chemical properties, humic acid is often used as a chemical raw material in the production of environmental remediation materials, battery materials, pharmaceuticals, and fertilizers.

[0004] Patent CN102515885A discloses a method for producing humic acid from weathered coal. Humic acid with a low phenolic hydroxyl content in the weathered coal is reacted with ammonia to produce ammonium humate, which is then oxidized with hydrogen peroxide to increase the phenolic hydroxyl content of the humic acid, resulting in highly active humic acid with a phenolic hydroxyl content exceeding 2 mmol / g. Patent CN1587303A discloses a new method for extracting humates from weathered coal. The weathered coal is crushed and added to a reactor. Water and an alkali metal silicate are then added. The mixture is heated and stirred at 40°C-80°C for 0.5-1 hour, then transferred to a sedimentation tank and the extract is filtered. This method offers a high extraction rate, low cost, and is pollution-free, representing an improvement over existing technologies. The humate solution can be directly formulated into a liquid fertilizer, combining the functions of both humic acid fertilizer and silicon fertilizer, significantly promoting the development of green agriculture. CN 1546554A discloses a method for producing humates using weathered coal or lignite as raw materials. The method comprises adding 100 parts of weathered coal or lignite powder, crushed to 0.1-2 mm, to a reactor equipped with a high-efficiency solid-liquid mixing agitator. 0.1-0.3 parts of a wetting activator and 200 parts of water are added to the reactor, stirring is initiated, and the temperature is raised to 60-85°C. 30-60 parts of an alkaline solution having a concentration of 25-45% by weight is added to the reactor, with the addition completed within 5-10 minutes. The reaction is continued at 60-85°C for 30 minutes, and the desired humate slurry is obtained. The humate slurry can be further dried and pulverized to produce humate powder.

[0005] Although the extraction methods of weathered coal humic acid are different, the existing technologies have at least the following technical problems:

[0006] (1) The catalytic method for preparing weathered coal humic acid has high yield, low molecular weight and high chemical activity, but it requires the preparation of catalysts and has high requirements for materials.

[0007] (2) The preparation of weathered coal humic acid by microbial dissolution method has simple equipment requirements. Weathered coal can be converted by fungi, bacteria and even enzymes, and the conversion conditions are mild, and high-quality humic acid can be obtained. However, the process is cumbersome and time-consuming.

[0008] (III) Alkali dissolution and acid precipitation method is used to prepare weathered coal humic acid. It is simple to operate and can separate humic acid and fulvic acid by taking advantage of the different solubility of coal-based macromolecular organic matter in acid and alkali. However, weathered coal humic acid mostly exists in the form of free state or metal salt, and Ca 2+ Mg 2+ etc. have a fixing effect on humic acid in weathered coal, and the yield is low when humic acid or fulvic acid is directly extracted.

[0009] It can be seen that the existing technology widely has the following problems: low development and utilization of weathered coal, single product, difficulty in comprehensive utilization, and low extraction efficiency when extracting humic acid from weathered coal by conventional methods.

[0010] Based on this, how to convert weathered coal into chemical raw materials and explore a green and environmentally friendly resource utilization method that can fully utilize the chemical components contained in weathered coal at multiple levels, thereby achieving the beneficial effects of increasing comprehensive output value, profit margin and high conversion value, is an urgent problem to be solved by technical personnel in this field. Summary of the Invention

[0011] The present invention aims to provide a method for extracting high-quality humic acid from weathered coal. Based on the raw material properties of weathered coal, this method develops a low-energy, high-yield utilization pathway for weathered coal and a high-value utilization route for weathered coal with a diverse range of conversion products. This method specifically activates and converts humic acid from weathered coal through a solid-phase reaction involving thermochemical reactions and oxidative activation. The overall preparation process is simple, energy-free, and requires minimal acid and alkali solutions, offering significant advantages in environmental friendliness and low cost. This method addresses the existing challenges of extracting humic acid from weathered coal, such as complex, time-consuming processes, low yields, and a single product.

[0012] To achieve the above object, the present invention provides a method for extracting high-quality humic acid from weathered coal, which specifically comprises the following steps:

[0013] (1) Physical treatment: taking weathered coal raw materials for crushing, grinding and pulverizing;

[0014] (2) Stacking: Pile the weathered coal after physical treatment in the open air, add the exothermic agent and mix evenly, and add water to carry out the exothermic reaction;

[0015] (3) Activation: Add activator to the weathered coal after reaction, mix well, and carry out activation reaction;

[0016] (4) Dissolution: Take out the activated weathered coal, add alkaline solution with a pH of 10-12 to completely submerge the surface of the weathered coal, and soak it overnight at room temperature to dissolve the weathered coal;

[0017] (5) Filtration: After the reaction is completed, the solution in step (4) is filtered to obtain a residue and an extract;

[0018] (6) Precipitating humic acid from the extract: Collect the extract obtained in step (5), add acid, adjust the pH of the mixed solution to 1-3, let it stand to precipitate, collect the precipitate and dry it to obtain humic acid.

[0019] In a preferred embodiment, in step (1), the particle size of the weathered coal after crushing, grinding and pulverizing is 0.044-0.125 mm.

[0020] The present invention utilizes mechanochemical effects to pretreat weathered coal. When subjected to mechanical forces (such as grinding, impact, friction, and shear), weathered coal undergoes chemical, physicochemical, and internal microstructural changes, resulting in fragmentation, particle size reduction, crystal form changes, and chemical bond changes, thereby increasing the rates of subsequent exothermic and oxidative activation reactions. Furthermore, mechanical treatment can reduce the energy required for some chemical reactions, facilitating their occurrence. Experimental verification has shown that pulverized weathered coal with a particle size above 0.125 mm prolongs subsequent reaction times, while a particle size below 0.044 mm is too small and prone to agglomeration, affecting the quality of the extracted humic acid.

[0021] In a preferred embodiment, the purpose of open-air stacking in step (2) is to create a certain moist heat reaction space for the weathered coal at a low cost and prevent rapid heat loss. Therefore, stacking can be performed using any method known to those skilled in the art. Preferably, to ensure sufficient reaction of the weathered coal and improve stacking efficiency, the weathered coal can be stacked into a conical, trapezoidal, or triangular shape with a height of 70-120 cm. Multiple experimental studies have found that when the height is 70-120 cm, the heat generated by exothermic heat can be well retained and not quickly dissipated into the air. The conical, trapezoidal, or triangular shape can also form a stable structure, ensuring sufficient activation and release of humic acid from the weathered coal.

[0022] In a preferred embodiment, in step (2), the exothermic agent includes one or both of potassium oxide and calcium oxide.

[0023] Humic acid in weathered coal often exists as calcium and magnesium salts. Direct extraction of humic acid or fulvic acid results in very low yields and water solubility. Therefore, the present invention inventively uses solid potassium oxide and solid calcium oxide as exothermic agents, mixed evenly with the weathered coal. This exothermic nature of the exothermic agent upon contact with water promotes the breaking and forming of chemical bonds within the accumulated weathered coal. Furthermore, the physicochemical dynamics provided by the heat generated by the reaction of the accumulated coal in a defined shape and height, combined with the effects of moist heat, further promote significant changes in the various chemical substances within the weathered coal, promoting the activation and release of humic acid, and increasing the yield of humic acid extracted from the weathered coal. Furthermore, the alkaline potassium hydroxide and calcium hydroxide produced by the exothermic agent dissolving in water convert the insoluble chelated humic salts in the weathered coal into readily soluble humates (potassium). Simultaneously, the alkaline oxygen properties remove some magnesium, iron, aluminum, copper, and sulfur ions. Finally, the present invention eliminates the high-temperature heating methods used in existing technologies, requiring less energy and effectively reducing the cost of humic acid production. It can be seen that the selection and dosage of the exothermic agent have an important influence on the co-production rate and quality of humic acid.

[0024] To improve the reaction effect, preferably, the alkaline solution with a pH of 10-12 completely submerges the surface of the weathered coal and exceeds the upper surface of the weathered coal by 2-5 cm to ensure that the reaction proceeds fully.

[0025] In a preferred embodiment, in step (2), the mass ratio of the weathered coal, the exothermic agent and water is 1: (0.03-0.10): (0.02-0.064).

[0026] In the present invention, solid potassium oxide and calcium oxide release reaction heat only when exposed to water. Water is also required for the breaking and forming of chemical bonds in weathered coal. Considering that weathered coal typically has a moisture content of 10%-45%, the mass ratio of weathered coal, exothermic agent, and water is designed accordingly. Too little water will prevent the exothermic agent from fully reacting and releasing heat. Too much water will cause the exothermic agent to react violently early on, posing a risk and preventing the reaction from continuing, resulting in reduced efficiency of the chemical reaction within the weathered coal.

[0027] In a preferred embodiment, in step (2), after the exothermic agent is added, the stacking reaction is continued at room temperature for 1-3 days.

[0028] The hydrophilic oxygen-containing groups on the surface of weathered coal easily form weak hydrogen bonds with water molecules in water, causing the surface of the weathered coal to be covered with a hydration film, and it takes time for the internal hydrophobic groups to be exposed; moreover, the alkaline solution formed by solid potassium oxide and solid calcium oxide when they meet water has a slow wetting, dissolution and internal diffusion rate in the weathered coal, and the solid-liquid mass transfer process is relatively slow. Therefore, the stacking reaction is continued at room temperature for 1-3 days to reach solid-liquid mass transfer equilibrium.

[0029] In a preferred embodiment, in step (3), the activator includes one or both of solid chlorine dioxide and liquid chlorine dioxide.

[0030] The chlorine dioxide used in the present invention is a highly efficient and fast-acting bactericide, preservative and oxidant. Chlorine dioxide is soluble in water and is stable in aqueous solution, existing as stable chlorine dioxide molecules. Chlorine dioxide is a strong oxidizing agent and is commonly used in paper and fiber bleaching. Moreover, chlorine dioxide can react with Zn, Ca, Mg, Ni, etc. to form corresponding chlorites. Humic acid in weathered coal is mostly in free state or Ca 2+ Mg 2+ It exists in the form of metal salts. After adding chlorine dioxide, it reacts with the Ca in weathered coal humic acid. 2+ Mg 2+ The metal salts react to produce an activation effect, thereby increasing the yield of humic acid from weathered coal.

[0031] In a preferred embodiment, in step (3), the mass ratio of the activator to the weathered coal is (1-4):100.

[0032] Chlorine dioxide is widely used as a disinfectant, but the present invention creatively uses it to activate weathered coal. Unlike conventional HNO3 and H2O2, the chlorine dioxide used in the present invention readily decomposes into hypochlorous acid upon heating, and hypochlorite has strong oxidizing properties. Using chlorine dioxide as a raw material for the oxidative activation reaction, the present invention, with an appropriate ratio, can break covalent bonds under mild reaction conditions, oxidizing and degrading the macromolecular structure of weathered coal into oxygen-containing compounds such as humic acid. However, after the chlorine dioxide dosage reaches a certain limit, the activation effect on weathered coal is no longer significant, and the yield and purity of humic acid no longer increase, which is why the aforementioned ratio was designed.

[0033] In a preferred embodiment, in step (3), after adding the activating agent, the activation reaction is continued at room temperature for 1-2 days.

[0034] The yield of humic acid shows an increasing trend with the increase of activation reaction time. As the activation reaction time continues to increase, single benzene ring aromatic compounds dissociate from the macromolecular structure of weathered coal, increasing the concentration of small molecular compounds, which in turn affects the yield and purity of humic acid.

[0035] In a preferred embodiment, in step (3), after the activation reaction is completed, the weathered coal can be taken out and washed with clean water 2-4 times to remove the raw materials that have not reacted fully and impurities, and the washing liquid can be retained for future use.

[0036] In a preferred embodiment, in step (4), the alkali solution includes one or more of sodium hydroxide, potassium hydroxide, and sodium carbonate; preferably, the mass concentration of the alkali solution is 2-10%.

[0037] In a preferred embodiment, in step (4), the solid-liquid mass ratio of the weathered coal to the alkali solution is 1:(3-6).

[0038] In a preferred embodiment, in step (4), the weathered coal is added to the alkali solution and then soaked overnight at room temperature. Preferably, the room temperature is 20-40°C.

[0039] In a preferred embodiment, in step (6), the acid solution is one or more of sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid; preferably, the acid concentration is 2-30%.

[0040] Steps (4) to (6) of the present invention utilize an acid-base extraction method, utilizing the difference in solubility of humic acid (humate) in acid and alkaline solutions to extract humic acid. In the present invention, the pH of the reaction system is directly controlled to increase solubility when dissolving weathered coal in alkaline solution. The amount of acid solution is then adjusted using the pH in the collected extract, thereby precisely controlling the amount of acid and alkaline reagents used and reducing waste and waste liquid discharge. Furthermore, the inventors have discovered that after physical treatment, stacking heat treatment, and oxidative activation reaction, followed by acid precipitation, the functional group content in the humic acid can be increased, thereby improving product quality.

[0041] Another object of the present invention is to provide high-quality humic acid extracted from weathered coal. The humic acid produced using the present invention has a purity increased from the conventional 67.20-69.31% in the prior art to 82.76-84.50%, and a yield increased from the conventional 35.6-38.0% in the prior art to 43.60-48.40%, achieving both high quality and high production efficiency.

[0042] Another object of the present invention is to provide a method for co-producing high-humic acid organic fertilizer using the above-mentioned method. This method requires only the collection of the residue and filtrate used in the humic acid production process and the addition of aquaculture waste to produce high-quality humic acid organic fertilizer as a byproduct. This method has a simple preparation process, can not only recycle the waste liquid residue generated by the humic acid production process, but also consume aquaculture waste, reducing accumulation pollution. While fully utilizing the economic value of weathered coal at multiple levels, it also reduces the production cost of humic acid and its byproducts, and has the beneficial effect of environmental protection and pollution reduction.

[0043] To achieve the above object, the present invention provides a method for co-producing high-humic acid organic fertilizer, which specifically comprises the following steps:

[0044] Collect the residue obtained in step (5) and the filtrate after precipitation in step (6), add the aquaculture waste, adjust the pH value of the material to 6.0-7.5, and ferment at room temperature until the I of the water-soluble organic matter of the organic fertilizer is 470 / I 435 When the pH value reaches 0.6132-0.6928, the solid-state fermentation ends and high humic acid organic fertilizer is obtained.

[0045] Different livestock wastes have different pH values. For example, the pH value of air-dried sheep manure is 9.22-9.38, which needs to be adjusted to a pH suitable for microbial growth. pH adjustment can be achieved by mixing residues, filtrate after precipitation, and livestock waste. Water-soluble organic matter is a type of mixture and is considered the most active part of organic fertilizer organic matter. It can reflect the structural evolution of organic matter during the composting process and can be used to quantitatively characterize the degree of humification of organic matter, determine the end time of organic fertilizer fermentation, and affect the production cycle and economic benefits. 470 / I435 It can be used to evaluate the humification degree of organic fertilizer, and the humification degree of organic matter in organic fertilizer increases with I 470 / I 435 Increase and rise. 470 / I 435 When the pH value reaches 0.6132-0.6928, the aromatic structure of humus increases, the organic fertilizer tends to be stable, the organic fertilizer reaction can be terminated, and high humic acid organic fertilizer can be obtained, in which the humic acid content is 23.63-28.33%.

[0046] In a preferred embodiment, the reaction raw materials may further include the washing liquid obtained by washing the weathered coal with clean water in step (3).

[0047] In a preferred embodiment, the breeding waste includes livestock and poultry excrement in the livestock and poultry breeding industry and wastewater used for cleaning livestock and poultry excrement; preferably, the livestock and poultry include sheep, pigs, cattle, chickens, ducks, and geese, and the excrement includes feces and urine.

[0048] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0049] 1. The present invention first uses physical treatment to pre-treat the weathered coal raw material by utilizing the mechanochemical effect, thereby increasing the subsequent reaction rate, reducing the energy required for the reaction, and promoting the chemical reaction. Subsequently, the weathered coal activation step is designed into two stages:

[0050] In the first stage of the stacking thermochemical reaction, the utilization method of weathered coal in the present invention is essentially a conversion process between different forms of energy and matter. In the weathered coal after pretreatment, the energy generated by the stacking heat causes the old bonds to break and new bonds to form, thereby forming a rearrangement of atoms or atomic groups. Specifically, the present invention utilizes potassium oxide solid and calcium oxide solid, which release heat when in contact with water, causing the breaking and formation of chemical bonds in the molecular structure of weathered coal. Then, by combining the physicochemical power provided by the reaction heat and the moist heat effect, a series of complex chemical reactions are promoted, prompting the various chemical substances in the weathered coal to undergo significant changes, thereby achieving the activation and release of regenerated humic acid in the weathered coal and improving the yield of humic acid extracted from weathered coal. In addition, potassium hydroxide and calcium hydroxide generated by potassium oxide solid and calcium oxide can convert chelated humic salts that are insoluble in water into humates (potassium) that are easily soluble in water, while utilizing the alkaline oxygen properties to destroy Ca 2+ Mg 2+ 、Fe 3+, S ions and chelate with humic acid, removing and activating some calcium, magnesium, iron, and sulfur ions. Especially when co-producing high-humic acid organic fertilizer, increasing the potassium content in the organic fertilizer can enhance crop photosynthesis, promote carbohydrate synthesis, and promote nitrogen conversion and protein synthesis within the crop. This can enhance crop resistance to drought, cold, disease, and lodging, improving crop quality. Alternatively, increasing the calcium content in the organic fertilizer can neutralize acidic soils, where most pathogenic fungi thrive. Adequate soil calcium can mitigate plant diseases.

[0051] In the second stage of the oxidation activation reaction, high concentration of chlorine dioxide can act as an oxidant to break the covalent bonds under mild conditions, oxidize the macromolecular structure of weathered coal, and degrade it into oxygen-containing compounds, humic acid, further improving the activation effect of humic acid.

[0052] 2. The present invention improves the yield of humic acid through physical-chemical coupled reaction conversion based on the characteristics of weathered coal raw materials, and realizes high-yield extraction of humic acid from weathered coal through stacking thermochemical reaction and solid-phase reaction of oxidative activation. The residual humic acid that has been activated but not extracted is compounded with aquaculture waste to achieve the combination of residual humic acid from weathered coal and organic matter in aquaculture waste. Humic acid-organic matter coupling is used to obtain high-humic acid organic fertilizer, which has diverse products and maximizes the comprehensive economic benefits of weathered coal conversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] These and / or other aspects and advantages of the present invention will become more apparent and more readily understood from the following detailed description of embodiments of the present invention in conjunction with the accompanying drawings, in which:

[0054] Figure 1 This is the infrared spectrum of the weathered coal humic acid prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0055] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. However, it should be understood that the protection scope of the present invention is not limited to the specific embodiments.

[0056] The embodiments of the present invention provide high-quality humic acid extracted from weathered coal, a preparation method thereof, and a method for co-producing high-humic acid organic fertilizer, thereby solving the technical difficulties in the prior art of extracting humic acid from weathered coal, such as the complex, time-consuming process, low yield, and single product with low comprehensive benefits. During the process, physical treatment, stacking thermal effect, and oxidative activation reaction are used to realize the graded conversion technology of weathered coal, thereby realizing the multi-level utilization of the chemical components of weathered coal, obtaining humic acid and high-humic acid organic fertilizer, with a simple process and diverse products, thereby maximizing the comprehensive benefits of weathered coal conversion.

[0057] The technical solution of this application is described in detail below through specific embodiments:

[0058] Unless otherwise specified, the technical means used in the present invention are conventional means well known to those skilled in the art. The various raw materials, reagents, instruments, and equipment used in the present invention can be purchased from the market or prepared by existing methods. Unless otherwise specified, the reagents used in the present invention are of analytical grade.

[0059] The weathered coal raw material of the present invention is produced in Ordos City, and has a humic acid content of 37.31%.

[0060] Example 1

[0061] Weathered coal raw material is crushed, ground, and pulverized to obtain powdered weathered coal with a particle size of 0.044 mm. 50 kg of powdered weathered coal is weighed and piled outdoors. 1.5 kg of exothermic potassium oxide is added and mixed evenly. 1.5 kg of water is then sprayed onto a conical reactor (70 cm high) to allow for an exothermic reaction for one day. After the reaction, 1 kg of 5% chlorine dioxide liquid activator is added to the weathered coal, mixed evenly, and activated for one day. The activated weathered coal is transferred to a container and potassium hydroxide solution with a pH of 11 is added at a solid-to-liquid ratio of 1:4 to completely submerge the coal surface, extending 3 cm above the upper surface. The mixture is then immersed overnight at 30°C to dissolve the coal. After the reaction, the dissolved weathered coal solution is filtered to obtain a residue and an extract. The extract is collected, 5% sulfuric acid is added to adjust the pH of the mixture to 3.0, and the mixture is allowed to stand to precipitate. The precipitate is then collected and dried to obtain humic acid. The humic acid obtained by testing has a purity of 83.90% and a yield of 48.40%.

[0062] The infrared spectrum of humic acid prepared is as follows Figure 1 The infrared spectrum of weathered coal humic acid is shown in the figure, 1033cm -1 The absorption peak represents the stretching vibration absorption peak of the CO carbon-oxygen single bond on alcohols, phenols, and ethers. The order of the absorption peak areas from largest to smallest is: humic acid standard > high-quality humic acid of the present invention (Example 1) > traditionally extracted humic acid (Comparative Example 2), indicating that the CO carbon-oxygen single bond content in the humic acid standard is the highest, followed by the high-quality humic acid of the present invention, and the carbon-oxygen single bond content in the humic acid obtained by traditional extraction is the lowest. 1600-1450 cm -1 The absorption peak represents the carbon-carbon double bond on the benzene ring. 1712 cm -1 The absorption peak vibration at 3000-2850 cm indicates the presence of carbonyl groups. -1The presence of absorption peak vibrations nearby indicates the presence of methyl and methylene groups. The standard sample humic acid has a high content of methyl, methylene, carbon-carbon double bonds on the benzene ring, and carbon-oxygen single bonds, and has a high aromaticity. Traditionally extracted humic acid and high-quality humic acid have a high carbonyl content, a low overall functional group content, and a low aromaticity. However, the oxygen-containing functional groups in the high-quality humic acid of the present invention, such as carboxyl, hydroxyl, phenolic hydroxyl, and carbonyl, are higher than those in humic acid obtained by traditional extraction. Higher oxygen-containing functional groups mean stronger activity, which affects the acidity, cross-linking, water solubility, ion exchange capacity, and complexation (chelation) of humic acid.

[0063] Collect the residue and the filtrate after precipitation, add breeding waste (sheep manure), adjust the pH value of the material to 7.0, add commercial organic fertilizer composting agent (HR composting agent of Henan Haorenyuan Biotechnology Co., Ltd.) at a dosage of 1% (mass ratio), and ferment at room temperature until the water-soluble organic matter of the organic fertilizer is 1%. 470 / I 435 When it reaches 0.6928, solid-state fermentation ends and high humic acid organic fertilizer is obtained.

[0064] The humic acid content in the organic fertilizer was found to be 24.15%.

[0065] Example 2

[0066] Weathered coal raw material is crushed, ground, and pulverized to obtain powdered weathered coal with a particle size of 0.044 mm. 50 kg of powdered weathered coal is weighed and piled outdoors. 3.0 kg of exothermic potassium oxide is added and mixed evenly. 1.5 kg of water is then sprayed onto a conical reactor (70 cm high) to allow for an exothermic reaction for one day. After the reaction, 1 kg of 5% chlorine dioxide liquid activator is added to the weathered coal, mixed evenly, and activated for one day. The activated weathered coal is transferred to a container and potassium hydroxide solution with a pH of 11 is added at a solid-to-liquid ratio of 1:4 to completely submerge the coal surface, extending 3 cm above the upper surface. The mixture is then soaked overnight at 30°C to dissolve the coal. After the reaction, the dissolved weathered coal solution is filtered to obtain a residue and an extract. The extract is collected, 5% sulfuric acid is added to adjust the pH of the mixture to 3.0, and the mixture is allowed to stand to precipitate. The precipitate is then collected and dried to obtain humic acid. The humic acid obtained by testing has a purity of 82.76% and a yield of 47.00%.

[0067] Collect the residue and the filtrate after precipitation, add breeding waste (sheep manure), adjust the pH value of the material to 7.0, add commercial organic fertilizer composting agent (HR composting agent of Henan Haorenyuan Biotechnology Co., Ltd.) at a dosage of 1% (mass ratio), and ferment at room temperature until the water-soluble organic matter of the organic fertilizer is 1%. 470 / I 435 When it reaches 0.6357, solid-state fermentation ends and high humic acid organic fertilizer is obtained.

[0068] The humic acid content in the organic fertilizer was found to be 23.72%.

[0069] Example 3

[0070] Weathered coal raw material is crushed, ground, and pulverized to obtain powdered weathered coal with a particle size of 0.044 mm. 50 kg of powdered weathered coal is weighed and piled outdoors. 1.5 kg of exothermic potassium oxide is added and mixed evenly. 1.5 kg of water is then sprayed onto a conical reactor (70 cm high) to allow for an exothermic reaction for one day. 2 kg of 5% chlorine dioxide liquid activator is added to the reacted weathered coal, mixed evenly, and activated for one day. The activated weathered coal is transferred to a container and potassium hydroxide solution with a pH of 11 is added at a solid-to-liquid ratio of 1:4 to completely submerge the coal surface, extending 3 cm above the upper surface. The activated coal is then soaked overnight at 30°C to dissolve the coal. After the reaction, the dissolved weathered coal solution is filtered to obtain a residue and an extract. The extract is collected, 5% sulfuric acid is added to adjust the pH of the mixed solution to 3.0, and the mixture is allowed to stand to precipitate. The precipitate is then collected and dried to obtain humic acid. The humic acid obtained by testing has a purity of 84.28% and a yield of 47.85%.

[0071] Collect the residue and the filtrate after precipitation, add breeding waste (sheep manure), adjust the pH value of the material to 7.0, add commercial organic fertilizer composting agent (HR composting agent of Henan Haorenyuan Biotechnology Co., Ltd.) at a dosage of 1% (mass ratio), and ferment at room temperature until the water-soluble organic matter of the organic fertilizer is 1%. 470 / I 435 When it reaches 0.6842, solid-state fermentation ends and high humic acid organic fertilizer is obtained.

[0072] The humic acid content in the organic fertilizer was found to be 24.95%.

[0073] Comparative Example 1

[0074] The weathered coal raw material was crushed, ground, and pulverized to obtain powdered weathered coal with a particle size of 0.044 mm. 50 kg of powdered weathered coal was weighed and piled in the open air. 1.5 kg of exothermic potassium oxide was added and mixed evenly. 1.5 kg of water was added and sprayed on a conical reactor (70 cm in height) to carry out an exothermic reaction for 1 day. After the exothermic reaction, the weathered coal was transferred to a container. A potassium hydroxide solution with a pH of 11 was added according to a solid-liquid ratio of 1:4 to completely submerge the surface of the weathered coal and exceed the upper surface of the weathered coal by 3 cm. The weathered coal was soaked overnight at room temperature of 30°C to dissolve the weathered coal. After the reaction, the dissolved weathered coal solution was filtered to obtain a residue and an extract. The extract was collected, 5% sulfuric acid was added, and the pH of the mixed solution was adjusted to 3.0. The solution was allowed to stand to precipitate. The precipitate was collected and dried to obtain humic acid with a purity of 77.60% and a yield of 47.00%.

[0075] The residue and the filtrate after precipitation were collected, and aquaculture waste (sheep manure) was added to adjust the pH value of the material to 7.0. A commercial organic fertilizer composting agent (HR composting agent of Henan Haorenyuan Biotechnology Co., Ltd.) was added at a dosage of 1% (mass ratio). Fermentation was carried out at room temperature until the I470 / I435 of the water-soluble organic matter in the organic fertilizer reached 0.6294. The solid-state fermentation was completed to obtain a high-humic acid organic fertilizer.

[0076] The humic acid content in the organic fertilizer was found to be 26.40%.

[0077] Comparative Example 2

[0078] Weathered coal raw material was crushed, ground, and pulverized to obtain powdered weathered coal with a particle size of 0.044 mm. 1 kg of powdered weathered coal was weighed into a container and added with 4000 mL of 5% KOH (solid-to-liquid ratio of 1:4). The mixture was soaked overnight at 30°C. Deionized water was then added at a solid-to-liquid ratio of 1:20. The pH was adjusted to 11 with potassium hydroxide solution. The mixture was stirred at 80°C for 2 hours and repeatedly centrifuged until the supernatant solution clarified. The supernatant solution was collected, adjusted to pH 3.0 with 5% sulfuric acid, filtered, and the precipitate was collected and dried to obtain humic acid with a purity of 67.20% and a yield of 35.60%.

[0079] Comparative Example 2 illustrates a conventional prior art method for extracting humic acid from weathered coal. While this method requires a relatively high reaction temperature, the purity and yield of the humic acid produced are significantly lower than those of the present invention. Comparative Example 1, due to the lack of an activator, exhibits low extraction efficiency and a low purity of the humic acid produced, making it difficult to apply in applications requiring high quality.

[0080] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many variations and modifications are possible in light of the foregoing teachings. The exemplary embodiments have been selected and described for the purpose of explaining the specific principles of the invention and their practical application, thereby enabling those skilled in the art to realize and utilize a variety of exemplary embodiments of the invention and various options and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for extracting high-quality humic acid from weathered coal, characterized in that: The following steps are involved: (1) Physical treatment: taking weathered coal raw materials for crushing, grinding and pulverizing; (2) Stacking: Pile the weathered coal after physical treatment in the open air, add the exothermic agent and mix evenly, and add water to carry out the exothermic reaction; (3) Activation: Add activator to the weathered coal after reaction, mix well, and carry out activation reaction; (4) Dissolution: Take out the activated weathered coal, add alkaline solution with a pH of 10-12 to completely submerge the surface of the weathered coal, and soak it overnight at room temperature to dissolve the weathered coal; (5) Filtration: After the reaction is completed, the solution in step (4) is filtered to obtain a residue and an extract; (6) Precipitating humic acid from the extract: Collect the extract obtained in step (5), add acid, adjust the pH of the mixed solution to 1-3, let it stand to precipitate, collect the precipitate and dry it to obtain humic acid; Wherein, in step (1), the particle size of the weathered coal after crushing, grinding and pulverizing is 0.044-0.125 mm; In step (3), the activator includes one or both of solid chlorine dioxide and liquid chlorine dioxide; the mass ratio of the activator to the weathered coal is (1-4):

100.

2. The method for extracting high-quality humic acid from weathered coal according to claim 1, wherein: In step (2), the exothermic agent includes one or both of potassium oxide and calcium oxide; the mass ratio of the weathered coal, the exothermic agent and water is 1: (0.03-0.10): (0.02-0.064).

3. The method for extracting high-quality humic acid from weathered coal according to claim 1, wherein: In step (4), the alkali solution includes one or more of sodium hydroxide, potassium hydroxide, and sodium carbonate; and the solid-liquid mass ratio of the weathered coal to the alkali solution is 1:(3-6).

4. The method for extracting high-quality humic acid from weathered coal according to claim 1, wherein: In step (6), the acid solution is one or more of sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid.

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