A preparation method of highly active humic acid and its application in the production of potassium fulvate

Abstract

This invention discloses a method for preparing highly active humic acid and its application in the production of potassium fulvate, belonging to the technical field of humic acid preparation methods. The method involves five steps to extract humic acid from lignite, optimizing extraction conditions, and selecting the optimal ratio of catalyst, oxidant, and promoter to improve the humic acid extraction rate. The resulting humic acid is rich in numerous acidic groups, phenolic hydroxyl groups, carboxyl groups, and other oxygen-containing functional groups. The type and content of these functional groups directly affect the activity of the humic acid. The activity of the prepared humic acid is significantly higher than that of commercially available humic acid, showing better application prospects in agriculture, medicine, environmental protection, and other fields. Furthermore, the humic acid prepared by this method has a smaller molecular weight, making it easier to enter plant cells and influence plant metabolism when used as fertilizer, thereby better promoting plant growth.

Description

Technical Field

[0001] This invention belongs to the technical field of humic acid preparation methods, specifically relating to a method for preparing highly active humic acid and its application in the production of potassium fulvate. Background Technology

[0002] With the transformation of agricultural development methods, the development of green and efficient new fertilizers is a major requirement for ensuring the ecological security of farmland and the quality and safety of agricultural products in my country. Humic acid is a heterogeneous polymer with aromatic rings and aliphatic chains as its basic structure, possessing acidity, hydrophilicity, interfacial activity, cation exchange, complexing, and adsorption capabilities. Humic acid contains a large amount of organic matter and various active functional groups, which can improve soil structure, enhance soil water and fertilizer retention capacity, promote plant growth and development, and strengthen crop resistance. Humic acid has become a major effective component in soil conditioners, drought-resistant agents, and compound fertilizers in agriculture, and its development and utilization have attracted the attention of fertilizer researchers and production enterprises.

[0003] Humic acid is a class of natural high-molecular polymers rich in various active functional groups, formed from organic matter such as plant and animal residues under physicochemical and microbial processes. It is widely found in soil, water, peat, and coal. Soil humic acid has an average concentration of less than one percent, but the total amount is the largest. Water humic acid has a low total amount and content, making it almost unusable for development. Mineral humic acid is mainly found in peat, weathered coal, and lignite, and is the most abundant source; most commercial humic acid is of mineral origin. my country has abundant and widely distributed mineral resources. Statistics show that my country's coal reserves are approximately 2.10 × 10⁻⁶. 11 The total reserves of peat are approximately 12.48 billion tons, the reserves of weathered coal are 100 billion tons, and the proven reserves of lignite are 130 billion tons. The renewable humic acid content in these mineral sources varies greatly, generally ranging from 5% to 80%.

[0004] Currently, the preparation technology of humic acid mainly includes two categories: (1) direct extraction from mineral resources such as lignite and weathered coal through pretreatment technology, with oxidation being a commonly used pretreatment method; (2) preparation using industrial and agricultural organic waste as raw materials under artificially regulated conditions, with wet hydrolysis and solid-state fermentation being commonly used preparation methods. Existing commercial humic acid is mainly extracted from peat, lignite, and weathered coal through chemical methods, belonging to mineral humic acid. Most mineral humic acids have low biological activity and high molecular weight, few chelating and hydrophilic groups, making them difficult to be decomposed and utilized by soil microorganisms in a short period of time. Therefore, mineral humic acids must be extracted and activated before utilization to maximize their application value. Currently, the commonly used activation methods mainly include: (1) extraction, alkaline dissolution and acid precipitation; (2) mechanical activation, which reduces the particle size of weathered coal or lignite; (3) ultrasonic activation; and (4) oxidation, with oxidation methods mainly including nitric acid and hydrogen peroxide oxidation, as well as non-catalytic oxidation under high temperature and high pressure, dry oxidation, alkaline-air oxidation, and O2-O3 oxidation. Extraction, mechanical activation, and ultrasonic activation methods cannot significantly improve the activity of humic acid. Oxidation methods are relatively complicated and not conducive to industrial production. Therefore, how to provide a new process and method to prepare highly active humic acid has become an urgent technical problem to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing highly active humic acid. This method achieves a high extraction rate of humic acid from lignite, and the resulting humic acid is rich in numerous acidic groups, phenolic hydroxyl groups, carboxyl groups, and other oxygen-containing functional groups. The type and content of these functional groups directly affect the activity of the humic acid. The activity of the prepared humic acid is significantly higher than that of commercially available humic acid, showing better application prospects in agriculture, medicine, environmental protection, and other fields. Furthermore, the humic acid prepared by this method has a smaller molecular weight, making it easier for it to enter plant cells and influence plant metabolism when used as fertilizer, thereby promoting plant growth.

[0006] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing highly active humic acid, comprising the following steps:

[0008] (1) Take raw lignite, clean it, dry it and crush it to a particle size of less than 0.2 mm to detect lignite particles. Add 10% HCl to the lignite particles according to a fixed material-liquid ratio for acid washing. Stir at high speed in a water bath at 80℃ for 100 min. Vacuum filter and wash until neutral. Dry the filter cake and grind it. Pass it through a 200-mesh sieve to obtain pretreated lignite powder.

[0009] (2) Take the pretreated lignite powder and catalyst and mix them according to the mass ratio. Then, mechanically ball mill them at a speed of 100-120 r / min for 30-45 min to obtain mixture A;

[0010] (3) Mix mixture A with oxidant, stir in a constant temperature water bath for 1 hour, filter under vacuum and wash several times with anhydrous ethanol, and dry the filter cake to obtain oxidized lignite;

[0011] (4) Mix oxidized lignite with alkaline solution and accelerator in a mass ratio, heat in a constant temperature water bath for 60-90 min, cool and separate solid and liquid, and take the filtrate for later use;

[0012] (5) Add hydrochloric acid solution to the filtrate obtained above, adjust the pH to 1-2, let stand for 24 hours, centrifuge to separate the solid, and vacuum dry to obtain highly active humic acid.

[0013] The catalyst is Ce-S modified biochar; the promoter is composed of polyethylene glycol and sodium N-cocoyl-N-methyltaurate in a mass ratio of 1:2.

[0014] Preferably, the Ce-S modified biochar is prepared by the following method:

[0015] (a) Ce(NO3)2·6H2O, dimethyl sulfoxide and walnut shell powder were added to methanol solvent and stirred at 180°C for 24 h. After cooling to room temperature, the product was washed with methanol 3-5 times and then dried to obtain solid powder.

[0016] (b) The solid powder was transferred into a tube furnace and calcined at high temperature for 4 hours under a nitrogen atmosphere, and then cooled to room temperature to obtain Ce-S modified biochar.

[0017] Preferably, in step (a), the ratio of Ce(NO3)2·6H2O, dimethyl sulfoxide, walnut shell powder, and methanol solvent is 1 mmol: 5 ml: 5 g: 50 ml.

[0018] Preferably, in step (b), the specific heating method in the tubular furnace is to heat to 700°C at a rate of 3°C / min and calcine for 4 hours.

[0019] Preferably, in step (1), the ratio of lignite particles to 10% HCl solution is 1g:10ml.

[0020] Preferably, in step (2), the ratio of pretreated lignite powder to catalyst is 1g:0.2-0.5g.

[0021] Preferably, in step (3), the oxidant is composed of 30% hydrogen peroxide and 0.5 mol / L sodium persulfate solution in a mass ratio of 1:0.2-0.5; the mass ratio of mixture A to oxidant is 1:0.7-0.8; and the water bath temperature is 80-90℃.

[0022] Preferably, in step (4), the mass ratio of oxidized lignite, alkaline solution, and accelerator is 1:50-60:3-6; the alkaline solution is prepared by mixing 2% NaOH solution and 5% Na2SO3 solution in equal proportions; and the water bath temperature is 70-80℃.

[0023] Using the highly active humic acid prepared by the above method of the present invention in the production of potassium fulvate can yield potassium fulvate fertilizer with good biocompatibility, environmental friendliness and multifunctionality.

[0024] The beneficial effects of this invention are:

[0025] (1) In this invention, walnut shell biochar is modified by co-modification with cerium nitrate and dimethyl sulfoxide to obtain modified biochar doped with both Ce and S elements as a catalyst. The biochar modified by co-doping with rare earth metals and non-metallic elements has a large atomic radius, which can increase the structural defects of the material, resulting in a significant increase in specific surface area and porosity. S-Ce in biochar changes the electronic structure of biochar, improves electron transfer ability, and enhances oxidation catalytic activity. This enhanced activity helps to accelerate the decomposition and release of humic acid in lignite, thereby improving the extraction rate.

[0026] (2) The oxidant of the present invention is composed of 30% hydrogen peroxide and a small amount of sodium persulfate. When the two are combined and used together with the catalyst prepared in the present invention, the synergistic effect is good, which promotes the deep oxygenation of lignite. The absorbance ratio of the prepared humic acid is larger than that of commercial humic acid, the molecular weight of the product is smaller, and the activity is higher. It is more conducive to the absorption and utilization of plants in agricultural production.

[0027] (3) The present invention employs a promoter component, which can promote more uniform penetration of the oxidant and catalyst into the lignite particles, enabling them to fully contact and react with the lignite, thereby improving the extraction efficiency of humic acid. Simultaneously, Ce-S-doped biochar serves as a catalyst, providing active sites during the reaction process to accelerate the decomposition of the oxidant and the release of humic acid from the lignite. The addition of the promoter further optimizes the reaction conditions and enhances the activity of the catalyst, thus achieving a more efficient and environmentally friendly extraction of humic acid.

[0028] (4) The catalyst and oxidant of the present invention can achieve excellent catalytic oxidation degradation of lignite to prepare highly active humic acid, avoiding the use of excessive nitric acid in conventional humic acid preparation methods, avoiding the generation of nitrogen oxide gas, reducing environmental pollution, and better meeting the needs of contemporary green environmental protection. Attached Figure Description

[0029] Figure 1 The images are scanning electron microscope (SEM) images of Ce-S modified biochar, the catalyst used in this invention, before and after Ce-S doping, where a is before doping and b is after doping.

[0030] Figure 2 The figure shows the effect of different catalyst dosages on the extraction rate of highly active humic acid in the method of this invention. Detailed Implementation

[0031] The technical solution of the present invention will be further described below with reference to specific embodiments, but it is not limited thereto.

[0032] Example 1

[0033] A method for preparing highly active humic acid, comprising the following steps:

[0034] (1) Take raw lignite, clean it, dry it and crush it to a particle size of less than 0.2 mm to detect lignite particles. Add 500 ml of 10% HCl to 100 g lignite particles for acid washing. Stir at high speed in a water bath at 80℃ for 100 min. Vacuum filter and wash until neutral. Dry the filter cake and grind it. Pass it through a 200 mesh sieve to obtain pretreated lignite powder.

[0035] (2) Take 5g of pretreated lignite powder and mix it with 1g of catalyst, then mechanically ball mill it at 100-120r / min for 30-45min to obtain mixture A; the catalyst is Ce-S modified biochar;

[0036] (3) Mix the mixture A with the oxidant at a mass ratio of 1:0.7, and stir the mixture in a water bath at 80-90℃ for 1 hour. After stirring, filter the mixture under vacuum and wash it several times with anhydrous ethanol. Dry the filter cake to obtain oxidized lignite. The oxidant is composed of 30% hydrogen peroxide and 0.5 mol / L sodium persulfate solution at a mass ratio of 1:0.2.

[0037] (4) Oxidized lignite, alkaline solution, and accelerator are mixed at a mass ratio of 1:50:3, heated in a constant temperature water bath at 70-80℃ for 60-90 min, and then cooled to separate the solid and liquid. The filtrate is used for later use. The accelerator is composed of polyethylene glycol and N-cocoyl-N-methyltaurate sodium at a mass ratio of 1:2. The alkaline solution is prepared by mixing 2% NaOH solution and 5% Na2SO3 solution in equal proportions.

[0038] (5) Add hydrochloric acid solution to the filtrate obtained above, adjust the pH to 1, let stand for 24 hours, centrifuge to separate the solid, and vacuum dry to obtain highly active humic acid.

[0039] The Ce-S modified biochar was prepared using the following method:

[0040] (a) Ce(NO3)2·6H2O, dimethyl sulfoxide and walnut shell powder were added to methanol solvent and stirred at 180°C for 24 h. After cooling to room temperature, the product was washed with methanol 3-5 times and then dried to obtain a solid powder. The ratio of Ce(NO3)2·6H2O, dimethyl sulfoxide, walnut shell powder and methanol solvent was 1 mmol: 5 ml: 5 g: 50 ml.

[0041] (b) The solid powder was transferred into a tube furnace and heated to 700°C at a rate of 3°C / min under a nitrogen atmosphere. The calcination was carried out for 4 hours and then cooled to room temperature to obtain Ce-S modified biochar.

[0042] Example 2

[0043] A method for preparing highly active humic acid, comprising the following steps:

[0044] (1) Take raw lignite, clean it, dry it and crush it to a particle size of less than 0.2 mm to detect lignite particles. Add 500 ml of 10% HCl to 100 g lignite particles for acid washing. Stir at high speed in a water bath at 80℃ for 100 min. Vacuum filter and wash until neutral. Dry the filter cake and grind it. Pass it through a 200 mesh sieve to obtain pretreated lignite powder.

[0045] (2) Take 5g of pretreated lignite powder and mix it with 2.5g of catalyst, and then mechanically ball mill it at 100-120r / min for 30-45min to obtain mixture A; the catalyst is Ce-S modified biochar;

[0046] (3) Mix the mixture A with the oxidant at a mass ratio of 1:0.8, and stir the mixture in a water bath at 80-90℃ for 1 hour. After stirring, filter the mixture under vacuum and wash it several times with anhydrous ethanol. Dry the filter cake to obtain oxidized lignite. The oxidant is composed of 30% hydrogen peroxide and 0.5 mol / L sodium persulfate solution at a mass ratio of 1:0.5.

[0047] (4) Oxidized lignite, alkaline solution, and accelerator are mixed at a mass ratio of 1:60:6, heated in a constant temperature water bath at 70-80℃ for 60-90 min, and then cooled to separate the solid and liquid. The filtrate is used for later use. The accelerator is composed of polyethylene glycol and N-cocoyl-N-methyltaurate sodium at a mass ratio of 1:2. The alkaline solution is prepared by mixing 2% NaOH solution and 5% Na2SO3 solution in equal proportions.

[0048] (5) Add hydrochloric acid solution to the filtrate obtained above, adjust the pH to 2, let stand for 24 hours, centrifuge to separate the solid, and vacuum dry to obtain highly active humic acid.

[0049] The Ce-S modified biochar was prepared using the following method:

[0050] (a) Ce(NO3)2·6H2O, dimethyl sulfoxide and walnut shell powder were added to methanol solvent and stirred at 180°C for 24 h. After cooling to room temperature, the product was washed with methanol 3-5 times and then dried to obtain a solid powder. The ratio of Ce(NO3)2·6H2O, dimethyl sulfoxide, walnut shell powder and methanol solvent was 1 mmol: 5 ml: 5 g: 50 ml.

[0051] (b) The solid powder was transferred into a tube furnace and heated to 700°C at a rate of 3°C / min under a nitrogen atmosphere. The calcination was carried out for 4 hours and then cooled to room temperature to obtain Ce-S modified biochar.

[0052] Example 3

[0053] A method for preparing highly active humic acid, comprising the following steps:

[0054] (1) Take raw lignite, clean it, dry it and crush it to a particle size of less than 0.2 mm to detect lignite particles. Add 500 ml of 10% HCl to 100 g lignite particles for acid washing. Stir at high speed in a water bath at 80℃ for 100 min. Vacuum filter and wash until neutral. Dry the filter cake and grind it. Pass it through a 200 mesh sieve to obtain pretreated lignite powder.

[0055] (2) Take 5g of pretreated lignite powder and mix it with 2.0g of catalyst, and then mechanically ball mill it at 100-120r / min for 30-45min to obtain mixture A; the catalyst is Ce-S modified biochar;

[0056] (3) Mix the mixture A with the oxidant at a mass ratio of 1:0.75, and stir the mixture in a water bath at 80-90℃ for 1 hour. After stirring, filter the mixture under vacuum and wash it several times with anhydrous ethanol. Dry the filter cake to obtain oxidized lignite. The oxidant is composed of 30% hydrogen peroxide and 0.5 mol / L sodium persulfate solution at a mass ratio of 1:0.4.

[0057] (4) Mix oxidized lignite with alkaline solution and accelerator at a mass ratio of 1:55:5, heat in a constant temperature water bath at 70-80℃ for 60-90 min, cool and separate the solid and liquid, and take the filtrate for later use; the accelerator is composed of polyethylene glycol and N-cocoyl-N-methyltaurate sodium at a mass ratio of 1:2; the alkaline solution is prepared by mixing 2% NaOH solution and 5% Na2SO3 solution in equal proportions;

[0058] (5) Add hydrochloric acid solution to the filtrate obtained above, adjust the pH to 1.5, let stand for 24 hours, centrifuge to separate the solid, and vacuum dry to obtain highly active humic acid.

[0059] The Ce-S modified biochar was prepared using the following method:

[0060] (a) Ce(NO3)2·6H2O, dimethyl sulfoxide and walnut shell powder were added to methanol solvent and stirred at 180°C for 24 h. After cooling to room temperature, the product was washed with methanol 3-5 times and then dried to obtain a solid powder. The ratio of Ce(NO3)2·6H2O, dimethyl sulfoxide, walnut shell powder and methanol solvent was 1 mmol: 5 ml: 5 g: 50 ml.

[0061] (b) The solid powder was transferred into a tube furnace and heated to 700°C at a rate of 3°C / min under a nitrogen atmosphere. The calcination was carried out for 4 hours and then cooled to room temperature to obtain Ce-S modified biochar.

[0062] Comparative Example 1

[0063] A method for preparing highly active humic acid, comprising the following steps:

[0064] (1) Take raw lignite, clean it, dry it and crush it to a particle size of less than 0.2 mm to detect lignite particles. Add 500 ml of 10% HCl to 100 g lignite particles for acid washing. Stir at high speed in a water bath at 80℃ for 100 min. Vacuum filter and wash until neutral. Dry the filter cake and grind it. Pass it through a 200 mesh sieve to obtain pretreated lignite powder.

[0065] (2) Take 5g of pretreated lignite powder and mix it with oxidant at a mass ratio of 1:0.75. After stirring and reacting in a water bath at 80-90℃ for 1h, vacuum filter and wash several times with anhydrous ethanol. Dry the filter cake to obtain oxidized lignite. The oxidant is composed of 30% hydrogen peroxide and 0.5mol / L sodium persulfate solution at a mass ratio of 1:0.4.

[0066] (3) Oxidized lignite, alkaline solution, and accelerator are mixed at a mass ratio of 1:55:5, heated in a constant temperature water bath at 70-80℃ for 60-90 min, and then cooled to separate the solid and liquid. The filtrate is used for later use. The accelerator is composed of polyethylene glycol and N-cocoyl-N-methyltaurate sodium at a mass ratio of 1:2. The alkaline solution is prepared by mixing 2% NaOH solution and 5% Na2SO3 solution in equal proportions.

[0067] (4) Add hydrochloric acid solution to the filtrate obtained above, adjust the pH to 1.5, let stand for 24 hours, centrifuge to separate the solid, and vacuum dry to obtain highly active humic acid.

[0068] The preparation method of this comparative example is basically the same as that of Example 3, except that it does not contain any catalyst components.

[0069] Comparative Example 2

[0070] A method for preparing highly active humic acid, comprising the following steps:

[0071] (1) Take raw lignite, clean it, dry it and crush it to a particle size of less than 0.2 mm to detect lignite particles. Add 500 ml of 10% HCl to 100 g lignite particles for acid washing. Stir at high speed in a water bath at 80℃ for 100 min. Vacuum filter and wash until neutral. Dry the filter cake and grind it. Pass it through a 200 mesh sieve to obtain pretreated lignite powder.

[0072] (2) Take 5g of pretreated lignite powder and mix it with 2.0g of catalyst, and then mechanically ball mill it at a speed of 100-120r / min for 30-45min to obtain mixture A; the catalyst is biochar;

[0073] (3) Mix the mixture A with the oxidant at a mass ratio of 1:0.75, and stir the mixture in a water bath at 80-90℃ for 1 hour. After stirring, filter the mixture under vacuum and wash it several times with anhydrous ethanol. Dry the filter cake to obtain oxidized lignite. The oxidant is composed of 30% hydrogen peroxide and 0.5 mol / L sodium persulfate solution at a mass ratio of 1:0.4.

[0074] (4) Mix oxidized lignite with alkaline solution and accelerator at a mass ratio of 1:55:5, heat in a constant temperature water bath at 70-80℃ for 60-90 min, cool and separate the solid and liquid, and take the filtrate for later use; the accelerator is composed of polyethylene glycol and N-cocoyl-N-methyltaurate sodium at a mass ratio of 1:2; the alkaline solution is prepared by mixing 2% NaOH solution and 5% Na2SO3 solution in equal proportions;

[0075] (5) Add hydrochloric acid solution to the filtrate obtained above, adjust the pH to 1.5, let stand for 24 hours, centrifuge to separate the solid, and vacuum dry to obtain highly active humic acid.

[0076] The biochar was prepared by the following method: walnut shell powder was placed in a tube furnace, heated to 700°C at a rate of 3°C / min under a nitrogen atmosphere, calcined for 4 hours, and then cooled to room temperature to obtain biochar.

[0077] The preparation method of this comparative example is basically the same as that of Example 3, except that the catalyst is only biochar and has not undergone any modification treatment.

[0078] Comparative Example 3

[0079] A method for preparing highly active humic acid, comprising the following steps:

[0080] (1) Take raw lignite, clean it, dry it and crush it to a particle size of less than 0.2 mm to detect lignite particles. Add 500 ml of 10% HCl to 100 g lignite particles for acid washing. Stir at high speed in a water bath at 80℃ for 100 min. Vacuum filter and wash until neutral. Dry the filter cake and grind it. Pass it through a 200 mesh sieve to obtain pretreated lignite powder.

[0081] (2) Take 5g of pretreated lignite powder and mix it with 2.0g of catalyst, and then mechanically ball mill it at 100-120r / min for 30-45min to obtain mixture A; the catalyst is Ce-S modified biochar;

[0082] (3) Mix the mixture A with the oxidant at a mass ratio of 1:0.75, and stir the mixture in a water bath at 80-90℃ for 1 hour. After stirring, filter the mixture under vacuum and wash it several times with anhydrous ethanol. Dry the filter cake to obtain oxidized lignite. The oxidant is composed of 30% hydrogen peroxide and 0.5 mol / L sodium persulfate solution at a mass ratio of 1:0.4.

[0083] (4) Mix oxidized lignite with alkaline solution at a mass ratio of 1:55, heat in a constant temperature water bath at 70-80℃ for 60-90 min, cool and separate solid and liquid, and take the filtrate for later use; the alkaline solution is prepared by mixing 2% NaOH solution and 5% Na2SO3 solution in equal proportion;

[0084] (5) Add hydrochloric acid solution to the filtrate obtained above, adjust the pH to 1.5, let stand for 24 hours, centrifuge to separate the solid, and vacuum dry to obtain highly active humic acid.

[0085] The Ce-S modified biochar was prepared using the following method:

[0086] (a) Ce(NO3)2·6H2O, dimethyl sulfoxide and walnut shell powder were added to methanol solvent and stirred at 180°C for 24 h. After cooling to room temperature, the product was washed with methanol 3-5 times and then dried to obtain a solid powder. The ratio of Ce(NO3)2·6H2O, dimethyl sulfoxide, walnut shell powder and methanol solvent was 1 mmol: 5 ml: 5 g: 50 ml.

[0087] (b) The solid powder was transferred into a tube furnace and heated to 700°C at a rate of 3°C / min under a nitrogen atmosphere. The calcination was carried out for 4 hours and then cooled to room temperature to obtain Ce-S modified biochar.

[0088] The preparation method of this comparative example is basically the same as that of Example 3, except that it does not contain any accelerator components.

[0089] Comparative Example 4

[0090] A method for preparing highly active humic acid, comprising the following steps:

[0091] (1) Take raw lignite, clean it, dry it and crush it to a particle size of less than 0.2 mm to detect lignite particles. Add 500 ml of 10% HCl to 100 g lignite particles for acid washing. Stir at high speed in a water bath at 80℃ for 100 min. Vacuum filter and wash until neutral. Dry the filter cake and grind it. Pass it through a 200 mesh sieve to obtain pretreated lignite powder.

[0092] (2) Take 5g of pretreated lignite powder and mix it with 2.0g of catalyst, and then mechanically ball mill it at 100-120r / min for 30-45min to obtain mixture A; the catalyst is Ce-S modified biochar;

[0093] (3) Mix the mixture A with the oxidant at a mass ratio of 1:0.75, stir and react in a water bath at 80-90℃ for 1 hour, then filter under vacuum and wash several times with anhydrous ethanol. The filter cake is dried to obtain oxidized lignite. The oxidant is 30% hydrogen peroxide.

[0094] (4) Mix oxidized lignite with alkaline solution and accelerator at a mass ratio of 1:55:5, heat in a constant temperature water bath at 70-80℃ for 60-90 min, cool and separate the solid and liquid, and take the filtrate for later use; the accelerator is composed of polyethylene glycol and N-cocoyl-N-methyltaurate sodium at a mass ratio of 1:2; the alkaline solution is prepared by mixing 2% NaOH solution and 5% Na2SO3 solution in equal proportions;

[0095] (5) Add hydrochloric acid solution to the filtrate obtained above, adjust the pH to 1.5, let stand for 24 hours, centrifuge to separate the solid, and vacuum dry to obtain highly active humic acid.

[0096] The Ce-S modified biochar was prepared using the following method:

[0097] (a) Ce(NO3)2·6H2O, dimethyl sulfoxide and walnut shell powder were added to methanol solvent and stirred at 180°C for 24 h. After cooling to room temperature, the product was washed with methanol 3-5 times and then dried to obtain a solid powder. The ratio of Ce(NO3)2·6H2O, dimethyl sulfoxide, walnut shell powder and methanol solvent was 1 mmol: 5 ml: 5 g: 50 ml.

[0098] (b) The solid powder was transferred into a tube furnace and heated to 700°C at a rate of 3°C / min under a nitrogen atmosphere. The calcination was carried out for 4 hours and then cooled to room temperature to obtain Ce-S modified biochar.

[0099] The preparation method of this comparative example is basically the same as that of Example 3, except that the oxidant consists of only 30% hydrogen peroxide.

[0100] Comparative Example 5

[0101] A method for preparing highly active humic acid, comprising the following steps:

[0102] (1) Take raw lignite, clean it, dry it and crush it to a particle size of less than 0.2 mm to detect lignite particles. Add 500 ml of 10% HCl to 100 g lignite particles for acid washing. Stir at high speed in a water bath at 80℃ for 100 min. Vacuum filter and wash until neutral. Dry the filter cake and grind it. Pass it through a 200 mesh sieve to obtain pretreated lignite powder.

[0103] (2) Take 5g of pretreated lignite powder and mix it with 2.0g of catalyst, and then mechanically ball mill it at 100-120r / min for 30-45min to obtain mixture A; the catalyst is Ce-S modified biochar;

[0104] (3) Mix the mixture A with the oxidant at a mass ratio of 1:0.75, stir in a water bath at 80-90℃ for 1 hour, filter under vacuum and wash several times with anhydrous ethanol, and dry the filter cake to obtain oxidized lignite; the oxidant is a 0.5 mol / L sodium persulfate solution.

[0105] (4) Mix oxidized lignite with alkaline solution and accelerator at a mass ratio of 1:55:5, heat in a constant temperature water bath at 70-80℃ for 60-90 min, cool and separate the solid and liquid, and take the filtrate for later use; the accelerator is composed of polyethylene glycol and N-cocoyl-N-methyltaurate sodium at a mass ratio of 1:2; the alkaline solution is prepared by mixing 2% NaOH solution and 5% Na2SO3 solution in equal proportions;

[0106] (5) Add hydrochloric acid solution to the filtrate obtained above, adjust the pH to 1.5, let stand for 24 hours, centrifuge to separate the solid, and vacuum dry to obtain highly active humic acid.

[0107] The Ce-S modified biochar was prepared using the following method:

[0108] (a) Ce(NO3)2·6H2O, dimethyl sulfoxide and walnut shell powder were added to methanol solvent and stirred at 180°C for 24 h. After cooling to room temperature, the product was washed with methanol 3-5 times and then dried to obtain a solid powder. The ratio of Ce(NO3)2·6H2O, dimethyl sulfoxide, walnut shell powder and methanol solvent was 1 mmol: 5 ml: 5 g: 50 ml.

[0109] (b) The solid powder was transferred into a tube furnace and heated to 700°C at a rate of 3°C / min under a nitrogen atmosphere. The calcination was carried out for 4 hours and then cooled to room temperature to obtain Ce-S modified biochar.

[0110] The preparation method of this comparative example is basically the same as that of Example 3, except that the oxidant is only a 0.5 mol / L sodium persulfate solution.

[0111] Test Example 1

[0112] Scanning electron microscopy was performed on the Ce-S modified biochar catalyst used in this invention, and the results are as follows: Figure 1 As shown, the results indicate that walnut shell powder obtains a loose porous structure after high-temperature calcination, and after doping with Ce and S, many small particles are dispersed on the surface of biochar. This shows that the metal element Ce and the non-metal element S have been successfully doped into the biochar structure, which can increase more catalytic active sites.

[0113] Test Example 2

[0114] Determination of active group content:

[0115] The total acid groups, carboxyl groups, phenolic hydroxyl groups, and E4 / E6 values ​​of the highly active humic acids prepared in Examples 1-3 and Comparative Examples 1-5, as well as commercially available mineralized humic acid products, were determined. The total acid groups were determined using the alkaline dissolution of barium chloride precipitation potentiometric titration method; the carboxyl groups were determined using the alkaline dissolution and acid precipitation of calcium acetate method; the phenolic hydroxyl group (differential subtraction method) was calculated as: phenolic hydroxyl group = total acid groups - carboxyl groups; the E4 / E6 value was the ratio of absorbance at 465 nm to that at 665 nm. The experimental results are shown in Table 1.

[0116] Table 1 Test Results

[0117]

[0118] As can be seen from Table 1 above, the total acidic group content of the highly active humic acid prepared in the embodiments of the present invention is significantly higher than that of commercially available products, and is also higher than that of the humic acid obtained in Comparative Examples 1-5. This indicates that the humic acid prepared by the method of the present invention has more oxygen-containing functional groups, and the content of these functional groups is positively correlated with the activity of humic acid; the more active functional groups, the higher the activity of humic acid. At the same time, the E4 / E6 value of the highly active humic acid obtained by the present invention is also significantly higher than that of the comparative examples and commercially available products. E4 / E6 is a measure of the degree of aromatic ring condensation and is negatively correlated with the molecular weight of humic acid; a larger ratio indicates a smaller molecular weight and a lower degree of condensation. As can be seen from the above data, the highly active humic acid prepared by the method of this invention has a relatively small molecular weight. This is mainly because, under the synergistic effect of catalyst, oxidant, and accelerator, lignite undergoes a deep oxidative degradation reaction, releasing a large amount of heat. The lactone ring of humic acid breaks during high-temperature oxidation, increasing the number of carboxyl groups. Simultaneously, the lactone ring undergoes demethylation due to oxidation, further increasing the carboxyl content. Additionally, the alkyl and aldehyde groups on humic acid may react with dissolved oxygen to generate carboxyl groups, leading to a significant increase in carboxyl groups and consequently an increase in total acidic groups. Carbon chain breakage and lactone ring opening reduce the molecular weight of humic acid and increase the E4 / E6 value. When the product obtained by this invention is used in the production and application of agricultural fertilizers such as potassium humate, the small molecules will be more easily absorbed and utilized by crops. Changing the raw materials and dosages in any step of this invention will result in the loss or weakening of the desired effect.

[0119] Test Example 3

[0120] Humic acid extraction rate determination

[0121] The extraction rates of humic acid products obtained in Examples 1-3 and Comparative Examples 1-5 were calculated respectively. Humic acid extraction rate = mass of humic acid product / mass of raw lignite × 100%. The specific results are shown in Table 2.

[0122] Table 2 Humic acid extraction rate results

[0123]

[0124] As can be seen from the results in Table 2 above, the humic acid extraction rate of the embodiments of the present invention is significantly better than that of comparative examples 1-5. This is the result of the combined action of the oxidant, catalyst and promoter used in the preparation steps of the present invention. Changing the amount of any of the raw materials will weaken or eliminate the corresponding effect.

[0125] This invention also investigated the effect of catalyst dosage on the extraction rate of highly active humic acid in the method of this invention. Specifically, the extraction rate of highly active humic acid was tested by changing the mass ratio of pretreated lignite powder to catalyst. The specific results are as follows: Figure 2 As shown. From Figure 2 As can be seen, the amount of catalyst has a very significant effect on highly active humic acid. Within the mass ratio range of this invention, the amount of catalyst can effectively improve the extraction rate of highly active humic acid. However, when the amount of catalyst is too large, the extraction rate of highly active humic acid decreases. Therefore, the catalyst ratio selected in this invention is the optimal experimental parameter.

[0126] When the highly active humic acid prepared by the method of this invention is combined with conventional potassium fertilizer and auxiliary materials to prepare potassium humate fertilizer, its application in crop planting has a significant effect on increasing crop yield. Compared with potassium humate fertilizer prepared from conventional commercially available mineral humic acid, crop yield is increased by 15-25%, which shows that the highly active humic acid prepared by this invention has good application prospects.

[0127] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

Claims

1. A method for preparing highly active humic acid, characterized in that, It includes the following steps: (1) Take raw lignite, clean it, dry it and crush it to a particle size of less than 0.2 mm to obtain lignite particles. Add 10% HCl to the lignite particles according to a fixed material-liquid ratio for acid washing. Stir at high speed in a water bath at 80℃ for 100 min. Vacuum filter and wash until neutral. Dry the filter cake and grind it. Pass it through a 200-mesh sieve to obtain pretreated lignite powder. (2) Take the pretreated lignite powder and catalyst and mix them according to the mass ratio. Then, mechanically ball mill them at a speed of 100-120 r / min for 30-45 min to obtain mixture A; (3) Mix the mixture A with the oxidant, heat it in a constant temperature water bath, stir and react for 1 hour, then filter it under vacuum and wash it several times with anhydrous ethanol. The filter cake is dried to obtain oxidized lignite. (4) Mix oxidized lignite with alkaline solution and accelerator in a mass ratio, heat in a constant temperature water bath for 60-90 min, cool and separate solid and liquid, and take the filtrate for later use; (5) Add hydrochloric acid solution to the filtrate obtained above, adjust the pH to 1-2, let stand for 24 hours, centrifuge to separate the solid, and vacuum dry to obtain highly active humic acid. The catalyst is Ce-S modified biochar; the promoter is composed of polyethylene glycol and sodium N-cocoyl-N-methyltaurate in a mass ratio of 1:

2. The Ce-S modified biochar was prepared using the following method: (a) Ce(NO3)2·6H2O, dimethyl sulfoxide and walnut shell powder were added to methanol solvent and stirred at 180°C for 24 h. After cooling to room temperature, the product was washed with methanol 3-5 times and then dried to obtain solid powder. (b) The solid powder was transferred into a tube furnace and calcined at high temperature for 4 hours under a nitrogen atmosphere, and then cooled to room temperature to obtain Ce-S modified biochar. In step (3), the oxidant is composed of 30% hydrogen peroxide and 0.5 mol / L sodium persulfate solution in a mass ratio of 1:0.2-0.5; the mass ratio of mixture A to the oxidant is 1:0.7-0.8; and the water bath temperature is 80-90℃.

2. The method for preparing highly active humic acid according to claim 1, characterized in that, In step (a), the ratio of Ce(NO3)2·6H2O, dimethyl sulfoxide, walnut shell powder, and methanol solvent is 1 mmol: 5 ml: 5 g: 50 ml.

3. The method for preparing highly active humic acid according to claim 1, characterized in that, In step (b), the specific heating method in the tubular furnace is to heat to 700°C at a rate of 3°C / min and calcine for 4 hours.

4. The method for preparing highly active humic acid according to claim 1, characterized in that, In step (1), the ratio of lignite particles to 10% HCl solution is 1g:10ml.

5. The method for preparing highly active humic acid according to claim 1, characterized in that, In step (2), the ratio of pretreated lignite powder to catalyst is 1g:0.2-0.5g.

6. The method for preparing highly active humic acid according to claim 1, characterized in that, In step (4), the mass ratio of oxidized lignite, alkaline solution, and accelerator is 1:50-60:3-6; the alkaline solution is prepared by mixing 2% NaOH solution and 5% Na2SO3 solution in equal proportions; the water bath temperature is 70-80℃.

7. A highly active humic acid prepared by the method according to any one of claims 1-6 for the production of potassium fulvate.

Images