Preparation method of high-activity humic acid and application of high-activity humic acid in production of potassium fulvate

Abstract

The invention discloses a preparation method of high-activity humic acid and application of the high-activity humic acid in potassium fulvate production, and belongs to the technical field of humic acid preparation methods. The method is divided into five steps to extract humic acid in lignite, extraction conditions are optimized, the optimal ratio of a catalyst to an oxidizing agent to an accelerant is selected to improve the extraction rate of the humic acid, the obtained humic acid is rich in oxygen-containing functional groups such as acid groups, phenolic hydroxyl groups and carboxyl groups, and the types and contents of the functional groups directly influence the activity of the humic acid. The activity of the prepared humic acid is obviously higher than that of commercialized humic acid, and the prepared humic acid has better application prospects in the fields of agriculture, medicine, environmental protection and the like. Meanwhile, the molecular weight of the humic acid prepared by the method is small, and the humic acid can more easily enter plant cells to influence plant metabolism when being used for fertilizers, so that the growth of plants is better promoted.

Description

Technical Field

[0001] The present invention belongs to the technical field of humic acid preparation methods, and particularly relates to a preparation method of highly active humic acid and its application in the production of potassium humate. Background Art

[0002] With the transformation of the agricultural development mode, the development of green and efficient new fertilizers is a major requirement for ensuring the ecological safety of farmland and the quality safety of agricultural products in China. Humic acid is a heterogeneous high-molecular polymer with an aromatic ring and an aliphatic chain as the basic structure, and has acidity, hydrophilicity, interfacial activity, cation exchange, complexation and adsorption capabilities. Humic acid contains a large amount of organic matter and various active functional groups, can improve soil structure, enhance the water and fertilizer retention capacity of the soil, promote plant growth and development, and enhance the stress resistance of crops. Humic acid has become the main active ingredient of soil conditioners, plant 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 natural high-molecular polymer rich in various active functional groups formed by organic substances such as animal and plant residues under the action of physical chemistry and microorganisms, and is widely present in soil, water, peat and coal. Among them, the average concentration of soil humic acid is less than one percent, but the total amount is the largest; the total amount and content of water humic acid are relatively low, and it is almost impossible to develop and utilize; mineral humic acid mainly exists in peat, weathered coal and lignite, with the richest content, and most commercial humic acids are mineral-source humic acids. China's mineral resources are rich in reserves and widely distributed. According to statistics, China's coal reserves are about 2.10×10 11 tons or more, the total peat reserves are about 12.48 billion tons, the retained amount of weathered coal is 100 billion tons, and the proven lignite reserves are 130 billion tons. The content of renewable humic acid in these mineral sources varies greatly, generally between 5% and 80%.

[0004] At present, the preparation technologies of humic acid mainly include two categories: (1) directly extracting from mineral resources such as lignite and weathered coal through pretreatment technologies, and the commonly used pretreatment technology is the oxidation preparation method; (2) under artificially regulated conditions, using industrial and agricultural organic waste as raw materials to prepare, and the commonly used preparation methods are the wet method and the solid-state fermentation method. The existing commercial humic acid is mainly obtained by chemical methods from peat, lignite and weathered coal, belonging to mineral humic acid. Most of the mineral humic acid has low biological activity, and has a relatively high molecular weight, fewer chelating and hydrophilic groups, and it is difficult to be decomposed and utilized by soil microorganisms in a short time. Therefore, mineral humic acid must be extracted, activated and then utilized to exert its maximum application value. The commonly used activation methods at present mainly include: (1) extraction, alkali dissolution and acid precipitation method; (2) mechanical activation to reduce the particle size of weathered coal or lignite; (3) ultrasonic activation; (4) oxidation, and the oxidation methods mainly include nitric acid and hydrogen peroxide oxidation, as well as non-catalytic oxidation of air under high temperature and high pressure, air dry oxidation, alkali-air oxidation method, O2-O3 oxidation method, etc. The extraction method, mechanical activation and ultrasonic activation method cannot significantly improve the activity of humic acid, and the oxidation process of the oxidation method is relatively cumbersome, which is not conducive to industrial production. Therefore, how to provide a new process and new method to prepare high-activity humic acid has become a technical problem to be solved urgently. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method of high-activity humic acid. This method has a high extraction rate of humic acid in lignite, and the obtained humic acid is rich in a large number of oxygen-containing functional groups such as acidic groups, phenolic hydroxyl groups, carboxyl groups, etc. The type and content of functional groups directly affect the activity of humic acid, and the prepared humic acid has significantly higher activity than commercially available humic acid, and has better application prospects in many fields such as agriculture, medicine, and environmental protection. At the same time, the humic acid prepared by the method of the present invention has a relatively small molecular weight, and is more likely to enter plant cells and affect plant metabolism when used as a fertilizer, thereby promoting the growth of plants.

[0006] To achieve the above technical purpose, the technical solution adopted by the present invention is as follows: A preparation method of high-activity humic acid, which comprises the following steps: (1) Take the raw lignite, clean it, dry it, and then crush it to coal particles with a particle size less than 0.2 mm. Add 10% HCl to the coal particles according to a fixed solid-liquid ratio, stir at a high speed in a water bath at 80 °C for 100 min, vacuum filter and wash until neutral, dry the filter cake and then grind it, and pass through a 200-mesh sieve to obtain pretreated lignite powder; (2) Take the pretreated lignite powder and the catalyst, mix them according to the mass ratio, and then mechanically ball-mill at a speed of 100-120 r / min for 30-45 min to obtain mixture A; (3) Mix mixture A with an oxidant, keep it in a constant-temperature water bath, stir and react for 1 h, then perform vacuum filtration and wash it several times with absolute ethanol. The filter cake is dried to obtain oxidized lignite; (4) Mix oxidized lignite, an alkali solution, and a promoter according to a mass ratio, heat and react in a constant-temperature water bath for 60 - 90 min, then cool and perform solid-liquid separation, and take the filtrate for standby; (5) Add a hydrochloric acid solution to the filtrate obtained above, adjust the pH to 1 - 2, then let it stand for 24 h, perform centrifugal separation to obtain the solid, and obtain highly active humic acid after vacuum drying; The catalyst is Ce-S modified biochar; the promoter is composed of polyethylene glycol and sodium N-methyl-N-coconut oil taurate according to a mass ratio of 1:2.

[0007] Preferably, the Ce-S modified biochar is prepared by the following method: (a) Add Ce(NO3)2·6H2O, dimethyl sulfoxide, and walnut shell powder to a methanol solvent, stir and react at 180 °C for 24 h, cool to room temperature, wash the product 3 - 5 times with methanol, and then dry it to obtain a solid powder; (b) Transfer the solid powder into a tubular furnace, under a nitrogen atmosphere, calcine at a high temperature for 4 h, and then cool to room temperature to obtain Ce-S modified biochar.

[0008] Preferably, in step (a), the dosage ratio of Ce(NO3)2·6H2O, dimethyl sulfoxide, walnut shell powder, and methanol solvent is 1 mmol:5 ml:5 g:50 ml.

[0009] 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 h.

[0010] Preferably, in step (1), the material ratio of lignite particles to 10% HCl is 1 g:10 ml.

[0011] Preferably, in step (2), the dosage ratio of pretreated lignite powder and the catalyst is 1 g:0.2 - 0.5 g.

[0012] Preferably, in step (3), the oxidant is composed of 30% hydrogen peroxide and a 0.5 mol / L sodium persulfate solution according to a mass ratio of 1:0.2 - 0.5; the mass ratio of mixture A to the oxidant is 1:0.7 - 0.8; the water bath temperature is 80 - 90 °C.

[0013] Preferably, in step (4), the mass ratio of oxidized lignite, alkali solution, and promoter is 1:50 - 60:3 - 6; the alkali solution is prepared by mixing 2% NaOH solution and 5% Na2SO3 solution in equal proportions; the water bath temperature is 70 - 80 °C.

[0014] The highly active humic acid prepared by the above method of the present invention is used in the production of potassium fulvate, and a potassium fulvate fertilizer with good biocompatibility, environmental friendliness and versatility can be obtained.

[0015] The beneficial effects of the present invention are as follows: (1) In the present invention, nitric cerium and dimethyl sulfoxide are used for co-modifying walnut shell biochar to obtain a modified biochar doped with both Ce and S elements as a catalyst. For the biochar modified by co-doping of rare earth metal and non-metal elements, due to the large atomic radius of sulfur atoms, the structural defects of the material can be increased, resulting in a significant increase in specific surface area and porosity. The S-Ce in the biochar changes the electronic structure of the biochar, improves the electron transfer ability, and enhances the oxidation catalytic activity. The enhancement of this activity helps to accelerate the decomposition and release of humic acid in lignite, thereby increasing the extraction rate.

[0016] (2) The oxidant of the present invention is composed of 30% hydrogen peroxide and a small amount of sodium persulfate. After the two are compounded and used together with the catalyst prepared by the present invention, the synergistic effect is good, which promotes the deep oxygenolysis of lignite. The absorbance ratio of the prepared humic acid becomes larger compared with that of commercial humic acid, the molecular weight of the product becomes smaller, and the activity is higher, which is more beneficial for plant absorption and utilization in agricultural production.

[0017] (3) The present invention adopts a promoter component, which can promote the more uniform penetration of the oxidant and the catalyst into lignite particles, so that they can fully contact and react with lignite, thereby improving the extraction efficiency of humic acid. The biochar doped with Ce-S as a catalyst can provide active sites during the reaction process to accelerate the decomposition of the oxidant and the release of humic acid in lignite. The addition of the promoter can further optimize the reaction conditions and improve the activity of the catalyst, thereby realizing a more efficient and environmentally friendly extraction of humic acid.

[0018] (4) The combination of the catalyst and the 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 the conventional humic acid preparation method, avoiding the generation of nitrogen oxide gases, reducing environmental pollution, and more meeting the requirements of contemporary green environmental protection. Description of the Drawings

[0019] Figure 1 It is the scanning electron microscope images of the Ce-S modified biochar used as the catalyst of the present invention before and after doping Ce-S, where a is before doping and b is after doping; Figure 2 It is the result diagram of the influence of the dosage of different catalysts on the extraction rate of highly active humic acid by the method of the present invention. Detailed Embodiments

[0020] The technical solution of the present invention will be further described below in conjunction with specific embodiments, but not limited thereto.

[0021] Example 1 A preparation method of highly active humic acid, which comprises the following steps: (1) Take the raw lignite, clean it, dry it, and then crush it to particles with a particle size less than 0.2 mm to obtain lignite particles. Add 500 ml of 10% HCl to 100 g of lignite particles for pickling, stir at high speed in a water bath at 80 °C for 100 min, vacuum filter and wash until neutral, dry the filter cake and then grind it, and pass through a 200-mesh sieve to obtain pretreated lignite powder; (2) Mix 5 g of the pretreated lignite powder with 1 g of the catalyst and mechanically ball-mill at a speed of 100 - 120 r / min for 30 - 45 min to obtain mixture A; the catalyst is Ce-S modified biochar; (3) Mix mixture A with the oxidant in a mass ratio of 1:0.7, in a water bath at 80 - 90 °C, stir and react for 1 h, then vacuum filter and wash several times with absolute ethanol, and dry the filter cake to obtain oxidized lignite; the oxidant is composed of 30% hydrogen peroxide and a 0.5 mol / L sodium persulfate solution in a mass ratio of 1:0.2; (4) Mix the oxidized lignite with the alkali solution and the promoter in a mass ratio of 1:50:3, heat and react in a constant temperature water bath at 70 - 80 °C for 60 - 90 min, then cool and separate the solid and liquid, and take the filtrate for standby; the promoter is composed of polyethylene glycol and N-coconut oil acyl-N-methyl taurine sodium in a mass ratio of 1:2; the alkali solution is prepared by mixing 2% NaOH solution and 5% Na2SO3 solution in equal proportion; (5) Add hydrochloric acid solution to the obtained filtrate above, adjust the pH to 1, then let it stand for 24 h, centrifuge to separate the solid, and vacuum dry to obtain highly active humic acid.

[0022] The Ce-S modified biochar is prepared by the following method: (a) Add Ce(NO3)2·6H2O, dimethyl sulfoxide and walnut shell powder to methanol solvent, stir and react at 180 °C for 24 h, cool to room temperature, wash the product with methanol 3 - 5 times and then dry to obtain solid powder; the dosage ratio of Ce(NO3)2·6H2O, dimethyl sulfoxide, walnut shell powder, and methanol solvent is 1 mmol:5 ml:5 g:50 ml; (b) Transfer the solid powder into a tubular furnace, under a nitrogen atmosphere, heat it to 700 °C at a rate of 3 °C / min, calcine for 4 h, and cool to room temperature to obtain Ce-S modified biochar.

[0023] Example 2 A preparation method of highly active humic acid, which comprises the following steps: (1) Take the raw lignite, clean it, dry it, and then crush it to a particle size less than 0.2 mm to obtain lignite particles. Add 500 ml of 10% HCl to 100 g of lignite particles for acid washing. Stir at a high speed in a water bath at 80 °C for 100 min, and then perform vacuum filtration and washing until neutral. After drying the filter cake, grind it and pass through a 200-mesh sieve to obtain pretreated lignite powder; (2) Take 5 g of pretreated lignite powder and mix it with 2.5 g of catalyst, and then mechanically ball mill it at a speed of 100 - 120 r / min for 30 - 45 min to obtain mixture A; the catalyst is Ce-S modified biochar; (3) Mix mixture A with the oxidant according to a mass ratio of 1:0.8. In a water bath at 80 - 90 °C, stir and react for 1 h, then perform vacuum filtration and wash it several times with absolute 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 according to a mass ratio of 1:0.5; (4) Mix the oxidized lignite with the alkali solution and the promoter according to a mass ratio of 1:60:6. Heat and react in a constant temperature water bath at 70 - 80 °C for 60 - 90 min, then cool and separate the solid and liquid. Take the filtrate for use; the promoter is composed of polyethylene glycol and N-coconut oil acyl-N-methyl taurine sodium salt according to a mass ratio of 1:2; the alkali solution is prepared by mixing 2% NaOH solution and 5% Na2SO3 solution in equal proportions; (5) Add hydrochloric acid solution to the above-obtained filtrate, adjust the pH to 2, then let it stand for 24 h, centrifuge to separate the solid, and vacuum dry it to obtain highly active humic acid.

[0024] The Ce-S modified biochar is prepared by the following method: (a) Add Ce(NO3)2·6H2O, dimethyl sulfoxide, and walnut shell powder to a methanol solvent, stir and react at 180 °C for 24 h, cool to room temperature, and wash the product 3 - 5 times with methanol and then dry it to obtain a solid powder; the dosage ratio of Ce(NO3)2·6H2O, dimethyl sulfoxide, walnut shell powder, and methanol solvent is 1 mmol:5 ml:5 g:50 ml; (b) Transfer the solid powder into a tubular furnace. Under a nitrogen atmosphere, heat it to 700 °C at a rate of 3 °C / min, calcine for 4 h, and cool to room temperature to obtain Ce-S modified biochar.

[0025] Example 3 A preparation method of highly active humic acid, which includes the following steps: (1)Take the raw lignite, clean it, dry it, and then crush it to a particle size less than 0.2 mm to obtain lignite particles. Add 500 ml of 10% HCl to 100 g of lignite particles for pickling. Stir at high speed in a water bath at 80 °C for 100 min, vacuum filter and wash until neutral. After drying the filter cake, grind it and pass through a 200-mesh sieve to obtain pretreated lignite powder; (2)Take 5 g of pretreated lignite powder and mix it with 2.0 g of catalyst, and then mechanically ball mill at a speed of 100 - 120 r / min for 30 - 45 min to obtain mixture A; the catalyst is Ce-S modified biochar; (3)Mix mixture A with the oxidant according to a mass ratio of 1:0.75. In a water bath at 80 - 90 °C, stir and react for 1 h, then vacuum filter and wash several times with absolute 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 according to a mass ratio of 1:0.4; (4)Mix oxidized lignite with the alkali solution and the promoter according to a mass ratio of 1:55:5. Heat and react in a constant temperature water bath at 70 - 80 °C for 60 - 90 min, then cool and separate the solid and liquid. Take the filtrate for use; the promoter is composed of polyethylene glycol and sodium N-cocoyl-N-methyl taurate according to a mass ratio of 1:2; the alkali solution is prepared by mixing 2% NaOH solution and 5% Na2SO3 solution in equal proportions; (5)Add hydrochloric acid solution to the filtrate obtained above, adjust the pH to 1.5, then let it stand for 24 h, centrifuge to separate the solid, and vacuum dry to obtain highly active humic acid.

[0026] The Ce-S modified biochar is prepared by the following method: (a)Add Ce(NO3)2·6H2O, dimethyl sulfoxide, and walnut shell powder to methanol solvent, stir and react at 180 °C for 24 h, cool to room temperature, and wash the product 3 - 5 times with methanol and then dry to obtain a solid powder; the dosage ratio of Ce(NO3)2·6H2O, dimethyl sulfoxide, walnut shell powder, and methanol solvent is 1 mmol:5 ml:5 g:50 ml; (b)Transfer the solid powder into a tubular furnace, under a nitrogen atmosphere, heat it to 700 °C at a rate of 3 °C / min, calcine for 4 h, and cool to room temperature to obtain Ce-S modified biochar.

[0027] Comparative Example 1 A preparation method of highly active humic acid, which includes the following steps: (1)Clean the raw lignite, dry it, and then crush it to particles with a particle size less than 0.2 mm to obtain lignite particles. Add 500 ml of 10% HCl to 100 g of lignite particles for acid washing. Stir at high speed in a water bath at 80 °C for 100 min, perform vacuum filtration and washing until neutral. Dry the filter cake and then grind it. Pass through a 200-mesh sieve to obtain pretreated lignite powder; (2)Take 5 g of the pretreated lignite powder and mix it with the oxidant in a mass ratio of 1:0.75. In a water bath at 80 - 90 °C, stir and react for 1 h, then perform vacuum filtration and wash several times with absolute 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 in a mass ratio of 1:0.4; (3)Mix the oxidized lignite with the alkali solution and the promoter in a mass ratio of 1:55:5. Heat and react in a constant temperature water bath at 70 - 80 °C for 60 - 90 min, then cool and separate the solid and liquid. Take the filtrate for use; The promoter is composed of polyethylene glycol and sodium N-cocoyl-N-methyl taurate in a mass ratio of 1:2; The alkali solution is prepared by mixing 2% NaOH solution and 5% Na2SO3 solution in equal proportions; (4)Add hydrochloric acid solution to the filtrate obtained above, adjust the pH to 1.5, then let it stand for 24 h, centrifuge to separate the solid, and vacuum dry to obtain high-activity humic acid.

[0028] The preparation method of this comparative example is basically the same as that of Example 3, and the only difference is that it does not contain a catalyst component.

[0029] Comparative Example 2 A preparation method of high-activity humic acid, which includes the following steps: (1)Clean the raw lignite, dry it, and then crush it to particles with a particle size less than 0.2 mm to obtain lignite particles. Add 500 ml of 10% HCl to 100 g of lignite particles for acid washing. Stir at high speed in a water bath at 80 °C for 100 min, perform vacuum filtration and washing until neutral. Dry the filter cake and then grind it. Pass through a 200-mesh sieve to obtain pretreated lignite powder; (2)Take 5 g of the pretreated lignite powder and mix it with 2.0 g of the catalyst, and then mechanically ball mill at a speed of 100 - 120 r / min for 30 - 45 min to obtain mixture A; The catalyst is biochar; (3)Mix mixture A with the oxidant in a mass ratio of 1:0.75. In a water bath at 80 - 90 °C, stir and react for 1 h, then perform vacuum filtration and wash several times with absolute 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 in a mass ratio of 1:0.4; (4) Mix oxidized lignite with an alkali solution and a promoter at a mass ratio of 1:55:5. After heating and reacting in a constant temperature water bath at 70 - 80 °C for 60 - 90 min, cool and then separate the solid and liquid. Take the filtrate for standby. The promoter is composed of polyethylene glycol and sodium N-methyl-N-coconut oil taurate at a mass ratio of 1:2. The alkali solution is prepared by mixing 2% NaOH solution and 5% Na2SO3 solution in equal proportions. (5) Add hydrochloric acid solution to the filtrate obtained above, adjust the pH to 1.5, then let it stand for 24 h, centrifuge to separate the solid, and obtain high-activity humic acid after vacuum drying.

[0030] The biochar is prepared by the following method: Put walnut shell powder into a tubular furnace. Under a nitrogen atmosphere, heat it to 700 °C at a rate of 3 °C / min, calcine for 4 h, and cool to room temperature to obtain biochar.

[0031] The preparation method of this comparative example is basically the same as that of Example 3. The only difference is that the catalyst is only biochar and no modification treatment is carried out.

[0032] Comparative Example 3 A preparation method of high-activity humic acid, which includes the following steps: (1) Take the raw lignite, clean it, dry it, and then crush it to particles with a particle size less than 0.2 mm to obtain lignite particles. Add 500 ml of 10% HCl to 100 g of lignite particles for acid washing. Stir at a high speed in a water bath at 80 °C for 100 min, vacuum filter and wash until neutral. Dry the filter cake and then grind it, and pass through a 200-mesh sieve to obtain pretreated lignite powder. (2) Mix 5 g of pretreated lignite powder with 2.0 g of catalyst and then mechanically ball mill at a speed of 100 - 120 r / min for 30 - 45 min to obtain mixture A. The catalyst is Ce-S modified biochar. (3) Mix mixture A with an oxidant at a mass ratio of 1:0.75. In a water bath at 80 - 90 °C, stir and react for 1 h, then 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 0.5 mol / L sodium persulfate solution at a mass ratio of 1:0.4. (4) Mix oxidized lignite with an alkali solution at a mass ratio of 1:55. After heating and reacting in a constant temperature water bath at 70 - 80 °C for 60 - 90 min, cool and then separate the solid and liquid. Take the filtrate for standby. The alkali solution is prepared by mixing 2% NaOH solution and 5% Na2SO3 solution in equal proportions. (5) Add hydrochloric acid solution to the filtrate obtained above, adjust the pH to 1.5, then let it stand for 24 h, centrifuge to separate the solid, and obtain high-activity humic acid after vacuum drying.

[0033] The Ce-S modified biochar is prepared by the following method: (a) Add Ce(NO3)2·6H2O, dimethyl sulfoxide and walnut shell powder into a methanol solvent, stir and react at 180 °C for 24 h, cool to room temperature, wash the product with methanol 3-5 times and then dry to obtain a solid powder; the dosage ratio of Ce(NO3)2·6H2O, dimethyl sulfoxide, walnut shell powder and methanol solvent is 1 mmol: 5 ml: 5 g: 50 ml; (b) Transfer the solid powder into a tube furnace, under a nitrogen atmosphere, heat it to 700 °C at a rate of 3 °C / min, calcine for 4 h, and cool to room temperature to obtain the Ce-S modified biochar.

[0034] The preparation method of this comparative example is basically the same as that of Example 3, the only difference being that: it does not contain a promoter component.

[0035] Comparative Example 4 A preparation method of highly active humic acid, which comprises the following steps: (1) Take the raw lignite, clean, dry and crush it to lignite particles with a particle size less than 0.2 mm, add 500 ml of 10% HCl to 100 g of lignite particles for pickling, stir at a high speed in an 80 °C water bath for 100 min, vacuum filter and wash until neutral, dry the filter cake and then grind it, and pass through a 200-mesh sieve to obtain pretreated lignite powder; (2) Mix 5 g of pretreated lignite powder with 2.0 g of a catalyst and mechanically ball mill at a speed of 100-120 r / min for 30-45 min to obtain mixture A; the catalyst is Ce-S modified biochar; (3) Mix mixture A with an oxidant according to a mass ratio of 1:0.75, in an 80-90 °C water bath, stir and react for 1 h, then vacuum filter and wash several times with absolute ethanol, and dry the filter cake to obtain oxidized lignite; the oxidant is 30% hydrogen peroxide; (4) Mix the oxidized lignite with an alkali solution and a promoter according to a mass ratio of 1:55:5, heat and react in a 70-80 °C constant temperature water bath for 60-90 min, cool and then separate the solid and liquid, and take the filtrate for standby; the promoter is composed of polyethylene glycol and N-coconut oil acyl-N-methyl taurine sodium in a mass ratio of 1:2; the alkali solution is prepared by mixing 2% NaOH solution and 5% Na2SO3 solution in equal proportions; (5) Add a hydrochloric acid solution to the filtrate obtained above, adjust the pH to 1.5, then stand for 24 h, centrifuge to separate and take the solid, and vacuum dry to obtain highly active humic acid.

[0036] The Ce-S modified biochar is prepared by the following method: (a) Ce(NO3)2·6H2O, dimethyl sulfoxide and walnut shell powder were added to a methanol solvent, and stirred at 180 °C for 24 h, then cooled to room temperature. The product was washed with methanol 3-5 times and dried to obtain a solid powder. The dosage ratio of Ce(NO3)2·6H2O, dimethyl sulfoxide, walnut shell powder and methanol solvent was 1 mmol: 5 ml: 5 g: 50 ml; (b) The solid powder was transferred into a tube furnace. Under a nitrogen atmosphere, it was heated to 700 °C at a rate of 3 °C / min and calcined for 4 h, then cooled to room temperature to obtain Ce-S modified biochar.

[0037] The preparation method of this comparative example was basically the same as that of Example 3, the only difference being that the oxidant consisted only of 30% hydrogen peroxide.

[0038] Comparative Example 5 A preparation method of highly active humic acid, which comprises the following steps: (1) The raw lignite was cleaned, dried and crushed to lignite particles with a particle size less than 0.2 mm. 500 ml of 10% HCl was added to 100 g of lignite particles for pickling. It was stirred at a high speed in a water bath at 80 °C for 100 min, vacuum filtered and washed until neutral. The filter cake was dried and ground, and passed through a 200-mesh sieve to obtain pretreated lignite powder; (2) 5 g of pretreated lignite powder was mixed with 2.0 g of catalyst and mechanically ball milled at a speed of 100-120 r / min for 30-45 min to obtain mixture A. The catalyst was Ce-S modified biochar; (3) Mixture A was mixed with the oxidant in a mass ratio of 1:0.75, and reacted in a water bath at 80-90 °C with stirring for 1 h. Then it was vacuum filtered and washed several times with absolute ethanol. The filter cake was dried to obtain oxidized lignite. The oxidant was a 0.5 mol / L sodium persulfate solution; (4) The oxidized lignite was mixed with an alkali solution and a promoter in a mass ratio of 1:55:5, and heated and reacted in a constant temperature water bath at 70-80 °C for 60-90 min. After cooling, solid-liquid separation was carried out, and the filtrate was taken for standby. The promoter was composed of polyethylene glycol and N-coconut oil acyl-N-methyl taurine sodium in a mass ratio of 1:2. The alkali solution was prepared by mixing 2% NaOH solution and 5% Na2SO3 solution in equal proportions; (5) Hydrochloric acid solution was added to the filtrate obtained above to adjust the pH to 1.5, then it was left standing for 24 h, centrifuged to separate the solid, and vacuum dried to obtain highly active humic acid.

[0039] The Ce-S modified biochar was prepared by the following method: (a) Ce(NO3)2·6H2O, dimethyl sulfoxide, and walnut shell powder were added to a methanol solvent, and the mixture was stirred and reacted 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 dosage ratio of Ce(NO3)2·6H2O, dimethyl sulfoxide, walnut shell powder, and methanol solvent was 1 mmol: 5 ml: 5 g: 50 ml; (b) The solid powder was transferred into a tubular furnace. Under a nitrogen atmosphere, the temperature was raised to 700 °C at a rate of 3 °C / min and calcined for 4 h. After cooling to room temperature, Ce-S modified biochar was obtained.

[0040] The preparation method of this comparative example was basically the same as that of Example 3, and the only difference was that the oxidant was only a 0.5 mol / L sodium persulfate solution.

[0041] Test Example 1 The Ce-S modified biochar used in the present invention was observed by scanning electron microscopy, and the results were as Figure 1 shown. The results showed that the walnut shell powder obtained a porous structure after high-temperature calcination. After doping with two elements of Ce and S, many tiny particles were dispersed on the surface of the biochar, indicating that the metal element Ce and the non-metal element S had been successfully doped into the biochar structure, which could increase more catalytic active sites.

[0042] Test Example 2 Determination of the content of active groups: The contents of total acidic groups, carboxyl groups, phenolic hydroxyl groups, and E4 / E6 values in the highly active humic acid prepared in Examples 1 - 3 and Comparative Examples 1 - 5 and the commercially available mineralized humic acid products were determined. The total acidic groups were determined by potentiometric titration with barium chloride precipitation after alkaline dissolution; the carboxyl groups were determined by the calcium acetate method with acid precipitation after alkaline dissolution; phenolic hydroxyl groups (by difference method): phenolic hydroxyl groups = total acidic groups - carboxyl groups; E4 / E6 value: the ratio of absorbance at 465 nm and 665 nm. The experimental results are shown in Table 1.

[0043] Table 1 Test results As can be seen from the content of Table 1 above, the total acidic group content of the highly active humic acid prepared in the examples of the present invention is significantly higher than that of the commercially available products, and is also higher than that of the humic acids obtained in Comparative Examples 1-5. This shows 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 in the present invention is also significantly higher than that of the comparative examples and commercially available products. And E4 / E6 is a measure of the degree of aromatic ring condensation, which is negatively correlated with the molecular weight of humic acid. The larger the ratio, the smaller the molecular weight and the lower the degree of condensation. From the above data, it can be seen that the molecular weight of the active molecules of the highly active humic acid prepared by the method of the present invention is relatively small. This is mainly because under the synergistic action of the catalyst, oxidant, and promoter in the present invention, the lignite undergoes a deep oxidation degradation reaction, releasing a large amount of heat. The lactone ring of humic acid breaks during high-temperature oxidation, and the carboxyl group increases; at the same time, the lactone ring is oxidized and broken to cause demethylation, and the carboxyl group content increases; in addition, the alkyl and aldehyde groups on humic acid may undergo an oxidation reaction with dissolved oxygen to form carboxyl groups, resulting in a significant increase in carboxyl groups, and then leading to an increase in the total acidic groups. The carbon chain breaks, and the opening of the lactone structure reduces the molecular weight of humic acid and increases the E4 / E6 value. When the product obtained in the present invention is used in the production and application of agricultural fertilizers such as potassium humate, small molecule substances will be more easily absorbed and utilized by crops. And changing the raw materials and dosages in any step of the present invention will cause the achieved effects to disappear or weaken.

[0044] Test Example 3 Determination of humic acid extraction rate Calculate the extraction rates of the humic acid products prepared in Examples 1-3 and Comparative Examples 1-5 respectively. The humic acid extraction rate = mass of humic acid finished product / mass of raw lignite × 100%. The specific results are shown in Table 2.

[0045] Table 2 Results of humic acid extraction rate As can be seen from the results of Table 2 above, the humic acid extraction rate of the examples 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 dosage of any one of the raw materials will cause the corresponding effect to weaken or disappear.

[0046] The present invention also studied the influence of the dosage of the catalyst on the extraction rate of the highly active humic acid in the method of the present invention. Specifically, the extraction rate of the highly active humic acid was tested by changing the mass ratio of the pretreated lignite powder to the catalyst. The specific results are as Figure 2 shown. From Figure 2It can be seen that the amount of catalyst has a very obvious effect on highly active humic acid. Within the mass ratio range of the present 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 instead. Therefore, the proportion of the amount of catalyst selected in the present invention is the optimal test parameter.

[0047] After preparing the potassium humate fertilizer by using the highly active humic acid prepared by the method of the present invention and conventional potassium fertilizers and accessories, and applying it to crop planting, the yield increase effect is remarkable. Compared with the potassium humate fertilizer prepared by conventional commercially available mineral humic acid, the crop yield increases by 15-25%. This shows that the highly active humic acid prepared by the present invention has good application prospects.

[0048] It should be noted that the above-mentioned embodiments are only some of the embodiments of the preferred implementation modes of the present invention, rather than all embodiments. Obviously, based on the above-mentioned embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Claims

1. A method for preparing highly active humic acid, characterized in that: It includes the following steps: (1) Wash and dry the raw lignite, crush it to a particle size of less than 0.2 mm, 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°C for 100 min, vacuum filter and wash until neutral, dry the filter cake, grind it, and pass it through a 200-mesh sieve to obtain pretreated lignite powder; (2) Pretreated lignite powder and catalyst were mixed according to the mass ratio and mechanically ball-milled at a speed of 100-120 r / min for 30-45 min to obtain a mixture A; (3) Mixing mixture A with an oxidant, placing in a constant temperature water bath, stirring for 1 hour, vacuum filtering and washing with anhydrous ethanol for several times, and drying the filter cake to obtain oxidized lignite; (4) Mix the oxidized lignite with the alkaline solution and the accelerator in a certain mass ratio, heat in a constant temperature water bath for 60-90 minutes, cool and separate the solid and liquid, and take the filtrate for later use; (5) Add hydrochloric acid solution to the filtrate obtained above to adjust the pH to 1-2, then let it 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 polyethylene glycol and sodium N-coconut oil acyl-N-methyl taurate in a mass ratio of 1:

2.

2. The method for preparing highly active humic acid according to claim 1, characterized in that: The Ce-S modified biochar is prepared by the following method: (a) Ce(NO3)2·6H2O, dimethyl sulfoxide and walnut shell powder were added to a methanol solvent, stirred and reacted at 180°C for 24 hours, cooled to room temperature, and the product was washed with methanol for 3-5 times and then dried to obtain a solid powder; (b) The solid powder was transferred into a tubular furnace and calcined at high temperature for 4 h under a nitrogen atmosphere and then cooled to room temperature to obtain Ce-S modified biochar.

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

4. The method for preparing highly active humic acid according to claim 2, characterized in that: The specific heating method in the tubular furnace in step (b) is to heat to 700° C. at a rate of 3° C. / min and calcine for 4 hours.

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

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

7. The method for preparing highly active humic acid according to claim 1, characterized in that: In the 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 the mixture A to the oxidant is 1:0.7-0.8; and the water bath temperature is 80-90°C.

8. The method for preparing highly active humic acid according to claim 1, characterized in that: In the 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°C.

9. Highly active humic acid prepared according to the method according to any one of claims 1 to 8 is used in the production of potassium fulvic acid.

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