Humic acid biostimulant and preparation method thereof

Abstract

The invention belongs to the technical field of biostimulants, and discloses a humic acid biostimulant and a preparation method thereof. Comprising the following steps: crushing weathered coal, adding the crushed weathered coal into a sodium hydroxide solution for activating treatment, and then carrying out solid-liquid separation to obtain an activating solution; concentrating and purifying the activated solution through an ultrafiltration membrane to obtain a humic acid concentrated solution; adding urea, potassium sulfate, monopotassium phosphate, magnesium sulfate and zinc sulfate into the humic acid concentrated solution, uniformly stirring and mixing, and then performing spray granulation to obtain the humic acid biostimulant. According to the method, a special ultrafiltration membrane is used for concentration and purification, so that the loss of effective components of humic acid is effectively reduced, and high purity and high quality of the product are ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of biostimulants, and particularly relates to a humic acid biostimulant and a preparation method thereof. Background Art

[0004] With the continuous enhancement of people's awareness of agricultural sustainable development and ecological environment protection, the research and development of new green, efficient, and environmentally friendly fertilizers have become an urgent need in the agricultural field. As a new type of agricultural input, biostimulants have received extensive attention in agricultural production in recent years. Biostimulants are not fertilizers in the traditional sense. They do not contain the major elements required for crop growth, but can have a positive impact on the growth and development of crops through various ways. It can activate the physiological and biochemical processes of plants themselves, enhance the absorption and utilization efficiency of nutrients by plants, and improve the stress resistance of plants, such as drought resistance, cold resistance, and disease resistance, thereby promoting the healthy growth of crops, reducing the use amount of chemical fertilizers, and ensuring the yield and quality of agricultural crops.

[0005] As an important source of biostimulants, humic acid widely exists in substances such as soil, peat, lignite, and weathered coal. Humic acid has a unique chemical structure and physical properties, which can improve the soil structure, promote the formation of soil aggregates, increase soil porosity, improve soil aeration and water permeability, and create a good soil environment for crop root growth. At the same time, humic acid can also complex and chelate with the nutrients in fertilizers, reduce the fixation and loss of nutrients, improve fertilizer utilization efficiency, and promote the absorption of nutrients by crops. In addition, humic acid also contains various bioactive substances, which can stimulate the growth and development of crops and enhance the stress resistance of crops.

[0006] However, the activity of natural humic acid is often low, making it difficult to fully exert its potential in agricultural production. Therefore, it is usually necessary to activate natural humic acid. In terms of separation treatment, the existing technology often uses centrifugal precipitation separation method, but this method is prone to introducing impurities and the precipitation is incomplete. In terms of purification, the ion exchange resin method has a high cost and the resin regeneration is difficult; the acid treatment method will cause certain damage to the structure of humic acid. In the concentration process, the common evaporation concentration method has high energy consumption, and the effective components of humic acid are easily decomposed at high temperatures. Summary of the Invention

[0007] In order to solve the above technical problems, the present invention proposes a humic acid biostimulant and a preparation method thereof. The present invention uses a special ultrafiltration membrane for concentration and purification, effectively reducing the loss of the effective components of humic acid and ensuring the high purity and high quality of the product.

[0008] In order to achieve the above invention purpose, the present invention adopts the following technical solutions: A preparation method of a humic acid biostimulant, comprising the following steps: S1. Crush weathered coal, add the crushed weathered coal to a sodium hydroxide solution for activation treatment, and then perform solid-liquid separation to obtain an activation solution. S2. Concentrate and purify the activation solution through an ultrafiltration membrane to obtain a humic acid concentrate. S3. Add urea, potassium sulfate, potassium dihydrogen phosphate, magnesium sulfate, and zinc sulfate to the humic acid concentrate, stir and mix evenly, and then perform spray granulation to obtain a humic acid biostimulant.

[0009] In the technical solution of the present invention, first crushing the weathered coal and then activating it with a sodium hydroxide solution can fully release the humic acid in the weathered coal, and the subsequent solid-liquid separation operation is simple and efficient, ensuring that the obtained activation solution has a low impurity content, laying a foundation for the subsequent preparation of high-quality humic acid biostimulant.

[0010] In the concentration and purification step, compared with the traditional method, the present invention has significant advantages in concentrating and purifying humic acid by using an ultrafiltration membrane. In the separation process, the disadvantages of the precipitation method, such as easy introduction of impurities and incomplete precipitation, are abandoned. The ultrafiltration membrane can accurately separate humic acid from other impurities, ensuring a higher product purity. In the purification stage, compared with the problems of high cost, difficult resin regeneration of the ion exchange resin method and the damage to the humic acid structure by the acid treatment method, the ultrafiltration membrane technology purifies under mild conditions, not only effectively reducing costs, but also maintaining the original structure and activity of humic acid to the greatest extent, ensuring product quality. And in the concentration process, overcoming the defects of high energy consumption of the evaporation concentration method and easy decomposition of the effective components of humic acid at high temperature, the ultrafiltration membrane concentration has low energy consumption and operates at room temperature, avoiding the loss of effective components, and greatly improving the quality and production efficiency of humic acid products.

[0011] Adding urea, potassium sulfate, potassium dihydrogen phosphate, magnesium sulfate, and zinc sulfate to the humic acid concentrate and stirring evenly can make various nutrient components fully blend, ensuring a balanced nutrition of the product and meeting the diverse needs of crop growth. The humic acid biostimulant obtained by spray granulation has uniform particles and good solubility, and is more easily absorbed and utilized by crops. It is rich in humic acid and various nutrient elements, can effectively stimulate crop growth, improve crop stress resistance, improve soil structure, increase soil fertility, and contribute to the sustainable development of agriculture, and has extremely high practical value in agricultural production applications.

[0012] Preferably, in step S1, the weathered coal is crushed to a particle size of 80 - 100 mesh.

[0013] Preferably, in step S1, the concentration of the sodium hydroxide solution is 1 - 3 mol / L.

[0014] Preferably, in step S3, the components of each substance are proportioned according to the following parts by weight: 40 - 60 parts of humic acid concentrate, 15 - 25 parts of urea, 10 - 20 parts of potassium sulfate, 5 - 15 parts of potassium dihydrogen phosphate, 3 - 8 parts of magnesium sulfate, 1 - 5 parts of zinc sulfate.

[0015] Humic acid can combine with metal ions in the soil, etc., reducing the fixation and loss of nutrients. At the same time, it can promote the growth and reproduction of beneficial microorganisms in the soil, enhance the biological activity of the soil, and indirectly improve the availability of soil nutrients. Secondly, it can promote the growth and development of plant roots, increase the absorption area and absorption capacity of the roots, improve the absorption efficiency of plants for water and nutrients, and also enhance the stress resistance of plants, such as drought resistance, cold resistance, pest and disease resistance, etc. Finally, it can also promote the formation of stable aggregates of soil particles, increase the porosity of the soil, improve the air permeability and water permeability of the soil, and is beneficial to the growth and respiration of plant roots. Urea is a high-concentration quick-acting nitrogen fertilizer, which can provide nitrogen element for plant growth. Nitrogen is a component of many important compounds in plants, such as proteins, nucleic acids, chlorophyll, etc., and plays a crucial role in physiological processes such as plant growth and development, photosynthesis, etc., enabling plants to have lush branches and leaves and dark green leaves. Potassium sulfate provides potassium element. Potassium is one of the essential macronutrients for plant growth. It can promote plant photosynthesis, improve photosynthetic efficiency, promote the transport and transformation of photosynthetic products, make the plant stems thick and strong, enhance the lodging resistance of plants, and at the same time improve the pest and disease resistance of plants, improve the quality of fruits, and increase the sweetness and color of fruits, etc. Potassium dihydrogen phosphate provides two important nutrient elements, phosphorus and potassium, for plants at the same time. Phosphorus element plays a key role in processes such as plant energy metabolism and genetic material synthesis. It can promote the development of plant roots, enhance the stress resistance of plants, promote flower bud differentiation, and improve the fruit setting rate, etc. Acting synergistically with the potassium element in potassium sulfate, it can better meet the phosphorus and potassium requirements of plants and promote the growth, development and quality improvement of plants. Magnesium sulfate provides magnesium element. Magnesium is the core component of chlorophyll and is crucial for plant photosynthesis. Lack of magnesium will cause plant leaves to turn yellowish-green, affecting the photosynthesis efficiency. At the same time, magnesium also participates in various enzymatic reactions in plants and plays an important regulatory role in processes such as plant metabolism and protein synthesis. Zinc sulfate provides zinc element. Zinc is a component or activator of many enzymes in plants and participates in physiological processes such as auxin synthesis, photosynthesis, and respiration in plants. Zinc can promote the growth and development of plants, especially has an important impact on the growth of plant roots and flower bud differentiation, can improve the stress resistance of plants, and prevent zinc deficiency symptoms such as little leaf disease and rosette disease in plants.

[0016] Preferably, in the step S2, the preparation method of the ultrafiltration membrane includes the following steps: S21. Add polyvinylidene fluoride and polyethylene glycol into N,N-dimethylformamide, heat to 60 - 70 °C, and stir until polyvinylidene fluoride and polyethylene glycol are completely dissolved to obtain a uniform and transparent casting solution; S22. The casting solution is left standing for defoaming treatment, and then poured onto a clean glass plate. A scraper is used to evenly scrape and coat the casting solution on the glass plate, and then the glass plate is immersed in deionized water for phase inversion to form a film. S23. The polyvinylidene fluoride membrane on the glass plate is peeled off and rinsed with deionized water to remove residual solvents and impurities, obtaining a polyvinylidene fluoride-based membrane. S24. Methacrylic acid and benzoyl peroxide are added to absolute ethanol and stirred to dissolve, obtaining a mixed solution. The polyvinylidene fluoride-based membrane is immersed in the mixed solution, and under nitrogen protection, it reacts in a constant temperature water bath at 60 - 80 °C for 3 - 5 h. After the reaction ends, the membrane body is taken out and rinsed with deionized water and absolute ethanol to remove unreacted methacrylic acid monomer and benzoyl peroxide, obtaining a grafted methacrylic acid polyvinylidene fluoride-based membrane. S25. Polyacrylonitrile is added to dimethyl sulfoxide solvent, heated and stirred to dissolve, and then benzoyl peroxide is added and stirred evenly to obtain a polyacrylonitrile solution. The grafted methacrylic acid polyvinylidene fluoride-based membrane is immersed in the polyacrylonitrile solution, and under nitrogen protection, it is heated in a water bath to 80 °C and stirred for reaction for 6 h. The membrane body is taken out and rinsed with dimethyl sulfoxide, absolute ethanol, and deionized water respectively, and then placed in an oven for drying treatment, thus obtaining.

[0017] In the technical solution of the present invention, the polyvinylidene fluoride ultrafiltration membrane is used to achieve the efficient concentration and purification of humic acid. Polyvinylidene fluoride itself has excellent chemical stability and mechanical properties and is an excellent base membrane material for constructing ultrafiltration membranes. On this basis, by grafting methacrylic acid, the polyvinylidene fluoride ultrafiltration membrane is given unique charged characteristics. Methacrylic acid contains carboxyl groups, and under certain conditions, the carboxyl groups will dissociate, releasing hydrogen ions, so that the surface of the ultrafiltration membrane is negatively charged. Since humic acid also has a negative charge, according to the principle of like charges repelling each other, humic acid is more easily intercepted during the ultrafiltration process, thereby achieving the efficient concentration and purification of humic acid.

[0018] However, through experiments, it was unexpectedly found that after the ultrafiltration membrane was used for a period of time, the retention performance of the membrane body for humic acid decreased significantly, resulting in a reduction in the recovery rate of humic acid. Through in-depth research by the team of this invention, it was found that the pH value of the filtered feed liquid has an important impact on the retention performance of the ultrafiltration membrane. When the pH value of the feed liquid is alkaline, it will damage the chemical structure of methacrylic acid and cause methacrylic acid to detach from the polyvinylidene fluoride membrane, thereby greatly reducing the retention rate of the membrane for humic acid. To further solve the above technical problems, this invention conducts a secondary grafting reaction on the polyvinylidene fluoride membrane, grafts polyacrylonitrile onto the polyvinylidene fluoride membrane, and conducts a secondary grafting reaction. Polyacrylonitrile has good alkali resistance. Through the grafting and crystallization processes, a stable alkali-resistant layer is formed on the surface of the polyvinylidene fluoride membrane. This alkali-resistant layer can not only effectively resist the erosion of alkaline substances, but also maintain the original structure and charged properties of the membrane, ensuring the smooth progress of the ultrafiltration process.

[0019] Preferably, in step S22, the static defoaming time is 2 - 5 h.

[0020] Preferably, in step S22, the gap between the scraper and the glass plate is controlled at 200 - 250 μm.

[0021] 8 Preferably, in step S24, the addition amount of benzoyl peroxide is 1 - 3 wt% of the mass of methacrylic acid.

[0022] Preferably, in step S25, the mass concentration of polyacrylonitrile in the polyacrylonitrile solution is 2 - 4%.

[0023] In the technical solution of this invention, as described above, grafting polyacrylonitrile onto the polyvinylidene fluoride-based membrane to form an alkali-resistant protective layer. Through experiments, it was found that a sufficient amount of polyacrylonitrile needs to be grafted onto the polyvinylidene fluoride-based membrane to form a protective layer with good alkali resistance. Therefore, this invention controls the mass concentration of polyacrylonitrile in the solution to be greater than 2%. However, when the mass concentration of polyacrylonitrile is controlled to be greater than 2%, a further problem encountered is that the flux of some ultrafiltration membranes decreases significantly, affecting the filtration effect of the ultrafiltration membrane. Through research by the team of this invention, it was found that this problem is importantly related to the grafting amount of polyacrylonitrile on the polyvinylidene fluoride membrane. When the mass concentration of polyacrylonitrile is controlled to be greater than 4%, excessive polyacrylonitrile is grafted on the surface and within the pores of the polyvinylidene fluoride membrane. During the subsequent drying process, polyacrylonitrile forms a local "bridging" structure within the membrane pores. This structure not only further reduces the effective pore size but also makes the through-holes of the membrane form tortuous channels, greatly increasing the resistance to fluid flow and causing a significant decrease in the membrane flux, seriously affecting the efficiency of material concentration and separation. Therefore, this invention simultaneously controls the concentration of polyacrylonitrile to be less than 4% to avoid excessive grafting of polyacrylonitrile on the surface and within the pores of the polyvinylidene fluoride membrane, maintain the flux of the ultrafiltration membrane, and keep the concentration and separation efficiency.

[0024] A humic acid biostimulant is prepared by the above method.

[0025] The present invention has the following beneficial effects: (1) Balanced nutritional formula: The humic acid concentrate is mixed with various nutrient elements in proportion, with balanced nutrition. The product has uniform particles, good solubility, is easily absorbed by crops, can stimulate growth, improve stress resistance, and improve soil structure and fertility.

[0026] (2) Outstanding advantages of ultrafiltration membrane: When concentrating and purifying, compared with traditional precipitation, ion exchange resin, acid treatment, and evaporation concentration methods, it can accurately separate impurities, has low cost, maintains the structural activity of humic acid, has low energy consumption, and avoids the loss of active ingredients, improving product quality and efficiency.

[0027] (3) Performance improvement of ultrafiltration membrane: Grafting methyl methacrylate on the polyvinylidene fluoride membrane can efficiently concentrate and purify humic acid, and secondary grafting of polyacrylonitrile forms an alkali-resistant layer to resist alkaline erosion and maintain the membrane structure and electrical properties. Specific embodiments

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0029] Example 1: (1) Preparation of humic acid biostimulant: S1. Crush weathered coal to a particle size of 90 mesh, add 100 g of crushed weathered coal to 1 L of sodium hydroxide solution with a concentration of 2 mol / L for activation treatment for 3 h, and then use a plate and frame filter press for solid-liquid separation to obtain an activation solution; S2. Concentrate and purify the activation solution through an ultrafiltration membrane. The operating pressure of the ultrafiltration membrane is controlled at 0.3 MPa, the temperature is maintained at 30 °C, and the final concentration multiple is set to 5 times to obtain a humic acid concentrate; S3. Add urea, potassium sulfate, potassium dihydrogen phosphate, magnesium sulfate, and zinc sulfate to the humic acid concentrate, and the components of each substance are proportioned according to the following parts by weight: 55 parts of humic acid concentrate, 23 parts of urea, 18 parts of potassium sulfate, 12 parts of potassium dihydrogen phosphate, 7 parts of magnesium sulfate, and 4 parts of zinc sulfate.

[0030] Stir and mix the above components evenly, and then perform spray granulation to obtain a humic acid biostimulant.

[0031] (2) Preparation of ultrafiltration membrane: S21. Add 15 g of polyvinylidene fluoride and 3 g of polyethylene glycol to 100 mL of N,N-dimethylformamide, heat to 65 °C, and stir until the polyvinylidene fluoride and polyethylene glycol are completely dissolved to obtain a uniform and transparent casting solution. S22. Let the casting solution stand for defoaming for 4 h, then pour it on a clean glass plate, and use a scraper to evenly spread the casting solution on the glass plate. The gap between the scraper and the glass plate is controlled at 240 μm, and then immerse the glass plate in deionized water for phase inversion film formation. S23. Peel off the polyvinylidene fluoride film on the glass plate, and rinse it with deionized water to remove residual solvents and impurities to obtain a polyvinylidene fluoride-based film. S24. Add 10 g of methacrylic acid and 0.25 g of benzoyl peroxide to 150 mL of absolute ethanol, stir to dissolve to obtain a mixed solution, immerse the polyvinylidene fluoride-based film in the mixed solution, and react in a constant temperature water bath at 70 °C for 4.5 h under nitrogen protection. After the reaction, take out the film body, and rinse it with deionized water and absolute ethanol to remove unreacted methacrylic acid monomer and benzoyl peroxide to obtain a grafted methacrylic acid polyvinylidene fluoride-based film. S25. Add polyacrylonitrile to dimethyl sulfoxide solvent, heat and stir to dissolve, then add benzoyl peroxide, and the addition amount of benzoyl peroxide is 0.05% of the mass of polyacrylonitrile. Stir evenly to prepare a polyacrylonitrile solution with a mass concentration of 3.5%. Immerse the grafted methacrylic acid polyvinylidene fluoride-based film in the polyacrylonitrile solution, and react under nitrogen protection by heating in a water bath to 80 °C and stirring for 6 h. Take out the film body, rinse it with dimethyl sulfoxide, absolute ethanol and deionized water respectively, and then place it in an oven to dry at 60 °C for 5 h to obtain the product.

[0032] Example 2: (1) Preparation of humic acid biostimulant: S1. Crush weathered coal to a particle size of 90 mesh, add 100 g of crushed weathered coal to 1 L of sodium hydroxide solution with a concentration of 2 mol / L for activation treatment for 3 h, and then use a plate and frame filter press for solid-liquid separation to obtain an activation solution. S2. Concentrate and purify the activation solution through an ultrafiltration membrane. The operating pressure of the ultrafiltration membrane is controlled at 0.3 MPa, the temperature is maintained at 30 °C, and the final concentration multiple is set to 5 times to obtain a humic acid concentrate. S3. Add urea, potassium sulfate, potassium dihydrogen phosphate, magnesium sulfate and zinc sulfate to the humic acid concentrate, and the components of each substance are proportioned according to the following parts by weight: 45 parts of humic acid concentrate, 18 parts of urea, 12 parts of potassium sulfate, 6 parts of potassium dihydrogen phosphate, 4 parts of magnesium sulfate, 2 parts of zinc sulfate.

[0033] Stir and mix the above components evenly, and then carry out spray granulation to obtain a humic acid biostimulant.

[0034] (2)Preparation of ultrafiltration membrane: S21. Add 15 g of polyvinylidene fluoride and 3 g of polyethylene glycol into 100 mL of N,N-dimethylformamide, heat to 65 °C, and stir until polyvinylidene fluoride and polyethylene glycol are completely dissolved to obtain a homogeneous and transparent casting solution; S22. Let the casting solution stand for defoaming for 3 h, then pour it on a clean glass plate, use a scraper to evenly spread the casting solution on the glass plate, control the gap between the scraper and the glass plate at 210 μm, and then immerse the glass plate in deionized water for phase inversion to form a membrane; S23. Peel off the polyvinylidene fluoride membrane on the glass plate, and rinse it with deionized water to remove residual solvents and impurities to obtain a polyvinylidene fluoride-based membrane; S24. Add 10 g of methacrylic acid and 0.15 g of benzoyl peroxide into 150 mL of absolute ethanol, stir and dissolve to obtain a mixed solution. Immerse the polyvinylidene fluoride-based membrane in the mixed solution, and react in a constant temperature water bath at 70 °C for 3.5 h under nitrogen protection. After the reaction, take out the membrane body, and rinse it with deionized water and absolute ethanol to remove unreacted methacrylic acid monomer and benzoyl peroxide to obtain a grafted polyvinylidene fluoride-based membrane with methacrylic acid; S25. Add polyacrylonitrile into dimethyl sulfoxide solvent, heat and stir to dissolve it, then add benzoyl peroxide, and the addition amount of benzoyl peroxide is 0.05% of the mass of polyacrylonitrile. Stir evenly to prepare a polyacrylonitrile solution with a mass concentration of 2.5%. Immerse the grafted polyvinylidene fluoride-based membrane with methacrylic acid in the polyacrylonitrile solution, and react under nitrogen protection by heating in a water bath to 80 °C with stirring for 6 h. Take out the membrane body, rinse it with dimethyl sulfoxide, absolute ethanol and deionized water respectively, and then place it in an oven to dry at 60 °C for 5 h to obtain the product.

[0035] Example 3: (1) Preparation of humic acid biostimulant: S1. Crush weathered coal to a particle size of 90 mesh, add 100 g of the crushed weathered coal into 1 L of sodium hydroxide solution with a concentration of 2 mol / L for activation treatment for 3 h, and then use a plate and frame filter press for solid-liquid separation to obtain an activated solution; S2. Concentrate and purify the activated solution through an ultrafiltration membrane. Control the operating pressure of the ultrafiltration membrane at 0.3 MPa, maintain the temperature at 30 °C, and set the final concentration multiple to 5 times to obtain a humic acid concentrate; S3. Add urea, potassium sulfate, potassium dihydrogen phosphate, magnesium sulfate and zinc sulfate to the humic acid concentrate, and the components of each substance are proportioned according to the following parts by weight: 50 parts of humic acid concentrate, 20 parts of urea, 15 parts of potassium sulfate, 10 parts of potassium dihydrogen phosphate, 5 parts of magnesium sulfate, 3 parts of zinc sulfate.

[0036] Stir and mix the above components evenly, and then carry out spray granulation to obtain humic acid biostimulant.

[0037] (2)Preparation of ultrafiltration membrane: S21. Add 15 g of polyvinylidene fluoride and 3 g of polyethylene glycol to 100 mL of N,N-dimethylformamide, heat to 65 °C, and stir until polyvinylidene fluoride and polyethylene glycol are completely dissolved to obtain a uniform and transparent casting solution. S22. Let the casting solution stand for defoaming for 3 h, then pour it on a clean glass plate, use a scraper to evenly scrape the casting solution on the glass plate, control the gap between the scraper and the glass plate at 220 μm, and then immerse the glass plate in deionized water for phase inversion to form a membrane. S23. Peel off the polyvinylidene fluoride membrane on the glass plate, and rinse it with deionized water to remove residual solvents and impurities to obtain a polyvinylidene fluoride base membrane. S24. Add 10 g of methacrylic acid and 0.2 g of benzoyl peroxide to 150 mL of absolute ethanol, stir and dissolve to obtain a mixed solution. Immerse the polyvinylidene fluoride base membrane in the mixed solution, and react in a constant temperature water bath at 70 °C for 4 h under nitrogen protection. After the reaction, take out the membrane body, and rinse it with deionized water and absolute ethanol to remove unreacted methacrylic acid monomer and benzoyl peroxide to obtain a grafted methacrylic acid polyvinylidene fluoride base membrane. S25. Add polyacrylonitrile to dimethyl sulfoxide solvent, heat and stir to dissolve it, then add benzoyl peroxide, and the addition amount of benzoyl peroxide is 0.05% of the mass of polyacrylonitrile. Stir evenly to prepare a polyacrylonitrile solution with a mass concentration of 3%. Immerse the grafted methacrylic acid polyvinylidene fluoride base membrane in the polyacrylonitrile solution, and react with stirring in a water bath heated to 80 °C for 6 h under nitrogen protection. Take out the membrane body, rinse it with dimethyl sulfoxide, absolute ethanol and deionized water respectively, and then place it in an oven to dry at 60 °C for 5 h to obtain it.

[0038] Example 4: (1) Preparation of humic acid biostimulant: S1. Crush weathered coal to a particle size of 100 mesh, add 100 g of the crushed weathered coal to 1 L of a sodium hydroxide solution with a concentration of 3 mol / L for activation treatment for 3 h, and then use a plate and frame filter press for solid-liquid separation to obtain an activation solution. S2. Concentrate and purify the activation solution through an ultrafiltration membrane. Control the operating pressure of the ultrafiltration membrane at 0.3 MPa, maintain the temperature at 30 °C, and set the final concentration multiple to 5 times to obtain a humic acid concentrate. S3. Add urea, potassium sulfate, potassium dihydrogen phosphate, magnesium sulfate and zinc sulfate to the humic acid concentrate, and the components of each substance are proportioned according to the following parts by weight: 60 parts of humic acid concentrate, 25 parts of urea, 20 parts of potassium sulfate, 15 parts of potassium dihydrogen phosphate, 8 parts of magnesium sulfate, 5 parts of zinc sulfate.

[0039] Stir and mix the above components evenly, and then carry out spray granulation to obtain humic acid biostimulant.

[0040] (2) Preparation of ultrafiltration membrane: S21. Add 15 g of polyvinylidene fluoride and 3 g of polyethylene glycol to 100 mL of N,N-dimethylformamide, heat to 70 °C, and stir until polyvinylidene fluoride and polyethylene glycol are completely dissolved to obtain a uniform and transparent casting solution; S22. Let the casting solution stand for degassing for 5 h, then pour it on a clean glass plate, use a scraper to evenly spread the casting solution on the glass plate, control the gap between the scraper and the glass plate at 250 μm, and then immerse the glass plate in deionized water for phase inversion to form a membrane; S23. Peel off the polyvinylidene fluoride membrane on the glass plate, and rinse it with deionized water to remove residual solvents and impurities to obtain a polyvinylidene fluoride base membrane; S24. Add 10 g of methacrylic acid and 0.3 g of benzoyl peroxide to 150 mL of absolute ethanol, stir and dissolve to obtain a mixed solution. Immerse the polyvinylidene fluoride base membrane in the mixed solution, and react in a constant temperature water bath at 80 °C for 5 h under nitrogen protection. After the reaction, take out the membrane body and rinse it with deionized water and absolute ethanol to remove unreacted methacrylic acid monomers and benzoyl peroxide to obtain a grafted methacrylic acid polyvinylidene fluoride base membrane; S25. Add polyacrylonitrile to dimethyl sulfoxide solvent, heat and stir to dissolve it, then add benzoyl peroxide, and the addition amount of benzoyl peroxide is 0.05% of the mass of polyacrylonitrile. Stir evenly to prepare a polyacrylonitrile solution with a mass concentration of 4%. Immerse the grafted methacrylic acid polyvinylidene fluoride base membrane in the polyacrylonitrile solution, react under nitrogen protection by heating in a water bath to 80 °C and stirring for 6 h, take out the membrane body, rinse it with dimethyl sulfoxide, absolute ethanol and deionized water respectively, and then place it in an oven to dry at 60 °C for 5 h to obtain the product.

[0041] Example 5: (1) Preparation of humic acid biostimulant: S1. Crush weathered coal to a particle size of 80 mesh, add 100 g of crushed weathered coal to 1 L of sodium hydroxide solution with a concentration of 1 mol / L for activation treatment for 3 h, and then use a plate and frame filter press for solid-liquid separation to obtain an activation solution; S2. Concentrate and purify the activation solution through an ultrafiltration membrane. The operating pressure of the ultrafiltration membrane is controlled at 0.3 MPa, the temperature is maintained at 30 °C, and the final concentration multiple is set to 5 times to obtain a humic acid concentrate; S3. Add urea, potassium sulfate, potassium dihydrogen phosphate, magnesium sulfate and zinc sulfate to the humic acid concentrate, and the components are proportioned according to the following parts by weight: 40 parts of humic acid concentrate, 15 parts of urea, 10 parts of potassium sulfate, 5 parts of potassium dihydrogen phosphate, 3 parts of magnesium sulfate, and 1 part of zinc sulfate.

[0042] Stir and mix the above components evenly, and then carry out spray granulation to obtain humic acid biostimulant.

[0043] (2) Preparation of ultrafiltration membrane: S21. Add 15 g of polyvinylidene fluoride and 3 g of polyethylene glycol to 100 mL of N,N-dimethylformamide, heat to 60 °C, and stir until polyvinylidene fluoride and polyethylene glycol are completely dissolved to obtain a uniform and transparent casting solution; S22. Let the casting solution stand for defoaming for 2 h, then pour it on a clean glass plate, use a scraper to evenly scrape the casting solution on the glass plate, control the gap between the scraper and the glass plate at 200 μm, and then immerse the glass plate in deionized water for phase inversion film formation; S23. Peel off the polyvinylidene fluoride membrane on the glass plate, and rinse it with deionized water to remove residual solvents and impurities to obtain a polyvinylidene fluoride base membrane; S24. Add 10 g of methacrylic acid and 0.1 g of benzoyl peroxide to 150 mL of absolute ethanol, stir and dissolve to obtain a mixed solution. Immerse the polyvinylidene fluoride base membrane in the mixed solution, and react in a constant temperature water bath at 60 °C for 3 h under nitrogen protection. After the reaction, take out the membrane body, and rinse it with deionized water and absolute ethanol to remove unreacted methacrylic acid monomers and benzoyl peroxide to obtain a grafted methacrylic acid polyvinylidene fluoride base membrane; S25. Add polyacrylonitrile to dimethyl sulfoxide solvent, heat and stir to dissolve, then add benzoyl peroxide, and the addition amount of benzoyl peroxide is 0.05% of the mass of polyacrylonitrile. Stir evenly to prepare a polyacrylonitrile solution with a mass concentration of 2%. Immerse the grafted methacrylic acid polyvinylidene fluoride base membrane in the polyacrylonitrile solution, and react under nitrogen protection by heating in a water bath to 80 °C and stirring for 6 h. Take out the membrane body, rinse it with dimethyl sulfoxide, absolute ethanol and deionized water respectively, and then place it in an oven to dry at 60 °C for 5 h to obtain it.

[0044] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that: Replace the ultrafiltration membrane filtration method in step S2 with an ordinary centrifugal precipitation separation method; The remaining operation steps are the same as those in Example 1.

[0045] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that: Steps S24 and S25 are omitted during the preparation process of the ultrafiltration membrane; The remaining operation steps are the same as those in Example 1.

[0046] Comparative Example 3 The difference between Comparative Example 3 and Example 1 lies in: Step S25 is omitted during the preparation process of the ultrafiltration membrane; The remaining operation steps are the same as those in Example 1.

[0047] Comparative Example 4 The difference between Comparative Example 4 and Example 5 lies in: In step S25 of the ultrafiltration membrane preparation, the mass concentration of polyacrylonitrile in the polyacrylonitrile solution is 1%; The remaining operation steps are the same as those in Example 5.

[0048] Comparative Example 5 The difference between Comparative Example 5 and Example 4 lies in: In step S25 of the ultrafiltration membrane preparation, the mass concentration of polyacrylonitrile in the polyacrylonitrile solution is 5%; The remaining operation steps are the same as those in Example 4.

[0049] Comparative Example 6 The difference between Comparative Example 6 and Example 4 lies in: In step S25 of the ultrafiltration membrane preparation, the mass concentration of polyacrylonitrile in the polyacrylonitrile solution is 6%; The remaining operation steps are the same as those in Example 4.

[0050] Performance Test I. In order to evaluate the effect of the humic acid biological growth hormone of the present invention on the growth regulation of tomato plants, the following index tests are carried out: 1. Germination rate test: Select 500 tomato seeds with plump grains and uniform sizes, randomly divide them into 5 groups, with 100 seeds in each group, corresponding to 5 examples. Prepare 5 sterile culture dishes with a diameter of 9 cm, and lay two layers of filter paper at the bottom. Prepare the humic acid biostimulant of each example into a solution with the same concentration. Add 10 mL of the corresponding solution to the filter paper in each culture dish to moisten it, evenly place each group of seeds on the filter paper, cover the lid, and place it in a constant temperature light incubator at a temperature of 25 °C, a light intensity of 3000 lx, and a light time of 12 h / d. Observe and record the germination situation of the seeds every day (using the radicle breaking through the seed coat by 1 mm as the germination standard), and continue for 7 days. Calculate the germination rate according to (number of germinated seeds ÷ number of tested seeds) × 100%.

[0051] 2. Measurement of plant height, root length, and number of leaves: Sow tomato seeds in a seedling tray filled with ordinary seedling substrate. When the seedlings have grown 2 - 3 true leaves, select the seedlings with strong growth and consistent growth vigor. Prepare 5 groups of plastic flower pots, with 10 pots in each group. Fill each pot with the same volume of sterilized nutrient soil, and mix the humic acid biostimulant of each example with the nutrient soil in a certain proportion. Transplant the selected seedlings into the corresponding flower pots, one seedling per pot, water thoroughly, and place them in a greenhouse with a temperature of 20 - 28°C and a relative humidity of 60% - 80% for cultivation. Regularly water with the same fertilizer and amount of water. When the tomatoes grow to 30 days, 60 days, and 90 days, measure the plant height (distance from the base of the stem to the growth point), root length (distance from the base of the stem to the tip of the longest root), and number of leaves of each tomato plant respectively, and take the average value of each group as the data of this example.

[0052] 3. Measurement of survival rate under drought stress: Select tomato plants that have grown for 45 days and have consistent growth conditions, with 10 plants in each group. Stop watering to allow the soil to gradually dry. When the soil water content drops to 30% - 35% of the field capacity, maintain it for 10 days, and then resume normal watering and cultivate for another 7 days. Observe and record the survival situation of the plants, and calculate the survival rate according to (number of surviving plants ÷ number of treated plants) × 100%.

[0053] 4. Measurement of survival rate under high - temperature stress: Select tomato plants that have grown for 50 days and have consistent growth conditions, with 10 plants in each group. Transfer them into an artificial climate chamber, set the temperature at 40°C, relative humidity at 60%, light intensity at 5000 lx, and light duration at 12 h / d, and treat them for 5 days. After 5 days, transfer them back to the normal greenhouse environment and continue to cultivate for 7 days. Observe and record the survival situation of the plants, and calculate the survival rate according to (number of surviving plants ÷ number of treated plants) × 100%.

[0054]

[0055] II. Humic acid purity test: Take 20 mL of the humic acid concentrate in Examples 1 - 5 and the supernatant after centrifugation in Comparative Example 1, and place them in pre - weighed evaporating dishes respectively. Heat and evaporate to dryness on a water - bath, and then put them into an oven and dry to a constant weight at 105°C to obtain humic acid solid samples. The purity of humic acid is determined by the potassium dichromate oxidation method.

[0056]

[0057] III. Humic acid yield test: To test the humic acid yield in Examples 1 - 5 and Comparative Example 2, accurately weigh the mass m 1 (g) of weathered coal, and determine the initial content w 1 (%) of humic acid in the weathered coal by elemental analysis, so as to calculate the initial mass M1 of humic acid in the weathered coal = m 1 × w 1According to the preparation method of the humic acid concentrate in each embodiment, the humic acid concentrate is obtained. The concentrate is completely evaporated and dried to obtain a solid humic acid product, and its mass m 2 (g) is accurately weighed. Using the above-mentioned humic acid purity test method, the purity w 2 (%) of the obtained solid humic acid product is measured, and then the actual mass M 2 of the obtained humic acid is calculated. 2 = m 1 × w 2 Furthermore, the yield of humic acid is calculated = (M 1 / M

[0058]

[0059] IV. The alkali resistance of the ultrafiltration membranes prepared in Examples 1-5 and Comparative Examples 3-6 is tested by the following method: The ultrafiltration membrane sheet is installed in the ultrafiltration device, and an ultrafiltration experiment is carried out with pure water at 0.1 MPa, and an ultrafiltration experiment is carried out with an aqueous solution of the standard solute polyethylene glycol with a molecular weight of 1000 Da to measure the initial rejection rate R 0 (%). Prepare a 0.1 mol / L sodium hydroxide solution, completely immerse the membrane sheet in the sodium hydroxide solution, soak it for 7 days at a constant temperature of 25 °C. After the soaking is completed, take out the membrane sheet from the sodium hydroxide solution and rinse it with a large amount of deionized water until the rinsing liquid is neutral. Install the membrane sheet in the ultrafiltration device again, and test the rejection rate R 1 (%) of the ultrafiltration membrane according to the conditions of the initial performance test. The smaller the change in the rejection rate, the better the alkali resistance of the ultrafiltration membrane.

[0060]

[0061] V. The pure water flux of the ultrafiltration membranes prepared in Examples 1-5 and Comparative Examples 5-6 is tested by the following method: Install the ultrafiltration membrane sheet in the membrane module, turn on the pressure pump, introduce pure water into the system, adjust the pressure to 0.1 MPa, and let the pure water permeate through the ultrafiltration membrane at this pressure. Run continuously for 30 min to make the performance of the membrane reach a stable state. After stable operation, test the pure water flux (L / (m²·h)) of the ultrafiltration membrane.

[0062]

[0063] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing humic acid biostimulant, characterized in that: The following steps are involved: S1, crushing the weathered coal, adding the crushed weathered coal into a sodium hydroxide solution for activation treatment, and then performing solid-liquid separation to obtain an activation solution; S2, concentrating and purifying the activated solution through an ultrafiltration membrane to obtain a humic acid concentrate; S3. Add urea, potassium sulfate, potassium dihydrogen phosphate, magnesium sulfate and zinc sulfate to the humic acid concentrate, stir and mix evenly, and then spray granulate to obtain humic acid biostimulant.

2. The method for preparing a humic acid biostimulant according to claim 1, characterized in that: In the step S1, the weathered coal is crushed to a particle size of 80-100 mesh.

3. The method for preparing a humic acid biostimulant according to claim 1, characterized in that: In step S1, the concentration of the sodium hydroxide solution is 1-3 mol / L.

4. The method for preparing a humic acid biostimulant according to claim 1, characterized in that: In step S3, the material components are mixed according to the following weight proportions: Humic acid concentrate 40-60 parts, urea 15-25 parts, potassium sulfate 10-20 parts, potassium dihydrogen phosphate 5-15 parts, magnesium sulfate 3-8 parts, zinc sulfate 1-5 parts.

5. The method for preparing a humic acid biostimulant according to claim 1, characterized in that: In step S2, the method for preparing the ultrafiltration membrane comprises the following steps: S21, adding polyvinylidene fluoride and polyethylene glycol to N,N-dimethylformamide, heating to 60-70° C., and stirring until the polyvinylidene fluoride and polyethylene glycol are completely dissolved to obtain a uniform and transparent casting solution; S22, placing the casting solution for degassing treatment, then pouring it onto a clean glass plate, using a scraper to evenly scrape the casting solution onto the glass plate, and then immersing the glass plate in deionized water for phase transformation to form a membrane; S23, peeling off the polyvinylidene fluoride film on the glass plate, and washing with deionized water to remove residual solvent and impurities to obtain a polyvinylidene fluoride film; S24, adding methacrylic acid and benzoyl peroxide to anhydrous ethanol, stirring and dissolving to obtain a mixed solution, immersing the polyvinyl fluoride film in the mixed solution, reacting in a constant temperature water bath at 60-80° C. for 3-5 hours under nitrogen protection, taking out the film after the reaction, and washing with deionized water and anhydrous ethanol to remove unreacted methacrylic acid monomer and benzoyl peroxide to obtain a methacrylic acid grafted polyvinyl fluoride film; S25. Add polyacrylonitrile to dimethyl sulfoxide solvent, heat and stir to dissolve, then add benzoyl peroxide and stir evenly to obtain polyacrylonitrile solution, immerse the grafted methacrylate polyvinylidene fluoride based membrane in the polyacrylonitrile solution, heat to 80°C in a water bath under nitrogen protection, stir and react for 6 hours, take out the membrane, rinse it with dimethyl sulfoxide, anhydrous ethanol and deionized water respectively, and then place it in an oven for drying.

6. The method for preparing a humic acid biostimulant according to claim 5, characterized in that: In step S22, the standing and degassing time is 2-5 hours.

7. The method for preparing a humic acid biostimulant according to claim 5, characterized in that: In the step S22, the gap between the scraper and the glass plate is controlled to be 200-250 μm.

8. The method for preparing a humic acid biostimulant according to claim 5, characterized in that: In the step S24, the amount of benzoyl peroxide added is 1-3 wt % of the mass of methacrylic acid.

9. The method for preparing a humic acid biostimulant according to claim 5, characterized in that: In step S25, the mass concentration of polyacrylonitrile in the polyacrylonitrile solution is 2-4%.

10. A humic acid biostimulant, characterized in that: The method is prepared by any one of claims 1 to 9.

Images