Humic acid water-soluble fertilizer for improving rooting and strengthening roots of crops and preparation method of humic acid water-soluble fertilizer

Abstract

The invention discloses a humic acid water-soluble fertilizer for improving rooting and strengthening roots of crops and a preparation method of the humic acid water-soluble fertilizer, and belongs to the technical field of fertilizer preparation. Mixing the ore source humic acid and an oxidizing agent for reaction to obtain an oxidized ore source humic acid mixture; heating the oxidized ore source humic acid mixture and solid alkali to react, performing centrifugal treatment to obtain an activating solution, performing acid treatment on the activating solution, and performing centrifugal separation to obtain a humic acid precipitate; mixing and dispersing the humic acid precipitate, methacrylic acid modified cyclodextrin and deionized water, heating and stirring to obtain a humic acid inclusion dispersion liquid; mixing the humic acid inclusion dispersion liquid, acrylic ester, an emulsifier and an initiator, heating, reacting and polymerizing to obtain polyacrylate-coated humic acid emulsion dispersion; and mixing the polyacrylate-coated humic acid emulsion dispersion and a calcium-containing phosphate fertilizer to form the humic acid water-soluble fertilizer. The humic acid water-soluble fertilizer prepared by the preparation method disclosed by the invention has good fertilizer efficiency when being applied to crops.

Description

Technical Field

[0001] This invention belongs to the field of fertilizer preparation technology, specifically relating to a humic acid water-soluble fertilizer that improves crop root growth and development, and its preparation method. Background Technology

[0002] In current agricultural production, chemical fertilizers are the most widely used fertilizer due to their high nutrient content, rapid onset of action, and excellent yield-increasing effects. However, with the large-scale use of chemical fertilizers, various negative problems have emerged, the most significant and direct being eutrophication of water bodies and soil degradation. Therefore, researching new, environmentally friendly, and effective fertilizers is of great importance in reducing the negative problems caused by chemical fertilizer application. Humic acid is a complex organic substance formed and accumulated through microbial decomposition and transformation of plant and animal residues and microbial cells, as well as a series of geochemical processes. Humic acid has beneficial effects such as promoting crop growth, increasing crop yield, and improving soil fertility. Furthermore, humic acid contains various active functional groups in its structure, exhibiting weak acidity, cation exchange capacity, and chelation adsorption capabilities, thus possessing significant application value in the fertilizer field. Humic acid water-soluble fertilizer is a new type of multifunctional fertilizer containing humic acid substances. It is mainly produced by using coal humic acid resources as raw materials and through deep oxidation, acid hydrolysis, activation and other technical methods to produce humic acid, which is then compounded with other materials to obtain water-soluble organic fertilizer.

[0003] Patent CN116082095A discloses a long-lasting and stable humic acid water-soluble fertilizer and its preparation method. This invention extracts humic acid through an alkali-soluble method, followed by oxidative activation treatment with hydrogen peroxide. The large molecular chains in the humic acid break down into smaller molecular chains due to oxidation, while simultaneously increasing the total acidic group content and the number of active groups, thus improving the efficiency of subsequent reactions. Furthermore, the activation process significantly increases the content of soluble humic acid, which then undergoes a complexation reaction with nitrogen, phosphorus, and potassium in the compound fertilizer. This further improved the effect of compound fertilizer. Next, the oxidized and activated potassium humate was sulfonated under the action of 1,3-propylsulfonate lactone to introduce hydrophilic sulfonic acid groups, thereby improving the hydrophilicity of potassium humate. Then, methacrylic acid, maleic anhydride, and 2-acrylamido-2-methylpropane sulfonic acid were added to chelate and modify the sulfonated potassium humate, grafting high molecular weight substances onto potassium humate. This not only improved the hydrophilicity of humic acid, but also allowed methacrylic acid to act as a water-retaining agent, increasing the water retention rate of the soil.

[0004] Patent CN1095747764A discloses a method for preparing humic acid water-soluble fertilizer. This invention prepares humic acid water-soluble fertilizer by mixing humic acid, eggshells and quicklime to obtain calcium-containing solutions, phosphorus-containing solutions and inorganic metal salts. This fertilizer improves the absorption rate of fertilizer from water-soluble fertilizer by crop roots on the one hand, and reduces the time farmers spend breaking up clumps of water-soluble fertilizer on the other hand, thereby improving the efficiency of farmers' fertilization work.

[0005] Although humic acid water-soluble fertilizers have promising application prospects, due to the chelating effect of humic acid, it readily combines with metal ions such as calcium, magnesium, and aluminum to form insoluble metal ion-bound humic acid, thus reducing its water solubility and affecting its fertilizer efficacy. Therefore, developing new types of humic acid water-soluble fertilizers is of great significance for improving the water solubility of humic acid and thereby enhancing its fertilizer efficacy. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention oxidizes mineral-derived humic acid, then activates it with a solid alkali through co-heating, followed by acid treatment to obtain humic acid. Modified methacrylic acid-modified cyclodextrin is used to first encapsulate the humic acid, which is then emulsion polymerized to form a polyacrylate-encapsulated humic acid emulsion dispersion. Finally, this dispersion is mixed with calcium-containing phosphate fertilizer to form a water-soluble humic acid fertilizer, thereby solving the technical problems mentioned in the background art. Specifically, the technical solution of this invention includes the following: One objective of this invention is to provide a method for preparing a humic acid water-soluble fertilizer that enhances root growth and development in crops. The preparation method includes the following steps: A mixture of oxidized mineral humic acid and an oxidant is obtained by mixing and reacting them in a weight ratio of 1:3~4. The mixture of oxidized mineral humic acid and solid alkali is heated to 60℃~70℃ and reacted for 50min~70min. After centrifugation, an activation solution is obtained. The activation solution is then treated with acid and centrifuged to obtain humic acid precipitate. Humic acid precipitate, methacrylic acid modified cyclodextrin and deionized water were mixed and dispersed, and then heated to 35℃~40℃ and stirred for 120min~150min to obtain humic acid inclusion dispersion. The humic acid inclusion dispersion, acrylate, emulsifier and initiator were mixed and heated to 70℃~75℃ for 2.5h~3h to polymerize and obtain polyacrylate-encapsulated humic acid emulsion dispersion; A humic acid water-soluble fertilizer is formed by mixing polyacrylate-encapsulated humic acid emulsion dispersion and calcium-containing phosphate fertilizer at a weight ratio of 1:0.1~0.2.

[0007] Furthermore, the mineral-derived humic acid includes weathered coal.

[0008] Furthermore, the oxidant is composed of hydrogen peroxide solution and ferrous sulfate in a weight ratio of 2~3:0.7~1.

[0009] Furthermore, the mass percentage concentration of the hydrogen peroxide solution is 20% to 25%.

[0010] Furthermore, the conditions for the mixed reaction of the mineral humic acid and the oxidant solution include a pH of 4.5 to 5.0, a temperature of 30°C to 40°C, and a reaction time of 40 to 50 minutes.

[0011] Furthermore, the solid alkali includes sodium hydroxide or potassium hydroxide.

[0012] Furthermore, the amount of solid alkali used is sufficient to adjust the pH of the oxidized mineral humic acid mixture to 10-11.

[0013] Furthermore, the acid treatment process includes adjusting the pH to 4-4.5 at a rotation speed of 100 r / min, followed by standing for 20-30 min.

[0014] Furthermore, the preparation method of the methacrylic acid modified cyclodextrin includes the following steps: Methacrylic acid, cyclodextrin, EDC hydrochloride, 4-dimethylaminopyridine, and dichloromethane were mixed and dispersed in a weight ratio of 1:0.6~0.8:2.5~3:1~1.5:20~30 to obtain a dispersion. The dispersion was reacted at 25℃~30℃ for 24h~30h and then dialyzed to obtain methacrylic acid modified cyclodextrin.

[0015] Furthermore, the cyclodextrin includes γ-cyclodextrin.

[0016] Furthermore, the acrylate is composed of methyl methacrylate, ethyl methacrylate and butyl acrylate in a weight ratio of 1:2:2.

[0017] Furthermore, the emulsifier is composed of sodium dodecyl sulfate and Span 40 in a weight ratio of 1:3.

[0018] Furthermore, the initiator includes ammonium persulfate.

[0019] Furthermore, the weight ratio of the humic acid precipitate, methacrylic acid modified cyclodextrin, deionized water, acrylate, emulsifier and initiator is 1:3~4:30~40:15~20:0.15~0.2:0.03~0.04.

[0020] Furthermore, the calcium-containing phosphate fertilizer includes triple superphosphate.

[0021] The second objective of this invention is to provide a humic acid water-soluble fertilizer that enhances root growth and strengthens the roots of crops.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention first degrades mineral-derived humic acid through oxidation, thereby reducing its molecular weight. Then, it is activated by co-heating with a solid alkali, causing the humic acid in the mineral source to be released in the form of more water-soluble humate salts. Subsequently, centrifugation yields an activated solution containing humate salts. Although the humic acid dissolves in the solution as a more water-soluble salt, when mixed with calcium-containing phosphate fertilizer, the humate salts readily chelate with the calcium in the fertilizer, leading to the formation of insoluble metal ion-bound humic acid. This causes it to easily flocculate and deposit, making it difficult for crops to absorb. Adding hydrochloric acid to the activated solution containing humate salts causes the alkali-treated humate salts to transform into less hydrophilic humic acid. Next, the cyclodextrin with a hydrophobic internal cavity structure was modified by esterification condensation of the hydrophilic functional groups (hydroxyl groups) on the outer surface of the cyclodextrin with the carboxyl groups on the methacrylic acid structure, thereby introducing methacrylic acid into the surface of the cyclodextrin to obtain methacrylic acid-modified cyclodextrin. Subsequently, the methacrylic acid-modified cyclodextrin was mixed and dispersed with humic acid, and the humic acid was encapsulated inside the methacrylic acid-modified cyclodextrin through the hydrophobic internal cavity to obtain humic acid inclusions. Finally, the humic acid inclusions and acrylates were encapsulated by emulsion polymerization to form a polyacrylate-encapsulated humic acid emulsion dispersion. Through the dual encapsulation effect of cyclodextrin and polyacrylate, the tendency of humic acid to chelate and bind with calcium ions and flocculate and deposit when mixed with calcium-containing phosphate fertilizers is greatly reduced, which would affect crop absorption. The dual encapsulation method of cyclodextrin and polyacrylate emulsion polymerization improves the defect of poor hydrophilicity of humic acid itself, so that humic acid can be well dispersed in water with the help of the encapsulation carrier, and then mixed with calcium phosphate fertilizer to form humic acid water-soluble fertilizer. In addition, the encapsulation of polyacrylate makes it have good film-forming properties during fertilization, which can reduce fertilizer loss and thus help improve fertilizer efficiency. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below through embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Unless otherwise stated, all raw materials and reagents used in this invention are commercially available or can be prepared by known methods.

[0025] Preparation Example 1: The preparation method of methacrylic acid modified cyclodextrin is as follows: One part by weight of methacrylic acid and 20 parts by weight of dichloromethane were dispersed evenly in an ultrasonic bath at 200 W. Then, 2.5 parts by weight of EDC hydrochloride and 1 part by weight of 4-dimethylaminopyridine were added and mixed, and stirred at 20°C for 20 min at 100 rpm. After stirring, 0.6 parts by weight of γ-cyclodextrin were added and dispersed in an ultrasonic bath at 200 W for 10 min to obtain a dispersion. The dispersion was placed in a water bath at 25°C and stirred with a magnetic stirrer at 200 rpm for 30 h. After the reaction, the reaction solution was poured into a dialysis bag with a molecular weight cutoff of 1 kDa and dialyzed with distilled water to remove impurities for 48 h. After dialysis, the dialysate was poured into a beaker, and then 2 times the weight of the dialysate in ice-cold ethanol was added while stirring at 100 r / min until turbidity appeared. Stirring was stopped and the mixture was allowed to stand for 1 h. The precipitate was then separated by centrifugation at 3000 r / min. The precipitate was washed with ethanol solution and then dried in a vacuum drying oven at 40℃ for 12 h to obtain methacrylic acid modified cyclodextrin.

[0026] Preparation Example 2: The preparation method of methacrylic acid modified cyclodextrin is as follows: One part by weight of methacrylic acid and 24 parts by weight of dichloromethane were dispersed evenly in an ultrasonic bath at 200 W. Then, 2.7 parts by weight of EDC hydrochloride and 1.2 parts by weight of 4-dimethylaminopyridine were added and mixed, and stirred at 100 rpm in 20 °C for 20 min. After stirring, 0.7 parts by weight of γ-cyclodextrin were added and dispersed in an ultrasonic bath at 200 W for 10 min to obtain a dispersion. The dispersion was placed in a water bath at 25 °C and stirred with a magnetic stirrer at 200 rpm for 26 h. After the reaction, the reaction solution was poured into a dialysis bag with a molecular weight cutoff of 1 kDa and dialyzed with distilled water to remove impurities for 48 h. After dialysis, the dialysate was poured into a beaker, and then 2 times the weight of the dialysate in ice-cold ethanol was added while stirring at 100 r / min until turbidity appeared. Stirring was stopped and the mixture was allowed to stand for 1 h. The precipitate was then separated by centrifugation at 3000 r / min. The precipitate was washed with ethanol solution and then dried in a vacuum drying oven at 40℃ for 12 h to obtain methacrylic acid modified cyclodextrin.

[0027] Preparation Example 3: The preparation method of methacrylic acid modified cyclodextrin is as follows: One part by weight of methacrylic acid and 30 parts by weight of dichloromethane were dispersed evenly in an ultrasonic bath at 200 W. Then, 3 parts by weight of EDC hydrochloride and 1.5 parts by weight of 4-dimethylaminopyridine were added and mixed, and stirred at 100 rpm at 20 °C for 20 min. After stirring, 0.8 parts by weight of γ-cyclodextrin were added and dispersed in an ultrasonic bath at 200 W for 10 min to obtain a dispersion. The dispersion was placed in a water bath at 30 °C and stirred with a magnetic stirrer at 200 rpm for 24 h. After the reaction, the reaction solution was poured into a dialysis bag with a molecular weight cutoff of 1 kDa and dialyzed with distilled water to remove impurities for 48 h. After dialysis, the dialysate was poured into a beaker, and then 2 times the weight of the dialysate in ice-cold ethanol was added while stirring at 100 r / min until turbidity appeared. Stirring was stopped and the mixture was allowed to stand for 1 h. The precipitate was then separated by centrifugation at 3000 r / min. The precipitate was washed with ethanol solution and then dried in a vacuum drying oven at 40℃ for 12 h to obtain methacrylic acid modified cyclodextrin.

[0028] Preparation Example 4: The preparation method of methacrylic acid modified cyclodextrin is as follows: In Preparation Example 1, γ-cyclodextrin was replaced with α-cyclodextrin, and the rest of the preparation process remained the same as in Preparation Example 1.

[0029] Preparation Example 5: The preparation method of methacrylic acid modified cyclodextrin is as follows: One part by weight of methacrylic acid and 20 parts by weight of dichloromethane were dispersed evenly in an ultrasonic power of 200W. Then, one part by weight of EDC hydrochloride and 0.5 parts by weight of 4-dimethylaminopyridine were added and mixed and stirred at 20°C for 20 min at a speed of 100 r / min. After stirring, 0.6 parts by weight of γ-cyclodextrin were added and mixed and dispersed in an ultrasonic power of 200W for 10 min to obtain a dispersion. The dispersion was placed in a water bath at 25°C and stirred with a magnetic stirrer at a speed of 200 r / min for 24 h. The rest of the preparation process was the same as in Preparation Example 1.

[0030] Example 1: A method for preparing a humic acid water-soluble fertilizer that enhances crop root growth and development specifically includes the following steps: The weathered coal was dried in a vacuum drying oven at 60℃ for 6 hours, then ground and passed through a 100-mesh sieve. Ten parts by weight of the dried and ground weathered coal were added to a reactor, followed by 30 parts by weight of an oxidant (comprising 20 parts by weight of 20% hydrogen peroxide and 10 parts by weight of ferrous sulfate; ferrous sulfate was added first, then hydrogen peroxide). The mixture was stirred at 200 rpm to ensure complete mixing and wetting. The pH was then adjusted to 4.5, and the mixture was heated to 30℃ and stirred for 40 minutes. After the reaction, the waste liquid was filtered to obtain an oxidized mineral humic acid mixture. Three times the weight of the oxidized mineral humic acid mixture of deionized water was added to the mixture, followed by sodium hydroxide while stirring until the pH reached 10. The mixture was then heated to 60℃ and reacted for 50 minutes. After the reaction, the residue was removed by centrifugation at 1000 r / min to obtain an activated solution. The pH of the activated solution was adjusted to 4 with dilute hydrochloric acid and then allowed to stand for 30 min. The precipitate was then obtained by centrifugation at 3000 r / min. The precipitate was washed with deionized water until the pH of the wastewater was neutral, and then dried in a vacuum drying oven at 50°C for 15 h to obtain humic acid precipitate. One part by weight of the humic acid precipitate, three parts by weight of the methacrylic acid-modified cyclodextrin obtained in Preparation Example 1, and 40 parts by weight of deionized water were weighed and mixed. The mixture was then dispersed using ultrasonic power at 200 W for 15 min, and then heated to 35°C and stirred at 200 r / min for 120 min to obtain a humic acid inclusion dispersion. 15 parts by weight of acrylate (derived from methyl methacrylate) was added to the above humic acid inclusion dispersion. A mixture of methyl acrylate, ethyl methacrylate, and butyl acrylate in a weight ratio of 1:2:2, and 0.15 parts by weight of emulsifier (composed of sodium dodecyl sulfate and Span 40 in a weight ratio of 1:3) was rapidly stirred at 500 rpm for 10 min, then reduced to 100 rpm. Subsequently, 0.03 parts by weight of ammonium persulfate were added, and the mixture was heated to 70°C and stirred for 2.5 h to polymerize and obtain a polyacrylate-encapsulated humic acid emulsion dispersion. One part by weight of the polyacrylate-encapsulated humic acid emulsion dispersion and 0.1 parts by weight of superphosphate were weighed and mixed evenly to obtain a humic acid water-soluble fertilizer.

[0031] Example 2: A method for preparing a humic acid water-soluble fertilizer that enhances crop root growth and development specifically includes the following steps: The weathered coal was dried in a vacuum drying oven at 60℃ for 6 hours, then ground and passed through a 100-mesh sieve. Ten parts by weight of the dried and ground weathered coal were added to a reactor, followed by 35 parts by weight of an oxidant (comprising 28 parts by weight of 25% hydrogen peroxide and 7 parts by weight of ferrous sulfate; ferrous sulfate was added first, then hydrogen peroxide). The mixture was stirred at 200 rpm to ensure complete mixing and wetting. The pH was then adjusted to 4.5, and the mixture was heated to 35℃ and stirred for 45 minutes. After the reaction, the waste liquid was filtered to obtain an oxidized mineral humic acid mixture. Three times the weight of the oxidized mineral humic acid mixture of deionized water was added to the mixture, followed by sodium hydroxide while stirring until the pH reached 10.5. The mixture was then heated to 65℃ and reacted for 60 minutes. After the reaction, the residue was removed by centrifugation at 1000 r / min to obtain an activated solution. The pH of the activated solution was adjusted to 4 with dilute hydrochloric acid and then allowed to stand for 25 min. The precipitate was then obtained by centrifugation at 3000 r / min. The precipitate was washed with deionized water until the pH of the wastewater was neutral, and then dried in a vacuum drying oven at 50°C for 15 h to obtain humic acid precipitate. One part by weight of the humic acid precipitate, 3.5 parts by weight of the methacrylic acid-modified cyclodextrin obtained in Preparation Example 2, and 35 parts by weight of deionized water were weighed and mixed. The mixture was then dispersed using ultrasonic power at 200 W for 15 min, and then heated to 35°C and stirred at 200 r / min for 140 min to obtain a humic acid inclusion dispersion. 18 parts by weight of acrylate (from...) was added to the above humic acid inclusion dispersion. Methyl methacrylate, ethyl methacrylate, and butyl acrylate were mixed in a weight ratio of 1:2:2, and 0.18 parts by weight of emulsifier (composed of sodium dodecyl sulfate and Span 40 in a weight ratio of 1:3) were added. The mixture was then rapidly stirred at 500 rpm for 10 min, then reduced to 100 rpm. Subsequently, 0.035 parts by weight of ammonium persulfate were added, and the mixture was heated to 70°C and stirred for 3 h to polymerize and obtain a polyacrylate-encapsulated humic acid emulsion dispersion. One part by weight of the polyacrylate-encapsulated humic acid emulsion dispersion and 0.15 parts by weight of superphosphate were weighed and mixed evenly to obtain a humic acid water-soluble fertilizer.

[0032] Example 3: A method for preparing a humic acid water-soluble fertilizer that enhances crop root growth and development specifically includes the following steps: The weathered coal was dried in a vacuum drying oven at 60℃ for 6 hours, then ground and passed through a 100-mesh sieve. Ten parts by weight of the dried and ground weathered coal were added to a reactor, followed by 40 parts by weight of an oxidant (comprising 30 parts by weight of 25% hydrogen peroxide and 10 parts by weight of ferrous sulfate; ferrous sulfate was added first, then hydrogen peroxide). The mixture was stirred at 200 rpm to ensure complete mixing and wetting. The pH was then adjusted to 5.0, and the mixture was heated to 40℃ and stirred for 50 minutes. After the reaction, the waste liquid was filtered to obtain an oxidized mineral humic acid mixture. Three times the weight of the oxidized mineral humic acid mixture of deionized water was added to the mixture, followed by sodium hydroxide while stirring until the pH reached 11. The mixture was then heated to 70℃ and reacted for 70 minutes. After the reaction, the residue was removed by centrifugation at 1000 r / min to obtain an activated solution. The pH of the activated solution was adjusted to 4.5 with dilute hydrochloric acid and then allowed to stand for 20 min. The precipitate was then obtained by centrifugation at 3000 r / min. The precipitate was washed with deionized water until the pH of the wastewater was neutral, and then dried in a vacuum drying oven at 50°C for 15 h to obtain humic acid precipitate. One part by weight of the humic acid precipitate, four parts by weight of the methacrylic acid-modified cyclodextrin obtained in Preparation Example 3, and 30 parts by weight of deionized water were weighed and mixed. The mixture was then dispersed using ultrasonic power at 200 W for 15 min, then heated to 40°C and stirred at 200 r / min for 150 min to obtain a humic acid inclusion dispersion. 20 parts by weight of acrylate (…) were added to the above humic acid inclusion dispersion. A polyacrylate-encapsulated humic acid emulsion dispersion was obtained by mixing methyl methacrylate, ethyl methacrylate, and butyl acrylate in a weight ratio of 1:2:2 and 0.2 parts by weight of emulsifier (composed of sodium dodecyl sulfate and Span 40 in a weight ratio of 1:3). The mixture was then rapidly stirred at 500 rpm for 10 min, then reduced to 100 rpm. Subsequently, 0.04 parts by weight of ammonium persulfate was added, and the mixture was heated to 75°C and stirred for 3 h to obtain a polyacrylate-encapsulated humic acid emulsion dispersion. One part by weight of the polyacrylate-encapsulated humic acid emulsion dispersion and 0.2 parts by weight of superphosphate were weighed and mixed evenly to obtain a humic acid water-soluble fertilizer.

[0033] Comparative Example 1: A method for preparing a humic acid water-soluble fertilizer that enhances crop root growth and development specifically includes the following steps: The methacrylic acid-modified cyclodextrin in Example 3 was replaced with the methacrylic acid-modified cyclodextrin obtained in Preparation Example 4, and the rest of the preparation process was the same as in Example 3.

[0034] Comparative Example 2: A method for preparing a humic acid water-soluble fertilizer that enhances crop root growth and development specifically includes the following steps: The methacrylic acid-modified cyclodextrin in Example 3 was replaced with the methacrylic acid-modified cyclodextrin obtained in Preparation Example 5, and the rest of the preparation process was the same as in Example 3.

[0035] Comparative Example 3: A method for preparing a humic acid water-soluble fertilizer that enhances crop root growth and development specifically includes the following steps: The weathered coal in Example 3 was replaced with peat, and the rest of the preparation process remained the same as in Example 3.

[0036] Comparative Example 4: A method for preparing a humic acid water-soluble fertilizer that enhances crop root growth and development specifically includes the following steps: The weathered coal was dried in a vacuum drying oven at 60℃ for 6 hours, then ground and passed through a 100-mesh sieve. Ten parts by weight of the dried and ground weathered coal were weighed and mixed with 30 times the amount of deionized water. Sodium hydroxide was then added while stirring until the pH reached 11. The mixture was then heated to 70℃ and reacted for 70 minutes. After the reaction, the residue was removed by centrifugation at 1000 rpm to obtain an activated solution. The pH of the activated solution was adjusted to 4.5 with dilute hydrochloric acid and then allowed to stand for 20 minutes. The precipitate was then separated by centrifugation at 3000 r / min. The precipitate was washed with deionized water until the pH of the rinsing wastewater was neutral. It was then dried in a vacuum drying oven at 50°C for 15 h to obtain humic acid precipitate. One part by weight of the humic acid precipitate, four parts by weight of the methacrylic acid-modified cyclodextrin obtained in Preparation Example 3, and 30 parts by weight of deionized water were weighed and mixed. The mixture was then dispersed using ultrasonic power at 200 W for 15 min, and then heated to 40°C and stirred at 200 r / min for 150 min to obtain a humic acid inclusion dispersion. 20 parts by weight of acrylate (…) were added to the above humic acid inclusion dispersion. A polyacrylate-encapsulated humic acid emulsion dispersion was obtained by mixing methyl methacrylate, ethyl methacrylate, and butyl acrylate in a weight ratio of 1:2:2 and 0.2 parts by weight of emulsifier (composed of sodium dodecyl sulfate and Span 40 in a weight ratio of 1:3). The mixture was then rapidly stirred at 500 rpm for 10 min, then reduced to 100 rpm. Subsequently, 0.04 parts by weight of ammonium persulfate was added, and the mixture was heated to 75°C and stirred for 3 h to obtain a polyacrylate-encapsulated humic acid emulsion dispersion. One part by weight of the polyacrylate-encapsulated humic acid emulsion dispersion and 0.2 parts by weight of superphosphate were weighed and mixed evenly to obtain a humic acid water-soluble fertilizer.

[0037] Comparative Example 5: A method for preparing a humic acid water-soluble fertilizer that enhances crop root growth and development specifically includes the following steps: The weathered coal was dried in a vacuum drying oven at 60℃ for 6 hours, then ground and passed through a 100-mesh sieve. Ten parts by weight of the dried and ground weathered coal were added to a reactor, followed by 50 parts by weight of an oxidant (comprising 40 parts by weight of 30% hydrogen peroxide and 10 parts by weight of ferrous sulfate; ferrous sulfate was added first, then hydrogen peroxide). The mixture was stirred at 200 rpm to ensure complete mixing and wetting. The pH was then adjusted to 5.0, and the mixture was heated to 40℃ and stirred for 60 minutes. After the reaction, the waste liquid was filtered to obtain an oxidized mineral humic acid mixture. Three times the weight of the oxidized mineral humic acid mixture of deionized water was added to the mixture, followed by sodium hydroxide while stirring until the pH reached 11. The mixture was then heated to 70℃ and reacted for 70 minutes. After the reaction, the residue was removed by centrifugation at 1000 r / min to obtain an activated solution. The pH of the activated solution was adjusted to 4.5 with dilute hydrochloric acid and then allowed to stand for 20 min. The precipitate was then obtained by centrifugation at 3000 r / min. The precipitate was washed with deionized water until the pH of the wastewater was neutral, and then dried in a vacuum drying oven at 50°C for 15 h to obtain humic acid precipitate. One part by weight of the humic acid precipitate, four parts by weight of the methacrylic acid-modified cyclodextrin obtained in Preparation Example 3, and 30 parts by weight of deionized water were weighed and mixed. The mixture was then dispersed using ultrasonic power at 200 W for 15 min, then heated to 40°C and stirred at 200 r / min for 150 min to obtain a humic acid inclusion dispersion. 20 parts by weight of acrylate (…) were added to the above humic acid inclusion dispersion. A polyacrylate-encapsulated humic acid emulsion dispersion was obtained by mixing methyl methacrylate, ethyl methacrylate, and butyl acrylate in a weight ratio of 1:2:2 and 0.2 parts by weight of emulsifier (composed of sodium dodecyl sulfate and Span 40 in a weight ratio of 1:3). The mixture was then rapidly stirred at 500 rpm for 10 min, then reduced to 100 rpm. Subsequently, 0.04 parts by weight of ammonium persulfate was added, and the mixture was heated to 75°C and stirred for 3 h to obtain a polyacrylate-encapsulated humic acid emulsion dispersion. One part by weight of the polyacrylate-encapsulated humic acid emulsion dispersion and 0.2 parts by weight of superphosphate were weighed and mixed evenly to obtain a humic acid water-soluble fertilizer.

[0038] Comparative Example 6: A method for preparing a humic acid water-soluble fertilizer that enhances crop root growth and development specifically includes the following steps: The weathered coal was dried in a vacuum drying oven at 60℃ for 6 hours, then ground and passed through a 100-mesh sieve. Ten parts by weight of the dried and ground weathered coal were added to a reactor, followed by 20 parts by weight of an oxidant (comprising 10 parts by weight of 20% hydrogen peroxide and 10 parts by weight of ferrous sulfate; ferrous sulfate was added first, then hydrogen peroxide). The mixture was stirred at 200 rpm to ensure complete mixing and wetting. The pH was then adjusted to 4.5, and the mixture was heated to 30℃ and stirred for 30 minutes. After the reaction, the waste liquid was filtered to obtain an oxidized mineral humic acid mixture. Three times the weight of the oxidized mineral humic acid mixture of deionized water was added to the mixture, followed by sodium hydroxide while stirring until the pH reached 10. The mixture was then heated to 60℃ and reacted for 50 minutes. After the reaction, the residue was removed by centrifugation at 1000 r / min to obtain an activated solution. The pH of the activated solution was adjusted to 4 with dilute hydrochloric acid and then allowed to stand for 30 min. The precipitate was then obtained by centrifugation at 3000 r / min. The precipitate was washed with deionized water until the pH of the wastewater was neutral, and then dried in a vacuum drying oven at 50°C for 15 h to obtain humic acid precipitate. One part by weight of the humic acid precipitate, three parts by weight of the methacrylic acid-modified cyclodextrin obtained in Preparation Example 1, and 40 parts by weight of deionized water were weighed and mixed. The mixture was then dispersed using ultrasonic power at 200 W for 15 min, and then heated to 35°C and stirred at 200 r / min for 120 min to obtain a humic acid inclusion dispersion. 15 parts by weight of acrylate (derived from methyl methacrylate) was added to the above humic acid inclusion dispersion. A mixture of methyl acrylate, ethyl methacrylate, and butyl acrylate in a weight ratio of 1:2:2, and 0.15 parts by weight of emulsifier (composed of sodium dodecyl sulfate and Span 40 in a weight ratio of 1:3) was rapidly stirred at 500 rpm for 10 min, then reduced to 100 rpm. Subsequently, 0.03 parts by weight of ammonium persulfate were added, and the mixture was heated to 70°C and stirred for 2.5 h to polymerize and obtain a polyacrylate-encapsulated humic acid emulsion dispersion. One part by weight of the polyacrylate-encapsulated humic acid emulsion dispersion and 0.1 parts by weight of superphosphate were weighed and mixed evenly to obtain a humic acid water-soluble fertilizer.

[0039] Comparative Example 7: A method for preparing a humic acid water-soluble fertilizer that enhances crop root growth and development specifically includes the following steps: The acrylate in Example 3 (composed of methyl methacrylate, ethyl methacrylate and butyl acrylate in a weight ratio of 1:2:2) was replaced with acrylate (composed of methyl methacrylate, ethyl methacrylate and butyl acrylate in a weight ratio of 2:1:1), and the rest of the preparation process was the same as in Example 3.

[0040] Comparative Example 8: A method for preparing a humic acid water-soluble fertilizer that enhances crop root growth and development specifically includes the following steps: In Example 3, the acrylate (composed of methyl methacrylate, ethyl methacrylate, and butyl acrylate mixed in a weight ratio of 1:2:2) was increased to 30 parts by weight. The rest of the preparation process was kept the same as in Example 3. It was found that the viscosity of the polyacrylate-encapsulated humic acid emulsion dispersion was too high, and it could not be mixed with superphosphate, resulting in preparation failure. This may be because when the amount of acrylate is too large, it may tend to be a water-in-oil system, which leads to an increase in overall viscosity and is not conducive to the preparation of humic acid water-soluble fertilizer.

[0041] According to the "Residue Method" described in Part 5 of GB / T 11957-2001, the total humic acid content in the oxidized mineral humic acid mixtures obtained in Examples 1-3, Comparative Examples 1-3 and Comparative Examples 5-7 was determined, and the results are shown in Table 1 below.

[0042] Table 1 Total Humic Acid Content

[0043] The fertilizer efficacy of the humic acid water-soluble fertilizers obtained in Examples 1-3 and Comparative Examples 1-7 was determined: The cultivated cabbage seedlings were transplanted into the soil in 10 rows with 10 seedlings per row. 50g of humic acid water-soluble fertilizer was diluted with 25kg of water. Then, 6kg of the diluted fertilizer was applied as a foliar spray per acre. The first fertilization was carried out on the first day after transplanting. After the first fertilization, a second fertilization was carried out after an interval of 10 days. Finally, the average fresh weight and average root length were measured on the 30th day. The results are shown in Table 2 below.

[0044] Table 2 Fertilizer Efficiency Test

[0045] The following conclusions can be drawn from the test results in Tables 1 and 2 above: (1) As can be seen from Examples 1 to 3, the humic acid water-soluble fertilizer prepared by the preparation method of the present invention has good fertilizer effect when used for crop fertilization.

[0046] (2) Comparative Example 1 shows that the prepared humic acid water-soluble fertilizer has poor fertilizer effect. This may be because the hydrophobic cavity of α-cyclodextrin is smaller than that of γ-cyclodextrin, resulting in poor encapsulation effect of humic acid. Finally, when mixed with superphosphate, the calcium in superphosphate may chelate the unencapsulated humic acid, leading to humic acid flocculation and deposition, which affects the fertilizer effect of humic acid.

[0047] (3) Comparative Example 2 shows that the prepared humic acid water-soluble fertilizer has poor fertilizer effect. This may be because in this system, methacrylic acid condenses to the surface of γ-cyclodextrin through carboxyl group. The amount of EDC hydrochloride and 4-dimethylaminopyridine is too low and the reaction time is too short, which may cause the carboxyl group to fail to effectively condense with γ-cyclodextrin, thereby affecting the subsequent emulsion polymerization and affecting the fertilizer effect of humic acid.

[0048] (4) Comparative Example 3 shows that the fertilizer effect of the prepared humic acid water-soluble fertilizer is poor. This may be because the oxidation system used in this system has a poor effect on the activation treatment of peat. The oxidation treatment method of this system has different effects on the types of raw materials for preparing humic acid and cannot be applied to the activation treatment of all raw materials that can be used to prepare humic acid.

[0049] (5) Comparative Example 4 shows that the prepared humic acid water-soluble fertilizer has poor fertilizer effect. This may be because oxidation in this system can break down large molecules into small molecules. If weathered coal is activated directly with alkali without oxidation treatment, the molecular weight of humic acid may be too high, making it difficult for cyclodextrin to effectively encapsulate it. Finally, when mixed with superphosphate, the calcium in superphosphate may chelate the unencapsulated humic acid, leading to humic acid flocculation and deposition, which affects the fertilizer effect of humic acid.

[0050] (6) Comparative Example 5 shows that the fertilizer effect of the prepared humic acid water-soluble fertilizer is poor. This may be because there is too much oxidant and the oxidation time is too long in this system, which causes serious degradation of humic acid, resulting in a low humic acid yield and poor fertilizer effect of the final prepared humic acid water-soluble fertilizer.

[0051] (7) Comparative Example 6 shows that the prepared humic acid water-soluble fertilizer has poor fertilizer effect. This may be because the amount of oxidant used in this system is low and the oxidation time is too short, so the oxidation of weathered coal is not thorough enough, resulting in a low yield of humic acid and poor fertilizer effect of the final prepared humic acid water-soluble fertilizer.

[0052] (8) Comparative Example 7 shows that the prepared humic acid water-soluble fertilizer has poor fertilizer effect. This may be because methyl methacrylate is a hard monomer. If too much is used, it may cause the film formed by the humic acid water-soluble fertilizer after coating and mixing to break when applied. This may cause the fertilizer effect of the humic acid water-soluble fertilizer to be lost too quickly and the fertilizer effect cannot be effectively exerted.

[0053] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A method for preparing a humic acid water-soluble fertilizer that enhances root growth and development in crops, characterized in that, The preparation method includes the following steps: A mixture of oxidized mineral humic acid and an oxidant is obtained by mixing and reacting them in a weight ratio of 1:3~4. The mixture of oxidized mineral humic acid and solid alkali is heated to 60℃~70℃ and reacted for 50min~70min. After centrifugation, an activation solution is obtained. The activation solution is then treated with acid and centrifuged to obtain humic acid precipitate. Humic acid precipitate, methacrylic acid modified cyclodextrin and deionized water were mixed and dispersed, and then heated to 35℃~40℃ and stirred for 120min~150min to obtain humic acid inclusion dispersion. The humic acid inclusion dispersion, acrylate, emulsifier and initiator were mixed and heated to 70℃~75℃ for 2.5h~3h to polymerize and obtain polyacrylate-encapsulated humic acid emulsion dispersion; A humic acid water-soluble fertilizer is formed by mixing polyacrylate-encapsulated humic acid emulsion dispersion and calcium-containing phosphate fertilizer at a weight ratio of 1:0.1~0.

2.

2. The method for preparing a humic acid water-soluble fertilizer to improve crop root growth and development according to claim 1, characterized in that, The oxidant is composed of hydrogen peroxide solution and ferrous sulfate in a weight ratio of 2~3:0.7~1.

3. The method for preparing a humic acid water-soluble fertilizer to improve crop root growth and development according to claim 1, characterized in that, The conditions for the mixed reaction of mineral humic acid and oxidant include a pH of 4.5-5.0, a temperature of 30℃-40℃, and a reaction time of 40-50 min.

4. The method for preparing a humic acid water-soluble fertilizer to improve crop root growth and development according to claim 1, characterized in that, The amount of solid alkali used is to adjust the pH of the oxidized mineral humic acid mixture to 10-11.

5. The method for preparing a humic acid water-soluble fertilizer to improve crop root growth and development according to claim 1, characterized in that, The acid treatment process includes adjusting the pH to 4-4.5 at a rotation speed of 100 r / min, followed by standing for 20-30 min.

6. The method for preparing a humic acid water-soluble fertilizer to improve crop root growth and development according to claim 1, characterized in that, The preparation method of the methacrylic acid modified cyclodextrin includes the following steps: Methacrylic acid, cyclodextrin, EDC hydrochloride, 4-dimethylaminopyridine, and dichloromethane were mixed and dispersed in a weight ratio of 1:0.6~0.8:2.5~3:1~1.5:20~30 to obtain a dispersion. The dispersion was reacted at 25℃~30℃ for 24h~30h and then dialyzed to obtain methacrylic acid modified cyclodextrin.

7. The method for preparing a humic acid water-soluble fertilizer to improve crop root growth and development according to claim 1, characterized in that, The acrylate is composed of methyl methacrylate, ethyl methacrylate and butyl acrylate in a weight ratio of 1:2:

2.

8. The method for preparing a humic acid water-soluble fertilizer to improve crop root growth and development according to claim 1, characterized in that, The weight ratio of the humic acid precipitate, methacrylic acid modified cyclodextrin, deionized water, acrylate, emulsifier and initiator is 1:3~4:30~40:15~20:0.15~0.2:0.03~0.

04.

9. The method for preparing a humic acid water-soluble fertilizer to improve crop root growth and development according to claim 1, characterized in that, The calcium-containing phosphate fertilizer includes superphosphate.

10. A humic acid water-soluble fertilizer prepared by the method for preparing a humic acid water-soluble fertilizer for improving root growth and strengthening crops as described in any one of claims 1 to 9.

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