A kind of medicine-fertilizer integrated biochar restoration controlled-release fertilizer and preparation method thereof

Abstract

The present invention relates to a medicine-fertilizer integrated biochar restoration controlled-release fertilizer and a preparation method thereof. The present invention prepares a controlled-release fertilizer composed of a nutrient layer, a buffer layer and an isolation layer from the inside to the outside through a reasonable preparation process, manufactures a pore structure and stabilizes the outer layer structure, achieves a good controlled-release effect, and prolongs the controlled-release cycle. Biochar bacteria and the like can be effectively coupled, and can provide full-cycle nutrients for plant growth, and has good application prospects and application value.

Description

Technical Field

[0001] The invention relates to the technical field of controlled-release fertilizers, and in particular to a medicine-fertilizer integrated biochar-remediation controlled-release fertilizer. Background Art

[0002] At present, the decline in soil fertility and bacterial infection caused by continuous cropping are important factors in reducing crop yields. Maintaining soil fertility and reducing crop disease without excessive use of chemical fertilizers has become an urgent problem to be solved. As a new type of fertilizer, controlled-release fertilizer can regulate the release rate of nutrients according to the nutrient needs of crops, so that fertilizers can match the growth cycle of plants, reduce the number of fertilizer applications and improve fertilizer utilization.

[0003] When applied in the field, traditional controlled-release fertilizers often cause the membrane layer to absorb water and burst due to water penetration, resulting in rapid loss of nutrients in a short period of time, and the controlled-release effect is limited to the early stage of application; in addition, the membrane layer of traditional controlled-release fertilizers has few and single pores, and the controlled-release effect is not ideal; biological pesticides cannot be well coupled with fertilizers and have a short efficacy period, and have limited effects on crop pathogen infection prevention and control and soil improvement in the short term after application. CN201910294900.4 discloses a method for preparing a modified corn cob biochar-based slow-release compound fertilizer. Although the modified corn cob biochar fertilizer can extend the effective period of fertilizer nutrients to a certain extent, it still faces the problem of membrane rupture in the later stage; CN201710785703.3 discloses a method for preparing a slow-release nutrient base with controlled pore formation and surface modification of biochar. Although modification and combined pore formation can enhance the slow-release performance of biochar, the process is complicated and the process parameters are difficult to accurately control. CN202011088518.7 discloses a method for the combined use of sludge biochar immobilized bacteria and plants to repair heavy metal contaminated soil. The method utilizes Robinia pseudoacacia rhizosphere bacteria and remediation plants to treat contaminated soil. However, the scheme is not universal, has a limited scope of application and a long preparation cycle.

[0004] Therefore, there is an urgent need for a long-term, efficient composite controlled-release fertilizer to solve the above problems. Summary of the invention

[0005] The technical problem to be solved by the present invention is that the existing controlled-release fertilizers have poor controlled-release effects, short controlled-release cycles, and are difficult to effectively couple with carbon bacteria. In view of the defects in the prior art, a drug-fertilizer integrated biochar restoration controlled-release fertilizer and a preparation method thereof are provided.

[0006] In order to solve the above technical problems, the present invention provides a method for preparing a controlled-release fertilizer containing integrated medicine and fertilizer and biochar restoration, the preparation method comprising the following steps:

[0007] (1) reacting formaldehyde and urea under alkaline conditions and under acidic conditions in sequence to obtain urea-formaldehyde particles;

[0008] (2) reacting the urea-formaldehyde particles obtained in step (1) with diammonium phosphate and potassium sulfate to obtain a nutrient layer;

[0009] (3) mixing the nutrient layer obtained in step (2) with the swelling film coating liquid in a granulator, and then adding humic acid, calcium-rich biochar, biopesticide bacteria spore powder and sodium carboxymethyl cellulose for granulation to obtain a buffer layer-wrapped nutrient layer;

[0010] (4) mixing vinyl-terminated dimethyl polysiloxane, liquefied biomass polyol, and polyether to form a first-level envelope surface; then heating and adding epoxy resin and diethylenetriamine to form a second-level envelope surface for cross-linking, and curing to obtain a three-dimensional envelope unit;

[0011] (5) adding the nutrient layer wrapped by the buffer layer in step (3) into a granulator, dripping the stereocomplexing unit and the curing agent to carry out a curing reaction, and then adding dopamine hydrochloride, polyethyleneimine and sodium alginate to granulate, thereby obtaining a drug-fertilizer integrated biochar restoration controlled-release fertilizer.

[0012] The preparation method of the integrated medicine-fertilizer biochar restoration controlled-release fertilizer provided by the present invention prepares a controlled-release fertilizer composed of a nutrient layer, a buffer layer and an isolation layer from the inside to the outside through a reasonable preparation process, and can provide full-cycle nutrients for plant growth.

[0013] Preferably, the mass ratio of formaldehyde to urea in step (1) is 1:2-3, for example, 1:2, 1:2.5 or 1:3.

[0014] Preferably, the alkaline condition in step (1) is provided by a potassium hydroxide solution, the pH value is 9.0, the reaction temperature is 30-50° C., and the reaction time is 2-3 h.

[0015] In the present invention, under alkaline conditions, the carboxyl group is deprotonated to form a carboxylate with anions, which makes it easier to undergo a nucleophilic addition reaction to form an intermediate 1,3,5-triazine urea with formaldehyde, and then form urea-formaldehyde particles through a polymerization reaction.

[0016] Preferably, the acidic condition in step (1) is provided by hydrochloric acid, the pH value is 5.0, the reaction temperature is 50-70° C., and the reaction time is 25-35 min.

[0017] In the present invention, under acidic conditions, the carboxyl groups that do not participate in the reaction will be protonated and then regenerated into urea through nucleophilic addition, thereby improving the utilization rate of the raw materials.

[0018] In the present invention, after the reaction in step (1), the mixture is generally dried at 60° C. to a constant weight to obtain urea-formaldehyde particles.

[0019] Preferably, the ratio of urea-formaldehyde particles, diammonium phosphate and potassium sulfate in step (2) is 1:0.4-0.6:1-1.5 in mass ratio of nitrogen, phosphorus and potassium. In the present invention, the typical but non-limiting mass ratio of nitrogen, phosphorus and potassium is 1:0.4:1, 1:0.5:1.2, 1:0.6:1.5, etc.

[0020] Preferably, the reaction temperature in step (2) is 50-70°C, for example, 50°C, 60°C or 70°C.

[0021] Preferably, after the reaction in step (2) is completed, drying and granulation are further performed to obtain the nutrient layer.

[0022] Preferably, the method for preparing the swelling film coating liquid in step (3) is: mixing silicon powder, polyvinyl alcohol, starch and potassium bicarbonate in proportion, and heating the mixture to react to obtain the swelling film coating liquid.

[0023] Preferably, the mass ratio of the silicon powder, polyvinyl alcohol, starch and potassium bicarbonate is (100-125):(20-30):(20-30):(0.5-1.5). Typically but not limitatively, the mass ratio may be 100:20:20:0.5, 110:25:25:1, 120:20:27:1.4 or 125:30:30:1.5, etc.

[0024] In the present invention, silicon powder, polyvinyl alcohol, starch and potassium bicarbonate have the following characteristics:

[0025] Silica powder is an inorganic material with good water resistance and antioxidant properties, which can increase the hardness and stability of the film layer.

[0026] Polyvinyl alcohol is a polymer material with good biodegradability and solubility, and can be used as a cross-linking agent in the film layer.

[0027] Starch is a natural polymer material that also has good biodegradability and solubility. Silicon powder and starch and other materials are bonded together to form a uniform film layer. In the film layer, starch can be used as a slow-release material. By adjusting the starch content in the film layer, the release rate of nutrients in the fertilizer can be controlled. At the same time, starch can also increase the flexibility and air permeability of the film layer, thereby improving the stability and adaptability of the film layer.

[0028] Potassium bicarbonate is easily decomposed by heat and is used to produce non-directional pores to further enrich the pore structure of the membrane layer.

[0029] In the present invention, silicon powder can also be replaced by calcium silicate or calcium carbonate, polyvinyl alcohol can be replaced by gelatin or polylactic acid, and starch can be replaced by chitosan, cellulose or the like.

[0030] Preferably, the temperature of the heating reaction is 70-80°C, for example, 70°C, 73°C, 75°C, 77°C or 80°C.

[0031] Preferably, the heating reaction time is 20 to 30 minutes, for example, 20 minutes, 24 minutes, 26 minutes or 30 minutes.

[0032] Preferably, the humic acid in step (3) is prepared by mixing weathered coal with an activator for reaction. The humic acid is activated and then sieved for later use.

[0033] Preferably, the activator is a mixed solution of potassium hydroxide and sodium hydroxide, wherein the mass ratio of potassium hydroxide to sodium hydroxide is (3-4):1.

[0034] Preferably, the mixing reaction is carried out at a rotation speed of 100 r / min for 50 to 70 min.

[0035] Preferably, the preparation method of the calcium-rich biochar in step (3) is: crushing the biomass to remove moisture, mixing it with calcium nitrate in water, and further heating it at high temperature to obtain the calcium-rich biochar. In the present invention, the biomass can be: can be rice straw, wood chips, husks and other biomass.

[0036] In the present invention, biochar has a dual role:

[0037] (1) The microbial growth environment constructed by calcium-rich biochar and activated weathered coal humic acid is used to protect the activity of bacteria and enhance colonization ability. Humic acid applied to the soil will improve the soil structure and increase the ability to retain water and fertilizer. Its acid-base functional groups can improve the acid-base buffering capacity of the soil and create a stable growth environment for plants and microorganisms; the functional groups carboxyl, phenolic hydroxyl, and alcoholic hydroxyl can chelate heavy metals and reduce heavy metal pollution in the soil.

[0038] (2) The rich surface pore structure of biochar can serve as an excellent carrier of calcium ions. When water in the environment invades the buffer layer and causes the surface membrane to rupture, the repair mechanism is activated, the calcium ion channel opens, and the biochar releases calcium ions to react with the sodium alginate on the surface to gel and repair the broken membrane.

[0039] Preferably, the corresponding calcium molar amount per 1g of biomass is 4-6mmol, for example, 4mmol, 5mmol or 6mmol, etc. If the calcium ion content is too low, the repair effect of the gel formed is not good, and if the calcium ion content is too high, it will compete with other nutrients, reduce the ability of plants to absorb other nutrients, and may also cause toxic effects on plants and microorganisms in the soil.

[0040] Preferably, the removal of moisture is drying the biomass at 105° C. for 2 hours until the weight change rate is less than 0.1%. The drying completely removes free moisture from the biomass.

[0041] Preferably, the temperature of mixing with calcium nitrate is 60-90°C, for example, 60°C, 70°C, 80°C or 90°C, etc. In the present invention, the calcium nitrate mixture is generally stirred continuously for more than 2 hours to ensure that the calcium ions are well adsorbed and dispersed on the surface of the biomass powder and its internal structure.

[0042] Preferably, the high temperature heating is performed in a tube furnace.

[0043] Preferably, the high temperature heating temperature is 600-800°C, for example, 600°C, 650°C, 700°C, 750°C or 800°C.

[0044] Preferably, the high temperature heating time is 1 to 2 hours, for example, 1 hour, 1.5 hours or 2 hours.

[0045] Preferably, the swelling film coating liquid in step (3) is evenly dripped onto the nutrient layer, and a dense film layer is obtained through high temperature healing. In step (3), the swelling film coating liquid dripping process can make the coating liquid evenly cover the urea-formaldehyde particles.

[0046] Preferably, the temperature of the high temperature healing is 90-110°C, for example, 90°C, 100°C or 110°C, etc. After high temperature healing, the polymer particles in the coating are further fused to form a dense membrane layer. At the same time, in this process, potassium bicarbonate is thermally decomposed to produce non-directional channels, which can provide primary derivative attachment sites for biochar and biopesticide bacteria; in addition, the non-directional channels produced by the chemical decomposition of potassium bicarbonate, the physical action of sodium carboxymethyl cellulose and the biological action of biopesticide bacteria constitute a three-level pore-forming unit, which jointly regulates the pore structure of the membrane layer.

[0047] In step (3), during the granulation process, a buffer layer is covered on the outside of the nutrient layer, wherein the sodium carboxymethyl cellulose is dissolved in water and then the pores are opened inwardly, and the amylase secreted by the biological pesticide bacteria catalyzes the decomposition of starch in the swollen film and then the pores are opened outwardly.

[0048] Preferably, in step (4), the mass ratio of the vinyl-terminated dimethylpolysiloxane, the liquefied biomass polyol and the polyether is 1:2:2.

[0049] Preferably, the preparation method of the liquefied biomass polyol in step (4) is: mixing polyethylene glycol, glycerol and concentrated sulfuric acid, adding biomass to react to obtain the liquefied biomass polyol;

[0050] Preferably, the mass ratio of the polyethylene glycol, glycerol and concentrated sulfuric acid is (35-40):(3-5):(1.0-1.5), for example, it can be 35:3:1, 37:4:1.4 or 40:5:1.5.

[0051] Preferably, in the liquefied biomass polyol, the reaction temperature is 150-180°C, for example, 150°C, 160°C, 170°C or 180°C.

[0052] Preferably, in the liquefied biomass polyol, the reaction time is 60 to 120 min, for example, 60 min, 70 min, 80 min, 90 min, 100 min or 120 min.

[0053] Preferably, the temperature of the heating in step (4) is 50-80°C, for example, 50°C, 60°C, 70°C or 80°C.

[0054] Preferably, in step (4), the mass ratio of the epoxy resin to diethylenetriamine is 1:1.

[0055] Preferably, the curing agent in step (5) is polymethylene polyphenyl polyisocyanate.

[0056] Preferably, in step (5), the mass ratio of the stereocomplexing unit to the polymethylene polyphenyl polyisocyanate is 1:1.

[0057] Preferably, in step (5), the mass ratio of dopamine hydrochloride, polyethyleneimine and sodium alginate is 5:5:4.

[0058] In the present invention, dopamine hydrochloride and polyethyleneimine can form a complex with certain adhesion in an aqueous solution, which can effectively promote the combination of the inner fertilizer and the coating material; sodium alginate is a natural polymer substance with good biocompatibility, and can react with calcium ions to produce a gel to repair the damaged film layer; the mass ratio of dopamine hydrochloride, polyethyleneimine and sodium alginate is 5:5:4, which can improve the stability and sustainability of the coating while ensuring the quality and biodegradability of the coating.

[0059] In a second aspect, the present invention provides a medicine-fertilizer integrated biochar restoration controlled-release fertilizer prepared by the preparation method described in the first aspect.

[0060] The medicine-fertilizer integrated biochar restoration controlled-release fertilizer provided by the present invention consists of three parts from the inside to the outside: a nutrient layer, a buffer layer, and an isolation layer.

[0061] The nutrient layer is the innermost nutrient storage membrane layer of the controlled-release fertilizer. It is mainly composed of urea-formaldehyde, diammonium phosphate, and potassium sulfate in a certain proportion to provide full-cycle nutrients for plant growth.

[0062] The buffer layer is the membrane layer in the middle of the controlled-release fertilizer. It is based on highly salt-tolerant rhizosphere growth-promoting bacteria (PGPR) biological pesticide bacteria represented by Rhizobium, Bacillus and Pseudomonas. The buffer layer is equipped with a carbon bacteria coupling unit and a three-level pore-forming unit. Among them, the three-level pore-forming unit jointly regulates the pore structure of the membrane layer through three groups of factors: physical, chemical and biological. The carbon bacteria coupling unit is a bacterial growth environment constructed with calcium-rich biochar and activated weathered coal humic acid. The rich pore structure is conducive to the initial derivation and colonization of the bacteria, and can also promote the controlled release of nutrients in the nutrient layer.

[0063] The isolation layer is the outermost film layer of the controlled-release fertilizer, which is composed of a three-dimensional enveloping unit and an enhanced repair unit. The three-dimensional enveloping unit is a super-hydrophobic film that is covered on the surface of the controlled-release fertilizer after secondary modification of liquefied polyol, which plays the role of vaporization isolation; the enhanced repair unit enhances the surface strength of the controlled-release fertilizer film layer through electrostatic action, and the sodium alginate reacts with the calcium ions released by the biochar to gel and repair the broken film layer on the surface.

[0064] In the present invention, calcium ions react with carboxylic acid groups in sodium alginate molecules to generate a calcium salt. This water-insoluble calcium salt forms solid particles, which can be combined with other calcium salt particles to form a three-dimensional network gel. In addition, the hydroxyl groups in the sodium alginate molecules can also interact with the calcium ions, further increasing the stability of the gel. The hydroxyl groups form a complex with the calcium ions through hydrogen bonding, and this complex is fixed in the gel structure, thereby making the gel more solid.

[0065] The product prepared by the preparation method of the present invention has the following beneficial effects:

[0066] The integrated medicine-fertilizer biochar restoration controlled-release fertilizer provided by the present invention consists of three parts from the inside to the outside: a nutrient layer, a buffer layer, and an isolation layer. By reasonably matching nutrients, creating a pore structure, and stabilizing the outer layer structure, a good controlled-release effect is achieved, and the controlled-release cycle is extended. Biochar bacteria, etc. can be effectively coupled to provide full-cycle nutrients for plant growth. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 This is a diagram of the mechanism of action of the integrated medicine-fertilizer biochar restoration controlled-release fertilizer provided in Example 1 of the present invention.

[0068] Figure 2 Schematic diagram of the structure of the medicine-fertilizer integrated biochar remediation controlled-release fertilizer provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0069] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0070] Example 1

[0071] This embodiment provides a controlled-release biochar restoration fertilizer with integrated medicine and fertilizer using rice straw as raw material.

[0072] (1) Formaldehyde and urea were placed in a beaker at a mass ratio of 1:3, stirred until the urea was completely dissolved, and then 5% (w / w) KOH was added to adjust the pH to 9.0, and the mixture was reacted in a water bath at 40°C for 2.5 hours. Subsequently, 2% (w / w) HCl was added to adjust the pH of the solution to 5.0, and the mixture was reacted in a water bath at 60°C for 30 minutes to obtain a white solid, which was then dried at 60°C to constant weight to obtain urea-formaldehyde particles.

[0073] (2) The urea-formaldehyde particles prepared above, diammonium phosphate and potassium sulfate were added into a round-bottom flask according to N:P:K=1:0.5:1.2 (w / w / w), and fully reacted at 60°C and 180 r / min using a constant temperature magnetic stirrer. After drying at 60°C to constant weight, granulation was performed to obtain a nutrient layer.

[0074] (3) The straw was crushed and sieved to 200 μm, and dried in an oven at 105°C for 2 h until the weight change rate was less than 0.1%, and free water was completely removed. 16.4 g of calcium nitrate was added to deionized water, and then 20 g of straw powder was added to the mixed solution to ensure that the molar amount of calcium per unit mass of straw was 5 mmol. The sample was stirred continuously at 80°C for 2 h to ensure that the calcium ions were well adsorbed and dispersed on the surface of the straw and its internal structure. After drying overnight at 100°C in air, a calcium-rich straw sample was obtained. The sample was placed in a tubular furnace, nitrogen was introduced at a rate of 100 mL / min, heated to 800°C at a rate of 20°C / min and kept warm for 1 h to obtain calcium-rich biochar.

[0075] (4) Weigh 100 g of air-dried weathered coal, grind it into powder and place it in a beaker, add 5% KOH / NaOH (w / w) activator, stir it with a magnetic stirrer at 100 r / min for 60 min to activate it, and sieve the activated sample for later use.

[0076] (5) 100 g of silicon powder, 25 g of polyvinyl alcohol, 25 g of starch, and 0.5 g of potassium bicarbonate were mixed in 350 mL of water, heated in a water bath at 80° C., and stirred at 100 r / min for 30 min using a magnetic stirrer to obtain a swelling film coating solution.

[0077] (6) Add 100g of the nutrient layer to the granulator and preheat it to 60°C, then drip the swelling film coating liquid into the granulator so that the swelling film is evenly covered on the urea-formaldehyde particles. After heating to 100°C, high-temperature healing is carried out for 10 minutes to further fuse the polymer particles in the coating to form a dense film layer. At the same time, potassium bicarbonate is decomposed by heat to open the pores inward. Then adjust the temperature to 30°C, add humic acid, calcium-rich biochar, Bacillus thuringiensis spore powder and sodium carboxymethyl cellulose for granulation, and cover the buffer layer outside the nutrient layer. Among them, sodium carboxymethyl cellulose seeps into water and dissolves to open the pores inward, and the amylase secreted by Bacillus thuringiensis catalyzes the decomposition of starch in the swelling film to open the pores outward.

[0078] (7) 36 g of polyethylene glycol, 4 g of glycerol, and 1.2 g of concentrated sulfuric acid were added to a reactor, and after oil bathing at 160° C., 8 g of straw was added, and the reaction was continued with stirring for 90 min. After cooling to room temperature, liquefied straw polyol was obtained.

[0079] (8) 5 g of vinyl-terminated dimethyl polysiloxane, 10 g of liquefied straw polyol, and 10 g of polyether were mixed by magnetic stirring and dispersed in an ultrasonic oscillator for 30 min to form a first-level envelope. The temperature was then raised to 60 ° C, and 5 g of epoxy resin and 5 g of diethylenetriamine were added for cross-linking to form a second-level envelope. After curing for 48 h, a three-dimensional envelope unit was obtained.

[0080] (9) Add the nutrient layer covered with the buffer layer into the granulator and preheat it to 60°C, then add 0.5g of stereocomplex unit and 0.5g of curing agent polymethylene polyphenyl polyisocyanate, and the coating material will complete the curing reaction on the surface of urea-formaldehyde particles for about 10 minutes. Then continue to add 0.25g of dopamine hydrochloride, 0.25g of polyethyleneimine, and 0.2g of sodium alginate to granulate, and finally obtain the integrated drug-fertilizer biochar remediation controlled-release fertilizer. The mechanism diagram of the prepared integrated drug-fertilizer biochar remediation controlled-release fertilizer is as follows: Figure 1 As shown, the structural diagram is as follows Figure 2 shown.

[0081] Example 2

[0082] This embodiment provides a kind of medicine and fertilizer integrated biochar repair controlled release fertilizer using sawdust as raw material

[0083] (1) Place formaldehyde and urea in a beaker at a mass ratio of 1:3, stir until urea is completely dissolved, add 5% (w / w) KOH to adjust the pH to 9.0, and react in a water bath at 40°C for 2.5 hours. Then add 2% (w / w) HCl to adjust the solution pH to 5.0, react in a water bath at 60°C for 30 minutes to obtain a white solid, which is dried at 60°C to constant weight to obtain urea-formaldehyde particles.

[0084] (2) The urea-formaldehyde particles prepared above, diammonium phosphate and potassium sulfate were added into a round-bottom flask according to N:P:K=1:0.5:1.2 (w / w / w), and fully reacted at 60°C and 180 r / min using a constant temperature magnetic stirrer. After drying at 60°C to constant weight, granulation was performed to obtain a nutrient layer.

[0085] (3) The sawdust was crushed and sieved to 200 μm, and dried in an oven at 105°C for 2 h until the weight change rate was less than 0.1%, and free water was completely removed. 16.4 g of calcium nitrate was added to deionized water, and then 20 g of sawdust powder was added to the mixed solution to ensure that the molar amount of calcium per unit mass of sawdust was 5 mmol. The sample was stirred continuously at 80°C for 2 h to ensure that the calcium ions were well adsorbed and dispersed on the surface of the sawdust and its internal structure. After drying overnight at 100°C in air, a calcium-rich sawdust sample was obtained. The sample was placed in a tubular furnace, nitrogen was introduced at a rate of 100 mL / min, heated to 800°C at a rate of 20°C / min and kept warm for 1 h to obtain calcium-rich biochar.

[0086] (4) Weigh 100 g of air-dried weathered coal, grind it into powder and place it in a beaker, add 5% KOH / NaOH (w / w) activator, stir it with a magnetic stirrer at 100 r / min for 60 min to activate it, and sieve the activated sample for later use.

[0087] (5) 100 g of silicon powder, 25 g of polyvinyl alcohol, 25 g of starch, and 0.5 g of potassium bicarbonate were mixed in 350 mL of water, heated in a water bath at 80° C., and stirred at 100 r / min for 30 min using a magnetic stirrer to obtain a swelling film coating solution.

[0088] (6) Add 100g of the nutrient layer to the granulator and preheat it to 60°C, then drip the swelling film coating liquid into the granulator so that the swelling film is evenly covered on the urea-formaldehyde particles. After heating to 100°C, high-temperature healing is carried out for 10 minutes to further fuse the polymer particles in the coating to form a dense film layer. At the same time, potassium bicarbonate is decomposed by heat to open the pores inward. Then adjust the temperature to 30°C, add humic acid, calcium-rich biochar, Bacillus thuringiensis spore powder and sodium carboxymethyl cellulose for granulation, and cover the buffer layer outside the nutrient layer. Among them, sodium carboxymethyl cellulose seeps into water and dissolves to open the pores inward, and the amylase secreted by Bacillus thuringiensis catalyzes the decomposition of starch in the swelling film to open the pores outward.

[0089] (7) 36 g of polyethylene glycol, 4 g of glycerol, and 1.2 g of concentrated sulfuric acid were added to a reactor, and after oil bathing at 160° C., 8 g of straw was added, and the reaction was continued with stirring for 90 min. After cooling to room temperature, liquefied straw polyol was obtained.

[0090] (8) 5 g of vinyl-terminated dimethyl polysiloxane, 10 g of liquefied straw polyol, and 10 g of polyether were mixed by magnetic stirring and dispersed in an ultrasonic oscillator for 30 min to form a first-level envelope. The temperature was then raised to 60 ° C, and 5 g of epoxy resin and 5 g of diethylenetriamine were added for cross-linking to form a second-level envelope. After curing for 48 h, a three-dimensional envelope unit was obtained.

[0091] (9) The nutrient layer covered with the buffer layer is added to the granulator and preheated to 60°C, followed by dropwise addition of 0.5g of the stereocomplex unit and 0.5g of the curing agent polymethylene polyphenyl polyisocyanate, and the coating material is cured on the surface of the urea-formaldehyde particles for about 10 minutes. Then, 0.25g of dopamine hydrochloride, 0.25g of polyethyleneimine, and 0.2g of sodium alginate are added to granulate, and finally a drug-fertilizer integrated biochar repair controlled-release fertilizer is obtained.

[0092] Example 3

[0093] This embodiment provides a kind of medicine and fertilizer integrated biochar restoration controlled release fertilizer using rice husk as raw material

[0094] (1) Formaldehyde and urea were placed in a beaker at a mass ratio of 1:3, stirred until the urea was completely dissolved, and then 5% (w / w) KOH was added to adjust the pH to 9.0, and the mixture was reacted in a water bath at 40°C for 2.5 hours. Subsequently, 2% (w / w) HCl was added to adjust the pH of the solution to 5.0, and the mixture was reacted in a water bath at 60°C for 30 minutes to obtain a white solid, which was then dried at 60°C to constant weight to obtain urea-formaldehyde particles.

[0095] (2) The urea-formaldehyde particles prepared above, diammonium phosphate and potassium sulfate were added into a round-bottom flask according to N:P:K=1:0.5:1.2 (w / w / w), and fully reacted at 60°C and 180 r / min using a constant temperature magnetic stirrer. After drying at 60°C to constant weight, granulation was performed to obtain a nutrient layer.

[0096] (3) The husk was crushed and sieved to 200 μm, and dried in an oven at 105°C for 2 h until the weight change rate was less than 0.1%, and free water was completely removed. 16.4 g of calcium nitrate was added to deionized water, and then 20 g of husk powder was added to the mixed solution to ensure that the molar amount of calcium per unit mass of husk was 5 mmol. The sample was stirred continuously at 80°C for 2 h to ensure that the calcium ions were well adsorbed and dispersed on the surface of the husk and its internal structure. After drying overnight at 100°C in air, a calcium-rich husk sample was obtained. The sample was placed in a tubular furnace, nitrogen was introduced at a rate of 100 mL / min, heated to 800°C at a rate of 20°C / min and kept warm for 1 h to obtain calcium-rich biochar.

[0097] (4) Weigh 100 g of air-dried weathered coal, grind it into powder and place it in a beaker, add 5% KOH / NaOH (w / w) activator, stir it with a magnetic stirrer at 100 r / min for 60 min to activate it, and sieve the activated sample for later use.

[0098] (5) 100 g of silicon powder, 25 g of polyvinyl alcohol, 25 g of starch, and 0.5 g of potassium bicarbonate were mixed in 350 mL of water, heated in a water bath at 80° C., and stirred at 100 r / min for 30 min using a magnetic stirrer to obtain a swelling film coating solution.

[0099] (6) Add 100g of the nutrient layer to the granulator and preheat it to 60°C, then drip the swelling film coating liquid into the granulator so that the swelling film is evenly covered on the urea-formaldehyde particles. After heating to 100°C, high-temperature healing is carried out for 10 minutes to further fuse the polymer particles in the coating to form a dense film layer. At the same time, potassium bicarbonate is decomposed by heat to open the pores inward. Then adjust the temperature to 30°C, add humic acid, calcium-rich biochar, Bacillus thuringiensis spore powder and sodium carboxymethyl cellulose for granulation, and cover the buffer layer outside the nutrient layer. Among them, sodium carboxymethyl cellulose seeps into water and dissolves to open the pores inward, and the amylase secreted by Bacillus thuringiensis catalyzes the decomposition of starch in the swelling film to open the pores outward.

[0100] (7) 36 g of polyethylene glycol, 4 g of glycerol, and 1.2 g of concentrated sulfuric acid were added to a reactor, and after oil bathing at 160° C., 8 g of straw was added, and the reaction was continued with stirring for 90 min. After cooling to room temperature, liquefied straw polyol was obtained.

[0101] (8) 5 g of vinyl-terminated dimethyl polysiloxane, 10 g of liquefied straw polyol, and 10 g of polyether were mixed by magnetic stirring and dispersed in an ultrasonic oscillator for 30 min to form a first-level envelope. The temperature was then raised to 60 ° C, and 5 g of epoxy resin and 5 g of diethylenetriamine were added for cross-linking to form a second-level envelope. After curing for 48 h, a three-dimensional envelope unit was obtained.

[0102] (9) The nutrient layer covered with the buffer layer is added to the granulator and preheated to 60°C, followed by dropwise addition of 0.5g of the stereocomplex unit and 0.5g of the curing agent polymethylene polyphenyl polyisocyanate, and the coating material is cured on the surface of the urea-formaldehyde particles for about 10 minutes. Then, 0.25g of dopamine hydrochloride, 0.25g of polyethyleneimine, and 0.2g of sodium alginate are added to granulate, and finally a drug-fertilizer integrated biochar repair controlled-release fertilizer is obtained.

[0103] Example 4

[0104] This embodiment is basically the same as the embodiment 1, except that step (6) does not include the step of heating to 100°C for high temperature healing. The rest is the same as the embodiment 1 to prepare the integrated medicine and fertilizer biochar restoration controlled release fertilizer.

[0105] Example 5

[0106] The only difference between this embodiment and embodiment 1 is that the molar amount of calcium per unit mass of straw in step (3) is 2 mmol.

[0107] Example 6

[0108] The only difference between this embodiment and embodiment 1 is that the molar amount of calcium per unit mass of straw in step (3) is 8 mmol.

[0109] Example 7

[0110] The only difference between this embodiment and embodiment 1 is that potassium bicarbonate is not used in the process of preparing the swelling membrane coating solution in step (3).

[0111] Comparative Example 1

[0112] This comparative example is basically the same as Example 1, except that step (9) of this comparative example does not include the process of adding 0.25 g dopamine hydrochloride, 0.25 g polyethyleneimine, and 0.2 g sodium alginate for granulation.

[0113] Comparative Example 2

[0114] The difference between this comparative example and Example 1 is that this comparative example does not include steps (7), (8) and (9), and only a control fertilizer with a buffer layer covering the outer surface of the nutrient layer is prepared.

[0115] Comparative Example 3

[0116] The difference between this comparative example and Example 1 is that this comparative example does not include the coating of the three-dimensional envelope unit in steps (7), (8) and step (9), and only 0.25g of dopamine hydrochloride, 0.25g of polyethyleneimine and 0.2g of sodium alginate are added to granulate in step (9) to obtain a controlled-release fertilizer.

[0117] The controlled-release fertilizer obtained above was subjected to a performance test using a soil column leaching experiment. The specific method was as follows: each sample fertilizer was evenly spread between two layers of quartz sand in the leaching bottle, 200 mL of distilled water was added on the first day, and the volume of the leaching liquid was measured every 24 hours thereafter, and 100 mL of distilled water was added to the leaching bottle. The test period was 5 days.

[0118] Test: Take the leaching solution to be tested and dilute it 10 times with water in a colorimetric tube. Use an ultraviolet spectrophotometer (λ=422nm) to measure the concentration of the leaching solution and calculate the single-day leaching rate and cumulative leaching rate.

[0119] The test results are shown in Table 1 below.

[0120] Table 1

[0121]

[0122]

[0123]

[0124] According to the data in Table 1, it can be seen that the controlled-release fertilizers provided in Examples 1 to 3 of the present invention have similar effects in the leaching experiment and show the most excellent controlled-release performance.

[0125] Example 4 did not undergo high-temperature healing, and the density of the membrane layer was significantly reduced. Although potassium bicarbonate was added, the pores could not be opened; the effect of Example 7 was better than that of Example 4, indicating that although Example 7 did not add potassium bicarbonate to the swollen membrane, the high-temperature healing process promoted the fusion of polymer particles in the membrane and strengthened its mechanical properties, thus presenting better controlled release performance than Example 4. In addition, due to the lack of potassium bicarbonate chemical pore formation process, Examples 4 and 7 had a poorer controlled release effect than Examples 1 to 3.

[0126] The calcium ion content in Example 5 is lower than that in Examples 1 to 3, so the effect of gel repair is limited and the controlled release performance is reduced; the calcium ion content in Example 6 is higher than that in Examples 1 to 3, because the excessive generation of gel leads to pore blockage and the utilization rate of the fertilizer is significantly reduced.

[0127] In Comparative Example 1, due to the hydrophobic mechanism of the stereoscopic enveloping unit in the early stage of leaching, its controlled release effect is equivalent to that of Examples 1 to 3; in the late stage of leaching, due to the intensified water intrusion leading to the rupture of the membrane layer and the lack of gel repair mechanism, its controlled release performance is far inferior to that of Examples 1 to 3. Comparing Example 5 with Comparative Example 1, it can be seen that although the gel repair process of Example 5 is limited, it can still promote the controlled release of fertilizer.

[0128] In Comparative Example 3, due to the lack of hydrophobic mechanism of stereoenvelope unit in the early stage of leaching, the controlled release effect is far inferior to that of Examples 1 to 3; in the late stage of leaching, the gel repair mechanism is activated and the controlled release performance is improved.

[0129] Comparative Example 2 lacks both the hydrophobic mechanism and the repair mechanism, so the controlled release performance is far inferior to that of Examples 1 to 3 and Comparative Examples 1 and 3.

[0130] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a controlled-release fertilizer containing integrated medicine and fertilizer and biochar restoration, characterized in that: The preparation method comprises the following steps: (1) reacting formaldehyde and urea under alkaline conditions and under acidic conditions in sequence to obtain urea-formaldehyde particles; (2) reacting the urea-formaldehyde particles obtained in step (1) with diammonium phosphate and potassium sulfate to obtain a nutrient layer; (3) mixing the nutrient layer obtained in step (2) with the swelling film coating liquid in a granulator, and then adding humic acid, calcium-rich biochar, biopesticide bacteria spore powder and sodium carboxymethyl cellulose for granulation to obtain a buffer layer-wrapped nutrient layer; (4) mixing vinyl-terminated dimethyl polysiloxane, liquefied biomass polyol, and polyether to form a first-level envelope surface; then heating and adding epoxy resin and diethylenetriamine to form a second-level envelope surface for cross-linking, and curing to obtain a three-dimensional envelope unit; (5) adding the nutrient layer wrapped in the buffer layer in step (3) into a granulator, dripping a stereocomplexing unit and a curing agent to carry out a curing reaction, and then adding dopamine hydrochloride, polyethyleneimine and sodium alginate to granulate to obtain a drug-fertilizer integrated biochar restoration controlled-release fertilizer; The preparation method of the swelling film coating liquid in step (3) is as follows: silicon powder, polyvinyl alcohol, starch and potassium bicarbonate are mixed in a mass ratio of (100-125):(20-30):(20-30):(0.5-1.5), and the heating reaction temperature is 70-80° C. for 20-30 min to obtain a swelling film coating liquid; the swelling film coating liquid in step (3) is uniformly dripped onto the nutrient layer, and a dense film layer is obtained by high-temperature healing at a temperature of 90-110° C.; The preparation method of the calcium-rich biochar in step (3) is as follows: the biomass is crushed and then the water is removed, mixed with calcium nitrate in water at a temperature of 60 to 90° C., and further heated at a high temperature of 600 to 800° C. in a tubular furnace for 1 to 2 hours to obtain the calcium-rich biochar; For every 1g of biomass, the corresponding calcium molar amount is 4-6mmol; the water removal is to dry the biomass at 105°C for 2h until the weight change rate is less than 0.1%.

2. The preparation method according to claim 1, characterized in that: The mass ratio of formaldehyde to urea in step (1) is 1:2-3.

3. The preparation method according to claim 1, characterized in that: The alkaline condition in step (1) is provided by potassium hydroxide solution, the pH value is 9.0, the reaction temperature is 30-50° C., and the reaction time is 2-3 h.

4. The preparation method according to claim 1, characterized in that: The acidic condition in step (1) is provided by hydrochloric acid, the pH value is 5.0, the reaction temperature is 50-70° C., and the reaction time is 25-35 min.

5. The preparation method according to claim 1, characterized in that: The ratio of urea-formaldehyde particles, diammonium phosphate and potassium sulfate in step (2) is such that the mass ratio of nitrogen element, phosphorus element and potassium element is 1:0.4-0.6:1-1.

5.

6. The preparation method according to claim 1, characterized in that: The reaction temperature in step (2) is 50-70°C.

7. The preparation method according to claim 1, characterized in that: After the reaction in step (2) is completed, the process further comprises drying and granulating to obtain a nutrient layer.

8. The preparation method according to claim 1, characterized in that: The preparation method of humic acid in step (3) is: preparing the humic acid by mixing weathered coal with an activator.

9. The preparation method according to claim 8, characterized in that: The activator is a mixed solution of potassium hydroxide and sodium hydroxide, wherein the mass ratio of potassium hydroxide to sodium hydroxide is (3-4):

1.

10. The preparation method according to claim 8, characterized in that: The mixing reaction is carried out at a rotation speed of 100 r / min for 50 to 70 min.

11. The preparation method according to claim 1, characterized in that: The mass ratio of the vinyl-terminated dimethylpolysiloxane, the liquefied biomass polyol and the polyether in step (4) is 1:2:

2.

12. The preparation method according to claim 1, characterized in that: The preparation method of the liquefied biomass polyol in step (4) is: polyethylene glycol, glycerol and concentrated sulfuric acid are mixed, and then added into biomass for reaction to obtain the liquefied biomass polyol.

13. The preparation method according to claim 12, characterized in that: The mass ratio of the polyethylene glycol, glycerol and concentrated sulfuric acid is (35-40):(3-5):(1.0-1.5).

14. The preparation method according to claim 12, characterized in that: The reaction temperature is 150-180°C.

15. The preparation method according to claim 12, characterized in that: The reaction time is 60 to 120 minutes.

16. The preparation method according to claim 1, characterized in that: The temperature of the heating in step (4) is 50-80°C.

17. The preparation method according to claim 1, characterized in that: The mass ratio of the epoxy resin to diethylenetriamine in step (4) is 1:

1.

18. The preparation method according to claim 1, characterized in that: The curing agent in step (5) is polymethylene polyphenyl polyisocyanate.

19. The preparation method according to claim 18, characterized in that: The mass ratio of the stereocomplex unit to the polymethylene polyphenyl polyisocyanate in step (5) is 1:

1.

20. The preparation method according to claim 1, characterized in that: The mass ratio of dopamine hydrochloride, polyethyleneimine and sodium alginate in step (5) is 5:5:

4.

21. A medicine-fertilizer integrated biochar restoration controlled-release fertilizer prepared according to the preparation method of any one of claims 1 to 20.

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