A method for preparing compound fertilizer by activating potassium fluosilicate slag

Abstract

The present invention provides a method for preparing compound fertilizer by activating potassium fluorosilicate slag, belonging to the technical field of compound fertilizer; the method includes activation, primary compounding and secondary compounding steps; the primary compounding step includes primary modified bentonite, secondary modified bentonite and a compounding step; the compounding step is to add acrylic acid and sodium hydroxide solution into a reaction vessel, stir evenly, then add secondary modified bentonite, mix evenly, add ammonium persulfate, raise the temperature to 50-54 °C and stir evenly, add N,N-methylenebisacrylamide, perform ultrasonic treatment at 50-55 °C, after the ultrasonic treatment ends, keep the temperature for reaction for 42-47 min, after the reaction ends, obtain the primary complex through separation and drying; the compound fertilizer prepared by the method of the present invention has a stable nutrient release rate, good fertilizer efficiency, meets the growth requirements of crops, can effectively promote the normal growth and pest and disease resistance of crops, and increases the crop yield.

Description

Technical Field

[0001] The present invention belongs to the technical field of compound fertilizers, and particularly relates to a method for preparing compound fertilizers by activating potassium fluosilicate slag. Background Art

[0002] China is a large agricultural country and also a large country in the production and use of chemical fertilizers; chemical fertilizers are important agricultural inputs, which have played a positive role in promoting agricultural production increase and income and ensuring food security. The use of chemical fertilizers has greatly promoted the development of agriculture in China; currently, China's agricultural development has entered a new stage, from a high-input and high-consumption quantity-scale type to a green development model that emphasizes both quality and efficiency.

[0003] Compound fertilizer refers to a chemical fertilizer containing at least two of the three main nutrient elements of nitrogen, phosphorus, and potassium. It has a high nutrient content, few by-products, good physical properties, has no adverse effects on the properties of the soil, is convenient for storage and transportation, and is convenient for mechanized application;

[0004] At present, compound fertilizer is an important chemical fertilizer variety used in agricultural production in China. It has a wide application area and a large application amount, and is an important guarantee for the safety of agricultural products.

[0005] However, the large-scale use of compound fertilizers has led to serious soil compaction and exceeded pH value, greatly reducing the quality of crops, increasing the farming costs of farmers, and in the later growth stage of crops, there have been serious pest and disease phenomena, which have greatly affected the crop yield.

[0006] As a high-quality fertilizer, slow-release fertilizer has a higher fertilizer efficiency than conventional chemical fertilizers. It can reduce the loss of chemical fertilizer nutrients in the soil, reduce environmental pollution and adverse effects on the soil, and can also reduce the number of fertilization operations, avoid adverse effects on crop seedlings caused by excessive fertilization, and is beneficial to promoting the quality and edible safety of agricultural products.

[0007] As a by-product of the phosphorus and potassium workshop, potassium fluosilicate slag contains about 50wt% of potassium fluosilicate, about 7.5wt% of water-soluble phosphorus, and about 9.0wt% of water-soluble potassium. It contains relatively high contents of phosphorus and potassium elements, which can participate in the regulation of plant cell osmotic pressure, promote the transportation of photosynthesis products, promote the development of plant roots, and promote the healthy growth of crops;

[0008] After searching by the applicant, there is no relatively mature process for using potassium fluosilicate slag to prepare compound fertilizers; therefore, it has important research significance to use potassium fluosilicate slag to prepare compound fertilizers with slow-release properties.

[0009] In the process of research and development, it is found that directly applying potassium fluorosilicate slag to the soil cannot meet the growth requirements of crops, and its fertilizer efficiency is poor. The absorption and utilization effect of crops on nutrients is not good, and the promotion effect on the yield and quality of crops is not obvious. The applicant also finds that the compound fertilizer with slow-release performance prepared by the existing technology still has the problem of unstable nutrient release rate, which affects the normal growth performance and pest and disease resistance of crops, and ultimately leads to low crop yield. Summary of the Invention

[0010] In order to solve the technical problems existing in the prior art, the present invention provides a method for preparing compound fertilizer by activating potassium fluorosilicate slag, with a stable nutrient release rate, meeting the growth requirements of crops, effectively promoting the normal growth and pest and disease resistance of crops, and increasing crop yield.

[0011] In view of the above technical problems, the present invention adopts the following technical solutions:

[0012] A method for preparing compound fertilizer by activating potassium fluorosilicate slag, including activation, primary compounding and secondary compounding steps, and the specific operations are as follows:

[0013] 1. Activation

[0014] Put potassium fluorosilicate in deionized water, stir evenly, add ammonia water solution, raise the temperature to 60-90 °C for stirring reaction, the reaction time is 90-120 min, after the reaction is completed, wait for it to naturally cool to room temperature, filter to obtain the filtrate, concentrate the filtrate to 28-33% of the original volume at 58-62 °C, and dry it at 50-54 °C to obtain the primary compound fertilizer;

[0015] The mass ratio of potassium fluorosilicate to deionized water is 10-50:50-90;

[0016] The mass concentration of the ammonia water solution is 15-25%;

[0017] The molar ratio of potassium fluorosilicate to ammonia is 1:5-10.

[0018] 2. Primary compounding

[0019] (1) Primary modification of bentonite

[0020] Soak bentonite in the pre-modification solution, the soaking temperature is 48-52 °C, the soaking time is 32-38 min, after the soaking is completed, add the amino acid mixture, continue to stir for 48-52 min, and then obtain the primary modified bentonite through filtration, washing and drying;

[0021] The particle size of the bentonite is 100-120 nm;

[0022] The mass ratio of the bentonite, the pre-modifying solution and the amino acid mixture is 9.3 - 9.8:95 - 110:3.2 - 3.7;

[0023] The pre-modifying solution is prepared by uniformly mixing a 37 - 42wt% ethanol solution, kH602, cetyltrimethylammonium bromide and sodium lignosulfonate. The mass ratio of the 37 - 42wt% ethanol solution, kH602, cetyltrimethylammonium bromide and sodium lignosulfonate is 120:1.1 - 1.5:1.5 - 2.0:0.8 - 1.2;

[0024] The preparation method of the amino acid mixture is as follows: Put calcium carbonate into a potassium hydroxide solution, raise the temperature to 52 - 57 °C for ball milling. The ball milling time is 1.8 - 2.2 h, the ball milling speed is 130 - 150 rpm, and the ball - to - material ratio is 3 - 5:1. After the ball milling is completed, after filtration, washing and drying, raise the temperature to 356 - 364 °C at a rate of 3.5 - 4.5 °C / min, keep warm for 33 - 37 min, then raise the temperature to 435 - 442 °C at a rate of 1.2 - 1.8 °C / min, keep warm for 1.8 - 2.2 h. After the heat preservation treatment is completed, wait for it to naturally return to room temperature, put it into the amino acid mixed solution, stir evenly, add hydrochloric acid solution, control the pH value to be 6.0 - 6.4, carry out ultrasonic treatment. The ultrasonic time is 38 - 42 min, the ultrasonic power is 147 - 153 W, and the ultrasonic frequency is 23 - 28 kHz. After the ultrasonic treatment is completed, raise the temperature to 70 - 74 °C, stir and react for 1.8 - 2.2 h, obtain the filtrate by suction filtration, concentrate the filtrate to 22 - 27% of the original volume, and after drying, obtain the amino acid mixture;

[0025] The particle size of the calcium carbonate is 70 - 80 nm;

[0026] The mass ratio of the calcium carbonate, the potassium hydroxide solution and the amino acid mixed solution is 11.7 - 12.4:106 - 115:112 - 118;

[0027] The mass concentration of the potassium hydroxide solution is 22 - 25%;

[0028] The amino acid mixed solution is a mixture of deionized water, L - glutamic acid, L - lysine and L - arginine. The mass ratio of the deionized water, L - glutamic acid, L - lysine and L - arginine is 200:12 - 14:8 - 12:5 - 8;

[0029] The mass concentration of the hydrochloric acid solution is 8 - 12%;

[0030] (2) Second - modified bentonite

[0031] Mix the primary compound fertilizer, potassium sulfate, urea, zinc sulfate and magnesium sulfate, and after stirring evenly, obtain a mixed material; place the mixed material in deionized water, add primary modified bentonite, raise the temperature to 40 - 44 °C, conduct homogenization treatment, the homogenization time is 3.5 - 4.5 min, the homogenization pressure is 5.7 - 6.2 MPa, and after the homogenization treatment is completed, filter and dry to obtain secondary modified bentonite;

[0032] The mass ratio of the primary compound fertilizer, potassium sulfate, urea, zinc sulfate and magnesium sulfate is 22 - 26:15 - 18:26 - 30:0.8 - 1.2:0.5 - 0.7;

[0033] The mass ratio of the mixed material, deionized water, and primary modified bentonite is 11.0 - 11.5:145 - 156:5.0 - 5.5;

[0034] (3)Compound

[0035] Add acrylic acid and sodium hydroxide solution to the reaction vessel, stir evenly, then add secondary modified bentonite, mix evenly, add ammonium persulfate, raise the temperature to 50 - 54 °C, continue to stir evenly, then add N,N - methylenebisacrylamide, conduct ultrasonic treatment at 50 - 54 °C, the ultrasonic time is 28 - 32 min, the ultrasonic frequency is 20 - 24 kHz, the ultrasonic power is 84 - 88 W, after the ultrasonic treatment is completed, keep the temperature for reaction for 42 - 47 min, and after the reaction is completed, separate and dry to obtain a primary complex;

[0036] The mass ratio of the acrylic acid, sodium hydroxide solution, secondary modified bentonite, ammonium persulfate and N,N - methylenebisacrylamide is 16 - 18:26 - 30:3.0 - 3.4:0.44 - 0.48:0.06 - 0.10;

[0037] The mass concentration of the sodium hydroxide solution is 18 - 22%.

[0038] 3. Secondary compounding

[0039] Place guar gum in deionized water, add Tween 20 and silane coupling agent kH602, raise the temperature to 60 - 64 °C, keep the temperature and stir for 2.4 - 2.7 h to obtain a mixed solution; add the mixed solution to the primary complex, add carboxymethyl cellulose, stir at 38 - 42 °C for 47 - 53 min, and after the stirring is completed, dry to obtain the compound fertilizer;

[0040] The mass ratio of the guar gum, deionized water, Tween 20, and silane coupling agent kH602 is 8.4 - 8.7:88 - 93:1.0 - 1.4:0.8 - 1.2;

[0041] The mass ratio of the primary composite, the mixed solution, and carboxymethyl cellulose is 15.3 - 15.8:34.0 - 34.3:1.5 - 1.7.

[0042] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0043] 1. The present invention prepares a compound fertilizer from potassium fluorosilicate slag. First, the potassium fluorosilicate slag is activated with ammonia water to generate ammonium fluoride and potassium fluoride. Ammonium fluoride is not easily lost in the compound fertilizer, has a long fertilizer effect, and contains nitrogen element, which can provide nutrients for crop growth. Potassium fluoride can enhance the absorption and utilization of fertilizer nutrients by crops. Then, the primary compound fertilizer is subjected to primary compounding. Specifically, bentonite is pre-modified. The pre-modifying solution can achieve the dispersion of bentonite, expand the layer spacing of bentonite, and make the surface of bentonite contain amino groups and sulfonic acid groups. Adding an amino acid mixture completes the primary modification of bentonite, thereby firmly attaching the amino acid mixture to the surface of bentonite. It can provide more calcium elements for crops, maintain the stability of cell structure, and the amino acid mixture has good stability, which can effectively reduce the loss of calcium elements, improve the utilization rate of fertilizer, promote the development of crop roots, enhance the stress resistance of crops, improve the structure and fertility of the soil, increase the aggregate structure of the soil. In the compounding step, the mixture is fully adsorbed into the pores of bentonite to complete the loading of the mixture. Then, in combination with the compounding step, under the action of an initiator, acrylic acid and sodium hydroxide generate sodium polyacrylate, and under the action of a cross-linking agent, polyacrylic acid cross-links and entangles with the primary composite to form a stable three-dimensional network structure, thereby realizing the stable coating of the mixture. Sodium polyacrylate has good water retention performance, which can continuously provide more water sources for crops, has strong water holding capacity, helps to promote the growth and development of plants, and realizes the good slow-release performance of the primary composite. In the secondary compounding step, the guar gum is amino-modified by a silane coupling agent. The amino groups in the mixed solution have good binding force with the amino groups, carboxyl groups and other groups on the surface of the primary composite. It combines with carboxymethyl cellulose to form a stable secondary coating layer on the surface of the primary composite, with tight and firm binding, enhancing the slow-release stability of the compound fertilizer, ensuring the stable nutrient release rate, promoting the healthy growth of crops, enhancing the ability to resist pests and diseases and stress resistance, and effectively increasing the crop yield.

[0044] 2. The compound fertilizer prepared by the method of the present invention has a water retention rate of 94.8 - 95.5% after standing for 24.0 h in an environment with a temperature of 26°C and a humidity of 30%.

[0045] 3. The compound fertilizer prepared by the method of the present invention has a nutrient release rate of 10.1-10.6% at 22°C for 10 days, 27.6-28.8% at 30 days, 58.4-60.3% at 45 days, and 85.2-85.9% at 90 days.

[0046] 3. The compound fertilizer prepared by the method of the present invention is used in the cultivation of Zhoumai 22. During the growth cycle of wheat, the incidence rate of scab is 3.5-3.8%, the incidence rate of leaf blight is 2.8-3.2%, the incidence rate of aphids is 2.1-2.5%, and the wheat yield per mu is 550.3-551.4 kg. Detailed implementation manners

[0047] For a clearer understanding of the technical features, objectives, and effects of the present invention, the detailed implementation manners of the present invention are described below.

[0048] Example 1

[0049] 1. Activation

[0050] Put 20 g of potassium fluorosilicate into 80 g of deionized water, stir evenly, add 10 wt% ammonia water solution, raise the temperature to 50°C and stir for reaction for 30 min. After the reaction, wait for it to cool to room temperature naturally, filter to obtain the filtrate, concentrate the filtrate to 30% of the original volume at 60°C, and dry it at 52°C to obtain the primary compound fertilizer;

[0051] The molar ratio of potassium fluorosilicate to ammonia is 1:8.

[0052] 2. First compounding

[0053] (1) First modified bentonite

[0054] Put 9.5 g of bentonite into 100 g of pre-modifying solution for soaking. The soaking temperature is 50°C and the soaking time is 35 min. After soaking, add 3.4 g of amino acid mixture, continue to stir for 50 min, and then filter, wash, and dry to obtain the first modified bentonite;

[0055] The particle size of the bentonite is 110 nm;

[0056] The pre-modifying solution is prepared by uniformly mixing 40 wt% ethanol solution, kH602, cetyltrimethylammonium bromide, and sodium lignosulfonate. The mass ratio of the 40 wt% ethanol solution, kH602, cetyltrimethylammonium bromide, and sodium lignosulfonate is 120:1.3:1.7:1.0;

[0057] The preparation method of the amino acid mixture is as follows: Place 12.0 g of calcium carbonate in 110 g of a 23 wt% potassium hydroxide solution, raise the temperature to 55 °C for ball milling treatment. The ball milling time is 2.0 h, the ball milling speed is 140 rpm, and the ball-to-material ratio is 4:1. After the ball milling is completed, filter, wash, and dry, then heat up to 360 °C at a rate of 4.0 °C / min and hold for 35 min, then heat up to 440 °C at a rate of 1.5 °C / min and hold for 2.0 h. After the heat preservation treatment is completed, wait for it to naturally return to room temperature, then put it into 115 g of the amino acid mixture solution, stir evenly, add a 10 wt% hydrochloric acid solution, control the pH value to 6.2, and perform ultrasonic treatment. The ultrasonic time is 40 min, the ultrasonic power is 150 W, and the ultrasonic frequency is 26 kHz. After the ultrasonic treatment is completed, raise the temperature to 72 °C and stir and react for 2.0 h. Filter to obtain the filtrate, concentrate the filtrate to 25% of the original volume, and dry to obtain the amino acid mixture;

[0058] The particle size of the calcium carbonate is 75 nm;

[0059] The amino acid mixture solution is a mixture of deionized water, L-glutamic acid, L-lysine, and L-arginine. The mass ratio of deionized water, L-glutamic acid, L-lysine, and L-arginine is 200:13:10:7;

[0060] (2) Secondary modified bentonite

[0061] Mix 24 g of primary compound fertilizer, 17 g of potassium sulfate, 28 g of urea, 1.0 g of zinc sulfate, and 0.6 g of magnesium sulfate, stir evenly to obtain a mixed material; place 11.3 g of the mixed material in 150 g of deionized water, add 5.2 g of primary modified bentonite, raise the temperature to 42 °C, and perform homogenization treatment. The homogenization time is 4.0 min, the homogenization pressure is 6.0 MPa. After the homogenization treatment is completed, filter and dry to obtain secondary modified bentonite;

[0062] (3) Composite

[0063] Add 17 g of acrylic acid and 28 g of a 20 wt% sodium hydroxide solution to the reaction vessel, stir evenly, add 3.2 g of secondary modified bentonite, mix evenly, add 0.46 g of ammonium persulfate, raise the temperature to 52 °C, continue to stir evenly, then add 0.08 g of N,N-methylenebisacrylamide, perform ultrasonic treatment at 52 °C. The ultrasonic time is 30 min, the ultrasonic frequency is 22 kHz, and the ultrasonic power is 86 W. After the ultrasonic treatment is completed, hold the reaction for 45 min. After the reaction is completed, separate and dry to obtain the primary composite.

[0064] 3. Secondary composite

[0065] Place 8.5 g of guar gum in 90 g of deionized water, add 1.2 g of Tween 20 and 1.0 g of silane coupling agent kH602, raise the temperature to 62 °C, keep warm and stir for 2.5 h to obtain a mixed solution; add 34.1 g of the mixed solution to 15.5 g of the primary composite, add 1.6 g of carboxymethyl cellulose, stir at 40 °C for 50 min, and after the stirring is completed, obtain a compound fertilizer through drying.

[0066] Example 2

[0067] 1. Activation

[0068] Place 10 g of potassium fluorosilicate in 90 g of deionized water, stir evenly, add 15 wt% ammonia water solution, raise the temperature to 60 °C for stirring reaction, the reaction time is 90 min, after the reaction is completed, wait for it to naturally cool to room temperature, filter to obtain a filtrate, concentrate the filtrate to 28% of the original volume at 58 °C, and dry at 50 °C to obtain a primary compound fertilizer;

[0069] The molar ratio of the potassium fluorosilicate to ammonia is 1:10.

[0070] 2. Primary compounding

[0071] (1) Primary modified bentonite

[0072] Place 9.3 g of bentonite in 95 g of pre-modified liquid for soaking, the soaking temperature is 48 °C, the soaking time is 32 min, after the soaking is completed, add 3.2 g of amino acid mixture, continue to stir for 48 min, and then obtain primary modified bentonite through filtration, washing and drying;

[0073] The particle size of the bentonite is 100 nm;

[0074] The pre-modified liquid is prepared by uniformly mixing 37 wt% ethanol solution, kH602, cetyltrimethylammonium bromide and sodium lignosulfonate, and the mass ratio of the 37 wt% ethanol solution, kH602, cetyltrimethylammonium bromide and sodium lignosulfonate is 120:1.1:1.5:0.8;

[0075] The preparation method of the amino acid mixture is as follows: Place 11.7 g of calcium carbonate in 106 g of a 22 wt% potassium hydroxide solution, raise the temperature to 52 °C and carry out ball milling treatment. The ball milling time is 1.8 h, the ball milling speed is 130 rpm, and the ball-to-material ratio is 3:1. After the ball milling is completed, filter, wash and dry, then heat up to 356 °C at a rate of 3.5 °C / min and hold for 37 min, and then heat up to 435 °C at a rate of 1.2 °C / min and hold for 1.8 h. After the heat preservation treatment is completed, wait for it to naturally return to room temperature, put it into 112 g of the amino acid mixture solution, stir evenly, add an 8 wt% hydrochloric acid solution, control the pH value to 6.0, carry out ultrasonic treatment, the ultrasonic time is 38 min, the ultrasonic power is 147 W, and the ultrasonic frequency is 23 kHz. After the ultrasonic treatment is completed, raise the temperature to 70 °C and stir and react for 1.8 h. Filter to obtain the filtrate, concentrate the filtrate to 22% of the original volume, and dry to obtain the amino acid mixture;

[0076] The particle size of the calcium carbonate is 70 nm;

[0077] The amino acid mixture solution is a mixture of deionized water, L-glutamic acid, L-lysine and L-arginine, and the mass ratio of deionized water, L-glutamic acid, L-lysine and L-arginine is 200:12:8:5;

[0078] (2) Secondary modified bentonite

[0079] Mix 22 g of primary compound fertilizer, 15 g of potassium sulfate, 26 g of urea, 0.8 g of zinc sulfate and 0.5 g of magnesium sulfate, stir evenly to obtain a mixture; place 11.0 g of the mixture in 145 g of deionized water, add 5.0 g of primary modified bentonite, raise the temperature to 40 °C, and carry out homogenization treatment. The homogenization time is 3.5 min, and the homogenization pressure is 6.2 MPa. After the homogenization treatment is completed, filter and dry to obtain secondary modified bentonite;

[0080] (3) Compound

[0081] Add 16 g of acrylic acid and 26 g of an 18 wt% sodium hydroxide solution to the reaction vessel, stir evenly, add 3.0 g of secondary modified bentonite, mix evenly, add 0.44 g of ammonium persulfate, raise the temperature to 50 °C, continue to stir evenly, then add 0.06 g of N,N-methylenebisacrylamide, carry out ultrasonic treatment at 50 °C, the ultrasonic time is 28 min, the ultrasonic frequency is 20 kHz, and the ultrasonic power is 84 W. After the ultrasonic treatment is completed, keep the temperature and react for 42 min. After the reaction is completed, separate and dry to obtain a primary complex.

[0082] 3. Secondary compound

[0083] 8.4 g of guar gum was placed in 88 g of deionized water, 1.0 g of Tween 20 and 0.8 g of silane coupling agent kH602 were added, the temperature was raised to 60 °C, and stirring was carried out for 2.7 h to obtain a mixed solution; 34.0 g of the mixed solution was added to 15.3 g of the primary composite, 1.5 g of carboxymethyl cellulose was added, and stirring was carried out at 38 °C for 47 min. After the stirring was completed, compound fertilizer was obtained through drying.

[0084] Example 3

[0085] 1. Activation

[0086] 50 g of potassium fluorosilicate was placed in 50 g of deionized water, and after stirring evenly, 25 wt% ammonia water solution was added. The temperature was raised to 90 °C for stirring reaction, the reaction time was 120 min. After the reaction was completed, it was allowed to naturally cool to room temperature, and the filtrate was obtained by suction filtration. The filtrate was concentrated to 33% of the original volume at 62 °C and dried at 54 °C to obtain primary compound fertilizer;

[0087] The molar ratio of the potassium fluorosilicate to ammonia is 1:5.

[0088] 2. Primary compounding

[0089] (1) Primary modified bentonite

[0090] 9.8 g of bentonite was soaked in 110 g of pre-modifying solution at an immersion temperature of 52 °C for 38 min. After the immersion was completed, 3.7 g of amino acid mixture was added, and stirring was continued for 52 min. After filtration, washing and drying, primary modified bentonite was obtained;

[0091] The particle size of the bentonite is 120 nm;

[0092] The pre-modifying solution was prepared by uniformly mixing 42 wt% ethanol solution, kH602, cetyltrimethylammonium bromide and sodium lignosulfonate. The mass ratio of the 42 wt% ethanol solution, kH602, cetyltrimethylammonium bromide and sodium lignosulfonate is 120:1.5:2.0:1.2;

[0093] The preparation method of the amino acid mixture is as follows: Place 12.4 g of calcium carbonate in 115 g of 25 wt% potassium hydroxide solution, raise the temperature to 57 °C and carry out ball milling treatment. The ball milling time is 2.2 h, the ball milling speed is 150 rpm, and the ball-to-material ratio is 5:1. After the ball milling is completed, filter, wash and dry, then heat up to 364 °C at a rate of 4.5 °C / min and keep warm for 33 min, and then heat up to 442 °C at a rate of 1.8 °C / min and keep warm for 2.2 h. After the heat preservation treatment is completed, wait for it to naturally return to room temperature, put it into 118 g of amino acid mixture solution, stir evenly, add 12 wt% hydrochloric acid solution, control the pH value to 6.4, carry out ultrasonic treatment, the ultrasonic time is 42 min, the ultrasonic power is 153 W, and the ultrasonic frequency is 28 kHz. After the ultrasonic treatment is completed, raise the temperature to 74 °C and stir and react for 2.2 h. Filter to obtain the filtrate, concentrate the filtrate to 27% of the original volume, and dry to obtain the amino acid mixture;

[0094] The particle size of the calcium carbonate is 80 nm;

[0095] The amino acid mixture solution is a mixture of deionized water, L-glutamic acid, L-lysine and L-arginine. The mass ratio of deionized water, L-glutamic acid, L-lysine and L-arginine is 200:14:12:8;

[0096] (2) Secondary modified bentonite

[0097] Mix 26 g of primary compound fertilizer, 18 g of potassium sulfate, 30 g of urea, 1.2 g of zinc sulfate and 0.7 g of magnesium sulfate, stir evenly to obtain a mixture; place 11.5 g of the mixture in 156 g of deionized water, add 5.5 g of primary modified bentonite, raise the temperature to 44 °C, and carry out homogenization treatment. The homogenization time is 4.5 min, the homogenization pressure is 5.7 MPa. After the homogenization treatment is completed, filter and dry to obtain secondary modified bentonite;

[0098] (3) Compound

[0099] Add 18 g of acrylic acid and 30 g of 22 wt% sodium hydroxide solution to the reaction vessel, stir evenly, add 3.4 g of secondary modified bentonite, mix evenly, add 0.48 g of ammonium persulfate, raise the temperature to 54 °C, continue to stir evenly, then add 0.10 g of N,N-methylenebisacrylamide, carry out ultrasonic treatment at 54 °C, the ultrasonic time is 32 min, the ultrasonic frequency is 24 kHz, and the ultrasonic power is 88 W. After the ultrasonic treatment is completed, keep warm and react for 47 min. After the reaction is completed, separate and dry to obtain the primary composite.

[0100] 3. Secondary compound

[0101] Put 8.7 g of guar gum into 93 g of deionized water, add 1.4 g of Tween 20 and 1.2 g of silane coupling agent kH602, raise the temperature to 64 °C, keep warm and stir for 2.4 h to obtain a mixed solution; add 34.3 g of the mixed solution to 15.8 g of the primary complex, add 1.7 g of carboxymethyl cellulose, stir at 428 °C for 53 min. After the stirring is completed, dry to obtain a compound fertilizer.

[0102] Comparative Example 1

[0103] On the basis of Example 1, the changes are as follows:

[0104] (1) Omit the activation step. In the step of secondary modification of bentonite in the primary compounding process, replace the primary compound fertilizer with potassium fluorosilicate in equal amounts;

[0105] (2) Omit the secondary compounding step, and the obtained primary complex is the compound fertilizer;

[0106] The remaining operations are the same.

[0107] Comparative Example 2

[0108] On the basis of Example 1, the changes are as follows: In the primary compounding process,

[0109] (1) Omit the step of primary modification of bentonite; in the step of secondary modification of bentonite, replace the primary modified bentonite with unprocessed bentonite in equal amounts, and the particle size of the bentonite is 110 nm;

[0110] (2) Omit the compounding step; in the secondary compounding step, replace the primary complex with secondary modified bentonite;

[0111] The remaining operations are the same.

[0112] Performance Test

[0113] Conduct the following performance tests on the compound fertilizers prepared in Examples 1-3 and Comparative Examples 1-2, specifically as follows:

[0114] 1. Water retention performance

[0115] Dry the compound fertilizers prepared in Examples 1-3 and Comparative Examples 1-2 at 80 °C for 2.0 h. After drying, place them in 8 times the mass of deionized water and soak at room temperature for 48.0 h. After soaking, wipe off the surface moisture until no more water drops, weigh and record as m1, then place them in an environment with a temperature of 26 °C and a humidity of 30% and let them stand. After standing for 24.0 h, weigh again and record as m2, and calculate the water retention rate of each compound fertilizer. The water retention rate = (m1 - m2) / m1 × 100%;

[0116] According to the above method, the water retention rate results of the compound fertilizers prepared in Examples 1-3 and Comparative Examples 1-2 are as follows:

[0117]

[0118] 2. Slow-release performance

[0119] According to the method in GB / T23348-2009 "Slow-release Fertilizers", the nutrient release performance of the compound fertilizers prepared in Examples 1-3 and Comparative Examples 1-2 at 22°C at different times was measured, and the test results are as follows:

[0120]

[0121] 3. Resistance to pests and diseases

[0122] Select 20 mu of an experimental base in Shouguang City, Shandong Province. The compound fertilizers prepared in Examples 1-3 and Comparative Examples 1-2 were used in the wheat planting experiment. The wheat variety was Zhoumai 22. Specifically, the experimental base was evenly divided into 5 mutually isolated experimental areas, and then the compound fertilizers of Examples 1-3 and Comparative Examples 1-2 were used for the wheat planting experiment respectively. During the planting process, the wheat was managed by conventional planting methods, and the management of compound fertilizer dosage, application timing, planting quantity, water, etc. was exactly the same. The incidence of pests and diseases of the wheat during the growth period of the wheat was counted, and the yield per mu of the wheat was counted after the wheat matured. The specific results are as follows:

[0123]

[0124] The present invention prepares compound fertilizers from potassium fluorosilicate slag. First, the potassium fluorosilicate slag is activated with ammonia water to generate ammonium fluoride and potassium fluoride. Ammonium fluoride is used in compound fertilizers and is not easily lost, has a long fertilizer effect, and contains nitrogen elements, which can provide nutrients for crop growth. Potassium fluoride can enhance the absorption and utilization of fertilizer nutrients by crops. Then, the primary compound fertilizer is subjected to a first compounding. Specifically, bentonite is pre-modified. The pre-modifying solution can achieve the dispersion of bentonite, expand the layer spacing of bentonite, and make the surface of bentonite contain amino groups and sulfonic acid groups. Adding an amino acid mixture completes the first modification of bentonite, thereby firmly attaching the amino acid mixture to the surface of bentonite. It can provide more calcium elements for crops, maintain the stability of cell structure, and the amino acid mixture has good stability, which can effectively reduce the loss of calcium elements, improve the utilization rate of fertilizers, promote the development of crop roots, enhance the stress resistance of crops, improve the structure and fertility of the soil, and increase the aggregate structure of the soil. In the compounding step, the mixture is fully adsorbed into the pores of bentonite to complete the loading of the mixture. Then, in combination with the compounding step, under the action of an initiator, acrylic acid and sodium hydroxide generate sodium polyacrylate, and under the action of a cross-linking agent, polyacrylic acid cross-links and entangles with the first complex to form a stable three-dimensional network structure, thus achieving the stable coating of the mixture. Sodium polyacrylate has good water retention performance, which can continuously provide more water sources for crops, has strong water holding capacity, helps to promote the growth and development of plants, and realizes the good slow-release performance of the first complex. In the second compounding step, guar gum is subjected to amino modification with a silane coupling agent. The amino groups in the mixed solution have good binding force with the amino groups, carboxyl groups and other groups on the surface of the first complex. Combining with carboxymethyl cellulose forms a stable second coating layer on the surface of the first complex, which is tightly and firmly combined, enhances the slow-release stability of the compound fertilizer, ensures the stability of the nutrient release rate, promotes the healthy growth of crops, enhances the ability to resist diseases and pests and stress resistance, and effectively improves the crop yield.

[0125] In Comparative Example 1, the activation step was omitted, and potassium fluorosilicate was directly used in the compound fertilizer. The fertilizer effect of potassium fluorosilicate was poor and could not meet the growth requirements of crops. Moreover, the second compounding step was also omitted, and the first complex was directly used as the compound fertilizer. Comparative Example 1 omitted the second coating layer, weakening the slow-release performance of the compound fertilizer, making the slow-release rate unstable, reducing the ability of crops to resist diseases and pests, and ultimately reducing the crop yield.

[0126] In Comparative Example 2, the step of modifying bentonite once was omitted, and potassium fluorosilicate was directly mixed with bentonite. The aggregability of bentonite was relatively strong, and its adsorbability for compound fertilizer was poor. In addition, the amino acid mixture component was omitted, reducing the stress resistance of crops, and the soil structure and fertility were poor. Moreover, the compounding step was also omitted, making it impossible to achieve the crosslinking of sodium polyacrylate and secondary modified bentonite, thus unable to form a stable crosslinked network structure, weakening the water absorption and water retention capacity of the compound fertilizer, resulting in an unstable slow-release rate of the compound fertilizer and poor slow-release performance, and ultimately reducing the crop yield.

[0127] Unless otherwise specified, the ratios described in the present invention are all mass ratios, and the percentages are all mass percentages.

[0128] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing compound fertilizer by activating potassium fluorosilicate slag, characterized in that: It includes activation, primary compounding and secondary compounding steps; The activation step is to place potassium fluorosilicate in deionized water, add ammonia solution, and react at 60-90° C. for 90-120 minutes to obtain primary compound fertilizer; The first compounding step includes first modified bentonite, second modified bentonite and compounding step; The step of primary modified bentonite is to place the bentonite in a pre-modified liquid for immersion, and then add the amino acid mixture to obtain the primary modified bentonite; The pre-modified liquid is prepared by mixing ethanol solution, KH602, hexadecyltrimethylammonium bromide and sodium lignin sulfonate; The preparation method of the amino acid mixture is as follows: placing calcium carbonate in a potassium hydroxide solution, raising the temperature to 52-57°C for ball milling, filtering, washing and drying after the ball milling, raising the temperature to 356-364°C at a rate of 3.5-4.5°C / min, keeping the temperature for 33-37min, and then raising the temperature to 435-442°C at a rate of 1.2-1.8°C / min, keeping the temperature for 1.8-2.2h, after the keeping temperature is completed, wait for the temperature to naturally return to room temperature, put it into the amino acid mixture, stir evenly, add hydrochloric acid solution, control the pH value to 6.0-6.4, perform ultrasonic treatment, after the ultrasonic treatment is completed, raise the temperature to 70-74°C, stir and react for 1.8-2.2h, obtain a filtrate by suction filtration, concentrate the filtrate to 22-27% of the original volume, and dry it to obtain the amino acid mixture; The amino acid mixture is a mixture of deionized water, L-glutamic acid, L-lysine and L-arginine; The secondary modified bentonite step comprises: mixing primary compound fertilizer, potassium sulfate, urea, zinc sulfate and magnesium sulfate, stirring evenly to obtain a mixture; placing the mixture in deionized water, adding primary modified bentonite, raising the temperature to 40-44° C., performing homogenization treatment, the homogenization time is 3.5-4.5 min, the homogenization pressure is 5.7-6.2 MPa, and after the homogenization treatment is completed, filtering and drying to obtain the secondary modified bentonite; The compounding step comprises adding acrylic acid and sodium hydroxide solution into a reaction container, adding secondary modified bentonite and mixing evenly, adding ammonium persulfate, stirring evenly at 50-54° C., adding N,N-methylenebisacrylamide for ultrasonic treatment, and keeping the temperature for reaction for 42-47 minutes to obtain a primary compound; The secondary compounding step comprises placing guar gum in deionized water, adding Tween 20 and silane coupling agent KH602, stirring and reacting at 60-64° C. to obtain a mixed solution; and adding the mixed solution and carboxymethyl cellulose to the primary compound to obtain a compound fertilizer.

2. The method for preparing composite fertilizer by activating potassium fluorosilicate slag according to claim 1, characterized in that: In the activation step, the mass ratio of potassium fluorosilicate to deionized water is 10-50:50-90; The mass concentration of the ammonia solution is 15-25%; The molar ratio of potassium fluorosilicate to ammonia is 1:5-10.

3. The method for preparing composite fertilizer by activating potassium fluorosilicate slag according to claim 1, characterized in that: In the step of once modifying bentonite, the soaking temperature is 48-52° C. and the soaking time is 32-38 min; The particle size of the bentonite is 100-120nm; The mass ratio of the bentonite, the pre-modified liquid and the amino acid mixture is 9.3-9.8:95-110:3.2-3.

7.

4. The method for preparing composite fertilizer by activating potassium fluorosilicate slag according to claim 1, characterized in that: In the step of modifying bentonite once, the mass concentration of the ethanol solution in the pre-modified liquid is 37-42%; The mass ratio of the ethanol solution, KH602, hexadecyltrimethylammonium bromide and sodium lignin sulfonate is 120:1.1-1.5:1.5-2.0:0.8-1.

2.

5. The method for preparing composite fertilizer by activating potassium fluorosilicate slag according to claim 1, characterized in that: In the preparation method of the amino acid mixture, the particle size of the calcium carbonate is 70-80 nm; The mass ratio of the calcium carbonate, potassium hydroxide solution and amino acid mixture is 11.7-12.4:106-115:112-118; The mass concentration of the potassium hydroxide solution is 22-25%; In the amino acid mixture, the mass ratio of the deionized water, L-glutamic acid, L-lysine and L-arginine is 200:12-14:8-12:5-8; The mass concentration of the hydrochloric acid solution is 8-12%.

6. The method for preparing compound fertilizer by activating potassium fluorosilicate slag according to claim 1, characterized in that: In the step of secondary modified bentonite, the mass ratio of the primary compound fertilizer, potassium sulfate, urea, zinc sulfate and magnesium sulfate is 22-26:15-18:26-30:0.8-1.2:0.5-0.7; The mass ratio of the mixture, deionized water and primary modified bentonite is 11.0-11.5:145-156:5.0-5.

5.

7. The method for preparing compound fertilizer by activating potassium fluorosilicate slag according to claim 1, characterized in that: In the compounding step, the ultrasonic treatment has an ultrasonic time of 28-32 min, an ultrasonic frequency of 20-24 kHz, and an ultrasonic power of 84-88 W.

8. The method for preparing compound fertilizer by activating potassium fluorosilicate slag according to claim 1, characterized in that: The mass ratio of the acrylic acid, the sodium hydroxide solution, the secondary modified bentonite, the ammonium persulfate and the N,N-methylenebisacrylamide is 16-18:26-30:3.0-3.4:0.44-0.48:0.06-0.10; The mass concentration of the sodium hydroxide solution is 18-22%.

9. The method for preparing compound fertilizer by activating potassium fluorosilicate slag according to claim 1, characterized in that: In the secondary compounding step, the mass ratio of the guar gum, deionized water, Tween 20, and silane coupling agent KH602 is 8.4-8.7:88-93:1.0-1.4:0.8-1.2; The mass ratio of the primary composite, the mixed solution and the carboxymethyl cellulose is 15.3-15.8:34.0-34.3:1.5-1.7.

Images