Molecular sieve slow-release potash fertilizer and preparation method thereof
By preparing 13x molecular sieves from fly ash and loading them with potassium ions, the problems of high price and environmental pollution of slow-release potassium fertilizers have been solved, realizing the high-value utilization of fly ash and improving the slow-release effect.
Patent Information
- Application Number
- CN202610081321.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-21
- Publication Date
- 2026-05-01
AI Technical Summary
Existing slow-release potassium fertilizers are expensive, have poor slow-release performance, and are prone to causing environmental pollution. Traditional polymer coating materials have long degradation cycles, which affect soil microbial activity and crop root health.
Using fly ash as raw material, 13x molecular sieves were prepared by extracting silica-alumina solution through acid leaching and alkali leaching. Potassium ions were then loaded onto the molecular sieves using a melt adsorption method to prepare slow-release potassium fertilizer, thereby controlling the slow adsorption and release of potassium ions.
This approach enables the high-value utilization of fly ash, producing inexpensive slow-release potassium fertilizer with good slow-release effect, reducing environmental pollution risks, and improving the utilization rate of potassium fertilizer and soil microbial activity.
Smart Images
Figure CN121949026A_ABST
Abstract
Description
A molecular sieve slow-release potassium fertilizer and its preparation method Technical Field
[0001] This invention belongs to the field of industrial solid waste utilization and slow-release fertilizer synthesis technology, specifically relating to a molecular sieve slow-release potassium fertilizer and its preparation method. Background Technology
[0002] Currently, slow-release fertilizers are mainly classified into four categories based on their preparation principles: coated slow-release fertilizers, chemically synthesized slow-release fertilizers, mixed slow-release fertilizers, and carrier-based slow-release fertilizers. At this critical juncture of sustainable agricultural development and green transformation, slow-release fertilizers, as an important technological means to improve fertilizer utilization, reduce nutrient loss, and mitigate agricultural non-point source pollution, are hampered by two core bottlenecks in their market performance: Firstly, the high price of existing slow-release fertilizer products makes them prohibitive for many farmers, especially small-scale growers, severely limiting their application; secondly, the long degradation cycle of traditional polymer coating materials in the natural environment not only exacerbates the risk of soil microplastic pollution but may also affect soil microbial activity and crop root health, posing a potential threat to the agricultural ecosystem. Therefore, developing slow-release fertilizers that combine price advantages with high-tech content is not only crucial to breaking the current industry predicament but also an inevitable choice for promoting green and high-quality agricultural development.
[0003] Fly ash contains essential elements for crop growth, such as phosphorus, magnesium, potassium, iron, boron, molybdenum, sodium, manganese, and silicon. It promotes crop growth, improves soil fertility, regulates soil pH, enhances soil physical properties, increases soil microbial activity, and improves plant disease resistance. Therefore, it can be used as a soil fertilizer. Using fly ash as a raw material to prepare molecular sieves, and then using these sieves to adsorb potassium ions to prepare slow-release potassium fertilizer, can overcome the problems of poor slow-release performance, high price, and environmental pollution associated with commercially available slow-release potassium fertilizers. This is an effective way to achieve high-value utilization of fly ash.
[0004] Therefore, developing a novel slow-release potassium fertilizer based on fly ash is of great significance. Summary of the Invention
[0005] The technical problem this invention aims to solve is to address the shortcomings of existing technologies by providing a slow-release potassium fertilizer made from industrial solid waste using molecular sieves and its preparation method. The molecular sieve is synthesized using fly ash leachate, yielding high-purity aluminum and silicon sources. The silicon-to-aluminum ratio of the molecular sieve is accurately controlled by adjusting the ratio of acid and alkaline leachates, overcoming problems such as impure crystal phases and small specific surface area caused by high fly ash impurities. Furthermore, adsorbing potassium ions into the molecular sieve via melt adsorption overcomes the slow adsorption rate of the molecular sieve, significantly increasing the potassium fertilizer loading. The molecular sieve slowly adsorbs and releases potassium ions through ion exchange, resulting in a good slow-release effect and easily controllable slow-release process.
[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:
[0007] The first aspect of this invention provides a molecular sieve slow-release potassium fertilizer and a method for preparing the same, comprising the following steps:
[0008] S1. Activation: The original fly ash sample is mixed with an activator and calcined to obtain activated fly ash;
[0009] S2. Extraction of aluminum-rich liquid: Activated fly ash is soaked in hydrochloric acid solution, dissolved and filtered to obtain aluminum-rich liquid, and the residue is collected;
[0010] S3. Extraction of silicon-rich liquid: Mix the dried residue with sodium hydroxide and distilled water evenly, heat to react, and filter to obtain silicon-rich liquid;
[0011] S4. Preparation of molecular sieves: Aluminum-rich liquid and silicon-rich liquid are mixed, and the silicon-aluminum ratio and pH are adjusted to obtain a reaction solution. Then, a crystallization reaction is carried out, followed by washing, drying, and grinding to obtain molecular sieves.
[0012] S5. Preparation of molecular sieve slow-release potassium fertilizer: Molecular sieve and inorganic potassium salt are mixed and ground evenly, and heated to obtain the molecular sieve slow-release potassium fertilizer.
[0013] In S1, the mass ratio of the fly ash to the activator is (1~2):1; the activator includes any one of sodium carbonate, calcium carbonate, ammonium sulfate, concentrated sulfuric acid, and sodium hydroxide.
[0014] In some embodiments of the present invention, in S1, the mass ratio of the fly ash to the activator is 1.25:1; the activator is sodium carbonate.
[0015] In S1, the calcination conditions are: temperature 600~900℃, time 60~120min.
[0016] In some embodiments of the present invention, in S1, the calcination conditions are: temperature 750°C and time 90 min.
[0017] In S2, the mass concentration of the hydrochloric acid solution is 10-30%; the soaking time is 6-24 hours.
[0018] In some embodiments of the present invention, in S2, the mass concentration of the hydrochloric acid solution is 25%, and the soaking time is 12 hours.
[0019] In S3, the mass ratio of the residue, sodium hydroxide, and distilled water is 10:(4~8):(20~60); the heating conditions are: temperature 60~100℃, time 6~24h.
[0020] In some embodiments of the present invention, in S3, the mass ratio of the residue, sodium hydroxide and distilled water is 10:6:40; the heating conditions are: temperature 80°C and time 12h.
[0021] In S4, the aluminum-silicon ratio in the reaction solution is (1~3):1, and the pH value is 7~11; the crystallization reaction is carried out under the following conditions: crystallization temperature is 80~120℃, and crystallization time is 6~36h.
[0022] In some embodiments of the present invention, in S4, the aluminum-silicon ratio in the reaction solution is 2:1, and the pH value is 9.5; the crystallization reaction is carried out under the following conditions: crystallization temperature is 95°C, and crystallization time is 24h.
[0023] In S5, the mass ratio of the molecular sieve to the inorganic potassium salt is 1:(1~5); the inorganic potassium salt includes any one of potassium nitrate, potassium chloride, potassium carbonate and potassium sulfate.
[0024] In some embodiments of the present invention, in step S5, the mass ratio of the molecular sieve to the inorganic potassium salt is 1:4; the inorganic potassium salt is potassium nitrate.
[0025] In S5, the heating conditions are: temperature 300~450℃, time 8h.
[0026] In some embodiments of the present invention, in step S5, the heating conditions are: a temperature of 350°C and a time of 8 hours.
[0027] A second aspect of the present invention provides a molecular sieve slow-release potassium fertilizer prepared by the above preparation method.
[0028] Specifically, in some embodiments of the present invention, molecular sieve slow-release potassium fertilizer was prepared by the above method. Characterization of the molecular sieve and the molecular sieve loaded with potassium fertilizer proved that the method provided by the present invention successfully converted fly ash into 13x molecular sieve and successfully loaded inorganic potassium fertilizer. Through slow-release experiments, it was shown that the original fly ash has excellent slow-release effect.
[0029] Beneficial effects:
[0030] Fly ash, as a major residue from coal combustion, contains abundant silicon and aluminum, making it an inexpensive and readily available source for preparing molecular sieves. Molecular sieves can slowly adsorb and release potassium ions through ion exchange, exhibiting excellent slow-release effects and easy process control, thus making them ideal for producing slow-release potassium fertilizer. The 13x type molecular sieve, with its good stability, high actual potassium ion adsorption capacity, and composition closely resembling that of fly ash, is chosen to fully utilize the silicon and aluminum in the fly ash, thus enabling its selection for slow-release potassium fertilizer. Furthermore, acid and alkali leaching effectively remove other impurities from the fly ash, extracting only the desired silicon and aluminum-containing solution, allowing for precise control of the silicon-to-aluminum ratio of the molecular sieve. Adsorbing potassium ions into the molecular sieve via melt adsorption overcomes the slow adsorption rate of molecular sieves, significantly increasing the potassium fertilizer loading capacity. Moreover, the preparation of this slow-release fertilizer overcomes the problems of poor slow-release performance, high price, and environmental pollution associated with commercially available slow-release potassium fertilizers, representing an effective way to achieve high-value utilization of fly ash. Attached Figure Description
[0031] The present invention will be further described in detail below with reference to the accompanying drawings, and the advantages of the present invention in the above and / or other aspects will become clearer.
[0032] Figure 1 is a SEM image of the original fly ash sample in Example 1 of the present invention.
[0033] Figure 2 is the XRD pattern of the original fly ash sample in Example 1 of the present invention.
[0034] Figure 3 is a BET diagram of the original fly ash sample in Example 1 of the present invention.
[0035] Figure 4 is a SEM image of the 13x molecular sieve in Example 1 of the present invention.
[0036] Figure 5 is the XRD pattern of the 13x molecular sieve in Example 1 of the present invention.
[0037] Figure 6 is a BET plot of the 13x molecular sieve in Example 1 of the present invention.
[0038] Figure 7 is a SEM image of the molecular sieve slow-release potassium fertilizer in Example 1 of the present invention. Detailed Implementation
[0039] The present invention will be further described in detail below with reference to specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.
[0040] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified.
[0041] Example 1:
[0042] The desulfurization ash from a thermal power plant was used as the original sample of fly ash. Table 1 shows the elemental composition of the original fly ash sample used in this embodiment. As can be seen from Table 1, the fly ash contains silicon, aluminum and other impurities.
[0043] Table 1. EDS elemental composition of fly ash
[0044]
[0045] The fly ash samples were characterized using scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and specific surface area and pore size analysis. Figure 1 shows the SEM image of the fly ash sample, which indicates that the sample has an irregular blocky structure. Figure 2 shows the XRD pattern of the fly ash sample, which shows that the sample contains multiple crystalline phases, with SiO2 being the main phase. Figure 3 shows the BET pattern of the fly ash sample, which indicates that the specific surface area of the fly ash sample is relatively small, only 4.07 m². 2 / g.
[0046] Weigh 10g of fly ash sample and 8g of sodium carbonate using an electronic balance. Mix them evenly in a ceramic boat and place the mixture in a muffle furnace. Heat the mixture to 750℃ at 2℃ / min and calcine for 90min to obtain activated fly ash.
[0047] Measure 26 mL of commercially available concentrated hydrochloric acid and 14 mL of water using a graduated cylinder to prepare a 40 mL 25% hydrochloric acid solution. Add the activated fly ash to the hydrochloric acid solution and stir to dissolve. After reacting for 12 hours, filter to obtain an aluminum-rich liquid.
[0048] The residue remaining after filtration was dried in an oven at 110℃ for 12 hours, then mixed thoroughly with sodium hydroxide and distilled water at a mass ratio of 10:6:40. The mixture was then placed in an oil bath and heated at 80℃ for 12 hours. After filtration, a silica-rich solution was obtained. The aluminum-rich solution and the silica-rich solution were then mixed, and sodium aluminate was added to adjust the silica-alumina ratio to 2:1. Simultaneously, the pH was adjusted to 9.5 to obtain a gel-like mother liquor.
[0049] The gel-like mother liquor was placed in a hydrothermal reactor for crystallization at 95℃ for 24 hours. The reaction product was filtered and washed until the pH of the washing solution reached 8, and then dried at 110℃ to obtain a 13x molecular sieve sample. The 13x molecular sieve was characterized by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and specific surface area and pore size analysis. Figure 4 shows the SEM image of the 13x molecular sieve, which shows that the molecular sieve also has an irregular blocky structure. Figure 5 shows the XRD pattern of the 13x molecular sieve, which shows the presence of the crystalline phase of the 13x molecular sieve. Figure 6 shows the BET pattern of the 13x molecular sieve, which shows that the specific surface area of the molecular sieve continues to increase, reaching 65.30 m². 2 / g, and its pore volume reaches 0.36cm. 3 / g; Table 2 shows the EDS elemental composition of the molecular sieve. As can be seen from Table 2, its elemental composition is similar to that of 13x molecular sieve and it has a good effect on removing impurities from fly ash.
[0050] Table 2. EDS elemental composition of 13x molecular sieve
[0051]
[0052] 1 g of 13x molecular sieve and 4 g of KNO3 were weighed into a porcelain crucible (the mass ratio of potassium salt to 13x molecular sieve was 4:1). After grinding evenly, the mixture was heated at 350℃ for 8 h. The heated mixture was cooled to room temperature, quickly washed with deionized water, centrifuged at 3000 rpm for 5 min, and repeated 4 times. The mixture was then dried at 110℃ for 12 h to obtain the molecular sieve slow-release potassium fertilizer. The molecular sieve slow-release potassium fertilizer was characterized by scanning electron microscopy. Figure 7 shows the SEM image of the molecular sieve slow-release potassium fertilizer, which shows that the slow-release potassium fertilizer has a small, irregular morphology. Table 3 shows the potassium ion release data of the molecular sieve slow-release potassium fertilizer over 28 days. As can be seen from Table 3, the molecular sieve slow-release potassium fertilizer released only 45.69% of the total load of potassium ions on day 14, and released a total of 87.04% of the total load of potassium ions after 28 days. At this time, the molecular sieve slow-release potassium fertilizer still has the ability to regulate soil fertility, indicating that the molecular sieve slow-release potassium fertilizer prepared in this embodiment has a good slow-release effect.
[0053] Table 3 Potassium ion release data of molecular sieve slow-release potassium fertilizer after 28 days
[0054]
[0055] Example 2:
[0056] Using desulfurization ash from a thermal power plant as the original fly ash sample, 10g of fly ash and 10g of sodium carbonate were weighed using an electronic balance, mixed evenly in a ceramic boat, and then placed in a muffle furnace. The temperature was increased to 600℃ at 2℃ / min and calcined for 60min to obtain activated fly ash.
[0057] Separately, measure 10 mL of commercially available concentrated hydrochloric acid and 30 mL of water using a graduated cylinder to prepare a 40 mL 10% hydrochloric acid solution. Add the activated fly ash to the hydrochloric acid solution and stir to dissolve. After reacting fully for 6 hours, filter to obtain an aluminum-rich liquid.
[0058] The residue remaining after filtration was dried in an oven at 110℃ for 12 hours, then mixed thoroughly with sodium hydroxide and distilled water at a mass ratio of 10:4:20. The mixture was then placed in an oil bath and heated at 60℃ for 6 hours. After filtration, a silica-rich solution was obtained. The aluminum-rich solution and the silica-rich solution were then mixed, and sodium aluminate was added to adjust the silica-alumina ratio to 1:1. Simultaneously, the pH was adjusted to 7 to obtain a gel-like mother liquor.
[0059] The gel-like mother liquor was placed in a hydrothermal reactor for crystallization at 80℃ for 6 hours. The reaction product was filtered and washed until the pH of the washing solution reached 7.5, and then dried at 110℃ to obtain a 13x molecular sieve sample.
[0060] Weigh 1g of 13x molecular sieve and 5g of KNO3 into a porcelain crucible (the mass ratio of potassium salt to 13x molecular sieve is 5:1). Grind them evenly and heat them at 450℃ for 8 hours. After heating, cool the mixed sample to room temperature, wash it quickly with deionized water, centrifuge it at 3000rpm for 5 minutes, repeat 4 times, and dry it at 110℃ for 12 hours to obtain molecular sieve slow-release potassium fertilizer.
[0061] Example 3:
[0062] Using desulfurization ash from a thermal power plant as the original fly ash sample, 10g of fly ash and 5g of sodium carbonate were weighed using an electronic balance, mixed evenly in a ceramic boat, and then placed in a muffle furnace. The temperature was increased to 900℃ at 2℃ / min and calcined for 120min to obtain activated fly ash.
[0063] Separately, measure 31 mL of commercially available concentrated hydrochloric acid and 9 mL of water using a graduated cylinder to prepare a 40 mL 30% hydrochloric acid solution. Add the activated fly ash to the hydrochloric acid solution and stir to dissolve. After reacting fully for 24 hours, filter to obtain an aluminum-rich liquid.
[0064] The residue remaining after filtration was dried in an oven at 110℃ for 12 hours, then mixed thoroughly with sodium hydroxide and distilled water at a mass ratio of 10:8:60. The mixture was then placed in an oil bath and heated to 100℃ for 24 hours. The resulting solution was filtered to obtain a silica-rich liquid. The aluminum-rich and silica-rich solutions were then mixed, and sodium aluminate was added to adjust the silica-alumina ratio to 3:1. Simultaneously, the pH was adjusted to 11 to obtain a gel-like mother liquor.
[0065] The gel-like mother liquor was placed in a hydrothermal reactor for crystallization at 120℃ for 36 hours. The reaction product was filtered and washed until the pH of the washing solution reached 7.5, and then dried at 110℃ to obtain a 13x molecular sieve sample.
[0066] Weigh 1g of 13x molecular sieve and 1g of KNO3 into a porcelain crucible (the mass ratio of potassium salt to 13x molecular sieve is 1:1). Grind them evenly and heat them at 300℃ for 8 hours. After heating, cool the mixed sample to room temperature, wash it quickly with deionized water, centrifuge it at 3000rpm for 5 minutes, repeat 4 times, and dry it at 110℃ for 12 hours to obtain molecular sieve slow-release potassium fertilizer.
[0067] This invention uses fly ash as raw material and employs hydrochloric acid soaking, sodium hydroxide alkali dissolution, and hydrothermal methods to convert fly ash produced by coal-fired power plants into 13x molecular sieves. This technology features low raw material prices, simple preparation process, relatively low energy consumption, and ease of industrial production. It not only realizes the resource utilization and high-value utilization of fly ash, but also provides a new preparation method for slow-release fertilizers, effectively improving fertilizer utilization.
[0068] This invention provides a molecular sieve slow-release potassium fertilizer and its preparation method. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.
Claims
1. A method for preparing a molecular sieve slow-release potassium fertilizer, characterized in that, The process includes the following steps: S1. Activation: Mix the original fly ash sample with an activator and calcine to obtain activated fly ash; S2. Extraction of aluminum-rich liquid: Soak the activated fly ash in hydrochloric acid solution, dissolve and filter to obtain aluminum-rich liquid, and collect the residue. S3. Extraction of silicon-rich liquid: Mix the dried residue with sodium hydroxide and distilled water evenly, heat to react, and filter to obtain silicon-rich liquid; S4. Preparation of molecular sieves: Aluminum-rich liquid and silicon-rich liquid are mixed, and the silicon-aluminum ratio and pH are adjusted to obtain a reaction solution. Then, a crystallization reaction is carried out, followed by washing, drying, and grinding to obtain molecular sieves. S5. Preparation of molecular sieve slow-release potassium fertilizer: Molecular sieve and inorganic potassium salt are mixed and ground evenly, and heated to obtain the molecular sieve slow-release potassium fertilizer.
2. The preparation method according to claim 1, characterized in that, In S1, the mass ratio of the fly ash to the activator is (1~2):1; the activator includes any one of sodium carbonate, calcium carbonate, ammonium sulfate, concentrated sulfuric acid, and sodium hydroxide.
3. The preparation method according to claim 1, characterized in that, In S1, the calcination conditions are: temperature 600~900℃, time 60~120min.
4. The preparation method according to claim 1, characterized in that, In S2, the mass concentration of the hydrochloric acid solution is 10-30%; the soaking time is 6-24 hours.
5. The preparation method according to claim 1, characterized in that, In S3, the mass ratio of the residue, sodium hydroxide, and distilled water is 10:(4~8):(20~60); the heating conditions are: temperature 60~100℃, time 6~24h.
6. The preparation method according to claim 1, characterized in that, In S4, the aluminum-silicon ratio in the reaction solution is (1~3):1, and the pH value is 7~11; the crystallization reaction is carried out under the following conditions: crystallization temperature is 80~120℃, and crystallization time is 6~36h.
7. The preparation method according to claim 1, characterized in that, In S5, the mass ratio of the molecular sieve to the inorganic potassium salt is 1:(1~5); the inorganic potassium salt includes any one of potassium nitrate, potassium chloride, potassium carbonate and potassium sulfate.
8. The preparation method according to claim 1, characterized in that, In S5, the heating conditions are: temperature 300~450℃, time 8h.
9. Molecular sieve slow-release potassium fertilizer prepared by the preparation method according to any one of claims 1 to 8.