Preparation method of porous calcium-based composite aerogel ball slow release fertilizer
By preparing porous calcium-based composite aerogel ball slow-release fertilizer, the problems of nutrient loss in traditional fertilizers and high cost of slow-release fertilizers have been solved, achieving efficient nutrient utilization and environmentally friendly slow-release effect.
Patent Information
- Application Number
- CN202511763218.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-27
- Publication Date
- 2026-02-06
AI Technical Summary
Traditional fertilizers suffer from severe nutrient loss and low utilization rates, while the coating materials for slow-release fertilizers are expensive and may be toxic to soil organisms, limiting their application rate.
Porous calcium carbonate is prepared by short-time multiple soaking and high-temperature calcination using calcium carbonate as raw material. Combined with carboxymethyl cellulose, sodium alginate and BAPTA, porous calcium-based composite aerogel ball slow-release fertilizer is prepared by sol-gel method and freeze-drying method, and the porous characteristics are used to realize two-stage slow release of nutrients.
It improves nutrient utilization, achieves two-stage slow release of nutrients, with a cumulative leaching rate of 70%, and has the function of regulating soil pH, thus reducing production costs.
Smart Images
Figure CN121471028A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of slow-release fertilizer technology, specifically relating to a method for preparing a porous calcium composite aerogel ball slow-release fertilizer. Background Technology
[0002] In modern agricultural production systems, scientific fertilization is a core element in ensuring high and stable crop yields and improving crop quality. As a crucial support for increased grain production, the efficient utilization and environmental friendliness of chemical fertilizers remain key issues for sustainable agricultural development. However, traditional chemical fertilizers (such as nitrogen and phosphate fertilizers) have significant drawbacks during application: on the one hand, nutrient loss is severe due to soil physicochemical processes (such as hydrolysis, adsorption, and leaching) and climatic conditions, resulting in generally low fertilizer utilization rates (e.g., nitrogen fertilizer utilization is often less than 40%); on the other hand, excessive nutrients enter water bodies, the atmosphere, and other ecosystems, causing environmental problems such as eutrophication, soil acidification, and greenhouse gas emissions, posing challenges to green agricultural development.
[0003] Controlled / slow-release fertilizers have become a research hotspot in the fertilizer field due to their characteristics such as synchronizing nutrient release with crop needs and meeting the needs of crops throughout their entire growth cycle with a single application. Currently, slow-release fertilizers have been applied to the growth of crops such as grains, vegetables, fruits, and tobacco, achieving good results. However, in actual agricultural production, the application rate of slow-release fertilizers is not high due to various factors and challenges. This is mainly because the coating materials and carrier materials for slow-release fertilizers are expensive, and their processing costs are high. In addition, some coating materials used in the production of slow-release fertilizers are non-biodegradable and may be toxic to soil organisms. Therefore, developing carrier materials with superior slow-release performance, environmental friendliness, and low cost is one of the current research trends in slow-release fertilizers both domestically and internationally.
[0004] Calcium carbonate (CaCO3) has attracted much attention due to its unique advantages. CaCO3 is not only widely available and inexpensive, but it can also react with acidic substances in the soil to regulate pH and function as a nutrient carrier. However, calcium carbonate lacks pores and cannot slowly release adsorbed nutrients. Summary of the Invention
[0005] To address the aforementioned issues, this invention utilizes calcium carbonate as a raw material, employing a combination of short-time, multiple soaking and high-temperature calcination to prepare porous calcium carbonate. Using self-made porous calcium carbonate, carboxymethyl cellulose, BAPTA, and sodium alginate as raw materials, porous calcium-based composite aerogel ball slow-release fertilizer is prepared using sol-gel method, freeze-drying method, and template method. This leverages the porous properties of both porous calcium carbonate and aerogel to achieve two-stage slow release of nutrients, improving nutrient utilization, and is particularly suitable for tobacco cultivation.
[0006] To achieve the objective of this invention, a method for preparing porous calcium-based composite aerogel ball slow-release fertilizer is provided, characterized in that the method includes the following steps: 1. A method for preparing a porous calcium-based composite aerogel ball slow-release fertilizer, characterized in that the method includes the following steps: a. According to the weight proportions, add 2 parts of porous calcium, 2.5-5 parts of nitrogen fertilizer, 1.6-3.5 parts of sodium alginate, 2 parts of sodium carboxymethyl cellulose, 0.5 parts of BAPTA, and 100 parts of water to the mixer. Heat the mixer to 50°C, stir for 1 hour, and then sonicate for 10 minutes to obtain a mixed gel solution. b. Add a 20% calcium chloride solution to the spherical mold; c. Pour the mixed gel solution from the mixer into a spherical mold to obtain hydrogel balls. Rinse with water to remove excess solution, place in the freezer compartment of a refrigerator and freeze for 2 hours. After freezing, place in a freeze dryer and freeze dry for 24 hours to obtain porous calcium-based composite aerogel ball slow-release fertilizer.
[0007] Preferably, the porous calcium preparation method described in step a includes the following steps: Weigh a quantitative amount of heavy calcium carbonate, place it in a filter bag, and immerse it three times in a prepared 10% hydrochloric acid solution, with each immersion time being 3-6 seconds. Filter and dry the solution. Then mix it with 5% calcium carbonate starch, place it in a 30 mL crucible, and preheat it in an electric universal furnace under a fume hood for 20 minutes (temperature controlled at 200℃). After the crucible cools to room temperature, place it in a muffle furnace for calcination. Set the muffle furnace calcination regime as follows: raise the temperature to 700℃ within 100 minutes, maintain this temperature for 120 minutes, and remove the sample after cooling to room temperature. This is the porous calcium.
[0008] Preferably, the nitrogen fertilizer mentioned in step a is one of urea, ammonium bicarbonate, ammonium sulfate, and ammonium chloride, with urea being the most preferred.
[0009] Preferably, the filter bag has a pore size of 0.1-1 mm.
[0010] The beneficial effects of this invention are as follows: 1. The water absorption and swelling properties of carboxymethyl cellulose and the porous nature of aerogel balls enable porous calcium-based composite aerogel ball slow-release fertilizer to have a water retention function; 2. The two-stage slow release of nutrients through porous calcium carbonate and aerogel membrane involves first the slow release of nutrients through the aerogel membrane, and then the slow release of nutrients from the porous calcium carbonate, thereby achieving full utilization of nutrients. The cumulative leaching rate is 70% within a 7-day cycle. 3. Porous calcium carbonate has the function of regulating pH; 4. The chelating effect of BAPTA on calcium ions and the cross-linking effect of alginate on calcium ions can promote the absorption of organic calcium by plants. Attached Figure Description
[0011] Figure 1 This is a scanning electron microscope image of porous calcium carbonate.
[0012] Figure 2 This is a scanning electron microscope image of the porous calcium-based composite aerogel ball slow-release fertilizer from Example 4. Detailed Implementation
[0013] The following embodiments are merely some, not all, of the embodiments of the present invention. The embodiments of the present invention described and illustrated herein can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
[0014] Examples 1-4 To better compare the slow-release effects of fertilizers, urea was chosen as the nitrogen fertilizer, and the amount of nitrogen fertilizer was set to be the same. According to the proportions in Table 1, porous calcium, nitrogen fertilizer, sodium alginate, sodium carboxymethyl cellulose, BAPTA, and water were added to the mixer. The mixer was heated to 50°C and stirred for 1 hour, followed by ultrasonication for 10 minutes to obtain a mixed gel solution. A 20% calcium chloride solution was added to a spherical mold. The mixed gel solution from the mixer was poured into the spherical mold to obtain hydrogel balls. Excess solution was rinsed off with water, and the balls were frozen in the freezer for 2 hours. After freezing, they were freeze-dried in a freeze dryer for 24 hours to obtain porous calcium-based composite aerogel slow-release fertilizer.
[0015] The nitrogen content of the leachate from the slow-release fertilizer was determined using the p-dimethylaminobenzaldehyde colorimetric spectrophotometric method. The main body of the leachate tube was custom-made from a 5 cm inner diameter and 25 cm high acrylic cylindrical tube, with a small hole at the bottom for filtrate collection. During the leaching experiment, three layers of 0.08 mm pore size filter cloth were added to the leaching outlet, and a 250 mL conical flask was used to collect the filtrate at the bottom. Simulating actual farmland soil conditions, the soil column height was set to 13 cm. After compaction, (1 ± 0.05) g of the finished slow-release fertilizer was evenly spread, and then covered with a 4 cm thick layer of soil as the topsoil. At the beginning of the slow-release experiment, since the soil used was air-dried, 250 mL of tap water was added to the soil column of the leachate tube to maintain soil moisture. Subsequently, 100 mL of tap water was slowly added daily. The leachate was collected in a 250 mL conical flask below the leachate tube, and the volume of the leachate was recorded daily. The experiment lasted for 7 days, and the laboratory temperature was maintained at room temperature.
[0016] Table 1. 7-day cumulative leukorrhea rate of the example
[0017] As shown in Table 1, the leaching rate of the comparative examples remained consistently at an extremely low level, with a very low cumulative leaching rate. Within the 7-day experimental period, the cumulative leaching rate of Examples 1-4 was almost 70%, indicating that the aerogel balls coated with different concentrations of sodium alginate (1.6 g, 1.9 g, 2.2 g, 2.5 g) experienced a rapid increase in leaching rate in the early stage (around 0-2 days), reaching a peak and then rapidly decreasing, stabilizing at a low level after 3-4 days, with a cumulative leaching rate of approximately 70% over 7 days. From the examples and comparative examples, it can be seen that the nutrient release of the porous calcium-based composite aerogel ball slow-release fertilizer is a two-stage slow release.
[0018] Figure 1 This is a scanning electron microscope image of porous calcium carbonate. Figure 2 This is a scanning electron microscope image of the porous calcium-based composite aerogel ball slow-release fertilizer from Example 4. Figure 1 It can be seen that porous calcium carbonate exhibits a relatively rough surface structure, with relatively uniform pore distribution, irregular undulations and grooves on the particle surface, and overall presents a loose and porous characteristic, with mostly irregular pore shapes. From Figure 2 It can be seen that when the porous calcium-based composite aerogel ball slow-release fertilizer is loaded with nitrogen fertilizer, the surface of the particles undergoes significant changes. Some granular-like substances adhere to the originally relatively smooth areas, making the surface more complex. There appears to be a filling phenomenon in the pores, indicating that the nitrogen fertilizer has entered the pore structure of the porous calcium carbonate and aerogel balls.
Claims
1. A method for preparing a porous calcium-based composite aerogel ball slow-release fertilizer, characterized in that, The method includes the following steps: a. According to the weight proportions, add 2 parts of porous calcium, 2.5-5 parts of nitrogen fertilizer, 1.6-3.5 parts of sodium alginate, 2 parts of sodium carboxymethyl cellulose, 0.5 parts of BAPTA, and 100 parts of water to the mixer. Heat the mixer to 50°C, stir for 1 hour, and then sonicate for 10 minutes to obtain a mixed gel solution. b. Add a 20% calcium chloride solution to the spherical mold; c. Pour the mixed gel solution from the mixer into a spherical mold to obtain hydrogel balls. Rinse with water to remove excess solution, place in the freezer compartment of a refrigerator and freeze for 2 hours. After freezing, place in a freeze dryer and freeze dry for 24 hours to obtain porous calcium-based composite aerogel ball slow-release fertilizer.
2. The preparation method of a porous calcium-based composite aerogel ball slow-release fertilizer as described in claim 1, characterized in that, The porous calcium preparation method described in step a includes the following steps: Weigh a quantitative amount of heavy calcium carbonate, place it in a filter bag, and immerse it in a prepared 10% hydrochloric acid solution for 2-3 extractions, each immersion time being 3-6 seconds. Filter and dry the mixture. Then, mix it with 5% calcium carbonate starch, place it in a 30 mL crucible, and preheat it in an electric universal furnace under a fume hood for 20 minutes (temperature controlled at 200℃). After the crucible cools to room temperature, place it in a muffle furnace for calcination. Set the muffle furnace calcination regime as follows: raise the temperature to 700℃ within 100 minutes, maintain this temperature for 120 minutes, and after cooling to room temperature, remove the sample, which is the porous calcium.
3. The preparation method of a porous calcium-based composite aerogel ball slow-release fertilizer as described in claim 1, characterized in that, The nitrogen fertilizer mentioned in step a is one of urea, ammonium bicarbonate, ammonium sulfate, and ammonium chloride, preferably urea.
4. The preparation method of a porous calcium-based composite aerogel ball slow-release fertilizer as described in claim 2, characterized in that, The filter bag has a pore size of 0.1-1mm.