Calcium-based composite modified charcoal as well as preparation method and application thereof
By preparing calcium-based composite modified biochar, the problem of insufficient slow-release performance and ion exchange capacity of biochar in saline soil is solved by utilizing the exchange reaction between calcium ions and metal ions in the soil. This achieves efficient improvement of saline soil and crop growth, reduces costs and environmental pollution.
Patent Information
- Application Number
- CN202510870503.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-26
- Publication Date
- 2025-10-31
AI Technical Summary
Existing biochar has insufficient slow-release performance and ion exchange capacity when improving soil structure deterioration caused by light to moderate concentrations of soluble salts, especially sodium ions, in saline soils, resulting in poor improvement effects. Furthermore, traditional methods are costly, cumbersome to operate, and prone to causing secondary pollution.
A calcium-based solution was prepared by using eggshell powder and citric acid solution. After soaking citrus peel particles, the solution was subjected to pyrolysis to prepare calcium-based composite modified biochar. The calcium ions react with metal ions in the soil to increase the cation exchange capacity of the soil. The loaded calcium ions form stable soil aggregates, thereby improving the physical and chemical properties of the soil.
The prepared calcium-based composite modified biochar has a well-developed pore structure and abundant surface active sites, which enhances adsorption capacity and slow-release performance, improves soil aeration and water retention capacity, promotes crop growth, and realizes efficient and low-cost improvement of saline soil, reduces environmental pollution and improves resource utilization.
Smart Images
Figure CN120860987A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of saline soil improvement technology, and particularly to calcium-based composite modified biochar, its preparation method, and its application. Background Technology
[0002] In my country, saline soil is widely distributed along the coast and in arid and semi-arid inland areas, severely impacting crop growth and agricultural productivity, and has become a significant obstacle to sustainable agricultural development and ecological restoration. For a long time, saline soil remediation has relied primarily on physical, chemical, and biological measures, such as salt leaching, lime application, and planting salt-tolerant plants. However, these traditional methods generally suffer from slow results, high costs, cumbersome operations, and a tendency to cause secondary pollution, making it difficult to achieve efficient, long-term, and green remediation of saline soil.
[0003] Biochar, a carbonaceous material prepared from agricultural organic waste through high-temperature pyrolysis, has received widespread attention in soil remediation in recent years due to its well-developed pore structure, large specific surface area, and abundant surface functional groups. This gives it excellent adsorption capacity, slow-release properties, and the ability to improve soil structure. However, existing biochar still suffers from limitations in slow-release performance and ion exchange capacity when facing soil structural degradation caused by light to moderate concentrations of soluble salts, especially sodium ions, in saline soils, resulting in limited remediation effects. Summary of the Invention
[0004] The main objective of this invention is to propose a calcium-based composite modified biochar, its preparation method, and its application, aiming to solve the problems of high cost and poor improvement effect in the practical application of saline soil improvement.
[0005] To achieve the above objectives, this invention proposes a method for preparing calcium-based composite modified biochar, comprising the following steps:
[0006] S10. Mix eggshell powder and citric acid solution, react until no more bubbles are produced, and then take the supernatant to obtain a calcium-based solution.
[0007] S20. The citrus peel particles are soaked in the calcium-based solution, and the pretreated citrus peel particles are obtained by solid-liquid separation. The pretreated citrus peel particles are then dried.
[0008] S30. The dried pretreated citrus peel particles are pyrolyzed in an inert gas atmosphere to obtain pyrolysis products. The pyrolysis products are washed with water and then dried to obtain calcium-based composite modified biochar.
[0009] In one embodiment, in step S10:
[0010] The concentration of the citric acid solution is 0.05–0.1 g / mL, and the mass ratio of the eggshell powder to the citric acid solution is 1:(5–10); and / or,
[0011] Mix eggshell powder and citric acid solution for 24–48 hours.
[0012] In one embodiment, step S20 includes:
[0013] Citrus peel particles are soaked in a calcium-based solution for 24–48 hours, and pretreated citrus peel particles are obtained by solid-liquid separation. The pretreated citrus peel particles are then dried.
[0014] In one embodiment, in step S20, the mass ratio of the citrus peel particles to the calcium-based solution is 1:(1-10).
[0015] In one embodiment, in step S30, the dried pretreated citrus peel particles are heated to 500-800°C in an inert gas atmosphere at a heating rate of 4-6°C / min, and then kept at that temperature for 2-3 hours for pyrolysis treatment.
[0016] This invention proposes a calcium-based composite modified biochar, which is prepared according to the preparation method of calcium-based composite modified biochar described in the aforementioned technical solution.
[0017] This invention proposes an application of the calcium-based composite modified biochar in the improvement of saline soil.
[0018] In one embodiment, the calcium-based composite modified biochar is used to promote crop growth in saline soil.
[0019] In one embodiment, calcium-based composite modified biochar is mixed with saline soil to improve the saline soil, and then crop seeds are sown in the treated saline soil.
[0020] In one embodiment, the salt content of the saline soil is 0.1% to 1.0%, and the amount of calcium-based composite modified biochar added is 1% to 5% of the total mass of the saline soil.
[0021] In one embodiment, the saline soil is improved over a period of 2 to 3 days; and / or,
[0022] The crop seeds mentioned include soybean seeds.
[0023] In this invention, a calcium-based solution is first prepared using eggshell powder and citric acid solution. Then, citrus peel particles are soaked in the calcium-based solution to obtain pretreated citrus peel particles, ensuring the calcium-based solution fully adheres to the surface of the particles. The dried pretreated citrus peel particles are then subjected to pyrolysis to obtain calcium-based composite modified biochar. The resulting calcium-based composite modified biochar combines the advantages of biochar and calcium-based solution, possessing a well-developed pore structure, a large specific surface area, and abundant surface active sites. This enhances the adsorption and ion exchange capacity of the calcium-based composite modified biochar, while also exhibiting good slow-release properties. Furthermore, the prepared calcium-based composite modified biochar can effectively improve the soil's cation exchange capacity and physical and chemical properties through ion exchange reactions between the loaded calcium ions and metal ions in the soil. In addition, calcium ions help form stable soil aggregates, which retain water during drought and release water during rainfall or irrigation, thereby improving soil aeration and water retention capacity. The technical solution of this invention prepares calcium-based composite modified biochar from common waste materials. The raw materials are widely available and inexpensive, realizing the recycling of waste resources, which is conducive to reducing environmental pollution and improving resource utilization. Furthermore, the calcium-based composite modified biochar can regulate the soil conductivity and cation exchange capacity of light and moderate saline soils, promote the growth of crops in saline soils, and improve high-salinity saline soils. It shows good economic efficiency and operability and has broad prospects for promotion. Attached Figure Description
[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.
[0025] Figure 1 This is a process flow diagram of an embodiment of the preparation of calcium-based composite modified biochar provided by the present invention.
[0026] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation
[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0028] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indications will also change accordingly.
[0029] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.
[0030] Saline soil remediation mainly relies on a variety of physical, chemical, and biological measures, such as salt leaching, lime application, and planting salt-tolerant plants. However, these traditional methods generally suffer from slow effectiveness, high cost, cumbersome operation, and a tendency to cause secondary pollution, making it difficult to achieve efficient, long-term, and green remediation of saline soils. Biochar, a carbonaceous material prepared from agricultural organic waste through high-temperature pyrolysis, has received widespread attention in the field of soil remediation in recent years due to its well-developed pore structure, large specific surface area, and abundant surface functional groups, giving it excellent adsorption capacity, slow-release properties, and the ability to improve soil structure. However, existing biochar still exhibits insufficient slow-release performance and ion exchange capacity when facing soil structure deterioration caused by light to moderate concentrations of soluble salts, especially sodium ions, in saline soils, resulting in a bottleneck in its limited remediation effect.
[0031] Eggshells are a common waste. The main component of eggshells is calcium carbonate (CaCO3). Eggshells also contain other trace elements, such as Mg and Zn, which are beneficial to soil and plant growth. For example, they can supplement the Mg element in the soil and prevent yellowing of plant leaves.
[0032] Based on the above background, please refer to Figure 1 This invention proposes a method for preparing calcium-based composite modified biochar, comprising the following steps:
[0033] S10. Mix eggshell powder and citric acid solution, react until no more bubbles are produced, and then take the supernatant to obtain a calcium-based solution.
[0034] S20. The citrus peel particles are soaked in the calcium-based solution, and the pretreated citrus peel particles are obtained by solid-liquid separation. The pretreated citrus peel particles are then dried.
[0035] S30. The dried pretreated citrus peel particles are pyrolyzed in an inert gas atmosphere to obtain pyrolysis products. The pyrolysis products are washed with water and then dried to obtain calcium-based composite modified biochar.
[0036] Single-component biochar suffers from limitations in its slow-release properties and ion exchange capacity, resulting in limited effectiveness and a singular mechanism in improving saline soils with low to medium concentrations of soluble salts. In this invention, a calcium-based solution is first prepared using eggshell powder and citric acid solution. Citrus peel particles are then soaked in the calcium-based solution to obtain pretreated citrus peel particles, ensuring the calcium-based solution fully adheres to the surface of the particles. Finally, the dried pretreated citrus peel particles are subjected to pyrolysis to obtain calcium-based composite modified biochar. Compared to single biochar, the calcium-based composite modified biochar prepared in this invention combines the advantages of both biochar and calcium-based solutions. It not only possesses a well-developed pore structure, a large specific surface area, and abundant surface active sites, exhibiting excellent adsorption capacity, slow-release properties, and soil structure improvement functions, but also effectively enhances soil cation exchange capacity and improves soil physicochemical properties through ion exchange reactions between loaded calcium ions and metal ions in the soil. Furthermore, calcium ions contribute to the formation of stable soil aggregates, which retain moisture during drought and release it during rainfall or irrigation, thereby improving soil aeration and water retention capacity. Compared to conventional biochar modified with calcium ion solutions, the composite biochar of this invention can also incorporate trace elements from eggshells, improving soil electrical conductivity and cation exchange capacity, thus enhancing the overall performance of the calcium-based composite modified biochar.
[0037] The technical solution of this invention prepares calcium-based composite modified biochar from common waste materials. The raw materials are widely available and inexpensive, realizing the recycling of waste resources, which is conducive to reducing environmental pollution and improving resource utilization. Moreover, the calcium-based composite modified biochar can regulate the soil conductivity and cation exchange capacity of light and moderate saline soils, promote the growth of crops in saline soils, and has a good improvement effect on light and moderate saline soils. It shows good economic efficiency and operability and has broad prospects for promotion.
[0038] In an embodiment of the present invention, the drying process includes drying in a constant temperature drying oven.
[0039] In an embodiment of the present invention, in step S10, the mass concentration of the citric acid solution is 0.05–0.1 g / mL, and the mass ratio of the eggshell powder to the citric acid solution is 1:(5–10). The main component of eggshells includes calcium carbonate (CaCO3), which can react with citric acid to form a soluble calcium citrate complex and release carbon dioxide gas. The technical solution of the present invention uses a citric acid solution with a concentration of 0.05–0.1 g / mL, and sets the amounts of eggshell powder and citric acid within the above range, which ensures that the calcium carbonate in the eggshell is fully dissolved and converted into a soluble calcium compound, thus improving reaction efficiency. In this document, the citric acid solution refers to an aqueous solution of citric acid.
[0040] In an embodiment of the present invention, the eggshell powder is prepared by the following steps:
[0041] Rinse the eggshells with deionized water, and then dry the cleaned eggshells in a constant temperature drying oven at 100-110℃ until constant weight to obtain dried eggshells.
[0042] The dried eggshells are placed in the grinding jar of a planetary ball mill for ball milling, and then sieved to obtain eggshell powder.
[0043] The ball milling speed is 200-400 rpm, and the ball milling time is 15-25 min; the ball-milled eggshell powder is passed through a 0.15 mm sieve.
[0044] In embodiments of the present invention, the eggshell is a poultry eggshell, including but not limited to chicken eggshells, duck eggshells, duck eggs, goose eggs, and quail eggs. Eggshells are common waste in kitchens, restaurants, and food processing plants. The technical solution of the present invention utilizes eggshells to prepare a calcium-based solution, which is then used to prepare subsequent calcium-based composite modified biochar, thus achieving effective recycling of waste resources.
[0045] In an embodiment of the present invention, in step S10, the eggshell powder and citric acid solution are mixed for 24–48 hours. This allows the calcium carbonate in the eggshell to fully react, dissolve, and transform into a soluble calcium compound. Exemplarily, the mixing time can be 24 hours, 30 hours, 36 hours, 42 hours, or 48 hours.
[0046] To further reduce impurities in the calcium-based solution, in an embodiment of the present invention, after the step of mixing eggshell powder and citric acid solution and reacting until no more bubbles are generated and then taking the supernatant, the supernatant is filtered 2 to 3 times.
[0047] In an embodiment of the present invention, the citrus peel granules are prepared by the following steps:
[0048] The citrus peels were rinsed with deionized water and then dried in a 105°C constant temperature drying oven until constant weight. The dried citrus peels were then crushed to obtain citrus peel granules.
[0049] In embodiments of the present invention, the citrus peels include, but are not limited to, grapefruit peels, orange peels, Wogan peels, and Papagan peels.
[0050] In an embodiment of the present invention, step S20 includes:
[0051] Citrus peel particles are soaked in a calcium-based solution for 24–48 hours, and then pretreated citrus peel particles are obtained by solid-liquid separation. The pretreated citrus peel particles are then dried.
[0052] For example, the soaking time can be 24h, 30h, 36h, 42h, or 48h. Setting the soaking time of citrus peel particles in the calcium-based solution within the above range allows the calcium-based solution to fully adhere to the surface of the citrus peel particles, which is beneficial for obtaining calcium-based composite modified biochar with good overall performance.
[0053] In an embodiment of the present invention, in step S20, the mass ratio of the citrus peel particles to the calcium-based solution is 1:(1-10). Exemplarily, the mass ratio of the citrus peel particles to the calcium-based solution can be 1:1, 1:3, 1:5, 1:8, or 1:10. Setting the amount of calcium-based solution within the above range provides an appropriate amount of calcium ions, allowing them to fully adhere to the surface of the citrus peel particles, thereby improving the specific surface area, pore size distribution, chemical activity, and stability of the prepared calcium-based composite modified biochar.
[0054] In an embodiment of the present invention, in step S30, the dried pretreated citrus peel particles are heated to 500-800°C in an inert gas atmosphere at a heating rate of 4-6°C / min, and then held at that temperature for 2-3 hours for pyrolysis. Exemplarily, the heating rate can be 4°C / min, 5°C / min, or 6°C / min; the pyrolysis temperature can be 500°C, 600°C, 700°C, or 800°C; and the holding time can be 2 hours, 2.5 hours, or 3 hours. Setting the heating rate to 4-6°C / min, a slower heating rate, helps the moisture and other volatile components inside the biomass material to gradually escape, reducing the sudden increase in internal pressure caused by rapid heating. This helps to ensure the integrity and porosity of the biochar structure and improve the quality of the obtained biochar. Setting the pyrolysis temperature in the range of 500-800°C decomposes components such as cellulose and hemicellulose, as well as lignin, in the citrus peel, which helps to increase the specific surface area and pore volume of the biochar. Keeping the temperature for 2-3 hours can ensure that the pre-treated citrus peel particles are fully pyrolyzed.
[0055] In an embodiment of the present invention, the dried pretreated citrus peel particles are subjected to pyrolysis under a nitrogen atmosphere.
[0056] This invention proposes a calcium-based composite modified biochar, which is prepared according to the preparation method of calcium-based composite modified biochar described in the aforementioned technical solution.
[0057] This invention proposes an application of the calcium-based composite modified biochar in the improvement of saline soil.
[0058] The calcium-based composite modified biochar provided by this invention possesses a well-developed porous structure and abundant surface functional groups, exhibiting a large specific surface area and demonstrating excellent adsorption capacity, slow-release properties, and soil structure improvement capabilities. Furthermore, the calcium-based composite modified biochar contains calcium ions, which, through ion exchange reactions with ions in the soil, effectively enhance the soil's cation exchange capacity and improve its physicochemical properties. Simultaneously, calcium ions contribute to the formation of stable soil aggregates, which retain moisture during drought and release it during rainfall or irrigation, thereby improving aeration and water retention capacity. Therefore, the calcium-based composite modified biochar prepared by this invention combines the advantages of biochar and calcium-based solutions, demonstrating significant potential for application in saline soil improvement. It can regulate the soil conductivity and cation exchange capacity of lightly to moderately saline soils, promote crop growth in saline soils, and exhibits good economic efficiency and operability, with broad prospects for widespread application.
[0059] In an embodiment of the present invention, the calcium-based composite modified biochar is used to promote crop growth in saline soil. Using biochar can reduce the bulk density of the topsoil, making the soil looser and more porous, and also helps to increase the ion content of the soil, thereby improving soil fertility.
[0060] In an embodiment of the present invention, the application of the calcium-based composite modified biochar in the improvement of saline soil includes the following steps:
[0061] Calcium-based composite modified biochar was mixed with saline soil to improve the saline soil, and then crop seeds were sown in the treated saline soil.
[0062] In embodiments of the present invention, the saline soil has a salt content of 0.1% to 1.0%, and the amount of calcium-based composite modified biochar added is 1% to 5% of the total mass of the saline soil. In this document, the amount of calcium-based composite modified biochar added refers to the amount calculated based on the mass of the air-dried saline soil. Typically, the salt content of lightly to moderately saline soil ranges from 0.1% to 1.0% (1 g / kg to 10 g / kg). Conventional biochar often suffers from insufficient slow-release performance and ion exchange capacity, resulting in limited improvement effects when dealing with lightly to moderately soluble saline soil. The calcium-based composite modified biochar provided by this invention can effectively improve lightly to moderately soluble saline soil. When improving saline soil, increasing the amount of calcium-based composite modified biochar within a certain range can improve crop growth and increase the ion content in the soil; however, exceeding a certain amount will actually decrease the soil's cation exchange capacity. Taking into account both cost and improvement effect, the present invention sets the amount of calcium-based composite modified biochar added within the above range, which can balance the overall effect of saline soil improvement.
[0063] In an embodiment of the present invention, the saline soil improvement time is 2-3 days. The use of calcium-based composite modified biochar provided by the present invention for saline soil improvement yields high improvement efficiency.
[0064] In an embodiment of the present invention, the crop seeds include soybean seeds.
[0065] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.
[0066] Example 1
[0067] A method for preparing calcium-based composite modified biochar includes the following steps:
[0068] (1) Preparation of eggshell powder: Rinse the eggshells with deionized water, and then dry the cleaned eggshells in a constant temperature drying oven at 105℃ until constant weight. Place the dried eggshells in the grinding jar of a planetary ball mill for ball milling. Set the rotation speed and time of the planetary ball mill to 200 rpm and 20 min, respectively. Then pass the ball-milled powder through a 0.15 mm sieve to obtain eggshell powder.
[0069] (2) Orange peel granules: Rinse the orange peel with deionized water, then dry it in a 105℃ constant temperature drying oven until constant weight, and crush the dried orange peel to obtain orange peel granules.
[0070] (3) Preparation of calcium-based solution: In a beaker, mix eggshell powder and citric acid aqueous solution with a concentration of 0.05 g / mL at a mass ratio of 1:10. After dissolving for 48 h, take the supernatant and filter the supernatant 2 to 3 times to obtain calcium-based solution.
[0071] (4) Preparation of pretreated orange peel granules: Soak orange peel granules in calcium-based solution for 24 hours (the mass ratio of orange peel granules to calcium-based solution is 1:10) to obtain pretreated orange peel granules, and dry them in a constant temperature drying oven.
[0072] (5) Preparation of calcium-based composite modified biochar: The pretreated orange peel particles after drying in step (4) are placed in a tubular vacuum muffle furnace pyrolysis device and heated to 600°C at a heating rate of 5°C / min under N2 atmosphere. The temperature is maintained for 3 hours to obtain the pyrolysis product. The pyrolysis product is rinsed under flowing deionized water for 3 hours and then dried in a constant temperature drying oven at 60°C to obtain calcium-based composite modified biochar.
[0073] Example 2
[0074] Compared to Example 1, the difference is that grapefruit peel is used instead of orange peel to prepare citrus peel granules.
[0075] Example 3
[0076] Compared with Example 1, the difference is that the peel of the citrus fruit is used instead of the peel of the orange to prepare citrus peel granules.
[0077] Example 4
[0078] The difference compared to Example 1 is that the mass ratio of orange peel particles to calcium-based solution is 1:1.
[0079] Example 5
[0080] The difference compared to Example 1 is that the mass ratio of orange peel particles to calcium-based solution is 1:5.
[0081] Example 6
[0082] The difference from Example 1 is that the pyrolysis temperature is 500°C.
[0083] Example 7
[0084] The difference from Example 1 is that the pyrolysis temperature is 800°C.
[0085] Example 8
[0086] Compared with Example 1, the difference is that the concentration of the citric acid solution is 0.1 g / mL, and the mass ratio of eggshell powder to citric acid solution is 1:5.
[0087] Example 9
[0088] The application of a calcium-based composite modified biochar includes the following steps:
[0089] The air-dried saline-alkali soil (with a salt content of 0.8%) and the calcium-based composite modified biochar from Example 1 were mixed evenly and placed in pots. Soybean seeds were sown 2-3 days later. Each pot was watered thoroughly with 2L of water at the time of sowing. During the growth period, each pot was watered with 1L of water per week. Other conditions were managed as usual. The amount of calcium-based composite modified biochar added accounted for 1% of the mass of the air-dried saline-alkali soil.
[0090] Example 10
[0091] The difference from Example 9 is that the amount of calcium-based composite modified biochar added is 3% of the total mass of the air-dried saline soil.
[0092] Example 11
[0093] The difference from Example 9 is that the calcium-based composite modified biochar is the calcium-based composite modified biochar of Example 2.
[0094] Example 12
[0095] The difference from Example 11 is that the amount of calcium-based composite modified biochar added is 3% of the total mass of the air-dried saline soil.
[0096] Example 13
[0097] The difference between Example 9 and Example 2 is that the calcium-based composite modified biochar is the calcium-based composite modified biochar of Example 3.
[0098] Example 14
[0099] The difference from Example 13 is that the amount of calcium-based composite modified biochar added is 3% of the total mass of the air-dried saline soil.
[0100] Example 15
[0101] The difference between Example 10 and Example 4 is that the calcium-based composite modified biochar is the calcium-based composite modified biochar of Example 4.
[0102] Example 16
[0103] The difference between Example 10 and Example 5 is that the calcium-based composite modified biochar is the calcium-based composite modified biochar of Example 5.
[0104] Example 17
[0105] The difference between Example 10 and Example 6 is that the calcium-based composite modified biochar is the calcium-based composite modified biochar of Example 6.
[0106] Example 18
[0107] The difference between Example 10 and Example 7 is that the calcium-based composite modified biochar is the calcium-based composite modified biochar of Example 7.
[0108] Example 19
[0109] The difference between Example 10 and Example 8 is that the calcium-based composite modified biochar is the calcium-based composite modified biochar of Example 8.
[0110] Example 20
[0111] The difference from Example 9 is that the amount of calcium-based composite modified biochar added is 5% of the total mass of the air-dried saline soil.
[0112] Example 21
[0113] The difference from Example 11 is that the amount of calcium-based composite modified biochar added is 5% of the total mass of the air-dried saline soil.
[0114] Example 22
[0115] The difference from Example 13 is that the amount of calcium-based composite modified biochar added is 5% of the total mass of the air-dried saline soil.
[0116] Comparative Example 1
[0117] Compared with Example 9, the difference is that an equal amount of untreated biochar was used instead of the calcium-based composite modified biochar of Example 1, that is, the step of soaking the pretreated orange peel particles in the calcium-based solution was omitted. The untreated biochar was prepared by the following steps: orange peel particles were placed in a tubular vacuum muffle furnace pyrolysis device, heated to 600°C at a heating rate of 5°C / min under N2 atmosphere, and held for 3 hours to obtain pyrolysis products. The pyrolysis products were then rinsed under flowing deionized water for 3 hours to obtain biochar.
[0118] Comparative Example 2
[0119] Compared with Example 9, the difference is that citric acid-modified biochar is used instead of calcium-based composite modified biochar, and the citric acid-modified biochar is prepared through the following steps:
[0120] (1) Preparation of pretreated orange peel granules: The orange peel granules were soaked in 0.05 g / mL citric acid solution for 48 h (the mass ratio of orange peel granules to citric acid solution was 1:10), and then the pretreated orange peel granules were obtained by solid-liquid separation. The pretreated orange peels were then dried in a constant temperature drying oven.
[0121] (2) Preparation of citric acid modified biochar: The pretreated orange peel particles dried in step (1) were placed in a tubular vacuum muffle furnace pyrolysis device and heated to 600°C at a heating rate of 5°C / min under N2 atmosphere. The temperature was maintained for 3 hours to obtain the pyrolysis product. The pyrolysis product was rinsed under flowing deionized water for 3 hours and then dried in a constant temperature drying oven at 60°C to obtain citric acid modified biochar.
[0122] Comparative Example 3
[0123] Compared with Example 9, the difference lies in that the calcium-based composite modified biochar is prepared through the following steps:
[0124] (1) Preparation of pretreated orange peel granules: The orange peel granules were soaked in a 0.05 g / mL calcium chloride solution for 48 h (the mass ratio of orange peel granules to calcium chloride solution was 1:10), and then the pretreated orange peel granules were obtained by solid-liquid separation. The pretreated orange peel granules were then dried in a constant temperature drying oven.
[0125] (2) Preparation of calcium-based composite modified biochar: The pretreated orange peel particles dried in step (1) were placed in a tubular vacuum muffle furnace pyrolysis device and heated to 600°C at a heating rate of 5°C / min under N2 atmosphere. The temperature was maintained for 3 hours to obtain the pyrolysis product. The pyrolysis product was rinsed under flowing deionized water for 3 hours and then dried in a constant temperature drying oven at 60°C to obtain calcium-based composite modified biochar.
[0126] Comparative Example 4
[0127] Compared with Example 9, the difference lies in that the calcium-based composite modified biochar is prepared through the following steps:
[0128] (1) Preparation of calcium-based solution: Calcium carbonate and citric acid solution with a concentration of 0.05 g / mL were mixed at a mass ratio of 1:10 for 48 h to obtain calcium-based solution.
[0129] (2) Preparation of pretreated orange peel granules: The orange peel granules were soaked in the calcium-based solution prepared in step (1) for 48 hours (the mass ratio of orange peel granules to calcium-based solution was 1:10) to obtain pretreated orange peel granules. The pretreated orange peel granules were then placed in a constant temperature drying oven to dry.
[0130] (3) Preparation of calcium-based composite modified biochar: The pretreated orange peel particles dried in step (2) were placed in a tubular vacuum muffle furnace pyrolysis device and heated to 600°C at a heating rate of 5°C / min under N2 atmosphere. The temperature was maintained for 3 hours to obtain the pyrolysis product. The pyrolysis product was rinsed under flowing deionized water for 3 hours and then dried in a constant temperature drying oven at 60°C to obtain calcium-based composite modified biochar.
[0131] Performance testing
[0132] Specific surface area: The specific surface area of the calcium-based composite modified biochar in Examples 1-8 was tested by the BET adsorption method, and the test results are shown in Table 1.
[0133] Table 1. Parameters and specific surface area test results for Examples 1-8
[0134]
[0135] As shown in Table 1, the specific surface area of the calcium-based composite modified biochar in Examples 1-8 ranges from 153.43 to 196.78 m². 2 / g, which shows that the calcium-based composite modified biochar provided by the present invention has a certain pore structure and adsorption capacity.
[0136] Soybean germination rate: Soybean seeds were sown according to the application methods of Examples 9-22 and Comparative Examples 1-4. The germination rate of soybean seeds sown in saline soil using the calcium-based composite modified biochar in the blank group, Examples 9-22, and Comparative Examples 1-4 was observed 14 days after sowing. The test results are shown in Table 2. The blank control group did not contain any calcium-based composite modified biochar from the examples or comparative examples; that is, the amount of biochar used was 0. Other parameters were the same as in the examples or comparative examples.
[0137] Soil samples from the upper 0-15cm soil layer of the blank group, Examples 9-22 and Comparative Examples 1-4 were taken respectively. After natural air drying, roots and other impurities were removed, and the samples were ground and passed through a 2mm sieve for soil pH, soil electrical conductivity (EC) and cation exchange capacity (CEC) testing.
[0138] Soil pH: pH was measured using a pH meter, with a water-to-soil ratio of 2.5:1.0. The test results are shown in Table 2.
[0139] Soil electrical conductivity (EC): Soil electrical conductivity was measured using a conductivity meter with a water-to-soil ratio of 5:1. The test results are shown in Table 2.
[0140] Cation exchange capacity: Cation exchange capacity (CEC) was assessed by thiodiamine cobalt leaching-spectrophotometry. The test results are shown in Table 2.
[0141] Table 2 Performance test results of blank control group, Examples 9-22 and Comparative Examples 1-4
[0142]
[0143] In Table 2, " / " indicates that no calcium-based composite modified biochar was added.
[0144] As shown in Table 2, the results of Examples 9-22 are all better than those of the blank group. Applying the calcium-based composite modified biochar provided by the present invention to the surface can improve saline soil.
[0145] Based on the test data from Examples 9-10, 20, 11-12, 21, 13-14, and 22, it can be seen that: for seed germination rate, the seedling emergence rate increases with the increase of calcium-based composite modified biochar application, which is beneficial to promoting crop growth; for soil pH, the pH shows a slight increase without significant change with the increase of calcium-based composite modified biochar application; for soil electrical conductivity, the soil electrical conductivity also increases with the increase of calcium-based composite modified biochar application, and soil electrical conductivity reflects the ion concentration in the soil. Therefore, increasing the application amount of calcium-based composite modified biochar is beneficial to increasing the ion content of the soil, thereby improving soil fertility. Regarding cation exchange capacity, as the application amount of modified biochar increases, cation exchange capacity shows a trend of first increasing and then decreasing. This may be because at low addition amounts, the rich pore structure on the surface of biochar can promote the exchange of substances in the soil, but at high addition amounts, cations in the soil may be adsorbed into the pores by biochar, or functional groups such as hydroxyl and carboxyl groups may be released and combine with cations in the soil to form stable complexes, thereby reducing the cation exchange capacity in the soil.
[0146] Based on the results of Example 9 and Comparative Examples 1-4, the calcium-based composite modified biochar prepared by first using eggshells and citric acid solution to prepare a calcium-based solution, then soaking citrus peel particles in the calcium-based solution before pyrolysis exhibits the best performance. It shows the best effects in promoting soybean emergence, increasing soil conductivity, and enhancing cation exchange capacity. Comparative Example 1, lacking the modification with a calcium-based solution, lacks the effects of citrate and calcium ions, resulting in a poorer effect of the calcium-based composite modified biochar in promoting plant growth, and also worsening the test results for soil conductivity and cation exchange capacity. Comparative Example 2, using citric acid solution for modification, lacks the presence of calcium ions. The effect of calcium-based composite modified biochar on promoting plant growth was worse, and the test results of soil electrical conductivity and cation exchange capacity were also worse. In Comparative Example 3, calcium chloride solution was used instead of calcium-based solution, and the test results of soil electrical conductivity and cation exchange capacity were worse. This may be because the calcium-based composite modified biochar contains fewer hydroxyl and carboxyl functional groups, resulting in a weaker adsorption capacity for cations. In Comparative Example 4, calcium citrate solution was used instead of the calcium-based solution of the present invention, and the test results of soil electrical conductivity and cation exchange capacity were worse than those of Example 9. This may be because eggshell powder also provides a small amount of other trace elements, which helps to improve the overall performance of calcium-based composite modified biochar.
[0147] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.
Claims
1. A method for preparing calcium-based composite modified biochar, characterized in that, Includes the following steps: S10. Mix eggshell powder and citric acid solution, react until no more bubbles are produced, and then take the supernatant to obtain a calcium-based solution. S20. The citrus peel particles are soaked in the calcium-based solution, and the pretreated citrus peel particles are obtained by solid-liquid separation. The pretreated citrus peel particles are then dried. S30. The dried pretreated citrus peel particles are pyrolyzed in an inert gas atmosphere to obtain pyrolysis products. The pyrolysis products are washed with water and then dried to obtain calcium-based composite modified biochar.
2. The method for preparing calcium-based composite modified biochar as described in claim 1, wherein in step S10: The concentration of the citric acid solution is 0.05–0.1 g / mL, and the mass ratio of the eggshell powder to the citric acid solution is 1:(5–10); and / or, Mix eggshell powder and citric acid solution for 24–48 hours.
3. The method for preparing calcium-based composite modified biochar as described in claim 1, characterized in that, Step S20 includes: Citrus peel particles were soaked in a calcium-based solution for 24–48 hours, and pretreated citrus peel particles were obtained by solid-liquid separation. The pretreated citrus peel particles were then dried.
4. The method for preparing calcium-based composite modified biochar as described in claim 1, characterized in that, In step S30, the dried pretreated citrus peel particles are heated to 500-800°C in an inert gas atmosphere at a heating rate of 4-6°C / min, and then kept at that temperature for 2-3 hours for pyrolysis treatment.
5. A calcium-based composite modified biochar, characterized in that, The calcium-based composite modified biochar is prepared according to the preparation method of calcium-based composite modified biochar according to any one of claims 1 to 4.
6. The application of the calcium-based composite modified biochar as described in claim 5 in the improvement of saline soil.
7. The application of the calcium-based composite modified biochar as described in claim 6 in the improvement of saline soil, characterized in that, The calcium-based composite modified biochar is used to promote crop growth in saline soil.
8. The application of calcium-based composite modified biochar as described in claim 7 in the improvement of saline soil, characterized in that, Includes the following steps: Calcium-based composite modified biochar was mixed with saline soil to improve the saline soil, and then crop seeds were sown in the treated saline soil.
9. The application of calcium-based composite modified biochar as described in claim 8 in the improvement of saline soil, characterized in that, The saline soil has a salt content of 0.1% to 1.0%, and the amount of calcium-based composite modified biochar added is 1% to 5% of the total mass of the saline soil.
10. The application of the calcium-based composite modified biochar as described in claim 8 in the improvement of saline soil, characterized in that, The time for improving the saline soil is 2-3 days; and / or, The crop seeds mentioned include soybean seeds.