Preparation method and application of cow dung hydrothermal carbon material
The preparation of hydrothermal carbon by cow dung hydrothermal reaction has solved the problem of poor soil slab improvement effect in the prior art, and achieved efficient and low-cost soil improvement, which is suitable for improving slab soil.
Patent Information
- Application Number
- CN202510353740.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-25
- Publication Date
- 2025-06-27
AI Technical Summary
The prior art is difficult to effectively improve the soil slab problem, especially because biochar preparation requires drying and pretreatment, which increases cost and energy consumption. At the same time, lignocellulose hydrothermal carbon is mostly acidic and has poor adaptability, making it difficult to maximize the improvement effect.
Using cow dung as raw material, it is converted into hydrothermal carbon by hydrothermal reaction. The preparation method includes mixing cow dung with water, placing it in a protective atmosphere for hydrothermal reaction, and then separating and drying to obtain cow dung hydrothermal carbon material.
This method simplifies the process flow, reduces energy consumption and cost, and the prepared cow dung hydrothermal carbon material has high organic matter content and is rich in hydrophilic functional groups on the surface. It can effectively improve the pore structure of the soil and water-retaining and fertilizer retention ability. It is suitable for improving plate-clad soil.
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Figure CN120209846A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of material preparation, and particularly relates to a preparation method and application of a cow dung hydrochar material. Background Art
[0002] Soil compaction has become a major environmental problem threatening global agricultural sustainable development. Due to the destruction of the aggregate structure, the reduction of porosity and the decline of permeability in compacted soil, the root development of crops is hindered, soil nutrients are lost, and the microbial activity is inhibited, seriously threatening agricultural production and ecological balance.
[0003] The current conventional methods for improving compacted soil have significant limitations. Although deep plowing can break the compacted soil layer in the short term, the loosened soil is easily recompacted by mechanical operations or livestock trampling, and the plowing process will destroy the soil aggregate structure, which will exacerbate the deterioration of the soil structure in the long run. Although biological fertilizers can improve the fertilizer utilization rate, their application needs to avoid mixing with pesticides, and the improvement effect on soils with an organic matter content lower than 1.5% is significantly reduced. Although applying organic fertilizers can supplement organic matter, its annual mineralization rate is as high as 30%-70%, especially in high-temperature regions, the mineralization loss is more serious. At the same time, long-term application may lead to an increase in pests and diseases and the growth of resistant bacteria. In contrast, biochar has become a research hotspot due to its strong stability (it can remain in the soil for hundreds of years) and well-developed pores. However, its preparation requires drying pretreatment of raw materials (the moisture content needs to be lower than 10%), which significantly increases the treatment cost of high-moisture biomass such as cow dung, and the content of hydrophilic functional groups on the surface of biochar is relatively low, and the improvement effect on soil water-holding capacity is limited.
[0004] As a derivative type of biochar, hydrochar shows better improvement potential. Compared with biochar, the preparation of hydrochar does not require raw material drying (it can directly process cow dung with a moisture content of more than 80%), which greatly reduces energy consumption and cost. The release amount of dissolved organic matter (DOM) in hydrochar can reach 405 mg / g, which is dozens of times that of biochar, and its surface is rich in hydrophilic functional groups such as hydroxyl and carboxyl, which can more effectively promote the formation of soil aggregates. However, the actual improvement effect of hydrochar highly depends on its adaptability to the target soil type. The lignocellulose hydrochar currently focused on in research is mostly acidic and has a low electrical conductivity. Although it is suitable for desalination improvement of saline-alkali soil, it will exacerbate the acidification problem of acidic compacted soil. Therefore, it is urgent to develop hydrochar materials that adapt to the physical and chemical properties of compacted soil to maximize its improvement effect. Summary of the Invention
[0005] The technical problem to be solved by the present invention is: to provide a preparation method and application of a cow dung hydrochar material to solve the technical problem of soil compaction.
[0006] To achieve the above object, the technical solution adopted by the present invention is: to provide a preparation method of a cow dung hydrochar material, which includes the following steps:
[0007] S1. Crush the cow dung, mix it with water in a mass ratio of 0.5-1.5:2-4, place the mixture in a protective atmosphere, and perform hydrothermal reaction at 2-6MPa and 170-190℃ for 1-3h. During the hydrothermal process, the biomass undergoes hydrolysis, dehydration, decarboxylation, condensation, polymerization and aromatization in the water medium, and is finally converted into a high energy density solid phase product, i.e. hydrothermal charcoal.
[0008] S2. Separate the solid-liquid mixture after the reaction, and dry the solid phase at 100-110° C. to a constant weight to obtain the cow dung hydrothermal carbon material.
[0009] On the basis of the above technical solution, the present invention can also be improved as follows:
[0010] Furthermore, the cow dung can be dried before being crushed in S1.
[0011] Furthermore, the drying temperature is 35-45° C., and the drying time is 2-5 h.
[0012] Furthermore, the protective atmosphere is made of nitrogen or argon.
[0013] Furthermore, the heating rate during the hydrothermal reaction is 1-3°C / min.
[0014] The invention also discloses a cow dung hydrothermal carbon material prepared by the preparation method.
[0015] The invention also discloses application of the cow dung hydrothermal carbon material in soil improvement.
[0016] Furthermore, the amount of cow dung hydrochar material applied during soil improvement is 5-10wt%.
[0017] The beneficial effects of the present invention are:
[0018] 1. The method of the present invention is simple and convenient, and the drying pretreatment step can be omitted, thereby reducing the energy consumption and time consumption of the process; the yield of the prepared cow dung hydrothermal carbon material reaches 65.46%, which is 11.76% higher than the maximum yield of hydrothermal carbon fired from conventional substrates such as kitchen waste and reed straw;
[0019] 2. The organic matter content of cow dung hydrochar material is as high as 413.87g / kg, far exceeding the agricultural standard of "NY / T 525-2021 Organic Fertilizer"; the high O / C and (O+N) / C indicate that the hydrochar has excellent polarity and hydrophilicity, which helps to increase the CEC of the soil, thereby improving the soil's fertilizer retention capacity;
[0020] 3. The specific surface area and total pore volume of the cow dung hydrothermal carbon materials are relatively large, which helps to improve the pore structure of the compacted soil and enhance the water and fertilizer retention capacity of the compacted soil. Description of the Drawings
[0021] Figure 1 is the scanning electron microscope image of the cow dung hydrothermal carbon materials;
[0022] Figure 2 is the effect of adding cow dung hydrothermal carbon materials with different mass fractions on the soil moisture content;
[0023] Figure 3 is the effect of adding cow dung hydrothermal carbon materials with different mass fractions on the soil aggregation;
[0024] Figure 4 is the effect of adding cow dung hydrothermal carbon materials with different mass fractions on the soil bulk density;
[0025] Figure 5 is the effect of adding cow dung hydrothermal carbon materials with different mass fractions on the soil organic matter content;
[0026] Figure 6 is the effect of adding cow dung hydrothermal carbon materials with different mass fractions on the soil pH value;
[0027] Figure 7 is the effect of adding cow dung hydrothermal carbon materials with different mass fractions on the soil EC;
[0028] Figure 8 is the effect of adding cow dung hydrothermal carbon materials with different mass fractions on the soil CEC;
[0029] Figure 9 is the effect of adding cow dung hydrothermal carbon materials with different mass fractions on the soil available nitrogen content;
[0030] Figure 10 is the effect of adding cow dung hydrothermal carbon materials with different mass fractions on the soil available phosphorus content;
[0031] Figure 11 is the effect of adding cow dung hydrothermal carbon materials with different mass fractions on the soil available potassium content. Detailed Embodiments
[0032] The specific embodiments of the present invention will be described below to facilitate those skilled in the art of this technology to understand the present invention. For those conditions not specified in the examples, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified for the manufacturer, they are all conventional products that can be obtained through commercial purchase. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those ordinary skilled in the art of this technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are within the scope of protection.
[0033] Example 1
[0034] A preparation method of a cow dung hydrothermal carbon material includes the following steps:
[0035] S1. Crush the cow dung through a 100-mesh sieve, then mix the crushed material and water at a mass ratio of 0.5:4. Place the mixture in argon, raise the reaction temperature from room temperature to 170°C at a heating rate of 1°C / min, and carry out hydrothermal reaction at 6 MPa for 3 h, and finally naturally cool to room temperature;
[0036] S2. Separate the solid-liquid mixture after the reaction, dry the solid phase at 100°C to constant weight, and then crush it through a 100-mesh sieve to obtain the cow dung hydrothermal carbon material.
[0037] Example 2
[0038] A preparation method of a cow dung hydrothermal carbon material includes the following steps:
[0039] S1. Dry the cow dung at 45°C for 2 h, then crush it through a 100-mesh sieve, and then mix the crushed material and water at a mass ratio of 1.5:2. Place the mixture in nitrogen, raise the reaction temperature from room temperature to 190°C at a heating rate of 3°C / min, and carry out hydrothermal reaction at 2 MPa for 1 h, and finally naturally cool to room temperature;
[0040] S2. Separate the solid-liquid mixture after the reaction, dry the solid phase at 110°C to constant weight, and then crush it through a 100-mesh sieve to obtain the cow dung hydrothermal carbon material.
[0041] Example 3
[0042] A preparation method of a cow dung hydrothermal carbon material includes the following steps:
[0043] S1. Dry the cow dung at 40°C for 3 h, then crush it through a 100-mesh sieve, and then mix the crushed material and water at a mass ratio of 1:3. Place the mixture in nitrogen, raise the reaction temperature from room temperature to 180°C at a heating rate of 2°C / min, and carry out hydrothermal reaction at 4 MPa for 2 h, and finally naturally cool to room temperature;
[0044] S2. Separate the solid-liquid mixture after the reaction, dry the solid phase at 105 °C until constant weight, and then pulverize it through a 100-mesh sieve to obtain the cow dung hydrothermal carbon material (NF-180).
[0045] Experimental Example 1
[0046] (1) SEM analysis
[0047] Perform SEM analysis on the cow dung hydrothermal carbon material prepared in Example 3 of the present invention, and the results are as Figure 1 shown. It can be seen from the scanning electron microscope images of cow dung and cow dung hydrothermal carbon (NF-180) that the surface of cow dung is relatively smooth. During the heating process of hydrothermal carbonization, the surface morphology structure of the raw material collapses and accumulates due to its inability to withstand this change, ultimately resulting in the surface of the generated hydrothermal carbon presenting the characteristics of disorder and roughness. The rich porous structure of cow dung hydrothermal carbon can create a good growth environment for soil microorganisms and is also more conducive to the storage of soil nutrients.
[0048] (2) Yield calculation
[0049] The calculation formula for the hydrothermal carbon yield is:
[0050]
[0051] Among them, Y is the hydrothermal carbon yield, %; m is the dry mass of the hydrothermal carbon, g; M is the dry mass of the raw material, g.
[0052] Taking the cow dung hydrothermal carbon material prepared in Example 3 as an example, its yield is calculated to be 65.46%, which is 11.76% higher than the highest yield (only 53.70% at most) of the hydrothermal carbon fired from conventional substrates such as kitchen waste and reed straws, indicating that the method of the present invention can improve the yield of cow dung hydrothermal carbon.
[0053] (3) Determination of organic matter content
[0054] The organic matter content of the hydrothermal carbon is determined by the potassium dichromate oxidation-external heating method, with "LY / T 1237—1999 Determination of Organic Matter in Forest Soils and Calculation of Carbon-Nitrogen Ratio" as the reference standard. The contents of C, H, N, and S elements in the hydrothermal carbon are determined using an elemental analyzer, and the ash content of the hydrothermal carbon is determined with reference to the standard "GB / T 212-2008 Industrial Analysis Method for Coal". Finally, the content of O element in the hydrothermal carbon is calculated, and the calculation formula is as follows:
[0055] C O = 100% - (C C + C H + C N + C S + C A );
[0056] Among them, C O is the content of O element, %; C C is the content of C element, %; C H is the content of H element, %; C N is the content of N element, %; C S is the content of S element, %; C A is the content of ash, %.
[0057] The content data of each element are shown in Table 1.
[0058] Table 1 Organic matter element content data
[0059]
[0060]
[0061] It can be seen from Table 1 that the organic matter content of the cow dung hydrochar material is as high as 413.87 g / kg, far exceeding the agricultural standard of "NY / T 525-2021 Organic Fertilizer"; the high O / C and (O + N) / C indicate that the hydrochar has excellent polarity and hydrophilicity, which helps to improve the CEC of the soil, thereby enhancing the soil's fertilizer retention capacity.
[0062] (4) Pore parameters
[0063] The specific surface area and pores of the hydrochar prepared in Example 3 were analyzed using a Quantachrome Autosorb iQ analyzer produced by Quantachrome Corporation in the United States, and the data are shown in Table 2.
[0064] Table 2 Pore parameter data
[0065]
[0066] It can be seen from Table 2 that the cow dung hydrochar material has a relatively large specific surface area and total pore volume, which helps to improve the pore structure of the compacted soil and enhance the water and fertilizer retention capacity of the compacted soil.
[0067] Experimental Example 2
[0068] Taking the cow dung hydrochar material prepared in Example 3 as an example, different mass fractions of the cow dung hydrochar material were added to the soil to explore the effect of the cow dung hydrochar on the compacted soil.
[0069] (1) The steps for testing the soil water retention performance are as follows: Set the application amounts of hydrothermal carbon at mass fractions of 0.5%, 1%, 2%, 5% and 10%. After uniformly mixing the hydrothermal carbon with the sieved compacted soil, place it in a plastic flower pot with a screen at the bottom. At the same time, set a control group (CK) without adding hydrothermal carbon according to the same method. Add ultrapure water according to the maximum water holding capacity (37.81%) to simulate the state of each treatment group and the CK group under sufficient water absorption. Place it in a constant temperature incubator with a day / night temperature of 25°C / 20°C and a daytime light intensity of 8500 lux for cultivation. Weigh regularly for 10 consecutive days and record the change of soil moisture content over time to reflect the influence of hydrothermal carbon with different application amounts on the soil water retention performance. Each treatment is set with 3 replicates.
[0070] The changes in soil moisture content after treating with cow dung hydrothermal carbon materials with different mass fractions are as Figure 2 shown. It can be seen from the soil moisture content change curve that compared with the control group (CK) without adding cow dung hydrothermal carbon materials, applying hydrothermal carbon with a mass fraction of 5% has the best effect on improving the water retention performance of the compacted soil.
[0071] The physical objects of the soil after treating with cow dung hydrothermal carbon materials with different mass fractions for 40 days are as Figure 3 shown. It can be seen from the figure that the higher the application amount of hydrothermal carbon, the darker the soil color and the looser the texture. During the 40-day cultivation process, the soil compaction in the CK group intensified, while applying hydrothermal carbon with mass fractions of 2%, 5% and 10% had obvious improvement effects on the compacted soil, not only curbing soil compaction but also forming an obvious aggregate structure.
[0072] (2) The soil bulk density is measured by the cutting ring method. The changes in soil bulk density after treating with cow dung hydrothermal carbon materials with different mass fractions are as Figure 4 shown. It can be seen from the figure that with the passage of cultivation time, the soil bulk densities of the CK group, the 0.5% hydrothermal carbon treatment group and the 1% hydrothermal carbon treatment group gradually increased, and were all higher than 1.35 g / cm 3 , indicating that the soil compaction gradually intensified; while applying hydrothermal carbon with mass fractions of 2%, 5% and 10% could all reduce the bulk density of the compacted soil to below 1.35 g / cm 3 , effectively alleviating the problem of the heavy texture of the compacted soil.
[0073] (3) The organic matter content is tested by the potassium dichromate oxidation-external heating method. Taking "LY / T 1237—1999 Determination of Organic Matter in Forest Soils and Calculation of Carbon-Nitrogen Ratio" as the reference standard, the changes in soil organic matter content after treating with cow dung hydrothermal carbon materials with different mass fractions are as Figure 5As shown. It can be seen from the figure that compared with the CK group, the addition of cow dung hydrochar significantly increased the organic matter content of the soil, and the higher the application rate of hydrochar, the more obvious the improvement effect on soil organic matter. At the end of the 40-day cultivation, the organic matter contents of the soils in each treatment group were 1.2, 1.28, 1.69, 2.92, and 5.18 times that of the CK group respectively.
[0074] (4) The soil pH value was tested according to the reference standard "HJ 962—2018 Determination of soil pH value - Potentiometric method". The changes in the soil pH value after treatment with cow dung hydrochar materials with different mass fractions are as Figure 6 shown. It can be seen from the figure that as the cultivation time progresses, the pH value of the soil in the CK group fluctuates around 5.9, while the pH values of the soils in other treatment groups generally show a trend of first increasing and then leveling off. At the end of the 40-day cultivation, the pH values of the soils in the 2% hydrochar treatment group, 5% hydrochar treatment group, and 10% hydrochar treatment group reached 6.77, 6.93, and 7.07 respectively, effectively adjusting the soil pH value to the range suitable for crop growth (6.5 - 7.32).
[0075] (5) EC was tested according to the reference standard "HJ 802—2016 Determination of soil electrical conductivity - Electrode method". The changes in the soil EC after treatment with cow dung hydrochar materials with different mass fractions are as Figure 7 shown. It can be seen from the figure that at the end of the 40-day cultivation, the ECs of the soils in the 2% hydrochar treatment group and 5% hydrochar treatment group reached 0.238 and 0.425 ms / cm respectively, indicating that the cow dung hydrochar materials prepared by the present invention can effectively adjust the soil EC to the range suitable for crop growth (0.2 - 0.6 ms / cm).
[0076] (6) CEC was tested according to the reference standard "HJ 889—207 Determination of soil cation exchange capacity - Extraction with hexaamminecobalt(III) chloride - Spectrophotometric method". The changes in the soil CEC after treatment with cow dung hydrochar materials with different mass fractions are as Figure 8 shown. It can be seen from the figure that the CECs of the soils in the treatment groups with added cow dung hydrochar are all significantly higher than those of the CK group, and the higher the application rate of hydrochar, the more obvious the change in soil CEC. As the cultivation time progresses, the CEC of the soil in the CK group fluctuates around 8.94 cmol / kg, belonging to level 3 soil with weak fertilizer retention performance. While the CECs of the soils in other treatment groups are all in the range of 10 - 20 cmol / kg, belonging to level 2 soil, indicating that the application of hydrochar significantly improves the fertilizer retention performance of the compacted soil. Among them, the 5% hydrochar treatment group and 10% hydrochar treatment group have the most significant improvement effect on the soil fertilizer retention performance.
[0077] (7) The determination of alkaline hydrolyzable nitrogen content was carried out by the alkaline hydrolysis diffusion method. The changes in the alkaline hydrolyzable nitrogen content of the soil treated with cow dung hydrochar materials with different mass fractions are as Figure 9 shown. It can be seen from the figure that the application of hydrochar with mass fractions of 2%, 5% and 10% can significantly increase the alkaline hydrolyzable nitrogen content of the soil. At the end of the 40-day cultivation, compared with the CK group, the alkaline hydrolyzable nitrogen content of the soil increased by 17.24%, 48.28% and 82.76% respectively.
[0078] (8) The determination of available phosphorus was carried out by the sodium bicarbonate method (Olsen method). The changes in the available phosphorus content of the soil are as Figure 10 shown. The application of hydrochar with mass fractions of 5% and 10% to the soil significantly increased the available phosphorus content of the soil. At the end of the 40-day cultivation, compared with the CK group, the available phosphorus content of the soil increased by 2.07 and 3.86 times respectively.
[0079] (9) The determination of available potassium was carried out by the cold nitric acid extraction-flame photometry method. The changes in the available potassium content of the soil are as Figure 11 shown. The application of hydrochar with mass fractions of 5% and 10% to the soil significantly increased the available potassium content of the soil. At the end of the 40-day cultivation, compared with the CK group, the available phosphorus content of the soil increased by 2.73 and 5.16 times respectively.
[0080] Generally speaking, the original compacted soil lacks nutrient elements and has low soil fertility. During the cultivation process, the application of hydrochar with mass fractions of 5% and 10% to the soil can significantly improve the soil fertility status and increase the soil nutrient content to a medium or even rich level.
Claims
1. A method for preparing cow dung hydrothermal carbon material, characterized in that: The following steps are involved: S1. Crush the cow dung, mix it with water in a mass ratio of 0.5-1.5:2-4, place the mixture in a protective atmosphere, and perform hydrothermal reaction at 2-6 MPa and 170-190°C for 1-3 hours; S2. Separate the solid-liquid mixture after the reaction, and dry the solid phase at 100-110° C. to a constant weight to obtain the cow dung hydrothermal carbon material.
2. The method for preparing cow dung hydrothermal carbon material according to claim 1, characterized in that: In the above-mentioned S1, the cow dung may be dried before being crushed.
3. The method for preparing cow dung hydrothermal carbon material according to claim 2, characterized in that: The drying temperature is 35-45° C., and the drying time is 2-5 hours.
4. The method for preparing cow dung hydrothermal carbon material according to claim 1, characterized in that: The protective atmosphere is nitrogen or argon.
5. The method for preparing cow dung hydrothermal carbon material according to claim 1, characterized in that: The heating rate during the hydrothermal reaction is 1-3°C / min.
6. A cow dung hydrothermal carbon material, characterized in that: The method for preparing the cow dung hydrothermal carbon material according to any one of claims 1 to 5 is used to prepare the cow dung hydrothermal carbon material.
7. Use of the cow dung hydrothermal carbon material according to claim 6 in soil improvement.
8. The use according to claim 7, characterized in that: The amount of cow dung hydrochar material applied during soil improvement is 5-10wt%.