Preparation method and application of multi-element catalytic iron modified biochar
By combining high-temperature and high-pressure pyrolysis with modification of ferrous salt solution and activation with mixed acid, multi-element catalytic iron-modified biochar was prepared, which solved the shortcomings of biochar raw material structure and function, and achieved efficient soil improvement and root promotion, and is suitable for various soil types.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 山东土秀才生物科技有限公司
- Filing Date
- 2026-02-26
- Publication Date
- 2026-05-01
AI Technical Summary
Existing biochar raw materials have small specific surface area, uneven pore structure, and weak surface cation exchange capacity, making it difficult to effectively improve soil structure and promote crop root growth. Moreover, existing improvement methods are costly and inefficient.
After crude biochar is prepared by high-temperature and high-pressure pyrolysis of straw, it is modified by ferrous salt solution and activated by mixed acid solution to form Fe-O and Fe-OH binding sites, increasing surface active sites and functional groups, and improving cation exchange capacity and phosphorus loading efficiency.
It significantly improves soil amendment and plant root growth promotion, reduces costs, is suitable for acidic and saline-alkali soils, and enhances the stability and adsorption capacity of biochar in soil.
Smart Images
Figure SMS_1 
Figure SMS_2
Abstract
Description
Technical Field
[0001] This invention relates to the field of soil conditioners, and in particular to a method for preparing and applying a multi-element catalytic iron-modified biochar. Background Technology
[0002] In modern agricultural planting, excessive and unreasonable fertilization over the years has led to problems such as soil compaction and salinization in field crops, severely impacting the efficiency of nutrient absorption and utilization by crops. To address these issues, soil improvement methods such as straw return to the field and application of organic fertilizers are commonly used in field crops like wheat and corn. However, straw return carries potential risks, including increased pests and diseases, nutrient competition, and higher costs. In particular, improper tillage depth and substandard pulverization pose significant risks to wheat emergence and overwintering. For example, insufficient tillage depth leads to a large accumulation of straw on the soil surface, causing frost damage to wheat in winter; incomplete pulverization results in poor seed-soil contact, uneven emergence, yellowing seedlings, and slow growth. Applying organic fertilizers, on the other hand, involves large application amounts and high transportation and labor costs. Therefore, for field soil improvement, it is crucial to control input costs while ensuring stable crop yields and maximizing soil health.
[0003] In recent years, the advantages of straw carbonization and returning to the field have become increasingly apparent, including low input costs, increased soil aggregate structure, and a significant reduction in pests and diseases. However, among existing technologies, biochar raw materials prepared from rice and corn straw have a small specific surface area, many large pores, and low surface cation exchange capacity, resulting in a relatively limited effect on soil improvement and no significant effect on promoting crop root growth, making it difficult to meet the needs of agricultural production. Therefore, there is still room for improvement. Summary of the Invention
[0004] To improve the effectiveness of soil improvement and enhance the effect on promoting plant root growth, this application provides a method for preparing and applying multi-element catalytic iron-modified biochar.
[0005] In a first aspect, this application provides a method for preparing iron-modified biochar using a multi-element catalytic catalyst, employing the following technical solution: A method for preparing iron-modified biochar using a multi-element catalytic process includes the following steps: Step 1) involves pyrolyzing straw under high temperature and pressure to obtain crude biochar; Step 2) Immerse the crude biochar in a ferrous salt solution and heat it continuously at 400-500℃ for 3-6 hours. Filter out the solid and dry it to obtain iron-modified biochar. Step 3) Immerse the iron-modified biochar in a mixed acid solution, heat to 60-70℃, continue to activate for 1-2 hours, filter out the solid, wash and dry to obtain a multi-element catalytic iron-modified biochar material. The mixed acid solution is a mixture of sulfuric acid, phosphoric acid, and water.
[0006] By adopting the above technical solution, and using ferrous iron modification combined with mixed acid activation, the shortcomings of conventional biochar raw materials, such as low trace element content and poor availability, are overcome. This increases the number of active sites on the raw material surface, effectively improving surface complexation and cation exchange capacity. Furthermore, it lowers the pH of the biochar, making it suitable for both acidic and saline-alkali soils. The introduction of oxygen-containing functional groups such as hydroxyl and phosphate groups results in a higher content of organic carbon available to crops, effectively promoting root development. This also compensates for the limited number of active adsorption sites and poor surface cation exchange capacity of crude biochar. The Fe-O and Fe-OH binding sites generated by iron modification can specifically chelate phosphate ions, effectively improving phosphorus loading efficiency, slowing down phosphorus release, and enhancing soil improvement and root growth promotion effects.
[0007] By precisely controlling the temperature at each stage, the problems of small specific surface area, uneven macroporous, mesoporous, and microporous structures, and weak adsorption capacity of conventional biochar raw materials are solved. This effectively enhances the cross-linking and solidification effect of functional groups, resulting in higher stability and better remediation effect on compacted soil when applied to farmland soil.
[0008] Preferably, in step 3), the mass ratio of sulfuric acid, phosphoric acid, and water in the mixed acid solution is 5-10:10-20:70-85.
[0009] By adopting the above technical solution and specifically selecting the mass ratio of sulfuric acid, phosphoric acid, and water, the activation effect of biochar is improved. The combination of oxygen-containing functional groups such as hydroxyl and phosphate groups in a specific ratio further enhances the effect of promoting plant root growth.
[0010] Preferably, in step 2), the ferrous salt solution is an aqueous solution of ferrous sulfate or ferrous chloride, wherein the concentration of the aqueous solution of ferrous sulfate or ferrous chloride is 0.5-1.0 mol / L and the pH is 6.5-7.5.
[0011] By adopting the above technical solution, and by adjusting the pH of the ferrous salt solution, the Fe... 2+ Hydrolysis causes the biochar to precipitate towards the Fe-OH surface, forming Fe-O and Fe-OH binding sites on the biochar surface. This not only increases the nutrient loading rate but also enhances the cross-linking and solidification of functional groups on the biochar surface, thereby improving the stability of the modified biochar in the soil.
[0012] Preferably, in step 2), the mass ratio of crude biochar to ferrous salt solution is 1:20-30, and in step 3), the mass ratio of iron-modified biochar to mixed acid solution is 1:15-30.
[0013] By adopting the above technical solution, the modification-activation effect is better, while reducing raw material waste and having high economic value.
[0014] Preferably, in step 1), the straw is cleaned, crushed, and dried, then filled with nitrogen to 0.8-1 MPa, heated and kept at a constant temperature of 350-450℃, and subjected to high-temperature and high-pressure pyrolysis for 2-3 hours.
[0015] By adopting the above technical solution and using high-temperature and high-pressure pyrolysis, the quality of crude biochar is improved.
[0016] Preferably, in step 1), during the heating process to 350-450℃, the heating rate is controlled at 5-10℃ / min.
[0017] By adopting the above technical solution and controlling the heating rate, the structure of crude biochar is better optimized, resulting in better subsequent modification and activation effects.
[0018] Preferably, in step 2), after drying, the material is pulverized and passed through an 80-100 mesh sieve to obtain iron-modified biochar; in step 3), after drying, the material is passed through an 80-100 mesh sieve to obtain multi-element catalytic iron-modified biochar material.
[0019] By adopting the above technical solutions and controlling the particle size of biochar, the application effect of biochar is better and it can improve the soil more effectively.
[0020] Secondly, this application provides a multi-element catalytic iron-modified biochar, which adopts the following technical solution: A multi-element catalytic iron-modified biochar, wherein the multi-element catalytic iron-modified biochar is prepared by the above-described preparation method of multi-element catalytic iron-modified biochar.
[0021] By adopting the above technical solution, the amount of multi-element catalytic iron-modified biochar required is only 40 kg per mu, which is less than that of conventional biochar. It also has a good effect on activating soil phosphorus after use. In addition, it has a certain adsorption effect on soil ammonium nitrogen, which reduces nitrification and ammonia volatilization to a certain extent, thereby reducing soil nitrogen loss. It is safe and efficient.
[0022] Thirdly, this application provides an application of multi-element catalytic iron-modified biochar, employing the following technical solution: An application of the above-mentioned multi-component catalytic iron-modified biochar, wherein the multi-component catalytic iron-modified biochar material is used for soil compaction improvement and soil phosphorus activation.
[0023] By adopting the above technical solutions, good soil improvement can be achieved at a relatively low cost, which is beneficial to crop growth and has high economic value.
[0024] In summary, this application has the following beneficial effects: 1. This application overcomes the shortcomings of conventional biochar raw materials, such as low trace element content and poor availability, by using ferrous iron modification combined with mixed acid activation. It increases the number of active sites on the raw material surface, effectively improving surface complexation and cation exchange capacity. Furthermore, it lowers the pH of the biochar, making it suitable for both acidic and saline-alkali soils. The introduction of oxygen-containing functional groups such as hydroxyl and phosphate groups results in a higher content of organic carbon available to crops, effectively promoting root development and compensating for the limited active adsorption sites and poor surface cation exchange capacity of crude biochar. The Fe-O and Fe-OH binding sites generated by iron modification can specifically chelate phosphate ions, effectively improving phosphorus loading efficiency, slowing down phosphorus release, and enhancing soil amendment and root growth promotion effects.
[0025] 2. This application preferably achieves precise temperature control at each stage, which solves the problems of small specific surface area, uneven macroporous, mesoporous and microporous structure, and weak adsorption capacity of conventional biochar raw materials. It effectively enhances the cross-linking and solidification effect of functional groups, resulting in higher stability and better soil compaction remediation when applied to farmland soil.
[0026] 3. In this application, the preferred method is to select the specific mass ratio of sulfuric acid, phosphoric acid, and water to achieve a better activation effect on biochar. The combination of oxygen-containing functional groups such as hydroxyl groups and phosphate groups in a specific ratio further enhances the effect of promoting plant root growth.
[0027] 4. In this application, it is preferred to accelerate the Fe process by adjusting the pH of the ferrous salt solution. 2+ Hydrolysis causes the biochar to precipitate towards the Fe-OH surface, forming Fe-O and Fe-OH binding sites on the biochar surface. This not only increases the nutrient loading rate but also enhances the cross-linking and solidification of functional groups on the biochar surface, thereby improving the stability of the modified biochar in the soil. Detailed Implementation
[0028] The present application will be further described in detail below with reference to the embodiments. Example
[0029] A method for preparing iron-modified biochar using a multi-element catalytic process includes the following steps: Step 1) After removing impurities, crushing and drying rice straw, nitrogen gas is filled to 0.8 MPa, the heating rate is controlled at 5℃ / min, and the rice straw is heated and kept at a constant temperature of 350℃ for 2 hours to obtain crude biochar.
[0030] Step 2): Prepare a ferrous sulfate aqueous solution with a concentration of 0.5 mol / L and a pH of 6.5. Immerse the crude biochar in the ferrous sulfate aqueous solution with a mass ratio of crude biochar to ferrous sulfate aqueous solution of 1:20. Under sealed conditions, heat continuously at 400℃ for 3 hours. After cooling to room temperature, centrifuge, separate, dry, pulverize, and pass through an 80-mesh sieve to obtain iron-modified biochar.
[0031] Step 3) Mix sulfuric acid, phosphoric acid, and water in a mass ratio of 5:10:85 to prepare a mixed acid solution. Immerse the iron-modified biochar in the mixed acid solution with a mass ratio of 1:15. Heat to 60°C and continue activation for 1 hour. Filter out the solid, wash with water, dry, and pass through an 80-mesh sieve to obtain a multi-element catalytic iron-modified biochar material.
[0032] The sulfuric acid was commercially available and had a concentration of 98%.
[0033] Phosphoric acid is commercially available and has a concentration of 85%.
[0034] Ferrous sulfate is commercially available, and is ferrous sulfate heptahydrate with a purity of 99%. Example
[0035] A method for preparing iron-modified biochar using a multi-element catalytic process includes the following steps: Step 1) After removing impurities, crushing and drying rice straw, nitrogen gas is filled to 0.9 MPa, the heating rate is controlled at 8℃ / min, and the rice straw is heated and kept at 400℃ for high temperature and high pressure pyrolysis for 2.5h to obtain crude biochar.
[0036] Step 2): Prepare a ferrous sulfate aqueous solution with a concentration of 0.75 mol / L and a pH of 7. Immerse the crude biochar in the ferrous sulfate aqueous solution with a mass ratio of crude biochar to ferrous sulfate aqueous solution of 1:25. Under sealed conditions, heat continuously at 450℃ for 4.5 hours. After cooling to room temperature, centrifuge, separate, dry, pulverize, and pass through a 100-mesh sieve to obtain iron-modified biochar.
[0037] Step 3) Mix sulfuric acid, phosphoric acid, and water in a mass ratio of 7.5:15:77.5 to prepare a mixed acid solution. Immerse iron-modified biochar in the mixed acid solution with a mass ratio of iron-modified biochar to mixed acid solution of 1:22.5. Heat to 65°C and continue to activate for 1.5 hours. Filter out the solid, wash with water, dry, and pass through a 100-mesh sieve to obtain a multi-element catalytic iron-modified biochar material.
[0038] The sulfuric acid was commercially available and had a concentration of 98%.
[0039] Phosphoric acid is commercially available and has a concentration of 85%.
[0040] Ferrous sulfate is commercially available, and is ferrous sulfate heptahydrate with a purity of 99%. Example
[0041] A method for preparing iron-modified biochar using a multi-element catalytic process includes the following steps: Step 1) After removing impurities, crushing and drying rice straw, nitrogen gas is filled to 1 MPa, the heating rate is controlled at 510℃ / min, and the rice straw is heated and kept at 450℃ for high temperature and high pressure pyrolysis for 3 hours to obtain crude biochar.
[0042] Step 2) Prepare a ferrous chloride aqueous solution with a concentration of 1.0 mol / L and a pH of 7.5. Immerse the crude biochar in the ferrous chloride aqueous solution with a mass ratio of crude biochar to ferrous sulfate aqueous solution of 1:30. Under sealed conditions, heat continuously at 500℃ for 6 hours. After cooling to room temperature, centrifuge, separate, dry, pulverize, and pass through a 100-mesh sieve to obtain iron-modified biochar.
[0043] Step 3) Mix sulfuric acid, phosphoric acid, and water in a mass ratio of 10:20:70 to prepare a mixed acid solution. Immerse the iron-modified biochar in the mixed acid solution with a mass ratio of 1:30. Heat to 70°C and continue activation for 2 hours. Filter out the solid, wash with water, dry, and pass through a 100-mesh sieve to obtain a multi-element catalytic iron-modified biochar material.
[0044] The sulfuric acid was commercially available and had a concentration of 98%.
[0045] Phosphoric acid is commercially available and has a concentration of 85%.
[0046] Ferrous chloride is commercially available; it is anhydrous ferrous chloride with a purity of 99%.
[0047] Comparative Example 1 A method for preparing iron-modified biochar using a multi-element catalytic catalyst, differing from Example 2 only in that: Replace sulfuric acid with an equal amount of nitric acid.
[0048] Nitric acid was obtained from a commercial source and had a concentration of 98%.
[0049] Comparative Example 2 A method for preparing iron-modified biochar using a multi-element catalytic catalyst, differing from Example 2 only in that: Acetic acid was used to replace phosphoric acid in equal amounts.
[0050] Acetic acid is commercially available and has a concentration of 99%.
[0051] Comparative Example 3 A method for preparing iron-modified biochar using a multi-element catalytic catalyst, differing from Example 2 only in that: Use nitric acid to replace sulfuric acid in equal amounts, and use acetic acid to replace phosphoric acid in equal amounts.
[0052] Nitric acid was obtained from a commercial source and had a concentration of 98%.
[0053] Acetic acid is commercially available and has a concentration of 99%.
[0054] Comparative Example 4 A method for preparing iron-modified biochar using a multi-element catalytic catalyst, differing from Example 2 only in that: The proportions of the components in the mixed acid solution change, as detailed below: A mixed acid solution was prepared by mixing sulfuric acid, phosphoric acid, and water in a mass ratio of 15:7.5:77.5. Comparative Example 5 A method for preparing iron-modified biochar using a multi-element catalytic catalyst, differing from Example 2 only in that: In step 2), the heating temperature changes, as detailed below: The crude biochar was immersed in an aqueous solution of ferrous sulfate and then heated at 300°C for 4.5 hours.
[0055] Comparative Example 6 A method for preparing iron-modified biochar using a multi-element catalytic catalyst, differing from Example 2 only in that: In step 3), the heating temperature changes, as detailed below: Iron-modified biochar was immersed in a mixed acid solution and then heated to 45°C for 1.5 hours for continuous activation.
[0056] Experiment 1: The experiment was conducted in the laboratory using a soil culture method. The multi-element catalytic iron-modified biochar of the examples and comparative examples was used as the experimental group, the crude biochar obtained in step 1 of example 2 was used as the control group, and the original soil without added biochar was used as the blank group.
[0057] The experimental and control groups were thoroughly mixed with compacted soil collected from the field and placed in 1000mL culture bottles. The biochar-to-soil mass ratio was 1:1000. Soil moisture was maintained at 30-40%, and the bottles were placed in a 25℃ constant temperature incubator for 60 days. During this period, soil moisture was replenished by gravimetric method. A control treatment without biochar was also included. Soil parameters were measured after 60 days. The background values of the field soil used in this experiment were: available potassium content 52.9 mg / kg, available phosphorus content 18.8 mg / kg, and water-stable macroaggregate content 18.3%. Available potassium and available phosphorus were detected according to the "Methods for Agricultural Chemical Analysis of Soil" (Lu Rukun, 2000), and water-stable macroaggregate content was detected according to NY / T 1121.19-2008. The results are shown in Table 1.
[0058] Table 1
[0059] The results showed that after adding the multi-element catalytic iron-modified biochar of each embodiment, the content of available potassium, available phosphorus and water-stable macroaggregates in the soil were significantly increased. Although the comparative examples showed some improvement compared with the control example, the increase was much lower than that of the examples, proving that the examples were more effective in activating soil nutrients and stabilizing soil structure.
[0060] Experiment 2: The experiment was conducted in a constant-temperature artificial climate chamber. The multi-element catalytic iron-modified biochar of the examples and comparative examples was used as the experimental group, and the crude biochar obtained in step 1 of Example 2 was used as the control group.
[0061] Each experimental group and control group underwent water extraction to prepare aqueous extracts, which were then added to the hydroponic experiment samples. The aqueous extracts were diluted to 200 ppm with deionized water. Cucumbers were used as the hydroponic material, and roots were uniformly pruned before the hydroponic experiment was conducted. Results were collected after 15 days, and root indicators were measured using a root scanner. The results are shown in Table 2.
[0062] Biochar water extraction method: Following the method described by Chen Weidan (2023, Effects of water-washed biochar on the peat microsphere and maize rhizosphere microenvironment), the following steps were performed: 20g of biochar was added to 400mL of distilled water and heated in a 100℃ water bath for 3 hours. The mixture was then shaken at 180rpm on a rotary shaker at room temperature (25℃) for 24 hours, followed by filtration. The extraction process was repeated twice, and the mixture was stored at 4℃ for later use.
[0063] Hydroponic Experiment Method: After 7 days of hydroponics in deionized water, cucumber seedlings were pruned to ensure that the root length of each cucumber seedling was uniform, retaining 8-9 cm. The biochar aqueous extracts were diluted with deionized water to 200 ppm, and then the cucumber seedlings were transferred to the hydroponic system and fixed in a hydroponic basket with a sponge, and cultured for 15 days.
[0064] Root scanner: Epson root scanner was used for root morphology scanning and index detection. The instrument model was Epson Perfection V850 Pro.
[0065] Table 2
[0066] The results showed that cucumbers with new root development were better when the modified biochar aqueous extract was applied in each embodiment. The root surface area, total root volume, root diameter and root biomass were significantly increased. Although the root surface area, total root volume, root diameter and root biomass of each comparative example were increased to some extent compared with the control example, the increase was much lower than that of the embodiments. This proves that the embodiments have a more significant effect on promoting plant root growth.
[0067] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.
Claims
1. A method for preparing iron-modified biochar using a multi-element catalytic process, characterized in that: Includes the following steps: Step 1) involves pyrolyzing straw under high temperature and pressure to obtain crude biochar; Step 2) Immerse the crude biochar in a ferrous salt solution and heat it continuously at 400-500℃ for 3-6 hours. Filter out the solid and dry it to obtain iron-modified biochar. Step 3) Immerse the iron-modified biochar in a mixed acid solution, heat to 60-70℃, continue to activate for 1-2 hours, filter out the solid, wash and dry to obtain a multi-element catalytic iron-modified biochar material. The mixed acid solution is a mixture of sulfuric acid, phosphoric acid, and water.
2. The method for preparing iron-modified biochar using a multi-element catalytic catalyst according to claim 1, characterized in that: In step 3), the mass ratio of sulfuric acid, phosphoric acid, and water in the mixed acid solution is 5-10:10-20:70-85.
3. The method for preparing iron-modified biochar using a multi-element catalytic catalyst according to claim 2, characterized in that: In step 2), the ferrous salt solution is an aqueous solution of ferrous sulfate or ferrous chloride, wherein the concentration of the aqueous solution of ferrous sulfate or ferrous chloride is 0.5-1.0 mol / L and the pH is 6.5-7.
5.
4. The method for preparing iron-modified biochar using a multi-element catalytic catalyst according to claim 3, characterized in that: In step 2), the mass ratio of crude biochar to ferrous salt solution is 1:20-30, and in step 3), the mass ratio of iron-modified biochar to mixed acid solution is 1:15-30.
5. A method for preparing iron-modified biochar using a multi-element catalytic catalyst according to any one of claims 1-4, characterized in that: In step 1), the straw is cleaned, crushed, and dried, then filled with nitrogen to 0.8-1 MPa, heated and kept at a constant temperature of 350-450℃, and subjected to high-temperature and high-pressure pyrolysis for 2-3 hours.
6. The method for preparing iron-modified biochar by a multi-element catalytic catalyst according to claim 5, characterized in that: In step 1), during the heating process to 350-450℃, the heating rate is controlled at 5-10℃ / min.
7. The method for preparing iron-modified biochar by a multi-element catalytic catalyst according to claim 6, characterized in that: In step 2), after drying, the material is pulverized and passed through an 80-100 mesh sieve to obtain iron-modified biochar; in step 3), after drying, the material is passed through an 80-100 mesh sieve to obtain multi-element catalytic iron-modified biochar material.
8. A multi-element catalytic iron-modified biochar, characterized in that: The multi-element catalytic iron-modified biochar is prepared by the preparation method of the multi-element catalytic iron-modified biochar according to any one of claims 1-7.
9. An application of the multi-element catalytic iron-modified biochar according to claim 8, characterized in that: The multi-element catalytic iron-modified biochar material is used for soil compaction improvement and soil phosphorus activation.