Highly active acid hydrolyzed biochar

Abstract

The present application belongs to the technical field of biochar, and particularly relates to a high-activity acidolysis biochar, which is prepared by the following steps: S1, pretreating agricultural and livestock waste; S2, acidolysing the pretreated biomass with dilute acid to obtain acidolysed biomass; S3, placing the acidolysed biomass into a high-temperature furnace to perform carbonization under an oxygen-free condition, and using a step-by-step heating mode to obtain preliminary biochar; and S4, mixing the preliminary biochar with a copolymer solution to prepare the high-activity acidolysis biochar. In the present application, the sodium lignosulfonate-polyglutamic acid copolymer forms a stable connection with the biochar through chemical bonding, the porous surface of the biochar is uniformly covered with the copolymer to form a nanoscale film, the composite has stronger complexing, chelating and ion exchange capacity for heavy metal ions and other cations in the soil, and is helpful to reduce toxic substances in the soil and improve the soil environment.

Description

Technical Field

[0001] This invention belongs to the field of biochar technology, and specifically relates to a highly active acid-hydrolyzed biochar. Background Technology

[0002] Biochar is a carbon-rich solid product obtained from the pyrolysis of agricultural and forestry waste. It not only effectively solves the problem of agricultural and forestry waste disposal but also brings numerous benefits to the soil. Biochar excels in increasing soil organic carbon content, improving soil structure, increasing soil nutrients, and regulating soil pH, especially in soil improvement. Biochar preparation is typically carried out under anaerobic and relatively low-temperature conditions. During this process, agricultural and forestry waste undergoes pyrolysis and transformation, forming a carbon-rich solid product with a porous structure and high cation exchange capacity. Simultaneously, the alkaline properties of biochar allow it to neutralize soil acidity to some extent, increasing soil pH and thus reducing the activity of heavy metal ions in the soil, improving the soil's physicochemical properties. Acid-hydrolyzed biochar, based on biochar preparation, undergoes acid hydrolysis treatment, increasing the number of functional groups and cation exchange capacity on the biochar surface, thereby greatly enhancing its interaction with soil and plant nutrients.

[0003] In existing technologies, the porous structure and high specific surface area of ​​highly active acid-hydrolyzed biochar give it excellent nutrient adsorption capacity, but this also leads to unstable nutrient release in the soil. Too rapid a release of nutrients results in ineffective plant absorption, while too slow a release fails to meet the plant's growth needs. Furthermore, different soil types possess different physicochemical properties, meaning that highly active acid-hydrolyzed biochar is not ideal under certain specific soil conditions. For example, its remediation effect is limited in saline-alkali soils or soils heavily contaminated with heavy metals. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a highly active acid hydrolysis biochar method.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A highly active acid-hydrolyzed biochar is prepared by the following steps:

[0007] S1. Crush rice husks and straw to an average particle size of 2-5 mm using a crusher, and dry them in an oven at 60-70℃ for 24-48 hours to obtain pretreated biomass.

[0008] S2. Mix the pretreated biomass with dilute sulfuric acid at a mass ratio of 1:10, place the mixture in a reaction vessel, and wash with deionized water until neutral to obtain acid-hydrolyzed biomass.

[0009] S3. The acid-hydrolyzed biomass is placed in a high-temperature furnace and carbonized under anaerobic conditions by gradually increasing the temperature to obtain preliminary biochar.

[0010] S4. Mix the preliminary biochar and copolymer solution, sonicate for 20-30 min, let stand for 24-48 h, dry and solidify, wash with deionized water 3-5 times, and finally dry in an oven at 60-80℃ to constant weight to obtain highly active acid-hydrolyzed biochar.

[0011] Furthermore, the agricultural and livestock waste in step S1 includes one or more of straw, plant debris, weeds, fallen leaves, fruit shells, rice husks, and livestock and poultry manure.

[0012] The dilute acid in step S2 includes one or more of dilute sulfuric acid, dilute hydrochloric acid, and dilute nitric acid.

[0013] In step S2, the reaction is stirred at a temperature of 60-80℃ for 2-4 hours.

[0014] The step of gradually increasing the temperature in step S3 is as follows: first, maintain the temperature at 200-300℃ for 1-2 hours, then increase the temperature to 400-500℃ and maintain it for 2-3 hours, and finally increase the temperature to 600℃ and maintain it for 1 hour.

[0015] In step S4, the mass ratio of the initial biochar to the copolymer solution is 1:(2-4).

[0016] In step S4, the product is dried in an oven at 40-50°C for 24 hours, and then cured by heating at 80-100°C.

[0017] The copolymer solution in step S4 is prepared by the following steps:

[0018] Prepare a 20% glutamic acid monomer solution using deionized water. Preheat the reactor to 60-70℃ and maintain a constant temperature. While continuously stirring at 500-600 rpm, slowly add sodium lignosulfonate and the 20% glutamic acid monomer solution dropwise into the reactor simultaneously using a constant flow pump. The dropwise addition rate is controlled at 10 mL per minute for each. After the addition is complete, add ammonium persulfate and sodium bisulfite to adjust the pH to 6.5. Control the reaction temperature at 80-90℃ and react for 4-6 hours. Perform post-processing to obtain a sodium lignosulfonate-polyglutamic acid copolymer solution, i.e., the copolymer solution.

[0019] Furthermore, the mass ratio of sodium lignosulfonate, 20% glutamic acid monomer solution, ammonium persulfate and sodium bisulfite is 100:(50-60):(5-7):(2-3).

[0020] The post-processing is as follows: stop heating and continue stirring for 10-20 minutes, cool to room temperature, centrifuge at 3000-4000 rpm for 20-30 minutes, and collect the supernatant.

[0021] The beneficial effects of this invention are:

[0022] 1. In the technical solution of the present invention, sodium lignosulfonate-polyglutamic acid copolymer forms a stable connection with biochar through chemical bonding. The porous surface of biochar is uniformly covered by the copolymer to form a nano-scale film, which makes the composite have a stronger complexing, chelating and ion exchange capacity for heavy metal ions and other cations in the soil, which helps to reduce toxic substances in the soil and improve the soil environment.

[0023] 2. In the technical solution of the present invention, the introduction of copolymers does not significantly block the pores of biochar, but optimizes its porous structure, provides a larger specific surface area, which is conducive to the adsorption and slow release of nutrients, and provides an ideal habitat and reproduction space for soil microorganisms, thereby promoting microbial activity and contributing to soil bioremediation and fertility improvement.

[0024] 3. In the technical solution of the present invention, a stable connection is formed between the copolymer and the biochar through chemical bonding, which not only enhances the overall stability of the composite, but also helps to prevent the rapid degradation and loss of biochar in the soil, thereby extending the duration of its soil improvement effect.

[0025] 4. In the technical solution of the present invention, the copolymer loading gives the biochar higher surface energy and larger specific surface area, which enhances the interaction force between the biochar and soil particles, helps to improve the aggregate structure of the soil, and improves the soil stability and water and fertilizer retention capacity.

[0026] 5. In the technical solution of the present invention, after the surface of biochar is modified with copolymer, its negatively charged functional groups can neutralize or attract positively charged ions in the soil, which not only helps to regulate the acid-base balance of the soil, but also increases the cation exchange capacity of the soil, further improving the soil fertility and buffering capacity. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1

[0029] The copolymer solution is prepared by the following steps:

[0030] Prepare a 20% glutamic acid monomer solution using deionized water. Preheat the reactor to 60°C and maintain a constant temperature. While stirring continuously at 500 rpm, slowly add 100 g of sodium lignosulfonate and 50 g of the 20% glutamic acid monomer solution dropwise into the reactor simultaneously using a constant flow pump. The dropping rate is controlled at 10 mL per minute for each. After the addition is complete, add 5 g of ammonium persulfate and 2 g of sodium bisulfite to adjust the pH to 6.5. Control the reaction temperature at 80°C and react for 4 hours. Stop heating and continue stirring for 10 minutes. Cool to room temperature and centrifuge at 3000 rpm for 20 minutes. Collect the supernatant to obtain the sodium lignosulfonate-polyglutamic acid copolymer solution, i.e., the copolymer solution.

[0031] Example 2

[0032] The copolymer solution is prepared by the following steps:

[0033] Prepare a 20% glutamic acid monomer solution using deionized water. Preheat the reactor to 65°C and maintain a constant temperature. While continuously stirring at 550 rpm, slowly add 100 g of sodium lignosulfonate and 55 g of the 20% glutamic acid monomer solution dropwise into the reactor simultaneously using a constant flow pump. The dropping rate is controlled at 10 mL per minute for each. After the addition is complete, add 6 g of ammonium persulfate and 2.5 g of sodium bisulfite to adjust the pH to 6.5. Control the reaction temperature at 85°C and react for 5 hours. Stop heating and continue stirring for 15 minutes. Cool to room temperature and centrifuge at 3500 rpm for 25 minutes. Collect the supernatant to obtain the sodium lignosulfonate-polyglutamic acid copolymer solution, i.e., the copolymer solution.

[0034] Example 3

[0035] The copolymer solution is prepared by the following steps:

[0036] Prepare a 20% glutamic acid monomer solution using deionized water. Preheat the reactor to 70°C and maintain a constant temperature. While continuously stirring at 600 rpm, slowly add 100 g of sodium lignosulfonate and 60 g of the 20% glutamic acid monomer solution dropwise into the reactor simultaneously using a constant flow pump. The dropping rate is controlled at 10 mL per minute for each. After the addition is complete, add 7 g of ammonium persulfate and 3 g of sodium bisulfite to adjust the pH to 6.5. Control the reaction temperature at 90°C and react for 6 hours. Stop heating and continue stirring for 20 minutes. Cool to room temperature and centrifuge at 4000 rpm for 30 minutes. Collect the supernatant to obtain the sodium lignosulfonate-polyglutamic acid copolymer solution, i.e., the copolymer solution.

[0037] Example 4

[0038] A highly active acid-hydrolyzed biochar is prepared by the following steps:

[0039] S1. Crush rice husks and straw to an average particle size of 2mm using a crusher, and dry them in an oven at 60℃ for 24 hours to obtain pretreated biomass.

[0040] S2. Mix the pretreated biomass with dilute sulfuric acid at a mass ratio of 1:10, place it in a reaction vessel, stir and react at 60°C for 2 hours, wash with deionized water until neutral, and obtain acid-hydrolyzed biomass.

[0041] S3. Place the acid-hydrolyzed biomass into a high-temperature furnace and carbonize it under anaerobic conditions. First, maintain the temperature at 200℃ for 1 hour, then raise the temperature to 400℃ and maintain it for 2 hours, and finally raise the temperature to 600℃ and maintain it for 1 hour to obtain preliminary biochar.

[0042] S4. Mix the preliminary biochar and the copolymer solution prepared in Example 1 at a mass ratio of 1:2, sonicate for 20 min, let stand for 24 h, dry in an oven at 40 °C for 24 h, then heat to cure at 80 °C, wash three times with deionized water, and finally dry in an oven at 60 °C to constant weight to obtain highly active acid-hydrolyzed biochar.

[0043] Example 5

[0044] A highly active acid-hydrolyzed biochar is prepared by the following steps:

[0045] S1. Crush rice husks and straw to an average particle size of 3.5 mm using a crusher, and dry them in an oven at 65℃ for 36 hours to obtain pretreated biomass.

[0046] S2. Mix the pretreated biomass with dilute sulfuric acid at a mass ratio of 1:10, place it in a reaction vessel, stir and react at 70°C for 3 hours, wash with deionized water until neutral, and obtain acid-hydrolyzed biomass.

[0047] S3. Place the acid-hydrolyzed biomass into a high-temperature furnace and carbonize it under anaerobic conditions. First, maintain the temperature at 250℃ for 1.5 hours, then raise the temperature to 450℃ and maintain it for 2.5 hours, and finally raise the temperature to 600℃ and maintain it for 1 hour to obtain preliminary biochar.

[0048] S4. Mix the preliminary biochar and the copolymer solution prepared in Example 2 at a mass ratio of 1:3, sonicate for 20-30 min, let stand for 36 h, dry in an oven at 45 °C for 24 h, then heat to cure at 90 °C, wash with deionized water 4 times, and finally dry in an oven at 70 °C to constant weight to obtain highly active acid hydrolyzed biochar.

[0049] Example 6

[0050] A highly active acid-hydrolyzed biochar is prepared by the following steps:

[0051] S1. Crush rice husks and straw to an average particle size of 5mm using a crusher, and dry them in an oven at 70℃ for 48 hours to obtain pretreated biomass.

[0052] S2. The pretreated biomass and dilute sulfuric acid are mixed at a mass ratio of 1:10 and placed in a reaction vessel. The mixture is stirred at 80°C for 4 hours and then washed with deionized water until neutral to obtain acid-hydrolyzed biomass.

[0053] S3. Place the acid-hydrolyzed biomass into a high-temperature furnace and carbonize it under anaerobic conditions. First, maintain the temperature at 300℃ for 2 hours, then raise the temperature to 500℃ and maintain it for 3 hours, and finally raise the temperature to 600℃ and maintain it for 1 hour to obtain preliminary biochar.

[0054] S4. Mix the preliminary biochar and the copolymer solution prepared in Example 3 at a mass ratio of 1:4, sonicate for 30 min, let stand for 48 h, dry in an oven at 50 °C for 24 h, then heat to cure at 100 °C, wash with deionized water 5 times, and finally dry in an oven at 80 °C to constant weight to obtain highly active acid hydrolyzed biochar.

[0055] Comparative Example 1

[0056] In this comparative example, a 20% glutamic acid monomer solution was used instead of the copolymer solution, and the remaining steps were the same as in Example 4.

[0057] Comparative Example 2

[0058] In this comparative example, sodium lignosulfonate was used instead of the copolymer solution, and the remaining steps were the same as in Example 5.

[0059] Comparative Example 3

[0060] In this comparative example, deionized water was used instead of the copolymer solution, and the remaining steps were the same as in Example 6.

[0061] Weigh 10g of the samples prepared in Examples 4-6 and Comparative Examples 1-3, and add them to 100mL of heavy metal ion solution, wherein Cu 2+ Hg 2+ and Pb 2+ The concentrations of the biochars were 100 mg / L, 50 mg / L, and 50 mg / L, respectively. The mixture was shaken on a constant temperature shaker for 24 h. After shaking, the mixture was centrifuged, and the concentration of heavy metal ions in the remaining solution was measured. The adsorption capacity of each biochar was calculated. The results are shown in Table 1.

[0062] Table 1. Heavy metal adsorption results of Examples 4-6 and Comparative Examples 1-3

[0063]

[0064]

[0065] Biochar from Examples 4-6 and Comparative Examples 1-3 were mixed evenly with garden soil at a ratio of 5% (w / w). Soil without added biochar was set up as a control group. The soil samples were placed in flowerpots of the same size and placed in a constant temperature and humidity incubation room to simulate field conditions. Soil samples were collected after 14 days for soil property determination. The results are shown in Table 2.

[0066] Table 2. Results of soil property measurements for each group

[0067]

[0068]

[0069] As shown in Table 1, the biochar of Examples 4-6 has a positive effect on Cu. 2+ Hg 2+ and Pb 2+ The adsorption effect was significant, and the concentration of heavy metal ions after adsorption was significantly reduced, compared with Comparative Examples 4-6 and Comparative Examples 1-3. The total adsorption capacity of the biochar in Examples 4-6 for the three heavy metal ions was much higher than that in Comparative Examples 1-3, indicating that the biochar prepared in Examples 4-6 has a good heavy metal adsorption capacity.

[0070] Table 2 shows that the biochar in Examples 4-6 significantly improved the physical properties of the soil after being added, reducing bulk density, increasing porosity, improving field water holding capacity, and increasing aeration. Compared with the control group, the soil property test results of Examples 4-6 all showed superiority, indicating that the addition of biochar has a positive effect on soil improvement. The biochar in Comparative Examples 1-3 was not as effective as that in Examples 4-6 in terms of soil improvement. Although Comparative Example 2 had a higher field water holding capacity, other soil property indicators were not ideal.

[0071] In summary, Examples 4-6 all demonstrated good effects in heavy metal adsorption and soil improvement.

[0072] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0073] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A highly active acid-hydrolyzed biochar, characterized in that, It is prepared by the following steps: S1. Use a crusher to crush agricultural and livestock waste to an average particle size of 2-5mm, and dry it in an oven at 60-70℃ for 24-48h to obtain pretreated biomass; S2. Mix the pretreated biomass with dilute acid at a mass ratio of 1:10, place the mixture in a reaction vessel, and wash with deionized water until neutral to obtain acid-hydrolyzed biomass. S3. The acid-hydrolyzed biomass is placed in a high-temperature furnace and carbonized under anaerobic conditions by gradually increasing the temperature to obtain preliminary biochar. The step of gradually increasing the temperature in step S3 is as follows: first, maintain the temperature at 200-300℃ for 1-2 hours, then increase the temperature to 400-500℃ and maintain it for 2-3 hours, and finally increase the temperature to 600℃ and maintain it for 1 hour. S4. Mix the preliminary biochar and copolymer solution, sonicate for 20-30 min, let stand for 24-48 h, dry and solidify, wash with deionized water 3-5 times, and finally dry in an oven at 60-80℃ to constant weight to obtain highly active acid hydrolyzed biochar. In step S4, the mass ratio of the initial biochar to the copolymer solution is 1:(2-4). The copolymer solution in step S4 is prepared by the following steps: Prepare a 20% glutamic acid monomer solution using deionized water. Preheat the reactor to 60-70℃ and maintain a constant temperature. While continuously stirring at 500-600 rpm, slowly add sodium lignosulfonate and the 20% glutamic acid monomer solution dropwise into the reactor simultaneously using a constant flow pump at a rate of 10 mL per minute for each. After the addition is complete, add ammonium persulfate and sodium bisulfite to adjust the pH to 6.

5. Control the reaction temperature at 80-90℃ and react for 4-6 hours. Perform post-processing to obtain a sodium lignosulfonate-polyglutamic acid copolymer solution, i.e., the copolymer solution.

2. The highly active acid-hydrolyzed biochar according to claim 1, characterized in that, The agricultural and livestock waste in step S1 includes one or more of the following: straw, plant debris, weeds, fallen leaves, fruit shells, rice husks, and livestock and poultry manure.

3. The highly active acid-hydrolyzed biochar according to claim 1, characterized in that, The dilute acid in step S2 includes one or more of dilute sulfuric acid, dilute hydrochloric acid, and dilute nitric acid.

4. The highly active acid-hydrolyzed biochar according to claim 1, characterized in that, In step S2, the reaction is stirred at 60-80℃ for 2-4 hours.

5. The highly active acid-hydrolyzed biochar according to claim 1, characterized in that, In step S4, the product is dried in an oven at 40-50℃ for 24 hours, and then cured by heating at 80-100℃.

6. The highly active acid-hydrolyzed biochar according to claim 1, characterized in that, The mass ratio of sodium lignosulfonate, 20% glutamic acid monomer solution, ammonium persulfate and sodium bisulfite is 100:(50-60):(5-7):(2-3).

7. The highly active acid-hydrolyzed biochar according to claim 1, characterized in that, The post-treatment process is as follows: stop heating and continue stirring for 10-20 minutes, cool to room temperature, centrifuge at 3000-4000 rpm for 20-30 minutes, and collect the supernatant.

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