An antioxidant aging biochar and its use

Abstract

This invention discloses an antioxidant aging biochar and its applications. The biochar is prepared by oxygen-limited pyrolysis of a mixture of sodium bicarbonate and giant Napier grass straw powder, with a mass ratio of sodium bicarbonate to giant Napier grass straw powder of 1:2. Ultrapure water is added to submerge the mixture during mixing, and the mixture is stirred evenly in a magnetic stirrer to ensure more uniform mixing. The mixture is then dried to obtain a dry mixture. This invention, by thoroughly mixing the giant Napier grass straw powder with sodium bicarbonate before pyrolysis, increases the ash content and pH value of the pyrolysis products. The resulting biochar has stronger mineral content, higher stability, abundant surface functional groups, strong cation exchange capacity, a large number of negatively charged surfaces, and strong adsorption capacity.

Description

Technical Field

[0001] This invention relates to an antioxidant aging biochar and its application, belonging to the field of cadmium pollution remediation technology for water bodies. Background Technology

[0002] Biochar is a carbon-rich solid material produced by the pyrolysis of biomass under anaerobic conditions, often referred to as "black gold." Due to the presence of sulfur and alkaline minerals on its surface, its high surface area (SSA), diverse active functional groups, abundant mineral elements, ability to bind many cations, and high chemical and biological stability, biochar can reduce the mobility, leaching, and availability of potentially toxic elements in polluted water. As a sustainable agricultural byproduct conversion material, straw biochar not only effectively addresses the environmental problems caused by straw burning but also plays a crucial role in multiple fields such as pollution control (effective removal of heavy metals, organic pollutants, and pharmaceuticals) and energy utilization (bioenergy production), demonstrating enormous application potential and economic value. Straw biochar is mostly alkaline, raising the pH of water bodies, and its surface has strong electronegativity, thereby increasing the adsorption of metal cations. Giant Napier grass has a large biomass in its aboveground parts, and biochar made from giant Napier grass straw has an H / C value of 0.4–0.6, indicating that giant Napier grass biochar possesses a compact aromatic structure. In the natural environment, biochar undergoes property changes due to oxidation by oxygen, experiencing short-term or long-term biochemical processes known as aging. This process affects the stability of biochar and ultimately leads to changes in its properties (e.g., elemental composition, specific surface area, pH, ash content, aromaticity, ion exchange capacity) and pollutant adsorption capacity. Furthermore, a significant risk of oxidative aging is the reduction in mineral content and pollutant removal capacity of the biochar after oxidative aging. Therefore, the preparation of an anti-aging biochar for long-term and stable water pollution remediation is a problem urgently needing to be solved by those skilled in the art. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide an antioxidant biochar that can maintain its adsorption properties for a long time, suitable for remediation of cadmium pollution in water bodies.

[0004] Another object of the present invention is to provide applications of the above-mentioned biochar.

[0005] This invention is achieved through the following technical solution:

[0006] An antioxidant aging biochar is characterized by being prepared by oxygen-limited pyrolysis of a mixture of sodium bicarbonate and giant Napier grass straw powder, wherein the mass ratio of sodium bicarbonate to giant Napier grass straw powder is 1:2. Sodium bicarbonate is weakly alkaline, which can increase the ash content and pH value of the biochar.

[0007] In this invention, the giant Napier grass straw powder has a particle size of 90-110 mesh, and the giant Napier grass straw is dried at 60°C for 12 hours before being ground into powder. At this particle size, the giant Napier grass straw powder is easier to mix with sodium bicarbonate, resulting in a higher biochar yield during pyrolysis.

[0008] In this invention, a mixture of sodium bicarbonate and giant reed straw powder is pyrolyzed in a muffle furnace at a temperature of 500°C for 120 min at a heating rate of 5°C / min.

[0009] In this invention, when sodium bicarbonate and giant reed straw powder are mixed, ultrapure water is added until the mixture is submerged, and the mixture is stirred in a magnetic stirrer for 30 minutes to allow the sodium bicarbonate powder and giant reed straw powder to be mixed more evenly, and then dried to form a dry mixture.

[0010] In this invention, a mixture of sodium bicarbonate and giant reed straw powder is pyrolyzed, cooled, washed once with 1% dilute hydrochloric acid solution, and then washed with ultrapure water until the washing solution is neutral. The mixture is then filtered to obtain a black substance, which is dried, cooled, and sieved to obtain biochar. In this invention, the drying temperature of the filtered black substance is 60℃, and the drying time is 12 hours. To ensure higher adsorption performance, the black substance is passed through a 100-mesh sieve after cooling to obtain antioxidant and anti-aging biochar.

[0011] The application of the aforementioned antioxidant and anti-aging biochar is characterized by its use in the remediation of cadmium-polluted water bodies. When remediating cadmium-polluted water bodies, the volume ratio of polluted water to biochar is 20 ml: 0.02 g.

[0012] Compared with the prior art, the present invention has the following advantages:

[0013] This invention involves thoroughly mixing giant Napier grass straw powder with sodium bicarbonate before pyrolysis to increase the ash content and pH value of the pyrolysis products. The resulting biochar is more mineral-rich, has higher stability, is rich in surface functional groups, has strong cation exchange capacity, carries a large number of negative charges on its surface, and has strong adsorption capacity. Detailed Implementation

[0014] An antioxidant aging biochar is prepared by the following method:

[0015] 1) Dry the giant reed straw and grind it into giant reed straw powder with a particle size of 100 mesh;

[0016] 2) Mix sodium bicarbonate powder and giant clover straw powder at a mass ratio of 1:2, then add ultrapure water to submerge the mixture and stir in a magnetic stirrer for 30 minutes to mix thoroughly, and then dry to obtain a dry mixture;

[0017] 3) Place the dried mixture obtained in step 2) into a muffle furnace, heat it to 500℃ at 5℃ / min, and calcine and pyrolyze the mixture for 120 min, then cool it.

[0018] 4) Soak, stir, wash and rinse the cooled mixture from step 3) in 1% dilute hydrochloric acid solution until neutral, filter and dry the black substance, then cool and pass it through a 100-mesh sieve to obtain biochar.

[0019] When the biochar prepared by this invention is used to remediate cadmium pollution in water bodies, the volume ratio of polluted water to biochar is 20 ml: 0.02 g.

[0020] The present invention will be further described in detail below with reference to specific embodiments.

[0021] Example:

[0022] The dried giant reed straw was crushed to a particle size of 100 mesh. Sodium bicarbonate powder and giant reed straw powder were added to ultrapure water at a mass ratio of 1:2 to submerge the mixture. The mixture was stirred in a magnetic stirrer for 30 minutes until homogeneous. The mixture was then placed in a quartz boat, compacted, covered, and placed in a muffle furnace for pyrolysis and carbonization. The pyrolysis temperature was 500℃, the pyrolysis time was 120 minutes, and the heating rate was 5℃ / min to obtain biochar A1.

[0023] Comparative example:

[0024] The dried giant reed straw was crushed to a particle size of 100 mesh, placed in a quartz boat, compacted, covered, and placed in a muffle furnace for pyrolysis and carbonization. The pyrolysis temperature was 500℃, the pyrolysis time was 120 min, and the heating rate was 5℃ / min, to obtain biochar A2.

[0025] Oxidative aging of biochar:

[0026] Biochars A1 and A2 obtained from the examples and comparative examples were respectively subjected to 200 r·min -1 Under a water bath at 25°C, 20% hydrogen peroxide solution was added for complete oxidation for 12 hours. After washing and filtration, the biochar was dried at 60°C to obtain biochar B1 and B2.

[0027] Application repair test:

[0028] Take 20 mg of each of biochar A1, biochar A2, and accelerated aging biochar B1 and biochar B2, and add each to 20 mL of 20 mg·L⁻¹ solution. -1 Cadmium solution, at 200 r·min -1 The biochar was shaken at 25℃ for 24 hours, the cadmium concentration was measured, and the adsorption capacity was calculated. The results are shown in Table 1.

[0029] Table 1: Adsorption results of biochar before and after aging in the examples and comparative examples

[0030] initial materials <![CDATA[Adsorption capacity (mg·g -1 )]]> Oxidized and aged materials <![CDATA[Adsorption capacity (mg·g -1 )]]> Example Biochar A1 18.65 Biochar B1 18.77 Comparative Example Biochar A2 14.04 Biochar B2 9.28

[0031] The experimental results from the examples show that once biochar is applied, it will begin to age due to environmental factors, and oxidative aging is a common natural aging process. This aging process may significantly affect the microstructure, surface chemical properties, and adsorption performance of biochar, thereby altering its adsorption capacity for Cd. 2+ The removal effect is good. The biochar A2 obtained in this invention has an initial adsorption capacity of 18.65 mg / g, and after aging, its adsorption capacity reaches 18.77 mg / g, maintaining good adsorption capacity and reducing the oxidative aging effect on Cd. 2+ The removal effect is affected by the fact that it can effectively adsorb heavy metal pollutants in water.

Claims

1. An antioxidant aging biochar, characterized in that: It is prepared by oxygen-limited pyrolysis of a mixture of sodium bicarbonate and giant Napier grass straw powder, wherein the mass ratio of sodium bicarbonate to giant Napier grass straw powder is 1:

2.

2. The antioxidant aging biochar according to claim 1, characterized in that... The giant reed straw powder has a particle size of 90-110 mesh, and the giant reed straw is dried at 60℃ for 12 hours before being ground into powder.

3. The antioxidant aging biochar according to claim 1, characterized in that... The mixture of sodium bicarbonate and giant reed straw powder was pyrolyzed in a muffle furnace at a temperature of 500°C for 120 min at a heating rate of 5°C / min.

4. The antioxidant aging biochar according to claim 1, characterized in that... When the sodium bicarbonate and giant reed straw powder are mixed, water is added to submerge the mixture, which is then ground and mixed thoroughly before being dried to form a dry mixture.

5. The antioxidant aging biochar according to claim 1, characterized in that... The mixture of sodium bicarbonate and giant reed straw powder was pyrolyzed and cooled. It was then washed once with a 1% dilute hydrochloric acid solution, followed by water washing until the washing solution was neutral. After filtration, a black substance was obtained, which was then dried, cooled, and sieved to obtain biochar.

6. The antioxidant aging biochar according to claim 5, characterized in that... The black substance obtained by filtration was dried at 60℃ for 12 hours.

7. The antioxidant aging biochar according to claim 5, characterized in that... The biochar was sieved through a 100-mesh screen.

8. The application of the antioxidant aging biochar according to claim 1, characterized in that... Used for remediation of cadmium pollution in water bodies.

9. The application of the antioxidant aging biochar according to claim 8, characterized in that... When remediating cadmium pollution in water bodies, the volume ratio of polluted water to biochar is 20 ml: 0.02 g.