Koh / cacl2 synergistically regulated hierarchical porous biochar, preparation method and application thereof
Patent Information
- Application Number
- CN202611307873.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-27
- Publication Date
- 2026-09-29
AI Technical Summary
[0006]本发明旨在解决现有技术中现有生物炭制备过程调控困难、孔结构可控性不足、比表面积有限以及微孔-介孔-大孔协同构筑难以实现等问题，提供一种基于KOH/ CaCl2协同活化策略调控分级多孔生物炭及其制备方法和应用
[0017]与现有技术相比，本发明具有如下有益效果：采用KOH与CaCl2协同活化策略，实现了生物质碳化过程中孔结构的可控调节，促进微孔、介孔及大孔协同形成，获得具有连续分级孔道的多孔生物炭；CaCl2在活化过程中促进生物质热解过程中挥发分释放，减缓碳骨架收缩，抑制KOH过度刻蚀造成的孔壁塌陷，促进介孔形成，实现微孔与介孔协同构筑，提高材料收率和结构稳定性，同时改善孔径分布，提高离子和分子的传输效率；通过调控KOH与CaCl2配比以及炭化条件，实现分级孔结构、比表面积、孔容及表面化学性质的协同调控，从而提高材料对污染物的吸附性能及电化学储能性能。所制备的分级多孔生物炭具有较高的比表面积、丰富的表面活性位点及优异的传质性能，可显著提升对有机污染物及PFAS类污染物的吸附能力，同时具有良好的电化学性能；本发明制备工艺简单，原料来源广泛，易于规模化生产，实现了废弃生物质的高值化利用；所得分级多孔生物炭可广泛应用于环境治理、电化学储能、催化、气体吸附及海水淡化等领域，具有良好的产业化应用前景。
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Abstract
Description
Technical Field
[0001] This invention relates to the field of functional carbon materials technology, and in particular to a KOH / CaCl2 synergistic regulation hierarchical porous biochar, its preparation method, and its application. Background Technology
[0002] With the increasing demands for global energy transition and ecological environmental protection, the preparation of high-value-added functional carbon materials from agricultural and forestry waste has become an important research direction in the utilization of biomass resources. Woody biomass, with its advantages of wide availability, low cost, renewability, and abundant natural multi-level structures, is an important precursor for the preparation of porous carbon materials. Through pyrolysis carbonization and chemical activation, the natural structure of biomass can be transformed into porous biochar with rich pore structure and excellent chemical stability, showing broad application prospects in pollutant adsorption, electrochemical energy storage, catalysis, and gas separation.
[0003] Currently, KOH activation is one of the most commonly used methods for preparing porous carbon materials with high specific surface area. It can effectively promote the etching of the carbon framework, forming a large number of micropores and increasing the specific surface area of the material. However, with the increase of KOH dosage, the carbon framework is prone to over-etching, leading to pore wall collapse, uneven pore size distribution, and reduced material yield. At the same time, the material obtained by KOH activation alone is mainly microporous with a low proportion of mesopores, which is not conducive to the diffusion of macromolecular pollutants and rapid electrolyte transport, thus limiting the further application of the material in environmental remediation and electrochemical energy storage.
[0004] In recent years, CaCl2 has gradually attracted attention as a mild activator and structure regulator. CaCl2 can reduce the shrinkage of the carbon skeleton during biomass pyrolysis, promote mesopore formation, and improve the stability of pore structure. However, there is currently little research on the synergistic activation and construction of hierarchical pore structures by KOH and CaCl2, and the synergistic mechanism is still unclear. In particular, there is a lack of methods for the synergistic construction of micropores and mesopores and the precise control of pore structure, which makes it difficult to meet the requirements of multifunctional applications for material structure and performance.
[0005] Therefore, developing a method to controllably prepare hierarchical pore structures by synergistically regulating the biomass carbonization and activation process using KOH and CaCl2 is of great significance for improving the utilization efficiency of biomass resources, improving the pore structure of biochar, and expanding the application of porous biochar in environmental remediation, electrochemical energy storage, and catalysis. Summary of the Invention
[0006] This invention aims to solve the problems of difficulty in controlling the existing biochar preparation process, insufficient controllability of pore structure, limited specific surface area, and difficulty in achieving the synergistic construction of micropores, mesopores, and macropores in the prior art. It provides a hierarchical porous biochar based on the KOH / CaCl2 synergistic activation strategy, its preparation method, and its application.
[0007] A method for preparing hierarchical porous biochar with synergistic regulation of KOH / CaCl2 includes the following steps: Step S1: Pretreatment, the biomass is washed, dried and crushed to obtain biomass precursor; Step S2: Thoroughly mix the biomass precursor with two activators, KOH and CaCl2, to obtain a mixture; Step S3: The mixture is activated and carbonized at high temperature in an inert gas atmosphere. The synergistic effect of KOH and CaCl2 is used to regulate the evolution of the pore structure of the carbon material, forming a carbon material with a hierarchical pore structure. Step S4: The obtained carbon material is acid-washed, water-washed until neutral, and then dried to obtain KOH / CaCl2 synergistic-regulated hierarchical porous biochar.
[0008] Preferably, the biomass is selected from one or more of agricultural and forestry waste and garden waste, including wood-based biomass, bamboo-based biomass, fruit shell biomass, sawdust biomass, and straw biomass. Branches, longan wood, pine wood, eucalyptus wood, bamboo, coconut shells, fruit shells, sawdust, straw, etc., can all be used as biomass sources for this technical solution, enabling high-value utilization of waste biomass.
[0009] Preferably, the biomass is selected from litchi wood, and the litchi wood raw material has a cellulose content of 42%-46%, a lignin content of 25%-29%, and a hemicellulose content of 22%-26%.
[0010] Preferably, in step S2, the mass ratio of biomass precursor, KOH and CaCl2 is 1:0.2:0.2-1:3:2, and the biomass precursor is mixed with KOH and CaCl2 by one or more of the following methods: direct mixing, mechanical stirring, ball milling, impregnation or ultrasonic-assisted impregnation.
[0011] Preferably, the inert gas in step S3 is nitrogen or argon, and the flow rate of the inert gas is 20-200 ml / min.
[0012] Preferably, the high-temperature activation carbonization temperature in step S3 is 600–950 °C, the heating rate is 3–10 °C / min, and the holding time is 1–3 h.
[0013] Preferably, in step S3, the high-temperature activation carbonization process firstly raises the temperature to 300-350°C at a rate of 3-10°C / min and holds it for 0.5-2 hours, and secondly raises the temperature to 600-950°C at a rate of 5-10°C / min and holds it for 1-3 hours.
[0014] A hierarchical porous biochar with KOH / CaCl2 synergistic regulation, obtained by the above-described method for preparing hierarchical porous biochar with KOH / CaCl2 synergistic regulation, has a hierarchical pore structure composed of micropores, mesopores, and macropores. The micropore volume accounts for 30%-80% of the total pore volume, and the mesopore volume accounts for 15%-60% of the total pore volume. The specific surface area of the porous biochar is 500-3000 m² / g, the total pore volume is 0.30-2.50 cm³ / g, and the average pore size is 1.7-50 nm.
[0015] An application of KOH / CaCl2 synergistic regulation hierarchical porous biochar is disclosed, which applies porous biochar to the field of environmental remediation. It is used to adsorb and remove one or more of the following substances from the environment: perfluorinated and polyfluoroalkyl substances, organic dyes, antibiotics, phenolic compounds, heavy metal ions, and organic pollutants. The porous biochar is placed in the environment to be treated and allowed to stand for adsorption and removal of pollutants.
[0016] An application of KOH / CaCl2 synergistic regulation hierarchical porous biochar is proposed, which applies porous biochar in the field of electrochemical energy storage, and uses porous biochar as an electrode material for supercapacitors, lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, or hybrid ion energy storage devices.
[0017] Compared with existing technologies, this invention has the following advantages: By employing a synergistic activation strategy of KOH and CaCl2, the pore structure during biomass carbonization is controllably regulated, promoting the synergistic formation of micropores, mesopores, and macropores to obtain porous biochar with continuous hierarchical channels. During activation, CaCl2 promotes the release of volatiles during biomass pyrolysis, slows carbon skeleton shrinkage, inhibits pore wall collapse caused by excessive KOH etching, promotes mesopore formation, and achieves synergistic construction of micropores and mesopores, improving material yield and structural stability. Simultaneously, it improves pore size distribution and enhances ion and molecule transport efficiency. By controlling the ratio of KOH to CaCl2 and carbonization conditions, the hierarchical pore structure, specific surface area, pore volume, and surface chemical properties are synergistically regulated, thereby improving the material's adsorption performance for pollutants and its electrochemical energy storage performance. The prepared hierarchical porous biochar has a high specific surface area, abundant surface active sites, and excellent mass transfer performance, which can significantly improve the adsorption capacity for organic pollutants and PFAS pollutants, while also exhibiting good electrochemical performance. The preparation process of this invention is simple, the raw materials are widely available, and it is easy to scale up production, realizing the high-value utilization of waste biomass. The obtained hierarchical porous biochar can be widely used in environmental remediation, electrochemical energy storage, catalysis, gas adsorption, and seawater desalination, and has good prospects for industrial application. Attached Figure Description
[0018] Figure 1 Here is a SEM image of the biochar from Example 1; Figure 2 Here is a SEM image of the biochar in the comparative example; Figure 3 The diagram shows the pore size distribution of biochar in Example 1 and the comparative example. Detailed Implementation
[0019] To make the objectives, technical solutions, and advantages of this invention clearer and more complete, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. Based on the content disclosed in this invention, any modifications, equivalent substitutions, or improvements made by those skilled in the art without departing from the principles and core design concepts of this invention should be included within the scope of protection of this invention.
[0020] In the following examples, the litchi wood raw material was obtained from Dongguan University of Technology. Unless otherwise specified, all conditions used in the examples were performed under standard conditions or conditions recommended by the manufacturer. Reagents and instruments used, unless otherwise specified, were all commercially available products. Example
[0021] S1, take litchi wood raw material with a cellulose content of 42%, a lignin content of 29%, and a hemicellulose content of 25%. The litchi wood raw material is thoroughly washed with deionized water to remove impurities, dried in an oven at 80℃ for 12 hours, and then ground in a mortar and passed through a 100-mesh sieve to obtain a biomass precursor; S2, take 10g of biomass precursor and mix it evenly with 2g KOH and 2g CaCl2, add 30mL of deionized water and stir and soak at room temperature for 12h, dry at 80℃ to constant weight and then put it into a tube furnace. S3, the mixture is subjected to one-step high-temperature activation and carbonization in a tube furnace under a nitrogen atmosphere. The flow rate of nitrogen is 200 ml / min, the heating rate of the tube furnace is 5℃ / min, the carbonization temperature is 950℃, and the holding time is 1.5 hours to obtain porous carbon. S4. After the porous carbon cools naturally, it is soaked in 1 mol / L dilute hydrochloric acid at room temperature for 2 hours to remove impurities. Then it is repeatedly washed with deionized water until the pH of the filtrate stabilizes at 6.5. After filtration, it is dried at 105℃ for 12 hours to obtain KOH / CaCl2 synergistic regulation hierarchical porous biochar. Example
[0022] S1, take litchi wood raw material with a cellulose content of 42%, a lignin content of 29%, and a hemicellulose content of 25%. The litchi wood raw material is thoroughly washed with deionized water to remove impurities, dried in an oven at 80℃ for 12 hours, and then ground in a mortar and passed through a 100-mesh sieve to obtain a biomass precursor; S2, take 10g of biomass precursor and mix it evenly with 30g KOH and 20g CaCl2, add 30mL of deionized water and stir and soak at room temperature for 12h, dry at 105℃ to constant weight and then put it into a tube furnace. S3, the mixture is subjected to two-step high-temperature activation and carbonization in a tube furnace under a nitrogen atmosphere. The flow rate of nitrogen is 20 ml / min. The first step of the tube furnace is heated at a rate of 3℃ / min to 350℃ and held for 2 hours. The second step is heated at a rate of 10℃ / min to 600℃ and held for 3 hours to obtain porous carbon. S4. After the porous carbon cools naturally, it is soaked in 1 mol / L dilute hydrochloric acid at room temperature for 2 hours to remove impurities. Then it is repeatedly washed with deionized water until the pH of the filtrate stabilizes at 6.5. After filtration, it is dried at 105℃ for 12 hours to obtain KOH / CaCl2 synergistic regulation hierarchical porous biochar.
[0023] Comparative Example 1 The comparative example follows the same method as Example 1, except that CaCl₂ is not added in step S2. 2。
[0024] Figure 1 and Figure 2 SEM images of biochar from Example 1 and Comparative Example 1 are shown below. As can be seen from the images, Figure 1 It exhibits a distinct layered stacking structure, with a surface that is not smooth but covered with tiny protrusions and depressions, indicating a high specific surface area, which is conducive to physical adsorption and chemical reactions. The image shows multiple pores of varying sizes, some elliptical or irregular in shape, with pore sizes generally in the micrometer range. These pores provide channels for gas or liquid molecules to enter the material's interior, forming a crucial basis for its adsorption performance. Figure 2 The biochar framework is composed of a large number of interconnected "honeycomb" or "mesh" micropores. Some of the pore walls have sharp or irregular fracture surfaces, reflecting the brittle characteristics of the material and the pores are prone to collapse.
[0025] like Figure 3 As shown, Example 1 exhibits extremely high peak values and large pore volumes between 2 nm and 50 nm, particularly a main peak near 3-4 nm, and significant secondary peaks at 10-20 nm, indicating that the material possesses extremely abundant mesopores. In Comparative Example 1, the pore volume decreases rapidly after 2 nm, almost reaching the X-axis. This indicates that the material lacks mesopores and relies mainly on micropores. Although there are many micropores, without mesopores as channels, many macromolecules cannot be transported to the internal micropore surface, resulting in low effective specific surface area utilization. Example 1 is a porous biochar with continuous hierarchical channels, where micropores, mesopores, and macropores synergistically form a continuous hierarchical pore structure, which has very broad application prospects in environmental remediation and new energy storage.
[0026] The physical properties of the porous biochar obtained in Examples 1-2 and Comparative Example 1 are shown in Table 1 below:
[0027] Experimental procedure: Adsorption experiment of perfluoroalkyl organic pollutants by porous biochar: Take 50 mL of reaction solution, containing 50 mg of fluoroalkyl organic pollutants. Add porous biochar at a concentration of 0.2g. An adsorption reaction was carried out. During the adsorption process, the magnetic stirrer was rotated at 500 rpm min⁻¹, and the solution temperature was 25 ℃. Approximately 1 mL of solution was sampled periodically during the reaction and filtered through a 0.22 μm polyethersulfone membrane. The target pollutant, perfluorooctanoic acid (PFOA), was quantitatively analyzed using high-performance liquid chromatography (HPLC) to investigate the removal efficiency of the porous biochar.
[0028]
[0029] In Table 2, Example 1 showed a perfluorooctanoic acid (PFOA) removal rate of 90.1% in the water, achieving deep purification. In Comparative Example 1, the PFOA removal rate in the water could only reach a maximum of 80.3%. The experimental results further demonstrate that porous biochar activated by the synergistic use of KOH and CaCl2 has a better adsorption effect on PFOA.
[0030] The KOH / CaCl2 synergistic hierarchical porous biochar provided by this invention can efficiently remove organic pollutants from wastewater. Moreover, its preparation process is simple, the product is stable and reliable, and the raw materials are inexpensive, so it can be widely prepared and used in the field of wastewater treatment.
Claims
1. A method for preparing hierarchical porous biochar with synergistic regulation of KOH / CaCl2, characterized in that, The preparation includes the following steps: Step S1: Pretreatment, the biomass is washed, dried and crushed to obtain biomass precursor; Step S2: Thoroughly mix the biomass precursor with two activators, KOH and CaCl2, to obtain a mixture; Step S3: The mixture is activated and carbonized at high temperature in an inert gas atmosphere. The synergistic effect of KOH and CaCl2 is used to regulate the evolution of the pore structure of the carbon material, forming a carbon material with a hierarchical pore structure. Step S4: The obtained carbon material is acid-washed, water-washed until neutral, and then dried to obtain KOH / CaCl2 synergistic-regulated hierarchical porous biochar.
2. The KOH / CaCl2 synergistic hierarchical porous biochar and its preparation method according to claim 1, characterized in that: The biomass is selected from one or more of agricultural and forestry waste and garden waste, including wood-based biomass, bamboo-based biomass, fruit shell biomass, sawdust biomass and straw biomass.
3. The method for preparing hierarchical porous biochar with synergistic regulation of KOH / CaCl2 according to claim 2, characterized in that: The biomass is selected from lychee wood, and the lychee wood raw material has a cellulose content of 42%-46%, a lignin content of 25%-29%, and a hemicellulose content of 22%-26%.
4. The method for preparing hierarchical porous biochar with synergistic regulation of KOH / CaCl2 according to claim 1, characterized in that: In step S2, the mass ratio of biomass precursor, KOH and CaCl2 is 1:0.2:0.2-1:3:
2. The biomass precursor is mixed with KOH and CaCl2 by one or more of the following methods: direct mixing, mechanical stirring, ball milling, impregnation or ultrasonic-assisted impregnation.
5. The method for preparing hierarchical porous biochar with synergistic regulation of KOH / CaCl2 according to claim 1, characterized in that: The inert gas mentioned in step S3 is nitrogen or argon, and the flow rate of the inert gas is 20-200 ml / min.
6. The method for preparing hierarchical porous biochar with synergistic regulation of KOH / CaCl2 according to claim 5, characterized in that: In step S3, the high-temperature activation carbonization is a one-step carbonization process, with a temperature of 600-950 ℃, a heating rate of 3-10 ℃ / min, and a holding time of 1-3 h.
7. The method for preparing hierarchical porous biochar with synergistic regulation of KOH / CaCl2 according to claim 5, characterized in that: The high-temperature activation carbonization process in step S3 is a two-step carbonization process. The first step is to raise the temperature to 300-350℃ at a rate of 3-10℃ / min and hold it for 0.5-2 hours. The second step is to raise the temperature to 600-950℃ at a rate of 5-10℃ / min and hold it for 1-3 hours.
8. A hierarchical porous biochar with KOH / CaCl2 synergistic regulation, characterized in that: The biochar prepared by the KOH / CaCl2 synergistic regulation hierarchical porous biochar preparation method according to any one of claims 1 to 5 has a hierarchical pore structure composed of micropores, mesopores and macropores, with micropores accounting for 30%-80% of the total pore volume and mesopores accounting for 15%-60% of the total pore volume; the porous biochar has a specific surface area of 500-3000 m² / g, a total pore volume of 0.30-2.50 cm³ / g, and an average pore diameter of 1.7-50 nm.
9. An application of KOH / CaCl2 synergistic regulation of hierarchical porous biochar, characterized in that: Porous biochar is applied in the field of environmental remediation to adsorb and remove one or more of the following: perfluorinated and polyfluoroalkyl substances, organic dyes, antibiotics, phenolic compounds, heavy metal ions, and organic pollutants. The porous biochar is placed in the environment to be treated and left to stand for adsorption and removal of pollutants.
10. An application of a KOH / CaCl2 synergistic regulation hierarchical porous biochar, characterized in that: Porous biochar can be applied to the field of electrochemical energy storage, and can be used as an electrode material for supercapacitors, lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, or hybrid ion energy storage devices.