A method for preparing a biomass-derived carbon material for use in the entire course of an enzymatic reaction

Abstract

The application discloses a preparation method of biomass-derived carbon material for utilization of whole enzymatic reaction process, and belongs to the technical field of biomass-derived carbon material. The preparation steps of the biomass-derived carbon material are as follows: cellulase is added into a buffer solution with a pH value of 4.6-5.0, and then an enzymatic reaction is carried out on cellulose-based biomass raw materials to obtain an enzymatic product; the enzymatic product is directly subjected to a hydrothermal reaction, and then is filtered by using a filter membrane; the mixture on the filter membrane is mixed with potassium dihydrogen phosphate and is ground to obtain enzymatic sawdust; the enzymatic sawdust is subjected to step-by-step carbonization, and then is subjected to acid immersion, water washing and drying to obtain the biomass-derived carbon material. The application provides a green method for treating cellulose-based biomass material, which takes into account the reaction period, does not have strict experimental environment and instrument requirements, and can effectively improve the specific surface area of the material.

Description

Technical Field

[0001] This invention belongs to the field of biomass-derived carbon materials technology, and more specifically, it relates to a method for preparing biomass-derived carbon materials that utilizes the entire enzymatic reaction process. Background Technology

[0002] Reducing environmental pollution and achieving efficient and high-value utilization of agricultural and forestry production waste are urgent problems that need to be solved. The high-value and multi-purpose utilization of cellulosic biomass can effectively conserve non-renewable energy, reduce environmental pollution, and achieve more sustainable development.

[0003] Biomass-derived carbon materials represent an important high-value utilization pathway for cellulosic biomass. They can be used as electrode materials in flexible supercapacitors or as adsorbents in water treatment. The abundant nitrogen and oxygen heteroatoms in biomass raw materials enhance the hydrophilicity of carbon materials, while their inherent mineral salt components act as pore-forming templates, synergistically constructing materials with high specific surface area and rich pore structure. As electrode materials, carbon materials determine the charge adsorption-desorption capacity, specific capacitance, and energy density of supercapacitors; as adsorbents, they determine wastewater treatment efficiency and adsorption degree. This enables the transformation of low-value utilization of agricultural and forestry waste from incineration or direct return to the field into high-value utilization in high-tech fields such as electrochemical energy storage and water pollution treatment. Traditional carbon material activation involves strong acids and bases such as phosphoric acid or potassium hydroxide. While this increases the specific surface area, it corrodes equipment, shortens equipment lifespan, and increases environmental burden. Therefore, there is an urgent need for a gentler and greener treatment method that avoids the use of strong acids and bases to treat biomass materials gently, while maximizing the utilization rate of materials and reagents and minimizing waste. While green treatment methods such as steam explosion, freeze-thaw cycles, and fungal treatment can increase the specific surface area of ​​materials, they all have certain drawbacks. Steam explosion and freeze-thaw cycles utilize physical processes to restructure the wood structure; however, steam explosion requires high-pressure vessels, placing high demands on equipment, and the increase in specific surface area is limited. Freeze-thaw cycles require three repeated freezing and thawing processes, each lasting 36 hours or longer, resulting in a long treatment cycle. Fungal treatment requires waiting for fungal growth, which takes at least 7 days to achieve performance improvements. This long treatment time, coupled with the need for a sterile and pollution-free environment and stringent experimental conditions, increases production costs and thus reduces the material's value.

[0004] Based on this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing biomass-derived carbon materials that utilize the entire enzymatic reaction process, in order to solve the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of this invention is to provide a method for preparing biomass-derived carbon materials that can be utilized throughout the entire enzymatic reaction process, comprising the following steps: Cellulase is added to a buffer solution with pH 4.6-5.0 to carry out enzymatic hydrolysis of cellulose-based biomass raw materials to obtain enzymatic hydrolysis products. The enzymatic hydrolysis products are directly subjected to hydrothermal reaction and then filtered using a filter membrane. The mixture on the filter membrane is mixed with an activator and ground to obtain enzymatically hydrolyzed sawdust. The enzymatically hydrolyzed sawdust is carbonized in steps, and then subjected to acid leaching, water washing, and drying to obtain the biomass-derived carbon material.

[0007] Preferably, the cellulose-based biomass raw material includes at least one of wood sawdust, straw, cotton and linen, bamboo powder, coconut shell powder, and pulp fiber.

[0008] Preferably, the mass ratio of the buffer solution, cellulase, and cellulose-based biomass raw material is 20~50:0.05~0.4:1~3.

[0009] Preferably, the enzymatic hydrolysis reaction is carried out at a temperature of 45-55°C for 20-30 hours.

[0010] Preferably, the hydrothermal reaction is carried out at a temperature of 160-200°C for 4-8 hours.

[0011] Preferably, before the mixture on the filter membrane is mixed and ground with the activator, a drying step is further included; the mass ratio of the mixture on the dried filter membrane to the activator is 1:1~2; the activator includes potassium dihydrogen phosphate or ammonium dihydrogen phosphate.

[0012] Preferably, the stepwise carbonization includes: first performing low-temperature carbonization under a nitrogen atmosphere, and then performing high-temperature carbonization; the low-temperature carbonization is performed by heating to 250-400℃ at a heating rate of 5-10℃ / min and holding for 0.5-1h, and the high-temperature carbonization is performed by heating to 700-800℃ at a heating rate of 5℃ / min and holding for 1.5-3h.

[0013] The second technical solution of the present invention: providing a biomass-derived carbon material prepared by the above preparation method, wherein the specific surface area of ​​the biomass-derived carbon material is ≥899 m². 2 / g, the biomass-derived carbon material is doped with nitrogen and phosphorus.

[0014] The third technical solution of this invention is to provide the application of the above-mentioned biomass-derived carbon materials in supercapacitors.

[0015] The fourth technical solution of this invention is to provide the application of the above-mentioned biomass-derived carbon materials in water treatment.

[0016] This invention provides a green method for treating cellulose-based biomass materials. While maintaining a reasonable reaction cycle, it requires no strict experimental environment or instrumentation, and effectively increases the specific surface area of ​​the material. First, cellulase treats the cellulose-based biomass material, directionally degrading the cellulose through a specific enzyme reaction. This degradation results in the cellulose being broken down into oligosaccharides such as cellobiose and glucose, while simultaneously leaving a rich porous structure that initially increases the material's specific surface area. Subsequently, a hydrothermal reaction is used to recombine the glucose and cellobiose released by the cellulase back onto the cellulose-based biomass material, improving material utilization and increasing electrochemical active sites and specific surface area. Furthermore, cellulase, as a protein, is reintroduced into the cellulose-based biomass material as a biological nitrogen source during the hydrothermal process. This avoids the waste associated with directly treating inactivated enzymes and their hydrolysis products in traditional enzymatic reactions. Simultaneously, nitrogen improves the material's wettability, reduces internal resistance, and increases ion transport speed. Subsequently, a green activator (potassium dihydrogen phosphate or ammonium dihydrogen phosphate) is added during the carbonization process for secondary activation, further increasing the specific surface area of ​​the material. Simultaneously, stepwise carbonization is performed by selecting the solid-liquid phase transition node of potassium dihydrogen phosphate or ammonium dihydrogen phosphate, ensuring efficient integration of the biomass material and the activator, resulting in a high specific surface area carbon material rich in heteroatoms. The high specific surface area and abundant heteroatoms enable the carbon material to transform simple physical adsorption of pollutants in water (such as methylene blue) into physicochemical synergistic adsorption, making adsorption easier and significantly increasing the adsorption capacity. Furthermore, in the field of supercapacitors, the heteroatoms and high specific surface area of ​​the material can provide more electrochemical active sites and pseudocapacitance, thereby greatly improving the specific capacitance and energy density of supercapacitors. The biomass-based carbon material prepared in this invention can be applied in the fields of supercapacitors and water pollution treatment.

[0017] The present invention discloses the following technical effects: 1. This invention is green and environmentally friendly, with efficient resource utilization. The entire process utilizes bio-enzyme treatment and the green activator potassium dihydrogen phosphate, avoiding the use of strong acids, strong alkalis, or heavy metal reagents, thus reducing the risk of environmental pollution. Cellulase is reintroduced into the material as a biological nitrogen source during the hydrothermal process, realizing the resource utilization of waste protein and avoiding the direct discharge of waste after traditional enzymatic hydrolysis, which aligns with the concept of a circular economy. The hydrothermal process repolymerizes the oligosaccharides produced by enzymatic hydrolysis onto the material surface, improving the overall utilization rate of raw materials and reducing carbon loss.

[0018] 2. The process conditions of this invention are mild, the operation method is simple, there are no harsh requirements on the experimental environment and equipment, no high pressure environment is required, thus reducing equipment investment and energy consumption, and making it easy to achieve large-scale production.

[0019] 3. This invention improves the material structure and performance, completing the hierarchical pore construction. Through a three-step synergistic process of "enzymatic hydrolysis-hydrothermal polymerization-activation," it achieves multi-level pore structure regulation from micropores to mesopores. Enzymatic hydrolysis initially increases the specific surface area, hydrothermal polymerization and nitrogen doping further enrich the pores, and the green activator significantly expands the pores, ultimately yielding a carbon material with a high specific surface area. Cellulase, as a nitrogen source, naturally introduces nitrogen during the hydrothermal process, achieving uniform doping of heteroatoms and initial nitrogen doping. Nitrogen doping not only improves the material's conductivity and wettability and increases ion transport speed but also introduces pseudocapacitive active sites. The synergistic effect of high specific surface area and heteroatoms gives the material excellent adsorption and electrochemical properties.

[0020] 4. This invention employs a stepwise carbonization process, selecting the solid-liquid conversion temperature of the green activator (potassium dihydrogen phosphate or ammonium dihydrogen phosphate) for preliminary carbonization, ensuring efficient bonding between the activator and the material, improving the utilization rate of the activator, and introducing more nitrogen and phosphorus elements, greatly increasing the functional groups of the material.

[0021] 5. This invention has diverse applications. In the field of adsorption, the high specific surface area and nitrogen-containing functional groups enable the material to transform the adsorption of organic pollutants (such as methylene blue) from simple physical adsorption to physicochemical synergistic adsorption, significantly improving adsorption capacity and binding strength. In the field of electrochemistry, the abundant porous structure facilitates electrolyte ion diffusion, and nitrogen doping provides pseudocapacitance and enhances conductivity, jointly improving the specific capacitance, energy density, and rate performance of supercapacitors.

[0022] 6. The method of this invention has strong universality and is applicable to a variety of cellulose-based biomass raw materials (such as wood, straw, cotton, and hemp). The raw materials are widely available and inexpensive, and have good potential for promotion.

[0023] 7. This invention balances efficiency and effectiveness. The enzymatic hydrolysis reaction is specific and can degrade cellulose in a targeted manner under mild conditions, shortening the pretreatment time. The subsequent hydrothermal and activation processes further optimize the structure, resulting in a reasonable overall reaction cycle and high efficiency. Attached Figure Description

[0024] Figure 1 Characterization images of the materials described in Example 1 are shown below. (a) to (c) are SEM images of elm sawdust without any treatment, (d) to (f) are SEM images of the products after enzymatic hydrolysis, (g) to (i) are SEM images of the products after hydrothermal reaction, (j) to (l) are SEM images of the carbon materials prepared in Example 1, and (m) to (r) are elemental mapping images of the carbon materials prepared in Example 1. Figure 2 The nitrogen adsorption-desorption curves are for the carbon materials prepared in Example 1 and Comparative Example 1. Figure 3 The pore size distribution diagrams are shown for the carbon materials prepared in Example 1 and Comparative Example 1. Figure 4 The GCD curve of the carbon material prepared in Example 1 in a two-electrode system; Figure 5 The CV curve of the carbon material prepared in Example 1 in a two-electrode system; Figure 6 The GCD curves of the carbon materials prepared in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 in a two-electrode system during the iteration process at a current density of 0.5 A / g. Figure 7 The UV absorbance curve of the carbon material prepared in Example 1 after adsorbing methylene blue; Figure 8 High-resolution N 1s spectrum of the carbon material prepared in Example 1; Figure 9 High-resolution O 1s spectrum of the carbon material prepared in Example 1; Figure 10 This is a high-resolution spectrum of the P 2p of the carbon material prepared in Example 1. Detailed Implementation

[0025] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0026] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0027] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0028] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0029] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0030] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0031] Unless otherwise specified, all raw materials used in the following embodiments of the present invention are commercially available products, and the source of these commercially available products does not affect the technical effects of the present invention. The cellulase (98% purity) used in the present invention was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0032] Example 1 (1) After soaking and washing the elm sawdust in deionized water, the sawdust was separated from the deionized water by a vacuum filter and the washed sawdust was vacuum dried at 60°C for 4 hours to obtain pretreated elm sawdust.

[0033] (2) Prepare a 0.2 mol / L acetate-sodium acetate buffer solution, and adjust the pH of the buffer solution to 5.0 using glacial acetic acid to obtain an enzyme-catalyzed buffer solution to provide an environment for the enzyme-catalyzed reaction.

[0034] (3) Add the buffer, cellulase and elm sawdust in a ratio of 50mL:0.4g:2g (50mL buffer, 0.4g cellulase and 2g elm sawdust) into a wide-mouth bottle, seal it and incubate it at 50℃ for 24h.

[0035] (4) The buffer solution after 24 hours of incubation was directly placed into a hydrothermal reactor with the mixture of elm sawdust and cellulase without any treatment, and the mixture was hydrothermally reacted at 160°C for 6 hours. After natural cooling, the mixture was filtered to remove the buffer solution, and the mixture was rinsed several times with deionized water. The mixture on the filter membrane was collected and dried at 60°C for 24 hours.

[0036] (5) Mix the mixture on the filter membrane with potassium dihydrogen phosphate (mass ratio 1:1) and grind thoroughly.

[0037] (6) The blend of the ground enzymatically hydrolyzed sawdust and potassium dihydrogen phosphate was placed in a tube furnace and heated to 250°C at a nitrogen flow rate of 0.5 L / min and a heating rate of 5°C / min, and held for 1 h. Then the temperature was increased to 800°C at a heating rate of 5°C / min and held for 2 h. After that, the material was naturally cooled to room temperature. The cooled material was soaked in 0.1 M HCl for 0.5 h, rinsed with deionized water until the washing solution was neutral, and vacuum dried at 60°C for 24 h to obtain carbon material.

[0038] Example 2 (1) After soaking and washing the fir sawdust in deionized water, the sawdust was separated from the deionized water by a vacuum filter and the washed sawdust was vacuum dried at 80°C for 6 hours to obtain pretreated fir sawdust.

[0039] (2) Prepare a 0.2 mol / L acetate-sodium acetate buffer solution, and adjust the pH of the buffer solution to 4.8 using glacial acetic acid to obtain an enzyme buffer solution to provide an environment for the enzyme reaction.

[0040] (3) Add the buffer, cellulase and fir sawdust in a ratio of 40mL:0.2g:1g (40mL buffer, 0.2g cellulase and 1g fir sawdust) into a wide-mouth bottle, seal it and incubate it at 50℃ for 30h.

[0041] (4) The buffer solution after 30 hours of culture was directly loaded into a hydrothermal reactor with the mixture of cedar sawdust and cellulase without any treatment, and the mixture was hydrothermally reacted at 180°C for 8 hours. After natural cooling, the mixture was filtered to remove the buffer solution, and the mixture was rinsed several times with deionized water. The mixture on the filter membrane was collected and dried at 80°C for 24 hours.

[0042] (5) Mix the mixture on the filter membrane with potassium dihydrogen phosphate (mass ratio 1:1.5) and grind thoroughly. (6) The blend of the ground enzymatically hydrolyzed sawdust and potassium dihydrogen phosphate was placed in a tube furnace and heated to 400°C at a nitrogen flow rate of 0.3 L / min and a heating rate of 10°C / min. The temperature was maintained for 1 h, and then heated to 700°C at a heating rate of 5°C / min and maintained for 1.5 h. The mixture was then allowed to cool naturally to room temperature. The cooled material was then soaked in 0.1 M HCl for 1 h, rinsed with deionized water until the washing solution was neutral, and then vacuum dried at 80°C for 24 h to obtain carbon material.

[0043] Example 3 (1) After soaking and washing camphor sawdust with deionized water, the sawdust and deionized water were separated by a vacuum filter and the washed sawdust was vacuum dried at 110°C for 6 hours to obtain pretreated camphor sawdust.

[0044] (2) Prepare a 0.3 mol / L acetate-sodium acetate buffer solution, and adjust the pH of the buffer solution to 5.0 using glacial acetic acid to obtain an enzyme-catalyzed buffer solution to provide an environment for the enzyme-catalyzed reaction.

[0045] (3) Add the buffer, cellulase and camphor sawdust in a ratio of 30mL:0.4g:2g (30mL buffer, 0.4g cellulase and 2g camphor sawdust) into a wide-mouth bottle, seal it and incubate it at 50℃ for 24h.

[0046] (4) The buffer solution after 24 hours of incubation was directly placed into a hydrothermal reactor with camphor sawdust and cellulase without any treatment, and the mixture was hydrothermally reacted at 160°C for 6 hours. After natural cooling, the mixture was filtered to remove the buffer solution, and the mixture was rinsed several times with deionized water. The mixture on the filter membrane was collected and dried at 80°C for 24 hours.

[0047] (5) Mix the mixture on the filter membrane with potassium dihydrogen phosphate (mass ratio 1:1) and grind thoroughly. (6) The blend of the ground enzymatically hydrolyzed sawdust and potassium dihydrogen phosphate was placed in a tube furnace and heated to 400°C at a nitrogen flow rate of 0.3 L / min and a heating rate of 10°C / min. The temperature was maintained for 0.5 h, and then heated to 800°C at a heating rate of 5°C / min and maintained for 3 h. The material was then naturally cooled to room temperature. The cooled material was soaked in 0.1 M HCl for 1 h, rinsed with deionized water until the washing solution was neutral, and then vacuum dried at 80°C for 24 h to obtain carbon material.

[0048] Example 4 (1) After soaking and washing larch sawdust with deionized water, the sawdust was separated from the deionized water by a vacuum filter and the washed sawdust was vacuum dried at 110°C for 6 hours to obtain pretreated larch sawdust.

[0049] (2) Prepare a 0.3 mol / L acetate-sodium acetate buffer solution, and adjust the pH of the buffer solution to 5.0 using glacial acetic acid to obtain an enzyme-catalyzed buffer solution to provide an environment for the enzyme-catalyzed reaction.

[0050] (3) Add the buffer, cellulase and larch sawdust in a ratio of 20mL:0.1g:1g (20mL buffer, 0.1g cellulase and 1g larch sawdust) into a wide-mouth bottle, seal it and incubate it at 50℃ for 24h.

[0051] (4) The buffer solution after 24 hours of incubation was directly placed into a hydrothermal reactor with the mixture of larch sawdust and cellulase without any treatment, and the mixture was hydrothermally reacted at 200°C for 6 hours. After natural cooling, the mixture was filtered to remove the buffer solution, and the mixture was rinsed several times with deionized water. The mixture on the filter membrane was collected and dried at 80°C for 24 hours.

[0052] (5) Mix the mixture on the filter membrane with potassium dihydrogen phosphate (mass ratio 1:2) and grind thoroughly. (6) The blend of the ground enzymatically hydrolyzed sawdust and potassium dihydrogen phosphate was placed in a tube furnace and heated to 250°C at a nitrogen flow rate of 0.3 L / min and a heating rate of 10°C / min. The temperature was maintained for 0.5 h, and then heated to 800°C at a heating rate of 5°C / min and maintained for 3 h. The material was then naturally cooled to room temperature. The cooled material was soaked in 0.1 M HCl for 1 h, rinsed with deionized water until the washing solution was neutral, and then vacuum dried at 80°C for 24 h to obtain carbon material.

[0053] Example 5 (1) After the corn stalks are crushed to 20 mesh, they are soaked and washed with deionized water. Then, the stalks are separated from the deionized water using a vacuum filter. The washed stalks are then vacuum dried at 110°C for 6 hours to obtain pretreated corn stalks.

[0054] (2) Prepare a 0.22 mol / L acetate-sodium acetate buffer solution, and adjust the pH of the buffer solution to 4.7 using glacial acetic acid to obtain an enzyme-catalyzed buffer solution to provide an environment for the enzyme-catalyzed reaction.

[0055] (3) Add the buffer, cellulase and corn stalks in a wide-mouth bottle at a ratio of 20mL:0.1g:1g (20mL buffer, 0.1g cellulase and 1g corn stalks), seal and incubate at 50℃ for 24h.

[0056] (4) The buffer solution after 24 hours of culture was directly loaded into a hydrothermal reactor without any treatment and reacted at 180°C for 6 hours. After natural cooling, the mixture was filtered to remove the buffer solution and rinsed several times with deionized water. The mixture on the filter membrane was collected and dried at 80°C for 24 hours.

[0057] (5) Mix the mixture on the filter membrane with potassium dihydrogen phosphate (mass ratio 1:1) and grind thoroughly. (6) The blend of ground enzyme-treated corn stalks and potassium dihydrogen phosphate was placed in a tube furnace and heated to 400°C at a nitrogen flow rate of 0.3 L / min and a heating rate of 10°C / min. The temperature was maintained for 0.5 h, and then heated to 800°C at a heating rate of 5°C / min and maintained for 3 h. The material was then naturally cooled to room temperature. The cooled material was soaked in 0.1 M HCl for 1 h, rinsed with deionized water until the washing solution was neutral, and then vacuum dried at 80°C for 24 h to obtain carbon material.

[0058] Example 6 (1) The 40-mesh bamboo powder was soaked and washed with deionized water and then separated from the deionized water by a vacuum filter. The washed bamboo powder was then vacuum dried at 60°C for 6 hours to obtain pretreated bamboo powder.

[0059] (2) Prepare a 0.3 mol / L acetate-sodium acetate buffer solution, and adjust the pH of the buffer solution to 4.6 using glacial acetic acid to obtain an enzyme buffer solution to provide an environment for the enzyme reaction.

[0060] (3) Add the buffer, cellulase and bamboo powder in a ratio of 20mL:0.1g:1g (20mL buffer, 0.1g cellulase and 1g bamboo powder) into a wide-mouth bottle, seal it and incubate it at 55℃ for 30h.

[0061] (4) The buffer solution after 30 hours of incubation was directly loaded into a hydrothermal reactor without any treatment, along with the mixture of bamboo powder and cellulase. The mixture was then hydrothermally reacted at 180°C for 6 hours. After natural cooling, the mixture was filtered to remove the buffer solution, and then rinsed several times with deionized water. The mixture on the filter membrane was collected and dried at 60°C for 24 hours.

[0062] (5) Mix the mixture on the filter membrane with potassium dihydrogen phosphate (mass ratio 1:2) and grind thoroughly. (6) The blend of enzyme-treated bamboo powder and potassium dihydrogen phosphate after grinding was placed in a tube furnace and heated to 400°C at a nitrogen flow rate of 0.3 L / min and a heating rate of 10°C / min. It was held for 0.5 h, then heated to 800°C at a heating rate of 5°C / min and held for 3 h. After that, it was naturally cooled to room temperature. The cooled material was taken out and soaked in 0.1 M HCl for 1 h, rinsed with deionized water until the washing solution was neutral, and then vacuum dried at 60°C for 24 h to obtain carbon material.

[0063] Example 7 (1) After soaking and washing the 40-mesh rice straw with deionized water, the rice straw was separated from the deionized water using a vacuum filter. The washed rice straw was then vacuum dried at 60°C for 6 hours to obtain pretreated rice straw.

[0064] (2) Prepare a 0.3 mol / L acetate-sodium acetate buffer solution, and adjust the pH of the buffer solution to 4.6 using glacial acetic acid to obtain an enzyme buffer solution to provide an environment for the enzyme reaction.

[0065] (3) Add the buffer, cellulase and rice straw in a wide-mouth bottle at a ratio of 20 mL: 0.4 g: 2 g (20 mL buffer, 0.4 g cellulase and 2 g rice straw), seal and incubate at 55 °C for 20 h.

[0066] (4) The buffer solution after 30 hours of culture was directly loaded into a hydrothermal reactor without any treatment and reacted at 180°C for 6 hours. After natural cooling, the mixture was filtered to remove the buffer solution and rinsed several times with deionized water. The mixture on the filter membrane was collected and dried at 60°C for 24 hours.

[0067] (5) Mix the mixture on the filter membrane with potassium dihydrogen phosphate (mass ratio 1:2) and grind thoroughly. (6) The blend of enzyme-treated rice straw and potassium dihydrogen phosphate after grinding was placed in a tube furnace and heated to 350°C at a nitrogen flow rate of 0.3 L / min and a heating rate of 5°C / min, and held for 0.5 h. Then the temperature was increased to 800°C at a heating rate of 5°C / min and held for 1.5 h. After that, it was naturally cooled to room temperature. The cooled material was taken out and soaked in 0.1 M HCl for 1.5 h. It was rinsed with deionized water until the washing solution was neutral and then vacuum dried at 80°C for 36 h to obtain carbon material.

[0068] Example 8 (1) After soaking and washing the 60-mesh coconut shell powder with deionized water, the coconut shell powder and deionized water were separated by a vacuum filter. The washed coconut shell powder was then vacuum dried at 60°C for 6 hours to obtain pretreated coconut shell powder.

[0069] (2) Prepare a 0.2 mol / L acetate-sodium acetate buffer solution, and adjust the pH of the buffer solution to 5.0 using glacial acetic acid to obtain an enzyme-catalyzed buffer solution to provide an environment for the enzyme-catalyzed reaction.

[0070] (3) Add the buffer, cellulase and coconut shell powder in a wide-mouth bottle at a ratio of 40mL:0.2g:1g (40mL buffer, 0.2g cellulase and 1g coconut shell powder), seal and incubate at 50℃ for 24h.

[0071] (4) The buffer solution after 24 hours of incubation was directly placed into a hydrothermal reactor without any treatment and reacted at 160°C for 4 hours. After natural cooling, the mixture was filtered to remove the buffer solution and rinsed several times with deionized water. The mixture on the filter membrane was collected and dried at 60°C for 24 hours.

[0072] (5) Mix the mixture on the filter membrane with potassium dihydrogen phosphate (mass ratio 1:1.5) and grind thoroughly. (6) The blend of enzyme-treated coconut shell powder and potassium dihydrogen phosphate after grinding was placed in a tube furnace and heated to 350°C at a nitrogen flow rate of 0.4 L / min and a heating rate of 5°C / min, and held for 1 h. Then, the temperature was increased to 800°C at a heating rate of 10°C / min and held for 1.5 h. After that, it was naturally cooled to room temperature. The cooled material was taken out and soaked in 0.1 M HCl for 3 h. It was rinsed with deionized water until the washing solution was neutral and then vacuum dried at 60°C for 24 h to obtain carbon material.

[0073] Example 9 (1) After soaking and washing the cotton fibers with deionized water, the cotton fibers are separated from the deionized water by a vacuum filter and the washed cotton fibers are vacuum dried at 60°C for 6 hours to obtain pretreated cotton fibers.

[0074] (2) Prepare a 0.2 mol / L acetate-sodium acetate buffer solution, and adjust the pH of the buffer solution to 5.0 using glacial acetic acid to obtain an enzyme-catalyzed buffer solution to provide an environment for the enzyme-catalyzed reaction.

[0075] (3) Add the buffer, cellulase and cotton fiber in a wide-mouth bottle at a ratio of 40mL:0.2g:1g (40mL buffer, 0.2g cellulase and 1g cotton fiber), seal and incubate at 50℃ for 24h.

[0076] (4) The mixture of buffer solution after 24 hours of culture with cotton fibers and cellulase was directly placed into a hydrothermal reactor without any treatment and reacted hydrothermally at 160°C for 4 hours. After natural cooling, the mixture was filtered to remove the buffer solution and rinsed several times with deionized water. The mixture on the filter membrane was collected and dried at 60°C for 24 hours.

[0077] (5) Mix the mixture on the filter membrane with potassium dihydrogen phosphate (mass ratio 1:1.5) and grind thoroughly. (6) The blend of enzyme-treated cotton fiber and potassium dihydrogen phosphate after grinding was placed in a tube furnace and heated to 350°C at a nitrogen flow rate of 0.4 L / min and a heating rate of 5°C / min, and held for 1 h. Then the temperature was increased to 800°C at a heating rate of 10°C / min and held for 1.5 h. After that, it was naturally cooled to room temperature. The cooled material was taken out and soaked in 0.1 M HCl for 3 h. It was rinsed with deionized water until the washing solution was neutral and then vacuum dried at 60°C for 24 h to obtain carbon material.

[0078] Example 10 (1) After soaking and washing the pulp fibers with deionized water, the pulp fibers are separated from the deionized water using a vacuum filter device, and the washed pulp fibers are vacuum dried at 60°C for 6 hours to obtain pretreated pulp fibers.

[0079] (2) Prepare a 0.2 mol / L acetate-sodium acetate buffer solution, and adjust the pH of the buffer solution to 5.0 using glacial acetic acid to obtain an enzyme-catalyzed buffer solution to provide an environment for the enzyme-catalyzed reaction.

[0080] (3) Add the buffer, cellulase and pulp fiber in a wide-mouth bottle at a ratio of 20mL:0.1g:1g (20mL buffer, 0.1g cellulase and 1g pulp fiber), seal and incubate at 50℃ for 24h.

[0081] (4) The buffer solution after 24 hours of incubation was directly loaded into a hydrothermal reactor without any treatment and reacted at 160°C for 4 hours. After natural cooling, the mixture was filtered to remove the buffer solution and rinsed several times with deionized water. The mixture on the filter membrane was collected and dried at 60°C for 24 hours.

[0082] (5) Mix the mixture on the filter membrane with potassium dihydrogen phosphate (mass ratio 1:1.5) and grind thoroughly. (6) The blend of the ground enzyme-treated pulp fiber and potassium dihydrogen phosphate was placed in a tube furnace and heated to 350°C at a nitrogen flow rate of 0.4 L / min and a heating rate of 5°C / min, and held for 1 h. Then the temperature was increased to 800°C at a heating rate of 10°C / min and held for 1.5 h. After that, it was naturally cooled to room temperature. The cooled material was taken out and soaked in 0.1 M HCl for 3 h. It was rinsed with deionized water until the washing solution was neutral and then vacuum dried at 60°C for 24 h to obtain carbon material.

[0083] Example 11 (1) After soaking and washing the 60-mesh coconut shell powder with deionized water, the coconut shell powder and deionized water were separated by a vacuum filter. The washed pulp fibers were then vacuum dried at 60°C for 6 hours to obtain pretreated coconut shell powder.

[0084] (2) Prepare a 0.2 mol / L acetate-sodium acetate buffer solution, and adjust the pH of the buffer solution to 5.0 using glacial acetic acid to obtain an enzyme-catalyzed buffer solution to provide an environment for the enzyme-catalyzed reaction.

[0085] (3) Add the buffer, cellulase and pulp fiber in a wide-mouth bottle at a ratio of 20mL:0.1g:1g (20mL buffer, 0.1g cellulase and 1g pulp fiber), seal and incubate at 50℃ for 24h.

[0086] (4) The buffer solution after 24 hours of incubation was directly placed into a hydrothermal reactor without any treatment and reacted at 160°C for 4 hours. After natural cooling, the mixture was filtered to remove the buffer solution and rinsed several times with deionized water. The mixture on the filter membrane was collected and dried at 60°C for 24 hours.

[0087] (5) Mix the mixture on the filter membrane with ammonium dihydrogen phosphate (mass ratio 1:1.5) and grind thoroughly. (6) The blend of the ground enzyme-treated pulp fiber and ammonium dihydrogen phosphate was placed in a tube furnace and heated to 250°C at a nitrogen flow rate of 0.4 L / min and a heating rate of 5°C / min, and held for 1 h. Then the temperature was increased to 800°C at a heating rate of 10°C / min and held for 1.5 h. After that, it was naturally cooled to room temperature. The cooled material was taken out and soaked in 0.1 M HCl for 3 h. It was rinsed with deionized water until the washing solution was neutral and then vacuum dried at 60°C for 24 h to obtain carbon material.

[0088] Example 12 This embodiment prepares carbon materials similar to those in Example 1, except that potassium dihydrogen phosphate in steps (5) and (6) is replaced with ammonium dihydrogen phosphate, while the rest of the process is exactly the same.

[0089] Comparative Example 1 This comparative example prepares carbon materials similar to those in Example 1, except that cellulase is not added in step (3) and potassium dihydrogen phosphate is not added in step (5), while the rest of the process is exactly the same.

[0090] Comparative Example 2 This comparative example prepares carbon materials similar to those in Example 1, except that potassium dihydrogen phosphate is not added in step (5), while the rest of the process is exactly the same.

[0091] Comparative Example 3 The carbon material prepared in this comparative example is similar to that in Example 1, except that cellulase is not added in step (3), while the rest of the process is exactly the same.

[0092] Comparative Example 4 The carbon material prepared in this comparative example is similar to that in Example 1. The difference is that step (6) does not involve stepwise carbonization. Instead, the carbonization is carried out directly at a heating rate of 5°C / min to 800°C. The rest of the process is exactly the same.

[0093] Comparative Example 5 The comparative example prepares carbon materials similar to those in Example 1, except that step (4) of the hydrothermal reaction is omitted, while the rest of the process is exactly the same.

[0094] Comparative Example 6 The carbon material prepared in this comparative example is similar to that in Example 1, except that the enzymatic hydrolysis processes in steps (2) and (3) are omitted, while the rest of the process is exactly the same.

[0095] Test 1, Characterization: Figure 1 The images shown are characterization diagrams of the materials described in Example 1, where (a) to (c) are SEM images of elm sawdust without any treatment, (d) to (f) are SEM images of the products after enzymatic hydrolysis, (g) to (i) are SEM images of the products after hydrothermal reaction, (j) to (l) are SEM images of the biomass-derived carbon materials prepared in Example 1, and (m) to (r) are elemental mapping diagrams of the biomass-derived carbon materials prepared in Example 1.

[0096] Depend on Figure 1 As shown in (a) to (c), the internal pores of untreated elm fibers are smooth with few surface pores. After cellulase treatment, the surface of the elm fibers becomes rougher, and dotted protrusions or curls appear inside the tube walls, thus increasing the specific surface area of ​​the material. After hydrothermal treatment, the surface of the material becomes even rougher, and the glucose and cellobiose hydrolyzed by cellulase are hydrothermally caramelized and aggregated on the wood, resulting in a large number of grape-like aggregates. Subsequent treatment with potassium dihydrogen phosphate further roughens the surface, significantly increasing the specific surface area. The elemental mapping diagram shows that after the above treatments, a carbon material containing a large number of heteroatoms is obtained, which is beneficial for enhancing the electrochemical performance and the chemisorption during the adsorption process.

[0097] Test 2, Elemental Analysis: Table 1. Element content (mass fraction) of carbon materials prepared in Examples 1-12 and Comparative Examples 1-6 Figure 8 This is a high-resolution N 1s spectrum of the carbon material prepared in Example 1. Figure 9 This is a high-resolution spectrum of the O1s of the carbon material prepared in Example 1. Figure 10 This is a high-resolution spectrum of the P 2p of the carbon material prepared in Example 1.

[0098] Combined with Table 1, Figures 8-10 The following conclusions can be drawn: Sources of nitrogen (N): Figure 8The (N 1s spectrum) shows that the material contains various nitrogen doping forms, such as pyrrole nitrogen and pyridine nitrogen. Combined with the N content (1.96~4.86%) in Table 1, and the differences in nitrogen content between Example 1 and Comparative Example 1 and Comparative Example 2, this indicates that cellulase was successfully introduced into the material as a biological nitrogen source during the hydrothermal process, achieving green and uniform nitrogen doping. Meanwhile, the differences in nitrogen content between Example 1 and Comparative Example 3 demonstrate that potassium dihydrogen phosphate or ammonium dihydrogen phosphate can introduce additional nitrogen on top of cellulase.

[0099] Sources of phosphorus (P): Figure 10 The (P 2p spectrum) shows that P exists in the form of PO, P=O, etc. Combined with the P element content (3.51~6.34%) in Table 1, and the difference in P element between Example 1 and Comparative Example 2, it can be seen that potassium dihydrogen phosphate or ammonium dihydrogen phosphate successfully introduces phosphorus element during the activation process, which enhances the chemical activity and surface polarity of the material.

[0100] Furthermore, the nitrogen and phosphorus content of Examples 12 and 1 demonstrates that potassium dihydrogen phosphate or ammonium dihydrogen phosphate produces similar effects in the field of heteroatom doping, proving their substitutability.

[0101] Synergistic effects of heteroatoms: The coexistence of heteroatoms such as N and P (Table 1) helps improve the conductivity, wettability, and pseudocapacitive activity of materials, enhancing their performance in electrochemistry and adsorption. Specifically, this is achieved through the synergistic effect of controllably introduced nitrogen and phosphorus heteroatoms. Nitrogen atoms are mainly doped in the form of pyridine nitrogen, pyrrole nitrogen, graphitic nitrogen, and nitrogen oxides, inducing electron-deficient regions in the carbon framework, forming n-type semiconductor characteristics, increasing carrier concentration and electron mobility, and providing Lewis basic active sites. Phosphorus atoms are introduced through PC and PO bonds; their larger atomic radius leads to lattice distortion and increases interlayer spacing, forming a p-type doping effect and providing lone pairs of electrons, promoting ion diffusion and charge transfer.

[0102] Heteroatom co-doping in materials induces charge redistribution and Fermi level modulation on the surface and in the bulk, constructing electron donor-acceptor pairs in the carbon matrix and optimizing the energy barrier for redox reactions. In electrochemical applications, nitrogen and phosphorus functional groups contribute reversible pseudocapacitive reactions (such as the redox reaction of pyridine nitrogen and P). 3+ / P 5+ The doping process transforms the material into a polar surface and defect sites that significantly enhance the binding energy and selective adsorption capacity for polar molecules (such as methylene blue). This synergistic modification mechanism effectively improves the specific capacity and rate performance of the material in energy storage devices.

[0103] Test 3, Specific Surface Area and Pore Size Analysis: Figure 2The nitrogen adsorption-desorption curves are for the biomass-derived carbon materials prepared in Example 1 and Comparative Example 1. Figure 3 The pore size distribution diagrams are for the biomass-derived carbon materials prepared in Example 1 and Comparative Example 1.

[0104] Depend on Figure 3 It can be seen that the number of micropores (pore size less than 2 nm) in the carbon material of Example 1 is significantly increased compared with that of Comparative Example 1, indicating that the cellulase treatment, combined with the hydrothermal reaction process and the activation by potassium dihydrogen phosphate, greatly increases the number of micropores in the material, thereby increasing the specific surface area of ​​the material. Figure 2 The nitrogen adsorption-desorption curves of Example 1 and Comparative Example 1 show that they are both type I adsorption-desorption curves, indicating that the material is predominantly microporous.

[0105] The specific surface areas of the carbon materials prepared in each embodiment and comparative example are shown in Table 2.

[0106] Table 2. Specific surface area of ​​carbon materials prepared in Examples 1-12 and Comparative Examples 1-6 Combined with Table 2, Figure 2 and Figure 3 The following conclusions can be drawn: Micropore-dominated structure: Figure 2 The nitrogen adsorption-desorption curves of Example 1 and Comparative Example 1 are both of type I, indicating that the material is mainly composed of microporous structure.

[0107] Cellulase and hydrothermal synergistic pore-forming: Figure 3 The number of micropores in Example 1 is significantly greater than that in Comparative Example 1, indicating that the enzymatic hydrolysis-hydrothermal process effectively creates micropores and initially increases the specific surface area.

[0108] Activator further expands pores: Example 1 Specific surface area (947.52m²) 2 The concentration of 593.75 m³ / g was significantly higher than that of Comparative Example 2 (593.75 m³ / g). 2 The figure ( / g) indicates that activation with potassium dihydrogen phosphate significantly increases the specific surface area and porosity.

[0109] Overall synergistic effect: The specific surface area of ​​Examples 1-12 is ≥899m². 2 / g (Table 2) indicates that the three-step process of enzymatic hydrolysis + hydrothermal treatment + activation synergistically constructs a high specific surface area hierarchical porous structure.

[0110] Test 4, Electrochemical Performance Test: The carbon materials prepared in each example and comparative example were uniformly mixed with acetylene black (conductive carrier) and polytetrafluoroethylene (PTFE, binder) in ethanol at a specific mass ratio of 8:1:1 and ultrasonically treated for 60 min. The well-dispersed slurry was then coated onto nickel foam, vacuum dried at 110 °C for 6 h, and then bonded to the nickel foam under pressure at 10 MPa. Two electrodes of identical mass were assembled into a CR2032 battery in an Ar atmosphere in a glove box. The electrolyte was a 1 M / L Na2SO4 solution, and the test voltage window was 0–1.8 V. The test results are shown in Table 3.

[0111] Table 3. Specific capacitance, energy density, and power density of the carbon materials prepared in Examples 1-12 and Comparative Examples 1-6 Figure 4 The GCD curve of the carbon material prepared in Example 1 is shown in a two-electrode system. Figure 5 The CV curve of the carbon material prepared in Example 1 in a two-electrode system. Figure 6 The GCD curves of the carbon materials prepared in Examples 1, 1, 2, and 3 under a two-electrode system during the iteration process at a current density of 0.5 A / g are shown.

[0112] Combined with Table 3, Figures 4-6 The following conclusions can be drawn: High specific capacitance and energy density: The specific capacitance (171.48~210.94F / g) and energy density (77.16~81.79Wh / kg) of Examples 1~12 were significantly higher than those of all comparative examples (Table 3).

[0113] The key role of cellulase: The specific capacitance of both Comparative Example 2 (without activator) and Comparative Example 3 (without enzyme) was significantly lower than that of Example 1, indicating that cellulase is not only a nitrogen source, but also enhances electrochemical performance by creating pores.

[0114] The importance of activators: Comparative Example 1 (no enzyme, no activator) has a specific capacitance of only 7.87 F / g, indicating that activators are key to constructing highly conductive and highly active carbon structures.

[0115] Advantages of stepwise carbonization: The specific capacitance of Comparative Example 4 (without stepwise carbonization) is lower than that of Example 1, indicating that stepwise carbonization is beneficial for the activator to fully interact with the material.

[0116] Test 5, Methylene Blue Adsorption Experiment: Take 100 mL of 100 mg / L methylene blue solution, add 40 mg of the carbon material prepared in each example and comparative example, and place in a shaker at 100 r / min for 3 h at 25 °C. Then place in a high-speed centrifuge and centrifuge at 10000 r / min for 3 min. Take the supernatant and place it in a UV spectrophotometer to calculate the adsorption performance of the carbon material.

[0117] Table 4. Adsorption capacity of carbon materials prepared in Examples 1-12 and Comparative Examples 1-6 Figure 7 The ultraviolet absorbance curve of the carbon material prepared in Example 1 after adsorbing methylene blue.

[0118] Combine Table 4 and Figure 7 The following conclusions can be drawn: High adsorption capacity: The adsorption capacity of methylene blue in Examples 1-12 (233.46-298.71 mg / g) was much higher than that in all comparative examples (Table 4).

[0119] Heteroatom-enhanced adsorption: The adsorption capacity of Example 1 (249.78 mg / g) was significantly higher than that of Comparative Example 2 (160.51 mg / g), indicating that N and P doping enhanced the chemical adsorption capacity of the material.

[0120] Specific surface area is positively correlated with adsorption: Example 8 has the highest specific surface area (1084.65 m²). 2 The adsorption capacity was also relatively high (283.64 mg / g), indicating that the high specific surface area provides more physical adsorption sites.

[0121] Synergistic effect of enzyme and hydrothermal: The adsorption amounts of Comparative Example 5 (without hydrothermal) and Comparative Example 6 (without enzymatic hydrolysis) were both lower than those of Example 1, indicating that the enzymatic hydrolysis-hydrothermal process synergistically improves the adsorption performance of the material.

[0122] The test results above show that the three steps of "enzymatic hydrolysis-hydrothermal activation" are indispensable; the absence of any step (Comparative Examples 1-6) leads to a significant decrease in performance. Enzymatic hydrolysis initially creates pores, hydrothermal activation introduces a nitrogen source, and activator expands pores and introduces phosphorus, synergistically constructing carbon materials with high specific surface area, hierarchical pores, and heteroatom doping. The carbon materials prepared by the method described in this invention exhibit excellent performance in supercapacitors (high specific capacitance, high energy density) and water treatment (high adsorption capacity).

[0123] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0124] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing biomass-derived carbon materials utilizing the entire enzymatic reaction process, characterized in that, Includes the following steps: Cellulase was added to a buffer solution with pH 4.6–5.0 to carry out enzymatic hydrolysis of cellulose-based biomass raw materials to obtain enzymatic hydrolysis products; the enzymatic hydrolysis products were directly subjected to hydrothermal reaction and then filtered using a filter membrane; the mixture on the filter membrane was mixed with an activator and ground to obtain enzymatically hydrolyzed sawdust; The enzymatically hydrolyzed sawdust is carbonized in steps, followed by acid leaching, water washing, and drying to obtain the biomass-derived carbon material.

2. The preparation method according to claim 1, characterized in that, The cellulose-based biomass raw materials include at least one of wood sawdust, straw, cotton and linen, bamboo powder, coconut shell powder, and pulp fiber.

3. The preparation method according to claim 1, characterized in that, The ratio of the buffer solution, cellulase, and cellulose-based biomass raw material is 20-50 mL: 0.05-0.4 g: 1-3 g.

4. The preparation method according to claim 1, characterized in that, The enzymatic hydrolysis reaction is carried out at a temperature of 45-55℃ for 20-30 hours.

5. The preparation method according to claim 1, characterized in that, The hydrothermal reaction is carried out at a temperature of 160-200℃ for 4-8 hours.

6. The preparation method according to claim 1, characterized in that, Before the mixture on the filter membrane is mixed and ground with the activator, the process further includes a drying step; the mass ratio of the mixture on the dried filter membrane to the activator is 1:1~2; and / or, the activator includes potassium dihydrogen phosphate or ammonium dihydrogen phosphate.

7. The preparation method according to claim 1, characterized in that, The stepwise carbonization includes: first, low-temperature carbonization under a nitrogen atmosphere, followed by high-temperature carbonization; the low-temperature carbonization involves heating to 250-400℃ at a heating rate of 5-10℃ / min and holding at that temperature for 0.5-1h, and the high-temperature carbonization involves heating to 700-800℃ at a heating rate of 5℃ / min and holding at that temperature for 1.5-3h.

8. The biomass-derived carbon material prepared by the preparation method according to any one of claims 1 to 7, characterized in that, The specific surface area of ​​the biomass-derived carbon material is ≥899m². 2 / g, the biomass-derived carbon material is doped with nitrogen and phosphorus.

9. The application of the biomass-derived carbon material as described in claim 8 in supercapacitors.

10. The application of the biomass-derived carbon material according to claim 8 in water treatment.

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