Biomass carbon material as well as preparation method and application thereof

Abstract

The invention relates to the field of agricultural ecology and the field of environmental protection, in particular to a biomass carbon material and a preparation method and application thereof.Biomass is treated, namely before pyrolysis, the biomass is soaked and stirred with absolute ethyl alcohol and rapidly evaporated at the temperature exceeding the boiling point of the absolute ethyl alcohol, and the biomass carbon material is obtained; after drying, ball-milling and mixing with an alkaline substance according to a certain proportion, and then carrying out high-temperature pyrolysis to achieve the effects of expanding a pore structure and reinforcing a carbon frame structure, so that the adsorption effect is improved.

Description

Technical Field

[0001] The present invention relates to the fields of agricultural ecology and environmental protection, and in particular to a biomass carbon material and a preparation method and application thereof. Background Art

[0002] The pace of climate change heralds an era of research and technology. Climate change leads to the production of greenhouse gases. In order to solve the problems related to greenhouse gas emissions and the growing energy demand caused by the depletion of fossil fuel reserves, harmful emissions of fossil fuels should be reduced by using renewable resources in electricity production and effectively utilizing waste resources. Converting biomass and other organic and inorganic wastes into fuels and other products that can add value to society and the economy is a potential solution to this problem. Various industries are working to reduce their dependence on petrochemical and petroleum-based industrial components and replace them with bio-based, sustainable and environmentally friendly alternatives. Among them, biomass waste has attracted much attention due to its renewable, environmentally friendly and wide range of sources.

[0003] Pyrolysis has emerged as the most cost-effective, scalable and simplest technology to date to convert biomass and other feedstocks into energy and other usable by-products. Pyrolysis is the thermal decomposition of biomass under oxygen-deficient conditions. Biomass pyrolysis technology is a cost-effective, scalable and simplest carbonization technology to convert biomass into energy and other usable by-products. Conventional pyrolysis is widely used for valorization of agricultural, forest and plastic wastes. The heating mechanism of the process is non-target selective, and the reactor receives heat energy from the heating source through conduction and radiation. The pyrolysis process conditions have a significant impact on the physicochemical properties, quality and yield of the pyrolysis products.

[0004] At present, biomass materials such as pine cones are mainly disposed of by landfill or direct incineration, which has caused serious environmental pollution and waste of resources. Biochar prepared from biomass materials usually has a high specific surface area and rich pore structure, and has been widely studied as electrodes for supercapacitors and lithium-ion batteries, as well as electrodes for water treatment. At present, existing methods usually directly pyrolyze biomass to prepare carbon materials. However, the specific surface area of ​​the carbon materials produced after direct pyrolysis is low, resulting in poor adsorption effect. Summary of the invention

[0005] In view of the deficiencies of the above-mentioned prior art, the object of the present invention is to provide a biomass carbon material and a preparation method and application thereof. The present invention produces a biomass carbon material by soaking the biomass material in anhydrous ethanol, rapidly evaporating it at a high temperature, and then mixing it with an alkaline substance by ball milling and then pyrolyzing and carbonizing it. The method of the present invention effectively improves the pore structure of the biomass, thereby effectively improving the adsorption effect.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A method for preparing a biomass carbon material comprises the following steps:

[0008] The biomass is pretreated to obtain biomass powder.

[0009] The biomass powder is mixed with ethanol and soaked, then evaporated and dried, and then the dried biomass powder is mixed with an alkaline substance and ball-milled to obtain a mixture.

[0010] The mixture is pyrolyzed and carbonized to obtain a pore-enlarged biomass carbon material.

[0011] The present invention mixes and soaks biomass powder with ethanol, and then places it in an oven with a temperature exceeding the boiling point of the ethanol to make it evaporate quickly. The process of rapid evaporation of ethanol and boiling and splashing of the lower layer of ethanol can make the pore structure of the biomass larger. After reaching the boiling point, the boiling will splash in the beaker. This process expands the pore structure of the biomass from the inside under certain conditions. Then, the dried biomass powder is mixed with an alkaline substance and ball-milled to obtain a mixture; the mixture is pyrolyzed and carbonized to obtain a pore-enlarged biomass, and the soaked biomass is ball-milled and mixed with the alkaline substance, and then carbonized at a high temperature. The coupling effect of the alkaline substance and ethanol can further expand the pore structure and enhance the specific surface area. Carbonization at a high temperature can further reinforce the pore structure formed by the coupling effect, so that the carbon framework structure will not collapse easily, thereby achieving the effect of improving the adsorption effect of the biomass carbon material as an adsorbent.

[0012] In a preferred embodiment of the present invention, the mass ratio of the dried pine cone powder to the alkaline substance is 1:1-8.

[0013] In a preferred embodiment of the present invention, an excess amount of anhydrous ethanol is used to soak and stir the pine cone biomass for 5 to 48 hours to allow the biomass powder to fully contact with the anhydrous ethanol.

[0014] In a preferred embodiment of the present invention, the ball milling time is 10 min to 30 min.

[0015] In a preferred embodiment of the present invention, the pyrolysis carbonization temperature is 500° C. to 1000° C. The pore structure and carbon framework can be further strengthened by carbonizing at high temperature.

[0016] In a preferred embodiment of the present invention, the volume ratio of the biomass powder mass to the ethanol is 50 g to 100 g: 100 mL to 200 mL.

[0017] In a preferred embodiment of the present invention, the alkaline substance is potassium hydroxide, sodium hydroxide or potassium carbonate, and the concentration of the alkaline substance is 95%.

[0018] In a preferred embodiment of the present invention, the biomass is selected from pine cones, rice straw or corn straw.

[0019] In a preferred embodiment of the present invention, the concentration of ethanol is ≥ 99.7%.

[0020] In a preferred embodiment of the present invention, the pine cone powder and an excess of anhydrous ethanol are placed in a high beaker to prevent the pine cone powder from being splashed due to evaporation at high temperature.

[0021] In a preferred embodiment of the present invention, the soaked pine cones are placed in an oven at a temperature greater than the boiling point of anhydrous ethanol, and the temperature range is 80°C to 200°C.

[0022] Another object of the present invention is to provide a biomass carbon material prepared by any of the methods described above.

[0023] The third object of the present invention is to provide an application of the above-mentioned biomass carbon material in adsorbing iodine pollutants.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The present invention provides a method for expanding the pore structure of a biomass material by soaking it in anhydrous ethanol and then mixing it with an alkaline substance by ball milling, followed by pyrolysis and carbonization. The biomass is soaked in anhydrous ethanol and placed in an oven with a temperature exceeding its boiling point to evaporate it quickly. The biomass is then mixed with an alkaline substance by ball milling and placed in a tube furnace for pyrolysis and carbonization. The biomass soaked in ethanol will produce splashing when it reaches the boiling point. This process expands the pore structure of the pine cone from the inside under certain conditions. At the same time, the soaked biomass is mixed with an alkaline substance by ball milling and then carbonized at a high temperature. The coupling effect of the two will not only further expand the pores, but also strengthen the macroporous structure in the early stage, so that the carbon framework structure will not collapse easily, and the adsorption effect is improved by 15% to 30% compared with that of untreated biomass. The adsorption effect of pine cone biochar as an adsorbent is improved by a low-cost and simple method.

[0026] 2. The materials used in the present invention are inexpensive, the preparation method is simple, the adsorption effect is high, and it has certain social and environmental benefits. The method of the present invention is conducive to the development of a more efficient, ecologically friendly and economically viable industrial system. The production of biochar from pine cone biomass can greatly contribute to waste management, soil improvement and carbon sequestration, and promote a sustainable and circular bioeconomy. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the SEM image of pine cone biochar prepared in Example 3 of the present invention.

[0028] Figure 2 Detailed description of the invention is given in Figure 1 for the iodine adsorption of pine cone biochar prepared in Examples 1 to 4 of the present invention. DETAILED DESCRIPTION

[0029] The following is a detailed description of the technical solutions in the embodiments of the present invention in combination with the preferred embodiments and the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] It should be noted that all professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0031] The present invention is based on the existing method that usually directly pyrolyzes biomass to prepare carbon materials. However, the carbon material produced after direct pyrolysis has a low specific surface area, resulting in a poor adsorption effect. A method for expanding the pores of biomass by coupling alkaline materials with ethanol to improve the adsorption effect is proposed. The biomass material is soaked in anhydrous ethanol and quickly evaporated at high temperature, and then ball-milled and mixed with alkaline substances in a certain proportion, followed by pyrolysis and carbonization to expand its pore structure. Before pyrolysis, the biomass is soaked in a high beaker with excess anhydrous ethanol, and then the sample is placed in an oven with a temperature exceeding the boiling point of anhydrous ethanol to make it evaporate quickly. The dried biomass is mixed with alkaline substances in a certain proportion, ball-milled, and then placed in a tubular furnace for pyrolysis and carbonization. The rapid evaporation of anhydrous ethanol and the boiling and splashing of the lower layer of anhydrous ethanol can make the pore structure of the biomass larger. In addition, the coupling effect of alkaline substances and ethanol will further expand the pore structure and enhance the specific surface area. Carbonization at high temperature can further strengthen the pore structure formed by the coupling effect. Through this method, the adsorption effect of biochar as an adsorbent can be improved, which has certain benefits to the environment and society.

[0032] The embodiment of the present invention takes pine cone biomass as an example to illustrate the above content of the present invention, and links pine cone biomass with porous carbon production processed from raw materials, which not only finds a way out for pine cone biomass, but also finds raw materials for material production, with good social and environmental benefits. The current industrial system for producing biochar using pinewood waste shows great potential for improvement. Pine cone biochar is a highly porous carbon-rich material produced by pyrolysis of pine cone biomass. A key point of improvement is to improve the adsorption effect. Technological advances can make the biochar produced by pyrolysis more effective, which will increase biochar production and ensure quality consistency.

[0033] Example 1

[0034] A method for preparing a pine cone biomass carbon material comprises the following steps:

[0035] (1) The pine cone biomass was washed with ultrapure water, dried in an oven at 75° C. for 24 h, crushed and sieved (<200 μm) to obtain pine cone powder.

[0036] (2) soaking the pine cone powder in excess ethanol and stirring and mixing for 5 hours, drying at 75° C. to evaporate the anhydrous ethanol; and ball milling the dried pine cone powder and potassium hydroxide at a mass ratio of 1:1 for 10 minutes.

[0037] (3) The ball-milled sample was placed in an alumina boat and placed in the center of a tube furnace for pyrolysis and carbonization. It was heated to 500 °C at a heating rate of 10 °C / min in a nitrogen atmosphere with a flow rate of 60 mL / min and kept at this temperature for 2 h.

[0038] (4) After the tubular furnace is cooled, ultrapure water is used to wash away the excess components in the biochar until the pH value reaches about 7, and then the biochar is filtered. The filtered biochar is dried in an oven at 75°C for 12 hours to obtain pine cone biochar material.

[0039] Example 2

[0040] A method for preparing a pine cone biomass carbon material comprises the following steps:

[0041] (1) The pine cone biomass was washed with ultrapure water, dried in an oven at 75° C. for 24 h, crushed and sieved (<200 μm) to obtain pine cone powder.

[0042] (2) soaking the pine cone powder in excess ethanol and stirring and mixing for 10 hours, drying at 75° C. to evaporate the anhydrous ethanol; and ball milling the dried pine cone powder and potassium hydroxide at a mass ratio of 1:2 for 10 minutes.

[0043] (3) The ball-milled sample was placed in an alumina boat and placed in the center of a tube furnace for pyrolysis and carbonization. It was heated to 700 °C at a heating rate of 10 °C / min in a nitrogen atmosphere with a flow rate of 60 mL / min and kept at this temperature for 2 h.

[0044] (4) After the tubular furnace is cooled, ultrapure water is used to wash away the excess components in the biochar until the pH value reaches about 7, and then the biochar is filtered. The filtered biochar is dried in an oven at 75°C for 12 hours to obtain pine cone biochar material.

[0045] Example 3

[0046] A method for preparing a pine cone biomass carbon material comprises the following steps:

[0047] (1) The pine cone biomass was washed with ultrapure water, dried in an oven at 75° C. for 24 h, crushed and sieved (<200 μm) to obtain pine cone powder.

[0048] (2) soaking the pine cone powder in excess ethanol and stirring and mixing for 20 hours, drying at 75° C. to evaporate the anhydrous ethanol; and ball milling the dried pine cone powder and potassium hydroxide at a mass ratio of 1:3 for 10 minutes.

[0049] (3) The ball-milled sample was placed in an alumina boat and placed in the center of a tube furnace for pyrolysis and carbonization. It was heated to 800 °C at a heating rate of 10 °C / min in a nitrogen atmosphere with a flow rate of 60 mL / min and kept at this temperature for 2 h.

[0050] (4) After the tubular furnace is cooled, ultrapure water is used to wash away the excess components in the biochar until the pH value reaches about 7, and then the biochar is filtered. The filtered biochar is dried in an oven at 75°C for 12 hours to obtain pine cone biochar material.

[0051] Example 4

[0052] A method for preparing a pine cone biomass carbon material comprises the following steps:

[0053] (1) The pine cone biomass was washed with ultrapure water, dried in an oven at 75° C. for 24 h, crushed and sieved (<200 μm) to obtain pine cone powder.

[0054] (2) soaking the pine cone powder in excess ethanol and stirring and mixing for 48 hours, and then drying at 75° C. to evaporate the anhydrous ethanol; and ball milling the dried pine cone powder and potassium hydroxide at a mass ratio of 1:4 for 10 minutes.

[0055] (3) The ball-milled sample was placed in an alumina boat and placed in the center of a tube furnace for pyrolysis and carbonization. It was heated to 1000 °C at a heating rate of 10 °C / min in a nitrogen atmosphere with a flow rate of 60 mL / min and kept at this temperature for 2 h.

[0056] (4) After the tubular furnace is cooled, ultrapure water is used to wash away the excess components in the biochar until the pH value reaches about 7, and then the biochar is filtered. The filtered biochar is dried in an oven at 75°C for 12 hours to obtain pine cone biochar material.

[0057] Example 5

[0058] A method for preparing a pine cone biomass carbon material comprises the following steps:

[0059] (1) The pine cone biomass was washed with ultrapure water, dried in an oven at 75° C. for 24 h, crushed and sieved (<200 μm) to obtain pine cone powder.

[0060] (2) soaking the pine cone powder in excess ethanol and stirring and mixing for 48 hours, and then drying at 75° C. to evaporate the anhydrous ethanol; and ball milling the dried pine cone powder and potassium hydroxide at a mass ratio of 1:8 for 20 minutes.

[0061] (3) The ball-milled sample was placed in an alumina boat and placed in the center of a tube furnace for pyrolysis and carbonization. It was heated to 1000 °C at a heating rate of 10 °C / min in a nitrogen atmosphere with a flow rate of 60 mL / min and kept at this temperature for 2 h.

[0062] (4) After the tubular furnace is cooled, ultrapure water is used to wash away the excess components in the biochar until the pH value reaches about 7, and then the biochar is filtered. The filtered biochar is dried in an oven at 75°C for 12 hours to obtain pine cone biochar material.

[0063] Example 6

[0064] A method for preparing a pine cone biomass carbon material comprises the following steps:

[0065] (1) The pine cone biomass was washed with ultrapure water, dried in an oven at 75° C. for 24 h, crushed and sieved (<200 μm) to obtain pine cone powder.

[0066] (2) soaking the pine cone powder in excess ethanol and stirring and mixing for 48 hours, and then drying at 75° C. to evaporate the anhydrous ethanol; and ball milling the dried pine cone powder and potassium hydroxide at a mass ratio of 1:6 for 30 minutes.

[0067] (3) The ball-milled sample was placed in an alumina boat and placed in the center of a tube furnace for pyrolysis and carbonization. It was heated to 1000 °C at a heating rate of 10 °C / min in a nitrogen atmosphere with a flow rate of 60 mL / min and kept at this temperature for 2 h.

[0068] (4) After the tubular furnace is cooled, ultrapure water is used to wash away the excess components in the biochar until the pH value reaches about 7, and then the biochar is filtered. The filtered biochar is dried in an oven at 75°C for 12 hours to obtain pine cone biochar material.

[0069] Example 7

[0070] A method for preparing a pine cone biomass carbon material comprises the following steps:

[0071] (1) The pine cone biomass was washed with ultrapure water, dried in an oven at 75° C. for 24 h, crushed and sieved (<200 μm) to obtain pine cone powder.

[0072] (2) soaking the pine cone powder in excess ethanol and stirring and mixing for 5 hours, drying at 75° C. to evaporate the anhydrous ethanol; and ball milling the dried pine cone powder and potassium hydroxide at a mass ratio of 1:5 for 10 minutes.

[0073] (3) The ball-milled sample was placed in an alumina boat and placed in the center of a tube furnace for pyrolysis and carbonization. It was heated to 500 °C at a heating rate of 10 °C / min in a nitrogen atmosphere with a flow rate of 60 mL / min and kept at this temperature for 2 h.

[0074] (4) After the tubular furnace is cooled, ultrapure water is used to wash away the excess components in the biochar until the pH value reaches about 7, and then the biochar is filtered. The filtered biochar is dried in an oven at 75°C for 12 hours to obtain pine cone biochar material.

[0075] Application Example 1

[0076] 0.02 g of the pine cone biochar sample prepared in Example 1 was placed in a glass culture dish together with 0.2 g of excess elemental iodine, and then both were placed in a 250 mL closed container and the container was placed in an oven at 75° C., heated for 6 hours, cooled, and weighed.

[0077] Application Example 2

[0078] 0.02 g of the pine cone biochar sample prepared in Example 2 was placed in a glass culture dish together with 0.2 g of excess elemental iodine, and then both were placed in a 250 mL closed container and the container was placed in an oven at 75° C., heated for 6 hours, cooled, and weighed.

[0079] Application Example 3

[0080] 0.02 g of the pine cone biochar sample prepared in Example 3 was placed in a glass culture dish together with 0.2 g of excess elemental iodine, and then both were placed in a 250 mL closed container and the container was placed in an oven at 75° C., heated for 6 hours, cooled, and weighed.

[0081] Application Example 4

[0082] 0.02 g of the pine cone biochar sample prepared in Example 4 was placed in a glass culture dish together with 0.2 g of excess elemental iodine, and then both were placed in a 250 mL closed container and the container was placed in an oven at 75° C., heated for 6 hours, cooled, and weighed.

[0083] Results Analysis

[0084] Figure 1 This is a SEM image of the pine cone biochar prepared in Example 3 of the present invention. It can be seen from the figure that the pine cone biomass treated with ethanol and potassium hydroxide has a larger pore structure, and the specific surface area of ​​the carbon material produced by direct pyrolysis of the pine cone biomass is 20m 2 / g~300m 2 / g, and the specific surface area after treatment by the method of the present invention is 1000m 2 / g~2500m 2 / g, indicating that the pine cone biochar produced by the method of the present invention has a better adsorption effect.

[0085] Figure 2 The iodine adsorption data of the pine cone biochar prepared in Examples 1 to 4 of the present invention indicate that different mass ratios of the pine cone biomass treated with ethanol and potassium hydroxide have different effects on iodine adsorption.

[0086] In summary, the present invention provides a method for expanding its pore structure by soaking in anhydrous ethanol and rapidly evaporating at high temperature, then mixing with potassium hydroxide in a certain proportion by ball milling, and then pyrolyzing and carbonizing. After the pine cone biomass is soaked in anhydrous ethanol, it is placed in an oven with a temperature exceeding its boiling point to evaporate rapidly, and then mixed with potassium hydroxide by ball milling and placed in a tube furnace for pyrolysis and carbonization. The soaked pine cones will produce splashing when boiling after reaching the boiling point, which can expand its pore structure. At the same time, through the coupling effect of potassium hydroxide and ethanol, the pore structure of the pine cones can be expanded from the inside. The process of pyrolysis and carbonization can not only expand the pore structure, but also further strengthen the carbon frame structure at high temperature. The adsorption effect of the pine cone biochar produced by this method is further improved. The materials used in the present invention are low in price, simple in preparation method, high in adsorption effect, and have certain social and environmental benefits.

[0087] It should be noted that when the present invention involves a numerical range, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes a preferred embodiment. Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the attached claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0088] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing a biomass carbon material, characterized in that: The following steps are involved: pre-treating the biomass to obtain biomass powder; The biomass powder is mixed with ethanol and soaked, then evaporated and dried, and the dried biomass powder is mixed with an alkaline substance and ball-milled to obtain a mixture; The mixture is pyrolyzed and carbonized to obtain a pore-enlarged biomass carbon material.

2. The method for preparing biomass carbon material according to claim 1, characterized in that: The mass ratio of the dried biomass powder to the alkaline substance is 1:1-8.

3. The method for preparing biomass carbon material according to claim 1, characterized in that: The ethanol soaking time is 5h to 48h.

4. The method for preparing biomass carbon material according to claim 1, characterized in that: The pyrolysis carbonization temperature is 500°C to 1000°C.

5. The method for preparing biomass carbon material according to claim 1, characterized in that: The ball milling time is 10 min to 30 min.

6. The method for preparing biomass carbon material according to claim 1, characterized in that: The mass ratio of the biomass powder to the volume of ethanol is 50g-100g:100mL-200mL.

7. The method for preparing biomass carbon material according to claim 1, characterized in that: The alkaline substance is potassium hydroxide, sodium hydroxide or potassium carbonate.

8. The method for preparing biomass carbon material according to claim 1, characterized in that: The biomass is selected from pine cones, rice straw or corn straw.

9. A biomass carbon material obtained by the method according to any one of claims 1 to 8.

10. Use of the biomass carbon material according to claim 9 in adsorbing iodine pollutants.

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