Preparation method of high specific surface area bamboo activated carbon

Abstract

This invention belongs to the technical field of activated carbon and discloses a method for preparing high specific surface area bamboo activated carbon. The method for preparing high specific surface area bamboo activated carbon includes the following steps: (1) carbonizing a powder including fresh bamboo powder to obtain carbon powder; (2) extruding a slurry including carbon powder, tar, and water to obtain a green body; (3) carbonizing the green body to obtain a precursor; (4) activating the precursor to obtain high specific surface area bamboo activated carbon; wherein, the powder also includes desulfurization by-product gypsum; the slurry also includes calcium sulfate powder or desulfurization by-product gypsum. The process of this invention is simple and easy to control, with high production efficiency, green and environmentally friendly raw materials and low cost. It can be implemented directly using equipment from traditional processes. The resulting bamboo activated carbon has a high specific surface area, good adsorption performance, and long lifespan, making it highly practical.

Description

[0001] This application is a divisional application of the invention patent application with application number 2023107362182, application date June 21, 2023, entitled "Preparation method of bamboo activated carbon with high specific surface area and bamboo activated carbon". Technical Field

[0002] This invention relates to the technical field of activated carbon, and more specifically, to a method for preparing high specific surface area bamboo-based activated carbon. Background Technology

[0003] Activated carbon possesses a unique microcrystalline structure, highly developed pores, and a large specific surface area. It exhibits both physical and chemical adsorption properties, selectively adsorbing various substances in both liquid and gas phases. Therefore, it is often used as an excellent adsorbent for decolorization, purification, disinfection, deodorization, and decontamination, and is widely applied in food, beverage, pharmaceutical, water treatment, gas purification and recovery, chemical, metallurgical, and agricultural fields. In recent years, with increasing demands for safety and purity in our living environment, the market demand for activated carbon has continued to expand, with increasingly stringent requirements for its adsorption capacity, controllability, and safety. Consequently, biomass activated carbon, especially bamboo-based activated carbon, has received extensive research due to its abundant and readily available raw materials. Simultaneously, microporous activated carbon, with its superior adsorption performance, has become a key area of ​​development.

[0004] Generally, the higher the specific surface area of ​​activated carbon, the better its adsorption performance. The preparation process of bamboo activated carbon mainly includes batching, kneading, extrusion molding, carbonization, and activation. Among these, the activation process has the most significant impact on the pore structure and specific surface area of ​​activated carbon. Currently, activation methods mainly include physical activation and chemical activation. Chemical activation mainly involves mixing the carbonized material with activating agents such as zinc chloride, phosphoric acid, and nitric acid, followed by heat treatment. The heat treatment temperature varies depending on the activating agent. Chemical activation introduces new chemical reagents, requires a large quantity, and is usually unfriendly to equipment and the environment. It also requires a relatively complex recovery process, which is detrimental to the safe use of activated carbon. Physical activation mainly uses water vapor, carbon dioxide, or a mixture of both as the activation atmosphere, and carries out the carbon oxidation reaction at high temperatures to produce activated carbon with a well-developed fine pore structure. Physical activation does not use chemical reagents, making it more environmentally friendly and currently the most commonly used activation method.

[0005] Currently, the mainstream high specific surface area biomass activated carbon is coconut shell activated carbon. However, coconut shell raw materials are limited and production costs are high. Bamboo activated carbon has abundant raw materials and low production costs, but the specific surface area of ​​bamboo activated carbon prepared by traditional processes is usually below 1000 square meters / gram, making it difficult to produce bamboo activated carbon with a high specific surface area. Summary of the Invention

[0006] The main objective of this invention is to provide a method for preparing high specific surface area bamboo activated carbon and bamboo activated carbon, so as to solve the technical problem of low specific surface area of ​​bamboo activated carbon in the prior art.

[0007] To achieve the above objectives, according to a first aspect of the present invention, a method for preparing high specific surface area bamboo activated carbon is provided, the technical solution of which is as follows:

[0008] A method for preparing high specific surface area bamboo-based activated carbon includes the following steps:

[0009] (1) Carbonize the powder, including fresh bamboo powder, to obtain charcoal powder;

[0010] (2) The slurry containing carbon powder, tar and water is extruded and molded to obtain a green body;

[0011] (3) Carbonize the green body to obtain the precursor;

[0012] (4) The precursor is activated to obtain bamboo activated carbon with high specific surface area.

[0013] The powder and / or slurry also include calcium sulfate powder.

[0014] As a further improvement to the first aspect of the present invention: the calcium sulfate powder is calcium sulfate whisker powder; and / or, the calcium sulfate powder is gypsum produced as a by-product of desulfurization.

[0015] As a further improvement of the first aspect of the present invention: the calcium sulfate whiskers are mainly composed of fibers with a length of 100-460 μm and a width of 12-25 μm.

[0016] As a further improvement of the first aspect of the present invention: the preparation of the calcium sulfate whiskers includes the following steps: adding sulfuric acid to an aqueous dispersion of calcium oxide, and then collecting, washing and drying the precipitate; dispersing the precipitate in sulfuric acid and heating it until the precipitate is completely dissolved, then letting it stand at room temperature until the precipitate precipitates, and then collecting, washing and drying the precipitate to obtain calcium sulfate whiskers.

[0017] As a further improvement of the first aspect of the present invention: when the powder contains calcium sulfate powder, the weight of the calcium sulfate powder is 10 to 15% of the weight of the fresh bamboo powder.

[0018] As a further improvement of the first aspect of the present invention: when the slurry contains calcium sulfate powder, the weight ratio of carbon powder, calcium sulfate powder, tar and water is 100:(7-11):(50-60):(15-30).

[0019] As a further improvement of the first aspect of the present invention: the preparation of the slurry includes the following steps: putting carbon powder and calcium sulfate powder into a mixer and stirring for 5 to 20 minutes to obtain a mixture; putting the mixture into a kneader, first adding tar and kneading for 5 to 15 minutes, then adding pure water and kneading for another 10 to 20 minutes to obtain the slurry.

[0020] As a further improvement of the first aspect of the present invention: the carbonization treatment is performed in an inert atmosphere at 500-600°C for 1-3 hours; the activation treatment is performed in an activating atmosphere at 800-1000°C for 2-4 hours.

[0021] As a further improvement to the first aspect of the invention: the slurry is extruded into spherical, columnar, or honeycomb shapes.

[0022] To achieve the above objectives, according to a second aspect of the present invention, bamboo-based activated carbon is provided, the technical solution of which is as follows:

[0023] Bamboo-based activated carbon is prepared by the preparation method described in the first aspect above; its BET specific surface area is ≥1201.37 m² / g.

[0024] The present invention has the following advantages:

[0025] (1) This invention utilizes the diffusion of carbon dioxide generated by the reaction of calcium sulfate and carbon at high temperature to form abundant pores in the material for pore creation. The calcium sulfate used is a raw material that is friendly to the human body and the environment, and is abundant and inexpensive. A small amount of calcium sulfate can significantly increase porosity. The small amount of calcium sulfide generated is further converted into calcium oxide that is tightly bound to the carbon matrix during the subsequent high-temperature activation process. It can be used as an adsorbent without further treatment.

[0026] (2) When calcium sulfate is made from whisker powder, the whiskers intertwine with other components to form a three-dimensional network structure, which reduces the use of molding additives and allows for a balance between mechanical strength and porosity. When calcium sulfate is made from desulfurization by-product gypsum, it enables high-value secondary recycling of the gypsum, solving the technical problem of limited application of existing gypsum-based desulfurization methods due to the large amount of solid waste. To obtain optimal performance and reduce the cost of using calcium sulfate, it is preferable to use desulfurization by-product gypsum for the powder and calcium sulfate whisker powder for the slurry.

[0027] (3) During the carbonization process, calcium sulfate can react with carbon to create pores without changing the original carbonization process. Furthermore, when a precursor with a certain porosity is activated, the activation effect and activation efficiency can be significantly improved.

[0028] (4) Because fresh bamboo powder is tough and difficult to pulverize into smaller particles, carbonized charcoal powder is usually used as the raw material for pulping. However, charcoal powder has high hardness and requires a long grinding time. In this invention, when fresh bamboo powder and calcium sulfate are carbonized together in one step, charcoal powder with a certain porosity can be obtained, reducing the hardness of the charcoal powder and making it easier to grind into a finer powder. This improves the homogeneity of the pulp, shortens the kneading time, and increases the efficiency of secondary carbonization and activation, thereby improving production efficiency.

[0029] (5) During the kneading process, the carbon powder and calcium sulfate powder are first thoroughly mixed before kneading, which helps the calcium sulfate to react fully with the carbon, improves the uniformity of the pores, and thus improves the mechanical strength.

[0030] It is evident that the preparation method of the high specific surface area bamboo activated carbon of the present invention is simple and easy to control, with high production efficiency, and uses green and environmentally friendly raw materials at low cost. It can be implemented directly using equipment from traditional processes. Verification has shown that the bamboo activated carbon prepared by the above method mainly contains micropores with well-developed and uniform pores, a specific surface area of ​​over 1201.37 m² / g, and good mechanical strength. When used as an adsorbent, it exhibits excellent adsorption performance and a long lifespan. Furthermore, due to its high specific surface area, the bamboo activated carbon of the present invention can also be used as a catalyst carrier. Therefore, the preparation method of the high specific surface area bamboo activated carbon and the bamboo activated carbon itself of the present invention have extremely high practicality.

[0031] The embodiments of the invention provided in this specification will be further described below with reference to the accompanying drawings and specific embodiments. Additional aspects and advantages of the embodiments of the invention provided in this specification will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the embodiments of the invention provided in this specification. Attached Figure Description

[0032] The accompanying drawings, which form part of the embodiments of the invention provided in this specification, are used to aid in understanding the embodiments of the invention provided in this specification. The content provided in the drawings and the related descriptions in the embodiments of the invention provided in this specification can be used to explain the embodiments of the invention provided in this specification, but do not constitute an improper limitation on the embodiments of the invention provided in this specification.

[0033] Figure 1 The graph shows the nitrogen adsorption-desorption curve of the bamboo activated carbon in Example 7.

[0034] Figure 2 This is a pore size distribution curve of the bamboo activated carbon in Example 7.

[0035] Figure 3 This is a scanning electron microscope image of the bamboo activated carbon from Example 7.

[0036] Figure 4 This is a morphological diagram of calcium sulfate whiskers. Detailed Implementation

[0037] The embodiments of the invention provided in this specification will now be clearly and completely described in conjunction with the accompanying drawings. Those skilled in the art will be able to implement the embodiments of the invention provided in this specification based on these descriptions. Before describing the embodiments of the invention provided in this specification in conjunction with the accompanying drawings, it should be particularly noted that:

[0038] The technical solutions and features provided in the embodiments of the invention provided in this specification, including the following description, can be combined with each other without conflict.

[0039] Furthermore, the embodiments of the inventions provided in this specification mentioned below are generally only a portion of the embodiments of the inventions provided in this specification, and not all of them. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the inventions provided in this specification without creative effort should fall within the scope of protection of the embodiments of the inventions provided in this specification.

[0040] Regarding the terminology and units in the embodiments of the invention provided in this specification: The terms "comprising," "including," "having," and any variations thereof in the description, claims, and related parts of the embodiments of the invention provided in this specification are intended to cover non-exclusive inclusion. Furthermore, other relevant terms and units in the embodiments of the invention provided in this specification can be reasonably interpreted based on the relevant content of the embodiments of the invention provided in this specification.

[0041] Example 1

[0042] The preparation method of high specific surface area bamboo activated carbon includes the following steps:

[0043] (1) Fresh bamboo powder was carbonized at 600°C for 2 hours under nitrogen atmosphere to obtain carbon powder.

[0044] (2) The slurry comprising carbon powder, calcium sulfate powder, tar, and water is extruded to obtain a columnar blank with a diameter of 4 mm; wherein,

[0045] The calcium sulfate powder is calcium sulfate whisker powder, mainly composed of fibers with a length of 100-460 μm and a width of 12-25 μm.

[0046] The weight ratio of charcoal powder, calcium sulfate powder, tar, and water is 100:7:55:25.

[0047] The preparation of the slurry includes the following steps: putting carbon powder and calcium sulfate powder into a mixer and stirring for 10 minutes to obtain a mixture; putting the mixture into a kneader with a kneader speed of 30 rpm, first adding tar and kneading for 10 minutes, then adding pure water and kneading for another 15 minutes to obtain the slurry.

[0048] The particle size of the charcoal powder is 200 mesh.

[0049] (3) The green body was carbonized at 600°C for 1 hour under nitrogen atmosphere to obtain the precursor.

[0050] (4) Pass 40 ml / hour of water vapor through each 100 g of precursor and activate the precursor in a water vapor atmosphere at 900 °C for 3 hours to obtain bamboo activated carbon with high specific surface area.

[0051] Example 2

[0052] Compared with Example 1, the difference in the preparation method of this example is that the weight ratio of charcoal powder, calcium sulfate powder, tar and water is 100:9:55:25.

[0053] Example 3

[0054] Compared with Example 1, the preparation method of this example differs in that the weight ratio of charcoal powder, calcium sulfate powder, tar, and water is 100:11:55:25.

[0055] Example 4

[0056] Compared with Example 1, the difference in the preparation method of this example is that the calcium sulfate powder is gypsum, a by-product of desulfurization.

[0057] Example 5

[0058] The preparation method of high specific surface area bamboo activated carbon includes the following steps:

[0059] (1) The powder, including fresh bamboo powder and calcium sulfate powder, is carbonized at 600°C for 2 hours under a nitrogen atmosphere to obtain carbon powder; wherein the calcium sulfate powder is calcium sulfate whisker powder, mainly composed of fibers with a length of 100-460 μm and a width of 12-25 μm; the weight of the calcium sulfate powder is 10% of the weight of the fresh bamboo powder.

[0060] (2) The slurry comprising charcoal powder, tar, and water is extruded to obtain a columnar blank with a diameter of 4 mm; wherein,

[0061] The weight ratio of charcoal powder, tar, and water is 100:55:25.

[0062] The preparation of the slurry includes the following steps: putting carbon powder into a kneader at a speed of 30 rpm, first adding tar and kneading for 10 minutes, then adding pure water and kneading for another 15 minutes to obtain the slurry.

[0063] The particle size of the charcoal powder is 200 mesh.

[0064] (3) The green body was carbonized at 600°C for 1 hour under nitrogen atmosphere to obtain the precursor.

[0065] (4) Pass 40 ml / hour of water vapor through each 100 g of precursor and activate the precursor in a water vapor atmosphere at 900 °C for 3 hours to obtain bamboo activated carbon with high specific surface area.

[0066] Example 6

[0067] Compared with Example 5, the difference in the preparation method of this example is that the weight of calcium sulfate powder is 12% of the weight of fresh bamboo powder.

[0068] Example 7

[0069] Compared with Example 5, the difference in the preparation method of this example is that the weight of calcium sulfate powder is 15% of the weight of fresh bamboo powder.

[0070] Example 8

[0071] Compared with Example 5, the difference in the preparation method of this example is that the calcium sulfate powder is gypsum produced as a by-product of desulfurization.

[0072] Example 9

[0073] The preparation method of high specific surface area bamboo activated carbon includes the following steps:

[0074] (1) The powder, including fresh bamboo powder and calcium sulfate powder, is carbonized at 600°C for 2 hours under a nitrogen atmosphere to obtain carbon powder; wherein the weight of calcium sulfate powder is 12% of the weight of fresh bamboo powder.

[0075] (2) The slurry comprising carbon powder, calcium sulfate powder, tar, and water is extruded to obtain a columnar blank with a diameter of 4 mm; wherein,

[0076] The weight ratio of charcoal powder, calcium sulfate powder, tar, and water is 100:9:55:25.

[0077] The calcium sulfate powder in steps (1) and (2) is calcium sulfate whisker powder, which is mainly composed of fibers with a length of 100-460 μm and a width of 12-25 μm.

[0078] The preparation of the slurry includes the following steps: putting carbon powder and calcium sulfate powder into a mixer and stirring for 10 minutes to obtain a mixture; putting the mixture into a kneader with a kneader speed of 30 rpm, first adding tar and kneading for 10 minutes, then adding pure water and kneading for another 15 minutes to obtain the slurry.

[0079] The particle size of the charcoal powder is 200 mesh.

[0080] (3) The green body was carbonized at 600°C for 1 hour under nitrogen atmosphere to obtain the precursor.

[0081] (4) Pass 40 ml / hour of water vapor through each 100 g of precursor and activate the precursor in a water vapor atmosphere at 900 °C for 3 hours to obtain bamboo activated carbon with high specific surface area.

[0082] Example 10

[0083] Compared with Example 9, the difference in the preparation method of this example is that the calcium sulfate powder in the powder is gypsum produced as a by-product of desulfurization.

[0084] Example 11 (Control Example)

[0085] The preparation method of high specific surface area bamboo activated carbon includes the following steps:

[0086] (1) Fresh bamboo powder was carbonized at 600°C for 2 hours under nitrogen atmosphere to obtain carbon powder.

[0087] (2) The slurry comprising charcoal powder, tar, and water is extruded to obtain a columnar blank with a diameter of 4 mm; wherein,

[0088] The weight ratio of charcoal powder, tar, and water is 100:55:25.

[0089] The preparation of the slurry includes the following steps: putting carbon powder into a kneader at a speed of 30 rpm, first adding tar and kneading for 10 minutes, then adding pure water and kneading for another 15 minutes to obtain the slurry.

[0090] The particle size of the charcoal powder is 200 mesh.

[0091] (3) The green body was carbonized at 600°C for 1 hour under nitrogen atmosphere to obtain the precursor.

[0092] (4) Pass 40 ml / hour of water vapor through each 100 g of precursor and activate the precursor in a water vapor atmosphere at 900 °C for 3 hours to obtain activated carbon.

[0093] The specific surface area and average pore size of the bamboo activated carbon in Examples 1-11 were tested using the test method for "Determination of pore volume and specific surface area of ​​coal-based granular activated carbon" (GB / T 7702.20-2008). The test results are shown in Table 1.

[0094] Table 1

[0095] Example number Specific surface area (square meters / gram) Average pore size (nanometers) Example 1 1387.65 1.697 Example 2 1423.60 1.724 Example 3 1352.71 1.778 Example 4 1311.52 1.671 Example 5 1232.62 1.687 Example 6 1309.37 1.702 Example 7 1279.59 1.728 Example 8 1201.37 1.654 Example 9 1551.52 1.822 Example 10 1498.69 1.814 Example 11 874.88 1.429

[0096] As can be seen from Table 1, compared with Example 11, the specific surface area of ​​the bamboo activated carbon in Examples 1-10 is significantly increased, indicating that the use of calcium sulfate in this invention can significantly improve porosity while retaining the microporous structure. In practical applications, it has good adsorption performance and no wear or breakage occurs even after long-term use.

[0097] Figure 1 The nitrogen adsorption-desorption curve is shown for the bamboo activated carbon in Example 7. Figure 2 The pore size distribution curve of the bamboo activated carbon in Example 7 was obtained by testing with a high-performance specific surface area and micropore analyzer (model BSD-PM) from Best Instrument Technology (Beijing) Co., Ltd.

[0098] like Figure 1 As shown, this bamboo-based activated carbon exhibits a standard Type I isotherm, namely the Langmuir isotherm, which is a typical characteristic of microporous materials. Figure 2 As shown, the pore size of this bamboo-based activated carbon is mainly distributed below 2 nm, exhibiting obvious microporous material characteristics.

[0099] Figure 3 This is a scanning electron microscope image of the bamboo activated carbon from Example 7.

[0100] like Figure 3 As shown, the bamboo activated carbon has a loose and porous three-dimensional network structure, thus possessing a high specific surface area and air permeability.

[0101] The calcium sulfate whiskers can be prepared, but is not limited to, the following steps:

[0102] 160 mL of 1.625 mol / L sulfuric acid was added to 80 mL of an aqueous dispersion of 20 g of calcium oxide. The resulting precipitate was then collected, washed, and dried. 3.513 g of the precipitate was dispersed in 500 mL of sulfuric acid and treated with a water bath at 80 °C and stirred. After the precipitate was completely dissolved, it was allowed to stand at room temperature for 20 hours. The precipitate was then collected, washed, and dried to obtain calcium sulfate whiskers.

[0103] Figure 4 This is a morphological diagram of calcium sulfate whiskers.

[0104] from Figure 4It can be seen that calcium sulfate whisker powder is mainly composed of fibers with a length of 100-460 μm and a width of 12-25 μm.

[0105] The desulfurization by-product gypsum is a byproduct of gypsum-based desulfurization. The principle of gypsum-based desulfurization is as follows: limestone or lime is used as the desulfurization absorbent. The limestone is crushed and ground into powder, then mixed with water to form an absorbent slurry. Alternatively, lime powder is digested and then mixed with water to form an absorbent slurry. The absorbent slurry is then mixed with the flue gas to be desulfurized. The sulfur dioxide in the flue gas reacts chemically with the calcium carbonate in the slurry and the injected oxidizing air, thus being removed. The final reaction product is gypsum. When using the desulfurization by-product gypsum in this invention, the gypsum is ground into powder and then sieved through a 200-mesh screen before use.

[0106] The embodiments of the invention provided in this specification have been described above. Those skilled in the art will be able to implement the embodiments of the invention provided in this specification based on these descriptions. All other preferred embodiments and implementations obtained by those skilled in the art based on the above description of the embodiments of the invention provided in this specification without inventive effort should fall within the protection scope of the embodiments of the invention provided in this specification.

Claims

1. A method for preparing high specific surface area bamboo-based activated carbon, characterized in that: Includes the following steps: (1) Carbonize the powder, including fresh bamboo powder, to obtain charcoal powder; (2) The slurry containing carbon powder, tar and water is extruded and molded to obtain a green body; (3) Carbonize the green body to obtain the precursor; (4) The precursor is activated to obtain bamboo activated carbon with high specific surface area; The powder also includes desulfurization by-product gypsum; the slurry also includes calcium sulfate powder, which is calcium sulfate whisker powder; the calcium sulfate whisker powder is mainly composed of fibers with a length of 100-460 μm and a width of 12-25 μm. The weight ratio of carbon powder, calcium sulfate powder, tar, and water in the slurry is 100:(7-11):(50-60):(15-30). The carbonization process is performed under an inert atmosphere at 500–600°C for 1–3 hours. The activation treatment is performed in an activating atmosphere at 800–1000°C for 2–4 hours.

2. The method for preparing high specific surface area bamboo activated carbon as described in claim 1, characterized in that: The preparation of the calcium sulfate whiskers includes the following steps: adding sulfuric acid to an aqueous dispersion of calcium oxide, then collecting, washing and drying the resulting precipitate; dispersing the precipitate in sulfuric acid and heating it until the precipitate is completely dissolved, then allowing it to stand at room temperature until the precipitate precipitates out, and then collecting, washing and drying the precipitate to obtain calcium sulfate whisker powder.

3. The method for preparing high specific surface area bamboo activated carbon as described in claim 1, characterized in that: The weight of the desulfurization by-product gypsum in the powder is 10-15% of the weight of the fresh bamboo powder.

4. The method for preparing high specific surface area bamboo activated carbon as described in claim 1, characterized in that: The preparation of the slurry includes the following steps: putting carbon powder and calcium sulfate powder into a mixer and stirring for 5 to 20 minutes to obtain a mixture; putting the mixture into a kneader, first adding tar and kneading for 5 to 15 minutes, then adding pure water and kneading for another 10 to 20 minutes to obtain the slurry.

5. The method for preparing high specific surface area bamboo activated carbon as described in claim 1, characterized in that: The slurry is extruded into spherical, columnar, or honeycomb shapes.

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