Layered porous bamboo-based activated carbon for broad-spectrum adsorption of VOCs as well as preparation method and application thereof

Abstract

The invention relates to layered pore bamboo-based activated carbon for broad-spectrum adsorption of VOCs (volatile organic compounds), which is prepared by a method comprising the following steps: (1) oxidation pretreatment: putting a bamboo sample into a tubular furnace, heating to 150-250 DEG C, and performing oxidation pretreatment in an air atmosphere to obtain a precursor; (2) carbonizing: placing the precursor in a tubular furnace, and carbonizing at 400-600 DEG C in an inert atmosphere to obtain a carbonized material; and (3) activation: placing the carbonized material in a tubular furnace, heating to 780-900 DEG C in an inert atmosphere, closing the inert atmosphere, introducing water vapor, and activating to obtain the layered porous bamboo-based activated carbon. The bamboo-based activated carbon has high specific surface area and total pore volume, has excellent adsorption capacity for carbon tetrachloride, benzene and toluene, has good cycle performance, and is an excellent VOCs adsorption material. The preparation method is green, environment-friendly, simple, efficient and suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of comprehensive utilization of biomass energy, and particularly to the field of bamboo-based activated carbon preparation and VOCs purification. Specifically, it relates to a layered porous bamboo-based activated carbon for broad-spectrum VOCs adsorption, its preparation method, and its application. Background Technology

[0002] Among VOCs purification methods, adsorption technology is one of the most efficient and economical solutions, and activated carbon has become the most commonly used adsorbent due to its high adsorption capacity and relatively low cost.

[0003] Industrial organic waste gas has a wide range of sources, contains a diverse array of VOCs, and often includes multiple VOCs. To achieve high selectivity for VOC molecules with varying diffusion diameters, the pore size distribution of activated carbon must match the geometry of the VOC adsorbate. Common VOC molecules have diameters ranging from 0.2 to 0.7 nm. Micropores (<2 nm) in activated carbon have high adsorption capacity for small molecules but high mass transfer resistance, while mesopores (2-50 nm) offer faster molecular diffusion rates but have a smaller specific surface area. Therefore, directional control of micropore and narrow mesopore segments, and the construction of activated carbon with hierarchical pore structures, are key to achieving broad-spectrum adsorption of VOCs from industrial organic waste gas.

[0004] my country is rich in bamboo resources, and the biomass composition and natural layered structure of bamboo make it an ideal raw material for preparing activated carbon. However, existing technologies for preparing bamboo-based layered porous activated carbon face bottlenecks. While steam physical activation for preparing bamboo-based activated carbon has achieved large-scale production, the pore structure control is limited. For example, Tian Huayu et al. (Tian Huayu, Liu Huan, Wang Guorui et al. Preparation and Adsorption Performance Study of Activated Carbon from Bamboo Shoots [J]. Journal of Zhejiang A&F University, 2024, 41(02): 429-436.) obtained bamboo-based activated carbon with a specific surface area of ​​837.05 m² using optimized steam activation. 2 / g, its micropore ratio is still as high as 79%, while lacking suitable mesopores. Although the chemical activation method using activators such as phosphoric acid and KOH has a good effect on pore size control, its high cost, large pollution, and equipment corrosion hinder its industrial application. For example, SALAS-ENRÍQUEZ BG et al. (SALAS-ENRÍQUEZ BG, TORRES-HUERTA AM, CONDE-BARAJAS E et al. Activated carbon production from the Guadua amplexifolia using a combination of physical and chemical activation[J]. Journal of Thermal Analysis and Calorimetry, 2016, 124(3):1383-1398) obtained an ultra-high specific surface area of ​​3299.44 m² using the KOH activation method. 2 / g of bamboo-based activated carbon, but the alkali-to-carbon ratio is as high as 4:1, the activation temperature is 900 °C, the amount of alkali used is large, and the activation temperature is high. Summary of the Invention

[0005] The technical problem solved by this invention is that existing methods for preparing bamboo-based activated carbon are highly polluting and energy-intensive. Existing techniques for controlling the pore structure of bamboo-based activated carbon are insufficient to meet the requirements for preparing activated carbon for broad-spectrum VOCs adsorption.

[0006] The purpose of this invention is to construct bamboo-based activated carbon with a hierarchical pore structure by directionally controlling the micropores and narrow mesopores of bamboo-based activated carbon through a simple and effective process, thereby achieving broad-spectrum adsorption of VOCs in industrial organic waste gas and providing a direction for the large-scale industrial production of bamboo-based activated carbon for VOCs adsorption.

[0007] To solve the above-mentioned technical problems, this invention pre-treats the main chemical components of bamboo, such as cellulose, hemicellulose and lignin, at low temperature to form defective pores, which serve as active sites and diffusion channels during carbonization and steam activation. With appropriate process conditions, the pore size distribution of bamboo-based activated carbon is controlled to increase pore volume and specific surface area, thereby preparing hierarchical porous bamboo-based activated carbon with broad-spectrum VOCs adsorption performance.

[0008] Specifically, in view of the shortcomings of the existing technology, the present invention provides the following technical solution:

[0009] This invention provides a layered porous bamboo-based activated carbon for broad-spectrum VOCs adsorption, characterized in that it is prepared by a method comprising the following steps:

[0010] (1) Oxidation pretreatment: Bamboo samples were placed in a tube furnace and heated to 150-250 °C. Oxidation pretreatment was carried out in an air atmosphere to obtain the precursor.

[0011] (2) Carbonization: The precursor is placed in a tube furnace and carbonized at 400-600 °C under an inert atmosphere to obtain carbonized material;

[0012] (3) Activation: The carbonized material is placed in a tube furnace and heated to 780-900 ℃ under an inert atmosphere. The inert atmosphere is then turned off, and steam is introduced to activate the material and obtain the layered porous bamboo-based activated carbon.

[0013] Preferably, the total pore volume of the bamboo-based activated carbon is 0.44-0.80 cm³. 3 / g, the pore volume of the bamboo-based activated carbon at 0.7-3.0 nm is 0.28-0.55 cm³. 3 / g.

[0014] Preferably, the total pore volume of the bamboo-based activated carbon is 0.55-0.78 cm³. 3 / g, preferably 0.58-0.78 cm 3 / g, more preferably 0.70-0.78 cm 3 / g.

[0015] Preferably, the pore volume of the bamboo-based activated carbon at 0.7-3.0 nm is 0.35-0.55 cm³. 3 / g, more preferably 0.38-0.55 cm 3 / g, more preferably 0.50-0.55 cm 3 / g or 0.38-0.40cm 3 / g.

[0016] Preferably, the specific surface area of ​​the bamboo-based activated carbon is 1000-1500 m². 2 / g, preferably 1110-1500 m 2 / g, more preferably 1200-1500 m 2 / g, more preferably 1300-1500 m 2 / g.

[0017] Preferably, the micropore volume of the above-mentioned bamboo-based activated carbon is 0.42-0.65 cm³. 3 / g.

[0018] Preferably, the mesopore volume of the above-mentioned bamboo-based activated carbon is 0.10-0.17 cm³. 3 / g, preferably 0.14-0.17 cm 3 / g.

[0019] Preferably, the mesoporosity of the bamboo-based activated carbon is 14% to 28%, more preferably 20% to 28%.

[0020] Preferably, the average pore size of the bamboo-based activated carbon is 1.9-2.1 nm.

[0021] This invention provides a method for preparing layered porous bamboo-based activated carbon for broad-spectrum VOCs adsorption, characterized by comprising the following steps:

[0022] (1) Oxidation pretreatment: Bamboo samples were placed in a tube furnace and heated to 150-250 °C. Oxidation pretreatment was carried out in an air atmosphere to obtain the precursor.

[0023] (2) Carbonization: The precursor is placed in a tube furnace and carbonized at 400-600 °C under an inert atmosphere to obtain carbonized material;

[0024] (3) Activation: The carbonized material is placed in a tube furnace and heated to 780-900 ℃ under an inert atmosphere. The inert atmosphere is then turned off, and steam is introduced to activate the material and obtain the layered porous bamboo-based activated carbon.

[0025] Preferably, in the above preparation method, the precursor obtained by the oxidation pretreatment process has a total cellulose and hemicellulose content of 17.0-47.5 wt%, preferably 17.0-25.0 wt%, and a lignin content of 26.5-75.0 wt%, preferably 70.0-75.0 wt%.

[0026] Preferably, in the above preparation method, the bamboo sample needs to be dried and crushed to 1-2 mm before oxidation pretreatment.

[0027] Preferably, in the above preparation method, in step (1), the flow rate of the air atmosphere is 6.0-10 ml / min per gram of bamboo sample.

[0028] Preferably, in the above preparation method, the oxidation pretreatment time is 60-180 min, more preferably 120-180 min.

[0029] Preferably, in the above preparation method, in step (1), the temperature of the oxidation pretreatment is 240-250 °C.

[0030] Preferably, in the above preparation method, the carbonization temperature in step (2) is 450-600 ℃, and more preferably 450-550 ℃.

[0031] Preferably, in the above preparation method, in step (2), the flow rate of the inert atmosphere is 50-200 ml / min, and the carbonization time is 50-80 min.

[0032] Preferably, in the above preparation method, during the activation process, the water vapor flow rate is 0.5-1.0 ml / g / min, more preferably 0.5-0.75 ml / g / min.

[0033] Preferably, in the above preparation method, the activation process in step (3) is selected from any of the following steps:

[0034] (1) Static activation process: Place the carbonized material in a tube furnace, heat it to 780-900 ℃ under an inert atmosphere, turn off the inert gas, introduce water vapor, and maintain the temperature for 60-120 min, or

[0035] (2) Dynamic activation process: The carbonized material is placed in a tube furnace and heated to 780-810℃ in an inert atmosphere. The inert gas is then turned off, and water vapor is introduced to raise the temperature to 880-900℃ at a rate of 1-2℃ / min.

[0036] Preferably, in the above preparation method, the heating rate during the activation process under an inert atmosphere is 5-10 °C / min.

[0037] Preferably, in the above preparation method, during the static activation process, the activation temperature is 780-850 ℃, more preferably 780-810 ℃; and the activation time is 90-100 min.

[0038] Preferably, the bamboo-based activated carbon has an adsorption capacity of 390-510 mg / g for carbon tetrachloride, 205-305 mg / g for benzene, and 200-325 mg / g for toluene.

[0039] The present invention also provides the application of the above-mentioned bamboo-based activated carbon in the field of industrial organic waste gas treatment.

[0040] The advantages of this invention are: (1) Green and environmentally friendly. No chemical reagents are required, avoiding the problem of acid and alkali waste liquid treatment and reducing environmental pollution; (2) High efficiency and simplicity. The pore size can be effectively controlled through simple air pretreatment and physical activation process, which is suitable for large-scale industrial production; (3) Broad-spectrum adsorption of VOCs. The prepared bamboo-based activated carbon has a specific surface area of ​​more than 1200 m² / g and a pore volume of more than 0.59 cm³ / g, and has excellent adsorption performance for typical VOCs. Attached Figure Description

[0041] Figure 1a The N2 adsorption-desorption isotherms are for the bamboo-based activated carbon obtained in Comparative Example 1 and Example 3. Figure 1b The image shows the pore size distribution of the bamboo-based activated carbon obtained in Comparative Example 1 and Example 3.

[0042] Figure 2The infrared spectra of bamboo-based activated carbon obtained in Comparative Example 1, Example 1, Example 2 and Example 3 are shown.

[0043] Figure 3a This is a scanning electron microscope image of the BAC-C1 sample obtained in Comparative Example 1. Figure 3b The image shows a scanning electron microscope (SEM) image of the BAC-250-120-800-90 sample obtained in Example 3, with a scale bar of 10 μm.

[0044] Figure 4a The results of three adsorption-desorption cycles of toluene on the bamboo-based activated carbon obtained in Comparative Example 1 are shown. Figure 4b The results of three adsorption-desorption cycles of toluene on bamboo-based activated carbon obtained in Example 3 are shown. Detailed Implementation

[0045] Current methods for preparing bamboo-based activated carbon are energy-intensive, cause serious pollution, have limited control over the pore structure of bamboo-based activated carbon, and result in bamboo-based activated carbon that can only adsorb a limited variety of VOCs. In view of this, this invention provides a bamboo-based activated carbon whose pore structure can be controlled through bamboo raw material pretreatment, suitable for the adsorption and purification of industrial organic waste gas containing multiple VOCs, as well as its preparation method and application.

[0046] In a preferred embodiment, the preparation method of bamboo-based activated carbon suitable for broad-spectrum VOCs adsorption according to the present invention includes the following steps:

[0047] The first step is bamboo drying: the bamboo is thoroughly washed and dried in an oven at 105 ℃ in air atmosphere until constant weight. After crushing and sieving, 1-2 mm fragments are obtained and weighed for later use.

[0048] The second step is the pretreatment of bamboo oxidation: Take 30 g ± 0.5 g of crushed and dried bamboo sample and place it in a tube furnace. Pass in air at 200 ml / min and simultaneously raise the temperature from room temperature to 150-250 ℃ at a rate of 10 ℃ / min, keep the temperature constant for 60-180 min, and take it out for use after cooling.

[0049] The third step is carbonization: 20 g ± 0.5 g of pretreated bamboo is placed in a tube furnace and heated from room temperature to 400-600 ℃ at a rate of 10 ℃ / min under a nitrogen atmosphere of 100 ml / min, and then held at that temperature for 60 min. After carbonization, the material is cooled to room temperature and removed to obtain carbonized bamboo material.

[0050] Step 4, activation: Take 10 g ± 0.5 g of carbonized material and place it in a tube furnace. Under a nitrogen atmosphere of 100 ml / min, heat the material from room temperature to 800 ℃ at a rate of 10 ℃ / min, then turn off the nitrogen. Introduce 0.5-1.0 ml / g / min of water vapor and activate the material at 780-900 ℃ for 60-120 min. After activation, turn off the water vapor, introduce nitrogen again, and remove the material after the temperature drops to room temperature. Dry the material to obtain bamboo-based activated carbon.

[0051] In this invention, the inert atmosphere refers to a nitrogen or argon atmosphere.

[0052] The following specific embodiments further illustrate the layered porous bamboo-based activated carbon for broad-spectrum VOCs adsorption, its preparation method, and its application.

[0053] In the following embodiments, the information on the reagents and instruments used is shown in the table below. All other reagents were purchased from Sinopharm Group. The bamboo used in the embodiments of the present invention is 3-year-old moso bamboo, and bamboo processing waste with an ash content of 1.0%~1.5% was selected.

[0054] Table 1. Reagent and Instrument Information Sheet

[0055]

[0056] Example 1

[0057] The preparation steps for bamboo-based activated carbon are as follows:

[0058] (1) Take bamboo materials, wash them thoroughly, place them in an oven, dry them at 105 ℃ in an air atmosphere until constant weight, and crush and sieve them to a size of 1-2 mm.

[0059] (2) Oxidation pretreatment: 30 g of broken bamboo sample was placed in a tube furnace and air was introduced at a rate of 200 ml / min. The temperature was increased from room temperature to 150 °C at a rate of 10 °C / min. After treatment in air atmosphere for 120 min, the sample was taken out and dried for later use. The pretreated sample was named B-150-120.

[0060] (3) Carbonization: 20 g of the pretreated precursor was placed in a tube furnace and heated from room temperature to 500 ℃ at a rate of 10 ℃ / min under nitrogen flow (100 ml / min) and held for 60 min to obtain carbonized material.

[0061] (4) Activation: Place 10 g of carbonized material in a tube furnace and heat it from room temperature to 800℃ at a rate of 10℃ / min under a nitrogen atmosphere of 100 ml / min. Turn off the nitrogen and introduce water vapor at a flow rate of 0.75 ml / g / min. Activate for 90 min to obtain bamboo-based activated carbon, labeled as BAC-150-120-800-90.

[0062] Example 2

[0063] The preparation steps for bamboo-based activated carbon are as follows:

[0064] (1) Take bamboo materials, wash them thoroughly, place them in an oven, dry them at 105°C in an air atmosphere until constant weight, and crush and sieve them to a size of 1-2 mm.

[0065] (2) Oxidation pretreatment: 30 g of broken bamboo sample was placed in a tube furnace and air was introduced at a rate of 200 ml / min. The temperature was increased from room temperature to 200 ℃ at a rate of 10℃ / min. After treatment in air atmosphere for 120 min, the sample was taken out and dried for later use. The pretreated sample was named B-200-120.

[0066] (3) Carbonization: 20 g of the pretreated precursor was placed in a tube furnace and heated from room temperature to 500 ℃ at a rate of 10 ℃ / min under nitrogen flow (100 ml / min) and held for 60 min to obtain carbonized material.

[0067] (4) Activation: Place 10 g of carbonized material in a tube furnace and heat it from room temperature to 800 ℃ at a rate of 10 ℃ / min under a nitrogen atmosphere of 100 ml / min. Turn off the nitrogen and introduce water vapor at a flow rate of 0.75 ml / g / min. Activate for 90 min to obtain bamboo-based activated carbon, labeled as BAC-200-120-800-90.

[0068] Example 3

[0069] The preparation steps for bamboo-based activated carbon are as follows:

[0070] (1) Take bamboo materials, wash them thoroughly, place them in an oven, dry them at 105 ℃ in an air atmosphere until constant weight, and crush and sieve them to a size of 1-2 mm.

[0071] (2) Oxidation pretreatment: 30 g of broken bamboo sample was placed in a tube furnace, and air was introduced at a rate of 200 ml / min. The temperature was increased from room temperature to 250 ℃ at a rate of 10 ℃ / min. After treatment in air atmosphere for 120 min, the sample was taken out and dried for later use. The pretreated sample was named B-250-120.

[0072] (3) Carbonization: 20 g of the pretreated precursor was placed in a tube furnace and heated from room temperature to 500 °C at a rate of 10 °C / min under nitrogen flow (100 ml / min) and held for 60 min to obtain carbonized material.

[0073] (4) Activation: Place 10 g of carbonized material in a tube furnace and heat it from room temperature to 800°C at a rate of 10°C / min under a nitrogen atmosphere of 100 ml / min. Turn off the nitrogen and introduce water vapor at a flow rate of 0.75 ml / g / min. Activate for 90 min to obtain bamboo-based activated carbon, labeled as BAC-250-120-800-90.

[0074] Example 4

[0075] The preparation steps for bamboo-based activated carbon are as follows:

[0076] (1) Take bamboo materials, wash them thoroughly, place them in an oven, dry them at 105 ℃ in an air atmosphere until constant weight, and crush and sieve them to a size of 1-2 mm.

[0077] (2) Oxidation pretreatment: 30 g of broken bamboo sample was placed in a tube furnace and air was introduced at a rate of 200 ml / min. The temperature was increased from room temperature to 250 °C at a rate of 10 °C / min. After treatment in air atmosphere for 60 min, the sample was taken out and dried for later use. The pretreated sample was named B-250-60.

[0078] (3) Carbonization: 20 g of the pretreated precursor was placed in a tube furnace and heated from room temperature to 500 ℃ at a rate of 10 ℃ / min under nitrogen flow (100 ml / min) and held for 60 min to obtain carbonized material.

[0079] (4) Activation: Place 10 g of carbonized material in a tube furnace and heat it from room temperature to 800 ℃ at a rate of 10 ℃ / min under a nitrogen atmosphere of 100 ml / min. Turn off the nitrogen and introduce water vapor at a flow rate of 0.75 ml / g / min. Activate for 90 min to obtain bamboo-based activated carbon, labeled as BAC-250-60-800-90.

[0080] Example 5

[0081] The preparation steps for bamboo-based activated carbon are as follows:

[0082] (1) Take bamboo materials, wash them thoroughly, place them in an oven, dry them at 105°C in an air atmosphere until constant weight, and crush and sieve them to a size of 1-2 mm.

[0083] (2) Oxidation pretreatment: 30 g of broken bamboo sample was placed in a tube furnace, and air was introduced at a rate of 200 ml / min. The temperature was increased from room temperature to 250 °C at a rate of 10 °C / min. After treatment in air atmosphere for 180 min, the sample was taken out and dried for later use. The pretreated sample was named B-250-180.

[0084] (3) Carbonization: Take 20 g of the pretreated precursor and place it in a tube furnace. Under nitrogen flow (100 ml / min), heat it from room temperature to 500℃ at a rate of 10℃ / min and hold it for 60 min to obtain carbonized material.

[0085] (4) Activation: Place 10 g of carbonized material in a tube furnace and heat it from room temperature to 800°C at a rate of 10°C / min under a nitrogen atmosphere of 100 ml / min. Turn off the nitrogen and introduce water vapor at a flow rate of 0.75 ml / g / min. Activate for 90 min to obtain bamboo-based activated carbon, labeled as BAC-250-180-800-90.

[0086] Example 6

[0087] Example 6 is similar to Example 3, except that in step (4), the activation temperature is 850°C.

[0088] If the activation temperature is adjusted to 900°C in a similar manner to Example 3, the activated product is grayish-white shavings, which turn into grayish-white powder after light grinding. The reason is speculated to be that the bamboo sample that has been oxidized at a higher activation temperature reacts more violently with water vapor than the untreated sample, resulting in excessive burn-off at high temperature.

[0089] Example 7

[0090] Example 7 is similar to Example 3, except that:

[0091] (4) Activation: Place 10 g of carbonized material in a tube furnace and heat it from room temperature to 800 ℃ at a rate of 10 ℃ / min under a nitrogen atmosphere of 100 ml / min. Turn off the nitrogen and introduce water vapor at a flow rate of 0.5 ml / g / min. Continue to heat at a constant rate for 90 min until the temperature reaches 900 ℃. The activation process is then complete and bamboo-based activated carbon is obtained, labeled as BAC-250-120-800 / 900-90.

[0092] Example 8

[0093] The preparation steps for bamboo-based activated carbon are as follows:

[0094] (1) Take bamboo materials, wash them thoroughly, place them in an oven, dry them at 105°C in an air atmosphere until constant weight, and crush and sieve them to a size of 1-2 mm.

[0095] (2) Oxidation pretreatment: 30 g of broken bamboo sample was placed in a tube furnace, and air was introduced at a rate of 200 ml / min. The temperature was increased from room temperature to 250 ℃ at a rate of 10 ℃ / min. After treatment in air atmosphere for 180 min, the sample was taken out and dried for later use to obtain the precursor.

[0096] (3) Carbonization: 20 g of the pretreated precursor was placed in a tube furnace and heated from room temperature to 550 ℃ at a rate of 10 ℃ / min under nitrogen flow (100 ml / min) and held for 60 min to obtain carbonized material.

[0097] (4) Activation: Place 10 g of carbonized material in a tube furnace and heat it from room temperature to 800 ℃ at a rate of 10 ℃ / min under a nitrogen atmosphere of 100 ml / min. Turn off the nitrogen and introduce water vapor at a flow rate of 0.5 ml / g / min. Activate for 120 min to obtain bamboo-based activated carbon, labeled as BAC-250-180-800-120.

[0098] Comparative Example 1

[0099] The preparation process of bamboo-based activated carbon is as follows:

[0100] (1) Take bamboo materials, wash them thoroughly, place them in an oven, dry them at 105°C in an air atmosphere until constant weight, and crush and sieve them to a size of 1-2 mm.

[0101] (2) Carbonization: Place 20 g of crushed bamboo sample in a tube furnace, introduce nitrogen gas at a flow rate of 100 ml / min, raise the temperature to 600℃ at 10℃ / min, and maintain it for 60 min to obtain carbonized material.

[0102] (3) Activation: 10g of carbonized material was placed in a tube furnace and heated from room temperature to 800℃ at a rate of 10℃ / min under a nitrogen atmosphere of 100 ml / min. The nitrogen atmosphere was then turned off, and the material was activated at 800℃ for 90min with a water vapor flow rate of 0.75 ml / g / min to obtain bamboo-based activated carbon. It was labeled as BAC-C1.

[0103] Comparative Example 2

[0104] The preparation process of bamboo-based activated carbon is as follows:

[0105] (1) Take bamboo materials, wash them thoroughly, place them in an oven, dry them at 105 ℃ in an air atmosphere until constant weight, and crush and sieve them to a size of 1-2 mm.

[0106] (2) Carbonization: 20 g of crushed bamboo sample was placed in a tube furnace, nitrogen gas was introduced at a flow rate of 100 ml / min, the temperature was raised to 600 °C at 10 °C / min and held for 60 min to obtain carbonized material.

[0107] (3) Activation: 10 g of carbonized material was placed in a tube furnace and heated from room temperature to 800 °C at a rate of 10 °C / min under a nitrogen atmosphere of 100 ml / min. The nitrogen atmosphere was then turned off, and the material was activated at 900 °C for 90 min with a water vapor flow rate of 0.75 ml / g / min to obtain bamboo-based activated carbon, labeled as BAC-C2.

[0108] The composition, structure, and performance testing procedures of bamboo and bamboo-based activated carbon materials in the examples and comparative examples are as follows:

[0109] (1) Bamboo raw material composition: The content of macro elements in the sample was analyzed by an elemental analyzer; the chemical composition of the bamboo sample was determined by ultra-high performance liquid chromatography according to the NREL (Determination of Structural Carbohydrates and Lignin in Biomass) laboratory analysis method.

[0110] (2) Determination of specific surface area and pore volume of activated carbon: The nitrogen adsorption-desorption isotherm of activated carbon was measured using a nitrogen adsorption instrument. The specific surface area was calculated according to the BET formula and the pore size distribution, pore volume and volume ratio of different pore size segments were analyzed in detail using the DFT method.

[0111] (3) Characterization of the microstructure of activated carbon: The microstructure was observed using cold field emission electron microscopy.

[0112] (4) Surface chemical properties of activated carbon: Fourier transform infrared spectroscopy was used to characterize the surface chemical properties of the samples.

[0113] (5) Determination of activated carbon adsorption performance indicators: Iodine adsorption value of sample was determined according to "Test Method for Iodine Adsorption Value of Wood Activated Carbon" (GB / T12496.8-2015); methylene blue adsorption value of sample was determined according to "Test Method for Methylene Blue Adsorption Value of Wood Activated Carbon" (GB / T12496.10-1999).

[0114] (6) Characterization of the broad-spectrum adsorption performance of activated carbon: Carbon tetrachloride, benzene, and toluene, which are common in industrial waste gases and have different molecular shapes, polarities, and kinetic diffusion diameters, were selected as representative VOCs. The VOC adsorption performance of the samples at room temperature was determined by a fixed-bed reactor. The fixed-bed dynamic adsorption experimental device mainly consists of three parts: a gas distribution system, a room-temperature adsorption column system, and a gas chromatography analysis system. Nitrogen gas was divided into two gas paths. One path passed through a bubbler containing liquid carbon tetrachloride, benzene, or toluene, and the other path was mixed with the bubbling gas in a buffer tank to prepare 1000 ppm VOC gas. The gas was passed through a fixed bed containing 0.25 g of adsorbent sample at a flow rate of 30 ml / min. The VOC concentration was detected by a gas chromatograph. When the outlet VOC concentration reached 5% of the inlet concentration, the adsorption was considered to have reached the breakthrough point; when the outlet concentration was equal to the inlet concentration (deviation ≤ 2%), the adsorption was considered to have reached the saturation point. The VOC adsorption capacity (mg / g) of the sample could be calculated by the integrated breakthrough curve.

[0115] A fixed-bed reactor was used to evaluate the toluene cyclic adsorption performance of the samples. Nitrogen gas was split into two streams: one stream passed through a bubbler containing liquid toluene, and the other stream was mixed with toluene gas in a buffer tank to prepare a toluene gas concentration of 1000 ppm. The toluene gas was then passed through the fixed bed containing 0.25 g of adsorbent sample at a flow rate of 30 ml / min. The concentration of toluene gas at the fixed bed outlet was measured using a gas chromatograph. Once adsorption reached saturation, the gas stream was switched to regeneration mode, and pure carrier gas was directly introduced into the reactor. Simultaneously, a programmed temperature rise system was activated to desorb the toluene adsorbed on the sample surface through a "thermal purge." The desorbed toluene was discharged with the carrier gas, completing the sample regeneration. This cycle was repeated three times.

[0116] Table 2 shows the industrial and elemental analysis results of the raw bamboo (B) and the pretreated samples obtained in the examples. Table 3 shows the pore structure characteristics of the bamboo-based activated carbon obtained in the examples and comparative examples. Table 2 shows that as the pretreatment temperature increases, the moisture and volatile matter content of the bamboo gradually decreases while the fixed carbon content increases. From the changes in chemical composition, it can be seen that at 250 ℃, a large amount of hemicellulose and cellulose in the pretreated samples decompose, precipitating out as water molecules or small molecule hydrocarbons, which also leads to a significant increase in C and a relative decrease in O content. Table 3 shows that after pretreatment, the composition and structure of the bamboo change, and the specific surface area and pore volume of the bamboo-based activated carbon both increase. Specifically, the specific surface area and pore volume of the bamboo-based activated carbon obtained in Example 3 reach 1236.62 m² / g and 0.5951 cm³ / g, respectively.

[0117] Table 2. Industrial analysis, elemental analysis, and chemical composition of pretreated samples.

[0118]

[0119] Table 3 Pore structure characteristics of activated carbon

[0120]

[0121] Figure 1a The N2 adsorption isotherms are for the bamboo-based activated carbon obtained in Comparative Example 1 and Example 3. Figure 1b The figure shows the pore size distribution of bamboo-based activated carbon obtained in Comparative Example 1 and Example 3. As can be seen from the figure, BAC-C1 has a narrow peak in the range of 0.6-1.5 nm and a distribution in the range of 3-4 nm, while BAC-250-120-800-90 has a good distribution in the range of 0.6-3 nm micropores to narrow mesopores, and also has a good distribution in the range of 6-15 nm mesopores. Figure 2 The infrared spectra of bamboo-based activated carbon obtained in Comparative Example 1, Example 1, Example 2 and Example 3 are shown in the figure. As can be seen from the figure, the surface of the BAC-250-120-800-90 sample obtained in Example 3 has more oxygen-containing functional groups.

[0122] Table 4 shows the adsorption performance test results of the bamboo-based activated carbon obtained in the comparative examples and the embodiments. As shown in Table 4, compared with BAC-C1, BAC-250-120-800-90 showed improved iodine adsorption value (1201 mg / g) and methylene blue adsorption value (273 mg / g), which verified its micropore / mesopore control effect. It also showed a significant improvement in the adsorption capacity of carbon tetrachloride, benzene and toluene.

[0123] Table 4 Adsorption performance of bamboo-based activated carbon

[0124]

[0125] Figure 3a and Figure 3b The images show scanning electron microscope (SEM) images of the BAC-C1 sample obtained in Comparative Example 1 and the BAC-250-120-800-90 sample obtained in Example 3, respectively. As can be seen from the images, BAC-C1 retains more of the multilayer structure composed of fibers and thin-walled tissues in the original bamboo structure, while the sample BAC-250-120-800-90, which has undergone air oxidation, has a relatively rough surface. The bamboo cell walls are damaged due to heat treatment, and the bamboo fiber bundles are more easily broken, with some exhibiting a fibrous distribution.

[0126] Figure 4a The results of three adsorption-desorption cycles of toluene on the bamboo-based activated carbon obtained in Comparative Example 1 are shown. Figure 4bThe figure shows the results of three adsorption-desorption cycles of toluene on the bamboo-based activated carbon obtained in Example 3. The vertical axis represents the ratio of the concentration detected at the outlet to the concentration detected at the inlet by chromatography. Under the same conditions, the BAC-250-120-800-90 of Example 3 exhibits excellent cycle stability. After three adsorption-desorption cycles, the toluene adsorption capacity does not decrease significantly, making it suitable for long-term cyclic use. This aligns with the resource efficiency requirements under the "dual carbon" target. Under the same test conditions, the toluene adsorption capacity of the bamboo-based activated carbon obtained in Example 6, which is mainly composed of micropores, decreased to 75% of its initial value after three cycles, showing a certain degree of attenuation.

[0127] In summary, the bamboo-based activated carbon prepared by the method described in this invention exhibits improved specific surface area and pore volume. Specifically, the activated carbon in Example 3 possesses a high specific surface area of ​​1236.62 m² / g and a total pore volume of 0.5951 cm³ / g. The static VOCs adsorption capacity of the bamboo-based activated carbon obtained in Example 3 is as follows: carbon tetrachloride adsorption capacity 410.6 mg / g, benzene adsorption capacity 239.21 mg / g, and toluene adsorption capacity 256.63 mg / g. After three adsorption-desorption cycles, the adsorption performance of the activated carbon showed no significant decline, indicating that the hierarchical porous bamboo-based activated carbon obtained by this invention is an excellent VOCs adsorption material. The preparation method described in this invention is green and environmentally friendly, avoiding pollution of the environment by acid and alkaline waste liquids. It is simple, efficient, and suitable for large-scale industrial production.

Claims

1. A layered porous bamboo-based activated carbon for broad-spectrum VOCs adsorption, characterized in that, It is prepared by a method including the following steps: (1) Oxidation pretreatment: The bamboo sample was placed in a tube furnace and heated to 150-250℃. Oxidation pretreatment was carried out in an air atmosphere to obtain the precursor. (2) Carbonization: The precursor is placed in a tube furnace and carbonized at 400-600℃ under an inert atmosphere to obtain carbonized material; (3) Activation: The carbonized material is placed in a tube furnace and heated to 780-900℃ under an inert atmosphere. The inert atmosphere is then turned off, and steam is introduced to activate the material and obtain the layered porous bamboo-based activated carbon.

2. The layered porous bamboo-based activated carbon for broad-spectrum VOCs adsorption according to claim 1, wherein, The total pore volume of the bamboo-based activated carbon is 0.44-0.80 cm³. 3 / g, the pore volume of the bamboo-based activated carbon at 0.7-3.0 nm is 0.28-0.55 cm³. 3 / g.

3. A method for preparing layered porous bamboo-based activated carbon for broad-spectrum VOCs adsorption, characterized in that, Includes the following steps: (1) Oxidation pretreatment: The bamboo sample was placed in a tube furnace and heated to 150-250℃. Oxidation pretreatment was carried out in an air atmosphere to obtain the precursor. (2) Carbonization: The precursor is placed in a tube furnace and carbonized at 400-600℃ under an inert atmosphere to obtain carbonized material; (3) Activation: The carbonized material is placed in a tube furnace and heated to 780-900℃ under an inert atmosphere. The inert atmosphere is then turned off, and steam is introduced to activate the material and obtain the layered porous bamboo-based activated carbon.

4. The preparation method according to claim 3, wherein, In step (1), the flow rate of the air atmosphere is 6.0-10 ml / min per gram of bamboo sample.

5. The preparation method according to claim 3 or 4, wherein, In step (1), the temperature of the oxidation pretreatment is 240-250℃.

6. The preparation method according to any one of claims 3-5, wherein, In step (2), the carbonization temperature is 450-600℃.

7. The preparation method according to any one of claims 3-6, wherein, During the activation process, the water vapor flow rate is 0.5-1.0 ml / g / min.

8. The preparation method according to any one of claims 3-7, wherein, The activation process in step (3) is selected from any of the following steps: (1) Static activation process: Place the carbonized material in a tube furnace, heat it to 780-900℃ under an inert atmosphere, turn off the inert gas, introduce water vapor, and maintain the temperature for 60-120 minutes, or (2) Dynamic activation process: The carbonized material is placed in a tube furnace and heated to 780-810℃ in an inert atmosphere. The inert gas is then turned off, and water vapor is introduced to raise the temperature to 880-900℃ at a rate of 1-2℃ / min.

9. The preparation method according to claim 8, wherein, During the static activation process, the activation temperature is 780-850℃.

10. The application of the bamboo-based activated carbon according to claim 1 or 2 in the field of industrial organic waste gas treatment.

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