Preparation method and application of traditional chinese medicine residue biochar

Abstract

The application discloses a preparation method and application of traditional Chinese medicine residue biochar. The preparation method comprises the following steps: mixing pretreated traditional Chinese medicine residue and pretreated wood chip material, performing steam explosion, obtaining explosion products, drying the explosion products, screening, and obtaining a compound; under a nitrogen or inert gas atmosphere, carbonizing the compound at 550-650 DEG C for 40-80 min, cooling to room temperature, and obtaining carbonized material; under a mixed gas atmosphere, heating the carbonized material to 450-550 DEG C at a heating rate of 8-12 DEG C / min, activating the carbonized material, cooling to room temperature, and obtaining traditional Chinese medicine residue biochar; and the mixed gas comprises carbon dioxide, water vapor, oxygen and nitrogen. The specific surface area of the prepared traditional Chinese medicine residue biochar is 508.52 m 2 / g, and the CO2 adsorption capacity is 2.15 mmol / g.

Description

Technical Field

[0001] This invention belongs to the field of adsorption materials technology, specifically relating to a method for preparing biochar from Chinese medicinal residues and its application. Background Technology

[0002] With the continuous development of global urbanization and industrialization, CO2 emissions are increasing daily, and the global atmospheric CO2 concentration has exceeded 410 ppm. Excessive CO2 emissions have led to a series of serious environmental problems, including global warming. Controlling CO2 emissions and reducing atmospheric CO2 concentration is currently an urgent priority for alleviating environmental problems. Utilizing adsorbent carbon for adsorption is an effective way to reduce CO2 concentration.

[0003] Traditional adsorbent carbon is mainly porous carbon obtained by carbonizing carbon materials. Although porous carbon can serve as an adsorbent for CO2, its CO2 capture performance still needs improvement. Based on this, the following two improvement methods are proposed in the existing technology:

[0004] The first method involves mixing an activator with carbon materials and heating the mixture at 500–800°C in an inert environment. This process creates a porous structure through etching between the activator and the carbon material. For example, Manyà JJ, González B, Azuara M, Arner G. Ultra-microporous adsorbents prepared from vine shoots-derived biochar with high CO2 uptake and CO2 / N2 selectivity. Chemical Engineering Journal 2018;345:631–9. https: / / doi.org / 10.1016 / j.cej.2018.01.092. Using KOH to activate grapevine shoot biochar, the CO2 adsorption capacity of the prepared AC-KOH-W-1-700 biochar was only 1.35 mmol / g. The second method involves mixing a heteroatom-containing precursor with biochar and heat-treating it. This allows the heteroatoms in the precursor to migrate to the surface of the biochar, resulting in porous carbon with abundant functional groups on the surface, such as LiH. Tang M, Wang L, Liu Q, Yao F, Gong Z, et al. Molecular simulation combined with DFT calculation guided heteroatom-doped biocharrational design for highly selective and efficient CO2 capture. Chemical Engineering Journal 2024;481:148362. https: / / doi.org / 10.1016 / j.cej.2023.148362. Boron-doped biochar was prepared by mixing and heat-treating a heteroatom-containing precursor (K2B2O4, K3PO4, and K2SO4, with K2B2O4 providing B atoms, K3PO4 providing P atoms, and K2SO4 providing S atoms) with coconut shell biochar. The CO2 adsorption capacity of the boron-doped biochar was only 1.45 mmol / g.

[0005] However, the porous carbon prepared by the above-mentioned existing technology has a low CO2 adsorption capacity, and there is an urgent need to study a method that can prepare porous carbon with higher performance and more adsorption sites. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for preparing biochar from Chinese medicinal residues.

[0007] Another object of the present invention is to provide biochar from Chinese medicinal residues obtained by the above preparation method.

[0008] Another objective of this invention is to provide the application of the aforementioned biochar made from medicinal herb residue in CO2 adsorption. This invention first involves steam explosion of the raw materials to expose the metal elements in the medicinal herb residue and sawdust more fully. Then, high-temperature carbonization is used to improve stability. Finally, a mixed gas is used for activation and pore expansion. High-temperature carbonization removes volatiles from the biomass, leaving a carbon-rich framework structure. Then, an oxidant (oxygen, carbon dioxide, and water vapor) in an activating atmosphere is used to regenerate the pore structure and introduce active functional groups, thereby increasing the CO2 adsorption capacity.

[0009] The objective of this invention is achieved through the following technical solution.

[0010] A method for preparing biochar from medicinal herb residue includes the following steps:

[0011] Step 1: Mix the pretreated Chinese medicine residue and pretreated wood chips, steam-explode to obtain explosives, dry the explosives, sieve to obtain a complex. The ratio of pretreated Chinese medicine residue to pretreated wood chips by mass is (0.8~1.2):(0.8~1.2).

[0012] In step 1, the medium for steam explosion is saturated steam, the pressure of steam explosion is 2~2.5MPa, the temperature of steam explosion is 180~220℃, and the pressure maintenance time of steam explosion is 8~12min.

[0013] In step 1, the particle size of the composite (powder) is 40-80 mesh.

[0014] In step 1, the method for obtaining pretreated Chinese medicine residue includes: crushing and sieving the Chinese medicine residue to obtain pretreated Chinese medicine residue with a particle size of 40-80 mesh.

[0015] In step 1, the method for obtaining pretreated wood chip material includes: crushing and sieving the wood chip material to obtain pretreated wood chip material with a particle size of 40-80 mesh.

[0016] In step 1, the Chinese medicine residue is a mixture of danshen residue, sanqi residue and borneol residue. By mass parts, the ratio of danshen residue, sanqi residue and borneol residue is (87~92):(17~18):(0.95~1).

[0017] In step 1, the wood chips are pine wood chips.

[0018] Step 2: Under a nitrogen or inert gas atmosphere, the composite is carbonized at 550~650℃ for 40~80 min, and then cooled to room temperature to obtain the carbonized material.

[0019] Step 3: In a mixed gas atmosphere, the carbonized material is heated to 450-550°C at a heating rate of 8-12°C / min to activate the carbonized material. After cooling to room temperature, the biochar of Chinese herbal medicine residue is obtained. The mixed gas includes carbon dioxide (CO2), water vapor (H2O), oxygen (O2) and nitrogen (N2). By volume, the ratio of carbon dioxide, water vapor, oxygen and nitrogen is (9-11):(9-11):(2-4):(74-80).

[0020] The biochar from the Chinese medicinal residue obtained by the above preparation method.

[0021] The application of the above-mentioned Chinese herbal medicine residue biochar in CO2 adsorption.

[0022] In the above technical solution, steam explosion promotes the generation of -OH, pyrrole nitrogen and pyridine nitrogen in Chinese herbal medicine residue and wood chips, and creates micropores to increase the CO2 adsorption capacity of Chinese herbal medicine residue biochar.

[0023] In the above technical solution, the CO2 adsorption capacity of biochar made from Chinese medicinal residue is 2.15 mmol / g.

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

[0025] (1) This invention uses steam explosion to prepare biochar from Chinese medicine residue and wood chips, which has unique synergistic advantages: high temperature and high pressure steam penetrates into the pores inside the Chinese medicine residue and wood chips. The shear force generated by instantaneous pressure release tears the fiber structure, generating -OH and pyrrole nitrogen and pyridine nitrogen. At the same time, it transforms the Chinese medicine residue and wood chips with different structures into a standardized solid fiber structure with relatively uniform physicochemical properties. Furthermore, the endogenous metals in the wood chips and Chinese medicine residue are fully exposed and more evenly distributed, generating more microporous structures. The mixing of wood chips and Chinese medicine residue avoids the defects of a single structure. Among them, the pyrolysis of pine wood chips can form a highly cross-linked and rigid aromatic skeleton, which effectively resists the structural collapse of high temperature activation, locks the metal active sites, and provides a stable matrix for the etching of mixed gas. The main components of Chinese medicine residue are hemicellulose and cellulose. After the pyrolysis of Chinese medicine residue, the volatile matter is fully removed, providing a dense pore structure, making the activation reaction more complete, and generating more nanoscale micropores. The final product is a biochar made from Chinese herbal medicine residue with stable structure, high specific surface area, high -OH content, high edge active nitrogen content, and rich active metal sites, which promotes CO2 adsorption.

[0026] (2) The specific surface area of ​​the biochar made from medicinal herb residue prepared in this invention is 508.52 m². 2 / g, CO2 adsorption capacity is 2.15mmol / g.

[0027] (3) This invention utilizes the combined activation of oxygen, carbon dioxide, and water vapor, representing an advanced process that optimizes pore structure and surface properties through the synergistic effect of multiple gases. Oxygen accelerates the reaction rate and rapidly opens pores; carbon dioxide acts gently, penetrating deep into the carbonized material to finely expand pores and stabilize the carbon skeleton; and water vapor has strong diffusion power, further regulating the pore structure and introducing abundant oxygen-containing functional groups. The synergistic effect of these three gases produces high-performance biochar from medicinal herb residues, characterized by high specific surface area, high micropore ratio, and abundant surface functional groups, demonstrating unique potential in fields such as energy storage and challenging CO2 adsorption. Attached Figure Description

[0028] Figure 1 Raman analysis diagram;

[0029] Figure 2 The N1s high-resolution XPS spectrum of the biochar from the medicinal herb residue prepared in Example 1;

[0030] Figure 3 The N1s high-resolution XPS spectrum of the biochar from the medicinal herb residue prepared in Example 2;

[0031] Figure 4 The N1s high-resolution XPS spectrum of the biochar from the medicinal herb residue prepared in Example 3;

[0032] Figure 5 The N1s high-resolution XPS spectrum of the biochar from the medicinal herb residue prepared in Example 4;

[0033] Figure 6 The N1s high-resolution XPS spectrum of the biochar from the medicinal herb residue prepared in Example 5;

[0034] Figure 7 The N1s high-resolution XPS spectrum of the biochar prepared in Example 6;

[0035] Figure 8 The N1s high-resolution XPS spectrum of the biochar from the medicinal herb residue prepared in Example 7;

[0036] Figure 9 The N1s high-resolution XPS spectrum of the biochar from the medicinal herb residue prepared in Example 8;

[0037] Figure 10 The O1s high-resolution XPS spectrum of the biochar from the medicinal herb residue prepared in Example 1;

[0038] Figure 11The O1s high-resolution XPS spectrum of the biochar from the medicinal herb residue prepared in Example 2;

[0039] Figure 12 The O1s high-resolution XPS spectrum of the biochar from the medicinal herb residue prepared in Example 3;

[0040] Figure 13 The O1s high-resolution XPS spectrum of the biochar from the medicinal herb residue prepared in Example 4;

[0041] Figure 14 The O1s high-resolution XPS spectrum of the biochar from the medicinal herb residue prepared in Example 5;

[0042] Figure 15 The O1s high-resolution XPS spectrum of the biochar prepared in Example 6;

[0043] Figure 16 The O1s high-resolution XPS spectrum of the biochar from the medicinal herb residue prepared in Example 7;

[0044] Figure 17 The O1s high-resolution XPS spectrum of the biochar from the medicinal herb residue prepared in Example 8;

[0045] Figure 18 The images show the morphology and elemental characterization of the biochar from the medicinal herb residue prepared in Example 1, where (a) shows the surface morphology and (b) shows the elemental analysis.

[0046] Figure 19 The images show the morphology and elemental characterization of the biochar from the medicinal herb residue prepared in Example 2, where (a) shows the surface morphology and (b) shows the elemental analysis.

[0047] Figure 20 The images show the morphology and elemental characterization of the biochar from the medicinal herb residue prepared in Example 5, where (a) shows the surface morphology and (b) shows the elemental analysis.

[0048] Figure 21 The images show the morphology and elemental characterization of the biochar prepared in Example 6, where (a) shows the surface morphology and (b) shows the elemental analysis. Detailed Implementation

[0049] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0050] The raw material information in the following examples is as follows:

[0051]

[0052] The instrument information in the following embodiments is as follows:

[0053]

[0054] In the following examples, the Chinese medicine residue is composed of danshen residue, sanqi residue and borneol residue (by mass, the ratio of danshen residue, sanqi residue and borneol residue is 90:17.6:1). Danshen residue, sanqi residue and borneol residue are all waste medicinal residues of Tasly Pharmaceutical Group Co., Ltd.

[0055] In the following embodiments, the method for obtaining pretreated Chinese medicine residue includes: crushing the Chinese medicine residue with a wall-breaking machine, drying it at 60°C for 24 hours, and sieving it to obtain pretreated Chinese medicine residue with a particle size of 40~80 mesh.

[0056] In the following embodiments, the method for obtaining pretreated wood chips (the wood chips are pine wood chips) includes: crushing the pine wood chips with a wall-breaking machine, drying them at 60°C for 24 hours, and sieving them to obtain pretreated pine wood chips with a particle size of 40~80 mesh.

[0057] Example 1 (Steam Explosion with Oxygen-Lean Mixing)

[0058] A method for preparing biochar from medicinal herb residue includes the following steps:

[0059] Step 1: Using a mixture of pretreated Chinese medicine residue and pretreated wood chips as raw materials, the raw materials are loaded into a steam explosion test bench for steam explosion (the steam explosion medium is saturated steam, the steam explosion pressure is 2.5 MPa, the steam explosion temperature is 200℃, and the steam explosion pressure holding time is 10 min) to obtain the explosion product. The explosion product is dried at 60℃ for 24 h, sieved, and the composite (powder) is obtained (the particle size of the composite is 40~80 mesh). By mass, the ratio of pretreated Chinese medicine residue to pretreated wood chips is 1:1.

[0060] Step 2: Heat the horizontal tube furnace at a rate of 10℃ / min while introducing nitrogen gas into the horizontal tube furnace to form a nitrogen atmosphere (the flow rate of nitrogen gas is 1L / min). When the temperature of the tube furnace reaches 600℃, place the composite in the horizontal tube furnace and carbonize the composite (powder) at 600℃ for 60 min under a nitrogen atmosphere. Cool to room temperature to obtain the carbonized material.

[0061] Step 3: Introduce a mixed gas into a horizontal tubular furnace (the flow rate of the mixed gas is 2 L / min), and simultaneously heat the horizontal tubular furnace to 500°C at a rate of 10°C / min to activate the carbonized material (no need to maintain the temperature at this temperature). Cool to room temperature to obtain biochar from Chinese herbal medicine residue. The mixed gas includes carbon dioxide (CO2), water vapor (H2O), oxygen (O2), and nitrogen (N2), and the volume ratio of carbon dioxide, water vapor, oxygen, and nitrogen is 10:10:3:77.

[0062] Example 2 (Blending with oxygen-deficient materials)

[0063] A method for preparing biochar from medicinal herb residue is basically the same as in Example 1, except that steam explosion is not performed (i.e., the raw materials are directly placed in a horizontal tubular furnace for carbonization). The ratio of pretreated medicinal herb residue to pretreated sawdust is 1:1 by mass.

[0064] Example 3 (Steam explosion with oxygen-free mixture)

[0065] A method for preparing biochar from Chinese medicinal residue is basically the same as in Example 1, except that the mixed gas is different. In Example 3, the mixed gas includes carbon dioxide (CO2), water vapor (H2O), and nitrogen (N2), and the ratio of carbon dioxide, water vapor, and nitrogen by volume is 10:10:80.

[0066] Example 4 (Steam explosion with high oxygen content)

[0067] A method for preparing biochar from Chinese medicinal residue is basically the same as in Example 1, except that the phrase "by volume parts, the ratio of carbon dioxide, water vapor, oxygen and nitrogen is 10:10:3:77" is replaced with "by volume parts, the ratio of carbon dioxide, water vapor, oxygen and nitrogen is 10:10:6:74".

[0068] Example 5 (Oxygen-deficient treatment of medicinal herb residue by steam explosion)

[0069] A method for preparing biochar from Chinese medicinal herb residue is basically the same as in Example 1, except that the raw material is only pretreated Chinese medicinal herb residue (excluding pretreated wood chips).

[0070] Example 6 (Steam Explosion of Wood Chips with Low Oxygen Content)

[0071] A method for preparing biochar is basically the same as that in Example 1, except that the raw material is only pretreated wood chips (pine wood chips).

[0072] Example 7 (Steam Explosion with Oxygen-Lean Mixing)

[0073] A method for preparing biochar from Chinese medicinal residue is basically the same as in Example 1, except that: the phrase "heating the horizontal tube furnace to 500°C at a rate of 10°C / min to activate the carbonized material" is replaced with "heating the horizontal tube furnace to 400°C at a rate of 10°C / min to activate the carbonized material".

[0074] Example 8 (Steam Explosion with Oxygen-Lean Mixing)

[0075] A method for preparing biochar from Chinese medicinal residue is basically the same as in Example 1, except that "heating the horizontal tube furnace to 500°C at a rate of 10°C / min to activate the carbonized material" is replaced with "heating the horizontal tube furnace to 600°C at a rate of 10°C / min to activate the carbonized material".

[0076] The dynamic CO2 adsorption capacity of the adsorbent was tested using a thermogravimetric analyzer: 10 mg of adsorbent was added to the thermogravimetric analyzer, and the temperature was raised to 120 °C under a N2 atmosphere and maintained at 120 °C for 60 min (during which N2 was continuously introduced at a flow rate of 100 mL / min) to remove impurities from the sample. The mass of the adsorbent at this point was recorded as [value missing]. m 0 (mg), cooled to 30℃, the mass of the adsorbent at this time is recorded as . m (mg); Switch to CO2 atmosphere and adsorb at 30℃ under CO2 atmosphere for 60 min (CO2 flow rate is 100 mL / min). The mass of adsorbent at this time is recorded as: m t (mg). Calculate the CO2 adsorption capacity according to the following formula. q t (mmol / g): The adsorbent was one of the following: the biochar prepared from medicinal herb residues in Examples 1-5, the biochar prepared in Example 6, and the biochar prepared from medicinal herb residues in Examples 7-8. The test results are shown in Table 1.

[0077] Table 1

[0078]

[0079] As shown in Table 1, the biochar made from medicinal residues prepared in Example 1 had the highest CO2 adsorption capacity, which was 2.15 mmol / g.

[0080] The specific surface area and pore structure ratio of the adsorbent were analyzed using a nitrogen adsorption analyzer. The test results are shown in Table 2. The adsorbent is one of the biochar of Chinese medicinal residue prepared in Examples 1-5, the biochar prepared in Example 6, and the biochar of Chinese medicinal residue prepared in Examples 7-8.

[0081] Table 2

[0082]

[0083] As shown in Table 2, the biochar made from medicinal residues prepared in Example 1 has the highest micropore content, at 85.67%. The micropores are a better match for the particle size of CO2 (0.33-0.51 nm).

[0084] Raman analysis was performed on the adsorbent using a Raman analyzer to determine the degree of defects. The test results are as follows: Figure 1 As shown, the adsorbent is one of the biochar of Chinese medicinal residue prepared in Examples 1-5, the biochar prepared in Example 6, and the biochar of Chinese medicinal residue prepared in Examples 7-8.

[0085] Depend on Figure 1 It can be seen that the biochar prepared from medicinal residues in Examples 1-5, the biochar prepared in Example 6, and the biochar prepared from medicinal residues in Examples 7-8 all have obvious D peaks (1345 cm⁻¹). -1 ) and G peak (1590cm) -1 The D peak corresponds to the disorder and edge defects of carbon, while the G peak corresponds to the sp2 particles in the graphite lattice. 2 E of carbon 2g Tensile mode. Intensity ratio of D peak to G peak (I D / I G I is an important parameter characterizing the degree of defects in carbon materials. D / I G The higher the value, the greater the degree of defect in the carbon material. Figure 1 It can be seen that the biochar from the medicinal herb residue prepared in Example 1 has I D / I G The maximum value is 2.53, indicating the highest degree of defect and the richest adsorption sites, which is more conducive to CO2 adsorption.

[0086] The adsorbent was analyzed for nitrogen-containing functional groups using X-ray photoelectron spectroscopy (XPS) to obtain N1s high-resolution XPS spectra. Peak area integration was performed on the characteristic peaks corresponding to pyrrole nitrogen (N-5, peak positions 399.3 eV~400.1 eV), pyridine nitrogen (N-6, peak positions 398.5 eV~398.8 eV), and graphitic nitrogen (NQ, peak positions 400.4 eV~400.9 eV) in the N1s high-resolution XPS spectra to obtain the peak areas of pyrrole nitrogen (N-5), pyridine nitrogen (N-6), and graphitic nitrogen (NQ). The integrated peak area corresponding to NQ); the integrated peak areas of pyrrole nitrogen (N-5) and pyridine nitrogen (N-6) are summed to obtain the edge active nitrogen peak area, and the sum of the integrated peak areas of pyrrole nitrogen (N-5), pyridine nitrogen (N-6) and graphitic nitrogen (NQ) is taken as the total nitrogen peak area. The proportion of edge active nitrogen is calculated by dividing the edge active nitrogen peak area by the total nitrogen peak area (represented by "(N-5) + (N-6)"). Edge active nitrogen can significantly enhance the adsorption affinity of the adsorbent for CO2. The adsorbent is one of the biochar of Chinese medicinal residue prepared in Examples 1-5, the biochar prepared in Example 6, and the biochar of Chinese medicinal residue prepared in Examples 7-8. The test results of the biochar of Chinese medicinal residue prepared in Examples 1-5, the biochar prepared in Example 6, and the biochar of Chinese medicinal residue prepared in Examples 7-8 are as follows. Figures 2-9 As shown, the percentage of edge active nitrogen is detailed in [reference needed]. Figures 2-9 The middle part is “(N-5)+(N-6)”.

[0087] Depend on Figures 2-9 It can be seen that the biochar prepared from medicinal herb residue in Example 1 has the highest proportion of edge-active nitrogen, at 81.54%. The proportion of edge-active nitrogen in the biochar prepared from medicinal herb residue in Example 1 is higher than that in Example 2, indicating that the steam explosion process promotes the generation of edge-active nitrogen. Comparing Examples 3-4 with Example 1 shows that the oxygen content in the mixed gas affects the generation of edge-active nitrogen. Comparing Examples 5-6 with Example 1 shows that using pretreated medicinal herb residue and pretreated sawdust as raw materials results in a higher proportion of edge-active nitrogen. Comparing Examples 7-8 with Example 1 shows that the activation temperature also affects the proportion of edge-active nitrogen.

[0088] The adsorbent was analyzed for oxygen-containing functional groups using X-ray photoelectron spectroscopy (XPS), yielding O1s high-resolution XPS spectra. Peak area integration was performed on the characteristic peaks corresponding to C=O (peak positions 531.6 eV–532.3 eV) and -OH (peak positions 533.5 eV–534.2 eV) in the O1s high-resolution XPS spectra to obtain the integrated peak areas for C=O and -OH, respectively. The peak area ratio of -OH was calculated. The adsorbent was one of the biochar prepared from medicinal herb residues in Examples 1-5, Example 6, and Examples 7-8. The O1s high-resolution XPS spectra of the biochar prepared from medicinal herb residues in Examples 1-5, Example 6, and Examples 7-8 are shown below. Figures 10-17 As shown, the peak area of ​​-OH accounts for... Figures 10-17 The "-OH" symbol is shown in the middle.

[0089] Depend on Figures 10-17 It can be seen that the biochar of medicinal herb residue prepared in Example 1 has the highest peak area ratio of -OH. -OH can enhance the adsorption of CO2 by the adsorbent through acid-base action, which is consistent with the conclusion that the biochar of medicinal herb residue prepared in Example 1 has the highest CO2 adsorption capacity. In Examples 1 to 8, the biochar of medicinal herb residue prepared in Example 4 has a lower peak area ratio of -OH, indicating that the high oxygen (O2) content in the mixed gas is not conducive to the formation of -OH structure; the biochar of medicinal herb residue prepared in Example 8 also has a lower peak area ratio of -OH, indicating that high temperature activation is not conducive to the formation of -OH structure.

[0090] The surface morphology and elemental analysis of the biochar prepared from medicinal herb residues in Examples 1, 2, and 5, as well as the biochar prepared in Example 6, were performed using scanning electron microscopy (Na, Al, Si, and K were selected as target elements before testing, and only the distribution data of these four elements were collected). The results are as follows: Figures 18-21 As shown. By Figures 18-21It can be seen that the biochar prepared from medicinal herb residues in Examples 1, 2, and 5, as well as the biochar prepared in Example 6, all contain Na, Al, Si, and K elements, and their distribution is relatively uniform. K element can react with the surface of the carbonized material to generate CO gas, leaving a large number of nanoscale pores and vacancies, forming abundant micropores that promote CO2 adsorption. The biochar prepared from medicinal herb residues in Example 1 has the highest proportion of K element. Comparing Examples 1 and 2, it can be seen that in Example 1, the powerful physical action generated by the instantaneous release of high-temperature and high-pressure steam during steam explosion better destroys the fibrous structure of the medicinal herb residues and sawdust materials, causing the alkali metal element K to be more completely exposed on the surface of the biochar, thus being more conducive to the subsequent activation etching reaction. Example 5 uses only pretreated medicinal herb residues as raw materials, and Example 6 uses only pretreated sawdust materials as raw materials, resulting in a significantly lower proportion of K element in the biochar prepared from medicinal herb residues in Example 5 and the biochar prepared from Example 6 compared to Example 1. Compared with Example 1, the proportion of K element in Examples 2, 5 and 6 decreased by 8.43%, 2.91% and 2.07% respectively, indicating that the powerful physical effect of the instantaneous release of high-temperature and high-pressure steam during steam explosion has a more significant contribution to increasing the proportion of K element.

[0091] For CO2 adsorption, specific surface area and micropore ratio are factors influencing physical structure, while the proportion of edge active nitrogen and the peak area ratio of -OH are factors influencing chemical functional groups. These different factors contribute differently to CO2 adsorption. Using specific surface area, micropore ratio, edge active nitrogen ratio, and -OH peak area ratio as evaluation indicators, in Examples 1-8, the biochar prepared from medicinal herb residue in Example 1 had the highest proportions of micropores, edge active nitrogen, and -OH peak area ratios, with only a slightly smaller specific surface area than Example 6. Examples 2-8 showed a decrease in one or more evaluation indicators compared to Example 1. In summary, the biochar prepared from medicinal herb residue in Example 1 achieved the optimal CO2 adsorption capacity through the synergistic effect of specific surface area, micropore ratio, edge active nitrogen ratio, and -OH peak area ratio.

[0092] In Example 1, high-temperature, high-pressure steam penetrates the internal pores of the raw materials (medicinal herbal residue and wood chips). The shear force generated by the instantaneous pressure release tears the fiber structure, generating -OH groups and pyrrolidone nitrogen (N-5) and pyridine nitrogen (N-6). Simultaneously, it exposes more endogenous metals (especially potassium) in the wood chips and medicinal herbal residue, promoting the etching reaction on the surface of the carbonized material and generating more microporous structures. The blending of wood chips (pine wood chips) and medicinal herbal residue avoids the defects of a single structure. The pyrolysis of pine wood chips can form a highly cross-linked, rigid aromatic framework, effectively resisting the structural collapse of high-temperature activation, locking the active sites of metals, and providing a stable matrix for the etching of the mixed gas (which acts as a gas activator). The main components of medicinal herbal residue are hemicellulose and cellulose. After pyrolysis, the volatile matter in the medicinal herbal residue is fully removed, providing a dense porous structure that promotes the transport of the gas activator, making the activation reaction more complete and generating more nanoscale micropores. Micropores are a better match for CO2 particle size (0.33-0.51 nm), and a high micropore ratio can promote the adsorption of CO2 by biochar made from medicinal herb residues. The final product is a biochar made from medicinal herb residues with stable structure, high micropore ratio, high specific surface area, high -OH content, high edge active nitrogen content, and rich in active metal sites, thereby promoting CO2 adsorption.

[0093] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing biochar from medicinal herb residue, characterized in that, Includes the following steps: Step 1: Mix the pretreated Chinese medicine residue and pretreated wood chips, steam-explode to obtain explosives, dry the explosives, sieve to obtain a complex. The ratio of pretreated Chinese medicine residue to pretreated wood chips by mass is (0.8~1.2):(0.8~1.2). Step 2: Under a nitrogen or inert gas atmosphere, the composite is carbonized at 550~650℃ for 40~80 min, and then cooled to room temperature to obtain the carbonized material. Step 3: In a mixed gas atmosphere, the carbonized material is heated to 450-550°C at a heating rate of 8-12°C / min to activate the carbonized material. After cooling to room temperature, the biochar of Chinese herbal medicine residue is obtained. The mixed gas includes carbon dioxide, water vapor, oxygen and nitrogen. The ratio of carbon dioxide, water vapor, oxygen and nitrogen by volume is (9-11):(9-11):(2-4):(74-80).

2. The preparation method according to claim 1, characterized in that, In step 1, the medium for steam explosion is saturated steam, the pressure of steam explosion is 2~2.5MPa, the temperature of steam explosion is 180~220℃, and the pressure maintenance time of steam explosion is 8~12min.

3. The preparation method according to claim 1, characterized in that, In step 1, the Chinese medicine residue is a mixture of danshen residue, sanqi residue and borneol residue. By mass parts, the ratio of danshen residue, sanqi residue and borneol residue is (87~92):(17~18):(0.95~1).

4. The preparation method according to claim 1, characterized in that, In step 1, the wood chips are pine wood chips.

5. The preparation method according to claim 1, characterized in that, In step 1, the particle size of the complex is 40-80 mesh.

6. The preparation method according to claim 1, characterized in that, In step 1, the method for obtaining pretreated Chinese medicine residue includes: crushing and sieving the Chinese medicine residue to obtain pretreated Chinese medicine residue with a particle size of 40-80 mesh.

7. The preparation method according to claim 1, characterized in that, In step 1, the method for obtaining pretreated wood chip material includes: crushing and sieving the wood chip material to obtain pretreated wood chip material with a particle size of 40-80 mesh.

8. Biochar from medicinal herb residue obtained by the preparation method according to any one of claims 1 to 7.

9. The application of biochar from medicinal herb residue as described in claim 8 in CO2 adsorption.

10. The application according to claim 9, characterized in that, The CO2 adsorption capacity of biochar from Chinese medicinal residues is 2.15 mmol / g.

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