Potassium salt-activated ginkgo outer seed coat-based carbon adsorbent, and preparation method and application thereof

Abstract

The application provides a potassium salt activated ginkgo outer seed coat based carbon adsorbent and a preparation method and application thereof, and belongs to the technical field of new materials. The preparation method of the potassium salt activated ginkgo outer seed coat based carbon adsorbent comprises the following steps: performing first heat treatment on white ginkgo outer seed coat powder in a protective atmosphere to obtain biochar powder; mixing the biochar powder and a potassium salt containing activator to obtain a suspension; drying the suspension to obtain a modified precursor; and performing second heat treatment on the modified precursor in a protective atmosphere to obtain the potassium salt activated ginkgo outer seed coat based carbon adsorbent. The white ginkgo outer seed coat is used as a raw material to prepare the biochar adsorbent, and the efficient resource utilization of waste is realized. The raw material is cheap and easy to obtain, and the preparation cost of the adsorbent is significantly reduced. The potassium salt containing activator is used to replace the traditional activator, the reagent is non-toxic, neutral and does not corrode the equipment, and the equipment loss and the alkaline wastewater treatment cost caused by KOH activation are effectively avoided.

Description

Technical Field

[0001] This invention relates to the field of new materials technology, and in particular to a potassium salt-activated Ginkgo biloba seed coat-based carbon adsorbent, its preparation method, and its application. Background Technology

[0002] Global climate change has become a major challenge facing humanity. Carbon dioxide (CO2), a major greenhouse gas, directly contributes to ecological crises such as glacial melting and frequent extreme weather events due to excessive emissions. Meanwhile, natural gas, as a clean and low-carbon fossil fuel, continues to increase its share in the global energy mix, becoming a key vehicle for energy transition. However, natural gas typically contains impurities such as CO2 and N2 after extraction. These impurities not only reduce the calorific value of natural gas but also react with water to form acidic solutions that corrode pipelines and equipment. Under low temperature and high pressure, they can also form hydrates that cause pipeline blockages, severely impacting transportation safety and efficiency. Therefore, the efficient removal of impurities such as CO2 and N2 during natural gas purification has become an urgent technical problem to be solved.

[0003] Currently, mainstream CO2 capture technologies include absorption, membrane separation, cryogenic separation, and adsorption separation. Among these, pressure swing adsorption (PSA) technology, as the core branch of adsorption separation, has become the preferred solution in the field of natural gas purification due to its significant energy consumption advantages, strong operational flexibility, good environmental compatibility, and excellent separation efficiency. The core of adsorption separation technology lies in the development of high-performance adsorbents. Currently, various porous adsorbents have been developed for the adsorption and separation of binary mixtures such as CO2 / N2, CO2 / CH4, and CH4 / N2, including metal-organic frameworks (MOFs), zeolite molecular sieves, and carbon-based materials (including activated carbon and carbon molecular sieves).

[0004] Biomass-based biochar, as a novel carbon-based adsorbent material, possesses significant structural and performance advantages: it has a well-developed hierarchical pore structure and ultra-high specific surface area, providing abundant active sites for CO2 adsorption; its surface is rich in oxygen-containing functional groups such as hydroxyl and carboxyl groups, as well as tunable basic sites, enhancing CO2 adsorption selectivity through the synergistic effect of physical adsorption (van der Waals forces) and chemical adsorption (covalent / ionic bonding). Simultaneously, biomass raw materials are widely available and inexpensive, enabling the resource utilization of agricultural and forestry waste and significantly reducing adsorbent preparation costs; the preparation process has low energy consumption, and biochar itself possesses carbon fixation properties, aligning with the environmentally friendly requirements under the "dual carbon" goal. Based on these advantages, biomass-based biochar shows broad application prospects in the field of gas adsorption and separation.

[0005] However, raw biochar suffers from problems such as incomplete pore development (low micropore ratio and poor pore connectivity), insufficient surface active sites, and adsorption capacity and selectivity not reaching optimal values ​​for industrial applications. To maximize its CO2 capture capacity, appropriate modification of the biochar is necessary. Among numerous modification methods, chemical activation with potassium-based compounds is a mature, simple, and relatively low-cost method with excellent pore-forming efficiency. + At high temperatures, KOH can embed into the carbon framework of biochar, breaking C-C bonds to form well-developed pores. Furthermore, during activation, potassium (K) can be converted into alkaline sites, enhancing CO2 chemisorption capacity. Among these, KOH has become a traditional mainstream activator due to its significant activation effect (allowing biochar specific surface area to exceed 2000 m² / g). Wang et al. prepared glucose-based carbon materials with high specific surface area, high CO2 adsorption capacity, and CO2 / CH4 / N2 selectivity using glucose as the carbon source and KOH as the activator. At 30 bar, its selectivity for CO2 / N2 (0.5:0.5) and CO2 / CH4 (0.5:0.5) mixed gases reached 20 and 4.5, respectively (Chemical Engineering Journal, 2017, 327:51-59). However, KOH is highly corrosive, causing severe corrosion to equipment, and generates a large amount of alkaline wastewater after activation, resulting in high environmental treatment costs and significant safety hazards and environmental pressures.

[0006] In recent years, researchers have begun to explore the use of potassium-containing salt activators as an alternative to KOH. Potassium-containing salt activators are neutral and non-toxic in their dissolved state, posing no risk of equipment corrosion, resulting in a safer operating environment, and avoiding the environmental treatment and equipment maintenance costs associated with KOH activation. Existing research has shown that potassium-containing salt activators can be effective activators for preparing porous carbon materials. For example, biochar prepared from rice husks activated with potassium-containing salt activators exhibits good CO2 adsorption performance; using cellulose aerogel as a precursor and potassium-containing salt activators as both activators and salt templates can promote the formation of well-developed nanostructures; activated carbon prepared using glucose as a carbon source and potassium-containing salt activators as activators can achieve a CO2 adsorption capacity of 3.57 mmol / g. However, research on the preparation of high-performance gas adsorbents using ginkgo seed coats as raw materials and activated with potassium-containing salt activators has not yet been reported.

[0007] The outer seed coat of ginkgo (Ginkgo biloba) is the fleshy part outside the hard shell of the ginkgo seed, commonly known as the ginkgo seed coat, accounting for about 75% of the total seed weight. The raw material for ginkgo outer seed coat can be fresh ginkgo outer seed coat, dried ginkgo outer seed coat, ginkgo outer seed coat extraction residue, defatting residue, deacidification residue, ginkgo outer seed coat, or a by-product of ginkgo seed processing. my country's annual total ginkgo production exceeds 12,000 tons, with outer seed coat production reaching 15,000 to 20,000 tons. In the past, when harvesting ginkgo kernels, people mostly discarded the outer seed coat, resulting in significant resource waste and environmental pollution. If this inexpensive and readily available agricultural and forestry waste could be used as a raw material to prepare high-performance biochar adsorbents, it would not only achieve resource utilization of waste but also provide a highly efficient, low-cost, and environmentally friendly CO2 / CH4 / N2 adsorption and separation material for the natural gas purification field.

[0008] Based on the innovative combination of biochar adsorbent and potassium salt activator, the current research still faces key challenges such as insufficient selectivity due to the close molecular diameters of CO2, CH4, and N2 (0.33~0.38nm), especially the low CH4 / N2 separation coefficient, the easy occupation of active sites by moisture and impurities in actual working conditions, and the collapse of biochar channels and loss of functional groups after multiple PSA cycles.

[0009] Therefore, it is of great significance to provide a biochar-based adsorbent that can accurately construct a microporous structure adapted to the separation of target gases, and has both high adsorption capacity and high selectivity, as well as its preparation method and application. Summary of the Invention

[0010] The purpose of this invention is to provide a potassium salt-activated ginkgo seed coat-based carbon adsorbent, its preparation method, and its application, in order to solve the technical problems existing in the prior art, such as the strong corrosivity of potassium-based activators, imperfect pore structure of biochar, low CO2 / CH4 / N2 adsorption selectivity, and low resource utilization rate of ginkgo seed coat waste.

[0011] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a potassium salt-activated Ginkgo biloba seed coat-based carbon adsorbent, comprising the following steps: 1) The outer seed coat powder of ginkgo was subjected to a first heat treatment under a protective atmosphere to obtain biochar powder; 2) Mix biochar powder and potassium salt activator to obtain a suspension; 3) Dry the suspension to obtain the modified precursor; 4) The modified precursor was subjected to a second heat treatment under a protective atmosphere to obtain potassium salt activated ginkgo seed coat-based carbon adsorbent.

[0012] Furthermore, in step 1), the particle size of the ginkgo seed coat powder is 80-120 mesh; The temperature of the first heat treatment is 400~600℃, the time of the first heat treatment is 1~4h, and the heating rate of the first heat treatment is 1~5℃ / min.

[0013] Furthermore, in step 2), the potassium-containing activator includes one or more of potassium citrate, potassium oxalate, potassium carbonate, potassium acetate, and potassium tartrate. The mass ratio of the potassium salt activator to the biochar powder is 0.5~3:1.

[0014] Furthermore, in step 2), the mixing is either a dry mix or a wet mix; The mixing is carried out by stirring at a speed of 400-600 rpm for a duration of 6-10 hours.

[0015] Furthermore, in step 3), the drying temperature is 100~120℃.

[0016] Furthermore, in step 4), the temperature of the second heat treatment is 700~900℃, the time of the second heat treatment is 1~4h, and the heating rate of the second heat treatment is 1~5℃ / min.

[0017] Furthermore, in step 4), after the second heat treatment is completed, centrifugation, washing, and drying are also included; The centrifugation speed is 8000~10000 rpm, and the centrifugation time is 3~5 min; The drying temperature is 100~120℃.

[0018] Furthermore, in steps 1) and 4), the protective atmosphere is independently a nitrogen atmosphere.

[0019] This invention provides a potassium salt-activated Ginkgo biloba seed coat-based carbon adsorbent prepared by the aforementioned preparation method.

[0020] The present invention also provides an application of the potassium salt activated ginkgo seed coat-based carbon adsorbent in gas adsorption and separation.

[0021] The beneficial effects of this invention are: 1) This invention realizes the resource utilization of agricultural waste, turning the outer seed coat of ginkgo into a valuable resource, significantly reducing raw material costs, and highly aligning with the green and environmentally friendly concept under the dual carbon target; it uses a neutral, non-toxic potassium salt activator to replace the traditional highly corrosive potassium hydroxide as the activator, which not only eliminates the risk of corrosion to production equipment and avoids the cumbersome alkaline wastewater treatment process, but also ensures the safety of the operating environment. At the same time, the potassium salt activator can uniformly release activating components during high-temperature pyrolysis, achieving gentle directional pore formation of material pores and synergistic optimization of surface functional groups; 2) The preparation method of the present invention is short and efficient, requiring only two heat treatment steps: pre-carbonization and high-temperature activation. The entire process is simple to operate, key parameters are controllable, and it does not rely on complex special equipment, which greatly reduces the difficulty of production. 3) Through the activation effect of potassium salt activator, the material has an ordered microporous structure adapted to gas separation and has a high specific surface area. Furthermore, the alkali metal potassium element introduced during the activation process can be embedded in the carbon skeleton, effectively enhancing electrostatic interaction, thereby significantly improving the binding energy and adsorption capacity of the material for carbon dioxide, and achieving a precise match between microstructure and adsorption performance. 4) This invention utilizes the synergistic effect of the carbon skeleton formed by the processing residue of ginkgo seed coat or ginkgo seed coat and potassium salt activator to regulate the microporous structure of carbon materials, thereby forming a pore size distribution and surface active sites suitable for the separation of small molecule gases such as CO2, CH4, and N2. This improves the adsorption selectivity of CO2 / N2, CO2 / CH4, CH4 / N2 and CO2 / CH4 / N2 systems, and can be widely used in natural gas purification, coalbed methane utilization and flue gas treatment. It is particularly suitable for pressure swing adsorption processes and has strong market competitiveness and potential for large-scale application. Attached Figure Description

[0022] Figure 1 Comparison of carbon dioxide adsorption capacity of the ginkgo seed coat modified biochar materials prepared in Examples 1-4; Figure 2 Comparison of methane adsorption capacity of the ginkgo seed coat modified biochar materials prepared in Examples 1-4; Figure 3 The nitrogen adsorption capacity comparison charts of the adsorbents prepared by the modified biochar material of ginkgo seed coat in Examples 1-4 are shown. Figure 4 Comparison of the adsorption selectivity of the Ginkgo biloba modified biochar materials prepared in Examples 1-4 for CO2 / N2 (15:85); Figure 5 Comparative graphs showing the adsorption selectivity of the Ginkgo biloba modified biochar materials prepared in Examples 1-4 for CO2 / CH4 (10:90); Figure 6 Comparative graphs of the adsorption selectivity of the modified biochar material from the outer seed coat of Ginkgo biloba prepared in Examples 1-4 for CH4 / N2 (30:70); Figure 7 This is a comparison chart of the carbon dioxide adsorption capacity of the ginkgo seed coat modified biochar materials prepared with different activators in Example 3 and Comparative Examples 1-3. Figure 8A comparison chart of the methane adsorption capacity of the ginkgo seed coat modified biochar materials prepared with different activators in Example 3 and Comparative Examples 1-3. Figure 9 A comparison chart of nitrogen adsorption capacity of the ginkgo seed coat modified biochar materials prepared with different activators in Example 3 and Comparative Examples 1-3. Figure 10 This is a comparison chart showing the adsorption selectivity of Ginkgo biloba modified biochar materials prepared with different activators in Example 3 and Comparative Examples 1-3 for CO2 / N2 (15:85). Figure 11 This is a comparison of the adsorption selectivity of Ginkgo biloba modified biochar materials prepared with different activators in Example 3 and Comparative Examples 1-3 for CO2 / CH4 (10:90). Figure 12 This is a comparison of the adsorption selectivity of Ginkgo biloba modified biochar materials prepared with different activators in Examples 3 and Comparative Examples 1-3 for CH4 / N2 (30:70). Detailed Implementation

[0023] This invention provides a method for preparing a potassium salt-activated Ginkgo biloba seed coat-based carbon adsorbent, comprising the following steps: 1) The outer seed coat powder of ginkgo was subjected to a first heat treatment under a protective atmosphere to obtain biochar powder; 2) Mix biochar powder and potassium salt activator to obtain a suspension; 3) Dry the suspension to obtain the modified precursor; 4) The modified precursor was subjected to a second heat treatment under a protective atmosphere to obtain potassium salt activated ginkgo seed coat-based carbon adsorbent.

[0024] In this invention, in step 1), the particle size of the ginkgo seed coat powder is 80-120 mesh, preferably 90-110 mesh, and more preferably 100 mesh; The temperature of the first heat treatment is 400~600℃, preferably 450~550℃, and more preferably 500℃; the time of the first heat treatment is 1~4h, preferably 1.5~3.5h, and more preferably 2~3h; the heating rate of the first heat treatment is 1~5℃ / min, preferably 2~4℃ / min, and more preferably 3℃ / min.

[0025] In this invention, in step 2), the potassium salt activator includes one or more of potassium citrate, potassium oxalate, potassium carbonate, potassium acetate, and potassium tartrate, preferably one or more of potassium citrate, potassium oxalate, potassium acetate, and potassium tartrate, and more preferably one or more of potassium citrate, potassium oxalate, and potassium tartrate. The mass ratio of the potassium salt activator to the biochar powder is 0.5~3:1, preferably 1~2.5:1, and more preferably 2:1.

[0026] In this invention, in step 2), the mixing is either dry mixing or wet mixing, preferably wet mixing; The mixing is carried out by stirring, with a stirring speed of 400~600 rpm, preferably 450~550 rpm, and more preferably 500 rpm; the stirring time is 6~10 h, preferably 7~9 h, and more preferably 8 h.

[0027] In this invention, the wet mixing method involves dispersing biochar powder in a potassium-containing activator and mixing it.

[0028] In this invention, the dry mixing method involves physically mixing biochar powder and a potassium-containing activator.

[0029] In this invention, in step 3), the drying temperature is 100~120℃, preferably 105~115℃, and more preferably 110℃.

[0030] In this invention, in step 4), the temperature of the second heat treatment is 700~900℃, preferably 750~850℃, and more preferably 800℃; the time of the second heat treatment is 1~4h, preferably 1.5~3.5h, and more preferably 2~3h; the heating rate of the second heat treatment is 1~5℃ / min, preferably 2~4℃ / min, and more preferably 3℃ / min.

[0031] In this invention, step 4) further includes centrifugation, washing, and drying after the second heat treatment is completed; The centrifugation speed is 8000~10000 rpm, preferably 8500~9500 rpm, and more preferably 9000 rpm; the centrifugation time is 3~5 min, preferably 3.5~4.5 min, and more preferably 4 min; The drying temperature is 100~120℃, preferably 105~115℃, and more preferably 110℃.

[0032] In this invention, in steps 1) and 4), the protective atmosphere is preferably a nitrogen atmosphere.

[0033] This invention provides a potassium salt-activated Ginkgo biloba seed coat-based carbon adsorbent prepared by the aforementioned preparation method.

[0034] The present invention also provides an application of the potassium salt activated ginkgo seed coat-based carbon adsorbent in gas adsorption and separation.

[0035] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0036] Example 1

[0037] After drying the outer seed coat of ginkgo, it was pulverized using a pulverizer and sieved through a 100-mesh sieve to obtain ginkgo outer seed coat powder. Then, under a nitrogen atmosphere, the temperature was increased to 500℃ at a rate of 2℃ / min for a first heat treatment for 2 hours to obtain biochar powder. Biochar powder was dispersed in potassium citrate solution and stirred at 500 rpm for 8 hours. The mass ratio of potassium citrate to biochar powder in the potassium citrate solution was 2:1. After mixing evenly, a suspension was obtained. The suspension was dried at 120°C to obtain the modified precursor; The modified precursor was transferred to a tube furnace and subjected to a second heat treatment at 800°C at a rate of 2°C / min under a nitrogen atmosphere for 2 hours. After the second heat treatment, it was centrifuged at 9000 rpm for 4 minutes, washed, and dried at 110°C to obtain a potassium salt activated ginkgo seed coat-based carbon adsorbent, denoted as AC-K3C6H5O7-2.

[0038] Example 2

[0039] Compared with Example 1, the only difference is that in Example 2, the mass ratio of potassium citrate to biochar powder in the potassium citrate solution is 0.5:1, denoted as AC-K3C6H5O7-0.5.

[0040] Example 3

[0041] Compared with Example 1, the only difference is that in Example 3, the mass ratio of potassium citrate to biochar powder in the potassium citrate solution is 1:1, denoted as AC-K3C6H5O7-1.

[0042] Example 4

[0043] Compared with Example 1, the only difference is that in Example 4, the mass ratio of potassium citrate to biochar powder in the potassium citrate solution is 3:1, denoted as AC-K3C6H5O7-3.

[0044] Example 5

[0045] Compared with Example 1, the only difference is that in Example 5, the mixing method of potassium citrate and biochar powder is physical mixing, denoted as AC / K3C6H5O7-2g.

[0046] The performance of the potassium salt-activated ginkgo seed coat-based carbon adsorbents prepared in Examples 1-5 was tested using a gas adsorption analyzer. The test method was as follows: Adsorbent pretreatment: Place the adsorbent to be tested in a 120℃ oven and dry overnight to remove residual gas on the adsorbent; Adsorbent loading: Weigh approximately 2g of adsorbent and place it in the adsorption tank. Seal the top with degreased cotton to prevent adsorbent powder from entering the pipeline and affecting the operation of the solenoid valve and measurement accuracy. Connect the adsorption tank to the adsorption device and wait for measurement. Leak detection of the adsorption device: Place the adsorption device in a constant temperature water bath at the temperature to be measured, and fill the adsorption device with 0.7MPa of He to check for leaks and ensure the airtightness of the gas path. Determination of adsorption isotherms: The measuring device is turned on and runs automatically. During automatic operation, helium is first introduced to measure the dead volume of the device, and then the adsorbent isotherm is measured. During the measurement process, the gas to be tested is charged to the specified pressure. Then, the pressures before and after adsorption are measured. Since the adsorption of N2, CH4, and CO2 on the adsorbent is reversible and can be desorbed and regenerated under vacuum, after the adsorption isotherm test of N2 is completed, vacuum desorption for 30 minutes is required before the isotherm of the next gas is measured. The adsorption isotherms of N2, CH4, and CO2 are tested sequentially under the same conditions.

[0047] Adsorbent recovery: After the measurement process is completed, the adsorbent is taken out and placed in a 120℃ oven to dry and regenerate, awaiting subsequent processing.

[0048] The adsorption isotherms of the potassium salt-activated ginkgo seed coat-based carbon adsorbents prepared in Examples 1-5 were fitted using the Sips isotherm model: The Sips isotherm model is a hybrid adsorption isotherm equation that combines the characteristics of the Langmuir and Freundlich models. It is often used to describe adsorption behavior on non-ideal surfaces. By introducing a heterogeneity parameter, this model can, to some extent, correct for biases introduced by the ideal adsorption assumption, making it suitable for non-uniform adsorbent systems with uneven energy distribution. Due to its applicability and rationality, the Sips model is widely used for isotherm data fitting and mechanism analysis in fields such as porous material adsorption and gas separation. Its expression 1 is shown below: Formula 1, Where, q t express t The amount of adsorption at time q m Indicates saturated adsorption capacity. K The constant of the Sips isotherm. n The Sips isotherm index represents the non-uniformity of energy on the adsorbent surface.

[0049] The formula for calculating the adsorption and separation selectivity (S) of the potassium salt activated ginkgo seed coat-based carbon adsorbents prepared in Examples 1-5 is shown in Equation 2: Equation 2, In Equation 2, x i With y i Represent i The mole fraction of the component in the adsorbed phase and the gas phase. This parameter is calculated based on adsorption isotherm data of the pure component, using the Ideal Adsorption Solution Theory (IAST) proposed by Myers and Prausnitz, and numerically solved using the open-source computational program pyIAST.

[0050] Adsorption isotherm test results are as follows Figures 1-3 As shown. By Figures 1-3 It can be seen that the biochar material AC-K3C6H5O7-2 modified from the outer seed coat of Ginkgo biloba has an adsorption capacity of 62.32 mL / g for carbon dioxide, 29.23 mL / g for methane, and 9.29 mL / g for nitrogen at 0.1 MPa and 30℃.

[0051] Adsorption selectivity test results as follows Figures 4-6 As shown. By Figures 4-6 It can be seen that the adsorption selectivity of the modified biochar material AC-K3C6H5O7-2 of ginkgo seed coat at 0.1 MPa is 29.62 for CO2 / N2 (15:85), 4.98 for CO2 / CH4 (10:90), and 5.68 for CH4 / N2 (30:70).

[0052] Comparative Example 1

[0053] Compared with Example 3, the only difference is that potassium oxalate was used instead of potassium citrate in Comparative Example 1, denoted as AC-K2C2O4-1.

[0054] Comparative Example 2

[0055] Compared with Example 3, the only difference is that potassium carbonate was used instead of potassium citrate in Comparative Example 2, denoted as AC-K2CO3-1.

[0056] Comparative Example 3

[0057] Compared with Example 3, the only difference is that potassium hydroxide was used instead of potassium citrate in Comparative Example 3, denoted as AC-KOH-1.

[0058] Adsorption isotherm test results are as follows Figures 7-9 As shown. By Figures 7-9It can be seen that the biochar material AC-KOH-1 modified from the outer seed coat of Ginkgo biloba has an adsorption capacity of 60.68 mL / g for carbon dioxide, 29.93 mL / g for methane, and 9.40 mL / g for nitrogen at 0.1 MPa and 30℃.

[0059] Adsorption selectivity test results as follows Figures 10-12 As shown. By Figures 10-12 It can be seen that the adsorption selectivity of the modified biochar material AC-KOH-1 of ginkgo seed coat at 0.1 MPa is 19.07 for CO2 / N2 (15:85), 3.82 for CO2 / CH4 (10:90), and 4.72 for CH4 / N2 (30:70).

[0060] The gas adsorption performance test results of the ginkgo seed coat-based carbon adsorbents prepared in Examples 1-4 and Comparative Examples 1-3 are shown in Table 1.

[0061] Table 1. Gas adsorption performance test results of the ginkgo seed coat-based carbon adsorbents prepared in Examples 1-4 and Comparative Examples 1-3.

[0062] As can be seen from the above embodiments, the present invention provides a potassium salt-activated Ginkgo biloba seed coat-based carbon adsorbent, its preparation method, and its application. The preparation method of the potassium salt-activated Ginkgo biloba seed coat-based carbon adsorbent of the present invention includes the following steps: subjecting Ginkgo biloba seed coat powder to a first heat treatment under a protective atmosphere to obtain biochar powder; mixing the biochar powder with a potassium salt-containing activator to obtain a suspension; drying the suspension to obtain a modified precursor; and subjecting the modified precursor to a second heat treatment under a protective atmosphere to obtain the potassium salt-activated Ginkgo biloba seed coat-based carbon adsorbent. The present invention compares the effects of activation by different activators on the adsorption and separation performance of the adsorbent. Potassium carbonate and potassium hydroxide, due to their stronger alkalinity and corrosive ability, produce more pores after activation, thus exhibiting higher gas adsorption capacity. Potassium salt-containing activators, after activation, more precisely construct microporous structures suitable for the separation of target gases, which is more conducive to the separation of CO2 / N2, CO2 / CH4, CH4 / N2, and CO2 / CH4 / N2.

[0063] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a potassium salt-activated Ginkgo biloba seed coat-based carbon adsorbent, characterized in that, Includes the following steps: 1) The outer seed coat powder of ginkgo was subjected to a first heat treatment under a protective atmosphere to obtain biochar powder; 2) Mix biochar powder and potassium salt activator to obtain a suspension; 3) Dry the suspension to obtain the modified precursor; 4) The modified precursor was subjected to a second heat treatment under a protective atmosphere to obtain potassium salt activated ginkgo seed coat-based carbon adsorbent.

2. The method for preparing the potassium salt-activated ginkgo seed coat-based carbon adsorbent according to claim 1, characterized in that, In step 1), the particle size of the ginkgo seed coat powder is 80-120 mesh. The temperature of the first heat treatment is 400~600℃, the time of the first heat treatment is 1~4h, and the heating rate of the first heat treatment is 1~5℃ / min.

3. The method for preparing the potassium salt-activated ginkgo seed coat-based carbon adsorbent according to claim 2, characterized in that, In step 2), the potassium salt activator includes one or more of potassium citrate, potassium oxalate, potassium carbonate, potassium acetate, and potassium tartrate. The mass ratio of the potassium salt activator to the biochar powder is 0.5~3:

1.

4. The method for preparing the potassium salt-activated ginkgo seed coat-based carbon adsorbent according to claim 2 or 3, characterized in that, In step 2), the mixing is either dry mixing or wet mixing; The mixing is carried out by stirring at a speed of 400-600 rpm for a duration of 6-10 hours.

5. The method for preparing the potassium salt-activated ginkgo seed coat-based carbon adsorbent according to claim 4, characterized in that, In step 3), the drying temperature is 100~120℃.

6. The method for preparing the potassium salt-activated ginkgo seed coat-based carbon adsorbent according to claim 5, characterized in that, In step 4), the temperature of the second heat treatment is 700~900℃, the time of the second heat treatment is 1~4h, and the heating rate of the second heat treatment is 1~5℃ / min.

7. The method for preparing the potassium salt-activated ginkgo seed coat-based carbon adsorbent according to claim 6, characterized in that, In step 4), after the second heat treatment is completed, centrifugation, washing, and drying are also included. The centrifugation speed is 8000~10000 rpm, and the centrifugation time is 3~5 min; The drying temperature is 100~120℃.

8. The method for preparing the potassium salt-activated ginkgo seed coat-based carbon adsorbent according to claim 1, characterized in that, In steps 1) and 4), the protective atmosphere is independently nitrogen.

9. A potassium salt-activated Ginkgo biloba seed coat-based carbon adsorbent prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the potassium salt activated ginkgo seed coat-based carbon adsorbent according to claim 9 in gas adsorption and separation.

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