CO2 adsorbent and preparation method thereof

Abstract

The invention belongs to the technical field of adsorbents, and particularly relates to a CO2 adsorbent and a preparation method thereof.The preparation method comprises the following steps that S1, after an organic magnesium precursor and a calcium carbonate precursor are fully stirred in absolute methanol, a mixed solution is formed and dried, an intermediate product is obtained, then the intermediate product is calcined and decomposed, and a calcium-magnesium mixture is obtained; s2, adding waste lithium iron phosphate battery powder and sodium nitrate into the prepared calcium-magnesium mixture, then fully stirring and mixing in absolute methanol to obtain a mixed solution, and drying to obtain a composite MgO-based adsorbent; fe < + > contained in the waste lithium iron phosphate battery powder can regulate and control the adsorption-desorption dynamic performance of CO2 through the oxidation-reduction characteristic, and the reaction activation energy is reduced; li < + > migrates in a sodium nitrate molten salt system, so that the density of alkaline sites on the surface of MgO can be increased, and the chemical adsorption capacity on CO2 is enhanced. The adsorbent has the characteristics of high adsorption capacity, high adsorption rate, excellent cycle stability and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of adsorbents, and particularly relates to a CO 2 adsorbent and a preparation method thereof. Background Art

[0002] Currently, the global emissions of CO 2 are increasing at an alarming rate year by year, which has led to global warming and the frequent occurrence of various extreme weather conditions. In order to slow down the emissions of CO 2 , countries are working hard to develop CO 2 capture technologies.

[0003] Carbon Capture, Utilization and Storage (CCUS) refers to the process of capturing, utilizing, transporting CO 2 produced by industrial and related energy industries to a storage site and isolating it from the atmosphere for a long time. The CO 2 capture technologies of CCUS include pre-combustion capture, post-combustion capture, and oxy-fuel combustion capture. Among them, the most technically mature is post-combustion capture. The technology based on the magnesium cycle and magnesium cycle for CO 2 capture is considered to be one of the most promising post-combustion CO 2 capture technologies today, and it can be directly used for the treatment of flue gas in various factories. For the capture of CO 2 , magnesium-based adsorbents can cyclically capture CO 2 in coal combustion tail gas. The reaction formula is as follows: MgO + CO 2 → MgCO 3 MgCO 3 → MgO + CO 2 However, for the cyclic adsorption of CO 2 using ordinary magnesium-based adsorbents, the CO 2 adsorption capacity of magnesium-based adsorbents will decrease significantly after multiple cyclic reactions. Therefore, it is of great significance to study how to improve the CO 2 adsorption capacity of MgO-based cyclic adsorption and reduce the CO 2 capture cost of the system. Summary of the Invention

[0004] The present invention discloses a CO 2 adsorbent and a preparation method thereof, mainly solving the problem of poor CO 2 adsorption capacity of MgO-based cyclic adsorption at present.

[0005] To achieve the above object, the present invention provides a CO2 Preparation method of adsorbent, comprising the following steps: S1: An organic magnesium precursor and a calcium carbonate precursor are fully stirred in anhydrous methanol to form a mixed solution, which is dried to obtain an intermediate product, and then the intermediate product is calcined and decomposed to obtain a calcium-magnesium mixture; S2: In the obtained calcium-magnesium mixture, waste lithium battery powder and sodium nitrate are added. The waste lithium battery powder includes waste lithium iron phosphate battery powder. The mass ratio of the calcium-magnesium mixture to the waste lithium iron phosphate battery powder is 95-97%, and the mass ratio of the calcium-magnesium mixture to sodium nitrate is 80-88%. Then, they are fully stirred and mixed in anhydrous methanol to obtain a mixed solution, which is dried to prepare a composite MgO-based adsorbent.

[0006] Preferably, the organic magnesium precursor is a MgO precursor.

[0007] Preferably, the MgO precursor includes any one or more of magnesium oxalate, magnesium citrate anhydrous, magnesium lactate, magnesium ethoxide, magnesium acetate, and magnesium gluconate.

[0008] Preferably, the calcium carbonate precursor includes any one or more of calcium lactate pentahydrate, dolomite, calcium acetate anhydrous, and calcium gluconate.

[0009] Preferably, in the intermediate product, the mass percentage of the organic magnesium precursor is 80%-90%, and the mass percentage of the calcium carbonate precursor is 10%-20%.

[0010] Preferably, the intermediate product is calcined and decomposed in a muffle furnace under an air atmosphere. The calcination temperature of the muffle furnace is 400-600°C, the heating rate is 2-10°C / min, and the reaction time is 1-3 h.

[0011] Preferably, the waste lithium battery powder is obtained by disassembling the recycled waste lithium battery, crushing it to a particle size <1 mm, passing a N 2 / H 2 mixed gas in a tubular furnace, pyrolyzing to remove the PVDF binder, and obtaining a nanoscale composite powder by ball milling.

[0012] The present invention also provides a CO 2 adsorbent prepared by the above CO 2 adsorbent preparation method.

[0013] The technical solution provided by the present invention has at least the following technical effects: By using an organic magnesium precursor and a calcium carbonate precursor to obtain a calcium-magnesium mixture, MgO with a high adsorption capacity is combined with calcium carbonate to construct a composite material rich in pore structure and large specific surface area, effectively reducing CO 2Mass transfer resistance during the adsorption process. Meanwhile, sodium nitrate and waste lithium battery powder are introduced as dopants. Sodium nitrate can provide additional adsorption active sites for MgO and reduce the CO 2 adsorption activation energy, improving the reaction kinetics performance. The main component of the waste lithium iron phosphate battery powder is lithium iron phosphate, and the contained Fe³ + can regulate the adsorption-desorption kinetics performance of CO 2 through its redox characteristics and reduce the reaction activation energy; meanwhile, the migration of Li + in the sodium nitrate molten salt system can increase the density of basic sites on the MgO surface, thereby enhancing the chemisorption capacity for CO 2 . This adsorbent has the characteristics of large adsorption capacity, fast adsorption rate, excellent cycle stability, etc. Brief Description of the Drawings

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0015] Figure 1 It is a schematic process flow diagram of the present invention; Figure 2(a) is an adsorption / cycle regeneration diagram in Embodiment 1 of the present invention; Figure 2(b) is an adsorption / cycle regeneration diagram in Comparative Example 1 of the present invention; Figure 3(a) is an adsorption / cycle regeneration diagram in Embodiment 2 of the present invention; Figure 3(b) is an adsorption / cycle regeneration diagram in Comparative Example 2 of the present invention; Figure 4(a) is an adsorption / cycle regeneration diagram in Embodiment 3 of the present invention; Figure 4(b) is an adsorption / cycle regeneration diagram in Comparative Example 3 of the present invention.

[0016] Adsorption conditions: 340 °C, 100% CO 2 , 15 min; regeneration conditions 420 °C, 100% N 2 , 5 min. Detailed Embodiments

[0017] The following details the embodiments of the present invention. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described below by referring to the drawings are exemplary and are intended to explain the embodiments of the present invention, and should not be construed as a limitation of the present invention.

[0018] Example 1: This example discloses a preparation method of a carbon dioxide adsorbent, as Figure 1 shown. The specific steps are as follows: First, prepare a calcium-magnesium mixture. Select magnesium oxalate anhydrous and calcium lactate pentahydrate as raw materials, where the mass percentage of magnesium oxalate anhydrous is 95% and the mass percentage of calcium lactate pentahydrate is 5%. Then, mix the two mixtures with anhydrous methanol and stir well until homogeneous. The mass-volume ratio of the mixture to anhydrous methanol is 1:32. Subsequently, perform a drying treatment. Specifically, place the sample in an oven and dry it at 120 °C for 12 h. Place the dried mixture in a muffle furnace and calcine it at a temperature of 480 °C with a heating rate of 2 °C per minute for 3 hours to obtain the calcium-magnesium mixture. Finally, add waste lithium battery powder and sodium nitrate to the obtained calcium-magnesium mixture. The waste lithium battery powder is obtained by disassembling the recycled waste lithium battery, crushing it to a particle size of <1 mm, and pyrolyzing it in a tube furnace by introducing N 2 / H 2 (95:5) mixed gas at 600 °C for 2 h to remove the PVDF binder, and then performing ball milling treatment (zirconia balls, rotation speed 300 rpm, 4 h) to obtain a nanoscale composite powder.

[0019] The waste lithium battery powder can be selected from waste lithium cobalt oxide batteries, ternary lithium batteries, lithium iron phosphate batteries, lithium manganese oxide batteries, and lithium titanate batteries. In this example, the waste lithium battery powder is mainly waste lithium iron phosphate battery powder. The Fe³ + contained in the waste lithium iron phosphate battery powder can regulate the adsorption-desorption kinetic performance of CO 2 through redox characteristics and reduce the reaction activation energy. At the same time, the migration of Li + in the sodium nitrate molten salt system can increase the density of basic sites on the MgO surface, thereby enhancing the chemical adsorption ability of CO 2 .

[0020] The mass ratio of the calcium-magnesium mixture to the waste lithium iron phosphate battery powder is 98%, and the mass ratio of the calcium-magnesium mixture to sodium nitrate is 83%. After adding the waste lithium iron phosphate battery powder and sodium nitrate, stir and mix well with anhydrous methanol. The mass-volume ratio of the mixture of the calcium-magnesium mixture, waste lithium iron phosphate battery powder, and sodium nitrate to anhydrous methanol is 1:32. Subsequently, place the sample in an oven and dry it at 120 °C for 12 h to obtain a composite MgO-based adsorbent after drying.

[0021] As shown in Figure 2(a), the adsorption rate of the composite MgO-based adsorbent in this example for carbon dioxide can reach 0.59 g gCO 2 / g adsorbent. After 20 cycles of use, its adsorption efficiency still remains at 0.32 g gCO 2 / g adsorbent.

[0022] Example 2: This example discloses a preparation method of a carbon dioxide adsorbent. As Figure 1 shown, the specific steps are as follows: First, prepare a calcium-magnesium mixture. Select magnesium citrate anhydrous and calcium lactate pentahydrate as raw materials, where the mass percentage of magnesium citrate anhydrous is 90% and the mass percentage of calcium lactate pentahydrate is 10%. Then, mix the two mixtures with anhydrous methanol and stir well until uniform, and then perform a drying treatment. Specifically, place the sample in an oven and dry it at 120 °C for 12 h. Place the dried mixture in a muffle furnace and calcine it at a temperature of 480 °C with a heating rate of 2 °C per minute for 3 hours to obtain the calcium-magnesium mixture. Finally, add waste lithium battery powder and sodium nitrate to the obtained calcium-magnesium mixture. The waste lithium battery powder is obtained by disassembling the recycled waste lithium battery, crushing it to a particle size < 1 mm, and pyrolyzing it in a tubular furnace by introducing N 2 / H 2 (95:5) mixed gas at 600 °C for 2 h to remove the PVDF binder, and then performing ball milling treatment (zirconia balls, rotation speed 300 rpm, 4 h) to obtain a nanoscale composite powder.

[0023] The waste lithium battery powder can be selected from waste lithium cobalt oxide batteries, ternary lithium batteries, lithium iron phosphate batteries, lithium manganese oxide batteries, and lithium titanate batteries. In this example, the waste lithium battery powder is mainly waste lithium iron phosphate battery powder. The Fe³ + contained in the waste lithium iron phosphate battery powder can regulate the adsorption-desorption kinetic performance of CO 2 by its redox characteristics and reduce the reaction activation energy; at the same time, the migration of Li + in the sodium nitrate molten salt system can increase the density of basic sites on the surface of MgO, thereby enhancing the chemical adsorption capacity for CO 2 2.

[0024] The mass ratio of the calcium-magnesium mixture to the waste lithium iron phosphate battery powder is 98%, and the mass ratio of the calcium-magnesium mixture to sodium nitrate is 84%. After adding the lithium iron phosphate battery powder and sodium nitrate, stir and mix well with anhydrous methanol. The mass-volume ratio of the mixture of the calcium-magnesium mixture, waste lithium iron phosphate battery powder, and sodium nitrate to anhydrous methanol is 1:32. Then, place the sample in an oven and dry it at 120 °C for 12 h to obtain a composite MgO-based adsorbent after drying.

[0025] As shown in Figure 3(a), the adsorption rate of the composite MgO-based adsorbent in this example for carbon dioxide can reach 0.56 ggCO 2 / g adsorbent. After 20 cycles of use, its adsorption efficiency still remains at 0.32 g gCO 2 / g adsorbent.

[0026] Example 3: This example discloses a preparation method of a carbon dioxide adsorbent, as Figure 1 shown. The specific steps are as follows: First, prepare a calcium-magnesium mixture. Select magnesium citrate anhydrous and calcium lactate pentahydrate as raw materials, where the mass percentage of magnesium citrate anhydrous is 93% and the mass percentage of calcium lactate pentahydrate is 7%. Then, mix the two mixtures with anhydrous methanol and stir well until uniform. The mass-volume ratio of the mixture to anhydrous methanol is 1:32. Subsequently, perform a drying treatment. Specifically, place the sample in an oven and dry it at 120 °C for 12 h. Place the dried mixture in a muffle furnace and calcine it at a temperature of 500 °C with a heating rate of 2 °C per minute for 3 hours to obtain the calcium-magnesium mixture. Finally, add waste lithium battery powder and sodium nitrate to the obtained calcium-magnesium mixture. The waste lithium battery powder is obtained by disassembling the recycled waste lithium battery, crushing it to a particle size of <1 mm, and pyrolyzing it in a tubular furnace by introducing N 2 / H 2 (95:5) mixed gas at 600 °C for 2 h to remove the PVDF binder, and then performing ball milling treatment (zirconia balls, rotation speed 300 rpm, 4 h) to obtain a nanoscale composite powder.

[0027] The waste lithium battery powder can be selected from waste lithium cobalt oxide batteries, ternary lithium batteries, lithium iron phosphate batteries, lithium manganese oxide batteries, and lithium titanate batteries. In this example, the waste lithium battery powder is mainly waste lithium iron phosphate battery powder. The Fe³ + contained in the waste lithium iron phosphate battery powder can regulate the adsorption-desorption kinetic performance of CO 2 through redox characteristics and reduce the reaction activation energy; at the same time, the migration of Li + in the sodium nitrate molten salt system can increase the density of basic sites on the surface of MgO, thereby enhancing the chemisorption ability of CO 2 .

[0028] The mass ratio of the calcium-magnesium mixture to the waste lithium iron phosphate battery powder is 98%, and the mass ratio of the calcium-magnesium mixture to sodium nitrate is 83%. After adding the waste lithium iron phosphate battery powder and sodium nitrate, stir and mix well with anhydrous methanol. The mass-volume ratio of the mixture of the calcium-magnesium mixture, waste lithium iron phosphate battery powder, and sodium nitrate to anhydrous methanol is 1:32. Subsequently, place the sample in an oven and dry it at 120 °C for 12 h to obtain a composite MgO-based adsorbent after drying.

[0029] As shown in Figure 4(a), the adsorption rate of the composite MgO-based adsorbent in this example for carbon dioxide can reach 0.57 ggCO 2 / g adsorbent. After 20 cycles of use, its adsorption efficiency still remains at 0.28 g gCO 2 / g adsorbent.

[0030] Comparative Example 1: In this comparative example, first, magnesium oxalate anhydrous, waste lithium iron phosphate battery powder, and sodium nitrate were fully stirred and mixed in anhydrous methanol. The mass-volume ratio of the mixture of magnesium oxalate anhydrous, waste lithium iron phosphate battery powder, and sodium nitrate to anhydrous methanol was 1:32. The waste lithium iron phosphate battery powder was obtained by disassembling the recycled waste lithium iron phosphate battery, crushing it to a particle size of <1 mm, passing an N 2 / H 2 (95:5) mixed gas in a tube furnace, pyrolyzing at 600 °C for 2 h to remove the PVDF binder, and then ball-milling (zirconia balls, rotation speed 300 rpm, 4 h) to obtain a nanoscale composite powder.

[0031] The waste lithium battery powder can be selected from waste lithium cobalt oxide battery, ternary lithium battery, lithium iron phosphate battery, lithium manganese oxide battery, and lithium titanate battery powder. In this comparative example, the waste lithium battery powder was mainly waste lithium iron phosphate battery powder, and the Fe³ + contained in the waste lithium iron phosphate battery powder can regulate the adsorption-desorption kinetic performance of CO 2 through its redox characteristics and reduce the reaction activation energy; at the same time, the migration of Li + in the sodium nitrate molten salt system can increase the density of basic sites on the MgO surface, thereby enhancing the chemical adsorption capacity of CO 2 .

[0032] The mass ratio of the magnesium oxalate anhydrous to the waste lithium iron phosphate battery powder was 98%, and the mass ratio of the magnesium oxalate anhydrous to the sodium nitrate was 87%. After adding the waste lithium iron phosphate battery powder and sodium nitrate, it was fully stirred and mixed with anhydrous methanol, and then the sample was placed in an oven and dried at 120 °C for 12 h to obtain a composite MgO-based adsorbent after drying.

[0033] As shown in Figure 2(b), the adsorption rate of the composite MgO-based adsorbent in this example for carbon dioxide can reach 0.56 ggCO 2 / g adsorbent. After 20 cycles of use, its adsorption efficiency was 0.19 g gCO 2 / g adsorbent.

[0034] Comparative Example 2: In this comparative example, first, a calcium-magnesium mixture was prepared, using magnesium oxalate anhydrous and calcium lactate pentahydrate as raw materials, where the mass percentage of magnesium oxalate anhydrous was 95% and the mass percentage of calcium lactate pentahydrate was 5%. Then, the mixture of the two was mixed with anhydrous methanol and stirred thoroughly until homogeneous, where the mass-volume ratio of the mixture to anhydrous methanol was 1:32. Subsequently, drying treatment was carried out. Specifically, the sample was placed in an oven and dried at 120 °C for 12 h. The dried mixture was placed in a muffle furnace and calcined at a temperature of 480 °C with a heating rate of 2 °C per minute for 3 hours to obtain the calcium-magnesium mixture. Finally, waste lithium battery powder was added to the obtained calcium-magnesium mixture. The waste lithium battery powder was obtained by disassembling the recycled waste lithium battery, crushing it to a particle size of <1 mm, and pyrolyzing it in a tube furnace by introducing N 2 / H 2 (95:5) mixed gas, pyrolyzing at 600 °C for 2 h to remove the PVDF binder, and obtaining the nanoscale composite powder through ball milling treatment (zirconia balls, rotation speed 300 rpm, 4 h).

[0035] The waste lithium battery powder can be selected from waste lithium cobalt oxide batteries, ternary lithium batteries, lithium iron phosphate batteries, lithium manganese oxide batteries, and lithium titanate batteries. In this comparative example, the waste lithium battery powder was mainly waste lithium iron phosphate battery powder, and the Fe³ + in the waste lithium iron phosphate battery powder can regulate the adsorption-desorption kinetics performance of CO2 through redox characteristics, reducing the reaction activation energy; at the same time, Li + migrating in the sodium nitrate molten salt system can increase the density of basic sites on the surface of MgO, thereby enhancing the chemical adsorption capacity for CO 2 2.

[0036] The mass ratio of the calcium-magnesium mixture to the waste lithium iron phosphate battery powder was 98%. After adding the waste lithium iron phosphate battery powder, it was stirred and mixed thoroughly with anhydrous methanol again. The mass-volume ratio of the mixture of the calcium-magnesium mixture, waste lithium iron phosphate battery powder to anhydrous methanol was 1:32. Subsequently, the sample was placed in an oven and dried at 120 °C for 12 h, and the composite MgO-based adsorbent was obtained after drying.

[0037] As shown in Figure 3(b), the adsorption rate of the composite MgO-based adsorbent in this example for carbon dioxide can reach 0.19 g gCO 2 2 / g adsorbent. After 20 cycles of use, its adsorption efficiency was 0.05 g gCO 2 2 / g adsorbent.

[0038] Comparative Example 3: First, a calcium-magnesium mixture was prepared, using anhydrous magnesium oxalate and calcium lactate pentahydrate as raw materials, where the mass percentage of anhydrous magnesium oxalate was 95% and the mass percentage of calcium lactate pentahydrate was 5%. Then the mixture of the two was mixed with anhydrous methanol and stirred thoroughly until homogeneous, where the mass-volume ratio of the mixture to anhydrous methanol was 1:32. Subsequently, drying treatment was carried out, specifically placing the sample in an oven and drying it at 120 °C for 12 h. The dried mixture was placed in a muffle furnace and calcined at a temperature of 480 °C with a heating rate of 2 °C per minute for 3 hours to obtain the calcium-magnesium mixture. Finally, sodium nitrate was added to the obtained calcium-magnesium mixture.

[0039] The mass ratio of the calcium-magnesium mixture to sodium nitrate was 83%. After adding sodium nitrate, it was stirred and mixed thoroughly with anhydrous methanol again, where the mass-volume ratio of the mixture of the calcium-magnesium mixture and sodium nitrate to anhydrous methanol was 1:32. Subsequently, the sample was placed in an oven and dried at 120 °C for 12 h, and a composite MgO-based adsorbent was obtained after drying.

[0040] As shown in Figure 4(b), the adsorption rate of the composite MgO-based adsorbent in this example for carbon dioxide can reach 0.51 g gCO 2 / g adsorbent. After 20 cycles of use, its adsorption efficiency is 0.23 g gCO 2 / g adsorbent.

[0041] As can be seen from the above figures, the adsorbent doped with calcium carbonate precursor exhibits more excellent adsorption cycle performance compared to the adsorbent without calcium carbonate precursor (Comparative Example 1). In addition, compared with the adsorbents without doping sodium nitrate (Comparative Example 2) and waste lithium iron phosphate battery powder (Comparative Example 3), the adsorbent doped with sodium nitrate and waste lithium iron phosphate battery powder obviously has a higher adsorption capacity.

[0042] In summary, the MgO-based composite adsorbent of the present invention is suitable for the selective adsorption of CO in power plant flue gas and industrial waste gas. It is prepared by calcining a mixture of organic magnesium and calcium carbonate precursor. High-temperature calcination makes MgO and CaCO 2 composite to form a porous structure. At the same time, sodium nitrate and waste lithium iron phosphate battery powder are introduced as dopants. Sodium nitrate can provide additional adsorption active sites for MgO, reduce the CO 3 adsorption activation energy, and improve the reaction kinetic performance. The main component of the waste lithium iron phosphate battery powder, lithium iron phosphate, contains Fe³ 2 which can regulate the adsorption-desorption kinetics of CO through redox characteristics and reduce the reaction activation energy. At the same time, the migration of Li + in the sodium nitrate molten salt system can increase the density of basic sites on the MgO surface, thereby enhancing the adsorption of CO 2 ; while, Li + in the sodium nitrate molten salt system can increase the density of basic sites on the MgO surface, thereby enhancing the adsorption of CO2 The chemisorption capacity. This adsorbent exhibits excellent adsorption stability and cycling performance under medium-temperature conditions, and has stronger industrial application potential than traditional adsorbents.

[0043] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope claimed by the present invention. The scope claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a CO2 adsorbent, characterized in that: The steps include: S1: fully stirring an organic magnesium precursor and a calcium carbonate precursor in anhydrous methanol to form a mixed solution, drying to obtain an intermediate product, and then calcining and decomposing the intermediate product to obtain a calcium-magnesium mixture; S2: Add waste lithium battery powder and sodium nitrate to the prepared calcium-magnesium mixture, wherein the waste lithium battery powder includes waste lithium iron phosphate battery powder, wherein the mass ratio of the calcium-magnesium mixture to the waste lithium iron phosphate battery powder is 95-97%, and the mass ratio of the calcium-magnesium mixture to sodium nitrate is 80-88%, and then fully stir and mix in anhydrous methanol to obtain a mixed solution, and obtain a composite MgO-based adsorbent after drying.

2. The method for preparing a CO2 adsorbent according to claim 1, characterized in that: The organic magnesium precursor is a MgO precursor.

3. The method for preparing a CO2 adsorbent according to claim 2, characterized in that: The MgO precursor includes any one or more of magnesium oxalate, anhydrous magnesium citrate, magnesium lactate, magnesium ethoxide, magnesium acetate and magnesium gluconate.

4. The method for preparing a CO2 adsorbent according to claim 3, characterized in that: The calcium carbonate precursor includes any one or more of calcium lactate pentahydrate, dolomite, anhydrous calcium acetate and calcium gluconate.

5. The method for preparing a CO2 adsorbent according to claim 1, characterized in that: In the intermediate product, the mass percentage of the organic magnesium precursor is 80% to 90%, and the mass percentage of the calcium carbonate precursor is 10% to 20%.

6. The method for preparing a CO2 adsorbent according to claim 1, characterized in that: The intermediate product is calcined and decomposed in a muffle furnace under air atmosphere, the calcination temperature of the muffle furnace is 400-600° C., the heating rate is 2-10° C. / min, and the reaction time is 1-3 hours.

7. The method for preparing a CO2 adsorbent according to claim 1, characterized in that: The waste lithium battery powder is obtained by disassembling recycled waste lithium batteries, crushing them to a particle size of less than 1 mm, introducing N2 / H2 mixed gas in a tubular furnace, pyrolyzing and removing PVDF binder, and ball milling to obtain a nano-scale composite powder.

8. A CO2 adsorbent, characterized in that: The CO2 adsorbent is prepared by the preparation method of any one of claims 1 to 7.

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