A direct air capture carbon sequestration material using salt solution desorption and its preparation and use

Abstract

The present application relates to a kind of salt solution desorption direct air capture carbon adsorption material and its preparation and application, the material is prepared by the following method: (1) the ion exchange resin is weighed and placed in CuCl2 solution and is treated by first impregnation, filtration, washing, and metal-loaded ion exchange resin is obtained;(2) the metal-loaded ion exchange resin in step (1) is placed in NaOH solution and is treated by second impregnation, filtration, and direct air capture carbon adsorption material is obtained, that is, the target product.The direct air capture carbon adsorption material of the present application can adsorb and desorb CO2 under room temperature and normal pressure conditions.Due to acid-base neutralization and the synergistic effect of electrostatic attraction, low concentration CO2 in air reacts to be HCO3 ‑ Combined on coordination site.Because the coordination priority of Cl ‑ Is higher than HCO3 ‑ , desorption can be completed using salt solution, and the operation is simple, without additional energy consumption.CO2 adsorbed in the form of carbonate exists stably in solution phase, and has great potential in CO2 resource utilization.

Description

Technical Field

[0001] This invention belongs to the field of gas separation materials technology, and relates to a direct air capture carbon adsorption material for salt solution desorption, its preparation and application. Background Technology

[0002] Direct air capture (DAC) technology refers to a carbon reduction method that directly captures CO2 from the atmospheric system. It addresses the problem of decentralized carbon emissions and is highly flexible with no geographical limitations, thus compensating for the shortcomings of CCUS technology. A typical DAC device includes a capture unit, an adsorption / absorption unit, and a desorption / regeneration unit. The materials used mainly include amine adsorbents, metal-organic frameworks (MOFs), and alkaline solutions. Amine adsorbents combine amine groups with a support material through physical impregnation, chemical grafting, in-situ polymerization, etc., achieving CO2 absorption or adsorption based on the reaction between the amine groups and CO2. Common support materials include SiO2 and activated carbon; amine groups include MEA, DEA, and PEI. However, due to the limited number of amine groups that the support can support, and the potential for material degradation and amine leaching or volatilization during temperature-dependent regeneration, the adsorption capacity of amine adsorbents for CO2 and their thermal stability during regeneration need further improvement. Metal-organic frameworks (MOFs) are topologically structured materials assembled from metal ion centers and organic ligands, capable of capturing CO2 based on extremely strong intermolecular forces. They are characterized by large specific surface area, well-developed pore structure, and diverse structures. Existing research has improved the physical adsorption capacity of MOFs for CO2 molecules by loading amine compounds or adjusting the pore size and distribution of active sites. However, due to the competitive adsorption between H2O and CO2, MOFs exhibit low adsorption selectivity for CO2 in high-humidity air. When using alkaline solutions, CO2 first reacts with alkaline hydroxide solutions to form carbonates, which are then regenerated through a causticization reaction to form CaCO3. CO2 is then released by calcining CaCO3. However, the calcination process requires temperatures of 900℃ and above. Therefore, using alkaline solutions as DAC materials results in high energy consumption during desorption, with 12–17 GJ required for desorption of each ton of CO2.

[0003] Ion exchange resins are commonly used in seawater desalination and wastewater treatment. They work by transferring metal ions (such as Cu) into the water. 2+ Ni 2+ Ag +Metal ions (such as ligands in solution or gas) are loaded onto ion exchange resins. Ligands in the solution or gas then form complexes with the metal ions and remain within the resin, thus achieving adsorption. When metal ions are complexed onto the ion exchange resin, they provide a strong driving force for the system. In this case, even extremely low concentrations of ligands in the solution or gas can be effectively adsorbed. Currently, metal-loaded ion exchange resins are commonly used to adsorb specific pollutants in aqueous solutions, such as arsenic, phosphates, ammonia, and fluorides. However, the application of ion exchange resins for the separation and adsorption of gaseous substances is relatively limited at present. Summary of the Invention

[0004] The purpose of this invention is to provide a direct air capture carbon adsorbent material for salt solution desorption, its preparation and application, which can achieve CO2 adsorption and desorption under room temperature and atmospheric pressure conditions (exemplary temperature is 23-25℃, 400-700ppm), solving the problems of small adsorption capacity, poor stability, weak selectivity and high desorption energy consumption that are common in current DAC materials. At the same time, it also makes up for the lack of application of ion exchange resins in the separation and adsorption of gas phase substances.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] One of the technical solutions of the present invention provides a method for preparing a direct air capture carbon adsorbent material by salt solution desorption, comprising the following steps:

[0007] (1) Weigh the ion exchange resin and place it in CuCl2 solution for one impregnation treatment, filter and wash to obtain metal-loaded ion exchange resin.

[0008] (2) The metal-loaded ion exchange resin in step (1) is placed in NaOH solution for a second impregnation treatment and filtered to obtain the direct air capture carbon adsorbing material, which is the target product.

[0009] Furthermore, the ion exchange resin in step (1) is a macroporous weakly basic styrene-based anion exchange resin with a volume exchange capacity of 1.0 eq / L to 2.0 eq / L.

[0010] Furthermore, in step (1), the concentration of the CuCl2 solution is 10 g / L to 20 g / L, and the ratio of the amount of ion exchange resin added to the amount of CuCl2 solution is 2 g: 100 mL to 150 mL.

[0011] Furthermore, in step (1), the soaking time is 72-84 hours and the temperature is 20-25℃.

[0012] Furthermore, in step (1), deionized water is used during the cleaning process.

[0013] Furthermore, in step (2), the mass fraction of the NaOH solution is 1% to 5%.

[0014] Furthermore, in step (2), the ratio of the amount of ion exchange resin to NaOH solution added in the metal-supported ion exchange resin is 2g: 100mL~150mL.

[0015] Furthermore, in step (2), the second soaking time is 36-48 hours and the temperature is 20-25℃.

[0016] Furthermore, the sieve used for filtration in steps (1) and (2) has a mesh size of 1800.

[0017] The second technical solution of the present invention provides a direct air capture carbon adsorbing material for salt solution desorption, which is prepared by any of the preparation methods described above.

[0018] The third technical solution of this invention provides an application of a direct air capture carbon adsorbent material that desorbs carbon from a salt solution. This material is used for CO2 adsorption at room temperature and atmospheric pressure. Specifically, the adsorption time is 48-96 hours.

[0019] Furthermore, after the carbon capture material directly adsorbs CO2 to saturation, a mixed solution of NaCl and NaOH is used for desorption treatment. The mass fractions of NaCl and NaOH in the mixed solution are 4%–8% and 1%–5%, respectively. The desorption process is kept sealed and takes 12–16 hours.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The extremely low concentration of CO2 in the air poses a significant challenge to DAC materials in terms of CO2 selectivity, capture kinetics, and adsorption capacity. The direct air capture carbon adsorbing material, its preparation method, and its application proposed in this invention can achieve irreversible directional adsorption of low concentrations of CO2 in the air under room temperature and atmospheric pressure conditions.

[0022] (2) Currently, DAC materials generally require changes in ambient temperature or water vapor partial pressure to achieve desorption. The direct air capture carbon adsorbing material, its preparation and use method proposed in this invention can complete desorption using a salt solution under room temperature and normal pressure conditions, without providing additional heat energy or relying on water to drive it. The operation process is simple and does not generate additional energy consumption.

[0023] (3) Currently, the storage methods for desorbed CO2 are compression, transportation, and injection into formation structures. The direct air capture carbon adsorbent material, its preparation, and its application method proposed in this invention can stably store adsorbed CO2 in the form of carbonate in the solution phase, avoiding the problems of high energy consumption and easy leakage associated with traditional methods. Moreover, carbonates are widely used in building materials, metallurgical industry, environmental protection, and other fields. The storage method proposed in this invention has great potential for the resource utilization of CO2. Attached Figure Description

[0024] Figure 1 This is a process flow diagram illustrating the preparation and use of the direct air capture carbon adsorbing material of the present invention.

[0025] Figure 2 This is a schematic diagram of the structure of an ion exchange resin.

[0026] Figure 3 This is a schematic diagram of the structure of a metal-supported ion exchange resin.

[0027] Figure 4 A schematic diagram of a direct air capture carbon adsorbent material.

[0028] Figure 5 A schematic diagram of a saturated direct air capture carbon adsorbent material.

[0029] Figure 6 A schematic diagram of the structure of a direct air capture carbon adsorbent material after desorption. Detailed Implementation

[0030] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0031] In the following embodiments, the ion exchange resin used is a weakly basic styrene-based anion exchange resin, purchased from Lanxess AG, model Lewait MonoPlus TP 109.

[0032] Unless otherwise specified, all other raw materials or processing techniques are commercially available materials or conventional processing techniques in the field.

[0033] Example 1

[0034] A method for preparing a direct air-capturing carbon adsorbent material by salt solution desorption includes the following steps:

[0035] (1) Weigh 2g of macroporous weakly basic styrene-based anion exchange resin;

[0036] (2) Prepare 125 mL of CuCl2 solution with a mass concentration of 15 g / L, add ion exchange resin and impregnate for 72 h, and filter through an 1800 mesh sieve to obtain metal-loaded ion exchange resin.

[0037] (3) Weigh 500 mL of deionized water, add metal-loaded ion exchange resin and stir for 1 h to wash away residual metal ions. Filter through an 1800 mesh sieve to obtain cleaned metal-loaded ion exchange resin.

[0038] (4) Prepare 125 mL of 3% NaOH solution, add the cleaned metal-loaded ion exchange resin and impregnate for 48 h, then filter through an 1800 mesh sieve to obtain the direct air capture carbon adsorbing material.

[0039] The method for using the direct air capture carbon adsorbent material prepared above for salt solution desorption includes the following steps:

[0040] A: The direct air capture carbon adsorbing material was placed in a room temperature and normal pressure environment (23-25℃, 400-700ppm) for 72 hours to complete CO2 adsorption and obtain saturated direct air capture carbon adsorbing material.

[0041] B: Prepare 125 mL of a mixed solution with mass fractions of 5% NaCl and 3% NaOH. The pH value is measured to be 13.69. A strongly alkaline environment can cause HCO3- to... 3- All of them can be reacted into CO3 2 - It exists stably in the solution phase. HCO3- 3- The hydrolysis constant is much greater than the ionization constant, and it readily hydrolyzes to form H₂CO₃ in solution. Furthermore, because H₂CO₃ is volatile, HCO₃⁻ is extremely unstable when present alone in the solution phase. Therefore, a strongly alkaline environment can prevent the volatilization and release of the desorbed carbon source. Saturated direct air capture carbon adsorbent material was added, and desorption was performed in a sealed container for 12 hours. Solid-liquid separation was then performed through an 1800-mesh sieve to obtain the desorbed direct air capture carbon adsorbent material and CO₃²⁻ containing OH⁻ and a weakly alkaline solution. 2- The desorption solution.

[0042] Figure 3 This is a schematic diagram of the metal-supported ion exchange resin structure in Example 1. Based on the Lewis acid-base reaction, Cu... 2+ It is connected to three N atoms through covalent bonds, because Cu 2+ Two positive charges remain unneutralized, serving as ion exchange sites for the entire material system.

[0043] Figure 4 This is a schematic diagram of the direct air capture carbon adsorbent material in Example 1. OH... -As a balancing ion, it will irreversibly and directionally adsorb low concentrations of CO2 in the air due to the principle of acid-base neutralization.

[0044] Figure 5 This is a schematic diagram of a saturated direct air capture carbon adsorbent. Due to the synergistic effect of acid-base neutralization and electrostatic attraction, weakly acidic CO2 will be reacted into HCO3. - It then binds to the coordination site.

[0045] Figure 6 This is a schematic diagram of the direct air capture carbon adsorbent material after desorption. In the ion exchange resin complexing metal ion system, due to the coordination of Cl... - It has a higher priority than HCO3 - Cl in NaCl solution can be used. - Replace the already combined HCO3 - HCO3 - It will enter the solution phase and react with OH- to generate stable CO3. 2- This allows for the desorption of CO2.

[0046] Comparative Example 1

[0047] The difference from Example 1 is that most of the steps are the same, except that in the preparation method of the direct air capture carbon adsorbent material, the step of (2) preparing CuCl2 solution and adding ion exchange resin for impregnation is omitted.

[0048] Comparative Example 2

[0049] The difference from Example 1 is that most of the steps are the same, except that in the preparation method of the direct air capture carbon adsorbing material, the mass concentration of the CuCl2 solution prepared in step (2) is 5 g / L.

[0050] Comparative Example 3

[0051] The difference from Example 1 is that most of the steps are the same, except that in the preparation method of the direct air capture carbon adsorbing material, the mass concentration of the CuCl2 solution prepared in step (2) is 25 g / L.

[0052] Comparative Example 4

[0053] The difference from Example 1 is that most of the steps are the same, except that in the preparation method of the direct air capture carbon adsorbent material, the step of (4) preparing NaOH solution and adding the cleaned metal-loaded ion exchange resin for impregnation is omitted.

[0054] Comparative Example 5

[0055] The difference from Example 1 is that most of the steps are the same, except that in the preparation method of the direct air capture carbon adsorbent material, the mass fraction of the NaOH solution prepared in step (4) is 0.5%.

[0056] Comparative Example 6

[0057] The difference from Example 1 is that most of the steps are the same, except that in the preparation method of the direct air capture carbon adsorbent material, the mass fraction of the NaOH solution prepared in step (4) is 10%.

[0058] Comparative Example 7

[0059] The difference from Example 1 is that most of the steps are the same, except that in the method of using the direct air capture carbon adsorbent material, the step of placing the direct air capture carbon adsorbent material in a room temperature and normal pressure environment to complete CO2 adsorption is omitted.

[0060] Comparative Example 8

[0061] The difference from Example 1 is that most of the steps are the same, except that in the method of using the direct air capture carbon absorber, the direct air capture carbon absorber is placed in a room temperature and normal pressure environment for 24 hours in step A.

[0062] Comparative Example 9

[0063] The difference from Example 1 is that most of the steps are the same, except that in the method of using the direct air capture carbon absorber, the direct air capture carbon absorber is placed in a room temperature and normal pressure environment for 120 hours in step A.

[0064] Comparative Example 10

[0065] The difference from Example 1 is that most of the steps are the same, except that in the method of using the carbon-absorbing material by direct air capture, the solution prepared in step B is a single 5% NaCl solution.

[0066] Comparative Example 11

[0067] The difference from Example 1 is that most of the steps are the same, except that in the method of using the carbon-absorbing material by direct air capture, the solution prepared in step B is a mixed solution of 5% NaCl and 0.5% NaOH.

[0068] Comparative Example 12

[0069] The difference from Example 1 is that most of the steps are the same, except that in the method of using the carbon-absorbing material by direct air capture, the solution prepared in step B is a mixed solution of 5% NaCl and 10% NaOH.

[0070] Comparative Example 13

[0071] The difference from Example 1 is that most of the steps are the same, except that in the method of using the carbon-absorbing material in direct air capture, the solution prepared in step B is a single 3% NaOH solution.

[0072] Comparative Example 14

[0073] The difference from Example 1 is that most of the steps are the same, except that in the method of using the carbon-absorbing material in direct air capture, the solution prepared in step B is a mixed solution of 1% NaCl and 3% NaOH.

[0074] Comparative Example 15

[0075] The difference from Example 1 is that most of the steps are the same, except that in the method of using the carbon-absorbing material by direct air capture, the solution prepared in step B is a mixed solution of 10% NaCl and 3% NaOH.

[0076] Comparative Example 16

[0077] The difference from Example 1 is that most of the steps are the same, except that in the method of using the direct air capture carbon adsorbent, the desorption time of the direct air capture carbon adsorbent in the closed container is 2 hours in step B.

[0078] Comparative Example 17

[0079] The difference from Example 1 is that most of the steps are the same, except that in the method of using the direct air capture carbon adsorbent, the desorption time of the direct air capture carbon adsorbent in the closed container is 24 hours in step B.

[0080] The pH values ​​of the desorption solutions obtained in Example 1 and each comparative example were measured, and the IC (inorganic carbon) concentration of the two groups of solutions was detected by a TOC (total organic carbon) analyzer. Three parallel samples were set up for each group of solutions, and the average value was taken. The test results are shown in Table 1 below.

[0081] Table 1. pH and TOC test results of the desorption solutions obtained in Example 1 and each comparative example.

[0082] Group pH IC (mg / L) Example 1 10.21 306.98 Comparative Example 1 13.63 2.43 Comparative Example 2 11.76 104.15 Comparative Example 3 10.20 307.43 Comparative Example 4 13.63 2.52 Comparative Example 5 11.95 88.90 Comparative Example 6 10.23 304.15 Comparative Example 7 13.39 14.47 Comparative Example 8 10.99 218.05 Comparative Example 9 10.21 307.20 Comparative Example 10 11.17 195.52 Comparative Example 11 10.64 268.17 Comparative Example 12 10.23 304.70 Comparative Example 13 13.64 2.09 Comparative Example 14 12.75 49.07 Comparative Example 15 10.21 306.39 Comparative Example 16 11.53 137.52 Comparative Example 17 10.22 305.86

[0083] As shown in Table 1 above, the pH value of the desorption solution obtained in Example 1 decreased from 13.69 before desorption to 10.21 after desorption, and the concentration of inorganic carbon in the solution after desorption was 306.98 mg / L. This is because during desorption, the saturated direct air capture carbon adsorbent introduced a large amount of HCO3 into the solution. - It reacts with alkaline solution and consumes a large amount of OH-. -The pH value decreased significantly. This result indicates that, excluding the trace amounts of CO2 that the alkaline solution itself can adsorb from the air, the carbonate ions in the desorption solution obtained in the examples all originate from the desorption process of the direct air capture carbon adsorbent material. Based on the solution volume, it can be calculated that 2g of the direct air capture carbon adsorbent material placed in a room temperature and atmospheric pressure environment (23–25°C, 400–700 ppm) for 160 hours can adsorb approximately 28.1mg of CO2.

[0084] According to the results of Comparative Examples 1, 2, and 3, in Comparative Example 1, when the step of preparing CuCl2 solution and impregnating with ion exchange resin was omitted during the preparation of the carbon capture material, the material did not exhibit a carbon capture effect. In Comparative Example 2, after preparing a low-concentration CuCl2 solution, the concentration of inorganic carbon in the desorption solution increased and the pH value decreased, but the concentration of inorganic carbon was only about 1 / 3 of that in Example 1. This is because CuCl2... 2+ The quantity is limited, and some ion exchange resins still do not bind Cu. 2+ As an ion exchange site, it cannot capture CO2 from the air; in Comparative Example 3, as the mass concentration of CuCl2 solution increased (greater than in Example 1), the concentration of inorganic carbon in the desorption solution and the decrease in pH were similar to those in Example 1. Therefore, it can be concluded that the ion exchange resin and CuCl2 solution are compatible. 2+ The binding of Cu was saturated in Example 1, although Cu 2+ A further significant increase in the quantity did not noticeably improve the carbon adsorption effect of the material. According to the results of Comparative Examples 4, 5, and 6, in Comparative Example 4, when the step of preparing the NaOH solution and impregnating the cleaned metal-loaded ion exchange resin was omitted during the preparation of the direct air capture carbon adsorption material, the material did not exhibit a significant carbon adsorption effect. In Comparative Example 5, after preparing a low-concentration NaOH solution, the concentration of inorganic carbon in the desorption solution increased and the pH value decreased, but the inorganic carbon concentration was still significantly lower than that of Example 1. In Comparative Example 6, the mass fraction of the NaOH solution was further increased (greater than in Example 1), and the concentration of inorganic carbon in the desorption solution and the decrease in pH value were close to those of Example 1. Therefore, in the preparation of direct air capture carbon adsorption materials, it is necessary to reasonably control the mass fraction of the NaOH solution to provide sufficient OH-. - As the equilibrium ion of the material, but OH - Excessive ions lead to saturation of the interaction with ion exchange sites, resulting in no significant increase in the carbon adsorption effect of the material.

[0085] According to the results of Comparative Examples 7, 8, and 9, Comparative Example 7 omitted the step of placing the direct air capture carbon adsorbent material in a room temperature and atmospheric pressure environment to complete CO2 adsorption. The small amount of inorganic carbon present in the desorption solution is likely because, although CO2 adsorption did not occur, the direct air capture carbon adsorbent material inevitably came into contact with the atmospheric environment during the addition of the desorption solution after preparation, adsorbing a small amount of CO2, thus introducing a small amount of HCO3 into the solution. - In Comparative Example 8, as the adsorption time increased, the concentration of inorganic carbon in the desorption solution increased, and the pH value decreased. However, due to insufficient adsorption time, the material did not reach adsorption saturation before desorption, and the test results were still different from those of Example 1. In Comparative Example 9, the adsorption time of the material was further increased (greater than that of Example 1), but the test results of inorganic carbon concentration and pH value decrease in the desorption solution were not significantly increased compared with Example 1, indicating that the adsorption of CO2 by the material had reached saturation, and further increasing the adsorption time did not significantly improve the carbon adsorption effect of the material.

[0086] The results of Comparative Examples 10, 11, and 12 show that in Comparative Example 10, the method of using direct air capture carbon adsorbent material, with the preparation of a single NaCl solution for desorption, resulted in a large amount of inorganic carbon in the desorbate and a significant decrease in pH value. However, this was still inferior to that of Example 1. This is because HCO3... - Cl - Once released into the solution phase, it cannot exist stably and readily undergoes hydrolysis to generate CO2, which escapes from the solution phase. As the mass fraction of NaOH solution in Comparative Example 11 increases, HCO3-... - With OH in the solution - The reaction produces stable CO3 2- The concentration of inorganic carbon in the desorbate further increased; the mass fraction of NaOH solution in Comparative Example 12 further increased (greater than in Example 1), but due to the desorbed HCO3... - The quantity is limited, and all the carbon has reacted and is stably present in the solution phase. Therefore, an overly alkaline solution environment has no significant effect on further increasing the inorganic carbon concentration in the desorbent. According to the results of Comparative Examples 13, 14, and 15, in Comparative Example 13, in the method of using carbon-absorbing materials for direct air capture, the preparation of a single NaOH solution for desorption, due to the absence of Cl... - Replaces the already combined HCO3 - In Comparative Example 14, the inorganic carbon concentration in the desorption solution was almost zero, and the pH did not decrease significantly. However, in Comparative Example 15, when the NaCl mass fraction increased further, the inorganic carbon concentration increased due to the presence of HCO3-. - All of it has been released into the solution phase; the excess Cl present... -It had no significant effect on increasing the inorganic carbon concentration in the desorbent. According to the results of Comparative Examples 16 and 17, in the direct air capture carbon adsorbent method, Comparative Example 16 had insufficient desorption time for the material, failing to remove the already combined HCO3-. - All were released into the solution phase; with the significant increase in desorption time in Comparative Example 17 (greater than in Example 1), Cl - For HCO3 - The substitution has been completed, so excessive desorption time has no significant effect on increasing the inorganic carbon concentration in the desorbent.

[0087] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a direct air-capturing carbon adsorbent material for desorption from salt solution, characterized in that, Includes the following steps: (1) Weigh the ion exchange resin and place it in CuCl2 solution for one impregnation treatment, filter and wash to obtain metal-loaded ion exchange resin; (2) The metal-loaded ion exchange resin in step (1) is placed in NaOH solution for a second impregnation treatment, filtered, and the direct air capture carbon adsorbing material is obtained, which is the target product. The ion exchange resin in step (1) is a macroporous weakly basic styrene-based anion exchange resin with a volume exchange capacity of 1.0 eq / L to 2.0 eq / L; In step (1), the concentration of the CuCl2 solution is 10 g / L to 20 g / L, and the ratio of the amount of ion exchange resin added to the amount of CuCl2 solution is 2 g: 100 mL to 150 mL. In step (2), the mass fraction of the NaOH solution is 1%~5%; In step (2), the ratio of the amount of ion exchange resin to NaOH solution added in the metal-supported ion exchange resin is 2g: 100mL~150mL.

2. The method for preparing a direct air-capturing carbon adsorbent material for salt solution desorption according to claim 1, characterized in that, In step (1), the soaking time is 72-84 hours and the temperature is 20-25℃.

3. The method for preparing a direct air-capturing carbon adsorbent material for salt solution desorption according to claim 1, characterized in that, In step (2), the second soaking time is 36-48 hours and the temperature is 20-25℃.

4. A direct air capture carbon adsorbent material for desorption from salt solution, prepared by the preparation method described in any one of claims 1-3.

5. The application of the direct air capture carbon adsorbent material for salt solution desorption as described in claim 4, characterized in that, This direct air capture carbon adsorbent material is used for CO2 adsorption under ambient temperature and pressure conditions.

6. The application of the direct air capture carbon adsorbent material for salt solution desorption according to claim 5, characterized in that, After the carbon adsorbent material directly captures CO2 to saturation, a mixed solution of NaCl and NaOH is used for desorption treatment. The mass fractions of NaCl and NaOH in the mixed solution are 4%~8% and 1%~5%, respectively. The desorption process is kept in a sealed environment and the desorption time is 12-16 hours.

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