An amine group modified corn starch-based aerogel for carbon dioxide adsorption and a preparation method thereof

Abstract

The present application relates to the technical field of carbon dioxide solid adsorbent, in particular to an amine group modified corn starch based aerogel for carbon dioxide adsorption and a preparation method thereof. The conventional biomass based aerogel adsorption material has poor stability and poor carbon dioxide adsorption effect. In view of the above problems, the present application provides an amine group modified corn starch based aerogel for carbon dioxide adsorption. The aerogel adopts sodium carboxymethyl cellulose to strengthen the starch-sodium laurate composite network, and adopts polyethyleneimine to modify the amino group of the starch based composite network. Before the amino group modification, trivalent iron ions are introduced into the aerogel material system. The iron ions can coordinate with the carboxylate groups in the sodium carboxymethyl cellulose and the oxygen-containing functional groups in the polysaccharide skeleton to form iron-containing coordination nodes on the pore wall of the aerogel. The carbon dioxide adsorption effect of the material can be significantly improved.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide solid adsorbent technology, specifically to an amine-modified corn starch-based aerogel for carbon dioxide adsorption and its preparation method. Background Technology

[0002] Large-scale carbon dioxide emissions contribute to the greenhouse effect. Flue gas emitted from coal-fired power plants, steel mills, cement plants, and chemical plants contains a certain concentration of carbon dioxide. Furthermore, there is a need for carbon dioxide concentration control in enclosed spaces, storage and transportation environments, and air purification scenarios. Developing low-cost, efficient, and renewable carbon dioxide capture materials is of great significance for reducing carbon emissions and promoting sustainable resource and environmental development.

[0003] Current carbon dioxide capture methods mainly include solvent absorption, membrane separation, cryogenic separation, and solid adsorption. Among these, solid adsorption has received widespread attention due to its advantages such as simple equipment, low energy consumption, renewable materials, and wide applicability. Common solid carbon dioxide adsorbents include activated carbon, zeolite molecular sieves, metal-organic frameworks (MOFs), mesoporous silica materials, and amine-modified porous materials. Activated carbon and biochar materials have certain specific surface areas and pore structures, but their surfaces are mainly composed of non-polar carbon structures, limiting their selectivity and low partial pressure adsorption capacity for carbon dioxide. Zeolite molecular sieves have regular channels and strong polar sites, but they are sensitive to moisture, and their adsorption performance easily degrades in humid gas environments. MOFs have high specific surface areas and tunable pore structures, but some materials have high preparation costs, and powdered materials suffer from problems such as agglomeration, inconvenience in filling, and recycling during practical use. Amine-modified adsorbent materials can enhance adsorption capacity and selectivity by utilizing the interaction between nitrogen-containing functional groups and carbon dioxide. Primary and secondary amines typically provide the main chemisorption sites, while tertiary amines and other nitrogen-containing sites can regulate the local alkalinity of the material surface and promote the capture of carbon dioxide in the form of bicarbonates in the presence of moisture. Polyethyleneimine, as a polymer containing a large number of amine groups, is often used to modify the surface of porous supports to improve carbon dioxide adsorption capacity. However, directly loading polyethyleneimine onto the surface of ordinary porous materials easily leads to problems such as uneven distribution of amine components, pore blockage, and amine group loss during recycling, resulting in reduced adsorption rates and decreased reusability. Therefore, constructing a low-cost porous framework suitable for stable loading of amine components is crucial for improving the application performance of amine-modified carbon dioxide adsorbent materials.

[0004] Biomass polysaccharide materials have advantages such as wide availability, low cost, renewability, and environmental friendliness, making them important raw materials for constructing green adsorbent materials. Corn starch, as a typical natural polysaccharide, can be gelatinized by heating, compounded into a gel, and freeze-dried to form lightweight porous aerogel materials with a certain pore structure, which can serve as carriers for gas adsorption materials. However, single corn starch-based aerogels have limited skeletal strength and structural stability, and their surface mainly contains oxygen-containing functional groups such as hydroxyl groups, lacking amine active sites with strong affinity for carbon dioxide, thus limiting their adsorption capacity when directly used for carbon dioxide adsorption. Sodium carboxymethyl cellulose, a water-soluble polysaccharide derivative containing hydroxyl and carboxyl groups, can form hydrogen bonds with starch molecular chains. Simultaneously, its carboxyl groups can also interact with metal ions or amine polymers through electrostatic, hydrogen bonding, or coordination interactions. Introducing it into corn starch-based aerogel systems is expected to enhance the polysaccharide composite network, improve aerogel formability and pore structure retention, and provide activation sites for the stable loading of amine functional components. Furthermore, introducing iron salts into the polysaccharide-based aerogel precursor allows iron ions to coordinate with oxygen-containing functional groups in the starch and sodium carboxymethyl cellulose molecular chains and be dispersed and fixed within the polysaccharide composite network. The resulting iron-containing coordination nodes help regulate the aerogel composite network, improve pore structure retention, and enhance surface polarity, while also facilitating stable loading of polyethyleneimine on the pore walls. Without suitable polysaccharide network coordination and confinement, iron ions may undergo localized hydrolysis or aggregation during introduction, affecting the aerogel pore structure and the loading effect of functional components. Based on this approach, a starch-sodium laurate composite system is constructed using corn starch as the main framework. Sodium carboxymethyl cellulose is then used to enhance the aerogel network. Simultaneously, iron-containing coordination components are introduced and fixed in the composite precursor, and further modified with polyethyleneimine for amine group modification. This approach promises to obtain a biomass-based aerogel adsorbent material with low raw material costs, mild preparation conditions, stable pore structure, stable amine site loading, and good carbon dioxide adsorption performance. Summary of the Invention

[0005] The existing technology has the problem that conventional biomass-based aerogel adsorbents lack stability and have poor adsorption effects on carbon dioxide. To address these problems, this invention provides an amino-modified corn starch-based aerogel for carbon dioxide adsorption and its preparation method, the preparation method comprising the following steps: (1) Add sodium carboxymethyl cellulose to deionized water to form a homogeneous sodium carboxymethyl cellulose solution; (2) After high-temperature gelatinization, corn starch is non-covalently associated with sodium lauryl to form a corn starch-sodium lauryl polyelectrolyte complex; the ratio of corn starch to sodium lauryl is 100g:(2-15)g; (3) Add sodium carboxymethyl cellulose solution to corn starch-sodium lauryl laurate polyelectrolyte complex and stir evenly at 60-70℃ to obtain complex solution. The amount of sodium carboxymethyl cellulose solution is determined according to the mass ratio of sodium carboxymethyl cellulose to corn starch used in the preparation of corn starch-sodium lauryl laurate polyelectrolyte complex is (1-20) g:100 g. (4) After the complex solution is cooled to below 50 °C, the ferric ion aqueous solution is added to the complex solution obtained in step (3), and after stirring evenly, the ferric ion modified complex solution is obtained. The amount of ferric ion aqueous solution is determined according to the ratio of ferric ion to sodium carboxymethyl cellulose used in the preparation of the complex solution as (0.5-1) mmol: (0.25-0.5) g. (5) After homogenizing the iron ion modified composite solution, it was first flash-frozen in liquid nitrogen and then freeze-dried in a freeze dryer to obtain an aerogel; (6) After the aerogel is dried by vacuum drying to remove free water, it is cooled to room temperature to obtain dry aerogel. The dry aerogel is completely immersed in polyethyleneimine solution at room temperature. After the immersion is completed, the solid product is collected by solid-liquid separation and then dried by vacuum to obtain amine-modified corn starch-based aerogel.

[0006] Preferably, the preparation method of the corn starch-sodium lauryl polyelectrolyte complex includes the following steps: (1) Add corn starch to deionized water to obtain a starch solution with a mass concentration of 3-10 wt%. After stirring evenly at room temperature, corn starch gelatinize liquid is formed in a hot water bath at 80-100 ℃. (2) Sodium laurate was added to hot water at 70-90 ℃ and stirred to disperse evenly to obtain a sodium laurate dispersion of 50 mg / mL. Then, while stirring, the sodium laurate dispersion was added to corn starch gelatinized liquid under a hot water bath at 80-95 ℃. After stirring evenly, corn starch-sodium laurate polyelectrolyte complex was obtained. During the reaction, the ratio of corn starch to sodium laurate was 100 g: (2-15) g.

[0007] Preferably, the mass concentration of the sodium carboxymethyl cellulose solution in step (1) is 0.5-3.0 wt%.

[0008] Preferably, the ferric ion aqueous solution is a homogeneous solution formed by dissolving water-soluble ferric ion inorganic salts in deionized water, and the concentration of the water-soluble ferric ion inorganic salt aqueous solution is (0.5-1) mol / L.

[0009] Preferably, the water-soluble ferric ion inorganic salt includes one of ferric nitrate, ferric chloride, and ferric sulfate.

[0010] Preferably, the homogenization speed in step (5) is 8000-15000 rpm, and the homogenization time is 1-5 min.

[0011] Preferably, the freeze dryer freezes at a temperature of -80°C to -20°C for 24-72 hours.

[0012] Preferably, the polyethyleneimine solution is a solution formed by dissolving polyethyleneimine in water, ethanol, methanol, an ethanol-water mixture, or a methanol-water mixture.

[0013] Preferably, in step (6), the mass-to-volume ratio of aerogel to polyethyleneimine solution is 100 mg: 5 mL, the vacuum drying temperature is 40-80 °C, and the vacuum drying time is 6-24 h.

[0014] Beneficial effects: (1) This invention uses corn starch as the main framework of the aerogel, which is widely available, inexpensive, renewable, and environmentally friendly. Through heating gelatinization, composite gelation, and freeze-drying, a corn starch-based aerogel with a three-dimensional porous structure can be obtained, providing channels for carbon dioxide diffusion and exposure of adsorption sites within the material. Introducing sodium laurate into the corn starch system and constructing a starch-sodium laurate composite network through the composite effect between sodium laurate and gelatinized starch molecular chains is beneficial to improving the formability of the aerogel precursor and providing a basic framework for subsequent sodium carboxymethyl cellulose reinforcement, introduction of iron-based components, and loading of amine functional components.

[0015] (2) This invention further introduces sodium carboxymethyl cellulose as a carboxyl polysaccharide reinforcing component, which not only strengthens the aerogel framework, but also allows the carboxyl groups and hydroxyl groups in its molecular chain to participate in the construction of the carbon dioxide adsorption functional interface. The formation of hydrogen bonds and chain entanglement between sodium carboxymethyl cellulose and starch molecular chains helps improve the integrity and connectivity of the aerogel pore structure after freeze-drying, maintaining channels for carbon dioxide diffusion into the material. Simultaneously, the carboxyl groups can form coordination nodes with iron ions and generate electrostatic and hydrogen bonding interactions with the protonated amine groups in polyethyleneimine, which is beneficial for the uniform dispersion and stable loading of polyethyleneimine on the aerogel pore walls, as well as the exposure of amine sites. The polar pore wall microenvironment formed by sodium carboxymethyl cellulose can also have an auxiliary affinity effect on carbon dioxide. Therefore, sodium carboxymethyl cellulose synergistically improves the carbon dioxide adsorption performance and cycling stability of the material by improving the pore structure, enhancing the loading stability of the amine functional components, and promoting the local enrichment of carbon dioxide near the amine sites.

[0016] (3) In this invention, iron salts are introduced into the corn starch-based composite precursor reinforced with sodium carboxymethyl cellulose. Iron ions can coordinate with the carboxylate groups in sodium carboxymethyl cellulose and the oxygen-containing functional groups in the polysaccharide backbone, forming iron-containing coordination nodes on the aerogel pore walls. These coordination nodes are beneficial for enhancing the polysaccharide composite network, maintaining the aerogel pore structure, and improving the surface polarity of the pore walls. At the same time, they provide interfacial interaction sites for the dispersion and stable loading of polyethyleneimine. Some unsaturated coordination iron sites or Fe-OH structures can also have an auxiliary affinity for carbon dioxide. The main carbon dioxide chemisorption sites of the material originate from the primary and secondary amines in polyethyleneimine, while the iron component mainly plays a role in structural regulation, interfacial fixation, and auxiliary adsorption.

[0017] (4) In this invention, polyethyleneimine is used to modify the sodium carboxymethyl cellulose (CMC)-reinforced corn starch-based aerogel containing iron coordination components, thereby loading polyethyleneimine onto the pore walls and surface of the aerogel. The primary and secondary amines in polyethyleneimine provide the main chemisorption sites for carbon dioxide, while tertiary amines and other nitrogen-containing sites can regulate the local alkalinity of the pore walls and participate in the carbon dioxide capture process under humid conditions. Compared to corn starch-based aerogels without amine modification, the resulting material has more carbon dioxide affinity sites, which is beneficial for improving carbon dioxide adsorption capacity. The synergistic effect between the iron-based components, the polysaccharide complex network, and the amine sites of polyethyleneimine is beneficial for improving the structural stability, functional component loading stability, and reusability of the material.

[0018] (5) The preparation process of this invention is mainly carried out in an aqueous phase or an alcohol-water mixture system, without the need for high-temperature carbonization, complex hydrothermal reactions or expensive precursors. The preparation conditions are mild, the operation steps are simple, the equipment requirements are low, and it is easy to achieve scale-up preparation. The resulting aerogel material is a block or porous solid material. After adsorption, carbon dioxide can be desorbed by heating, vacuum treatment or inert gas purging, and it has good recycling potential. Attached Figure Description

[0019] Figure 1 Scanning electron microscope image of the Fe-CMC / MSA aerogel obtained in Comparative Example 3.

[0020] Figure 2 Scanning electron microscope image of the Fe-CMC / MSA-PEI aerogel obtained in Example 1.

[0021] Figure 3 Fourier transform infrared spectra of Fe-CMC / MSA-PEI obtained in Example 1 and Fe-CMC / MSA obtained in Comparative Example 3.

[0022] Figure 4Thermogravimetric signal-time curves of Fe-CMC / MSA obtained in Comparative Example 3 and Fe-CMC / MSA-PEI obtained in Example 1 during atmosphere switching.

[0023] Figure 5 Adsorption time curve of carbon dioxide by Fe-CMC / MSA-PEI obtained in Example 1.

[0024] Figure 6 : Cyclic adsorption-desorption performance diagram of Fe-CMC / MSA-PEI obtained in Example 1. Detailed Implementation

[0025] The present invention will be described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely illustrative examples of implementation of the present invention and are not intended to limit the scope of the present invention.

[0026] The methods for testing carbon dioxide adsorption performance in this invention are as follows: Thermogravimetric analysis (TGA) was used to test the adsorption performance of the material for carbon dioxide. Approximately 10 mg of the sample was weighed and placed in an alumina crucible. The crucible was heated to 100 °C under a nitrogen atmosphere and maintained for 60 min to remove pre-adsorbed moisture and carbon dioxide. Subsequently, the temperature was lowered to 25 °C under a nitrogen atmosphere. After the sample mass stabilized, the atmosphere was switched to carbon dioxide and maintained for 150 min. The change in sample mass over time was recorded. The amount of carbon dioxide adsorbed was calculated based on the increase in sample mass before and after adsorption.

[0027] The amount of carbon dioxide adsorbed was calculated using the formula q = Δm / m0 × 1000 / 44.01, where q is the amount of carbon dioxide adsorbed in mmol / g; Δm is the increase in sample mass during the carbon dioxide adsorption stage; m0 is the sample mass before adsorption; and 44.01 is the molar mass of carbon dioxide.

[0028] To eliminate the influence of instrument baseline changes on the test results during thermogravimetric analysis, an empty crucible was used for baseline testing, which was then used for baseline correction in the subsequent calculation of carbon dioxide adsorption.

[0029] Example 1 A method for preparing an amino-modified corn starch-based aerogel for carbon dioxide adsorption is as follows: (1) Weigh 5.00 g of ordinary corn starch, add it to 95 mL of deionized water, stir and disperse it evenly at room temperature, then transfer it to a water bath at 95 °C and stir at 500 rpm for 1 h to fully gelatinize the corn starch and obtain corn starch gelatinized liquid; (2) Weigh 0.5 g of sodium laurylate, add 10 mL of 80℃ hot water for pre-dispersion, and then add the obtained sodium laurylate dispersion to the corn starch gelatinized liquid obtained in step (1) while stirring. Continue stirring at 90℃ to fully combine sodium laurylate with gelatinized corn starch to obtain starch-sodium laurylate electrolyte complex. (3) Weigh 0.5 g of sodium carboxymethyl cellulose, add it to 20 mL of deionized water, and stir at 50°C until a homogeneous solution is formed to obtain sodium carboxymethyl cellulose solution; (4) Slowly add the sodium carboxymethyl cellulose solution obtained in step (3) to the starch-sodium lauryl electrolyte complex obtained in step (2), and continue stirring at 60°C for 30 min to obtain the complex solution; (5) After the complex solution obtained in step (4) is cooled to 50 °C, 1 mL of 1 mol / L Fe(NO3)3 aqueous solution is added to it and stirred at 1000 rpm for 10 min to obtain the iron ion modified complex solution. (6) The iron ion modified composite solution obtained in step (5) was homogenized at 12000 rpm for 5 min, and then dispensed into a cylindrical polypropylene mold (inner diameter 50 mm, height 20 mm). After being rapidly frozen in liquid nitrogen for 5 min, it was placed in a freeze dryer and dried for 48 h to obtain an aerogel, denoted as Fe-CMC / MSA, where MSA represents corn starch base. (7) The Fe-CMC / MSA obtained in step (6) was placed in a vacuum drying oven at 60 °C for 12 h to remove the adsorbed free water in the aerogel; after drying, it was taken out and cooled to room temperature to obtain the dried aerogel. (8) Prepare a polyethyleneimine solution with a mass fraction of 10 wt.% using anhydrous ethanol-water mixed solvent, wherein the volume ratio of anhydrous ethanol to water in the solvent is 9:1; (9) Add 100 mg of dried aerogel obtained in step (7) to 5 mL of polyethyleneimine solution obtained in step (8), stir evenly, and soak at room temperature for 6 h to allow polyethyleneimine to enter the aerogel pores and be loaded onto the aerogel pore walls and surface. (10) After impregnation, the aerogel was removed and the residual solution on the outer surface of the aerogel was gently absorbed with filter paper. Then it was placed at 60 °C and vacuum dried for 12 h to obtain the target product, which was named Fe-CMC / MSA-PEI.

[0030] Comparative Example 1 is the same as Example 1, except that in step (3) of Comparative Example 1, the amount of sodium carboxymethyl cellulose used is 0.25 g, in step (5) the amount of Fe(NO3)3 aqueous solution used is 0.5 mL, and in step (8) the mass concentration of polyethyleneimine solution is 5 wt.%. The product obtained in Comparative Example 1 is denoted as Fe-CMC / MSA-PEI-2.

[0031] Comparative Example 2 is the same as Example 1, except that in step (3) of Comparative Example 2, the amount of sodium carboxymethyl cellulose used is 0.75 g, in step (5) the amount of Fe(NO3)3 aqueous solution used is 1.5 mL, and in step (8) the mass concentration of polyethyleneimine solution is 15 wt.%. The product obtained in Comparative Example 2 is denoted as Fe-CMC / MSA-PEI-3.

[0032] Under the same test conditions, the materials obtained in Example 1 and Comparative Examples 1-2 were used to conduct adsorption tests on carbon dioxide, and the test results are shown in Table 1.

[0033] Table 1 Comparative Example 3 is the same as Example 1, except that the material obtained in Comparative Example 3 is the dried aerogel obtained in step (7) of Example 1.

[0034] The material obtained in Comparative Example 4 did not contain ferric ions, and the preparation method is as follows: (1) Weigh 5.00 g of ordinary corn starch, add it to 95 mL of deionized water, stir and disperse it evenly at room temperature, then transfer it to a water bath at 95 °C and stir at 500 rpm for 1 h to fully gelatinize the corn starch and obtain corn starch gelatinized liquid; (2) Weigh 0.5 g of sodium laurylate, add 10 mL of 80℃ hot water for pre-dispersion, and then add the obtained sodium laurylate dispersion to the corn starch gelatinized liquid obtained in step (1) while stirring. Continue stirring at 90℃ to fully combine sodium laurylate with gelatinized corn starch to obtain starch-sodium laurylate electrolyte complex. (3) Weigh 0.5 g of sodium carboxymethyl cellulose, add it to 20 mL of deionized water, and stir at 50°C until a homogeneous solution is formed to obtain sodium carboxymethyl cellulose solution; (4) Slowly add the sodium carboxymethyl cellulose solution obtained in step (3) to the starch-sodium lauryl electrolyte complex obtained in step (2), and continue stirring at 60°C for 30 min to obtain the complex solution; (5) After the composite solution obtained in step (4) is cooled to 50 °C, it is homogenized at 12000 rpm for 5 min, dispensed into molds of the same size as in Example 1, rapidly frozen in liquid nitrogen for 5 min, and then dried in a freeze dryer for 48 h to obtain aerogel. (6) The aerogel obtained in step (5) was placed in a vacuum drying oven at 60 °C for 12 h to remove the adsorbed free water in the aerogel; after drying, it was taken out and cooled to room temperature to obtain the dried aerogel. (7) Prepare a polyethyleneimine solution with a mass fraction of 10 wt.% using anhydrous ethanol-water mixed solvent, wherein the volume ratio of anhydrous ethanol to water in the solvent is 9:1; (8) Add 100 mg of dried aerogel obtained in step (6) to 5 mL of polyethyleneimine solution obtained in step (7), stir evenly, and soak at room temperature for 6 h to allow polyethyleneimine to enter the aerogel pores and be loaded onto the aerogel pore walls and surface. (9) After impregnation, the aerogel was removed and the residual solution on the outer surface of the aerogel was gently absorbed with filter paper. Then it was placed at 60 °C and vacuum dried for 12 h to obtain CMC / MSA-PEI.

[0035] The material obtained in Comparative Example 5 did not contain sodium carboxymethyl cellulose, and the preparation method is as follows: (1) Weigh 5.00 g of ordinary corn starch, add it to 95 mL of deionized water, stir and disperse it evenly at room temperature, then transfer it to a water bath at 95 °C and stir at 500 rpm for 1 h to fully gelatinize the corn starch and obtain corn starch gelatinized liquid; (2) Weigh 0.5 g of sodium laurylate, add 10 mL of 80℃ hot water for pre-dispersion, and then add the obtained sodium laurylate dispersion to the corn starch gelatinized liquid obtained in step (1) while stirring. Continue stirring at 90℃ to fully combine sodium laurylate with gelatinized corn starch to obtain starch-sodium laurylate electrolyte complex. (3) Add 1 mL of 1 mol / L Fe(NO3)3 aqueous solution to the starch-sodium lauryl electrolyte complex and stir at 1000 rpm for 10 min to obtain an iron ion modified complex solution. (4) The iron ion modified composite solution obtained in step (3) was homogenized at 12000 rpm for 5 min, and then dispensed into molds of the same size as in Example 1. After being rapidly frozen in liquid nitrogen for 5 min, it was dried in a freeze dryer for 48 h to obtain an aerogel, denoted as Fe / MSA, where MSA represents corn starch base. (5) Place the Fe / MSA obtained in step (4) in a vacuum drying oven at 60 °C for 12 h to remove the adsorbed free water in the aerogel; after drying, take it out and cool it to room temperature to obtain the dried aerogel. (6) Prepare a polyethyleneimine solution with a mass fraction of 10 wt.% using anhydrous ethanol-water mixed solvent, wherein the volume ratio of anhydrous ethanol to water in the solvent is 9:1; (7) Add 100 mg of dried aerogel obtained in step (5) to 5 mL of polyethyleneimine solution obtained in step (6), stir evenly, and soak at room temperature for 6 h to allow polyethyleneimine to enter the aerogel pores and be loaded onto the aerogel pore walls and surface. (8) After impregnation, the aerogel was removed and the residual solution on the outer surface of the aerogel was gently absorbed with filter paper. Then it was placed at 60 °C and vacuum dried for 12 h to obtain the target product, which was denoted as Fe / MSA-PEI.

[0036] The material obtained in Comparative Example 6 did not contain iron ions or sodium carboxymethyl cellulose. The preparation method is as follows: (1) Weigh 5.00 g of ordinary corn starch, add it to 95 mL of deionized water, stir and disperse it evenly at room temperature, then transfer it to a water bath at 95 °C and stir at 500 rpm for 1 h to fully gelatinize the corn starch and obtain corn starch gelatinized liquid; (2) Weigh 0.5 g of sodium laurylate, add 10 mL of 80℃ hot water for pre-dispersion, and then add the obtained sodium laurylate dispersion to the corn starch gelatinized liquid obtained in step (1) while stirring. Continue stirring at 90℃ to fully combine sodium laurylate with gelatinized corn starch to obtain starch-sodium laurylate electrolyte complex. (3) The starch-sodium lauryl electrolyte complex was homogenized at 12000 rpm for 5 min, then dispensed into molds of the same size as in Example 1, rapidly frozen in liquid nitrogen for 5 min, and then dried in a freeze dryer for 48 h to obtain aerogel; (4) The aerogel obtained in step (3) was placed in a vacuum drying oven at 60 °C for 12 h to remove the adsorbed free water in the aerogel; after drying, it was taken out and cooled to room temperature to obtain the dried aerogel. (5) Prepare a polyethyleneimine solution with a mass fraction of 10 wt.% using anhydrous ethanol-water mixed solvent, wherein the volume ratio of anhydrous ethanol to water in the solvent is 9:1; (6) Add 100 mg of dried aerogel obtained in step (4) to 5 mL of polyethyleneimine solution obtained in step (5), stir evenly, and soak at room temperature for 6 h to allow polyethyleneimine to enter the aerogel pores and be loaded onto the aerogel pore walls and surface. (7) After impregnation, the aerogel was removed and the residual solution on the outer surface of the aerogel was gently absorbed with filter paper. Then it was placed at 60 °C and vacuum dried for 12 h to obtain the target product, which was denoted as MSA-PEI.

[0037] The material obtained in Comparative Example 7 did not contain sodium laurate, and the preparation method is as follows: (1) Weigh 5.00 g of ordinary corn starch, add it to 95 mL of deionized water, stir and disperse it evenly at room temperature, then transfer it to a water bath at 95 °C and stir at 500 rpm for 1 h to fully gelatinize the corn starch and obtain corn starch gelatinized liquid; (2) Weigh 0.5 g of sodium carboxymethyl cellulose, add it to 20 mL of deionized water, and stir at 50°C until a homogeneous solution is formed to obtain sodium carboxymethyl cellulose solution; (3) Slowly add the sodium carboxymethyl cellulose solution obtained in step (2) to the corn starch gelatinized liquid obtained in step (1), and continue stirring at 60°C for 30 min to obtain the complex solution; (4) After the complex solution obtained in step (3) is cooled to 50 °C, 1 mL of 1 mol / L Fe(NO3)3 aqueous solution is added to it and stirred at 1000 rpm for 10 min to obtain the iron ion modified complex solution. (5) The iron ion modified composite solution obtained in step (4) was homogenized at 12000 rpm for 5 min, and then dispensed into molds of the same size as in Example 1. After being rapidly frozen in liquid nitrogen for 5 min, it was dried in a freeze dryer for 48 h to obtain an aerogel, denoted as Fe-CMC / MSA-noSL, where MSA represents corn starch base. (6) The Fe-CMC / MSA-noSL obtained in step (5) was placed in a vacuum drying oven at 60 °C for 12 h to remove the adsorbed free water in the aerogel; after drying, it was taken out and cooled to room temperature to obtain the dried aerogel. (7) Prepare a polyethyleneimine solution with a mass fraction of 10 wt.% using anhydrous ethanol-water mixed solvent, wherein the volume ratio of anhydrous ethanol to water in the solvent is 9:1; (8) Add 100 mg of dried aerogel obtained in step (6) to 5 mL of polyethyleneimine solution obtained in step (7), stir evenly, and soak at room temperature for 6 h to allow polyethyleneimine to enter the aerogel pores and be loaded onto the aerogel pore walls and surface. (9) After impregnation, the aerogel was removed and the residual solution on the outer surface of the aerogel was gently absorbed with filter paper. Then it was placed at 60 °C and vacuum dried for 12 h to obtain the target product, which was named Fe-CMC / MSA-PEI-noSL.

[0038] Comparative Example 8 is an empty crucible.

[0039] The carbon dioxide adsorption capacity of the materials obtained in Comparative Examples 3-8 of this invention was tested, and the test results are shown in Table 2.

[0040] Table 2 In Comparative Example 9, iron ions were added in step (1), and the preparation method is as follows: (1) Weigh 5.00 g of ordinary corn starch, add it to 95 mL of deionized water, stir and disperse it evenly at room temperature, then add 1 mL of 1 mol / L Fe(NO3)3 aqueous solution to the solution, stir at 1000 rpm for 10 min, then transfer it to a water bath at 95℃ and stir at 500 rpm for 1 h to fully gelatinize the corn starch and obtain corn starch gelatinized liquid; (2) Weigh 0.5 g of sodium laurylate, add 10 mL of 80℃ hot water for pre-dispersion, and then add the obtained sodium laurylate dispersion to the corn starch gelatinized liquid obtained in step (1) while stirring. Continue stirring at 90℃ to fully combine sodium laurylate with gelatinized corn starch to obtain starch-sodium laurylate electrolyte complex. (3) Weigh 0.5 g of sodium carboxymethyl cellulose, add it to 20 mL of deionized water, and stir at 50°C until a homogeneous solution is formed to obtain sodium carboxymethyl cellulose solution; (4) Slowly add the sodium carboxymethyl cellulose solution obtained in step (3) to the starch-sodium lauryl electrolyte complex obtained in step (2), and continue stirring at 60°C for 30 min to obtain the complex solution; (5) After the composite solution obtained in step (4) is cooled to 50°C, it is homogenized at 12000 rpm for 5 min, then dispensed into molds of the same size as in Example 1, rapidly frozen in liquid nitrogen for 5 min, and then dried in a freeze dryer for 48 h to obtain aerogel; (6) The aerogel obtained in step (5) was placed in a vacuum drying oven at 60 °C for 12 h to remove the adsorbed free water in the aerogel; after drying, it was taken out and cooled to room temperature to obtain the dried aerogel. (7) Prepare a polyethyleneimine solution with a mass fraction of 10 wt.% using anhydrous ethanol-water mixed solvent, wherein the volume ratio of anhydrous ethanol to water in the solvent is 9:1; (8) Add 100 mg of dried aerogel obtained in step (6) to 5 mL of polyethyleneimine solution obtained in step (7), stir evenly, and soak at room temperature for 6 h to allow polyethyleneimine to enter the aerogel pores and be loaded onto the aerogel pore walls and surface. (9) After impregnation, the aerogel was removed and the residual solution on the outer surface of the aerogel was gently absorbed with filter paper. Then it was placed at 60 °C and vacuum dried for 12 h to obtain the target product, which was named Fe(pre-gel)-CMC / MSA-PEI.

[0041] In Comparative Example 10, iron ions were added in step (2), and the preparation method is as follows: (1) Weigh 5.00 g of ordinary corn starch, add it to 95 mL of deionized water, stir and disperse it evenly at room temperature, then transfer it to a water bath at 95 °C and stir at 500 rpm for 1 h to fully gelatinize the corn starch and obtain corn starch gelatinized liquid; (2) Weigh 0.5 g of sodium laurylate and pre-disperse it in 10 mL of 80℃ hot water. Then, while stirring, add the obtained sodium laurylate dispersion to the corn starch gelatinized solution obtained in step (1). Continue stirring at 90℃ to fully combine sodium laurylate with gelatinized corn starch. Then, reduce the temperature to 70℃ and add 1 mL of 1 mol / L Fe(NO3)3 aqueous solution to the solution. After stirring evenly, starch-sodium laurylate electrolyte complex is obtained. (3) Weigh 0.5 g of sodium carboxymethyl cellulose, add it to 20 mL of deionized water, and stir at 50°C until a homogeneous solution is formed to obtain sodium carboxymethyl cellulose solution; (4) Slowly add the sodium carboxymethyl cellulose solution obtained in step (3) to the starch-sodium lauryl electrolyte complex obtained in step (2), and continue stirring at 60°C for 30 min to obtain the complex solution; (5) After the composite solution obtained in step (4) is cooled to 50 °C, it is homogenized at 12000 rpm for 5 min, then dispensed into molds of the same size as in Example 1, rapidly frozen in liquid nitrogen for 5 min, and then dried in a freeze dryer for 48 h to obtain aerogel. (6) The aerogel obtained in step (5) was placed in a vacuum drying oven at 60 °C for 12 h to remove the adsorbed free water in the aerogel; after drying, it was taken out and cooled to room temperature to obtain the dried aerogel. (7) Prepare a polyethyleneimine solution with a mass fraction of 10 wt.% using anhydrous ethanol-water mixed solvent, wherein the volume ratio of anhydrous ethanol to water in the solvent is 9:1; (8) Add 100 mg of dried aerogel obtained in step (6) to 5 mL of polyethyleneimine solution obtained in step (7), stir evenly, and soak at room temperature for 6 h to allow polyethyleneimine to enter the aerogel pores and be loaded onto the aerogel pore walls and surface. (9) After impregnation, the aerogel was removed and the residual solution on the outer surface of the aerogel was gently absorbed with filter paper. Then it was placed at 60 °C and vacuum dried for 12 h to obtain the target product, which was named Fe(pre-CMC)-CMC / MSA-PEI.

[0042] In Comparative Example 11, iron ions were added in step (4), and the preparation method is as follows: (1) Weigh 5.00 g of ordinary corn starch, add it to 95 mL of deionized water, stir and disperse it evenly at room temperature, then transfer it to a water bath at 95 °C and stir at 500 rpm for 1 h to fully gelatinize the corn starch and obtain corn starch gelatinized liquid; (2) Weigh 0.5 g of sodium laurylate, add 10 mL of 80℃ hot water for pre-dispersion, and then add the obtained sodium laurylate dispersion to the corn starch gelatinized liquid obtained in step (1) while stirring. Continue stirring at 90℃ to fully combine sodium laurylate with gelatinized corn starch to obtain starch-sodium laurylate electrolyte complex. (3) Weigh 0.5 g of sodium carboxymethyl cellulose, add it to 20 mL of deionized water, and stir at 50°C until a homogeneous solution is formed to obtain sodium carboxymethyl cellulose solution; (4) Slowly add the sodium carboxymethyl cellulose solution obtained in step (3) to the starch-sodium lauryl electrolyte complex obtained in step (2), continue stirring at 60°C for 30 min, then add 1 mL of 1 mol / L Fe(NO3)3 aqueous solution to the solution, stir evenly to obtain the complex solution; (5) After the composite solution obtained in step (4) is cooled to 50 °C, it is homogenized at 12000 rpm for 5 min, then dispensed into molds of the same size as in Example 1, rapidly frozen in liquid nitrogen for 5 min, and then dried in a freeze dryer for 48 h to obtain aerogel. (6) The aerogel obtained in step (5) was placed in a vacuum drying oven at 60 °C for 12 h to remove the adsorbed free water in the aerogel; after drying, it was taken out and cooled to room temperature to obtain the dried aerogel. (7) Prepare a polyethyleneimine solution with a mass fraction of 10 wt.% using anhydrous ethanol-water mixed solvent, wherein the volume ratio of anhydrous ethanol to water in the solvent is 9:1; (8) Add 100 mg of dried aerogel obtained in step (6) to 5 mL of polyethyleneimine solution obtained in step (7), stir evenly, and soak at room temperature for 6 h to allow polyethyleneimine to enter the aerogel pores and be loaded onto the aerogel pore walls and surface. (9) After impregnation, the aerogel was removed and the residual solution on the outer surface of the aerogel was gently absorbed with filter paper. Then it was placed at 60 °C and vacuum dried for 12 h to obtain the target product, which was denoted as Fe-CMC (precomplex) / MSA-PEI.

[0043] Carbon dioxide adsorption tests were conducted on the materials obtained in Example 1 and Comparative Examples 9-11 of the present invention, and the test results are shown in Table 3.

[0044] Table 3 The Fe-CMC / MSA-PEI obtained in Example 1 and the Fe-CMC / MSA obtained in Comparative Example 3 were observed using scanning electron microscopy. The scanning electron microscope images show that... Figure 1 The results of Comparative Example 3 show that the Fe-CMC / MSA obtained exhibits a layered porous structure with pores and interconnected gaps between the pore walls, indicating that the homogenization, rapid freezing, and freeze-drying processes can construct a porous aerogel framework. Figure 2 The results show that Example 1, after modification with polyethyleneimine, still maintains a certain layered porous structure, indicating that the polyethyleneimine impregnation and vacuum drying processes did not cause complete collapse of the aerogel skeleton. Some pore wall surfaces are smoother or denser than those in Comparative Example 1, which can be attributed to the loading of polyethyleneimine on the pore walls and channel surfaces.

[0045] Fourier transform infrared spectroscopy analysis was performed on the Fe-CMC / MSA-PEI obtained in Example 1 and the Fe-CMC / MSA obtained in Comparative Example 3. The results are as shown in the appendix to the specification. Figure 3 As shown. (Attached to the instruction manual) Figure 3 It can be seen that both Fe-CMC / SA and Fe-CMC / SA-PEI are in the range of 3200-3500 cm⁻¹ -1 A broad absorption peak appears in the range of 1000-1150 cm⁻¹, which is mainly attributed to the stretching vibration of hydroxyl groups in the polysaccharide backbone. Both materials show absorption peaks in the 1000-1150 cm⁻¹ range. -1 The presence of COC and CO-related absorption peaks within the range indicates that the material retains the polysaccharide backbone structure composed of corn starch and sodium carboxymethyl cellulose. Compared to Fe-CMC / SA, Fe-CMC / SA-PEI exhibits higher absorption peaks at 2920 cm⁻¹. -1 The nearby CH stretching vibration peak and 1600 cm⁻¹ -1 The absorption peaks associated with amine or carboxyl groups change, particularly in the 1000-1150 cm⁻¹ range. -1 The change in peak shape within the range indicates that polyethyleneimine has been successfully introduced into the aerogel material and interacts with the corn starch-based composite network reinforced with sodium carboxymethyl cellulose.

[0046] The thermogravimetric signal changes of Fe-CMC / MSA-PEI obtained in Example 1 and Fe-CMC / MSA obtained in Comparative Example 3 during the carbon dioxide adsorption test were compared, and the results are shown in the appendix to the specification. Figure 4 As shown, after the atmosphere switch, the thermogravimetric signals of both materials changed significantly. Fe-CMC / MSA-PEI exhibited a different mass response than Fe-CMC / MSA in the subsequent carbon dioxide adsorption stage.

[0047] The pore structure parameters of Fe-CMC / MSA-PEI obtained in Example 1 are shown in Table 4. As shown in Table 4, the BET specific surface area of ​​Fe-CMC / MSA-PEI is 18.0151 m². 2 / g, pore volume is 0.01772 cm³ 3 The average pore size was 3.9301 nm / g. This result indicates that the polyethyleneimine-modified material still possesses a good specific surface area and measurable pore structure. Combined with scanning electron microscopy results, it can be seen that the lamellar porous structure in the material facilitates the diffusion of carbon dioxide within the material and its contact with amino groups.

[0048] Table 4 The adsorption time curve of Fe-CMC / MSA-PEI for carbon dioxide obtained in Example 1 is shown in the attached specification. Figure 5 As shown.

[0049] Included in the instruction manual Figure 5 It can be seen that the Fe-CMC / MSA-PEI obtained in Example 1 exhibits a continuous mass increase process in a carbon dioxide atmosphere, indicating that the material can adsorb carbon dioxide. With prolonged adsorption time, the amount of carbon dioxide adsorbed by the material gradually increases, with a rapid increase in the initial stage followed by a slower rate of increase, indicating that carbon dioxide gradually enters the aerogel channels and interacts with the amino sites provided by polyethyleneimine. This result demonstrates that the iron-containing sodium carboxymethyl cellulose-reinforced amino-modified corn starch-based aerogel possesses a certain carbon dioxide adsorption capacity.

[0050] The cyclic adsorption-desorption performance diagram of Fe-CMC / MSA-PEI obtained in Example 1 is shown in the attached specification. Figure 6 As shown.

[0051] As shown in Tables 1, 2, and 3, the carbon dioxide adsorption capacity of Fe-CMC / MSA-PEI obtained in Example 1 after adsorption at 25 °C for 150 min is 0.934 mmol·g. -1The adsorption capacity was higher than that of Fe-CMC / MSA, CMC / MSA-PEI, Fe / MSA-PEI, and MSA-PEI. Fe-CMC / MSA, without polyethyleneimine modification, had a carbon dioxide adsorption capacity of only 0.20 mmol·g. -1 This indicates that the amino sites provided by polyethyleneimine are the main functional sites for carbon dioxide adsorption in the material.

[0052] Compared with CMC / MSA-PEI, Fe / MSA-PEI and MSA-PEI, Fe-CMC / MSA-PEI showed a higher carbon dioxide adsorption capacity, indicating that the introduction of sodium carboxymethyl cellulose and iron-containing coordination components is beneficial to improving the aerogel pore structure and the loading and site exposure of polyethyleneimine.

[0053] The carbon dioxide adsorption capacities of 9-11 after adsorption at 25 °C for 150 min were 0.724, 0.642, and 0.888 mmol·g, respectively. -1 Compared with Example 1, the above results show that the timing of the addition of Fe(NO3)3 solution affects the dispersion and fixation of iron ions in the polysaccharide complex network. When iron salt is added after the formation of the sodium carboxymethyl cellulose-reinforced starch-sodium lauryl ester complex precursor, iron ions can more fully coordinate with oxygen-containing functional groups such as carboxylate groups and hydroxyl groups in the complex precursor, which is beneficial for forming more uniform iron-containing coordination nodes and promoting the stable loading of polyethyleneimine on the aerogel pore walls and the exposure of amine sites, thereby obtaining a higher carbon dioxide adsorption capacity.

[0054] The results of the test on the change of carbon dioxide adsorption capacity of Fe-CMC / MSA-PEI obtained in Example 1 with adsorption time are shown in Table 5.

[0055] Table 5 As shown in Table 5, Fe-CMC / MSA-PEI exhibits a certain adsorption rate in a carbon dioxide atmosphere. With prolonged adsorption time, the amount of carbon dioxide adsorbed by the material gradually increases, indicating that the porous aerogel structure retained by the Fe-CMC / MSA-PEI obtained in Example 1 facilitates the diffusion of carbon dioxide within the material. Simultaneously, the amino sites provided by polyethyleneimine enhance the material's ability to capture carbon dioxide.

[0056] To further investigate the recycling performance of the Fe-CMC / MSA-PEI obtained in this invention, a carbon dioxide adsorption-desorption cycle experiment was conducted using the Fe-CMC / MSA-PEI obtained in Example 1. After each adsorption cycle, the atmosphere was switched to nitrogen, and the temperature was raised to 100 °C for desorption and regeneration, followed by a decrease to 25 °C for the next round of carbon dioxide adsorption. The cycle test results are shown in Table 6. Figure 6 As shown.

[0057] Table 6 As shown in Table 6, the adsorption capacity of Fe-CMC / MSA-PEI obtained in Example 1 decreased only from 0.934 mmol·g in the first five consecutive carbon dioxide adsorption-desorption cycles. -1 It decreased to 0.901 mmol·g on the 5th test. -1 The adsorption retention rate remained at 96.50% after the 5th cycle. The decrease in adsorption amount between cycles was small, indicating that the material can achieve relatively effective desorption and regeneration under a nitrogen atmosphere at 100 °C and has good stability for repeated use.

[0058] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. An amino-modified corn starch-based aerogel for carbon dioxide adsorption and its preparation method, characterized in that, The preparation method includes the following steps: (1) After high-temperature gelatinization, corn starch is non-covalently associated with sodium lauryl to form a corn starch-sodium lauryl polyelectrolyte complex; the ratio of corn starch to sodium lauryl is 100g:(2-15)g; (2) Add sodium carboxymethyl cellulose solution to corn starch-sodium lauryl laurate polyelectrolyte complex and stir evenly at 60-70℃ to obtain complex solution. The amount of sodium carboxymethyl cellulose solution is determined according to the mass ratio of sodium carboxymethyl cellulose to corn starch used in the preparation of corn starch-sodium lauryl laurate polyelectrolyte complex is (1-20) g:100 g. (3) After the complex solution is cooled to below 50 °C, the ferric ion aqueous solution is added to the complex solution obtained in step (2), and after stirring evenly, the ferric ion modified complex solution is obtained. The amount of ferric ion aqueous solution is determined according to the ratio of ferric ion to sodium carboxymethyl cellulose used in the preparation of the complex solution as (0.5-1) mmol: (0.25-0.5) g. (4) After homogenizing the iron ion modified composite solution, it was first flash-frozen in liquid nitrogen and then freeze-dried in a freeze dryer to obtain aerogel; (5) After the aerogel is dried by vacuum drying to remove free water, it is cooled to room temperature to obtain dry aerogel. The dry aerogel is completely immersed in polyethyleneimine solution at room temperature. After the immersion is completed, the solid product is collected by solid-liquid separation and then dried by vacuum to obtain amine-modified corn starch-based aerogel.

2. The amine-modified corn starch-based aerogel for carbon dioxide adsorption and its preparation method according to claim 1, characterized in that, The preparation method of corn starch-sodium lauryl polyelectrolyte complex includes the following steps: (1) Add corn starch to deionized water to obtain a starch solution with a mass concentration of 3-10 wt%. After stirring evenly at room temperature, corn starch gelatinize liquid is formed in a hot water bath at 80-100 ℃. (2) Sodium laurate was added to hot water at 70-90 ℃ and stirred to disperse evenly to obtain a sodium laurate dispersion of 50 mg / mL. Then, while stirring, the sodium laurate dispersion was added to corn starch gelatinized liquid under a hot water bath at 80-95 ℃. After stirring evenly, corn starch-sodium laurate polyelectrolyte complex was obtained. During the reaction, the ratio of corn starch to sodium laurate was 100 g: (2-15) g.

3. An amino-modified corn starch-based aerogel for carbon dioxide adsorption according to claim 1, and its preparation method thereof, characterized in that, Sodium carboxymethyl cellulose solution is prepared by adding sodium carboxymethyl cellulose to deionized water to form a homogeneous sodium carboxymethyl cellulose solution with a mass concentration of 0.5-3.0 wt%.

4. An amino-modified corn starch-based aerogel for carbon dioxide adsorption according to claim 1, and its preparation method thereof, characterized in that, Ferric ion aqueous solution is a homogeneous solution formed by dissolving water-soluble ferric ion inorganic salts in deionized water. The concentration of the water-soluble ferric ion inorganic salt aqueous solution is (0.5-1) mol / L.

5. An amino-modified corn starch-based aerogel for carbon dioxide adsorption according to claim 1, and its preparation method thereof, characterized in that, Water-soluble ferric ion inorganic salts include one or more of ferric nitrate, ferric chloride, and ferric sulfate; preferably, the water-soluble ferric ion inorganic salt is ferric nitrate, and more preferably ferric nitrate nonhydrate.

6. An amino-modified corn starch-based aerogel for carbon dioxide adsorption according to claim 1, and its preparation method thereof, characterized in that, In step (4), the homogenization speed is 8000-15000 rpm and the homogenization time is 1-5 min.

7. An amino-modified corn starch-based aerogel for carbon dioxide adsorption according to claim 1, and its preparation method thereof, characterized in that, The freeze dryer operates at a temperature of -80℃ to -20℃ for 24-72 hours.

8. An amino-modified corn starch-based aerogel for carbon dioxide adsorption according to claim 1, and its preparation method thereof, characterized in that, A polyethyleneimine solution is a solution formed by dissolving polyethyleneimine in water, ethanol, methanol, an ethanol-water mixture, or a methanol-water mixture.

9. An amino-modified corn starch-based aerogel for carbon dioxide adsorption according to claim 1, and its preparation method thereof, characterized in that, In step (5), the mass-to-volume ratio of aerogel to polyethyleneimine solution is 100 mg: 5 mL, the vacuum drying temperature is 40-80 °C, and the vacuum drying time is 6-24 h.

10. A method for capturing carbon dioxide, characterized in that, The amine-modified corn starch-based aerogel obtained according to any one of claims 1-9 is used as a solid adsorbent.

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