Gel microspheres, and methods of making and using the same

Abstract

The application discloses a gel microsphere and a preparation method and application thereof, and is characterized in that natural high-molecular chitosan is used as a matrix, eggshell membranes are added to control the pore structure of the trapping gel material, the high-molecular chitosan and the eggshell membranes used in the application are both natural biomass, have a high potential response to CO2, are renewable and degradable, are rich in resources, are low in cost, and are non-toxic, harmless and non-polluting.

Description

Technical Field

[0001] This invention belongs to the field of carbon dioxide capture and storage technology, specifically relating to a chitosan / egg shell membrane gel microsphere, its preparation method, and its application. Background Technology

[0002] In existing CO2 chemical capture methods, traditional organic solvents (organic amines / alkanolamines) absorb CO2 rapidly and selectively, but they are corrosive, suffer from high solvent loss during operation, poor resistance to oxidative and thermal degradation, and high regeneration energy consumption. Among inorganic absorbents, ammonia absorbents have a large absorption capacity, low regeneration energy consumption, low corrosivity, and resistance to oxidative and thermal degradation, and can achieve the combined removal of multiple acidic gaseous pollutants. However, their slow reaction rate and volatility limit their further development. Potassium carbonate absorbents have advantages such as low cost, low regeneration energy consumption, good stability, and strong resistance to oxidation and impurities. However, their CO2 absorption rate is low at normal pressure and low temperature, and they are prone to forming solid crystals that clog pipelines.

[0003] In recent years, semi-solid absorbents, which encapsulate liquid absorbents in porous solid materials to form microspheres, have been continuously explored. This effectively improves the gas-liquid interface, thereby increasing the CO2 absorption rate and giving new life to chemical absorption methods. CN202210380635.3 provides a solid amine absorbent, in which hollow silica microspheres are used as the framework to impregnate the amination reagent. The resulting product has an adsorption capacity of 180 mg / g, which remains stable during 50 consecutive adsorption-desorption cycles. Although semi-solid absorbents have advantages such as fast absorption rates and easy product separation, they still suffer from problems such as high preparation costs and poor mechanical properties.

[0004] Currently, gel materials made from natural biomass such as cellulose, chitosan, and cyclodextrin have shown potential application advantages in separation and adsorption purification in recent years due to their rich three-dimensional cross-linked networks, large specific surface area, high porosity, and abundant functional groups. However, their small pore size results in poor coating ability for absorbents, thus failing to demonstrate the advantages of semi-solid absorbents. Eggshell membranes, as natural biological fibers, possess excellent mechanical strength, biodegradability, and renewability. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an environmentally friendly, natural biomass, low-cost gel microsphere material and its preparation method, as well as its application as a carbon dioxide capture agent with good adsorption and absorption effect, which can bring huge economic benefits, environmental benefits and low energy consumption benefits. The method uses natural high molecular weight chitosan as a matrix and regulates the pore structure of the capture gel material by adding eggshell membrane.

[0006] This invention provides a gel microsphere, the raw materials of which are natural high molecular weight chitosan and eggshell membrane.

[0007] This invention also provides a method for preparing the gel microspheres, the specific steps of which are as follows:

[0008] (1) Take eggshell membrane, wash, dry, grind and sieve to obtain eggshell membrane powder;

[0009] (2) Dissolve natural high molecular weight chitosan powder in an aqueous acetic acid solution and stir until homogeneous to obtain a chitosan solution;

[0010] (3) Add eggshell membrane powder to chitosan solution, stir the solution with a magnetic stirrer until it becomes an emulsion, let it stand to eliminate air bubbles in the solution, and obtain a composite solution;

[0011] (4) Use a syringe to draw a certain amount of the composite solution and drip it into the sodium hydroxide solution to carry out the cross-linking reaction;

[0012] (5) After the addition is complete, let it stand until all the microspheres settle, then filter it, wash it repeatedly with water until the pH of the filtrate is neutral, and freeze dry to obtain gel microspheres.

[0013] In step (1), the eggshell membrane powder is passed through a 200-mesh sieve.

[0014] In step (2), the acetic acid aqueous solution contains 2-3% acetic acid by mass; the chitosan solution contains 5-10% chitosan by mass.

[0015] In step (3), the mass ratio of the eggshell membrane powder to the chitosan in the chitosan solution is 0.1 to 1:10.

[0016] In step (3), the magnetic stirring time is 30-45 min and the standing defoaming time is 60 min.

[0017] In step (4), the mass fraction of the sodium hydroxide solution is 8-15%.

[0018] The average diameter of the gel microspheres prepared by this invention is 2 mm to 3 mm.

[0019] The present invention also provides the application of the gel microspheres as a carbon dioxide capture agent. The gel microspheres are soaked in an absorbent for 8-12 hours and swelled to saturation before use as a carbon dioxide capture agent. Before use, they can also be soaked in an absorbent containing an indicator to swell them, making the capture process visible. Magnetic materials can also be added to facilitate recycling and reuse.

[0020] The absorbent is one of the following: 20-30 wt% potassium carbonate solution, 20-30 wt% sodium carbonate solution, MEA, MEA / propanol aqueous solution, or potassium taurate solution.

[0021] The indicator is one of thymol blue, phenolphthalein, and o-cresol blue.

[0022] The magnetic material is one or more of the following: ferrite particles, magnetic nanoparticles, tungsten carbide powder, and cobalt carbide powder.

[0023] The preparation mechanism of chitosan / egg shell membrane gel microspheres of this invention:

[0024] Chitosan can form hydrogels through physical cross-linking. In an acidic environment, the amino groups on the surface of chitosan are protonated, thus dissolving in the acidic solution. When the pH of the solution is increased to neutral or alkaline, the amino groups on the surface of chitosan are deprotonated. The chitosan chains form a supramolecular network system through physical cross-linking effects such as hydrogen bonding, hydrophobic interactions, and entanglement of chitosan polymer chains, thus transforming the solution into a gel. Eggshell membranes are organic fiber networks composed of tough keratin, which are structurally stable and have a high amino acid content on the membrane surface. This allows for the modification of chitosan gels to form gel microspheres with greater mechanical strength.

[0025] Effects and advantages of the present invention:

[0026] (1) The present invention introduces eggshell membrane as a pore-forming agent into gel microspheres, which can not only improve the CO2 absorption capacity and mechanical strength of gel microspheres, but also generate great economic benefits. The high molecular weight chitosan and eggshell membrane used in the present invention are both natural biomass, and have a potentially high response to CO2. They are renewable, degradable, abundant in resources, low in cost, non-toxic, harmless and pollution-free.

[0027] (2) The gel microspheres of the present invention combine the advantages of liquid absorbents (i.e., high capacity, high selectivity and water resistance) and solid adsorbents (e.g., high surface area and low volatility).

[0028] (3) Gel microspheres prepared from single natural high molecular weight chitosan are unstable and easily eroded. This invention introduces eggshell membrane, which interacts with high molecular weight chitosan, and significantly improves the stability of gel microspheres.

[0029] (4) The preparation process of the gel microspheres of the present invention is simple and is conducive to large-scale collection and use of CO2.

[0030] (5) The gel microspheres of this invention have a large specific surface area, porosity, and certain mechanical strength, and have a good adsorption effect on CO2. (6) This invention can also add indicators as needed to realize the visualization function of CO2 capture process; or add magnetic particles to realize the magnetic recovery function, which can make the capture gel microspheres have magnetic properties, and use the magnetic force of external magnetic field to quickly and efficiently separate the magnetic capture gel microspheres from the reactor, reduce absorbent loss and avoid secondary pollution. Attached Figure Description

[0031] Figure 1 The images show actual photos of the gel microspheres, where a, b, and c are actual photos of the hydrogels from Examples 1, 2, and 3, respectively.

[0032] Figure 2 These are scanning electron microscope images, where a and b are scanning electron microscope images of Examples 1 and 3, respectively;

[0033] Figure 3 The figures are for demonstration purposes, where a and b are the capture visualization of Example 2 and the magnetic separation performance of Example 3, respectively. Detailed Implementation

[0034] The present invention will now be described in further detail with reference to specific embodiments, so that those skilled in the art can understand it.

[0035] Example 1

[0036] A method for preparing gel microspheres, the specific steps of which are as follows:

[0037] (1) Take eggshell membranes, wash, dry, and grind them through a 200-mesh sieve to obtain eggshell membrane powder;

[0038] (2) Dissolve 2.5g of chitosan powder in 25mL of 3wt% acetic acid aqueous solution and stir until homogeneous to obtain chitosan solution;

[0039] (3) Take 0.25g of eggshell membrane powder and add it to 25mL of chitosan solution. Stir with a magnetic stirrer for 30min to completely dissolve it. Let it stand for 60min to eliminate the air bubbles in the solution and obtain a composite solution.

[0040] (4) Use a syringe to draw 5 mL of the composite solution and drop it into 50 mL of 8% sodium hydroxide solution to carry out the cross-linking reaction, so as to prepare gel microspheres with an average size of about 2 mm to 3 mm.

[0041] (5) After standing until all the gel microspheres have settled, filter them and wash them repeatedly with water until the pH of the filtrate is neutral. After freeze drying, dry gel microspheres are obtained.

[0042] The dried gel microspheres were soaked in a 30 wt% K2CO3 mixture until they swelled to saturation, thus obtaining gel microsphere 1.

[0043] Example 2

[0044] A method for preparing gel microspheres, the specific steps of which are as follows:

[0045] (1) Take eggshell membranes, wash, dry, and grind them through a 200-mesh sieve to obtain eggshell membrane powder;

[0046] (2) Dissolve 2g of chitosan powder in 25mL of 2wt% acetic acid aqueous solution and stir until homogeneous to obtain chitosan solution;

[0047] (3) Take 0.1g of eggshell membrane powder and add it to 25mL of chitosan solution. Stir with a magnetic stirrer for 40min to completely dissolve it. Let it stand for 60min to eliminate the bubbles in the solution and obtain a composite solution.

[0048] (4) Use a syringe to draw 5 mL of the composite solution and drop it into 50 mL of sodium hydroxide solution with a mass fraction of 12% to carry out the cross-linking reaction, so as to prepare gel microspheres with an average size of about 2 mm to 3 mm.

[0049] (5) After standing until all the gel microspheres have settled, filter them and wash them repeatedly with water until the pH of the filtrate is neutral. After freeze drying, dry gel microspheres are obtained.

[0050] The dried gel microspheres were immersed in a 30 wt% K2CO3 mixture containing thymol blue indicator. After swelling and saturation, gel microspheres 2 were obtained.

[0051] Carbon dioxide trapping gel microspheres 2 were exposed to air and pure CO2, respectively. After equilibration in air, the hydrogel turned blue-purple. Upon exposure to pure CO2, the hydrogel rapidly turned into a turbid and uniform pale yellow. After heating to remove CO2, it returned to its original blue-purple color. This method can be used as a qualitative method to assess the overall absorption and desorption of CO2 by the gel.

[0052] Example 3

[0053] A method for preparing gel microspheres, the specific steps of which are as follows:

[0054] (1) Take eggshell membranes, wash, dry, and grind them through a 200-mesh sieve to obtain eggshell membrane powder;

[0055] (2) Dissolve 1.25g of chitosan powder in 25mL of 2.5wt% acetic acid aqueous solution and stir until homogeneous to obtain chitosan solution;

[0056] (3) Take 0.04g of eggshell membrane powder and add it to 25mL of chitosan solution. Stir with a magnetic stirrer for 45min to completely dissolve it. Let it stand for 60min to eliminate the bubbles in the solution and obtain a composite solution.

[0057] (4) Use a syringe to draw 5 mL of the composite solution and drop it into 50 mL of 15% sodium hydroxide solution to carry out the cross-linking reaction, so as to prepare gel microspheres with an average size of about 2 mm to 3 mm.

[0058] (5) After standing until all the gel microspheres have settled, filter them and wash them repeatedly with water until the pH of the filtrate is neutral. After freeze drying, dry gel microspheres are obtained.

[0059] The dried gel microspheres were soaked in a 30 wt% K2CO3 mixture containing iron oxide particles until they swelled to saturation, thus obtaining gel microsphere 3.

[0060] Figure 1 a is a physical image of the gel microsphere 1 obtained in Example 1. The microsphere is a milky white particle with a diameter of 2 mm to 3 mm. Figure 1 b is a physical image of the gel microspheres 2 obtained in Example 2. The microspheres are light blue particles with a diameter of 2 mm to 3 mm. Figure 1 c is a physical image of the gel microspheres 3 obtained in Example 3. The microspheres are black particles with a diameter of 2 mm to 3 mm.

[0061] The gel microspheres 1 prepared in Example 1 were placed under an electron microscope to obtain their surface and internal structure as shown below. Figure 2 As shown in Figure a, observations reveal that with a high amount of eggshell membrane added, the gel interior contains mostly large pores of 10 μm, which facilitates carbon dioxide diffusion and improves absorption efficiency. The gel microspheres 3 prepared in Example 3 were placed under an electron microscope, and their surface and internal structures were obtained as shown in Figure a. Figure 2 b. Observation shows that with a low amount of eggshell membrane added, pores with a diameter of 0.5 μm appear inside the gel microspheres, and the pores are densely and neatly distributed. At the same time, the ferrite particles act as a skeleton and enter the interior of the pores, giving them greater mechanical strength.

[0062] Figure 3 a) is a visualization of the gel microspheres 2 prepared in Example 2. Before absorbing carbon dioxide, the gel particles in the container are light blue. After carbon dioxide is introduced into the container, the color of the gel particles gradually lightens and finally turns into light yellow. It can be seen that the gel microspheres can visualize the carbon dioxide capture process by adding an indicator. The entire capture process can be monitored intuitively, and the absorption-desorption node can be easily determined, which is beneficial for industrial operation.

[0063] Figure 3 b is a magnetic separation photograph of the gel microspheres 3 prepared in Example 3. The gel microspheres scattered in the container are quickly and tightly attracted by the external magnetic force. It can be seen that the gel microspheres can be efficiently magnetically separated in a large-volume reactor by an external strong magnetic field, reducing leakage and loss, avoiding secondary pollution, and improving the recycling rate of gel microspheres.

[0064] Gel microspheres 1 were placed in the reaction vessel of a gas chromatography system for CO2 absorption experiments to determine the absorption capacity. The absorption capacity and the time to reach absorption equilibrium of the prepared gel microspheres 1 and the pure absorbent (30 wt% K2CO3 solution) were analyzed and compared to explore its absorption performance. The results are shown in Table 1. As can be seen from Table 1, the absorption capacity of gel microspheres 1 is greater than that of the pure absorbent K2CO3 solution due to its higher specific surface area, and its time to reach absorption equilibrium is shortened by nearly 38% compared with the K2CO3 solution absorbent.

[0065] Table 1

[0066] sample Absorption conditions <![CDATA[Absorption capacity (mg CO2 / g)]]> Equilibrium time (min) Gel microspheres 1 0.1MPa 25℃ 73.64 57 <![CDATA[30 wt% K2CO3 solution]]> 0.1MPa 25℃ 64.23 92

[0067] While specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Based on the technical solutions of the present invention, various modifications or variations that can be made by those skilled in the art without creative effort are still within the protection scope of the present invention.

Claims

1. The application of a gel microsphere in a CO2 trap, characterized in that, The specific steps are as follows: (1) Take eggshell membranes, wash, dry, grind and pass through a 200-mesh sieve to obtain eggshell membrane powder; (2) Dissolve 2g of chitosan powder in 25mL of 2% acetic acid aqueous solution and stir until homogeneous to obtain chitosan solution; (3) Take 0.1g of eggshell membrane powder and add it to 25mL of chitosan solution. Stir magnetically for 40min to completely dissolve it. Let it stand for 60min to eliminate the bubbles in the solution and obtain a composite solution. (4) Use a syringe to draw 5 mL of the composite solution and drop it into 50 mL of 12% sodium hydroxide solution to carry out the cross-linking reaction, and prepare gel microspheres with an average size of 2 mm to 3 mm. (5) After standing until all the gel microspheres have settled, filter them and wash them repeatedly with water until the pH of the filtrate is neutral. After freeze drying, dry gel microspheres are obtained. (6) Soak the dried gel microspheres in a K2CO3 mixture containing 30% by mass of thymol blue indicator. After swelling and saturation, saturated gel microspheres are obtained. When saturated gel microspheres are exposed to air and pure CO2, the hydrogel turns blue-purple after equilibration in air. When exposed to pure CO2, the hydrogel quickly turns into a turbid and uniform pale yellow. After heating to remove CO2, it returns to its original blue-purple color. This can be used as a qualitative method to assess the overall absorption and desorption of CO2 by the gel.

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