Amino acid-dispersant composite system and application thereof in preparation of nano calcium carbonate

Abstract

The application discloses an amino acid-dispersant composite system and application thereof in preparation of nano calcium carbonate. The amino acid-dispersant composite system comprises a leaching agent and a dispersant. The leaching agent comprises at least one amino acid, and the dispersant comprises a high-molecular polymer. The concentration of the leaching agent in the amino acid-dispersant composite system is 0.2-0.5 mol / L, and the concentration of the dispersant in the amino acid-dispersant composite system is 0.05-0.5 g / L. The amino acid-dispersant composite system prepared by the application can not only leach calcium ions, but also regulate the generation of nano calcium carbonate in the CO2 mineralization stage. The whole process does not need additional acid-base adjustment, avoids the ammonia volatilization and chlorine-containing waste liquid pollution problems in the traditional ammonium salt process, and has the advantages of short process flow, low reagent consumption, low-toxicity or non-toxic materials, good environmental friendliness and industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization technology, specifically relating to an amino acid-dispersant composite system and its application in the preparation of nano-calcium carbonate. Background Technology

[0002] The global problem of climate change caused by carbon emissions is becoming increasingly serious, and carbon capture, utilization, and storage (CCUS) technology is one of the key pathways to achieve carbon neutrality. Among them, mineral mineralization technology can use calcium / magnesium-containing raw materials to convert CO2 into stable carbonates, achieving permanent CO2 sequestration and potentially producing economically valuable products such as precipitated calcium carbonate (PCC), thus attracting widespread attention.

[0003] Indirect mineralization technology selectively leaches active calcium components from calcium-containing solid waste using chemical reagents to obtain a pure, calcium-rich solution. This solution is then reacted with CO2 for mineralization, effectively separating impurities and yielding high-purity, high-whiteness calcium carbonate products. However, the core bottleneck for the large-scale application of indirect mineralization technology lies in the performance and cost of the leaching agent. An ideal leaching agent needs to possess high calcium ion mineralization efficiency, high selectivity, good chemical stability, recyclability, and low environmental impact.

[0004] Currently, research in this field is active, and various extraction agent systems have been developed:

[0005] CN119954196A discloses a method for preparing monodisperse nano-calcium carbonate from calcium-containing industrial solid waste. The method involves mixing and reacting the calcium-containing solid waste with an ammonium salt solution to obtain a calcium-containing filtrate. Then, the calcium-containing filtrate, CO2 gas, and a crystal form control agent are mixed and reacted to obtain nano-calcium carbonate. Finally, the nano-calcium carbonate is mixed and reacted with an aqueous solution containing a surfactant, followed by centrifugation, washing, and drying to obtain monodisperse nano-calcium carbonate. While this method can improve the calcium leaching rate and achieve explosive nucleation of calcium carbonate, its process flow is relatively long, involving two additions of the crystal form control agent and surfactant, increasing reagent consumption and process complexity. Furthermore, this method relies on the ammonium salt leaching agent, which may lead to ammonia volatilization and chlorine-containing wastewater treatment issues. Additionally, the selective mineralization of calcium ions is not optimized, and impurity ions may affect the purity of the final product.

[0006] CN119287176A discloses a method for leaching calcium ions from calcium-containing solid waste. The method includes pre-screening and ball milling the calcium-containing solid waste, followed by mixing and reacting it with a leaching agent containing a protonated organic amine to obtain a calcium ion leachate; then, CO2 is introduced into the leachate to react and separate calcium carbonate solids and a regenerated leaching agent. This method uses a protonated organic amine as the leaching agent, which has advantages such as good selectivity, high calcium ion leaching rate, and low ammonia slip, and the leaching agent has good regeneration performance. However, this method still relies on the addition of acid to achieve the protonation of the organic amine, failing to eliminate dependence on acidic media. Furthermore, this method mainly focuses on the calcium ion leaching process, with limited ability to control the crystal form and particle size of the calcium carbonate product. The prepared calcium carbonate product is difficult to meet the requirements of high-end applications for nanoscale sizes and specific crystal forms (such as aragonite).

[0007] CN121023221A discloses a method for enhancing calcium ion leaching from solid waste by utilizing the synergistic effect of organic alcohol amines and amino acids to regulate the coordination structure. This method involves mixing calcium-containing solid waste with a composite leaching agent solution containing organic alcohol amines, amino acids, and water for mineralization, yielding a calcium ion mineralization solution. This method enhances calcium ion leaching through the synergistic effect of organic alcohol amines and amino acids, utilizing the coordination structure to regulate the leaching. However, this composite system has a complex composition, and the organic alcohol amines may face volatilization or degradation risks during long-term recycling. More importantly, this method also focuses on improving mineralization efficiency, while lacking in-depth research on the control of the crystal form and size of the subsequent calcium carbonate product. The prepared calcium carbonate product typically has a large particle size, making it difficult to obtain uniform nanoscale particles. Summary of the Invention

[0008] The purpose of this invention is to provide an amino acid-dispersant composite system and its application in the preparation of nano-calcium carbonate. By rationally combining amino acids and dispersants, efficient mineralization of calcium ions can be achieved. During the mineralization stage, crystal nucleus growth and agglomeration are effectively inhibited, and high-purity aragonite-type nano-calcium carbonate with a particle size in the range of 300-500 nm is prepared.

[0009] To achieve the above objectives, the present invention discloses an amino acid-dispersant composite system, comprising an extractant and a dispersant, wherein the extractant comprises at least one amino acid, and the dispersant comprises a polymer; the concentration of the extractant in the amino acid-dispersant composite system is 0.2~0.5 mol / L, and the concentration of the dispersant in the amino acid-dispersant composite system is 0.05~0.5 g / L.

[0010] Preferably, the amino acids include glycine, alanine, and arginine; the polymers include polyacrylic acid and its salts, polyethylene glycol and its derivatives, and polycarboxylic acid series polymers.

[0011] Preferably, the polyacrylic acid and its salts include sodium polyacrylate and ammonium polyacrylate; the polyethylene glycol and its derivatives include polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, and polyethylene glycol 800; and the polycarboxylic acid series polymers include polycarboxylic acid ethers and polycarboxylic acid copolymers.

[0012] Preferably, the extractant comprises glycine and alanine, the total concentration of glycine and alanine in the amino acid-dispersant composite system is 0.4 mol / L, and the ratio of glycine to alanine is 1:(1-2).

[0013] Preferably, the extractant includes arginine and glycine, the total concentration of arginine and glycine in the amino acid-dispersant composite system is 0.3 mol / L, and the ratio of glycine to arginine is (1-2):1.

[0014] This invention also discloses the application of an amino acid-dispersant composite system in the preparation of nano-calcium carbonate. The above-mentioned amino acid-dispersant composite system is added to calcium-containing solid waste, and the mixture is stirred at 25-45℃ and 200-800 rpm for 1-2 hours, then stopped. Solid-liquid separation is performed to obtain a calcium-rich solution. CO2 is bubbled into the calcium-rich solution to carry out a mineralization reaction until the solution pH remains stable. After filtration, washing, and drying, nano-sized high-purity calcium carbonate precipitate is obtained. The ratio of the calcium-containing solid waste to the amino acid-dispersant composite system is 10:1.

[0015] Preferably, the flow rate of the CO2 is 80-120 mL / min.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] This invention achieves highly selective calcium ion mineralization and pH self-regulation by rationally compounding amino acids and dispersants, utilizing the amphoteric properties of amino acids. This results in highly efficient calcium ion mineralization (mineralization rate of 20%~35%), with a calcium ion conversion rate (mineralization efficiency) exceeding 70%, while maintaining high selectivity for calcium ions (>99.5%). It effectively inhibits the dissolution of impurity ions such as iron, aluminum, and magnesium, ensuring the high purity of the calcium carbonate product. Simultaneously, by utilizing the steric hindrance and electrostatic repulsion effect of the dispersant, crystal nucleus growth and agglomeration are effectively suppressed during the mineralization stage, successfully preparing high-purity aragonite-type nano-calcium carbonate with a particle size in the range of 300-500 nm.

[0018] The amino acid-dispersant composite system prepared by this invention can not only leach calcium ions, but also regulate the generation of nano-sized calcium carbonate during the CO2 mineralization stage. The entire process does not require external acid or alkali adjustment, avoiding the ammonia volatilization and chlorine-containing wastewater pollution problems of traditional ammonium salt processes. Moreover, the entire process is short, with low reagent consumption, and all components are low-toxic or non-toxic materials, showing good environmental friendliness and industrial application prospects. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the experimental apparatus for preparing calcium-rich solutions by leaching calcium-containing solid waste in this invention;

[0020] Figure 2 This is a schematic diagram of the mineralization experimental apparatus in this invention;

[0021] Figure 3 This is a surface morphology image of the nano-calcium carbonate prepared using the amino acid-dispersant composite system of Example 4 of this invention;

[0022] Figure 4 This is a surface morphology diagram of the nano-calcium carbonate prepared using the amino acid-dispersant composite system of Example 8 of this invention.

[0023] In the diagram: 1. Thermostatic magnetically stirred water bath; 2. Three-necked flask; 3. pH meter; 4. Vacuum filtration; 5. CO2 cylinder; 6. Mass flow meter. Detailed Implementation

[0024] The invention will now be further described with reference to the accompanying drawings.

[0025] An amino acid-dispersant composite system includes an extractant and a dispersant. The extractant includes at least one amino acid, which may include not only glycine, alanine, and arginine, but also other amino acids with amino and carboxyl groups. The dispersant includes a polymer, which may include not only polyacrylic acid and its salts, polyethylene glycol and its derivatives, and polycarboxylic acid series polymers, but also other polymers that can stabilize particles through steric hindrance or electrostatic repulsion. All of these are within the scope of protection of this invention.

[0026] The concentration of amino acids in the amino acid-dispersant composite system is 0.2~0.5 mol / L, and the concentration of the polymer in the amino acid-dispersant composite system is 0.05~0.5 g / L. An amino acid-dispersant composite system can be obtained by mixing the above-mentioned amino acids and polymers at the specified concentrations. This system is then added to calcium-containing solid waste for the preparation of nano-calcium carbonate. The calcium-containing solid waste mainly includes steel slag or coal fly ash. The amino acid-dispersant composite system includes the following examples:

[0027] Example 1

[0028] An amino acid-dispersant composite system is disclosed, wherein glycine is used as the extractant and sodium polyacrylate is used as the dispersant. The concentration of glycine in the amino acid-dispersant composite system is 0.3 mol / L, and the concentration of sodium polyacrylate in the amino acid-dispersant composite system is 0.10 g / L.

[0029] Example 2

[0030] An amino acid-dispersant composite system is disclosed, wherein glycine is used as the extractant and polyethylene glycol 400 is used as the dispersant. The concentration of glycine in the amino acid-dispersant composite system is 0.3 mol / L, and the concentration of polyethylene glycol 400 in the amino acid-dispersant composite system is 0.15 g / L.

[0031] Example 3

[0032] An amino acid-dispersant composite system is disclosed, wherein the extractant is alanine and the dispersant is sodium polyacrylate. The concentration of alanine in the amino acid-dispersant composite system is 0.3 mol / L, and the concentration of sodium polyacrylate in the amino acid-dispersant composite system is 0.10 g / L.

[0033] Example 4

[0034] An amino acid-dispersant composite system is disclosed, wherein the extractant is arginine, the dispersant is a polycarboxylate copolymer, the concentration of arginine in the amino acid-dispersant composite system is 0.2 mol / L, and the concentration of polycarboxylate copolymer in the amino acid-dispersant composite system is 0.05 g / L.

[0035] Example 5

[0036] An amino acid-dispersant composite system is disclosed, wherein the extractants are glycine and alanine, the dispersant is sodium polyacrylate, the total concentration of glycine and alanine in the amino acid-dispersant composite system is 0.4 mol / L, the ratio of glycine to alanine is 1:1, and the concentration of sodium polyacrylate in the amino acid-dispersant composite system is 0.15 g / L.

[0037] Example 6

[0038] An amino acid-dispersant composite system is disclosed, wherein the extractants are glycine and arginine, the dispersant is polyethylene glycol 600, the total concentration of glycine and arginine in the amino acid-dispersant composite system is 0.3 mol / L, the ratio of glycine to arginine is 2:1, and the concentration of polyethylene glycol 600 in the amino acid-dispersant composite system is 0.10 g / L.

[0039] Example 7

[0040] An amino acid-dispersant composite system is disclosed, wherein glycine is used as the extractant and ammonium polyacrylate is used as the dispersant. The concentration of glycine in the amino acid-dispersant composite system is 0.5 mol / L, and the concentration of ammonium polyacrylate in the amino acid-dispersant composite system is 0.20 g / L.

[0041] Example 8

[0042] An amino acid-dispersant composite system is disclosed, wherein glycine is used as the extractant and polycarboxylic acid ether is used as the dispersant. The concentration of glycine in the amino acid-dispersant composite system is 0.25 mol / L, and the concentration of polycarboxylic acid ether in the amino acid-dispersant composite system is 0.08 g / L.

[0043] Example 9

[0044] An amino acid-dispersant composite system is disclosed, wherein the extractant is alanine and the dispersant is polyethylene glycol 800. The concentration of alanine in the amino acid-dispersant composite system is 0.4 mol / L, and the concentration of polyethylene glycol 800 in the amino acid-dispersant composite system is 0.12 g / L.

[0045] Example 10

[0046] An amino acid-dispersant composite system is disclosed, wherein the extractants are glycine and arginine, the dispersant is sodium polyacrylate, the total concentration of glycine and arginine in the amino acid-dispersant composite system is 0.3 mol / L, the ratio of glycine to arginine is 2:1, and the concentration of sodium polyacrylate in the amino acid-dispersant composite system is 0.12 g / L.

[0047] First, add steel slag or coal fly ash to three-necked flask 2. Then, add the amino acid-dispersant composite system from Examples 1-10 to the three-necked flask 2 containing steel slag or coal fly ash. The solid-liquid ratio of steel slag or coal fly ash to the amino acid-dispersant composite system is 1:10, that is, 10 g of calcium-containing solid waste is added for every 100 mL of the amino acid-dispersant composite system. Place three-necked flask 2 in a constant-temperature magnetically stirred water bath 1, and insert the test head of pH meter 3 into the solution in three-necked flask 2 to observe the pH change of the solution during the leaching process. Stir at 25-45℃ and 200-800 rpm for 1-2 hours, then stop stirring. Transfer the solid-liquid mixture in three-necked flask 2 to the filter flask of vacuum filtration 4, and obtain a calcium-rich solution by filtration. The calcium-rich solution was then added to a three-necked flask 2, which was placed in a constant-temperature magnetically stirred water bath 1. The calcium-rich solution was connected to a CO2 gas cylinder 5, and the test head of a pH meter 3 was inserted into the calcium-rich solution. The CO2 gas cylinder 2 was then opened, and the CO2 flow rate was set using a mass flow meter 6. CO2 was introduced into the calcium-rich solution at a flow rate of 100 mL / min to carry out the mineralization reaction until the pH of the solution no longer decreased (approximately 30-60 min). After filtration, washing, and drying, nano-sized high-purity calcium carbonate precipitate was obtained.

[0048] The test operation parameters are shown in Table 1.

[0049] The effective concentrations and experimental results of the amino acid-dispersant composite systems in Examples 1-10 are shown in Table 2:

[0050] Table 1. Experimental parameters for mineralization of calcium-containing solid waste

[0051]

[0052] Table 2. Effective concentrations and mineralization test results of the amino acid-dispersant composite systems in Examples 1-10

[0053]

[0054] As can be seen from the experimental results in Table 2, the amino acid-dispersant composite system provided by this invention achieves a calcium ion mineralization rate of 14% to 29% in steel slag or coal fly ash under mild conditions, with a calcium ion mineralization selectivity exceeding 99.7%, demonstrating that this composite system can effectively inhibit the dissolution of impurity ions. The mineralization efficiency of all examples exceeds 70%, with the systems involving arginine (Examples 4, 6, and 10) achieving a mineralization efficiency of over 85%, indicating that the synergistic effect of amino acids and dispersants significantly promotes CO2 conversion. Particularly noteworthy is that the average particle size of the calcium carbonate products prepared in all examples is within the range of 300-500 nm, successfully achieving the controllable preparation of nano-sized calcium carbonate.

[0055] In Example 4, the dispersant used arginine + polycarboxylate and in Example 8, the dispersant used glycine + polycarboxylate ether, respectively, yielded uniform nanoparticles of 300 nm and 500 nm, with the crystal form mainly being aragonite, resulting in high added value for the products.

[0056] In the amino acid-dispersant composite system, amino acids play a central role in the leaching of calcium ions from calcium-containing solid waste. This is because the amino and carboxyl groups in the amino acid molecules form stable five-membered ring chelates with calcium ions through a dual-coordination structure, significantly reducing the concentration of free calcium ions in the solution. This disrupts the dissolution equilibrium of solid-phase calcium (such as calcium hydroxide and calcium silicate) in calcium-containing solid waste, driving continuous calcium dissolution. Simultaneously, the amphoteric properties of amino acids endow them with excellent pH buffering capacity, which can neutralize excess hydroxide ions released from solid waste, maintaining the system pH within a suitable weakly alkaline range for chelation reactions. As the pH increases, amino acids gradually transform into a deprotonated form, further enhancing their coordination affinity for calcium. This enables selective and efficient leaching of active calcium phases (such as CaO, Ca(OH)2, and calcium aluminum silicates). In contrast, the dispersant only plays a physical auxiliary role in stabilizing the suspension system and preventing particle aggregation in industrial cycles and does not participate in the calcium coordination reaction. Therefore, the calcium leaching mechanism is entirely dominated by the synergistic effect of chelation and buffering of amino acids.

[0057] The amino and carboxyl groups in amino acid molecules form zwitterions, providing an inherent pH buffering capacity for mineralization and the mineralization process. This is crucial for the recycling and regeneration of the leaching agent. During the mineralization stage, the dispersant adsorbs onto the surface of CaCO3 particles through its long-chain structure or charge effect, generating steric hindrance or electrostatic repulsion, effectively preventing the aggregation and growth of nanoparticles, thus obtaining nanoscale products with uniform particle size. Studies have shown that glycine can act as a proton donor and complexing agent during mineralization, promoting calcium ion dissolution; it can also act as a proton acceptor, accelerating CO2 mass transfer, achieving a mineralization efficiency of over 70%.

[0058] In this invention, both mineralization and dispersant occur at low temperatures. Under these conditions, the volatility of amino acids and dispersants is extremely low, which can effectively reduce reagent loss caused by solvent evaporation.

[0059] In summary, this invention, through the rational combination of amino acids and polymers, develops a composite mineralization system capable of efficiently extracting calcium ions from calcium-containing solid waste and simultaneously preparing high-purity nano-sized aragonite calcium carbonate. This system integrates high selective mineralization, high mineralization efficiency, nanoscale size control, crystal form control, and environmental friendliness, providing a new technical solution for the high-value utilization and CO2 mineralization of calcium-containing solid waste.

[0060] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.

Claims

1. An amino acid-dispersant composite system, characterized in that, The mixture includes an extractant and a dispersant, wherein the extractant comprises at least one amino acid, and the dispersant comprises a polymer; the concentration of the extractant in the amino acid-dispersant composite system is 0.2~0.5 mol / L, and the concentration of the dispersant in the amino acid-dispersant composite system is 0.05~0.5 g / L.

2. The amino acid-dispersant composite system according to claim 1, characterized in that, The amino acids include glycine, alanine, and arginine; the polymers include polyacrylic acid and its salts, polyethylene glycol and its derivatives, and polycarboxylic acid series polymers.

3. The amino acid-dispersant composite system according to claim 2, characterized in that, The polyacrylic acid and its salts include sodium polyacrylate and ammonium polyacrylate; the polyethylene glycol and its derivatives include polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, and polyethylene glycol 800; the polycarboxylic acid series polymers include polycarboxylic acid ethers and polycarboxylic acid copolymers.

4. The amino acid-dispersant composite system according to claim 2, characterized in that, The extractant includes glycine and alanine, the total concentration of glycine and alanine in the amino acid-dispersant composite system is 0.4 mol / L, and the ratio of glycine to alanine is 1:(1-2).

5. The amino acid-dispersant composite system according to claim 2, characterized in that, The extractant includes arginine and glycine, the total concentration of arginine and glycine in the amino acid-dispersant composite system is 0.3 mol / L, and the ratio of glycine to arginine is (1-2):

1.

6. The application of an amino acid-dispersant composite system in the preparation of nano-calcium carbonate, characterized in that, The amino acid-dispersant composite system according to any one of claims 1-5 is added to calcium-containing solid waste, and the mixture is stirred at 25-45℃ and 200-800 rpm for 1-2 hours, then the mixture is stopped, and solid-liquid separation is performed to obtain a calcium-rich solution. CO2 is introduced into the calcium-rich solution to carry out a mineralization reaction until the pH of the solution is stable. After filtration, washing, and drying, nano-sized high-purity calcium carbonate precipitate is obtained. The ratio of the calcium-containing solid waste to the amino acid-dispersant composite system is 10:

1.

7. The application of the amino acid-dispersant composite system according to claim 6 in the preparation of nano-calcium carbonate, characterized in that, The CO2 flow rate is 80-120 mL / min.

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