Grain-size-controllable oversized cubic calcium carbonate and preparation method thereof

Abstract

The invention discloses a preparation method of oversized cubic calcium carbonate with controllable particle size, which comprises the following steps: adding a saccharide additive into a CaCl2 solution, and uniformly mixing to obtain a CaCl2 mixed solution; then placing the CaCl2 mixed solution in a carbonization tower, slowly adding Ca (OH) 2 as a pH regulator into the CaCl2 mixed solution, and preparing large cubic calcium carbonate at 25 DEG C by a carbonization method; by monitoring the reaction pH value, stopping introducing CO2 when the pH value is about 7, separating a product through suction filtration, and then drying to obtain the large cubic calcium carbonate. Large cubic calcium carbonate is prepared through a carbonization method, the large cubic calcium carbonate with different sizes is obtained by controlling the pH value of a reaction system, the maximum particle size can reach about 30 microns, and the monodispersity is good.

Description

Technical Field

[0001] The invention belongs to the technical field of inorganic materials, and particularly relates to an ultra-large cubic calcium carbonate with controllable particle size and a preparation method thereof. Background Art

[0002] Due to its low price, excellent performance and good biocompatibility, calcium carbonate is widely used as industrial raw materials and biomedical research materials. As an industrial filler, it has been widely used in papermaking, plastics, rubber, environmentally friendly rubber and other fields (Li CQ, et al. Surface modification of calcium carbonate: A review of theories, methods and applications [J]. Journal of Central South University, 2021, 28, 2589-2611.). For calcium carbonate, the particle size and crystal morphology determine its performance and application areas. Therefore, the particle size and crystal morphology of calcium carbonate have always been the focus of research.

[0003] The chemical methods for preparing calcium carbonate mainly include carbonization method and double decomposition method. In the process of producing calcium carbonate by both methods, the morphology of calcium carbonate particles can be changed by adding crystal control agents (Fan Kexin et al. Research progress on the influence of crystal control agents on the morphology of nano calcium carbonate [J]. Coal and Chemical Industry, 2023, 46(02): 143-146+160.). The addition of organic and inorganic control agents in the preparation process has synthesized calcium carbonate with cubic, spherical, spindle-shaped, disc-shaped, flake-shaped, and chain-shaped morphologies (Ma JP, et al. A promising strategy for the large-scale preparation of spherical calcium carbonate by efficiently using carbon dioxide [J]. Journal of CO2 Utilization, 2022, 63: 102136; Zhang YZ, et al. Vaterite Microdisc Mesocrystals Exposing the (001) Facet Formed via Transformation from Proto-Vaterite Amorphous Calcium Carbonate [J]. Crystal Growth & Design, 2020, 20 (5): 3482-3492; Chinese invention patent CN116040671B; Kezuka Y, et al. Synthesis of Tunable-Aspect-Ratio Calcite Nanoparticles via Mg 2+ Doping[J].Crystal Growth&Design,2019,19(11):6794-6791.), the particle size of the above calcium carbonate particles ranges from nanometer to micrometer.

[0004] In addition to additives, reaction pH is also a key parameter for regulating product morphology and particle size. Majekodunmi OT et al. continuously dispersed a CaCl2 / Na2CO3 mixture in a Ca(OH)2 solution and found that the particle size of calcium carbonate decreased linearly with increasing pH by adjusting the pH of the Ca(OH)2 solution. When pH>11.5, submicron-sized calcium carbonate (about 400 nm) was obtained (Majekodunmi OT, et al. Contributory roles of concentration and pH in CaCO3 growth inhibition for submicron particles synthesis with additive Ca 2+ [J]. Powder Technology, 2024, 437: 119588.). Patent CN118479521A uses NH3·H2O to adjust the pH of the CaCl2 solution, and then passes CO2 to prepare spherical, needle-shaped, rose-shaped and regular dodecahedral light calcium carbonate, with particle sizes ranging from 0.1 to 15 μm. Patent CN113800548A adds an alkyl phosphate surfactant to the calcium chloride solution, and then passes a sodium carbonate mixed solution containing a soluble alkali into the calcium chloride mixed solution to accurately prepare 80nm, 110nm, and 300nm calcium carbonate. Although the above studies have achieved the adjustment of calcium carbonate particle size by adjusting the pH, there is little research on micron-sized calcium carbonate, especially for calcium carbonate systems above 10μm. Summary of the invention

[0005] To this end, the present invention aims to provide an ultra-large cubic calcium carbonate with controllable particle size and a preparation method thereof, and to provide a large cubic calcium carbonate with a particle size of more than 10 μm and a regular morphology. The present invention uses calcium chloride as the initial reaction raw material, uses a sugar additive as a crystal form control agent, controls the pH of the reaction system by calcium hydroxide, and then introduces CO2 to achieve control of the particle size of calcium carbonate. For this reason, the present invention provides a direction for the particle size control of industrially produced precipitated calcium carbonate.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing super-large cubic calcium carbonate with controllable particle size comprises the following steps:

[0008] S1: calcine the ore, crush and sieve it to obtain CaO for later use;

[0009] S2: Ca(OH)2 suspension prepared by the above CaO digestion;

[0010] S3: preparing a CaCl2 solution, and adding the sugar additive into the CaCl2 solution to obtain a mixed solution A;

[0011] S4: placing the mixed solution A in a carbonization tower and adjusting the pH with Ca(OH)2;

[0012] S5: Start stirring, introduce CO2 mixed gas into the above mixed solution, and monitor the pH of the carbonation reaction process. When the pH drops to about 7, stop the reaction, filter the product and dry it to obtain large cubic calcium carbonate.

[0013] Preferably, the ore calcining temperature in step S1 is 1300°C.

[0014] Preferably, the digestion temperature in step S2 is room temperature digestion.

[0015] Preferably, the concentration of the Ca(OH)2 suspension in step S2 is 0.5 to 1.5 mol / L.

[0016] Preferably, in step S3, the CaCl2 concentration is 0.5-2 mol / L, and the concentration of the sugar additive is 0.2%-0.8% of the theoretical yield of calcium carbonate.

[0017] Preferably, the sugar additive in step S3 is one or more of glucose, fructose, sucrose and starch.

[0018] Preferably, the pH value is adjusted to 8-11 in step S4, and the pH change should be controlled within 0.02-0.05 each time the solution is added until the set pH value is reached.

[0019] Preferably, the stirring speed in step S5 is 200-600 r / min.

[0020] The concentration of the CO2 mixed gas in step S5 is 5% to 10%, and the flow rate of the mixed gas is 0.5 to 1.2 m 3 / h.

[0021] Preferably, the drying temperature in step S5 is 95-105°C.

[0022] Compared with the existing calcium carbonate preparation technology, the present invention exhibits the following significant technical advantages, which not only achieves a breakthrough in scientific principles, but also brings substantial progress in industrial application:

[0023] (1) The present invention regulates the crystallization process of calcium carbonate by introducing a sugar crystal form controller, thereby guiding the calcium carbonate to arrange in a specific manner to form cubic calcium carbonate with uniform morphology.

[0024] (2) The present invention further enhances the adjustability of the particle size and morphology of calcium carbonate by adjusting the pH value of the reaction system. The pH range of the solution is precisely controlled by slowly adding calcium hydroxide, thereby controlling the growth rate and morphological evolution of calcium carbonate crystals, increasing the adjustable range of calcium carbonate particle size, and the adjustment process is simple to operate and easy to master, which is conducive to improving production efficiency and product quality.

[0025] (3) The present invention successfully achieves precise control of the particle size and morphology of calcium carbonate by introducing a crystal form control agent and adjusting the pH of the reaction system. The prepared calcium carbonate has the characteristics of regular morphology and good monodispersity. The morphology is a regular cube, and the maximum particle size of calcium carbonate can reach 30 μm. Therefore, the above research provides a practical solution for the industrial production of high value-added precipitated calcium carbonate products, which has broad market application prospects and far-reaching social and economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the SEM image of the extra-large cubic calcium carbonate prepared in Example 1.

[0027] Figure 2 This is the SEM image of the extra-large cubic calcium carbonate prepared in Example 2.

[0028] Figure 3 This is the SEM image of the extra-large cubic calcium carbonate prepared in Example 3.

[0029] Figure 4 This is the SEM image of the extra-large cubic calcium carbonate prepared in Example 4.

[0030] Figure 5 This is the SEM image of cubic calcium carbonate prepared in Comparative Example 1. DETAILED DESCRIPTION

[0031] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0032] In an embodiment of the present invention, a method for preparing super-large cubic calcium carbonate with controllable particle size comprises the following steps:

[0033] S1: calcine the ore, crush and sieve it to obtain CaO for later use;

[0034] S2: Ca(OH)2 suspension prepared by the above CaO digestion;

[0035] S3: preparing a CaCl2 solution, and adding the sugar additive into the CaCl2 solution to obtain a mixed solution A;

[0036] S4: placing the mixed solution A in a carbonization tower and adjusting the pH with Ca(OH)2;

[0037] S5: Start stirring, introduce CO2 mixed gas into the above mixed solution, and monitor the pH of the carbonation reaction process. When the pH drops to about 7, stop the reaction, filter the product and dry it to obtain large cubic calcium carbonate.

[0038] The ore calcination temperature in step S1 is 1100-1300°C.

[0039] The digestion temperature in step S2 is room temperature digestion.

[0040] The concentration of the Ca(OH)2 suspension in step S2 is 0.5-1.5 mol / L.

[0041] In step S3, the CaCl2 concentration is 0.5-2 mol / L, and the sugar additive concentration is 0.2%-0.8% of the theoretical yield of calcium carbonate.

[0042] The sugar additive in step S3 is one or more of glucose, fructose, sucrose and starch.

[0043] In step S4, the pH is adjusted to 8-11, and the pH change should be controlled within 0.02-0.05 each time the solution is added until the set pH value is reached.

[0044] The stirring speed in step S5 is 200-600 r / min.

[0045] The concentration of the CO2 mixed gas in step S5 is 5% to 10%, and the flow rate of the mixed gas is 0.5 to 1.2 m 3 / h.

[0046] The drying temperature in step S5 is 95-105°C.

[0047] The technical principles of the present invention are as follows:

[0048] The method for preparing super-large cubic calcium carbonate with controllable particle size of the present invention has a sophisticated process flow and rigorous parameter setting, which not only ensures the high-quality output of the product, but also deeply reveals the scientific principles and necessity behind each step of the operation, so that this preparation technology shows excellent performance and wide applicability in practical applications, which is specifically manifested in the following aspects:

[0049] (1) S1: Ore calcination and crushing and screening

[0050] The ore is calcined at high temperature (e.g. 1300°C) to completely decompose the carbonate components in the ore, generating high-purity calcium oxide (CaO), which is then crushed and sieved through a screen to ensure that the CaO particles are uniform and small, providing a good foundation for subsequent digestion reactions.

[0051] (2) S2: Preparation of Ca(OH)2 suspension by digestion of CaO

[0052] Digestion at room temperature saves energy and is easy to operate. CaO reacts with water to generate Ca(OH)2, forming a uniform and stable suspension. The concentration of 0.5-1.5 mol / L ensures sufficient supply of hydroxide ions in subsequent reactions, while avoiding the problem of local oversaturation and excessive pH fluctuations in the solution that may be caused by excessive concentration.

[0053] (3) S3: Mixture of CaCl2 solution and sugar additive

[0054] As one of the calcium sources, CaCl2 has a concentration controlled within the range of 0.5 to 2 mol / L, aiming to form the main system of the carbonation reaction together with Ca(OH)2. Sugar additives (such as glucose, fructose, sucrose, and starch) serve as crystal form regulators. They form weak bonds with calcium ions through hydroxyl groups, adsorb on the surface of calcium carbonate, affect the crystal growth dynamics, and promote the formation of super-large cubes. Its concentration is set at 0.2% to 0.8% of the theoretical yield of calcium carbonate, and is precisely controlled to ensure that the crystal form can be effectively regulated without interfering with the main reaction.

[0055] (4) S4: pH adjustment and carbonization reaction

[0056] Place mixed solution A in a carbonization tower, and adjust the pH to the range of 8 to 11 by dripping Ca(OH)2 suspension. Each time the pH is dripped, the pH change must be strictly controlled within 0.02 to 0.05 until the target pH value is reached. The pH control strategy is used to optimize the formation conditions of calcium carbonate nuclei, and the dual control of crystal size and morphology is achieved by precisely controlling the supersaturation of the system. Slight adjustments to the pH value can significantly affect the nucleation rate and the number of nuclei, and is one of the core means of particle size control.

[0057] (5) S5: Carbonization reaction and product treatment

[0058] Under the condition of stirring speed of 200-600r / min, a CO2 mixed gas with a concentration of 5%-10% is introduced into the mixed liquid, and the flow rate is controlled at 0.5-1.2m 3 / h. By selecting the appropriate stirring speed, the gas and liquid are fully contacted, the CO2 absorption efficiency is improved, and the carbonation reaction is uniformly carried out. The precise control of CO2 concentration is directly related to the growth rate and structural integrity of calcium carbonate crystals. When the pH of the system drops to about 7, the reaction reaches the end point, and the ventilation is stopped. The product is then filtered to remove excess water and dried at a temperature of 95-105°C to obtain super-large cubic calcium carbonate with controllable particle size.

[0059] (6) Necessity and technical effect of optimizing process parameters

[0060] The present invention uses calcium chloride as the initial raw material of the reaction, uses a saccharide additive as a crystal form controller, controls the pH of the reaction system by calcium hydroxide, and then passes CO2 to obtain a large cubic calcium carbonate with a regular morphology. Wherein, due to the unique molecular structure of the saccharide crystal form controller, its hydroxyl group is easy to form an electrostatic effect with Ca, and can be effectively adsorbed on the surface of the calcium carbonate nucleus, affecting the kinetic process of calcium carbonate crystal growth, guiding the calcium carbonate molecules to arrange in a predetermined direction, thereby achieving accurate regulation of the morphology of calcium carbonate crystals; at the same time, using calcium hydroxide as a pH regulator, by adjusting the pH of the reaction system to control the supersaturation of the calcium carbonate solution after passing CO2, the formation of the number of calcium carbonate nuclei can be optimized, and when the pH is raised, the saturation of the calcium carbonate solution increases, the nucleation rate is accelerated, the number of nucleations increases, and it is easy to form calcium carbonate crystals with a smaller particle size, therefore, an effective means of controlling the crystal size by adjusting the pH, which provides a strong guarantee for the accurate control of the calcium carbonate particle size.

[0061] Through the fine regulation of various parameters in each step of the present invention, the morphology of calcium carbonate crystals can be accurately controlled, and the purity, particle size uniformity and mechanical properties of the product can be improved. After the introduction of sugar additives and the adjustment of pH, it is conducive to the stable formation of a large cubic structure, while optimizing the number of calcium carbonate nuclei formed, and achieving accurate control of the particle size of calcium carbonate. The optimization of process parameters plays a role in reducing costs and increasing efficiency, and also provides solid technical support for the application of calcium carbonate materials in high-end fields, showing the huge potential and broad prospects of this preparation method.

[0062] In order to make the disclosure of the present invention more complete, it is described below through more specific embodiments.

[0063] Example 1

[0064] A method for preparing super-large cubic calcium carbonate with controllable particle size comprises the following steps:

[0065] Prepare 8 kg of 1 mol / L CaCl2 solution, add 0.5% sucrose (theoretical calcium carbonate mass) into the CaCl2 solution to obtain a mixed solution A.

[0066] The mixed solution A was placed in a carbonization tower, and Ca(OH)2 was used to adjust the pH of the mixed solution to 8.

[0067] Start stirring and introduce CO2 mixed gas into the above mixed solution while monitoring the pH of the carbonation reaction process. Stop the reaction when the pH drops to about 7.

[0068] The product is then filtered and dried at 105°C to obtain large cubic calcium carbonate.

[0069] SEM test results are as follows Figure 1As shown, the calcium carbonate obtained according to the method of the present invention has a cubic morphology, a uniform size of about 30 μm, and good dispersibility.

[0070] Example 2

[0071] A method for preparing super-large cubic calcium carbonate with controllable particle size comprises the following steps:

[0072] Prepare 8 kg of 1 mol / L CaCl2 solution, add 0.5% sucrose (theoretical calcium carbonate mass) into the CaCl2 solution to obtain a mixed solution A.

[0073] The mixed solution A was placed in a carbonization tower, and the pH of the mixed solution was adjusted to 9 using Ca(OH)2.

[0074] Start stirring and introduce CO2 mixed gas into the above mixed solution while monitoring the pH of the carbonation reaction process. Stop the reaction when the pH drops to about 7.

[0075] The product is then filtered and dried at 105°C to obtain large cubic calcium carbonate.

[0076] SEM test results are as follows Figure 2 As shown, the calcium carbonate obtained according to the method of the present invention has a cubic morphology. Compared with Example 1, the size of most calcium carbonate particles is reduced, mostly around 20 μm, and has good dispersibility.

[0077] Example 3

[0078] A method for preparing super-large cubic calcium carbonate with controllable particle size comprises the following steps:

[0079] Prepare 8 kg of 1 mol / L CaCl2 solution, add 0.5% sucrose (theoretical calcium carbonate mass) into the CaCl2 solution to obtain a mixed solution A.

[0080] The mixed solution A was placed in a carbonization tower, and the pH of the mixed solution was adjusted to 10 using Ca(OH)2.

[0081] Start stirring and introduce CO2 mixed gas into the above mixed solution while monitoring the pH of the carbonation reaction process. Stop the reaction when the pH drops to about 7.

[0082] The product is then filtered and dried at 105°C to obtain large cubic calcium carbonate.

[0083] SEM test results are as follows Figure 3 As shown, the calcium carbonate obtained according to the method of the present invention has a cubic morphology, a uniform size of about 10 μm, and good dispersibility.

[0084] Example 4

[0085] A method for preparing super-large cubic calcium carbonate with controllable particle size comprises the following steps:

[0086] Prepare 8 kg of 1 mol / L CaCl2 solution, add 0.5% sucrose (theoretical calcium carbonate mass) into the CaCl2 solution to obtain a mixed solution A.

[0087] The mixed solution A was placed in a carbonization tower, and the pH of the mixed solution was adjusted to 11 using Ca(OH)2.

[0088] Start stirring and introduce CO2 mixed gas into the above mixed solution while monitoring the pH of the carbonation reaction process. Stop the reaction when the pH drops to about 7.

[0089] The product is then filtered and dried at 105°C to obtain large cubic calcium carbonate.

[0090] SEM test results are as follows Figure 4 As shown, the calcium carbonate obtained according to the method of the present invention has a cubic shape and a uniform size of about 0.8 μm, but is agglomerated relative to Examples 1 to 3.

[0091] Comparative Example 1

[0092] A method for preparing large cubic calcium carbonate comprises the following steps:

[0093] Prepare 8kg of 1mol / L CaCl2 solution.

[0094] The CaCl2 solution was placed in a carbonization tower, and the pH of the mixed solution was adjusted to 8 using Ca(OH)2.

[0095] Start stirring and introduce CO2 mixed gas into the above mixed solution while monitoring the pH of the carbonation reaction process. Stop the reaction when the pH drops to about 7.

[0096] The product is then filtered and dried at 105°C to obtain large cubic calcium carbonate.

[0097] SEM test results are as follows Figure 5 As shown, according to the method of the present invention, without adding sucrose, the calcium carbonate obtained has an uneven morphology, which is a mixture of cubic and loose flakes.

[0098] The embodiments described above are only descriptions of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, improvements and adjustments made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the scope of protection determined by the claims of the present invention.

Claims

1. A method for preparing super-large cubic calcium carbonate with controllable particle size, characterized in that: The steps include: (1) Calcinate the ore, crush and sieve it to obtain CaO for later use; (2) the above CaO digestion preparation Ca(OH)2 suspension; (3) preparing a CaCl2 solution, and adding the sugar additive into the CaCl2 solution to obtain a mixed solution A; (4) placing the mixed solution A in a carbonization tower and adjusting the pH with Ca(OH)2; (5) Start stirring and introduce CO2 mixed gas into the above mixed solution while monitoring the pH of the carbonation reaction process. When the pH drops to about 7, stop the reaction, filter the product and dry it to obtain large cubic calcium carbonate.

2. The method for preparing super-large cubic calcium carbonate with controllable particle size as claimed in claim 1, characterized in that: The ore calcination temperature in step (1) is 1100-1300°C.

3. The method for preparing super-large cubic calcium carbonate with controllable particle size as claimed in claim 1, characterized in that: The concentration of the Ca(OH)2 suspension in step (2) is 0.5 to 1.5 mol / L.

4. The method for preparing super-large cubic calcium carbonate with controllable particle size as claimed in claim 1, characterized in that: The CaCl2 concentration in step (3) is 0.5-2 mol / L, and the concentration of the sugar additive is 0.2%-0.8% of the theoretical yield of calcium carbonate.

5. The method for preparing super-large cubic calcium carbonate with controllable particle size as claimed in claim 1, characterized in that: The sugar additive in step (3) is one or more of glucose, fructose, sucrose and starch.

6. The method for preparing super-large cubic calcium carbonate with controllable particle size as claimed in claim 1, characterized in that: The pH value of step (4) is adjusted to 8-11, and the pH change should be controlled within 0.02-0.05 each time the solution is added until the set pH value is reached.

7. The method for preparing super-large cubic calcium carbonate with controllable particle size as claimed in claim 1, characterized in that: The stirring speed in step (5) is 200 to 600 r / min.

8. The method for preparing super-large cubic calcium carbonate with controllable particle size as claimed in claim 1, characterized in that: The concentration of the CO2 mixed gas in step (5) is 5% to 10%, and the flow rate of the mixed gas is 0.5 to 1.2 m 3 / h.

9. The method for preparing super-large cubic calcium carbonate with controllable particle size as claimed in claim 1, characterized in that: The drying temperature in step (5) is 95-105°C.

10. An ultra-large cubic calcium carbonate with controllable particle size prepared according to the method according to any one of claims 1 to 9.

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