Multifunctional nitrogen-rich calcium carbonate nano material and preparation method thereof
By using a non-classical solid-liquid reaction crystallization method, multifunctional nitrogen-rich calcium carbonate nanomaterials were prepared from natural limestone or carbide slag and carbon nitride nanofibers. This solved the problem of hybrid composite structure and morphology control in the preparation process of nano-calcium carbonate materials, and achieved efficient carbon dioxide capture and thermochemical energy storage.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHENYANG UNIVERSITY OF TECHNOLOGY
- Filing Date
- 2026-01-27
- Publication Date
- 2026-05-19
AI Technical Summary
Existing nano-calcium carbonate materials suffer from problems such as lack of hybrid composite structures, difficulty in controlling the ordered assembly morphology at the mesoscale, difficulty in introducing active heteroatoms, high raw material costs, and easy agglomeration of nanomaterials during preparation.
A non-classical solid-liquid reaction crystallization method was adopted, using natural limestone or high-calcium carbide slag as the calcium source, and carbon nitride nanofibers as the solid carbon source and functional modifier, to prepare multifunctional nitrogen-rich calcium carbonate nanomaterials composed of calcium carbonate mesocrystalline particles and carbon nitride nanofibers. This method achieves precise control of nanocrystal size, crystal form and morphology, and regulation of surface properties.
Multifunctional nitrogen-rich calcium carbonate nanomaterials with high specific surface area, hierarchical structure and abundant interfacial micropores were prepared for high carbon dioxide capture and high thermochemical energy storage, realizing fine structural control of calcium-based inorganic materials and polymer composites, breaking through the traditional application boundaries.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of inorganic nanomaterial preparation technology, and relates to a multifunctional nitrogen-rich calcium carbonate nanomaterial and its preparation method. Background Technology
[0002] Calcium carbonate, as an important inorganic chemical product, is widely used in plastics, rubber, coatings, papermaking, pharmaceuticals, food, and other fields. With the development of high-tech industries, higher performance requirements are being placed on calcium carbonate materials. Nanocrystalline calcium carbonate, due to its small particle size (≤100 nm), large specific surface area, high surface activity, and excellent reinforcing and toughening properties, has become an upgraded alternative to traditional calcium carbonate and a key material for improving the quality and added value of downstream products. Current research on the preparation of nanocrystalline calcium carbonate focuses on achieving precise control of the product's morphology, size, and composition through process innovation, while also considering efficiency and environmental protection. Current research has shifted from simply pursuing nanoscale formation to "customized" synthesis for specific applications, multifunctional applications, and green manufacturing.
[0003] Traditional carbonation utilizes the reaction of CO2 with lime slurry (gas-liquid), offering low raw material costs and enabling large-scale industrial production. It is widely used to prepare precipitated calcium carbonate as a functional filler in industries such as plastics and rubber. Current research on this method focuses primarily on the low gas-liquid mass transfer efficiency, exploring hypergravity-micro-interface coupling and designing novel reactors. Hypergravity-micro-interface coupling technology combines a hypergravity field with micro-interface technology, breaking carbon dioxide bubbles down to the micrometer scale, significantly increasing the reaction area and reducing carbonation time from 1-2 hours to 15-20 minutes. It can also produce uniform cubic, rod-shaped, and spherical nano-calcium carbonate. The Qingdao Institute of Energy, Chinese Academy of Sciences, has developed a novel multi-process coupled airlift reactor that can directly utilize phosphogypsum solid waste and CO2 to produce nano-calcium carbonate and ammonium sulfate fertilizer in a one-step process under ambient temperature and pressure, facilitating the co-resource utilization of waste. Although the carbonization method uses inexpensive raw materials, the various crystal form control agents (mostly organic acids or phosphates) added to achieve nano-sized particles and desired morphology may increase the difficulty and cost of post-processing and bring potential environmental pressures. At the same time, how to accurately and stably control the particle size distribution, crystal form, and morphology of the product (such as rod-shaped crystals with a specific aspect ratio or uniform hollow structures) remains a major challenge.
[0004] Another important method for preparing calcium carbonate nanomaterials is the metathesis method. This method utilizes the reaction of soluble calcium salts with carbonates (liquid-liquid). It has shown advantages in laboratory settings and in the production of specific high-value-added products, producing products with high purity and easily controllable morphology. It can be used to produce high-value-added products such as pharmaceuticals, high-end coatings, and special fillers. Reports indicate that the metathesis method can already achieve the industrial-scale production of hollow calcium carbonate particles. By controlling the reactant concentration and temperature, and using magnesium hydroxide / barium hydroxide as crystal form control agents, hollow calcium carbonate particles with controllable average particle size and a specific surface area of 10⁻²⁵ m² can be successfully prepared. 2 / g. However, the metathesis method has high raw material costs and complex post-processing. The separation and resource utilization of by-products (such as ammonium chloride and sodium sulfate) are also significant issues. If closed-loop or high-value utilization cannot be achieved, large amounts of wastewater and waste salt will be generated, greatly diminishing both economic and environmental benefits.
[0005] Furthermore, existing nano-calcium carbonate products lack sufficient integration with functional applications. Research on the precise "in-situ" or "post-processing" control of key application properties such as the surface properties (hydrophilic / oleophilic, surface energy), interfacial compatibility with polymer matrices, and heteroatom coordination structure of nano-calcium carbonate is still insufficient. This results in the synthesized materials failing to fully realize their theoretical reinforcement, toughening, or functionalization effects in practical composite systems. In summary, developing a method for preparing multifunctional nanocrystalline calcium carbonate hybrid materials based on low-cost natural limestone calcium sources or solid waste calcium sources (such as carbide slag) that can precisely and stably control the size, crystal form, and morphology of nanocrystals, and achieve heteroatom control and nanocrystal surface modification, is of great significance and practical application value. Summary of the Invention
[0006] Purpose of the invention To address the problems of lack of hybrid composite structures, difficulty in controlling the ordered assembly morphology at the mesoscale, difficulty in introducing active heteroatoms, high raw material costs, and easy agglomeration of nanomaterials in the preparation of calcium carbonate nanomaterials using existing technologies, this invention proposes a multifunctional nitrogen-rich calcium carbonate nanomaterial and its preparation method that does not require the addition of morphology control agents, uses natural limestone and high-calcium carbide slag as calcium sources, and can simultaneously introduce functional modifiers (such as carbon-nitrogen polymers) and active heteroatoms during the synthesis process. Technical solution
[0007] A multifunctional nitrogen-rich calcium carbonate nanomaterial is a hybrid nanomaterial composed of calcium carbonate mesocrystalline particles and carbon nitride nanofibers. The calcium carbonate mesocrystalline particles in the hybrid nanomaterial are formed by non-classical crystal growth through solid-liquid reaction using carbon nitride nanofibers as a solid carbon source. The carbon and nitrogen functional groups on the surface of the carbon nitride nanofibers induce the orientation and assembly of mesocrystalline particles at the mesoscale to form superstructured calcium carbonate mesocrystalline particles. Furthermore, when carbon nitride is used as a carbon source for solid-liquid reaction non-classical crystal growth, nitrogen atoms are simultaneously introduced into the calcium carbonate crystals, forming nitrogen-rich superstructured calcium carbonate mesocrystalline particles.
[0008] Furthermore, the calcium carbonate mesocrystalline particles are uniformly dispersed in a three-dimensional network of carbon nitride nanofibers. The carbon nitride nanofibers have a diameter of 1-10 nm and a length of 500 nm-1 mm. The carbon nitride nanofibers interweave to form a network with a pore size of 20-200 nm. The individual calcium carbonate mesocrystalline particles are supported by the carbon nitride nanofibers, thus preventing the aggregation of nanomaterials and forming an ordered arrangement of nanostructural units with a specific surface area of 42-55 m². 2 / g of highly active and highly dispersed multifunctional nitrogen-rich calcium carbonate nanomaterials.
[0009] Furthermore, the calcium carbonate mesocrystalline particles are pod-shaped, with a major axis of 0.3-1 mm, a diameter of 200-500 nm at the widest point in the middle, and narrowing to 20-50 nm at both ends. Each calcium carbonate mesocrystalline particle is assembled in an orderly manner from oblique quadrangular prism nanocrystals as basic structural units, exhibiting hierarchical structural characteristics and abundant internal interfaces. The oblique quadrangular prism nanocrystals are composed of nitrogen-containing calcite-type calcium carbonate, with conjugated networks of triazine or triazine-homogeneous triazine rings attached to the interfaces between adjacent grains. Adjacent oblique quadrangular prism nanocrystals have the same orientation and are regularly arranged along directions parallel to the edges, assembling into hybrid nanostructures containing carbon and nitrogen heterocycles, i.e., nitrogen-rich mesocrystalline superstructure particles.
[0010] Furthermore, the oblique quadrangular prism nanocrystals have an edge length of 5-80 nm and an included angle between adjacent side edges ranging from 30° to 90°. The directional stacking of the oblique quadrangular prism nanocrystals introduces abundant interfacial micropores and mesopores into the calcium carbonate mesocrystalline particles. The size of the interfacial micropores between adjacent oblique quadrangular prism nanocrystals is 0.5-1.8 nm, and the size of the mesopores inside the mesocrystalline particles is 8-60 nm.
[0011] A method for preparing the multifunctional nitrogen-rich calcium carbonate nanomaterial as described above belongs to the solid-liquid reaction non-classical crystallization method, and the steps are as follows: Step 1: Prepare a urea aqueous solution A with a concentration of 90~100g / L and a melamine aqueous solution B with a concentration of 70~80g / L. Mix the solutions A and B at a volume ratio of 1:(0.9~1.1) and stir. Adjust the pH of the mixed solution to 8-10 to obtain an alkaline mixed solution. Step 2: Pour the alkaline mixed solution obtained in Step 1 into a liquid container. Stir the liquid container evenly under water bath conditions, and then perform hydrothermal treatment in a hydrothermal reactor. Wash the precipitate obtained after hydrothermal treatment, dry it and let it cool naturally to room temperature. Then put it into a muffle furnace and heat it from room temperature to 480-550℃ for 3-6 hours to obtain carbon nitride nanofiber precursor. Step 3: Calcining limestone or carbide slag, and then placing the solid product obtained from calcination into a 30-50% ethanol solution under stirring conditions, and continuously stirring to form a suspension C with a concentration of 1.0-1.5 g / L; Step 4: Introduce carbon nitride nanofiber precursor into suspension C, and ultrasonically disperse it at -5~-10℃ for 15-25 min. The mass ratio between the carbon nitride precursor and the solid product obtained by calcination is (0.5:1)~(1:1) to obtain black suspension D. Step 5: Place the black suspension D into a hydrothermal reactor and keep it at a constant temperature. After centrifugation, a grayish-white solid product is obtained. After drying, a multifunctional nitrogen-rich calcium carbonate nanomaterial composed of calcium carbonate mesocrystalline particles and carbon nitride nanofibers is obtained.
[0012] Furthermore, in step one, the pH value of the alkaline mixed solution is adjusted by adding sodium hydroxide solution dropwise. The concentration of the sodium hydroxide solution is 0.1-0.2 mol / L, the dropping rate is 10-20 drops / min, and the droplet volume is 30-40 drops / mL.
[0013] Furthermore, in step two, the water bath temperature is 90-110℃, the stirring speed under water bath conditions is 200-300 rpm, and the stirring time is 30-90 min; the hydrothermal temperature is 160-200℃, and the hydrothermal time is 18-30 h.
[0014] Furthermore, in step two, the filling ratio of the hydrothermal reactor is 60-80%, the precipitate obtained after hydrothermal treatment is washed with excess deionized water at least three times, and dried at a temperature of 60-90°C; the heating rate of the muffle furnace is 2-5°C / min.
[0015] Furthermore, in step three, limestone or carbide slag is calcined at 860-900℃ for 20-40 minutes; continuous stirring is carried out at 30-45℃ and a stirring speed of 400-800 rpm for 30-80 minutes.
[0016] Furthermore, in step five, the hydrothermal reactor is filled with 60-80% of its contents and kept at 140-200℃ for 3-10 hours; drying is carried out at 80-100℃ for 5-8 hours.
[0017] Advantages and effects This invention utilizes a simple hydrothermal method, without the need for morphology modifiers, to prepare nitrogen-rich calcium carbonate nanomaterials through a one-step solid-liquid reaction and non-classical crystallization process. The multifunctional nitrogen-rich calcium carbonate nanomaterials are hybrid nanomaterials composed of calcium carbonate mesocrystalline particles and carbon nitride nanofibers. These multifunctional nitrogen-rich calcium carbonate nanomaterials allow for simultaneous and precise control of the synthesis of ordered hybrid structure materials and particle surface properties. The calcium carbonate mesocrystalline particles are orderly assembled from oblique quadrangular prism-shaped nanocrystals and are rich in triazine or triazine-homogeneous triazine ring (carbon-nitrogen heterocyclic) conjugated networks, exhibiting hierarchical and hybrid structural characteristics. Their internal pore structure is more developed, possessing several composite microstructures and more active sites, thus enhancing application performance. This patented multifunctional nitrogen-rich calcium carbonate nanomaterial possesses specific exposed crystal faces and an ordered assembly structure, enabling the preparation of multifunctional calcium carbonate hybrid materials doped with heteroatoms (Ni, Mg, Mn, Fe, Co, Al, etc., or N atoms), resulting in calcium-based multifunctional nanomaterials with high carbon dioxide capture efficiency, high cycling stability, and high thermochemical energy storage efficiency. Furthermore, the method for preparing nitrogen-rich superstructured calcium carbonate mesocrystalline particles provided by this invention facilitates in-situ composite and fine-structure control of calcium-based inorganic materials and functional polymers. It is an innovative method that deeply couples the production of high-value calcium carbonate nanomaterials with multifunctional applications such as mineralized solid waste and CO2 capture, and is of significant value in breaking through the traditional application boundaries of calcium carbonate nanomaterials and the cost limitations of calcium sources. In addition, based on the principle of solid-liquid non-classical crystallization, guiding inorganic nanounits to undergo mesoscopic assembly in polymer templates or microenvironments allows for the design of a series of high-performance organic-inorganic hybrid materials with well-defined structures and interface integration. Attached Figure Description
[0018] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The scope of protection of the present invention is not limited to the descriptions below.
[0019] Figure 1 The image shows a scanning electron microscope (SEM) image of the multifunctional nitrogen-rich calcium carbonate nanomaterials prepared in Example 1. Figure 2 This is a transmission electron microscope (TEM) image of the multifunctional nitrogen-rich calcium carbonate nanomaterial prepared in Example 2; Figure 3 This is a pore size distribution diagram of the multifunctional nitrogen-rich calcium carbonate nanomaterial prepared in Example 2; Figure 4The image shows the X-ray diffraction (XRD) pattern of the multifunctional nitrogen-rich calcium carbonate nanomaterial prepared in Example 2. Figure 5 The image shows a transmission electron microscope (TEM) image of calcium carbonate mesocrystalline particles, which are formed by the orderly assembly of oblique quadrangular prism nanocrystals as basic structural units in the multifunctional nitrogen-rich calcium carbonate nanomaterial prepared in Example 2. Figure 6 The CO2 capture efficiency and cycle performance of the multifunctional nitrogen-rich calcium carbonate nanomaterial-derived absorbent prepared in Example 2; Figure 7 The thermochemical energy storage efficiency and cycle stability of the multifunctional nitrogen-rich calcium carbonate nanomaterial-derived absorbent prepared in Example 2; Figure 8 This is a scanning electron microscope (SEM) image of the multifunctional nitrogen-rich calcium carbonate nanomaterials prepared in Example 3; Figure 9 This is a scanning electron microscope (SEM) image of the multifunctional nitrogen-rich calcium carbonate nanomaterial prepared in Example 4. Detailed Implementation
[0020] The urea, melamine, and sodium hydroxide used in the embodiments of this invention are commercially available analytical grade reagents.
[0021] In this embodiment of the invention, microstructure detection was performed using a Hitachi SU8010 field emission scanning electron microscope. Hybrid structure analysis was performed using a FEI Talos F200X G2 transmission electron microscope. Pore size analysis was performed using a V-sorb 2800P surface area analyzer. Phase composition analysis was performed using a Shimadzu XRD-7000S diffractometer.
[0022] A multifunctional nitrogen-rich calcium carbonate nanomaterial is a hybrid nanomaterial composed of calcium carbonate mesocrystalline particles and carbon nitride nanofibers. The calcium carbonate mesocrystalline particles in the hybrid nanomaterial are formed by solid-liquid reaction non-classical crystallization growth (nanocrystalline grain-mediated directional attachment crystallization growth) using carbon nitride nanofibers as a solid carbon source. The carbon and nitrogen functional groups on the surface of the carbon nitride nanofibers induce the orientation and assembly of mesoscale (1-100nm) nanocrystals to form superstructure (an ordered structure in which nanocrystals are ordered and oriented to achieve uniform stacking at the mesoscale) calcium carbonate mesocrystalline particles. Furthermore, when carbon nitride is used as a carbon source for solid-liquid reaction non-classical crystallization, nitrogen atoms are simultaneously introduced into the calcium carbonate crystals, forming nitrogen-rich superstructure calcium carbonate mesocrystalline particles. The calcium carbonate mesocrystalline particles are uniformly dispersed in a three-dimensional network of carbon nitride nanofibers. The carbon nitride nanofibers have a diameter of 1-10 nm and a length of 500 nm-1 mm. The interwoven carbon nitride nanofibers form a network with pore sizes of 20-200 nm. The individual calcium carbonate mesocrystalline particles are separated and supported by the carbon nitride nanofibers, thus preventing the aggregation of nanomaterials. This results in an ordered arrangement of nanostructural units with a specific surface area of 42-55 m². 2 / g of highly active and highly dispersed multifunctional nitrogen-rich calcium carbonate nanomaterials.
[0023] The calcium carbonate mesocrystalline particles are pod-shaped, with a major axis of 0.3-1 mm, a diameter of 200-500 nm at the widest point in the middle, and narrowing to 20-50 nm at both ends. Each calcium carbonate mesocrystalline particle is assembled in an orderly manner from oblique quadrangular prism nanocrystals as basic structural units, exhibiting hierarchical structural characteristics and abundant internal interfaces. The edge length of the oblique quadrangular prism nanocrystals is 5-80 nm, and the included angle between adjacent side edges ranges from 30° to 90°. The directional stacking of the oblique quadrangular prism nanocrystals introduces abundant interfacial micropores and mesopores into the calcium carbonate mesocrystalline particles. The size of the interfacial micropores between adjacent oblique quadrangular prism nanocrystals is 0.5-1.8 nm, and the size of the mesopores inside the mesocrystalline particles is 8-60 nm. The oblique quadrangular prism nanocrystals are composed of nitrogen-containing calcite-type calcium carbonate. The interfaces between adjacent grains are attached with a conjugated network of triazine or triazine-homogeneous triazine rings. Adjacent oblique quadrangular prism grains have the same orientation and are regularly arranged in a direction parallel to the edges, assembling into a hybrid nanostructure containing carbon and nitrogen heterocycles, namely nitrogen-rich mesocrystalline superstructure particles.
[0024] A method for preparing multifunctional nitrogen-rich calcium carbonate nanomaterials, belonging to the solid-liquid reaction non-classical crystallization method (nanocrystalline grain-mediated directional adhesion crystallization growth), includes the following steps: Step 1: Prepare a urea aqueous solution A with a concentration of 90~100g / L and a melamine aqueous solution B with a concentration of 70~80g / L. Mix solutions A and B at a volume ratio of 1:(0.9~1.1) and stir. Add sodium hydroxide solution dropwise to adjust the pH of the mixed solution to 8-10. The concentration of sodium hydroxide solution is 0.1-0.2mol / L, the dropping rate is 10~20 drops / min, and the droplet volume is 30~40 drops / mL to obtain an alkaline mixed solution. Step Two: Pour the alkaline mixed solution obtained in Step One into a liquid container, preferably a glass container. Stir the liquid in a water bath at a temperature of 90-110℃ for 200-300 rpm for 30-90 minutes. Then, perform hydrothermal treatment in a hydrothermal reactor at a filling ratio of 60-80% (the filling ratio refers to the percentage of the reaction liquid volume to the total reactor volume; different filling ratios at the same temperature will affect the pressure inside the hydrothermal reactor, and excessive or insufficient pressure will affect the reaction quality of the alkaline mixed solution). The hydrothermal temperature is 160-200℃ for 18-30 hours. After hydrothermal treatment, wash the precipitate with excess deionized water at least three times, dry it at 60-90℃, and allow it to cool naturally to room temperature. Next, place it in a muffle furnace and heat it from room temperature to 480-550℃ at a heating rate of 2-5. Calcination at ℃ / min for 3-6 h yields carbon nitride nanofiber precursor; Step 3: Calcine limestone or carbide slag at 860-900℃ for 20-40 minutes. The solid product obtained from calcination is placed in a 30-50% ethanol solution under stirring conditions and continuously stirred to form a suspension C with a concentration of 1.0-1.5 g / L. The continuous stirring is carried out at 30-45℃ and a stirring speed of 400-800 rpm for 30-80 minutes. Step 4: Introduce carbon nitride nanofiber precursor into suspension C, and ultrasonically disperse it at -5~-10℃ for 15-25 min. The mass ratio between the carbon nitride precursor and the solid product obtained by calcination is (0.5:1)~(1:1) to obtain black suspension D. Step 5: Place the black suspension D into a hydrothermal reactor with a filling ratio of 60-80%, and keep it at 140-200℃ for 3-10 hours. After centrifugation, a grayish-white solid product is obtained. Dry it at 80-100℃ for 5-8 hours. After drying, a multifunctional nitrogen-rich calcium carbonate nanomaterial composed of calcium carbonate mesocrystalline particles and carbon nitride nanofibers is obtained.
[0025] The present invention will be described in detail below with reference to the embodiments. Example 1
[0026] The preparation method of multifunctional nitrogen-rich calcium carbonate nanomaterials belongs to the solid-liquid reaction non-classical crystallization method, and includes the following steps: Step 1: Prepare a urea aqueous solution A with a concentration of 90 g / L and a melamine aqueous solution B with a concentration of 70 g / L. Mix solutions A and B at a volume ratio of 1:0.9 and stir. Add sodium hydroxide solution with a concentration of 0.1 mol / L at a dropping rate of 20 drops / min and a drop volume of 30 drops / mL. Adjust the pH of the mixed solution to 8 to obtain an alkaline mixed solution. Step 2: The alkaline mixed solution obtained in Step 1 was stirred in a water bath at 90℃ for 90 min, and then subjected to hydrothermal treatment at 160℃ for 30 h with a filling ratio of 60%. The precipitate obtained after hydrothermal treatment was washed three times, dried at 60℃, and then placed in a muffle furnace and heated to 480℃ at a heating rate of 2℃ / min for 6 h to obtain carbon nitride nanofiber precursor. Step 3: Calcine limestone or carbide slag at 860℃ for 40 min. The solid product obtained from calcination is placed in a 30% ethanol solution under stirring and stirred continuously at 800 rpm for 30 min at 30℃ to form a suspension C with a concentration of 1.0 g / L. Step 4: Introduce carbon nitride nanofiber precursor into suspension C, and ultrasonically disperse at -5℃ for 25 min. The mass ratio between carbon nitride precursor and solid product obtained by calcination is 0.5:1, resulting in black suspension D. Step 5: Place the black suspension D into a hydrothermal reactor with a filling ratio of 60%, keep it at 140℃ for 10 hours, and centrifuge to obtain a grayish-white solid product. Dry it at 80℃ for 8 hours to obtain a multifunctional hybrid nanomaterial composed of nitrogen-rich superstructured calcium carbonate mesocrystalline particles and carbon nitride nanofibers.
[0027] Scanning electron microscope (SEM) images of the multifunctional nitrogen-rich calcium carbonate nanomaterials prepared in Example 1 are shown below. Figure 1As shown, calcium carbonate mesocrystalline particles are dispersed within and on the surface of an interwoven network of carbon nitride nanofibers. The pod-like calcium carbonate mesocrystalline particles exhibit a major axis of 0.3-1.0 mm, a maximum diameter of 200-500 nm at the center, and narrow to approximately 20-50 nm at both ends. Each calcium carbonate mesocrystalline particle is composed of ordered, obliquely squared prism-shaped nanocrystals, exhibiting hierarchical structural features and abundant internal interfaces. Adjacent obliquely squared prism-shaped nanocrystals have the same orientation and are regularly arranged along directions parallel to their edges. The edge length of the obliquely squared prism-shaped nanocrystals is 5-50 nm, and the included angle between adjacent side edges ranges from 30° to 90°. The carbon nitride nanofibers surrounding the mesocrystalline particles have a diameter of 1-10 nm and a length of 500 nm-1 mm, forming an interwoven network with pore sizes of 20-200 nm. The primary calcium carbonate mesocrystalline particles reveal a hybrid structure characterized by conjugated networks of triazine or triazine-homogeneous triazine rings attached to the interfaces between adjacent grains. Example 2
[0028] Step 1: Prepare a urea aqueous solution A with a concentration of 93 g / L and a melamine aqueous solution B with a concentration of 73 g / L. Mix solutions A and B at a volume ratio of 1:0.95 and stir. Add sodium hydroxide solution with a concentration of 0.2 mol / L at a dropping rate of 10 drops / min and a drop volume of 40 drops / mL. Adjust the pH of the mixed solution to 8.5 to obtain an alkaline mixed solution. Step 2: The alkaline mixed solution obtained in Step 1 was stirred in a water bath at 95℃ for 60 min, and then subjected to hydrothermal treatment at 180℃ for 24 h with a filling ratio of 70%. The precipitate obtained after hydrothermal treatment was washed four times, dried at 70℃, and then placed in a muffle furnace and heated to 500℃ at a heating rate of 3℃ / min for 5 h to obtain carbon nitride nanofiber precursor. Step 3: Calcine limestone or carbide slag at 880℃ for 30 min. The solid product obtained from calcination is placed in a 40% ethanol solution under stirring and stirred continuously at 35℃ and 600 rpm for 60 min to form a suspension C with a concentration of 1.2 g / L. Step 4: Introduce carbon nitride nanofiber precursor into suspension C, and ultrasonically disperse at -8℃ for 20 min. The mass ratio between carbon nitride precursor and solid product obtained by calcination is 0.6:1, resulting in black suspension D. Step 5: Place the black suspension D into a hydrothermal reactor with a filling ratio of 70%, keep it at 160℃ for 8 hours, and centrifuge to obtain a grayish-white solid product. Dry it at 90℃ for 6 hours to obtain a multifunctional hybrid nanomaterial composed of nitrogen-rich superstructured calcium carbonate mesocrystalline particles and carbon nitride nanofibers.
[0029] Transmission electron microscopy (TEM) images of the prepared multifunctional nitrogen-rich calcium carbonate nanomaterials are as follows: Figure 2As shown. By Figure 2 It can be observed that a large number of bean-shaped calcium carbonate mesocrystalline particles, composed of orderly assembled oblique quadrangular prism-shaped nanocrystals, are uniformly distributed within an interwoven network of carbon nitride filaments, resulting in a highly uniform and dispersed hybrid structure. The long axis of these bean-shaped calcium carbonate mesocrystalline particles is 0.3-1.0 mm, with a maximum (midpoint) diameter of 200-400 nm, narrowing to approximately 20 nm at both ends. The individual calcium carbonate mesocrystalline particles are separated and supported by carbon nitride nanofibers, preventing the aggregation of nanomaterials and forming an ordered arrangement of nanostructural units with a specific surface area of 52.3 m². 2 / g ( Figure 3 Highly active, highly dispersed, multifunctional nitrogen-rich calcium carbonate nanomaterials. The pore size distribution characteristics of these multifunctional nitrogen-rich calcium carbonate nanomaterials are as follows: Figure 3 As shown, it simultaneously possesses abundant micropores (0.5-1.8 nm), mesopores (8-60 nm), and macropores (80-180 nm).
[0030] Figure 4 The X-ray diffraction (XRD) spectra of the prepared multifunctional nitrogen-rich calcium carbonate nanomaterials are obtained from... Figure 4 It can be seen that the main composition of the multifunctional nitrogen-rich calcium carbonate nanomaterial is calcite-type calcium carbonate (about 80.54 wt.%), containing a small amount of calcium hydroxide. The diffraction peak of the (104) crystal plane of calcium carbonate is significantly shifted to the left, indicating that in the non-classical crystallization process of solid-liquid reaction with carbon nitride as carbon source, active nitrogen heteroatoms are simultaneously introduced into the calcium carbonate crystal, providing more active sites and thus improving the multifunctional application performance.
[0031] The prepared multifunctional nitrogen-rich calcium carbonate nanomaterials, consisting of calcium carbonate mesocrystalline particles assembled in an orderly manner from oblique quadrangular prism nanocrystals as basic structural units, are shown in the transmission electron microscope image below. Figure 5 As shown. By Figure 5 It can be clearly observed that the calcium carbonate mesocrystalline particles are composed of orderly assembled oblique quadrangular prism nanocrystals. Adjacent oblique quadrangular prism nanocrystals have the same orientation and are regularly arranged in a direction parallel to the edges, assembling into a hybrid nanostructure containing carbon and nitrogen heterocycles, that is, forming calcium carbonate mesocrystalline particles with nitrogen-rich superstructures. Figure 5This study visually confirms that during the solid-liquid reaction crystallization process using carbon nitride as the carbon source, a non-classical crystallization phenomenon occurred, characterized by the ordered arrangement and orientational correlation of oblique quadrangular prism nanocrystals as nano-units. This indicates that the solid-liquid reaction crystallization process using carbon nitride as the nitrogen-carbon source is a nanocrystal-mediated directional attachment crystallization growth, resulting in a uniformly stacked ordered structure (calcium carbonate mesocrystalline particles) at a mesoscopic scale of 1-100 nm. The oblique quadrangular prism nanocrystals in the figure have edge lengths of 10-50 nm and included angles between adjacent edges ranging from 40° to 80°. Furthermore, the directional stacking of the oblique quadrangular prism nanocrystals introduces abundant interfacial micropores and mesopores into the nitrogen-rich calcium carbonate mesocrystalline particles. The interfacial micropore size between adjacent oblique quadrangular prism nanocrystals is 0.5-1.8 nm, and the mesopore size within the mesocrystalline particles is 8-60 nm.
[0032] The CO2 capture efficiency, thermochemical energy storage density, and cycling performance of multifunctional nitrogen-rich calcium carbonate nanomaterial-derived absorbents are as follows: Figure 6 , Figure 7 As shown. By Figure 6 It can be seen that the prepared multifunctional nitrogen-rich calcium carbonate nanomaterial-derived absorbent possesses high carbon dioxide capture activity and cycling stability. Its CO2 capture efficiency reaches 0.692 g-CO2 / g-CaO after two cycles, and its capture capacity remains above 80% of its initial capture capacity after 15 cycles. Figure 7 It can be observed that the initial thermochemical energy storage density of the prepared multifunctional nitrogen-rich calcium carbonate nanomaterial-derived absorbent is 2551.1 kJ / kg, and the energy storage density remains around 2117.5 kJ / kg after 15 cycles. These results demonstrate that the multifunctional nitrogen-rich calcium carbonate nanomaterial and its preparation method of this invention can yield calcium-based functionalized nanomaterials with high carbon dioxide capture efficiency, high cycling stability, and high thermochemical energy storage efficiency. Example 3
[0033] Step 1: Prepare a urea aqueous solution A with a concentration of 97 g / L and a melamine aqueous solution B with a concentration of 77 g / L. Mix solutions A and B at a volume ratio of 1:0.97 and stir. Add sodium hydroxide solution with a concentration of 0.15 mol / L at a dropping rate of 14 drops / min and a drop volume of 36 drops / mL. Adjust the pH of the mixed solution to 9 to obtain an alkaline mixed solution. Step 2: The alkaline mixed solution obtained in Step 1 was stirred in a water bath at 100℃ for 40 min, and then subjected to hydrothermal treatment at 190℃ for 21 h with a filling ratio of 75%. The precipitate obtained after hydrothermal treatment was washed three times, dried at 80℃, and then placed in a muffle furnace and heated to 520℃ at a heating rate of 4℃ / min for 4 h to obtain carbon nitride nanofiber precursor. Step 3: Calcine limestone or carbide slag at 890℃ for 25 minutes. The solid product obtained from calcination is placed in a 45% ethanol solution under stirring and stirred continuously at 500 rpm at 40℃ for 35 minutes to form a suspension C with a concentration of 1.3 g / L. Step 4: Introduce carbon nitride nanofiber precursor into suspension C, and ultrasonically disperse it at -9℃ for 18 min. The mass ratio between the carbon nitride precursor and the solid product obtained by calcination is 0.8:1, resulting in black suspension D. Step 5: Place the black suspension D into a hydrothermal reactor with a filling ratio of 75%, keep it at 180℃ for 5 hours, and centrifuge to obtain a grayish-white solid product. Dry it at 100℃ for 5 hours to obtain a multifunctional hybrid nanomaterial composed of nitrogen-rich superstructured calcium carbonate mesocrystalline particles and carbon nitride nanofibers.
[0034] Scanning electron microscope (SEM) image of the prepared multifunctional nitrogen-rich calcium carbonate nanomaterials is shown below. Figure 8 As shown. By Figure 8 It is observed that the calcium carbonate mesocrystalline particles are pod-shaped and uniformly dispersed within a three-dimensional network of carbon nitride nanofibers. Some mesocrystalline particles are embedded within the carbon nitride nanofiber network, while others are exposed on its surface. Simultaneously, there is an intertwined and symbiotic relationship between the carbon nitride nanofibers and the calcium carbonate mesocrystalline particles, forming a hybrid structure. The long axis of the pod-shaped calcium carbonate mesocrystalline particles is 0.3-1.0 mm, with a maximum diameter (midpoint) of 200-500 nm, narrowing to approximately 20-50 nm at both ends. Each calcium carbonate mesocrystalline particle is composed of orderly assembled oblique quadrangular prism-shaped nanocrystals. Adjacent oblique quadrangular prism-shaped nanocrystals have the same orientation and are regularly arranged along directions parallel to their edges, assembling into a hybrid nanostructure containing carbon-nitrogen heterocycles. This indicates that the solid-liquid reaction crystallization process using carbon nitride as the nitrogen-carbon source is a nanocrystal-mediated directional attachment crystallization growth, belonging to non-classical crystallization. The length of the oblique quadrangular prism grains is 5-80 nm, and the included angle between adjacent side edges ranges from 30° to 90°. Example 4
[0035] Step 1: Prepare a urea aqueous solution A with a concentration of 100 g / L and a melamine aqueous solution B with a concentration of 80 g / L. Mix solutions A and B at a volume ratio of 1:1.1 and stir. Add sodium hydroxide solution with a concentration of 0.12 mol / L at a dropping rate of 18 drops / min and a drop volume of 36 drops / mL. Adjust the pH of the mixed solution to 10 to obtain an alkaline mixed solution. Step 2: The alkaline mixed solution obtained in Step 1 was stirred in a water bath at 110℃ for 30 min, and then subjected to hydrothermal treatment at 200℃ for 18 h with a filling ratio of 80%. The precipitate obtained after hydrothermal treatment was washed five times, dried at 90℃, and then placed in a muffle furnace and heated to 550℃ at a heating rate of 5℃ / min for 3 h to obtain carbon nitride nanofiber precursor. Step 3: Calcine limestone or carbide slag at 900℃ for 20 minutes. The solid product obtained from calcination is placed in a 50% ethanol solution under stirring and stirred continuously at 400 rpm for 80 minutes at 45℃ to form a suspension C with a concentration of 1.5 g / L. Step 4: Introduce carbon nitride nanofiber precursor into suspension C, and ultrasonically disperse it at -10℃ for 15 min. The mass ratio between the carbon nitride precursor and the solid product obtained by calcination is 1:1, resulting in black suspension D. Step 5: Place the black suspension D into a hydrothermal reactor with a filling ratio of 80%, keep it at 200℃ for 3 hours, and centrifuge to obtain a grayish-white solid product. Dry it at 100℃ for 5 hours to obtain a multifunctional hybrid nanomaterial composed of nitrogen-rich superstructured calcium carbonate mesocrystalline particles and carbon nitride nanofibers.
[0036] Scanning electron microscope (SEM) image of the prepared multifunctional nitrogen-rich calcium carbonate nanomaterials is shown below. Figure 9 As shown, the long axis of the pod-like calcium carbonate mesocrystalline particles is 0.3-1.0 mm, the diameter at the widest point (middle part) is 200-500 nm, and it narrows to about 20-50 nm at both ends. Each calcium carbonate mesocrystalline particle is formed by the orderly assembly of oblique quadrangular prism nanocrystals to form a superstructure. Adjacent oblique quadrangular prism nanocrystals have the same orientation and are regularly arranged along a direction parallel to the edges, assembling into a hybrid nanostructure containing carbon-nitrogen heterocycles. This indicates that the solid-liquid reaction crystallization process with carbon nitride as the nitrogen-carbon source is a nanocrystal-mediated directional attachment crystallization growth, which belongs to non-classical crystallization. The edge length of the oblique quadrangular prism grains is 5-50 nm, and the included angle between adjacent side edges ranges from 30° to 90°.
[0037] The raw materials required for the preparation process of this invention are inexpensive, the operation is simple, the process is straightforward and highly reproducible, making it easy to promote on a large scale, and requiring minimal equipment. The method for preparing nanocrystalline calcium carbonate provided by this invention features an innovative solid-liquid reaction-based non-classical crystallization principle, precise and simple process control, superior hybrid and mesocrystalline structures in product performance, and economic and green characteristics in its industrialization prospects. The implementation of this invention will strongly promote the advancement of nanocrystalline calcium carbonate preparation technology, providing downstream industries with high-performance, customized key materials, and is of great significance for promoting the technological upgrading and sustainable development of related industries.
[0038] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all embodiments here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.
Claims
1. A multifunctional nitrogen-rich calcium carbonate nanomaterial, characterized in that: Multifunctional nitrogen-rich calcium carbonate nanomaterials are hybrid nanomaterials composed of calcium carbonate mesocrystalline particles and carbon nitride nanofibers. The calcium carbonate mesocrystalline particles in the hybrid nanomaterials are formed by non-classical crystal growth through solid-liquid reaction using carbon nitride nanofibers as a solid carbon source. The carbon and nitrogen functional groups on the surface of carbon nitride nanofibers induce the orientation and assembly of mesocrystalline nanocrystals at the mesoscale to form superstructured calcium carbonate mesocrystalline particles. Furthermore, when carbon nitride is used as a carbon source for solid-liquid reaction non-classical crystal growth, nitrogen atoms are simultaneously introduced into the calcium carbonate crystals, forming nitrogen-rich superstructured calcium carbonate mesocrystalline particles.
2. The multifunctional nitrogen-rich calcium carbonate nanomaterial according to claim 1, characterized in that: The calcium carbonate mesocrystalline particles are uniformly dispersed in a three-dimensional network of carbon nitride nanofibers. The carbon nitride nanofibers have a diameter of 1-10 nm and a length of 500 nm-1 mm. The interwoven carbon nitride nanofibers form a network with a pore size of 20-200 nm. The individual calcium carbonate mesocrystalline particles are separated and supported by the carbon nitride nanofibers, thus preventing the aggregation of nanomaterials and forming an ordered arrangement of nanostructural units with a specific surface area of 42-55 m². 2 / g of highly active and highly dispersed multifunctional nitrogen-rich calcium carbonate nanomaterials.
3. The multifunctional nitrogen-rich calcium carbonate nanomaterial according to claim 1, characterized in that: The calcium carbonate mesocrystalline particles are pod-shaped, with a major axis of 0.3-1 mm, a diameter of 200-500 nm at the widest point in the middle, and narrowing to 20-50 nm at both ends. Each calcium carbonate mesocrystalline particle is assembled in an orderly manner from oblique quadrangular prism nanocrystals as basic structural units, exhibiting hierarchical structural characteristics and abundant internal interfaces. The oblique quadrangular prism nanocrystals are composed of nitrogen-containing calcite-type calcium carbonate, with conjugated networks of triazine or triazine-homogeneous triazine rings attached to the interfaces between adjacent grains. Adjacent oblique quadrangular prism nanocrystals have the same orientation and are regularly arranged along directions parallel to the edges, assembling into hybrid nanostructures containing carbon and nitrogen heterocycles, i.e., nitrogen-rich mesocrystalline superstructure particles.
4. The multifunctional nitrogen-rich calcium carbonate nanomaterial according to claim 3, characterized in that: The oblique quadrangular prism nanocrystals have an edge length of 5-80 nm and an included angle between adjacent side edges ranging from 30° to 90°. The directional stacking of the oblique quadrangular prism nanocrystals introduces abundant interfacial micropores and mesopores into the calcium carbonate mesocrystalline particles. The size of the interfacial micropores between adjacent oblique quadrangular prism nanocrystals is 0.5-1.8 nm, and the size of the mesopores inside the mesocrystalline particles is 8-60 nm.
5. A method for preparing the multifunctional nitrogen-rich calcium carbonate nanomaterial as described in claim 1, characterized in that: This is a non-classical crystallization method based on a solid-liquid reaction, and the steps are as follows: Step 1: Prepare a urea aqueous solution A with a concentration of 90~100g / L and a melamine aqueous solution B with a concentration of 70~80g / L. Mix the solutions A and B at a volume ratio of 1:(0.9~1.1) and stir. Adjust the pH of the mixed solution to 8-10 to obtain an alkaline mixed solution. Step 2: Pour the alkaline mixed solution obtained in Step 1 into a liquid container. Stir the liquid container evenly under water bath conditions, and then perform hydrothermal treatment in a hydrothermal reactor. Wash the precipitate obtained after hydrothermal treatment, dry it and let it cool naturally to room temperature. Then put it into a muffle furnace and heat it from room temperature to 480-550℃ for 3-6 hours to obtain carbon nitride nanofiber precursor. Step 3: Calcining limestone or carbide slag, and then placing the solid product obtained from calcination into a 30-50% ethanol solution under stirring conditions, and continuously stirring to form a suspension C with a concentration of 1.0-1.5 g / L; Step 4: Introduce carbon nitride nanofiber precursor into suspension C, and ultrasonically disperse it at -5~-10℃ for 15-25 min. The mass ratio between the carbon nitride precursor and the solid product obtained by calcination is (0.5:1)~(1:1) to obtain black suspension D. Step 5: Place the black suspension D into a hydrothermal reactor and keep it at a constant temperature. After centrifugation, a grayish-white solid product is obtained. After drying, a multifunctional nitrogen-rich calcium carbonate nanomaterial composed of calcium carbonate mesocrystalline particles and carbon nitride nanofibers is obtained.
6. The method for preparing multifunctional nitrogen-rich calcium carbonate nanomaterials according to claim 5, characterized in that: In step one, the pH value of the alkaline mixed solution is adjusted by adding sodium hydroxide solution dropwise. The concentration of the sodium hydroxide solution is 0.1-0.2 mol / L, the dropping rate is 10-20 drops / min, and the drop volume is 30-40 drops / mL.
7. The method for preparing multifunctional nitrogen-rich calcium carbonate nanomaterials according to claim 5, characterized in that: In step two, the water bath temperature is 90-110℃, the stirring speed under water bath conditions is 200-300 rpm, and the stirring time is 30-90 min; the hydrothermal temperature is 160-200℃, and the hydrothermal time is 18-30 h.
8. The method for preparing multifunctional nitrogen-rich calcium carbonate nanomaterials according to claim 5, characterized in that: In step two, the filling ratio of the hydrothermal reactor is 60-80%, the precipitate obtained after hydrothermal treatment is washed with excess deionized water at least three times, and dried at a temperature of 60-90℃; the heating rate of the muffle furnace is 2-5℃ / min.
9. The method for preparing multifunctional nitrogen-rich calcium carbonate nanomaterials according to claim 5, characterized in that: In step three, limestone or carbide slag is calcined at 860-900℃ for 20-40 minutes; continuous stirring is carried out at 30-45℃ and a stirring speed of 400-800 rpm for 30-80 minutes.
10. The method for preparing multifunctional nitrogen-rich calcium carbonate nanomaterials according to claim 5, characterized in that: In step five, the hydrothermal reactor is filled with 60-80% of its contents and kept at 140-200℃ for 3-10 hours; drying is carried out at 80-100℃ for 5-8 hours.