Preparation method of monodisperse nano calcium carbonate powder

Abstract

The application discloses a preparation method of monodisperse nano calcium carbonate powder, which comprises the following steps: placing a mixed solution of calcium hydroxide, alcohol-based liquid fuel and deionized water in a stirring ball mill tank for ball milling, continuously generating micro-dissolution of the calcium hydroxide in the ball mill, and passing a certain amount of carbon dioxide gas into the ball mill at a certain flow rate to generate calcium carbonate precursors; subsequently, placing the generated calcium carbonate powder into a double-inner-tank hydrothermal reaction kettle, placing the calcium carbonate precursors in one inner tank, and placing urea in the other inner tank; and then, carrying out hydrothermal reaction at a certain temperature for a certain time to obtain 80-350 nm monodisperse nano calcium carbonate powder. The application has the advantages of low raw material price, simple process, safety and high efficiency, ecological environmental protection and the like, and can realize large-scale continuous production.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of nanomaterials, and particularly to a method for preparing monodisperse nano calcium carbonate powder. BACKGROUND

[0002] Calcium carbonate is an inorganic compound, which is the main component of limestone, marble, etc. and is widely used in modern industry. In addition to being the main raw material for manufacturing cement and lime and being applied in the construction industry, calcium carbonate with different morphologies can also be applied in the manufacture of products such as papermaking, rubber, paint, coating, medicine, and feed, etc. According to different production methods, calcium carbonate can be divided into heavy calcium carbonate, light calcium carbonate, colloidal calcium carbonate, crystal calcium carbonate, and nano calcium carbonate. The main methods for producing calcium carbonate powder include physical method and chemical method.

[0003] The physical method refers to a method of obtaining calcium carbonate powder by mechanically pulverizing marble or limestone. The obtained calcium carbonate is also called heavy calcium carbonate. The physical method has poor uniformity of particle size and irregular morphology, and it is difficult to obtain small particle size calcium carbonate powder.

[0004] The chemical method mainly includes carbonation method and double decomposition method. The carbonation method is to pass carbon dioxide gas into calcium hydroxide solution or suspension to completely convert it into calcium carbonate, and a certain crystal control agent is added during this period to control the required crystal form. Wang Shuang et al. prepared calcite type micro-nano rod-like calcium carbonate by using sodium hexametaphosphate as a crystal control agent and calcium hydroxide as a calcium source based on the carbonation method with pressurization. Ma Jun et al. used carbonation method to explore the influence of MgCl2 and ZnSO4 as crystal control agents on the morphology of calcium carbonate. Ding et al. prepared high-purity ball-shaped calcite calcium carbonate by using carbonation method without adding crystal control agent by controlling the reaction temperature. The carbonation method generally produces calcium carbonate with large particle size. Although some literatures report that calcium carbonate with a primary particle size of less than 100 nm is prepared, the agglomeration is very serious, which is difficult to meet the demand of high-performance powder raw materials for electronic ceramics.

[0005] The double decomposition method is to react with water-soluble calcium salt under certain conditions to obtain monodisperse nano calcium carbonate powder. Song Huating et al. used calcium chloride and ammonium carbonate as reactants to explore the influence of different additives on the micro-morphology of calcium carbonate. Chang Yuefan et al. used calcium chloride and ammonium carbonate as raw materials, added ethanol, citric acid, and sodium pyrophosphate as dispersants, and prepared calcium carbonate powder with different particle sizes by using double decomposition method. However, the double decomposition method generally uses calcium chloride as raw material, and involves a washing process of chloride ions after the product is synthesized, which produces wastewater containing chlorine.

[0006] In addition, due to the difficulty in controlling the shape and particle size of spherical calcium carbonate, in order to obtain a spherical calcium carbonate preparation method with ideal morphology, particle size, and relatively simple process control and suitable for large-scale production, a large number of researchers are still studying it. Some use crystal nucleus control agent or template method to realize the morphology control of calcium carbonate, but most of the calcium carbonate is square or needle-shaped, and the spherical one is less. In the particle size control, the published patent CN114655976 invents a calcium carbonate manufacturing method, calcium carbonate and a calcium carbonate crystallization growth method. Different particle sizes of calcium carbonate can be prepared by using the method, but the dispersity is still poor, and the morphology of the prepared product is mainly square and needle-shaped.

[0007] Based on the above background, the preparation of monodisperse nano calcium carbonate is the focus of development, and the morphology is spherical or spherical as much as possible, especially in the field of electronic ceramic functional materials. The existing calcium carbonate preparation method is difficult to meet the application demand of high-performance calcium carbonate powder for electronic functional ceramics. SUMMARY

[0008] The purpose of the present application is to overcome the technical deficiencies of the existing calcium carbonate preparation method in dispersity, uniformity and particle size control, and to realize a preparation method of monodisperse nano calcium carbonate powder. The method can prepare nano calcium carbonate powder with uniform grain size, high monodispersity, high purity and good performance without adding crystal type control agent, and meet the application demand of high-performance calcium carbonate powder for electronic functional ceramics.

[0009] The present application is realized as follows: a preparation method of monodisperse nano calcium carbonate powder, comprising the following steps:

[0010] (1) Put the mixture of calcium hydroxide, alcohol-based liquid fuel and deionized water into a stirring ball mill jar for ball milling.

[0011] (2) Carbon dioxide gas is introduced at a certain flow rate during ball milling to generate calcium carbonate precursor.

[0012] (3) The calcium carbonate precursor is placed in a double-internal water heat reaction kettle for hydrothermal reaction, one internal tank is placed with calcium carbonate precursor, and the other internal tank is placed with a certain concentration of urea aqueous solution, and reacts at a certain temperature for a certain time.

[0013] (4) The calcium carbonate slurry after hydrothermal reaction is dried by spray drying to obtain monodisperse nano calcium carbonate powder.

[0014] Further, the concentration of calcium hydroxide is 0.1-3 mol / L.

[0015] Further, the alcohol-based liquid fuel is used in an amount of 0.1-0.5 mol / L of calcium carbonate calcium hydroxide / water mixture.

[0016] Further, the ball milling rotation speed is 100-350 r / min.

[0017] Further, the flow rate of the carbon dioxide gas is 0.001-0.05 cubic meters per second.

[0018] Further, the carbon dioxide gas is stopped when the pH value of the ball milling slurry reaches 6-7.5.

[0019] Further, the calcium carbonate precursor adopts a double inner container hydrothermal reaction, one of which places the calcium carbonate precursor, and the other places the urea solution, and the molar concentration ratio of urea to calcium carbonate precursor is 1:1-3.

[0020] Further, the hydrothermal reaction temperature is 80-200 DEG C, and the hydrothermal reaction time is 2-24 h.

[0021] Further, the temperature of the spray drying is 100-240 DEG C.

[0022] Further, the alcohol-based liquid fuel is the alcohol-based liquid fuel developed by Guangxi Henglan Environmental Protection Technology Co., Ltd., namely the product of Chinese patent CN201510349716.7, a preparation method of an alcohol-based liquid fuel and an alcohol-based liquid fuel additive thereof.

[0023] Further, the SEM particle size of the monodisperse nano calcium carbonate powder is 80-350 nm, the D 50 particle size distribution is 100-800 nm, and the specific surface area is 6-15 m 2 / g.

[0024] Technical features and beneficial effects of the present application:

[0025] 1. A preparation method of a monodisperse nano calcium carbonate powder, the SEM particle size of the calcium carbonate powder is 80-350 nm, the D 50 particle size distribution is 100-400 nm, and the specific surface area is 5-20 m 2 / g, the morphology is a spherical or spherical-like monodisperse nano calcium carbonate powder, the preparation of the nano-sized particle size and the monodisperse calcium carbonate powder is realized, and compared with the calcium carbonate powder of patents CN103717681A, CN116528963 and literature (Mengmei et al., Preparation of food-grade aragonite calcium carbonate microspheres from limestone and its mechanism, Bulletin of the Chinese Ceramic Society, 2023, 42(9):3176-3185), the present application has significant advantages in particle size, morphology and dispersity.

[0026] 2.The present application uses calcium hydroxide as raw material, places it in a stirring ball mill tank for ball milling, continuously generates micro-dissolution of calcium hydroxide in the ball mill, and introduces carbon dioxide gas during the stirring ball milling process to prepare calcium carbonate powder, wherein the stirring ball milling process accelerates the dissolution process of calcium hydroxide in the liquid phase, and the carbonation process is more uniform, and the energy of the stirring ball mill effectively controls the grain size of the calcium carbonate during the carbonation process, compared with the traditional ordinary carbonation method for preparing calcium carbonate powder, the particle size, uniformity and dispersibility are greatly improved.

[0027] 3.The present application adds a small amount of alcohol-based liquid fuel in the liquid phase, which has strong penetration and good water solubility, is completely dissolved and dissolved quickly, is non-flammable and non-toxic, and is safe and reliable, which can effectively realize the morphology control of calcium carbonate, and can provide a microemulsion environment under liquid phase conditions, and can improve the dispersity of calcium carbonate slurry and accelerate the uniformity of ball-milled calcium carbonate powder particles.

[0028] 4.The present application adopts double inner tank hydrothermal reaction, and places the ball-milled calcium carbonate precursor powder and urea solution in AB inner tanks for hydrothermal reaction, which solves the technical problem that the calcium carbonate powder prepared by carbonation reaction is unstable and will continue to grow by absorbing carbon dioxide in the air during storage, further improves the dispersity of the calcium carbonate powder, refines the particle size and uniformity, and stabilizes the crystal form.

[0029] In particular, since the calcium carbonate powder prepared by carbonation reaction is not stable itself and will continue to grow by absorbing carbon dioxide in the air during storage, the present application uses a double inner tank hydrothermal reaction kettle for the precursor after carbonation reaction, and uses the carbon dioxide gas generated by the decomposition of urea solution to realize the partial dissolution-recrystallization of calcium carbonate powder in the sealed reaction kettle, so as to realize the stable crystal form and single dispersion state of calcium carbonate.

[0030] 5.The present application sprays and dries the calcium carbonate slurry after hydrothermal reaction at a temperature of 100-240 DEG C, further protects the particle size and uniformity of the calcium carbonate, and obtains single dispersion nanometer calcium carbonate powder meeting the application requirements of high-performance electronic functional ceramics.

[0031] 6.The single dispersion nanometer calcium carbonate prepared by the present application has simple process, easy operation, safety and reliability, can be continuously produced in industrialization, the production wastewater can be reused, is ecological and environmentally friendly, has low production cost, the product morphology is spherical or spherical-like, can meet the application requirements of high-performance calcium carbonate powder for electronic functional ceramics, and has good economic benefit, social benefit and ecological benefit. BRIEF DESCRIPTION OF DRAWINGS

[0032] ATTACHMENT Figure 1 It is a double inner tank hydrothermal reaction kettle structure schematic diagram.

[0033] ATTACHMENTFigure 2 SEM image of calcium carbonate powder prepared in Example 1;

[0034] Figure 2 Figure 3 SEM image of calcium carbonate powder prepared in Example 2;

[0035] Figure 3 Figure 4 SEM image of calcium carbonate powder prepared in Example 3;

[0036] Figure 4 Figure 5 SEM image of calcium carbonate powder prepared in Example 4;

[0037] Figure 5 Figure 6 SEM image of calcium carbonate powder prepared in Example 5;

[0038] Figure 6 Figure 7 SEM image of calcium carbonate powder prepared in Example 6. DETAILED DESCRIPTION

[0039] The following description is presented to enable any person skilled in the art to practice the application as claimed. The preferred embodiments disclosed herein are only examples of the application and alternative embodiments, modifications, improvements, equivalents, and the like can be made thereto without departing from the spirit and scope of the application as set forth in the following claims. The detailed description is not intended to limit the scope of the application.

[0040] It is to be understood that the term "a" or "an" shall not be construed as limiting the number of items to a single item, but rather "one or more". In other words, "a" or "an" should be construed as "at least one" or "one or more" unless otherwise indicated by context.

[0041] The present application provides a method for preparing monodisperse nanometer calcium carbonate powder. The method comprises the following steps: taking calcium hydroxide as raw material, putting the mixture of calcium hydroxide, alcohol-based liquid fuel and deionized water into a stirring ball mill tank for ball milling, continuously generating micro-dissolution of calcium hydroxide in the ball mill, and passing a certain amount of carbon dioxide gas to generate calcium carbonate precursor, then putting the generated calcium carbonate powder into a double-internal water heat reaction kettle, putting calcium carbonate precursor in one internal tank and urea in the other internal tank, and then carrying out water heat reaction at a certain temperature for a certain time to obtain 80-350 nm monodisperse nanometer calcium carbonate powder.

[0042] It is worth mentioning that in the process of ball-milling dissolution of calcium hydroxide, by adding an appropriate amount of alcohol-based liquid fuel in the aqueous solution, since the liquid fuel can be quickly miscible with water, a microemulsion environment is formed, which effectively realizes the morphology control of calcium carbonate, makes calcium carbonate more tend to be spherical or spheroidal growth when nucleation, and can improve the dispersity of calcium carbonate slurry. In the process of carbonization reaction, plus the effect of continuous ball-milling, the uniformity of calcium carbonate powder particles is greatly improved.

[0043] In particular, since the calcium carbonate powder obtained by carbonization method is not stable itself, it will continue to grow by absorbing carbon dioxide in the air during storage, therefore, the precursor after carbonization reaction is used in the double inner water-heating reaction kettle, and the carbon dioxide gas generated by the decomposition of urea solution is used to realize the partial dissolution-recrystallization of calcium carbonate powder in the closed reaction kettle, so as to realize the stable crystal form and monodisperse state of calcium carbonate.

[0044] It is further need to be explained that the present application provides a preparation scheme of monodisperse nano calcium carbonate powder, and the prepared calcium carbonate powder has monodisperse characteristics. For monodispersion, the present application respectively tests from SEM particle size, particle size distribution and specific surface area three test methods, for example: for about 150nm calcium carbonate powder, the SEM test, in the SEM picture with magnification of 100,000 times, the particle size of calcium carbonate nanoparticles is measured by the size measuring tool of SEM, and the average value is obtained, the SEM average particle size is 150.3nm, and the particle size test distribution D 50 is also in the range of 150±10nm, and the test result of specific surface area is 12.82m 2 / g, and according to the relationship between the specific surface area S of spherical particles and the diameter d of the particles:

[0045]

[0046] In the formula, S is the weight specific surface area (m 2 / g); d is the particle diameter (m); and p is the particle density (kg / m 3 ). Through calculation, the value of d is 157.7nm.

[0047] At this time, the SEM average particle size, the average particle size of particle size distribution D 50 and the particle size calculated by the specific surface area are basically consistent, so it is determined that the powder is in monodisperse state.

[0048] For preparing the calcium carbonate powder, the present application provides a preparation method of monodisperse nano calcium carbonate powder, which comprises the following steps:

[0049] (1) Put the mixture of a certain concentration of calcium hydroxide, alcohol-based liquid fuel and deionized water into a stirring ball mill tank for ball milling.

[0050] (2) During the ball milling, carbon dioxide gas is introduced at a certain flow rate to generate calcium carbonate precursor.

[0051] (3) The calcium carbonate precursor is placed in a double-internal-tank hydrothermal reaction kettle, one of the internal tanks is placed with the calcium carbonate precursor, and the other internal tank is placed with a certain concentration of urea aqueous solution, and the reaction is carried out at a certain temperature for a certain time.

[0052] (4) The calcium carbonate slurry after hydrothermal reaction is spray dried to obtain monodisperse nano calcium carbonate powder.

[0053] The technical solution of the present application can be further fully understood through the following specific examples.

[0054] Example 1:

[0055] A preparation method of monodisperse nano calcium carbonate powder, comprising the following steps:

[0056] 1. A calcium hydroxide / water mixture with a concentration of 1 mol / L is configured, and alcohol-based liquid fuel is added, and the addition amount of alcohol-based liquid fuel is 0.2 mol / L of the calcium hydroxide / water mixture.

[0057] 2. Ball milling is carried out under the condition that the stirring ball milling rotation speed is 250 r / min, and carbon dioxide is introduced at a flow rate of 0.001 cubic meters per second until the pH value of the solution is equal to 7.

[0058] 3. The calcium carbonate precursor after ball milling is placed in one of the double-internal-tank reaction kettle, and the other is placed with urea solution, and the molar concentration of urea to calcium carbonate precursor is 1:1, and the hydrothermal reaction is carried out at 100°C for 12h.

[0059] 4. When the reaction is completed and the reaction kettle is lowered to below 60°C, the calcium carbonate is taken out, and after spray drying at 150°C, monodisperse nano calcium carbonate powder is obtained, and the implementation effect is shown in the attached Figure 2 .

[0060] Example 2:

[0061] A preparation method of monodisperse nano calcium carbonate powder, except that alcohol-based liquid fuel is not added, the same operation as example 1 is carried out to prepare monodisperse nano calcium carbonate powder, and the implementation effect is shown in the attached Figure 3 . At the same time, the SEM average particle size, D 50 particle size distribution graph of the calcium carbonate powder, and the particle size calculated by the specific surface area and the powder shape are shown in Table 1.

[0062] Comparative Example 1:

[0063] A method for preparing monodisperse nano calcium carbonate powder, except that the ball mill is not opened during the carbonization reaction, and other operations are the same as those in Example 1, to try to prepare calcium carbonate powder. However, the prepared calcium carbonate powder has a larger particle size and more serious agglomeration.

[0064] Comparative Example 2:

[0065] A method for preparing monodisperse nano calcium carbonate powder, except that the calcium carbonate after the carbonization reaction is not subjected to hydrothermal treatment, and other operations are the same as those in Example 1, to try to prepare calcium carbonate powder. However, the prepared calcium carbonate powder has a smaller particle size, but the agglomeration and uniformity are general. The results of the above four examples are as follows:

[0066]

[0067] Example 3:

[0068] A method for preparing monodisperse nano calcium carbonate powder, comprising the following steps:

[0069] 1. A calcium hydroxide / water mixture with a concentration of 3 mol / L is configured, and the addition amount of alcohol-based liquid fuel is 0.5 mol / L of the calcium hydroxide / water mixture.

[0070] 2. Ball milling is performed under the condition that the stirring ball mill rotation speed is 350 r / min, and carbon dioxide is introduced at a flow rate of 0.01 cubic meters per second until the solution pH value is equal to 6.5.

[0071] 3. The calcium carbonate precursor after ball milling is placed in one of the two inner tanks of the reaction kettle, and the other is placed with a urea solution, and the molar concentration of urea to calcium carbonate precursor is 1:2, and hydrothermal reaction is performed at 160℃ for 2h.

[0072] 4. When the reaction kettle is reduced to below 60℃ after the reaction is completed, the calcium carbonate is taken out, and monodisperse nano calcium carbonate powder is obtained after spray drying at 180℃. The implementation effect is shown in the accompanying Figure 4 SEM particle size of the prepared calcium carbonate powder is 150.3 nm, D 50 particle size distribution is 157.7 nm, and the specific surface area is 12.82 m 2 / g.

[0073] Example 4:

[0074] A method for preparing monodisperse nano calcium carbonate powder, comprising the following steps:

[0075] 1. A calcium hydroxide / water mixture with a concentration of 0.5 mol / L is configured, and the addition amount of alcohol-based liquid fuel is 0.1 mol / L of the calcium hydroxide / water mixture.

[0076] 2. Ball-milling under the condition of 300r / min stirring speed, and passing carbon dioxide into the solution at the flow rate of 0.005 cubic meters per second until the pH value of the solution is equal to 7.

[0077] 3. Placing the ball-milled calcium carbonate precursor into one of the two inner tanks of the double-tank reactor, and placing urea solution into the other inner tank according to the inner tank, and the molar concentration of urea to the calcium carbonate precursor is 1:1.5, and hydrothermal reaction is carried out at 120℃ for 6h.

[0078] 4. When the reactor is cooled to below 60℃ after the reaction is completed, the calcium carbonate is taken out of the reactor, and monodisperse nano calcium carbonate powder is obtained after spray drying at 100℃, and the implementation effect is shown in the accompanying Figure 5 SEM particle size of the prepared calcium carbonate powder is 220nm, D 50 particle size distribution is 232nm, and the specific surface area is 10.35m 2 / g.

[0079] Example 5:

[0080] A preparation method of monodisperse nano calcium carbonate powder, comprising the following steps:

[0081] 1. Configuring calcium hydroxide / water mixed solution with the concentration of 1.5mol / L, and the added amount of alcohol-based liquid fuel is 0.4mol / L of the calcium hydroxide / water mixed solution.

[0082] 2. Ball-milling under the condition of 350r / min stirring speed, and passing carbon dioxide into the solution at the flow rate of 0.008 cubic meters per second until the pH value of the solution is equal to 7.

[0083] 3. Placing the ball-milled calcium carbonate precursor into one of the two inner tanks of the double-tank reactor, and placing urea solution into the other inner tank according to the inner tank, and the molar concentration of urea to the calcium carbonate precursor is 1:2, and hydrothermal reaction is carried out at 100℃ for 24h.

[0084] 4. When the reactor is cooled to below 60℃ after the reaction is completed, the calcium carbonate is taken out of the reactor, and monodisperse nano calcium carbonate powder is obtained after spray drying at 120℃, and the implementation effect is shown in the accompanying Figure 6 SEM particle size of the prepared calcium carbonate powder is 285nm, D 50 particle size distribution is 320nm, and the specific surface area is 10.12m 2 / g.

[0085] Example 6:

[0086] A preparation method of monodisperse nano calcium carbonate powder, comprising the following steps:

[0087] 1. The concentration of the calcium hydroxide / water mixture is 0.1 mol / L, and the amount of alcohol-based liquid fuel added is 0.3 mol / L of the calcium hydroxide / water mixture.

[0088] 2. The ball milling is carried out under the condition that the stirring ball mill rotates at 100 r / min, and carbon dioxide is introduced into the solution at a flow rate of 0.005 cubic meters per second until the pH value of the solution is equal to 7.

[0089] 3. The calcium carbonate precursor after ball milling is placed in one of the two inner tanks of the double-tank reaction kettle, and the other tank is filled with urea solution, and the molar concentration of urea to calcium carbonate precursor is 1:1, and the hydrothermal reaction is carried out at 180℃ for 8h.

[0090] 4. When the reaction kettle is cooled to below 60℃ after the reaction is completed, the calcium carbonate is taken out, and then the monodisperse nano calcium carbonate powder is obtained after spray drying at 160℃, and the implementation effect is shown in the attached Figure 7 SEM particle size of the prepared calcium carbonate powder is 348 nm, D 50 50% particle size distribution is 363 nm, and the specific surface area is 9.86 m 2 / g.

[0091] It is understood by those skilled in the art that the above examples are only examples, and the features of different examples can be combined with each other to obtain embodiments that are easily thought of according to the disclosure of the present application but are not explicitly indicated in the drawings, and the present application does not limit this.

[0092] It is understood by those skilled in the art that the above description and the embodiments of the present application shown in the drawings are only examples and do not limit the present application. The purpose of the present application has been completely and effectively achieved. The preparation method of the present application has been shown and described in the examples, and any modification or modification of the embodiments of the present application can be made without departing from the principles described.

Claims

1. A method for preparing monodisperse nano-sized calcium carbonate powder, characterized in that, The preparation method comprises the following steps: (1) placing a mixture of calcium hydroxide, alcohol-based liquid fuel and deionized water in a stirring ball mill tank for ball milling; (2) introducing carbon dioxide gas into the ball mill at a certain flow rate to generate a calcium carbonate precursor during the ball milling; (3) placing the calcium carbonate precursor in a double-internal-tank hydrothermal reaction kettle for hydrothermal reaction, wherein one internal tank is placed with the calcium carbonate precursor and the other internal tank is placed with a urea aqueous solution with a certain concentration, and the reaction is carried out at a certain temperature for a certain time; (4) obtaining monodisperse nano calcium carbonate powder by spray drying the calcium carbonate slurry obtained through the hydrothermal reaction.

2. The method according to claim 1, wherein the method is characterized by: The molar concentration of the calcium hydroxide is 0.1-3 mol / L.

3. The method according to claim 1, wherein the method is characterized by: The alcohol-based liquid fuel is used in an amount of 0.1-0.5 mol / L of the molar concentration of the calcium hydroxide.

4. The method according to claim 1, wherein the method is characterized by: The ball milling rotation speed is 100-350 r / min.

5. The method according to claim 1, wherein the method is characterized by: The flow rate of the introduced carbon dioxide is 0.001-0.05 cubic meters per second, and the reaction is completed when the pH value of the ball milling slurry is 6-7.5 to obtain the calcium carbonate precursor.

6. The method according to claim 1, wherein the method is characterized by: The double-internal-tank hydrothermal reaction is used for the calcium carbonate precursor, wherein one internal tank is placed with the calcium carbonate precursor and the other internal tank is placed with the urea solution, and the molar concentration ratio of the urea to the calcium carbonate precursor is 1:1-3.

7. The method according to claim 1, wherein the method is characterized by: The temperature of the hydrothermal reaction is 80-200 DEG C, and the reaction time is 2-24 h.

8. The method according to claim 1, wherein the method is characterized by: The temperature of the spray drying is 100-240 DEG C.

9. The method according to claim 1, wherein the method is characterized by: The SEM particle size of the final calcium carbonate powder is 80-350 nm, and the D 50 The particle size distribution is 100-800 nm, and the specific surface area is 6-15 m 2 / g.

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