TW202208278A - Hollow calcium carbonate microspheres and method for preparing the same - Google Patents

Abstract

The present disclosure provides a hollow calcium carbonate microspheres and method for preparing the same. The method includes: performing a precipitation reaction of a reaction solution and a carbon source to obtain a slurry of calcium carbonate; separating and get the hollow calcium carbonate microspheres. With the method above, the hollow calcium carbonate microspheres show the advantage of high-purity, and it thus has a bright prospect in the fields of rubber, plastics, paper-making, ink-printing, coating and pharmacy.

Description

Hollow calcium carbonate microspheres and preparation method thereof

The present disclosure relates to a calcium carbonate particle and a preparation method thereof, in particular, to a light calcium carbonate particle with a hollow spherical structure and a preparation method thereof.

Calcium carbonate is a common inorganic material in industrial production. It is widely used in rubber, plastic, paper, ink, paint, medicine and other fields to improve the stability, hardness, rigidity, heat resistance and processing performance of products. low cost advantage.

In terms of morphology, calcium carbonate also has cube, prism, spherical and needle shapes, and different shapes have different applications, and spherical calcium carbonate is the most widely used, because of its large specific surface area and good dispersion. It is often used as a filler to improve coating performance and improve the gloss, flow and physical properties of its products.

Recently, hollow calcium carbonate spheres have attracted special attention. In addition to the physical properties of spherical calcium carbonate, the hollow structure also gives the material the characteristics of low density; especially in the field of pharmaceuticals, hollow calcium carbonate spheres become carriers for drug delivery by virtue of the hollow structure. , has the ability to change the release and absorption distribution of the embedded drug.

However, the current preparation technology is mainly based on solid calcium carbonate spheres, and there is still little ink on the hollow calcium carbonate spheres. However, the current manufacturing method has problems such as complicated process steps or complex solvent components, which increases the difficulty of reuse, and reduces the purity of the product due to the use of additives or other factors.

In view of this, it is necessary to propose a high-purity hollow calcium carbonate sphere and a method for preparing the hollow calcium carbonate sphere with improved process, so as to meet the actual needs of current application and production and preparation.

The present disclosure provides a method for preparing hollow calcium carbonate microspheres, which includes: feeding a reaction solution into a hypergravity reaction device at a flow rate of 1.2 to 1.8 liters/min, so that the reaction solution and a carbon source are subjected to a precipitation reaction, wherein the The reaction solution contains an ammonium salt aqueous solution with a calcium ion concentration of 0.15 to 1 wt % to form a calcium carbonate slurry; and the liquid in the calcium carbonate slurry is separated to obtain the hollow calcium carbonate microspheres.

The present disclosure further provides a hollow calcium carbonate microsphere, which includes a calcium carbonate shell layer and an inner cavity, and in the Fourier transform infrared spectrum, the hollow calcium carbonate microsphere contains characteristic peaks of crystalline calcium carbonate, There are no characteristic peaks of additives, and the additives include crystal form control agents or emulsifiers.

According to the present disclosure, through the adjustment and control of the operating conditions of the precipitation reaction, the process of the present disclosure can directly prepare high-purity hollow calcium carbonate microns without using any additives (such as crystal control agents or emulsifiers). Therefore, it has application prospects in many fields such as rubber, plastic, paper, ink, paint, medicine and so on.

Furthermore, the preparation method of the present disclosure does not use any additives (such as crystal form control agent or emulsifier), and the solvent composition is simple, so the solvent can be recovered and reused, and the process improvement effect can be achieved.

On the other hand, the production method of the present disclosure can use low-purity calcium-containing materials as the calcium source for calcium ions, and is not limited to high-purity pharmaceuticals, so it has a competitive advantage over the prior art in terms of raw material cost.

In general, the method for preparing hollow calcium carbonate microspheres of the present disclosure is simple in preparation procedure, environmentally friendly, and has no doubts about the residue of additives in its products, and has practical value in industrial application.

The following describes the implementation of the present disclosure through specific embodiments, and those skilled in the art can easily understand the advantages and effects of the present disclosure from the content disclosed in this specification. The present disclosure can also be implemented or applied by other different embodiments, and various details in this specification can also be given different modifications and changes based on different viewpoints and applications without departing from the spirit disclosed in the present disclosure. Furthermore, all ranges and values herein are inclusive and combinable. Any value or point falling within a range described herein, eg, any integer, can be taken as a minimum or maximum value to derive a lower range, etc.

Please refer to FIG. 1 , which illustrates the process flow of the preparation method of the hollow calcium carbonate microspheres of the present disclosure. First, a reaction solution is prepared (step S11); then, in a reaction tank, the reaction solution and a carbon source are subjected to a precipitation reaction (step S12) to form calcium carbonate slurry; and the liquid in the calcium carbonate slurry is separated , namely, the hollow calcium carbonate microspheres are obtained (step S13).

Herein, the "reaction solution" is an ammonium salt aqueous solution containing calcium ions, and the calcium ion concentration is 0.15 to 1% by weight; in other embodiments, the calcium ion concentration can be 0.2, 0.3, 0.4 , 0.5, 0.6, 0.7, 0.8 or 0.9 wt %, and not limited thereto. In a specific embodiment, the calcium ion concentration is too low, the structure of the prepared calcium carbonate particles is partially solid spherical, and partially square, the overall shape uniformity is poor, and the overall particle size distribution is not easy. control. In another embodiment, when the calcium ion concentration is too high, the structure of the prepared calcium carbonate particles is still partly solid sphere, partly square, with poor overall shape uniformity and serious agglomeration.

In another embodiment, the pH value of the reaction solution is 8.0 to 11.0; in other embodiments, the pH value of the reaction solution may be 8.5, 9.0, 9.5, 10.0 or 10.5, and not limit.

The preparation method of the reaction solution includes: using an aqueous solution dissolved with ammonium salt as an extraction solvent, dispersing or dissolving a calcium-containing raw material in the extraction solvent to dissolve the calcium ions in the calcium-containing raw material to prepare A reaction solution with a calcium ion concentration of 0.15 to 1 wt % is obtained. By using the extraction solvent in which the ammonium salt is dissolved, the extraction selectivity of the calcium ion can be improved by more than 95%, and the dissolution of other metal ions can be effectively improved to avoid affecting the whiteness of the product.

In a specific embodiment, the preparation of the reaction solution is dispersed or dissolved in a mixing tank with a stirring device until the pH value of the solution is above 8.0 and does not change, then a reaction solution is obtained.

In another specific embodiment, the preparation system of the reaction solution includes: dispersing or dissolving the calcium-containing raw material in the ammonium salt-dissolved extraction under the conditions of a mixing tank at a temperature of 0 to 50 ^° C and normal pressure. The procedure of calcium ion extraction in the solvent is carried out until the pH value of the solution is above 8.5 and no longer changes, and then the solid components are removed by suction filtration or centrifugal filtration to obtain the reaction solution for precipitation reaction.

Herein, the "ammonium salt" is a compound composed of ammonium ions and acid ions, and non-limiting examples thereof include one or more compounds selected from the group consisting of ammonium chloride, ammonium nitrate and ammonium acetate, wherein the The volume molar concentration of the ammonium salt in the extraction solvent is 0.01 to 3M or 0.1 to 2.5M.

In other embodiments, the volume molar concentration of the ammonium salt in the extraction solvent may be 0.1, 0.2, 0.3, 0.4, 0.5, 1, 1.5, 2 or 2.5M, but not limited thereto.

Herein, the term "calcium-containing raw materials" refers to calcium-containing chemicals (such as calcium oxide or calcium chloride), calcium-containing natural materials (such as calcium-containing ore or oyster shells), or recycled calcium-containing wastes (such as industrial by-products). In one embodiment, the calcium-containing raw material is recycled calcium-containing waste to increase its added value, especially the by-products of iron and steel smelting, such as blast-furnace slag, converter stone (basic- oxygen-furnace slag) or electric-arc-furnace slag for electric arc furnace steelmaking.

In a specific embodiment, the particle size of the calcium-containing material is not limited, and may be determined by the type of the calcium-containing raw material. In one embodiment, the particle size of the calcium-containing material is less than 10 cm. In one embodiment, the particle size of the calcium-containing material is less than or equal to 500 microns; in another embodiment, the particle size of the calcium-containing material is screened to be less than 200 microns.

In the preparation method of the present disclosure, the calcium-containing raw materials used can be low-purity calcium-containing materials, and the minimum calcium content can be as high as 20%, and is not limited to high-purity drugs, so it is more competitive with the prior art in terms of raw material cost. Advantage.

In one embodiment, the calcium content of the calcium-containing raw material is 30 to 80%; in other embodiments, the calcium content of the calcium-containing raw material may be 35, 40, 45, 50, 55, 60, 65, 70 or 75%, and not limited to this.

In the preparation method of the present disclosure, the "precipitation reaction" is performed in a liquid phase system to form an insoluble calcium carbonate product through the combination of calcium ions and carbonate ions. In one embodiment, the precipitation reaction is carried out at 20 to 60 ^° C and normal pressure. In one embodiment, the precipitation reaction is carried out at room temperature of about 23 to 30 ^° C and normal pressure of about 1 standard atmosphere (atm). In other embodiments, the temperature of the precipitation reaction may be 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 35, 40, 45, 50 or 55 ^° C, and not limit.

Regarding the "reaction tank" used for the precipitation reaction of the present disclosure, a carbon source supply device can be installed and connected upstream of the "reaction tank" to provide a stable carbon source in a batch or continuous manner, and the reaction solution is fed into contact with precipitation reaction.

In addition, the flow rate of the reaction solution fed into the reaction tank is 1.2 to 1.8 L/min; in other embodiments, the flow rate of the reaction solution fed into the reaction tank may be 1.3, 1.4, 1.5, 1.6 or 1.7 L/min minutes, and not limited to this.

In one embodiment, the flow rate at which the carbon source is fed into the reaction tank is 1 to 5 liters/min; in other embodiments, the flow rate at which the carbon source is fed into the reaction tank may be 1.5, 2, 2.5, 3, 3.5, 4 or 4.5 liters/min, without limitation.

In the preparation method of the present disclosure, the "carbon source" includes a mixed gas containing carbon dioxide, an aqueous carbonic acid solution or an aqueous carbonate solution.

Herein, the preparation of the "carbonated water solution" can be obtained by injecting carbon dioxide into water for carbonation reaction through an aeration device, or by dissolving carbonate compounds in water.

In the article, in addition to the collection of carbon dioxide from the air, it can also be integrated with other processes to recover the carbon dioxide in industrial exhaust gas for further utilization, and at the same time achieve the purpose of reducing carbon emissions.

In one embodiment, the carbon source is a mixed gas containing carbon dioxide, and the concentration of the carbon dioxide accounts for 20 to 100% of its total volume; in other embodiments, the concentration of the carbon dioxide accounts for its total volume. The volume can be 30, 40, 50, 60, 70, 80 or 90% without limitation.

When the "mixed gas containing carbon dioxide" is used as the carbon source, since the carbon source and the reaction solution are in the gas phase and the liquid phase, respectively, the precipitation reaction occurs and is also subject to the progress of the carbonation reaction. Therefore, In order to improve the reaction rate and conversion rate, the reaction tank used in the present disclosure has the function of fully contacting the gas-liquid phase. Wherein, the contact form of the gas-liquid phase includes: making the carbon source gas flow contact the liquid film layer formed by the reaction solution in the same direction or in the opposite direction, or making the carbon source gas flow form bubble groups to be distributed in the reaction solution , but not limited to this.

In addition, the carrier gas system used in the mixed gas of the present disclosure does not affect the progress of the overall carbonation reaction and precipitation reaction.

In a specific embodiment, the reaction tank of the present disclosure is a hypergravity reaction device with a rotating disk. Please refer to FIG. 2A , which is an exemplary cross-sectional view of a hypergravity reaction device, but it is not intended to be limiting. The aspect or structure of the reaction device used in the present disclosure.

The hypergravity reaction device 1 is a continuous reaction device, and its device structure includes: a shell 10; , so that the reaction solution forms a liquid film layer on the rotating disk 11. In one embodiment, the radius of the rotating disk 11 is 5 to 200 cm or 5 to 50 cm, and the size of the opening of the nozzle is 3 to 100 cm. mm; the motor transmission part 12 connected with the rotating disk 11; the infusion pipe 131 for introducing the reaction solution and communicating with the rotating disk 11; the feeding port 141 or 142 provided in the shell 10 and removing the calcium carbonate slurry The drain pipe 132.

The present disclosure provides a method for preparing hollow calcium carbonate microspheres. The reaction solution is fed to the rotating disk 11 through the infusion tube 131 , and the motor transmission member 12 of the hypergravity reaction device 1 is used to feed the reaction solution at 1000 to 4000 rpm or 1000 to 2000 rpm. At the same time, the carbon source is fed into the hypergravity reaction device 1 through the feeding port 141 or 142, so that the carbon source and the reaction solution are fully contacted and the precipitation reaction is carried out; the calcium carbonate formed by the reaction The slurry flows to the inner cavity wall of the casing by gravity again, and is removed through the drain pipe 132 .

In a specific embodiment, the preparation method is to feed the reaction solution having a calcium ion concentration of 0.15 to 1 wt % and a volume molar concentration of ammonium salt of 0.01 to 3 M through the infusion tube 131 at a flow rate of 1.2 to 1.8 liters/min. On the rotating disk 11, when the temperature is 20 to 60 ^° C, the rotating disk 11 is rotated at a speed of 1000 to 2000 rpm by the motor transmission element 12 of the hypergravity reaction device 1, so that the reaction solution is rotated. A liquid film layer is formed on the plate 11; at the same time, the carbon source is fed into the hypergravity reaction device 1 through the feed port 141, so that the carbon source and the reaction solution are fully contacted and subjected to a precipitation reaction to form calcium carbonate slurry. Through the control of the above operating conditions, the process of the present disclosure does not need to use other additional additives (such as emulsifiers or crystal form control agents), so that high-purity hollow calcium carbonate microspheres can be obtained.

Regarding the "separation" procedure after the precipitation reaction in the present disclosure, the solid-liquid separation can be performed by means of air extraction and drying or centrifugation.

In a specific embodiment, the temperature of the air-drying is 15 to 40 ^o C; in other embodiments, the temperature of the air-drying can be 20, 25, 30 or 35 ^o C, and not limited.

In another embodiment, the method for preparing hollow calcium carbonate microspheres of the present disclosure further includes refluxing the separated liquid for preparing the reaction solution. Please refer to FIG. 3 , which is a schematic diagram of a reaction system with a hypergravity reaction device, which includes: a hypergravity reaction device 1 ; a carbon source supply device 2 disposed upstream of the hypergravity reaction device 1 and feed into its feed port 141 by pipeline connection; a mixing tank 3 for preparing the reaction solution is set upstream of the hypergravity reaction device 1 and fed into its infusion pipe 131 by pipeline connection; a solid The liquid separation device 4 is connected through the liquid discharge pipe 132 of the supergravity reaction device 1 to process the calcium carbonate slurry after the reaction; after the separation treatment of the solid-liquid separation device 4, the separated liquid is returned to the mixing Slot 3, to receive hollow calcium carbonate microspheres 5.

As can be seen from the above, because the preparation method of the present disclosure does not use any additives (such as crystal form control agent or emulsifier), and the solvent composition is simple, the solvent can be recovered and reused, which is beneficial to reduce the overall process cost.

The present disclosure further provides a hollow calcium carbonate microsphere prepared according to the above method, which comprises a calcium carbonate outer shell layer and an inner cavity, and the hollow calcium carbonate microsphere has the following characteristics: (a) its average particle size is is in the range of 0.5 to 50 microns; and (b) has characteristic peaks at 678, 743, 872, 1088, 1389 to 1458, 1764 and 2503 cm ^-1 in the Fourier transform infrared spectrum, as shown in Figure 4 , and does not contain the characteristic peaks of additives.

In a specific embodiment, the surface morphology of the hollow calcium carbonate microspheres of the present disclosure is observed with a scanning electron microscope (SEM), and the overall particle size ranges from 1 to 10 microns.

In other specific embodiments, the overall particle size range of the hollow calcium carbonate microspheres may be 2, 3, 4, 5, 6, 7, 8 or 9 microns, but not limited thereto.

From the Fourier transform infrared spectrum, it can be seen that the surface of the calcium carbonate shell layer of the hollow calcium carbonate microspheres prepared according to the above method includes: crystal water, amorphous calcium carbonate and N-H groups from ammonium salts, Compared with the conventional preparation technology of calcium carbonate spheres, the process of the present disclosure does not use additives (such as crystal form control agents or emulsifiers), so the surface of the calcium carbonate shell layer of the hollow calcium carbonate microspheres of the present disclosure does not have any The bonding of the functional groups corresponding to the additive is formed. The above-mentioned crystal control agents include alcohols (such as methanol, ethanol or ethylene glycol), alkanes (such as n-hexane) or alkenes (such as epichlorohydrin); for example, the above-mentioned emulsifiers have both hydrophilic ends and Compounds at the lipophilic end, such as sodium stearate, sodium lauryl sulfate or span 20.

In addition, through transmission electron microscope (TEM) equipment, the thickness of the calcium carbonate shell layer is measured to be 20 nm to 20 microns, for example: 56 nm to 310 nm or 0.9 microns to 1.42 microns.

In addition, the hollow calcium carbonate microspheres of the present disclosure can also pass through an X-ray diffractometer. In the powder X-ray diffraction spectrum, as shown in FIG. 5 , it can be seen that the hollow calcium carbonate microspheres of the present disclosure include vaterite. (Vaterite) crystal form of calcium carbonate.

The hollow calcium carbonate microspheres provided by the above preparation method can be used in the field of papermaking or plastics. Due to the characteristics of the hollow structure, the surface roughness of the applied material can be adjusted, the material density can be reduced, and the mechanical strength and optimization of the applied material can be improved. Its surface ink coating effect.

In addition, since the method for preparing the hollow calcium carbonate microspheres of the present disclosure does not use other additional additives, there is no doubt about the residue of the additives in the product. Avoid unnecessary side effects.

The present disclosure is further described in detail below through specific embodiments, but the scope of the present disclosure is not limited by the description of the embodiments.

Example 1 : Preparation of hollow calcium carbonate microspheres

Preparation of the reaction solution : at room temperature (about 25 ^o C), in a mixing tank with a blade stirrer and the stirrer rotating speed of 400rpm, under normal pressure, dissolve calcium oxide in 1 liter of 0.2 Calcium ion extraction is carried out in M ammonium chloride aqueous solution. When the pH value of the solution is above 8, the undissolved solid components are removed by suction filtration or centrifugal filtration to obtain a clear reaction solution, and the calcium ion concentration is 0.2% by weight.

Precipitation reaction : take the hypergravity reaction device of FIG. 2 as the reaction tank to carry out the precipitation reaction, and feed the reaction solution to the rotating disk 11 (the radius of the rotating disk is about 6 cm) at a flow rate of 1.5 liters/min from the infusion pipe 131, and The opening size of the nozzle on the rotating disk is about 3 mm; the rotating disk 11 is rotated at a speed of 2000 rpm by the motor transmission member 12 of the hypergravity reaction device 1, so that the reaction solution forms a liquid film layer on the rotating disk 11 .

At the same time, take carbon dioxide gas as carbon source, make this carbon source feed into hypergravity reaction device 1 from feed port 141 at the flow rate of 5 liters/min, make this carbon source contact with this reaction solution and carry out precipitation reaction, to form carbonic acid Calcium Serum.

Separation procedure : The liquid in the calcium carbonate slurry is subjected to solid-liquid separation through suction filtration or centrifugal filtration to obtain calcium carbonate particles.

The calcium carbonate particles obtained above are subjected to the following analysis:

(1) Observation of appearance, shape and structure: through scanning electron microscope (Scanning Electron Microscope, SEM) and transmission electron microscope (Transmission Electron Microscopy, TEM) to observe the appearance and cross section of the obtained calcium carbonate particles, it can be seen that the carbonic acid The calcium particles have a hollow spherical shape, and the average thickness of the calcium carbonate shell layer is about 200 nanometers, which are hollow calcium carbonate microspheres.

(2) Measurement of average particle size: The hollow calcium carbonate microspheres obtained were observed by SEM, and the average particle size of the hollow calcium carbonate microspheres was about 1.72±0.40 microns through Image J image analysis software analysis.

(3) Thermogravimetric analysis: It was analyzed with a thermogravimetric analyzer (TGA) at a temperature of 25 ^o C to 850 ^o C, and it was known that the calcium carbonate purity of the hollow calcium carbonate microspheres was 99.6%.

Example 2 : Preparation of hollow calcium carbonate microspheres

The preparation method is the same as in Example 1, except that converter stone (calcium content of about 35% to 40%) is used as the calcium-containing raw material, and the pH value of the obtained reaction solution is above 8 and its calcium ion concentration is 0.17% by weight. Calcium carbonate particles are obtained after the separation procedure.

Finally, according to the analysis method of Example 1, the appearance and structure of the calcium carbonate particles obtained above were evaluated. They were hollow calcium carbonate microspheres, and their average particle size was in the range of 4.1±1.4 microns, and the calcium carbonate purity reached 95.3%.

Example 3 : Preparation of hollow calcium carbonate microspheres

The preparation of reaction solution : at room temperature (about 25 ^℃ ), with converter stone (calcium content about 40% by weight) as calcium-containing raw material, in a mixing tank with a blade stirrer and the stirring speed of 400rpm, Dissolve 106 grams of converter stone in 1 liter of 1M ammonium chloride aqueous solution for calcium ion extraction, when the pH value of the solution is above 8, remove the undissolved converter stone to obtain a clear reaction solution, and the calcium ion The concentration is 0.89% by weight.

Precipitation reaction : The beaker is used as the reaction tank to carry out the precipitation reaction, and the temperature is 28 ^o C, and the stirring device is used for stirring at a speed of 400 rpm; at the same time, carbon dioxide gas is used as the carbon source, so that the carbon source is 1 liter/ The flow rate of 10 minutes was fed into the reaction tank, the carbon source was contacted with the reaction solution and a precipitation reaction was carried out to form a calcium carbonate slurry.

Separation procedure : The liquid in the calcium carbonate slurry is subjected to solid-liquid separation through suction filtration or centrifugal filtration to obtain calcium carbonate particles.

Finally, according to the analysis method of Example 1, the appearance and structure of the calcium carbonate particles obtained above were evaluated, and they were hollow calcium carbonate microspheres, and their average particle size was 3.34±1.82 microns, and the average thickness of the calcium carbonate shell layer was about in the 2.4 micron range.

Example 4 : Preparation of hollow calcium carbonate microspheres

The preparation method is the same as in Example 2, except that 2M aqueous ammonium nitrate solution is used as the extraction solvent, and the calcium ion concentration thereof is 0.19% by weight, and calcium carbonate particles are obtained after the separation procedure.

According to the particle size measurement method in Example 1, the appearance and structure of the calcium carbonate particles prepared above were analyzed, and they were hollow calcium carbonate microspheres with an average particle size in the range of 3.96±1.32 microns.

In addition, from the weight change of the converter stone before and after the preparation, the calcium ion extraction rate during the preparation process was calculated, the influence of the extraction solvent was evaluated, and the number of reuses of the extraction solvent and the corresponding calcium ion extraction rate were recorded in in FIG. 1.

Comparative example 1 : Influence of extraction solvent

The preparation method is the same as in Example 1, except that water is used instead of ammonium chloride as the extraction solvent, so the reaction solution has no ammonium salt component, the pH value of the prepared reaction solution is above 8, and its calcium ion concentration is 0.06% by weight.

Finally, according to the analysis method of Example 1, the obtained calcium carbonate particles are observed by scanning electron microscope, and it can be seen that the calcium carbonate particles are square and have agglomeration phenomenon.

In addition, the calcium carbonate particles were analyzed by X-ray diffractometry, and it was found that the crystal structure of the calcium carbonate particles was Calcite crystal type.

Comparative example 2 : Influence of extraction solvent and preparation procedure

The preparation method is the same as in Example 1, except that water and calcium oxide are mixed and stirred for about 30 minutes to obtain a solution with a pH value of 8 or more, and 0.2 M ammonium chloride solution is added as a reaction solution, and its calcium ion concentration is 0.13 weight %.

Finally, according to the analysis method of Example 1, the appearance and structure of the prepared calcium carbonate particles were evaluated, and it was found that the prepared calcium carbonate particles had a solid structure, and their overall particle sizes were different.

Comparative example 3 : Influence of extraction solvent

The preparation method is the same as that of Comparative Example 1, except that 10 ml of 4.2% ammonia water is used as the extraction solvent and calcium chloride is used as the calcium-containing raw material, and the pH value of the obtained reaction solution is above 8 and its calcium ion concentration is 0.72% by weight; After the precipitation reaction and separation procedure, calcium carbonate particles were obtained; and according to the analysis method of Example 1, the appearance and cross-section of the obtained calcium carbonate particles were observed, and it was found that the calcium carbonate particles were mostly solid spheres.

Comparative example 4 : Influence of extraction solvent

The reaction solution of Example 4 was prepared, except that 2M ammonium nitrate aqueous solution and 0.1M ammonia water were used as extraction solvents. The pH value of the obtained reaction solution was above 8, and its calcium ion concentration was 1.07% by weight.

Next, through the analysis of the weight change of the converter stone before and after preparation as in Example 4, the calcium ion extraction ability of the solvent reuse was evaluated, and recorded in Table 1. It was found that adding ammonia water in the process would reduce the extraction ability of the reused solvent.

Table 1 extraction solvent Calcium ion extraction rate of each reuse times 0 times 1 time 2 times The reaction solution of Example 4 2M NH ₄ NO ₃ (aq) 25.96% 27.06% 26.57% The reaction solution of Comparative Example 4 2M _{NH4NO3 (} aq) and 0.1M _NH4OH (aq) 25.96% 18.95% 13.41%

Comparative example 5 : Effect of calcium ion concentration

The preparation method is the same as that in Example 3, except that the calcium-containing raw material is 20 grams of converter stones with a calcium content of 40% by weight (particle size is 177 to 297 microns), so the pH value of the resulting reaction solution is above 8 and its calcium ion The concentration is 0.13% by weight; after precipitation reaction, calcium carbonate slurry is obtained; after solid-liquid separation, calcium carbonate particles are obtained.

Finally, according to the analysis method of Example 1, the appearance of the calcium carbonate particles prepared above was evaluated, and it was found that the calcium ion concentration was too low, and the structure of the prepared calcium carbonate particles was partly solid spherical, and partly square. , the overall shape uniformity is poor, and the overall particle size distribution is not easy to control.

Comparative example 6 : Effect of calcium ion concentration

The preparation method is the same as in Example 3, except that the 2M ammonium nitrate aqueous solution is used as the extraction solvent, the pH value of the obtained reaction solution is more than 8, and its calcium ion concentration is 1.71% by weight; after the precipitation reaction, calcium carbonate slurry is obtained; After solid-liquid separation, calcium carbonate particles are obtained.

Finally, according to the analysis method of Example 1, the appearance of the calcium carbonate particles prepared above was evaluated. It can be seen from the above that when the calcium ion concentration is too high, the structure of the prepared calcium carbonate particles is still partly solid sphere type, partly square type, the overall shape uniformity is poor, and the agglomeration phenomenon is serious.

Comparative example 7 : Influence of the flow rate of the reaction solution

The preparation method is the same as in Example 1, except that the pH value of the prepared reaction solution is above 8 and its calcium ion concentration is 0.18% by weight, and the flow rate of the reaction solution during the precipitation reaction is 1 liter/min, To obtain calcium carbonate slurry; finally, according to the analysis method of Example 1, the appearance of the obtained calcium carbonate particles was evaluated, and the structure of the prepared calcium carbonate particles was partly in the form of a solid sphere, and partly in the form of a square, The overall shape uniformity is poor, and the overall particle size distribution is not easy to control.

Comparative example 8 : Influence of the flow rate of the reaction solution

The preparation method is the same as that of Example 1, except that when the pH value of the prepared reaction solution is above 8 and the calcium ion concentration thereof is 0.19% by weight, the flow rate of the reaction solution for the precipitation reaction is changed to 2 liters/min, with Calcium carbonate slurry was prepared; finally, according to the analysis method of Example 1, the appearance of the prepared calcium carbonate particles was evaluated, and the structure of the prepared calcium carbonate particles was solid spherical hollow calcium carbonate microspheres.

To sum up, the present disclosure is based on the adjustment and control of the operating conditions of the precipitation reaction, so that the process of the present disclosure can directly prepare high-purity hollow calcium carbonate microspheres without using any additives. It has application prospects in many fields such as plastics, paper, ink, paint, and medicine.

On the other hand, the raw material of the production method of the present disclosure can use low-purity calcium-containing materials as the calcium source of calcium ions, which is not limited to high-purity medicines, and the production method of the present disclosure does not use any additive control, and the solvent can be recovered at the back end of the process and Repeated use has the advantages of simple preparation procedure, environmental protection, no doubts about the residue of additives in its products, and lower overall process cost.

The above-mentioned embodiments are only illustrative, and are not intended to limit the present disclosure. Any person skilled in the art can modify and change the above embodiments without departing from the spirit and scope of the present disclosure. Therefore, the protection scope of the right of the present disclosure is defined by the scope of the patent application attached to the present disclosure, and shall be included in the technical content of this disclosure as long as the effect and implementation purpose of the present disclosure are not affected.

1: Hypergravity Reactor 10: Shell 11: Spinning disc 12: Motor transmission parts 131: Infusion tube 132: Drain pipe 141, 142: Feed port 2: Carbon source supply device 3: Mixing tank 4: Solid-liquid separation equipment 5: Hollow calcium carbonate microspheres S11-S13: Steps

Embodiments of the present disclosure are described by way of illustrative reference to the accompanying drawings: 1 is a flow chart of the preparation method of the hollow calcium carbonate microspheres of the present disclosure; 2 is a schematic cross-sectional view of the hypergravity reaction device of the present disclosure; 3 is a schematic diagram of a reaction system with a hypergravity reaction device of the present disclosure; FIG. 4 is a Fourier transform infrared spectrogram of the hollow calcium carbonate microspheres of the present disclosure; and FIG. 5 is a powder X-ray diffraction spectrum diagram of hollow calcium carbonate microspheres of the present disclosure.

S11-S13: Steps

Claims (17)

A preparation method of hollow calcium carbonate microspheres, comprising: The reaction solution is fed into the hypergravity reaction device at a flow rate of 1.2 to 1.8 liters/minute, and the reaction solution is subjected to a precipitation reaction with a carbon source to form a calcium carbonate slurry, wherein the reaction solution contains calcium ions with a concentration of 0.15 to 1 % by weight of an aqueous ammonium salt solution; and The liquid in the calcium carbonate slurry is separated to obtain the hollow calcium carbonate microspheres. The preparation method according to claim 1, wherein the preparation of the reaction solution comprises using an aqueous solution in which an ammonium salt is dissolved as an extraction solvent, and dispersing or dissolving calcium-containing raw materials in the extraction solvent. The preparation method according to claim 1, wherein the ammonium salt comprises one or more compounds selected from the group consisting of ammonium chloride, ammonium nitrate and ammonium acetate. The preparation method according to claim 2, wherein the volume molar concentration of the ammonium salt in the extraction solvent is 0.01 to 3M. The preparation method according to claim 2, wherein the calcium content of the calcium-containing raw material is at least 20%. The preparation method according to claim 1, wherein the pH value of the reaction solution is 8.0 to 11.0. The preparation method according to claim 1, wherein the carbon source comprises a mixed gas containing carbon dioxide, an aqueous carbonic acid solution or an aqueous carbonate solution. The preparation method according to claim 7, wherein the carbon source is a mixed gas containing carbon dioxide, and the concentration of the carbon dioxide accounts for 20 to 100% of its total volume. The preparation method according to claim 8, wherein the flow rate of the carbon source feeding into the hypergravity reaction device is 1 to 5 liters/min. The preparation method according to claim 1, wherein the temperature of the precipitation reaction is 20 to 60 ^° C. The preparation method of claim 1, further comprising refluxing the separated liquid for preparing the reaction solution. According to the preparation method of claim 1, the reaction solution does not contain a crystal form control agent or an emulsifier. A hollow calcium carbonate microsphere, comprising a calcium carbonate shell layer and an inner cavity, and in the Fourier transform infrared spectrogram, the characteristic wave peak of the hollow calcium carbonate microsphere contains the characteristic wave peak of crystalline calcium carbonate and There are no characteristic peaks of additives, and the additives include crystal form control agents or emulsifiers. The hollow calcium carbonate microspheres according to claim 13, wherein, in the Fourier transform infrared spectrum, the characteristic peaks of amorphous calcium carbonate and calcium carbonate containing crystal water are further included. The hollow calcium carbonate microspheres according to claim 13, wherein the average particle size of the hollow calcium carbonate microspheres is 0.5 to 50 microns. The hollow calcium carbonate microspheres according to claim 13, wherein the calcium carbonate shell layer has a thickness of 20 nanometers to 20 micrometers. The hollow calcium carbonate microspheres according to claim 13, wherein the hollow calcium carbonate microspheres comprise calcium carbonate of vaterite crystal form.

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