METHOD FOR PRODUCING CALCIUM CARBONATE BY UTILIZING SEA WATER AND BURNED SHELLS, AND CALCIUM CARBONATE AND CALCIUM AGENT PRODUCED THEREBY

Abstract

There is provided a method for producing calcium carbonate by utilizing seawater and calcinated shells, and calcium carbonate and a calcium agent produced thereby. The method for producing calcium carbonate includes: eluting calcium by mixing calcinated shells, seawater, and sugar; and generating calcium carbonate by injecting carbon dioxide into the calcium eluate generated in the eluting calcium. The calcium agent includes vaterite-type calcium carbonate.

Claims

1. A method for producing calcium carbonate, the method comprising: a first step of eluting calcium by mixing calcined shells, seawater, and sugar; and a second step of producing calcium carbonate by injecting carbon dioxide into the calcium eluate produced in the first step.

2. The method for producing calcium carbonate according to claim 1, wherein when the solid-liquid ratio of the sugar and seawater added in the first step is 1:80 (g:mL) or less, the vaterite content of calcium carbonate is 100%.

3. The method for producing calcium carbonate according to claim 1, wherein the amount of elution of calcium is increased in the first step.

4. The method for producing calcium carbonate according to claim 1, wherein the sugar is sucrose.

5. The method for producing calcium carbonate according to claim 1, wherein when the solid-liquid ratio of the sugar and seawater added in the first step is 1:5000 to 1:500 (g:mL), the vaterite crystal has a particle size of 600 to 800 nm.

6. The method for producing calcium carbonate according to claim 1, wherein the pH after the completion of the first step is 12.5 or higher.

7. The method for producing calcium carbonate according to claim 1, wherein the second step comprises applying ultrasonic waves to the solution into which carbon dioxide has been injected.

8. The method for producing calcium carbonate according to claim 1, wherein the production method further comprises a step of stirring the produced calcium carbonate at room temperature after the carbonation reaction of the second step.

9. The method for producing calcium carbonate according to claim 8, wherein the step of stirring is performed for 60 minutes or less.

10. The method for producing calcium carbonate according to claim 9, wherein the particle size of the calcium carbonate produced by the production method is in a range of 600 nm to 800 nm.

11. The method for producing calcium carbonate according to claim 1, wherein the calcium carbonate produced by the production method has porosity.

12. A calcium agent comprising vaterite-type calcium carbonate.

13. The calcium agent according to claim 12, wherein the calcium agent is produced by a method for producing calcium carbonate, the method comprising: a first step of eluting calcium by mixing calcined shells, seawater, and sugar; and a second step of producing calcium carbonate by injecting carbon dioxide into the calcium eluate produced in the first step.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] FIG. 1 shows a schematic flowchart of the method for producing calcium carbonate recited in the present invention.

[0044] FIG. 2 shows a schematic diagram of a reactor for the carbonation reaction of the second step.

[0045] FIG. 3 shows an XRD graph of calcium carbonate with respect to the amount of sugar added in the first step.

[0046] FIG. 4 shows an FT-IR graph of calcium carbonate with respect to the amount of sugar added in the first step.

[0047] FIG. 5 shows an SEM image of calcium carbonate particles produced when the amount of sugar added in the first step was 2.34 mM.

[0048] FIG. 6 shows a graph about the vaterite particle size change with respect to the stirring speed, and a graph about the vaterite particle size change with respect to the ultrasonic intensity, respectively.

[0049] FIG. 7 shows a graph about the vaterite particle size change with respect to the stirring speed and the ultrasonic intensity when stirring and ultrasonic waves were used at the same time.

[0050] FIG. 8 shows a table representing the particle size of calcium carbonate produced under different aging conditions after carbonation.

[0051] FIG. 9 shows a graph of the relative activity of ALP with respect to the calcium carbonate particle size and crystalline form depending on the amount of injected calcium carbonate.

[0052] FIG. 10 shows a graph about the solubility with respect to the calcium carbonate particle size and crystalline form depending on the pH of the surrounding environment.

DETAILED DESCRIPTION

[0053] Hereinafter, Examples of the present invention will be described in detail. Since the present invention can have various changes and can have various forms, specific embodiments are illustrated in the drawings and described in detail in the text. However, the Examples are not intended to limit the present invention to the specific forms of disclosure, and they should be understood to include all modifications, equivalents and substitutes included in the principles and technical scope of the present invention.

[0054] Terms such as first, second and so on may be used to describe various features, but the features should not be limited by the terms. The terms are used only for the purpose of distinguishing one feature from another.

[0055] Throughout the specification, when a part “includes” or “contains” a certain feature, it means that other features may be further included unless otherwise defined. In addition, the singular expression used in the present Specification includes the plural expression unless the context clearly dictates otherwise.

[0056] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs, and unless explicitly defined in the present application, the terms are not understood in an ideal or overly formal sense.

[0057] Hereinafter, the method for producing calcium carbonate utilizing seawater and calcinated shells recited in the present invention, in particular, the method for producing vaterite calcium carbonate, will be described in more detail with reference to the drawings of the present invention.

[0058] FIG. 1 shows a schematic flowchart of the method for producing calcium carbonate recited in the present invention, in particular, the method for producing vaterite calcium carbonate.

[0059] As shown in FIG. 1, the method for producing calcium carbonate of the present invention comprises a first step of eluting calcium by mixing calcinated shells, seawater, and sugar; and a second step of producing calcium carbonate by injecting carbon dioxide into the calcium eluate produced in the first step.

[0060] The shell of the first step is a source of calcium carbonate which is a raw material of the manufacturing method, and as the types of the shell, shells of oysters, mussels, shellfish, short-neck clams, or abalones may be used.

[0061] The sugar in the first step may be sucrose, glucose, lactose, starch, or fructose, preferably, sucrose. In the manufacturing method of an Example for the experimental demonstration of the present invention, sucrose was treated in the first step.

[0062] The amount of sugar added in the first step is 0.58 mM to 5.84 mM, preferably, 2.34 mM. In an Example of the present invention, when the amount of added sucrose was 2.34 mM, the crystal form of calcium carbonate was 100% vaterite, and the size of the synthesized particles was 683 nm.

[0063] The pH after completion of the first step is preferably 12.5 or higher.

[0064] FIG. 2 below shows a schematic diagram of a reactor in which carbon dioxide is injected, ultrasonic waves are applied, stirring is performed, and pH is measured for the carbonation reaction of the second step.

[0065] To reduce the particle size of vaterite produced through the carbonation reaction of the second step, ultrasonic waves were additionally applied during the carbonation reaction of the second step.

[0066] The carbon dioxide injection was discontinued, and the produced calcium carbonate was stirred at 200 rpm for 60 minutes, preferably, for 10 minutes.

[0067] The calcium carbonate obtained from the process above may have a particle size in a range of 600 nm to 800 nm, preferably, 683 nm.

[0068] As shown in FIG. 5 below, the calcium carbonate obtained from the process above may have porosity through which the calcium carbonate of the present invention may have high solubility and absorption rate.

[0069] Additionally, the calcium carbonate obtained from the process above can be used as a calcium agent.

[0070] A test of the effective ingredient of the calcium agent was conducted by measuring the relative activity of ALP with respect to the calcium carbonate particle size depending on the amount of injected calcium carbonate, and by measuring the solubility according to the calcium carbonate particle size depending on the pH of the surrounding environment. The test is described more specifically in the Examples and Evaluation Examples below.

EXAMPLES

Examples Depending on the Sugar Content

[0071] In order to investigate the change of calcium carbonate depending on the amount of the sugar added in the first step, Examples 1 to 12 and Comparative Examples were prepared as described below by adding sucrose in different amounts.

Example 1: Solid-Liquid Ratio of Sugar and Seawater 1:5000 (g:mL)

[0072] In 100 mL of seawater, sucrose was mixed and dissolved so that the solid-liquid ratio of sugar and seawater became 1:5000, and then the seawater in which sucrose was dissolved and the calcinated CaO were mixed so that the solid-liquid ratio became 1:50. After that, the resulting mixture was stirred at 25° C. at 200 rpm for 1 hour, and then filtered through a 0.45 .Math.m membrane filter (MCE04547A, HYUNDAI Micro Co.).

[0073] The calcium eluate filtered through the process above was poured into a beaker and stirred at 400 rpm using a stirrer (HS-30D, WISD), while 99.9% carbon dioxide was injected at a flow rate of 0.15 L/min by a gas disperser (Sigma). A gas flow meter and a flow regulator (TSM-D220, MKP) were used to control the flow rate to be constant, and when ultrasound waves were required, ultrasound waves were applied at a 30% intensity by using a Branson SFX 550 model with a ¼ diameter tip. Ultrasound waves were applied in advance before injecting carbon dioxide. The carbonation reaction was stopped by discontinuing the injection of carbon dioxide gas, and aging was performed by stirring at 200 rpm for 10 minutes. The generated solid was filtered through a 0.1 .Math.m membrane filter (A010A047A, Toyo Roshi Kaisha) and dried at 60° C. for 4 hours.

Example 2: Solid-Liquid Ratio of Sugar and Seawater 1:2500 (g:mL)

[0074] Calcium carbonate was produced in the same manner as in Example 1, except that sucrose was added at a solid-liquid ratio of 1:2500 between sugar and seawater.

Example 3: Solid-Liquid Ratio of Sugar and Seawater 1:1250 (g:mL)

[0075] Calcium carbonate was produced in the same manner as in Example 1, except that sucrose was added at a solid-liquid ratio of 1:1250 between sugar and seawater.

Example 4: Solid-Liquid Ratio of Sugar and Seawater 1:625 (g:mL)

[0076] Calcium carbonate was produced in the same manner as in Example 1, except that sucrose was added at a solid-liquid ratio of 1:625 between sugar and seawater.

Example 5: Solid-Liquid Ratio of Sugar and Seawater 1:312 (g:mL)

[0077] Calcium carbonate was produced in the same manner as in Example 1, except that sucrose was added at a solid-liquid ratio of 1:312 between sugar and seawater.

Example 6: Solid-Liquid Ratio of Sugar and Seawater 1:156 (g:mL)

[0078] Calcium carbonate was produced in the same manner as in Example 1, except that sucrose was added at a solid-liquid ratio of 1:156 between sugar and seawater.

Example 7: Solid-Liquid Ratio of Sugar and Seawater 1:78 (g:mL)

[0079] Calcium carbonate was produced in the same manner as in Example 1, except that sucrose was added at a solid-liquid ratio of 1:78 between sugar and seawater.

Example 8: Solid-Liquid Ratio of Sugar and Seawater 1:39 (g:mL)

[0080] Calcium carbonate was produced in the same manner as in Example 1, except that sucrose was added at a solid-liquid ratio of 1:39 between sugar and seawater.

Example 9: Solid-Liquid Ratio of Sugar and Seawater 1:27 (g:mL)

[0081] Calcium carbonate was produced in the same manner as in Example 1, except that sucrose was added at a solid-liquid ratio of 1:27 between sugar and seawater.

Example 10: Solid-Liquid Ratio of Sugar and Seawater 1:19 (g:mL)

[0082] Calcium carbonate was produced in the same manner as in Example 1, except that sucrose was added at a solid-liquid ratio of 1:19 between sugar and seawater.

Example 11: Solid-Liquid Ratio of Sugar and Seawater 1:14 (g:mL)

[0083] Calcium carbonate was produced in the same manner as in Example 1, except that sucrose was added at a solid-liquid ratio of 1:14 between sugar and seawater.

Comparative Example: No Sucrose Added

[0084] Calcium carbonate was produced in the same manner as in Example 1, except that no sucrose was added.

EVALUATION EXAMPLE

1. Change of Calcium Carbonate Depending on the Production Method

[0085] The calcium concentration was measured using an atomic absorption spectrophotometer (AAS, AA200, Perkin Elmer), and the pH was measured by using a pH meter (Orion star 211, Thermo).

[0086] In addition, the particle size of calcium carbonate was measured using a laser scattering particle size analyzer (Mastersizer 3000, Malvern).

Change of the Amount of Calcium Elution Depending on the Sugar Content

[0087] First, in order to investigate the total calcium concentration of the calcium eluate after the first step, experiments were prepared in an environment of various solid-liquid ratios between sugars and seawater. As the amount of added sucrose was increased, the concentration of calcium was increased. When the amount of added sucrose was the highest, the calcium concentration was 7125 mg/L, and when no sucrose was added, it was 3100 mg/L.

[0088] Table 1 below shows the pH and calcium concentration of the calcium eluate according to the change of the solid-liquid ratio between sugar and seawater in the first step.

[0089] Changes in the pH and calcium concentration of the calcium eluate according to the change in the ratio between sucrose and seawater

TABLE-US-00001 Sucrose: seawater (g:mL) Amount of added sucrose (mM) pH Total calcium concentration (mg/L) Comparative Example 0 0 11.7 3100 Example 1 1:5000 0.58 12.5 3402 Example 2 1:2500 1.17 12.6 3750 Example 3 1:1250 2.34 12.7 4000 Example 4 1:625 4.67 12.7 4025 Example 5 1:312 9.35 12.9 4100 Example 6 1:156 18.70 12.9 4842 Example 7 1:78 37.51 12.6 5675 Example 8 1:39 75.02 12.5 6390 Example 9 1:27 107.48 12.5 6425 Example 10 1:19 150.04 12.5 6503 Example 11 1:14 214.99 12.4 7125

[0090] As shown in Table 1 above, the pH of the calcium eluate was increased and then decreased as the amount of added sucrose was increased. When the solid-liquid ratio between sugar and seawater was 1:312 or less, as the amount of added sucrose was increased, more calcium sources were dissolved and thereby increasing the pH. When the solid-liquid ratio between sucrose and seawater was 1:312, calcium particles were dissolved in the aqueous sucrose solution, and so the pH of the calcium eluate was the highest, 12.9.

Change of the Crystalline Form of Calcium Carbonate Depending on the Sugar Content

[0091] In order to investigate the change of calcium carbonate depending on the amount of sugar added in the first step, X-ray diffraction analysis (XRD, Smart lab, Rigaku) and Fourier transform infrared spectroscopy (FTIR, Thermo Fisher, iS50) were performed.

[0092] Table 2 below shows the changes in the size and shape of the produced calcium carbonate particles according to the change in the amount of added sucrose.

[0093] Change of the size and shape of the produced calcium carbonate particles according to the change in the amount of added sucrose.

TABLE-US-00002 Sucrose: seawater (g: mL) Amount of added sucrose (mM) Median of particle size (D50, um) Type of CaCO.sub.3 Vaterite (%) Calcite (%) Comparative Example 0 0 0.870 100 0 Example 1 1:5000 0.58 0.765 100 0 Example 2 1:2500 1.17 0.732 100 0 Example 3 1:1250 2.34 0.683 100 0 Example 4 1:625 4.67 0.759 100 0 Example 5 1:312 9.35 0.816 100 0 Example 6 1:156 18.70 0.844 100 0 Example 7 1:78 37.51 0.927 100 0 Example 8 1:39 75.02 0.965 97 3 Example 9 1:27 107.48 1.07 97 3 Example 10 1:19 150.04 1.09 96 4 Example 11 1:14 214.99 1.27 92 8

[0094] As shown in Table 2, the particle size of the produced calcium carbonate was the smallest when the solid-liquid ratio between sugar and seawater was 1:1250, that is, when the amount of added sugar was 2.34 mM. In addition, when the solid-liquid ratio between sucrose and seawater was 1:80 or lower, 100% vaterite was produced, whereas when it was higher than that, some calcite was produced.

[0095] In addition, sucrose was added to calcium carbonate as in (a) Example 11, (b) Example 10, (c) Example 9, (d) Example 8, (e) Example 7, or (f) Example 3, respectively, to analyze the difference of the calcium carbonate depending on the sugar added in the first step.

[0096] FIG. 3 depicts an XRD graph of the calcium carbonate with respect to the amount of sugar added in the first step. In Examples 8-11 where sucrose was added in amounts of (a) 215 mM, (b) 150 mM, (c) 107 mM, or (d) 75 mM, a calcite peak (indicated by C at the top of the peak) was found between the vaterite peaks (indicated by V at the top of the peak). On the other hand, in Example 7 ((e) 38 mM) or Example 3 ((f) 2.34 mM) where a smaller amount of sucrose was added, no calcite peak was observed on the XRD graph.

[0097] In addition, FIG. 4 shows an FT-IR graph of the calcium carbonate with respect to the amount of sugar added in the first step. FT-IR analysis was performed by using the same samples as in FIG. 3, and the results showed that the calcite peak (indicated by C at the bottom of the peak) disappeared as the amount of added sucrose was reduced as in FIG. 3.

[0098] This demonstrates that the addition of excessive sugar increases the calcite crystal form of calcium carbonate, making it unsuitable for the production of calcium carbonate including a large amount of vaterite crystal form which has excellent solubility and absorption rate.

[0099] FIG. 5 shows a SEM image of calcium carbonate particles produced when the amount of sugar added in the first step was 2.34 Mm. When the amount of added sugar was 2.34 Mm, the calcium carbonate particle size was about 0.68 to 0.69 .Math.m, indicating that calcium carbonate having an ideally small size was produced, as shown in Table 2 above.

Change of the Calcium Carbonate Depending on the Ultrasonic Intensity and Stirring Speed

[0100] In order to investigate the change of the calcium carbonate depending on the ultrasonic intensity and the stirring speed of the second step, an experiment was performed by adjusting the ultrasonic intensity and the stirring speed of the second step to the ranges of 0 to 70% and 0 to 600 rpm, respectively.

[0101] Table 3 below shows the particle size and shape of calcium carbonate produced under various ultrasonic intensity and stirring speed conditions. FIG. 6 shows graphs illustrating the change of the vaterite particle size with respect to the stirring speed and the change of the vaterite particle size with respect to the ultrasonic intensity. FIG. 7 shows a graph illustrating the change of the vaterite particle size with respect to the stirring speed and the ultrasonic intensity when stirring and ultrasonic waves were used at the same time.

[0102] Comparison of the particle size and shape of calcium carbonate particles produced under various ultrasonic intensity and stirring speed conditions

TABLE-US-00003 Ultrasonic intensity (%) RPM Median of particle size (D50, um) Type of CaCO.sub.3 Vaterite (%) Calcite (%) 0 0 5.57 93 7 200 4.47 95 5 400 4.29 97 3 600 4.26 97 3 10 0 1.48 100 0 200 1.12 400 0.897 600 0.866 20 0 1.04 100 0 200 0.892 400 0.806 600 0.775 30 0 0.897 100 0 200 0.874 400 0.683 600 0.694 50 0 0.793 100 0 200 0.783 400 0.803 600 0.817 70 0 0.743 100 0 200 0.717 400 0.804 600 0.809

[0103] As shown in Table 3, FIG. 6, and FIG. 7 above, when the ultrasonic intensity and the stirring speed were 30% and 400 rpm, respectively, the particle size of the produced vaterite was the smallest as 683 nm. At a stirring speed of 200 rpm or lower, the stronger the ultrasonic intensity, the smaller the particle size. However, from a stirring speed higher than that, an offset effect with respect to the strong ultrasonic waves was generated. The vaterite particle size was simultaneously affected by stirring and ultrasonic waves. When the ultrasonic intensity was 10% and 20%, the smallest vaterite was formed at a stirring speed of 600 rpm. When the ultrasonic intensity was 30%, the vaterite particle size was the smallest at a stirring speed of 400 rpm. When the ultrasonic intensity was 70%, the vaterite particle size was the smallest at a stirring speed of 200 rpm. As previously stated, the smallest nano-sized vaterite was formed under the conditions of the ultrasonic intensity of 30% and the stirring speed of 400, at which the mutual offset effect was minimized and the advantages of both ultrasonic waves and stirring were maximized.

Change of Particle Size and Shape of the Produced Calcium Carbonate Depending on the Sugar Content Without Applying Ultrasonic Waves

[0104] Item above showed that the ultrasonic intensity of the second stage affects the calcium carbonate. Therefore, in order to investigate the change in calcium carbonate depending on the sugar content without applying ultrasonic waves, an experiment was performed by setting the stirring speed to 200 rpm without using ultrasonic waves in the second step. A method for producing calcium carbonate to which the process of applying ultrasonic waves is not applied is described below.

[0105] After mixing and dissolving sucrose in 100 mL of seawater so that the solid-liquid ratio between sugar and seawater became 0 to 1:5000, the seawater in which sucrose was dissolved and the calcinated CaO were mixed so that the solid-liquid ratio became 1:50. The combinations of solutions used in this evaluation example were the same as those described in Table 1 above. Then, the resulting mixture was stirred at 25° C. at 200 rpm for 1 hour, and then filtered through a 0.45 .Math.m membrane filter (MCE04547A, HYUNDAI Micro Co.).

[0106] The calcium eluate filtered through the process above was poured into a beaker and stirred at 200 rpm by using a stirrer (HS-30D, WISD), while 99.9% carbon dioxide was injected at a flow rate of 0.15 L/min by using a gas disperser (Sigma). A gas flow meter and a flow regulator (TSM-D220, MKP) were used to control the flow rate to be constant. The carbonation reaction was stopped by discontinuing the injection of carbon dioxide gas, and aging was performed by stirring at 200 rpm for 10 minutes. The generated solid was filtered through a 0.1 .Math.m membrane filter (A010A047A, Toyo Roshi Kaisha) and dried at 60° C. for 4 hours.

[0107] Table 4 below shows the particle size and shape of the calcium carbonate produced in the absence of ultrasonic wave application.

[0108] Change in particle size and shape of the produced calcium carbonate according to the change in the amount of added sucrose

TABLE-US-00004 Elution conditions Results of carbonation Amount of added sucrose (mM) Calcium: sucrose molar ratio (mol:mol) Median of calcium carbonate particle size (D.sub.50 (.Math.m) ) Type of CaCO.sub.3 (%) Vaterite Calcite 0 0 4.09 70.5 29.5 0.58 1 : 0.01 4.12 82.1 17.9 1.17 1 : 0.01 4.03 85.4 14.6 2.34 1 : 0.02 3.57 90.2 9.8 4.67 1 : 0.05 3.43 91.2 8.8 9.35 1 : 0.09 3.22 92.7 7.3 18.70 1 : 0.16 3.12 93.2 6.8 37.51 1 : 0.26 2.57 94.5 5.5 75.02 1 : 0.47 2.41 94.6 5.4 107.48 1 : 0.67 2.65 72.4 27.6 150.04 1 : 0.92 3.15 70.2 29.8 214.99 1 : 1.20 3.28 82.5 17.5

[0109] As shown in Table 4 above, as the amount of added sucrose was increased, the vaterite content of the produced calcium carbonate tended to increase, and the particle size of the produced calcium carbonate gradually decreased and tended to increase from the time when the ratio of calcium to sucrose became approximately 2:1, that is, after the amount of added sucrose was 75.02 mM. In this case, the median of the calcium carbonate particle size was the smallest as 2.41 .Math.m, and the vaterite content was also the highest as 94.6%. On the other hand, in the case of Table 4 where no ultrasonic wave was applied, 100% vaterite calcium carbonate was not formed, indicating that the application of ultrasonic waves is necessary to produce 100% vaterite calcium carbonate, which has a better effect.

[0110] Therefore, items (3) and (4) above showed that the ultrasonic intensity of the second step also significantly affects the production of 100% vaterite calcium carbonate.

* Change of Calcium Carbonate Depending on the Aging Step

[0111] FIG. 8 shows a graph illustrating the particle size of calcium carbonate produced under different aging conditions after carbonation. As shown in FIG. 8, after the second step, when the calcium carbonate was left in the solution to which carbon dioxide injection was discontinued, recrystallization of vaterite did not occur under any conditions, and 100% vaterite form was maintained for 120 minutes. In addition, the particle size of vaterite was the smallest when stirring was performed at 200 rpm for 60 minutes or less, preferably for 2 to 20 minutes, and more preferably for 10 minutes, and the particle size was decreased by about 200 nm when the solution was filtered immediately without a step of stirring. Therefore, even when all conditions of the carbonation step are optimal, an appropriate aging step must be carried out in order to generate smaller nano-sized vaterite.

2. Analysis of Efficacy of Vaterite Calcium Carbonate

[0112] In order to investigate the efficacy of the calcium carbonate produced by the production method of the present invention in the body, the difference of the efficacy of calcium carbonate was analyzed by differently adjusting the particle size and crystalline form of calcium carbonate as shown in Table 5 below. Examples V1 to V4 used in the analysis below are examples of calcium carbonate of the vaterite crystalline form, wherein the calcium carbonate particle size of V1 was 9.18 .Math.m, the calcium carbonate particle size of V2 was 4.17 .Math.m, the calcium carbonate particle size of V3 was 1.33 .Math.m, and the calcium carbonate particle size of V4 was 0.85 .Math.m, as the calcium carbonate was adjusted to have different particle sizes. The particle size of the vaterite calcium carbonate claimed in the present invention is most similar to V4. In addition, examples C1 to C4 are examples of calcium carbonate of the calcite crystalline form for comparison with the calcium carbonate of the vaterite crystalline form. As in the case of vaterite, the calcium carbonate particle size of C1 was 11.4 um, the calcium carbonate particle size of C2 was 2.83 .Math.m, the calcium carbonate particle size of C3 was 1.54 .Math.m, and the calcium carbonate particle size of C4 was 0.657 .Math.m. In addition, biomarkers that are related with the efficacy of calcium agent were selected, and an in vitro experiment was performed by measuring the calcium solubility and the cytotoxicity and ALP activity in osteoblast MG-63 to analyze examples of V1 to V4 and C1 to C4.

TABLE-US-00005 No. Type of calcium carbonate Calcium carbonate particle size (D50, .Math.m) V1 Vaterite 9.18 V2 Vaterite 4.17 V3 Vaterite 1.33 V4 Vaterite 0.85 C1 Calcite 11.4 C2 Calcite 2.83 C3 Calcite 1.54 C4 Calcite 0.657

ALP Activity Measurement

[0113] FIG. 9 shows a graph about the relative activity of ALP with respect to the calcium carbonate particle size depending on the amount of injected calcium carbonate.

[0114] Alkaline phosphatase (ALP) is the most commonly used bone formation marker in clinical practices and is a glycoprotein enzyme

##STR00010##

which is generated during osteoblastic bone formation and part of which is secreted into the blood. Therefore, when osteoblasts are actively accumulated in the bone matrix, the expression of ALP is increased, and its concentration is increased along with the increase of the bone activity.

[0115] In order to measure the relative activity of the ALP, the cells were treated with the calcium carbonate produced differently by the production method of the present invention at concentrations of 1, 5, and 10 mM, respectively. One-way ANOVA was used for the analysis after the measurement.

[0116] First, a 6-well plate in which MG-63 cells were cultured was left overnight to 3.5 × 10.sup.5 cells, treated with the test substances at different concentrations, and the cultured for 24 hours. The cells were washed twice with PBS, and were detached by using a cell scraper (SPL, 90030). After that, the cells were precipitated at 1,200 rpm for 1 minute, and the supernatant was removed. Thereafter, 100 .Math.l of the ALP buffer included in the ALP kit (alkaline phosphatase assay kit, ab83369) was added and homogenized. The cell homogenate was centrifuged at 10,000 × g at 4° C. for 15 minutes to separate the supernatant, and then the intracellular ALP activity was measured by using an ALP kit through a microplate reader.

[0117] In all the examples of V1 to V4 and C1 to C4, it was confirmed that the relative ALP activity was increased as the concentration of the treated calcium carbonate was increased. At this time, the ALP was increased depending on the concentration of calcium carbonate. Therefore, it was confirmed that the treatment with the calcium carbonate of the present invention increases the ALP activity of cells.

Solubility Measurement

[0118] FIG. 10 shows a graph about the solubility with respect to the calcium carbonate particle size depending on the pH of the surrounding environment.

[0119] In order to have excellent efficacy when a calcium agent is used as an oral calcium agent, the absorption rate must be good at a low pH, which is a gastric acid environment in the body. Therefore, to prove this, the solubility was measured in the environment of pH 2, pH 8, and pH 14 in respective examples. One-way ANOVA was used for the analysis after the measurement.

[0120] First, 0.5 mL of the sample, 0.5 mL of 10 mM calcium chloride, and 1.0 mL of 20 mM phosphate buffer (pH 8) were mixed, and then subject to a reaction at 37° C. for 2 hours. Thereafter, centrifugation was performed at 25° C. at 2,000 × g for 30 minutes. A calcium colorimetric analysis (OCPC method) was performed to measure absorbance at a wavelength of 575 nm, and based on the results, the calcium solubility was calculated by using the formula below.

[00001]$\begin{array}{l}\text{Calcium solubility}\left(\%\right)=\left(\text{calcium concentration in the supernatant}/\right)\\ \left(\text{total calcium concentration in the solution}\right)\times 100\end{array}$

[0121] In all the examples, the solubility was significantly higher in an acidic environment of pH 2, and in particular, the highest solubility was found in V3 and V4 where the crystalline form was vaterite and the particle size was small. The results showed that the calcium carbonate produced through the present invention is easy to use as an oral calcium agent, because of its high solubility in the gastric acid environment.

[0122] As described above, the present invention has been mainly described with reference to preferable Examples, but those of ordinary skill in the art to which the present invention pertains may understand that the present invention may be variously modified and changed without departing from the principle and scope of the present invention as recited in the following claims.