A porous calcium carbonate with high specific surface area and its preparation method and application

Abstract

The present invention relates to the technical field of calcium carbonate preparation, specifically disclosing a method for preparing porous calcium carbonate with a high specific surface area. The method comprises: adding silicon dioxide to a sodium citrate solution and stirring to obtain solution A; adding polyethylene glycol to solution A, stirring at 70-85°C for 60-90 minutes, and cooling to obtain solution B; adding sodium bicarbonate to solution B and stirring to adjust the pH of the solution to 13; adding calcium chloride under ultrasound and mixing under ultrasound for 5-10 minutes; adding the obtained solution to a reactor, performing a hydrothermal reaction at 160-180°C for 5-7 hours, and centrifuging to obtain a solid; adding the solid to a sodium hydroxide solution, stirring and centrifuging at 80-95°C to obtain a precipitate; and washing and drying the precipitate to obtain porous calcium carbonate. The method for preparing porous calcium carbonate with a high specific surface area of ​​the present invention provides a porous calcium carbonate having a hollow structure, a high specific surface area, and good stability. The raw materials used in the preparation are all relatively inexpensive, commonly used, green, and non-toxic reagents, and the preparation process is simple.

Description

Technical Field

[0001] The present invention relates to the technical field of calcium carbonate preparation, in particular to a porous calcium carbonate with a high specific surface area and a preparation method and application thereof. Background Art

[0002] Calcium carbonate, a naturally occurring mineral material, exists primarily in the forms of limestone, marble, and chalk. Its anhydrous crystalline forms primarily include calcite, aragonite, and vaterite. Calcite exhibits the best thermal stability, while vaterite has the worst. With the continuous advancement of science and technology, research on porous calcium carbonate has rapidly developed over the past decade. Due to its numerous advantages, including large specific surface area, stable properties, and controllable structure, it has found widespread application in papermaking, biomacromolecule loading, sustained drug release, superhydrophobic surface construction, ceramics, bone repair, and the removal of heavy metal ions from soil.

[0003] At present, the application performance of commercial calcium carbonate is poor, and the specific surface area is relatively small, which cannot meet the application requirements. Therefore, it is necessary to modify calcium carbonate to obtain porous calcium carbonate, obtain a large specific surface area, and obtain better performance; the morphology, performance and use of porous calcium carbonate are closely related to its preparation method and process. For the production of porous calcium carbonate, the carbonization method is mainly used in China. The main principle is to pass carbon dioxide into calcium hydroxide solution for carbonization to prepare porous calcium carbonate. After development, a variety of relatively mature production processes such as intermittent bubbling, continuous bubbling, and continuous spraying have been formed; the porous calcium carbonate produced by the carbonization method has the advantages of large specific surface area, low oil absorption value, and stable product performance, but the initial Ca in the preparation process of this method is 2+ The disadvantages include low concentration, low production efficiency, high equipment requirements, and high process energy consumption. The template method for preparing porous calcium carbonate has the advantages of being simple, not requiring special solvents, and having mild preparation conditions. Dai Hongxing et al. (Dai Hongxing, Deng Jiguang, Zhang Lei et al., Synthesis of porous magnesium oxide, calcium oxide, and calcium carbonate using soft and hard templates [J], Inorganic Salt Industry, 2011, 43(5): 18-21) studied the porous calcium carbonate prepared by hydrothermal treatment at 240°C for 72 hours using polyethylene glycol (PEG) as a soft template. The result showed that the porous calcium carbonate had a high specific surface area, but was lower than the specific surface area of ​​calcium carbonate prepared by the currently disclosed CO2 bubbling technology. Therefore, a method for preparing porous calcium carbonate with a simple process and high specific surface area is studied to improve its specific surface area and stability, which is conducive to improving the application performance and application scenarios of porous calcium carbonate. Summary of the Invention

[0004] In view of the above shortcomings, the present invention provides a method for preparing porous calcium carbonate with a high specific surface area, which can improve the specific surface area and stability of porous calcium carbonate. The specific technical solution is as follows:

[0005] A method for preparing porous calcium carbonate with a high specific surface area comprises the following steps:

[0006] (1) adding silicon dioxide to a sodium citrate solution and stirring to obtain a solution A;

[0007] (2) Add polyethylene glycol to solution A, stir at 70-85°C for 60-90 minutes, and cool to obtain solution B;

[0008] (3) Sodium bicarbonate was added to solution B and stirred to mix thoroughly. The pH of the solution was adjusted to 13. Calcium chloride was added under ultrasonication and mixed thoroughly for 5 to 10 minutes.

[0009] (4) adding the solution obtained in step (3) into a reactor, hydrothermally reacting at 160-180° C. for 5-7 h, and removing the supernatant after centrifugation to obtain a solid;

[0010] (5) adding the solid obtained in step (4) to a sodium hydroxide solution, stirring at 80-95° C. for 3-4 hours, centrifuging, and removing the supernatant to obtain a precipitate; washing and drying the precipitate to obtain porous calcium carbonate.

[0011] Preferably, in the above-mentioned method for preparing porous calcium carbonate with a high specific surface area, the mass ratio of the silicon dioxide to the polyethylene glycol is 0.3:0.5-8.

[0012] Preferably, in the above-mentioned method for preparing porous calcium carbonate with a high specific surface area, the molecular weight of the polyethylene glycol is 200 to 10,000.

[0013] Preferably, in the above-mentioned method for preparing porous calcium carbonate with a high specific surface area, the molar ratio of sodium citrate, sodium bicarbonate and calcium chloride is 1:1.4-1.6:1.4-1.6.

[0014] Preferably, in the above-mentioned method for preparing porous calcium carbonate with a high specific surface area, the mass of the silicon dioxide is 1.1 to 1.3 times the mass of sodium bicarbonate.

[0015] Preferably, in the above-mentioned method for preparing porous calcium carbonate with a high specific surface area, the concentration of the sodium citrate solution is 0.018 to 0.022 mol / L.

[0016] Preferably, in the above-mentioned method for preparing porous calcium carbonate with a high specific surface area, in step (3), sodium hydroxide solution is used to adjust the pH.

[0017] Preferably, in the above-mentioned method for preparing porous calcium carbonate with a high specific surface area, in step (4), the hydrothermal reaction is carried out at 170° C. for 6 hours.

[0018] Preferably, in the above-mentioned method for preparing porous calcium carbonate with a high specific surface area, in step (5), the precipitate is centrifugally washed with deionized water and ethanol for more than three times, and then dried at 80°C after washing.

[0019] The porous calcium carbonate is prepared by the above-mentioned preparation method of porous calcium carbonate with high specific surface area.

[0020] The above-mentioned porous calcium carbonate is used as an adsorbent or template.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The method for preparing porous calcium carbonate with a high specific surface area of ​​the present invention has the advantages of hollow structure, high specific surface area and good stability. The raw materials used in the preparation are all relatively low-priced, commonly used, green and non-toxic reagents, and the preparation process is simple.

[0023] 2. In the method for preparing porous calcium carbonate with a high specific surface area of ​​the present invention, PEG is used as a soft template to regulate the structure of the calcium carbonate, and nano-silica is used as a hard template on which calcium carbonate crystals grow, making the porous calcium carbonate skeleton structure more solid. After the silica is removed with sodium hydroxide, the hollow structure of the obtained calcium carbonate provides a larger surface area and a large channel capacity, thereby increasing the opportunity for the porous calcium carbonate to contact impurities in the environment, increasing the reaction area, improving its adsorption effect, and improving its application performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are some embodiments of the present invention, and those skilled in the art can derive other drawings based on these drawings without inventive effort.

[0025] Figure 1 XRD spectra of porous calcium carbonate prepared in Example 1, Example 4, Example 7 and Example 10 of the present invention;

[0026] Figure 2 N2 adsorption and desorption isotherms of calcium carbonate prepared in Examples 1 to 12 and Comparative Examples 1 to 4 of the present invention: (a) Examples 1 to 3 and Comparative Example 1; (b) Examples 4 to 6 and Comparative Example 2; (c) Examples 7 to 9 and Comparative Example 3; (d) Examples 10 to 12 and Comparative Example 4;

[0027] Figure 3The following are SEM images of calcium carbonate in the present invention: (a) Comparative Example 4; (b) Comparative Example 3; (c) Comparative Example 2; (d) Comparative Example 1; (e) Example 10; (f) Example 7; (g) Example 4; (g) Example 1; (i) commercial calcium carbonate.

[0028] Figure 4 XPS spectra of porous calcium carbonate prepared in Example 1, Example 4, Example 7 and Example 10 of the present invention: (a) scanning spectrum of porous calcium carbonate; (b) Ca 2p Narrow scan spectrum; (c) Si 2p Narrow scan spectrum. DETAILED DESCRIPTION

[0029] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited by the specific embodiments. Unless otherwise defined, all technical terms used hereinafter have the same meaning as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or can be prepared by existing methods.

[0030] Example 1

[0031] A method for preparing porous calcium carbonate with a high specific surface area comprises the following steps:

[0032] (1) Weigh 0.3 g SiO2 and prepare 1 mol / L sodium citrate solution, 5 mol / L NaOH solution, and 1 mol / L NaOH solution;

[0033] (2) Take 2 ml of 1 mol / L sodium citrate solution and 90 mL of deionized water, mix well, and then add weighed SiO2 to obtain solution A;

[0034] (3) After stirring solution A for 10 min, 0.5 g of polyethylene glycol PEG-200 (molecular weight 200) was added and stirred at 80°C for 60 min to obtain solution B to form a uniform template;

[0035] (4) After solution B is cooled to room temperature, 0.252 g of sodium bicarbonate (NaHCO3) is added and the pH is adjusted to 13 with 5 mol / L NaOH. 0.333 g of calcium chloride (CaCl2) is added under ultrasound and ultrasound is applied for 10 min until the mixture is uniformly mixed.

[0036] (5) The obtained solution was added to a reactor, and the reaction was carried out hydrothermally at 170°C for 6 h. After centrifugation, the supernatant was removed to obtain a solid;

[0037] (6) The obtained solid was added to 50 ml of 1 mol / L NaOH solution, stirred at 90°C for 3 h, and then centrifuged and the supernatant was removed to obtain a precipitate;

[0038] (7) The obtained precipitate is washed with deionized water and ethanol by centrifugation for more than three times, and then dried at 80°C. The solid obtained is collected to obtain porous calcium carbonate.

[0039] Example 2

[0040] A method for preparing porous calcium carbonate with a high specific surface area comprises the following steps:

[0041] (1) Weigh 0.3 g SiO2 and prepare 1 mol / L sodium citrate solution, 5 mol / L NaOH solution, and 1 mol / L NaOH solution;

[0042] (2) Take 2 ml of 1 mol / L sodium citrate solution and 90 mL of deionized water, mix well, and then add weighed SiO2 to obtain solution A;

[0043] (3) After stirring solution A for 10 min, 2 g of polyethylene glycol PEG-200 (molecular weight 200) was added and stirred at 80°C for 60 min to obtain solution B;

[0044] (4) After solution B is cooled to room temperature, 0.252 g of sodium bicarbonate (NaHCO3) is added and the pH is adjusted to 13 with 5 mol / L NaOH. 0.333 g of calcium chloride (CaCl2) is added under ultrasound and ultrasound is applied for 10 min until the mixture is uniformly mixed.

[0045] (5) The obtained solution was added to a reactor, and the reaction was carried out hydrothermally at 170°C for 6 h. After centrifugation, the supernatant was removed to obtain a solid;

[0046] (6) The obtained solid was added to 50 ml of 1 mol / L NaOH solution, stirred at 90°C for 3 h, and then centrifuged and the supernatant was removed to obtain a precipitate;

[0047] (7) The obtained precipitate is washed with deionized water and ethanol by centrifugation for more than three times, and then dried at 80°C. The solid obtained is collected to obtain porous calcium carbonate.

[0048] Example 3

[0049] The difference between this embodiment and embodiment 1 is that in step (3), the amount of polyethylene glycol PEG-200 added is 5 g; the other steps and parameters are the same as those in embodiment 1.

[0050] Example 4

[0051] The difference between this embodiment and embodiment 1 is that: in step (3), the molecular weight of polyethylene glycol is 400 (PEG-400), and the added amount is 0.5 g; the other steps and parameters are the same as those in embodiment 1.

[0052] Example 5

[0053] The difference between this embodiment and embodiment 1 is that: in step (3), the molecular weight of polyethylene glycol is 400 (PEG-400), and the added amount is 2 g; the other steps and parameters are the same as those in embodiment 1.

[0054] Example 6

[0055] The difference between this embodiment and embodiment 1 is that: in step (3), the molecular weight of polyethylene glycol is 400 (PEG-400) and the added amount is 5 g; the other steps and parameters are the same as those in embodiment 1.

[0056] Example 7

[0057] The difference between this embodiment and embodiment 1 is that: in step (3), the molecular weight of polyethylene glycol is 2000 (PEG-2000) and the added amount is 0.5 g; the other steps and parameters are the same as those in embodiment 1.

[0058] Example 8

[0059] The difference between this embodiment and embodiment 1 is that: in step (3), the molecular weight of polyethylene glycol is 2000 (PEG-2000) and the added amount is 2 g; the other steps and parameters are the same as those in embodiment 1.

[0060] Example 9

[0061] The difference between this embodiment and embodiment 1 is that: in step (3), the molecular weight of polyethylene glycol is 2000 (PEG-2000) and the added amount is 5 g; the other steps and parameters are the same as those in embodiment 1.

[0062] Example 10

[0063] The difference between this embodiment and embodiment 1 is that: in step (3), the molecular weight of polyethylene glycol is 10000 (PEG-10000), and the added amount is 0.5 g; the other steps and parameters are the same as those in embodiment 1.

[0064] Example 11

[0065] The difference between this embodiment and embodiment 1 is that: in step (3), the molecular weight of polyethylene glycol is 10000 (PEG-10000), and the added amount is 2 g; the other steps and parameters are the same as those in embodiment 1.

[0066] Example 12

[0067] The difference between this embodiment and embodiment 1 is that: in step (3), the molecular weight of polyethylene glycol is 10000 (PEG-10000), and the added amount is 5 g; the other steps and parameters are the same as those in embodiment 1.

[0068] Comparative Example 1

[0069] The difference between this embodiment and embodiment 1 is that in step (3), the amount of polyethylene glycol added is 10 g; the other steps and parameters are the same as those in embodiment 1.

[0070] Comparative Example 2

[0071] The difference between this embodiment and embodiment 1 is that: in step (3), the molecular weight of polyethylene glycol is 400 (PEG-400) and the added amount is 10 g; the other steps and parameters are the same as those in embodiment 1.

[0072] Comparative Example 3

[0073] The difference between this embodiment and embodiment 1 is that: in step (3), the molecular weight of polyethylene glycol is 2000 (PEG-2000) and the added amount is 10 g; the other steps and parameters are the same as those in embodiment 1.

[0074] Comparative Example 4

[0075] The difference between this embodiment and embodiment 1 is that: in step (3), the molecular weight of polyethylene glycol is 10000 (PEG-10000), and the added amount is 10 g; the other steps and parameters are the same as those in embodiment 1.

[0076] The porous calcium carbonate prepared in Example 1, Example 4, Example 7 and Example 10 was subjected to X-ray diffraction analysis, and the results are shown in FIG. Figure 1 . Figure 1 It can be seen that the characteristic peaks of the sample at 23.022°, 29.405°, 31.418°, 35.965°, 39.401°, 43.145°, 47.123° and 48.512° correspond to the calcite (012)(104)(006)(110)(113)(202)(024)(116) crystal planes. The XRD spectra of the samples synthesized in the presence of different molecular weights of PEG-200, PEG-400, PEG-2000 and PEG-10000 show basically consistent diffraction peak trends, and no other characteristic peaks appear, which proves that the prepared calcium carbonate crystal belongs to calcite type and has high purity.

[0077] The calcium carbonate prepared in Examples 1 to 12 and Comparative Examples 1 to 4 was subjected to N2 adsorption-desorption isotherm test and pore size test. The test method is: a high-performance specific surface area pore size analyzer (BSD-PS) was used to determine the specific surface area of ​​different samples. The test principle was the static capacity method, and the specific surface area was calculated using the BET multi-point method. A certain amount of sample was taken and ground into fine powder using an agate mortar. After loading, it was degassed at the interface of the degassing station for 180 minutes at a degassing temperature of 200°C. After completion, the nitrogen adsorption amount of the sample at different preset pressure points was measured at liquid nitrogen temperature, with N2 as the adsorbed gas and He as the carrier gas, to obtain the adsorption isotherm; the results are as follows: Figure 2 As shown in Table 1. According to the physical adsorption isotherm classification proposed by the International Union of Pure and Applied Chemistry (IUPAC), the adsorption curve and the desorption curve do not completely overlap at around P / P0=0.8, and the adsorption / desorption isotherm of porous calcium carbonate conforms to its type IV isotherm type, H4 hysteresis loop (IUPAC classification) ( Figure 2 Combined with the data in Table 1, it can be concluded that the pore size of the porous calcium carbonate prepared under hydrothermal conditions using polyethylene glycol / nanosilica as a template is roughly distributed between 20 and 35 nm, indicating that the modified calcium carbonate is a mesoporous material and its adsorption is mesoporous. In the reaction, PEG acts as a soft template to regulate the structure of the calcium carbonate, while nanosilica acts as a hard template on which calcium carbonate crystals grow, making the porous calcium carbonate skeleton more solid. After removing the silica with sodium hydroxide, the resulting hollow structure of the calcium carbonate provides a larger surface area and a large channel capacity, thereby increasing the opportunity for the porous calcium carbonate to come into contact with impurities in the environment and increasing the reaction area.

[0078] Table 1 Average pore diameter (nm) of porous calcium carbonate prepared by adding different PEG

[0079]

[0080] The specific surface area of ​​the calcium carbonate prepared in Examples 1 to 12 and Comparative Examples 1 to 4 was tested, and the results are shown in Table 2. The amount of PEG used has a greater effect on the specific surface area of ​​calcium carbonate. The porous calcium carbonate prepared in Example 10 (with 0.5 g of PEG-10000 added) has the largest specific surface area of ​​411.8299 m 2 / g, which is roughly the specific surface area of ​​commercial calcium carbonate, 1.6520m 2 The specific surface area of ​​the porous calcium carbonate prepared in Comparative Example 1 (adding 10 g of PEG-200) is the lowest, which is 28.2285 m 2 / g, but also the specific surface area of ​​commercial calcium carbonate is 1.6520m 2The above description shows that the specific surface area of ​​calcium carbonate prepared under hydrothermal conditions using polyethylene glycol / nanosilica as a template is significantly improved compared with that of commercial calcium carbonate.

[0081] Table 2 Specific surface area of ​​porous calcium carbonate prepared by adding different PEG (m 2 / g)

[0082]

[0083] The SEM images of the porous calcium carbonate prepared in Example 1, Example 4, Example 7 and Example 10 are shown in FIG. Figure 3 (h) to (e), SEM images of porous calcium carbonate prepared in Comparative Examples 1 to 4 are shown in Figure 3 (d)~(a), Figure 3 (i) is the SEM image of commercial calcium carbonate (analytical grade, Shanghai McLean Biochemical Technology Co., Ltd.). Figure 3 (i) It can be seen that the particles of commercial calcium carbonate are between 2μm, and no porous structure is observed on the surface, indicating that commercial calcium carbonate does not have a porous structure. Compared with the calcium carbonate sample prepared by the present invention, it can be clearly observed that the synthesized calcium carbonate has a very good pore structure, which is consistent with the specific surface area comparison results of commercial calcium carbonate and products obtained in the BET test. Using polyethylene glycol / nanosilica as a template, under hydrothermal conditions, silica acts as a hard template, and calcium carbonate crystals grow on its spherical structure. The size of the calcium carbonate particles formed will increase slightly, about 2.5 to 10μm, and the particle shape is close to spherical. After sodium hydroxide removes silica, calcium carbonate forms a hollow structure, showing a special morphology composed of a bonded lamellar structure, and as the amount of PEG added decreases, the pore structure composed of the lamellar structure on the surface of calcium carbonate becomes more obvious.

[0084] from Figure 4 It can be seen that the spectrum of the synthesized calcium carbonate has characteristic peaks of four target elements: C, O, Ca, and Si, indicating the presence of silicon in the sample calcium carbonate. Figure 4 (b) It can be seen that Ca 2p The peak envelope consists of a spin-orbit doublet: Ca 2p1 / 2 At 351.1 eV, Ca 2p 3 / 2 At 347.5 eV, the area ratio is 1:2, separated by about 3.6 eV, which is characteristic of calcium carbonate. 1s The characteristic peak of the binding energy is 531.2eV. After fitting analysis by the software Avantage, O 1sIt can be divided into three peaks, one at 531.4eV, which is the peak attributable to the CO bond; one at 532.9eV, which is the peak attributable to the Si-O bond; and one at 532.2eV, which is the peak attributable to the Si-O-Ca bond. Figure 4 (c) It can be seen that Si 2p The characteristic peak of the binding energy is about 102.2eV, and the Si 2p The characteristic peak has a binding energy of 103.3 eV, confirming it is not silica. The binding energy range for silicates is 101.5 to 103.5 eV, indicating that the silicon exists in the form of silicates (calcium silicate and sodium silicate). The three peaks of porous calcium carbonate are not consistent. The slight variation in binding energy is due to the varying amount of silicate retained during each wash. This inconsistent silicate content causes chemical shifts. PEG-200 has a silicon content of approximately 9.48%, while PEG-10000 has a silicon content of approximately 1.01%. Silicates form when silicate reacts with sodium hydroxide to form silicate radicals, which combine with free calcium and sodium ions. Silicates have a viscous texture and are insoluble in water and ethanol. Due to their insolubility in water and ethanol, they remain in the product during the centrifugal washing step, but their content is extremely low, with only the presence of silicon detected in XPS testing. This does not affect the performance and structure of the porous calcium carbonate. Subsequent washing steps can be performed to completely remove the silicates.

[0085] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many variations and modifications are possible in light of the foregoing teachings. The exemplary embodiments have been selected and described for the purpose of explaining the specific principles of the invention and their practical application, thereby enabling those skilled in the art to realize and utilize a variety of exemplary embodiments of the invention and various options and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for preparing porous calcium carbonate with a high specific surface area, characterized in that: The following steps are involved: (1) Add silicon dioxide to sodium citrate solution and stir to obtain solution A; (2) Add polyethylene glycol to solution A with a mass ratio of silicon dioxide to polyethylene glycol of 0.3:0.5-8, stir at 70-85°C for 60-90 min, and cool to obtain solution B; (3) Add sodium bicarbonate to solution B and stir to mix thoroughly. Adjust the pH of the solution to 13. Add calcium chloride under ultrasonic conditions and mix thoroughly under ultrasonic conditions for 5-10 minutes. (4) adding the solution obtained in step (3) into a reactor, hydrothermally reacting at 160-180°C for 5-7 h, and removing the supernatant after centrifugation to obtain a solid; (5) The solid obtained in step (4) is added to a sodium hydroxide solution, stirred at 80-95° C. for 3-4 h, and then centrifuged to remove the supernatant to obtain a precipitate; the precipitate is washed and dried to obtain porous calcium carbonate.

2. The method for preparing porous calcium carbonate with a high specific surface area according to claim 1, wherein The molecular weight of the polyethylene glycol is 200-10000.

3. The method for preparing porous calcium carbonate with a high specific surface area according to claim 1, wherein The molar ratio of the sodium citrate, sodium bicarbonate and calcium chloride is 1:1.4-1.6:1.4-1.

6.

4. The method for preparing porous calcium carbonate with a high specific surface area according to claim 1, wherein The mass of the silicon dioxide is 1.1 to 1.3 times that of sodium bicarbonate.

5. The method for preparing porous calcium carbonate with a high specific surface area according to claim 1, wherein The concentration of the sodium citrate solution is 0.018-0.022 mol / L.

6. The method for preparing porous calcium carbonate with a high specific surface area according to claim 1, wherein: In the step (3), the pH is adjusted using a sodium hydroxide solution.

7. The method for preparing porous calcium carbonate with a high specific surface area according to claim 1, wherein: In the step (5), the precipitate is washed three or more times by centrifugation with deionized water and ethanol respectively, and then dried at 80°C after washing.

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