An ultrafine calcium carbonate and a preparation method thereof

Abstract

The present invention relates to the technical field of calcium carbonate material preparation, and specifically discloses an ultrafine calcium carbonate and a preparation method thereof. The preparation method of the ultrafine calcium carbonate provided by the present invention first carries out a digestion reaction on quicklime and water, and then for the obtained calcium hydroxide suspension, uses modified cotton hull powder as a dispersant for calcium hydroxide and a crystal form control agent for calcium carbonate to prepare ultrafine calcium carbonate; the process for preparing ultrafine calcium carbonate in the present invention solves the problems of easy agglomeration of calcium hydroxide and complex preparation process of ultrafine calcium carbonate, reduces the particle size of ultrafine calcium carbonate, greatly improves the purity and yield of ultrafine calcium carbonate, the entire preparation process has low cost, easily available raw materials and does not cause a burden on the environment, greatly saves the process cost, has strong operability, is suitable for industrial production, and provides a new idea for the preparation of ultrafine calcium carbonate.

Description

Technical Field

[0001] The present invention relates to the technical field of calcium carbonate material preparation, and particularly relates to an ultrafine calcium carbonate and a preparation method thereof. Background Art

[0002] Ultrafine calcium carbonate is a very important functional inorganic material and is widely used in industrial fields such as rubber, plastics, coatings, and papermaking. It is usually used as a filler to increase the volume of products. However, in some special fields, such as the field of fire extinguishing powder, ultrafine calcium carbonate usually acts as a smoke adsorbent by virtue of its good adsorption property. The finer the powder particle size of the calcium carbonate product, the better its surface adsorption capacity, which poses new requirements for the fineness of the calcium carbonate product. The methods for preparing ultrafine calcium carbonate in the prior art include: wet preparation, vapor deposition, mechanical grinding, high-energy grinding, and ultrasonic method, etc. However, the preparation methods of the prior art also have various problems. For example, wet grinding has the disadvantages of high energy consumption, wastewater and waste gas generation; vapor deposition has a high cost and strong reaction condition restrictions and is not suitable for all places; both mechanical grinding and high-energy grinding have the defects of high energy consumption and long preparation time; the ultrasonic method not only requires special equipment but also requires the aid of solvents and is complicated to operate; since the current preparation methods of ultrafine calcium carbonate have the disadvantages of high energy consumption, high cost, environmental impact, and process complexity, it is of great significance to provide a preparation method of ultrafine calcium carbonate with low energy consumption, low cost, and simple process. Summary of the Invention

[0003] In view of this, the present invention provides an ultrafine calcium carbonate and a preparation method thereof. The present invention selects a specific modified cotton hull powder, solves the problems of easy agglomeration of calcium hydroxide and difficult preparation of ultrafine calcium carbonate, reduces the particle size of ultrafine calcium carbonate, greatly improves the purity and yield of ultrafine calcium carbonate, the entire preparation process has a low cost, the raw materials are easy to obtain and do not cause a burden on the environment, greatly saves the process cost, is highly operable, and is suitable for industrial production.

[0004] To solve the above technical problems, the technical solution provided by the present invention is:

[0005] The first aspect of the present invention provides a preparation method of ultrafine calcium carbonate, which includes the following steps:

[0006] S1. Carry out a digestion reaction on quicklime and water. After the reaction ends, age the reaction solution and filter to obtain a calcium hydroxide suspension;

[0007] S2. Add the modified cotton hull powder to the calcium hydroxide suspension, introduce carbon dioxide until the pH is 7 - 8, filter, and dry to obtain the ultrafine calcium carbonate;

[0008] Wherein, the modified cotton hull powder is a cotton hull powder modified by sodium hydroxide and sodium citrate.

[0009] Compared with the prior art, the preparation method of ultrafine calcium carbonate provided by the present invention adds modified cotton hull powder to the calcium hydroxide suspension, wherein the modified cotton hull powder can be used as a dispersant for calcium hydroxide and also as a crystal form controller for subsequent calcium carbonate, while ensuring high purity and yield of calcium carbonate, it can also ensure that the calcium carbonate reaches ultrafine standards; specifically, the modified cotton hull powder has a large specific surface area and active groups, and has a certain complexing effect on calcium hydroxide, thereby increasing the molecular interaction force between calcium hydroxide and the modified cotton hull powder, and because the modified cotton hull powder has good dispersing function, it can be well dispersed in the calcium hydroxide suspension, thereby improving the subsequent carbon dioxide and calcium hydroxide. contact area, thereby improving the purity and yield of calcium carbonate; further, the specific modified cotton hull powder can also change the morphology of calcium carbonate and control the directional growth of calcium carbonate. Compared with the use of sodium citrate alone, the prepared calcium carbonate has a smaller particle size and a more uniform particle size distribution, with a D95 particle size of 10nm-20nm; the present invention solves the problems of easy agglomeration of calcium hydroxide and difficulty in preparing ultrafine calcium carbonate by selecting specific modified cotton hull powder, reduces the particle size of ultrafine calcium carbonate, greatly improves the purity and yield of ultrafine calcium carbonate, and has low cost for the entire preparation process, easy-to-obtain raw materials and no burden on the environment, greatly saving process costs, strong operability, and suitable for factory production.

[0010] Preferably, the particle size of the modified cotton hull powder is 1.0 mm to 1.3 mm.

[0011] Preferably, in S2, the method for preparing the modified cotton hull powder comprises the following steps:

[0012] Step 1, adding cotton hull powder to a sodium hydroxide solution, reacting at 100° C.-130° C. to obtain primary modified cotton hull powder;

[0013] Step 2: adding a sodium citrate aqueous solution to the primary modified cotton hull powder, keeping the mixture warm at 80° C.-100° C., washing with water, filtering, and drying to obtain modified cotton hull powder.

[0014] In the preparation method of modified cotton hull powder, first, the cotton hull powder is modified with sodium hydroxide. On the one hand, sodium hydroxide improves the alkaline conditions to a certain extent, which is beneficial to the stable formation of calcium carbonate. The cotton hull powder modified with sodium hydroxide has a relatively high specific surface area and active groups. Further modification with sodium citrate greatly improves the complexing ability of the modified cotton hull powder with calcium hydroxide and the dispersion performance of the modified cotton hull powders in water. The cotton hull powder modified with sodium hydroxide and sodium citrate can be used as both a dispersant for calcium hydroxide and a crystal form controller for subsequent calcium carbonate, solving the problems of easy agglomeration of calcium hydroxide and difficulty in preparing ultrafine calcium carbonate. While reducing the particle size of ultrafine calcium carbonate, it greatly improves the purity and yield of ultrafine calcium carbonate.

[0015] Preferably, in step 1, the mass concentration of the sodium hydroxide solution is 3%-5%.

[0016] Preferably, in step 1, the mass-volume ratio of the cotton hull powder to the sodium hydroxide solution is 1 g:(18-22) mL.

[0017] Preferably, in step 1, the reaction time is 2 h-4 h.

[0018] Preferably, in step 2, the concentration of the sodium citrate aqueous solution is 1 mol / L-1.4 mol / L.

[0019] Preferably, in step 2, the mass-volume ratio of the primary modified cotton hull powder to the sodium citrate aqueous solution is 1 g:(30-35) mL.

[0020] Preferably, in step 2, the heat preservation time is 6 h-8 h.

[0021] Preferably, in S1, the concentration of calcium hydroxide in the calcium hydroxide suspension is 2.8 mol / L-3 mol / L.

[0022] Preferably, in S1, the temperature of the digestion reaction is 83°C-90°C, and the digestion reaction time is 5 h-6 h.

[0023] Preferably, in S1, the aging time is 10 h-12 h.

[0024] Preferably, in S2, the mass ratio of the calcium hydroxide suspension to the modified cotton hull powder is 80-110:1.

[0025] Preferably, in S2, the gas flow rate of carbon dioxide is 900 mL / min-1000 mL / min.

[0026] Further preferably, in S2, after the reaction between calcium hydroxide and carbon dioxide is completed, 3-5 times the amount of water is added, and the mixture is heated at 90°C - 100°C for 30 min - 50 min, and then filtered while it is hot.

[0027] The second aspect of the present invention provides an ultrafine calcium carbonate, which is prepared by the above-mentioned preparation method of ultrafine calcium carbonate.

[0028] The present invention provides an ultrafine calcium carbonate. First, quicklime and water are subjected to a digestion reaction, and then for the obtained calcium hydroxide suspension, using modified cotton hull powder as a dispersant for calcium hydroxide and a crystal form control agent for calcium carbonate, ultrafine calcium carbonate is prepared. The process for preparing ultrafine calcium carbonate in the present invention solves the problems of easy agglomeration of calcium hydroxide and complex preparation process of ultrafine calcium carbonate, reduces the particle size of ultrafine calcium carbonate, greatly improves the purity and yield of ultrafine calcium carbonate, the entire preparation process has low cost, the raw materials are easily available and do not impose a burden on the environment, greatly saves the process cost, has strong operability, is suitable for industrial production, and provides a new idea for the preparation of ultrafine calcium carbonate. Specific Embodiments

[0029] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following further elaborates on the present invention in combination with implementation cases. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0030] Example 1

[0031] This example provides a preparation method of ultrafine calcium carbonate, which includes the following steps:

[0032] S1. Mix quicklime and water evenly, react at 83°C for 5 h, and after the reaction ends, age the reaction solution for 10 h to obtain a calcium hydroxide suspension with a concentration of 2.5 mol / L;

[0033] S2. Add modified cotton hull powder with a particle size of 1 mm to the calcium hydroxide suspension, introduce carbon dioxide at a gas flow rate of 900 mL / min until the pH is 7 - 8. After the reaction ends, add 3 - 5 times the amount of water, heat at 90°C for 30 min, filter while it is hot, and dry to obtain the ultrafine calcium carbonate; wherein, the mass ratio of the calcium hydroxide suspension to the modified cotton hull powder is 80:1;

[0034] Among them, the preparation method of the modified cotton hull powder includes the following steps:

[0035] Step 1. Add cotton hull powder to a sodium hydroxide solution with a mass concentration of 3%, react at 130°C for 2 h to obtain primary modified cotton hull powder; wherein, the mass - volume ratio of the cotton hull powder to the sodium hydroxide solution is 1 g:18 mL;

[0036] Step 2: Add an aqueous solution of sodium citrate with a concentration of 1 mol / L to the primary modified cotton hull powder, keep it warm at 80 °C for 6 h, filter, and dry to obtain the modified cotton hull powder; wherein, the mass-volume ratio of the primary modified cotton hull powder to the aqueous solution of sodium citrate is 1 g:35 mL.

[0037] Example 2

[0038] This example provides a method for preparing ultrafine calcium carbonate, which includes the following steps:

[0039] S1: Mix quicklime and water evenly, react at 90 °C for 6 h, and age the reaction solution for 12 h after the reaction ends to obtain a calcium hydroxide suspension with a concentration of 3 mol / L;

[0040] S2: Add the modified cotton hull powder with a particle size of 1.3 mm to the calcium hydroxide suspension, introduce carbon dioxide at a gas flow rate of 1000 mL / min until the pH is 7 - 8. After the reaction ends, add 3 - 5 times the amount of water, heat at 100 °C for 50 min, filter while it is hot, and dry to obtain the ultrafine calcium carbonate; wherein, the mass ratio of the calcium hydroxide suspension to the modified cotton hull powder is 110:1;

[0041] Among them, the preparation method of the modified cotton hull powder includes the following steps:

[0042] Step 1: Add cotton hull powder to a sodium hydroxide solution with a mass concentration of 5%, react at 100 °C for 4 h to obtain the primary modified cotton hull powder; wherein, the mass-volume ratio of the cotton hull powder to the sodium hydroxide solution is 1 g:22 mL;

[0043] Step 2: Add an aqueous solution of sodium citrate with a concentration of 1.4 mol / L to the primary modified cotton hull powder, keep it warm at 100 °C for 8 h, filter, and dry to obtain the modified cotton hull powder; wherein, the mass-volume ratio of the primary modified cotton hull powder to the aqueous solution of sodium citrate is 1 g:30 mL.

[0044] Example 3

[0045] This example provides a method for preparing ultrafine calcium carbonate, which includes the following steps:

[0046] S1: Mix quicklime and water evenly, react at 87 °C for 5.5 h, and age the reaction solution for 11 h after the reaction ends to obtain a calcium hydroxide suspension with a concentration of 2.8 mol / L;

[0047] S2. Add modified cotton hull powder with a particle size of 1.2 mm to the calcium hydroxide suspension, and introduce carbon dioxide at a gas flow rate of 950 mL / min until the pH is 7 - 8. After the reaction is completed, add 3 - 5 times the amount of water, heat at 95 °C for 40 min, filter while it is hot, and dry to obtain the ultrafine calcium carbonate; wherein, the mass ratio of the calcium hydroxide suspension to the modified cotton hull powder is 90:1;

[0048] Among them, the preparation method of the modified cotton hull powder includes the following steps:

[0049] Step 1. Add cotton hull powder to a sodium hydroxide solution with a mass concentration of 4%, and react at 120 °C for 3 h to obtain primary modified cotton hull powder; wherein, the mass - to - volume ratio of the cotton hull powder to the sodium hydroxide solution is 1 g:20 mL;

[0050] Step 2. Add a sodium citrate aqueous solution with a concentration of 1.2 mol / L to the primary modified cotton hull powder, keep it warm at 90 °C for 7 h, filter, and dry to obtain the modified cotton hull powder; wherein, the mass - to - volume ratio of the primary modified cotton hull powder to the sodium citrate aqueous solution is 1 g:32 mL.

[0051] Comparative Example 1

[0052] Compared with Example 1, the difference in this comparative example is as follows:

[0053] The preparation method of the modified cotton hull powder includes the following steps:

[0054] Add a sodium citrate aqueous solution with a concentration of 1 mol / L to the cotton hull powder, keep it warm at 80 °C for 6 h, filter, and dry to obtain the modified cotton hull powder; wherein, the mass - to - volume ratio of the cotton hull powder to the sodium citrate aqueous solution is 1 g:35 mL.

[0055] Other steps and components are exactly the same as those in Example 1.

[0056] Comparative Example 2

[0057] Compared with Example 1, the difference in this comparative example is as follows:

[0058] The preparation method of the modified cotton hull powder includes the following steps:

[0059] Add cotton hull powder to a sodium hydroxide solution with a mass concentration of 3%, and react at 130 °C for 2 h to obtain the modified cotton hull powder; wherein, the mass - to - volume ratio of the cotton hull powder to the sodium hydroxide solution is 1 g:18 mL;

[0060] Other steps and components are exactly the same as those in Example 1.

[0061] Comparative Example 3

[0062] This comparative example is different from Example 1 in that the cotton hull powder is replaced with an equal amount of corn flour;

[0063] The other steps and components are exactly the same as those in Example 1.

[0064] Comparative Example 4

[0065] This comparative example is different from Example 1 in that the sodium citrate aqueous solution is replaced with an equal amount of glucose aqueous solution;

[0066] The other steps and components are exactly the same as those in Example 1.

[0067] The calcium carbonate prepared in Examples 1-3 and Comparative Examples 1-4 was tested for relevant indicators. The specific test indicators and test results are shown in Table 1:

[0068] Table 1

[0069] Test Items Purity / % Yield / % D95 Particle Size / nm Example 1 99.2 91.8 11.3 Example 2 99.1 90.2 12.6 Example 3 98.6 91.3 15.9 Comparative Example 1 92.3 76.5 42.3 Comparative Example 2 91.4 79.2 51.7 Comparative Example 3 95.6 83.5 36.9 Comparative Example 4 90.9 76.6 59.4

[0070] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, or improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing ultrafine calcium carbonate, characterized in that, It includes the following steps: S1. Carry out a slaking reaction on quicklime and water. After the reaction ends, age the reaction solution, filter it to obtain a calcium hydroxide suspension; S2. Add modified cotton hull powder to the calcium hydroxide suspension, introduce carbon dioxide until the pH is 7 - 8, filter it, and dry it to obtain the ultrafine calcium carbonate; Among them, the preparation method of the modified cotton hull powder includes the following steps: Step 1. Add cotton hull powder to a sodium hydroxide solution, and carry out a reaction at 100°C - 130°C to obtain primary modified cotton hull powder; Step 2. Add a sodium citrate aqueous solution to the primary modified cotton hull powder, keep it warm at 80°C - 100°C, wash it with water, filter it, and dry it to obtain modified cotton hull powder.

2. The preparation method of ultrafine calcium carbonate according to claim 1, characterized in that, The particle size of the modified cotton hull powder is 1.0 mm - 1.3 mm.

3. The preparation method of ultrafine calcium carbonate according to claim 1, characterized in that, In Step 1, the mass concentration of the sodium hydroxide solution is 3% - 5%; and / or In Step 1, the mass - volume ratio of the cotton hull powder to the sodium hydroxide solution is 1 g:(18 - 22) mL; and / or In Step 1, the reaction time is 2 h - 4 h.

4. The method for preparing ultrafine calcium carbonate according to claim 1, characterized in that, In Step 2, the concentration of the sodium citrate aqueous solution is 1 mol / L - 1.4 mol / L; and / or In Step 2, the mass - volume ratio of the primary modified cotton hull powder to the sodium citrate aqueous solution is 1 g:(30 - 35) mL; and / or In Step 2, the heat - preservation time is 6 h - 8 h.

5. The preparation method of ultrafine calcium carbonate according to claim 1, characterized in that, In S1, the concentration of calcium hydroxide in the calcium hydroxide suspension is 2.5 mol / L - 3 mol / L; and / or In S1, the temperature of the slaking reaction is 83°C - 90°C, and the slaking reaction time is 5 h - 6 h.

6. The preparation method of ultrafine calcium carbonate according to claim 1, characterized in that, In S1, the aging time is 10 h - 12 h.

7. The preparation method of ultrafine calcium carbonate according to claim 1, characterized in that, In S2, the mass ratio of the calcium hydroxide suspension to the modified cotton hull powder is 80 - 110:

1.

8. The preparation method of ultrafine calcium carbonate according to claim 1, characterized in that, In S2, the gas flow rate of the carbon dioxide is 900 mL / min - 1000 mL / min.