Calcium carbonate production method

Abstract

The invention discloses a calcium carbonate production method. The method comprises the following steps: adding soluble sodium salt and soluble potassium salt into the calcium-containing waste liquid, mixing, monitoring the pH value and the conductivity of the mixed liquid in the mixing process, adding carbonate when the pH value and the conductivity of the mixed liquid do not change, reacting at room temperature, monitoring the pH value and the conductivity of a reaction system in the reaction process, and calculating the content of the sodium salt in the calcium-containing waste liquid. And when the pH and the conductivity of the reaction system do not change, collecting the product. Compared with the prior art, the one-time conversion rate of calcium ions in the method can be increased by 20% or above, and the yield of calcium carbonate can be increased by 50% or above. Therefore, the problem of low calcium ion conversion rate in the production process of preparing light calcium carbonate by a chemical method can be solved, the calcium carbonate yield is reduced, the energy consumption in the reaction process is reduced, the production efficiency of calcium carbonate is improved, and great economic value is achieved.

Description

Technical Field

[0001] The invention relates to the field of light calcium carbonate preparation, and in particular to a calcium carbonate production method capable of improving calcium ion conversion rate and yield. Background Art

[0002] As an important functional material, calcium carbonate has been widely used in many fields. Calcium carbonate has excellent physical and chemical properties such as non-toxic, non-polluting, high temperature resistance, non-irritating, high stiffness and high thermal performance. At the same time, due to its wide source, low cost and simple production process, it has been widely used in industrial fields such as building materials, food, electronics, papermaking, ink, pigment, cosmetics, plastics, paint, sealant, adhesive and medicine.

[0003] Calcium carbonate is mainly produced by physical and chemical methods in industry. The product produced by physical method of mechanically crushing natural limestone is called heavy calcium carbonate (GCC); the product produced by chemical precipitation reaction method is called light calcium carbonate (PCC).

[0004] The production of light calcium carbonate is synthesized by chemical methods. During the synthesis process, it is difficult for calcium ions to react in one go, resulting in a low recovery rate and difficulty in complete utilization. The low conversion efficiency seriously reduces the yield of calcium carbonate, affects production efficiency, and increases production costs. Summary of the invention

[0005] In view of the defects or shortcomings of the prior art, the present invention provides a method for producing calcium carbonate.

[0006] To this end, the calcium carbonate production method provided by the present invention comprises:

[0007] Step 1, adding soluble sodium salt and soluble potassium salt to the calcium-containing waste liquid to mix, monitoring the pH value and conductivity of the mixed liquid during the mixing process, and executing step 2 when the pH value and conductivity of the mixed liquid do not change;

[0008] Step 2, adding carbonate to the mixed solution obtained in step 1, reacting at room temperature, monitoring the pH value and conductivity of the reaction system during the reaction, and collecting the product when the pH value and conductivity of the reaction system do not change.

[0009] An optional solution is that the calcium ion concentration in the calcium-containing waste liquid is 1.20-1.40 mol / L; the sum of the concentrations of potassium ions and sodium ions in the mixed solution is 1.10-1.50 mol / L, and the concentration of sodium ions or potassium ions is not less than 0.4 mol / L. The concentration of carbonate ions in the reaction system is 1:1 with the concentration of calcium ions in the reaction system.

[0010] An optional solution is that if the pH value fluctuation range does not exceed 5%, the pH value does not change; if the conductivity fluctuation range does not exceed 5%, the conductivity does not change.

[0011] An optional solution is that the reaction in step 2 is carried out under stirring.

[0012] An optional scheme is that the soluble potassium salt is potassium chloride, the soluble sodium salt is sodium chloride, and the carbonate is ammonium carbonate.

[0013] The present invention uses inorganic salt sodium and potassium ions that cannot form precipitation with carbonate ions as adjusting agents to change the properties of the solution system such as pH and conductivity of the reaction system during the formation of light calcium carbonate, thereby improving the reaction rate, calcium ion conversion rate and calcium carbonate yield in a relatively short time, and has a relatively large economic effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a morphology diagram of the calcium carbonate product prepared in Example 1 of the present invention.

[0015] Figure 2 This is the XRD pattern of the product prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0016] Unless otherwise specified, the terms herein are understood according to the knowledge of ordinary technicians in the relevant fields. It should also be understood that the temperatures and concentrations involved in this article are approximate values ​​for illustrative purposes. Although methods and materials similar or equivalent to the methods and materials described herein can be used for the implementation of the present disclosure, some suitable methods and materials are described below. The publications, patent applications, patents and other references mentioned herein are partially incorporated herein by reference. If there is a conflict, this article shall prevail. In addition, the materials, methods, solution concentrations and embodiments are merely exemplary and are not intended to be limiting. In the specific scheme, those skilled in the art can use conventional experimental time periods to optimize the material ratios, concentrations, and operating parameter values ​​involved in the method according to the disclosure of the present invention to achieve the purpose of the present invention.

[0017] The calcium-containing waste liquid of the present invention comes from the calcium-containing waste liquid discharged from the process of producing chemical products such as sodium and magnesium, such as the calcium-containing waste liquid discharged from the process of producing chemical products such as sodium and magnesium by relevant companies in Delingha City in the Qinghai Salt Lake area. The present invention is further described below in conjunction with specific embodiments. The calcium-containing waste liquid used in the following embodiments comes from the calcium-containing waste liquid discharged from the process of producing chemical products such as sodium and magnesium by Qinghai Western Magnesium Industry Co., Ltd., and the remaining raw materials are all commercially available products.

[0018] Embodiment 1:

[0019] The Ca in the calcium-containing wastewater used in this embodiment 2+The concentration is 1.25 mol / L, and the preparation method is:

[0020] Step 1, adding calcium-containing waste liquid and KCl and NaCl solids into a reactor for mixing, so that the KCl concentration in the reaction system is 0.50 mol / L and the NaCl concentration is 0.62 mol / L; monitoring the solution pH and conductivity of the mixed solution during the mixing process, and continuing the next step of reaction when the pH and conductivity of the mixed solution do not change, that is, are stable (both monitored values ​​fluctuate by no more than 5%);

[0021] Step 2, add (NH4)2CO3(CO3 2- With Ca 2+ The concentration ratio is about 1:1), at room temperature, the reactor speed is adjusted to 600 rpm / min, and after reacting for 4 minutes, the pH value and conductivity of the reaction system no longer change (the fluctuation of the monitoring values ​​of both does not exceed 5%), and then the product is collected. Specifically, the product is filtered three times, and the filtrate containing sodium ions and potassium ions is collected. The filtrate is concentrated and recycled; the filter cake is washed and dried to obtain light calcium carbonate. The micromorphology and XRD of the obtained product are as follows: Figure 1 and Figure 2 As shown; the primary conversion rate of calcium ions in the production of this embodiment is 86.39%, and the yield of calcium carbonate is 84.39%.

[0022] Comparative Example 1:

[0023] The scheme of this comparative example is that, based on the scheme of Example 1, KCl and NaCl are not added to the reaction system, and after adding ammonium carbonate and reacting for 4 minutes, the primary conversion rate of calcium ions is 59.48%, and the yield of calcium carbonate is 57.58%;

[0024] In addition, based on the scheme of Example 1, when KCl and NaCl are not added to the reaction system, and the reaction time is 30 min after adding ammonium carbonate, the primary conversion rate of calcium ions is 80.32%, the yield of calcium carbonate is 77.42%, and the yield of calcium carbonate is only increased by 34.45%; as the reaction time is further increased, the yield of the reaction hardly increases.

[0025] Comparative Example 2:

[0026] The difference between this comparative example and Example 1 is that no KCl is added and the Na + The concentration is 1.12 mol / L. The primary conversion rate of calcium ions in this comparative example is 74.21%, and the calcium carbonate yield is 71.51%.

[0027] Comparative Example 3:

[0028] The difference between this comparative example and Example 1 is that no NaCl is added and K+ The concentration is 1.12 mol / L. The primary conversion rate of calcium ions in this comparative example is 78.21%, and the calcium carbonate yield is 76.31%.

[0029] Comparative Example 4:

[0030] The difference between this comparative example and Example 1 is that after adding KCl solid and NaCl, pH and conductivity monitoring is not performed, and step 2 is directly performed, and the product is collected after reacting for 4 minutes in step 2. The calcium ion conversion rate of this comparative example is 71.20%, and the calcium carbonate yield is 68.28%.

[0031] Embodiment 2:

[0032] The Ca in the calcium-containing wastewater used in this embodiment 2+ The concentration is 1.30 mol / L. The preparation method thereof is different from that of Example 1 in that the concentration of KCl in step 1 is 0.74 mol / L and the concentration of NaCl is 0.64 mol / L; and the pH value and conductivity of the reaction system do not change after reacting for 5 minutes in step 2. The primary conversion rate of calcium ions in this example reaches 89.69%, and the yield of calcium carbonate is 85.57%.

[0033] Comparative Example 5:

[0034] The scheme of this comparative example is that, based on the scheme of Example 2, KCl and NaCl are not added to the reaction system, and when ammonium carbonate is added and reacted for 5 minutes, the primary conversion rate of calcium ions is 61.20%, and the yield of calcium carbonate is 59.86%;

[0035] In addition, based on the scheme of Example 2, KCl and NaCl were not added to the reaction system, and when ammonium carbonate was added for a reaction time of 30 min, the primary conversion rate of calcium ions was 74.52%, and the yield of calcium carbonate was 72.67%. As the reaction time further increased, the yield of the reaction hardly increased.

[0036] Embodiment 3:

[0037] The Ca in the calcium-containing wastewater used in this embodiment 2+ The concentration is 1.40 mol / L. The preparation method is different from that of Example 1 in that the concentration of KCl in step 1 is 0.68 mol / L and the concentration of NaCl is 0.72 mol / L; and the pH value and conductivity of the reaction system do not change after reacting for 5 minutes in step 2. The primary conversion rate of calcium ions in this example is 90.97%, and the yield of calcium carbonate is 88.78%.

[0038] Comparative Example 6:

[0039] The scheme of this comparative example is that, based on the scheme of Example 3, no KCl and NaCl are added to the reaction system, and ammonium carbonate is added to react for 5 minutes in the same manner as step 2. The primary conversion rate of calcium ions is 63.45%, and the yield of calcium carbonate is 61.25%;

[0040] In addition, based on the scheme of Example 3, when KCl and NaCl are not added to the reaction system and ammonium carbonate is added for a reaction time of 30 min, the primary conversion rate of calcium ions is 79.20%, and the yield of calcium carbonate is 77.30%. Thereafter, as the reaction time further increases, the yield of the reaction hardly increases.

[0041] The present invention has been described in detail above. The above description is only a preferred embodiment of the present invention and should not limit the scope of implementation of the present invention. That is, all equivalent changes and modifications made within the scope of this application should still fall within the scope of the present invention.

Claims

1. A method for producing calcium carbonate, characterized in that, Methods include: Step 1, adding soluble sodium salt and soluble potassium salt to the calcium-containing waste liquid to mix, monitoring the pH value and conductivity of the mixed liquid during the mixing process, and executing step 2 when the pH value and conductivity of the mixed liquid do not change; Step 2, adding carbonate to the mixed solution obtained in step 1, reacting at room temperature, monitoring the pH value and conductivity of the reaction system during the reaction, and collecting the product when the pH value and conductivity of the reaction system do not change.

2. The calcium carbonate generating method according to claim 1, wherein The calcium ion concentration in the calcium-containing waste liquid is 1.20-1.40 mol / L; the sum of the concentrations of potassium ions and sodium ions in the mixed liquid is 1.10-1.50 mol / L, and the concentration of sodium ions or potassium ions is not less than 0.4 mol / L.

3. The calcium carbonate generating method according to claim 1, wherein The concentration of carbonate ions in the reaction system is 1:1 with the concentration of calcium ions in the reaction system.

4. The calcium carbonate generating method according to claim 1, wherein If the pH value fluctuation range does not exceed 5%, the pH value does not change; if the conductivity fluctuation range does not exceed 5%, the conductivity does not change.

5. The calcium carbonate generating method according to claim 1, wherein The reaction in step 2 is carried out under stirring.

6. The method for producing calcium carbonate according to claim 1, wherein The soluble potassium salt is potassium chloride, the soluble sodium salt is sodium chloride, and the carbonate is ammonium carbonate.

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