A method for preparing light calcium carbonate of different crystal forms using carbonized white carbon black mother liquor

Abstract

The present invention discloses a method for preparing light calcium carbonate with different crystal forms using carbonized silica mother liquor. The carbonized silica mother liquor is directly reacted with an ultrafine Ca(OH)2 emulsion to produce light calcium carbonate powder. Light calcium carbonate with different crystal forms and morphologies can be obtained by regulating a crystal form modifier, the alkalinity of the reaction system, and process parameters. This method conveniently utilizes the alkaline mother liquor from the carbonized silica production process to control the crystal form and morphology of the light calcium carbonate powder, while also significantly improving the recycling rate of the carbonized silica mother liquor.

Description

Technical Field

[0001] The invention belongs to the technical field of powder preparation, and particularly relates to a method for preparing light calcium carbonate with different crystal forms by utilizing carbonized white carbon black mother liquor. Background Art

[0002] Calcium carbonate is a white, odorless, non-toxic inorganic compound with three crystalline phases: calcite, aragonite, and vaterite. In nature, calcite is the most thermodynamically stable phase, aragonite is the metastable phase, and vaterite is unstable. Under certain conditions, vaterite and aragonite can easily convert to calcite. Therefore, calcite is the most common form in synthesis. Unstable calcium carbonate crystals, such as vaterite and amorphous calcium carbonate, are generally obtained from biominerals such as pearls, fish otoliths, ascidian bones, and crustaceans.

[0003] There are three main synthetic methods for the industrial production of calcium carbonate: biomimetic synthesis, double decomposition, and carbonization. The biomimetic synthesis method attempts to mimic the natural formation process of calcium carbonate by adding organic compounds as templates for crystal growth to control the particle size, shape, or other parameters of the resulting calcium carbonate. Biomimetic synthesis methods can be divided into precipitation and reverse emulsion methods, with precipitation methods further divided into spontaneous precipitation reactions and slow carbonization reactions. Carbonation is the most widely used method in industry. Carbonation, also known as the CO2 bubbling method, involves introducing CO2 gas into slaked lime (Ca(OH)2) to produce calcium carbonate. The resulting calcium carbonate is primarily rhombohedral or cubic, an atypical form of calcite. Because the CO2 bubbling method uses raw materials obtained from nature, it is simple to operate and inexpensive, making it the primary method for industrial-scale production of calcium carbonate. However, because vaterite is an unstable crystal form, the carbonization method is difficult to control the crystal form of calcium carbonate. The double decomposition reaction method is to react a soluble calcium salt or calcium hydroxide with a soluble carbonate to obtain calcium carbonate precipitation. Patent application 200910085908.6 discloses a process route for precipitating white carbon black with carbon dioxide and simultaneously preparing ultrafine calcium carbonate, but it cannot achieve the crystal form and morphology control of calcium carbonate. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing light calcium carbonate with different crystal forms using carbonized silica mother liquor, thereby solving the problem that the existing preparation methods cannot control the crystal form and morphology of light calcium carbonate, and at the same time improving the recycling rate of the carbonized mother liquor.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing light calcium carbonate of different crystal forms using carbonized silica mother liquor comprises the following steps:

[0007] 1) Mixing carbonized silica mother liquor and crystal form regulator to obtain solution A;

[0008] 2) Add 40~100% of the total carbon content of Ca(OH)2 emulsion to solution A, control the process conditions, and react to obtain light calcium carbonate with different crystal forms and morphologies.

[0009] In step 1), the carbonized silica mother liquor is a liquid containing sodium carbonate, sodium bicarbonate, and a trace amount of soluble silicon. Furthermore, the carbonized silica mother liquor contains 1.5-5.0 g / L sodium carbonate, preferably 2.0-4.0 g / L; 15-50 g / L sodium bicarbonate, preferably 20-40 g / L; and 100-600 mg / L SiO2, preferably 200-300 mg / L.

[0010] In step 1), the crystal form modifier is one or both of an inorganic crystal form modifier and an organic crystal form modifier.

[0011] The inorganic crystal form modifier is modified water glass with a modulus of 1.5 to 2.4. The modified water glass is added in an amount such that the SiO2 content in Solution A is 500 to 1000 mg / L. The modified water glass is prepared by adding a water glass solution having a silica content of 4 to 20 g / L and adjusting the pH to 10 to 12. The modifier is one or more of sulfuric acid, hydrochloric acid, acetic acid, sodium bicarbonate, and carbon dioxide.

[0012] The organic crystal form modifier is an amino acid, and the amino acid is one or two of glycine, leucine, aspartic acid, glutamic acid, histidine, methionine, and β-cyanoalanine. The amount of the amino acid added is 2.5-5% of the total carbon content in solution A.

[0013] In step 2), the particle size of the Ca(OH)2 emulsion is 0.1-10 μm, preferably 0.5-2 μm, and is evenly distributed.

[0014] In step 2), when preparing vaterite-phase light calcium carbonate, the temperature is controlled between 5°C and 35°C, preferably between 10°C and 20°C; and the pH is controlled between 7.0 and 9.5, preferably between 8.5 and 9.5. Furthermore, the morphology of the vaterite-phase calcium carbonate can be controlled by adjusting the type and concentration of amino acids. For example, a leucine concentration greater than 5.0% can produce spherical vaterite-phase calcium carbonate.

[0015] In step 2), when preparing calcite-phase light calcium carbonate, the temperature is controlled between 40°C and 80°C, preferably between 40°C and 60°C; the pH is between 9.5 and 13.8, preferably between 10.0 and 13.0. Furthermore, the morphology of the calcite-phase light calcium carbonate can be controlled by adjusting the type and concentration of amino acids or the concentration of modified water glass. For example, an L-leucine concentration of less than 1.5% can produce prismatic calcite-phase light calcium carbonate; a modified water glass with a silica concentration of 4.0 g / L can produce spherical calcite-phase light calcium carbonate.

[0016] Furthermore, by regulating the amount of Ca(OH)2 added and the pH value at the reaction end point, the mother liquor can be regulated to obtain sodium carbonate or sodium hydroxide after the reaction and returned to the water glass preparation unit.

[0017] The reaction equation is as follows:

[0018] 2NaHCO3 + Ca(OH)2= Na2CO3 + CaCO3 + 2H2O

[0019] NaHCO3 + Ca(OH)2 = NaOH + CaCO3 + H2O

[0020] When the end point pH value is 10-12.0 (preferably 11.0-12.0), the mother liquor after the reaction is mainly composed of sodium carbonate; when the end point pH value is 12.0-13.8 (preferably 12.8-13.4), the mother liquor after the reaction is mainly composed of NaOH.

[0021] The present invention uses carbonized silica mother liquor as raw material, and can adjust the crystal form of the prepared calcium carbonate to be a calcite phase or a spherical haze phase. At the same time, the morphology can be adjusted to be spherical, prismatic and rod-shaped, thereby improving the crystal form and morphology of the calcium carbonate powder and increasing the recycling efficiency of the carbonized silica mother liquor.

[0022] Compared with the prior art, the advantages of the present invention are:

[0023] (1) The present invention produces light calcium carbonate by performing a double decomposition reaction on carbonized white carbon black mother liquor, thereby improving the circulation performance of the mother liquor.

[0024] (2) The production process of the present invention can conveniently control the crystal phase and morphology of light calcium carbonate powder through the crystal form regulator and reaction process conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The following are the XRD pattern of calcium carbonate prepared in Example 1 and the SEM image of spherical calcite phase calcium carbonate.

[0026] Figure 2The following are the XRD pattern of calcium carbonate prepared in Example 2 and the SEM image of flaky calcite phase calcium carbonate.

[0027] Figure 3 The following are the XRD pattern of calcium carbonate prepared in Example 3 and the SEM image of rhombohedral calcite phase calcium carbonate.

[0028] Figure 4 The following are the XRD pattern of calcium carbonate prepared in Example 4 and the SEM image of spherical vaterite phase calcium carbonate. DETAILED DESCRIPTION Example 1

[0029] 1) 1.0 L of a carbonized silica mother liquor composed of 3.5 g / L sodium carbonate, 35 g / L sodium bicarbonate, and 170 mg / L SiO2 was added to a solution of water glass having a modulus of 2.4 and a silica content of 4.0 g / L, and CO2 was introduced to a pH of 11.2 to obtain a modified water glass solution. The SiO2 content in the carbonized silica mother liquor was adjusted to 240 mg / L using the modified water glass having a pH of 11.2, and leucine was added at 2.5% of the total carbon content in the solution to obtain reaction solution A.

[0030] 2) Add Ca(OH)2 emulsion according to 50% of the total carbon content, the Ca(OH)2 particle size D50 in the emulsion is 1.0μm, the Ca(OH)2 content is 15.0g / L, heat to 70℃ and stir for 1 hour, the pH value of the carbonization mother liquor is 12.0, cool and filter to obtain spherical calcite phase calcium carbonate powder, its XRD crystal phase and SEM morphology are as follows Figure 1 As shown, the main inorganic species in the mother liquor after the reaction is Na2CO3. Example 2

[0031] 1) Take 1.0L of carbonized silica mother liquor composed of 4.5g / L sodium carbonate, 45g / L sodium bicarbonate, and 120mg / L SiO2, and introduce CO2 into water glass with a modulus of 2.0 and a silica content of 12g / L until the pH value reaches 10.8 to obtain a modified water glass solution. The SiO2 content of the reaction solution is adjusted to 300mg / L with the modified water glass to obtain reaction solution A.

[0032] 2) Add Ca(OH)2 emulsion according to 100% of the total carbon material amount, the Ca(OH)2 particle size D50 in the emulsion is 0.8μm, the Ca(OH)2 content is 10.0g / L, and the carbonization mother liquor A and Ca(OH)2 emulsion are added dropwise to the reactor at the same time. The feeding rate is 2L / h. After the feeding is completed, the temperature is raised to 60℃ and stirred for 1 hour. The pH value of the carbonization mother liquor is 13.73. Cool and filter to obtain flaky stacked calcite phase calcium carbonate powder. Its XRD crystal phase and SEM morphology are as follows: Figure 2 As shown, the main species in the mother liquor after the reaction is NaOH. Example 3

[0033] 1) 1.0 L of a carbonized silica mother liquor composed of 3.5 g / L sodium carbonate, 35 g / L sodium bicarbonate, and 200 mg / L SiO2 was prepared. Water glass with a modulus of 2.0 and a silica content of 12 g / L was added with NaHCO3 to adjust the pH to 10.5 to obtain a modified water glass solution. The SiO2 content of the reaction solution was adjusted to 300 mg / L using the modified water glass. Leucine was added at 0.5% of the total carbon content in the solution to obtain reaction solution A.

[0034] 2) Add Ca(OH)2 emulsion according to 100% of the total amount of carbon matter in the solution, the Ca(OH)2 particle size D50 in the emulsion is 3.0μm, the Ca(OH)2 content is 10.0g / L, and the carbonization mother solution A and Ca(OH)2 emulsion are added dropwise to the reactor at the same time. The feeding rate is 2L / h. After the feeding is completed, the temperature is raised to 40℃ and stirred for 1 hour. The pH value of the carbonization mother solution is 13.5. Cool and filter to obtain rhombohedral calcite phase calcium carbonate powder. Its XRD crystal phase and SEM morphology are as follows: Figure 3 As shown, the main species in the mother liquor after the reaction is NaOH. Example 4

[0035] 1) To 1.0 L of a carbonized silica mother liquor containing 2.5 g / L sodium carbonate, 25 g / L sodium bicarbonate, and 100 mg / L SiO2, L-leucine was added in an amount equivalent to 6.0% of the total carbon content in the solution to obtain reaction solution A.

[0036] 2) Add Ca(OH)2 emulsion according to 40% of the total carbon material, the Ca(OH)2 particle size D50 in the emulsion is 1.0μm, the Ca(OH)2 content is 10.0g / L, and the carbonization mother liquor A and Ca(OH)2 emulsion are added dropwise to the reactor at the same time. The feeding rate is 500mL / h. After the feeding is completed, the temperature is raised to 35℃ and stirred for 1 hour. The pH value of the reaction liquid is 10.0. Cool and filter to obtain vaterite phase calcium carbonate powder. Its XRD crystal phase and SEM morphology are as follows: Figure 4 As shown, the main inorganic species in the mother liquor after the reaction are Na2CO3 and NaHCO3, each accounting for 50%.

Claims

1. A method for preparing light calcium carbonate of different crystal forms using carbonized silica mother liquor, characterized in that: The following steps are involved: 1) Mixing carbonized silica mother liquor and crystal form regulator to obtain solution A; The carbonized silica mother liquor contains 1.5-5.0 g / L of sodium carbonate, 15-50 g / L of sodium bicarbonate, and 100-600 mg / L of SiO2; the crystal form regulator is one or both of an inorganic crystal form regulator and an organic crystal form regulator; The inorganic crystal form regulator is modified water glass with a modulus of 1.5 to 2.4, and the amount of modified water glass added is such that the SiO2 content in solution A is 500 to 1000 mg / L. The preparation method of the modified water glass is as follows: adding the modifier to a water glass solution with a silicon dioxide content of 4 to 20 g / L, and adjusting the pH value to 10 to 12; the modifier is one or two of sulfuric acid, hydrochloric acid, acetic acid, sodium bicarbonate, and carbon dioxide; The organic crystal form regulator is an amino acid, and the amino acid is one or two of glycine, leucine, aspartic acid, glutamic acid, histidine, methionine, and β-cyanoalanine, and the amount of the amino acid added is 2.5-5% of the total carbon matter in solution A; 2) adding a Ca(OH)2 emulsion with a content of 40-100% of the total carbon matter to solution A, controlling the process conditions, and reacting to obtain light calcium carbonate with different crystal forms and morphologies; when preparing calcite phase light calcium carbonate, controlling the temperature to 40°C-80°C, and controlling the pH to 9.5-13.

8.

2. The method for preparing light calcium carbonate of different crystal forms by using carbonized silica mother liquor according to claim 1, characterized in that: By adjusting the amount of Ca(OH)2 added and the pH value at the reaction end point, the mother liquor after the reaction is mainly composed of sodium carbonate or sodium hydroxide, and the mother liquor after the reaction is returned to the water glass preparation unit.

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