Preparation method of high-whiteness light calcium carbonate

Abstract

The present application relates to the technical field of calcium carbonate manufacturing, and particularly relates to a preparation method of high-whiteness light calcium carbonate. The method comprises the following steps: efficient leaching of calcium element in carbide slag; preparation of microbial crystal form control agent; and electric dispersion treatment and precipitation of calcium ions. The microbial crystal form control agent is prepared by adjusting the mixing ratio of Bacillus pumilus fermentation liquor and Pseudomonas fluorescens fermentation liquor, so that Ca 2+ The stearic acid and sodium polyacrylate in the microbial crystal form control agent can make the particles more stable and provide ion adsorption capacity after the larger calcium carbonate particles are mineralized, CO2 is introduced after temperature rising, and the crystal form of the calcium carbonate is optimized, so that the vaterite type crystallization with smaller crystal form is formed. The Bacillus pumilus can also assist in generating small-particle-size calcium carbonate over time, so that the high-whiteness small-particle-size light calcium carbonate is obtained.

Description

Technical Field

[0001] This invention relates to the field of calcium carbonate manufacturing technology, and in particular to a method for preparing high-whiteness light calcium carbonate. Background Technology

[0002] Calcium carbonate is an important inorganic chemical raw material, widely used in industries such as rubber, plastics, and inks. It is characterized by its low price and abundant sources. Depending on the production process, calcium carbonate powder is mainly divided into two types: one is heavy calcium carbonate (GCC) obtained by crushing and grinding natural calcium carbonate (such as marble and shells), and the other is light calcium carbonate synthesized by chemical reaction of materials such as phosphogypsum and carbide slag in liquid. The production process of heavy calcium carbonate is relatively simple, but due to its higher impurity content and larger particle size, it is usually less used in the fine chemical industry, while light calcium carbonate is commonly used in the fine chemical industry.

[0003] Light calcium carbonate is currently commonly prepared using the carbonation method. First, materials such as limestone and carbide slag are processed to obtain calcium oxide, which is then digested and separated to obtain a solution containing calcium ions. Carbon dioxide gas is then introduced to obtain a calcium carbonate slurry, followed by solid-liquid separation to obtain light calcium carbonate. To obtain smaller and more uniform calcium carbonate particles, many processes add additives to the calcium ion-containing solution. These additives include mineralizing microbial additives. While these additives can assist CO2 in rapidly forming calcium carbonate crystals, to better facilitate CO2 activation, the mineralizing microorganisms need to be uniformly dispersed in the calcium ion-containing solution before CO2 is introduced. This results in the mineralizing microorganisms mineralizing some of the calcium ions, forming some larger-sized calcium carbonate particles when the CO2 concentration is low, affecting the particle size and uniformity of the subsequently prepared light calcium carbonate. Summary of the Invention

[0004] To address the aforementioned technical deficiencies, this invention presents a method for preparing high-whiteness light calcium carbonate, which not only produces light calcium carbonate with fine and uniform particle size but also high purity and high whiteness.

[0005] A method for preparing high-whiteness light calcium carbonate includes the following steps:

[0006] S1: High-efficiency leaching of calcium from carbide slag

[0007] After mixing deionized water and PEG-400 evenly, ammonium acetate is slowly added. After the ammonium acetate is completely dissolved, ethanol is added and stirred. The stirring speed is increased and the temperature is raised. Triethyl citrate is added dropwise while stirring. Stirring is continued to obtain an organic ammonium salt leaching agent. The powder of carbide slag is added to the preheated organic ammonium salt leaching agent for leaching and filtration. The filter residue is treated to render it harmless. The calcium-containing filtrate is sealed and stored in a dark place for later use.

[0008] S2: Preparation of microbial crystal form control agents

[0009] Bacillus pumilus was activated and cultured with shaking. The bacterial solution was collected and the concentration was adjusted. Mannose was added to obtain Bacillus pumilus fermentation broth. Pseudomonas fluorescens was activated and cultured with shaking. The bacterial solution was collected and the concentration was adjusted to obtain Pseudomonas fluorescens fermentation broth. Sodium polyacrylate was dissolved in deionized water and barium sulfate was added and stirred evenly to obtain sodium polyacrylate solution. Stearic acid was melted and added to sodium polyacrylate solution. After ultrasonic dispersion, it was freeze-dried and pulverized to obtain solid powder. Bacillus pumilus fermentation broth, Pseudomonas fluorescens fermentation broth, solid powder, tricalcium phosphate, sodium citrate and magnesium sulfate were mixed evenly in a mass ratio of 1:(0.2-0.3):(0.5-0.6):(0.02-0.025):(0.01-0.02):(0.02-0.03) and stored at low temperature to obtain microbial crystal form control agent.

[0010] S3: Electrodispersion and precipitation of calcium ions

[0011] The calcium-containing filtrate was placed in a container and continuously stirred using an electric stirrer. A microbial crystal form control agent was added, and after stirring, pure carbon dioxide was introduced. Stirring was continued to obtain a suspension. The calcium carbonate precipitate in the suspension was separated, and after washing and drying, high-whiteness light calcium carbonate was obtained.

[0012] Furthermore, the efficient leaching of calcium from the carbide slag in step S1 includes the following steps:

[0013] S1.1: Place 80-100 parts by weight of deionized water and 0.3-0.4 parts by weight of PEG-400 in a container and stir continuously at a stirring speed of 300-350 rpm. Then slowly add 4-5 parts by weight of ammonium acetate. After the ammonium acetate is completely dissolved, add 5-6 parts by weight of ethanol and continue stirring for 3-5 minutes. Then increase the stirring speed to 550-600 rpm and raise the temperature to 35-40℃. While stirring, slowly add 0.8-1 parts by weight of triethyl citrate. After the addition is complete, continue stirring for 10-15 minutes to obtain the organic ammonium salt leaching agent.

[0014] S1.2: Take the organic ammonium salt leaching agent obtained in step S1.1 and place it in a container. Heat it in a water bath to 30-35℃ to obtain a preheated organic ammonium salt leaching agent. Place 4-5 parts by weight of carbide slag in a ball mill and grind it into powder. After passing it through a 120-130 mesh sieve, add it to the preheated organic ammonium salt leaching agent and stir magnetically for 25-30 minutes. Then filter to obtain calcium-containing filtrate and filter residue. The filter residue is treated to render it harmless. The calcium-containing filtrate is sealed and stored in a dark place for later use.

[0015] Furthermore, the preparation of the microbial crystal form control agent in step S2 includes the following steps:

[0016] S2.1: After activating Bacillus pumilus, inoculate it into LB medium and incubate it in a constant temperature shaker at 37-37.5℃ and 180-200 rpm for 22-24 hours. After centrifuging to collect the bacterial solution, adjust the bacterial concentration to 1×10⁻⁶. 8 -3×10 8 Add 0.1-0.2 wt% mannose to CFU / mL to obtain Bacillus pumilus fermentation broth. Activate Pseudomonas fluorescens and inoculate into LB medium. Incubate in a constant temperature shaker at 29.5-30℃ and 175-180 rpm for 22-24 hours. After centrifugation, collect the bacterial solution and adjust the bacterial concentration to 1×10⁻⁶. 7 -2×10 7 CFU / mL was used to obtain the fermentation broth of *Pseudomonas fluorescens*.

[0017] S2.2: Dissolve 5-6 parts by weight of sodium polyacrylate in 15-20 parts by weight of deionized water, then add 0.01-0.02 parts by weight of barium sulfate and stir until homogeneous to obtain a sodium polyacrylate solution. Place 18-20 parts by weight of stearic acid in a container and heat to 70-75°C. After the stearic acid has completely melted, slowly add 20-25 parts by weight of the sodium polyacrylate solution over 1-1.5 hours. Perform ultrasonic dispersion at a frequency of 20-25 kHz for 10-12 minutes, then freeze-dry and pulverize to obtain a solid powder.

[0018] S2.3: Mix Bacillus pumilus fermentation broth, Pseudomonas fluorescens fermentation broth, solid powder, tricalcium phosphate, sodium citrate and magnesium sulfate in a mass ratio of 1:(0.2-0.3):(0.5-0.6):(0.02-0.025):(0.01-0.02):(0.02-0.03) and store at 2-4℃ to obtain a microbial crystal form control agent.

[0019] Further, step S3, the electrodispersion treatment and precipitation of calcium ions, includes the following steps:

[0020] S3.1: Take 20-30 parts by weight of the calcium-containing filtrate obtained in step S1.2 and place it in a container. Attach an insulated stirring rod with copper wire wound around it to a stirrer. Connect the two ends of the copper wire to the positive and negative terminals of the power supply, respectively. Adjust the voltage to 2-5V. Then place the rod in the calcium-containing filtrate and stir continuously at a speed of 200-250 rpm. Add 8-10 parts by weight of the microbial crystal form control agent. After stirring for 40-50 minutes, introduce pure carbon dioxide and adjust the temperature to 37-37.5℃. Then continue stirring at a speed of 80-100 rpm until the pH of the calcium-containing filtrate does not change, thus obtaining a suspension.

[0021] S3.2: The suspension is placed in a centrifuge for solid-liquid separation to obtain calcium carbonate precipitate. The calcium carbonate precipitate is washed 2-3 times with anhydrous ethanol and then dried at 80-85℃ to obtain high-whiteness light calcium carbonate.

[0022] Furthermore, the fluorescent Pseudomonas in step S2.1 is Fluorescent Pseudomonas AbⅢ745-6.

[0023] Further, the LB medium in step S2.1 is prepared as follows: 1% peptone, 0.5% yeast extract and 1% sodium chloride are added to deionized water to prepare a 1000mL solution, which is then boiled and the pH is adjusted to 7. Finally, it is sterilized at 121℃ for 20 minutes.

[0024] Furthermore, in step S3.1, the volume ratio of the pure carbon dioxide introduced to the calcium-containing filtrate is 1:(1.8-2).

[0025] The beneficial effects are: 1. This invention involves separately shaking-culturing Bacillus pumilus and Pseudomonas fluorescens to obtain Bacillus pumilus fermentation broth and Pseudomonas fluorescens fermentation broth. During this process, the Pseudomonas fluorescens fermentation broth produces various antibacterial substances, such as aniline-methylacetic acid, due to the metabolism of Pseudomonas fluorescens. By adjusting the mixing ratio of the Bacillus pumilus fermentation broth and the Pseudomonas fluorescens fermentation broth, a microbial crystal form control agent is prepared. This agent can inhibit the activity of Bacillus pumilus to a certain extent in the initial stage of adding calcium-containing filtrate, slowing down the mineralization efficiency of Bacillus pumilus and preventing Ca from being fully mixed with the microbial crystal form control agent and calcium-containing filtrate. 2+ The mineralization process forms larger calcium carbonate particles, which facilitates the subsequent formation of fine and uniform calcium carbonate particles. After heating and introducing CO2, the activity of Bacillus pumilus recovers rapidly over time and with the increase in bacterial population, which can assist in the formation of small-particle calcium carbonate. By adjusting the mixing mass ratio of Bacillus pumilus fermentation broth to Pseudomonas fluorescens fermentation broth to 1:(0.2-0.3), not only can the mineralization efficiency of Bacillus pumilus be effectively inhibited in the early stage, but its activity can also be rapidly restored in the later stage, thereby obtaining high-purity, high-whiteness, small-particle-size, lightweight calcium carbonate.

[0026] 2. In this invention, a solid powder is prepared by using stearic acid, barium sulfate, and sodium polyacrylate. The solid powder is then added to the preparation of the microbial crystal form control agent. After adding the microbial crystal form control agent to the calcium-containing filtrate and heating and introducing CO2, the stearic acid and sodium polyacrylate in the microbial crystal form control agent can make the particles more stable and provide ion adsorption capacity, thereby optimizing the crystal form of calcium carbonate and forming smaller spheroidal aragonite crystals.

[0027] 3. This invention prepares an organic ammonium salt leaching agent by mixing deionized water and surfactant PEG-400, adding ammonium acetate, and then adding triethyl citrate dropwise. When this organic ammonium salt leaching agent leaches calcium ions from carbide slag, acetate ions react with calcium ions to form soluble calcium acetate, while triethyl citrate can form a stable chelate with calcium ions, reducing the calcium ion concentration. The synergistic effect of the two can effectively increase the speed and depth of acetate ions penetrating into the carbide slag, thereby increasing the calcium ion leaching rate.

[0028] 4. This invention uses an electrified stirring rod to stir the calcium-containing filtrate. Compared with ordinary stirring processes, this can fully drive the movement of ions in the solution, prevent calcium carbonate from depositing and agglomerating into large particles, and make the calcium carbonate crystallization more uniform, with higher purity and finer crystal form. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating the preparation method of high-whiteness light calcium carbonate used in embodiments of the present invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] A method for preparing high-whiteness light calcium carbonate, such as... Figure 1 As shown, it includes the following steps:

[0033] S1: High-efficiency leaching of calcium from carbide slag

[0034] S1.1: Place 80 parts by weight of deionized water and 0.3 parts by weight of PEG-400 in a container and stir continuously at a stirring speed of 300 rpm. Then slowly add 4 parts by weight of ammonium acetate. After the ammonium acetate is completely dissolved, add 5 parts by weight of ethanol and continue stirring for 3 minutes. Then increase the stirring speed to 550 rpm and raise the temperature to 35°C. While stirring, slowly add 0.8 parts by weight of triethyl citrate. After the addition is complete, continue stirring for 10 minutes to obtain the organic ammonium salt leaching agent.

[0035] S1.2: Take the organic ammonium salt leaching agent obtained in step S1.1 and place it in a container. Heat it in a water bath to 30°C to obtain a preheated organic ammonium salt leaching agent. Place 4 parts by weight of carbide slag in a ball mill and grind it into powder. After passing it through a 120-mesh sieve, add it to the preheated organic ammonium salt leaching agent and stir magnetically for 25 minutes. Then filter to obtain calcium-containing filtrate and filter residue. The filter residue is treated to render it harmless. The calcium-containing filtrate is sealed and stored in a dark place for later use.

[0036] S2: Preparation of microbial crystal form control agents

[0037] S2.1: Activated Bacillus pumilus was inoculated into LB medium. LB medium was prepared by adding 1% peptone, 0.5% yeast extract, and 1% sodium chloride to deionized water to a solution of 1000 mL. After boiling, the pH was adjusted to 7, and then sterilized at 121℃ for 20 minutes. The culture was then placed in a constant temperature shaker at 37℃ and 180 rpm for 22 hours. After centrifugation, the bacterial solution was collected and the concentration was adjusted to 1×10⁻⁶. 8 CFU / mL was added to obtain the fermentation broth of Bacillus pumilus. Activated Pseudomonas fluorescens AbⅢ745-6 was inoculated into LB medium and cultured in a constant temperature shaker at 29.5℃ and 175 rpm for 22 hours. After centrifugation, the bacterial culture was collected and the concentration was adjusted to 1×10⁻⁶. 7 CFU / mL was used to obtain the fermentation broth of *Pseudomonas fluorescens*.

[0038] S2.2: Dissolve 5 parts by weight of sodium polyacrylate in 15 parts by weight of deionized water, then add 0.01 parts by weight of barium sulfate and stir until homogeneous to obtain a sodium polyacrylate solution. Place 18 parts by weight of stearic acid in a container and heat to 70°C. After the stearic acid has completely melted, slowly add 20 parts by weight of the sodium polyacrylate solution within 1 hour. After ultrasonic dispersion at a frequency of 20 kHz for 10 minutes, freeze dry and pulverize to obtain a solid powder.

[0039] S2.3: Mix Bacillus pumilus fermentation broth, Pseudomonas fluorescens fermentation broth, solid powder, tricalcium phosphate, sodium citrate and magnesium sulfate in a mass ratio of 1:0.2:0.5:0.02:0.01:0.02, and then store at 2℃ to obtain a microbial crystal form control agent.

[0040] S3: Electrodispersion and precipitation of calcium ions

[0041] S3.1: Take 20 parts by weight of the calcium-containing filtrate obtained in step S1.2 and place it in a container. Attach an insulated stirring rod with copper wire wound around it to a stirrer. Connect the two ends of the copper wire to the positive and negative terminals of the power supply, respectively. Adjust the voltage to 2V. Then place the rod in the calcium-containing filtrate and stir continuously at a stirring speed of 200rpm. Add 8 parts by weight of the microbial crystal form control agent. After stirring for 40 minutes, introduce pure carbon dioxide. The volume ratio of pure carbon dioxide to calcium-containing filtrate is 1:1.8. Adjust the temperature to 37℃. Then stir continuously at a stirring speed of 80rpm until the pH of the calcium-containing filtrate does not change, thus obtaining a suspension.

[0042] S3.2: The suspension was placed in a centrifuge for solid-liquid separation to obtain calcium carbonate precipitate. The calcium carbonate precipitate was washed twice with anhydrous ethanol and then dried at 80°C to obtain high-whiteness light calcium carbonate.

[0043] Example 2

[0044] A method for preparing high-whiteness light calcium carbonate, such as... Figure 1 As shown, it includes the following steps:

[0045] S1: High-efficiency leaching of calcium from carbide slag

[0046] S1.1: Place 100 parts by weight of deionized water and 0.4 parts by weight of PEG-400 in a container and stir continuously at a stirring speed of 300 rpm. Then slowly add 5 parts by weight of ammonium acetate. After the ammonium acetate is completely dissolved, add 6 parts by weight of ethanol and continue stirring for 3 minutes. Then increase the stirring speed to 550 rpm and heat to 35°C. While stirring, slowly add 1 part by weight of triethyl citrate. After the addition is complete, continue stirring for 10 minutes to obtain the organic ammonium salt leaching agent.

[0047] S1.2: Take the organic ammonium salt leaching agent obtained in step S1.1 and place it in a container. Heat it in a water bath to 30°C to obtain a preheated organic ammonium salt leaching agent. Place 5 parts by weight of carbide slag in a ball mill and grind it into powder. After passing it through a 120-mesh sieve, add it to the preheated organic ammonium salt leaching agent and stir magnetically for 25 minutes. Then filter to obtain calcium-containing filtrate and filter residue. The filter residue is treated to render it harmless. The calcium-containing filtrate is sealed and stored in a dark place for later use.

[0048] S2: Preparation of microbial crystal form control agents

[0049] S2.1: Activated Bacillus pumilus was inoculated into LB medium. LB medium was prepared by adding 1% peptone, 0.5% yeast extract, and 1% sodium chloride to deionized water to a solution of 1000 mL. After boiling, the pH was adjusted to 7, and then sterilized at 121℃ for 20 minutes. The culture was then placed in a constant temperature shaker at 37℃ and 180 rpm for 22 hours. After centrifugation, the bacterial solution was collected and the concentration was adjusted to 1×10⁻⁶. 8 CFU / mL was added with 0.2 wt% mannose to obtain the Bacillus pumilus fermentation broth. Activated Pseudomonas fluorescens AbⅢ745-6 was inoculated into LB medium and cultured in a constant temperature shaker at 29.5℃ and 175 rpm for 22 hours. After centrifugation, the bacterial culture was collected and the concentration was adjusted to 1×10⁻⁶. 7 CFU / mL was used to obtain the fermentation broth of *Pseudomonas fluorescens*.

[0050] S2.2: Dissolve 6 parts by weight of sodium polyacrylate in 20 parts by weight of deionized water, then add 0.02 parts by weight of barium sulfate and stir until homogeneous to obtain a sodium polyacrylate solution. Place 20 parts by weight of stearic acid in a container and heat to 70°C. After the stearic acid has completely melted, slowly add 25 parts by weight of the sodium polyacrylate solution within 1 hour. After ultrasonic dispersion at a frequency of 20 kHz for 12 minutes, freeze dry and pulverize to obtain a solid powder.

[0051] S2.3: Mix Bacillus pumilus fermentation broth, Pseudomonas fluorescens fermentation broth, solid powder, tricalcium phosphate, sodium citrate and magnesium sulfate in a mass ratio of 1:0.3:0.6:0.025:0.02:0.03, and then store at 2℃ to obtain a microbial crystal form control agent.

[0052] S3: Electrodispersion and precipitation of calcium ions

[0053] S3.1: Take 30 parts by weight of the calcium-containing filtrate obtained in step S1.2 and place it in a container. Attach an insulated stirring rod with copper wire wound around it to a stirrer. Connect the two ends of the copper wire to the positive and negative terminals of the power supply, respectively. Adjust the voltage to 2V. Then place the rod in the calcium-containing filtrate and stir continuously at a stirring speed of 200rpm. Add 10 parts by weight of the microbial crystal form control agent. After stirring for 40 minutes, introduce pure carbon dioxide. The volume ratio of pure carbon dioxide to calcium-containing filtrate is 1:1.8. Adjust the temperature to 37℃. Then stir continuously at a stirring speed of 80rpm until the pH of the calcium-containing filtrate does not change, thus obtaining a suspension.

[0054] S3.2: The suspension was placed in a centrifuge for solid-liquid separation to obtain calcium carbonate precipitate. The calcium carbonate precipitate was washed twice with anhydrous ethanol and then dried at 80°C to obtain high-whiteness light calcium carbonate.

[0055] Example 3

[0056] A method for preparing high-whiteness light calcium carbonate, such as... Figure 1 As shown, it includes the following steps:

[0057] S1: High-efficiency leaching of calcium from carbide slag

[0058] S1.1: Place 80 parts by weight of deionized water and 0.3 parts by weight of PEG-400 in a container and stir continuously at a stirring speed of 350 rpm. Then slowly add 4 parts by weight of ammonium acetate. After the ammonium acetate is completely dissolved, add 5 parts by weight of ethanol and continue stirring for 5 minutes. Then increase the stirring speed to 600 rpm and heat to 40°C. While stirring, slowly add 0.8 parts by weight of triethyl citrate. After the addition is complete, continue stirring for 15 minutes to obtain the organic ammonium salt leaching agent.

[0059] S1.2: Take the organic ammonium salt leaching agent obtained in step S1.1 and place it in a container. Heat it in a water bath to 35°C to obtain a preheated organic ammonium salt leaching agent. Place 4 parts by weight of carbide slag in a ball mill and grind it into powder. After passing it through a 130-mesh sieve, add it to the preheated organic ammonium salt leaching agent and stir magnetically for 30 minutes. Then filter to obtain calcium-containing filtrate and filter residue. The filter residue is treated to render it harmless. The calcium-containing filtrate is sealed and stored in a dark place for later use.

[0060] S2: Preparation of microbial crystal form control agents

[0061] S2.1: Activated Bacillus pumilus was inoculated into LB medium. LB medium was prepared by adding 1% peptone, 0.5% yeast extract, and 1% sodium chloride to deionized water to a solution of 1000 mL. After boiling, the pH was adjusted to 7, and then sterilized at 121℃ for 20 minutes. The culture was then placed in a constant temperature shaker at 37.5℃ and 200 rpm for 24 hours. After centrifugation, the bacterial solution was collected and the concentration was adjusted to 3 × 10⁻⁶. 8 CFU / mL was added to obtain the fermentation broth of Bacillus pumilus. Activated Pseudomonas fluorescens AbⅢ745-6 was inoculated into LB medium and cultured in a constant temperature shaker at 30℃ and 180 rpm for 24 hours. After centrifugation, the bacterial culture was collected and the concentration was adjusted to 2 × 10⁻⁶. 7 CFU / mL was used to obtain the fermentation broth of *Pseudomonas fluorescens*.

[0062] S2.2: Dissolve 5 parts by weight of sodium polyacrylate in 15 parts by weight of deionized water, then add 0.01 parts by weight of barium sulfate and stir until homogeneous to obtain a sodium polyacrylate solution. Place 18 parts by weight of stearic acid in a container and heat to 75°C. After the stearic acid has completely melted, slowly add 20 parts by weight of the sodium polyacrylate solution over 1.5 hours. After ultrasonic dispersion at a frequency of 25 kHz for 12 minutes, freeze dry and pulverize to obtain a solid powder.

[0063] S2.3: Mix Bacillus pumilus fermentation broth, Pseudomonas fluorescens fermentation broth, solid powder, tricalcium phosphate, sodium citrate and magnesium sulfate in a mass ratio of 1:0.25:0.5:0.02:0.01:0.02, and then store at 4℃ to obtain a microbial crystal form control agent.

[0064] S3: Electrodispersion and precipitation of calcium ions

[0065] S3.1: Take 20 parts by weight of the calcium-containing filtrate obtained in step S1.2 and place it in a container. Attach an insulated stirring rod with copper wire wound around it to a stirrer. Connect the two ends of the copper wire to the positive and negative terminals of the power supply, respectively. Adjust the voltage to 5V. Then place the rod in the calcium-containing filtrate and stir continuously at a stirring speed of 250 rpm. Add 8 parts by weight of the microbial crystal form control agent. After stirring for 50 minutes, introduce pure carbon dioxide. The volume ratio of pure carbon dioxide to calcium-containing filtrate is 1:2. Adjust the temperature to 37.5℃. Then stir continuously at a stirring speed of 100 rpm until the pH of the calcium-containing filtrate does not change, thus obtaining a suspension.

[0066] S3.2: The suspension was placed in a centrifuge for solid-liquid separation to obtain calcium carbonate precipitate. The calcium carbonate precipitate was washed three times with anhydrous ethanol and then dried at 85°C to obtain high-whiteness light calcium carbonate.

[0067] Comparative Example 1

[0068] Compared with Example 1, the difference of Comparative Example 1 is that the fluorescent Pseudomonas fermentation broth was not added in step S2.3 to obtain the microbial crystal form control agent. The remaining steps are the same as those in Example 1. The high whiteness light calcium carbonate obtained is referred to as Comparative Example 1.

[0069] Comparative Example 2

[0070] Compared with Example 1, Comparative Example 2 differs in that step S2.2 is removed and solid powder is not added in step S2.3 to obtain the microbial crystal form control agent. The remaining steps are the same as in Example 1. The high whiteness light calcium carbonate obtained is referred to as Comparative Example 2.

[0071] Comparative Example 3

[0072] Compared with Example 1, the difference of Comparative Example 3 is that the insulating stirring rod with copper wire wound in step S3.1 is replaced with an ordinary stirring rod. The remaining steps are the same as those in Example 1. The high whiteness light calcium carbonate obtained is referred to as Comparative Example 3.

[0073] Comparative Example 4

[0074] Compared with Example 1, Comparative Example 4 differs in that triethyl citrate was not added in step S1.1 to prepare the ammonium salt leaching agent, and the organic ammonium salt leaching agent in step S1.2 was replaced with an equal mass of ammonium salt leaching agent. The remaining steps were the same as in Example 1.

[0075] Comparative Example 5

[0076] Compared with Example 1, Comparative Example 5 differs in that, in step S2.3, the fermentation broth of Bacillus pumilus, the fermentation broth of Pseudomonas fluorescens, the solid powder, tricalcium phosphate, sodium citrate and magnesium sulfate are mixed evenly in a mass ratio of 1:0.1:0.5:0.02:0.01:0.02, and then stored at 2°C to obtain a microbial crystal form control agent. The remaining steps are the same as in Example 1. The high whiteness light calcium carbonate obtained is referred to as Comparative Example 5.

[0077] Comparative Example 6

[0078] Compared with Example 1, Comparative Example 6 differs in that, in step S2.3, the fermentation broth of Bacillus pumilus, the fermentation broth of Pseudomonas fluorescens, the solid powder, tricalcium phosphate, sodium citrate and magnesium sulfate are mixed evenly in a mass ratio of 1:0.15:0.5:0.02:0.01:0.02, and then stored at 2°C to obtain a microbial crystal form control agent. The remaining steps are the same as in Example 1. The high-whiteness light calcium carbonate obtained is designated as Comparative Example 6.

[0079] Comparative Example 7

[0080] Compared with Example 1, Comparative Example 7 differs in that, in step S2.3, the fermentation broth of Bacillus pumilus, the fermentation broth of Pseudomonas fluorescens, the solid powder, tricalcium phosphate, sodium citrate and magnesium sulfate are mixed evenly in a mass ratio of 1:0.35:0.5:0.02:0.01:0.02, and then stored at 2°C to obtain a microbial crystal form control agent. The remaining steps are the same as in Example 1. The high-whiteness light calcium carbonate obtained is referred to as Comparative Example 7.

[0081] Comparative Example 8

[0082] Compared with Example 1, Comparative Example 8 differs in that, in step S2.3, the fermentation broth of Bacillus pumilus, the fermentation broth of Pseudomonas fluorescens, the solid powder, tricalcium phosphate, sodium citrate and magnesium sulfate are mixed evenly in a mass ratio of 1:0.4:0.5:0.02:0.01:0.02, and then stored at 2°C to obtain a microbial crystal form control agent. The remaining steps are the same as in Example 1. The high-whiteness light calcium carbonate obtained is referred to as Comparative Example 8.

[0083] Experiment 1: Take equal masses of high-whiteness light calcium carbonate prepared in Examples 1-3, Comparative Examples 1-3, and Comparative Examples 5-8. First, measure the whiteness using a digital whiteness meter (XT-48B / BN). Then, grind the high-whiteness light calcium carbonate into calcium carbonate powder samples and disperse them in ethanol solution. Place the powder in an ultrasonic cleaner and ultrasonically disperse for 5 minutes. Use disposable sizing cuvettes to test the particle size distribution, and test the particle size distribution using a particle size analyzer. Then, use a thermogravimetric analyzer to test the content of high-whiteness light calcium carbonate. The heating gas atmosphere is air, and the heating temperature is 800℃. Record the calcium carbonate content as the purity. Record the above data on whiteness, particle size distribution, and purity and make a table, as shown in Table 1.

[0084] Table 1: Whiteness, particle size, and purity of high-whiteness light calcium carbonate

[0085]

[0086] As can be seen from the data of Examples 1-3 and Comparative Examples 1-3 in Table 1, the whiteness and purity of the high-whiteness light calcium carbonate prepared in Examples 1-3 are greater than those of Comparative Examples 1-3, and the particle size distribution is smaller than that of Comparative Examples 1-3. This proves that adding the fermentation broth of Pseudomonas fluorescens to the microbial crystal form control agent, as well as the solid powder prepared by adding sodium polyacrylate and stearic acid, and adding the obtained microbial crystal form control agent to the calcium-containing filtrate can not only improve the whiteness and purity of the prepared light calcium carbonate, but also reduce the particle size of the prepared high-whiteness light calcium carbonate. It also proves that stirring the calcium-containing filtrate with an electric stirring rod during the carbonation process can fully drive the movement of ions in the solution, avoid the deposition and aggregation of calcium carbonate to form large particles, thereby making the crystallization of calcium carbonate more uniform, with higher purity, and the formed crystal form finer.

[0087] As can be seen from the data in Examples 1-3 and Comparative Examples 5-8 in Table 1, when the ratio of Bacillus pumilus fermentation broth to Pseudomonas fluorescens fermentation broth is not within the range of 1:(0.2-0.3) when preparing the microbial crystal form control agent, the whiteness and purity of the high-whiteness light calcium carbonate are reduced, and the particle size distribution is increased. This proves that when the ratio of Bacillus pumilus fermentation broth to Pseudomonas fluorescens fermentation broth is within the range of 1:(0.2-0.3), the microbial crystal form control agent has the best effect. It can not only effectively inhibit the mineralization efficiency of Bacillus pumilus in the early stage, but also enable its activity to recover rapidly in the later stage, thereby obtaining high-purity, high-whiteness, small-particle-size light calcium carbonate.

[0088] Experiment 2: Two equal masses of calcium carbide slag were ground into powder. The chemical composition of the raw materials was analyzed by XRF analysis. The mass m of the calcium carbide slag before leaching and the mass fraction w of calcium in the calcium carbide slag before leaching were recorded. The leaching was carried out using the process of step S1.2 in Example 1 and Comparative Example 4, respectively, to obtain filter residue. The chemical composition of the raw materials was analyzed by XRF analysis. The mass m1 of the filter residue and the mass fraction w1 of calcium in the filter residue were recorded. The calcium ion leaching rate was calculated as (m·w-m1·w1) / m×100%. Three parallel experiments were conducted, and the calcium ion leaching rate was recorded and compiled into a table, as shown in Table 2.

[0089] Table 2: Leaching rate of calcium ions

[0090]

[0091] It can be seen that the calcium ion leaching rate of Example 1 was greater than that of Comparative Example 4 in all three cases, which proves that the addition of triethyl citrate to ammonium acetate can synergistically leach calcium ions and improve the calcium ion leaching rate.

[0092] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing high-whiteness light calcium carbonate, characterized in that, Includes the following steps: S1: High-efficiency leaching of calcium from carbide slag After mixing deionized water and PEG-400 evenly, ammonium acetate is slowly added. After the ammonium acetate is completely dissolved, ethanol is added and stirred. The stirring speed is increased and the temperature is raised. Triethyl citrate is added dropwise while stirring. Stirring is continued to obtain an organic ammonium salt leaching agent. The powder of carbide slag is added to the preheated organic ammonium salt leaching agent for leaching and filtration. The filter residue is treated to render it harmless. The calcium-containing filtrate is sealed and stored in a dark place for later use. S2: Preparation of microbial crystal form control agents Bacillus pumilus was activated and cultured with shaking. The bacterial solution was collected and the concentration was adjusted. Mannose was added to obtain Bacillus pumilus fermentation broth. Pseudomonas fluorescens was activated and cultured with shaking. The bacterial solution was collected and the concentration was adjusted to obtain Pseudomonas fluorescens fermentation broth. Sodium polyacrylate was dissolved in deionized water and barium sulfate was added and stirred evenly to obtain sodium polyacrylate solution. Stearic acid was melted and added to sodium polyacrylate solution. After ultrasonic dispersion, it was freeze-dried and pulverized to obtain solid powder. Bacillus pumilus fermentation broth, Pseudomonas fluorescens fermentation broth, solid powder, tricalcium phosphate, sodium citrate and magnesium sulfate were mixed evenly in a mass ratio of 1:(0.2-0.3):(0.5-0.6):(0.02-0.025):(0.01-0.02):(0.02-0.03) and stored at low temperature to obtain microbial crystal form control agent. S3: Electrodispersion and precipitation of calcium ions The calcium-containing filtrate was placed in a container and continuously stirred using an electric stirrer. A microbial crystal form control agent was added, and after stirring, pure carbon dioxide was introduced. Stirring was continued to obtain a suspension. The calcium carbonate precipitate in the suspension was separated, and after washing and drying, high-whiteness light calcium carbonate was obtained.

2. The method for preparing high-whiteness light calcium carbonate according to claim 1, characterized in that, Step S1, efficient leaching of calcium from carbide slag, includes the following steps: S1.1: Place 80-100 parts by weight of deionized water and 0.3-0.4 parts by weight of PEG-400 in a container and stir continuously at a stirring speed of 300-350 rpm. Then slowly add 4-5 parts by weight of ammonium acetate. After the ammonium acetate is completely dissolved, add 5-6 parts by weight of ethanol and continue stirring for 3-5 minutes. Then increase the stirring speed to 550-600 rpm and raise the temperature to 35-40℃. While stirring, slowly add 0.8-1 parts by weight of triethyl citrate. After the addition is complete, continue stirring for 10-15 minutes to obtain the organic ammonium salt leaching agent. S1.2: Take the organic ammonium salt leaching agent obtained in step S1.1 and place it in a container. Heat it in a water bath to 30-35℃ to obtain a preheated organic ammonium salt leaching agent. Place 4-5 parts by weight of carbide slag in a ball mill and grind it into powder. After passing it through a 120-130 mesh sieve, add it to the preheated organic ammonium salt leaching agent and stir magnetically for 25-30 minutes. Then filter to obtain calcium-containing filtrate and filter residue. The filter residue is treated to render it harmless. The calcium-containing filtrate is sealed and stored in a dark place for later use.

3. The method for preparing high-whiteness light calcium carbonate according to claim 1, characterized in that, Step S2, the preparation of the microbial crystal form control agent, includes the following steps: S2.1: After activating Bacillus pumilus, inoculate it into LB medium and incubate it in a constant temperature shaker at 37-37.5℃ and 180-200 rpm for 22-24 hours. After centrifuging to collect the bacterial solution, adjust the bacterial concentration to 1×10⁻⁶. 8 -3×10 8 Add 0.1-0.2 wt% mannose to CFU / mL to obtain Bacillus pumilus fermentation broth. Activate Pseudomonas fluorescens and inoculate into LB medium. Incubate in a constant temperature shaker at 29.5-30℃ and 175-180 rpm for 22-24 hours. After centrifugation, collect the bacterial solution and adjust the bacterial concentration to 1×10⁻⁶. 7 -2×10 7 CFU / mL was used to obtain the fermentation broth of *Pseudomonas fluorescens*. S2.2: Dissolve 5-6 parts by weight of sodium polyacrylate in 15-20 parts by weight of deionized water, then add 0.01-0.02 parts by weight of barium sulfate and stir until homogeneous to obtain a sodium polyacrylate solution. Place 18-20 parts by weight of stearic acid in a container and heat to 70-75°C. After the stearic acid has completely melted, slowly add 20-25 parts by weight of the sodium polyacrylate solution over 1-1.5 hours. Perform ultrasonic dispersion at a frequency of 20-25 kHz for 10-12 minutes, then freeze-dry and pulverize to obtain a solid powder. S2.3: Mix Bacillus pumilus fermentation broth, Pseudomonas fluorescens fermentation broth, solid powder, tricalcium phosphate, sodium citrate and magnesium sulfate in a mass ratio of 1:(0.2-0.3):(0.5-0.6):(0.02-0.025):(0.01-0.02):(0.02-0.03) and store at 2-4℃ to obtain a microbial crystal form control agent.

4. The method for preparing high-whiteness light calcium carbonate according to claim 2, characterized in that, Step S3, the electrodispersion and precipitation of calcium ions, includes the following steps: S3.1: Take 20-30 parts by weight of the calcium-containing filtrate obtained in step S1.2 and place it in a container. Attach an insulated stirring rod with copper wire wound around it to a stirrer. Connect the two ends of the copper wire to the positive and negative terminals of the power supply, respectively. Adjust the voltage to 2-5V. Then place the rod in the calcium-containing filtrate and stir continuously at a speed of 200-250 rpm. Add 8-10 parts by weight of the microbial crystal form control agent. After stirring for 40-50 minutes, introduce pure carbon dioxide and adjust the temperature to 37-37.5℃. Then continue stirring at a speed of 80-100 rpm until the pH of the calcium-containing filtrate does not change, thus obtaining a suspension. S3.2: The suspension is placed in a centrifuge for solid-liquid separation to obtain calcium carbonate precipitate. The calcium carbonate precipitate is washed 2-3 times with anhydrous ethanol and then dried at 80-85℃ to obtain high-whiteness light calcium carbonate.

5. The method for preparing high-whiteness light calcium carbonate according to claim 3, characterized in that, The fluorescent Pseudomonas in step S2.1 is Fluorescent Pseudomonas AbⅢ745-6.

6. The method for preparing high-whiteness light calcium carbonate according to claim 3, characterized in that, The method for preparing LB medium in step S2.1 is as follows: add 1% peptone, 0.5% yeast extract and 1% sodium chloride to deionized water to prepare a 1000mL solution, boil it and adjust the pH to 7, and then sterilize it at 121℃ for 20 minutes.

7. The method for preparing high-whiteness light calcium carbonate according to claim 4, characterized in that, In step S3.1, the volume ratio of the pure carbon dioxide introduced to the calcium-containing filtrate is 1:(1.8-2).

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