Preparation method of high-purity granular aluminum fluoride trihydrate

Abstract

In order to solve the technical problem that high-purity particle-state aluminum fluoride trihydrate is difficult to prepare by an existing preparation method, the invention provides the preparation method of the high-purity particle-state aluminum fluoride trihydrate. According to the method, the property that fluoroaluminate can be solidified after being cooled and hydrolyzed into aluminum fluoride trihydrate and hydrofluoric acid in ice water is utilized, aluminum fluoride trihydrate crystal particles are formed by controlling the hydrolysis temperature and the hydrolysis speed, and redundant hydrofluoric acid is removed through centrifugal water washing, so that multiple crushing steps are omitted, and the purity of particle-state aluminum fluoride trihydrate is ensured.

Description

Technical Field

[0001] The present invention relates to a preparation method of particulate aluminum fluoride trihydrate. Background Art

[0002] Particulate aluminum fluoride trihydrate has a more uniform particle size distribution, a larger specific surface area, and can provide more active sites. Therefore, it is superior to ordinary aluminum fluoride trihydrate in terms of reaction activity, solubility, purity, etc. Its applications are mostly concentrated in high-tech industries such as new energy, electronics, advanced ceramics, optics, and the nuclear industry.

[0003] In the field of new energy, particulate aluminum fluoride trihydrate can be used as a solid electrolyte additive for battery materials to improve the thermal stability and ionic conductivity of the electrolyte; it can also be used as a surface coating material for electrode materials to inhibit side reactions of electrode materials (such as high-nickel ternary cathodes) and extend the battery cycle life.

[0004] In the field of electronics, due to its low dielectric constant and excellent heat resistance, particulate aluminum fluoride trihydrate can be used as a dielectric material in the electronics and semiconductor industries and as an insulating layer material in integrated circuits.

[0005] In the fields of advanced ceramics and optics, particulate aluminum fluoride trihydrate can be used as a flux and additive for preparing high-performance ceramics (such as transparent ceramics, structural ceramics) and optical glass, which can reduce the sintering temperature and improve the material density; high-purity particulate aluminum fluoride trihydrate is also suitable for vacuum coating processes to manufacture antireflection coatings or ultraviolet (UV) cut-off filters.

[0006] In the field of the nuclear industry, the neutron absorption ability of particulate aluminum fluoride trihydrate enables it to be used as a composite component of nuclear reactor control rods or radiation shielding materials, solidify radioactive waste and combine with nuclear waste to form stable compounds, reducing the risk of radioactive substance leakage.

[0007] Currently, the production of particulate aluminum fluoride trihydrate usually adopts the fluosilicic acid method, but the aluminum fluoride trihydrate generated by fluosilicic acid generally has high impurities and cannot meet the usage requirements of high-end industries. And when directly using electronic-grade hydrofluoric acid to react with aluminum hydroxide to form aluminum fluoride, it generally solidifies entirely in the barrel, and particulate aluminum fluoride trihydrate cannot be obtained. Summary of the Invention

[0008] In order to solve the technical problem that it is difficult to prepare high-purity particulate aluminum fluoride trihydrate by the existing preparation methods, the present invention provides a preparation method of high-purity particulate aluminum fluoride trihydrate.

[0009] The technical solution of the present invention is as follows:

[0010] A preparation method of high-purity particulate aluminum fluoride trihydrate, characterized in that it includes the following steps:

[0011] Step 1: Prepare fluoroaluminate acid;

[0012] Slowly add high-purity aluminum hydroxide to electronic-grade hydrofluoric acid, taking care not to add it too quickly to prevent boiling over. Keep it warm and stir until it becomes colorless and transparent to obtain a fluoroaluminate acid solution; the reaction equation is: 4HF + Al(OH) 3 ==== HAlF 4 + 3H 2 O;

[0013] Step 2: Concentrate the fluoroaluminate acid solution;

[0014] Heat up and concentrate the fluoroaluminate acid solution until its specific gravity reaches 1.5 - 1.6, then stop heating and stir to cool it down to 40 - 45 °C to obtain a concentrated fluoroaluminate acid solution; the concentration to a specific gravity of 1.5 - 1.6 is the near-limit concentration explored through production practice and a large number of experiments, which can ensure that it will not easily agglomerate during the subsequent preparation of aluminum fluoride trihydrate; cooling down to 40 - 45 °C is the limit temperature for condensation at a solution specific gravity of 1.5 - 1.6. If the temperature is too low, it cannot ensure that it will not agglomerate during the subsequent preparation of aluminum fluoride trihydrate;

[0015] Step 3: Prepare particulate aluminum fluoride trihydrate;

[0016] Step 3.1: Mix crushed ice cubes formed from high-purity water with high-purity cold water at 0 - 5 °C to form a high-purity ice-water mixture; the reason for using high-purity cold water at 0 - 5 °C in this step is to ensure that after adding the concentrated fluoroaluminate acid solution to the high-purity ice-water mixture subsequently, it can prevent the temperature from being too high and dissolving it in water, so that the fluoroaluminate acid can be fully hydrolyzed and condensed into aluminum fluoride trihydrate particles, improving the yield;

[0017] Step 3.2: Slowly add the concentrated fluoroaluminate acid solution to the high-purity ice-water mixture, continuously stir the ice-water mixture during the process. During the addition of the concentrated fluoroaluminate acid solution, aluminum fluoride trihydrate particles gradually form. After adding, stop stirring. When the temperature of the synthesis solution is measured to be 0 - 5 °C, obtain an aluminum fluoride trihydrate synthesis solution; the reaction equation is: HAlF 4 + 3H 2 O ==== AlF 3 ·3H 2 O + HF;

[0018] Step 4: Prepare aluminum fluoride trihydrate crystal particles;

[0019] Step 4.1: Let the aluminum fluoride trihydrate synthesis solution stand still, remove the supernatant to obtain an aluminum fluoride trihydrate precipitate;

[0020] Step 4.2: Centrifuge the aluminum fluoride trihydrate precipitate, wash away the excess acid with high-purity water during the process. When the free hydrofluoric acid in the washing solution is less than or equal to 0.03%, obtain aluminum fluoride trihydrate crystal particles;

[0021] Step 5: Drying

[0022] Dry the aluminum fluoride trihydrate crystal particles at 100 - 110°C for 10 - 15 hours. When the free water is measured to be less than 0.3%, the finished product of particulate aluminum fluoride trihydrate is obtained. Drying at 100 - 110°C can, on the one hand, ensure that the moisture in the aluminum fluoride trihydrate crystal particles can be evaporated, and on the other hand, prevent the decomposition of aluminum fluoride trihydrate.

[0023] Use ion chromatography to detect the finished product of aluminum fluoride trihydrate obtained in Step 5. Measure that the contents of elements such as iron, cobalt, nickel, copper, cadmium, and vanadium are all less than 0.0001%, sodium is less than 0.01%. Use turbidimetry to test that the contents of chlorine and sulfate are both less than 0.005%. The sieving rate above 60 mesh is 80%. Use an X-rd diffractometer to qualitatively identify it as aluminum fluoride trihydrate.

[0024] Furthermore, in Step 1: The mass fraction of the electronic grade hydrofluoric acid is 25 - 50%.

[0025] Furthermore, in Step 1: High-purity aluminum hydroxide refers to aluminum hydroxide with the contents of elements such as iron, cobalt, nickel, copper, cadmium, and vanadium less than 0.0001% and sodium less than 0.1%.

[0026] Furthermore, in Step 1: The molar ratio of hydrofluoric acid to aluminum hydroxide is 4 - 4.5:1. Keep the temperature at 80 - 100°C and stir until it becomes colorless and transparent. Here, the molar ratio of hydrogen fluoride to aluminum hydroxide being 4 - 4.5:1 is to fully form a fluoroaluminate solution, and the holding temperature of 80 - 100°C is to dissolve aluminum hydroxide more thoroughly.

[0027] Furthermore, in Step 2: Heat the fluoroaluminate solution to 105 - 120°C for concentration.

[0028] Furthermore, in Step 3.1: The mass ratio of cold water to crushed ice cubes is 3 - 5:1, which can not only improve the crystallization yield but also prevent excessive wastewater from affecting the production efficiency.

[0029] Furthermore, in Step 3.2, the mass ratio of the fluoroaluminate concentrate to the high-purity ice-water mixture is 1:2 - 3, which can not only improve the crystallization yield but also prevent excessive wastewater from affecting the production efficiency; the stirring speed of the ice-water mixture is 30 - 100 revolutions per minute; the fluoroaluminate concentrate is added to the high-purity ice-water mixture at a speed of 10 liters per minute.

[0030] Furthermore, in Step 4.1, let the aluminum fluoride trihydrate synthesis solution stand for 30 - 60 minutes so that the crystals sink to the bottom of the container, facilitating the collection of crystals.

[0031] Further, in step 4.2: Wrap the aluminum fluoride trihydrate precipitate with a filter cloth of 500 - 1000 mesh, place it in a centrifuge, and perform centrifugation at a rotational speed of 500 - 1000 revolutions per minute.

[0032] The present invention also provides a high - purity particulate aluminum fluoride trihydrate, which is characterized in that it is prepared by the above - mentioned method.

[0033] The advantages of the present invention are as follows:

[0034] 1. Usually, when synthesizing aluminum fluoride / aluminum fluoride trihydrate with hydrofluoric acid and aluminum hydroxide, it will coagulate into large pieces, resulting in the inability to handle the excess hydrofluoric acid on the surface of aluminum fluoride / aluminum fluoride trihydrate and corroding the equipment. Therefore, it often needs to be dried and pulverized multiple times, resulting in a relatively high impurity content in the final product. However, the present invention utilizes the property that fluoroaluminum acid will solidify after cooling and hydrolyze into aluminum fluoride trihydrate and hydrofluoric acid in ice water. After forming aluminum fluoride trihydrate crystal particles by controlling the hydrolysis temperature and hydrolysis rate, centrifugation and water washing are used to remove the excess hydrofluoric acid, eliminating the need for multiple pulverization steps and ensuring the purity of the particulate aluminum fluoride trihydrate.

[0035] 2. The present invention uses crushed ice cubes formed by high - purity water and high - purity cold water at 0 - 5 °C to form a high - purity ice - water mixture, and slowly adds concentrated fluoroaluminum acid to this high - purity ice - water mixture to prevent the dissolution of fluoroaluminum acid in water due to excessive temperature, ensuring the full hydrolysis and condensation of fluoroaluminum acid into aluminum fluoride trihydrate particles and improving the yield. Description of the Drawings

[0036] Figure 1 is the XRD pattern of the aluminum fluoride trihydrate prepared by the present invention. Detailed Embodiments

[0037] The present invention will be further described below with reference to the drawings and embodiments.

[0038] Embodiment 1

[0039] The high - purity particulate aluminum fluoride trihydrate is prepared in this embodiment through the following steps:

[0040] Step 1: Prepare fluoroaluminum acid;

[0041] Take electronic - grade hydrofluoric acid with a mass fraction of 25%, add it to a tetrafluoro reaction kettle, and slowly add high - purity aluminum hydroxide to it. The molar ratio of hydrofluoric acid to aluminum hydroxide is 4:1, and keep it warm at 80 °C and stir until it becomes colorless and transparent to obtain a fluoroaluminum acid solution; among them, high - purity aluminum hydroxide refers to aluminum hydroxide with the contents of iron, cobalt, nickel, copper, cadmium, and vanadium elements less than 0.0001% and the sodium content less than 0.1%.

[0042] Step 2: Concentrate the fluoroaluminum acid solution;

[0043] Heat up the fluoroaluminate solution obtained in Step 1.1 to 120 °C for concentration. The colorless and transparent fluoroaluminate solution is concentrated until it gradually turns white. When the specific gravity of the solution reaches 1.5, stop heating and stir to cool down to 40 °C to obtain a concentrated fluoroaluminate solution;

[0044] Step 3: Prepare particulate aluminum trifluoride trihydrate;

[0045] Step 3.1: Prepare high-purity cold water at 3 °C, add crushed ice cubes made from high-purity water to it, and the mass ratio of cold water to crushed ice cubes is 3:1 to obtain a high-purity ice-water mixture;

[0046] Step 3.2: Slowly add the concentrated fluoroaluminate solution obtained in Step 2 to the high-purity ice-water mixture obtained in Step 3.1. The mass ratio of the concentrated fluoroaluminate solution to the high-purity ice-water mixture is 1:2. During this process, continuously stir the ice-water mixture at a speed of 30 revolutions per minute. As the concentrated fluoroaluminate solution is added, aluminum trifluoride trihydrate particles gradually form. After adding, stop stirring. When the temperature of the synthesis solution is measured at 4 °C, an aluminum trifluoride trihydrate synthesis solution is obtained.

[0047] Step 4: Prepare aluminum trifluoride trihydrate crystalline particles;

[0048] Step 4.1: Let the aluminum trifluoride trihydrate synthesis solution obtained in Step 3.2 stand for 30 minutes. At this time, the aluminum trifluoride trihydrate particles sink to the bottom, remove the supernatant to obtain an aluminum trifluoride trihydrate precipitate;

[0049] Step 4.2: Wrap the aluminum trifluoride trihydrate precipitate obtained in Step 4.1 with a 500-mesh filter cloth, place it in a centrifuge, and perform centrifugation at a speed of 500 revolutions per minute. During the process, appropriately wash it with high-purity water. When the content of free electron-grade hydrofluoric acid is measured to be 0.023%, aluminum trifluoride trihydrate crystalline particles are obtained;

[0050] Step 5: Dry;

[0051] Place the aluminum trifluoride trihydrate crystalline particles obtained in Step 4.2 in a tetrafluoro plate, then put it into a steam oven, dry it at a temperature of 100 - 110 °C for 15 hours. When the free water is measured to be 0.22% by the Karl Fischer method, a finished product of particulate aluminum trifluoride trihydrate is obtained.

[0052] Use ion chromatography to detect the finished product of particulate aluminum trifluoride trihydrate obtained in this example. The contents of elements such as iron, cobalt, nickel, copper, cadmium, and vanadium are all less than 0.0001%, sodium is less than 0.01%. Use the turbidimetry method to test that the contents of chlorine and sulfate radicals are both less than 0.005%. The screening above 60 meshes is 82%. Use an X-rd diffractometer to qualitatively identify it as aluminum trifluoride trihydrate. The XRD pattern is as Figure 1 shown.

[0053] Example 2

[0054] In this embodiment, high-purity particulate aluminum trifluoride trihydrate is prepared through the following steps

[0055] Step 1: Prepare fluoroaluminum acid;

[0056] Take electronic-grade hydrofluoric acid with a mass fraction of 35%, add it to a tetrafluoro reactor, and slowly add high-purity aluminum hydroxide to it. The molar ratio of hydrofluoric acid to aluminum hydroxide is 4.2:1. Keep the temperature at 85°C and stir until it becomes colorless and transparent to obtain a fluoroaluminum acid solution. Among them, high-purity aluminum hydroxide refers to aluminum hydroxide with the content of iron, cobalt, nickel, copper, cadmium, and vanadium elements less than 0.0001% and the sodium content less than 0.1%.

[0057] Step 2: Concentrate the fluoroaluminum acid solution;

[0058] Heat up the fluoroaluminum acid solution obtained in Step 1.1 to 110°C for concentration. The colorless and transparent fluoroaluminum acid solution is concentrated until it gradually turns white. When the specific gravity of the solution is 1.52, stop heating and stir to cool down to 43°C to obtain a concentrated fluoroaluminum acid solution;

[0059] Step 3: Prepare particulate aluminum trifluoride trihydrate;

[0060] Step 3.1: Prepare high-purity cold water at 2°C, add crushed ice cubes made of high-purity water to it, and the mass ratio of cold water to crushed ice cubes is 4:1 to obtain a high-purity ice-water mixture;

[0061] Step 3.2: Slowly add the concentrated fluoroaluminum acid solution obtained in Step 2 to the high-purity ice-water mixture obtained in Step 3.1. The mass ratio of the concentrated fluoroaluminum acid solution to the high-purity ice-water mixture is 1:2.5. During this process, continuously stir the ice-water mixture at a speed of 50 revolutions per minute. As the concentrated fluoroaluminum acid solution is added, aluminum trifluoride trihydrate particles are gradually formed. After adding, stop stirring. When the temperature of the synthesis solution is measured at 5°C, an aluminum trifluoride trihydrate synthesis solution is obtained.

[0062] Step 4: Prepare aluminum trifluoride trihydrate crystal particles;

[0063] Step 4.1: Let the aluminum trifluoride trihydrate synthesis solution obtained in Step 3.2 stand for 35 minutes. At this time, the aluminum trifluoride trihydrate particles sink to the bottom, remove the supernatant to obtain an aluminum trifluoride trihydrate precipitate;

[0064] Step 4.2: Wrap the aluminum trifluoride trihydrate precipitate obtained in Step 4.1 with a 1000-mesh filter cloth, put it into a centrifuge, and perform centrifugation at a speed of 1000 revolutions per minute. During the process, appropriately wash it with high-purity water. When the content of free electronic-grade hydrofluoric acid is measured to be less than 0.03%, aluminum trifluoride trihydrate crystal particles are obtained;

[0065] Step 5: Dry;

[0066] Place the aluminum fluoride trihydrate crystal particles obtained in Step 4.2 in a Teflon tray, and then put it into a steam oven. Dry it at a temperature of 110°C for 13 hours. When the free water is measured to be 0.28% by the Karl Fischer method, the finished product of particulate aluminum fluoride trihydrate is obtained.

[0067] Use ion chromatography to detect the finished product of particulate aluminum fluoride trihydrate obtained in this example. The contents of elements such as iron, cobalt, nickel, copper, cadmium, and vanadium are all less than 0.0001%, sodium is less than 0.01%. Use the turbidimetry method to test that the contents of chlorine and sulfate are both less than 0.005%. The screening above 60 mesh is 84%. Use an X-rd diffractometer to qualitatively identify it as aluminum fluoride trihydrate. The XRD pattern is as Figure 1 shown.

[0068] Example 3

[0069] The high-purity particulate aluminum fluoride trihydrate is prepared in this example through the following steps

[0070] Step 1: Prepare fluoroaluminum acid;

[0071] Take electronic-grade hydrofluoric acid with a mass fraction of 50% and add it to a Teflon reaction kettle. Slowly add high-purity aluminum hydroxide to it. The molar ratio of hydrofluoric acid to aluminum hydroxide is 4.5:1. Keep the temperature at 100°C and stir until it becomes colorless and transparent to obtain a fluoroaluminum acid solution. Among them, high-purity aluminum hydroxide refers to aluminum hydroxide with the contents of elements such as iron, cobalt, nickel, copper, cadmium, and vanadium less than 0.0001% and sodium content less than 0.1%.

[0072] Step 2: Concentrate the fluoroaluminum acid solution;

[0073] Heat up the fluoroaluminum acid solution obtained in Step 1.1 to 105°C for concentration. The colorless and transparent fluoroaluminum acid solution is concentrated until it gradually turns white. When the specific gravity of the solution is 1.55, stop heating and stir to cool down to 45°C to obtain a concentrated fluoroaluminum acid solution.

[0074] Step 3: Prepare particulate aluminum fluoride trihydrate;

[0075] Step 3.1: Prepare high-purity cold water at 4-5°C, and add crushed ice cubes made of high-purity water to it. The mass ratio of cold water to crushed ice cubes is 5:1 to obtain a high-purity ice-water mixture;

[0076] Step 3.2: Slowly add the concentrated fluoroaluminum acid solution obtained in Step 2 to the high-purity ice-water mixture obtained in Step 3.1. The mass ratio of the concentrated fluoroaluminum acid solution to the high-purity ice-water mixture is 1:3. During this process, continuously stir the ice-water mixture at a speed of 100 revolutions per minute. As the concentrated fluoroaluminum acid solution is added, aluminum fluoride trihydrate particles gradually form. After adding, stop stirring. When the temperature of the synthesis solution is measured to be 2°C, a synthesis solution of aluminum fluoride trihydrate is obtained.

[0077] Step 4: Prepare aluminum fluoride trihydrate crystalline particles;

[0078] Step 4.1: Let the aluminum fluoride trihydrate synthesis solution obtained in Step 3.2 stand for 60 minutes. At this time, the aluminum fluoride trihydrate particles sink to the bottom. Remove the supernatant to obtain aluminum fluoride trihydrate precipitate;

[0079] Step 4.2: Wrap the aluminum fluoride trihydrate precipitate obtained in Step 4.1 with a 1000-mesh filter cloth, place it in a centrifuge, and perform centrifugation at a speed of 800 revolutions per minute. During the process, wash it appropriately with high-purity water. When the content of free electron-grade hydrofluoric acid is measured to be less than 0.021%, aluminum fluoride trihydrate crystalline particles are obtained;

[0080] Step 5: Dry;

[0081] Place the aluminum fluoride trihydrate crystalline particles obtained in Step 4.2 in a tetrafluoro plate, and then put it into a steam oven. Dry it at a temperature of 105°C for 12 hours. When the free water measured by the Karl Fischer method is less than 0.18%, the finished product of particulate aluminum fluoride trihydrate is obtained.

[0082] Use ion chromatography to detect the finished product of particulate aluminum fluoride trihydrate obtained in this example. The contents of elements such as iron, cobalt, nickel, copper, cadmium, and vanadium are all less than 0.0001%, sodium is less than 0.01%. Use turbidimetry to test that the contents of chlorine and sulfate are both less than 0.005%. The sieving above 60 meshes is 88%. Use an X-rd diffractometer to qualitatively identify it as aluminum fluoride trihydrate. The XRD pattern is as Figure 1 shown.

[0083] Example 4

[0084] High-purity particulate aluminum fluoride trihydrate is prepared in this example through the following steps

[0085] Step 1: Prepare fluoroaluminate acid;

[0086] Take electronic-grade hydrofluoric acid with a mass fraction of 40%, add it to a tetrafluoro reaction kettle, and slowly add high-purity aluminum hydroxide to it. The molar ratio of hydrofluoric acid to aluminum hydroxide is 4.3:1. Keep the temperature at 90°C and stir until it is colorless and transparent to obtain a fluoroaluminate acid solution; among them, high-purity aluminum hydroxide refers to aluminum hydroxide with the contents of elements such as iron, cobalt, nickel, copper, cadmium, and vanadium less than 0.0001% and the sodium content less than 0.1%.

[0087] Step 2: Concentrate the fluoroaluminate acid solution;

[0088] Heat up the fluoroaluminate acid solution obtained in Step 1.1 to 105°C for concentration. The colorless and transparent fluoroaluminate acid solution is concentrated until it gradually turns white. When the specific gravity of the solution is 1.6, stop heating and stir to cool down to 45°C to obtain a concentrated fluoroaluminate acid solution;

[0089] Step 3: Prepare particulate aluminum fluoride trihydrate;

[0090] Step 3.1: Prepare high-purity cold water at 0 - 2°C, add crushed ice cubes made from high-purity water to it, and the mass ratio of cold water to crushed ice cubes is 4.5:1 to obtain a high-purity ice-water mixture;

[0091] Step 3.2: Slowly add the fluoroaluminate concentrate obtained in Step 2 to the high-purity ice-water mixture obtained in Step 3.1, and the mass ratio of fluoroaluminate concentrate to high-purity ice-water mixture is 1:3. During this process, continuously stir the ice-water mixture at a speed of 70 revolutions per minute. As the fluoroaluminate concentrate is added, aluminum fluoride trihydrate particles gradually form. After adding, stop stirring. When the temperature of the synthesis liquid is measured to be 0 - 3°C, an aluminum fluoride trihydrate synthesis liquid is obtained.

[0092] Step 4: Prepare aluminum fluoride trihydrate crystal particles;

[0093] Step 4.1: Let the aluminum fluoride trihydrate synthesis liquid obtained in Step 3.2 stand for 40 minutes. At this time, the aluminum fluoride trihydrate particles sink to the bottom, remove the supernatant to obtain an aluminum fluoride trihydrate precipitate;

[0094] Step 4.2: Wrap the aluminum fluoride trihydrate precipitate obtained in Step 4.1 with an 800-mesh filter cloth, place it in a centrifuge, and perform centrifugation at a speed of 800 revolutions per minute. During the process, appropriately wash with high-purity water. When the content of free electron-grade hydrofluoric acid is measured to be less than 0.021%, aluminum fluoride trihydrate crystal particles are obtained;

[0095] Step 5: Dry;

[0096] Place the aluminum fluoride trihydrate crystal particles obtained in Step 4.2 in a tetrafluoro plate, then put it into a steam oven and dry at a temperature of 100°C for 15 hours. When the free water is measured to be less than 0.3% by the Karl Fischer method, a particulate aluminum fluoride trihydrate finished product is obtained.

[0097] Use ion chromatography to detect the particulate aluminum fluoride trihydrate finished product obtained in this example. The contents of elements such as iron, cobalt, nickel, copper, cadmium, and vanadium are all less than 0.0001%, sodium is less than 0.01%. Use the turbidimetry method to test that the contents of chlorine and sulfate radicals are both less than 0.005%. The sieving above 60 meshes is 85%. Use an X-rd diffractometer to qualitatively identify it as aluminum fluoride trihydrate. The XRD pattern is as Figure 1 shown.

[0098] The above four examples illustrate that the method provided by the present invention is very stable, the obtained products have high repeatability, and the indicators meet the requirements.

Claims

1. A method for preparing high-purity particle-state aluminum fluoride trihydrate, characterized in that: The following steps are involved: Step 1: preparing fluoroaluminic acid; Slowly add high-purity aluminum hydroxide to electronic grade hydrofluoric acid, keep warm and stir to react until it becomes colorless and transparent, to obtain a fluoroaluminate solution; Step 2: Concentrating the fluoroaluminate solution; After the fluoroaluminate solution is heated and concentrated to a specific gravity of 1.5-1.6, the heating is stopped, and the temperature is cooled to 40-45° C. with stirring to obtain a fluoroaluminate concentrated solution; Step 3: preparing aluminum fluoride trihydrate in particle form; Step 3.1: Mix crushed ice cubes frozen from high-purity water with high-purity cold water at 0-5°C to form a high-purity ice-water mixture; Step 3.2: slowly adding the fluoroaluminate concentrated solution to the high-purity ice-water mixture, stirring the ice-water mixture continuously during the process, stopping stirring after the addition is completed, and measuring the temperature of the synthetic solution to be 0-5° C. to obtain aluminum fluoride trihydrate synthetic solution; Step 4: preparing aluminum fluoride trihydrate crystalline particles; Step 4.1: allowing the aluminum fluoride trihydrate synthesis solution to stand, removing the supernatant, and obtaining aluminum fluoride trihydrate precipitation; Step 4.2: centrifuging the aluminum fluoride trihydrate precipitate, washing it with high-purity water, and obtaining aluminum fluoride trihydrate crystalline particles when the free hydrofluoric acid in the washing liquid is measured to be less than or equal to 0.03%; Step 5: Drying; The aluminum fluoride trihydrate crystalline particles are dried at 100-110° C. for 10-15 hours, and when the free water content is less than 0.3%, a particle-state aluminum fluoride trihydrate finished product is obtained.

2. The method for preparing high-purity particulate aluminum fluoride trihydrate according to claim 1, characterized in that: In step 1: the mass fraction of the electronic grade hydrofluoric acid is 25-50%.

3. The method for preparing high-purity particulate aluminum fluoride trihydrate according to claim 1, characterized in that: In step 1: high-purity aluminum hydroxide refers to aluminum hydroxide with iron, cobalt, nickel, copper, cadmium, and vanadium elements less than 0.0001% and sodium less than 0.1%.

4. The method for preparing high-purity particulate aluminum fluoride trihydrate according to claim 1, characterized in that: In step 1: the molar ratio of hydrogen fluoride to aluminum hydroxide is 4-4.5:1, and the mixture is stirred at 80-100°C until it becomes colorless and transparent.

5. The method for preparing high-purity particulate aluminum fluoride trihydrate according to claim 1, characterized in that: In step 2: the fluoroaluminate solution is heated to 105-120° C. for concentration.

6. The method for preparing high-purity particulate aluminum fluoride trihydrate according to any one of claims 1 to 5, characterized in that: In step 3.1: the mass ratio of cold water to crushed ice is 3-5:

1.

7. The method for preparing high-purity particulate aluminum fluoride trihydrate according to claim 6, characterized in that: In step 3.2, the mass ratio of the fluoroaluminate concentrate to the high-purity ice-water mixture is 1:2-3, the stirring speed of the ice-water mixture is 30-100 rpm, and the fluoroaluminate concentrate is added to the high-purity ice-water mixture at a speed of 10 L / min.

8. The method for preparing high-purity particulate aluminum fluoride trihydrate according to claim 7, characterized in that: In step 4.1, the aluminum fluoride trihydrate synthetic solution is allowed to stand for 30-60 minutes.

9. The method for preparing high-purity particulate aluminum fluoride trihydrate according to claim 8, characterized in that: In step 4.2: the aluminum fluoride trihydrate precipitate is wrapped with a 500-1000 mesh filter cloth, placed in a centrifuge, and centrifuged at a speed of 500-1000 rpm.

10. A high-purity particle-state aluminum fluoride trihydrate, characterized in that: The method is prepared by any one of claims 1 to 9.

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