Preparation method of high-purity strontium fluoride powder

Abstract

The invention discloses a preparation method of high-purity strontium fluoride powder, and relates to the technical field of inorganic material preparation. The method comprises the following steps: crushing and grinding a strontianite block into powder, calcining at high temperature to obtain a first mixture, adding the first mixture into hydrochloric acid, stirring for a certain time, and filtering to remove insoluble substances to obtain first filtrate; regulating and controlling the pH and temperature of the first filtrate, adding tartrate, reacting for a period of time while stirring, and quickly filtering to obtain a second filtrate; adding a fluorine-containing salt solution into the second filtrate at normal temperature, stirring for a period of time, filtering and collecting insoluble substances; and finally, washing the insoluble substance with absolute ethyl alcohol, and carrying out vacuum drying, crushing and grinding to obtain the high-purity strontium fluoride powder. The method is simple and efficient, the purity of the prepared strontium fluoride powder is larger than 99.9%, and the strontium fluoride powder can be used for manufacturing optical glass, advanced electronic elements and the like.

Description

Technical Field

[0001] The present application relates to the technical field of inorganic material preparation, and in particular to a method for preparing high-purity strontium fluoride powder. Background Art

[0002] As an important inorganic compound, strontium fluoride has broad and critical applications in numerous high-end fields. For example, it is used in the manufacture of optical glass, improving its optical properties. It also plays an important role in advanced electronic components, serving as a key material for the preparation of some specialized electronic devices. With the continuous development of these fields, the demand for high-purity strontium fluoride powder is growing.

[0003] The existing preparation methods of strontium fluoride have many shortcomings, such as complex preparation process, difficulty in ensuring product purity, and high cost. There is an urgent need to develop a simple and efficient method that can prepare high-purity strontium fluoride powder. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this application provides a method for preparing high-purity strontium fluoride powder. By subjecting strontianite blocks to a series of steps, including pulverizing and grinding, high-temperature calcination, dissolution with hydrochloric acid, pH and temperature adjustment, addition of a tartrate salt for reaction, and precipitation with a fluoride-containing salt solution, impurities can be effectively removed, reaction efficiency is improved, and high-purity strontium fluoride powder is ultimately produced.

[0005] In order to achieve the above-mentioned object, the present application provides a method for preparing a high-purity strontium fluoride powder, comprising the following steps:

[0006] Step S1: crushing and grinding a strontianite block to obtain a strontianite powder, and calcining the powder to obtain a first mixture;

[0007] Step S2: adding the cooled first mixture to hydrochloric acid, stirring at a first temperature for a first time, and filtering to remove the residue to obtain a first filtrate;

[0008] Step S3: adjusting the pH and temperature of the first filtrate, adding tartaric acid, reacting for a second time while stirring, and then filtering to obtain a second filtrate;

[0009] Step S4: adding an excess amount of fluoride-containing salt solution to the second filtrate at room temperature, stirring for a third time, and then filtering and collecting the resulting insoluble matter;

[0010] Step S5: washing the insoluble matter with anhydrous ethanol, vacuum drying the insoluble matter, taking it out, crushing and grinding it, and obtaining the high-purity strontium fluoride powder.

[0011] This application effectively removes non-strontium impurities in the raw material strontianite through multi-step impurity removal and precise control of reaction conditions, and finally obtains strontium fluoride powder with a purity of ≥99.9wt%, which can meet the demand for high-purity strontium fluoride in high-end fields.

[0012] In step S1, strontianite (mainly composed of strontium carbonate) is crushed and then calcined to convert strontium carbonate into strontium oxide, which is more soluble in acid, laying the foundation for acid dissolution in the subsequent step S2.

[0013] In step S2, strontium oxide reacts with hydrochloric acid to generate SrCl3 solution, and the accompanying major impurities (such as CaO, BaO, etc.) are also dissolved into corresponding chlorides, and insoluble impurities such as silicon dioxide are removed by filtration.

[0014] In step S3, tartrate is added after adjusting pH and temperature, and the tartrate ions react with the main impurity ions Ca 2+ 、Ba 2+ A stable complex is formed and precipitated, while Sr 2+ Due to its weak complexing ability, it remains in the solution, achieving selective removal of impurity ions.

[0015] In step S4, a fluorine-containing salt solution is added to the impurity-removed solution, and F- and Sr 2+ A reaction occurs to form strontium fluoride precipitation. At the same time, by controlling the concentration of the fluorine-containing salt solution and the reaction time, the precipitation reaction is promoted to proceed fully and the precipitation rate of the strontium element is increased.

[0016] In step S5, the precipitate is washed with anhydrous ethanol to remove impurities remaining on the surface, and vacuum drying is performed to avoid the introduction of moisture and impurities, thereby ensuring the purity of the final strontium fluoride powder.

[0017] In one feasible implementation, in step S1, the strontium ore powder has a particle size of 100-200 mesh, is calcined at a temperature of 900-1100°C, and lasts for 2-4 hours. This ensures the complete conversion of strontium carbonate into oxide, reduces unreacted strontium carbonate residue in the subsequent acid dissolution step, and improves raw material utilization.

[0018] In one feasible embodiment, in step S2, the concentration of hydrochloric acid is 2 to 4 mol / L, the first temperature is 50 to 80°C, the first time is 1 to 3 hours, and the stirring rate is 200 to 300 rpm. This can promote rapid dissolution of the calcined product, shorten the reaction time, and avoid excessive dissolution of impurities caused by excessive acid concentration or temperature.

[0019] In a feasible embodiment, in step S3, the pH of the first filtrate is 5.0-6.5, the temperature of the first filtrate is controlled at 5-10°C, the stirring rate is 400-500 rpm, the second time is 1-2 hours, and the mass ratio of the first filtrate to the tartrate is (85-95): (5-15). In the present application, by setting a weakly acidic environment of pH 5.0-6.5 and controlling the temperature, tartrate ions form insoluble calcium tartrate and barium tartrate precipitates with calcium ions and barium ions. Under this condition, strontium tartrate has a high solubility, so strontium still exists in the solution in the form of ions, achieving the separation of calcium, barium and strontium.

[0020] In one feasible embodiment, in step S3, the tartrate is at least one of potassium sodium tartrate, potassium hydrogen tartrate, sodium hydrogen tartrate, sodium tartrate, potassium tartrate, and ammonium tartrate. These tartrates are all readily soluble in water and release a large amount of tartrate ions upon dissolution, providing sufficient reactants for complexing impurity ions such as calcium and barium ions, thereby avoiding incomplete impurity removal due to the low solubility of the tartrate. Furthermore, these tartrates do not introduce new impurities that are difficult to remove.

[0021] In one feasible embodiment, in step S4, the concentration of the fluoride-containing salt solution is 20-40 wt%, the third time is 2-3 hours, and the mass ratio of the second filtrate to the fluoride-containing salt solution is 1:(1.2-1.5). This ensures that the strontium ions are completely converted into SrF2 precipitate, reduces residual strontium ions in the second filtrate, and improves product yield.

[0022] In one feasible embodiment, the solute of the fluoride-containing salt solution includes at least one of sodium fluoride, potassium fluoride and ammonium fluoride. The above fluoride-containing salt will not introduce new impurities that are difficult to remove.

[0023] In one feasible implementation, the anhydrous ethanol wash in step S5 is performed 3 to 5 times, each wash lasting 5 to 10 minutes. The vacuum drying temperature is 80 to 120°C, and the drying time is 6 to 12 hours. Anhydrous ethanol dissolves soluble impurities adsorbed on the precipitate surface, and 3 to 5 washes ensure complete impurity removal.

[0024] In one feasible embodiment, the particle size of the strontium fluoride powder after pulverization and grinding in step S5 is D50 ≤ 5 μm. This can increase the specific surface area of ​​the strontium fluoride powder, improve the powder's dispersibility and reactivity in applications, and meet the stringent particle size requirements of high-end applications.

[0025] In one feasible implementation, the resulting high-purity strontium fluoride powder has a purity of ≥99.9% by weight, with a calcium content of ≤50 ppm and a barium content of ≤30 ppm. This powder has extremely low impurity levels and is suitable for applications requiring extremely high purity, such as semiconductor and optical device manufacturing.

[0026] Beneficial technical effects:

[0027] The method for preparing high-purity strontium fluoride powder provided in this application achieves efficient impurity removal and precise control of product properties through multi-step coordinated optimization. Specifically, strontianite blocks are crushed and calcined at high temperature to fully decompose strontium carbonate into strontium oxide, increasing the specific surface area and improving the efficiency of subsequent acid dissolution. After the calcined product is dissolved with hydrochloric acid, a strontium chloride solution is generated and insoluble impurities are preliminarily separated; by setting a weakly acidic environment of pH 5.0 to 6.5 and controlling the temperature, tartrate ions, calcium ions and barium ions form insoluble calcium tartrate and barium tartrate precipitates. The present application found that under this condition, the solubility of strontium tartrate is relatively high, so strontium still exists in the solution in the form of ions, thereby achieving efficient separation of calcium, barium and strontium; a fluorine-containing salt solution is added to the filtrate after impurity removal, and excess fluoride ions are used to promote the complete conversion of strontium ions into strontium fluoride precipitates, thereby reducing mother liquor residue; water-soluble impurities on the surface of the precipitate are removed by washing with anhydrous ethanol, and the solvent is completely removed by vacuum drying to avoid impurity residues and oxidative deterioration. The obtained strontium fluoride powder can be ground to D50≤5μm, so that it has good dispersibility and reaction activity. The preparation method provided in the present application forms a synergistic impurity removal effect by precisely controlling the parameters of each step: tartrate selectively removes calcium and magnesium ions, and fluoride precipitation further inhibits the co-precipitation of barium ions. Combined with an efficient cleaning and drying process, the purity of the obtained strontium fluoride powder is ≥99.9wt%, the calcium content is ≤50ppm, the barium content is ≤30ppm, and the impurity content is extremely low, which meets the demand for ultra-high purity strontium fluoride in high-end fields such as semiconductors, precision ceramics, and optical materials, and has both process efficiency and product stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a physical picture of the high-purity strontium fluoride powder prepared as provided in this application.

[0029] Figure 2 This is a schematic flow chart of a method for preparing high-purity strontium fluoride powder provided in this application. DETAILED DESCRIPTION

[0030] In order to make the technical problems, technical solutions, and beneficial effects to be solved by this application more clearly understood, the present application is further described in detail below with reference to the following examples. However, this should not be construed as limiting the scope of this application to the following examples. Without departing from the above-mentioned method concepts of this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0031] The present application provides a method for preparing high-purity strontium fluoride powder. The high-purity strontium fluoride powder prepared by the preparation method is as follows: Figure 1 shown.

[0032] The following will describe in detail a method for preparing a high-purity strontium fluoride powder provided by the present application in combination with different embodiments.

[0033] Example 1

[0034] like Figure 2 As shown, a method for preparing high-purity strontium fluoride powder comprises the following steps:

[0035] S1: crushing and grinding a strontianite block to obtain a strontianite powder, and calcining the powder at 900° C. for 4 h to obtain a first mixture;

[0036] S2: adding the cooled first mixture to 2 mol / L hydrochloric acid, stirring at 50° C. and 200 rpm for 3 h, and filtering to remove the residue to obtain a first filtrate;

[0037] S3: The pH of the first filtrate was adjusted to 5.0 and the temperature was adjusted to 5°C. Potassium sodium tartrate was added so that the mass ratio of the first filtrate to potassium sodium tartrate was 85:15. The mixture was stirred at 400 rpm for 2 h, and then filtered to obtain a second filtrate.

[0038] S4: adding an excess of sodium fluoride solution to the second filtrate at room temperature, with the mass ratio of the second filtrate to the sodium fluoride solution being 1:1.2, stirring for 3 hours, and then filtering and collecting the resulting insoluble matter;

[0039] S5: The insoluble matter is washed three times with anhydrous ethanol, each washing time is 10 minutes, and then the insoluble matter is vacuum dried at 80° C. for 10 hours, taken out and crushed to obtain the high-purity strontium fluoride powder.

[0040] Example 2

[0041] like Figure 2 As shown, a method for preparing high-purity strontium fluoride powder comprises the following steps:

[0042] S1: crushing and grinding a strontianite block to obtain a strontianite powder, and calcining the powder at 1000° C. for 3 h to obtain a first mixture;

[0043] S2: adding the cooled first mixture to 3 mol / L hydrochloric acid, stirring at 65° C. and 250 rpm for 2 h, and filtering to remove the residue to obtain a first filtrate;

[0044] S3: The pH of the first filtrate was adjusted to 5.5 and the temperature was adjusted to 8°C. Potassium hydrogen tartrate was added so that the mass ratio of the first filtrate to potassium hydrogen tartrate was 90:10. The mixture was stirred at 450 rpm for 1.5 hours and then filtered to obtain a second filtrate.

[0045] S4: adding an excess amount of potassium fluoride solution to the second filtrate at room temperature, with the mass ratio of the second filtrate to the potassium fluoride solution being 1:1.3, stirring for 2.5 hours, and then filtering and collecting the resulting insoluble matter;

[0046] S5: The insoluble matter was washed 4 times with anhydrous ethanol, each washing time was 7 minutes, and then the insoluble matter was vacuum dried at 100° C. for 8 hours, taken out and crushed to obtain the high-purity strontium fluoride powder.

[0047] Example 3

[0048] like Figure 2 As shown, a method for preparing high-purity strontium fluoride powder comprises the following steps:

[0049] S1: crushing and grinding a strontianite block to obtain a strontianite powder, and calcining the powder at 1100° C. for 2 h to obtain a first mixture;

[0050] S2: adding the cooled first mixture to 4 mol / L hydrochloric acid, stirring at 80° C. and 300 rpm for 1 h, and filtering to remove the residue to obtain a first filtrate;

[0051] S3: The pH of the first filtrate was adjusted to 6.0 and the temperature was adjusted to 10°C. Sodium hydrogen tartrate was added so that the mass ratio of the first filtrate to the sodium hydrogen tartrate was 95:5. The mixture was stirred at a stirring rate of 500 rpm for 1 hour, and then filtered to obtain a second filtrate.

[0052] S4: adding an excess amount of ammonium fluoride solution to the second filtrate at room temperature, with the mass ratio of the second filtrate to the ammonium fluoride solution being 1:1.5, stirring for 2 hours, and then filtering and collecting the resulting insoluble matter;

[0053] S5: The insoluble matter is washed 5 times with anhydrous ethanol, each washing time is 5 minutes, and then the insoluble matter is vacuum dried at 120° C. for 6 hours, taken out and crushed to obtain the high-purity strontium fluoride powder.

[0054] Example 4

[0055] like Figure 2 As shown, a method for preparing high-purity strontium fluoride powder comprises the following steps:

[0056] S1: crushing and grinding a strontianite block to obtain a strontianite powder, and calcining the powder at 950° C. for 3.5 hours to obtain a first mixture;

[0057] S2: adding the cooled first mixture to 2.5 mol / L hydrochloric acid, stirring at 60° C. and 250 rpm for 2.5 h, and filtering to remove the residue to obtain a first filtrate;

[0058] S3: The pH of the first filtrate was adjusted to 5.5 and the temperature was adjusted to 6°C. Sodium tartrate was added so that the mass ratio of the first filtrate to the sodium tartrate was 88:12. The mixture was stirred at 400 rpm for 1.5 hours and then filtered to obtain a second filtrate.

[0059] S4: adding an excess of sodium fluoride solution to the second filtrate at room temperature, with the mass ratio of the second filtrate to the sodium fluoride solution being 1:1.4, stirring for 2.5 hours, and then filtering and collecting the resulting insoluble matter;

[0060] S5: The insoluble matter was washed 4 times with anhydrous ethanol, each washing time was 8 minutes, and then the insoluble matter was vacuum dried at 90° C. for 9 hours, taken out and crushed to obtain the high-purity strontium fluoride powder.

[0061] Example 5

[0062] like Figure 2 As shown, a method for preparing high-purity strontium fluoride powder comprises the following steps:

[0063] S1: crushing and grinding a strontianite block to obtain a strontianite powder, and calcining the powder at 1050° C. for 2.5 hours to obtain a first mixture;

[0064] S2: adding the cooled first mixture to 3.5 mol / L hydrochloric acid, stirring at 75° C. and 280 rpm for 1.5 h, and filtering to remove the residue to obtain a first filtrate;

[0065] S3: The pH of the first filtrate was adjusted to 6.0 and the temperature was adjusted to 7°C. Potassium tartrate was added so that the mass ratio of the first filtrate to potassium tartrate was 92:8. The mixture was stirred at 500 rpm for 1.2 hours, and then filtered to obtain a second filtrate.

[0066] S4: adding an excess of sodium fluoride solution to the second filtrate at room temperature, with the mass ratio of the second filtrate to the sodium fluoride solution being 1:1.4, stirring for 2.5 hours, and then filtering and collecting the resulting insoluble matter;

[0067] S5: The insoluble matter was washed 4 times with anhydrous ethanol, each washing time was 8 minutes, and then the insoluble matter was vacuum dried at 90° C. for 9 hours, taken out and crushed to obtain the high-purity strontium fluoride powder.

[0068] Example 6

[0069] like Figure 2 As shown, a method for preparing high-purity strontium fluoride powder comprises the following steps:

[0070] S1: crushing and grinding a strontianite block to obtain a strontianite powder, and calcining the powder at 950° C. for 3 h to obtain a first mixture;

[0071] S2: adding the cooled first mixture to 3 mol / L hydrochloric acid, stirring at 55° C. and 250 rpm for 2 h, and filtering to remove the residue to obtain a first filtrate;

[0072] S3: The pH of the first filtrate was adjusted to 6.5 and the temperature was adjusted to 9°C. Ammonium tartrate was added so that the mass ratio of the first filtrate to ammonium tartrate was 86:14. The mixture was stirred at 450 rpm for 1.5 hours and then filtered to obtain a second filtrate.

[0073] S4: adding an excess amount of ammonium fluoride solution to the second filtrate at room temperature, with the mass ratio of the second filtrate to the ammonium fluoride solution being 1:1.5, stirring for 2.5 hours, and then filtering and collecting the resulting insoluble matter;

[0074] S5: The insoluble matter was washed 5 times with anhydrous ethanol, each washing time was 7 minutes, and then the insoluble matter was vacuum dried at 85° C. for 12 hours, taken out and crushed to obtain the high-purity strontium fluoride powder.

[0075] Comparative Example 1 (Comparative Example 1, not using tartrate, using sulfate)

[0076] A method for preparing high-purity strontium fluoride powder comprises the following steps:

[0077] S1: crushing and grinding a strontianite block to obtain a strontianite powder, and calcining the powder at 900° C. for 4 h to obtain a first mixture;

[0078] S2: adding the cooled first mixture to 2 mol / L hydrochloric acid, stirring at 50° C. and 200 rpm for 3 h, and filtering to remove the residue to obtain a first filtrate;

[0079] S3: The pH of the first filtrate was adjusted to 5.0 and the temperature was adjusted to 5°C. Sodium sulfate was added so that the mass ratio of the first filtrate to sodium sulfate was 85:15. The mixture was stirred at 400 rpm for 2 h, and then filtered to obtain a second filtrate.

[0080] S4: adding an excess of sodium fluoride solution to the second filtrate at room temperature, with the mass ratio of the second filtrate to the sodium fluoride solution being 1:1.2, stirring for 3 hours, and then filtering and collecting the resulting insoluble matter;

[0081] S5: The insoluble matter is washed three times with anhydrous ethanol, each washing time is 10 minutes, and then the insoluble matter is vacuum dried at 80° C. for 10 hours, taken out and crushed to obtain the high-purity strontium fluoride powder.

[0082] Comparative Example 2 (Comparative Example 3, tartrate was not used, oxalate was used)

[0083] A method for preparing high-purity strontium fluoride powder comprises the following steps:

[0084] S1: crushing and grinding a strontianite block to obtain a strontianite powder, and calcining the powder at 1100° C. for 2 h to obtain a first mixture;

[0085] S2: adding the cooled first mixture to 4 mol / L hydrochloric acid, stirring at 80° C. and 300 rpm for 1 h, and filtering to remove the residue to obtain a first filtrate;

[0086] S3: The pH of the first filtrate was adjusted to 6.0 and the temperature was adjusted to 10°C. Sodium hydrogen oxalate was added so that the mass ratio of the first filtrate to sodium hydrogen oxalate was 95:5. The mixture was stirred at 500 rpm for 1 hour, and then filtered to obtain a second filtrate.

[0087] S4: adding an excess amount of ammonium fluoride solution to the second filtrate at room temperature, with the mass ratio of the second filtrate to the ammonium fluoride solution being 1:1.5, stirring for 2 hours, and then filtering and collecting the resulting insoluble matter;

[0088] S5: The insoluble matter is washed 5 times with anhydrous ethanol, each washing time is 5 minutes, and then the insoluble matter is vacuum dried at 120° C. for 6 hours, taken out and crushed to obtain the high-purity strontium fluoride powder.

[0089] Comparative Example 3 (Comparative Example 6, pH and temperature were not adjusted)

[0090] A method for preparing high-purity strontium fluoride powder comprises the following steps:

[0091] S1: crushing and grinding a strontianite block to obtain a strontianite powder, and calcining the powder at 950° C. for 3 h to obtain a first mixture;

[0092] S2: adding the cooled first mixture to 3 mol / L hydrochloric acid, stirring at 55° C. and 250 rpm for 2 h, and filtering to remove the residue to obtain a first filtrate;

[0093] S3: adding ammonium tartrate directly to the first filtrate at room temperature, with a mass ratio of the first filtrate to ammonium tartrate being 86:14, and then reacting with stirring at a stirring rate of 450 rpm for 1.5 hours, and then filtering to obtain a second filtrate;

[0094] S4: adding an excess amount of ammonium fluoride solution to the second filtrate at room temperature, with the mass ratio of the second filtrate to the ammonium fluoride solution being 1:1.5, stirring for 2.5 hours, and then filtering and collecting the resulting insoluble matter;

[0095] S5: The insoluble matter was washed 5 times with anhydrous ethanol, each washing time was 7 minutes, and then the insoluble matter was vacuum dried at 85° C. for 12 hours, taken out and crushed to obtain the high-purity strontium fluoride powder.

[0096] The calcium and barium contents in the strontium fluoride powders prepared in the above examples and comparative examples were tested to demonstrate the high purity of the strontium fluoride powders. The test results are shown in Table 1 below.

[0097] Table 1 Test results of high-purity strontium fluoride powder prepared in Examples and Comparative Examples

[0098]

[0099]

[0100] As can be seen from Table 1, the purity of the high-purity strontium fluoride powders prepared in Examples 1-6 is better than that in Comparative Examples 1-3.

[0101] This is because, in Examples 1 to 6, the strontianite is crushed and calcined at high temperature, so that the strontium carbonate is fully decomposed into strontium oxide, which increases the specific surface area and improves the subsequent acid dissolution efficiency. After the calcined product is dissolved with hydrochloric acid, a strontium chloride solution is generated and insoluble impurities are preliminarily separated; by setting a weakly acidic environment of pH 5.0 to 6.5 and controlling the temperature, tartrate ions, calcium ions and barium ions form insoluble calcium tartrate and barium tartrate precipitates. The present application found that under this condition, the solubility of strontium tartrate is relatively high, so strontium still exists in the solution in the form of ions, thereby achieving efficient separation of calcium, barium and strontium; a fluorine-containing salt solution is added to the filtrate after impurity removal, and excess fluoride ions are used to promote the complete conversion of strontium ions into strontium fluoride precipitates, thereby reducing mother liquor residue; water-soluble impurities on the surface of the precipitate are removed by washing with anhydrous ethanol, and the solvent is completely removed by vacuum drying to avoid impurity residues and oxidative deterioration. The obtained strontium fluoride powder can be ground to D50≤5μm, so that it has good dispersibility and reaction activity. This preparation method forms a synergistic impurity removal effect by precisely controlling the parameters of each step: tartrate selectively removes calcium and magnesium ions, and fluoride precipitation further inhibits the co-precipitation of barium ions. Combined with an efficient cleaning and drying process, the resulting strontium fluoride powder has a purity of ≥99.9wt%, a calcium content of ≤50ppm, a barium content of ≤30ppm, and extremely low impurity content.

[0102] In Comparative Example 1, tartrate is not used in step S3, but sulfate is used instead. Since barium sulfate and strontium sulfate are both insoluble, they cannot be effectively separated, and the generation of strontium sulfate causes a certain loss of strontium content, increasing costs.

[0103] In Comparative Example 2, tartrate was not used in step S3, but oxalate was used instead. Since calcium oxalate, barium oxalate and strontium oxalate are difficult to dissolve, they cannot be effectively separated. In addition, the generation of strontium oxalate will also cause a certain loss of strontium content, increasing costs.

[0104] In Comparative Example 3, the pH and temperature were not adjusted in step S3, so it was difficult for tartrate ions to form insoluble calcium tartrate and barium tartrate precipitates with calcium ions and barium ions; without adjusting the pH and temperature, calcium ions and barium ions would still remain, and therefore efficient separation of calcium, barium and strontium could not be achieved.

[0105] The above results show and describe the basic principles and main features of this application as well as the advantages of this application.

[0106] Those skilled in the art should understand that the present application is not limited to the above-described embodiments. The above-described embodiments and descriptions are merely illustrative of the principles of the present application. Various changes and improvements may be made to the present application without departing from the spirit and scope of the present application. Such changes and improvements are intended to fall within the scope of the present application. The scope of protection claimed in the present application is defined by the equivalents of the appended claims.

Claims

1. A method for preparing high-purity strontium fluoride powder, characterized in that: The following steps are involved: Step S1: crushing and grinding a strontianite block to obtain a strontianite powder, and calcining the powder to obtain a first mixture; Step S2: adding the cooled first mixture to hydrochloric acid, stirring at a first temperature for a first time, and filtering to remove the residue to obtain a first filtrate; Step S3: adjusting the pH and temperature of the first filtrate, adding tartaric acid, reacting for a second time while stirring, and then filtering to obtain a second filtrate; Step S4: adding an excess amount of fluoride-containing salt solution to the second filtrate at room temperature, stirring for a third time, and then filtering and collecting the resulting insoluble matter; Step S5: washing the insoluble matter with anhydrous ethanol, vacuum drying the insoluble matter, taking it out, crushing and grinding it, and obtaining the high-purity strontium fluoride powder.

2. The method for preparing high-purity strontium fluoride powder according to claim 1, wherein: In step S1, the particle size of the strontium ore powder is 100-200 mesh, the calcination temperature is 900-1100° C., and the calcination time is 2-4 hours.

3. The method for preparing high-purity strontium fluoride powder according to claim 1, wherein: In step S2, the concentration of hydrochloric acid is 2-4 mol / L, the first temperature is 50-80°C, the first time is 1-3 hours, and the stirring rate is 200-300 rpm.

4. The method for preparing high-purity strontium fluoride powder according to claim 1, wherein: In step S3, the pH of the first filtrate is 5.0-6.5, the temperature of the first filtrate is controlled at 5-10°C, the stirring rate is 400-500 rpm, the second time is 1-2h, and the mass ratio of the first filtrate to tartrate is (85-95): (5-15).

5. The method for preparing high-purity strontium fluoride powder according to claim 1, wherein: In step S3, the tartrate is at least one of potassium sodium tartrate, potassium hydrogen tartrate, sodium hydrogen tartrate, sodium tartrate, potassium tartrate, and ammonium tartrate.

6. The method for preparing high-purity strontium fluoride powder according to claim 1, wherein: In step S4, the concentration of the fluorine-containing salt solution is 20-40 wt %, the third time is 2-3 h, and the mass ratio of the second filtrate to the fluorine-containing salt solution is 1:(1.2-1.5).

7. The method for preparing high-purity strontium fluoride powder according to claim 1, characterized in that: The solute of the fluoride-containing salt solution includes at least one of sodium fluoride, potassium fluoride and ammonium fluoride.

8. The method for preparing high-purity strontium fluoride powder according to claim 1, wherein: In step S5, the number of times of washing with anhydrous ethanol is 3 to 5 times, and the time of each washing is 5 to 10 minutes; the vacuum drying temperature is 80 to 120° C., and the drying time is 6 to 12 hours.

9. The method for preparing high-purity strontium fluoride powder according to claim 1, wherein: The particle size of the strontium fluoride powder after crushing and grinding in step S5 is D50≤5μm.

10. The method for preparing high-purity strontium fluoride powder according to claim 1, characterized in that: The purity of the prepared high-purity strontium fluoride powder is ≥99.9wt%, wherein the calcium content is ≤50ppm and the barium content is ≤30ppm.

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