Method for preparing high-purity rubidium chloride from rubidium crude salt

Abstract

The invention discloses a method for preparing high-purity rubidium chloride from rubidium crude salt, which comprises the following steps: (1) obtaining an acidic rubidium-containing solution from rubidium crude salt, and adding a precipitant to obtain a precipitate; (2) dissolving the precipitate to obtain a rubidium-containing double salt solution; (3) recrystallizing to obtain crystals; (4) washing the crystals to obtain high-purity crystals; (5) adding the high-purity crystals into water to carry out size mixing, and then adding ammonia water to react completely to obtain a solution containing rubidium chloride; according to the method for preparing the high-purity rubidium chloride from the rubidium crude salt, the purity of an obtained final product can reach 99.99% or above, the technological process is simple, the production process is environmentally friendly, raw material consumption and production cost are low, and a feasible technical scheme is provided for large-scale industrial production of the high-purity rubidium chloride.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial preparation of rubidium salts, and in particular to a method for preparing high-purity rubidium chloride with high product purity, high purification efficiency, simple process and low cost. Background Art

[0002] With the rapid development of laser technology, quantum technology, ultrafine spectroscopy, and high-end electronic chip manufacturing, the industry's purity requirements for rubidium chloride have increased to over 99.9%. However, alkali metal impurities such as sodium, potassium, and cesium in rubidium salts are difficult to remove due to their highly similar chemical properties to rubidium. Furthermore, trace impurities can affect material properties, necessitating the development of innovative processes that combine high selectivity with industrial feasibility.

[0003] Regarding the preparation of rubidium chloride, solvent extraction, ion exchange, and precipitation are the primary methods for purifying rubidium salts in existing public technologies. However, these methods still suffer from issues such as insufficient product purity, low purification efficiency, complex process flows, and high process costs. For example, Chinese patent application CN112194154A discloses a method for extracting rubidium and cesium from complex underground brine. While optimizing the extraction process increases the purity of rubidium chloride to 99%, it still fails to meet the cutting-edge purity standards of 99.9% and above, resulting in insufficient product purity. Chinese patent application CN120229747A discloses a method for removing trace impurity elements (such as sodium, potassium, and cesium) from high-purity rubidium salts. While the selective precipitation method employed shortens the process and achieves a maximum purity of rubidium chloride exceeding 99.9%, this technical solution places high demands on raw materials, requiring impurity content to be less than 1%, and the precipitant used cannot be recycled, resulting in high production costs. Patent CN114350950A proposes a method for extracting rubidium and cesium from complex underground brine. The brine treatment process achieves a final product purity of 99.5%, but the process is complex, with low purification efficiency and significant technical difficulty. Ultrasonic-assisted gradient crystallization can precisely control crystal nucleation and growth, reducing impurity carryover, but has not yet been applied to rubidium salt purification. Summary of the Invention

[0004] The present invention provides a method for preparing high-purity rubidium chloride from crude rubidium salt, which is used to solve the technical problems mentioned in the background technology.

[0005] In order to solve the above technical problems, the technical solution proposed by the present invention is: A method for preparing high-purity rubidium chloride from crude rubidium salt comprises the following steps: (1) dissolving the crude rubidium salt in an acid solution to obtain an acidic rubidium-containing solution, and adding a precipitant to the acidic rubidium-containing solution to obtain a rubidium-containing double salt precipitate; the hydrogen ion concentration in the acidic rubidium-containing solution is 3 to 6 mol / L, and the precipitant is a tin-containing precipitant, including at least one of tin tetrachloride, tin tetrachloride hydrate, tin chloride, and tin chloride hydrate; (2) heating the rubidium double salt precipitate in an acid solution having a hydrogen ion concentration of 0.5 to 2 mol / L until it is completely dissolved to obtain an acid solution containing the rubidium double salt; (3) recrystallizing the acid solution containing the rubidium double salt to obtain rubidium double salt crystals; (4) washing the rubidium-containing double salt crystals with an acid solution having a hydrogen ion concentration of 4 to 6 mol / L to obtain high-purity rubidium chlorostannate crystals; (5) Adding the washed high-purity rubidium chlorostannate crystals into water for slurry preparation, and then adding ammonia water to react until complete, thereby obtaining a rubidium chloride solution and a tin-containing precipitate; (6) Post-treating the rubidium chloride-containing solution to obtain high-purity rubidium chloride.

[0006] The present invention adopts a streamlined process. First, rubidium in crude rubidium salt is converted into rubidium-containing precipitate efficiently and at low cost by using a single precipitant. Then, the purity of the finished product is greatly improved by recrystallization of the double salt. This provides a practical technical solution for the large-scale industrial production of high-purity rubidium chloride.

[0007] Based on the characteristic that the solubility of rubidium chlorostannate in acid solution decreases with increasing acidity, the present invention first forms a precipitate under high acidity to remove some impurities, while a large amount of impurities will be entrained in the precipitate. Then, the precipitate is heated and dissolved under low acidity, and then cooled and crystallized to leave the impurities in the crystallization residue. The impurities are then washed and removed with a high acidity solution to repeatedly reduce the impurity content.

[0008] As a further preferred embodiment of the above technical solution, the purity of the crude rubidium salt is no less than 98%, and the main impurity elements are sodium, potassium, and cesium. The purity of the prepared high-purity rubidium chloride is no less than 99.9%. Existing rubidium salt purification methods generally require the purity of the crude rubidium salt to be above 99% to obtain a product with a purity of 99.9% or more (i.e., the purity can only be improved by one order of magnitude). The present application can achieve the purification of crude rubidium salt with a purity of 97% or more, significantly reducing the production threshold and cost, and improving economic benefits.

[0009] Prior to the recrystallization in step (3), a seed crystal of high-purity rubidium chlorostannate is added to the acid solution containing the rubidium double salt, and crystallization is performed by cooling under the assistance of ultrasound to obtain rubidium double salt crystals. In terms of the recrystallization operation, although recrystallization purification technology is often used in the preparation process of high-purity compounds, the traditional recrystallization method has problems such as uneven crystal growth rate and severe impurity inclusion. Therefore, the recrystallization operation is further designed by using the addition of seed crystals and ultrasound assistance to ensure the recrystallization rate, improve the recrystallization effect, and thus improve the product purity.

[0010] As a further preferred embodiment of the above technical solution, the molar amount of seed crystals added in step (3) is 0.1-1.0% of the total molar amount of rubidium ions in the acid solution containing rubidium double salt.

[0011] As a further preferred embodiment of the above technical solution, when the seed crystal is added in step (3), the temperature of the acid solution containing rubidium double salt is 80-95°C.

[0012] As a further preferred embodiment of the above technical solution, the cooling crystallization in step (3) adopts a multi-stage gradient cooling method, with the terminal temperature of the cooling crystallization being 5-10°C, divided into 3-5 cooling sections, each with a cooling range of 20-40°C, and the total crystallization time for a single cooling section being 0.5-5 hours. By using multi-stage gradient cooling and adjusting the cooling parameters, the recrystallization rate and crystal nucleation / growth effect can be precisely controlled, impurity carryover can be reduced, and the purity of the final product can be improved.

[0013] As a further optimization of the above technical solution, the cooling rate of each cooling section in step (3) is 0.5~2℃ / min. In order to ensure that the total crystallization time of each cooling section is sufficient, the heat preservation crystallization time can be extended.

[0014] As a further preferred embodiment of the above technical solution, the ultrasonic power of the ultrasonic-assisted treatment in step (3) is 100-500 W, and the ultrasonic-assisted treatment time in a single cooling section is 0.5-3.0 h.

[0015] As a further preferred embodiment of the above technical solution, the ultrasonic-assisted treatment in step (3) is carried out continuously or intermittently.

[0016] As a further preferred embodiment of the above technical solution, the molar ratio of the tin element in the precipitant to the rubidium element in the acidic rubidium-containing solution is (0.5-3):1.

[0017] As a further preferred embodiment of the above technical solution, after obtaining the rubidium-containing double salt precipitate in step (1), the residual precipitate is reused multiple times in step (1) to precipitate the acidic rubidium-containing solution and then perform open circuit recovery treatment.

[0018] As a further preferred embodiment of the above technical solution, in step (2), the heating temperature is 95-100°C.

[0019] As a further preferred embodiment of the above technical solution, the residual solution obtained by recrystallization in step (3) can be reused multiple times in step (1) or in open circuit recovery treatment after step (2).

[0020] As a further preferred embodiment of the above technical solution, the washing times are 1 to 3 times.

[0021] As a further preferred embodiment of the above technical solution, the high-purity rubidium chlorostannate crystals obtained in step (4) are subjected to the operations of step (2) to step (4) to improve the purity of the high-purity rubidium chlorostannate crystals.

[0022] As a further preferred embodiment of the above technical solution, the rubidium ion concentration in the acidic rubidium-containing solution is 300-550 g / L; and the heating temperature in step (2) is 95-100°C.

[0023] As a further preferred embodiment of the above technical solution, in step (5), when the rubidium-containing double salt crystals are added to water for slurry adjustment, the solid-liquid ratio is 1:(3-7), the ammonia concentration is 25%-28%, and the pH is controlled at 7.0-8.5 during the reaction.

[0024] As a further preferred embodiment of the above technical solution, the tin-containing precipitate is reused in step (1) as a precipitant.

[0025] As a further preferred embodiment of the above technical solution, the post-treatment in step (6) is evaporation roasting, and the evaporation roasting temperature is 450-550° C. and the time is 1-5 hours.

[0026] As a further preferred embodiment of the above technical solution, the post-treatment in step (4) further includes a recrystallization operation after evaporation and roasting, and the number of recrystallizations is 1 to 2 times, which is determined by the cesium content in the raw material crude rubidium salt.

[0027] Based on the same technical concept, the present invention also provides high-purity rubidium chloride prepared by the above method.

[0028] Based on the same technical concept, the present invention also provides an application of the high-purity rubidium chloride of the above technical solution, which is used as a doping material in electronic chips or optoelectronic materials.

[0029] The present invention has the following beneficial effects: The purity of the final product obtained by the method for preparing high-purity rubidium chloride from crude rubidium salt can reach over 99.99%. The ultrasonic-assisted gradient cooling crystallization technology is introduced for the first time for the preparation of high-purity rubidium salt. The ultrasonic cavitation effect suppresses local supersaturation, and combined with gradient cooling, the crystals grow in an orderly manner, reducing impurity entrainment. During the production process, the use of organic solvents such as glacial acetic acid is completely avoided by streamlining the process flow, making the production process more environmentally friendly. A single precipitant system is adopted during the production process, and efficient recycling and reuse of the precipitant is achieved, greatly reducing raw material consumption and production costs. The method not only further shortens the process flow and improves purification efficiency, but also achieves breakthrough progress in industrial implementation difficulty and production cost control, providing a practical and feasible technical solution for large-scale industrial production of high-purity rubidium chloride.

[0030] The present invention will be further described in detail below with reference to specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the process flow chart of Example 1.

[0032] Figure 2 2-6 is a process flow chart of Examples 2-6. DETAILED DESCRIPTION

[0033] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered by the claims.

[0034] Example 1: In the method for preparing high-purity rubidium chloride of this embodiment, the raw material is a low-purity rubidium-containing raw material, specifically rubidium carbonate with a purity of 98%. The main impurity contents of the raw material are shown in Table 1 (mass fraction, %).

[0035] like Figure 1 As shown, the preparation method of high-purity rubidium chloride in this embodiment comprises the following steps: (1) Dissolution: Dissolve 2 kg of rubidium carbonate raw material in 4 L of hydrochloric acid solution, and control the hydrogen ion concentration in the acidic rubidium solution to 5.0 mol / L.

[0036] (2) Precipitation: Add 1.05 times the theoretical amount of tin tetrachloride pentahydrate (the molar ratio of tin to rubidium is 2.1:1) to the obtained acidic rubidium-containing solution. After the reaction is completed by stirring, filter to obtain a rubidium-containing double salt precipitate (rubidium chlorostannate).

[0037] (3) Complex salt recrystallization: The obtained rubidium complex salt precipitate was heated and dissolved in a 1.0 mol / L hydrochloric acid solution, and the temperature was lowered for one recrystallization. The cooling end point was 10°C, and the rubidium complex salt crystals (rubidium chlorostannate crystals) were obtained by filtration.

[0038] (4) Washing: Use hydrochloric acid solution with a hydrogen ion concentration of 5.0 mol / L to wash the rubidium complex salt crystals twice.

[0039] (5) Decomposition of double salt: The washed rubidium-containing double salt crystals are slurried with high-purity water at a solid-liquid ratio of 1:3, and then ammonia water is added to adjust the pH value to 7.5. The rubidium chloride solution (including rubidium chloride solution and ammonium chloride solution) and the tin-containing precipitate (tin hydroxide) are obtained by filtration.

[0040] (6) Evaporation and calcination: The rubidium chloride solution was evaporated to dryness and then calcined in a calcination furnace at 500°C for 2 h to obtain high-purity rubidium chloride with a purity of >99.93%. The impurity content is shown in Table 2.

[0041] Example 2: The preparation method of high-purity rubidium chloride in this embodiment uses the same raw materials as in Example 1, which are low-purity rubidium-containing raw materials, specifically rubidium carbonate with a purity of 98%. The main impurity contents of the raw materials are shown in Table 1 (mass fraction, %).

[0042] like Figure 2 As shown, the preparation method of high-purity rubidium chloride in this embodiment comprises the following steps: (1) Dissolution: Dissolve 2 kg of rubidium carbonate raw material in 4 L of hydrochloric acid solution, and control the hydrogen ion concentration in the acidic rubidium solution to 5.0 mol / L.

[0043] (2) Precipitation: Add 1.05 times the theoretical amount of tin tetrachloride pentahydrate (the molar ratio of tin to rubidium is 2.1:1) to the obtained acidic rubidium-containing solution. After the reaction is completed by stirring, filter to obtain a rubidium-containing double salt precipitate (rubidium chlorostannate).

[0044] (3) Dissolution: The obtained rubidium complex salt precipitate was placed in a 1.0 mol / L hydrochloric acid solution and heated until completely dissolved to obtain a clear solution at 100°C.

[0045] (4) Cooling crystallization: The clarified solution was cooled with the assistance of ultrasound, with the cooling end point being 10°C, the ultrasonic treatment power being 200W, and the time being 2.0h; when the temperature dropped to 95°C, high-purity rubidium chlorostannate seed crystals were added to the solution, with the molar addition amount of the seed crystals being 0.2% of the total molar amount of rubidium ions in the solution, and the rubidium complex salt crystals (rubidium chlorostannate crystals) were obtained by filtration.

[0046] (5) Washing: Use hydrochloric acid solution with a hydrogen ion concentration of 5.0 mol / L to wash the rubidium complex salt crystals twice.

[0047] (6) Decomposition of double salt: The washed rubidium double salt crystals are slurried with high-purity water, with a solid-liquid ratio of 1:3, and then ammonia water is added to adjust the pH value to 7.5. The rubidium chloride solution (including rubidium chloride solution and ammonium chloride solution) and the tin-containing precipitate (tin hydroxide) are obtained by filtration.

[0048] (7) Evaporation and calcination: The rubidium chloride solution was evaporated to dryness and then calcined in a calcination furnace at 500°C for 2 h to obtain high-purity rubidium chloride with a purity of >99.97%. The impurity content is shown in Table 2.

[0049] Comparing the production effects of Example 1 and Example 2, it was found that the natural cooling crystallization method without adding seed crystals resulted in a slower crystallization rate and longer crystallization time. At the same time, the double salt crystals obtained without ultrasound were prone to agglomeration and wall adhesion, resulting in a decrease in yield, and the impurity content such as potassium and sodium was still high, making it difficult to obtain a rubidium chloride product with a purity of >99.99%.

[0050] Example 3: The preparation method of high-purity rubidium chloride in this embodiment uses the same raw materials as in Example 1, which are low-purity rubidium-containing raw materials, specifically rubidium carbonate with a purity of 98%. The main impurity contents of the raw materials are shown in Table 1 (mass fraction, %).

[0051] like Figure 2 As shown, the preparation method of high-purity rubidium chloride in this embodiment comprises the following steps: (1) Dissolution: Dissolve 2 kg of rubidium carbonate raw material in 4 L of hydrochloric acid solution, and control the hydrogen ion concentration in the acidic rubidium solution to 6.0 mol / L.

[0052] (2) Precipitation: Add 1.05 times the theoretical amount of tin tetrachloride pentahydrate (the molar ratio of tin to rubidium is 2.1:1) to the obtained acidic rubidium-containing solution. After the reaction is completed by stirring, filter to obtain a rubidium-containing double salt precipitate (rubidium chlorostannate).

[0053] (3) Dissolution: The obtained rubidium complex salt precipitate was placed in a 2.0 mol / L hydrochloric acid solution and heated until completely dissolved to obtain a clear solution at 100°C.

[0054] (4) Cooling crystallization: The clarified solution was cooled with the assistance of ultrasound, with the cooling end point being 10°C, the ultrasonic treatment power being 300W, and the time being 2.0h; when the temperature dropped to 90°C, high-purity rubidium chlorostannate seed crystals were added to the solution, with the molar addition amount of the seed crystals being 0.8% of the total molar amount of rubidium ions in the solution, and the rubidium complex salt crystals (rubidium chlorostannate crystals) were obtained by filtration.

[0055] (5) Washing: Use hydrochloric acid solution with a hydrogen ion concentration of 6.0 mol / L to wash the rubidium complex salt crystals twice.

[0056] (6) Decomposition of double salt: The washed rubidium double salt crystals are slurried with high-purity water, with a solid-liquid ratio of 1:3, and then ammonia water is added to adjust the pH value to 7.5. The rubidium chloride solution (including rubidium chloride solution and ammonium chloride solution) and the tin-containing precipitate (tin hydroxide) are obtained by filtration.

[0057] (7) Evaporation and calcination: The rubidium chloride solution was evaporated to dryness and then calcined in a calcination furnace at 500°C for 2 h to obtain high-purity rubidium chloride with a purity of >99.95%. The impurity content is shown in Table 2.

[0058] Example 4: In the method for preparing high-purity rubidium chloride from crude rubidium salt of this embodiment, the raw materials are the same as those in Example 1, which are low-purity rubidium-containing raw materials, specifically rubidium carbonate with a purity of 98%. The main impurity contents of the raw materials are shown in Table 1 (mass fraction, %).

[0059] like Figure 2 As shown, the method for preparing high-purity rubidium chloride from crude rubidium salt in this embodiment includes the following steps: (1) Dissolution: Dissolve 2 kg of rubidium carbonate raw material in 4 L of hydrochloric acid solution, and control the hydrogen ion concentration in the acidic rubidium solution to 5.0 mol / L.

[0060] (2) Precipitation: Add 1.05 times the theoretical amount of tin tetrachloride pentahydrate (the molar ratio of tin to rubidium is 2.1:1) to the obtained acidic rubidium-containing solution. After the reaction is completed by stirring, filter to obtain a rubidium-containing double salt precipitate (rubidium chlorostannate).

[0061] (3) Dissolution: The obtained rubidium-containing complex salt was heated and dissolved in a 1.0 mol / L hydrochloric acid solution to obtain a clear solution at a temperature of 100°C.

[0062] (4) Cooling crystallization: The first stage of ultrasonic crystallization: the cooling end temperature is 80℃, the cooling rate is 2℃ / min, the total crystallization time is 0.5h, and when the solution temperature is 95℃, high-purity chlorostannate seeds are added. The molar amount of the seeds added is 0.2% of the total molar amount of rubidium ions in the solution. The ultrasonic treatment power is 200w, continuous ultrasonic treatment is used, and the ultrasonic time is 0.5h.

[0063] The second stage of ultrasonic crystallization: the cooling end temperature is 50°C, the cooling rate is 1°C / min, the total crystallization time is 1.0h, the ultrasonic treatment power is 200w, intermittent ultrasonic treatment is used, and the ultrasonic time is 0.5h.

[0064] The third stage of ultrasonic crystallization: the cooling end temperature is 10°C, the cooling rate is 0.5°C / min, the total crystallization time is 5.0h, the ultrasonic treatment power is 300w, intermittent ultrasonic treatment is used, and the ultrasonic time is 1.0h.

[0065] High-purity rubidium chlorostannate crystals were obtained after three stages of cooling and crystallization.

[0066] (5) Washing: Wash the high-purity rubidium chlorostannate crystals twice with a hydrochloric acid solution with a hydrogen ion concentration of 5 mol / L.

[0067] (6) Decomposition of double salt: The washed high-purity rubidium chlorostannate crystals are added with high-purity water to prepare a slurry with a solid-liquid ratio of 1:3, and then ammonia water is added to adjust the pH value to 7.5. The rubidium chloride solution (including rubidium chloride solution and ammonium chloride solution) and the tin-containing precipitate (tin hydroxide) are obtained by filtration.

[0068] (7) Evaporation and Calcination: The rubidium chloride solution was evaporated to dryness and then calcined in a calcination furnace at 500°C for 2 hours to obtain high-purity rubidium chloride with a purity of >99.99%. The impurity content is shown in Table 2. Comparing the production results of this embodiment with those of the previous embodiment, it can be seen that the product purity of this embodiment is further improved. This is because the gradient cooling can better control the growth rate of the crystal and avoid the entrainment of impurities during the crystal growth process due to uncontrollable growth rate.

[0069] Example 5: In the method of preparing high-purity rubidium chloride from crude rubidium salt of this embodiment, the raw material is a low-purity rubidium-containing raw material, specifically 98% pure rubidium chloride. The main impurity contents of the raw material are shown in Table 1 (mass fraction, %).

[0070] like Figure 2 As shown, the method for preparing high-purity rubidium chloride from crude rubidium salt in this embodiment includes the following steps: (1) Dissolution: Dissolve 3 kg of rubidium chloride raw material in 6 L of hydrochloric acid solution, and control the hydrogen ion concentration in the acidic rubidium solution to 5.5 mol / L.

[0071] (2) Precipitation: Add 1.1 times the theoretical amount of tin tetrachloride pentahydrate (the molar ratio of tin to rubidium is 2.2:1) to the obtained acidic rubidium-containing solution. After the reaction is completed by stirring, filter to obtain a rubidium-containing double salt precipitate (rubidium chlorostannate).

[0072] (3) Dissolution: Heat and dissolve the obtained rubidium-containing complex salt in a 1.2 mol / L hydrochloric acid solution. The temperature of the clear solution is 100°C.

[0073] (4) Cooling crystallization: The first stage of ultrasonic crystallization: the cooling end temperature is 80℃, the cooling rate is 2℃ / min, the total crystallization time is 0.5h, and when the solution temperature is 98℃, high-purity chlorostannate seed crystals are added. The amount of seed crystals added is 0.1% of the total amount of rubidium ions in the solution. The ultrasonic treatment power is 300w, and continuous ultrasonic treatment is carried out for 0.5h.

[0074] The second stage of ultrasonic crystallization: the cooling end temperature is 60°C, the cooling rate is 1°C / min, the total crystallization time is 1.0h, the ultrasonic treatment power is 200w, intermittent ultrasonic treatment is performed, and the ultrasonic time is 0.5h.

[0075] The third stage of ultrasonic crystallization: the cooling end temperature is 40°C, the cooling rate is 0.5°C / min, the total crystallization time is 1.0h, the ultrasonic treatment power is 200w, intermittent ultrasonic treatment is performed, and the ultrasonic time is 0.5h.

[0076] The fourth stage of ultrasonic crystallization: the cooling end temperature is 10°C, the cooling rate is 1.0°C / min, the total crystallization time is 3.0h, the ultrasonic treatment power is 500w, intermittent ultrasonic treatment is performed, and the ultrasonic time is 0.5h.

[0077] After four stages of cooling and crystallization, high-purity rubidium chlorostannate crystals were obtained.

[0078] (5) Washing: Wash the high-purity rubidium chlorostannate crystals once with a hydrochloric acid solution having a hydrogen ion concentration of 4 mol / L.

[0079] (6) Decomposition of double salt: The washed high-purity rubidium chlorostannate crystals are added with high-purity water to prepare a slurry with a solid-liquid ratio of 1:3, and then ammonia water is added to adjust the pH value to 8.0. The rubidium chloride solution (including rubidium chloride solution and ammonium chloride solution) and the tin-containing precipitate are obtained by filtration.

[0080] (7) Evaporation and calcination: The obtained rubidium chloride solution was evaporated to dryness and then calcined in a calcination furnace at 500°C for 3.5 hours to obtain high-purity rubidium chloride with a purity of >99.99%. The impurity content is shown in Table 2.

[0081] Example 6: In the method of preparing high-purity rubidium chloride from crude rubidium salt of this embodiment, the raw material is a low-purity rubidium-containing raw material, specifically rubidium sulfate with a purity of 97%. The main impurity contents of the raw material are shown in Table 1 (mass fraction, %).

[0082] like Figure 2 As shown, the method for preparing high-purity rubidium chloride from crude rubidium salt in this embodiment includes the following steps: (1) Dissolution: Dissolve 5 kg of rubidium sulfate raw material in 10 L of hydrochloric acid solution, and control the hydrogen ion concentration in the acidic rubidium solution to 5.0 mol / L.

[0083] (2) Precipitation: Add 1.15 times the theoretical amount of tin tetrachloride pentahydrate (the molar ratio of tin to rubidium is 2.3:1) to the obtained acidic rubidium-containing solution. After the reaction is completed by stirring, filter to obtain a rubidium-containing double salt precipitate (rubidium chlorostannate).

[0084] (3) Dissolution: Heat and dissolve the obtained rubidium-containing complex salt in 0.8 mol / L hydrochloric acid solution. The temperature of the clear solution is 100°C.

[0085] (4) Cooling crystallization: The first stage of ultrasonic crystallization: the cooling end temperature is 60℃, the cooling rate is 2℃ / min, the total crystallization time is 0.5h, and when the solution temperature is 98℃, high-purity chlorostannate seeds are added. The amount of seeds added is 0.4% of the total amount of rubidium ions in the solution. The ultrasonic treatment power is 500w, and continuous ultrasonic treatment is carried out for 0.5h.

[0086] The second stage of ultrasonic crystallization: the cooling end temperature is 30°C, the cooling rate is 1°C / min, the total crystallization time is 1.0h, the ultrasonic treatment power is 200w, intermittent ultrasonic treatment is performed, and the ultrasonic time is 0.5h.

[0087] The third stage of ultrasonic crystallization: the cooling end temperature is 10°C, the cooling rate is 0.5°C / min, the total crystallization time is 3.0h, the ultrasonic treatment power is 200w, intermittent ultrasonic treatment is performed, and the ultrasonic time is 1.0h.

[0088] High-purity rubidium chlorostannate crystals were obtained after three stages of cooling and crystallization.

[0089] (5) Washing: Wash the high-purity rubidium chlorostannate crystals twice with a hydrochloric acid solution with a hydrogen ion concentration of 5 mol / L.

[0090] (6) High-purity rubidium chlorostannate crystals The washed high-purity rubidium chlorostannate crystals are returned to step (3), and steps (3) to (5) are repeated once to obtain high-purity rubidium chlorostannate crystals.

[0091] (7) Decomposition of double salt: Add high-purity rubidium chlorostannate crystals to high-purity water to prepare a slurry with a solid-liquid ratio of 1:3, then add ammonia water to adjust the pH value to 7.5, and filter to obtain a rubidium chloride solution (including rubidium chloride solution and ammonium chloride solution) and a tin-containing precipitate.

[0092] (8) Evaporation and calcination: The obtained rubidium chloride solution is evaporated to dryness and then calcined in a calcination furnace at 500°C for 2.5 hours to obtain high-purity rubidium chloride.

[0093] (9) Recrystallization: The rubidium chloride obtained by roasting was dissolved in water and recrystallized once to obtain high-purity rubidium chloride with a purity of >99.99%. The impurity content is shown in Table 2.

[0094] Comparative Example 1: The raw material used in this comparative example is rubidium carbonate with a purity of 99%, which is the same as that in Example 1. The main impurity contents of the raw materials are shown in Table 1 (mass fraction, %).

[0095] The preparation method of rubidium chloride in this comparative example comprises the following steps: (1) Dissolution: Dissolve 2 kg of rubidium carbonate raw material in hydrochloric acid solution to obtain a nearly neutral rubidium chloride solution.

[0096] (2) Recrystallization: Without the double salt precipitation step, a single recrystallization operation was performed to obtain the rubidium chloride product, the purity of which was still 99.70%. The impurity content is shown in Table 2. The results showed that only the cesium impurity was reduced, while the remaining impurities were not significantly removed.

[0097] Comparative Example 2: The raw material used in this comparative example is rubidium chloride with a purity of 98%, which is the same as that in Example 5. The main impurity contents of the raw materials are shown in Table 1 (mass fraction, %).

[0098] The preparation method of rubidium chloride in this comparative example comprises the following steps: (1) Dissolution: Dissolve 3 kg of rubidium chloride raw material in 6 L of hydrochloric acid solution, and control the hydrogen ion concentration in the acidic rubidium solution to 5.5 mol / L.

[0099] (2) Precipitation: Add 1.1 times the theoretical amount of tin tetrachloride pentahydrate (the molar ratio of tin to rubidium is 2.2:1) to the obtained acidic rubidium-containing solution. After the reaction is completed by stirring, filter to obtain a rubidium-containing double salt precipitate.

[0100] (3) Decomposition of double salt: without going through the double salt dissolution and crystallization steps, the obtained rubidium-containing double salt precipitate is directly slurried with high-purity water, with a solid-liquid ratio of 1:3, and then ammonia water is added to adjust the pH value to 8.0, and the rubidium-containing solution and the tin-containing precipitate are obtained by filtration.

[0101] (4) Evaporation and calcination: The obtained rubidium-containing solution is evaporated to dryness and then calcined in a calcination furnace at 500°C for 3.5 hours to obtain rubidium chloride.

[0102] (5) Recrystallization: The rubidium chloride obtained by roasting was dissolved in water and recrystallized once to obtain rubidium chloride with a purity of >99.67%. The impurity content is shown in Table 2. The results show that the purity of rubidium chloride obtained without the double salt dissolution and crystallization steps is significantly reduced, and the content of impurities such as potassium is still high, making it difficult to obtain a higher purity rubidium chloride product.

[0103] Comparative Example 3: In the method for preparing rubidium chloride from crude rubidium salt in this comparative example, the raw materials are the same as those in Example 1, namely, low-purity rubidium-containing raw materials. The main impurity contents of the raw materials are shown in Table 1 (mass fraction, %).

[0104] The method for preparing rubidium chloride from crude rubidium salt in this comparative example comprises the following steps: (1) Dissolution: Dissolve 2 kg of rubidium carbonate raw material in 4 L of hydrochloric acid solution, and control the hydrogen ion concentration in the acidic rubidium solution to 2.0 mol / L.

[0105] (2) Precipitation: Add 1.05 times the theoretical amount of tin tetrachloride pentahydrate (the molar ratio of tin to rubidium is 2.1:1) to the obtained acidic rubidium-containing solution. After the reaction is completed by stirring, filter to obtain a rubidium-containing double salt precipitate (rubidium chlorostannate).

[0106] (3) Dissolution: The obtained rubidium-containing double salt is heated and dissolved in a 4 mol / L hydrochloric acid solution, and the temperature is lowered for one recrystallization. The cooling end point is 10°C, and the rubidium-containing double salt crystals (rubidium chlorostannate crystals) are obtained by filtration.

[0107] (4) Washing: Wash twice with a hydrochloric acid solution with a hydrogen ion concentration of 2 mol / L.

[0108] (5) Decomposition of double salt: The obtained rubidium-containing double salt crystals are slurried with high-purity water at a solid-liquid ratio of 1:3, and then ammonia water is added to adjust the pH value to 7.5. The rubidium chloride solution (including rubidium chloride solution and ammonium chloride solution) and the tin-containing precipitate are obtained by filtration.

[0109] (6) Evaporation and calcination: The obtained rubidium chloride solution is evaporated to dryness and then calcined in a calcination furnace at 500°C for 2 hours to obtain high-purity rubidium chloride.

[0110] (7) Recrystallization: Since the raw materials of this comparative example still contain a small amount of cesium impurities, the rubidium chloride obtained by roasting is dissolved in water and recrystallized once to obtain rubidium chloride with a purity of >99.9%. The impurity content is shown in Table 2. Analysis of the results of Example 1 and this comparative example shows that controlling the acidity of the acid solution in different steps can improve the purity of the final product.

[0111] Table 1: Types, purity and main impurity contents of raw materials in various examples and comparative examples (mass fraction, %)

[0112] Table 2: Purity and main impurity content of products in various examples and comparative examples (mass fraction, %)

[0113] The above are only preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. For those skilled in the art, improvements and modifications obtained without departing from the technical concept of the present invention should also be considered as the scope of protection of the present invention.

[0114] Although embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for preparing high-purity rubidium chloride from crude rubidium salt, characterized in that: The following steps are involved: (1) dissolving crude rubidium salt in an acid solution to obtain an acidic rubidium-containing solution, and adding a precipitant to the acidic rubidium-containing solution to obtain a rubidium-containing double salt precipitate; the hydrogen ion concentration in the acidic rubidium-containing solution is 3 to 6 mol / L, and the precipitant is a tin-containing precipitant, including at least one of tin tetrachloride, tin tetrachloride hydrate, tin chloride, and tin chloride hydrate; (2) heating the rubidium double salt precipitate in an acid solution having a hydrogen ion concentration of 0.5 to 2 mol / L until it is completely dissolved to obtain an acid solution containing the rubidium double salt; (3) recrystallizing the acid solution containing the rubidium double salt to obtain rubidium double salt crystals; (4) washing the rubidium-containing double salt crystals with an acid solution having a hydrogen ion concentration of 4 to 6 mol / L to obtain high-purity rubidium chlorostannate crystals; (5) Adding the washed high-purity rubidium chlorostannate crystals into water for slurry preparation, and then adding ammonia water to react until complete, thereby obtaining a rubidium chloride solution and a tin-containing precipitate; (6) Post-treating the rubidium chloride-containing solution to obtain high-purity rubidium chloride.

2. The method for preparing high-purity rubidium chloride from crude rubidium salt according to claim 1, wherein The purity of the crude rubidium salt is not less than 97%, and the main impurity elements are sodium, potassium and cesium. The purity of the prepared high-purity rubidium chloride is not less than 99.9%.

3. The method for preparing high-purity rubidium chloride from crude rubidium salt according to claim 1, wherein: In step (1), the molar ratio of the tin element in the precipitant to the rubidium element in the acidic rubidium-containing solution is (0.5-3):

1.

4. The method for preparing high-purity rubidium chloride from crude rubidium salt according to claim 1, wherein: Before the recrystallization in step (3), seed crystals of high-purity rubidium chlorostannate are added to the acid solution containing the rubidium double salt, and crystallization is performed by cooling under the assistance of ultrasound to obtain rubidium double salt crystals.

5. The method for preparing high-purity rubidium chloride from crude rubidium salt according to claim 4, wherein: The molar amount of the seed crystal added is 0.1-1.0% of the total molar amount of rubidium ions in the acid solution containing the rubidium double salt; when the seed crystal is added, the temperature of the acid solution containing the rubidium double salt is 80-95°C.

6. The method for preparing high-purity rubidium chloride from crude rubidium salt according to claim 4, characterized in that: The cooling crystallization in step (3) adopts a multi-stage gradient cooling method, the terminal temperature of the cooling crystallization is 5~10℃, divided into 3~5 cooling sections, each cooling range is 20~40℃, the total crystallization time of a single cooling section is 0.5~5h, and the cooling rate of each cooling section is 0.5~2℃ / min.

7. The method for preparing high-purity rubidium chloride from crude rubidium salt according to claim 6, wherein: The ultrasonic power of the ultrasonic-assisted treatment in step (3) is 100-500 W, and the ultrasonic-assisted treatment time in a single cooling section is 0.5-3.0 h; the ultrasonic-assisted treatment is carried out continuously or intermittently.

8. The method for preparing high-purity rubidium chloride from crude rubidium salt according to any one of claims 1 to 7, characterized in that: After obtaining the rubidium-containing double salt precipitate in step (1), the residual precipitate solution is reused multiple times in step (1) to perform open circuit recovery treatment after precipitation of the acidic rubidium-containing solution; the residual solution after recrystallization in step (3) is reused in step (2); and the tin-containing precipitate obtained in step (5) is reused in step (1) as a precipitant.

9. The method for preparing high-purity rubidium chloride from crude rubidium salt according to any one of claims 1 to 7, characterized in that: The rubidium ion concentration in the acidic rubidium-containing solution in step (1) is 300-550 g / L; the heating temperature in step (2) is 95-100° C.

10. The method for preparing high-purity rubidium chloride from crude rubidium salt according to any one of claims 1 to 7, characterized in that: Repeat the operations of steps (2) to (4) on the high-purity rubidium chlorostannate crystals obtained in step (4) to improve the purity of the high-purity rubidium chlorostannate crystals.

11. The method for preparing high-purity rubidium chloride from crude rubidium salt according to any one of claims 1 to 7, characterized in that: In step (5), when the rubidium-containing double salt crystals are added to water for slurry adjustment, the solid-liquid ratio is 1: (3-7), the ammonia concentration is 25%-28%, and the pH is controlled at 7.0-8.5 during the reaction.

12. The method for preparing high-purity rubidium chloride from crude rubidium salt according to any one of claims 1 to 7, characterized in that: The post-treatment in step (6) is evaporation roasting and recrystallization operations performed in sequence, the evaporation roasting temperature is 450~550℃, the time is 1~5h, and the number of recrystallizations is 1~2 times.

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