A simple and efficient method for preparing high-purity rubidium chloride

Abstract

A simple and efficient method for preparing high-purity rubidium chloride includes the following steps: Adding crude rubidium salt to glacial acetic acid, heating and stirring to dissolve, filtering to remove insoluble impurities, yielding a crude rubidium salt solution in glacial acetic acid; adding a certain amount of antimony trichloride solution to the crude rubidium salt solution in glacial acetic acid, stirring the reaction to obtain a small amount of pale yellow precipitate and solution until the reaction reaches equilibrium, yielding a clear liquid and precipitate, the precipitate being used to prepare high-purity cesium salt; secondary precipitation: adding a certain amount of tin tetrachloride solution in glacial acetic acid to the clear liquid, stirring the reaction to obtain a white precipitate and solution; standing, filtering, and washing: cooling and standing the solution until the reaction reaches equilibrium, filtering, washing the precipitate with glacial acetic acid, yielding a precipitate and washing liquid; double salt decomposition: adding high-purity water to the precipitate to form a slurry, then adding ammonia to adjust the pH value, filtering to obtain tin hydroxide precipitate and rubidium chloride solution; sending the filtrate for testing: evaporating the qualified rubidium chloride solution to dryness, calcining to obtain rubidium chloride; recrystallization: obtaining the high-purity rubidium chloride product. It has the advantages of effectively removing cesium ions from crude rubidium salt and avoiding the influence of alkali metal ions on the purity of the final product, without loss, and with high product purity.

Description

Technical Field

[0001] This invention relates to the field of rubidium chloride production technology, and in particular to a simple and efficient method for preparing high-purity rubidium chloride. Background Technology

[0002] Precipitation is commonly used for the separation of radioactive elements from fission products and in early industrial production. It is generally used to separate and extract rubidium from brines or aqueous solutions with high rubidium content. Precipitation is also highly effective for the further purification of lower-purity rubidium salts or crude products. Among the more studied precipitants are silylamic acid (tungstenic acid), chloroplatinic acid, tin tetrachloride, antimony trichloride, sodium tetraphenylborate, and potassium bismuth iodoate.

[0003] Sodium tetraphenylborate is an ideal precipitant for rubidium, mainly because the precipitate it produces has extremely low solubility in water; the solubility of rubidium tetraphenylborate in water is only 0.378 mg. However, since sodium tetraphenylborate is also a good precipitant for potassium and cesium ions, its precipitation method is not feasible for purifying rubidium salts in actual production. Potassium iodobismuthate can accurately precipitate rubidium and cesium in the presence of alkali metal elements such as potassium ions. However, because potassium iodobismuthate itself is insoluble in water, and its raw material iodide requires special treatment such as light protection during production, it is not suitable for industrial production.

[0004] Antimony trichloride has been reported as an ideal reagent for precipitating cesium since the 1950s. However, the complex salt precipitate formed by antimony trichloride and cesium ions has a certain solubility at room temperature (Cs+>5g / L), resulting in poor cesium removal efficiency and making it impossible to directly obtain high-purity rubidium salts. Furthermore, the solubility of the complex salt precipitate formed by antimony trichloride and cesium ions in glacial acetic acid is even lower (Cs+ approximately 0.15g / L). Using glacial acetic acid as the medium and an antimony trichloride solution in glacial acetic acid as the precipitant, lower-purity rubidium salts can be purified efficiently.

[0005] The industry standard YS / T 1019-2015 "Rubyium Chloride," drafted by Jiangxi Dongpeng New Materials Co., Ltd., Jiangxi Benyuan New Materials Technology Co., Ltd., and Jiangxi Ganfeng Lithium Co., Ltd., stipulates that rubidium chloride produced by various methods is classified into three grades according to its chemical composition: 99%, 99.5%, and 99.9%. Its chemical composition should conform to the following table:

[0006]

[0007] According to industry standards, high-purity rubidium chloride with a purity of 99.9% requires the Cs content to be reduced to below 0.030%. Therefore, it is difficult for existing technologies to achieve such a high rubidium-cesium separation effect in a short process and at low cost.

[0008] To address the aforementioned issues, several patents have been published: Patent CN 107217156 A, "Method for Extracting Rubidium and Cesium Salts from Lithium Extraction Mother Liquor from Spodumene," uses tin tetrachloride as a precipitant to non-selectively precipitate rubidium and cesium salts from lithium extraction mother liquor under acidic conditions. This method only involves using a precipitant to separate rubidium and cesium ions from other impurity ions, and has drawbacks such as not being able to separate rubidium and cesium ions separately, requiring additional extraction steps for further purification, resulting in a complex and costly process. Patent CN114350950A, "A Method for Extracting Rubidium and Cesium from Complex Underground Brine," uses brine... The process of purifying, enriching, precipitating, refining to remove potassium, and extracting rubidium and cesium stepwise separates and purifies rubidium and cesium salts, ultimately yielding rubidium chloride and cesium chloride with a purity of approximately 99%. The average overall yield of rubidium and cesium is approximately 80% and 75%, respectively. However, this method suffers from drawbacks such as complex processes and high costs. The paper or article "Research on the Separation of Cs and Rb by Precipitation Method" discloses a method for separating rubidium and cesium in glacial acetic acid medium. First, K3Bi2I9 is ​​synthesized by reacting Bi2O3 and KI, and then Cs... + It reacts with K3Bi2I9 to produce an orange-red precipitate, while Rb + Almost no precipitate was formed between Cs+ and K3Bi2I9. Experimental results showed that when the separation coefficient of cesium and rubidium was greater than 100, the precipitation rate of Cs+ was 70% to 80%; while when the precipitation rate of Cs+ was 96.0% to 98.9%, the separation coefficient of cesium and rubidium dropped to 26 to 38. However, it had shortcomings such as complex process, low separation coefficient of rubidium and cesium, and low raw material utilization.

[0009] Therefore, it is of great significance to develop a simple and efficient method for preparing high-purity rubidium chloride. Summary of the Invention

[0010] The objective of this invention is to overcome the shortcomings of the prior art and provide a simple and efficient method for preparing high-purity rubidium chloride. This method uses crude rubidium salt obtained from lithium extraction mother liquor as raw material, and uses antimony trichloride as a primary precipitant and tin tetrachloride as a secondary precipitant to prepare high-purity rubidium chloride.

[0011] The objective of this invention is achieved through the following technical solution:

[0012] 1. A simple and efficient method for preparing high-purity rubidium chloride, addressing the problem of high-purity rubidium chloride preparation, characterized by using crude rubidium salt obtained from lithium extraction mother liquor as raw material, using antimony trichloride as a primary precipitant and tin tetrachloride as a secondary precipitant to prepare high-purity rubidium chloride. The specific process steps and conditions are as follows:

[0013] (1) Dissolution: Add crude rubidium salt to glacial acetic acid, heat and stir to dissolve, filter to remove insoluble impurities, and obtain a glacial acetic acid solution of crude rubidium salt;

[0014] (2) Precipitation: Add a certain amount of antimony trichloride acetic acid solution to the acetic acid solution of crude rubidium salt, react and stir for 10 - 15 min, generating a small amount of pale yellow precipitate and solution;

[0015] (3) Static filtration: Cool the solution in step (2) to 16 - 20 °C, stand for 10 - 30 min until the reaction reaches equilibrium, filter, generating clear liquid and precipitate, and the precipitate is used for preparing high - purity cesium salt;

[0016] (4) Secondary precipitation: Add a certain amount of stannic chloride acetic acid solution to the clear liquid, react and stir for 10 - 15 min, generating white precipitate and solution;

[0017] (5) Static filtration and washing: Cool and stand the solution until the reaction reaches equilibrium, filter, and wash the precipitate with acetic acid 3 - 5 times, generating precipitate and washing liquid;

[0018] (6) Double - salt decomposition: Slurry the precipitate with high - purity water, then add ammonia water to adjust the pH value to 7 - 8, filter to obtain stannic hydroxide precipitate and rubidium chloride solution; The filtrate is sent for inspection, and the ion concentration in the solution Rb + :Cs + >2000 is qualified, otherwise it is unqualified;

[0019] (7) Evaporation to dryness and calcination: Evaporate the qualified rubidium chloride solution to dryness and send it to a muffle furnace for calcination to obtain rubidium chloride;

[0020] (8) Recrystallization: Perform multiple recrystallizations on the rubidium chloride after evaporation to dryness and calcination to obtain high - purity rubidium chloride finished product.

[0021] Compared with the prior art, the present invention has the following advantages or effects:

[0022] (1) Because the double - salt precipitate formed by antimony trichloride and cesium ions in acetic acid medium has extremely low solubility, cesium ions in crude rubidium salt can be effectively removed after cooling and standing.

[0023] (2) At the same time, since no other impurity ions are introduced in the process except ammonium ions and can be completely removed during subsequent calcination, the influence of other alkali metal ions on the purity of the final product is avoided.

[0024] (3) In addition, since the medium acetic acid can be distilled, condensed and recycled, there is basically no loss.

[0025] (4) In addition, because the solubility of the double - salt formed by antimony trichloride and alkali metals is Cs < Rb < K < Na < Li, the purity of the finished product can be greatly improved through multiple recrystallizations.

[0026] The percentages involved in the application documents are mass percentages. Brief Description of the Drawings

[0027] Figure 1 Schematic diagram of a simple and efficient method for preparing high-purity rubidium chloride according to the present invention.

[0028] The present invention will be further described in detail below with reference to the accompanying drawings. Specific embodiments

[0029] As Figure 1 shown, a simple and efficient method for preparing high-purity rubidium chloride, aiming at the problem of preparing high-purity rubidium chloride, is characterized in that the crude rubidium salt obtained from the lithium extraction mother liquor is used as the raw material, antimony trichloride is used as the primary precipitant, and tin tetrachloride is used as the secondary precipitant to prepare high-purity rubidium chloride. The specific process steps and conditions are as follows:

[0030] (1) Dissolution: Add the crude rubidium salt to glacial acetic acid, dissolve it by heating and stirring, and filter to remove insoluble impurities to obtain a glacial acetic acid solution of the crude rubidium salt.

[0031] (2) Precipitation: Add a certain amount of glacial acetic acid solution of antimony trichloride to the glacial acetic acid solution of the crude rubidium salt obtained in step 1, react and stir for 10 - 15 min to produce a small amount of pale yellow precipitate and solution.

[0032] (3) Standing and filtration: Cool the solution obtained in step (2) to 16 - 20 °C, stand for 10 - 30 min until the reaction reaches equilibrium, filter to produce a clear liquid and a precipitate, and the precipitate is used to prepare high-purity cesium salt.

[0033] (4) Secondary precipitation: Add a certain amount of glacial acetic acid solution of tin tetrachloride to the clear liquid obtained in step (3), react and stir for 10 - 15 min to produce a white precipitate and solution.

[0034] (5) Standing, filtration and washing: Cool and stand the solution obtained in step (4) until the reaction reaches equilibrium, filter, and wash the precipitate with glacial acetic acid 3 - 5 times to produce a precipitate and a washing solution.

[0035] (6) Double salt decomposition: Make a slurry of the precipitate obtained in step (5) with high-purity water, then add ammonia water to adjust the pH value to 7 - 8, filter to obtain a tin hydroxide precipitate and a rubidium chloride solution; the filtrate is sent for inspection, and the ion concentration in the solution Rb + :Cs + > 2000 is qualified, otherwise it is unqualified.

[0036] (7) Evaporation to dryness and calcination: Evaporate the qualified rubidium chloride solution to dryness and send it to a muffle furnace for calcination to obtain rubidium chloride.

[0037] (8) Recrystallization: Recrystallize the rubidium chloride obtained by evaporation to dryness and calcination in step (7) multiple times to obtain high-purity rubidium chloride finished product.

[0038] The process of the present invention can further be:

[0039] The washing solution in step (5) is recycled into the rubidium salt glacial acetic acid solution in step (1).

[0040] After dissolving the tin hydroxide precipitate in step (6) with excess hydrochloric acid, it is returned to step (4) for recycling.

[0041] If the rubidium chloride solution in step (6) does not meet the standard, return to step (1) for further impurity removal.

[0042] In step (1), the purity of the rubidium salt is ≥95%, and the concentration of rubidium ions after dissolving in glacial acetic acid is 20-100 g / L.

[0043] In step (2), the amount of antimony trichloride added is Sb:Cs = 2:3, with a slight excess of 5-10%.

[0044] The static cooling temperature in steps (3) and (5) is 16-20°C, and the static equilibration time is 10-120 min.

[0045] In step (4), the amount of tin tetrachloride added is Sn:Rb = 1:2, with a slight excess of 2-10%.

[0046] In step (4), the amount of tin tetrachloride added is Sn:Rb = 1:2, with a slight excess of 2-10%.

[0047] In step (6), the solid-liquid ratio of water added for slurry preparation is 1:2.5-7, and the ammonia concentration is 25%-28%.

[0048] The calcination temperature in step (7) is 450-550℃, and the calcination time is 2-6h.

[0049] The recrystallization process in step (8) is repeated 1 to 3 times.

[0050] Example 1

[0051] 100g of crude rubidium chloride (98% purity) was added to 2L of glacial acetic acid, heated and stirred to dissolve, and filtered to remove insoluble impurities. 1.9g of antimony trichloride in glacial acetic acid was added to the solution, and the mixture was stirred for 10 minutes. The resulting solution was cooled to 18°C ​​and allowed to stand for 20 minutes until equilibrium was reached, then filtered. 108g of tin tetrachloride in glacial acetic acid was added to the resulting clear liquid, and the mixture was stirred for 10 minutes, producing a white precipitate. The resulting solution was cooled and allowed to stand until equilibrium was reached, then filtered. The precipitate was washed three times with glacial acetic acid. The precipitate was slurried with high-purity water at a solid-liquid ratio of 1:3.12, and then ammonia was added dropwise to adjust the pH to 7.24. The tin hydroxide precipitate and rubidium chloride solution were filtered to obtain the precipitate. The filtered rubidium chloride solution was evaporated to dryness and calcined in a muffle furnace at 500°C for 4 hours to obtain refined rubidium chloride. The calcined refined salt was recrystallized a second time to obtain the final rubidium chloride product.

[0052] The purity of the sample was >99.95%, and the concentration of impurity elements is shown in Table 1 below.

[0053] Table 1. Impurity element content (%)

[0054]

[0055] Example 2

[0056] 100g of crude rubidium chloride (99% purity) was added to 2L of glacial acetic acid, heated and stirred to dissolve, and filtered to remove insoluble impurities. 1g of antimony trichloride in glacial acetic acid was added to the solution, and the mixture was stirred for 10 minutes. The resulting solution was cooled to 16°C and allowed to stand for 30 minutes until equilibrium was reached, then filtered. 109g of tin tetrachloride in glacial acetic acid was added to the resulting clear liquid, and the mixture was stirred for 15 minutes, producing a white precipitate. The resulting solution was cooled and allowed to stand until equilibrium was reached, then filtered. The precipitate was washed three times with glacial acetic acid. The precipitate was slurried with high-purity water at a solid-liquid ratio of 1:2.87, and then ammonia was added dropwise to adjust the pH to 7.45. The tin hydroxide precipitate and rubidium chloride solution were filtered to obtain the purified rubidium chloride solution. The filtered rubidium chloride solution was evaporated to dryness and calcined in a muffle furnace at 500°C for 6 hours to obtain refined rubidium chloride. The calcined refined salt was recrystallized a second time to obtain the final rubidium chloride product.

[0057] The purity of the sample was >99.95%, and the concentration of impurity elements is shown in Table 2 below.

[0058] Table 2. Impurity element content (%)

[0059]

[0060] Example 3

[0061] 100g of crude rubidium chloride (99.5% purity) was added to 2L of glacial acetic acid, heated and stirred to dissolve, and filtered to remove insoluble impurities. 0.5g of antimony trichloride in glacial acetic acid was added to the solution, and the mixture was stirred for 15 minutes. The resulting solution was cooled to 16°C and allowed to stand for 30 minutes until equilibrium was reached, then filtered. 110g of tin tetrachloride in glacial acetic acid was added to the resulting clear liquid, and the mixture was stirred for 15 minutes, producing a white precipitate. The resulting solution was cooled and allowed to stand until equilibrium was reached, then filtered. The precipitate was washed three times with glacial acetic acid. The precipitate was slurried with high-purity water to a solid-liquid ratio of 1:2.94, and then ammonia was added dropwise to adjust the pH to 7.81. The tin hydroxide precipitate and rubidium chloride solution were filtered to obtain the purified rubidium chloride solution. The filtered rubidium chloride solution was evaporated to dryness and calcined in a muffle furnace at 500°C for 4 hours to obtain refined rubidium chloride. The calcined refined salt was recrystallized a second time to obtain the final rubidium chloride product.

[0062] The purity of the sample was >99.95%, and the concentration of impurity elements is shown in Table 3 below.

[0063] Table 3. Impurity element content (%)

[0064]

[0065] Comparative Example 1

[0066] Add 100g of crude rubidium chloride (98% purity) to 2L of pure water, stir to dissolve, then add concentrated hydrochloric acid to adjust the H+ concentration to 2.5mol / L. Filter to remove insoluble impurities. Add 1.9g of concentrated hydrochloric acid solution of antimony trichloride to the solution, stir for 15min, cool the resulting solution to 2℃, and let it stand for 30min until the reaction reaches equilibrium and no precipitate forms. Add 145g of tin tetrachloride pentahydrate to the resulting clear solution, stir for 15min, and a white precipitate forms. Cool the resulting solution and let it stand until the reaction reaches equilibrium, filter, and wash the precipitate three times with hydrochloric acid. The obtained precipitate was mixed with high-purity water to form a slurry with a solid-liquid ratio of 1:3.01. Then, ammonia water was added dropwise to adjust the pH value to 7.21. The tin hydroxide precipitate and rubidium chloride solution were filtered. The filtered rubidium chloride solution was evaporated to dryness and then calcined in a muffle furnace at 500°C for 4 hours to obtain refined rubidium chloride. The refined salt after calcination was recrystallized a second time to obtain the finished rubidium chloride product.

[0067] Since cesium ions did not produce a double salt precipitate and were thus removed by filtration, the purification effect of the two precipitations and recrystallizations was poor. The purity was >99.6% as determined by the analysis. The concentration of impurity elements is shown in Table 4 below.

[0068] Table 4. Impurity element content (%)

[0069]

[0070] Comparative Example 2

[0071] 100g of crude rubidium chloride (99.5% purity) was added to 2L of glacial acetic acid, heated and stirred to dissolve, and filtered to remove insoluble impurities. 0.5g of antimony trichloride in glacial acetic acid was added to the solution, and the mixture was stirred for 15 minutes. The resulting solution was cooled to 16°C and allowed to stand for 30 minutes until equilibrium was reached, then filtered. 110g of tin tetrachloride in glacial acetic acid was added to the resulting clear liquid, and the mixture was stirred for 15 minutes, producing a white precipitate. The resulting solution was cooled and allowed to stand until equilibrium was reached, then filtered. The precipitate was washed three times with glacial acetic acid. The precipitate was slurried with high-purity water to a solid-liquid ratio of 1:2.94, and then ammonia was added dropwise to adjust the pH to 7.81. The resulting tin hydroxide precipitate and rubidium chloride solution were filtered to obtain a purified solution. The filtered rubidium chloride solution was evaporated to dryness and calcined in a muffle furnace at 500°C for 4 hours to obtain refined rubidium chloride.

[0072] The purity of the sample was >99.75%. No recrystallization of the finished product was performed. The sodium and potassium content was relatively high. The concentration of impurity elements is shown in Table 5 below.

[0073] Table 5. Impurity element content (%)

[0074]

[0075] As described above, the present invention can be well implemented. The above embodiments are only the best implementations of the present invention, but the implementation of the present invention is not limited to the above embodiments. Other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are all included within the protection scope of the present invention.

Claims

1. A simple and efficient method for preparing high-purity rubidium chloride, characterized in that... The specific process steps and conditions are as follows: (1) Dissolution: Add crude rubidium salt to glacial acetic acid, heat and stir to dissolve, filter to remove insoluble impurities, and obtain a glacial acetic acid solution of crude rubidium salt; (2) Precipitation: Add glacial acetic acid solution of antimony trichloride to the glacial acetic acid solution of crude rubidium salt obtained in step (1), stir the reaction for 10-15 min, and a small amount of pale yellow precipitate and solution will be produced; (3) Static filtration: Cool the solution obtained in step (2) to 16~20℃, let it stand for 10~30 min until the reaction reaches equilibrium, filter, and produce clear liquid and precipitate. The precipitate is used to prepare high-purity cesium salt; (4) Secondary precipitation: Add glacial acetic acid solution of tin tetrachloride to the clear liquid obtained in step (3), stir the reaction for 10-15 min, and a white precipitate and solution are produced; (5) Standing, filtering and washing: Cool the solution obtained in step (4) and let it stand until the reaction reaches equilibrium. Filter and wash the precipitate with glacial acetic acid 3 to 5 times to produce precipitate and washing liquid. (6) Decomposition of double salts: Add high-purity water to the precipitate obtained in step (5) to make a slurry, then add ammonia water to adjust the pH value to 7-8, and filter to obtain tin hydroxide precipitate and rubidium chloride solution; The filtrate was sent for testing, and the ion concentration Rb in the solution was measured. + :Cs + A value greater than 2000 indicates a pass; otherwise, it indicates a fail. If the rubidium chloride solution is unqualified, return to step (1) for further impurity removal. (7) Evaporation and calcination: Evaporate the qualified rubidium chloride solution to dryness and calcine it in a muffle furnace to obtain rubidium chloride; (8) Recrystallization: The rubidium chloride after evaporation and calcination in step (7) is recrystallized multiple times to obtain high-purity rubidium chloride product.

2. The preparation method according to claim 1, characterized in that: In step (5), the washing liquid is recycled into the glacial acetic acid in step (1).

3. The preparation method according to claim 1, characterized in that: After dissolving the tin hydroxide precipitate in step (6) with excess hydrochloric acid, it is returned to step (4) for recycling.

4. The preparation method according to claim 1, characterized in that: In step (1), the purity of crude rubidium salt is ≥95%, and the concentration of rubidium ions after dissolving in glacial acetic acid is 20~100 g / L.

5. According to the preparation method of claim 1, the cooling and settling temperature in step (5) is 16~20℃, and the settling and equilibration time is 10~120 min.

6. According to the preparation method of claim 1 or 3, the solid-liquid ratio of adding high-purity water to adjust the slurry in step (6) is 1:2.5~7, and the ammonia concentration is 25%~28%.

7. According to the preparation method of claim 1, the calcination temperature in step (7) is 450~550℃ and the calcination time is 2~6 h.

8. According to the preparation method of claim 1, the recrystallization in step (8) is performed 1 to 3 times.

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