Method for removing impurities in rubidium or cesium metal

Abstract

The invention discloses a method for removing impurities in rubidium or cesium metal, which comprises the following steps: (1) in a protective atmosphere environment, heating low-purity rubidium or cesium metal to a temperature higher than a melting point and lower than a boiling point, and preserving heat to completely melt the low-purity rubidium or cesium metal; impurity elements in the low-purity rubidium or cesium metal comprise calcium and magnesium; (2) gradient cooling is conducted at the cooling rate smaller than or equal to 2 DEG C / min, the molten low-purity rubidium or cesium metal is cooled to the temperature below the melting point, solid rubidium or cesium metal is formed through condensation, and impurities are enriched on the solid rubidium or cesium metal in the form of rubidium multi-element alloy or cesium multi-element alloy; and (3) after the solidification is completed, removing the impurity enrichment region at the upper part to obtain the purified rubidium or cesium metal. According to the method, impurities in the rubidium or cesium metal are removed through heating and melting, the primary rubidium or cesium metal can be treated, the rubidium or cesium metal product with the higher purity is prepared, the method is short in technological process, low in equipment requirement and easy to operate, and the problem of low production efficiency is solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of metal purification, and particularly relates to a method for purifying alkali metals. BACKGROUND

[0002] Rb and Cs have become one of the core metal materials supporting the upgrading of China's cutting-edge national defense, aerospace and military equipment due to their irreplaceable physical and chemical properties. With the acceleration of technology iteration, the downstream field continues to put forward higher requirements for the purity index of metal Rb / Cs, which promotes the preparation technology of high-purity Rb / Cs to become the frontiers of current international material science and the focus of industrial competition.

[0003] For the purification of metal Rb / Cs, the most common way is distillation purification. Patent application document CN117305609A discloses a purification system for metal Cs. The patent utilizes the difference in vapor pressure between metal Cs and impurities, separates the condensing device from the heating evaporation device, and splits the condenser into two parts used in combination in the vertical direction, so that the Cs liquid flows back into the heating evaporation device by gravity, and is repeatedly evaporated and condensed at 300-350℃ in a vacuum environment, thereby separating Cs from other metal impurities and hydride impurities, to achieve the purification of Cs. The patent uses distillation means, which requires high temperature and vacuum degree of the equipment, and has long process flow, complex operation and low production efficiency. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the deficiencies and defects mentioned in the above background technology, and to provide a method for removing impurities in Rb or Cs metal, which has short process flow, simple operation, high production efficiency, low energy consumption and good impurity removal effect.

[0005] To solve the above technical problems, the technical solution provided by the present application is as follows: A method for removing impurities in Rb or Cs metal, comprising the following steps: (1) In a protective atmosphere environment, heat the low-purity Rb or Cs metal to a temperature above the melting point and below the boiling point, and heat it to completely melt; the impurity elements in the low-purity Rb or Cs metal include calcium and magnesium; the mass purity of the low-purity Rb or Cs metal is ≤99.70%; (2) Gradually cool down at a cooling rate of ≤2℃ / min to cool down the melted low-purity Rb or Cs metal below the melting point, and condense to form solid Rb or Cs metal, and the impurities are enriched in the upper part in the form of Rb or Cs multi-element alloy; (3) After solidification, remove the upper impurity enrichment area to obtain the purified Rb or Cs metal.

[0006] In the above method, preferably, when treating Rb metal, the heating temperature of step (1) is controlled to be 40-90℃; when treating Cs metal, the heating temperature of step (1) is controlled to be 29-90℃.

[0007] In the above method, preferably, the holding time is 0.5-10h. Within the holding time, the rubidium or cesium metal is fully melted, and the impurities in the rubidium or cesium metal float up based on the density difference.

[0008] In the above method, preferably, in step (2), the gradient cooling process comprises a first stage and a second stage, wherein the first stage is cooling from the holding temperature to the melting point of the rubidium or cesium metal +10℃ at a rate of 1-2℃ / min; the second stage is cooling from the temperature at the end of the first stage to below the melting point of the rubidium or cesium metal at a rate of 0.5-1℃ / min. The first stage can be cooled at a faster rate to improve production efficiency, and the second stage involves the separation process of the impurities, which requires accurate temperature control to ensure the separation effect of the impurities. If the cooling rate of the second stage is too fast, the impurities will not have enough time to float up and separate from the solidified rubidium or cesium metal, and will remain in the rubidium or cesium metal, affecting the removal effect of the impurities.

[0009] In the above method, preferably, when the gradient cooling is performed, a temperature control tube is inserted into the center of the rubidium or cesium metal melt, and the temperature of the temperature control tube is set to the melting point of the rubidium or cesium metal ±1℃.

[0010] More preferably, the distance from the bottom of the temperature control tube to the bottom of the rubidium or cesium metal melt is not less than 1 / 3 of the liquid level height of the rubidium or cesium metal melt, such as 1 / 3 of the liquid level height of the rubidium or cesium metal melt.

[0011] More preferably, after the gradient cooling is performed to 5-10min below the melting point of the rubidium or cesium metal, the heating of the temperature control tube is stopped.

[0012] More preferably, after the temperature control tube is inserted, ultrasonic treatment is simultaneously applied to the rubidium or cesium metal melt.

[0013] In the present application, after low-purity rubidium or cesium metal is melted, the impurities lithium, sodium and potassium contained therein will mostly float under the action of gravity and separate from the rubidium or cesium metal due to the large difference in density, which is beneficial to the separation of the part of lithium, sodium and potassium impurities. However, the density difference between calcium, magnesium and the rubidium or cesium metal is not large, and the cesium impurities contained in the rubidium metal and the rubidium impurities contained in the cesium metal also have the above-mentioned problem, which will result in poor separation effect of the part of impurity elements with small density difference from the main metal by gravity. The multi-element alloy formed by the part of impurity elements with small density difference from the main metal and the main metal is mainly enriched upward under the action of surface tension, and a small part of lithium, sodium and potassium that does not float upward will also be enriched upward by this principle to realize separation from the main metal. However, we found in the research that the multi-element alloy melt formed by the impurity elements and the main metal may be tiny droplets dispersed in the grain boundaries of the solid main metal, and the surface tension may make it "anchored" in place instead of floating freely, resulting in incomplete separation of the multi-element alloy melt and the main metal and residual in the main metal.

[0014] Based on the above problems, in the present application, a temperature control tube is inserted in the center of the rubidium or cesium metal melt during gradient cooling, so that the center of the rubidium or cesium metal melt is maintained near the melting point of the rubidium or cesium metal. This will form a temperature gradient field between the center of the rubidium or cesium metal melt and the outside (including the outer side and the bottom), and the rubidium or cesium metal at the outer side and the bottom will have a tendency to solidify, while the rubidium or cesium metal at the center will remain in a molten state, giving the multi-element alloy melt sufficient time to "overflow" from the grain boundaries of the main metal and enrich upward in the center of the rubidium or cesium metal. After the subsequent temperature control tube stops heating, due to temperature residue, the temperature near the temperature control tube will still be higher than other parts, and the solidification rate of the main metal at this part will be slower, which will also give the multi-element alloy droplets sufficient time to float upward. With ultrasonic treatment, the effect of the above-mentioned temperature control tube will be more obvious, because the strong shock wave generated by the cavitation effect of ultrasonic waves can effectively "shake" the tiny multi-element alloy droplets away from the grain boundaries and greatly promote their collision and coalescence. The action time of the temperature control tube should not be too long, otherwise the main metal with a tendency to solidify outside the container will continue to melt, and the temperature gradient field will be difficult to maintain. The contact part of the above-mentioned temperature control tube with the rubidium or cesium metal should use a substance that does not react with the rubidium or cesium metal, such as stainless steel or borosilicate glass.

[0015] In the above method, preferably, the impurity elements in the low-purity rubidium metal include lithium, sodium, potassium, cesium, calcium and magnesium; and the impurity elements in the low-purity cesium metal include lithium, sodium, potassium, rubidium, calcium and magnesium.

[0016] In the above method, preferably, the protective atmosphere is argon with a purity of ≥99.999%.

[0017] The application is to use primary rubidium or cesium metal as raw material, the metal impurities in the raw material will form multi-element alloy with rubidium or cesium metal, and the difference between the melting point and density of rubidium or cesium metal and multi-element alloy is used to heat and melt rubidium or cesium metal and then gradiently cool it, and during the cooling process, because the melting point of multi-element alloy is lower than that of rubidium or cesium metal, rubidium or cesium metal will solidify first, and the liquid multi-element alloy melt will enrich upward under the action of gravity and surface tension, and the impurity enrichment zone in the upper part is removed to obtain high-purity rubidium or cesium metal. More specific method includes the following steps: S1, first, transfer the container sealed with primary rubidium or cesium metal in vacuum to the argon-protected glove box; S2, after opening the container, heat the container containing primary rubidium or cesium metal, control the temperature between the melting point and boiling point (rubidium: 39.3-688℃, cesium: 28.44-671℃), and after melting, keep warm for 0.5-10h; S3, after S2 keeps warm, gradiently cool at a cooling rate of ≤2℃ / min, cool the melted low-purity rubidium or cesium metal to below the melting point, and condense to form solid rubidium or cesium metal, and the impurities are enriched in the upper part in the form of rubidium multi-element alloy or cesium multi-element alloy; S4, after S3 condenses, remove the impurity enrichment zone of Li, Na, K, Rb / Cs, Ca and Mg in the upper part, and high-purity rubidium / cesium metal is obtained.

[0018] The application can remove the impurities in rubidium or cesium metal by heating and melting, can process primary rubidium or cesium metal, and can prepare high-purity rubidium or cesium metal product, the process flow of the method is short, the requirement for equipment is low, the operation is simple, and the problem of low production efficiency is solved.

[0019] Compared with the prior art, the application has the following advantages: (1) The method for removing impurities in rubidium or cesium metal can effectively remove the impurities in rubidium or cesium metal, especially the removal effect of calcium and magnesium impurities can be guaranteed, and high-purity rubidium / cesium metal product can be prepared.

[0020] (2) The method for removing impurities in rubidium or cesium metal has low melting temperature and low energy consumption.

[0021] (3) The method for removing impurities in rubidium or cesium metal has simple operation, short process flow, high production efficiency, only needs three steps of heating and melting, cooling and solidification, and scraping the upper metal, simultaneously uses few equipment, has low requirement for vacuum degree, and is suitable for large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort based on these drawings.

[0023] Figure 1 is a process flow chart of the method for removing impurities in rubidium or cesium metal of the present application.

[0024] Figure 2 is a schematic diagram of the equipment for removing impurities in the method for removing impurities in rubidium or cesium metal of the present application. DETAILED DESCRIPTION

[0025] In order to facilitate the understanding of the present application, the following will make a more comprehensive and detailed description of the present application in combination with the drawings of the specification and the preferred embodiments, but the protection scope of the present application is not limited to the following specific embodiments.

[0026] Unless otherwise defined, all the professional terms used in the following have the same meaning as that generally understood by those skilled in the art. The professional terms used in the present application are only for the purpose of describing the specific embodiments and are not intended to limit the protection scope of the present application.

[0027] Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by the existing method.

[0028] As shown in Figure 1 , Figure 2 , the method for removing impurities in metal rubidium or cesium of one specific embodiment of the present application comprises the following steps: (1) First, the container containing the primary rubidium / cesium metal is transferred to the argon-protected glove box.

[0029] Preferably, the purity of the primary rubidium metal is 99.50-99.70% (mass percent), and the impurity elements include lithium, sodium, potassium, cesium, calcium, and magnesium; the purity of the cesium metal is 99.50-99.70% (mass percent), and the impurity elements include lithium, sodium, potassium, rubidium, calcium, and magnesium.

[0030] Preferably, the argon in the glove box has a purity of ≥99.999%.

[0031] The container can be sequentially cleaned with 3-5% hydrochloric acid and deionized water before use, and then rinsed with ethanol and dried.

[0032] (2) Open the container seal cover, and use the heating table to heat the container, so that the furnace temperature rises to 40-90℃, and the temperature is maintained for 0.5-10h.

[0033] (3) After the temperature holding in step (2) is completed, the molten low-purity rubidium or cesium metal is cooled to below the melting point at a cooling rate of ≤2 ℃ / min, and solid rubidium or cesium metal is condensed to form, and impurities are enriched in the upper part in the form of rubidium or cesium multi-element alloy.

[0034] (4) After the solidification is completed, the upper part of the impurity enrichment zone is removed, and high-purity rubidium or cesium metal is obtained.

[0035] Preferably, the container mentioned in steps (1) and (2) is made of stainless steel or borosilicate glass.

[0036] Example 1: A method for removing impurities from rubidium metal, comprising the following steps: (1) The container is cleaned with 3-5% hydrochloric acid and deionized water in sequence before use, and then rinsed with ethanol and dried.

[0037] (2) The vacuum-sealed vial containing 26g of primary rubidium metal is transferred to an argon (purity 99.999%) protected glove box, the vial cap is opened, the heating system is started, and the temperature is raised to 60℃, and the temperature holding time is 0.5h.

[0038] (3) After the temperature holding is completed, the cooling rate is controlled to be 1℃ / min to cool to 49℃, and then the cooling rate is 0.5℃ / min to cool to 25℃, and solid rubidium metal is condensed to form, 1.58g of the top impurity enrichment zone metal is scraped off with a spoon and sampled for analysis, and the upper and lower samples of the metal in the vial are analyzed after being heated and melted, as shown in Table 1.

[0039] Table 1: Element content table of top impurities and upper and lower rubidium metal

[0040] Example 2: A method for removing impurities from cesium metal, comprising the following steps: (1) The container is cleaned with 3-5% hydrochloric acid and deionized water in sequence before use, and then rinsed with ethanol and dried.

[0041] (2) The vacuum-sealed vial containing 37g of primary cesium metal is transferred to an argon (purity 99.999%) protected glove box, the vial cap is opened, the heating system is started, and the temperature is raised to 60℃, and the temperature holding time is 0.5h.

[0042] (3) After the end of the heat preservation, the cooling rate is controlled to be 1 °C / min to reduce the temperature to 39 °C, and then the cooling rate is controlled to be 0.5 °C / min to reduce the temperature to 25 °C, and solid cesium metal is condensed, 2.42 g of top impurity enrichment zone metal is scraped with a spoon and sampled, and the upper and bottom samples of the metal in the vial are analyzed after being heated and melted, as shown in Table 2.

[0043] Table 2: Element content table of top impurities and upper and lower metal cesium

[0044] Example 3: A method for removing impurities in rubidium metal, comprising the following steps: (1) The container is sequentially cleaned with 3-5% hydrochloric acid and deionized water before use, and then rinsed with ethanol and dried.

[0045] (2) The vacuum-sealed vial containing 26 g of primary metal rubidium is transferred to an argon (purity 99.999%) protected glove box, the vial cap is opened, the heating system is started, and the temperature is raised to 60 °C, and the heat preservation time is 0.5 h.

[0046] (3) After the end of the heat preservation, a temperature control tube is inserted at 1 / 3 of the height of the metal melt, and the temperature is set to 39 °C; the cooling rate is controlled to be 1 °C / min to reduce the temperature to 49 °C, and then the cooling rate is controlled to be 0.5 °C / min to reduce the temperature to 25 °C. When the metal melt is cooled to 39 °C, the temperature control tube works for 10 min and then stops heating. After solid rubidium metal is condensed, 1.58 g of top impurity enrichment zone metal is scraped with a spoon and sampled, and the upper and bottom samples of the metal in the vial are analyzed after being heated and melted, as shown in Table 3.

[0047] Table 3: Element content table of top impurities and upper and lower metal rubidium

[0048] Example 4: A method for removing impurities in cesium metal, comprising the following steps: (1) The container is sequentially cleaned with 3-5% hydrochloric acid and deionized water before use, and then rinsed with ethanol and dried.

[0049] (2) The vacuum-sealed vial containing 37 g of primary metal cesium is transferred to an argon (purity 99.999%) protected glove box, the vial cap is opened, the heating system is started, and the temperature is raised to 60 °C, and the heat preservation time is 0.5 h.

[0050] (3) After the end of the heat preservation, the temperature control tube is inserted at 1 / 3 of the height of the metal melt level, and the temperature is set to 29°C; the cooling rate is controlled to be 1°C / min to reduce the temperature to 39°C, and then the cooling rate is 0.5°C / min to reduce the temperature to 25°C. Among them, when the metal melt is cooled to 29°C, the temperature control tube stops heating after working for 5 min. After the solid cesium metal is formed by condensation, 2.42 g of metal in the top impurity enrichment area is scraped with a spoon and sampled for analysis, and the upper and lower samples of the metal in the westling bottle are analyzed after being heated and melted, as shown in Table 4.

[0051] Table 4: Element content table of top impurities and upper and lower cesium metal

[0052] Example 5: A method for removing impurities in rubidium metal, comprising the following steps: (1) The container is sequentially cleaned with 3-5% hydrochloric acid and deionized water before use, and then rinsed with ethanol and dried.

[0053] (2) The vacuum-sealed westling bottle containing 26g of primary rubidium metal is transferred to the glove box protected by argon (purity 99.999%), the lid of the westling bottle is opened, the heating system is started, and the temperature is raised to 60°C, and the heat preservation time is 0.5h.

[0054] (3) After the end of the heat preservation, the temperature control tube is inserted at 1 / 3 of the height of the metal melt level, and the temperature is set to 39°C, and ultrasonic treatment is applied; the cooling rate is controlled to be 1°C / min to reduce the temperature to 49°C, and then the cooling rate is 0.5°C / min to reduce the temperature to 25°C. Among them, when the metal melt is cooled to 39°C, the temperature control tube stops heating after working for 10 min. After the solid rubidium metal is formed by condensation, the ultrasonic treatment is stopped, 1.58 g of metal in the top impurity enrichment area is scraped with a spoon and sampled for analysis, and the upper and lower samples of the metal in the westling bottle are analyzed after being heated and melted, as shown in Table 5.

[0055] Table 5: Element content table of top impurities and upper and lower rubidium metal

[0056] Example 6: A method for removing impurities in cesium metal, comprising the following steps: (1) The container is sequentially cleaned with 3-5% hydrochloric acid and deionized water before use, and then rinsed with ethanol and dried.

[0057] (2) The vacuum-sealed westling bottle containing 37g of primary cesium metal is transferred to the glove box protected by argon (purity 99.999%), the lid of the westling bottle is opened, the heating system is started, and the temperature is raised to 60°C, and the heat preservation time is 0.5h.

[0058] (3) After the end of the heat preservation, the temperature control tube is inserted at 1 / 3 of the height of the metal melt, the temperature is set to 29°C, and ultrasonic treatment is applied; the cooling rate is controlled to be 1°C / min to reduce the temperature to 39°C, and then the cooling rate is 0.5°C / min to reduce the temperature to 25°C. Among them, when the metal melt is cooled to 29°C, the temperature control tube stops heating after working for 5 min. After the solid cesium metal is formed by condensation, the ultrasonic is stopped, 2.42 g of the metal in the top impurity enrichment area is scraped with a spoon and sampled for analysis, and the upper and bottom samples are analyzed after the metal in the west bottle is heated and melted. See Table 6.

[0059] Table 6: Element content table of top impurities and upper and lower metal cesium

[0060] Comparative Example 1: A method for removing impurities in rubidium metal, comprising the following steps: (1) The container is sequentially cleaned with 3-5% hydrochloric acid and deionized water before use, and then rinsed with ethanol and dried.

[0061] (2) The vacuum-sealed west bottle containing 26g of primary metal rubidium is transferred to the glove box protected by argon (purity 99.999%), the west bottle cap is opened, the heating system is started, and the temperature is raised to 60°C, and the heat preservation time is 0.5h.

[0062] (3) After the end of the heat preservation, the cooling rate is controlled to be 5°C / min to reduce the temperature to 49°C, and then the cooling rate is 0.5°C / min to reduce the temperature to 25°C. After the solid rubidium metal is formed by condensation, 1.58 g of the metal in the top impurity enrichment area is scraped with a spoon and sampled for analysis, and the upper and bottom samples are analyzed after the metal in the west bottle is heated and melted. See Table 7.

[0063] Table 7: Element content table of top impurities and upper and lower metal rubidium

[0064] Comparative Example 2: A method for removing impurities in cesium metal, comprising the following steps: (1) The container is sequentially cleaned with 3-5% hydrochloric acid and deionized water before use, and then rinsed with ethanol and dried.

[0065] (2) The vacuum-sealed west bottle containing 37g of primary metal cesium is transferred to the glove box protected by argon (purity 99.999%), the west bottle cap is opened, the heating system is started, and the temperature is raised to 60°C, and the heat preservation time is 0.5h.

[0066] (3) After the end of the holding, the cooling rate is controlled to be 5°C / min to decrease to 40°C, and then the cooling rate is 0.5°C / min to decrease to 25°C. After the condensation forms solid cesium metal, 2.42g of the top impurity-rich region metal is scraped with a spoon and sampled for analysis, and the upper and bottom samples are analyzed after the metal in the Schlenk flask is heated and melted, as shown in Table 8.

[0067] Table 8: Element content table of top impurities and upper and lower cesium metal

Claims

1. A method for removing impurities from rubidium or cesium metal, characterized by, The method comprises the following steps: (1) heating low-purity rubidium or cesium metal to a temperature above the melting point and below the boiling point in a protective atmosphere, and keeping the temperature to make the low-purity rubidium or cesium metal completely melt; the impurity elements in the low-purity rubidium or cesium metal include calcium and magnesium; the mass purity of the low-purity rubidium or cesium metal is ≤99.70%; (2) cooling the melted low-purity rubidium or cesium metal to below the melting point at a cooling rate gradient of ≤2 ℃ / min, and condensing to form solid rubidium or cesium metal, and the impurities are enriched in the upper part in the form of rubidium or cesium multi-element alloy; (3) removing the upper part of the impurity enrichment area after solidification to obtain purified rubidium or cesium metal.

2. The method of claim 1, wherein, When treating rubidium metal, the heating temperature in step (1) is controlled to be 40-90 ℃; when treating cesium metal, the heating temperature in step (1) is controlled to be 29-90 ℃.

3. The method of claim 1, wherein, The holding time is 0.5-10 h.

4. The method of claim 1, wherein, In step (2), the gradient cooling process comprises a first stage and a second stage, wherein the first stage is to reduce the temperature from the holding temperature to the melting point of rubidium or cesium metal +10 ℃ at a rate of 1-2 ℃ / min; and the second stage is to reduce the temperature at the end of the first stage to below the melting point of rubidium or cesium metal at a rate of 0.5-1 ℃ / min.

5. The method of claim 1, wherein, When gradient cooling, a temperature control tube is inserted into the center of the rubidium or cesium metal melt, and the setting temperature of the temperature control tube is the melting point of rubidium or cesium metal ±1 ℃.

6. The method of claim 5, wherein, The distance from the bottom of the temperature control tube to the bottom of the rubidium or cesium metal melt is not less than 1 / 3 of the liquid level height of the rubidium or cesium metal melt.

7. The method of claim 5, wherein, When the gradient cooling is stopped 5-10 min after the temperature is reduced to below the melting point of rubidium or cesium metal, the heating of the temperature control tube is stopped.

8. The method of claim 5, wherein, After the temperature control tube is inserted, ultrasonic treatment is applied to the rubidium or cesium metal melt at the same time.

9. The method of claim 1, wherein, The impurity elements in the low-purity rubidium metal include lithium, sodium, potassium, cesium, calcium and magnesium; the impurity elements in the low-purity cesium metal include lithium, sodium, potassium, rubidium, calcium and magnesium.

10. The method of claim 1, wherein, The protective atmosphere is argon with a purity of ≥99.999%.

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