A method for removing impurities from rubidium or cesium metal

Abstract

The application discloses a method for removing impurities in rubidium or cesium metal, which 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; (2) cooling the melted low-purity rubidium or cesium metal to below the melting point at a cooling rate gradient of <=2 DEG C / 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. The application removes the impurities in the rubidium or cesium metal by heating and melting, can process the primary rubidium or cesium metal, and prepares rubidium or cesium metal products with higher purity. The method has a short technological process, low requirement on equipment, and simple operation, and solves the problem of low production efficiency.

Description

Technical Field

[0001] This invention belongs to the field of metal purification, and particularly relates to a method for purifying alkali metals. Background Technology

[0002] Due to their irreplaceable physicochemical properties, rubidium and cesium have become core metallic materials supporting the upgrading of my country's advanced national defense, aerospace, and military equipment. With the accelerated pace of technological iteration, downstream sectors are continuously raising the purity requirements for metallic rubidium / cesium, making high-purity rubidium / cesium preparation technology a cutting-edge topic in international materials science and a focus of industrial competition.

[0003] The most common method for purifying metallic rubidium / cesium is distillation. For example, patent application CN117305609A discloses a cesium purification system. This patent utilizes the difference in vapor pressure between metallic cesium and impurities, separating the condenser from the heating and evaporation device. The condenser is split into two vertically aligned units for combined use, allowing the cesium liquid to flow back into the heating and evaporation device under gravity. Repeated evaporation and condensation at 300-350℃ under vacuum separate cesium from other metallic impurities and hydrides, thus achieving cesium purification. However, this patent uses distillation, which requires high temperature and vacuum levels from the equipment, and the process is lengthy, complex, and inefficient. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a method for removing impurities from rubidium or cesium metals that has a short process flow, simple operation, high production efficiency, low energy consumption, and good impurity removal effect.

[0005] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0006] A method for removing impurities from rubidium or cesium metals, comprising the following steps:

[0007] (1) In a protective atmosphere, low-purity rubidium or cesium metal is heated to a temperature above its melting point but below its boiling point and held at that temperature until it is completely melted; 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%;

[0008] (2) The molten low-purity rubidium or cesium metal is cooled to below the melting point by a cooling rate of ≤2℃ / min, and solidified to form solid rubidium or cesium metal. Impurities are enriched on the surface in the form of rubidium multi-element alloys or cesium multi-element alloys.

[0009] (3) After solidification, remove the impurity enrichment zone above to obtain purified rubidium or cesium metal.

[0010] In the above method, preferably, when processing rubidium metal, the heating temperature in step (1) is controlled at 40-90℃; when processing cesium metal, the heating temperature in step (1) is controlled at 29-90℃.

[0011] In the above method, preferably, the holding time is 0.5-10 hours. Within this holding time, it is beneficial for the complete melting of rubidium or cesium metal, and also for impurities to float to the surface based on density differences.

[0012] In the above method, preferably, in step (2), the gradient cooling process includes a first stage and a second stage. The first stage involves cooling from the holding temperature at a rate of 1-2℃ / min to the melting point of rubidium or cesium metal +10℃; the second stage involves cooling the temperature at the end of the first stage at a rate of 0.5-1℃ / min to below the melting point of rubidium or cesium metal. The first stage can cool at a relatively fast rate to improve production efficiency. The second stage involves the separation of impurities, which requires precise temperature control to ensure the separation effect of impurities. If the cooling rate in the second stage is too fast, impurities will not have enough time to float and separate from the solidified rubidium or cesium metal, and will remain in the rubidium or cesium metal, affecting the removal effect of impurities.

[0013] In the above method, preferably, during gradient cooling, 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℃.

[0014] More preferably, the distance between the bottom of the temperature control tube and the bottom of the rubidium or cesium molten metal is not less than 1 / 3 of the height of the rubidium or cesium molten metal liquid level, such as 1 / 3 of the height of the rubidium or cesium molten metal liquid level.

[0015] More preferably, the heating of the temperature control tube is stopped 5-10 minutes after the gradient cooling is reduced to below the melting point of rubidium or cesium metal.

[0016] More preferably, after inserting the temperature control tube, ultrasonic treatment is simultaneously applied to the rubidium or cesium metal melt.

[0017] In this invention, after low-purity rubidium or cesium metal is melted, the impurities lithium, sodium, and potassium contained therein, due to their significant density difference from rubidium or cesium metal, will mostly float to the surface under gravity, separating from the rubidium or cesium metal, which is beneficial for the separation of these lithium, sodium, and potassium impurities. However, the density of calcium and magnesium is not significantly different from that of rubidium or cesium metal, and the cesium impurities contained in rubidium metal and the rubidium impurities contained in cesium metal also suffer from the aforementioned problem. This results in poor separation of these impurity elements with low density from the main metal by gravity. The multi-element alloy formed by these impurity elements with low density from the main metal mainly accumulates upwards under the action of surface tension, forming an impurity enrichment zone at the top. A small portion of the lithium, sodium, and potassium that do not float to the surface will also accumulate upwards through this principle, achieving separation from the main metal. However, our research found that since the multi-element alloy melt formed by impurity elements and the host metal may be tiny droplets dispersed in the grain boundaries of the solid host metal, the surface tension may "anchor" it in place instead of allowing it to float freely, resulting in incomplete separation of the multi-element alloy melt from the host metal, leaving residues in the host metal.

[0018] To address the aforementioned issues, this invention employs a temperature control tube inserted at the center of the rubidium or cesium metal melt during gradient cooling. This keeps the center of the rubidium or cesium metal melt near its melting point, creating a temperature gradient field between the center and the outside (including the outer and bottom sides). The rubidium or cesium metal at the outer and bottom sides tends to solidify, while the rubidium or cesium metal at the center remains molten. This provides ample time for the multi-element alloy melt to "overflow" from the grain boundaries of the main metal and accumulate above the center of the rubidium or cesium metal. Even after the temperature control tube stops heating, the temperature near the tube remains higher than other areas due to residual heat, resulting in a slower solidification rate of the main metal in that area. This also allows sufficient time for the multi-element alloy droplets to rise. Combined with ultrasonic treatment, the effect of the aforementioned temperature control tube will be even more pronounced. This is because the powerful shock waves generated by the cavitation effect of ultrasound can effectively dislodge tiny multi-element alloy droplets from grain boundaries and greatly promote their collision and coalescence. The temperature control tube should not be used for too long, otherwise the main metal on the outside of the container, which has a tendency to solidify, will continue to melt, making it difficult to maintain the temperature gradient field. The contact points between the temperature control tube and the rubidium or cesium metal should be made of materials that do not react with rubidium or cesium metal, such as stainless steel or borosilicate glass.

[0019] In the above method, preferably, the impurity elements in low-purity rubidium metal include lithium, sodium, potassium, cesium, calcium, and magnesium; the impurity elements in low-purity cesium metal include lithium, sodium, potassium, rubidium, calcium, and magnesium.

[0020] In the above method, preferably, the protective atmosphere is argon gas with a purity of ≥99.999%.

[0021] This invention uses primary rubidium or cesium metal as raw material. Metal impurities in the raw material will form a multi-element alloy with the rubidium or cesium metal. Taking advantage of the difference in melting point and density between the rubidium or cesium metal and the multi-element alloy, the rubidium or cesium metal is heated and melted, and then cooled in a gradient. During the cooling process, since the melting point of the multi-element alloy is lower than that of the rubidium or cesium metal, the rubidium or cesium metal will solidify first. The liquid multi-element alloy melt accumulates upward under the action of gravity and surface tension, forming an impurity enrichment zone at the top. By removing the impurity enrichment zone at the top, high-purity rubidium or cesium metal is obtained. More specifically, the method includes the following steps: S1, first, transfer the vacuum-sealed container containing primary rubidium or cesium metal to an argon-protected glove box; S2, after opening the container, heat the container containing primary rubidium or cesium metal, controlling the temperature between the melting point and boiling point (rubidium: 39.3-688℃, cesium: 28.44-671℃), and hold it at that temperature for 0.5-10 hours after melting; S3, after the holding time in S2 is completed, cool the molten low-purity rubidium or cesium metal at a gradient cooling rate of ≤2℃ / min to cool it below the melting point, condensing it to form solid rubidium or cesium metal, with impurities enriched in the upper part in the form of rubidium multi-element alloys or cesium multi-element alloys; S4, after the condensation in S3 is completed, remove the impurity enrichment zone of Li, Na, K, Rb / Cs, Ca, and Mg in the upper part to obtain higher purity rubidium / cesium metal.

[0022] This invention removes impurities from rubidium or cesium metals by heating and melting, thereby processing primary rubidium or cesium metals to obtain rubidium or cesium metal products with higher purity. The method of this invention has a short process flow, low equipment requirements, and simple operation, solving the problem of low production efficiency.

[0023] Compared with the prior art, the advantages of the present invention are as follows:

[0024] (1) The method for removing impurities from rubidium or cesium metals of the present invention can effectively remove impurities from rubidium or cesium metals, especially calcium and magnesium impurities, and can also ensure the removal effect, and can produce higher purity rubidium / cesium metal products.

[0025] (2) The method for removing impurities from rubidium or cesium metal according to the present invention has a low melting temperature and low energy consumption.

[0026] (3) The method for removing impurities from rubidium or cesium metal of the present invention is simple to operate, has a short process flow, and high production efficiency. It only requires three steps: heating and melting, cooling and solidifying, and scraping off the upper metal. At the same time, it uses less equipment and has low requirements for vacuum degree, making it suitable for large-scale production. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a process flow diagram of the method for removing impurities from rubidium or cesium metal according to the present invention.

[0029] Figure 2 This is a schematic diagram of the equipment used for impurity removal in the method for removing impurities from rubidium or cesium metals according to the present invention. Detailed Implementation

[0030] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0031] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0032] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0033] like Figure 1 , Figure 2 As shown, a specific embodiment of the present invention describes a method for removing impurities from metallic rubidium or cesium, comprising the following steps:

[0034] (1) First, transfer the vacuum-sealed container containing primary rubidium / cesium metal to an argon-protected glove box.

[0035] Preferably, the purity of the primary rubidium metal is 99.50-99.70% (mass percentage), and the impurity elements include lithium, sodium, potassium, cesium, calcium, and magnesium; the purity of the cesium metal is 99.50-99.70% (mass percentage), and the impurity elements include lithium, sodium, potassium, rubidium, calcium, and magnesium.

[0036] Preferably, the argon gas in the glove box has a purity of ≥99.999%.

[0037] Before use, the container can be cleaned with 3-5% hydrochloric acid and deionized water in sequence, and then rinsed with ethanol and dried.

[0038] (2) Open the container seal and heat the container with a heating table to raise the furnace temperature to 40-90℃ and keep it warm for 0.5-10h.

[0039] (3) After the heat preservation in step (2) is completed, the molten low-purity rubidium or cesium metal is cooled down to below the melting point at a cooling rate of ≤2℃ / min, and solidified to form solid rubidium or cesium metal. Impurities are enriched on the surface in the form of rubidium multi-element alloys or cesium multi-element alloys.

[0040] (4) After solidification, remove the impurity enrichment zone above to obtain high-purity rubidium or cesium metal.

[0041] Preferably, the containers mentioned in steps (1) and (2) are made of stainless steel or borosilicate glass.

[0042] Example 1:

[0043] A method for removing impurities from rubidium metal includes the following steps:

[0044] (1) Before use, the container should be cleaned with 3-5% hydrochloric acid and deionized water, rinsed with ethanol and then dried.

[0045] (2) Transfer the vacuum-sealed vial containing 26g of primary rubidium metal to a glove box protected by argon gas (purity of 99.999%), open the vial cap, start the heating system, raise the temperature to 60°C, and keep it warm for 0.5h.

[0046] (3) After the heat preservation is completed, the cooling rate is controlled at 1℃ / min to cool down to 49℃, and then the cooling rate is controlled at 0.5℃ / min to cool down to 25℃. Solid rubidium metal is condensed and formed. 1.58g of metal from the top impurity enrichment area is scraped with a spoon and sampled for analysis. The metal in the vial is heated and melted, and the upper and bottom samples are taken for analysis. See Table 1.

[0047] Table 1: Elemental content of top impurities and upper and lower rubidium metals

[0048]

[0049] Example 2:

[0050] A method for removing impurities from cesium metal includes the following steps:

[0051] (1) Before use, the container should be cleaned with 3-5% hydrochloric acid and deionized water, rinsed with ethanol and then dried.

[0052] (2) Transfer the vacuum-sealed vial containing 37g of primary metal cesium to a glove box protected by argon (purity 99.999%), open the vial cap, start the heating system, raise the temperature to 60°C, and keep it warm for 0.5h.

[0053] (3) After the heat preservation is completed, the cooling rate is controlled at 1℃ / min to cool down to 39℃, and then the cooling rate is controlled at 0.5℃ / min to cool down to 25℃. Solid cesium metal is condensed and formed. 2.42g of metal from the top impurity enrichment area is scraped with a spoon and sampled for analysis. The metal in the vial is heated and melted, and the upper and bottom samples are taken for analysis. See Table 2.

[0054] Table 2: Elemental content of top impurities and upper and lower cesium metals

[0055]

[0056] Example 3:

[0057] A method for removing impurities from rubidium metal includes the following steps:

[0058] (1) Before use, the container should be cleaned with 3-5% hydrochloric acid and deionized water, rinsed with ethanol and then dried.

[0059] (2) Transfer the vacuum-sealed vial containing 26g of primary rubidium metal to a glove box protected by argon gas (purity of 99.999%), open the vial cap, start the heating system, raise the temperature to 60°C, and keep it warm for 0.5h.

[0060] (3) After the heat preservation is completed, insert the temperature control tube at 1 / 3 of the height of the molten metal and set the temperature to 39°C; control the cooling rate to 1°C / min to lower the temperature to 49°C, and then cool it down to 25°C at a cooling rate of 0.5°C / min. When the molten metal cools down to 39°C, the temperature control tube works for 10 minutes and then stops heating. After solid rubidium metal is formed by condensation, scrape 1.58g of the metal from the top impurity enrichment area with a spoon and take a sample for analysis. After the metal in the vial is heated and melted, take samples from the top and bottom for analysis, as shown in Table 3.

[0061] Table 3: Elemental content of top impurities and upper and lower rubidium metals

[0062]

[0063] Example 4:

[0064] A method for removing impurities from cesium metal includes the following steps:

[0065] (1) Before use, the container should be cleaned with 3-5% hydrochloric acid and deionized water, rinsed with ethanol and then dried.

[0066] (2) Transfer the vacuum-sealed vial containing 37g of primary metal cesium to a glove box protected by argon (purity 99.999%), open the vial cap, start the heating system, raise the temperature to 60°C, and keep it warm for 0.5h.

[0067] (3) After the heat preservation is completed, insert the temperature control tube at 1 / 3 of the height of the molten metal, and set the temperature to 29℃; control the cooling rate to 1℃ / min to lower the temperature to 39℃, and then lower the temperature to 25℃ at a cooling rate of 0.5℃ / min. Among them, when the molten metal is cooled to 29℃, the temperature control tube works for 5 minutes and then the heating is stopped. After solid cesium metal is formed by condensation, scrape 2.42g of metal from the top impurity enrichment area with a spoon and take a sample for analysis. After the metal in the vial is heated and melted, take the upper and bottom samples for analysis, as shown in Table 4.

[0068] Table 4: Elemental content of top impurities and upper and lower cesium metals

[0069]

[0070] Example 5:

[0071] A method for removing impurities from rubidium metal includes the following steps:

[0072] (1) Before use, the container should be cleaned with 3-5% hydrochloric acid and deionized water, rinsed with ethanol and then dried.

[0073] (2) Transfer the vacuum-sealed vial containing 26g of primary rubidium metal to a glove box protected by argon gas (purity of 99.999%), open the vial cap, start the heating system, raise the temperature to 60°C, and keep it warm for 0.5h.

[0074] (3) After the heat preservation is completed, insert the temperature control tube at 1 / 3 of the height of the molten metal, set the temperature to 39℃, and apply ultrasonic treatment; control the cooling rate to reduce the temperature to 49℃ at 1℃ / min, and then reduce the temperature to 25℃ at a cooling rate of 0.5℃ / min. When the molten metal is cooled to 39℃, stop heating after the temperature control tube has been working for 10 minutes. After solid rubidium metal is formed by condensation, stop ultrasonic treatment, scrape 1.58g of metal from the top impurity enrichment area with a spoon and take a sample for analysis, and heat and melt the metal in the vial and take samples from the top and bottom for analysis, as shown in Table 5.

[0075] Table 5: Elemental content of top impurities and upper and lower rubidium metals

[0076]

[0077] Example 6:

[0078] A method for removing impurities from cesium metal includes the following steps:

[0079] (1) Before use, the container should be cleaned with 3-5% hydrochloric acid and deionized water, rinsed with ethanol and then dried.

[0080] (2) Transfer the vacuum-sealed vial containing 37g of primary metal cesium to a glove box protected by argon (purity 99.999%), open the vial cap, start the heating system, raise the temperature to 60°C, and keep it warm for 0.5h.

[0081] (3) After the heat preservation is completed, insert the temperature control tube at 1 / 3 of the height of the molten metal, set the temperature to 29℃, and apply ultrasonic treatment; control the cooling rate to reduce the temperature to 39℃ at 1℃ / min, and then reduce the temperature to 25℃ at a cooling rate of 0.5℃ / min. Among them, when the molten metal is cooled to 29℃, the temperature control tube works for 5 minutes and then the heating is stopped. After solid cesium metal is formed by condensation, stop the ultrasonic treatment, scrape 2.42g of metal from the top impurity enrichment area with a spoon and take a sample for analysis. After the metal in the vial is heated and melted, take the upper and bottom samples for analysis, as shown in Table 6.

[0082] Table 6: Elemental content of top impurities and upper and lower cesium metals

[0083]

[0084] Comparative Example 1:

[0085] A method for removing impurities from rubidium metal includes the following steps:

[0086] (1) Before use, the container should be cleaned with 3-5% hydrochloric acid and deionized water, rinsed with ethanol and then dried.

[0087] (2) Transfer the vacuum-sealed vial containing 26g of primary rubidium metal to a glove box protected by argon gas (purity of 99.999%), open the vial cap, start the heating system, raise the temperature to 60°C, and keep it warm for 0.5h.

[0088] (3) After the heat preservation is completed, the temperature is reduced to 49°C at a cooling rate of 5°C / min, and then reduced to 25°C at a cooling rate of 0.5°C / min. After solid rubidium metal is formed by condensation, 1.58g of metal from the top impurity enrichment area is scraped with a spoon and sampled for analysis. The metal in the vial is heated and melted, and samples from the top and bottom are taken for analysis, as shown in Table 7.

[0089] Table 7: Elemental content of top impurities and upper and lower rubidium metals

[0090]

[0091] Comparative Example 2:

[0092] A method for removing impurities from cesium metal includes the following steps:

[0093] (1) Before use, the container should be cleaned with 3-5% hydrochloric acid and deionized water, rinsed with ethanol and then dried.

[0094] (2) Transfer the vacuum-sealed vial containing 37g of primary metal cesium to a glove box protected by argon (purity 99.999%), open the vial cap, start the heating system, raise the temperature to 60°C, and keep it warm for 0.5h.

[0095] (3) After the heat preservation is completed, the temperature is reduced to 40°C at a cooling rate of 5°C / min, and then reduced to 25°C at a cooling rate of 0.5°C / min. After solid cesium metal is formed by condensation, 2.42g of metal from the top impurity enrichment area is scraped with a spoon and sampled for analysis. The metal in the vial is heated and melted, and samples from the top and bottom are taken for analysis, as shown in Table 8.

[0096] Table 8: Elemental content of top impurities and upper and lower cesium metals

[0097]

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. 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 from the end temperature of the first stage to below the melting point of rubidium or cesium metal at a rate of 0.5-1 ℃ / min.

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, 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 ℃.

5. The method of claim 4, 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.

6. The method of claim 4, wherein, When the gradient cooling is stopped 5-10 min after the gradient cooling is stopped, the heating of the temperature control tube is stopped.

7. The method of claim 4, wherein, After the temperature control tube is inserted, ultrasonic treatment is applied to the rubidium or cesium metal melt at the same time.

8. 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.

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

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