A method for preparing cesium iodide from rubidium and cesium enriched material

Abstract

The invention belongs to the technical field of extraction, and specifically relates to a method for preparing cesium iodide from rubidium-cesium enriched material. The method comprises the following steps: S1: high-temperature roasting; S2: dissolving the roasting residue in deionized water and filtering to obtain solution A and filter residue; S3: adding acid to solution A to adjust the pH of solution A to acidic, and at the same time, adding iodide ions to obtain yellow solution B; S4: weighing bismuth oxide and dissolving it in hydrochloric acid to obtain solution C; S5: adding the yellow solution B to solution C to obtain a red solid precipitate D containing cesium and a rubidium-containing solution E; S6: solid-liquid separation; and S7: thermal decomposition treatment. The invention uses bismuth ions and iodide ions as precipitants, adds bismuth ions and iodide ions to a solution containing rubidium-cesium potassium, and reacts to generate precipitated cesium iodide bismuthate, thereby achieving almost selective recovery of cesium in the rubidium-cesium potassium solution. In addition, cesium iodide with a purity greater than 99% can be directly obtained by thermal decomposition of the cesium iodide bismuthate, and the bismuth iodide can be recovered to further prepare the precipitant.

Description

Technical Field

[0001] The invention belongs to the field of extraction technology, in particular to a method for preparing cesium iodide from rubidium and cesium enriched materials. Background Art

[0002] Cesium is an expensive, rare alkaline metal. Due to its unique physical and chemical properties, it is widely used in atomic clocks, biomedicine, electronic devices, new energy, and aerospace. Rubidium and cesium are widely distributed in the Earth's crust, primarily found in mineral resources such as cesium garnet, lepidolite, and salt lake brine. They rarely form as independent minerals. Ceium garnet is the basic raw material for the production of various cesium compounds and cesium metal, and is also the primary mineral used in industrial cesium extraction. In industry, rubidium and cesium are primarily found in post-lithium extraction solutions or wastewater. Salt lake brine contains significant reserves of rubidium and cesium, but the concentration is relatively low, with rubidium at only 10-20 mg / L and cesium at a much lower concentration.

[0003] Whether in high-salinity wastewater or brine, cesium often coexists with large amounts of rubidium, potassium, and sodium. Rubidium and cesium have extremely similar properties and can even be used interchangeably in some applications, making the selective separation of rubidium and cesium very difficult. Methods for extracting rubidium and cesium from solutions include precipitation, adsorption, and solvent separation. Adsorption primarily involves ion exchange between rubidium and cesium ions and adsorbents, or adsorption of rubidium and cesium ions onto porous surfaces. Adsorption offers high selectivity and a simple process, but adsorbents often have relatively low adsorption capacities, making it more suitable for separating low concentrations of rubidium and cesium. Solution extraction is the most widely studied and fastest-growing technology for separating rubidium and cesium. Solvent extraction allows for high throughput and continuous production. However, the extractant can be toxic, the process is lengthy, and wastewater discharge is high. Precipitation, a traditional separation technique, offers advantages such as simplicity, ease of operation, and suitability for large-scale production. However, it also suffers from the formation of secondary waste and low product purity. Commonly used precipitants for rubidium and cesium include vanadium salts, polyhalides, heteropoly acids and ferrocyanide.

[0004] Chinese Patent 202010712906.1 proposes a method for extracting cesium and rubidium from lepidolite. A mixed alum of rubidium and cesium is calcined at high temperature to produce a sulfate solution enriched with rubidium and cesium. Cesium sulfate and rubidium sulfate with a purity exceeding 98% are then extracted through multi-stage extraction. The total recovery rate of cesium and rubidium is over 80%. Chinese Patent 202110474179.4 proposes a method for extracting rubidium and cesium from complex underground brine, using tin tetrachloride precipitation to enrich rubidium and cesium. Chinese Patent 201710615317. X proposed a method for separating and extracting rubidium and cesium from coal, using iodine chloride to generate a precipitate containing rubidium and cesium, and then combining it with t-BAMBP extraction to obtain high-purity rubidium chloride and cesium chloride; China 201910583379 proposed a precipitation flotation separation system for rubidium and cesium in aqueous solution and its application, using phosphotungstate as a precipitant in the precipitation flotation system for the separation and purification of rubidium and cesium resources; U.S. Patent 4432893 proposed a precipitation-adsorption process for the decontamination of nuclear waste supernates, using sodium tetraphenylborate to precipitate cesium and potassium in high-level nuclear waste to purify cesium.

[0005] In summary, most precipitants can only extract rubidium and cesium indiscriminately, and the subsequent separation of rubidium and cesium can only rely on extraction and other processes.

[0006] Therefore, the present invention provides a method for preparing cesium iodide from rubidium and cesium enriched material. Summary of the Invention

[0007] In order to make up for the deficiencies of the prior art and solve the technical problems existing in the background technology, the present invention proposes a method for preparing cesium iodide from rubidium and cesium enriched materials.

[0008] The present invention is achieved through the following technical solution: a method for preparing cesium iodide from rubidium and cesium enriched material, the method comprising the following steps:

[0009] S1: Weigh an appropriate amount of rubidium-cesium enriched material and put it into a high-temperature calcining furnace for high-temperature calcination to obtain calcined slag;

[0010] S2: adding the calcined slag in S1 into a container filled with deionized water, dissolving the calcined slag in the deionized water and allowing the calcined slag to stand. After the calcined slag is completely dissolved, filtering the solution to obtain solution A and filter residue;

[0011] S3: Add an acidic solution to solution A in S2 to adjust the pH of solution A to acidic. At the same time, add an amount of iodide ions calculated according to the cesium concentration and continue stirring to obtain a yellow solution B.

[0012] S4: Weigh an appropriate amount of bismuth oxide, and then dissolve it in a container containing an appropriate amount of hydrochloric acid solution to obtain solution C;

[0013] S5: adding the solution C in S4 to the yellow solution B in S3 while stirring continuously to obtain a red solid precipitate D containing cesium and a rubidium-containing solution E;

[0014] S6: performing solid-liquid separation on the red solid precipitate D containing cesium and the filtrate E containing rubidium in S5 to obtain a solid precipitate D containing cesium and a solution containing rubidium E;

[0015] S7: placing the red solid precipitate D of cesium in S6 into a thermal decomposition device for thermal decomposition treatment to obtain a volatile product, bismuth iodide, and a residual product, cesium iodide.

[0016] The rubidium-cesium enriched material of the present invention is mainly a mixture of rubidium, cesium, potassium, sodium, magnesium, and iron, and also includes non-metallic elements such as carbon and nitrogen. The contents of the main elements are shown in the following table:

[0017]

[0018] Preferably, the rubidium-cesium enriched material in S1 is calcined in an atmosphere at a temperature of 500-600° C. Due to the presence of carbon, the rubidium-cesium potassium mainly exists in the calcined slag in the form of carbonate.

[0019] Preferably, the roasted slag in S2 is mixed with deionized water in a mass ratio of 1:4-5; the filter residue includes magnetic material and non-magnetic material; the magnetic material is Fe2O3, Fe3O4, MgFeO4; and the non-magnetic material is MgO.

[0020] Preferably, the pH value of solution A in S3 is adjusted to 1-3; the amount of iodide ions added is calculated based on 100%-150% of the required amount of Cs3Bi2I9 to be formed.

[0021] Preferably, the amount of bismuth oxide added to S4 is calculated based on 100%-150% of the amount required to form Cs3Bi2I9.

[0022] Preferably, the solution C in S5 is added dropwise to the yellow solution B; the precipitation reaction equation is: 3Cs + +2Bi 3+ +9I - →Cs3Bi2I9.

[0023] Preferably, the solid-liquid separation in S6 is carried out by sedimentation filtration, and the solution is washed five times with an aqueous solution having a pH of 1; the main purpose of the water washing is to remove rubidium and potassium entrained in the cesium iodide bismuthate, and the use of water having a pH of 1 is to prevent the decomposition of the cesium iodide bismuthate.

[0024] Preferably, the red solid precipitate D of cesium in S7 is thermally decomposed in a vacuum environment or a protective atmosphere of nitrogen or argon at a temperature of 550-650°C; the decomposition equation is: Cs3Bi2I9→3CsI+2BiI3, the boiling point of cesium iodide is 1280°C, and the boiling point of bismuth iodide is 500°C. After thermal decomposition, the product cesium iodide is obtained, and the bismuth iodide is sublimed and collected to prepare a precipitant for recycling.

[0025] Preferably, the amount of iodide ions selected includes sodium iodide and potassium iodide.

[0026] The beneficial effects of the present invention are:

[0027] The invention uses bismuth ions and iodide ions as precipitants, adds bismuth ions and iodide ions to a solution containing rubidium and cesium potassium, and controls reaction conditions and the amount of the precipitant, so that the bismuth ions, iodide ions and cesium react to generate precipitated cesium iodide bismuthate, thereby separating cesium from rubidium potassium. The rubidium content in the cesium iodide bismuthate is less than 0.2%, and the potassium and sodium contents are less than 0.1%, thereby almost achieving selective recovery of cesium from the rubidium and cesium potassium solution. In addition, the cesium iodide bismuthate can be directly decomposed into cesium iodide with a purity greater than 99%, and the bismuth iodide can be recovered to further prepare the precipitant. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present invention only and are not intended to limit the scope of the invention. The experimental methods in the following examples, for which specific conditions are not specified, are generally performed under conventional conditions or as recommended by the manufacturer.

[0030] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. The reagents or raw materials used in the present invention can be purchased through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in a conventional manner in the art or in accordance with the product instructions. In addition, any method and material similar to or equivalent to the described content can be applied to the method of the present invention. The present invention is further described with reference to the accompanying drawings and specific embodiments. The preferred embodiments and materials described in the present invention are for demonstration purposes only.

[0031] like Figure 1 As shown:

[0032] Example 1

[0033] 20 g of rubidium-cesium enriched material was calcined at 520°C for 2 h in an atmosphere to obtain 17.6 g of slag with a weight loss rate of approximately 12%.

[0034] The roasted slag is leached with deionized water at a solid-liquid ratio of 1:3-5, and filtered with filter paper to obtain a rubidium-cesium enriched solution and leached slag. The leached slag accounts for about one-third of the roasted slag. The magnetic substances are mainly ferric oxide, ferroferric oxide and magnesium ferrite, and the non-magnetic substance is magnesium oxide.

[0035] The contents of rubidium and cesium in the rubidium and cesium enriched solutions were 17.3 g / L and 14.5 g / L, respectively, and the contents of potassium and sodium were 5 g / L and 2 g / L;

[0036] Add hydrochloric acid to 100 mL of rubidium-cesium enriched solution until the pH is 1, then add 4.9 g of sodium iodide and continue stirring;

[0037] Take 1.69g of bismuth oxide and add appropriate amount of hydrochloric acid until the solid is completely dissolved. Add the bismuth ion solution dropwise to the rubidium-cesium enriched solution. After the addition is complete, continue stirring for 10 minutes, then filter with fast filter paper, and wash five times with weak acid solution with pH 1;

[0038] The solid precipitate was dried in an oven at 80 °C for 4 h to obtain 5.072 g of a red solid;

[0039] 5 g of the solid precipitate was placed in a quartz crucible and placed in a vacuum environment at 550°C for 1 h to decompose. 1.66 g of solid was obtained in the quartz crucible, which was analyzed and found to be cesium iodide with a purity of 99%; 3.3 g of bismuth iodide was obtained in the vacuum tube wall.

[0040] Example 2

[0041] 20 g of rubidium-cesium enriched material was calcined at 520°C for 2 h in an atmosphere to obtain 18 g of slag with a weight loss rate of approximately 10%.

[0042] The roasted slag is leached with deionized water at a solid-liquid ratio of 1:3-5, and filtered with filter paper to obtain a rubidium-cesium enriched solution and leached slag. The leached slag accounts for about one-third of the roasted slag. The magnetic substances are mainly ferric oxide, ferroferric oxide and magnesium ferrite, and the non-magnetic substance is magnesium oxide.

[0043] The contents of rubidium and cesium in the rubidium and cesium enriched solutions were 17.3 g / L and 14.5 g / L, respectively, and the contents of potassium and sodium were 5 g / L and 2 g / L;

[0044] Add hydrochloric acid to 100 mL of rubidium-cesium enriched solution until the pH is 2, then add 5.88 g of sodium iodide and continue stirring;

[0045] Take 2.028g of bismuth oxide and add appropriate amount of hydrochloric acid until the solid is completely dissolved. Add the bismuth ion solution dropwise to the rubidium-cesium enriched solution. After the addition is complete, continue stirring for 10 minutes, then filter with fast filter paper, and wash five times with weak acid solution with pH 1;

[0046] The solid precipitate was dried in an oven at 80 °C for 4 h to obtain 6.6 g of a red solid;

[0047] 5 g of the solid precipitate was placed in a quartz crucible and placed in a vacuum environment at 580°C for 1 hour to decompose. 1.65 g of solid was obtained in the quartz crucible, which was analyzed and found to be cesium iodide with a purity of 99%; 3.4 g of bismuth iodide was obtained in the vacuum tube wall.

[0048] Example 3

[0049] 100 g of rubidium-cesium enriched material was calcined at 550°C for 5 h in an atmosphere to obtain 85 g of slag with a weight loss rate of approximately 15%.

[0050] The roasted slag is leached with deionized water at a solid-liquid ratio of 1:3-5. After filtering with filter paper, a rubidium-cesium enriched solution and leached slag are obtained. The leached slag mass accounts for about one-third of the roasted slag. The magnetic substances are mainly ferric oxide, ferroferric oxide and magnesium ferrite, and the non-magnetic substance is magnesium oxide.

[0051] The contents of rubidium and cesium in the rubidium and cesium enriched solutions were 51 g / L and 40 g / L, respectively, and the contents of potassium and sodium were 10 g / L and 3 g / L;

[0052] Add hydrochloric acid to 50 mL of rubidium-cesium enriched solution until the pH is 1, then add 8.68 g of sodium iodide and continue stirring;

[0053] Take 3g of bismuth oxide and add appropriate amount of hydrochloric acid until the solid is completely dissolved. Add the bismuth ion solution dropwise to the rubidium-cesium enriched solution. After the addition is complete, continue stirring for 10 minutes, then filter with fast filter paper, and wash five times with weak acid solution with pH 1;

[0054] The solid precipitate was dried in an oven at 80 °C for 4 h to obtain 10.66 g of a red solid;

[0055] 10 g of the solid precipitate was placed in a quartz crucible and placed in a vacuum environment at 580°C for 1 h to obtain 3.4 g of solid in the quartz crucible, which was analyzed to be cesium iodide with a purity of 99%, and 6.2 g of bismuth iodide was obtained in the vacuum tube wall.

[0056] Example 4

[0057] 100 g of rubidium-cesium enriched material was calcined at 550°C for 5 h in an atmosphere to obtain 85 g of slag with a weight loss rate of approximately 15%.

[0058] The roasted slag is leached with deionized water at a solid-liquid ratio of 1:3-5. After filtering with filter paper, a rubidium-cesium enriched solution and leached slag are obtained. The leached slag mass accounts for about one-third of the roasted slag. The magnetic substances are mainly ferric oxide, ferroferric oxide and magnesium ferrite, and the non-magnetic substance is magnesium oxide.

[0059] The contents of rubidium and cesium in the rubidium and cesium enriched solutions were 51 g / L and 40 g / L, respectively, and the contents of potassium and sodium were 10 g / L and 3 g / L;

[0060] Add hydrochloric acid to 300 mL of rubidium-cesium enriched solution until the pH is 1, then add 57.3 g of sodium iodide and continue stirring;

[0061] Take 19.5g of bismuth oxide and add appropriate amount of hydrochloric acid until the solid is completely dissolved. Add the bismuth ion solution dropwise to the rubidium-cesium enriched solution. After the addition is complete, continue stirring for 10 minutes, then filter with fast filter paper, and wash five times with weak acid solution with pH 1;

[0062] The solid precipitate was dried in an oven at 80 °C for 4 h to obtain 64.38 g of a red solid;

[0063] 50 g of the solid precipitate was placed in a quartz crucible and placed in a vacuum environment at 580°C for 1 h. 16 g of solid was obtained in the quartz crucible, which was analyzed to be cesium iodide with a purity of 99%, and 33.8 g of bismuth iodide was obtained in the vacuum tube wall.

[0064] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structures or equivalent process changes made using the contents of the present invention's description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing cesium iodide from a rubidium-cesium enriched material, characterized in that: The method comprises the following steps: S1: Weigh an appropriate amount of rubidium-cesium enriched material and put it into a high-temperature calcining furnace for high-temperature calcination to obtain calcined slag; S2: adding the calcined slag in S1 into a container filled with deionized water, dissolving the calcined slag in the deionized water and allowing the calcined slag to stand. After the calcined slag is completely dissolved, filtering the solution to obtain solution A and filter residue; S3: Add an acidic solution to solution A in S2 to adjust the pH of solution A to acidic. At the same time, add an amount of iodide ions calculated according to the cesium concentration and continue stirring to obtain a yellow solution B. S4: Weigh an appropriate amount of bismuth oxide, and then dissolve it in a container containing an appropriate amount of hydrochloric acid solution to obtain solution C; S5: adding the solution C in S4 to the yellow solution B in S3 while stirring continuously to obtain a red solid precipitate D containing cesium and a rubidium-containing solution E; S6: performing solid-liquid separation on the red solid precipitate D containing cesium and the filtrate E containing rubidium in S5 to obtain a solid precipitate D containing cesium and a solution containing rubidium E; S7: placing the red solid precipitate D of cesium in S6 into a thermal decomposition device for thermal decomposition treatment to obtain a volatile product, bismuth iodide, and a residual product, cesium iodide.

2. The method for preparing cesium iodide from a rubidium-cesium enriched material according to claim 1, wherein: The rubidium-cesium enriched material in S1 is calcined at a temperature of 500-600° C. in an atmospheric atmosphere.

3. The method for preparing cesium iodide from a rubidium-cesium enriched material according to claim 1, wherein: The calcined slag in S2 is mixed with deionized water in a mass ratio of 1:4-5; the filter residue includes magnetic material and non-magnetic material; the magnetic material is Fe2O3, Fe3O4, MgFeO4; the non-magnetic material is MgO.

4. The method for preparing cesium iodide from a rubidium-cesium enriched material according to claim 1, wherein: The pH value of solution A in S3 is adjusted to 1-3; the amount of iodide ions added is calculated based on 100%-150% of the required amount of Cs3Bi2I9 to be formed.

5. The method for preparing cesium iodide from rubidium and cesium enriched material according to claim 1, wherein: The amount of bismuth oxide added to the S4 is calculated based on 100%-150% of the amount required to form Cs3Bi2I9.

6. The method for preparing cesium iodide from rubidium and cesium enriched material according to claim 1, wherein: The solution C in S5 is added dropwise to the yellow solution B.

7. The method for preparing cesium iodide from rubidium and cesium enriched material according to claim 1, wherein: The solid-liquid separation in S6 is carried out by sedimentation filtration and washed five times with a pH=1 aqueous solution.

8. The method for preparing cesium iodide from rubidium and cesium enriched material according to claim 1, wherein: The red solid precipitate D of cesium in the S7 is thermally decomposed in a vacuum environment or a protective atmosphere of nitrogen or argon at a temperature of 550-650°C.

9. The method for preparing cesium iodide from rubidium and cesium enriched material according to claim 4, characterized in that: The amount of iodide ions can be selected from sodium iodide and potassium iodide.

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