Method for preparing high-purity rubidium and cesium from lithium-sinking mother liquor

Abstract

The application discloses a method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor, and belongs to the field of chemical technology.The method comprises the following steps: adding sulfuric acid solution to the lithium precipitation mother liquor to remove carbon, and then evaporating and concentrating; cooling the concentrated mother liquor to precipitate potassium glaserite; cooling the potassium-precipitated mother liquor to precipitate sodium sulfate; adding an extractant for extracting rubidium and cesium into the sodium-precipitated mother liquor, separating, and obtaining an extract solution; adding sulfuric acid solution into the extract solution to perform back extraction, separating an aqueous solution layer and an extractant layer; and concentrating, crystallizing and drying the aqueous solution layer to prepare high-purity rubidium sulfate and cesium sulfate.The lithium precipitation mother liquor produced by the sulfuric acid method is used as raw material to extract rubidium and cesium, the concentrated mother liquor is cooled to precipitate potassium glaserite, and then the sodium is precipitated by cooling, so that the potassium and sodium ions in the mother liquor can be effectively separated, and high-purity rubidium salt and cesium salt are obtained.The method is simple and easy to operate, realizes full utilization of resources, and has good economic value.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology, specifically relating to a method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor. Background Technology

[0002] Lithium is an important metallic element widely used in batteries, alloys, ceramics, and other fields. The sulfuric acid process, using lithium ore as raw material, is a crucial route for obtaining lithium. Besides lithium, lithium ore also contains other metallic elements such as sodium, potassium, rubidium, and cesium. The sulfuric acid process for producing lithium carbonate involves dissolving the metal oxides in the lithium ore with sulfuric acid to generate soluble lithium sulfate, resulting in acidified clinker. After pulping and impurity removal, the acidified clinker undergoes a primary lithium precipitation process. The precipitate is then refined to obtain lithium carbonate.

[0003] The mother liquor after primary lithium precipitation contains not only some incompletely precipitated lithium ions, but also sodium, potassium, rubidium, and cesium ions. Rubidium and cesium are rare metals with excellent photoelectric properties and chemical reactivity, holding unique applications in various technological fields that cannot be replaced by other metallic elements. Furthermore, rubidium and cesium are expensive; if they could be separated from the lithium precipitation mother liquor, it would have excellent economic prospects.

[0004] How to separate rubidium and cesium ions from primary lithium precipitation mother liquor to obtain high-purity rubidium and cesium salts and realize resource utilization has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor. The method uses lithium precipitation mother liquor from the sulfuric acid process for lithium carbonate production as raw material to extract rubidium and cesium. The method is simple, easy to operate, and can obtain high-purity rubidium and cesium salts, thus achieving full utilization of resources.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] This invention discloses a method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor, comprising the following steps:

[0008] S1. Add sulfuric acid solution to the primary lithium precipitation mother liquor to remove carbon, and then evaporate and concentrate to obtain concentrated mother liquor;

[0009] S2. Cool the concentrated mother liquor to precipitate potassium mirabilite, separate the liquid and solid to obtain potassium mirabilite crystal slurry and potassium precipitation mother liquor, respectively;

[0010] S3. Cool the potassium precipitation mother liquor to precipitate sodium sulfate, then separate the liquid and solid to obtain sodium sulfate slurry and sodium precipitation mother liquor, respectively.

[0011] S4. The sodium precipitation mother liquor is subjected to secondary lithium precipitation, and after centrifugation, secondary crude lithium carbonate and secondary lithium precipitation mother liquor are obtained. The secondary lithium precipitation mother liquor is recycled back to the primary lithium precipitation mother liquor clear tank and combined with the primary lithium precipitation mother liquor. This process is repeated in steps S1-S4.

[0012] S5. When the concentration of rubidium and cesium in the secondary lithium precipitation mother liquor reaches a certain level, the extraction process begins: an extractant for extracting rubidium and cesium is added to the secondary lithium precipitation mother liquor, and the organic layer is separated as the extractant, while the aqueous layer is collected and reused as the replenishing extractant.

[0013] S6. Add sulfuric acid solution to the extract for back-extraction to separate the aqueous layer and the organic layer;

[0014] S7. The aqueous solution layer was concentrated, crystallized, and dried to obtain high-purity rubidium sulfate and cesium sulfate.

[0015] In some embodiments of the present invention, the primary lithium precipitation mother liquor is the primary lithium precipitation mother liquor from the sulfuric acid process for producing lithium carbonate.

[0016] In some embodiments of the present invention, in step S1, sulfuric acid solution is added to the primary lithium precipitation mother liquor to adjust the pH value to 4-8;

[0017] Preferably, the decarbonized mother liquor is evaporated and concentrated until the lithium sulfate concentration is greater than or equal to 30 g / L to obtain concentrated mother liquor.

[0018] In some embodiments of the present invention, in step S2, the concentrated mother liquor is cooled to 25℃±5℃, potassium sulfate precipitates, and liquid-solid separation is performed to obtain potassium sulfate crystal slurry and potassium sulfate precipitate mother liquor, respectively.

[0019] In some embodiments of the present invention, preferably, in step S3, the potassium precipitation mother liquor is cooled to less than or equal to 0°C, sodium sulfate precipitates, and liquid-solid separation is performed to obtain sodium sulfate slurry and sodium precipitation mother liquor, respectively.

[0020] Preferably, the sodium sulfate content in the sodium precipitation mother liquor is below 50 g / L.

[0021] In some embodiments of the present invention, in step S5, the extraction process begins when the concentrations of rubidium and cesium in the secondary lithium precipitation mother liquor are both 2 mg / L.

[0022] In some embodiments of the present invention, the extractant includes a diluent and at least one of phenolic alcohol reagents and crown ethers; preferably, a phenolic alcohol reagent.

[0023] The phenolic alcohol reagents include 4-sec-butyl-2-(α-methylbenzyl)phenol and 4-tert-butyl-2-(α-benzyl)phenol;

[0024] Preferably, the diluent is sulfonated kerosene or cyclohexane; more preferably, cyclohexane.

[0025] Preferably, the concentration of phenolic alcohol reagents in the extractant is 0.8-1.2 mol / L; more preferably, it is 1.0 mol / L.

[0026] Preferably, the volume ratio of the extractant to the secondary lithium precipitation mother liquor is 0.2-2:1.

[0027] Preferably, in step S5, sodium hydroxide is first added to adjust the pH of the secondary lithium precipitation mother liquor to 11-14, preferably 13, and then an extractant is added for extraction.

[0028] In some embodiments of the present invention, in step S6, the concentration of the sulfuric acid solution added to the extract is 0.1-1 mol / L, and the volume ratio of the sulfuric acid solution to the extract is 0.2-2:1.

[0029] In some embodiments of the present invention, the organic layer separated in step S6 is collected and reused as an extractant for the extraction of rubidium and cesium. In some embodiments of the present invention, in step S4, excess sodium carbonate is added to the sodium precipitation mother liquor for secondary lithium precipitation. Preferably, an excess of 5-10% sodium carbonate is added based on the lithium content in the sodium precipitation mother liquor.

[0030] Preferably, after centrifugation, the secondary crude lithium carbonate is washed, carbonized, and thermally precipitated to obtain battery-grade lithium carbonate.

[0031] In some embodiments of the present invention, the impurities in the high-purity rubidium sulfate and cesium sulfate obtained in step S6 do not exceed 1 wt.%.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] This invention is scientifically designed and ingeniously conceived. It uses the lithium precipitation mother liquor from the sulfuric acid process for lithium carbonate production as raw material to extract rubidium and cesium. By first cooling the concentrated mother liquor to precipitate potassium sulfate and then cooling it again to precipitate sodium, the potassium and sodium ions in the mother liquor can be effectively separated, thereby obtaining high-purity rubidium and cesium salts.

[0034] The method of this invention is simple, easy to operate, and makes full use of resources, thus having good economic value. Attached Figure Description

[0035] Appendix Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0037] A method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor includes the following steps:

[0038] S1. Add sulfuric acid solution to the primary lithium precipitation mother liquor to remove carbon, and then evaporate and concentrate to obtain concentrated mother liquor;

[0039] The primary lithium precipitation mother liquor is the mother liquor from the sulfuric acid process for producing lithium carbonate, wherein the lithium sulfate content is less than or equal to 7 wt.%, the sodium sulfate content is 5-27 wt.%, and the potassium sulfate content is 8-19 wt.%. In some embodiments of the present invention, decarbonization is achieved by adding sulfuric acid solution to the primary lithium precipitation mother liquor to adjust its pH value to 4-8.

[0040] In some embodiments of the present invention, an MVR high-efficiency evaporator is used to evaporate and concentrate the decarbonized mother liquor to a lithium sulfate concentration greater than or equal to 30 g / L to obtain concentrated mother liquor.

[0041] S2. Cool the concentrated mother liquor to 25℃±5℃, potassium sulfate precipitates out, and the liquid and solid are separated to obtain potassium sulfate crystal slurry and potassium sulfate precipitate mother liquor, respectively.

[0042] S3. Cool the potassium precipitation mother liquor to less than or equal to 0℃, sodium sulfate precipitates out, and the liquid and solid are separated to obtain sodium sulfate slurry and sodium precipitation mother liquor, respectively;

[0043] S4. The sodium precipitation mother liquor is subjected to secondary lithium precipitation, and centrifugation is used to separate the two to obtain secondary crude lithium carbonate and secondary lithium precipitation mother liquor. The secondary lithium precipitation mother liquor is recycled back to the primary lithium precipitation mother liquor clear tank and combined with the primary lithium precipitation mother liquor, repeating steps S1-S4. Preferably, excess sodium carbonate is added to the sodium precipitation mother liquor for secondary lithium precipitation. Preferably, 5-10% excess sodium carbonate is added according to the lithium content in the sodium precipitation mother liquor.

[0044] Preferably, after centrifugal separation, the secondary crude lithium carbonate is stirred, washed, and subjected to carbonization and thermal precipitation to obtain battery-grade lithium carbonate.

[0045] S5. When the concentration of rubidium and cesium in the secondary lithium precipitation mother liquor reaches a certain level, the extraction process begins: an extractant for extracting rubidium and cesium is added to the secondary lithium precipitation mother liquor, and the organic layer is separated as the extractant, while the aqueous layer is collected and reused as the replenishing extractant.

[0046] Preferably, the extraction process begins when the concentrations of rubidium and cesium in the secondary lithium precipitation mother liquor are both 2 mg / L.

[0047] The extractant includes at least one of a diluent, a phenolic alcohol reagent, and a crown ether; preferably a phenolic alcohol reagent.

[0048] The phenolic alcohol reagents include 4-sec-butyl-2-(α-methylbenzyl)phenol and 4-tert-butyl-2-(α-benzyl)phenol;

[0049] Preferably, the diluent is sulfonated kerosene or cyclohexane; more preferably, cyclohexane.

[0050] Preferably, the concentration of phenolic alcohol reagents in the extractant is 0.8-1.2 mol / L; more preferably, it is 1.0 mol / L.

[0051] Preferably, the volume ratio of the extractant to the secondary lithium precipitation mother liquor is 0.2-2:1.

[0052] Preferably, in step S5, sodium hydroxide is first added to adjust the pH of the secondary lithium precipitation mother liquor to 11-14, preferably 13, and then an extractant is added for extraction.

[0053] S6. Add sulfuric acid solution to the extract for back-extraction to separate the aqueous layer and the organic layer;

[0054] The concentration of sulfuric acid solution added to the extract is 0.1-1 mol / L, and the volume ratio of sulfuric acid solution to extract is 0.2-2:1.

[0055] The organic layer separated in step S6 is collected and reused as an extractant for the extraction of rubidium and cesium.

[0056] S7. The aqueous solution layer obtained in step S6 is concentrated, crystallized, and dried to obtain high-purity rubidium sulfate and cesium sulfate.

[0057] In some embodiments of the present invention, the impurity content in the high-purity rubidium sulfate and cesium sulfate obtained in step S7 does not exceed 1 wt.%.

[0058] In some embodiments of the present invention, high-purity potassium sulfate is prepared using potassium mirabilite obtained in step S2 and sodium sulfate obtained in step S3.

[0059] Preferably, the steps for preparing high-purity potassium sulfate are as follows:

[0060] Step A. Add potassium chloride solution to sodium sulfate, heat to react, and potassium sodium chloride and sodium chloride are produced. Then separate the sodium chloride to obtain potassium sodium chloride.

[0061] Step B. Combine the potassium sulfate obtained from Step S2 and Step A, then add potassium chloride solution to react and produce potassium sulfate and sodium chloride; separate them to obtain sodium chloride and high-purity potassium sulfate respectively.

[0062] Preferably, in step A, an equimolar amount of potassium chloride solution is added to sodium sulfate, and the mass concentration of the potassium chloride solution is preferably 5-10%; preferably, the reaction temperature is 80-100℃.

[0063] Preferably, the mixture of potassium sulfate and sodium chloride generated in step A is cooled to -5 to 0°C to crystallize and separate the potassium sulfate, and then evaporated and crystallized to separate the sodium chloride.

[0064] Preferably, in step B, an equimolar amount of potassium chloride solution is added, and the mass concentration of the potassium chloride solution is preferably 5-10%; preferably, the reaction temperature is 25-50℃.

[0065] Preferably, the mixture of potassium sulfate and sodium chloride generated in step B is cooled to -5 to 0°C to crystallize and separate potassium sulfate, and then evaporated and crystallized to separate sodium chloride.

[0066] Example 1

[0067] This embodiment discloses a method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor, comprising the following steps:

[0068] S1. Add sulfuric acid solution to the primary lithium precipitation mother liquor to adjust its pH to 4, decarbonize it, and then use an MVR high-efficiency evaporator to evaporate and concentrate it to obtain concentrated mother liquor; the lithium sulfate content in the concentrated mother liquor is 30.5 g / L;

[0069] The primary lithium precipitation mother liquor is the lithium precipitation mother liquor from the sulfuric acid process for producing lithium carbonate, containing 6.5 wt.% lithium sulfate, 26.8 wt.% sodium sulfate, and 12 wt.% potassium sulfate.

[0070] S2. Cool the concentrated mother liquor to 25°C, potassium sulfate precipitates out, and the liquid and solid are separated to obtain potassium sulfate crystal slurry and potassium sulfate precipitate mother liquor, respectively.

[0071] S3. Cool the potassium precipitation mother liquor to less than or equal to 0℃, sodium sulfate precipitates, and the liquid and solid are separated to obtain sodium sulfate slurry and sodium precipitation mother liquor with a sodium sulfate concentration of less than 50g / L, respectively; after drying, sodium sulfate slurry yields sodium sulfate product with a purity of 88.6%.

[0072] S4. Add 5% excess sodium carbonate to the sodium precipitation mother liquor for secondary lithium precipitation, and centrifuge to obtain secondary crude lithium carbonate and secondary lithium precipitation mother liquor.

[0073] The secondary lithium precipitation mother liquor is recycled back to the primary lithium precipitation mother liquor clearing tank and combined with the primary lithium precipitation mother liquor, in the circulation steps S1-S4.

[0074] S5. When the rubidium concentration in the secondary lithium precipitation mother liquor is 2.0 mg / L and the cesium concentration is 2.3 mg / L, the extraction process begins: sodium hydroxide solution is added to the secondary lithium precipitation mother liquor to adjust its pH value to 13, then the extractant is added for extraction, and then the aqueous layer and organic layer are separated. The organic layer is used as the extractant, and the aqueous layer is collected and reused as the extraction replenishment solution.

[0075] The extractant was a mixed solution of 4-tert-butyl-2-(α-benzyl)phenol and cyclohexane, wherein the concentration of 4-tert-butyl-2-(α-benzyl)phenol was 1.0 mol / L; the volume ratio of extractant to secondary lithium precipitation mother liquor was 1:1.

[0076] S6. Add a 1 mol / L sulfuric acid solution to the extract for back-extraction. The volume ratio of sulfuric acid solution to extract is 1:1. Separate the aqueous layer and the organic layer. Collect the organic layer as an extractant and reuse it for the extraction of rubidium and cesium.

[0077] S7. The aqueous solution layer obtained in step S6 is concentrated, crystallized, and dried to obtain high-purity rubidium sulfate and cesium sulfate.

[0078] In some embodiments of the present invention, the impurity content in the high-purity rubidium sulfate and cesium sulfate obtained in step S7 is 0.81 wt%. After centrifugation, the secondary crude lithium carbonate is obtained, which is then stirred, washed, and subjected to carbonization and thermal precipitation to obtain battery-grade lithium carbonate.

[0079] Example 2

[0080] This embodiment discloses a method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor according to the present invention, comprising the following steps:

[0081] S1. Add sulfuric acid solution to the primary lithium precipitation mother liquor to adjust its pH to 8, decarbonize it, and then use an MVR high-efficiency evaporator to evaporate and concentrate it to obtain concentrated mother liquor; the lithium sulfate content in the concentrated mother liquor is 30.1 g / L;

[0082] The primary lithium precipitation mother liquor in Example 2 is the same as in Example 1.

[0083] S2. Cool the concentrated mother liquor to 20°C, potassium sulfate precipitates out, and the liquid and solid are separated to obtain potassium sulfate crystal slurry and potassium sulfate precipitate mother liquor, respectively.

[0084] S3. Cool the potassium precipitation mother liquor to less than or equal to 0℃, sodium sulfate precipitates, and the liquid and solid are separated to obtain sodium sulfate slurry and sodium precipitation mother liquor with a sodium sulfate concentration of less than 50g / L, respectively; after drying, sodium sulfate slurry yields sodium sulfate product with a purity of 88.4%.

[0085] S4. Add 5% excess sodium carbonate to the sodium precipitation mother liquor for secondary lithium precipitation, and centrifuge to obtain secondary crude lithium carbonate and secondary lithium precipitation mother liquor.

[0086] The secondary lithium precipitation mother liquor is recycled back to the primary lithium precipitation mother liquor clearing tank and combined with the primary lithium precipitation mother liquor, in the circulation steps S1-S4.

[0087] S5. When the rubidium concentration in the secondary lithium precipitation mother liquor is 2.1 mg / L and the cesium concentration is 2.5 mg / L, the extraction process begins: sodium hydroxide solution is added to the secondary lithium precipitation mother liquor to adjust its pH value to 11, then the extractant is added for extraction, and then the aqueous layer and organic layer are separated. The organic layer is used as the extractant, and the aqueous layer is collected and reused as the extraction replenishment solution.

[0088] The extractant was a mixed solution of 4-tert-butyl-2-(α-benzyl)phenol and cyclohexane, wherein the concentration of 4-tert-butyl-2-(α-benzyl)phenol was 0.8 mol / L; the volume ratio of extractant to secondary lithium precipitation mother liquor was 2:1.

[0089] S6. Add a 0.1 mol / L sulfuric acid solution to the extract for back-extraction. The volume ratio of sulfuric acid solution to extract is 2:1. Separate the aqueous layer and the organic layer. Collect the organic layer as an extractant and reuse it for the extraction of rubidium and cesium.

[0090] S7. The aqueous solution layer obtained in step S6 is concentrated, crystallized, and dried to obtain high-purity rubidium sulfate and cesium sulfate.

[0091] In some embodiments of the present invention, the impurity content in the high-purity rubidium sulfate and cesium sulfate obtained in step S7 is 0.9 wt%.

[0092] After centrifugation, secondary crude lithium carbonate is obtained, which is then washed, carbonized, and thermally precipitated to obtain battery-grade lithium carbonate.

[0093] Example 3

[0094] This embodiment discloses a method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor according to the present invention, comprising the following steps:

[0095] S1. Add sulfuric acid solution to the primary lithium precipitation mother liquor to adjust its pH to 7, decarbonize it, and then use an MVR high-efficiency evaporator to evaporate and concentrate it to obtain concentrated mother liquor; the lithium sulfate content in the concentrated mother liquor is 30.2 g / L;

[0096] The raw material, primary lithium precipitation mother liquor, is the lithium precipitation mother liquor from the sulfuric acid process for producing lithium carbonate, containing 5.9 wt.% lithium sulfate, 5.0 wt.% sodium sulfate, and 19.2 wt.% potassium sulfate.

[0097] S2. Cool the concentrated mother liquor to 30°C, potassium sulfate precipitates out, and the liquid and solid are separated to obtain potassium sulfate crystal slurry and potassium sulfate precipitate mother liquor, respectively.

[0098] S3. Cool the potassium precipitation mother liquor to less than or equal to 0℃, sodium sulfate precipitates, and the liquid and solid are separated to obtain sodium sulfate slurry and sodium precipitation mother liquor with a sodium sulfate concentration of less than 50g / L, respectively; after drying, sodium sulfate slurry yields sodium sulfate product with a purity of 87.4%.

[0099] S4. Add 5% excess sodium carbonate to the sodium precipitation mother liquor for secondary lithium precipitation, and centrifuge to obtain secondary crude lithium carbonate and secondary lithium precipitation mother liquor.

[0100] The secondary lithium precipitation mother liquor is recycled back to the primary lithium precipitation mother liquor clearing tank and combined with the primary lithium precipitation mother liquor, in the circulation steps S1-S4.

[0101] S5. When the rubidium concentration in the secondary lithium precipitation mother liquor is 2.3 mg / L and the cesium concentration is 2.1 mg / L, the extraction process begins: sodium hydroxide solution is added to the secondary lithium precipitation mother liquor to adjust its pH value to 14, then the extractant is added for extraction, and then the aqueous layer and organic layer are separated. The organic layer is used as the extractant, and the aqueous layer is collected and reused as the extraction replenishment solution.

[0102] The extractant was a mixed solution of 4-tert-butyl-2-(α-benzyl)phenol and cyclohexane, wherein the concentration of 4-tert-butyl-2-(α-benzyl)phenol was 1.2 mol / L; the volume ratio of extractant to secondary lithium precipitation mother liquor was 0.2:1.

[0103] S6. Add a 2 mol / L sulfuric acid solution to the extract for back-extraction. The volume ratio of sulfuric acid solution to extract is 0.2:1. Separate the aqueous layer and the organic layer. Collect the organic layer as an extractant and reuse it for the extraction of rubidium and cesium.

[0104] S7. The aqueous solution layer obtained in step S6 is concentrated, crystallized, and dried to obtain high-purity rubidium sulfate and cesium sulfate.

[0105] In some embodiments of the present invention, the impurity content in the high-purity rubidium sulfate and cesium sulfate obtained in step S7 is 0.96 wt%.

[0106] After centrifugation, secondary crude lithium carbonate is obtained, which is then washed, carbonized, and thermally precipitated to obtain battery-grade lithium carbonate.

[0107] Example 4

[0108] This embodiment utilizes the potassium sulfate obtained in step S2 of Example 1 and the sodium sulfate obtained in step S3 to prepare high-purity potassium sulfate. The specific steps are as follows:

[0109] Step A. Add an equimolar amount of potassium chloride solution to sodium sulfate and react at 100°C to produce potassium sulfate and sodium chloride. The concentration of the potassium chloride solution is 10 wt.%.

[0110] The reaction mixture of potassium sulfate and sodium chloride is cooled to -5 to 0°C, and potassium sulfate is separated by crystallization. Then, sodium chloride is separated by evaporation and crystallization.

[0111] Step B. Combine the potassium sulfate obtained from Step S2 and Step A, and then add an equimolar amount of potassium chloride solution to react at 50°C to produce potassium sulfate and sodium chloride. The concentration of the potassium chloride solution is 10 wt.%.

[0112] The resulting mixture of potassium sulfate and sodium chloride was cooled to -5 to 0°C, and potassium sulfate was separated by crystallization. Then, sodium chloride was separated by evaporation and crystallization.

[0113] After dehydration and drying, the potassium sulfate slurry separated by crystallization yields a potassium sulfate product with a purity of 99.1%.

[0114] Comparative Example 1

[0115] This comparative example discloses a method for preparing rubidium and cesium from lithium precipitation mother liquor. Compared with Example 1, this comparative example omits step S2, which involves separating potassium sulfate; all other conditions remain the same. Details are as follows:

[0116] Step 1. Same as step S1 in Example 1.

[0117] Step 2. Cool the concentrated mother liquor to below 0°C, and solids will precipitate out. After liquid-solid separation, solid crystal slurry and mother liquor are obtained respectively.

[0118] Step 3. Add 5% excess sodium carbonate to the mother liquor from which the solid crystal slurry has been separated for secondary lithium precipitation. After centrifugation, secondary crude lithium carbonate and secondary lithium precipitation mother liquor are obtained.

[0119] The secondary lithium precipitation mother liquor is recycled back to the primary lithium precipitation mother liquor clear tank and combined with the primary lithium precipitation mother liquor, repeating steps 1-3.

[0120] Step 4. Same as step S5 in Example 1.

[0121] Step 5. Same as step S6 in Example 1.

[0122] Step 6. Same as step S7 in Example 1.

[0123] The results showed that the solid slurry obtained in step 2 contained a variety of substances, including sodium sulfate, potassium sulfate and potassium nitrate. The rubidium sulfate and cesium sulfate obtained in step 6 were not of high purity and still contained some sodium sulfate and potassium sulfate.

[0124] Finally, it should be noted that the above embodiments are merely preferred embodiments of the present invention used to illustrate the technical solutions of the present invention, and are not intended to limit the invention, nor are they intended to limit the patent scope of the present invention. Any modifications or refinements made to the main design concept and spirit of the present invention that are not of substantial significance, but which still solve the same technical problem as the present invention, should be included within the protection scope of the present invention; in addition, the direct or indirect application of the technical solutions of the present invention to other related technical fields are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor, characterized in that, The steps include the following: S1. Add sulfuric acid solution to the primary lithium precipitation mother liquor to remove carbon, and then evaporate and concentrate to obtain concentrated mother liquor; S2. Cool the concentrated mother liquor to 25℃±5℃, potassium sulfate precipitates out, and the liquid and solid are separated to obtain potassium sulfate crystal slurry and potassium sulfate mother liquor, respectively. S3. Cool the potassium precipitation mother liquor to less than or equal to 0℃, sodium sulfate precipitates out, and the liquid and solid are separated to obtain sodium sulfate slurry and sodium precipitation mother liquor, respectively; S4. The sodium precipitation mother liquor is subjected to secondary lithium precipitation, and after centrifugation, secondary crude lithium carbonate and secondary lithium precipitation mother liquor are obtained. The secondary lithium precipitation mother liquor is recycled back to the primary lithium precipitation mother liquor clear tank and combined with the primary lithium precipitation mother liquor. This process is repeated in steps S1-S4. S5. When the concentrations of rubidium and cesium in the secondary lithium precipitation mother liquor are both greater than 2 mg / L, the extraction process begins: first, sodium hydroxide is added to adjust the pH of the secondary lithium precipitation mother liquor to 11-14, then extractant for extracting rubidium and cesium is added to the secondary lithium precipitation mother liquor, and the organic layer is separated as the extractant, while the aqueous layer is collected and reused as the replenishing extractant. S6. Add sulfuric acid solution to the extract for back-extraction to separate the aqueous layer and the organic layer. S7. The aqueous solution layer is concentrated, crystallized, and dried to obtain high-purity rubidium sulfate and cesium sulfate.

2. The method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor according to claim 1, characterized in that, The primary lithium precipitation mother liquor is the primary lithium precipitation mother liquor used in the sulfuric acid process for producing lithium carbonate.

3. The method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor according to claim 1 or 2, characterized in that, In step S1, sulfuric acid solution is added to the primary lithium precipitation mother liquor to adjust the pH value to 4-8.

4. A method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor according to claim 1 or 2, characterized in that, The decarbonized mother liquor was evaporated and concentrated until the lithium sulfate concentration was greater than or equal to 30 g / L to obtain concentrated mother liquor.

5. A method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor according to claim 1 or 2, characterized in that, In step S3, the sodium sulfate content in the sodium precipitation mother liquor is below 50 g / L.

6. A method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor according to claim 1 or 2, characterized in that, The extractant includes at least one of a diluent, a phenolic alcohol reagent, and a crown ether.

7. The method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor according to claim 6, characterized in that, The extractant is a phenolic alcohol reagent; The phenolic alcohol reagents include 4-sec-butyl-2-(α-methylbenzyl)phenol and 4-tert-butyl-2-(α-benzyl)phenol.

8. The method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor according to claim 6, characterized in that, The diluent is sulfonated kerosene or cyclohexane.

9. The method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor according to claim 6, characterized in that, The diluent is cyclohexane.

10. The method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor according to claim 6, characterized in that, The concentration of phenolic alcohol reagents in the extractant is 0.8-1.2 mol / L.

11. The method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor according to claim 6, characterized in that, The concentration of phenolic alcohol reagents in the extractant is 1.0 mol / L.

12. The method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor according to claim 6, characterized in that, The volume ratio of the extractant to the secondary lithium precipitation mother liquor is 0.2-2:

1.

13. The method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor according to claim 6, characterized in that, In step S5, sodium hydroxide is first added to adjust the pH of the secondary lithium precipitation mother liquor to 13, and then an extractant is added for extraction.

14. A method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor according to claim 1 or 2, characterized in that, In step S6, the concentration of the sulfuric acid solution added to the extract is 0.1-1 mol / L, and the volume ratio of the sulfuric acid solution to the extract is 0.2-2:

1.

15. A method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor according to claim 1 or 2, characterized in that, The organic layer separated in step S6 is collected and reused as an extractant for the extraction of rubidium and cesium.

16. A method for preparing high-purity rubidium and cesium from lithium precipitation mother liquor according to claim 1 or 2, characterized in that, The impurities in the high-purity rubidium sulfate and cesium sulfate obtained in step S7 do not exceed 1 wt.%.

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