Method for extracting and separating rubidium and cesium from lithium precipitation mother liquor
By co-extraction and multi-stage countercurrent extraction technology from the precipitated lithium mother liquor, the problems of low separation efficiency and difficult to guarantee purity in the existing technology are solved, and efficient and low-cost separation of rubidium cesium and the preparation of high-purity products are achieved. .
Patent Information
- Application Number
- CN202411292742.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-14
- Publication Date
- 2024-12-27
AI Technical Summary
The prior art has problems such as high cost, high energy consumption, low separation efficiency and difficult to guarantee purity when extracting rubidium cesium from salt lake brine and cesium garnet, especially in the brine where rubidium cesium content is low and symbiotic with other elements. Under the following, it is difficult to achieve efficient separation and high purity extraction.
By co-extracting rubidium cesium from the precipitated lithium mother liquor, using multi-stage countercurrent extraction and countercurrent washing/removal extraction technology, the pH value and extractant ratio are adjusted, and rubidium and cesium are gradually separated to achieve high concentration rubidium-rich liquid and pure cesium back extraction Obtain liquid.
It realizes efficient separation and high purity extraction of rubidium cesium, reduces production costs, improves the yield and product purity of rubidium cesium, adapts to changes in different raw material concentrations, and reduces the difficulty of subsequent concentration and separation.
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Figure CN119194103A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of hydrometallurgy, and in particular relates to a method for extracting and separating rubidium and cesium from lithium precipitation mother liquor. Background Art
[0002] As an important alkali metal resource, rubidium and cesium are abundant in the earth's crust, ranking 16th and 40th in element abundance, respectively. They are mainly found in solid minerals such as lepidolite, cesium garnet, and amazonite, as well as geothermal water, salt lake brine, and seawater. In minerals, rubidium and cesium mainly exist in the form of isomorphism instead of potassium atoms. In salt lake brine, rubidium coexists with alkali metal elements with very similar properties such as potassium and sodium, which makes it very difficult to separate and purify rubidium. The basic raw materials for the industrial production of rubidium and cesium are mainly cesium garnet and lepidolite, but the extraction process is complicated, costly, and energy-intensive. Rubidium and cesium exist in brine in the form of cations, and the extraction process is relatively simple, low-cost, and low-energy-consuming, which is the current development trend of rubidium and cesium industrial technology. However, the rubidium-cesium resources in brine have not been effectively developed and utilized. The reason is that the rubidium-cesium content in brine is low (average 0-20 ppm), and it coexists with a large amount of elements such as sodium, potassium and magnesium, making separation and extraction extremely difficult.
[0003] With the development of high-tech, the demand for rubidium and cesium will further increase. It is of great significance to continue to expand new sources of rubidium and cesium based on existing resource reserves and develop corresponding efficient extraction and separation technologies.
[0004] At present, the rubidium-cesium content in salt lake brine is low, and it needs to be concentrated in large quantities before it can be used, and the production cost is high; although the cesium content of cesium garnet ore is high, the raw material price is expensive, and a large amount of aluminum, silicon, and calcium waste residues are produced during the leaching process. Patent application CN107217156A discloses a low-cost method for extracting rubidium-cesium salts from spodumene lithium extraction mother liquor. The method uses spodumene lithium extraction mother liquor as raw material, first adds an excess of precipitants such as iron sulfate to precipitate the rubidium-cesium in the lithium extraction mother liquor, and then dissolves and extracts and separates rubidium-cesium after solid enrichment, and comprehensively utilizes rubidium-cesium valuable metals, reduces the cost of rubidium-cesium extraction, and can produce relatively considerable economic benefits. The method extracts rubidium-cesium, can be carried out at low temperature and normal pressure, is simple to operate, has low energy consumption, large processing capacity, is conducive to continuous operation, has low production cost, and the wastewater returns to the lithium extraction workshop. The process realizes closed-loop circulation and zero wastewater discharge. However, the efficiency of recovering rubidium and cesium by precipitation method is low, and the reagents after precipitating rubidium and cesium cannot be directly reused like extraction agents, and the cost is significantly higher than the extraction method.
[0005] Patent CN107130111A discloses a method for separating and extracting rubidium and cesium from coal mine water, comprising the following steps: step 1, evaporating the coal mine water and adjusting the pH value to 8-11.5; step 2, passing the treated coal mine water through a first ion exchange column filled with a mixture of zirconium phosphate, titanium phosphate and a binder to adsorb cesium to obtain a filtrate; step 3, passing the filtrate passed through the first ion exchange column in step 2 through a second ion exchange column filled with calcium alginate-ammonium phosphomolybdate to adsorb rubidium; step 4, taking out the raw material in the first ion exchange column, using ammonium chloride solution to perform ion exchange to desorb cesium ions, and evaporating and concentrating to obtain a cesium solution; step 5, taking out the calcium alginate-ammonium phosphomolybdate in the second ion exchange column, using an aqueous solution of nitric acid and hydrobromic acid to desorb rubidium ions, and evaporating and concentrating to obtain a rubidium solution. This method requires the coal mine water to be evaporated and concentrated in advance, and the zirconium phosphate ion exchange column has a slow adsorption rate for rubidium and cesium, low capacity, and short life, making it unsuitable for large-scale production.
[0006] Patent CN105256150B discloses a method for extracting rubidium and cesium from acidic brine, comprising: pumping brine into an adsorption column containing an ammonium chelate resin, calcium ions and magnesium ions are adsorbed by the ammonium chelate resin adsorption column, and the effluent is brine after the calcium ions and magnesium ions are removed; the effluent is mixed and oscillated with t-BAMBP, kerosene or sulfonated kerosene, and the aqueous phase and the organic phase are separated after standing and stratification; then the organic phase is stripped to obtain an aqueous phase containing rubidium chloride and cesium chloride. This method has a simple process. Since there is only one adsorption and extraction operation, the separation efficiency of rubidium and cesium is low, and only a mixed solution containing rubidium and cesium can be obtained. The problem of efficient separation of rubidium and cesium and how to obtain high-purity cesium salt has not yet been solved. More importantly, it is difficult to take into account both high purity and increasing the concentration of cesium salt solution by relying on only one extraction process. Therefore, either the impurity content in the stripping solution is high, or the cesium concentration in the stripping solution is low and a large amount of water needs to be evaporated to crystallize the cesium salt.
[0007] Patent CN107354323A discloses a method for separating and extracting rubidium and cesium from coal, which comprises crushing the coal, dissolving it in mixed acid and filtering it, evaporating and concentrating the extracted filtrate, adding iodine chloride to form a precipitate, adding the precipitate to potassium iodide to dissolve the precipitate to form rubidium chloride, cesium chloride, potassium chloride and iodine, extracting the iodine with an organic solvent, and then extracting the solution containing rubidium chloride, cesium chloride and potassium chloride with t-BAMBP to form a precipitate, dissolving the precipitate in dilute hydrochloric acid, evaporating and crystallizing it, and finally obtaining high-purity rubidium chloride and cesium chloride. This method utilizes the property of iodine chloride and rubidium cesium to form a precipitate, but iodine chloride is highly toxic and expensive, and the second stage still uses BAMBP for extraction, and the process is complicated.
[0008] Therefore, it is necessary to develop a new method for efficient separation of rubidium and cesium to achieve the dual goals of high yield and high product purity. Summary of the invention
[0009] The object of the present invention is to provide a method for extracting and separating rubidium and cesium from lithium precipitation mother liquor, so as to simplify the process, reduce the cost and improve the separation efficiency and purity of rubidium and cesium.
[0010] To achieve the above object, the present invention provides a method for extracting and separating rubidium and cesium, comprising the following steps:
[0011] Step (1): adjusting the alkalinity of the raw material solution containing rubidium and cesium to 0.6-1.0 mol / L to obtain a pre-extraction aqueous phase 1;
[0012] Step (2): mixing the unloaded organic phase 1 with the aqueous phase 1 before extraction obtained in step (1), and performing multi-stage countercurrent extraction to transfer rubidium and cesium into the organic phase, thereby obtaining a loaded organic phase 1 and a raffinate 1;
[0013] Step (3): the loaded organic phase 1 obtained in step (2) is mixed with an acidic solution, and multi-stage countercurrent washing of potassium, washing of rubidium and stripping of cesium are performed in sequence, so that the pH range of the stripping solution in the last stage is 0.4 to 0.8, thereby obtaining an unloaded organic phase 2, a rubidium-rich solution and a pure cesium stripping solution;
[0014] Step (4): adjusting the alkalinity of the rubidium-rich solution obtained in step (3) to 0.2-0.4 mol / L to obtain a pre-extraction aqueous phase 2;
[0015] Step (5): the unloaded organic phase 2 obtained in step (3) is mixed with the aqueous phase 2 before extraction obtained in step (4), and multi-stage countercurrent extraction is performed to transfer cesium into the organic phase to obtain a loaded organic phase 2 and a raffinate 2, and the loaded organic phase 2 obtained is combined with the loaded organic phase 1 to enter step (3);
[0016] Step (6): adjusting the alkalinity of the raffinate 2 obtained in step (5) to 0.6-1.0 mol / L to obtain a pre-extraction aqueous phase 3;
[0017] Step (7): the unloaded organic phase 1 is mixed with the pre-extraction aqueous phase 3 obtained in step (6), and multi-stage countercurrent extraction is performed to transfer rubidium into the organic phase to obtain a loaded organic phase 3 and a raffinate 3. The raffinate 3 is combined with the pre-extraction aqueous phase 1 to enter step (2);
[0018] Step (8): The loaded organic phase 3 obtained in step (7) is mixed with an acidic solution, and multi-stage countercurrent washing of potassium and stripping of rubidium is performed, so that the pH range of the last stripping solution is 1.0 to 1.5, to obtain an empty organic phase 3 and a pure rubidium stripping solution, and the obtained empty organic phase 3 is returned to step (7).
[0019] The alkalinity in the present invention refers to the OH- concentration, which is usually adjusted by NaOH.
[0020] Furthermore, in step (2), the empty organic phase 1 is composed of 4-tert-butyl-2-(α-methylbenzyl)phenol (t-BAMBP) and a diluent; and the volume fraction of 4-tert-butyl-2-(α-methylbenzyl)phenol in the empty organic phase 1 is 20% to 35%;
[0021] The diluent is one or both of kerosene and xylene.
[0022] Furthermore, in step (2), the extraction phase ratio of the empty organic phase 1 to the aqueous phase 1 before extraction is (3-5):1; the extraction stages of the multi-stage countercurrent extraction are 4-6. The phase ratio in the present invention refers to the volume ratio.
[0023] Furthermore, in step (3) and step (8), the acidic solution is dilute hydrochloric acid, dilute nitric acid or dilute sulfuric acid, preferably 0.8 to 1.3 mol / L hydrochloric acid, nitric acid or sulfuric acid.
[0024] The phase ratio R(O / A) of the multi-stage countercurrent potassium washing is (85-100):1 (O represents the organic phase, A represents the aqueous phase); the number of potassium washing stages is 5-7 stages.
[0025] The relative ratio R(O / A) of washed rubidium is (18-22):1, and the number of washed rubidium levels is 6-8.
[0026] The phase ratio R(O / A) of cesium stripping is (10-15):1, and the number of stages of cesium stripping is 1-3. In practical applications, the number of stages is flexibly adjusted according to production data.
[0027] Furthermore, in step (3), the obtained unloaded organic phase 2 is returned to step (2) and step (5) for repeated use.
[0028] Furthermore, in step (5), the extraction ratio of the empty organic phase 2 to the aqueous phase 2 before extraction is (0.9-1.2):1; and the extraction stages of the multi-stage countercurrent extraction are 8-11 stages.
[0029] Furthermore, in step (7), the extraction ratio of the empty organic phase 1 to the aqueous phase 3 before extraction is (10-13):1; and the extraction stages of the multi-stage countercurrent extraction are 6-9 stages.
[0030] Furthermore, in step (8), the multi-stage countercurrent washing of potassium has a phase ratio R (O / A) of (45-54):1; the phase ratio R (O / A) of stripping rubidium is (9-13):1. The number of stages of countercurrent washing of potassium is 5-7, and the number of stages of stripping rubidium is 1-3.
[0031] Furthermore, in step (1), the raw material solution is derived from lithium precipitation mother liquor. Lithium precipitation mother liquor refers to the mother liquor discharged after lithium carbonate is precipitated by chemical reaction between refined high-lithium solution and sodium carbonate solution in the production process of lithium carbonate.
[0032] The raw material solution usually contains rubidium, cesium, potassium and other ions, for example, the rubidium concentration is 0.5-20 g / L, the cesium concentration is 0.5-12 g / L, and the potassium concentration is 10-120 g / L.
[0033] The process of extracting and separating rubidium and cesium from lithium precipitation mother liquor of the present invention is usually carried out at 10-40° C., preferably at room temperature.
[0034] Compared with the prior art solutions, the present invention has at least the following beneficial effects:
[0035] (1) Different from the existing technical solution of extracting cesium first and then extracting rubidium, the present invention proposes the idea of first co-extracting rubidium and cesium and then separating rubidium and cesium. First, because the potassium concentration in the lithium precipitation mother liquor is relatively high, co-extraction of rubidium and cesium can obtain a rubidium-rich solution containing high concentration of rubidium and low concentration of potassium, reducing the difficulty of subsequent separation of rubidium and potassium; second, considering the possible fluctuation of the subsequent rubidium and cesium raw material concentration, rubidium and cesium co-extraction can adapt to the recovery of lower concentration of rubidium and cesium, ensuring the yield of higher value rubidium; third, the raw material composition in the lithium precipitation mother liquor is complex, containing impurities such as silicon and aluminum that are easy to cause emulsification, which can minimize the number of contacts between the raw material and the organic phase, and reduce emulsification and organic phase losses.
[0036] (2) The present invention utilizes the difference in the binding ability between rubidium potassium and the extractant to propose a new method of washing / stripping, that is, using the stripping solution as washing water to wash the co-extracted impurities. The main principle of washing is to use the Cs in the aqueous phase to + Replacement Rb + , and Rb + Permutation K + , rather than using H in dilute acid in the prior art + Replace alkali metal ions. In this process, due to Rb + Both the replacement ion (Rb + Permutation K + ) and the replaced ion (Cs + Replacement Rb +), so there will be a peak value in the rubidium concentration in the washing water of the washing section, and a rubidium-rich solution outlet can be set here or nearby. At the same time, the present invention can obtain high-concentration washing water or stripping solution by using a large ratio of washing / stripping, and by setting the current-stage reflux, the efficiency of washing / stripping can be significantly improved (the mass ratio of rubidium to potassium in the rubidium stripping solution is greater than 10,000, and the mass ratio of cesium to rubidium in the cesium stripping solution is greater than 40,000), and at the same time, a high-concentration rubidium-rich solution (the rubidium concentration reaches up to 100 g / L), a rubidium stripping solution (the rubidium concentration is greater than or equal to 107 g / L) or a cesium stripping solution (the cesium concentration is greater than or equal to 168 g / L) is obtained, saving subsequent concentration time and cost.
[0037] (3) The present invention makes full use of the differences in the distribution ratio of rubidium and cesium and the difficulty of stripping during the extraction process, and regulates the rubidium and cesium concentration in the empty organic phase by accurately controlling the pH of the last-stage stripping solution within a specific range, so as to achieve the purpose of the rubidium extraction rate being greater than the cesium extraction rate in step (7), thereby realizing further separation of rubidium and cesium. This is because when the stripping acidity is not excessive, rubidium stripping is easy to cesium, rubidium can be stripped more thoroughly, while cesium cannot be stripped thoroughly, and a certain concentration remains in the empty organic phase. When the empty organic phase returns to the extraction section, according to the extraction distribution equilibrium, the low concentration of cesium in the solution cannot be transferred to the organic phase; while the rubidium stripping in the empty organic phase is more thorough, so rubidium can be transferred into the organic phase in large quantities, resulting in the "abnormal phenomenon" that the rubidium extraction rate is greater than the cesium extraction rate. The method can be used to control the rubidium-cesium mass ratio to be further increased, which is beneficial to obtaining a high-purity rubidium stripping solution (the rubidium-cesium mass ratio in the rubidium stripping solution is greater than 10,000). BRIEF DESCRIPTION OF THE DRAWINGS
[0038] Figure 1 A schematic diagram of the structure of extracting and separating rubidium and cesium from lithium precipitation mother liquor provided by the present invention;
[0039] Figure 2 The present invention provides a schematic diagram of a process for extracting and separating rubidium and cesium from lithium precipitation mother liquor. DETAILED DESCRIPTION
[0040] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
[0041] Example 1
[0042] like Figure 1 and 2 As shown, this embodiment provides a method for extracting and separating rubidium and cesium from lithium precipitation mother liquor, and the method includes the following contents:
[0043] Step (1): adjusting the alkalinity of the lithium precipitation mother solution (rubidium concentration of 13 g / L, cesium concentration of 6 g / L, potassium concentration of 100 g / L, pH of 10.5) to 0.8 mol / L to obtain a pre-extraction aqueous phase 1;
[0044] Step (2): mixing the unloaded organic phase 1 (volume fraction of 30% t-BAMBP + 70% kerosene) with the aqueous phase 1 obtained before extraction in step (1), with the extraction phase ratio (O / A, i.e., organic phase / aqueous phase) being 3:1, and performing 5-stage countercurrent extraction to transfer rubidium and cesium into the organic phase, thereby obtaining a loaded organic phase 1 and a raffinate 1, wherein the extraction rate of rubidium is 92%, and the extraction rate of cesium is 99%;
[0045] Step (3): the loaded organic phase 1 obtained in step (2) is mixed with 1.3 mol / L hydrochloric acid (aqueous phase), and 15 stages of countercurrent potassium washing, rubidium washing and cesium stripping are performed (6 stages of potassium washing, 7 stages of rubidium washing, and two stages of cesium stripping); wherein the potassium washing phase ratio (O / A) is 100:1, the rubidium washing phase ratio (O / A) is 22:1, and the cesium stripping phase ratio (O / A) is 15:1, and the pH value of the aqueous phase outlet at the 15th stage stripping section is set to 0.4, and the 7th stage washing and the 14th stage stripping are open circuit (such as Figure 1 ), finally obtaining an empty organic phase 2, a rubidium-rich solution (containing 90 g / L rubidium, 7 g / L potassium, and 5 g / L cesium) and a pure cesium stripping solution (containing 170 g / L cesium and 2 mg / L rubidium), and the obtained empty organic phase 2 is returned to step (2) and step (5); this step reduces the amount of water used and can increase the rubidium and cesium concentrations by using a large phase ratio;
[0046] Step (4): adjusting the alkalinity of the rubidium-rich solution obtained in step (3) to 0.3 mol / L to obtain a pre-extraction aqueous phase 2;
[0047] Step (5): the unloaded organic phase 2 obtained in step (3) is mixed with the aqueous phase 2 before extraction obtained in step (4), and 10 levels of countercurrent extraction are performed, the extraction phase ratio (O / A) is 1:1, and cesium is transferred to the organic phase to obtain a loaded organic phase 2 and a raffinate 2. The loaded organic phase 2 obtained is combined with the loaded organic phase 1 to enter step (3). The rubidium concentration of the obtained raffinate 2 is 75 g / L, the cesium concentration is 5 mg / L, the rubidium extraction rate is 16.7%, and the cesium extraction rate is 99.9%. This step can separate rubidium from cesium. Although part of rubidium is also extracted into the organic phase, by combining the loaded organic phase 2 with the loaded organic phase 1 and entering step (3) for co-extraction again, closed-loop extraction is achieved, thereby improving the recovery rate.
[0048] Step (6): adjusting the alkalinity of the raffinate 2 obtained in step (5) to 0.8 mol / L to obtain a pre-extraction aqueous phase 3;
[0049] Step (7): the unloaded organic phase 1 (volume fraction of 30% t-BAMBP + 70% kerosene) is mixed with the aqueous phase 3 before extraction obtained in step (6), and 7-stage countercurrent extraction is performed, and the extraction phase ratio (O / A) is 11:1, so that rubidium is transferred to the organic phase to obtain a loaded organic phase 3 and a raffinate 3, at which the rubidium concentration in the raffinate 3 is 4.2 g / L, the cesium concentration is 0.5 mg / L, the rubidium extraction rate is 94.4%, and the cesium extraction rate is 90%. The obtained raffinate 3 is combined with the aqueous phase 1 before extraction and enters step (2) to achieve cyclic extraction;
[0050] Step (8): The loaded organic phase 3 obtained in step (7) is mixed with 1.3 mol / L hydrochloric acid, and 8-stage countercurrent washing of potassium and stripping of rubidium (6-stage washing of potassium and 2-stage stripping of rubidium) are performed, wherein the washing potassium phase ratio (O / A) is 54:1, and the stripping rubidium phase ratio (O / A) is 13:1, and the pH value of the water phase outlet at the 8th stripping stage is set to 1.0. The 7th stripping stage is opened to obtain an unloaded organic phase 3 and a pure rubidium stripping solution (containing 117 g / L rubidium, 7 mg / L potassium, and 10 mg / L cesium). The unloaded organic phase 3 obtained is returned to step (7).
[0051] The obtained pure cesium stripping solution and pure rubidium stripping solution have high cesium and rubidium concentrations and low impurity content, thus being helpful in obtaining high-purity rubidium salt and cesium salt products.
[0052] Example 2
[0053] This embodiment provides a method for extracting and separating rubidium and cesium from lithium precipitation mother liquor, the method comprising the following contents:
[0054] Step (1): adjusting the alkalinity of the lithium precipitation mother solution (rubidium concentration of 17 g / L, cesium concentration of 11 g / L, potassium concentration of 110 g / L, pH of 9.5) to 1.0 mol / L to obtain a pre-extraction aqueous phase 1;
[0055] Step (2): mixing the unloaded organic phase 1 (volume fraction of 35% t-BAMBP + 65% xylene) with the aqueous phase 1 before extraction obtained in step (1), with an extraction phase ratio (O / A) of 4:1, and performing 6-stage countercurrent extraction to transfer rubidium and cesium into the organic phase to obtain a loaded organic phase 1 and a raffinate 1, at which the rubidium extraction rate is 95% and the cesium extraction rate is 99%;
[0056] Step (3): the loaded organic phase 1 obtained in step (2) is mixed with 0.8 mol / L sulfuric acid, and 17 levels of countercurrent washing of potassium, washing of rubidium and stripping of cesium are performed (7 levels of washing potassium, 7 levels of washing rubidium, and 3 levels of stripping of cesium), wherein the ratio (O / A) of the washing potassium phase is 90:1, the ratio (O / A) of the washing rubidium phase is 18:1, and the ratio (O / A) of the stripping cesium phase is 12:1, and the pH value of the water phase outlet of the 17th stripping section is set to 0.6, and the 6th level washing and the 15th level stripping are opened to obtain an unloaded organic phase 2, a rubidium-rich solution (containing 100 g / L of rubidium, 9 g / L of potassium, and 7 g / L of cesium) and a pure cesium stripping solution (containing 182 g / L of cesium and 3 mg / L of rubidium), and the unloaded organic phase 2 obtained is returned to step (2) and step (5);
[0057] Step (4): adjusting the alkalinity of the rubidium-rich solution obtained in step (3) to 0.4 mol / L to obtain a pre-extraction aqueous phase 2;
[0058] Step (5): the unloaded organic phase 2 obtained in step (3) is mixed with the aqueous phase 2 before extraction obtained in step (4), and 11-stage countercurrent extraction is performed, and the extraction phase ratio (O / A) is 1.2:1, so that cesium is transferred to the organic phase to obtain a loaded organic phase 2 and a raffinate 2. The loaded organic phase 2 obtained is combined with the loaded organic phase 1 to enter step (3), and the obtained raffinate has a rubidium concentration of 88 g / L, a cesium concentration of 6 mg / L, a rubidium extraction rate of 12%, and a cesium extraction rate of 99.9%;
[0059] Step (6): adjusting the alkalinity of the raffinate 2 obtained in step (5) to 1.0 mol / L to obtain a pre-extraction aqueous phase 3;
[0060] Step (7): the unloaded organic phase 1 (volume fraction of 35% t-BAMBP + 65% xylene) is mixed with the aqueous phase 3 before extraction obtained in step (6), and 9-stage countercurrent extraction is performed, and the extraction phase ratio (O / A) is 13:1, so that rubidium is transferred to the organic phase to obtain a loaded organic phase 3 and a raffinate 3, at which the rubidium concentration of the raffinate is 5.4 g / L, the cesium concentration is 1 mg / L, the rubidium extraction rate is 93.9%, and the cesium extraction rate is 83.3%. The obtained raffinate 3 is combined with the aqueous phase 1 before extraction and enters step (2);
[0061] Step (8): The loaded organic phase 3 obtained in step (7) is mixed with 0.9 mol / L sulfuric acid, and 7-stage countercurrent washing of potassium and stripping of rubidium (5-stage washing of potassium and 2-stage stripping of rubidium) is performed, wherein the washing potassium phase ratio (O / A) is 48:1, and the stripping rubidium phase ratio (O / A) is 11:1, and the pH value of the water phase outlet at the 7th stripping section is set to 1.3. The 6th stripping is opened to obtain an unloaded organic phase 3 and a pure rubidium stripping solution (containing 124 g / L rubidium, 6 mg / L potassium, and 11 mg / L cesium). The unloaded organic phase 3 obtained is returned to step (7).
[0062] Example 3
[0063] This embodiment provides a method for extracting and separating rubidium and cesium from lithium precipitation mother liquor, the method comprising the following contents:
[0064] Step (1): adjusting the alkalinity of the lithium precipitation mother solution (rubidium concentration of 8 g / L, cesium concentration of 5 g / L, potassium concentration of 85 g / L, pH of 8.7) to 0.6 mol / L to obtain a pre-extraction aqueous phase 1;
[0065] Step (2): mixing the unloaded organic phase 1 (volume fraction of 20% t-BAMBP + 40% xylene + 40% kerosene) with the aqueous phase 1 before extraction obtained in step (1), with an extraction phase ratio (O / A) of 5:1, and performing 4-stage countercurrent extraction to transfer rubidium and cesium into the organic phase to obtain a loaded organic phase 1 and a raffinate 1, at which the extraction rate of rubidium is 98% and the extraction rate of cesium is 99%;
[0066] Step (3): the loaded organic phase 1 obtained in step (2) is mixed with 1.3 mol / L nitric acid, and 14 levels of countercurrent washing of potassium, washing of rubidium and stripping of cesium are performed (6 levels of potassium washing, 6 levels of rubidium washing, and 2 levels of stripping of cesium), wherein the ratio (O / A) of the washing potassium phase is 85:1, the ratio (O / A) of the washing rubidium phase is 20:1, and the ratio (O / A) of the stripping cesium phase is 10:1, and the pH value of the water phase outlet of the 14th stripping section is set to 0.8, and the 7th level washing and the 13th level stripping are opened to obtain an unloaded organic phase 2, a rubidium-rich solution (containing 80 g / L of rubidium, 5 g / L of potassium, and 3 g / L of cesium) and a pure cesium stripping solution (containing 168 g / L of cesium and 4 mg / L of rubidium), and the unloaded organic phase 2 obtained is returned to step (2) and step (5);
[0067] Step (4): adjusting the alkalinity of the rubidium-rich solution obtained in step (3) to 0.2 mol / L to obtain a pre-extraction aqueous phase 2;
[0068] Step (5): the unloaded organic phase 2 obtained in step (3) is mixed with the aqueous phase 2 before extraction obtained in step (4), and 8-stage countercurrent extraction is performed, and the extraction phase ratio (O / A) is 0.9:1, so that cesium is transferred to the organic phase to obtain a loaded organic phase 2 and a raffinate 2. The loaded organic phase 2 obtained is combined with the loaded organic phase 1 to enter step (3). The obtained raffinate has a rubidium concentration of 72 g / L, a cesium concentration of 4 mg / L, a rubidium extraction rate of 10%, and a cesium extraction rate of 99.9%;
[0069] Step (6): adjusting the alkalinity of the raffinate 2 obtained in step (5) to 0.6 mol / L to obtain a pre-extraction aqueous phase 3;
[0070] Step (7): the unloaded organic phase 1 (volume fraction of 20% t-BAMBP + 40% xylene + 40% kerosene) is mixed with the aqueous phase 3 before extraction obtained in step (6), and 6-stage countercurrent extraction is performed, and the extraction phase ratio (O / A) is 10:1, so that rubidium is transferred to the organic phase to obtain a loaded organic phase 3 and a raffinate 3, at which the rubidium concentration of the raffinate is 3.4 g / L, the cesium concentration is 0.8 mg / L, the rubidium extraction rate is 95.3%, and the cesium extraction rate is 80%. The obtained raffinate 3 is combined with the aqueous phase 1 before extraction and enters step (2);
[0071] Step (8): The loaded organic phase 3 obtained in step (7) is mixed with 1.3 mol / L nitric acid, and 6-stage countercurrent washing of potassium and stripping of rubidium (5-stage potassium washing and 1-stage stripping of rubidium) is performed, wherein the washing potassium phase ratio (O / A) is 45:1, and the stripping rubidium phase ratio (O / A) is 9:1, and the pH value of the water phase outlet of the 6th stripping section is set to 1.5. The 6th stripping is opened to obtain an unloaded organic phase 3 and a pure rubidium stripping solution (containing 107 g / L rubidium, 7 mg / L potassium, and 10 mg / L cesium). The unloaded organic phase 3 obtained is returned to step (7).
[0072] In summary, the present invention provides a new method for extracting and separating rubidium and cesium from lithium precipitation mother liquor, which uses lithium precipitation mother liquor as raw material, co-extracts rubidium and cesium after adjusting the pH, and then obtains rubidium-rich solution and pure cesium stripping solution through multi-stage countercurrent washing / stripping. The obtained rubidium-rich solution is subjected to deep separation of rubidium and cesium, and then rubidium potassium is separated to obtain pure rubidium stripping solution. The rubidium stripping solution and cesium stripping solution obtained by this method can be used to prepare rubidium salt and cesium salt products with a purity of more than 99.9%. At the same time, the use of large-scale washing and stripping not only reduces the amount of water used for washing, but also produces a high-concentration stripping solution with a rubidium or cesium concentration greater than 1.25 mol / L.
[0073] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.
Claims
1. A method for extracting and separating rubidium and cesium, characterized in that: The following steps are involved: Step (1): adjusting the alkalinity of the raw material solution containing rubidium and cesium to 0.6-1.0 mol / L to obtain a pre-extraction aqueous phase 1; Step (2): mixing the unloaded organic phase 1 with the pre-extraction aqueous phase 1 obtained in step (1), and performing multi-stage countercurrent extraction to transfer the rubidium and cesium into the organic phase, thereby obtaining a loaded organic phase 1 and a raffinate 1; Step (3): the loaded organic phase 1 obtained in step (2) is mixed with an acidic solution, and multi-stage countercurrent washing of potassium, washing of rubidium and stripping of cesium are performed in sequence, so that the pH range of the stripping solution in the last stage is 0.4-0.8, thereby obtaining an unloaded organic phase 2, a rubidium-rich solution and a pure cesium stripping solution; Step (4): adjusting the alkalinity of the rubidium-rich solution obtained in step (3) to 0.2-0.4 mol / L to obtain a pre-extraction aqueous phase 2; Step (5): the unloaded organic phase 2 obtained in step (3) is mixed with the aqueous phase 2 before extraction obtained in step (4), and multi-stage countercurrent extraction is performed to transfer cesium into the organic phase to obtain a loaded organic phase 2 and a raffinate 2. The loaded organic phase 2 obtained is combined with the loaded organic phase 1 to enter step (3); Step (6): adjusting the alkalinity of the raffinate 2 obtained in step (5) to 0.6-1.0 mol / L to obtain a pre-extraction aqueous phase 3; Step (7): the unloaded organic phase 1 is mixed with the pre-extraction aqueous phase 3 obtained in step (6), and multi-stage countercurrent extraction is performed to transfer rubidium into the organic phase to obtain a loaded organic phase 3 and a raffinate 3. The raffinate 3 is combined with the pre-extraction aqueous phase 1 and enters step (2); Step (8): The loaded organic phase 3 obtained in step (7) is mixed with an acidic solution, and multi-stage countercurrent washing of potassium and stripping of rubidium is performed, so that the pH range of the stripping solution in the last stage is 1.0-1.5, to obtain an unloaded organic phase 3 and a pure rubidium stripping solution, and the unloaded organic phase 3 obtained is returned to step (7).
2. The method for extracting and separating rubidium and cesium according to claim 1, characterized in that: In step (2), the empty organic phase 1 is composed of 4-tert-butyl-2-(α-methylbenzyl)phenol and a diluent; and the volume fraction of 4-tert-butyl-2-(α-methylbenzyl)phenol in the empty organic phase 1 is 20% to 35%; The diluent is one or both of kerosene and xylene.
3. The method for extracting and separating rubidium and cesium according to claim 1, characterized in that: In step (2), the extraction ratio of the empty organic phase 1 to the aqueous phase 1 before extraction is (3-5):1; and the extraction stages of the multi-stage countercurrent extraction are 4-6 stages.
4. The method for extracting and separating rubidium and cesium according to claim 1, characterized in that: In step (3), the multi-stage countercurrent washing potassium has a relative R(O / A) ratio of (85-100):1; The relative ratio R(O / A) of washed rubidium is (18~22):1; The relative ratio R(O / A) of cesium stripping is (10~15):1; The obtained empty organic phase 2 is returned to step (2) and step (5) for repeated use.
5. The method for extracting and separating rubidium and cesium according to claim 1, characterized in that: In step (3) and step (8), the acidic solution is 0.8-1.3 mol / L hydrochloric acid, nitric acid or sulfuric acid.
6. The method for extracting and separating rubidium and cesium according to claim 1, characterized in that: In step (5), the extraction ratio of the empty organic phase 2 to the aqueous phase 2 before extraction is (0.9-1.2):1; and the extraction stages of the multi-stage countercurrent extraction are 8-11 stages.
7. The method for extracting and separating rubidium and cesium according to claim 1, characterized in that: In step (7), the extraction ratio of the empty organic phase 1 to the aqueous phase 3 before extraction is (10-13):1; and the extraction stages of the multi-stage countercurrent extraction are 6-9 stages.
8. The method for extracting and separating rubidium and cesium according to claim 1, characterized in that: In step (8), the relative R(O / A) of the multi-stage countercurrent washing of potassium is (45-54):1; the relative R(O / A) of the stripping of rubidium is (9-13):
1.
9. The method for extracting and separating rubidium and cesium according to claim 1, characterized in that: In step (1), the raw material solution is derived from lithium precipitation mother liquor.