A method for the preparation of single rubidium cesium salt by intensifying separation of rubidium cesium from lithium precipitation solution with synergistic extractant

Abstract

This invention provides a synergistic extractant and a method for enhancing the separation of rubidium and cesium from lithium precipitation solution to prepare single rubidium and cesium salts, belonging to the field of separation and extraction technology. The invention provides a synergistic extractant comprising 2-ethylhexylphosphonic acid mono-(2-ethylhexyl) and 4-tert-butyl-2-(α-methylbenzyl)phenol, wherein the molar ratio of 2-ethylhexylphosphonic acid mono-(2-ethylhexyl) and 4-tert-butyl-2-(α-methylbenzyl)phenol is 0.1–0.6:1. The synergistic extractant of this invention improves the extraction efficiency of rubidium and cesium, reduces costs, and achieves the extraction of rubidium and cesium under low alkalinity conditions, avoiding the difficulties in phase separation caused by emulsification of the extraction system due to high alkalinity and the consumption of large amounts of acid during back-extraction.

Description

Technical Field

[0001] This invention relates to the field of separation and extraction technology, and in particular to a synergistic extractant and a method for enhancing the separation of rubidium and cesium from lithium precipitation liquid to prepare single rubidium and cesium salts. Background Technology

[0002] Lepidolite contains various valuable metals, mainly lithium, rubidium, and cesium. Current processes primarily extract lithium from lepidolite, with limited research on the extraction of other valuable metals such as rubidium and cesium, resulting in a significant waste of these resources. Chinese patent CN102828052A provides a method for separating potassium, rubidium, and cesium sulfate from lepidolite raw materials after lithium extraction, recovering and extracting potassium, rubidium, and cesium sulfate salts separately. While this method recovers the valuable metals rubidium and cesium, it does not yield individual rubidium and cesium salts, leading to low utilization of these resources.

[0003] Existing methods for separating rubidium and cesium mainly include precipitation, ion exchange, and extraction. Compared with ion exchange and precipitation, extraction has the advantages of simple process and high extraction rate. Extraction is currently the primary method used for separating and extracting rubidium and cesium.

[0004] Extractants for rubidium and cesium separation mainly include phenolic alcohols, crown ethers, and borides. The primary phenolic alcohol is 4-tert-butyl-2-(α-methylbenzyl)phenol (t-BAMBP). Crown ether extractants have only been studied in the laboratory and lack industrial application. t-BAMBP exhibits selectivity for rubidium, cesium, potassium, sodium, and lithium, making it a commonly used extractant in rubidium and cesium extraction. However, this extractant has several drawbacks: large quantities are required, and t-BAMBP is expensive (approximately 500,000 to 800,000 RMB / ton), significantly increasing the cost of rubidium and cesium extraction. Furthermore, t-BAMBP extraction requires strongly alkaline conditions, leading to severe emulsification that complicates phase separation, and the back-extraction process consumes a large amount of acid.

[0005] Since rubidium, cesium, lithium, sodium, and potassium belong to the same group of alkali metal elements, elements in the same group have similar chemical properties. The closer the elements are in the periodic table, the smaller the difference in ionic radius, and the same number of valence electrons. Therefore, the separation and extraction of rubidium and cesium are most severely affected by potassium. Generally, potassium needs to be removed before separating rubidium and cesium, which increases costs. For example, Chinese patent CN115180640A proposes a method for extracting rubidium and cesium salts from lithium-extracting solution of lepidolite. This method uses the lithium-extracting solution of lepidolite as raw material, first removes potassium and sodium impurities, and then introduces high-purity carbon dioxide gas during the extraction process. Rubidium and cesium are extracted under weakly acidic conditions. Then, back-extraction is performed to finally obtain rubidium carbonate and cesium carbonate. The process for extracting rubidium and cesium salts is long and costly.

[0006] Moreover, the existing technology for preparing single rubidium and cesium salts generally adopts a two-stage extraction method. For example, Chinese patent CN115124054A proposes a first extraction to separate the cesium-loaded organic phase and the rubidium salt solution in the first extraction residue, followed by a first back-extraction and crystallization separation of the cesium-loaded organic phase to obtain the cesium salt, and an alkalization of the rubidium salt solution followed by a second extraction to separate the rubidium-loaded organic phase, followed by a second back-extraction and crystallization separation of the rubidium-loaded organic phase to obtain the rubidium salt.

[0007] Therefore, how to overcome the defects of extractants, enhance the extraction effect, shorten the process, reduce costs, and provide a method to enhance the separation of rubidium and cesium to prepare single rubidium and cesium salt products has become an urgent problem to be solved in the industry. Summary of the Invention

[0008] In view of this, the object of the present invention is to provide a synergistic extractant and a method for enhancing the separation of rubidium and cesium from lithium precipitation solution to prepare single rubidium and cesium salts. The synergistic extractant of the present invention improves the extraction efficiency of rubidium and cesium, reduces costs, and enables the extraction of rubidium and cesium under low alkalinity conditions, avoiding the difficulties in phase separation caused by emulsification of the extraction system due to high alkalinity and the consumption of a large amount of acid during the back-extraction process.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0010] The present invention provides a synergistic extractant comprising 2-ethylhexylphosphonic acid mono-(2-ethylhexyl) and 4-tert-butyl-2-(α-methylbenzyl)phenol, wherein the molar ratio of 2-ethylhexylphosphonic acid mono-(2-ethylhexyl) and 4-tert-butyl-2-(α-methylbenzyl)phenol is 0.1 to 0.6:1.

[0011] Preferably, the molar ratio of 2-ethylhexylphosphonic acid mono-(2-ethylhexyl) and 4-tert-butyl-2-(α-methylbenzyl)phenol is 0.3 to 0.4:1.

[0012] This invention also provides a method for preparing single rubidium-cesium salts by enhanced separation of rubidium and cesium from lithium precipitation solution, comprising the following steps:

[0013] The pH value of the lithium mica precipitation solution was adjusted to 8-10 to obtain the feed solution;

[0014] The synergistic extractant is mixed with a diluent to obtain an extraction solution; the synergistic extractant is the synergistic extractant described in the above technical solution;

[0015] The feed solution is subjected to multi-stage countercurrent extraction and washing using the extraction solution to obtain a cesium-rich organic phase and a rubidium-rich washing solution;

[0016] The cesium-rich organic phase was back-extracted to obtain a cesium-rich back-extract.

[0017] The cesium-rich back-extraction solution was concentrated to obtain a single cesium salt product;

[0018] The rubidium-rich washing solution was concentrated to obtain a single rubidium salt product.

[0019] Preferably, the extraction conditions for the multi-stage countercurrent extraction are: an extraction ratio of O / A of 0.5 to 3:1 to 1.5, and an extraction stage number n of 4 to 7.

[0020] Preferably, the washing conditions are as follows: the washing ratio O / A is 1-3:1-1.5, the number of washing stages m is 6-10, the cesium-rich organic phase is obtained at the outlet of the washing section, and the rubidium-rich washing liquid is obtained in stages m-2 to m-4.

[0021] Preferably, the washing solution is a sodium hydroxide solution.

[0022] Preferably, the concentration of the sodium hydroxide solution is 0.01–0.1 mol / L.

[0023] Preferably, the O / A ratio of the back-extraction is 2-5:1-1.5, and the number of back-extraction stages is 1-3.

[0024] Preferably, the extractant for back-extraction is dilute sulfuric acid, and the concentration of the dilute sulfuric acid is 0.1 to 0.5 mol / L.

[0025] Preferably, the lithium mica precipitated liquid is obtained by sequentially processing lithium mica through roasting, leaching, purification and lithium precipitation processes.

[0026] The present invention provides a synergistic extractant comprising 2-ethylhexylphosphonic acid mono-(2-ethylhexyl) and 4-tert-butyl-2-(α-methylbenzyl)phenol, wherein the molar ratio of 2-ethylhexylphosphonic acid mono-(2-ethylhexyl) and 4-tert-butyl-2-(α-methylbenzyl)phenol is 0.1 to 0.6:1.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] This invention provides a synergistic extractant for separating rubidium and cesium from lithium precipitation liquid. The synergistic extractant improves the extraction efficiency of rubidium and cesium, reduces costs, and can achieve the extraction of rubidium and cesium under low alkalinity conditions, avoiding the difficulties in phase separation caused by emulsification of the extraction system due to high alkalinity and the consumption of a large amount of acid during the back-extraction process.

[0029] This invention also provides a method for preparing single rubidium-cesium salts by enhanced separation of rubidium and cesium from lithium precipitation liquid. This method is a short-process extraction and separation method for preparing single rubidium-cesium salts from lithium precipitation liquid. This method does not require potassium and sodium impurity removal treatment of the lithium mica post-lithium precipitation liquid. Moreover, the extraction and washing are connected in series. In the washing section, a cesium-rich organic phase and a rubidium-rich washing liquid are obtained. This eliminates the need for the cumbersome process of first extracting cesium and then extracting rubidium from the raffinate, greatly reducing operating costs. This invention completely separates rubidium and cesium from the lithium precipitation liquid, and the prepared single rubidium-cesium product has high purity and high rubidium-cesium resource utilization rate, thus improving the comprehensive utilization rate of lithium mica. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of multi-stage countercurrent extraction and washing. Detailed Implementation

[0031] The present invention provides a synergistic extractant comprising 2-ethylhexylphosphonic acid mono-(2-ethylhexyl) (P507) and 4-tert-butyl-2-(α-methylbenzyl)phenol (t-BAMBP), wherein the molar ratio of 2-ethylhexylphosphonic acid mono-(2-ethylhexyl) and 4-tert-butyl-2-(α-methylbenzyl)phenol is 0.1 to 0.6:1.

[0032] In this invention, the molar ratio of 2-ethylhexylphosphonic acid mono-(2-ethylhexyl) and 4-tert-butyl-2-(α-methylbenzyl)phenol is preferably 0.3 to 0.4:1, more preferably 0.3:1 or 0.4:1.

[0033] The present invention does not impose any particular limitation on the preparation method of the synergistic extractant; it can be prepared by a composition preparation method well known to those skilled in the art.

[0034] The present invention also provides the application of the synergistic extractant described in the above technical solution in the separation of rubidium and cesium.

[0035] This invention also provides a method for preparing single rubidium-cesium salts by enhanced separation of rubidium and cesium from lithium precipitation solution, comprising the following steps:

[0036] The pH value of the lithium mica precipitation solution was adjusted to 8-10 to obtain the feed solution;

[0037] The synergistic extractant is mixed with a diluent to obtain an extraction solution; the synergistic extractant is the synergistic extractant described in the above technical solution;

[0038] The feed solution is subjected to multi-stage countercurrent extraction and washing using the extraction solution to obtain a cesium-rich organic phase and a rubidium-rich washing solution;

[0039] The cesium-rich organic phase was back-extracted to obtain a cesium-rich back-extract.

[0040] The cesium-rich back-extraction solution was concentrated to obtain a single cesium salt product;

[0041] The rubidium-rich washing solution was concentrated to obtain a single rubidium salt product.

[0042] The present invention adjusts the pH value of the lithium mica precipitation solution to 8-10 to obtain the feed solution.

[0043] The present invention preferably uses an alkali to adjust the pH value to 8-10, more preferably 9. The alkali is preferably sodium hydroxide or potassium hydroxide. The present invention does not have a special limitation on the amount of alkali used, as long as it can ensure that the pH value is adjusted to 8-10.

[0044] In this invention, both P507 and t-BAMBP in the synergistic extractant are acidic extractants. The extraction mechanism of acidic extractants is that the hydrogen ions of the extractant exchange with the metal ions in the solution, thereby extracting the metal ions from the aqueous phase to the organic phase. Adjusting the pH of the lithium mica precipitation solution to alkaline conditions can promote the exchange of hydrogen ions with metal ions.

[0045] In this invention, the preferred content range of each element in the lithium mica precipitation solution is: lithium 1.08-5 g / L, rubidium 11-15 g / L, cesium 1-5 g / L, potassium 30-50 g / L, and sodium 30-50 g / L.

[0046] In this invention, the lithium mica precipitated liquid is preferably obtained by sequentially processing lithium mica through roasting, leaching, purification and lithium precipitation processes.

[0047] In this invention, the calcination process preferably includes the addition of a composite sulfate, and the mass ratio of the lepidolite to the composite sulfate is preferably 1:0.5 to 0.7.

[0048] In this invention, the composite sulfate preferably includes calcium sulfate and magnesium sulfate.

[0049] In this invention, the roasting temperature is preferably 850-900°C, and the roasting time is preferably 1-2 hours.

[0050] In this invention, the leaching time is preferably 0.5 to 1 hour, and the liquid-to-solid ratio (g / g) is preferably 2 to 3:1.

[0051] In this invention, the purification is preferably carried out by adjusting the pH value with sodium hydroxide, and filtering out impurities at pH = 8 and 12 respectively.

[0052] In this invention, the lithium precipitation process preferably involves concentrating the purified liquid obtained from the purification process to a lithium ion concentration of 12-14 g / L, and then adding sodium carbonate to precipitate lithium. The molar amount of sodium carbonate is preferably 1.05-1.2 times the lithium content.

[0053] The present invention mixes a synergistic extractant with a diluent to obtain an extraction solution; the synergistic extractant is the synergistic extractant described in the above technical solution.

[0054] In this invention, the diluent preferably includes one or more of sulfonated kerosene, xylene, and cyclohexane, more preferably sulfonated kerosene.

[0055] In this invention, the concentration of the co-extractant in the extraction solution is preferably 0.5 to 1.5 mol / L, more preferably 1 mol / L.

[0056] In this invention, the diluent is used to reduce the viscosity of the synergistic extractant, improve phase separation performance, and reduce the loss of the synergistic extractant, so as to achieve a more ideal extraction rate and extraction selectivity.

[0057] After obtaining the feed solution and the extraction solution, the present invention uses the extraction solution to perform multi-stage countercurrent extraction and washing on the feed solution to obtain a cesium-rich organic phase and a rubidium-rich washing solution.

[0058] In this invention, the preferred extraction conditions for the multi-stage countercurrent extraction are: an extraction ratio of O / A of 0.5 to 3:1 to 1.5, more preferably 2 to 3:1, and an extraction stage number n of 4 to 7, more preferably 5.

[0059] In this invention, the washing conditions are preferably: the washing ratio O / A is 1-3:1-1.5, more preferably 2-3:1, the number of washing stages m is 6-10, more preferably 9, and the cesium-rich organic phase is preferably obtained at the outlet of the washing section, and the rubidium-rich washing liquid is obtained in stages m-2 to m-4, more preferably in stage m-3.

[0060] In this invention, the washing liquid is preferably a sodium hydroxide solution.

[0061] In this invention, the concentration of the sodium hydroxide solution is preferably 0.01 to 0.1 mol / L, more preferably 0.04 to 0.06 mol / L, and most preferably 0.05 mol / L.

[0062] Figure 1 This is a schematic diagram of a multi-stage countercurrent extraction and washing process, including a washing section and an extraction section.

[0063] In this invention, rubidium is mainly present in the aqueous phase, while cesium is almost entirely in the organic phase. Cesium in the organic phase needs to be back-extracted before it can be concentrated to obtain a single salt product. Rubidium in the aqueous phase can be directly concentrated without back-extraction.

[0064] After obtaining the cesium-rich organic phase, the present invention back-extracts the cesium-rich organic phase to obtain a cesium-rich back-extract.

[0065] In this invention, the O / A ratio of the back-extraction is preferably 2-5:1-1.5, and the number of back-extraction stages is preferably 1-3, more preferably 2.

[0066] In this invention, the extractant for back-extraction is preferably dilute sulfuric acid, and the concentration of the dilute sulfuric acid is preferably 0.1 to 0.5 mol / L.

[0067] After obtaining the cesium-rich back-extraction solution, the present invention concentrates the cesium-rich back-extraction solution to obtain a single cesium salt product.

[0068] In this invention, the single cesium salt product is preferably cesium sulfate.

[0069] In this invention, the concentration is preferably evaporation. This invention does not impose any special limitations on the specific parameters of the concentration, and any method known to those skilled in the art can be used.

[0070] After obtaining the rubidium-rich washing solution, the present invention concentrates the rubidium-rich washing solution to obtain a single rubidium salt product.

[0071] In this invention, the single rubidium salt product is preferably rubidium sulfate.

[0072] In this invention, the concentration is preferably evaporation. This invention does not impose any special limitations on the specific parameters of the concentration, and any method known to those skilled in the art can be used.

[0073] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0074] The composition of the lithium-precipitated liquid from a certain lepidolite used in the examples and comparative examples is shown in Table 1, and it comes from a certain lepidolite lithium extraction section.

[0075] Table 1. Composition of the lithium-precipitated solution from lepidolite

[0076] Concentration (g / L) 1.08 35.87 36.85 12.64 4.68 3.5

[0077] Example 1

[0078] 1. Prepare the extraction solution. The molar ratio of the co-extractant P507 to t-BAMBP is 0.3:1. Dilute the co-extractant with sulfonated kerosene to a concentration of 1 mol / L (calculated by the amount of extractant).

[0079] 2. Adjust the pH value of the lithium precipitation solution by using sodium hydroxide to adjust the pH value to 9 to obtain the feed solution.

[0080] 3. According to Figure 1 The process shown involves multi-stage countercurrent extraction and washing of the feed solution using an extraction solution. The extraction conditions are: an extraction ratio (O / A) of 2:1 and 5 extraction stages (n). The washing conditions are: an extraction ratio (O / A) of 2:1 and 9 washing stages (m). The washing solution is a 0.04 mol / L sodium hydroxide solution. After reaching equilibrium, a cesium-rich organic phase is obtained at the outlet of the washing section, and a rubidium-rich washing solution is obtained in the 6th stage of the washing section.

[0081] 4. Back-extraction: Using dilute sulfuric acid as the back-extraction agent, with a concentration of 0.5 mol / L, the cesium-rich organic phase obtained in step 3 is back-extracted. The back-extraction conditions are: back-extraction ratio (O / A) of 1:1, and 2 back-extraction stages, to obtain a cesium-rich back-extraction solution (cesium sulfate solution).

[0082] 5. Preparation of single cesium salt products: Cesium-rich back-extraction solution is evaporated and concentrated to obtain cesium sulfate product, and rubidium-rich washing solution is evaporated and concentrated to obtain rubidium sulfate product.

[0083] The concentrations of each ion in the cesium-rich back-extraction solution and the rubidium-rich washing solution were measured, and the results are shown in Table 2.

[0084] Table 2. Detection results of cesium-rich back-extraction solution and rubidium-rich washing solution in Example 1.

[0085] Cesium-rich back-extraction solution (g / L) <0.001 <0.001 0.003 0.004 4.53 Rubidium-rich detergent (g / L) <0.001 <0.001 0.018 10.58 0.008

[0086] 6. Product Testing: The purity of cesium sulfate is 99.8%, and the purity of rubidium sulfate is 99.2%.

[0087] Example 2

[0088] 1. Prepare the extraction solution. The molar ratio of the co-extractant P507 to t-BAMBP is 0.4:1. Dilute the co-extractant with sulfonated kerosene to a concentration of 1 mol / L (calculated by the amount of extractant).

[0089] 2. Adjust the pH value of the lithium precipitation solution by using sodium hydroxide to adjust the pH value to 10 to obtain the feed solution.

[0090] 3. According to Figure 1 The process shown involves multi-stage countercurrent extraction and washing of the feed solution using an extraction solution. The extraction conditions are: an extraction ratio (O / A) of 2:1 and 4 extraction stages (n). The washing conditions are: an extraction ratio (O / A) of 2:1 and 9 washing stages (m). The washing solution is a 0.05 mol / L sodium hydroxide solution. After reaching equilibrium, a cesium-rich organic phase is obtained at the outlet of the washing section, and a rubidium-rich washing solution is obtained in the 7th stage of the washing section.

[0091] 4. Back-extraction: Using dilute sulfuric acid as the back-extraction agent, with a concentration of 0.5 mol / L, the cesium-rich organic phase obtained in step 3 is back-extracted. The back-extraction conditions are: back-extraction ratio (O / A) of 1:1, and 2 back-extraction stages, to obtain a cesium-rich back-extraction solution (cesium sulfate solution).

[0092] 5. Preparation of single cesium salt products: Cesium-rich back-extraction solution is evaporated and concentrated to obtain cesium sulfate product, and rubidium-rich washing solution is evaporated and concentrated to obtain rubidium sulfate product.

[0093] The concentrations of each ion in the cesium-rich back-extraction solution and the rubidium-rich washing solution were measured, and the results are shown in Table 3.

[0094] Table 3. Detection results of cesium-rich back-extraction solution and rubidium-rich washing solution in Example 2.

[0095] Cesium-rich back-extraction solution (g / L) <0.001 <0.001 0.002 0.005 4.56 Rubidium-rich detergent (g / L) <0.001 <0.001 0.012 10.45 0.006

[0096] 6. Product Testing: The purity of cesium sulfate is 99.8%, and the purity of rubidium sulfate is 99.3%.

[0097] Example 3

[0098] 1. Prepare the extraction solution. The molar ratio of the co-extractant P507 to t-BAMBP is 0.5:1. Dilute the co-extractant with sulfonated kerosene to a concentration of 1 mol / L (calculated by the amount of extractant).

[0099] 2. Adjust the pH value of the lithium precipitation solution by using sodium hydroxide to adjust the pH value to 10 to obtain the feed solution.

[0100] 3. According to Figure 1 The process shown involves multi-stage countercurrent extraction and washing of the feed solution using an extraction solution. The extraction conditions are: an extraction ratio (O / A) of 3:1 and 4 extraction stages (n). The washing conditions are: an extraction ratio (O / A) of 2.5:1 and 9 washing stages (m). The washing solution is a 0.06 mol / L sodium hydroxide solution. After reaching equilibrium, a cesium-rich organic phase is obtained at the outlet of the washing section, and a rubidium-rich washing solution is obtained in the 6th stage of the washing section.

[0101] 4. Back-extraction: Using dilute sulfuric acid as the back-extraction agent, with a concentration of 0.5 mol / L, the cesium-rich organic phase obtained in step 3 is back-extracted. The back-extraction conditions are: back-extraction ratio (O / A) of 1:1, and 2 back-extraction stages, to obtain a cesium-rich back-extraction solution (cesium sulfate solution).

[0102] 5. Preparation of single cesium salt products: Cesium-rich back-extraction solution is evaporated and concentrated to obtain cesium sulfate product, and rubidium-rich washing solution is evaporated and concentrated to obtain rubidium sulfate product.

[0103] The concentrations of each ion in the cesium-rich back-extraction solution and the rubidium-rich washing solution were measured, and the results are shown in Table 4.

[0104] Table 4. Detection results of cesium-rich back-extraction solution and rubidium-rich washing solution in Example 3.

[0105] Cesium-rich back-extraction solution (g / L) <0.001 <0.001 0.003 0.006 4.49 Rubidium-rich detergent (g / L) <0.001 <0.001 0.019 10.42 0.005

[0106] 6. Product Testing: The purity of cesium sulfate is 99.6%, and the purity of rubidium sulfate is 99.2%.

[0107] As can be seen from Examples 1 to 3, the extraction method that uses a synergistic extractant and combines the extraction and washing stages can effectively separate rubidium and cesium in the lithium precipitation solution, and the purity of the obtained cesium sulfate and rubidium sulfate products is greater than 99%.

[0108] Comparative Example

[0109] After adjusting the pH of the lithium precipitation solution, sodium hydroxide was used to adjust the pH to 8 to obtain the feed solution.

[0110] Three organic phases with different compositions were prepared, numbered 1, 2 and 3. Organic phase 1 was 1 mol / L of P507, organic phase 2 was 1 mol / L of t-BAMBP, and organic phase 3 was 1 mol / L of a synergistic extractant (the molar ratio of P507 to t-BAMBP was 0.4:1). The solvent for all phases was sulfonated kerosene.

[0111] Single-stage extraction separation experiment: The above three organic phases were subjected to single-stage extraction with the aqueous phase at a ratio of 1:1. The extraction time was 5 min and the temperature was 25℃. The experimental results are shown in Table 5. As shown in Table 5, under single-stage extraction conditions, the extraction rates of rubidium, cesium, potassium, sodium, and lithium were all very low when P507 was used alone. When t-BAMBP was used alone, the extraction rates of cesium were 75.0%, rubidium 35.7%, potassium 8.3%, and sodium 0.5%. With the use of a synergistic extractant, the extraction rates of both cesium and rubidium increased. The single-stage extraction rate of cesium reached 92.7%, and the extraction rate of rubidium reached 66.4%, significantly improving the extraction rates of both rubidium and cesium. The extraction rate of potassium was 5.6%, which was lower than that of t-BAMBP used alone. This indicates that the synergistic extractant composed of P507 and t-BAMBP can significantly enhance the extraction effect of rubidium and cesium, reduce the extraction effect of other ions, and selectively extract rubidium and cesium from the lithium precipitation solution.

[0112] Table 5. Single-stage extraction effect of different extractants

[0113] Cesium extraction rate (%) 5.5％ 75.0％ 92.7％ Rubidium extraction rate (%) 3.6％ 35.7％ 66.4％ Potassium extraction rate (%) 4.8％ 8.3％ 5.6％ Sodium extraction rate (%) 5.7％ 0.5％ 0.6％ Lithium extraction rate (%) 2.6％ 0.7％ 0.7％

[0114] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing single rubidium-cesium salts by enhanced separation of rubidium and cesium from lithium precipitation solution, characterized in that, The specific steps are as follows: The pH value of the lithium mica precipitation solution was adjusted to 8-10 to obtain the feed solution; The synergistic extractant and diluent are mixed to obtain an extraction solution; the synergistic extractant is specifically 2-ethylhexylphosphonic acid mono-(2-ethylhexyl) and 4-tert-butyl-2-(α-methylbenzyl)phenol, and the molar ratio of 2-ethylhexylphosphonic acid mono-(2-ethylhexyl) and 4-tert-butyl-2-(α-methylbenzyl)phenol is 0.3~0.4:1; the concentration of the synergistic extractant in the extraction solution is 1 mol / L; the diluent is sulfonated kerosene. The feed solution is subjected to multi-stage countercurrent extraction and washing using the extraction solution to obtain a cesium-rich organic phase and a rubidium-rich washing solution; The cesium-rich organic phase is back-extracted to obtain a cesium-rich back-extract; the extractant for back-extraction is dilute sulfuric acid, and the concentration of the dilute sulfuric acid is 0.1~0.5 mol / L. The cesium-rich back-extraction solution was concentrated to obtain a single cesium salt product; The rubidium-rich washing solution was concentrated to obtain a single rubidium salt product.

2. The method according to claim 1, characterized in that, The extraction conditions for the multi-stage countercurrent extraction are: an extraction ratio of O / A of 0.5~3:1~1.5, and an extraction stage number n of 4~7.

3. The method according to claim 1, characterized in that, The washing conditions are as follows: the washing ratio O / A is 1~3:1~1.5, the number of washing stages m is 6~10, the cesium-rich organic phase is obtained at the outlet of the washing section, and the rubidium-rich washing liquid is obtained in stages m-2~m-4.

4. The method according to claim 1 or 3, characterized in that, The washing solution is a sodium hydroxide solution.

5. The method according to claim 4, characterized in that, The concentration of the sodium hydroxide solution is 0.01~0.1 mol / L.

6. The method according to claim 1, characterized in that, The back-extraction ratio O / A is 2~5:1~1.5, and the number of back-extraction stages is 1~3.

7. The method according to claim 1, characterized in that, The lithium-precipitated liquid from lepidolite is obtained by sequentially roasting, leaching, purifying, and precipitating lepidolite.

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