Method for extracting rubidium and cesium salts from environment-friendly lepidolite lithium precipitation mother liquor

Abstract

The invention discloses a method for extracting rubidium and cesium salts from lepidolite lithium precipitation mother liquor, and particularly relates to the following steps: acidifying the lithium precipitation mother liquor, then alkalizing, concentrating and filtering to remove most of potassium and sodium salts after the pH reaches the requirement, then extracting and separating rubidium and cesium, comprehensively utilizing rubidium and cesium valuable metal elements, and generating considerable economic benefits. The method is short in technological process, simple to operate, high in production continuity, large in treatment capacity, low in production cost and high in total recovery rate, wastewater returns to a lithium precipitation workshop, internal circulation is achieved in the process, and wastewater discharge is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of lithium precipitation mother liquor treatment, and in particular to a method for extracting rubidium-cesium salt from an environmentally friendly lithium precipitation mother liquor of lepidolite. Background Art

[0002] China is rich in rubidium and cesium resources. Rubidium and cesium resources in solid form are mainly found in lepidolite and cesium garnet; rubidium and cesium resources in liquid form are mainly distributed in salt lakes and geothermal waters in Qinghai, Tibet and other places. Regardless of whether the initial output is solid ore or liquid ore, the separation of rubidium and cesium can only be achieved in aqueous solution. Rubidium and cesium are rare non-ferrous metals with very small reserves worldwide. Both elements are typical dispersed elements and rarely form separate minerals. They are often doped in lithium ores. At present, most manufacturers of ore extraction lithium process use lepidolite as the main ore. Extracting and separating rubidium and cesium elements from lepidolite lithium precipitation mother liquor can generate considerable economic benefits. At present, the methods for separating and extracting rubidium and cesium mainly include precipitation, ion exchange and solvent extraction. Among them, the precipitation method has a long process, low recovery rate and low product purity, and is mainly used for analytical testing or crude product purification; the ion exchange method has a simple process, good selectivity and high recovery rate, but the exchange capacity of the ion exchanger is relatively small, which is suitable for the separation and extraction of low concentrations of rubidium and cesium; the solvent extraction method has a large processing capacity, good separation effect, and is easy to realize continuous operation. It is a separation and extraction technology that has been studied more and developed faster. Summary of the invention

[0003] To this end, the present invention provides an environmentally friendly method for extracting rubidium-cesium salt from lithium-precipitated mother liquor of lepidolite, the steps comprising:

[0004] (1) Add dibenzo-18-crown-6 ether to N,N-dimethylformamide in a reaction kettle, stir for more than 5 minutes, then add glacial acetic acid to the reaction kettle under stirring, stir for more than 20 minutes after the addition is completed, then add concentrated nitric acid to the reaction kettle under stirring, stir for more than 30 minutes after the addition is completed, then seal the reaction kettle, heat to 130±5° C. and keep warm for more than 2 hours, cool to room temperature after the insulation is completed, open the reaction kettle, add palladium carbon catalyst and hydrazine hydrate to the reaction kettle, seal the reaction kettle again after the addition is completed, heat to 120±3° C. and keep warm for more than 1 hour, then naturally cool to room temperature, open the reaction kettle, centrifuge to remove the catalyst, add 4-nitrobenzene isocyanate to the liquid after centrifugation under stirring, stir at room temperature for more than 8 hours after the addition is completed, then remove N,N-dimethylformamide by reduced pressure distillation to obtain an extraction promoter;

[0005] (2) Acidifying the lithium precipitation mother liquor to remove carbonate in the lithium precipitation mother liquor to obtain an acidified liquid; adding alkali to the acidified liquid to adjust the pH to 8-10, then concentrating to precipitate potassium and sodium salt crystals, removing the precipitate by solid-liquid separation to obtain a concentrated solution, then adding alkali to adjust the pH of the concentrated solution to 10-12, adding a primary extractant to the concentrated solution for extraction to obtain a cesium-loaded organic phase and a primary extraction residual liquid; the primary extractant is a mixture of 4-tert-butyl-2-(α-methylbenzyl)phenol, the extraction promoter and sulfonated kerosene; washing, stripping and crystallizing the cesium-loaded organic phase to obtain a cesium salt;

[0006] (3) adding alkali to adjust the pH of the primary extraction residue to 12-14, then adding a secondary extractant for extraction to obtain a rubidium-loaded organic phase and an extracted liquid; the secondary extractant is a mixture of 4-tert-butyl-2-(α-methylbenzyl)phenol, the extraction promoter, N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt and sulfonated kerosene; washing, stripping and crystallizing the rubidium-loaded organic phase to obtain a rubidium salt.

[0007] Furthermore, in the step (1), dibenzo-18-crown-6 ether is added to N,N-dimethylformamide in a mass ratio of dibenzo-18-crown-6 ether:N,N-dimethylformamide=1:50.

[0008] Furthermore, in the step (1), the amounts of the glacial acetic acid, concentrated nitric acid, palladium-carbon catalyst, hydrazine hydrate and 4-nitrobenzene isocyanate added and the amount of dibenzo-18-crown-6 ether added to the reaction kettle are calculated in parts by weight: 1 part of dibenzo-18-crown-6 ether, 14-18 parts of glacial acetic acid, 1-2 parts of concentrated nitric acid, 0.03-0.04 parts of palladium-carbon catalyst, 4-6 parts of hydrazine hydrate, and 0.8-1.6 parts of 4-nitrobenzene isocyanate; wherein the mass percentage of the solute in the concentrated nitric acid is 68%, and the palladium-carbon catalyst is 10% Pd / C.

[0009] Furthermore, in the step (2), the lithium precipitation mother liquor is acidified by adding sulfuric acid with a solute mass percentage of 98% to the lithium precipitation mother liquor to adjust the pH of the mother liquor to 1-2; and the alkali is sodium hydroxide.

[0010] Furthermore, in the step (2), the mass ratio of the components in the primary extractant is 4-tert-butyl-2-(α-methylbenzyl)phenol: extraction promoter: sulfonated kerosene = 2:0.5-0.6:1; the mass ratio of the primary extractant added to the concentrated solution for extraction is primary extractant: concentrated solution = 1-2:1, and the extraction is stirred for 3-5 minutes; the stripping uses sulfuric acid with a solute mass percentage of 98%, and the mass ratio of the added mass of sulfuric acid to the stripping organic phase is stripping organic phase: sulfuric acid = 15:1.

[0011] Furthermore, in the step (3), the mass ratio of the components in the secondary extractant is 4-tert-butyl-2-(α-methylbenzyl)phenol: extraction promoter: N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt: sulfonated kerosene = 3:0.6-0.7:0.2-0.4:2; the mass ratio of the secondary extractant added to the primary extraction residue for extraction is secondary extractant: primary extraction residue = 10:1, and the extraction is stirred for 3-5 minutes; the stripping uses sulfuric acid with a solute mass percentage of 98%, and the mass ratio of the added mass of sulfuric acid to the stripping organic phase is stripping organic phase: sulfuric acid = 15:1.

[0012] The beneficial effect of the present invention is that the method of the present invention can efficiently extract rubidium and cesium elements from lithium mica precipitation mother liquor, comprehensively utilize rubidium and cesium valuable metal elements, reduce resource waste, and generate considerable economic benefits. At present, the prior art discloses a process of simply using 4-tert-butyl-2-(α-methylbenzyl)phenol and sulfonated kerosene, but because 4-tert-butyl-2-(α-methylbenzyl)phenol has a greater extraction effect on potassium, sodium and other ions, an ion competition effect is formed, and part of the extractant resources are occupied by potassium ions and sodium ions, thereby reducing the extraction of the target ion Cs + Ions and Rb + By comparing Example 3 of the present application with the comparative example, it can be seen that by adding the extraction promoter of the present invention, the extraction rate of rubidium and cesium can be further improved. The present invention first introduces a nitro group into dibenzo-18-crown-6 ether, then reductively aminates the nitro group, and then connects the active group to the amino group through 4-nitrobenzene isocyanate, thereby improving the extraction promoter for Cs in the aqueous phase. + Ions and Rb + ion coordination ability, improve the extraction promoter and Cs + Ion, Rb + On the other hand, the selectivity of the extraction promoter to ions is used to reduce the coordination of potassium, sodium and other ions, thereby achieving the separation of target ions and impurity ions. + Ions and Rb + The ions first coordinate with the extraction promoter and enter the oil phase. + Ion, Rb + The coordination ability of the ions is stronger and the complex formed is more stable, so the extraction promoter and Cs + Ion, Rb + The complex of ions is easy to 4-tert-butyl-2-(α-methylbenzyl)phenol and Cs + Ion, Rb + The complex transformation of ions enables the extraction promoter to coordinate Cs in the aqueous phase again.+ Ion, Rb + Ions are recycled. In addition, the extraction of rubidium by the extractant can be improved by adding N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt, which may be due to the fact that N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt can improve the hydrophilicity of the extraction promoter and promote the coordination of the extraction promoter to ions. The process of the present invention is short, simple to operate, strong in production continuity, large in processing capacity, low in production cost, high in total recovery rate, and the wastewater is returned to the lithium precipitation workshop, which is internally circulated in the process and can reduce the discharge of wastewater. DETAILED DESCRIPTION

[0013] The present invention will be further described below in conjunction with the embodiments.

[0014] Example 1

[0015] An environmentally friendly method for extracting rubidium-cesium salt from lithium-precipitated mother liquor of lepidolite, comprising the following steps:

[0016] (1) Add dibenzo-18-crown-6 ether to N,N-dimethylformamide in a reaction kettle, and add dibenzo-18-crown-6 ether to N,N-dimethylformamide in a mass ratio of dibenzo-18-crown-6 ether to N,N-dimethylformamide in a ratio of dibenzo-18-crown-6 ether to N,N-dimethylformamide = 1:50; stir for 5 minutes, then add glacial acetic acid to the reaction kettle under stirring, stir for 20 minutes after the addition is completed, then add concentrated nitric acid to the reaction kettle under stirring, stir for 30 minutes after the addition is completed, then seal the reaction kettle, heat to 130±5°C and keep warm for 2 hours, cool to room temperature after the insulation is completed, open the reaction kettle, add palladium carbon catalyst and hydrazine hydrate to the reaction kettle, seal the reaction kettle again after the addition is completed, heat to 120±3°C and keep warm The mixture was stirred at room temperature for 1 hour, then cooled naturally to room temperature, the reactor was opened, the catalyst was removed by centrifugation, 4-nitrobenzene isocyanate was added to the liquid after centrifugation under stirring, and the mixture was stirred at room temperature for 8 hours after the addition was completed, and then N,N-dimethylformamide was removed by reduced pressure distillation to obtain an extraction promoter; wherein the amount of glacial acetic acid, concentrated nitric acid, palladium-carbon catalyst, hydrazine hydrate and 4-nitrobenzene isocyanate added and the amount of dibenzo-18-crown-6 ether added to the reactor were calculated by weight: 1 part of dibenzo-18-crown-6 ether, 14 parts of glacial acetic acid, 1 part of concentrated nitric acid, 0.03 parts of palladium-carbon catalyst, 4 parts of hydrazine hydrate, and 0.8 parts of 4-nitrobenzene isocyanate; wherein the mass percentage of the solute in the concentrated nitric acid is 68%, and the palladium-carbon catalyst is 10% Pd / C;

[0017] (2) Acidifying the lithium precipitation mother liquor (the components are shown in Table 1) to remove carbonate ions in the lithium precipitation mother liquor and obtain an acidified solution; acidifying the lithium precipitation mother liquor is to add sulfuric acid with a solute mass percentage of 98% to the lithium precipitation mother liquor to adjust the pH of the mother liquor to 2; adding sodium hydroxide to the acidified solution to adjust the pH to 9, and then concentrating. Since the content of potassium and sodium salts is relatively large, it is easier to reach a saturated state first, so part of the potassium and sodium salts are precipitated first, which can remove most of the potassium and sodium salts on the one hand, and enrich the rubidium and cesium in the lithium precipitation mother liquor on the other hand; solid-liquid separation to remove the precipitate to obtain a concentrated solution, and then adding sodium hydroxide to adjust the pH of the concentrated solution to 11, adding a primary extractant to the concentrated solution for extraction, The method comprises the following steps: obtaining a cesium-loaded organic phase and a primary extraction residual liquid; wherein the primary extraction agent is a mixture of 4-tert-butyl-2-(α-methylbenzyl)phenol, the extraction promoter and sulfonated kerosene; wherein the mass ratio of the components in the primary extraction agent is 4-tert-butyl-2-(α-methylbenzyl)phenol: extraction promoter: sulfonated kerosene = 2:0.5:1; wherein the mass ratio of the primary extraction agent added to the concentrated liquid for extraction is the primary extraction agent: concentrated liquid = 1:1, and the extraction is stirred for 5 minutes; washing, stripping and crystallization separation of the cesium-loaded organic phase are performed to obtain a cesium salt; wherein the stripping uses sulfuric acid with a solute mass percentage of 98%, and the mass ratio of the added mass of sulfuric acid to the stripping organic phase is the stripping organic phase: sulfuric acid = 15:1;

[0018] (3) adding sodium hydroxide to adjust the pH of the primary extraction residue to 13, and then adding a secondary extractant to extract to obtain a rubidium-loaded organic phase and an extracted liquid; the secondary extractant is a mixture of 4-tert-butyl-2-(α-methylbenzyl)phenol, the extraction promoter, N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt and sulfonated kerosene; the mass ratio of the components in the secondary extractant is 4-tert-butyl-2-(α-methylbenzyl)phenol: extraction promoter: N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt. -methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt: sulfonated kerosene = 3:0.6:0.2:2; the mass ratio of adding a secondary extractant to the primary extraction residue for extraction is secondary extractant: primary extraction residue = 10:1, and the extraction is stirred for 5 minutes; the rubidium-loaded organic phase is washed, stripped, and crystallized to obtain a rubidium salt; the stripping uses sulfuric acid with a solute mass percentage of 98%, and the mass ratio of the added mass of sulfuric acid to the stripping organic phase is stripping organic phase: sulfuric acid = 15:1.

[0019] Example 2

[0020] An environmentally friendly method for extracting rubidium-cesium salt from lithium-precipitated mother liquor of lepidolite, comprising the following steps:

[0021] (1) Add dibenzo-18-crown-6 ether to N,N-dimethylformamide in a reaction kettle, and add dibenzo-18-crown-6 ether to N,N-dimethylformamide in a mass ratio of dibenzo-18-crown-6 ether to N,N-dimethylformamide in a ratio of dibenzo-18-crown-6 ether to N,N-dimethylformamide = 1:50; stir for 5 minutes, then add glacial acetic acid to the reaction kettle under stirring, stir for 20 minutes after the addition is completed, then add concentrated nitric acid to the reaction kettle under stirring, stir for 30 minutes after the addition is completed, then seal the reaction kettle, heat to 130±5° C. and keep warm for 2 hours, cool to room temperature after the insulation is completed, open the reaction kettle, add palladium carbon catalyst and hydrazine hydrate to the reaction kettle, seal the reaction kettle again after the addition is completed, and heat to 120±3° C. The mixture is kept warm for 1 hour, then cooled naturally to room temperature, the reactor is opened, the catalyst is removed by centrifugation, 4-nitrobenzene isocyanate is added to the liquid after centrifugation under stirring, and after the addition is completed, the mixture is stirred at room temperature for 8 hours, and then N,N-dimethylformamide is removed by reduced pressure distillation to obtain an extraction promoter; wherein the amount of glacial acetic acid, concentrated nitric acid, palladium-carbon catalyst, hydrazine hydrate and 4-nitrobenzene isocyanate added and the amount of dibenzo-18-crown-6 ether added to the reactor are calculated by weight: 1 part of dibenzo-18-crown-6 ether, 16 parts of glacial acetic acid, 1 part of concentrated nitric acid, 0.03 parts of palladium-carbon catalyst, 5 parts of hydrazine hydrate, and 1 part of 4-nitrobenzene isocyanate; wherein the mass percentage of the solute in the concentrated nitric acid is 68%, and the palladium-carbon catalyst is 10% Pd / C;

[0022] (2) Acidifying the lithium precipitation mother liquor (the components are shown in Table 1) to remove carbonate ions in the lithium precipitation mother liquor and obtain an acidified solution; acidifying the lithium precipitation mother liquor is to add sulfuric acid with a solute mass percentage of 98% to the lithium precipitation mother liquor to adjust the pH of the mother liquor to 2; adding sodium hydroxide to the acidified solution to adjust the pH to 9, and then concentrating. Since the content of potassium and sodium salts is relatively large, it is easier to reach a saturated state first, so part of the potassium and sodium salts are precipitated first, which can remove most of the potassium and sodium salts on the one hand, and enrich the rubidium and cesium in the lithium precipitation mother liquor on the other hand; solid-liquid separation to remove the precipitate to obtain a concentrated solution, and then adding sodium hydroxide to adjust the pH of the concentrated solution to 11, adding a primary extractant to the concentrated solution for extraction, The method comprises the following steps: obtaining a cesium-loaded organic phase and a primary extraction residual liquid; wherein the primary extraction agent is a mixture of 4-tert-butyl-2-(α-methylbenzyl)phenol, the extraction promoter and sulfonated kerosene; wherein the mass ratio of the components in the primary extraction agent is 4-tert-butyl-2-(α-methylbenzyl)phenol: extraction promoter: sulfonated kerosene = 2:0.5:1; wherein the mass ratio of the primary extraction agent added to the concentrated liquid for extraction is the primary extraction agent: concentrated liquid = 1:1, and the extraction is stirred for 5 minutes; washing, stripping and crystallization separation of the cesium-loaded organic phase are performed to obtain a cesium salt; wherein the stripping uses sulfuric acid with a solute mass percentage of 98%, and the mass ratio of the added mass of sulfuric acid to the stripping organic phase is the stripping organic phase: sulfuric acid = 15:1;

[0023] (3) adding sodium hydroxide to adjust the pH of the primary extraction residue to 13, and then adding a secondary extractant to extract to obtain a rubidium-loaded organic phase and an extracted liquid; the secondary extractant is a mixture of 4-tert-butyl-2-(α-methylbenzyl)phenol, the extraction promoter, N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt and sulfonated kerosene; the mass ratio of the components in the secondary extractant is 4-tert-butyl-2-(α-methylbenzyl)phenol: extraction promoter: N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt. -methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt: sulfonated kerosene = 3:0.6:0.3:2; the mass ratio of adding a secondary extractant to the primary extraction residue for extraction is secondary extractant: primary extraction residue = 10:1, and the extraction is stirred for 5 minutes; the rubidium-loaded organic phase is washed, stripped, and crystallized to obtain a rubidium salt; the stripping uses sulfuric acid with a solute mass percentage of 98%, and the mass ratio of the added mass of sulfuric acid to the stripping organic phase is stripping organic phase: sulfuric acid = 15:1.

[0024] Example 3

[0025] An environmentally friendly method for extracting rubidium-cesium salt from lithium-precipitated mother liquor of lepidolite, comprising the following steps:

[0026] (1) Add dibenzo-18-crown-6 ether to N,N-dimethylformamide in a reaction kettle, and add dibenzo-18-crown-6 ether to N,N-dimethylformamide in a mass ratio of dibenzo-18-crown-6 ether to N,N-dimethylformamide in a ratio of dibenzo-18-crown-6 ether to N,N-dimethylformamide = 1:50; stir for 5 minutes, then add glacial acetic acid to the reaction kettle under stirring, stir for 20 minutes after the addition is completed, then add concentrated nitric acid to the reaction kettle under stirring, stir for 30 minutes after the addition is completed, then seal the reaction kettle, heat to 130±5°C and keep warm for 2 hours, cool to room temperature after the insulation is completed, open the reaction kettle, add palladium carbon catalyst and hydrazine hydrate to the reaction kettle, seal the reaction kettle again after the addition is completed, heat to 120±3°C and keep warm The mixture was stirred at room temperature for 1 hour, then cooled naturally to room temperature, the reactor was opened, the catalyst was removed by centrifugation, 4-nitrobenzene isocyanate was added to the liquid after centrifugation under stirring, and the mixture was stirred at room temperature for 8 hours after the addition was completed, and then N,N-dimethylformamide was removed by reduced pressure distillation to obtain an extraction promoter; wherein the amount of glacial acetic acid, concentrated nitric acid, palladium-carbon catalyst, hydrazine hydrate and 4-nitrobenzene isocyanate added and the amount of dibenzo-18-crown-6 ether added to the reactor were calculated by weight: 1 part of dibenzo-18-crown-6 ether, 16 parts of glacial acetic acid, 2 parts of concentrated nitric acid, 0.04 parts of palladium-carbon catalyst, 5 parts of hydrazine hydrate, and 1.2 parts of 4-nitrobenzene isocyanate; wherein the mass percentage of the solute in the concentrated nitric acid is 68%, and the palladium-carbon catalyst is 10% Pd / C;

[0027] (2) Acidifying the lithium precipitation mother liquor (the components are shown in Table 1) to remove carbonate ions in the lithium precipitation mother liquor and obtain an acidified solution; acidifying the lithium precipitation mother liquor is to add sulfuric acid with a solute mass percentage of 98% to the lithium precipitation mother liquor to adjust the pH of the mother liquor to 2; adding sodium hydroxide to the acidified solution to adjust the pH to 9, and then concentrating. Since the content of potassium and sodium salts is relatively large, it is easier to reach a saturated state first, so part of the potassium and sodium salts are precipitated first, which can remove most of the potassium and sodium salts on the one hand, and enrich the rubidium and cesium in the lithium precipitation mother liquor on the other hand; solid-liquid separation to remove the precipitate to obtain a concentrated solution, and then adding sodium hydroxide to adjust the pH of the concentrated solution to 11, adding a primary extractant to the concentrated solution for extraction, The method comprises the following steps: obtaining a cesium-loaded organic phase and a primary extraction residual liquid; wherein the primary extraction agent is a mixture of 4-tert-butyl-2-(α-methylbenzyl)phenol, the extraction promoter and sulfonated kerosene; wherein the mass ratio of the components in the primary extraction agent is 4-tert-butyl-2-(α-methylbenzyl)phenol: extraction promoter: sulfonated kerosene = 2:0.6:1; wherein the mass ratio of the primary extraction agent added to the concentrated liquid for extraction is the primary extraction agent: concentrated liquid = 1:1, and the extraction is stirred for 5 minutes; wherein the cesium-loaded organic phase is washed, stripped and crystallized to obtain a cesium salt; wherein the stripping uses sulfuric acid with a solute mass percentage of 98%, and the mass ratio of the added mass of sulfuric acid to the stripping organic phase is the stripping organic phase: sulfuric acid = 15:1;

[0028] (3) adding sodium hydroxide to adjust the pH of the primary extraction residue to 13, and then adding a secondary extractant to extract to obtain a rubidium-loaded organic phase and an extracted liquid; the secondary extractant is a mixture of 4-tert-butyl-2-(α-methylbenzyl)phenol, the extraction promoter, N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt and sulfonated kerosene; the mass ratio of the components in the secondary extractant is 4-tert-butyl-2-(α-methylbenzyl)phenol: extraction promoter: N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt. -methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt: sulfonated kerosene = 3:0.7:0.3:2; the mass ratio of adding a secondary extractant to the primary extraction residue for extraction is secondary extractant: primary extraction residue = 10:1, and the extraction is stirred for 5 minutes; the rubidium-loaded organic phase is washed, stripped, and crystallized to obtain a rubidium salt; the stripping uses sulfuric acid with a solute mass percentage of 98%, and the mass ratio of the added mass of sulfuric acid to the stripping organic phase is stripping organic phase: sulfuric acid = 15:1.

[0029] Example 4

[0030] An environmentally friendly method for extracting rubidium-cesium salt from lithium-precipitated mother liquor of lepidolite, comprising the following steps:

[0031] (1) Add dibenzo-18-crown-6 ether to N,N-dimethylformamide in a reaction kettle, and add dibenzo-18-crown-6 ether to N,N-dimethylformamide in a mass ratio of dibenzo-18-crown-6 ether to N,N-dimethylformamide in a ratio of dibenzo-18-crown-6 ether to N,N-dimethylformamide = 1:50; stir for 5 minutes, then add glacial acetic acid to the reaction kettle under stirring, stir for 20 minutes after the addition is completed, then add concentrated nitric acid to the reaction kettle under stirring, stir for 30 minutes after the addition is completed, then seal the reaction kettle, heat to 130±5°C and keep warm for 2 hours, cool to room temperature after the insulation is completed, open the reaction kettle, add palladium carbon catalyst and hydrazine hydrate to the reaction kettle, seal the reaction kettle again after the addition is completed, heat to 120±3°C and keep warm The mixture was stirred at room temperature for 1 hour, then cooled naturally to room temperature, the reactor was opened, the catalyst was removed by centrifugation, 4-nitrobenzene isocyanate was added to the liquid after centrifugation under stirring, and the mixture was stirred at room temperature for 8 hours after the addition was completed, and then N,N-dimethylformamide was removed by reduced pressure distillation to obtain an extraction promoter; wherein the amount of glacial acetic acid, concentrated nitric acid, palladium-carbon catalyst, hydrazine hydrate and 4-nitrobenzene isocyanate added and the amount of dibenzo-18-crown-6 ether added to the reactor were calculated by weight: 1 part of dibenzo-18-crown-6 ether, 18 parts of glacial acetic acid, 2 parts of concentrated nitric acid, 0.04 parts of palladium-carbon catalyst, 6 parts of hydrazine hydrate, and 1.6 parts of 4-nitrobenzene isocyanate; wherein the mass percentage of the solute in the concentrated nitric acid is 68%, and the palladium-carbon catalyst is 10% Pd / C;

[0032] (2) Acidifying the lithium precipitation mother liquor (the components are shown in Table 1) to remove carbonate ions in the lithium precipitation mother liquor and obtain an acidified solution; acidifying the lithium precipitation mother liquor is to add sulfuric acid with a solute mass percentage of 98% to the lithium precipitation mother liquor to adjust the pH of the mother liquor to 2; adding sodium hydroxide to the acidified solution to adjust the pH to 9, and then concentrating. Since the content of potassium and sodium salts is relatively large, it is easier to reach a saturated state first, so part of the potassium and sodium salts are precipitated first, which can remove most of the potassium and sodium salts on the one hand, and enrich the rubidium and cesium in the lithium precipitation mother liquor on the other hand; solid-liquid separation to remove the precipitate to obtain a concentrated solution, and then adding sodium hydroxide to adjust the pH of the concentrated solution to 11, adding a primary extractant to the concentrated solution for extraction, The method comprises the following steps: obtaining a cesium-loaded organic phase and a primary extraction residual liquid; wherein the primary extraction agent is a mixture of 4-tert-butyl-2-(α-methylbenzyl)phenol, the extraction promoter and sulfonated kerosene; wherein the mass ratio of the components in the primary extraction agent is 4-tert-butyl-2-(α-methylbenzyl)phenol: extraction promoter: sulfonated kerosene = 2:0.6:1; wherein the mass ratio of the primary extraction agent added to the concentrated liquid for extraction is the primary extraction agent: concentrated liquid = 1:1, and the extraction is stirred for 5 minutes; wherein the cesium-loaded organic phase is washed, stripped and crystallized to obtain a cesium salt; wherein the stripping uses sulfuric acid with a solute mass percentage of 98%, and the mass ratio of the added mass of sulfuric acid to the stripping organic phase is the stripping organic phase: sulfuric acid = 15:1;

[0033] (3) adding sodium hydroxide to adjust the pH of the primary extraction residue to 13, and then adding a secondary extractant to extract to obtain a rubidium-loaded organic phase and an extracted liquid; the secondary extractant is a mixture of 4-tert-butyl-2-(α-methylbenzyl)phenol, the extraction promoter, N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt and sulfonated kerosene; the mass ratio of the components in the secondary extractant is 4-tert-butyl-2-(α-methylbenzyl)phenol: extraction promoter: N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt. -methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt: sulfonated kerosene = 3:0.7:0.4:2; the mass ratio of adding a secondary extractant to the primary extraction residue for extraction is secondary extractant: primary extraction residue = 10:1, and the extraction is stirred for 5 minutes; the rubidium-loaded organic phase is washed, stripped, and crystallized to obtain a rubidium salt; the stripping uses sulfuric acid with a solute mass percentage of 98%, and the mass ratio of the added mass of sulfuric acid to the stripping organic phase is stripping organic phase: sulfuric acid = 15:1.

[0034] Comparative Example 1

[0035] A comparative method for extracting rubidium-cesium salt from lithium-precipitated mother liquor of lepidolite comprises the following steps:

[0036] (1) Acidifying the lithium precipitation mother liquor (the components are shown in Table 1) to remove carbonate ions in the lithium precipitation mother liquor and obtain an acidified solution; acidifying the lithium precipitation mother liquor is to add sulfuric acid with a solute mass percentage of 98% to the lithium precipitation mother liquor to adjust the pH of the mother liquor to 2; adding sodium hydroxide to the acidified solution to adjust the pH to 9, and then concentrating it. Since the content of potassium and sodium salts is relatively large, it is easier to reach a saturated state first, so part of the potassium and sodium salts are precipitated first, which can remove most of the potassium and sodium salts on the one hand, and enrich the rubidium and cesium in the lithium precipitation mother liquor on the other hand; solid-liquid separation to remove the precipitate to obtain a concentrated solution, and then adding sodium hydroxide to adjust the pH of the concentrated solution to 11, and adding a portion of potassium and sodium salts to the concentrated solution. The first extractant is used for extraction to obtain a cesium-loaded organic phase and a first extraction residual liquid; the first extractant is a mixture of 4-tert-butyl-2-(α-methylbenzyl)phenol and sulfonated kerosene; the mass ratio of each component in the first extractant is 4-tert-butyl-2-(α-methylbenzyl)phenol: sulfonated kerosene = 2:1; the mass ratio of the first extractant added to the concentrated liquid for extraction is the first extractant: concentrated liquid = 1:1, and the extraction is stirred for 5 minutes; the cesium-loaded organic phase is washed, stripped, and crystallized to obtain a cesium salt; the stripping uses sulfuric acid with a solute mass percentage of 98%, and the mass ratio of the added mass of sulfuric acid to the stripping organic phase is stripping organic phase: sulfuric acid = 15:1;

[0037] (2) adding sodium hydroxide to adjust the pH of the primary extraction residue to 13, and then adding a secondary extractant to extract to obtain a rubidium-loaded organic phase and an extracted liquid; the secondary extractant is a mixture of 4-tert-butyl-2-(α-methylbenzyl)phenol, N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide and sulfonated kerosene; the mass ratio of each component in the secondary extractant is 4-tert-butyl-2-(α-methylbenzyl)phenol: N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt: The invention discloses a method for preparing a rubidium salt of bis(trifluoromethanesulfonyl)imide salt and sulfonated kerosene in a ratio of 3:0.3:2; a secondary extractant is added to the primary extraction residue for extraction in a mass ratio of secondary extractant:primary extraction residue=10:1, and the extraction is stirred for 5 minutes; the rubidium-loaded organic phase is washed, stripped, and crystallized to obtain a rubidium salt; the stripping adopts sulfuric acid with a solute mass percentage of 98%, and the mass ratio of the added sulfuric acid to the stripping organic phase is stripping organic phase: sulfuric acid=15:1.

[0038] Comparative Example 2

[0039] A comparative method for extracting rubidium-cesium salt from lithium-precipitated mother liquor of lepidolite comprises the following steps:

[0040] (1) Acidifying the lithium precipitation mother liquor (the components are shown in Table 1) to remove carbonate in the lithium precipitation mother liquor and obtain an acidified solution; acidifying the lithium precipitation mother liquor is to add sulfuric acid with a solute mass percentage of 98% to the lithium precipitation mother liquor to adjust the pH of the mother liquor to 2; adding sodium hydroxide to the acidified solution to adjust the pH to 9, and then concentrating. Since the content of potassium and sodium salts is relatively large, it is easier to reach a saturated state first, so part of the potassium and sodium salts are precipitated first, which can remove most of the potassium and sodium salts on the one hand, and enrich the rubidium and cesium in the lithium precipitation mother liquor on the other hand; solid-liquid separation to remove the precipitate to obtain a concentrated solution, and then adding sodium hydroxide to adjust the pH of the concentrated solution to 11, adding a primary extractant to the concentrated solution for extraction, and obtaining a loaded cesium The organic phase and the primary extraction residue are prepared; the primary extraction agent is a mixture of 4-tert-butyl-2-(α-methylbenzyl)phenol, dibenzo-18-crown-6 ether and sulfonated kerosene; the mass ratio of the components in the primary extraction agent is 4-tert-butyl-2-(α-methylbenzyl)phenol: dibenzo-18-crown-6 ether: sulfonated kerosene = 2:0.6:1; the mass ratio of the primary extraction agent added to the concentrated solution for extraction is the primary extraction agent: concentrated solution = 1:1, and the extraction is stirred for 5 minutes; the cesium-loaded organic phase is washed, stripped, and crystallized to obtain a cesium salt; the stripping uses sulfuric acid with a solute mass percentage of 98%, and the mass ratio of the added mass of sulfuric acid to the stripping organic phase is stripping organic phase: sulfuric acid = 15:1;

[0041] (2) adding sodium hydroxide to adjust the pH of the primary extraction residue to 13, and then adding a secondary extractant to extract to obtain a rubidium-loaded organic phase and an extracted liquid; the secondary extractant is a mixture of 4-tert-butyl-2-(α-methylbenzyl)phenol, dibenzo-18-crown-6 ether, N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt and sulfonated kerosene; the mass ratio of each component in the secondary extractant is 4-tert-butyl-2-(α-methylbenzyl)phenol: dibenzo-18-crown-6 ether: N -butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt: sulfonated kerosene = 3:0.7:0.3:2; a secondary extractant is added to the primary extraction residue for extraction at a mass ratio of secondary extractant: primary extraction residue = 10:1, and the extraction is stirred for 5 minutes; the rubidium-loaded organic phase is washed, stripped, and crystallized to obtain a rubidium salt; the stripping uses sulfuric acid with a solute mass percentage of 98%, and the mass ratio of the added sulfuric acid to the stripping organic phase is stripping organic phase: sulfuric acid = 15:1.

[0042] Comparative Example 3

[0043] A comparative method for extracting rubidium-cesium salt from lithium-precipitated mother liquor of lepidolite comprises the following steps:

[0044] (1) Add dibenzo-18-crown-6 ether to N,N-dimethylformamide in a reaction kettle, and add dibenzo-18-crown-6 ether to N,N-dimethylformamide in a mass ratio of dibenzo-18-crown-6 ether to N,N-dimethylformamide in a ratio of dibenzo-18-crown-6 ether to N,N-dimethylformamide = 1:50; stir for 5 minutes, then add glacial acetic acid to the reaction kettle under stirring, stir for 20 minutes after the addition is completed, then add concentrated nitric acid to the reaction kettle under stirring, stir for 30 minutes after the addition is completed, then seal the reaction kettle, heat to 130±5° C. and keep warm for 2 hours, cool to room temperature after the insulation is completed, open the reaction kettle, and then add palladium carbon catalyst and hydrazine hydrate to the reaction kettle, After the addition is completed, the reactor is sealed again, heated to 120±3°C and kept warm for 1h, then naturally cooled to room temperature, the reactor is opened, the catalyst is removed by centrifugation, and the N,N-dimethylformamide is removed by vacuum distillation after centrifugation to obtain the extraction promoter of this comparative example; wherein the amount of glacial acetic acid, concentrated nitric acid, palladium carbon catalyst, hydrazine hydrate added and the amount of dibenzo-18-crown-6 ether added to the reactor are calculated by weight: 1 part of dibenzo-18-crown-6 ether, 16 parts of glacial acetic acid, 2 parts of concentrated nitric acid, 0.04 parts of palladium carbon catalyst, and 5 parts of hydrazine hydrate; wherein the mass percentage of the solute in the concentrated nitric acid is 68%, and the palladium carbon catalyst is 10% Pd / C;

[0045] (2) Acidifying the lithium precipitation mother liquor (the components are shown in Table 1) to remove carbonate ions in the lithium precipitation mother liquor and obtain an acidified solution; acidifying the lithium precipitation mother liquor is to add sulfuric acid with a solute mass percentage of 98% to the lithium precipitation mother liquor to adjust the pH of the mother liquor to 2; adding sodium hydroxide to the acidified solution to adjust the pH to 9, and then concentrating. Since the content of potassium and sodium salts is relatively large, it is easier to reach a saturated state first, so part of the potassium and sodium salts are precipitated first, which can remove most of the potassium and sodium salts on the one hand, and enrich the rubidium and cesium in the lithium precipitation mother liquor on the other hand; solid-liquid separation to remove the precipitate to obtain a concentrated solution, and then adding sodium hydroxide to adjust the pH of the concentrated solution to 11, adding a primary extractant to the concentrated solution for extraction, The method comprises the following steps: obtaining a cesium-loaded organic phase and a primary extraction residual liquid; wherein the primary extraction agent is a mixture of 4-tert-butyl-2-(α-methylbenzyl)phenol, the extraction promoter and sulfonated kerosene; wherein the mass ratio of the components in the primary extraction agent is 4-tert-butyl-2-(α-methylbenzyl)phenol: extraction promoter: sulfonated kerosene = 2:0.6:1; wherein the mass ratio of the primary extraction agent added to the concentrated liquid for extraction is the primary extraction agent: concentrated liquid = 1:1, and the extraction is stirred for 5 minutes; wherein the cesium-loaded organic phase is washed, stripped and crystallized to obtain a cesium salt; wherein the stripping uses sulfuric acid with a solute mass percentage of 98%, and the mass ratio of the added mass of sulfuric acid to the stripping organic phase is the stripping organic phase: sulfuric acid = 15:1;

[0046] (3) adding sodium hydroxide to adjust the pH of the primary extraction residue to 13, and then adding a secondary extractant to extract to obtain a rubidium-loaded organic phase and an extracted liquid; the secondary extractant is a mixture of 4-tert-butyl-2-(α-methylbenzyl)phenol, the extraction promoter, N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt and sulfonated kerosene; the mass ratio of the components in the secondary extractant is 4-tert-butyl-2-(α-methylbenzyl)phenol: extraction promoter: N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt. -methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt: sulfonated kerosene = 3:0.7:0.3:2; the mass ratio of adding a secondary extractant to the primary extraction residue for extraction is secondary extractant: primary extraction residue = 10:1, and the extraction is stirred for 5 minutes; the rubidium-loaded organic phase is washed, stripped, and crystallized to obtain a rubidium salt; the stripping uses sulfuric acid with a solute mass percentage of 98%, and the mass ratio of the added mass of sulfuric acid to the stripping organic phase is stripping organic phase: sulfuric acid = 15:1.

[0047] Comparative Example 4

[0048] A comparative method for extracting rubidium-cesium salt from lithium-precipitated mother liquor of lepidolite comprises the following steps:

[0049] (1) Add dibenzo-18-crown-6 ether to N,N-dimethylformamide in a reaction kettle, and add dibenzo-18-crown-6 ether to N,N-dimethylformamide in a mass ratio of dibenzo-18-crown-6 ether to N,N-dimethylformamide in a ratio of dibenzo-18-crown-6 ether to N,N-dimethylformamide = 1:50; stir for 5 minutes, then add glacial acetic acid to the reaction kettle under stirring, stir for 20 minutes after the addition is completed, then add concentrated nitric acid to the reaction kettle under stirring, stir for 30 minutes after the addition is completed, then seal the reaction kettle, heat to 130±5°C and keep warm for 2 hours, cool to room temperature after the insulation is completed, open the reaction kettle, add palladium carbon catalyst and hydrazine hydrate to the reaction kettle, seal the reaction kettle again after the addition is completed, heat to 120±3°C and keep warm The mixture was stirred at room temperature for 1 hour, then cooled naturally to room temperature, the reactor was opened, the catalyst was removed by centrifugation, 4-nitrobenzene isocyanate was added to the liquid after centrifugation under stirring, and the mixture was stirred at room temperature for 8 hours after the addition was completed, and then N,N-dimethylformamide was removed by reduced pressure distillation to obtain an extraction promoter; wherein the amount of glacial acetic acid, concentrated nitric acid, palladium-carbon catalyst, hydrazine hydrate and 4-nitrobenzene isocyanate added and the amount of dibenzo-18-crown-6 ether added to the reactor were calculated by weight: 1 part of dibenzo-18-crown-6 ether, 16 parts of glacial acetic acid, 2 parts of concentrated nitric acid, 0.04 parts of palladium-carbon catalyst, 5 parts of hydrazine hydrate, and 1.2 parts of 4-nitrobenzene isocyanate; wherein the mass percentage of the solute in the concentrated nitric acid is 68%, and the palladium-carbon catalyst is 10% Pd / C;

[0050] (2) Acidifying the lithium precipitation mother liquor (the components are shown in Table 1) to remove carbonate ions in the lithium precipitation mother liquor and obtain an acidified solution; acidifying the lithium precipitation mother liquor is to add sulfuric acid with a solute mass percentage of 98% to the lithium precipitation mother liquor to adjust the pH of the mother liquor to 2; adding sodium hydroxide to the acidified solution to adjust the pH to 9, and then concentrating. Since the content of potassium and sodium salts is relatively large, it is easier to reach a saturated state first, so part of the potassium and sodium salts are precipitated first, which can remove most of the potassium and sodium salts on the one hand, and enrich the rubidium and cesium in the lithium precipitation mother liquor on the other hand; solid-liquid separation to remove the precipitate to obtain a concentrated solution, and then adding sodium hydroxide to adjust the pH of the concentrated solution to 11, adding a primary extractant to the concentrated solution for extraction, The method comprises the following steps: obtaining a cesium-loaded organic phase and a primary extraction residual liquid; wherein the primary extraction agent is a mixture of 4-tert-butyl-2-(α-methylbenzyl)phenol, the extraction promoter and sulfonated kerosene; wherein the mass ratio of the components in the primary extraction agent is 4-tert-butyl-2-(α-methylbenzyl)phenol: extraction promoter: sulfonated kerosene = 2:0.6:1; wherein the mass ratio of the primary extraction agent added to the concentrated liquid for extraction is the primary extraction agent: concentrated liquid = 1:1, and the extraction is stirred for 5 minutes; wherein the cesium-loaded organic phase is washed, stripped and crystallized to obtain a cesium salt; wherein the stripping uses sulfuric acid with a solute mass percentage of 98%, and the mass ratio of the added mass of sulfuric acid to the stripping organic phase is the stripping organic phase: sulfuric acid = 15:1;

[0051] (3) adding sodium hydroxide to adjust the pH of the primary extraction residue to 13, then adding a secondary extractant for extraction to obtain a rubidium-loaded organic phase and an extracted liquid; the secondary extractant is a mixture of 4-tert-butyl-2-(α-methylbenzyl)phenol, the extraction promoter and sulfonated kerosene; the mass ratio of the components in the secondary extractant is 4-tert-butyl-2-(α-methylbenzyl)phenol: extraction promoter: sulfonated kerosene = 3:0.7:2; the mass ratio of the secondary extractant added to the primary extraction residue for extraction is secondary extractant: primary extraction residue = 10:1, and the extraction is stirred for 5 minutes; the rubidium-loaded organic phase is washed, stripped and crystallized to obtain a rubidium salt; the stripping uses sulfuric acid with a solute mass percentage of 98%, and the mass ratio of the added sulfuric acid to the stripping organic phase is stripping organic phase: sulfuric acid = 15:1.

[0052] Example 5

[0053] The extraction rates of cesium and rubidium in the cesium-loaded organic phase and the rubidium-loaded organic phase obtained by the methods described in the embodiments and comparative examples were tested, and the results are shown in Table 2.

[0054] As shown in Table 2, the method of the present invention can efficiently extract rubidium and cesium elements from lithium mica precipitation mother liquor, comprehensively utilize rubidium and cesium valuable metal elements, reduce resource waste, and generate considerable economic benefits. At present, the prior art discloses a process of simply using 4-tert-butyl-2-(α-methylbenzyl)phenol and sulfonated kerosene, but since 4-tert-butyl-2-(α-methylbenzyl)phenol has a greater extraction effect on potassium, sodium and other ions, an ion competition effect is formed, and part of the extractant resources are occupied by potassium ions and sodium ions, thereby reducing the extraction of the target ion Cs + Ions and Rb + By comparing Example 3 of the present application with the comparative example, it can be seen that by adding the extraction promoter of the present invention, the extraction rate of rubidium and cesium can be further improved. The present invention first introduces a nitro group into dibenzo-18-crown-6 ether, then reductively aminates the nitro group, and then connects the active group to the amino group through 4-nitrobenzene isocyanate, thereby improving the extraction promoter for Cs in the aqueous phase. + Ions and Rb + ion coordination ability, improve the extraction promoter and Cs + Ion, Rb + On the other hand, the selectivity of the extraction promoter to ions is used to reduce the coordination of potassium, sodium and other ions, thereby achieving the separation of target ions and impurity ions. + Ions and Rb + The ions first coordinate with the extraction promoter and enter the oil phase.+ Ion, Rb + The coordination ability of the ions is stronger and the complex formed is more stable, so the extraction promoter and Cs + Ion, Rb + The complex of ions is easy to 4-tert-butyl-2-(α-methylbenzyl)phenol and Cs + Ion, Rb + The complex transformation of ions enables the extraction promoter to coordinate Cs in the aqueous phase again. + Ion, Rb + In addition, the addition of N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt can improve the extraction of rubidium by the extractant, which may be due to the fact that N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt can improve the hydrophilicity of the extraction promoter and promote the coordination of the extraction promoter to ions.

[0055] Table 1

[0056] Element Li Na K R Cs <![CDATA[SO 4 2- ]]> <![CDATA[CO 3 2- ]]> Content (g / L) 2.56 32.98 5.03 2.51 0.54 180.21 3.45

[0057] Table 2

[0058] Experimental Group Cesium extraction rate Extraction rate of rubidium Example 1 93.65％ 90.24％ Example 2 93.71％ 91.08％ Example 3 93.76％ 91.15％ Example 4 93.72％ 91.11％ Comparative Example 1 84.19％ 77.34％ Comparative Example 2 86.90％ 83.86％ Comparative Example 3 90.33％ 88.67％ Comparative Example 4 93.74％ 88.09％

[0059] The technical solution provided by the present invention is introduced in detail above. For those skilled in the art, according to the concept of the embodiments of the present invention, there may be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for extracting rubidium-cesium salt from lithium-precipitated mother liquor of lepidolite, characterized in that the steps include: (1) Add dibenzo-18-crown-6 ether to N,N-dimethylformamide in a reaction kettle, stir for more than 5 minutes, then add glacial acetic acid to the reaction kettle under stirring, stir for more than 20 minutes after the addition is completed, then add concentrated nitric acid to the reaction kettle under stirring, stir for more than 30 minutes after the addition is completed, then seal the reaction kettle, heat to 130±5° C. and keep warm for more than 2 hours, cool to room temperature after the insulation is completed, open the reaction kettle, add palladium carbon catalyst and hydrazine hydrate to the reaction kettle, seal the reaction kettle again after the addition is completed, heat to 120±3° C. and keep warm for more than 1 hour, then naturally cool to room temperature, open the reaction kettle, centrifuge to remove the catalyst, add 4-nitrobenzene isocyanate to the liquid after centrifugation under stirring, stir at room temperature for more than 8 hours after the addition is completed, then remove N,N-dimethylformamide by reduced pressure distillation to obtain an extraction promoter; (2) Acidifying the lithium precipitation mother liquor to remove carbonate in the lithium precipitation mother liquor to obtain an acidified liquid; adding alkali to the acidified liquid to adjust the pH to 8-10, then concentrating to precipitate potassium and sodium salt crystals, removing the precipitate by solid-liquid separation to obtain a concentrated solution, then adding alkali to adjust the pH of the concentrated solution to 10-12, adding a primary extractant to the concentrated solution for extraction to obtain a cesium-loaded organic phase and a primary extraction residual liquid; the primary extractant is a mixture of 4-tert-butyl-2-(α-methylbenzyl)phenol, the extraction promoter and sulfonated kerosene; washing, stripping and crystallizing the cesium-loaded organic phase to obtain a cesium salt; (3) adding alkali to adjust the pH of the primary extraction residue to 12-14, then adding a secondary extractant for extraction to obtain a rubidium-loaded organic phase and an extracted liquid; the secondary extractant is a mixture of 4-tert-butyl-2-(α-methylbenzyl)phenol, the extraction promoter, N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt and sulfonated kerosene; washing, stripping and crystallizing the rubidium-loaded organic phase to obtain a rubidium salt.

2. The method for extracting rubidium-cesium salt from an environmentally friendly lithium-precipitated lithium mother liquor of lepidolite according to claim 1, characterized in that: In the step (1), dibenzo-18-crown-6 ether is added to N,N-dimethylformamide in a mass ratio of dibenzo-18-crown-6 ether:N,N-dimethylformamide=1:

50.

3. The method for extracting rubidium-cesium salt from an environmentally friendly lithium-precipitated lithium mother liquor of lepidolite according to claim 1, characterized in that: In the step (1), the amounts of glacial acetic acid, concentrated nitric acid, palladium-carbon catalyst, hydrazine hydrate and 4-nitrobenzene isocyanate added and the amount of dibenzo-18-crown-6 ether added to the reaction kettle are calculated in parts by weight: 1 part of dibenzo-18-crown-6 ether, 14-18 parts of glacial acetic acid, 1-2 parts of concentrated nitric acid, 0.03-0.04 parts of palladium-carbon catalyst, 4-6 parts of hydrazine hydrate, and 0.8-1.6 parts of 4-nitrobenzene isocyanate; wherein the mass percentage of the solute in the concentrated nitric acid is 68%, and the palladium-carbon catalyst is 10% Pd / C.

4. The method for extracting rubidium-cesium salt from an environmentally friendly lithium-precipitated lithium mother liquor of lepidolite according to claim 1, characterized in that: In the step (2), the lithium precipitation mother liquor is acidified by adding sulfuric acid with a solute mass percentage of 98% to the lithium precipitation mother liquor to adjust the pH of the mother liquor to 1-2; the alkali is sodium hydroxide.

5. The method for extracting rubidium-cesium salt from an environmentally friendly lithium-precipitated lithium mother liquor of lepidolite according to claim 1, characterized in that: In the step (2), the mass ratio of the components in the primary extractant is 4-tert-butyl-2-(α-methylbenzyl)phenol: extraction promoter: sulfonated kerosene = 2:0.5-0.6:1; the mass ratio of the primary extractant added to the concentrated solution for extraction is primary extractant: concentrated solution = 1-2:1, and the extraction is stirred for 3-5 minutes; the stripping uses sulfuric acid with a solute mass percentage of 98%, and the mass ratio of the added mass of sulfuric acid to the stripping organic phase is stripping organic phase: sulfuric acid = 15:

1.

6. The method for extracting rubidium-cesium salt from an environmentally friendly lithium-precipitated lithium mother liquor of lepidolite according to claim 1, characterized in that: In the step (3), the mass ratio of the components in the secondary extractant is 4-tert-butyl-2-(α-methylbenzyl)phenol: extraction promoter: N-butyl-N-methylpyrrolidine bis(trifluoromethanesulfonyl)imide salt: sulfonated kerosene = 3:0.6-0.7:0.2-0.4:2; the mass ratio of the secondary extractant added to the primary extraction residue for extraction is secondary extractant: primary extraction residue = 10:1, and the extraction is stirred for 3-5 minutes; the stripping uses sulfuric acid with a solute mass percentage of 98%, and the mass ratio of the added mass of sulfuric acid to the stripping organic phase is stripping organic phase: sulfuric acid = 15:1.