Efficient separation method based on hexafluoroaluminate salt step-by-step precipitation in rubidium / potassium / lithium mixed solution

Abstract

The invention discloses an efficient separation method based on hexafluoroaluminate salt step-by-step precipitation in a rubidium / potassium / lithium mixed solution, which comprises the following steps: 1) dissolving a proper amount of Al < 3 + > in a mixed ion solution containing Li < + >, K < + > and Rb < + > to obtain a mixed solution; (2) adding a proper amount of fluorinating agent and rubidium cryolite crystal seeds into the mixed solution obtained in the step (1), and carrying out solid-liquid separation to obtain a rubidium-removed solution and a rubidium cryolite solid; and (3) adding a proper amount of fluorinating agent and potassium cryolite crystal seeds into the rubidium-removed solution obtained in the step (2), and carrying out solid-liquid separation to obtain a lithium-rich solution and a potassium cryolite solid. According to the method, the characteristic that the solubility of lithium cryolite, potassium cryolite and rubidium cryolite is reduced along with increase of the ion radius is utilized, a proper amount of fluorinating agent and aluminum salt are added step by step, Rb < + > and K < + > in the solution can be sequentially precipitated, Li < + > is kept in the solution all the time, and then separation of Li < + >, K < + > and Rb < + > in the solution is achieved; and pure potassium cryolite, rubidium cryolite, lithium carbonate and other products can be directly prepared.

Description

Technical Field

[0001] The invention belongs to the technical field of three wastes treatment and resource utilization, and particularly relates to a high-efficiency separation method based on step-by-step precipitation of hexafluoroaluminate in a rubidium / potassium / lithium mixed solution. Background Art

[0002] In the extraction and purification of alkali metal resources such as lithium, potassium, and rubidium, the efficient separation of these ions from complex solution systems has long been a research focus in both industry and academia. With the rapid development of the new energy industry, demand for lithium resources has surged, and rubidium, due to its unique applications in high-tech fields such as optoelectronic materials, specialty glass, and atomic clocks, has gradually become a high-value-added strategic resource. However, the chemical properties of lithium, potassium, and rubidium are similar (e.g., similar ionic radius and small difference in hydration energy), and the separation coefficient between rubidium and potassium is particularly low. This leads to traditional separation technologies generally facing problems such as poor selectivity, complex processes, and high costs.

[0003] Facing Li + , K + , Rb + 、Al 3+ Traditional separation methods (such as solvent extraction and precipitation) in complex plasma solutions are cumbersome, costly, and produce low-purity products. Therefore, there is an urgent need to develop an efficient, low-cost separation technology to achieve precise separation of lithium, potassium, and rubidium, while improving resource utilization. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the main purpose of the present invention is to provide an efficient separation method based on the step-by-step precipitation of hexafluoroaluminate in a rubidium / potassium / lithium mixed solution, which utilizes the solubility difference between lithium cryolite, potassium cryolite and rubidium cryolite to add appropriate amounts of fluorinating agent and Al step-by-step to the mixed ion solution. 3+ Rb in the leaching solution + and K + The formation of rubidium cryolite and potassium cryolite precipitation, Li + Always remain in the solution, achieving Li + , K + , Rb + step-by-step separation.

[0005] The purpose of the present invention is achieved through the following technical solutions: An efficient separation method based on step-by-step precipitation of hexafluoroaluminate in a rubidium / potassium / lithium mixed solution comprises the following steps: Step (1): Add Li + , K + , Rb + Dissolve an appropriate amount of Al in the mixed ion solution3+ , obtaining a mixed solution; Step (2): Add appropriate amount of fluorinating agent and rubidium cryolite seed to the mixed solution obtained in step (1) to promote the Rb + and Al 3+ forming rubidium cryolite precipitation, and performing solid-liquid separation to obtain rubidium removal solution and rubidium cryolite solid; Step (3): Add an appropriate amount of fluorinating agent and potassium cryolite seed crystals to the rubidium removal solution obtained in step (2) to promote the removal of K + and Al 3+ Rubidium cryolite precipitate is formed, and solid-liquid separation is performed to obtain lithium-rich solution and potassium cryolite solid.

[0006] In some embodiments, the mixed solution further comprises Al 3+ and F － .

[0007] In certain embodiments, the Al in step (1) 3+ A mixed solution containing one or more of Al(OH)3, Al2(SO4)3, AlCl3, Al2(CO3)3, and AlF3.

[0008] In certain embodiments, the Al in step (1) 3+ / (K + +Rb + ) is 0.1-2.1.

[0009] In certain specific embodiments, the rubidium cryolite seed in step 2) is 1-10 wt% (mass fraction, relative to the theoretical amount of Rb3AlF6 produced in the reaction system), and the F in the fluorinating agent is － Rb in the mixed solution + The mass ratio of is 0.4-0.6, and the reaction pH is 4.0~8.0.

[0010] In certain specific embodiments, the potassium cryolite seed crystals in step 3) are 1-10 wt% (mass fraction, relative to the theoretical amount of K3AlF6 generated in the reaction system), and the F in the fluorinating agent is － With K in the mixed solution + The mass ratio of is 0.9-1.3, and the reaction pH is 5 ~ 9.

[0011] In certain specific embodiments, the fluorinating agent in step (2) and step (3) is one or more of HF, KF, NaF, NH4F, AlF3, CaF2 or fluorides of lepidolite roasting flue gas.

[0012] The fluoride produced in the flue gas from the calcination of lepidolite can be directly used as the above-mentioned fluorinating agent after purification, thus completing the comprehensive utilization of the calcination flue gas.

[0013] In certain embodiments, the pH adjuster in step (2) and step (3) is one or more of KOH, Al(OH)3, NH3•H2O, and CaO.

[0014] In certain embodiments, the reaction conditions in step (2) and step (3) are: the reaction temperature is 30-90°C.

[0015] In some specific embodiments, the step further includes: + Directly produce lithium carbonate products.

[0016] Furthermore, the lithium-rich solution obtained in step (3) can be extracted with an extractant to extract lithium and then stripped to produce carbonic acid; or CO2 can be directly introduced to form lithium carbonate.

[0017] Compared with the prior art, the present invention has at least the following advantages: The separation method of the present application utilizes the solubility difference of lithium cryolite, potassium cryolite and rubidium cryolite to add appropriate amount of fluorinating agent and Al2O3 into the mixed ion solution step by step. 3+ Rb in the leaching solution + and K + The formation of rubidium cryolite and potassium cryolite precipitation, Li + Always remain in the solution, achieving Li + , K + , Rb + The step-by-step separation avoids the long and complicated purification process.

[0018] The separation method of the present invention not only realizes the recovery of lithium resources, but also realizes the coordinated recovery of elements such as rubidium, potassium, and aluminum, thereby significantly improving economic benefits. At the same time, the operability is enhanced, the solution separation and purification process is simple and reasonable, which conforms to the development trend of green metallurgy and is easy to promote and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific embodiments of the present invention, the following briefly introduces the drawings required for the specific embodiments or the description of the prior art.

[0020] Figure 1 This is a process flow chart of an efficient separation method based on step-by-step precipitation of hexafluoroaluminate in a rubidium / potassium / lithium mixed solution provided by one embodiment of the present invention. DETAILED DESCRIPTION

[0021] The application will be further described in conjunction with the accompanying drawings and examples. The following examples are only descriptive and not limiting, and cannot limit the protection scope of the application.

[0022] When expressing a quantity, concentration or other value or parameter either as an amount, a range, preferably a range, or a preferred upper and lower limit, it is intended to encompass any and all subranges of the recited amount, range, preferably a range, or preferred limit, even if not expressly stated. The statement "about X to Y" means that X and Y are approximate endpoints and the exact value will fall within the range, but also that the range itself is only approximately understood to encompass any value or range falling within the approximate endpoints and all integers and fractions within that range.

[0023] All percentages, parts by weight, ratios, etc. herein are based on weight unless otherwise indicated.

[0024] The materials, methods, and examples herein are illustrative only and, except as specifically stated, are not to be construed as limitations.

[0025] Example 1 The present example provides a high-efficiency separation method based on hexafluoroaluminate step-by-step precipitation in a rubidium / potassium / lithium mixed solution, which comprises the following steps: Step (1): preparing a mixed solution containing Li + 4 g / L, Rb + 4 g / L with sulfate; Step (2): dissolving aluminum sulfate in the mixed solution obtained in step (1) in advance, so that the Al 3+ concentration in the solution is 0.42 g / L, then adding ammonium fluoride so that the F - concentration in the solution is 1.78 g / L, and then adding 5% mass fraction (relative to the theoretical generation amount of Rb3AlF6 in the reaction system) rubidium cryolite as a crystal seed, controlling the solution pH to be 4.8 through NH3•H2O, keeping the reaction temperature at 45°C, and the reaction time being 90 min, to obtain rubidium cryolite and a lithium-rich solution through filtration. Through detection, the ion concentrations in the lithium-rich solution are: Li + 3.97 g / L, Rb + 0.10 g / L, Al 3+ 0.04 g / L, F - 0.07 g / L.

[0026] Example 2 The present example provides a high-efficiency separation method based on hexafluoroaluminate step-by-step precipitation in a rubidium / potassium / lithium mixed solution, which comprises the following steps: Step (1): preparing a mixed solution containing Li + 4 g / L, K +10 g / L of mixed solution; Step (2): The mixed solution obtained in step (1) is pre-dissolved with aluminum sulfate, so that the Al 3+ concentration is 2.31 g / L, and then ammonium fluoride is added so that the F - concentration is 9.74 g / L, and then 5% by mass (relative to the theoretical amount of K3AlF6 generated in the reaction system) of potassium cryolite is added as a crystal seed, the pH of the solution is controlled to 4.8 by NH3•H2O, the reaction temperature is kept at 45°C, the reaction time is 90 min, and rubidium cryolite and a potassium-rich solution are obtained by filtration. It is detected that the ion concentrations in the lithium-rich solution are: Li + 3.89 g / L, K + 0.47 g / L, Al 3+ 0.03 g / L, F - 0.11 g / L.

[0027] Example 3 The present example provides a high-efficiency separation method based on hexafluoroaluminate step-by-step precipitation in a rubidium / potassium / lithium mixed solution, which includes the following steps: Step (1): A mixed solution containing K + 10 g / L, Rb + 4 g / L is prepared by using sulfate; Step (2): The mixed solution obtained in step (1) is pre-dissolved with aluminum sulfate, so that the Al 3+ concentration is 2.73 g / L, and then ammonium fluoride is added so that the F - concentration is 1.78 g / L, and then 5% by mass (relative to the theoretical amount of Rb3AlF6 generated in the reaction system) of rubidium cryolite is added as a crystal seed, the pH of the solution is controlled to 5.0 by NH3•H2O, the reaction temperature is kept at 45°C, the reaction time is 90 min, and rubidium cryolite and a potassium-rich solution are obtained by filtration. It is detected that the ion concentrations in the potassium-rich solution are: K + 9.77 g / L, Rb + 0.08 g / L, Al 3+ 0.05 g / L, F - 0.09 g / L.

[0028] Example 4 The present example provides a high-efficiency separation method based on hexafluoroaluminate step-by-step precipitation in a rubidium / potassium / lithium mixed solution, which includes the following steps: Step (1): A mixed solution containing Li + 4 g / L, K + 10 g / L, Rb +4 g / L mixed solution; Step (2): Dissolve aluminum sulfate in the mixed solution obtained in step (1) to make the Al 3+ The concentration was 2.73 g / L, and then ammonium fluoride was added to make the solution - The concentration was 1.78 g / L, and 5% mass fraction (relative to the theoretical amount of Rb3AlF6 produced in the reaction system) of rubidium cryolite was added as a seed crystal. The pH of the solution was controlled at 6.0 by NH3•H2O, the reaction temperature was maintained at 45℃, the reaction time was 90 min, and the rubidium cryolite and rubidium removal solution were obtained by filtration. After testing, the concentrations of various ions in the rubidium removal solution were: Li + 3.94 g / L, K + 9.48 g / L, Rb + 0.11 g / L, Al 3+ 2.30 g / L, F - 0.17 g / L.

[0029] Step (3): Add ammonium fluoride to the rubidium removal solution obtained in step (2) to make the solution - The concentration was 9.74 g / L, and 5% mass fraction (relative to the theoretical amount of K3AlF6 produced in the reaction system) of potassium cryolite was added as a seed crystal. The pH of the solution was controlled to 5.0 by NH3•H2O, the reaction temperature was maintained at 45℃, the reaction time was 90 min, and potassium cryolite and lithium-rich solution were obtained by filtration. After testing, the concentrations of various ions in the lithium-rich solution were: Li + 3.77 g / L, K + 0.58 g / L, Rb + 0.04 g / L, Al 3+ 0.09 g / L, F - 0.88 g / L.

[0030] Example 5 This embodiment provides an efficient separation method based on step-by-step precipitation of hexafluoroaluminate in a rubidium / potassium / lithium mixed solution, which comprises the following steps: Step (1): Prepare Li-containing + 4 g / L, K + 10 g / L, Rb + 4 g / L mixed solution; Step (2): Dissolve aluminum chloride in the mixed solution obtained in step (1) to make the Al 3+ The concentration was 2.73 g / L, and then ammonium fluoride was added to make the solution -The concentration was 1.78 g / L, and 5% mass fraction (relative to the theoretical amount of Rb3AlF6 produced in the reaction system) of rubidium cryolite was added as a seed crystal. The pH of the solution was controlled at 6.0 by NH3•H2O, the reaction temperature was maintained at 45℃, the reaction time was 90 min, and the rubidium cryolite and rubidium removal solution were obtained by filtration. After testing, the concentrations of various ions in the rubidium removal solution were: Li + 3.91 g / L, K + 9.68 g / L, Rb + 0.19 g / L, Al 3+ 2.33 g / L, F - 0.16 g / L.

[0031] Step (3): Add ammonium fluoride to the rubidium removal solution obtained in step (2) to make the solution - The concentration was 9.74 g / L, and 5% mass fraction (relative to the theoretical amount of K3AlF6 produced in the reaction system) of potassium cryolite was added as a seed crystal. The pH of the solution was controlled to 5.0 by NH3•H2O, the reaction temperature was maintained at 45℃, the reaction time was 90 min, and potassium cryolite and lithium-rich solution were obtained by filtration. After testing, the concentrations of various ions in the lithium-rich solution were: Li + 3.88 g / L, K + 0.61 g / L, Rb + 0.07 g / L, Al 3+ 0.06 g / L, F - 0.43 g / L.

[0032] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. An efficient separation method based on step-by-step precipitation of hexafluoroaluminate in a rubidium / potassium / lithium mixed solution, characterized in that: The following steps are involved: Step (1): Add Li + , K + , Rb + Dissolve an appropriate amount of Al in the mixed ion solution 3+ , obtaining a mixed solution; Step (2): Add appropriate amount of fluorinating agent and rubidium cryolite seed to the mixed solution obtained in step (1) to promote the Rb + and Al 3+ forming rubidium cryolite precipitation, and performing solid-liquid separation to obtain rubidium removal solution and rubidium cryolite solid; Step (3): Add an appropriate amount of fluorinating agent and potassium cryolite seed crystals to the rubidium removal solution obtained in step (2) to promote the removal of K + and Al 3+ Rubidium cryolite precipitate is formed, and solid-liquid separation is performed to obtain lithium-rich solution and potassium cryolite solid.

2. The efficient separation method based on step-by-step precipitation of hexafluoroaluminate in a rubidium / potassium / lithium mixed solution according to claim 1, characterized in that: The mixed solution also contains Al 3+ and F － .

3. The efficient separation method based on step-by-step precipitation of hexafluoroaluminate in a rubidium / potassium / lithium mixed solution according to claim 1, characterized in that: Al in step (1) 3+ A mixed solution containing one or more of Al(OH)3, Al2(SO4)3, AlCl3, Al2(CO3)3, and AlF3.

4. The efficient separation method based on step-by-step precipitation of hexafluoroaluminate in a rubidium / potassium / lithium mixed solution according to claim 1, characterized in that: The Al in step (1) 3+ / (K + +Rb + ) is 0.1-2.

1.

5. The efficient separation method based on step-by-step precipitation of hexafluoroaluminate in a rubidium / potassium / lithium mixed solution according to claim 2, characterized in that: The amount of rubidium cryolite seed added in step 2) is 1-10 wt% of the theoretical amount of Rb3AlF6 produced in the reaction system, and the amount of F in the fluorinating agent is 1-10 wt%. － Rb in the mixed solution + The mass ratio of is 0.4-0.6, and the reaction pH is 4.0~8.

0.

6. The efficient separation method based on step-by-step precipitation of hexafluoroaluminate in a rubidium / potassium / lithium mixed solution according to claim 2, characterized in that: The amount of potassium cryolite seed crystals added in step 3) is 1-10 wt% of the theoretical amount of K3AlF6 produced in the reaction system, and the amount of F in the fluorinating agent is 1-10 wt%. － With K in the mixed solution + The mass ratio of is 0.9-1.3, and the reaction pH is 5 ~ 9.

7. The efficient separation method based on step-by-step precipitation of hexafluoroaluminate in a rubidium / potassium / lithium mixed solution according to claim 2, characterized in that: The fluorinating agent in step (2) and step (3) is one or more of HF, KF, NaF, NH4F, AlF3, CaF2 or fluorides of lepidolite roasting flue gas.

8. The efficient separation method based on step-by-step precipitation of hexafluoroaluminate in a rubidium / potassium / lithium mixed solution according to claim 2, characterized in that: The pH regulator in step (2) and step (3) is one or more of KOH, Al(OH)3, NH3•H2O, and CaO.

9. The efficient separation method based on step-by-step precipitation of hexafluoroaluminate in a rubidium / potassium / lithium mixed solution according to claim 2, characterized in that: The reaction conditions in step (2) and step (3) are: the reaction temperature is 30-90°C.

10. The efficient separation method based on step-by-step precipitation of hexafluoroaluminate in a rubidium / potassium / lithium mixed solution according to claim 2, characterized in that: The step also includes the step of converting the lithium-rich solution obtained in step (3) into + Directly produce lithium carbonate products.

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