Methods for recovering lithium
The method addresses lithium recovery challenges by using a carbonation and membrane electrolysis process with sodium as an alkali source, enhancing recovery rates and reducing costs through efficient recycling.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- ASAKA RIKEN
- Filing Date
- 2024-11-08
- Publication Date
- 2026-05-20
AI Technical Summary
Existing lithium recovery methods face challenges in achieving high recovery rates and efficient resource recycling due to the need for separating lithium from other alkalis, leading to alkali loss and high initial chemical costs, particularly when using lithium hydroxide as the alkali source.
A method involving a carbonation step, lithium carbonate dissolution, and membrane electrolysis is employed to recover lithium without separating it from alkalis, utilizing sodium as a cheaper alkali source and recycling chemicals, with power from renewable energy sources.
This approach enhances lithium recovery rates and reduces initial chemical costs by eliminating alkali loss and enabling resource recycling, while increasing lithium concentration.
Smart Images
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Abstract
Description
Technical Field
[0006] , , , ,
[0001] The present invention relates to a method for recovering lithium.
Background Art
[0002] In recent years, with the widespread use of lithium-ion batteries, methods for recovering valuable metals such as cobalt, nickel, manganese, and lithium from waste lithium-ion batteries and reusing them as materials for lithium-ion batteries have been studied.
[0003] Conventionally, when recovering the valuable metals from the waste lithium-ion batteries, the waste lithium-ion batteries are subjected to heat treatment (roasting), or the valuable metals contained in the powder obtained by pulverizing, classifying, etc. without heat treatment are separated and purified by a wet process for each of cobalt, nickel, manganese, and lithium (see, for example, Patent Documents 1 and 2).
[0004] Patent Document 1 discloses a method for recovering valuable metals in which lithium hydroxide is used as an alkali source. In the recovery method, the generated salt is reused as a mineral acid and an alkali in the process, and resource circulation is possible. Further, in the recovery method, since there is no alkali source other than lithium which is the recovery target, a high-concentration aqueous lithium salt solution is obtained, and the recovery rate of lithium by membrane electrolysis is high.
[0005] On the other hand, Patent Document 2 discloses a method for recovering valuable metals using sodium hydroxide or potassium hydroxide which is cheaper than lithium hydroxide as an alkali source. In the recovery method disclosed in Patent Document 2, sodium hydroxide or potassium hydroxide is obtained as a salt, and resource circulation is possible in the same manner as the recovery method disclosed in Patent Document 1.
Prior Art Documents
Patent Documents
[0006]
Patent Document 1
[0007] However, the recovery method described in Patent Document 2 uses alkalis other than lithium, which is the target product to be recovered. Therefore, lithium and other alkalis need to be separated by methods such as the lithium phosphate method, evaporation concentration method, or solvent extraction method. Complete separation is difficult with any of these separation methods, which can lead to the loss of circulating alkali and an insufficient amount for reuse. In addition, the concentration of the separated lithium salt aqueous solution is low, resulting in poor efficiency of lithium recovery by various methods, and concentration operations may be necessary to improve recovery efficiency. For this reason, a recovery method that does not include an alkali source other than lithium, such as the one disclosed in Patent Document 1, is desirable. However, lithium hydroxide is a very expensive chemical as an alkali source and is not suitable as an initial alkali source when starting up a process.
[0008] One problem that this invention aims to solve is to provide a method for recovering lithium that allows for resource recycling without reducing the lithium recovery rate. Another problem that this invention aims to solve is to provide a method for recovering lithium with low initial chemical costs. [Means for solving the problem]
[0009] In view of the above problems, the inventors of the present invention have conducted extensive studies and found that a method for recovering lithium, comprising a carbonation step of carbonizing an aqueous solution containing lithium and sodium, a lithium carbonate dissolution step of dissolving the lithium carbonate obtained through the carbonation step in a mineral acid, and a membrane electrolysis step of performing membrane electrolysis on the lithium salt aqueous solution obtained through the lithium carbonate dissolution step, can solve the above problems of the present invention. The present invention was completed based on these findings.
[0010] The present invention relates to a method for recovering lithium from an aqueous solution containing lithium and sodium, comprising a carbonation step of carbonizing the aqueous solution, a lithium carbonate dissolution step of dissolving the lithium carbonate obtained through the carbonation step in a mineral acid, and a membrane electrolysis step of performing membrane electrolysis on the lithium salt aqueous solution obtained through the lithium carbonate dissolution step.
[0011] The method for recovering lithium preferably includes a dissolution step of dissolving the active material powder obtained by pre-treating a waste lithium-ion battery in a mineral acid to obtain an acid solution, a neutralization step of neutralizing the acid solution with sodium, and an organic solvent extraction step of separating at least one metal other than lithium from the metals contained in the active material powder from the solution obtained through the neutralization step by organic solvent extraction, and obtaining a first lithium and sodium salt aqueous solution as the residue of the organic solvent extraction, wherein in the membrane electrolysis step, the lithium chloride aqueous solution and the first lithium salt and sodium salt aqueous solution The mixture obtained by mixing is subjected to membrane electrolysis using an ion exchange membrane to obtain an aqueous solution of lithium hydroxide and sodium hydroxide, an acid, and a second aqueous solution of lithium salt and sodium salt that is more dilute than the first aqueous solution of lithium salt and sodium salt. The aqueous solution of lithium hydroxide and sodium hydroxide obtained in the membrane electrolysis step is reused in at least one selected from the group consisting of the neutralization step and the organic solvent extraction step. The acid obtained in the membrane electrolysis step is reused as a mineral acid used in at least one selected from the group consisting of the dissolution step and the lithium carbonate dissolution step.
[0012] The mineral acid preferably comprises at least one selected from the group consisting of hydrochloric acid, sulfuric acid, and nitric acid, and more preferably comprises hydrochloric acid. The power used in the film electrolysis step preferably includes power obtained from renewable energy sources, and more preferably includes power obtained from at least one selected from the group consisting of solar power generation, wind power generation, geothermal power generation, hydroelectric power generation, and biomass power generation. [Effects of the Invention]
[0013] The lithium recovery method of the present invention is performed in a membrane electrolysis step without separating lithium from alkali, thus eliminating the loss of alkali source and enabling resource recycling. Furthermore, since the lithium concentration can be increased during the process, the lithium recovery rate is high. In addition, since the chemical solution can be recycled without the addition of lithium hydroxide, the initial chemical cost is low, providing a lithium recovery method. [Brief explanation of the drawing]
[0014] [Figure 1] An explanatory diagram showing the configuration of one embodiment of the method for recovering valuable metals according to the present invention. [Modes for carrying out the invention]
[0015] One embodiment of the valuable metal recovery method of the present invention will be described in more detail with reference to the attached drawings.
[0016] In this invention, "waste lithium-ion battery" refers to a used lithium-ion battery whose lifespan as a battery product has been exhausted, a lithium-ion battery discarded as a defective product during the manufacturing process, and residual positive electrode material, negative electrode material, etc., used in the manufacturing process. Furthermore, the powder containing positive and negative electrodes obtained from the said waste lithium-ion battery, as well as crushed, coarse, and fine fragments of positive electrode plates, etc., are referred to as the active material powder. In addition, "impurity" refers to metals contained in the active material powder that do not require recovery.
[0017] The present invention's method for recovering valuable metals may use active material powder 1 as a starting material. The active material powder 1 will now be described. If the waste lithium-ion battery is a used lithium-ion battery whose lifespan as a battery product has been exhausted, or a lithium-ion battery that has been discarded as a defective product during the manufacturing process, first, a discharge treatment is performed. Various highly safe methods, such as resistive discharge, can be used for the discharge treatment. After discharging all residual charge, an opening is formed in the housing of the waste lithium-ion battery, and then, for example, the battery is heat-treated (roasted) at a temperature in the range of 100 to 800°C, or, without heat treatment, it is crushed with a crusher such as a hammer mill or jaw crusher, and the housing, current collector, etc. that constitute the waste lithium-ion battery are removed by sieving (classification) to obtain the active material powder. Alternatively, the waste lithium-ion battery after the discharge treatment may be crushed with the crusher, the housing, current collector, etc. are removed by sieving, and then the active material powder 1 may be obtained by heat treatment at the temperature in the range mentioned above.
[0018] If the waste lithium-ion battery is the residual positive electrode material, etc., used in the manufacturing process, the discharge treatment and opening formation may be omitted, and the material may be heated at the temperature within the range, or without heating, and then crushed in the crusher to remove the current collector, etc., by sieving, in order to obtain the active material powder. Furthermore, the waste lithium-ion battery may be crushed in the crusher, the current collector, etc., may be removed by sieving, and then the material may be heated at the temperature within the range, or without heating, in order to obtain the active material powder 1.
[0019] <Dissolution Step> The method for recovering valuable metals according to the present invention may include a dissolution step (STEP 1 in Figure 1) in which the active material powder 1 is dissolved in a mineral acid to obtain an acid solution. The active material powder 1 may contain valuable metals other than lithium, such as aluminum, manganese, cobalt, and nickel. The mineral acid preferably contains at least one selected from the group consisting of hydrochloric acid, sulfuric acid, and nitric acid, more preferably hydrochloric acid, and even more preferably hydrochloric acid.
[0020] <Neutralization Step> The method for recovering valuable metals of the present invention may include a neutralization step (STEP 2 in FIG. 1) in which the acid dissolution solution obtained through the dissolution step is neutralized with an alkali containing sodium. The alkali may be added in at least one form selected from the group consisting of an aqueous solution and a solid form. Further, the alkali preferably contains at least one selected from the group consisting of alkali metal hydroxides and ammonia. Still further, the alkali metal other than sodium constituting the alkali metal hydroxide may contain at least one selected from the group consisting of lithium, potassium, rubidium, cesium, and francium.
[0021] <Organic solvent extraction step> The method for recovering valuable metals of the present invention may include an organic solvent extraction step (STEP 3 in FIG. 1) in which at least one metal selected from the group consisting of at least one metal other than lithium, such as manganese, cobalt, and nickel, contained in the active material powder is separated by organic solvent extraction from the dissolution solution obtained through the neutralization step, and a first lithium and sodium salt aqueous solution is obtained as the residue of the organic solvent extraction.
[0022] <Evaporation concentration step> The method for recovering valuable metals of the present invention may include an evaporation concentration step (STEP 4 in FIG. 1) in which the first lithium and sodium salt aqueous solution is evaporated and concentrated.
[0023] <Membrane electrolysis step> The method for recovering valuable metals of the present invention includes a membrane electrolysis step (STEP 5 in FIG. 1) in which a lithium salt aqueous solution obtained through a lithium carbonate dissolution step described later is membrane electrolyzed. The membrane electrolysis step may be carried out, for example, by the method described in International Publication No. 2023 / 195533. Further, the concentrated first lithium and sodium salt aqueous solution obtained through the evaporation concentration step may be mixed with the lithium salt aqueous solution obtained through the lithium carbonate dissolution step described later, and then subjected to the membrane electrolysis step.
[0024] <Carbonation Step> The present invention provides a method for recovering valuable metals, which includes a carbonation step (STEP 6 in Figure 1) in which an aqueous solution containing lithium and sodium is carbonated. The solubility of sodium carbonate in water is much greater than that of lithium carbonate in water, and a large portion of the lithium in the aqueous solution containing lithium and sodium is recovered as lithium carbonate in the carbonation step. On the other hand, a large portion of the sodium in the aqueous solution containing lithium and sodium remains in the filtrate in the carbonation step, but some is recovered as sodium carbonate together with lithium carbonate. A portion or all of the aqueous solution containing lithium and sodium obtained through the membrane electrolysis step may be subjected to the carbonation step.
[0025] <Lithium carbonate dissolution step> The present invention provides a method for recovering valuable metals, which includes a lithium carbonate dissolution step (STEP 7 in Figure 1) in which the lithium carbonate obtained through the carbonation step is dissolved in a mineral acid. A small amount of sodium carbonate recovered together with the lithium carbonate is dissolved in the mineral acid in the lithium carbonate dissolution step and is dissolved in the lithium salt aqueous solution. The lithium salt aqueous solution may be concentrated by the method described in Japanese Patent No. 7166653. The mineral acid used in the lithium carbonate dissolution step is the same as the mineral acid used in the dissolution step.
[0026] The aqueous solution obtained in the membrane electrolysis step, in which lithium hydroxide and sodium hydroxide are dissolved, may be reused in at least one of the steps selected from the group consisting of the neutralization step and the organic solvent extraction step.
[0027] Furthermore, the acid obtained in the film electrolysis step may be reused as a mineral acid used in at least one of the steps selected from the group consisting of the dissolution step and the lithium carbonate dissolution step.
[0028] The electricity used in the aforementioned membrane electrolysis step includes electricity obtained from renewable energy sources. Furthermore, the electricity obtained from renewable energy sources includes electricity obtained from at least one selected from the group consisting of solar power generation, wind power generation, geothermal power generation, hydroelectric power generation, and biomass power generation.
[0029] For example, in the initial stages of the valuable metal recovery method described in International Publication No. 2023 / 195533, the valuable metal recovery method of the present invention is useful when sodium, which is cheaper than lithium, is used as the alkali in the neutralization step.
Claims
1. A method for recovering lithium from an aqueous solution containing lithium and sodium, Carbonation step of carbonating the aqueous solution, A lithium carbonate dissolution step is performed in which the lithium carbonate obtained through the carbonation step is dissolved in a mineral acid, and A method for recovering lithium, comprising a membrane electrolysis step of performing membrane electrolysis on an aqueous lithium salt solution obtained through the lithium carbonate dissolution step.
2. In the method for recovering lithium as described in claim 1, Dissolution step: Dissolve the active material powder obtained by pre-treating waste lithium-ion batteries in mineral acid to obtain an acid solution. A neutralization step in which the acid solution is neutralized with sodium, and The process further includes an organic solvent extraction step, in which at least one metal, excluding lithium, from the solution obtained through the neutralization step is separated by organic solvent extraction, and a first aqueous solution of lithium and sodium salt is obtained as the residue from the organic solvent extraction. In the membrane electrolysis step, the lithium chloride aqueous solution and the mixture obtained by mixing the first lithium salt and sodium salt aqueous solution are subjected to membrane electrolysis using an ion exchange membrane to obtain a lithium hydroxide and sodium hydroxide aqueous solution, an acid, and a second lithium salt and sodium salt aqueous solution that is more dilute than the first lithium salt and sodium salt aqueous solution. The aqueous solutions of lithium hydroxide and sodium hydroxide obtained in the membrane electrolysis step are reused in at least one selected from the group consisting of the neutralization step and the organic solvent extraction step. A method for recovering lithium, wherein the acid obtained in the film electrolysis step is reused as a mineral acid used in at least one selected from the group consisting of the dissolution step and the lithium carbonate dissolution step.
3. A method for recovering lithium according to claim 2, wherein the mineral acid comprises at least one selected from the group consisting of hydrochloric acid, sulfuric acid, and nitric acid.
4. A method for recovering lithium according to claim 3, wherein the mineral acid includes hydrochloric acid.
5. A method for recovering lithium according to any one of claims 1 to 4, wherein the power used in the membrane electrolysis step includes power obtained from renewable energy.
6. A method for recovering lithium according to claim 5, wherein the electricity obtained by renewable energy includes electricity obtained by at least one selected from the group consisting of solar power generation, wind power generation, geothermal power generation, hydroelectric power generation, and biomass power generation.