KR20210129042A - Lithium recovery method - Google Patents

Abstract

Provided is a lithium recovery method capable of recovering lithium with high purity from a liquid to be treated in which lithium and inorganic salts are dissolved. The lithium recovery method includes a concentration step (S8) of evaporating and concentrating the liquid to be treated in which lithium and inorganic salts are at least dissolved, and a crystallization step (S9) of cooling and crystallizing the liquid to be treated after the concentration step (S8) to precipitate inorganic salts as crystals (S9). ), a solid-liquid separation step (S10) of separating a precipitate containing inorganic salt crystals from the target liquid after the crystallization step (S9), and mixing carbon dioxide into the target liquid after the solid-liquid separation step (S10) and/or It has a carbonation process (S11) of adding a water-soluble carbonate, and a solid-liquid separation process (S12) of separating a precipitate containing crystals of lithium carbonate precipitated in the carbonation process (S11) from a liquid to be treated.

Description

Lithium recovery method

The present disclosure relates to a lithium recovery method for recovering lithium from a liquid to be treated in which lithium is at least dissolved, and in particular, a lithium recovery method used for recovering lithium from a waste lithium ion battery.

In addition, the present disclosure relates to a cobalt recovery method for recovering cobalt from a liquid to be treated in which at least cobalt and impurity metals are dissolved, in particular, to a cobalt recovery method used when recovering cobalt from a spent lithium ion battery.

Lithium ion batteries are attracting attention as lightweight and high energy density batteries, and are used in large quantities as batteries for various portable devices, electric vehicles, electric assist bicycles, and the like. For the positive electrode of this lithium ion battery, a lithium transition metal oxide such as lithium cobaltate or lithium nickelate is used as a positive electrode active material, and recovery of valuable metal cobalt and nickel from a waste lithium ion battery is an effective use of resources. Many methods have been proposed because it is very important from the point of view of

As a method of recovering cobalt from a spent lithium ion battery, for example, in Patent Document 1, a spent lithium ion battery is leached with sulfuric acid to elute cobalt, and an alkali is added to the acid leachate to adjust the pH to 4 to 5. Then, a salt of an impurity metal such as aluminum eluting with cobalt is precipitated and precipitated as a crystal, and then the pH is adjusted to 7-10 by adding an alkali again, and the cobalt salt is precipitated and precipitated as a crystal to obtain cobalt. Methods of recovery are described.

On the other hand, a method for recovering lithium from a spent lithium ion battery has a low unit cost of lithium, and therefore, not many methods have been proposed. However, the demand for lithium ion batteries is gradually increasing, and since an increase in waste is expected in the future, it is advantageous if lithium can be efficiently recovered.

In Patent Document 2, a used lithium metal gel and a solid polymer electrolyte secondary battery are dissolved in sulfuric acid, and lithium hydroxide or ammonium hydroxide is added to the resulting lithium sulfate-containing liquid containing lithium sulfate to neutralize the impurity metal. A method is described in which a salt (aluminum hydroxide) is precipitated as crystals, separated, and the lithium sulfate-containing liquid is evaporated and concentrated, followed by carbonation, whereby lithium contained in the lithium sulfate-containing liquid is precipitated as lithium carbonate crystals, followed by separation and recovery. has been

Patent Document 1: Patent Publication No. 5077788 Patent Document 2: Japanese Patent Application Laid-Open No. 2004-508694

However, in the method described in Patent Document 2, when ammonium hydroxide is used for neutralization at the time of removing impurities (aluminum hydroxide) from the lithium sulfate-containing liquid, the inorganic salt ammonium sulfate is contained in the lithium sulfate-containing liquid after neutralization. If carbonation is carried out in a state in which inorganic salts are contained in the lithium sulfate-containing liquid, there is a possibility of crystallization due to the increase in the inorganic salt concentration in the lithium sulfate-containing liquid due to concentration. Therefore, there is room for improvement in that the purity of the recovered lithium carbonate decreases because the lithium carbonate contains inorganic salts during carbonation.

In order to solve the above problems, an object of the present disclosure is to provide a lithium recovery method capable of recovering lithium with high purity from a liquid to be treated in which lithium and an inorganic salt are dissolved.

A lithium recovery method of one embodiment of the present disclosure includes a concentration step of evaporating and concentrating a liquid to be treated in which lithium and inorganic salts are at least dissolved, and crystallization by cooling and crystallization of the liquid to be treated after the concentration step to precipitate inorganic salts as crystals. a first solid-liquid separation step of separating a precipitate containing inorganic salt crystals from the liquid to be treated after the crystallization step; and a second solid-liquid separation step of separating a precipitate including crystals of lithium carbonate precipitated by the carbonation step from a liquid to be treated.

According to the lithium recovery method of one aspect of the present disclosure, by evaporating and concentrating the liquid to be treated in the concentration step before the carbonation step, the amount of the liquid to be treated is reduced and the lithium concentration in the liquid to be treated is increased. Therefore, the recovery rate of lithium carbonate in the carbonation process can be improved favorably.

Further, in the crystallization step after the concentration step, by cooling and crystallizing the target solution, the temperature of the target solution after evaporation and concentration is lowered to decrease the solubility until the inorganic salt contained in the target solution crystallizes. Thereby, the concentration of the inorganic salt in the liquid to be treated can be reduced. In addition, in the carbonation step, since the temperature of the liquid to be treated is raised for the purpose of lowering the solubility of lithium carbonate, the solubility of the inorganic salt remaining in the liquid to be treated increases, and crystallization of the inorganic salt can be suppressed. Accordingly, when lithium carbonate is recovered in the carbonation process, the purity of lithium carbonate can be increased.

According to the lithium recovery method of the present disclosure, lithium can be recovered with high purity from the liquid to be treated in which lithium and inorganic salt are dissolved.

1 is a flowchart schematically showing the sequence of the lithium recovery method of the first aspect.
FIG. 2 is a schematic diagram showing a schematic configuration of a processing device used in the lithium recovery method of FIG. 1 .
3 is a schematic diagram showing a schematic configuration of a bipolar membrane electrodialysis apparatus.
4 is a flowchart schematically showing a sequence of a modification of the lithium recovery method of the first aspect.
FIG. 5 is a schematic diagram showing a schematic configuration of a processing device used in the lithium recovery method of FIG. 4 .
6 is a flowchart schematically showing a sequence of a modification of the lithium recovery method of the first aspect.
FIG. 7 is a schematic diagram showing a schematic configuration of a processing device used in the lithium recovery method of FIG. 6 .
8 is a flowchart schematically showing the sequence of the lithium recovery method of the second aspect.
9 is a schematic diagram showing a schematic configuration of a processing device used in the lithium recovery method of FIG. 8 .
10 is a schematic diagram showing a schematic configuration of a bipolar membrane electrodialysis apparatus.
11 is a flowchart schematically showing the sequence of a modification of the lithium recovery method of the second aspect.
12 is a schematic diagram showing a schematic configuration of a processing device used in the lithium recovery method of FIG. 11 .
13 is a flowchart schematically showing the sequence of a modification of the lithium recovery method of the second aspect.
Fig. 14 is a schematic diagram showing a schematic configuration of a processing apparatus used in the method for recovering the retweet of Fig. 13;
15 is a flowchart schematically illustrating a sequence of a cobalt recovery method.
FIG. 16 is a schematic diagram showing a schematic configuration of a processing apparatus used for the cobalt recovery method of FIG. 15 .
17 is a schematic diagram showing a schematic configuration of a bipolar membrane electrodialysis apparatus.
18 is a flowchart schematically illustrating a sequence of a modification of the cobalt recovery method.
19 is a schematic diagram showing a schematic configuration of a processing apparatus used for the cobalt recovery method of FIG. 18 .
20 is a photograph of the surface state of the filtration residue of Example 1. FIG.
21 is a photograph of the surface state of the filtration residue of Example 2. FIG.
22 is a photograph of the surface state of the filtration residue of Example 3. FIG.

Hereinafter, embodiments of the lithium recovery method of the present disclosure will be described with reference to the accompanying drawings. In addition, in the following description, "~" means above and below.

Lithium recovery method of the first aspect

The lithium recovery method of the first aspect of the present disclosure includes a concentration step of evaporating and concentrating a liquid to be treated in which lithium and inorganic salts are at least dissolved; a crystallization step of cooling and crystallizing the liquid to be treated after the concentration step to precipitate inorganic salts as crystals; , a first solid-liquid separation step of separating precipitates containing inorganic salt crystals from the liquid to be treated after the crystallization step; and a second solid-liquid separation step of separating a precipitate including crystals of lithium carbonate precipitated by the carbonation step from a liquid to be treated.

In the lithium recovery method described in paragraphs 0016 and 0017, it is preferable that at least a part of the liquid to be treated after the second solid-liquid separation step is concentrated by evaporation in the concentration step.

Further, in the lithium recovery method described in Paragraph 0016, Paragraph 0017, or Paragraph 0018, it is preferable to further include an impurity removal step of at least removing calcium and/or magnesium contained in the liquid to be treated before the concentration step.

Further, in the lithium recovery method according to any one of paragraphs 0016 to 0019, in the first solid-liquid separation step, a dissolution step of dissolving inorganic salt crystals contained in the precipitate separated from the liquid to be treated to produce an inorganic salt solution; , it is preferable to further have an electrodialysis step of separating and recovering an inorganic acid together with an alkali from the inorganic salt solution by performing bipolar membrane electrodialysis on the inorganic salt solution obtained by the dissolution step.

Further, in the lithium recovery method described in paragraph 0020, it is preferable to evaporate and concentrate the inorganic salt solution after desalting by the bipolar membrane electrodialysis in the concentration step.

Further, in the lithium recovery method described in paragraph 0020 or paragraph 0021, before the electrodialysis step, at least substances that interfere with scaling such as calcium and/or magnesium contained in the inorganic salt solution in operating electrodialysis are removed. It is preferable to further have an impurity removal process.

Further, in the lithium recovery method according to any one of paragraphs 0020 to 0022, the recrystallization step of recrystallizing the inorganic salt contained in the inorganic salt solution before the electrodialysis step and separating the crystal of the inorganic salt from the inorganic salt solution; , it is preferable to further have a re-dissolving step of dissolving the crystals of the inorganic salt obtained by the recrystallization step to produce an inorganic salt solution.

Further, in the lithium recovery method according to any one of paragraphs 0020 to 0023, it is preferable to use the condensed water generated in the concentration step for dissolving the inorganic salt in the dissolution step.

Further, in the lithium recovery method according to any one of paragraphs 0020 to 0023, it is preferable to use the inorganic acid recovered in the electrodialysis step for the regeneration solution of the chelate resin or ion exchange resin used in the impurity treatment step.

Further, in the lithium recovery method according to any one of paragraphs 0016 to 0025, in this case, a precipitate containing inorganic salt crystals obtained in the first solid-liquid separation step by the condensed water generated in the concentration step and/or the first agent It is preferable to wash|clean the precipitate containing the crystal|crystallization of lithium carbonate obtained by 2 solid-liquid separation process.

Further, in the lithium recovery method according to any one of paragraphs 0016 to 0026, an acid leaching step of leaching lithium by leaching a spent lithium ion battery with an inorganic acid before the concentration step, and a lithium-containing liquid obtained by the acid leaching step It is preferable that the liquid to be treated is produced by further comprising a pH adjustment step of adjusting the pH by adding an alkali to the solution, and separating the precipitates precipitated by the pH adjustment step from the lithium-containing liquid.

Further, in the lithium recovery method described in paragraph 0027, it is preferable to reuse at least a part of the liquid to be treated after the second solid-liquid separation step as the alkali added in the pH adjustment step.

Further, in the lithium recovery method described in paragraph 0027 or 0028, the alkali recovered in the electrodialysis step is reused as an alkali added in the pH adjustment step, and the inorganic acid recovered in the electrodialysis step is used in the acid leaching step. It is preferable to reuse as an inorganic acid to be used.

Further, in the lithium recovery method according to any one of paragraphs 0027 to 0029, it is preferable to wash the precipitates deposited in the pH adjustment step with the condensed water generated in the concentration step.

Further, in the lithium recovery method according to any one of paragraphs 0027 to 0030, the method further includes a roasting step of roasting the spent lithium ion battery before the acid leaching step, and in the carbonation step, exhaust gas generated in the roasting step It is preferable to mix the gas with the liquid to be treated as carbon dioxide gas.

According to the lithium recovery method of the first aspect of the present disclosure, by evaporating and concentrating the liquid to be treated in the concentration step before the carbonation step, the amount of the liquid to be treated is reduced and the lithium concentration in the liquid to be treated is increased. Therefore, the recovery rate of lithium carbonate in the carbonation process can be improved favorably.

Further, in the crystallization step after the concentration step, by cooling and crystallizing the target solution, the temperature of the target solution after evaporation and concentration is lowered to decrease the solubility until the inorganic salt contained in the target solution crystallizes. Thereby, the concentration of the inorganic salt in the liquid to be treated can be reduced. In addition, in the carbonation step, since the temperature of the liquid to be treated is raised for the purpose of lowering the solubility of lithium carbonate, the solubility of the inorganic salt remaining in the liquid to be treated is increased, and crystallization of the inorganic salt can be suppressed. Accordingly, when lithium carbonate is recovered in the carbonation process, the purity of lithium carbonate can be increased.

1 shows the sequence of each process with respect to the embodiment of the lithium recovery method of the first aspect of the present disclosure, and FIG. 2 shows a schematic configuration of a processing apparatus 10 for implementing the lithium recovery method of FIG. 1 . The lithium recovery method of this embodiment is suitable for treating a liquid to be treated containing, in addition to lithium, strong acids such as hydrochloric acid, sulfuric acid, hydrofluoric acid and phosphoric acid, and inorganic salts of alkali metals or alkaline earth metals such as potassium and sodium. In particular, it can be suitably used for recovering lithium from a waste lithium ion battery. Hereinafter, the case of recovering lithium from a waste lithium ion battery will be described as an example.

The lithium recovery method of this embodiment comprises:

-Acid leaching process (S1) of leaching lithium by leaching the spent lithium ion battery with an inorganic acid;

- a solid-liquid separation step (S2) of separating insoluble residues from the lithium-containing liquid obtained by the acid leaching step (S1);

- A pH adjustment step (S3, S5) of adjusting the pH by adding an alkali to the lithium-containing liquid after the solid-liquid separation step (S2);

- a solid-liquid separation step (S4, S6) of separating the precipitate from the lithium-containing liquid after the pH adjustment step (S3, S5);

an impurity removal step (S7) of performing a chelating treatment on the liquid to be treated in which precipitates are separated from the lithium-containing liquid after the pH adjustment step (S3, S5);

- Concentration step (S8) of evaporating and concentrating the liquid to be treated in which lithium and inorganic salts are at least dissolved after the impurity removal step (S7);

- A crystallization step (S9) of cooling and crystallizing the liquid to be treated after the concentration step (S8) to precipitate inorganic salts as crystals;

- A solid-liquid separation step (S10) of separating a precipitate containing inorganic salt crystals from the liquid to be treated after the crystallization step (S9) (corresponding to the “first solid-liquid separation step” described in paragraphs 0016 and 0017);

- Carbonation step (S11) of mixing carbon dioxide gas and/or adding water-soluble carbonate to the liquid to be treated after the solid-liquid separation step (S10);

- A solid-liquid separation step (S12) (corresponding to the “second solid-liquid separation step” described in paragraphs 0016 and 0017) of separating the precipitate containing lithium carbonate crystals precipitated by the carbonation step (S11) from the liquid to be treated; have The lithium recovery method of the present embodiment further comprises:

- A dissolution step (S13) of dissolving inorganic salt crystals contained in the precipitate separated from the liquid to be treated in the solid-liquid separation step (S10) to produce an inorganic salt solution;

- Bipolar membrane electrodialysis is performed on the inorganic salt solution after the dissolution step (S13) to separate and recover alkalis and inorganic acids from the inorganic salt solution (S14).

Waste lithium ion batteries subject to lithium recovery include used lithium ion batteries whose charge capacity has decreased due to use of a predetermined number of charge/discharge cycles, as well as semi-finished products and product type changes caused by defects in the battery manufacturing process. It includes outdated inventory clearances that accompany the The waste lithium ion battery may be pulverized or roasted, or may be a powder obtained by pulverization and roasting treatment.

First, in the acid leaching step (S1), metals such as aluminum, nickel, cobalt, and iron are eluted in addition to lithium by leaching the above-described spent lithium ion battery with an inorganic acid. As the inorganic acid, for example, sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid and the like can be used, but in the present embodiment, sulfuric acid is used because of its low cost and ease of handling.

In the acid leaching step (S1), the method for leaching a spent lithium ion battery with an inorganic acid is not particularly limited, and a method commonly used can be used. For example, in the acid leaching tank 1, a waste lithium ion battery is immersed in an aqueous solution of an inorganic acid such as an aqueous sulfuric acid solution and stirred for a predetermined time to obtain a lithium-containing liquid in which a metal such as lithium is dissolved. In the acid leaching step (S1), the concentration of the inorganic acid in the aqueous solution is preferably 1 mol to 5 mol/L, and the temperature of the aqueous solution is preferably 60° C. or higher.

In the next solid-liquid separation step (S2), the lithium-containing liquid obtained in the acid leaching step (S1) is filtered, for example, to separate insoluble residues from the lithium-containing liquid. The insoluble residues are mainly carbon materials, metal materials, and organic materials that do not dissolve in inorganic acids. As a method of solid-liquid separation, well-known solid-liquid separation apparatuses, such as various filtration apparatuses, such as pressure filtration (filter press), vacuum filtration, and centrifugal filtration, and a centrifugal separation apparatus like a decanter type, can be used, for example. The same applies to the following solid-liquid separation steps (S4, S6, S10, S12).

In the following pH adjustment steps (S3 and S5), an alkali is added to the lithium-containing liquid (filtrate) after the solid-liquid separation step (S2) and the pH is adjusted to a predetermined range, so that among the above metals in the lithium-containing liquid, lithium Other metals are removed from the lithium-containing liquid. As the alkali, for example, sodium hydroxide, potassium hydroxide, lithium hydroxide, etc. can be used, but in the present embodiment, sodium hydroxide is used because of its low cost and ease of handling.

In the pH adjustment step (S3, S5), the method for adjusting the pH of the lithium-containing liquid is not particularly limited, and a method generally used can be used. For example, by adding an aqueous alkali solution such as sodium hydroxide aqueous solution while stirring the lithium-containing liquid in the first pH adjusting tank 2 and the second pH adjusting tank 3, metals other than lithium in the lithium-containing liquid is precipitated and precipitated as crystals of inorganic salts such as hydroxide. In this embodiment, the pH adjustment process (S3, S5) is divided into the 1st pH adjustment process (S3) and the 2nd pH adjustment process (S5).

In the first pH adjustment step (S3), the pH of the lithium-containing liquid is adjusted to 4 to 7, preferably 4 to 6, more preferably 4 to 5 by addition of an alkali. As a result, impurity metals (eg, aluminum, iron) in the lithium-containing liquid are precipitated and precipitated as crystals of inorganic salts such as hydroxides (eg, aluminum hydroxide and iron hydroxide). In the first pH adjustment step (S3), it is preferable to carry out the lithium-containing liquid while heating the lithium-containing liquid to a constant temperature, for example, from 30°C to 80°C.

It is preferable that the alkali concentration of the aqueous solution of the alkali added in the 1st pH adjustment process (S3) is less than 1.0 mol/L and a dilute thing. Accordingly, although details will be described later, it is possible to suppress the cobalt in the lithium-containing liquid from being removed from the lithium-containing liquid by precipitation and precipitation as crystals of a cobalt salt together with the impurity metal in the first pH adjustment step (S3). However, if the alkali concentration is excessively low, it is necessary to use a large amount of an aqueous alkali solution for pH adjustment in the first pH adjustment step S3, and the amount of the lithium-containing liquid after pH adjustment also becomes large, so the alkali concentration It is preferable that the lower limit of is 0.1 mol/L or more. In addition, in order to effectively suppress the removal of cobalt in the lithium-containing liquid from the lithium-containing liquid in the first pH adjustment step (S3), the alkali concentration of the aqueous alkali solution added in the first pH adjustment step (S3) is 0.5 mol/ It is preferable that it is L or less, and it is more preferable that it is 0.2 mol/L or less.

In addition, in this 1st pH adjustment process (S3), in order to reduce the amount of the aqueous solution of alkali used for pH adjustment, until the pH of a lithium-containing liquid becomes a predetermined value smaller than 4, a deep alkali of 1.0 mol/L or more An aqueous solution of alkali having a concentration is added to the lithium-containing liquid, and after the pH of the lithium-containing liquid reaches a predetermined value, an aqueous solution of an alkali having a light alkali concentration of less than 1.0 mol/L is added to the lithium-containing liquid to contain lithium It is also possible to adjust the pH of the liquid to 4-7. As a predetermined value of the pH of the above-described lithium-containing liquid, it can be set within the range of 2-3.

The precipitates deposited and precipitated in the first pH step (S3) are separated from the lithium-containing liquid by, for example, filtering the lithium-containing liquid in the following solid-liquid separation step (S4). In addition, copper etc. may be contained in the impurity metal removed from the lithium-containing liquid in the 1st pH adjustment process (S3). In the solid-liquid separation step (S4), it is preferable to wash the precipitate with a washing liquid, and to supply the washing waste liquid after washing to the next second pH adjustment process (S5) together with the lithium-containing liquid (filtrate). Accordingly, even lithium contained in the washing waste liquid can be supplied together with lithium contained in the lithium-containing liquid from the second pH adjustment step (S5) to the carbonation step (S11), and lithium is carbonated by carbonation in the carbonation step (S11) described later. can be recovered with a high recovery rate. Although the water used for washing|cleaning this precipitate is not specifically limited, It is preferable to use the condensed water generated when the to-be-processed liquid is evaporated and concentrated in the concentration process (S8) mentioned later, Thus, the effective use of condensed water is possible.

In the second pH adjustment step (S5), an alkali is added to the lithium-containing liquid (filtrate) after the solid-liquid separation step (S4) to raise the pH to 7 or more, preferably 7 to 13, more preferably 7 to 11, still more preferably Usually, it is adjusted in the range of 8-10. Thereby, valuable metals (eg, cobalt, nickel) in the lithium-containing liquid are precipitated and precipitated as crystals of inorganic salts such as hydroxides (eg, cobalt hydroxide, nickel hydroxide). In the second pH adjustment step (S5), it is preferable to carry out the lithium-containing liquid while heating the lithium-containing liquid to a constant temperature, for example, from 30°C to 80°C. Although the alkali concentration of the aqueous solution of alkali added in the 2nd pH adjustment process (S5) is not specifically limited, It is preferable that it is more than the alkali concentration of the aqueous solution of alkali used in the 1st pH adjustment process (S3), Furthermore, the alkali concentration It is preferable that is 0.2 mol/L or more.

The precipitates deposited and precipitated in the second pH adjustment step (S5) are separated from the lithium-containing liquid by, for example, filtering the lithium-containing liquid in the following solid-liquid separation step (S6). In addition, manganese etc. may be contained in the valuable metal removed from the lithium-containing liquid in the 2nd pH adjustment process (S5).

On the other hand, to the lithium-containing liquid (filtrate) after the solid-liquid separation step (S6), in addition to lithium, inorganic acids (sulfuric acid in this embodiment) and alkalis ( in this embodiment it is dissolved inorganic salt (in the present embodiment, sodium sulfate (Na ₂ SO _4), by sodium) hydroxide). The lithium-containing liquid after this pH adjustment step (S3, S5) corresponds to the "to-be-processed liquid" of the lithium recovery method of the present disclosure. At least one of calcium, magnesium and silica may be further dissolved in this to-be-processed liquid.

In the solid-liquid separation step (S6), it is preferable to wash the precipitate with a washing liquid, and to supply the washing waste liquid after washing to the next impurity removal process (S7) together with the liquid to be treated (filtrate). Accordingly, even lithium contained in the washing waste liquid can be supplied from the impurity removal process (S7) to the carbonation process (S11) together with the lithium contained in the liquid to be treated, and lithium is recovered by carbonation in the carbonation process (S11) to be described later. It can be recovered with a recovery rate. Although the water used for washing|cleaning this precipitate is not specifically limited, It is preferable to use the condensed water generated when the to-be-processed liquid is evaporated and concentrated in the concentration process (S8) mentioned later, Thus, the effective use of condensed water is possible.

In the next impurity removal step (S7), at least polyvalent cations such as calcium and/or magnesium contained in the liquid to be treated after the solid-liquid separation step (S6) are removed. By removing calcium, magnesium, etc. contained as impurities in the liquid to be treated, in the concentration step (S8) to be described later, it is possible to suppress the occurrence of scale and adhesion to the heat transfer surface of the heat exchanger of the evaporative concentration device 5, Heat exchange efficiency can be maintained high. In addition, if the liquid to be treated contains calcium or magnesium, polyvalent cations such as calcium and magnesium contained in the inorganic solution are converted into the cation exchange membrane of the bipolar membrane electrodialysis apparatus 9 in the electrodialysis step (S14) to be described later. There is a fear that it precipitates in the lining, leading to a decrease in the performance of the film. Therefore, it is possible to prevent adverse effects on the cation exchange membrane of the bipolar membrane electrodialysis apparatus 9 by removing substances that interfere with scaling, such as calcium or magnesium, from the liquid to be treated in advance. The performance of electrodialysis can be maintained high.

In the impurity removal step (S7), the method for removing calcium or magnesium from the liquid to be treated is not particularly limited, and, for example, the polyvalent cation removal device 4 can be used. The polyvalent cation removal device 4 is a device for removing divalent or higher polyvalent cations such as calcium ions and magnesium ions, and, for example, a configuration capable of passing a liquid to be treated through a column filled with a chelate resin can be exemplified. As a chelate resin, what can selectively capture|acquire calcium ion and a magnesium ion can be used, For example, iminodiacetic acid type, aminophosphoric acid type, etc. can be illustrated. As the polyvalent cation removal device 4, in addition, adding a chelating agent, using an ion exchange resin, etc. are mentioned. In addition to calcium or magnesium, silica (silicate ions) may be contained in the impurities removed from the liquid to be treated in the impurity removal step S7.

In the next concentration step (S8), the liquid to be treated after the impurity removal step (S7) is heated and concentrated by evaporation. That is, the to-be-processed liquid is concentrated by evaporating the water|moisture content in the heat processing liquid. Accordingly, the liquid amount of the liquid to be treated decreases, and the lithium concentration in the liquid to be treated increases. Therefore, it is possible to improve the recovery rate of lithium carbonate in the carbonation process (S11) to be described later.

In the concentration step (S8), it is preferable to concentrate the liquid to be treated to a concentration such that lithium does not precipitate as crystals of lithium salts such as lithium sulfate in the liquid to be treated after concentration. Accordingly, the concentration of lithium in the liquid to be treated after concentration can be increased, and the recovery rate of lithium carbonate in the carbonation step (S11) described later can be improved.

In the concentration step (S8), the method of evaporating and concentrating the liquid to be treated is not particularly limited, and, for example, the evaporation concentrator 5 can be used. The evaporative concentration device 5 is not particularly limited as long as it can concentrate the liquid to be treated by evaporation. For example, a known evaporative concentration device such as a heat pump type, an ejector drive type, a steam type, or a flash type can be used. However, it is preferably a heat pump type evaporative concentration device. When a heat pump type evaporation system is used, the energy to be used can be significantly suppressed. In addition, further energy saving can be achieved by concentrating the liquid to be treated in a reduced pressure atmosphere.

In the next crystallization process (S9), the to-be-processed liquid after a concentration process (S8) is cooled and crystallized. In this crystallization step (S9), the temperature of the liquid to be treated after evaporation and concentration is lowered to lower the solubility until the inorganic salt contained in the liquid to be treated crystallizes, whereby the inorganic salt in the liquid to be treated (sodium sulfate in this embodiment) concentration can be reduced. Therefore, when recovering lithium carbonate in the carbonation process (S11) mentioned later, the purity of lithium carbonate can be improved.

In the crystallization process (S9), it does not specifically limit about the method of cooling and crystallizing a to-be-processed liquid, For example, the cooling and crystallization apparatus 6 can be used. The cooling and crystallization apparatus 6 cools the supplied to-be-processed liquid in a crystallization tank, and deposits the target inorganic salt crystal|crystallization. As the cooling and crystallization apparatus 6, well-known cooling and crystallization apparatuses, such as a cooling system crystallization apparatus by a jacket or an internal coil, and an external circulation cooling type crystallization apparatus, can be used, and it is not specifically limited.

In the crystallization process (S9), only the crystal|crystallization of the objective inorganic salt is precipitated using the thing from which saturated solubility and the temperature dependence of solubility differ with an inorganic salt. In this embodiment, the temperature dependence of the solubility of lithium salts, such as lithium sulfate, compared with inorganic salts other than lithium salts, such as sodium sulfate, is used. That is, inorganic salts other than lithium salts are precipitated as crystals by cooling below the precipitation temperature of inorganic salts other than lithium salts above the precipitation temperature of the lithium salt in the supply concentration. Specifically, the cooling temperature for precipitating sodium sulfate crystals is 30°C or less, preferably 5°C or more and 20°C or less. At this time, sodium sulfate is precipitated in the form _{of sodium sulfate + hydrate (Na 2} SO ₄ ·10H _{2 O).}

In the next solid-liquid separation process (S10), the precipitate containing the crystal|crystallization of an inorganic salt (sodium sulfate in this embodiment) is isolate|separated from the to-be-processed liquid by filtering, for example, the to-be-processed liquid after the crystallization process (S9).

In the following carbonation step (S11), lithium in the liquid to be treated is converted into lithium carbonate crystals by mixing carbon dioxide gas and/or adding a water-soluble carbonate to the liquid to be treated after the precipitates containing the inorganic salt crystals are separated. precipitation and precipitation. Thereby, lithium in the liquid to be treated can be recovered as lithium carbonate. As carbonate, sodium carbonate, ammonium carbonate, potassium carbonate, etc. can be used, for example.

In this carbonation step (S11), it is preferable to precipitate and precipitate crystals of lithium carbonate by mixing carbon dioxide gas with the liquid to be treated. In this way, in the carbonation step (S11), for example, by using a material that does not contain alkali metals such as sodium, it is possible to suppress mixing of alkali metals other than lithium into the precipitated crystals of lithium carbonate. Therefore, lithium carbonate with high purity can be recovered.

However, when the carbon dioxide gas is continuously mixed, the pH of the liquid to be treated decreases, so that the amount of lithium carbonate precipitated may decrease. Therefore, it is preferable to stop mixing the carbon dioxide gas before the pH of the liquid to be treated becomes 7 or less. Moreover, you may make it so that pH does not fall by adding an alkali to the to-be-processed liquid. In that case, it is preferable to maintain pH at 9 or more by alkali addition. As an alkali to be added, sodium hydroxide, potassium hydroxide, lithium hydroxide, etc. can be used.

In the carbonation step (S11), the method of mixing the carbon dioxide gas with the liquid to be treated is not particularly limited, and a method usually performed can be used. For example, carbon dioxide gas can be uniformly mixed with the liquid to be treated by supplying carbon dioxide gas into the liquid to be treated in the form of fine bubbles by means of a nozzle while stirring the liquid to be treated in the carbonation tank 7, Lithium in the liquid and carbon dioxide gas can be reacted efficiently. Moreover, you may make it react with carbon dioxide gas by spraying a to-be-processed liquid in the atmosphere of carbon dioxide gas.

Since the solubility of lithium carbonate decreases as the temperature increases, it is preferable to heat the liquid to be treated in the carbonation step S11. Accordingly, since the solubility of lithium carbonate generated by the reaction of lithium and carbon dioxide in the liquid to be treated decreases, the amount of precipitated lithium carbonate crystals can be increased. In addition, by heating the liquid to be treated, the solubility of the inorganic salt (sodium sulfate in the present embodiment) remaining in the liquid to be treated increases, and crystallization of the inorganic salt can be suppressed. Therefore, since it is possible to suppress the deposition of crystals of inorganic salts together with crystals of lithium carbonate, it is possible to increase the purity of lithium carbonate when recovering lithium carbonate in the carbonation step.

In the next solid-liquid separation step (S12), the precipitate containing lithium carbonate crystals is separated from the lithium-containing liquid by, for example, filtering the liquid to be treated after the carbonation step (S11). In the solid-liquid separation step (S12), impurities are removed by washing the precipitate separated from the lithium-containing liquid with water or the like, and the purity of lithium carbonate can be increased. Although the water used for washing|cleaning this precipitate is not specifically limited, It is preferable to use the condensed water which arises when the to-be-processed liquid is evaporated and concentrated in the concentration process (S8), Thus, the effective use of condensed water is possible.

The liquid to be treated (filtrate) after the solid-liquid separation step (S12) is not particularly limited, but since it contains impurities, a part is discharged as a burrow's solution, but it is preferable to circulate a part back into the system. . Accordingly, since the lithium remaining in the liquid to be treated can be recovered, lithium can be recovered at a high recovery rate. In addition, it is preferable that the washing waste liquid after washing the precipitate containing the lithium carbonate crystals is also circulated back into the system together with the liquid to be treated after the solid-liquid separation step (S12).

When the liquid to be treated after the solid-liquid separation step (S12) is circulated back into the system, it may be supplied to the evaporator 5 and concentrated by evaporation in the concentration step (S8), but preferably the first pH adjusting tank 2 and/ Alternatively, it is supplied to the second pH adjustment tank (3). Since the liquid to be treated after the solid-liquid separation step (S12) is alkaline, it can be used as an alkali added in the pH adjustment steps (S3, S5). Furthermore, if the liquid to be treated after the solid-liquid separation step S12 contains a large amount of carbonate ions (CO ₃ ² − ), the heat transfer surface of the heat exchanger of the evaporative concentrator 5 when evaporating and concentrating in the concentration step S8 . carbonate crystals are precipitated. Therefore, since the lithium-containing liquid after the solid-liquid separation step (S2, S4) is acidic, the liquid to be treated after the solid-liquid separation step (S12) is neutralized with the lithium-containing liquid to extract carbonate ions from the liquid to be treated as carbon dioxide gas. Precipitation of carbonate crystals on the heat transfer surface of the heat exchanger of the evaporative concentration device 5 in the concentration step S8 can be prevented.

On the other hand, the crystal of the inorganic salt (sodium sulfate in this embodiment) contained in the precipitate separated from the liquid to be treated in the solid-liquid separation step (S10) (cooling and crystallization device 6) is dissolved in the dissolution step (S13) (dissolution tank 8) is supplied to In a dissolution process (S13), it melt|dissolves using water so that it may become a desired density|concentration in the crystal|crystallization of an inorganic salt in the dissolution tank 8, and produces|generates an inorganic salt solution. The temperature at this time is not specifically limited, What is necessary is just a temperature which can melt|dissolve the crystal|crystallization of an inorganic salt. In addition, the water used for dissolution of the inorganic salt is not particularly limited, but it is preferable to use condensed water generated when the target liquid is evaporated and concentrated in the concentration step (S8), so that the condensed water can be effectively used. The resulting inorganic salt solution is supplied to the bipolar membrane electrodialysis device 9 .

In the next electrodialysis step (S14), the alkali and inorganic acids are separated and recovered from the inorganic salt solution after the dissolution step (S13) by the bipolar membrane electrodialysis apparatus 9 . As the bipolar membrane electrodialysis apparatus 9, for example, as shown in FIG. 3, an anion exchange membrane 91, a cation exchange membrane 92, and two bipolar membranes are interposed between the anode 95 and the cathode 96. A three-cell type bipolar membrane electrodialysis apparatus in which a plurality of cells 90 having (93, 94) are stacked can be suitably used. In the bipolar membrane electrodialysis apparatus 9 of this embodiment, a desalting chamber R1 is formed by an anion exchange membrane 91 and a cation exchange membrane 92, and between the anion exchange membrane 91 and one bipolar membrane 93. An acid chamber (R2) is formed therein, and an alkali chamber (R3) is formed between the cation exchange membrane (91) and the other bipolar membrane (94). An anode chamber R4 and a cathode chamber R5 are formed outside each of the bipolar films 93 and 94, an anode 95 is provided in the anode chamber R4, and a cathode 96 is formed in the cathode chamber R5. each is placed.

In this electrodialysis step (S14), an inorganic salt solution is introduced into the desalting chamber R1, and pure water is introduced into the acid chamber R2 and the alkali chamber R3, respectively. Accordingly, when the inorganic salt solution contains, for example, sodium sulfate, sodium ions (Na ⁺ ) pass through the cation exchange membrane 92 in the _{desalting chamber (R1), and sulfate ions (SO 4} ²⁻ ) It passes through the anion exchange membrane (91). On the other hand, in the acid chamber (R2) and the alkali chamber (R3), the supplied pure water is ^{dissociated into hydrogen ions (H +} ) and hydroxide ions (OH ⁻ ) in the bipolar membranes 93 and 94, and in the acid chamber (R2), hydrogen ions ( H ⁺ ) combines with sulfate ions (SO ₄ ²⁻ ) to form sulfuric acid (H ₂ SO ⁴ ), and in the alkali chamber (R3), hydroxide ions (OH ⁻ ) combine with sodium ions (Na ⁺ ) to form sodium hydroxide (NaOH) is formed. _{Thereby, sulfuric acid (H 2} SO ₄ ) as an inorganic acid from the acid chamber (R2) and sodium hydroxide (NaOH) as an alkali from the alkali chamber (R3) are respectively recovered. In addition, as the pure water introduced into the acid chamber R2 and the alkali chamber R3, condensed water generated when the liquid to be treated is evaporated and concentrated in the concentration step S8 may be used.

The dilute inorganic salt solution (desalting solution) after desalting discharged from the desalting chamber R1 is not particularly limited, but since it contains a little lithium, it is supplied to the concentration step S8 (evaporative concentration device 5), After concentration again, carbonation is preferably carried out in the carbonation step (S11). Accordingly, lithium can be recovered with a high recovery rate. In addition, although the demineralization liquid is supplied to the concentration process (S8) in this embodiment, when calcium and/or magnesium remain in the desalination liquid, you may supply the demineralization liquid to the impurity removal process S7. Thereby, after removing calcium and magnesium from a desalting liquid, it can supply to a concentration process (S8). In addition, you may supply the desalting liquid to the 1st pH adjustment process (S3). Accordingly, when cobalt remains in the desalting solution, the recovery rate of cobalt can be increased.

In addition, the inorganic acid (sulfuric acid in this embodiment) recovered from the acid chamber (R2) is not particularly limited, but is supplied to the acid leaching tank 1 and used as an inorganic acid for leaching the spent lithium ion battery in the acid leaching step (S1). It is preferable to reuse it. Moreover, it is preferable to supply it to the polyvalent cation removal apparatus 4, and to reuse it as a regeneration liquid of the chelate resin or ion exchange resin used in the impurity treatment process (S7).

In addition, although the alkali (sodium hydroxide in this embodiment) recovered|recovered from alkali chamber R3 is not specifically limited, Lithium-containing liquid is supplied to the pH adjustment tanks 2 and 3, and pH adjustment process S3, S5. It is preferable to reuse it as an alkali for pH adjustment. Moreover, it is preferable to supply it to the polyvalent cation removal apparatus 4, and to reuse it as a regeneration liquid of the chelate resin or ion exchange resin used in the impurity treatment process (S7).

According to the lithium recovery method of the present embodiment described above, by evaporating and concentrating the liquid to be treated in the concentration step (S8) before the carbonation step (S11), the amount of the liquid to be treated is reduced and the lithium concentration in the liquid to be treated is increased. Therefore, the recovery rate of the crystals of lithium carbonate in the carbonation step (S11) can be improved favorably.

Further, in the crystallization step (S9) after the concentration step (S8), the target solution is cooled and crystallized to lower the temperature of the target solution after evaporation and concentration, and the inorganic salt (sodium sulfate in this embodiment) contained in the target solution is crystallized. Since the solubility is lowered until the In addition, in the carbonation step (S11), since the temperature of the liquid to be treated is raised for the purpose of lowering the solubility of lithium carbonate, the solubility of the inorganic salt remaining in the liquid to be treated increases, and crystallization of the inorganic salt can be suppressed. Accordingly, when lithium carbonate is recovered in the carbonation step S11, the purity of the lithium carbonate can be increased.

Further, according to the lithium recovery method of the present embodiment, the lithium carbonate remaining in the liquid to be treated is recovered by circulating it in the system without disposing of the liquid to be treated after the crystals of lithium carbonate are recovered in the carbonation step (S11). Therefore, lithium can be recovered with a high recovery rate.

Further, according to the lithium recovery method of the present embodiment, crystals of an inorganic salt (sodium sulfate in this embodiment) contained in the precipitate separated from the liquid to be treated in the solid-liquid separation step (S10) are dissolved in the dissolution step (S13) to obtain inorganic After making the salt solution, inorganic acids and alkalis are recovered from the inorganic salt solution by performing bipolar membrane electrodialysis in the electrodialysis step (S14), and the dilute inorganic salt solution after desalting is evaporated and concentrated in the concentration step (S8), In the carbonation step (S11), lithium contained in the dilute inorganic salt solution is recovered. Therefore, lithium can be recovered with a high recovery rate. In addition, the inorganic acids and alkalis recovered in the electrodialysis step (S14) are recycled and reused in the acid leaching step (S1), the pH adjustment step (S3, S5), and the impurity removal step (S7) to be reused in each step (S1, S3, S5). , it is possible to reduce the amount of inorganic acid or alkali used in S7).

In addition, according to the lithium recovery method of the present embodiment, polyvalent cations such as calcium and magnesium contained in the liquid to be treated are removed in the impurity removal step (S7). Accordingly, the amount of impurities in the liquid to be treated from which precipitates are separated in the solid-liquid separation step (S12) after the carbonation step (S11) is reduced, so that most of the liquid to be treated after the solid-liquid separation step (S12) can be circulated back into the system. . Therefore, since more lithium remaining in the liquid to be treated after the solid-liquid separation step S12 can be recovered, lithium can be recovered at a high recovery rate. In addition, since the amount of impurities in the inorganic solution to be electrodialyzed in the electrodialysis step S14 is reduced, it is possible to prevent the performance of the cation exchange membrane of the bipolar electrodialysis apparatus 9 from being deteriorated due to scaling, so that the performance of the bipolar membrane is maintained high. can

In addition, according to the lithium recovery method of this embodiment, since the condensed water generated in the concentration step S8 is used for various treatments, the condensed water can be effectively used. In addition, by washing the crystals obtained by the respective solid-liquid separation steps S4, S6, S10, and S12 using condensed water, the recovery rate of each crystal can be improved favorably.

As mentioned above, although one embodiment of the lithium recovery method of the first aspect has been described, the lithium recovery method of the first aspect is not limited to the embodiments shown in Figs. There are several possible changes.

For example, in the embodiment of FIGS. 1 and 2 , an impurity removal step (S7) of at least removing calcium and/or magnesium from the liquid to be treated before the concentration step (S8) is performed, but instead of or in addition to this Thus, an impurity removal step of removing at least calcium and/or magnesium may be performed similarly to the inorganic salt solution before the electrodialysis step (S14).

1 and 2, the alkali recovered in the electrodialysis step (S14) is supplied to the first pH adjustment step (S3) and the second pH adjustment step (S5), but only either one is supplied. good to do

In addition, in the embodiment of FIG. 1 and FIG. 2, although the pH adjustment process (S3, S5) includes the 1st pH adjustment process (S3) and the 2nd pH adjustment process (S5), the component contained in a waste lithium ion battery It may be configured to include three or more steps, or may be configured to include only one step.

In addition, in the embodiment of Figs. 1 and 2, as shown in Figs. 4 and 5, after the dissolution step (S13) and before the electrodialysis step (S14), the inorganic salt solution contains, for example, silica, etc. A treatment step for removing impurities of This treatment step can be performed instead of the impurity removing step S7 or in addition to the impurity removing step S7.

Specifically, first, the inorganic salt (sodium sulfate in the present embodiment) contained in the inorganic salt solution in the recrystallization step (S13-1) is recrystallized. It does not specifically limit about the method of recrystallizing the inorganic salt contained in an inorganic salt solution, For example, cooling and crystallization by the cooling and crystallization apparatus 10 similar to the cooling and crystallization apparatus 6 of the above-mentioned crystallization process (S9). is available. That is, only the crystals of the inorganic salt can be precipitated by using the inorganic salt and the silica having different saturation solubility and the temperature dependence of the solubility, and the inorganic salt is crystallized by cooling below the precipitation temperature of the inorganic salt above the silica precipitation temperature at the feed concentration. to precipitate At this time, sodium sulfate is precipitated in the form _{of sodium sulfate + hydrate (Na 2} SO ₄ ·10H _{2 O).} Moreover, you may concentrate the inorganic salt solution to the density|concentration of the inorganic salt suitable for the crystallization of an inorganic salt in advance. In this embodiment, although the cooling and crystallization apparatus 10 is used in the recrystallization process (S13-1), what is necessary is just a crystallization method in which high-purity crystal|crystallization precipitates, for example, an evaporation crystallization apparatus etc. can also be used.

After recrystallizing the crystals of the inorganic salts, the crystals of the inorganic salts are separated from the aqueous solution containing the crystals of the inorganic salts in the solid-liquid separation step (S13-2), and the crystals of the inorganic salts subjected to the recrystallization treatment are recovered. As a method of solid-liquid separation, well-known solid-liquid separation apparatuses, such as various filtration apparatuses, such as pressure filtration (filter press), vacuum filtration, and centrifugal filtration, and a centrifugal separation apparatus like a decanter type, can be used, for example.

Then, in the re-dissolving step (S13-3), the recovered inorganic salt crystals are dissolved in the re-dissolving tank 11 to a desired concentration using, for example, water to produce an inorganic salt solution again. The temperature at this time is not specifically limited, What is necessary is just a temperature which can melt|dissolve the crystal|crystallization of an inorganic salt. In addition, the water used for dissolution of the inorganic salt is not particularly limited, but it is preferable to use condensed water generated when the target liquid is evaporated and concentrated in the concentration step (S8), so that the condensed water can be effectively used. The regenerated inorganic salt solution is supplied to the bipolar membrane electrodialysis device 9 . Moreover, in addition to silica, calcium and/or magnesium may be contained in the impurity removed from the inorganic salt solution in the re-dissolution process (S13-3) from the recrystallization process (S13-1).

4 and 5, the silica contained in the inorganic salt solution is removed before the electrodialysis step (S14). Accordingly, since the amount of impurities in the inorganic solution electrodialyzed in the electrodialysis step S14 is reduced, the performance of the bipolar film can be maintained high. In addition, when the dilute inorganic salt solution (desalted solution) after the electrodialysis step (S14) is supplied to the evaporator 5 and concentrated again by evaporation in the concentration step (S8), the amount of impurities in the desalted solution is decreasing. It can suppress that scale generate|occur|produces and adheres to the heat-transfer surface of the heat exchanger of the evaporator 5 in a concentration process (S8) by this. In addition, since the amount of impurities in the liquid to be treated from which precipitates are separated in the solid-liquid separation step (S12) after the carbonation step (S11) is reduced, most of the liquid to be treated after the solid-liquid separation step (S12) can be circulated back into the system. Therefore, since more lithium remaining in the liquid to be treated after the solid-liquid separation step S12 can be recovered, lithium can be recovered at a high recovery rate.

In addition, in the embodiment of FIGS. 1 and 2 , as shown in FIGS. 6 and 7 , a roasting step S0 of roasting the spent lithium ion battery before the acid leaching step S1 may be further included. In the roasting step S0, the method of roasting the spent lithium ion battery is not particularly limited, and a known roasting apparatus 12 can be used.

6 and 7, the exhaust gas generated in the roasting device 12 (roasting step S0) is supplied to the carbonation tank 7, and the exhaust gas is used as carbon dioxide gas as the target liquid in the carbonation step S11. is mixed in Accordingly, it is possible to reduce the amount of carbon dioxide gas used in the carbonation process (S11). It goes without saying that the roasting step S0 of roasting the spent lithium ion battery before the acid leaching step S1 can be performed also in the embodiments of FIGS. 4 and 5 .

Lithium recovery method of the second aspect

The lithium recovery method of the second aspect of the present disclosure includes a concentration step of heating and concentrating a liquid to be treated, in which lithium and inorganic salts are at least dissolved, under a low pressure lower than atmospheric pressure, and mixing carbon dioxide gas with the liquid to be treated after the concentration step. and/or a carbonation step of adding a water-soluble carbonate, and a solid-liquid separation step of separating a precipitate including crystals of lithium carbonate precipitated by the carbonation step from a target liquid, wherein in the carbonation step, the target liquid It is characterized in that the temperature of is equal to or higher than the evaporation temperature of the liquid to be treated in the concentration step.

In the lithium recovery method described in paragraphs 0102 and 0103, in the concentration step, it is preferable to evaporate and concentrate the liquid to be treated under a pressure of 10 kPa or more and 70 kPa or less.

Further, in the lithium recovery method described in Paragraph 0102, Paragraph 0103, or Paragraph 0104, it is preferable that at least a part of the liquid to be treated after the solid-liquid separation step is concentrated by evaporation in the concentration step.

Further, in the lithium recovery method according to any one of paragraphs 0102 to 0105, in the concentration step, inorganic salts contained in the liquid to be treated are precipitated as crystals, and as crystals in the precipitate separated from the liquid to be treated after the concentration step. Dissolution step of dissolving the inorganic salt contained therein to produce an inorganic salt solution, and bipolar membrane electrodialysis on the inorganic salt solution obtained by the dissolution step to separate and recover the inorganic acid together with the alkali from the inorganic salt solution It is preferable to further include a dialysis process.

Further, in the lithium recovery method according to any one of paragraphs 0102 to 0106, an acid leaching step of leaching lithium by leaching a spent lithium ion battery with an inorganic acid before the concentration step, and a lithium-containing liquid obtained by the acid leaching step It is preferable that the liquid to be treated is produced by further comprising a pH adjustment step of adjusting the pH by adding an alkali to the solution, and separating the precipitates precipitated by the pH adjustment step from the lithium-containing liquid.

Further, in the lithium recovery method described in paragraph 0107, it is preferable to reuse at least a part of the liquid to be treated after the solid-liquid separation step as the alkali added in the pH adjustment step.

Further, in the lithium recovery method described in paragraph 0107 or 0108, the alkali recovered in the electrodialysis step is reused as an alkali added in the pH adjustment step, and the inorganic acid recovered in the electrodialysis step is used in the acid leaching step. It is preferable to reuse as an inorganic acid to be used.

According to the lithium recovery method of the second aspect of the present disclosure, by evaporating and concentrating the liquid to be treated in the concentration step before the carbonation step, the amount of the liquid to be treated is reduced and the lithium concentration in the liquid to be treated is increased. Therefore, the recovery rate of lithium carbonate in the carbonation process can be improved favorably.

Further, in the concentration step, by evaporating and concentrating the liquid to be treated under low pressure, the temperature of the liquid to be treated after evaporation and concentration can be lowered than that of evaporating the liquid to be treated under atmospheric pressure. Therefore, it is possible to secure a large room for raising the temperature of the liquid to be treated in the subsequent carbonation step, and since the evaporation temperature of the liquid to be treated (boiling point of water contained in the liquid to be treated) is lowered under low pressure, the temperature of the liquid to be treated is lowered. Energy required for evaporation and concentration can be suppressed to a low level, and energy saving can be achieved. In addition, if the temperature of the liquid to be treated in the carbonation step is low, the inorganic salt contained in the liquid to be treated crystallizes. Therefore, the temperature of the liquid to be treated during carbonation is raised above the evaporation temperature of the liquid to be treated in the concentration step, thereby increasing the temperature of the liquid to be treated. The solubility of the inorganic salt remaining in the mixture is increased, and crystallization of the inorganic salt can be suppressed during carbonation. In addition, if the temperature of the liquid to be treated is high during carbonation, the solubility of lithium carbonate decreases, and the amount of recovery of crystals of lithium carbonate can be increased. Accordingly, it is possible to increase the efficiency in obtaining high-purity lithium carbonate.

FIG. 8 shows the sequence of each step with respect to the embodiment of the lithium recovery method of the second aspect of the present disclosure, and FIG. 9 shows a schematic configuration of a processing apparatus 10 implementing the lithium recovery method of FIG. 8 . The lithium recovery method of this embodiment is suitable for treating a liquid to be treated containing, in addition to lithium, strong acids such as hydrochloric acid, sulfuric acid, hydrofluoric acid and phosphoric acid, and inorganic salts of alkali metals or alkaline earth metals such as potassium and sodium. In particular, it can be suitably used for recovering lithium from a waste lithium ion battery. Hereinafter, the case of recovering lithium from a waste lithium ion battery will be described as an example.

The lithium recovery method of this embodiment comprises:

-Acid leaching process (S1) of leaching lithium by leaching the spent lithium ion battery with an inorganic acid;

- a solid-liquid separation step (S2) of separating insoluble residues from the lithium-containing liquid obtained by the acid leaching step (S1);

- A pH adjustment step (S3, S5) of adjusting the pH by adding an alkali to the lithium-containing liquid after the solid-liquid separation step (S2);

- a solid-liquid separation step (S4, S6) of separating the precipitate from the lithium-containing liquid after the pH adjustment step (S3, S5);

an impurity removal step (S7) of performing a chelating treatment on the liquid to be treated in which precipitates are separated from the lithium-containing liquid after the pH adjustment steps (S3, S5);

- Concentration step (S8) of evaporating and concentrating the liquid to be treated in which lithium and inorganic salts are at least dissolved after the impurity removal step (S7);

- A solid-liquid separation step (S9) of separating a precipitate containing inorganic salt crystals from the liquid to be treated after the concentration step (S8);

- Carbonation step (S10) of mixing carbon dioxide gas and/or adding water-soluble carbonate to the liquid to be treated after the solid-liquid separation step (S9);

- Solid-liquid separation process (S11) of separating the precipitate containing the crystals of lithium carbonate precipitated by the carbonation process (S10) from the liquid to be treated

includes The lithium recovery method of this embodiment comprises:

- A dissolution step (S12) of dissolving inorganic salt crystals contained in the precipitate separated from the liquid to be treated in the solid-liquid separation step (S9) to produce an inorganic salt solution;

- Electrodialysis step (S1) of separating and recovering alkali and inorganic acids from the inorganic salt solution by performing bipolar membrane electrodialysis on the inorganic salt solution after the dissolution step (S12)

have more

A waste lithium ion battery to be recovered from lithium is the same as in the first aspect.

First, in the acid leaching step (S1), metals such as aluminum, nickel, cobalt, and iron are eluted in addition to lithium by leaching the above-described spent lithium ion battery with an inorganic acid. As the inorganic acid, for example, sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid and the like can be used, but hydrochloric acid is used in the present embodiment.

In the acid leaching step (S1), the method for leaching a spent lithium ion battery with an inorganic acid is not particularly limited, and a method commonly used can be used. For example, in the acid leaching tank 1, a waste lithium ion battery is immersed in an aqueous solution of an inorganic acid such as an aqueous hydrochloric acid solution and stirred for a predetermined time to obtain a lithium-containing liquid in which a metal such as lithium is dissolved.

In the next solid-liquid separation step (S2), the lithium-containing liquid obtained in the acid leaching step (S1) is filtered, for example, to separate insoluble residues from the lithium-containing liquid. The insoluble residues are mainly carbon materials, metal materials, and organic materials that do not dissolve in inorganic acids. As a method of solid-liquid separation, well-known solid-liquid separation apparatuses, such as various filtration apparatuses, such as pressure filtration (filter press), vacuum filtration, and centrifugal filtration, and a centrifugal separation apparatus like a decanter type, can be used, for example. The same applies to the following solid-liquid separation steps (S4, S6, S9, S11).

In the following pH adjustment steps (S3 and S5), an alkali is added to the lithium-containing liquid (filtrate) after the solid-liquid separation step (S2) and the pH is adjusted to a predetermined range, so that among the above metals in the lithium-containing liquid, lithium Other metals are removed from the lithium-containing liquid. As the alkali, for example, sodium hydroxide, potassium hydroxide, lithium hydroxide, etc. can be used, but in the present embodiment, sodium hydroxide is used because of its low cost and ease of handling.

In the pH adjustment step (S3, S5), the method for adjusting the pH of the lithium-containing liquid is not particularly limited, and a method generally used can be used. For example, by adding an aqueous alkali solution such as sodium hydroxide aqueous solution while stirring the lithium-containing liquid in the first pH adjusting tank 2 and the second pH adjusting tank 3, metals other than lithium in the lithium-containing liquid is precipitated and precipitated as crystals of inorganic salts such as hydroxide. In this embodiment, the pH adjustment process (S3, S5) is divided into the 1st pH adjustment process (S3) and the 2nd pH adjustment process (S5).

In the first pH adjustment step (S3), the pH of the lithium-containing liquid is adjusted to 4 to 7, preferably 4 to 6, more preferably 4 to 5 by addition of an alkali. As a result, impurity metals (eg, aluminum, iron) in the lithium-containing liquid are precipitated and precipitated as crystals of inorganic salts such as hydroxides (eg, aluminum hydroxide and iron hydroxide). In the first pH adjustment step (S3), it is preferable to carry out the lithium-containing liquid while heating the lithium-containing liquid to a constant temperature, for example, from 30°C to 80°C.

It is preferable that the alkali concentration of the aqueous solution of the alkali added in the 1st pH adjustment process (S3) is less than 1.0 mol/L and the dilute thing. Accordingly, although details will be described later, it is possible to suppress the cobalt in the lithium-containing liquid from being removed from the lithium-containing liquid by precipitation and precipitation as crystals of a cobalt salt together with the impurity metal in the first pH adjustment step (S3). However, if the alkali concentration is excessively low, it is necessary to use a large amount of an aqueous alkali solution for pH adjustment in the first pH adjustment step S3, and the amount of the lithium-containing liquid after pH adjustment also becomes large, so the alkali concentration It is preferable that the lower limit of is 0.1 mol/L or more. In addition, in order to effectively suppress the removal of cobalt in the lithium-containing liquid from the lithium-containing liquid in the first pH adjustment step (S3), the alkali concentration of the aqueous alkali solution added in the first pH adjustment step (S3) is 0.5 mol/ It is preferable that it is L or less, and it is more preferable that it is 0.2 mol/L or less.

In addition, in this 1st pH adjustment process (S3), in order to reduce the amount of aqueous solution of the alkali used for pH adjustment, it is a deep alkali 1.0 mol/L or more until the pH of a lithium-containing liquid becomes a predetermined value smaller than 4. An aqueous alkali solution having a concentration is added to the lithium-containing liquid, and after the pH of the lithium-containing liquid reaches a predetermined value, an aqueous alkali solution having a light alkali concentration of less than 1.0 mol/L is added to the lithium-containing liquid by adding lithium The pH of the contained liquid can also be adjusted to 4-7. As a predetermined value of the pH of the above-described lithium-containing liquid, it can be set within the range of 2-3.

The precipitates deposited and precipitated in the first pH step (S3) are separated from the lithium-containing liquid by, for example, filtering the lithium-containing liquid in the following solid-liquid separation step (S4). In addition, copper etc. may be contained in the impurity metal removed from the lithium-containing liquid in the 1st pH adjustment process (S3). In the solid-liquid separation step (S4), it is preferable to wash the precipitate with a washing liquid, and to supply the washing waste liquid after washing to the next second pH adjustment process (S5) together with the lithium-containing liquid (filtrate). Accordingly, even lithium contained in the washing waste liquid can be supplied together with lithium contained in the lithium-containing liquid from the second pH adjustment step (S5) to the carbonation step (S10), and lithium is carbonated by carbonation in the carbonation step (S10) described later. can be recovered with a high recovery rate. Although the water used for washing|cleaning this precipitate is not specifically limited, It is preferable to use the condensed water generated when the to-be-processed liquid is evaporated and concentrated in the concentration process (S8) mentioned later, Thus, the effective use of condensed water is possible.

In the second pH adjustment step (S5), an alkali is added to the lithium-containing liquid after the solid-liquid separation step (S4) to raise the pH to 7 or more, preferably 7 to 13, more preferably 7 to 11, still more preferably 8 Adjust in the range of ~10. Thereby, valuable metals (eg, cobalt, nickel) in the lithium-containing liquid are precipitated and precipitated as crystals of inorganic salts such as hydroxides (eg, cobalt hydroxide, nickel hydroxide). In the second pH adjustment step (S5), it is preferable to carry out the lithium-containing liquid while heating the lithium-containing liquid to a constant temperature, for example, from 30°C to 80°C. Although the alkali concentration of the aqueous solution of alkali added in the 2nd pH adjustment process (S5) is not specifically limited, It is preferable that it is more than the alkali concentration of the aqueous solution of alkali used in the 1st pH adjustment process (S3), Furthermore, the alkali concentration It is preferable that is 0.2 mol/L or more.

The precipitates deposited and precipitated in the second pH adjustment step (S5) are separated from the lithium-containing liquid by, for example, filtering the lithium-containing liquid in the following solid-liquid separation step (S6). In addition, manganese etc. may be contained in the valuable metal removed from the lithium-containing liquid in the 2nd pH adjustment process (S5).

On the other hand, in the lithium-containing liquid after the solid-liquid separation step (S6), in addition to lithium, inorganic acids (hydrochloric acid in this embodiment) and alkalis (hydroxylated in this embodiment) added in the acid leaching step (S1) and the pH adjustment step (S3, S5) Inorganic salt (sodium chloride (NaCl) in this embodiment) is melt|dissolved by sodium). The lithium-containing liquid after this pH adjustment step (S3, S5) corresponds to the "to-be-processed liquid" of the lithium recovery method of the present disclosure. At least one of calcium, magnesium and silica may be further dissolved in this to-be-processed liquid.

In the solid-liquid separation step (S6), it is preferable to wash the precipitate with a washing liquid, and to supply the washing waste liquid after washing to the next impurity removal process (S8) together with the liquid to be treated (filtrate). Accordingly, even lithium contained in the washing waste liquid can be supplied from the impurity removal process (S8) to the carbonation process (S10) together with the lithium contained in the liquid to be treated, and lithium is recovered by carbonation in the carbonation process (S10) to be described later. It can be recovered with a recovery rate. Although the water used for washing|cleaning this precipitate is not specifically limited, It is preferable to use the condensed water generated when the to-be-processed liquid is evaporated and concentrated in the concentration process (S8) mentioned later, Thus, the effective use of condensed water is possible.

In the next impurity removal step (S7), at least polyvalent cations such as calcium and/or magnesium contained in the liquid to be treated after the solid-liquid separation step (S6) are removed. By removing calcium, magnesium, etc. contained as impurities in the liquid to be treated, in the concentration step (S8) to be described later, it is possible to suppress the occurrence of scale and adhesion to the heat transfer surface of the heat exchanger of the evaporative concentration device 5, Heat exchange efficiency can be maintained high. In addition, if the liquid to be treated contains calcium or magnesium, polyvalent cations such as calcium and magnesium contained in the inorganic solution are converted into the cation exchange membrane of the bipolar membrane electrodialysis apparatus 9 in the electrodialysis step (S13) to be described later. There is a fear that it precipitates in the lining, leading to a decrease in the performance of the film. Therefore, the adverse effect on the cation exchange membrane of the bipolar membrane electrodialysis apparatus 9 can be prevented by removing substances that interfere with scaling, such as calcium or magnesium, in the operation of electrodialysis from the liquid to be treated in advance. The performance of electrodialysis can be maintained high.

In the impurity removal step (S7), the method for removing calcium or magnesium from the liquid to be treated is not particularly limited, and, for example, the polyvalent cation removal device 4 can be used. The polyvalent cation removal device 4 is a device for removing divalent or higher polyvalent cations such as calcium ions and magnesium ions, for example, having an ion exchange resin inside, and bringing the liquid to be treated into contact with the ion exchange resin. The thing of the structure which can adsorb|suck calcium ion and a magnesium ion can be illustrated. As the polyvalent cation removal apparatus 4, the thing of the structure which can pass the to-be-processed liquid into the column filled with the chelate resin other than that can be illustrated. As a chelate resin, what can selectively capture|acquire calcium ion and a magnesium ion can be used, For example, iminodiacetic acid type, aminophosphoric acid type, etc. can be illustrated. Moreover, as the polyvalent cation removal apparatus 4, adding a chelating agent, etc. are mentioned. In addition to calcium and magnesium, silica (silicate ion) may be contained in the impurity removed from the to-be-processed liquid in the impurity removal process (S7).

In the next concentration step (S8), the liquid to be treated after the impurity removal step (S7) is heated and concentrated by evaporation. That is, the to-be-processed liquid is concentrated by evaporating the water|moisture content in the to-be-processed liquid. Accordingly, the liquid amount of the liquid to be treated decreases, and the lithium concentration in the liquid to be treated increases. Therefore, it is possible to improve the recovery rate of lithium carbonate in the carbonation process (S10) to be described later.

In the concentration step (S8), it is preferable to evaporate and concentrate the liquid to be treated to a concentration such that lithium does not precipitate as crystals of lithium salts such as lithium chloride in the liquid to be concentrated after concentration. Accordingly, the concentration of lithium in the liquid to be treated after concentration can be increased, and the recovery rate of lithium carbonate in the carbonation step (S10) described later can be improved.

In this concentration step (S8), since the concentration of the inorganic salt in the liquid to be treated increases due to evaporation of the liquid to be treated, there is a possibility of crystallization. The inorganic salt contained in the liquid to be treated may be precipitated as crystals in the concentration step (S8), or may not be precipitated. In the present embodiment, the inorganic salt contained in the liquid to be treated is precipitated as crystals in the concentration step (S8), and the precipitate is separated from the liquid to be treated in the next solid-liquid separation step (S9).

In the concentration step (S8), the method of evaporating and concentrating the liquid to be treated is not particularly limited, and, for example, the evaporation concentrator 5 can be used. The evaporative concentration device 5 is not particularly limited as long as it can concentrate the liquid to be treated by evaporation. For example, a known evaporative concentration device such as a heat pump type, an ejector drive type, a steam type, or a flash type can be used. However, it is preferably a heat pump type evaporative concentration device. When a heat pump type evaporation system is used, the energy to be used can be significantly suppressed.

The inside of the evaporative concentration apparatus 5 is maintained at a low pressure by a vacuum pump (not shown) connected thereto, and in the concentration step S8, the liquid to be treated is heated under a low pressure lower than atmospheric pressure to evaporate and concentrate. When the liquid to be treated is evaporated and concentrated, the temperature of the liquid to be treated increases, but the evaporation temperature of the liquid to be treated (boiling point of water contained in the liquid to be treated) is lower than that under atmospheric pressure under low pressure. The temperature of the liquid to be treated is lowered by that much. Therefore, it is possible to secure a large room for raising the temperature of the liquid to be treated in the carbonation step (S10) described later. In addition, since the evaporation temperature of the liquid to be treated is lowered under low pressure, the energy required for evaporative concentration of the liquid to be treated can be kept low and energy saving can be achieved.

The pressure inside the evaporator 5, that is, the atmospheric pressure when evaporating the liquid to be treated is not particularly limited, but is preferably 10 kPa or more and 70 kPa or less, and more preferably 15 kPa or more and 50 kPa or less. The evaporation temperature of the liquid to be treated is preferably 45°C or more and 95°C or less, and more preferably 55°C or more and 80°C or less in relation to the above pressure (saturated water vapor pressure curve).

When the pressure is 10 kPa or more, the temperature of the liquid to be treated after evaporation and concentration can be set to a suitable low temperature that does not decrease excessively, so that the energy required when raising the temperature of the liquid to be treated in the carbonation step (S10) described later can be suppressed low. can Moreover, since it is not necessary to make the evaporative concentration apparatus 5 into a thing with very high pressure-resistant performance, the manufacturing cost of an apparatus can be kept low. On the other hand, since the pressure can be set to a suitable low temperature that does not excessively increase the temperature of the liquid to be treated after evaporation and concentration by the pressure being 70 kPa or less, sufficient room to raise the temperature of the liquid to be treated in the carbonation step (S10) described later can be sufficiently secured. have. In addition, the energy required for evaporative concentration of the liquid to be treated does not become excessively large, and energy saving can be effectively achieved.

Although not shown, a temperature sensor is installed in the liquid storage part of the liquid to be treated at the bottom of the evaporation and concentration apparatus 5 or in the supply path of the liquid to be treated between the evaporation and concentration apparatus 5 and the carbonation tank 7 to be described later. and the evaporation temperature of the liquid to be treated (the temperature of the liquid to be treated after evaporation and concentration) is monitored by a temperature sensor. In addition, although not illustrated, a pressure sensor is provided in the space above the evaporator 5 , and the pressure inside the evaporator 5 (atmospheric pressure when evaporating and concentrating the liquid to be treated) is the pressure. It is monitored by a sensor.

In the following solid-liquid separation process (S9), the precipitate containing the crystal|crystallization of an inorganic salt (sodium chloride in this embodiment) is isolate|separated from the to-be-processed liquid by filtering, for example, the to-be-processed liquid after the concentration process (S8).

In the following carbonation step (S10), lithium in the liquid to be treated is converted into lithium carbonate crystals by mixing carbon dioxide gas and/or adding a water-soluble carbonate to the liquid to be treated after the precipitates containing crystals of the inorganic salt are separated. precipitation and precipitation. Thereby, lithium in the liquid to be treated can be recovered as lithium carbonate. As carbonate, sodium carbonate, ammonium carbonate, potassium carbonate, etc. can be used, for example.

In this carbonation step (S10), it is preferable to precipitate and precipitate crystals of lithium carbonate by mixing carbon dioxide gas with the liquid to be treated. In this way, in the carbonation step (S10), for example, by using a material that does not contain alkali metals such as sodium, it is possible to suppress mixing of alkali metals other than lithium into the precipitated crystals of lithium carbonate. Therefore, lithium carbonate with high purity can be recovered.

However, when the carbon dioxide gas is continuously mixed, the pH of the liquid to be treated decreases, so that the amount of lithium carbonate precipitated may decrease. Therefore, it is preferable to stop mixing the carbon dioxide gas before the pH of the liquid to be treated becomes 7 or less. Moreover, you may make it so that pH does not fall by adding an alkali to the to-be-processed liquid. In that case, it is preferable to maintain pH at 9 or more by alkali addition. As an alkali to be added, sodium hydroxide, potassium hydroxide, lithium hydroxide, etc. can be used.

In the carbonation step (S10), the method of mixing the carbon dioxide gas with the liquid to be treated is not particularly limited, and a method commonly used can be used. For example, carbon dioxide gas can be uniformly mixed with the liquid to be treated by supplying carbon dioxide gas into the liquid to be treated in the form of fine bubbles by means of a nozzle while stirring the liquid to be treated in the carbonation tank 7, Lithium in the liquid and carbon dioxide gas can be reacted efficiently. Moreover, you may make it react with carbon dioxide gas by spraying a to-be-processed liquid in the atmosphere of carbon dioxide gas.

In the carbonation step (S10), the temperature of the liquid to be treated is equal to or higher than the evaporation temperature of the liquid to be treated in the concentration step (S8). If the temperature of the liquid to be treated is low during carbonation, the inorganic salt (sodium chloride in the present embodiment) contained in the liquid to be treated may crystallize. Therefore, by heating the liquid to be treated in the carbonation step (S10) and raising the temperature of the liquid to be treated at the time of carbonation above the evaporation temperature of the liquid to be treated, the solubility of the inorganic salt remaining in the liquid to be treated during carbonation increases, Salt crystallization can be inhibited. Accordingly, when lithium carbonate is recovered in the carbonation step ( S10 ), the purity of the lithium carbonate can be increased.

The temperature of the liquid to be treated at the time of carbonation is not particularly limited as long as it is equal to or higher than the evaporation temperature of the liquid to be treated, but is preferably higher than the evaporation temperature of the liquid to be treated, and preferably less than 100°C. A method of heating the liquid to be treated in the carbonation step S10 is not particularly limited, and for example, a method of heating the liquid to be treated in the carbonation tank 7 using a known heating means such as a heater may be used. can In addition, before supplying the target liquid to the carbonation tank 7, you may comprise so that the to-be-processed liquid may be heated in advance using preheating means, such as a heat exchanger.

In addition, the solubility of lithium carbonate decreases as the temperature of the liquid to be treated increases. Therefore, as the temperature of the liquid to be treated rises in the carbonation step S10, the solubility of lithium carbonate generated by the reaction of lithium and carbon dioxide gas in the liquid to be treated decreases. Accordingly, the recovery amount of the crystals of lithium carbonate can be increased, and the amount of precipitation of the crystals of the inorganic salt can be suppressed, so that high-purity lithium carbonate can be obtained with high efficiency.

In the next solid-liquid separation step (S11), the precipitate containing lithium carbonate crystals is separated from the lithium-containing liquid by, for example, filtering the liquid to be treated after the carbonation step (S10). In the solid-liquid separation step (S11), impurities are removed by washing the precipitate separated from the lithium-containing liquid with water or the like, and the purity of lithium carbonate can be increased. Although the water used for washing|cleaning this precipitate is not specifically limited, It is preferable to use the condensed water which arises when the to-be-processed liquid is evaporated and concentrated in the concentration process (S8), Thus, the effective use of condensed water is possible.

The liquid to be treated (filtrate) after the solid-liquid separation step (S11) is not particularly limited, but since it contains impurities, part of it is discharged as a counter-fluid, but it is preferable that a part is circulated back into the system. Accordingly, since the lithium remaining in the liquid to be treated can be recovered, lithium can be recovered at a high recovery rate. In addition, it is preferable that the washing waste liquid after washing the precipitate containing the lithium carbonate crystals is also circulated back into the system together with the liquid to be treated after the solid-liquid separation step (S11).

When the liquid to be treated after the solid-liquid separation step (S11) is circulated back into the system, it may be supplied to the evaporator 5 and concentrated by evaporation in the concentration step (S8), but preferably the first pH adjustment tank 2 and/or It is supplied to the 2nd pH adjustment tank (3). Since the liquid to be treated after the solid-liquid separation step (S11) is alkaline, it can be used as an alkali added in the pH adjustment steps (S3, S5). Furthermore, if the liquid to be treated after the solid-liquid separation step (S11) contains a large amount of carbonate ions (CO ₃ 2−), the heat transfer surface of the heat exchanger of the evaporative concentrator 5 when evaporating and concentrating in the concentration step (S8). carbonate crystals are precipitated. Therefore, since the lithium-containing liquid after the solid-liquid separation step (S2, S4) is acidic, the liquid to be treated after the solid-liquid separation step (S11) is neutralized with the lithium-containing liquid to extract carbonate ions from the liquid to be treated as carbon dioxide gas. Precipitation of carbonate crystals on the heat transfer surface of the heat exchanger of the evaporative concentration device 5 in the concentration step S8 can be prevented.

On the other hand, the crystals of the inorganic salt (sodium chloride in this embodiment) produced in the concentration step (S8) (evaporative concentration device 5) and contained in the precipitate separated from the liquid to be treated in the solid-liquid separation step (S9) are dissolved in the dissolution step ( S12) (dissolving tank 8). In a dissolution process (S12), it melt|dissolves using water so that the crystal|crystallization of an inorganic salt may become a desired density|concentration in the dissolution tank 8, and produces|generates an inorganic salt solution. The temperature at this time is not specifically limited, What is necessary is just a temperature which can melt|dissolve the crystal|crystallization of an inorganic salt. In addition, the water used for dissolution of the inorganic salt is not particularly limited, but it is preferable to use condensed water generated when the target liquid is evaporated and concentrated in the concentration step (S8), so that the condensed water can be effectively used. The resulting inorganic salt solution is supplied to the bipolar membrane electrodialysis device 9 .

In the next electrodialysis step (S13), the alkali and inorganic acids are separated and recovered from the inorganic salt solution after the dissolution step (S12) by the bipolar membrane electrodialysis apparatus 9 . As the bipolar membrane electrodialysis device 9, for example, as shown in FIG. 10, an anion exchange membrane 91, a cation exchange membrane 92, and two bipolar membranes are disposed between the anode 95 and the cathode 96. A three-cell type bipolar membrane electrodialysis apparatus in which a plurality of cells 90 having (93, 94) are stacked can be suitably used. In the bipolar membrane electrodialysis apparatus 9 of this embodiment, a desalting chamber R1 is formed by an anion exchange membrane 91 and a cation exchange membrane 92, and between the anion exchange membrane 91 and one bipolar membrane 93. An acid chamber (R2) is formed therein, and an alkali chamber (R3) is formed between the cation exchange membrane (92) and the other bipolar membrane (94). An anode chamber R4 and a cathode chamber R5 are formed outside each of the bipolar films 93 and 94, an anode 95 is provided in the anode chamber R4, and a cathode 96 is formed in the cathode chamber R5. each is placed.

In this electrodialysis step (S13), an inorganic salt solution is introduced into the desalting chamber (R1), and pure water is introduced into the acid chamber (R2) and the alkali chamber (R3), respectively. Accordingly, when the inorganic salt solution contains sodium chloride, for example, in the desalting chamber R1, sodium ions (Na ⁺ ) pass through the cation exchange membrane 92, and chloride ions (Cl ⁻ ) It passes through the anion exchange membrane (91). On the other hand, in the acid chamber (R2) and the alkali chamber (R3), the supplied pure water is ^{dissociated into hydrogen ions (H +} ) and hydroxide ions (OH ⁻ ) in the bipolar membranes 93 and 94, and in the acid chamber (R2), hydrogen Ions (H ⁺ ) combine with chloride ions (Cl ⁻ ) to produce hydrochloric acid (HCl), and in the alkali chamber (R3), hydroxide ions (OH ⁻ ) combine with sodium ions (Na ⁺ ) to form sodium hydroxide (NaOH) this is created Thereby, hydrochloric acid (HCl) as an inorganic acid from the acid chamber (R2) and sodium hydroxide (NaOH) as an alkali from the alkali chamber (R3) are respectively recovered. In addition, as the pure water introduced into the acid chamber R2 and the alkali chamber R3, condensed water generated when the liquid to be treated is evaporated and concentrated in the concentration step S8 may be used.

The dilute inorganic salt solution (desalting solution) after desalting discharged from the desalting chamber R1 is not particularly limited, but since it contains a little lithium, it is supplied to the evaporator 5 and evaporated again in the concentration step S8. Concentration is preferred.

In addition, the inorganic acid (hydrochloric acid in this embodiment) recovered from the acid chamber (R2) is not particularly limited, but as an inorganic acid supplied to the acid leaching tank 1 and leaching the spent lithium ion battery in the acid leaching step (S1). It is preferable to reuse it. Moreover, it is preferable to supply it to the polyvalent cation removal apparatus 4, and to reuse it as a regeneration liquid of the chelate resin or ion exchange resin used in the impurity treatment process (S7).

In addition, although the alkali (sodium hydroxide in this embodiment) recovered|recovered from alkali chamber R3 is not specifically limited, Lithium-containing liquid is supplied to the pH adjustment tanks 2 and 3, and pH adjustment process S3, S5. It is preferable to reuse it as an alkali for pH adjustment. Moreover, it is preferable to supply it to the polyvalent cation removal apparatus 4, and to reuse it as a regeneration liquid of the chelate resin or ion exchange resin used in the impurity treatment process (S7).

According to the lithium recovery method of the present embodiment described above, by evaporating and concentrating the liquid to be treated in the concentration step (S8) before the carbonation step (S10), the amount of the liquid to be treated is reduced and the lithium concentration in the liquid to be treated is increased. Accordingly, the recovery rate of crystals of lithium carbonate in the carbonation step (S10) can be improved favorably.

In addition, in the carbonation step (S10), if the temperature of the liquid to be treated is low, the inorganic salt (sodium chloride in the present embodiment) contained in the liquid to be treated crystallizes. By raising the temperature of is higher than the evaporation temperature, the solubility of the inorganic salt remaining in the liquid to be treated increases, and crystallization of the inorganic salt during carbonation can be suppressed. In addition, if the temperature of the liquid to be treated is high during carbonation, the solubility of lithium carbonate decreases and the amount of recovery of crystals of lithium carbonate increases. Accordingly, it is possible to increase the efficiency in obtaining high-purity lithium carbonate.

Further, according to the lithium recovery method of the present embodiment, the first pH adjusting tank 2, the second pH adjusting tank 3, and evaporation are not disposed of the liquid to be treated after the lithium carbonate crystals are recovered in the carbonation step (S10). The lithium remaining in the liquid to be treated is recovered by circulating it into the system such as the concentrator 5 . Therefore, lithium can be recovered with a high recovery rate.

In addition, according to the lithium recovery method of this embodiment, crystals of an inorganic salt (sodium chloride in this embodiment) contained in the precipitate separated from the liquid to be treated in the solid-liquid separation step (S9) are dissolved in the dissolution step (S12) to obtain inorganic After making a salt solution, inorganic acids and alkalis are recovered from the inorganic salt solution by performing bipolar membrane electrodialysis in the electrodialysis step (S13), and the dilute inorganic salt solution after desalting is evaporated and concentrated in the concentration step (S8), In the carbonation step (S10), lithium contained in the dilute inorganic salt solution is recovered. Therefore, lithium can be recovered with a high recovery rate. In addition, the inorganic acids and alkalis recovered in the electrodialysis step (S13) are recycled and reused in the acid leaching step (S1), the pH adjustment step (S3, S5), and the impurity removal step (S7) to be reused in each step (S1, S3, S5). , it is possible to reduce the amount of inorganic acid or alkali used in S7).

In addition, according to the lithium recovery method of the present embodiment, polyvalent cations such as calcium and magnesium contained in the liquid to be treated are removed in the impurity removal step (S7). Accordingly, the amount of impurities in the liquid to be treated from which the precipitate is separated in the solid-liquid separation step (S11) after the carbonation step (S10) is reduced, so that most of the liquid to be treated after the solid-liquid separation step (S11) can be circulated back into the system. . Therefore, since more lithium remaining in the liquid to be treated after the solid-liquid separation step S11 can be recovered, lithium can be recovered at a high recovery rate. In addition, since the amount of impurities in the inorganic solution electrodialyzed in the electrodialysis step S13 is reduced, it is possible to prevent the performance of the cation exchange membrane of the bipolar electrodialysis apparatus 9 from being deteriorated due to scaling, so that the performance of the bipolar membrane is maintained high. can

In addition, according to the lithium recovery method of this embodiment, since the condensed water generated in the concentration step S8 is used for various treatments, the condensed water can be effectively used. In addition, by washing the crystals obtained by each solid-liquid separation step (S4, S6, S9, S11) using condensed water, the recovery rate of each crystal can be improved favorably.

As mentioned above, although one embodiment of the lithium recovery method of the second aspect has been described, the lithium recovery method of the second aspect is not limited to the embodiments shown in Figs. There are several possible changes.

For example, in the embodiment of FIGS. 8 and 9 , an impurity removal step (S7) of at least removing calcium and/or magnesium from the liquid to be treated before the concentration step (S8) is performed, but instead of or in addition to this Accordingly, an impurity removal step of removing at least calcium and/or magnesium may be performed similarly to the inorganic salt solution before the electrodialysis step (S13).

8 and 9, the alkali recovered in the electrodialysis step (S13) is supplied to the first pH adjustment step (S3) and the second pH adjustment step (S5), but only one of them is supplied good to do

In addition, in the embodiment of FIG. 8 and FIG. 9, although the pH adjustment process (S3, S5) includes the 1st pH adjustment process (S3) and the 2nd pH adjustment process (S5), the component contained in a waste lithium ion battery It may be configured to include three or more steps, or may be configured to include only one step.

In addition, in the embodiment of FIGS. 8 and 9, as shown in FIGS. 11 and 12, after the dissolution step (S12) and before the electrodialysis step (S13), the inorganic salt solution contains, for example, silica, etc. A treatment step for removing impurities of This treatment step can be performed instead of the impurity removing step S7 or in addition to the impurity removing step S7.

Specifically, first, the inorganic salt (sodium chloride in this embodiment) contained in the inorganic salt solution in the recrystallization process (S12-1) is recrystallized. It does not specifically limit about the method of recrystallizing the inorganic salt contained in an inorganic salt solution, For example, evaporation crystallization by the evaporation and crystallization apparatus 13 can be used. In evaporation crystallization, inorganic salt crystals are precipitated by heating the inorganic salt solution to evaporate the solvent and increasing the inorganic salt concentration. In addition, it is preferable to perform evaporation of the inorganic salt solution under a low pressure lower than atmospheric pressure. In evaporation crystallization, you may crystallize the inorganic salt contained in the inorganic salt solution using the evaporation concentrating apparatus 5, without providing the evaporation and crystallization apparatus 10 separately.

After recrystallizing the crystals of the inorganic salts, the crystals of the inorganic salts are separated from the aqueous solution containing the crystals of the inorganic salts in the solid-liquid separation step (S12-2), and the crystals of the inorganic salts subjected to the recrystallization process are recovered. As a method of solid-liquid separation, well-known solid-liquid separation apparatuses, such as various filtration apparatuses, such as pressure filtration (filter press), vacuum filtration, and centrifugal filtration, and a centrifugal separation apparatus like a decanter type, can be used, for example.

Then, in the re-dissolving step (S12-3), the recovered inorganic salt crystals are dissolved in the re-dissolving tank 11 to a desired concentration, for example, using water to produce an inorganic salt solution again. The temperature at this time is not specifically limited, What is necessary is just a temperature which can melt|dissolve the crystal|crystallization of an inorganic salt. In addition, the water used for dissolution of the inorganic salt is not particularly limited, but it is preferable to use condensed water generated when the target liquid is evaporated and concentrated in the concentration step (S8), so that the condensed water can be effectively used. The regenerated inorganic salt solution is supplied to the bipolar membrane electrodialysis device 9 . In addition to silica, calcium and/or magnesium may be contained in the impurities removed from the inorganic salt solution in the re-dissolution step (S12-3) from the recrystallization step (S12-1).

11 and 12, the silica contained in the inorganic salt solution is removed before the electrodialysis step (S13). Accordingly, since the amount of impurities in the inorganic solution electrodialyzed in the electrodialysis step S13 is reduced, the performance of the bipolar film can be maintained high. In addition, when the dilute inorganic salt solution (demineralized solution) after the electrodialysis step (S13) is supplied to the evaporator 5 and concentrated again by evaporation in the concentration step (S8), the amount of impurities in the desalted solution is decreasing. Accordingly, in the concentration step (S8), it is possible to suppress the occurrence and adhesion of scale to the heat transfer surface of the heat exchanger of the evaporative concentration device 5 . In addition, since the amount of impurities in the liquid to be treated from which precipitates are separated in the solid-liquid separation step (S11) after the carbonation step (S10) is reduced, most of the liquid to be treated after the solid-liquid separation step (S11) can be circulated back into the system. Therefore, since more lithium remaining in the liquid to be treated after the solid-liquid separation step S11 can be recovered, lithium can be recovered at a high recovery rate.

Further, in the embodiment of FIGS. 8 and 9 , as shown in FIGS. 13 and 14 , a roasting step S0 of roasting the spent lithium ion battery before the acid leaching step S1 may be further included. In the roasting step S0, the method of roasting the spent lithium ion battery is not particularly limited, and a known roasting apparatus 12 can be used.

13 and 14, the exhaust gas generated in the roasting device 12 (combustion step S0) is supplied to the carbonation tank 7, and the exhaust gas is used as carbon dioxide gas in the carbonation step S10 as a target liquid is mixed in Accordingly, it is possible to reduce the amount of carbon dioxide gas used in the carbonation process (S10). In addition, the liquid to be treated may be heated in the carbonation step ( S10 ). 11 and 12, it goes without saying that the roasting step S0 of roasting the spent lithium ion battery before the acid leaching step S1 can be performed.

Although the lithium recovery method of the above embodiment takes the case of recovering lithium from a waste lithium ion battery as an example, the lithium recovery method of the present disclosure is not limited to a method used for recovering lithium from a waste lithium ion battery.

How to recover cobalt

Recovering cobalt as a valuable metal from a waste lithium ion battery is very important from the viewpoint of effective use of resources. However, in the method for recovering cobalt from a spent lithium ion battery described in Patent Document 1 in the background art, the pH of the acid leachate is set to 4 or higher in order to remove impurity metals such as aluminum from the acid leachate. There is a problem that the crystallinity of the cobalt salt is also precipitated and precipitated, and the cobalt is removed from the acid leach solution together with the impurity metal, and there is a problem that the recovery rate of cobalt may be lowered during the subsequent cobalt recovery.

In order to solve the above problems, an object of the present disclosure is to provide a cobalt recovery method capable of recovering cobalt at a high recovery rate from a liquid to be treated in which cobalt and impurity metals are dissolved.

As a result of intensive studies to solve the above problems, the present inventors have found that an aqueous solution of alkali added to the liquid to be treated when the salt of the impurity metal is precipitated as crystals by adjusting the pH of the liquid to be treated in which at least cobalt and impurity metals are dissolved. It was found that when the concentration was high, crystals of a cobalt salt were precipitated together with crystals of a salt of an impurity metal, and cobalt was removed together with an impurity metal from the to-be-processed liquid. The recovery method of the present disclosure was completed as a result of further research based on such knowledge. That is, the present disclosure provides a method for recovering cobalt of the following aspects.

The cobalt recovery method of the present disclosure includes a first pH adjustment step of precipitating a salt of the impurity metal as crystals by adding an aqueous alkali solution to an acidic to-be-treated solution in which at least cobalt and impurity metal are dissolved, and adjusting the pH to 4-7; , a first solid-liquid separation step of separating a precipitate containing crystals of a salt of an impurity metal precipitated in the first pH adjustment step from the target liquid, and adding an aqueous alkali solution to the target solution after the first solid-liquid separation step a second pH adjustment step of precipitating cobalt salt crystals by adjusting the pH to 7 or higher, and a second solid-liquid separation step of separating the precipitate containing the cobalt salt crystals precipitated by the second pH adjustment step from the liquid to be treated and, characterized in that the alkali concentration of the aqueous solution of alkali added in the first pH adjustment step is less than 1.0 mol/L.

In the cobalt recovery method described in Paragraph 0190, it is preferable that the alkali concentration of the aqueous solution of alkali added in the said 1st pH adjustment process is 0.1 mol/L or more.

Further, in the cobalt recovery method described in paragraph 0190 or paragraph 0191, in the first pH adjustment step, an aqueous solution of alkali having an alkali concentration of 1.0 mol/L or more until the pH of the liquid to be treated becomes a predetermined value smaller than 4 is added to the liquid to be treated, and thereafter, an aqueous alkali solution having an alkali concentration of less than 1.0 mol/L is added to the liquid to be treated to adjust the pH of the liquid to be treated to 4-7.

Further, in the cobalt recovery method according to any one of paragraphs 0190 to 0192, a concentration step of evaporating and concentrating the target liquid after the second solid-liquid separation step in which lithium is dissolved in the target liquid, and the concentration step It is preferable to have a carbonation process of mixing carbon dioxide gas and/or adding a water-soluble carbonate to the liquid to be treated.

Further, in the cobalt recovery method described in Paragraph 0193, a third solid-liquid separation step of separating a precipitate containing crystals of lithium carbonate precipitated in the carbonation step from the target liquid; an electrodialysis step of separating and recovering alkali from the solution to be treated by subjecting the solution to bipolar membrane electrodialysis, wherein the alkali recovered in the electrodialysis step is used in the first pH adjustment step and/or the second pH It is preferable to reuse as an alkali used in an adjustment process.

According to the cobalt recovery method of the present disclosure, with respect to the liquid to be treated in which cobalt and impurity metal are dissolved, when the impurity metal is removed from the liquid to be treated in the first pH adjustment step, an aqueous solution of a dilute alkali having an alkali concentration of less than 1.0 mol/L The removal of cobalt together with impurity metals from the liquid to be treated can be suppressed by adjusting the pH of the liquid to be treated. Therefore, since the amount of cobalt in the to-be-processed liquid supplied to the 2nd pH adjustment process can be maintained high, cobalt can be collect|recovered with a high recovery rate in the 2nd pH adjustment process.

15 shows the sequence of each process with respect to the embodiment of the cobalt recovery method of the present disclosure, and FIG. 16 shows a schematic configuration of a processing apparatus 10 for performing the cobalt recovery method of FIG. 15 . The cobalt recovery method of this embodiment is demonstrated taking the case of recovering lithium in addition to cobalt from a waste lithium ion battery as an example.

The cobalt recovery method of the present embodiment includes:

- An acid leaching process (S1) of leaching a spent lithium ion battery with an inorganic acid to elute cobalt and lithium;

- a solid-liquid separation step (S2) of separating insoluble residues from the liquid to be treated obtained by the acid leaching step (S1);

- A first pH adjustment step (S3) of adjusting the pH to 4-7 by adding an aqueous alkali solution to the liquid to be treated after the solid-liquid separation step (S2);

- A solid-liquid separation step (S4) of separating a precipitate containing crystals of a salt of an impurity metal precipitated by the first pH adjustment step (S3) from the liquid to be treated (corresponding to the “first solid-liquid separation step” described in paragraph 0190) class,

- A second pH adjustment step (S5) of adjusting the pH to 7 or higher by adding an aqueous alkali solution to the liquid to be treated after the solid-liquid separation step (S4);

- A solid-liquid separation step (S6) of separating the precipitate containing the crystals of the cobalt salt precipitated by the second pH adjustment step (S5) from the liquid to be treated (corresponding to the “second solid-liquid separation step” described in paragraph 0190);

- Concentration step (S7) of evaporating and concentrating the liquid to be treated after the solid-liquid separation step (S6);

- Carbonation step (S8) of mixing carbon dioxide gas and/or adding water-soluble carbonate to the liquid to be treated after the concentration step (S7);

- A solid-liquid separation step (S9) of separating a precipitate containing crystals of lithium carbonate precipitated by the carbonation step (S8) from the liquid to be treated (corresponding to the “third solid-liquid separation step” described in paragraph 0194);

- Bipolar membrane electrodialysis is performed on the liquid to be treated after the solid-liquid separation step (S9) to separate and recover alkali and inorganic acids containing at least lithium hydroxide from the liquid to be treated (S10).

A waste lithium ion battery for recovering cobalt is the same as the lithium recovery method described above.

First, in the acid leaching step (S1), metals such as aluminum, nickel, and iron are eluted in addition to cobalt and lithium by leaching the above-described spent lithium ion battery with an inorganic acid. As the inorganic acid, for example, sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid and the like can be used, but in the present embodiment, sulfuric acid is used because of its low cost and ease of handling.

In the acid leaching step (S1), the method for leaching a spent lithium ion battery with an inorganic acid is not particularly limited, and a method commonly used can be used. For example, in the acid leaching tank 1, a waste lithium ion battery is immersed in an aqueous solution of an inorganic acid such as an aqueous sulfuric acid solution and stirred for a predetermined time to obtain an acidic to-be-treated solution in which the cobalt or the like is dissolved. In the acid leaching step (S1), the concentration of the inorganic acid in the aqueous solution is preferably 1 mol/L to 5 mol/L, and the temperature of the aqueous solution is preferably 60° C. or higher.

In the next solid-liquid separation step (S2), the insoluble residue is separated from the liquid to be treated by filtering, for example, the liquid to be treated obtained in the acid leaching step (S1). The insoluble residues are mainly carbon materials, metal materials, and organic materials that do not dissolve in inorganic acids. As a method of solid-liquid separation, well-known solid-liquid separation apparatuses, such as various filtration apparatuses, such as pressure filtration (filter press), vacuum filtration, and centrifugal filtration, and a centrifugal separation apparatus like a decanter type, can be used, for example. The same applies to the following solid-liquid separation steps (S4, S6, S9).

In the next first pH adjustment step (S3), an aqueous alkali solution is added to the liquid to be treated (filtrate) after the solid-liquid separation step (S2), and the pH is adjusted to 4-7, preferably 4-6, more preferably Adjust it to 4-5. Thereby, among the above-mentioned metals in the liquid to be treated, impurity metals (eg, aluminum and iron) are removed from the liquid to be treated. Although sodium hydroxide, potassium hydroxide, lithium hydroxide, etc. can be used as an alkali, lithium hydroxide is used in this embodiment.

In the 1st pH adjustment process (S3), it does not specifically limit about the method of adjusting the pH of a to-be-processed liquid, The method normally implemented can be used. For example, by adding an aqueous solution of an alkali such as an aqueous lithium hydroxide solution while stirring the liquid to be treated in the first pH adjustment tank 2, the impurity metal in the liquid to be treated is converted to a hydroxide (e.g., aluminum hydroxide, It is precipitated and precipitated as crystals of inorganic salts such as iron hydroxide). In the 1st pH adjustment process (S3), it is preferable to carry out, heating the to-be-processed liquid to a fixed temperature to 30 degreeC - 80 degreeC, for example.

The alkali concentration of the aqueous solution of alkali added in the 1st pH adjustment process (S3) is less than 1.0 mol/L and is thin. Accordingly, although details will be described later, it is possible to suppress the cobalt in the liquid to be treated in the first pH adjustment step S3 from being removed from the liquid to be treated by precipitation and precipitation as crystals of cobalt salt together with impurity metals. However, if the alkali concentration is excessively low, it is necessary to use a large amount of an aqueous alkali solution for pH adjustment in the first pH adjustment step S3, and the amount of the liquid to be treated after the pH adjustment is also large, so the alkali concentration It is preferable that the lower limit of is 0.1 mol/L or more. In addition, in order to effectively suppress removal of cobalt in the liquid to be treated in the first pH adjustment step (S3) from the liquid to be treated, the alkali concentration of the aqueous alkali solution added in the first pH adjustment step (S3) is 0.5 mol/ It is preferable that it is L or less, and it is more preferable that it is 0.2 mol/L or less.

In addition, in this 1st pH adjustment process (S3), in order to reduce the amount of the aqueous solution of the alkali used for pH adjustment, until the pH of the to-be-processed liquid becomes a predetermined value smaller than 4, the dark alkali of 1.0 mol/L or more An aqueous solution of alkali having a concentration is added to the liquid to be treated, and after the pH of the liquid to be treated has reached a predetermined value, an aqueous solution of alkali having a light alkali concentration of less than 1.0 mol/L is added to the liquid to be treated. It is also possible to adjust the pH of the liquid to 4-7. As a predetermined value of the pH of the above-mentioned to-be-processed liquid, it can set within the range of 2-3.

The precipitate deposited and precipitated in the first pH adjustment step (S3) is separated from the liquid to be treated by, for example, filtering the liquid to be treated in the next solid-liquid separation step (S4). In addition, copper etc. may be contained in the impurity metal removed from the to-be-processed liquid in the 1st pH adjustment process (S3). In the solid-liquid separation step (S4), it is preferable to wash the precipitate with a washing solution and supply the washing waste solution after washing to the next second pH adjustment step (S5) together with the liquid to be treated (filtrate). Accordingly, even lithium contained in the washing waste liquid can be supplied together with lithium contained in the liquid to be treated from the second pH adjustment step (S5) to the carbonation step (S8), and lithium is carbonated by carbonation in the carbonation step (S8) described later. can be recovered with a high recovery rate. The water used for washing the precipitate is not particularly limited, but it is preferable to use condensed water generated when the liquid to be treated is evaporated and concentrated in the concentration step (S7) to be described later, so that the condensed water can be effectively used.

In the second pH adjustment step (S5), an aqueous alkali solution is added to the to-be-treated liquid (filtrate) after the solid-liquid separation step (S4) to adjust the pH to 7 or more, preferably 7 to 13, more preferably 7 to 11 , More preferably, it adjusts to 8-10. Thereby, among the above-mentioned metals in the to-be-processed liquid, valuable metals, such as cobalt and further nickel, are removed from the to-be-processed liquid. Although sodium hydroxide, potassium hydroxide, lithium hydroxide, etc. can be used as an alkali, lithium hydroxide is used in this embodiment.

In the 2nd pH adjustment process (S5), it does not specifically limit about the method of adjusting the pH of a to-be-processed liquid, The method normally implemented can be used. For example, by adding an aqueous solution of an alkali such as an aqueous lithium hydroxide solution while stirring the liquid to be treated in the second pH adjustment tank 3, the valuable metal in the liquid to be treated is converted to a hydroxide (eg, iron cobalt hydroxide, Furthermore, it precipitates and precipitates as crystals of inorganic salts, such as nickel hydroxide). Thereby, cobalt in the liquid to be treated can be recovered as a cobalt salt such as cobalt hydroxide. It is preferable to carry out, heating the to-be-processed liquid to a fixed temperature to 30 degreeC - 80 degreeC in 2nd pH adjustment process (S5), for example. Although the alkali concentration of the aqueous solution of alkali added in the 2nd pH adjustment process (S5) is not specifically limited, It is preferable that it is more than the alkali concentration of the aqueous solution of alkali used in the 1st pH adjustment process (S3), Furthermore, the alkali concentration It is preferable that is 0.2 mol/L or more.

The precipitate deposited and precipitated in the second pH adjustment step (S5) is separated from the liquid to be treated by, for example, filtering the liquid to be treated in the next solid-liquid separation step (S6). In addition, manganese etc. may be contained in the valuable metal removed from the to-be-processed liquid in the 2nd pH adjustment process (S5). On the other hand, the to-be-treated liquid (filtrate) after the solid-liquid separation step (S6) contains lithium and anions of an inorganic acid (eg, sulfate ions).

In the solid-liquid separation step (S6), it is preferable to wash the precipitate with a washing liquid and supply the washing waste liquid after washing to the next concentration step (S7) together with the liquid to be treated (filtrate). Accordingly, even lithium contained in the washing waste liquid can be supplied from the concentration step (S7) to the carbonation step (S8) together with the lithium contained in the liquid to be treated, and the lithium is highly recovered by carbonation in the carbonation step (S8) described later. can be recovered with Although the water used for washing|cleaning this precipitate is not specifically limited, It is preferable to use the condensed water which arises when the to-be-processed liquid is evaporated and concentrated in the concentration process (S7), Thus, effective use of the condensed water is possible.

Moreover, in this 1st pH adjustment process (S3) and 2nd pH adjustment process (S5), the carbonation process mentioned later compared with the case where the hydroxide of other alkali metals, such as sodium hydroxide, is used by making the alkali to be used lithium hydroxide. Mixing of alkali metals other than lithium, such as sodium, can be suppressed with respect to the crystal|crystallization of lithium carbonate precipitated in (S8). Therefore, lithium carbonate with high purity can be recovered.

In the next concentration step (S7), the liquid to be treated is concentrated by heating the lithium-containing liquid after the solid-liquid separation step (S6), that is, the liquid to be treated is concentrated by evaporating moisture in the liquid to be treated. Accordingly, the liquid amount of the liquid to be treated decreases and the lithium concentration in the liquid to be treated increases. Accordingly, it is possible to improve the recovery rate of lithium carbonate in the carbonation process (S8), which will be described later.

In addition, in the concentration step (S7), the temperature of the target solution after concentration can be increased by evaporating the target solution, so that the recovery rate of lithium carbonate can be improved in the carbonation step (S8) described later. Since the solubility of lithium carbonate decreases as the temperature increases, in the carbonation step S8, as the temperature of the liquid to be treated increases, the solubility of lithium carbonate generated by the reaction of lithium and carbon dioxide in the liquid to be treated decreases. It is possible to increase the amount of precipitation of crystals.

In the concentration step (S7), it is preferable to concentrate the liquid to be treated to a concentration such that lithium does not precipitate as crystals of lithium salts such as lithium sulfate in the liquid to be treated after concentration. Accordingly, the concentration of lithium in the liquid to be treated after concentration can be increased, and the recovery rate of lithium carbonate in the carbonation step (S8) described later can be improved. In addition, when a precipitate has precipitated in the concentration step (S7), a solid-liquid separation step of isolating it from the liquid to be treated may be performed.

In the concentration step (S7), the method for evaporating and concentrating the liquid to be treated is not particularly limited, and, for example, the evaporation concentrator 5 can be used. The evaporative concentration device 5 is not particularly limited as long as it can concentrate the liquid to be treated by evaporation. For example, a known evaporative concentration device such as a heat pump type, an ejector drive type, a steam type, or a flash type can be used. However, it is preferably a heat pump type evaporative concentration device. When a heat pump type evaporation system is used, the energy to be used can be significantly suppressed. In addition, further energy saving can be achieved by concentrating the liquid to be treated in a reduced pressure atmosphere.

In the following carbonation step (S8), lithium in the target solution is precipitated as crystals of lithium carbonate by mixing carbon dioxide gas and/or adding a water-soluble carbonate to the target solution after the concentration step (S7). Thereby, lithium in the liquid to be treated can be recovered as lithium carbonate. As carbonate, sodium carbonate, ammonium carbonate, potassium carbonate, etc. can be used, for example.

In this carbonation step (S8), it is preferable to precipitate and precipitate crystals of lithium carbonate by mixing carbon dioxide gas with the liquid to be treated. In this way, in the carbonation step (S8), for example, by using a material that does not contain alkali metals such as sodium, it is possible to suppress mixing of alkali metals other than lithium into the precipitated crystals of lithium carbonate. Therefore, lithium carbonate with high purity can be recovered.

In the carbonation step (S8), the method of mixing the carbon dioxide gas with the liquid to be treated is not particularly limited, and a method commonly used can be used. For example, carbon dioxide gas can be uniformly mixed with the liquid to be treated by supplying carbon dioxide gas into the liquid to be treated in the form of fine bubbles by means of a nozzle while stirring the liquid to be treated in the carbonation tank 7, Lithium in the liquid and carbon dioxide gas can be reacted efficiently. Moreover, you may make it react with carbon dioxide gas by spraying a to-be-processed liquid in the atmosphere of carbon dioxide gas.

Since the solubility of lithium carbonate decreases as the temperature increases, it is preferable to heat the liquid to be treated in the carbonation step S8. Accordingly, since the solubility of lithium carbonate generated by the reaction of lithium and carbon dioxide gas in the liquid to be treated decreases, the amount of precipitated lithium carbonate crystals can be increased.

In the next solid-liquid separation step (S9), the to-be-treated liquid after the carbonation step (S8) is filtered, for example, to separate a precipitate containing lithium carbonate crystals from the to-be-treated liquid. In the solid-liquid separation step (S9), by washing the precipitate separated from the liquid to be treated with water or the like, impurities are removed and the purity of lithium carbonate can be increased. Although the water used for washing|cleaning this precipitate is not specifically limited, It is preferable to use the condensed water which arises when the to-be-processed liquid is evaporated and concentrated in the concentration process (S7), Thus, effective use of the condensed water is possible. In addition, it is preferable to supply the washing waste liquid after washing the precipitates together with the liquid to be treated (filtrate) after the solid-liquid separation process (S9) to the bipolar membrane electrodialysis apparatus 6 of the electrodialysis process (S10) described later.

In the next electrodialysis step (S10), the liquid to be treated after the solid-liquid separation step (S9) is supplied to the bipolar membrane electrodialysis apparatus 6 to separate and recover alkalis and inorganic acids from the treated liquid. As the bipolar membrane electrodialysis device 9, for example, as shown in FIG. 17, an anion exchange membrane 91, a cation exchange membrane 92, and two bipolar membranes are interposed between the anode 95 and the cathode 96. A three-cell type bipolar membrane electrodialysis apparatus in which a plurality of cells 90 having (93, 94) are stacked can be suitably used. In the bipolar membrane electrodialysis apparatus 9 of the present embodiment, a desalting chamber R1 is formed by an anion exchange membrane 91 and a cation exchange membrane 92 , and an anion exchange membrane 91 and one bipolar membrane 93 are formed. An acid chamber (R2) is formed therebetween, and an alkali chamber (R3) is formed between the cation exchange membrane (92) and the other bipolar membrane (94). An anode chamber R4 and a cathode chamber R5 are formed outside each of the bipolar films 93 and 94, an anode 95 is provided in the anode chamber R4, and a cathode 96 is formed in the cathode chamber R5. each is placed.

In this electrodialysis step (S10), the liquid to be treated is introduced into the desalting chamber R1, and pure water is introduced into the acid chamber R2 and the alkali chamber R3, respectively, so that the liquid to be treated is an anion of lithium and an inorganic acid (this embodiment). In the desalting chamber (R1), lithium ions (Li ⁺ ) pass through the cation exchange membrane 92 , and sulfate ions (SO ₄ ²⁻ ) pass through the anion exchange membrane 91 . . On the other hand, in the acid chamber (R2) and the alkali chamber (R3), the supplied pure water ^{dissociates into hydrogen ions (H +} ) and hydroxide ions (OH ⁻ ) in the bipolar membranes 93 and 94, and in the acid chamber (R2), hydrogen Ions (H ⁺ ) combine with sulfate ions (SO ₄ ²⁻ ) to form sulfuric acid (H ₂ SO ₄ ), and in the alkali chamber (R3), hydroxide ions (OH ⁻ ) combine with lithium ions (Li ^{+ )} Lithium hydroxide (LiOH) is produced. _{Thereby, sulfuric acid (H 2} SO ₄ ) as an inorganic acid from the acid chamber (R2) and lithium hydroxide (LiOH) as an alkali from the alkali chamber (R3) are respectively recovered. In addition, as the pure water introduced into the acid chamber R2 and the alkali chamber R3, condensed water generated when the liquid to be treated is evaporated and concentrated in the concentration step S8 may be used.

The dilute to-be-treated liquid (desalting liquid) after desalting discharged from the desalting chamber R1 is not particularly limited, but since it contains a small amount of lithium, at least a part of it is concentrated in the concentration step S7 (evaporative concentration unit 5) or It is preferable to supply to the impurity removal process (polyvalent cation removal apparatus) before a concentration process (S7) mentioned later, and to carbonize in a carbonation process (S8) after concentrating again in a concentration process (S7). Accordingly, lithium can be recovered with a high recovery rate. In addition, although the desalination liquid is supplied to the concentration process (S7) in this embodiment, you may supply to the 1st pH adjustment process (S3). Accordingly, when cobalt remains in the desalting solution, the recovery rate of cobalt can be increased.

In addition, the inorganic acid (sulfuric acid in this embodiment) recovered from the acid chamber (R2) is not particularly limited, but is supplied to the acid leaching tank 1 and used as an inorganic acid for leaching the spent lithium ion battery in the acid leaching step (S1). It is preferable to reuse it.

In addition, although the alkali (lithium hydroxide in this embodiment) recovered|recovered from alkali chamber R3 is not specifically limited, It is supplied to the pH adjustment tanks 2 and 3, and the to-be-processed liquid in pH adjustment process S3, S5. It is preferable to reuse it as an alkali for pH adjustment.

According to the cobalt recovery method of the present embodiment described above, the alkali concentration of the liquid to be treated in which cobalt and impurity metals are dissolved is 1.0 mol/L when the impurity metal is removed from the liquid to be treated in the first pH adjustment step (S3). By adjusting the pH of the liquid to be treated with an aqueous solution of less than a dilute alkali, it is possible to suppress removal of cobalt from the liquid to be treated together with impurity metals. Therefore, since the amount of cobalt in the to-be-processed liquid supplied to the 2nd pH adjustment process S5 can be maintained high, cobalt can be collect|recovered with a high recovery rate in the 2nd pH adjustment process S5.

Further, according to the cobalt recovery method of the present embodiment, since an aqueous solution of a dilute alkali having an alkali concentration of less than 1.0 mol/L is used in the first pH adjustment step (S3), a carbonation step for recovering lithium thereafter (S8) ), the liquid amount of the liquid to be treated becomes large, but by evaporating and concentrating the liquid to be treated in the concentration step (S7) before the carbonation step (S8), the amount of the liquid to be treated is reduced and the lithium concentration in the liquid to be treated is increased. . Therefore, the recovery rate of lithium carbonate in the carbonation step (S8) can be improved favorably. In addition, since the temperature of the liquid to be treated supplied to the carbonation step S8 increases along with the evaporation and concentration of the liquid to be treated, the solubility of lithium carbonate decreases and the amount of lithium carbonate precipitated can be increased.

In addition, when the pH of the liquid to be treated is adjusted to 4 to 7 in the first pH adjustment step S3, an aqueous solution of alkali having an alkali concentration of 1.0 mol/L or more is treated until the pH of the liquid to be treated becomes a predetermined value. After adding to the liquid and the pH of the liquid to be treated reaches a predetermined value, an aqueous solution of alkali having an alkali concentration of less than 1.0 mol/L is added to the liquid to be treated, thereby reducing the amount of aqueous alkali solution used for pH adjustment .

In addition, according to the cobalt recovery method of the present embodiment, the inorganic acid and alkali recovered in the electrodialysis step (S10) are circulated in the acid leaching step (S1) and the pH adjustment step (S3, S5), respectively, and reused in each step (S1). , S3, S5) can reduce the amount of inorganic acid or alkali used.

As mentioned above, although one embodiment of the cobalt recovery method of this indication was described, the cobalt recovery method of this indication is not limited to the embodiment of FIGS. 15 and 16, Unless it deviates from the meaning of this indication, it is various branch changes are possible.

For example, in the embodiment of FIGS. 15 and 16 , the alkali recovered in the electrodialysis step (S10) is supplied to the first pH adjustment step (S3) and the second pH adjustment step (S5), but only either one is supplied. It may be configured to do so.

15 and 16, at least a portion of the dilute to-be-processed liquid (demineralized liquid) after lithium hydroxide is recovered by the electrodialysis process (S10) is supplied to the concentration process (S7). Alternatively or in addition to this, you may comprise so that it may supply to the electrodialysis process (S10).

In addition, in embodiment of FIG. 15 and FIG. 16, although it has a concentration process S7 before carbonation process S8, it is not necessary to necessarily have a concentration process S7. Moreover, in this case, it can be comprised so that at least a part may be supplied to the carbonation process (S8) with respect to the thin to-be-processed liquid (demineralization liquid) after lithium hydroxide is collect|recovered by the electrodialysis process (S10).

15 and 16, with respect to the liquid to be treated before the concentration step (S7) and/or the liquid to be supplied to the electrodialysis step (S10), a polyvalent cation (divalent or higher) in the liquid to be treated ( Typically, you may comprise so that the impurity of calcium ion and magnesium ion) may be removed. If polyvalent cations such as calcium ions or magnesium ions are present in the liquid to be treated, these polyvalent cations are precipitated in the cation exchange membrane of the bipolar membrane electrodialysis apparatus 9, and there is a risk that the performance of the membrane may deteriorate. By removing it from the liquid to be treated in advance, the adverse effect on the cation exchange membrane in the bipolar membrane electrodialysis apparatus 9 can be prevented. The specific structure of this polyvalent cation removal is not specifically limited, For example, the well-known polyvalent cation removal apparatus which can pass a to-be-processed liquid through the column filled with the chelate resin can be illustrated. As a chelate resin, what can selectively capture|acquire calcium ion and a magnesium ion can be used, For example, iminodiacetic acid type, aminophosphoric acid type, etc. can be illustrated. Other examples of the polyvalent cation removal device include adding a chelating agent, using an ion exchange resin, and the like. In addition to calcium and magnesium, silica (silicate ions) may be contained in the impurities removed from the liquid to be treated.

15 and 16 , as shown in FIGS. 18 and 19 , a roasting step S0 of roasting the spent lithium ion battery before the acid leaching step S1 may be further included. In the roasting step S0, the method of roasting the spent lithium ion battery is not particularly limited, and a known roasting apparatus 12 can be used.

18 and 19, the exhaust gas generated in the roasting device 12 (roasting step S0) is supplied to the carbonation tank 7 (carbonation step S8) and mixed with the liquid to be treated as carbon dioxide gas, have. Accordingly, it is possible to reduce the amount of carbon dioxide gas used in the carbonation process (S8).

15 and 16 , the method for recovering lithium in the step after the concentration step (S7) is not particularly limited, and the lithium recovery method of the present disclosure described above may be used. In the lithium recovery method of the above-described embodiment, the cobalt recovery method of the present disclosure is used in the solid-liquid separation step (S6) from the acid leaching step (S1).

In addition, although the cobalt recovery method of the above embodiment takes the case of recovering cobalt from a waste lithium ion battery as an example, the cobalt recovery method of the present disclosure is not limited to the method used for recovering cobalt from a waste lithium ion battery. .

test example

About the alkali concentration of the aqueous solution of alkali added in the 1st pH adjustment process (S3), this inventor implemented the following test. Specifically, to 200 ml of the to-be-processed liquid having the components shown in Table 1 below, the process (1st pH adjustment process (S3)) of adjusting the pH of the to-be-processed liquid by adding an aqueous alkali solution was performed. As the aqueous alkali solution to be added, an aqueous lithium hydroxide solution was used. The alkali concentration of the lithium hydroxide aqueous solution was 0.2 mol/L (Example 1), 0.5 mol/L (Example 2), and 1.0 mol/L (Example 3), and lithium hydroxide so that the pH of the solution to be treated was 4.7. The addition amount of the aqueous solution was adjusted. The amount of lithium hydroxide aqueous solution added was 418.6 ml in Example 1, 168.5 ml in Example 2, and 86.3 ml in Example 3. In addition, the content of lithium in the liquid to be treated by the addition of the aqueous lithium hydroxide solution further increases by 582 mg in Example 1, 585 mg in Example 2, and 599 mg in Example 3.

Co Al Li density
(mg/L) 21,290 4493 1963 content
(mg) 4,258 899 393

And the to-be-processed liquid after pH adjustment was filtered using filter paper, and content of each component contained in the filtrate obtained by filtration was measured. The results are shown in Table 2.

Co Al Li Example 1
(Alkali Concentration:
0.2 ㏖/L) content
(mg) 3,844 4.14 906 recovery rate
(%) 90.3 0.46 93 Example 2
(Alkali Concentration:
0.5 ㏖/L) content
(mg) 3,759 3.50 911 recovery rate
(%) 88.3 0.39 93.2 comparative example
(Alkali Concentration:
1.0 ㏖/L) content
(mg) 3,595 0.28 891 recovery rate
(%) 84.4 0.28 89.9

On the other hand, the surface state of the filtration residue obtained by filtration of the to-be-processed liquid after pH adjustment was confirmed. The results are shown in FIGS. 20 to 22 . 20 shows Example 1, FIG. 21 shows Example 2, and FIG. 22 shows Example 3. FIG. According to FIG. 22, it was visually confirmed that cobalt hydroxide was contained in the filtration residue in Example 3, but according to FIGS. 20 and 21, in Examples 1 and 2, it was visually observed that cobalt hydroxide was contained in the filtration residue. could not be verified with

From the above results, according to FIGS. 20 to 22 , when the alkali concentration of the aqueous alkali solution added to the liquid to be treated in the first pH adjustment step (S3) is 1.0 mol/L, the filtration residue after pH adjustment of the liquid to be treated It was confirmed that many cobalt salts were contained in In addition, according to Table 2, when the alkali concentration of the aqueous alkali solution added to the liquid to be treated in the first pH adjustment step (S3) is 1.0 mol/L, the cobalt recovery rate of the liquid to be treated (filtrate) after pH adjustment is When the alkali concentration is less than 1.0 mol/L compared to less than 85%, the cobalt recovery rate of the liquid to be treated (filtrate) after pH adjustment is 85% or more, and a large amount of cobalt remains in the liquid to be treated (filtrate). It has been confirmed that

As described above, by setting the alkali concentration of the aqueous alkali solution added to the liquid to be treated in the first pH adjustment step S3 to less than 1.0 mol/L, cobalt is converted from the liquid to be treated in the first pH adjustment step S3 to an impurity metal (eg, For example, it can be seen that removal together with aluminum) can be suppressed, and the content of cobalt in the to-be-processed liquid supplied to the next 2nd pH adjustment process (S5) can be maintained high. Therefore, it is possible to recover cobalt with a high recovery rate in the second pH adjustment step (S5).

S0: roasting process
S1: acid leaching process
S3: 1st pH adjustment process (pH adjustment process)
S5: 2nd pH adjustment process (pH adjustment process)
S7: Impurity removal process
S8: Concentration process
S9: crystallization process
S10: solid-liquid separation step (first solid-liquid separation step)
S11: carbonation process
S12: solid-liquid separation step (second solid-liquid separation step)
S13: melting process
S13-1: recrystallization process
S13-3: remelting process
S14: electrodialysis process

Claims (7)

a concentration step of evaporating and concentrating the liquid to be treated in which lithium and inorganic salts are at least dissolved;
a crystallization step of cooling and crystallizing the liquid to be treated after the concentration step to precipitate inorganic salts as crystals;
a first solid-liquid separation step of separating precipitates containing inorganic salt crystals from the liquid to be treated after the crystallization step;
a carbonation step of mixing carbon dioxide gas and/or adding water-soluble carbonate to the liquid to be treated after the first solid-liquid separation step;
and a second solid-liquid separation step of separating a precipitate including crystals of lithium carbonate precipitated by the carbonation step from the liquid to be treated;
Lithium recovery method.
According to claim 1,
At least a part of the liquid to be treated after the second solid-liquid separation step is concentrated by evaporation in the concentration step.
Lithium recovery method.
3. The method of claim 1 or 2,
a dissolution step of dissolving the inorganic salt contained as crystals in the precipitate separated from the liquid to be treated in the first solid-liquid separation step to produce an inorganic salt solution;
an electrodialysis step of separating and recovering an inorganic acid together with an alkali from the inorganic salt solution by performing bipolar membrane electrodialysis on the inorganic salt solution obtained by the dissolution step;
Lithium recovery method.
4. The method of claim 3,
The inorganic salt solution after desalting by the bipolar membrane electrodialysis is evaporated and concentrated in the concentration step.
Lithium recovery method.
5. The method according to any one of claims 1 to 4,
Before the concentration process,
an acid leaching process for leaching lithium by leaching a spent lithium ion battery with an inorganic acid;
a pH adjustment step of adjusting the pH by adding an alkali to the lithium-containing liquid obtained by the acid leaching step;
The liquid to be treated is produced by separating the precipitates precipitated by the pH adjustment process from the lithium-containing liquid.
Lithium recovery method.
6. The method of claim 5,
At least a part of the liquid to be treated after the second solid-liquid separation step is reused as an alkali added in the pH adjustment step.
Lithium recovery method.
7. A method according to claim 5 or claim 6 citing claim 3,
The alkali recovered in the electrodialysis step is reused as an alkali added in the pH adjustment step, and the inorganic acid recovered in the electrodialysis step is reused as an inorganic acid used in the acid leaching step.
Lithium recovery method.

Images