WO2020171009A1

WO2020171009A1 - Lithium recovery method

Info

Publication number: WO2020171009A1
Application number: PCT/JP2020/006013
Authority: WO
Inventors: 慶明三保; 幸則紀平; 佳帆横山; 和彦石田; 平野　悟; 義浩藤原
Original assignee: 株式会社ササクラ
Priority date: 2019-02-20
Filing date: 2020-02-17
Publication date: 2020-08-27
Also published as: CN118063026A; KR20210129042A; CN113453788A

Abstract

Provided is a lithium recovery method whereby highly pure lithium can be recovered from a fluid to be processed that has lithium and an inorganic salt dissolved therein. The lithium recovery method has: a concentration step S8 in which the fluid to be processed that has at least lithium and an inorganic salt dissolved therein is concentrated by evaporation; a crystallization step S9 in which the fluid to be processed is cooled and crystallized after the concentration step S8 and the inorganic salt is precipitated as crystals; a solid/liquid separation step S10 in which a precipitate including inorganic salt crystals is separated from the fluid to be processed, after the crystallization step S9; a carbonation step S11 in which carbon dioxide gas is mixed into and/or a water-soluble carbonate is added to the fluid to be processed, after the solid/liquid separation step S10; and a solid/liquid separation step S12 in which a precipitate including lithium carbonate crystals precipitated in the carbonation step S11 is separated from the fluid to be processed.

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 particularly to a lithium recovery method used when recovering lithium from a waste lithium-ion battery.

The present disclosure also 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, and particularly to a cobalt recovery method used when recovering cobalt from a waste 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 mobile devices, electric vehicles, electrically assisted bicycles, etc. For the positive electrode of this lithium-ion battery, a lithium transition metal oxide such as lithium cobalt oxide or lithium nickel oxide is used as a positive electrode active material, and valuable metals such as cobalt and nickel cannot be recovered from a waste lithium-ion battery. Many methods have been proposed because they are extremely important from the viewpoint of effective use of resources.

As a method for recovering cobalt from a waste lithium-ion battery, for example, in Patent Document 1, a waste lithium-ion battery is leached with sulfuric acid to elute cobalt, and alkali is added to this acid leachate to adjust the pH to 4-5. Then, after depositing and precipitating a salt of an impurity metal such as aluminum, which is eluted together with cobalt, as a crystal, the pH is adjusted to 7 to 10 by further adding an alkali to deposit and precipitate the cobalt salt as a crystal. By this, a method for recovering cobalt is described.

On the other hand, many methods have not been proposed for recovering lithium from waste lithium-ion batteries because the unit price of lithium is low. However, the demand for lithium-ion batteries is increasing more and more, and the amount of waste is expected to increase in the future. Therefore, it would be beneficial if lithium can be efficiently recovered.

In Patent Document 2, a used lithium metal gel and a solid polymer electrolyte secondary battery are dissolved with sulfuric acid, and lithium hydroxide or ammonium hydroxide is added to a lithium sulfate-containing liquid containing lithium sulfate obtained by this. By neutralizing, a salt of an impurity metal (aluminum hydroxide) is precipitated and separated as crystals, and the lithium sulfate-containing liquid is evaporated and concentrated, and then carbonated to give lithium contained in the lithium sulfate-containing liquid. Is described as a crystal of lithium carbonate, which is separated and recovered.

Japanese Patent No. 5077788 Special table 2004-508694 publication

However, in the method described in Patent Document 2, when ammonium hydroxide is used in the neutralization when removing impurities (aluminum hydroxide) from the lithium sulfate-containing liquid, the inorganic salt ammonium sulfate is added to the neutralized lithium sulfate-containing liquid. Is included. If carbonation is carried out in a state where the lithium sulfate-containing liquid contains an inorganic salt, the concentration may cause crystallization because the concentration of the inorganic salt in the lithium sulfate-containing liquid is increased. Therefore, there is room for improvement in that lithium carbonate contains an inorganic salt during carbonation, which reduces the purity of the lithium carbonate to be recovered.

In order to solve the above problems, the present disclosure aims 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 according to one aspect of the present disclosure includes a concentration step of evaporating and concentrating a liquid to be treated in which lithium and an inorganic salt are at least dissolved, and a liquid to be treated after the concentration step is cooled and crystallized to precipitate an inorganic salt as crystals. And a first solid-liquid separation step of separating a precipitate containing crystals of an inorganic salt from the liquid to be treated after the crystallization step, and carbon dioxide gas in the liquid to be treated after the first solid-liquid separation step. And/or adding a water-soluble carbonate, and a second solid-liquid separation step of separating a precipitate containing lithium carbonate crystals precipitated by the carbonation step from the liquid to be treated. It is characterized by having.

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

Further, in the crystallization step after the concentration step, by cooling crystallization of the liquid to be treated, the temperature of the liquid to be treated after evaporation and concentration is lowered, and the solubility is lowered until the inorganic salt contained in the liquid to be crystallized. I am letting you. Thereby, the concentration of the inorganic salt in the liquid to be treated can be reduced. Moreover, in the carbonation step, the temperature of the liquid to be treated is raised in order to reduce the solubility of lithium carbonate, so that the solubility of the inorganic salt remaining in the liquid to be treated is increased, and crystallization of the inorganic salt can be suppressed. Therefore, when recovering lithium carbonate in the carbonation step, 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 a liquid to be treated in which lithium and an inorganic salt are dissolved.

It is a flow chart which shows roughly the procedure of the lithium recovery method of the first mode. It is a schematic diagram which shows schematic structure of the processing apparatus used for the lithium recovery method of FIG. It is a schematic diagram which shows schematic structure of a bipolar membrane electrodialysis apparatus. It is a flow chart which shows roughly the procedure of the modification of the lithium recovery method of the first mode. It is a schematic diagram which shows schematic structure of the processing apparatus used for the lithium recovery method of FIG. It is a flow chart which shows roughly the procedure of the modification of the lithium recovery method of the first mode. It is a schematic diagram which shows schematic structure of the processing apparatus used for the lithium recovery method of FIG. It is a flow chart which shows roughly the procedure of the lithium recovery method of the 2nd mode. It is a schematic diagram which shows schematic structure of the processing apparatus used for the lithium recovery method of FIG. It is a schematic diagram which shows schematic structure of a bipolar membrane electrodialysis apparatus. It is a flow chart which shows roughly the procedure of the modification of the lithium recovery method of the 2nd mode. It is a schematic diagram which shows schematic structure of the processing apparatus used for the lithium recovery method of FIG. It is a flow chart which shows roughly the procedure of the modification of the lithium recovery method of the 2nd mode. It is a schematic diagram which shows schematic structure of the processing apparatus used for the lithium recovery method of FIG. It is a flow chart which shows a procedure of a cobalt recovery method roughly. It is a schematic diagram which shows schematic structure of the processing apparatus used for the cobalt recovery method of FIG. It is a schematic diagram which shows schematic structure of a bipolar membrane electrodialysis apparatus. It is a flow chart which shows a procedure of a modification of a cobalt recovery method roughly. It is a schematic diagram which shows the schematic structure of the processing apparatus used for the cobalt recovery method of FIG. 3 is a photograph of the surface state of the filtration residue of Example 1. 5 is a photograph of the surface state of the filtration residue of Example 2. 7 is a photograph of the surface condition of the filtration residue of Example 3.

Hereinafter, the actual form of the lithium recovery method of the present disclosure will be described with reference to the accompanying drawings. In the following description, "to" means the following.

Lithium Recovery Method of First Aspect The lithium recovery method of the first aspect of the present disclosure is a concentration step of evaporating and concentrating a liquid to be treated in which at least lithium and an inorganic salt are dissolved, and cooling and crystallization of the liquid to be treated after the concentration step. Crystallization step of precipitating inorganic salt 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 the first solid-liquid separation step A carbonation step of mixing carbon dioxide gas and/or adding a water-soluble carbonate to the liquid to be treated, and separating a precipitate containing lithium carbonate crystals precipitated by the carbonation step from the liquid to be treated. And a solid-liquid separation step.

In the lithium recovery method described in Paragraph 0016, it is preferable to evaporate and concentrate at least a part of the liquid to be treated after the second solid-liquid separation step in the concentration step.

The lithium recovery method described in paragraph 0016 or paragraph 0017 preferably further includes an impurity removal step of removing at least calcium and/or magnesium contained in the liquid to be treated before the concentration step.

In the lithium recovery method according to any one of paragraphs 0016 to 0018, the inorganic salt solution is prepared by dissolving the crystals of the inorganic salt contained in the precipitate separated from the liquid to be treated in the first solid-liquid separation step. And a electrodialysis step of separating and recovering an inorganic acid together with an alkali from the inorganic salt solution by performing a bipolar membrane electrodialysis on the inorganic salt solution obtained by the dissolving step. It is preferable to have.

In the lithium recovery method described in paragraph 0019, it is preferable that the inorganic salt solution after desalting by the bipolar membrane electrodialysis is evaporated and concentrated in the concentration step.

Further, in the lithium recovery method described in paragraph 0019 or paragraph 0020, a substance such as scaling that may be an obstacle in operating electrodialysis such as calcium and/or magnesium contained in the inorganic salt solution before the electrodialysis step is used. It is preferable to further include an impurity removing step of removing at least the impurities.

In the lithium recovery method according to any one of paragraphs 0019 to 0021, the inorganic salt contained in the inorganic salt solution is recrystallized and the crystals of the inorganic salt are separated from the inorganic salt solution before the electrodialysis step. It is preferable to further include a recrystallization step and a remelting step of dissolving the crystal of the inorganic salt obtained by the recrystallization step to generate an inorganic salt solution.

Moreover, in the lithium recovery method according to any one of paragraphs 0019 to 0022, 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 0019 to 0022, it is preferable to use the inorganic acid recovered in the electrodialysis step as a regenerant for a chelate resin or an ion exchange resin used in the impurity treatment step. ..

Further, in the lithium recovery method according to any one of paragraphs 0016 to 0024, condensed water generated in the concentration step causes a precipitate containing crystals of an inorganic salt obtained in the first solid-liquid separation step, and/or Alternatively, it is preferable to wash the precipitate containing the crystals of lithium carbonate obtained in the second solid-liquid separation step.

Further, in the lithium recovery method according to any one of paragraphs 0016 to 0025, before the concentration step, an acid leaching step of leaching a waste lithium ion battery with an inorganic acid to elute lithium, and the acid leaching step A pH adjusting step of adjusting the pH by adding an alkali to the obtained lithium-containing liquid is further included, and the liquid to be treated is generated by separating the precipitate deposited by the pH adjusting step from the lithium-containing liquid. Preferably.

In the lithium recovery method described in paragraph 0026, it is preferable to reuse at least a part of the liquid to be treated after the second solid-liquid separation step as an alkali added in the pH adjustment step.

In the lithium recovery method according to paragraph 0026 or paragraph 0027, 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 converted into the acid. It is preferably reused as an inorganic acid used in the leaching step.

Further, in the lithium recovery method according to any one of paragraphs 0026 to 0028, it is preferable to wash the precipitate deposited in the pH adjusting step with the condensed water generated in the concentrating step.

Further, in the lithium recovery method according to any one of paragraphs 0026 to 0029, before the acid leaching step, a roasting step of roasting the waste lithium-ion battery is further included, and in the carbonation step, Exhaust gas generated in the roasting step is preferably mixed 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 liquid amount of the liquid to be treated is reduced and the lithium concentration in the liquid to be treated is increased. I am letting you. Therefore, the recovery rate of lithium carbonate can be favorably improved in the carbonation step.

FIG. 1 shows the procedure of each step in the actual form of the lithium recovery method according to the first aspect of the present disclosure, and FIG. 2 shows a schematic configuration of a processing apparatus 10 for carrying out the lithium recovery method of FIG. The lithium recovery method of the present embodiment, in addition to lithium, a treatment liquid containing a strong acid such as hydrochloric acid, sulfuric acid, hydrofluoric acid, phosphoric acid, and an inorganic salt of an alkali metal or alkaline earth metal such as potassium or sodium. It can be preferably used for processing, and particularly preferably for recovering lithium from a waste lithium-ion battery. Hereinafter, a case of recovering lithium from a waste lithium-ion battery will be described as an example.

The lithium recovery method of the present embodiment is
-An acid leaching step S1 of leaching a waste lithium-ion battery with an inorganic acid to elute lithium
-A solid-liquid separation step S2 for separating an insoluble residue from the lithium-containing liquid obtained in the acid leaching step S1,
-PH adjusting steps S3 and S5 in which an alkali is added to the lithium-containing solution after the solid-liquid separation step S2 to adjust the pH,
-Solid-liquid separation steps S4 and S6 for separating precipitates from the lithium-containing solution after the pH adjustment steps S3 and S5,
-Impurity removing step S7 in which a chelate treatment is performed on the liquid to be treated, in which the precipitate is separated from the lithium-containing liquid after the pH adjusting steps S3 and S5,
-A concentration step S8 for evaporating and concentrating the liquid to be treated in which at least lithium and an inorganic salt are dissolved after the impurity removal step S7,
-A crystallization step S9 in which the liquid to be treated after the concentration step S8 is cooled and crystallized to precipitate an inorganic salt as crystals,
-A solid-liquid separation step S10 (corresponding to the "first solid-liquid separation step" in paragraph 0016) for separating a precipitate containing crystals of an inorganic salt from the liquid to be treated after the crystallization step S9;
-A carbonation step S11 of mixing carbon dioxide gas and/or adding a 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" in paragraph 0016) for separating the precipitate containing the crystals of lithium carbonate precipitated in the carbonation step S11 from the liquid to be treated. The lithium recovery method of the present embodiment further includes
A dissolution step S13 in which crystals of an inorganic salt contained in the precipitate separated from the liquid to be treated in the solid-liquid separation step S10 are dissolved to generate an inorganic salt solution;
An electrodialysis step S14 for separating and recovering an alkali and an inorganic acid from the inorganic salt solution by performing bipolar membrane electrodialysis on the inorganic salt solution after the dissolution step S13;
Have.

The waste lithium-ion batteries for which lithium is collected are used lithium-ion batteries whose charge capacity has decreased due to the use of the specified number of times of charging and discharging, as well as semi-finished products and product specifications that occur due to defects in the battery manufacturing process. Includes old model inventory items that are generated due to changes. The waste lithium-ion battery may be crushed or roasted, or may be powder obtained by crushing or roasting.

First, in the acid leaching step S1, by leaching the waste lithium ion battery described above with an inorganic acid, not only lithium but also metals such as aluminum, nickel, cobalt and iron are eluted. As the inorganic acid, for example, sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid or the like can be used, but in the present embodiment, sulfuric acid is used because of its low cost and easy handling.

In the acid leaching step S1, the method of leaching the waste lithium ion battery with an inorganic acid is not particularly limited, and a commonly used method can be used. For example, the waste lithium-ion battery is immersed in an aqueous solution of an inorganic acid such as an aqueous solution of sulfuric acid in the acid leaching tank 1 and stirred for a predetermined time to obtain a lithium-containing solution in which the above-described 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 insoluble residue is separated from the lithium-containing solution by, for example, filtering the lithium-containing solution obtained in the acid leaching step S1. The insoluble residue is mainly a carbon material, a metal material, or an organic material that does not dissolve in an inorganic acid. As the method for solid-liquid separation, for example, various filtration devices such as pressure filtration (filter press), vacuum filtration, centrifugal filtration, and known solid-liquid separation devices such as a decanter type centrifugal separation device can be used. .. The same applies to the following solid-liquid separation steps S4, S6, S10, S12 and the like.

In the next pH adjusting steps S3 and S5, alkali is added to the lithium-containing liquid (filtrate) after the solid-liquid separation step S2 to adjust the pH to a predetermined range, so that the above-mentioned metal in the lithium-containing liquid Of these, metals other than lithium are removed from the lithium-containing liquid. As the alkali, for example, sodium hydroxide, potassium hydroxide, lithium hydroxide or the like can be used, but in the present embodiment, sodium hydroxide is used because of its low cost and easy handling.

In the pH adjusting steps S3 and S5, the method of adjusting the pH of the lithium-containing liquid is not particularly limited, and a commonly used method can be used. For example, while stirring the lithium-containing solution in the first pH adjusting tank 2 and the second pH adjusting tank 3, by adding an alkaline aqueous solution such as an aqueous solution of sodium hydroxide, the metal other than lithium in the lithium-containing solution is hydroxylated. Precipitate and precipitate as crystals of inorganic salts such as substances. In this embodiment, the pH adjusting steps S3 and S5 are divided into a first pH adjusting step S3 and a second pH adjusting step S5.

In the first pH adjusting step S3, the pH of the lithium-containing liquid is adjusted to 4 to 7, preferably 4 to 6, and more preferably 4 to 5 by adding alkali. Thereby, the impurity metal (eg, aluminum, iron) in the lithium-containing liquid is precipitated and precipitated as crystals of an inorganic salt such as hydroxide (eg, aluminum hydroxide, iron hydroxide). In the first pH adjusting step S3, it is preferable that the lithium-containing liquid is heated, for example, at a constant temperature of 30° C. to 80° C.

It is preferable that the aqueous alkali solution added in the first pH adjusting step S3 has a dilute alkali concentration of less than 1.0 mol/L. Thereby, although the details will be described later, it is possible to prevent cobalt in the lithium-containing liquid from being precipitated and precipitated as crystals of a cobalt salt together with the impurity metal in the first pH adjusting step S3 and being removed from the lithium-containing liquid. However, if the alkali concentration is excessively low, it is necessary to use a large amount of an alkaline aqueous solution for pH adjustment in the first pH adjusting step S3, and the amount of the lithium-containing liquid after the pH adjustment is also large. The lower limit of the alkali concentration is preferably 0.1 mol/L or more. Further, in order to effectively suppress the removal of cobalt in the lithium-containing liquid from the lithium-containing liquid in the first pH adjusting step S3, the alkali concentration of the aqueous solution of alkali added in the first pH adjusting step S3 is It is preferably 0.5 mol/L or less, more preferably 0.2 mol/L or less.

In the first pH adjusting step S3, in order to reduce the amount of alkali aqueous solution used for pH adjustment, a concentrated alkali concentration of 1.0 mol/L or more is used until the pH of the lithium-containing solution becomes a predetermined value smaller than 4. After adding an aqueous solution of alkali having a pH of the lithium-containing solution to a predetermined value, an aqueous solution of alkali having a low alkali concentration of less than 1.0 mol/L is added to the lithium-containing solution. Then, the pH of the lithium-containing liquid can be adjusted to 4 to 7. The above-mentioned predetermined value of the pH of the lithium-containing liquid can be set within the range of 2 to 3.

The precipitate deposited and precipitated in the first pH step S3 is separated from the lithium-containing solution by filtering the lithium-containing solution in the next solid-liquid separation step S4, for example. In addition, copper etc. may be contained in addition to the impurity metal removed from the lithium-containing liquid in the first pH adjusting step S3. In the solid-liquid separation step S4, it is preferable that the precipitate is washed with a washing liquid, and the washing waste liquid after washing is supplied to the next second pH adjusting step S5 together with the lithium-containing liquid (filtrate). Thereby, the lithium contained in the cleaning waste liquid can also be supplied to the carbonation step S11 from the second pH adjusting step S5 together with the lithium contained in the lithium-containing solution, and the lithium can be supplied by carbonation in the carbonation step S11 described later. Can be recovered at 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 S8 described later. Can be effectively used.

In the second pH adjusting step S5, an alkali is added to the lithium-containing 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, and further preferably 8 Adjust to a range of ~10. As a result, valuable metals (for example, cobalt and nickel) in the lithium-containing liquid are precipitated and precipitated as crystals of inorganic salts such as hydroxides (for example, cobalt hydroxide and nickel hydroxide). In the second pH adjusting step S5, it is preferable that the lithium-containing liquid is heated, for example, at a constant temperature of 30° C. to 80° C. The alkali concentration of the aqueous alkali solution added in the second pH adjusting step S5 is not particularly limited, but is preferably equal to or higher than that of the alkali aqueous solution used in the first pH adjusting step S3, It is preferable that the concentration is 0.2 mol/L or more.

The precipitate that is deposited and precipitated in the second pH step S5 is separated from the lithium-containing solution by filtering the lithium-containing solution in the next solid-liquid separation step S6, for example. The valuable metal removed from the lithium-containing liquid in the second pH adjusting step S5 may also contain manganese or the like.

On the other hand, in the lithium-containing liquid (filtrate) after the solid-liquid separation step S6, in addition to lithium, the inorganic acid (sulfuric acid in this embodiment) and alkali (sulfuric acid in the present embodiment) added in the acid leaching step S1 and the pH adjusting steps S3 and S5. An inorganic salt (sodium sulfate (Na ₂ SO ₄ ) in this embodiment) is dissolved by sodium hydroxide in this embodiment. The lithium-containing liquid after the pH adjusting steps S3 and S5 corresponds to the “processed liquid” of the lithium recovery method of the present disclosure. At least one of calcium, magnesium and silica may be further dissolved in the liquid to be treated.

In the solid-liquid separation step S6, it is preferable that the precipitate is washed with a washing liquid, and the washing waste liquid after washing is supplied to the next impurity removing step S7 together with the liquid to be treated (filtrate). As a result, the lithium contained in the cleaning waste liquid can be supplied together with the lithium contained in the liquid to be treated from the impurity removal step S7 to the carbonation step S11, and the lithium is contained by carbonation in the carbonation step S11 described later. It can be collected at 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 S8 described later. Can be effectively used.

In the next impurity removing 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, and the like contained as impurities in the liquid to be treated, it is possible to prevent scale from occurring and adhering to the heat transfer surface of the heat exchanger of the evaporative concentration device 5 in the concentration step S8 described later. Therefore, the heat exchange efficiency can be maintained high. Further, when the liquid to be treated contains calcium, magnesium or the like, in an electrodialysis step S14 described later, polyvalent cations such as calcium or magnesium contained in the inorganic solution become cations of the bipolar membrane electrodialysis device 9. It may be deposited in the exchange membrane and cause deterioration of the performance of the membrane. Therefore, it is possible to prevent adverse effects on the cation exchange membrane of the bipolar membrane electrodialysis device 9 by removing substances that may cause problems such as scaling when operating electrodialysis such as calcium and magnesium from the liquid to be treated in advance. It is possible to maintain high electrodialysis performance.

The method of removing calcium and magnesium from the liquid to be treated in the impurity removing step S7 is not particularly limited, and for example, the polyvalent cation removing device 4 can be used. The polyvalent cation removing device 4 is a device for removing divalent or more polyvalent cations such as calcium ions and magnesium ions. For example, the polyvalent cation removing device 4 has a configuration in which a liquid to be treated can be passed through a column filled with a chelate resin. It can be illustrated. As the chelate resin, those capable of selectively capturing calcium ions and magnesium ions can be used, and examples thereof include iminodiacetic acid type and aminophosphoric acid type. Other examples of the polyvalent cation removing device 4 include a device to which a chelating agent is added and a device using an ion exchange resin. The impurities removed from the liquid to be treated in the impurity removal step S7 may include silica (silicate ions) in addition to calcium and magnesium.

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 liquid in the liquid to be treated is evaporated to concentrate the liquid to be treated. As a result, the liquid amount of the liquid to be processed is reduced and the lithium concentration in the liquid to be processed is increased. Therefore, the recovery rate of lithium carbonate can be improved in the carbonation step S11 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 a lithium salt such as lithium sulfate in the liquid to be treated after concentration. Thereby, the concentration of lithium in the liquid to be treated after concentration can be increased, and the recovery rate of lithium carbonate can be improved in the carbonation step S11 described later.

The method of evaporating and concentrating the liquid to be treated in the concentrating step S8 is not particularly limited, and, for example, the evaporative concentrating device 5 can be used. The evaporative concentration device 5 is not particularly limited as long as the liquid to be treated can be concentrated by evaporation, and a known evaporative concentration device such as a heat pump type, an ejector driven type, a steam type, or a flash type can be used. A heat pump type evaporative concentrator is preferable. When a heat pump type evaporative concentrator is used, the energy used can be significantly suppressed. Further, energy can be further saved by concentrating the liquid to be treated under a reduced pressure atmosphere.

In the next crystallization step S9, the liquid to be treated after the concentration step 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 decrease the solubility until the inorganic salt contained in the liquid to be crystallized, so that the inorganic salt in the liquid to be treated (main In embodiments, the concentration of sodium sulfate) can be reduced. Therefore, when recovering lithium carbonate in the carbonation step S11 described later, the purity of lithium carbonate can be increased.

In the crystallization step S9, the method of cooling and crystallizing the liquid to be treated is not particularly limited, and for example, the cooling and crystallizing device 6 can be used. The cooling crystallization device 6 cools the supplied liquid to be treated in a crystallization tank to precipitate crystals of an intended inorganic salt. As the cooling crystallization device 6, for example, a known cooling crystallization device such as a cooling type crystallization device using a jacket or an internal coil, an external circulation cooling type crystallization device, or the like can be used and is not particularly limited.

In the crystallization step S9, utilizing the fact that the saturation solubility and the temperature dependence of the solubility differ depending on the inorganic salt, only the crystal of the desired inorganic salt is precipitated. In the present embodiment, it is utilized that the temperature dependence of the solubility of a lithium salt such as lithium sulfate is smaller than that of an inorganic salt other than the lithium salt such as sodium sulfate. That is, the inorganic salt other than the lithium salt is precipitated as crystals by cooling to a temperature not lower than the precipitation temperature of the lithium salt at the supply concentration and lower than the precipitation temperature of the inorganic salt other than the lithium salt. Specifically, the cooling temperature for precipitating sodium sulfate crystals is 30° C. or lower, preferably 5° C. or higher and 20° C. or lower. At this time, sodium sulfate is precipitated in the form of sodium sulfate decahydrate (Na ₂ SO ₄ ·10H ₂ O).

In the next solid-liquid separation step S10, the liquid to be treated after the crystallization step S9 is filtered, for example, to separate a precipitate containing crystals of an inorganic salt (sodium sulfate in this embodiment) from the liquid to be treated.

In the next carbonation step S11, the liquid to be treated is mixed with carbon dioxide gas and/or a water-soluble carbonate is added to the liquid to be treated after the precipitate containing the crystals of the inorganic salt is separated. The lithium therein is deposited and precipitated as crystals of lithium carbonate. Thereby, lithium in the liquid to be treated can be recovered as lithium carbonate. As the carbonate, for example, sodium carbonate, ammonium carbonate, potassium carbonate or the like can be used.

In this carbonation step S11, it is preferable that the liquid crystal to be treated is mixed with carbon dioxide to precipitate and precipitate lithium carbonate crystals. As described above, in the carbonation step S11, by using a material containing no alkali metal such as sodium, it is possible to prevent alkali metal other than lithium from mixing into the precipitated lithium carbonate crystals. Therefore, highly pure lithium carbonate can be recovered.

However, if the mixing of carbon dioxide is continued, the pH of the liquid to be treated will drop, and the amount of lithium carbonate deposited 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. Further, the pH may not be lowered by adding an alkali to the liquid to be treated. At that time, it is preferable to maintain the pH at 9 or more by adding an alkali. As the alkali to be added, sodium hydroxide, potassium hydroxide, lithium hydroxide or the like can be used.

In the carbonation step S11, the method of mixing carbon dioxide gas with the liquid to be treated is not particularly limited, and a commonly used method 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 through a nozzle while stirring the liquid to be treated in the carbonation tank 7. The lithium in the liquid to be treated and carbon dioxide can be reacted efficiently. Alternatively, the liquid to be treated may be sprayed in an atmosphere of carbon dioxide to react with the carbon dioxide.

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. As a result, the solubility of lithium carbonate produced by the reaction between lithium in the liquid to be treated and carbon dioxide gas decreases, so that the amount of precipitated lithium carbonate crystals can be increased. Further, 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 is increased, and crystallization of the inorganic salt can be suppressed. Therefore, the precipitation of the inorganic salt crystals together with the lithium carbonate crystals can be suppressed, so that the purity of the lithium carbonate can be increased when the lithium carbonate is recovered in the carbonation step.

In the next solid-liquid separation step S12, the liquid containing lithium carbonate crystals is separated from the lithium-containing liquid by filtering the liquid to be treated after the carbonation step S11, for example. In the solid-liquid separation step S12, the precipitate separated from the lithium-containing liquid is washed with water or the like to remove impurities and increase the purity of lithium carbonate. The water used for washing the precipitate is not particularly limited, but it is preferable to use the condensed water generated when the liquid to be treated is evaporated and concentrated in the concentration step S8. It is available.

The liquid to be treated (filtrate) after the solid-liquid separation step S12 is not particularly limited, but since it contains impurities, part of it is discharged as blow liquid, but part of it is re-introduced into the system. It is preferable to circulate. As a result, lithium remaining in the liquid to be treated can be recovered, so that lithium can be recovered at a high recovery rate. In addition, it is preferable that the cleaning waste liquid after cleaning the precipitate containing the lithium carbonate crystals described above is also circulated again in 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 again in the system, it may be supplied to the evaporative concentration device 5 to be evaporated and concentrated in the concentration step S8, but preferably the first pH adjusting tank 2 and / Or supply to the second pH adjusting 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 adjusting steps S3 and S5. Furthermore, when 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 of the heat exchanger of the evaporative concentration apparatus 5 when evaporating and concentrating in the concentration step S8. Crystals of carbonate are deposited on the surface. Therefore, since the lithium-containing liquid after the solid-liquid separation steps S2 and S4 is acidic, the liquid to be treated after the solid-liquid separation step S12 is neutralized with the lithium-containing liquid to use carbonate ions as carbon dioxide gas. By removing from the liquid, it is possible to prevent precipitation of carbonate crystals on the heat transfer surface of the heat exchanger of the evaporative concentration device 5 in the concentration step S8.

On the other hand, the crystals 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 crystallization device 6) are dissolved in the dissolution step S13 (dissolution tank 8). Is supplied to. In the dissolving step S13, the inorganic salt crystals are dissolved in the dissolving tank 8 to have a desired concentration using, for example, water to form an inorganic salt solution. The temperature at this time is not particularly limited and may be a temperature at which the crystals of the inorganic salt can be dissolved. Further, the water used for dissolving the inorganic salt is not particularly limited, but it is preferable to use the condensed water generated when the liquid to be treated is evaporated and concentrated in the concentration step S8. It can be effectively used. The generated inorganic salt solution is supplied to the bipolar membrane electrodialysis device 9.

In the next electrodialysis step S14, the bipolar membrane electrodialysis device 9 separates and recovers the alkali and the inorganic acid from the inorganic salt solution after the dissolution step S13. As the bipolar membrane electrodialysis device 9, for example, as shown in FIG. 3, a cell 90 including an anion exchange membrane 91, a cation exchange membrane 92, and two

bipolar membranes

93, 94 between an anode 95 and a cathode 96. A three-chamber cell type bipolar membrane electrodialysis device in which a plurality of cells are laminated can be suitably used. The bipolar membrane electrodialysis device 9 of the present embodiment forms a desalting chamber R1 with the anion exchange membrane 91 and the cation exchange membrane 92, and the acid chamber R2 is provided between the anion exchange membrane 91 and one bipolar membrane 93. 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, 94. An anode 95 is arranged in the anode chamber R4 and a cathode 96 is arranged in the cathode chamber R5.

In this electrodialysis step S14, an inorganic salt solution is introduced into the desalting chamber R1, and pure water is introduced into each of the acid chamber R2 and the alkaline chamber R3. Accordingly, when the inorganic salt solution contains, for example, sodium sulfate, in the desalting chamber R1, sodium ions (Na ⁺ ) pass through the cation exchange membrane 92, 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 alkaline chamber R3, the supplied pure water is dissociated into hydrogen ions (H ⁺ ) and hydroxide ions (OH ⁻ ) in the

bipolar films

93 and 94, and hydrogen ions ( H ⁺ ) combines with sulfate ions (SO ₄ ²⁻ ) to generate sulfuric acid (H ₂ SO ₄ ), and in the alkaline chamber R3, hydroxide ions (OH ⁻ ) combine with sodium ions (Na ⁺ ). Sodium hydroxide (NaOH) is produced. As a result, sulfuric acid (H ₂ SO ₄ ) is recovered as an inorganic acid from the acid chamber R2, and sodium hydroxide (NaOH) is recovered as an alkali from the alkaline chamber R3. The pure water introduced into the acid chamber R2 and the alkaline chamber R3 may be condensed water generated when the liquid to be treated is evaporated and concentrated in the concentration step S8.

Although the demineralized diluted inorganic salt solution (desalination solution) discharged from the desalination chamber R1 is not particularly limited, it contains a small amount of lithium, so that the concentration step S8 (evaporation concentration device 5 It is preferable to supply to () and concentrate again, and then to carbonate in the carbonation step S11. Thereby, lithium can be recovered at a high recovery rate. Although the desalted solution is supplied to the concentration step S8 in the present embodiment, when calcium and/or magnesium remains in the desalted solution, the desalted solution is supplied to the impurity removal step S7. Good. As a result, calcium and magnesium can be supplied to the concentration step S8 after being removed from the desalted solution. Further, the desalted solution may be supplied to the first pH adjusting step S3. Thereby, when cobalt remains in the desalination solution, the recovery rate of cobalt can be increased.

Further, the inorganic acid (sulfuric acid in the present embodiment) recovered from the acid chamber R2 is not particularly limited, but is supplied to the acid leaching tank 1 and the inorganic acid leaching the waste lithium ion battery in the acid leaching step S1. It is preferably reused as an acid. Further, it is preferable to supply the polyvalent cation removing device 4 and reuse it as a regenerating liquid of the chelate resin or the ion exchange resin used in the impurity treatment step S7.

The alkali (sodium hydroxide in the present embodiment) recovered from the alkali chamber R3 is supplied to the

pH adjusting tanks

2 and 3, but is not particularly limited, and the lithium-containing liquid is used in the pH adjusting steps S3 and S5. It is preferable to reuse it as an alkali for pH adjustment. Further, it is preferable to supply the polyvalent cation removing device 4 and reuse it as a regenerating liquid of the chelate resin or the ion exchange resin used in the impurity treatment step S7.

According to the lithium recovery method of the present embodiment described above, by evaporating and concentrating the liquid to be treated in the concentrating 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 reduced. Is increasing. Therefore, the recovery rate of the lithium carbonate crystals in the carbonation step S11 can be favorably improved.

Further, in the crystallization step S9 after the concentration step S8, by cooling and crystallizing the liquid to be treated, the temperature of the liquid to be treated after evaporation and concentration is lowered and the inorganic salt (in this embodiment, sulfuric acid) contained in the liquid to be treated is reduced. Since the solubility is lowered until the sodium) crystallizes, the concentration of the inorganic salt in the liquid to be treated can be reduced. In addition, in the carbonation step S11, the temperature of the liquid to be treated is raised for the purpose of lowering the solubility of lithium carbonate, so that the solubility of the inorganic salt remaining in the liquid to be treated is increased and crystallization of the inorganic salt can be suppressed. .. Therefore, when recovering lithium carbonate in the carbonation step S11, the purity of lithium carbonate can be increased.

Moreover, according to the lithium recovery method of the present embodiment, the lithium remaining in the liquid to be treated is circulated in the system without discarding the liquid to be treated after the crystals of lithium carbonate are recovered in the carbonation step S11. Collected. Therefore, lithium can be recovered at a high recovery rate.

Further, according to the lithium recovery method of the present embodiment, the crystal of the inorganic salt (sodium sulfate in the present embodiment) contained in the precipitate separated from the liquid to be treated in the solid-liquid separation step S10 is dissolved in the dissolution step S13. After making the inorganic salt solution, the bipolar membrane electrodialysis is performed in the electrodialysis step S14 to recover the inorganic acid and the alkali from the inorganic salt solution, and the diluted inorganic salt solution after desalting is evaporated in the concentration step S8. After concentration, lithium contained in the dilute inorganic salt solution is recovered in the carbonation step S11. Therefore, lithium can be recovered at a high recovery rate. Furthermore, the inorganic acids and alkalis recovered in the electrodialysis step S14 are circulated and reused in the acid leaching step S1, the pH adjusting steps S3, S5, and the impurity removing step S7, so that each step S1, S3, S5, S7 is performed. It is possible to reduce the amount of inorganic acid or alkali used in.

Further, 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 removing step S7. As a result, the amount of impurities in the liquid to be treated from which the precipitate has been separated in the solid-liquid separation process S12 after the carbonation process S11 is reduced, and most of the liquid to be processed after the solid-liquid separation process S12 is returned to the system. It can circulate. Therefore, more lithium remaining in the liquid to be treated after the solid-liquid separation step S12 can be recovered, so that lithium can be recovered at a high recovery rate. Furthermore, since the amount of impurities in the inorganic solution electrodialyzed in the electrodialysis step S14 is also reduced, it is possible to prevent the performance of the cation exchange membrane of the bipolar electrodialysis device 9 from being deteriorated due to scaling, and maintain the performance of the bipolar membrane at a high level. can do.

Further, according to the lithium recovery method of the present embodiment, the condensed water generated in the concentration step S8 is used for various treatments, so that the condensed water can be effectively used. Furthermore, by washing the crystals obtained in the solid-liquid separation steps S4, S6, S10, and S12 with condensed water, the recovery rate of each crystal can be favorably improved.

Although one embodiment of the lithium recovery method of the first aspect has been described above, the lithium recovery method of the first aspect is not limited to the embodiments of FIGS. 1 and 2, and does not depart from the gist of the present disclosure. Various changes are possible in.

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

Further, in the embodiment of FIGS. 1 and 2, the alkali recovered in the electrodialysis step S14 is supplied to the first pH adjusting step S3 and the second pH adjusting step S5, but it is configured to be supplied to only one of them. May be.

Further, in the embodiment of FIGS. 1 and 2, the pH adjusting steps S3 and S5 include the first pH adjusting step S3 and the second pH adjusting step S5, but three pH adjusting steps S3 and S5 are included depending on the components contained in the waste lithium ion battery. It may be configured to include the above 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, for removing impurities such as silica contained in the inorganic salt solution after the dissolution step S13 and before the electrodialysis step S14. Treatment steps may be performed. This processing step can be performed instead of or in addition to the impurity removing step S7.

Specifically, first, in the recrystallization step S13-1, the inorganic salt (sodium sulfate in this embodiment) contained in the inorganic salt solution is recrystallized. The method of recrystallizing the inorganic salt contained in the inorganic salt solution is not particularly limited, and for example, cooling crystallization by the cooling crystallization device 10 similar to the cooling crystallization device 6 of the crystallization step S9 described above is used. be able to. That is, it is possible to deposit only the crystals of the inorganic salt by utilizing the fact that the saturation solubility and the temperature dependence of the solubility are different between the inorganic salt and silica, and the precipitation temperature of the silica is not less than the deposition temperature of silica at the supply concentration. Crystals of the inorganic salt are precipitated by cooling to below the temperature. At this time, sodium sulfate is precipitated in the form of sodium sulfate decahydrate (Na ₂ SO ₄ ·10H ₂ O). The inorganic salt solution may be concentrated in advance to a concentration of the inorganic salt suitable for crystallization of the inorganic salt. In the present embodiment, the cooling crystallization device 10 is used in the recrystallization step S13-1, but any crystallization method by which highly pure crystals are deposited may be used, and for example, an evaporation crystallization device may be used. it can.

After reprecipitating the inorganic salt crystals, in the solid-liquid separation step S13-2, the inorganic salt crystals are separated from the aqueous solution containing the inorganic salt crystals, and the recrystallized inorganic salt crystals are collected. As the method for solid-liquid separation, for example, various filtration devices such as pressure filtration (filter press), vacuum filtration, centrifugal filtration, and known solid-liquid separation devices such as a decanter type centrifugal separation device can be used. ..

Then, in the re-dissolution step S13-3, the crystals of the recovered inorganic salt are dissolved in the re-dissolution tank 11 using, for example, water so as to have a desired concentration, and an inorganic salt solution is regenerated. The temperature at this time is not particularly limited and may be a temperature at which the crystals of the inorganic salt can be dissolved. Further, the water used for dissolving the inorganic salt is not particularly limited, but it is preferable to use the condensed water generated when the liquid to be treated is evaporated and concentrated in the concentration step S8. It can be effectively used. The regenerated inorganic salt solution is supplied to the bipolar membrane electrodialysis device 9. The impurities removed from the inorganic salt solution in the recrystallization step S13-1 to the re-dissolution step S13-3 may contain calcium and/or magnesium in addition to silica.

In the embodiment of FIGS. 4 and 5, silica contained in the inorganic salt solution is removed before the electrodialysis step S14. As a result, the amount of impurities in the inorganic solution electrodialyzed in the electrodialysis step S14 is also reduced, so that the performance of the bipolar membrane can be maintained high. Further, when the dilute inorganic salt solution (desalted solution) after the electrodialysis step S14 is supplied to the evaporative concentration apparatus 5 and evaporated and concentrated again in the concentration step S8, the amount of impurities in the desalted solution is reduced. In the concentration step S8, it is possible to suppress the generation and adhesion of scale on 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 which has separated the precipitate in the solid-liquid separation process S12 after the carbonation process S11 is reduced, most of the liquid to be processed after the solid-liquid separation process S12 is circulated into the system again. can do. Therefore, more lithium remaining in the liquid to be treated after the solid-liquid separation step S12 can be recovered, so that lithium can be recovered at a high recovery rate.

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

In the embodiment of FIGS. 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 mixed with the liquid to be treated as carbon dioxide in the carbonation step S11. doing. As a result, the amount of carbon dioxide gas used in the carbonation step S11 can be reduced. It is needless to say that the roasting step S0 of roasting the waste lithium-ion battery before the acid leaching step S1 can also be executed in the embodiments of FIGS. 4 and 5.

Second Embodiment Lithium Recovery Method A second embodiment of the lithium recovery method of the present disclosure is a concentration step of heating and evaporating and concentrating a liquid to be treated in which lithium and an inorganic salt are at least dissolved at a low pressure lower than atmospheric pressure. A carbonation step of mixing carbon dioxide gas and/or adding a water-soluble carbonate to the liquid to be treated after the concentration step, and a precipitate containing lithium carbonate crystals deposited by the carbonation step to be treated liquid In the carbonation step, 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.

In the lithium recovery method described in paragraph 0089, it is preferable that the liquid to be treated is evaporated and concentrated under a pressure of 10 kPa or more and 70 kPa or less in the concentration step.

In the lithium recovery method described in paragraph 0089 or paragraph 0090, it is preferable that at least a part of the liquid to be treated after the solid-liquid separation step is evaporated and concentrated in the concentration step.

In the lithium recovery method according to any one of paragraphs 0089 to 0091, in the concentration step, an inorganic salt contained in the liquid to be treated is precipitated as crystals and separated from the liquid to be treated after the concentration step. Dissolving the inorganic salt contained as crystals in the precipitate to produce an inorganic salt solution, and an alkali from the inorganic salt solution by performing bipolar membrane electrodialysis on the inorganic salt solution obtained by the dissolving step. It is preferable to further include an electrodialysis step of separating and recovering the inorganic acid.

Further, in the lithium recovery method according to any of paragraphs 0089 to 0092, before the concentration step, an acid leaching step of leaching a waste lithium ion battery with an inorganic acid to elute lithium, and an acid leaching step are performed. A pH adjusting step of adjusting the pH by adding an alkali to the obtained lithium-containing liquid is further included, and the liquid to be treated is generated by separating the precipitate deposited by the pH adjusting step from the lithium-containing liquid. It is preferable.

In the lithium recovery method described in paragraph 0093, it is preferable to reuse at least a part of the liquid to be treated after the solid-liquid separation step as an alkali added in the pH adjusting step.

In the lithium recovery method described in paragraph 0093 or paragraph 0094, 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 converted into the acid. It is preferably reused as an inorganic acid used in the leaching step.

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 liquid amount of the liquid to be treated is reduced and the lithium concentration in the liquid to be treated is increased. I am letting you. Therefore, the recovery rate of lithium carbonate can be favorably improved in the carbonation step.

Also, 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 evaporative concentration can be lowered as compared with evaporating and concentrating the liquid to be treated under atmospheric pressure. Therefore, there is a large room for raising the temperature of the liquid to be treated in the subsequent carbonation step, and 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. Energy required for evaporative concentration can be suppressed to a low level to save energy. When the temperature of the liquid to be treated is low in the carbonation step, the inorganic salt contained in the liquid to be treated is crystallized, so that the temperature of the liquid to be treated during carbonation is higher than the evaporation temperature of the liquid to be treated in the concentration step. By increasing the solubility, the solubility of the inorganic salt remaining in the liquid to be treated is increased, and crystallization of the inorganic salt can be suppressed during carbonation. Further, when the temperature of the liquid to be treated is high during carbonation, the solubility of lithium carbonate decreases, and the amount of lithium carbonate crystals recovered can be increased. Therefore, highly pure lithium carbonate can be obtained with high efficiency.

FIG. 8 shows the procedure of each step in the embodiment of the lithium recovery method of the second aspect of the present disclosure, and FIG. 9 shows a schematic configuration of the processing apparatus 10 for carrying out the lithium recovery method of FIG. The lithium recovery method of the present embodiment, in addition to lithium, a treatment liquid containing a strong acid such as hydrochloric acid, sulfuric acid, hydrofluoric acid, phosphoric acid, and an inorganic salt of an alkali metal or alkaline earth metal such as potassium or sodium. It can be preferably used for processing, and particularly preferably for recovering lithium from a waste lithium-ion battery. Hereinafter, a case of recovering lithium from a waste lithium-ion battery will be described as an example.

The lithium recovery method of the present embodiment is
-An acid leaching step S1 of leaching a waste lithium-ion battery with an inorganic acid to elute lithium
-A solid-liquid separation step S2 for separating an insoluble residue from the lithium-containing liquid obtained in the acid leaching step S1,
-PH adjusting steps S3 and S5 in which an alkali is added to the lithium-containing solution after the solid-liquid separation step S2 to adjust the pH,
-Solid-liquid separation steps S4 and S6 for separating precipitates from the lithium-containing solution after the pH adjustment steps S3 and S5,
-Impurity removing step S7 in which a chelate treatment is performed on the liquid to be treated, in which the precipitate is separated from the lithium-containing liquid after the pH adjusting steps S3 and S5,
-A concentration step S8 for evaporating and concentrating the liquid to be treated in which at least lithium and an inorganic salt are dissolved after the impurity removal step S7,
-A solid-liquid separation step S9 for separating a precipitate containing inorganic salt crystals from the liquid to be treated after the concentration step S8,
-A carbonation step S10 of mixing carbon dioxide gas and/or adding a water-soluble carbonate to the liquid to be treated after the solid-liquid separation step S9;
-A solid-liquid separation step S11 for separating a precipitate containing lithium carbonate crystals precipitated by the carbonation step S10 from the liquid to be treated,
including. The lithium recovery method of the present embodiment further includes
-A dissolution step S12 in which crystals of an inorganic salt contained in the precipitate separated from the liquid to be treated in the solid-liquid separation step S9 are dissolved to generate an inorganic salt solution;
An electrodialysis step S13 for separating and recovering an alkali and an inorganic acid from the inorganic salt solution by performing a bipolar membrane electrodialysis on the inorganic salt solution after the dissolution step S12,
Have.

The waste lithium-ion battery for which lithium is to be collected is the same as that in the above-described first mode.

First, in the acid leaching step S1, by leaching the waste lithium ion battery described above with an inorganic acid, not only lithium but also metals such as aluminum, nickel, cobalt and iron are eluted. As the inorganic acid, for example, sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid or the like can be used, but hydrochloric acid is used in the present embodiment.

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

In the next solid-liquid separation step S2, the insoluble residue is separated from the lithium-containing solution by, for example, filtering the lithium-containing solution obtained in the acid leaching step S1. The insoluble residue is mainly a carbon material, a metal material, or an organic material that does not dissolve in an inorganic acid. As the method for solid-liquid separation, for example, various filtration devices such as pressure filtration (filter press), vacuum filtration, centrifugal filtration, and known solid-liquid separation devices such as a decanter type centrifugal separation device can be used. .. The same applies to the following solid-liquid separation steps S4, S6, S9 and S11.

It is preferable that the aqueous alkali solution added in the first pH adjusting step S3 has a dilute alkali concentration of less than 1.0 mol/L. Thereby, although the details will be described later, it is possible to prevent cobalt in the lithium-containing liquid from being precipitated and precipitated as crystals of a cobalt salt together with the impurity metal in the first pH adjusting step S3 and removed from the lithium-containing liquid. However, if the alkali concentration is excessively low, it is necessary to use a large amount of an alkaline aqueous solution for pH adjustment in the first pH adjusting step S3, and the amount of the lithium-containing liquid after the pH adjustment is also large. The lower limit of the alkali concentration is preferably 0.1 mol/L or more. Further, in order to effectively suppress the removal of cobalt in the lithium-containing liquid from the lithium-containing liquid in the first pH adjusting step S3, the alkali concentration of the aqueous solution of alkali added in the first pH adjusting step S3 is It is preferably 0.5 mol/L or less, more preferably 0.2 mol/L or less.

The precipitate deposited and precipitated in the first pH step S3 is separated from the lithium-containing solution by filtering the lithium-containing solution in the next solid-liquid separation step S4, for example. In addition, copper etc. may be contained in addition to the impurity metal removed from the lithium-containing liquid in the first pH adjusting step S3. In the solid-liquid separation step S4, it is preferable that the precipitate is washed with a washing liquid, and the washing waste liquid after washing is supplied to the next second pH adjusting step S5 together with the lithium-containing liquid (filtrate). As a result, the lithium contained in the cleaning waste liquid can be supplied to the carbonation step S10 from the second pH adjusting step S5 together with the lithium contained in the lithium-containing solution. Can be recovered at 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 S8 described later. Can be effectively used.

In the second pH adjusting step S5, alkali is added to the lithium-containing liquid after the solid-liquid separation step S4 to adjust the pH to 7 or more, preferably 7 to 13, more preferably 7 to 11, and further preferably 8 to 10. Adjust to. As a result, valuable metals (for example, cobalt and nickel) in the lithium-containing liquid are precipitated and precipitated as crystals of inorganic salts such as hydroxides (for example, cobalt hydroxide and nickel hydroxide). In the second pH adjusting step S5, it is preferable that the lithium-containing liquid is heated, for example, at a constant temperature of 30° C. to 80° C. The alkali concentration of the aqueous alkali solution added in the second pH adjusting step S5 is not particularly limited, but is preferably equal to or higher than that of the alkali aqueous solution used in the first pH adjusting step S3, It is preferable that the concentration is 0.2 mol/L or more.

On the other hand, in the lithium-containing liquid after the solid-liquid separation step S6, in addition to lithium, the inorganic acid (hydrochloric acid in the present embodiment) and alkali (in the present embodiment) added in the acid leaching step S1 and the pH adjusting steps S3 and S5. An inorganic salt (sodium chloride (NaCl) in this embodiment) is dissolved by sodium hydroxide. The lithium-containing liquid after the pH adjusting steps S3 and S5 corresponds to the “processed liquid” of the lithium recovery method of the present disclosure. At least one of calcium, magnesium and silica may be further dissolved in the liquid to be treated.

In the solid-liquid separation step S6, it is preferable that the precipitate is washed with a washing liquid, and the washing waste liquid after washing is supplied to the next impurity removing step S8 together with the liquid to be treated (filtrate). As a result, the lithium contained in the cleaning waste liquid can be supplied together with the lithium contained in the liquid to be treated from the impurity removal step S8 to the carbonation step S10, and the lithium is contained by carbonation in the carbonation step S10 described later. It can be collected at 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 S8 described later. Can be effectively used.

In the next impurity removing 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, and the like contained as impurities in the liquid to be treated, it is possible to prevent scale from occurring and adhering to the heat transfer surface of the heat exchanger of the evaporative concentration device 5 in the concentration step S8 described later. Therefore, the heat exchange efficiency can be maintained high. Further, when the liquid to be treated contains calcium, magnesium or the like, in the electrodialysis step S13 described later, polyvalent cations such as calcium or magnesium contained in the inorganic solution become cations of the bipolar membrane electrodialysis device 9. It may be deposited in the exchange membrane and cause deterioration of the performance of the membrane. Therefore, it is possible to prevent adverse effects on the cation exchange membrane of the bipolar membrane electrodialysis device 9 by removing substances that may cause problems such as scaling when operating electrodialysis such as calcium and magnesium from the liquid to be treated in advance. It is possible to maintain high electrodialysis performance.

The method of removing calcium and magnesium from the liquid to be treated in the impurity removing step S7 is not particularly limited, and for example, the polyvalent cation removing device 4 can be used. The polyvalent cation removing device 4 is a device that removes divalent or more polyvalent cations such as calcium ions and magnesium ions. For example, the polyvalent cation removing device 4 is provided with an ion exchange resin inside, and the liquid to be treated is an ion exchange resin. As an example, it is possible to bring them into contact with each other to adsorb calcium ions or magnesium ions. Other examples of the polyvalent cation removing device 4 include a device in which a liquid to be treated can be passed through a column filled with a chelate resin. As the chelate resin, those capable of selectively capturing calcium ions and magnesium ions can be used, and examples thereof include iminodiacetic acid type and aminophosphoric acid type. Further, the polyvalent cation removing device 4 may include a device to which a chelating agent is added. The impurities removed from the liquid to be treated in the impurity removal step S7 may include silica (silicate ions) in addition to calcium and magnesium.

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 liquid in the liquid to be treated is evaporated to concentrate the liquid to be treated. As a result, the liquid amount of the liquid to be processed is reduced and the lithium concentration in the liquid to be processed is increased. Therefore, the recovery rate of lithium carbonate can be improved in the carbonation step S10 described below.

In the concentration step S8, it is preferable to evaporate and concentrate the liquid to be treated to a concentration at which lithium does not precipitate as crystals of a lithium salt such as lithium chloride in the liquid to be treated after concentration. Thereby, the concentration of lithium in the liquid to be treated after concentration can be increased, and the recovery rate of lithium carbonate can be improved in the carbonation step S10 described later.

In this concentration step S8, the concentration of the inorganic salt in the liquid to be treated may be crystallized due to the concentration of the inorganic salt in the liquid to be treated being evaporated and concentrated. The inorganic salt contained in the liquid to be treated may or may not be precipitated as crystals in the concentration step S8. 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.

The method of evaporating and concentrating the liquid to be treated in the concentrating step S8 is not particularly limited, and, for example, the evaporative concentrating device 5 can be used. The evaporative concentration device 5 is not particularly limited as long as the liquid to be treated can be concentrated by evaporation, and a known evaporative concentration device such as a heat pump type, an ejector driven type, a steam type, or a flash type can be used. A heat pump type evaporative concentrator is preferable. When a heat pump type evaporative concentrator is used, the energy used can be significantly suppressed.

The evaporative concentration apparatus 5 is maintained at a low pressure inside by connecting a vacuum pump (not shown), and in the concentration step S8, the liquid to be treated is heated at a low pressure lower than atmospheric pressure to evaporate and concentrate. doing. When the liquid to be treated is evaporated and concentrated, the temperature of the liquid to be treated rises, but under low pressure the evaporation temperature of the liquid to be treated (boiling point of water contained in the liquid to be treated) is lower than under atmospheric pressure, so evaporation at low pressure By concentrating, the temperature of the liquid to be treated after evaporating and concentrating becomes correspondingly lower. Therefore, a large room for raising the temperature of the liquid to be treated can be secured in the carbonation step S10 described later. Moreover, since the evaporation temperature of the liquid to be treated decreases under low pressure, the energy required for evaporating and concentrating the liquid to be treated can be kept low to save energy.

The pressure inside the evaporative concentration apparatus 5, that is, the atmospheric pressure when evaporating and concentrating the liquid to be treated is not particularly limited, but is preferably 10 kPa or more and 70 kPa or less, and 15 kPa or more and 50 kPa or less. Is more preferable. The evaporation temperature of the liquid to be treated is preferably 45° C. or higher and 95° C. or lower, and more preferably 55° C. or higher and 80° C. or lower in view of the relationship with the 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 excessively decrease. Therefore, when raising the temperature of the liquid to be treated in the carbonation step S10 described later. The energy required for it can be kept low. Further, since the evaporative concentration device 5 does not need to have a very high pressure resistance, the manufacturing cost of the device can be kept low. On the other hand, when the pressure is 70 kPa or less, the temperature of the liquid to be treated after evaporation and concentration can be set to a suitable low temperature that does not rise excessively. There is enough room to raise. Further, the energy required for evaporative concentration of the liquid to be treated does not become too large, and energy saving can be effectively achieved.

Although illustration is omitted, a temperature sensor is provided in a liquid pool of the liquid to be treated at the bottom of the evaporative concentration device 5 or in a supply path of the liquid to be treated between the evaporative concentration device 5 and a carbonation tank 7 described later. The evaporation temperature of the liquid to be treated (the temperature of the liquid to be treated after evaporative concentration) is monitored by the temperature sensor. Although not shown, a pressure sensor is provided in the space above the evaporative concentration apparatus 5, and the pressure inside the evaporative concentration apparatus 5 (atmospheric pressure when evaporating and concentrating the liquid to be treated) is a pressure sensor. Being monitored by.

In the next solid-liquid separation step S9, the precipitate containing the crystals of the inorganic salt (sodium chloride in this embodiment) is separated from the liquid to be processed after the concentration process S8 by filtering, for example.

In the next carbonation step S10, the liquid to be treated is mixed with carbon dioxide gas and/or a water-soluble carbonate is added to the liquid to be treated after the precipitate containing the crystals of the inorganic salt is separated. The lithium therein is deposited and precipitated as crystals of lithium carbonate. Thereby, lithium in the liquid to be treated can be recovered as lithium carbonate. As the carbonate, for example, sodium carbonate, ammonium carbonate, potassium carbonate or the like can be used.

In this carbonation step S10, it is preferable to mix carbon dioxide gas into the liquid to be treated to precipitate and precipitate lithium carbonate crystals. As described above, in the carbonation step S10, by using a material containing no alkali metal such as sodium, it is possible to prevent alkali metal other than lithium from mixing into the precipitated lithium carbonate crystals. Therefore, highly pure lithium carbonate can be recovered.

In the carbonation step S10, the method of mixing carbon dioxide with the liquid to be treated is not particularly limited, and a commonly used method 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 through a nozzle while stirring the liquid to be treated in the carbonation tank 7. The lithium in the liquid to be treated and carbon dioxide can be reacted efficiently. Alternatively, the liquid to be treated may be sprayed in an atmosphere of carbon dioxide to react with the carbon dioxide.

In the carbonation step S10, the temperature of the liquid to be treated is set to be 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 this embodiment) contained in the liquid to be treated may be crystallized. 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 inorganic substances remaining in the liquid to be treated during carbonation are increased. The solubility of the salt is increased, and crystallization of the inorganic salt can be suppressed. Therefore, when recovering lithium carbonate in the carbonation step S10, the purity of lithium carbonate can be increased.

The temperature of the liquid to be treated during carbonation is not particularly limited as long as it is equal to or higher than the vaporization temperature of the liquid to be treated, but is preferably higher than the vaporization temperature of the liquid to be treated, and preferably lower than 100°C. The method of heating the liquid to be treated in the carbonation step S10 is not particularly limited, and a method of heating the liquid to be treated in the carbonation tank 7 using a known heating means such as a heater is used. You can The liquid to be treated may be heated in advance by using a preheating means such as a heat exchanger before supplying the liquid to be treated to the carbonation tank 7.

Also, the solubility of lithium carbonate decreases as the temperature of the liquid to be treated increases. Therefore, the temperature of the liquid to be treated rises in the carbonation step S10, so that the solubility of lithium carbonate produced by the reaction between lithium in the liquid to be treated and carbon dioxide gas decreases. Therefore, the amount of lithium carbonate crystals deposited can be increased.

In this way, the amount of lithium carbonate crystals recovered can be increased and the amount of inorganic salt crystals precipitated can be suppressed, so that highly pure lithium carbonate can be obtained with high efficiency.

In the next solid-liquid separation step S11, the liquid to be treated after the carbonation step S10 is filtered, for example, to separate the precipitate containing lithium carbonate crystals from the lithium-containing liquid. In the solid-liquid separation step S11, the precipitate separated from the lithium-containing liquid is washed with water or the like to remove impurities and improve the purity of lithium carbonate. The water used for washing the precipitate is not particularly limited, but it is preferable to use the condensed water generated when the liquid to be treated is evaporated and concentrated in the concentration step S8. It is available.

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 blow liquid, but part of it is re-introduced into the system. It is preferable to circulate. As a result, lithium remaining in the liquid to be treated can be recovered, so that lithium can be recovered at a high recovery rate. In addition, it is preferable that the cleaning waste liquid after cleaning the precipitate containing the lithium carbonate crystals is also circulated in 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 in the system again, it may be supplied to the evaporative concentration apparatus 5 to be evaporated and concentrated in the concentration step S8, but preferably the first pH adjusting tank 2 and / Or supply to the second pH adjusting 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 adjusting steps S3 and S5. Furthermore, when 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 of the heat exchanger of the evaporative concentration apparatus 5 when evaporating and concentrating in the concentration step S8. Crystals of carbonate are deposited on the surface. Therefore, since the lithium-containing liquid after the solid-liquid separation steps S2 and S4 is acidic, the liquid to be treated after the solid-liquid separation step S11 is neutralized with the lithium-containing liquid to use carbonate ions as carbon dioxide gas. By removing from the liquid, it is possible to prevent precipitation of carbonate crystals on the heat transfer surface of the heat exchanger of the evaporative concentration device 5 in the concentration step S8.

On the other hand, the crystals of the inorganic salt (sodium chloride in this embodiment) contained in the precipitate generated in the concentration step S8 (evaporative concentration device 5) and separated from the liquid to be treated in the solid-liquid separation step S9 are dissolved in the dissolution step. It is supplied to S12 (melting tank 8). In the dissolving step S12, the inorganic salt crystals are dissolved in the dissolving tank 8 to have a desired concentration using, for example, water to produce an inorganic salt solution. The temperature at this time is not particularly limited and may be a temperature at which the crystals of the inorganic salt can be dissolved. Further, the water used for dissolving the inorganic salt is not particularly limited, but it is preferable to use the condensed water generated when the liquid to be treated is evaporated and concentrated in the concentration step S8. It can be effectively used. The generated inorganic salt solution is supplied to the bipolar membrane electrodialysis device 9.

In the next electrodialysis step S13, the bipolar membrane electrodialysis device 9 separates and recovers the alkali and the inorganic acid from the inorganic salt solution after the dissolution step S12. As the bipolar membrane electrodialysis device 9, for example, as shown in FIG. 10, a cell 90 including an anion exchange membrane 91, a cation exchange membrane 92, and two

bipolar membranes

bipolar films

In this electrodialysis step S13, an inorganic salt solution is introduced into the desalting chamber R1, and pure water is introduced into each of the acid chamber R2 and the alkaline chamber R3. Thus, when the inorganic salt solution contains, for example, sodium chloride, sodium ions (Na ⁺ ) pass through the cation exchange membrane 92 and chloride ions (Cl ⁻ ) remain in the anion chamber in the desalting chamber R1. It passes through the ion exchange membrane 91. On the other hand, in the acid chamber R2 and the alkaline chamber R3, the supplied pure water is dissociated into hydrogen ions (H ⁺ ) and hydroxide ions (OH ⁻ ) in the

bipolar films

93 and 94, and hydrogen ions ( H ⁺ ) combines with chloride ions (Cl ⁻ ) to generate hydrochloric acid (HCl), and in the alkaline chamber R3, hydroxide ions (OH ⁻ ) combine with sodium ions (Na ⁺ ) to form sodium hydroxide (HCl). NaOH) is produced. As a result, hydrochloric acid (HCl) is recovered as an inorganic acid from the acid chamber R2, and sodium hydroxide (NaOH) is recovered as an alkali from the alkali chamber R3. The pure water introduced into the acid chamber R2 and the alkaline chamber R3 may be condensed water generated when the liquid to be treated is evaporated and concentrated in the concentration step S8.

The demineralized diluted inorganic salt solution (desalination solution) discharged from the desalination chamber R1 is not particularly limited, but is supplied to the evaporative concentration device 5 because it contains a small amount of lithium. It is preferable to evaporate and concentrate again in the concentration step S8.

Further, the inorganic acid (hydrochloric acid in the present embodiment) recovered from the acid chamber R2 is not particularly limited, but is supplied to the acid leaching tank 1 so as to leach the waste lithium ion battery in the acid leaching step S1. It is preferably reused as an acid. Further, it is preferable to supply the polyvalent cation removing device 4 and reuse it as a regenerating liquid of the chelate resin or the ion exchange resin used in the impurity treatment step S7.

pH adjusting tanks

According to the lithium recovery method of the present embodiment described above, by evaporating and concentrating the liquid to be treated in the concentrating 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 reduced. Is increasing. Therefore, the recovery rate of the lithium carbonate crystals in the carbonation step S10 can be favorably improved.

In the carbonation step S10, when 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 is crystallized. By raising the temperature of the liquid to be treated above the evaporation temperature, the solubility of the inorganic salt remaining in the liquid to be treated is increased, and crystallization of the inorganic salt can be suppressed during carbonation. In addition, when the temperature of the liquid to be treated is high during carbonation, the solubility of lithium carbonate decreases and the amount of lithium carbonate crystals recovered increases. Therefore, highly pure lithium carbonate can be obtained with high efficiency.

Further, according to the lithium recovery method of the present embodiment, the first pH adjusting tank 2, the second pH adjusting tank 3, the evaporative concentrating device are disposed without discarding 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 in the system such as No. 5 or the like. Therefore, lithium can be recovered at a high recovery rate.

Further, according to the lithium recovery method of the present embodiment, the crystal of the inorganic salt (sodium chloride in the present embodiment) contained in the precipitate separated from the liquid to be treated in the solid-liquid separation step S9 is dissolved in the dissolution step S12. After making the inorganic salt solution, a bipolar membrane electrodialysis is performed in the electrodialysis step S13 to recover the inorganic acid and the alkali from the inorganic salt solution, and the diluted inorganic salt solution after desalting is evaporated in the concentration step S8. After concentration, lithium contained in the dilute inorganic salt solution is recovered in the carbonation step S10. Therefore, lithium can be recovered at a high recovery rate. Furthermore, the inorganic acids and alkalis recovered in the electrodialysis step S13 are circulated and reused in the acid leaching step S1, the pH adjusting steps S3, S5, and the impurity removing step S7, so that each step S1, S3, S5, S7 is performed. It is possible to reduce the amount of inorganic acid or alkali used in.

Further, 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 removing step S7. As a result, the amount of impurities in the liquid to be treated from which the precipitate has been separated in the solid-liquid separation process S11 after the carbonation process S10 is reduced, so that most of the liquid to be processed after the solid-liquid separation process S11 is returned to the system. It can circulate. Therefore, more lithium remaining in the liquid to be treated after the solid-liquid separation step S11 can be recovered, and thus lithium can be recovered at a high recovery rate. Furthermore, since the amount of impurities in the inorganic solution electrodialyzed in the electrodialysis step S13 is also reduced, it is possible to prevent the performance of the cation exchange membrane of the bipolar electrodialysis device 9 from being deteriorated due to scaling, and maintain the performance of the bipolar membrane at a high level. can do.

Further, according to the lithium recovery method of the present embodiment, the condensed water generated in the concentration step S8 is used for various treatments, so that the condensed water can be effectively used. Further, by washing the crystals obtained in the solid-liquid separation steps S4, S6, S9, and S11 with condensed water, the recovery rate of each crystal can be improved satisfactorily.

Although one embodiment of the lithium recovery method of the second aspect has been described above, the lithium recovery method of the second aspect is not limited to the embodiment of FIG. 8 and FIG. 9 and does not depart from the gist of the present disclosure. Various changes are possible in.

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

In the embodiment of FIGS. 8 and 9, the alkali recovered in the electrodialysis step S13 is supplied to the first pH adjusting step S3 and the second pH adjusting step S5, but it is configured to be supplied to only one of them. May be.

Further, in the embodiment of FIGS. 8 and 9, the pH adjusting steps S3 and S5 include the first pH adjusting step S3 and the second pH adjusting step S5, but three pH adjusting steps S3 and S5 are included depending on the components contained in the waste lithium-ion battery. It may be configured to include the above 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, for removing impurities such as silica contained in the inorganic salt solution after the dissolution step S12 and before the electrodialysis step S13. Treatment steps may be performed. This processing step can be performed instead of or in addition to the impurity removing step S7.

Specifically, first, in the recrystallization step S12-1, the inorganic salt (sodium chloride in this embodiment) contained in the inorganic salt solution is recrystallized. The method of recrystallizing the inorganic salt contained in the inorganic salt solution is not particularly limited, and evaporative crystallization by the evaporative crystallizer 13 can be used, for example. In evaporative crystallization, the inorganic salt solution is heated to evaporate the solvent, and the concentration of the inorganic salt is increased to precipitate crystals of the inorganic salt. In addition, it is preferable to evaporate the inorganic salt solution under a low pressure lower than atmospheric pressure. In the evaporative crystallization, the evaporative concentration device 5 may be used to crystallize the inorganic salt contained in the inorganic salt solution without separately installing the evaporative crystallization device 10.

After re-precipitating the inorganic salt crystals, in the solid-liquid separation step S12-2, the inorganic salt crystals are separated from the aqueous solution containing the inorganic salt crystals, and the recrystallized inorganic salt crystals are recovered. As the method for solid-liquid separation, for example, various filtration devices such as pressure filtration (filter press), vacuum filtration, centrifugal filtration, and known solid-liquid separation devices such as a decanter type centrifugal separation device can be used. ..

Then, in the re-dissolution step S12-3, the crystals of the recovered inorganic salt are dissolved in the re-dissolution tank 11 using water, for example, so as to have a desired concentration, and an inorganic salt solution is regenerated. The temperature at this time is not particularly limited and may be a temperature at which the crystals of the inorganic salt can be dissolved. Further, the water used for dissolving the inorganic salt is not particularly limited, but it is preferable to use the condensed water generated when the liquid to be treated is evaporated and concentrated in the concentration step S8. It can be effectively used. The regenerated inorganic salt solution is supplied to the bipolar membrane electrodialysis device 9. The impurities removed from the inorganic salt solution in the recrystallization step S12-1 to the redissolution step S12-3 may include calcium and/or magnesium in addition to silica.

In the embodiments of FIGS. 11 and 12, silica contained in the inorganic salt solution is removed before the electrodialysis step S13. As a result, the amount of impurities in the inorganic solution electrodialyzed in the electrodialysis step S13 is also reduced, so that the performance of the bipolar membrane can be maintained high. Furthermore, when the dilute inorganic salt solution (desalted solution) after the electrodialysis step S13 is supplied to the evaporative concentration apparatus 5 and evaporated and concentrated again in the concentration step S8, the amount of impurities in the desalted solution is reduced. In the concentration step S8, it is possible to suppress the generation and adhesion of scale on 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 which has separated the precipitate in the solid-liquid separation process S11 after the carbonation process S10 is reduced, most of the liquid to be processed after the solid-liquid separation process S11 is circulated into the system again. can do. Therefore, more lithium remaining in the liquid to be treated after the solid-liquid separation step S11 can be recovered, and thus 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, before the acid leaching step S1, a roasting step S0 of roasting the waste lithium-ion battery may be further included. In the roasting step S0, the method of roasting the waste lithium ion battery is not particularly limited, and a known roasting device 12 can be used.

In the embodiment of FIGS. 13 and 14, the exhaust gas generated in the roasting device 12 (roasting step S0) is supplied to the carbonation tank 7, and the exhaust gas is mixed with the liquid to be treated as carbon dioxide in the carbonation step S10. doing. As a result, the amount of carbon dioxide gas used in the carbonation step S10 can be reduced. Further, the liquid to be treated can be heated in the carbonation step S10. It is needless to say that the roasting step S0 of roasting the waste lithium-ion battery before the acid leaching step S1 can also be executed in the embodiments of FIGS. 11 and 12.

Although the lithium recovery method of the above-described embodiment exemplifies the case of recovering lithium from a waste lithium-ion battery, the lithium recovery method of the present disclosure is applicable to a method used to recover lithium from a waste lithium-ion battery. Is not limited.

Cobalt recovery method Recovery of valuable metal cobalt from waste lithium-ion batteries is extremely important from the viewpoint of effective use of resources. However. In the method of recovering cobalt from the waste lithium-ion battery described in Patent Document 1 in the background art, the pH of the acid leachate is set to 4 or more in order to remove the impurity metal such as aluminum from the acid leachate. There is a problem that cobalt crystals may be precipitated and precipitated together with the salt crystals of, and cobalt may be removed from the acid leachate together with impurity metals, and the recovery rate of cobalt may be low during subsequent cobalt recovery. ..

In order to solve the above problems, the present disclosure aims 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.

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

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

In the cobalt recovery method described in paragraph 0163, it is preferable that the alkali concentration of the aqueous alkali solution added in the first pH adjusting step is 0.1 mol/L or more.

Further, in the cobalt recovery method according to paragraph 0163 or paragraph 0164, in the first pH adjusting step, an alkali having an alkali concentration of 1.0 mol/L or more is used until the pH of the liquid to be treated reaches a predetermined value smaller than 4. It is preferable that the pH of the liquid to be treated is adjusted to 4 to 7 by adding the aqueous solution of 1 to the liquid to be treated and then adding the aqueous solution of alkali having an alkali concentration of less than 1.0 mol/L to the liquid to be treated. ..

Further, in the cobalt recovery method according to any one of paragraphs 0163 to 0165, lithium is dissolved in the liquid to be treated, and a concentration step of evaporating and concentrating the liquid to be treated after the second solid-liquid separation step, It is preferable to have a carbonation step of mixing carbon dioxide gas and/or adding a water-soluble carbonate to the liquid to be treated after the concentration step.

Further, in the cobalt recovery method according to paragraph 0166, a third solid-liquid separation step of separating a precipitate containing crystals of lithium carbonate precipitated by the carbonation step from a liquid to be treated, and the third solid-liquid separation step. An electrodialysis step of separating and recovering an alkali from the liquid to be treated by performing a bipolar membrane electrodialysis on the liquid to be treated later, wherein the alkali recovered in the electrodialysis process is treated at the first pH. It is preferably reused as an alkali used in the adjusting step and/or the second pH adjusting step.

According to the cobalt recovery method of the present disclosure, when the impurity metal is removed from the liquid to be treated in the first pH adjusting step, the alkali concentration is less than 1.0 mol/L for the liquid to be treated in which cobalt and the impurity metal are dissolved. By adjusting the pH of the liquid to be treated with the dilute aqueous alkali solution, it is possible to suppress the removal of cobalt together with the impurity metal from the liquid to be treated. Therefore, since the amount of cobalt in the liquid to be treated supplied to the second pH adjusting step can be maintained high, cobalt can be recovered at a high recovery rate in the second pH adjusting step.

FIG. 15 shows the procedure of each step in the embodiment of the cobalt recovery method of the present disclosure, and FIG. 16 shows a schematic configuration of the processing apparatus 10 for carrying out the cobalt recovery method of FIG. The cobalt recovery method of the present embodiment will be described by taking the case of recovering lithium in addition to cobalt from a waste lithium-ion battery as an example.

The cobalt recovery method of this embodiment is
-An acid leaching step S1 of leaching a waste lithium-ion battery with an inorganic acid to elute cobalt and lithium;
-Solid-liquid separation step S2 for separating insoluble residues from the liquid to be treated obtained in the acid leaching step S1, and-Adding an aqueous alkali solution to the liquid to be treated after the solid-liquid separation step S2 to adjust the pH to 4 to 7. A first pH adjusting step S3 for adjusting,
-A solid-liquid separation step S4 (corresponding to the "first solid-liquid separation step" described in paragraph 0163) for separating the precipitate containing the crystals of the impurity metal salt precipitated by the first pH adjusting step S3 from the liquid to be treated;
-A second pH adjusting step S5 of adjusting the pH to 7 or more 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 (corresponding to the "second solid-liquid separation step" described in paragraph 0163) for separating the precipitate containing the cobalt salt crystals precipitated by the second pH adjusting step S5 from the liquid to be treated,
-A concentration step S7 of evaporating and concentrating the liquid to be treated after the solid-liquid separation step S6,
-A carbonation step S8 of mixing carbon dioxide gas and/or adding a water-soluble carbonate to the liquid to be treated after the concentration step S7,
-A solid-liquid separation step S9 (corresponding to the "third solid-liquid separation step" in paragraph 0167) for separating a precipitate containing crystals of lithium carbonate precipitated in the carbonation step S8 from the liquid to be treated;
An electrodialysis step S10 in which an alkali and inorganic acid containing at least lithium hydroxide is separated from the liquid to be treated by performing bipolar membrane electrodialysis on the liquid to be treated after the solid-liquid separation step S9, and
Have.

The waste lithium-ion battery for which cobalt is to be recovered is the same as the lithium recovery method described above.

First, in the acid leaching step S1, not only cobalt and lithium but also metals such as aluminum, nickel and iron are eluted by leaching the above-mentioned waste lithium-ion battery with an inorganic acid. As the inorganic acid, for example, sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid or the like can be used, but in the present embodiment, sulfuric acid is used because of its low cost and easy handling.

In the acid leaching step S1, the method of leaching the waste lithium ion battery with an inorganic acid is not particularly limited, and a commonly used method can be used. For example, the waste lithium-ion battery is immersed in an aqueous solution of an inorganic acid such as a sulfuric acid aqueous solution in the acid leaching tank 1 and stirred for a predetermined time to obtain an acidic liquid to be treated in which the above-described metal such as cobalt 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 insoluble residue is separated from the liquid to be treated by, for example, filtering the liquid to be treated obtained in the acid leaching step S1. The insoluble residue is mainly a carbon material, a metal material, or an organic material that does not dissolve in an inorganic acid. As the method for solid-liquid separation, for example, various filtration devices such as pressure filtration (filter press), vacuum filtration, centrifugal filtration, and known solid-liquid separation devices such as a decanter type centrifugal separation device can be used. .. The same applies to the following solid-liquid separation steps S4, S6 and S9.

In the next first pH adjusting step S3, an aqueous alkali solution is added to the liquid to be treated (filtrate) after the solid-liquid separation step S2 to adjust the pH to 4 to 7, preferably 4 to 6, and more preferably 4 to 5. adjust. Thereby, of the above-mentioned metals in the liquid to be treated, the impurity metal (eg, aluminum or iron) is removed from the liquid to be treated. Although sodium hydroxide, potassium hydroxide, lithium hydroxide or the like can be used as the alkali, lithium hydroxide is used in the present embodiment.

The method of adjusting the pH of the liquid to be treated in the first pH adjusting step S3 is not particularly limited, and a commonly used method can be used. For example, by adding an alkaline aqueous solution such as an aqueous solution of lithium hydroxide while stirring the liquid to be treated in the first pH adjusting tank 2, the impurity metals in the liquid to be treated are converted into hydroxides (for example, aluminum hydroxide and water). It precipitates and precipitates as crystals of an inorganic salt such as iron oxide. The first pH adjusting step S3 is preferably performed while heating the liquid to be treated at a constant temperature of, for example, 30°C to 80°C.

The aqueous alkali solution added in the first pH adjusting step S3 has a dilute alkali concentration of less than 1.0 mol/L. Thereby, although the details will be described later, it is possible to prevent cobalt in the liquid to be treated from being precipitated and precipitated as crystals of a cobalt salt together with the impurity metal in the first pH adjusting step S3 and removed from the liquid to be treated. 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 pH adjustment will also be large. The lower limit of the alkali concentration is preferably 0.1 mol/L or more. Further, in order to effectively suppress the removal of cobalt in the liquid to be treated from the liquid to be treated in the first pH adjusting step S3, the alkali concentration of the aqueous solution of alkali added in the first pH adjusting step S3 is It is preferably 0.5 mol/L or less, more preferably 0.2 mol/L or less.

In the first pH adjusting step S3, in order to reduce the amount of the alkali aqueous solution used for pH adjustment, a concentrated alkali concentration of 1.0 mol/L or more is used until the pH of the liquid to be treated reaches a predetermined value smaller than 4. After adding an aqueous solution of alkali having a pH of the solution to be treated to a predetermined value, an aqueous solution of an alkali having a low alkali concentration of less than 1.0 mol/L is added to the solution to be treated. Then, the pH of the liquid to be treated can be adjusted to 4 to 7. The predetermined value of the pH of the liquid to be treated can be set within the range of 2 to 3.

The precipitate deposited and precipitated in the first pH step S3 is separated from the liquid to be treated in the next solid-liquid separation step S4 by filtering the liquid to be treated, for example. The impurity metal removed from the liquid to be treated in the first pH step S3 may further contain copper or the like. In the solid-liquid separation step S4, it is preferable that the precipitate is washed with a washing liquid, and the washing waste liquid after washing is supplied to the next second pH adjusting step S5 together with the liquid to be treated (filtrate). As a result, the lithium contained in the cleaning waste liquid can be supplied together with the lithium contained in the liquid to be treated from the second pH adjusting step S5 to the carbonation step S8. Can be recovered at a high recovery rate. The water used for washing the precipitate is not particularly limited, but it is preferable to use the condensed water generated when the liquid to be treated is evaporated and concentrated in the concentration step S7 described later. Can be effectively used.

In the second pH adjusting step S5, an aqueous solution of alkali is added to the liquid to be treated (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, and further preferably. Adjust to 8-10. As a result, among the above-mentioned metals in the liquid to be treated, valuable metals such as cobalt and nickel are removed from the liquid to be treated. Although sodium hydroxide, potassium hydroxide, lithium hydroxide or the like can be used as the alkali, lithium hydroxide is used in the present embodiment.

In the second pH adjusting step S5, the method of adjusting the pH of the liquid to be treated is not particularly limited, and a commonly used method can be used. For example, by adding an aqueous alkali solution such as an aqueous lithium hydroxide solution while stirring the liquid to be treated in the second pH adjusting tank 3, the valuable metal in the liquid to be treated is converted into a hydroxide (for example, iron cobalt hydroxide, Further, it is precipitated and precipitated as crystals of an inorganic salt such as nickel hydroxide). Thereby, cobalt in the liquid to be treated can be recovered as a cobalt salt such as cobalt hydroxide. The second pH adjusting step S5 is preferably performed while heating the liquid to be treated at a constant temperature of, for example, 30°C to 80°C. The alkali concentration of the aqueous alkali solution added in the second pH adjusting step S5 is not particularly limited, but is preferably equal to or higher than that of the alkali aqueous solution used in the first pH adjusting step S3, It is preferable that the concentration is 0.2 mol/L or more.

The precipitate deposited and precipitated in the second pH step S5 is separated from the liquid to be treated in the next solid-liquid separation step S6 by filtering the liquid to be treated, for example. The valuable metal removed from the liquid to be treated in the second pH adjusting step S5 may further contain manganese or the like. On the other hand, the liquid to be treated (filtrate) after the solid-liquid separation step S6 contains anions (for example, sulfate ions) of lithium and an inorganic acid.

In the solid-liquid separation step S6, it is preferable that the precipitate is washed with a washing liquid, and the washing waste liquid after washing is supplied to the next concentration step S7 together with the liquid to be treated (filtrate). As a result, the lithium contained in the cleaning waste liquid can be supplied to the carbonation step S8 from the concentration step S7 together with the lithium contained in the liquid to be treated. It can be recovered with a recovery rate. The water used for washing the precipitate is not particularly limited, but it is preferable to use the condensed water generated when the liquid to be treated is evaporated and concentrated in the concentration step S7. It is available.

In addition, in the first pH adjusting step S3 and the second pH adjusting step S5, by using lithium hydroxide as an alkali to be used, as compared with the case of using a hydroxide of another alkali metal such as sodium hydroxide, it will be described later. With respect to the lithium carbonate crystals precipitated in the carbonation step S8, the mixing of alkali metals other than lithium such as sodium can be suppressed. Therefore, highly pure lithium carbonate can be recovered.

In the next concentration step S7, the liquid to be treated containing lithium after the solid-liquid separation step S6 is evaporated and concentrated by heating, that is, the liquid to be treated is concentrated by evaporating the water in the liquid to be treated. As a result, the liquid amount of the liquid to be processed is reduced and the lithium concentration in the liquid to be processed is increased. Therefore, the recovery rate of lithium carbonate can be improved in the carbonation step S8 described later.

Further, in the concentration step S7, the temperature of the concentrated liquid to be treated can be raised by evaporating and concentrating the liquid to be treated, and 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, the solubility of lithium carbonate generated by the reaction between lithium in the liquid to be treated and carbon dioxide gas decreases as the temperature of the liquid to be treated increases in the carbonation step S8. Therefore, the amount of crystals of lithium carbonate deposited can be increased.

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 a lithium salt such as lithium sulfate in the liquid to be treated after concentration. Thereby, the concentration of lithium in the liquid to be treated after concentration can be increased, and the recovery rate of lithium carbonate can be improved in the carbonation step S8 described later. In addition, when a deposit is deposited in the concentration step S7, a solid-liquid separation step of separating it from the liquid to be treated may be performed.

In the concentration step S7, the method of evaporating and concentrating the liquid to be treated is not particularly limited, and, for example, the evaporative concentration device 5 can be used. The evaporative concentration device 5 is not particularly limited as long as the liquid to be treated can be concentrated by evaporation, and a known evaporative concentration device such as a heat pump type, an ejector driven type, a steam type, or a flash type can be used. A heat pump type evaporative concentrator is preferable. When a heat pump type evaporative concentrator is used, the energy used can be significantly suppressed. Further, energy can be further saved by concentrating the liquid to be treated under a reduced pressure atmosphere.

In the next carbonation step S8, carbon dioxide is mixed with the liquid to be treated after the concentration step S7 and/or a water-soluble carbonate is added to deposit lithium in the liquid to be treated as crystals of lithium carbonate, Allow to settle. Thereby, lithium in the liquid to be treated can be recovered as lithium carbonate. As the carbonate, for example, sodium carbonate, ammonium carbonate, potassium carbonate or the like can be used.

In this carbonation step S8, it is preferable that the liquid crystal to be treated is mixed with carbon dioxide gas to precipitate and precipitate lithium carbonate crystals. As described above, in the carbonation step S8, by using a material containing no alkali metal such as sodium, it is possible to prevent alkali metal other than lithium from mixing into the precipitated lithium carbonate crystals. Therefore, highly pure lithium carbonate can be recovered.

In the carbonation step S8, the method of mixing carbon dioxide with the liquid to be treated is not particularly limited, and a commonly used method 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 from the nozzle while stirring the liquid to be treated in the carbonation tank 7. Lithium in the liquid to be treated and carbon dioxide can be reacted efficiently. Alternatively, the liquid to be treated may be sprayed in an atmosphere of carbon dioxide to react with the carbon dioxide.

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. As a result, the solubility of lithium carbonate produced by the reaction between lithium in the liquid to be treated and carbon dioxide gas decreases, so that the amount of precipitated lithium carbonate crystals can be increased.

In the next solid-liquid separation step S9, the liquid to be treated after the carbonation step S8 is filtered, for example, to separate precipitates containing lithium carbonate crystals from the liquid to be treated. In the solid-liquid separation step S9, the precipitate separated from the liquid to be treated can be washed with water or the like to remove impurities and increase the purity of lithium carbonate. The water used for washing the precipitate is not particularly limited, but it is preferable to use the condensed water generated when the liquid to be treated is evaporated and concentrated in the concentration step S7. It is available. The washing waste liquid after washing the precipitate is preferably supplied to the bipolar membrane electrodialysis device 6 in the electrodialysis step S10 described later together with the liquid to be treated (filtrate) after the solid-liquid separation step S9.

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 device 6 to separate and recover the alkali and inorganic acid from the liquid to be treated. As the bipolar membrane electrodialysis device 9, for example, as shown in FIG. 17, a cell 90 including an anion exchange membrane 91, a cation exchange membrane 92, and two

bipolar membranes

bipolar films

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 alkaline chamber R3 respectively, so that the liquid to be treated is 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 in the desalting chamber R1. .. On the other hand, in the acid chamber R2 and the alkaline chamber R3, the supplied pure water is dissociated into hydrogen ions (H ⁺ ) and hydroxide ions (OH ⁻ ) in the

bipolar films

93 and 94, and hydrogen ions ( H ⁺ ) combines with sulfate ions (SO ₄ ²⁻ ) to generate sulfuric acid (H ₂ SO ₄ ), and in the alkaline chamber R3, hydroxide ions (OH ⁻ ) combine with lithium ions (Li ⁺ ) Lithium hydroxide (LiOH) is produced. As a result, sulfuric acid (H ₂ SO ₄ ) as an inorganic acid is recovered from the acid chamber R2, and lithium hydroxide (LiOH) is recovered as an alkali from the alkaline chamber R3. The pure water introduced into the acid chamber R2 and the alkaline chamber R3 may be condensed water generated when the liquid to be treated is evaporated and concentrated in the concentration step S8.

The dilute desalination liquid (desalination liquid) discharged from the desalting chamber R1 is not particularly limited, but since it contains a small amount of lithium, at least a part of the concentration step S7 ( It is preferable to supply it to the evaporative concentrating device 5) or the impurity removing process (multivalent cation removing device) before the concentrating process S7 described later, concentrate again in the concentrating process S7, and then carbonate in the carbonating process S8. Thereby, lithium can be recovered at a high recovery rate. Although the desalted solution is supplied to the concentration step S7 in this embodiment, it may be supplied to the first pH adjustment step S3. Thereby, when cobalt remains in the desalination solution, the recovery rate of cobalt can be increased.

Further, the inorganic acid (sulfuric acid in the present embodiment) recovered from the acid chamber R2 is not particularly limited, but is supplied to the acid leaching tank 1 and the inorganic acid leaching the waste lithium ion battery in the acid leaching step S1. It is preferably reused as an acid.

The alkali (lithium hydroxide in the present embodiment) recovered from the alkali chamber R3 is supplied to the

pH adjusting tanks

2 and 3, but is not particularly limited, and the liquid to be treated in the pH adjusting steps S3 and S5. It is preferable to reuse it as an alkali for pH adjustment.

According to the above-described cobalt recovery method of the present embodiment, when the impurity metal is removed from the liquid to be treated in the first pH adjusting step S3, the alkali concentration is 1. By adjusting the pH of the liquid to be treated with a dilute alkaline aqueous solution of less than 0 mol/L, it is possible to suppress the removal of cobalt together with the impurity metal from the liquid to be treated. Therefore, the amount of cobalt in the liquid to be treated supplied to the second pH adjusting step S5 can be kept high, so that cobalt can be recovered at a high recovery rate in the second pH adjusting step S5.

Further, according to the cobalt recovery method of the present embodiment, since a dilute alkaline aqueous solution having an alkali concentration of less than 1.0 mol/L is used in the first pH adjusting step S3, carbon dioxide for recovering lithium thereafter is used. Although the liquid amount of the liquid to be processed supplied to the liquefying process S8 becomes large, the liquid amount of the liquid to be processed is reduced by evaporating and concentrating the liquid to be processed in the concentrating process S7 before the carbonation process S8. Increasing the lithium concentration in the liquid. Therefore, the recovery rate of lithium carbonate can be favorably improved in the carbonation step S8. In addition, since the temperature of the liquid to be treated supplied to the carbonation step S8 rises with the evaporation and concentration of the liquid to be treated, the solubility of lithium carbonate decreases and the amount of lithium carbonate deposited can be increased.

When the pH of the liquid to be treated is adjusted to 4 to 7 in the first pH adjusting step S3, the aqueous alkali solution having an alkali concentration of 1.0 mol/L or more is applied until the pH of the liquid to be treated reaches a predetermined value. After the pH of the liquid to be treated reaches a predetermined value after being added to the treatment liquid, an aqueous solution of alkali having an alkali concentration of less than 1.0 mol/L is added to the liquid to be treated so that an aqueous alkali solution used for pH adjustment. The amount can be reduced.

Further, according to the cobalt recovery method of the present embodiment, the inorganic acid and the alkali recovered in the electrodialysis step S10 are circulated and reused in the acid leaching step S1 and the pH adjusting steps S3 and S5, respectively. The amount of inorganic acid or alkali used in S1, S3, S5 can be reduced.

Although one embodiment of the cobalt recovery method of the present disclosure has been described above, the cobalt recovery method of the present disclosure is not limited to the embodiments of FIGS. 15 and 16, and various modifications are possible without departing from the spirit of the present disclosure. Can be changed.

For example, in the embodiment of FIGS. 15 and 16, the alkali recovered in the electrodialysis step S10 is supplied to the first pH adjusting step S3 and the second pH adjusting step S5, but it is configured to be supplied to only one of them. May be.

Further, in the embodiment of FIGS. 15 and 16, at least a part of the diluted liquid to be treated (desalted liquid) after the lithium hydroxide is recovered in the electrodialysis process S10 is supplied to the concentration process S7. Alternatively, or in addition to this, it may be configured to supply to the electrodialysis step S10.

Also, in the embodiment of FIGS. 15 and 16, the concentration step S7 is provided before the carbonation step S8, but the concentration step S7 does not necessarily have to be provided. In this case, at least a part of the diluted liquid to be treated (desalted liquid) after the lithium hydroxide is recovered in the electrodialysis process S10 can be configured to be supplied to the carbonation process S8.

Further, in the embodiment of FIGS. 15 and 16, with respect to the liquid to be treated before the concentration step S7 and/or the liquid to be treated to be supplied to the electrodialysis step S10, polyvalent cations having a valence of 2 or more in the liquid to be treated. (Typically, calcium ions or magnesium ions) may be removed. When polyvalent cations such as calcium ions and magnesium ions are present in the liquid to be treated, these polyvalent cations are deposited in the cation exchange membrane of the bipolar membrane electrodialysis device 9 to reduce the performance of the membrane. However, by removing the polyvalent cations from the liquid to be treated in advance, it is possible to prevent the cation exchange membrane of the bipolar membrane electrodialysis device 9 from being adversely affected. The specific structure for removing the polyvalent cations is not particularly limited, and for example, a known polyvalent cation removing device capable of passing a liquid to be treated through a column filled with a chelate resin is exemplified. You can As the chelate resin, those capable of selectively capturing calcium ions and magnesium ions can be used, and examples thereof include iminodiacetic acid type and aminophosphoric acid type. Other examples of the polyvalent cation removing device include a device adding a chelating agent and a device utilizing an ion exchange resin. The impurities removed from the liquid to be treated may contain silica (silicate ions) in addition to calcium and magnesium.

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

In the embodiment of FIGS. 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. ing. Thereby, the amount of carbon dioxide gas used in the carbonation step S8 can be reduced.

Further, in the embodiments of FIGS. 15 and 16, the method of recovering lithium in the steps after the concentration step S7 is not particularly limited, and the lithium recovery method of the present disclosure described above may be used. The lithium recovery method of the above-described embodiment uses the cobalt recovery method of the present disclosure in the acid leaching step S1 to the solid-liquid separation step S6.

Further, although the cobalt recovery method of the above-described embodiment exemplifies the case of recovering cobalt from a waste lithium-ion battery, the cobalt recovery method of the present disclosure is used to recover cobalt from a waste lithium-ion battery. The method is not limited.

Test Example The present inventor conducted the following test on the alkali concentration of the aqueous solution of alkali added in the first pH adjusting step S3. Specifically, a process (first pH adjusting step S3) of adjusting the pH of the liquid to be processed by adding an alkaline aqueous solution to 200 ml of the liquid to be processed having the components shown in Table 1 below was performed. An aqueous solution of lithium hydroxide was used as the aqueous solution of alkali to be added. 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 the pH of the liquid to be treated was 4 The addition amount of the lithium hydroxide aqueous solution was adjusted so as to be 0.7. The amount of the 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. The content of lithium in the liquid to be treated was increased by 582 mg in Example 1, 585 mg in Example 2, and 599 mg in Example 3 by the addition of the aqueous lithium hydroxide solution.

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

On the other hand, the surface condition of the filtration residue obtained by filtering the liquid to be treated after pH adjustment was confirmed. The results are shown in FIGS. 20 to 22. 20 shows the first embodiment, FIG. 21 shows the second embodiment, and FIG. 22 shows the third embodiment. According to FIG. 22, it was confirmed visually that the filtration residue contained cobalt hydroxide in Example 3, but according to FIGS. 20 and 21, in Examples 1 and 2, water was added to the filtration residue. It was not possible to visually confirm that cobalt oxide was contained.

From the above results, according to FIGS. 20 to 22, when the alkaline concentration of the alkaline aqueous solution added to the liquid to be treated in the first pH adjusting step S3 is 1.0 mol/L, the filtration of the liquid to be treated after the pH adjustment is performed. It was confirmed that the residue contained a large amount of cobalt salt. Further, according to Table 2, when the alkaline concentration of the alkaline aqueous solution added to the liquid to be treated in the first pH adjusting step S3 is 1.0 mol/L, the cobalt recovery rate of the liquid to be treated (filtrate) after pH adjustment Is less than 85%, whereas when the alkali concentration is less than 1.0 mol/L, the cobalt recovery rate of the liquid to be treated (filtrate) after pH adjustment is 85% or more. It was confirmed that a large amount of cobalt remained in the liquid (filtrate).

In this way, by setting the alkali concentration of the alkaline aqueous solution added to the liquid to be treated in the first pH adjusting step S3 to be less than 1.0 mol/L, cobalt is removed from the liquid to be treated in the first pH adjusting step S3 as an impurity metal (eg, aluminum It can be seen that the content of cobalt in the liquid to be treated supplied to the next second pH adjusting step S5 can be maintained high. Therefore, it is possible to recover cobalt at a high recovery rate in the second pH adjusting step S5.

S0 Roasting step S1 Acid leaching step S3 First pH adjusting step (pH adjusting step)
S5 Second pH adjustment step (pH adjustment step)
S7 Impurity removal step S8 Concentration step S9 Crystallization step S10 Solid-liquid separation step (first solid-liquid separation step)
S11 Carbonation step S12 Solid-liquid separation step (second solid-liquid separation step)
S13 Dissolution process S13-1 Recrystallization process S13-3 Redissolution process S14 Electrodialysis process

Claims

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