JP7031263B2 - Lithium recovery method - Google Patents

Description

The present invention relates to a method for recovering lithium from waste in a manufacturing process containing lithium and aluminum as a positive electrode material for a lithium secondary battery.

Lithium is widely used in industries such as additives for pottery and glass, glass flux for continuous steel casting, grease, pharmaceuticals, and batteries. In particular, lithium secondary batteries have high energy density and high voltage, so their use as batteries for electronic devices such as laptop computers and in-vehicle batteries for electric vehicles and hybrid vehicles has recently expanded, and demand has increased sharply. ing.

Recently, in order to make effective use of resources, it has been promoted to recover lithium from wastewater discharged in the manufacturing process of positive electrode materials for lithium secondary batteries (hereinafter, also referred to as “manufacturing process wastewater”).

For example, the manufacturing process wastewater in a nickel-based positive electrode material (NCA) contains lithium and aluminum. In order to recover lithium from this manufacturing process wastewater, it is necessary to separate lithium and aluminum. As separation methods, a neutralization precipitation method is proposed in Patent Document 1, and a solvent extraction method is proposed in Patent Documents 2 and 3.

Japanese Unexamined Patent Publication No. 2004-33984 Japanese Unexamined Patent Publication No. 2012-21186 Japanese Unexamined Patent Publication No. 2002-121623

However, in the neutralization precipitation method of Patent Document 1 and the solvent extraction method of Patent Document 2, lithium remains in the wastewater in the manufacturing process after aluminum separation. Since the concentration of lithium remaining in the wastewater from the manufacturing process is low, it is necessary to evaporate the wastewater from the manufacturing process to concentrate lithium in order to recover lithium as a carbonate or hydroxide salt. Therefore, there is a problem that the cost of lithium recovery becomes high and it is economically unfavorable.

In the solvent extraction method of Patent Document 3, lithium is separated from the wastewater in the manufacturing process using crown ether, and then lithium is back-extracted from the crown ether. Since this method can concentrate lithium at the time of back extraction, it does not require concentration by evaporation and is advantageous in terms of cost. However, there are problems that the cost of lithium recovery is high because the crown ether is expensive and the solvent extraction method requires wastewater treatment and the process is complicated.

The present invention has been made in view of the above problems, and provides a method for more easily recovering lithium from wastewater in the manufacturing process of a positive electrode material for a lithium secondary battery containing lithium and aluminum, and reducing the recovery cost. The purpose is.

One aspect of the present invention is a method for recovering lithium from a manufacturing process wastewater containing lithium and aluminum as a positive electrode material for a lithium secondary battery, in which an ion exchange resin is brought into contact with the manufacturing process wastewater to exchange ions. Elution to elute lithium ions from the ion exchange resin by contacting an aqueous solution containing a sodium salt with the ion exchange resin that selectively adsorbs lithium ions in the adsorption step and the adsorption step that selectively adsorbs lithium ions to the resin. The ion exchange resin is a strongly acidic cation exchange resin having a sodium-type functional group of a sulfonic acid group , and the pH of the manufacturing process wastewater in the adsorption process is 9 or more, and the ion exchange resin is in the adsorption process. The lithium concentration of the manufacturing process wastewater is 0.3 g / L or more .

In this way, lithium can be selectively recovered from the wastewater from the manufacturing process. Since lithium can be concentrated without the process of evaporating wastewater from the manufacturing process and concentrating lithium, lithium can be recovered more easily and the recovery cost can be reduced.

By doing so, in the adsorption process, aluminum and lithium in the wastewater of the manufacturing process can be separated, and the ion exchange reaction can be prevented from being hindered. Therefore, lithium can be recovered more easily and the recovery cost can be reduced. Can be reduced.

By doing so, lithium ions having low selectivity in the adsorption step can be adsorbed on the ion exchange resin.

Further, in one aspect of the present invention, the substitution step further comprises a substitution step of substituting the functional group contained in the ion exchange resin before the adsorption step, and the substitution step changes the functional group from the sulfonic acid group to the sodium type . May be replaced with.

By doing so, it is possible to prevent a decrease in pH in the adsorption step and prevent the ion exchange reaction in the adsorption step from being hindered.

Further, in one aspect of the present invention, the sodium salt in the elution step may be sodium sulfate.

For example, when sodium chloride is used in the elution step, chlorine remains in the precipitated lithium carbonate, but in this way it is possible to prevent chlorine from remaining in the precipitated lithium carbonate. It is possible to prevent corrosion of structural materials.

According to the present invention, lithium can be selectively recovered from the wastewater in the manufacturing process, and lithium can be concentrated without the step of evaporating the wastewater in the manufacturing process and concentrating lithium. Therefore, lithium ion containing lithium and aluminum can be concentrated. Lithium can be more easily recovered from the wastewater in the manufacturing process of the positive electrode material for the next battery, and the recovery cost can be reduced.

It is a flow diagram which shows the outline of the manufacturing process of the positive electrode material for a lithium secondary battery. It is a flow figure which shows the outline of the lithium recovery method which concerns on one Embodiment of this invention. It is a figure which shows the adsorption curve (relationship between BV and the concentration of lithium and aluminum in the liquid after adsorption) in Example 1. FIG. It is a figure which shows the elution curve (relationship between BV and the concentration of lithium and aluminum in an eluent) in Example 1. FIG. It is a figure which shows the adsorption curve (relationship between BV and the concentration of lithium and aluminum in the liquid after adsorption) in the comparative example 1. FIG. It is a figure which shows the elution curve (relationship between BV and the concentration of lithium and aluminum in an eluent) in the comparative example 1. FIG.

Hereinafter, a specific embodiment of the present invention (hereinafter, referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiments, and can be carried out with appropriate modifications within the scope of the object of the present invention.

[1. Overview of the manufacturing process of positive electrode materials for lithium secondary batteries]
First, an outline of the manufacturing process of the positive electrode material for a lithium secondary battery will be described with reference to the drawings. FIG. 1 is a flow chart showing an outline of a manufacturing process of a positive electrode material for a lithium secondary battery. As shown in FIG. 1, the manufacturing process of the positive electrode material for a lithium secondary battery includes a crystallization step S101, a separation step S102, a firing step S103, and a washing step S104. Specifically, in the crystallization step S101, a sodium hydroxide aqueous solution is added to a mixed aqueous solution of each metal sulfate salt made of a raw material such as nickel, cobalt, or aluminum, and these metal hydroxides are co-precipitated into a metal. This is a step of obtaining a slurry containing hydroxide. Further, the separation step S102 is a step of separating the metal composite hydroxide from the obtained slurry containing the metal hydroxide by solid-liquid separation or the like. Further, the firing step S103 is a step of mixing the obtained metal composite hydroxide and lithium hydroxide and firing this mixture at a predetermined temperature to obtain a lithium metal composite oxide. The water washing step S104 is a step of washing the obtained lithium metal composite oxide with water.

In the washing step S104 of the manufacturing process of the positive electrode material for the lithium secondary battery, since the positive electrode material is washed with water, wastewater containing a high concentration of lithium ions and aluminum ions is discharged.
The wastewater concentration is, for example, 1 to 4 g / L for lithium ions and 0.04 to 0.18 g / L for aluminum ions. Discharging such wastewater into public water bodies is not preferable because lithium is an industrially useful metal. In the recycling of resources, it is required to recover lithium discharged in the manufacturing process without discarding it and effectively utilize it.

As described above, for example, the wastewater from the manufacturing process of NCA becomes an aqueous solution containing lithium and aluminum, and therefore, when trying to recover the lithium compound from the wastewater from the manufacturing process, it is necessary to separate aluminum.

To separate aluminum from an aqueous solution containing aluminum and lithium, there are a neutralization precipitation method (for example, Patent Document 1), a solvent extraction method (for example, Patent Documents 2 and 3), and an ion exchange method.

In the neutralization precipitation method, the pH is adjusted in the pH range where aluminum becomes a hydroxide, and aluminum is separated as a precipitate. When this method is used, lithium remains in the aqueous solution.

In the solvent extraction method, for example, an acidic extractant having a carboxylic acid or a phosphoric acid as a functional group is widely used. However, it is usually difficult to extract an acidic extractant as the oxide having a higher basicity is formed. Therefore, lithium is more difficult to extract than aluminum. Therefore, aluminum is extracted and separated. Even when this method is used, lithium remains in the aqueous solution.

In the ion exchange method, cation exchange resins and chelate resins are widely used to capture cations, but since there is no resin that selectively captures lithium over aluminum, aluminum is captured and separated from the liquid. Lithium remains in the aqueous solution even when this method is used.

In this way, there are many separation methods that selectively remove aluminum and leave lithium in the liquid, but when trying to recover lithium as a carbonate or hydroxide, it is disadvantageous if the lithium concentration in the liquid is low. become. For example, when trying to recover with lithium carbonate, a carbonic acid source such as sodium carbonate is added to precipitate and recover lithium carbonate, but since lithium carbonate has a solubility of about 13 g / L at 20 ° C, the lithium concentration is high. Must be above this concentration. Lithium concentration can be increased by adjusting the conditions of the leachate of ore and process intermediate products, but it may be economically unfavorable because it consumes a large amount of acid to lower the pH at the time of leachation. There is. Further, since the lithium concentration in the wastewater from the manufacturing process is usually kept low in order to reduce the loss, it rarely exceeds this concentration.

Therefore, if the lithium concentration in the wastewater from the manufacturing process is low, it is necessary to concentrate it. Even when recovery is attempted with lithium hydroxide, lithium hydroxide is often converted by adding slaked lime to lithium carbonate, so it is necessary to concentrate it in order to obtain an intermediate lithium carbonate.

There is an evaporation concentration method as a well-known concentration method, but it is economically unfavorable because a large amount of energy of 539 kcal / kg at standard atmospheric pressure is required to evaporate water and the energy cost is high.

In the solvent extraction method and the ion exchange method, the metal to be recovered is extracted or adsorbed, and then back-extracted or eluted to obtain a purified aqueous solution. The metal can be concentrated. Therefore, if lithium can be selectively extracted or adsorbed, it becomes possible to obtain a purified liquid having a lithium concentration capable of precipitating lithium carbonate without using an energy-intensive evaporative concentration method.

As an extractant or a resin capable of selectively extracting an alkali metal or an alkaline earth metal, an extractant or a resin having a crown ether as a macrocyclic compound as a functional group is known (for example, Patent Document 3). Crown ethers are known to form complexes by incorporating metal ions into the ring, and have selectivity for metal ions with an ionic radius that matches the radius of the ring. It is known that crown ethers in which the elements constituting the ring are carbon and oxygen have an particular affinity for alkali metals and alkaline earth metals, and that 12-crown-4 specifically forms a complex with lithium. However, since crown ethers are water-soluble, they are not suitable for solvent extraction methods that require phase separation. It is conceivable to modify crown ethers with lipophilic alkyl groups to make them water-insoluble, but if special synthesis is required and industrial use is attempted, the cost will be high. It is not realistic to use because of the problem that supply stability cannot be maintained.

Further, in the solvent extraction method, since the organic phase is mixed in the extraction residual liquid after extraction in the form of minute droplets, activated carbon treatment or the like is usually required to discharge the wastewater. In addition, water-soluble impurities derived from organic solvents such as extractants and water-soluble decomposition products dissolve in the aqueous phase, and COD in the wastewater increases, which requires wastewater treatment such as oxidative decomposition treatment, which complicates the process. Therefore, the processing cost tends to be high.

For this reason, it is the simplest method to use a resin on which crown ether is supported, but the reagent itself is expensive and the resin is also expensive for crown ether, and at present, it is only practically used as a column for analysis. There is no. Therefore, large-scale purification using crown ethers is currently disadvantageous in terms of cost.

Due to such a problem, there has been a demand for a simple method for selectively recovering lithium from an aqueous solution containing aluminum and lithium to obtain an aqueous solution having a concentration suitable for obtaining lithium carbonate or lithium hydroxide. ..

In view of such circumstances, as a result of diligent studies, the inventors adjusted the wastewater from the manufacturing process containing aluminum and lithium to a predetermined pH, and adjusted the functional group to a sodium type (hereinafter referred to as Na type). A adsorption step that selectively adsorbs lithium ions by contacting them with a strongly acidic cation exchange resin having a sulfonic acid group to leave aluminum ions in the liquid, and a strong acid cation exchange using an aqueous solution containing a sodium salt. By combining with an elution process that elutes lithium ions adsorbed on the resin, lithium can be easily recovered selectively from the wastewater from the manufacturing process containing aluminum and lithium, and the concentration is suitable for obtaining lithium carbonate and lithium hydroxide. We have found that it is possible to make an aqueous solution of the above, and have completed the present invention.

[2. Lithium recovery process]
The lithium recovery method according to the present embodiment recovers lithium from the wastewater from the manufacturing process of the positive electrode material for a lithium secondary battery, and includes a replacement step, an adsorption step, and an elution step. Hereinafter, the outline of the lithium recovery method and each step will be described.

[2-1. Overview of lithium recovery method]
First, an outline of the lithium recovery method will be described with reference to the drawings. FIG. 2 is a flow chart showing an outline of a lithium recovery method. As shown in FIG. 2, the lithium recovery method according to the embodiment of the present invention comprises a substitution step S1, an adsorption step S2, and an elution step S3.

[2-2-1. Replacement process]
In the replacement step S1, the sulfonic acid group (hereinafter, also referred to as “H type”), which is a functional group contained in the strongly acidic cation exchange resin, is replaced with a sodium type (hereinafter, also referred to as “Na type”). It is a process. The reason for substituting the H type with the Na type in the present embodiment will be described in the item of the adsorption step. The replacement step can be performed for the purpose of regenerating the adsorptivity of the strongly acidic cation exchange resin to lithium ions by repeating the adsorption step and the elution step described later a plurality of times. .. The replacement step can be omitted when the strong acid ion exchange resin is of the Na type.

[2-2-2. Adsorption process]
In the adsorption step S2, the strong acid cation exchange resin is brought into contact with the wastewater from the manufacturing process, and the lithium ions are selectively adsorbed on the strong acid cation exchange resin. The lithium solution containing aluminum and lithium may have any metal concentration, but by adjusting the pH of the aqueous solution to 9 or higher, the aluminum ion becomes an aluminate ion [Al (OH) ₄ ] ^- . When this liquid is passed through a strongly acidic cation exchange resin containing a sulfonic acid group adjusted to Na type, lithium ions, which are cations, are adsorbed, but aluminate ions, which are anions, are not adsorbed. Here, aluminum ions are more selective than lithium ions. Therefore, when aluminum ions are present in the wastewater from the manufacturing process, it is difficult to selectively adsorb lithium to the strongly acidic cation exchange resin. Therefore, in the adsorption step according to the embodiment of the present invention, lithium ions can be selectively adsorbed by converting aluminum ions into aluminate ions. At this time, if the functional group is of the hydrogen type (hereinafter referred to as H type), the hydrogen ion exchanged with the lithium ion is released into the aqueous solution, and the pH in the vicinity of the resin is lowered. In this case, aluminum hydroxide having poor filterability precipitates and adheres to the resin, which hinders liquid passage and ion exchange reaction. In the worst case, the adsorption process using a column becomes impossible. When the pH in the vicinity of the resin is further lowered and aluminum becomes an acidic region in which it exists as a cation, it is selectively adsorbed from lithium ions and separation becomes difficult. In the case of a strongly acidic cation exchange resin, the base such as aluminum hydroxide is decomposed and ion-exchanged with aluminum to be adsorbed, which makes separation from lithium difficult.

However, by adjusting to the Na type in advance, such a decrease in pH can be prevented, the generation of aluminum hydroxide and aluminum ions can be suppressed, and aluminum can be maintained in the state of aluminate ions, so that it is adsorbed by the resin. There is no such thing. Since lithium ion is inferior in selectivity between sodium ion and lithium ion, the lithium concentration must be 0.3 g / L or more in order to adsorb lithium ion in Na type, and at 0.5 g / L or more. It is desirable to have. If the lithium concentration in the wastewater from the manufacturing process is less than 0.3 g / L, it may be difficult for lithium ions to be adsorbed on the Na-type strongly acidic cation exchange resin. Since the strongly acidic cation exchange resin has high durability, more adsorption steps and elution steps can be performed as compared with the weakly acidic cation exchange resin having a carboxy group as a functional group.

[2-2-3. Elution process]
In the elution step S3, lithium ions are eluted using an aqueous solution containing a sodium salt. For example, an aqueous solution of sodium sulfate can be used. Cation exchange resins are usually eluted using an acid, but when adsorption and elution are performed using a column, if the liquid that has passed through the adsorption step remains, aluminum hydroxide will drop due to the pH drop due to the mixing of the liquid. Elution occurs, aluminum becomes a cation form in the acidic region and is adsorbed by the resin, and other problems occur.

The same applies to the case of shifting from the elution step to the adsorption step. The pH of the aqueous solution containing aluminum and lithium adjusted to pH 9 or higher is lowered by mixing with the residual acid, and the pH is lowered to reduce the pH of aluminum hydroxide. Precipitation occurs, aluminum becomes a cation form in the acidic region and is adsorbed by the resin.

As a workaround for such a problem, it is conceivable to provide a thorough washing step between each step, but since a strong acid is usually used for elution in a strongly acidic cation exchange resin, the liquid in the column is near neutral. A large amount of water is required to wash with water until it becomes full, and there are major disadvantages such as a decrease in the amount of treatment and an increase in the load of wastewater treatment, which is not realistic.

Further, when eluted with an acid, the functional group becomes H-type, so that it is necessary to pass an aqueous solution containing a sodium salt in order to perform the next adsorption step, which has the disadvantage of increasing the number of steps. If an aqueous solution containing sodium is used as the eluent, problems due to pH fluctuation can be avoided, and the functional group can be returned to the Na type at the same time as elution, so that the process is simplified. In addition, lithium in the eluent can be concentrated by adjusting the flow rate of the eluent. Therefore, lithium can be recovered without using the evaporation concentration method, which has a high energy cost.

The eluent is an aqueous solution containing lithium and sodium, but since sodium carbonate is added to precipitate and recover lithium carbonate, the use of a sodium salt does not adversely affect the precipitation formation of lithium carbonate. The obtained lithium carbonate is required to have a quality according to the intended use, but the concentration of sodium as an impurity can be reduced by washing with water as necessary.

Sodium salts include sodium chloride and sodium sulfate, but when sodium chloride is used, chlorine remains in the precipitated and recovered lithium carbonate. The recovered lithium carbonate is recycled as a raw material for the positive electrode material of the secondary battery, but it is desirable to use sodium sulfate because chlorine has the disadvantage of corroding the structural material of the equipment.

Hereinafter, specific examples to which the present invention is applied will be described, but the present invention is not limited to these examples.

<Example 1>
[3-1. Replacement process]
50 mL of a strongly acidic cation exchange resin (Duolite CF20LF manufactured by Sumika Chemtech Co., Ltd.) was packed in a glass column having a diameter of 20 mm, and the following operation was repeated three times to make the resin Na type.
a) A 73 g / L hydrochloric acid aqueous solution was passed through 500 mL (BV10) with SV10.
b) After passing the aqueous hydrochloric acid solution, 500 mL (BV10) of pure water was passed through SV10 to wash the resin.
c) After washing, 500 mL (BV10) of a 50 g / L sodium sulfate aqueous solution was passed through SV10.

[3-2. Adsorption process]
[3-1. ], 10 mL of the resin washed in the replacement step was taken and packed in another column having a diameter of 10 mm. This column contains 2.0 g / L of lithium, 0.07 g / L of sodium, 0.1 g / L of aluminum, and 0.6 L of waste from the manufacturing process of the positive electrode material of the secondary battery having a pH of about 12 (SV20). BV60) The liquid was passed through to adsorb lithium ions. Pure water was passed through the adsorbed resin with SV20 in an amount of 2.0 L (BV200) to wash the residual liquid.

[3-3. Elution process]
[3-2. ], A 150 g / L sodium sulfate aqueous solution was passed through the washed resin in the adsorption step, and 70 mL (BV7) was passed through SV1 to elute the lithium ions adsorbed on the resin.

[3-1. ] From the replacement step [3-3. Elution step] was performed at room temperature. Regarding the results obtained in Example 1, the adsorption curve (relationship between BV and the concentration of lithium and aluminum in the eluent after adsorption) is shown in FIG. 3, and the elution curve (the concentration of lithium and aluminum in the BV and the eluent) is shown in FIG. Relationship) is shown.

<Comparative Example 1>
In Comparative Example 1, unlike Example 1, lithium ions contained in the wastewater from the manufacturing process of the positive electrode material for a lithium secondary battery were eluted by the following operation using an H-type strongly acidic cation exchange resin.

[4-1. Replacement process]
50 mL of strongly acidic cation exchange resin (Duolite CF20LF manufactured by Sumika Chemtech) was packed in a glass column with a diameter of 20 mm, and the following operations were repeated twice, and then only a) and b) were performed the third time. Then, the resin was made H-shaped.
a) A 73 g / L hydrochloric acid aqueous solution was passed through 500 mL (BV10) with SV10.
b) After passing the aqueous hydrochloric acid solution, 500 mL (BV10) of pure water was passed through SV10 to wash the resin.
c) After washing, 500 mL (BV10) of a 50 g / L sodium sulfate aqueous solution was passed through SV10.

[4-2. Adsorption process]
[4-1. ], 10 mL of the resin washed in the replacement step was taken and packed in another column having a diameter of 10 mm. This column contains 2.0 g / L of lithium, 0.07 g / L of sodium, 0.1 g / L of aluminum, and 0.6 L of waste from the manufacturing process of the positive electrode material of the secondary battery having a pH of about 12 (SV20). BV60) The liquid was passed through to adsorb lithium ions. Pure water was passed through the adsorbed resin with SV20 in an amount of 2.0 L (BV200) to wash the residual liquid.

[4-3. Elution process]
A 150 g / L sodium sulfate aqueous solution was passed through the washed resin, and 70 mL (BV7) was passed through SV1 to elute the lithium ions adsorbed on the resin.

<Discussion by Example>
In FIG. 3, which shows the adsorption curve of Example 1, the aluminum concentration after BV20 is 0.1 g / L of the undiluted solution, and it can be seen that the aluminum is not adsorbed. At BV10, the aluminum concentration of the post-adsorption liquid is lowered, but this is due to the diluting effect of the column residual liquid, and it cannot be concluded that the liquid is adsorbed. From FIG. 4, which shows the elution curve, it can be seen that the eluent containing a high concentration of lithium could be recovered. On the other hand, the amount of aluminum in the eluent was almost 0, indicating that almost no aluminum was adsorbed in the adsorption step.

In FIG. 5, which shows the adsorption curve of Comparative Example 1, the concentration of aluminum in the liquid after adsorption is low even in BV20, and it can be confirmed that aluminum is adsorbed as compared with Example 1. In BV10, the aluminum concentration is 0, but even if there is a diluting effect of the residual liquid, it does not become 0 if it is not adsorbed, so it can be seen that aluminum is definitely adsorbed. From FIG. 6 showing the elution curve, it can be seen that the eluent containing a high concentration of lithium can be recovered, but the aluminum concentration in the eluent is high, and it is 15 mg / L or more at BV4 or higher. From this, it can be seen that in the case of the H type, aluminum ions are adsorbed in the adsorption step and eluted in the elution step, so that they cannot be separated from lithium. From these results, it was found that lithium can be selectively separated from the aluminum-containing liquid by using the lithium recovery method according to the embodiment of the present invention.

Although each embodiment and each embodiment of the present invention have been described in detail as described above, those skilled in the art will be able to make many modifications that do not substantially deviate from the new matters and effects of the present invention. , Will be easy to understand. Therefore, all such modifications are included in the scope of the present invention.

For example, a term described at least once in a specification or drawing with a different term in a broader or synonymous manner may be replaced by that different term anywhere in the specification or drawing. Further, the configuration and operation of the lithium recovery method are not limited to those described in each embodiment and each embodiment of the present invention, and various modifications can be carried out.

S1 replacement step, S2 adsorption step, S3 elution step, S101 crystallization step, S102 separation step, S103 firing step, S104 washing step

Claims (3)

A method for recovering lithium from wastewater in a manufacturing process containing lithium and aluminum, which are positive electrode materials for lithium secondary batteries.
An adsorption step in which an ion exchange resin is brought into contact with the wastewater in the manufacturing process to selectively adsorb lithium ions to the ion exchange resin.
The adsorption step comprises an elution step in which an aqueous solution containing a sodium salt is brought into contact with the ion exchange resin on which the lithium ions are selectively adsorbed to elute lithium ions from the ion exchange resin.
The ion exchange resin is a strongly acidic cation exchange resin having a sodium-type functional group of a sulfonic acid group .
The pH of the wastewater from the manufacturing process in the adsorption step is 9 or more, and the pH is 9 or more.
A method for recovering lithium, wherein the lithium concentration of the wastewater from the manufacturing process in the adsorption step is 0.3 g / L or more . Prior to the adsorption step, a substitution step of substituting the functional group contained in the ion exchange resin is further provided.
The method for recovering lithium according to claim 1 , wherein the replacement step replaces the functional group with the sodium type from the sulfonic acid group. The method for recovering lithium according to claim 1 or 2 , wherein the sodium salt in the elution step is sodium sulfate.

Images