JP7102743B2 - Lithium recovery method - Google Patents

Description

The present invention relates to a method for recovering lithium, which recovers lithium from manufacturing process wastewater containing lithium and calcium 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”).

As a method for recovering lithium from manufacturing process wastewater, Patent Document 1 proposes a solvent extraction method, and Patent Document 2 proposes a method using electrodialysis using an ion exchange membrane.

Japanese Unexamined Patent Publication No. 2006-57142 Japanese Unexamined Patent Publication No. 2012-234732

However, the solvent extraction method of Patent Document 1 has problems that safety measures are required, the process is long, and the cost is high. Further, the method using electrodialysis using the ion exchange membrane of Patent Document 2 is disadvantageous in terms of cost and operation.

On the other hand, as an inexpensive and simple method, there is a recovery method using a cation exchange resin.

However, when the wastewater from the manufacturing process contains a small amount of calcium, there is a problem that the quality of lithium recovered as lithium carbonate is deteriorated. Further, adding a calcium removing step before the lithium recovery step has a problem that the cost is deteriorated.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for efficiently and easily separating calcium from wastewater from a manufacturing process containing lithium and calcium and recovering lithium. ..

One aspect of the present invention is a method for recovering lithium from manufacturing process wastewater containing lithium and calcium as a positive electrode material for a lithium secondary battery, wherein the manufacturing process wastewater is connected in series to a plurality of ions. It has an adsorption step of contacting with an exchange resin and an elution step of separating the plurality of ion exchange resins after the adsorption step and bringing an eluent into contact with each ion exchange resin, and lithium ions are selected in the adsorption step. It is characterized in that lithium is recovered from the ion-exchange resin that has been specifically adsorbed.

In this way, calcium can be efficiently and easily separated from the wastewater from the manufacturing process containing lithium and calcium, so that high-quality lithium can be recovered and the recovery cost can be reduced.

Further, in one aspect of the present invention, in the elution step, the calcium ions may be removed from the ion exchange resin in which calcium ions are selectively adsorbed in the adsorption step.

In this way, lithium can be recovered by performing the adsorption step again using the ion exchange resin from which calcium ions have been removed.

Further, in one aspect of the present invention, the ion exchange resin may be a strongly acidic cation exchange resin.

Since the strong acid cation exchange resin has high durability, more adsorption steps and elution steps can be performed.

Further, in one aspect of the present invention, in the elution step, the ion exchange resin selectively adsorbed by the lithium ions in the adsorption step may be connected in series.

In this way, lithium can be recovered with less eluate.

Further, in one aspect of the present invention, in the adsorption step, the wastewater from the manufacturing process is brought into contact with two ion exchange resins connected in series, the two ion exchange resins are separated, and the second ion exchange resin is separated. Lithium may be recovered from.

In this way, calcium can be efficiently and easily separated from the waste in the manufacturing process containing lithium and calcium, so that high-quality lithium can be recovered and the recovery cost can be reduced.

Further, in one aspect of the present invention, the eluent in the elution step may be an aqueous solution containing sodium sulfate.

In this way, the cation exchange resin is converted from the H type to the Na type in the elution step, so that the regeneration step can be omitted.

According to the present invention, calcium can be efficiently and easily separated from the wastewater from the manufacturing process containing lithium and calcium, so that high-quality lithium can be recovered and the recovery cost can be reduced.

It is a flow chart which shows the outline of the manufacturing process of the positive electrode material for a lithium secondary battery. It is a flow chart which shows the outline of the lithium recovery method which concerns on one Embodiment of this invention. It is a block diagram of the column in the adsorption process which concerns on one Embodiment of this invention. It is a block diagram of the column in the elution step which concerns on one Embodiment of this invention. It is explanatory drawing of the relationship between the liquid passing amount and the lithium concentration in an eluent. It is explanatory drawing of the relationship between the liquid passing amount and the calcium concentration in an eluent.

Hereinafter, specific embodiments 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 is composed of a crystallization step S101, a separation step S102, a firing step S103, and a water 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 made of a raw material such as nickel, cobalt, or aluminum, and these metal hydroxides are co-precipitated to form 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 the 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.

Among the manufacturing steps of the positive electrode material for the lithium secondary battery, in the washing step S104, wastewater from the manufacturing process containing a high concentration of lithium ions and a trace amount of calcium ions is discharged. The wastewater concentration in the manufacturing process is, for example, 1 to 3 g / L for lithium ions and 1 to 10 mg / L for calcium ions. Lithium is an alkali metal, and like sodium and potassium, there are no restrictions on water pollution. Since only metals regulated by the Water Pollution Law and regulations are usually treated and removed in the wastewater treatment process of factories, lithium in the wastewater from the manufacturing process is not removed in the wastewater treatment process and is discharged into public water bodies. Lithium is a metal contained in seawater, and there is no environmental problem even if it is released into public water bodies. However, lithium is a valuable metal, and from the viewpoint of resource saving, it is not preferable to discharge such manufacturing process wastewater into public water bodies. Then, in the recycling of resources, it is required to collect lithium discharged in the manufacturing process without discarding it and effectively utilize it.

To recover lithium from manufacturing process wastewater, there are a solvent extraction method (for example, Patent Document 1), a method using electrodialysis using an ion exchange membrane (for example, Patent Document 2), and a recovery method using an ion exchange resin. ..

However, when the solvent extraction method is used, it is necessary to treat organic substances in the wastewater, it is necessary to take safety measures because it is a facility that handles dangerous substances under the Fire Service Act, and it is a multi-stage extraction. Therefore, the problem is that the process is long and the cost is high. Further, the method using electrodialysis using an ion exchange membrane requires a large-scale device for using the electrodialysis device as wastewater treatment, which is disadvantageous in terms of cost and operation.

In contrast to these recovery methods, a recovery method using an ion exchange resin can be considered as an inexpensive and simple method. Examples of the ion exchange resin include a strongly acidic cation exchange resin having a sulfonic acid group as a functional group and a weakly acidic cation exchange resin having a carboxylic acid group as a functional group. In each resin, the hydrogen or sodium atom of the functional group is exchanged with the cation in the manufacturing process wastewater, and the metal is recovered from the manufacturing process wastewater by utilizing the exchange reaction between the manufacturing process wastewater and the metal. Further, the strongly acidic cation exchange resin can be used in all pH ranges (0 to 14).

However, since the stronger the acid cation exchange resin has a higher valence, the higher the selectivity, when the divalent metal such as calcium is contained in the wastewater from the manufacturing process, it is preferentially adsorbed over lithium, so even a small amount of calcium is contained. In that case, it becomes impossible to selectively recover lithium. When lithium is recovered from manufacturing process wastewater using a cation exchange resin, the lithium concentration in the eluent is increased, that is, concentrated by reducing the amount of eluent in the elution process compared to the manufacturing process wastewater through which the eluent is passed. .. This is a necessary operation for improving the recovery efficiency when lithium carbonate is precipitated and recovered from the eluate, and at this time, calcium, which is a trace impurity, is also concentrated. When lithium carbonate is precipitated and recovered from the eluent using a carbon dioxide source such as soda ash, the presence of calcium precipitates as calcium carbonate, which deteriorates the quality of lithium carbonate. Therefore, it is necessary to remove calcium before passing it through the cation exchange resin, but it is difficult to remove the calcium contained in a trace amount, and adding the calcium removing step to the previous stage causes a deterioration in cost. From such a background, a method for easily removing a trace amount of calcium contained has been desired.

In view of this situation, the inventors have conducted diligent studies and focused on the fact that calcium is preferentially adsorbed over lithium, so that the adsorption operation using a resin column is biased toward the front stage of the column. , The present invention was completed by finding that it is possible to obtain an eluent having a low calcium concentration by separately eluting the resin in the front portion having a high proportion of calcium and the resin in the rear portion having a low proportion of calcium. I arrived.

Hereinafter, the method for recovering lithium according to the embodiment of the present invention will be described in detail.

[2. Lithium recovery method]
The method for recovering lithium according to an embodiment of the present invention recovers lithium from the wastewater from the manufacturing process of the positive electrode material for a lithium secondary battery, and as shown in FIG. 2, the replacement step S1 and the adsorption step S2 It is composed of an elution step S3 and a regeneration step S4. Hereinafter, each step will be described.

Here, the ion exchange resin according to the embodiment of the present invention is preferably a strongly acidic cation exchange resin. The ion exchange resin column according to the embodiment of the present invention elutes separately in the first stage and the second stage at the time of elution, but since it is difficult to perform this operation with one single column, a plurality of columns, for example, several columns, are used. It consists of columns.

[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. Further, in the replacement step S1, the carboxy group (hereinafter, also referred to as “H type”), which is a functional group contained in the weakly acidic cation exchange resin, is replaced with a sodium type (hereinafter, also referred to as “Na type”). You can also do it. Since the adsorptivity of the cation exchange resin to lithium ions is lowered by repeating the adsorption step and the elution step described later a plurality of times, the replacement step can also be performed for the purpose of regenerating this adsorptivity. The replacement step can be omitted when the cation exchange resin is of the Na type. Further, it does not necessarily have to be "Na type", and the replacement step S1 may be omitted and used in "H type".

[2-2. Adsorption process]
In the adsorption step S2, the ion exchange resin is brought into contact with the wastewater from the manufacturing process, and calcium ions or lithium ions are adsorbed on the ion exchange resin. When the adsorption step is performed, as shown in FIG. 3, a plurality of columns filled with ion exchange resins are connected in series, and for example, a pump P is used to pass the wastewater from the manufacturing process to adsorb lithium ions and calcium ions. .. For example, when there are four columns, the wastewater from the manufacturing process flows in the order of the first C1 → the second C2 → the third C3 → the fourth C4, and is discharged as a liquid after adsorption.

Here, as described above, the calcium ion is a divalent cation, has higher selectivity than the monovalent cation lithium ion, and is easily adsorbed on the ion exchange resin. Therefore, in one embodiment of the present invention, almost all calcium ions present in the wastewater from the manufacturing process are adsorbed on the column C1. That is, in one embodiment of the present invention, the calcium ions in the manufacturing process wastewater are concentrated and separated in the column C1 which is the first part of the resin, and almost no calcium ions remain in the manufacturing process wastewater passing through the column C1. ..

On the other hand, lithium ions have low selectivity and are not easily adsorbed on ion exchange resins. Therefore, a part of the lithium ions is adsorbed on the column C1, but the rest is adsorbed on the second and subsequent columns.

Due to the difference in selectivity between calcium ions and lithium ions described above, in one embodiment of the present invention, lithium and calcium in the wastewater from the manufacturing process can be separated by the column C1. Then, since an eluent having a low calcium concentration can be obtained in the elution step described later, high-quality lithium can be recovered.

Further, in one embodiment of the present invention, the concentration of calcium ions in the wastewater from the manufacturing process is 1 to 3 g / L, whereas the amount of calcium ions is 1 to 10 mg / L, which is a very small amount. The ion exchange reaction is an equilibrium reaction, and in view of the difference in these concentrations, it is possible that the calcium ions adsorbed on the ion exchange resin are replaced with a large amount of lithium ions and eluted from the column C1. However, calcium ions have high selectivity and lithium ions have low selectivity. Therefore, in one embodiment of the present invention, it is considered that the calcium ions adsorbed on the ion exchange resin of the column C1 are less likely to be eluted by the lithium ions and are less likely to be adsorbed on the second and subsequent columns.

Further, in one embodiment of the present invention, calcium ion separation and lithium ion adsorption can be performed in one step in the adsorption step. Then, in one embodiment of the present invention, a separate calcium removal step can be omitted, which is advantageous in terms of cost.

Further, in another embodiment of the present invention, two ion exchange resins (columns) are used to selectively adsorb calcium ions on the first column C1 and selectively lithium ions on the second column C2. It may be adsorbed to. As a result, the number of columns can be reduced, which is advantageous in terms of cost.

In one embodiment of the present invention, the lithium recovery rate from wastewater from the manufacturing process can be improved by increasing the number of columns. In addition, the optimum number of columns is appropriately determined in consideration of the profit from the improvement of the lithium recovery rate, the capital investment cost and the resin cost due to the increase in the number of columns.

[2-3. Elution process]
In the elution step S3, an aqueous solution containing an acid such as hydrochloric acid or sulfuric acid or a sodium salt is used as an eluent to elute calcium ions or lithium ions. In the elution step in one embodiment of the present invention, the ion exchange resins linked in series in the adsorption step are separated. Thereby, the ion exchange resin in which calcium ions are selectively adsorbed and the ion exchange resin in which lithium ions are selectively adsorbed can be separated.

In the elution step in one embodiment of the present invention, after separating the ion exchange resin, as shown in FIG. 4, each column is arranged in parallel, and for example, the pumps P1, P2, P3, P4 are used to use columns C1, C2, C3, An eluent is passed through each of C4 to obtain an eluent 1, an eluent 2, an eluent 3, and an eluent 4.

At this time, as described above, the eluate of the first column C1 contains more calcium, and the calcium in the eluate is reduced in the second, third, and fourth stages and the latter stage at the time of adsorption. By recovering only the eluate having a low calcium concentration, for example, the eluate of the second to fourth columns after the elution step, calcium as an impurity can be separated and high-grade lithium can be recovered.

In the elution step in another embodiment of the present invention, ion exchange resins selectively adsorbed by lithium ions may be connected in series to allow the eluent to pass through. This may allow lithium to be recovered with less eluent than passing the eluent separately.

The ion exchange resin in which the eluent is passed and lithium ions are eluted can be used again in the adsorption step after performing the regeneration step described later. Further, the ion exchange resin obtained by elution and removing calcium ions by passing an eluent can also be used again in the adsorption step after performing the regeneration step described later. The elution step may be omitted by discarding the ion exchange resin on which calcium ions are selectively adsorbed and replacing it with a new ion exchange resin.

[2-4. Regeneration process]
In the regeneration step S4, calcium ions and lithium ions are eluted with an acid such as sulfuric acid or hydrochloric acid, and then converted to Na type by passing NaOH through an H type cation exchange resin. When calcium ions and lithium ions are eluted with an aqueous solution containing sodium salts, the elution reaction results in Na type, so this step is not 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.

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

<Example 1>
Four ion exchange resin columns packed with a strongly acidic cation exchange resin having a capacity of 1 L (manufactured by Sumika Chemtec Co., Ltd .: Duolite CF20LF) were prepared.

[1. Replacement process]
Sumika Chemtech Co., Ltd .: The type of Duolite CF20LF at the time of purchase was Na type, so it was used as it was without replacement operation.

[2. Adsorption process]
Four columns were connected in series, and 100 L of wastewater from the manufacturing process of a positive electrode material for a secondary battery having a pH of 12 containing 2100 mg / L of lithium and 2 mg / L of calcium was passed.

[3. Elution process]
After the adsorption step, the columns connected in series were arranged in parallel, and 10 L of pure water was flowed through each column to wash the resin in the column. Then, in a parallel state, 6 L of 150 g / L sodium sulfate aqueous solution was passed through each column to elute lithium and calcium. The relationship between the flow rate and the lithium concentration in the eluent is shown in FIG. 5, and the relationship between the flow rate and the calcium concentration in the eluent is shown in FIG. It can be seen that the lithium concentration in the eluent (FIG. 5) is almost the same in the 2nd to 4th lines, the peak concentration is about 13 g / L, and the peak concentration is slightly lower in the 1st line and is about 9 g / L. On the other hand, it can be seen that the calcium concentration in the eluent (FIG. 6) has a peak concentration of about 80 mg / L only in the first one and several mg / L in the second to fourth ones.

From this result, it was found that high-purity lithium carbonate having a low calcium grade can be obtained by using the second to fourth eluates having a low calcium concentration as a raw material for lithium carbonate.

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 the 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 substitution process, S2 adsorption process, S3 elution process, S4 regeneration process S101 crystallization process, S102 separation process, S103 firing process, S104 washing process P pump C column

Claims (6)

A method for recovering lithium from manufacturing process wastewater containing lithium and calcium, which is a positive electrode material for lithium secondary batteries.
The adsorption step of bringing the wastewater from the manufacturing process into contact with a plurality of ion exchange resins connected in series, and
It has an elution step of separating the plurality of ion exchange resins after the adsorption step and bringing an eluent into contact with each ion exchange resin.
A method for recovering lithium, which comprises recovering lithium from the ion exchange resin in which lithium ions are selectively adsorbed in the adsorption step. The method for recovering lithium according to claim 1, wherein in the elution step, the calcium ions are removed from the ion exchange resin in which calcium ions are selectively adsorbed in the adsorption step. The method for recovering lithium according to claim 1 or 2, wherein the ion exchange resin is a strongly acidic cation exchange resin. The method for recovering lithium according to any one of claims 1 to 3, wherein in the elution step, the ion exchange resins selectively adsorbed by the lithium ions in the adsorption step are connected in series. In the adsorption process, the wastewater from the manufacturing process is brought into contact with two ion exchange resins connected in series.
The method for recovering lithium according to any one of claims 1 to 3, wherein the two ion exchange resins are separated and lithium is recovered from the second ion exchange resin. The method for recovering lithium according to any one of claims 1 to 5, wherein the eluent in the elution step is an aqueous solution containing sodium sulfate.

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