JP7155696B2 - Lithium elution method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for eluting lithium adsorbed on an ion-exchange resin from lithium-containing manufacturing process wastewater of positive electrode materials for lithium secondary batteries.

Lithium is widely used in industry as an additive for pottery and glass, glass flux for continuous steel casting, grease, pharmaceuticals, and batteries. In particular, lithium-ion batteries, which are secondary batteries, have high energy density and high voltage. Demand is soaring. Along with this, demand for raw materials such as lithium hydroxide and lithium carbonate is rapidly increasing.

Recently, for the purpose of effective utilization of resources, the recovery of lithium from wastewater discharged from the manufacturing process of positive electrode materials for lithium secondary batteries (hereinafter also referred to as "manufacturing process wastewater") has been promoted.

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

As a method for recovering ions using an ion exchange resin, Patent Document 3 proposes a method using a so-called merry-go-round system.

JP-A-2006-57142 JP 2012-234732 A Japanese Patent Application Laid-Open No. 2012-030208

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

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

In the recovery method using an ion-exchange resin, an eluent is passed through the ion-exchange resin on which lithium is adsorbed, and lithium is recovered from the eluted solution. However, since lithium has low selectivity and elution progresses in a short period of time, it becomes difficult to recover the solution after elution with a stable lithium concentration. Therefore, there is a problem that equipment is required to stabilize the lithium concentration, impairing economic efficiency. In addition, since the concentration of lithium in the solution after elution varies each time, there is a problem in terms of production management.

Patent Document 3 proposes a method using a so-called merry-go-round system as a method for recovering the ions with low selectivity described above using an ion exchange resin. However, Patent Document 3 does not consider metals with low selectivity.

Under these circumstances, there has been a demand for a method of keeping the lithium concentration constant after elution in the elution process.

The present invention has been made in view of the above circumstances, and in a method for eluting lithium adsorbed on an ion-exchange resin from lithium-containing manufacturing process wastewater of a positive electrode material for lithium secondary batteries, the lithium concentration after elution is always constant.

The inventors can suppress the change in the lithium concentration in the post-elution solution by moving the multiple columns that have adsorbed lithium in the adsorption step step by step to the elution step and eluting the lithium. I found out.

One aspect of the present invention for achieving the above object is a method for eluting lithium adsorbed on an ion-exchange resin from lithium-containing manufacturing process wastewater of a positive electrode material for a lithium secondary battery, comprising: An adsorption step is performed in which some of the resins are connected in series and contacted by passing water through the manufacturing process wastewater, and an elution step is performed in which the remaining plurality of ion exchange resins are connected in series and an eluent is passed through and contacted. The first ion exchange resin in the adsorption step is connected to the end of the ion exchange resin in the elution step, the first ion exchange resin is transferred to the elution step, and the first ion exchange resin in the elution step is connected to the ion exchange resin in the adsorption step. After connecting to the end of the resin, the first ion exchange resin is transferred to the adsorption step, the adsorption step and the elution step are alternately repeated for the plurality of ion exchange resins, and the liquid passing in the elution step is BV ( When the bed volume) value reaches a predetermined value of 1.0 or more and 3.0 or less, the elution step is shifted to the adsorption step, and the waste water from the manufacturing process contains aluminum, and the adsorption step is performed. It is characterized in that the pH of the manufacturing process wastewater in the process is set to 9 or higher .

In this way, the lithium concentration in the eluted solution can be kept constant, so that equipment for homogenizing the total amount of the eluent, such as a stirring mixing tank, is not required, which is economically advantageous. Moreover, production management becomes easy. In addition, when lithium is eluted from manufacturing process waste water containing aluminum, it is possible to suppress a decrease in the capacity of the ion-exchange resin.

In one aspect of the present invention, the SV (space velocity) of the liquid passing in the elution step may be 2 hr ⁻¹ or more and 6 hr ⁻¹ or less.

In this way, the processing efficiency per unit time and the lithium elution efficiency can be improved.

In one aspect of the present invention, the SV (space velocity) of the water flow in the adsorption step may be 5 hr ⁻¹ or more and 15 hr ⁻¹ or less.

In this way, the processing efficiency per unit time and the lithium elution efficiency can be improved.

Further, in one aspect of the present invention, a washing step of washing the ion exchange resin after the elution step is further provided, and the SV (space velocity) of water passing through the ion exchange resin in the washing step is 2 hr ⁻ It may be ¹ or more and 6 hr ⁻¹ or less.

By doing so, it is possible to improve the cleaning efficiency per unit time.

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

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

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 regeneration step can be omitted because the cation exchange resin is converted from the H-type to the Na-type in the elution step.

According to the present invention, in a method of eluting lithium from manufacturing process wastewater containing lithium of a positive electrode material for a lithium secondary battery by an ion exchange treatment, the lithium concentration in the post-elution solution is kept constant. A stirring and mixing tank for homogenizing the total amount is not required, and only a storage tank with a minimum capacity for dispensing is required, which is economically advantageous and facilitates production control.

FIG. 2 is a flow diagram showing an outline of a manufacturing process of a positive electrode material for lithium secondary batteries. FIG. 4 is a conceptual diagram showing the change in the amount of liquid passed in the elution step in a single column and the concentration of lithium in the liquid after elution. 1 is a flowchart showing an outline of a lithium elution method according to an embodiment of the present invention; FIG. 1 is a conceptual diagram showing a column operation method in a lithium elution method according to an embodiment of the present invention; FIG. FIG. 4A is a conceptual diagram showing the state before switching columns in the adsorption step and the elution step. FIG. 4B is a conceptual diagram showing a state after switching columns. FIG. 4 is a diagram showing the relationship between the BV in the elution step and the lithium concentration in the post-elution solution according to one embodiment of the present invention. FIG. 5 is a diagram showing the relationship between the BV in the elution step and the lithium concentration in the post-elution solution in a comparative example.

Specific embodiments of the present invention (hereinafter referred to as "present embodiments") will be described in detail below. It should be noted that the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the purpose of the present invention.

[1. Overview of manufacturing process of positive electrode material for lithium secondary battery]
First, the outline of the manufacturing process of the positive electrode material for lithium secondary batteries will be described with reference to the drawings. FIG. 1 is a flow diagram showing an outline of the manufacturing process of a positive electrode material for lithium secondary batteries. As shown in FIG. 1, the manufacturing process of the positive electrode material for lithium secondary batteries comprises a crystallization step S101, a separation step S102, a baking step S103, and a water washing step S104. Specifically, in the crystallization step S101, an aqueous sodium hydroxide solution is added to a mixed aqueous solution of metal sulfates made of raw materials such as nickel, cobalt, and aluminum to coprecipitate these metal hydroxides 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.

In the water washing step S104 of the manufacturing steps of the positive electrode material for lithium secondary batteries, waste water containing high concentrations of lithium ions and aluminum ions is discharged in order to wash the positive electrode material with water.
The effluent concentration is, for example, 1 to 5 g/L for lithium ions and 0.04 to 0.18 g/L for aluminum ions. Lithium is an alkali metal and, like sodium and potassium, has no water pollution regulations. In the wastewater treatment process of factories, usually only metals regulated by the Water Pollution Law and ordinances are treated and removed, so lithium in wastewater from the manufacturing process is not removed in the wastewater treatment process and is discharged into public waters. Lithium is a metal contained in seawater, and there is no environmental problem even if it is discharged into public water areas. 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 areas. In the recycling of resources, it is required to collect and effectively utilize lithium discharged in the manufacturing process without discarding it.

Methods for recovering lithium from manufacturing process wastewater include 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 using the solvent extraction method, it is necessary to treat organic matter in the wastewater, safety measures are required because it is a facility that handles dangerous substances under the Fire Service Law, and multi-stage extraction is required. 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 electrodialysis apparatus for wastewater treatment, which is disadvantageous in terms of cost and operation.

Compared to these recovery methods, the recovery method using an ion-exchange resin is considered to be a cheap and simple method. When using a cation exchange resin industrially, a column system is generally used.

In the column method, wastewater from the manufacturing process is passed through a column filled with an ion exchange resin, and lithium is adsorbed on the ion exchange resin. An eluent is then passed through the column to elute lithium from the ion exchange resin. However, lithium tends to be eluted from the ion exchange resin due to its low selectivity. Therefore, the lithium concentration in the post-elution increases as the eluent passes through.

Here, FIG. 2 is a conceptual diagram showing the change in the amount of solution passed in the elution step in a single column and the concentration of lithium in the solution after elution. As shown in Fig. 2, when eluting lithium adsorbed on ion exchange resin by the column method, in a single column (single column), a sharp peak rises at the same time as the eluent is passed through, and then the concentration increases with the passage of the solution. A decreasing elution curve is obtained. Therefore, when trying to partially recover the post-elution solution, the concentration of lithium varies depending on the timing of recovery. It is necessary to store it in a tank and homogenize it by stirring and mixing. In other words, in production, the number of facilities increases, impairing economic efficiency. Furthermore, when only a small amount of the post-elution solution needs to be shipped, the concentration varies depending on the timing of extraction, which is undesirable from the standpoint of production management.

However, if the lithium concentration in the post-elution solution is always constant, such a stirring and mixing tank for homogenizing the total amount of the post-elution solution becomes unnecessary, and only a storage tank with a minimum capacity for dispensing is required. , which is economically advantageous and facilitates production management.

Patent Document 3 proposes a method using a so-called merry-go-round system as a method for recovering the ions with low selectivity described above using an ion exchange resin. However, Patent Document 3 does not consider metals with low selectivity.

Under these circumstances, there has been a demand for a method for keeping the lithium concentration in the post-elution solution constant in the elution process.

In view of this situation, the inventors have made extensive studies and found that the columns that have adsorbed lithium in the adsorption step are moved step by step to the elution step, and the lithium is eluted, resulting in a post-elution solution The inventors have found that it is possible to suppress the change in the lithium concentration in the medium, and have completed the present invention.

Hereinafter, a lithium elution method according to an embodiment of the present invention will be described in detail.

[2. Elution method of lithium]
A method for eluting lithium according to an embodiment of the present invention is for eluting lithium from waste water produced during the manufacturing process of positive electrode materials for lithium secondary batteries, and includes an adsorption step and an elution step. An outline of the lithium elution method and each step will be described below.

[2-1. Overview of Lithium Elution Method]
First, an overview of the lithium elution method will be described with reference to the drawings. FIG. 3 is a flowchart showing an outline of a lithium elution method according to one embodiment of the present invention. As shown in FIG. 3, the lithium elution method according to one embodiment of the present invention comprises an adsorption step S1 and an elution step S2.

[2-2. Adsorption process]
In the adsorption step S1, an ion-exchange resin is brought into contact with waste water from the manufacturing process to selectively adsorb lithium ions on the ion-exchange resin. Here, as the ion exchange resin, a strongly acidic cation exchange resin is preferred. Since the strongly acidic cation exchange resin has high durability, more adsorption steps and elution steps can be performed. In addition, when aluminum is contained in the wastewater from the manufacturing process, the lithium solution containing aluminum and lithium may have any metal concentration. Al(OH) ₄ ] ^- . When this solution is passed through a strongly acidic cation exchange resin containing sulfonic acid groups adjusted to Na type, lithium ions, which are cations, are adsorbed, but aluminate ions, which are anions, are not adsorbed. Since aluminum ions have a higher selectivity than lithium ions, it is difficult to selectively adsorb lithium to strongly acidic cation exchange resins when aluminum ions are present in wastewater from the manufacturing process. Lithium can be selectively adsorbed by making At this time, if the functional group is of a hydrogen type (hereinafter referred to as H type), the hydrogen exchanged with lithium ions is released as hydrogen ions into the aqueous solution, and the pH in the vicinity of the resin is lowered. In this case, aluminum hydroxide with poor filterability precipitates and adheres to the resin, inhibiting the flow of liquid and the ion exchange reaction. In the worst case, the adsorption step using the column becomes impossible. When the pH in the vicinity of the resin is further lowered to an acidic region in which aluminum exists as a cation, aluminum is selectively adsorbed over lithium and separation becomes difficult. In the case of a strongly acidic cation exchange resin, it decomposes a base such as aluminum hydroxide and ion-exchanges with aluminum for adsorption, making separation from lithium difficult.

However, by adjusting it 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 retained in the state of aluminate ions, so it is adsorbed by the resin. never.

In addition, when the pH becomes an acidic region where aluminum exists as a cation due to a decrease in pH, aluminum, which has a higher selectivity than lithium, is adsorbed on the strongly acidic cation exchange resin, accumulates in the resin, and reduces the capacity of the resin. .

[2-3. Elution process]
In the elution step S2, lithium ions are eluted using an aqueous solution containing a sodium salt. For example, an aqueous sodium sulfate solution can be used. Cation exchange resins are usually eluted with an acid, but when adsorption and elution are performed using a column, if the solution passed through the adsorption process remains, the pH will drop due to mixing of the solutions and aluminum hydroxide will be removed. Problems such as precipitation occurring and aluminum being in the form of cations in the acidic region and being adsorbed by the resin occur.

The same is true when shifting from the elution step to the adsorption step. By mixing with the remaining acid, the pH of the aqueous solution containing aluminum and lithium adjusted to pH 9 or higher is lowered, and the lowered pH causes aluminum hydroxide. In the acidic region, aluminum becomes a cationic form and is adsorbed by the resin.

Furthermore, 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 carry out 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 fluctuations can be avoided, and the functional group can be returned to the Na form at the same time as the elution, thus simplifying the process. Also, by adjusting the flow rate of the eluent, the lithium in the eluent can be concentrated. Therefore, lithium can be recovered without using the evaporative concentration method, which requires high energy cost.

Although the eluent is an aqueous solution containing lithium and sodium, sodium carbonate is added to precipitate and recover lithium carbonate, so the use of a sodium salt does not adversely affect the precipitation of lithium carbonate. The obtained lithium carbonate is required to have a grade according to the application, but the concentration of sodium, which is 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 positive electrode materials for lithium secondary batteries, but chlorine has the disadvantage of corroding the structural materials of equipment, so it is desirable to use sodium sulfate.

[3. Column operation method]
First, an overview of the column operation method will be explained using the drawings. FIG. 4 is a conceptual diagram showing a column operation method in the lithium elution method according to one embodiment of the present invention, and adsorption and elution are performed in the following procedure. Here, FIG. 4A shows the state before switching columns in the adsorption step and the elution step, and FIG. 4B shows the state after switching columns.

A method for adsorbing lithium according to an embodiment of the present invention uses a plurality of ion exchange resins. Then, as shown in FIGS. 4(A) and 4(B), some of the ion-exchange resins are subjected to the adsorption step, and the remaining ion-exchange resins are subjected to the elution step.

Before the columns are switched, as shown in FIG. 4A, among the plurality of ion exchange resins 1 to 3, columns 1 and 2 are used for the elution process, and the remaining column 3 is used for the adsorption process. Here, columns 1 and 2 are adsorbed with lithium in the adsorption step performed before the elution step. Then, the columns 1 and 2 are connected in series and an eluent is passed through them, and placed in an elution step. At this time, the column 3 is arranged in the adsorption step. The total number of columns and the number of columns arranged in the adsorption step or elution step can be increased or decreased as necessary.

After passing a certain amount of eluent, all of the lithium in the ion-exchange resin packed in column 1 is eluted. Since lithium remains in the ion exchange resin filled in 2, the concentration of lithium in the post-elution solution coming out of the elution step is slightly low, but a high concentration can be maintained.

Here, as shown in FIG. 4B, the column 1 is separated from the column 2 and arranged in the adsorption step, so that the column 1 is shifted from the elution step to the adsorption step. Column 2 remains in the elution step, and column 3 is connected in series after column 2 and placed at the end of the elution step, thereby allowing column 3 to transition from the adsorption step to the elution step. Here, the columns are connected to each other by a water pipe or a liquid pipe used for passing waste water from the manufacturing process and for passing the eluent. Valves are provided in the water pipes and the liquid pipes, and the separation and connection of the columns are performed by switching the flow paths of the manufacturing process waste water, the eluent, etc. by opening and closing the valves.

Since column 3 has lithium adsorbed to its full exchange capacity, the lithium concentration in the post-elution solution, which was slightly lowered in the elution step in FIG. It is possible to return to high concentrations.

After all the lithium in the ion exchange resin packed in the column 2 is eluted in the elution step in FIG. 4B, the column 2 is separated from the column 3 and placed in the adsorption step, The same operation is repeated such that column 3 is connected in series after column 3 and placed in the final stage of the elution step, and the adsorption step and the elution step are alternately repeated for the ion exchange resin. By continuously eluting lithium while switching columns from the adsorption step to the elution step and from the elution step to the adsorption step, it is possible to always obtain a post-elution solution with a high lithium concentration.

Moreover, although not shown, a washing step such as washing with water may be inserted between the adsorption step and the elution step, if necessary.

The above description is for the case where there are two columns in the elution step, and all the lithium is eluted from the ion exchange resin in the first column 1 . However, the number of columns separated in the elution step and transferred to the adsorption step is not limited to one. As described above, the total number of columns and the number of columns arranged in the adsorption step or elution step can be increased or decreased as necessary. When the number of columns in the elution step is two or more, and all lithium is eluted from the ion-exchange resin in the first and subsequent multiple columns (hereinafter referred to as "first stage"). can perform the elution and adsorption steps for the plurality of columns (first-stage columns) and the plurality of ion-exchange resins (first-stage ion-exchange resins).

Also, in the above description, the number of columns in the adsorption step is one. However, as described above, the number of columns can be increased or decreased as needed, and a plurality of columns can be connected in series in the adsorption step. Also, the number of columns transferred from the adsorption step to the elution step is not limited to one. When multiple columns are connected in series in the adsorption step, the first column and the first ion exchange resin can be transferred from the adsorption step to the elution step.

In the case of eluting lithium from waste water from the manufacturing process of positive electrode materials for lithium secondary batteries, the lithium concentration in the solution after elution can be made constant by specifically using the following method.

(Step 1: adsorption step)
In the adsorption step, 5-8 columns are arranged. From the first column, wastewater from the manufacturing process of positive electrode materials for lithium secondary batteries is passed through 5 to 8 columns in series. The SV (space velocity) in the adsorption step is preferably 5 hr ^-1 or more and 15 hr ^-1 or less. If the SV (space velocity) is less than 5 hr ⁻¹ , the flow rate of waste water from the manufacturing process becomes small and the amount of lithium processed in the adsorption process decreases, resulting in deterioration of the treatment efficiency per unit time. If the SV (space velocity) exceeds 15 hr ⁻¹ , the flow rate of waste water from the manufacturing process increases, and lithium flows out without being fully adsorbed on the ion exchange resin, resulting in poor lithium adsorption efficiency.

In addition, the timing of switching the column varies depending on the concentration of lithium in the waste water from the manufacturing process of the positive electrode material for lithium secondary batteries. 7.5 or less is preferable. Here, BV in the present application refers to a value for the volume of ion exchange resin packed in one column. If the BV is less than 2.5, the adsorption step is switched to the elution step in a state in which lithium is not sufficiently adsorbed on the ion exchange resin, so that only an amount of lithium smaller than the exchange capacity can be adsorbed on the ion exchange resin. Therefore, the amount of ion exchange resin required for lithium adsorption increases. If the BV exceeds 7.5, the flow rate of waste water from the manufacturing process increases, and lithium flows out without being fully adsorbed on the ion-exchange resin, resulting in poor lithium adsorption efficiency.

(Step 2: Washing step)
Two columns are arranged in the washing step after adsorption. The columns that have moved from the column switching adsorption step are washed by passing water through them successively. SV (space velocity) is preferably 2 hr ^-1 or more and 6 hr ^-1 or less. The SV (space velocity) of the washing process may be a speed at which wastewater from the manufacturing process of positive electrode materials for lithium secondary batteries in the column can be replaced while the column is in the washing process.

(Step 3: Elution step)
In the elution step, two columns are arranged. Columns are switched and eluted by passing the eluent sequentially through the columns that have moved from the washing step. The SV (space velocity) in the adsorption step is preferably 2 hr ^-1 or more and 6 hr ^-1 or less. If the SV (space velocity) is less than 2 hr ⁻¹ , the amount of the eluent that elutes lithium becomes small, and the processing efficiency per unit time deteriorates. If the SV (space velocity) exceeds 6 hr ⁻¹ , the amount of the eluent that does not participate in the elution of lithium increases, resulting in poor elution efficiency of lithium.

In addition, the BV (Bed Volume) at the timing of switching columns and shifting from the elution process to the adsorption process is 1.0 or more and 3.0 or less. If the BV is less than 1.0, the elution process is switched to the adsorption process in a state in which lithium is not sufficiently eluted, so the elution efficiency of lithium deteriorates. When the BV exceeds 3.0, the lithium concentration in the post-elution solution rises to a sharp peak, and then the elution step is switched to the adsorption step, so the lithium concentration in the post-elution solution does not become constant.

(Step 4: Washing step)
In the post-elution wash step, two columns are arranged. Columns are switched and washed by passing water through the columns that have moved from the elution step. As in the washing step of step 2, the liquid passing speed should be such a speed that the eluent in the column can be replaced while the column is in the washing step. SV (space velocity) is preferably 2 hr ^-1 or more and 6 hr ^-1 or less.

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

<Example>
Elution was performed using a continuous column device (manufactured by Outotec Inc.). Two of the 20 columns with a capacity of 250 mL/column of the continuous column apparatus were used for the elution step. The column was packed with 240 mL/tube of strongly acidic cation exchange resin (manufactured by Sumika Chemtech Co., Ltd.: Duolite C20LF), and lithium was adsorbed to the full exchange capacity in the adsorption step. In the elution step, an eluent having a sodium sulfate concentration of about 150 g / L is flowed through the two columns at a flow rate of SV4 = 16 mL / min, and contacted with the strongly acidic cation exchange resin in the column to elute lithium. rice field. The operation of switching the column at the first stage of the elution process to the last stage of the adsorption process was repeated for each BV2. During elution, the post-elution solution from the second column was sampled every BV2, and the lithium concentration in the post-elution solution was measured by ICP-AES.

FIG. 5 shows the relationship between the BV of the eluent and the lithium concentration in the post-elution solution. It can be seen that after BV10, the lithium concentration in the eluted solution stabilizes in the range of 4000 to 5000 mg/L.

<Comparative example>
One column with a capacity of 1 L was filled with 1 L of strongly acidic ion exchange resin (manufactured by Sumika Chemtech Co., Ltd.: Duolite C20LF), and lithium was adsorbed to the full exchange capacity in the adsorption step.

An eluent having a sodium sulfate concentration of about 150 g/L was passed through this column at a flow rate of SV4=67 mL/min, and contacted with the strongly acidic cation exchange resin in the column to elute lithium. During the elution, the effluent from the column was sampled every BV1, and the lithium concentration in the eluate after elution was measured by ICP-AES. FIG. 6 shows the relationship between the BV of the eluent at this time and the lithium concentration in the eluted solution.

It can be seen that the concentration of lithium in the liquid after elution rises immediately after the start of elution, peaks at BV2, and then immediately decreases, unlike in the examples. From this, it can be seen that it is difficult to continuously obtain a post-elution solution with a stable lithium concentration when elution is performed using only one column. In addition, since the selectivity of lithium is low and elution progresses rapidly, elution from multiple small-capacity columns is performed successively rather than eluting from one large-capacity column. It is considered that the lithium concentration in the liquid could be kept constant.

Although the embodiments and examples of the present invention have been described in detail as described above, it should be understood by those skilled in the art that many modifications are possible without substantially departing from the novel matters and effects of the present invention. , will be easily understood. Accordingly, all such modifications are intended to be included within the scope of the present invention.

For example, a term described at least once in the specification or drawings together with a different, broader or synonymous term can be replaced with the different term anywhere in the specification or drawings. Also, the configuration and operation of the lithium elution method are not limited to those described in the embodiments and examples of the present invention, and various modifications are possible.

S1 adsorption step, S2 elution step, S101 crystallization step, S102 separation step, S103 calcination step, S104 water washing step 1, 2, 3 columns

Claims (6)

A method for eluting lithium adsorbed on an ion-exchange resin from lithium-containing manufacturing process wastewater of a positive electrode material for a lithium secondary battery, comprising:
A part of the plurality of ion exchange resins are connected in series to carry out an adsorption step in which waste water from the manufacturing process is passed through and brought into contact, and the remaining plurality of ion exchange resins are connected in series and an eluent is passed through. perform an elution step of contacting,
connecting the first-stage ion-exchange resin in the adsorption step to the end of the ion-exchange resin in the elution step, and transferring the first-stage ion-exchange resin to the elution step;
connecting the first-stage ion-exchange resin in the elution step to the end of the ion-exchange resin in the adsorption step, and transferring the first-stage ion-exchange resin to the adsorption step;
Repeating an adsorption step and an elution step alternately for the plurality of ion exchange resins,
When the BV (Bed volume) value of the liquid passing in the elution step reaches a predetermined value of 1.0 or more and 3.0 or less, the elution step is transferred to the adsorption step ,
The method for eluting lithium, wherein the manufacturing process waste water contains aluminum, and the pH of the manufacturing process waste water in the adsorption process is adjusted to 9 or higher . 2. The method for eluting lithium according to claim 1, wherein the SV (space velocity) of the liquid passing in the elution step is 2 hr ⁻¹ or more and 6 hr ⁻¹ or less. 3. The lithium elution method according to claim 1, wherein the SV (space velocity) of the water flow in the adsorption step is 5 hr ⁻¹ or more and 15 hr ⁻¹ or less. further comprising a washing step of washing the ion exchange resin after the elution step;
The lithium according to any one of claims 1 to 3, wherein SV (space velocity) of water passing through the ion exchange resin in the washing step is 2 hr ^-1 or more and 6 hr ^-1 or less. elution method. 5. The method for eluting lithium according to claim 1, wherein the ion exchange resin is a strongly acidic cation exchange resin. 6. The lithium elution method according to claim 1 , wherein the eluent in the elution step is an aqueous solution containing sodium sulfate.

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