JP2020011193A - Elution method of lithium - Google Patents

Abstract

To provide a method for always keeping lithium concentration after elution constant in an elution method of lithium adsorbed to an ion exchange resin from a manufacturing process wastewater including lithium of a positive electrode material for lithium secondary battery to the ion exchange resin.SOLUTION: There is provided an elution method of lithium including: conducting an adsorption process by connecting a part of a plurality of ion exchange resins in series, conducting an elution process by connecting a plurality of remaining ion exchange resins in series, connecting the ion exchange resins in the first step in the adsorption process to an end of the ion exchange resins in the elution process to move them to the elution process, connecting the ion exchange resins in the first step in the elution process to an end of the ion exchange resins in the adsorption process to move them to the adsorption process, conducting the adsorption process and the elution process on the plurality of ion exchange resins repeatedly, and conducting transition from the elution process to the adsorption process when water conduction in the adsorption process becomes 1.0 to 3.0 by BV (Bed volume) value.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for eluting lithium adsorbed on an ion-exchange resin from wastewater of a manufacturing process containing lithium as a cathode material for a lithium secondary battery.

  Lithium is widely used in industries such as ceramics and glass additives, glass flux for continuous casting of steel, grease, pharmaceuticals, and batteries. In particular, lithium-ion batteries, which are secondary batteries, have a high energy density and a high voltage, and their use as batteries for electronic devices such as notebook computers and on-board batteries for electric vehicles and hybrid vehicles has recently expanded. Demand is soaring. Accordingly, the demand for lithium hydroxide and lithium carbonate as raw materials has been rapidly increasing.

  In recent years, in order to make effective use of resources, it has been promoted to recover lithium from wastewater discharged in a manufacturing process of a positive electrode material for a lithium secondary battery (hereinafter, also referred to as “manufacturing process wastewater”).

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

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

JP 2006-57142 A JP 2012-234732 A JP 2012-030208 A

  However, the solvent extraction method of Patent Document 1 has problems that safety measures are required and that the steps are long and costly. Further, the method using electrodialysis using an ion exchange membrane disclosed 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 an ion exchange resin on which lithium is adsorbed, and lithium is recovered from the solution after the elution. However, since lithium has low selectivity and elution proceeds in a short period of time, it is difficult to recover a solution after elution with a stable lithium concentration. For this reason, there has been a problem that equipment is required for stabilizing the lithium concentration, which impairs economic efficiency. In addition, since the concentration of lithium in the solution after elution is different each time, there is a problem in production control.

  Patent Literature 3 proposes a method using a so-called merry-go-round method as a method for recovering the above-mentioned low selectivity ions using an ion exchange resin. However, Patent Literature 3 did not discuss metals with low selectivity.

  From such circumstances, there has been a demand for a method for always keeping the lithium concentration after elution constant in the elution step.

  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 a manufacturing process wastewater containing lithium of a cathode material for a lithium secondary battery, the lithium concentration after elution Provide a way to keep the constant at all times.

  The inventors can move a plurality of columns that have adsorbed lithium in the adsorption step to the elution step in a stepwise manner to elute lithium, thereby suppressing a change in lithium concentration in the solution after elution. I found that.

  One embodiment of the present invention that achieves the above-described object is a method for eluting lithium adsorbed on an ion-exchange resin from a manufacturing process wastewater containing lithium of a positive electrode material for a lithium secondary battery, comprising the steps of: Perform an adsorption step in which a part is connected in series and the manufacturing process wastewater is passed through and brought into contact, and an elution step in which the remaining plurality of ion exchange resins are connected in series and an eluent is passed through and contacted Connecting the first-stage ion exchange resin in the adsorption step to the end of the ion-exchange resin in the elution step, transferring the first-stage ion exchange resin to the elution step, and replacing the first-stage ion exchange resin in the elution step with the ion exchange resin in the adsorption step. At the end of the resin, the first-stage ion exchange resin is transferred to the adsorption step, and the adsorption step and the elution step are alternately repeated for the plurality of ion exchange resins. A transition from the elution step to the adsorption step is performed when the flow rate in the elution step reaches a predetermined value of 1.0 to 3.0 in BV (Bed volume) value. .

  In this case, since the lithium concentration in the solution after elution can be kept constant, a facility such as a stirring and mixing tank for equalizing the entire amount of the eluate is not required, which is economically advantageous. Also, production management becomes easy.

In one embodiment of the present invention, the SV of the liquid passing in the elution step (space velocity) may be less ^{2 hr -1} or more ^{6hr -1.}

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

Further, in one embodiment of the present invention, an SV (space velocity) of the water flow in the adsorption step may be not less than 5 hr ^{-1 and not} more than 15 hr ^-1 .

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

In one embodiment of the present invention, the method further includes a washing step of washing the ion-exchange resin after the elution step, wherein an SV (space velocity) of passing water to the ion-exchange resin in the washing step is 2 hr ^{−. It} may be ¹ or more and 6 hr- ¹ or less.

  In this way, the cleaning efficiency per unit time can be improved.

  In one embodiment 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, the adsorption step and the elution step can be performed more.

  In one embodiment of the present invention, the production process wastewater may contain aluminum, and the pH of the production process wastewater in the adsorption step may be 9 or more.

  In this manner, when lithium is eluted from the manufacturing process wastewater containing aluminum, a decrease in the capacity of the ion exchange resin can be suppressed.

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

  By doing so, the cation exchange resin is converted from H-type to Na-type in the elution step, so that the regeneration step can be omitted.

  According to the present invention, in a method of eluting lithium by ion exchange treatment from a manufacturing process wastewater containing lithium of a cathode material for a lithium secondary battery, the lithium concentration in the eluted solution is kept constant, and the There is no need for a stirring and mixing tank for making the whole amount uniform, and only a storage tank with a minimum capacity for dispensing is required, which is economically advantageous and can facilitate production management.

It is a flowchart which shows the outline of the manufacturing process of the positive electrode material for lithium secondary batteries. FIG. 4 is a conceptual diagram showing a flow rate of a liquid in an elution step in a single column and a transition of a lithium concentration in a liquid after elution. FIG. 1 is a flowchart showing an outline of a method for eluting lithium according to an embodiment of the present invention. FIG. 2 is a conceptual diagram showing a column operation method in a lithium elution method according to one embodiment of the present invention. FIG. 4A is a conceptual diagram showing a 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 a relationship between BV and a lithium concentration in a solution after elution in an elution step according to one embodiment of the present invention. FIG. 9 is a diagram showing a relationship between BV and a lithium concentration in a solution after elution in an elution step in a comparative example.

  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 at all, and can be implemented with appropriate modifications within the scope of the present invention.

[1. Overview of manufacturing process of positive electrode material for lithium secondary battery]
First, an outline of a manufacturing process of a positive electrode material for a lithium secondary battery will be described with reference to the drawings. FIG. 1 is a flowchart 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 process S101, a separation process S102, a firing process S103, and a water washing process S104. Specifically, the crystallization step S101 is performed by adding an aqueous solution of sodium hydroxide to a mixed aqueous solution of metal sulfates made of a raw material such as nickel, cobalt, or aluminum to coprecipitate these metal hydroxides. This is a step of obtaining a slurry containing a hydroxide. 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. 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 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 process of the positive electrode material for a lithium secondary battery, in order to wash the positive electrode material with water, wastewater containing a high concentration of lithium ions and aluminum ions is discharged.
The concentration of waste water 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 regulations on water pollution. In a factory wastewater treatment process, usually, only metals regulated by the Water Pollution Law and the regulations are treated and removed, so lithium in the production process wastewater is not removed in the wastewater treatment process but discharged into public water bodies. Lithium is a metal contained in seawater, and there is no environmental problem if it is discharged into public water bodies. However, lithium is a precious metal, and it is not preferable to discharge such production process wastewater to public water bodies from the viewpoint of resource saving. In the recycling of resources, it is required to recover and effectively utilize lithium discharged in the manufacturing process without discarding it.

  In order to recover lithium from wastewater from the manufacturing process, 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), a recovery method using an ion exchange resin, and the like. .

  However, when the solvent extraction method is used, it is necessary to treat the organic matter in the wastewater, and it is necessary to take safety measures because it is a facility that handles dangerous substances under the Fire Service Law, and multi-stage extraction Therefore, there is a problem that the process is long and the cost is high. Also, the method using electrodialysis using an ion exchange membrane requires a large-scale electrodialysis apparatus to be used for 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 is considered as an inexpensive and simple method. When a cation exchange resin is used industrially, a column method is generally used.

  In the column method, the production process wastewater is passed through a column filled with an ion exchange resin, and lithium is adsorbed on the ion exchange resin. Thereafter, the eluent is passed through the column to elute lithium from the ion exchange resin. However, lithium has a low selectivity and is easily eluted from the ion exchange resin. For this reason, the lithium concentration during the elution increases with the passage of the eluent.

  Here, FIG. 2 is a conceptual diagram showing the amount of liquid passed in the elution step and the transition of lithium concentration in the eluted liquid in the single column. As shown in FIG. 2, when eluting lithium adsorbed on the ion-exchange resin by the column method, a sharp peak rises simultaneously with the passage of the eluent in the single-stage column (single column), and then the concentration is increased with the passage of the eluent. A lower elution curve is obtained. For this reason, when partially recovering the eluted solution, the concentration of lithium will vary depending on the timing of recovery.When attempting to recover the eluted solution at a stable lithium concentration, the entire amount of the eluted solution will be reduced. It is necessary to store it in a tank and stir and mix it to make it uniform. That is, in production, the number of facilities increases, which impairs economic efficiency. Further, when only a small amount of the eluted solution needs to be shipped, the concentration differs at the timing of withdrawal, which is not desirable from the viewpoint of production management.

  However, if the lithium concentration in the eluted solution is always constant, such a stirring and mixing tank for homogenizing the entire amount of the eluted solution becomes unnecessary, and only a minimum capacity storage tank for dispensing is required. In addition, it is economically advantageous, and production management becomes easy.

  Patent Literature 3 proposes a method using a so-called merry-go-round method as a method for recovering the above-mentioned low selectivity ions using an ion exchange resin. However, Patent Literature 3 did not discuss metals with low selectivity.

  From such circumstances, there has been a demand for a method of always keeping the lithium concentration in the solution after elution constant in the elution step.

  In view of such circumstances, the inventors have conducted intensive studies, and as a result, by sequentially moving a plurality of columns that have adsorbed lithium in the adsorption step to the elution step to elute lithium, the eluent The present inventors have found that it is possible to suppress a change in lithium concentration in the medium, and have completed the present invention.

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

[2. Lithium elution method]
The method for eluting lithium according to one embodiment of the present invention is for eluting lithium from wastewater of a process for producing a positive electrode material for a lithium secondary battery, and has an adsorption step and an elution step. Hereinafter, the outline of the method of eluting lithium and each step will be described.

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

[2-2. Adsorption process]
In the adsorption step S1, the ion exchange resin is brought into contact with the wastewater from the production step to selectively adsorb lithium ions on the ion exchange resin. Here, as the ion exchange resin, a strongly acidic cation exchange resin is preferable. Since the strongly acidic cation exchange resin has high durability, the adsorption step and the elution step can be performed more. Further, when aluminum is contained in the production process wastewater, the lithium solution containing aluminum and lithium may have any metal concentration, but by adjusting the pH of the aqueous solution to 9 or more, aluminum ions can be converted to aluminate ions [ Al (OH) ₄ ] ^— . When this solution is passed through a strongly acidic cation exchange resin containing a sulfonic acid group adjusted to Na type, lithium ions as cations are adsorbed, but aluminate ions as anions are not adsorbed. Since aluminum ions have higher selectivity than lithium ions, it is difficult to selectively adsorb lithium to the strongly acidic cation exchange resin when aluminum ions are present in the wastewater of the manufacturing process. By doing so, lithium can be selectively adsorbed. At this time, if the functional group is of a hydrogen type (hereinafter, referred to as an H type), hydrogen exchanged with lithium ions is released into the aqueous solution as hydrogen ions, and the pH near the resin decreases. In this case, aluminum hydroxide having poor filterability precipitates and adheres to the resin, thereby impeding the passage of liquid and the ion exchange reaction. In the worst case, the adsorption step using a column becomes impossible. When the pH in the vicinity of the resin further decreases and becomes an acidic region where aluminum is present as a cation, it is more selectively adsorbed than lithium and separation becomes difficult. In the case of a strongly acidic cation exchange resin, a base such as the above-mentioned aluminum hydroxide is decomposed and ion-exchanged with aluminum and adsorbed, so that separation from lithium becomes difficult.

  However, by pre-adjusting to the Na type, such a decrease in pH is prevented, the production of aluminum hydroxide and aluminum ions is suppressed, and aluminum can be kept in the state of aluminate ions, so that it is adsorbed by the resin. Never.

  In addition, when the pH falls to an acidic region where aluminum is present as a cation, aluminum having 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 liquid that has passed in the adsorption step remains, the pH of the mixture decreases and the pH of the aluminum hydroxide decreases. Problems such as the occurrence of precipitation and the aluminum being in the form of cation in the acidic region and being adsorbed by the resin occur.

  The same applies to the case where the process shifts 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 more is lowered. There are problems such as precipitation of aluminum, aluminum being in a cation form in an acidic region and being adsorbed by a resin.

  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. Further, by adjusting the flow rate of the eluent, lithium in the eluent can be concentrated. For this reason, it is possible to recover lithium without using an evaporative concentration method that requires high energy costs.

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

  Sodium salts include sodium chloride and sodium sulfate. 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 for lithium secondary batteries, but it is desirable to use sodium sulfate because chlorine has the disadvantage of corroding structural materials of equipment.

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

  In the lithium adsorption method according to one embodiment of the present invention, a plurality of ion exchange resins are used. Then, as shown in FIGS. 4A and 4B, the adsorption step is performed on some of the ion exchange resins, and the elution step is performed on the other ion exchange resins.

  In the state before the column is switched, as shown in FIG. 4A, the elution step is performed in the columns 1 and 2 and the adsorption step is performed in the remaining columns 3 among the plurality of ion exchange resins 1 to 3 described above. Here, in columns 1 and 2, lithium was adsorbed in the adsorption step performed before the elution step. Then, the columns 1 and 2 are connected in series, the eluent is passed, and the column is placed in the elution step. At this time, the column 3 is placed in the adsorption step. The total number of columns and the number of columns arranged in the adsorption step or the elution step can be appropriately increased or decreased as necessary.

  After passing a certain amount of eluent, all the lithium in the ion exchange resin packed in column 1 is eluted, so that the lithium concentration in the eluate after elution of column 1 is equal to 0 g / L. Since lithium remains in the ion-exchange resin filled in No. 2, the lithium concentration in the eluted solution coming out of the elution step is slightly reduced, but can be kept high.

  Here, as shown in FIG. 4B, by separating the column 1 from the column 2 and arranging it in the adsorption step, the column 1 is shifted from the elution step to the adsorption step. The column 2 is kept in the elution step, and the column 3 is connected in series after the column 2 and is arranged at the last stage of the elution step, thereby shifting the column 3 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 water flow of manufacturing process wastewater or eluent. A valve is provided in the water pipe or the liquid pipe, and the separation and connection of the column are performed by switching the flow path of the manufacturing process drainage and the eluent by opening and closing the valve.

  Since lithium has been adsorbed on the column 3 with the full exchange capacity of lithium, the lithium concentration in the eluted solution slightly lowered in the elution step in FIG. 4 (A) is again reduced in the elution step in FIG. 4 (B). High concentrations can be returned.

  Then, 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, and the column 1 is moved to the adsorption step. The same operation is repeated such that the column 3 is connected in series after the column 3 and is arranged at the last stage of the elution step, and the adsorption step and the elution step are alternately repeated for the ion exchange resin. Then, by continuously eluting lithium while switching the column from the adsorption step to the elution step and from the elution step to the adsorption step, it is possible to always obtain an eluted liquid having a high lithium concentration.

  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 describes the case where the number of columns in the elution step is two and all the lithium is eluted from the ion-exchange resin in the column 1 arranged in the first column. 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 the elution step can be appropriately increased or decreased as necessary. In the case where two or more columns are used in the elution step, and all lithium is eluted from the ion exchange resin in the first column and a plurality of columns (hereinafter referred to as “first stage”) connected thereafter. Can perform the above-mentioned elution and adsorption steps on the plurality of columns (first-stage column) and the plurality of ion-exchange resins (first-stage ion-exchange resin).

  In the above description, the number of columns in the adsorption step is one. However, as described above, the number of columns can be appropriately increased or decreased as necessary, and a plurality of columns can be connected in series in the adsorption step. Further, the number of columns transferred from the adsorption step to the elution step is not limited to one. When a plurality of 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.

  When lithium is eluted from wastewater in the production process of a positive electrode material for a lithium secondary battery, specifically, the following method can be used to keep the lithium concentration in the solution after elution constant.

(Step 1: adsorption step)
In the adsorption step, 5 to 8 columns are arranged. Process for producing a positive electrode material for a lithium secondary battery in series from the first column. Wastewater 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 the wastewater in the production process becomes small and the amount of lithium to be treated in the adsorption process decreases, so that the treatment efficiency per unit time deteriorates. If the SV (space velocity) exceeds 15 hr ⁻¹ , the flow rate of the wastewater in the production process increases, and lithium cannot be completely absorbed by the ion exchange resin and flows out, so that the lithium adsorption efficiency is deteriorated.

  In addition, the timing of switching the column varies depending on the lithium concentration in the wastewater of the positive electrode material for a lithium secondary battery, but when the lithium ion concentration is 1 to 5 g / L, the BV (Bed Volume) is 2.5 or more, 7.5 or less is preferred. Here, BV in the present application refers to a value with respect to the volume of the ion exchange resin packed in one column. If the BV is less than 2.5, the process is switched from the adsorption process to the elution process in a state where lithium is not sufficiently adsorbed on the ion exchange resin, so that only a smaller amount of lithium than the exchange capacity can be adsorbed on the ion exchange resin. For this reason, the amount of ion exchange resin required for adsorption of lithium increases. If the BV exceeds 7.5, the flow rate of the wastewater in the production process becomes large, and lithium cannot be completely absorbed by the ion exchange resin and flows out, so that the lithium adsorption efficiency is deteriorated.

(Step 2: washing step)
In the washing step after the adsorption, two columns are arranged. The column is sequentially washed by passing water through the column that has been moved from the switching adsorption step. SV (space velocity) is, ^{2 hr -1} or more, ^{6hr -1} or less. The SV (space velocity) in the washing step may be any speed at which the wastewater from the manufacturing process of the positive electrode material for a lithium secondary battery in the column can be replaced while the column is in the washing step.

(Step 3: elution step)
In the elution step, two columns are arranged. The column is sequentially eluted by passing the eluent through the column moved from the switching washing step. Adsorption step SV (space velocity) is, ^{2 hr -1} or more, ^{6hr -1} or less. If the SV (space velocity) is less than 2 hr ⁻¹ , the amount of the eluent eluted with lithium becomes small, and the processing efficiency per unit time deteriorates. When the SV (space velocity) exceeds 6 hr ^-1 , the amount of the eluent not involved in the elution of lithium increases, and the elution efficiency of lithium deteriorates.

  The timing at which the column is switched to shift from the elution step to the adsorption step is BV (Bed Volume) of 1.0 or more and 3.0 or less. When the BV is less than 1.0, the elution step is switched to the adsorption step in a state where lithium is not sufficiently eluted, so that the lithium elution efficiency deteriorates. When the BV exceeds 3.0, the lithium concentration in the solution after elution rises to a sharp peak, and then the process is switched from the elution step to the adsorption step, so that the lithium concentration in the solution after elution is not constant.

(Step 4: washing step)
In the washing step after elution, two columns are arranged. The column is sequentially washed by passing water through the column that has been moved from the switching and elution step. As with the washing step in step 2, the flow rate may be any rate at which the eluent in the column can be replaced while the column is in the washing step. SV (space velocity) is, ^{2 hr -1} or more, ^{6hr -1} or less.

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

<Example>
The elution operation was performed using a continuous column apparatus (manufactured by Autotec Inc.). Two columns of a continuous column apparatus having a capacity of 250 mL / 20 columns were used for the elution step. The column was packed with 240 mL / piece of a 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 was passed through the two columns at a flow rate of SV4 = 16 mL / min to contact the strongly acidic cation exchange resin in the columns to elute lithium. Was. The operation of switching the column at the first stage of the elution step to the last stage of the adsorption step was repeated for each BV2. During the elution, the solution after the elution from the second column was sampled for each BV2, and the lithium concentration in the solution after the elution was measured by ICP-AES.

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

<Comparative example>
One column having a capacity of 1 L was filled with 1 L of a 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 was brought into contact with a strongly acidic cation exchange resin in the column to elute lithium. During the elution, the effluent from the column was sampled for each BV1, and the concentration of lithium in the liquid was measured after elution by ICP-AES. FIG. 6 shows the relationship between the eluent BV and the lithium concentration in the eluted liquid at this time.

  Unlike the example, it can be seen that the lithium concentration in the solution after the elution increases immediately after the start of the elution, and decreases immediately after peaking at BV2. This indicates that it is difficult to continuously obtain a solution after elution at a stable lithium concentration when elution is performed with only one column. In addition, since lithium has low selectivity and elutes rapidly, elution is carried out successively from a plurality of small-capacity columns, rather than from a single large-capacity column. It is considered that the lithium concentration in the liquid could be kept constant.

  Although each embodiment and each example of the present invention have been described in detail as described above, it is obvious to those skilled in the art that many modifications that do not substantially depart from the novel matter and effects of the present invention are possible. , Will be easy to understand. Therefore, such modified examples are all included in the scope of the present invention.

  For example, in the description or drawings, a term described at least once together with a broader or synonymous different term can be replaced with the different term in any part of the description or drawing. Further, the configuration and operation of the lithium elution method are not limited to those described in each embodiment and each example of the present invention, and various modifications can be made.

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

Claims (7)

A method for eluting lithium adsorbed on an ion-exchange resin from a manufacturing process wastewater containing lithium of a positive electrode material for a lithium secondary battery,
Perform an adsorption step of connecting a part of a plurality of ion exchange resins in series and passing the manufacturing process wastewater through and contacting, and connecting an eluent by connecting the remaining plurality of ion exchange resins in series. Perform the 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;
The first-stage ion exchange resin in the elution step is connected to the end of the ion exchange resin in the adsorption step, and the first-stage ion exchange resin is transferred to the adsorption step,
Repeating the adsorption step and the elution step alternately for the plurality of ion exchange resins,
A transition from the elution step to the adsorption step is performed when the flow rate in the elution step reaches a predetermined value of 1.0 to 3.0 in BV (Bed volume) value. To elute lithium. Elution method lithium according to claim 1, wherein the liquid passing in the elution step SV (space velocity) is not more than 2 hr ^-1 or more 6hr ^-1. The method for eluting lithium according to claim 1, wherein an SV (space velocity) of the water passing in the adsorption step is 5 hr ⁻¹ or more and 15 hr ⁻¹ or less. 4. Further comprising a washing step of washing the ion exchange resin after the elution step,
Lithium according to any one of claims 1 to 3, wherein the said in the washing step of water passing water to the ion exchange resin SV (space velocity) is not more than 2 hr ^-1 or more 6hr ^-1 Elution method.   The method for eluting lithium according to any one of claims 1 to 4, wherein the ion exchange resin is a strongly acidic cation exchange resin.   The method according to any one of claims 1 to 5, wherein the production process wastewater contains aluminum, and the pH of the production process wastewater in the adsorption process is set to 9 or more.   The method for eluting lithium according to any one of claims 1 to 6, wherein the eluent in the elution step is an aqueous solution containing sodium sulfate.

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