Method for purifying lithium aqueous solution

Abstract

To provide a method, in removing metals other than lithium in a lithium aqueous solution by using a strongly acidic cation exchange resin in a lithium-ion form, for efficiently regenerating the strongly acidic cation exchange resin having captured the metals other than the lithium into a lithium-ion form.SOLUTION: A method for purifying a lithium aqueous solution includes: a purification step of removing metals other than lithium in a lithium aqueous solution containing lithium and metals other than the lithium, which is a treatment target solution, by using a strongly acidic cation exchange resin in a lithium-ion form; and a regeneration step of regenerating the strongly acidic cation exchange resin having captured the metals other than the lithium into a lithium-ion form, wherein a lithium aqueous solution having a lithium concentration of 0.1 to 1.5 eq / L is used as a regeneration agent in the regeneration step.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for purifying an aqueous lithium solution, and more particularly to a method for regenerating a strongly acidic cation exchange resin in the lithium ion form that has been used in the purification of an aqueous lithium solution. [Background technology]

[0002] Lithium is used as an additive for ceramics and glass, optical glass, and as a material for batteries (primary and secondary batteries). The main use of lithium is for ceramics and glass, but in recent years, the demand for lithium for secondary batteries has been increasing. Lithium hydroxide is mainly used as a positive electrode material for secondary batteries, but high-purity lithium hydroxide is desired to obtain high-performance batteries.

[0003] As a method for reducing the content of metals other than lithium in an aqueous solution of lithium hydroxide, Patent Document 1 describes a method for reducing or removing alkaline earth metals such as calcium and magnesium and alkali metals such as sodium and potassium in the aqueous solution of lithium hydroxide by using a strongly acidic cation exchange resin converted into a lithium ion form (hereinafter also referred to as "Li form"). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2011-31232 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, Patent Document 1 does not disclose a method for regenerating a strongly acidic cation exchange resin that has captured metals other than lithium back to the Li form. The selectivity of strongly acidic cation exchange resins for lithium (Li) is low, lower than that for the same alkali metals, sodium (Na) and potassium (K). Therefore, it is relatively easy to remove metals other than lithium, such as sodium, contained in a lithium aqueous solution using a strongly acidic cation exchange resin in the Li form. On the other hand, there is a problem in that a large amount of regenerant is required to regenerate a strongly acidic cation exchange resin that has captured metals other than lithium, such as sodium, back to the Li form.

[0006] Therefore, an object of the present invention is to provide a method for removing metals other than lithium from an aqueous lithium solution using a strongly acidic cation exchange resin in the lithium ion form, and for efficiently regenerating the strongly acidic cation exchange resin that has captured the metals other than lithium into the lithium ion form. [Means for solving the problem]

[0007] In view of the above problems, the present inventors conducted extensive research and found that by using an aqueous lithium solution having a lithium concentration in the range of 0.1 to 1.5 eq / L as a regenerant, a strongly acidic cation exchange resin that has captured metals other than lithium, such as sodium, can be efficiently regenerated into the Li form.

[0008] The present invention is a method for purifying an aqueous lithium solution, comprising: a purification step of removing metals other than lithium from an aqueous lithium solution containing lithium and metals other than lithium, which is a treatment liquid, by using a strongly acidic cation exchange resin in a lithium ion form; and a regeneration step of regenerating the strongly acidic cation exchange resin that has captured the metals other than lithium into a lithium ion form, wherein the regeneration step is characterized in that an aqueous lithium solution having a lithium concentration of 0.1 to 1.5 eq / L is used as a regenerant. Effect of the Invention

[0009] According to the present invention, when metals other than lithium are removed from an aqueous lithium solution using a strongly acidic cation exchange resin in the lithium ion form, a method can be provided in which the strongly acidic cation exchange resin that has captured the metals other than lithium is efficiently regenerated into the lithium ion form. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] <Method for purifying lithium aqueous solution> The method for purifying a lithium aqueous solution according to the present invention comprises a purification step of removing metals other than lithium from a lithium aqueous solution containing lithium and metals other than lithium, which is a treatment liquid, by using a strongly acidic cation exchange resin in a lithium ion form, and a regeneration step of regenerating the strongly acidic cation exchange resin that has captured the metals other than lithium into a lithium ion form. The regeneration step is characterized in that a lithium aqueous solution having a lithium concentration of 0.1 to 1.5 eq / L is used as a regenerant. The present invention will be described in detail below.

[0011] [Refining process] In the purification step, metals other than lithium in the lithium aqueous solution, which is the liquid to be treated, are reduced and removed using a strongly acidic cation exchange resin in the lithium ion form, to obtain a purified treated liquid.

[0012] (Liquid to be treated) The lithium aqueous solution containing lithium and metals other than lithium as the liquid to be treated is not particularly limited, but examples thereof include lithium hydroxide aqueous solution, lithium chloride aqueous solution, lithium carbonate aqueous solution, and lithium sulfate aqueous solution, which contain metals other than lithium as impurities. Among these, from the viewpoint of demand, lithium hydroxide aqueous solution used as a raw material for secondary battery positive electrode material is preferred. In addition, the liquid to be treated is preferably the same type of lithium aqueous solution as the regenerant described later.

[0013] (metal) Metals other than lithium contained as impurities in the lithium aqueous solution to be treated include alkali metals other than lithium (sodium, potassium, etc.) and alkaline earth metals (magnesium, calcium, etc.). Among these, the method for purifying a lithium aqueous solution according to the present invention is particularly preferably used for removing sodium and potassium from the lithium aqueous solution. The lithium aqueous solution to be treated contains, for example, 50 to 1000 mg / L of metals other than lithium.

[0014] (Strongly acidic cation exchange resin) In the present invention, in order to remove metals other than lithium from a lithium aqueous solution, a Li-type strong acid cation exchange resin is used from the viewpoint of metal removal performance. The type of strong acid cation exchange resin is not limited, and any of those in which the structure of the base material is gel type, porous type, or macroporous type can be used. However, from the viewpoint of total exchange capacity, a gel-type strong acid cation exchange resin is preferred. The harmonic mean diameter of the strong acid cation exchange resin is not particularly limited, and can be, for example, 500 to 800 μm. In addition, the crosslinking degree of the strong acid cation exchange resin is not particularly limited, but from the viewpoint of regeneration efficiency, it is preferable that the crosslinking degree is 8 to 12%. If the crosslinking degree is 8% or more, the elution of organic matter derived from the resin can be suppressed. In addition, if the crosslinking degree is 12% or less, the decrease in regeneration efficiency can be suppressed.

[0015] As the Li-form strong acid cation exchange resin, for example, a hydrogen ion form (hereinafter also referred to as "H-form") strong acid cation exchange resin converted to the Li-form by a known method can be used. As the H-form strong acid cation exchange resin, for example, Amberlite (registered trademark) HPR1024 H, HPR1200 H, HPR1006NNC can be used. H (all trade names, manufactured by DuPont), Amberjet (registered trademark) 1020, 1024, 1060 (all trade names, manufactured by DuPont), Diaion (registered trademark) SK104H, SK1BH, PK208LH, PK212LH, PK216H, PK216LH, PK228LH, UBK08H, UBK10H (all trade names, manufactured by Mitsubishi Chemical Corporation), Orlight (registered trademark) DS-1, DS-4 (all trade names, manufactured by Organo Corporation), C100, C100E, C120E, C100x10, C100x12, C150, C160, SGC650 (all trade names, manufactured by Purolite Co., Ltd.), Lewatit (registered trademark) Monoplus S108H, (all trade names, manufactured by Lanxess), and the like, but are not limited thereto.

[0016] In the purification step, the liquid to be treated is passed through a container filled with Li-type strongly acidic cation exchange resin, so that metals other than lithium in the liquid to be treated can be captured by the strongly acidic cation exchange resin. As the liquid passing method, a conventionally known method can be appropriately adopted. Here, in the present invention, the container means all those that can be filled with ion exchange resin such as a "tower" or "tank" such as an adsorption tower and can purify the liquid to be treated, and is not limited thereto. Specifically, for example, a method in which a strongly acidic cation exchange resin is filled in a column having an inlet at the top and an outlet at the bottom, and the liquid to be treated is continuously passed through the column using a pump as appropriate (column method), or a method in which the liquid to be treated is passed through a container filled with a strongly acidic cation exchange resin, contacted for an appropriate time, and the supernatant liquid is removed (batch method) can be mentioned. When the column method is adopted, the size of the column may be appropriately determined according to the performance and amount of the ion exchange resin to be used. From the viewpoint of efficient purification, for example, it is preferable that the ratio (L / D) of the column height (L) to the diameter (D) is 0.5 to 70, and the space velocity (SV, liquid passing rate) of the liquid to be treated is 0.1 to 50 (L / L-resin / hour). SV (space velocity) means the liquid passing flow rate per unit time and unit resin volume. The liquid passing rate, which indicates the flow rate multiple of the liquid to be treated relative to the amount of resin, may be appropriately adjusted, but may be, for example, 1 to 100 (L / L-resin). As the liquid to be treated passes through the container, a treated liquid in which the content of metals other than lithium has been reduced or removed flows out from one end of the container, and the treated liquid is collected in a storage tank or the like. After passing through the liquid to be treated, the liquid to be treated is pushed out and washed out using pure water or ultrapure water as necessary until the column outlet water becomes neutral or has a low conductivity.

[0017] [Regeneration process] The regeneration step is a step of regenerating the strongly acidic cation exchange resin that has captured metals other than lithium in the purification step into the Li form using a regenerant.

[0018] (Regenerator) In the regeneration step according to the present invention, from the viewpoint of regeneration efficiency, a lithium aqueous solution having a lithium concentration of 0.1 to 1.5 eq / L is used as the regenerant. From the viewpoint of regeneration efficiency, the lithium concentration is preferably 0.1 to 1.0 eq / L, more preferably 0.1 to 0.5 eq / L, and particularly preferably 0.1 to 0.3 eq / L. If the lithium concentration is lower than 0.1 eq / L, there is a concern that the amount of lithium aqueous solution required for regeneration will be very large. In addition, the reason why the regeneration efficiency decreases when the lithium concentration is outside the above range is not clear, but it is presumed that the shrinkage of the resin due to the increase in the dissociation degree of lithium ions and the osmotic pressure is related to this. In addition, the concentration of metals such as lithium in the lithium aqueous solution can be analyzed using an atomic absorption spectrophotometer.

[0019] Examples of the lithium aqueous solution used as the regenerant include a lithium hydroxide aqueous solution, a lithium chloride aqueous solution, a lithium carbonate aqueous solution, and a lithium sulfate aqueous solution. The regenerant is preferably a lithium aqueous solution of the same type as the liquid to be treated. That is, when the liquid to be treated is a lithium hydroxide aqueous solution, the regenerant is preferably a lithium hydroxide aqueous solution.

[0020] The lithium aqueous solution used as the regenerant is preferably a high-purity lithium aqueous solution from the viewpoint of suppressing contamination during regeneration. Specifically, for example, a lithium aqueous solution having a sodium concentration of 1 mg / L or less is preferably used.

[0021] In the regeneration step, regeneration is performed by passing the regenerant through a container filled with a strongly acidic cation exchange resin that has captured metals other than lithium. Examples of the method of passing the regenerant include the same method as described in the purification step. The container used in the purification step can be used as it is as the container filled with the strongly acidic cation exchange resin that has captured metals other than lithium. When a column method is adopted, the flow rate, which represents the flow rate of the regenerant relative to the amount of resin, can be, for example, 0.5 to 150 (L / L-resin). The flow rate of the regenerant can be appropriately adjusted depending on the lithium concentration of the regenerant, regeneration efficiency, and the like. The spatial velocity (SV, flow rate) of the regenerant can be, for example, 1 to 50 (L / L-resin / hour). The flow rate can be appropriately adjusted depending on the flow rate of the regenerant, and the like. The amount of lithium contained in the regenerant per unit volume of resin (regeneration level) can be appropriately adjusted, and can be, for example, 2 to 10 eq / L-resin. After passing the regenerant through the column, the regenerant is pushed out and washed away, if necessary, with pure water or ultrapure water until the column outlet water becomes neutral or has a low conductivity.

[0022] The strongly acidic cation exchange resin regenerated into the Li form in the above manner can be reused as the strongly acidic cation exchange resin in the Li form to be used in the purification step.

[0023] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. EXAMPLES

[0024] [Example 1] (purification process) An acrylic column with an inner diameter of 1.9 cm and a height of 100 cm was packed with 130 mL of a Li-form converted product of Amberlite HPR1024H (trade name, manufactured by DuPont, harmonic mean diameter: 0.60-0.70 mm, degree of cross-linking: 12%), which is a strongly acidic cation exchange resin. A sodium-containing lithium hydroxide aqueous solution (lithium concentration: 11500 mg / L, sodium concentration: 60 mg / L, pH: 12) was passed through the column as the liquid to be treated under the following conditions to obtain a treated liquid. <Liquid passing (purification)> Liquid passing amount (double volume): 1300mL (10L / L-resin) Liquid flow rate (speed): 650mL / hr (SV=5L / L-resin / hr) <Extrusion after passing liquid> Pass pure water through the resin at 1L / L at the same speed as when passing liquid (purification)

[0025] (Regeneration process) Next, a high-purity lithium hydroxide aqueous solution (sodium concentration: less than 1 mg / L) with a lithium concentration of 0.1 eq / L was passed through the strongly acidic cation exchange resin after trapping sodium in the column under the following conditions as a regenerant. <Liquid passage (regeneration)> Liquid passing amount (double volume): 3900mL (30L / L-resin) Regeneration level: 3.0eq / L-resin Liquid flow rate: 1950mL / hr (15L / L-resin / hr) <Extrusion after recycling> Pass pure water through the resin at 1L / L at the same speed as when passing liquid (regeneration)

[0026] (analysis) The sodium concentration of the treated liquid after the purification process and the regenerated / extrusion waste liquid discharged from the column outlet in the regeneration process was analyzed using an atomic absorption spectrophotometer (product name: ZA3300, Hitachi High-Tech Science Corporation). As a result, the amount of sodium captured by the liquid passing (purification) in the purification process was 29.9 mg, that is, 230 mg / L-resin (sodium removal rate: 38%). In addition, the sodium desorption rate in the regeneration process was 64%. The sodium desorption rate is calculated using the following formula. Sodium desorption rate (%) = (sodium content in regenerated / extrusion waste liquid / amount of sodium captured by passing liquid (purification) in the purification process) x 100

[0027] [Examples 2 and 3 and Comparative Examples 1 and 2] The purification step and the regeneration step were carried out in the same manner as in Example 1, except that the regeneration conditions were changed as shown in Table 1. The sodium concentration of the high-purity lithium hydroxide aqueous solution used as the regenerant was less than 1 mg / L in each case. The amount of the regenerant passing through was adjusted so that the regeneration level was the same as in Example 1. The flow rate of the regenerant differs for each example, but this was appropriately adjusted in consideration of the time required for regeneration, and does not affect the regeneration efficiency. The sodium desorption rate was calculated in the same manner as in Example 1. The results are shown in Table 1. The amount of sodium captured by passing the liquid (purification) in the purification step was 230 mg / L-resin (sodium removal rate: 38%) in all Examples and Comparative Examples, similar to Example 1.

[0028] [Table 1]

[0029] As shown in Table 1, in Examples 1 to 3, in which a regenerant with a lithium concentration of 0.1 to 1.5 eq / L was used, a sodium desorption rate of 50% or more was obtained. On the other hand, in Comparative Examples 1 and 2, in which a regenerant with a lithium concentration outside the above range was used, the sodium desorption rate was less than 50%. Note that, when the lithium concentration of the regenerant is very low, as in Comparative Example 1, there is a concern that the amount of liquid passed through the regenerant increases and a large amount of water is required for regeneration.

Claims

1. A method for purifying an aqueous lithium solution, comprising: a purification step of removing metals other than lithium from an aqueous lithium solution containing lithium and metals other than lithium as a treatment liquid by using a strongly acidic cation exchange resin in a lithium ion form; and a regeneration step of regenerating the strongly acidic cation exchange resin that has captured the metals other than lithium into a lithium ion form, wherein the regeneration step uses an aqueous lithium solution having a lithium concentration of 0.1 to 1.5 eq / L as a regenerant.

2. 2. The method for purifying an aqueous lithium solution according to claim 1, wherein the lithium concentration of the regenerant is 0.1 to 0.3 eq / L.

3. 3. The method for purifying an aqueous lithium solution according to claim 1, wherein the regenerant is an aqueous lithium hydroxide solution.

4. The method for purifying an aqueous lithium solution according to any one of claims 1 to 3, wherein the liquid to be treated is an aqueous lithium hydroxide solution.

5. The method for purifying a lithium aqueous solution according to any one of claims 1 to 4, wherein the crosslinking degree of the strongly acidic cation exchange resin is 8 to 12%.

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