Lithium concentration method

Abstract

One aspect of the present invention is to provide a lithium concentration method for efficiently concentrating lithium from a low-concentration lithium aqueous solution.

Description

Lithium Concentration Method

[0001] The present invention relates to a method for concentrating lithium, and more specifically, to a method for concentrating high-purity lithium from industrial waste liquid or a leaching solution of a lithium secondary battery.

[0002] As the electric vehicle market grows rapidly, the industry for recovering valuable metals such as lithium, nickel, cobalt, and manganese from spent batteries is gradually developing. To recover valuable metals from spent batteries, black mass, which is mainly composed of components of positive and negative active materials, must first be obtained through pretreatment processes such as discharge, dismantling, heat treatment, and crushing of the spent batteries. Subsequently, a solution containing a mixture of various metals can be obtained from the black mass by using a strong acid, such as sulfuric acid, as a leachate. Then, the individual valuable metals are separated and recovered through a solvent extraction process using metal extractants such as D2EHPA, PC88A, LIX 984, and Cyanex272.

[0003] In particular, the solution obtained from the above black mass contains valuable metals such as cobalt, nickel, and lithium, which are used as main materials for the positive electrode active material of lithium-ion batteries, at extremely low concentrations.

[0004] According to one embodiment of the present invention, a lithium concentration method capable of concentrating lithium with high reaction efficiency can be provided.

[0005] The problems of the present invention are not limited to those described above. A person skilled in the art to which the present invention pertains will have no difficulty understanding additional problems of the present invention from the overall contents of this specification.

[0006] A lithium concentration method according to one embodiment of the present invention comprises: an extraction step of mixing a feed solution and an organic solvent to extract lithium; a washing step of washing the extracted organic phase using a washing agent; and a stripping step of stripping the washed organic phase; wherein the feed solution comprises lithium and sodium, the washing step utilizes three or more steps, and the washing step may satisfy the following equation 1.

[0007] [Relationship 1]

[0008] FL1 > FLf > FLa

[0009] Here, FL1 represents the flow rate of the detergent at the first stage (ml / min), FLf represents the flow rate of the detergent at the last stage (ml / min), and FLa represents the average flow rate of the detergent at the intermediate stage (ml / min) derived by the following relationship 2.

[0010] [Relationship 2]

[0011] FLa =

[0012] Here, FLk represents the flow rate (ml / min) of the cleaning agent at stage k, and n represents the total number of stages used in the cleaning step.

[0013] The organic solvent described above may be at least one of D2EHPA, PC88A, LIX 984, Aliquat 336, Cyanex272, P204, and P507.

[0014] The above-described feed solution may contain 100 to 3500 mg / L of lithium and 50 to 500 mg / L of sodium.

[0015] In the extraction step described above, the pH of the aqueous phase may be 4.0 to 5.5.

[0016] The extraction in the extraction step described above can be repeated at least twice.

[0017] In the extraction step described above, at least one of an aqueous solution of sodium hydroxide (NaOH) and lithium hydroxide (LiOH) may be used as a pH adjuster, wherein the molar concentration of the aqueous solution of lithium hydroxide (LiOH) is 3M to 5M and the concentration of the aqueous solution of sodium hydroxide (NaOH) is 10 to 30% by weight.

[0018] In the cleaning step described above, sulfuric acid at a concentration of 1 to 10 weight percent can be used as a cleaning agent.

[0019] In the aforementioned cleaning step, the pH range can be maintained at 3.0 or higher and 5.6 or lower.

[0020] The cleaning rate (%) of sodium ions derived by the following formula in the cleaning step described above may be 80% or more.

[0021] Sodium ion cleaning rate (%) = (1-(AB))×100(%)

[0022] Here, A is the concentration of sodium ions (mg / L) when the organic phase is removed before the cleaning step, and B is the concentration of sodium ions (mg / L) when the organic phase is removed after the cleaning step.

[0023] In the aforementioned removal step, sulfuric acid at a concentration of 15 to 25 weight percent can be used as a removal agent.

[0024] In the above-described removal step, the pH range can be maintained at 0.5 to 2.0.

[0025] The above-described lithium concentration method may include a washing step for washing the removed organic phase after the removal step.

[0026] In the washing step described above, at least one of distilled water and deionized water may be used as a washing agent.

[0027] The lithium concentration method of the present invention can efficiently concentrate lithium from a low-concentration lithium aqueous solution while removing sodium, which is an impurity.

[0028] Preferred embodiments of the present invention are described below. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

[0029] In addition, embodiments of the present invention are provided to more fully explain the present invention to those with average knowledge in the relevant technical field.

[0030] In describing the embodiments of the present invention, if it is determined that a detailed description of known technology related to the present invention may unnecessarily obscure the essence of the present invention, such detailed description will be omitted. Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intentions or conventions of the user or operator. Therefore, such definitions should be based on the content throughout this specification. The terms used in the detailed description are merely for describing the embodiments of the present invention and should not be limited in any way. Unless explicitly stated otherwise, expressions in the singular form include the meaning of the plural form.

[0031] In this description, expressions such as “include” or “equipped” are intended to refer to certain characteristics, numbers, steps, actions, elements, parts or combinations thereof, and should not be interpreted to exclude the existence or possibility of one or more other characteristics, numbers, steps, actions, elements, parts or combinations thereof other than those described.

[0032] Unless otherwise specifically defined in the specification of the present invention, % units mean weight %.

[0033] The present invention will be described in detail below through each embodiment or example of the invention. It should be noted that each embodiment or example described in this specification is not limited to a single embodiment or example, but may also be combined with other embodiments or examples. Accordingly, the citation of claims in the patent claims is merely an example of an embodiment, and the technical concept of the present invention should not be interpreted as being limited only to a combination with the cited claims; rather, combinations with various claims are also included within the scope of the technical concept of the present invention.

[0034] The leaching solution obtained from black mass contains lithium at extremely low concentrations along with various valuable metals. However, to produce cathode active materials from solutions containing low concentrations of lithium, such as this leaching solution, a high-concentration aqueous lithium solution is required. Therefore, to utilize lithium for various purposes, it is necessary to concentrate lithium from the low-concentration aqueous solution to a higher concentration.

[0035] And, sodium, which has chemical and physical properties similar to lithium, is inevitably present in the above lithium aqueous solution.

[0036] Accordingly, the inventors have deeply considered a method to concentrate the lithium while reducing the weight ratio of sodium relative to lithium to below a certain level.

[0037] Accordingly, the inventors derived the present invention by recognizing that the existing solvent extraction method, which is primarily used for the separation and recovery of specific valuable metals, can also be usefully applied to the lithium concentration described above.

[0038] Hereinafter, the lithium concentration method according to the present invention will be described in detail.

[0039] First, a method for recovering valuable metals according to one embodiment of the present invention can extract lithium by mixing a feed solution and an organic solvent.

[0040] As an example, the term "feed solution" used in the present invention may be a solution in which metal ions other than lithium, such as iron (Fe) and aluminum (Al), are removed through neutralization purification, solid-liquid separation, and solvent extraction after adding sulfuric acid to black powder of a lithium secondary battery to leach a solution containing valuable metals, and may be a solution containing a low concentration of lithium.

[0041] As another example, the 'feed solution' may be purified industrial waste liquid, and the purified industrial waste liquid may be prepared by the steps of: removing foreign substances through solid-liquid separation from the unrefined industrial waste liquid; and adding an aqueous acid solution to the industrial waste liquid from which foreign substances have been removed to adjust the pH to 4 to 6. The unrefined industrial waste liquid may be basic and have a pH of 11 or higher.

[0042] More specifically, the feed solution according to one embodiment of the present invention may be a solution containing 100 to 3500 mg / L of lithium.

[0043] In addition, the feed solution according to one embodiment of the present invention may contain a certain amount of sodium, which is an impurity. Although not necessarily limited thereto, the feed solution may be a solution containing 50 to 500 mg / L of sodium.

[0044] Meanwhile, the organic solvent according to one example of the present invention may be at least one of Cyanex 272, PC88A, D2EHPA, and Cyanex 301. However, since a person skilled in the art can adopt a suitable organic solvent according to the purpose and use, the organic solvent of the present invention is not limited to the organic solvents mentioned above.

[0045] In the present invention, the extraction may be performed by a solvent extraction method. More specifically, solvent extraction is a chemical process that uses two phases (liquid-liquid) to separate specific components by utilizing the property that a specific substance dissolves better in one of two immiscible solvents.

[0046] That is, the present invention can extract lithium by mixing the above-described feed solution and the above-described organic solvent, and when the layers are separated, separating only the organic phase from the separated layers.

[0047] The volume ratio of the organic phase to the aqueous phase (O / A Ratio) of such organic solvent and feed solution is not limited as it is a means that a person skilled in the art can easily adopt for the purpose, but as an example, the volume ratio of the organic phase to the aqueous phase in the extraction step may be 2.0 to 4.0. Throughout this specification, the volume ratio of the organic phase to the aqueous phase (O / A Ratio) may be a value calculated by dividing the average input amount (mL / min) of the organic solvent to be added by the average input amount (mL / min) of the aqueous solution to be added at each step.

[0048] Solvent extraction can be performed by adjusting the pH of the solution using acids and bases typically used for solvent extraction.

[0049] Specifically, in the extraction step of the present invention, the pH of the aqueous phase may be 4.0 to 5.5. If the pH is too low during extraction, there may be a problem of reduced extraction rate, and if the pH is too high during extraction, there may be a problem of a third phase with a shape different from the organic solvent and the lithium ion desorbent forming. As another example, in the extraction step, the pH of the aqueous phase may be 4.5 to 5.4 or 5.0 to 5.3.

[0050] Furthermore, the present invention may be characterized by using at least one of an aqueous solution of sodium hydroxide (NaOH) and lithium hydroxide (LiOH) as a pH regulator for adjusting the pH in the extraction step.

[0051] As a more non-limiting example, the present invention may use an aqueous solution of lithium hydroxide (LiOH) as the pH adjuster.

[0052] In this case, the present invention can reduce the amount of sodium by-products generated during the extraction step by using an aqueous lithium hydroxide (LiOH) solution instead of a conventional aqueous sodium hydroxide solution used as a pH adjuster. By doing so, the amount of sodium sulfate (Na2SO4) generated inevitably during the sodium by-product removal process is reduced, thereby eliminating the need for an additional process to remove sodium sulfate by-products and saving time and costs associated with the process.

[0053] At this time, the concentration of the above lithium hydroxide (LiOH) aqueous solution is not separately limited within a range that can be performed while adjusting the pH of the solution, but as an example, the molar concentration of the above lithium hydroxide (LiOH) aqueous solution may be 3M to 5M.

[0054] In addition, according to a lithium concentration method according to a non-limiting example of the present invention, the present invention may additionally use an aqueous sodium hydroxide (NaOH) solution together with the aqueous lithium hydroxide (LiOH) solution as a pH regulator for more efficient pH control, and the concentration of the aqueous sodium hydroxide (NaOH) solution may be 10 to 30 weight%. However, as described above, in order to achieve the purpose of sodium reduction, it is preferable that the sodium hydroxide be included in an amount of 10 volume% or less relative to the volume of the lithium hydroxide.

[0055] At this time, the extraction can be performed in multiple extraction stages, and the sodium hydroxide can be introduced into an extraction stage located near the side where the organic solvent is introduced, and the lithium hydroxide can be introduced into an extraction stage located near the side where the feed solution is introduced. In this way, by separating the introduction points of the sodium hydroxide and the lithium hydroxide, the mixing of sodium can be prevented, and at the same time, the extraction rate of lithium can be increased to improve the recovery rate.

[0056] As described above, the method for recovering valuable metals according to the present invention can extract lithium through the extraction step.

[0057] As a result, for example, the extraction rate of lithium in the extraction process can be 75.0% or higher.

[0058] The extraction rate of lithium ions can be calculated by the following formula.

[0059]

[0060] Through the above extraction step, sodium, which has chemical properties similar to lithium, can also be extracted together.

[0061] In particular, throughout this specification, the concentrations of lithium and sodium can be measured by selectively using either Nuclear Magnetic Resonance Spectroscopy (NMR Spectroscopy), which is fast and simple to analyze, or Inductively Coupled Plasma Optical Emission Spectrometer (ICP Spectroscopy), which requires relatively longer analysis time.

[0062] Furthermore, the present invention may be characterized by having a ratio of the analysis value measured through the high-frequency inductively coupled plasma (hereinafter NMR / ICP(%)) to the analysis value measured through the nuclear magnetic resonance analysis method of the above 90% or more.

[0063] Then, the method for recovering valuable metals according to one embodiment of the present invention can clean the extracted organic phase using a cleaning agent.

[0064] At this time, an aqueous acid solution may be used as the cleaning agent, and as a more specific example, sulfuric acid with a concentration of 1 to 10 weight percent may be used.

[0065] That is, the present invention can separate the co-extracted sodium into the aqueous phase by introducing and mixing the extracted organic phase with a low-concentration acidic aqueous solution.

[0066] This washing step may be performed in a pH range of 3.0 or higher and 5.6 or lower. This is because if the pH is less than 3.0, there is a possibility that lithium ions will also be separated into the aqueous phase. On the other hand, if the pH is greater than 5.6, the washing of the organic phase may not proceed smoothly. As another example, the pH in the washing step may be 3.4 to 4.7 or 3.5 to 4.5.

[0067] In this process, lithium ions in the organic solvent may inevitably be included in some of the aqueous phase. Therefore, in a solvent extraction method according to another embodiment of the present invention, the aqueous phase separated from the washing step is fed back into the extraction step together with the feed solution to increase the extraction efficiency of lithium ions.

[0068] In particular, the inventors found that the cleaning rate of sodium can be improved by appropriately controlling the flow rate at each stage during the cleaning step.

[0069] That is, the cleaning step according to one embodiment of the present invention is arranged with three or more stages, and the cleaning step can satisfy the following relationship.

[0070] [Relationship]

[0071] FL1 > FLf > FLa

[0072] Here, FL1 represents the flow rate of the detergent at the first stage (mL / min), FLf represents the flow rate of the detergent at the last stage (mL / min), and FLa represents the average flow rate of the detergent at the intermediate stage (mL / min) derived by the following relationship 2.

[0073] [Relationship 2]

[0074] FLa =

[0075] Here, FLk represents the flow rate (ml / min) of the cleaning agent at stage k, and n represents the total number of stages used in the cleaning step.

[0076] Thus, the present invention can achieve a high cleaning rate of sodium while minimizing cleaning agent consumption by increasing the flow rate of the cleaning agent in the order of the middle stage, the last stage, and the first stage.

[0077] As an example, the cleaning rate (%) of sodium in the above cleaning step may be 80% or more. In this case, the cleaning rate of sodium can be derived by the following formula.

[0078] Sodium cleaning rate (%) = (1-(AB))×100(%)

[0079] Here, A is the sodium concentration (mg / L) when the organic phase is removed before the cleaning step, and B is the sodium concentration (mg / L) when the organic phase is removed after the cleaning step.

[0080] By removing the sodium from the organic phase through the washing step described above, the organic phase can maintain a low weight ratio of sodium to lithium. As an example, the weight ratio of sodium to lithium in the organic phase may be 25% by weight or less. Since a smaller weight ratio of sodium to lithium is preferable, the present invention does not separately limit the lower limit; however, considering that sodium is inevitably present, the lower limit of the weight ratio of sodium to lithium may be 15% by weight.

[0081] To achieve the purpose of cleaning sodium as described above, a lithium concentration method according to one example of the present invention may set the O / A Ratio in the cleaning step described above to 5.0 or higher, and maintain the pH at 3.0 or higher and 5.6 or lower.

[0082] After the washing step described above, the lithium concentration method according to one embodiment of the present invention may include a step of removing the organic phase after washing using a stripping agent. This allows the lithium present in the organic phase to be separated into the aqueous phase.

[0083] As an example, the stripping agent may be a high-concentration aqueous acid solution. As a more specific example, the stripping agent may be sulfuric acid (H2SO4) at a concentration of 15 to 25 weight percent, but the stripping agent is not necessarily limited thereto within the range that can achieve the purpose described above. Furthermore, since the O / A Ratio and pH in the stripping step can be appropriately selected by a person skilled in the art within a range that can achieve the purpose of back-extracting the lithium, the present specification does not limit them separately. However, as an example, the O / A Ratio in the stripping step may be 10.0 or higher, and the pH may be maintained at 0.1 to 2.0.

[0084] Next, a lithium concentration method according to one embodiment of the present invention may optionally include a washing step for washing the removed organic phase.

[0085] Through this process, the high concentration of sulfuric acid contained in the removed organic solvent is eliminated, thereby obtaining a purified recycled organic solvent. Since the recycled organic solvent can be reused as the organic solvent in the solvent extraction step, it is possible to implement an economical process.

[0086] The washing solution used in the above washing step may be distilled water.

[0087] At this time, the ratio of the input volume of the removed organic solvent to the input volume of the washing solution (O / A Ratio) and the pH in the washing step can also be appropriately designed by a person skilled in the art, so the present invention does not describe this separately. However, as an example, the O / A Ratio in the washing step may be 3.0 or less, and the pH may be maintained at 2.5 or higher.

[0088] The lithium concentration method of the present invention described above has the advantage of being able to concentrate high concentrations of lithium through high extraction efficiency, as well as reduce sodium, which is a byproduct of solvent extraction.

[0089] The present invention will be described in detail below through examples. However, it should be noted that the examples described below are intended merely to illustrate and embody the present invention and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the matters described in the patent claims and matters reasonably inferred therefrom.

[0090] (Example)

[0091] 1. Extraction step

[0092] First, a feed solution having the components shown in Table 1 below was prepared. The units in Table 1 are mg / L, and the concentration of each ion was measured via ICP analysis. Then, to concentrate and recover lithium ions from the feed solution, a solvent extraction process was performed using a mixed-precipitation reactor with five extraction stages to obtain an extraction solution. At this time, di-2-ethylhexyl phosphate (D2EHPA) was used as the organic solvent, and the lithium ion extraction rate was tested within the extraction equilibrium pH range of 4.0 to 5.5. The average input flow rates of the organic solvent and the feed solution were 135 mL / min and 45 mL / min, respectively, and the OA ratio in the extraction stage was 3.0. Additionally, a 20 wt% NaOH aqueous solution was used as the first pH raiser and a 4 M LiOH aqueous solution was used as the second pH raiser for pH adjustment. The first pH increasing agent was introduced into the extraction unit located near the side where the organic solvent is introduced, and the second pH increasing agent was introduced into the extraction unit located near the side where the feed solution is introduced.

[0093] ICP Analysis Li Concentration (mg / L) Na Concentration (mg / L) Feed Solution 1769138

[0094] In each example, the lithium and sodium content (mg / L) in the raffinate was measured by ICP analysis after extraction was completed, and the measurement results are shown in Table 2 below along with the lithium ion extraction rate (%). The lithium ion extraction rate (%) was calculated by the following formula.

[0095]

[0096] Raffinate - ICP Analysis Li Concentration (mg / L) Na Concentration (mg / L) Li Extraction Rate (%) Inventive Example 1: 175535585% Inventive Example 2: 44591796% Inventive Example 3: 660390363% Comparative Example 1: 27492273% Comparative Example 2: 380283779% Comparative Example 3: 366283879% Comparative Example 4: 299315483%

[0097] It can be seen that most of the lithium ions in the feed solution were extracted into the organic phase.

[0098] 2. Cleaning step

[0099] Since sodium is co-extracted and present in the above extraction solution, a 5 wt% low-concentration aqueous sulfuric acid solution was added to the extraction solution to wash away the co-extracted sodium. At this time, the sodium washing rate was evaluated while adjusting the pH to between 4.0 and 5.0, and the flow rate of the aqueous sulfuric acid solution was 4.97 mL / min, with an OA ratio of 27.2. In the washing step consisting of three stages, the flow rates at each washing stage are shown in Table 3 below. In Table 3 below, FL1, FL2, FL3, and FLa represent the flow rates (mL / min) at the 1st, 2nd, and 3rd stages, respectively, and the average flow rate (mL / min) at the intermediate stage. Additionally, the sodium ion washing rate (%) in Table 3 below was derived by the following formula as described above.

[0100] Sodium ion cleaning rate (%) = (1-(AB))×100(%)

[0101] Here, A is the concentration of sodium ions (mg / L) when the organic phase is removed before the washing step, and B is the concentration of sodium ions (mg / L) when the organic phase is removed after the washing step. At this time, A and B were measured through ICP or NMR analysis.

[0102] Flow rate (mL / min) at the washing stage Satisfying Equation 1 Sodium ion concentration (mg / L) during organic phase removal Sodium ion washing rate (%) Stage 1 (FL1) Stage 2 (FL2) Stage 3 (FL3) Intermediate stage average (FLa) Washing stage Pre-washing stage After-washing stage Inventive Example 1 13.49 0.713.87 0.71O1165 10291 Inventive Example 2 12.82.072.87 2.07O166 111593 Inventive Example 3 9.59 1.43.91 1.4O165 816790 Comparative Example 19.59 3.91 1.40 3.91X2225 40282 Comparative Example 20.64 12.41 561 2.4X136 37872 Comparative Example 312.511.660.431.66X138731477 Comparative Example 42.6710.361.5610.36X176342276

[0103] Looking at Table 3 above, in the case of Inventive Examples 1 to 3, which satisfy Equation 1 presented by the present invention, a high cleaning rate of sodium ions can be secured, whereas in the case of Comparative Examples 1 to 4, which do not satisfy this, a lower cleaning rate was shown compared to Inventive Examples 1 to 3. This is because a problem occurred in which sodium ions that were not cleaned could not be sufficiently cleaned due to insufficient flow rate of FL3.

[0104] As a result, it can be seen that even if Comparative Examples 1 to 4 undergo the removal step described later, a large amount of sodium, an impurity, remains in the aqueous lithium sulfate solution obtained after removal.

[0105] 3. Removal Step

[0106] In order to recover a high-concentration aqueous lithium sulfate solution from the organic phase obtained from Invention Examples 1 to 3 above, a high-concentration aqueous sulfuric acid solution with a concentration of 18 wt% was mixed to obtain an aqueous lithium sulfate solution and a stripped organic phase. At this time, lithium was stripped while adjusting the pH to between 0.5 and 2.0.

[0107] 4. Cleaning Step

[0108] Then, after the aforementioned removal step, the removed organic phase was washed with deionized water. Through this, residual sulfuric acid remaining in the organic phase was removed, allowing the organic phase to be reused as an organic solvent.

[0109] 5. Conclusion

[0110] The lithium ion concentration of the feed solution before extraction and the lithium ion concentration of the aqueous lithium sulfate solution obtained according to the above were evaluated and are shown in Table 4 below along with the lithium concentration ratio (times). The lithium concentration ratio was derived by the following formula.

[0111]

[0112] Aqueous Lithium Sulfate Solution - NMR Analysis Lithium Concentration (mg / L) Lithium Concentration Ratio (Times) Invention Example 1 3370619.1 Invention Example 2 3235718.3 Invention Example 3 3291818.6

[0113] Referring to Table 4, it was confirmed that the lithium ion concentration of the lithium sulfate aqueous solutions of Invention Examples 1 to 3 increased by approximately 20 times compared to the feed solution. Through this, it was confirmed that according to the present invention, it is possible to effectively concentrate and recover trace amounts of lithium ions contained in the feed solution while efficiently removing sodium, which is an impurity.

Claims

1. An extraction step of mixing a feed solution and an organic solvent to extract an organic phase containing lithium; A cleaning step of cleaning the above organic phase using a cleaning agent; and It includes a removal step for removing the above organic phase, and The above feed solution contains lithium and sodium, and The above cleaning step utilizes three or more stages, and The above washing step is a lithium enrichment method satisfying the following relationship 1. [Relationship 1] FL1 > FLf > FLa Here, FL1 represents the flow rate of the detergent at the first stage (ml / min), FLf represents the flow rate of the detergent at the last stage (ml / min), and FLa represents the average flow rate of the detergent at the intermediate stage (ml / min) derived by the following relationship 2. [Relationship 2] FLa = 2. In Paragraph 1, A lithium enrichment method in which the organic solvent is at least one of D2EHPA, PC88A, LIX 984, Aliquat 336, Cyanex272, P204, and P507.

3. In Paragraph 1, A lithium concentration method in which the above feed solution contains 100 to 3500 mg / L of lithium and 50 to 500 mg / L of sodium.

4. In Paragraph 1, A lithium concentration method in which the pH of the aqueous phase in the above extraction step is 4.0 to 5.

5.

5. In Paragraph 4, A lithium concentration method comprising repeating the extraction in the above extraction step at least twice.

6. In Paragraph 1, In the above extraction step, at least one of an aqueous solution of sodium hydroxide (NaOH) and lithium hydroxide (LiOH) is used as a pH adjuster, and The molar concentration of the above lithium hydroxide (LiOH) aqueous solution is 3M to 5M, and A lithium concentration method in which the concentration of the above sodium hydroxide (NaOH) aqueous solution is 10 to 30 weight percent.

7. In Paragraph 1, A lithium concentration method using sulfuric acid at a concentration of 1 to 10 weight percent as a cleaning agent in the above cleaning step.

8. In Paragraph 1, A lithium concentration method in which the pH range is maintained at 3.0 or higher and 5.6 or lower during the washing step.

9. In Paragraph 1, A lithium concentration method in which the cleaning rate (%) of sodium ions derived by the following formula in the above cleaning step is 80% or more. Sodium ion cleaning rate (%) = (1-(AB))×100(%) Here, A is the concentration of sodium ions (mg / L) when the organic phase is removed before the cleaning step, and B is the concentration of sodium ions (mg / L) when the organic phase is removed after the cleaning step.

10. In Paragraph 1, A lithium concentration method using sulfuric acid at a concentration of 15 to 25 weight percent as a stripping agent in the above stripping step.

11. In Paragraph 1, A lithium concentration method in which the pH range is maintained at 0.5 to 2.0 during the above stripping step.

12. In Paragraph 1, A lithium concentration method comprising, after the above removal step, a washing step for washing the removed organic phase.

13. In Paragraph 12, A lithium concentration method in which at least one of distilled water and deionized water is used as a washing agent in the washing step.

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