Lithium concentration method using solvent extraction

Abstract

One aspect of the present invention is to provide a lithium concentration method in which lithium can be concentrated in a short time with high reaction efficiency. More particularly, one aspect of the present invention is to provide a lithium concentration method capable of increasing the production of a lithium concentrate by concentrating lithium in a short time with high reaction efficiency using a centrifugal reactor.

Description

Lithium concentration method using solvent extraction

[0001] The present invention relates to a lithium concentration method, and more specifically, to a lithium concentration method using a solvent extraction method.

[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 in a short time 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 the steps of: pre-treating a solvent extractant; introducing a feed solution into the pre-treated solvent extractant to extract an organic phase; washing the organic phase using a cleaning agent; removing the organic phase using a stripping agent; and washing the organic phase obtained from the removal step. The extraction step is performed by extraction through a liquid-liquid reaction using a centrifugal reactor, and the feed solution may contain lithium.

[0007] The above-described solvent extractant may be a mixed solvent extractant comprising, in volume %, 10 to 20% of di-2-ethylhexyl phosphate (D2EHPA), 10% or less (including 0%) of tributyl phosphate (TBP), and the remainder being kerosene.

[0008] The above-described pretreatment may be a step of saponifying with sodium hydroxide (NaOH) at a saponification rate of 20% or more and 60% or less.

[0009] The rotational speed of the centrifugal reactor described above may be 30 to 33 Hz.

[0010] The above-described solvent extractant is a mixed solvent extractant containing, in volume %, 10 to 20% of di-2-ethylhexyl phosphate (D2EHPA) and 10% or less (including 0%) of tributyl phosphate (TBP), with the remainder being kerosene, and the rotation speed of the above-described centrifugal reactor is 30 to 33 Hz, and the degree of phase separation (%) derived by the following equation may be 92.0% or higher.

[0011] [Relationship] Phase Separation (%) = {C + A×exp[-0.5×((f - μ) / σ)²]}×100(%)

[0012] In the relationship described above, C is the basic separation constant, A is the maximum increase constant, f is the rotational speed (Hz) of the centrifugal reactor described above, μ is the center value in the Gaussian distribution of the phase separation and corresponds to the optimal rotational speed (Hz), and σ corresponds to the standard deviation (Hz).

[0013] In the above-described relationship, C can be 0.106, A can be 0.864, μ can be 31.5, and σ can be 9.82.

[0014] The above-described solvent extractant may be a mixed solvent extractant comprising, in volume %, 15% di-2-ethylhexyl phosphate (D2EHPA) and 5% tributyl phosphate (TBP), with the remainder being kerosene.

[0015] The pH in the extraction step described above may be 5.0 or higher and 6.5 or lower.

[0016] The volume ratio of the organic phase to the aqueous phase (O / A Ratio) in the extraction step described above may be 0.1 to 10.

[0017] The pH in the aforementioned cleaning step may be 3.0 or higher and 5.6 or lower.

[0018] The process can be characterized by continuously introducing the aqueous phase separated in the aforementioned washing step back into the aforementioned extraction step together with the aforementioned feed solution.

[0019] In the removal step described above, the removal agent may be sulfuric acid at a concentration of 15 to 25 weight percent.

[0020] In the removal step described above, the pH may be 0.5 or higher and 1.0 or lower.

[0021] The lithium concentration method of the present invention can efficiently concentrate lithium from a low-concentration lithium aqueous solution within a short period of time, and thereby the present invention can also increase the production volume of the lithium concentrate.

[0022] Thus, the present invention can reduce the number of facilities required for the lithium concentration method, thereby reducing the land and operating costs involved in the process.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] Unless otherwise specifically defined in the specification of the present invention, % units mean weight %.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] In addition, the inventors have discovered that lithium can be concentrated more efficiently from a low-concentration lithium aqueous solution when using a centrifugal extractor.

[0032] That is, compared to the mixed sedimentation type reactor used in conventional solvent extraction reactions, the centrifugal extractor has a higher reaction efficiency and a faster reaction rate, so when using the lithium concentration method of the present invention, lithium can be concentrated in a short time with high reaction efficiency.

[0033] A lithium concentration method according to one embodiment of the present invention may include the steps of: pre-treating a solvent extractant; introducing a feed solution into the pre-treated solvent extractant to extract an organic phase; washing the organic phase using a cleaning agent; removing the organic phase using a stripping agent; and washing the organic phase obtained from the removal step.

[0034] Each step is explained in detail below.

[0035] Pretreatment step of solvent extractant

[0036] The solvent extractant according to one example of the present invention may be a carboxylic acid-based solvent, an organic phosphate-based solvent, a solvent diluent, or a mixture thereof. However, since a person skilled in the art can select a suitable solvent extractant according to the purpose and use, the solvent extractant of the present invention is not limited to the aforementioned solvent extractants.

[0037] In particular, the solvent extractant according to one example of the present invention may be a mixed solvent extractant. As such, the present invention has experimentally found that by using a mixed solvent extractant as a solvent extractant, the target metal lithium can be removed with a higher removal rate in the removal step described later. As an example, the solvent extractant may be a mixed solvent extractant containing, in volume %, 10 to 20% of di-2-ethylhexyl phosphate (D2EHPA) and 10% or less (including 0%) of tributyl phosphate (TBP), with the remainder being kerosene. In this case, as an example, the kerosene may be hydrodesulfurized kerosene. As a more preferred example, the solvent extractant may be a mixed solvent extractant containing, in volume %, 15% of di-2-ethylhexyl phosphate (D2EHPA) and 5% of tributyl phosphate (TBP), with the remainder being kerosene.

[0038] Meanwhile, the present invention can pre-treat the solvent extractant used during solvent extraction to ensure that extraction is carried out smoothly in the subsequent extraction step.

[0039] To this end, a lithium concentration method according to one embodiment of the present invention may include a saponification step as a pretreatment step for the solvent extractant. The pretreatment agent that can be used in the saponification step is not significantly limited as long as it is an alkaline solution, but as an example, sodium hydroxide (NaOH) may be used.

[0040] That is, the present invention may perform a saponification step to prevent the solvent's reactivity with lithium ions from decreasing as the pH of the solution increases during extraction. To this end, sodium hydroxide (NaOH) may be added as a pretreatment agent. This allows for the exchange of sodium ions (Na+) from sodium hydroxide with hydrogen ions (H+) from the organic solvent, thereby reducing changes in the pH of the solution depending on the degree of the extraction reaction. However, as described above, the sodium hydroxide is merely an example of a pretreatment agent and is not necessarily limited thereto.

[0041] To achieve the above-mentioned purpose, the saponification step can be performed using sodium hydroxide (NaOH) to have a saponification rate of 20% or more and 60% or less.

[0042] If the saponification rate is less than 20%, pH stability may not be sufficient. On the other hand, if the saponification rate exceeds 60%, the physical properties of the solvent extractant may change, which may cause problems with process efficiency.

[0043] In order to achieve the saponification rate described above, the volume ratio of the organic phase to the aqueous phase (O / A Ratio) of the present invention can be set to 70.0 to 80.0.

[0044] extraction step

[0045] A lithium concentration method according to one embodiment of the present invention can separate the organic phase by introducing a feed solution into a pretreated solvent extractant after pretreatment.

[0046] 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.

[0047] 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 from the unrefined industrial waste liquid through solid-liquid separation; 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.

[0048] More specifically, the feed solution according to one embodiment of the present invention may be a solution containing 0.1 to 2.5 g / mL of lithium.

[0049] The present invention allows for solvent extraction by introducing a feed solution into the aforementioned pretreated solvent extractant, thereby enabling the acquisition of an organic phase containing lithium.

[0050] More specifically, solvent extraction is a chemical process that uses two phases (liquid-liquid) to separate specific components by utilizing the property that a particular substance dissolves better in one of two immiscible solvents.

[0051] 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.

[0052] As described above, the present invention may use a centrifugal reactor instead of a mixed sedimentation reactor, which is mainly used in conventional solvent extraction, for such solvent extraction.

[0053] Thus, unlike conventional methods, the present invention can reduce the time required for sedimentation, thereby improving the reaction speed. As a result, the flow rate of the feed solution that can be processed in the same amount of time can be increased by about 2 to 3 times compared to the case where a mixed sedimentation type reactor is used. Thus, the present invention has the advantage of being able to concentrate lithium with high extraction efficiency in a short period of time.

[0054] In addition, in this case, since the number of equipment required for the extraction process can be reduced or the installation area can be minimized, economically advantageous effects can also be obtained.

[0055] In addition, unlike conventional centrifugal reactors which are mainly used in the solid-liquid separation stage, the solvent extraction according to one embodiment of the present invention is significant in that it is performed through extraction via a liquid-liquid reaction using a centrifugal reactor.

[0056] As a non-limiting example, the rotational speed of the centrifugal reactor may be 30 to 33 Hz. That is, it has been found that a lithium concentration method according to one embodiment of the present invention can achieve a high lithium extraction rate by setting the rotational speed to 30 Hz or higher. If the rotational speed is less than 30 Hz, the suction force due to rotation is weak, making process operation difficult. On the other hand, if the rotational speed exceeds 33 Hz, problems may arise where oil-water separation is not properly performed; therefore, the present invention may set the upper limit of the rotational speed to 33 Hz. As another example, the rotational speed may be 30 to 31 Hz.

[0057] In particular, the present invention can secure a high degree of phase separation (%) by using the aforementioned mixed solvent extractant and controlling the rotation speed of the centrifugal reactor to an appropriate level.

[0058] In this context, phase separation refers to a measure expressed as a volume ratio indicating the degree to which an organic phase is mixed into an aqueous phase or an aqueous phase into an organic phase.

[0059] As such, the present invention can secure a phase separation degree of 92.0% or higher by applying a rotation speed suitable for the solvent extractant described above. By doing so, the present invention can prevent the reduction of the lithium extraction rate caused by the organic phase being mixed into the aqueous phase or the aqueous phase being mixed into the organic phase.

[0060] More specifically, according to a lithium concentration method according to one example of the present invention, the solvent extractant is a mixed solvent extractant comprising, in volume %, 10 to 20% of di-2-ethylhexyl phosphate (D2EHPA) and 10% or less (including 0%) of tributyl phosphate (TBP), and the remainder being kerosene, the rotational speed of the centrifugal reactor is 30 to 33 Hz, and the degree of phase separation (%) derived by the following equation may be 92.0% or higher.

[0061] [Relationship] Phase Separation (%) = {C + A×exp[-0.5×((f - μ) / σ)²]}×100(%)

[0062] In the above relationship, C is the basic separation constant, A is the maximum increase constant, f is the rotational speed (Hz) of the centrifugal reactor, μ is the center value in the Gaussian distribution of the phase separation and corresponds to the optimal rotational speed (Hz), and σ corresponds to the standard deviation (Hz).

[0063] If the degree of phase separation derived by the above relationship is less than 92.0%, the lithium extraction rate may decrease due to mixing between the organic phase and the aqueous phase; therefore, the present invention may make the degree of phase separation derived by the above relationship 92.0% or higher. As another example, the degree of phase separation may be 95.0% or higher.

[0064] In particular, the constants C, A, μ, and σ applied in the above-described relationship can be derived using curve fitting through experimental data. However, as an example, for the above-described solvent extractant and the rotation speed of the above-described centrifugal reactor, C may be 0.106, A may be 0.864, μ may be 31.5, and σ may be 9.82.

[0065] According to one embodiment of the present invention, the volume ratio of the organic phase to the aqueous phase (O / A Ratio) in the extraction step may be 0.1 to 10. In one example of the present invention, if the ratio of the organic phase to the aqueous phase is less than 0.1, the aqueous phase may be mixed into the organic phase, and if the ratio of the organic phase to the aqueous phase exceeds 10, a problem may arise where the organic phase is mixed into the aqueous phase; therefore, in one embodiment of the present invention, the upper limit of the ratio of the organic phase to the aqueous phase may be 10. In another embodiment, the ratio of the organic phase to the aqueous phase may be 0.4 to 5.0, and in yet another embodiment, it may be 3.0 to 4.0.

[0066] For the volume ratio of the organic phase and the aqueous phase described above, according to a lithium concentration method according to a non-limiting example of the present invention, the flow rate of the feed solution may be 160 mL / min or more and 220 mL / min or less.

[0067] As an example, the pH in the extraction step above may be 5.0 or higher and 6.5 or lower.

[0068] If the pH is too low during extraction, there may be a problem with the lithium extraction rate decreasing, and if the pH is too high during extraction, there may be a problem with the formation of a third phase with a shape different from the solvent extractant and the lithium ion extract. As another example, the pH of the solution in the above extraction step may be 5.5 to 6.0.

[0069] Cleaning step

[0070] A lithium concentration method according to one embodiment of the present invention may clean the extracted organic phase using a cleaning agent. At this time, an aqueous acid solution may be used as the cleaning agent, and as a more specific example, 1 to 10 weight percent of sulfuric acid may be used.

[0071] That is, the present invention can separate impurity ions, such as sodium, co-extracted by introducing and mixing the extracted organic phase with a low-concentration acidic aqueous solution into the aqueous phase.

[0072] If sulfuric acid at a concentration of 1 to 10 weight percent is used as the cleaning agent, the volume ratio of the organic phase to the aqueous phase (O / A Ratio) in the cleaning step may be 3.0 to 13.0.

[0073] In addition, to satisfy the volume ratio of the organic phase and the aqueous phase described above, the lithium concentration method according to a non-limiting example of the present invention may have the input flow rate of the 1 to 10 weight percent sulfuric acid set to 40 mL / min or more and 90 mL / min or less.

[0074] At this time, the 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.

[0075] In this process, lithium ions within the solvent extractant may inevitably be included in some of the aqueous phase. Therefore, in a lithium concentration 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.

[0076] Removal step

[0077] According to one embodiment of the present invention, the present invention may include a step of removing the organic phase after cleaning using a stripping agent. This allows lithium present in the organic phase to be separated into the aqueous phase. As an example, the stripping agent may be an inorganic acid comprising at least one of sulfuric acid (H2SO4), nitric acid (HNO3), and hydrochloric acid (HCl), but the stripping agent is not necessarily limited thereto within the scope of achieving the above-described purpose. Furthermore, when extracting lithium in the form of lithium sulfate, it may be more preferable for the stripping agent to be sulfuric acid (H2SO4) with a concentration of 15 to 25 weight percent.

[0078] Since the pH in the above stripping step can be appropriately selected by a person skilled in the art within a range that can achieve the purpose of back-extracting lithium, the present specification does not limit it separately, but as an example, the pH in the stripping step may be 0.5 or higher and 1.0 or lower.

[0079] If sulfuric acid at a concentration of 15 to 25 weight percent is used as the stripping agent, according to a lithium concentration method according to a non-limiting example of the present invention, the volume ratio of the organic phase to the aqueous phase (O / A Ratio) in the stripping step may be 5.0 to 15.0.

[0080] For the purpose of achieving this, the present invention may set the flow rate of the sulfuric acid to 40 mL / min or more and 60 mL / min or less.

[0081] Washing step

[0082] According to a lithium concentration method according to one embodiment of the present invention, the present invention may include a step of washing the obtained organic phase.

[0083] Through this, residual sulfuric acid remaining in the organic phase can be removed, thereby increasing the purity of the organic phase so that it can be reused as a solvent extractant.

[0084] The solvent used as a cleaning agent in the normal washing step may be at least one of distilled water and deionized water. In this case, when deionized water is used as the cleaning agent, the volume ratio of the organic phase to the aqueous phase (O / A Ratio) in the washing step may be 5.0 to 15.0.

[0085] For the purpose of achieving this, the present invention may set the flow rate of the deionized water to 40 mL / min or more and 80 mL / min or less.

[0086] The lithium concentration method of the present invention described above not only enables the concentration of high-concentration lithium through high extraction efficiency, but also has a reaction rate faster than that of solvent extraction using a conventional mixed-precipitation type reactor. Accordingly, the present invention has the advantage of reducing the equipment required for the solvent extraction process, thereby reducing the installation area and operating costs of the equipment.

[0087] 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.

[0088] (Example 1)

[0089] 1. Preprocessing step

[0090] First, a mixed solvent extractant was prepared comprising 15 volume% of di-2-ethylhexyl phosphate (D2EHPA) and 5 volume% of tributyl phosphate (TBP) based on the total volume, with the remainder being desulfurized kerosene (ISD159). Next, sodium hydroxide (NaOH) having a concentration of 40 weight% was mixed with the mixed solvent extractant to saponify the mixed solvent extractant. At this time, the average flow rate of the mixed solvent extractant during saponification was 666 mL / min, and the average flow rate of sodium hydroxide (NaOH) was 8.8 mL / min, so the O / A ratio, which is the volume ratio of the organic phase to the aqueous phase, was 75.7. Through the steps described above, the mixed solvent extractant could be saponified with a saponification rate of 20% or more and 60% or less.

[0091] 2. Extraction Step

[0092] Next, a feed solution was prepared. The Li concentration in the feed solution measured by ICP analysis was 1000 mg / L.

[0093] Then, each example performed solvent extraction by mixing the above-described feed solution with a saponified mixed solvent extractant according to the conditions described below.

[0094] (1) Example of invention

[0095] In the invention example, solvent extraction was performed using a centrifugal reactor with five extraction stages, and the pH during solvent extraction was maintained at 5.0 to 6.5. In addition, the flow rate of the feed solution was 200 mL / min, and the O / A ratio during the extraction stage was 3.3. Furthermore, the rotation speed of the centrifugal reactor was 30 to 33 Hz.

[0096] The concentrations of Li and Na in the raffinate after extraction were measured using ICP analysis, and the results, along with the lithium extraction rate (%), are shown in Table 1 below.

[0097] The lithium extraction rate (%) was calculated by the following formula.

[0098]

[0099] ICP (mg / L)LiNaLi Extraction Rate (%) Invention Example 1 <165 48 100% Invention Example 2 157 98 99.9% Invention Example 3 258 34 99.8% Invention Example 4 <159 10 100%

[0100] (2) Comparative example

[0101] In the comparative example, lithium was extracted using a mixed sedimentation reactor with 7 extraction stages. As with the inventive example, the pH during extraction was maintained at 5.0 to 6.5, and the O / A ratio during the extraction stage was 3.

[0102] The concentrations of Li and Na in the raffinate after extraction were measured using ICP analysis, and the results are shown in Table 2 below.

[0103] ICP (mg / L)LiNaLi Extraction Rate (%) Comparative Example 111N / A 99.2% Comparative Example 28N / A 99.5%

[0104] (3) Sintering

[0105] Looking at the experimental data described above, it can be seen that Invention Examples 1 to 4 enabled the extraction of lithium at a higher extraction rate even when operating the extraction process with fewer stages compared to Comparative Examples 1 and 2.

[0106] Furthermore, the inventive example was composed of fewer extraction stages compared to the comparative example, and by using a centrifugal reactor, the extraction time could be reduced by shortening the time required for sedimentation. In addition, the present invention was able to improve the throughput of the feed solution that can be processed per hour.

[0107] 3. Cleaning step

[0108] For the above-described example of the invention, the organic phase obtained after the extraction was completed was washed using a 5 wt% aqueous sulfuric acid solution. The flow rate of the aqueous sulfuric acid solution during the washing step was 75 mL / min, and the O / A ratio was 8.9. In addition, the pH at this time was maintained at 3.0 to 5.6.

[0109] 4. Removal Step

[0110] In addition, the organic phase obtained after the washing step in the invention example was mixed with an aqueous sulfuric acid solution of 18.75 wt% to remove lithium ions from the organic phase into the aqueous phase. The flow rate of the aqueous sulfuric acid solution in that step was 50 mL / min, and the O / A ratio was 13.3. Also, the pH at this time was maintained at 0.5 to 1.0.

[0111] In addition, the concentrations of Li and Na were measured using ICP analysis on the aqueous phase obtained after the stripping described above in the invention example. The lithium enrichment rate (times) was calculated along with the measured results and is shown in Table 3 below.

[0112] The lithium enrichment ratio (times) can be expressed by the following formula.

[0113]

[0114] ICP (mg / L) LiNaLi Concentration Ratio (times) Invention Example 18 428 969 58.4 Invention Example 23 90 126 95 83.9 Invention Example 33 63 92 723 53.6 Invention Example 44 0 77 565 94.1

[0115] Looking at Table 3, it can be seen that lithium can be efficiently concentrated even when solvent extraction is performed using a centrifugal reactor rather than a mixed sedimentation reactor.

[0116] 5. Cleaning Step

[0117] Then, for each of the inventive example and comparative example, the organic phase was washed with deionized water. The flow rate of the washing solution was 50 mL / min, and the O / A ratio was 13.3. Through this, residual sulfuric acid remaining in the organic phase was removed, allowing the organic phase to be reused as a solvent extractant.

[0118] (Example 2)

[0119] 1. Preprocessing step

[0120] First, the solvent extractants of Table 4 below were prepared as solvent extractants.

[0121] Classification Solvent Extractant Ingredients (Volume %) Di-2-Ethylhexyl Phosphate (D2EHPA) Tributyl Phosphate (TBP) Desulfurized Kerosene (ISD159) Solvent Extractant A155 Residue Solvent Extractant B15- Residue

[0122] Next, sodium hydroxide (NaOH) having a concentration of 40% by weight was mixed with the solvent extractant to saponify the solvent extractant. Through the steps described above, the solvent extractant could be saponified with a saponification rate of 20% or more and 60% or less.

[0123] 2. Extraction Step

[0124] Next, a feed solution was prepared. The Li concentration in the feed solution measured by ICP analysis was 1000 mg / L.

[0125] Then, each example performed solvent extraction by mixing the above-described feed solution and the saponified solvent extractant according to the conditions described below.

[0126] At this time, solvent extraction was performed using a centrifugal reactor with 5 extraction stages, and the pH during solvent extraction was maintained between 4.7 and 6.5. In addition, the rotation speed of the centrifugal reactor was 30 to 33 Hz. The O / A ratio during extraction is shown in Table 5 below.

[0127] Then, the Li concentration in the raffinate after extraction was measured using ICP analysis, and the lithium extraction rate (%) was calculated and shown in Table 5 below.

[0128] The lithium extraction rate (%) was calculated by the same method as in Example 1.

[0129] Classification Solvent Extractant Type O / A Ratio Li Extraction Rate (%) Example 2-1 Solvent Extractant A 0.568.8 Example 2-2 Solvent Extractant B 0.568.1 Example 2-3 Solvent Extractant A 1.068.8 Example 2-4 Solvent Extractant B 1.068.6

[0130] 3. Cleaning step

[0131] For each example, the organic phase obtained after extraction was washed with a 5% by weight aqueous sulfuric acid solution. The pH was maintained at 3.0 to 5.6.

[0132] 4. Removal Step

[0133] In addition, in each embodiment, the organic phase obtained after the washing step was mixed with an aqueous sulfuric acid solution of 18.75 wt% to remove lithium ions from the organic phase into the aqueous phase. Also, the pH at this time was maintained at 0.5 to 1.0.

[0134] Then, the Li concentration was measured using ICP analysis on the aqueous phase obtained after the aforementioned stripping. The lithium stripping rate (%) was calculated based on the results and is shown in Table 6 below.

[0135] Classification Solvent Extractant Type O / A Ratio Li Removal Rate (%) Example 2-1 Solvent Extractant A 0.5 5 7.4 Example 2-2 Solvent Extractant B 0.5 5 0.8 Example 2-3 Solvent Extractant A 1.06 7.3 Example 2-4 Solvent Extractant B 1.05 7.9

[0136] Looking at Table 6, it can be seen that when using solvent extractant A, which is a mixed solvent extractant, the removal rate can be improved more than when using solvent extractant B, which is a single solvent extractant.

[0137] The present invention is a technology developed through the following national research and development project:

[0138] [Private Information]

[0139] National R&D project that supported this invention

[0140] [Project ID] 2410006298

[0141] [Assignment No.] 20217510100020

[0142] [Ministry Name] Ministry of Trade, Industry and Energy

[0143] [Project Management (Specialized) Agency Name] Korea Institute of Energy Technology Evaluation and Planning

[0144] [Research Project Name] Development of Common Utilization Technology for Rare Metal Recovery Using Circular Resources

[0145] [Project Title] Establishment of a Common Core (Concentration, Separation / Recovery) Process Platform for Rare Metal Recovery from Low-Grade Process Wastewater and Development of Materialization Technology

[0146] [Name of Project Performing Organization] Pohang Institute of Industrial Science and Technology

[0147] [Research Period] 2024.01.01 ~ 2024.12.31

Claims

1. Step of pre-treating the solvent extractant; A step of extracting the organic phase by adding a feed solution to the pretreated solvent extractant; A step of cleaning the above organic phase using a cleaning agent; A step of removing the above organic phase using a stripping agent; and It includes a step of washing the organic phase obtained from the above removal step, and The above extraction step is performed by extraction through a liquid-liquid reaction using a centrifugal reactor, and The above feed solution is a lithium concentration method containing lithium.

2. In Paragraph 1, A lithium concentration method in which the above solvent extractant is a mixed solvent extractant comprising, in volume %, 10 to 20% of di-2-ethylhexyl phosphate (D2EHPA), 10% or less (including 0%) of tributyl phosphate (TBP), and the remainder being kerosene.

3. In Paragraph 1, A lithium concentration method in which the above pretreatment is a step of saponifying using sodium hydroxide (NaOH) at a saponification rate of 20% or more and 60% or less.

4. In Paragraph 1, A lithium concentration method in which the rotational speed of the above centrifugal reactor is 30 to 33 Hz.

5. In Paragraph 1, The above solvent extractant is a mixed solvent extractant comprising, in volume %, 10 to 20% of di-2-ethylhexyl phosphate (D2EHPA) and 10% or less (including 0%) of tributyl phosphate (TBP), and the remainder comprising kerosene. The rotational speed of the above centrifugal reactor is 30 to 33 Hz, and A lithium enrichment method having a phase separation (%) of 92.0% or higher derived by the following relationship. [Relationship] Phase Separation (%) = {C + A×exp[-0.5×((f - μ) / σ)²]}×100(%) In the above relationship, C is the basic separation constant, A is the maximum increase constant, f is the rotational speed (Hz) of the centrifugal reactor, μ is the center value in the Gaussian distribution of the phase separation and corresponds to the optimal rotational speed (Hz), and σ corresponds to the standard deviation (Hz).

6. In Paragraph 5, A lithium enrichment method in which, in the above relationship, C is 0.106, A is 0.864, μ is 31.5, and σ is 9.

82.

7. In Paragraph 6, A lithium concentration method in which the above solvent extractant is a mixed solvent extractant comprising, in volume %, 15% of di-2-ethylhexyl phosphate (D2EHPA) and 5% of tributyl phosphate (TBP), and the remainder being kerosene.

8. In Paragraph 1, A lithium concentration method in which the pH in the above extraction step is 5.0 or higher and 6.5 or lower.

9. In Paragraph 1, A lithium concentration method in which the volume ratio of the organic phase to the aqueous phase (O / A Ratio) in the extraction step is 0.1 to 10.

10. In Paragraph 1, A lithium concentration method in which the pH in the above washing step is 3.0 or higher and 5.6 or lower.

11. In Paragraph 1, A lithium concentration method characterized by being continuously carried out by reintroducing the aqueous phase separated in the washing step together with the feed solution into the extraction step.

12. In Paragraph 1, In the above removal step, the removal agent is sulfuric acid at a concentration of 15 to 25 weight%, lithium concentration method.

13. In Paragraph 1, A lithium concentration method in which, in the above-mentioned removal step, the pH is 0.5 or higher and 1.0 or lower.

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