Method for recovering lithium from cathode material washing solution

Abstract

The present invention relates to a method for recovering lithium, the method comprising the steps of: preparing a waste liquid containing lithium and having a pH of at least 8; injecting a Ca compound into the waste liquid to remove impurities; and recovering lithium in the waste liquid from which the impurities have been removed.

Description

Method for recovering lithium from cathode ash solution

[0001] The present invention relates to a method for recovering lithium, and more particularly, to a method for recovering lithium from a cathode material washing solution.

[0002] Secondary batteries are widely used in everything from small electronic devices like mobile phones and laptops to larger devices like electric vehicles (EVs) and energy storage systems (ESS). As their applications expand across all aspects of daily life, their production is also increasing.

[0003] The core component of secondary batteries is lithium, which is used as the main component of the cathode material. The lithium is generally manufactured from lithium-containing ore, and since the cost of the manufacturing process and the price of the raw materials themselves are high, research is actively being conducted to lower the manufacturing cost.

[0004] Among these studies, active research is being conducted on methods for recovering lithium from washing solutions used to remove byproducts generated during the manufacturing process of lithium secondary battery cathode materials. Specifically, the manufacturing process for lithium secondary battery cathode materials generates a large amount of lithium byproduct on the cathode material's surface. A washing process is performed to remove these lithium byproducts, and this process can generate large amounts of washing solution containing lithium, impurities, sulfate ions, carbonate ions, and some phosphorus ions.

[0005] To recover high-grade lithium compounds from the above-mentioned washing solution, a concentration process must be performed first to increase the lithium concentration within the washing solution. However, the washing solution contains various dissolved components, making it difficult to recover high-grade lithium compounds.

[0006] In particular, phosphorus ions and carbonate ions in the washing solution may exist as impurities in the raw materials used in the manufacturing process of the cathode material, and may be precipitated as lithium phosphate (Li3PO4) and lithium carbonate (Li2CO3) respectively during the concentration process of the washing solution, which may cause Li loss and hinder the recovery of high-grade lithium compounds. Even if there is no Li loss during the concentration process of the washing solution, it is difficult to recover high-grade lithium compounds due to the influence of sulfate ions. In particular, there is a problem that sulfate ions are contained in Li2CO3 during the crystallization process of Li2CO3, making it difficult to recover high-grade lithium.

[0007] The technical problem to be solved by the present invention is to provide a method for recovering lithium, which can easily remove phosphorus ions and carbonate ions when recovering lithium from a cathode material washing solution, thereby recovering high-quality lithium.

[0008] According to one embodiment of the present invention, a method for producing lithium hydroxide may include a step of preparing a waste liquid containing lithium having a pH of 8 or higher, a step of removing impurities by adding a Ca compound to the waste liquid, and a step of recovering lithium in the waste liquid from which the impurities have been removed.

[0009] In one embodiment, the waste liquid containing lithium having a pH of 8 or higher may be a cathode material washing liquid. In one embodiment, by the step of removing the impurities, P in the waste liquid may be removed to 0.003 g / L or less.

[0010] In one embodiment, by the step of removing the impurities, Si can be eluted to 0.003 g / L or less. In one embodiment, by the step of removing the impurities, carbonate ions in the waste liquid can be removed in the form of CaCO3.

[0011] In one embodiment, the phosphorus (P) ions in the waste liquid are first removed, followed by carbonate ions (CO3 2-) can be removed. In one embodiment, the step of removing the impurity comprises removing the Ca compound from the waste liquid at a concentration of 1,000 m 3 A standard of 0.09 t or more can be input. In one embodiment, the step of removing the impurities comprises adding the Ca compound to the waste liquid 1,000 m 3 It is possible to invest more than 15 tons.

[0012] In one embodiment, the step of removing the impurities may convert phosphorus (P) ions into Ca5(OH)(PO4)3 (hydroxyapatite) and be removed. In one embodiment, the step of recovering lithium may include a step of concentrating the waste liquid from which the impurities have been removed, and the step of concentrating the waste liquid may concentrate the waste liquid by 80 to 95% based on the waste liquid before concentration.

[0013] In one embodiment, the step of concentrating the waste liquid may concentrate the lithium to 20 to 35 g / L. In one embodiment, the step of concentrating the waste liquid may not cause precipitation of at least one of lithium phosphate (Li3PO4) and lithium carbonate (Li2CO3).

[0014] In one embodiment, the step of concentrating the waste liquid from which the impurities have been removed may include a causticization step of adding sodium hydroxide (NaOH) to the waste liquid. In one embodiment, after the causticization step, a cooling crystallization step of cooling and crystallizing the waste liquid at a temperature of 0° C. or lower may be included. In one embodiment, after the causticization step, at least one crystallization step satisfying a crystallization rate of 3 to 10% may be included.

[0015] A method for recovering lithium according to one embodiment of the present invention provides a method for recovering high-grade lithium by easily removing phosphorus ions and carbonate ions in a basic waste liquid by adding a Ca compound in an impurity removal step.

[0016] Figure 1 shows the XRD analysis results of the residue after adding a raw material to the washing solution of the present invention.

[0017] FIG. 2a shows the amount of phosphorus ions removed from the washing solution according to the amount of raw material added in one embodiment of the present invention and the amount of Ca5(OH)(PO4)3 (hydroxyapatite) generated according to the removal of phosphorus ions, FIG. 2b shows the change in the concentration of phosphorus ions and the change in the concentration of lithium ions according to the amount of raw material added in one embodiment of the present invention, FIG. 2c shows the change in the concentration of phosphorus ions and the change in the concentration of carbonate ions according to the amount of raw material added in one embodiment of the present invention, and FIG. 2d shows the change in the concentration of carbonate ions and the amount of CaCO3 generated according to the amount of raw material added.

[0018] FIG. 3 is a schematic diagram of a process for recovering LiOH·H2O from a concentrated washing solution according to one embodiment of the present invention.

[0019] The terms first, second, and third, etc., are used to describe, but are not limited to, various parts, components, regions, layers, and / or sections. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Accordingly, a first part, component, region, layer, or section described below may be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0020] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used herein, the singular forms "a," "an," and "the" include plural forms as well, unless the context clearly dictates otherwise. The word "comprising," as used herein, specifies particular features, regions, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of other features, regions, integers, steps, operations, elements, and / or components.

[0021] When a part is referred to as being "on" or "over" another part, it can be directly on or over the other part, or there may be other parts intervening. Conversely, when a part is referred to as being "directly on" another part, there are no other parts intervening.

[0022] Although not defined otherwise, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries are further interpreted to have meanings consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or overly formal unless otherwise defined.

[0023] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0024] According to one embodiment of the present invention, a lithium recovery method may include the steps of preparing a waste liquid containing lithium, removing impurities from the waste liquid, and recovering lithium from the waste liquid from which the impurities have been removed. Specifically, the lithium recovery method of the present invention may include adding a Ca-based compound to prevent lithium loss and recover high-grade lithium while removing impurities from the waste liquid.

[0025] The waste liquid may be a cathode material washing solution. Specifically, the cathode material washing solution may be a waste liquid generated during the cathode material manufacturing process. More specifically, the waste liquid may refer to a solution obtained by stirring a lithium transition metal oxide in a washing solution and filtering the solution to reduce impurities such as lithium byproducts present on the surface of the lithium transition metal oxide after manufacturing the lithium transition metal oxide. More specifically, the waste liquid may be a solution containing a metal such as nickel, cobalt, or manganese, or containing lithium together with impurities such as phosphorus ions or carbonate ions.

[0026] The step of preparing a waste solution may be a step of preparing a waste solution containing lithium having a pH of 8 or higher. Specifically, the waste solution may have a pH of 9 or higher, more specifically, 11 or higher. This may be due to the addition of an aqueous NaOH or NH4OH solution, depending on the co-precipitation reaction during the cathode material manufacturing process, resulting in alkalinity.

[0027] The step of removing impurities in the waste liquid may include injecting a Ca compound into the waste liquid. The Ca compound may be, for example, a sulfuric acid-based substance. More specifically, the Ca compound may be, for example, CaSO4·H2O.

[0028] In one embodiment, the step of removing the impurity comprises adding the Ca compound to the waste liquid at a concentration of 1,000 m 3 A step of injecting 0.09 t or more of the standard may be included. Specifically, the Ca compound may be injected in an amount of 0.10 t or more, more specifically, 0.15 t or more. As the Ca compound is injected in an amount exceeding the above-mentioned range, phosphorus (P) ions in the waste liquid can be easily removed.

[0029] In one embodiment, the step of removing the impurity comprises adding the Ca compound to the waste liquid at a concentration of 1,000 m 3A step of injecting 15 t or more of the standard may be included. Specifically, the step of injecting 15 t or more of the Ca compound, more specifically, 15.5 t or more, may be included. When the Ca compound is injected in excess of the above-mentioned range, carbonate ions may be removed after phosphorus (P) ions are removed. Specifically, the carbonate ions may begin to be removed after the phosphorus ions are removed. This is because when the Ca compound is injected into the waste liquid, phosphorus ions are initially removed due to differences in solubility.

[0030] In one embodiment, by the step of removing the impurities, P in the waste liquid can be removed to 0.003 g / L or less. Specifically, P in the waste liquid can be removed to 0.001 g / L or less, more specifically, 0.085 mg / L or less.

[0031] As the above Ca compound is injected into the waste liquid, phosphorus (P) ions and carbonate ions (CO3) in the waste liquid 2- ) can be removed. Specifically, the Ca compound can react with phosphorus ions in the waste liquid and be removed as Ca5(OH)(PO4)3(hydroxyapatite). Through the precipitation of the hydroxyapatite, the phosphorus ions can be removed within the aforementioned range.

[0032] In one embodiment, the step of removing the impurities may result in the extraction of Si to a concentration of 0.003 g / L or less. Specifically, the Si may be reduced to the aforementioned concentration. Specifically, the Si may be extracted from impurities contained in the raw material.

[0033] As the above Ca compound is injected into the waste liquid, carbonate ions in the waste liquid can be removed in the form of CaCO3. Specifically, carbonate ions in the waste liquid can be removed as CaCO3 due to the Ca source in the Ca compound, which is a secondary raw material.

[0034] The step of recovering lithium from the waste liquid from which the impurities have been removed may include a step of concentrating the waste liquid from which the impurities have been removed. Specifically, the step of concentrating the waste liquid may concentrate the waste liquid to 80 to 95% based on the waste liquid before concentration. More specifically, the waste liquid may be concentrated to 85 to 90%. By concentrating the waste liquid within the aforementioned range, a waste liquid containing a high concentration of lithium may be obtained. More specifically, the concentration of lithium ions in the waste liquid may be increased.

[0035] In one embodiment, the lithium may be concentrated to 20 to 35 g / L by the step of concentrating the waste liquid. Specifically, the lithium may be concentrated to 25 to 30 g / L. As the lithium is concentrated to the aforementioned range, a high concentration of lithium may be recovered.

[0036] In one embodiment, the step of concentrating the waste liquid may not cause precipitation of at least one of lithium phosphate (Li3PO4) and lithium carbonate (Li2CO3). Specifically, the result of concentrating the waste liquid may not include lithium phosphate (Li3PO4), may not include lithium carbonate (Li2CO3), or may not include both lithium phosphate (Li3PO4) and lithium carbonate (Li2CO3). This is because impurities are removed by the Ca compound in the step of removing impurities in the waste liquid. Accordingly, the concentrated result does not include lithium phosphate (Li3PO4) or lithium carbonate (Li2CO3) as a precipitate, thereby enabling recovery of high-concentration lithium without loss of lithium raw materials.

[0037] In one embodiment, the step of concentrating the waste liquid may include at least one of Ca5(OH)(PO4)3, CaCO3, and Ca(OH)2 as the residue. As described above, this may be formed as a residue by the reaction of Ca compounds with phosphorus ions and carbonate ions in the step of removing impurities in the waste liquid. Since the residue includes the aforementioned substances in the step of concentrating the waste liquid, high-concentration lithium with impurities removed can be recovered.

[0038] In one embodiment, the step of concentrating the waste liquid from which the impurities have been removed may include a step of performing an ion exchange resin method (IX) on the waste liquid. Specifically, the ion exchange resin method (IX) may be a step for removing Ca and B from the waste liquid. By including the step of performing the ion exchange resin method, Ca and B, which are impurities remaining in the concentrated waste liquid, can be easily removed.

[0039] In one embodiment, the step of concentrating the waste liquid from which the impurities have been removed may include a causticization step of adding sodium hydroxide (NaOH) to the waste liquid. Specifically, the causticization step may be performed after the step of performing the ion exchange resin method. Specifically, the causticization step may easily remove impurities including Na or S in a subsequent process by adding sodium hydroxide to the concentrated waste liquid.

[0040] In one embodiment, after the causticization step, a cooling crystallization step may be included for cooling and crystallizing the waste liquid at a temperature of 0°C or lower. Specifically, the cooling and crystallization step may be performed at -5°C or lower, more specifically, at -10°C or lower.

[0041] Specifically, impurities including Na or S in the waste liquid can be easily removed in the cooling crystallization step. If the cooling crystallization step is not included, there is a problem that lithium recovery is difficult because S in the solution is highly concentrated and may be included in the double salt or water.

[0042] In one embodiment, the causticization step may be followed by at least one crystallization step. Specifically, the crystallization step may be a step of crystallizing the waste liquid that has undergone the causticization step. The crystallization step may include at least one step and may be performed once or multiple times.

[0043] In one embodiment, the crystallization step can satisfy a crystallization rate of 3 to 10%. Specifically, the crystallization rate can be 4 to 8%, and more specifically, 5 to 7%. By satisfying the crystallization rate within the aforementioned range, the precipitation of the double salt can be suppressed, thereby maximizing the lithium yield.

[0044] If the crystallization rate exceeds the upper limit of the aforementioned range, there is a possibility of precipitation of a double salt. If the crystallization rate exceeds the lower limit of the aforementioned range, there is a problem in that the final product, a lithium-containing solution, does not precipitate properly.

[0045]

[0046] Specific examples of the present invention are described below. However, the following examples are merely specific examples of the present invention, and the present invention is not limited to the following examples.

[0047]

[0048] <Experimental Example>

[0049] The present invention relates to a method for adding a secondary raw material in a process for removing phosphorus ions and carbonate ions, which are impurities in a cathode material washing solution, and comprises the steps of adding a secondary raw material to the washing solution to remove phosphorus ions and carbonate ions, concentrating the washing solution from which impurities have been removed to increase the concentration of lithium ions, and performing primary and secondary crystallization from the concentrated washing solution. The specific experimental method is as follows.

[0050]

[0051] Step of adding raw materials to the water solution

[0052] <Example>

[0053] Table 1 below shows the analysis results of the above washing solution.

[0054] The concentration of cations in the above-mentioned washing solution was measured using an inductively coupled plasma optical emission spectrometer (ICP-OES) device, and carbonate ions were measured using a total organic carbon analyzer (TOC).

[0055] pHICP analysis results [g / L]CO3 2- [g / L]LiSPBKNaEtc.Wash solution 13.034.5043.5950.0120.0310.0100.253<0.0034.6

[0056] Among the Ca-based raw materials, 1.1 equivalents of 95% purity CaSO4·0.5H2O were added to the above washing solution based on the removal of phosphorus ions. <Comparative Example>

[0057] Among the Ca-based raw materials, 1.1 equivalents of 95% purity Ca(OH)2 was added to the above washing solution based on the removal of phosphorus ions.

[0058] Table 2 below shows the analysis results of solutions after adding Ca-based raw materials to the washing liquid according to examples and comparative examples.

[0059] pHICP analysis results [g / L] Note LiSCaPBKNaSiEtc. Washing solution 13.034.5043.595<0.0030.0120.0310.0100.253<0.003<0.003-Ca(OH)2 13.014.4603.5740.091<0.0030.0310.0090.2520.010<0.003 Comparative example CaSO4·0.5H2O 13.114.5037.5460.483<0.0030.0300.0090.251<0.003<0.003 Example

[0060] FIG. 1 shows the XRD analysis results of the residue after adding a raw material to the washing solution of the present invention. Referring to FIG. 1, FIG. 1 (a) shows the XRD analysis results when 1.1 equivalents of Ca(OH)2 were added as a raw material based on the removal of phosphorus ions, and FIG. 1 (b) shows the XRD analysis results when 1.1 equivalents of CaSO4·0.5H2O were added as a raw material based on the removal of phosphorus ions. Looking at FIG. 1 and Table 2, it can be confirmed from the XRD analysis results that when Ca(OH)2 was used, the added Ca(OH)2 remained due to the high pH. In contrast, in the example where the same equivalent amount of CaSO4·0.5H2O was added, it was confirmed that all of it was converted to CaCO3 and no CaSO4·0.5H2O remained. Through this, it can be confirmed that in the case of a washing solution with a pH of approximately 13, adding CaSO4·0.5H2O is more efficient than adding Ca(OH)2.

[0061] In addition, when Ca(OH)2 was used as a raw material, 0.010 g / L of Si was eluted among the impurities contained, and this was confirmed to have a high Si content because the pH of the washing solution was approximately 13, which is an environment in which Si can be eluted. In contrast, when CaSO4·0.5H2O was added as a raw material, it was confirmed that small amounts of Si and other impurities were detected.

[0062] Therefore, when Ca(OH)2 is used as a raw material as in the comparative example, there is a problem that an additional neutralization process is required to neutralize the pH by lowering it to a level of 6 to 8 to remove Si. In contrast, when CaSO4·0.5H2O is used as a raw material as in the example, it was confirmed that no additional purification process was required.

[0063] Specifically, when the pH of the waste liquid is 13 or higher, it was confirmed that the efficiency was excellent when CaSO4·0.5H2O was used as a Ca compound as a secondary raw material.

[0064]

[0065] Control of the amount of raw materials added at the stage of adding raw materials to the water solution

[0066] FIG. 2a shows the removal of phosphorus ions and the amount of hydroxyapatite generated in the washing solution according to the amount of raw material input in one embodiment of the present invention, FIG. 2b shows the change in the concentration of lithium ions according to the amount of raw material input in one embodiment of the present invention, FIG. 2c shows the change in the concentration of phosphorus ions and the change in the concentration of carbonate ions according to the amount of raw material input in one embodiment of the present invention, and FIG. 2d shows the change in the concentration of carbonate ions and the amount of CaCO3 generated according to the amount of raw material input.

[0067] Referring to Figure 2a, the water solution is 1000 m 3 The content (t) of CaSO4·0.5H2O as a raw material was changed and added. When the content of the raw material is 0.09 t, specifically 0.10 t or more, it can be confirmed that phosphorus (P) ions are almost removed. Specifically, when the raw material is 0 t, it can be confirmed that the phosphorus ions are 12 mg / L, and CO3 2- It can be confirmed that the content is 4.6 g / L. Under these conditions, 1,000 m of washing liquid 3It was confirmed that at least 15.5 t of the reference raw material was required to prevent lithium carbonate from being generated during the concentration process. For example, when the raw material was 15.0 t, lithium phosphate was not generated during the concentration process, but some lithium carbonate could be generated. Accordingly, when the raw material was 0.10 t, phosphorus ions were removed at a level of 0.085 mg / L.

[0068] Specifically, it can be confirmed that the phosphorus ions in the washing solution react with the auxiliary material, CaSO4·0.5H2O, and are converted into hydroxyapatite and removed. As the phosphorus ions are removed into the hydroxyapatite, the precipitation of lithium phosphate in the concentration process can be prevented, thereby preventing the loss of lithium (Li).

[0069] Additionally, it was confirmed that carbonate ions in the washing solution were removed as CaCO3 due to the Ca source in the auxiliary material. Accordingly, scale caused by lithium carbonate precipitation during the concentration process can be prevented.

[0070] Referring to Fig. 2b, when the auxiliary material CaSO4·0.5H2O is added, phosphorus ions are removed, but the concentration of Li ions does not change significantly, confirming that lithium is not lost. Specifically, it was confirmed that the Li source is not lost to impurities such as lithium phosphate.

[0071] Referring to Fig. 2c, it was confirmed that after the raw material was added, the phosphorus ions were removed and then the carbonate ions were removed. Specifically, when about 0.1 t of the raw material was added, it was confirmed that the phosphorus ions were initially removed due to the difference in solubility. After most of the phosphorus ions were removed, the carbonate ions (CO3 2- ) was confirmed to be removed.

[0072] Referring to Fig. 2d, it was confirmed that carbonate ions in the washing solution were removed as CaCO3 as the amount of additive added increased. Specifically, when the amount of additive added was 15.6 t, it was confirmed that carbonate ions decreased to less than 10 mg / L, and CaCO3 increased to more than 10 t. Accordingly, it was confirmed that carbonate ions were converted to CaCO3 and removed. In this way, it was confirmed that the addition of additives could reduce impurities in the washing solution and prevent Li loss.

[0073]

[0074] Step of concentrating the washing liquid from which impurities have been removed

[0075] A pretreatment step may be performed before recovering Li products from the washing solution from which impurities have been removed. Specifically, this may be a step of concentrating the Li concentration from 4 g / L to 20 to 30 g / L through the concentration of the washing solution.

[0076] <Example>

[0077] In the above pretreatment step, impurities such as phosphorus and carbonate ions in the washing solution were removed using CaSO4·0.5H2O as a secondary raw material, and then lithium was concentrated from 4 g / L to 27 g / L.

[0078] <Comparative Example>

[0079] In the above pretreatment step, lithium was concentrated from 4 g / L to 27 g / L without removing impurities such as phosphorus and carbonate ions in the washing solution.

[0080] Table 3 below shows the change in ion concentration in the washing solution when lithium was concentrated according to examples and comparative examples.

[0081] Table 4 below shows the precipitates generated when lithium is concentrated according to examples and comparative examples and when the washing solution is concentrated.

[0082] The above precipitate was confirmed to be lithium phosphate or lithium carbonate through OLI simulation results.

[0083] ClassificationConcentration VolumepHConcentration (g / L)LiSNaBKCaPCO3 -2 Example Before Concentration 1003.113.024.497.020.250.310.0100.09<0.003<0.003After Concentration 166.812.0527.0042.211.520.190.0600.03<0.003<0.003Comparative Example Before Concentration 1021.313.044.263.600.250.030.010<0.003<0.0035.06After Concentration 113.112.2427.031.802.240.270.090-<0.003<0.003

[0084] ClassificationConcentration volumePrecipitation amount (t)Li3PO4Li2CO3Ca5(OH)(PO4)3CaCO3Ca(OH)2ExampleBefore concentration1003.100000After concentration166.82Not generatedNot generated0.06510.450.143Comparative exampleBefore concentration1021.300---After concentration113.10.0446.436---

[0085] Looking at Table 3 and Table 4 above, in the comparative example, the water content was 1021.3 m 3 113.1 m from 3 When concentrated to about 89%, it was confirmed that the Li concentration could be concentrated from 4 g / L to 27 g / L. In the case of the comparative example, since the impurities were not removed, it was confirmed that lithium phosphate and lithium carbonate were generated as precipitates and the Li raw material was lost. Specifically, in the case of the comparative example, since the concentration was performed without adding Ca-based auxiliary materials, Ca-based precipitates were not generated, which means that phosphorus ions or carbonate ions were lost as Li3PO4 or Li2CO3 because Ca-based auxiliary materials did not exist. In contrast, in the example, the washing solution was 1003.1 m 3 166.82 m from 3When concentrated to about 84%, it was confirmed that the Li concentration could be concentrated from 4 g / L to 27 g / L. In the case of the above example, it was confirmed that the concentration rate could be reduced because Li was not lost to the precipitate, and thus the cost could be reduced. In addition, in the case of the above example, since the concentration step was performed after removing impurities by adding a secondary raw material, it could be confirmed that there was no loss of Li raw material to the precipitate, and Ca5(OH)(PO4)3, CaCO3, and Ca(OH)2 were generated as residues. Accordingly, it was confirmed that lithium loss in the washing solution was minimized and impurities were easily removed.

[0086] Primary and secondary crystallization steps from concentrated water solution

[0087] FIG. 3 is a schematic diagram of a process for recovering LiOH·H2O from a concentrated washing solution according to one embodiment of the present invention.

[0088] Referring to Fig. 3, Ca and B were removed from the concentrated washing solution using an ion exchange resin method, and then 50% NaOH was added to perform a causticization process, and then cooling crystallization, primary crystallization, and secondary crystallization were performed to recover LiOH·H2O.

[0089] Specifically, Ca and B in the concentrated washing solution were removed using the ion exchange resin method (IX). Afterwards, a causticization process was performed by adding 50% NaOH.

[0090] Table 5 below shows the concentration of the washing solution before and after adding NaOH to the concentrated washing solution.

[0091] Separation volume (m) 3 )pH concentration (g / L) LiSNaK Before addition 166.82 12.05 27.00 42.2 11.5 17 0.06 0 After addition 189.09 12.6 123.82 37.24 56.6 7 0.05 3

[0092] Looking at Table 5 above, it was confirmed that the concentration of the washing solution was controlled to a state where it was easy to separate Na in the subsequent process by reducing the concentration of S and increasing the concentration of Na by going through the causticization step. Afterwards, the causticized result was subjected to cooling crystallization at -10℃ conditions to separate Na2SO4·10H2O. Through the causticization and cooling crystallization steps, the problem of S in the solution being highly concentrated and included in the double salt or water when recovering LiOH·H2O was prevented. Table 6 below shows the concentration of the washing solution before and after performing the cooling crystallization process of the solution that went through the causticization process.

[0093] Separation volume (m) 3 ) pH concentration (g / L) Na2SO4·10H2O generation amount (t) LiSNaK Before cooling 189.09 12.61 23.82 37.24 56.67 0.059 - After cooling 146.34 14 <30.78 12.80 22.58 0.06 85 1.93

[0094] Looking at Table 6 above, it was confirmed that when the causticized solution was cooled to -10 ℃, Na2SO4·10H2O was generated, and by removing the generated Na2SO4·10H2O, the concentration effect of Li could be increased. Thereafter, the resultant product excluding Na2SO4·10H2O from the causticized resultant product was subjected to the first and second crystallization to recover lithium hydroxide (LiOH·H2O). Specifically, after removing Na2SO4·10H2O from the causticized resultant product, LiOH·H2O was recovered. Table 7 below shows the resulting values ​​of the filtrate and precipitate when the crystallization step was performed with a crystallization rate of 6%. Since a significant amount of Li remains in the filtrate after evaporation crystallization, there is a possibility of precipitation of double salts if the crystallization rate increases during evaporation crystallization, so an appropriate crystallization rate had to be selected, and the selected crystallization rate is 6%.

[0095] Crystallization rate (%) Solution precipitate volume (m 3)pH concentration (g / L)LiOH·H2OLiSNaK weight (t) ratio (%) 0 1 46.34 > 1 43 0.78 12.80 22.58 0.068--6 1 16.38 13.7 136.38 16.10 28.39 0.08 6 1.64 100

[0096] Looking at Table 7 above, when a crystallization rate of 6% was applied to the filtrate after cooling crystallization, only high-quality LiOH·H2O was confirmed in the precipitate, and no double salt was formed. The present invention is not limited to the above-described embodiments and / or examples, but can be manufactured in various different forms, and a person having ordinary skill in the art to which the present invention pertains will understand that the present invention can be implemented in other specific forms without changing the technical spirit or essential characteristics of the present invention. Therefore, it should be understood that the above-described embodiments and / or examples are exemplary in all respects and not restrictive.

Claims

1. A step of preparing a waste liquid containing lithium having a pH of 8 or higher; A step of removing impurities by adding a Ca compound into the waste liquid; and A lithium recovery method comprising a step of recovering lithium in a waste liquid from which the above impurities have been removed.

2. In paragraph 1, A lithium recovery method in which the waste liquid containing lithium having a pH of 8 or higher is a cathode material washing liquid.

3. In paragraph 1, By the step of removing the above impurities, A lithium recovery method in which P in the above waste liquid is removed to 0.003 g / L or less.

4. In paragraph 1, If the pH of the above waste liquid is 13 or higher, A lithium recovery method wherein the above Ca compound is CaSO4·0.5H2O.

5. In paragraph 1, By the step of removing the above impurities, A lithium recovery method in which carbonate ions in the above waste liquid are removed in the form of CaCO3.

6. In paragraph 1, After the phosphorus (P) ions in the above waste liquid are removed, carbonate ions (CO3) 2- ) A method for recovering lithium from which lithium is removed.

7. In paragraph 6, The step of removing the above impurities is to add the Ca compound to 1,000 m of the waste liquid. 3 A lithium recovery method using an input of 0.09 t or more.

8. In paragraph 1, The step of removing the above impurities is to add the Ca compound to 1,000 m of the waste liquid. 3 A lithium recovery method using an input of 15 tons or more.

9. In paragraph 1, By the step of removing the above impurities A lithium recovery method in which phosphorus (P) ions are removed by being converted to Ca5(OH)(PO4)3 (hydroxyapatite).

10. In paragraph 1, The above step of recovering lithium is Comprising a step of concentrating the waste liquid from which the impurities have been removed, The step of concentrating the waste liquid is a lithium recovery method in which the waste liquid is concentrated by 80 to 95% based on the waste liquid before concentration.

11. In Article 10, A lithium recovery method wherein the lithium is concentrated to 20 to 35 g / L by the step of concentrating the waste liquid.

12. In paragraph 10, A method for recovering lithium, wherein at least one of lithium phosphate (Li3PO4) and lithium carbonate (Li2CO3) is not precipitated by the step of concentrating the waste liquid.

13. In paragraph 1, The step of concentrating the waste liquid from which the above impurities have been removed is A lithium recovery method comprising a causticization step of adding sodium hydroxide (NaOH) to the above waste solution.

14. In paragraph 13, A lithium recovery method comprising a cooling crystallization step of cooling and crystallizing the waste liquid at a temperature of 0° C or lower after the above-mentioned causticization step.

15. In paragraph 13, A lithium recovery method comprising at least one crystallization step satisfying a crystallization rate of 3 to 10% after the above-mentioned causticization step.

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