Water washing liquid for recovering lithium and method for recovering lithium from lithium-containing waste liquid

Abstract

The invention relates to a method for recovering lithium from lithium-containing waste liquid. The method can comprise the following steps: filtering a positive electrode material washing liquid to separate out solid metal contained in the alkaline waste liquid; adding sulfuric acid into the positive electrode material washing liquid from which the solid metal is filtered to acidify the positive electrode material washing liquid; and converting lithium carbonate or lithium hydroxide into lithium sulfate, a step of concentrating the aqueous washing solution converted into the lithium sulfate to obtain a high-concentration lithium sulfate solution; and a step of mixing the high-concentration lithium sulfate solution into a product leached from the ore.

Description

Technical Field

[0001] The present invention relates to a method for recovering lithium. More specifically, the present invention relates to a washing liquid for recovering lithium and a method for recovering lithium from a lithium-containing waste liquid. Background Art

[0002] Among the positive electrode active materials of lithium secondary batteries, there are materials such as lithium, nickel, cobalt, and manganese. In order to improve the performance of electric vehicles, it is necessary to increase the capacity and life of the battery, so the demand for high-nickel series batteries with high energy density is increasing. When the nickel content is relatively high, nickel tends to maintain a +2 valence state, and there is a problem that a large amount of lithium by-products such as LiOH and Li2CO3 are generated on the surface. For the lithium by-products, they must be sufficiently removed through a washing process. If a large amount of the lithium by-products are generated on the surface, there is a problem of a decrease in the performance of the lithium battery.

[0003] However, the washing liquid generated by the washing process contains sulfates and lithium. Recovering the lithium in the washing liquid can be used as a raw material for preparing lithium hydroxide and lithium carbonate.

[0004] Most of the related technologies for recovering lithium from lithium-containing solutions are directed at the acid leaching solutions of waste batteries, and there are few technologies regarding the washing liquid generated in the positive electrode material preparation process. Some technologies adopt the following methods: In order to recover lithium from a lithium-containing waste liquid, after removing impurities such as sulfates by chemical precipitation, concentration is carried out to precipitate lithium carbonate.

[0005] However, for the method of precipitating lithium carbonate in the washing liquid to recover lithium, the precipitate will adhere to the equipment and become an obstacle to the stable operation of the equipment, and there is a problem that removing the adhered precipitate will cause lithium loss. In addition, in order to separately separate the solid-phase precipitate, equipment such as sedimentation tanks or filters needs to be used, which may increase the equipment investment cost.

[0006] In addition, the precipitate contains a large amount of impurities and a refining process is required to remove these impurities. In order to feed the precipitate into the refining process, the precipitate needs to be redissolved. From the perspective of lithium, lithium is dissolved in the washing liquid and becomes a solid phase when precipitating, and it needs to go through the dissolution process again, so the process becomes complicated and there are economic problems.

[0007] Therefore, the technology of directly feeding the waste liquid into the refining process has received more and more attention. However, the concentration of lithium in the waste liquid is low, so the process efficiency decreases and there is a problem of decreased productivity. In order to effectively recover the lithium in the waste liquid, it is necessary to concentrate the waste liquid as much as possible and prevent the precipitation of lithium. Summary of the Invention

[0008] Technical Problem

[0009] The technical problem to be solved by the present invention is to provide a concentrated washing solution that can concentrate lithium as much as possible and does not produce precipitates when recovering lithium from a lithium-containing washing solution by evaporation and concentration.

[0010] Another technical problem to be solved by the present invention is to provide a method for recovering lithium from a lithium-containing waste liquid that can concentrate lithium as much as possible and does not produce precipitates when recovering lithium from a lithium-containing washing solution by evaporation and concentration.

[0011] Technical solution

[0012] The washing solution for lithium recovery according to an embodiment of the present invention is a washing solution prepared from a lithium-containing waste liquid and can satisfy the following formula 1.

[0013] <Formula 1>

[0014] [Li] / ([Na]+[K]+[S])≤0.50

[0015] In the above formula 1, [Li], [Na], [K], and [S] respectively represent the contents [g / L] of Li, Na, K, and S in the washing solution.

[0016] The method for recovering lithium from a lithium-containing waste liquid according to another embodiment of the present invention may include: a step of filtering a cathode material washing solution to separate solid metal contained in an alkaline waste liquid, a step of adding sulfuric acid to the cathode material washing solution from which the solid metal has been filtered to acidify it and converting lithium carbonate or lithium hydroxide into lithium sulfate, a step of concentrating the washing solution converted into the lithium sulfate to obtain a high-concentration lithium sulfate solution, and a step of mixing the high-concentration lithium sulfate solution into the product obtained from ore leaching.

[0017] In one embodiment, the step of mixing the high-concentration lithium sulfate solution into the product obtained from ore leaching may be performed before the step of refining the leached product. In one embodiment, in the step of adding sulfuric acid to the alkaline washing solution from which the solid metal has been filtered to acidify it and converting lithium carbonate or lithium hydroxide into lithium sulfate, the acidification may control the pH to 6 or less.

[0018] In one embodiment, in the step of concentrating the washing solution converted into the lithium sulfate to obtain a high-concentration lithium sulfate solution, the concentrated washing solution may satisfy the following formula 1.

[0019] <Formula 1>

[0020] [Li] / ([Na]+[K]+[S])≤0.50

[0021] In the above formula 1, [Li], [Na], [K], and [S] respectively represent the contents [g / L] of Li, Na, K, and S in the washing solution.

[0022] In one embodiment, the step of concentrating the water-washed solution converted to the lithium sulfate to obtain a high-concentration lithium sulfate solution may be to concentrate the mass of the water-washed solution to less than 1 / 2. In one embodiment, the step of concentrating the water-washed solution converted to the lithium sulfate to obtain a high-concentration lithium sulfate solution may be to concentrate the mass of the water-washed solution to the range of 1 / 2 to 1 / 8.

[0023] In one embodiment, the step of concentrating the water-washed solution converted to the lithium sulfate to obtain a high-concentration lithium sulfate solution may be to control the solid-phase ratio to 1.0% or less by weight. In one embodiment, the solid phase may be a Li2CO3 precipitate.

[0024] In one embodiment, carbon dioxide may be removed in the step of adding sulfuric acid to acidify the alkaline water-washed solution from which the solid metal has been filtered out and converting lithium carbonate or lithium hydroxide to lithium sulfate. In one embodiment, the high-concentration lithium sulfate solution obtained via the step of concentrating the water-washed solution converted to the lithium sulfate to obtain a high-concentration lithium sulfate solution may have a carbon content reduced by more than 50% compared with the alkaline water-washed solution.

[0025] In one embodiment, in the step of adding sulfuric acid to acidify the water-washed solution of the positive electrode material from which the solid metal has been filtered out and converting lithium carbonate or lithium hydroxide to lithium sulfate, 10 to 15 parts by weight of the sulfuric acid may be added based on 100 parts by weight of the water-washed solution of the positive electrode material. In one embodiment, the method for recovering lithium from the lithium-containing waste liquid may be a method for recovering the lithium component in the metal containing lithium and nickel and the water-washed solution of the positive electrode material containing sulfate in the preparation process of the positive electrode active material.

[0026] Advantageous Effects

[0027] The water-washed solution for recovering lithium according to one embodiment of the present invention provides a concentrated water-washed solution in which the lithium content satisfies less than 0.5 relative to sodium, potassium, and sulfur, so that lithium can be concentrated as much as possible or no precipitate is generated, and high-concentration lithium can be recovered.

[0028] The method for recovering lithium from a lithium-containing waste liquid according to another embodiment of the present invention provides a method for recovering lithium from a lithium-containing water-washed solution by adding an acid solution to lower the pH and then evaporating and concentrating, so that lithium can be concentrated as much as possible or no precipitate is generated. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a flowchart of a method for recovering lithium from a lithium-containing waste liquid according to one embodiment of the present invention.

[0030] Figure 2Schematic diagram of a method for recovering lithium from lithium-containing waste liquid according to an embodiment of the present invention.

[0031] Figure 3 Chart of the solid-phase ratio according to the concentration ratio according to an embodiment of the present invention. Detailed implementation manners

[0032] The terms first, second, third, etc. are used to describe various parts, components, regions, layers, and / or segments, but these parts, components, regions, layers, and / or segments should not be limited by these terms. These terms are only used to distinguish one part, component, region, layer, or segment from another part, component, region, layer, or segment. Therefore, without departing from the scope of the present invention, the first part, component, region, layer, or segment described below can also be described as the second part, component, region, layer, or segment.

[0033] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. Unless otherwise clearly indicated to the contrary in the context, the singular forms used herein are also intended to include the plural forms. The term "comprising" used in the specification can specifically refer to a certain property, field, integer, step, action, element, and / or component, but does not exclude the existence or addition of other properties, fields, integers, steps, actions, elements, and / or components.

[0034] If a part is described as being above another part, there may be other parts directly above or between the other part. When a part is described as being directly above another part, there are no other parts therebetween.

[0035] Although not otherwise defined, the meanings of all terms (including technical terms and scientific terms) used herein are the same as those commonly understood by those of ordinary skill in the art to which the present invention pertains. For terms defined in a dictionary, they should be interpreted as having a meaning consistent with the relevant technical literature and the content disclosed herein, and should not be interpreted in an idealized or overly formal sense.

[0036] In addition, unless otherwise specifically stated, % represents weight %, and 1 ppm is 0.0001 weight %.

[0037] Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art to which the present invention pertains can easily implement the present invention. However, the present invention can be implemented in various different ways and is not limited to the embodiments described herein.

[0038] Figure 1 Flowchart of a method for recovering lithium from lithium-containing waste liquid according to an embodiment of the present invention.

[0039] See Figure 1, A method for recovering lithium from a lithium-containing waste liquid according to an embodiment of the present invention is a method for recovering lithium components from a metal-containing lithium and nickel and a sulfate-containing positive electrode material washing liquid in a positive electrode active material preparation process, comprising: a step S100 of filtering the positive electrode material washing liquid to separate solid metal contained in the positive electrode material waste liquid, a step S200 of adding sulfuric acid to the positive electrode material washing liquid from which the solid metal has been filtered to acidify it and convert lithium carbonate or lithium hydroxide into lithium sulfate, a step S300 of concentrating the washing liquid converted into lithium sulfate to obtain a high-concentration lithium sulfate solution, and a step S400 of mixing the high-concentration lithium sulfate solution into the product obtained from ore leaching.

[0040] In the step S100 of filtering the positive electrode material washing liquid to separate solid metal contained in the positive electrode material waste liquid, the positive electrode material waste liquid may be a waste liquid generated in a positive electrode active material preparation process. Specifically, the waste liquid refers to a solution obtained by filtering after stirring a lithium transition metal oxide in a washing solution in order to reduce by-products such as lithium by-products present on its surface after preparing the lithium transition metal oxide. More specifically, the waste liquid may be a solution containing metals such as nickel, cobalt or manganese or containing lithium together with impurities such as nickel or sulfate.

[0041] In one embodiment, the positive electrode material washing liquid may be an alkaline solution. Specifically, the positive electrode material washing liquid may be an alkaline solution with a pH of 7 to 15, specifically 10 to 15. This may be due to the co-precipitation reaction in the positive electrode material preparation process, resulting in alkalinity due to the addition of an aqueous solution of NaOH or NH4OH.

[0042] In one embodiment, the positive electrode material washing liquid may contain lithium hydroxide or lithium carbonate. Specifically, the lithium hydroxide or the lithium carbonate may contain several hundred ppm to several thousand ppm of lithium.

[0043] The step S100 of filtering the positive electrode material washing liquid to separate solid metal contained in the positive electrode material waste liquid may be a step of separating a solid phase such as a metal oxide of the positive electrode material through a filtration process. Specifically, it may be a step of removing impurities contained in the waste liquid in the form of solids, i.e., the metal oxide. In one embodiment, the solid metal may be an oxide containing at least one of nickel, cobalt and manganese.

[0044] In one embodiment, the filtration process for separating the solid metal may be carried out by vacuum filtration using filter paper, and the pore size of the filter paper may be smaller than the average particle size (D50) of the solid metal. Specifically, the filter paper may contain pores of 1 μm to 5 μm, specifically 1 μm to 3 μm. In this way, through the filter paper, metal oxides in the waste liquid are filtered by the filter paper, and the remaining components pass through the filter paper, so that the solid phase and the liquid phase can be separated.

[0045] In step S200 of adding sulfuric acid to the washed solution of the positive electrode material after filtering out the solid metal to acidify it and converting lithium carbonate or lithium hydroxide into lithium sulfate, adding sulfuric acid to the basic washed solution can acidify the washed solution of the positive electrode material which is alkaline. Specifically, acidifying the washed solution of the positive electrode material can convert lithium carbonate and lithium hydroxide contained in the waste liquid into lithium sulfate through reactions such as the following reaction formulas 1 and 2.

[0046] [Reaction formula 1]

[0047] Li2CO3 + H2SO4 → Li2SO4 + CO2 + H2O

[0048] [Reaction formula 2]

[0049] 2LiOH + H2SO4 → Li2SO4 + 2H2O

[0050] In one embodiment, the step of adding sulfuric acid to the washed solution of the positive electrode material after filtering out the solid metal to acidify it and converting lithium carbonate or lithium hydroxide into lithium sulfate may include a step of removing carbon dioxide. Through reaction formula 1, carbon dioxide (CO2) is discharged in the form of a separate gas, and by discharging the carbon dioxide, the carbon content in the washed solution of the positive electrode material can be reduced.

[0051] In one embodiment, in step S200 of adding sulfuric acid to the basic washed solution after filtering out the solid metal to acidify it and converting lithium carbonate or lithium hydroxide into lithium sulfate, the acidification may control the pH to 6 or less. Specifically, the acidification may control the pH to 5 or less. If the pH is higher than the foregoing range, there is a problem that lithium carbonate precipitates during concentration.

[0052] In one embodiment, in step S200 of adding sulfuric acid to the washed solution of the positive electrode material after filtering out the solid metal to acidify it and converting lithium carbonate or lithium hydroxide into lithium sulfate, based on 100 parts by weight of the washed solution of the positive electrode material, 10 to 15 parts by weight of the sulfuric acid may be added. Specifically, based on 100 parts by weight of the washed solution of the positive electrode material, 12.0 to 14.5 parts by weight, specifically 12.9 to 14.1 parts by weight of the sulfuric acid may be added.

[0053] If the content of the sulfuric acid exceeds the upper limit value of the foregoing range, there is a problem that the sulfur (S) removal load increases in the refining process steps during the reuse of the washed solution. If the content of the sulfuric acid exceeds the lower limit value of the foregoing range, there is a problem that precipitates are generated during concentration.

[0054] Step S300 of concentrating the washing solution converted to the lithium sulfate to obtain a high-concentration lithium sulfate solution is a step of evaporating the washing solution using an evaporator to obtain a high-concentration lithium sulfate solution. Specifically, for the step of obtaining the high-concentration lithium sulfate solution, by evaporating the washing solution, the mass of the aqueous solution is reduced, and thus the concentration multiple can be confirmed. For example, when the mass of the aqueous solution is reduced to 1 / 2, 1 / 4, 1 / 5, 1 / 8 or 1 / 10, the concentration multiple of the aqueous solution can be 2 times, 4 times, 5 times, 8 times or 10 times.

[0055] In one embodiment, step S300 of concentrating the washing solution converted to the lithium sulfate to obtain a high-concentration lithium sulfate solution may be to concentrate the mass of the washing solution to less than 1 / 2. Specifically, the mass of the washing solution may be concentrated in the range of 1 / 2 to 1 / 8.

[0056] If concentrated beyond the upper limit value of the range, the solid-phase ratio is too high, and there is a problem of excessive formation of precipitates. If concentrated beyond the lower limit value of the range, there is a problem of low lithium recovery rate.

[0057] In one embodiment, step S300 of concentrating the washing solution converted to the lithium sulfate to obtain a high-concentration lithium sulfate solution may be to control the solid-phase ratio to 1.0% or less by weight. The solid phase may be a Li2CO3 precipitate. Specifically, the solid-phase ratio may be controlled to 0.56% or less. More specifically, the solid-phase ratio may be controlled to 0.26% or less. More specifically, the solid-phase ratio may be controlled to 0.16% or less.

[0058] If the solid-phase ratio exceeds the aforementioned range, the precipitates will adhere to the equipment and become an obstacle to the stable operation of the equipment, and there is a problem of lithium loss caused by removing the adhered precipitates.

[0059] In one embodiment, step S300 of concentrating the washing solution converted to the lithium sulfate to obtain a high-concentration lithium sulfate solution may be carried out in the temperature range of 50°C to 90°C. Specifically, the temperature range is 50°C to 80°C, and more specifically, it may be in the range of 60°C to 80°C. In one embodiment, the step of obtaining a high-concentration lithium sulfate solution by concentrating the washing solution converted to lithium sulfate may be carried out under an absolute pressure of 100 mbar to 300 mbar, specifically in the range of 150 mbar to 250 mbar.

[0060] If the temperature range exceeds the upper limit value, there is a problem of carry over. Specifically, as the temperature becomes too high, the pressure becomes too high, and not only water is removed, but also the lithium-containing solution is extracted, resulting in a problem of reduced lithium recovery rate. If the temperature range exceeds the lower limit value, there is a problem that evaporation and concentration cannot be carried out.

[0061] In one embodiment, in step S300 of concentrating the washed solution that is converted into the lithium sulfate to obtain a high-concentration lithium sulfate solution, the concentrated washed solution can satisfy the following formula 1.

[0062] <Formula 1>

[0063] [Li] / ([Na]+[K]+[S])≤0.50

[0064] In the above formula 1, [Li], [Na], [K], and [S] respectively represent the contents [g / L] of Li, Na, K, and S in the washed solution.

[0065] The above formula 1 is a relational expression of the lithium content in the washed solution converted into the lithium sulfate with respect to the total amount of impurities Na, K, and S. The above formula 1 can be 0.50 or less, specifically 0.40 to 0.50 or less. By satisfying the value of the above formula 1, lithium will not precipitate during concentration, thereby obtaining a concentrated washed solution with a high lithium content, which can improve the recovery rate of lithium recovered from the waste liquid.

[0066] If it exceeds the upper limit value of the above formula 1, there will be a problem that lithium precipitates during concentration. If it exceeds the lower limit value of the above formula 1, there will be a problem of excessive impurity content.

[0067] In step S400 of mixing the high-concentration lithium sulfate solution into the product obtained from ore leaching, the high-concentration lithium sulfate solution can be sent between the leaching process and the preliminary refining process of a conventional ore lithium recovery process. Specifically, the ore lithium recovery process can be carried out in the order of a calcination process of heating the lithium concentrate or ore to a high temperature to make the concentrate or the ore react easily with sulfuric acid, a roasting process of reacting the calcined concentrate or ore with sulfuric acid to convert lithium ions into lithium sulfate, and a leaching process and a refining process of dissolving lithium sulfate in water. By mixing the high-concentration lithium sulfate solution into the leaching process and the refining process in the aforementioned process, a lithium sulfate solution can be formed as in the prior art, and the lithium existing in the washed solution can be recycled. Therefore, no additional equipment is required, which has economic efficiency and environmental friendliness.

[0068] In one embodiment, step S400 of mixing the high-concentration lithium sulfate solution into the product obtained from ore leaching can be carried out before the step of refining the leached product. The concentrated lithium sulfate solution prepared from the washed solution of the positive electrode material is sent between the leaching process and the refining step, mixed with the lithium sulfate solution in the leaching process, and through the existing ore lithium process, it has the advantage of being able to recycle the lithium existing in the washed solution.

[0069] The washing solution for lithium recovery according to another embodiment of the present invention refers to the concentrated washing solution prepared in the step of obtaining high-concentration lithium sulfate by concentrating the washing solution converted into lithium sulfate in the above-mentioned method for lithium recovery. The washing solution for lithium recovery can satisfy the following formula (1).

[0070] <Formula (1)>[Li] / ([Na]+[K]+[S])≤0.50

[0071] [Li] / ([Na]+[K]+[S])≤0.50

[0072] In the above formula (1), [Li], [Na], [K], and [S] respectively represent the contents [g / L] of Li, Na, K, and S in the washing solution.

[0073] The detailed description of the above formula (1) is the same as the description in the foregoing Figure 1 .

[0074] Hereinafter, specific embodiments of the present invention will be described. However, the following embodiments are only specific embodiments of the present invention, and the present invention is not limited to the following embodiments.

[0075] Figure 2 is a schematic diagram of a method for recovering lithium from a lithium-containing waste liquid according to an embodiment of the present invention.

[0076] See Figure 2 , and the concentrated lithium sulfate solution can be added before the preliminary refining of the ore lithium extraction process by the same method as in Experimental Examples 1 to 3 below.

[0077] Experimental Example 1 - Example 1

[0078] 0.74 kg of 10% dilute sulfuric acid was added to 5.7 kg of the washing solution to prepare a mixed solution with a pH of 6, and the solution was evaporated using an evaporation concentrator at 70 °C and an absolute pressure of 200 mbar. Specifically, when concentrated 2 times, 4 times, 5 times, 8 times, and 10 times (the mass was reduced to 1 / 2, 1 / 4, 1 / 5, 1 / 8, and 1 / 10), the mass of the solution and the precipitated solid phase, and the concentrations of Li, Na, K, S, and C in the solution are shown in Table 1 below.

[0079] At this time, the pH of the washing solution was 12.7, and C existed in the solution in the form of HCO3 - or CO3 2- , and the washing solution satisfied Li: 4.4 g / L, S: 4.4 g / L, P: 0.009 g / L, K: 0.005 g / L, Na: 0.30 g / L, and C: 1.06 g / L.

[0080]

Table 1

[0081]

[0082] As can be confirmed from Table 1 above, the pH of the washing liquid decreased from 12.7 to 6, and the C concentration decreased by about 50%. Therefore, the amount of Li2CO3 precipitation can be reduced during concentration. In addition, when concentrated 8 times, the solid-phase precipitation amount can be controlled to be less than 1% of the total weight. Most of the solid-phase precipitates are Li2CO3.

[0083] Experimental Example 2 - Example 2

[0084] 0.74 kg of 10% dilute sulfuric acid was added to 5.7 kg of the washing liquid to prepare a mixed solution with a pH of 5, and the solution was evaporated using an evaporation concentrator at 70 °C and an absolute pressure of 200 mbar. Specifically, when concentrated 2 times, 4 times, 5 times, 8 times, and 10 times (the mass is reduced to 1 / 2, 1 / 4, 1 / 5, 1 / 8, and 1 / 10), the mass of the solution and the precipitated solid phase, as well as the concentrations of Li, Na, K, S, and C in the solution, are shown in Table 2 below.

[0085]

Table 2

[0086]

[0087] Referring to Table 2 above, when the pH is reduced to 5, the C concentration decreases by about 70%. Specifically, when the pH is reduced to 5, the solid-phase precipitation ratio after concentration 8 times is reduced to 0.16 wt%.

[0088] Experimental Example 3 - Example 3

[0089] 0.80 kg of 10% dilute sulfuric acid was added to 5.7 kg of the washing liquid to prepare a mixed solution with a pH of 4, and the solution was evaporated using an evaporation concentrator at 70 °C and an absolute pressure of 200 mbar. Specifically, when concentrated 2 times, 4 times, 5 times, 8 times, and 10 times (the mass is reduced to 1 / 2, 1 / 4, 1 / 5, 1 / 8, and 1 / 10), the mass of the solution and the precipitated solid phase, as well as the concentrations of Li, Na, K, S, and C in the solution, are shown in Table 3 below.

[0090]

Table 3

[0091]

[0092]

[0093] Referring to Table 3 above, when the pH is reduced to 4, the C concentration decreases by about 70%. When the pH is reduced to 4, the solid-phase precipitation ratio after concentration 8 times is reduced to 0.17 wt%.

[0094] Experimental Example 4 - Comparative Example

[0095] 5.7 kg of the water-washed solution was evaporated using an evaporation concentrator at 70 °C and an absolute pressure of 200 mbar. When concentrated 2-fold, 4-fold, 5-fold, 8-fold, and 10-fold (mass reduced to 1 / 2, 1 / 4, 1 / 8, 1 / 10), the mass of the solution and the precipitated solid phase, as well as the concentrations of Li, Na, K, S, and C in the solution, are shown in Table 4 below.

[0096]

Table 4

[0097]

[0098] It was confirmed from Table 4 above that even when concentrated 2-fold, more than 1 wt% of Li2CO3 precipitate was produced relative to the total weight.

[0099] Figure 3 is a graph of the solid phase ratio according to the concentration ratio according to an embodiment of the present invention.

[0100] See Figure 3 It was confirmed that the production ratio of solid phase lithium carbonate according to the concentration ratio can be controlled within 1 wt%. Specifically, when the pH is reduced to less than 6, the production ratio of solid phase lithium carbonate is within 1 wt%, and the water-washed solution can be concentrated 8-fold.

[0101] The present invention is not limited to the above-described embodiments and / or examples and can be prepared in various different ways. Those of ordinary skill in the art to which the present invention pertains can understand that the present invention can be implemented in other specific ways without changing the technical idea or essential features 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 method for recovering lithium from lithium-containing waste liquid, comprising: filtering the washing liquid of the positive electrode material to separate the solid metal contained in the alkaline waste liquid; adding sulfuric acid to the washing liquid of the positive electrode material after filtering out the solid metal to acidify it and converting lithium carbonate or lithium hydroxide into lithium sulfate; concentrating the washing liquid converted into the lithium sulfate to obtain a high-concentration lithium sulfate solution; and mixing the high-concentration lithium sulfate solution into the product obtained from the ore leaching.

2. The method for recovering lithium from lithium-containing waste liquid according to claim 1, wherein the step of mixing the high-concentration lithium sulfate solution into the product obtained from the ore leaching is carried out before the step of refining the leached product.

3. The method for recovering lithium from lithium-containing waste liquid according to claim 1, wherein in the step of adding sulfuric acid to the alkaline washing liquid after filtering out the solid metal to acidify it and converting lithium carbonate or lithium hydroxide into lithium sulfate, the acidification is to control the pH to below 6.

4. The method for recovering lithium from lithium-containing waste liquid according to claim 1, wherein in the step of concentrating the washing liquid converted into the lithium sulfate to obtain a high-concentration lithium sulfate solution, the concentrated washing liquid satisfies the following formula 1, [Formula 1] [Li] / ([Na]+[K]+[S])≤0.50 In the above formula 1, [Li], [Na], [K], and [S] respectively represent the contents [g / L] of Li, Na, K, and S in the washing liquid.

5. The method for recovering lithium from lithium-containing waste liquid according to claim 1, wherein the step of concentrating the washing liquid converted into the lithium sulfate to obtain a high-concentration lithium sulfate solution is to concentrate the mass of the washing liquid to less than 1 / 2.

6. The method for recovering lithium from lithium-containing waste liquid according to claim 1, wherein the step of concentrating the washing liquid converted into the lithium sulfate to obtain a high-concentration lithium sulfate solution is to concentrate the mass of the washing liquid to the range of 1 / 2 to 1 / 8.

7. The method for recovering lithium from lithium-containing waste liquid according to claim 1, wherein the step of concentrating the washing liquid converted into the lithium sulfate to obtain a high-concentration lithium sulfate solution is to control the solid phase ratio to 1.0% or less by weight.

8. The method for recovering lithium from lithium-containing waste liquid according to claim 7, wherein the solid phase is a lithium carbonate precipitate.

9. The method for recovering lithium from lithium-containing waste liquid according to claim 1, wherein in the step of adding sulfuric acid to the alkaline washing liquid after filtering out the solid metal to acidify it and converting lithium carbonate or lithium hydroxide into lithium sulfate, carbon dioxide is removed.

10. The method for recovering lithium from lithium-containing waste liquid according to claim 1, wherein the high-concentration lithium sulfate solution obtained through the step of concentrating the washing liquid converted into the lithium sulfate to obtain a high-concentration lithium sulfate solution has a carbon content reduced by more than 50% compared with the alkaline washing liquid.

11. The method for recovering lithium from lithium-containing waste liquid according to claim 1, wherein In the step of acidifying the washing solution of the positive electrode material by adding sulfuric acid to filter out the solid metal and converting lithium carbonate or lithium hydroxide into lithium sulfate, 10 to 15 parts by weight of the sulfuric acid is added based on 100 parts by weight of the washing solution of the positive electrode material.

12. The method for recovering lithium from a lithium-containing waste liquid according to claim 1, wherein the method is a method for recovering lithium components from a washing solution of a positive electrode material containing lithium, nickel, and sulfate during the preparation process of a positive electrode active material.

13. A washing solution for recovering lithium, wherein the washing solution is a washing solution prepared from a lithium-containing waste liquid and satisfies the following formula 1: <Formula 1> [Li] / ([Na]+[K]+[S])≤0.50 In the above formula 1, [Li], [Na], [K], and [S] respectively represent the contents [g / L] of Li, Na, K, and S in the washing solution.

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