Method for purifying lithium sulfate solution

Abstract

Provided is a method for purifying a lithium sulfate solution, the method comprising the steps of: obtaining a lithium sulfate solution from an ore-based lithium mixed raw material comprising a lithium-containing ore and pulverized waste refractory sagger; and adding a carbonate supplementary material to the lithium sulfate solution to precipitate and remove magnetic impurities.

Description

Method for purifying lithium sulfate solution

[0001] The present invention relates to a method for purifying a lithium sulfate solution.

[0002] The positive electrode active material of a lithium secondary battery is manufactured by firing salts of cobalt, nickel, manganese, etc., containing lithium, at high temperatures in a refractory box mainly composed of silicon, aluminum, and magnesium oxides. During this process, some of the raw materials of the positive electrode active material react with the surface of the refractory box, causing deterioration of the refractory box and, in severe cases, breakage during the process. Therefore, the refractory box is discarded after a certain number of uses.

[0003] The object of the present invention is to provide a method for purifying a lithium sulfate solution capable of effectively removing magnetic foreign matter.

[0004] The objects of the present invention are not limited to those mentioned above, and other unmentioned objects and advantages of the present invention may be understood from the following description and will be more clearly understood by the embodiments of the present invention. Furthermore, it will be readily apparent that the objects and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0005] In one embodiment of the present invention, a method for purifying a lithium sulfate solution is provided, comprising the steps of: obtaining a lithium sulfate solution from an ore-based lithium mixed raw material including a lithium-containing ore and crushed waste refractory armor; and adding a carbonate auxiliary raw material to the lithium sulfate solution to precipitate and remove magnetic impurities.

[0006] The lithium sulfate solution from which the above magnetic foreign matter has been removed by precipitation may have a total content of magnetic foreign matter of 20 μg / L or less.

[0007] The pH can be adjusted to 9 to 11 by adding a carbonate auxiliary material to the above lithium sulfate solution.

[0008] The above carbonate auxiliary raw material may include at least one selected from the group consisting of Na2CO3, Li2CO3, and combinations thereof.

[0009] The above magnetic foreign material may include at least one selected from the group consisting of nickel, cobalt, chromium, and combinations thereof.

[0010] The method for purifying the above lithium sulfate solution may further include the step of adding a hydroxide auxiliary material to the above lithium sulfate solution to precipitate and remove magnesium.

[0011] The pH can be adjusted to 10 to 13 by adding a hydroxide auxiliary material to the above lithium sulfate solution.

[0012] The above hydroxide auxiliary material may include at least one selected from the group consisting of NaOH, LiOH, and combinations thereof.

[0013] The step of removing the magnetic foreign matter by precipitating it and the step of removing the magnesium by precipitating it can be performed sequentially.

[0014] The method for purifying the above lithium sulfate solution further includes the step of adding a basic auxiliary material to the above lithium sulfate solution to precipitate and remove impurities, and after adding the basic auxiliary material, the carbonate may be added to the above lithium sulfate solution.

[0015] The pH can be adjusted to 7 to 9 by adding a basic auxiliary material to the above lithium sulfate solution.

[0016] The above basic auxiliary raw material may include at least one selected from the group consisting of NaOH, LiOH, Ca(OH)2, CaCO3, CaO, and combinations thereof.

[0017] The impurities precipitated by adding the above basic auxiliary raw material may include at least one selected from the group consisting of silica, aluminum, iron, and combinations thereof.

[0018] The above lithium-containing ore and the above crushed waste refractory material may be mixed in a mass ratio of 86 to 96: 4 to 14.

[0019] The above lithium-containing ore may contain spodumene.

[0020] By purifying the above lithium sulfate solution, a high-purity lithium sulfate solution from which magnetic impurities are effectively removed can be obtained. From the high-purity lithium sulfate solution obtained by purifying the above lithium sulfate solution, a high-purity lithium compound that can be used as a material for a secondary battery can be obtained.

[0021] In addition to the effects described above, the specific effects of the present invention are described together with the specific details for implementing the invention below.

[0022] Figure 1 is a graph showing the change in solubility of metal element hydroxides according to pH.

[0023] Figure 2 is a graph showing the results of measuring the content of magnetic impurities, such as nickel, cobalt, and chromium, in a high-purity lithium sulfate solution obtained by a method of purifying a lithium sulfate solution according to one embodiment of the present invention by analyzing it with Mass Spectroscopy.

[0024] The aforementioned objectives, features, and advantages are described in detail below with reference to the attached drawings, thereby enabling those skilled in the art to easily implement the technical concept of the present invention. In describing the present invention, detailed descriptions of known technologies related to the present invention are omitted if it is determined that such descriptions would unnecessarily obscure the essence of the invention. Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the attached drawings. In the drawings, the same reference numerals are used to indicate the same or similar components.

[0025] In the following, the statement that any configuration is placed on the "upper (or lower)" of a component or on the "upper (or lower)" of a component may mean not only that any configuration is placed in contact with the upper (or lower) surface of said component, but also that another configuration may be interposed between said component and any configuration placed on (or below) said component.

[0026] In addition, where it is stated that one component is "connected," "combined," or "connected" to another component, it should be understood that while the components may be directly connected or connected to each other, another component may be "interposed" between each component, or each component may be "connected," "combined," or "connected" through another component.

[0027] In this specification, lithium, sulfur, magnesium, calcium, sodium, potassium, etc., may be in a form that exists in raw materials, extracts, or precipitates, and are collectively referred to as types of elements without being limited to a specific form, such as metal atoms, atoms, ions, or salts, and when distinction is necessary, they may be understood as being in a state that exists according to the laws of nature.

[0028] In one embodiment of the present invention, a method for purifying a lithium sulfate solution is provided, comprising the steps of: obtaining a lithium sulfate solution from an ore-based lithium mixed raw material including a lithium-containing ore and crushed waste box saggar; and adding a carbonate auxiliary raw material to the lithium sulfate solution to precipitate and remove magnetic foreign matter.

[0029] The method for purifying the above lithium sulfate solution can be applied to a method for recovering lithium from lithium-containing ore and crushed waste refractory materials, and a high-purity lithium sulfate solution can be obtained by the method for purifying the above lithium sulfate solution, and a high-purity lithium compound that can be used as a material for a secondary battery can be obtained therefrom.

[0030] Refractory casings, whose main components are silicon, aluminum, and magnesium oxides, are used in the manufacture of positive electrode active materials for secondary batteries. Therefore, waste refractory casings contain not only the main components of the refractory casings but also additionally contain salts of cobalt, nickel, manganese, etc., including lithium, which is a raw material for the positive electrode active material. The method for purifying the lithium sulfate solution is a method that can recover lithium with high purity by removing impurities from a raw material in which crushed waste refractory casings are mixed with lithium-containing ore.

[0031] The above magnetic foreign material may include at least one selected from the group consisting of nickel (Ni), cobalt (Co), chromium (Cr), and combinations thereof.

[0032] As the amount of waste refractory materials generated increases due to the rapid increase in demand for lithium secondary batteries, the method of purifying the above lithium sulfate solution is significant as a method to utilize waste refractory materials as raw materials for the lithium process. In addition to lithium, waste refractory materials contain magnetic impurities such as cobalt, nickel, and manganese originating from the raw materials of the cathode active material, as well as small amounts of chromium derived from impurities in the raw materials of cobalt or nickel. It is known that when these magnetic impurities are included in the cathode material, they migrate from the cathode to the anode during the charging and discharging process, forming dendrites that penetrate the separator and cause internal short circuits, thereby degrading battery stability. The method of purifying the above lithium sulfate solution is a method to obtain a lithium sulfate solution from which these magnetic impurities have been effectively removed.

[0033] In one embodiment, the lithium sulfate solution obtained by precipitating and removing magnetic foreign matter by a method of purifying the lithium sulfate solution may contain a total content of magnetic foreign matter of 20 μg / L or less. Given the current situation where the management standards for magnetic foreign matter by secondary battery material manufacturers are becoming increasingly strict and are expected to be tightened to less than 20 ppb, the lithium sulfate solution obtained by the method of purifying the lithium sulfate solution may be a method for obtaining a lithium sulfate solution that satisfies these standards.

[0034] The above ore-based lithium mixed raw material can be prepared by mixing the above lithium-containing ore and the above crushed waste refractory material in a mass ratio of 86 to 96: 4 to 14.

[0035] The above lithium-containing ore may contain spodumene. For example, the above lithium-containing ore may be prepared as a calcined spodumene product heat-treated at 1,100°C.

[0036] The above lithium sulfate solution can be obtained as a sulfuric acid leachate by mixing the above ore-based lithium mixed raw material with sulfuric acid and then roasting it. Specifically, the above lithium sulfate solution can be obtained by mixing the above ore-based lithium mixed raw material with sulfuric acid, roasting it at 200 to 250°C, mixing it with water to leach it, and then separating the solid and liquid.

[0037] A carbonate auxiliary material can be added to the above lithium sulfate solution, and the magnetic impurity can be removed by precipitating it in the form of a carbonate.

[0038] In one embodiment, a carbonate auxiliary material can be added to the lithium sulfate solution to adjust the pH to 9 to 11. The removal rate of magnetic foreign matter can be increased by increasing the proportion of magnetic foreign matter that can be precipitated in the form of carbonate within the above pH range. For example, the amount of carbonate auxiliary material added can be adjusted to achieve the above pH range.

[0039] In addition to the magnetic foreign matter, impurities such as calcium and manganese can be removed by precipitating them in the form of carbonates by adding a carbonate auxiliary material to the above lithium sulfate solution.

[0040] Figure 1 is a graph showing the change in solubility of metal element hydroxides according to pH (Source: Ajiboye, TO, et. al., Metal hydroxide solubility against pH, J. Inorg. Organomet. Polym. Mater., 31, 1419-1442 (2021)). In Figure 1, cobalt, nickel, chromium, etc. in aqueous solution commonly exhibit the lowest solubility around pH 10, forming precipitates in the form of hydroxide salts.

[0041] The above carbonate auxiliary raw material may include, for example, at least one selected from the group consisting of Na2CO3, Li2CO3, and combinations thereof.

[0042] The method for purifying the above lithium sulfate solution may additionally include the step of adding a hydroxide auxiliary material to the above lithium sulfate solution to precipitate and remove magnesium.

[0043] In one embodiment, a carbonate auxiliary material can be added to the lithium sulfate solution to adjust the pH to 10 to 13. The removal rate of magnesium can be increased by increasing the proportion of magnesium that can be precipitated in the form of a hydroxide salt within the above pH range. For example, the amount of hydroxide auxiliary material added can be adjusted to achieve the above pH range.

[0044] The above hydroxide auxiliary material may include at least one selected from the group consisting of NaOH, LiOH, and combinations thereof.

[0045] In one embodiment, the step of precipitating and removing the magnetic foreign matter and the step of precipitating and removing the magnesium can be performed sequentially.

[0046] The method for purifying the above lithium sulfate solution may additionally include the step of adding a basic auxiliary material to the lithium sulfate solution to precipitate and remove impurities.

[0047] Since the above-mentioned added basic auxiliary raw material can form salts and precipitate impurities such as silica, aluminum, and iron, it is possible to remove them to remove impurities such as silica, aluminum, and iron.

[0048] The step of adding the basic auxiliary material can be performed in advance of the step of adding the carbonate to remove magnetic foreign matter. That is, after adding the basic auxiliary material to the lithium sulfate solution to precipitate and remove impurities, the carbonate can be added to the lithium sulfate solution to precipitate and remove magnetic foreign matter.

[0049] In one embodiment, a basic auxiliary material can be added to the lithium sulfate solution to adjust the pH to 7 to 9. The removal rate of impurities can be increased by increasing the proportion of impurities, such as silica, aluminum, and iron, that can be precipitated within the above pH range. For example, the amount of basic auxiliary material added can be adjusted to achieve the above pH range.

[0050] The above basic auxiliary raw material may include at least one selected from the group consisting of NaOH, LiOH, Ca(OH)2, CaCO3, CaO, and combinations thereof.

[0051] In one embodiment, a process of purifying impurities by the method of purifying the lithium sulfate solution and obtaining lithium hydroxide from the obtained lithium sulfate solution can be further performed.

[0052] In one embodiment, a process of purifying impurities by the method of purifying the lithium sulfate solution and obtaining lithium carbonate from the obtained lithium sulfate solution can be further performed.

[0053] The process for obtaining lithium hydroxide or the process for obtaining lithium carbonate may be based on a method known as a method for obtaining lithium hydroxide or lithium carbonate from lithium sulfate.

[0054]

[0055] Examples and comparative examples of the present invention are described below. The following examples are merely embodiments of the present invention, and the present invention is not limited to the following examples.

[0056]

[0057] (Example)

[0058] Example 1

[0059] An ore-based lithium mixed raw material was prepared by mixing calcined spodumene and crushed waste refractory metal in a mass ratio of 91:9. The ore-based lithium mixed raw material was roasted with sulfuric acid to obtain a lithium sulfate solution. Ca(OH)2 was added to the lithium sulfate solution to precipitate it at pH 8.2, and then the precipitate was removed by solid-liquid separation to perform primary purification. To 1 L of the low-purity lithium sulfate solution at pH 8.2 obtained through solid-liquid separation, 31.8 g of Na2CO3, a carbonate auxiliary raw material, was added to precipitate magnetic impurities such as cobalt, nickel, and chromium at pH 10.23 and removed through solid-liquid separation to perform the first step of secondary purification. Next, 31.5g of NaOH, a hydroxide auxiliary material, was added to the above lithium sulfate solution to raise the pH to 12.1 to form magnesium as a precipitate, and the magnesium was removed by solid-liquid separation to perform the second step of secondary purification, thereby producing a high-purity lithium sulfate solution.

[0060]

[0061] Example 2

[0062] An ore-based lithium mixed raw material was prepared by mixing calcined spodumene and crushed waste refractory armor in a mass ratio of 91:9. The ore-based lithium mixed raw material was roasted with sulfuric acid to obtain a lithium sulfate solution. Ca(OH)2 was added to the lithium sulfate solution to precipitate it at pH 8.2, and then the precipitate was removed by solid-liquid separation to perform primary purification. To 1 L of the low-purity lithium sulfate solution at pH 8.2 obtained through solid-liquid separation, 31.8 g of Na2CO3, a carbonate auxiliary raw material, and 31.5 g of NaOH, a hydroxide auxiliary raw material, were simultaneously added to raise the pH to 12.2 to form a precipitate, which was then removed by solid-liquid separation to perform secondary purification and produce a high-purity lithium sulfate solution.

[0063]

[0064] Experimental Example

[0065] The content of magnetic impurities such as nickel, cobalt, and chromium in the high-purity lithium sulfate solutions obtained in Examples 1 and 2 was measured by mass spectroscopy, and the results are shown in Figure 2.

[0066] Referring to Fig. 2, the total amount of magnetic foreign substances such as nickel, cobalt, and chromium in the high-purity lithium sulfate aqueous solution obtained by sequentially performing the first and second steps of secondary purification in Example 1 was 4 μg / L, and the total amount of magnetic foreign substances such as nickel, cobalt, and chromium in the high-purity lithium sulfate aqueous solution obtained in Example 2 was 12 μg / L. In Example 1, since the first and second steps of secondary purification were performed separately, magnetic foreign substances such as chromium, which have higher solubility at the pH of the second step, were sufficiently removed in the first step, and then additional magnetic foreign substances suitable for removal at the pH of the second step could be removed, so it is understood that more magnetic foreign substances were removed as a result. In Example 2, since the first and second steps of secondary purification were performed simultaneously, the solubility of chromium at the corresponding pH was slightly higher, so it is understood that the removal rate of magnetic foreign substances was lower compared to Example 1.

[0067]

[0068] Although the present invention has been described above with reference to embodiments, the present invention is not limited by the embodiments disclosed in this specification, and it is obvious that various modifications can be made by a person skilled in the art within the scope of the technical concept of the present invention. Furthermore, even if the effects of the configuration of the present invention were not explicitly described while describing the embodiments of the present invention above, it is natural to acknowledge that the effects predictable by said configuration should also be recognized.

Claims

1. A step of obtaining a lithium sulfate solution from an ore-based lithium mixed raw material comprising lithium-containing ore and crushed waste refractory materials; and A method for purifying a lithium sulfate solution comprising the step of adding a carbonate auxiliary material to the lithium sulfate solution to precipitate and remove magnetic impurities.

2. In Paragraph 1, The lithium sulfate solution from which the above magnetic impurities have been precipitated and removed has a total magnetic impurity content of 20 μg / L or less. Method for purifying lithium sulfate solution.

3. In Paragraph 1, Adding a carbonate auxiliary material to the above lithium sulfate solution to adjust the pH to 9 to 11 Method for purifying lithium sulfate solution.

4. In Paragraph 1, The above carbonate auxiliary raw material comprises at least one selected from the group consisting of Na2CO3, Li2CO3, and combinations thereof. Method for purifying lithium sulfate solution.

5. In Paragraph 1, The above magnetic foreign material comprises at least one selected from the group consisting of nickel, cobalt, chromium, and combinations thereof. Method for purifying lithium sulfate solution.

6. In Paragraph 1, The method further includes the step of adding a hydroxide auxiliary material to the above lithium sulfate solution to precipitate and remove magnesium. Method for purifying lithium sulfate solution.

7. In Paragraph 6, Adding a hydroxide auxiliary material to the above lithium sulfate solution to adjust the pH to 10 to 13 Method for purifying lithium sulfate solution.

8. In Paragraph 6, The above hydroxide auxiliary material comprises at least one selected from the group consisting of NaOH, LiOH, and combinations thereof. Method for purifying lithium sulfate solution.

9. In Paragraph 6, The step of precipitating and removing the magnetic foreign matter and the step of precipitating and removing the magnesium are performed sequentially. Method for purifying lithium sulfate solution.

10. In Paragraph 1, The method further includes the step of adding a basic auxiliary material to the above lithium sulfate solution to precipitate and remove impurities, and After adding the above basic auxiliary raw material, the carbonate is added to the above lithium sulfate solution. Method for purifying lithium sulfate solution.

11. In Paragraph 10, Adding a basic auxiliary material to the above lithium sulfate solution to adjust the pH to 7 to 9 Method for purifying lithium sulfate solution.

12. In Paragraph 10, The above basic auxiliary raw material comprises at least one selected from the group consisting of NaOH, LiOH, Ca(OH)2, CaCO3, CaO, and combinations thereof. Method for purifying lithium sulfate solution.

13. In Paragraph 12, The impurity precipitated by adding the above basic auxiliary raw material comprises at least one selected from the group consisting of silica, aluminum, iron, and combinations thereof. Method for purifying lithium sulfate solution.

14. In Paragraph 1, The above lithium-containing ore and the above crushed waste refractory material are mixed in a mass ratio of 86 to 96: 4 to 14. Method for purifying lithium sulfate solution.

15. In Paragraph 1, The above lithium-containing ore includes spodumene Method for purifying lithium sulfate solution.

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