Method for purifying lithium sulfate solution

Abstract

Provided is a method for purifying a lithium sulfate solution, comprising the steps of: leaching a lithium-containing ore with sulfuric acid to obtain a lithium sulfate solution mixed with a leach residue; adding an alkaline supplementary material to the lithium sulfate solution mixed with the leach residue to form a magnesium precipitate; and removing the magnesium precipitate and the leach residue by solid-liquid separation, wherein the step of forming the magnesium precipitate is performed at a pH higher than the isoelectric point of the magnesium precipitate and lower than the isoelectric point of the leach residue.

Description

Method for purifying lithium sulfate solution

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

[0002] With the imminent arrival of the electric vehicle era, the lithium-ion battery industry is growing rapidly, and the demand for lithium as a battery material is continuously increasing. Commercial production of lithium is broadly categorized into methods of extraction from ore and production from brine in the form of lithium carbonate or lithium hydroxide. Most of the lithium produced from ore is generated from spodumene ore using the sulfuric acid method, while lithium produced from brine is primarily obtained from underground brine in South America through natural drying followed by the removal of byproducts and additional processing.

[0003] The objective of the present invention is to provide a method for purifying a lithium sulfate solution that can reduce the excessive process load applied to a solid-liquid separation facility caused by the large amount of magnesium precipitate generated when removing magnesium impurities from a lithium sulfate solution.

[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: leaching a lithium-containing ore with sulfuric acid to obtain a lithium sulfate solution mixed with a leaching residue; adding an alkaline auxiliary material to the lithium sulfate solution mixed with the leaching residue to produce a magnesium precipitate; and removing the magnesium precipitate and the leaching residue by solid-liquid separation, wherein the step of producing the magnesium precipitate is performed at a pH higher than the isoelectric point of the magnesium precipitate and lower than the isoelectric point of the leaching residue.

[0006] A lithium sulfate solution mixed with the leaching residue can be obtained by performing a sulfuric acid roasting process on the above lithium-containing ore.

[0007] The pH may be 8.5 to 9.5, which is higher than the isoelectric point of the magnesium precipitate and lower than the isoelectric point of the leaching residue.

[0008] The above alkaline auxiliary raw material may include at least one selected from the group consisting of Ca(OH)2, CaCO3, CaO, NaOH, LiOH, and combinations thereof.

[0009] CaCO3 can be added as a primary alkaline auxiliary raw material to adjust the pH to 6 to 8, and then at least one selected from the group consisting of Ca(OH)2, CaO, NaOH, LiOH, and combinations thereof can be added as a secondary step to adjust the pH to 8.5 to 9.5.

[0010] The above magnesium precipitate may contain Mg(OH)2.

[0011] The above leaching residue may include an aluminosilicate-based material.

[0012] The step of generating the magnesium precipitate above can be performed at a pH higher than the isoelectric point of Mg(OH)2 and lower than the isoelectric point of an aluminosilicate-based material.

[0013] In the step of generating the above magnesium precipitate, Si4+ , Al 3+ , Fe 3+ Cation impurities including at least one selected from the group consisting of combinations thereof may be precipitated together.

[0014] If the above alkaline auxiliary material is the first alkaline auxiliary material, the method for purifying the above lithium sulfate solution may further include the step of precipitating magnesium by adding the second alkaline auxiliary material after removing the above magnesium precipitate and the above leaching residue by solid-liquid separation.

[0015] The step of precipitating the magnesium above can be performed at a pH of 10 to 12.

[0016] The method for purifying the above lithium sulfate solution further includes a first purification step of first adding the above alkaline auxiliary raw material to adjust the pH to 6 to 8, and following the first purification step, may perform a step of generating the above magnesium precipitate and a step of removing the above magnesium precipitate and the above leaching residue by solid-liquid separation.

[0017] The method for purifying the above lithium sulfate solution may further include: a step of generating the above magnesium precipitate and a step of removing the above magnesium precipitate and the above leaching residue by solid-liquid separation, followed by a secondary purification step of precipitating and removing magnesium at a pH of 10 to 12.

[0018] The method for purifying the above lithium sulfate solution is,

[0019] If the above alkaline auxiliary material is referred to as the first alkaline auxiliary material,

[0020] In the above first purification step, CaCO3 is added as the first alkaline auxiliary raw material, and

[0021] In the step of generating the magnesium precipitate, the first alkaline auxiliary raw material comprising at least one selected from the group consisting of Ca(OH)2, CaO, NaOH, LiOH, and combinations thereof is added, and

[0022] In the above second purification step, a second alkaline auxiliary raw material comprising at least one selected from the group consisting of NaOH, Na2CO3, LiOH, Li2CO3 and combinations thereof may be added.

[0023] In the step of precipitating the magnesium above, Ca 2+ , Mn 2+ , Mn 3+ , Mn 4+ , Mn 5+ , Mn 6+ , Mn 7+ Cation impurities including at least one selected from the group consisting of combinations thereof may be precipitated together.

[0024] The above method for purifying the lithium sulfate solution can reduce the excessive process load applied to the solid-liquid separation facility by generating a large amount of magnesium precipitate when removing magnesium impurities from the lithium sulfate solution.

[0025] 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.

[0026] Figure 1 is a graph showing the isoelectric point by measuring the zeta potential of the leaching residue and Mg(OH)2.

[0027] Figure 2 is a graph showing the results of measuring the concentrations of Mg and Li components according to pH change for a lithium sulfate solution.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] In one embodiment of the present invention,

[0032] A method for purifying a lithium sulfate solution is provided, comprising the steps of: leaching a lithium-containing ore with sulfuric acid to obtain a lithium sulfate solution mixed with a leaching residue; adding an alkaline auxiliary material to the lithium sulfate solution mixed with the leaching residue to produce a magnesium precipitate; and removing the magnesium precipitate and the leaching residue by solid-liquid separation. In the method for purifying the lithium sulfate solution, the step of producing the magnesium precipitate is performed at a pH that is higher than the isoelectric point of the magnesium precipitate and lower than the isoelectric point of the leaching residue.

[0033] The method for purifying the lithium sulfate solution described above may be performed as a preliminary purification step prior to a purification step primarily aimed at removing magnesium ions contained as impurities, or as a primary purification process, followed by a secondary purification process primarily aimed at removing magnesium ions as a subsequent process. In this way, by partially removing magnesium ions contained as impurities from the lithium sulfate solution through the method for purifying the lithium sulfate solution described above, the amount of precipitate generated from magnesium ions contained as impurities in the purification step primarily aimed at removing magnesium ions or in the secondary purification process may be reduced, and the process load associated with this can be alleviated.

[0034] In one embodiment, a lithium sulfate solution mixed with the leaching residue can be obtained by performing a sulfuric acid roasting process on the lithium-containing ore.

[0035] For example, in a process for producing lithium carbonate or lithium hydroxide from ore, the lithium sulfate solution can be produced by a sulfuric acid method based on a leaching process in which a concentrate containing α-spodumene is heat-treated at around 1,000°C to convert it into a highly reactive β-spodumene phase, then undergoes a calcination process in which the concentrate is reacted with concentrated sulfuric acid at 200 to 250°C to synthesize lithium sulfate, and then is dissolved in water to extract the lithium sulfate solution.

[0036] In the lithium sulfate solution obtained from the leaching process in the above sulfuric acid method, in addition to lithium, Si 4+ , Al 3+ , Fe 3+ , Mg 2+ , Ca 2+ , Mn 2+ , Mn 3+ , Mn 4+ , Mn 5+ , Mn 6+ , Mn 7+ Various polyvalent cation impurities of divalent or higher valence coexist, and these polyvalent cation impurities can be removed by forming a precipitate based on differences in solubility according to pH, followed by a solid-liquid separation step. However, since the pH ranges at which impurities form precipitates may vary, and in the case of magnesium ions, precipitates form in high pH regions, the process is generally performed in a neutral pH range of 7 to remove Si along with water-insoluble residue components. 4+ , Al 3+ , Fe 3+ A process to remove etc. is performed as a primary purification process, and a secondary purification process is performed at a pH of approximately 11 or higher to remove Mg 2+ , Ca 2+..., Mn polyvalent cations, etc., can be removed. For example, since the material that has undergone the roasting process contains sulfuric acid, the lithium sulfate solution dispersed in water becomes acidic; therefore, alkaline auxiliary materials such as Ca(OH)2, CaCO3, CaO, NaOH, and LiOH can be added in the first purification process, and alkaline auxiliary materials such as NaOH, Na2CO3, LiOH, and Li2CO3 can be added in the second purification process. Among various polyvalent cation impurities, Mg 2+ As pH increases, solubility decreases and it precipitates as Mg(OH)2, so it is removed by precipitating as Mg(OH)2 in the above secondary purification process. Since the Mg(OH)2 generated as a precipitate has very small particles and exists in the form of a viscous gel in an aqueous solution, it is known to cause process issues such as filter cloth clogging and poor separation in filter cloth type solid-liquid separation equipment, such as filter presses and candle filters, which are mainly used in the solid-liquid separation stage after the above secondary purification process.

[0037] The method of purifying the lithium sulfate solution described above is performed before the secondary purification process, thereby generating and removing magnesium precipitates to a certain level in advance. As mentioned earlier, this allows for the avoidance of processing an excess amount of Mg(OH)2 precipitates all at once, thereby reducing or improving process issues such as clogging of the filter cloth and poor detachment in a filter cloth type solid-liquid separation facility.

[0038] For example, spodumene concentrate used in the process of extracting lithium from lithium-containing ore contains approximately 5–6% lithium. After undergoing a leaching process in which lithium sulfate is dissolved in water, most of the material exists in a solid form, which is referred to as the leaching residue. During the solid-liquid separation process following the aforementioned primary purification process, Si 4+ , Al 3+ , Fe 3+It can be removed along with impurities. The main component of the above-mentioned leaching residue is an aluminosilicate-based material (HAlSiO6) in which the lithium of spodumene (LiAlSiO6) is substituted with hydrogen, and it can be seen from the zeta potential measurement results that it has an isoelectric point around pH 11.3. Meanwhile, the isoelectric point of Mg(OH)2 known in the literature is around pH 9. At pH lower than the isoelectric point of Mg(OH)2 (Reference: Pilarska, A., Nowacka, M., Pilarski, K., Paukszta, D., Klapiszewski, L., Jesionowski, T. Preparation and characterisation of unmodified and poly(ethylene glycol) grafted magnesium hydroxide. Physicochem. Probl. Miner. Process. 49(2), 701-712 (2013)), both the leaching residue and Mg(OH)2 have positively charged surface charges. However, at pH 9, the surface charge of the leaching residue remains positively charged while the surface charge of Mg(OH)2 becomes negatively charged, and Mg(OH)2 can be removed from the solution by aggregating with each other due to electrostatic attraction.

[0039] Figure 1 is a graph showing the isoelectric point obtained by measuring the zeta potential of the leaching residue when NaOH is used as an alkaline auxiliary material, along with the zeta potential of Mg(OH)2 known in the literature (when NH4OH is used as an alkaline auxiliary material). Referring to Figure 1, it can be confirmed that at around pH 9, the surface charge of the leaching residue is positively charged, while the surface charge of Mg(OH)2 can be negatively charged. The exact pH value corresponding to the above isoelectric point may vary slightly or have an error depending on the type of alkaline auxiliary material.

[0040] According to this principle, the step of generating the magnesium precipitate can generate the magnesium precipitate (Mg(OH)2) even in an environment that is not a high pH where the surface charge of the leaching residue is positively charged and the surface charge of the magnesium precipitate (Mg(OH)2) is negatively charged at a pH that is higher than the isoelectric point of the magnesium precipitate and lower than the isoelectric point of the leaching residue, and they aggregate by electrostatic attraction.

[0041] Accordingly, in the method for purifying the lithium sulfate solution, the step of generating the magnesium precipitate is performed at a pH higher than the isoelectric point of the magnesium precipitate and lower than the isoelectric point of the leaching residue, thereby generating the magnesium precipitate and removing it. By doing so, the method for purifying the lithium sulfate solution can reduce the amount of Mg(OH)2 precipitate formed when the subsequent secondary purification process is performed by partially removing Mg(OH)2, which is mostly removed in the secondary purification process, in advance. Since the method for purifying the lithium sulfate solution can reduce the solid-liquid separation load when performing the subsequent secondary purification process, process issues such as filter cloth clogging and poor detachment can be prevented.

[0042] In one embodiment, the pH may be 8.5 to 9.5, which is higher than the isoelectric point of the magnesium precipitate and lower than the isoelectric point of the leaching residue. In one embodiment, when the isoelectric point of the magnesium precipitate is measured by adding an alkaline auxiliary raw material, the pH may be 8.5 to 9.5, which is higher than the isoelectric point of the magnesium precipitate and lower than the isoelectric point of the leaching residue. It can be confirmed in FIG. 1 that at the pH of the above numerical range, the pH is higher than the isoelectric point of the magnesium precipitate and lower than the isoelectric point of the leaching residue. By performing the process at the pH of the above numerical range, other polyvalent cation impurities that can be removed in the primary purification process can be removed together, for example, Si 4+, Al 3+ , Fe 3+ Precipitates of impurities such as the above can be formed together with the magnesium precipitate and removed together with the leaching residue.

[0043] In one embodiment, the step of generating a magnesium precipitate can be performed at a pH higher than the isoelectric point of Mg(OH)2 and lower than the isoelectric point of an aluminosilicate-based material.

[0044] The magnesium precipitate and the leaching residue generated in the step of generating the magnesium precipitate can be removed together by solid-liquid separation.

[0045] The alkaline auxiliary material introduced in the step of producing the magnesium precipitate may include at least one selected from the group consisting of CaCO3, Ca(OH)2, CaO, NaOH, LiOH, and combinations thereof.

[0046] In the step of generating the magnesium precipitate above, impurities that can be removed by precipitation in the primary purification process may be removed together. For example, at the pH of 8.5 to 9.5, Si 4+ , Al 3+ , Fe 3+ It can generate precipitates of impurity cations.

[0047] Since the amount of leaching residue relative to the precipitate generated in the step of generating the magnesium precipitate is very large, there is little possibility of causing process issues that add an excessive load to removing the magnesium precipitate together with the leaching residue. However, by removing some of the magnesium impurities together with the leaching residue in advance, process issues that cause an excessive load during the removal of magnesium leaching in the subsequent process can be significantly reduced.

[0048] In one embodiment, in a method for purifying the lithium sulfate solution, if the alkaline auxiliary material is referred to as the first alkaline auxiliary material, the method for purifying the lithium sulfate solution may further include the step of removing the magnesium precipitate and the leaching residue by solid-liquid separation, and then adding a second alkaline auxiliary material to precipitate magnesium. The step of adding the second alkaline auxiliary material to precipitate magnesium may correspond to the aforementioned second purification step. That is, the first alkaline auxiliary material may be added to generate a magnesium precipitate and first remove a portion of the magnesium contained as an impurity, and then the second alkaline auxiliary material may be added to further remove the remaining magnesium.

[0049] In one embodiment, the step of precipitating magnesium can be performed at a pH of 10 to 12. By adjusting the pH to the above numerical range, most of the remaining magnesium impurities that are not separated into the magnesium precipitate can be removed. As described above, since the method for purifying the lithium sulfate solution has previously removed some of the magnesium precipitate, the process of handling the precipitate generated during the step of precipitating magnesium is not overloaded, thereby preventing process issues related to this from occurring.

[0050] In the step of precipitating the magnesium above, Ca 2+ , Mn 2+ , Mn 3+ , Mn 4+ , Mn 5+ , Mn 6+ , Mn 7+ Cation impurities including at least one selected from the group consisting of combinations thereof may be precipitated together.

[0051] The second alkaline auxiliary raw material may include at least one selected from the group consisting of NaOH, LiOH, Na2CO3, Li2CO3, and combinations thereof. The second alkaline auxiliary raw material may be the same as or different from the first alkaline auxiliary raw material.

[0052] In one embodiment, the method for purifying the lithium sulfate solution may further include a first purification step of adjusting the pH to 6 to 8 by first adding CaCO3 as the alkaline auxiliary raw material, and following the first purification step, a step of removing the magnesium precipitate and the leaching residue by solid-liquid separation may be performed.

[0053] In one embodiment, the method for purifying the lithium sulfate solution is:

[0054] A first purification step is performed by first adding the above alkaline auxiliary raw material to adjust the pH to 6 to 8, and

[0055] Following the above first purification step, a step of generating the magnesium precipitate and a step of removing the magnesium precipitate and the leaching residue by solid-liquid separation may be performed.

[0056] In one embodiment, the method for purifying the lithium sulfate solution is:

[0057] A first purification step is performed by first adding the above alkaline auxiliary raw material to adjust the pH to 6 to 8, and

[0058] Following the above first purification step, after performing the step of generating the magnesium precipitate and the step of removing the magnesium precipitate and the leaching residue by solid-liquid separation,

[0059] Subsequently, a secondary purification step can be performed to precipitate and remove magnesium at a pH of 10 to 12.

[0060]

[0061] The alkaline auxiliary material introduced in the first purification step and the step of generating the magnesium precipitate may include at least one selected from the group consisting of CaCO3, Ca(OH)2, CaO, NaOH, LiOH, and combinations thereof. The alkaline auxiliary material introduced in the first purification step and the step of generating the magnesium precipitate may be the same or different from each other in each step.

[0062] In one embodiment, CaCO3 is added as an alkaline auxiliary material in the first purification step, and an alkaline auxiliary material comprising at least one selected from the group consisting of Ca(OH)2, CaO, NaOH, LiOH, and combinations thereof may be added in the step of generating the magnesium precipitate.

[0063]

[0064] If the above alkaline auxiliary raw material is referred to as the first alkaline auxiliary raw material, the first alkaline auxiliary raw material may include at least one selected from the group consisting of Ca(OH)2, CaO, NaOH, LiOH, and combinations thereof; and the second alkaline auxiliary raw material introduced in the second purification step may include at least one selected from the group consisting of NaOH, LiOH, Na2CO3, Li2CO3, and combinations thereof.

[0065]

[0066] In one embodiment, the method for purifying the lithium sulfate solution is:

[0067] In the above first purification step, CaCO3 is added as the first alkaline auxiliary raw material, and

[0068] In the step of generating the magnesium precipitate, the first alkaline auxiliary raw material comprising at least one selected from the group consisting of Ca(OH)2, CaO, NaOH, LiOH, and combinations thereof is added, and

[0069] In the above second purification step, a second alkaline auxiliary raw material comprising at least one selected from the group consisting of NaOH, Na2CO3, LiOH, Li2CO3 and combinations thereof may be added.

[0070]

[0071] 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.

[0072]

[0073] (Example)

[0074] Example 1

[0075] Spodumene was prepared, and after the sulfuric acid roasting process, a mixed phase of lithium sulfate solution and leaching residue was obtained as the sulfuric acid leaching solution through water leaching.

[0076] Ca(OH)2 was added to the mixture of the above lithium sulfate solution and leaching residue at 40°C and pH 9, and Si 4+ , Al 3+ , Fe 3+ Mg along with impurities 2+ The two were precipitated together. At pH 9, an electrostatic attraction was formed between the surface charge of the positively charged leaching residue and the surface charge of the negatively charged Mg(OH)2, causing Mg(OH)2 to be adsorbed onto the surface of the leaching residue and precipitated as Mg(OH)2. The precipitate was separated together with the leaching residue by solid-liquid separation.

[0077] Next, NaOH and Na2CO3 were added to the lithium sulfate solution from which the solids of the precipitate and leaching residue had been separated to precipitate the remaining magnesium impurities at pH 11, and calcium ions and manganese polyvalent ions were also precipitated and removed.

[0078]

[0079] Comparative Example 1

[0080] The lithium sulfate solution was purified in the same manner as in Example 1, except that Ca(OH)2 was added to the mixture of the lithium sulfate solution and the leaching residue to precipitate and remove impurities at pH 7.

[0081]

[0082] Figure 2 is a graph showing the results of measuring the concentrations of Mg and Li components according to pH change at 40°C for the lithium sulfate solution used as the feed solution in Example 1 and Comparative Example 1.

[0083] In Fig. 2, Mg at pH 8, which is close to the isoelectric point of Mg(OH)2 2+ The content of began to decrease rapidly. In Figure 2, the concentration of Mg(OH)2 decreased from a maximum of 1.5 g / L to 0.06 g / L around pH 9. This is understood to be because, as previously explained, Mg(OH)2 was adsorbed onto the surface of the leaching residue and precipitated as Mg(OH)2.

[0084] Meanwhile, the reason the lithium content in the lithium sulfate solution of Figure 2 decreases is that the lithium sulfate solution is partially diluted as Ca(OH)2, an alkaline auxiliary material, is injected in the form of a slurry.

[0085] Referring to the graph in Figure 2, it was confirmed that in Example 1, magnesium was not removed all at once at pH 11, but could be partially removed first at the pH where leaching residue and aggregation are formed due to the zeta potential characteristics.

[0086] In Figure 2, Mg of the lithium sulfate solution at around pH 7 2+ With a content of 1.35 g / L, it can be predicted that the impurities precipitated at pH 7 in Comparative Example 1 will contain almost no magnesium impurities.

[0087]

[0088] 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 leaching lithium-containing ore with sulfuric acid to obtain a lithium sulfate solution mixed with the leaching residue; A step of generating a magnesium precipitate by adding an alkaline auxiliary material to the lithium sulfate solution mixed with the above-mentioned leaching residue; and The method comprises the step of removing the magnesium precipitate and the leaching residue by solid-liquid separation. The step of generating the magnesium precipitate is performed at a pH higher than the isoelectric point of the magnesium precipitate and lower than the isoelectric point of the leaching residue. Method for purifying lithium sulfate solution.

2. In Paragraph 1, A pH of 8.5 to 9.5 that is higher than the isoelectric point of the magnesium precipitate and lower than the isoelectric point of the leaching residue Method for purifying lithium sulfate solution.

3. In Paragraph 1, The above alkaline auxiliary raw material comprises at least one selected from the group consisting of Ca(OH)2, CaCO3, CaO, NaOH, LiOH, and combinations thereof. Method for purifying lithium sulfate solution.

4. In Paragraph 1, CaCO3 is first added as the above alkaline auxiliary raw material to adjust the pH to 6 to 8, and then at least one selected from the group consisting of Ca(OH)2, CaO, NaOH, LiOH, and combinations thereof is secondarily added to adjust the pH to 8.5 to 9.

5. Method for purifying lithium sulfate solution.

5. In Paragraph 1, The above magnesium precipitate contains Mg(OH)2 Method for purifying lithium sulfate solution.

6. In Paragraph 1, The above leaching residue includes an aluminosilicate-based material. Method for purifying lithium sulfate solution.

7. In Paragraph 1, The step of generating the magnesium precipitate above is performed at a pH higher than the isoelectric point of Mg(OH)2 and lower than the isoelectric point of aluminosilicate-based materials. Method for purifying lithium sulfate solution.

8. In Paragraph 1, In the step of generating the above magnesium precipitate, Si 4+ , Al 3+ , Fe 3+ Cation impurities that precipitate together, comprising at least one selected from the group consisting of combinations thereof Method for purifying lithium sulfate solution.

9. In Paragraph 1, The above alkali auxiliary raw material is the first alkali auxiliary raw material, and The method further comprises the step of precipitating magnesium by adding a second alkaline auxiliary raw material after removing the magnesium precipitate and the leaching residue by solid-liquid separation. Method for purifying lithium sulfate solution.

10. In Paragraph 9, The step of precipitating the magnesium above is performed at a pH of 10 to 12. Method for purifying lithium sulfate solution.

11. In Paragraph 1, It further includes a first purification step of first adding the above alkaline auxiliary raw material to adjust the pH to 6 to 8, and Following the above first purification step, the method comprises the step of generating the magnesium precipitate and the step of removing the magnesium precipitate and the leaching residue by solid-liquid separation. Method for purifying lithium sulfate solution.

12. In Paragraph 11, After performing the step of generating the magnesium precipitate and the step of removing the magnesium precipitate and the leaching residue by solid-liquid separation, the method further comprises a secondary purification step of precipitating and removing magnesium at a pH of 10 to 12. Method for purifying lithium sulfate solution.

13. In Paragraph 12, The above alkaline auxiliary raw material is referred to as the first alkaline auxiliary raw material, and In the above first purification step, CaCO3 is added as the first alkaline auxiliary raw material, and In the step of generating the magnesium precipitate, the first alkaline auxiliary raw material comprising at least one selected from the group consisting of Ca(OH)2, CaO, NaOH, LiOH, and combinations thereof is added, and In the above second purification step, a second alkaline auxiliary raw material comprising at least one selected from the group consisting of NaOH, Na2CO3, LiOH, Li2CO3, and combinations thereof is added. Method for purifying lithium sulfate solution.

14. In Paragraph 9, In the step of precipitating the magnesium above, Ca 2+ , Mn 2+ , Mn 3+ , Mn 4+ , Mn 5+ , Mn 6+ , Mn 7+ Cation impurities that precipitate together, comprising at least one selected from the group consisting of combinations thereof Method for purifying lithium sulfate solution.

15. In Paragraph 1, A lithium sulfate solution mixed with the leaching residue is obtained by performing a sulfuric acid roasting process on the above lithium-containing ore. Method for purifying lithium sulfate solution.

Images