KR-20260063301-A - Methods for extracting lithium from lithium containing clay

Abstract

The present disclosure relates to a method for recovering lithium from clay, comprising: (S1) a step of heat-treating a mixture of lithium-containing clay and calcium sulfate ( CaSO₄ ) to produce a calcined product; (S2) a step of leaching the calcined product with water to produce a water-leached product; and (S3) a step of separating the water-leached product into a lithium-containing solution and a residue.

Inventors

• 강종혁
• 박종선
• 정종언
• 김준태
• 이명규
• 박석준
• 허성원
• 유주연

Assignees

• 주식회사 에코프로이노베이션

Dates

Publication Date

20260507

Application Date

20241030

Claims (15)

1. (S1) A step of preparing a calcined product by heat-treating a mixture of lithium-containing clay and calcium sulfate ( CaSO₄ ); (S2) A step of preparing a water-leached product by water-leaching the above-mentioned calcined product; and (S3) A step of separating the above-mentioned water-leaching product into a lithium-containing solution and a residue; a method for recovering lithium.
2. In paragraph 1, A method for recovering lithium, wherein the above mixture comprises 1 to 50 parts by weight of calcium sulfate ( CaSO₄ ) based on 100 parts by weight of lithium-containing clay.
3. In paragraph 1, A lithium recovery method comprising, after the above step (S3), a step (S4) of recovering residual lithium contained in the residue.
4. In paragraph 3, A lithium recovery method in which the above (S4) step is performed two or more times.
5. In paragraph 3, A lithium recovery method in which the above (S4) step is performed by a countercurrent washing (CCW) method.
6. In paragraph 3, A lithium recovery method further comprising, after the above step (S4), (S5) a step of mixing the residual lithium with the lithium-containing solution to recover a concentrated lithium-containing solution.
7. In paragraph 1, A method for recovering lithium, wherein the above lithium-containing clay contains less than 5000 mg/kg of lithium.
8. In paragraph 1, A lithium recovery method in which lithium is selectively leached in the above (S2) step.
9. In paragraph 1, A lithium recovery method in which the calcination of the above (S1) step is performed under temperature conditions of 800 to 1200 ℃.
10. In paragraph 1, A lithium recovery method further comprising the step of crushing the calcined material after the above step (S1) and before the above step (S2).
11. In paragraph 1, A lithium recovery method in which the leaching rate of impurities represented by the following Formula 1 is less than 5%. [Equation 1] Leaching rate (%) = (w s /w c ) X 100 (In Equation 1 above, w s represents the weight of impurities contained in the lithium-containing solution, and w c represents the weight of impurities contained in the clay.)
12. In paragraph 1, A lithium recovery method in which the above (S2) step is performed under temperature conditions of 40 to 100 ℃.
13. In paragraph 1, A lithium recovery method having a lithium recovery rate of 98% or higher.
14. In paragraph 1, A lithium recovery method in which, in step (S1) above, a water-soluble compound containing lithium and an insoluble compound containing impurities are produced.
15. In Paragraph 14, A method for recovering lithium, wherein the above-mentioned insoluble compound comprises calcium magnesium silicate.

Description

Methods for extracting lithium from lithium-containing clay The present disclosure relates to a method for extracting lithium from lithium-containing clay. As the demand for small home appliances, IT devices, electric vehicles (EVs), and energy storage systems (ESS) increases rapidly, the demand for lithium-ion batteries, characterized by their lightweight nature, high energy density, and high capacity, is also rising sharply. Since the cathode materials and electrolytes of lithium-ion batteries contain large amounts of lithium, research is underway to extract lithium contained in minerals at high concentrations and purity to meet the high demand for lithium. Among them, since the lithium contained in clay accounts for 7% of the total lithium reserves, it is essential to develop a method to recover the lithium contained in clay in order to secure lithium. Conventionally , an acid leaching method has been developed to recover lithium from clay by mixing the clay with an acid such as sulfuric acid ( H₂SO₄ ) to leach the lithium. However, during acid leaching, impurities such as calcium, magnesium, and iron are leached along with the lithium, making it impossible to recover high-purity lithium, and there is a problem that the process becomes complicated as an additional impurity removal process is required. In addition, there is a disadvantage in that acid usage is very high in order to improve the low lithium leaching efficiency. Therefore, a beneficiation process is essential to recover concentrate with a high lithium concentration by removing gangue from the clay using wet sieving, wet cyclones, etc., before performing acid leaching. However, even if a beneficiation process is performed to remove impurities from the clay in advance, acid usage still accounts for more than 50% of the clay weight, and there are limitations in obtaining high-purity lithium. Furthermore, due to the inherent characteristics of clay, the solid-liquid separation efficiency is very low, leading to a problem of reduced lithium recovery rates. Since the purity of lithium recovered through acid leaching is low and solid-liquid separation is difficult, the solvent must be evaporated to concentrate the lithium. However, not only is the evaporation process required to incur additional costs, but impurities leached out along with lithium during the process precipitate in a solid state. Consequently, scale—a solid impurity—accumulates in reactors and piping, causing blockages and poor flow. This leads to problems with process equipment and incurs additional process costs to resolve them, resulting in reduced economic viability. Accordingly, there is a need for a method to obtain high-purity lithium with a high recovery rate by improving solid-liquid separation performance through the selective leaching of lithium contained in clay while simultaneously effectively removing impurities. FIG. 1 is a flowchart illustrating a lithium recovery method according to one embodiment of the present disclosure. Figures 2 to 4 are X-ray diffraction (XRD) spectra of the clay, calcined product, and water leaching product of Example 1, respectively. The terms used in this specification have been selected to be as widely used as possible, taking into account the function of this disclosure; however, these terms may vary depending on the intent of those skilled in the relevant field, case law, the emergence of new technologies, etc. Unless otherwise defined, technical and scientific terms used may have the meaning commonly understood by those skilled in the art to which this invention pertains. In this specification and the appended claims, terms such as “comprising” or “having” mean that the features or components described in the specification exist, and unless specifically limited, do not preclude the possibility that one or more other features or components may be added. In this specification and the appended claims, terms such as "first," "second," etc. are used not in a limiting sense, but for the purpose of distinguishing one component from another. Singular expressions used in this specification and the appended claims include plural expressions unless the context clearly indicates that they are singular. Additionally, plural expressions include singular expressions unless the context clearly indicates that they are plural. Additionally, numerical ranges used herein include lower and upper limits and all values within the range, increments logically derived from the form and width of the defined range, all of which are limited values, and all possible combinations of upper and lower limits of numerical ranges defined in different forms. Unless otherwise specifically defined in the specification of this disclosure, values outside the numerical range that may occur due to experimental error or rounding of values are also included in the defined numerical range. Terms such as "approximately" used in this specification and the appended claims are used to