A method for synergistically extracting lithium from lepidolite and spodumene based on a sodium sulfide-sulfate composite additive

Abstract

The application discloses a method for cooperatively extracting lithium from lepidolite and spodumene based on a sodium sulfide-sulfate composite additive, which comprises the following steps: firstly, lepidolite concentrate, spodumene concentrate, sodium sulfide and sulfate are uniformly mixed in proportion to obtain a mixed reaction material; then, the mixed reaction material is subjected to high-temperature roasting to obtain a roasted material; finally, the roasted material is subjected to water immersion in water, and then solid-liquid separation is performed to obtain a lithium leaching solution and a lithium-impregnated tailing; the sodium sulfide is creatively introduced as an additive, the synergistic effect of high-temperature reduction and oxygen capture of the sodium sulfide and the sulfate can be used as a supplementary path of the conventional sulfate lithium extraction mechanism, cooperates with fluorine in the lepidolite, and further reduces the reaction energy barrier required for mineral phase destruction, the sodium sulfide can directly participate in the displacement reaction of lithium, forms a sodium source synergistic effect with the sulfate additive in the system, promotes the generation of soluble lithium double salt, improves the conversion efficiency of lithium, and can greatly improve the lithium extraction effect.

Description

Technical Field

[0001] This invention relates to the field of lithium extraction technology from lithium ore, specifically to a method for synergistic lithium extraction from lepidolite and spodumene based on sodium sulfide-sulfate composite additive. Background Technology

[0002] With the continuous development of new energy vehicles and energy storage industries, the global demand for lithium, an energy metal, is increasing dramatically. my country has extremely rich reserves of unconventional low-grade lepidolite in Yichun, Jiangxi Province, and Chenzhou, Hunan Province. Sulfate roasting is currently the mainstream technology for processing lepidolite resources; however, its techno-economic viability faces severe challenges when directly applied to these unconventional low-grade lepidolite ores. Due to the low grade and stable crystal structure of these ores, traditional processing methods necessitate increasing the reaction temperature and the proportion of roasting aids, resulting in high production costs and energy consumption. Even so, lithium extraction is still unsatisfactory, with large fluctuations and generally low leaching rates. Furthermore, high-temperature sulfate treatment easily triggers severe melting and wall adhesion, not only encapsulating lithium and inhibiting leaching but also hindering continuous production. Therefore, developing a new technology that can specifically address the challenges of lithium extraction from low-grade lepidolite and achieve low energy consumption, high efficiency, and stable operation has become a core issue urgently needing to be solved in the industry. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for synergistic lithium extraction from lepidolite and spodumene based on a sodium sulfide-sulfate composite additive. The method includes the following steps: First, lepidolite concentrate and spodumene concentrate, along with sodium sulfide and sulfate additives, are uniformly mixed in a certain proportion to obtain a mixed reaction material; second, the mixed reaction material is subjected to high-temperature roasting to obtain a roasted material; finally, the roasted material is placed in water for leaching, followed by solid-liquid separation to obtain a lithium leaching solution and lithium leaching tailings. This invention creatively introduces sodium sulfide as an additive, which, through the synergistic effect of sodium sulfide and sulfate additives, strengthens the destruction of the ore's crystal structure, promoting the release, migration, and formation of soluble lithium salts. Specifically, sodium sulfide contains sodium sulfate (S). 2- It possesses strong reducing activity, capable of stripping some lattice oxygen from the aluminosilicate structure of the ore during high-temperature roasting, reducing the stability of the mineral phase structure, promoting the release of lithium from the lattice, and forming insoluble sulfide precipitates with harmful impurities such as iron and aluminum in the ore, reducing the amount of impurities entering the solution during water leaching and lowering the impurity removal load of the subsequent leaching solution. Simultaneously, sodium sulfide can undergo redox reactions with sulfates under high-temperature conditions, generating more reactive low-valence sulfur intermediates, further enhancing the reducing power of the system, preventing the rapid oxidation and deactivation of sodium sulfide alone at high temperatures, significantly extending the effective reduction time of the system, further enhancing its reducing power, and making the mineral phase destruction process more complete. Furthermore, sodium sulfide provides Na... +It can participate in lithium-ion exchange reactions, promoting the conversion of lithium to soluble lithium salts, and forming a sodium-source synergistic effect with sulfate auxiliaries in the system, thereby reducing the amount of sulfate added. The reducing synergistic effect of sodium sulfide and sulfate can serve as a supplementary pathway to the conventional sulfate lithium extraction mechanism. Combined with fluorine in lepidolite, the reducing synergistic effect of sodium sulfide and sulfate, and the synergistic effect of fluorine in lepidolite further reduce the reaction energy barrier required for mineral phase destruction. The addition of lepidolite to spodumene not only improves the overall lithium grade of the mixed raw materials, thus facilitating the replacement reaction between cations and lithium ions in sulfate, but also fully utilizes the fluorine released by lepidolite to promote its low-temperature transformation. The synergistic reduction effect of fluorine-containing components with sulfate and sodium sulfide further contributes to lithium release.

[0004] Compared with existing technologies, the technical solution described in this invention can significantly improve the overall extraction efficiency of lithium in mixed low-grade lepidolite and spodumene ores, and steadily increase the leaching rate to over 95%. By co-processing the two types of ores in the same process, the production process is greatly simplified, and equipment utilization and production efficiency are improved. Through optimized compound additive formulation, the roasting temperature of spodumene transformation is reduced while avoiding the addition of exogenous fluorides. Furthermore, all additives are inexpensive and readily available, effectively reducing production costs and demonstrating significant industrial application prospects and value.

[0005] Compared to traditional sulfate roasting processes, this method reduces the dependence of the spodumene and lepidolite activation processes on high-temperature conditions, thus decreasing energy consumption during roasting. Simultaneously, the lower roasting temperature helps suppress material sintering caused by high-temperature sulfate melting, reducing the risk of ring formation in the kiln and improving the continuity and stability of the production process. Furthermore, the sodium sulfide and sulfate additives used are widely available and inexpensive, achieving efficient lithium extraction while reducing production costs, demonstrating significant industrial application value.

[0006] To achieve the above technical effects, the following technical solution is adopted: A method for synergistic lithium extraction from lepidolite and spodumene based on sodium sulfide-sulfate composite additive includes the following steps: Step S1: Mix lepidolite concentrate, spodumene concentrate, sodium sulfide, and sulfate additives in a uniform ratio to obtain a mixed reaction mixture; Step S2: The mixed reactants are calcined at high temperature to obtain calcined material; Step S3: The roasted material is placed in water for immersion, and then solid-liquid separation is performed to obtain lithium leaching solution and lithium leaching tailings. Furthermore, in step S1, the lithium content in the lepidolite concentrate is 0.20~2.00 wt%, and the lithium content in the spodumene concentrate is 1.40~3.80 wt%. Furthermore, in step S1, the sulfate auxiliary is selected from one or more of sodium sulfate, calcium sulfate, potassium sulfate, and ferric sulfate; Furthermore, in the mixture prepared in step S1, the mass ratio of lepidolite concentrate to spodumene concentrate is 1:0.1~3; Furthermore, in the mixture prepared in step S1, the mass ratio of lepidolite-spodumene mixed concentrate to sodium sulfide is 1:0.03~0.3; Furthermore, in the mixture prepared in step S1, the mass ratio of lepidolite-spodumene mixed concentrate to sulfate additive is 1:0.2~1; Furthermore, in step S2, the calcination temperature is 750~850 ℃, and the calcination time is 30~40 min; Furthermore, step S2 also includes: ball milling the obtained calcined material to below 100 mesh; Furthermore, in step S3, the water immersion reaction conditions are: liquid-to-solid ratio of 2-8 mL: 1 g, reaction temperature of 20-80℃, and reaction time of 30-90 min; Furthermore, in step S3, the lithium extraction rate in the leachate is greater than 95%.

[0007] The beneficial effects of this invention are as follows: (1) Significantly improved the overall lithium extraction rate. This invention creatively introduces sodium sulfide as a calcination aid, and at high temperatures, the S in sodium sulfide... 2- As a strong reducing component, it can directly provide a reducing environment in high-temperature roasting, stripping some oxygen atoms from the ore lattice and destroying the stable aluminosilicate structure. Simultaneously, the sulfate acts as a mechanism for lithium extraction in the traditional sulfate process, and can also undergo a redox reaction with sodium sulfide at high temperatures to produce elemental sulfur and sulfur. 3- Low-valent sulfur intermediates, such as low-valent polysulfides, are more reactive than the original sulfur. 2- This invention further enhances the system's reducing power, preventing sodium sulfide from rapidly oxidizing and failing at high temperatures, extending the effective reduction duration, and more efficiently destroying stable mineral structures. The combination of sodium sulfide and sulfate allows the reduction reaction to proceed stably over a wider temperature range. Compared to using sodium sulfide alone, it more fully and continuously destroys the dense lattice of lithium ore, reducing the formation of insoluble lithium salts and ultimately improving lithium leaching efficiency. The core of conventional lithium ore sulfate roasting is to destroy the stable aluminosilicate structure and release lithium through high-temperature treatment and sulfate additives. In this invention, the synergistic effect of high-temperature reduction of sodium sulfide and sulfate can serve as a supplementary pathway to the conventional sulfate lithium extraction mechanism. Combined with the effect of fluorine in lepidolite, the two work synergistically to further reduce the reaction energy barrier required for mineral phase destruction. The Na released from sodium sulfide... +It can directly participate in the lithium displacement reaction and form a sodium source synergistic effect with the sulfate additive in the system, reducing the overall amount of sulfate added. At the same time, it promotes the formation of soluble complex salt Li2NaK(SO4)2, improving the lithium conversion efficiency and achieving a significant improvement in lithium extraction. Compared with the traditional sulfate method for treating low-grade lepidolite, where the lithium leaching rate is only 70%-80%, this invention improves the overall lithium grade of the raw material by introducing spodumene and, with the synergistic effect of composite additives, stabilizes the lithium leaching rate at over 95%. This achieves efficient recycling and utilization of low-grade lepidolite resources and greatly expands the utilization boundaries of lithium resources.

[0008] (2) Effectively reduces production costs. Compared with the traditional sulfuric acid process for spodumene and the sulfate process for lepidolite, which require high-temperature roasting with high energy consumption, this invention utilizes the synergistic effect of lepidolite and lepidolite to fully leverage the activation effect of fluorine in lepidolite during roasting. On the one hand, the crystal structure of lepidolite is destroyed after defluorination, which is conducive to the release of lithium; on the other hand, the released fluorine-containing components can promote the activation of the aluminosilicate structure of spodumene. The synergistic reduction effect of the fluorine-containing components with sulfate and sodium sulfide further enhances the overall reactivity of the system, thereby achieving synergistic enhanced extraction of the two minerals. This synergistic effect not only helps to reduce the roasting reaction temperature, but also significantly reduces or even avoids the addition of exogenous fluoride additives. In addition, the additives used in this invention are widely available and inexpensive, and the water immersion process effectively controls the overall energy consumption and material costs, resulting in good economic benefits.

[0009] (3) The process flow is greatly simplified and the production efficiency is improved. The technology proposed in this invention avoids the complicated process of building separate lines for lepidolite and spodumene in the same process route, thus significantly improving equipment utilization and overall production efficiency. Attached Figure Description

[0010] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0011] Figure 1 This is a schematic diagram of the process of the lithium extraction method synergistically using lepidolite and spodumene based on sodium sulfide-sulfate composite additive in an embodiment of the present invention. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0013] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0014] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, and / or combinations thereof.

[0015] In the following examples, unless otherwise specified, all reagents and consumables were purchased from conventional reagent manufacturers in the art; unless otherwise specified, the experimental methods and techniques used are conventional methods and techniques in the art.

[0016] The technical solutions provided by the present invention will be described below with reference to the embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0017] See Figure 1 , Figure 1 This is a schematic diagram of the process of the lithium extraction method of lepidolite and spodumene based on sodium sulfide-sulfate composite additive in Examples 1-3 of the present invention.

[0018] Example 1: 10 g of lepidolite concentrate with a Li content of 0.29 wt.%, 5 g of spodumene concentrate with a Li content of 3.30 wt.%, 10.5 g of sodium sulfate, and 1.5 g of sodium sulfide were uniformly mixed and then placed in a muffle furnace for high-temperature roasting at 800 ℃ for 30 min. After roasting, the roasted material was cooled to room temperature and then ball-milled to below 100 mesh. Subsequently, the roasted material was immersed in water at a liquid-to-solid ratio of 4 mL: 1 g for leaching at 50 ℃ for 30 min. After leaching, the material was filtered to obtain lithium leachate and lithium leaching tailings.

[0019] According to the test and analysis, the leaching rate of Li in the leachate obtained in Example 1 was 98.38%, which means that Example 1 achieved an ideal lithium extraction rate in the synergistic smelting of lepidolite and spodumene.

[0020] Example 2: 10 g of lepidolite concentrate with a Li content of 0.29 wt.%, 2.5 g of spodumene concentrate with a Li content of 3.30 wt.%, 8.75 g of calcium sulfate, and 2.5 g of sodium sulfide were uniformly mixed and then placed in a muffle furnace for high-temperature roasting at 820 ℃ for 40 min. After roasting, the roasted material was cooled to room temperature and then ball-milled to below 100 mesh. Subsequently, the roasted material was immersed in water at a liquid-to-solid ratio of 8 mL: 1 g for leaching at 20 ℃ for 90 min. After leaching, the lithium leachate and lithium leaching tailings were obtained by filtration.

[0021] According to the test and analysis, the leaching rate of Li in the leachate obtained in Example 2 was 97.27%, which means that Example 2 also achieved an ideal lithium extraction rate in the synergistic smelting of lepidolite and spodumene.

[0022] Example 3: 10 g of lepidolite concentrate with a Li content of 0.29 wt.%, 5 g of spodumene concentrate with a Li content of 3.30 wt.%, 10.5 g of potassium sulfate, and 0.75 g of sodium sulfide were uniformly mixed and then placed in a muffle furnace for high-temperature roasting at 780 ℃ for 30 min. After roasting, the roasted material was cooled to room temperature and then ball-milled to below 100 mesh. Subsequently, the roasted material was immersed in water at a liquid-to-solid ratio of 2 mL: 1 g for leaching at 80 ℃ for 30 min. After leaching, the material was filtered to obtain lithium leachate and lithium leaching tailings.

[0023] According to the test and analysis, the leaching rate of Li in the leachate obtained in Example 3 was 97.89%, which means that Example 3 also achieved an ideal lithium extraction rate in the synergistic smelting of lepidolite and spodumene.

[0024] Comparative Example 1: The difference from Example 1 is that only lepidolite, spodumene, and sodium sulfate are added as reaction raw materials, and the amount of sodium sulfate added is 12 g. The specific reaction conditions are as follows: 10 g of lepidolite concentrate with a Li content of 0.29 wt.%, 5 g of spodumene concentrate with a Li content of 3.30 wt.%, and 12 g of sodium sulfate were mixed evenly and then placed in a muffle furnace for high-temperature roasting at 800 ℃ for 30 min. After roasting, the roasted material was cooled to room temperature and then ball-milled to below 100 mesh. Subsequently, the roasted material was immersed in water at a liquid-to-solid ratio of 4 mL: 1 g for leaching at 50 ℃ for 30 min. After leaching, the lithium leachate and lithium leaching tailings were obtained by filtration.

[0025] Analysis showed that the leaching rate of Li in the leachate obtained from Comparative Example 1 was 27.92%.

[0026] Comparative Example 2: The difference from Example 1 is that only lepidolite, spodumene, and sodium sulfide are added as reaction raw materials, and the amount of sodium sulfide added is 12 g. The specific reaction conditions are as follows: 10 g of lepidolite concentrate with a Li content of 0.29 wt.%, 5 g of spodumene concentrate with a Li content of 3.30 wt.%, and 12 g of sodium sulfide were mixed evenly and then placed in a muffle furnace for high-temperature roasting at 800 ℃ for 30 min. After roasting, the roasted material was cooled to room temperature and then ball-milled to below 100 mesh. Subsequently, the roasted material was immersed in water at a liquid-to-solid ratio of 4 mL: 1 g for leaching at 50 ℃ for 30 min. After leaching, the lithium leachate and lithium leaching tailings were obtained by filtration.

[0027] Analysis showed that the leaching rate of Li in the leachate obtained under these comparative conditions was only 22.08%.

[0028] Examples 1-3 above, using the sodium sulfide-sulfate composite additive described in this invention for calcination treatment, all achieved lithium leaching rates of over 95%, indicating that the method of this invention has good applicability to spodumene and lepidolite mixtures with different grades and process conditions, and can effectively promote the release of lithium. Comparing Example 1 with Comparative Examples 1-2, it can be found that under the same conditions, when only sodium sulfate or only sodium sulfide is used as a single additive, the lithium leaching rate is significantly lower than that of the examples using the sodium sulfide-sulfate composite additive. This indicates that the combined use of sodium sulfide and sulfate can produce a significant strengthening effect, significantly improving the leaching rate of Li in spodumene. Example 1 achieved a lithium leaching rate of 98.38% at a calcination temperature of 800 °C, compared to 27.92% for Comparative Example 1 and only 22.08% for Comparative Example 2. In summary, this invention discloses a method for synergistic lithium extraction from lepidolite and spodumene based on a sodium sulfide-sulfate composite additive, comprising the following steps: First, lepidolite concentrate and spodumene concentrate, along with sodium sulfide and sulfate additives, are uniformly mixed in a certain proportion to obtain a mixed reaction material; second, the mixed reaction material is subjected to high-temperature roasting to obtain a roasted material; finally, the roasted material is placed in water for leaching, followed by solid-liquid separation to obtain a lithium leaching solution and lithium leaching tailings. This invention creatively introduces sodium sulfide as an additive, which, through the synergistic effect of sodium sulfide and sulfate additives, strengthens the destruction of the ore crystal structure, promoting the release, migration, and formation of soluble lithium salts. Specifically, sodium sulfide contains sodium sulfate (S2). 2-It possesses strong reducing activity, capable of stripping some lattice oxygen from the aluminosilicate structure of the ore during high-temperature roasting, reducing the stability of the mineral phase structure, promoting the release of lithium from the lattice, and forming insoluble sulfide precipitates with harmful impurities such as iron and aluminum in the ore, reducing the amount of impurities entering the solution during water leaching and lowering the impurity removal load of the subsequent leaching solution. Simultaneously, sodium sulfide can undergo redox reactions with sulfates under high-temperature conditions, generating more reactive low-valence sulfur intermediates, further enhancing the reducing power of the system, preventing the rapid oxidation and deactivation of sodium sulfide alone at high temperatures, significantly extending the effective reduction time of the system, further enhancing its reducing power, and making the mineral phase destruction process more complete. Furthermore, sodium sulfide provides Na... + It can participate in lithium-ion exchange reactions, promoting the conversion of lithium to soluble lithium salts, and forming a sodium-source synergistic effect with sulfate auxiliaries in the system, thereby reducing the amount of sulfate added. The reducing synergistic effect of sodium sulfide and sulfate can serve as a supplementary pathway to the conventional sulfate lithium extraction mechanism. Combined with fluorine in lepidolite, the reducing synergistic effect of sodium sulfide and sulfate, and the synergistic effect of fluorine in lepidolite further reduce the reaction energy barrier required for mineral phase destruction. The addition of lepidolite to spodumene not only improves the overall lithium grade of the mixed raw materials, thus facilitating the replacement reaction between cations and lithium ions in sulfate, but also fully utilizes the fluorine released by lepidolite to promote its low-temperature transformation. The synergistic reduction effect of fluorine-containing components with sulfate and sodium sulfide further contributes to lithium release.

[0029] Compared with existing technologies, the technical solution of this invention can significantly improve the overall extraction efficiency of lithium in low-grade lepidolite and spodumene mixed ores, steadily increasing the leaching rate to over 95%. By co-processing the two types of ores in the same process, the production process is greatly simplified, and equipment utilization and production efficiency are improved. Through optimized compound additive formulation, the roasting temperature of spodumene transformation is lowered while avoiding the addition of exogenous fluorides. Compared with traditional sulfate roasting processes, this method reduces the dependence of the spodumene and lepidolite activation processes on high-temperature conditions, reducing energy consumption during roasting. Simultaneously, the lower roasting temperature helps suppress material sintering caused by high-temperature sulfate melting, reducing the risk of kiln ring formation and improving the continuity and stability of the production process. Furthermore, the sodium sulfide and sulfate additives used are widely available and inexpensive, reducing production costs while achieving efficient lithium extraction, and have good industrial application value.

[0030] Therefore, those skilled in the art will recognize that although embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Therefore, the scope of the present invention should be understood and recognized as covering all such other variations or modifications.

Claims

1. A method for synergistic lithium extraction from lepidolite and spodumene based on sodium sulfide-sulfate composite additive, characterized in that, Includes the following steps: Step S1: Mix lepidolite concentrate, spodumene concentrate, sodium sulfide, and sulfate additives in a uniform ratio to obtain a mixed reaction mixture; Step S2: The mixed reactants are calcined at high temperature to obtain calcined material; Step S3: The roasted material is placed in water for immersion, and then solid-liquid separation is performed to obtain lithium leaching solution and lithium leaching tailings.

2. The method for synergistic lithium extraction from lepidolite and spodumene based on sodium sulfide-sulfate composite additive as described in claim 1, characterized in that, In step S1, the lithium content in the lepidolite concentrate is 0.20~2.00 wt%, and the lithium content in the spodumene concentrate is 1.40~3.80 wt%.

3. The method for synergistic lithium extraction from lepidolite and spodumene based on sodium sulfide-sulfate composite additive as described in claim 1, characterized in that, In step S1, the sulfate auxiliary is selected from one or more of sodium sulfate, calcium sulfate, potassium sulfate, and ferric sulfate.

4. The method for synergistic lithium extraction from lepidolite and spodumene based on sodium sulfide-sulfate composite additive as described in claim 1, characterized in that, In the mixture prepared in step S1, the mass ratio of lepidolite concentrate to spodumene concentrate is 1:0.1~3.

5. The method for synergistic lithium extraction from lepidolite and spodumene based on sodium sulfide-sulfate composite additive as described in claim 1, characterized in that, In the mixture prepared in step S1, the mass ratio of lepidolite-spodumene mixed concentrate to sodium sulfide is 1:0.03~0.

3.

6. The method for synergistic lithium extraction from lepidolite and spodumene based on sodium sulfide-sulfate composite additive as described in claim 1, characterized in that, In the mixture prepared in step S1, the mass ratio of lepidolite-spodumene mixed concentrate to sulfate additive is 1:0.2~1.

7. The method for synergistic lithium extraction from lepidolite and spodumene based on sodium sulfide-sulfate composite additive as described in claim 1, characterized in that, In step S2, the roasting temperature is 750~850 ℃ and the roasting time is 30~40 min.

8. The method for synergistic lithium extraction from lepidolite and spodumene based on sodium sulfide-sulfate composite additive as described in claim 1, characterized in that, Step S2 also includes: ball milling the obtained calcined material to below 100 mesh.

9. The method for synergistic lithium extraction from lepidolite and spodumene based on sodium sulfide-sulfate composite additive as described in claim 1, characterized in that, In step S3, the water immersion reaction conditions are: liquid-to-solid ratio of 2-8 mL: 1 g, reaction temperature of 20-80℃, and reaction time of 30-90 min.

10. The method for synergistic lithium extraction from lepidolite and spodumene based on sodium sulfide-sulfate composite additive as described in claim 1, characterized in that, In step S3, the lithium extraction rate in the leachate is greater than 95%.

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