A method for lithium extraction from lepidolite by calcination based on sulfate co-grinding activation and atmosphere regulation

Abstract

The application discloses a lithium mica roasting lithium extraction method based on sulfate co-grinding activation and atmosphere regulation, and the method comprises the following steps: mixing lithium mica concentrate and sulfate composite additives, and then performing mechanical-chemical activation treatment to obtain activated materials; performing roasting treatment on the activated materials in a water-containing atmosphere to obtain roasting products; performing refinement treatment, normal-pressure water immersion and solid-liquid separation on the roasting products to obtain a lithium-rich leaching solution. The lithium mica concentrate and the sulfate composite additives are subjected to mechanical-chemical activation treatment to form a sulfate co-grinding activation reaction interface, so that, in the roasting process in the water-containing atmosphere, water vapor in the water-containing atmosphere can promote the migration of fluorine-containing structure units, and the sulfate composite additives can promote the solubilization of lithium, and the lithium extraction rate and the defluorination rate of the lithium extraction method are improved.

Description

Technical Field

[0001] This application belongs to the fields of comprehensive utilization of lithium resources, mineral processing and hydrometallurgical technology, and specifically relates to a method for lithium extraction by roasting lepidolite based on sulfate co-grinding activation and atmosphere control. Background Technology

[0002] Lithium is a crucial strategic resource in the fields of new energy batteries, energy storage materials, and specialty materials. Lithium mica is a layered silicate fluorine-containing mineral, with lithium primarily occurring in an aluminum-oxygen octahedral structure and its associated lattice environment, forming a relatively stable structure with silicon-oxygen tetrahedra, aluminum-oxygen octahedra, and fluorine-containing structural units. Lithium mica concentrate often coexists with muscovite, albite, quartz, lepidolite, and fluorinated phlogopite, presenting challenges such as complex composition, stable lattice, coexistence of fluorine and lithium, and poor direct leaching efficiency.

[0003] Existing methods for lithium extraction from lepidolite include the sulfuric acid method, chlorination roasting method, alkaline or pressure cooking method, fluorination chemical method, and sulfate roasting method. The sulfate roasting method utilizes the metal ions and other components provided by sulfates to promote mineral phase reconstruction and ion replacement, converting lattice-state lithium into soluble lithium salts. However, it still suffers from problems such as insufficient roasting reaction and inadequate coupling between the defluorination process and the lithium soluble conversion process, making it difficult to effectively improve both lithium leaching rate and defluorination rate.

[0004] In view of this, this application provides a method for lithium extraction from lepidolite by calcination based on sulfate co-milling activation and atmosphere control. Summary of the Invention

[0005] To address the aforementioned issues, this application aims to provide a lithium extraction method for lepidolite roasting based on sulfate co-grinding activation and atmosphere control. This application simultaneously performs mechanochemical activation of lepidolite concentrate and a sulfate composite additive, followed by roasting in a water-containing atmosphere. This couples the mechanoactivation interface, the water-containing atmosphere interface reaction, and the sulfate ion exchange at the same roasting temperature, thereby achieving fluorine migration / removal and lithium soluble conversion in lepidolite. This effectively solves the problems of insufficient roasting reaction and inadequate coupling between the defluorination process and the lithium soluble conversion process in existing technologies, achieving a balance between improving lithium leaching rate and defluorination rate in the lithium extraction method.

[0006] This application provides a method for lithium extraction from lepidolite by roasting based on sulfate co-milling activation and atmosphere control.

[0007] In this application, the method includes the following steps: A method for lithium extraction from lepidolite by calcination based on sulfate co-milling activation and atmosphere control includes the following steps: Step 1, Mechanochemical activation treatment: Lithium mica concentrate is mixed with sulfate composite additive to obtain a mixture to be activated; the mixture to be activated is subjected to mechanochemical activation treatment to obtain an activated material.

[0008] The sulfate composite additive includes at least two of sodium sulfate, potassium sulfate, and calcium sulfate. Step 2, calcination treatment: The activated material is calcined under a water-containing atmosphere and a calcination temperature of 800℃~950℃ to obtain the calcined product.

[0009] The water-containing atmosphere includes water vapor.

[0010] Step 3, Leaching treatment: The calcined product is cooled and then refined to obtain calcined product particles; the calcined product particles are subjected to atmospheric pressure water leaching and solid-liquid separation to obtain lithium-rich leachate.

[0011] Based on the above scheme, this application utilizes the synergistic effect between mechanochemical activation treatment and roasting treatment. By jointly activating lepidolite concentrate with sulfate composite additives through mechanochemical activation and roasting treatment in an aqueous atmosphere, the mechanical activation interface, aqueous atmosphere interface reaction, and sulfate ion exchange are coupled at the same roasting temperature. This achieves the migration / removal of fluorine and the soluble conversion of lithium in lepidolite, effectively solving the problems of insufficient roasting reaction and insufficient coupling between the defluorination process and the soluble conversion of lithium in the prior art.

[0012] The synergistic effect between the mechanochemical activation treatment and the roasting treatment in this application is specifically manifested in the following aspects: First, this application uses a sulfate composite additive to perform mechanochemical activation on lepidolite concentrate, so that the sulfate composite additive is pre-distributed on the exposed sites of lepidolite fractures, new interfaces, and layer edges during the mechanochemical activation stage, thereby improving the interfacial contact efficiency between the sulfate composite additive and the active sites of lepidolite during subsequent roasting. Second, this application uses an aqueous atmosphere (including water vapor) as an interfacial reaction medium and a mass transfer promoting medium, which can promote the disturbance of the phase-key bonding environment of F-Li, Al-F, etc., and promote the migration of fluorine-containing structural units (to the gas phase or calcium-enriched regions) on the defect interfaces formed by mechanochemical activation, thereby reducing Na + K + The structural barrier of plasma approaching lithium sites. Third, this application utilizes an aqueous atmosphere-sulfate co-roasting process, enabling defluorination, layered structure deconstruction, lithium site ion exchange, and lithium sulfation conversion to occur simultaneously within the same roasting stage, which is beneficial for improving lithium leaching and defluorination rates. Fourth, the roasted product obtained after the mechanochemical activation and roasting treatment in an aqueous atmosphere of this application can be directly used to obtain a lithium-rich leachate through pressure water leaching, eliminating the need for complex pressure boiling and acid leaching processes.

[0013] In some embodiments of this application, the sulfate composite additive satisfies at least one of the following conditions: (1) the sulfate composite additive includes sodium sulfate, potassium sulfate, and calcium sulfate; (2) the sodium sulfate includes Na2SO4; (3) the potassium sulfate includes K2SO4; (4) the calcium sulfate includes CaSO4; (5) the amount of sulfate composite additive added is a fraction of the total mass of the lepidolite concentrate. a %,and a The value is 25~45, preferably 30~40, and even more preferably 35.

[0014] In some embodiments of this application, the sulfate composite additive includes Na2SO4, K2SO4 and CaSO4; and the mass ratio of Na2SO4, K2SO4 and CaSO4 in the sulfate composite additive is (0.8~3):(0.3~2):(1~3); preferably, the mass ratio of Na2SO4, K2SO4 and CaSO4 is 1:0.5:2.

[0015] In some embodiments of this application, the mechanochemical activation treatment is performed using a mechanical activation device.

[0016] In some embodiments of this application, the activated material obtained after the mechanochemical activation treatment has lithium mica particles with a particle size D90 of 80 μm to 130 μm.

[0017] In some embodiments of this application, the mechanical activation equipment includes any one of a ball mill, a vibratory mill, and a stirred mill.

[0018] In some embodiments of this application, the mechanochemical activation treatment satisfies at least one of the following conditions: (1) the rotation speed is 350 rpm to 650 rpm, preferably 450 rpm to 550 rpm, and more preferably 500 rpm; (2) the activation time is 0.5 h to 4 h, preferably 1.5 h to 2.5 h, and more preferably 2 h; (3) the ball-to-material mass ratio is 5:1 to 25:1, preferably 10:1 to 20:1.

[0019] In some embodiments of this application, the water-containing atmosphere includes any one of water vapor, air-water vapor mixture, nitrogen-water vapor mixture, and inert gas-water vapor mixture.

[0020] In some embodiments of this application, the water-containing atmosphere satisfies any one of the following conditions: (1) the water vapor in the water-containing atmosphere is 0.1~1.0 g / (g·h) based on the dry basis mass of the activating material; (2) the water vapor volume fraction in the water-containing atmosphere is 20%~100%.

[0021] In some embodiments of this application, the calcination treatment satisfies at least one of the following conditions: (1) the calcination temperature is 850℃~930℃; (2) the calcination time is 1h~2h.

[0022] In some embodiments of this application, the water immersion temperature under normal pressure is 50℃~90℃, the liquid-to-solid ratio is 5mL / g~10mL / g, and the immersion time is 0.5h~2h.

[0023] In some embodiments of this application, the method further includes fluorine-containing tail gas treatment: using an absorbent to absorb and treat the fluorine-containing tail gas generated by the calcination process.

[0024] In some embodiments of this application, the absorbent includes one or more of water, alkaline solution, lime milk, sodium hydroxide solution, and calcium hydroxide slurry.

[0025] In some embodiments of this application, the method further includes post-processing: removing impurities, concentrating and precipitating lithium in the lithium-rich leachate to prepare a lithium product.

[0026] In some embodiments of this application, the roasting process simultaneously completes defluorination, lithium site ion exchange, and lithium sulfation conversion in the same roasting process.

[0027] In some embodiments of this application, during the roasting process, the lithium in the lepidolite concentrate is converted into one or more water-leached lithium salts selected from Li2SO4, LiNaSO4, and LiKSO4.

[0028] In some embodiments of this application, the roasted product is directly soaked in water without undergoing acid pressure cooking.

[0029] Compared with the prior art, this application has the following beneficial effects: This application utilizes the synergistic effect of mechanochemical activation and roasting. By jointly activating lepidolite concentrate with a sulfate composite additive and roasting it in a water-containing atmosphere, the mechanochemical activation interface, the water-containing atmosphere interface reaction, and the sulfate ion exchange are coupled at the same roasting temperature. This achieves the migration / removal of fluorine and the soluble conversion of lithium in lepidolite, effectively solving the problems of insufficient roasting reaction and inadequate coupling between the defluorination process and the soluble conversion of lithium in the prior art.

[0030] Furthermore, the synergistic effect between the mechanochemical activation treatment and the calcination treatment in this application is specifically manifested in the following aspects: First, this application introduces sulfate composite additives into the mechanochemical activation stage, allowing the additives to be pre-distributed in the cracks, new interfaces, and exposed sites at the layer edges of lepidolite, thereby improving the interfacial contact efficiency between the sulfate composite additives and the active sites of lepidolite during subsequent calcination. Second, this application uses an aqueous atmosphere (containing water vapor) as the interfacial reaction medium and mass transfer promoting medium, which can promote the disturbance of the phase-key bonding environment of F-Li, Al-F, etc., and promote the migration of fluorine-containing structural units (to the gas phase or calcium-rich regions) on the defect interfaces formed by mechanochemical activation, thereby reducing Na + K + The structural barrier of plasma approaching lithium sites. Third, this application utilizes an aqueous atmosphere-sulfate co-roasting process, enabling defluorination, layered structure deconstruction, lithium site ion exchange, and lithium sulfation conversion to occur simultaneously within the same roasting stage, which is beneficial for improving lithium leaching and defluorination rates. Fourth, the roasting product of this application can be directly used to obtain a lithium-rich leachate through pressure water leaching, eliminating the need for complex pressure boiling and acid leaching processes.

[0031] In this application, the sulfate composite additive participates in the mechanochemical activation process. During the co-milling process, the sulfate composite additive and the lithium mica particles are subjected to impact, shearing and friction, which enables them to be more fully distributed in cracks, new interfaces and exposed sites at the layer edges, so that the subsequent calcination reaction changes from "contact to the outer surface of the particles" to "contact to the defect interface".

[0032] In this application, an aqueous atmosphere including water vapor is used as the interfacial reaction medium and mass transfer promoting medium. The aqueous atmosphere, as the interfacial reaction medium, participates in the reaction, which can promote the migration of fluorine-containing structural units and disturb the bonding environment of phases such as F-Li and Al-F. Furthermore, after the fluorine-containing structural units migrate, Na… + K + Ca 2+ and SO4 2- It allows for easier access to lithium sites in the layered structure, thereby promoting lithium-ion exchange and sulfation conversion. Specifically, during calcination, it acts as a reaction medium that promotes the migration of fluorine-containing structural units and interfacial ion exchange. It can facilitate the migration of fluorine-containing structural units at defect interfaces formed by mechanical activation, thereby reducing the amount of metal ions (Na+) provided by the sulfate composite additive. + K + Ca 2+ The structure of lithium sites is approached by at least two types of ions, which allows defluorination, layered structure deconstruction, lithium site ion exchange and lithium sulfation conversion to occur simultaneously in the same roasting stage, which is beneficial to improving lithium leaching rate and defluorination rate. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the process flow for lithium extraction from lepidolite by roasting based on sulfate co-milling activation and atmosphere control, as described in this application.

[0035] Figure 2 This is a SEM-EDS image of the activated material from Example 1.

[0036] Figure 3 The images show the XRD patterns of the lithium mica concentrate raw material used in this application and the activated material obtained in Example 1. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0038] In the description of this application, the terms "upper," "lower," "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings, and are used only for ease of description and simplification of operation. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. In addition, the terms "first" and "second" are used only for descriptive distinction and have no special meaning.

[0039] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values, and such ranges or values ​​should be understood to include values ​​close to such ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0040] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0041] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0042] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0043] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0044] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0045] It should be emphasized that the preparation methods or operation steps not specifically described in this application all refer to the prior art in this field, which should be known by those skilled in the art, and therefore will not be described again in this application.

[0046] As described in the background section, existing technologies for lithium extraction using the sulfate roasting method suffer from problems such as excessive additive dosage, insufficient roasting reaction, and inadequate coupling between the defluorination process and the lithium soluble conversion process.

[0047] To address the aforementioned technical issues, CN110042225A discloses a method for roasting and leaching lepidolite with sodium sulfate. This method involves mixing lepidolite concentrate with sodium sulfate, calcium oxide, and calcium carbonate, followed by calcination at 850-1000℃. The roasted ore is then ground and leached with sulfuric acid, followed by pulping and washing to recover lithium and rubidium. However, this method also requires acid leaching and washing after roasting, making the overall lithium extraction process cumbersome and difficult to simultaneously improve both lithium leaching and defluorination rates.

[0048] In view of this, this application provides a method for lithium extraction from lepidolite by calcination based on sulfate co-milling activation and atmosphere control.

[0049] Please see Figure 1 In this application, the lithium extraction method for lithium mica roasting based on sulfate co-milling activation and atmosphere control includes the following steps: Step 1, Mechanochemical activation treatment: S11, Lithium mica concentrate is mixed with sulfate composite additive to obtain the mixture to be activated.

[0050] S12, the mixture to be activated is subjected to mechanical and chemical activation treatment to obtain activated material.

[0051] The sulfate composite additive includes at least two of sodium sulfate, potassium sulfate, and calcium sulfate.

[0052] It should be noted that, considering the binding or shielding effect of fluorine-containing structural units in lepidolite on lithium sites in the layered structure, directly roasting lepidolite concentrate with sulfate composite additives would hinder effective contact between the sulfate composite additives and the active sites of lepidolite. Therefore, this application addresses this problem through sulfate co-grinding activation. It should be understood that "sulfate co-grinding activation" in this application refers to introducing sulfate composite additives during the mechanochemical activation stage, allowing the sulfate composite additives and lepidolite concentrate to undergo mechanical grinding and chemical activation together. Specifically, introducing sulfate composite additives during the mechanochemical activation stage allows them to be pre-distributed in lepidolite fissures, new interfaces, and exposed sites at layer edges, improving the interfacial contact efficiency between the sulfate composite additives and the active sites of lepidolite during subsequent roasting.

[0053] This application premixes lepidolite concentrate with a sulfate composite additive to improve the uniformity of the sulfate composite additive's distribution in the lepidolite concentrate, forming a homogeneous mixture to be activated. Then, the mixture is subjected to mechanochemical activation treatment to further promote particle refinement of the lepidolite concentrate and sulfate composite additive under mechanical mixing, thereby facilitating the exposure of defect crystal faces or increasing specific surface area, and thus promoting the growth of metal ions (Na+) in the sulfate composite additive. + K + Ca 2+ At least two types of ions in the sulfate composite agent are further evenly distributed on the surface, cracks, new interfaces, and exposed sites at the layer edges of lepidolite particles, improving the interfacial contact efficiency and effective contact area between the sulfate composite agent and the lithium active sites in the layered structure of lepidolite, and enabling the metal ions (such as Na+) provided by the sulfate composite agent to be more uniformly distributed on the surface, cracks, new interfaces, and exposed sites at the layer edges of lepidolite particles. + K + Ca 2+ At least two types of ions in the crystalline lithium can effectively approach and replace the lattice-state lithium, providing a good foundation for subsequent reactions such as defluorination, layered structure deconstruction, and lithium solubility conversion during calcination.

[0054] It should also be noted that, unlike traditional mixing methods and methods that involve mechanically activating lepidolite separately before adding the sulfate composite additive, this application simultaneously performs mechanochemical activation treatment on lepidolite concentrate and the sulfate composite additive. During this mechanochemical activation process, the presence of the sulfate composite additive allows for the refinement of lepidolite particles and the generation of lattice disturbances. Furthermore, the sulfate composite additive and lepidolite particles are subjected to impact, shearing, and friction, enabling the sulfate composite additive to adhere, embed, or accumulate on the surface, cracks, new interfaces, and exposed sites at layer edges of the lepidolite particles under mechanical force, thus forming a composite activation structure with overlapping "lepidolite activation interface - sulfate contact interface." This structure improves the efficiency of subsequent roasting by increasing the concentration of metal ions (such as Na₂O₃). + K + Ca 2+ (at least two of them) and SO4 2- The increased probability of approaching the active sites of the lithium-containing layered structure causes the reaction to change from "contact to the outer surface of the particle" to "contact to the defect interface" during the subsequent calcination process.

[0055] It should also be noted that this application does not limit the specific method of adding the sulfate composite additive. All the sulfate composite additive can be mixed with the lepidolite concentrate and then subjected to mechanochemical activation treatment; alternatively, a portion of the sulfate composite additive can be mixed with the lepidolite concentrate first and then subjected to mechanochemical activation treatment, and the activated material can then be directly mixed with the remaining sulfate composite additive, as long as a composite activation structure with overlapping "lepidolite activation interface - sulfate contact interface" can be formed. Preferably, mixing all the sulfate composite additive with the lepidolite concentrate before mechanochemical activation treatment can better improve the metal ion (such as Na) concentration during subsequent roasting. + K + Ca 2+ (at least two of them) and SO4 2- The probability of approaching the active sites of lithium-containing layered structures.

[0056] This application does not limit the specific type of sulfate composite additive, as long as it can achieve the functions of this application. For example, in some embodiments of this application, the sulfate composite additive used includes at least two of sodium sulfate, potassium sulfate, and calcium sulfate. Specifically, when the sulfate composite additive used includes sodium sulfate and / or potassium sulfate, it is beneficial to provide Na during the calcination process. + K + It also promotes ion exchange at interlayer lithium sites. When the sulfate composite additive used includes calcium sulfate, it is beneficial to provide Ca during the calcination process. 2+This is beneficial for participating in mineral phase reconstruction and improving mineral phase sintering. For example, it helps promote the migration and removal of fluorine in the lithium mica concentrate as fluorine-containing volatile components and / or fixation in the roasting product or the subsequent leaching residue obtained through solid-liquid separation as CaF2. Therefore, when the sulfate composite additive used in this application meets the above conditions, it enables the various metal ions provided by the sulfate composite additive to work synergistically, thereby better promoting lithium ion exchange and sulfation conversion.

[0057] In some embodiments of this application, the sulfate composite additive satisfies at least one of the following conditions: (1) the sulfate composite additive includes sodium sulfate, potassium sulfate, and calcium sulfate; (2) the sodium sulfate includes Na2SO4; (3) the potassium sulfate includes K2SO4; (4) the calcium sulfate includes CaSO4; (5) the amount of sulfate composite additive added is a fraction of the total mass of the lepidolite concentrate. a %,and a The temperature should be between 25 and 45, preferably 30 to 40, and even more preferably 35. Based on the above scheme, satisfying any of the above conditions can better promote lithium-ion exchange and sulfation conversion during the roasting process.

[0058] For example, in some embodiments of this application, the sulfate composite additive includes sodium sulfate, potassium sulfate, and calcium sulfate. Based on the above scheme, when sodium sulfate, potassium sulfate, and calcium sulfate are used together as the sulfate composite additive, the sulfate composite additive can, during the calcination process, utilize the provided Na... + K + Ca 2+ and SO4 2- By better accessing the lithium sites in the layered structure of lepidolite particles, the various metal ions can work synergistically to better achieve the effects of the aforementioned sulfate composite additive, thereby better promoting lithium ion exchange and sulfation conversion.

[0059] For example, in some embodiments of this application, the sulfate composite additive includes Na₂SO₄, K₂SO₄, and CaSO₄. Based on the above scheme, when the above conditions are met, the sulfate composite additive can better provide Na₂SO₄. + K + Ca 2+ and SO4 2- This further improves the Na content during subsequent roasting. + K + Ca 2+ and SO4 2- The probability of approaching the active sites of the lithium-containing layered structure is increased, thereby further promoting lithium-ion exchange and sulfation conversion.

[0060] Exemplary, in some embodiments of this application, when a The concentration should be between 25% and 45%. Based on the above scheme, when the amount of sulfate composite additive added meets the above conditions, the added sulfate composite additive can better adhere to, embed, or accumulate on the surface, cracks, new interfaces, and exposed sites at the layer edges of lepidolite particles under mechanical force, thereby forming a composite activation structure with overlapping "lepidolite activation interface - sulfate contact interface," which is beneficial to improving the Na+ concentration during subsequent calcination. + K + Ca 2+ and SO4 2- The probability of proximity to active sites in lithium-containing layered structures. Especially when... a When the concentration is between 30 and 40%, the added sulfate composite additive can better achieve the above-mentioned effects. Specifically, when... a When the temperature is 35°C, the added sulfate composite additive can further improve the Na+ content during subsequent roasting. + K + Ca 2+ and SO4 2- The probability of approaching the active sites of the lithium-containing layered structure, thereby increasing the Na provided by the sulfate composite additive. + K + It can promote ion exchange at interlayer lithium sites, Ca 2+ and SO4 2- It is beneficial to participate in mineral phase reconstruction and improve mineral phase sintering.

[0061] In some embodiments of this application, the mass ratio of Na₂SO₄, K₂SO₄, and CaSO₄ in the sulfate composite additive is (0.8~3):(0.3~2):(1~3). Based on the above scheme, when the above conditions are met, Na₂SO₄, K₂SO₄, and CaSO₄ can cooperate well, especially during the roasting process, where Na₂SO₄, K₂SO₄, and CaSO₄ undergo ion exchange, mineral phase reconstruction, and sulfation reactions with the lepidolite phase, converting sparingly soluble lattice lithium into water-leached lithium salts such as Li₂SO₄, LiNaSO₄, or LiKSO₄. In particular, when the mass ratio of Na₂SO₄, K₂SO₄, and CaSO₄ is 1:0.5:2, Na₂SO₄, K₂SO₄, and CaSO₄ can cooperate even better and exert the above-mentioned effects more effectively.

[0062] This application does not limit the specific degree of mechanochemical activation treatment, as long as it can refine the lepidolite, creating fissures, new interfaces, and exposed sites at layer edges, thereby enabling the pre-distribution of the sulfate composite additive at these fissures, interfaces, and exposed sites during subsequent roasting, thus improving the interfacial contact efficiency between the sulfate composite additive and the active sites of the lepidolite. For example, in some embodiments of this application, the lepidolite particles in the activated material obtained after the mechanochemical activation treatment meet the requirement of a particle size D90 of 80 μm to 130 μm. Based on the above scheme, by obtaining lepidolite concentrate with suitable particle size, the sulfate composite additive can be promoted to adhere, embed, or accumulate on the surface, fissures, new interfaces, and exposed sites at layer edges of the lepidolite particles under mechanical force.

[0063] In some embodiments of this application, the mechanochemical activation treatment is performed using a mechanical activation device. Based on the above scheme, the mechanical action provided by the mechanical activation device can pre-distribute the sulfate composite additive in the cracks, new interfaces, and exposed sites at the layer edges of lepidolite, thereby improving the interfacial contact efficiency between the sulfate composite additive and the active sites of lepidolite during subsequent calcination.

[0064] It should be noted that this application does not limit the specific type of mechanical activation equipment used in the mechanochemical activation treatment, as long as it can achieve the above-mentioned effects. For example, in some embodiments of this application, the mechanical activation equipment includes any one of a ball mill, a vibratory mill, and a stirred mill.

[0065] For example, in some embodiments of this application, the mechanical activation equipment used is a ball mill, specifically a planetary ball mill.

[0066] In some embodiments of this application, the mechanochemical activation treatment satisfies at least one of the following conditions: (1) the rotation speed is 350 rpm to 650 rpm, preferably 450 rpm to 550 rpm, and more preferably 500 rpm; (2) the activation time is 0.5 h to 4 h, preferably 1.5 h to 2.5 h, and more preferably 2 h; (3) the ball-to-material mass ratio is 5:1 to 25:1, preferably 10:1 to 20:1. Based on the above scheme, when any of the above conditions are met, the uniformity of the distribution of sulfate composite additives in lithium mica cracks, new interfaces, and exposed sites at layer edges can be promoted.

[0067] This application does not limit the specific type of lepidolite concentrate, and it can be selected according to actual needs. For example, it can be at least one of the following complex lepidolite concentrates containing mineral phases such as lepidolite, lepidolite, muscovite, fluorophlogopite, feldspar, and quartz.

[0068] In some embodiments of this application, step 1 further includes S10, raw material pretreatment: The lepidolite concentrate is dried, crushed, and screened to obtain lepidolite concentrate with suitable particle size.

[0069] In some embodiments of this application, the lepidolite concentrate is pretreated until the particle size D90 of the lepidolite concentrate is less than or equal to 350 μm. Based on the above scheme, by obtaining lepidolite concentrate with suitable particle size, the sulfate composite additive is promoted to adhere, embed, or accumulate on the surface, cracks, new interfaces, and exposed sites at the edge of lepidolite particles under mechanical force.

[0070] Step 2, roasting treatment: The activated material is roasted under a water-containing atmosphere and a roasting temperature of 800℃~950℃ to obtain a roasted product; wherein the water-containing atmosphere includes water vapor.

[0071] It should be noted that, during the research process, this application found that although mechanochemical activation treatment can weaken the integrity of the layered structure of lepidolite and promote the growth of metal ions (Na+), + K + Ca 2+ At least two ions in the fluorine-containing structure approach and replace lattice-state lithium, but if the calcination atmosphere is unsuitable, the migration of fluorine-containing structural units and interfacial mass transfer remain limited. Therefore, this application aims to further improve the migration of fluorine-containing structural units and interfacial mass transfer through atmosphere control. It should be understood that "atmosphere control" in this application refers to controlling the calcination atmosphere of the calcination process, specifically controlling the calcination atmosphere to a water-containing atmosphere. Specifically, this application uses a water-containing atmosphere including water vapor as the interfacial reaction medium and mass transfer promoting medium, so that the activated material is calcined in a water-containing atmosphere, allowing defluorination, layered structure deconstruction, lithium site ion exchange, and lithium sulfation conversion to occur simultaneously at the same calcination temperature, thereby improving the lithium leaching rate and defluorination rate. Specifically, during the calcination process, the reaction medium that promotes the migration of fluorine-containing structural units and interfacial ion exchange can promote the migration of fluorine-containing structural units on the defective interfaces formed by mechanical activation, thereby reducing the amount of metal ions (Na+, Na+, Na+) provided by the sulfate composite additive. + K + Ca 2+The presence of at least two types of ions in the lithium mica concentrate near the structural barriers of lithium sites allows for simultaneous defluorination, layered structure deconstruction, lithium site ion exchange, and lithium sulfation conversion within the same roasting stage, which is beneficial for improving lithium leaching and defluorination rates. It is worth noting that after the treatment in step 1 of this application, the lepidolite particles possess cracks and defect sites, making it easier for water vapor to enter the surface and reaction interface of the lepidolite particles. This promotes disturbance of the key bonding environments of F-Li and Al-F phases, and causes fluorine-containing structural units to migrate to the gas phase or calcium-rich regions. Simultaneously, the metal ions and sulfate ions provided by the sulfate composite additive undergo ion exchange, phase reconstruction, and sulfation reactions with the lepidolite mineral phase, converting sparingly soluble lattice lithium into corresponding water-leached lithium salts. It should be understood that the composition of the formed water-leached lithium salt varies depending on the choice of the sulfate composite additive. For example, during the roasting process, lithium in the lepidolite concentrate is converted into one or more water-leached lithium salts selected from Li₂SO₄, LiNaSO₄, and LiKSO₄.

[0072] This application does not limit the specific type of water-containing atmosphere, as long as it includes water vapor and can achieve the above-mentioned effects. It should be understood that "including water vapor" in this application means that the water-containing atmosphere can be pure water vapor or a mixture of water vapor and other atmospheres.

[0073] In some embodiments of this application, the water-containing atmosphere includes any one of water vapor, air-water vapor mixture, nitrogen-water vapor mixture, and inert gas-water vapor mixture.

[0074] This application does not limit the specific content of the water-containing atmosphere, as long as it contains water vapor to achieve the above-mentioned function. For example, in some embodiments of this application, the water-containing atmosphere satisfies any one of the following conditions: (1) the water vapor in the water-containing atmosphere, based on the activating material, is introduced at a rate of 0.1~1.0 g / (g·h); (2) the water vapor volume fraction in the water-containing atmosphere is 20%~100%. Based on the above scheme, when any of the above conditions are met, the water-containing atmosphere can better achieve the above-mentioned function. It should be understood that when the above condition (1) is met, the water vapor introduction rate is adjusted accordingly according to the dry basis mass of the activating material. For example, for every 1g of the activating material (dry basis mass), the water vapor introduction rate is 0.1g / h.

[0075] This application does not limit the specific process parameters of the roasting treatment, as long as the purpose of this application (to simultaneously complete defluorination, lithium site ion exchange, and lithium sulfation conversion in the same roasting stage) can be achieved. For example, in some embodiments of this application, the roasting treatment meets at least one of the following conditions: (1) the roasting temperature is 850℃~930℃; (2) the roasting time is 1 h~2 h. Based on the above scheme, when any of the above conditions are met, it is beneficial to simultaneously complete defluorination, lithium site ion exchange, and lithium sulfation conversion in the same roasting stage.

[0076] For example, in some embodiments of this application, the roasting temperature for the roasting process is 800℃~950℃. Based on the above scheme, defluorination, layered structure deconstruction, lithium site ion exchange, and lithium sulfation conversion can be carried out simultaneously within the same roasting temperature, which is beneficial to improving the lithium leaching rate and defluorination rate. In particular, when the roasting temperature is 850℃~930℃, the lithium leaching rate and defluorination rate can be improved even more.

[0077] Step 3, Leaching treatment: The roasted product is cooled and then refined to obtain roasted product particles; the roasted product particles are subjected to atmospheric pressure water leaching and solid-liquid separation to obtain lithium-rich leachate and leachate residue.

[0078] Based on the above scheme, this application achieves efficient leaching of lithium from the roasted product directly through atmospheric pressure water leaching without the need for acid pressure cooking after the synergistic effect of mechanochemical activation treatment and roasting treatment. This not only avoids the complicated pressure cooking and acid leaching process and simplifies the process, but also avoids the generation of acid waste liquid after acid leaching, further improving the green and environmentally friendly nature of the process.

[0079] It should be noted that this application does not limit the specific method of refining, as long as the roasted product is refined to a particle size suitable for water immersion. For example, in some embodiments of this application, the refining process includes any one or more of crushing, grinding, and sieving processes.

[0080] This application does not limit the specific particle size of the calcined product particles, as long as they are within a range suitable for water leaching. For example, in some embodiments of this application, the calcined product is processed to a particle size that meets the requirement that D90 is less than or equal to 100 μm, and then subjected to atmospheric pressure water leaching to ensure that the calcined product particles can fully contact the water, thereby further improving the lithium leaching rate in the calcined product.

[0081] In some embodiments of this application, the leaching temperature of the atmospheric pressure water leaching is 50℃~90℃, the liquid-to-solid ratio is 5 mL / g~10 mL / g, and the leaching time is 0.5h~2h. Based on the above scheme, the leaching rate of lithium in the calcined product can be better improved.

[0082] This application does not limit the specific method of solid-liquid separation, as long as it can separate the lithium-rich leachate. For example, in some embodiments of this application, the solid-liquid separation method used includes, but is not limited to, filtration, sedimentation, centrifugation, or other solid-liquid separation operations.

[0083] In summary, this application achieves the migration / removal of fluorine and the soluble conversion of lithium in lepidolite by synergistically combining mechanochemical activation and roasting. This is accomplished by jointly activating lepidolite concentrate with a sulfate composite additive and then roasting it in a water-containing atmosphere. This coupling of the mechanochemical activation interface, the water-containing atmosphere interface reaction, and the sulfate ion exchange at the same roasting temperature effectively solves the problems of insufficient roasting reaction and inadequate coupling between the defluorination process and the soluble conversion of lithium in existing technologies.

[0084] The synergistic effect between the mechanochemical activation treatment and the calcination treatment in this application is specifically manifested in the following aspects: First, this application introduces sulfate composite additives into the mechanochemical activation stage, allowing the additives to be pre-distributed in the cracks, new interfaces, and exposed sites at the layer edges of lepidolite, thereby improving the interfacial contact efficiency between the sulfate composite additives and the active sites of lepidolite during subsequent calcination. Second, this application uses an aqueous atmosphere (containing water vapor) as the interfacial reaction medium and mass transfer promoting medium, which can promote the disturbance of the phase-key bonding environment of F-Li, Al-F, etc., and promote the migration of fluorine-containing structural units (to the gas phase or calcium-rich regions) on the defect interfaces formed by mechanochemical activation, thereby reducing Na + K + The structural barrier of plasma approaching lithium sites. Third, this application utilizes an aqueous atmosphere-sulfate co-roasting process, enabling defluorination, layered structure deconstruction, lithium site ion exchange, and lithium sulfation conversion to occur simultaneously within the same roasting stage, which is beneficial for improving lithium leaching and defluorination rates. Fourth, the roasting product of this application can be directly used to obtain a lithium-rich leachate through pressure water leaching, eliminating the need for complex pressure boiling and acid leaching processes.

[0085] In some embodiments of this application, the method further includes step 4, fluorine-containing tail gas treatment: using an absorbent to absorb and treat the fluorine-containing tail gas generated by the calcination process.

[0086] It should be noted that this application does not limit the specific type of absorbent, as long as it can achieve the function of this application. For example, in some embodiments of this application, the absorbent used includes one or more of water, alkaline solution, lime milk, sodium hydroxide solution, and calcium hydroxide slurry. It should also be noted that some of the fluorine in the leaching residue can be fixed into a more stable form such as CaF2 by calcium salts, thereby reducing the difficulty of subsequent processing.

[0087] In some embodiments of this application, the method further includes step 5, post-processing: removing impurities, concentrating and precipitating lithium in the lithium-rich leachate to prepare a lithium product.

[0088] It should be noted that this application does not limit the specific type of lithium product. The lithium product can be made from the product obtained through lithium precipitation according to actual needs. For example, in some embodiments of this application, the lithium product includes any one or more of lithium carbonate, lithium hydroxide, and other lithium salt products.

[0089] This application does not limit the specific processes for impurity removal, concentration, and lithium precipitation. Processing can be carried out using conventional techniques in the field to obtain the corresponding lithium products.

[0090] For example, in some embodiments of this application, the impurity removal includes: adding a precipitant to the lithium-rich leachate to adjust the pH of the lithium-rich leachate to above 12, in order to remove aluminum / fluorine impurities therein, thereby obtaining a purified lithium-rich leachate. This application does not limit the specific type of precipitant, as long as it can achieve the above-mentioned effect. For example, in some embodiments of this application, the precipitant includes calcium hydroxide. Using calcium hydroxide as a precipitant can achieve the above-mentioned effect while avoiding the introduction of other new metal ions.

[0091] For example, in some embodiments of this application, the concentration includes: evaporating and concentrating the purified lithium-rich leachate to obtain a concentrated solution. Preferably, this application uses evaporation and concentration, and the concentrated solution is concentrated to 1 / 4 to 1 / 3 of the volume of the purified lithium-rich leachate.

[0092] For example, in some embodiments of this application, the lithium precipitation process includes: adding a lithium precipitation agent to the concentrate to perform a lithium precipitation reaction at room temperature and pressure, followed by solid-liquid separation to obtain a lithium precipitate product and a filtrate. This application does not limit the specific type of lithium precipitation agent and can select one according to the target lithium product. For example, the lithium precipitation agent used may include sodium dihydrogen phosphate, and the amount of the lithium precipitation agent used may be 4 to 6 times the mass of Li2O in the lithium-rich leachate after impurity removal.

[0093] The physical properties mentioned in this application can be measured using the following methods, and the physical properties in the following embodiments and comparative examples are measured using the following methods.

[0094] Test method: (a) Particle size analysis: The test was conducted using a laser particle size analyzer in accordance with the test method in the national standard GB / T 19077-2024 "Particle Size Analysis by Laser Diffraction".

[0095] (ii) Defluorination rate test: The defluorination rate is calculated using the following formula. η F : η F (%) = [( m 0× F 0- m 1× F 1) / ( m 0× F 0)]×100%.

[0096] In the formula, m 0 represents the dry weight of the lithium mica concentrate feed, in g; F 0 represents the total fluorine mass fraction of lepidolite concentrate, % m 1 represents the dry weight of the roasted product obtained after roasting, in grams; F 1 represents the total solid fluorine mass fraction of the calcined product.

[0097] The total fluorine mass fraction of the above-mentioned lithium mica concentrate F 0 and the mass fraction of total solid fluorine in the calcination product F 1. All tests were performed according to the test method in HJ 999-2018 "Determination of Fluorine in Solid Waste by Alkali Fusion-Ion Selective Electrode Method"; the test samples were dried to obtain dry basis samples, the dry basis solid sample was weighed and placed in a nickel crucible, sodium hydroxide was added for high-temperature alkali fusion digestion, and after cooling, the melt was extracted by water leaching, the pH of the test solution was adjusted, and total ionic strength adjustment buffer solution (TISAB) was added. The fluorine content was determined by fluoride ion selective electrode combined with standard curve; all pretreatment vessels were made of polyethylene material to avoid the introduction of test errors by fluoride corrosion of glassware.

[0098] The following examples and comparative examples illustrate the implementation of this application in more detail. It should be noted that in the following examples and comparative examples, the lepidolite concentrate used in this application is lepidolite from a lepidolite mining area in Yichun City, Jiangxi Province, and the Li₂O content, as determined by testing and analysis, is 1.41%. Other reagents or pharmaceuticals not specifically mentioned are commercially available.

[0099] Example 1 This embodiment provides a lithium extraction method for lepidolite calcination based on sulfate co-milling activation and atmosphere control, including the following steps: Step 1, Mechanochemical activation treatment: S10, Raw material pretreatment: The lepidolite concentrate raw material is dried, crushed and screened to obtain lepidolite concentrate with a particle size D90 of 310 μm.

[0100] S11, Mixing: The lithium mica concentrate obtained in S10 above is mixed with the sulfate composite additive to obtain the mixture to be activated.

[0101] S12, co-milling activation: The mixture to be activated obtained in S11 is placed in a planetary ball mill for mechanical and chemical activation treatment to obtain activated material.

[0102] In this embodiment, the sulfate composite additive used is composed of Na2SO4, K2SO4 and CaSO4, and the mass ratio of Na2SO4, K2SO4 and CaSO4 is 1:0.5:2.

[0103] In this embodiment, the amount of sulfate composite additive added is 35% of the total mass of lepidolite concentrate.

[0104] In this embodiment, the ball milling speed for co-milling mechanical chemical activation is 500 rpm, the activation time is 2 h, and the ball-to-material mass ratio is 15:1.

[0105] Tests show that, compared to the raw material of lepidolite concentrate, after step 1 treatment in this embodiment, the particle size D90 of lepidolite decreased from 310 μm to 100 μm, and the intensity of the characteristic diffraction peaks of lepidolite decreased or the half-peak width increased, indicating that co-grinding activation produced the effects of particle refinement and lattice disorder.

[0106] Step 2, roasting treatment: The activated material obtained in step S12 is placed in a tubular roasting furnace and roasted in a water-containing atmosphere to obtain a roasted product.

[0107] In this embodiment, the water-containing atmosphere used is water vapor, and the amount of water vapor introduced is 0.5 g / (g·h) based on the dry basis mass of the activated material obtained in S12.

[0108] In this embodiment, the calcination temperature is 900℃ and the calcination time is 2 h.

[0109] Step 3, Leaching treatment: S31, the calcined product obtained above is cooled and then ground to obtain calcined product particles with a particle size D90 of 100 μm.

[0110] S32, the calcined product particles obtained above are subjected to atmospheric pressure water leaching and solid-liquid separation in sequence to obtain lithium-rich leachate and leachate residue.

[0111] In this embodiment, the water immersion temperature under normal pressure is 80°C, the liquid-to-solid ratio is 8 mL / g, and the immersion time is 1 h.

[0112] In this embodiment, the solid-liquid separation method used is filtration.

[0113] Step 4, Treatment of Fluorine-Containing Exhaust Gas: The fluorine-containing tail gas generated during the roasting process was absorbed and treated using a two-stage 0.10 mol / L sodium hydroxide solution, with 250 mL per stage.

[0114] Step 5, Post-processing: S51, Impurity Removal: Calcium hydroxide is added to the lithium-rich leachate to adjust the pH value of the lithium-rich leachate to 12, thereby removing aluminum / fluorine impurities and obtaining the impurity-removed lithium-rich leachate.

[0115] S52, Concentration: The lithium-rich leachate after impurity removal is evaporated and concentrated to 1 / 4 of the volume of the lithium-rich leachate after impurity removal, to obtain a concentrated solution.

[0116] S53, Lithium precipitation treatment: Add sodium dihydrogen phosphate lithium precipitant to the concentrate and perform lithium precipitation treatment at room temperature and pressure, filter, and obtain lithium precipitate product and filtrate.

[0117] To verify the synergistic effect of sulfate co-milling activation and aqueous atmosphere interface regulation reaction, this application also sets up the following comparative examples.

[0118] Comparative Example 1 The only difference between this comparative example and Example 1 is that: In this comparative example, no mechanical and chemical activation treatment is performed in step 1. Instead, the sulfate composite additive and lepidolite concentrate are directly mixed in a conventional manner.

[0119] Furthermore, in this comparative example, the roasting atmosphere used in step 2 is air.

[0120] Comparative Example 2 The only difference between this comparative example and Example 1 is that: In this comparative example, no mechanochemical activation treatment is performed in step 1. Instead, the lepidolite concentrate is placed in a planetary ball mill for mechanochemical activation treatment. The activated lepidolite concentrate is then mixed with a sulfate composite additive before proceeding to step 2.

[0121] Furthermore, in this comparative example, the roasting atmosphere used in step 2 is air.

[0122] Comparative Example 3 The only difference between this comparative example and Example 1 is that: In this comparative example, no mechanical and chemical activation treatment is performed in step 1. Instead, the sulfate composite additive and lepidolite concentrate are directly mixed in a conventional manner.

[0123] Comparative Example 4 The only difference between this comparative example and Example 1 is that: In this comparative example, no mechanochemical activation treatment is performed in step 1. Instead, the lepidolite concentrate is placed in a planetary ball mill for mechanochemical activation treatment. The activated lepidolite concentrate is then mixed with a sulfate composite additive before proceeding to step 2.

[0124] Comparative Example 5 The only difference between this comparative example and Example 1 is that: In this comparative example, the roasting atmosphere used in step 2 is air.

[0125] Example 2 The only difference between this embodiment and Embodiment 1 is that: In this embodiment, in step 1, half of the sulfate composite additive is first mixed with lepidolite concentrate and then subjected to mechanochemical activation treatment. The activated material is then directly mixed with the remaining half of the sulfate composite additive.

[0126] This application tested the lithium extraction effect of Example 1 and Comparative Examples 1 to 5, and the test results are summarized in Table 1.

[0127] Table 1

[0128] Based on the test results in Table 1, it is clear that compared to Comparative Example 1, which uses a conventional mixing method to introduce the sulfate composite additive, Comparative Example 2, which first performs mechanochemical activation treatment on lepidolite before mixing it with the sulfate composite additive, can improve the lithium leaching rate and defluorination rate to some extent, but the improvement effect is limited. Comparing the test results of Comparative Example 3 with Comparative Example 1, it is shown that compared to the air atmosphere of Comparative Example 1, using steam as the roasting atmosphere in Comparative Example 3 can improve the lithium leaching rate and defluorination rate to some extent, but the improvement effect is also limited. Comparing the test results of Comparative Example 4 with Comparative Examples 3 and 2, it is shown that simultaneously using mechanochemical activation treatment and roasting treatment is beneficial for further improving the lithium leaching rate and defluorination rate. Comparing the test results of Comparative Example 5 with Comparative Examples 4 and 2, it is shown that when the lepidolite and sulfate composite additive undergo mechanochemical activation treatment, or roasting treatment is performed in a water-containing atmosphere, the lithium leaching rate and defluorination rate can be further improved, but the improvement effect is limited. In particular, the mechanochemical activation treatment of the lithium mica and sulfate composite additive can improve the interfacial distribution between raw materials through co-grinding, thereby better improving the lithium leaching rate and defluorination rate. Furthermore, comparing the test results of Example 1 and Comparative Examples 1 to 5 shows that the lithium leaching rate of Example 1 was 97.38%, and the defluorination rate was 99.73%, both higher than those of Comparative Examples 1 to 5.

[0129] The test results in Table 1 also clearly show that, compared to the single activation of lepidolite in Comparative Example 4, this application, by introducing a portion of the sulfate composite additive with the mechanochemical activation treatment of lepidolite, or by mixing lepidolite with all the sulfate composite additives and then performing mechanochemical activation treatment together, is better able to ensure that the introduced sulfate composite additives are effectively distributed within the structure of lepidolite, thereby forming a special reaction interface to better balance the improvement of lithium leaching rate and defluorination rate in the lithium extraction method. In particular, mixing all the sulfate composite additives with lepidolite concentrate and then performing mechanochemical activation treatment can better improve the subsequent roasting of metal ions (such as Na+). + K + Ca 2+ (at least two of them) and SO4 2- The probability of approaching the active sites of lithium-containing layered structures.

[0130] Based on the above, this application achieves the synergistic effect between mechanochemical activation treatment and calcination treatment, which couples the mechanical activation interface, the aqueous atmosphere interface reaction, and the sulfate ion exchange at the same calcination temperature. This indicates that the reaction interface formed by sulfate co-grinding activation and the aqueous atmosphere interface reaction jointly promote the defluorination of lepidolite and the soluble conversion of lithium, thereby improving both the lithium leaching rate and the defluorination rate of the lithium extraction method.

[0131] This application takes Example 1 as an example, performs SEM-EDS testing on the activated material of Example 1, and summarizes the distribution of the main elements as follows: Figure 2 As shown.

[0132] Depend on Figure 2 The test results show that in the activated material obtained in Example 1, Na, K and S elements are present in the cracks or interface regions of lepidolite. This indicates that by using lepidolite and all sulfate composite additives for mechanochemical activation, this application can pre-distribute the sulfate composite additives in the cracks, new interfaces and exposed sites at the layer edges of lepidolite through co-milling activation, thereby improving the interfacial contact efficiency between the sulfate composite additives and the active sites of lepidolite during subsequent calcination.

[0133] This application also uses Example 1 as an example, and XRD tests were performed on the lithium mica concentrate raw material used therein and the activated material obtained in Example 1, and the test results are as follows: Figure 3 As shown.

[0134] Depend on Figure 3The test results show that the characteristic peaks of lepidolite in the XRD spectrum of the activated material obtained in Example 1 (such as the diffraction peaks of 2θ at 8.9 and 18) have changed significantly. Not only has the peak intensity decreased, but the half-peak width has also increased significantly. This indicates that the mechanical and chemical activation treatment of lepidolite and sulfate composite additives in this application can achieve co-milling activation and produce particle refinement and lattice disorder effects. This facilitates the pre-distribution of sulfate composite additives in the cracks, new interfaces and layer edge exposure sites of lepidolite, thereby improving the interfacial contact efficiency between sulfate composite additives and active sites of lepidolite in subsequent calcination.

[0135] To further investigate the effects of rotation speed and activation time of mechanochemical activation treatment on lithium extraction efficiency, this application also includes the following comparative examples and embodiments.

[0136] Comparative Example 6, and Examples 3 to 12, differ from Example 1 only in that the rotation speed and activation time of the mechanochemical activation treatment are adjusted according to Table 2.

[0137] Table 2

[0138] According to the test results in Table 2, it is clear that when the rotation speed of the mechanochemical activation treatment is 350 rpm to 650 rpm and the activation time is 0.5 h to 4 h, it can promote the uniform distribution of sulfate composite additives in the cracks, new interfaces and exposed sites at the edge of the layer in lepidolite, better promote the formation of special reaction interfaces, and thus better balance the improvement of lithium leaching rate and defluorination rate of the lithium extraction method.

[0139] Considering that excessive mechanical speed or excessively long activation time will lead to increased equipment energy consumption, this application preferably sets the mechanical chemical activation speed at 450 rpm to 550 rpm and the activation time at 1.5 h to 2.5 h, so as to better balance the overall energy consumption and economic cost of the process while improving the lithium leaching rate and defluorination rate of the lithium extraction method.

[0140] To further investigate the effects of a water-containing atmosphere on the defluorination rate and lithium leaching effect, the following embodiments are also provided in this application.

[0141] Examples 13 and 14 differ from Example 1 only in that the water vapor content of the water-containing atmosphere is adjusted according to Table 3.

[0142] Table 3

[0143] The test results in Table 3 clearly show that, compared to Comparative Example 5, this application, through calcination in a water-containing atmosphere, enables the water-containing atmosphere to synergistically enhance the mechanochemical activation process, thereby achieving a better balance between improving lithium leaching rate and defluorination rate. In particular, when the water vapor flow rate in the water-containing atmosphere is 0.1~1.0 g / (g·h), it better balances the improvement of both lithium leaching rate and defluorination rate. Specifically, when the water vapor flow rate in the water-containing atmosphere is 0.5 g / (g·h), both the defluorination and lithium leaching effects show superior results, with lithium leaching rate and defluorination rate reaching 97.38% and 99.73%, respectively. This demonstrates that, by controlling the water-containing atmosphere, including water vapor, this application enables the water-containing atmosphere used in this application to participate in the migration and interfacial reaction processes of fluorine-containing structural units, thereby achieving a balance between improving lithium leaching rate and defluorination rate.

[0144] To further investigate the effects of the amount of sulfate composite additive and the calcination temperature on the lithium extraction effect, this application also includes the following comparative examples and embodiments.

[0145] The only difference between Comparative Examples 7, 8, and Examples 15 to 20 and Example 1 is that the amount of sulfate composite additive added and the calcination temperature were adjusted according to Table 4.

[0146] Table 4

[0147] Based on the test results in Table 4, it is clear that when the amount of sulfate composite additive added is equal to the total mass of lepidolite concentrate... a %,and a When the concentration is between 25 and 45, both lithium leaching rate and defluorination rate can be improved. However, further increasing the amount of sulfate composite additive does not significantly improve the lithium leaching rate and defluorination rate. Therefore, this application will... a The preferred calcination temperature is 30-40°C, which balances improving lithium leaching and defluorination rates while also considering production costs. A calcination temperature of 800°C-950°C also balances improving lithium leaching and defluorination rates. This application considers that both lithium leaching and defluorination rates decrease when the calcination temperature exceeds 930°C; therefore, the preferred calcination temperature is 850°C-930°C to balance improving lithium leaching and defluorination rates while also considering production costs and energy consumption. Specifically, when... a When the concentration is 35 and the calcination temperature is 900℃, the lithium leaching rate is 97.38% and the defluorination rate is 99.73%, resulting in a superior treatment effect.

[0148] In summary, this application involves mechanically and chemically activating lepidolite concentrate with a sulfate composite additive to form a sulfate co-milling activation reaction interface. The resulting roasting is then carried out under a water-containing atmosphere. During roasting, the water vapor provided by the water-containing atmosphere promotes the migration of fluorine-containing structural units, and the sulfate composite additive promotes lithium solubility. In other words, the lithium extraction method of this application is not a simple process superposition, but rather a synergistic effect between the steps. This couples the mechanical activation reaction interface, the water-containing atmosphere interface reaction, and the sulfate ion exchange at the same roasting temperature, forming a coupling effect of "sulfate co-milling activation interface - atmosphere interface reaction - isothermal ion exchange." This achieves the migration / removal of fluorine and the solubility conversion of lithium in lepidolite, effectively solving the problems of insufficient roasting reaction and insufficient coupling between the defluorination process and the lithium solubility conversion process in existing technologies. This method achieves a balance between improving the lithium leaching rate and the defluorination rate.

[0149] Obviously, the above embodiments of this application are merely examples for clear illustration and are not intended to limit the implementation of this application. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection claimed by this application.

Claims

1. A method for lithium extraction from lepidolite by calcination based on sulfate co-milling activation and atmosphere control, characterized in that, Includes the following steps: Mechanochemical activation treatment: Lithium mica concentrate is mixed with sulfate composite additive to obtain a mixture to be activated; the mixture to be activated is subjected to mechanochemical activation treatment to obtain an activated material; The sulfate composite additive includes at least two of sodium sulfate, potassium sulfate, and calcium sulfate. Calcination treatment: The activated material is calcined under a water-containing atmosphere and a calcination temperature of 800℃~950℃ to obtain the calcined product; The water-containing atmosphere includes water vapor; Leaching treatment: The roasted product is cooled and then refined to obtain roasted product particles; the roasted product particles are subjected to atmospheric pressure water leaching and solid-liquid separation to obtain lithium-rich leachate.

2. The method according to claim 1, characterized in that, The sulfate composite additive meets at least one of the following conditions: (1) The sulfate composite additive includes sodium sulfate, potassium sulfate and calcium sulfate; (2) The sodium sulfate includes Na2SO4; (3) The potassium sulfate includes K2SO4; (4) The calcium sulfate includes CaSO4; (5) The amount of the sulfate composite additive added is equal to the total mass of the lepidolite concentrate. a %,and a Satisfying 25~45.

3. The method according to claim 1 or 2, characterized in that, The sulfate composite additive includes Na2SO4, K2SO4 and CaSO4; Furthermore, in the sulfate composite additive, the mass ratio of Na2SO4, K2SO4 and CaSO4 is (0.8~3):(0.3~2):(1~3).

4. The method according to claim 1, characterized in that, The activated material obtained by the mechanochemical activation treatment has lithium mica particles with a particle size D90 of 80 μm to 130 μm.

5. The method according to claim 1, characterized in that, The mechanochemical activation treatment is carried out using mechanical activation equipment; The mechanical activation equipment includes any one of a ball mill, a vibratory mill, and a stirred mill.

6. The method according to claim 1 or 5, characterized in that, The mechanochemical activation treatment satisfies at least one of the following conditions: (1) The rotational speed is 350 rpm to 650 rpm; (2) The activation time is 0.5 h to 4 h; (3) The mass ratio of ball material is 5:1 to 25:

1.

7. The method according to claim 1, characterized in that, The water-containing atmosphere includes any one of water vapor, air-water vapor mixture, nitrogen-water vapor mixture, and inert gas-water vapor mixture.

8. The method according to claim 1 or 7, characterized in that, The water-containing atmosphere satisfies any one of the following conditions: (1) In the water-containing atmosphere, the amount of water vapor introduced is 0.1~1.0 g / (g·h) based on the dry basis mass of the activated material; (2) In the water-containing atmosphere, the volume fraction of water vapor is 20%~100%.

9. The method according to claim 1, characterized in that, The calcination treatment satisfies at least one of the following conditions: (1) The roasting temperature is 850℃~930℃; (2) The roasting time is 1 h to 2 h.

10. The method according to claim 1, characterized in that, The water immersion temperature under normal pressure is 50℃~90℃, the liquid-to-solid ratio is 5 mL / g~10 mL / g, and the immersion time is 0.5 h~2 h.

11. The method according to claim 1, characterized in that, The method further includes fluorine-containing tail gas treatment: using an absorbent to absorb and treat the fluorine-containing tail gas generated by the calcination process; The absorbent includes one or more of water, alkaline solution, lime milk, sodium hydroxide solution, and calcium hydroxide slurry.

12. The method according to claim 1 or 11, characterized in that, The method further includes post-processing: removing impurities, concentrating and precipitating lithium in the lithium-rich leachate to prepare lithium products.

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