A method for promoting low-temperature calcination of lithium mica bisulfate to extract lithium based on mechanical activation

Abstract

The application provides a method for promoting lithium mica hydrogen sulfate low-temperature calcination lithium extraction based on mechanical activation, comprising the following steps: S1, providing a mixture; the mixture comprises lithium mica and hydrogen sulfate, and the mass percentage of the hydrogen sulfate and the lithium mica is 35-45%; S2, performing mechanical activation treatment on the mixture to obtain a precursor material; the mechanical activation treatment comprises: performing ball milling on the mixture, the ball milling adopts a ball-to-material ratio of 2-6:1, the ball milling rotation speed is 500-800 rpm, and the ball milling time is 1.8-6 h; S3, performing calcination on the precursor material to obtain a calcined material; the calcination temperature is 400-800 DEG C; and S4, sequentially performing water immersion and solid-liquid separation on the calcined material to obtain a lithium-containing leaching solution. The application can realize high-efficiency leaching of lithium in lithium mica under the conditions of low auxiliary material ratio, low calcination temperature and water immersion.

Description

Technical Field

[0001] This invention relates to the field of chemical metallurgy technology, and in particular to a method for lithium extraction by low-temperature roasting of lepidolite bisulfate based on mechanical activation. Background Technology

[0002] With the rapid development of the global new energy industry, the importance of lithium resources is becoming increasingly prominent. Lithium mica, as one of the key raw materials for preparing battery-grade lithium carbonate, has been included in the list of national strategic resources. Currently, lithium extraction processes from lepidolite mainly include several technical routes such as pressure cooking, chlorination, and sulfate roasting. The main process of sulfate roasting includes: first, crushing and flotation of the lepidolite ore to obtain lepidolite concentrate; then, mixing the concentrate with sulfate additives in a specific ratio and roasting at high temperature to release lithium from the lepidolite; the roasted clinker is then dissolved in water through a water leaching process to form a lithium-containing leachate; finally, through a series of purification, concentration, and lithium precipitation steps, battery-grade lithium carbonate is obtained.

[0003] Chinese invention patent application CN118479501A discloses a method for preparing lithium carbonate from lepidolite. The method involves mixing lepidolite, sulfate, calcium hydroxide, sulfur, and water, pressing the mixture into bricks, drying the material, and then calcining it at 870-950℃. After calcination, lithium carbonate is obtained through crushing, leaching, impurity removal, extraction, and lithium precipitation. Although lithium is extracted from lepidolite, the calcination temperature is high, and the sources of the auxiliary materials are complex, introducing other substances such as calcium hydroxide and sulfur. The method does not specify the amount of sulfate used as a single auxiliary material.

[0004] Therefore, it is necessary to provide a method for lithium extraction from lepidolite by promoting low-temperature roasting of lepidolite bisulfate based on mechanical activation, in order to solve or at least alleviate the technical problem of how to achieve efficient lithium leaching from lepidolite under conditions of low auxiliary material ratio, low roasting temperature and water immersion. Summary of the Invention

[0005] The main objective of this invention is to provide a method for lithium extraction from lepidolite bisulfate by promoting low-temperature roasting based on mechanical activation, aiming to solve the technical problem of how to achieve efficient lithium leaching from lepidolite under conditions of low auxiliary material ratio, low roasting temperature and water immersion.

[0006] To achieve the above objectives, the present invention provides a method for lithium extraction by low-temperature roasting of lepidolite bisulfate based on mechanical activation, comprising the following steps:

[0007] S1 provides the mixture;

[0008] The mixture comprises lepidolite and bisulfite, wherein the mass percentage of bisulfite and lepidolite is 35-45%.

[0009] S2, the mixture is mechanically activated to obtain a precursor material;

[0010] The mechanical activation treatment includes: ball milling the mixture, wherein the ball-to-material ratio is 2-6:1, the ball milling speed is 500-800 rpm, and the ball milling time is 1.8-6 hours;

[0011] S3, the precursor material is calcined to obtain calcined clinker; the calcination temperature is 400-800℃, and the calcination time is not less than 30 minutes;

[0012] S4, the roasted clinker is subjected to water immersion and solid-liquid separation in sequence to obtain lithium-containing leachate.

[0013] Furthermore, the lepidolite is lepidolite concentrate; the lepidolite concentrate contains lithium, iron, potassium, sodium, magnesium, and calcium.

[0014] Furthermore, in the lepidolite concentrate, the mass percentage of lithium is 0.9-1.1%, the mass percentage of iron is 2-2.3%, the mass percentage of potassium is 7-7.2%, the mass percentage of sodium is 0.5-0.7%, the mass percentage of magnesium is 0.02-0.04%, and the mass percentage of calcium is 0.1-0.2%.

[0015] Furthermore, the lithium mica concentrate contains lithium iron ore mica.

[0016] Furthermore, the mass percentage of the hydrogen sulfate and the lepidolite is 35-40%.

[0017] Furthermore, the bisulfate includes one or more of sodium bisulfate and potassium bisulfate.

[0018] Furthermore, the ball mill uses a ball-to-material ratio of 4-6:1, the ball mill rotates at 600-700 rpm, and the ball milling time is 1.9-2.1 h.

[0019] Furthermore, the roasting temperature is 600-650℃, and the roasting time is 80-120 minutes.

[0020] Furthermore, the duration of the water immersion is not less than 60 minutes.

[0021] Furthermore, the water immersion process includes: placing the roasted clinker in water and agitating it; the solid-liquid ratio of the roasted clinker to the water is 1g:20-30mL.

[0022] The main principles of this invention include:

[0023] The key to lithium extraction from lepidolite lies in breaking down its structure at high temperatures, followed by a displacement reaction with alkali metals in sulfates, converting insoluble interlayer lithium into soluble lithium for leaching. Mechanical activation treatment increases the specific surface area of ​​lepidolite, providing more active sites for chemical reactions. Through mechanical activation, the crystal lattice structure of lepidolite is disrupted, and collisions and friction introduce strain and thermal effects, injecting additional energy into the crystal structure and causing irregular changes. These changes may induce dislocations and defects in the lepidolite crystal, lowering its activation energy and thus enhancing its chemical activity, allowing its structure to be destroyed at lower temperatures.

[0024] In this invention, the lithium leaching rate is significantly improved through mechanical activation treatment after mixing. First, during ball milling, the mixing between lepidolite and auxiliary materials is more uniform, and some reactants have already formed good contact and undergone preliminary reactions after mixing, thereby enhancing the reactivity of the subsequent roasting process. More importantly, this invention strengthens the destruction of the lithium site structure in lepidolite by mechanically activating it after mixing it with specific auxiliary materials such as sodium bisulfate. Analysis revealed that during the activation process of this invention, lithium in lepidolite migrates from the interlayers of its structure, making lithium exist in the precursor in the form of aluminosilicate. This makes it more susceptible to destruction by bisulfate during the subsequent roasting process, ultimately existing in the form of sodium lithium sulfate. In addition, this invention utilizes the water solubility of lithium sulfate, and efficient lithium extraction can be achieved from the roasted clinker through simple water leaching.

[0025] It should be emphasized that the ball milling in this invention is not merely providing a mixing environment; this invention co-ball mills specific auxiliary materials such as lepidolite and sodium bisulfate, enabling lepidolite and sodium bisulfate to undergo a pre-reaction under ball milling conditions; in conjunction with the embodiments of this invention, after co-ball milling, based on the pre-reaction of lepidolite and sodium bisulfate, a change in intermediate products occurs, promoting the efficient leaching of lithium in lepidolite after calcination at a lower temperature and with fewer auxiliary materials.

[0026] Compared with the prior art, the present invention has at least the following advantages:

[0027] This invention enables efficient lithium leaching from lepidolite under conditions of low auxiliary material ratio, low roasting temperature, and water leaching. Therefore, this invention effectively controls production costs and solves problems such as high roasting temperature, high energy consumption, large slag volume, and excessive impurity leaching in traditional methods. Specifically, this invention is based on a method for efficient lithium extraction from lepidolite bisulfate through low-temperature roasting using mechanical activation. By simply performing mechanical activation treatment on both the bisulfate and lepidolite, the required reaction temperature and auxiliary material usage for roasting can be significantly reduced, resulting in high energy efficiency. This method ensures efficient lithium leaching while reducing energy consumption. Furthermore, this invention uses a simple and easy-to-operate water leaching method, which greatly reduces the risk of impurity element leaching compared to other leaching methods such as acid leaching. Attached Figure Description

[0028] 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. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0029] Figure 1 This is a graph showing the changes in lithium ion leaching rate in the leachate for each experiment in Example 1 of the present invention;

[0030] Figure 2 This is a phase composition diagram of concentrate, activated concentrate, activated precursor after mixing (corresponding to activated after mixing in the figure), activated concentrate after mixing and roasting clinker, and activated roasting clinker after mixing in Example 1 of the present invention.

[0031] Figure 3 This is a graph showing the changes in lithium ion leaching rate in the leachate under different calcination temperatures and conditions where the auxiliary material (sodium bisulfate) accounts for 40% of the total content, and the conditions of mixing before activation (as shown in the figure) and activation before mixing (as shown in the figure).

[0032] Figure 4 This is a graph showing the change in lithium ion leaching rate in the leachate at different calcination temperatures under the condition that the proportion of excipient (sodium bisulfate) is 35% in Example 3 of the present invention.

[0033] Figure 5 This is a comparison chart of lithium ion concentrations in the leachate of lithium mica concentrate and sodium bisulfate additive at different ball milling speeds in Example 4 of the present invention.

[0034] Figure 6 This is a comparison chart of lithium ion concentrations in the leachate of lithium mica concentrate and sodium bisulfate additive at different ball-to-material ratios in Example 5 of the present invention.

[0035] Figure 7 This is a comparison chart of lithium ion concentrations in the leachate of lithium mica concentrate and sodium bisulfate additive at different ball milling times in Example 6 of the present invention.

[0036] Figure 8 This is a comparison chart of lithium leaching rates in the leachates of lepidolite concentrate and different types of sulfates (auxiliaries) after roasting, as shown in Example 7 of the present invention.

[0037] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The embodiments described below are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0040] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of this invention, may be implemented using any prior art methods, devices, and materials similar to or equivalent to those described, used, or made of materials in the embodiments of this invention.

[0041] It should be noted that Chinese invention patent application CN112624161A discloses a method for extracting lithium from lepidolite using mechanical activation to prepare lithium carbonate. The method involves weighing lepidolite concentrate powder and oxalic acid at a mass ratio of 3-6:1, then ball-milling the mixture for 24-48 hours to obtain precursor powder. This precursor powder is then calcined in a rotary kiln at 600-800℃ for 0.5-2 hours to obtain calcined material. A solid-phase reaction is then carried out with concentrated sulfuric acid at a medium-low temperature, followed by water leaching to dissolve the alkali metal sulfate. Different crystallization inducing agents are added to continuously induce crystallization and remove impurities. Finally, the resulting lithium hydroxide solution is reacted with carbon dioxide to prepare battery-grade lithium carbonate. Although this method extracts lithium using a low auxiliary material ratio, ball milling activation, and a relatively low calcination temperature, the activation process is time-consuming. Furthermore, the addition of oxalic acid during activation and the pre-reaction with concentrated sulfuric acid before water leaching completely destroy the lepidolite structure, leading to the leaching of a large amount of other impurities within the mineral phase, significantly increasing the difficulty of subsequent leachate treatment. Therefore, the present invention requires a method for obtaining highly efficient metallic lithium based on a system of bisulfate and water immersion.

[0042] This invention provides a method for lithium extraction from lepidolite bisulfate at low temperature based on mechanical activation, comprising the following steps:

[0043] S1 provides the mixture.

[0044] In this invention, the mixture includes or may be lepidolite and bisulfite, wherein the mass percentage of the bisulfite and the lepidolite is 35-45%, preferably 35-40%, and specifically 39-41%; the bisulfite can be used as an auxiliary material alone, that is, only the bisulfite is mixed with the lepidolite.

[0045] In this invention, the lepidolite is lepidolite concentrate; the lepidolite concentrate is derived from lepidolite ore, and the lepidolite concentrate is obtained after lithium pretreatment of the lepidolite ore, the pretreatment including crushing, impurity removal, drying and other processes.

[0046] In this invention, the lepidolite concentrate contains lithium, iron, potassium, sodium, magnesium, and calcium. The lithium content in the lepidolite concentrate is 0.9-1.1% by mass, the iron content is 2-2.3% by mass, the potassium content is 7-7.2% by mass, the sodium content is 0.5-0.7% by mass, the magnesium content is 0.02-0.04% by mass, and the calcium content is 0.1-0.2% by mass. The lepidolite concentrate also contains aluminum and silicon; the aluminum content is 14-15% by mass, and the silicon content is 22-23% by mass. The lepidolite concentrate also contains thallium and beryllium; the thallium content is 0.001-0.003% by mass, and the beryllium content is 0.01-0.02% by mass.

[0047] In the lepidolite of this invention, the lithium element exists in the form of lithium oxide (Li₂O), the iron element exists in the form of iron oxide (Fe₂O₃), the potassium element exists in the form of potassium oxide (K₂O), the sodium element exists in the form of sodium oxide (Na₂O), the magnesium element exists in the form of magnesium oxide (MgO), the calcium element exists in the form of calcium oxide (CaO), the aluminum element exists in the form of aluminum oxide (aluminum oxide), and the silicon element exists in the form of silicon dioxide. Specifically, the lepidolite concentrate of this invention contains lithium oxide, iron oxide, potassium oxide, sodium oxide, magnesium oxide, and calcium oxide; the remaining components mainly include aluminum oxide and silicon dioxide.

[0048] In this invention, the lithium oxide in the lepidolite concentrate can account for 2-3% by mass, the iron oxide can account for 2-4% by mass, the potassium oxide can account for 8-9% by mass, the sodium oxide can account for 0.5-1% by mass, the magnesium oxide can account for 0.03-0.08% by mass, and the calcium oxide can account for 0.15-0.3% by mass. Furthermore, the aluminum oxide can account for 25-30% by mass, and the silicon dioxide can account for 45-50% by mass. In this invention, the lepidolite concentrate mainly contains lepidolite K(AlFeLi)(Si3Al)O. 10 (OH)F; the lepidolite concentrate has a lamellar structure.

[0049] In this invention, the bisulfate includes or is one or more of sodium bisulfate and potassium bisulfate; as a preferred embodiment, the bisulfate is sodium bisulfate.

[0050] S2, the mixture is mechanically activated to obtain the precursor material.

[0051] The lithium in the precursor material exists primarily in the form of aluminosilicate (mainly in the form of aluminosilicate); the phases of the precursor material include aluminosilicate, with the remaining phases mainly consisting of sodium aluminum silicate and other mica phases; specifically, the precursor material contains KAl3Si3O 10 (0H)2, LiAlSiO4, NaAlSi3O8.

[0052] In this invention, the mechanical activation treatment includes: ball milling (activation) of the mixture, wherein the ball-to-material ratio (mass ratio) used in the ball milling is 2-6:1, preferably 4-6:1 or 5-6:1; the ball milling speed is 500-800 rpm, preferably 600-700 rpm; and the ball milling time is 1.8-6 h or 2-6 h, preferably 1.9-2.1 h or 4.9-5.1 h. Specifically, the ball-to-material ratio can be 5:1, the ball milling speed can be 600 rpm, and the ball milling time can be 2 h.

[0053] S3, the precursor material is roasted to obtain roasted clinker.

[0054] In this invention, the roasting temperature is 400-800℃, and the roasting time is not less than 30 minutes; preferably, the roasting temperature is 500-800℃, 600-800℃, 600-700℃, 600-650℃, or 500-600℃, and the roasting time is not less than 80 minutes or 80-120 minutes. More specifically, the roasting temperature can be 600℃, and the roasting time can be 100 minutes.

[0055] As another illustration of the embodiments of the present invention, for the above-mentioned calcination temperatures and calcination times, the mass percentage of the bisulfite and the lepidolite can also be 35-37% or 40-45%; furthermore, when the mass percentage of the bisulfite and the lepidolite is 35-37%, the calcination temperature can be 700-800℃ or 600-700℃; when the mass percentage of the bisulfite and the lepidolite is 40-45%, the calcination temperature can be 600-620℃ or 600-700℃ or 600-800℃.

[0056] S4, the roasted clinker is subjected to water immersion and solid-liquid separation in sequence to obtain lithium-containing leachate.

[0057] In this invention, the water immersion can be carried out at 20-35°C, specifically at room temperature; the duration of the water immersion is not less than 60 minutes, and can be further 100-150 minutes. The water immersion process includes: placing the roasted clinker in water and shaking it; the solid-liquid ratio of the roasted clinker to the water can be 1g:20-30mL.

[0058] The process of this invention is simple and has less environmental pollution. Through mechanical activation, this invention achieves efficient lithium extraction under low auxiliary material ratio and low temperature roasting conditions, which significantly reduces the roasting temperature and auxiliary material usage of the traditional sulfate roasting method, thereby reducing energy consumption and cost. This invention adopts a simple and easy-to-operate water leaching process, and the resulting lithium-containing leachate has low impurity content and a lithium leaching rate of over 90%, which has broad application prospects in the field of lithium extraction by roasting lepidolite.

[0059] It should be noted that existing studies generally suffer from high roasting temperatures or the need for additional auxiliary conditions such as pressurization or microwaves. Furthermore, some methods employ acid or alkali leaching in the leaching step, which is not only complex but may also lead to the leaching of large amounts of impurities. Therefore, this invention uses bisulfate as an auxiliary material and combines it with mechanical activation technology to treat the mixture. Under conditions of low auxiliary material ratio and low-temperature roasting, combined with a water leaching process, efficient lithium leaching is achieved. This invention effectively controls production costs and solves the problems of high energy consumption, high roasting temperatures leading to sintering, large slag volume, and excessive impurity leaching in traditional methods.

[0060] The following are specific examples of the present invention:

[0061] Example 1

[0062] This embodiment is a comparative analysis of the activation methods of lithium mica concentrate and sodium bisulfate mixture. The specific implementation process is as follows:

[0063] Alone roasting of concentrate (Experiment 1): Lithium mica concentrate was roasted to obtain roasted clinker; the roasted clinker was leached in water, and after solid-liquid separation, leachate and leachate residue were obtained.

[0064] Alone roasting of activated concentrate (Experiment 2): The lepidolite concentrate was ball-milled to obtain the ball-milled product; the ball-milled product was roasted to obtain roasted clinker; the roasted clinker was leached in water, and after solid-liquid separation, leachate and leachate residue were obtained.

[0065] Concentrate roasting (Experiment 3): Lithium mica concentrate and sodium bisulfate (auxiliary material) are mixed to obtain a mixture; the mixture is roasted to obtain roasted clinker; the roasted clinker is leached in water, and after solid-liquid separation, leachate and leachate residue are obtained.

[0066] Activated concentrate followed by roasting (Experiment 4): Lithium mica concentrate was ball-milled to obtain ball-milled product; the ball-milled product was mixed with sodium bisulfate (auxiliary material) and then roasted to obtain roasted clinker; the roasted clinker was leached in water, and after solid-liquid separation, leachate and leachate residue were obtained.

[0067] Activation and roasting after mixing (Experiment 5): Lithium mica concentrate and sodium bisulfate (auxiliary material) are mixed to obtain a mixture; the mixture is ball-milled to obtain a precursor material; the precursor material is roasted to obtain roasted clinker; the roasted clinker is leached in water, and after solid-liquid separation, leachate and leachate residue are obtained.

[0068] The specific conditions in each of the above experiments are as follows:

[0069] When sodium bisulfate is involved, the mass of sodium bisulfate is 40% of that of lepidolite concentrate;

[0070] When ball milling is involved, the ball milling process is completed in a planetary ball mill with a ball-to-material ratio of 6:1, a ball milling speed of 500 rpm, and a ball milling time of 120 min.

[0071] When calcination is involved, the calcination process is as follows: the material to be calcined is placed in a quartz crucible and then placed in a muffle furnace. The calcination temperature of the muffle furnace is set to a constant 600℃ and the holding time is 100min. After calcination, the material is removed when the temperature has cooled to room temperature.

[0072] When water immersion and solid-liquid separation are involved, the process of water immersion and solid-liquid separation is as follows: at room temperature, the roasted clinker is poured into an Erlenmeyer flask, pure water is added, the solid-liquid ratio of roasted clinker to pure water is 1g:25mL, after sealing, it is placed in a constant temperature shaking box (25℃) for shaking, and taken out after shaking for 120min; and filtered through a Buchner funnel.

[0073] The lepidolite concentrate used in this embodiment has a lamellar structure; the contents of some elements in the lepidolite concentrate are shown in Table 1, and the contents of some components are shown in Table 2.

[0074] Table 1. Elemental analysis of lepidolite concentrate (mass percentage)

[0075] content 1.05 14.77 2.16 22.58 7.09 0.58 0.03 0.16 0.002 0.0177

[0076] Table 2. Compositional analysis of lepidolite concentrate (mass percentage %)

[0077] content 27.9 48.3 0.05 0.22 0.78 8.54 3.09 2.27

[0078] This embodiment analyzes the lithium ion leaching rate in the leachate corresponding to each of the above experiments using ICP-OES. Specific results are as follows: Figure 1 As shown.

[0079] analyze Figure 1 The results show that the lithium leaching rate in lepidolite concentrate increased from 1.85% (Experiment 1: concentrate roasted alone) to 2.19% (Experiment 2: activated concentrate roasted alone), indicating that mechanical activation disrupted the structure of the concentrate, thereby promoting the roasting reaction process. However, this increase was relatively limited, suggesting that the advantages brought by activation were not fully realized under the condition of roasting alone. Under the condition of low sodium bisulfate dosage (40%), ball milling activation significantly improved the lithium leaching rate, increasing from 32.01% (Experiment 3: concentrate mixed roasting) to 49.14% (Experiment 4: activated concentrate followed by mixed roasting) and 90.57% (Experiment 5: mixed roasting followed by activation), with the method of mixing first and then activating showing the highest lithium leaching rate.

[0080] XRD analysis was performed on the concentrate (lepidolite concentrate), activated concentrate (ball milling product in Experiment 4), activated precursor after mixing (precursor material in Experiment 5), activated concentrate mixed and roasted clinker (roasted clinker in Experiment 4), and activated roasted clinker after mixing (roasted clinker in Experiment 5). The results are as follows: Figure 2 As shown.

[0081] Analysis revealed that the concentrate had a relatively simple phase composition, mainly composed of lepidolite. After activating the concentrate alone, the phase composition did not change significantly, remaining predominantly lepidolite, but the characteristic peak intensity decreased, and the corresponding θ angle shifted to the left, indicating that the activation process had some, but not significant, impact on the stability of the lepidolite structure. Phase analysis of the precursor obtained after activation with mixed materials showed a significant change in phase composition compared to the concentrate. The lepidolite phase essentially disappeared, and lithium mainly existed in the form of aluminosilicates, with the remaining phases being mainly sodium aluminum silicate and other mica phases. Mechanical activation after mixing significantly enhanced the activation effect on lepidolite. The addition of sodium bisulfate further disrupted lithium sites in the lepidolite, promoting interlayer lithium migration and ensuring that lithium remained stably in the precursor in the form of aluminosilicates, thus facilitating reaction with sulfates during subsequent roasting. Analysis of the two types of roasted clinker showed that lithium mainly existed in the form of sodium lithium sulfate, with no significant difference observed.

[0082] Impurity element analysis was performed on the leachate of the activated roasted clinker after mixing (corresponding to Experiment 5), and the results are shown in Table 3. The table shows that the leaching rates of all impurity elements are at a low level, with the leaching rates of the toxic elements thallium and beryllium both around 1%, which is extremely ideal.

[0083] Table 3. Leaching rate of impurity elements

[0084] Leaching rate (%) 0.0026 0.0291 0.0135 19.53 27.63 1.2 1.4

[0085] Example 2

[0086] This embodiment compares the lithium leaching results at different calcination temperatures under two methods: activation before mixing and mixing before activation, with an auxiliary material ratio of 40%. The specific implementation process is as follows:

[0087] The pre-activation and post-mixing experiment in this embodiment differs from Experiment 4 in Example 1 only in the calcination temperature; all other conditions remain the same.

[0088] The pre-mixing and post-activation experiment in this embodiment differs from Experiment 5 in Example 1 only in the calcination temperature; all other conditions remain the same.

[0089] In this embodiment, the experiments of activation before mixing and mixing before activation were carried out at calcination temperatures of 400℃, 500℃, 600℃, 700℃, and 800℃ respectively.

[0090] This embodiment analyzes the lithium ion leaching rate in the leachate corresponding to the pre-activation-then-mixing experiment and the pre-mixing-then-activation experiment using ICP-OES. Specific results are as follows: Figure 3 As shown.

[0091] analyze Figure 3The results show that the lithium leaching rate gradually increases with increasing calcination temperature, indicating that higher temperatures promote the reaction and ensure complete reaction of the reactants. Notably, at 800℃, the lithium leaching rate exceeded 90% in both methods, demonstrating that temperature is a key factor influencing the transformation of interlayer lithium into soluble lithium due to the disruption of the lepidolite structure. However, when the method of mixing before activation was chosen, the lithium leaching rate reached approximately 90% at a lower temperature (600℃), while activation followed by mixing required a higher temperature (800℃) to achieve a similar effect.

[0092] Example 3

[0093] This embodiment compares the lithium leaching at different calcination temperatures under activation conditions after mixing, with an auxiliary material ratio of 35%. The specific implementation process is as follows:

[0094] In this embodiment, compared to Experiment 5 in Example 1, only the proportion of sodium bisulfate and the calcination temperature were changed, while other conditions remained unchanged.

[0095] In this embodiment, the mass of sodium bisulfate is 35% of that of lepidolite concentrate; and this embodiment is carried out at roasting temperatures of 400°C, 500°C, 600°C, 700°C, and 800°C respectively.

[0096] This embodiment analyzes the lithium ion leaching rate in the leachate using ICP-OES, and the specific results are as follows: Figure 4 As shown.

[0097] analyze Figure 4 The results show that when the calcination temperature is between 400-500℃, the lithium leaching rate does not exceed 50%, which is at a low level. When the calcination temperature is between 600-800℃, the lithium leaching rate increases significantly, reaching 84.5% at 600℃ and 88.03% at 700℃; when the calcination temperature is 800℃, the lithium leaching rate exceeds 90%, reaching 92.03%.

[0098] Example 4

[0099] This embodiment compares the lithium leaching rate of lepidolite and sodium bisulfate additives at different ball milling speeds. The specific implementation process is as follows:

[0100] In this embodiment, compared to Experiment 5 in Example 1, only the proportion of sodium bisulfate and the ball milling speed were changed, while other conditions remained unchanged.

[0101] In this embodiment, the mass of sodium bisulfate is 35% of that of lepidolite concentrate; and this embodiment is carried out at ball milling speeds of 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, and 800 rpm respectively.

[0102] This embodiment analyzes the lithium ion leaching rate in the leachate using ICP-OES, and the specific results are as follows: Figure 5 As shown.

[0103] analyze Figure 5 The results show that the treatment effect is poor at low frequencies (300 rpm), possibly due to insufficient mechanical energy, which fails to fully break the crystal structure of lepidolite, resulting in insufficient contact area and uniformity between sodium bisulfate and lepidolite. Consequently, the activated precursor exhibits low reactivity. In the mid-frequency range (400-600 rpm), the treatment effect significantly improves with increasing frequency, indicating that the mechanical activation intensity at this frequency effectively enhances the reactivity of the precursor. At 600-700 rpm, the lithium leaching rate reaches the ideal value, exceeding 90%. However, when the ball mill speed is further increased to 800 rpm, the lithium leaching rate decreases, indicating that further increasing the ball mill speed has limited effect. Furthermore, under high-frequency conditions, other factors (such as excessive wear or overheating) may limit the lithium leaching effect.

[0104] Example 5

[0105] This embodiment compares the lithium leaching rate of lepidolite and sodium bisulfate additives under different ball-to-material ratios. The specific implementation process is as follows:

[0106] In this embodiment, compared to Experiment 5 in Example 1, only the proportion of sodium bisulfate, the ball milling speed, and the ball-to-material ratio were changed, while other conditions remained unchanged.

[0107] In this embodiment, the mass of sodium bisulfate is 35% of that of lepidolite concentrate, and the ball mill speed is 600 rpm; furthermore, this embodiment is implemented at ball-to-material ratios of 6:1, 5:1, 4:1, 3:1, 2:1, 1:1, and 1:2.

[0108] This embodiment analyzes the lithium ion leaching rate in the leachate using ICP-OES, and the specific results are as follows: Figure 6 As shown.

[0109] analyze Figure 6 The results show the change in lithium leaching rate as the ball-to-material ratio increases from 1:2 to 6:1. The leaching rate shows an upward trend, reaching a maximum of 94.91% when the ball-to-material ratio is 5:1, and slightly decreasing to 90.21% when the ball-to-material ratio is 6:1.

[0110] Low ball-to-material ratio (1:2, 1:1): The leaching rate is low at low ball-to-material ratios, at 36.49% and 41.89% respectively. This may be because the grinding effect is insufficient at low ball-to-material ratios, resulting in poor mechanical activation and thus affecting the reaction. Medium ball-to-material ratio (2:1, 3:1, 4:1): The leaching rate increases significantly with increasing ball-to-material ratio (68.7%, 84.55%, and 88.87% respectively).

[0111] When the ball-to-material ratio is 5:1, the lithium leaching rate is the highest at 94.91%. The increase in the number of grinding media further enhances the activation of the concentrate. As the ball-to-material ratio further increases to 6:1, the leaching rate decreases slightly to 90.21%. This may be because excessive grinding leads to overly fine particles, which in turn causes reactant accumulation, local overheating, or a reduction in the reaction surface, resulting in a lower leaching rate.

[0112] Example 6

[0113] This embodiment compares the lithium leaching rate of lepidolite and sodium bisulfate additives at different activation times. The specific implementation process is as follows:

[0114] In this embodiment, compared to Experiment 5 in Example 1, only the proportion of sodium bisulfate, the ball milling speed, and the ball milling time were changed, while other conditions remained unchanged.

[0115] In this embodiment, the mass of sodium bisulfate is 35% of that of lepidolite concentrate, and the ball milling speed is 600 rpm; furthermore, this embodiment is implemented at ball milling times of 1 h, 2 h, 3 h, 4 h, 5 h, and 6 h.

[0116] This embodiment analyzes the lithium ion leaching rate in the leachate using ICP-OES, and the specific results are as follows: Figure 7 As shown.

[0117] analyze Figure 7 The results show that the effect is not obvious under short-term (1 hour) activation conditions, possibly due to insufficient activation time, resulting in inadequate contact and reaction time between sodium bisulfate and lepidolite. With the activation time extended to 2 hours, the reaction effect significantly improved, indicating that appropriately extending the activation time enhances the transfer of mechanical energy, thereby effectively improving the reaction activity. However, after 2 hours (2-6 hours), the experimental effect tends to plateau, the growth trend slows down, and it tends to reach equilibrium.

[0118] Example 7

[0119] This embodiment compares the lithium leaching rate of mixtures of lepidolite and different sulfates at a calcination temperature of 500 degrees Celsius after calcination. The specific implementation process is as follows:

[0120] The auxiliary materials and lepidolite concentrate (same as in Example 1) were mixed at a mass ratio of 2:1 to obtain a mixture. The mixture was placed in a quartz crucible and then placed in a muffle furnace. The muffle furnace was set to a constant roasting temperature of 500°C and held for 100 minutes. After roasting, the mixture was removed when the temperature cooled to room temperature to obtain roasted clinker. The roasted clinker was poured into a conical flask, pure water was added, and the solid-liquid ratio of roasted clinker to pure water was 1 g: 25 mL. After sealing, the flask was placed in a constant temperature shaking box (25°C) and shaken for 60 minutes. After shaking, the flask was removed and filtered through a Buchner funnel to obtain a lithium-containing leachate.

[0121] This embodiment was carried out under the condition that the excipients were sodium sulfate, ammonium sulfate, ammonium bisulfate, sodium bisulfate, calcium bisulfate, and potassium bisulfate.

[0122] This embodiment analyzes the lithium ion leaching rate in the leachate using ICP-OES, and the specific results are as follows: Figure 8 As shown.

[0123] analyze Figure 8 The results show that different types of sulfates have a significant impact on the lithium leaching rate. When calcined at 500℃, the ammonium bisulfate system has the lowest leaching rate, approximately 12.34%; the sodium sulfate system has a lithium leaching rate of 13.56%; the ammonium sulfate system shows a slight increase, with a lithium leaching rate of 26.37%; the calcium bisulfate system has a leaching rate of 37.08%; while the sodium bisulfate and potassium bisulfate systems have lithium leaching rates of 72.96% and 72.71%, respectively.

[0124] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for lithium extraction from lepidolite bisulfate by low-temperature roasting based on mechanical activation, characterized in that, Including the following steps: S1, providing a mixture; the mixture is lepidolite and hydrogen sulfate; the lepidolite is lepidolite concentrate, and the main phase contained in the lepidolite concentrate is lithium iron mica; The mass percentage of the hydrogen sulfate and the lepidolite is 39-41%; the hydrogen sulfate is used alone as an excipient, and the hydrogen sulfate is sodium bisulfate. S2, the mixture is mechanically activated to obtain a precursor material; the precursor material contains KAl3Si3O 10 (OH)2, LiAlSiO4, NaAlSi3O8; The mechanical activation treatment is as follows: the mixture is ball-milled at a ball-to-material ratio of 5-6:1, at a speed of 600-700 rpm, and for a time of 1.9-2.1 h. S3, the precursor material is calcined to obtain calcined clinker; The roasting temperature is 600-650℃, and the roasting time is 80-120min; S4, the roasted clinker is subjected to water immersion and solid-liquid separation in sequence to obtain a lithium-containing leachate; the water immersion is carried out at room temperature.

2. The lithium extraction method according to claim 1, characterized in that, The lepidolite concentrate contains lithium, iron, potassium, sodium, magnesium, and calcium.

3. The lithium extraction method according to claim 2, characterized in that, In the lepidolite concentrate, the mass percentage of lithium is 0.9-1.1%, the mass percentage of iron is 2-2.3%, the mass percentage of potassium is 7-7.2%, the mass percentage of sodium is 0.5-0.7%, the mass percentage of magnesium is 0.02-0.04%, and the mass percentage of calcium is 0.1-0.2%.

4. The lithium extraction method according to claim 1, characterized in that, The duration of the immersion in water shall not be less than 60 minutes.

5. The lithium extraction method according to any one of claims 1-4, characterized in that, The water immersion process includes: placing the roasted clinker in water and shaking it; the solid-liquid ratio of the roasted clinker to the water is 1g:20-30mL.

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