A method for extracting lithium from lepidolite

Abstract

This invention provides a method for lithium extraction from lepidolite, comprising the following steps: S1, mixing lepidolite ore with ferrous sulfate heptahydrate and sodium bisulfate, followed by mechanical activation to obtain a pretreated mixture; the mass ratio of lepidolite ore, ferrous sulfate heptahydrate, and sodium bisulfate is 1:0.07-0.5:0.07-0.5; S2, calcining the pretreated mixture to obtain clinker; the calcination temperature is 700-900℃; S3, sequentially subjecting the clinker to water leaching and solid-liquid separation to obtain a lithium leachate. This invention can increase the lithium extraction efficiency from lepidolite to over 98% at a relatively low calcination temperature.

Description

Technical Field

[0001] This invention relates to the field of lithium ore, and more particularly to a method for extracting lithium from lepidolite. Background Technology

[0002] As lepidolite plays an increasingly important role in China's lithium resource supply, the problems in its lithium extraction process are becoming more and more prominent. The complex structure and low lithium grade of lepidolite make lithium extraction difficult. Although lithium extraction technology from lepidolite has made continuous progress in recent years, existing processes still suffer from high energy consumption, heavy pollution, low recovery rates, and large amounts of slag, hindering the large-scale development of lithium resources. Therefore, developing lithium extraction technologies with low energy consumption, low auxiliary material usage, and high recovery rates is particularly important.

[0003] Chinese invention patent application CN119410912A discloses a method for lithium extraction from lepidolite by low-temperature roasting with bisulfate based on mechanical activation. The method includes: mechanically activating lepidolite and an auxiliary material (bisulfate) to obtain a precursor material; roasting the precursor material to obtain roasted clinker at a temperature of 400-800℃; and finally, sequentially subjecting the roasted clinker to water leaching and solid-liquid separation to obtain a lithium leachate. Compared to the traditional sulfate method for lithium extraction, although the above patent application achieves efficient lithium leaching from lepidolite under conditions of low auxiliary material ratio, low roasting temperature, and water leaching, even a 1% improvement in extraction rate is significant in the field of lithium extraction. The lithium extraction efficiency of the above patent application does not reach over 98%, indicating room for optimization and requiring further improvement in the lithium extraction efficiency of lepidolite.

[0004] Therefore, it is necessary to provide a method for lithium extraction from lepidolite to solve the technical problem of how to improve the lithium extraction efficiency of lepidolite to over 98%. Summary of the Invention

[0005] The main objective of this invention is to provide a method for lithium extraction from lepidolite, aiming to solve the aforementioned technical problem of how to improve the lithium extraction efficiency from lepidolite to over 98%.

[0006] To achieve the above objectives, the present invention provides a method for lithium extraction from lepidolite, comprising the following steps: S1, after mixing lithium mica ore with ferrous sulfate and sodium bisulfate, mechanical activation is performed to obtain a pretreated mixture; The mass ratio of the lithium mica ore, the ferrous sulfate, and the sodium bisulfate is 1:0.07-0.5:0.07-0.5; S2, the pretreated mixture is roasted to obtain clinker; the roasting temperature is 700-900℃. S3, the clinker is subjected to water immersion and solid-liquid separation in sequence to obtain lithium leachate.

[0007] Furthermore, the lithium leaching solution and the lithium mica ore have a lithium element mass percentage of 98-99%.

[0008] Furthermore, the calcination temperature is 750-850℃.

[0009] Furthermore, the ferrous sulfate is ferrous sulfate heptahydrate; the mass ratio of the lepidolite ore, the ferrous sulfate heptahydrate, and the sodium bisulfate is 1:0.2-0.25:0.28-0.32.

[0010] Furthermore, the mechanical activation method includes ball milling; the ball milling speed is 400-600 rpm, the ball milling time is 1-3 hours, and the ball-to-material ratio is 2-4:1.

[0011] Furthermore, the particle size of the pretreated mixture is no larger than the aperture of a 100-mesh sieve.

[0012] Furthermore, the holding time for the calcination treatment is 80-160 minutes.

[0013] Furthermore, the liquid-to-solid ratio used in the water immersion is 10-50 mL: 1 g; the immersion time is 1-3 h; the immersion temperature is 20-80 °C; the immersion is carried out under shaking conditions; and the shaking frequency is 100-300 rpm.

[0014] Furthermore, the solid-liquid separation method includes vacuum filtration.

[0015] Furthermore, the mass percentage of Li2O in the lithium mica ore is 2-3%.

[0016] Compared with the prior art, the present invention has at least the following advantages: Compared to the traditional sulfate method for lithium extraction, this invention can improve the lithium extraction efficiency of lepidolite to over 98% at a relatively low roasting temperature and a relatively low proportion of auxiliary materials. Furthermore, this invention can achieve near-complete lithium extraction through only mechanical activation, roasting treatment, and water immersion. The extraction process is simple, efficient, and easy to promote industrially.

[0017] Specifically, compared to the traditional sulfate method for lithium extraction, this invention not only reduces the roasting temperature and the amount of auxiliary materials used, but also significantly improves lithium extraction efficiency. Furthermore, at specific roasting temperatures and with specific auxiliary material ratios, compared to the lithium extraction efficiencies achieved by using sodium bisulfate alone or ferrous sulfate heptahydrate alone, this invention, by using sodium bisulfate and ferrous sulfate heptahydrate in combination, achieves a significant increase in lithium extraction rate under the same auxiliary material amounts and extraction conditions, producing an unexpected synergistic effect. Attached Figure Description

[0018] 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.

[0019] Figure 1 This is a schematic diagram of the lithium extraction process from lepidolite in this invention; Figure 2 XRD analysis of lepidolite concentrate in Example 1 of this invention, and clinker after roasting in Experiments 1, 3 and 4; In the figure, concentrate refers to lepidolite concentrate, sodium bisulfate and ferrous sulfate composite roasting refers to clinker after roasting in Experiment 1, sodium bisulfate roasting refers to clinker after roasting in Experiment 3, and ferrous sulfate heptahydrate roasting refers to clinker after roasting in Experiment 4. Figure 3 The following is a SEM analysis of the clinker after roasting treatment in Experiments 1, 3, and 4 of Example 1 of this invention. In the figure, ferrous sulfate and sodium bisulfate composite roasting refers to the clinker after roasting treatment in Experiment 1, sodium bisulfate roasting refers to the clinker after roasting treatment in Experiment 3, and ferrous sulfate roasting refers to the clinker after roasting treatment in Experiment 4.

[0020] 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

[0021] 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.

[0022] 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.

[0023] 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.

[0024] See Figure 1 To understand this, the present invention provides a method for extracting lithium from lepidolite, comprising the following steps: S1, after uniformly mixing lepidolite ore (lepidolite ore sample), ferrous sulfate (ferrous sulfate heptahydrate), and sodium bisulfate, mechanically activate the mixture to obtain a pretreated mixture.

[0025] The lepidolite ore of the present invention is lepidolite concentrate, and further, it is dried lepidolite concentrate; in the lepidolite ore, the mass percentage of Li2O is 2-3%.

[0026] In this invention, the mass ratio of the lepidolite ore, the ferrous sulfate heptahydrate, and the sodium bisulfate is 1:0.07-0.5:0.07-0.5; further, the mass ratio of the lepidolite ore, the ferrous sulfate heptahydrate, and the sodium bisulfate is 1:0.2-0.25:0.28-0.32; further, the mass ratio of the lepidolite ore, the ferrous sulfate heptahydrate, and the sodium bisulfate is 1:0.22-0.24:0.29-0.31.

[0027] In this invention, the mechanical activation method includes ball milling; the rotation speed of the ball mill is 400-600 rpm, further 500-600 rpm; the ball milling time is 1-3 hours; the ball-to-material ratio of the ball mill is 2-4:1, further 3-4:1; in this invention, when performing the ball milling, the forward and reverse rotation times are the same, and the interval between forward and reverse rotation is 4-6 minutes.

[0028] In this invention, the mechanically activated material is then sieved to a mesh size of 100 to ensure that the particle size of the pretreated mixture is not larger than the aperture of the 100-mesh sieve.

[0029] S2, the pretreated mixture is roasted to obtain cooked material.

[0030] In this invention, the calcination temperature is 700-900℃; further, the calcination temperature is 750-850℃; further, the calcination temperature is 780-820℃.

[0031] In this invention, the heating rate of the calcination treatment is 5-15℃ / min, further 8-12℃ / min, and the heating rate is the rate at which the temperature is raised to the holding temperature. In the example of this invention, the heating rate is 10℃ / min.

[0032] In this invention, the holding time for the calcination treatment is 80-160 min, more specifically 100-150 min. Furthermore, the calcination treatment is carried out in a sealed environment.

[0033] In this invention, since an oxidation-reduction reaction occurs during the roasting process, the roasting treatment can also be called reduction roasting.

[0034] S3, the clinker is subjected to water immersion and solid-liquid separation in sequence to obtain lithium leachate.

[0035] In this invention, the liquid-to-solid ratio used in the water immersion is 10-50 mL:1 g, more specifically 18-22 mL:1 g; the immersion time is 1-3 hours; the immersion temperature is 20-80°C, more specifically 55-65°C; the immersion is carried out under agitation conditions; and the agitation frequency is 100-300 rpm. The water immersion process includes: placing the clinker in water and agitating it, while using the aforementioned immersion conditions.

[0036] In this invention, the solid-liquid separation method includes filtration; through the solid-liquid separation, leaching residue and lithium leaching solution are obtained. In this invention, the mass percentage of lithium element in the lithium leaching solution and the lepidolite ore is 98-99%, 98.12-98.76%, 98-98.2%, or 98.5-98.8%.

[0037] In this invention, the mass percentage of lithium in the lithium leaching solution and the lepidolite ore refers to the mass percentage of lithium in the total lithium in the lithium leaching solution, where the mass of the total lithium is the mass of lithium in the lepidolite ore.

[0038] The following are specific examples of the present invention: Analysis example 1 Experiment 1: Lithium extraction from lepidolite was carried out using ferrous sulfate heptahydrate and sodium bisulfate as excipients, with the following steps: The dried lepidolite concentrate contained 2.59 wt% Li2O.

[0039] Mixing and ball milling: The dried lepidolite concentrate, ferrous sulfate heptahydrate, and sodium bisulfate are mixed evenly in a mass ratio of 13:3:4. The mixture is then pulverized and mixed in a ball mill and passed through a 100-mesh sieve to obtain a pretreated mixture. Ferrous sulfate heptahydrate and sodium bisulfate are auxiliary materials. The ball milling speed is 600 rpm, the ball-to-material ratio is 4:1, the ball milling time is 2 hours, with 1 hour for forward rotation and 1 hour for reverse rotation, and an interval of 5 minutes.

[0040] Calcination treatment: The pretreated mixture is placed in a crucible and sealed. Then the crucible is placed in a muffle furnace and calcined at 800°C for 2 hours. After cooling, the crucible is removed to obtain the clinker.

[0041] Water immersion: After the crucible is cooled to room temperature, the calcined material is placed in an Erlenmeyer flask, and water is added at a liquid-to-solid ratio of 20 mL: 1 g. The mixture is then immersed for 2 hours at a constant temperature of 60 °C and a shaking frequency of 300 rpm using a constant temperature water bath shaker.

[0042] Separation: Solid-liquid separation is performed by vacuum filtration to obtain lithium leaching solution and leaching residue.

[0043] Experiment 2: Experiment 2 in this analysis example is lithium extraction using the sodium sulfate method.

[0044] Compared to Experiment 1, in Experiment 2 of this analytical example, ferrous sulfate heptahydrate and sodium bisulfate were changed to sodium sulfate (i.e., the auxiliary material was only sodium sulfate), the mass ratio of lepidolite concentrate to sodium sulfate was 1:2, and the roasting temperature was adjusted to 1000℃, while other conditions remained unchanged.

[0045] Experiment 3: Compared to Experiment 1, in Experiment 3 of this analysis example, ferrous sulfate heptahydrate and sodium bisulfate were changed to sodium bisulfate (i.e., the auxiliary material was only sodium bisulfate), the mass ratio of lepidolite concentrate to sodium bisulfate was 13:7, and other conditions remained unchanged.

[0046] Experiment 4: Compared to Experiment 1, in Experiment 4 of this analytical example, ferrous sulfate heptahydrate and sodium bisulfate were changed to ferrous sulfate heptahydrate (i.e., the auxiliary material was only ferrous sulfate heptahydrate), the mass ratio of lepidolite concentrate to ferrous sulfate heptahydrate was 13:7, and other conditions remained unchanged.

[0047] Experimental Analysis: As shown in Table 1, in Experiment 1 of this analytical example, the lithium leaching rate reached 98.12%, demonstrating a highly efficient lithium recovery rate; while in Experiment 2, the lithium leaching rate using the sodium sulfate method was only 90.4%. Compared to Experiment 2, Experiment 1 of this analytical example had a lower proportion of auxiliary materials and a lower calcination temperature during the processing, reducing costs, saving energy, and decreasing the amount of slag produced. Furthermore, in the sodium sulfate method, sodium sulfate undergoes sintering at high temperatures, and the resulting sodium silicate glass phase encapsulates soluble lithium, reducing the lithium leaching rate. Simultaneously, the high temperature and high auxiliary material usage put pressure on costs and the environment.

[0048] In this analysis, experiments 3 and 4 used sodium bisulfate and ferrous sulfate heptahydrate as auxiliary materials separately. Compared with experiments 3 and 4, experiment 1 showed better performance in lithium leaching rate under the same auxiliary material ratio and calcination temperature, demonstrating the advantages of combined lithium extraction using sodium bisulfate and ferrous sulfate heptahydrate.

[0049] In summary, Experiment 1 achieved a lower temperature, lower auxiliary material usage, and higher lithium leaching rate through compound sulfate roasting lithium extraction technology. In this invention, the lithium leaching rate is defined as the mass percentage of lithium in the lithium leachate and the total lithium, where the mass of the total lithium is the mass of lithium in the lepidolite concentrate used.

[0050] Table 1. Lithium extraction analysis in Experiments 1-4 To further demonstrate the advantages of synergistic lithium extraction using ferrous sulfate heptahydrate and sodium bisulfate, XRD analysis was performed on the phase composition of lepidolite concentrate and the phase composition of the clinker after roasting in Experiments 1, 3, and 4. The results are as follows: Figure 2 As shown.

[0051] See Figure 2 As shown, the addition of sulfate disrupts the structure of lepidolite, causing the lepidolite phase to disappear and replaced by muscovite lacking Li and Fe, with the appearance of soluble lithium phases such as lithium sulfate. This indicates that the presence of sulfate disrupts the structure of lepidolite, causing interlayer lithium to be converted into soluble lithium.

[0052] Comparing different roasting methods reveals that in the combined roasting of ferrous sulfate heptahydrate and sodium bisulfate, the Al and Si element signals are significantly enhanced, indicating that more Al and Si are released from the interlayer, and the destruction of the lepidolite structure is more significant. In the combined roasting of ferrous sulfate heptahydrate and sodium bisulfate, the lithium sulfate phase peak intensity is higher, indicating that Li is released more thoroughly, the lepidolite structure is destroyed more completely, and it is more conducive to the migration of Li element in the water immersion section.

[0053] To fully demonstrate the advantages of synergistic lithium extraction using ferrous sulfate heptahydrate and sodium bisulfate, the microstructure changes of the clinker after roasting in Experiments 1, 3, and 4 were analyzed by SEM. The results are as follows: Figure 3 As shown.

[0054] See Figure 3 As shown, the surface of the calcined lepidolite particles exhibits obvious corrosion. Many fine filaments become denser and more numerous, the smooth surface becomes uneven, and the lepidolite crystal form becomes blurred or disappears.

[0055] After calcination of ferrous sulfate heptahydrate and sodium bisulfate, the structure of the lithium mica crystal structure was more severely collapsed and peeled off, and the particles exhibited high porosity and a looser needle-like aggregate morphology. This indicates that the calcination method of ferrous sulfate heptahydrate and sodium bisulfate significantly enhances the degree of damage to the lithium mica crystal structure during the calcination process. It also confirms that the lithium extraction by combining ferrous sulfate heptahydrate and sodium bisulfate is more advantageous than lithium extraction by single sulfate.

[0056] Analysis example 2 Experiment 5: Experiment 5 in this analysis example is the same as Experiment 1 in Analysis Example 1.

[0057] Experiment 6: Compared to Experiment 5, in Experiment 6 of this analysis example, ferrous sulfate heptahydrate was changed to ferric sulfate, while other conditions remained unchanged.

[0058] Experiment 7: Compared to Experiment 5, in Experiment 7 of this analysis example, ferrous sulfate heptahydrate was changed to ferric oxide, while other conditions remained unchanged.

[0059] Experimental Analysis: As shown in Table 2, it can be seen that Experiment 5 in this analysis example has a higher lithium leaching rate than Experiments 6 and 7, indicating that the combined roasting method of sodium bisulfate and ferrous sulfate heptahydrate is better than the combined roasting method of sodium bisulfate and ferric sulfate, and also better than the combined roasting method of sodium bisulfate and ferric oxide.

[0060] It is worth noting that Experiment 6 in this analysis example has a better lithium leaching rate than Experiment 3 in Analysis Example 1, that is, it is better than sodium bisulfate alone as an auxiliary material during calcination. This indicates that the presence of ferric sulfate in Experiment 6 still promotes the destruction of the lepidolite structure, releasing more interlayer lithium and converting it into soluble lithium. However, the lithium leaching rate in Experiment 7 of this analysis example shows that ferric oxide actually affects the extraction of lithium.

[0061] Table 2. Lithium extraction analysis in Experiments 5-7 Analysis example 3 Experiment 8: Experiment 8 in this analysis example is the same as Experiment 1 in Analysis Example 1.

[0062] Experiment 9: Compared to Experiment 8, in Experiment 9 of this analysis example, ferrous sulfate heptahydrate was replaced with calcium sulfate, while other conditions remained unchanged.

[0063] Experiment 10: Compared to Experiment 8, in Experiment 10 of this analysis example, ferrous sulfate heptahydrate was replaced with potassium bisulfate, while other conditions remained unchanged.

[0064] Experiment 11: Compared to Experiment 8, in Experiment 11 of this analysis example, ferrous sulfate heptahydrate was replaced with magnesium sulfate, while other conditions remained unchanged.

[0065] Experiment 12: Compared to Experiment 8, in Experiment 12 of this analysis example, ferrous sulfate heptahydrate was replaced with potassium sulfate, while other conditions remained unchanged.

[0066] Experimental Analysis: As shown in Table 3, it can be seen that the effects of sodium bisulfate combined with different types of sulfate on the lithium leaching rate are significantly different; the combined roasting of sodium bisulfate and ferrous sulfate heptahydrate as auxiliary materials results in a higher lithium leaching rate than the combined roasting of sodium bisulfate with other sulfates as auxiliary materials.

[0067] Table 3. Lithium extraction analysis in Experiments 8-12 Analysis example 4 Experiment 13: Lithium extraction from lepidolite was carried out using sodium bisulfate and ferrous sulfate heptahydrate as excipients, with the following steps: 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 auxiliary materials were sodium bisulfate and ferrous sulfate heptahydrate at a mass ratio of 1:1. The mixture was placed in a quartz crucible, sealed, and placed in a muffle furnace. The muffle furnace was set to a constant calcination temperature of 800℃ and held for 100 minutes. After calcination, the mixture was removed after cooling to room temperature to obtain the calcined material. Pour the calcined material into an Erlenmeyer flask, add pure water, and the solid-liquid ratio of the calcined material to the pure water is 1g:50mL. After sealing, place it in a constant temperature shaking oven (60℃) for shaking. After shaking for 60 minutes, take it out and filter it through a funnel to obtain lithium leaching solution.

[0068] Experiment 14: Compared to Experiment 13, in Experiment 14 of this analytical example, the excipients were adjusted to sodium bisulfate and potassium carbonate in a mass ratio of 1:1, while other conditions remained unchanged.

[0069] Experiment 15: Compared to Experiment 13, in Experiment 15 of this analytical example, the excipients were adjusted to a mass ratio of sodium carbonate and potassium carbonate of 1:2, while other conditions remained unchanged.

[0070] Experiment 16: Compared to Experiment 13, in Experiment 16 of this analytical example, the excipients were adjusted to a mass ratio of sodium carbonate, potassium carbonate, and magnesium carbonate of 1:1:1, while other conditions remained unchanged.

[0071] Experimental Analysis: As shown in Table 4, it can be seen that the effects of different types of composite salts on lithium leaching rate are significantly different. When roasted at 800℃, the lithium leaching rate of the carbonate system does not exceed 60%; the lithium leaching rate of the carbonate and sulfate composite roasting system reaches 83.74%; while the lithium leaching rate of the sodium bisulfate and ferrous sulfate heptahydrate composite roasting system is as high as 98.76%.

[0072] Table 4. Lithium extraction analysis in Experiments 13-16 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 extracting lithium from lepidolite, characterized in that, Including the following steps: S1, after mixing lithium mica ore with ferrous sulfate and sodium bisulfate, mechanical activation is performed to obtain a pretreated mixture; The mass ratio of the lithium mica ore, the ferrous sulfate, and the sodium bisulfate is 1:0.07-0.5:0.07-0.5; S2, the pretreated mixture is roasted to obtain clinker; the roasting temperature is 700-900℃. S3, the clinker is subjected to water immersion and solid-liquid separation in sequence to obtain lithium leachate.

2. The method for lithium extraction from lepidolite according to claim 1, characterized in that, The lithium leaching solution and the lithium mica ore have a lithium element mass percentage of 98-99%.

3. The method for lithium extraction from lepidolite according to claim 1, characterized in that, The roasting temperature is 750-850℃.

4. The method for lithium extraction from lepidolite according to claim 1, characterized in that, The ferrous sulfate is ferrous sulfate heptahydrate; the mass ratio of the lepidolite ore, the ferrous sulfate heptahydrate, and the sodium bisulfate is 1:0.2-0.25:0.28-0.

32.

5. The method for lithium extraction from lepidolite according to claim 1, characterized in that, The mechanical activation method includes ball milling; the ball milling speed is 400-600 rpm, the ball milling time is 1-3 hours, and the ball-to-material ratio is 2-4:

1.

6. The method for lithium extraction from lepidolite according to claim 1, characterized in that, The particle size of the pretreated mixture is no larger than the aperture of a 100-mesh sieve.

7. The method for lithium extraction from lepidolite according to claim 1, characterized in that, The holding time for the roasting process is 80-160 minutes.

8. The method for lithium extraction from lepidolite according to claim 1, characterized in that, The liquid-to-solid ratio used in the water immersion is 10-50 mL: 1 g; the immersion time is 1-3 h; the immersion temperature is 20-80 °C; the immersion is carried out under shaking conditions; and the shaking frequency is 100-300 rpm.

9. The method for lithium extraction from lepidolite according to claim 1, characterized in that, The solid-liquid separation method includes vacuum filtration.

10. The method for lithium extraction from lepidolite according to any one of claims 1-9, characterized in that, The mass percentage of Li2O in the lithium mica ore is 2-3%.

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