Method for extracting lithium by mechanically activating lepidolite

Abstract

The invention provides a method for extracting lithium from lepidolite through mechanical activation, and relates to the technical field of extraction of lithium from lepidolite. The method comprises the following steps: firstly, mechanically activating lepidolite concentrate in a chrome steel disc mill, and then uniformly roasting the mechanically activated concentrate and potassium-sodium mixed salt to obtain clinker; and crushing the clinker to a proper size, mixing with pure water, heating, stirring, and carrying out solid-liquid separation to obtain a lithium extraction mother solution and filter residues. According to the method, mechanical activation and potassium and sodium salt mixed roasting have a synergistic effect, and efficient extraction of lithium in the lepidolite concentrate is achieved. The method has the characteristics of high lithium ore phase conversion and high lithium leaching rate.

Description

Technical Field

[0001] The invention relates to the technical field of lithium extraction from lepidolite, in particular to a method for mechanically activating lepidolite to extract lithium. Background Art

[0002] The chemical formula of lithium mica is K [ Li2-xAl 1+x ( Al 2x Si4-2 x O 10 ) ( F , OH)2 ] ( x = 0 ~0.5), with glass luster, is a common monoclinic, layered silicate mineral. Its chemical composition varies greatly depending on the degree of crystal differentiation, generally 3%~7.7%Li2O, 5%~10%K2O, 22%~29%Al2O3 and 47%~60%SiO2. The lithium ions are mainly distributed in the lamellar structure, in the gaps between the two silicon-oxygen tetrahedral layers and the aluminum-oxygen octahedral layers. Yichun area is an important solid lithium resource producing area in my country and the main distribution area of ​​lepidolite, represented by Yichun 414 tantalum-niobium-lithium ore. Tantalum-niobium-lithium ore is relatively rare and has high economic value.

[0003] The bond strength of lithium oxygen bond in the structure of lithium mica is restrained by silicon oxygen bond and becomes larger, and the reaction activity is low. Therefore, at present, conventional lithium leaching is often achieved by using proton acid or high temperature environment to destroy the stable layer structure of lithium mica. The two methods are represented by sulfuric acid digestion method and sulfate roasting method. Among them, the sulfuric acid method has serious equipment corrosion and environmental pollution problems, and the sulfate method consumes a lot of potassium sulfate, high energy consumption, and poor comprehensive benefits.

[0004] In the existing production process, CN 112624161 discloses a method for mechanically activating and assisting sulfuric acid digestion to extract lithium from lithium mica, wherein oxalic acid is mixed and mechanically activated to produce catalytic activation, and finally the lithium from lithium mica is extracted by acid leaching with concentrated sulfuric acid. CN 113104867 A discloses a method for preparing lithium carbonate by compound sulfate acidification and roasting of lithium mica, wherein sulfate is mixed with lithium mica as an activation aid and activated, and then mixed with concentrated sulfuric acid and roasted, and finally a lithium sulfate solution is obtained by leaching with a neutral leaching agent. The use of acid cannot be avoided in the existing methods, which brings great pollution to the environment and easily causes equipment corrosion problems.

[0005] The present invention reduces the amount of sulfate and the roasting temperature requirements through the synergistic effect of mechanical activation and sulfate method, avoids the environmental pollution and equipment corrosion problems caused by acidification roasting and leaching, and on this basis realizes the efficient extraction of lithium from lepidolite. Summary of the invention

[0006] In order to solve the above technical problems existing in the prior art, the embodiment of the present invention provides a method for extracting lithium from lepidolite by mechanical activation. On the basis of the traditional sulfate roasting method, a mechanical activation scheme is introduced, and finally the lithium element is transferred from the lepidolite concentrate to the lithium extraction mother liquor by pure water leaching. The technical scheme is as follows:

[0007] S1. placing the lepidolite in a chrome steel disc mill for mechanical activation;

[0008] S2, mixing the lepidolite concentrate after mechanical activation in step S1 with potassium salt and sodium salt, and roasting to obtain roasted clinker;

[0009] S3, crushing the roasted clinker obtained in step S2, mixing with pure water, stirring and heating, and obtaining a lithium extraction mother liquor and a filter residue after solid-liquid separation.

[0010] The lithium mica in step S1 is lithium mica concentrate, and the component contents are as follows: 52-54wt% SiO2, 29-31wt% Al2O3, 8-10wt% K2O, and 4.0-4.25wt% Li2O.

[0011] In step S1, the rotation speed of the chrome steel disc mill is 700-960 r / min, and the mechanical activation time is 1-3 h.

[0012] In step S2, the potassium salt is potassium sulfate, and the sodium salt is sodium sulfate.

[0013] The mass ratio of the mechanically activated lepidolite concentrate to the potassium salt and the sodium salt in step S2 is 1:(0.2-0.5):(0.2-0.5).

[0014] In step S2, the calcination temperature is 800-950° C. and the calcination time is 60-150 min.

[0015] In the step S3, the roasted clinker is crushed to -200 mesh.

[0016] In step S3, the mass ratio of the roasted clinker to pure water is 1:(2-10).

[0017] In the step S3, the temperature during stirring and heating is 80-120° C., the stirring speed is 400-600 rpm, and the duration is 1-3 hours.

[0018] The lithium leaching rate in the lithium extraction mother liquor in step S3 is not less than 95%.

[0019] The beneficial effects brought about by the technical solution provided by the embodiment of the present invention include at least:

[0020] The above scheme, through the mechanical activation of the chrome steel disc mill, effectively destroys the lepidolite sheet structure before roasting, promotes the reaction with potassium salt and sodium salt during roasting, improves the efficiency of lithium conversion into soluble sulfate, reduces the amount of additives used and reduces the need for high temperature conditions on the basis of traditional processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 is a SEM image of the activated lepidolite concentrate in Example 1 of the present invention;

[0023] Figure 2 This is a SEM image of the unactivated lepidolite concentrate in Comparative Example 1 of the present invention;

[0024] Figure 3 is a SEM image of the clinker corresponding to the activated lepidolite concentrate in Example 1 of the present invention;

[0025] Figure 4 This is a SEM image of the clinker corresponding to the unactivated lepidolite concentrate in Comparative Example 1 of the present invention;

[0026] Figure 5 is a SEM image of the filter residue corresponding to the activated lepidolite concentrate in Example 1 of the present invention;

[0027] Figure 6 This is a SEM image of the filter residue corresponding to the unactivated lepidolite concentrate in Comparative Example 1 of the present invention;

[0028] Figure 7 is the XRD spectrum of the activated lepidolite concentrate, the corresponding clinker and the filter residue in Example 1 of the present invention;

[0029] Figure 8 It is the XRD spectrum of the activated lepidolite concentrate, the corresponding clinker and the filter residue in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is described below in conjunction with the accompanying drawings.

[0031] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the word "example" is intended to present the concept in a specific way. In addition, in the embodiments of the present invention, the meaning expressed by "and / or" can be both, or it can be either of the two.

[0032] In the embodiments of the present invention, sometimes a subscript such as W1 may be written as a non-subscript such as W1. When the difference is not emphasized, the meanings to be expressed are the same.

[0033] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0034] The embodiment of the present invention provides a method for extracting lithium from lepidolite by mechanical activation. The method may include the following steps:

[0035] S1. placing the lepidolite in a chrome steel disc mill for mechanical activation;

[0036] S2, mixing the lepidolite concentrate after mechanical activation in step S1 with potassium salt and sodium salt, and roasting to obtain roasted clinker;

[0037] S3, crushing the roasted clinker obtained in step S2, mixing with pure water, stirring and heating, and obtaining a lithium extraction mother liquor and a filter residue after solid-liquid separation.

[0038] This will be described below with reference to specific embodiments.

[0039] Example 1

[0040] The lithium mica concentrate (lithium grade 4.16%) was fed into a chrome steel disc mill and ground at 960r / min for 3h to obtain activated lithium mica concentrate. Potassium sulfate, sodium sulfate and activated lithium mica concentrate were mixed evenly in a mass ratio of 0.3:0.3:1, placed in a muffle furnace, roasted at 800℃ for 120min, and then taken out and cooled at room temperature to obtain roasted clinker. The roasted clinker was crushed to -200 mesh, mixed evenly at a mass ratio of pure water: roasted clinker of 10:1 to obtain a slurry, mixed and heated at 105℃ at a speed of 500rpm for 1.5h, and after completion, the mixed slurry was filtered while hot to separate the solid and liquid to obtain lithium extraction mother liquor and filter residue.

[0041] The lithium leaching rate in the lithium extraction mother liquor reached 98.7%.

[0042] The SEM images of activated lepidolite concentrate, corresponding clinker and filter residue are shown in Figure 2. Figure 1 , Figure 3 and Figure 5 As shown, the XRD spectrum is Figure 7 shown.

[0043] Comparative Example 1

[0044] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 omits the step of activating and grinding the lithium mica concentrate in a chrome steel grinder, and the remaining steps are the same. Potassium sulfate, sodium sulfate and lithium mica concentrate (lithium grade 4.16%) are mixed evenly in a mass ratio of 0.3:0.3:1, placed in a muffle furnace, roasted at 800°C for 120 minutes, and then taken out and cooled at room temperature to obtain roasted clinker. The roasted clinker is crushed to -200 mesh, mixed evenly at a mass ratio of pure water: roasted clinker of 10:1 to obtain a slurry, mixed and heated at 105°C at a speed of 500rpm for 1.5h, and after completion, the mixed slurry is filtered while hot to separate the solid and liquid to obtain a lithium extraction mother liquor and a filter residue. The lithium leaching rate in the lithium extraction mother liquor reaches 88.27%.

[0045] The SEM images of unactivated lepidolite concentrate, corresponding clinker and filter residue are shown in Figure 2. Figure 2 , Figure 4 and Figure 6 shown.

[0046] Comparative Example 2

[0047] The difference between Comparative Example 2 and Example 1 is that in Comparative Example 2, the lithium mica concentrate is ground in a chrome steel disc mill alone, and potassium sulfate, sodium sulfate and lithium mica concentrate are mixed in a mass ratio of 0.3:0.3:1 and ground in a chrome steel disc mill, and potassium sulfate and sodium sulfate are not repeatedly added during the roasting process, and the remaining steps are the same. Potassium sulfate, sodium sulfate and lithium mica concentrate (lithium grade 4.155%) are mixed uniformly in a mass ratio of 0.3:0.3:1, put into a chrome steel disc mill, and grind for 3 hours at 960r / min. The activated material obtained is put into a muffle furnace and roasted at 800°C for 120 minutes. After the end, it is taken out and cooled at room temperature to obtain a roasted clinker. The roasted clinker was crushed to -200 mesh, mixed evenly at a mass ratio of pure water to roasted clinker of 10:1 to obtain a slurry, and mixed, heated and stirred at 105°C at a speed of 500 rpm for 1.5 hours. After completion, the mixed slurry was filtered while hot to separate the solid and liquid to obtain a lithium extraction mother liquor and a filter residue. The lithium leaching rate in the lithium extraction mother liquor reached 7.13%.

[0048] Comparative Example 2: The XRD patterns of the lithium mica concentrate after mixed sulfate activation, the corresponding clinker and the filter residue are as follows: Figure 8 shown.

[0049] The lithium grade and lithium extraction efficiency (in terms of oxide) of the filter residues obtained in the embodiments and comparative examples are shown in Table 1.

[0050] Table 1

[0051]

[0052] It can be seen from Example 1 and Comparative Example 1 in the table that the mechanical activation lithium extraction method introduced in the present invention can effectively improve the lithium extraction efficiency and reduce the lithium residue in the filter residue. The results of Example 1 and Comparative Example 2 show that the mechanical activation introduction in the present invention needs to be placed before the mixed salt is roasted. From the XRD spectrum, it can be seen that Comparative Example 2 cannot produce soluble lithium salt after the roasting process to achieve lithium extraction.

[0053] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for extracting lithium from mechanically activated lepidolite, characterized in that: The method comprises: S1. placing the lepidolite in a chrome steel disc mill for mechanical activation; S2, mixing the lepidolite concentrate after mechanical activation in step S1 with potassium salt and sodium salt, and roasting to obtain roasted clinker; S3, crushing the roasted clinker obtained in step S2, mixing with pure water, stirring and heating, and obtaining a lithium extraction mother liquor and a filter residue after solid-liquid separation.

2. The method for extracting lithium from mechanically activated lepidolite according to claim 1, characterized in that: The lithium mica in step S1 is lithium mica concentrate, and the component contents are as follows: 52-54wt% SiO2, 29-31wt% Al2O3, 8-10wt% K2O, and 4.0-4.25wt% Li2O.

3. The method for extracting lithium from mechanically activated lepidolite according to claim 1, characterized in that: In step S1, the rotation speed of the chrome steel disc mill is 700-960 r / min, and the mechanical activation time is 1-3 h.

4. The method for extracting lithium from mechanically activated lepidolite according to claim 1, characterized in that: In step S2, the potassium salt is potassium sulfate, and the sodium salt is sodium sulfate.

5. The method for extracting lithium from mechanically activated lepidolite according to claim 1, characterized in that: The mass ratio of the mechanically activated lepidolite concentrate to the potassium salt and the sodium salt in step S2 is 1:(0.2-0.5):(0.2-0.5).

6. The method for extracting lithium from mechanically activated lepidolite according to claim 1, characterized in that: In step S2, the calcination temperature is 800-950° C. and the calcination time is 60-150 min.

7. The method for extracting lithium from mechanically activated lepidolite according to claim 1, characterized in that: In the step S3, the roasted clinker is crushed to -200 mesh.

8. The method for extracting lithium from mechanically activated lepidolite according to claim 1, characterized in that: In step S3, the mass ratio of the roasted clinker to pure water is 1:(2-10).

9. The method for extracting lithium from mechanically activated lepidolite according to claim 1, characterized in that: During the stirring and heating in step S3, the stirring speed is 400-600 rpm, the temperature is 80-120° C., and the duration is 1-3 hours.

10. The method for extracting lithium from mechanically activated lepidolite according to claim 1, characterized in that: The lithium leaching rate in the lithium extraction mother liquor in step S3 is not less than 95%.

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