Method for recycling lithium mica lithium sinking mother liquor

Abstract

This invention provides a method for reusing lithium mica precipitation mother liquor, relating to the field of lithium salt smelting technology. The method includes the following steps: S1, calcining lithium mica to obtain calcined lithium mica clinker, grinding the calcined lithium mica clinker, adding it to water, stirring, and preparing an initial slurry with a pH of 6.50-8.00; S2, taking the lithium precipitation mother liquor to be reused, adding it to the initial slurry, adjusting the pH, stirring, and filtering to obtain a lithium-containing leachate and leachate residue; S3, adding a calcium removal agent to the lithium-containing leachate, then performing lithium precipitation and separation to obtain lithium carbonate and lithium precipitation mother liquor, part of which is used for future reuse. This method for reusing lithium mica precipitation mother liquor offers significant advantages in reducing calcium and inhibiting scale.

Description

Technical Field

[0001] This invention relates to the field of lithium salt smelting technology, specifically to a method for recycling lithium mica precipitation mother liquor. Background Technology

[0002] Lithium mica is one of my country's important lithium resources. The mainstream process for preparing lithium carbonate from lepidolite typically includes roasting, crushing, fine grinding, leaching, purification, and concentration / lithium precipitation. The leaching process usually involves mixing roasted and finely ground lepidolite powder with water to form a slurry, which is then leached to obtain a lithium-containing leachate. Because the lepidolite sulfate roasting formulation typically includes calcium salts for fluorine fixation, the leaching process results in a high concentration of calcium ions in the leachate. In subsequent processing, these calcium ions readily combine with sulfate ions in the system to form slightly soluble calcium sulfate, causing scaling in equipment such as belt filters and vacuum-liquid separators in the leaching section, as well as on the walls of the drain pipes. This not only increases pipeline resistance and reduces filtration efficiency but can also lead to pipeline blockage and production interruptions in severe cases, requiring periodic shutdowns for scaling removal, significantly increasing production costs and maintenance complexity.

[0003] To reduce the scaling rate on pipe walls, existing technologies typically involve adding a calcium removal agent after leaching to lower the calcium ion content in the leachate. However, this method requires additional reagent consumption, increases the amount of impurities removed, and easily leads to lithium entrainment losses. Therefore, providing a lithium extraction method from lepidolite that consumes less impurities while reducing the scaling rate inside equipment and on pipe walls has become a pressing technical problem in this field. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for reusing lithium mica precipitate mother liquor, which solves the technical problem of easy scaling inside the leaching section equipment and on the walls of the discharge pipes during the lithium extraction process from lithium mica.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for reusing lithium mica precipitation mother liquor, comprising the following steps:

[0007] S1. Calcining lepidolite to obtain calcined lepidolite clinker, grinding the calcined lepidolite clinker into fine powder, adding it to water, stirring, and preparing an initial slurry with a pH of 6.50-8.00;

[0008] S2. Take the lithium precipitated mother liquor to be recycled, add the lithium precipitated mother liquor to the initial slurry, adjust the pH, stir the reaction, filter, and obtain lithium-containing leachate and leachate residue.

[0009] S3. Add a calcium removal agent to the lithium-containing leachate, then perform lithium precipitation and separation to obtain lithium carbonate and lithium precipitation mother liquor. Part of the lithium precipitation mother liquor is used for future reuse.

[0010] Preferably, the lithium mica calcined clinker is ground to a particle size ≤150μm, accounting for 30%-70%.

[0011] Preferably, the concentration of free calcium ions in the initial slurry is 650 mg / L-835 mg / L.

[0012] Preferably, the concentration of carbonate ions in the lithium precipitation mother liquor to be reused is 11-19 g / L.

[0013] Preferably, the lithium mother liquor to be recycled is added to the initial slurry at a ratio of 10%-30% of the initial slurry mass.

[0014] Preferably, the pH is further adjusted in step S2 to 7.00-8.50.

[0015] Preferably, the stirring speed of S2 is 80-200 rpm, the reaction time is 30-90 min, and the reaction temperature is 50-70℃.

[0016] Preferably, the free calcium ion concentration in the S2 lithium-containing leachate is 230.0 mg / L-365.0 mg / L.

[0017] Preferably, the liquid-to-solid mass ratio of the finely ground lithium mica calcined clinker added to water is (0.8-1.2):1.

[0018] Preferably, the lithium mother liquor to be reused has a free calcium ion removal rate of 56%-65% in the initial slurry.

[0019] Compared with existing technologies, it has the following beneficial effects:

[0020] The present invention relates to a method for reusing lithium-containing mother liquor from lepidolite. In the process of lithium extraction from lepidolite, the method utilizes carbonate ions in the mother liquor to be reused beforehand, thereby reducing the consumption of sodium carbonate, a calcium removal agent, in the traditional process. This method achieves a high removal rate of free calcium ions in the initial slurry and reduces the scaling rate in pipelines. It has significant advantages in reducing calcium and inhibiting scale formation in high-calcium systems for lithium extraction using the lepidolite sulfate method. Attached Figure Description

[0021] 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 these drawings without creative effort.

[0022] Figure 1This is a schematic diagram of the process flow for recycling lithium precipitation mother liquor to reduce equipment scaling during the preparation of lithium carbonate from lepidolite in Embodiment 1 of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, 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.

[0024] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0025] I. Preparation Method

[0026] Example 1

[0027] This embodiment provides a method for reusing lithium mica precipitation mother liquor, such as... Figure 1 As shown, it includes the following steps:

[0028] S1. Lithium mica was calcined using the sulfate method to obtain calcined lepidolite clinker. Specifically, lepidolite was mixed with a sodium-potassium sulfate mixture, calcium sulfate, and calcium hydroxide at a ratio of lepidolite:sodium-potassium sulfate mixture:calcium sulfate:calcium hydroxide = 1:0.3:0.25:0.06. The mixture was then passed through a brick-making machine and subsequently calcined in a tunnel kiln at 900℃ for 1 hour. After cooling, the calcined material was coarsely crushed using a shredder to obtain calcined lepidolite clinker. This clinker was then finely ground using a vertical mill until the particle size was ≤150μm (30% of the total particle size). The finely ground clinker was added to water at a liquid-to-solid mass ratio of 0.8:1 and stirred to obtain an initial slurry with a pH of 7.01. The initial slurry was filtered to obtain the supernatant, which was tested using inductively coupled plasma optical emission spectrometry (ICP-OES). The concentration of free calcium ions in the supernatant was 830.4 mg / L.

[0029] S2. The lithium precipitation mother liquor generated in the lithium precipitation process is taken out and filtered to remove solid suspended matter ≥1μm to obtain a clear lithium precipitation mother liquor. The concentration of carbonate ions in the clear lithium precipitation mother liquor is 11g / L when tested by acid-base titration.

[0030] S3. First, add 10% of the clarified lithium precipitation mother liquor to the initial slurry while stirring. Then adjust the pH to 7.31 to ensure sufficient contact between carbonate and calcium ions for calcium ion precipitation, but not enough for lithium ion precipitation to avoid lithium ion loss. Stir and mix at 80 rpm, control the reaction temperature at 50℃, and leaching for 90 minutes. During the reaction, carbonate ions in the lithium precipitation mother liquor react with calcium ions in the initial slurry to form calcium carbonate precipitate. After the reaction is complete, use a belt filter to separate the lithium-containing leachate and leaching residue. Inductively coupled plasma optical emission spectrometry (ICP-OES) was used to test the concentration of free calcium ions in the obtained lithium-containing leachate, which was 363.5 mg / L.

[0031] S4. Add sodium carbonate as a calcium remover to the lithium-containing leachate for further purification and concentration to remove calcium to a level of 25 mg / L. Then, remove calcium again using a resin decalcification method to a level of 5 mg / L. Finally, perform a lithium precipitation process and centrifuge to obtain battery-grade lithium carbonate product and lithium precipitation mother liquor. Part of the lithium precipitation mother liquor is used for future reuse, and part is neutralized and concentrated with concentrated sulfuric acid for recovery.

[0032] According to this embodiment, in the process of preparing lithium carbonate from lepidolite, the mother liquor to be reused is recycled to the leaching section to reduce the calcium ion concentration in the initial slurry. The continuous operation cycle of the pipeline in the leaching section is extended by 1.55 times compared with the traditional process, the scale thickness of the equipment is significantly reduced, and the scale removal cycle is extended from the traditional 27 days to 42 days.

[0033] Example 2

[0034] This embodiment provides a method for reusing lithium mica precipitation mother liquor, including the following steps:

[0035] S1. Lithium mica was calcined using the sulfate method to obtain calcined lepidolite (calcination process same as in Example 1). The calcined lepidolite was then finely ground until the particle size was ≤150μm, accounting for 40%. At a liquid-to-solid mass ratio of 1.0:1, the finely ground calcined lepidolite was added to water and stirred to obtain an initial slurry with a pH of 6.52. The initial slurry was filtered to obtain the supernatant, and its free calcium ion concentration was measured to be 738.2 mg / L using inductively coupled plasma optical emission spectrometry (ICP-OES).

[0036] S2. The lithium precipitation mother liquor generated in the lithium precipitation process is taken out and filtered to remove solid suspended matter ≥1μm to obtain a clear lithium precipitation mother liquor. The concentration of carbonate ions in the clear lithium precipitation mother liquor is 13g / L when tested by acid-base titration.

[0037] S3. First, add the clarified lithium precipitation mother liquor at 12% of the initial slurry mass while stirring. Then adjust the pH to 7.68 to ensure sufficient contact between carbonate and calcium ions for calcium ion precipitation, but not enough for lithium ion precipitation to avoid lithium ion loss. Stir and mix at 100 rpm, control the reaction temperature at 55℃, and leaching for 80 minutes. During the reaction, carbonate ions in the lithium precipitation mother liquor react with calcium ions in the initial slurry to form calcium carbonate precipitate. After the reaction is complete, use a belt filter to separate the lithium-containing leachate and leaching residue. Inductively coupled plasma optical emission spectrometry (ICP-OES) shows that the free calcium ion concentration in the lithium-containing leachate is 312.7 mg / L.

[0038] S4. Add sodium carbonate as a calcium remover to the lithium-containing leachate for further purification and concentration to remove calcium to a level of 25 mg / L. Then, remove calcium again using a resin decalcification method to a level of 5 mg / L. Finally, perform a lithium precipitation process and centrifuge to obtain battery-grade lithium carbonate product and lithium precipitation mother liquor. Part of the lithium precipitation mother liquor is used for future reuse, and part is neutralized and concentrated with concentrated sulfuric acid for recovery.

[0039] According to this embodiment, in the lithium carbonate preparation section of lepidolite, the mother liquor from lepidolite precipitation is reused to prepare lithium carbonate, which significantly reduces the thickness of scale on the equipment.

[0040] Example 3

[0041] This embodiment provides a method for reusing lithium mica precipitation mother liquor, including the following steps:

[0042] S1. Lithium mica was calcined using the sulfate method to obtain calcined lepidolite (the specific calcination process is the same as in Example 1). The calcined lepidolite was then finely ground until 50% of the particles were ≤150μm in size. The finely ground calcined lepidolite was added to water at a liquid-to-solid mass ratio of 1.1:1 and stirred to obtain an initial slurry with a pH of 7.50. The initial slurry was filtered to obtain the supernatant, and the free calcium ion concentration was measured to be 732.1 mg / L using inductively coupled plasma optical emission spectrometry (ICP-OES).

[0043] S2. The lithium precipitation mother liquor generated in the lithium precipitation process is taken out and filtered to remove solid suspended matter ≥1μm to obtain a clear lithium precipitation mother liquor. The concentration of carbonate ions in the clear lithium precipitation mother liquor is 15g / L when tested by acid-base titration.

[0044] S3. First, add 15% of the clarified lithium precipitation mother liquor to the initial slurry while stirring. Then adjust the pH to 8.00 to ensure sufficient contact between carbonate and calcium ions for calcium ion precipitation, but not enough for lithium ion precipitation to avoid lithium ion loss. Stir and mix at 120 rpm, control the reaction temperature at 60℃, and leaching for 70 minutes. During the reaction, carbonate ions in the lithium precipitation mother liquor react with calcium ions in the initial slurry to form calcium carbonate precipitate. After the reaction is complete, use a belt filter to separate the leaching solution and leaching residue. The free calcium ion concentration in the obtained lithium-containing leachate is 292.7 mg / L.

[0045] S4. Add sodium carbonate as a calcium remover to the lithium-containing leachate for further purification and concentration to remove calcium to a level of 20 mg / L. Then, use resin to remove calcium again to reduce the calcium level to 3 mg / L. Finally, perform the lithium precipitation process and centrifuge to obtain battery-grade lithium carbonate product and lithium precipitation mother liquor. Part of the lithium precipitation mother liquor is used for future reuse, and part is neutralized and concentrated with concentrated sulfuric acid for recovery.

[0046] According to this embodiment, in the lithium carbonate preparation section of lepidolite, the mother liquor from lepidolite precipitation is reused to prepare lithium carbonate, which significantly reduces the thickness of scale on the equipment.

[0047] Example 4

[0048] This embodiment provides a method for reusing lithium mica precipitation mother liquor, including the following steps:

[0049] S1. Lithium mica was calcined using the sulfate method to obtain calcined lepidolite (the specific calcination process is the same as in Example 1). The calcined lepidolite was then finely ground until the particle size was ≤150μm, accounting for 60%. At a liquid-to-solid mass ratio of 1.2:1, the finely ground calcined lepidolite was added to water and stirred to obtain an initial slurry with a pH of 7.25. The initial slurry was filtered to obtain the supernatant, and its free calcium ion concentration was measured to be 683.2 mg / L.

[0050] S2. The lithium precipitation mother liquor generated in the lithium precipitation process is taken out and filtered to remove solid suspended matter ≥1μm to obtain a clear lithium precipitation mother liquor. The concentration of carbonate ions in the clear lithium precipitation mother liquor is 17g / L when tested by acid-base titration.

[0051] S3. First, add 20% of the clarified lithium precipitation mother liquor to the initial slurry while stirring. Then adjust the pH to 8.45 to ensure sufficient contact between carbonate and calcium ions for calcium ion precipitation, but not enough for lithium ion precipitation to avoid lithium ion loss. Stir and mix at 150 rpm, control the reaction temperature at 70℃, and leaching for 30 minutes. During the reaction, carbonate ions in the lithium precipitation mother liquor react with calcium ions in the initial slurry to form calcium carbonate precipitate. After the reaction is complete, use a belt filter to separate the leaching solution and leaching residue containing lithium. The concentration of free calcium ions in the obtained lithium-containing leaching solution is 257.2 mg / L.

[0052] S4. Add sodium carbonate as a calcium remover to the lithium-containing leachate for further purification and concentration to remove calcium to a lower level of 18 mg / L. Then, use resin to remove calcium again to a lower level of 2 mg / L. Finally, perform a lithium precipitation process and centrifuge to obtain battery-grade lithium carbonate product and lithium precipitation mother liquor. Part of the lithium precipitation mother liquor is used for future reuse, and part is neutralized and concentrated with concentrated sulfuric acid for recovery.

[0053] According to this embodiment, in the lithium carbonate preparation section of lepidolite, the mother liquor from lepidolite precipitation is reused to prepare lithium carbonate, which significantly reduces the thickness of scale on the equipment.

[0054] Example 5

[0055] This embodiment provides a method for reusing lithium mica precipitation mother liquor, including the following steps:

[0056] S1. Lithium mica was calcined using the sulfate method to obtain calcined lepidolite (the specific calcination process is the same as in Example 1). The calcined lepidolite was then finely ground until 70% of the particles were ≤150μm in size. The finely ground calcined lepidolite was added to water at a liquid-to-solid mass ratio of 1.2:1 and stirred to obtain an initial slurry with a pH of 7.24. The initial slurry was filtered to obtain the supernatant, and its free calcium ion concentration was measured to be 650.8 mg / L.

[0057] S2. The lithium precipitation mother liquor generated in the lithium precipitation process is taken out and filtered to remove solid suspended matter ≥1μm to obtain a clear lithium precipitation mother liquor. The concentration of carbonate ions in the clear lithium precipitation mother liquor is 19g / L when tested by acid-base titration.

[0058] S3. First, add 30% of the clarified lithium precipitation mother liquor to the initial slurry while stirring. Then adjust the pH to 8.50 to ensure sufficient contact between carbonate and calcium ions for calcium ion precipitation, but not enough for lithium ion precipitation to avoid lithium ion loss. Stir and mix at 200 rpm, control the reaction temperature at 70℃, and leaching for 30 minutes. During the reaction, carbonate ions in the lithium precipitation mother liquor react with calcium ions in the initial slurry to form calcium carbonate precipitate. After the reaction is complete, use a belt filter to separate the leaching solution and leaching residue containing lithium. The concentration of free calcium ions in the lithium-containing leaching solution, measured by inductively coupled plasma optical emission spectrometry (ICP-OES), is 230.1 mg / L.

[0059] S4. Add sodium carbonate as a calcium remover to the lithium-containing leachate for further purification and concentration to remove calcium to a level of 25 mg / L. Then, remove calcium again using a resin decalcification method to a level of 5 mg / L. Finally, perform a lithium precipitation process and centrifuge to obtain battery-grade lithium carbonate product and lithium precipitation mother liquor. Part of the lithium precipitation mother liquor is used for future reuse, and part is neutralized and concentrated with concentrated sulfuric acid for recovery.

[0060] According to this embodiment, in the lithium carbonate preparation section of lepidolite, the lithium precipitation mother liquor of lepidolite is reused to prepare lithium carbonate. The continuous operation cycle of the pipeline in this section is extended by 2.6 times compared with the traditional process, and the scale thickness of the equipment is significantly reduced.

[0061] Comparative Example 1

[0062] The difference between this comparative example and Example 1 is that recycled water is used instead of the recycled lithium precipitation mother liquor in S2 and S3; otherwise, they are the same as in Example 1. The supernatant of the initial slurry, after filtration, was tested using inductively coupled plasma optical emission spectrometry (ICP-OES) and found to have a free calcium ion concentration of 664.1 mg / L. The lithium-containing leachate obtained by belt filter separation was tested using ICP-OES and found to have a free calcium ion concentration of 663.8 mg / L.

[0063] II. Testing Methods

[0064] The efficiency of the lithium mica precipitation mother liquor reuse method in the examples and comparative examples was characterized by the removal rate of free calcium ions in the initial slurry. The removal rate of free calcium ions from the initial slurry by the precipitation mother liquor was calculated according to the following formula:

[0065] The free calcium ion removal rate of the lithium precipitation mother liquor on the initial slurry = (free calcium ion concentration in the initial slurry - free calcium ion concentration in the lithium-containing leachate) / free calcium ion concentration in the initial slurry. The results are shown in Table 1.

[0066] Table 1

[0067]

[0068] Note: The sodium carbonate consumption in Table 1 includes sodium carbonate consumed in the deep calcium removal stage of purification and concentration, as well as sodium carbonate consumed in the lithium carbonate precipitation process. Because it is difficult to distinguish between them in actual production, they are combined. The amount of sodium carbonate consumed in the lithium carbonate precipitation process remains basically unchanged. Therefore, the decrease in sodium carbonate consumption indicates that the amount of sodium carbonate consumed in the deep calcium removal stage of purification and concentration has decreased.

[0069] As shown in Table 1, the lithium mica precipitation mother liquor reuse method of the present invention reduces the consumption of sodium carbonate, a calcium removal agent, in traditional processes by pre-utilizing carbonate ions in the lithium precipitation mother liquor. It achieves a high removal rate of free calcium ions in the initial slurry and simultaneously reduces the scaling rate in pipelines. For the high-calcium lithium extraction system using the lithium mica sulfate method, it exhibits significant advantages in calcium reduction and scale inhibition. Furthermore, it reduces the amount of lithium precipitation mother liquor generated, thus lowering the amount of concentrated sulfuric acid used to neutralize the lithium precipitation mother liquor.

[0070] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0071] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0072] The present invention has been illustrated with the above embodiments to describe the detailed process flow of the present invention. However, the present invention is not limited to the above detailed process flow, that is, it does not mean that the present invention must rely on the above detailed process flow to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for recycling lithium mica precipitation mother liquor, characterized in that, Includes the following steps: S1. Calcining lepidolite to obtain calcined lepidolite clinker, grinding the calcined lepidolite clinker into fine powder, adding it to water, stirring, and preparing an initial slurry with a pH of 6.50-8.00; S2. Take the lithium precipitating mother liquor to be recycled, add the lithium precipitating mother liquor to be recycled into the initial slurry, adjust the pH, stir the reaction, filter, and obtain lithium-containing leachate and leachate residue. S3. Add a calcium removal agent to the lithium-containing leachate, then perform lithium precipitation and separation to obtain lithium carbonate and lithium precipitation mother liquor. Part of the lithium precipitation mother liquor is used for future reuse.

2. The method for recycling lithium mica precipitation mother liquor as described in claim 1, characterized in that, The calcined lithium mica clinker is ground to a particle size ≤150μm, accounting for 30%-70%.

3. The method for recycling lithium mica precipitation mother liquor as described in claim 1, characterized in that, The concentration of free calcium ions in the initial slurry is 650 mg / L-835 mg / L.

4. The method for recycling lithium mica precipitation mother liquor as described in claim 1, characterized in that, The concentration of carbonate ions in the lithium precipitation mother liquor to be reused is 11-19 g / L.

5. The method for recycling lithium mica precipitation mother liquor as described in claim 1, characterized in that, The lithium mother liquor to be reused is added to the initial slurry at a ratio of 10%-30% of the initial slurry mass.

6. The method for recycling lithium mica precipitation mother liquor as described in claim 1, characterized in that, The pH of S2 is then adjusted to 7.00-8.

50.

7. The method for recycling lithium mica precipitation mother liquor as described in claim 1, characterized in that, The stirring speed of S2 is 80-200 rpm, the reaction time is 30-90 min, and the reaction temperature is 50-70℃.

8. The method for recycling lithium mica precipitation mother liquor as described in claim 1, characterized in that, The free calcium ion concentration in the S2 lithium-containing leachate is 230.0 mg / L-365.0 mg / L.

9. The method for recycling lithium mica precipitation mother liquor as described in claim 1, characterized in that, The liquid-to-solid mass ratio of the finely ground lithium mica calcined clinker added to water is (0.8-1.2):

1.

10. The method for reusing lithium mica precipitation mother liquor as described in claim 1, characterized in that, The lithium precipitation mother liquor to be reused has a free calcium ion removal rate of 56%-65% in the initial slurry.

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