Novel process for preparing battery-grade lithium carbonate from lithium precipitation mother liquor

Abstract

The invention discloses a novel process for preparing battery-grade lithium carbonate from lithium precipitation mother liquor. The process comprises the following steps: mixing quick lime and the lithium precipitation mother liquor, adjusting alkali and removing fluorine; filtering calcium ions in the mixed solution, calcining the filtered calcium slag, and supplementing quick lime and carbon dioxide; mixing the obtained filtrate with an organic extraction agent for extraction; mixing the obtained loaded organic phase with pure water, and washing; carrying out reverse extraction on the obtained washed loaded organic phase; the obtained strip liquor is subjected to oil removal; decalcifying the deoiled strip liquor through resin; and pyrolyzing the obtained strip liquor, filtering and drying to obtain battery-grade lithium carbonate, and circulating the pyrolyzed liquor back to the strip-extraction section to supplement the water phase. According to the method, the mother liquor obtained after lithium precipitation of the lepidolite leaching solution serves as the raw material, the extraction-carbon dioxide reverse extraction process is carried out after alkali adjustment, the technological process is greatly shortened, the lithium recovery rate is increased, and the problems that energy consumption is large due to the fact that the lithium precipitation mother liquor is concentrated again or the grade of the lithium precipitation raw material solution is reduced due to the fact that the lithium precipitation mother liquor and the leaching solution are mixed are solved.

Description

Technical Field

[0001] The invention relates to the field of lithium extraction from lepidolite, and in particular to a novel process for preparing battery-grade lithium carbonate from lithium precipitation mother liquor. Background Art

[0002] Lithium is praised as the "green energy metal" and "white oil" that will change the world in the 21st century due to its unique physical and chemical properties. Lithium-ion batteries produced with lithium carbonate as raw material have been widely used, and the lithium battery industry has become a pillar industry in my country. In addition, lithium also plays a key role in many other fields such as glass, ceramics, alloys, lubricants, and pharmaceutical materials. As a multifunctional material, the strategic significance and application potential of lithium are becoming increasingly prominent in various industries.

[0003] Since there is a precipitation-dissolution equilibrium of lithium carbonate when lithium is precipitated in the lithium mica leachate, the lithium precipitation mother liquor also contains a relatively high concentration of lithium ions, resulting in a low utilization rate of lithium. It is of great significance to efficiently recover this part of lithium ions. Solvent extraction is widely used in the lithium extraction process because of its mild reaction conditions, good lithium extraction performance, low energy consumption, and convenience for continuous production. The endpoint pH of the lithium precipitation reaction often does not reach the optimal pH condition for extraction with commonly used lithium extractants, and additional alkali solution needs to be added in the extraction section, resulting in large alkali solution consumption and high production costs. The lithium precipitation mother liquor of the lithium mica leachate contains a relatively high concentration of fluoride ions. If they are not removed, the quality of the finished lithium carbonate will not meet the requirements. Summary of the invention

[0004] The main purpose of the present invention is to provide a new process for preparing battery-grade lithium carbonate from lithium precipitation mother liquor, aiming to provide a process for preparing battery-grade lithium carbonate from lithium precipitation mother liquor which does not require additional alkali adjustment, has a high recovery rate and can fully utilize the rich carbonate resources in the lithium precipitation mother liquor.

[0005] To achieve the above object, the present invention proposes a novel process for preparing battery-grade lithium carbonate from lithium precipitation mother liquor, comprising:

[0006] S1, mixing quicklime and lithium precipitation mother liquor to adjust alkali and remove fluorine;

[0007] S2, filtering the calcium ions in the mixed solution of step S1, calcining the filtered calcium slag and then adding quicklime and carbon dioxide;

[0008] S3, mixing the filtrate obtained in step S2 with an organic extractant for extraction;

[0009] S4, mixing the loaded organic phase obtained in step S3 with pure water for washing;

[0010] S5, mixing the washed loaded organic phase obtained in step S4 with pure water and carbon dioxide for stripping;

[0011] S6, removing oil from the stripping solution obtained in step S5 by using an oil removal resin;

[0012] S7, removing calcium from the stripping solution after deoiling in step S6 by resin;

[0013] S8. Pyrolyze the stripping solution obtained in step S7, filter and dry to obtain battery-grade lithium carbonate, and circulate the pyrolysis solution back to the stripping stage to supplement the water phase.

[0014] In one embodiment, the ratio of quicklime added in step S1 to lithium precipitation mother liquor is 10-50 g / L, and the reaction time is 1-2 h.

[0015] In one embodiment, the quicklime added in step S1 and the lithium precipitation mother liquor are adjusted to an end point pH of 11 to 13.5.

[0016] In one embodiment, the calcium slag obtained by calcining and filtering in step S2 is calcined at a temperature of 850-1000°C.

[0017] In one embodiment, the volume ratio of the lithium organic extractant added during the extraction in step S3 to the lithium precipitation mother liquor after alkali adjustment is 0.5-4:1.

[0018] In one embodiment, the extractant used in the extraction process of step S3 is a ketone extractant and / or a neutral organic phosphorus oxide extractant.

[0019] In one embodiment, the extraction reaction pH in step S3 is 10.5-13.

[0020] In one embodiment, the raffinate obtained by the extraction in step S3 is deoiled by resin and then discharged, and the discharged raffinate is used to recover the sodium salt.

[0021] In one embodiment, during the washing in step S4, the volume ratio of the loaded organic phase to pure water is 10 to 30:1, and the washing water is mixed with the mother liquor after alkali adjustment for extraction.

[0022] In one embodiment, during the stripping step S5, the volume ratio of the loaded organic phase, water and carbon dioxide is 0.5-4:1:20-40.

[0023] In one embodiment, the oil removal and calcium removal in steps S6 and S7 are performed in an oil removal resin column and a calcium removal resin column respectively.

[0024] In one embodiment, the pyrolysis temperature in step S8 is 70-100° C., the pyrolysis time is 0.75-2 h, and the pyrolysis liquid is circulated back to the stripping section to supplement the water phase.

[0025] In one embodiment, the stripping endpoint pH value during stripping in step S5 is 6-8.

[0026] In one embodiment, the drying temperature in step S8 is 100-300° C. and the drying time is 1-2.5 hours.

[0027] In summary, the present invention has the following beneficial effects:

[0028] (1) The present invention uses the mother liquor after lithium precipitation from the lithium mica leachate as raw material, and performs an extraction-carbon dioxide stripping process after alkali adjustment, which greatly shortens the process flow, improves the lithium recovery rate, and avoids the problem of high energy consumption caused by re-concentration of the lithium precipitation mother liquor, or the problem of reduced taste of the lithium precipitation raw material liquid caused by mixing the lithium precipitation mother liquor with the leachate.

[0029] (2) The present invention adopts calcium oxide to adjust the alkali, thereby avoiding the problem of additionally supplementing alkali solution in the extraction stage and reducing production costs; and recovering calcium oxide and carbon dioxide by calcining calcium slag to supplement the alkali adjustment process and the stripping process respectively, thereby comprehensively utilizing the abundant carbonate resources in the lithium precipitation mother liquor and further reducing production costs; at the same time, the addition of calcium oxide can remove the fluoride ions with a high concentration in the lithium precipitation mother liquor, which is beneficial to improving product quality.

[0030] (3) The extraction rate of sodium and potassium in the present invention is extremely low during the extraction stage, and the sodium and potassium ions are discharged along with the extract, thereby improving the product quality.

[0031] (4) During the pyrolysis stage, due to the dissolution equilibrium of lithium carbonate precipitation, there is still a certain concentration of lithium ions in the pyrolysis solution. The present invention improves the lithium recovery rate by recycling the pyrolysis solution to supplement the water phase of the stripping stage, while avoiding the generation of excessive wastewater and increasing the treatment cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 the structures shown in these drawings without paying creative work.

[0033] Picture 1 The present invention is a schematic diagram of the process flow of a novel process for preparing battery-grade lithium carbonate from lithium precipitation mother liquor according to an embodiment of the present invention.

[0034] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0037] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0038] Furthermore, the technical solutions between the various embodiments of the present invention may be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in the field. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0039] The invention provides a novel process for preparing battery-grade lithium carbonate from lithium precipitation mother liquor.

[0040] like Picture 1 As shown, the novel process for preparing battery-grade lithium carbonate from lithium precipitation mother solution provided in the embodiment of the present invention comprises:

[0041] S1, mixing quicklime and lithium precipitation mother liquor to adjust alkali and remove fluorine;

[0042] S2, filtering the calcium ions in the mixed solution of step S1, calcining the filtered calcium slag and then adding quicklime and carbon dioxide;

[0043] S3, mixing the filtrate obtained in step S2 with an organic extractant for extraction;

[0044] S4, mixing the loaded organic phase obtained in step S3 with pure water for washing;

[0045] S5, mixing the washed loaded organic phase obtained in step S4 with pure water and carbon dioxide for stripping;

[0046] S6, removing oil from the stripping solution obtained in step S5 by using an oil removal resin;

[0047] S7, removing calcium from the stripping solution after deoiling in step S6 by resin;

[0048] S8. Pyrolyze the stripping solution obtained in step S7, filter and dry to obtain battery-grade lithium carbonate, and circulate the pyrolysis solution back to the stripping stage to supplement the water phase.

[0049] Example 1

[0050] like Picture 1 As shown, a method for preparing battery-grade lithium carbonate from lithium precipitation mother liquor comprises the following steps: step S1, stirring and mixing calcium oxide and lithium precipitation mother liquor at a ratio of 20 g / L for reaction for 1 hour, and then filtering with suction, the reaction end point pH = 12.8, filtering with a filter membrane after suction filtration; step S2, mixing and stirring the lithium precipitation mother liquor after alkali adjustment with an organic extractant at a ratio of O / A = 2 / 1, the reaction pH = 12.3, and obtaining a loaded organic phase; step S3, mixing and stirring the obtained loaded organic phase with pure water at a ratio of O / A = 15 / 1, and washing for 10 minutes to obtain a clean loaded organic phase; step S4, The loaded organic phase is mixed with water and carbon dioxide in a volume ratio of 2:1:20, and then stripped to obtain a lithium bicarbonate solution, and the stripping endpoint pH is 7.6; step S5, first the stripping solution is passed through the oil removal resin column at a uniform speed, with a total amount of 2BV and a passing time of 1.5h, and then the stripping solution is passed through the calcium removal resin column at a uniform speed, with a total amount of 2BV and a passing time of 2.5h; step S6, the stripping solution is pyrolyzed at 95°C for 1.5h, and after suction filtration, the lithium carbonate is dried at 260°C for 2h to obtain a product, please refer to Table 1, which is a composition table (wt.%) of lithium carbonate in Example 1.

[0051] <![CDATA[Li2CO3]]> Na Mg Ca K Al Cu Fe Mn Ni Zinc 99.73％ 0.0214 0.0009 0.0036 0.0007 0.0005 <0.0001 0.0007 <0.0001 <0.0001 <0.0001 S <![CDATA[SO4 2- ]]> <![CDATA[Cl - ]]> 0.0021 0.0723 0.0018

[0052] Table 1

[0053] Example 2

[0054] A method for preparing battery-grade lithium carbonate from lithium precipitation mother liquor, comprising the following steps: step S1, stirring and mixing calcium oxide and lithium precipitation mother liquor at a ratio of 30 g / L for 45 minutes, filtering after suction, the pH at the reaction end point is 13.2, filtering with a filter membrane after suction filtration; step S2, mixing and stirring the lithium precipitation mother liquor after alkali adjustment with an organic extractant at a ratio of O / A=1.5 / 1, reacting with a pH of 12.5, and obtaining a loaded organic phase; step S3, mixing and stirring the obtained loaded organic phase with pure water at a ratio of O / A=15 / 1, washing for 10 minutes to obtain a clean The loaded organic phase; step S4, mixing the washed loaded organic phase with water and carbon dioxide in a volume ratio of 2.5:1:25, and then stripping to obtain a lithium bicarbonate solution, wherein the stripping end point pH is 7.5; step S5, firstly passing the stripping solution through an oil removal resin column at a uniform speed, with a total amount of 2BV and a passing time of 1h, and then passing the stripping solution through a calcium removal resin column at a uniform speed, with a total amount of 2BV and a passing time of 2.5h; step S6, pyrolyzing the stripping solution at 95°C for 1.5h, and drying the lithium carbonate at 260°C for 2h after suction filtration to obtain the product.

[0055] The quicklime added during alkali adjustment in this embodiment is prepared by mixing the product of the calcium slag in Example 1 after calcination at 900°C for 1.5 hours with fresh calcium oxide in a ratio of 1:1; the aqueous phase during stripping in this embodiment is composed of the pyrolysis solution in Example 1 and fresh pure water in a ratio of 1.5:1. Please refer to Table 2, which is a composition table (wt.%) of lithium carbonate in Example 2.

[0056] <![CDATA[Li2CO3]]> Na Mg Ca K Al Cu Fe Mn Ni Zinc 99.65％ 0.0284 0.0016 0.0041 0.0006 0.0004 <0.0001 0.0003 <0.0001 <0.0001 <0.0001 S <![CDATA[SO4 2- ]]> <![CDATA[Cl - ]]> 0.0025 0.0753 0.0026

[0057] Table 2

[0058] Example 3

[0059] A method for preparing battery-grade lithium carbonate from lithium precipitation mother liquor, comprising the following steps: step S1, stirring and mixing calcium oxide and lithium precipitation mother liquor at a ratio of 40 g / L for 45 minutes, filtering after suction, the pH at the reaction end point is 13.5, filtering with a filter membrane after suction filtration, and then passing through a calcium removal resin column; step S2, mixing and stirring the lithium precipitation mother liquor after alkali adjustment with an organic extractant at a ratio of O / A=1.5 / 1, reacting with a pH of 12.9, and obtaining a loaded organic phase; step S3, mixing and stirring the obtained loaded organic phase with pure water at a ratio of O / A=15 / 1, washing for 5 minutes to obtain a to a clean loaded organic phase; step S4, mixing the washed loaded organic phase with water and carbon dioxide in a volume ratio of 2.5:1:25, and then stripping to obtain a lithium bicarbonate solution, with a stripping endpoint pH of 7.6; step S5, first passing the stripping solution through an oil removal resin column at a uniform speed, with a total amount of 2BV and a passing time of 1h, and then passing the stripping solution through a calcium removal resin column at a uniform speed, with a total amount of 2BV and a passing time of 2.5h; step S6, pyrolyzing the stripping solution at 95°C for 1.5h, and after suction filtration, drying the lithium carbonate at 260°C for 2h to obtain the product.

[0060] The quicklime added during alkali adjustment in this embodiment is prepared by mixing the product of the calcium slag in Example 1 after calcination at 900°C for 1.5 hours with fresh calcium oxide in a ratio of 1.5:1; the aqueous phase during stripping in this embodiment is composed of the pyrolysis solution in Example 1 and fresh pure water in a ratio of 1.5:1. Please refer to Table 3, which is a composition table (wt.%) of lithium carbonate in Example 3.

[0061]

[0062]

[0063] Table 3

[0064] In summary, the present invention uses the mother liquor after lithium precipitation of lithium mica leachate as raw material, and performs extraction-carbon dioxide stripping process after alkali adjustment, which greatly shortens the process flow, improves the recovery rate of lithium, and avoids the problem of high energy consumption caused by re-concentration of the lithium precipitation mother liquor, or the problem of reduced taste of lithium precipitation raw material liquid caused by mixing the lithium precipitation mother liquor with the leachate.

[0065] The present invention adopts calcium oxide to adjust the alkali, thereby avoiding the problem of additionally supplementing alkali solution in the extraction stage and reducing the production cost; and recovers calcium oxide and carbon dioxide by calcining calcium slag to supplement the alkali adjustment process and the stripping process respectively, thereby comprehensively utilizing the abundant carbonate resources in the lithium precipitation mother liquor and further reducing the production cost; and at the same time, the addition of calcium oxide can remove fluoride ions with a relatively high concentration in the lithium precipitation mother liquor, thereby facilitating improving product quality.

[0066] In the present invention, the extraction rate of sodium and potassium is extremely low during the extraction stage, and the sodium and potassium ions are discharged along with the extract, thereby improving the product quality.

[0067] During the pyrolysis stage, due to the dissolution equilibrium of lithium carbonate precipitation, there is still a certain concentration of lithium ions in the pyrolysis solution. The present invention improves the recovery rate of lithium by recycling the pyrolysis solution to supplement the water phase of the stripping stage, while avoiding the generation of excessive wastewater and increasing the treatment cost.

[0068] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A novel process for preparing battery-grade lithium carbonate from lithium precipitation mother liquor, characterized in that: The novel process for preparing battery-grade lithium carbonate from lithium precipitation mother solution comprises: S1, mixing quicklime and lithium precipitation mother liquor to adjust alkali and remove fluorine; S2, filtering the calcium ions in the mixed solution of step S1, calcining the filtered calcium slag and then adding quicklime and carbon dioxide; S3, mixing the filtrate obtained in step S2 with an organic extractant for extraction; S4, mixing the loaded organic phase obtained in step S3 with pure water for washing; S5, mixing the washed loaded organic phase obtained in step S4 with pure water and carbon dioxide for stripping; S6, removing oil from the stripping solution obtained in step S5 by using an oil removal resin; S7, removing calcium from the stripping solution after deoiling in step S6 by resin; S8. Pyrolyze the stripping solution obtained in step S7, filter and dry to obtain battery-grade lithium carbonate, and circulate the pyrolysis solution back to the stripping stage to supplement the water phase.

2. The novel process for preparing battery-grade lithium carbonate from lithium precipitation mother solution according to claim 1, characterized in that: The ratio of quicklime added in step S1 to lithium precipitation mother liquor is 10-50 g / L, and the reaction time is 1-2 h.

3. The novel process for preparing battery-grade lithium carbonate from lithium-precipitated mother liquor according to claim 1, characterized in that: The quicklime added in step S1 and the lithium precipitation mother liquor are adjusted to an end point pH of 11 to 13.

5.

4. The novel process for preparing battery-grade lithium carbonate from lithium precipitation mother solution according to claim 1, characterized in that: The volume ratio of the lithium organic extractant added during the extraction in step S3 to the lithium precipitation mother liquor after alkali adjustment is 0.5 to 4:

1.

5. The novel process for preparing battery-grade lithium carbonate from lithium precipitation mother solution according to claim 1, characterized in that: The extractant used in the extraction process of step S3 is a ketone extractant and / or a neutral organic phosphorus oxide extractant.

6. The novel process for preparing battery-grade lithium carbonate from lithium precipitation mother solution according to claim 1, characterized in that: The extraction reaction pH in step S3 is 10.5-13.

7. The novel process for preparing battery-grade lithium carbonate from lithium precipitation mother solution according to claim 1, characterized in that: In the step S4, the volume ratio of the loaded organic phase to pure water is 10 to 30:1 during washing, and the washing water is mixed with the mother liquor after alkali adjustment for extraction.

8. The novel process for preparing battery-grade lithium carbonate from lithium precipitation mother solution according to claim 1, characterized in that: In the step S5, the volume ratio of the loaded organic phase, water and carbon dioxide during the stripping is 0.5-4:1:20-40.

9. The novel process for preparing battery-grade lithium carbonate from lithium precipitation mother solution according to claim 1, characterized in that: The oil removal and calcium removal in steps S6 and S7 are carried out in an oil removal resin column and a calcium removal resin column respectively.

10. The novel process for preparing battery-grade lithium carbonate from lithium precipitation mother solution according to claim 1, characterized in that: In the step S8, the pyrolysis temperature is 70-100° C., the pyrolysis time is 0.75-2 h, and the pyrolysis liquid is circulated back to the stripping section to supplement the water phase.

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