A method for extracting lithium from electrolyte

Abstract

The present invention discloses a method for extracting lithium from electrolyte, which includes crushing waste electrolyte lithium-containing electrolytic waste residue; slurrying the electrolyte and sodium hydroxide solution and filtering; filtering the leached liquid to obtain a first filtrate and a first filter residue; adding malonic acid after hydrating the first filter residue, using ultrasound to assist in leaching and stirring to obtain a second filtrate and a second filter residue; adding sodium hydroxide to the second filtrate for neutralization and impurity removal, filtering, washing, and drying to obtain cryolite and a third filtrate; the third filtrate is electrolyzed to obtain a lithium-containing concentrated solution; sodium carbonate is added to the lithium-containing concentrated solution after lithium precipitation, and a constant temperature water bath is used for heating reaction, and filtering, washing, and drying after the reaction to obtain finished lithium carbonate. The present application can extract lithium with a high recovery rate, and the by-products in the recovery process can be recycled, which can significantly reduce production costs.

Description

Technical Field

[0001] The invention relates to a method for extracting lithium from electrolyte. Background Art

[0002] Lithium-rich aluminum electrolytes are a byproduct of the aluminum industry, presenting a vast inventory. The rational development of these electrolytes and the extraction of their lithium resources can supplement my country's market demand for lithium resources, enabling the resource-based utilization of these electrolytes and reducing dependence on external lithium resources. This is also consistent with the path of green industrial development. Currently, the resource-based utilization of lithium-rich aluminum electrolytes is primarily achieved through inorganic acid digestion followed by the addition of carbonates to obtain the lithium element. This method is costly and complex, and is still under investigation. Summary of the Invention

[0003] The main purpose of the present invention is to provide a method for extracting lithium from electrolyte, aiming to solve the above technical problems.

[0004] To achieve the above object, the present invention provides a method for extracting lithium from an electrolyte, comprising:

[0005] Step 1: crushing and grinding the waste electrolyte containing lithium electrolytic waste residue;

[0006] Step 2: slurrying the electrolyte and sodium hydroxide solution in proportion, leaching and filtering;

[0007] Step 3: filter the leachate to obtain a first filtrate and a first filter residue, and the first filtrate is slurried instead of the sodium hydroxide solution to be recycled;

[0008] Step 4: After the first filter residue is replenished with water, malonic acid is added, and ultrasonic wave-assisted leaching and stirring are performed under certain conditions to obtain a second filtrate and a second filter residue, and the second filter residue can be used as a raw material for carbon recovery;

[0009] Step 5: adding sodium hydroxide to the second filtrate for neutralization and impurity removal, filtering, washing, and drying to obtain cryolite and a third filtrate;

[0010] Step 6: The third filtrate is subjected to electrolysis and electrodialysis to obtain a lithium-containing concentrate and malonic acid that can be added to the step 4;

[0011] Step 7: After lithium is precipitated, sodium carbonate is added to the lithium-containing concentrated solution and heated in a constant temperature water bath for reaction. After the reaction, the solution is filtered, washed, and dried to obtain finished lithium carbonate.

[0012] In one embodiment, the ratio of the electrolyte to the sodium hydroxide solution is 1:10 to 3:10.

[0013] In one embodiment, the concentration of the sodium hydroxide solution is 10%.

[0014] In one embodiment, the steps of slurrying the electrolyte and the sodium hydroxide solution in proportion and filtering after leaching are specifically as follows:

[0015] The electrolyte and sodium hydroxide solution are slurried in proportion and leached at a solid-liquid ratio of 1:3 to 1:3.5 and a temperature of 90°C to 95°C, and then filtered.

[0016] In one embodiment, the step of adding malonic acid after replenishing water to the first filter residue is specifically as follows:

[0017] The first filter residue is watered to form a mixture with a solid-liquid ratio of 1:3, and malonic acid is added to adjust the pH to 3-4.

[0018] In one embodiment, the step of using ultrasound to assist in leaching, stirring and filtering under certain conditions to obtain the second filtrate and the second filter residue is specifically as follows:

[0019] Ultrasonic wave is used to assist leaching at 90° to 95° for 3 to 5 hours, and then stirring and filtering are performed to obtain a second filtrate and a second filter residue.

[0020] In one embodiment, the steps of adding sodium carbonate to the lithium-containing concentrated solution after lithium precipitation and heating the solution in a constant temperature water bath for reaction are specifically as follows:

[0021] After lithium precipitation, the lithium-containing concentrated solution was added with 1.2 times of sodium carbonate and heated in a constant temperature water bath for reaction.

[0022] In the technical solution of the present invention, the lithium-rich aluminum electrolyte is first subjected to alkaline leaching (sodium hydroxide) and then acid leaching and digestion (organic acid) to leach the solid lithium resources into the solution. During the lithium extraction process, the first filtrate obtained after alkaline leaching and filter pressing can be returned to the slurry preparation process for recycling. At the same time, the by-product cryolite obtained in the subsequent process can be sold, and the malonic acid obtained in the electrolysis process of the third filtrate can also be put into the previous process for reuse, and finally the finished lithium carbonate is obtained. In this application, lithium can be extracted with a high recovery rate, and the by-products in the recovery process can be recycled, which can significantly reduce production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 any creative work.

[0024] Figure 1Schematic diagram of the process of extracting lithium from electrolyte according to an embodiment of the present invention.

[0025] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0027] In addition, the terms "first," "second," and so on, used in this disclosure are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referenced. Thus, a feature specified as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of this disclosure, "plurality" means at least two, such as two or three, unless otherwise specifically defined.

[0028] Moreover, 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 ordinary technicians in this field can implement them. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0029] The invention provides a method for extracting lithium from an electrolyte.

[0030] like Figure 1 As shown, the electrolyte lithium extraction method provided by the embodiment of the present invention includes:

[0031] Step 1: crushing and grinding the waste electrolyte containing lithium electrolytic waste residue;

[0032] In this step, the ratio of electrolyte to sodium hydroxide solution is 1:10 to 3:10, and the concentration of the sodium hydroxide solution is 10%.

[0033] Step 2: slurrying the electrolyte and sodium hydroxide solution in proportion, leaching and filtering;

[0034] In this step, the solid-liquid ratio of the electrolyte and the sodium hydroxide solution is 1:3~1:3.5, and the slurry mixing environment temperature is 90℃-95℃, which is mainly used to reduce the consumption of organic acid in the next step and reduce costs.

[0035] Step 3: filter the leachate to obtain a first filtrate and a first filter residue, and the first filtrate is slurried instead of the sodium hydroxide solution to be recycled;

[0036] In this step, the first filter residue is hydrated to form a mixture with a solid-liquid ratio of 1:3, and then malonic acid is added to adjust the pH to 3-4. This step mainly dissolves the lithium in the electrolyte in the form of lithium salt, undergoes a lithiation reaction, and the hydrogen in the organic compound molecule is replaced by lithium to form a complex salt. Organic acid plays a key role in hydrometallurgical processes as a more environmentally friendly leaching agent. Compared with inorganic acids, organic acids have the advantages of good biodegradability, low acidity, low corrosiveness, recyclability, and environmental friendliness, and organic acids usually have chelating or complexing properties, which will produce more efficient recovery efficiency and provide the possibility for subsequent recycling and reuse processes.

[0037] Step 4: After the first filter residue is replenished with water, malonic acid is added, and ultrasonic wave-assisted leaching and stirring are performed under certain conditions to obtain a second filtrate and a second filter residue, and the second filter residue can be used as a raw material for carbon recovery;

[0038] In this step, ultrasonic leaching is performed at 90°-95° ​​for 3 hours with stirring (ultrasound facilitates lithium leaching and increases lithium yield). Filtration produces a second filtrate and a second residue. The flotation method used in the carbon industry is relatively simple to operate, economical, and easy to implement. More importantly, it leverages the hydrophobicity differences between carbon and electrolyte to achieve a good separation of these two valuable components. Therefore, the second residue can be provided to the carbon industry for recycling, thereby reducing production costs.

[0039] Step 5: adding sodium hydroxide to the second filtrate for neutralization and impurity removal, filtering, washing, and drying to obtain cryolite and a third filtrate;

[0040] In this step, the second filtrate contains impure cations such as magnesium, aluminum, and iron. Sodium hydroxide is added primarily to adjust the pH of the solution, reacting with the impurity ions to ultimately precipitate hydroxides. The fluorine removal rate is 98.10%, the aluminum removal rate is 99.08%, and the lithium loss rate is 5.68%. Cryolite, a byproduct, can also be recovered and sold, further reducing production costs.

[0041] Step 6: The third filtrate is subjected to electrolysis and electrodialysis to obtain a lithium-containing concentrate and malonic acid that can be added to the step 4; after lithium precipitation, the lithium-containing concentrate is added with 1.2 times the amount of sodium carbonate and heated in a constant temperature water bath for reaction, and after the reaction, filtered, washed, and dried to obtain the finished lithium carbonate.

[0042] In this step, electrolysis and electrodialysis utilize the selective permeability of the hydrogen and hydroxide ion exchange membranes in the electrode reactions to produce acids and bases and convert salt solutions. The principle is to exploit the redox reactions of the cathode and anode during water electrolysis. Increasing the voltage triggers a reduction reaction at the cathode, where water gains electrons to generate hydrogen and hydroxide. The cations then pass through the cation exchange membrane to the cathode chamber, where a concentrated lithium solution (concentration: 12 g / L) can be recovered. An oxidation reaction occurs at the anode, where water loses electrons to generate oxygen and hydrogen ions. The anions then pass through the anion exchange membrane to the anode chamber, where organic acids can be recovered and regenerated. The pH of the anode solution is 3.

[0043] The technical solutions of the present invention are further illustrated below by specific examples. Those skilled in the art should understand that the examples are only provided to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0044] Example 1

[0045] 1. Crushing and ball milling: Add lithium-containing electrolytic waste slag (lithium content: 1.6284%) into the crusher and perform wet ball milling. After ball milling to 200 mesh, dry it and sieve it to form a gray powder.

[0046] 2. Preparation of sodium hydroxide solution: Add 900g of sodium hydroxide solid to a mixing axe, then add water, stir and dissolve to form a sodium hydroxide solution with a mass fraction of 20%.

[0047] 3. First Alkaline Leaching: Mix 1.5 kg of lithium-containing electrolytic waste residue with 20 wt% sodium hydroxide solution (solid-to-liquid ratio 1:3-3.5) and add it to a stirring axe. Leach at 85°C and a stirring speed of 300 r / min. Keep the temperature for 2 hours, filter press for 0.5 hours, and obtain filtrate 1 and filter residue. The obtained filtrate is returned to step 2 for recycling.

[0048] 4. Second Acid Leaching: Add water to the filter residue from step 3) to prepare a slurry (solid-to-liquid ratio of 1:3-3.5). After thorough mixing, add malonic acid to adjust the slurry pH to 2. Leach using ultrasonic technology at 90°C-95°C, stirring at 300 rpm, and maintaining the leaching temperature for 2 hours. Filter press for 0.5 hours to obtain filtrate 2 and filter residue 2.

[0049] 5. Impurity removal: sodium hydroxide was added to the filtrate in step 4) to adjust the pH value of the solution system to 11, stirred for 30 minutes, filtered, and the filtrate was transported to an electrolysis electrodialysis tank through a pipeline. The filter cake was rinsed with 500 g of pure water and then dried. The filter cake was transferred to a drying oven at a temperature of 75°C and dried for 10 hours to obtain cryolite (SRD characterization).

[0050] 6. Concentration: Add the filtrate from step 5) to an electrolysis and electrodialysis instrument for electrolysis. Increase the voltage by 10%. After electrolysis, organic acid is produced at the anode and a concentrated lithium-containing solution is produced at the cathode. The organic acid is returned to step 4 for recycling.

[0051] 7. Lithium precipitation: Add sodium carbonate (1.2 times the theoretical value) to the concentrated lithium solution in step 6) and heat in a constant temperature water bath for reaction. After the reaction, filter, wash, and dry to obtain lithium carbonate.

[0052] The overall process is based on the lithium and fluorine contents in the lithium-containing waste electrolyte, with a lithium recovery rate of 91% and a fluorine removal rate of 97%.

[0053] Example 2

[0054] 1. Crushing and ball milling: Add lithium-containing electrolytic waste slag (lithium content: 1.6284%) into the crusher and perform wet ball milling. After ball milling to 200 mesh, dry it and sieve it to form a gray powder.

[0055] 2. Preparation of sodium hydroxide solution: Add 675g of sodium hydroxide solid to a mixing axe, then add water, stir and dissolve to form a sodium hydroxide solution with a mass fraction of 15%.

[0056] 3. First alkaline leaching: Add 1.5 kg of lithium-containing electrolytic waste residue and mix with 15 wt% sodium hydroxide solution (solid-to-liquid ratio 1:3-3.5). Leach at 90°C and stirring at 300 rpm. Keep warm for 2.5 hours, filter press for 1 hour, and obtain a filtrate and a filter residue. The filtrate is returned to step 2 for recycling.

[0057] 4. Second Acid Leaching: Add water to the residue from step 3) to prepare a slurry (solid-to-liquid ratio of 1:3-3.5). After thorough mixing, add malonic acid to adjust the slurry pH to 3. Leach using ultrasonic-assisted leaching at 90°C-95°C, stirring at 300 rpm, and maintaining the leaching temperature for 2.5 hours. Filter press for 1 hour to obtain a secondary filtrate and secondary residue.

[0058] 5. Impurity removal: sodium hydroxide was added to the filtrate in step 4) to adjust the pH value of the solution system to 12, stirred for 40 minutes, filtered, and the filtrate was transported to an electrolysis electrodialysis cell through a pipeline. The filter cake was rinsed with 500 g of pure water and then dried. The filter cake was transferred to a drying oven at a temperature of 80°C and dried for 11 hours to obtain cryolite (characterized by SRD).

[0059] 6. Concentration: Add the filtrate from step 5) to an electrolysis and electrodialysis instrument for electrolysis. Increase the voltage by 15%. After electrolysis, organic acid is produced at the anode and a concentrated lithium-containing solution is produced at the cathode. The organic acid is returned to step 4 for recycling.

[0060] 7. Lithium precipitation: Add sodium carbonate (1.2 times the theoretical value) to the concentrated lithium solution in step 6) and heat in a constant temperature water bath for reaction. After the reaction, filter, wash, and dry to obtain lithium carbonate.

[0061] The overall process has a lithium recovery rate of 91.5% and a fluorine removal rate of 97%, based on the lithium and fluorine contents in the lithium-containing waste electrolyte.

[0062] Example 3

[0063] 1. Crushing and ball milling: Add lithium-containing electrolytic waste slag (lithium content: 1.6284%) into the crusher and perform wet ball milling. After ball milling to 200 mesh, dry it and sieve it to form a gray powder.

[0064] 2. Preparation of sodium hydroxide solution: Add 450g of sodium hydroxide solid to a mixing axe, then add water, stir and dissolve to form a sodium hydroxide solution with a mass fraction of 10%.

[0065] 3. First Alkaline Leaching: Mix 1.5 kg of lithium-containing electrolytic waste residue with 10 wt% sodium hydroxide solution (solid-to-liquid ratio 1:3-3.5) and add it to a stirring axe. Leach at 95°C and a stirring speed of 300 r / min. Keep the temperature for 2.5 hours, filter press for 1 hour, and obtain filtrate 1 and filter residue. The obtained filtrate is returned to step 2 for recycling.

[0066] 4. Second Acid Leaching: Add water to the filter residue from step 3) to prepare a slurry (solid-to-liquid ratio of 1:3-3.5). After thorough mixing, add malonic acid to adjust the slurry pH to 4. Leach using ultrasonic technology at 90°C-95°C, stirring at 300 rpm, and maintaining the leaching temperature for 3 hours. Filter press for 1.5 hours to obtain filtrate II and filter residue II.

[0067] 5. Impurity removal: sodium hydroxide was added to the filtrate in step 4) to adjust the pH value of the solution system to 13, stirred for 50 minutes, filtered, and the filtrate was transported to an electrolysis electrodialysis cell through a pipeline. The filter cake was rinsed with 500 g of pure water and then dried. The filter cake was transferred to a drying oven at a temperature of 85°C and dried for 12 hours to obtain cryolite (SRD characterization).

[0068] 6. Concentration: Add the filtrate from step 5) to an electrolysis and electrodialysis instrument for electrolysis. Increase the voltage by 20%. After electrolysis, organic acid is produced at the anode and a concentrated lithium-containing solution is produced at the cathode. The organic acid is returned to step 4 for recycling.

[0069] 7. Lithium precipitation: Add sodium carbonate (1.2 times the theoretical value) to the concentrated lithium solution in step 6) and heat in a constant temperature water bath for reaction. After the reaction, filter, wash, and dry to obtain lithium carbonate.

[0070] The overall process has a lithium recovery rate of 92.1% and a fluorine removal rate of 97%, based on the lithium and fluorine contents in the lithium-containing waste electrolyte.

[0071] In summary, the lithium-rich aluminum electrolyte is first subjected to alkali leaching (sodium hydroxide) and then acid leaching and digestion (organic acid) to leach the solid lithium resources into the solution. In the process of lithium extraction, the first filtrate obtained after alkali leaching and filter pressing can be returned to the slurry preparation process for recycling. At the same time, the by-product cryolite obtained in the subsequent process can be sold, and the malonic acid obtained in the electrolysis process of the third filtrate can also be put into the previous process for reuse, and finally the finished lithium carbonate is obtained. In this application, lithium can be extracted with a high recovery rate, and the by-products in the recovery process can be recycled, which can significantly reduce production costs.

[0072] 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 transformations made by using the contents of the present invention description and drawings under the concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for extracting lithium from an electrolyte, characterized in that: The electrolyte lithium extraction method comprises: Step 1: crushing and grinding the waste electrolyte containing lithium electrolytic waste residue; Step 2: slurrying the electrolyte and sodium hydroxide solution in proportion and leaching; Step 3: filter the leachate to obtain a first filtrate and a first filter residue, and the first filtrate is slurried instead of the sodium hydroxide solution to be recycled; Step 4: After the first filter residue is hydrated, a mixture with a solid-liquid ratio of 1:3 is formed, and malonic acid is added to adjust the pH to 3-4. Ultrasonic stirring is performed at 90°-95° ​​to assist leaching for 3-5 hours, and a second filtrate and a second filter residue are obtained after filtration. The second filter residue is used as a raw material for carbon recovery; Step 5: adding sodium hydroxide to the second filtrate for neutralization and impurity removal, filtering, washing, and drying to obtain cryolite and a third filtrate; Step 6: The third filtrate is subjected to electrolysis and electrodialysis to obtain a lithium-containing concentrate and malonic acid that can be added to the step 4; Step 7: Add sodium carbonate to the lithium-containing concentrated solution and heat it in a constant temperature water bath for reaction. After the reaction, filter, wash and dry to obtain finished lithium carbonate.

2. The electrolyte lithium extraction method according to claim 1, characterized in that The ratio of the electrolyte to the sodium hydroxide solution is 1:10 to 3:

10.

3. The electrolyte lithium extraction method according to claim 1, characterized in that The concentration of the sodium hydroxide solution is 10%.

4. The electrolyte lithium extraction method according to claim 1, characterized in that The steps of slurrying the electrolyte and the sodium hydroxide solution in proportion and filtering after leaching are specifically as follows: The electrolyte and sodium hydroxide solution are slurried in proportion and leached at a solid-liquid ratio of 1:3 to 1:3.5 and a temperature of 90°C to 95°C, and then filtered.

5. The electrolyte lithium extraction method according to claim 1, characterized in that The steps of adding sodium carbonate to the lithium-containing concentrate and heating the reaction in a constant temperature water bath are specifically as follows: The lithium-containing concentrated solution was added with 1.2 times of sodium carbonate and heated in a constant temperature water bath for reaction.

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