Method for recovering valuable metals from subcritical lithium extraction residues
By using the stirring reaction under the synergistic effect of formic acid and oxygen, and the separation based on differences in solubility and complexing ability, the problem of efficient separation of nickel, cobalt, and manganese in subcritical lithium extraction residue was solved, achieving efficient and environmentally friendly metal recovery, simplifying the process and reducing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-30
- Publication Date
- 2026-04-17
AI Technical Summary
Existing technologies for recovering subcritical lithium extraction residues suffer from problems such as high acid consumption, high cost, lengthy process flow, low efficiency, and difficulty in metal separation, especially in efficiently separating valuable metals such as nickel, cobalt, and manganese, as well as impurity elements.
The reaction is carried out under stirring with the synergistic effect of formic acid and oxygen. Then, nickel, cobalt and manganese are separated in sequence by differences in solubility and complexing ability. The process includes steps such as distillation, calcination, low acid leaching, extraction and carbon dioxide charging. The selective dissolution and separation of nickel, cobalt and manganese are achieved by utilizing differences in solubility and complexing ability.
The process has been simplified, the recovery rate of lithium, nickel, cobalt and manganese has been improved, the cost and environmental pollution have been reduced, and efficient and environmentally friendly metal separation has been achieved, avoiding high-temperature roasting and the use of large amounts of acids and alkalis.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of waste lithium battery recycling technology, specifically to a method for recovering valuable metals from subcritical lithium extraction residue. Background Technology
[0002] With the rapid development of the new energy vehicle industry, the demand for lithium-ion batteries has surged, making the recycling of spent lithium-ion batteries increasingly urgent and important. Subcritical lithium extraction residue, the solid residue remaining after lithium extraction from spent lithium-ion batteries under subcritical hydrothermal conditions, has a complex and varied composition. It is rich in high-value transition metals such as nickel, cobalt, and manganese, as well as their oxides / carbonates, and contains various impurities such as lithium, iron, aluminum, and copper. This complexity directly leads to multiple challenges in the recycling process, including high acid consumption, increased costs, lengthy and inefficient processes, difficulty in metal separation, and poor performance of recycled materials. Specifically, traditional recycling methods often rely on high-concentration acid leaching, which not only increases raw material costs but may also generate large amounts of acidic wastewater requiring additional treatment. The lengthy multi-step separation and purification process further reduces recycling efficiency and increases time and labor costs. At the same time, interference from transition metals and impurities with similar chemical properties makes efficient separation extremely difficult.
[0003] Therefore, researching and developing an efficient, environmentally friendly, and economical method for recovering subcritical lithium extraction residue is of great practical significance. Summary of the Invention
[0004] In view of the content mentioned in the background art, the purpose of this invention is to provide a method for recovering valuable metals from subcritical lithium extraction residue, which utilizes differences in solubility and complexation ability to achieve sequential separation of nickel, cobalt and manganese.
[0005] To achieve the above objectives, the present invention specifically adopts the following technical solution: This invention provides a method for recovering valuable metals from subcritical lithium extraction residue, comprising the following steps: S1. Mix the subcritical lithium extraction residue with formic acid, stir and react under an oxygen atmosphere, filter, and obtain a lithium-containing solution and solid residue. S2. Distill the lithium-containing solution to separate lithium formate, calcine to obtain crude lithium carbonate, and then purify it to obtain high-purity lithium carbonate. S3. The solid residue is leached with low acid, filtered to obtain leachate, and an extractant is added to the leachate to remove impurities, resulting in a nickel-cobalt-manganese raffinate. S4. Carbon dioxide is introduced into the nickel-cobalt-manganese raffinate, and the mixture is filtered to obtain a carbonate mixture. Deionized water is added to the carbonate mixture, and carbon dioxide is introduced again and filtered. This process is repeated several times until the nickel is completely dissolved. The filtrates are then combined and aged to obtain basic nickel carbonate precipitate. S5. Place the final filtered solid in ammonia water, sonicate, filter, and obtain a cobalt-containing ammonia complex solution and manganese carbonate; acidify the cobalt-containing ammonia complex solution, heat, add sodium carbonate solution, and filter to obtain cobalt carbonate.
[0006] As a preferred embodiment, the main metal elements and their contents in the subcritical lithium extraction residue of S1 are: Ni 15%-20%, Co 15%-20%, Mn 20%-30%, Li 0.01%-0.1%, Fe 0.01%-0.06%, Al 2%-3%, Cu 0.01%-0.05%.
[0007] In a preferred embodiment, the solid-liquid ratio of the subcritical lithium extraction residue and formic acid in S1 is 1:(4-6), with the unit of solid-liquid ratio being g:mL; the concentration of the formic acid is 95%-99%.
[0008] In a preferred embodiment, the oxygen atmosphere in S1 is as follows: oxygen is continuously introduced at a flow rate of 25-35 cc / min; the temperature of the stirring reaction is 70-90℃, and the time is 15-20 h.
[0009] This invention uses formic acid as the main driving force for lithium extraction, introduces an appropriate amount of oxygen to maintain the stability of the reaction environment, and destroys the structure of the subcritical lithium extraction residue; oxygen can oxidize the reducing substances generated in the reaction, prevent formic acid from being excessively consumed, thereby maintaining acidic activity and improving lithium leaching efficiency.
[0010] In a preferred embodiment, the distillation temperature in S2 is 130-140℃; the calcination temperature is 400-500℃; and acetone is used to purify the crude lithium carbonate. Formic acid recovered during distillation can be returned to S1 for reuse; acetone, when miscible with water, reduces the solution polarity, disrupts the hydration layer of lithium carbonate, and promotes its crystallization, achieving further purification.
[0011] As a preferred embodiment, the low-acid leaching described in S3 specifically involves using a 1-2 mol / L sulfuric acid solution and leaching at 60-80°C for 0.5-2 hours.
[0012] In a preferred embodiment, the extractant in S3 is 15 vol% di-(2-ethylhexyl)phosphoric acid, and the diluent is sulfonated kerosene; the O / A ratio is 1:1, and the pH is adjusted to 0.8. The removal rates of solid residue leachate by this extractant are: iron ≥87.8%, aluminum ≥96.5%, and copper ≥88.6%, with nickel, cobalt, and manganese losses not exceeding 1.2%.
[0013] In a preferred embodiment, the pH of the nickel-cobalt-manganese raffinate in step S4 needs to be adjusted to 7.5-8.0 before carbon dioxide is introduced. The initial carbon dioxide introduction volume is 0.03%-0.05% at a temperature of 20-25°C. Subsequent repeated carbon dioxide introductions are carried out at a pressure of 0.4-0.6 MPa, a temperature of 38-42°C, and a time of 10-14 h. For the nickel-cobalt-manganese raffinate, the process of this invention first introduces carbon dioxide. By adjusting specific parameters, basic nickel carbonate, cobalt carbonate, and manganese carbonate are produced. The resulting solid mixture is then repeatedly treated with deionized water and carbon dioxide at a specific pressure. At this pressure, the solubility of basic nickel carbonate reaches a high value, while the increased carbon dioxide pressure strongly inhibits the dissolution of cobalt carbonate and manganese carbonate, resulting in only basic nickel carbonate dissolving to form a filtrate. This process is repeated to completely dissolve the residual nickel in the solid. Finally, the filtrates are combined, aged, and the basic nickel carbonate is redeprecipitated.
[0014] In a preferred embodiment, the concentration of the ammonia water in S5 is 5-10 mol / L, the ultrasonic frequency is 30-40 kHz, and the time is 10-20 min.
[0015] In a preferred embodiment, the acidification in step S5 involves adding hydrochloric acid to the cobalt-ammonia complex solution to adjust the pH to 5.5-6.5, and heating at a temperature of 65-75°C. Cobalt ions react with ammonia to form a stable soluble complex [Co(NH3)6]. 2+ However, manganese ions, due to their weak complexing ability, remain in the form of manganese carbonate; ultimately, acidification destroys [Co(NH3)6]. 2+ Release cobalt ions.
[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. The process of this invention utilizes the synergistic effect of formic acid and oxygen to effectively leach subcritical lithium extraction residues, resulting in higher selectivity for lithium and a simplified process. Formic acid can be recycled and reused, reducing raw material waste and environmental pollution, and lowering costs. Oxygen, as an oxidant, avoids the use of toxic oxidants, making it more environmentally friendly.
[0017] 2. The method of the present invention is simple to operate. By controlling the carbon dioxide charging and dissolution parameters, a carrier is provided for metal separation. The selective dissolution of nickel is achieved by utilizing the difference in solubility (basic nickel carbonate dissolves preferentially under high pressure carbon dioxide), and the sequential separation of cobalt and manganese is achieved by utilizing the difference in complexing ability (cobalt ions strongly complex with ammonia).
[0018] 3. The process of this invention has a high recovery rate of lithium, nickel, cobalt and manganese in subcritical lithium extraction residue, and avoids high-temperature roasting and the use of large amounts of acid and alkali, effectively reducing wastewater generation and energy consumption. Detailed Implementation
[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with embodiments. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.
[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.
[0021] The subcritical lithium extraction residue used in this invention mainly contains transition metals nickel, cobalt, and manganese, their oxides and carbonates, as well as small amounts of lithium, iron, aluminum, and copper. The main metal elements and their contents are as follows: Table 1. Elemental content of subcritical lithium extraction residue
[0022] Example 1 A method for recovering valuable metals from subcritical lithium extraction residue includes the following steps: Step 1: Mix the subcritical lithium extraction residue with 98% formic acid at a solid-liquid ratio of 1:5, then continuously introduce oxygen (flow rate 30 cc / min) while heating to 80°C, and stir the reaction for 18 h under these conditions; filter to obtain a lithium-containing solution and solid residue.
[0023] Step 2: Distill the lithium-containing solution at 135℃ to separate lithium formate, then calcine at 450℃ for 1 h to obtain crude lithium carbonate. Dissolve the crude lithium carbonate in sufficient deionized water, filter to remove water-insoluble impurities, add an appropriate amount of acetone, stir slowly, precipitate, let stand, filter, wash the product with a small amount of acetone to remove residual impurities and water, and dry to obtain high-purity lithium carbonate.
[0024] Step 3: The solid residue obtained in Step 1 is leached with 1.5 mol / L sulfuric acid solution at 70℃ for 1 h, and the leachate is obtained by filtration. Extraction agent (15 vol% di-(2-ethylhexyl)phosphoric acid / sulfonated kerosene) is added to the leachate, with an O / A ratio of 1:1, and the pH is adjusted to 0.8. The extract is then extracted for 15 min to remove impurities, resulting in a nickel-cobalt-manganese raffinate.
[0025] Step 4: Adjust the pH of the raffinate to 7.5 with sodium bicarbonate. At room temperature, introduce carbon dioxide (0.04% by volume, dissolve for 12 h) into the nickel-cobalt-manganese raffinate and filter to obtain a carbonate mixture. Add deionized water to the mixture and continue to introduce carbon dioxide at 0.5 MPa at 40°C for 12 h to dissolve. Filter. Repeat this process several times until the nickel is completely dissolved. Then combine the filtrates and age them to obtain basic nickel carbonate precipitate.
[0026] Step 5: Place the solid obtained from the final filtration in Step 4 into 7 mol / L ammonia water and sonicate it (35 kHz, 15 min). Filter to obtain a cobalt-containing ammonia complex solution and manganese carbonate solid. Add hydrochloric acid (0.5 mol / L) to the cobalt-containing ammonia complex solution to adjust the pH to 6, heat to 70°C, add sodium carbonate solution to precipitate, and filter to obtain cobalt carbonate solid.
[0027] Example 2 A method for recovering valuable metals from subcritical lithium extraction residue includes the following steps: Step 1: Mix the subcritical lithium extraction residue with 98% formic acid at a solid-liquid ratio of 1:4, then continuously introduce oxygen (flow rate 25 cc / min) while heating to 70°C, and stir the reaction for 20 h under these conditions; filter to obtain a lithium-containing solution and solid residue.
[0028] Step 2: Distill the lithium-containing solution at 130℃ to separate lithium formate, then calcine at 500℃ for 1 h to obtain crude lithium carbonate. Dissolve the crude lithium carbonate in sufficient deionized water, filter to remove water-insoluble impurities, add an appropriate amount of acetone, stir slowly, precipitate, let stand, filter, wash the product with a small amount of acetone to remove residual impurities and water, and dry to obtain high-purity lithium carbonate.
[0029] Step 3: The solid residue obtained in Step 1 is leached with 1 mol / L sulfuric acid solution at 80℃ for 1 h, and the leachate is obtained by filtration. Extraction agent (15 vol% di-(2-ethylhexyl)phosphoric acid / sulfonated kerosene) is added to the leachate, with an O / A ratio of 1:1, and the pH is adjusted to 0.8. The extract is then extracted for 15 min to remove impurities, resulting in a nickel-cobalt-manganese raffinate.
[0030] Step 4: Adjust the pH of the raffinate to 7.5 with sodium bicarbonate. At room temperature, introduce carbon dioxide (0.04% by volume, dissolve for 12 h) into the nickel-cobalt-manganese raffinate and filter to obtain a carbonate mixture. Add deionized water to the mixture and continue to introduce carbon dioxide at 0.5 MPa at 40°C for 12 h to dissolve. Filter. Repeat this process several times until the nickel is completely dissolved. Then combine the filtrates and age them to obtain basic nickel carbonate precipitate.
[0031] Step 5: Place the solid obtained from the final filtration in Step 4 into 5 mol / L ammonia water and sonicate (35 kHz, 20 min). Filter to obtain a cobalt-containing ammonia complex solution and manganese carbonate solid. Add hydrochloric acid (0.5 mol / L) to the cobalt-containing ammonia complex solution to adjust the pH to 6, heat to 70℃, add sodium carbonate solution to precipitate, and filter to obtain cobalt carbonate solid.
[0032] Example 3 A method for recovering valuable metals from subcritical lithium extraction residue includes the following steps: Step 1: Mix the subcritical lithium extraction residue with 98% formic acid at a solid-liquid ratio of 1:6, then continuously introduce oxygen (flow rate 35 cc / min) while heating to 90°C, and stir the reaction for 15 h under these conditions; filter to obtain a lithium-containing solution and solid residue.
[0033] Step 2: Distill the lithium-containing solution at 140℃ to separate lithium formate, then calcine at 400℃ for 1 h to obtain crude lithium carbonate. Dissolve the crude lithium carbonate in sufficient deionized water, filter to remove water-insoluble impurities, add an appropriate amount of acetone, stir slowly, precipitate, let stand, filter, wash the product with a small amount of acetone to remove residual impurities and water, and dry to obtain high-purity lithium carbonate.
[0034] Step 3: The solid residue obtained in Step 1 is leached with 2 mol / L sulfuric acid solution at 60℃ for 1 h, and the leachate is obtained by filtration. Extraction agent (15 vol% di-(2-ethylhexyl)phosphoric acid / sulfonated kerosene) is added to the leachate, with an O / A ratio of 1:1, and the pH is adjusted to 0.8. The extract is then extracted for 15 min to remove impurities, resulting in a nickel-cobalt-manganese raffinate.
[0035] Step 4: Adjust the pH of the raffinate to 7.5 with sodium bicarbonate. At room temperature, introduce carbon dioxide (0.04% by volume, dissolve for 12 h) into the nickel-cobalt-manganese raffinate and filter to obtain a carbonate mixture. Add deionized water to the mixture and continue to introduce carbon dioxide at 0.5 MPa at 40°C for 12 h to dissolve. Filter. Repeat this process several times until the nickel is completely dissolved. Then combine the filtrates and age them to obtain basic nickel carbonate precipitate.
[0036] Step 5: Place the solid obtained from the final filtration in Step 4 into 10 mol / L ammonia water and sonicate it (35 kHz, 10 min). Filter to obtain a cobalt-containing ammonia complex solution and manganese carbonate solid. Add hydrochloric acid (0.5 mol / L) to the cobalt-containing ammonia complex solution to adjust the pH to 6, heat to 70℃, add sodium carbonate solution to precipitate, and filter to obtain cobalt carbonate solid.
[0037] Comparative Example 1 The steps and parameters are the same as in Example 1, except that oxygen is not introduced in step one.
[0038] Comparative Example 2 Referring to the steps and parameters of Example 1, the only difference is that the pressure value of the carbon dioxide repeated in step four is atmospheric pressure.
[0039] Comparative Example 3 Referring to the steps and parameters of Example 1, the only difference is that the pressure value of the subsequent repeated carbon dioxide filling in step four is 3 MPa.
[0040] The purity of the products obtained from the above examples and comparative examples (calculated as lithium carbonate, basic nickel carbonate, cobalt carbonate, and manganese carbonate) was tested and the recovery rate was calculated. The results are shown in Table 2.
[0041] Table 2 Test Results
[0042] The test results show that the process of this invention has good repeatability and good recovery effect on metal elements in subcritical lithium extraction residue. The lithium recovery rate exceeds 97%, and the recovery rates of transition metals nickel, cobalt, and manganese are all above 96%-98%. Comparing the test results of Comparative Example 1, it can be seen that oxygen can maintain the stability of the reaction environment and disrupt the structure of the subcritical lithium extraction residue. This not only significantly improves the lithium leaching efficiency but also has a key impact on the recovery of nickel, cobalt, and manganese in the subsequent lithium extraction solid residue. Comparing the test results of Comparative Example 2, it can be seen that the solubility of basic nickel carbonate under normal pressure carbon dioxide is insufficient. Even with repeated addition of water and carbon dioxide, a considerable portion of nickel remains undissolved in the solid, leading to a decrease in nickel recovery and affecting the purity of subsequent cobalt and manganese products. Comparing the test results of Comparative Example 3, it can be seen that excessively high pressure carbon dioxide causes partial dissolution of cobalt carbonate and manganese carbonate, resulting in a decrease in the purity of the three products and a significant decrease in the recovery rate.
[0043] The embodiments described above are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they are not intended to limit the present invention. It should be noted that various changes and modifications can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the concept and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for recovering valuable metals from subcritical lithium extraction residue, characterized in that, Includes the following steps: S1. Mix the subcritical lithium extraction residue with formic acid, stir and react under an oxygen atmosphere, filter, and obtain a lithium-containing solution and solid residue. S2. Distill the lithium-containing solution to separate lithium formate, calcine to obtain crude lithium carbonate, and then purify it to obtain high-purity lithium carbonate. S3. The solid residue is leached with low acid, filtered to obtain leachate, and an extractant is added to the leachate to remove impurities, resulting in a nickel-cobalt-manganese raffinate. S4. Carbon dioxide is introduced into the nickel-cobalt-manganese raffinate, and the mixture is filtered to obtain a carbonate mixture. Deionized water is added to the carbonate mixture, and carbon dioxide is introduced again and filtered. This process is repeated several times until the nickel is completely dissolved. The filtrates are then combined and aged to obtain basic nickel carbonate precipitate. S5. Place the final filtered solid in ammonia water, sonicate, filter, and obtain a cobalt-containing ammonia complex solution and manganese carbonate; acidify the cobalt-containing ammonia complex solution, heat, add sodium carbonate solution, and filter to obtain cobalt carbonate.
2. The method for recovering valuable metals from subcritical lithium extraction residue according to claim 1, characterized in that, The main metal elements and their contents in the subcritical lithium extraction residue described in S1 are: Ni 15%-20%, Co 15%-20%, Mn 20%-30%, Li 0.01%-0.1%, Fe 0.01%-0.06%, Al 2%-3%, Cu 0.01%-0.05%.
3. The method for recovering valuable metals from subcritical lithium extraction residue according to claim 1, characterized in that, The solid-liquid ratio of the subcritical lithium extraction residue and formic acid in S1 is 1:(4-6), with the unit of solid-liquid ratio being g:mL; the concentration of the formic acid is 95%-99%.
4. The method for recovering valuable metals from subcritical lithium extraction residue according to claim 1, characterized in that, The oxygen atmosphere described in S1 is as follows: oxygen is continuously introduced at a flow rate of 25-35 cc / min; the temperature of the stirring reaction is 70-90℃, and the time is 15-20 h.
5. The method for recovering valuable metals from subcritical lithium extraction residue according to claim 1, characterized in that, The distillation temperature in S2 is 130-140℃; the calcination temperature is 400-500℃; and the crude lithium carbonate is purified using acetone.
6. The method for recovering valuable metals from subcritical lithium extraction residue according to claim 1, characterized in that, The low-acid leaching described in S3 specifically involves using a 1-2 mol / L sulfuric acid solution and leaching at 60-80℃ for 0.5-2 hours.
7. The method for recovering valuable metals from subcritical lithium extraction residue according to claim 1, characterized in that, The extractant in S3 is 15 vol% di-(2-ethylhexyl)phosphoric acid, and the diluent is sulfonated kerosene; the O / A ratio is 1:1, and the pH is adjusted to 0.
8.
8. The method for recovering valuable metals from subcritical lithium extraction residue according to claim 1, characterized in that, Before introducing carbon dioxide into the nickel-cobalt-manganese raffinate described in S4, the pH needs to be adjusted to 7.5-8.0 with sodium bicarbonate; the initial carbon dioxide injection volume is 0.03%-0.05% at a temperature of 20-25℃; subsequent repeated carbon dioxide injections are carried out at a pressure of 0.4-0.6 MPa, a temperature of 38-42℃, and a time of 10-14 h.
9. The method for recovering valuable metals from subcritical lithium extraction residue according to claim 1, characterized in that, The concentration of ammonia in S5 is 5-10 mol / L, the ultrasonic frequency is 30-40 kHz, and the time is 10-20 min.
10. The method for recovering valuable metals from subcritical lithium extraction residue according to claim 1, characterized in that, The acidification described in S5 involves adding hydrochloric acid to a solution containing a cobalt-ammonia complex to adjust the pH to 5.5-6.5, and heating at a temperature of 65-75°C.