A ternary eutectic solvent and application thereof in separating lithium and transition metals in lithium battery leaching solution

Abstract

The application belongs to the technical field of hydrometallurgy, and particularly relates to a ternary eutectic solvent and application thereof in separating lithium and transition metals in a lithium battery leaching solution. The ternary eutectic solvent is obtained by mixing propylcaine, lauric acid and tributyl phosphate according to a molar ratio of 1:1.5:(0.5-2). The method for separating lithium and valuable metals in waste ternary lithium batteries by using the ternary eutectic solvent comprises the following steps: (1) taking the ternary eutectic solvent as an organic phase, adding the lithium battery leaching solution into the organic phase for extraction, and centrifuging to separate phases, so as to obtain a nickel-cobalt-manganese loaded organic phase and a lithium-containing raffinate; and (2) adding a stripping agent into the nickel-cobalt-manganese loaded organic phase for back extraction, and centrifuging to separate phases, so as to obtain a nickel-cobalt-manganese stripping solution and a regenerated organic phase. The separation method has excellent selective extraction effect.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgical technology, specifically relating to a ternary eutectic solvent and its application in separating lithium and transition metals in lithium battery leachate. Background Technology

[0002] In the global drive for green energy transformation, lithium-ion batteries (LIBs), with their superior energy density, have become core components of electric vehicles, portable electronics, and renewable energy storage, significantly reducing the transportation sector's reliance on fossil fuels. As a core battery material, lithium possesses unique advantages in the energy sector due to its lightweight properties; industry research indicates that global demand for lithium carbonate may climb to 3.37 million tons by 2030. Meanwhile, data shows that the recovery rate (RC) of transition metals such as nickel and cobalt in waste LIBs is leading, while the natural reserves of these metals are rapidly decreasing. It is predicted that the Chinese market for LIBs used in electric vehicles will exceed US$148.6 billion by 2026. However, the rapid development of the LIB industry has brought two problems: First, the supply shortage of key metals such as lithium, nickel, and cobalt is becoming increasingly severe; second, if waste LIBs are not properly disposed of, the high-grade valuable metals they contain (far exceeding the content of ore) will result in a huge waste of resources, while heavy metals and electrolyte components in the batteries may damage the ecological environment, which conflicts with the international community's advocacy of sustainable development and resource recycling.

[0003] Currently, the recycling technology for waste lithium-ion batteries is mainly based on two process routes: pyrometallurgy and hydrometallurgy. Compared with the high energy consumption and high pollution of pyrometallurgy, hydrometallurgy has advantages such as low energy consumption, environmental friendliness and high recovery rate, which are more in line with the requirements of green and sustainable development. A typical hydrometallurgical process includes: (1) Pretreatment stage: the battery components are initially separated by physical sorting (such as crushing, screening, magnetic separation, etc.); (2) Acid leaching stage: inorganic acid leaching agents (usually hydrochloric acid or sulfuric acid, because they are more economical than other reagents) are used to dissolve the valuable metals in the electrode materials to form a leachate containing Li, Co, Ni and Mn; (3) Metal separation stage: the leachate is purified and the components are separated. Among them, solvent extraction technology has become the core means to achieve efficient separation of multiple metals due to its simple operation, controllable recovery rate (usually >95%) and adjustable selectivity.

[0004] In terms of existing technologies, CN114717419A discloses a synergistic extraction process based on acidic phosphorus extractants. This technology mainly targets battery materials containing nickel, cobalt, and manganese, achieving the separation and recovery of these valuable metals. CN111850302B discloses a process for separating metals from spent lithium batteries using diketone compounds as extractants and organophosphorus compounds as synergists. After multi-stage countercurrent extraction, the extraction rates of nickel, cobalt, and manganese can all reach over 97%. However, these existing extraction processes generally require multi-stage extraction operations, leading to increased extractant consumption, which not only increases process costs but also wastes resources. The traditional extractants used, such as acidic phosphorus and diketone compounds, have inherent drawbacks such as high volatility and high environmental toxicity. It is difficult to simultaneously ensure high extraction rates (e.g., over 99%) and ease of operation and environmental friendliness. Therefore, developing a green solvent system that combines high extraction efficiency, ease of operation, and environmental friendliness has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] This invention addresses the shortcomings of existing technologies by providing a ternary eutectic solvent and its application in separating lithium and transition metals from lithium battery leachate.

[0006] To achieve the objectives of this invention, the technical solution adopted is as follows: The first aspect of the present invention provides a ternary eutectic solvent, wherein the eutectic solvent is obtained by mixing prilocaine, lauric acid and tributyl phosphate in a molar ratio of 1:1.5:(0.5-2).

[0007] Preferably, the mixing temperature is 70–80°C.

[0008] Preferably, the structural formulas of prilocaine, lauric acid, and tributyl phosphate are as follows:

[0009] The second aspect of this invention provides the application of the ternary eutectic solvent described in the first aspect in separating lithium and transition metals in lithium battery leachate.

[0010] A third aspect of this invention provides a method for separating lithium and transition metals in lithium battery leaching solutions using a ternary eutectic solvent, comprising the following steps: (1) Using the ternary eutectic solvent described in the first aspect as the organic phase, the lithium battery leaching solution is added to the organic phase for extraction. After extraction, the phases are separated by centrifugation to obtain a transition metal-supported organic phase and a lithium-containing raffinate. (2) The back-extraction agent is added to the transition metal-loaded organic phase in step (2) for back-extraction. After the back-extraction is completed, the phases are separated by centrifugation to obtain the transition metal back-extraction solution and the regenerated organic phase.

[0011] Preferably, the lithium battery leachate is prepared by dissolving lithium battery electrode materials with inorganic acid.

[0012] Preferably, the inorganic acid is hydrochloric acid, and the pH of the lithium battery leachate is 1 to 6.

[0013] More preferably, the pH of the lithium battery leachate is 4.

[0014] Preferably, the lithium battery leaching solution contains Li + The concentration is 200–400 mg / L, Ni 2+ The concentration is 1300–1600 mg / L, Co 2+ The concentration is 500-800 mg / L, Mn 2+ The concentration is 700–900 mg / L.

[0015] Preferably, the transition metal is nickel, cobalt, or manganese.

[0016] Preferably, in step (1), the volume ratio of lithium battery leaching solution to organic phase is 3:1 to 1:3.

[0017] More preferably, in step (1), the volume ratio of lithium battery leaching solution to organic phase is 1:1.

[0018] Preferably, the extraction temperature in step (1) is 10–30°C.

[0019] Preferably, in step (2), the stripping agent is 2 mol / L HCl, and the volume ratio of the stripping agent to the transition metal supported organic phase is (1-3):1.

[0020] Preferably, the temperature for back-extraction in step (3) is 10–30°C.

[0021] Preferably, before extraction in step (1), the mixture is stirred for 10 to 15 minutes and the stirring speed is 400 to 600 r / min; the centrifugation speed in step (1) is 8000 to 9000 r / min and the centrifugation time is 5 to 10 minutes.

[0022] Preferably, in step (2), the mixture is stirred before extraction for 10 to 15 minutes at a speed of 500 to 1000 r / min; in step (2), the centrifugation speed is 9000 to 10000 r / min and the centrifugation time is 5 to 10 minutes.

[0023] (1) In this invention, prilocaine, lauric acid and tributyl phosphate are mixed in a molar ratio to obtain a ternary eutectic solvent. The ternary eutectic solvent is used as the organic phase for extraction, which has excellent selective extraction effect on lithium and ensures high purity retention of lithium.

[0024] (2) The method of separating lithium and transition metals in lithium battery leachate of the present invention can efficiently recover valuable metals. The ternary eutectic solvent used has advantages such as environmental friendliness, simple synthesis process and low cost, and is a new type of green extraction system. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the separation of lithium and transition metals in lithium battery leachate using a ternary eutectic solvent according to the present invention. Detailed Implementation

[0026] The embodiments described herein are merely illustrative of the technical content of the invention and are not intended to limit the scope of protection of the invention. The invention can be implemented in many forms and should not be construed as limited to the specific examples listed below.

[0027] (I) The effect of aqueous phase pH on separation efficiency Example

[0028] A method for separating lithium and transition metals from lithium battery leaching solutions using a ternary eutectic solvent, the process flow of which is as follows: Figure 1 As shown, the specific steps are as follows: (1) Preparation of aqueous phase: Simulate the composition of leachate from spent ternary lithium batteries and prepare a solution containing Li + Ni 2+ Co 2+ and Mn 2+ The aqueous phase with a pH of 2, the Li + The concentration was 360.2 mg / L, Ni 2+ The concentration was 1434.7 mg / L, Co 2+ The concentration was 661.0 mg / L, Mn 2+ The concentration was 833.8 mg / L; (2) Preparation of ternary eutectic solvent: weigh propriocaine, lauric acid and tributyl phosphate in a molar ratio of 1:1.5:0.5, mix them under water bath heating at 70°C to obtain ternary eutectic solvent, i.e. organic phase; (3) According to the volume ratio of aqueous phase to organic phase (A / O) of 1:1, the aqueous phase prepared in step (1) is added to the organic phase prepared in step (2), and the mixture is stirred at 10℃ and 500r / min for 10min for extraction. The extraction stage is 1. After thorough mixing, the mixture is placed in a centrifuge and centrifuged at 9000r / min for 10min to separate the phases, and nickel-cobalt-manganese supported organic phase and lithium-containing raffinate are obtained. (4) According to the volume ratio (A / O) of the back-extraction agent to the nickel-cobalt-manganese supported organic phase of 3:1, 2 mol / L HCl back-extraction agent was added to the nickel-cobalt-manganese supported organic phase in step (3). The mixture was stirred at 24℃ and 500 r / min for 10 min for back-extraction. The back-extraction stage was 1. After thorough mixing, the mixture was placed in a centrifuge and centrifuged at 9000 r / min for 5 min to separate the phases, thus obtaining the nickel-cobalt-manganese back-extraction solution and the regenerated organic phase. Example

[0029] A method for separating lithium and valuable metals from waste ternary lithium batteries using a ternary eutectic solvent is basically the same as that in Example 1, except that the pH value of the aqueous phase in step (1) is adjusted to 4 using hydrochloric acid solution. Example

[0030] A method for separating lithium and valuable metals from waste ternary lithium batteries using a ternary eutectic solvent is basically the same as in Example 1, except that the pH value of the aqueous phase in step (1) is adjusted to 5 using hydrochloric acid solution. Example

[0031] A method for separating lithium and valuable metals from waste ternary lithium batteries using a ternary eutectic solvent is basically the same as that in Example 1, except that the pH value of the aqueous phase in step (1) is adjusted to 3 using hydrochloric acid solution.

[0032] The extraction results of Examples 1 to 4 are shown in Table 1 below.

[0033]

[0034] As can be seen from the extraction results in Table 1, the extraction rates of nickel, cobalt and manganese can reach over 97.5% after single-stage extraction. At the same time, a high-purity lithium salt solution is obtained from the raffinate, thus achieving effective separation of lithium and valuable metals from waste ternary lithium batteries.

[0035] As shown in Table 1, the extraction results indicate that the extraction efficiency first increases and then decreases with increasing aqueous phase pH. The extraction and separation effect is best at an aqueous phase pH of 4, because pH is a key factor affecting the extraction efficiency of DES. Under strongly acidic conditions (pH 1–3) below 4, the high concentration of H⁺ in the solution competes with metal ions for active coordination sites in DES (such as carboxyl and amide groups). Simultaneously, these functional groups lose their coordination ability due to protonation, leading to the loss of Co. 2+ Ni 2+ and Mn 2+ The extraction efficiency is low. As the pH increases to 4, H... +As the concentration decreases, the competitive effect weakens, and the carboxyl groups in the DES begin to partially deprotonate, enhancing their electrostatic attraction and coordination ability for metal ions. At this point, the metal ions still exist in a free state and have not yet undergone significant hydrolysis. Furthermore, the three-dimensional hydrogen bond network of the DES remains intact, effectively enriching coordination sites and thus achieving peak extraction efficiency. When the pH further increases to 5, the metal ions begin to hydrolyze, forming hydroxyl complexes or hydroxide precipitates, reducing the concentration of extractable free metal ions and causing a decrease in extraction efficiency. Therefore, pH = 4 is the optimal extraction condition for this DES system, representing a balance between H⁺ competition, the protonated state of functional groups, and the hydrolysis behavior of metal ions.

[0036] (II) Effect of initial concentration on separation effect Example

[0037] A method for separating lithium and valuable metals from waste ternary lithium batteries using a ternary eutectic solvent is basically the same as in Example 1, except that: the Li in step (1) + The concentration was 377.9 mg / L, Ni 2+ The concentration was 1502.6 mg / L, Co 2+ The concentration was 601.9 mg / L, Mn 2+ The concentration was 885.3 mg / L.

[0038] The extraction results of Example 5 are shown in Table 2 below.

[0039]

[0040] As shown in Table 2, after single-stage extraction, the extraction rates of nickel, cobalt, and manganese all reached over 97.5%. At the same time, a high-purity lithium salt solution was obtained from the raffinate, which achieved effective separation of lithium and valuable metals from waste ternary lithium batteries. This indicates that the extractant of this application is suitable for solutions with different initial concentrations.

[0041] (III) The effect of the ratio of aqueous phase to organic phase on the separation effect Example

[0042] A method for separating lithium and valuable metals from spent ternary lithium batteries using a ternary eutectic solvent, comprising the following specific steps: (1) Preparation of aqueous phase: Simulate the composition of leachate from spent ternary lithium batteries and prepare a solution containing Li + Ni 2+ Co 2+ and Mn 2+ The aqueous phase with a pH of 4, the Li + The concentration was 3701 mg / L, Ni 2+ The concentration was 6358 mg / L, Co 2+The concentration was 15446 mg / L, Mn 2+ The concentration was 9122 mg / L; (2) Preparation of ternary eutectic solvent: weigh prilocaine, lauric acid and tributyl phosphate in a molar ratio of 1:1.5:0.5, mix them under water bath heating at 70°C to obtain ternary eutectic solvent, i.e. organic phase; (3) According to the volume ratio of aqueous phase to organic phase (A / O) of 3:1, the aqueous phase prepared in step (1) is added to the organic phase prepared in step (2), and the mixture is stirred at 10℃ and 500r / min for 10min for extraction. The extraction stage is 1. After thorough mixing, the mixture is placed in a centrifuge and centrifuged at 9000r / min for 10min to separate the phases, and nickel-cobalt-manganese supported organic phase and lithium-containing raffinate are obtained. (4) According to the volume ratio (A / O) of the back-extraction agent to the nickel-cobalt-manganese supported organic phase of 3:1, 2 mol / L HCl back-extraction agent was added to the nickel-cobalt-manganese supported organic phase in step (3). The mixture was stirred at 24℃ and 500 r / min for 10 min for back-extraction. The back-extraction stage was 1. After thorough mixing, the mixture was placed in a centrifuge and centrifuged at 9000 r / min for 5 min to separate the phases, thus obtaining the nickel-cobalt-manganese back-extraction solution and the regenerated organic phase. Example

[0043] A method for separating lithium and valuable metals from waste ternary lithium batteries using a ternary eutectic solvent is basically the same as that in Example 6, except that the volume ratio (A / O) of the aqueous phase to the organic phase in step (3) is 2:1. Example

[0044] A method for separating lithium and valuable metals from waste ternary lithium batteries using a ternary eutectic solvent is basically the same as that in Example 6, except that the volume ratio (A / O) of the aqueous phase to the organic phase in step (3) is 1:1. Example

[0045] A method for separating lithium and valuable metals from waste ternary lithium batteries using a ternary eutectic solvent is basically the same as that in Example 6, except that the volume ratio (A / O) of the aqueous phase to the organic phase in step (3) is 1:2. Example

[0046] A method for separating lithium and valuable metals from waste ternary lithium batteries using a ternary eutectic solvent is basically the same as that in Example 6, except that the volume ratio (A / O) of the aqueous phase to the organic phase in step (3) is 1:3.

[0047] The metal concentrations after extraction in Examples 6 to 10 are shown in Table 3, the extraction efficiencies are shown in Table 4, the partition coefficients are shown in Table 5, and the selectivity is shown in Table 6.

[0048]

[0049] As shown in Tables 3-6, the volume ratio of aqueous phase to organic phase (A / O) significantly affects the extraction efficiency of metal ions during the extraction process. When the volume ratio of aqueous phase to organic phase (A / O) changes from 3:1 to 1:1, and the ratio of organic phase increases, the extraction efficiency of Co... 2+ Ni 2+ and Mn 2+ The extraction efficiency reached its peak. However, when the volume of the organic phase further increased (i.e., the A / O ratio was greater than 1:1), the extraction efficiency of these three metal ions showed a decreasing trend. This phenomenon is related to the change in phase equilibrium of the extraction system caused by excess organic phase, thereby reducing the extraction efficiency for Co. 2+ Ni 2+ and Mn 2+ The extraction efficiency. For Li + In general, its extraction efficiency gradually increases with the increase of the organic phase. This indicates that after the organic phase is completely extracted from Co... 2+ Ni 2+ and Mn 2+ Afterwards, the remaining organic phase still possesses sufficient extraction capacity to selectively extract Li. + Furthermore, both the partition coefficient and selectivity reached their maximum values ​​at an A / O ratio of 1:1, further confirming the optimal selectivity and extraction efficiency of the extraction system for the target metal ions at this ratio. Considering factors such as extraction efficiency, partition coefficient, and selectivity, an A / O ratio of 1:1 was ultimately determined to be the optimal extraction condition.

[0050] (iv) The effect of different organic phase compositions on separation efficiency Comparative Examples 1 to 5 Comparative Examples 1 to 5 are basically the same as Example 8, except that: Step (2) prepares a binary eutectic solvent: weigh prilocaine and lauric acid according to different molar ratios, mix them under water bath heating at 70°C to obtain a binary eutectic solvent, i.e., an organic phase; wherein the molar ratios of prilocaine and lauric acid are 2:1, 1.5:1, 1:1, 1:1.5, and 1:2, respectively.

[0051] The metal concentrations after extraction of Comparative Examples 1 to 5 are shown in Table 7, the extraction efficiencies are shown in Table 8, the partition coefficients are shown in Table 9, and the selectivity is shown in Table 10.

[0052]

[0053]

[0054] As can be seen from Tables 7 to 10, the extraction effect of the binary eutectic solvents of Comparative Examples 1 to 5 is significantly lower than that of the ternary eutectic solvent of Example 8. The ternary eutectic solvent system of this application has a better extraction effect.

[0055] From the perspective of extraction efficiency, in Comparative Examples 1 to 5, when the molar ratio of prilocaine to lauric acid is 1:1, Co 2+ Ni 2+ and Mn 2+ The extraction efficiencies all reached high levels, at 77.49%, 80.84%, and 60.72%, respectively. As the lauric acid ratio increased to 1:1.5, Co... 2+ The extraction efficiency further increased slightly to 79.08%, but Ni 2+ and Mn 2+ The extraction efficiency began to decline. When the molar ratio reached 1:2, the extraction efficiencies of the three transition metals all decreased significantly, dropping to 65.98%, 55.59%, and 41.48%, respectively. This indicates that an appropriate HBA to HBD ratio is crucial for maintaining the hydrogen bond network structure and coordination ability of DES. Excessive lauric acid may disrupt the ordered structure of DES and weaken its coordination with metal ions.

[0056] For Li + Its extraction efficiency remained low across all molar ratios (8.84%–20.02%), reaching a maximum of 20.02% at a 1:1 ratio. This further confirms that the DES system has selective extraction capabilities for transition metal ions, while its extraction efficiency for Li... + Its extraction ability is relatively weak.

[0057] The trends in partition coefficient (D) and selectivity (β) are consistent with the extraction efficiency. At a 1:1 molar ratio, Co... 2+ Ni 2+ and Mn 2+ The allocation coefficients for Li were 3.44, 4.22, and 1.55, respectively. + The selectivity reached 13.75, 16.86, and 6.18, respectively. When the molar ratio was adjusted to 1:1.5, Co 2+ and Ni 2+ For Li + The selectivity was further improved to 21.38 and 20.11, which may be due to the moderate increase in the proportion of lauric acid enhancing the coordination strength of DES with transition metal ions, while suppressing the selection of Li. + Extraction.

[0058] Considering extraction efficiency, partition coefficient, and selectivity, a molar ratio of prilocaine to lauric acid of 1:1 to 1:1.5 represents the optimal range for extracting transition metal ions using this DES system. The 1:1 ratio achieves a good balance between extraction efficiency and selectivity, while the 1:1.5 ratio is more favorable for improving Co extraction efficiency. 2+ Ni 2+ For Li + Selective separation.

[0059] The above embodiments are merely specific examples of the present invention and are intended to illustrate the invention, not to limit it. Any obvious modifications or equivalent alternatives guided by the core technical concept of the present invention fall within the scope of protection defined by the claims of the present invention.

Claims

1. A ternary eutectic solvent, characterized in that, The ternary eutectic solvent is obtained by mixing prilocaine, lauric acid and tributyl phosphate in a molar ratio of 1:1.5:(0.5-2).

2. The ternary eutectic solvent according to claim 1, characterized in that, The mixing temperature is 70–80°C.

3. The application of the ternary eutectic solvent according to any one of claims 1-2 in separating lithium and transition metals in lithium battery leachate.

4. A method for separating lithium and transition metals in lithium battery leaching solution using a ternary eutectic solvent, characterized in that, Includes the following steps: (1) Using the ternary eutectic solvent of any one of claims 1-2 as the organic phase, the lithium battery leaching solution is added to the organic phase for extraction. After extraction, the phases are separated by centrifugation to obtain a transition metal-supported organic phase and a lithium-containing raffinate. (2) The back-extraction agent is added to the transition metal-supported organic phase prepared in step (1) for back-extraction. After the back-extraction is completed, the phases are separated by centrifugation to obtain the transition metal back-extraction solution and the regenerated organic phase.

5. The preparation method according to claim 4, characterized in that, The lithium battery leachate is prepared by dissolving lithium battery electrode materials with inorganic acids.

6. The preparation method according to claim 5, characterized in that, The inorganic acid is hydrochloric acid, and the pH of the lithium battery leaching solution is 1 to 6.

7. The preparation method according to claim 4, characterized in that, The transition metals are nickel, cobalt, and manganese.

8. The preparation method according to claim 7, characterized in that, Step (1) The volume ratio of lithium battery leachate to organic phase is 3:1 to 1:

3.

9. The preparation method according to claim 8, characterized in that, The extraction temperature in step (1) is 10–30 °C.

10. The preparation method according to claim 7, characterized in that, In step (2), the stripping agent is 2 mol / L HCl, and the volume ratio of the stripping agent to the transition metal supported organic phase is (1-3):1; in step (3), the temperature of the stripping is 10-30℃.

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