Method for recovering cobalt from waste lithium battery leachate by using beta-diketone eutectic solvent

Abstract

The invention relates to a method for recovering cobalt from a waste lithium battery leachate by using a beta-diketone eutectic solvent. The method uses the hydrophobic deep-eutectic solvent for extracting the organic phase. Wherein the deep eutectic solvent is prepared by mixing 4, 4, 4-trifluoro-1-(2-furyl)-1, 3-butanedione (HFTA) and trioctylphosphine oxide (TOPO) according to a molar ratio of 2: 1, and the catalyst is used for preparing the catalyst. The method comprises the following steps: taking a waste lithium ion battery leaching solution as an extraction water phase, wherein the extraction water phase contains CoSO4. 7H2O, NiSO4. 7H2O and Li2SO4; h2SO4 and NaOH are added into the extraction water phase to adjust the pH of the water phase, the extraction organic phase and the water phase are fully mixed according to the volume ratio of 1: 2-5: 2 and then stand still, phase separation is conducted, and an organic phase rich in cobalt and a water phase containing a small amount of cobalt are obtained. The method has the advantages of low energy consumption, simple process, high cobalt extraction efficiency and the like, the adopted extraction agent eutectic solvent is low in price, and the preparation method is simple and non-toxic.

Description

[Technical field]

[0001] The present invention belongs to the field of extraction chemistry, chemical purification and separation process, and specifically relates to a method for recovering cobalt from waste lithium battery leachate using a low eutectic solvent. [Background technology]

[0002] With the rapid development of science and technology, lithium-ion batteries are widely used in electronic products and electric vehicles. Lithium-ion batteries contain a variety of valuable metal resources, such as cobalt, nickel, lithium, etc. The reserves of these metals on the earth are not infinite. With the continuous increase in mining and use, their reserves are gradually decreasing, facing the pressure of resource shortage. By recycling metals from waste lithium-ion batteries, these valuable metal resources can be effectively recycled and utilized, alleviating resource shortages to a certain extent. In addition, harmful substances in batteries may leak into the soil and water bodies, causing damage to the ecosystem, affecting biodiversity and human health. If these waste batteries are not properly handled, they will also occupy a large amount of land resources and form a waste of resources. An effective metal recycling mechanism can reduce the negative impact of waste batteries on the environment and achieve the goal of environmental protection.

[0003] Cobalt is a key metal element in lithium-ion batteries and plays a vital role in the performance and stability of batteries. As the lithium-ion battery market continues to expand, the demand for cobalt is also rising. Recycling cobalt in lithium-ion batteries can not only effectively alleviate the problem of cobalt resource shortage, but also reduce environmental pollution and meet the requirements of sustainable development.

[0004] For the extraction of cobalt, solvent extraction has become a research hotspot due to its high extraction efficiency and simple operation. Due to these significant advantages, solvent extraction has gradually been applied to lithium extraction technology and has gradually become one of the most promising technologies. At present, the commonly used extractants are organic solvents and ionic liquids. However, there are problems such as organic phase corrosion equipment during the extraction process, difficulty in phase separation after extraction, and strong pollution, which are not conducive to industrial application. [Summary of the invention]

[0005] The present invention provides a method for recovering cobalt from lithium battery leachate. The method uses a hydrophobic low eutectic solvent as an extractant, which not only solves the problem of corrosion of equipment caused by organic solvents, but also solves the problem of difficult phase separation after extraction and environmental pollution caused by organic solvents dissolving in water.

[0006] [Technical solution]

[0007] In view of the problems existing in extracting cobalt from lithium battery leachate, the present invention proposes a method for extracting cobalt using a low eutectic solvent, which not only achieves the purpose of separation and purification, but also makes the process cleaner and more environmentally friendly, and the single extraction efficiency of cobalt reaches more than 95%.

[0008] The present invention is achieved through the following technical solutions.

[0009] A method for recovering cobalt from waste lithium battery leachate using a β-diketone-based low eutectic solvent comprises the following steps: (1) synthesizing an extraction organic phase, wherein the extraction organic phase is composed of a hydrophobic low eutectic solvent; wherein the hydrophobic low eutectic solvent is a mixture of 4,4,4-trifluoro-1-(2-furanyl)-1,3-butanedione (HFTA) and trioctylphosphine oxide (TOPO) in a molar ratio of 2:1. (2) using a simulated lithium battery leachate as an extraction aqueous phase; the extraction aqueous phase contains CoSO4·7H2O, NiSO4·7H2O and Li2SO4; (3) adding H2SO4 and NaOH to the extraction aqueous phase to adjust the pH of the aqueous phase; wherein the specific pH range is 1.5 to 6.5; (4) fully mixing the extraction organic phase and the aqueous phase in a volume ratio of 1:2 to 5:2, then standing and performing phase separation to obtain an organic phase rich in metal ions and an aqueous phase containing a small amount of metal.

[0010] According to another preferred embodiment of the present invention, it is characterized in that: the extraction organic phase consists of a hydrophobic low eutectic solvent.

[0011] According to another preferred embodiment of the present invention, it is characterized in that: the extractant is synthesized from HFTA and TOPO at 353.15K.

[0012] According to another preferred embodiment of the present invention, it is characterized in that the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 2:1.

[0013] According to another preferred embodiment of the present invention, it is characterized in that the extraction temperature during the extraction process is 298.15K.

[0014] According to another preferred embodiment of the present invention, it is characterized in that the stirring rate during the extraction process is 120 rpm to 780 rpm.

[0015] According to another preferred embodiment of the present invention, it is characterized in that the extraction time during the extraction process is 5 min to 20 min.

[0016] According to another preferred embodiment of the present invention, it is characterized in that the mass concentrations of CoSO4·7H2O, NiSO4·7H2O and Li2SO4 are 2.36 g·L -1 , 0.12g·L -1 and 0.7 g·L -1 .

[0017] According to another preferred embodiment of the present invention, it is characterized in that the volume ratio of the extraction organic phase to the aqueous phase is 1:2 to 5:2.

[0018] [Beneficial Effects]

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) This method is used to extract cobalt from waste lithium battery leachate to obtain high-purity cobalt, solving the problem of difficulty in recovering cobalt from lithium battery leachate.

[0021] (2) This method has the advantages of simple process, less investment in equipment, and high purity of extracted cobalt. The extractant used is a low eutectic solvent, which has the advantages of simple preparation, low cost, easy recovery, good chemical and thermal stability, and is green and pollution-free.

[0022] (3) The low eutectic solvent used in this method has a low viscosity as an extractant, which is conducive to mass transfer and has low water solubility. In addition, the extractant is easy to recycle and the preparation method is simple, which reduces the extraction cost.

Brief Description of the Drawings

[0023] Figure 1 The present invention is a process flow chart for recovering cobalt from waste lithium battery leachate using a β-diketone low eutectic solvent. [Specific implementation method]

[0024] Embodiment 1:

[0025] Add a certain amount of sulfuric acid to the prepared simulated lithium battery leachate of known concentration to adjust the pH value of the system. Thoroughly mix the required organic phase with the aqueous phase, shake it at 560rpm with a magnetic stirrer for a few minutes, and it is sufficient to reach equilibrium in 15 minutes or less. Carefully draw a certain amount of water sample from the bottom of the centrifuge tube with a syringe with a long needle, dilute it to 25ml, and use an atomic absorption spectrophotometer (AAS) to determine the metal concentration in the aqueous phase. The low eutectic solvent composed of HFTA and TOPO in a molar ratio of 2:1 has a cobalt extraction efficiency of 95.2% at pH 2.5.

[0026] Embodiment 2:

[0027] Prepare a simulated lithium battery leachate of known concentration, adjust the pH of the aqueous solution to 2.5, and fully mix the required organic phase and aqueous phase in a volume ratio of 1:1. Use a magnetic stirrer to shake for a few minutes until the extraction reaches equilibrium. Use a syringe with a long needle to carefully draw a certain amount of water sample from the bottom of the centrifuge tube, dilute to 25ml, and use an atomic absorption spectrophotometer (AAS) to determine the metal concentration in the aqueous phase. The extraction stirring rate is 560rpm, the extraction time is 15min, and the single extraction efficiency of cobalt is 90.47%.

[0028] Embodiment 3:

[0029] The prepared simulated lithium battery leachate was fully mixed with the required organic phase in a volume ratio of 1:2. The mixture was shaken at 560 rpm with a magnetic stirrer for 15 minutes. After the extraction reached equilibrium, a certain amount of water sample was carefully drawn from the bottom of the centrifuge tube with a syringe with a long needle, diluted to 25 ml, and the metal concentration in the aqueous phase was determined using an atomic absorption spectrophotometer (AAS). The single extraction efficiency of cobalt was 88.94%.

[0030] Embodiment 4:

[0031] The pH of the prepared simulated lithium battery leachate was adjusted to 3.5, and the required organic phase and aqueous phase were fully mixed in different volume ratios of 1:2. A magnetic stirrer was used to shake at 560rpm for 15 minutes, and after the extraction reached equilibrium. A certain amount of water sample was carefully drawn from the bottom of the centrifuge tube with a syringe with a long needle, diluted to 25ml, and the metal concentration in the aqueous phase was determined by an atomic absorption spectrophotometer (AAS). The single extraction efficiency of cobalt was 84.52%.

[0032] Embodiment 4:

[0033] The pH of the prepared simulated lithium battery leachate was adjusted to 5.5, and the required organic phase and aqueous phase were fully mixed in different volume ratios of 1:2. A magnetic stirrer was used to shake at 560rpm for 15 minutes, and after the extraction reached equilibrium. A certain amount of water sample was carefully drawn from the bottom of the centrifuge tube with a syringe with a long needle, diluted to 25ml, and the metal concentration in the aqueous phase was determined by an atomic absorption spectrophotometer (AAS). The single extraction efficiency of cobalt was 87.05%.

[0034] Embodiment 4:

[0035] The pH of the prepared simulated lithium battery leachate was adjusted to 5.5, and the required organic phase and aqueous phase were fully mixed in different volume ratios of 1:2. A magnetic stirrer was used to shake at 560rpm for 15 minutes, and after the extraction reached equilibrium. A certain amount of water sample was carefully drawn from the bottom of the centrifuge tube with a syringe with a long needle, diluted to 25ml, and the metal concentration in the aqueous phase was determined by an atomic absorption spectrophotometer (AAS). The single extraction efficiency of cobalt was 88.23%.

Claims

1. A method for recovering cobalt from waste lithium battery leachate using a β-diketone deep eutectic solvent, characterized in that: Includes steps: (1) Synthesizing an organic extraction phase, wherein the organic extraction phase is mainly a hydrophobic low eutectic solvent; wherein the hydrophobic low eutectic solvent is a mixture of 4,4,4-trifluoro-1-(2-furyl)-1,3-butanedione (HFTA) and trioctylphosphine oxide (TOPO) in a molar ratio of 2:

1. (2) The simulated waste lithium-ion battery leaching solution is used as the extraction water phase; the extraction water phase contains CoSO4·7H2O, NiSO4·7H2O, and Li2SO4. (3) adding H2SO4 and NaOH to the aqueous phase to adjust the pH of the aqueous phase; wherein the specific pH range is 1.5 to 6.5; (4) The extracted organic phase and the aqueous phase are fully mixed in a volume ratio of 1:2 to 5:2, and then allowed to stand for phase separation to obtain an organic phase rich in cobalt and an aqueous phase containing a small amount of cobalt.

2. The method for extracting cobalt from simulated waste lithium-ion battery leachate according to claim 1, characterized in that: The extractant was synthesized from HFTA and TOPO at 353.15K.

3. The method for extracting cobalt from simulated waste lithium-ion battery leachate according to claim 1, characterized in that: The molar ratio of HFTA to TOPO is 2:

1.

4. The method for extracting cobalt from a simulated lithium-ion battery leachate according to claim 1, characterized in that: The extraction temperature was 298.15K during the extraction process.

5. The method for extracting cobalt from simulated waste lithium-ion battery leachate according to claim 1, characterized in that: The stirring rate during the extraction process is 120 rpm to 780 rpm.

6. The method for extracting cobalt from simulated waste lithium-ion battery leachate according to claim 1, characterized in that: In the extraction process, the extraction time is 5 min to 20 min.

7. The method for extracting cobalt from simulated waste lithium-ion battery leachate according to claim 1, characterized in that: In the simulated waste lithium-ion battery leachate, the mass concentrations of CoSO4·7H2O, NiSO4·7H2O, and Li2SO4 were 2.36 g·L -1 , 0.12g·L -1 and 0.7 g·L -1 .

8. The method for extracting cobalt from simulated waste lithium-ion battery leachate according to claim 1, characterized in that: The volume ratio of the extraction organic phase to the aqueous phase is 1:2 to 5:2.

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