Co(II) Recovery from Hydrochloric Acid Solution Using Menthol-Based Deep Eutectic Solvents (DESs): Application to NMC
María Isabel Martín-Hernández1, María Lourdes Rodríguez1, Irene García-Díaz1
1Centro Nacional de Investigaciones Metalúrgicas (CENIM-CSIC), Avda. Gregorio del Amo, 8, 28040 Madrid, Spain.
Molecules (Basel, Switzerland)
|November 27, 2025
Summary
This study demonstrates a novel method for recovering cobalt from spent nickel-cobalt-manganese (NMC) batteries using deep eutectic solvents (DESs). The developed DES selectively extracts cobalt, achieving high recovery rates and enabling its transformation into a valuable salt for recycling.
Area of Science:
- Materials Science
- Chemical Engineering
- Environmental Science
Background:
- Lithium-ion batteries, particularly nickel-cobalt-manganese (NMC) types, are crucial for electric mobility and reducing transportation emissions.
- Effective recycling of these batteries is vital for resource sustainability and minimizing environmental impact.
- Selective metal recovery technologies are needed to process battery waste streams.
Purpose of the Study:
- To investigate the selective recovery of cobalt (Co(II)) from hydrochloric acid solutions using a specific deep eutectic solvent (DES).
- To optimize parameters for cobalt extraction from dissolved NMC battery black mass.
- To evaluate the DES's efficiency and selectivity for cobalt recovery and subsequent salt formation.
Main Methods:
- Utilized a deep eutectic solvent composed of 3 Aliquat 336:7 L-Menthol for cobalt extraction.
- Optimized extraction parameters using synthetic Co(II) solutions.
- Applied optimized conditions to cobalt recovery from NMC 622 battery black mass dissolved in 10 M HCl.
- Investigated stripping with 0.5 M H2SO4 for cobalt salt recovery.
- Optimized conditions for separating copper (Cu(II)) using Aliquat 336 in kerosene.
Main Results:
- The DES demonstrated high selectivity for Co(II) recovery over Ni, Li, and Mn.
- Cobalt recovery rates reached up to 90% from the NMC battery black mass solution.
- Cobalt was successfully recovered as crystalline cobalt sulfate monohydrate (CoSO4.H2O) via stripping with H2SO4.
- Efficient separation of Cu(II) was achieved under optimized conditions.
Conclusions:
- Deep eutectic solvents offer a promising technology for the selective recovery of cobalt from spent NMC batteries.
- The developed method enables efficient cobalt extraction and purification, facilitating its recycling into valuable materials.
- This approach contributes to sustainable battery recycling and the circular economy for critical metals.
