Multistage three-phase extraction as a tool for application of deep eutectic solvents in non-ferrous metals separation processes

Advancing highly efficient hydrometallurgical technologies non-ferrous metals from mineral and secondary raw materials involves the development of both of new extraction systems and hardware solutions based on closed-loop principles. In this paper, the authors propose, and report on the implementation of, a model process for the extraction of non-ferrous metals from aqueous solutions using the deep eutectic solvent D2EHPA/menthol (4:6) in a laboratory extraction plant comprising a cascade of mixer-settlers. Optimal conditions for the extraction of copper and nickel, using the deep eutectic solvent, were established. A comparative analysis of the processes in the cascade of extractors, operating in the mode of multistage three-phase extraction versus counter current multistage extraction-stripping mode, was conducted. It was shown that the hardware solution based on the multistage three-phase extraction provides the greatest level of efficiency of metal extraction and is suitable for the extraction and concentration of the metals from dilute solutions. The obtained experimental data allowed us to calculate the real scheme of separation considering the thermodynamic equilibrium establishment time. It was established that the multistage three-phase extraction technique is a very promising hardware solution for implementing hydrometallurgical processes for separation and concentration non-ferrous metals from solutions using deep eutectic solvents.