Cobalt/nickel purification by solvent extraction with ionic liquids in millifluidic reactors: From single-channel to numbered-up configuration with solvent recycle

This work describes the continuous separation of cobalt and nickel by solvent extraction in a numbered-up millifluidic system (1 mm ID) using Cyphos IL 101 (C101) as extractant, which is recycled. A dilution of 50 vol% C101 in p-cymene was chosen as the optimal trade-off between extraction performance and hydrodynamic properties of the solvent. The effects of channel length (20-100 cm), flow rate (1-2.5 mL min-1) and temperature (20-70 degrees C) were investigated on the extraction, scrubbing and stripping performance in a single-channel system. Subsequently, the developed manifold structure (five parallel reactors) was benchmarked against the single-channel system, which displayed a maldistribution of only 1% and performed equally well as the single-channel system. Then, a continuous separation process of one extraction and two countercurrent stripping stages was executed for 6 h with the proven manifold. A cobalt and nickel purity of, respectively, 99.7 and 97.7 % were achieved at a rate of 5 mL min-1. Stable slug flow was observed in the entire system throughout the operating period.

Automated summary

This work presents a continuous solvent extraction method for the separation of cobalt and nickel in a millifluidic system using Cyphos IL 101 (C101) as the extractant. The optimal conditions for extraction performance and solvent properties were determined by investigating the effects of channel length, flow rate, and temperature. The performance of a developed manifold structure was compared to a single-channel system, and excellent separation results were achieved. The continuous separation process using the manifold structure resulted in high purity cobalt and nickel products.