Selective recovery of cobalt from the secondary streams after NiMH batteries processing using Cyanex 301

Abstract

Cobalt is considered to be a critical raw material for the European Union. Since it has limited supply, substantial efforts should be made to develop sustainable methods to recover cobalt from alternative sources. Hydrometallurgical processing of spent NiMH batteries generates a concentrated stream containing, preferably, Co (11.8 g/L) and impurities (2.3 g/L Ni, 0.2 g/L Al, 9.3 g/L Mn and 4.6 g/L rare earth elements) in the nitric acid media. In this study, the selective separation of Co from the other ions present was investigated. Co was selectively separated from Al, Mn and REEs using 1 M Cyanex 301 in kerosene. The different kinetic behaviour during extraction with Cyanex 301 was utilized to separate Co and Ni ions selectively. The calculated ΔH for the Co extraction process equals – 11.37 ± 0.5 kJ/mol, which indicates that the extraction of Co in the system tested is an exothermic reaction. The effect of temperature on the Co extraction was used to obtain better selectivity towards Ni. Co was recovered by selective stripping with 4 M HCl at ambient temperature. The final purity of the stripping product was 99.9%.