Metals extraction with organic solvents is a powerful tool to aid separation of complex mixtures of elements present in spent batteries and electronic devices, thus avoiding the use of toxic chemicals or experimental routes which generate high amounts of final wastes. This work describes a recovery process for cobalt present in spent Ni-MH batteries by a new hydrometallurgical route. The element was extracted in a chloride-bearing medium with Cyanex 272 (2,4,4-trimethyl-pentyl fosfinic acid) dissolved in kerosene. The best results were obtained when pH was slightly alkaline (7,2) and Cyanex concentration in kerosene was 5% vol. Cobalt recovery reached 99 wt%. It was also possible to recover a crude precipitate containing lanthanides (La, Ce, Pr) and yttrium, which was purified by dissolving it in HCl followed by addition of ammonium oxalate. Nickel was also isolated as an impure precipitate after cobalt and lanthanides recoveries. Final wastes generated along the separation processes are mainly sodium chloride solutions with no color, turbidity or heavy metals present in significant amounts.
Cobalt; cyanex 272; Ni-MH batteries
