Process for the recovery of cobalt oxalate from spent lithium-ion batteries

A hydrometallurgical process for the recovery of cobalt oxalate from spent lithium-ion batteries (LIBs) has been developed using alkali leaching followed by reductive acid leaching, solvent extraction and chemical deposition of cobalt oxalate. The active cathode powder material was first leached with 5 wt.% NaOH solution for the selective removal of aluminum; and the residues were further leached with 4 M H2SO4 + 10% v/v H2O2 solution. The leaching efficiency of cobalt was 95% and lithium was 96% under optimum conditions of liquid/solid ratio 10:1, leaching time 120 min and a temperature 85 °C. The impurity ions of Fe(III), Cu(II), Mn(II) in the leach liquor were precipitated by adjusting the pH value. Cobalt(II) was then extracted selectively from the purified aqueous phase with saponified P507 (2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester) and chemically deposited as oxalate from the strip liquor with a yield of ~ 93% and purity > 99.9%. This process is simple, environmentally friendly and adequate for the recovery of valuable metals from spent LIBs.