The precipitation tests with NH4OH were carried out using
the liquor obtained in the leaching step (S/L ratio of 1/30 gml−1,
temperature of 65 ◦C, H2SO4 concentration of 6% (v/v) and
H2O2 concentration of 1.0% (v/v)), which contains 2.44 g l−1
of aluminium, 11.48 g l−1 of cobalt and 1.01 g l−1 of lithium.
The presence of aluminium in the leach liquor may hinder the
separation of cobalt in the liquid–liquid extraction step with
Cyanex 272 because aluminium will be fully extracted with
cobalt [2], so it might be advantageous to reduce the concentration
of aluminium in the leach solution by precipitation with
NH4OH.