High Pure Co (II) Precursor Liquor From Spent Catalyst Leach Liquor

Abstract

The increasing demand for cobalt within the last two decades supports the reservation and recycling of cobalt bearing spent catalyst. This paper deals with the generation of high pure Co(II) solution as a precursor liquor for the synthesis of either battery grade material or fine chemicals of cobalt. The extraction of cobalt from Co bearing spent catalyst containing about 22.3% of Co with Fe, Mn, Ni and Cu in trace amount was carried out by leaching with nitric acid. The recovery of cobalt was 99.78% at 4 h, whereas recovery of iron was 72.78% with 12.5% acid concentration at 90 degrees C. The first step was Fe separation through hydrothermal route giving a valuable by product as Fe2O3. To generate a high pure solution; the minor impurities like Cu(II) and Ni(II) and Mn(II) should be removed. Since Co(II), Cu(II) and Ni(II) have similar responses to the precipitating reagents the cobalt (II) needs to get converted to a different form such as Co(III) so that it can be selectively taken out leaving other elements. The Co(III) oxide is dissolved through reductive acid leaching to get Co(II) precursor solution back. The leaching efficiency of cobalt (III) obtained was 99.9% with sample to charcoal ratio (w/w) of 10:3, 2 M HNO3 at 90 degrees C. The Fe residue and Co(III) oxide is characterized by XRD, SEM to study the phases and structures.