Extraction of cobalt from a cobaltiferrous pyrite concentrate using H2SO4-NaNO3 lixiviant system

Cobalt is a "critical raw material" owing to its important role in the green transition towards low-carbon tech-nologies. Due to the ever-increasing demand for cobalt, attention is turned to its production from alternative secondary resources. This study investigated the extraction of cobalt and base metals (Cu, Zn) from a cobalti-ferrous pyrite concentrate (6407 g/t Co) in H2SO4 media in the presence of a strong oxidant (i.e., NaNO3). The effect of parameters (i.e., the concentration of NaNO3 (0.1-1 M), temperature (20-70 degrees C) and fineness of the material (as grinding time: up to 15 min) were investigated on the extraction of cobalt using response surface methodology. The statistical analysis of the results demonstrated that the concentration of NaNO3 and tem-perature were the most significant factors affecting cobalt extraction into solution. Effect of addition of high levels of NaNO3 (by up to 2 M) and ultra-fine grinding of the concentrate (down to 3 mu m (d80)) improved the extraction of cobalt extraction while increased solids ratio (2-10 % w/v) adversely affected. The results demonstrated that complete extraction of cobalt can be achieved under highly oxidising conditions (i.e., at high NaNO3 levels). There appeared a close relationship between the oxidation of pyrite and the extraction of cobalt, confirming that cobalt presents as an iron substitute in pyrite lattice. It can be concluded from these findings that the H2SO4-NaNO3 leaching system is a promising alternative to extract cobalt from cobaltiferrous pyrite con-centrates/tailings.