The article presents results of thermodynamic calculations and laboratory studies, focusing on the
cobalt behaviour during oxidative smelting of copper-nickel mattes. The compositions of the studied
solutions are related to the products formed during the second stage of the converting process of
copper-nickel matte at the Nadezhdinsky Metallurgical Plant (NMP) of MMC Norilsk Nickel company.
These sulfide products typically contain from 1.5 to 12 wt per cent of iron. The obtained experimental
results and thermodynamic calculations indicate that adjusting the CaO ratio to increase the
proportion of CaO or complete replacement of SiO2 with fluxes containing CaO leads to a significant
increase in cobalt recovery rates in the matte phase (with an iron concentration of 2.5 wt per cent)
raising them from 30 per cent to 45 per cent. Meanwhile, the recovery rates of copper and nickel
remain constant.