The thermochemistry of the Cu–Ni–S system largely determines the recovery of nickel, copper, and platinum group metals from sulfide ores and the production of nickel speiss in polymetallic recycling through lead bullion route. This study evaluates the accuracy of the FactSage 8.3 FTsulf thermodynamic database for predicting phase equilibria and element distribution within this system and provides data for further model improvements. Existing experimental data from literature were critically assessed against model predictions, identifying key areas where data were either lacking or controversial. New experiments were designed in these areas. Experimental investigation focused on two key areas: the matte-metal miscibility gap at 1100 and 1200 °C, and the solubility of copper sulfide in the β-Ni 3 S 2 solid phase, often referred to as high-temperature heazlewoodite. The experimental method of equilibration and quenching, followed by Electron Probe X-ray Microanalysis (EPMA) was refined to apply it for highly fluid matte and liquid metal phases. While the FactSage 8.3 FTsulf database generally agreed with most literature data, our results revealed a systematic underestimation of the nickel distribution coefficient, ratio of wt.% Ni in liquid Cu 2 S-rich matte to wt.% Ni in liquid copper metal. The solubility of copper sulfide in the β-Ni 3 S 2 solid phase was underestimated by the model compared to the experimental results of this study. These findings will inform future thermodynamic model optimizations and contribute to a broader research program focused on characterizing phase equilibria, heat balance, and elemental distribution in complex nickel-, copper-, and lead-based polymetallic processes. • Assessed FactSage 8.3 FTsulf for Cu-Ni-S phase equilibria/element distribution • Focused experiments on matte-metal miscibility gap and β-Ni 3 S 2 non-stoichiometry • Model underestimated Ni distribution coefficient in matte/metal phases. • Cu 2 S solubility in β-Ni 3 S 2 solid phase was also underestimated. • Findings support improvement of thermodynamic models for polymetallic processes
Shakirova et al. (Sun,) studied this question.