Combined experimental and thermodynamic modelling investigation of the distribution of antimony and tin between phases in the Cu-Fe-O-S-Si system

The distributions of Sb and Sn between slag and matte in equilibrium with tridymite in the Cu-Fe-O-S-Si system at 1200 degrees C (1473 K) have been measured. The experimental technique involves high-temperature equilibration in sealed quartz ampoule, rapid quenching, and direct measurement of phase compositions using Electron Probe X-ray Microanalysis (EPMA). The closed system equilibration approach was used to minimize the evaporation of Sb and Sn from the samples. The experimentally-determined distribution coefficients of Sb and Sn between slag and matte were found to increase with increasing Cu concentration in matte above 40 wt%. The new data have been used to refine the computational thermodynamics model for the system containing Sb and Sn at dilute concentrations. The molten slag phase is described using the Modified Quasichemical Model in the Quadruplet Approximation. Liquid matte and metal phases were modelled using single solution built within the Modified Quasichemical Model in the Pair Approximation. The thermodynamic model can be used to assess and predict the deportments of Sb and Sn between the slag and matte phases in the high-temperature pyrometallurgical production, refining and recycling of copper.