Phase equilibrium and minor elements distribution between SiO2-CaO-FeOx-MgO Slag and copper matte at 1573 K under high partial pressures of SO2

Abstract

Phase equilibrium between copper matte and SiO2-CaO-FeOx-MgO slag with Q=0.35 (Q=mass%CaO/ (mass%CaO + mass%SiO2)) was investigated at 1573 K under the SO2 partial pressures of 10.1, 50.7 and 101.3 kPa as a fundamental study for thermodynamically discussing oxygen-smelting processes to produce copper. The copper and sulfur solubilities in the slag were found to be independent of pSO2 when the matte grade was specified, and it was considered that this behavior was ascribed to the constancy of (pO2/pS2) against pSO2 at a given matte grade. When the distribution ratio of a minor element, X, between the slag and matte phases was defined as Lxs/m=(mass%X in slag)/{mass%X in matte}, Lxs/m for As, Sb and Bi at a given matte grade increased with increasing pSO2. This behavior was explained reasonably by assuming a mutual reaction between a metallic species in the matte and an oxidic species in the slag. The distribution ratio, LAgs/m, at a given matte grade was almost constant against pSO2. This was considered to be ascribed to the sulfidic species of AgS0.5 prevailing in the matte phase and the constancy of (pO2/PS2) against pSO2.