Phase Relations and Activity of Antimony in Cu-Fe-S-Sb System at 1473 K

Abstract

To analyze the behavior of antimony in the copper smelting process, the phase relations and the activity of antimony in the miscibility gap of Cu–Fe–S–Sb system with antimony as a minor element have been determined at 1473 K by the quenching method and the double Knudsen cell-mass spectrometric method, respectively. The experiments have been conducted for the charges in the miscibility gap with mass%Fe/mass%Cu ratios of 0, 0.023, 0.072 and 0.113 with varying antimony content. The activity measurements indicate that the antimony activities in both the metal and matte phases show extremely negative deviation from the ideal behavior. The Raoultian activity coefficients at infinite dilution in the metal and matte phases are found to be almost constant against the charges in the miscibility gap and they are 1.1×10−2 and 2.5×10−1 for the metal and matte phases, respectively. The vapor pressures of predominant species of Sb, Sb2 and SbS in the gas phase equilibrated with the immiscible solutions have been calculated on the basis of the determined activity coefficients and they are very small at less than 1 Pa even when the antimony content in the metal phase is increased up to 10 mass%.