Phase equilibrium and distribution of minor elements between Ni-S melt and Al₂O₃-CaO-MgO Slag at 1873 K

Abstract

Distribution of nickel and minor elements such as Au, Ag, Fe, Co, Cu, As, and Sb between the Ni-S alloy and the CaO-Al₂O₃ based slag phases in a magnesia crucible was studied at 1873 K. Partial pressure of SO₂ was controlled at 10.1 kPa, while partial pressures of O₂ and S₂ ranged between the point of NiO precipitation (po₂ of 10.1 Pa) and the point at which Ni₃S₂ is formed (ps₂ of 4.0 kPa). The nickel content in the slag and the sulfur and oxygen contents in the metal at a given po₂ or pso₂ decrease when the temperature is increased from 1773 to 1873 K. The distribution ratios of iron, cobalt, and copper, defined by (wt pct X in slag)/{wt pct X in alloy}, where X is the minor element in the slag, have larger values than that of nickel, while the values of Au, Ag, Sb, and As are lower than that of nickel. The distribution behavior of nickel and minor elements is discussed based on the concept of oxidic and sulfidic dissolution.