Equilibrium Distribution of Precious Metals Between Slag and Copper Matte at 1250–1350 °C

Abstract

Metal value recoveries in extraction are the key issue for sustainability of metals. The distributions of precious metals (Ag, Au, Pd, Pt, and Rh) between copper matte (a Cu–Fe–S–O melt) and silica-saturated iron silicate slag were determined at 1250–1350 °C, under controlled oxygen and sulfur pressures and at fixed partial pressure of sulfur dioxide, in silica saturation for target matte grades of 55, 65, and 75 wt% Cu. High-temperature equilibration/quenching was performed followed by electron probe X-ray microanalysis and laser ablation–inductively coupled plasma–mass sectrometry for measuring the major elements of the matte and slag, and trace elements of the slag, respectively. The distribution coefficient of silver at 65 % matte was found to be 150, which agrees well with the most recent studies in the literature. The other values obtained were gold 1500, palladium 3000, platinum 5000, and rhodium 7000–8000. The distribution coefficients increased along with matte grade, and for palladium it was approximately 1000 at 50 % Cu and 4000–5000 at 70 % Cu. The distribution coefficients decreased along with temperature but its impact was small. The distribution mechanism of the trace elements between iron silicate slag and copper matte appear to be dominated by properties of the matte phase.