Influence of gold content on copper oxidation from silver-gold-copper alloys

In the final stages of the smelting of copper anode slimes, a silver alloy, known as "dore", is produced. Oxidation refining is used to remove Cu since this element interferes with subsequent electroparting of the small amounts of gold and platinum group metals in the dore. The Au content of dore can be greatly increased by Au scrap additions and this may affect the minimum achievable Cu content of dore. In this work, Ag-Au-Cu alloys were oxidized by injecting pure oxygen at 1100 deg C in the absence of any slag cover. For the Au contents expected in practice, the equilibrium Cu content of the dore did not increase significantly as the Au content increased. However, at the other extreme of composition, the equilibrium Cu content was a very strong function of the Ag content of the Au bullion. The activity coefficient of Cu in Ag-Au alloys was calculated and compared to those predicted from a ternary subregular solution model of the system Ag-Au-Cu. Satisfactory agreement was found.