Slag-Copper Equilibria of Selected Trace Elements in Black-Copper Smelting. Part II. Trace Element Distributions

The distribution equilibria of silver, indium, gallium, and tin between a copper alloy and alumina-containing iron silicate slag have been measured experimentally at 1300°C. In reducing conditions, copper acts as a collector for gallium, but its distribution coefficient between metal and slag is always less than one. Indium will be almost completely oxidized to the slag in high oxygen partial pressures and reduced fully back to the copper alloy in the slag cleaning conditions, around pO2 ≈ 10−10 atm. The behavior of tin is similar to indium in low oxygen pressures, where copper alloy dissolves most tin from the slag (log10 Lm/s(Sn) ≈ 2). In high oxygen partial pressures, most tin was volatilized from the system, and tin concentrations were below the detection limit (0.02 wt-%), less than 0.005 wt-% in slag and less than 0.002–0.003 wt-% in the alloy. Up to 90% of its initial silver amount in the copper alloy was lost in the gas at pO2 > 10−6 atm and its concentration in copper was less than 0.1 wt-% [Ag]. The observations suggest that addition of lime to iron silicate slags with alumina, in reducing conditions below pO2 ≈ 10−7 atm at silica saturation, lowers slightly the metal-to-slag distribution coefficients.