Properties of Na₂O–SiO₂ slags in Doré smelting

Solubilities of metals in sodium silicate slags have been studied at 1000–1300°C in oxygen pressures of P(O₂) = 10⁻⁴ to 0.5 atm, in Doré alloy smelting of copper anode slimes. The boundary conditions for the slags were silica saturation, magnesia saturation with about 10 wt% and without BaO. The trace elements studied were copper, gold, palladium, rhodium, and tellurium. The analytical methods used in the phase composition analyses of equilibrated samples, quenched in brine, were electron probe X-ray microanalysis and laser ablation-inductively coupled plasma-mass spectrometry. Thermodynamic features of the slags, trace element solubilities with the given constraints, and their oxidation mechanisms were determined. The data allow optimizing the anode slime-smelting for the metals’ maximum recovery in sodium silicate fluxing.