Precious metal recoveries in secondary copper smelting with high-alumina slags

Waste electrical and electronic equipment (WEEE) represents a significant urban resource for precious metals. To maximize the recoveries and sustainable use of these metals, their behavior needs to be characterized in the secondary copper smelting of WEEE. The current study experimentally determined the distributions of gold, silver, platinum and palladium between copper alloy and FeO_x–SiO₂–Al₂O₃/FeO_x–SiO₂–Al₂O₃–CaO slags (L^Cu/s[M] = [M]_Copper/[M]_Slag) over the oxygen partial pressure range of 10⁻⁵ – 10⁻¹⁰ atm at 1300 °C. In addition, the equilibria of copper alloy, slag and Al–Fe spinel system are presented and discussed. The experiments were conducted employing an equilibration—drop-quenching technique followed by major element analysis with Electron Probe MicroAnalysis (EPMA) and trace element analysis with sensitive Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). The results showed that the distribution coefficient of silver increased from 10 to 10³ as a function of decreasing oxygen partial pressure. For gold, platinum and palladium, the distribution coefficients were at minimum 10⁵. Lime addition improved the recovery of silver notably and had a small positive effect on gold recovery into copper. Overall, the precious metals can be recovered very efficiently in copper alloy via secondary copper smelting with alumina-rich iron-silicate slags.