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

摘要

AbstractWaste electrical and electronic equipment (WEEE) represents a significant urban resource for precious metals. To maximizethe recoveries and sustainable use of these metals, their behavior needs to be characterized in the secondary copper smeltingof WEEE. The current study experimentally determined the distributions of gold, silver, platinum and palladium betweencopper alloy and FeO_x–SiO_2–Al_2O_3/FeO_x–SiO_2–Al_2O_3–CaO slags (L~(Cu/s)[M] = [M]_(Copper)/[M]_(Slag)) over the oxygen partialpressure range of 10~(−5) – 10~(−10) atm at 1300℃. In addition, the equilibria of copper alloy, slag and Al–Fe spinel system arepresented and discussed. The experiments were conducted employing an equilibration—drop-quenching technique followedby major element analysis with Electron Probe MicroAnalysis (EPMA) and trace element analysis with sensitive Laser AblationInductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). The results showed that the distribution coefficient ofsilver increased from 10 to 10~3as a function of decreasing oxygen partial pressure. For gold, platinum and palladium, thedistribution coefficients were at minimum 10~5.Lime addition improved the recovery of silver notably and had a small positiveeffect on gold recovery into copper. Overall, the precious metals can be recovered very efficiently in copper alloy viasecondary copper smelting with alumina-rich iron-silicate slags.