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

Abstract

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-SiO 2-Al 2 O 3 /FeO x-SiO 2-Al 2 O 3-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 10 3 as a function of decreasing oxygen partial pressure. For gold, platinum and palladium, the distribution coefficients were at minimum 10 5. 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.

Equilibrium of Copper Matte and Silica-Saturated Iron Silicate Slags at 1300 °C and $$ P_{{{\text{SO}}_{ 2} }} $$ of 0.5 atm

“…This positive impact of Al 2 O 3 and CaO on decreasing copper loss in the slags can be also found in other studies. [13,29,31,[42][43][44][45][46][47] However, the increasing order of Al 2 O 3 and CaO on lowering the copper loss in slags observed in the present work is contrary to the results by Shimpo et al, [48] in which the phase equilibrium between copper matte and FeO x -SiO 2 -based slag was studied at metallic copper and silica double saturation. They reported that the concentration of copper in the CaO-containing slags was higher than that in the Al 2 O 3 -containing slags when the matte grade was < 60 wt pct Cu, after which the CaO-containing slag exhibited a lower copper solubility.…”

Slag Chemistry and Behavior of Nickel and Tin in Black Copper Smelting with Alumina and Magnesia-Containing Slags

“…Adhesion of some small and medium-sized copper alloy droplets to individual spinel grains restricted droplet movement, resulting in incomplete phase separation by preventing the droplets from settling fully into the underlying liquid alloy. This phenomenon was indicated in previous studies [28][29][30]. De Wilde and Bellemans et al [28,[31][32][33] have published numerous articles investigating this phenomenon; the origin of the droplets and the effect of slag-spinel composition on the droplet attachment.…”

Metal mobility and toxicity of reclaimed copper smelting fly ash and smelting slag

“…For example, the concentrations of Cu, Zn, Fe and Al in RCS y ash and smelting slag were 172.24, 124.54, 21.66, and 6.00 mg g À1 and 11.47, 13.70, 19.73, and 17.20 mg g À1 , respectively. The levels of Cu and Zn in RCS y ash were found to be much higher than their corresponding ores, 34,35 and can be used as resources for resource recovery. In addition, smelting slag can also be reused as a raw material for construction materials as it contains minerals of Si, Al, Fe and Ca.…”