Abstract
With the aim of investigating deportments of precious metals in pyrometallurgical processing of waste electrical and electronic equipment, the distributions of selected precious metals (gold, silver, platinum, and palladium) between copper matte and three different silica-saturated slags (pure FeOx-SiO2, FeOx-SiO2-Al2O3, and FeOx-SiO2-Al2O3-CaO slag) were investigated at 1300 °C in controlled flowing CO-CO2-SO2-Ar gas atmosphere by a high-temperature isothermal equilibration technique. The phase compositions were analyzed by Electron Probe X-ray Microanalysis and Laser Ablation-High Resolution Inductively Coupled Plasma-Mass Spectrometry. It was shown that the distribution coefficients of gold, platinum, and palladium between matte and slag (Lm/s(Me) = [Me]in matte/(Me)in slag) were very high and increased with increasing matte grade. The distributions to the matte phase were increased by adding basic oxides alumina and lime into the acidic silicate slags. The experimentally measured distribution coefficients Lm/s(Me) followed the order of platinum > palladium > gold > silver. The present experimental results can be used for upgrading thermodynamic databases for the complex recycling processes through nonferrous smelting.
Highlights
COPPER has been playing an essential role in our daily lives for thousands of years
The concentrations of Cu, S, and O in copper matte reached constant values after 4 hours, and 4 hours was chosen as the equilibration time
As a contribution to the understanding of recycling precious metals from waste electrical and electronic equipment (WEEE) through the copper flash smelting technology, the distribution coefficients of precious metals Au, Ag, Pt, and Pd between copper matte and three different silica-saturated FeOx-SiO2-based slags were determined at 1300 °C in controlled CO-CO2-SO2-Ar gas atmospheres by high-temperature isothermal equilibration technique
Summary
WEEE is currently one of the fastest-growing waste streams[5,6,7,8] and its utilization as a secondary raw material is called urban mining It is a valuable raw material as it is higher than the natural ores in precious metals (PMs) and platinum group metals (PGMs),[8,9] used in the electronics industry as a hybrid paste in the printed circuit board for improving electrical conductivity of joints.[10,11] the environmental impact, as well as the associated production cost of precious metals from secondary sources, is much lower than those in the primary production from original ores.[9]. The behaviors of other trace metals in copper smelting have been extensively investigated,[19,20,21,22,23,24,25,26,27,28,29,30] and further attention has been directed towards the behavior of minor elements in copper/slag/gas systems,[31,32,33,34] but only few systematic studies concerning precious metals distributions between the copper matte and slag have been published.[35, 36] With the purpose to determine the optimal conditions for the recycling of precious metals from WEEE, a significant effort is required to clarify their distribution mechanisms between matte/metal and different types of smelting and refining slags
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