Experimental Study and Thermodynamic Calculations of the Distribution of Ag, Au, Bi, and Zn Between Pb Metal and Pb–Fe–O–Si slag

The present article continues the series reviewing the thermochemistry of complex multicomponent pyrometallurgical systems. The recovery of multiple metals through the Pb-based primary and recycling processes is an economic driving force for the circular economy of the future. In this study, equilibrium distributions of Ag, Au, Bi, and Zn between PbO–FeO–FeO–SiO silica saturated slag and Pb metal phases were investigated experimentally, using high-temperature equilibration followed by rapid quenching. The measurement of phase compositions was done using microanalytical methods. Electron Probe X-ray Microanalysis (EPMA) was applied for those elements which present at relatively high concentrations. The Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) was used to measure very low concentrations of Ag and Au in slag. The starting mixtures of materials were planned using FactSage software and preliminary thermodynamic database to target specific proportions of phases and concentrations of Pb in slag after the achievement of equilibrium. Measured slag/metal distribution coefficients follow the sequence Zn ≫ Ag > Bi ≫ Au. Newly obtained results were critically assessed and used to improve the thermodynamic database. Integration between experiments and thermodynamic database development permits cross-analysis of distribution coefficients obtained in the present study with the parallel measurements of distribution in copper-based systems. The liquid slag phase was described using a two-sublattice Modified Quasichemical Model (MQM). Single sublattice MQM was applied for the liquid metal phase