Phase equilibria and thermodynamic modelling of the PbO–ZnO-“CuO0.5”-SiO2 system

Abstract

The phase equilibria of the PbO–ZnO-“CuO0.5“- SiO2 system were studied as part of the investigation of the 19-component PbO–ZnO–Cu2O–FeO–Fe2O3–CaO–SiO2–Al2O3–MgO–S-(As, Sn, Sb, Bi, Ag, Au, Ni, Cr, Co as minor elements) slag/matte/metal/speiss/gas system in support of the development and optimization of pyrometallurgical processes. In the experimental study, samples were equilibrated at high temperatures, then quenched, and the lead, zinc, copper and silicon concentration in the phases were directly measured by electron probe X-ray microanalysis (EPMA). The cristobalite (SiO2) primary phase field of the PbO–SiO2 system was experimentally studied between 1575 and 1717 °C. The massicot (PbO), zincite ((Zn,Cu)O), cuprite (Cu2O), copper plumbite (Cu2PbO2) and Pb2SiO4 primary phase fields of the PbO-“CuO0.5”-SiO2, PbO–ZnO-“CuO0.5” and PbO–ZnO–SiO2 systems were studied between 664 and 1100 °C. The cuprite (Cu2O), willemite ((Zn,Cu)2SiO4), larsenite (PbZnSiO4) and melilite (Pb2ZnSi2O4) secondary phase fields of the PbO–ZnO-“CuO0.5”-SiO2 system in equilibrium with metal and tridymite/quartz (SiO2) or zincite ((Zn,Cu)O) were studied between 745 and 1100 °C. The zincite ((Zn,Cu)O), tenorite ((Cu,Zn)O) and willemite ((Zn,Cu)2SiO4) solid solutions in equilibrium with air or pure O2 at 1 atm were studied between 900 and 1100 °C. Using the FactSage thermodynamic calculation software, a self-consistent set of parameters based on the Modified Quasichemical Model (MQM) were developed to describe the newly obtained and existing experimental data.