Experimental and Thermodynamic Modeling Study of Phase Equilibria in the FeO–Fe2O3–SnO–SnO2–SiO2 System

Abstract

Experimental investigation and thermodynamic modeling of the phase equilibria in the FeO–Fe₂O₃–SnO–SnO₂–SiO₂ system have been undertaken to characterize Sn behavior in iron silicate slags for recycling of waste electrical and electronic materials (WEEE) through black copper process. Phase equilibria data at 865–1740°C were obtained through equilibration of synthetic mixtures in sealed silica ampoules or open crucibles, on Ir wires, or Pt–Ir foils, followed by rapid quenching and electron probe x-ray microanalysis. Phase equilibria and liquidus isotherms of the “FeO”–“SnO”–SiO₂ system in equilibrium with Sn metal, “Fe₂O₃”–“SnO₂”–SiO₂ system in air and 1 atm oxygen, FeO–Fe₂O₃–SnO–SnO₂–SiO₂–Au₂O in equilibrium with Au–Fe–Sn metal, and hematite(spinel)–cassiterite equilibria in the Fe–Sn–O system at various p(O₂) in the presence of CaO–SiO₂ or PbO–SiO₂ flux were measured in the tridymite/cristobalite SiO₂, cassiterite SnO₂, hematite (Fe,Sn)₂O₃, spinel (Fe,Sn)₃O_4+x, and fayalite Fe₂SiO₄ phase fields. New data were used for developing a self-consistent set of thermodynamic parameters for all phases to describe the Pb/Zn/Cu/Fe-containing complex system for characterizing Sn behavior in industrial primary smelting and recycling slags.