Activities of Solid FeO-ZnO and Fe-Zn Systems

Fundamental studies of zinc extraction by the iron-reduction distillation process

Abstract

Phase relations of iron-zinc-oxygen system at 1100K have been determined by the X-ray microanalysis and X-ray diffraction studies of the quenched samples. Also the partial oxygen pressure have been measured by the e.m.f. method using the zirconium oxide solid electrolytes. The activities of Fe and Zn in the alloys as well as the activities of FeO and ZnO in the oxides were obtained by applying the Gibbs-Duhem relation to the alloy and oxide phases. The results are summarized as follows:(1) Phase relations of Fe-Zn-ZnO-FeO system at 1100K were composed of two-phase fields (Fe+FeOs.s., Fes.s.+ZnOs.s. Zn (1)+ZnO) and three-phase fields (Fe+ZnOs.s.+FeOs.s., Fes.s.+Zn (1)+ZnO). The mutual solubilities between FeO and ZnO were determined.(2) Activities in Fe-Zn alloys at 1100K showed considerable positive deviations from Raoult's law except the activity of zinc at Zn-rich region which exhibited a negative deviation.(3) Both the activities of FeO and ZnO in solid FeO-ZnO system at 1100K showed considerable positive deviations from Raoult's law except the activity of zinc oxide at ZnO-rich side which exhibited no deviation from Raoult's law in the range up to the solid solubility limit. The activity coefficients at infinite dilution, γ⁰FeO andγ⁰ZnO, at at 1100K were estimated at 4.4 and 6.6, respectively.