Oxygen transport in iron oxide-containing melts and the role of electronic conduction

S. Sun and S. Jahanshahi

G K Williams Cooperative Research Centre for Extractive Metallurgy

CSIRO Division of Minerals

Box 312, Clayton South, VIC, Australia, 3169

Fax: 61 3 9562 8919

Diffusion of oxygen in molten slags is a critical rate step in many smelting processes. Recent attempts in determining the chemical diffusivity in iron oxide slags have overcome the interference of slow chemical reaction steps at the surface. The diffusivity thus obtained for liquid ‘FeO’ is nearly two orders of magnitude higher than previously reported. Diffusivity of similar magnitude has been found for calcium ferrite and iron silicate melts. Measurements on ‘FeO’-CaO-SiO2 have also been made. These data will be reviewed. It is known that these melts exhibit semiconductive characteristics. The electronic or hole conduction may play a positive role in the chemical diffusion and promote the transport of oxygen ions. It is speculated that as oxidation proceeds, locally generated positive holes move concurrently with the oxygen. Having higher mobility, they effectively drag the negatively charged oxygen ion.