The Electrification of Iron Oxide in Water

Abstract

The electrification of iron oxides pretreated at various temperatures from 600 to 1200 °C has been investigated in water by measuring the ζ-potential as a function of the pH. From the surface-chemical point of view, iron oxides pretreated at temperatures lower than 800 °C behave differently from those pretreated at higher temperatures ; the isoelectric point of the former samples reaches an equilibrium value in a few hours, while that of the latter samples increases slowly to an equilibrium value with an increase in the surface hydration. On the other hand, the equilibrium isoelectric point of iron oxide decreases sharply upon heat treatment at 800–1000 °C, corresponding to the change in the chemical composition of iron oxide from Fe2O3 to Fe3O4.