The Adsorption of Hematite Particles on Steel in Strongly Alkaline Electrolyte

The adsorption of hematite particles is an important but poorly understood elementary step in the electrolytic preparation of iron metal. In this work, a quantitative method of measuring the quantity of particles adsorbed onto a steel surface from a hematite suspension in concentrated sodium hydroxide electrolyte is proposed. The experimental procedure involves a preadsorption step in a hematite suspension and transfer to a particle-free solution, followed by a potentiostatic reduction of the film of adsorbed particles. The resulting current transient yields a quantitative analysis of the quantity of Fe2O3 adsorbed in the original solution. This work demonstrates that adsorption is only weakly dependent on the hematite particle concentration and pH (between 12 and 15). A simple phenomenological model for hematite reduction is proposed based on the form of the current-time transients.