An electrokinetic study by the straming potential method of ion exchange at oxide mineral surfaces

Abstract

The streaming potential method has been used to observe changes in the electrical double layer at the surfaces of the minerals Al₂O₃, SnO₂, Fe₂O₃, and TiO₂ in the presence of electrolytes. In addition to the normal effects of preferential physical adsorption of ions, ion exchange involving surface hydroxyl groups offers a useful hypothesis for explaining the results. Anion-exchange mechanisms appeared to be of particular importance in the reactions of phosphate, molybdate, and citrate with the oxide surfaces. In general for the particular samples used, Al₂O₃ and SnO₂ (having basic surfaces) exhibited more pronounced anion exchange than Fe₂O₃ and TiO₂ which had acidic surface.