Adsorption and zeta potential studies relevant to hematite ore reverse froth flotation

Reverse froth flotation is the most commonly used concentration method for iron ores, where the quartz gangue is floated, while the iron oxides are depressed by starches. In this paper, the mechanisms related to iron ore anionic reverse flotation are investigated by flotation, electrokinetic and high pulp density (20% solids) adsorption studies in alkaline medium using sodium oleate as the model collector. Distribution diagrams of silicate and oleate species are employed to interpret the effects of pH on the electrokinetic and adsorption studies. The flotation experimental results showed that with Ca2+ as activator, quartz responded to flotation well, whereas hematite does not. The changes in zeta potential for quartz are attributed to the hydroxylation of the quartz surface at different pH values and collector concentrations. Coated starch can shift the zeta potential of hematite particles to less positive values and increase its potential differences from quartz and support quartz-hematite separation during flotation. Adsorption results indicated that sodium oleate adsorbs onto the mineral surfaces to form surfactant multilayers due to the lateral interaction between hydrocarbon chains. Adsorption kinetics studies showed that calcium ions can change the collector adsorption kinetics curve on quartz from first order to second order. Minerals & Metallurgical Processing, 2012, Vol. 29, No. 3, pp. 148-155. An official publication of the Society for Mining, Metallurgy, and Exploration, Inc.