Surface chemistry and oleate flotation of three South Australian micaceous hematites

• Paucity of surface chemistry data on micaceous hematites.
• Values of isoelectric point affected by presence of inherent silica.
• Zero point of charge by titration gave better indication of surface chemistry.
• Maximum flotation using oleate observed in the neutral pH region.
• Chemisorption of oleate was the dominant mechanism of adsorption.

Previous surface chemical and flotation publications involving natural hematites have mainly focussed on the so-called massive hematites, but little has been published on the characteristics of micaceous or specular hematites which find specialist applications as pigment grade iron oxides. These include use in protective paints and as an additive in resin fillers. The surface chemistry and oleate flotation characteristics of three South Australian micaceous hematites (Warrakimbo, Williamstown and Iron Knob) have been examined using zeta potential, surface titration and oleate flotation techniques. The optimum technique for investigating the surface chemical properties as a function of pH was the surface titration technique, since inherent silica in the natural hematite samples can dominate the zeta potential measurements, even though it often represented less than 1% of the overall mineral assemblage. It was also found that both oleate solution chemistry and mineral surface characteristics dominated the flotation behaviour of these hematites. Maximum hematite recoveries were obtained at neutral pH values, close to the zero point of charge of the hematites. Chemisorption was confirmed as the dominant mechanism of oleate adsorption on the surface of the hematites.