Role of Mixed Cationic/Anionic Collector Systems on Hematite Flotation

Abstract

The adsorption mechanism of mixed cationic alkyl diamine and anionic sulphate/oleate collectors was investigated on hematite through Hallimond flotation studies. The flotation response of hematite independently with cationic and anionic collectors and with mixed cationic/anionic collector systems is assessed. The Hallimond flotation response of hematite as a function of pH and collector concentration was investigated. The study revealed that hematite flotation recovery is maximum at acidic pH with sulphate, neutral pH 6-7 with oleate, and at basic pH about 9.5 with diamine. It is the first time that the hematite flotation results show increased adsorption of cationic collector in the presence of anionic collector apart from its own co-adsorption. The presence of oleate increased the diamine adsorption due to a decrease in the electrostatic head-head repulsion between the adjacent surface ammonium ions and thereby increasing the lateral tail-tail hydrophobic bonds. The increase in oleate concentration beyond diamine concentration leads to the formation of soluble 1:2 diamine-oleate complex or precipitate and the adsorption of these species decreased the flotation since the alkyl groups of these adsorbed species are randomly oriented at the surface.