Effect of calcium minerals reactivity on fatty acids adsorption and flotation

The separation between calcium minerals such as apatite and calcite by flotation relies on the use of long chain fatty acid collectors. Oleic acid, and its salt, is the main fatty acid collector and many studies have reported on the mechanisms of its interaction with calcium at the mineral surface and in solution, and on the oleic acid species present at the mineral surface. Although collector adsorption and mineral flotation depend mainly on solution pH and collector concentration, other factors such as mineral crystallinity and impurity affect mineral dissolution, influence collector adsorption and may explain the different flotation results reported in the literature on the same minerals. In this study the flotation of two calcites, with different degrees of purity, and one apatite was compared and related to the amount and type of collector adsorbed on the mineral surface, and to the reactivity of these minerals (acid-base interaction and dissolution). The results obtained in this study indicate that calcium dioleate (or dilinoleate) is the species present on the minerals surface at pH 9 and its amount increases with collector addition and calcium mineral dissolution, which results in a higher flotation of the calcium minerals. The influence of calcium site density and impurity in the minerals on flotation was also discussed.