Effect of hydrocarbon chain configuration on the surface activity of fatty acids-effect of solution pH

The flotation behaviour of fluorite mineral was studied using fatty acids with different configurations. These include oleic, linoleic, and linolenic acids with one-, two- and three double bonds, respectively, in their hydrocarbon chain. The study showed that the solution pH has a diversable effect on the surface activity of the unsaturated fatty acids. Adsorption density measurements, at low pH's, revealed that the equilibrium concentration of the surfactant, at which there is a steep increase in the isotherm, decreases with increasing unsaturation. On the other hand, at high pH, it was noticed that there is a specific equilibrium concentration, for each surfactant, at which the adsorption density decreases. This equilibrium concentration increases with increasing unsaturation. Besides, it was found that the double bonds shifts the flotation pH towards the acidic region. This behaviour was studied in the light of surface tension measurements.