Adsorption of Oleic Acid on Calcium Minerals

Adsorption of oleic acid on nuorite and calcite was studied by adsorption isotherms and Electro kinetic measurements. The adsorption of oleic acid on calcium minerals was observed to proceed initially by monolayer formation at lower concentrations followed by the physical adsorption of hydrocarbon chains in the second layer and finally the precipitated calcium oleate at higher concentrations. Compared to calcite. oleic acid was found to adsorb on fluorite at very low equilibrium concentrations. From the zeta potential measurements.
the iso electric point (iep) values of fluorite and calcite are found to be 10.5 and 8,5 respectively. In presence of oleic acid the iep values of fluorite and calcite are shifted to 3.0 and 5.8 indicating specific chemical-interaction between surface calcium and oleate ions. The Free energy of adsorption was calculated from adsorption and Zetapotential measurements. The sign and magnitude of free energy of adsorption suggest the chemisorption of oleic acid on fluorite.