ADHESION OF AIR BUBBLES TO A FLUORITE SURFACE IN THE PRESENCE OF OLEATE SPECIES

Measurements of the detachment force of air bubbles from a surface of fluorite covered with an oleate film immersed in an aqueous sodium oleate solution or water were carried out. The contact angles for the systems fluorite/oleate film-drop of aqueous sodium oleate solution-air, fluorite/oleate film-air bubble-aqueous sodium oleate solution, and fluorite/oleate film-air bubble-water were also measured. The detachment forces were also calculated from the measured contact angles. It was found that the adhesion of air bubbles to the fluorite surface increased considerably in the presence of an oleate film on the fluorite surface, but decreased if the oleate film was at the water-air interface. Good agreement between the theoretically calculated and the measured values of the detachment force for the system fluorite/oleate film-air bubble-sodium oleate aqueous solution when the concentration of this latter solution was in the range 0 to 87.1 mg/dm3 was also found, but for concentrations over 87.1 mg/dM3 the calculated values of the detachment force were higher than the measured values. The calculations and measurements indicate that the most favourable condition for the adhesion of air bubbles to fluorite grains is the presence of a chemisorbed film of oleate without surface precipitation of calcium oleate salt at low concentrations of oleate species in water.