Three-Phase Contact Formation and Flotation of Highly Hydrophobic Polytetrafluoroethylene in the Presence of Increased Dose of Frothers

The time of a single bubble attachment to a rough hydrophobic solid surface with contact angle greater than 90 degrees in aqueous solutions at different frothers (n-octanol, alpha-terpineol and N-octyl-trimethylammonium bromide) in the concentration ranges of 10(-6) to 10(-3) M was compared with flotation performed under corresponding conditions. A relationship between the time of three-phase contact (TPC) formation at the bubble/liquid/solid interface and flotation rate was obtained. It was found that above a certain frother dose, irrespective of frother type, one could observe significantly longer bubble solid surface attachment time, which increases from about 2 ms to above 50-60 ms for higher frother concentrations. Accordingly, the flotation rate for the corresponding frothers concentrations decreased from ca. 0.8 s(-1) to values below 0.01 s(-1). The obtained results confirm that air can be entrapped at rough highly hydrophobic solid surfaces and show the importance of the bubble attachment time for the flotation kinetics.