The Influence of Static Pressure on Bubble Size and Contact Angle of Quartz: Mimicking What May Happen Inside a Hypothetical Flotation Column

This paper addresses the influence of hydrostatic pressure (P-hyd) on bubble diameter (d(b)) and contact angle (theta) of quartz in pure water versus collector solution (Flotigam (R) EDA, gamma(LG) = 57 mN/m) at 20 degrees C. The pressure range (0-300 kPa) applied against the bubbles' walls mimics what may happen along the vertical axis of a hypothetical flotation column (HFC) that processes iron ore slurry via cationic reverse flotation of quartz. From the column's bottom (P-hyd approximate to 300 kPa) to its top (P-hyd approximate to 0 kPa), a continuous relief of P-hyd occurs steadily. Results indicate that a decrease of Phyd promotes a decrease of 0 from 47 degrees to 16 degrees in pure water and from 61 degrees to 42 degrees in the presence of collector. Likewise, d(b) increases approximately 60% from the column's bottom to its top and, consequently promoting an increase in bubble ascending velocity (v(b)). Values of v(b) and d(b) were used to assess the bubble Eotvos number (Eo) and the Weber number (We) aiming at characterizing bubble hydrodynamics. It was found that inertial forces dominate surface forces (We > 1) as d(b) > 1.86 mm. This dominance constitutes a preliminary indication of a greater likelihood of coarse particles (diameter > 100 mu m) detaching from bubbles. This situation is typically found in the upper parts of the HFC addressed in this paper.