BUBBLE SPREADING KINETICS AND MINERAL FLOTATION

The rate of movement of the three phase contact line when a gas bubble displaces an aqueous solution from silica surfaces of varing hydrophobicity has been examined. Bubbles with radii from 0.4 x 10(-3) to 2.6 x 10(-3) m have been studied, on surfaces hydrophobized with short chain organosilanes and long chain alcohols. The difference between the cosines of the dynamic and static contact angles is shown to be linearly related to the spreading velocity as well as a term which reflects the molecular structure of the hydrophobic surface layer. Small bubbles have a shorter spreading time than do large bubbles. Implications for flotation practice are discussed.