Nanobubble effects on hydrodynamic interactions between particles and bubbles

Particle-bubble interactions play a vital role in froth flotation that is widely used for the recovery of valuable minerals from gangue minerals. In this study the effects of nanobubbles on partide-bubble interactions were visualized using a specially designed apparatus to show the trajectory of solid particles of different degrees of hydrophobicity moving around a regular sized flotation bubble. It has been shown that particle hydrophobidty and the nanobubbles generated on particle surface enhance the partide-bubble interaction process by affecting the balance between the hydrodynamic and surface chemistry forces that control the trajectory of a particle moving around a bubble surface. Increased particle surface hydrophobicity in terms of contact angle from 50 degrees to 85 degrees and 110 degrees enhanced the particle-bubble interaction by reducing the induction time from 75 ms to 52 ms and 48 ms, respectively. In the presence of nanobubbles on particle surface, the thin film between the particle and the bubble ruptures up to 50% faster. It has also been observed that nanobubbles are capable of producing fine particle aggregates that facilitate the particle-bubble interaction process. (C) 2019 Elsevier B.V. All rights reserved.