Bubble-particle attachment science:Advances and dilemma in bubble-particle attachment on a macroscopic scale

Bubble-particle attachment is defined as the processes of film thinning and rupture from bubble-particle en- counter,three phased contact line spreading and the formation of a stable mineralized gas floc,which is the key process in flotation. However,the underlying mechanism for bubble-particle attachment is not well understood. The attachment process is mainly influenced by the physical and chemical properties of particle and bubble,and the chemical condi- tions of the solution. The thinning rupture behavior of the thin liquid film between bubble and particle is controlled by the synergistic effect between surface force and hydrodynamic force. The deformation of gas-liquid interface further increases the complexity of the system,making the theoretical research and experimental exploration on bubble-particle at- tachment challenging. Early researches on attachment have been mainly focused on attachment probability. The induction time test on a macroscopic scale is the dominant and the attachment probability can be calculated based on induction time result. A comprehensive review on the current bubble-particle attachment probability models and the existing tech- nical bottlenecks was carried out. The existing technical bottlenecks and limitations were also analyzed. Experimental techniques such as the induction timer and high speed visualization have significantly contributed to a better understand- ing of bubble-particle attachment. It has been demonstrated that the induction time correlates well with flotation recovery. However,surface forces and film drainage information between bubble and particle could not be identified, leading to the fundamental adhesion mechanism could not be revealed by macroscopic induction time. It is an inevitable trend of the development of technology to measure the interaction force between bubble and particle and the thinning dy- namics of the thin liquid film on a nanometer scale. It can shed new light on flotation micro-mineralization process,and also provide a theoretical support for the flotation intensification of difficult-to-float coal and refractory ore.