Bubble–particle collision interaction in flotation systems

•Particle trajectories and particle–bubble collisions observed experimentally.•Model developed to describe particle trajectories around single bubble.•Comparison between experimental and theoretical particle trajectories.•Assessment of effects influencing bubble–particle interaction: gravity, inertia, microhydrodynamic drag.

This work studies single bubble–single particle interactions of interest to flotation applications. An experimental device has been developed where a standing bubble is approached at prescribed flow velocity by an aqueous dispersion of particles – much smaller than the bubble. Two separate high-speed cameras are employed to monitor the bubble surface from two different Cartesian directions allowing thus a 3D perspective of particles trajectories and collisions with the bubble. A special feature of the device is that the velocity of the suspension and the size of the bubble can be independently adjusted in a range of values that corresponds to the flotation process. This paper presents experimental trajectories and velocities of particles as they approach and flow past a bubble. A theoretical model has been developed to describe such particle trajectories and velocities. Comparison between experimental observations with model predictions allows a detailed assessment of governing forces and better understanding of their contribution to particle–bubble interactions. It is shown that microhydrodynamic drag has a distinct role in matching experiments with predictions.

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