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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