Influence of microturbulence on the bubble-particle interaction investigated with Positron Emission Particle Tracking (PEPT)

In a flotation cell, turbulence significantly affects the recovery rate. Microturbulence influences the motion of solid particles and thus, the probability of bubble-particle aggregation. We investigated the effect of microturbulence on bubble-particle interactions with positron emission particle tracking (PEPT). Single air bubbles (db=2.5mm) were captured generated on a needle in a water flow channel. Upstream, a mesh produced an isotropic turbulent flow with 5-15% turbulence intensity. Depending on the distance to the grid, the incident flow near the captive bubble (Re=600) was characterized by eddies of different length scales and magnitude. The liquid contained up to 0.3% PMMA particles (dp=200-400µm) and up to six radiolabelled particles coated with PMMA (dp=300-400µm). The trajectories of the labelled particles were recorded, allowing us to determine the average particle distribution in the turbulent field and describe the bubble-particle interactions. These results provide valuable information to enhance our understanding of key flotation phenomena.