A review of bubble surface loading and its effect on bubble dynamics

In mineral flotation, surface loading dynamics of bubbles due to particle attachment and detachment in a turbulent environment is central to the understanding of separation kinetics of valuable minerals from gauge that governs the final product recovery. This review presents a comprehensive account of the current understanding of different bubble surface loading (BSL) measurement techniques both in quiescent liquid and typical flotation environment. It is noted that acoustic emission method is a potentially useful technique for online measurement of bubble surface loading in industrial systems although its translation to industry practice has not been satisfactory yet. From theoretical perspective, estimation of the BSL parameter is not quite straightforward due to limited understanding of the effect of surface loading on the flow field around the rising particle laden bubbles which governs the drag coefficient. Lack of knowledge in estimating drag coefficient affects estimation of rise velocity of the aggregates hence the recovery rate constant. It is also noted that bubble coalescence behaviour is delayed in presence of surface loading. Nevertheless, when coalescence occurs, it leads to loss of surface loading due to liberation of surface energy as oscillatory waves on bubble surfaces. Finally, a summary of the current challenges in this space is presented, and possible solutions are laid out to which future research endeavour should be directed.