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Minerals Engineering, Vol.99, 170-178, 2016
Multi-scale analysis of the effect of surfactants on bubble properties
The effect of surfactants on bubble properties was examined in turbulent conditions. A multi-scale analysis was accomplished with the primary aim to identify the relationship between the size-scale determined surface properties leading to the decrease in bubble size. The adsorption of the surfactants triggers chain reactions acting along different size-scales: it diminishes the tension at the air-liquid interface and increases its surface elasticity (micro/nano-scale; 10(-10) to 10(-5) m) leading to modified coalescence and breakup properties and lower bubble rise velocity (meso-scale; 10(-5) to 10(-2) m) that finally result a smaller bubble size (macro-scale; >10(-2) m). The weakly surface-active DF200 and Pentanol cause a different change in the dynamic properties of the air-liquid interface compared to the strongly surface-active DF250 and PPG leading to differences in size-scale properties and eventually in bubble size. The main result of this work is a comprehensive picture of the dynamics of surface-active molecules affecting bubble size in the presence of random momentum transfer. (C) 2016 Elsevier Ltd: All rights reserved.
Keywords:Flotation frother;Turbulent condition;Sauter mean diameter;Bubble coalescence;Bubble breakup;Dynamic surface activity