Micro- and nano-scale phenomena effect on bubble size in mechanical flotation cell

• In dynamic conditions, the molecular level behaviour of frothers becomes significant.
• Frother effect on dynamic surface properties of the air/liquid interface was studied.
• The change in DSP affect the bubble size (D32) observed in mechanical cell.
• Distinct effect of “weak” and “strong” frothers on DSP and D32 was evaluated.

The micro/nano-scale phenomena affecting the bubble size observed in a mechanical flotation cell were investigated using an extensive dynamic surface property study with commercial laboratory instruments. The results highlighted two distinct dynamic surface properties: a rapid adsorption/desorption rate leading to undetectable dilatation surface elasticity, and a slow adsorption/desorption process taking place within minutes and leading to a significant increase in the dilatation elasticity of the interface. The latter is observed in highly surface-active reagent grade Polypropylene Glycol and in commercial Dowfroth 250 frothers while the rapid adsorption/desorption rate is a characteristic of weakly surface-active reagent grade 1-Pentanol and commercial Dowfroth 200.The bubble size distribution and therefore the Sauter mean diameter results also highlighted the unambiguous similarity in the effect of frother on bubble size between the I-Pentanol and the Dowfroth 200 and indeed between the Polypropylene Glycol and the Dowfroth 250. The present paper examines the similarity between the two groups in order to gain understanding on how the dynamic surface properties affect the bubble size in two-phase systems.

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