Bubble break-up and the role of frother and salt

Abstract

Frothers are used in flotation to aid generation of small bubbles, but little is known about the mechanisms that take place in the flotation machine to produce such an effect. Coalescence prevention is the common explanation with less attention to a frother effect on bubble break-up. This communication presents a technique to study bubble coalescence and break-up. The technique is based on the exposure of a mono-size distribution of bubbles to a turbulent field generated by a three-bladed axial flow impeller. Analysis of bubble size distributions after contact with the turbulent field gives the coalescence and break-up fraction. The presence of frother shows a significant reduction of coalescence and an effect on break-up that increases the fraction of bubbles that are 90% of the original volume. A model relating uneven frother distribution on the stretching bubble prior to rupture is developed to explain the effect of frothers on bubble break-up. The work extends to salt (NaCl) which like frother can reduce bubble size.