Role of in situ gas nucleation/hydrodynamic cavitation in fine particle flotation

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Flotation of fine particles for mineral recovery is a recognized challenge in mining and minerals industry, often leading to low recovery due to low collision and attachment efficiency of fine particles with air bubbles, and poor froth quality mainly by unintentional activation, slime coating and inevitable mechanical entrainment. In literature, high intensity agitation (HIA) under controlled pulp chemistry conditions has found some success for improving fine particle flotation. However, lack of suitable instrumentation in previous studies has limited the progress in fundamental understanding of fine particle flotation systems. In a recent study, we demonstrated that dissolved air played a key role in enhancing the aggregation of hydrophobized fine particles and hence their flotation. Due to limited solubility of air under ambient conditions, the improvement of selective fine particle aggregation was rather limited. To improve fine particle flotation by taking full advantage of dissolved gases, saturating the slurry with a gas of high solubility, such as CO2 or designing a system in which air or CO2 can be continuously introduced into the slurry during HIA is highly desirable. The key gap between the concept and practice is to generate a sufficient number of cavity bubbles in situ selectively on target particles by HIA. To fill this gap, it is essential to understand gas nucleation in a given HIA system.