Particle–bubble interaction and attachment in flotation

Verrelli, David I., Koh, Peter T. L. and Nguyen, Anh V. (2011) Particle–bubble interaction and attachment in flotation. Chemical Engineering Science, 66 23: 5910-5921. doi:10.1016/j.ces.2011.08.016

Author Verrelli, David I.
Koh, Peter T. L.
Nguyen, Anh V.
Title Particle–bubble interaction and attachment in flotation
Journal name Chemical Engineering Science   Check publisher's open access policy
ISSN 0009-2509
Publication date 2011-12-01
Sub-type Article (original research)
DOI 10.1016/j.ces.2011.08.016
Volume 66
Issue 23
Start page 5910
End page 5921
Total pages 12
Place of publication Oxford, United Kingdom
Publisher Pergamon
Collection year 2012
Language eng
Formatted abstract
Flotation is an important unit operation in the minerals industry, among others. Current state-of-the-art flotation modelling combines computational fluid dynamics (CFD) with user-defined algorithms based on the "induction time" concept to describe selective bubble-particle attachment and separation of hydrophobic and hydrophilic particles.
     We have undertaken experimental studies permitting direct observation of particle-bubble interaction and attachment at the microscale to provide empirical data for comparison with new theoretical predictions.
     Observations were made on a model system in which 150 μm glass particles were dropped onto a captive 1.3 mm air bubble formed in water within a glass cell. The interactions were recorded on high-speed digital video, permitting direct estimation of relevant parameters such as the approach velocity, and the duration of particle sliding over the bubble surface. A new experimental configuration has allowed the particle path toward, around, and away from the bubble to be totally unimpeded.
     Particle trajectories show a significant deviation at separations much larger than their own diameter; such deviations are due to the hydrodynamics. Comparisons with theoretical predictions indicate that the bubble surface exhibited mobility intermediate between "full slip" and "no slip". Theoretical predictions for an immobile bubble surface were practically symmetrical about the bubble's equator, while asymmetry was apparent in the theoretical predictions for a mobile bubble surface. However, the strongest asymmetries were seen in the observed particle trajectories and speeds.
     Particles dropping more centrally were seen to slide over the surface of the bubble. In several cases the sliding particle 'jumped in' toward the bubble, which is interpreted as the precise moment of attachment. This provides for a direct estimate of the threshold duration to achieve attachment, i.e. "induction time". Among the events observed were rotation of the particle upon jumping in, and particle jump-in below the bubble's equator. Explanations are proposed in terms of particle properties and flow phenomena.
Keyword Bubble
High-speed video microscopy
Mathematical modelling
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Chemical Engineering Publications
Official 2012 Collection
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Citation counts: TR Web of Science Citation Count  Cited 27 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 40 times in Scopus Article | Citations
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Created: Wed, 12 Oct 2011, 23:03:38 EST by Professor Anh Nguyen on behalf of School of Chemical Engineering