Influence of particle shape and roughness on the induction period for particle-bubble attachment

David I. Verrelli, Warren J. Bruckard, P. T. L. Koh, M. P. Schwarz, B. Follink

Research output: Chapter in Book/Report/Conference proceedingConference PaperResearchpeer-review

9 Citations (Scopus)


Within the flotation community a belief has developed that some particle shapes are more 'floatable' than others. This is usually attributed to an influence of particle shape or roughness on the induction period required to achieve attachment between the particles and the air bubbles in the pulp. Up to now, such measurements have not been able to readily isolate the effect on individual flotation subprocesses. In contrast, our experimental apparatus, the CSIRO Milli-Timer, enables us to directly observe the process of particle-bubble interaction and attachment by means of a high-speed video recording, thus providing a direct measure of the induction period for attachment. To assess the influence of particle shape on induction time we used two varieties of methylated borosilicate glass particles - spheres and angular 'frit' - in a range of tightly-sized fractions. In doing this, we take care to account for the influence of other factors that could affect the induction time, such as the polar angle of sliding commencement, and approach velocity. These parameters are recorded as variables for each interaction, and corrected for using multiple nonlinear regression. Our results illustrate the importance of particle shape on induction period, with angular particles exhibiting induction periods that were an order of magnitude lower than those of spheres. Furthermore, the induction period was seen to decrease with increasing particle velocity, or kinetic energy on approach, but increased as the trajectory approached the limit of just grazing the bubble. Particle shape in mineral processing is a consequence chiefly of the mineral type and the type of grinding employed. The results presented herein indicate that attention should be paid to the shape of particles obtained from the grinding operation, besides particle size.

Original languageEnglish
Title of host publication26th International Mineral Processing Congress, IMPC 2012: Innovative Processing for Sustainable Growth - Conference Proceedings
PublisherInternational Mineral Processing Congress (IMPC)
Number of pages12
ISBN (Print)8190171437, 9788190171434
Publication statusPublished - 2012
Externally publishedYes
EventInternational Mineral Processing Congress 2012: Innovative Processing for Sustainable Growth - New Delhi, India
Duration: 24 Sept 201228 Sept 2012
Conference number: 26th


ConferenceInternational Mineral Processing Congress 2012
Abbreviated titleIMPC 2012
CityNew Delhi
Internet address


  • Attachment
  • Bubbles
  • Flotation
  • Induction period
  • Particles
  • Shape effects
  • Surface roughness

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