Stochastic induction time of attachment due to the formation of transient holes in the intervening water films between air bubbles and solid surfaces

Saiwei Li; Anh V Nguyen; Zhiqiang Sun

doi:10.1016/j.jcis.2020.01.027

Stochastic induction time of attachment due to the formation of transient holes in the intervening water films between air bubbles and solid surfaces

J Colloid Interface Sci. 2020 Apr 1:565:345-350. doi: 10.1016/j.jcis.2020.01.027. Epub 2020 Jan 16.

Authors

Saiwei Li¹, Anh V Nguyen², Zhiqiang Sun³

Affiliations

¹ School of Energy Science and Engineering, Central South University, Changsha 410083, China; School of Chemical Engineering, The University of Queensland, Brisbane 4072, Australia.
² School of Chemical Engineering, The University of Queensland, Brisbane 4072, Australia. Electronic address: Anh.Nguyen@eng.uq.edu.au.
³ School of Energy Science and Engineering, Central South University, Changsha 410083, China. Electronic address: zqsun@csu.edu.cn.

PMID: 31981843
DOI: 10.1016/j.jcis.2020.01.027

Abstract

Hypothesis: Bubble attachment to hydrophobic solid surfaces is influenced by the liquid film instability. Inclusion of transiently formed holes within the film rather than the so-called hydrophobic force in the theory is expected to better describe and explain film rupture and triple contact line formation in the bubble-surface attachment process. The significance of surface hydrophobicity and hole formation renders the stochastic nature of the induction time of attachment.

Experiments: A combination of high-speed video microscopy and theoretical analysis was applied to investigate the induction time of attachment and critical film thickness of air bubbles rising freely perpendicularly to silica surfaces of different hydrophobicities.

Findings: Film rupture occurred statistically for shorter induction times and thicker films on the more hydrophobic surface, rejecting the conjecture of hydrophobic force. Computed results of the critical base radius of the transient holes causing film rupture were merged together nicely, independently of surface hydrophobicity. The paper sheds light on the significance of hydrophobicity on the attachment process by means of a novel and easily implemented methodology, without relying on the debatable hydrophobic force.

Keywords: Critical film thickness; Film rupture; Flotation.