Collision of Bubbles with Solid Surface in the Presence of Specific Surfactants

Maria Zednikova,Pavlína Basařová,Lucie Vobecká,Jaroslav Tihon,Jakub Crha,Jiri Vejrazka

doi:10.3390/min11050442

Abstract

The present work is motivated by the effort to understand basic processes occurring in three-phase systems where small bubbles interact with large particles. The simplified system of a single bubble rising in a stagnant liquid and colliding with a solid surface is studied. The effect of two specific surfactants, α-Terpineol and n-Octanol, is investigated. Two independent measurements are combined: (i) bubble–solid surface collision experiments and (ii) the bubble shape oscillations induced by a movable capillary. Both experiments are based on high-speed imaging resulting in the evaluation of the restitution coefficient characterizing the collision process and the relative damping time characterizing the bubble shape oscillations in the presence of surfactants. It was observed that even for small concentrations of a surfactant, both the bubble shape oscillations and the bubble bouncing on the solid surface are significantly suppressed. Two predictions for the restitution coefficient are proposed. The equations include a term characterizing the suppression of the damping time in the presence of surfactants and a term balancing the inertia, capillary and viscous forces in the liquid film separating the bubble and the solid surface. The proposed equations successfully predict the restitution coefficient of bubble bouncing on the solid surface in liquids with the addition of specific surfactants.

Highlights

Gas–liquid–solid three-phase systems are found in many industrial applications
Even the dynamic surface tension is not a suitable correlation parameter, its magnitude obtained for the two surfactant solutions with similar restitution coefficients is the same
The restitution coefficients characterizing the energy dissipation during the bubble contact with the solid surface are obtained for different bubble sizes and concentrations for two specific types of surfactants, α-Terpineol and n-Octanol

Summary

Introduction

An important one is the separation of solid materials by flotation. This process is based on the ability of some solids to remain attached to the bubble surface or bubbles to be captured on the solid surface. Particles and bubbles create agglomerates floating to the liquid surface, from which they can be separated [1,2,3,4]. The small bubble and larger particle interactions can be simplified by replacing the particle with a horizontal solid surface. The present research is motivated by the study of this simplified system to characterize the effect of surfactants and frothing agents on the interaction process of small bubbles and larger particles

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Conclusion