Inertial hydrodynamic particle–bubble interaction in flotation

Abstract

The flotation rate of particles of different size and with different contact angles, provided by surface modification of the surface of broken quartz particles, with single monodisperse bubbles was investigated. A monotonic increase of collection efficiency was observed with increasing particle size at high particle hydrophobicity where attachment and stability are at a maximum. At smaller particle hydrophobicity the dependence of collection efficiency on particle diameter for E col is interpreted as a manifestation of particle rebound. At the moment of inertial impact a particle deforms the bubble surface, creates a water layer between particle and bubble and causes the particle to recoil from the bubble surface. These phenomena as well as the influence of centrifugal force were incorporated in a model of particle–bubble inertial hydrodynamic interaction complicated by bubble surface mobility. The purpose of this chapter is an experimental test of the model based on the Generalised Sutherland Equation (GSE), incorporating the angular dependence of attachment efficiency as well as the influence of hydrophobicity in the model. Attachment is impossible at the bubble front pole (angle θ=0) vicinity because of particle rebound and at θ> θ t ( θ t angle of tangency for the particle grazing trajectory) because of the influence of centrifugal forces. With increasing particle diameter and decreasing hydrophobicity, the attachment area confined between angles θ t and θ 1 ( θ 1< θ t) shrinks, causing the collection efficiency E col to decrease and determining the slope of the descending branch of the collection efficiency–particle diameter dependence. This is quantified by means of a modification of the GSE accounting for the shrinkage of the attachment area and attachment at repetitive collision.