Fine particles inside boundary layers on rising bubbles

The aim of the present study is to find the individual paths of fine hydrophilic particles inside boundary layers on rising bubbles. Single solids with different dimensions are treated on the basis of the analytical model developed previously [E. Mileva, L. Nikolov, Colloids Surf. A132 (1998) 95]. Explicit formulae for the forces that act on these particles are presented. The obtained trajectories show that the bubbles do retain fine particles of certain dimensions. In general, smaller bubbles are more efficient in retaining micron species. Larger bubbles predominantly eject the already entrained solids. The proposed model investigation gives an explanation for the observed entrapment of fine solids in some separation processes.