Coarse particles sedimentation within a quasi two-dimensional rising foam

Flotation is extensively used in wastewater treatment or within the minerals processing industry. Foam and its function in those processes are not completely understood yet. Consequently, we investigated on liquid films and on particle behaviours within a quasi. two-dimensional rising foam, depending on (i) surfactant concentrations and (ii) particle sizes. Experimental conditions were free-drainage in polydispersed foam. (i) The surfactant concentrations influenced foam rising velocities and particles trajectories. A minimum particle sedimentation velocity was found for a specific surfactant concentration. (ii) The particles size affected their sedimentation. Larger particles moved more slowly in Plateau borders due to their larger contact area. They had the tendency to reside within foam nodes longer than smaller particles. However, when they did not reside within the nodes, particle instantaneous sedimentation velocities attained maximum values within nodes. (c) 2007 Elsevier B.V. All rights reserved.