A technique for measuring flotation bubble shell thickness and concentration

Froth structure is known to significantly affect flotation performance. However, little information is generally available on the loading of solids on bubbles in the froth. It has been noted in foam studies that the bubble shell is very viscous and distinctly separate from the inter-bubble lamellae. In froth flotation, these bubble shells contain hydrophobic solids selectively attached, while the inter-bubble lamellae contain both hydrophobic and hydrophilic solids, which are non-selectively entrained. In this technical note we introduce a measurement technique to measure directly the bubble shell thickness and solids concentration. This measurement allows the collection of particles due to attachment to bubbles and from transport in the inter-bubble lamellae to be estimated. It is found that an increase in the surfactant concentration decreases the solids concentration in the bubble shell. The average bubble shell thickness closely corresponds to the particle size, which is in agreement with previous studies.