THE EFFECT OF SURFACTANT CONCENTRATION ON BATCH FLOTATION MINERAL FLUX AND FROTH STRUCTURE

It is known that the froth structure plays an important role in the po tation separation achieved. The appearance of the upper bubble surface is indicative of the internal froth structure, and is used qualitativ ely as a basis for control in industrial flotation cells. A quantitati ve kinetic model based on the flux of loaded bubble surface overflowin g the concentrate weir in a free-flowing froth is described. The froth is divided into two distinct phases; the bubble shells which contain hydrophobic solids selectively attached, and the inter-bubble lamellae , which contain non-selectively entrained solids. The flux of coal, mi neral and water for three surfactant concentrations was measured. Neit her the solids concentration nor the thickness of the bubble shells va ried significantly during the tests. The flux of bubble surface overfl owing the weir decreases to zero during the course of a test. The resu lt of this is that selectively collected solids and water that were pr esent in the bubble shells fall back into the froth and enter the lame llae. This is confirmed by estimates of the lamella thickness, which i ncreases significantly during the test, and are thicker for higher sur factant concentrations. The concentration of coal in the lamellae incr eases sharply towards the end of the test. In contrast, the transport of mineral in the lamellae decreases during the test. By developing qu antitative relationships between the froth structure and flotation per formance, the froth structure can be optimised and flotation control b ased on froth appearance automated. (C) 1998 Elsevier Science Ltd. All rights reserved.