Foaming and aggregation behaviours of polyethylene oxide and polyacrylamide in inhibiting mechanical entrainment of kaolinite in flotation using saline water

Abstract

The recovery of fine gangue particles by mechanical entrainment through the liquid between air bubbles in flotation is a major challenge in resource processing. This study explored high molecular weight polyacrylamide copolymer Magnafloc 1011 (MF1011) and polyethylene oxide (PEO), two widely used flocculants, in inhibiting mechanical entrainment of kaolinite in flotation using saline water. It was found that anionic MF1011 effectively inhibited kaolinite entrainment, but non-ionic PEO did not. The measurement of in-situ particle sizes, network structures of kaolinite and the foamability of polymer solutions indicated that the inhibition of kaolinite entrainment in flotation was governed by the network structures induced by the polymer and the polymer’s foamability. MF1011 produced a compact network structure which facilitated the drainage of kaolinite from the liquid between air bubbles and therefore the inhibition of kaolinite entrainment. By contrast, PEO produced a sponge-like network structure with a larger size which retained more water and slowed down the drainage of kaolinite. In addition, PEO was surface-active and increased the foam stability with a thicker film of liquid between air bubbles to carry kaolinite, further slowing down the drainage of kaolinite. This study demonstrates that the reduction of mechanical entrainment in flotation by flocculants is not only related to the size enlargement but also highly dependent on the aggregation structure and the flocculants’ foamability. The findings from this work will provide important guidance to select flocculants to minimize fine gangue entrainment in flotation.