The interaction between kaolinite and saline water in affecting the microstructure, rheology and settling of coal flotation products

The low settling efficiency of flotation froth products is a major challenge confronting the coal industry and studies on the effect of interfacial properties of coal flotation products on their rheology and settling behaviours are limited. In this work, the effect of two important variables in coal flotation, the content of kaolinite (a clay mineral) and the water salinity, on the settling of coal flotation products was studied through understanding their microstructures and rheology properties. It was found that network structures in Plateau border of coal froth were generated with the presence of kaolinite recovered through entrainment in coal flotation, while the network structure had the tendency to vanish with the increase of water salinity due to the change in the microstructure of kaolinite. Meanwhile, the storage modulus G' in oscillatory rheology and the volume of froth floating on top of water in settling exhibited the same pattern. With the presence of kaolinite and the increase of water salinity, the value of G' and the volume of froth floating on top of water both increased. However, the effect of kaolinite on the results of rheology and settling was diminished with the increase of water salinity. It was the structure of Plateau border that determined the rheology and settling behaviours of coal flotation products.