Comparison of flotation performances of low-rank coal with lower ash content using air and oily bubbles

The attachment interaction in a flotation process is critical because it controls the recovery of mineral particles and is dominated by the interaction energy barrier between bubbles and solid particles. In this investigation, the surface properties of coal particles and oily bubbles were evaluated via the X-ray photoelectron spectroscopy (XPS) analysis, zeta potential measurement and induction time tests. The results proved that the classical Derjagin–Landau–Verwey–Overbeek (DLVO) theory did not adequately predict the flotation performances of oily bubble flotation. The attractive interaction or hydrophobic force induced by the hydrophobic force should be considered in the extended DLVO (EDLVO) theory. Throughout this paper, therefore, it is significant to consider the attractive interaction or hydrophobic force between low-rank coal particles and oily bubbles when comparing the advantages of the flotation response using air and oily bubbles. [Display omitted] •Both DLVO and extended DLVO theory were applied to calculate the energy barrier of oily bubble-coal particle interaction.•Long-flame coal concentrate with 83.33% yield was obtained from oily bubble flotation.•Hydrophobic force is the primary driving force for oily bubble–particle adhesion.