Mechanism of enhanced flotation of difficult-to-float coking coal with soot-hydrocarbon oil collector

The common oily collectors,such as diesel,kerosene and others are not effective for difficult-to-float coal flotation.In this paper,the difficult-to-float coking coal was used as the coal sample,based on the super-hydrophobicity characteristics of soot particles,and the soot particles and n-dodecane were mixed in 1 g:150 mL ratio to form a novel soot- dodecane collector.The flotation results of coking coal using dodecane or novel collector were analyzed and compared.X-ray photoelectron spectroscopy (XPS) and contact angle measurements were used to indicate the surface hydrophobicity of soot.Scanning electron microscopy with energy dispersive spectrometer (SEM/EDS) was used to show the surface morphology and elements of the coal before and after the reaction with the two kinds of collectors.The results show that the soot particles mainly consisted of carbon,the surface functional groups are dominated by C—C and Cwidth=23,height=11,dpi=110C while the contact angle reaches 136°,and they are extremely hydrophobic.The coal surface after the new collector reactions adsorbed more nanoparticles and ultra-fine particles,and contained higher carbon content than that after dodecane reaction.It indicates that the soot particles can adsorb on the coal surface.The soot- dodecane mixture acts as a collector not only improving the surface hydrophobicity of coal but also increasing the surface solid convexity through the adsorption of soot particles on the coal surface,thereby speeds up the rupture of water film during bubble-coal adhesion,promotes the coal particle-bubble adhesion efficiency and improves the flotation recovery of difficult-to-float coal.