Improving coal flotation using the mixture of candle soot and hydrocarbon oil as a novel flotation collector

An effective flotation collector determines the flotation performance and efficiency of fine coal particles. Generally, hydrocarbon oils, such as diesel and kerosene are widely applied in the flotation circuit in coal preparation plants. However, hydrocarbon oils are not effective enough for difficult-to-float coals, such as low rank coal and difficult to float coking coal. In this study, the mixture of candle soot and hydrocarbon oil (dodecane) was used as a novel flotation collector in the flotation of coking coal and low rank coal. X-ray photoelectron spectroscopy (XPS) and contact angle measurements were used to indicate the surface properties of candle soot. Scanning electron microscopy with energy dispersive spectrometer (SEM/EDS) and attachment time measurer were used to show the adsorption of candle soot on coal particle surface. XPS and contact angle results showed that the candle soot was very hydrophobic. SEM/EDS results showed the candle soot consisted of plenty of carbon nanoparticles which could attach and adsorb on the coal particle surface and hence shortens the attachment time of coal particle and bubble. The flotation recovery of both coking and low rank coals using the mixture of candle soot and dodecane as a collector were higher than that using solo dodecane as collector. The adsorption of candle soot and other ultra-fine particles on coal particle surface enhanced the surface hydrophobicity and floatability of coking and low rank coal particles. (C) 2018 Elsevier Ltd. All rights reserved.