Flotation of oxidized coal using coal tar as a new collector

In this study, coal tar, an industrial by-product of the carbonization/gasification of coal, was adopted as an economical flotation collector for recovering clean oxidized coal. The characteristics of high-temperature coal tar (HTCT), its performance as a flotation collector, and the interaction mechanism between HTCT and oxidized coal were analyzed by gas chromatography/mass spectrometry, flotation experiments, X-ray photoelectron spectroscopy, and dynamic contact angle measurements. The results revealed that HTCT has a strong selective collection ability because it contains a large number of aliphatic and aromatic compounds with oxygen-containing functional groups. At HTCT dosage of 3000 g/t, 79.23% of combustible matter with an ash content of 9.99% was obtained. The major mechanism responsible for the enhanced oxidized coal separation is that, with the adsorption of HTCT onto oxidized coal, the C-O hydrophilic functional groups were covered and an increased amount of the C-C/C-H hydrophobic functional groups of the oxidized coal surface was exposed, resulting in improved surface hydrophobicity and floatability of the oxidized coal. This study provides valuable guidelines for the re-utilization of coal tar and the flotation upgradation of oxidized coal.