Evaluating the wettability of coal and non-coal mineral particles by microcalorimetry

The surface wettability of coal and non-coal minerals is one of the critical factors influencing their separation and processing. In this study, ten common coal and non-coal minerals were selected to analyze the quantitative relationship between their surface wettability and wetting heat through contact angle, specific surface area and microcalorimeter measurements. For all minerals except anthracite, the heat flow curves measured by microcalorimetry initially rose rapidly, then gradually declined and stabilized, which was opposite to the wetting curve change of anthracite. Both the theoretical calculation and microcalorimeter measurement indicated that the wetting process of anthracite was endothermic, while those of other minerals were exothermic. The wetting heat gradually decreased with the increase of surface contact angle of minerals. The wetting heat of minerals measured by the microcalorimeter exhibited a positive proportional linear correlation with the cosine of the mineral contact angle, which is consistent with the theoretical model. This paper will provide a valuable insight into the surface wettability of coal and non-coal mineral particles from a thermodynamic perspective. • The wettability of minerals was analyzed by theoretical and measured wetting heat. • The wetting heat of coal gradually reduced with the increase of contact angle. • The wetting shifted from exothermic to endothermic as contact angle increased. • The measured wetting heat linearly correlated with the cosine of contact angle.