Changes in surface properties of anthracite coal before and after inside/outside weathering processes

XPS, SEM and contact angle measurements were used to indicate the changes in surface properties of anthracite coal before and after inside/outside weathering processes. Weathering processes of anthracite coal were conducted on the roof and in the room respectively. XPS results showed that the content of CC and CH groups on the surface of anthracite coal was decreased after weathering processes while the content of CO, CO and OCO groups was increased. SEM results showed that the surface roughness of anthracite coal was increased after the weathering processes. Contact angle measurements showed that the contact angle of weathered coal was lower than that of fresh coal. Throughout this paper, it was found that inside weathering processes were less intense than outside weathering processes. The hydrophobicity of anthracite coal was less changed by inside weathering processes than outside weathering processes. Hydrophobic coal surface should be more useful for the flotation processes of fine coals than hydrophilic coal surface. It was recommended that storing coal inside, such as in the room or in the raw coal barns could avoid the heavy weathering processes.