Changes in the hydrophobicity of anthracite coals before and after high temperature heating process

Coal spontaneous combustion can make coal suffer a high temperature heating process. This heating process can change physical and chemical properties of coal, but the changes in the hydrophobicity of coals before and after high temperature heating process have not been investigated adequately since the natural hydrophobicity of coal usually determines the flotation behavior of fine coals. Therefore, this paper is to investigate the changes in the hydrophobicity of coals before and after the high temperature heating process. X-ray photoelectron spectroscopy (XPS) and contact angle measurements were used to indicate these changes. The heating temperature was 600 degrees C. The heating times were 0 (original coal), 10, 20, 60, and 120 min, respectively. An ultra-low-ash anthracite coal with ash content of 1.55% was used to conduct the high temperature heating process in the laboratory. Throughout this study, the hydrophobicity of anthracite coal can be reduced quickly after high temperature heating process since the content of hydrophilic functional groups on anthracite coal surface is increased while the content of hydrophobic functional groups is reduced by the high temperature heating process. (C) 2014 Elsevier B.V. All rights reserved.