Role of surface roughness in the attachment time between air bubble and flat ultra-low-ash coal surface

Surface roughness plays an important role in the floatability and wettability of mineral and coal particles. However, the role of surface roughness in the floatability of coal particles has not been sufficiently investigated because coal consists of organic and inorganic materials. This paper is to obtain some insights into the role of surface roughness in the coal surface wettability. In this investigation, Taixi ultra-low-ash coal particles, with ash content of 1.55%, were polished and the polished flat coal surfaces with various roughness were obtained. The attachment time between air bubble and flat coal surface were tested at the water solution without flotation reagents. Throughout this paper, it was found that the attachment time increased with the increase of roughness of coal surface. The attachment area between bubble and flat coal surface was decreased with the increase of surface roughness. The attachment between bubble and flat rough coal surface was unstable, compared to the attachment between bubble and smooth coal surface. The rougher coal surface makes the detachment between bubble and coal surface easier than the smoother coal surface. The higher the roughness of coal surface is, the more pores and grooves the coal surface has. The pores, gaps and grooves are filled up with the water in the slurry and have negative effects on the attachment between bubble and flat coal surface.