Molecular Dynamics Simulation Study of Bubble Attachment at the Coal Surface with Varying Coalification Degrees

Establishing the dynamics of wetting film thinning and rupture during the bubbles attached on the coal surface is extremely important for flotation. However, studying the dynamics of bubble attachment from the molecular level using molecular dynamics simulation (MDS) has rarely been reported. In this work, the dynamics of bubble attachment at three different coal [low-rank coal (LRC), bituminous coal (BC), and anthracite coal (AC)] surfaces with varying degrees of coalification were studied using MDS. In the bubble attachment process, the wetting film between the bubble and coal surface gradually become thinner until it ruptures. By comparing the bubble attachment dynamics on three different coal surfaces, the results indicate that the bubble attachment rate on the surface with strong hydrophobicity is faster than that on the surface with weak hydrophobicity. Besides, the number of hydrogen bonds between the molecules of the wetting film is decreased with the attachment of bubbles; however, it is sharply decreased on the BC surface and slowly reduces on the LRC surface before the film rupture. At the same time, the radial distribution functions (RDFs) of hydrogen bonds in the wetting film at the moment of bubble attachment on the coal surface are analyzed, indicating that the peak intensity of the RDF decreases at the time of bubble attachment. The findings in this study may help to better comprehend the dynamics of bubble attachment, which is valuable for future design in practical applications.