Understanding the role of kerosene on the coal particle and bubble attachment process

Abstract Kerosene is akin to attach to both the particle and bubble surface, however, its role in the particle and bubble attachment process is still the subject of much debate. In this paper, we explore the role of kerosene from both macroscopic and microscopic scales using the contact angle, wrap angle and thin liquid films (TLFs) measurements on four experimental configurations, i.e., the clean coal-bubble configuration (C-B), coal and bubble with only coal treated with kerosene (Ck-B), coal and bubble with only bubble treated with kerosene (C-Bk) and both coal and bubble were treated with kerosene (Ck-Bk). On a macroscopic scale, it was demonstrated that the hydrophobicity of coal and the bubble collecting capacity could be enhanced by the addition of kerosene, and the presence of kerosene on both the bubble and coal surface produced the most pronounced outcomes. The largest contact angle and wrap angle value attained were 52.50° and 178.03° for the Ck-Bk configuration, this was in sharp contrast with the C-B configuration with the numbers being 25.25° and 86.17° respectively. On a microscopic scale, a much earlier rupture of the TLFs was observed with the Ck-Bk in comparison with the C-B, Ck-B and C-Bk configurations, with the critical rupture thickness being 192.8 nm at 1.192 s, indicating the fact that kerosene facilitated the kinetics of film thinning, however, the resultant film rupture was due to kerosene acting as surface protrusions rather than the attractive disjoining pressure. We experimentally demonstrated that kerosene manifested as thin oil films rather than microdroplets on both the coal particle and bubble surface. Based on the above experimental results, a preferential binding behavior amongst the coal particles, bubbles and oil droplets was proposed and applied to explain coal flotation in plant practice.