Interaction force between coal and Na-, K- and Ca- montmorillonite 001 surfaces in aqueous solutions

In coal beneficiation, the clean coal would be easily contaminated with the super fine montmorillonite particles coating on it. This interaction between coal (hydrophobic) and montmorillonite (hydrophilic) surfaces is the interactions between the asymmetric systems. Previous studies detected the force between the montmorillonite and graphite or between the montmorillonite mounted tip and coal substrate to represent the interactions between 001 surface and coal. However, there is still lack of experimental direct measurement on the interaction between montmorillonite 001 surface and coal macerals. In this study, proposes methods for determinine the interactions between coal macerals and 001 surface of Na-, K- and Ca- montmorillonite directly by using an atomic force microscope (AFM). The results indicate that the 001 surface of Na- and Ca- montmorillonite served as the chaotropic and kosmotropic surface when it is adjacent to coal surfaces, with an attractive force and repulsive force occurring between them, respectively. The 001 surface of K-montmorillonite served as the chaotropic surface and kosmotropic surface while it is close to liptinite and inertinite, respectively. This chaotropic or kosmotropic property of the surface is determined by the coordination number of the cations and wettability of the hydrophobic surface simultaneously.