Probing the interaction between coal particle and collector using atomic force microscope and density functional theory calculation

Revealing the interaction mechanism between coal and collector is essential for coal flotation. However, direct determination of the interaction force between coal and collector has rarely been reported. In this work, an atomic force microscope (AFM) was used to directly measure the interaction between collectors, i.e., n-dodecane, nonyl benzene and sub-bituminous coal (SC), bituminous coal (BC) and anthracite coal (BC) with different metamorphic degrees, and density functional theory calculation (DFT) was used to simulate the interaction mechanism of coal and collectors at the molecular level. The results indicate that the interaction force between coal and collector improves with the increase of coal metamorphic degrees for the same type of collector. Extended DLVO fitting reveals that the hydrophobic interaction decays exponentially. Consistent with the AFM force measurement results, the adsorption energy between the coal and the collector calculated by DFT all show that the interaction between n-dodecane and the three types of coals is weaker than that of nonyl benzene. This work provides quantitative information on the molecular interaction mechanism underlying the adsorption of collectors on the coal of varying surface chemistry at the nanoscale, with valuable implications for developing influential collectors for coal preparation and many other engineering processes.