Strengthen mechanism of low-rank coal flotation: Analysis of interaction force and contact line behavior

Interaction forces between oil and coal surfaces were analyzed by AFM with oil-probe. • The mechanism between polar/non-polar oil and coal surfaces was elucidated. • The forces and contact line between bubble and modified coal surface were analyzed. • A method based interaction force and coal property analysis can enhance flotation. The challenge in intensifying coal flotation is the precise regulation of interfacial hydrophobicity. In this study, coal models with controllable surface properties were employed to investigate the intensification mechanism of collectors, using atomic force microscopy (AFM) with oil droplet probes, adhesion force measurement, and flotation kinetics analysis. AFM results revealed that nonpolar oil exhibited “jump-in” adhesion exclusively on hydrophobic coal model surfaces, whereas polar oil could adhere to weakly hydrophobic surface. Not only the surface forces, but also the hydrodynamic forces influenced the collector droplet-particle interaction, increasing the repulsion to hinder the adhesion behavior. Adhesion tests demonstrated that the heterogeneous reagent adsorption induced localized pinning/recession of the contact line between bubbles and particles, thereby influencing adhesion strength. Flotation kinetics indicated that collectors with varying chain lengths achieved optimal performance at a nonpolar-to-polar ratio of 2:1. Notably, the optimal polar content (33.33%) in composite collectors exhibited a correlation with the coal surface’s polar composition (40.48%). Important theoretical insights for the accurate management of low-quality coal separation interfaces are provided by this study. Download: Download high-res image (97KB) Download: Download full-size image