Effect of frothers on the interaction between air bubbles and coal particles

Abstract

Frothers not only modify gas–liquid interfacial properties, but also alter coal particle surface properties, thereby influencing bubble–coal particle interactions in froth flotation processes. While previous studies have focused on frothers’ effects on gas-liquid interfaces, their impact on coal surface hydrophilicity and coal-bubble interactions remains underexplored. In this study, we measured the bubble–coal interactions using an anthracite coal sample under varying concentrations of MIBC and DF250 frothers during attachment and detachment processes of coal, in combination with surface tension measurement, XPS, FTIR, contact angle measurements, and quantum chemistry calculations. The results demonstrate that both MIBC and DF250 will adsorb on the coal surface and impart hydrophilicity onto it. Increasing frother concentration will render the coal surface more hydrophilic, which will prolong liquid drainage time (t_drain) and enhance the attachment repulsive force (F_adr) during bubble–coal particle attachment. At the same time, this also will decrease the detachment attraction force (F_det) of coal particle. In the examined concentration range, DF250 exhibits more pronounced effects than MIBC, meaning that it is less suitable for coal flotation. For both frothers and in the studied concentration range, F_adr consistently exceeds F_det, meaning that immediately removal of coal-bubble aggregates from the mixing zone of flotation cell seems to be desirable. In addition, regardless of the presence or absence of frother in water and the structure difference in MIBC and DF250, the contact angle of coal surface should be a good indicator of the strength of coal-bubble interactions.