Emulsified flotation: Does higher emulsion stability lead to better low-rank coal flotation performance?

The flotation of low rank coal (LRC) is an important method to achieve LRC clean utilization and environment sustainable development. Emulsified diesel (ED) is an effective LRC flotation collector, but the instability limited its industrial application. In this study, diesel-sodium dodecyl sulfate (SDS) mixed collectors were used to produce ED with different stability. The ED stability and its relationship to LRC flotation performance was evaluated by flotation kinetics tests. Then the Turbiscan Stability Index (TSI) value, the contact angle, zeta potential, adhesion force test and induction time were selected to further understand the mechanism from the interactions between emulsion droplets, emulsion droplets/coal particles and coal particles/air bubbles. It was interesting to find an optimal ED stability (SDS = 2.0%) where the LRC flotation had the maximum flotation rate and the best selectivity. The mechanism analysis demonstrated that the effect of ED stability on LRC flotation is controlled by ED and air bubble dispersibility in slurry, and concentration of adsorbed SDS molecules on each ED droplet surface.