Synergistic optimization of flotation reagent formulation for low-rank oxidized coal using Box-Behnken design

The surface of low-rank oxidized coal is rich in oxygen-containing functional groups, making it highly hydrophilic and difficult to achieve efficient flotation using traditional oil-based collectors. Aiming to achieve optimal flotation reagent regulation, this study employed Box-Behnken design combined with response surface methodology (RSM) to establish a second-order regression model for combustible recovery in low-rank oxidized coal flotation, systematically investigating the synergistic effects between oxygenated polar collectors and frothers. Flotation experiments were conducted to examine the impacts of three critical parameters: polar/nonpolar component ratio in collector, collector dosage, and frother dosage on combustible recovery. Experimental results demonstrated that under optimal reagent conditions (40.60% polar component in collector, 1500.00 g/t collector dosage, and 602.44 g/t frother dosage), the combustible recovery reached 94.47%, closely matching the model prediction of 95.27%. Mechanistic analysis revealed that polar components in the collector selectively anchored onto oxygen-containing sites on coal surfaces through hydrogen bonding, while nonpolar components formed hydrophobic oil films, synergistically reducing coal-water interfacial energy. The interaction between frother and collector further stabilized bubbles and enhanced particle-bubble adhesion. This study provides theoretical guidance and technical support for the efficient and clean utilization of low-rank oxidized coal.