Froth flotation is the predominant method for fine coal cleaning, in which hydrophobic coal particles selectively attach to air bubbles and report to the froth layer, achieving separation from gangue minerals. However, when the feed contains a high proportion of ultrafine high-ash gangue, these fine particles are readily entrained into the froth by the upward water flow, raising the ash content of clean coal and deteriorating product quality—a key bottleneck limiting further improvement of flotation performance. Polyaluminum chloride (PAC), a cost-effective and easy-to-use composite coagulant, can induce the selective flocculation of gangue minerals at low dosage through charge neutralization, thereby suppressing fine-slime entrainment. Nevertheless, how PAC basicity (OH/Al molar ratio) and its aluminum species distribution affect the entrainment of high-ash fines remains poorly understood. This study therefore systematically investigates the mechanism by which the aluminum species distribution in PAC of different basicity governs the selective flocculation of kaolinite and its flotation entrainment behavior, aiming to provide a theoretical basis for reducing clean coal ash and optimizing flotation.
 

Flotation; Ash content; Entrainment; Kaolinite; Polyaluminum chloride