Specific Cation Effect on the Flotation of Graphite

Inorganic electrolytes are assumed to significantly impact the flotation performance of graphite resources; however, the underlying mechanism is still unclear. In this work, the effect of three inorganic salts, including KCl, MgCl2, and AlCl3, was studied on the flotation of graphite. Flotation results indicated significantly increased graphite recovery with the addition of KCl regardless of pulp pH. MgCl2 improved the flotation performance under acidic and slightly alkaline conditions, while AlCl3 had a better activation on graphite flotation under strong acidic and alkaline conditions. Contact angle and Zeta potential results confirmed that electrolytes substantially reduced the absolute value of surface charge and the hydration of graphite surface, thus improving the hydrophobicity. Froth stability studies indicated that multivalent Al3+ and Mg2+ ions exhibit superior foaming performance than K+ ions and contribute to more stable and abundant foam. Additionally, these salt ions increased the surface tension and prevented bubble coalescence, contributing to nanobubble formation. Therefore, adding MgCl2 and KCl is of great significance for improved graphite flotation under neutral conditions.