Characterization and Flotation of a Complex Low-Grade Copper Ore: Implications of Collector Chemistry on Gangue Selectivity

The flotation performance of a low-grade, polymetallic copper ore, dominated by chalcocite and transitional copper phases, was investigated to assess the interplay between collector chemistry, gangue mineralogy, and entrainment. QEMSCAN analysis identified chalcocite as the main copper host (62%), with minor covellite and bornite, and gangue, predominantly quartz (94%), with variable muscovite (up to 50%). Chalcocite was moderately liberated (100–200 µm), while secondary copper phases showed low exposure and strong gangue association, challenging selective recovery. Baseline flotation with potassium amyl xanthate (PAX) and sodium isobutyl xanthate (SIBX) across pH and dosage ranges showed that PAX yielded higher copper recovery but lower grade, indicating unselective gangue entrainment; SIBX offered lower recovery but higher grade, reflecting superior selectivity. Controlled muscovite doping experiments (10–50 wt.%) were employed to decouple gangue-driven selectivity loss from collector-specific interactions. Results indicate a collector-dependent sensitivity to gangue loading: PAX exhibited a pronounced decline in both copper recovery (82%–67%) and grade under increasing muscovite content, with water recovery rising by approximately 32%, whereas SIBX showed more gradual performance degradation and lower entrainment (15% increase in water recovery), highlighting its resilience in gangue-rich systems. UV-Vis and zeta potential (electrokinetic) measurements confirmed stronger PAX adsorption, consistent with its longer hydrocarbon chain, while flotation trends demonstrated a shift from true flotation-dominated recovery to entrainment-dominated regimes at high muscovite levels, particularly for PAX. This framework links mineralogy, collector chemistry, and gangue entrainment, guiding optimization of circuits for ores like Mt. Gunson while enhancing critical metal recovery, including cobalt.