Enhancement of the Flotation of Copper–Cobalt Oxide Ore Using the Auxiliary Collector BKG721 and Its Mechanism of Action

This study examined the efficacy of BKG721 (BK), an auxiliary collector, in the flotation of an oxidized copper–cobalt ore from the Democratic Republic of the Congo (DRC). The run-of-mine ore assays 2.22% Cu and 0.25% Co, with an oxidation degree exceeding 30%. A sulfide-then-oxide locked-cycle flotation process using NaHS as a sulfidizer and sodium butyl xanthate (SBX) as a primary collector was employed. With the addition of BK, copper oxide recovery in closed-circuit tests rose from 22.49% to 26.26% and cobalt recovery from 20.00% to 28.09%, representing absolute increases of 3.77 and 8.09 percentage points, respectively. To elucidate the underlying mechanisms, contact angle, zeta potential, FTIR, and XPS measurements were performed. Contact angle results showed that BK significantly increased surface hydrophobicity. Zeta potential determinations revealed a pronounced negative shift in the surface potential of the treated malachite, indicating strong adsorption of collector anions. FTIR spectra exhibited more intense Cu–S vibration at 617 cm−1 for the NaHS + BK + SBX system compared to NaHS + SBX alone, implying strengthened chemical bonding. XPS analysis further detected the characteristic phosphorus element of the dithiophosphate constituent on treated malachite surfaces, confirming chemical adsorption. Collectively, these findings demonstrate that BK chemisorbs onto copper–cobalt oxide minerals, synergizes with the primary collector, and enhances bubble-particle attachment, thereby achieving superior flotation performance. The NaHS + BK + SBX reagent scheme provides a viable route for processing similar refractory oxidized ores.