Malachite flotation using carbon black nanoparticles as collectors: Negative impact of suspended nanoparticle aggregates

•Carbon black nanoparticles (CB-NPs) significantly influenced malachite floatability.•Malachite floatability increased with increasing CB-NP concentrations at low levels.•Malachite floatability sharply decreased at high CB-NP concentrations.•Bulk CB-NP aggregates reduced the kinetic rates of interaction between malachite and bubbles.