Experimental study on enhanced flotation of fine molybdenite by CO2 nanobubbles with positive charge

The flotation efficiency of fine molybdenite remains low because of the strong hydrophilicity and electronegativity of the edges and the low probability of bubble-particle collision. In this work, an effective approach has been proposed to enhance the flotation of fine molybdenite using positively charged CO 2 nanobubbles (NBs) based on electrostatic driving and NB bridging effects. The positively charged CO 2 NBs with an average size of approximately 210 nm and a zeta potential of about 9 mV were prepared using a micro-nano bubble generator based on circulating countercurrent and multiphase vortex gas-liquid shearing technology. The flotation test results showed that compared with conventional flotation, the introduction of NBs could significantly improve the flotation efficiency of fine molybdenite, and the strengthening effect of CO 2 NBs on the flotation of fine molybdenite was better than that of air NBs. The interaction mechanism was illustrated through contact angle measurements, turbidity measurements, zeta potential measurements, hydrophobic agglomeration behavior analysis and fractal dimension analysis. On one hand, positively charged CO 2 NBs could be adsorbed onto the basal and edge surfaces through hydrophobic attraction and electrostatic attraction, respectively, to enhance the overall hydrophobicity of molybdenite particles, facilitate hydrophobic agglomeration of particles, and thereby increase the apparent size of particles and the probability of collision between particles and macro-sized bubbles. On the other hand, CO 2 NBs could boost the attachment between particles and macro-sized bubbles through bridging effect, thereby significantly improving the flotation efficiency of fine molybdenite. This research has important theoretical and practical value in expanding the enhanced methods for the flotation process of fine molybdenite