New insights into mechanisms of pyrite flotation enhancement by hydrodynamic cavitation nanobubbles

Although it is well known that cavitation nanobubbles significantly improve the flotation performance of mineral particles, the effects of nanobubbles on sulfide mineral surface oxidation and reagent adsorption have not been studied sufficiently. The present study was conducted to investigate the effects of cavitation nanobubbles on oxidation characteristics and xanthate adsorption behavior of pyrite surface by means of micro-flotation tests, UV-visible spectroscopy, X-ray photoelectron spectroscopy (XPS) and zeta potential measurements. The experimental results have shown that the presence of cavitation nanobubbles in the pyrite flotation pulp enhanced the floatability and flotation kinetics of pyrite and improved the adsorption capacity of sodium amyl xanthate (SAX) and dixanthogen on pyrite surface as a result of stronger hydrophobic interactions. The reactive species generated by nanobubbles were identified to be dissolved oxygen (DO) and center dot OH by quenching experiments. In addition, the zeta potential measurements have demonstrated that the rapid formation of cavitation nanobubbles on pyrite reduced the oxidation of pyrite surface. The results from this study have revealed important new mechanisms of cavitation nanobubbles enhancing sulfide mineral flotation from the perspectives of mineral surface oxidation and collector adsorption capacity and their synergistic effects that originate from unique characteristics of cavitation nanobubbles.