Nanobubble-enhanced flotation of auriferous pyrite in gold ore: behavior and mechanisms

Gold ores in the Jiaozhou region of China are characterized by their abundant reserves, low grade, fine dissemination, and challenges in upgrading. Froth flotation, with xanthate as the collector, is a commonly employed method for enriching auriferous pyrite from these ores. This study aimed to develop a more efficient flotation process by utilizing cavitation nanobubbles for a low-grade gold ore. Batch flotation tests demonstrated that nanobubbles significantly enhanced the flotation performance of auriferous pyrite, as evidenced by improved concentrate S and Au grades and their recoveries. The mechanisms underlying this enhancement were explored by investigating surface nanobubble (SNB) formation, bulk nanobubble (BNB) attachment to hydrophobic pyrite surfaces, and nanobubble-induced agglomeration using atomic force microscopy (AFM) and focused beam reflectance measurement (FBRM). The results revealed that nanobubble coverage on the pyrite surface is a critical factor influencing surface hydrophobicity and agglomeration. SNBs exhibited higher coverage on pyrite surfaces with increased surface hydrophobicity, flow rate, and cavitation time. Similarly, BNB attachment on pyrite surfaces was significantly increased with surface hydrophobicity and cavitation time. Enhanced surface hydrophobicity, along with higher flow rates and cavitation times, promoted pyrite particle agglomeration owing to the increased nanobubble coverage, ultimately leading to improved flotation performance.