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

Gold ores located in the Jiaozhou region of China are well known for their huge reserve, low grade, fine dissemination, and difficulty in upgrading and froth flotation is commonly used for enriching these ores with xanthate being the collector for auriferous pyrite. This study was performed to develop a more efficient flotation process with cavitation nanobubbles for the low-grade gold ore. The batch flotation test results have shown that the introduction of nanobubbles significantly improved the flotation performance of auriferous pyrite evaluated by concentrate S and Au grade and their recoveries. The fundamental aspects of surface nanobubbles (SNBs) formation and bulk nanobubbles (BNBs) attachment on hydrophobic pyrite surface and nanobubble induced agglomeration have been investigated to understand the mechanisms of flotation performance enhancement by nanobubbles using atomic force microscopy (AFM) and focused beam reflectance measurement (FBRM). It has been revealed that the nanobubble coverage on pyrite surface is the key factor that determines pyrite surface hydrophobicity and agglomeration performance. SNBs exhibit higher coverage on pyrite surfaces with increasing surface hydrophobicity, flow rate and cavitation time, while the attachment of BNBs on pyrite surfaces increases significantly with surface hydrophobicity and cavitation time. Higher surface hydrophobicity, flow rate and cavitation time are beneficial in promoting pyrite particle agglomeration due to higher nanobubble coverage on the pyrite surface, which leads to an improved flotation performance.