• Nanobubble-enhanced flotation significantly improves the grade and recovery of auriferous pyrite from low-grade gold ores.
• Surface nanobubbles (SNBs) and bulk nanobubbles (BNBs) both contribute to enhanced flotation, with SNBs playing a critical role in surface hydrophobicity and agglomeration.
• Increased surface hydrophobicity, flow rate, and cavitation time promote nanobubble coverage and particle agglomeration, leading to better flotation performance.
• The study provides mechanistic insights into nanobubble-assisted flotation, offering a promising approach for upgrading refractory gold ores.