Hydrodynamic cavitation (HC) is gaining traction in the mining industry as an effective means to improve flotation performance, particularly for fine and ultrafine minerals [1, 2]. While HC has shown promising results in industrial flotation circuits, the lack of mechanistic understanding has hindered its optimal implementation. In particular, the specific ways in which HC influences key subprocesses – such as bubble–particle attachment – remain insufficiently explored. This study addresses this gap by investigating how HC alters the physicochemical environment of flotation systems, focusing on the role of soluble gases and the formation of surface nanobubbles (NBs).

We hypothesize that HC enhances flotation primarily by increasing dissolved gas concentrations in water and facilitating the nucleation and stabilization of interfacial nanobubbles. These NBs can alter surface properties by increasing hydrophobicity and strengthening hydrophobic interactions [3, 4], thereby improving the efficiency of bubble–particle attachment – a crucial step in flotation that dictates recovery and kinetics. Despite the increasing application of HC in industry, this surface-science-based mechanism has not been systematically studied or linked to flotation outcomes.

To test this hypothesis, two complementary experimental systems were used. A modified laboratory-scale mechanical flotation cell was applied to coal, representing an industrially relevant mineral system. In parallel, a modified Hallimond tube was employed to float hydrophobized silica particles under controlled conditions, allowing for assessment of the attachment process. Both systems were tested with and without HC treatment to distinguish their specific effects on flotation performance and surface interactions.

The results confirm that HC significantly enhances flotation outcomes. In the coal system, flotation recovery improved by 11% using HC-treated water, and by 15% when particles were directly exposed to HC, with marked increases in flotation rate and collection efficiency. In the silica system, recovery rose by 21%, and attachment efficiency increased by more than threefold. These improvements were associated with larger particle aggregates, greater bubble wrap angles, elevated gas solubility, reduced surface tension, and disappearance of SFG (Sum-Frequency-Generation Vibrational Spectroscopy) peak at 3700 cm^-1 of the free OH dangling at the bubble surface – all indicative of favorable conditions for nanobubble formation and enhanced surface hydrophobicity [5].

This work provides compelling evidence that the flotation benefits of HC are underpinned by its effects on surface chemistry – specifically, the generation of soluble gases and interfacial nanobubbles that promote more efficient bubble–particle interactions. By bridging industrial flotation performance with fundamental surface science, this study offers novel insights into the mechanisms of HC-enhanced flotation. These findings lay the groundwork for more rational design and optimization of cavitation-based technologies in mineral processing, advancing the development of efficient and sustainable flotation strategies.