Dodecylamine-promoted persistence of ultrasonication-generated microbubbles and its implications for quartz flotation

Dodecylamine (DDA), a cationic surfactant widely used in quartz flotation, can promote microbubble formation during ultrasonication; however, these ultrasonication-generated ( UG ) microbubbles may rapidly dissolve once the ultrasonic field is removed. This study hypothesizes that combining DDA with air oversaturation can markedly suppress post-ultrasonication microbubble dissolution and thereby enhance quartz flotation. UG bulk and surface microbubbles were characterized using dissolved-air measurements and optical imaging, while surface tension and contact angle measurements were used to elucidate the role of DDA. Flotation performance was evaluated using bubble pick-up and micro-flotation tests. DDA markedly increases the population of persistent UG microbubbles under air-oversaturated conditions, whereas no clear DDA-induced increase is observed under non-oversaturated conditions. This behavior is consistent with the coupled effects of air oversaturation and the DDA-induced reduction in gas–liquid interfacial tension, which together enhance the diffusive stability of microbubbles. The unexpectedly rapid decrease in bubble contact angle following bubble-solid contact in DDA solution suggests possible interfacial redistribution of DDA from the solid surface to the gas–liquid interface, which may accelerate the local reduction in gas–liquid interfacial tension. The resulting larger population of persistent microbubbles markedly enhances quartz-particle attachment to carrier bubbles and improves flotation recovery, highlighting the coupled roles of air oversaturation and surfactant adsorption in ultrasound-assisted flotation