Using sound to study bubble coalescence

Frothers are surfactants used in flotation to aid generation of small bubbles, an effect attributed to coalescence prevention. Studying coalescence at the moment of bubble creation is a challenge because events occur over a time frame of milliseconds. This communication introduces a novel acoustic technique to study coalescence as bubbles are generated at a capillary. The sound signal was linked to bubble formation and coalescence events using high-speed cinematography. The technique has the resolution to detect events that occur within 1–2 ms. The results show that for common flotation frothers and n-alcohols (C4–C8) coalescence prevention is not simply related to surface activity. A total stress model is used to give a qualitative explanation to the action observed. Results for salt (sodium chloride) are included for comparison.

Graphical abstractA novel acoustic technique to study coalescence as bubbles are generated at a capillary is presented. Results of coalescence prevention in presence of surfactants and salt are also included.Figure optionsDownload full-size imageDownload as PowerPoint slide