Direct force measurement of critical detachment force between a particle and an air bubble using dynamic interaction force apparatus

Bubble-particle detachment is the main factor to limit the recovery of coarse particle in flotation. A dynamic interaction force apparatus (DIFA) was designed to investigate the bubble-particle detachment process. The DIFA could directly measure the detachment force and visually observe the interfacial behavior during a particle detaching from an air bubble. The detachment process was composed of three sub-processes: bubble stretching process, bubble sliding process, and bubble necking process. Calculated detachment force showed good agreement with measurement force. The critical detachment force, defined as the maximum detachment force during detachment process, was proposed to determine whether a particle completely detached from a bubble. The Bond number was modified using the critical detachment force. The modified Bond number, which considers the bubble-particle detachment process, was more appropriate to evaluate the bubble-particle aggregate stability. It was found that the bubble-particle aggregate stability was enhanced by increasing surface hydrophobicity, whereas the stability was weakened by increasing particle size. The weak stability of bubble-particle aggregate results in a low recovery in coarse particle flotation.