In mineral processing, the flotation behaviour of particles is governed by particle-bubble interactions. These include bubble-particle collision, attachment of particles to bubbles and stability of bubble-particle aggregates. Flotation of fine particles is mostly determined by the efficiency of particle-bubble collision. In contrast, the disruption of bubble-particle aggregates in the turbulent zone is the main reason for the low recovery of coarse particles.
In this paper, a detachment of particles from bubbles was investigated using a novel electro-acoustical technique. The experimental setup consisted of a loudspeaker connected to a computer trough an amplifier. A teflon capillary tube was attached to the membrane of a loudspeaker. A bubble-particle aggregate on the other end of the capillary tube was subjected to vibration when the sinusoidal signal of fixed frequency and amplitude generated by the computer was transmitted to the loudspeaker. A range of amplitudes and frequencies was investigated. The critical amplitude of particle detachment was determined.
The detachment experiments were conducted using model quartz particles of various size and hydrophobicity. Results showed that particles with high contact angle (90°) required high amplitudes for detachment from bubbles. In contrast, quartz particles with low contact angle (49°) exhibited the considerably lower critical detachment amplitude. The critical detachment amplitude was related to the stability of bubble-particle aggregates. The results of electro-acoustical experiments correlated well with the recovery of particles observed in corresponding bench flotation tests.

Keywords: coarse particle flotation; bubble-particle detachment; stability of bubble-particle aggregates