Flotation which exploits the difference in wettability on valuable
and ganguemineral surfaces, is an important technology to concentrate
minerals. However, flotation becomes more and more difficult as a result
of the need to treat fine and ultrafine mineral particles. One challenge
in the flotation of fine and ultrafine mineral particles is the high
gangue entrainment resulting in low concentrate quality. Fine hydrophilic
gangue particles are easily dragged by the interstitial liquid film
between air-bubbles and enter the froth layer with liquids in flotation,
resulting in mechanical entrainment. It is the primary recovery mechanism
for gangue, especially fines [1].
Trahar [2] and Smith andWarren [3] found that mechanical entrainment
became significant for particles smaller than about 30 μm, and it
was proportional to the recovery of water into froth products. The severe
mechanical entrainment of fine gangue mineral particles has
been observed in many flotation testing programs [4,5]. For example,
in the bulk flotation of copper and lead, the recovery of non-metallic
gangue minerals as well as pyrite and sphalerite was increased from
about 5% for 40 μm particles to 20–30% for 10 μm particles [4].