The influence of particle size and contact angle in mineral flotation

The flotation behaviour of quartz particles, whose surfaces have been hydrophobized to varying extents with an organosilane compound, has been studied over the particle-size range from 15 to 125 μm in diameter under conditions of known bubble size and relative turbulent velocity. For a given particle size, there is a unique contact angle below which the particle will not float. This leads to the concept of a flotation domain, a region determined by particle size and contact angle, within which flotation is possible. Coarse-particle behaviour is predicted by the kinetic theory of flotation proposed by Schulze, whereas there is only a qualitative agreement with Scheludko's theory of fine-particle flotation. Calculated induction times, in conjunction with observed flotation behaviour, indicate that the attachment process is most efficient for particles of about 38 μm in diameter under the experimental conditions. The dependence of rate constant on particle size was found to be essentially linear. Implications for flotation practice are discussed.