Effect of particles on bubble size distribution and gas hold-up in column flotation

In flotation systems, it is generally assumed that the bubble size presents an inverse correlation with the gas hold-up. However, this hypothesis is not systematically true. The focus of this work is to study the effect of solid particles on the bubble size distribution and gas hold-up, as well as the correlation between the bubble size distribution and gas hold-up in column flotation. Experiments were conducted in two and three-phase systems using a laboratory flotation column (5.6 cm internal diameter, total height of 650 cm), and mixtures of quartz (hydrophilic gangue) and talc (naturally hydrophobic mineral), classified in four different size fractions. For the studied flotation system, experimental results are compared with literature correlations and models to reveal that hydrophobic particles affect the gas hold-up through three different mechanisms modifying the Sauter mean diameter and rise velocity, namely (1) surface interactions, and the joint antagonistic effect of (2) bubble loading and (3) coalescence.