The interaction between bubbles and solid particles is an important mechanism in many industrial processes and flotation is a significant component of the most utilized applications. While flotation of mineral ores deals with fine particles and larger bubbles, the aim of this review is to focus on the opposite case; the interaction between smaller bubbles and larger particles encountered mostly in plastic flotation. Plastic flotation seems to be one of the appropriate methods for separating plastics, which is necessitated by increasing plastic consumption and the growing need to recycle. The first part of the article focuses on the problem of the collision of a bubble with a particle, both spherical and planar. The collision efficiency is discussed. The second part is devoted to the problem of liquid film rupture and the creation of the three-phase contact line. The third and final part focuses on the problem of the three-phase line expansion and the effect of surfactants on the resulting bubble stability.

The paper presents a brief overview of experiments on volumetric mass transfer coefficient in bubble columns. The available experimental data published are often incomparable due to the different type of gas distributor and different operating conditions used by various authors. Moreover, the value of the coefficient obtained experimentally is very sensitive to the particular method and to the physical models used in its evaluation. It follows that the Dynamic Pressure Method (DPM) is able to provide physically correct values not only in lab-scale contactors but also in pilot-scale reactors. However, the method was not correctly proven in bubble columns. In present experiments, DPM was employed in a laboratory-scale bubble column with a coalescent phase and tested in the pure heterogeneous flow regime. The method was successfully validated by the measurements under two different conditions relevant to the mass transfer. First, the ideal pressure step was compared with the non-ideal pressure step. Second, the pure oxygen absorption was compared with the simultaneous oxygen-and-nitrogen absorption. The obtained results proved that DPM is suitable for measuring the mass transport in bubble columns and to provide reliable data of volumetric mass transfer coefficient.