Maximum size of floating particles in different flotation cells

Two flotation models, particle at the liquid–gas interface and particle–bubble aggregate, both based on balance of forces, were used for evaluation of experimental data relating the maximum size of floating particles dmax and their advancing contact angle. It was noticed, by comparing the experimental and model data, that for a given flotation device and material the maximum size of floating particle dmax increases with increasing particle hydrophobicity and at the same time the acceleration a, experienced by the dmax particle at the moment of rupture, decreases with particle hydrophobicity. The acceleration values change with cell dynamics and type of flotation device and are usually not available, therefore empirical apparent cell constants A, which characterize flotation dynamics and relate particle acceleration with advancing contact angle have been proposed instead. The values of A were determined by evaluation of experimental data relating dmax and advancing (detachment) contact angle for constant: particle density, medium density, surface tension, and flotation cell dynamics. Since A depends on particle density, a tentative formula was proposed to link A with density-independent flotation cell constant Ao. The values of Ao for selected flotation cells were calculated and presented.Using quartz as an example, it was shown in the paper that a positive advancing contact angle does not guarantee flotation because a prerequisite for flotation is non-zero receding contact angle.

Graphical abstractModels of flotation, (a) particle at the liquid–gas interface, (b) particle–bubble aggregate.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights► Acceleration of particles at detachment from bubbles depends on hydrophobicity. ► No theory relating particle acceleration at detachment and hydrophobicity exists. ► Formula relating dmax with acceleration as flotation cell constant was presented. ► Equation is based on theory of “static” flotation and flotation cell constant.