A theory of combined microflotation is proposed which reasonably accurately describes the kinetics of fine particles flotation utilising small quantities of fine bubbles in combination with the coarse bubbles. The theory has been applied to analyse the experimental findings of fine quartz flotation by the method of combined microflotation. The theory predicts the capture efficiency of particles and fine bubbles by the coarse bubbles and the efficiency of hetero-aggregation of particles and fine bubbles in the non-uniform hydrodynamic field of a flotation cell. It is shown that the optimal size of the fine bubbles increases approximately linearly with increase of the size of particles and diameter of the coarse bubbles; the dependence on the size of particles is stronger than on the diameter of the coarse bubbles. A theoretical explanation is offered for the linear dependence of the combined microflotation rate constant on the volume dosage of fine bubbles per weight unit of solids.

The impact of microbubbles on flotation efficiency has been studied for ultrafine ( < 12 μm) chalcopyrite recovery from chalcopyrite/quartz artificial mixtures using laboratory pneumomechanical and column flotation cells. The findings show that significant enhancement in the efficiency of ultrafine minerals beneficiation is ensured by using the method known as combined microflotation based on simultaneous use of both coarse air bubbles (conventionally produced in flotation cells) and microbubbles generated by a standalone generator in the form of air in water microdispersion. Introduction of microbubbles at the dosage of 8–16 L per 1 kg of chalcopyrite before its treatment in a pneumomechanical flotation cell increased the flotation rate by several times. In the case of column flotation, introduction of microbubbles at the dosage of around 50 L per 1 kg of chalcopyrite following pulp treatment in a static mixer for 60 s before feeding it into the column cell increased the copper recovery by more than 50%. Increasing the treatment time of the pulp in the static mixer to 80 s led to gains in copper recovery by more than 60%, even in the absence of cell aeration by coarse air bubbles (turbulent microflotation regime).

This paper discusses the results of flotation tests on finely dispersed Cu–Pb–Zn–Fe–sulphide ore of the in which microbubbles finer than 50 µm were used as carriers. It was found that volume dosage of microbubbles in the amount of 0.1 liter per kilogram of solids increased the flotation rate of various sulphide ore components by factors of 2–4 and recovery by 0.5–3%. An analysis of the recovery kinetics was performed using previously developed theory of combined microflotation. It was found that the major effect of using microbubble carriers, which has led to the gain in flotation rate efficiency, can be attributed to the fact that the effectiveness of particles and microbubbles hetero-aggregation exceeds the capture efficiency of particles by coarse bubbles by factors of more than 50–70 and the flotation rate of mineralised microbubbles by coarse bubbles by several times compared to the flotation rate of separate particles.