Limitations of the Nano-Bubbles Application for Beneficiation of Fine and Ultrafine Particle Flotation

The flotation of small particles is one of the considerable global challenges facing the mineral raw materials processing industry today. In the recent 10 years, the effects of cavitation Nanobubbles (NB) on the efficiency of selective flotation of fine and ultrafine mineral particles have been explored in several experimental studies. Since the findings obtained in these studies are inconsistent and contradictory, there has been a need for a theoretical assessment of the potential of the above approach for practical applications in the area of poor fine-disseminated ores beneficiation. Application of the kinetic laws, describing the behavior of dispersed systems in a turbulent flow, has allowed establishing that, similar to flocculants, NB could bind hydrophobic particles into large aggregates and thus increase the efficiency of their capture by conventional coarse bubbles in flotation. It has been demonstrated that the optimal volumetric dose of NB per unit mass of particles could be calculated by the formula 2 b pp f dd = ρ , where db is NB size, and dp and ρp – respectively are the size and density of particles. Based on the real data, the optimal numerical concentration of NB was calculated, and the established value was found to be in the range (108 -109 ) mL/L. The essential factor that limits practical applications of NB resides both in the low productivity of the known methods of NB generation and in the engineering difficulties of producing NB in sufficient quantities directly in the pulp. The last, but not the least important limiting factor is that the low concentration of small particles of valuable mineral in real pulps leads to very slow growth of such aggregates since the turbulence level in the flotation machines is almost by two orders of magnitude lower than the level required.