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This thesis investigates the effect of energy dissipation (also called energy input) on the flotation kinetics of apatite in basic medium (pH10.5) with sodium oleate (40mg/L and 80mg/L) as collector. A special equipment called Oscillating Grid Flotation Cell (OGC) was adopted because the movement of the grids inside OGC creates a near isotropic turbulence, whereas the conventional mechanical flotation cells generate regions with different levels of turbulence: the intensity of turbulence is strongly higher close to the impeller and is very low far from it. The agitation created by the impeller influences all flotation sub process: particle/bubble collision, adhesion and detachment. Macroturbulence promotes the particle suspension inside the cell, whilst microturbulence disperses the bubbles and promotes collisions between bubbles and particles. All these phenomena influence the kinetics of the process. Moreover, because very coarse (+150μm) and fine (-44μm) particles of apatite show lower recovery than an optimum size range, it is important to study the influence of energy input on the kinetics of these sort of particles. The results showed that flotation kinetics of apatite is strongly influenced by the energy input, particle size and collector concentration (contact angle). Fine particles (-44μm) require high energy input (2 kW∙m) probably to promote collision and the increase of energy input did not destroy the bubble/particle aggregate. Conversely, the flotation kinetics of coarse particles (+150μm) was strongly affected by energy input: 0,1 kW∙m promoted high flotation rate, but increasing the energy input to any higher level the flotation kinetics exhibits a clear decay, probably due to the destruction of the aggregate particle/bubble. The effect of hydrophobicity is evaluated testing two collector concentrations. With high collector concentration the flotation rate increased for all levels of energy input, these results evidenced the influence of hydrophobicity on the attachment and stability of the aggregate particle/bubble.

Influência da dissipação de energia na cinética da flotação aniônica direta de apatita em meio básico.