Froth flotation of sphalerite: Collector concentration, gas dispersion and particle size effects

• The effect of particle size, bubble size distribution, superficial air velocity, and collector dosage were studied.
• Main results showed that each particle-size distribution required an optimal bubble-size profile.
• Carrying capacity of the microbubbles was found to be higher for the fine than for the coarser sphalerite.
• Sphalerite recovery proceeded from mechanisms as true flotation, entrainment and aggregate-flotation.

This experimental work on sphalerite flotation investigated the effect on flotation performance of three particle size fractions, namely, coarse (d80 = 100 μm), medium (d80 = 39 μm) and fine (d80 = 15 μm), bubble size distribution, superficial air velocity, and collector dosage. Bubble size distributions were characterized with the image analysis technique. The two-phase (liquid–gas) centrifugal pump and frother addition (MIBC, 5–30 ppm) allowed generating bubble diameters between 150 and 1050 μm, and air holdup ranging from 0.2% and 1.3%. Main results showed that each particle-size distribution required an optimal bubble-size profile, and that sphalerite recovery proceeded from mechanisms involving true flotation (when Jg = 0.04 cm/s and 1.9 × 10−4 M SIPX). However, cluster-flotation occurs at high collector dosage (when Jg = 0.04 cm/s and d32 between 285 and 1030 μm), and requiring further investigation.