Influence of Particle Size on Flotation Separation of Ilmenite and Forsterite

In addition to bubble–particle interaction, particle–particle interaction also has a significant influence on mineral flotation. Fine particles that coat the mineral surface prevent direct contact with collectors and/or air bubbles, thereby lowering flotation recovery. Calculating the particle interaction energy can help in evaluating the interaction behavior of particles. In this study, the floatability of coarse ilmenite (−151 + 74 μm) and different particle sizes (−45 + 25, −25 + 19, −19 μm) of forsterite with NaOL as a collector was investigated. The results showed that forsterite sizes of −45 + 25 and −25 + 19 μm had no effect on the ilmenite floatability, whereas −19 μm forsterite significantly reduced ilmenite floatability. A particle size analysis of artificially mixed minerals and a scanning electron microscopy (SEM) analysis of the flotation products showed that heterogeneous aggregation occurred between ilmenite and −19 μm forsterite particles. The extended DLVO (Derjaguin–Landau–Verwey–Overbeek) theory was applied to calculate the interaction energy between mineral particles using data from zeta potential and contact angle measurements. The results showed that the interaction barriers between ilmenite (−151 + 74 μm) and forsterite (−45 + 25, −25 + 19, and −19 μm) were 11.94 × 103 kT, 8.23 × 103 kT and 4.09 × 103 kT, respectively. Additionally, the interaction barrier between forsterite particles smaller than 19 μm was 0.51 × 103 kT. The strength of the barrier decreased as the size of the forsterite decreased. Therefore, fine forsterite particles and aggregated forsterite can easily overcome the energy barrier, coating the ilmenite particle surface. This explains the effect of different forsterite sizes on the floatability of ilmenite and the underlying mechanism of particle interaction.