Influence of the hydrophobicity of mineral particles on the energy of interaction with air bubbles during flotation. Part II. Monomineral flotation of quartz, coal, and pyrite

Abstract

The energy of interaction of particles with dissimilar wettability (quartz, coal, and pyrite) and air bubbles in neutral and alkaline media are analyzed on the basis of the extended DLVO theory to assess the floatability of these minerals. It is established that for hydrophilic materials such as quartz, the formation of particle-bubble complexes (at both the primary, and also secondary potential minima) is impossible owing to existence of a high potential barrier and weak force of attraction. For coal and pyrite, the pattern of the potential curves (energy of interaction versus distance between particle and bubble) will depend largely on the pH of the medium: an increase in this parameter will lead to manifestation of a potential barrier (when pH ≈ 7.8 for coal, and pH ≈ 9.8 for pyrite), and to an increase in its height. This causes unstable flotation of the coal and pyrite even for relatively small changes in the surface potential, pH, and ionic composition of the medium. An increase in the effectiveness of flotation benefication of coal and pyrite can be achieved by hydrophobization of the minerals by reagents-collectors: the wetting angle is increased from 50-80°to 90-100°. In turn, the potential barrier is eliminated, the effect of the pH of the medium is neutralized, and stable attachment of particles of the minerals under consideration to air bubbles is ensured in the region of the secondary potential minimum. Analysis of the forces of particle-bubble interaction made it possible to determine the forces of adhesion and detachment. Computed values of the forces in question for an air-bubble/hydrophobized-pyrite-particles system are comparable to experimental values of the indicated forces for a similar system.In this paper, interaction of air bubbles with the following minerals was examined:• quartz (θ = 20°); • pit coal (θ = 50°); • pyrite (θ = 80°); and • pyrite hydrophobized by hexyl xanthate (θ = 100°). For each of these minerals, calculations were performed for a dispersion medium at two pH levels:• 7 (neutral medium); and • 9 (weakly alkaline medium). Methylisobutylcarbinol (MIBC) served as a frothing reagent: an empirical formula C 6 H 13 OH, molecular mass of 102 kg/kmole, and a concentration of (4-5)·10 -4 kmole/m 3 in the dispersion medium. According to Wang and Yoon [1], K H = 3.4·10 -19 J, A * = 1.2·10 -20 J, and σ = 0.07 N/m for the concentration in question. The medium consisted of an NaCl

Foam in grinding and role of ground mineral in its stability

“…The shift was higher at pH 4. The shift, at pH 10, can be explained by the affinity of talc as a hydrophobic mineral, particularly the fine particles, to be attached to and stabilize the foam bubbles (Vigdergauz & Golberg, 2012) which gives a higher chance for grinding of larger particles. Another possibility is the attachment of bubbles to coarse talc particles which makes them more dispersed by keeping them away from each other.…”