Attachment of solid elongated particles on the surface of a stationary gas bubble

Abstract

Froth flotation is a separation process which plays a major role in the mining industry. It is essentially employed to recover a vast array of different valuable commodities such as rare earth minerals essential to the manufacture of high-tech products. Owing to its simplicity, the process is also widely used for de-inking recycled paper fibres and for waste water treatment. The flotation process essentially relies on the attachment of solid particles on the surface gas bubbles immersed in water. The present study seeks to investigate the effect of the particle shape on the attachment mechanism. Using an in-house optical micro-bubble sensor the approach, the sliding and the adhesion of micron milled glass fibres on the surface of a stationary air bubble immersed in stagnant water is thoroughly investigated. The translational and rotational velocities were measured for fibres of various aspect ratios. The results are compared with a theoretical model and with experimental data obtained with spherical glass beads. It is found that the fibre orientation during the sliding motion largely depends on the collision area. Upon collision near the upstream pole of the gas bubble the major axis of the fibre aligns with the local bubble surface (tangential fibre alignment). If collision occurs at least 30° further downstream only head of the fibre is in contact with the gas-liquid interface (radial fibre alignment).

Direct numerical simulation of a particle attachment to an immersed bubble

“…This tendency is in-line with the reference data. 27 The same evolution of the particle velocity is also shown in Figure 6(b) as a function of the polar angle and brings a more natural visualisation of the collision and sliding processes. The polar angle ranges from α ≈ 0…”

“…The data from the first reference were obtained from a particle-point model 3 and proved accurate in the simulation of finely attaching particles. 27 In the second comparative experiment, 28 the liquid was brought in slow laminar motion around a pinned gas bubble. Although the microspheres later detached after a temporary sliding, the experimental trajectories are suitable for comparison during the particle approach.…”

Visualization of Angular Particle-Bubble Surface Interaction using a High Speed Video Camera

“…This observation result is similar to results found in previous works. Figures 9 and 10 show particle movement in experimental and numeric calculations from the 45° angle up to the 120° angle of the previous experiments by Wang et al (2015) and Lecrivain et al (2015).…”

“…Frames 4-7 show the bubble rising, the particle detaching, and the particle moving downward. result Figure 10 Illustration of bubble-spherical particles interaction, experimental result, and numerical result (Lecrivain et al, 2015) Sliding movements on the bubble surface have different velocity values. It was observed that after collision with the bubble surface at quadrant 1, the particle slides slowly, and it then accelerates when moving into quadrant 2.…”

“…This was also investigated by Verrelli et al (2011). Further research in the field of sliding particles on the surface of the bubble has been done by Nguyen and Evans (2004), Koh et al (2009), Verrelli et al (2015, Lecrivain et al (2015), Wang et al (2015), and others. Research on particles' rebounding from bubble surface has been done by Zhao et al (2015).…”