Modelling detachment rates of hydrophobic particles from bubbles in a froth phase

Effect of Particle Size and Hydrophobicity on Bubble-Particle Collision Detachment at the Slurry-Foam Phase Interface

The slurry phase, foam phase, and slurry-foam phase interfaces are the typical locations for bubble-particle detachment, and significant advancements have been achieved in the detachment theory of the slurry phase and foam phase. However, the microscopic detachment mechanism of particles at the slurry-foam phase interface is still unclear. Specifically, there is still debate concerning the collision detachment mechanism of bubble-particle aggregates. Thus, this work investigated the effects of particle size and hydrophobicity on bubble-particle collision detachment. First, a tensiometer detected the detachment force between particles and bubbles. Next, using a high-speed dynamic camera, the collision detachment probability and detachment behavior of bubble-particle aggregates at the interface (solid surface) were statistically recorded and captured. Last, MATLAB software was used to analyze the trajectory and velocity of the particles and the velocity and projected area of the bubbles in the process of bubble-particle collision detachment. This allows for a deeper investigation of the mechanism underlying the detachment of particles of various sizes and hydrophobicity. It is discovered that as particle hydrophobicity increases, the probability of bubble-particle collision detachment reduces. This is because when particle hydrophobicity increases, so does the interaction force between particles and bubbles, improving the stability of the bubble-particle aggregates. Simultaneously, it is discovered that there are notable differences in the collision detachment mechanisms of various particle sizes. Due to their low gravity, the fine particles in the bubble-particle aggregate will slide down the bubble's surface when it collides with the solid surface. This differential velocity motion between the particle and the bubble plays a significant role in the fine particles' detachment. However, the gravity of the coarse particles is strong enough to squeeze the bubbles vertically, and bubble oscillation is an important reason for the detachment of the bubble-particle aggregates. The study's findings advance our understanding of the bubble-particle collision detachment mechanism and offer a theoretical direction for investigating collision detachment behavior at the real slurry-foam phase interface.

The role of the pulp-froth interface on particle detachment and selectivity

The region between the pulp and the froth also known as pulp/froth interface in mineral flotation processes separates the pulp from the froth. Various researchers suggest particle detachment occurs around this region significantly affecting mineral recovery and grade. One of the causes pointed out is sudden deceleration of bubble-particle aggregate upon collision with the interface while another theory suggests detachment to be caused by bubble coalescence. A possible cause of divergence in views may be in the different methods of investigation employed. Though, more than several researchers indicate that detachment occurs, it is not conclusive whether kinetic energy changes or bubble coalesce or a combination of the two is responsible for detachment if any. Thus, this review examines and presents work that has been done on the role of the pulp-froth interface on particle detachment and selectivity. The review also considers the behaviour of a bubble with various interface as found in literature with a view of inferring the dominant cause of detachment at the interface.