Rising dynamics of particle-laden bubbles in presence of surfactant and turbulence

•Rising dynamics of particle-laden bubbles in presence of surfactant and turbulence.•At high bubble surface loadings, the bubble rise velocity increases in turbulence.•At low surface loadings however, the rise velocity decreases due to surfactant.•Both surfactant and turbulence significantly dampen bubble shape oscillations.•Turbulence causes non-rectilinear bubble trajectory across all surface loadings. In the minerals industry, froth flotation is a commonly used method for separating valuable minerals from gangue. The design and efficient operation of flotation cells require a knowledge of the interplay between the system hydrodynamics and its chemistry. These parameters however are often examined in isolation using bare bubbles due to the system complexity. This study aims at investigating the coupled effect of surfactant and turbulence on the rising dynamics of particle-laden bubbles of different bubble surface loadings. Specifically, the rise velocity and trajectories of particle-laden bubbles with bubble surface loadings of 0–87 % were examined in presence of methyl isobutyl carbinol surfactant in a near isotropic turbulent flow generated by oscillating grids. Particle-bubble aggregates were formed using a microfluidics T-Junction-based approach to attach coarse glass bead particles of 316 µm in size to bubbles with a diameter of 2.15 mm. The rising dynamics of the particle-laden bubbles were captured using a high-speed camera. The collected data on rise velocities and trajectories were then benchmarked against the rising behaviour of particle-laden bubbles in a quiescent water with no surfactant. The experimental results showed that, in a quiescent water, addition of methyl isobutyl carbinol surfactant reduces the mean bubble rise velocity at low bubble surface loadings of less than 13%. At bubble surface loadings greater than 13%, the effect of methyl isobutyl carbinol surfactant on the bubble rise velocity was found to be negligible. The increased bubble surface immobility due to an increase in the bubble surface loading is believed to be responsible for the observed behaviour. Turbulence in the absence of surfactant on the other hand, consistently led to an increase in bubble rise velocity over the examined conditions. Under the coupled effect of surfactant and turbulence conditions, the particle laden bubbles with bubble surface loadings greater than 13% exhibited an overall increase in the rise velocity indicating that turbulence was the govern