Imaging study of surfactant effect on bubble behaviors in froth flotation

Bubble motion is fundamental to the performance of flotation system, but single bubble motion under flotation-related conditions is a relatively neglected research field. The objective of this study is to characterize the behaviors of single bubbles with 2 ~ 5 millimeter in diameter in the presence of surfactant. Experiments were carried out to investigate the effect of surfactant on trajectory, shape and velocity of single bubbles rising in liquid. Distilled water and Triton X-100 solutions with various concentrations were chosen as liquid phases. The motion of single bubbles was recorded using high-speed camera in a laboratory scale flotation column. Trajectory, shape and velocity of single bubbles were then determined using the image process technique. The results clearly show that bubble trajectory takes more regular pattern in Triton X-100 solution than in pure water. It is also found that the right amount of surfactant used here can dampen bubble deformation, reduce shape oscillation amplitude and slow down the bubble rising velocity significantly due to the Marangoni effect. Compared to pure water, Triton X-100 of concentration 0.15×10^-3 mol/L reduces the oscillation amplitude of the aspect ratio of the bubble by 57% while Triton X-100 of concentration 0.05×10^-3 mol/L slows the terminal velocity of the bubble by 35%.