Temperature effect on single bubble velocity profile in water and surfactant solution

Abstract Surfactants called frothers control bubble properties in flotation. Two properties of single bubbles, the rise velocity profile (velocity vs. time from release) and terminal velocity, are investigated as a function of temperature (6–45 °C) in water and solutions of Triton X-100 (12.5×10−5 mol m−3) and Dowfroth 250 (0.06 and 0.25 ppm). The bubbles sizes (diameter) were 130. This corresponds to the finding of Karamanev [AIChE J. 40 (1994) 1418], namely that the drag coefficient is constant (∼0.95) for this Re region. The profile showed the time to reach constant velocity tended to decrease as temperature increased. This is analyzed by considering factors that may increase the mass transfer rate of the surfactant. Some observations are offered of possible relevance to flotation.

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