Experimental study on the shape–velocity relationship of an ellipsoidal bubble in inorganic salt solutions

• Bubbles of ca. 2.3 mm in diameter were produced at a capillary.
• Bubble aspect ratio and velocity were measured in inorganic salt solution.
• Unique bubble shape–velocity relationship found independent of salt type.

Individual bubbles ca. 2.3 mm in diameter were produced at a capillary in water containing an inorganic salt (NaClO4, KCl, NaCl, Na2SO4, or CaCl2). Using high speed photography and image analysis techniques, bubble aspect ratio and rise velocity were measured at 1 ms time intervals over a distance ca. 1.15–1.20 m above the capillary. All conditions showed oscillations in bubble aspect ratio and velocity that were related. Increasing concentration, on average, created more spherical bubbles that rose at lower velocities. The same observations were made in the presence of MIBC frother. Results suggest a unique relationship between bubble shape and rise velocity independent of solute type. The effect of inorganic salts on bubble behavior and gas dispersion in flotation systems is discussed.

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