The influence of gas velocity, salt type and concentration on transition concentration for bubble coalescence inhibition and gas holdup

The influence of gas velocity (3.5, 10, and 18mm/s), salt type (NaCl, NaF, NaBr, NaI and CsCl) and salt concentration (0.001–3M) on bubble coalescence in a small bubble column were studied. The bubble coalescence was determined by the relative change in the measured light intensities passing through the salt solutions and clean deionised water. It was shown that the transition salt concentration for bubble coalescence inhibition (determined at 50% of bubble coalescence) of all investigated salts decreases with increasing superficial gas velocity. The difference in the transition concentration between NaCl, NaF, NaBr and CsCl does not significantly change with the gas velocity. However that difference between NaI and the other salts significantly decreases with increasing the gas velocity. The gas holdup significantly increases with NaCl, NaF, NaBr and CsCl concentrations but does not significantly change with NaI concentration. These new results imply that the transition salt concentration for bubble coalescence and gas holdup depend not only on the salt properties (i.e. the ion type and their combination) as previously reported, but also on the hydrodynamic conditions.

[1]  Richard R. Lessard,et al.  Bubble Coalescence and Gas Transfer in Aqueous Electrolytic Solutions , 1971 .

[2]  G. Evans,et al.  Influence of electrical double-layer interaction on coal flotation. , 2002, Journal of colloid and interface science.

[3]  F. Kaštánek,et al.  The Effect of Electrolytes on Bubble Coalescence and Gas Holdup in Bubble-Column Reactors , 1995 .

[4]  D. Fornasiero,et al.  The terminal rise velocity of 10-100 microm diameter bubbles in water. , 2008, Journal of colloid and interface science.

[5]  V. I Klassen,et al.  An introduction to the theory of flotation , 1963 .

[6]  G. Marrucci,et al.  A theory of coalescence , 1969 .

[7]  Richard M. Pashley,et al.  Hydration forces between mica surfaces in aqueous electrolyte solutions , 1981 .

[8]  H. Blanch,et al.  Bubble coalescence and break‐up in air‐sparged bubble columns , 1990 .

[9]  Werner Kunz,et al.  Specific ion effects in colloidal and biological systems , 2010 .

[10]  Pavel Jungwirth,et al.  Specific ion effects at the air/water interface. , 2006, Chemical reviews.

[11]  G. Marrucci,et al.  Coalescence of gas bubbles in aqueous solutions of inorganic electrolytes , 1967 .

[12]  H. Allen,et al.  Vibrational Spectroscopy of Aqueous Sodium Halide Solutions and Air-Liquid Interfaces: Observation of Increased Interfacial Depth , 2004 .

[13]  R. Pugh,et al.  Hydrophobicity and Rupture of Thin Aqueous Films , 1994 .

[14]  Y. H. Tsang,et al.  A theory on bubble-size dependence of the critical electrolyte concentration for inhibition of coalescence. , 2005, Journal of colloid and interface science.

[15]  Barry W. Ninham,et al.  The effect of electrolytes on bubble coalescence in water , 1993 .

[16]  M. C. Ruzicka,et al.  Bubble Column with Electrolytes: Gas Holdup and Flow Regimes , 2009 .

[17]  K. D. Collins,et al.  Ions from the Hofmeister series and osmolytes: effects on proteins in solution and in the crystallization process. , 2004, Methods.

[18]  V. Craig,et al.  The link between ion specific bubble coalescence and Hofmeister effects is the partitioning of ions within the interface. , 2010, Langmuir : the ACS journal of surfaces and colloids.

[19]  James A. Finch,et al.  Comparing the effect of salts and frother (MIBC) on gas dispersion and froth properties , 2007 .

[20]  H. Christenson,et al.  Electrolytes that Show a Transition to Bubble Coalescence Inhibition at High Concentrations , 2008 .

[21]  O. Paulson,et al.  Flotation of Inherently Hydrophobic Particles in Aqueous Solutions of Inorganic Electrolytes , 1996 .

[22]  Michael J. Prince,et al.  Transition electrolyte concentrations for bubble coalescence , 1990 .

[23]  E. G. Babakhani,et al.  EXPERIMENTAL STUDY OF GAS HOLDUP AND BUBBLE BEHAVIOR IN GAS -LIQUID BUBBLE COLUMN , 2009 .

[24]  S. Marčelja.  Selective coalescence of bubbles in simple electrolytes. , 2006, The journal of physical chemistry. B.

[25]  Jan D. Miller,et al.  Understanding the role of ion interactions in soluble salt flotation with alkylammonium and alkylsulfate collectors. , 2011, Advances in colloid and interface science.

[26]  A. K. Chesters,et al.  Bubble coalescence in pure liquids , 1982 .

[27]  J. Ralston,et al.  A Mobile Gas−Water Interface in Electrolyte Solutions , 2008 .

[28]  H. Christenson,et al.  Observations of Solute Effects on Bubble Formation , 1995 .

[29]  Vincent S. J. Craig,et al.  Bubble coalescence and specific-ion effects , 2004 .

[30]  D. Koch,et al.  Bubble-size dependence of the critical electrolyte concentration for inhibition of coalescence. , 2004, Journal of colloid and interface science.

[31]  R. Pugh,et al.  Surface Tension of Aqueous Solutions of Electrolytes: Relationship with Ion Hydration, Oxygen Solubility, and Bubble Coalescence , 1996, Journal of colloid and interface science.