Chemical Papers

, Volume 72, Issue 10, pp 2539–2559 | Cite as

Estimation of transition concentration of aqueous mixtures of single and binary electrolytes for bubble coalescence inhibition

  • Ajay Sujan
  • Raj K. VyasEmail author
Original Paper


A bubble column was investigated in which a swarm of air bubbles was dispersed in aqueous electrolyte (NaCl, MgSO4·7H2O, CaCl2·2H2O, and Na2SO4) solutions. In the present work, study of coalescence inhibition has been targeted by applying gas holdup enhancement and surface tension gradient approaches for aqueous solutions in single and binary mixtures (CaCl2·2H2O + NaCl and Na2SO4 + NaCl) of electrolytes. Transition concentrations of a series of coalescence inhibiting inorganic electrolytes were determined. A qualitative comparison of these electrolytes revealed that strong electrolytes (Na2SO4, and CaCl2·2H2O) yield gas holdup enhancement ≥ 60% whereas moderate electrolytes (NaCl and MgSO4·7H2O) give gas holdup enhancement values ≤ 46%. It has been also found that the values of transition concentration for different electrolytes are of the same order in most of the cases and in line with those reported in the literature. Inhibition of bubble coalescence was also analyzed in terms of the parameter \( C\left( {{\text{d}}\sigma /{\text{d}}C} \right)^{2} \). The large value of the parameter \( ({\text{d}}\sigma /{\text{d}}C)^{2} \) indicates that the electrolyte will inhibit bubble coalescence, and a smaller value indicates moderate effect on bubble coalescence. Surface elasticity values at transition concentration of various electrolytes were also determined. It was found that the surface elasticity values at transition concentration were in the order CaCl2·2H2O > MgSO4·7H2O > Na2SO4 > NaCl. Surface elasticity for binary electrolytes was also estimated at their transition concentrations. The values were found in the order CaCl2·2H2O + NaCl > Na2SO4 + NaCl. Furthermore, analysis of variance was employed to estimate significance of the parameters.

Graphical abstract


Inorganic electrolyte Surface tension gradient Transition concentration Bubble coalescence inhibition Gas holdup Bubble column 



Analysis of variance


Gas holdup


Material of construction


Homogenous regime


Heterogenous regime



Hamaker constant (non-retarded) for water, (3.5 × 10−20 J)

a ± 

Mean ion activity coefficient


Free area of the disc


Force defined by Eq. (2), N


Transition concentration (mol/L)


Electrolyte concentration (mol/L)


Change in surface tension of solute (electrolyte)


Liquid height in bubble column (m)


Aerated froth height in bubble column (m)


Defined by Eq. (3) (l/m)


Universal gas constant, J/mol K


Bubble radius (m)


Absolute temperature (K)


Velocity of air (m/s)


Velocity of liquid (m/s)

Greek letters


Gas holdup in aqueous solution of electrolyte (dimensionless)


Gas holdup in distilled water (dimensionless)


Number of ions formed on dissociation (i.e., υ = 2 for most inorganic salt)

σσel or σaqueous

Surface tension of electrolyte solutions (mN/m)


Surface tension of water (mN/m)


Mean change in surface tension (mN/m)


Surface tension gradient


Density of aqueous solution of electrolyte (kg/m3)


Conductivity of aqueous solution of electrolyte (µS/m)


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Copyright information

© Institute of Chemistry, Slovak Academy of Sciences 2018

Authors and Affiliations

  1. 1.Department of Chemical EngineeringMalaviya National Institute of Technology JaipurJaipurIndia

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