Novel methodology for predicting the critical salt concentration of bubble coalescence inhibition

Bubble coalescence in some salt solutions can be inhibited if the salt concentration reaches a critical concentration Ccr. There are three models available for Ccr in the literature, but they fail to predict Ccr correctly. The first two models employ the van der Waals attraction power laws to establish Ccr from the discriminant of quadratic or cubic polynomials. To improve the two models, the third model uses the same momentum balance equation of the previous models but different intermolecular force generated by water hydration with exponential decaying. The third prediction for Ccr requires the experimental input for film rupture thickness and is incomplete. We show further in this paper that the third model is incorrect. We propose a novel methodology for determining C cr which resolves the mathematical uncertainties in modeling C cr and can explicitly predict it from any relevant intermolecular forces. The methodology is based on the discovery that Ccr occurs at the local maximum of the balance equation for the capillary pressure, disjoining pressure, and pressure of the Gibbs-Marangoni stress. The novel generic approach is successfully validated using nonlinear equations for complicated disjoining pressure

Frothing behavior of nonionic surfactant solutions in the presence of organic and inorganic electrolytes

The influence of inorganic salts (KCI, KBr, NaI, KI) and organic salts, tetrapentyl ammonium bromide (TPeAB) and tetrabutyl ammonium bromide (TBuAB), on the decay of a foam column from aqueous solutions of octaethyleneglycol mono-n-decylether (C10E8) has been investigated, The salt concentration in all cases was maintained constant (0.01 M), The results from the measurements of the foam decay rates indicate that, of the inorganic electrolytes, KBr is a foam destabilizer, KCI does not influence the froth stability, and NaI and KI act as foam stabilizers. Both TBuAB and TPeAB generate greater initial quantities of foam. Concurrently, both organic salts accelerate the destruction of the foam in the initial stage of drainage, the effect of TBuAB being stronger. It was established also that in the later stage of drainage, where black films form there C10E8 bulk concentration is 5 x 10(-4) M and its C-bl=10(-4) M), TPeAB acts as foam destabilizer, while TBuAB does not influence the foam stability, (C) 2001 Academic Press

An investigation of bubble coalescence and post-rupture oscillation in non-ionic surfactant solutions using high-speed cinematography

Most processes involving bubbling in a liquid require small bubbles to maximise mass/energy transfer. A common method to prevent bubbles from coalescing is by the addition of surfactants. In order to get an insight into the coalescence process, capillary bubbles were observed using a high speed cinematography. Experiments were performed in solutions of 1-pentanol, 4-methyl-2-pentanol, tri(propylene glycol) methyl ether, and poly(propylene glycol) for which information such as the coalescence time and the deformation of the resultant bubble upon coalescence was extracted. It is shown in this study that the coalescence time increases with surfactant concentration until the appearance of a plateau. The increase in coalescence time with surfactant concentration could not be attributed only to surface elasticity. The oscillation of the resultant bubble was characterised by the damping of the oscillation. The results suggested that a minimum elasticity is required to achieve an increased damping and considerable diffusion has a detrimental effect on the dynamic response of the bubble, thereby reducing the damping

Investigation of Interfacial Free Energy of Three-Phase Contact on a Glass Sphere in Case of Cationic-Anionic Surfactant Aqueous Mixtures

The wetting of adsorbed surfactants solids is important for various technological applications in particular for the process of foam flotation. The present work aims at calculating the surface tensions of the three phase interfaces at different surfactant concentrations using the Girifalco and Good method. For this purpose, the surface tension and contact angle vs. surfactant concentration of the test substances amines and sulfonates and their mixture were measured for liquid–air interface. Calculated surface tension of solid–air interface vs. concentration for C10 amine and mixed systems are close to those for the liquid–air surface, but are slightly lower. In the case of mixed systems, the graph has a specific structure similar to that of liquid–air surface dependence. In contrast to the solid–air interface results, the solid–liquid surface tension values are significantly lower. In case of the mixed surfactant systems, C10amine/C10 sulfonate, a synergetic effect on the surface tension is observed. The specific behavior of the mixed systems is interpreted with the emergence of aggregates consisting of the anionic and cationic surfactants. It is shown that in the whole area of concentrations complete wetting does not occur

Adsorption of ionic surfactants

Two adsorption models for ionic surfactants based on the Frumkin equation are examined to describe the measured surface tension isotherms of a series of alkali dodecylsulphates. In the model A the number of optimization parameters is reduced by additional modeling. The adsorption of counter-ions in the Stern layer is described via forming of ionic bonds, which free energy is significantly higher than that obtained by the model B. Concurrently the lateral interactions on the water/air interface are also found to be orders of magnitude stronger. Thus, the values of the adsorption parameters are more realistic, which supports the model A as a more relevant one

Ion Specific Electrolyte Effects on Thin Film Drainage in Nonaqueous Solvents Propylene Carbonate and Formamide

Electrolytes have been found to stabilize thin films in nonaqueous solvents propylene carbonate and formamide, in the absence of surfactant. The thin film balance microinterferometry technique has been used to measure film lifetimes, drainage kinetics, and rupture thicknesses for thin films between air-nonaqueous solution interfaces. Electrolytes that were previously found to inhibit bubble coalescence in bulk bubble column measurements also increase the lifetimes of individual thin films across it similar concentration range (from 0 to 0.3 M). We report that increasing the concentration of inhibiting electrolyte stabilizes the thin liquid film in two ways: the rate of film drainage decreases, and the film reaches a lower thickness before rupturing. In contrast, non-inhibiting electrolyte shows little to no effect on film stability. We have here demonstrated that both drainage and rupture processes are affected by the addition of electrolyte and the effect on the thin film is thus ion specific