M.Sc Student | Valal Dorit |
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Subject | Interfacial Tension in Liquid-Liquid Systems |

Department | Department of Chemical Engineering |

Supervisor | Professor Emeritus Abraham Marmur |

Wetting of solid surfaces by liquids is a fundamental research area with considerable implications in many fields, such as nano-particles, coating, catalysis, oil recovery, and many more. The surface tension of a solid is its wetting characteristic, but it cannot be directly measured. In order to evaluate the surface tension of a solid surface, contact angle measurement and calculation of the solid-liquid interfacial tension need to be done. This calculation is usually done by using semi-empirical correlations that have been developed over the last fifty years. However, many uncertainties exist regarding this calculation because of the absence of a theoretical foundation and the need to measure contact angles for a variety of liquids.

A new correlation for the liquid-liquid interfacial tension has been developed in this research. The new correlation is based on the Gibbs theory of the mathematical dividing surface. The mathematical dividing surface is located within the interfacial region, parallel to the liquid-gas surface, generating two separate phases, one of the liquid and the other of the fluid, apparently with uniform bulk properties. According to the Gibbs theory, the total internal energy of the interfacial region equals the sum of the liquid and fluid bulk internal energies, and the internal energy of the mathematical dividing surface. In other words, the interfacial tension is the difference between the actual and Gibbsian total internal energy per unit area.

The correlation has been tested on a large number of liquid-fluid systems, for which the individual surface tensions as well as the interfacial tension are known from direct measurements. All liquid-fluid systems involved in the calculations were mutually saturated with each other. Experimental data were divided into three groups, according to mutual miscibility of the liquid and fluid, and experimental temperature.

The results are in better agreement with experimental data then any previously published correlation.