Dynamic interfacial tension in water/n-pentane system: An experimental study using the oscillating-jet method

Abstract

The interfacial tension working at an interface created by sudden contact of liquid water with saturated common vapors of n-pentane and water under atmospheric pressure (0.101MPa) was experimentally studied, focusing on the behavior of its relaxation to an equilibrium value in response to the progress of the adsorption of n-pentane molecules onto the interface. The oscillating-jet method was used to measure the dynamic interfacial tension, i.e., the interfacial tension varying with time during a short relaxation period (less than 0.1s) after the creation of the interface. It was observed that during the first ~50ms after the creation of the interface, the tension quasi-exponentially decreased from the normal surface-tension value for pure water (70.5mN/m) to the equilibrium value (61.5mNm) which had been obtained in a previous study using the pendant-drop method. An attempt was made to correlate the obtained “interfacial tension versus time” data based on an adsorption/desorption kinetics model.