Specific ion effects on the interfacial tension of water/hydrocarbon systems

Abstract

Specific ion effects - also known as Hofmeister effects - are ubiquitous in several areas of chemistry, chemical engineering and biology. The interfacial tension corresponds to the energy per unit of area at the interface. Thus, the presence of different salts in different concentrations changes the interfacial tension of a system containing an aqueous phase. This effect can be explained based on the concentration profile of different ions in the vicinity of the interface. In order to study this effect we measured the surface tension of aqueous electrolyte solutions and the interfacial tension of various systems containing hydrocarbons and different aqueous electrolyte solutions as a function of the ionic strength of the aqueous phase. We classify the tested ions for their ability to alter the interfacial tension of each system. These data provide valuable information that can be related to the stability of the corresponding emulsions, since the ions with higher capability of increasing the interfacial tension tend to be more effective in destabilizing the corresponding emulsion.