REMOVAL OF SURFACE ACTIVE CONTAMINANTS FROM A LIQUID-LIQUID INTERFACE

A further understanding of coalescence is important for applications such as foam stability.  Surface-active agents, or surfactants, complicate the study of coalescence phenomena.  The purpose of this study is to design an apparatus to remove surfactants from a liquid-liquid interface so that coalescence can be understood without the added complications of surfactants.  Surfactants are generally amphiphilic molecules.  It is because of this amphiphilic nature that surfactants prefer to be at the interface of two liquids.  This study takes advantage of this preferential adsorption to the interface, and the main focus of the apparatus is to isolate and remove interface while retaining as much liquid as possible.  Before designing a surfactant removal apparatus an isotherm for the interfacial tension of water and polydimethylsiloxane (PDMS) as a function of the bulk concentration of the surfactant hexadecyl trimethyl ammonium bromide (HTAB) was constructed.  This isotherm will be used when the device is tested so that graph for HTAB concentration as a function of either iterations or volume loss can be constructed by measuring the interfacial tension.  A proof of concept experiment was also conducted to ensure that removal of interface results in the removal of surfactants.  This experiment was conducted by simply removing interface with a syringe and measuring interfacial tension.  The results of this experiment show that interface removal does indeed result in an increase in interfacial tension and hence a decrease in surfactant concentration.  The apparatus is currently under construction and will be tested upon completion.