An Investigation into the Effects of Salt Concentration on Surfactant Adsorption Using a Quartz Crystal Microbalance

Surfactant adsorption from aqueous electrolyte solutions onto metal surfaces was characterized through the use of a Quartz Crystal Microbalance (QCM). The need for a better understanding of the surfactant adsorption process became apparent in previous studies by Morton et al., who used estimated and extrapolated properties in a thermodynamically-based model of oil removal from metal surfaces. These modeling efforts overlap existing data on surfactant adsorption data and require an estimation of surfactant adsorption phenomena, especially the transition between monolayer adsorption and multi-layer adsorption, which corresponds to the critical micelle concentration (CMC). Thus, the purpose of this study was to gain surfactant adsorption data in an effort to increase the efficacy of surfactant degreasing techniques.

A survey of the literature and a summary of the research in this thesis is provided in Chapter 1. Chapter 2 reports the experimental work to establish the mass of surfactant adsorbed from an aqueous electrolyte-surfactant solution onto a vibrating crystal of a quartz crystal microbalance (QCM). Density and viscosity of the aqueous solutions were measured separately so that the change in mass could be observed from the frequency change measurements. Conclusions about the behavior of the surfactant adsorption phenomena taking place at varying salt concentrations were discussed.

Chapter 3 presents future direction for the continued study of the cleaning and degreasing studies in this thesis.