Interfacial Films Adsorbed from Bitumen in Toluene Solution at a Toluene−Water Interface: A Langmuir and Langmuir−Blodgett Film Approach

Abstract

Using Langmuir and Langmuir−Blodgett (LB) film techniques, the present study shows that interfacial film formation is due to the adsorption of bituminous compounds at a toluene−water interface. Langmuir films formed using various concentrations of the bituminous compounds below their critical micelle concentration or critical nanoaggregate concentration in the toluene phase indicate that asphaltenes, a constituent of bitumen, irreversibly adsorb at the toluene−water interface. Based on Langmuir and LB film studies, the pressure−area isotherms as well as the morphology, thickness, and the hydrophobicity of the interfacial films are similar when bitumen and asphaltenes were independently used as the source for the surface active materials present in the bulk organic phase. Morphology and thickness studies on the corresponding LB films suggest the formation of discoid nanoaggregates with a definite size at the interface.