(181d) Mixture Effects on Adsorption Kinetics of Asphaltenes at the Water/Toluene Interface

Interfacial tension decay between water and organic phases containing asphaltenes is generally ascribed to slow interfacial reorganization/relaxation. One of the arguments allegedly supporting this conclusion is that the dynamics of this process seem way too slow compared to diffusion timescale as calculated from the bulk asphaltenes concentration. Such reasoning however neglects that asphaltenes are a solubility class comprising a wide variety of molecular structures, only a minority of them signicantly adsorbing at the water/oil interface. As a consequence the timescale of the global equilibration process is to be the diffusion timescale of the component present at the lowest concentration among those effectively populating the interface. To support this demonstration experimental data will be shown to be accurately represented by a simple model coupling Langmuir isotherm and diffusion kinetics of a mixture of three components of decreasing concentration but increasing adsorption coefficient.