Dynamics and Structure of a Bitumen Emulsion as Studied by 1H NMR Diffusometry

Self-diffusion in a bitumen emulsion was studied by H-1 NMR. The emulsion forms two phases: continuous and dispersed. The continuous aqueous phase contains mainly water, with the energy of activation of the diffusion process equal to that of bulk water, while its diffusivity is smaller than that of bulk water by a factor of 2. The dispersed phase consists of bitumen droplets containing confined water, whose dynamics is characterized by a fully restricted diffusion regime in cavities with sizes of similar to 0.11 mu m. Therefore, the studied bitumen emulsion can be described by a model of a complex multiple emulsion of the water/oil/water (WOW) type. The suggested model does agree well with data from H-1 NMR spectroscopy and diffusometry of the bitumen emulsion doped with paramagnetic MnSO4(aq) as well as with an additional H-1 NMR study of the emulsion structure, in which emulsion stability was compromised by freezing at 253 K.

Automated summary

Self-diffusion in a bitumen emulsion was investigated using H-1 NMR. The emulsion consists of two phases: continuous and dispersed. The continuous aqueous phase contains mainly water and has the same activation energy for diffusion as bulk water but a lower diffusivity. The dispersed phase is made up of bitumen droplets containing confined water, and their diffusion is fully restricted in cavities with sizes around 0.11 μm. The observed bitumen emulsion can be described by a complex multiple emulsion model of water/oil/water (WOW) type.