High resolution transmission electron microscopy study of clay mineral particles from streams of simulated water based bitumen extraction of Athabasca oil sands

Understanding the interaction of clay minerals with bitumen in the oil sands is of great interest in developing water-free or water-reduced bitumen extraction processes. Previous work by Kaminsky et al. has shown, by X-ray diffraction (XRD), that there is a difference between clay minerals that partition to the froth stream and the clay minerals that remain in the middlings. However, XRD analysis was insufficient in determining why the different minerals partitioned the way they did. This work focuses on transmission electron microscopy (TEM) investigations of the clay minerals in the streams to examine the characteristic structural and morphological differences in the clay mineral particles. High resolution TEM (HRTEM) investigations revealed the presence of discrete smectite in the froth stream, while no discrete smectite phases were detected by XRD analysis. Illite–smectite expandability results calculated from HRTEM data has made it possible to explain the observed differences in cation exchange capacities (CEC). Based on HRTEM studies, a pronounced bimodal thickness distribution of the clay mineral particles containing a large number of very thin particles with smectitic layers is observed. The thin particles are responsible for the high surface activity in the primary froth stream especially with iron compounds and organic matter.