Poster Session

Is It Possible to Measure Silica/Clay Interactions Directly?

Hongying Zhao, PhD student in Chemical Engineering

Supervisor - Dr. Jacob Masliyah and Dr. Zhenghe Xu

The stability of oil sands tailings sludge with respect to sedimentation and consolidation is attributed to the colloidal interactions of the component minerals like silica-clay. In this study, a microtome was employed to prepare clay surfaces. The atomic force microscope (AFM) colloidal probe technique was used to study the interaction forces between a silica probe and basal plane and edge surface of clays to estimate the isoelectric point for these surfaces. The previous measurements show that for the basal planes of mica, talc, and illite, the long-range forces are all repulsive at pH 6-10. This is in agreement with the prediction from the knowledge that the surface charge of basal planes is pH independent in this pH range. In the case of edge surface, the forces are repulsive at pH 10 and attractive at pH 6 indicating that the charge of edge surface is pH dependent. The estimated isoelectric points of edge surfaces for these three clays are approximately at pH 6~8. For future study, efforts are continuing to improve the quality of produced basal and edge surfaces.