| Abstract
| - Bitumen recovery from oil sands was found to severely deteriorate at operating temperatureslower than a “critical” value, suggesting a substantial change in one or more key process variables.A sharp increase in bitumen viscosity at lower temperatures has been considered as the majorcontributor to such deterioration. On the basis of the fact that the addition of selected chemicalsdoes improve bitumen recovery without affecting bitumen viscosity, there must be otherphysicochemical factors that affect bitumen recovery and undergo a sharp change withtemperature. In the present study, the interaction and adhesion forces between bitumen andsand grains or clays in water were measured as a function of temperature using an atomic forcemicroscope. The results show that the measured adhesion force between clay and bitumendecreases with increasing temperature until a critical value of about 32−35 °C, above which theadhesion force disappears. As the adhesion force between clay and bitumen controls clay slimecoating on bitumen surface and subsequently bitumen aeration, increase in the adhesion forcewith decreasing processing temperature would lead to slime coating and lower bitumen recovery.The effect of a chemical additive, methylisobutyl carbinol (MIBC), on the colloidal forces wasalso studied. The results show that MIBC addition can reduce the adhesion force between clayand bitumen, thus facilitating bitumen aeration.
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