Applications of colloidal force measurements using a microcollider apparatus to oil sand studies

Two colloidal force measurement techniques have been applied to oil sand studies both using the same apparatus called the microcollider. The techniques are colloidal particle scattering method for repulsion-dominant systems and hydrodynamic force balance method for attraction-dominant systems. The former is based on calculating the colloidal forces from the magnitude of particle–particle collision trajectory deflections. The latter is based on separating a colloidal doublet with increasing shear and calculating the maximum attractive force at the onset of the doublet breakup. Both methods involve the microscopic observation on two individual particles. The methods are also well suited to emulsion systems where the interaction forces as small as 10−13 N between two droplets can be detected. In oil sand research, two stable emulsions: water-in-diluted bitumen and bitumen-in-water have been receiving considerable attention because of their detrimental effects on the industrial process. The droplet–droplet forces and the emulsion stability mechanism were determined for both emulsions using either one of the techniques. For the w/o emulsion, steric repulsion is the main contributor to the emulsion stability. For the o/w emulsion, all interactions are exclusively DLVO-type forces and the electrostatic force plays a major role in stabilizing the emulsion. Isolated protrusions of tens of nanometers in thickness have also been detected on bitumen surfaces. The protrusions enhance the repulsive force at a long distance but reduce it near the energy barrier, a useful feature that might help in destabilizing the system.