Interaction forces between bitumen droplets in water

The interaction forces between micron-sized bitumen (heavy crude oil) dropl ets in an aqueous medium were determined with colloidal particle scattering , a method based on calculating colloidal forces from droplet-droplet colli sion trajectories. The results indicate that, in addition to an electrostat ic force, a heterogeneous protrusion structure on bitumen surface further i ncreases the repulsive force. This structure was found to contain "bumps" o f 50-100 nm in horizontal diameter and of 0-20 nm or more in thickness. The protrusion structure helps in stabilizing the emulsion at salt (KCI) conce ntrations up to 0.1 M. but fails to prevent droplet coalescence at 1 M KCl. This nonuniform structure was not found in the previous study using a surf ace force apparatus.