Effect of Velocity, Solid Wettability, and Temperature on Drainage Dynamics of C5PeC11-in-Toluene Liquid Films between Silica and Water Droplet

Properties of thin liquid films between two approaching droplets or between a droplet and a surface are critical for emulsion stability, oil and gas extraction, and mineral flotation. The dynamic force apparatus (DFA)—simultaneous measurement of interfacial film thickness, drainage time, and interaction forces at precisely controlled approach velocities—was used to study the interactions of a water drop with silica surfaces in toluene containing the model asphaltene compound N-(1-undecyldodecyl)-N′-(5-carboxypentyl)-perylene-3,4,9,10-tetracarboxylic bisimide (C5PeC11). A water droplet in toluene containing 0.1 g/L C5PeC11 was driven toward a silica surface of varying wettability (contact angles of 0 and 107°) at two different droplet approach velocities (0.1 and 1 mm/s) and temperatures (22 and 40 °C). Rupture of thin liquid films between a water droplet and silica surfaces was observed, with a moving three phase contact line and strong attachment for hydrophilic silica and minor, local attachment and an easily detachable water drop for hydrophobic silica. Increasing the approach velocity of water droplets toward solid surfaces resulted in a larger dimple and longer film lifetime. Interestingly, higher temperature led to a faster film rupture for hydrophilic silica, in line with industrially observed improvements in removal of water-in-oil emulsions at higher temperatures. The experimentally determined dynamics of the thin liquid film drainage were modeled successfully using the Stokes–Reynolds–Young–Laplace (SRYL) theoretical model.