Studies on Bitumen−Silica Interaction in Aqueous Solutions by Atomic Force Microscopy

The forces between spin-coated bitumen on a silica wafer and a silica particle in aqueous solutions were measured with an atomic force microscope. The effect of solution pH, salinity, divalent ion addition, and temperature on the interaction/adhesion forces was studied. The results showed that higher solution pH and temperature and lower salinity and calcium concentration resulted in a system of a stronger long-range repulsive force and a weaker adhesive force, which is favorable for bitumen detachment from the silica surface and the subsequent stabilization. The long-range interaction forces between bitumen and silica can be well described with the classical Derjaguin−Landau−Verwey−Overbeek theory, suggesting that the electrostatic forces play a dominant role in a bitumen−silica colloidal system. The best-fitted Stern potentials of bitumen and silica were in excellent agreement with the corresponding zeta potential values measured independently using an electrophoresis technique. An additional repulsive ...