Abstract:
The effects of visible and UV light on the characteristics and properties of Prudhoe Bay (PB) and South
Louisiana (SL) emulsions were investigated to better understand the role of sunlight on the fate of spilled
crude oils that form emulsions with a dispersant in the aquatic environment. Before irradiation, crude oil
emulsions showed the presence of dispersed crude oil micelles in a continuous water phase and crude oil
components floating on the surface. The crude oil micelles decreased in size with irradiation, but
emulsions retained their high degree of polydispersity. UV irradiation reduced the stability of emulsions
more effectively than visible light. The reduction of micelles size caused the viscosity of emulsions to
increase and melting point to decrease. Further, irradiation increased acid concentrations and induced ion
formation which lowered the pH and increased the conductivity of emulsions, respectively. Ni and Fe in
PB emulsions were extracted from crude oil with UV irradiation, which may provide an efficient process
for metal removal. The emulsions were stable toward freeze/thaw cycles and their melting temperatures
generally decreased with irradiation. Evidence of ˙OH production existed when emulsions were exposed
to UV but not to visible light. The presence of H2O2 enhanced the photodegradation of crude oil. Overall,
the changes in emulsion properties were attributed to direct photodegradation and photooxidation of crude
oil components.
