Effects of visible and UV light on the characteristics and properties of crude oil-in-water (O/W) emulsionsElectronic supplementary information (ESI) available: five figures and seven tables showing additional study details. See DOI: 10.1039/c2pp05275j

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 &z.rad;OH production existed when emulsions were exposed to UV but not to visible light. The presence of H 2 O 2 enhanced the photodegradation of crude oil. Overall, the changes in emulsion properties were attributed to direct photodegradation and photooxidation of crude oil components. Prudhoe Bay and South Louisiana crude oil-in-water emulsions were prepared, characterized, and exposed to both visible and UV light irradiation. The unique changes in physico-chemical properties of these emulsions as a result of photodegradation were investigated.