| During the Deepwater Horizon Oil Spill in 2010 approximately 210 million gallons of crude oil was released into the Gulf of Mexico. To enable bacterial degradation the oil had to be dispersed into small oil droplets, which was achieved using 1.84 million gallons of chemical surfactants. As these surfactants have questionable environmental impacts, the idea of this research project is to use silica nanoparticles as a model particle to form Pickering emulsions and to study oil-mineral aggregate (OMA) formation. Pickering emulsions typically consist of oil droplets stabilized by solid particles instead of surfactants. Silica might be suitable for this as it already occurs in the ecosystem ocean, e.g. as sand. Furthermore it is known that seawater, oil and particulate matter form OMAs, but the interactions between particles, OMAs, and surfactants are still poorly understood. This is why the commercial available surfactant Aerosol OT (AOT) as a model surfactant was used to estimate the interactions between surfactant and OMAs.;To determine the suitability of silica nanoparticle as oil dispersants, defined silica aggregates were created and fractionated to yield distinct size fractions. These aggregates were mixed with ethyl acetate, octanol and octane as model oils to determine the aggregate adhesion to oil/water interfaces and the formation of Pickering emulsions or OMAs. The reason for choosing these oils is their different polarity. With these results the formation of Pickering emulsions and OMAs are determined using silica agglomerates of three different sizes. The theory suggests that that the stability of Pickering emulsion in DI-water increases with increasing particle size. During the experiments an optimum particle size for Pickering emulsions in DI-water was observed. Furthermore it was observed that the formation of a significant OMA layer requires seawater. As soon as the surfactant Aerosol OT was added, the thickness of the sedimentation layer was reduced. AOT is believed to bind to the silica nanoparticles through divalent cation bridging, but the exact nature of this interaction is still unknown. BP/The Gulf of Mexico Research Initiative Grant No. SA 12-05/GOMRI-002 supports this project. |
