adsorption of nanoparticles, oil/water interface, interfacial tension, contact angle, silica nanoparticles
We investigate the retention of silica nanoparticles at water/crude oil interface. Silica nanoparticles with three different surfaces (unmodified, surface modified with anionic (sulfonate), or nonionic (PEG) surfactant) are used. Interfacial tension (IFT) measurements provide us means to investigate the adsorption of silica nanoparticles at the crude oil/water interface. Unmodified nanoparticles do not change the IFT of crude oil/water interface. However, the presence of sulfonate or PEG modified nanoparticles in solution lower the. The presence of unmodified or surface modified nanoparticles in solution does not alter the contact angle of a crude oil droplet on clean calcite (water-wet) or aged calcite plate (oil-wet). We also carry out flow experiments with PEG coated silica nanoparticles through a glass bead pack. In the absence of crude oil, the nanoparticles act like a conservative tracer with insignificant interaction with the glass beads. This result is in good agreement with our previous work on the adsorption of silica nanoparticles on mineral surfaces. However, at the residual oil saturation of 12%, PEG coated silica nanoparticles are retained at crude oil/water interface as shown by the concentration profile. These results are also in good agreement with IFT and contact angle measurements carried out in this study.