Contributions\nof Colloidal Forces to the Heterogeneous\nSeparation of Stable Oil-In-Water Emulsions

We use theory to study the distribution of spherical\nemulsion oil\ndroplets in water near a lipophilic surface as a guideline for designing\nmembranes for oil/water phase separation. Heterogeneous phase separations\nare shown in our laboratory using hydrophilic and hydrophobic membrane\ndesigns, where the affinity of the membrane surface to one of the\nphases in the mixture locally increases its concentration. Considering\na colloidal emulsion (nano- to microemulsions) of spherical and noncoalescing\ndroplets, we assess the contribution of colloidal forces, i.e., van\nder Waals, electrical double layer, and hydrophobic interactions and\nthe finite size of the droplets to the accumulation of spherical emulsion\ndroplets near a surface. We use our theory to study an experiment-inspired\ncase study and find that an isolated lipophilic membrane surface in\ncontact with an oil-in-water emulsion supports the oil-enriched emulsion\nphase in a thin layer near the membrane surface, suggesting that a\nmembrane pore size comparable to this thickness should support oil-enriched\nemulsion in the membrane pores and hence past the membrane.