Enhanced coalescence of two oil droplets with clay particles

In order to investigate the effects of clay particles on the coalescence of oil droplets, a typical head-on experiment was carried out. The coalescence of two oil drops containing clay was observed depending on the clay types. The influence of clay on the coalescence of oil droplets is successfully distinguished from the coalescence of pure oil droplets. When two oil droplets make direct contact, pure oil droplets never coalesce due to a lack of compressive stress against the colloidal force. Meanwhile, when oil drops with hydrophobic types of clay make contact, the oil drops quickly merge despite the fact that there is no change in colloidal interaction and capillary force relative to those of the pure oil droplet. Hydrophobic clay particles in the oil drop are able to pierce through the medium film to enhance the coalescence because particles in the oil drop have also hydrophobic attraction with the other oil drop. With the natural clay, the coalescence of two oil droplets is still enhanced despite the slight delay due to the balanced wetting behavior of the natural clay between the oil and the water. Thus, regardless of the wetting behavior of clay between oil and water, clay can enhance the coalescence of the oil drops by transporting particles through the medium between two oil droplets when they come into contact.