INTERACTION OF OIL DROPLETS WITH SILICA SURFACES

Measurements of contact angles, emulsion him thicknesses, movement of oil droplets in thin capillaries and surface charges are used for inve stigation of oil droplet interaction with silica surfaces in aqueous s olutions of the cationic surfactant cetyltrimethylammonium bromide (CT AB) of various concentrations from 10(-7) and 10(-3) M. As model syste ms tetradecane and silicone oil, polished optical quartz plates and qu artz capillaries were used. Surface charges were obtained from measure ments of streaming potentials in thin capillaries. In this case a para ffin wax coating on the inner capillary surface was used as the oil/so lution interface. Emulsion film stability and oil adhesion to silica s urfaces are determined by electrostatic and hydrophobic attraction for ces influenced by addition of cationic surfactants. Strong adhesion ta kes place when the quartz surface is hydrophobized owing to CTAB adsor ption, and electrical potentials of emulsion film interfaces become di fferent in magnitude. In the case under investigation, the strongest a dhesion of oils takes place at 10(-5) M CTAB. In general, the results of these experiments offer the possibility of controlling oil adhesion , depending on the surface properties of porous bodies and oils.