Abstract: The adsorption of cetyl trimethylammonium bromide (CTAB) at a smooth surface of SiO2 film was determined by ellipsometry. The result is in agreement with a two steps model. Its monolayer and bilayer adsorption occurred at different concentrations. The adsorption is consistant with the wettability change of the film surface. The wettability of a silica gel powder was determined by a modified Washburn equation expressed as contact angles. The interfacial tension (γ) between the dodecane and the dilute CTAB aqueous solution was obtained using the pendant method. The relationship between the wettability of the powder surface, the critical micelle concentration (CMC) of CTAB and the mimic oil recovery of the resident oil on the powder surface has been explored. It has been found that good residual oil could be achieved by surface wettability changes at normal interfacial tensions (100～102 mN•m－1) and no formation of emulsion (see Table 4).

Key words: Adsorption, Wettability, Interfacial tension, Mimic oil recovery