Adsorption of cetyldimethylbenzylammonium chloride on octane emulsions droplets: The effect of the presence of Tween 80

The adsorption of the cationic surfactant cetyldimethylbenzylammonium chloride (CDBACI) on octane-in-water emulsion droplets is estimated and the adsorption isotherms are determined. The adsorbed amount of CDBACI is also measured in the presence of the nonionic surfactant Tween 80, at concentrations below and above its critical micellar concentration (CMC). Various combinations are made concerning the preparation of the emulsions and the incorporation of the surfactants, before or after the emulsification. The addition of surfactants before emulsification results in a reduction in the droplet size. An increased adsorption of CDBACI on the emulsion droplets is observed when it is added before the emulsification, in the absence of the nonionic surfactant. The molecules of Tween 80 hinder the adsorption of CDBACI on the surface of emulsion droplets. In some cases a competitive adsorption of the emulsifiers for the oil droplet is observed leading to a displacement of the molecules of the cationic surfactant from the interface. The surface tension of the mixture of the surfactants is also measured. The CMC of the aqueous solutions of mixed surfactants is determined and the adsorption parameters is calculated. A synergy is found in the reduction of the surface tension. The displacement of CDBACI from the emulsion droplets is broadly consistent with the interfacial tension data. (C) 1998 Academic Press.