Kemp's Triacid at Oil-Water Interfaces

Abstract

Kemp's triacid is studied as an emulsion-stabilizing agent by taking advantage of its conformation with three carboxyl groups triaxially oriented. Its surface active nature is investigated through interfacial tension measurements and electrokinetic studies on emulsions, with and without the acid. A hexadecane-water system provides the basis for all studies, and the effects of the presence of Kemp's triacid are then highlighted. Appreciable adsorption of the triacid molecule on the oil-water interface, particularly at very low pH of about 3.40, is evident from this study. The surface activity deteriorates with increase in pH, due to the conformation change in the molecule. Hence, emulsions stabilized with Kemp's triacid at low pH may be destabilized by simply raising the pH, through desorption of the acid from the oil-water interface. In the course of these studies, some interesting aspects of pure oil-in-water emulsions are revealed, which are justified by correlating the various data for interfacial tension, electrokinetic measurements, the size distribution of emulsions, and the change in initial aqueous phase pH after emulsification. A unique feature of the Kemp's acid emulsions observed is floc formation, at all initial solution pH's higher than 6.50. These flocs appear as solid-like flakes upon mild shaking of the emulsions, which is in contrast to the usual instability of the pure oil-in-water emulsions by drop coalescence and creaming.