MECHANISMS FOR LOWERING OF INTERFACIAL-TENSION IN ALKALI ACIDIC OIL SYSTEMS .2. THEORETICAL-STUDIES

A new interfacial activity model has been developed to predict, qualitatively as well as quantitatively, the equilibrium interfacial tension of alkali/acidic oil systems. The model accounts for a mixed interfacial layer and mixed micelle formation by ionized and unionized acid. Comparison of the model with experiments confirms the mechanisms proposed in Part 1 of this series. It has been found that interfacial tension goes through a minimum with pH at constant ionic strength. The ultralow value of interfacial tension is shown to result from the simultaneous adsorption of ionized and unionized acid upon the interface, and the lowering results from the formation of mixed micelles of ionized and unionized acid.