Mass transfer and dynamic liquid—liquid interfacial tension. II. Theory of the relation between change of interfacial tension and change of phase volume with time, in a stirred system

Abstract

We have shown that, for a nonequilibrium, closed liquid-liquid multicomponent system, with agitation, at constant temperature and pressure, a quantitative relation exists, between the rate of change of interfacial tension (IFT) and mass transfer through the interface. The conditions in which there is an increase in γ with increase in drop volume, or decrease, or constancy, are developed. We have also shown that regimes in which γ increases, or decreases, may succeed each other. This conclusion is in agreement with observations. For systems that are relevant to surfactant flooding for enhanced oil recovery, it has been shown that the Gibbsian adsorption of adsorbable and transferrable components is small: ∑ 1 n θ 1 《 1 . This is in accord with the current theories of interfacial structure in such systems: that the low values of γ observed are due to the gentle concentration gradients in the interfacial region, and not to high surfactant adsorption. While the “gradient” mechanism is responsible for the low magnitudes of IFT in systems in which one phase is a microemulsion, an “adsorption” mechanism should be invoked to explain the time rate of change of IFT, and the change of IFT with phase volume.