Estimation of Diffusion Coefficients Based on Adsorption Measurements in Model Extraction Systems

Abstract

The drop volume technique has been used to measure the equilibrium and dynamic interfacial tension at the liquid/liquid interfaces of selected hydroxyoximes, as examples of chelating type hydrophobic metal ion extractants. The measurements for the kinetics of adsorption enable the calculation of diffusion coefficients. In this paper, new methods for the estimation of the diffusion coefficient by Fick's and the Maxwell-Stefan equations are presented. The calculated values of the diffusion coefficient were compared with the values obtained from the short and long time approximation models of the Ward-Tordai equation. The influence of the organic phase and the addition of non-organic electrolyte to the aqueous phase on the estimated values of the diffusion coefficients were investigated.

Synthesis and Interfacial Activity of Novel Heterogemini Sulfobetaines in Aqueous Solution

“…For the surfactant in a low concentration, in the bulk phase, the values of dynamic interfacial tension reach the equilibrium value in a longer time than in the systems with the surfactant at a higher concentration. A similar relationship was observed by other researchers [18, 19]. The higher the concentrations of heterogemini surfactants, the faster the adsorptions at the air–water interface.…”

A Linear Diffusion Model of Adsorption Kinetics at Fluid/Fluid Interfaces

“…There exist several simplified approaches, e.g., Fainermann [ 10 ] proposed the so called long and short time approximations which are widely used in the literature to give estimations of the diffusion coefficient in the sublayer. Direct estimation of diffusion coefficients using the Maxwell–Stefan approach is also presented by other works [ 11 ]. On the other hand, the kinetically controlled adsorption process kinetics is described by the rate constants k ads / k des dependent on the temperature according to the Arrhenius–Eyring law [ 12 ].…”