Measurement of Diffusion in Ternary Liquid Mixtures by Light Scattering Technique and Comparison with Taylor Dispersion Data

Abstract

Results of diffusion coefficient measurements by dynamic light scattering (DLS) in the ternary liquid systems, glycerol-acetone-water (GAW), and cyclohexane-methanol-toluene (CMT), are reported. Data for the GAW system are compared with Taylor dispersion (TD) measurements in overlapping concentration regions close to the critical solution point at 298.15 K. A fit of the intensity autocorrelation function (ACF) could be used to predict values and explain the physical character of the corresponding diffusion coefficients. In the vicinity of the critical solution point, the DLS measurements reveal two and more hydrodynamic relaxation modes with well separated characteristic relaxation times. From the ACF, at least two effective diffusivities, D 1 and D 2 , can be experimentally determined. Theoretical predictions reveal that they may result from pure mass diffusion and pure thermal diffusion transport processes. A possible physical meaning of the modes D 1 and D 2 in the ternary liquid mixtures is discussed. When we compare the transport modes from DLS with the Taylor dispersion results, only the slowest mode represents mass diffusion, and this mode agrees very well with one of the eigenvalues of Fick's diffusion matrix. There is no relation between the mass diffusion mode from DLS and any one of the four diffusion coefficients obtained by TD.

Investigation of Fickian diffusion in the ternary mixture of 1,2,3,4-tetrahydronaphthalene, isobutylbenzene, and dodecane

“…Consequently, they are not comparable with our present results and we do not further analyze them here. Regarding non-hydrocarbon ternary liquid mixtures, there exist several recent experimental investigations, [3][4][5][6][7] due to the different nature of the system they also are not comparable with our present results.…”

“…But the liquids appearing in nature and in industrial applications are essentially multicomponent, a fact that leads research focus to move lately to diffusion in multicomponent liquid systems, starting with ternary mixtures. [1][2][3][4][5][6][7][8][9][10] However, mainly due to experimental and mathematical difficulties, even in ternary mixtures, diffusion coefficients are so far available only for a very limited number of these systems. Furthermore, in those cases where more than one data exist, quite often measurements by different experimental groups or by different techniques do not agree.…”

Diffusivities of an Equimolar Methane–Propane Mixture Across the Two-Phase Region by Dynamic Light Scattering

“…The limitation regarding the resolution of multiple hydrodynamic modes accessible by DLS is not only restricted to the supercritical state close to the vicinity of the plait critical point. It was also observed close to the consolute critical point of a ternary mixture [8,9], in the saturated liquid phase of a binary mixture at vapor-liquid equilibrium [10][11][12], and in the liquid state for binary mixtures near their plait critical point [13]. For the last two cases, this limitation was observed close to the region where thermal and Fick diffusivities match.…”

Ternary Diffusion Coefficients of Cyclohexane + Toluene + Methanol by Taylor Dispersion Measurements at 298.15 K. Part 1. Toluene-Rich Area

“…The eigenvalues of the ternary diffusion matrix and the respective determinants were calculated to check the quality and internal consistency of the experimental data. These measurements will complete DLS experiments of the same system in the vicinity of the critical solution point by Ivanov and Winkelmann …”

“…These measurements will complete DLS experiments of the same system in the vicinity of the critical solution point by Ivanov and Winkelmann. 43 Taylor dispersion method. In a ternary mixture, the diffusion processes are described by a coupled set of Fick's equations…”