Dispersion and electrokinetics of scattered objects in ethanol-water mixtures

Abstract

Scattered objects ranging from 100 to 300 nm were detected in ethanol-water mixtures at increasing concentrations – 10–90% v/v ethanol using a particle size analyzer. To evaluate the structural transitions, two mechanisms of nanostructure formation from previous studies were considered: (1) molecular clustering and (2) nanobubble formation. Measurement of particle counts, polydispersities and sub-micron particle diameters were made available with the Dynamic Light Scattering (DLS) system and high resolution of detectors on the equipment (as small as 1 nm under dilute conditions). The electrokinetic property of colloidal dispersion through its zeta potential was simultaneously determined using the Phase Analysis Light Scattering (PALS) function of the instrument. Results suggest that the structural changes can be rooted, starting from an accumulation and amphiphilic encapsulation of gaseous phases forming nanobubble-like clusters at initial additions of ethanol, followed by bigger, and mostly aggregated ethanol-water and ethanol-ethanol clusters at higher concentrations. An inflection in the measured particle counts and zeta potentials at about 20% v/v ethanol as may be caused by the substantial amount of nanobubble clusters was observed similar to the reported anomalous trend in the measured thermophysical properties of ethanol-water mixtures.