Effects of Electrolytes on Solubilized States of Water by Aerosol OT Reversed Micelles

Abstract

Aqueous NaCl, NaNO3, and MgCl2 solubilized by Aerosol OT reversed micelles in isooctane media were determined as a function of surfactant concentration. Three solubilization regions I, II and III were apparent based on chemical shifts of water at given AOT concentrations. The states of water in these regions were examined based on change in near infrared spectra with Rw (= [H2O] / [AOT]), and were found the same in the absence of electrolytes. Water in reversed micelles was bounded, interacted with polar groups of the surfactant, and in swollen micelles, was metabounded and interacted with hydrated polar groups by hydrogen bonds. Water in W/O microemulsions was bulk-like. Based on minimal solubilized water required for swollen micelle and W/O microemulsion formation, bounded and metabounded water in reversed and swollen micelles respectively were shown not affected by these electolytes, whereas bulk-like water in W/O microemulsions was so. Electrolytes effect intensity followed the order of Cl->NO3- for sodium salts and Na+>Mg2+ for chloride salts.