ION EXCHANGE PROCESSES IN AQUEOUS-ORGANIC MEDIA

Alkali metal ion exchange on Bio-Rad AG 50W X-1 resin in 0, 5, 10, 25, 50, 75 and 90% methanol-water, ethanol-water and dioxane-water and alkali metal barium Ion exchange in acetic acid-water systems were investigated at 25 °C. In part, observed changes in selectivity coefficient with solvent changes can be explained on the basis of dielectric constant effects on coulombic interactions, but the observed maxima or minima and changes in order of selectivity as the water content of the solvent is decreased can be accounted for by the electrostatic model only if it is assumed that Ion solvation also changes in an appropriate manner. Some correlation between selectivity data and swelling data was noted. Radiotracer techniques were used to determine alkali metal exchange coefficients and gravimetric techniques for exchanges involving barium. From the solvent distribution data, there appeared to be no selective solvation of the resin phase. © 1969, American Chemical Society. All rights reserved.