NONAQUEOUS ION EXCHANGE. II. UNIVALENT CATION EXCHANGE IN ALCOHOLS AND METHANOL-WATER, ETHANOL-WATER, AND METHANOL-ETHANOL MIXTURES^1,2

Abstract

Concentration equilibrium quotients, Le., selectivity coefficients, have been measured a t 30" for the following cation-exchange systems and solvents using Dowex 50 X8: Li-H, and Li-Ya in methanol-water mixtures; Sa-H in methanol-ethanol and in ethanol-water mixtures; Sa-H as a function of resin composition in pure ethanol; and Li-8 as a function of resin composition in pure methanol. External solutions were maintained a t 0.1 m ionic strength. Alterations in the degree of ion solvation and ionpair formation are believed to account for the generally enhanced metal selectivities in alcoholic s) stems as compared with similar aqueous systems. A maximum in the selectivity for the "metallic" ion was noted in every "metal"-hydrogen exchange in methanol-water and ethanol-water a t external solution concentrations of from about 15 to 30 mole yo of water. An interpretation is offered based on the effect of the medium on ionic activity coefficients, especially that of the proton. The equilibrium quotients for the Na-H and K-H exchanges in methanol-water are corrected for activity effects in the external solution. The absence of maxima in the Na-H system in methanol-ethanol and in the Ka-Li system in methanol-water is discussed.

Water sorption and cation-exchange selectivity of a perfluorosulfonate ion-exchange polymer

“…Ion-exchange isotherms for Nafion 120, 25 °C, 0.01 M, methanol. •, Li+; , Na+; , K+, A, Rb+; , Cs+ K+, 18; and Cs+, 10.0 (23). The affinity reversals here are well described by the Eisenman theory of ion exchange (24), and can be ascribed to increasing electrostatic attractions between exchange sites and alkali metal ions of increasing crystallographic radius and lower solvation energy (10).…”

Competitive substitution of hexammine cobalt(III) for Na+ and K+ ions in oriented DNA fibers

“…The finding that DNA (in its condensed state, in the presence of water/organic solvent, and with variation of K/Na ratio in the eluent) never selects between K + and Na + is interesting to compare with the results obtained for the most common anionic polyelectrolytes and with DNA selectivity for other alkali cations. For sulfonic cation exchange resins, selectivity for K + has been observed, and separation between K + and Na + depends on the content of organic component in alcohol/water mixtures 34. Carboxylic cation exchangers demonstrate selectivity toward Na + at low degrees of cross‐linking, but this selectivity reverses with the increase of cross‐linking 35.…”

Strong oxide-oxide interactions in silica-supported magnetite catalysts. 2. The core/shell nature of the interaction

“…Earlier, Gupta applied his theory to the Na+/H+, Li+/H+, and K+/H+ exchanges up to 80 mol % methanol11 and in pure methanol,12 in effect passing over the region of selectivity maximum at about 80 mol % . 13 As will be shown, the theory does fit each trend successfully and provides insight into the factors contributing to the trend.…”